bluuebunny/crossref_metadata_2025 huggingface dataset:
Light Scattering Properties for PLZT Transparent Ceramics of Different Zr/Ti Ratios
Authors: Xia Bin , He Xi Yun , Zheng Xin Sen , Qiu Ping Sun , Cheng Wen Xiu , Zeng Xia
Published: June 2012

Lead lanthanum zirconate titanate (PLZT) transparent ceramics present an attractive electrically controlled light scattering performance with high transmittance and large contrast ratio. PLZT ceramics of 8 mole% lanthanum with different Zr/Ti ratios (Zr/Ti=68/32, 70/30, 72/28) were prepared by the hot pressing method to figure out the influence of Zr/Ti ratios to the light scattering performance. X-ray diffraction patterns confirm that all the samples are perovskite structure with no secondary impurity phase detected. All the three compositions show double tending slim hysteresis loops which due to antiferroelectric phase coexisted. Besides, within the range of near-infrared to ultraviolet wavelength, all the PLZT samples show high transmittance. While the Zr/Ti ratio increasing from 68/32 to 72/28, the transmittance reduced value RT of the sample decreases gradually (λ: 632.8 nm). PLZT (8/68/32) sample shows a maximum RT, it promises a good application in optical modulators, goggles and so on.
Fuel Processing in Direct Methanol and Carbon Deposition Behaviour on Ni/CeO2-ZnO Anodes for Solid Oxide Fuel Cell
Authors: Shen Guo Yang , Wu Ye Fan , Luo Ling Hong , Su Hui , Zhang Jia Song
Published: June 2012

The activities of cermet catalysts composed of Ni/CeO2-ZnO anode for steam reforming of methanol were investigated for internal reforming of solid oxide fuel cell. Ni/CeO2-ZnO anodes with specific percentage of ceria versus zinc were fabricated by wet impregnation method. The catalysts were characterized by X-ray diffraction, Scanning electron microscope (SEM) and temperature-programmed reduction. Area specific resistance (ASR) of these anodes was also examined to prove the thermal stability of them, and possible reasons for degradation were analyzed. Furthermore, The promoting effect of zinc metals included a decrease in the reduction temperature of NiO species interacting with the support, due to the hydrogen spillover effect. It was seen that the addition of zinc metal stabilized the Ni sites in the reduced state along the reforming reaction, increasing the methanol conversions and decreasing the coke formation. The maximum power density of the single cell reached 560mW cm-2 and 380mW cm-2 at 750°C in hydrogen and methanol steam respectively, and the cell obtained stable output in methanol steam over an operation period of 30 h.
Application of Rape Pollen in Anode Substrates of Solid Oxide Fuel Cell
Authors: Su Hui , Wu Ye Fan , Luo Ling Hong , Zhang Jia Song , Sheng Guo Yang
Published: June 2012

The physical properties and microstructures of supporting anodes are crucial for the performances of the entire SOFCs. In this investigation, the rape pollen was developed as a novel pore-former to improve the properties of the conventional NiO–YSZ(yttria-stabilized zirconia) anode substrate of solid oxide fuel cell. The advantage of using this pore-former over the conventional ones (e.g. polymethyl methacrylate (PMMA), carbon and flour) is that this pore-former had high porosity、global pore shape and uniform pore size distribution in the anode substrates, which are beneficial for rapid transport of the fuel and byproduct. The microstructure was observed by SEM, and the porosity of anode was measured by Archimedes method. The results showed that the optimum weight percent concentration was 15%, correspondingly, porosity was 40.3%, which was suitable for supporting anodes for SOFC application. And the open-circuit voltage (OCV) as high as 1.058V was obtained ,and the maximum power densities of 0.794W/cm2 was achieved at 750°C, respectively, using hydrogen as fuel and ambient air as oxidant.
Synthesis of Sr2Fe1-xMnxNbO6-δ Powders and their Stability as Electrode of Solid Oxide Electrolysis Cell
Authors: Ge Ben , Ai De Sheng , Deng Chang Sheng , Ma Jing Tao , Lin Xu Ping
Published: June 2012

Double-perovskite Sr2Fe1-xMnxNbO6-δ (x = 0, 0.1, 0.2, 0.3, 0.5, 0.8) (SFMN) powders which will be applied to the electrode of solid oxide electrolysis cells (SOEC) were synthesized by Solid State Reaction Method. The mixed oxide powders SrCO3, Fe2O3, MnO2 and Nb2O5, were homogeneously calcined at different temperatures and in different atmospheres. The influence of the preparation process on the structure and the morphology of the powder were investigated by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). It is found that the formation of perovskite structure is directly related to the content of Mn and calcining temperature. Controllable synthesis of pure phase of double perovskite powders was realized after calcining for12h at 1150 °C in air. Moreover, the experimental results show that the perovskite structure of SFMN is stable in whether oxidizing or reducing atmosphere, which indicates that this material has a potential to be used as electrode of solid oxide electrolysis cell.
An Energy Storage Material Fabricated by Coating Ba0.40Sr0.60TiO3 Nano Particles with Aluminum Oxide Doped with Zinc Oxide Shell
Authors: Xu Chao , Shen Bo , Zhai Ji Wei
Published: June 2012

For energy storage devices such as capacitances, pulsed power applications and other any electronic systems, high permittivity and high breakdown strength (BDS) are necessary for dielectric materials used in high energy storage capacitors. Ba0.4Sr0.6TiO3 nano-powders were directly synthesized from solution and then wrapped by a thin surrounding shell with composition of zinc oxides dopants in aluminum oxides. This core-shell structure was characterized by a conjunction of XRD, and TEM analysis. The core-shell nanoparticles were pressed into pellets with 10 mm diameter and then sintered at different temperature in air. The specimen coated with 2.0wt% compounds of aluminum oxides doped with zinc oxides showed the maximum breakdown strength of 475kV/cm and the energy storage density of 4.7J/cm3 while the tanδ was only 0.002, whereas the uncoated Ba0.4Sr0.6TiO3 was only 86.9kV/cm, 0.23J/cm3 and 0.005, respectively. And the energy storage density and the BDS decreased when the shell content was more than 2.0wt%.
Affection of Post-Core Materials on the Resultant Color of Lithium Disilicate Ceramic Restorations
Authors: Sun Ting , Shao Long Quan , Wang Yan Liang , Yi Yuan Fu , Deng Bin , Wen Ning
Published: June 2012

