bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Performs Structure on Liquid Molding SiO2f/ SiO2f Composites
Authors: Wei Qi Hong , Wang Chong Hai , Wang Hong Sheng , Li Ling , Liao Rong , Dong Bo
Published: March 2014

2.5D and needle-punched performs of silica fiber were studied in the paper,pore structures and slurry diffusion were studied. Mechanical properties of two prefoms composites were different,and influence of pore structures and volume fraction on performance of composites were researched.The results indicated that 2.5D composites had obvious advantages on tensile properties.But needle-punched composites had isotropic properties in their plane ,that were better than 2.5D composites which had anisotropic properties. Needle-punched composites had obvious advantages on compression properties,which overcomed compression strength of was weaker 2.5D composites in some direction.
Synthesis and Microstructure of Porous Ceramics Made from Industrial Solid Residues
Authors: Di Yong Jiang , Jia Bi , Wang Jun
Published: March 2014

Industrial solid residues and poor quality clay as main raw material were used to prepare porous ceramic balls by ceramics process with coal and wood powder as pore-forming additive to improve the porosity of the ceramics ball. Effect of pore-forming additive on the properties of ceramic ball was investigated. The phase composition and section morphology of the ceramics balls was characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The apparent porosity and crushing force of the ceramic balls were tested by Archimedes hydrostatic weighing method and crushing strength tester respectively. The tested results showed that the apparent porosity of the porous ceramic balls mainly influenced by species and addition amount of the pore-forming additive. The apparent porosity increases with the adding of the pore-forming additive. The apparent porosity and crushing force of the optimized porous ceramic balls was 49.68% and 1.17 kN respectively, which is a potential candidate used for waste water filtration.
Effect of Pore-Forming Agent on Porous Mullite Ceramics from Pyrolysis of Alumina Powders Filled Silicone Resin
Authors: Ma Qing Song , Peng Hai Jun , Duan Li Qun , Chen Zhao Hui
Published: March 2014

Mesoporous and macroporous mullite ceramics were fabricated from pyrolysis of alumina nanopowders filled silicone resin. The effect of pore-forming agent (carbon nanopowders) on the pore structure and mechanical property of the porous mullite ceramics were investigated. By varying the carbon content, the porosity and flexural strength of the obtained ceramics could be easily tuned. Both of the open porosity and average pore size of the obtained samples increased at elevated carbon content, and reached the maximum value of 61.0%, 225.5 nm respectively when the carbon content got the highest point (40 Vol.%). The flexural strength of nanoporous mullite ceramics changed almost with an opposite trend of open porosity, with the biggest value of 36 MPa when 10 Vol.% carbon was adopted. The microstructure of porous mullite ceramics consists of dense region and loose region when the added carbon content was at relatively low level. However, the dense area gradually disappeared with the increasing of carbon content.
Effects of Single-Substitution and Co-Substitution on BiFeO3 Nanoparticles
Authors: Li Xing Ao , Mao Wei Wei , Wang Xing Fu , Wang Xi Wang , Li Yong Tao , Yang Tao , Yang Jian Ping
Published: March 2014

Multiferroic BiFeO3 nanoparticles have been prepared by solgel method. The effects of single-substituted and co-substituted on the structures and magnetism of all the samples are investigated systematically. X-ray diffraction and Raman spectra results confirm that the samples simulate from a distorted rhombohedral structure to a cubic structure. Surface morphology of the samples were examined by scanning electron microscope (SEM). The ferroelectric and magnetic hysteresis loops shows coexistence of magnetism and ferroelectricity in the room temperature. The structure transition may be the main cause for the origin of improved magnetic and ferroelectric properties.
Influence of Sintering Temperature on Phase Behavior of Products from Rutile and Quartz by Aluminothermic Reduction Nitridation
Authors: Zhu Ling , Chen Kai , Huang Zhao Hui , Fang Ming Hao , Liu Yan Gai , Wu Xiao Wen , Yang De Xin , Liu Bao Lin
Published: March 2014

The effects of sintering temperatures on phase behavior of products from rutile and quartz by aluminothermic reduction nitridation (ARN) were investigated in this study. The crystalline phase and morphology of the samples were determined by X-ray diffraction (XRD), scanning electron microscopy (SEM), respectively. As the temperature was 1200 oC, the phases were corundum, TiN, Si and a small amount of cristobalite. Mullite were initially observed when it reached 1300 oC. A small amount of Si3Al3O3N5 was detected when the temperature rose to 1400 oC. More corundum, TiN and Si3Al3O3N5 were obtained at 1500 oC. The quantities of TiN and corundum increased slightly at 1550 oC while Si3Al3O3N5 reduced. In addition, the microstructure of well-developed β-Sialon crystals was long columnar and the TiN particles distributed in the composites.
Fabrication of Yb:YAG Transparent Ceramics Using Stearate Melting Derived Ultrafine Powders
Authors: Li Jin Sheng , Sun Xu Dong , Liu Shao Hong , Huo Di , Li Xiao Dong , Li Ji Guang , Zhu Qi , Zhang Mu
Published: March 2014

Yb rare earth doped YAG ultrafine particles were synthesized by the stearate melting method using yttrium stearate, ytterbium stearate and aluminum tristearate as starting materials. The phase formation of Yb:YAG, the properties and the sintering activity of the powders were investigated by means of XRD, SEM, dilatometry and vacuum sintering. The results show that pure Yb:YAG nanopowders can be obtained by calcining the co-melted precursor at a relatively low temperature of 800 °C for 4 h. The powders calcined at 1000°C have better sintering activity than the powders calcined at other temperatures. For the Yb:YAG powders doping with 0.5% TEOS, the compact can be sintered to 99.2% of the theoretical density at 1600 °C and 99.7% at 1700 °C. The transparent Yb:YAG ceramics obtained by vacuum sintering at 1700 °C for 5 h exhibit a pore-free and uniform microstructure.
Preparation and Properties of B4C/Graphite Neutron Absorption Ball
Authors: Guo Ting , Wang Chen , Dong Li Min , Liang Tong Xiang
Published: March 2014

