bluuebunny/crossref_metadata_2025 huggingface dataset:
Stability of the Perovskite Compounds in the Ce‐Ga‐O and Pu‐Ga‐O Systems
Authors: Stan Marius , Armstrong Tad J. , Butt Darryl P. , Wallace Terry C. , Park Young Soo , Haertling Carol L. , Hartmann Thomas , Jr. Hanrahan Robert J.
Published: July 2010

Cerium oxides are used as surrogates for plutonium oxides because of the similarities in their thermodynamic properties. In this study, the stability limits of both CeGaO3 and PuGaO3 with respect to the partial pressure of oxygen and temperature have been predicted by theoretical calculations. Using the results of the calculations as guidance, mixtures of CeO2 and Ga2O3 have been prepared and thermally treated at 1273, 1473, and 1673 K, in atmosphere of air, argon, or Ar–6% H2. In the samples annealed under low oxygen partial pressures, the CeGaO3 perovskite‐type compound was identified. Based on Rietveld structure refinement, the orthorhombic space group (Pnma, 62) was confirmed.
New Hydrolytic Process for Producing Zirconium Dioxide, Tin Dioxide, and Titanium Dioxide Nanoparticles
Authors: Deng Zhao‐Xiang , Wang Cheng , Li Ya‐Dong
Published: July 2010

Nanocrystalline ZrO2, SnO2, and TiO2 were synthesized through a simple hydrolytic process based on the etherification of alcohols. The obtained products had good uniformity and were less aggregated than in other synthesis techniques. The synthesis of ZrO2 and SnO2 in this process was dependent mainly on the reaction temperature, whereas the morphologies of TiO2 exhibited a dependence on the alcohols used.
Mechanical Properties of Three‐Layered Monolithic Silicon Nitride–Fibrous Silicon Nitride/Boron Nitride Monolith
Authors: Koh Young‐Hag , Kim Hae‐Won , Kim Hyoun‐Ee
Published: July 2010

A three‐layered composite, composed of a strong outer layer (monolithic S3N4) and a tough inner layer (fibrous Si3N4/BN monolith), was fabricated by hot‐pressing. For the inner layer, a Si3N4–polymer fiber made by extrusion was coated by dipping it into a 20 wt% BN‐containing slurry. The three‐layered composite exhibited excellent mechanical properties, including high strength, work of fracture, and crack resistance, because of the combination of a strong outer layer and a tough inner layer. In other words, the strong outer layer withheld the applied stress, while the tough inner layer promoted crack interactions through the weak BN cell boundaries. Also, the residual thermal stress on the surface due to the anisotropy in the coefficient of thermal expansion of BN affected a median/radial crack generation after indentation.
Formation of Titanium Carbide/Aluminum Oxide Nanocomposite Powder by High‐Energy Ball Milling and Subsequent Heat Treatment
Authors: Li Jianlin , Li Fei , Hu Keao
Published: July 2010

The preparation of titanium carbide/aluminum oxide (TiC/Al2O3) nanocomposite powders from a mixture of titanium, carbon, and Al2O3 powders via a high‐energy ball milling process and subsequent heat treatment was investigated. The microstructure development of the powder mixtures was monitored by X‐ray diffraction and transmission electron microscopy. The ball milling of an elemental carbon, titanium, and Al2O3 powder mixture at ambient temperature resulted in the formation of TiC within 15 h of milling. With further milling of up to 25 h, the resulting powder mixture was composed of nanosized TiC particles and nanocrystalline carbon, titanium, and Al2O3. The nanocrystalline titanium and carbon were transformed into nanosized TiC particles after subsequent heat treatment. The final product was composed of nanosized TiC and microcrystalline Al2O3. Most of the nanosized TiC particles were located within Al2O3 grains.
Side‐Surface Structure of a Commercial β‐Silicon Carbide Whisker
Authors: Geng Lin , Zhang Jie , Meng Qing‐Chang , Yao Cong‐Kai
Published: July 2010

The side surfaces of a commercial β‐SiC whisker were analyzed by calculating the surface energy and observing the microstructure of the whiskers. The results indicated that the side surfaces displayed a type of zigzag structure and were composed of {111}, {110}, and {100} crystal planes.
Glass‐Ceramic Protective Coating for Titanium Alloys
Authors: Wang Lianjun , Meng Changgong , Liu Changhou , Wang Liqiu
Published: July 2010

A glass‐ceramic coating that protects a titanium alloy against oxidation during heat treatment has been successfully developed. In the present study, the conditions for preparing this glass‐ceramic coating were investigated. In addition, the prepared coating was characterized by X‐ray diffractometry, energy‐dispersive spectroscopy analysis, and oxygen weight‐gain testing. The results showed that the glass‐ceramic coating has excellent oxygen‐proof properties to protect the titanium alloy from oxidation by the atmosphere at high temperature (900°C).
Solid Yttria‐Stabilized Zirconia Films by Pulsed Chemical Vapor Deposition from Metal‐organic Precursors
Authors: Krumdieck Susan P. , Sbaizero Orfeo , Bullert Angela , Raj Rishi
Published: July 2010

A pulsed chemical vapor deposition from metal‐organic precursors (MOCVD) system was used to produce solid zirconia, and yttria‐stabilized zirconia (YSZ) films. A total of six candidate metal‐organic precursors for zirconia and three for yttria were investigated. Three precursor solutions for YSZ proved suitable for pulsed‐MOCVD processing. Layers were deposited on metal, alumina, and porous nickel cermet substrates. Under optimal deposition conditions, precursor conversion efficiency of 90% was achieved using a solution of 3.74 vol% zirconium 2‐methyl‐2‐butoxide + 0.42% yttium methoxyethoxide in toluene. The film growth rate was 7.5 μm·h−1 at 525°C deposition temperature. Two alkoxide precursors produced YSZ layers with material costs under $0.50/(μm·cm2).
Thermochemical Modeling of Oxide Glasses
Authors: Besmann Theodore M. , Spear Karl E.
Published: July 2010