Abstract. The purpose of the study was to evaluate the affection of post-core materials on the resultant color of lithium disilicate ceramic restorations. Twenty disk-shaped core-veneer specimens were prepared with IPS e.max Press and IPS e.max Ceram. Twenty-five substructure specimens were also prepared. Color measurements were performed for all specimens with each substructure by a calibrated spectrophotometer. Lab chromatic values were obtained. The chromatic aberration (△E) compared with dentine substructure was 1.33 for ziconia based combinations , 1.40 for resin based combinations, 4.37 for cobalt chromium alloy based combinations and 3.05 for gold metal alloy based combinations. The zirconia and resin post-core materials are recommended to form substructures for the lithium disilicate ceramic restorations. Cobalt chromium alloy and Gold metal alloy post-core materials are not recommended.
Luminescent Properties of MgLaLiSi2O7:Eu3+ Phosphors via Sol-Gel Process
Authors: Han Xiu Mei , Ren Deng Hui , Wang Ying Ling , Sun Gui Fang , Qi Xi Wei
Published: June 2012

MgLaLiSi2O7:Eu3+ phosphors have been prepared through the sol-gel process. X-ray diffraction (XRD), thermogravimetric and ddifferential thermal analysis (TG-DTA), FT-IR spectra and photoluminescence spectra were used to characterize the resulting phosphors. FT-IR spectra suggested that crystallized silicates have formed in the powders annealed at 1050°C. The results of XRD indicated that the phosphors crystallized completely at 1050°C. In MgLaLiSi2O7:Eu3+ phosphors, the Eu3+ shows its characteristic red (613nm, 5D0–7F2) emissions.
Effects of the Mechanical Properties of Veneering Porcelain on Stress Distribution of Dental Zirconia Layered Structure: A Finite Element Model Study
Authors: Yi Yuan Fu , Shao Long Quan , Wang Chen , Wen Ning , Deng Bin , Tian Jie Mo
Published: June 2012

The purpose of this study was to study effects of the mechanical properties of veneering porcelain on stress distribution of dental zirconia layered structure by three-dimensional finite element analysis. A 3-D geometric model of the first maxillary molar was established, a tooth preparation was simulated by the Imageware software. A crown was designed and divided into three layers: core, middle layer and outer veneer layer. The elasticity modulus of the middle layer was 70GPa for the control model up to 175GPa for the tested models. Loads of 200N were applied over a 1 mm diameter area beneath the tip of the mesial-distal cusp, simulating typical occlusal contact areas, the stress distribution of the crown systems were analyzed. Results show that within the geometry of the crown configuration, one concentration district of maximum principal stress occurred on the occlusal surface closely proximal to the loading position, several sub-maximum principal stress area were observed, such as margin regions of the mesial face, lingual face, distal faces, buccal face and occlusal fossa. Middle layer with higher modulus can effectively disperse the stress concentration in the layered zirconia all-ceramic crown system.
Colorimetric Comparison of Two Kinds of VITA Shade Guides
Authors: Lu Huai Xiu , Yi Yuan Fu , Deng Bin , Shao Long Quan , Zhao Li Sheng , Shi Guang , Lu Rong Jian , Wen Ning
Published: June 2012

Our aim was to analyze the color ranges of two kinds of Vita shade guides and compare these color ranges with that of Chinese teeth. To do this, the color range and ordering of the Vita Classical and Vita 3D-Master shade guides were measured and analyzed with a MINOLTA CM-2600d spectrophotometer under a D65 standard source. The CIE-1976-L* a* b* system was adopted. We found that compared with the Vita Classical shade guide, Vita 3D Master covers a greater range of a*, and b*, which includes more yellow -reddish and more saturated color tabs. The range of L* extends further towards darker values, while in higher range the two guides are the same. Comparing these color ranges with that of Chinese teeth, the Vita 3D-Master is preferred to the Vita Classical Guide. Because of the larger range of teeth-colors covered, and the logical arrangement, we recommend the clinical use of the Vita 3D-Master shade guide.
Effect of Acticarbon on the Electrochemical Characteristics of LiFePO4 Battery Powder by Microwave Hydrothermal
Authors: Sun Ying , Huang Jian Feng , Cao Li Yun , Wu Jian Peng
Published: June 2012

Olivine LiFePO4 and LiFePO4-C composite cathode materials were prepared by microwave hydrothermal process using FeC2O4·2H2O, NH4H2PO4, LiOH·H2O and acticarbon as source materials. The effect of acticarbon on the structure and charge-discharge property of LiFePO4 crystallites was investigated. The as-prepared battery powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometer(EDS). The charge-discharge behavior was investigated for the characterization of the electrochemical performances of the powder. Results show that the introduction of acticarbon will not change the LiFePO4 crystal structure, but achieve more uniform and fine crystallites and result in better electrochemical performance. Initial discharge capacity of the as-prepared LiFePO4 is 103.4 mAh·g-1 at 0.1 C rate. The discharge capacity of LiFePO4-C is 136.1 mAh·g-1 at the first cycle and 133.9 mAh·g-1 after 30 cycles at 0.1 C rate.
Synthesis and Characterization of SnS Flake-Like Microcrystals with a Microwave Hydrothermal Processing
Authors: Zhang Pei Pei , Huang Jian Feng , Cao Li Yun , Wu Jian Peng
Published: June 2012

