bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Composite Sintering Additive on Al2O3 Ceramic Foam
Authors: Chai Yu Xin , Zhou Xin Gui , Zhang Hua Yu
Published: March 2014

In this study, the environment-friendly egg white protein was used as foaming agents and binders to fabricate Al2O3 ceramic foams, owing to its excellent foaming and binding properties. The CaO-SiO2-MgO-ZnO-TiO2-B2O3 composite sintering additive was added into Al2O3 ceramic foam to develop the mechanical performance of Al2O3 ceramic foam and facilitate sintering. The modified Al2O3 ceramic foam was investigated on porosity, density, compressive strength, pore morphology and grain size. The investigation revealed that: compared with ordinary Al2O3 ceramic foam, although the samples adding sintering additive had lower porosity, larger density and bigger grain, its compressive strength was significantly much stronger than samples without sintering additive. The XRD result indicated that samples adding sintering additive had spinel, anorthite and a small amount of mullite phase besides the main corundum phase. Adding sintering additive is a new way to develop the mechanical performance of Al2O3 ceramic foam and facilitate sintering which can help grain growth, thereby improving the mechanical properties of Al2O3 ceramic foam.
Synthesis and Characterization of Yttria-Doped Mesoporous Zirconia
Authors: Liu Rui Ping , Wang Chang An
Published: March 2014

The yttria-doped mesoporous zirconia was successfully synthesized by evaporation induced self-assembly (EISA) method, and the microstructure and textural properties of the as-made product were studied extensively. The results showed that the as-made product possessed crystallized framework walls and a worm-like mesopore with a narrow pore distribution. The BET specific surface area and pore volume of the as-made product calcined at 500°C are 111 m2/g and 0.16 cm3/g respectively, and the corresponding data changed to 73 m2/g and 0.052 cm3/g after calcined at 700°C, which indicated that the as-made yttria-doped mesoporous zirconia possess a higher thermal stability.
Large Scale Al2O3-ZrO2 (Y2O3) Eutectic and Hypereutectic Achieved by Combustion Synthesis in High Gravity Field
Authors: Lu Xiao Bo , Liu Hong Bo , Zhang Yu Fei
Published: March 2014

By introducing ZrO2 (4Y) powder into the thermit, the solidified Al2O3-ZrO2 (4Y) ceramic composites with eutectic and hypereutectic microstructures were prepared via combustion synthesis in high gravity field, and the microstructures and mechanical properties of the solidified ceramic composites were discussed. XRD, SEM and EDS showed that the Al2O3-33%ZrO2 (4Y) as the eutectic were composed of random-orientated rod-shaped colonies consisting of a triangular dispersion of orderly submicron-nanometer t-ZrO2 fibers, surrounded by inter-colony regions consisting of spherically-shaped micrometer t-ZrO2 grains, whereas Al2O3-45%ZrO2 (4Y) as the hypereutectic were comprised of spherically-shaped micron-meter t-ZrO2 grains, surround by irregularly-shaped α-Al2O3 grains and a few colonies. Compared to the directionally solidified Al2O3-ZrO2 (Y2O3), the increase in hardness and flexural strength of the eutectic obtained in current experiment was due to high densification, small-size defect and high fracture toughness induced by residual stress toughening and transformation toughening mechanisms; meanwhile, in despite of the moderate decrease in hardness, high flexural strength of the hypereutectic was considered to be a result of small-size defect and high fracture toughness induced by transformation toughening and microcrack toughening mechanisms.
Ceramizable Composites for Fire Resistant Applications
Authors: Pędzich Zbigniew , Bieliński Dariusz M. , Anyszka Rafał , Lach Radosław , Ziąbka Magdalena
Published: March 2014

The paper concerns composite materials made of silicone rubber matrix and ceramic fillers used as flame resistant coverings for electrical cables. Under fire, such materials must be able to form, relatively quickly, compact and stiff protecting coating, strong enough to maintain integrity of electrical circuit, even up to melting temperature of metal core. The residue of fired silicone rubber or silica filled elastomer exhibit a form of white powder. There is no evidence of solidification of silica particles, even after heating at 1100°C. However, the addition of some ceramic phases results in reaction with silica matrix (starting at about 900°C) producing a liquid phase, what facilitates particle binding. At lower firing temperatures (600°C) the problem of binding between the product of pyrolysis (silica) and filler is also present, what results in formation of fragile surface shield. The problem can be overcome by the addition of certain inorganic materials to the silicone rubber matrix. The paper discusses their influence on ability of silicone rubber composites, additionally containing glassy phase, wollastonite, mica, aluminium hydroxide, montmorillonite or calcined caoline, to ceramization.
Morphology Controlling of CaCO3 in 3D Bacterial Cellulose Nanofibres
Authors: Li Zhen You , Xing Li , Xiang Jun Hui , Zhao Chun Lin , Sai Hua Zheng , Li Fei
Published: March 2014

Hierarchical structure of biomaterials comprised of three dimensional organic matrix and inorganic minerals exhibit unique morphologies and outstanding properties. Herein, modified bacterial cellulose (BC) nanofibres/CaCO3 composites are prepared using the ammonium carbonate diffusion method at room temperature. The copper coinage shaped aragonite has been synthesized in the 3D matrix and investigated by X-ray powder diffraction, Fourier transform infrared spectrometry, and scanning electron microscopy. It can be concluded that the carboxyl modified BC nanofibres can control the mineralization in vivo by physical confinement within the organic structure to allow the growth of non-equilibrium morphology and chemical interaction to influence polymorph selection and oriented nucleation. The system which was to mimic the biomineralization in vivo can help to produce bio-mimetic materials similarly in living creatures.
Influence of Raw Material Ratio of Ba/Ti on Fabrication of Nanocrystalline BaTiO3 Powder
Authors: Zhang Hui , Wang Xiao Hui , Shen Zheng Bo , Hao Ya Nan
Published: March 2014

