bluuebunny/crossref_metadata_2025 huggingface dataset:
Starch-Based Microparticles as a Novel Strategy for Tissue Engineering Applications
Authors: Silva Gabriela A. , Coutinho Olga P. , Ducheyne Paul , Shapiro I.M. , Reis Rui L.
Published: March 2009

Current tissue engineering strategies involve the use of scaffold materials with properties specific for the target tissue. When the tissue being treated is bone, properties such as bone bonding behaviour and excellent biological performance are very desirable. Many strategies involve the creation in vitro of a suitable hybrid construct (i.e., comprising a scaffold material and cells). These
scaffolds are then inserted into the defect site, thus achieving faster integration and hence, repair. Herein, we describe the synthesis and characterization of starch-based microparticles for bone tissue engineering. This study describes the properties of two types of starch-based microparticles: their
bioactivity in vitro (when processed with Bioactive Glass 45S5), the good biological performance and also the ability to be used as controlled release vehicles of bioactive molecules, such as steroids and growth factors.
A Novel Cell-Loading Method into Porous β-TCP Blocks
Authors: Torigoe Ichiro , Sotome Shinichi , Tsuchiya A. , Shinomiya Kenichi
Published: March 2009

In the field of bone tissue engineering using cells combined with scaffolds, it is
important to efficiently load cells into porous scaffolds. We devised a novel cell-loading method into porous beta-tricalcium phosphate (β-TCP) blocks. In this study, we compared this method with two conventional cell-loading methods in terms of cell-loading efficiency and in vivo bone formation capability. Bone marrow stromal cells (BMSCs) were obtained from the femurs of Fisher rats. After about 10 days of culture, BMSCs were harvested and suspended in the plasma
of the Fisher rats at a concentration of 2×106 cells/ml. This cell suspension was loaded into porous β-TCP cubes (5×5×5mm) by using three loading methods: a soaking method, a post low-pressure method and a pre low-pressure method (the novel method). These β-TCP cubes were cross-sectioned and stained with toluidine blue and cell-counted. Cell-loading efficiency was significantly higher when using the novel methods. For the study of in vivo bone formation
capability, nearly confluent BMSCs were exposed in an osteogenic medium supplemented with 10-7 M dexamethasone, 50µg/ml L-ascorbic acid phosphate and 10mM β-glycerophosphate for 4 days. These osteogenic cells were harvested and suspended in the plasma of the Fisher rats at a concentration of 2×106 cells/ml. This cell suspension was loaded into porous β-TCP cubes (5×5×5mm) by using the three cell-loading methods. Immediately, these β-TCP cubes were
implanted at subcutaneous sites in the backs of 7-week-old male Fisher rats and harvested at postoperative 3 and 6 weeks. After cross-sectioning, these sections were stained with hematoxylin and eosin, and the new bone formation area was quantified. Consistent with cell-loading efficiency, in vivo bone formation capability was significantly higher in the novel method at postoperative 6 weeks. We showed the usefulness of the novel cell-loading method in bone tissue engineering.
Thermal Fatigue and Creep Fracture Behaviors of a Nanocomposite Solder in Microelectronic/Optoelectronic Packaging
Authors: Zhang Xiao Ping , Lim C.S.H. , Mai Yiu Wing , Shi Yao Wu
Published: March 2009

Thermal fatigue performance and creep resistance of soldered connections are crucial to the integrity and reliability of microelectronics, optoelectronics and photonics packaging systems. In this work, creep and thermal fatigue behaviours of lap shear joints soldered by a tin-based nanocomposite solder were characterized at different temperatures, with a comparison to a traditional Sn60Pb40 solder. The results show that the nano-composite solder has much better creep resistance and thermal creep fatigue property than the Sn60Pb40 solder. This is mainly due to the uniformly dispersed nano-sized Ag particles that have provided effective impediment to dislocation movement and grain boundary sliding, in addition to the alloying effect. The creep fractography analysis by SEM shows that a progressive shear deformation occurred as the main creep fracture mechanism. Sn60Pb solder joints deform dominantly by transgranular sliding, while the nano-composite solder joints creep by intergranular mechanism through grain boundary sliding and voids growth.
Interfacial Fracture Toughness of Synthetic Bone-Cement Interface
Authors: Tong Jie
Published: March 2009

Conventionally, the bonding strength of bone-cement interface is obtained by mechanical strength testing which tends to produce large variability between specimens and test methods. In this work, interfacial fracture toughness of synthetic bone-cement interface has been determined using sandwiched Brazilian disk specimens. Experiments were carried out under selected loading angles from 0 to 25 degrees to achieve full loading conditions from mode I to mode II. Solutions for complex stress intensity factors as well as strain energy release rates were obtained for a sandwich disk with a finite interlayer using the finite element method. Phase angles were obtained at a fixed distance to the crack tip. The fracture loads were obtained from the load displacement curves and the values of interfacial fracture toughness were calculated from the fracture loads and the finite element J-integral solutions. The implication of this information on the assessment of fixation in acetabular replacements was discussed in the light of in-vitro fatigue testing of implanted acetabula.
Characterization of Crack Initiation Behavior in Ceramics under Thermal Shock
Authors: Wakayama Shuichi
Published: March 2009

A new experimental technique, Disc-on-Rod test, was developed for evaluating the thermal shock fracture characteristics of ceramic materials. The specimen is disc shaped with a diameter of 20 mm and a thickness of 0.6 mm, and the 2-dimensional thermal stress field was obtained. The specimen was heated to a high temperature and the center region was quenched by means of contact with a cool metal rod with a diameter of 4 mm. The temperature distribution of the specimen was measured by a high speed IR camera and used for the determination of the thermal stress field in the specimen using FEM calculations. In order to evaluate the fracture process, AE signals during thermal shock fracture were detected. It was observed that the maincrack was initiated at the center region, which was subjected to the maximum balanced biaxial stress. The critical stress for maincrack formation was evaluated and compared with that under mechanical loading, considering the volume effect of strength based on Weibull statistics.
Thermosets Toughening by Creation of Residual Compressive Stresses
Authors: Kim Ho Sung , Kim Nam Ho
Published: March 2009

