bluuebunny/crossref_metadata_2025 huggingface dataset:
Pressureless Sintering of Ultra-High Temperature ZrB2-SiC Ceramics
Authors: Cheng Zhi Qiang , Zhou Chang Ling , Tian Ting Yan , Sun Cheng Gong , Shi Zhi Hong , Fan Jie
Published: March 2009

ZrB2-SiC ultra-high temperature ceramics (UHTCs) were pressureless sintered with
Y2O3-Al2O3 as the sintering additives. The effects of sintering additive and crystallization annealing on
the microstructure and properties of ZrB2-SiC UHTCs were investigated. Sintering was activated by
producing liquid phase of Y2O3 and Al2O3. The relative density of sintered ZrB2-20wt%SiC ceramic
could reach 96% when the content of sintering additive was 6% and the sintering temperature was 1750°C
and its bending strength, Vickers hardness, and fracture toughness were 412 MPa, 13 GPa, and 6.0
MPa•m1/2, respectively. The crystallization annealing can result in YAG phase from grain boundary and
enhance the high temperature properties of the UHTCs. The UHTCs have excellent ablation resistance at
ultra-high temperatures, and a very low ablation rate of 0.0006 mm/s after ablation for 900s at 2800°C.
Preparation and Characterization of Stable ZrB2-Based Ultra-High Temperature Ceramics Slurry by Aqueous Gelcasting
Authors: Zhang Hui , Yan Yong Jie , Huang Zheng Ren , Liu Xue Jian , Jiang Dong Liang
Published: March 2009

Stable ZrB2-based ultra-high temperature ceramic slurries were prepared and characterized
with a solid content 40 vol% by aqueous gelcasting which was suitable to form high quality and complexshaped
ceramic parts. In the present work, Ammonium Citrate Tribasic (ACT) was used as the dispersant.
The properties of ZrB2 slurry, and the influencing factors were investigated by conventional techniques
such as sedimentation tests, particle size distribution measurements, electrokinetic measurements and
rheological analysis. High solids loading and low viscosity slurry was obtained by controlling the optimal
conditions for the ZrB2-based ceramic powders.
Low Temperature Sinter-Ability of Microwave Dielectric Ceramics 0.4(Ca0.61Nd0.26)TiO3-0.6(Li0.5Sm0.5)TiO3
Authors: Guo Xiao Dong , Tang Zi Long , Zhang Zhong Tai
Published: March 2009

Microwave dielectric ceramics 0.4(Ca0.61Nd0.26)TiO3-0.6(Li0.5Sm0.5)TiO3 (CNLST) were prepared by doping CuO as the liquid-phase sintering aid. The effects of CuO on the microstructures and dielectric properties were investigated. Due to the liquid-phase effect, the sintering temperature of CNLST with 0.5wt.% CuO addition has be effectively reduced to 1100°C, while good microwave dielectric properties of εr=83.4, Q•f=3880GHz, τf =2.1ppm/°C.
Properties and Microstructure of an HfB2-HfC-SiC Ultra High Temperature Ceramics
Authors: Li Jin Ping , Meng Song He , Han Jie Cai , Zhang Xing Hong
Published: March 2009

HfB2-HfC-SiC ultrahigh temperature ceramics (UHTCs) were prepared and characterized in
this paper. It is showed that the densities of the HfB2-HfC-SiC reach 98.5% of the theory density. The
room temperature compressive properties of the HfB2-HfC-SiC are good, while those at high temperature
decrease rapidly. The volume expansion ratio monotonously increases (up to 2.35% at 2300°C) with
increasing temperature. Furthermore, with increasing temperature, the average linear expansion
coefficient hardly changes, while the instant linear expansion coefficient decreases first, and followed by
an increase. The minimum value of the instant linear expansion coefficient is 5.65×10-6/K at 900°C and
that of the mean linear expansion coefficient is 7.39×10-6/K at 1340°C. HfB2-HfC-SiC were burned with
the plasma arc heater. After 8-second ablation, part of the SiC particles melted and spurted from the
composites, and holes appeared.
Thermal Shock Resistance of Ultra-High Temperature Ceramics
Authors: Li Wei Guo , Fang Dai Ning
Published: March 2009

Thermal shock resistance of Ultra-High Temperature Ceramics is one of the most important
parameters in UHTCs characterization since it determines their performance in many applications. In
order to reflect practical cases, the temperature-dependent thermal shock resistance parameter of UHTCS
was measured since the material parameters of UHTCs are very sensitive to the changes of temperature.
The influence of some important thermal environment parameters and the size of the material on the
thermal shock resistance and critical temperature difference of rupture of UHTCs at different stages in the
thermal-shock process were investigated. The results show that thermal shock behaviour of the UHTCs is
strongly affected by the size of the material and the thermal environments parameters, such as the surface
heat transfer coefficient, heat transfer condition and initial temperature of the thermal shock.
TiN/Al2O3 Functionally Graded Material Fabricated by In Situ Reaction
Authors: Nie Jian Hua , Li Ya Wei , Yan Hao , Liang Yong He , Li Yuan Bing
Published: March 2009

TiN/Al2O3 functionally graded composite was fabricated by in-situ aluminothermic reduction
of TiO2 in coke bed from mixtures of TiO2 powder and metal Al powder. The reaction process, phase
composition, and microstructure of sample treated at 1500°C for 3h were analyzed by XRD, SEM and
EPMA. The results indicated that the thermite reduction of TiO2 involves several transitional stages and
its initial reaction temperature is lowered by prior reaction between Al and TiO2. EPMA analysis showed
that the TiN/Al2O3 ratio in TiN/Al2O3 functionally graded material products changes gradually across the
samples without distinct interface between the different layers. The microstructure of the composite
changes gradually, and the size of TiN grains increases from the verge region of samples to the centre of
samples. These results above were in agreement with thermodynamic analysis.
Corrosion Protection of Stainless Steel by ZrO2-CeO2 Sol-Gel Coatings
Authors: Ye Jian Xiong , Yu Xin Gang , Bi Wen Yue , Li De Jun , Ma Hong Wen , Zhao Hui Feng , Qiu Guo Hong , Wang Li
Published: March 2009

