bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of Tobacco Etch Virus and Tobacco Mosaic Virus Enhancers for Expression of Human Calcitonin Gene in Transgenic Potato Plant
Authors: Ofoghi H. , Moazami N. , Ivanov I.
Published: March 2009

The translational enhancement of the 5′-leader sequence of the tobacco mosaic virus (TMV) and tobacco etch viral 5′-leader sequence (TEV) was compared in relation to the expression of the human calcitonin (hCT) gene in transgenic potato plants. The synthetic human calcitonin tetrameric genes were cloned under the control of the 35S Cauliflower mosaic virus (CaMV)promoter linked to the TMV or TEV leader sequences. The resulting constructs were cloned into the binary vector Bin19 and potato minituber discs transformed using an agrobacterium strain. The expression of the hCT gene was studied by mRNA-DNA hybridization, a RT-PCR, ELISA and RIA. The results showed that the TMV omega element increased the yield of the expressed recombinant protein two to three-fold in comparison with the TEV leader sequence.
Evaluation of the Friction Coefficient from the Dynamometer Test of the Aircraft
Authors: Woo Gui Aee , Jeon Jeong Woo , Lee Ki Chang , Kim Young Joo
Published: March 2009

The friction force is the most important factor for the design of control unit in a braking system. For a long time, many researchers have been striving to improve the accuracy in the measurements of friction coefficients [1,2]. However, there were many difficulties because the friction coefficients are affected by a number of conditions and parameters, such as normal force, temperature, characteristics of road condition, and weather. For the development of ABS of the aircraft, the HILS (Hardware-In-the-Loop-Simulation) test and dynamometer test were carried out.
For the calculation of the friction coefficients, the wheel moment was measured using the load cell mounted on the housing of the wheel. The test conditions were dry and greasy, with friction coefficients of 0.7 and 0.4, respectively. In this paper, the test results of the friction coefficients were represented and the improvement method was suggested.
Characterization of Nanoporous Low Dielectric Polysilsesquioxane Thin Films
Authors: Hyeon Lee Jingyu , Lyu Yi Yeol , Lee Mong Sup , Yim Jin Heong , Kim Sang Youl
Published: March 2009

Poly(methyl-co-cyclosiloxane bearing silsesquioxane)s (P(M-co-CSSQs)) were prepared. Using poly(e-caprolactone) (PCL) as a template, PCL / P(M-co-CSSQ) nanohybrid films were fabricated. The electrical, morphological, and mechanical properties of the PCL / P(M-co-CSSQ) films were investigated. The dielectric constant of a cured PCL / P(M-co-CSSQ) film at 420°C scaled down from 2.55 to 2.05 and refractive index from 1.41 to 1.33 when 20 vol. % of the PCL was admixed with the polymer matrix. The elastic modulus and hardness of the cured PCL / P(Mco- CSSQ) (2:8, vol./vol.) film were 2.50 and 0.32 GPa, respectively, showing dependency on the PCL content.
Enhanced Sensitivity of the Pirani Vacuum Gauge by the AC Driving Method
Authors: Seong Dae Jin , Shin Yong Hyeon , Chung Kwang Hwa , Kim D.H. , Shin Je Sik , Yun Y.J.
Published: March 2009

We improved the sensitivity of existing commercial Pirani-vacuum gauges employing
the AC method in the vacuum range above 1 Torr. The signals obtained through the use of the AC method yield information related to the specific heat and heat conductivity of gas. The output signal is obtained by two components: the oscillating temperature amplitude, and its phase. The amplitude increases with the decrease of pressure in the vacuum range from the atmosphere to about 1 Torr, which arises from the decrease of the heat capacity with the decrease of gas density. In contrast, the phase decreases monotonically as pressure decreases and the slop of a dΘ/d(log P) is large at higher than 1 Torr. This provides a good advantage for developing a new Pirani gauge with high sensitivity.
The Effect of Zirconia Sol-Gel Coatings on Mild Steel Oxidation Resistance
Authors: Mei Le Fu , Liang Kai Ming , Li Hai Bin
Published: March 2009

The effect of zirconia coatings deposited by the sol-gel technique on the oxidation of mild steel was studied by scanning electron microscopy (SEM), X-ray diffraction (XRD) and measuring weight gain. It was found that the thickness of zirconia coatings is a crucial factor affecting the oxidation kinetics and the multilayer dip–coating is much more effective than the single coatings. Auger electron spectroscope (AES) was used to evaluate the depth composition of scale. The results suggest that the growth mechanism of the oxide scale for coated mild steel change from outward cation to inward anion diffusion, during oxidation.
Effects of Solid Volume Fraction on the Gelcasting of Alumina Suspensions
Authors: Huang Yong , Zhang Li Ming , Li Hai Feng , Ma Tian
Published: March 2009

The effects of solid volume fraction (SVF) on the gelation of alumina suspensions for gelcasting, debonding and sintering of the green body were studied. It was found that with SVF rising, the gelation of alumina suspension delayed; and the strength of green body decreased. On the other hand, high SVF resulted in that polymerized acrylamide split at a relative low temperature. These phenomena manifest
that the fast polymerization of monomers in high SVF alumina suspension was inhibited, and the flexibility of the gelcasting was improved. However, Excessive solid volume fraction was prone to a bad rheological behavior of alumina suspension, and deteriorated the microstructure and properties of sintered body.
Mechanical and Wear Properties of Al2O3-15wt%ZrO2 Composites
Authors: Rao Ping Gen , Wu Jian Qing , Ye Jian Dong , Wang Ying Jun , Iwasa Mikio
Published: March 2009