SnS powders were obtained by the microwave hydrothermal (M-H) systhesis technique using SnCl2•2H2O and CH3CSNH2 as precursors. By changing the M-H processing temperature, SnS crystallites with differernt sizes and morphologies could be achieved. The phase compositions, microstructures and optical properties of the-prepared SnS crystallites were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), UV-Vis spectroscopy and photoluminescence spectroscopy (PL). Results show that the SnS powders present a herzenbergite-type orthorhombic structure and free of secondary phases. FE-SEM images indicate that the composite crystals are stacked with smaller flake-like crystals. By UV-Vis spectra analysis, the optical band gap of SnS powders is about 1.48 eV, which shows a blue shift of 0.18 eV compared to the bulk SnS. A near-infrared photoluminescence (PL) emission (830 nm) at room temperature is verified for the SnS powders when exited by 551 nm wavelength.
Influence of S⁄La Molar Ratio on the Morphology and Optical Property of La2S3 Microcrystalline Prepared by Microwave Hydrothermal
Authors: Zhang Ye , Cao Li Yun , Huang Jian Feng , Wu Jian Peng
Published: June 2012

The La2S3 microcrystalline were prepared by microwave hydrothermal method (M–H). The influences of different S⁄La molar ratio on the phase composition, and morphology of the La2S3 microcrystalline were particularly investigated. The obtained samples were characterized by X–ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet and visible–spectroscopy (UV–vis) and photoluminescence spectroscopy (PL) at room temperature. XRD results show that the decrease of S⁄La molar ratio from 6⁄3 to 6⁄6, the improving in crystallization of the obtained microcrystalline is observed with the decrease in S⁄La molar ratio. The morphology of prepared La2S3 transforms from irregular shapes to quasi-sphere structure. The as-prepared microcrystalline show excellent absorbency of ultraviolet light and are almost transparent to visible light to exhibit stable violet-blue photoluminescence properties under the ultraviolet light excitation at room temperature.
Ba–Ferrites Hollow Microspheres Prepared by Self–Reactive Flame Spraying Method
Authors: Xu Bao Cai , Duan Rong Xia , Wang Jian Jiang , Lou Hong Fei , Zhang Long
Published: June 2012

Barium ferrites hollow microspheres were prepared by self-propagating high-temperature synthesis self-reactive flame spraying method. The droplets enter in the cooling medium and solidified rapidly so that the gas can not escape to remain holes inside the products. The powder samples were used for characterization. The microstructure and crystal structure were studied by SEM, EDS and XRD. The results show that the obtained particles are hollow microspheres. They are spherical or ellipsoidal shapes from nanometer dimension to several micrometers. The phase structure of composite powders is the mixtures of barium ferrite and Fe2O3.
Preparation and Microstructures of Nano-Porous SiO2 Thermal Insulation Materials by Freeze-Casting of SiO2 in TBA/H2O Suspensions
Authors: Tang Jie , Chen Yu Feng , Liu Hai Lin , Huo Yan Li , Wang Chun Peng
Published: June 2012

A kind of porous SiO2 bulk materials with pore size distributed in nano and micron scales has been fabricated by freeze-casting of SiO2 nano-size powders in TBA (tert-butyl alcohol)/H2O suspensions. The content of TBA in the well mixed TBA/H2O binary co-solvent plays an important role in size and morphology control of the pores in the obtained SiO2 monolithic materials, since the ratio of TBA/H2O determines the competition of crystallization of TBA and ice, therefore, the microstructure of the monolithic SiO2. It was found that the content of TBA in the range from 30 to 40% was suitable for formation of more nano-pores in the SiO2 monolith. The insulation materials freeze-casted from the suspension of SiO2 in 13wt% and TBA in 40wt% has the density of 0.17g/cm3, and the specific surface area of 282m2/g. The pore size has a trimodal size distribution with three mean diameters of 15nm, 100nm and 4μm, respectively.
Calculation of Tape Thickness for Ceramic Tape Casting
Authors: Liu Shu Long , Shen Qiang , Luo Guo Qiang , Li Mei Juan , Zhang Lian Meng
Published: June 2012

Tape casting play a significant role in industrial area, such as multilayered ceramic (MLC) packages, functionally graded materials (FGM), low temperature co-fired ceramics (LTCC) and so on. For the complexity of the rheology for slurry during tape casing process, the control of tape thickness by experience was unstable. Although few numerical and analytical studies on predicting the tape thickness have been done, but these efforts have focused on Newtonian, Bingham, Power law, respectively. There is no unified equation to calculate the tape thickness among different rheological models. In this paper, the calculation results are characterized by wide adaptability; the blade gap, the casting speed and the slurry rheological property are incorporated into calculation; the effect of parameters in the result is studied; Parameter Pnd can be used as a guide to check which mark patterns of the flow velocity profiles in the channel. The results proposed and the experimental measurements from existing publications are in close agreement. Compared with the prediction of the existing models, the calculation results proposed has good agreement with them.
Novel Zn-Doped SnO2 Hierarchical Architectures: Facile Synthesis, Structural Characterization and Enhanced Photocatalytic Property
Authors: Jia Tie Kun , Zhang Fan , Wang Xiao Feng , Wang Wei Min
Published: June 2012

