Abstract:To improve the anti-ablation property of carbon/carbon (C/C) composites, the double-layer coatings with SiC/Al₂O₃ as an inner layer and ZrB₂/SiC/Ta₂O₅ as an outer layer were prepared by atmosphere plasma spraying. The phase composition, microstructure and element distribution of the coatings before and after ablation were analyzed using X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy, respectively. There are no cracks on the surface coating and the connection of two coatings and the SiC/Al₂O₃ coating with substrate is well. The distribution of elements Zr, Si and Ta on the coating are similar, which indicates the good homogeneity of coating. Ablation resistance of coated C/C was tested by the oxyacetylene flame at 1800 °C. The mosaic structure formed during the ablation process is conducive to prevent the diffusion of O₂, and the Ta-Si-O glassy layer formed on the surface coating has a protective effect. The coating exhibits a good anti-ablation ability.

Abstract:Using tetrabutyl titanate as the raw materials, the surface of TiB₂ powders was coated with TiO₂ nanoparticles prepared by the peptization and reflux method at low temperature. The surface morphology, the phase composition of coating layers and specific surface area of composite particles were characterized by SEM, XRD and BET, respectively. The results show that the TiO₂ nanoparticles are coated on the surface of powders uniformly and discretely and the main phase of coating layers is anatase. The surface of TiB₂ powders is rougher after nano-modification and the value of specific surface area of the composite particles is elevated by over 35 times compared with that before coating. Wear-resistant composite coatings are prepared by adding coated TiB₂ powders to epoxy resins. The abrasive loss of composite coatings decreases to 50% of the coatings filled with uncoated TiB₂ powders. Finally, the wear properties, worn surface morphologies and antiwear mechanisms of wear-resistance coatings were analyzed.

Abstract:The effects of ball milling with simultaneous addition of multiwall carbon nanotubes (MWCNTs) on the thermoelectric properties of BiSbTe based nanocomposites were investigated in the temperature range from 300 K to 500 K. The MWCNTs in 0.5 vol% and 1.0 vol% were incorporated in fine BiSbTe powder that was processed from commercially available BiSbTe lumps and consolidated through pressure assisted induction heated sintering. The results show that the electrical and thermal transport properties of the composites are altered substantially. The thermal conductivity of the composites decreases significantly from pure BiSbTe bulk due to enhanced phonon scattering caused by nanostructuring and nanoinclusion effects. While the electrical conductivity deteriorates with the addition of MWCNTs, which is attributed partly to enhanced electron scattering and predominantly, rather low densification of the composites. The figure of merit of 1.0 vol% MWCNTs/BiSbTe composite remains close to that of pristine BiSbTe, snice the decrease in electrical conductivity is compensated by the significant reduction in thermal conductivity. The result suggests that optimizing the processing parameters for enhanced densification could improve the figure of merit for BiSbTe based MWCNTs composites.

Abstract:Pt-Fe2O3 composite nanoceramics were prepared from Pt and Fe2O3 nanoparticles through traditional pressing and sintering. SEM analyses showed that numerous nanosized pores were present in the ceramics and Fe2O3 grains were around 30nm in size. Sensors based-on the nonoceramics were found to show strong responses to hydrogen at room temperature. To 5% H2 in N2, the sensitivity was over 90, and the response and recovery times were 20s and 30s, respectively. To explore the room-temperature hydrogen sensing mechanism, hydrogen concentration in surrounding N2 was decreased from 5% to 0. The resistance of the sensors was found to show no response to the hydrogen concentration variation. It indicates that hydrogen-induced decrease in resistance of Fe2O3 results from the reaction between chemisorbed oxygen on Fe2O3 and hydrogen at room temperature with the catalytic effect of Pt. Fe2O3 based ceramics are quite different from TiO2based ceramics in room-temperature hydrogen sensing properties and mechanism, and systematic investigations should be conducted on room-temperature hydrogen sensing of various metal oxide semiconductor ceramics.

Abstract:Eu-doped Ca-α-SiAlON phosphors were prepared by a newly-developed thermal-insulation-assisted combustion synthesis method. With Si₃N₄ powders cladding on the reactant mixtures, the duration of the CS system in the high temperature period remarkably enhanced due to the low heat dissipation. The as-produced Ca-α-sialon:Eu₂₊ phosphors feature high purity, good uniformity and outstanding luminescence properties with a yellow emission peaking at 568 nm under a UV or blue light excitation. The excitation and emission intensities for the as-synthesized phosphors were notably improved with the assisted by Si₃N₄ insulating layer.

Abstract:In this paper, the monodisperse nano-SiO2 particles were obtained via a novel improved stober method, and the micro-meso porous SiO2 xerogels was further obtained after drying in air. The nano-SiO2 particles with the average size of 20 nm, exhibited good dispersibility in alcohol.The as-obtained amorphous SiO2 xerogels were featured with Si-OH and Si-OR groups on the surface, implying a imcomplete hydrolysis and condensation process. Meanwhile, a large number of defects were remained inside and on the surface of the SiO2 xerogels, thus displaying good photoluminescence behaviors. The ultraviolet (λem = 355 nm) fluorescence under λex = 300 nm excitation as well as the visible light (λem = 430nm) phosphorescent under λex = 380nm excitation was observed in the as-obtained SiO2 xerogels. The calculated results according to N2 sorption isotherms demonstrated that specific surface area of the SiO2 xerogels was 559 m2 /g, the pore volume was 0.62 cc/g and a large number of micropores and mesopores were existed in the SiO2 xerogels.

Abstract:5Y-TZP/TiB₂ nano-composite ceramic material was prepared by vacuum hot pressing technique, study oh the effect of two-step sintering on the microstructure and mechanical properties of the composite. 5Y-TZP/TiB₂ nano-composite ceramic materials were obtained from 80% ZrO₂(as stabilized 5mol%Y₂O₃), 10% TiB₂, 5% Al₂O₃, 2% MgO, 2% Mo and 1% Ni. Two-step sintering has been carried out for two different sintering times: 120 minutes at 1100 °C and 60 minutes at 1450 °C。The results have shown that with the two-step sintering could be benefit to make the m-ZrO₂ to the t-ZrO₂, densification, refinement and strengthening. Compared with the ordinary materials, the flexural strength, fracture toughness and hardness of 5Y-TZP/TiB₂ nano-composite ceramic material was 1023 MPa, 11.33 MPa?m_1/2 and 13.91 GPa, increased by 12.2%、17.9% and 13.5%, respectively. Toughening and strengthen mechanism of 5Y-TZP/TiB₂ nanocomposite ceramic material including crack deflection and crack bridging, and the trans-granular fracture mode was occurred.

Abstract:The phase structure plays an important role on the transmittance of zirconia ceramics. In this paper, 3 mol% Y2O3-stabilized ZrO2 (3YSZ) and 5 mol% Y2O3-stablized ZrO2 (5YSZ) were prepared, and sintered at 1450℃, 1500℃ and 1550℃ respectively. The phase structure and constitution of the specimens were characterized by XRD, SEM and EMPA. And the transmittance of the specimens was tested by UV-Vis spectrophotometer in the visible range. The relationship between the phase structure and the transmittance is discussed. The results reveal that 3YSZ and 5YSZ both have a binary assemblage of t and t′ phases, while more t phase was found in the 3YSZ, and more t′ phase was found in 5YSZ, the content of which increase with the sintering temperature seperately. The transmittance of 5YSZ is higher than that of 3YSZ in the visible light range. Concerning the phase structures and the transmittance of 3YSZ and 5YSZ, the conclusion that the transmittance of t′ phase is higher than that of t phase is brought forth.

Abstract:Direct coagulation casting via dispersant reaction is a novel colloidal forming method for ceramics. The well disperse silicon carbide suspension can be coagulated in-situ by DCC via dispersant reaction. Silicon carbide suspension was prepared using surface chemical treatment powder. Ammonium carbonate ((NH₄)₂CO₃) was used to leach the silicon carbide powder. Tetramethyl ammonium hydroxide (TMAH) with content of 0.2 wt% was used as dispersant. 2 vol% glycerol diacetate (GDA) was added as coagulation agent. Tetramethyl ammonium hydroxide reacted with acetic acid which hydrolyzed from glycerol diacetate at elevated temperature, and then desorbed from silicon carbide particles. Zeta potential of suspension decreased due to desorption of dispersant, and the suspension coagulated in-suit from the instability of the silicon carbide particle. The silicon carbide green body with compressive strength of 1.13 MPa was coagulated at 70°C. The silicon carbide ceramic with fracture strength of 697 MPa was pressureless sintered at 1950°C for 2h under 0.1MPa argon atmosphere.

Abstract:In this paper, long-chain surfactant cetyl sodium sulfate was used to modify alumina particles for the first time. Alumina particle-stabilized foams were prepared by mechanical agitation of suspensions with solid loading of 8~40 wt%. The wet foams were dried at normal temperature and pressure and subsequently sintered at 1550 °C for 2 h and finally light weight alumina ceramic foams with density of 76~355 kg/m3 (namely porosity of 91.1%~98.1 %) were prepared. Effects of pH value and cetyl sodium sulfate concentration and solid loading on the stability of alumina wet foams and properties of alumina ceramic fomas were studied. It was found that stable wet foams can be prepared and the strength of dried foams was improved effectivity by adding 0.2~1.0 wt% PVA.

Abstract:Elongated mullite (Al₆Si₂O₁₃) was synthesized at 1 773 K for 5 h via an in-situ solid-reaction method using granular mullite powders as raw materials, and TiO₂ as an additive. Based on thermodynamic analysis of the reaction process, the effects of TiO₂ contents on the phase composition, phase contents and microstructure of synthesized samples were investigated, and the growth mechanism of elongated mullite was discussed. The results showed that elongated mullite with the length of 15.2 μm were formed for the sample with TiO₂ contents ≥ 7 wt%. Lattice distortion of mullite and the formation of liquid phase in the sample with addition of TiO₂ resulted in the anisotropic grain growth of mullite.

Abstract:High Energy ball milling is a simple and effective method in preparing nano-particles, which can be used to low size of starting dielectric powder for building thin casting film, favoring to enhance the capacitance density of multilayer ceramic capacitors. In this paper, Bi_0.5Na_0.5TiO₃-NaNbO₃ (BNT-NN) binary system has been selected as research goal. After high temperature calcining, the obtained pure phase BNT-NN coarse powder has been further pulverized by high energy milling method. The results revealed that high energy milling method can realize the refinement of BNT-NN nano-powders in a short time. Using these nano-powders as precursor, the grain size of the densified ceramics decreased about one third in comparison with those derived from normal coarse powders. Moreover, the temperature stability of capacitance of fine ceramics was below 15% in a wide temperature region between -60_oC to 300_oC, showing potential application in high-temperature multilayer ceramic capacitors.

Abstract:In this research, as pore-forming agents, silica poly-hollow microspheres were added into Si₃N₄ slurries, and Si₂N₂O phase was generated by the liquid phase sintering reaction between SiO₂ and Si₃N₄. Moreover, the space occupied by the silica poly-hollow microspheres would become the pores after the sintering process, and porous Si₂N₂O ceramics were fabricated. The morphology and mechanical properties of porous Si₂N₂O ceramics could be well regulated by adjusting the solid loading of Si₃N₄ slurry. The results show that with the increase of Si₃N₄ slurry solid loading, the content of Si₂N₂O phase increases and their porous structure has great changes. Besides, their open porosity decreases to 51.7% and their flexural strength increases to 26.74 MPa.

