bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis of Solid, Spherical CeO2 Particles Prepared by the Spray Hydrolysis Reaction Method
Authors: Xu Huarui , Gao Lian , Gu Hongchen , Guo Jingkun , Yan Dongsheng
Published: July 2010

To avoid the formation of hollow particles during spray pyrolysis, a spray hydrolysis reaction method (SHRM) was studied. Unlike the conventional spray pyrolysis that uses metal salt as a precursor and dry air as a carrier gas, the SHRM introduces a mixture of metal salt and dimethyl oxalate (DMO) as precursors and a gas mixture of water vapor and air as the carrier gas. Spherical, solid CeO2 particles characterized by SEM, BET, and density analysis were produced by the SHRM using Ce(NO3)3 and DMO as the precursors. DMO, as an internal precipitant, hydrolyzed and produced oxalic acid, which precipitated with cerium ions to form volume precipitation in the whole droplet at enough temperature and relative humidity. The volume precipitation induced by the in situ formation of oxalic acid in the whole droplet prevented Ce(NO3)3 nucleation at the droplet surfaces, thus avoiding the formation of hollow particles which usually occur in the conventional spray pyrolysis process. XRD and IR analysis showed that cerium oxalate was an intermediate product in the SHRM process.
Novel Two‐Step Sintering Process to Obtain a Bimodal Microstructure in Silicon Nitride
Authors: Kim Hai‐Doo , Han Byung‐Dong , Park Dong‐Soo , Lee Byong‐Taek , Becher Paul F.
Published: July 2010

A two‐step sintering process is described in which the first step suppresses densification while allowing the α‐to‐β phase transformation to proceed, and the second step, at higher temperatures, promotes densification and grain growth. This process allows one to obtain a bimodal microstructure in Si3N4 without using β‐Si3N4 seed crystals. A carbothermal reduction process was used in the first step to modify the densification and transformation rates of the compacts consisting of Si3N4, Y2O3, Al2O3, and a carbon mixture. The carbothermal reduction process reduces the oxygen:nitrogen ratio of the Y‐Si‐Al‐O‐N glass that forms, which leads to the precipitation of crystalline oxynitride phases, in particular, the apatite phase. Precipitation of the apatite phase reduces the amount of liquid phase and retards the densification process up to 1750°C; however, the α‐to‐β phase transformation is not hindered. This results in the distribution of large β‐nuclei in a porous fine‐grained β‐Si3N4 matrix. Above 1750°C, liquid formed by the melting of apatite resulted in a rapid increase in densification rates, and the larger β‐nuclei also grew rapidly, which promoted the development of a bimodal microstructure.
Preparation of CuAlO2 Films by Wet Chemical Synthesis
Authors: Ohashi Masayoshi , Iida Yasuo , Morikawa Hisashi
Published: July 2010

CuAlO2 is a delafossite‐type compound and is a known p‐type semiconductor. Transparent CuAlO2 thin films were prepared using a sol–gel technique. The films with an Al/Cu atomic ratio of 1.0 consisted of CuAlO2, Cu2O, and CuO after heat treatment at 800°–900°C in nitrogen gas. The electrical resistivity of the film heated at 800°C was 250 Ω·cm.
Effect of Acid Cleaning and Calcination on Rheological Properties of Concentrated Aqueous Suspensions of Silicon Nitride Powder
Authors: Dai Jian‐Qing , Huang Yong , Xie Zhi‐Peng , Xu Xing‐Li , Yang Jin‐Long
Published: July 2010

The powder characteristics of two types of Si3N4 (referred to as FD1 and FD2), as well as the rheological properties of their aqueous suspensions, were studied in this paper. There are distinctive differences in size distribution, soluble counterions, and surface groups. Highly concentrated aqueous slurries could not be prepared from these two as‐received powders. Acid cleaning and calcination improved the solids loading of their aqueous slurries, but the improvement varied with the powder. For the as‐received FD1 powder, poor dispersibility was caused by high‐valence counterions, which can be eliminated through acid‐cleaning. However, for the as‐received FD2 powder, it was the surface group of amine structures and carbon‐hydrogen bonding that limited the dispersibility. The calcination of FD2 can remove the amine structure and carbon‐hydrogen bonding and improve the slurry's rheological properties almost perfectly. For acid‐cleaned and calcined FD1, and calcined FD2, the solids loading of their aqueous suspensions reached 50 vol% with a viscosity below 300 mPa·s.
Photocatalytic Characteristics of Nanometer‐Sized Titania Powders Fabricated by a Homogeneous‐Precipitation Process
Authors: Lee Kang Ryeol , Kim Sun Jae , Song Jae Sung , Lee Ju Hyeon , Chung Yun Joong , Park Sung
Published: July 2010

The photocatalytic characteristics of nanometer‐sized TiO2 powder prepared by a homogeneous‐precipitation process (HPP) were compared with those of a commercial powder to determine which powder was better able to remove metal ions, such as lead and copper, from aqueous equimolar metal‐ethylenediaminetetraacetic acid (EDTA) solution. In aqueous lead‐EDTA solution, the TiO2 powder fabricated by HPP had 3.5 times higher initial adsorption of lead ion and a 1.5 times faster rate for the complete elimination of lead ions than did the commercial powder. In an aqueous copper‐EDTA solution, the TiO2 powder fabricated by HPP also showed higher initial adsorption and a faster elimination rate for copper ions than did the commercial powder. Similarly, the photocatalytic properties were enhanced as the specific surface area increased, and the TiO2 powder fabricated by HPP, which consisted of coagulated primary particles 20 nm in size, with chestnut‐burr shapes, had a larger specific surface area (∼180 m2/g) than that of the commercial powder (∼55 m2/g).
Results of an International Round‐Robin for Tensile Creep Rupture of Silicon Nitride
Authors: Luecke William E.
Published: July 2010