The neutron absorption ball for High Temperature Gascooled Reactor contains 25wt% B4C, dispersed in graphite matrix. Good compressive strength, wear resistance and thermal shock resistance are essential to absorption ball. B4C and graphite were selected as the filler, and phenolic resin was chosen as the binder. A certain amount of phenolic resin and silane coupling agent were used for the surface preparation of inorganic aggregate. Results showed that the residual weights of pretreating powders after carbonizing were higher than that of powders without pretreatment. The compressive strength of the neutron absorption ball was studied. Dipping can effectively improve the strength. Within a certain range, the compressive strength increased with the increase of dipping times. Compared with the thermoplastic resin, higher compressive strength sample was obtained when the thermosetting resin was used as impregnant. The average crushing force of the absorption ball prepared by the optimal process was up to 612 N.
Preparation of Anti-Static Ceramics by Fe-Infiltration on Sintered Zirconia Body
Authors: Yang Xian Feng , Li Yong , Xu Xie Wen , Xie Zhi Peng
Published: March 2014

Anti-static materials are widely used in the fields of textile, petrochemical processing, aerospace and electronics. An innovative processing method for fabricating anti-static ceramics has been developed based on Fe-infiltration on the sintered zirconia body. The sintered zirconia ceramics infiltrated by metal Fe in the inner atmosphere showed both perfect anti-resistive and mechanical properties. In this study, infiltration temperature and time was optimized to control the surface resistivity. It was shown that the lower surface resistivity could be obtained at higher infiltration temperature and longer infiltration time. However, the surface hardness was decreased. The surface resistivity reached 5.6×107Ω/ at 1300°C for 12 hours. The phase transformation and microstructure changes were characterized by XRD and SEM. The existence state of Fe was analyzed by EDS.
Growth and Characterization of LaFeO3 Crystals
Authors: Liu Wei Liang , Zeng Xiao Jun , Liu Shuo Qi , Zhu Yan Feng , Wu An Hua
Published: March 2014

The LaFeO3 polycrystalline feed rod was prepared by sintering La2O3 and Fe2O3 powder at 1400 °C for 24 h. The LaFeO3 crystal was grown by the floating zone method. The crystal preferred to crystallize along <100> direction. The X-ray rocking curve of the (100) crystal plane has a FWHM of 26 arcsec, confirming the high crystal quality of the sample. Some voids were observed on the polished surface. The thermal properties of LaFeO3 crystal during 298~773 K were tested. The specific heat of LaFeO3 crystal variation range was 0.58~0.76 J/(g·K), The thermal diffusivity of LaFeO3 crystal variation range was 3.47~0.85 mm2/s, The thermal conductivity of LaFeO3 crystal variation range was 13.10~4.21 W/(m·K).
Wetting Behaviors of Nickel-Based Alloys on Sintered Silicon Carbide Ceramics
Authors: Zhang Hui , Liu Yan , Yan Yong Jie , Liang Han Qin , Liu Xue Jian , Huang Zheng Ren
Published: March 2014

Wetting behaviors of pure nickel and nickel-based alloys on sintered silicon carbide ceramics and their interfacial microstructures were investigated in this presentation. The nickel-based alloys were mainly the commercial nickel-molybdenum-chromium products. The wetting and spreading properties were observed by a real-time thermal optical measurement system under flowing argon-5%hydrogen atmosphere. As temperature increased, the pure nickel cylinder sample had few changes before 1356°C except for the thermal expansion in size and changed to liquid drop-shape when the temperature reached 1366°C. The contact angle was about 90o. And nickel could not contact sintered silicon carbide ceramics well. However, the introduction of molybdenum and/or chromium in the pure nickel was good for the wetting properties of pure nickel on sintered silicon carbide ceramics. The contact angles of nickel-based alloys (B-1, C-1 and C-2) on sintered silicon carbide ceramics after holding 15min at 1400°C were 25o, 12.5o, 11.5o, respectively. And they hardly reduced as temperature increased. The SEM images indicated that the interfacial microstructures of B-1 and C-1 on sintered silicon carbide ceramic substrates were uniform and the dissolved interface near silicon carbide ceramics indicated that they had a good bonding. At the same time, the reciprocal diffusion was clear in the intermediate layer. Besides that, the introduction of chromium was supposed to reduce the diffusion rate of molybdenum from the alloy to the ceramic substrate.
Effect of Heat-Treatment in Ar Atmosphere on Pore Structure of Carbonaceous Materials from Polysiloxane
Authors: Duan Li Qun , Zhang Chen Chen , Ma Qing Song , Chen Zhao Hui
Published: March 2014

Nanoporous carbonaceous materials derived from polysiloxane were first prepared by pyrolysis at 1300°C followed with hydrofluoric acid (HF) etching treatment. Their thermal stability of pore structure in inert condition was investigated in this paper by nitrogen adsorption technique in detail. The specific surface area (SSA) and pore volume (total pore volume, micropore volume, mesopore volume) decreased continually in the heat-treatment temperature range of 1000~1400°C. The average pore size almost kept the same with the raw sample. However, when the temperature exceeded 1400°C, the micropore interconnection began transforming to mesopore structure, which led to the decline of SSA and the increase of average pore size. Furthermore, the pore size distributions (PSDs) curves showed that heat-treatment had an advantage on the transition process of pore structure from disorder to regularity to some extent when heat-treated in the range 1000~1400°C for the most possible reason of relief of residue strain in the carbonaceous materials.
Surface Functionalization of Ordered Mesoporous Carbon by Immobilization of Diamine for Cobalt-Ion Adsorption
Authors: Geng Shu Ya , Dong Li Min , Wang Chen , Liang Tong Xiang
Published: March 2014