Abstract:The property of MnO2 precursor has a great effect on the performance of LiMn2O4 product. In this study, Birnessite-type layered MnO2 was obtained through liquid phase coprecipitation reaction under neutral and acidic conditions. After heat treatment, the final product synthesized from MnO2 under neutral condition possesses the impurity phase MnO2 without any carbon layer, while the product synthesized from MnO2 under acidic condition is proved to be pure spinel LiMn2O4 with a thin carbon layer. The latter carbon-coated LiMn2O4 delivers the initial discharge capacity of 129.7 mAh/g at 0.2C, which is higher than that of the former product with only 58.5 mAh/g; even at higher rate of 30C, the discharge capacity can reach 117.8 mAh/g and retain about 92% capacity after 1500 cycles. The results show that when precursor MnO2 is optimized under acidic condition, the as-synthesized spinel LiMn2O4 can exhibit superior high-rate capability and long-life cycling stability, proving to be a promising cathode material for market applications.

Abstract:BiPO₄ was synthesized with Bi(NO₃) ₃.5H₂O, Na₃PO₄.12 H₂O hybridized by g-C₃N₄, and the g-C₃N₄/BiPO₄ presents enhanced performance in the paper. The g-C₃N₄/BiPO₄ photocatalysts were characterized by XRD, FT-IR, SEM, TEM and BET. The photocatalytic activities were evaluated by the degradation of methylene blue under the visible light in the photocatalytic reaction device. TheSexperimentalSresults show that the visible light photocatalytic activity of BiPO₄ was greatly enhanced by the hybridization of g-C₃N₄. A loading amount of 7% g-C₃N₄ over BiPO₄ led to the most obvious increase of the photocatalytic activity under the visible light irradiation. Keywords: Composite photocatalysts; BiPO₄; g-C₃N₄; visible light

Abstract:In order to study the technological conditions to prepare Cr₇C₃, the carbonization products of Cr₂O₃ were analyzed from the aspects of thermodynamics and the thermodynamic simulation of Cr₇C₃ was carried out by method of standard reaction thermal effect calculation. The effects of reaction temperature, reaction atmosphere and material ratio on the preparation of Cr₇C₃ were studied, and the principle of high purity Cr₇C₃ prepared by carbon thermal reduction method from the melt was explained. The results show that minimum formation temperature of Cr₇C₃ is 1368 K, the increase of the reaction temperature helps to increase the yield of Cr₇C₃; Lowering the CO partial pressure of the system is beneficial to reduce the initial temperature of the reaction and the formation of Cr₇C₃; Cr₇C₃ can react with C in the system to generate Cr₃C₂. Meanwhile increasing the reaction temperature and optimizing the material ratio are conducive to inhibit the excessive carbonization of Cr₇C₃.

Abstract:The lanthanum magnesium hexaaluminate (LaMgAl₁₁O₁₉) powder was prepared via reverse chemical coprecipitation and high-temperature calcination method. The phase composition, microstructure, crystal structure and anisotropic lattice thermal expansion were ananlyzed using X-ray diffractometer (XRD), field emission scanning electron microscope (FSEM), in-situ high temperature X-ray diffraction (HD-XRD) and Rietveld refnement. The results showed that the precursors were final transformed to LaMgAl₁₁O₁₉ at sintering temperature of 1600 _oC, in which the hexagonal plane was regular and smooth. Anisotropic lattice thermal expansion of LaMgAl₁₁O₁₉ was investigated by HD-XRD using rietveld refnement method. The influence of temperature-related parameter on cell parameters was analyzed, of which a_T=5.5821+1.625×10_-5T+1.757×10_-8T₂+4.24×10_-12T₃ and c_T=21.9189+1.1952×10_-4T+4.587×10_-8T₂+5.463×10_-11T₃. Lattice thermal expansion of LaMgAl₁₁O₁₉ presented anisotropic characteristics. At ambient temperature to 1300 ℃, average coefficient of thermal expansion of LMA were obtained with TECs(//a)= 8.42×10_-6 /℃, TECs(//c)=12.54×10_-6 /℃. The variation of lattice thermall expansion of LaMgAl₁₁O₁₉ mainly due to the changes of La-O bond caused by temperatute.

Abstract:A series of BaZr_xTi_1-xO₃(x = 0.05, 0.1, 0.15, 0.2) ceramics were prepared by solid-state reaction. The effect of Zr content in BaTiO₃ system on the structure, phase composition, dielectric and ferroelectric properties had been investigated. The results showed that all samples were found to crystallize in the perovskite single phase, without any second phase. The SEM pictures showed that the grain size increased obviously with the increasing of Zr content, which acted as a grain growth promotor. The dielectric constants were affected by the doping level of Zr, and increased to the maximum of 4900 for the sample of x = 0.15 at 3 MHz. In addition to the sample of x = 0.15, the remnant polarization of other ceramics was decreased with the increase of Zr content, while the coercive field increased. There was the tendency of increase the leakage current with the increase of Zr, which leaded to the deterioration of the ferroelectric properties.

Abstract:The phase decomposition of single ZrW2O8 was investigated by sintering at different temperatures. After quenching, the decomposition of ZrW2O8 was estimated by the phase analysis and the phase decomposition mechanism was discussed combining the solid phase transition theories and crystallographic theories. Then the solid phase synthesis method was used to investigate the influences of the sintering temperatures and cooling ways on the synthetic ratio of ZrW2O8. The results showed that the phase decomposition temperature region is 780~1108 °C and ZrW2O8 can exist steadily in the form of metastable state below 770 °C. The solid phase synthesis of ZrW2O8 occurred above 1108 °C and the maximum synthetic ratio was obtained when the sintering temperature was 1200 °C and water cooling way was adopted.

Abstract:Blue persistent luminescent β-Ga₂O₃: B₃₊ was synthesized by high solid-state reaction. The phosphor exhibits more than 0.5 h afterglow in the wavelength range of 380-600 nm after ceasing the ultraviolet light (260 nm) irradiation. The emission and excitation spectra, persistent luminescence decay curve, and thermoluminescence curve were measured. The emission and excitation spectra indicate that the B₃₊ doping improves on photoluminescent properties of β-Ga₂O₃. The thermoluminescence (TL) curve of β-Ga₂O₃: 80% B₃₊ shows that B₃₊ increased the traps and improved the depth of the traps.

Abstract:In this paper, LaAl1-xGaxO3 powder and its amorphous sphere have been prepared by sol-gel method and containerless solidification technology, respectively. Ga3+is used to substitute Al3+ in B-site with the composition of x from 0 to 1. The X-ray diffraction results show that powders with no impurity phase were obtained when calcined at 850℃ which are all perovskite structure. The transparent spheres are proved to be amorphous by XRD analysis. With the increase of Ga₃₊ content, the dielectric constant ranges from 15 to 19 at 100KHz and it￠s corresponding dielectric loss is smaller than that of 0.007. The amorphous material has a low leakage current of 10-1A/cm2, and showed a high refractive index, which was more than 1.8 in 633nm.

Abstract:In this paper, a series of La0.85Bi0.15Al1-xGaxO3powders with the composition of x from 0 to 1 have been firstly prepared by sol-gel method. Then as-prepared powders were pressed into 10 mm diameter discs of 1-2 mm thickness, part of one disc rapidly solidified to form homogeneous amorphous sphere by means of aerodynamic levitator method, which involved a containerless solidification process. The prepared La0.85Bi0.15Al1-xGaxO3 amorphous samples are spherical shape and transparent property with wide-banded transmittance from 1000nm to 3000nm, the apparent transmittance had a maximum of about 81.7% for x=0. The dielectric constant is higher 19 and dielectric loss is lower 0.006 for all the fabricated samples from 10kHz to 1MHz. The nature of La0.85Bi0.15Al1-xGaxO3 amorphous spheres were identified by XRD and Raman spectrum.

Abstract:Aluminum doped zinc oxide (AZO) thin films were deposited by the radio frequency magnetron sputtering with double target, used as the low resistance window layers of Cu₂ZnSnS₄ (CZTS) solar cells. The influences of Ar flow on the optic-electronic performances of AZO thin films were investigated with 60W sputtering power and 30 mins sputtering time, such as the crystallinity, surface morphology, transmittance, carrier concentration and resistivity. It is showed that, 22 sccm is the saturated Ar flow. Under this flow, AZO grains are bigger, the crystallinity of films are better, the carrier concentration is higher, while the resistivity is lower. The average transmittance of the AZO film is 87.2% range from 400 nm to 1100 nm wavelength.

Abstract:β-SiC powders were synthesized at 1400 ℃ for 3 h under Ar atomosphere via catalytic reaction method using industrial diatomite powders and phenolic resin as raw materials, and nickel nitrate as catalyst precursor. The effects of temperature, holding time and catalyst content on the formation of the SiC powders were investigated. XRD, SEM and TEM analyses were employed to characterize the phase composition and microstructure of the final products. The results indicated that: 1) β-SiC can be synthesized at 1400 ℃ for 3 h with 1.5 wt% Ni as catalysts. In contrast, for the sample without Ni catalysts, the yield of β-SiC was only 17% in the final products under identical condition; 2) The as-prepared β-SiC were granular in morphology, and the particle size were less than 100 nm.

Abstract:Silicon nitride (Si₃N₄) which possess excellent mechanical properties, chemical properties and physical properties have been widely used in chemical industry, metallurgy, aerospace and other fields. Y₂O₃ nanoparticle (NP) catalysts were homogeneously deposited on the surface of Si powders by an in-situ precipitation method using PEG as surfactant and NH₃.H₂O as precipitant. The effects of various processing parameters including the amount of catalyst and nitridation temperature on the synthesis of Si₃N₄ were investigated. Phase composition and microstructure of the Si₃N₄ were characterized by X-ray diffraction, field emission-scanning electron microscopy equipped with EDS. The results showed that: 1) For the sample nitrided at 1350 ℃ for 2 h with 1 wt% of Y₂O₃ NPs as catalysts, residual silicon in the final sample was less than 1 wt%; 2) Lots of Si₃N₄ whiskers with 20~200 nm in diameter and several microns in length was formed in the final products. Vapor-Vapor-Solid (VVS) growth mechanism might be responsible for the growth of Si₃N₄ whiskers.

Abstract:Tailing porous ceramics that iron tailings as the raw material were prepared by foam-gelcasting method and pressureless sintering process. The effect of sintering temperature on prosity, bulk density, compressive strength, Phase composition, microstructure and pore size distribution. Results show that as sintering temperature increased, porosity declined to 72% from 89%, the volume density and coirpressive strength increased to 0.76 g/cm3 and 6.19MPa respectively. When the sintering temperature is 1100°C, the diffraction peak of Quartz become wider and weak. It means that quartz is melting in liquid phase to increase the density and mechanical properties of tailing porous ceramics. The pore size is uniformly distributed in the 20μm to 70μm as the sintering temperature increases.