ZrO2-CeO2 thin film was successfully prepared on 316L stainless steel by sol-gel process and
the corrosion characteristics of the substrate coated with ZrO2-CeO2 thin film were evaluated through
potentiodynamic polarization curve obtained in deaerated 15% H2SO4. The results show that, with the
increase of CeO2 content, the corrosion rate of 316L stainless steel substrates coated with ZrO2-CeO2 thin
film decreases. The surface morphology of the coating was observed by field scanning electron
microscopy and the elements in the surface of coated substrate analyzed by FEM-EDX.
Accurate FEM/BEM Simulation of Wireless Passive Surface Acoustic Wave Sensors
Authors: Luo Wei , Fu Qui Yun , Wang Jian Lin , Liu Huan , Zhou Dong Xiang
Published: March 2009

The wireless passive surface acoustic wave (SAW) impedance-loaded sensors offer new and
exciting perspectives for remote monitoring and controlling of moving parts, even in harsh environments.
However, the classical simulation models such as equivalent circuit model (ECM) and coupling of modes
(COM) model are not rigorous enough for these sensors since these sensors usually work in the RF band.
We try to make it more accurate by using FEM/BEM (combined finite element method and boundary
element method) model to determine some key parameters used in the COM model of impedance-loaded
SAW sensors. In this paper, we use periodic Green function which is the basis of FEM/BEM model to
determine the key parameters. The result of measurements on real SAW is nearly in accordance with that
of simulations.
Electrical Behavior of PSZT Ferroelectric Ceramic under Shock Wave Compression
Authors: Jiang Dong Dong , Du Jin Mei , Gu Yan , Feng Yu Jun
Published: March 2009

Electric power of hundreds of kilowatts can be produced in a few microseconds by sudden
release of bound charge on the surface of ferroelectric ceramic through shock wave compression. In order
to understand the depolarization process, knowledge of the discharge behavior of ferroelectric ceramic
under shock wave compression is essential. Gas-gun facility has been used to investigate the
shock-induced depolarization kinetics of tin-modified lead zirconate titanate ferroelectric ceramic.
Experiments were conducted in the normal mode in which the shock propagation vector was
perpendicular to the remanent polarization. Two kinds of specimens with the ferroelectric-toantiferroelectric
transformation hydraulic pressure respectively at 80 MPa and 180 MPa were tested. The
output currents as a function of load resistance were measured. A computation model was developed to
describe the electrical behavior of PSZT ceramic under shock wave compression, which adequately
explained the observed experimental results.
Properties of YSZ Electrolyte Sintered at 1250°C
Authors: Han Min Fang , Cheng Ling Zhi , Yin Hui Yan , Tang Xiu Ling
Published: March 2009

With the YSZ nano-powders as raw materials, the thin electrolyte film was prepared by tape
calendaring, then fired by a three-step sintering method. The YSZ film sintered at 1250°C is dense with a
grain size of 0.4~3μm.The electrical conductivity, up to 0.2s/cm at 1000°C, and active energy, 0.99~1ev,
are nearly the same for the samples sintered at 1250°C for 10, 15 and 20 h.
Effects of Microstructure and Relative Density on the Dielectric Constant of Porous Silica
Authors: Mao Xiao Jian , Wang Shi Wei , Shimai Shunzo
Published: March 2009

This work studies the effects of microstructure and relative density on the dielectric constant of
porous silica prepared by two different techniques: gelcasting of suspension (GCS) and gelcasting of
foams (GCF). Both routes are carried out from the preparation of silica suspension containing starch
granules. In GCS route, the resultant suspensions were heated for consolidation, while in GCF route, the
suspension was foamed before consolidation. The results indicated that the dielectric constant of porous
silica was obviously determined by relative density, but scarcely influenced by microstructure. The
logarithmic fitting equation lnε = ρ·lnεs was a good model to describe the relationship between the
dielectric constant and the relative density of porous silica prepared by both GCS and GCF routes.
Optical Scattering Mechanisms of Functional Nano-Material Films on Transmission Display Screen
Authors: Wang Lin , Zhong Jia Xiang , Ma Bin , Wang Shu Jun
Published: March 2009

In this paper, the application of new functional nano-material films prayed on transmission
display screen is studied. Optical properties, such as luminance gain and scattering angle, of the screens
are measured to investigate the particle size effects on the properties. The results show that the optical
properties of screen sprayed with nano-material film improve notably compared with those screens with
films of conventional particle sizes. When the particle size is less than 100nm, the gain is high and the
viewing angle low. With increasing particle sizes, the characteristics of screens vary with particle sizes. In
order to solve the contradictory relationship between gain and viewing angle and to obtain screens with
desirable optical properties, suitable nano-particle sizes ranging from 400nm to 700nm should be chosen
for the spraying film. The scattering mechanisms between nano-particles and light are also discussed.
Luminescence Properties of LnZr(BO3)2:Re (Ln=Ba, Sr; Re=Eu, Ce,Tb)
Authors: He Da Wei , Shen Fang , Li Xin , Lu Peng Zhi , Wang Yong Sheng
Published: March 2009

The excitation spectrum of BaZr(BO3)2:Eu3+ is composed of two broad bands. One band in the range from 120 nm to 170 nm is attributed to the borate groups, and the other band at 230 nm is due to the charge-transfer state (CTS) of the Eu3+ ion. The excitation spectrum of BaZr(BO3)2:Tb3+consists of one broad band in the range from 120 nm to 170 nm and the bands peaking at 226 nm, 245 nm and 272 nm respectively. The former is also attributed to the absorption of the BO3 groups. The latter correspond to the 4f8-4f75d transition of Tb3+.Main peak of the host absorption moves about 30 nm to high energy region as Sr2+ replaces Ba2+ partially.
Sol-Gel Deposition and Luminescence Properties of Spherical Phosphors Ca2Y8(SiO4)6O2:Eu3+
Authors: Han Xiu Mei , Lin J. , Yu M. , Lin C.K. , Qi Xi Wei , Wang Xiao Qin
Published: March 2009