Fourteen laboratories participated in an interlaboratory study to establish the within‐ and between‐laboratory repeatability of tensile creep rupture of silicon nitride. In air at 1375°C at 200 MPa, the times to failure ranged over a factor of 50, and the minimum creep rates ranged over a factor of 20. Despite these large ranges, taken individually, no one laboratory stands out from any other; all produced equally acceptable data. Consumers of silicon nitride tensile creep data must accept this magnitude of variability in reported creep data. The wide variety of specimen shapes and sizes, gripping systems, extensometry techniques, and temperature measurement strategies makes it impossible to assign definitively the root cause of the variability. However, there was a significant specimen size effect. As a group, the small‐diameter specimens lasted roughly five times longer and crept three times more slowly than the large‐diameter buttonhead specimens. A possible interpretation of the origin of this difference is that the oxidizing conditions affected more of the volume of the small specimens during the test.
Oxidation Kinetics and Composite Scale Formation in the System Mo(Al,Si)2
Authors: Ramberg C. Eric , Worrell Wayne L.
Published: July 2010

The oxidation kinetics of hot‐pressed Mo(Al0.01Si0.99)2 and Mo(Al0.1Si0.9)2 were measured at 480°C, and between 1200° and 1600°C. The qualitative oxidation of arc‐melted Mo(Al0.1Si0.9)2, Mo(Al0.3Si0.7)2, Mo(Al0.5Si0.5)2, and Mo3Al8 was examined after 600°C for 1000 h in air. At all temperatures, the compositional difference between the materials yielded very different oxidation rates and scale microstructures. At 1400° and 1500°C, microstructural evolution of the oxide scales resulted in improved oxidation resistance at long times (>400 h). At these temperatures, a significant reduction in the long‐time oxidation kinetics was correlated with the in situ formation of an inner mullite scale. At 480° and 600°C, oxidation resistance improved significantly with increasing aluminum concentration. Contrary to the behavior of MoSi2, samples of Mo(Al0.01Si0.99)2 did not demonstrate catastrophic oxidation, and samples of Mo(Al0.1Si0.9)2 were very oxidation resistant.
Preliminary Experiments of In Situ Atomic Force Microscopy Observation of Hydroxyapatite Formation on Bioactive Glass Surface
Authors: Leonelli Cristina , Lusvardi Gigliola , Menabue L. , Tonelli Massimo
Published: July 2010

This paper demonstrates the use of atomic force microscopy (AFM) to image the bioactivity of phosphate glasses that are well‐known to react rapidly in simulated body fluid. The present study demonstrates that the hydroxyapatite (HAP) crystalline layer found via AFM in the examined samples coincides with that identified using scanning electron microscopy. Moreover, the effect of a notorious bacteriostatic cation—tetravalent cerium, Ce(IV)—on the kinetics of the HAP layer is investigated in CeO2‐doped bioactive glasses.
Infrared, Raman, and Electron Spin Resonance Studies of Vitreous Alkaline Tungsten Phosphates and Related Glasses
Authors: Boudlich Driss , Bih Lahcen , Archidi Moulay El Hassane , Haddad Mustapha , Yacoubi Abdelmajid , Nadiri Abdelilah , Elouadi Brahim
Published: July 2010

Ternary phosphates are found to vitrify within large domains of compositions inside the phase diagrams P2O5–WO3–A2O (A = Li, Na). Structural approach of the highly modified glasses P2O5–A2MoO4–A2O (M = Mo,W) was investigated using various spectroscopic techniques such as infrared, Raman, and electron spin resonance (ESR). These glasses were found to contain MO6octahedra, MO4tetrahedra, M2O7dimers, PO4tetrahedra, and also P2O7or metaphosphate chains, depending on the composition considered. As shown in earlier studies, the glass network is progressively depolymerized as the content of A2O increases. ESR experiments were conducted on both X‐ray irradiated and unirradiated samples. Unirradiated glasses exhibit two ESR signals attributed to W5+ and Mo5+ centers that are octahedrally coordinated. Irradiation of these glasses induces new paramagnetic centers ascribed to the phosphorus–oxygen–hole–center and peroxy radicals. The M5+ concentration depends strongly on the sample composition and temperature. ESR parameters are determined using a computer simulation approach adapted for vitreous materials.
Nucleation and Crystal Growth of a MgO–CaO–Al2O3–SiO2Glass with Added Steel Fly Ash
Authors: Barbieri Luisa , Corradi Anna , Lancellotti Isabella , De Oliveira Antonio Pedro Novaes , Alarcon Orestes Estevam
Published: July 2010

The nucleation and growth of diopside Ca(Mg,Al)(Si,Al)2O6crystals on the free surface of a 24 wt% MgO, 14 wt% CaO, 9 wt% Al2O3, and 53 wt% SiO2glass, with a 2 wt% addition of steel fly ash, were investigated through DTA, XRD, SEM, and optical microscopy. Crystallization was complete at ∼920°C with an activation energy of 589 kJ/mol. Samples with polished free surfaces were nucleated at selected temperatures in the range of 730° to 820°C, and then heat‐treated at 870°C for 15 min for crystal growth. Nucleation was predominantly observed at the surface, and the number of diopside crystals per unit of area and the mechanism of crystallization were determined. It was concluded that nucleation reaches a maximum at 750°C, corresponding to an average density of diopside crystals of 8.4 × 106 nuclei/cm2, and that between 900° and 1100°C, a uniformly crystallized layer is formed at an exponential rate. The crystallized volume fraction increased significantly in the 880°–890°C growth range, and remained almost constant at higher temperatures. In the 860°–910°C range, the size of the diopside crystals formed in the samples nucleated at the temperature of the maximum nucleation rate, and linearly increased, reaching values between 1.0 and 3.0 μm at 870° and at 910°C, respectively.
Low‐Temperature Synthesis of Calcium Hexa‐Aluminate
Authors: Singh Vipin Kant , Sharma Krishna Kumar
Published: July 2010