Nanocrystalline BaTiO3 powder was directly synthesized by a convenient one-step solvothermal route. 8~10 nm BaTiO3 with different Ba/Ti ratios are obtained by adjusting the raw material ratios. The optimum raw material ratio of Ba/Ti is obtained. And the as-prepared BaTiO3 nanoparticles are all small and uniform. Influence of the nominal Ba/Ti ratios on diameter of nanocrystalline BaTiO3 powder was investigated by XRD, TEM and XRF analyses. It was found that the Ba/Ti ratios of the raw materials have a great influence on the process of powder fabrication. When the raw material Ba/Ti ratio is low (<0.9), the reaction cannot be finished and strong BaCO3 peaks were founded as the alkalinity of the system at the later reaction stage is too low. Besides, the Ba/Ti ratio of the product rises as the raw material Ba/Ti ratio increases.
Application of Improved Back-Propagation Neural Network to the Technologic Processing of Korshunskite Whiskers
Authors: Ren Qing Li , Luo Qiang , Yang Miao Miao
Published: March 2014

The korshunskite samples were prepared in precipitation by the one-step reaction method at atmospheric pressure. The three-layer structure back-propagation network model based on the non-linear relationship between the amount of the korshunskite whiskers and the technological factors, such as the adding amount of raw materials NaOH, MgCl2, MgO, and reaction temperature, is established. And the results show that the improved back propagation neural networks model is very efficient for predication of the korshunskite whiskers preparation.
High Temperature Micro Structural Evolution of ZrO2 Fibers Thermal Insulation Materials
Authors: Wang Guang Hai , Sun Hao Ran , Wang Chun Peng , Zhou Jian , Huo Yan Li , Zhang Shi Chao , Chen Yu Feng
Published: March 2014

Yttria-stabilized zirconia fibers thermal insulation materials may be the main developmental direction of high temperature thermal protection materials, due to their high temperature resistance (above 2000 °C), high strength and toughness, low thermal conductivity ( about 2 W/m·K), oxidation resistance and other excellent properties. However, mechanical property of zirconia fibers thermal insulation materials is decrease after high temperature heat treatment. In this paper, the evolution of microscopic structure of zirconia fibers is studied by using the method of oxyacethlene ablation. The gain growth and high temperature creep are observed after 600 s heat treatment at 1800 °C. Crystal phase of zirconia fibers is not changed and still cubic. Moreover, crystallinity is more higher form XRD patterns. Controlling grain growth can improve high temperature mechanical property of zirconia fibers thermal insulation materials.
Luminescence Behavior of Tm3+ Activated GdAlO3 Phosphors Synthesized Using Solid-Reaction Method
Authors: Wu Nan , Li Xiao Dong , Liu Shao Hong , Dong Yu , Li Ji Guang , Sun Xu Dong
Published: March 2014

Trivalent thulium ions (Tm3+) doped GdAlO3 (Gd1-xTmxAlO3) phosphors which show a blue luminescence of high color purity have been synthesized by using solid-state reaction method starting from nanosized powders. X-ray diffraction (XRD) measurements were used to analyze the phase transformations that take place during the preparation of the phosphors. The morphologies of the powders calcined at different temperatures were studied by using scanning electron microscopy (SEM). The luminescence properties of the compounds were investigated. Pure phase of orthorhombic type GdAlO3 (GAP) was yielded by calcining the phosphors at 1200°C for 8 h. The PL spectra showed representative Tm3+ emission. The strong band centered at ~488 nm and the weak one centered at 697 nm were attributed to the 1D2-3F4 and 1G4-3F4 transitions of Tm3+, respectively. The quenching concentration of Tm3+ was estimated to be ~0.75at.% (x=0.0075), for which can be ascribed to the exchange interactions. The decay curve was fitted to be a single exponent and the estimated fluorescent lifetime of the GdAlO3:Tm3+ phosphor was 1.73±0.08 ms.
The Effect of Nano-Al2O3 on Sintering Behavior and Mechanical Property of ZrO2 Ceramics
Authors: Yi Zhong Zhou , Sun Hong Yan , Wang Bo , Zhai Feng Rui , Xie Zhi Peng
Published: March 2014

The effect of addition nanoAl2O3 on sintering behavior and mechanical property of ZrO2 was studied. It was shown that the addition of nanoAl2O3 with the Al2O3 content from 0.5mol% to 2.0mol% in ZrO2 ceramics could accelerate the sintering of ZrO2 and increase the flexural strength and fracture toughness of ZrO2. ZrO2 added with 1.0mol% nanoAl2O3 has the maximum in strength of 650MPa and toughness of 15MPa·m1/2 sintered at 1450°C. Compared with undoped ZrO2 being sintered at 1500°C, the strength and toughness was improved by 12% and 18%, respectively.
Chemical Stability of (Sm1-xLax)2Zr2O7 and Al2O3 at High Temperature
Authors: Cui Lin Ru , Zhu Shi Zhen , Xu Qiang , Liu Ling , Ma Zhuang
Published: March 2014

