bluuebunny/crossref_metadata_2025 huggingface dataset:
Morphology and Reaction Mechanism of AlN Fibers Synthesized by Carbothermal Reduction
Authors: Shen Chun Ying , Qiu Tai , Lu Yu Ming
Published: March 2009

AlN fibers were synthesized by carbothermal reduction using Al2O3 fibers as starting material. The N content of AlN fibers synthesized at 1780°C was more than 31%. The morphology and microstructure of AlN fibers were studied with XRD, SEM and TG-DSC. The fibers containing small AlN grains were pipe-shaped, in which the particle size is about 1µ, diameter 4 ~ 6µ, length/diameter ratio 20 ~ 30. The main reaction process is as follows: Firstly, alumina is reduced by carbon to lower-valent aluminum oxide, which further reacts with nitrogen and forms AlN. Secondly,
when the alumina fibers are coated by AlN layer, the reaction takes place simultaneously on both interfaces of the AlN layer.
Influence of Powder Characteristics on Sintering of AlN Ceramics
Authors: Qiu Jin Yu , Watari Koji , Hotta Yuji , Mitsuishi Kenshi
Published: March 2009

The sintering behavior of AlN powders with different particle sizes and specific surface areas was investigated in the present work. 4.5-8.0mass% of the as-synthesized sintering aid from the Li2O-Y2O3-CaO system was added to these AlN powders, and they were then fired at 1400-1650oC for 6h. At the initial stage of sintering the fine AlN powder, it was recognized that sintering of primary particles
occurred in agglomerations. With an increase of firing temperature, particles were rearranged and grains grew rapidly at the final stage. On contrary, in sintering of samples using the coarse AlN powder, the densification increased with raising sintering temperatures slowly, and the sintering temperature higher than 1650oC was required to obtain densified specimens.
Combustion Synthesis and Two-Time Densification of TiB2-Cu Composites
Authors: Hong Chang Qing , Zhang Xing Hong , Han Jie Cai , Xu Qiang , He Xiao Dong
Published: March 2009

TiB2 -Cu cermet with the relative density of 92% was produced from titanium, boron and copper powders by combustion synthesis and subsequently pseudo hot isostatic pressing. To improve its mechanical and thermal physical properties, the two-time hot pressing sintering test was carried out at 1050°, 1090° and 1150°C respectively. The deformation behavior and variation of micro- structure and
mechanical properties were investigated in detail. The results showed that the relative density and the flexural strength increase remarkably after two-time hot pressing. The relative density reaches 605.5MPa and the flexural strength reaches 96% when the two-time pressing temperature is at 1090°C, and the values increase 12% and 6% compared to that before two-time pressing.
Effect of Pressure on TiB2-Cu Composite via In-Situ Reaction Synthesis
Authors: Sun Yue Feng , Xu Qiang , Zhang Xing Hong , Han Jie Cai , Liu Jin Huai
Published: March 2009

TiB2-Cu matrix composites from titanium, boron and copper powders were in-situ
fabricated by exothermic reaction. The effect of the applied pressure on the mechanical properties of the composite was investigated. The results showed that when the applied pressure increasing, the relative density, bending strength, fracture toughness and hardness of the composites were on the increase due to the formation of fine microstructure and the improvement of densification with the
pressure increasing. The high pressure is beneficial to the better mechanical properties.
The Structure and Hardness of rf-Reactive Sputtered Ti-Zr-N Films
Authors: Park Hyun Ah , Hong Hyun Seok , Hwang Sun Keun , Lee Chong Mu
Published: March 2009

Ternary Ti-Zr-N thin films were synthesized by rf-reactive sputtering in Ar–N2 plasma. Effects of the substrate temperature in the sputtering process on the microstructures of Ti-Zr-N thin films were investigated using SEM, TEM, XRD and AES techniques. The hardness of the Ti-Zr-N film increases as the substrate temperature in reactive sputtering increases. The reactive sputtered Ti-Zr-N film is characterized as polycrystalline in nature with two dominant orientations of (111) and (200). A substrate temperature of 300°C is suggested for getting a densely packed film structure with the highest hardness.
Microwave Plasma Sintering and In Vitro Study of Porous HA/β-TCP Biphasic Bioceramics
Authors: Ji Jin Gou , Ran Jun Guo , Gou Li , Wang Fang Hu , Sun Lu Wei
Published: March 2009

Porous HA/β-TCP biphasic calcium phosphate (BCP) bioceramics were prepared by microwave plasma in order to solve the problems on sintering of Ca-P bioceramics by a conventional furnace. The plasma-sintered samples exhibit a higher densification rate, smaller grain size and higher compressive strength compared to those of conventional sintered samples. The [Ca2+] concentration and
the dissolution rate are also higher than those of conventional sintered samples in physiological saline. After immersed in simulated body fluid (SBF) and simulated inflammation body fluid, the amount of bone-like apatite formed on plasma-sintered samples is more than that formed on conventional sintered samples. The results indicate that plasma sintered porous BCP bioceramics have better mechanical
properties and may also have better biological properties. On the other hand, the surface of samples that underwent a simulated inflammation procedure is smoother and the amount of bone-like apatite formed on them is less than that formed on the samples immersed in normal SBF all the time, which may indicate that the light acid in an inflammation response would affect the bone reconstruction when Ca-P bioceramics implanted in living body.
Effect of Electrodeposited Hydroxyapatite Coatings on Biomedical Titanium by Cathode Revolving
Authors: Meng Xiang Cai , Li Xing Yi , Wang Tao
Published: March 2009