A modified associate species approach is used to model the liquid phase in oxide systems. The relatively simple technique treats oxide liquids as solutions of end‐member and associate species. The model is extended to representing glasses by treating them as undercooled liquids. Equilibrium calculations using the model allow the determination of species activities, phase separation, precipitation of crystalline phases, and volatilization. In support of nuclear waste glass development, a model of the Na2O–Al2O3–B2O3–SiO2 system has been developed that accurately reproduces its phase equilibria. The technique has been applied to the CaO–SiO2 system, which is used to demonstrate how two immiscible liquids can be treated.
Complex Phase Equilibria in Refractories Design and Use
Authors: Lee William E. , Argent Bernard B. , Zhang Shaowei
Published: July 2010

The current applications of phase diagrams and thermodynamic calculations to studies of refractories are reviewed highlighting links to microstructural analyses. Improved understanding of microstructural evolution and chemical corrosion mechanisms has resulted from such work. The limitation of the calculations/diagrams to thermodynamic equilibria has led to imaginative attempts to incorporate some dynamic aspect in them so they are more relevant to practical conditions. These include varying temperature to model a temperature gradient, PO2 to model atmosphere permeation into a brick, slag/refractory ratio to model slag penetration and altering the slag composition after reaction with the fine matrix phases. The potential future development of such techniques is discussed.
Tentative Phase Relationships in the System CaHfTi2O7‐Gd2Ti2O7 with up to 15 mol% Additions of Al2TiO5 and MgTi2O5
Authors: Perera Dan S. , Stewart Martin W. A. , Li Huijun , Day R. Arthur , Vance Eric R.
Published: July 2010

The phase relationships in the CaHfTi2O7‐Gd2Ti2O7 (zirconolite‐pyrochlore) pseudobinary system were investigated, after heating at 1500°C, because of their importance in the design of pyrochlore‐rich titanate ceramics for immobilization of impure surplus plutonium. Up to 15 mol% of MgTi2O5 and Al2TiO5 were added to CaHfTi2O7‐Gd2Ti2O7 compositions to elucidate the effects of divalent and trivalent impurities on the phase stability within these systems. From X‐ray diffractometry analysis, scanning electron microscopy, and energy dispersive X‐ray spectrometry, phase formation and compositional stability limits were evaluated. The main phases observed in these systems were pyrochlore, perovskite, and polytypes of zirconolite. The formation of the 2M‐, 4M‐, and 3O‐zirconolite polytypes was dependent on the amount of aluminum or magnesium present. In the magnesium system, a large area of pyrochlore‐only was observed, which indicated that divalent impurities of appropriate ionic size could be readily incorporated in the eightfold site of the pyrochlore. The locations of the tentative phase boundaries are discussed with respect to the chemical composition.
In Situ Observations of Phase Transition Using High‐Temperature Neutron and Synchrotron X‐ray Powder Diffractometry
Authors: Yashima Masatomo
Published: July 2010

It is of vital importance for the study of phase diagrams to investigate in situ diffusionless phase transition points at high temperatures. We have developed high‐temperature techniques to measure in situ neutron and synchrotron X‐ray powder diffractometry profiles. This paper reviews our recent studies obtained using these methods. The new furnace for high‐temperature neutron diffraction study yields no extra peaks caused by heaters and refractory; thus, we have been able to measure very small neutron signals from the sample. Quality neutron diffraction data at high temperatures up to ∼1590°C have been analyzed using the Rietveld method for various materials, such as zirconia solid solutions and calcium titanate. High‐resolution synchrotron X‐ray diffractometry enables exact determination of the phase transition temperatures of perovskite‐related materials.
Simultaneous Synthesis and Densification of Titanium Nitride/ Titanium Diboride Composites by High Nitrogen Pressure Combustion
Authors: Shibuya Masachika , Ohyanagi Manshi , Munir Zuhair A.
Published: July 2010

Composites of TiN/TiB2 were synthesized by a combustion process of BN, Ti in a nitrogen atmosphere. The effect of the BN/Ti ratio and the nitrogen gas pressure on the synthesis of these composites was investigated. Dense TiN/TiB2 composites with relatively high hardness and toughness were fabricated by combustion synthesis from Ti and BN under a nitrogen pressure of 4.0 MPa. The Vickers microhardness of the products obtained from reactants with a BN/Ti mole ratio of 0.11 increased with an increase in nitrogen pressure and had a maximum value of ∼25 GPa. Fracture toughness, KIC, of the products increased from 3.1 to 5.9 MPa·m1/2 as the BN/Ti ratio increased from 0.11 to 0.20. However, products formed under nitrogen pressures higher than 6.0 MPa exhibited circumferential macrocracks due to thermal shock.
Rheological Property Evolution in Concentrated Cement‐Polyelectrolyte Suspensions
Authors: Kirby Glen H. , Lewis Jennifer A.
Published: July 2010

We have studied the rheological property evolution and hydration behavior of pure white portland cement (Type I) pastes and concentrated cement‐polyelectrolyte suspensions. Polyelectrolyte species have a marked effect on the initial stability, elastic property evolution (G′(t)), and hydration behavior of this cement system. Pure cement pastes exhibited an initial G′ value of ∼104 Pa and fully reversible G′(t) behavior until the onset of the acceleratory period (t∼ 2 h), where the pastes stiffened irreversibly. In contrast, cement‐polyelectrolyte suspensions exhibited initial G′ values of ∼1 Pa and G′(t) behavior comprised of both reversible and irreversible features. Their initial G′ values, measured after disrupting the particle network under high shear conditions, grew exponentially with hydration time, where Gi′=Gi,0′ exp(t/τc) and τc corresponds to the characteristic hydration time determined from calorimetry measurements. Our observations of these cement‐polyelectrolyte systems suggest that hydration phenomena impact interparticle forces during early stage hydration and, ultimately, lead to initial setting through the formation of solid bridges at the contact points between particles within the gelled network.
Synthesis of Magnesium Aluminate Spinels from Bauxites and Magnesias
Authors: Cunha‐Duncan Flavia N. , Bradt Richard C.
Published: July 2010

