bluuebunny/crossref_metadata_2025_split huggingface dataset:
New Processing and Evaluation of Porous PZT with High Connectivity Using Capsule-Free O2 HIP
Authors: Sugihara Sunao , Hayashi Takashi , Okazaki Kiyoshi 
Published: March 2011

ABSTRACTNew processing of porous PZT ceramics with high connectivity was investigated using capsule-free O2 HIP technology. Porous PZT bodies were prepared by pressureless-sintering of green compacts with various amounts of spherical PMMA particles, followed by hot isostatically pressed at 1100°C and 200 MPa for 1 hour in 5%O2/Ar mixture gas atmosphere. The densification of porous PZT sintered bodies hardly occurred by capsule-free O2 treatment, resulting in the formation of well-developed neck growth between PZT grains. They exhibted a homogeneous microstructure with a bimodal pore size distribution consisting of both several ¼m and 50–80¼m pore sizes.The capsule-free O2 HIPed porous PZT bodies have a larger permittivity and a smaller depolarizing factor about a half than the specimens before O2 -HIPing, suggesting that the HIPed PZT has a higher connectivity. Piezoelectric g33 constant-porosity relations were also described and mechanical property was discussed to indicate an increase of bending strength more than 20% compared to conventional sintering.
Influence of Hipping Pressure on the Strength and the Porosity of Porous Copper
Authors: Takata Atsushi , Ishizaki K. , Kondo Y. , Shioura T. 
Published: March 2011

ABSTRACTOpen porous copper metals, which have high strength, high open porosity and well controlled pore size distribution, were produced by a hot isostatic press (HIP) process. They were sintered at different temperatures from 973 to 1273K under various HIPping pressures up to 200MPa. Pore size distribution and Young's modulus of the sintered samples were analyzed. The HIPped products have greater strength and higher open porosity than those of the normally sintered ones. The internal structural parameters such as pore size distribution were controlled by changing the HIPping pressure.
The Production of Porous Si3N4 Ceramics with 100% β Phase
Authors: Saito Naruki , Ishizaki K. , Kuzjukevics A. 
Published: March 2011

ABSTRACTPorous silicon nitride ceramics with open porosity fraction of about 0.25 were obtained by capsule-free hot isostatic pressing from as-received and aqueous Soxlet washed powders. Particle surface modification by aqueous washing increases green density of cold isostatically pressed bodies and leads to a decrease in open pore fraction. At the same time, the α–β transition rate of the treated powder decreases.
Efficient Densification of Fine-Grained Ceramics by Hybrid (RCS-Plus-HIP) Processing
Authors: Palmour Hayne , Hare Thomas M. , Russell Roger L. 
Published: March 2011

ABSTRACTIn this paper, we consider certain technological and economic advantages associated with rate controlled sintering (RCS) as the critical first step in a two-step hybrid densification cycle: RCS-plus-HIP. With proper combinations of(a) powder processing (to obtain narrow initial particle size distribution and high green density) and (b) carefully optimized RCS sintering profile (to assure effective pore closure with minimal grain growth), one can readily produce technically dense (gas-tight) sintered ceramic components that can then be rather easily HIPed to full density with very little additional grain growth.The experimental background and underlying concepts for RCS are briefly reviewed, and are related to the broader issue of establishing and maintaining control of microstructural evolution during densification processes, including those that are best concluded in the high pressure gas atmospheres typically employed for hot isostatic pressing (HIP). To illustrate these points, some examples of RCS-plus-HIP processed oxide ceramics – dense, optically translucent and/or transparent, yet also quite uniformly fine-grained – are shown and discussed.
Influence of High Oxygen Partial Pressure on the Positive Temperature Coefficient Resistivity of BaTiO3
Authors: Huybrechts Ben , Ishizaki K. , Takata M. 
Published: March 2011