A commercial a-alumina powder was mixed with Zr(OH)4 gel synthesized by a precipitation method. The mixture was calcined at 600°C for 2h. The Al2O3−15 wt% ZrO2 composites were sintered for 2 h in the temperature range between 1400°C and 1650°C in air. At the sintering temperature of 1550°C the highest density, the best wear resistance, the maximum bending strength of 708 MPa and the highest
fracture toughness of 5.8 MPa×m1/2 were achieved, respectively. Improvement of the mechanical and wear properties of the Al2O3 matrix should mainly be attributed to the addition of ZrO2.
Manufacture and Properties of AlON-TiN Particulate Composites
Authors: Zhang Zuo Tai , Wang Xi Dong , Zhang Mei , Li Wen Chao
Published: March 2009

Dense aluminum oxynitride-titanium nitride (AlON-TiN) composites with 3~15wt% TiN were fabricated by hot pressing technique. The effect of the content of a dispersion-toughening aid, TiN, on the mechanical properties, oxidation resistance and wear resistance were studied and related to the microstructure. The composites with a content of 15wt% were characterized with the highest
strength, 487 MPa, and the highest wear resistance properties. Oxidation behavior was studied and the results showed that AlON-TiN composites have excellent oxidation resistance.
Preparation and Formation Mechanisms of Monodispersed Mesoporous SiO2 Microspheres by the PICA Method
Authors: Zhao Li , Yu Jia Guo , Guo Rui , Cheng Bei
Published: March 2009

Monodispersed mesoporous silicon dioxide microspheres were prepared by polymerization-induced colloid aggregation (PICA) method and calcined at 850oC. The prepared samples were characterized with scanning electron microscopy (SEM), thermogravimetry (TG) and BET surface areas.
The results showed that the obtained SiO2 microspheres had an average diameter of about 2.0 µm, a surface area of 253.3 m2g-1, an average pore volume of 0.62 mLg-1, and an average pore diameter of 7.9 nm. The formation mechanism of SiO2 spherical particles was discussed.
Mullite Composite Phase Nanocrystalline from High-Silica Kaolin under Normal Pressure and Temperature: An Experimental Study
Authors: Chen Nan Chun , Chen Dong
Published: March 2009

The synthesis and characterization of mullite composite nanocrystaline from high-silica kaolin sampled from Tianyang County of Guangxi Zhuang Autonomous Region is presented in this paper. Rough kaolin is firstly grounded and processed to remove impurities, iron and carbon before burned to produce composite oxides with mullite as major components. The composite oxides are further synthesized into composite mullite nanocrystaline by using hydrothermal crystallization process under
low temperature and normal pressure. Tests on the composite nanocrystalline by TEM, TG-TDA, and X-ray diffraction methods show that the nanocrystalline range in size from 40 to 100 nm and are well textured. They also show significantly enhanced thermal stability at temperature as high as 1000oC.
Effect of Cation Extraction on the Oxidation Resistance of Si3N4
Authors: Wu Jian Qing , Yuan Fang Li , Zeng Xin Jun , Rao Ping Gen
Published: March 2009

A new method called cation extraction process has been applied to improve the oxidation resistance of silicon nitride ceramics with sintering additives. It is found that the high temperature oxidation rate of the Si3N4 ceramic treated by the process decreased remarkably in contrast to the oxidation rate of the Si3N4 without the process. The oxidation rate of Si3N4 ceramics with the cation extraction process is reduced more than 50% comparing with that of the Si3N4 ceramics without the
process. The morphological characteristic and phase composition of the oxides were analyzed by means of SEM and XRD. The oxidation rate of silicon nitride after cation extraction treatment is determined by the quality of the “purified layer” formed below the pre-oxide scale. Thicker oxide layer formed in pre-oxidation, higher extraction temperature and longer extraction time are helpful to form a good
“purified layer”.
Ultra-Fine Treatment of SiC Powder and Its Effect on Microstructure and Properties of SiC Ceramic
Authors: Guo Xing Zhong , Li Li , Gao Li Hua , Fu Pei Xin
Published: March 2009

The ultra-fine treatment of industrial SiC powder was carried out by fluidized bed opposed jet milling (QLM-100K), and the influences of grinding parameters on the ultra-fine treatment were studied. A better grinding result is achieved through a higher crushing pressure and a higher sorter frequency and the ultra-fine treated SiC powder possesses a smaller particle size, a narrower particle-size distribution, a higher specific surface area and reduced agglomeration. The effects of
ultra-fine treatment on the compaction behaviors, sintering behaviors, properties and microstructure of SiC ceramics were investigated. The compact with ultra-fine treated powder has a higher density and a lower sintering temperature. The densification and mechanical properties of the ceramics can be ameliorated obviously and the microstructure defects of the ceramics decrease.
Friction and Wear Characteristics of SiC and Si3N4 Ceramics Against ZrO2 Ceramic under Dry Friction
Authors: Tian X. , Lin Bin , Zhang W.L.
Published: March 2009

The friction and wear of the silicon carbide (SiC) and hot pressed silicon nitride (Si3N4) against zirconia (Y–TZP) sliding under dry friction and room temperature conditions were investigated with pin-on-disk tribometer at sliding speed of 0.56 m·s-1 and normal load of 50 N, 80 N and 120 N, respectively. It was found that, the coefficient of friction and wear rate are dependent on the test duration as well as the normal load. Through analyzing and comparing, the wear rates of the two frictional couples both are in the 10-6 mm3 (N·m)-1. Based on the variety regulation of the wear maps, the wear mechanisms of the two couples were analyzed. Between the two couples, the friction and wear characteristics of the SiC/ZrO2 couple are better than the Si3N4/ZrO2 couple’s.
Erosion Wear Characteristics of Si3N4 Fabricated from Low-Cost Powders
Authors: Wu Bing , Qi Long Hao , Shen Jian
Published: March 2009