The synthesis of refractory Mg‐Al spinel aggregates from bauxites and magnesias was addressed by applying the alumina–magnesia–silica ternary equilibrium phase diagram as the fundamental basis. Four different alumina sources (bauxites) and four different magnesia sources were investigated. These were fired in air through 1700°C and their reactions were monitored using X‐ray diffraction. Evolution of their microstructure was observed by scanning electron microscopy. Initially, the periclase reacts with the free corundum of the bauxite to produce Mg‐Al spinel. The periclase then reacts with the mullite in the bauxites to yield additional spinel and also some forsterite. Spinels were produced for all sixteen different raw‐material combinations.
Abnormal Grain Growth of Pb(Mg1/3Nb2/3)O3‐35 mol% PbTiO3 Ceramics Induced by the Penetration Twin
Authors: Chung Ui‐Jin , Park Jong‐Keuk , Hwang Nong‐Moon , Lee Ho‐Yong , Kim Doh‐Yeon
Published: July 2010

Pb(Mg1/3Nb2/3)O3‐35 mol% PbTiO3 (PMN‐35PT) specimens with a 5 mol% excess PbO were prepared by excessive heat treatment at 1150°C to induce abnormal grain growth. Through electron backscatter diffraction analysis and the observation of a three‐dimensional morphology, the abnormally grown PMN‐35PT grains were found to be twinned crystals with penetration characteristics. The morphology of the PMN‐35PT twinned crystal was crystallographically analyzed. The abnormal grain growth of PMN‐35PT is suggested to be due to preferential growth at the reentrant angles formed by twins.
Microstructural Characterization of High‐Thermal‐Conductivity Aluminum Nitride Ceramic
Authors: Nakano Hiromi , Watari Koji , Hayashi Hiroyuki , Urabe Kazuyori
Published: July 2010

An aluminum nitride (AlN) ceramic with a thermal conductivity value of 272 W·(m·K)−1, which is as high as the experimentally measured thermal conductivity of an AlN single crystal, was successfully fabricated by firing at 1900°C with a sintering aid of 1 mol% Y2O3 under a reducing N2 atmosphere for 100 h. Oxygen concentrations were determined to be 0.02 and 0.03 mass% in the grains and in the grain‐boundary phases, respectively. Neither stacking fault in the grains nor crystalline phase in the grain‐boundary regions was found by transmission electron microscopy. An amorphous phase possessing yttrium and oxygen elements was detected between the grains as thin films with a thickness of <1 nm. Because the amount of grain‐boundary phase was small, the high‐thermal conductivity of the ceramic was attributable to the low oxygen concentration in the AlN grains.
Densification Energy during Nanoindentation of Silica Glass
Authors: Suzuki Keiichi , Benino Yasuhiko , Fujiwara Takumi , Komatsu Takayuki
Published: July 2010

Load/unload displacement curves at room temperature (humidity 49%) for silica glass have been measured in the penetration range of 0.5–1.2 μm using a Vickers nanoindentation technique (load/unload speed 50 mN/s). Deformation energies have been estimated for the first time. The universal (dynamic) hardness, Hu, and elastic recovery, ER, at the penetration depth, ht, of 1.0 μm are Hu= 4.1 GPa and ER= 0.7. The following energies for total deformation, Ut, elastic deformation, Ue, and plastic deformation (i.e., densification during loading), Up, are obtained: Ut=190, Ue=135 and Up= 55 kJ/mol at ht= 0.5 μm and Ut= 139, Ue= 96 and Up= 43 kJ/mol at ht=1.0 μm. All these deformation energies increase with decreasing penetration depth. It is found that plastic deformation energies of 38–55 kJ/mol for 0.5 < ht < 1.2 μm are very close to the activation energy (46–54 kJ/mol) for the recovery of densification in silica glass, but are very small compared with the single bond strength (443 kJ/mol for Si—O bond) of SiO2.
Effect of Oxidation on Mechanical Properties of Fibrous Monolith Si3N4/BN at Elevated Temperatures in Air
Authors: Koh Young‐Hag , Kim Hae‐Won , Kim Hyoun‐Ee , Halloran John W.
Published: July 2010

The oxidation behavior and its effect on the mechanical properties of fibrous monolith Si3N4/BN after exposure to air at temperatures ranging from 1000° to 1400°C for up to 20 h were investigated. After exposure at 1000°C, only the BN cell boundary was oxidized, forming a B2O3 liquid phase. With increasing exposure temperature, the Si3N4 cells began to oxidize, forming crystalline Y2Si2O7, SiO2, and silicate glass. However, in this case, a weight loss was observed due to extensive vaporization of the B2O3 liquid. After exposure at 1400°C, large Y2Si2O7 crystals with a glassy phase formed near the BN cell boundaries. The oxidation behavior significantly affected the mechanical properties of the fibrous monolith. The flexural strength and work‐of‐fracture decreased with increasing exposure temperature, while the noncatastrophic failure was maintained.
Calcium Phosphate Bioceramics with Various Porosities and Dissolution Rates
Authors: Kwon Soon‐Ho , Jun Youn‐Ki , Hong Seong‐Hyeon , Lee In‐Seop , Kim Hyoun‐Ee , Won Ye Yeon
Published: July 2010