Abstract:ZnO is considered as a promising oxide thermoelecreic material based on its excellent electrical properties, however, its thermoelectric properties is hard to improve limited by its high thermal conductivity. In this paper, Al doped ZnO powders were fabricated by co-precipitation, and then coated with different quantity TiO₂, forming Zn_0.98Al_0.02O@TiO₂ core-shell heterogeneous structure, at last sintered to ceramics by SPS. The electrical and thermal properties both were optimized with TiO₂ coating. The power factor of 15 wt% TiO₂ coated sample was improved about 10% than that of the uncoated sample at 1023 K, and the thermal conductivity of 15 wt% TiO₂ coated sample was depressed about 30% than that of the uncoated sample. As a result, the maximum ZT value was enhanced about 43% from 0.030 of the uncoated sample to 0.043 of 15 wt% TiO₂ coated sample at 1023 K, which shows that Zn_0.98Al_0.02O@TiO₂ core-shell heterogeneous structure is an effective approach to enhance the thermoelectric properties of ZnO.

Abstract:选用42CrMo合金钢板为金属基底，以（Ti-B4C）为反应体系，采用离心反应熔铸工艺成功制备出TiB2基陶瓷/42CrMo合金钢梯度纳米结构复合材料。结合XRD、FESEM与HRTEM分析，可以认为由于离心反应熔铸工艺诱发热爆反应，促使液态陶瓷与合金钢发生熔合扩散，在两者之间生成成分浓度梯度的中间液相，并在陶瓷凝固与离心力的双重作用下发生陶瓷晶核Stokes迁移粗化与合金液相流动汇集，最终在复合材料层间生成相界尺度呈空间连续梯度演化的梯度纳米复合结构。

Abstract:Based on fusion bonding and atomic interdiffusion between the liquid ceramic and molten Ti-based alloy, the laminated composites of TiB2-based ceramic and Ti-6Al-4V alloy were achieved by centrifugal reactive casting, and within the interlaminar region the composite microstructures of nano-structured gradient developed with the continously-graded evolution of TiB2 and TiB in spatial size. Interlaminar shear strength, flexural strength and fracture toughness measured 335 ± 35 MPa, 862 ± 45MPa and 45 ± 15 MPa, respectively.

Abstract:Based on liquid fusion and interdiffusion between the ceramic and the titanium alloy, the laminated composites of TiB2-Based ceramic and Ti-6Al-4V alloy with the nano-structured gradient were achieved by centrifugal reactive casting processing. By conducting DOP test with 14.5mm army AP projectiles on TiB2-based ceramic and the laminated composite, the average ballistic mass effectiveness of two materials measured 3.05 and 7.30. Hence, it was considered that because the interlaminar interface developed the nano-structured gradient from the ceramic to Ti-6Al-4V alloy, the laminated composite not only presented high interlaminar cleavage resistance and high mechanical properties, but also exhibited high ballistic preformance by the dual mechanisms of interlaminar load transfer and multi-scale (micro/micro-nano/nanometer) interface shear-coupling.

Abstract:By taking centrifugal reactive casting processing to prepare the TiB2/42CrMo laminated composites, flexural strength, fracture toughness and interlaminar shear strength of the laminated composite measured 1250 ± 35 MPa, 75 ± 12 MPa·m1/2 and 450 ± 20 MPa respectively. Because the microstructure with the nano-structured gradient directly developed in the ceramic/steel interlaminar region, the ceramic/alloy phase-boundary size with continuous gradient was spatially formed from the ceramic to the steel. As a result, the laminated composite not only had the plastic deformation capacity similar to the metal, but more importantly also exhibited strong mechanical behaviors of failure delay in both load-displacement curves during 3-point bending test and short-beam interlaminar-shearing test.

Abstract:Vertically aligned Au decorated WO3 nanorods (Au-WO3 NRs) were investigated as cheap and sensitive surface-enhanced Raman scattering (SERS)-active substrates. The WO3 NRs were prepared through a simple, low-temperature hydrothermal route and made SERS-active through deposition of Au nanoparticles by ion sputtering. The structure and morphology of WO3 were investigated through XRD, SEM and TEM. The probe molecule rhodamine 6G (R6G) has been detected by using the substrate. It is found that the Au nanoparticles about 5 nm were uniformly distributed on the WO3 nanorod which has a rectangular cross-section. The Au-WO3 NRs substrate shows high sensitivity for R6G, suggesting a promising potential for application in rapid detection of environmental pollutants.

Abstract:In recent years, composites with nonlinear dielectric or resistive properties exhibited good performance in homogenizing electric field and space charge suppression, which provide a new method to reduce the accelerated aging problem of insulation materials under inhomogeneous field in high voltage transmission and distribution system. For the purpose of obtaining insulation materials with desirable dielectric and electrical resistance properties, electrical properties of nonlinear fillers doped silicon rubber composites and its dependency of temperature and field were investigated in this study. By choosing barium strontium titanate (BST) and zinc oxide (ZnO) as the filler and high temperature vulcanized silicone rubber (SiR) as the matrix., the samples of silicone rubber composites with different components were prepared respectively. Experimental investigations into the electrical properties of silicon rubber composites at different filler loadings revealed few unique behaviors (at certain filler loadings) and also advantageous characteristics. Results demonstrated that it was possible to achieve higher values of permittivity and lower values of tanδ and resistivity with respect to unfilled silicone rubber composites over a wide electrical strength range.,which verified the prospect of the application of non-linear composites in high-voltage insulation.

Abstract:Carbonaceous spheres with high yield and narrow size distribution were prepared by hydrothermal carbonization process using sucrose as carbon source, sodium polyacrylate (PAANa), polyvinyl pyridine (PVP) and polyethylene maleic anhydride (ISOBAM) as dispersants. The effects of type and content of these dispersants on the preparation of carbonaceous spheres were investigated. The results showed that, for the sample without using any dispersants, the yield of carbonaceous spheres increased with sucrose concentration increasing, nevertheless, clearly aggregation was also observed in the samples. Using 0.5 wt% and 1.5 wt% sodium polyacrylate (PAANa) as dispersants, carbonaceous spheres with average diameters of 1.6 μm and 0.23 μm can be respectively prepared at the sucrose concentrations of 0.7 mol/L. Polyvinyl pyridine (PVP) and polyethylene maleic anhydride (ISOBAM) can’t play effective roles for the preparation of carbonaceous spheres with small size and narrow size distribution by this method.

Abstract:Porous anorthite ceramics were fabricated by foam-gelcasting and pressureless sintering method, using α-Al₂O₃,SiO₂ and CaCO₃ as raw materials . By adjusting the foaming agent concentration during foaming process, pore structure could be tailored. XRD was used to analyze phase composition of prepared materials. The microstructure of prepared materials was observed by SEM. Some porperties such as the porosity, bulk density, compressive strength were tested. The influences of foaming agent concentration on the microstructure and properties of materials were studied. The results show that concentration of foaming agent has little effects on the phase composition. While the porosity and pore structure are significantly effected by foaming agent concentration. The compressive strength is obviously influenced too. Through adjusting foaming agent concentration in the range of 0.5 ~ 32 g/L, single phase porous anorthite ceramics with compressive strength of 0.14~3.84 MPa, porosity of 82.14~90.61 % could be fabricated.

Abstract:The alumina-spinel refractory castables were prepared by using tabular alumina and spinel as main raw materials, calcium aluminate cement as binder, metallic Al powder (≤0.15mm) as additives. The anti-explosion temperature of castable samples was detected. The characteristics of microstructure, pore size distribution and air permeability were analyzed by techniques of SEM, Mercury Injection Apparatus and Pressure-difference Method respectively. The influence of Al powder on explosive spalling resistance of alumina–spinel castables were studied, and the pore formation mechanism and explosion-proof of Al powder in castables were investigated. The results showed that the anti-explosion temperature of alumina-spinel castables increased and then decreased with the increase of Al powder content, which is consistent with the changing tendency of the air permeability. During the curing of castable samples, the exothermic peak moved forward steadily with the increase of Al content; however, it moved forward significantly when Al powder content over 0.075%. Microstructure analysis showed that the number of pores increased significantly with the Al powder addition,it is found that the pore size of the castables increased with increase of Al powder addition.

Abstract:TiC_x/Ni composite materials was prepared using Ti₃AlC₂ and Ni alloy powders as raw materials by in-situ hot-pressing sintering. Ni alloy, under the high temperature, triggers Ti₃AlC₂ dissociation, Al atoms and a small number of Ti atoms seperate from the matrix of Ti₃AlC₂ and react with Ni alloy. TiC_x in the value of x equal to 0.625 and 0.715 was formed as adding 20Vol%Ti₃AlC₂ and 40Vol% Ti₃AlC₂, respectively.XRD, SEM and EDS were used to analysize the phase composition and microstructure of composite.The interface between in situ generated TiC_x and Ni alloy combined strongly, therefore the composite materials perform excellent mechanical properties. After adding 20Vol% and 40Vol%Ti₃AlC₂, the compression strength of composite material reached to 2.09 GPa and 2.2 GPa, and corresponding compression fracture strain was 9.6% and 8.5%, respectively.#$NLKeywords: In-situ TiC_x; hot-pressing sintering; mechanical properties; microstructure

Abstract:Porous carbon fiber reinforced ceramic matrix composite is a good thermal insulation material with low thermal conductivity, light weight, which has a huge application prospect in aeronautics and astronautics field. But the material is easy to destroyed by oxidation erosion and ablation. Double-layer structure ceramic coating was designed, and the ZrB₂-SiC-glass internalScoating was prepared by slurry sintering method , the ZrB₂-MoSi₂-glass coating was prepared by atmospheric plasma spraying in the outer layer. The phase structure and microstructure of the coating were examined by XRD and SEM, and the coating was ablated by oxygen - acetylene flame. It showed that the sealing effect is better When the glass content of the inner coating is 30% and dense inner coating can be sintered at 1300 ℃ for 2h. Outer coating , with good adhesion the inner coating , was prepared by using optimized plasma spraying with good adhesion the inner coating. The anti-erosion performance is good when surface temperature is below 1500 ℃. Ablation oxidation formed a dense layer with SiO₂ as the filling phase, ZrO₂, ZrSiO₄ as the supporting phase, and the pores were sealed which effectively protect the matrix material.

Abstract:Ceramic powder Ba(Mg_1/3Ta_2/3)O₃ (BMT) was synthesized by the way of solid-phase synthesis method with the raw materials powder of BaCO₃、MgO、Ta₂O₅. BMT/YSZ coatings were prepared by atmospheric plasma spraying (APS). The phase composition and microstructure of the BMT powder and coatings were analyzed by XRD, SEM and optical microscope. The thermal shock resistance was evaluated by water quenching. The results show that the BMT powder with perovskite structure can be synthesized at 1450 ℃ for 4 h. The BMT powder reveals desirable phase stability. The BMT/YSZ coatings have a compact microstructure and higher binding strength between every coating. Spallation was observed within the BMT coatings after 9 cycle thermal shock testing from 1150 ℃to room temperature. Low fracture toughness of BMT and the precipitation of Ba₃Ta₅O₁₅ phase are the main reason for failure of BMT/YSZ coatings.