High producing cost is one of the important reasons that silicon nitride ceramics can’t be widely used today. In this paper, one kind of commercial low-cost silicon nitride powder was used as raw material. High density samples were obtained through pressureless sintering with alumina, yttria and magnesia as sintering aids. The Si3N4 material was tested and the erosion wear rate was measured.
It was found that the low cost and dense Si3N4 ceramics exhibited a better erosion wear resistance than the hot-press ceramics produced with the UBE Si3N4 powder and much better then the Cr-26 cast iron. The worn surface was observed with the SEM and the erosion wear mechanisms were analyzed.
Synthesis of High Purity Ti3AlC2 Bulk Material by Hot-Pressing
Authors: Peng Chun Qing , Wang Chang An , Huang Yong
Published: March 2009

A new method to synthesize high-purity Ti3AlC2 bulk material by hot-pressing was
presented through adding a little amount of B2O3 as a low-temperature aid. The elemental Ti, Al, and active carbon powders were used as raw materials with a molar ratio of 3:1.2:2.The effect of sintering temperature on the purity of Ti3AlC2 was investigated at the range of 1200°C to 1500°C. XRD and SEM were used to characterize the product synthesized. High-purity Ti3AlC2 bulk materials, in which
almost no TiC phase could be found, were synthesized by hot-pressing at 1400°C and 1500°C for 1h in flow Ar atmosphere. The roles of B2O3 addition were considered as weakening the thermal explosive reaction in the mixture of elemental Ti, Al, and active carbon and increasing the purity of Ti3AlC2 in addition.
Bending Creep and Stress Relaxation of Ti3AlC2 at High Temperature
Authors: Bao Yi Wang , Zhou Yan Chun
Published: March 2009

Creep and stress relaxation of Ti3AlC2 were investigated using three-point bending tests at 800-1200°C under various load levels. The results show that the creep rate significantly increases with increasing temperature in the rang of 1000-1200°C. Subcritical crack growth during the creep process was found to be the main failure mechanism, i.e., the stress intensity factor increases with the creep-induced crack growth and results in the ultimate fracture. The lower limit of stress relaxation
was considered as the threshold value of zero-creep stresses, and the ratio of the threshold stress to the applied stress was defined to be a parameter of creep resistance for estimating deformation behavior at high temperature. SEM examination confirmed that the creep failure in Ti3AlC2 was governed by such a damage evolution: cavitation ® crack initiation ® crack extension ® fracture.
Synthetic of Zr2Al3C5 Material
Authors: Leela-adisorn Uraiwan , Yamaguchi Akira
Published: March 2009

Synthesis method of Zr2Al3C5 via solid state reaction between Al, ZrC and carbon powder was studied. Al-ZrC-C compact with equivalent mol ratio of Zr2Al3C5 was heated up to 1600oC in Ar atmosphere for 1 h and 4 h but ZrC phase still existed as major phase with very small amount of Zr2Al3C5. Because ZrC started to oxidize at low temperature under very low oxygen partial pressure, the same mol ratio of Al-ZrC-C compact was heated at 1600oC in vacuum for 1 h as parallel test. After
firing in vacuum, some carbon still exist with small amount of AlZrC2 occurred with Zr2Al3C5 as a main phase, but no ZrC was found. Different result from firing in Ar atmosphere and in vacuum had been discussed here. It was believed that very small amount of impurities in Ar had some effect on the formation of Al-Zr-Ccompound. The effect of very small amount of impurities in Ar was studied by
thermal analysis (DTA/TG) and XRD. It was found that very small amount of impurities in Ar haseffect on the reaction between Al, ZrC and carbon by diffusion through the surface and formZr-C-O-N solid solution. This solid solution cannot differentiate from ZrC by XRD. With help ofthermal analysis method (DTA/TG), Zr-C-O-N solid solution can be differentiated from ZrC.Therefore, synthesis of Al-Zr-C compound should be done in vacuum. Zr2Al3C5 can be prepared from mixture of Al-ZrC-C with excess amount of Al at 1600oC for 1 h.
Reaction Synthesized Boron Nitride-Containing Composites (BNCC)
Authors: Zhang Guo Jun , Ohji Tatsuki , Kanzaki Shuzo
Published: March 2009

Based on the proposed inorganic reactions a series of high performance hexagonal boron nitride-containing composites (BNCC), include SiC-BN, Si3N4-SiC-BN, SiAlON-BN, AlN-BN, Al2O3-BN, AlON-BN and mullite-BN, have been prepared via reactive hot pressing or pressureless reactive sintering. Various boron-bearing components such as B, B4C, AlB2, SiB4, SiB6, B2O3 or H3BO3, 9Al2O3×2B2O3 (9A2B) and 2Al2O3×B2O3 (2AB) are used as the boron source. On the other hand, nitrogen gas or solid state nitirgen-bearing metal nitrides such as Si3N4 and AlN can be used as the nitrogen source. The in situ synthesized composites demonstrated homogeneous and isotropical microstructures with very fine (nano-sized) BN platelets or their agglomerates distributed in the matrixes. These composites showed high strength, low elasticity and improved strain tolerance. In this article the reaction design, thermodynamics, reaction mechanisms, reactive hot pressing or pressureless reactive sintering, microstructures and mechanical properties will be discussed.
Study on the Performance of CBN Abrasives with Ti Coatings
Authors: Li Zhi Hong , Zheng H.F. , Zhu Y.M. , Yuan Q.M.
Published: March 2009

In this paper, the performances of CBN abrasives with and without Ti coatings and their changes during heat treatment were investigated under the same conditions. The results showed that the single particle compressive strength and the impact toughness for CBN abrasives with Ti coatings were lower than these of CBN abrasives without Ti coating. Ti coating on the surface of CBN abrasive particles oxidized and formed TiO2 with discontinuous structure at above 650°C during the
firing process. The poor oxidation resistance of Ti coating and the discontinuous structure of its oxidation product could not protect CBN abrasives from heat damage, therefore could not improve properties of CBN abrasives.
Combustion Synthesis of Ti(C,N) Powder
Authors: Wang Yan An , Chen Ke Xin , Zhou He Ping
Published: March 2009