The paper deals with a kind of new method of the electro-deposition on titanium by a
cathode revolves. The depositing characteristic and mechanic were studied by scanning electron microscopy and X-ray diffraction. The experimental results show that the more fine uniformity and compact calcium phosphate bioactive coatings could be produced, compared with the conventional methods. The gradient Coating, which is fine inside and porous outside, could be obtained by controlling
revolving velocity. The coating would transform to the hydroxyapatite after heat-treatment. After soaking in a simulated body fluid (SBF), nano-depositions were formed on the surface of the coating, then those particles would grow up needle-like, net-like, and an apatite-like layer could be observed finally. The gradient porosity coatings produced by cathode revolving electrochemical deposition would have high anti-dissolution and bioactive.
Co-Firing Behavior of Co2Z Hexagonal Ferrite/Ag Internal Electrode for MLCIs
Authors: Miao Chun Lin , Wang Mao , Yue Zhen Xing , Zhou Ji , Cui Xue Min
Published: March 2009

This paper presents the shrinkage behavior, phase transformation and interfacial character of the hexagonal ferrite/silver electrode composite. The shrinkage analysis shows apparent sintering mismatch between hexagonal ferrite ceramic and silver electrode material and improvement of the co-fired characteristics was obtained by adding appropriate amount of sintering additive. Scanning
electron microscopy observations indicate that silver grains distribute uniformly in the composite. Drawn from the back-scattered (BS) electron image, no silver dispersed into the ferrite grains and there’re no obvious chemical reactions between Co2Z hexagonal ferrite and silver, which can be confirmed by X-ray diffraction spectrum. Silver induction exerts remarkable effect on the electronic
properties of the composite and could increase the dielectric constant and dielectric loss to a certain extent.
Mechanism of Apatite Formation on Sol-Gel Derived PDMS-Modified SiO2-CaO-P2O5 Hybrids with Various P2O5 Content
Authors: Whang Chin Myung , Seo Do Won , Kim Y.H.
Published: March 2009

The mechanism of apatite formation on the surface of novel PDMS modified SiO2-CaO- P2O5 hybrids is presented. The bioactive hybrids with different P2O5 content were synthesized by sol-gel method and soaked in the simulated body fluid (SBF) for different periods. The surface and the cross-section of the specimens were examined by use of Fourier transform infrared reflection spectroscopy, thin-film X-ray diffraction technique and scanning electron microscopy. The PDMS-SiO2-CaO-P2O5 hybrid containing 0.03 mole ratio of TEP(triethyl phosphate) / TEOS
(tetraethoxysilane) exhibited faster apatite formation compared to P2O5-free hybrids. This composition resulted in the thickest apatite layer (~6µm) and this might be attributed to faster formation of the silica hydrogel on the surface of the P2O5-containing hybrids than on the surface of the P2O5-free hybrids. Resultingly, the apatite nucleation on the surface of the P2O5-containing hybrids is effectively induced by the hydrated silica at a lower degree of supersaturation.
Changes in concentrations of the calcium, silicon and phosphorus in the SBF and the SEM-EDS line analysis depicting the variation of Si, Ca and P elements for the bulk, the interface and the apatite are reported. These were found to be quite correlative with each other. The rate of the concentration changes for the P2O5-containing hybrids is higher than that of the P2O5-free hybrids. The increases in the calcium and silicon concentrations are attributed to dissolution of the calcium and silicate ions from the hybrids, and the decrease in the phosphorus concentration is ascribed to formation of the amorphous calcium phosphate and crystalline apatite on the surface of hybrids by consuming the phosphate ion from the fluid.
Microstructure and Controllable Degradation of Bioglass Reinforced Calcium Phosphate Scaffolds
Authors: Nan Kai Hui , Wang Ying Jun , Chen Xiao Feng , Zhao Na Ru , Wang L.Y.
Published: March 2009

A porous bioglass reinforced tricalcium phosphate scaffold was prepared. The microstructure, degradability and reaction products of the scaffold after immersed in a simulated body fluid for different days were emphatically investigated using scanning electron microscopy, energy-dispersive X-ray analysis, X-ray diffraction, Fourier transformed infrared spectroscopy and induced coupled plasma spectroscopy. The results showed that a homogeneous hydroxy-carbonate-apatite (HCA) layer forms on the surface of the scaffold for over 30- day immersion and the oriented growth of the HCA occurs. In addition, this paper discussed the competing mechanism between the dissolution and the precipitation via the measurement of calcium and silicon ionic concentrations in the SBF.
Preparation and Characterization of the Nano Powder for Al2O3-SiO2-CaF2 Glass by Homo-Precipitation Method
Authors: Yuan G.C. , Wu Q.G. , Zeng G.X. , Zhang X.H.
Published: March 2009

The nano-powder of Al2O3-SiO2-CaF2 bio-glass was prepared by the homo-precipitation method with some inorganic salts containing Al3+, Ca2+, Na+, F-, SiO3
2+, Cl- as starting-reagents. The composition and characteristics of the powders were studied with XRD, EDAX, TEM and DTA. The results indicate that the prepared powder belongs to amorphous compounds containing Al, Ca, Si, O and
F atoms and the size of particle is in the range of 30 ~ 70 nm. Adding citric acid and the well-controlled desiccation process can slightly improve the dispersing effect of the powders; the mixture ratio of the reagents rarely affects the characteristic of powder. The crystal phase CaF2 was precipitated firstly from the amorphous structure when the temperature is above 600°C, with the temperature rising, Al2SiO5 and Al4.4Si1.2O9.5 etc. crystal phases were precipitated sequentially.
Surface Crystallization of ZnO-Al2O3-SiO2 Glass
Authors: Li Xiao Dong , Tian Jie Mo , Wang Chen , Dong Li Min
Published: March 2009

ZnO-Al2O3-SiO2 glasses with different surface conditions were surface crystallized by different heat treatment process. Differential thermal analysis (DTA), X-ray diffraction analysis (XRD) and scanning electronic microscope (SEM) were used to investigate the crystallization behavior of glasses, the crystalline components and microstructure of the as-got glass-ceramics.
According to the DTA results, different heat treatment processes of surface crystallization on the glass were adopted. The SEM results show that surface conditions of glasses are important for the surface crystallization, and the thickness of surface crystalline layer increases with heat treatment time.
Study of Thermal Shock Resistance of Sagger Plate Used in Floppy Magnets Sintering
Authors: Cao Feng , Wu Xing Rong , Telle Rainer
Published: March 2009