Calcium hexa‐aluminate (CaO·6Al2O3) has been prepared from calcium nitrate and aluminum sulfate solutions in the temperature range of 1000°–1400°C. A 0.3 mol/L solution of aluminum sulfate was prepared, and calcium nitrate was dissolved in it in a ratio that produced 6 mol of Al2(SO4)3·16H2O for each mole of Ca(NO3)2·4H2O. It was dried over a hot magnetic stirrer at ∼70°C and fired at 1000°–1400°C for 30–360 min. The phases formed were determined by XRD. It was observed that CaO·Al2O3 and CaO·2Al2O3 were also formed as reaction intermediates in the reaction mix of CaO·6Al2O3. The kinetics of the formation of CaO·6Al2O3 have been studied using the phase‐boundary‐controlled equation 1 − (1 −x)1/3=K log t and the Arrhenius plot. The activation energy for the low‐temperature synthesis of CaO·6Al2O3 was 40 kJ/mol.
Microstructure and Mechanical Properties of Heat‐Treated Silicon Carbide–Aluminum Nitride Solid Solutions
Authors: Lubis Ahmad H. , Hecht Norman L. , Watkins Thomas R. , More Karren L. , Ruh Robert
Published: July 2010

Nanophase‐structured composites were fabricated by heat treating hot‐pressed 2H‐wurtzite SiC‐AlN solid‐solution specimens of 25, 50, and 75 mol% AlN within the spinodal decomposition zone. Heat‐treatment conditions were 1750°C for 150 h, in flowing nitrogen gas. The hot‐pressed specimens contained 2H‐wurtzite equiaxed grains, and the grain size increased with AlN content. Lattice parameters followed Vegard's law. Nanoprecipitates with typical modulated tweed‐type structures were observed along the [2110] zone axis and were orthogonal to the {0112} planes that make angles of 46.70°, 46.90°, and 47.11° to the [0001] for the three compositions. The microhardness, flexural strength, and fracture‐toughness values of the heat‐treated specimens were not significantly different from the hot‐pressed values.
Morphologies Adopted by Al2O3 Single‐Crystal Surfaces in Contact with Cu Droplets
Authors: Ghetta Véronique , Chatain Dominique
Published: July 2010

The morphologies of α‐Al2O3 single‐crystal substrates, annealed in contact with Cu droplets ranging in size from 1 to 10 μm, are observed by high‐resolution scanning electron microscopy. After 45 min at 1373 K in a He‐5% H2 atmosphere, the alumina substrates display different shapes depending on their orientation and on the addition of small amounts of titanium to the copper. The alumina surface may remain flat, display a hollow of faceted spherical shape at the solid/liquid interface, or develop anisotropic ridges at the triple line. The shape changes result from the diffusion of the components of alumina that takes place to achieve a minimum interfacial energy of the drop–substrate system. Explanations of these features are proposed with a discussion of the conditions under which the Young equation can be used for characterizing wetting at high temperature.
Preparation and Electric Properties of Dense Nanocrystalline Zinc Oxide Ceramics
Authors: Gao Lian , Li Qiang , Luan Weiling , Kawaoka Hirokazu , Sekino Tohru , Niihara Koichi
Published: July 2010

This communication reports on the preparation and electric properties of dense nanocrystalline ZnO ceramics. By spark plasma sintering, nanocrystalline (∼100 nm) ZnO ceramics with a high density of 98.5% were obtained at a very low temperature of 550°C. Electric property measurement revealed a novel conduction nonlinearity in the sample sintered at 500°C. This phenomenon is due to the nanometerization of ZnO crystal and the grain boundary layer with an amorphous interfacial layer.
La2O3‐Al2O3‐SiO2Glasses for High‐Power, Yb3+‐Doped, 980‐nm Fiber Lasers
Authors: Dejneka Matthew J. , Hanson Benjamin Z. , Crigler Steve G. , Zenteno Luis A. , Minelly John D. , Allan Douglas C. , Miller William J. , Kuksenkov Dmitri
Published: July 2010

Single‐mode semiconductor pumps have failed to keep pace with the increasing power requirements of Er‐doped fiber amplifiers (EDFAs), so there is a need for high‐powered 980‐nm sources. Yb3+‐doped tapered fiber lasers can provide high‐power output by conversion of a low‐brightness, high‐powered, 920‐nm, multimode broad stripe laser diode to a high‐brightness, 980‐nm, single‐mode output. The tapered fiber laser requires a fiber with high numerical aperture (NA) (>0.4), a rectangular core, and good Yb3+spectroscopy for efficient operation. CVD‐based fiber fabrication methods are incapable of delivering fibers with an NA > ∼0.3 or with good efficiency at 980 nm so a new method of high‐NA fiber fabrication was developed. The core glass composition is critical for maintaining a high‐NA fiber with good power extraction while avoiding phase separation, loss, and clustering. The SiO2level controlled the NA and interdiffusion between core and clad, while the Al2O3/La2O3ratio controlled phase separation. A La2O3‐Al2O3‐SiO2glass was developed that is compatible with a pure SiO2cladding glass and has a laser slope efficiency of 70% at 980 nm. The optimized fiber composition yielded 450 mW of 980‐nm power in a single‐mode fiber.
Role of Redistribution Reactions in the Polymer Route to Silicon–Carbon–Oxygen Ceramics
Authors: Mutin P. Hubert
Published: July 2010