Spherical SiO2 particles were coated with Ca2Y8(SiO4)6O2:Eu3+ phosphor layers through a sol-gel process. The results of XRD (X-ray diffraction) analysis indicated that the phosphors crystallized completely at 1000oC. AFM study revealed that the average grain size is 500 nm. In Ca2Y8(SiO4)6O2:Eu3+ spherical phosphors , the Eu3+ showed its characteristic red emission at 612 nm(5D0-7F2) upon excitation into its charge transfer band of Eu3+-O2- at 242nm.
Optical Properties and Microstructure of Mn: MgAl2O4 Transparent Ceramic after HIP Treatment
Authors: Sun Yue Feng , Lu Tie Cheng , Wang Xue Jun , Lei Mu Yun , Huang Cun Xin
Published: March 2009

5.0at% and 10.0at% Mn-doped MgAl2O4 transparent ceramics have been prepared through
vacuum sintering (1750°C /2h) and subsequent hot isostatic pressing (HIP) (1650°C /2h). The effect of
microstructure on the light transmittance of the sintered MgAl2O4 is discussed. Results showed that the
grains became dense and grain boundary became clear and most of pores inside and between grains were
removed, so the transmittance of two samples increased. The optical transmittance of the 5.0at%
specimens was increased by one times in the visible light wavelength region. HIP treatment has a great
effect on improving the transparency of samples with low doping concentrations.
Preparation of Aluminum Oxynitride Powder by Solid State Reaction Method
Authors: Wen Jin Song , Lu Tie Cheng , Qi Jian Qi , Zhou Ji Cheng , Pang Wei , Wang Hai Ping , He Jun Feng , Liao Zhi Jun , Wu Deng Xue
Published: March 2009

Single-phase aluminum oxynitride powders were obtained by varying the holding temperature
(T) and the weight percentage of α-Al2O3 in Al2O3 (X) with nano-sized Al2O3 and AlN powders as raw
materials. Influences of T and X on the phase composition of obtained powders were studied. The results
showed that the content of aluminum oxynitride increased with increasing T or X. When X was 50% and
T was 1750°C, obtained powders had better properties than those of others.
Influence of Raw Materials on the Carbothermal Synthesis of Single-Phase Aluminum Oxynitride Powder
Authors: Wang Hai Ping , Wu Deng Xue , Pang Wei , Qi Jian Qi , Zhou Ji Cheng , Wen Jin Song , Cheng Zi Meng , Wen Ya , Liao Zhi Jun , Lu Tie Cheng
Published: March 2009

Aluminum oxynitride powders were synthesized by carbothermal reduction, using nano-sized alpha-alumina, gamma-alumina and carbon as raw materials. Effects of the weight percentages of alpha-alumina in alumina (R) and synthesizing temperatures (T) on the preparation of single-phase AlON powders have been studied. The results showed that proper R can reduce the shrinkage and increase the formation rate of AlON phase, but a high R will reduce the formation rate of AlON phase, because the activity of alpha-alumina was lower than that of gamma-alumina. Single-phase AlON powder with excellent properties can be obtained under the condition of R=0.15, T=1700°C. Moreover, this single-phase AlON powder was well-dispersed with an average size of about 2 μm.
Hot-Pressed Translucent Aluminum Oxynitride (AlON) Ceramics
Authors: Xue Jun Ming , Liu Qian , Xiu Tong Ping , Ma Li Li , Fang Ming , Gui Lin Hua
Published: March 2009

AlON with a composition of Al23O27N5 was prepared by hot pressing at temperatures lower
than 1900 °C. The microstructures and final properties, including both mechanical properties and optical
properties, of the sintered specimens were studied. The results showed that sintering temperature had a
great influence on the densification of specimens and could lead to very different properties, especially
the optical transmittance and the maximum infrared transmission.
Synthesis, Characterization and Electrical Properties of Barium Titanate Films Fabricated by Hydrothermal Method
Authors: Zhao Jian Ling , Wang Xiao Hui , Li Long Tu , Wang Xi Xin , Li Yang Xian
Published: March 2009

BaTiO3 films with a thickness up to 3 μm were fabricated under the hydrothermal conditions. It was found that the crystallinity of BaTiO3 increases with the concentration of Ba(OH)2 solutions. Along with the increasing of time, the crystallinity of BaTiO3 increases, reaches the maximum value and then decreases. The measured values of remanent polarization (Pr) and coercive field (Ec) are 1.74μC/cm2 and 24KV/cm. The leakage of the films at 1V is 10-7A/cm2. The dielectric constant and loss tangent of hydrothermal derived BaTiO3 film at a frequency of 1 KHz were 600 and 0.2, respectively.
Roles of Dopants in Sintering Behavior of ZnO-Based Varistor
Authors: Peng Zhi Jian , Wang Cheng Biao , Gauckler Ludwig J. , Miao He Zhuo
Published: March 2009

Three series of ZnO-based materials with different doping levels were prepared. The correlation
between the composition and microstructure, and the roles of main dopants, Bi2O3 and Sb2O3, in the
sintering behaviors were proposed. Both Bi2O3 and Sb2O3 evaporated at 1115°C, but the amount of them,
in which bismuth is the majority, is not significant. Bi2O3 functioned mainly as liquid during sintering to
promote the sintering of ZnO, but it doesn’t mean the materials will be denser. The bismuth-rich phase
retracted into small pores during cooling, leaving the big pores as voids at room temperature. More Bi2O3
added would result in less increase in material densities and dramatic decrease in relative densities, and a
little bit increase in grain sizes of matrix ZnO. Sb2O3 would react with ZnO matrix into spinel, Zn7Sb2O12,
which will pin at the grain boundary of ZnO to control the ZnO grain growth. The more Sb2O3 added, the
smaller the grain sizes of ZnO. Appropriate amount of Sb2O3 added will yield denser materials.
Synthesis of TiO2 Nanotube Arrays Through Multistep Anodization
Authors: Yang Yang , Wang Xiao Hui , Li Long Tu
Published: March 2009