Due to its high melting point, low thermal conductivity, and good phase stability at high-temperature, rare earth zirconates material (A2B2O7) will be one of the candidate materials used for the thermal barrier coating. At high temperature, the chemical stability between rare earth zirconates and TGO layer (mainly Al2O3) affects much the performance of coating, so the study of the chemical stability is of great significance. In this paper, (Sm1-xLax)2Zr2O7(x=0, 1) were prepared by the co-precipitation method and the chemical stability between (Sm1-xLax)2Zr2O7(x=0, 1) and Al2O3 was investigated at the temperature of 1 200 ° ?C,1 300 ° ?C, 1 400 ° ?C, 1 500 ° ?C, 1 600 ° ?C respectively for 8 h¡¢24 h. The microstructures were analyzed by scanning electron microscope (SEM) and the crystallographic phases were determined by X-ray diffraction (XRD). The results showed that the chemical reaction occurred between Sm2Zr2O7 and Al2O3 above 1 200 ° ?C producing SmAlO3. With the heating temperature increased, the content of SmAlO3 increased. The chemical reaction between La2Zr2O7 and Al2O3 began at 1 200 ° ?C producing LaAlO3 and ZrO2. LaAl11O18 appeared at 1 300 ° ?C. As the increase of heating temperature, the content of LaAlO3 and ZrO2 with tetragonal phase reduced gradually in the heated samples, and the content of LaAl11O18 and ZrO2 with monoclinic phase increased gradually in the heated samples. With the increase of heating temperature, the doping amount decreases in ZrO2 with tetragonal phase, the structure of ZrO2 with tetragonal phase tend to be more complete. So ZrO2 with tetragonal phase transformed to ZrO2 with monoclinic phase in cooling process easily, which leads to the increase of ZrO2 with monoclinic phase in the heated samples. As the time of heating temperature prolonged, the kinds of reaction products didn ?t change, but the amount of reaction products increased.
Property Changes of SiO2 Aerogel on Insulation Performance under Different Time and High Temperature Condition
Authors: Yang Jie , Liu Jing , Sui Xue Ye , Liu Rui Xiang , Zhou Chang Ling , Lv Yan Hong , Wang Shou , Wang Shou Xing , Wei Ming Ling
Published: March 2014

To study the impacts of structural change of SiO2 aerogel on its insulating properties, the samples were treated in long time (0-12h) at 500°C, 600°C, 700°C and 800°C. The results show that with the time increased, the shrink extends in thickness, the weight loss and the density is basically unchanged under the 500°Cand 600°C. As for 700°C and 800°C, the results were treated with 0-12h, the shrink extends in thickness, the weight loss and density increases considerably. Besides, the structure and composition of SiO2 aerogel after the different temperature treaded with 0.5h were tested. The results show that when the heat treatment temperature is between 200-800°C, the small pores in SiO2 aerogel collapses and large pores increase, and the density is stil1 able to maintain the 1ow value due to the unbroken skeleton. When the heat temperature is between 800-1000°C, the secondary particle size increases and the rnutual integration of the secondary particles occurs, the density will be significantly increased.
The Effect of pH of the Aging Solution on Microstructure of Silica/Zirconia Aerogel
Authors: He Jian , Li Xiao Lei , Ji Hui Ming , Wang Qing Pu
Published: March 2014

ZrO2 wet gel was prepared using zirconium n-butoxide as precursor and 1,2-propylene oxide (PO) as a gelation agent in sol-gel process. Then, tetraethoxysilane (TEOS) was used to strengthen the wet gel in aging process. Finally, the monolithic silica/zirconia aerogel was obtained by supercritical fluid drying. N2 adsorption-desorption method, scanning electron microscope (SEM), and Fourier transform infrared spectroscopy (FTIR) were used to characterize microstructure of the aerogel. The influence of pH of the aging solution on microstructure of silica/zirconia aerogel was studied. The results indicate that the particle size distribution of SiO2/ZrO2 aerogel was more uniform and less aggregate when aging in acid solution. However, the average pore diameter and particle size of SiO2/ZrO2 aerogel was increased by aging in alkaline solution. Aging in alkaline condition was useful for largening the pore size of SiO2/ZrO2 aerogel, and the maximum specific surface area and pore volume were obtained at pH=9. Meanwhile, different reactions were produced between the acid/alkaline solution and the hydroxyl of SiO2/ZrO2 aerogel, and the ester group/amino group was obtained relatively which can modify the network of aerogel and decrease the shrinkage of aerogel during the supercritical fluid drying.
Microstructure of Hydrated Magnesia and MgAl2O4 Spinel Layer between Magnesia and Alumina
Authors: Lu Cheng Long , Peng Wei Ke , Zhu Hong Xi , Deng Cheng Ji , Yuan Wen Jie , Li Jun
Published: March 2014

Tests were performed to investigate the microstructure of MgAl2O4 spinel layer between magnesia and alumina after high temperature thermal treatment (1500 °C and 1600°C). The first test involved fused magnesia and alumina sol. Hydration of magnesia powders was studied in a controlled condition that soaked in aqueous solution at 80 °C for up to 1h and 2h. Microstructures of the samples were investigated by SEM, EDS, which showed that the formation of Mg (OH)2 made magnesia particles cracking, separated many punier particles. The punier particles combined with alumina sol, generated spinel at high temperature. A microstructurally distinct layer with granulate grains of up to 50μm width was observed after 3 h at 1600 °C. Spinel layer bordered alumina layer, and separated from magnesia layer. However, it was not found distinct spinel layer after 3 h at 1500 °C. The formation of small amount of spinel embedded in the layer of alumina, and penetrated the alumina layer. In the spinel layer , Spinel phase close to alumina layer contained 8.79% Mg by atomic, while spinel phase away from alumina layer contained 13.07% Mg by atomic.
Study on Porous Si3N4 Material with Hexagonal BN
Authors: Liao Rong , Liu Jing , Wang Hong Sheng , Wang Chong Hai , Wei Qi Hong , Zhu Bao Xin
Published: March 2014

The influences of hexagonal BN content on the porous Si3N4 material was investigated. SEM micrographs showed that the columnar crystal overlapping structure of the porous Si3N4 material with a small BN addition was almost invariant. BN uniformly dispersed in the spaces of crystal overlapping. The experiment showed that the apparent densities of the porous Si3N4 material with a small BN addition marginally increased, the porosity, the strength and the dielectric constant marginally decreased, but The thermal shock resistance was greatly improved.
Studies on the Pyrolysis Kinetic Behaviours of Polycarbosilan
Authors: Qiu Hai Peng , Chen Ming Wei , Jiao Jian , Li Xu Qian , Wang Yu , Gao Shu Ya
Published: March 2014

