bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Pore Morphology on the Fabrication and Mechanical Properties of Porous Si3N4 Ceramics
Authors: Yang Jian Feng , Gao Ji Qiang , Zhang Guo Jun , Hayashi Ichiro , Ohji Tatsuki
Published: March 2009

Porous Si3N4 ceramics with different pore morphology have been fabricated, utilizing either organic whiskers or starch as the fugitive agents, through slip-casting and die-pressing technique, respectively. The obtained porous ceramics have rod shaped or equiaxial pore morphology, originated from there two kinds of pore forming agents. The mechanical properties were investigated. The strength
decreased considerably when small amount of whiskers were added, however, further increase in the whisker content only cause a moderate decrease of the strength. Gas permeability were measured for the samples with high whisker content of 60 vol% (corresponding to porosity of about 45% in the sintered
bodies), and was compared with the counterpart contained the same porosity in which pores were equiaxial. The flexural strength of the samples with these two types of fugitive particles was almost the same, but the permeability of samples with rod-shaped pores were much higher than that with equiaxial pores, which can be understood in terms of a short pass model.
Combustion Synthesis of β-SiAlON Whiskers
Authors: Fu Ren Li , Chen Ke Xin , Ferreira José Maria F.
Published: March 2009

In this paper, b-SiAlON whiskers were synthesized by combustion of silicon and aluminium powders with SiO2 and Y2O3 as additives and a-Si3N4 or b-SiAlON powders as diluents. SEM observation of the products showed that the crystals with an aspect ratio higher that 5, which could be assigned to almost pure and well crystallized b-SiAlON. The influence of the amount of NH4F additive, the type of diluent on the phase formation and on the morphology of products was investigated.
Study on Thermal Conductivity of Spark-Plasma-Sintered Silicon Nitride Ceramics
Authors: Lu Xin , Ning Xiao Shan , Xu Wei , Zhou He Ping , Chen Ke Xin
Published: March 2009

In the study, the spark plasma sintering (SPS) method was adopted to fabricate Si3N4 ceramics with Y2O3-MgO additives. Specimens with different grain dimensions, grain shapes, α/β phase ratios, densities were obtained by changing the heating rate and dwell time of SPS. The relationship between the microstructure and the thermal conductivity was studied. Results show that the heating rate and the dwell time have great influence on the microstructure and properties of Si3N4
ceramics. Both equiaxed and columnar β- Si3N4 grains are formed during sintering, but the thermal conductivity of Si3N4 ceramics is affected only by columnar grains. The thermal conductivity of the ceramics increases together with the formation and the growth of the β- Si3N4 columnar grains.
Microstructure and Properties of Reaction-Formed Silicon Carbide
Authors: Wang Yan Xiang , Tan Shou Hong , Jiang Dong Liang
Published: March 2009

The effects of microstructure on strength, toughness and corrosion resistance of reactionformed silicon carbide and heat treatment on the properties of reaction-formed silicon carbide have been investigated in this paper. The results show strength and corrosion resistance of reaction-formed silicon carbide decrease with increasing Si content. Fracture toughness shows no rule with free Si content. The average SiC grain size and bonding area of SiC grain increase during heat treatment at 1850°C. The strengths of the samples after heat treatment decrease compared with that of the samples before heat treatment due to the pores in the heat treatment bodies.
Preparation of Oriented Porous Silicon Carbide Bodies by Freeze-Casting Process
Authors: Tang Jie , Chen Yu Feng , Wang Hua , Liu Hai Lin , Fan Qi Sheng
Published: March 2009

Porous ceramics green bodies of silicon carbide were formed by freeze-casting of silicon carbide/carbon black aqueous slurries in a mold where temperature distribution was controlled. The influence of solid loading on the pore structure of green bodies was investigated. Pore morphology of green bodies formed from slurries with various solid loading ranging from 25 to 50vol% experienced a
gradual change. Appropriate solid loading of silicon carbide/carbon black slurry was concluded for fabrication of SiC ceramics with oriented pore structure. Two means were employed for changing ice crystallizing velocity, so that the influence of ice crystallizing velocity on pore size of green bodies was explored. It was concluded that pore size became larger under slow freezing condition, whereas smaller
with the pre-cooling of silicon carbide/carbon black slurry.
Characterization of Fiber-Reinforced SiC Composites by Precursor-Pyrolysis and Hot-Pressing
Authors: He Xin Bo , Qu Xuan Hui , Zhang Chang Rui , Zhou Xin Gui
Published: March 2009

CF/SiC and Hi-Nicalon/SiC composites were prepared by precursor pyrolysis-hot pressing, and the microstructure and fracture behavior of the composites were investigated. Because of a strongly bonded fiber/matrix interface primarily resulting from the direct reactions between the fibers and matrix, Hi-Nicalon/SiC composite exhibited a typical brittle fracture behavior. However, CF/SiC composite displayed a tough fracture behavior with extensive fiber pullout, which was primarily attributed
to a weakly bonded fiber/matrix interface as well as higher strength retention of the fibers. As a result, CF/SiC composite achieved better mechanical properties of 691.6 MPa in strength and 20.7 MPa•m1/2 in toughness, which were much higher than those of Hi-Nicalon/SiC composite.
SiC Coatings Deposited by RF Magnetron Sputtering
Authors: Tang Hui Dong , Tan Shou Hong , Huang Zheng Ren
Published: March 2009

Amorphous SiC coatings were deposited by RF magnetron sputtering from a sintered SiC target onto Si(100) substrate at room temperature. The influence of RF power on the surface morphology and the RMS surface roughness of the resulting SiC coatings was studied by using atomic force microscopy.
Two types of surface morphologies were obtained. The corresponding forming mechanisms were also discussed.
Erosive Wear Behavior of Reaction Sintered Si3N4-SiCp Composite Ceramic in Liquid-Solid Flow
Authors: Huang Zhao Hui , Pan Wei , Qi Long Hao , Miao He Zhuo
Published: March 2009