Multistep electrochemical anodization is an electrochemical experiment orderly conducting in different electrolytes. In this paper, TiO2 nanotube arrays have been firstly anodic grown in aqueous electrolyte (H3PO4/HF) and later anodic grown in organic electrolyte (glycerol/NH4F). Compared with separately anodizing in aqueous and organic electrolyte, the morphology of the resulting nanotube arrays can be optimized. SEM images showed that the obtained nanotubes have a length of more than 2 μm and single-pore diameter ranging from 120 to 150 nm. The current work indicates that the multistep electrochemical anodization has a contribution to the optimization of the morphology of TiO2 nanotube arrays.
Thermoelectric Properties of n-type (Bi2Se3)x(Bi2Te3)1-x Crystals Prepared by Zone Melting
Authors: Jiang Jun , Li Ya Li , Xu Gao Jie , Cui Ping , Chen Li Dong
Published: March 2009

In the present study, n-type (Bi2Se3)x(Bi2Te3)1-x crystals with various chemical compositions were fabricated by the zone melting method. Thermoelectric properties, including Seebeck coefficient (α), electrical conductivity (σ) and thermal conductivity (κ), were measured in the temperature range of 300-500 K. The influence of the variations of Bi2Te3 and Bi2Se3 content on thermoelectric properties was studied. The increase of Bi2Se3 content (x) caused an increase in carrier concentration and thus an increase of σ and a decrease of α. The maximum figure of merit (ZT = α2σT/κ) of 0.87 was obtained at about 325 K for the composition of 93%Bi2Te3-7%Bi2Se3 with doping TeI4.
Synthesis of YIG Nanopowders by Sol-Gel Method
Authors: Sun Zhan Xing , Fang Ming Hao , Chen De Hua , Wei Li Xian , Liu Yan Gai , Huang Zhao Hui
Published: March 2009

Yttrium iron garnet (YIG) nanopowders were synthesized by sol-gel method using Fe(NO3)3·9H2O, Y(NO3)3·6H2O as raw materials. The influence of heat treatment, the citric acid to metal nitrates molar ratio (CA / MN) and PH value on the synthesized powders were investigated using scanning electron microscopy (SEM), thermal analyses (DTA/TGA) and X-ray diffraction (XRD). YIG powders with average grain size of 80~90nm were synthesized after calcining at 1000°C for 4h.
Structure and Magnetic Properties of BaLa0.5Fe11.5O19/ SiO2
Authors: Han Zhi Dong , Dong Li Min , Wu Ze , Zhang Xian You
Published: March 2009

The paper aims at synthesizing La substituted BaM hexaferrites (BaLa0.5Fe11.5O19) in the presence of SiO2 nano-particles by sol-gel method. Effects of SiO2 nano-particles on the structure and particle size of hexaferrites are investigated by XRD and SEM. Magnetic properties of BaFe12O19, BaLa0.5Fe11.5O19 and BaLa0.5Fe11.5xO19/SiO2 are compared by vibrating sample magnetometer (VSM). The XRD patterns of BaLa0.5Fe11.5O19/SiO2 calcined at 1000°C manifest that all the species have hexagonal crystal structure and no diffraction peaks of SiO2 are found. Compared with BaLa0.5Fe11.5O19 powders, those synthesized in the presence of SiO2 nanoparticles present in smaller powder size, as proved by SEM. The results of VSM reveal that BaLa0.5Fe11.5O19 possesses much higher saturation magnetization than BaFe12O19. BaLa0.5Fe11.5xO19/SiO2 also shows higher saturation magnetization than BaFe12O19, but lower than BaLa0.5Fe11.5O19 because of addition of nano-SiO2.
Synthesis of Y2BaCuO5 Nanopowder by Co-Precipitation under Ultrasonic Irradiation
Authors: Huang Jian Feng , Cao Li Yun , Wu Jian Peng , He Hai Yan
Published: March 2009

Nanocrystalline Y2BaCuO5 was prepared by a co-precipitation method with aid of ultrasonic
irradiation using Y2O3, CuCl2 and BaCl2 as source materials. The crystallization and morphology of the
prepared nanoparticles were characterized by X-ray diffraction and transmission electron microscopy.
Results showed that Y2BaCuO5 monophase can be prepared at 900°C with NaOH + NaCO3 mixture as
precipitator. Particle size of Y2BaCuO5 crystallites decreases with the increase of sonicating power.
Around 30 nm Y2BaCuO5 crystallites could be achieved when sonicating power increased to 300 W.
Effect of Lead Oxide Compounds on the Microstructure and Properties of Bi-2223/Ag Tapes
Authors: Li Ming Ya , Han Zheng He
Published: March 2009

The effect of lead oxide compounds in (Bi,Pb)2Sr2Ca2Cu3Ox ((Bi,Pb)-2223) precursor powder
on the microstructure and properties of Bi-2223/Ag tapes was investigated. Firstly, precursor powders
containing different types of lead-rich phases were prepared by controlling the calcination temperature
and atmosphere. Then monofilament (Bi,Pb)-2223/Ag tapes were fabricated using these powders. Lastly,
samples scissor from these tapes were heat treated under different conditions. The phase composition and
microstructure of these powders and tapes were analyzed using XRD and SEM. Experimental results
show that the lead-rich phases in BSCCO precursor powders played an important role on the formation of
the (Bi,Pb)-2223 phase, the microstructure and critical current of Bi-2223/Ag tapes.
Electro-Mechanical and Thermal Properties of Multiwalled Carbon Nanotube Reinforced Alumina Composites
Authors: Ahmad Kaleem , Pan Wei , Wan Chun Lei
Published: March 2009