Abstract:Composite electrolyte made of La_0.9Sr_0.1Ga_0.8Mg_0.2O_3-δ (LSGM) and a mixture of Li₂CO₃/Na₂CO₃ (48/52 at.%) was investigated with respect to their structure, morphology and ionic conductivity. Several proportions of polymethyl methacrylate (PMMA) was introduced during preparation of macro-porous LSGM matrices to create interconnected pore structures with different porosity factor that were found conducive for carbonate infiltration and integration with the membrane materials. Both mercury intrusion method and drainage method were used to investigate the porosity factor of LSGM matrices. The structure and morphology of composite electrolyte were studied by SEM. The ac impedance method was used to test the ionic conductivity. The conductivity of composite electrolytes were increased with the increasing proportions of PMMA after the melting point of carbonate and reached 0.088 S/cm while the proportion of PMMA was 40 wt.% at 600 oC. A watershed can be found from the Arrhenius plots [ln(σ.T) vs T_-1] of composite electrolytes at about 480 oC indicating the shift of the conduction mechanism caused by the melting of carbonate.

Abstract:In this paper, W₁₈O₄₉ nano-/micro-structures (NMS) were first prepared by evaporating of WO₃ and elemental S powders, and then W₁₈O₄₉@Cu₂O NMS composite was successfully fabricated by dipping the prepared W₁₈O₄₉NMS in saturated cupric acetate solution and thereafter thermal treatment. The prepared W₁₈O₄₉NMS and the finally obtained W₁₈O₄₉@Cu₂O NMS composite were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and transmission electron microscopy. Finally, the photocatalytic performances of the prepared W₁₈O₄₉NMS and the final W₁₈O₄₉@Cu₂O NMS composite were evaluated by the degradation of methylene blue under simulated sunlight irradiation. It was revealed that a longer dipping time would result in more Cu₂O loaded on the W₁₈O₄₉ NMS; and the loading of Cu₂O on W₁₈O₄₉ NMS can effectively improve its photocatalytic performance.

Abstract:In this work, BaFe12-2xCuxTixO19 (x=0, 0.05, 0.10, 0.15 and 0.20) ferrites were fabricated at the optimum temperature of 1200 oC from BaCO3, Fe2O3, CuO and TiO2 powders by using a conventional solid-state-reaction sintering method. The co-doping effect of Cu2+-Ti4+ on the microstructure and magnetic properties of the as-prepared ferrites was investigated. It was revealed that the doped Cu2+-Ti4+ could enter into the lattice of BaFe12O19, and no second phase was observed in the doped samples. The coericivity of the prepared samples decreased from 204.46 to 86.82 kA/m with increasing doping amount of Cu2+-Ti4+ ions. The saturation magnetization fluctuated somewhat between 54.61 and 58.42 A?m2/kg with increasing content of Cu2+-Ti4+ ions. With increasing doping amount of Cu-Ti ions, the dielectric constant increases first and then decreases, but the change in dielectric loss is very weak.

Abstract:ZrB₂-SiC composite powders were prepared in NaCl-KCl flux using zirconium, silica, boron oxide as main raw materials, magnesium powder as reducing agent by a combined molten salt and carbothermal/magnesium reduction method. The phase compositions of the resulted powders were investigated by X-ray diffraction. The influences of molar ratio of Zr/Si, content of activated carbon, silica and boron oxide on the phase composition and contents of the crystalline phase of ZrB₂-SiC composite powders were investigated. The results show that high purity ZrB₂-SiC composite powders can be synthesized with the molar ratio of n(Zr)/n(Si) is 1 and the amount of activated carbon, silica and boron oxide was respectively 120 mol%, 120 mol% and 150 mol% in NaCl-KCl flux with the molar ratio of n(NaCl)/n(KCl) is 1 at 1 200 ℃ for 2 h, and the amount of ZrB₂ and SiC was calculated as 59 wt% and 35 wt% in the prepared powders. FE-SEM results show that there exits aggregation in the final powders with the particle size of about 0.5μm. Compared with the conventional carbothermal/magnesium reduction method, the synthesis temperature of ZrB₂-SiC composite powders was reduced about 200 ℃ in the present work.

Abstract:With the development of large-scale energy storage, sodium-ion batteries gradually get more attention. Iron oxide is cheap, non-toxic and its high theoretical capacity makes it promising as the dominant anode material for commercial scale sodium storage. A simple hydrothermal method and carbon-template method for preparing porous α-Fe₂O₃ nanospheres were employed. The nano-material shows high-rate capability and long-term cyclability when applied as an anode material for Na-ion batteries (SIBs). As a result, porous α-Fe₂O₃ nanospheres show an initial discharge specific capacity of up to 520 mAh/g at a current density of 50 mA/g. Due to the simple synthesis technique and high electrochemical performance, porous α-Fe₂O₃ nanospheres have a great potential as anode materials for rechargeable SIBs. The unique structure of the porous α-Fe₂O₃ nanospheres offers a synergistic effect to alleviate stress, accommodate large volume change and facilitate the transfer of electrons and electrolyte during prolonged cycling.

Abstract:Li₂NiTiO₄ with rock-salt structure is a kind of layered cathode materials for lithium ion battery which can extract 2 lithium ions per formula. This material has larger charged capacity, however the reversible discharge capacity is limited. In this Study, molybdenum was doped into Li₂NiTiO₄cell by citric acid sol-gel method using LiNO₃, Ni(NO₃)₂?6H₂O, and Tetrabutyl titanate as starting materials, Mo₇O₂₄ (NH₄)₆?4H₂O as molybdenum source. The structure, micro morphology and elements’ valences were characterized by XRD, SEM and XPS. The electrochemical properties was tested with charge-discharge cycle, CV and EIS. Through Mo-doping, the electrochemical properties was enhanced: the reversible specific capacity was increased from 85mAh/g to162mAh/g. What’s more, when the Mo doped Li₂NiTiO₄ was composited with carbon, the conductivities was improved and the reversible specific capacity further increased to 210mAh/g.

Abstract:A series of Ce_1-xFe_xO₂(x=0, 0.05, 0.1, 0.15, 0.2) composite oxides hollow nanospheres were successfully synthesized using the template method. Carbon spheres prepared by hydrothermal method were used as the hard template. The coating was induced by the strong oxidizing K₂FeO₄, and the electrostatic adsorption between Ce₄₊ and CS. The catalysts were characterized by means of SEM, TEM, XRD, Raman and BET. The sizes and thicknesses of hollow nanospheres were about 300 nm on average and 20~25 nm, respectively. The ratio of Fe/Ce had a significant effect on the morphology of hollow spheres. Catalytic properties were tested by catalytic oxidation of CO. Ce_0.95Fe_0.05O₂ hollow nanospheres showed an enhanced catalytic performance that the total conversion of CO was 297_oC, and also showed high stability against high temperature.

Abstract:Carbon spheres with different sizes has been synthesized through a hydrothermal method using glucose and water. Then single-factor contrast experiments about the size of carbon spheres, the concentration of KMnO₄ and the temperature of the reaction were carried out to probe into the effect of these factors on the morphology of the MnO₂ products. Kirkendall Effect is an effective theory to interprete the result, and though a series of replication experiments, we came to the final conclusion: The flower-like MnO₂ can be fabricated through the reaction of low-concentration KMnO₄ and small-size carbon spheres; The hollow-sphere-structure MnO₂ can be obtained by the reaction of low-concentration KMnO₄ and big-size carbon spheres; The porous solid-structure MnO₂ corresponds to high-concentration KMnO4, whatever size the carbon spheres are; Tempetature is not a notable fator.

Abstract:Grapheme/ whiskery magnesium hydroxide sulfate composite powders were prepared by hydrothermal synthesis method with anhydrous magnesium sulfate, ammonia and graphite oxide as raw material, and sodium dodecy benzene sulfonic acid as surface active agent in this paper. The effect of hydrothermal synthesis temperature and holding time on the preparation of grapheme/ whiskery magnesium hydroxide sulfate composite powders were discussed. The phase composition, microstructure of the products were investigated by powder X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). It indicated that: 1) The magnesium hydroxide sulfate whisker can be synthesized under the hydrothermal temperature of 190℃. 2) Increasing holding time was beneficial to the growth of whisker, there are only few of whiskers formed at holding time of 9h, however, the quantity of the whisker evidently increases as the holding time increases to 12h and 15h.

Abstract:In this paper,precursor powders of Cr₃₊,Nd₃₊:GSGG laser ceramic were carried out by coprecipitation method with different ratio of Cr₃₊ and Nd₃₊. Polycrystalline materials were obtained at different sintering temperature. The phase transformation, micro-morphology and luminescent property were analyzed by XRD, TG-DTA, FESEM and fluorescence spectrum. And the optimum doped concentration of composite doping ions was characterized. The results show that GSGG nano-powder with uniform distribution can be obtained from the precursor powder at 900℃ sintering temperature, and the energy transfer mechanism between Cr₃₊ and Nd₃₊ can enhance the luminescence.

Abstract:Porous TiB₂-TiC multiphase ceramics were prepared by Self-propagation High-temperature Synthesis (SHS) and the reactant mole ratios of Ti:B₄C were 3:1, 3.5:1 and 4:1. The combustion characteristics, phase composition, microstructure,porosity and oxidation resistance of the products were investigated. The results show that the highest combustion temperature is 2458 K and the combustion products are mainly composed of TiB₂ and TiC. The open porosity of the porous products are within the range of 30.67%~31.19% and TiB₂-TiC multiphase ceramics possess good high temperature oxidation resistance at 923 K in air. The main pore formation mechanism includes the residual pores among the particles of the green powder compacts, and the in-situ pores owing to the molten titanium particles flowing during the combustion synthesis reaction. The large pores are formed by the interstitial hole combining with the in-situ pores, and the small pores are formed during the solution-precipitation process.

Abstract:The V₂O₅-MoO₃-CeO_x/TiO₂ catalyst was coated on the cordierite honeycomb ceramics by the coating method. First, the relationship between the solid content and the viscosity of the coating slurry and the choice of the organic binder in the coating slurry were studied and optimized, and the best solid content and the organic binder were screened out. Secondly, the catalytic activity of denitration in V₂O₅-MoO₃-CeO_x/TiO₂ catalyst was studied. The morphology and the crystal forms were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD). The results showed that when the solid content was 32%, sodium carboxymethyl cellulose was used as the organic binder, the loading rate of the catalyst powder was high and the coating was firm. Compared with V₂O₅-MoO₃/TiO₂, the denitrification activity of V₂O₅-MoO₃-CeO_x/TiO₂ at 180-260 ℃ was significantly improved, and the active temperature window was widened obviously.

Abstract:CaB₆ powders were prepared by the carbothermal reduction method in medium-frequency induction furnace, using CaCO₃ and B₂O₃ as raw materials, using pitch, activated carbon, ultrafine graphite, petroleum coke as reducing agent, respectively. The effects of the carbon source species on the phase composition, particle size distribution and microscopic morphology of CaB₆ powders synthesized by induction heating were studied. The results show that the reaction time is obviously shortened by using induction heating. When the pitch and activated carbon are used as the carbon source, high purity CaB₆ powders can be obtained at 1650 ℃ for 20 min. The grain size is approximately 10.9μm with a regular cubic shape when using the pitch as carbon source; However, when the ultrafine graphite and petroleum coke are used, the grain size of CaB₆ is relatively small, and lots of purity exist; When the petroleum coke is used, there has an obvious hard agglomeration between the CaB₆ grains; Appropriate excess carbon can improve the purity of CaB₆.