Si3N4-SiCp composites were prepared using fine Si powders as the starting materials for Si3N4, and SiCp as the aggregates. The erosive wear behavior of reaction sintered Si3N4-SiCp composite ceramic was investigated in liquid-solid flow. The results display that the composite ceramic hold a better capability
of erosive wear resistance than 92 Al2O3 ceramics. The SEM pictures of the worn surface indicate that the main erosive wear mechanism of the composite ceramic is coexistence of micro-cutting and chisel-cutting.
Study on Erosion Resistance of Structural Ceramics
Authors: Bao Chong Gao , Pan Wei , Miao He Zhuo , Qi Long Hao
Published: March 2009

The erosion resistance performances of high-Cr cast iron Cr15Mo3 and three kinds of structural ceramics, a-Al2O3, ZTA, Si3N4, were investigated in flowing suspensions of solid particles with a rotary disk erosion wear tester. The microcosmic failure mechanisms of their wear surfaces were analyzed. The results showed that the erosion resistance of Si3N4, ZTA, a-Al2O3 is 21.8, 8.2, 5.6
times than that of Cr15Mo3 respectively. For ceramic materials, toughness and strength are two main factors that affect erosion resistance rather than hardness. The wear rate of ceramic materials is in proportion to the strength and the biquadratic toughness. Due to erosion, Cr15Mo3 is worn out most in the whole, the erosion holes are very clear and its failure pattern is in “W” shape. The wear of ZTA and Al2O3 mainly occurs in the binding phase of the crystal boundary. Thus, the crystal grains are exposed, but without breaks and cracks. The failure pattern is in the shape of “U”. Si3N4 only loses some binding phase of the crystal boundary and the erosion surface is smooth.
Synthesis of Ti3SiC2 Bulk Materials with B2O3 Additive
Authors: Wu Li Feng , Wang Chang An , Huang Yong
Published: March 2009

Ti3SiC2 bulk materials by hot-pressing sintering were presented through adding a little amount of B2O3 as a low-temperature additive in different raw-material systems. In one system, elemental titanium, silicon and active carbon were used as reactants with a molar ratio of 3: 1: 2. In another one, titanium carbide, titanium and silicon reacted together with a molar ratio of 2:1:1. At different temperatures, samples were synthesized by hot-pressing with a heating rate of 30°C min-1
before 1200°C and then 10°C min-1 to peak temperatures, holding for 2h. The effect of sintering temperature on the purity of Ti3SiC2 was investigated at the range of 1200°C to 1500°C. The products mainly contained Ti3SiC2 with TiC as the second phase. In some cases, Ti5Si3 appeared as well. When sintered at 1300°C, above 98vol% Ti3SiC2 was obtained in the elemental system. The roles of B2O3
additive were considered as weakening the thermal explosion reaction in the elemental mixture and affecting the diffusion procedure at low temperature in both systems.
Tribo-Chemical Reaction in Bulk Ti3SiC2 under Sliding Friction
Authors: Zhang Zhi Li , Zhai Hong Xiang , Huang Zhen Ying , Li Cui Wei , Wang Yi Fan , Zhouyang
Published: March 2009

The Ti3SiC2 samples with a second phase TiC, prepared by hot-pressing progress route, were rubbed against low carbon steel disk with a sliding speed of 20 m/s under normal pressure 0.8 Mpa in atmosphere on a block-on-disk type friction tester. The morphology was observed by scanning electron microscope (SEM) and meanwhile the composition was checked by energy dispersion spectroscopy (EDS). X-ray diffraction (XRD) patterns show some impurity phases containing Ti, Si and Fe oxides in the samples. The possible tribo-chemical reaction mechanism on surface layer of Ti3SiC2 was suggested.
Preparation and Electrical Properties of Dense Bi4Ti3O12 Ceramics by Spark Plasma Sintering
Authors: Hao Jun Jie , Wang Xiao Hui , Li Long Tu , Gui Zhi Lun
Published: March 2009

The family of bismuth layer-structured ferroelectrics is attractive from the viewpoint of their application as electronic materials such as dielectrics, piezoelectrics and pyroelectrics. However, during conventional sintering method, high sintering temperature and long sintering time were needed and it is difficult to get BIT ceramic with a density more than 95% of its theoretic value. In the present paper, we produce dense BIT pellet using a spark plasma sintering process. The results show that at a sintering temperature as low as 7000C/5min under a pressure of 25MPa, BIT ceramics with a density about 99% of its theoretic can be produced. The densities, grain size and electrical properties of the resulting ceramic were also investigated.
Preparation and Properties of Low-Temperature Sintered SrBi4Ti4O15/Ag Composites
Authors: Huang Ping , Xu Ting Xian , Hou Feng , Zou Qiang
Published: March 2009

Strontium bismuth titanate (SBTi) matrix composites containing Ag particles were synthesized by the conventional solid-state reaction method. The SBTi/Ag composites have been characterized by various techniques: x-ray diffraction, optical metallurgical microscope, scanning electron microscope and dielectric measurement. It is found that Ag doping significantly affect the physical properties of
composites. By adding Ag particles to the SBTi matrix, the single-phase layered perovskite structure of the matrix is preserved and the sintering temperature of the system decrease from 1120°C of the single-phase SBTi to 950°C of the SBTi/Ag composites. With the increase of sintering temperature, the size of silver particles increase, but the SBTi grains have no significant growth. The SBTi/Ag composites
show a significant change of the dielectric constant. By increasing Ag content, a gradual increase of the dielectric constant is observed and the dielectric loss of the SBTi/Ag composites remain unchanged when the temperature rangers from room temperature to 200°C, however, the Curie peak of dielectric constant is repressed, which has been interpreted based on the effective dielectric fields developed around
conducting phases and the inhibition effect of nonferroelectric secondary phase to electro-strain.
Effect of Oxidation on the Wear Behavior of a ZrN Coating
Authors: Atar Erdem , Çimenoğlu H. , Kayali E.S.
Published: March 2009