The pyrolysis kinetic behaviors and reaction mechanism of polycarbosilane (PCS) were characterized by means of XRD, SEM and on-line TG-DSC-FTIR-MS coupling technique, which showed that the pyrolysis process accorded with the F2 integral model (300-600°C), and the values of apparent activation energy (Ea) and pre-exponential factor (A) were 56.10KJ/mol and 10.84, respectively. During the pyrolysis process, PCS was converted into amorphous inorganic solid from organic polymer with breakage and rearrangement of chemical bonds, then to well-defined crystal structure of good thermal stability. Furthermore, the weight loss occurred mainly among 300°C and 800°C with CH4, (CH3)4Si,(CH3)3SiH,(CH3)2SiH2and other silane gases releasing from pyrolysis product leading to the conversion from organic polymers to inorganic ceramic. The pyrolysis product was converted into β-SiC crystal completely at 1400°C, and the crystallization of α-SiC phase occurred after 1550°C which might influence the stability of SiC matrix. Key words:polycarbosilane, organic precursor, pyrolysis kinetic behavior
Synthesis and Characteristics of Porous Silicon Carbide Ceramic Reinforced by Silicon Carbide Whiskers
Authors: Liu Xiao Xue , Zhao Hong Sheng , Yang Hui , Zhang Kai Hong , Li Zi Qiang
Published: March 2014

Silicon powder and phenolic resin were used as raw materials to produce porous silicon carbide (SiC) ceramics, with SiC whiskers (SiCw) as reinforcement additionally. Starting with the preparation of core-shell structure precursor powder through coat-mix method, and then by carrying out molding, carbonization and sintering processes, SiCw/SiC ceramic examples were produced. The phase composite, fracture surface morphology, pore size and porosity, bending strength and thermal expansion coefficient of the final product were measured. Results show that the addition of SiCw apparently improved the intensive property of the products and the changing pattern were quantitatively analyzed; while little influence was observed on some other properties such as phase composition and thermal expansion coefficient. It means that SiCw can strengthen porous silicon carbide ceramics without weakening their thermal properties, which is particularly important because of its application in the field of high temperature fluid filtration. Incorporated SiCw is supposed to work in accordance with some toughening mechanism such as load transferring and matrix prestressing. Microstructure, pore evaluation and weight loss rate during carbonation and sintering were also noted to describe the procedure better.
Preparation and Properties of In Situ Formed YAG Bonded Porous SiC Ceramics
Authors: Li Shi Bin , Song Jie Guang , Ru Hong Ying
Published: March 2014

Yttrium aluminium garnet (YAG) possesses many good properties, and usually uesd as sintering additives for silicon carbide ceramics. The YAG precursor solution was preformed by the coprecipitation process, then 8wt% prepared precursor solution was added and uesed as binder for samples' green bodies dry mould pressing. The dried pressed samples were directly sintered at 1850¡æ under vaccum atmosphere, and the precursor Al2O3-Y2O3 could be formed YAG during sintering process. The oxidation resistance property was performed at 1500¡æ in air. Bulk density and porosity were about 2.42g/cm3 and 24.98% respectively, and three-point bonding strength was up to 90MPa. Phase composition of sintered specimen was determined by X-ray diffraction and fracture morphology was detected by scanning electron microscope (SEM). The results showed that the as-fabricated porous SiC ceramics exhlibted excellent oxidation resistance abilities, its oxidation resistance improvement was benefited from silicon carbide particle coated with a compact YAG layer. The relationship between microstructure and properties was analyzed, and the finally formed phase composition was discussed.
Studying SiC/SiC Composites by X-Ray Tomography
Authors: Zhou Xin Gui , Zhao Shuang , Mummery Paul , Marrow James
Published: March 2014

Continuous SiC fiber reinforced SiC matrix composites (SiC/SiC) have been studied and developed for high temperature applications and nuclear applications. In this study, SiC/SiC composites were fabricated via polymer impregnation and pyrolysis (PIP) process and studied by X-ray tomography. The SiC/SiC composites were first scanned using a Metris X-tek 320 kV source at the Henry Moseley X-ray Imaging Facility at the University of Manchester, the closed porosities were investigated after three dimensional (3D) imaging of the samples. Furthermore, high-resolution synchrotron X-ray tomography was applied to the SiC/SiC composite at Diamond Light Source. Digital volume correlation was employed for Hertzian indentation testing of the SiC/SiC composite, quantifying damage by measurement of the displacement fields within the material. A Cellular Automata integrated with Finite Elements (CAFE) method was developed to account for the effect of microstructure on the fracture behavior of the SiC/SiC composite. Graded microstructures, textures and multiple phases were simulated and a mesh-free framework was developed to compute the damage development through the microstructure. The results indicated that we could study the development of discontinuous cracking and damage coalescence, and its sensitivity to microstructure with this method.
Honeycomb Sandwich Structure of Cf/SiC Ceramic Matrix Composites Prepared by PIP-CVI
Authors: Huang Xiao Ting , Chen Shu Guang , Sun Hao Ran , Chen Yu Feng , Liang Hai Long , Huo Yan Li , Wang Chun Peng , Hu Chuan Qi
Published: March 2014

continuous carbon fiber reinforced silicon carbide (Cf/SiC) ceramic matrix composites were prepared by precursor infiltration pyrolysis and chemical vapor infiltration (PIP-CVI process), in which the honeycomb sandwich structure preforms were fabricated by the three dimensional braid method. In this paper, the microstructure and the bending strength were observed and analyzed by SEM and three point bending method. The results of the study show that: The Cf/SiC ceramic matrix composites, which were lightweight and high strength, were prepared by that technique. The composite samples have a fiber volume fraction of 20%, a density of 0.38 g/cm3 and a flexural strength of 3.81 MPa. The honeycomb sandwich fiber reinforced ceramic matrix composite with a light weight, corrosion resistance and excellent physical and mechanical properties is a kind of structure and functional ceramic materials, which can realize the structure and the requirement of heat integration.
Application Study of Cf/SiC Composites Screw
Authors: Wang Yan Yan , Wang Wei Wei , Zhou Chang Ling , Wang Chong Hai , Liu Rui Xiang
Published: March 2014