Toughening of thermosets by creation of residual compressive stresses around microspheres is studied. Expandable hollow micro-spheres containing liquefied gas were used for the creation of residual compressive stresses. Microscopic compressive residual stresses around the micro-spheres in the vicinity of the crack tip were graphically analysed and related to macroscopic mechanical behaviour for mode I fracture. It was confirmed that toughening was due to residual compressive stresses rather post-cure effect.
Numerical Study on Two-Dimensional Crack Problems in Three-Layered Isotropic Elastic Materials
Authors: Zhang Xi , Jeffrey Rob
Published: March 2009

Two-dimensional crack problems in a three-layered material are analysed numerically
under the conditions of plane strain. An image method is proposed to obtain a fundamental solution for dislocation dipoles in trilayered media. The governing equations can be constructed by distributed dislocation technique and the solutions are sought in terms of the displacement discontinuity method. Comparisons are made between existing results in the literature and numerical results for different cases and good agreements are found.
Microstructure and Dielectric Properties of Heat-Treated SiC-AlN Multiphase Ceramics
Authors: Shi Xiao Mei , Yang Jian Hua , Pan Yu Bai , Guo Jing Kun
Published: March 2009

Silicon carbide is widely used as an important structural material. It is known for its
extreme hardness, high temperature antioxygenic properties and good tribological properties. Moreover, SiC is also an intrinsic semiconductor. SiC can react with AlN and form an extensive solid solution at temperatures between 1800 to 21000C, and has excellent mechanical properties. However, in this article, we study the influence of the microstructure and the dielectric properties of SiC ceramics. SiC-AlN solid-solution ceramics were prepared by hot-pressed sintering using Y2O3 as the sintering additive. The size of SiC and AlN powders were 0.6μm and 1.06µm respectively. The content of AlN starting powders was 14vol%. The hot-processing sintered SiC-AlN multiphase ceramics have reached high density at 1950oC in Ar atmosphere under 30MPa.The hot-processed ceramics were subjected to
thermal treatments in a range of temperatures between 11000C and 16000C for 3hr. The grain size increased with the annealing temperature. X-ray diffraction profiles show that phase relationships. Scanning electron microscopy (SEM)) was used to determine fracture surface and the local compositions. Dielectric permittivities and dissipation factor of SiC-AlN composites were investigated with the varieties of annealing temperature and the content of AlN particles. Dielectric constants (ε) and Dielectric loss tangents (tanδ) were measured within the microwave frequency range from 40Hz to10MHz.
Solid State Reaction Synthesis and Thermoelectric Properties of Ag-Doped Mg2Si0.8Ge0.2
Authors: Liu Qiong Zhen , Zhang Lian Meng , Shen Qiang , Jiang Hong Yi , Wang Chuan Bin
Published: March 2009

By two-step solid state reaction, Mg2Si0.8Ge0.2 was successfully synthesized .The effect of Ag-doping concentration on the thermoelectric transport properties of p-type Mg2Si0.8Ge0.2 was investigated. With the increasing of Ag-doping concentration, the electrical conductivity σ and Seebeck coefficient α increase correspondingly over the measuring temperature range (300-800K).The peaks of the curves of Seebeck coefficient versus temperature shift towards the lower temperature .When the doping concentration of Ag is 16000ppm(nominal molar percent), the power factor P of Mg2Si0.8Ge0.2 reaches 4.4×10-4W/mK2 at 800K,obviously improved in comparison with the sample with no additive .
Electrophoretic Deposition of Nanocrystalline BaTiO3 in Ethanol Medium
Authors: Dogan Aydin , Günkaya Göktuğ , Suvaci E. , Niederberger Markus
Published: March 2009

Electrophoretic deposition technique is a versatile coating method. With this method
not only flat surfaces but also curved or rough surfaces can be coated in various
thicknesses. In this study, BaTiO3 nanocrystals were synthesized with a novel nonaqueous
method. In a simple one pot reaction process, the metallic barium is
directly dissolved in benzyl alcohol at slightly elevated temperatures. After the
addition of titanium isopropoxide and subsequent solvothermal treatment nearly
spherical BaTiO3 nanocrystals typically 5 nm in diameter were obtained. The
stability of the suspension in ethanol and nanocrystalline particle size distribution
was measured by Malvern Nano-ZS. The BaTiO3 suspensions were directly used in
an electrophoretic deposition process without any additional operation. Pt plated
alumina was used as substrate. Various voltages were applied by altering the
cathode to anode distance as well as deposition time for optimal process control.
Because of the ethanol adsorbed on the surface of the nanoparticles, application of
high voltages was possible without causing hydrolysis. The deposited surface
coatings were dried in air atmosphere and sintered at different temperatures. SEM,
EDX and XRD analysis were employed for the investigation of the coating.
Thermogelation of Composite Films Produced by Electrophoretic Codeposition
Authors: Ferrari Begoña , Santacruz Isabel , De Francisco Isabel M. , Nieto María Isabel , Moreno Rodrigo
Published: March 2009