In the present study tribological performance of ZrN coatings deposited on hardened AISI D2 quality cold work tool steel by arc-Physical Vapor Deposition technique has been examined in as-deposited and oxidized conditions. ZrN coatings were oxidized at 400 oC for various times up to 12 h. Reciprocating wear tests carried out by rubbing Al2O3 balls on the coatings, revealed significant
improvement in wear resistance of ZrN coating upon oxidation. Oxidation treatment at 400 oC for 12 h yielded seven times higher wear resistance than as-deposited ZrN coating, beside significant reduction in the wear of counterface (Al2O3 ball).
Resource Recovery of WC-Co Cermet Using Hydrothermal Oxidation Technique
Authors: Gao Ningfeng , Inagaki Fumihito , Sasai Ryo , Itoh Hideaki , Watari Koji
Published: March 2009

WC-Co cermet is widely used in industrial applications such as cutting tools, dies, wear parts and so on. It is of great importance to establish the recycling process for the precious metal resources contained in WC-Co cermet, because all these metals used in Japan are imported. In this paper we reported a hydrothermal oxidation technique using nitric acid for the reclamation of WC and Co. The WC-Co cermet specimens with various WC particle sizes and Co contents were hydrothermally treated in HNO3 aqueous solutions at temperatures of 110-200°C for durations of 6-240 h. The Co was preferentially leached out into the acidic solution, while the WC was oxidized to insoluble WO3 hydrate which was subsequently separated by filtration. The hydrothermal treatment parameters such as solvent concentrations, treatment temperatures, holding time were optimized in respect to different kinds of
WC-Co cermets. A hydrothermal oxidation treatment in 3M HNO3 aqueous solution at 150°C for 24 h was capable of fully disintegrating the cermet chip composed of coarse WC grains of 1-5 µm in size with 20 wt% of Co as binder. While the more oxidation resistant specimen composed of fine WC grains of 0.5-1.0 µm in size with 13 wt% of Co, was completely disintegrated by a treatment in 7 M HNO3 aqueous
solution at 170°C for 24 h. The filtered solid residues were composed of fine WO3.0.33H2O powder and a small amount of WO3. The recovered WO3.0.33H2O powder can be easily returned to the industrial process for the synthesis of WC powder so that the overall recycling cost can be possibly lowered.
Thermal Conductivity of the New Candidate Materials for Thermal Barrier Coatings
Authors: Wang Jing Dong , Pan Wei , Xu Qiang , Mori Kazutaka , Torigoe Taiji
Published: March 2009

Rare-earth zirconate ceramics (Gd2Zr2O7, Sm2Zr2O7, Nd2Zr2O7, Dy2Zr2O7, Er2Zr2O7 and Yb2Zr2O7) were successfully prepared by pressureless sintering at 1550oC for 10 hours. The thermal conductivities of these ceramics were measured and the results indicated that the thermal conductivities of rare-earth zirconates were much lower than that of YSZ in the temperature range 20-800oC.
Preparation and Characterisation of Gd2Zr2O7 Ceramic by Spark Plasma Sintering
Authors: Xu Qiang , Pan Wei , Wang Jing Dong , Qi Long Hao , Miao He Zhuo , Mori Kazutaka , Torigoe Taiji
Published: March 2009

Rare earth Gd2Zr2O7 ceramic was prepared by spark plasma sintering from Gd2O3 and ZrO2 powders. The powders were sintered at 1400°C for 10min. The synthesized ceramic was annealed at 800°C for 2h under air atmosphere. XRD structural and SEM microstructural characterization showed the formation of a single phase material with pyrochlore crystal structure. The relative density of Gd2Zr2O7 ceramic was measured by the Archimedes method with an immersion medium of water and the results revealed that the relative density of the ceramic was 92%. The thermal conductivity of the ceramic was tested by laser flash method from room temperature to 700°C. The result shows the thermal conductivity
of Gd2Zr2O7 ceramic is lower than that of 7YSZ.
Effects of Ag-Pd Powder on Ferroelectric and Mechanical Properties of PLZT Ceramics
Authors: Yue Zhen Xing , Zhang Jian Bo , Gui Zhi Lun , Li Long Tu
Published: March 2009

The Ag-Pd/PLZT composites were prepared by the conventional electronic ceramics method. The electrical and mechanical properties of the composites were investigated. As the amount of doped Ag-Pd particles increased, the fatigue and mechanical properties of the composites were improved, and the dielectric and ferroelectric properties after electric fatigue dropped less. The results indicate that the fatigue process leaves less damage on the composites due to the Ag-Pd particles incorporation. It is proposed that the improvement of fatigue property may be attributed mainly to the improvement of mechanical property.
Hydrolysis of α-TCP and Development of Hydroxyapatite Whiskers
Authors: Park Young Min , Yang Tae Young , Yoon Seog Young , Stevens Ron , Park Hong Chae
Published: March 2009

Calcium deficient (Ca/P = 1.53-1.61, molar ratio) whisker shaped hydroxyapatite (HAp) with a high aspect ratio ~26 (diameter: 0.2-0.3 µm) has been prepared by the hydrolysis of a-Ca3(PO4)2 (a-TCP) in an aqueous solvent system under controlled conditions. The influence of processing variables on the conversion of a-TCP to HAp, and the microstructure and composition of the HAp was characterized by means of XRD, SEM, TEM and ICP instruments.
Gelcasting of Mechanochemically Synthesized Hydroxyapatite
Authors: Jia Yu , Hotta Yuji , Sato Kimiyasu , Watari Koji , Kanno Yoshinori
Published: March 2009