Highly ordered mesoporous carbon (CMK-3) was fabricated for the adsorption of cobalt from aqueous solutions. With the high surface area of1112.7m2/g and pore size of 17.2 nm, its abundant mesopores were benefit for providing channels for liquid propagate. In order to improve the adsorption properties,CMK-3 was modified by hydroxylation and amination. Fourier transform infrared (FTIR) spectroscopy can be seen that the amino group was successfully grafted onto the CMK-3 with highly ordered mesoporous structure. The functionalized ordered mesoporous carbon (CMK-3-EDA) ,CMK-3 and CMK-3-OX were used as absents for the adsorption of Co (II) from aqueous solution. The results showed that CMK-3-EDA were more twice effective in adsorption of Co (II) compared to CMK-3, which indicated that CMK-3-EDA had great potential for the adsorption of Co (II).
Synthesis of Mullite Using Low-Grade Bauxite and Coal Gangue
Authors: Zeng Chun Yan , Huang Zhao Hui , Fang Ming Hao , Liu Yan Gai
Published: March 2014

The total bauxite reserves of China are about 3.7 billion tons, however the principal and the first-class bauxite reserves account for only about 20%. A large number of coal gangue was accumulated on the surface of earth, which not only encroaches land but also pollutes the environment. In this study, low-grade bauxite with alumina content of 53.18 wt.% originating from Shanxi Yangquan and coal gangue with alumina content of 38.07 wt.% originating from Shanxi Datong were used to synthesize mullite materials. Bauxite and gangue were mixed by the ratio of 1 to 1. The ingredients were prepared according to the alumina content of 45.63 wt.% and 70 wt.%, by adding a certain amount of industrial alumina, respectively. The samples were sintered at 1350°C to 1600°C after being milled, dried and formed. The influence of alumina content and sintering temperature on the phase, microscopic morphology and properties of samples were discussed. The results show that, the main phases of the sample with the alumina content of 70 wt.% were mullite (more than 60 %) and corundum after being sintered for 4h at 1600 °C. The phenomenon of columnar mullite and granular corundum staggering had been observed. The bulk density and the bending strength of sample is 3.21 g/cm3and of 220.73 MPa respectively.
Influence of Adding ZrO2 on the Properties of La2Zr2O7 Ceramic
Authors: Zhu Shi Zhen , Chen Long , Xu Qiang , Liu Ling , Ma Zhuang
Published: March 2014

La2Zr2O7 as the thermal barrier coating material draws more and more attention because of its greater thermal physical properties than YSZ, while its further application is restricted by its poor mechanical properties. In this paper, certain ZrO2 is added into the La2Zr2O7 ceramics in order to improve its mechanical properties. La2Zr2O7 ceramic superfine powder was synthesized by the co-precipitation method and samples of La2Zr2O7-xZrO2(x=0, 10%, 20%, 30%)were prepared by pressureless sintering process. The microstructure and properties of the samples were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), three-point bend tests, SENB, laser impulse thermal conductivity instrument and high-temperature expansion instrument. Owing to the partial solid solubility in the La2Zr2O7-xZrO2 ceramics, ZrO2 exists in the form of m-ZrO2 and t-ZrO2. With the addition of ZrO2, the mechanical properties of La2Zr2O7-xZrO2 ceramics first increase, then decrease. When the addition amount of ZrO2 reaches 20%, the fracture toughness comes to the greatest value 2.41 MPa·m1/2. When the addition amount of ZrO2 reaches 10%, the bending strength comes to the greatest value 202.4 MPa. The thermal conductivity of the La2Zr2O7-xZrO2 ceramics is lower than YSZ. The thermal conductivity of the La2Zr2O7-xZrO2 ceramic decrease at 1400 °C as the addition amount of ZrO2 increases, resulting from the higher intrinsic thermal conductivity of ZrO2 than that of La2Zr2O7. The thermal expansion coefficient of the La2Zr2O7-xZrO2 ceramics decreases slowly after about 350 °C and decrease rapidly at about 1000 °C, and then increase rapidly due to the transformation of m-ZrO2 to t-ZrO2.
Preparation and Mechanical Properties of ReAl11O18 Ceramics
Authors: Zhang Jun Dong , Fang Ming Hao , Huang Zhao Hui , Liu Yan Gai , Min Xin , Wu Xiao Wen
Published: March 2014

In this paper, plate-like ReAl11O18 (Re = La, Pr, Nd) toughened ceramics were prepared by pressureless sintering at 1650 °C for 5 h in air. The bulk densities of the sintered samples were between 4.7 to 5.3g/cm3. The mechanical properties of the ReAl11O18 ceramics were studied systematically at room temperature. The flexure strength and fracture toughness of ReAl11O18 ceramics were 97.5 to 102.7 Mpa and 3.8 to 4.2Mpa.m1/2. The results show that: The optimal temperature to synthesis ReAl11O18 ceramics was 1650 °C; The flexural strength and fracture toughness of the ReAl11O18 ceramics increase with the increasing of its bulk density.
Effect of Rare-Earth Oxides Additive on Liquid Phase Sintered SiC
Authors: Chen Yu Hong , Jiang Liang , Zhang Li Li , Huang Zhen Kun , Wu Lan Er
Published: March 2014