The rapid development of magnetic materials has witnessed a sustained consumption increase in corundum-mullite kiln furniture application, yet a comparatively short duration of them. In this view, the thermal shock resistance of sagger plate in floppy magnets sintering turns out a factor of critical importance. This paper makes a study concerning the influence of factors including the size of critical electro-melted mullite particles, the electro-melted corundum or mullite as medium particles and the addition of upon the thermal shock resistance. The result shows that, with critical particles of 2 mm, the sheet of about 10mm thickness is characterized by better performance in modulus of rapture and thermal shock resistance. The latter proves to be more outstanding in samples rather than mullite. When zircon powder is added in a two-hour sintering process at the temperature of 1550°C, a remarkable improvement is made by the sample in terms of its thermal shock resistance. SEM analysis shows the existence of micropores in the section of samples with corundum as medium particles, whereas the glasses phase in
that of mullite sample, resulting in a dense structure. Finally, zircon powder added makes for the improvement of thermal shock resistance due to the formation of baddeleyite on the particle surface of the corundum.
Preparation and Characterization of Al2O3 Coated Graphite Powders
Authors: Wang Zhou Fu , Hong Yan Ruo , Wang Hou Zhi , Deng Cheng Ji
Published: March 2009

Heterogeneous-nucleation formation of Al2O3 coatings on graphite powders via a
controlled hydrolysis process of aluminum chloride was investigated, and surface morphology and properties of the coated graphite were examined. The formed Al2O3 coatings were uniform and essentially amorphous. They were bonded well with graphite via chemical interaction between their O atoms and C atoms on graphite surface. Graphite particle size increased from 7.61 µm (as-received
graphite) to 9.53 µm (the coated graphite), revealing that average thickness of the coating was ~1µm. Compared with those of as-received graphite, specific surface area and fractal dimension of the coated graphite also increased, which was caused by the porosity present in the coating. The isolectric point (IEP) of the coated graphite (~9) was close to that of pure Al2O3, indicating that the electro-kinetic behavior of the coated graphite was similar to that of Al2O3.
Effect of CaO Content and Microstructure on Hydration Resistance of MgO-CaO Clinkers
Authors: Gu Hua Zhi , Wang Hou Zhi , Hong Yan Ruo , Sun Jia Lin , Zhang Wen Jie
Published: March 2009

Hydration resistance of three commercially available high-purity MgO-CaO clinkers were investigated and compared in the present paper. The results show that, as well as CaO content, microstructural morphology of MgO–CaO clinker affects its hydration resistance. The microstructure in which CaO is present at the grain boundaries of MgO leads to poorer hydration resistance, whereas the one in which CaO and MgO are distributed alternately confers much improved hydration resistance on the clinker, especially when MgO level is high enough to cover most of the CaO crystals.
Oxidation Properties of Three Dimensional (3-D) Carbon Fiber Preform Coated by SiC-SiO2
Authors: Gao Peng Zhao , Wang Hong Jie , Jin Zhi Hao
Published: March 2009

A SiO2-SiC coating on 3-D carbon fiber perform (raw perform) was successfully prepared through several steps. The appearance and composition of the coating/3-D carbon fiber preform (coated perform=CP) was studied through IR, XRD and SEM. The isothermal weight-loss and non-isothermal thermogravimetric (TGA) were used to study the oxidation behavior of CP. The results showed that a uniform coating on every fiber of preform was achieved and the coating adhered
well with fiber. The oxidation process of CP in isothermal condition was reaction-controlled in the first step, gas diffusion and reaction-controlled in the second step. The characteristic of the oxidation process in non-isothermal condition was self-catalytic.
Phase Changes in Fe-Si Powder Mixtures by Mechanical Alloying and Subsequent Heat Treatment
Authors: Zhao Y. , Shen Qiang , Wang Chuan Bin , Zhang Lian Meng
Published: March 2009

In the present study, Fe and Si powders (3:1 in atomic proportion) were mechanical alloyed and subsequently treated under different anneal conditions. The changes of phase composition and structure during the mechanical alloying and following heat treatment processes were mainly studied. The results showed that the XRD peaks of Fe were gradually broadened and weakened with the
increase of the milling time associated with the shifting from low angles to high angles, and the main phase changed into α-Fe (Si) solid solution after milling for 20h. When the product was heat treated below 400oC, the main phase remained α-Fe (Si). While it was treated above 400oC, ordered Fe3Si phase was found and the XRD peaks of Fe3Si became sharper with the further increase of the temperature.
Improving the Suspension Property of Non-Plastic Material Slurry with Lecithin
Authors: Ma Guang Hua , Wang Ying Jun , Ma Aili , Shen Huijuan
Published: March 2009

Lecithin is a natural amphipathic surfactant. In this paper, lecithin was experimented to improve the suspension property of non-plastic materials with aluminum oxide slurry. The suspension property was compared by adding different types and amounts of lecithin into the aluminum oxide slurry in acid and alkaline conditions. The experiments showed that the 6090-type lecithin with the optimal amount (0.2%) of dry base best modified the suspension property of the aluminum oxide slurry.
Study on the High Efficiency Organic Grinding Fluid Used for Ceramic Grinding
Authors: Tian Xin Li , Wu Z.Y. , Hu Zhong Xiang
Published: March 2009