Hydroxyapatite powders were prepared via mechanochemical synthesis method. The starting reagents for HAP powders were vibration ball milled for 2 h and then calcined at 800°C for 1 h. X-ray diffraction patterns and IR spectrum shown that pure crystalline apatite powder (HAP) was obtained. The as-synthesized powders were gelcasted and then sintered at 1200°C for 2 h. It was observed from SEM micrographs that the prepared green body has uniform microstructure. The bending strength of the dried green body was as high as 18 MPa that is enough to be machined into required form before sintering. The sintered ceramics has a density of 2.5 g/cm3 and a flexural strength of 72 MPa with a homogenous
microstructure.
Apatite Formation on Porous TCP In Vitro: A Comparative Study between Static and Dynamic RSBF Systems
Authors: Deng Chun Lin , Chen Ji Yong , Leng Yang , Wang Xin Long , Wu Yao , Fan Hong Song , Zhang Xing Dong
Published: March 2009

Porous tricalcium phosphate ceramics were immersed in static and dynamic revised
simulated body fluid (RSBF) at 37°C. Morphology, composition and phase of precipitates on TCP were identified by SEM, FTIR and TEM methods. FTIR and TEM results indicated the deposits on the inner pore walls of TCP were OCP, and SEM results implied that the deposited way of precipitates in static system was different from that in dynamic system.
Study of Animal Bio-Ceramic Implants with 3D High Resolution CT
Authors: Wang X.G. , Tian Jie Mo , Zhang Chuan Zeng , Guo Zhi Ping , Dong Li Min , Wang Chang An
Published: March 2009

Animal implants experiments are obligatory when developing human artificial hard tissues, such as bio-ceramics. Optical microscope is often used to inspect implant slices but may destroy original status when slicing up. We tried 3D high resolution CT to nondestructively study biocompatibility and degradation of bio-ceramics implants. 3D CT provides 3D structure information. Typical pixel size of 3D
high resolution CT is 50 microns. Generally, implants differs with tissues in density and structure, on basis of which we can identify details with CT slice. Experiments of bio-ceramic implanted into rabbit hip are also showed. Interaction could be identified at interface between implant and tissue.
The Monolithic Glass-Ceramic Lined Steel Elbow Made by SHS Gravitational-Thermite Process
Authors: Wang Shuang Xi , Gao W.-Y. , Ma T.C. , Liang Kai Ming , Zhang X.H.
Published: March 2009

A monolithic glass-ceramic lined steel elbow with 900-bend angle was fabricated using a self-propagating high-temperature synthesis gravitational-thermite process (SHS G-T process). The manufacture principle and some technologies were introduced. Experiment results showed that the inner surface of the composite elbow was smooth and there were no visible cracks and pores in it. The coating layer was symmetry and was of ~ 2.5 mm thick. It consisted of two zones (glass-like zone, columnar zone) and that there existed three phases (Al2O3, glass and Fe particles) in both of the two zones. However, the Al2O3 grains were different evidently in the two zones. XRD results showed that there was no hercynite phase in the coating layer.
Crystallization and Thermal Expansion of MgO-Al2O3-SiO2-TiO2 Glass-Ceramics
Authors: Shao Hua , Liang Kai Ming , Zhou Feng , Peng Fei
Published: March 2009

Crystallization sequence of MgO-Al2O3-SiO2-TiO2 system glass was investigated by means of DTA, XRD, SEM and EDS. The relationship between crystalline phases, heat treatment methods and thermal expansion coefficient (α) were well discussed. The results have shown that: The glass first underwent extensive phase separation into titanium-rich droplets in a silica-rich matrix,
then magnesium aluminotitanate (MAT) initially precipitated in the droplet phases. With the crystallization temperature increased, β-quartzss, sapphirine, α-quartzss and α-cordierite made their appearance successively. The thermal expansion coefficient as a function of the heat treatment condition was studied.
Corrosion Behavior of BF Slag to SiAlON Bonded Corundum Refractories
Authors: Huang Zhao Hui , Pan Wei , Wang Jing Xia , Hong Yan Ruo
Published: March 2009

The corrosion behavior of BF slag to sialon bonded corundum refractories using reaction nitriding technology at 1500°C was investigated by crucible test method. The results show that the reaction products of slag corrosion are anorthite, magnalium-spinel and glass phases. The corundum grains can react with MgO in the slag to produce magnalium-spinel, accompanying by expansion and
liquating stepwise by slag. Erosion mechanism is oxidation-erosion-dissolving. This study is very necessary and useful to improve the property of BF slag resistance and to yield better overall properties of sialon bonded corundum refractories.
Thermal Expansion Behavior of Al Hybrid Composite Reinforced with Aluminum Borate Whisker and Magnetic Ceramic Particle
Authors: Li Gang , Li Zhen Jia , Fei Wei Dong
Published: March 2009

Magnetic ceramic particles (NiFe2O4) and aluminum borate whiskers reinforced aluminum matrix composite was fabricated by squeeze casting technique, which had lower coefficients of thermal expansion (CTEs). The components and microstructure were characterized by X-ray diffraction (XRD), optical microscopy (OM) and scanning electron microscopy (SEM). The results
showed that the CTE of the composite was lower than that of the composite only reinforced by aluminum borate whisker, and with increasing the number of thermal cycling, the CTE of the composite became low. The results indicated that the lower CTEs of composite resulted from ferromagnetic-paramagnetic transformation of the magnetic ceramic particles.
Determination of the Load-Independent Hardness by Analyzing the Peak-Load-Dependence of the Unloading Slope in Nanoindentation
Authors: Gong Jiang Hong
Published: March 2009