Porous bioceramics, such as hydroxyapatite (HA), tricalcium phosphate (TCP), and biphasic HA/TCP, were fabricated using the polyurethane sponge technique. The porosity of the ceramics was controlled by a multiple coating of the porous body. When a porous body was produced by a single coating, the porosity was ∼90%, and the pores were completely interconnected. When the sintered body was coated five times after the porous network had been made, the porosity decreased to 65%. As the porosity decreased, the strength increased exponentially. The TCP exhibited the highest dissolution rate in a Ringer's solution, and the HA had the lowest rate. The biphasic HA/TCP showed an intermediate dissolution rate.
Cement Composition Effects on the Rheological Property Evolution in Concentrated Cement–Polyelectrolyte Suspensions
Authors: Kirby Glen H. , Lewis Jennifer A.
Published: July 2010

We have studied the rheological property evolution and hydration behavior of white and ordinary portland cement (type I) pastes and concentrated cement–polyelectrolyte suspensions. Cement composition had a marked effect on the elastic property evolution (G′(t)) and hydration behavior of these suspensions in the presence of poly(acrylic acid)/poly(ethylene oxide) copolymer (PAA/PEO), even though their affinity to adsorb such species was nearly identical. Both white and ordinary portland cement pastes exhibited G′0 values of ∼104 Pa and fully reversible G′(t) behavior until the onset of the acceleratory period (t= 2 h), where the pastes stiffened irreversibly. In contrast, cement–PAA/PEO suspensions exhibited G′0 values of ∼1 Pa and G′(t) behavior comprised of both reversible and irreversible features. Interestingly, ordinary portland cement–PAA/PEO suspensions experienced a gel‐to‐fluid transition on high shear mixing at short hydration times (<1 h), and the particle network did not rebuild until ∼24 h of hydration. In sharp contrast, white portland cement–PAA/PEO suspensions remained weakly gelled throughout the initial stage of hydration even after high shear mixing. At longer hydration times (>1 h), both cement–PAA/PEO suspensions exhibited G′i(t) ∼ exp(t/τc) with τc values of 5.6 and 1.3 h for ordinary and white portland cement, respectively. Our observations suggest that hydration phenomena impact interparticle forces during early stage hydration and, ultimately, lead to initial setting through the formation of solid bridges at the contact points between particles within the gelled network.
In Situ Synthesis of TiN Particulate/Titanium Silicide Matrix Composite Powder by Mechanochemical Process
Authors: Shim Jae‐Hyeok , Byun Jung‐Soo , Cho Young Whan
Published: July 2010

TiN particulate/Ti5Si3 matrix composite powder has been synthesized from Ti and Si3N4 powders employing high‐energy ball milling. The milled powders have been characterized by X‐ray diffraction, scanning electron microscopy, and transmission electron microscopy. TiN/Ti5Si3 composite powder is formed by a displacement reaction between Ti and Si3N4 during milling, and the reaction progresses in a mechanically induced self‐propagating reaction form. The milled powder consists of TiN crystallites of a few hundred nanometers embedded in Ti5Si3 matrixes. After 20 h of milling, the crystallite size of TiN becomes about 5 nm.
New Freeze‐Casting Technique for Ceramics with Sublimable Vehicles
Authors: Araki Kiyoshi , Halloran John W.
Published: July 2010

A new ceramic freeze‐casting technique capable of manufacturing near room temperature with a sublimable vehicle was accomplished. Fluid‐concentrated slurries of Al2O3 powder in molten camphene (C10H16) were prepared at 55°C. These slurries were quickly solidified (frozen) at room temperature to yield rigid solid green bodies, followed by frozen camphene removal by sublimation (freeze‐drying) with negligible shrinkage. Sintering without any special binder burnout process yielded sintered bodies with over 98% theoretical density. The proposed advantages include (1) elimination of extremely cold temperatures, (2) elimination of troublesome binder burnout process, and (3) fast manufacturing cycle due to quick solidification.
Ultrasonic Spray Pyrolysis for Synthesis of Spherical Zirconia Particles
Authors: Song Y. L. , Tsai S. C. , Chen C. Y. , Tseng T. K. , Tsai C. S. , Chen J. W. , Yao Y. D.
Published: July 2010

This paper presents new findings on ultrasonic spray pyrolysis of zirconium hydroxyl acetate precursor drops whose sizes were precisely measured using laser light diffraction technique. Precursor concentration plays a predominant role in determination of product particle size. At 0.01 wt% precursor concentration, conventional spray pyrolysis at 750°C using precursor drops 5–8 μm in diameter, generated by an ultrasonic nebulizer at 2.66 MHz, yielded uniform spherical yttria‐stabilized zirconia (YSZ) particles 73 nm in diameter measured by scanning electron microscopy. The YSZ particle diameters were much smaller than those predicted by the one‐particle‐per‐drop mechanism. Under similar reaction conditions, the high‐throughput ultrasound‐modulated two‐fluid (UMTF) spray pyrolysis of larger precursor drops (28‐μm peak diameter) also yielded spherical dense particles; they were significantly smaller in size than those produced by the low‐throughput conventional ultrasonic spray pyrolysis of smaller drops (6.8‐μm peak diameter).
Characterization of Thermoelectric Metal Oxide Elements Prepared by the Pulse Electric‐Current Sintering Method
Authors: Fujishiro Yoshinobu , Miyata Motoyuki , Awano Masanobu , Maeda Kunihiro
Published: July 2010

Thermoelectric elements consisting of the layered polycrystalline materials of Al‐doped ZnO and NaCo2O4 were prepared using the pulse electric‐current sintering (PECS) method at 900°C for 3 min. Direct contact between the polycrystalline Al‐doped ZnO and the NaCo2O4 was obtained in a single‐step process for the stacked powders. The electrical conductivities of the polycrystalline materials prepared by PECS were higher than those of materials prepared by conventional sintering, despite their porous structure. The thermoelectric voltage of the 1‐mol%‐Al‐doped ZnO and NaCo2O4 polycrystalline element (measuring ∼6 mm × 3 mm × 15 mm) was 83 mV at dT= 500 K, when the junction of the elements was at 800°C.
Preparation of Hydroxyapatite Fibers by Electrospinning Technique
Authors: Wu Yiquan , Hench Larry L. , Du Jing , Choy Kwang‐Leong , Guo Jingkun
Published: July 2010