Based on retrieval for domestic and international literatures about the grinding fluids
special for ceramic machining use, this paper put forward a method to enhance the engineering ceramic grinding machining efficiency using the organic grinding fluid added with the long chain alcohol The experiment, performed on the constant force cutter, greatly increased the ceramic grinding efficiency by 2.4 times through the comparative experiment for several normal grinding fluids as well as by adding additives. In addition, this paper conducted the matter structural analysis for the liquid-solid interface using the Raman Spectrum technology and preliminarily discussed the mechanism of this grinding fluid.
Carbo-Nitride Coating Treatment of Titanium by a Diffusional Method
Authors: Matsuura Kiyotaka , Kudoh Masayuki
Published: March 2009

Titanium surface was covered with thin layers of titanium monocarbo-nitride, Ti(C,N) and nitrogen-rich a-titanium, after a titanium specimen was heat-treated at a temperature between 1388 and 1573 K in a graphite cup in an atmosphere of pure nitrogen. The total thickness of those layers increased in accordance with the parabolic law when both temperature and time of the heat treatment increased. The
parabolic rate constants was described as k = 4.83 × 10-6 exp (-178000/RT)m2/s using Arrhenius’ equation. Vickers hardness of the Ti(C, N) layer remained at approximately 2000 but that of the a-titanium layer gradually decreased from 1500 to 500, as the distance from the surface increased. The carbo-nitridetreated titanium exhibited excellent resistances in wear and corrosion compared with those of pure titanium.
Effects of SiO2 Substitution on Piezoelectric and Mechanical Properties of PMS-PZT Ternary Piezoelectric Ceramics
Authors: Zhu Zhi Gang , Li Bao Shan , Li Guo Rong , Yin Qing Rui
Published: March 2009

The effects of SiO2 additives on microstructure, piezoelectric and mechanical properties were investigated for Pb0.98Sr0.02(Mn1/3Sb2/3)0.05Zro.48Ti0.47O3 (PMS-PZT) ternary system close to the morphotropic phase boundary. Piezoelectric coefficient (d33) and electromechanical coupling factor (Kp) considerably deteriorated with the substitution of SiO2 increased. On the other hand, the mechanical quality factor (Qm) increased, the maximum value was 1800. Fracture strength of 1.0 wt% SiO2 added the specimens reached to 106.54 MPa which was about 1.4 times higher than pure PMS-PZT ceramic. The rapid
improvement of fracture strength probably due to the decrease of grain size, pore distribute and the second phase (redundant Si4+ ions) segregating on the grain boundary which enhanced the bond energy of grain boundary. The optimized concentration of SiO2 doped PMS-PZT ceramics was 0.4 wt% for high power
application: d33 = 300 PC/N, Kp = 0.51, Qm = 1500, tand = 0.32% and the fracture strength was 88.5MPa.
The Influence and Mechanism of the Electrical Conductivity of (Ca,Sr)Bi4Ti4O15 Piezoelectric Ceramics by Doping of CeO2
Authors: Zheng Liao Ying , Li Guo Rong , Zhang Wang Zhong , Yin Qing Rui
Published: March 2009

In this paper, the bismuth-layered structure piezoelectric ceramics (Ca,Sr)Bi4Ti4O15 doped with CeO2 are prepared by the solid state reaction method. The crystal structure of the ceramics is determined by X-ray diffraction and the single orthorhombic structure phase is found. However, the doping of CeO2 increase the lattice parameters a, b, c. As a result, the ions of Ce enter into the lattice of the bismuth-layered structure and occupy A sites in the perovskite layer of bismuthlayered structure lattice. The temperature dependence of the conductivity shows that the resistivity increases by doping of CeO2 and reaches its maximum when the doping content is 0.4mol%. The mechanism of the CeO2 doping is also analyzed. By the investigation of XPS, the Ce ions have two types of valences: Ce3+ and Ce4+. The existence of Ce ions strengthened the weak Bi-O bonding and
decreased the oxygen vacancies in the lattice, so the ceramics have lower conductivity.
Preparation and Photoluminescence Properties of Quantum Size Zinc Oxide Colloids
Authors: Hao Wei Chang , Zhang Jun Ying , Feng Hai Bing , Wang Tian Min
Published: March 2009

Quantum size ZnO colloids were prepared by sol-gel method and size of colloids together with the luminescence properties were changed by varying preparing time and temperature. The absorption onset and the maximum of fluorescence peak of the ZnO colloid have obvious shift in UV region and visible light region respectively. The relationship between luminescence properties and energy level splitting is discussed in detail based on the experimental results.
Voltage Response of ZnO Varistors to 8/20 µs Surge Current
Authors: Lu Zhen Ya , Chen Zhi Wu , Yang Feng Jin
Published: March 2009

The voltage response of ZnO varistors to 8/20 µs surge current was investigated. The observed frontal spikes on the residual voltage waveforms are caused by the ignition gap, and no frontal spike was observed when a thyristor was used as the discharge trigger. The rear part of the waveform is determined by the damping coefficient of the RLC-circuit. Near the critical point, the residual voltage waveform
changes from non-oscillating attenuation modes to distinct across zero oscillating modes along with the increase of the peak current, but there will be no oscillation happen when a thyristor is used as the discharge trigger. The residual voltage peak is not synchronized with the current peak, and the voltage peak is leading, implying that the ZnO varistor appears to be inductive. According to the experiment results, it can be reasonably explained that the voltage peak leading phenomenon is attributed to the transient skin effect of the varistor materials.
Preparation of Humidity Control Ceramics from Selectively Leached Kaolin
Authors: Du Shang Feng , Chen Yun Fa , Liang Yun
Published: March 2009

The humidity control ceramics were prepared by selective leaching and sintering of Suzhou kaolin clay. Effects of sintering temperature and solid/liquid ratio of selecting leaching of the kaolin clay on the humidity controlling properties of ceramics were analyzed. It was found that the ceramic had the best properties when the kaolin clay was sintered at 1000oC for 2 hours and leached with the solid/liquid ratio being 1:50. Water vapor adsorption isotherms of the ceramic possessed a sharp increase in the
relative humidity between 45 and 85%.
Effect of Li+ and Mn2+ Doping on the Electrical Properties of SrTiO3-Based Varistor Ceramics
Authors: Xu Yu Xing , Zhang Zhong Tai , Zhang Xin Yue , Tang Zi Long , Luo Shao Hua , Dong Li Min
Published: March 2009