Multi-walled carbon nanotube (MWNT) reinforced alumina composites with different MWNT
contents (5 and 10 vol %) were fabricated by spark plasma sintering. The room temperature dc electrical
conductivity, thermal conductivity, and mechanical properties were investigated. Results showed that the
electrical conductivity has improved around twelve orders of magnitude by addition of 5 vol% of MWNT.
The fracture toughness changed from 3.2 to 4.4 MPa m1/2 with 39% improvement over monolithic Al2O3.
The thermal conductivity decreased with increase of MWNT contents. The low values of thermal
conductivity suggest that interfacial thermal barrier play an important role in determining these properties.
MWNT can be used to improve concurrently electrical, mechanical properties of Al2O3 but with lower
values of thermal properties.
Mechanical Properties and Microstructure of Al2O3/(W, Ti)C Nanocomposite
Authors: Zhou Yong Hui , Ai Xing , Zhao Jun , Yuan Xun Liang , Xue Qiang
Published: March 2009

The Al2O3/(W, Ti)C nanocomposite was fabricated by hot pressing technique at 1650-1700°C
under 30MPa for 10min. The fracture toughness remarkably increased by adding nano-scale Al2O3 (11vol
%) particles into Al2O3 matrix. The flexural strength, fracture toughness and Vickers hardness are 840
MPa, 6.55 MPa•m1/ 2 and 20.1 GPa, respectively. The microstructure of the nanocomposite is
homogenous skeleton structure. Nano particles could refine matrix grains and lead to the crack deflection
as well as branching and bridging. The coexistence of nano-scale Al2O3, micro-scale Al2O3 and (W, Ti)C
can reduce the sintering temperature and sintering time as well as the grain size, and improve the
densification and mechanical properties of materials.
Rheological Properties and Gelcasting Behavior of Ultrafine ZrO2 Suspension
Authors: Wang Jin Feng , Gao Ya Chun , Yang Xian Feng , Sun Jia Lin , Xie Zhi Peng
Published: March 2009

Ultrafine ZrO2 suspension with stable high solid loading was prepared, and ZrO2 ceramic
materials with uniform structures were fabricated through gelcasting. Zeta potential of the ultrafine ZrO2
suspensions with A-type dispersant, triammonium citrate, and without dispersant was measured. The
influencing factors on suspension flowability as the content of dispersant, pH value, solid loading, and
milling time were studied in detail. And the optimum premixed solution/initiator (APS)/catalyst
(TEMED) ratio for gelcasting was investigated. The results showed that A-type dispersant was suitable
for dispersing of ultrafine ZrO2 particles in aqueous premixed solutions; the optimized content of
dispersant was 2%~2.5% of ZrO2 volume; ZrO2 suspension displayed a minimum viscosity at pH 10.66;
the upper limit of solid loading was 54vol.%; and the appropriate milling time was 12 hours. When
premixed solution/initiator (APS)/catalyst (TEMED) ratio was 100/1/0.5, ZrO2 suspension has a better
gelcasting behavior.
Low Temperature Synthesis and Characterization of CaO and MgO- Stabilized Nanocrystalline Tetragonal Zirconia by Citrate Gel Process
Authors: Gocmez Hasan , Fujimori Hirotaka
Published: March 2009

The citrate gel method, similar to the polymerized complex method, was used to synthesize
homogenous tetragonal zirconia at 800oC and 1000oC. Nanocrystalline tetragonal single phase has been
fully stabilized with 3, 7, 10 mol% CaO and 10, 15 mol% MgO at 800oC, respectively. In addition, the
XRD analysis showed the absence of monoclinic phase after addition of 7 and 10 mol% CaO into
zirconia-based solid solutions, which have been fully stabilized both 800oC and 1000oC. The crystallite
sizes of the t-ZrO2 with 3, 7 and 10 mol% CaO at 1000oC were 32, 28 and 29nm, respectively. For
ZrO2- x mol% MgO (x=3, 10, 15) solid solution, the crystallite sizes of samples at 800oC were less than
29nm, however it was increased up to 69nm at 1000oC. The prepared gel and subsequent heat-treated
powders were characterized by X-ray diffraction (XRD), Raman spectroscopy and transmission electron
microscopy (TEM) to get detail information regarding to differentiation of polymorphs of zirconia as well
as formation of powders.
Fabrication of Porous Zirconia Ceramics by Injection Molding Method
Authors: Yang Xian Feng , Xie Zhi Peng , Wang Lin Lin
Published: March 2009

An innovative processing route for fabricating porous zirconia ceramics has been developed based on traditional injection molding method. Azodicarbonamide (AC) was used as the foaming agents and mixed with the zirconia powder and conventional binders (polypropylene, ethylene/vinyl acetate, paraffin wax and stearic acid). There were three stages in the foaming course: (1) Small bubbles nucleated when AC decomposed into N2 and CO in the barrel. (2) Viscosity and pressure drop led to the growth of the bubbles when the melt feedstock was injected into the die cavity. (3) The porous structure was kept in the solidified body. The AC content and injection parameters were optimized to control the pore density and size. The porous green body was debinded at the heating-up rate of 0.5 °C /min to 450°C and sintered at 1550°C. Samples with porosity of 40%-50% and pore sizes from 200-250μm were prepared when the addition of AC was 0.3% by weight. The results showed that ceramic injection molding method was also suitable for fabricating the porous ceramics.
Synthesis of Mullite Nanocomposite from Natural Kaolin
Authors: Chen Nan Chun , Ao Han Mei , Chen Dong
Published: March 2009

A new method of synthesizing mullite nanocomposite from raw natural kaolin is presented in
the paper. Raw kaolin is processed by oxidation-reduction fining method and then baked to produce fine
kaolin powder. The fine kaolin powder is further synthesized into mullite nanocomposite by open-system
hydrothermal crystallization method under normal pressure. With proper controls of NaOH mole ratio in
the hydrothermal solution, crystallization time, and constant temperature, the average grain size of
synthesized nanocomposite changed from 80nm to 100nm. The morphology of the nanocomposite could
gradually change from platy to short prismatic, lamellar, and needle-like with increasing nucleation rate.
Preparation of Ultrafine SiC Powders by Carbothermal Reduction
Authors: Wang Fu , Cao Wen Bin , Sun Jia Lin , He Rong Liang
Published: March 2009