Titanium carbonitride powders were synthesized directly by a combustion synthesis
process between titanium and carbon in a nitrogen atmosphere. The relationships between properties of the final product and the combustion reaction parameters were systematically investigated. Especially, the effects of nitrogen pressure on the phase formation and microstructure of the as-synthesized products were experimentally investigated. The reaction mechanism of Ti(C,N) was
proposed through quench experiment, the variation of combustion temperature on time and thermodynamics analysis.
Fabrication of TiC-Ti Porous Materials by Combustion Synthesis
Authors: Shen Wei Ping , Ma Wen , Gu Shu-Yuan , Zhang Ye
Published: March 2009

TiC-Ti porous materials have been successfully prepared using combustion synthesis in this paper. Adiabatic temperature of Ti-C and Ti-C-TiC systems was calculated. As to the Ti-C system, the studies show that when the ratio of C/Ti is the range of 0.5-0.6, the pressure of protecting atmosphere is 2-4 MPa, and the density of green compact is about 60%, the synthesized sample exhibits excellent properties such as porosity of 40%, volume density of 2.6 g/cm3, compressive strength over 4 MPa. Pore size is as large as 5-25 µm and the majority pores belong to interconnected pore.
Fabrication of Vanadium Nitride by Carbothermal Nitridation Reaction
Authors: Wang Xi Tang , Wang Zhou Fu , Zhang Bao Guo , Deng Cheng Ji
Published: March 2009

Vanadium nitride is produced from V2O5 by carbon-thermal reduction and nitridation.
When the sintered temperature is above 1273K, VN can be formed, and the nitrogen content of the products increased with the firing temperature raised, and then is the largest when the sintered temperature is 1573K. The C/V2O5 mass ratio of the green samples is the other key factor affecting on the nitrogen contents of the products. The nitrogen content of the products reaches the most when the
C/V2O5 mass ratio is 0.33, which is the theoretical ratio of the carbothermal nitridation of V2O5.
Study on the Wear Resistance of Micro-Nanostructured WC Composite Coating Sintered by Induced Heating
Authors: Wang Zhen Ting , Chen Hua Hui
Published: March 2009

Micro-nanostructured WC composite coatings were successfully fabricated by induced heating sintering method on the surface of Q235 steel .The microstructure, micro-hardness and the wear resistance of the composite coatings were studied .The results show that the microstructure of induced heat layer is mainly composed of Ni-based solid solutions and WC particles. And there exists excellent
metallurgical bonding between coating and substrate. The wear resistance of micro-nanostructured WC Composite Coatings is increased by 1.5 times on an average as compared with that of micron.
Precipitation of Hydroxyapatite on Oxide Film Containing Ca and P by Hydrothermal Treatment
Authors: Liu Fu , Wang Fu Ping , Shimizu Tadao , Igarashi K. , Zhao Lian Cheng
Published: March 2009

An oxide film containing Ca and P was obtained in an electrolyte containing calcium
glycerphosphate (Ca-GP) and calcium acetate (CA) by microarc oxidation. The surfaces of the oxide films were porous and rough, and the Ca/P ratio in the oxide film was 1.71 when the oxide film was formed in the electrolyte containing 0.06 M Ca-GP and 0.25 M CA at current density 50 A/m2 and final voltage 350 V. The oxide film with Ca/P ration 1.71 was treated hydrothermally at 190°C for 10
hours in an autoclave. It was found that hydroxyapatite crystals were precipitated on the oxide film after hydrothermal treatment. The oxide films were investigated by means of electron probe micro analyzer, X-ray diffraction, scanning electron microcopy before and after hydrothermal treatment.
Processing of Calcium Phosphate Porous Materials by 'Self-Setting'
Authors: Cai Shu , Wang Yan Wei , Yao Kang De
Published: March 2009

Macroporous biomaterials based on a-tricalcium phosphate (a-TCP) bone cement with porous structures suitable for implantation purposes were prepared in the present work. According to the reversible swelling/deswelling behavior of gelatin at a single temperature or pH, a “self-setting” method that uses gelatin granules as pore formers was developed to process the porous microstructure. By mixing gelatin powder and bone cement powder (BCP), and adding water (1% solution of NaH2PO4×HO) to form pastes which set within 15 to 30 min, this setted cement was then immerged in deionized water of temperature 25°C or 32°C for hydration. During the hydration, the pH of deionized water after cement pastes were introduced at 32°C changed from 8.6 to 7.2 which caused by the transformation of a-TCP to hydroxyapatite (HA). Meanwhile, gelatin particles will swell by water uptake to form large size spheres in cementmatrix. This swelling behavior is sensitive to the variation of pH value. After hydration for 4 day, a body containing gelatin gel spheres was obtained. Then heating the deionized water to temperature 50°C, gelatin spheres in cement matrix were solved and porous microstructure composed of larger pore sizes corresponding approximately to the average size of
the swelling gelatin granules was obtained. The porous bodies by this technique were found to have tractable and interconnected porosity in the range of 60~84%, with typical pore sizes ranging from 100~300 microns. This new processing technique can be used in the manufacture of unsintered biomaterials.
Setting Behavior of Fast-Setting Calcium Phosphate Cement with Mineral Phase of Bone
Authors: Pan Jian , Tian Jie Mo , Dong Li Min , Wang Chen
Published: March 2009