Cf/SiC composites were fabricated by chemical vapor infiltration with CH3SiCl3 as precursor and H2 as carrier gas. The carbon preform was noodled by continuous carbon fiber and network tires layer. The screws were processed with Cf/SiC composites by diamond tool. The mechanical properties of screws were studied in this paper. Results show that the tensile and double shear strength reach separately 128.15 Mpa and 58Mpa. The microstructure of fracture surfaces from tensile and shear test were analysized.
Synthesis and Analysis of Carbide-Derived Carbon from TiC by Chlorination
Authors: Jia Jin , Zhu Yuan Yuan , Zhang Ya Fei , Chen Ruo Yu , Xing Bao Lin , Zhou Ai Guo
Published: March 2014

Carbide-derived carbons (CDCs) are produced from carbides by removing non-carbon elements in the process of selective etching. In this paper, CDC was prepared from TiC by chlorination at the temperature range of 600~1100°C. In the chlorinating process, carbide-derived carbon with different microstructure was obtained by controlling the reaction temperature. The structures of CDC were revealed with X-ray diffraction and Raman spectroscopy. The morphologies of CDC were analyzed by scanning electron microscope. From X-ray diffraction analysis, the CDC obtained from TiC in this experiment mainly consisted of amorphous carbon. Basing on scanning electron microscopy, carbide-derived carbon from TiC maintained the shape and size of TiC particles. Keywords: Carbide-derived carbons; chlorination; TiC
Microstructure and Properties of MoSi2-RSiC Composites Prepared by PIP and MoSi2-Si-Al Alloy Melting Infiltration Composite Process
Authors: Gao Peng Zhao , Zhang Xiao Liang , Liu Jing Xiong , Huang Shi Ting , Xie Wen , Xiao Han Ning
Published: March 2014

The combination of phenolic resin (PF) impregnation-pyrolysis (PIP) and MoSi2-Si-Al alloy activated melting infiltration (AAMI) combination process were used to prepare MoSi2-RSiC composites, in which the RSiC works as a matrix. Influence of infiltrated temperatures on the composition, microstructure, mechanical and electrical properties of the composites were studied by XRD, SEM, mechanical test et. al.. The results showed that an almost fully dense MoSi2-RSiC composite with 3-D interpenetrated network structure was obtained, the compositions of it were mainly SiC, MoSi2 , Mo (Si,Al)2, and small amount of residual Si. With the increase of infiltrated temperatures, the flexural strength of the composites increased first and then decreased, it reached 171.40MPa when infiltrated at 1800°C, which was 107.63% higher than that of RSiC matrix. The fracture properties of the composites exhibited a typical brittle rupture. The composites possessed a volume resistivity of 2.90×10-3 Ω·cm when infiltrated temperature equaled to 1900°C, which was nearly four order of magnitude lower than that of RSiC.
Synthesis and Decomposition of Ti3SiC2 under 1-5GPa at 1400°C
Authors: Zhu Yuan Yuan , Li Shang Sheng , Li Liang , Zhou Ai Guo
Published: March 2014

Ternary carbide Ti3SiC2 is a good binder to make superhard composites with diamonds or cubic boron nitride. Superhard composites are normally made at high temperature and under high pressure around 5 GPa to avoid the phase transformation of diamonds or cubic boron nitride. This paper researched the synthesis of Ti3SiC2 from the powders of Ti, Si, and graphite by a cubic presser under 1 GPa to 4 GPa at 1400°C. The decomposition of Ti3SiC2 under 5GPa at 1400°C was also researched. From X-ray diffraction (XRD) and scanning electron microscopy (SEM) results, Ti3SiC2 was synthesized in 30 min under 1 GPa at 1400°C. The impurities were TiSi2, Ti5Si3Cx, and TiC. As the pressure increased from 1GPa to 4GPa, less Ti3SiC2 more TiSi2 was synthesized. Therefore, high presser > 1GPa is unfavorable for the synthesis of Ti3SiC2. After treated under 5GPa at 1400°C, pure Ti3SiC2 was decomposed.
Synthesis and Characterization of Ti3SiC2 Matrix Multiphase Ceramic
Authors: Li Jun Shou , Li Su , Zhao Fang , Wang Ming Yuan
Published: March 2014

Titanium powder, silicon powder and carbon powder were used for the preparation of Ti3SiC2 matrix multiphase ceramic by self-propagating high temperature synthesis method (SHS) in air condition. The product was examined by XRD for qualitative and quantitative analysis, SEM for morphology analysis and infrared spectroscopy for transmittance analysis. It was shown in the research that product which was with titanium powder, silicon powder, and carbon powder as raw material was consist of three phases, Ti3SiC2 (76.6 wt%), TiC (21.2 wt%) and TiSi2 (2.2 wt%). TiC phase and TiSi2 phase distributed on the Ti3SiC2 phase matrix of the multiphase ceramic in the form of particles. Ti3SiC2 matrix multiphase ceramic which was with titanium powder, silicon powder, boron carbide powder and carbon powder as the raw material was also consist of three phases, Ti3SiC2, TiC and TiB2. The infrared transmittance in the wave numbers of 1500-4000 cm-1 is less than 15 %. The infrared transmittance of the product with a certain additive in the wave numbers of 600-4000 cm-1 can be dropped below 10 %. Ti3SiC2 matrix multiphase ceramic may be a new high radiation infrared material, which has high temperature resistance, wear resistance and wide band.
Friction and Wear of Ti3SiC2-Ag/Inconel 718 Tribo-Pair under a Hemisphere-on-Disk Contact
Authors: Zeng Jun Ling , Hai Wan Xiu , Meng Jun Hu , Lu Jin Jun
Published: March 2014