Effect of Li+ and Mn2+ doping on the electrical properties of SrTiO3-based varistor
ceramics was investigated. The results showed that the varistor ceramics cannot possess ideal electrical properties when only Li+ or Mn2+ was doped. However, when Li+ and Mn2+ were properly doped together, the samples acquired excellent electrical properties: V1mA = (5.7 ~ 11.7)V/mm; α = 6.8 ~ 11.0; er = (2.4 ~ 4.4) × 105; tan d = (7.1 ~ 10.4)%. When the contents of Li2CO3 and MnCO3 were
1.00 mol% and 0.05 mol% respectively, the nonlinear coefficient α reached the largest value of 11.0. Compared with only Mn2+ doping, the addition of Li+ increases the α value significantly.
Impedance Analysis Study on the Sensing Process of BaTiO3 Based PTC Ceramics in CO Gas
Authors: Zhou Zhi Gang , Tang Zi Long , Zhang Zhong Tai
Published: March 2009

Impedance spectroscopy is suitable to evaluate the electric structure and behavior by probing the relaxational processes during the charge transport within this kind of electrically inhomogeneous PTCR ceramics. This technique has been used to characterize the change of structure and behavior in sensing process of La-doped PTC-type BaTiO3 as a CO gas sensor. The kinetic behavior of PTCR-CO
ceramics in sensing process was detected. The sensitivity of the PTCR-CO comes from the change in the grain-boundary resistance of the ceramics with different temperatures in surrounding atmosphere. An important indirect evidence for the creation of new electron traps in grain boundaries of the semiconducting PTCR ceramics have been found using by impedance spectrum. And the creation of the
new defects and electron traps in grain boundaries, [VO •], [e¢], and/or [Vo
×], still plays a dominate role.
Microstructure and Electrical Properties of CeO2-Doped WO3 Ceramics Prepared by Nanopowders
Authors: Yang Xin Sheng , Wang Yu , Dong Liang
Published: March 2009

CeO2-doped WO3 ceramics were fabricated by using nanometer WO3 and CeO2 powders as raw materials. The microstructure and electrical properties were studied. The ceramics have relatively low breakdown voltage and high dielectric constant. The nonlinear coefficient does not decrease with the increase of the ambient temperature. The electrical conductivity decreases with increasing temperature, indicating that the ceramics have metallic behavior instead of semiconducting behavior.
Synthesis and Electrical Transport Properties of TiCo1-xPdxSb Half-Heusler Compounds
Authors: Zhou Min , Chen Li Dong , Feng Chu De , Huang Xiang Yang
Published: March 2009

Pd-doped TiCo1-xPdxSb (0 £ x £ 0.08) half-Heusler compounds were synthesized by a solid-state reaction method and their electrical transport properties in the temperature range of 300-900 K were investigated. Single phase TiCo1-xPdxSb was obtained in the range of 0 £ x £ 0.08. The lattice parameters increased with Pd content. Doping of Pd on the Co site resulted in a great
increase of electrical conductivity without significant decrease of Seebeck coefficient. A large power factor of 26 µW/K2 cm was observed for TiCo0.92Pd0.08Sb compound at 300 K.
Surface Modification of Long Afterglow Sr4Al14O25: Dy,Eu Phosphor by Silica Coating
Authors: Yan Jun Ping , Tang Zi Long , Luo Shao Hua , Zhang Zhong Tai
Published: March 2009

In order to improve water resistance of phosphors and the stability of particles in aqueous suspensions, the phosphor particles were coated with varying amounts of silica via the hydrolysis of tetraethyl orthosilicate. The composite particles were characterized by transmission electron spectroscopy, BET N2 gas adsorption, sedimentation time studies and fluorescent spectrometer. The specific surface area of the silica-coated phosphor particles showed a non-systematic increase. In
comparison to the uncoated phosphor (3.65m2/g), silica coatings of 13, 25, 50, 75wt% yielded specific surface areas of 15.19, 14.29, 37.90 and 226.12 m2/g respectively. This behavior can be explained based on a heterocoagulation coating mechanism in which silica clusters adsorb onto the phosphor particles surface. The sedimentation data display the stability of the coated particles improved as the silica content increased. The excitation and emission spectra show that the
luminescent properties of the phosphors are unimpaired or even better. The optimum luminescent properties obtained when coating 50wt% silica after calcining at 400oC.
Photoluminescence Properties of Zn2SiO4:Mn 2+ Inverse Opals
Authors: Li Bo , Zhou Ji , Zong Rui Long , Li Long Tu
Published: March 2009

Mn2+-doped Zn2SiO4 inverse opals were synthesized by sol-gel technique combined with the self-assembly of the opal template. Zn2SiO4:Mn2+ precursors were infiltrated into the interstices of the opal template assembled by polystyrene spheres. The polystyrene template was removed by calcining and nanocrystals of Mn2+-doped Zn2SiO4 were obtained in the void of opal template. The inverse opals show photonic crystal behavior and emit yellow light initially with the luminescent peak at 562 nm corresponding with the fact that β-phase is the dominant phase for nanocrystals less than 30nm. As the β-phase transformed to α-phase with the gradual increase of treating temperature and the growth of the crystal, the luminescence from Zn2SiO4:Mn2+ phosphors change from yellow to green.
MgAl2O4 Transparent Nano-Ceramics Prepared by Sintering under Ultrahigh Pressure
Authors: Chang Xiang Hui , Lu Tie Cheng , Zhang Ying , Luo Xiang Jie , Liu Qiang , Huang Cun Bing , Qi Jian Qi , Lei Mu Yun , Huang Cun Xin , Lin Li Bin
Published: March 2009