By assuming that the test material has a load-independent nanohardness number, a linear relationship was predicted to exist between the reciprocal of the initial unloading stiffness, 1/SM, and the inverse square root of the peak load, (1/Pmax)0.5, and the load-independent hardness can be obtained directly from the slope of the 1/SM−(1/Pmax)0.5 straight line. This prediction was then verified by analyzing
the experimental data obtained on soda-lime glass and a tetragonal ZrO2 polycrystalline. The indenter area function established based on the resultant load-independent hardness was found to deviate from the perfect Berkovich indenter and such a deviation can be attributed to the indenter deformation occurring during indentation as well as the indenter tip rounding.
Thermal Fatigue Life Prediction of Ni Base Alloy Ceramic Composite Coating
Authors: Liu Xie Quan , Ni Xin Hua , Wang Jun Ying
Published: March 2009

Ni base alloy ceramic grain composite coating is used mostly in high temperature condition, so thermal fatigue failure will be easy. If the thermal expansion coefficients and elastic modulus of Ni base alloy and ceramic grain are different, there will be thermal stresses between grain and matrix in thermosyphon. The thermal stress will arouse the initiation and growth of thermal fatigue crack. We use Eshebly-Mori-Tanaka method to study the thermal stress field in matrix and grain. It can be shown that the more difference of thermal expansion coefficients between Ni base alloy and ceramic grain is, the bigger the thermal stress is. The thermal stress relates to volume fractions and elastic constants of Ni base alloy and ceramic grain. Based on low-cycle fatigue crack growth rate formation, the thermal fatigue life was computed. The bigger thermal stress is, the smaller thermal fatigue life is. Thermal life is an
exponential function of crack initiation length and critical length.
Design and Fabrication of an Advanced Ceramic Material Based on the Wear Resistance
Authors: Xu Chong Hai , Sun De Ming
Published: March 2009

An optimum model for the composition design of the advanced ceramic material is built based on the wear resistance with the combination of both theoretical and experimental methods, with KIC 3/4×H1/2 working as the coefficient of wear resistance when the abrasive wear dominates. Results show that the tested SiC/(W,Ti)C/Al2O3 ceramic material can be expected to achieve the highest wear
resistance when the volume fraction of SiC and (W,Ti)C is about 15% and 17%, respectively. The optimum composite is then fabricated with the hot pressing technique. Its wear resistance is approximately 43% higher than that of the pure alumina ceramic when used as the tool material in the machining of the hardened tool steel. The increment of the wear resistance of the developed ceramic material coincides well with that predicted from the optimum model. It proves that the method proposed in the present study is feasible for the ceramic materials mainly with wear mechanisms of abrasive wear.
A Numerical Simulation for Temperature Field of Plasma Arc Cutting Ceramics
Authors: Xu Wen Ji , Fang Jian Cheng , Wang T. , Liu F.
Published: March 2009

To solve the difficult problem of selecting processing parameters of plasma arc cutting ceramic (PACC), the heat conduction model of PACC has been established and the calculating formulations of temperature field have been derived. Then, the distributions and influence factors, such as arc power, cutting speed and workpiece thickness, of temperature field of the ceramic plate and the anode plate have been studied. Based on the work above, the required arc power can be
calculated. Moreover, the relation between thickness of ceramic plate and anode plate can be determined, which provides a helpful reference for selecting the thickness of additional anode plate.
Near Net Forming of Metal-Ceramic Parts by Plasma Spraying
Authors: Zhao Zhi Yu , Wang L. , Fang Jian Cheng , Xu Wen Ji
Published: March 2009

A novel technology of metal-ceramic parts with special functions formed by plasma
spraying has become an important research trend. In this paper, the technical characteristics and spray parameters have been analyzed in detail based on the experiments of metal-ceramic near net forming, and some important techniques such as spray mould fabricating, backing and demoulding have been researched and summarized. Furthermore, the microstructure and property have been analyzed to forecast the quality of spray-formed parts. The research results show that plasma spraying is suitable for the production of metal-ceramic parts of any size with special
mechanical and thermomechanical properties, which can realize the contemporary integration of forming and machining. Therefore, this technology with simple process and low cost is a method of metal-ceramic fabrication with a broad and brilliant prospect.
Characterization Methods of Pores in Ceramics and Their Analysis
Authors: Chen Rui Feng , Huang Yong , Wang Chang An
Published: March 2009

Pores in ceramics have their peculiarity different from common porous materials, so the existing characterization methods should be re-recognized. In the present work, thermal shrinkage curves adequately characterize the dynamic process of porosity evolution in ceramics, and the results are checked by Archimedes method. In order to detect pore-size distribution quantitatively, gas adsorption (BET method), mercury penetration and a new Scanning Acoustic Microscope (SAM)
technique are used on Alumina ceramics with large and median pores. The results acquired by these three methods are discussed in detail and unified by the introduction of effective pore-size coefficient t. It shows that a complete characterization system adapt to pores in ceramics should be established.
Electron Structure and Piezoelectric Characteristics of PMZN System Piezoceramics
Authors: Zhou Jing , Chen Wen , Sun Hua Jun , Xu Qing
Published: March 2009

The electron structure of Pb(Zr1/2Ti1/2)O3(PZT), Pb(Zn1/3Nb2/3)O3(PZN) and Pb(Mn1/3Sb2/3)O3 (PMS) systems was calculated by the SCF-DV-Xα calculation method. The effects of ABO3-type perovskite and pyrochlore ceramic electron structure on their piezoelectricity were also studied. The
results showed that the ferroelectric phase is more stable than paraelectric phase and the necessary condition of stable existing ferroelectric is the mixed orbit of O2p orbit and the out layer d orbit of B-site atom. The stability of ferroelectricity can be indicated by the strength of mixed orbit. When (Zr, Ti) was substituted by Mn1/3Sb2/3, Zn1/3Nb2/3, if it could form tetragonal perovskite structure, the total system energy would reduce and the mixed orbit will enhance, which improves the ferroelectricity of PZT system. However, if it forms a cubic pyrochlore structure, the ferroelectricity would lose because the covalent bond strength of B-O (axial direction) and B-O (vertical axial direction) is different obviously, which lead
to the system structure become unstable.
Development of Functionally Graded Anti-Oxidation Coatings for Carbon/Carbon Composites
Authors: Jeon Jae Ho , Fang Hai Tao , Lai Zhong Hong , Yin Zhong Da
Published: March 2009