There is a growing interest to develop reliable, economic and environmentally-friendly
methods for manufacturing thick coatings and layered systems. For thick films, the adhesion to the
substrate and the shape retention become important problems that lead to low density, cracking, and
heterogeneous surfaces. To overcome these problems, a processing route is proposed consisting in
the formation of a thick deposit by EPD in water and its immediate consolidation by thermogelation
of polysaccharides. The process is based on the use of aqueous suspensions containing low
concentration of biopolymers (i.e. carrageenan) and the formation of the film by dipping and/or
EPD on suspensions heated at 60°C. On withdrawal at constant rate a film is obtained after cooling
at room conditions. Maintaining the stability of the hot suspensions and during gelation is a key
parameter to produce controlled deposits with good adhesion to the substrate and uniform
microstructure. In this work, ceramic suspensions or Ni-containing suspensions have been stabilized
with acrylic-based polyelectrolytes at controlled pH. Self-supported films of Al2O3/Y-TZP have
been produced by dipping and EPD on graphite substrates that are burnt out on heating. On the
other hand, Ni/YSZ composites have been deposited on graphite to produce either monolithic or
laminated films. The optimization of the rheological behaviour of the suspensions and the EPD
kinetics allows manufacturing a variety of complex structures with layers having controlled
thickness ranging from 10 to 200 6m.
Theoretical Analysis on the Machining Mechanism in Ultrasonic Vibration Abrasive Waterjet
Authors: Zhu Hong Tao , Huang Chuan Zhen , Wang Jun , Feng Yan Xia , Hou Rong Guo
Published: March 2009

As a unique machining way, Abrasive Waterjet Machining (AWJ) is one of the fastest
developing new non-traditional machining methods and has a wide range of machinable materials.
In this paper, the machining mechanism in AWJ is theoretically analyzed by impact dynamic
mechanics method. There is stagnancy layer between waterjet and workpiece surface. It is found
that the stagnancy layer and low energy abrasive particle are the main factors, which weaken
machining capability and effective utilizing ratio of energy of AWJ machining. Ultrasonic
Vibration Abrasive Waterjet Machining, a new machining method, is put forward and the influence
of ultrasonic vibration on machining mechanism of AWJ machining is discussed.
Cutting Temperature in High Speed Milling of a Near Alpha Titanium Alloy
Authors: Geng Guo Sheng , Xu Jiu Hua , Fu Yu Can , Ge Y.F. , Su C.
Published: March 2009

Cutting temperature has direct effects on tool wear and tool life, as well as machining
accuracy and machining quality. Titanium alloys, however, are generally machined at lower cutting
speeds with cemented carbide tools due to its low thermal conductivity and high chemical reactivity
with cutting tool materials. This paper deals with cutting temperature in high-speed milling of a
near alpha titanium alloy. The measuring principle of cutting temperature by the
workpiece-constantan thermocouple method was illustrated and the physical meaning of the
electromotive force (EMF) signals was described in the paper. The effects of cutting parameters and
wear status on cutting temperature were studied, and the temperature distribution along the cutting
edge was investigated.
The Development of Special Drills for High-Efficient Drilling Austenitic Stainless Steel Part I: Drill Comparison and Experiment Research
Authors: Liu Gang , Chen Ming , Jing Lu Lu , Hu Z.G. , Zhu X.F. , Li Z.W. , Xu H.
Published: March 2009

Austenitic stainless steel is a kind of difficult-to-cut material widely utilized in various
industry fields. But cutting tools is the uppermost obstacle in the application of high efficient and
precise machining of austenitic stainless steel. Drill is the one of the most complicated universal
cutting tools, whose geometry structure influences greatly on drilling performance. So the
development of special drills is imperative for high-efficient drilling. This paper presented the
optimal geometrical characteristics of the special drills, with138° point angle and 38° helix angle,
for high-efficient drilling austenitic stainless steel. The drilling performance has been evaluated
completely and comprehensively through the experiments including measuring cutting deformation
coefficient, thrust force, torque, cutting temperature near the cutting point, cutting tool life, drill
wear mechanism and so on. The special drill indicated appreciated cutting performance during
drilling austenitic stainless steel with high efficiency. Compared to the commercial available
standard drill with 118° point angle and 32° helix angle, the cutting tool life of the special drill was
1.6 times of the standard drill and the special drill yielded good performance of chip evacuation,
good wear resistance and great drilling quality.
Research on Properties and Formation Mechanism of Ceramic Coatings Prepared by Micro-Arc Oxidation on 2024 Aluminum Alloy Surface
Authors: Zhao Wan Sheng , Xin T.Z. , Wang Zhen Long , Liu J.C.
Published: March 2009

In this paper, ceramic coatings prepared on 2024 Al alloy surface in electrolyte by
micro-arc oxidation are studied. The parameter of discharge and rate of ceramic coating formation
are investigated. We analyzed microstructure and phase composition of the coatings by scanning
electronic microscopy (SEM) and X-ray diffraction (XRD), and studied the tribological
performance of the coatings. The reactions on the electrode surface are deduced and the mechanism
of coating formation has been analyzed. The results show that the relation between the thickness
and reaction time is not linear. The ceramic coatings contain phase γ-Al2O3 andα-Al2O3; there is a
big difference in contents of phase composition between inner coating and outer coating due to the
different cooling rates of them. In MAO process, the coating undergoes a course of melting,
solidifying and cooling. The coating can be divided into three layers, namely, transition layer,
compact layer, and loose layer. The coating and substrate adheres firmly by a metallurgical process.
Not only the elements of electrolyte (K, Si) and substrate (Cu) are found in the coatings but also the
element of cathode (Fe). The Si-Al-O complex compound is formed in the discharge channels under
high energy density condition.
Modeling of Material Removal in Workpiece Lateral Ultrasonic Vibration Grinding of Fine-Crystalline Zirconia Ceramics
Authors: Wu Yan , Zhao Bo , Zhu Xun Sheng
Published: March 2009