Hydroxyapatite (Ca10(PO4)6(OH)2, HA) fibers were prepared by electrospinning a precursor mixture of Ca(NO3)2·4H2O and (C2H5O)3PO with a polymer additive, followed by a thermal treatment. The X‐ray diffraction (XRD) analysis of the annealed composite fibers revealed that pure HA phase could be obtained by annealing at 600°C for 1 h. The scanning electron microscopy (SEM) analysis showed the surface of as‐electrospun composite fibers with an average diameter of 50 μm was smooth due to the amorphous nature of the polymer. However, the surface of the calcined HA fibers was rough because of the complete removal of the polymer. The pure HA fibers obtained by electrospinning in this work were up to 10 mm in length and 10–30 μm in diameter and the hydroxyapatite grain size was ∼1 μm in the HA fibers.
Electronic Structure and Bonding of All Crystalline Phases in the Silica–Yttria–Silicon Nitride Phase Equilibrium Diagram
Authors: Ching Wai‐Yim
Published: July 2010

This paper reviews the structures and properties of 10 binary, ternary, and quaternary crystals within the equilibrium phase diagram of the SiO2–Y2O3–Si3N4system. They are binary compounds SiO2, Y2O3, Si3N4; ternary compounds Si2N2O, Y2Si2O7, and YSi2O5; and quaternary crystals Y2Si3N4O3(M‐melilite), Y4Si2O7N2, (N‐YAM), YSiO2N (wallastonite), and Y10(SiO4)6N2(N‐apatite, N‐APT). Although the binary compounds are well‐known and extensively studied, the ternary and the quaternary crystals are not. Most of the ternary and the quaternary crystals simply have been referenced as secondary phases in the processing of nitrogen ceramics. Their crystal structures are complex and not precisely determined. In the quaternary crystals, there exists O/N disorder in that the exact atomic positions of the anions cannot be uniquely determined. It is envisioned that a variety of cation–anion bonding configurations exist in these complex crystals. The electronic structure and bonding in these crystals are, therefore, of great interest and are indispensable for a fundamental understanding of structural ceramics. We have usedab initiomethods to study the structure and bonding properties of these 10 crystals. For crystals with unknown or incomplete structural information, we use an accurate total energy relaxation scheme to obtain the most likely atomic positions. Based on the theoretically modeled structures, the electronic structure and bonding in these crystals are investigated and related to various local cation–anion bonding configurations. These results are presented in the form of atom‐resolved partial density of states, Mulliken effective charges, and bond order values. It is shown that Y–O and Y–N bonding are not negligible and should be a part of the discussion of the overall bonding schemes in these crystals. Spectroscopic properties in the form of complex, frequency‐dependent dielectric functions, X‐ray absorption near‐edge structure (XANES), and the electron energy‐loss near‐edge structure (ELNES) spectra in these crystals also are calculated and compared. These results are discussed in the context of specific bonding configurations between cations (silicon and yttrium) and anions (oxygen and nitrogen) and their implications on intergranular thin films in polycrystalline Si3N4containing rare‐earth elements.
Simultaneous Synthesis and Sintering of α‐Ti1–xAlx(N) (0 ≤x≤ 0.08) by a Self‐Propagating High‐Temperature Combustion Method
Authors: Hirota Ken , Hayashi Hiromasa , Yoshinaka Masaru , Yamaguchi Osamu
Published: July 2010

Simultaneous synthesis and sintering of hexagonal α‐Ti1−x‐Alx(N) (0 ≤x≤ 0.08) solid solutions, which contain a small amount of nitrogen, have been performed by a self‐propagating high‐temperature combustion method under a nitrogen pressure of 4 MPa. Dense materials (∼99% of theoretical) prepared directly from a mixture of elemental (Ti and Al) powders reveal homogeneous microstructure composed of fine grains (12–16 μm). α‐Ti1−xAlx(N) (x= 0.02; Ti0.98Al0.02N0.26) exhibits a three‐point bending strength σb of 390 MPa, a Vickers hardness Hv of 9.24 GPa, and a fracture toughness KIC of 4.89 MPa·m1/2; their mechanical properties are much improved by doping Al into α‐Ti(N), in comparison with those (σb= 245 MPa, Hv= 9.02 GPa, and KIC= 3.77 MPa·m1/2) of α‐Ti(N) fabricated under the same conditions.
Mechanism for Developing the Boundary Barrier Layers of CaCu3Ti4O12
Authors: Fang Tsang‐Tse , Shiau Hsu‐Kai
Published: July 2010

CaCu3Ti4O12 (CCTO) was prepared by solid‐state reaction and identified by X‐ray diffractometry. The evolution of the microstructure was observed by scanning electron microscopy (SEM). It was found that discontinuous grain growth developed during sintering, and large abnormal grains played a very significant role in the dielectric behavior. Cu ions segregated to the boundaries and CuO located at the triple‐point sites of the abnormal large grains were observed by electron energy loss and energy‐dispersive X‐ray spectroscopy, respectively. Moreover, two kinds of morphologies, i.e., terraces with ledges and bump domains, were discovered inside the grains under the thermal etching conditions at 960°C for 72 min, which solves the contradiction related to the interpretation of the giant dielectric response between ceramic and single‐crystal CCTO. Complex impedance spectroscopy was used to analyze the conductivity of ceramic CCTO, which suggests that it consists of conducting domains with two kinds of insulating barrier layers of domain and grain boundaries. The insulating domain and grain boundaries were attributed to orderly arranged dislocations and segregation of Cu ions, respectively. The conduction of CCTO was found to be related to the porosity, the grain size, and the thickness of the insulating boundary layers. For a sample sintered at 1065°C for 3 h, the anomalously low resistivity and temperature‐dependent dielectric constant were due to the fact that domain boundaries were not substantially formed. The possible reasons for the development of barrier layers and the variation of the dielectric constant with the sintering time are discussed. A barrier‐layer model with dielectric response based on the Maxwell–Wagner type of relaxation for ceramic CCTO is proposed. Two kinds of dielectric responses occur, depending on the microstructure: they are dominated by the domain and domain boundary and by the grain and grain boundary for large grains and fine grains, respectively.
Structure and Dielectric Properties of Pb(Sc2/3W1/3)O3–Pb(Zr/Ti)O3 Relaxors
Authors: Juhás Pavol , Davies Peter K. , Akbas Mehmet A.
Published: July 2010