The densification of α-SiC occurred by liquid-phase sintering mechanism with AlN-RE2O3(RE=Nd, Gd, Y, Lu) was studied. The total additive content was fixed at 15 wt%. Cold isostatically pressed samples were sintered at 1800-1950 °C under N2atmosphere for 1 h. The linear shrinkage and weight loss of the samples were about 17-20% and 2-5%, respectively. The mechanical properties and microstructure of sintered samples were investigated. The experimental results showed that the fracture toughness of samples was 6-8 MPa·m1/2, the hardness was in the range of 18-21 GPa and the bending strength was in the range of 400-500 MPa. It was found that a decrease in the cationic radius of the rare-earth oxides was accompanied by an increase in hardness and flexural strength of the SiC ceramics, whereas the fracture toughness was improved by incorporating rare-earth oxides of larger cationic radius. The morphology (SEM) of sintered sample showed a fine grained microstructure with equiaxed grains. Fracture mode was intergranular fracture.
Oxidation Resistant Behaviour of Mullite/Yttrium Silicate Multilayer Coating for C/SiC Composites at 1500°C
Authors: Zhao Shuang , Zhou Xin Gui , Wang Hong Lei
Published: March 2014

Continuous carbon fibre reinforced silicon carbide (C/SiC) composites were fabricated by precursor infiltration and pyrolysis (PIP) process, a mullite/yttrium silicate multilayer coating was prepared by plasma spray method as the oxidation protective coating. The efficiency of the coating against oxidation was characterized by means of heat treatment of the C/SiC composites at 1500 °C in static air for 1 hour. The results indicated that the weight loss of the coated composites was only 3.4 %, and the flexural strength of the composites retained 95.3 % of the original strength.
Processing and Properties of ZrB2-Cu Composites Sintered by Hot-Pressing Sintering
Authors: Shang Wei , Wang Hai Long , Zhao Shi Jing , Zhao Xiao Tong , Xu Hong Liang , Lu Hong Xia , Chen De Liang , Fan Bing Bing , Zhang Rui
Published: March 2014

ZrB2-Cu composite is a new electrical contact materials in the integration of high conductivity, high wear resistance and good mechanical strength. In this paper, ZrB2-Cu composites were prepared by hot-pressing sintering at 800~900 °C under a pressure of 20 MPa.The densification of ZrB2-Cu composites was improved by the addition of nickel using an electroless metal plating technique. X-ray diffraction and scan electron microscopy were used to analyze the phase and microstructure of ZrB2-Cu composites. The results showed that ZrB2-Cu composites with 60 vol % Cu which was sintered at 900 °C had a higher relative density, highest flexural strength of 381 MPa and higher hardness of 2.16 GPa(HV). ZrB2-Cu composites with 50 vol % Cu which was sintered at 900 °C had higher flexural strength of 297 MPa and the highest hardness of 2.66 GPa.
Effects of SiC on Oxidation Behavior of ZrB2-Based Composites with MoSi2 and SiC Additives
Authors: Guo Shu Qi
Published: March 2014

In this study, oxidation behavior of ZrB2-MoSi2-SiC composite was investigated in the hot-pressed 5-20 vol% SiC-containing ZrB2-20 vol% MoSi2-based composites which were exposed to dry air between 1100°C and 1500°C up to 10 hours. The effects of SiC additive on the oxidation behavior were assessed. Experimental results showed that the weight gain due to oxidation exposure in air increased with increasing exposure temperature and exposure time. Parabolic oxidation behavior was observed for all the compositions composites. On the other hand, the weight gain decreased with increasing amount of SiC added. The addition of SiC improved the oxidation resistance of the composites, and the improvement was enhanced with increasing amount of SiC added. In addition, X-ray diffraction was used to identify major crystalline phases present in both the as-received and the post-oxidized composites. The oxidized sample surface was characterized by scanning electron microscopy and energy-dispersive X-ray spectroscopy. The microstructure of the post-oxidized composites consisted of two characteristic regions: oxidized reactive region and unreactive bulk material region. Furthermore, the oxidized reactive region divided into an outermost dense silica-rich scale layer and oxidized reactive mixture layer. The improvement of the oxidation resistance due to the addition of SiC is associated with the presence of the thicker dense outermost scale layer which inhibited inward diffusion of oxygen through it.
Effects of Ball Milling Processing on Solidified TiC-TiB2 Composites Prepared by Combustion Synthesis in High Gravity Field
Authors: Zhao Zhong Min , Yin De Jun , Zhang Long , Wang Shuan Jie , Wang Min Quan
Published: March 2014

By combining ball milling processing with combustion synthesis in ultrahigh gravity field, the solidified TiC-TiB2 composite was achieved with fine-grained and ultrafine-grained microstructure. It is considered that taking balling milling processing to mechanically activate powder blend promotes thermal explosion to occur in ultrahigh gravity field by reducing ignition temperature, increases sharply the actual temperature of full-liquid product, thereby not only accelerating liquid-liquid separation of TiC-TiB2 liquid and Al2O3 droplets, but also refining the solidified microstructure by enhancing undercooling of TiC-TiB2 liquid, finally, brings about a series of dramatic improvements in densification and mechanical properties of the ceramic.
Laminated Composite of Solidified TiC-TiB2 Ceramic to 1Cr18Ni9Ti Stainless Steel Achieved by Combustion Synthesis in High-Gravity Field
Authors: Zhang Hao , Zhao Zhong Min , Zhang Long , Ding Ning , Ye Wei Min
Published: March 2014