Based on the grain movement model of ultrasonic grinding, models representing the grinding force of single abrasive and the material removal rate (MRR) are deduced and verified. Mechanism of high efficiency material removal in work lateral ultrasonic vibration grinding (WLUVG) was analyzed. The MRR of fine-crystalline ZrO2 ceramics in WLUVG and conventional grinding (CG) with diamond wheel were researched experimentally in this work. The effects on the MRR, the surface roughness and microstructure of the process parameters and the size of abrasive are measured. It has been concluded that: (1) the MRR in ultrasonic grinding process is two times as large as that of in CG. (2) any increase in the amount of energy imparted to the workpiece in terms of the average diameter of grains, grinding depth both in with and without ultrasonic grinding, will result in an increase in the MRR and the surfaces roughness. (3) the ultrasonic grinding surface had no spur and build-up edge and its surface roughness was smaller than CG significantly. Surface quality of vibration grinding is superior to that of CG, it is easy for ultrasonic vibration grinding that material removal mechanism is ductile mode grinding.
PCBN Tool Wear Mechanism in Interrupted Hard Turning SAE8822 Hardened Steel
Authors: Xiao Lu , Zeng M.X. , Wen Dong Hui , Wu H.H. , Si B.H.
Published: March 2009

The wear behaviour in the precision interrupted hard part turning SAE8822 case
hardened steel by BN250 PCBN cutting tool was studied. Experimental results showed that the
main wear mechanism for the PCBN tool was the edge chipping by the fluctuation of cutting forces
and cutting temperature. The oxidization and diffusion of the elements between workpiece and
PCBN tool decrease the bonded strength between binder and cBN crystal, then lead to the damage
of PCBN cutting tool.
Effect of DC-Plasma Arc Behavior on Growth of Diamond Film
Authors: Li Duo Sheng , Zuo Dun Wen , Chen Rong Fa , Xiang Bing Kun , Zhao Li Gang
Published: March 2009

DC-Plasma arc behavior is one of the key factors on growth of diamond film. The results
show that keeping steady DC-Plasma arc can grow better quality diamond film. In a long-time
growth of diamond film, there is sediment carbon on about 5mm border-entad anode annulus, which
was proved to be graphite. It results in fluctuating and instability of DC-Plasma arc and in the
DC-Plasma density, which causes graphite generation and much stress in the film. By means of
adjusting anode annulus assembly, pausing the supply of carbon source and increasing H2, the
problem of sediment carbon cab be effectively resolved. Finally, the mechanism of the effect of arc
behavior on growth of diamond film is discussed.
Intelligent Matching of Cutting Tools with Workpiece Materials
Authors: Zhou Jun , Deng Jian Xin , Liu Li Li , Liu Zhan Qiang , Ai Xing
Published: March 2009

With the advantage of Case-Based Reasoning (CBR), selection method about matching of
cutting tools with workpiece materials is presented through establishing the matching knowledge and
rules in such respects as mechanical, physical and chemical properties of cutting and workpiece
materials. Intelligent matching system of cutting tools with workpiece materials is developed based
on CBR. This system has such advantages as higher matching speed and better accuracy, which offers
a strong support tool for material selection between the cutter and workpiece.
Pulse Electric Current Sintering of Iron-Base Powders Prepared by High Energy Milling
Authors: Li Yuan Yuan , Li Xiao Qiang , Long Yan , Shao Ming , Xia Wei
Published: March 2009

Fe-2Cu-2Ni-1Mo-0.8C (wt. pct) alloys were successfully fabricated from elemental mixed
powders by high energy milling and pulse electric current sintering, and the effects of milling time
and sintering parameters on the densification degree, microstructure, mechanical properties and
fracture characteristic of sintered material were investigated. Results showed that with increasing
milling time, pulse electric current peak and sintering time, the density and transverse rupture strength
of sintered alloy were improved. However, higher pulse electric current peak and/or longer sintering
time were unfavorable to the density and strength of sintered alloy, because of generating overhigh
sintering temperature. The density and transverse rupture strength of sintered alloy could reach 7.74
103 kg/m3 and 2231 MPa, respectively, and the corresponding fracture morphology was
characterized as intergranular fracture.
Electrode Characteristics of High Pressure Synthetic High Boron Doped Diamond
Authors: Zang Jian Bing , Wang Yan Hui , Tang W. , Huang H.
Published: March 2009

B-doped diamond is an excellent grinding material owing to its high hardness, oxidation
resistance and chemical inertness as well as low resistance. The recent developments of Boron
doped conductive diamond has further increased the scale of diamond applications including the
manufacture of electrically conductive grinding wheel or the use as an electrode in EDM. The
unique electrochemical properties also attract the researchers’ attention on the applications of
electrode, sensor and detectors etc. This paper presents a viable technology that high boron doped
diamond is synthesized under high pressure and high temperature using B-doped GICs as carbon
sources. The synthetic diamond grains with electrically resistivity of 2cm are sufficiently
conductive for electrochemistry measurement. Cyclic voltammotry was performed to evaluate the
electrode characteristics of diamond powder. The results shows that B-doped diamond powder
electrode is electrochemically stable in the supporting electrolytes such as 0.1M KCl, 0.5M Na2SO4
and 0.1M H2SO4 over a wide potential range. The level of background current is very low. The
electrode reaction is quasi-reversible in 0.5M Na2SO4 containing the ferricyanide-ferrocyanide
redox couple.
Research on Software Error Compensation of Ultra-Precision Lathe
Authors: Du Jian Jun , Lee Wing Bun , Cheung Chi Fai , To Suet , Yao Ying Xue , Gao Dong , Li Jian Guang
Published: March 2009

Based on the theory of kinematics for multi-body system, the relative motion constraint
equation is deduced according to the structure layout and the error distribution of the ultra-precision
lathe Nanoform200. By solving the constraint equation, the corrective NC code is derived that can
compensate the geometric errors. The error compensation software is developed aimed at the ultra
precision manufacturing of optics parts. The cutting experiments show that the method and model
in this paper can improve the accuracy about 50% for the ultra-precision turning of optical parts.
Development of High-Speed Cutting Database System with Hybrid Intelligent Reasoning
Authors: Xiang Ke Jun , Liu Zhan Qiang , Ai Xing
Published: March 2009