Abstract:La2O3-Nb2O5 glass has prospective applications in optical devices such as endoscopes, camera, microscope and so on. Containerless solidification is a suitable technique to vitrify the materials with low glass-forming ability. But only millimeter scaled amorphous products can be obtained by this method, which severely limits the application of these new glasses. To solve this problem, we proposed a synthetic route to get large-sized glass via hot-press sintering of amorphous oxides at the temperatures in the kinetic window (?Tx). First, amorphous oxide was made by containerless solidification technology. Then, under the external pressure, amorphous oxides powders were hot-press sintered in ?Tx when the glass appears superplastic. The influences of sintering pressure and temperature on the densification process were investigated. The results showed that, the samples have higher density and demonstrate significant densification when the sintering pressure was improved from 60 MPa to 200 MPa. The shrinkage process consisted of three stages, including accelerating shrinkage, rapid shrinkage and shrinkage stagnation. Under the pressure of 200 MPa, the sintering temperature is very low as 710 ℃ and the increasing sintering temperature could promote the densification, demonstrating the moderate and swift features of this synthetic approach.

Abstract:In general, it is believed that the charge storage ability of MnO₂ as electrode materials of supercapacibility sorts as α-MnO₂>d-MnO₂>γ-MnO₂ in series. In this study, the polymorphy of MnO₂ were synthesized directly at room temperature by the ball milling of KMnO₄, MnSO₄.H₂O and NaOH using different synthetic media with different doping leve of Ca₂₊. Deionized water as the medium results in α-MnO₂, while absolute ethanol results in γ-MnO₂. Very slight dopant of Ca₂₊, such as lower than 100ppm, leads to lattice distortion and partial transformation to γ-MnO₂ from α-MnO₂. The hybrid phase is benefit to the increase of charge storage ability of MnO₂. The polymorphy of MnO₂ can be modulated by some impurities, such as Ca₂₊. The charge storage ability of MnO₂ as electrode materials of supercapacibility can be determined as, hybrid phase(a and g) of MnO₂>α-MnO₂>γ-MnO₂ by cyclic voltammetry analysis.

Abstract:The high-performance silicon nitride ceramics were prepared by spark plasma sintering (SPS) with Al₂O₃–Y₂O₃ as a sintering aid.A novel approch was adopted to fabricate the silicon nitride by introducting WC via mechanical ball milling.The effects of tungsten carbide on densification and mechanical properties of silicon nitride ceramics were inverstigated.The results show that the introduction of tungsten carbide effectively reduces the activation energy of β phase precipitation and growth, which promotes the phase transformation of silicon nitride ceramic , and the densification of sintered samples. Tungsten carbide can dissolve into the matrix lattice partly.With the increase of the amount of tungsten carbide, the flexural strength of sintered samples increased from 735.2MPa to 1091.2MPa, which increased by 48.4%.

Abstract:In paper, it prepared the (100-x)B4C-xTi(wt.%) ceramic that through the hot press sintering in 1680℃, the effect of Ti to the microstructure and the mechanical properties of B₄C ceramic is studied. The results showed: it promoted the sintering of B₄C ceramic through Ti doping, the relative density would increase firstly, then it tends to increase slowly down. The relative density of the sample is 99.5%, when Ti doping get up to 40wt.%. The XRD result in the sample, in addition to the B₄C and unreacted Ti besides, there are TiB₂ and TiC phase,and with the increasing Ti content, the diffraction peaks of those two phase gradually increased; With the addition of Ti, bending strength, hardness and fracture toughness of samples increased, the doping amount was 40wt.%, respectively, up to 481±24MPa, 828±41Kgf.mm_-2, 18.55±0.9MPa.mm_1/2. It analysis that because Ti interface reaction with B₄C, generated at the interfaces of TiC and TiB₂ phase transition layer, connecting the B₄C substrate and Ti, have played an important role in bridging toughening, make the material mechanical performance is improved.

Abstract:In this study, we chose Sr₂Co_xNb_2-xO_6-δ (SCN) as the electrode materials. Due to the similar radii size and small covalent difference between Co and Nb, cation disorder is intrinsic within this perovskite. A combination of first-principles and density-functional-theory (DFT) calculations was performed on both SCN and SCN with Co_Nb-Nb_Co antisite defects, focusing on the formation of bulk oxygen vacancies, which plays a pivotal role in oxygen ion diffusion process. It is found that the covalent states are +2, +3 and +4 for Co(most is +3, and the ratio of +4 is very small ) and +4 and +5 for Nb at their regular sites while in the antisite Co is +2 and Nb is +4. The oxygen vacancies formation energies follow the trend Co₃₊-O-Nb₅₊ >Co₂₊-O-Co₃₊ > Nb₄₊-O-Nb₅₊. The more electron delocalization between Co₂₊-O-Co₃₊ and Nb₄₊-O-Nb₅₊ is beneficial to weaken the electronic repulsion and stabilize vacancies. Therefore, we can see that higher degree of cation disorder can enhance oxygen ionic conductivity.

Abstract:In this paper,the porous YSZ film was prepared by aqueous tape casting and the YSZ electrolyte film was prepared by organic tape casting. The porous YSZ-compact YSZ film composite was prepared via the stack pressure co-firing of the porous YSZ film and YSZ electrolyte film. The impregnated anode SOFC single cell was prepared by chemical impregnation method with the solution of ferricSnitrateS、cobalt nitrate and nickel nitrate was impregnated in porous YSZ layer of the composite matrix. The performance of iron-based anode catalysts was studied,the electrical properties of different anode SOFC single cell at different temperature were tested and the morphology of the anode was observed by SEM. The anti-carbon performance of Co-YSZ and Ni-YSZ anode single cell was tested and compared. Experimental results show the catalytic activity of cobalt in the hydrogen atmosphere was the highest,the nickel is the second,and the iron is the worst. The catalytic activity of cobalt in alcohol atmosphere was still better than that of nickel, and the anti-carbon performance of Co-YSZ anode single cell was better than that of Ni-YSZ single cell. The catalytic activity and the anti-carbon performance of cobalt in Iron-based catalyst were best.

Abstract:Fluoramphibole glass-ceramics were fabricated by reactive crystallization sintering the powder mixtures of crystallization promoters (fluormica) and waste glass with added LiF, NaF, MgF₂, CaF₂, BaF₂, respectively. The phase composition, microstructure and mechanical properties were investigated by means of XRD, SEM, hardness test etc methods. The results show that the excellent bonding between the fluoramphibole crystal and the glass matrix was obtained when added CaF₂, it can improve the hardness of fluoramphibole glass-ceramics. The mechanical properties of fluoramphibole glass-ceramics with single addition of fluoride were better than combined addition.

Abstract:Magnesia ceramic with excellent sintering properties and thermal shock resistance was prepared by using coprecipitation method, and the nanometer magnesia, titanium(IV) sulfate and ammonia as raw materials. The samples sintered at 1450℃ and 1550℃. The mechanical properties at room temperature, thermal shock resistance, analysis and characterization were characterized by the XRD and SEM methods. The effect of the TiO₂ on sintering property and thermal shock property of magnesium oxide ceramics were studied. The result shows that Mg₂TiO₄ and MgTiO₃ were generated by TiO₂ and MgO which in the grain boundaries to hinder the growth of the grain. The linear change rate and relative density of the sintering samples increased first and then decreased. When the content of TiO₂ is 4% and the sintering temperature is 1550℃, the relative density of the sample is maximum, 98.64%. It illustrated that the sintering process of MgO ceramic was promoted by TiO₂. The Mg₂TiO₄ and MgTiO₃ in the grain boundaries slowed the tip stress of the cracks and hindered the cracks extend. It make the thermal shock behavior of MgO ceramic improved effectively.

Abstract:One-dimensional Co2P nanowires were synthesized by microwave hydrothermal (MWH) method using CoCl2·6H2O and yellow phosphorus as raw materials, and CTAB surfactant as a structure-directed agent. The effect of surfactants on the Co2P nanostructures was studied. As-synthesized nanowires were characterized by XRD, SEM, and TEM. The results showed that One-dimensional Co2P nanostructures were synthesized with the presence of surfactants, and a number of Co2P nanowires with 50-200 nm in diameter were obtained using CTAB. The yield and length of Co2P nanowires were increased with CTAB contents increase. The electrochemical properties indicated that Co2P nanowires had typical pseudo-capacitive characteristics and remained capacitance retention of 68 % after 1000 cycles.

Abstract:Due to severe radiation heat transfer at high temperature, the thermal conductivity of hard carbon felt is high. In this paper, the layered hard alumina fiber insulation felt was derived successfully by vacuum impregnation and carbonization process, from alumina fiber as the main material, graphite foil as radiation shielding layer, phenolic resin as impregnant. The materials were tested and analyzed on microstructure, mechanical properties and thermal insulation properties. The results show that the sample has a certain rigidity due to the role of armored" and "anchoring" effect which is produced by carbonization of phenolic resin; The tensile strength of the sample with the 35% concentration of phenolic resin was 70KPa and the thermal conductivity is 0.18 W/m.K at 1000 degrees; In the thermal insulation testing, keeping the hot surface of the sample with thickness of 10mm at constant temperature of 1000 degrees, the temperature of its cold face at steady state is only 640 degrees, which is 200 degrees lower than the temperature, if a commercial carbon felt were used in the same testing. The material has excellent performance and wide application prospect.

Abstract:Effect of using SrCl₂?6H₂O-SrCO₃and hydroxylate carbon nanotubes (CNTs) as composite nucleating agent on the energy storage properties in the induced crystallization nucleation process of MgCl₂?6H₂O-CaCl₂?6H₂O were investigated. It is suggested that the addition of CNTs can reduce system supercooling degree (SSD), which decreases with increased CNTs. When the composite nucleating agents consisting SrCl₂?6H₂O-SrCO₃ and CNTs were introduced SSD can be further decreased when the composite nucleating agents consisting SrCl₂?6H₂O-SrCO₃ and CNTs were introduced because of the good thermal conductivity and high phase change latent heat. SSD decreased to a minimum of 0.6 ℃ when the ratio of CNTs, SrCO₃ and SrCl₂?6H₂O was optimized as 0.25 wt.%、1 wt.% and 3 wt.%, respectively.

Abstract:The ZrB₂/SiC/Zr₂Al₄C₅ composite ceramics with various content of SiC were sintered at 1800 _oC and 20 MPa by spark plasma sintering. The sintering behavior, microstructure, mechanical properties and oxidation resistance were studied. The results indicate that SiC promoted the sintering of the composite ceramics and suppressed the growth of ZrB₂ grains. When the content of SiC was 20 vol%, the composite ceramic showed a toughness of 4.81 MPa×m_1/2. As increasing the content of SiC, the oxidation resistance of composite ceramics was obviously enhanced. The oxidation-resulted increase in weight of composite ceramic with 20vol% SiC was the best performance in oxidation resistance at 1500 _oC. The high-temperature oxidation resulted in dense and stable Al₂O₃, B₂O₃-Al₂O₃, SiO₂ and Al-Si-O glass due to adding SiC into the composite ceramics, those resulting products effectively blocked the oxygen atoms entering into the ceramic matrix, which led to the apparent enhancement of the oxidation resistance.