Zn-doped SnO2 seaflower like hierarchical architectures have been synthesized via a solvothermal synthesis route in the mixed solvents of ethanol and deionized water. The observations of field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) showed that Zn-doped SnO2 seaflower like hierarchical architectures were assembled by the nanowires. The preferential growth direction of nanowires was determined based on the analysis of high resolution transmission electron microscopy (HRTEM). The products were also characterized by X-ray diffraction (XRD) and X-photoelectron spectrum (XPS), and the results indicated that Sn4+ ions were successfully substituted by Zn2+. The photocatalytic activity of Zn-doped SnO2 seaflower like hierarchical architectures was evaluated by the degradation of RhB aqueous solution and the results showed that the product had high photocatalytic activity efficiency.
Fusion-Induced Diffusion Joints of Solidified TiC-TiB2 Ceramic with Stainless Steel and Ti-6Al-4V Alloy Achieved by Combustion Synthesis in High-Gravity Field
Authors: Ma Tao , Zhang Long , Zhao Zhong Min , Zhang Yi Fei
Published: June 2012

Based on taking combustion synthesis to prepare high-performance TiC-TiB2 composite in high-gravity field, joint of TiC-TiB2 with stainless steel and Ti-6Al-4V alloy were achieved respectively by the introduction of stainless steel and Ti alloy plates at the bottom of combustion system. Instant melting at surface part of stainless steel and Ti alloy, followed by atom diffusion between liquid TiC-TiB2 ceramic and the molten metal was considered a reason for the achievement of the joint. Because of the presence of both coarsened Al2O3 inclusions nearby the ceramic and the partition layers of Al2O3 between the ceramic and the intermediate, shear strength of joint between the ceramic and stainless steel presented a low value of 120 ± 30 MPa. In contrast, because of the interdiffusion of C, B and Ti atoms between the liquid ceramic and the molten Ti alloy, ultrafine-grained microstructure develops in the ceramic nearby the joint, while the joint characterized by constitutional continuous gradient is also achieved from the ceramic to Ti alloy, resulting in high shear strength of 650 ± 25 MPa between TiC-TiB2 ceramic and Ti-6Al-4V alloy.
Structural and Optical Properties of TiO2 Nanoarray Films Prepared by Liquid Phase Deposition
Authors: Wang Xiao Qiang , Wang Meng , Wang Jian Min , Zha Chun Lei , Zhen Cong Mian
Published: June 2012

In this thesis, highly ordered TiO2 nanotube array films were fabricated via liquid phase depostition (LPD) method, based on different anodized aluminum (AAO) templates. The surface morphology, structure and diffuse reflection spectrum were analyzed by XRD, SEM, UV diffuse reflection spectrum. The results show that the crystal structure of the TiO2 nano array was anatase after heat-treating at 400 °C. SEM photographs show that nanobube arrays have an average diamieter of 50~80nm, the surface morphology is flat, and the tublar structure is not violated after heat-treating. As the growth times increased, red-shift effect was abserved in diffuse reflection spectra. And the optical band gap is respectively 1.48ev, 1.70ev and 2.08ev as the growth time is 10mins, 20 mins and 30mins.
Gel Casting of Large-Sized, Complex-Shaped RBSC Component
Authors: Liu Hai Lin , Huo Yan Li , Wang Chun Peng , Tang Jie , Chen Yu Feng
Published: June 2012

In this paper, gel casting process of RBSC was deeply studied. The rheological property of C/SiC slurry was analyzed, high solid loading (67%) slurry with low viscosity was produced. Also the properties of green body and sintered body were studied. Finally, through optimizations of process parameters, a large-sized (650mm), complex-shaped (with thin ribs about 2.5mm) was fabricated through gel casting process with no cracks and deformation. It was showed that gel casting process is suitable for producing large-sized, complex-shaped RBSC components.
Aging Properties of Yttria-Stabilized Zirconia Ceramics
Authors: Huan Chang Tian , Xia Jin Feng , Jiang Dan Yu , Li Qiang
Published: June 2012

This paper compares the low-temperature aging performance of 5Y-TZP and 8Y-TZP by coprecipitation and solid-phase synthesis methods in the steam. Analysis the weight changes of samples using analytical balance, and the sample surface microstructure and phase changes with SEM, XRD. The results show that the content of Y2O3 and synthesis method all affect the aging properties of zirconia ceramics; solid-phase synthesis of 8Y-TZP has the best anti-aging performance.
Solid Particle Erosion Behavior of NiCr-Al2O3-ZrO2 (8Y) Ceramic Composites
Authors: Liu Feng Jiao , Fang Ming Hao , Liu Yan Gai , Huang Zhao Hui
Published: June 2012

The erosion wear resistance of YSZ ceramics is worth studying because solid particle erosion is one of the main causes of destroying the materials and apparatuses. In this paper, 8YSZ ceramics reinforced by NiCr alloy and Al2O3 particles were pressureless sintered at an optimized sintering condition. The facture toughness reached a maximum value of 4.6 MPa•m 1/2 when the addition of NiCr alloy is 12 vol.%, which was much higher than that of the pure 8YSZ ceramic (2.0 MPa•m 1/2) fabricated in the same condition. Solid particle erosion wear behavior of NiCr-Al2O3-ZrO2 (8Y) ceramics composites was performed by self-designed sand blasting type solid particle erosion wear equipment, using 36# SiC particles as abrasive particles with the 90o erosion angle. The effect of the volume addition of NiCr alloy on the erosion wear of NiCr-Al2O3-ZrO2 (8Y) ceramic composites at room temperature was investigated. The results show that the volume erosion rate of the ceramic composites decreased as the volume addition of the NiCr alloy increasing. Crossing cracks, plastic deformation and minor chipping are the major erosion mechanisms.
Design, Preparation and Thermal Properties of (La0.4Sm0.5Yb0.1)2Zr2O7 Ceramic for Thermal Barrier Coatings
Authors: Liu L. , Ma Z. , Wang F.C. , Xu Q.
Published: June 2012