The first experimental work to produce transparent MgAl2O4 nano-ceramics was reported in this paper. The sintering characteristics of transparent nano-ceramics were investigated at relatively low temperature (800 ~ 1100°C) under ultrahigh pressure (2 ~ 5 GPa) using hydrostatic equipment. The morphologies
and phases of ceramics were observed by means of SEM and XRD, respectively. The grain sizes of the ceramics are shown to be less than one hundred nanometers, far smaller than the sizes of common transparent ceramics. Furthermore, the higher the sintering temperature and pressure are, the
greater the extent of densification is. At the same temperature, the higher the pressure is, the smaller the average grain size is. Under the same pressure, the higher the temperature is, the larger the average grain size is. The optimal sintering condition for preparing transparent nano-ceramics was also determined.
Preparation of MgAl2O4 Nanopowder by Homogeneous Precipitation Method
Authors: Jia Xiao Lin , Zhong Xiang Chong
Published: March 2009

MgAl2O4 nanopowder is synthesized by homogeneous precipitation method, using MgCl2,AlCl3 and ammonium bicarbonate as starting materials. The influences of the concentration of metallic salt solution, pH value and type and concentration of surface-active agents on agglomeration have been discussed. The results show that with addition of suitable amount of anion surface-activeagent, MgAl2O4 nanopowder with particle size of less than 12nm and secondary particle diameter of
less than 170nm can be obtained by heated precursor at 850°C for 1h.
Synthesis of BiFeO3-PbTiO3 Powders by Sol-Gel Auto-Combustion Process
Authors: Sheng Hao , Yue Zhen Xing , Gui Zhi Lun , Li Long Tu
Published: March 2009

BiFeO3-PbTiO3 powders were synthesized by a novel sol-gel auto-combustion method. The gels, transformed from the aqueous solutions of metal nitrate and citric acid, undergo a selfpropagatingcombustion process when being ignited and yield voluminous ashes. These ashes are single phase perovskite BiFeO3-PbTiO3 powders. The redox behaviors of the dried gels were studied by DTA-TG technique and IR spectra. The synthesized powders were characterized in terms of XRD,
SEM and BET techniques.
Process for Non-Agglomerated Nanometer-Sized Barium Titanate Powders by Sol-Gel Auto-Igniting Synthesis
Authors: Yan Qing Zhi , Su Xin Tai , Zhang Wen Feng , Ge Chang Chun
Published: March 2009

Non-agglomerated nano-sized BaTiO3 powders were prepared by a 3 step decomposition of barium titanyl citric acid chelate derived from Ba(NO3)2-TiO(NO3)2-citric acid-NH4NO3 based complex compound system. The 1st step was the thermal treatment of chelate wet gel at 150°C for 40min to remove water and non-bridging hydroxyl groups and to form expanded gel intermediate. The 2nd step was the decomposition of the organic fuel by igniting expanded gel intermediate at 300°C. The 3rd step was the formation of the high purity BaTiO3 by calcining the decomposed powders at 700°C for 2 hours. The most expanded gel intermediate was found to be a decisive factor for the elimination of hard agglomerate. In addition, the initial oxidant/fuel molar ratio was shown to strongly influence the characteristics of the powders thus obtained. The optimum oxidant/fuel value was 3 for obtaining non-agglomerated pure BaTiO3 powders with a particle size of 50 nm. The
agglomerate degree of BaTiO3 powders was determined by particle morphology and uniformity of the green compact microstructure observed by field emission scanning electron microscopy and scanning electron microscope.
Synthesis of Perovskite Pb(Zr0.52Ti0.48)O3 (PZT) Powders by a Modified Coprecipitation Method
Authors: Xu Gang , Ren Zhao Hui , Weng Wen Jian , Du Pi Yi , Han Gao Rong
Published: March 2009

Lead zirconate titanate (PZT) ceramics are of great technological interest due to their excellent piezoelectric and ferroelectric properties. In the present work, a modified coprecipitation method for PZT phase preparation was proposed by combining the advantages of partial oxalate method and coprecipitation method. Firstly, the zirconium and titanium hydroxides were coprecipitated to form the precipitate of (Zr,Ti)O(OH)2. Then, the lead hydroxide was precipitated
into a ammonia solution in which the precipitate of (Zr,Ti)O(OH)2 obtained above was well dispersed. The single perovskite PZT phase was directly synthesized without any intermediate phase appearing by calcinations the precursor at 500oC-800oC. The method proposed in the paper is an effective route
for the synthesis of PZT powders.
Properties of Sr-Doped BaTiO3 Based X7R Ceramic Materials
Authors: Wen Hai , Wang Xiao Hui , Li Long Tu , Gui Zhi Lun
Published: March 2009

In this paper, Sr-doped BaTiO3 based X7R ceramic was prepared. This material has dielectric constant of about 2000, temperature coefficients of capacitance (TCC) at 125°C of 11%, insulation resistivity of 12 × 1012 Ω⋅cm and grain size of 350 nm. The effects of Sr doping on the properties of the ceramics were also investigated.
The Factors Affecting Colloidal Processing of 8YSCZ Ceramics
Authors: Tekeli Süleyman , Gürü Metin
Published: March 2009