Abstract:Al₂O₃/YAG/ZrO₂ powders with eutectic composition have been synthesized by the chemical co-precipitation in acohol-water aqueous solution and calcination method, and are characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The precursors were calcined at temperatures of 600_oC-1350_oC in air, and the phase transition process was then revealed with increasing the calcination temperature. Al₂O₃/YAG/ZrO₂ powders calcined at 1300_oC for 1h consist of α-Al₂O₃, YAG and c-ZrO₂ phases. Al₂O₃/YAG/ZrO₂ ceramics with eutectic composition were hot-pressed at 1550_oC with the above-mentioned powders. The Al₂O₃/YAG/ZrO₂ ceramic sintered at 1550_oC contains an intragranular microstructure, and exhibits a relative density of 98.8%, a room-temperature flexural strength of 420 MPa, a fracture toughness of 3.69 MPa.m_1/2 and a high-temperature (1000_oC) flexural strength of 464MPa, respectively. The formation mechanism of an intragranular microstructure in the Al₂O₃/YAG/ZrO₂ ceramic has been proposed.

Abstract:SiC coating for protecting graphite materials against oxidation was prepared using SiC, Si and thermosetting phenolic resin as materials by vapor silicon infiltration process(VSI). SEM and XRD showed that a dense SiC coating was obtained with a C/SiC gradient inner layer acting as bonding layer and combined well with the outlayer SiC coating , the main phases of coating consisted of α-SiC, β-SiC and Si, and free Si was residual after the VSI process. The as-obtained SiC coating can effectively protect graphite after oxidation for 16 h at 1200 ℃ with a weight gain about 2.18 mg/cm₂ in air and endured the thermal shock between 1000℃ and room temperature for 15 cycles with only 0.17wt% weight loss.

Abstract:Two types of commeriacl silicon nitride powders with poor dispersibilities have been studied, and influences of acid leaching and 950 ℃ thermal oxidation on the coprecipitation for the powders have been investigated sysmatically. The evolution of nano-oxides during the reaction causes the product to precipitation, and the calcinations of this precipitation gives nanocomposites powders(Al₂O₃-Y₂O₃) with extremely fine, uniform grains, and phase domains. microstructure properties of composites were investigated with scanning electron microscopy (SEM) (TEM) and Fourier Transform infrared spectroscopy (FTIR). The peak of the Si-O-Si groups emerge at higher frequencies after thermal oxidation, and the isoelectric point of 950 ℃ thermal oxidation powders was found to be less than 2, respectively. For the coprecipitation powders, the size of Al₂O₃-Y₂O₃ composites powders is 20~ 100nm.

Abstract:_{:The carbon black granulated granules were prepared by dry pressing and sieving granulation.The effects of the mass fraction of carbon black on the microstructure, mechanical properties and tribological properties of Cu-Fe friction materials were studied. The results show thatthe carbon black granulated granules were easy to be pressed into strip shape.When the mass fraction of granulated carbon black is low, it can form a complete interface with the metal matrix, and the interface was prone to form holes and cracks when the content is high.With the increase of the the mass fraction of granulated carbon black, the friction coefficient and the wear loss decline initially and then increases,while the bending strength and compressive strengthof the materials show the opposite trend.In particular,When the mass percentage of granulated carbon black is 5%, the friction material exhibits the highest mechanical properties, the lowest friction coefficient, the minimum wear loss and the best comprehensive performance.}

Abstract:Mo–Cu functionally graded material was fabricated by a method which combines combustion synthesis with centrifugal infiltration. During the process, Cu melt produced by combustion reaction was infiltrated into a homogeneous Mo powder bed under high gravity. The as-prepared sample showed gradually-varying properties in terms of relative density, thermal diffusion coefficient and hardness. The content of heavy Mo phase decreases gradually from 75 to 40 vol.% along high gravity direction. The relative density of Mo–Cu FGM decreases from 97.6 to 96.5%, which can be attributed primarily to the increase in shrinkage cavity along high gravity direction. The thermal diffusion coefficient of Mo–Cu FGM increases from 43.2 to 66.6 mm₂ s_-1 due to the increase in Cu content along high gravity direction. The hardness of Mo–Cu FGM decreases gradually from 1390 to 710 MPa, as the content of Cu and porosity increases along high gravity direction.

Abstract:Mo alloy was prepared with Al, MoO₃, SiO₂ and B₂O₃ as raw materials by combustion synthesis under high gravity, and the effects of B₂O₃ contents on the phase composition, microstructure and mechanical properties of the prepared Mo alloy were discussed. In a high gravity field with an acceleration of 1000g, the metal melt and ceramic melt obtained by combustion synthesis were rapidly separated. After cooling and solidification, the dense Mo alloy was obtained. The phase composition and microstructure of the Mo alloy were characterized by X-ray diffraction(XRD) and scanning electron microscope(SEM). The XRD results show that with the increasing of the B₂O₃ contents, there was a new phase in the product. And the new phase was composed of Mo₃Si and Mo₅SiB₂. It is found that when the contents of B₂O₃ increased from 0 to 12wt%, the density of the prepared Mo alloy was dropped from 9.76g/cm₃ to 9.35g/cm₃; hardness was increased from 300MPa to 1035MPa and flexural strength was dropped from 711MPa to 460MPa. In a high gravity field, the increasing of the B₂O₃ contents promoted the formation of the new phase which was composed of Mo₃Si and Mo₅SiB₂, and the new phase played an important role in enhancing the Mo alloy.

Abstract:SiC/Al composites were fabricated by pressureless infiltration technique using the silicon carbide powder and aluminum alloy as the starting materials. The phase, microstructure and mechanical properties of the sample were characterized by SEM, XRD and universal testing machine. The results showed that the SiC/Al composite was infiltrated completely by aluminum alloy. The microstructure of the sample was homogeneous. No obvious pores were detected. The major phases of SiC/Al composites were SiC and Al. Othe weak XRD characteristic peaks such as Si, Mg₂Si and MgAl₂O₄ phase were also observed in SiC/Al composites. The soaking property of liquid Al could be enhanced by the addition of Mg into aluminum alloy. Compared with The composites of 7 Mg, the composites of 10 Mg have higher dentity and better structure. Composites showed the characteristics of brittle fracture. SiC particles were destroyed by the way of transcrystalline cleavage.

Abstract:With one step sintering technique the in-situ synthesis high content TiB₂/SiC composites were synthed using SiC, TiO₂ and B₄C as the main raw material. The effect of TiB₂ content on volume resistivity, microstructure and mechanical properties of TiB₂/SiC composites were studied by the Vivtorinox hardness tester, electronic universal testing machine, volt ohmmeter, optical microscope and SEM. The results show that with the increase of TiB₂ content, the average particle porosity decreased firstly and then increased, the flexural strength and fracture toughness were increased first and then decreased, the Vivtorinox hardness increased gradually, electrical resistivity decreased rapidly and then tended to be stable and TiB₂ particle size increased. After sintering at 1950 C, the content of 40 wt% TiB₂ has the best performance, the open porosity, flexural strength, fracture toughness and volume electrical resistivity were 0.56%, 412 MPa, 5.77 MPa m_1/2 and 2.6×10_-1 (Ω?cm).

Abstract:The aqueous SiC slurry for gelatin gelcasting was prepared by submicron SiC, gelatin and TMAH as the main raw material. The effects of pH, sintering aid, dispersant, gelatin and solid content on rheological properties were studied. The results show that 12 is the best pH value of slurry. Sintering aid slightly increased the viscosity of the slurry. 0.6wt% TMAH got the lowest viscosity. Effect of gelatin concentration on viscosity is not obvious, and increasing the content of gelatin solution, the viscosity of slurry decreased. The viscosity of the slurry increased with the increasing of the solid content. When pH is 12, the dispersant content is 0.6wt%, adding 20 wt% concentration of 10 wt% gelatin, the SiC slurry can get the 55 wt% solid content, viscosity of 132 mPa.s which is conducive to the gel casting.

Abstract:In gas turbine, thermal barrier coating system (TBCs) is usually used to increase the operation temperature and protect the turbine components like blades and vanes. A TBC system consists typically of a superalloy substrate, a metallic bond coat, the thermally grown oxide and a heat-insulating ceramic top coat. The thermally grown oxide(TGO) grows at bond coat / top coat interface is a dominate factor leading to the failure of TBCs, thus determining the thickness of TGO non-destructively is essential for monitoring the performance of TBCs and predicting the lifetime of TBCs in service. Our work here uses impedance spectroscopy to analysis the TBCs samples with 0.1mm YSZ top coat after oxidation at 1000℃. The SEM and EDS result shows that a continuous alumina layer formed after 100h oxidation and the thickness increases with increasing oxidation time, meanwhile, the chemical composition changes from alumina to mixed oxides. The oxidation kinetics demonstrates that the oxidation procedure is controlled by diffusion. By equivalent circuit model analysis, we obtain the direct proportional relationship between TGO thickness and capacitance, so the TGO thickness can be measured.

Abstract:In this work, 2 ?m-thick CrN/TiN superlattice coatings with modulated period of 6.3 nm were deposited by the combined deep oscillation magnetron sputtering (DOMS) and pulsed dc magnetron sputtering (PDCMS), and single PDCMS, respectively. Microstructure of coatings was characterized using XRD, SEM and TEM. Mechanical and tribological properties of coatings were analysized using nanoindenter, scratch test and ball-on-disc tribometer. Anode polarization tests in 3.5 wt.% NaCl aqueous solution were used to evaluate corrosion resistance of coatings. As compared with the coatings deposited by single PDCMS, the coatings deposited by combined DOMS+PDCMS showed higher mechanical properties, endurable wear resistance and antifriction properties and corrosion resistance due to the improved architecture.

Abstract:Three different components of (La_xYb_1-x) ₂Zr₂O₇ (x = 0, 0.5, 1.0) thermal barrier coating materials were prepared by solid state synthesis method using zirconia, ytterbium oxide and lanthanum oxide. The relative theoretical densities were above 97% for all samples, which were prepared by pressureless sintering for mechanical properties test. The room temperature bending strength and high temperature Young "s modulus of the materials were tested by three-point bending method and thermomechanical analysis method respectively. The experimental results show that LaYbZr₂O₇, which is a finite solid solution consisting of La₂Zr₂O₇-based pyrochlore and Yb₂Zr₂O₇-based fluorite with fine grains, could improve room temperature bending strength compared with that of pure La₂Zr₂O₇. It also benefits the high temperature Young"s modulus above 1200℃.

Abstract:Samarium and neodymium co-doped ceria (Ce0.8Sm0.1Nd0.1O2-δ or SNDC) and apatite-type lanthanum silicate (La10Si6O27or LSO) powders were prepared by citric-nitrate self-combustion and Sol-gel method respectively.Composite materials were obtained by mixing two powders at different proportion.Powders were molded into shaps and isostatic cool pressed, then sintering at different temperature (1500℃,1550℃,1600℃) for 10 hours. Samples were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), and electrical conductivity measurement. What we can know from the results is that no impurity phase exists in SNDC/LSO composites, and the grain size decreases with the addition of LSO. High sintering temperature can help to improve the conductivity of 30wt%LSO sample, moreover, the addition of LSO reduced the conductivity of composite electrolytes which sintered at 1500℃.