The setting behavior of fast-setting calcium phosphate cement (FSCPC) with mineral phase of bone was investigated to evaluate the possible value of the CPC for medical and dental application. Various aspects of the setting behavior such as setting time, mechanical strength and phase change of cement with time were measured by the Vicat needle method, diametral tensile strength measurement, and quantitative powder X-ray diffraction (XRD) analysis, respectively. The
change of microstructure during the setting process was observed by Scanning Electron Microscope (SEM). The setting time of the CPC was 10-15min. As a result of its fast setting, set specimens of FSCPC showed high mechanical strength. Powder XRD analysis revealed faster conversion of FSCPC into HAP. SEM observation showed that the specimens are mainly formed with micropores and crystallites, and the phase composition of the set specimens is mainly low-crystallinity HAP at last.
Structural Assessment of Microsphere-Based Tissue Engineered Scaffold from Poly(Lactic Acid)/ß-Tricalcium Phosphate
Authors: Wang Ying Jun , Ge Jian Hua , Zheng Yu Dong , Zhang Xiao Hui , Chen Xiao Feng , Ran Wei , Wu Gang
Published: March 2009

The addition of b-tricalcium phosphate improves the biocompatibility and the bioactivity of scaffolds made from poly(lactic acid)(PLA). In this paper, a developed method was used to prepare poly(lactic acid)/ b-tricalcium phosphate microsphere-based tissue engineered scaffolds. It was found that the porosity and the compressive modulus of the scaffolds increased with increasing stirring time.
The PLA scaffolds with a higher strength and porosity could be obtained under the optimum conditions (i.e., 2.0 g of PLA, 0.2 g of b-tricalcium phosphate, 300 rpm, stirring time for 2h ). In addition, the corresponding mechanism has been discussed.
Effects of Ingredients and Post-Heat Treatment on Phase Transformation and Structure of Bioactive Composite Coatings
Authors: Li Mu Qin , Shang Da Shan , Ma Chen , Yang Shi Qin
Published: March 2009

Bioactive composite coatings containing sub-layer and working-layer with different
ingredients were prepared using subsonic thermal spraying technology and then heat-treated at 700°C for 1h. Two types of bioglasses, named BG1 and BG2, and Y2O3 were used as additives of the sublayer and working layer respectively. Phase transformation and structure changes of the coatings were investigated
with XRD, DSC and SEM. Results showed that the phases of as-sprayed Ti/BG1 sub-layer were TiN, TiO2 (rutile and anatase), etc. Post-heat treatment changed the phase composition. TiN and anatase transformed into rutile and some new phases generated, which often enriched at pores and cracks. In the working-layer, part of nano-hydroxyapatite powders decomposed during coating preparation. Y2O3
impaired the decomposition to some extent and BG2 enhanced greatly. Post-heat treatment increased the crystallinity of all coatings effectively. The analysis of TG-DSC showed that BG2 added in working-layer crystallized at 700°
Micro-Morphology of Crystal Separated from Glass by the Heat-Treatment with an Electric Field
Authors: Wang Guoliang , Liang Kai Ming , Liu Wei , Hu An Min , Zhou Feng , Shao Hua
Published: March 2009

By means of SEM, the micro-morphology of silver particles separated from borosilicate glass by the heat-treatment with an electric field is investigated. The distribution of the silver particles appears clusters. This result is explained by an energy viewpoint. Based on hermodynamics theory of phase separation, the calculation of the free energy change during the heat-treatment in an electric
field is performed by means of the Ansoft Maxwell software. The results of this calculation analysis are found to be very close to the experimental data.
Nucleation and Crystallization of Glass-Ceramics from Coal Fly Ash
Authors: Peng Fei , Liang Kai Ming , Shao Hua , Hu An Min , Zhou Feng
Published: March 2009

The nucleation and crystallization kinetics of glass obtained by melting coal fly ash with additives at 1550°C have been investigated. The optimum heat treatment schedule for the glass was nucleation at 825°C for 60min before crystallization at 962°C for 4h. The activation energy for crystallization of the glass-ceramics, obtained by the DDTA result, was 280.03 kJ/mol, lower than that of glass-ceramics obtained from pure reagents. The low activation energy is caused by impurities in fly ash, serving as nucleation agent. The results of XRD and SEM show that glass-ceramics developed nano-sized spherical wollastonite.
β-SiAlON Bonded Corundum Material and Its Application as Sliding Gate Plate for Continuous Casting
Authors: Zhu Bo Quan , Li Xiang Cheng , Jin Cong Jin , Li Zeya , Tian Shou Xin
Published: March 2009

β-sialon bonded corundum-based sliding gate plate was developed from raw materials of Al, metallic silicon and alumina through nitriding-reaction process. It was found that the effects of β-sialon content on the physical properties are significant and the mechanical properties of developed sliding gate plate are strongly related to the Z-value. The materials with Z value of 2 and 20wt% β-sialon, exhibit the
highest hot modulus of rupture and cold crushing strength. It was also found that sialon bonded corundum-based material has good oxidation resistance because a protective layer is formed during oxidation process.
Novel Estimation of Critical Frontal Process Zone of Ceramics by a Single-Edge V-Notched-Beam Technique
Authors: Chen Chun Hong , Awaji Hideo
Published: March 2009

A novel estimation for the critical size of the frontal process zone of ceramics is proposed using a single-edge V-notched beam (SEVNB) technique. A three-point flexure test is carried out on aluminum titanate ceramics containing a sharp V-shaped notch with different depth. An exact solution of the critical local stress is analyzed at a critical distance from the notch tip. The critical frontal process zone size is determined as the distance between the notch tip and the point where the
critical local stress equals the flexural strength of specimens without notches, based on the local fracture criterion and the Griffith-Irwin criterion. The critical size of the frontal process zone, the fracture toughness and the flexural strength were also estimated for several materials, such as, alumina, porous alumina, and alumina-based nanocomposites. The relationship between these mechanical properties indicated that there was an almost linear relationship between the fracture
toughness and the resultant of strength and square root of the critical frontal process zone size, and that both of them must be increased to improve the fracture toughness of ceramics.
Microstructure and Characteristics of PbTiO3-PbZrO3-Pb(Mg1/3Nb2/3)O3- Pb(Zn1/3Nb2/3)O3 Ceramics
Authors: Wang Chun Huy
Published: March 2009