To achieve improvements in the mechanical properties, fine grain size, homogeneous microstructure and high density are desirable. The poor dispersion of the powders produce difficulties in the densification and the presence of agglomerates is responsible for poor mechanical properties. Slurry casting is an important colloidal processing method for the ceramic industry and helps to prevent the agglomeration of fine particles. In the present study, the effect of processing parameters, namely solid content, dispersing agent concentration, slurry viscosity and milling time on slurry casting of 8YSCZ ceramics were investigated and optimum values were determined. The results showed that ceramic powder used was castable under limited conditions. The effect of shaping processon sintering behaviour and microstructure was also investigated for slurry-cast and die-pressed specimens. The results showed that specimen processed by slurry-casting had a faster sintering rate and lower sintering temperatures, compared to die-pressed specimen. The reason for better sintering was due to the homogeneous
dispersion of the powder and elimination of agglomerates in slurry-cast specimen.
Fabricating Metal Patterned Ceramic Substance by Tape-Casting
Authors: Hao Li Feng , Zhou Ji , Li Bo , Li Long Tu
Published: March 2009

Tape-casting technology is introduced to fabricate metal-arrayes patterned ceramic substance containing periodic multilayer silver wire structure in the low dielectric constant ceramic matrix for microvave bandgap materials and left hand material application. One important advantage of the metal patterned ceramic substance comparing with the periodic structures fabricated on the printed circuit boards (PCB) using a shadow mask/etching technique is that complex multilayer structure can be designed and fabricated in the ceramic body as well as on the surface by the tape-casting process, while the shadow mask/etching technique technology can only design patterns on the surface of printed circuit
boards. An Hp8720ES network analyzer was used to measure the transmission properties of the metal patterned ceramic substance. The experimental result shows some novel properties at X-band microwave frequencies. The metal patterned ceramic substance can be used in the microwave communication, such as
microwave antenna.
Preparation of Li+-Doped TiO2 Films by Sol-Gel Process
Authors: Zhou Feng , Liang Kai Ming , Shao Hua , Hu An Min
Published: March 2009

LiNO3-doped TiO2 thin films on glass-ceramics were prepared by sol-gel dip coating. The influence of LiNO3 addition on the phase transformation temperature was studied. The transformation temperatures of non-crystalline to anatase and anatase to rutile are originally 520°C and 880°C without the addition of LiNO3. By adding 5%LiNO3 the two transformation temperatures decrease to 440°C and
580°C, respectively. The average size of the particles was found to be around 40nm for the LiNO3- doped TiO2 film annealed at 600°C.
Influence of MgO Content on Microstructure and Dielectric Properties in (BaSr)TiO3 Ceramics
Authors: Hu Lin , Zhou He Ping , Xue Hao , Xu Chun Lai
Published: March 2009

Barium strontium titanium oxide (BSTO) has great advantages and potentiality for the application of microwave technology. In order to be used in phased array antennas, high dielectric tunability, relatively low dielectric constant and low dielectric loss are required. In this paper, MgO was mixed into BSTO and the microstructure and dielectric properties of MgO-mixed BSTO bulk ceramics
were investigated. The mole ratio of Ba and Sr was rather fixed to 5:5 in this study. It is observed that a small amount of MgO (5 wt%) has gone beyond the solubility limits of Mg in BSTO. The dielectric constant and dielectric loss of BSTO ceramics decreased with the increase of the content of MgO mixed. However, the tunability of MgO-mixed BSTO ceramics decreased at the same time. 20wt% MgO-mixed
BSTO ceramics exhibits preferable dielectric properties with acceptable tunability.
Pore Size Determination of Supported Organic-Inorganic Hybrid Membranes by Modified Gas Permeation Method
Authors: Zhang G.C. , Zhang Bao Qing , Lin Xu Ping , Chen Yun Fa , Xie Yu Xheng
Published: March 2009

The pore structure of supported organic-inorganic hybrid membranes was tested by
modified gas permeation method. The results were discussed and compared with gas separation performances of the membrane. For the intermediate layer, the pore size is 225nm, which is in relatively good continent with the SEM observation. The pore size of SiO2/C6H5 organic-inorganic hybrid layer is 40-50nm, which is a little bigger compared with the gas separation performances. And for the SiO2/C6H5/MMA organic-inorganic hybrid layer, the pore is 24nm, which is close to the gas separation performances.
Joining between Ceramics and Metal in Composite Pipes Fabricated by the SHS Metallurgical Process
Authors: Zhao Zhong Min , Zhang Long , Wang Jian Jiang , Yan Shi , Cao Jin Rong
Published: March 2009

The design on joining of metal and ceramics in composite pipes fabricated by the SHS metallurgical process is carried on with adding (TiO2 +Al+C+Ni) subsystem in(CrO3+Al) system, and the composite pipes with three-layer structure of steel substrate, intermediate alloy and lined ceramics are fabricated with low cost and high performance. Combustion determination and mechanical test indicate
that adding suitable amount of Ni powder in combustion system rather than (NiO+Al) subsystem can cause combustion behavior of a whole system and volume fraction of the carbides to be controlled easily, and is beneficial to improve joining of the intermediate alloy and steel substrate, causing compression
strength and compression shear strength of the composite pipes to be increased greatly.
Effect of CaTiO3 Content on the Dielectric Properties of Ba0.5Sr0.5TiO3
Authors: Xu Chun Lai , Zhou He Ping
Published: March 2009

In this paper, a microwave material (Ba0.85Ca0.15)0.5Sr0.5TiO3 with 5 wt% MgO additive was prepared by traditional solid-state reactions, i.e., mixing BaTiO3 and SrTiO3 powders and then doping CaTiO3 and MgO. It was found that, with the increasing CaTiO3 content, the dielectric constant of the resultant material decreases and the tunability and dielectric loss increase.
Formation and Oxidation Resistance of NbSi2 Coatings on Niobium by Pack Cementation
Authors: Li Ming , Song Lixin , Le Jun , Zhang Xiao Wei , Pei Bao Gen , Hu Xing Fang
Published: March 2009