Room temperature friction and wear of Ti3SiC2-Ag sliding against Inconel 718 with a hemisphere-on-disc configuration were investigated in air. The effects of Ag content and TiAlN coating on Inconel 718 substrate were also included. Ti3SiC2/Inconel 718 tribo-pair showed high friction coefficient (0.6) and severe wear due to pullout of Ti3SiC2 grains was observed at a sliding speed of 1 m/s. Ti3SiC2-Ag composites had better tribological behavior than that of monolithic Ti3SiC2 in sliding against Inconel 718. At a sliding speed of 0.01 m/s, Ti3SiC2-Ag/Inconel 718 tribo-pairs exhibited moderate friction coefficient (0.32-0.4). At a sliding speed of 1 m/s, severe wear was not observed for Ti3SiC2-15vol.%Ag and Ti3SiC2-20vol.%Ag composites although the tribo-layer was not rich in Ag. When Ti3SiC2-Ag composites mated with TiAlN coating on Inconel 718 substrate, moderate friction coefficient (0.29-0.36) and low wear rate (10-6 mm3N-1m-1) were obtained at 0.01 m/s. A transition from mild wear to severe wear of Ti3SiC2-Ag composites at 0.1 m/s can be attributed to the ploughing effect by hard asperities on TiAlN coating.
Synthesis and Characterization of WO3/S Core/Shell Nanoparticles by Thermal Evaporation
Authors: Qian Jing Wen , Peng Zhi Jian , Wu Dian Zhong , Fu Xiu Li
Published: March 2014

WO3 has been widely applied in many fields such as electrochromic window, photocatalyst, and gas-senor. In this paper, WO3/S core/shell nanoparticles were synthesized in high density and large scale on silicon substrates via simple thermal evaporation of WO3 and S powders at 950 °C in a tube furnace. The morphology, composition and structure of the nanoparticles were characterized by scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, and energy dispersive X-ray spectroscopy. The results indicate that the nano-particles have a uniform morphology with a diameter in the range of 150-250 nm and well crystalline structure. The growth mechanism of the nanoparticles was also proposed.
Variation of Surface Roughness of Ti3SiC2 Disk during Polishing in Water and Alcohols
Authors: Hai Wan Xiu , Zeng Jun Ling , Meng Jun Hu , Lu Jin Jun
Published: March 2014

The surface polishing of Ti3SiC2 disk in fluids (water, ethanol, propanol, glycol, and glycerol) is conducted on a Buehler grinder/polisher and evaluated using surface roughness. Using Buehler automatic grinder/polisher, the Ti3SiC2 disks are grinded and polished in the as-mentioned lubricants by grinding disk of diamond with sizes of 45 μm to 3 μm. The surface roughnesses of Ti3SiC2 disks at each stage are measured by 3D surface profiler. The results show that the lowest surface roughness (Ra) of Ti3SiC2 disk obtained by mechanical polishing is 0.04 μm. The optimum polishing process of Ti3SiC2 disk is as follows: using water as lubricant, at a load of 5 N, for steps 1 to 4, the Ti3SiC2 and grinding disk rotates comparatively and the sizes of diamond particles on the abrasive disk are 45, 15, 9, and 3 μm, respectively. For step 5, the abrasive disk is woven cloth with no diamond particles. The duration of each step is 5 min. Using the same polishing process, the surface roughness of Ti3SiC2 disk by direct hot pressing is lower than that by in situ reactive hot pressing. Using the same polishing process but different lubricants, the surface roughness of the Ti3SiC2 disks increases in the order of water, ethanol, propanol, glycol, and glycerol. In water, the surface roughness of Ti3SiC2 disk decreases with the increasing quantity of water and polishing duration.
Tribological Properties of Ti3SnC2/Cu Composite
Authors: Zhan Zai Ji , Zhang Dan Dan , Guo Chang Hong , Chai Wei
Published: March 2014

In this study, 5 wt. % Ti3SnC2/Cu composite was synthesized by hot pressed sintering, and its tribological properties against AISI52100 steel balls were investigated using a ball-on-disk wear tester. The effects of sliding speeds and applied loads on the tribological behavior of Ti3SnC2/Cu were studied. The results showed the wear rate of Ti3SnC2/Cu composite increased with the increase of applied load and decreased with increase of sliding speed. The main tribological mechanisms of Ti3SnC2/Cu were abrasive wear and slightly oxidative wear. The friction coefficient of Ti3SnC2/Cu composite was stable and much lower than that of Cu at the same conditions. The loads were effectively born by the Ti3SnC2particles and the wear resistance of the matrix was obviously improved.
First Principles Calculations of the Relative Stability, Structure and Electronic Properties of Two Dimensional Metal Carbides and Nitrides
Authors: Sun Dan Dan , Hu Qian Ku , Chen Jin Feng , Zhou Ai Guo
Published: March 2014

Recently, a number of graphene-like early transition metal carbides and nitrides named as MXenes were fabricated by exfoliating MAX phases in hydrofluoric acid at room temperature. From experiments results and theory calculations, MXenes are promising anode materials in batteries as well as in metal-ion capacitors. To the best of our knowledge, experimental or calculated evidence has been supported the existence of more than 70 MAX phases members. Therefore, many counterparts MXene may be exist. Herein, employing density functional theory (DFT) computations, we have systematically examined the relative stability, structure and electronic properties of a series of two-dimensional metal carbides and nitrides including M2C (M=Sc, Ti, V, Cr, Zr, Nb, Hf, Mo and Ta), M2N (M=Ti, V, Cr, Zr, Hf), M3C2(M=Ti, V, Nb, Ta), Ti3N2, M4C3(M=Ti, V, Nb, Ta) and Ti4N3. The results demonstrate that all MXenes are metallic and have the similarly electronic structure with bulk transition metal carbides and nitrides, indicating that MXene may have superior catalysis and adsorption instead of expensive pure transition metal.
Preparation of 10B Enriched B4C Ceramics by Pressureless Sintering
Authors: Zhang Yu Jun , Tan Sha Li , Wei Ru Bin , Ai Shu He , Sun Hai Bin
Published: March 2014