Redistribution reactions are used in the synthesis of several preceramic polymers. Moreover, redistributions play a major role in the pyrolysis of these precursors. Examples of thermal redistributions involving the exchange of Si—O/Si—X bonds (X = O, H, C, …) in polysiloxanes, precursors to silicon–oxygen–carbon ceramics, are given. Redistributions account for the escape of volatile organosilicon compounds, decreasing the yield and modifying the composition of the final ceramic. Moreover, they deeply modify the environment of Si atoms in the residue. At ∼900°C, Si—O/Si—C redistributions have reached equilibrium, leading to a random, entropically controlled distribution of sites. At higher temperatures, redistribution equilibria are displaced by the crystallization of SiC. Thus, the structure of the silicon oxycarbide phase (environment of Si atoms) is dependent on the O/Si ratio of the glass and the pyrolysis temperature, but is not directly dependent on the structure of the precursor.
Viscoelastic Indentation of Silicate Glasses
Authors: Sakai Mototsugu , Shimizu Satoshi , Ito Seturo
Published: July 2010

The time‐dependent viscoelastic deformation and flow of various types of silicate glasses are examined by the use of a pyramidal Berkovich indenter. It is demonstrated that a pyramidal indenter is an efficient microprobe for viscoelastic studies of glass‐forming materials at temperatures near the glass transition point. Some important rheological functions of silicate glasses are determined as functions of time on the basis of a linear viscoelastic constitutive equation for pyramidal indentation. The test results are theoretically related to the dimension of flow units of these glasses, suggesting that a model of thermally fragmented silicate clusters is appropriate for consistently understanding the present rheological test results. However, the microstructural details (crystallite‐like or network‐like microstructures) of fragmented clusters are not inferred from the rheological information.
C70 Nanowhiskers Fabricated by Forming Liquid/Liquid Interfaces in the Systems of Toluene Solution of C70 and Isopropyl Alcohol
Authors: Miyazawa Kun'ichi
Published: July 2010

C70 whiskers with submicrometer diameters (C70 nanowhiskers, or C70NWs) have been successfully fabricated by forming liquid/liquid interfaces in systems that involve a toluene solution of C70 and isopropyl alcohol. Transmission electron microscopy observations show that the C70NWs have a 〈110〉 growth axis and that the intercluster distance of C70 molecules in the C70NWs are shortened by ∼3%, compared with that of face‐centered cubic C70 crystals in the 〈110〉 close‐packed growth direction, which indicates the formation of strong chemical bonds between the C70 molecules. It is suggested that the C70 molecules are polymerized, with their short axis parallel to the growth axis of the C70NWs, from observation via high‐resolution transmission electron microscopy.
Synthesis and Optical Properties of Rare‐Earth–Aluminum Oxide Glasses
Authors: Weber J. K. Richard , Abadie Johan G. , Key Thomas S. , Hiera Kirsten , Nordine Paul C. , Waynant Ronald W. , Ilev Ilko K.
Published: July 2010

Single‐phase glasses containing 37.5 mol% Y2O3, 7 mol% La2O3, and 1 mol% Pr, Ho, Nd, Er, Sm, Tm, Eu, or Yb oxide substituted for part of the Y2O3 were synthesized by containerless melting. The spectral transmission and absorption cross sections of the glasses were determined at wavelengths from 360 to 3300 nm. The electronic transitions were broadened compared with results obtained in a crystalline yttrium aluminum garnet (YAG) host. The infrared transmission of the host glass extended to 6000 nm. The optical and physicochemical properties of these glasses are well suited for optical device applications.
Microstructural Evolution in Liquid‐Phase‐Sintered SiC: Part III, Effect of Nitrogen‐Gas Sintering Atmosphere
Authors: Ortiz Angel L. , Bhatia Tania , Padture Nitin P. , Pezzotti Giuseppe
Published: July 2010

Effects of N2sintering atmosphere and the starting SiC powder on the microstructural evolution of liquid‐phase‐sintered (LPS) SiC were studied. It was found that, for the β‐SiC starting powder case, there was complete suppression of the β→α phase transformation, which otherwise goes to completion in Ar atmosphere. It was also found that the microstructures were equiaxed and that the coarsening was severely retarded, which was in contrast with the Ar‐atmosphere case. Chemical analyses of the specimens sintered in N2atmosphere revealed the presence of significant amounts of nitrogen, which was believed to reside mostly in the intergranular phase. It was argued that the presence of nitrogen in the LPS SiC helped stabilize the β‐SiC phase, thereby preventing the β→α phase transformation and the attendant formation of elongated grains. To investigate the coarsening retardation, internal friction measurements were performed on LPS SiC specimens sintered in either Ar or N2atmosphere. For specimens sintered in N2atmosphere, a remarkable shift of the grain‐boundary sliding relaxation peak toward higher temperatures and very high activation energy values were observed, possibly due to the incorporation of nitrogen into the structure of the intergranular liquid phase. The highly refractory and viscous nature of the intergranular phase was deemed responsible for retarding the solution–reprecipitation coarsening in these materials. Parallel experiments with specimens sintered using α‐SiC starting powders further reinforce these arguments. Thus, processing of LPS SiC in N2atmosphere open the possibility of tailoring their microstructures for room‐temperature mechanical properties and for making high‐temperature materials that are highly resistant to coarsening and creep.
Original Monte Carlo Methodology Devoted to the Study of Sintering Processes
Authors: Bordère Sylvie
Published: July 2010