The structure and dielectric properties of (1−x)Pb(Sc2/3W1/3)O3–(x)Pb(Zr/Ti)O3 ceramics have been investigated over a full substitution range. All compositions with x < 0.5 adopt a cubic perovskite structure; however, for x≤ 0.25 a doubled cell results from a 1:1 ordered distribution of the B‐site cations. The structural order in Pb(Sc2/3W1/3)O3 (PSW) can be described by a random‐site model with one cation site occupied by Sc3+ and the other by a random distribution of (Sc1/33+W2/36+). The ordering is destabilized in solid solutions of PSW with PbZrO3 (PSW–PZ), but stabilized by PbTiO3 in the (1−x)PSW–(x)PT system. The changes in order are accompanied by alterations in the dielectric response of the two systems. For PSW–PZ the temperature of the permittivity maximum (Tɛ,max) increases linearly with x; however, for PSW–PT Tɛ,max decreases in the ordered region (up to x= 0.25) and then increases rapidly as the order is lost. Similar effects were produced by modifying the degree of order of (0.75)PSW–(0.25)PT; when the order parameter was reduced from ∼1.0 to ∼0.65, Tɛ,max increased by more than 60°C.
Subsurface Indentation Damage and Mechanical Characterization of α‐Sialon Ceramics
Authors: Xie Z.‐H. , Hoffman M. , Moon R. J. , Munroe P. R. , Cheng Y.‐B.
Published: July 2010

Two hot‐pressed sintered α‐sialon samples of differing microstructures, but identical chemical composition, were evaluated first, in terms of indentation hardness and modulus, by depth‐sensing indentation (DSI) tests on planes parallel and normal to the hot‐pressed surface. The surface and subsurface cracks created under the DSI tests have also been investigated in relation to the effect of microstructure. Subsequently, Vickers indentation tests were conducted to explore the deformation and fracture characteristics in the two samples. The effect of microstructure and grain orientation on the development of different types of cracks, in particular subsurface cracks, was revealed and analyzed. Additionally, it suggested that the focused ion beam (FIB) miller is a preferred tool, in comparison to the conventional cross‐sectioning techniques, for examining subsurface crack formation and structural characteristics.
Critical Factors Affecting the Wettability of α‐Alumina by Molten Aluminum
Authors: Shen Ping , Fujii Hidetoshi , Matsumoto Taihei , Nogi Kiyoshi
Published: July 2010

The wetting behaviors of α‐Al2O3 single crystals with three different faces—R(0112), A(01120), and C(0001)—and polycrystals (PC) by molten aluminum were studied over a wide temperature range using both a conventional and an improved sessile‐drop method. The critical factors affecting the wettability, such as temperature, atmosphere, substrate surface roughness, and crystallographic orientation, and the influence from the experimental technique, were thoroughly investigated. The results show that the aluminum surface oxidation and the thickness of the oxide film have a pronounced effect on the wettability, especially at low temperatures. To eliminate this effect, the experimental temperature must be over a critical value. Vacuum favors lowering this value compared with atmosphere, and the improved sessile‐drop method, particularly using an impingement‐dropping mode (I‐mode), helps to weaken this effect by mechanical disruption and removal of the oxide film. However, the dropping distance and the dropping force must be controlled to prevent an overspreading of the drop. The effects of the substrate surface roughness and temperature are not significant in the case of a clean aluminum surface and a fine‐prepared alumina surface. On the other hand, the effect of the alumina surface crystallographic orientation is noticeable and the wettability is in the order of R > A > PC > C. The intrinsic contact angles of the Al/α‐Al2O3 system in the temperature range of 1000°–1500°C were estimated to be 76°–85° for the R and A faces, 88°–100° for the C face, and 77°–90° for the polycrystal, depending on the temperature.
The Cytotoxic Reactivity and Sialic Acid Content of Human Lymphoid Cells
Authors: Reisner E. G. , Flye M. W. , SU Chung K. S. , Amos D. B.
Published: July 2010

Human lymphocytes treated with neuraminidase show cytotoxicity reactions with a larger number of alloantisera against human leukocyte antigens than do untreated lymphocytes. In general, untreated thymus cells from the lymphocyte donor give reactions comparable to those of the neuraminidase treated lymphocytes with both alloantisera and sera which fail to react with untreated lymphocytes. However, certain sera show clear distinctions between lymphocytes and thymocytes, some reacting only with thymus cells and others only with lymphocytes. The cytotoxic reactivity of lymphocytes and thymocytes correlates with the amount of sialic acid released from the cells by neuraminidase treatment in that thymocytes release less acid than cells from spleen, adenoids, tonsils, or peripheral blood.
HL–A Antigens and Thyrotoxicosis
Authors: NELSON S. D. , POLLET J. E.
Published: July 2010

HL–A phenotypes were determined in 60 patients with primary thyrotoxicosis and in 60 age‐sex matched controls living in the same region in order to establish the frequencies of ten HL–A antigens in the two populations. HL–Al was present in 28 patients and 18 controls (X2 = 2.86, P > 0.05). HL–A13 was present in eight patients and only one control (X2 = 4.32, 0.05 > P > 0.025). These findings suggest that HL–A phenotypes may be of value in studies on the aetiology of primary thyrotoxicosis. The statistical significance of these results is discussed as these findings may be due to chance deviations.
Renal Transplantation and Cancer. The Scandia Transplant Material
Authors: BIRKELAND S. A. , KEMP E. , HAUGE M.
Published: July 2010

Between 1965 and 1973, 30 malignant tuniours were found in patients transplanted in Scandinavia.