Abstract:glycine-nitrateSprocessS(GNP) and Sol-Gel method are used to synthesis Sm_0.1Nd_0.1Ce_0.8O_1.9(SNDC) and La₂Mo₂O₉(LAMOX)powders, respectively. Different ratio of SNDC/LAMOX composites were fabracated through pressureless sintering. XRD and SEM were used to characterize the material phase and morphology of the samples with different composition. The conductivity of samples were test and the result shows an reverse trend with La₂Mo₂O₉ amount near the phase transformation point. The conductivity of sample with 20mol% LAMOX reaches 0.01S/cm at 550℃, higher than that of SNDC at the same temperature.

Abstract:20% Er₂O₃-stabilized Bi₂O₃ (ESB) nano?bers were prepared through electrospinning followed by calcination. The phase structures, morphology and electrical conductivities of the nano?bers have been investigated. The results show that the monoclinic phase (α) and tetragonal phase (β) coexisted in the un-doped Bi₂O₃ nanofibers, however, the cubic (c) phase could be stabilized in Bi₂O₃ nano?bers when Er₂O₃ doped in the sample. What’s more, the 500℃ and 600℃ calcined ESB nanofibers possessed high length–diameter ratio, uniform morphology and relatively smooth surfaces. An high oxide ion conductivity of the nano?bers was observed at 500℃, which is about 0.03 S?cm_-1.

Abstract:Herein, we report highly sensitive photodetectors, prepared by a thin film of electrospun polycrystalline tungsten oxide (WO₃) nanofibers. Structural properties have been investigated by using X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. UV-Visible absorption spectra was used to calculate the band gap of the electrospun nanofibers which shows a broad range in the UV spectrum. A high photosensitivity has been observed in our prepared photodetectors by using WO₃ nanofibers. A facile assembly method has been used to make the device. All our investigations about structural and optoelectronics properties suggest that WO₃ can be used as UV –visible photodetectors.

Abstract:_{: A series of Ag loadedAg/BiVO4 composite nanofibers were synthesized through electrospinning and heat treatment process. The phase structure, morphology and photocatalytic performance were tested. The result shows that Ag loading can significantly enhance the photocatalytic activity. RhB can be completely degraded in 20min under visible light irradiation of 10% Ag loading. The heterostructure promoted the charge separation as well as the lifetime of the photo generated electron and holes, resulting in the enhancement of the photocatalytic activity.}

Abstract:In this paper, the red phosphor of SrSiN2: Eu2 + was synthesized by field assisted sintering technique rapidly. Combined with X-ray diffraction patterns, scanning electron microscopy and fluorescence spectrometer testing technology, the effects of synthesis parameters (synthesis temperature and holding time) on the crystal structure, microstructure, photoluminescence and thermal quenching properties were investigated. The results show that when the synthesis temperature is 1250 ℃ and holding time for 6min, the sample is pure SrSiN2 phase with high crystallinity. PL spectra showed that improve the crystallinity of the sample, the luminous intensity was significantly improved,and the thermal quenching performance of samples synthesized by field assisted sintering technique are better than those synthesized by solid state reaction.

Abstract:This paper presents a spectroscopic study of Er, Yb co-doped Y₂O₃ transparent ceramics with 20 at.% Yb₃₊ and varied Er₃₊ concentration (0.5 at.% to 5 at.%). Room-temperature absorption spectra and refractive indices were measured. Standard Judd-Ofelt analysis was applied and the intensity parameters were calculated. With Er₃₊ concentration increasing, Ω₂ decreases from 5.41 to 3.36, Ω₄ ranges from 0.96 to 1.29 and Ω₆ ranges from 0.64 to 0.72. The spectroscopic quality factor X_4/6 ranges from 1.46 to 1.88. The radiative lifetime of ₄I_13/2 manifold is longest in the Er, Yb co-doped Y₂O₃ transparent ceramic with 0.5 at.% Er₃₊ content. All suggest that the Er, Yb co-doped Y₂O₃ transparent ceramic could be a potential material for near-infrared laser application.

Abstract:C/C composites are a kind of ideal structural materials used at high temperatures. Their high temperature elastic modulus are very important for the thermal stress analysis and composite structure design. The inductance micrometer can be used to determin the deflection accurately in the three-point bending tests, and the tested results can be used to calculate the elastic modulus at room temperature (RT). However, the application of three-point bending method at high temperature is scarcely reported due to the difficulty of the deformation measurement. In this study, the ralative deflection method based on the relative method was utilized to evaluate the elastic modulus at various temperatures. The measured results of elastic modulus of 2D and 3D C/C composites at RT by inductance micrometer and relative deflection method are similar. The elastic modulus of C/C composites at RT ~ 1700℃ were measured by relative deflection method, and the results show that the maxium of the 2D and 3D C/C composites which appear at 1200 ℃ are 82.22 GPa and 66.73 GPa, respectively. The elastic modulus decreased gradually with the increased temperature ranged from 1200 ℃ to 1700 ℃, and the modulus of 2D C/C composites decrease more quickly. These results demonstrate that the C/C composites measurement by relative deflection method for determining high-temperature elastic modulus is accurate and reliable, which could be used to evaluate the modulus of other high-temperature structural materials.

Abstract:_{:Preparation of colored zirconia by impregnation of liquid precursors Ceramic is a hot spot for preparing high-grade decorative materials. Colored zirconia ceramics produced on the market are only black and white, and common preparation methods such as mechanical mixing, sol-gel method, chemical coprecipitation are not suitable for the coloring of zirconia ceramics due to the low sintering temperature. In this paper, a series of blue, pink, green and black zirconia ceramics with pure color and uniform doping were prepared by the method of liquid phase precursor impregnation. XRD analysis showed that the main crystal phase of the sample was zirconia tetragonal phase. The CIE L * a * b * system was used to study the chromaticity of the samples, and the four color samples were determined to have corresponding chromaticity. SEM analysis showed that grain size was uniform and no obvious defects were observed. Mechanical properties analysis shows that several colored ceramics have high strength and toughness.}

Abstract:Ca-doped TiO₂ nanofibers have been synthesized by sol-gel and electrospinning techniques with calcium acetate as the calcium source and titanium isopropoxide as titanium source. Their structures and morphologies of the samples were analyzed and characterized by XRD and SEM, which reveal TiO₂ nanofibers are mainly composed of the rutile structure with small amounts of anatase phase. Meanwhile, the photocatalytic activity of TiO₂ nanofiber catalyst has been evaluated with the photodegradation reaction of the water-soluble Rhodamine B. The results show that the Ca-doping of the TiO₂ nanofiber can effectively improve its photocatalytic activity for the degradation of the water-soluble Rhodamine B. The degradation percentage of rhodamine B in the solution of 1 × 10_-5 mol / L is about 95% as the Ca-doping concentration = 5at. % (optimum value), the content of TiO₂ in solution = 1.2 × 10_-2 g / L and UV light irradiation time =100 min.

Abstract:The heterojunction photoanode of CdS, CdSe quantum dots Co-sensitized ZnO nanorod arrays were designed and fabricated through simple methods. In this process, CdS and CdSe quantum dots were prepared by successive ion layer adsorption reaction (SILAR) method, and one-dimensional ZnO nanorod array films were prepared via ZnO seed layers by hydrothermal method. The structure, morphology and photoelectrochemical properties of the samples were studied by X-ray diffraction (XRD), field emission scanning electron microscope (SEM), electrochemical workstation. The results show that the photoelectric properties of CdS, CdSe quantum dot sensitized electrodes have been greatly improved compared with ZnO nanorod film electrode. Among them, the photoelectric conversion efficiency value of CdSe(4c)/CdS(4c)/ZnO is 17 times as large as ZnO nanorod film electrode, up to 1.894%.

Abstract:The direct laser engineered net shaping ceramic structure is a kind of additive manufacturing technology which uses the high energy laser beam to directly melt ceramic powders and then the melted material deposites to form three dimensional parts. In this technology, doping binder or sintering agent is needless, traditional shaping and sintering steps will be made one. Furthermaore, this technology omits steps, mixing, drying and discharging, and can achieve complex ceramic parts of high-purity compact shape and preparation. In this paper, direct fabrication of Al₂O₃/TiO₂(13 wt.%) ceramic structure is conducted by laser engineered net shaping system and the deposition process is studied. XRD and SEM are used to analyze the phase and microstructure. Results show that the main phases of fabricated specimens are Al2TiO5and Al2O3, and the Al2O3 columnar grains distributed in the Al2TiO5 matrix. Due to the presence of the chemical reaction in the process, the Al2O3/TiO2 ceramic has a certain amount of macro pores, but it still has a micro hardness of more than 21 GPa, and the bending strength is up to 170 MPa. The study shows that laser engineered net shaping technology can realize the complete melting and solidification of ceramic materials, and provides a new choice for direct and rapid fabrication of high performance ceramic structures.

Abstract:h-BN-ZrO₂-SiC multiphase ceramics were prepared rapidly by spark plasma sintering (SPS) with h-BN, ZrO₂ and SiC powders as raw materials and 8%(Al₂O₃+Y₂O₃) as sintering aids. The effects of nano SiC content on the densification, microstructure and mechanical properties of h-BN-ZrO₂-SiC multiphase ceramics were systematically investigated. The results show that the addition of nano SiC particles can effectively promote the sintering and increase density and mechanical properties of the sintered samples at a low sintering temperature. The flexural strength, fracture toughness and elastic modulus all increase with the content increase of nano SiC, especially, the increasement of the elastic modulus is obvious. The comparison of all results shows that the sample with the SiC content of 25% has optimal mechanical properties than other samples, and the flexural strength, fracture toughness and elastic modulus are 268.4 MPa, 3.24 MPa.m_1/2 and 115 GPa, respectively. The reason is mainly due to the nano SiC particles can better play a gap filling, dispersion strengthening and grain boundary pinning effect than ZrO₂, which are beneficial to improve the bonding strength between the phases and reduce the residual stress due to thermal mismatch. As a result, the more fracture energy was absorbed during the crack propagation process, and the flexural strength and fracture toughness increased.

Abstract:Reaction bonded boron carbide (RBBC) composites were fabricated based on molten Si infiltration method. The mechanical properties of the composites were improved by the reaction formed silicon carbide (SiC) nano-particulates. The role of SiC nano-particulates in the microstructure, density and mechanical properties of RBBC composites, and the strengthening mechanism were researched. The XRD results showed that the composites consist of four phases, namely, B4C, Si, reaction formed SiC and ternary phase B12(C,Si,B)3. The SiC nano-particulates were introduced in the RBBC composites by using phenolic resin as carbon sources. The bending strength, fracture toughness and Vickers-hardness of the RBBC composites fabricated with phenolic resin as carbon sources were 442 MPa, 4.9 MPa?m1/2 and 23 GPa, which increased of 35 %, 36 % and 15 % respectively, compared with those of RBBC composites fabricated with black carbon as carbon sources. Clearly, an introduction of the nano-sized SiC particles to RBBC composites is responsible for the increase in the mechanical properties of the composites.

Abstract:This study was conducted to investigate the influence of different monomer on degree of conversion (DC) and color stability of dental resin/ceramic composite materials, as well as the effect of different curing methods. The degrees of conversion of monomer group were found to increase in the order of Bis-GMA, Bis-EMA, UDMA, as 51.87%, 69.29%, 79.98% respectively. And the color changes of these specimens showed the opposite trend, as 1.780, 1.244, 0.534 respectively. When cured in different curing conditions, the degrees of conversion showed a slow-growth with the increase of temperature, and light-cured specimens’ degrees of conversion on specimens’ surface was similar to that of heat-cured ones. Dual cured specimens showed higher DC than merely light-cured or heat-cured ones. Thereinto, in dual cured system of heat-light-cured, the DC reached 87.52%, much higher than merely heat-cured ones of 77.24%, which had clinical significance.