By combining mechanical activation and combustion synthesis in ultrahigh gravity field, the laminated composite of TiB2based ceramic to stainless steel was achieved in continuously-graded composition and microstructure, and within the Fe-Cr based intermediate Ti-Fe enriched carbides and fine TiB2platelets decreased gradually in size and volume fraction from the ceramic to stainless steel. Because of the sequent presence of thermal explosion, the dissolution of the molten stainless steel to TiC-TiB2liquid, the formation of diffusion-controlled concentration gradient from the ceramic liquid to the alloy liquid, the rapid sequent solidification of the ceramic and the alloy, the laminated composite is achieved in multilevel, scale-span hybrid microstructure that the different-size, different-morphology Fe-Cr alloy phases alternate with TiB2platelets and irregular TiC grains in size from micrometer to micro-nanometer.
Microstructures and Properties of Solidified TiC-TiB2 Composites Prepared by Combustion Synthesis in Enhanced High-Gravity Field
Authors: Song Ya Lin , Zhao Zhong Min , Zhang Long , Song Yi Gang
Published: March 2014

By taking combustion synthesis to prepare a series of solidified TiC-TiB2composites under the increased high-gravity acceleration from 500g to 2500g, then in the near-full-density composite the ultrafine-grained microstructure with the matrix of TiB2platelets smaller than 1 μm in thickness was achieved, and all TiB2 platelets almost shared in the contributions of bridging and pullout to toughening ceramic, thereby presenting fracture toughness of 16.5 ± 1.0 MP · m0.5and flexural strength of 982 ± 20 MPa.
Microstructures and Crack Propagation in the Joint of Solidified TiC-TiB2 to Ti-6Al-4V Prepared by Reactive Fusion Bonding in Ultrahigh Gravity Field
Authors: Huang Xue Gang , Zhao Zhong Min , Zhang Long , Sun Lei
Published: March 2014

By taking combustion synthesis in ultrahigh gravity field to prepare solidified TiC-TiB2 composite ceramic, laminated composite of the ceramic to Ti-6Al-4V was achieved by fusion bonding and atomic inter-diffusion, and within the joint there formed the unique microstructure of multiscale (micrometer-micro/nanometer-nanometer) and multilevel characterized by size and distribution of TiB2 and TiB due to the presence of a series of metallurgical reaction including peritectic reaction of solidified and Ti liquid, direct growth of TiB solids from liquid Ti and subsequent eutectic reaction of TiB solids and liquid Ti. FEMSEM images of crack propagation paths at the joint showed despite the contribution from crack bridging of micro-nanometer TiB2 and TiB platelets to crack propagation resistance, residual stress toughening and subsequent crack pinning by micro-nanometer TiB2 ,TiB platelets and needle-like nanometer TiB grains as well as ductile phase toughening and bridging toughening by Ti metallic phases became the primary resistances to crack propagation, thereby presenting the delayed fracture behavior in the joint, so that shear fracture usually occurred at the solidified Ti alloy rather than the joint, and shear strength of 375 ± 55 MPa was achieved between the solidified ceramic and Ti alloy.
Preparation and Characterization of Reaction Sintering B4C/SiC Composite Ceramic
Authors: Sun Hai Bin , Zhang Yu Jun , Li Qi Song
Published: March 2014

High hardness, high strength, high fracture toughness and low density are required for novel bulletproof materials. B4C/SiC composite ceramic is one of the most potential candidates. In this study, B4C/SiC composite ceramic was prepared by reaction sintering. The influence of B4C content, species and content of carbon, sintering temperature on the mechanical properties of B4C/SiC composite ceramic were studied. A high performance B4C/SiC composite ceramic was sintered at 1750°C for 30 min. Phenolic resin and carbon black were both chosen as carbon sources, whose favorable contents were 10wt%, 5wt%, respectively. The density of sintered bodies reduces with B4C content increases. To some extent, fracture toughness, bending strength improve initially and then deteriorate with the increase of B4C content whose optimal amount is 30wt%. The optimal fracture toughness and bending strength of the B4C/SiC composite ceramic are 5.07MPa·m1/2 and 487MPa, respectively. Meanwhile, the Viker-hardness of the sintered body is 30.2GPa, the density is as low as 2.82g/cm3.
Evolution of Indentation Induced Cracks on WC Ceramic under Cavitation Loading in Water
Authors: Gong Xue , Han Jie Sheng , Lu Jin Jun , Wang Jian Rong , Meng Jun Hu
Published: March 2014

For engineering ceramics, cracks produced in preparation process, i.e. sintering and surface finishing, have a profound impact on the mechanical strength and wear. Under cavitation loading, the flaws on the surface and subsurface are preferentially eroded. In this paper, artificial cracks are introduced on WC ceramic by indentation of a Vickers indenter at a load of 10 kgf. Five positions on the cavitation eroded area are selected. The average length of the cracks is 71.6 mm. The cavitation erosion tests are terminated at 1, 3, and 5 min to reveal the evolution of cracks. A single pattern for the evolution of cracks is recognized. Two new cracks at the tip of indentation cracks first nucleate and then propagate (accompanied by pullout of grains). The angle between the two new cracks ranges from 30° to 45°. The evolution of adjunct two groups of cracks gives birth to local breakout finally. Steps which are provided limited resistance to breakout are observed. The nucleation and propagation of the four indentation cracks do not always occur simultaneously.
Phase Composition and Microstructure of Binderless WC-ZrC Cemented Carbides Fabricated by Spark Plasma Sintering
Authors: Ren Xiao Yong , Peng Zhi Jian , Rong Hui Yong , Peng Ying , Wang Cheng Biao , Fu Zhi Qiang , Qi Long Hao , Miao He Zhuo
Published: March 2014