According to the theory of phonon transport and thermal expansion, a new complex rare-earth zirconate ceramic (La0.4Sm0.5Yb0.1)2Zr2O7, with low thermal conductivity and high thermal expansion coefficient, has been designed by doping proper ions at A sites. The complex rare-earth zirconate (La0.4Sm0.5Yb0.1)2Zr2O7 powder for thermal barrier coatings (TBCs) was synthesized by coprecipitation-calcination method. The phase, microstructure and thermal properties of the new material were investigated. The results revealed that single phase (La0.4Sm0.5Yb0.1)2Zr2O7 with pyrochlore structure was synthesized. The thermal conductivity and the thermal expansion coefficient of the designed complex rare-earth zirconate ceramic is about 1.3W/m•K and 10.5×10-6/K, respectively. These results imply that (La0.4Sm0.5Yb0.1)2Zr2O7 can be explored as the candidate material for the ceramic layer in TBCs system.
Fabrication and Dielectric Properties of Fe-CNT/Al2O3 Bulk Composite Materials
Authors: Hou Qing , Zhang Zi Dong , Shi Zhi Cheng , Fan Run Hua , Li Jing , Zhang Dong Yue
Published: June 2012

In this paper, carbon nanotubes (CNT)/Fe powders were synthesized by a simple catalytic pyrolysis routine and the Fe-CNT/Al2O3 bulk composites were fabricated by hot-pressing sintering. The CNT/Fe powders were characterized by X-ray diffraction (XRD) and TGA-DSC. The dielectric properties of the Fe-CNT/Al2O3 bulk composites were measured by using Agilent E4991A impedance analyzer from 100MHz to 1GHz. Both real part and imaginary part of the permittivity increased as added CNT into the composites. The imaginary part of permittivity (ε'') ranged from 137 to 1300 with the frequency, which indicated a good dielectric loss properties.
Fabrication and Properties of CaAl12O19-Al2O3 Composite Ceramics
Authors: Liu Xue Yin , Liu Yan Gai , Yang De Xin , Ye Ding Yun , Huang Zhao Hui , Fang Ming Hao
Published: June 2012

CaAl12O19-Al2O3 composite ceramics were synthesized by in situ solid state reaction using CaCO3 and industrial α-Al2O3 powders. The effects of sintering temperature and ratio of CA6 (CaAl12O19) content on phases and microstructure of the final composite ceramics were studied by XRD and SEM. The result showed that sheet-like CA6 appeared in the materials when sintering temperature was higher than 1400°C and grew up with the increased of the sintering temperature. The optimum sintering temperature was 1600°C, when the sample containing 20wt% CA6 was sintered at 1600°C, the bulk density was 3.21g/cm3, the apparent porosity achieved 9.94% and the bending strength gained 149.88MPa. With the increasing of CA6 content in the final composite ceramics, the bulk density and the bending strength increased firstly and then decreased. The lowest apparent porosity 1.42%, a density of 3.60g/cm3 and the highest bending strength of 265.10MPa were achieved for the sample containing 10wt% CA6 sintered at 1600°C.
Effect of Al3+ Additions on the Properties of Quartz Ceramics
Authors: Han Xiao Mei , Zhang Li , Lu Jia
Published: June 2012

Quartz ceramic has a great potential use in engineering ceramic materials. However, due to the cristobalite transformation in sintering process, the mechanical properties are weakened. The influence of Al3+ additions on bending strength and open porosity of quartz ceramics was determined by adding Al2O3 (sample 1) and aluminum sulfate solution (sample 2). The content of Al3+ ranged from 1% to 7%. Both samples were sintered at 1200°C for 2h. The bulk density of samples was measured by Archimede’s displacement method and the flexural strength of the specimens was tested using a conventional three point flexural method. The addition of 3% Al3+ of aluminum sulfate leads to better properties (bending strength at 14Mpa and open porosity at 23%). Glass theory was applied to explain the mechanisms of inhibiting crystallization of Al3+ additions.
Disposing of Silica Fiber’ Surface
Authors: Wei Qi Hong , Wang Chong Hai , Wang Hong Sheng , Li Ling , Luan Qiang , Liao Rong , Dong Bo
Published: June 2012

Silica fibers are widely used in superhigh velocity radome and antenna windows. The methods of eliminating the agents on the surface silica fibers were sdudied in this paper. SEM was engaged in studying the effects of silica fibers disposed by different methods,and the tensile strength of disposed silica fbers was compared with the originals. The results show that the heat treatment in the high temperature was a useful means to eliminate the agent on the surface of silica fiber, but there was great thermal damage for silica fibers,and the tensile strenth decreased significantly. The combination of volvent treatment and heat tratment could eliminate the agent on tht surface of silica fibers completely,and the tensile strength retained more, which was a good means to eliminate the agents on the surface of silica fiber.
Fabrication of Porous Mullite Ceramics with High Porosity Using Foam-Gelcasting
Authors: Yang Feng Kun , Li Cui Wei , Lin Ya Mei , Wang Chan Gan
Published: June 2012

In this paper, porous mullite ceramics with an apparent porosity up to 81 % were fabricated by foam-gelcasting using mullite powder as raw material with solid loading of 40 vol.%. The monomers content and sitering temperature have obvious effect on the properties of porous mullite ceramics. The apparent porosity of the prepared samples was in the range of 75~82%, compressive strength, was in the range of 3.0~16.02 MPa, and thermal conductivity was between 0.14 and 0.47 W/(m•K). A complex porous microstructure was formed, where large spherical pores contained small cellular pores on their internal walls.
Effect of Al2O3 Addition on Microstructure, Thermal Expansion and Mechanical Properties of Ta2O5 Ceramics
Authors: Zhou Jian Er , Zhang Jing , Zhang Xiao Zhen , Hu Xue Bing
Published: June 2012