The new piezoelectric ceramic of PbTiO3-PbZrO3-Pb(Mg1/3Nb2/3)O3 -Pb(Zn1/3Nb2/3)O3 with composition close to the morphotropic phase boundary was studied. The dielectric and piezoelectric properties of Pb0.96Sr0.04[(Zr1-yTiy)0.74(Mg1/3Nb2/3)0.20(Zn1/3Nb2/3)0.06]O3 were investigated, the
composition range examined are 0.47 £ y £ 0.57. From the results of XRD and piezoelectric measurement, it is supposed that the composition with y = 0.51 corresponds to M.P.B. between tetragonal and pseudocubic perovskite. Some developed phenomena or models are introduced and take it to interpret well. After optimal choice of these conditions, the planar coupling factor close to 0.65, mechanical quality factor Qm close to 75, the longitude wave velocity close to 4100 m/s and the poled dielectric constant close to 2600 can be approached in this study.
The Toughening Action of Comprehensive Transformation on Mixed Mode II-III Ceramics
Authors: Ni Xin Hua , Liu Xie Quan , Wang Jun Ying , Lu Xiao Bo
Published: March 2009

By the use of comprehensive transformation criterion and the method of weight function, the fracture enhancement of mixed-mode II-III crack in transformation toughened ceramics is predicated. The theoretical expressions of the toughening effect for both the stationary and steady-state growing crack are given respectively. The results show there is no toughening effect for the stationary crack and the toughening effect for the steady-state growing crack is associated with the
modulus of elasticity, the width of transformation and its volume fraction.
Stages of Reactive Wetting
Authors: Agathopoulos Simeon , Tulyaganov D.U. , Ferreira José Maria F.
Published: March 2009

A universal model for describing the wetting kinetics at solid/liquid interfaces, where
interfacial chemical reaction occurs, is proposed, whereby four distinct stages separated from each other by transition points are anticipated. The stages are described by means of comparing the dimensions of the base of the liquid sessile drop with the evolution of the reaction product forming on the solid/liquid interface, over time.
Effect of TiC Content on Fracture Toughness of TiC-Ti5Si3 Composites
Authors: Wang Lian Jun , Jiang Wan , Bai Sheng Qiang , Chen Li Dong
Published: March 2009

In-situ toughened TiC-Ti5Si3 composites were fabricated using reactive sintering of Ti and SiC via spark plasma sintering (SPS). The focus of this work on the content of TiC in final composites was different. The phase constituents and microstructures of the samples were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Fracture toughness at room temperature
was also measured by indentation tests. The results showed that the corporation of TiC greatly enhances the fracture toughness of TiC-Ti5Si3 composites.
Electrophoretic Deposition of Pb(Zr,Ti)O3 Powders on Silicon Wafer and Sintering Densification Approach
Authors: Kang Ni , Li Jing Feng
Published: March 2009

Electrophoretic deposition (EPD) is a promising, simple and cost-effective method for fabrication of piezoelectric ceramic films. In this study, commercial lead zirconate titanate (PZT) powders were deposited onto silicon wafers coated with platinum electrodes by using EPD method in ethanol solution with a few amount of HCl to introduce surface charges to PZT particles. The sintering densification of the
EPD-derived green PZT films were attempted with approaches: addition of a low-temperature eutectic sintering aid consists of Cu2O and PbO, infiltration of PZT sol into the green film. Thick PZT films on Si wafers were obtained by sintering at 700oC with sintering aid and sol-infiltration.
The Preparation and Properties of New Silver-Metal Oxide Graded Composite Electrical Contact Materials
Authors: Wang Yu , Zhang F. , Qi L.Z. , Wang L. , Cheng L.C.
Published: March 2009

Electrical contact material is a very important material for the electric power industry. An electrical contact material should display good structural characteristics (suitable hardness, high thermal conductivity and stabilization) as well as a good functional characteristic (low electrical resistivity). It is difficult to fabricate such a contact material with all these good performing parameters by common techniques because these physical parameters influence each other. In this paper, we report a novel investigation to design and prepare silver-metal oxide composite materials according to functionally layered and graded material (FLGM) concept and meeting requirement as electrical contact material. The silver-based composite samples characterized by layered component were prepared with conventional
solid-phase sintering technique. One kind of sample consists of tin dioxide and silver material, in which SnO2 exhibits a graded distribution. Another consists of two metal oxides, cadmium and zinc oxides, and silver material, in which each layer has different metal oxide. Hardness, thermal conductivity and electrical conductivity, were measured and related problems are discussed. Especially, welding resistance
as an important parameter for practical application was tested. SEM analyses before and after electrical erosion were also performed. We conclude that the functionally graded material (FGM) concept as a novel designing and fabricating method has potential for electrical contact composite material.
Preparation of Multilayer Barium Titanate PTC Thermistor with Low Room Temperature Resistance
Authors: Zhou Dong Xiang , Liu Huan , Gong Shu Ping , Zhang Dao Li
Published: March 2009

Chip-type PTC thermistors with multilayer stacked structure have been fabricated by
bonding sintered ceramic chips with internal electrodes to offer low resistance at room temperature and correspondence to surface mounted technology. The resistance-temperature characteristics of multiplayer stacked PTC thermistors made up of different numbers (N = 1, 3, 5) of layers were experimentally investigated (the typical size of each layer was 10 mm × 7.0 mm × 0.38 mm). The
selection and extraction of additives in roll-forming process were also discussed. This resulted in a crack-free multiplayer stacked PTC thermistor.
Effects of Lanthanum Modification on the Structure and Electrical Properties of PZN-PZT Ceramics
Authors: Zeng X. , Ding Ai Li , Zheng X.S. , Zhang Yong , Qiu Ping Sun
Published: March 2009