Boron carbide is an attractive neutron absorbing material used both in Fast Breeder Reactors (FBR) and in Pressurised Water Reactors (PWR) owing to its very high absorption cross section for thermal neutrons, chemical stability and refractory character. In the present paper, 10B enriched B4C ceramics are prepared by pressureless sintering at 19602160°C, under argon, using 10B boron carbide powder as raw material, 18 wt% phenolic resin as sintering aid. In the sintering temperature range, with the increasing of sintering temperature, both the relative density and flexural strength increase linearly, the average particle sizes increase from about 3μm at 1960°C to more than 30μm at 2160°C. The sample sintered at 1960°C has a 91.7% of relative density and 192 MPa of flexural strength and a homogeneous texture with 3-4μm particle size, which are enough for pellet application of reactors.
Surface Oxidation Behaviour of Cubic BN Powders
Authors: Yue Xin Yan , Zhang Yue , Wang Jian Jun , Wang Wei , Ru Hong Qiang
Published: March 2014

In order to improve the sinterability of the cBN, surface oxidation treatment was conducted to form a B2O3 film on the surface of the cBN powders. The cBN powders (d50 = 7.5 μm) were used as original powders. The heat treatment processes were 500, 800, 900, 950, 980 and 1000 °C holding for 30 minutes, respectively. The oxidation reactions which probably happened were calculated based on the thermodynamics. The experimental results showed that the oxidation starting temperature of cBN powders was higher than 800 °C. The higher the oxidation temperature, the greater the mass gain of the cBN powders.
Growth of AlN Films on Silicon Substrates by Radio Frequency Magnetron Sputtering
Authors: Huang Jian , Tang Ke , Yang Hui Min , Lin Mei Ai , Zhang Lei , Ren Bing , Xu Hai Tao , Wang Lin Jun
Published: March 2014

Polycrystalline aluminum nitride (AlN) films were deposited on Si (111) substrates by radio frequency (RF) magnetron sputtering method in an nitrogen (N2) + argon (Ar) gas mixture. The effect of the preparation conditions- sputtering pressure (p), sputtering power (w), gas mixture (Ar/N2) and post-deposition annealing treatment -on the properties of AlN films were investigated by means of X-ray diffraction (XRD). Highly c-axis oriented AlN films were obtained with optimized growth parameters: p=0.3Pa, w=400w and Ar/N2=2.
The Microemulsion Method for Preparing TiO2 Coated SiO2 Core-Shell Particles
Authors: Xie Jing , Mei Le Fu , Liao Li Bing , Lv Guo Cheng , Xia Zhi Guo , Du Gao Xiang
Published: March 2014

In this paper, the monodisperse TiO2 particles and TiO2 coated SiO2 core-shell particles were prepared by the method of microemulsion, and the phase and morphology of TiO2 and TiO2 coated SiO2 core-shell structure particles were analyzed by using X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). At the same time, the phase changes and morphology changes of the two different kinds of structural particles as the changes of sintering temperature were compared. The results show that when the TiO2 particles were prepared by the method of microemulsion, the content of anatase TiO2 decreased gradually and the rutile TiO2 increased gradually as the sintering temperature increases from 550 °C to 650 °C; the core-shell particles of TiO2 coated SiO2 prepared were anatase when the sintering temperature increases from 600 °C to 800 °C; all of the particles size were about 1μm, the monodispersity of the particles were optimal and the particles were coated evenly, smoothly. Keywords: TiO2; SiO2; core-shell structure
Effect of Surface Treatment and Resin Cement on Microtensile Bond Strength of Zirconia to Dentin
Authors: Feng Xiao Li , Liu Ruo Yu , Zhang Yan Li , Chen Liang Jiao , Zhang Yao Kun , Shao Long Quan
Published: March 2014

To evaluate the effect of three surface treatments and two resin cements on microtensile bond strength of zirconia to dentin. Sixty human molars were embedded in acrylic resin and sectioned 3 mm below the occlusal plane. Teeth specimens and sixty zirconia specimens were randomized into 3 groups according to the following surface treatments (n=20): no treatment (control), sandblasting and silane application (SB+SI), sandblasting then silica coating and silane application (SB+SC+SI). In each group, half of the ceramic-tooth assemblies were cemented with PanaviaTM F (Kurary Dental), the rest with RelyX Unicem (3M ESPE). All specimens were cut into microtensile sticks that were loaded in tension until failure. Data were analyzed using two-way ANOVA and Tukey’s HSD test (α=0.05). The SB+SC+SC group presented higher values than SB+SI and the control group (P<0.05). Bond strength in PanaviaTM F groups were significantly higher than those in RelyX Unicem regardless of the surface treatment (P<0.05). Data indicated that both surface treatment and resin cement have significant effects on bond strength of zirconia to dentin.
Influence of Different Thickness of Zirconia Core on the Flexural Strength of Bilayered Ceramics in Artificial Saliva
Authors: Zhang Yan Li , Liu Ruo Yu , Feng Xiao Li , Chen Liang Jiao , Zhang Yao Kun , Shao Long Quan
Published: March 2014

To study the effect of different core thickness on the flexural strength of zirconia and feldspathic ceramics. Bilayered zirconia-feldspathic samples of three commercial brands were made in three different thickness(n=10): 0.5 mm, 0.8 mm and 1.0 mm respectively. On zirconia core specimens of each thickness, feldspathic dentin porcelain was added to reach a total crown thickness of 2 mm. Samples were stored in artificial saliva with neutral pH for 10 days at 37°C. Flexural strength was conducted with 3-point bending test. Data were analyzed by one-way ANOVA, and multiple comparisons were performed using Student-Newman-Keuls test(α=0.05). The measurement of 1.0 mm group was higher than the other groups, and 0.5 mm group was the lowest(P＜0.05), regardless of any commercial brand. Commercial dental zirconia blocks had varied flexural strength, Zirkonzahn expressed highest value in any thickness group compared with the other materials. Moreover, the fracture mode of zirconia bilayered composites was different in this study, 0.5 mm and 0.8 mm groups exhibited higher number of fragments and appeared to delamination compared with 1.0 mm group. So we infer that the thickness of core can have an effect on the flexural strength of bilayered zirconia-feldspathic crown, as well as different kinds of materials.
Effect of Particle Size on Properties of Novel Thermal Insulation Materials Synthesized by Molten Salt Method
Authors: Zhang Xiao Jun , Ding Jun , Zhu Hong Xi , Deng Cheng Ji , Yuan Wen Jie
Published: March 2014