The concept of functionally graded materials (FGMs) was originated in the research field of thermal barrier coatings. Continuous changes in the composition, grain size, porosity, etc., of these materials result in gradients in such properties as mechanical strength and thermal conductivity. In recent years, functionally graded structural composite materials have received increased attention as promising
candidate materials to exhibit better mechanical and functional properties than homogeneous materials or simple composite materials. Therefore the research area of FGMs has been expending in the development of various structural and functional materials, such as cutting tools, photonic crystals, dielectric and piezoelectric ceramics, thermoelectric semiconductors, and biomaterials. We have
developed functionally graded structural ceramic/metal composite materials for relaxation of thermal stress, functionally graded anti-oxidation coatings for carbon/carbon composites, and functionally graded dielectric ceramic composites to develop advanced dielectric ceramics with flat characteristics of dielectric constant in a wide temperature range. This paper introduces functionally graded coatings for
C/C composites with superior oxidation resistance at high temperatures.
Mechanical Properties and Oxidation Behavior of Si3N4/BN Laminated Ceramics
Authors: Li Cui Wei , Wang Chang An , Huang Yong
Published: March 2009

Laminated ceramics with high mechanical properties were fabricated in the Si3N4/BN
system. The mechanical properties at elevated temperatures were tested, and the oxidation behavior during tested procedure was studied at the same time. The flexure strength of the Si3N4/BN laminated ceramics changed a little below 1000°C. The displacement-load curves appeared non-linear characteristic even at high temperature. During testing procedure at high temperature, oxidation behavior of silicon nitride and silicon carbide happened, and no oxidation product of boron nitride
was found. The silicon nitride layers were oxidized to form a protective silicate scale, which prevented oxidation of the boron nitride interlayers. The stability of boron nitride was beneficial to the boron nitride interlayer to partition the silicon nitride matrix layers at high temperature.
Laminated Si3N4/SiC Composites with Self-Sealed Structure
Authors: Yu Zhengbo , Krstić Zoran , Krstić Vladimir D.
Published: March 2009

Self-sealed laminar Si3N4/SiC composites, with different cross-section shapes and various thickness ratios of Si3N4 to SiC, have been fabricated. The laminates consist alternately of thicker Si3N4 layers ranging from 100 to 500µm and thinner SiC layers ranging from 6 to 15µm after sintering. Preliminary results indicate that SiC thin layer forms during sintering according to the reaction Si3N4 + 3C
® 3SiC + 2N2, which is confirmed by X-ray diffraction. An excellent physical and chemical compatibility between Si3N4 and SiC layers was observed. The self-sealed Si3N4/SiC composites not only demonstrate a superb resistance to delamination, usually associated with the plate-form ones, but also show a high damage-tolerance behavior. The laminated Si3N4/ SiC composite with a layer thickness ratio of Si3N4 to SiC of approximately 40 gives the highest value of work of fracture (WOF) of approximately 406 kJ/m3, whereas the highest toughness of 21 MPam1/2 was achieved at the layer thickness ratio of 50. The effects of the relative thickness of Si3N4 and SiC layers on the densification of the laminates are
examined and fracture behavior and microstructure of the Si3N4/SiC laminates discussed.
High-Temperature Mechanical Properties of Al2O3/Ti3SiC2 Multilayer Ceramics
Authors: Zan Qing Feng , Wang Chang An , Dong Li Min , Huang Yong
Published: March 2009

The high-temperature mechanical properties were very important to structural materials, especially structural ceramics. Hence, the strength, elastic modulus, stress relaxation and creep behavior of the multilayer materials at elevated temperature were studied in this paper. According to the curves of mechanical properties varieties with temperature risen from room-temperature to 1300°C, the multilayer materials could remain relatively high mechanical properties until 1150°C.
Otherwise, the creep function of the multilayer composites was also determined, in which the stress exponent was 1.4 and activation energy was 204kJ/mol. By contrasting to the monolithic ceramics of Al2O3 and Ti3SiC2, the main creep mechanisms include: interface diffusion creep (in Al2O3 layers), dislocation movement creep, grain delamination and sliding (in Ti3SiC2 layers).
TiB2/AlN/Cu Functionally Graded Materials (FGMs) Fabricated by Spark Plasma Sintering (SPS) Method
Authors: Jin Song Zhe , Zhang Hai Long , Li Jing Feng , Jia Shu Sheng
Published: March 2009

The TiB2/(TiB2+AlN)/AlN/(AlN+Cu)/Cu functionally graded materials were successfully fabricated via spark plasma sintering (SPS) method, in which a temperature gradient was achieved by using a specially designed mold and different sintering sequences were carried out. XRD analysis and SEM observations were respectively performed upon the TiB2/AlN/Cu composites. The results show that no
new phases were introduced into the composites after mechanically milling or SPS process. The layered composites were found to have a dense microstructure, which changes gradually along a composition gradient. The present FGMs are developed as electrode materials of a solar thermoelectric module.
Microstructure and Characteristics of Pb(Ti,Zr)O3 Ceramics with Addition of Pb-Based Glass Frit
Authors: Wang Chun Huy
Published: March 2009