La-modified PZN-PZT compositions with representative formula Pb1-0.7xLa0.7x(Zn1/3Nb2/3)0.3- (Zr0.55Ti0.45)0.7(1-x/4)O3 were prepared by the columbite precursor method. La content, x, was varied from 0 to 8mol%. Effects of La doping on microstructure, dielectric and piezoelectric properties were
investigated. The results showed that in present system La doping promotes the formation of pyrochlore phase and the phase shifted from rhombohedral to tetragonal structure with increasing La content. It was also found that La doping makes dielectric permittivity maximum decrease and the degree of diffuse
phase transition enhance. Appropriate amount of La doping could improve the piezoelectric properties.
Sol-Gel Process and Properties of Textured Pb(Zr, Ti)O3 Films on Silicon Wafers
Authors: Gong Wen , Chu Xiang Cheng , Li Jing Feng , Gui Zhi Lun , Li Long Tu
Published: March 2009

Lead zirconate titanate (PZT) thin films with a composition near the morphotropic phase boundary were deposited on silicon wafers by using a modified sol-gel method. Introducing a seeding layer between the interface of PZT film and platinum electrode controlled the texture of PZT films. The lead oxide seeding layer results in highly (001)-textured PZT film, while the titanium dioxide seeding layer results in (111)-textured one. SEM and XRD were used to characterize the PZT thin
films. The ferroelectric and piezoelectric properties of the PZT films were evaluated and discussed in association with different preferential orientations.
Fabrication of BST Films by Electrophoretic Deposition from Nano-Scaled (Ba,Sr)TiO3 Synthesized by Different Methods
Authors: Zhao Jian Ling , Wang Xiao Hui , Li Long Tu
Published: March 2009

(Ba,Sr)TiO3 films with thickness between 1 ~ 20 µm are fabricated by electrophoretic deposition using (Ba,Sr)TiO3 nanopowder synthesized by different methods including sol-gel, coprecipitation and conventional solid phase synthesis. Experiments show that conventional solid phase synthesis need higher crystallization temperature (>1000°C) and result in larger size of particle
while in sol-gel and coprecipitation process (Ba,Sr)TiO3 crystallizes at lower temperature and results in smaller size of particle . Powders synthesized from various routes have different surface property. Deposition parameter must be adjusted accordingly to obtain dense and smooth (Ba,Sr)TiO3 film.
Electrical Properties of the Mixed Bismuth Layer-Structured Bi7Ti4NbO21 Ceramics
Authors: Zhang Lina , Li Guo Rong , Zhao Su Chuan , Zheng Liao Ying , Yin Qing Rui
Published: March 2009

A mixed bismuth layer-structured compound, Bi7Ti4NbO21, has been prepared by the conventional solid state reaction. It showed an orthorhombic symmetry with a = 5.4428, b = 5.4043 and c = 29.041 Å by X-ray powder diffraction analysis. The hysteresis loops as a function of temperature were observed with a standardized ferroelectric test system. The remanent polarization and the coercive field of the material at 140°C were 14.06 µC/cm2 and 78.6 kV/cm, respectively.
Thermal dependence of dielectric permittivity showed two-phase transitions at around 670°C and 845°C, which were also investigated by TSC and DSC. Finally, piezoelectric properties were obtained with a piezoelectric coefficient d33 = 10 pC/N. It was observed that Bi7Ti4NbO21 underwent a ferroelectric–paraelectric phase transition at 845°C by depolarization experiments.
Effects of Donor Doping on Microstructure and Electrical Properties of Bismuth Layer-Structured Bi4Ti3O12 Ceramics
Authors: Zhang Lina , Zhao Su Chuan , Zheng Liao Ying , Li Guo Rong , Yin Qing Rui
Published: March 2009

A study was conducted on the effects of donor dopants, Nb2O5 and WO3, on microstructure and electric properties of Bi4Ti3O12 (BIT) ceramics. X-ray diffraction patterns of the materials showed a single orthorhombic phase structure. The microstructure results revealed the appearance of plate-like grain. The donor doping decreased the conductivity of BIT by as much as 3 orders of magnitude. The dielectric and ferroelectric properties of doped-BIT materials were also investigated.
The decrease in the electrical conductivity allowed the doped samples to be poled to develop piezoelectricity. Thermal annealing studies of the samples indicated the donor-doped BIT were suitable candidate materials for high-temperature piezoelectric applications.
Experimental Study on Damping Characteristics of Piezoceramic Materials Shunted by Passive Electrical Circuits
Authors: Yan Shao Ze , Zhang Fu Xing , Li Yang Min
Published: March 2009

Piezoelectric materials have an ability to efficiently transform mechanical energy to electric energy and vice versa, which makes them useful as structural dampers. The objective of this work is to investigate the damping capabilities of a piezoceramic shunted by different types of passive electrical circuits. The material properties of the shunted piezoceramic are modeled and the analytical results show
that the shunted piezoceramic exhibits different damping potentials depending on the piezoelectric properties of the material and the shunt circuits. An experimental set-up of a cantilever beam with surface bonded piezoceramics is proposed to investigate the damping characteristics of the shunted piezoceramic. An analytical model is developed to describe the influence of the shunted piezoceramic on the dynamic response of the beam. The damping performances of the piezoceramic shunted by different circuits are compared respectively and the experimental results show approximate agreement with the numerical simulations of the model.
Effects of CuO-V2O5-Bi2O3 Additions on the Microstructure and Microwave Dielectric Properties of 0.42ZnNb2O6-0.58TiO2 Ceramics
Authors: Wang Jin , Yue Zhen Xing , Zhang Ying Chun , Gui Zhi Lun , Li Long Tu
Published: March 2009