A Monte Carlo methodology different from others based on the Potts model has been developed to solve capillary‐driven mass transport involved in the sintering process. The addition of a cohesive energy term to the energetic model enables quantification of the stress gradients within grains, as well as the induced mass fluxes. The study of two‐particle sintering involving volume diffusion has been chosen as a first example. The morphological evolution of the two‐particle system to a single particle is followed. Real‐time‐dependent neck growth and shrinkage rates are defined. The rheological behavior of the particles induced by the Monte Carlo procedure is discussed.
Bismuth Titanate from Mechanical Activation of a Chemically Coprecipitated Precursor
Authors: Ng Szu Hwee , Xue Junmin , Wang John
Published: July 2010

Most of the chemistry‐based preparation routes for bismuth titanate (BIT) involve calcination at elevated temperatures in order to realize precursor‐to‐ceramic conversion. In a completely different approach using an amorphous BIT hydroxide precursor, nanocrystalline particles of layered perovskite BIT are synthesized by mechanical activation, skipping the detrimental crystallite coarsening and particle aggregation encountered at high temperatures. Mechanical activation leads to nucleation and steady growth of BIT crystallites in the amorphous precursor matrix, while Bi2O3 is involved as an intermediate transitional phase. The activation‐derived BIT particles demonstrate a rounded morphology of ∼50 nm in size. This is in contrast to the BIT derived from calcination of the coprecipitated precursor at 600°C that is dominated by coarsened platelike particles. The former is sintered to a density of >95% theoretical at 875°C for 2 h, leading to a dielectric constant of ∼1260 when measured at 1 MHz and the Curie temperature of 646°C.
Nonstoichiometry in A2B2O7 Pyrochlores
Authors: Stanek Christopher R. , Minervini Licia , Grimes Robin W.
Published: July 2010

Energies associated with deviations from stoichiometry for an extensive series of A2B2O7 pyrochlores have been predicted. A3+ cations range in size from Lu to La and B4+ cations from Ti to Pb. Results are presented in the form of contour maps as a means of conveying large quantities of data as well as predicting characteristics for pyrochlore compounds not explicitly modeled. These contour maps indicate that the BO2 excess nonstoichiometry in the pyrochlore structure is distinct from solid‐solution fluorite. Within the limitations of this methodology, the contour maps provide a means to understand and predict distinct compositional variations. Defect cluster formation is discussed.
Deformation of Monoclinic ZrO2 Polycrystals and Y2O3‐Stabilized Tetragonal ZrO2 Polycrystals below the Monoclinic–Tetragonal Transition Temperature
Authors: Yoshida Michiyuki , Shinoda Yutaka , Akatsu Takashi , Wakai Fumihiro
Published: July 2010

Ultrafine‐grained monoclinic ZrO2 polycrystals (MZP) and 3‐mol%‐Y2O3‐stabilized tetragonal ZrO2 polycrystals (3Y‐TZP) were obtained by hot isostatic pressing (HIP). Both MZP and TZP were “high‐purity” materials with impurities less than 0.1 wt%. The deformation behavior was studied at 1373 K, which was lower than the monoclinic ↔ tetragonal transition temperature. The stress exponent of 3Y‐TZP with grain size of 63 nm was 3 in the higher stress region, and increased from 3 to 4 with decreasing stress. The deformation of MZP was characterized by a stress exponent of 2.5 over a wide stress range. The strain rate of 3Y‐TZP was slower than that of MZP by 1 order of magnitude. It was suggested that either the doped yttrium or the difference in the crystal structure affected the diffusion coefficients of ZrO2.
Indirect Determination of the Piezospectroscopic Coefficients of Ceria‐Stabilized Tetragonal Zirconia Polycrystals
Authors: Tomaszewski Henryk , Strzeszewski Jan , Adamowicz Lech , Sergo Valter
Published: July 2010

A method is proposed for the indirect determination of the stress dependence (expressed as piezospectroscopic (PS) coefficients) of spectroscopic bands of ceramic materials/phases. This method is based on the intimate mixture (intimate at the microstructural, grain‐size level) of two phases/materials when the stress in one is independently known; it is used to determine the PS coefficients of the most intense Raman bands in ceria‐stabilized tetragonal zirconia polycrystals (Ce‐TZP). Different amounts of Ce‐TZP were mixed with alumina and the composite pellets sintered; subsequently, the stress in alumina was determined through the PS coefficient of its R2 luminescence band and the stress in Ce‐TZP derived from the static equilibrium condition. The frequency shifts of each Raman band of Ce‐TZP have been plotted against the stress and the slopes provide the PS coefficients. The method has the advantage of not requiring any type of loading device (i.e., diamond anvil‐cell, bending jig). Finally, the limits are also discussed, the most important one being the requirement of immiscibility of the two materials/phases.
Atomic‐Scale {101¯0} Interfacial Structure in Hydroxyapatite Determined by High‐Resolution Transmission Electron Microscopy
Authors: Sato Kimiyasu , Kogure Toshihiro , Iwai Hayato , Tanaka Junzo
Published: July 2010

The atomic structure of {101¯0} interfaces in sintered hydroxyapatite (HAp) was characterized using high‐resolution electron microscopy (HRTEM). When subjected to electron beam radiation parallel to the [0001] zone axis, a characteristic damage of HAp occurred. The damage was identified by hexagonally shaped regions surrounded with {101¯0} planes, in which the crystalline phase was thinned and amorphized. HRTEM study at the crystalline‐amorphous interfaces revealed that the HAp crystal structure was terminated by a plane crossing the hydroxyl columns on which Ca (Ca2 site) and PO4 tetrahedra were placed. The grain boundaries parallel to the {101¯0} planes were also examined and the structure was identical to that observed in the crystalline‐amorphous interface. The interface structure observed in the crystalline‐amorphous interfaces and grain boundaries is probably a stable atomic arrangement of HAp {101¯0} surfaces with a low surface energy.
Core‐Shell Structure of Acceptor‐Rich, Coarse Barium Titanate Grains
Authors: Yoon Seok‐Hyun , Lee Je‐Hun , Kim Doh‐Yeon , Hwang Nong M.
Published: July 2010