The paper tries to prepare dense piezoceramics by way of reactive liquid phase sintering. Technique concerning a low-temperature sinterable process is developed by incorporating 4PbO×B2O3. The host system is a perovskite type piezoceramic, Pb(Ti,Zr)O3. If small amounts of 4PbO.B2O3 glass powder are added to the
calcined Pb(Ti,Zr)O3 ceramics, the liquid phase is formed during sintering. Hence, the piezoelectric and dielectric properties are enhanced and the sintering temperature can be reduced. The value of the kp, KT 33 and Qm is increased and dielectric loss tangent is decreased when a small amounts of 4PbO.B2O3 dopant (i.e. 0.2 wt%) are added to the PZT system. With more 4PbO.B2O3 doping (i.e. 2 wt%), the value of the kp and KT 33 is decreased due to the glassy phase segregation at the grain boundary.
Fabrication and Evaluation of PZT/Ag Piezoelectric Composites and Graded Actuator
Authors: Zhang Hai Long , Li Jing Feng
Published: March 2009

Homogeneous PZT/Ag composites and compositionally graded PZT/Ag actuators were fabricated and evaluated in this work. The piezoelectric constant decreases gradually and the dielectric constant increases significantly with an increase in silver content of the PZT/Ag composites. The fracture toughness of the PZT/Ag composites is enhanced with addition of the silver powders. Based on the corresponding piezoelectric properties of the monolithic PZT/Ag composites, a graded material with symmetric silver compositions from 1 to 10 vol % then inversely to 1 vol % was successfully fabricated by conventional sintering. This study indicates that the PZT/Ag composites can be used to acting as bimorph actuator materials.
A Novel Micro-Actuator Made from PZT
Authors: Li Mao Qiang , Chen Xue Feng
Published: March 2009

Ceramic discs are prepared with PZT powder doped with Sr and Mn, which is prepared through a modified Pechini process. A micro-actuator consists of two concentric rings with thickness of 0.15 mm made of PZT doped with Sr and Mn, a copper disc, on which the PZT rings are firmly mounted with organic glue, and a ceramic rod of φ2.5x100 mm stuck at the center of the disc. The top of the ceramic rod serves as pointer of the actuator. The outer PZT ring is equally divided into four
quadrants separated each other, of which two vicinal parts are poled with the same direction as that of the inner PZT ring. The other two quadrants in the outer ring are poled with the opposite direction. The inner ring and the four quadrants of the outer ring are excited by three DC powers, respectively. Bending deformation of the copper disc is caused by properly regulating the excitation voltages exerted on the PZT ceramics. The position of the top of the ceramic rod varies with the bending
deformation of the copper disc.
Properties of Na1/2Bi1/2TiO3 Ceramic Prepared by Sol-Gel Method
Authors: Shi Hui , Pan Wei , Fang Ming Hao , Xie Dan
Published: March 2009

Bismuth sodium titanate ceramic was prepared by sol-gel method. The crystallization, density and microstructure were determined. The grains of BNT ceramic prepared by sol-gel method were equiaxial, ~ 2 µm, which was smaller than that prepared by solid-state reaction method. The piezoelectric and dielectric properties were investigated. When the sintering temperature was 1140°C, maximum
relative dielectric constant and piezoelectric constant can be obtained. The piezoelectric constant of BNT ceramic prepared by sol-gel method was higher than those prepared by solid-state reaction method.
Influences of MnCO3 Doping on Processing Parameters and Dielectric Properties of ZnNb2O6 Microwave Ceramics
Authors: Luo J. , Pang Z.Y. , Lin Y.S. , Xiong Zhao Xian
Published: March 2009

MnCO3 was added into ZnNb2O6 ceramics to obtain excellent microwave dielectric properties. The samples were prepared by conventional solid-state reaction method. The effects of the amount of MnCO3 on sintering temperatures, ceramic densities and contraction were systematically investigated. The crystalline structure of ceramic body was analyzed by XRD. The ceramic microstructure was observed
by SEM. The dielectric properties of ZnNb2O6 ceramics were measured by a vector network analyzer at microwave frequency, which showed: er = 22.65, Q×f = 36700 GHz (loaded value) and tf = -40 ppm/°C.
Effect of Gd2O3 on the Electrical Properties of (Co, Nb)-Doped SnO2 Varistors
Authors: Zang Guo Zhong , Wang Jin Feng , Chen Hong Cun , Su Wen Bin , Wang Chun Ming , Qi Peng , Ming Bao Quan
Published: March 2009

The effect of Gd2O3 on the electrical properties of (Co, Nb)-doped SnO2 varistors was investigated. It was found that the nonlinear coefficient presents a peak of α = 30 for the sample doped with 1.5mol% Gd2O3. The increase of the breakdown electrical field from 325V/mm to 1560V/mm with increasing Gd2O3 concentration is mainly attributed to the decrease of the grain size. The
decrease of relative density and resistance of grain boundary indicate that Gd2O3 should be a two-sided dopant and the nonlinear coefficient peak was explained. To illustrate the grain-boundary barrier formation of (Gd, Co, Nb) doped SnO2 varistors, a modified defect barrier model was introduced, in which the negatively charged acceptors substituting for Sn ions should not be located at
the grain interfaces instead at SnO2 lattice sites of depletion layers.
Oxygen Sensitivity of SrFeO3-δ Thin Films Prepared by Sol-Gel Method
Authors: Liang Chong , Yang De An , Song Jian Jing , Xu Ming Xia
Published: March 2009