Binderless WC-based cemented carbides with different fractions (0-9 wt.%) of ZrC nanopowder were fabricated through spark plasma sintering at 1600 °C under a uniaxial pressure of 50 MPa. The addition effect of ZrC nanopowder on the phase composition and microstructure of the fabricated materials were explored with the help of X-ray diffraction and scanning electron microscope. The results indicated that W2C phase was detected in the samples with 0-3 wt.% ZrC nanopowder, but with further increase in ZrC added fraction, ZrO2 phase instead of W2C phase was detected. The apparent density decreased gradually with the increase in added fraction of ZrC nanopowder, while the relative density increased initially and then decreased, reaching its maximum of about 98.2% when the added fraction of ZrC nanopowder was about 3 wt.%, indicating that appropriate added fraction of ZrC nanopowder can improve the densification of binderless WC cemented carbides. Without ZrC nanopowder, the coarsening and abnormal growth of WC grains were serious, resulting in many large prismatic WC grains in the samples. However, Such phenomena could be suppressed by adding ZrC nanopowder, resulting in much finer and more homogenous microstructure after 1-3 wt.% ZrC nanopowder was added. When the added fraction of ZrC nanopowder was higher than 3 wt.%, the agglomeration of ZrC nanopowder became more and more serious.
Preparation of SiCp/Al Functionally Gradient Composites
Authors: Ma Jian Jun , Chen Yu Hong , Wang Li Hui , Jiang Liang
Published: March 2014

In this study, functionally gradient aluminum reinforced by Silicon carbide particles (FGMSiCp/Al) composites are prepared by microwave sintering and pressureless sintering processing. The sintering behaviors, mechanical properties of composites were measured, and microstructure was observed by optical microscope and SEM. The results showed that the density of sintered samples which prepared by microwave sintering were better than that presureless sintering one. The highest density of sintered sample by microwave sintering reached 2.64 g/cm3, the relative density was 95.65%. Whatever preparing process, the mechanical properties of sintered samples were related to the temperature. The distribution of silicon carbide particles is uniform in the aluminum matrix, however, slight agglomeration can be observed. The interface between other layers is not obvious except interface between Al and 5% SiC/Al layer.
Synthesis of Coloured Dental Zirconia Ceramics and their Mechanical Behaviors
Authors: Li Jing , Liu Shi Ming , Lin Yuan Hua
Published: March 2014

The effects of Pr6O11and Er2O3dopants on microstructure and mechanical properties of zirconia ceramics were investigated. The phase composition and microstructure analysis indicate that samples are all tetragonal phase and grain size is about 50-100 nm. The relative density of zirconia ceramics was above 99.1%, linear shrinkage was nearly 20%, while Vickers hardness was over 12.5 GPa. Three-points bending strength was over 850 MPa which was slightly lower than that of the pure samples, and fracture toughness was above 4.9 MPa*m1/2. The results show that the dopants can be used to obtain the colored zirconia ceramic, and also have effects on its mechanical properties.
One-Step Approach for the Fabrication and Characterization of Hydroxyapatite/TiO2 Composite Ceramic Coatings by Micro-Arc Oxidation In Situ on the Surface of Pure Titanium
Authors: Shi Wu Chao , Dong Li Min , Li Qiang , Wang Chen , Liang Tong Xiang , Tian Jie Mo
Published: March 2014

The hydroxyapatite (HA)/ TiO2composite ceramic coatings were formed by micro-arc oxidation (MAO) on pure titanium in mixed electrolyte of calcium glycerophosphate and calcium acetate with DC pulse power. Microstructure, phase composition, porosity and thickness of the coatings were examined using SEM, XRD, Image-Pro Plus 6.0 Image analysis system and Eddy current thickness gauge. Results indicate that MAO coatings containing calcium and phosphorus were formed in situ on pure titanium surface. Pores formed by the discharge channels distribute uniformly on the coatings surface, and the inner layer is dense. The principal crystalline phases of the MAO coatings are anatase TiO2, rutile TiO2, HA, Ca3(PO4)2and matrix Ti. The interface is metallurgical bonding and the bonding strength is strong. And reaction time makes a greater influence than voltage in thickness and voltage makes a greater influence than time in porosity.
Color Reproduction and Shade Stability of Zirconia Ceramics
Authors: Liu Shi Ming , Liu Jing , Deng Xu Liang , Lin Yuan Hua , Liu Feng
Published: March 2014

The use of zirconia crown has attracted considerable attention due to its good mechanical and optimal biocompatility. The white color of zirconia does not allow for perfect aesthetic characteristics though. Colorized zirconia blocks with Pr6O11, Er2O3and Fe2O3gradient concentration and the shade stability were investigated. Chromatic values of the samples were presented in CIELab system, and the shade stability was evaluated by color comparison of samples in the same group. The value of L* from 68.2-84.0, a* from-1.8-5.9, and b* from 18.6-33.2 can be obtained. These values can be comparable to the Vita 3D master system. The E between the samples of every group was below 2.2. The results showed that by adding combined oxides of gradient concentration could reproduce the tooth-like color of zirconia ceramics, and the shade stability was satisfied.
Formation Mechanism and its Pozzolanic Activity of Metakaolin
Authors: Wang Mei Rong , Guo Ning , He Pei Gang , Yu Jing Bo , Jia De Chang
Published: March 2014

In this paper, the process of the transformation from kaolin to metakaolin was investigated. The kaolin was calcined at different temperatures and analyzed by Xray diffraction (XRD), Fourier transform infrared spectra (FTIR) and solid state nuclear magnetic resonance (NMR). The formation of metakaolin structure was based on the stacking polyhedrons changes, which originated from dehydroxylation of kaolinite. With increasing temperature, kaolin kept structure of kaolinite unchanged in the course of dehydroxylation and then structure of kaolinite transformed to metakaolin when the dehydroxylation was over. It was demonstrated that the essence of pozzolanic activity of metakaolin. The result revealed that the pozzolanic activity of metakaolin increased with increasing temperature at the range of 600~900 °C.
Study on Properties and Application of PG/CS Composite PCMs
Authors: Zhang Shi Chao , Wang Guang Hai , Wu Wei , Chen Yu Feng , Sun Hao Ran
Published: March 2014