NbSi2 coatings were formed on niobium by halide-activated pack cementation process. The as-coated niobium samples were oxidized in air up to 1723 K by thermogravimetry method. The surface and cross-sectional morphology, phase composition and element distribution of the NbSi2 coatings before and after oxidation were characterized by SEM, XRD and EPMA. The results show that the as-formed coatings consist of single phase of hexagonal NbSi2 and the oxidation resistance of
pure niobium can be greatly improved by pack siliconizing.
Effect of ZnO on Thermo Physical and Structural Properties of Lithium Zinc Silicate Glass-Ceramics
Authors: Kothiyal Govind P. , Sharma B.I. , Shrikhande V.K. , Goswami Madhumita , Yakhmi J.V.
Published: March 2009

Lithium zinc silicate (LZS) glass-ceramics with compositions: (a) Li2O-ZnO-SiO2-Na2OB2O3- P2O5 and (b) Li2O-ZnO-SiO2-K2O-Al2O3-B2O3-P2O5 have been prepared by controlled nucleation and crystallization. The effect of ZnO/(ZnO+SiO2) ratio on various thermo-physical properties was investigated by changing the ratio from 0.1 to 0.31 in the case of (a). Different crystalline phases have been identified by X-ray diffraction studies in glass-ceramics including cristobalite, Li3Zn0.5SiO4 and Li2SiO3. Density ( r) was found to increase from 2.62 to 2.82 gm cm-3 while microhardness (VHN) decreased from 6.56 to 5.79 GPa with increase in ZnO/(ZnO+SiO2) ratio in the glass-ceramics. Average
thermal expansion coefficient (TEC) in the temperature range 30 to 450oC increased from 125x10-7 to 185x10-7 /oC. The increase in TEC and decrease in microhardness are thought to be due to the formation of different phases, which in turn influence the rigidity/bonding in the glass-ceramics. A remarkable difference in the microstructure close to interface of the glass-ceramics to Cu seal was seen in both the cases [high ZnO content (a) of ZnO/(ZnO+SiO2) ratio 0.31 and low ZnO content (b) of ZnO/(ZnO+SiO2) ratio 0.024]. Both the microstructures showed globally two contrast phases of bright and dark dispersed in
the glass matrix. An interesting dandritic phase observed towards core in the microstructure for the high zinc content is not seen in the microstructure for low zinc content glass-ceramic. The seal withstands a vacuum of ~ 10-6 torr at helium leak rate of 3x10-10 torr litre/sec.
Effect of Alkaline-Earth Metal Composition on Spectroscopic Properties of Er3+ in Fluorophosphate Glasses
Authors: Li Tao , Zhang Qin Yuan , Feng Zhou Ming , Liu Yue Hui , Deng Zai De , Jiang Zhong Hong
Published: March 2009

Optical spectroscopic properties of Er3+-doped alkaline-earth metal modified fluoropho sphate glasses have been investigated experimentally for developing broadband fiber and planar amplifiers. The results show a strong correlation between the alkaline-earth metal content and the spectroscopic
parameters such as absorption and emission cross sections, full widths at half-maximum and Judd-Ofelt intensity parameters. It is found that strontium ions could have more influences on the Judd-Ofelt intensity parameters and the absorption and emission cross sections than other alkaline-earth metal ions such as Mg2+, Ca2+, Ba2+. The sample containing 23 mol% strontium fluoride exhibits the maximum
emission cross section of 7.58 × 10-21 cm2, the broadest full width at half-maximum of 65 nm and the longer lifetime of 8.6 ms among the alkaline-earth metal modified fluorophosphates glasses studied. The Judd-Ofelt intensity parameter W6s, the emission cross sections and the full widths at half-maximum in the Er3+-doped fluorophosphate glasses studied are larger than in the silicate and phosphate glasses.
Modification of Inner Pores with Silicon Carbide Whiskers onto the Al2O3 Substrate by CVI Process
Authors: Park W.S. , Choi Doo Jin , Kim Hai Doo
Published: March 2009

In this study, SiC whiskers were grown in porous alumina substrate in order to enhance the filtering efficiency, performance, and durability by controlling pore morphology. This experiment was performed by chemical vapor infiltration (CVI) in order to obtain the whiskers on the inside of pores as well as on the surface of porous the Al2O3 substrate. The deposition morphology was changed remarkably with the deposition position and temperature. First, the mean diameter of whisker was decreased as the position of observation moved into the inside of substrate due to ‘the depletion effect’ and ‘the pressure effect’. Second, the deposition temperature caused the changes of the deposition type such as debris, whiskers and films and these changes of morphology affect the various properties. When SiC films were deposited, the gas permeability and the specific surface area decreased. However, the whisker showed the opposite result; a large specific surface area provides the absorption site and the whiskers in gas traveling path hinder the particles from easily flowing. Comparing with the normal pores (inter-grain open pores), the pores formed by the whiskers have relatively large volume fraction under the same pore size. Porous ceramic filters with whisker will be expected to increase the filtering efficient and gas permeability simultaneously. It is the main advantage of our whiskered filter. Therefore the porous alumina body which deposited the SiC whisker will be the promising material in order to apply to the particulate filter.
Microstructure and Mechanical Properties of Spark-Plasma-Sintered SiC-TiC Composites
Authors: Cho Kyeong Sik , Lee Kwang Soon
Published: March 2009

Rapid densification of the SiC-10, 20, 30, 40wt% TiC powder with Al, B and C additives was carried out by spark plasma sintering (SPS). In the present SPS process, the heating rate and applied pressure were kept at 100°C/min and at 40 MPa, while the sintering temperature varied from 1600-1800°C in an argon atmosphere. The full density of SiC-TiC composites was achieved at a
temperature above 1800°C by spark plasma sintering. The 3C phase of SiC in the composites was transformed to 6H and 4H by increasing the process temperature and the TiC content. By tailoring the microstructure of the spark-plasma-sintered SiC-TiC composites, their toughness could be maintained without a notable reduction in strength. The strength of 720 MPa and the fracture
toughness of 6.3 MPa·m1/2 were obtained in the SiC-40wt% TiC composite prepared at 1800°C for 20 min.