The Ta2O5-based ceramics were prepared by dry pressing/sintering technique using Ta2O5and Al2O3as the starting materials. The present work investigated the effect of alumina (Al2O3) additions on the composition, microstructure, thermal expansion coefficient (TEC) and bending strength of Ta2O5ceramics. The thermal expansion of the samples was measured by the dilatometry method. It was found that Al2O3additions can effectively inhibit the β to α phase transformation in Ta2O5ceramics. Orthorhombic AlTaO4as the minor phase formed when 2.5 and 7.0 wt% Al2O3was added. The addition of Al2O3results in obvious change of TEC and an increase of bending strength. This work demonstrated that the addition of Al2O3is an effective way to modify the TEC and mechanical strength of Ta2O5ceramics.
High-Temperature Chemical Stability of Hf6Ta2O17 Ceramic for Thermal Barrier Coatings
Authors: Li Miao , Xu Qiang , Wang Lu
Published: June 2012

Subscript textHigh-temperature chemical stabilities of Hf6Ta2O17/Al2O3, Hf6Ta2O17/YSZ and Hf6Ta2O17/Sm2Zr2O7were studied for thermal barrier coatings (TBCs). The mixed powders of Hf6Ta2O17/Al2O3and Hf6Ta2O17/YSZ were annealed at 1600°C for 8 hours in air, and the mixed powders of Hf6Ta2O17/Sm2Zr2O7were annealed at 1200°C for 8 hours in air. The phases of the annealed mixed powders were observed by X-ray diffractometry (XRD). The sample of Hf6Ta2O17/Al2O3mixed powder was molded and sintered at 1600°C for 8 hours in air, and the microstructures of the sintered sample were investigated by scanning electron microscopy (SEM). The XRD results revealed that the crystal structure of Hf6Ta2O17had no remarkable changes in the mixed powders of Hf6Ta2O17/YSZ and it had changes in the mixed powders of Hf6Ta2O17/Al2O3. The monocline HfO2/ZrO2phases were found in the mixed powders of Hf6Ta2O17/Sm2Zr2O7. The SEM results showed that the boundaries of Hf6Ta2O17and Al2O3crystals were clear. The element composes in crystals were analyzed by energy dispersive spectrometer (EDS), and the EDS results showed that a little amount of Al diffused into Hf6Ta2O17crystals.
Preparation and Characterization of Activated Sericite Modified by Fluorosilicate and Acid
Authors: Wang Yue Bo , Ding Hao , Mei Le Fu , Jiang Wei
Published: June 2012

Although sericite belongs to 2:1 clay minerals, it hardly has intercalation properties because it has high layer charge density, which produces pretty strong electrostatic force. Therefore, the purpose of activation is to permanently reduce the layer charge of sericite and obtain numbers of exchangeable cations. The original sericite (S0) was sintered at 800 °C for 1 h. After that, thermal-treated sericite (S1) was activated with sodium fluosilicate and nitric acid, whose effects were characterized by X-ray diffraction (XRD) analysis, chemical analysis and zeta electric potential analysis. The dissolving-out amount of Al3+ of acid-treated product (S2) reached circa 65 mg/g at the optimal processing conditions. After sodium modification with NaCl, CEC of final resulting product (S3) was increased to 14.34 meq/100g compared with that of original sericite (4.94 meq/100g). The results of chemical analysis and zeta electric potential analysis indicated that acid activation with sodium fluosilicate and nitric acid decreased the layer charge of sericite.
Fabrication and Properties of Cf/Ti3SiC2-SiC Composites Using Ti3SiC2 as Inert Filler
Authors: Yang Jin Shan , Dong Shao Ming , He Ping , Li Qing Gang , Wu Bin , Hu Jian Bao , Hu Zhi Hui
Published: June 2012

Because of its combined characteristics of metals and ceramics, such as low density, high Young’s modulus, thermal and chemical resistance with low hardness, high electrical and thermal conductivity, it was expected that the introduction of Ti3SiC2 to fiber reinforced ceramic matrix can make the composite own some unique properties. In the present research, Ti3SiC2 powders used as inert fillers were fabricated by the in-situ reaction between Ti and polycarbosilane mixtures. The purity of Ti3SiC2 powders analyzed by XRD was determined by RIR method, which is a semi-quantitative XRD analysis. The results showed that the purity of Ti3SiC2 powders is about 96%. Cf/Ti3SiC 2-SiC composites are obtained by polymer infiltration and pyrolysis process using Ti3SiC2 powders as the inert fillers. The bending strength of Cf/Ti3SiC2-SiC composites was about 160 MPa.
Crystal Growth, Fracture Behavior and Toughening of Rapidly-Solidified TiC-TiB2 Prepared by Combustion Synthesis in High-Gravity Field
Authors: Zhao Zhong Min , Zhang Long , Song Yi Gang , Wang Wei Guo , He Jian Qiang
Published: June 2012

Micro-nanocrystalline microstructures characterized by TiB2 platelets of the average thickness close to or smaller than 1 μm, were achieved in full-density solidified TiC-TiB2 composites by combustion synthesis in high-gravity field. XRD, FESEM and EDS results showed that a large number of fine TiB2 platelets were uniformly embedded in irregular TiC grains, a few Cr-Al metallic phases or in between those phases. The achievement of micro-nanocrystalline microstructures results from low-velocity faceting growth of TiB2 crystal, high-velocity non-faceting growth of TiC solid and high diffusion rate of C relative to B in liquid TiC-TiB2. The relative density, Vickers hardness, flexural strength and fracture toughness of TiC-TiB2 composites measured 99.3%, 21.5 ± 1.5 GPa, 845 ± 35 GPa and 16.8 ± 1.5 MP • m0.5, respectively. High flexural strength of the materials benefits mainly from the achievement of micro-nanocrystalline microstructure in the full-density solidified ceramic and high fracture toughness contributed from intensive coupled toughening mechanisms by a large number of fine TiB2 platelets and a few Cr-Al metallic phases.
Synthesis of Fiber-Like SiС by Carbothermal Reduction of Used Silica Bricks
Authors: Pan Zi He , Huang Zhao Hui , Li Wen Juan , Liu Yan Gai , Fang Ming Hao
Published: June 2012