Tris (hydroxymethyl) ethane (PG) as a phase change material, micro-porous xonotlite (CS) as matrix, PG/CS composite PCMs were prepared by melt-soaking method, and the effect of micro-porous structure of xonotlite on heat absorption capacity, bending strength and insulation performance of composites, and the exudation of PG was studied. Otherwise, for the work environment and characteristics of propulsive device of vehicle, this paper explored the feasibility that phase change materials (PCMs) worked as the insulation material in short-time insulation system of the vehicle. Experimental results show that, when the most probable pore diameters of xonotlite was not less than 63nm, the composites presented better and almost same absorption capacities of matrix (CS) to PCM (PG) in different composites; when up to 85nm, the composite exhibited the lowest leakage rate (less than 5%), the optimal mechanical property and thermal insulation performance. This Study proposed a new idea for the design of the insulation material in the thermal protection system of propulsive device of vehicle.
Effect of Soaking Time on the Properties of Al2O3-C Refractory
Authors: Huang Yong Liang , Zhu Hong Xi , Deng Cheng Ji , Peng Nai , Yuan Wen Jie
Published: March 2014

Al2O3-C refractory has many advantages, high strength, good corrosion resistance and good thermal shock resistance, so Al2O3-C refractory is widely used in the steel-making process. In this paper, the effect of different soaking time on the properties of Al2O3-C refractory at 1450°Cin nitrogen atmosphere was studied. The phase composition of the sintered sample has little change when the soaking time was from 2h to 5h. Cylindrical sialon appeared as the soaking time being 3h, and its grain size increased and became uniform, about 2.5um when the soaking time being 4~5h. In the general performance, with the soaking time changing from 2h to 5h, the samples increment percentage in weight decreased gradually, and the compressive strength of the sintered was first increased, and then decreased, reaching the maximum when the soaking time is 4h. Both the apparent porosity and bulk density of the samples had little different changing.
Effect of Water Gap in Delivery System on Twin Roll Strip Caster by Simulation
Authors: Yang Luo Cheng , Zhu Hong Xi , Deng Cheng Ji , Yuan Wen Jie , Ding Jun
Published: March 2014

In continuous casting process, the mould is the core of the continuous caster, and the vast majority of the surface defects of steel is originated in the crystallizer. Choosing a reasonable water gap in the delivery system is particularly important, especially in twin roll strip continuous casting, the flow delivery system thin belt has a close relationship with the quality of the products. Experiments to skateboard and water gap, STEEL AISI 4340 materials chosen as the simulation material at the same time, distribution water gap taking the form of a set themselves by using the finite element software COMSOL simulation calculation of different gaps opening mode of velocity field, and fluid line back to the high wall, made a comprehensive analysis in different speak way open comprehensive effect is best, the most conducive to the production of high quality material. The experiment determines the best form of water gap, improving the efficiency of the actual production. Make it to the actual production has a certain guiding significance.
Fatigue Crack Initiation and Mechanism of GH4133B Superalloy Used in Turbine Disk of Aero-Engine
Authors: Zhao Rong Guo , Li Jun Fei , Jiang Yong Zhou , Luo Xi Yan , Li Wei , Li Qi Bang , Liu Ya Feng , Yan Yi
Published: March 2014

The fatigue crack initiation life at various stress ratios for GH4133B superalloy specimen with different circular notch radios are studied at ambient temperature and atmospheric pressure utilizing the fracture mechanics method. It is shown that a controlling parameter ΔKI/ρ0.5 can be adopted to characterize the fatigue crack initiation life, and the effect of notch radius on fatigue crack initiation life increases with increasing control parameter, while the fatigue crack initiation life firstly increases and then decreases with increasing stress ratio. The fatigue fracture surfaces of circular notched compact tension specimens of GH4133B superalloy for fatigue crack initiation tests at various stress ratios are investigated using a scanning electron microscopy, and the fracture surface morphologies in the fatigue source region are analyzed. It is found that the separation between carbide inclusion on the surface or subsurface and matrix, or the separation between nickel-rich second phase particle and matrix, or the interaction between persistent slip bands and inclusion, mainly results in the fatigue crack initiation.
Synthesis of Mesoporous Silica Nanoparticles for Drug Delivery
Authors: Wu Ya Zhen , Jia Xiao Yun , Lin Yuan Hua , Liu De Ping
Published: March 2014

Mesoporous silica nanoparticles (MSNs) is an attractive candidate as a drug delivery carrier due to their large surface area, high pore volume and t intrinsic biocompatibility. Here, MSNs were synthesized by the hydrolysis and condensation of tetraethyl orthosilicate (TEOS) with cetyltrimethylammonium bromide (CTAB) acting as structural directing agent. A large mesopore with diameter of 3.8 to 5.5 nm of MCM-41style can be obtained via the addition of 1,3,5-trimethylbenzene. Metoprolol tartrate as a selective β1 receptor blocker was embedded on MSNs by the incipient wetness impregnation. The delivery profiles were collected in vitro in SBF at pH 7.4. A close correlation can be observed between the drug release kinetic and the mesopore size and specific surface area of MSNs.
Microstructures and Highly Accelerated Lifetime Test of X5R Type BaTiO3-Based Ni-MLCC with Ultra-Thin Active Layers
Authors: Gong Hui Ling , Wang Xiao Hui , Zhang Shao Peng , Yang Xin Ye , Li Long Tu
Published: March 2014