Abstract:: _{(0%, 7.6%, 15.61%, 24.07%, 33.47%)TiCx-Fe matrix composites were prepared by in-situ hot pressing of Ti3AlC2(Volume content of 0% to 40%)and Fe powders and the effects of TiCx content on the microstructure and mechanical properties of the composites were investigated. . The results show that at 1400 ℃, when the volume fraction of Ti3AlC2 varies from 10% to 40%, the Al atoms escape from Ti3AlC2 to form TiCx, and the TiCx-Fe matrix composites are formed in situ. In the three-point bending test, when the TiCx content in the reinforcement phase is 7.6%, the composite material is not bent, showing good toughness,when the content of TiCx is 15.61%, and the bending strength of the composites is 900MPa , When the content of TiCx is 15.61%, the tensile strength reaches 518MPa and the elongation after fracture reaches 5.19%. The tensile strength of composites with TiCx content is (0%, 7.6%, 15.61%); Which is attributed to the diffusion of Al and the good wettability between TiCx and Fe in the composites.With the increase of TiCx content, the bending strength and toughness of the composites decrease and the hardness increases.}

Abstract:The cadmium selenide nanoparticles with a narrow size distribution diameter ranging from 20 to 25 nm were synthesized by a solution chemical route. The growth process of the cadmium selenide nanoparticles is discussed. And the key factors that influence the diameter distribution of the cadmium selenide nanoparticles are revealed.

Abstract:Sr₂Bi₅FeTi₅O₂₁(SBFTi) ceramic was prepared by sol-gel self method. The dielectric constant-temperatures from room temperature to 500 ℃, AC impedance and AC conductivity of SBFTi ceramic were tested and analyzed. The results showed that SBFTi ceramic exhibit high dielectric constant, good frequency stability and high Curie temperature compared with Sr₂Bi₄Ti₅O₁₈(SBTi) ceramic and it also exhibit characteristics of diffuse ferroelectrics. The electrical structure of SBFTi ceramics was relatively uniform and the macro resistance, which was attributed to the grain show negative coefficient characteristic with temperature. The activation energies for conductivity was 0.6eV and the oxygen vacancy is the main carrier of the SBFTi ceramic at 200~480℃.

Abstract:In order to improve the dielectric constants of BT/PVDF composites, two-layer and three-layer BT/PVDF composites were designed, which were PVDF||BT/PVDF and PVDF||BT/PVDF||PVDF, respectively. These layered composites were prepared by combining a spin coating method and a solution casting method in which BT contents were 7~45 vol%, respectively. The results show that the dielectric constants of the composites with the same thickness increase with the increase of BT content. The dielectric constants of the composites are 7-39, 13-50 and 14-79 for the one, double and tripper layers respectively. When the BT content is the same, the dielectric constant of the composite increases with the number of layers. The dielectric constants of the three composites were found to be significantly higher than those of the two layers and one layer when the BT contents were both 15vol%. At the same time, when the test frequency was 40Hz-1000Hz. The multi-layered BT/PVDF composites exhibit strong polarization relaxation, which indicates that the interfacial polarization of the composites increases, leading to the increase of the dielectric constant of the composites. In this study, the breakdown properties of three composites with BT content of 7~30 vol% were investigated. It was found that the breakdown strength of composites decreased with the increase of BT content and the number of layers in the range of 60-100 KV/mm.

Abstract:LiFe_1-xMn_xPO₄ (x=0.0, 0.1, 0.2, 0.3) and LiFe_1-xNi_xPO₄ (x=0.00, 0.03, 0.05, 0.07) powders were synthesized in a rotor-stator reactor and the reactor possesses high efficient performances of mass transfer and micro-mixing. The powders are used as cathode materials in the batteries and the battery test system is employed to explore the dependence of electrochemical property on temperature. The particle is in the shape of near-sphere, uniformly distributed and in the particle size of 5~10 μm. The crystallographic evidence demonstrates that the introduction of Mn and Ni does not change the host crystal structure. The powders have favorable electrochemical and high-temperature electrical properties. Particularly, LiFe_0.8Mn_0.2PO₄ and LiFe_0.95Ni_0.05PO₄ exhibit the best performance. At room temperature and 50 _oC, their first charge-discharge specific capacities are 153.2/155.7 mAh/g and 156.4/160.4 mAh/g separately with 0.1 C fixed. The capacity retention ratios are 95.4/96.5% and 93.8/95.0% separately after 100 cycles. On one hand, the rotor-stator reactor makes the obtained particle homogeneously dispersed. On the other hand, it also leads the doping Mn and Ni distributing uniformly in the particle. Both of the two advantages increase the Li₊ ionic diffusion rate and enhance the electrochemical and high-temperature electrical properties of the materials.

Abstract:The novel co-continuous SiC/Al composites were prepared by vaccum-infiltration technology. The effects of strain rates and surface oxidation modification of 3D-SiC preforms on the mechanical properties of co-continous SiC/Al composites were investigated in this study. The strain rate hardening effect of the co-ontiounsous SiC/Al composites is observed obviously, and there was the maximum increasement in compressive strength by 25% at strain rate from 10-3/s to 10/s. Furthermore, the compressive strength of the SiC3D/Al composites are also improved by surface oxidation modification of SiC preforms, and the maximum increasement is observed in the composite with 3D-SiC preform at 1200℃ for 6h. Its the compressive strength is higher about 10% than the SiC3D/Al composite without surface oxidation modification at 10-3/s, which suggests that the surface oxidization modification for SiC preforms can play an important role in the fracture behaviours of the SiC3D/Al composites due to the improvement of SiC/Al interfacial characteristics. But the three-point bending strengths of SiC3D/Al composites are not sensitive to surface oxidization modification.

Abstract:A novel amperometric-type NO2 sensor based on 6 wt%Y2O3- La10Si6O27 (LSO) and CuCr2O4-CuO composites sensing electrode was fabricated. CuCr2O4-CuO composites were prepared by ammonium hydrocarbonate precipitation method. And then these particles were dispersed in LSO porous layer by Screen printing method to preparation the sensor. X-ray diffraction (XRD) and scanning electron microscope (SEM) were used to characterize the phase composition and morphology of the samples. The phase composition of CuCr2O4-CuO composites characterized by XRD were CuCr2O4 and CuO, and the morphology characterized by SEM were irregular sheets with 200-300 nm. These particles is evenly distributed in the porous layer with a thickness of about 20 μm. The polarization curves and the AC impedance results showed that the sensor is a mixed-potential type. The sensor exhibited well response-recovery characteristics to NO2. The response signal was almost linear to NO2 concentration in the range between 25 ppm and 300 ppm at 600- 700 °C. The sensitivity increased and reached 19.3 mV/dec. at 600°C. The response potential of the sensor is slightly affected by co-existant NH3, CH4, H2 and CO2. However, within the concentration range of 5-21%, the potential value of the sensor decreases linearly with the increase of oxygen concentration. The actual application can be calibrated with another O2 sensor.

Abstract:A composite glass solder, which composed of PbO-B2O3-ZnO system and PbTiO3 crystal was designed to braze 60vol.% SiCp / 6063Al composites in air. Assisted by anodic oxidation of the composites and hot press sintering of the composite glass solder can improve the strength of the joint. The effects of temperature and holding time on brazed joints were studied by the methods of DSC, XRD, SEM and EDS. The results show that the strength of the joint can be improved by the anodic oxidation of the composites, the increase of the brazing temperature and the prolongation of the holding time to a certain extent. Using the composite glass welding piece to braze composites which was anodic oxidation already ,when the brazing temperature is 450℃ and the holding time is 30min, the shear strength of the brazed joint is 33MPa. During the brazing process, the oxide film of the composites is dissolved in the galss, and the Al element is diffused in a slight amount. At last, a weld similar to the base metal structure formed.

Abstract:The thermal barrier coating samples of different thickness with alumina coated zirconia and zirconia as coating materials were prepared on theSsurfaceSof heat resistant alloy steel substrate after activationStreatment with NiCoCrAlY as adhesive transition layer by plasma spraying method and spray gun quick spraying process. The bonding strength and thermal insulation property of two kinds of ceramic coating with the same thickness were compared by the test results of bonding strength, high temperature heat insulation and microstructure, and the relationship between the coating thickness and heat insulation effect were investigated. The results indicate that the structure and property of thermal barrier coating using nano-Al₂O₃ coated ZrO₂-Y₂O₃ powder are superior to that using single zirconia powder. The thermal insulation property of the thermal barrier coating increased with the increasing of coating thickness, and the advantage is more obvious with temperature increasing.

Abstract:7wt%YSZ powder was used as feedstocks during Air Plasma Spray (APS). Through controlling the spraying distance during the process, we got three different TBC samples. The properties including porosity, thermal conductivity and microstructure were characterized. Through comparison, we found that the spraying distance largely influenced the shape and distribution of the pores, gave different levels of porosities, and thus produced different thermal conductivity.

Abstract:The observation of scanning electron microscope shows that the cuticle of lobster is a natural bioceramic composite consisting of mineral chitin fiber layers and collagen protein matter. The mineral chitin fiber layers are parallel with the surface of the cuticle and the collagen protein matter is distributed in the layers as the matrix felting the fiber layers. The careful observation shows that the mineral chitin fiber layers are further composed of thin and orderly mineral chitin fiber sheets which are vertical to the fiber layers. The observation also shows that the mineral chitin fiber sheets in different fiber layers have different orientations, which compose a fiber crossed microstructure. The maximum pullout force of the fiber crossed microstructure is investigated and compared with that of the fiber parallel microstructure based on their representative models. The result indicates that the maximum pullout force of the fiber crossed structure is markedly larger than that of the fiber parallel structure. The analytical result is experimentally validated. The research result provides profitable guidance for the design of the high-performance ceramic composites.

Abstract:The observation of scanning electron microscope shows that the cortical layer of antler is a kind of nature bioceramic composite consisting of mineral-collagen fibers and collagen-protein matrix. The observation also shows that there are many micro-holes in the cortical layer and that the strengthening mineral-collagen fibers circuitously round these holes which compose a kind of the circuitously-rounding-hole structure of the mineral-collagen fibers. The analytical models of the composites, respective with the circuitously-rounding-hole and non-circuitously-rounding-hole structures of the fibers are built. The fracture strength of the composite model with the circuitously-rounding-hole structure is analyzed and compared with that of the composite model with the non-circuitously-rounding-hole structure. The analytical result shows that the fracture strength of the composite model with the circuitously-rounding-hole structure is remarkably larger than that of the composite model with the non-circuitously-rounding-hole structure. Based on the results of the experimental observations and model analyses, a kind of biomimetic composite laminate with the circuitously-rounding-hole structure is fabricated with carbon fibers and epoxy resin. The fracture strength of the composite with the circuitously-rounding-hole structure was tested and compared with that of the composite with the non-circuitously-rounding-hole structure. The testing results show that the fracture strength of the composite with the circuitously-rounding-hole structure is remarkably larger than that of the composite with the non-circuitously-rounding-hole structure.