Heavily doped barium titanate (BaTiO3) powders, one with a donor‐rich and the other with an acceptor‐rich composition, were prepared. After sintering, the donor‐rich specimen exhibited a fine‐grained microstructure but significant grain growth occurred in the acceptor‐rich specimen. A stable dielectric behavior was observed only in the donor‐rich fine‐grained specimen over the temperature range studied. However, in both specimens, an undoped core region several hundred nanometers in size was detected. The core‐shell structure appeared to be maintained in BaTiO3 under the conventional sintering conditions.
Determination of the Thermal Resistance of the Polymer–Ceramic Interface of Alumina‐Filled Polymer Composites
Authors: Hill Richard F. , Supancic Peter H.
Published: July 2010

To model the thermal conductivity of polymer composites that are filled with ceramic powders, the conductivity of each component as well as the interfacial resistance at each ceramic–polymer boundary must be known. An indirect method to determine this interfacial boundary resistance is proposed by preparing large‐scale “macromodel” simulations of the polymer–ceramic interface. Macromodels, prepared by spin‐coating a polymer layer onto sapphire wafers, were formed in a sapphire–polymer–sapphire sandwich type structure. The interfacial boundary thermal resistance was calculated from thermal resistance measurements made on the macromodels.
Acicular Mullite Crystals in Vitrified Kaolin
Authors: Lu Hong‐Yang , Wang Wei‐Lin , Tuan Wei‐Hsing , Lin Ming‐Hong
Published: July 2010

The microstructure of vitrified kaolin ceramic tapes has been studied via scanning and transmission electron microscopy (SEM and TEM). The sintered samples contained crystalline phase of predominantly stoichiometric mullite (3Al2O3·2SiO2), which consisted of high aspect ratio, acicular crystals that are often referred to as secondary mullite. These crystals were interlocked and embedded in an aluminosilicate glass matrix of inhomogeneous composition. The glass matrix contained an average of ∼3.63 wt% K as determined by energy‐dispersive X‐ray analysis (EDS), whose composition could be approximated to 5Al2O3·16SiO2·0.1MgO·0.3K2O·0.15TiO2·0.12Fe2O3. The acicular crystals have approximately the stoichiometric composition of Al2O3:SiO2= 3:2. They have grown along a specific crystallographic orientation along the [001] axis. The crystal growth front exhibited facetting on the {110) planes with microfacetting on both the {100) and {010) planes.
Weak‐Beam Dark‐Field Microscopy of Complex Stress States in X7R‐Type BaTiO3 Dielectric Core–Shell Structures
Authors: Feng Qiquan , McConville Caspar J.
Published: July 2010

X7R‐type BaTiO3 materials were analyzed using X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Powder XRD indicated that the materials had pseudocubic lattices, but core–shell grain structures predominated in bright‐field (BF) TEM images. Electron diffraction patterns across the core–shell boundaries and convergent beam electron diffraction patterns of cores and shells indicated that coherent grain boundaries existed between cores and shells. The flat dielectric constant–temperature curves obtained from these materials can be interpreted in terms of the internal stress states in individual grains. The stress states were observed using weak‐beam dark‐field (WBDF) microscopy, and strain contours formed by distorted crystal planes were visible in the WBDF images. The contours observed were dependent on the stress state of the crystal instead of crystal symmetry and the stress distribution in individual grains was determined by both the thickness ratio of shell and core, and the geometrical relationship of the core and the shell. Twins observed in this material were determined to be growth rather than mechanical twins, through observation of the strain contour distribution.
Structural Characterization of Lanthanum Chromite Perovskite Coating Deposited by Magnetron Sputtering on an Iron‐Based Chromium‐Containing Alloy as a Promising Interconnect Material for SOFCs
Authors: Orlovskaya Nina , Coratolo Anthony , Johnson Christopher , Gemmen Randall
Published: July 2010

Chromium‐containing stainless steel (SS) is a prospective material for use as an interconnect in solid oxide fuel cells (SOFCs). However, during operations at high temperatures, the growth of oxide scales causes the performance of the interconnect and SOFC as a whole to deteriorate. The coating of SS 446 with a conducting perovskite is a potential method of slowing the growth of oxide scale and, therefore, improving overall SOFC performance. In the present research, the structural characterization of a pure LaCrO3 thin film on the SS 446 substrates has been performed as a model material that can be used as a barrier coating for the metallic interconnect. The deposition of an amorphous La‐Cr‐O thin film on SS 446 was performed using radio‐frequency (rf) magnetron sputtering. The deposited amorphous film was annealed in air to form the desired perovskite phase. The film underwent an amorphous to LaCrO4 phase transition during annealing at 500°C with further transformation to LaCrO3 orthorhombic phase during annealing at 700°C. A self‐organized dendritic structure was reported as a result of the perovskite‐phase formation. Although formation of various oxides, such as Fe2O3 and Fe3O4, was observed during the annealing of uncoated SS 446 in air, the coating of SS 446 surface with LaCrO3 film prevented formation of various oxide phases at the interconnect surface. The structural characterization of the films and SS 446 surfaces was accomplished using scanning electron microscopy with energy‐dispersive X‐ray analysis, X‐ray diffractometry, micro‐Raman spectroscopy, and nanoindentation.
Aluminum Phosphates Derived from Alumina and Alumina‐Sol–Gel Systems
Authors: Moorlag Carolyn , Yang Quanzu , Troczynski Tom , Bretherton Jeremy , Fyfe Colin
Published: July 2010