Sr(NO3)2, Fe(NO3)3 and citric acid (the mole ratio was 1:1:2) were mixed in water to form sol. Alumina substrate, which had been treated by ultrasonic cleaner, were dipped in the sol and pulled out, and the coating film was heated for 1h at 900oC. Through seventeen times treatment, SrFeO3-d thin film was coated on the alumina substrate. The remainder sol was dried and heated at 400oC,
800oC, 900oC for 2 h. The thin films and the powders were characterized by XRD. The morphologies of thin films were observed by SEM. The results showed that SrFeO3-δ was formed at 900oC on alumina substrate and the grain size was 100 ~ 200 nm. The oxygen sensitivity was measured in the temperature range of 377 ~ 577oC under different oxygen partial pressures. SrFeO3-δ thin film showed
p-type conduction. The response time was less than 2 min when being exposed to a change from N2 to 0.466% O2 at 377oC.
A Potentiometric SO2 Gas Sensor with Solid Reference Electrode
Authors: Wang Ling , Bu Jing Long , Kumar R.V. , Hong Yan Ruo
Published: March 2009

A SO2 sensor based on Na-b-Al2O3 interfaced with an auxiliary electrode of Na2SO4 formed in situ and a solid mixture of Fe3O4, Fe2O3, 3Na2O.5Fe2O3 as the reference electrode was developed. The sensor displayed a Nernstian response to changes in the partial pressure of SO2.
Effects of Glass-Additives on the Properties of Ni/Ceramic PTC Composites
Authors: Qu Yuan Fang , Wang Hua Tao , Li Xiao Lei , Ma Wei Bing
Published: March 2009

The effects of glass additives on the sintering and properties of Ni/(Ba0.92Sr0.08)TiO3 composites were investigated. Due to the addition of glass additives, Ni/ceramic composites with low room-temperature resistivity and obvious PTC effect were obtained at a low sintering temperature. It was shown that glass-additives could form liquid phase that aided the solution and diffusion of solid atoms, acting as sintering aids to accelerate the sintering and lower the sintering temperature. The
room-temperature resistivity decreased first and increased later with the increasing content of glassadditives, which was explained by two functions of glass-additives, decreasing interface contact resistance as sintering aids and adding volume resistance as insulators. Moreover, a suitable amount of glass-additives could enhance the PTC effect unexpectedly, which was attributed to the decrease of
the contact resistance existing at the ceramic/ceramic interface.
Preparation and Properties of Titanium Oxide Photocatalyst with Visible Light Activity
Authors: E Lei , Xu Ming Xia , Ge Lei , Tian Yu Ming , Li Yan , Xu Tiantian
Published: March 2009

TiO2 photocatalyst were obtained from the hydrolysis product of TiOSO4 with ammonia and the photocatalytic activities were investigated by the photocatalytic degradation of methyl orange aqueous solution under UV-light and visible-light. The results showed that the absorption intensity in visible-light was dependent on the concentration of the materials, pH value and heat-treatment temperature. The color of the TiO2 varied from yellowish to vivid yellow when the TiO2 was calcined at
different temperatures from 300°C to 500°C for 1h. The photocatalytic activity of TiO2 under visible light was determined by the photo-absorption feature in visible light region, which was related to the heattreatment temperature. The TiO2 calcined at 400°C shows stronger photo-absorption in visible light region and exhibits higher visible-light activity than the TiO2 calcined at other temperature.
Effect of TeI4 Content on Thermoelectric Properties of N-Type Bi2(Te,Se)3 Materials Prepared by Spark Plasma Sintering
Authors: Jiang Jun , Chen Li Dong , Bai Sheng Qiang , Yao Qin , Wang Qun
Published: March 2009

The n-type Bi2(Te,Se)3 thermoelectric materials doped with different contents of TeI4 were fabricated through the spark plasma sintering (SPS) technique at 693K under a pressure of 60MPa. The sintered materials were rather dense and showed preferred grain orientation. Electrical conductivity (s), Seebeck coefficient (a), and thermal conductivity (k) were measured in the
temperature range of 300-500K. The optimal figure of merit ZT (ZT=a2sT/k) of the sintered material in the direction perpendicular to the pressing direction showed a value of 0.75 for the sample containing 0.14wt% TeI4.
Sulphate-Ceria Composite Ceramics for Energy Environmental Co-Generation Technology
Authors: Liu Xiang Rong , Zhu Bin , Xu Jin Rui , Sun Jun Cai , Mao Z.Q.
Published: March 2009

In this work ion conductivity and FC application were studied for the new type composite material based on SDC (samarium doped ceria) and Li2SO4. Significant conductivity enhancement was achieved, e.g. 10-2 – 0.4 Scm-1 for the SDC-Li2SO4 compared to 10-4 -10-2 Scm-1 for the SDC between 400 and 650°C. Some ion conductivity mechanisms were proposed correspondingly. Using the SDC-Li2SO4 composite materials as the electrolytes, we achieved high performances, 200-540 mWcm-2, for intermediate temperature (450-650°C) solid oxide FC (ITSOFC) applications. Sulfates, typically Li2SO4, have an excellent chemical stability in sulfur containing atmosphere. The sulfate-ceria (SDC-Li2SO4) composite materials can thus meet the demands to develop the sulfur tolerant and H2S FC technologies, which was also demonstrated successfully with significant importance for both fundamental and applied research.
Effect of Iron Oxide on the Structure, Electrical and Magnetic Properties of (SiO2-B2O3-Li2O) Ionic Conducting Glass System
Authors: Assem E.E.
Published: March 2009

A glass system according to the molar formula (35% mole SiO2- 40% mole B2O3 -(25-x) Li2O), where x=0,1,2 and 3 % mole Fe2O3, was prepared by melting the pure powder chemicals at porcelain crucibles at 1200Co for three hours until the homogenous glass was obtained. The samples were heat treated at 600 and 700 Co for 10 hours. The density, the molar volume, the electrical conductivity and
magnetic properties were measured before and after the heat treatment. Replacing the lithium oxide with the iron oxide increases the density, the electrical and magnetic properties. The heat treatment decreases the electrical conductivity and the magnetic susceptibility while increases the density. The crystalline phases due to heat treatment were determined using x-ray diffraction.