First, the problems in cutting database are analyzed and primary factors that should be
considered in establishing high-speed cutting database are pointed out, including data presenting
modes, data collecting and updating, the intelligence of the database, and the integration with CAD,
CAPP and CAM. Secondly, high-speed cutting system is analyzed. On the basis of the
categorization of the variables, the function model and the information model of cutting database
are set up, which leads to the establishment of the architecture of high-speed cutting database.
Finally, the combination mechanism of the rule-based reasoning and the case-based reasoning is
analyzed and the process of the hybrid reasoning is given.
Static Performance Analysis of Orifice Compensated Externally Pressurized Gas Spherical Bearing Based on FEM
Authors: Yao Ying Xue , Qin Dong Li , Zhang H.B.
Published: March 2009

In order to optimize static performance of a new orifices compensated externally
pressurized gas spherical bearing, the paper presents a theoretical study using finite element method
(FEM). Galerkin weighted residual method is applied to reduce the order of derivatives of the
transformed Reynolds equation. On the basis of theoretical analysis, the influence of supplying
pressure and geometrical parameters to radial load carrying capacity and stiffness was analyzed. As a
result, the reasonable range of the bearing’s parameters was proposed.
Fabrication and Structure of TiO2 Coated Open-Cell Mullite Ceramics
Authors: Park Seong Hwan , Kim Jae Won , Jung Yeon Gil , Lee Je Hyun , Paik Ung Yu , Lee Hee Soo
Published: March 2009

TiO2 coated open-cell mullite ceramics were fabricated with coating TiO2 sol on pores of
mullite, and its processing parameters were investigated. Open-cell mullite ceramics were fabricated
through a gel-casting process. Two kinds of mullite precursor powders were prepared by dissolution
of two kinds of aluminum salts (Al(NO3)3·9H2O; type I and Al2(SO4)3·16H2O; type II) into colloidal
silica sols. To produce porous mullite ceramics, both mullite precursor powders and PMMA beads (≈
5μm) were co-dispersed by electrosteric stabilized mechanism in an aqueous system and then
gel-casted. The green bodies were sintered above 1300°C for 3hrs in air. The PMMA was offered as
pores in sintered mullite bodies. The prepared open-cell mullite ceramics were dipped in TiO2
precursor solution. The sintered bodies coated with TiO2 sols were re-sintered below 1000°C for 3hrs
after drying at room temperature. The TiO2 was successfully coated into the open-cell mullite
ceramics. The characteristics of each TiO2 coated porous mullite ceramics were investigated by XRD,
SEM, porosimetry, as functions of aluminum salt and pH of sol. It was found that the synthesis
behavior and the porosity of the mullite are strongly dependent upon aluminum salt species, resulting
in different grain size, morphology, and pore size.
Microstructural Characterization of Fine-Grained Pb(Zr0.52Ti0.48)O3 Ceramics Fabricated by a Spark Plasma Sintering
Authors: Koo Sang Mo , Shim Seung Hwan , Yoon Jong Won , Shim Kwang Bo
Published: March 2009

The dense Pb(Zr0.52Ti0.48)O3 (PZT) piezoelectric ceramics have been prepared at a low
temperature by a spark plasma sintering (SPS) method without excess PbO addition and their
structural features including domains were systematically investigated. The fine microstructure
consisting of submicrometer-sized grains as well as relative density reaching 99% was achieved by
sintering at 950°C which is 400°C lower than that of pressureless sintering (PLS). Transmission
electron microscopy (TEM) results confirmed that the sintered specimen contained very dense
domain structures inside each grain, showing the nanoscaled single-domains even at the small
grains (below 100 nm). The SPS-processed PZT exhibited better piezoelectric properties than those
of the PLS-processed one, which is attributed to its fine-microstructural feature.
Hydrogen Reduction and Sintering Behavior of Al2O3/CuO Powder Mixtures Prepared from Different Raw Powders
Authors: Oh Sung Tag , Yoon Se Joong
Published: March 2009

The reduction behavior of Al2O3/CuO powder mixtures, prepared from Al2O3/CuO or
Al2O3/Cu-nitrate, was investigated by using thermogravimetry and hygrometry. Also, the influence of
powder characteristics on the microstructure and properties of hot-pressed composites is analyzed. It
was found that the hydrogen reduction process of nano-sized oxide particles and properties of sintered
composites strongly depends on their distribution and size in composite powder. The formation
mechanisms of nano-sized Cu dispersions are discussed based on the powder characteristics and
reduction kinetics. In addition, the dependence of the microstructure and mechanical properties of
hot-pressed composites on powder characteristics is discussed in terms of the initial size and
distribution of Cu particles.
Low Cost Si3N4/SiC Nanocomposites, Processing, RT and HT Properties
Authors: Šajgalík Pavol , Hnatko Miroslav , Lenčéš Zoltán , Dusza Ján , Kašiarová Monika , Kovalčík J. , Šída Vladimír
Published: March 2009