The effects of additions on the microstructure and microwave dielectric properties of
0.42ZnNb2O6-0.58TiO2 (ZNT) ceramics were investigated systematically. The sintering temperature of ZNT ceramics doped with different amounts of CuO, Bi2O3 and V2O5 can be effectively reduced. The phase of doped samples was studied compared to the undoped ZNT ceramics. For densified ZNT ceramics with the increasing amount of dopant CuO-Bi2O3-V2O5, the dielectric constants (εr) of
densified samples ranges from 38 to 42, the Q×f values decrease evidently and ranges from 13300 GHz to 5000 GHz and the τf values are shifted toward negative.
The Role of Niobium in (Ca, Si, Ce, Nb)-Doped TiO2 Varistors
Authors: Luo Shao Hua , Tang Zi Long , Li Hong Yun , Zhang Zhong Tai , Xiong Xi Zhou
Published: March 2009

The present work attempted to investigate the effect of Nb addition on the electrical properties of the (Ca,Si,Ce,Nb)-doped TiO2 ceramics. The content of added niobium is in the range 0.1-1.0mol %, while that of the other additives keeps constant. The results showed that an optimal composition doped with 0.8mol% Nb2O5, followed by sintering at 1350°C, was obtained with low V1 mA of 7.22V, high
nonlinear coefficient of 5.76, ultrahigh dielectric constant (er = 86000) as well as relatively low loss (tgd = 0.52) in room temperature at 1 kHz. SEM studies show that change of niobium had significant influence on grain growth and micro structural characteristics of the sintered samples.
Preparation of Ni/BaTiO3 Composites and PTC Effect
Authors: Li Xiao Lei , Qu Yuan Fang , Ma Wei Bing , Zheng Zhan Shen
Published: March 2009

Ni/BaTiO3 composite was prepared by decomposition of NiC2O4·2H2O/BaTiO3 precursor, which was prepared by precipitating of nickel in the form of oxalate into the BaTiO3 slurry. The composite must be sintered in reducing atmosphere. Otherwise NTC effect would be introduced. The prepared composite almost had no PTC effect. But PTC effect of the Ni/BaTiO3 composite can be effectively renewed by heat-treatment in air. Under a proper composition and method, the composite
shows low room-temperature resistivity (ρRT=6.0 Ω·cm) and obvious PTC effect (ρmax/ρmin=102).
(Ba,Sr,Pb) TiO3-BaPbO3 System Compound PTC Ceramic
Authors: Sun Xiao Long , Ma Wei Bing , Li Xiao Lei
Published: March 2009

This paper made a thorough investigation on (Ba,Sr,Pb) TiO3-BaPbO3 system compound PTC ceramic. The optimum compound method is determined by lots of experiments in different compound schemes. Also the formula and process are optimized and improved. The best properties acquired are: ρroom-temperature=18.8Ω·cm, ρmax/ρmin >103. In the end, the phenomena in the experiment are illustrated with electron trap model.
Spin and Valence States of Manganese Ions in Mn-Doped BaTiO3 Ceramics by Electron Paramagnetic Resonance
Authors: Zhou Zhi Gang , Tang Zi Long , Zhang Zhong Tai
Published: March 2009

A number of paramagnetic defects and defect complexes in BaTiO3 have been detected by the Electron Paramagnetic Resonance (EPR) technique. The signal intensity, the g factors and the hyperfine splitting constants A of Mn2+ at the different temperatures were distributed with temperatures in a U-shape. In this paper, a new direct evidence for the presence of manganese with an electron spin of S=5/2 (Mn2+) in all four phases (R, O, T and C) and the high spin state of the electron configuration in MnTi² at the high temperature cubic phase is presented by EPR method in La-Mn codoped BaTiO3 PTCR ceramics.
Thermoelectric Properties on SixGe1-x Containing Fullerite
Authors: Xu Gui Ying , Wu Xiao Feng , Zhang Li Li , Ge Chang Chun
Published: March 2009

SixGe1-x (x = 0.75 for n-type and 0.7 for p-type) is a typical thermoelectric material used at higher temperature as thermoelectric generator. Its property is dependent on the composition. SixGe1-x containing different amount of fullerite added as hollow quantum dot were fabricated by hot-pressing method. The relations among thermoelectric property, the amount of fullerite and the microstructure were investigated by normal measurement and analytical method.
Advanced Hybrid Ion Conducting Ceramic Composites and Applications in New Fuel Cell Generation
Authors: Zhu Bin
Published: March 2009

Our developments on ceramic composite conductors have experienced about 15 years from the oxyacid-salts oxide proton-based conductors, non-oxide containment salts, the ceria-based composite electrolytes, hybrid proton and oxygen ion conductors and nano-composites. A special emphasis is paid to new functional nano-composites based on hybrid proton and oxygen ion
conductors that have demonstrated advanced properties and fuel cell applications, e.g., excellent ionic conductivity of 0.01 to 1 Scm-1 and performances of 200 - 1000 mWcm-2 for temperatures achieved for fuel cells between 400 and 700°C. Some proton and oxygen ion conducting mechanisms in the materials are reviewed and discussed. The hybrid ion conduction and dual electrode reactions and processes create a new generation fuel cell system.
Dielectric Polarization of Ba2Ti9O20 Ceramics for Microwave Applications
Authors: Xiong Zhao Xian , Xiao F. , Huang J.R. , Qiu Hong
Published: March 2009

Dielectric constant of Ba2Ti9O20 ceramics are theoretically calculated based on the chemical structure of the oxides and the mixing rule of dielectric material in this paper. Meanwhile, the microwave properties (εr, Q and τf) of practical Ba2Ti9O20 ceramics are experimentally measured at microwave frequencies. Some of useful suggestions are therefore provided for material optimization of practical
ceramics.