SiC powder was synthesized by carbothermal reduction method using silica sol and amylum as
reactants in closed and open graphite crucibles, respectively. The phase composition and morphology of
the powders were characterized. Formation of phase-pure silicon carbide can be achieved at 1700°C for
1h. Increasing reaction temperature and extending holding time can greatly promote the production of
SiC. The products synthesized in open graphite crucibles are mainly composed of equiaxial β-SiC
particles while those synthesized in closed graphite crucibles are β-SiC particles and nanorods.
Transpirational Performance of Oriented Porous SiC Transpiration Cooling Materials
Authors: Tang Jie , Chen Yu Feng , Sun Ji Guo , Wang Hua , Liu Hai Lin
Published: March 2009

The application and the transpirational behavior of oriented porous SiC as transpiration cooling materials in a simulating test were studied. The test sample was shaped by freeze-casting process and reaction sintered. The testing device was composed by an electric arc combustor and a hydrogen coolant providing system. It was found that the permeability, the amount of coolant required and the uniformity of coolant infiltration were all effected by the microstructure of porous SiC, which furthermore influced the cooling efficiency of the testing system. In this test, the inner face temperature of the combustion chamber was maintained less than 400K throughout the thermal testing period contrasting with the fire temperature up to 3600K by the utilization of oriented porous SiC transpiration cooling materials.
Effects of Sintering Additives on Properties of Porous Silicon Nitride Ceramics Fabricated by Carbothermal Reduction
Authors: Lu Yuan , Yang Jian Feng , Shan Shao Yun , Gao Ji Qiang , Jin Zhi Hao
Published: March 2009

In this paper, porous Si3N4 ceramics were fabricated by carbothermal reduction between silicon dioxide and carbon. The influences of four types of sintering additives on the microstructure and mechanical properties of the porous Si3N4 ceramics were investigated. XRD analysis proved complete formation of a single-phase β-Si3N4. SEM analysis showed that the resultant porous Si3N4 ceramics occupied fine microstructure and a uniform pore structure. The sintered sample with Lu2O3 as sintering additive showed finer, a higher aspect ratio β-Si3N4 grains. The addition of Eu2O3 accelerated the densification of porous Si3N4 ceramics, decreased the porosity and increased the flexural strength.
Synthesis of Rod-Like α-SiAlON by Carbothermal Reduction-Nitridation
Authors: Leng Xian Feng , Liu Yan Gai , Fang Ming Hao , Huang Zhao Hui
Published: March 2009

Rod-like α-sialon was synthesized successfully using pure SiO2 and AlN as the starting
materials, carbon black as reductant, CaF2 and Y2O3 as addition agent by carbothermal
reduction-nitridation. The effects of reaction temperature (1450°C, 1500°C, 1600°C and 1700°C) and
additive (Li2CO3, CaF2, Y2O3 and Y2O3+CaF2) on phases and microstructure of the final products were
studied by XRD and SEM. The results showed that α-sialon was synthesized by carbothermal
reduction-nitridation at 1700°C for 3 hours. The morphology of the synthesized α-sialon was rod-like.
Fabrication of MgSiN2 Powders via Combustion Synthesis Process
Authors: Wang Fei
Published: March 2009

The feasibility of synthesizing MgSiN2 powders through combustion synthesis process is
demonstrated. A self-sustained combustion wave can be initiated with or without the addition of active
diluent. The wave propagation resulted in a product with several secondary phases in addition to the main
phase MgSiN2 when the combustion reaction was initiated without the addition of active diluent. As the
active diluent was used in the reactant mixtures, the amounts of the secondary phases were decreased. The
effect of active diluent addition on the phase composition and morphology of the final product was
discussed. Furthermore, the use of MgSiN2 crystal seeds in the reactant mixtures was also investigated. It
is found that the active diluent can facilitate the nitridation reaction. The experimental results showed that
changing the experimental parameters such as the amount of active diluent and the MgSiN2 crystal seeds
could optimize the fabrication of MgSiN2 powders through combustion synthesis process.
Microstructure Change of Molybdenum Disilicide Heating Unit in Nitrogen Atmosphere at 1700°C
Authors: Liu Bao Lin , Yang Jing Zhou , Huang Zhao Hui , Liu Yan Gai , Fang Ming Hao
Published: March 2009

Transformation of the microstructure of molybdenum disilicide heating unit in nitrogen
atmosphere at 1700°C was investigated by XRD, SEM and EDS. The results showed that MoSi2 was
transformed to polyhedral Si3N4 crystals groups distributed across in the matrix with irregular
geometry Mo5Si3 and Mo3Si crystals, and the Si3N4 crystal groups were dense areas, while the Mo5Si3
and Mo3Si groups were loose areas after being heated in nitrogen atmosphere at 1700°C for 3h. The
thickness of conversion zone of MoSi2 matrix was about 30μm and the loose Mo5Si3 and Mo3Si areas
can damage the dense structure of MoSi2 matrix.
Densification of Aluminum Nitride Ceramics with CaF2 Additive
Authors: Xiong Yan , Fu Zheng Yi , Wang Hao
Published: March 2009

Effect of adding up to 5wt% CaF2 on the densification and microstructural development of hot pressed aluminum nitride (AlN) was investigated. SEM investigation showed that the grain size of the sintered sample decreases with the increasing content of CaF2. Secondary-phase evolution paths converge from CA6 to CA phase above 1650°C. TEM micrographs showed that formed secondary phases could evaporate from sintered bodies at higher temperatures in the carbon-containing nitrogen atmosphere and the residuals were mainly distributed at triple grain junctions, keeping direct connections of AlN grains. Translucnet AlN ceramics were prepared using CaF2 additive sintered at 1850°C for 5 h.
Microstructure and Phase Composition of AlN/Al Composite Fabricated by Directed Melt Nitridation
Authors: Jin Sheng Li , Li Ya Wei , Liu Jing , Li Yuan Bing , Zhao Lei , Liu Xiao Hua , Ni Yu Ee , Li Ze Ya
Published: March 2009