Silicon nitride - silicon carbide nanocomposite has been prepared by an in-situ
method that utilizes formation of SiC nanograins by C+ SiO2 carbothermal reduction during
the sintering process. The developed C/SiO2 derived nanocomposite consists of a silicon
nitride matrix with an average Si3N4 matrix grain diameter of approximately 200 nm with
inter- and intra- granular SiC inclusions with sizes of approximately 150 nm and 40 nm,
respectively. The mean value of room temperature 4-point bending strength is 670 MPa with
the Weibull modulus of 7.5 and indentation fracture toughness of 7.4 MPa.m1/2. The creep
behaviour was investigated in bending at temperatures from 1200°C to 1450°C, under stresses
ranking from 50 to 150 MPa in air. A significantly enhanced creep resistance was achieved by
the incorporation of SiC nanoparticles into the matrix. The inserts machined from this
composite have three times longer life time compared to those available on the market.
Synthesis of Nanocrystalline α-Al2O3 Using a 2-Step Calcination Method
Authors: Cho M.J. , Youn Sang Heum , Kim Jae Jun , Hwang Kyu Hong , Jun B.S. , Yoon Seog Young , Lee Jong Kook
Published: March 2009

Nanocrystalline α-Al2O3 powders have been prepared by the pyrolysis of a resin compound of aluminum with polyester by a two-step calcination process. A polymeric precursor was prepared using a complexing agent to keep the metal ions in homogeneous solution, which gives sufficient flexibility for the system to exist homogeneously throughout the reaction without undergoing precipitation. The metal-ion-polyester resin forms the precursor material on complete polymerization reaction of aluminum nitrate, citric acid and ethylene glycol. A single-phase α-Al2O3 powder resulted after calcinations above 1150°C, but during heat treatment α-Al2O3 particles grow very fast by coalescence. So 2-step calcination was used, where the first step was done in a reducing atmosphere at above 1150°C and second calcinations were done in oxidizing atmosphere at the relatively low temperature of 1000°C. The precursors and the heat-treated final powders have been characterized by X-ray diffractometry, thermogravimetry , transmission electron microscopy(TEM), and BET surface area analysis. The nanocrystalline α-Al2O3 particles obtained by this 2-step calcinations method had an average specific surface area of >170m2/g, with an average particle size between 40 and 60nm.
Fabrication and Applications of Nano-Metal Particle Composites by Ultrasonic Eco-Process
Authors: Hayashi Yamato , Takizawa Hirotsugu , Saijo Yoshitaka , Sekino Tohru , Suganuma Katsuaki , Niihara Koichi
Published: March 2009

Nano-sized metal particles have recently attracted considerable interest owing to their
application potential. Such particles can be synthesized using physical and chemical methods. In
this study, nano-sized noble metals were synthesized through the reaction of metal oxides by
ultrasonic. This means that the chemical reactions which take place under conventional conditions
can be accelerated by ultrasonic cavitations. In general, the chemical effects of ultrasonic
irradiation fall into three areas: homogeneous sonochemical efffects of liquids, heterogeneous
sonochemical effects of liquid-liquid or liquid-solid systems, and sonocatalytic effects. It has been
proposed that liquid-liquid systems are used for the fabrication of nano-metal particles in the past.
In this study, the fabrication of nano-metal particles and supported composites was investigated for
the liquid-solid system from a viewpoint of economy and ecology. By choosing suitable
conditions, it is reasonable to expect that these simple ultrasonic processes can be extended to
obtain nano-sized metal particles. Thus applications by using these reactions were investigated to
prepare the nano-sized metal particle supported materials, and mechanisms were investigated.
Growth of Carbon Nanotubes on Surface of Carbon Fibers Rod
Authors: Lim Yun Soo , Kim Woo Sik , Moon Sook Young , Han Dong Yun , Lee Jin Yong
Published: March 2009

The growth of carbon nanotubes (CNTs) from surface of carbon fibers rods (CFRs) as used
supports is under investigation using the Fe-catalytic chemical vapor deposition method. TEM studies
indicate that under the experimental conditions Fe catalysts on CFRs produces mostly bundles of
multiwall carbon nanotubes (MWCNTs). SEM results show the best presence of bundles of
MWCNTs for Fe catalysts of 6.5 mol % at 800°C.
Sintering and Characterization of Zr2Al3C5 Monolith
Authors: Leela-adisorn Uraiwan , Choi Seong Min , Hashimoto Shinobu , Honda Sawao , Awaji Hideo , Hayakawa K. , Yamaguchi Akira
Published: March 2009

Zr2Al3C5 has been successfully synthesized via solid state reaction between Al, ZrC and
carbon powder at 1600 in vacuum. This complex carbide has very strong bond between metal
atoms and carbon atoms. Thus, this material has a potential to be utilized as structural materials.
Some properties of Zr2Al3C5 powder from solid-state reaction in vacuum had been tested. It was
found that this powder was completely oxidized in air at 900 1 h, and can be hydrated in moist
air. These drawbacks might come from the high reactivity of the powder due to synthesis in vacuum.
Zr2Al3C5 powder from solid state reaction in vacuum was sintered at various temperatures from
1500 to 2000 under vacuum with pulse electric current sintering (PECS) and pressureless
sintering. Zr2Al3C5 started to sinter at 1500 and got partially dense from 1700. Physical
properties and mechanical properties of this material were investigated and discussed.
Estimation of Residual Stress in a Ceramic Coating Layer
Authors: Ohtsuka Shigehiro , Sekiguchi Yutaka , Tochino Shigemi , Pezzotti Giuseppe
Published: March 2009

We attempted to characterize by Raman piezo-spectroscopy residual stresses as they
develop in chemical vapor deposition (CVD) Al2O3 coatings on Si3N4 ceramic substrates. According
to a piezo-spectroscopic procedure coupled with a confocal configuration of the optical probe used,
two-dimensional stress maps could be collected at various depths along the thickness of the coating.
By comparing Al2O3 coatings produced on Si3N4 substrates at different CVD temperatures, a tensile
residual stress field has been detected in the coating, whose magnitude increased with increasing the
CVD temperature. As for the three-dimensional distribution of tensile residual stress within the
Al2O3 coating, it was found that the stress value was minimum at the coating external surface, while it
gradually increased to reach a maximum near the coating/substrate interface. Similarly, the
compressive stress within the Si3N4 substrate was maximized near the coating/substrate interface and
decreased with proceeding towards the substrate material bulk. It could be concluded that confocal
Raman piezo-spectroscopy is a very suitable tool for three-dimensional stress characterization of
ceramic coating materials.
Microscopic Study of Sliding Wear Surfaces of Alumina
Authors: Senda Tetsuya , Kawagoe Yoh-Ichi , Kotani Noriyuki , Murakami Kenji , Adachi Koshi
Published: March 2009