Microstructure control in thin-layer multilayer ceramic capacitors (MLCCs) is one of the challenges for increasing capacitive volumetric efficiency and high voltage dielectric properties. In this paper, the X5R-MLCCs with ultra-thin dielectric layers (~1.2 μm) owning uniform grain size distribution were prepared by wet casting process. The microstructures and dielectric properties of the MLCCs were investigated. The existence of core-shell structure was proved by transmission electron microscopy observation and energy dispersive spectroscopy analysis. The existence of core-shell structure makes the temperature coefficient of capacitance (TCC) performance meet X5R standard. Moreover, a highly accelerated lifetime test (HALT) result shows that MLCCs with ultra-thin layers under high electric field are more easily to fail with increasing test temperatures. And the results reveal that the activation energy is similar to the value reported for mid-dielectric constant dielectrics.
Hydrothermal Synthesis of Spherical Bismuth Titanate Crystals
Authors: Feng Xiang Ning , Zhao Wei , Wang Hong Xing , Jiang Wang Yang , Li Qin
Published: March 2014

Spherical bismuth titanate (Bi4Ti3O12) particles were synthesized by hydrothermal method using Bi(OH)3, Ti(SO4)2 and KOH as raw materials, using polyvinylpyrrolidone (PVP) as the surfactant. The effects of concentration of the alkali solution, the reaction temperature and soaking time on the bismuth titanate crystal structure and morphology have been analyzed. XRD, SEM were used to characterize the crystal structure and microstructure of the as-prepared Bi4Ti3O12.The results show that the temperature plays an important role on the morphology of the Bi4Ti3O12.As the increase of the hydrothermal temperature, the Bi4Ti3O12 has been transformed from the spherical morphology to fibrous morphology. The spherical Bi4Ti3O12 powders with uniform distribution can be obtained when the concentration of KOH is from 1mol/L to 2 mol/L,the reaction temperature and hydrothermal time are 160°C and 24h respectively. SEM observation showed that the diameter of spherical Bi4Ti3O12 is about 500 nm.
Synthesis of High Crystallinity Zeolite P from Stellerite
Authors: Zhang Chun Ying , Chen Nan Chun , Zhang Xiao Hu , Zhan Feng
Published: March 2014

Zeolite P was synthesized for hydrothermal route at crystallization temperature of 95°C and crystallization time of 7h, using“acid-treated stellerite-NaOH-NaAlO2-H2O” as precursor, with different molar ratios n (SiO2/Al2O3), n (Na2O/SiO2) and n (H2O/Na2O). The as-fabricated samples were characterized by scanning electron microscopy, X-ray diffraction, FT-IR techniques. The result shows that: the crystal structure of zeolite P has been determined in the tetragonal crystal system, lattice constants are 10.049Å,10.047 Å and the crystallinity of zeolite P is 97%. Influences of synthetic parameters were investigated systematically to achieve high quality pure zeolite P phases. Moreover, this morphology and high crystallinity control approach might be further extended to the synthesis of other zeolite and used in industry, agriculture, environmental protection and biotechnology industries.
Effect of Mn2+ Additive on the Sinterability and Dielectric Properties of Ba0.55Sr0.4Ca0.05TiO3-MgO Composite Ceramics
Authors: Wang Da Hao , Ji Hui Ming , Jia Qian Qian
Published: March 2014

Ba0.55Sr0.4Ca0.05TiO3-MgO (BSCTM) with Mn2+additive composite ceramics were prepared by the conventional solid state method with BaCO3, SrCO3, CaCO3, MgO and MnCO3as raw materials and B2O3and Li2CO3as sintering agent. The influence of the MnCO3additive on the sinterability and dielectric properties of BSCTM composite ceramics are investigated. The morphologies were analysized by scanning electron microscopy (SEM). The dielectric constant and dielectric loss of ceramics were measured by LCR meter at 1 kHz and 1 MHz. The temperature dependences of dielectric constant were measured by high-low temperature incubator tank and LCR meter at 1 MHz and a temperature range from-55 to 125 °C. The dielectric tunabilities were tested by C-T-V converter and LCR meter at 1 MHz and room temperature (25 °C). SEM results showed that BSCTM ceramics became more compact with the increase of Mn2+content, because Mn2+helped to form more oxygen vacancies for accelerating densification process. The addition of Mn2+largely reduced the dielectric loss while had little effect on dielectric constant. The dielectric constant and dielectric loss of 0.5mol% Mn2+doped BSCTM ceramics were 222 and 0.001, respectively. The dielectric tunability increased at first and then decreased with the increase of Mn2+content. The tunability of 0.5mol% Mn2+doped BSCTM ceramics were 4.04% under a DC electric field of 8.2 kV/cm.
Dielectric Properties of BiNbO4-Based Ceramic-Polymer Composites with 0-3 Connectivity
Authors: Lisińska-Czekaj Agata , Micior Joanna , Adamczyk Małgorzata , Czekaj Dionizy
Published: March 2014

In the present study two-phase BiNbO4//PVDF composites with 0-3 connectivity were studied by impedance spectroscopy within the frequency range Δν=100Hz-1MHz at room temperature. Polyvinylidene fluoride (PVDF) acted as a matrix whereas bismuth niobate (BiNbO4) powder acted as a dispersed phase. The volume fraction of the ceramic phase was cV=2, 4, 6, 8, 10, 16 and 20vol%. Analysis of the impedance data registered for composites as well as for BiNbO4 ceramics and PVDF polymer was performed on the base of complex dielectric permittivity mathematical formalism. It was found by impedance spectroscopy that concentration of the dispersed phase had an effect on dielectric properties of ceramic-polymer composite. Experimental data of impedance spectroscopy were fitted to the corresponding equivalent circuit using the complex non-linear least squares method. An equivalent electric circuit consisting of a series combination of two parallel combinations of a resistance R and a constant phase element CPE was found to describe well the dynamic dielectric response of the objects under study. Parameters of the equivalent electric circuit were calculated and it was found that two distinct relaxation processes were present in the composite samples. It was also found that volume fraction of the dispersed phase cV=8vol% corresponded to a local minimum of resistance whereas cV=10vol% of the dispersed phase corresponded to a local minimum of capacitance.