Of these tumours, 24 were found in the 1,254 patients transplanted in Scandinavia as part of the Scandia Transplant Programme between 1969 and 1972. Using the inforniation recorded in the programme, 418 Danish patients who received their first and only transplant between 1969 and 1972 were selected and followed until 31/12 1973. Twelve tumours occurred in these patients. A comparison with the expected age, sex and time‐specific incidence rates from the Danish Cancer Register was made and the observed tumour incidence was found to be significantly (P < 0.001) greater than expected.

Tumour incidence was found to be associated with inconipatibility in the FOUR series, but was unrelated to number of rejections, the presence of HL‐A antibodies and sex differcnce between donor and recipient. Apart from certain special forms of immunosuppression which could be oncogenic, the cause of tumour development appears to be rnultifactorial, both the allograft itself and imniunosuppressive treatment playing a role.
Cell Mediated Lympholysis in Man. The HL‐A Third Locus Antigen, AJ (W20) as Sensitizing and/or Target Determinant
Authors: KRISTENSEN TOM , GRUNNET NIELS , KISSMEYER‐NIELSEN FLEMMINC
Published: July 2010

The Indirect Cell Mediated Lympholysis (ICML) test has become a reliable in uitro tool in investigations of the immunogenetic background of the cellular immune response. It is well established that the antigens of the LA and FOUR loci of the human Major Histocompati bility Complex (MHC) or antigens governed by closely linked loci exhibiting a marked linkage disequilibrium are of major qualitative and quantitative importance in ICML.

This communication is concerned with the importance of the HL‐A third series antigen AJ (W20) on lympholysis in ICML. From investigations of 47 combinations where only the AJ (W20) antigen may be attacked, it is concluded that this antigen is, in itself, a poor ICML target determinant, but that AJ (W20) may function as a stronger ICML target determinant in concert with a FOUR antigen, although the actual FOUR antigen cannot be attacked.
A Crossover in the HL‐A System Traced through Three Generations
Authors: CROSS D. E. , WHITTIER F. C. , SCHIMKE R. N. , GREINER R. F. , FOXWORTH J. A. , OKELL R. T.
Published: July 2010

A case of recombination in the HL‐A system that was traced through three generations is presented. The recombinant gene was shown to be inherited intact by the son of the recombinant.
Serological Identification of la Antigens: Report of a British Region la Workshop
Authors: Bodmer Julia , Pickbourne Penelope , Bodmer Walter , Batchelor Richard , Dewar Patrick , Dick Heather , Entwistle Colin , Festenstein Hilliard , Gelsthorpe Keith , Joysey Valerie , Mackintosh Pauline , Lawler Sylvia , Morris Peter , Pegrum G.D. , Harris Rodney , Taylor Malcolm
Published: July 2010

In preparation for the 7th International Histocompatibility Workshop 13 laboratories in the British Region participated in a local workshop. One hundred and twenty‐three sera which had been previously shown to have activity on either normal B cells, CLL cells or B cell lymphoid lines in the absence of HLA‐A, B or C activity were exchanged between the laboratories. These sera were tested on a total of 212 B cells, 101 CLL cells, 76 T cells and 76 lymphoid cell lines. The data was collected and analyzed in Oxford. The analysis showed that six groups of sera could be distinguished. When these groups were compared with the D locus typing of some of the lymphoid lines which were derived from individuals used as MLC typing cells, they were seen to have significant associations with D locus antigens. The serological groups defined were therefore given numbers corresponding to the D locus numbers they associate with, i.e. UKl is associated with DW1 and so on for UK2, 3 4, 5 and 7. Comparison of typing techniques showed that long incubation both with antiserum and then with complement, 1 hour + 2 hours gave the best and most reproducible reactions on normal B cells. Residual anti‐HLA‐A, B or C activity in some of the sera even after platelet absorption showed the importance of adequate checking on T cells after absorption.
Different Stimulating Capacity of Monocytes and B Lymphocytes in Mixed Leukocyte Cultures: A Dose Response Study
Authors: Gluckman J. C. , Degoulet P.
Published: July 2010

Cell fractions highly enriched either for monocytes or for B lymphocytes were separated from human peripheral blood. They were tested for their capacity to stimulate allogeneic lymphocytes in mixed leukocyte cultures, using dose‐response titrations. Neither population could be stimulated to proliferate by allogeneic cells, but both proved strong stimulators. In this respect monocytes were more efficient than B cell preparations. Differences were pronounced at the lower numbers of stimulating cells but were no longer significant with large amounts of cells.
HLA—B17 and the HLA—A1, B17 Haplotype in Acute Myelogenous Leukemia
Authors: Heise Eugene , Parrish Edward , Cooper Robert
Published: July 2010

Seventy‐nine Caucasians with acute myelogenous leukemia (AML) were genotyped to determine whether AML, the induction of remission or patient survival were associated with particular HLA phenotypes or haplotypes. HLA—B17 and B27 were increased in AML patients over 40 years of age. Combined analysis of four independent studies indicates that HLA‐B17 is significantly but weakly associated with AML, relative risk = 1.48 (.01 < P < .025). The A1, B17 and Aw24, Bw35 haplotypes occurred more frequently in the AML group as compared to racial and geographic controls (uncorrected P= 0.0068 and 0.0098, respectively Fisher's Exact Test). Induction of remission occurred less frequently in patients with the B17 phenotype as compared to patients lacking this antigen (P= 0.047). Patient survival was associated with remission status (P= 0.002) but was not significantly associated with particular HLA phenotypes or haplotypes. These results indicate that a gene or genes in the HLA—B region of the major histocompatibility complex can influence susceptibility to AML and also the response to chemotherapy.