Novel heat insulation materials were synthesized by molten salt method by using natural forsterite and NaSO4 molten salt. The insulation materials which have light weight and small size pore were obtained by using different particle size (44 μm, 74 μm and 250 μm) natural forsterite and NaSO4 molten salt at 1000 °C-1150 °C for 10 h after treating by distilled water. The effects of particle size of forsterite on phase composition, sintering porperties, physical property and microstructure were studied. The results showed that the main pahse in all samples was Mg2SiO4Fe2O3 and MgFe2O4 which indicate that the NaSO4 molten salt just play the role of Promoting particles sintering. The particle size of 74 μm have better bulk density and comprssive strength in all sample, at 1100 °C, the sample of bulk density is 1.54 g/cm3 and the apparent porosity is 0.498. In addition, the strength of the sample made of 44 μm forsterite materials was always higher than that used 74 μm forsterit, and was the lowest strength of sample used 250 μm forsterite.
Preparation of Utralight Alumina Lightweight Insulation Brick
Authors: Jia Liao , Li Yuan Bing , Li Shu Jing , Li Ya Wei , Sang Shao Bai
Published: March 2014

Alumina lightweight insulation bricks were prepared from alumina powders using foaming method. In this paper the influences of foam addition amount (600, 800, 1000, 1200ml/kg) on properties of Alumina lightweight insulation brick were discussed. The phase composition is analyzed by XRD and the microstructure is characterized by SEM. The results show that the bulk density of alumina lightweight insulation brick is 0.63g/cm3,cold compressive strength is 10.53MPa, linear change rate after firing is -4.5% and reheat linear change rate is -0.27%,which synthesized under 1000ml/kg foam amount after firing at 1550°C for 3h. The results indicate that the density of alumina lightweight insulation brick is reduced with the increase of foam addition amount, when the addition amount is more than 1000ml/kg, cold compressive strength decreased significantly and linear shrinkage increased obviously.
Study on Mechanical Property of Silica Glassfiber/Aluminum Phosphate Composite
Authors: Wang Chun Peng , Chen Shu Guang , Liang Hai Long , Huo Yan Li , Wang Guang Hai , Hu Chuan Qi , Huang Xiao Ting
Published: March 2014

Fiber reinforced and aluminum phosphate-based composite was studied in this experiment. The composite was prepared through the process of lamination- hot press- sintering, binding material and fillers. The proper mixture ratio of Al2O3:AlPO4:H2O was 10:2.88:2.88.The slurry with this ratio was proper to prepare the composite. It indicated that the mechanical property of composite was excellent which was prepared by the slurry with this ratio. In order to improve the Mechanical property of silica glass fiber / aluminum phosphate composite, Al2O3 powders were graded in the slurry. Mechanical properties of composites were improved evidently.
Controllable Thermal Expansion in In2-xFexMoxO12
Authors: Wu Mei Mei , Liu Yun Tao
Published: March 2014

The structural and thermal expansion properties of solid solutions In2-xFexMo3O12have been characterized using X-ray diffraction. The lattice parameters decrease linearly with increasing Fe content at room temperature. All compounds exhibit monoclinic structure at room temperature, and transform to orthorhombic phase upon heating. Monoclinic In2-xFexMo3O12(x= 0.3, 1.0 and 1.3) possess strong positive thermal expansion, while the linear thermal expansion coefficient of orthorhombic phase varies from zero/near-zero to positive with increasing Fe3+content.
Influence of Phase Composition on Dielectric Properties of Bismuth-Based Ceramics with Scheelite-Type Structure
Authors: Czekaj Dionizy , Lisińska-Czekaj Agata
Published: March 2014

Goal of the present research was to study dielectric properties of BiNbO4ceramics fabricated by solid state reaction route followed with pressureless sintering. The samples were fabricated from the mixture of oxides, viz. Nb2O5and Bi2O3. Apart from stoichiometric amount an excess of 3%, 5% and 10% by mole of Bi2O3was used. It was found that an excess amount of Bi2O3oxide caused formation of Bi5Nb3O15minor phase in amount of 9wt%, 18wt% and 25wt%, respectively. The dielectric properties were studied by impedance spectroscopy within the frequency rangeν=20Hz1MHz and temperature rangeT=RT550°C. It was found that the presence of the minor phase in amount of 18wt% caused a decrease in dielectric losses of the material under studies.
Dielectric Properties and Microstructure of Y-Al-Ga-Si Co-Doped Barium Titanate Ceramics
Authors: Wang Min Jia , Zhang Qi Long , Zhao Xin Hui , Yang Hui
Published: March 2014

Multilayer ceramic capacitors (MLCC) are important functional components of electronic information technology. The development of AC MLCC requires low dielectric loss and high AC breakdown voltage. In this paper, Y-Al-Ga-Si co-doped barium titanate ceramics were prepared by conventional solid state method. Microstructures, surface morphology and dielectric properties were investigated by X-ray diffraction, SEM, and LCR analyzer, respectively. Y3+ entered into the lattice of BaTiO3, replaced A-sites and B-sites, suppressed grain growth effectively, and made crystal structure change from tetragonal to pseudo-cubic, which reduced dielectric loss and lowered the Curie peak. The sintering characteristic and permittivity can be improved by the incorporation of Al and Ga. BaTiO3 -0.06Y2O3 - 0.02Ga2O3 -0.01Al2O3 -0.01SiO2 ceramics sintered at 1380°C achieved good dielectric properties: εr= ~2223, tanδ =~1.1% (at 1kHz), ΔC/C25 <~15.26% (from 55°C to 150°C).