Aluminum phosphate products formed by the reactions of alumina and alumina‐gel systems with acidic phosphates were analyzed. Drying of alumina‐gel to form microcrystalline boehmite and conversion to γ‐alumina by thermal treatment was indicated by the appearance of octahedral, pentacoordinate, or tetrahedral sites, which were established using 27Al magic‐angle‐spinning solid‐state nuclear magnetic resonance spectroscopy. Crystalline aluminum phosphate products and amorphous material were identified using this technique. α‐alumina and heat‐treated alumina‐gel that were reacted with phosphate in an Al:P ratio of 1:1 yielded dramatically different aluminum orthophosphate:aluminum metaphosphate product ratios of 8.2:1 and 1:1.1, respectively. When alumina‐gel was heat‐treated with phosphate, an abundance of aluminum orthophosphate, aluminum metaphosphate, and hydrated aluminum phosphate products were affected by varying conditions of temperature and time of heat treatment and by the amount of phosphate present. An α‐alumina/alumina‐gel composite sol–gel phase that was reacted with phosphoric acid (H3PO4) in a Al:P ratio of 1:1 exhibited an increased quantity of aluminum metaphosphate products compared with an α‐alumina:H3PO4 ratio of 1:1 and a higher percentage of reaction (79%) compared with the reactions of an α‐alumina:H3PO4 ratio of 1:1 or an alumina‐gel:H3PO4 ratio of 1:1. The morphologies of aluminum triphosphate hydrate and aluminum metaphosphate product phases were observed using scanning electron microscopy.
Depth‐Profiling of Crystal Structure, Texture, and Microhardness in a Functionally Graded Tooth Enamel
Authors: Low It‐Meng
Published: July 2010

The graded nature of crystal structure, texture, and microhardness of human enamel has been characterized by grazing‐incidence synchrotron radiation diffraction and Vickers indentation. Results show that the composition of tooth enamel consists mainly of calcium apatite or hydroxyapatite (HAP). The HAP crystals formed near the occlusal surface are aligned approximately orthogonal to each other between the axial and occlusal sections. In addition, the tooth enamel has been shown to be a hierarchical graded biomaterial with a distinct gradation in crystallinity, texture, crystallite size, and hardness, which is somewhat akin to that of the fibrous microstructures found in natural plants. A “graded‐interface” approach is proposed as a biomimetic model for designing new dental or restorative materials as well as for joining of dissimilar materials.
Heterogeneity of HL—A Specificities Shown by Platelet Complement‐Fixation
Authors: MITTAL KAMAL K. , MICKEY M. R. , TERASAKI PAUL I.
Published: July 2010

Six sets of unrelated healthy individuals, phenotypically “identical” in each set for the four antigens of the two HL—A segregant series, were tested with 153 antiplatelet antisera by microcomplement‐fixation. In five of the six sets the results unequivocally show that the individuals were not identical by complement‐fixation reactions. It is proposed that sera which manifest nonidentity between individuals within these sets identify either “variants” of the known HL—A antigens or antigens of a third segregant series of the HL—A system or of a non‐HL—A system. Accurate and complete matching for HL—A antigens among unrelated individuals will require further definition of specificities.
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Authors: Lymphoma Burkitt's , Antigens HL–A , DICK HEATHER M. , STEEL C. M. , LEVIN A. G. , HENDERSON NANCY
Published: July 2010

Studies were carried out on the distribution of HL–A antigens in 33 patients with Burkitt lymphoma from several tribal groups in Kenya. The frequency of distribution of the HL–A antigens was not significantly different in these patients from that in a selected control population. Difficulty was experienced in the precise identification of some HL–A antigen in Africans using a Caucasoid serum panel, in particular those associated wlth HL–A7 and to a lesser extent, the “W19” complex.
Improved HL–A Typing of Cadaveric Renal Donors. I. Quantitation of HL–A Gene Dosage
Authors: DUMBLE LYNETTE , MORRIS PETER J.
Published: July 2010

A quantitative microabsorption technique has been used to determine a gene dosage effect on HL–A. This allows homozygosity or heterozygosity of HL–A antigens to be determined prospectively in cadaver donors of renal allografts where less than four antigens were detected by standard lymphocytotoxicity. This in turn provides more precise matching of donor and recipient.
Ankylosing Spondylitis and the Major Histocompatibility System
Authors: SACHS J. A. , STERIOFF S. , ROBINETTE M. , WOLF E. , GURRY H. L. F. , FESTENSTEIN H.
Published: July 2010

The purpose of this investigation was to see whether or not the hypothetical disease susceptibility locus to ankylosing spondylitis is linked to the MLC determinant 27a. Firstly, we discovered a strong MLC determinant which we called 27a because of its association with the second series specificity W27. Later, we found that this determinant was the same as that which Jorgensen et al. (1973) found to be associated with the second series specificity W5. These MLC determinants may, therefore, be in linkage disequilibrium with more than one HL–A specificity (in this case, of the second series) as previously described by Dupont et al. (1973). However, we found no association between 27a and ankylosing spondylitis.

On the other hand, we confirmed the association of ankylosing spondylitis with W27 and also found an increase of HL–A2 of the first series which, however, was not statistically significant. In view of the high incidence of HL–A2 in the general population, more information is required to definitely establish such an association. We found no special association with specificities A J and Hu (Sa 532), third series antigens, but confirmed their linkage disequilibrium with W27.