The authors are grateful to Paula Barnes and H. R. Shey for statistical assistance, Andrea Jordan for technical help and Linda Caudill for typing the manuscript.
H–2L: Demonstration of Four New Allelic Products and Independence of H–2D and H–2L Molecules
Authors: Iványi Dagmar , Snoek Margriet , Démant Peter
Published: July 2010

The H–2L molecules were detected for the first time in the Dd region products using antisera against the public specificity H‐2.28. This specificity was analyzed because its presence in K as well as in D region products and its apparent allelism with another public specificity, H‐2.1, indicated that these two specificities may have a special position in the H‐2 system. This was corroborated by subsequent identification of H‐2L molecules in Dq and Dk products using anti‐H‐2.28 and anti‐H‐2.1 sera, respectively, while none of the other previously known public or private specificities was detected on H‐2L molecules. We tested the products of four D region alleles which had not been analyzed previously. In each of them we identified two distinct types of molecules: H–2D, which reacts with sera against the D region private specificity, and H–2L, which does not react with these sera, but which is detectable either by anti‐H‐2.28 sera (H‐2Lb, H‐2Lf, H‐2Ls) or by anti‐H‐2.1 sera (H‐2Ldx). This increases the number of identified H‐2L alleles to seven (five H‐2.8+, two H‐2.1+). No association between H‐2D and H‐2L molecules on the cell surface was detected in capping experiments.
A Monoclonal Mouse Anti‐Rat Ia Antibody which Cross Reacts with a Human HLA—DRw Determinant
Authors: McMaster W. Robert , Winearls Beryl C. , Parham Peter
Published: July 2010

A mouse monoclonal antibody, called MRC OX 3, which detects a polymorphic Ia determinant in the rat and cross reacts with an Ia determinant coded for by the I‐A subregion in the mouse, detects a polymorphic determinant on human B cell lines. MRC OX 3 antibody binds to human B cell lines which express HLA‐DRw specificities DRw 1, DRw2 and DRw6 but does not bind to those cells which only express other HLA‐DRw specificities. No significant binding of MRC OX 3 antibody to either normal or mitogen stimulated human peripheral blood leukocytes, some of which are typed as HLA‐DRw1, DRw2 or DRw6, could be detected. The binding of MRC OX 3 antibody to a human B cell line could be completely inhibited by pre‐absorbing the antibody with purified rat Ia antigen.
HLA Haplotype Associations with Disease
Authors: Thomson Glenys , Bodmer Walter
Published: July 2010

Interest recently has extended to the problem of looking for HLA haplotype associations with particular diseases. Higher order interactions, that is to say of particular haplotypes with a disease, are much more complicated than individual antigen associations, with which most disease studies have so far been concerned. Our aim in this work is to explain the concept of higher order interactions and to discuss the difficulties involved when trying to measure such haplotype associations. The main emphasis is to point out that it is not easily possible to detect haplotype associations if an individual antigen association with the disease exists.
Standardization of the Human in vitro Cell‐mediated Lympholysis Technique
Authors: Schendel Dolores J. , Wank Rudolf , Dupont Bo
Published: July 2010

Cytotoxic lymphocytes (CTL) can be generated in mixed lymphocyte culture and cryopreserved after a 6‐day sensitization phase. CTL tested after storage in liquid nitrogen do not show lysis of autologous target cells and can mediate strong cytotoxicity against other target cells. This lysis shows the same specificity as that of the corresponding fresh CTL. The ability to cryopreserve CTL enables performance of sequential CML testing. Data from separate CML experiments can be pooled using a percent relative cytotoxic response (% RCR) to normalize values within individual experiments. Together, these methods provide a standardized cell‐mediated lympholysis technique.
HLA‐A, B Haplotype Frequencies in 5,202 Unrelated Danes by a Maximum‐Likelihood Method of Gene Counting
Authors: Hansen H.E. , Larsen S. Olesen , Ryder L.P. , Nielsen L. Staub
Published: July 2010

A population sample of 5,202 persons comprising normal, healthy individuals from three laboratories in Copenhagen was used for estimating HLA‐A, ‐B antigen, gene, and haplotype frequencies, besides delta‐values and their standard errors. The serum panels used allowed the determination of a total of 273 HLA‐A, ‐B haplotypes, and the most significant Δ‐values were in agreement with those found in other Caucasian populations. The methods used for the calculations of frequencies, delta‐values, and standard errors are described.
HLA‐A, B and C Antigens in South Indian Families with Leprosy
Authors: Wolf Eva , Fine P. E. M. , Pritchard Janet , Watson Bridget , Bradley D. J. , Festenstein H. , Chacko C. J. G. , Stevens A.
Published: July 2010

Seventy‐two families, selected for having at least two children affected with leprosy, were HLA typed for 57 A, B and C locus antigens recognized by the WHO Nomenclature Committee. In addition, 20 possible new “splits” were investigated. The distribution of A, B and C locus antigens in affected and unaffected family members was similar, irrespective of the type of leprosy in the family. Gene frequencies (derived by direct gene counting from 253 haplotypes), haplotype frequencies and delta values were calculated. There is evidence for heterogeneity of B5, B15, B17, Bw16 and Bw35 and for the existence of at least one A locus and one B locus antigen not previously detected. The value of the HLA system for detecting expaternal children in a highly inbred population and the effect of inbreeding on the HLA system is discussed.
HLA Antigens in South American Indians
Authors: Black Francis L. , Berman Lee Lucas , Gabbay Yvone
Published: July 2010

New HLA data for the Tirio, Parakanã, Kayapo and Mapuche tribes, as well as supplementary data for the Waiãpi are presented. Taken together with previously published information on South American Indians, these typings show a remarkably homogeneous gene pool with a restricted range of polymorphisms and a further restricted set of haplotypes.