Sliding wear surfaces of alumina were observed by transmission and scanning electron microscopy. Wear loss was very low (<10-7 mm3/Nm) at room temperature whereas it was high (>10-5 mm3/Nm) at 500oC. In a mild wear regime at room temperature, a layer of very fine particles (10 nm or less) is observed on the wear surface. Beneath the layer, a deformed bulk surface with extensive dislocations is observed. The layer exhibits a diffraction pattern of a meta-stable phase which is dissimilar to the original α-alumina. The layer appears to act as lubrication film at the contact interface to reduce the wear loss. In a severe wear regime at 500oC, a similar structure consisting of a fine-particle layer and deformed bulk surface is observed. However, extensive microcracks are observed in the layer and the bulk underneath that cause further material removal resulting in a high wear rate.
Sinterability of Alumina-Dispersed 3Y-TZP
Authors: Cho Bum Rae , Yeoum Dong Guk
Published: March 2009

The effect of Al2O3 addition on sinterability of Tetragonal Zirconia Polycrystal powders including 3mol% Y2O3 (3Y-TZP) was investigated. Each 3Y-TZP powder dispersed with 0.3, 0.6, 0.9 and 1.2wt.% of Al2O3 was prepared by the spray-drying method. The prepared powders were pressed into a disk type and sintered at 1350, 1400, 1450 and 1500 for 2 hours in the air. Resultant microstructures and mechanical properties of specimens were investigated by using Vickers/Micro hardness Tester, FE-SEM and XRD. Most of the specimens showed high relative density over 99% and a higher fracture toughness than pure 3Y-TZP. Al2O3 particles dispersed in 3Y-TZP microstructure depressed grain growth of 3Y-TZP by the pinning effect. Increase in fracture toughness of 3Y-TZP was explained by the crack deflection due to dispersed Al2O3 particles.
High-Temperature Properties of Silicon Nitride with Lu-Si-O-N Grain Boundary Phases
Authors: Yamamoto Yoshinobu , Nishimura Toshiyuki , Hirosaki Naoto , Guo S. , Cao J. , Mitomo Mamoru
Published: March 2009

High-temperature properties of silicon nitride ceramics with Lu-silicon-oxynitride grain boundary phases were investigated. Si3N4 powder with 1.2 mol% (SN12) and 4.8 mol% (SN48) of Lu2O3 were gas-pressure hot-pressed at 1950°C for 2 h under 20 MPa in 1 MPa N2. SN12 consisted of elongated β-Si3N4 and a secondary phase, Lu4Si2O7N2, whilst SN48 consisted of elongated β-Si3N4 and Lu4Si2O7N2 + Lu2SiO5. At 1500°C and 1600°C, the stress-strain curve of SN48 was nonlinear, whilst that of SN12 was linear, indicating that SN12 broke as a brittle fracture at these temperatures. SN12 had excellent oxidation resistance and weight gain during the oxidation at 1500°C for 1000 h was 4 g/m2. Creep lifetime of SN12 at 1500°C under tensile stress of 137 MPa exceeded 1678.5 h.
Crack Propagation Behavior of Alumina with Different Grain Sizes under Static and Cyclic Fatigue
Authors: El Attaoui Hassan , Saâdaoui Malika , Chevalier Jérôme , Fantozzi Gilbert
Published: March 2009

A compliance function is used to quantify the shielding capacity of grain bridging, the
degradation of which is the main cyclic fatigue mechanism in alumina. Materials with different
grain sizes were processed and the fatigue experiments were performed using the double torsion
test. Significant degradation is observed in the coarse grain material and a marked sensitivity to
the loading level is outlined. At moderate loads, bridging degradation occurs prior to fatigue
crack growth during an incubation period. At low cyclic loads, the shielding capacity can be
entirely degraded, leading to a cyclic fatigue threshold equivalent to that of the fine grain
material.
Grinding of Agglomerate AlN Powder by Wet Milling
Authors: Qiu Jin Yu , Watari Koji , Hotta Yuji , Kinemuchi Yoshiaki , Mitsuishi Kenshi
Published: March 2009

Fine AlN powder doped with Y2O3 and CaO as sintering additives was ground by a ball mill, a planetary ball mill and a super-fine grinding mill in order to obtain fine homogenous powder for low-temperature sintering. The size reduction and the sinterability of ground powders at 1500oC for 6 h were investigated. The size and shape of the agglomeration showed no significant change after the ball mill and planetary mill processes, resulting in poor densification. On the contrary, AlN particles with size of 50~100 nm was pulverized and dispersed by a super-fine grinding mill with very small ZrO2 beads as a mill media. The microstructures of the specimen exhibited equiaxed and homogenous grains with size of 0.3~0.4 μm. Pores in the specimens were eliminated. The thermal conductivity was 70W/mK, which is better than that of Al2O3 ceramics (~20W/mK).
Simultaneous Removal of SOx and NOx by Catalytic Cordierite Filter
Authors: Shin Min Chul , Cha Jin Sun , Lee Jun Han , Lee See Hee , Lee Hee Soo
Published: March 2009