AlN/Al ceramic composite was fabricated by directed melt nitridation of pure Al block covered
with 10wt% Mg powder at 1300°C in a high purity flowing N2. Microstructure and phase composition of
the composite were investigated by scanning electron microscopy with energy dispersive spectroscopy
and X-ray diffraction. Results showed that AlN is the main phase in the composite and its lattice parameters
of a and c are 3.1110Å and 4.9806Å, respectively. The phase composition of the composite changes
along the growth direction and a gradient sandwich structure forms. The surface of the composite is made
up of a dense and thin nodular AlN layer, underneath which an AlN/Al layer appears, followed by an
AlN/Al/MgAl2O4 layer. Thermodynamic calculations predicted the formation of possible phases with the
addition of Mg. It suggested that the content of Mg at the reaction frontier of nitridation is considerably
lower to 0.15wt% where MgAl2O4 was stable, because of escape and reaction exhaustion of Mg. Once Mg
is lower than 0.05wt%, only a dense AlN layer can exist, which prevents the further nitridation of Al melt.
Microstructure and Tribological Properties of Layer Deposited by Micro-Plasma Arc Welding on Worn Gear
Authors: Liu Cun Long , Lv Yao Hui , Xu Bin Shi , Xia Dan
Published: March 2009

Surface of gear that works continuously tends to be wore. Hardfacing on worn gear can
repair its worn surface, restore its precision, consolidate its surface property, and save cost.
Micro-Plasma Arc Welding (micro-PAW) has low heat input and narrow heat-affected zone, and it
has good properties of energy concentration and high energy density. Therefore, hardfacing by
micro-PAW is an effective method to repair worn gear surface. KF-Ni60A Ni-based alloy powder has
good weldability property, and KF-Ni60A welding layer has low friction coefficient and good
property of wear resistance between metallic hard surface, so it is a kind of good overlaying material
that can be applied to the welding process to repair the worn gear surface. In this research, the method
of overlaying on worn gear using KF-Ni60A Ni-based alloy powder by micro-PAW is studied. The
microstructure of deposition layer and the elementary distribution of cross-section are analyzed, the
surface hardness and wear resistant property of the layer are measured. The result indicates that the
deposition layer and the base metal bond well, the layer has high adhesive strength and hardness, low
porosity, and good property of wear resistance.
Argon-Oxygen Post-Discharge Treatment of Hexatriacontane: Heat Transfer between Gas Phase and Sample
Authors: Mafra M. , Belmonte Thierry , Maliska A.M. , da Silva Sobrinho A.S. , Cvelbar U. , Poncin-Epaillard F.
Published: March 2009

Characterization of the interaction between an argon-oxygen post-discharge and
hexatriacontane (C36H74) is carried out. Optical emission spectroscopy using the atmospheric band
O2 (b1Σg
+, v=0 X3Σg
−, v’=0) at 760 nm gives simultaneously the evolution of the O(3P)
concentration above the surface and the gas temperature by simulation of the rotational spectrum of
the transition. Surface reactions contribute to the heating in the sample and to a substantial increase
in the gas temperature. Finally, a strong correlation between the time evolutions of the transition
intensity and the sample temperature is observed, suggesting that O(3P) is the main reactive species
that produces the heating and the chemical changes in the HTC.
Study on the Characteristics of Wear Resistance Using Silicate Particles as Additive on the Metal Friction Pairs
Authors: Zhao Yang , Xu Bin Shi , Xu Yi , Shi Pei Jing , Wang Xiao Li , Zhang Bo
Published: March 2009

Tribological properties of silicate particles as 50CC additive were evaluated on an end-face
friction and wear tester. The morphologies, element distributions and micro-mechanical properties of
the worn surface were investigated by means of scanning electron microscopy (SEM), energy
dispersive spectrometry (EDS) and nanoindentation tester, respectively. Results indicate that friction
reduction and wear resistance properties of 50CC are improved effectively by adding silicate
particles, whose main composition is Mg3[Si2O5](OH)4. The friction coefficient and surface
temperature are reduced 60.6% and 35.6%. The nano-hardness of the self-repairing film is increased
30.03% compared with that of the ordinary film. It can be inferred that a high nano-hardness
protective film composed of Mg, Al and O is formed on the worn surface, which has a good effect on
the tribological performances.
Effects of Shape and Distribution of M7C3 on Wear Resistance of Iron Based Composite
Authors: Liu Zheng Jun , Su Yun Hai , Sun J.G.
Published: March 2009

Effects of shape and distribution of the hard phases (Fe, Cr)7C3 and Cr7C3 on wear
resistance of Fe5 deposited metal obtained by plasma arc welding with electromagnetic stirring were
investigated. The deposited layers were subsequently characterized by SEM observation, wear tests
and hardness measurements. The hardness of the deposited layers was increased and then decreased
with increasing the applied current. With the current of 3 A and the electromagnetic frequency of 10
Hz, the hardness of deposited metal reached maximum value of about HRC 68, which was increased
about 19% compared with that of the deposited metal without electromagnetic stirring. The wear
weight loss of the deposited metal with 3 A and 10 Hz is greatly decreased. It is confirmed that the
shape and the distribution of hard phase significantly affect wear resistance of the deposited metal.
The slag M7C3 is transformed into hexagon during electromagnetic stirring with 3 A and 10 Hz. And
the regular distribution of hexagon M7C3 in the deposited metal resulted in the excellent wear
resistance.
Analysis of the Axial Tensile Properties of Multidirectional Filament Wound Tubes
Authors: Xie Xia , Jiang Ya Ming , Qiu Guan Xiong , Wang Peng , Xu Ai Fen
Published: March 2009