Fiber-like SiC had been synthesized using used silica bricks and carbon powder as raw materials by carbothermal reduction. A new kind of beaded SiC also had been found in the specimen. The result showed that well-crystallized β-SiC fibers began to appear at 1550 °C with excessive of 100 wt% content of carbon. While at 1600 °C for 6 h with excessive of 100 wt% content of carbon, the as-synthesized SiC fibers were grown with some beads in the fiber strings. The beaded SiC consisted of strings with diameters of less than 0.5 μm (or even 0.1μm) and periodic beads with diameters of 0.5-1.0 μm. Vapor-solid (VS) mechanism and vapor-liquid-solid (VLS) mechanism were also discussed in the synthesizing process of fiber-like SiC. This kind of fiber-like SiC may used as reinforce materials in ceramic composites, the fracture toughness of brittle ceramics can be effectively improved via the incorporation of strong SiC fibers into the matrix due to crack deflection, bridging and fiber pull-out. Moreover, these toughening mechanisms do not diminish as temperature increases.
Fabrication of ZrC-SiC Powders by Means of Liquid Precursor Conversion Method Using ZrC Precursor and Polycarbosilane
Authors: Li Qing Gang , Dong Shao Ming , Wang Zhen , He Ping , Zhou Hai Jun , Yang Jin Shan , Wu Bin , Hu Jian Bao
Published: June 2012

ZrC-SiC powders were fabricated by means of liquid precursor conversion method, using Zr containing polymer precursor and polycarbosilane. The effects of staring reagents and the pyrolysis temperature on the fabrication of ZrC-SiC powders were studied. Results show that ZrC-SiC powders with different ZrC/SiC ratio could be formed when the staring reagents were different. Pyrolysis temperature affects the pyrolysed product. When temperature was lower, less amount of ZrC was formed in the powder. The size of crystallite and morphology of the synthesized powders were characterized by transmission electron microscopy and scanning electron microscopy.
Preparation and Properties of ZrB2-Cu Composites by Spark Plasma Sintering
Authors: Zhu S.Z. , Gong D.L. , Fang Z. , Xu Q.
Published: June 2012

For high thermal conductivity and high electrical conductivity, copper is a good electrode material. The wearing resistance and spark resistance of Cu can be improved with the addition of ZrB2. ZrB2-Cu composites with high Cu volume fraction was successfully prepared by spark plasma sintering (SPS) process in this paper. The microstructure and properties of the sintered samples were characterized. The effect of the sintering temperature and the ZrB2 content in composites on the relative density and properties of the composites were investigated. The results show that the relative density and mechanical properties increase with the sintering temperature increasing. The optimum sintering temperature is 900 °C for 10wt.% ZrB2-Cu, 1000 °C for 20wt.% ZrB2-Cu and 1050 °C for 30wt.% ZrB2-Cu. With the ZrB2 content in composites increasing from 10wt.% to 30 wt.%, the electrical resistivity increases from 2.25×10-6 Ω.cm to 8.82×10-6 Ω.cm, the flexural strength decreases from to 539.1 MPa to 482.2 MPa and the fracture toughness decreases from to 15 MPa.m 1/2 to 9 MPa.m 1/2. The hardness (HV) of ZrB2-Cu composites is significantly enhanced by the ZrB2 particulate reinforcement, increasing from 1410 MPa for 10 wt.% ZrB2 to 2480 MPa for 30wt.% ZrB2.
Investigation of Microstructure and Thermal Shock Resistance of the B4C/BN Composites Fabricated by Hot-Pressing Process
Authors: Jiang Tao , Tian Chen Chao
Published: June 2012

The B4C/BN composites were fabricated by hot-pressing process. The B4C/BN composites included the B4C/BN microcomposites and B4C/BN nanocomposites. The B4C/BN microcomposites were fabricated by hot-pressing process, and the B4C/BN nanocomposites were fabricated by chemical reaction and hot-pressing process. In this research, the phase composition, microstructure, mechanical property and thermal shock resistance of the B4C/BN microcomposites and B4C/BN nanocomposites were investigated. The B4C/BN microcomposites and the B4C/BN nanocomposites exhibited the homogenous and compact microstructure, and the h-BN particles were homogenously distributed in the B4C matrix. The mechanical property of the B4C/BN microcomposites and B4C/BN nanocomposites decreased gradually with the increase of h-BN content, but the B4C/BN nanocomposites exhibited the higher mechanical property than that of the B4C/BN microcomposites. The thermal shock resistances of the B4C monolith and the B4C/BN composites were measured by water-quenching method. The thermal shock resistances of the B4C/BN microcomposites and the B4C/BN nanocomposites were remarkably improved in comparison with the B4C monolith. The thermal shock resistance of the B4C/BN nanocomposites was much better than that of the B4C/BN microcomposites. The thermal shock temperature difference (ΔTc) of the B4C monolith was about 300oC, the ΔTc of the B4C/BN microcomposites was about 500oC and the ΔTc of the B4C/BN nanocomposites was about 600oC. The B4C/BN composites exhibited the high thermal shock resistance due to the high fracture strength and low elastic modulus. The microstructure showed that the weak interface of B4C/BN and cleavage behavior of laminate structured h-BN particles would remarkably improve the thermal shock resistance of the B4C/BN composites.
Effects of Carbon Fiber Dispersion on Bending Property of Cf/SiC Brake Materials
Authors: He Bo Lin , Yu Ying Xia , Sun Jia , Liu Jing , Shi Jian Ping
Published: June 2012