A cordierite filter was fabricated by an extrusion method and it was loaded with LaCoO3
catalyst by a vacuum impregnation method. The simultaneous removal efficiency of NOx/SOx was
measured by passing NO and SO2 through the catalyst-loaded ceramic filter. The cordierite porous
filter had an apparent porosity of 61.6%, compressive strength of 12.3 MPa, and a pressure drop of
1200 Pa at a face velocity of 5 cm/sec, at 400. These values are sufficient to apply the filters for the
removal of hazardous gas in incineration systems, etc. NOx & SOx simultaneous removal efficiency
of LaCoO3 loaded on the porous cordierite filter was about 98% of NOx and over 90% of SOx
between 600 and 650. We could find no poisoning of the catalyst by SO2.
Titania Nanocrystals-Dispersed Coatings from SiO2-TiO2 Gel Films through Hydrolysis and Dissolution
Authors: Matsuda Atsunori , Kogure T. , Muto Hiroyuki , Sakai Mototsugu , Tadanaga Kiyoharu , Minami T. , Tatsumisago Masahiro
Published: March 2009

Anatase nanocrystals were formed on sol-gel derived SiO2-TiO2 coatings with water vapor or hot water treatments. The anatase nanocrystals were precipitated through hydrolysis of Si-O-Ti bonds, dissolution of SiO2 component, migration of hydrolyzed titania species, and nucleation and growth. The process temperatures can be lowered below 60oC, which should open new applications. It was found that the crystal habit of titania was changes from roundish anatase to sheet-like titania by applying vibration during the hot water treatment. The nanosheets were identified as hydrated titania, TiO2 . mH2O, with layerd structure. The coatings of hydrated titania showed high photocatalytic activities and excellent antifogging properties due to their unique morphology.
Fabrication and Characterization of Zirconia-Based New Ceramic Composites for Thermal Barrier Coatings
Authors: Hirvonen Ari T. , Yamamoto Yoo , Sekino Tohru , Nowak Roman , Niihara Koichi
Published: March 2009

Ceramic nanocomposites became nowadays an important ingredient of many structural
and electronic ceramics, as well as ceramic coatings. The same applies to chemically processed and
environmental related ceramics. The performance and characteristics of ceramic components are
considerably influenced by the characteristics of precursor powder. The outstanding properties
possessed by advanced nanoceramics are achieved through exceptional composition and
microstructure that require very careful control throughout the successive stages of the applied
processing.
Fabrication and Characteristics of Hypereutectic Prealloyed Al-Si Powders by Gas Atomization Process
Authors: Kim Yong Jin , Wang L.F. , Chung In Sang , Kim Jin Chun , Jang Tae Suk
Published: March 2009

The hypereutectic prealloyed Al-Si powders were prepared by gas atomization process.
The microstructure and compacting ability of the atomized Al-Si powders were investigated. With
increasing the gas pressure of the atomization, the average powder size and oxygen content were
decreased. The size of primary eutectic Si particles in the as-atomized powders was about 8~10.
As-atomized powders were hot-pressed into a cylindrical shape. Relative density of the hot-pressed
samples was achieved about 96~99 % of theoretical density. Some properties of the samples were
evaluated in this paper.
High-Toughness Tetragonal Zirconia/Alumina Nano-Ceramics
Authors: Vasylkiv Oleg , Sakka Yoshio , Skorokhod Valeriy
Published: March 2009

The 0.75 to 3 mol% Y2O3-stabilized tetragonal ZrO2 and Al2O3/Y-TZP nano-composite ceramics with 0.2 to 0.7 wt% of alumina were produced by a colloidal technique and low-temperature sintering. The influence of the resulting density, microstructure, the yttria-stabilizer and the alumina content on toughness was determined. The bulk 2.7Y-TZP ceramic with an average grain size of 110 nm reached fracture toughness of 11.2 MPa·m1/2. A nano-grained alumina/zirconia composite with an average grain size of 92 nm was obtained. Y-TZP ceramics with a reduced yttria-stabilizer content were shown to reach fracture toughness of 13.8 MPa·m1/2 (2Y-TZP), and 14.5 MPa·m1/2 (1.5Y-TZP). Y-TZP/alumina composites with 0.35 wt% of Al2O3 were shown to reach fracture toughness of 15.7 MPa·m1/2 (2Y), 15.3 MPa·m1/2 (1.5Y).
Fabrication and Evaluation of β-SiAlON Nanoceramics
Authors: Hiratsuka Daisuke , Tatami Junichi , Meguro Takeshi , Komeya Katsutoshi , Hayashi Ichiro , Yang Jian Feng , Omori Mamoru
Published: March 2009

β-SiAlON nanoceramics were fabricated from β-SiAlON nano powder using
the spark-plasma sintering (SPS) technique. The β-SiAlON nanopowder (Si4Al2O2N6)
was synthesized from a mixture of SiO2 (QS-102, Tokuyama Co., Japan), AlOOH
(Tomita, Japan) and C (Mitsubishi Chemical, Japan) using the carbothermal reduction
nitridation (CRN) method. The heating rate for SPS was 50/min. The β-SiAlON
nanoceramics had high strength (500 MPa). TEM observation showed that the
intergranular glassy phase was scarcely present at the grain boundary of the β-SiAlON
nanoceramics. Aqueous corrosion resistance was evaluated by measuring the weight
loss after soaking in 5 and 35 wt.% H2SO4aq. and 5 wt.% HNO3aq. at 80 for 100 h. It
was found that β-SiAlON nanoceramics have much higher corrosion resistance than
commercialized silicon nitride ceramics in acid solutions. Commercialized Si3N4
ceramics have an intergranular glassy phase created as a result of the sintering aids in
them. Thus, they are easily corroded by acid solutions because the intergranular glassy
phase is easily corroded under such conditions. The excellent corrosion resistance of the
β-SiAlON nanoceramics stems from their glass-free grain boundaries, since the
β-SiAlON nanoceramics were produced without using a sintering aid.