This paper studied the axial tensile properties of the multidirectional filament wound
tubes (MFWT) both theoretically and experimentally. Based on the Classical Laminate Theory, the
mechanical analysis model of the tubes was established and implemented by the program of Matlab
language, from which the axial tensile strength was predicted. Then the specimens with different
parameters were fabricated and tested under axial tensile load respectively. The theoretical model
met the experimental results well. Furthermore, the test results, the stress-strain curve and the
failure form were analyzed, which showed that the axial properties of the MFWT were obviously
strengthened with the incorporation of the axial reinforcement.
Study of the Thermal and Intrinsic Stress of Large Area Diamond Film Prepared by HFCVD
Authors: Xu Feng , Zuo Dun Wen , Lu Wen Zhuang , Wang Min , Zhang Hai Yu
Published: March 2009

High residual stress that includes thermal and intrinsic stress is an obstacle to the further
application of chemical vapor deposited diamond thick film. In this paper, CVD diamond thick film
was deposited on silicon substrate by hot filament chemical vapor deposited (HFCVD) system. The
finite element analysis (FEA) simulation and experimental research were carried out on the thermal
and intrinsic stress of large area diamond thick film. The FEA model is set up to investigate the
distribution and magnitude of thermal stress. The intrinsic stress is studied by X-Ray diffraction
“sin2ψ” method. The thermal stress and intrinsic stress are both compression stress. Simulation
results show the discontinuous sharp of the diamond film result in the stress concentration and low
cooling velocity is a good way to reduce thermal stress. The intrinsic stress is correlative with the
microstructure and non-diamond component of diamond film. The origin of the intrinsic stress is
discussed in detail in this paper.
Research on the Advanced Ceramic Die Materials and Their Properties
Authors: Xu Chong Hai , Xiao Guang Chun , Zhang Rong Bo , Feng Yu Mei
Published: March 2009

The composition, processing technology, mechanical property and engineering
performance of ceramic materials such as cermet, ZTA, TZP, TZP/Al2O3, PSZ, Si3N4 and Sialon, etc,
have been predominantly summarized when they are used as die materials in various operations
such as drawing, extrusion, punching and stamping etc. The problems existed in the research and
application of ceramic die materials are discussed, and the perspectives in the application of
ceramic die materials are pointed out. It is concluded that advanced ceramic material is one of the
most promising die materials because of its high hardness, high wear resistance, superior
high-temperature property and chemical stability and good engineering performance, compared
with other die materials such as die steel and cemented carbides. It is proposed that nano composite
and functionally gradient ceramic, surface modification technology with ceramic, optimal design of
die structures and die reliability research, etc. are all the potential and effective methods in the
improvement of mechanical property and engineering performance of ceramic die materials.
Development and Application of Cermet Cutting Tools Material
Authors: Fu Tie , Yu Qi Xun , Liu Bin , Wu Yu Guang
Published: March 2009

In this paper, the development and mechanical, physical properties on cermet cutting tool
material are described. By using the cermet insert NT7 developed in recent years and WC based
carbide insert YT14, the tool wear, impact and cutting force tests to high strength steel
38CrNi3MoVA (hardened and tempered, HRC36~40) are processed respectively. The results of
these tests demonstrate that NT7 cutting tools have better performance on some characteristics, such
as wear resistance, tool life and cutting force. And its ability of impact resistance is similar to YT14.
These researches will benefit to the poplarizaion and application of cermet cutting tool.
The Influence of Material Constitutive Constants on Numerical Simulation of Orthogonal Cutting of Titanium Alloy Ti6Al4V
Authors: Chen Jian Ling , Li Jian Feng , Sun Jie , Wang Zhong Qiu , Xu Zhi Ping
Published: March 2009

Johnson-Cook (JC) constitutive model is extensively used in the simulation of metal
machining. There are several different sets of JC material constants for titanium alloy Ti6Al4V
fitted by split-Hopkinson bar (SHPB) tests. However, few researches have been done to study their
sensitivity on the behavior of cutting. In this work, four different sets of material constants were
performed in a 2D numerical model to simulate the cutting process of titanium alloy Ti6Al4V. The
effects of the four sets of material constants on the predicted cutting forces, chip morphology and
temperature were studied. It is shown that all the considered process outputs are very sensitive to
material constitutive constants. Some quantitive comparisons with experimental results reported in
the literature were also made.
Optics Manufacturing Using Magnetorheological Finishing
Authors: Kang Gui Wen , Zhang Fei Hu
Published: March 2009

Magnetorheological finishing (MRF) is a novel precision optical machining technology.
Owing to its flexible finishing process, MRF can eliminate subsurface damage, smooth rms micro
roughness and correct surface figure errors. The finishing process can be easily controlled by a
computer. Through proper designing of numerical control, sphere and asphere optics can be machined
by magnetorheological finishing with high quality. Optical sphere is machined using dwell time
algorithm and surface shape 2 pt. PV has been improved from 0.17um to 0.07um.
Study on Technology of Block Electro-Discharge Grinding with Lower Working Voltage for Fabricating Micro Electrode
Authors: Wang Zhen Long , Zeng Wei Liang , Gao Qiang
Published: March 2009

Micro electrical discharge machining (EDM) with block electro discharge grinding
(BEDG), is explored and assessed as a method for developing micro electrode, for wire electro
discharge grinding (WEDG) has shortcoming of low working efficiency, especially in the case of
micro machining. For fabricating micro electrode by BEDG, mechanics of initial clamping errors
are analyzed, the technology of electrode movement is proposed to compensate the clamping errors
and control the finish size of micro electrodes. On the basis of a great deal of experiments, the effect
of working voltage on machining efficiency has been found out and been analyzed theoretically,
threshold value of working voltage is determined to be about 30V.As shown by result with the
technology, at a high machining speed, the minimum diameter of micro electrodes reaches 3*m, its
slenderness ratio is more than 5.