With increasing of the speed of the train, the requirement of the performance of the braking friction materials is more and more higher. It is urgent to find new braking materials to satisfy the rigorous using environment. Cf/SiC has the broad application prospects when it is used as a new kind of braking material. On this article, in order to shorten preparation cycle and reduced production costs, short carbon fiber is substituted continuous carbon fiber felt. Cf/SiC brake materials were prepared by the way of molding compression-pressureless sintering with resin binder. The effect of short carbon fiber dispersion on bending properties of brake materials was researched. The experimental results show that the bending strength of Cf/SiC brake materials, which manufactured by dispersing short carbon fibers, is higher than the composites manufactured by using fiber bundle. When the distribution of carbon fiber in composites is in single fiber state, the interfacial strength between carbon fibers and matrix were increased. At the experimental condition, compared to the sample with fiber bundle, the bending strength of the specimen with dispersed fiber is increased 40.79%. The toughening mechanism of carbon fiber debonding and fiber pull were generated in the process of bending fracture. The fracture model of composites is pseudo-ductile type.
Design on Thermal Protection Structure of C/SiC Lattice Composite Materials
Authors: Gao Yu , Zeng Tao , Fang Dai Ning , Yan Shi
Published: June 2012

A new double-layer lattice structure based on C/SiC composite material is described and being investigated as a means to increase the service temperature of thermal protection structure. The design incorporates a C/SiC double-layer sandwich comprising two pyramidal truss cores. The outer layer of the sandwich structure is the thermal protection layer, which can make the heat redistribute. The internal layer is the insulation layer, which can decrease the temperature of the hot components and increase their reliability. The temperature field of C/SiC lattice thermal protection structures with different geometrical parameters was calculated by the finite element software ANSYS. It is found that the thermal behavior of the double-layer lattice thermal structure is affected by the truss geometry, such as truss length and inclination angle. The thermal protection capacity of C/SiC lattice structure is analyzed and compared with the equivalent solid structure. The results indicated that C/SiC lattice thermal protection structure has lower density and better thermal protection property than the traditional thermal protection structures.
Preparation of Silicon Nitride Porous Ceramics
Authors: Liu Jian , Liu Kai , Wang Hong Sheng , Gao Fang , Liao Rong
Published: June 2012

A silicon nitride porous ceramics having excellent mechanical strength and dielectric properties can be employed as a wave-transparent material. The silicon nitride porous ceramic contains a plurality of silicon nitride crystal grains with pores formed in grain boundary which forms a three-dimensional network structure. The properties of the silicon nitride porous ceramics was studied , the porous ceramics was prepared by different process parameters, including the pressure of cold isostatic pressing, temperature of sintering and sintering atmosphere, etc.; A high porosity(>50%), high strength(>120MPa), low dielectric properties(ε<3.2) silicon nitride ceramic can be prepared by appropriate process parameters.
Preparation and Properties of Porous Si3N4/SiO2/BN Composite Ceramics
Authors: Dong Wei , Wang Chang An , Yu Lei , Ouyang Shi Xi
Published: June 2012

Porous Si3N4/SiO2/BN composite ceramics with high strength and low dielectric constant were prepared by dry-pressing process and pressureless sintering at 1750°C for 1.5 h in flow nitrogen. The influences of BN content on microstructure, porosity, mechanical and dielectric properties of the porous Si3N4/SiO2/BN composite ceramics were discussed. The results showed that the porous Si3N4/SiO2/BN composite ceramics with porosity ranging from 29% to 48% were fabricated by adjusting the content of BN. The flexural strength of the porous Si3N4/SiO2/BN composite ceramics was 78215 MPa. The dielectric constant of the porous Si3N4/SiO2/BN composite ceramics was 3.9~5 at 1 MHz.
Dispersion of Si3N4 Powders in Tert-Butyl Alcohol
Authors: Yao Sheng Lian , Lin Xu Ping , Ma Jing Tao , Wang Chang An , Deng Chang Sheng
Published: June 2012

A high molecular weight block copolymer dispersant with pigment affinic groups — DISPERBYK163 (BYK163) was chosen to disperse submicron-sized Si3N4 in tert-butyl alcohol (TBA) solvent. The stability of Si3N4 powders in TBA with dispersant BYK163 was studied by sedimentation. To achieve good casting behavior, rheological measurement was employed to find a reasonable dispersant content in the slurry. The adsorption isotherm of BYK163 on Si3N4particles surface was obtained by thermogravimetric analysis (TGA). Based on the surface chemical properties of Si3N4particles, the dispersing phenomena and mechanism of BYK163 in TBA were summarized. BYK163 could form a steric layer on the surface of Si3N4particles, and effectively prevent particles agglomeration. Therefore, porous Si3N4samples with porosity of 40% to 80% could be prepared from Si3N4slurries with low and high solid loadings due to well dispersion with BYK163 addition.
Sintering Behavior and Properties of Si3N4 Ceramics with Yttrium Chloride Additive
Authors: Lu Du , Ning Xiao Shan , Chen Ke Xin , Zhou He Ping
Published: June 2012

The big gap between the thermal conductivity of Si3N4 ceramics and the theoretical value of beta-Si3N4 single crystal implies that the low thermal conductive oxide grain-boundary phases in the ceramics possibly have a great influence on the thermal conductivity of the ceramics. In this work, yttrium chloride (YOCl) is introduced as sintering additive instead of the commonly-used Y2O3, in order to decrease the amount of the grain-boundary oxide; and the influence of YOCl on the sintering and the properties of Si3N4 ceramics was studied. Results show that YOCl additive can react with Si3N4 powders to form similar Y-Si-O-N grain-boundary phases just like Y2O3 while the Cl disappears during sintering. The thermal conductivity of the ceramics sintered with YOCl additive (85 W/m•K) increases about 15% as comparing with the ceramics sintered with Y2O3 additive, even though the relative density of the former reaches merely 97%. The microstructure of the sample sintered at different temperatures was investigated in the work, for elucidating the sintering process and the relationship between the properties and the microstructure of the YOCl added ceramics.