Disease predisposition loci seem, therefore, to be associated with either type of MHS marker, multiple sclerosis and MLC determinant 7 a, or ankylosing spondylitis and the second series antigen W27. It will be interesting to discover whether there is any special significance of the association of one marker rather than another.
Partition of the Antigen W16 into Two Subtypic Determinants
Authors: SCHREUDER IEKE , D'AMARO2. J. , SANDBERG L. , ROOD J. J. VAN
Published: July 2010

The partition of W16 into two subtypic determinants was suggested by its segregation with either W4(4a) or W6(4b) in families. It was confirmed by the serologic reactions of two antisera each of which recognized only one of its subtypic determinants. Gene frequencies of 0.01417 and 0.02711 were tentatively assigned to its W4 and W6 variants respectively.
Typing for MLC Determinants using Lymphocytes from Cousin‐Marriage Offspring as Typing Cells
Authors: SINGAL D. P. , VILLANUEVA R. , NAIPAUL N.
Published: July 2010

A first cousin marriage family with three children was studied. One sibling (AW) was homo‐zygous for W32.WlO. When used as stimulator in one way MLC, AW elicited a very low response in family members possessing this haplotype. Serologically identical sibling and father combination showed bidirectional non‐stimulation in one way MLC. Therefore, AW is assumed to be homozygous not only for SD antigens, but also for LD determinants which we call LD WlOa. Among the 43 unrelated individuals tested with AW, an association be‐tween LD WlOa and W10 antigen of the second HL‐A locus was observed. Of 12 W10 positive individuals tested, five carry this allele as compared to one out of 31 W10 negative individuals. The data suggest a strong linkage disequilibrium between the FOUR locus de‐terminant W10 and LD determinant LD WlOa.
HL‐A Transplantation Antigens in Subjects Susceptible to Recrudescent Herpes Labialis
Authors: RUSSELL ANTHONY S. , SCHLAUT JOY
Published: July 2010

We have shown in retrospective and prospective studies that there is an increased frequency of HL‐A1 in subjects with recrudescent circum‐oral herpes when compared with the frequency in the background population. This is the first association of a human disease of known viral aetiology with a specific transplantation antigen, and it is possible that this may represent a marker for an immune response gene.
Cold Lymphocytot oxin Reactivity with Lymphocytes from Donors in Various Physiological Conditions
Authors: MAYER S. , BIGEL P. , TONGIO M. M.
Published: July 2010

Sera containing cold lymphocytotoxins were studied in the presence of lymphocytes from neonates, pregnant women, blood donors and old people and the degree of positivity varied according to the lymphocyte population investigated: a strongly positive response to lymphocytes from neonates and pregnant women, a weaker response to lymphocytes from old people and a very weak response to chronic leukemic lymphocytes. Cold lymphocytotoxins seem to be a supplementary method of demonstrating a difference in lymphocytic behavior.
Phenotypic Variations with Time of some HL‐A Antigens
Authors: PELLEGRIS G. , ILLENI M. T. , ILLENI E. , VECCHIO M. DEL
Published: July 2010

In order to study the HL‐A antigen turnover in vivo, the HL‐A reactivities of the lymphocytes of eight blood donors were tested every week for six weeks with antisera HL‐A1, 2, 3, 5, 7, 8 and 11.

The analysis of variance showed that the “time” effect and the “time x donors” interaction were statistically significant for the HL‐A2, 3, 5 and 11 specificities. This supports the hypothesis that phenotypic expression of such antigens on the lymphocyte membrane of some of the blood donors examined varied with time.

From a practical point of view, the HL‐A antigenic fluctuation with time should be taken into consideration when lymphocyte typing is required for tissue transplantation.
Preparation of Monospecific HLA Antibodies from Cross‐Reactive Multispecific Antisera
Authors: Cross D.E. , Whittier F.C. , Greiner R.F. , Foxworth J. , Weaver P. , Ann Ross Jo
Published: July 2010

Multispecific, cross‐reactive sera can be demonstrated by absorption studies to be of two types; a single antibody that is multivalent, and some that are mixtures of monospecific and multispecific antibody populations. The second type can be separated by a differential absorption technique. The characteristics of these sera that can be separated and the techniques are discussed.
Lack of Linkage between Acute Intermittent Porphyria and the A and B Loci of the HLA System
Authors: Tongio M. M. , Mayer S. , Hauptmann G. , North M. L. , Koehl C. , Abecassis J. , Mandel P. , Wertenschlag J.
Published: July 2010

Forty‐six members of a family known to have Porphyria were studied. As the disease is often latent clinically, erythrocyte uroporphyrinogen I synthetase activity was determined to classify the subjects as being healthy or carriers. HLA—A, B, C, Bf, GLO antigens were determined. No linkage between acute intermittent Porphyria and the HLA system was noted in this family.
The Specificity of Secondary MLC Assayed by Titration of Primed Lymphocyte Populations
Authors: Singal D. P.
Published: July 2010

The specificity of responses in secondary MLC was studied by titration (100 × 103 to 5 × 103) of responder primed lymphocytes. In all instances, significant proliferative responses of responder primed lymphocytes to the specific stimulator occurred using lower responding cell numbers. When tested against allogeneic stimulating donors, three patterns of responses were observed: no significant responses, responses only at higher (100 × 103) responding cell densities, and responses at lower responding cell densities, similar to those with the priming donor. In instances where primed lymphocytes responded significantly to allogeneic stimulating cells at lower cell densities, the responses were considered positive and the stimulating cells positive for the PL determinant. In several instances, primed lymphocytes responded significantly to allogeneic stimulators negative for the specific HLA—D and/or HLA—DR specificities. On the other hand, in experiments where allogeneic stimulating donors shared either HLA—D or DR specificity with the priming donor, a significant response was always observed. Thus, the PL determinant was present on stimulating allogeneic cells negative for specific HLA—D and DR specificities.

The present data suggest that an analysis of the specificity of primed populations could be profoundly affected by the responder cell density at which the assay is performed. Also, the data suggest that other MHC determinants, including non‐HLA loci may be important in secondary MLC.