ABSTRACTThe influence of high oxygen partial pressures on the PTC behavior of non acceptor doped BaTiO3 is studied by using oxygen-hot-isostatic-press (O2-HIP). Annealing in high oxygen partial pressures increased the maximum resistivity with a factor 3, also the minimum resistivity and the gradient in the Arrhenius plot, i.e. resistivity versus the reciprocal of the temperature, increased. The results are analyzed using the well accepted Heywang model. The changes after O2-HIPping can be explained with an increase in acceptor density at the grain boundaries.
Single Crystal Growth of YBa2Cu4O8 and Y2Ba4Cu7O15 Under High Oxygen Pressure
Authors: Miyatake T. , Takata T. , Yamaguchi K. , Takamuku K. , Koshizuka N. , Tanaka S. , Shibutani K. , Hayashi S. , Ogawa R. , Kawate Y. 
Published: March 2011

ABSTRACTWe investigate the crystal growth of YBa2Cu4O8 (124) and Y2Ba4Cu7O15 (247) in Al2O3 crucibles at an oxygen partial pressure of 20MPa employing an O2- HIP apparatus in a mixed gas environment of Ar-20%O2. Various melts compositions, rich in Ba and Cu, are explored to optimize crystal growth of 124. Large 124 single crystals up to a size of 1×0.5×0.05mm3 are obtained from compositions with about 65˜67%CuO. 247 single crystals having a maximum size of 3×1.5×0.05mm3 are grown from the same composition of melts. 124 crystals exhibit superconductivity at 75K. 247 crystals show Tc of 20K.
AgO Doped YBa2Cu4O8 Superconductor Under High Oxygen Partial Pressure
Authors: Sawai Yuichi , Ishizaki K. , Takata M. , Kuzjukevics A. 
Published: March 2011

ABSTRACTGeneraly silver doping into YBa2Cu3O7 superconductor improves the critical temperature and critical current density. In this work the silver peroxide was doped into YBa2Cu4O8 superconductor and sintered by the Oxygen Hot Isostatically Pressing method. The critical temperature of the 124 phase increased by silver peroxide doping.
High Nitrogen Concentration in Fe-Cr-Ni Alloys
Authors: Rawers James C. , Gokcen Nev A. , Pehlke Robert D. 
Published: March 2011

ABSTRACTIncreasing the nitrogen concentration in iron and iron alloys significantly improves their mechanical properties. A recent technique for melting in a hot-isostatic pressure furnace using nitrogen as the pressurizing gas has been developed by U.S. Bureau of Mines researchers for making massive nitrogen additions to iron (up to 1.6 weight percent nitrogen) and iron-chromium-nickel alloys (up to 6.6 weight percent nitrogen). The total nitrogen concentration measured at atmospheric pressure and room temperature was determined to be the equilibrium nitrogen concentration in the molten alloy. Statistical correlations were derived to explain the effects of melt pressure and alloy composition on the resulting nitrogen concentration. Nitrogen concentrations measured in solidified alloys made by high pressure melting techniques at lower pressures are consistent with previous published data. Computer generated phase diagrams for high nitrogen-chromium concentrations are also consistent with nitride microstructure observed after high-pressure melting. Extension of existing atmospheric nitrogen concentration data to higher pressure nitrogen concentrations shows Sievert's law (nitrogen concentration is proportional to the square root of the nitrogen melt pressure) to be valid for pure iron. However, substantial deviations from Sievert's law are observed for higher alloy compositions. Statistical fits of thermodynamic concentration data to the high-pressure melt nitrogen data requires evaluating element concentration terms, interaction effect terms, pressure terms, and pressure-composition effects terms. Examination of the nitrogen concentration data suggests several methods of correlation.
Osteogenic Cell Attachment to Degradable Polymers
Authors: Healy Kevin E. , Tsai Davis , Kim Jung E. 
Published: March 2011

ABSTRACTModifications were made to increase osteogenic cell adhesion to homo and copolymers of lactic and glycolic acid. A synthetic peptide containing the cell attachment signal Arginine-Glycine-Aspartate (RGD) was loaded into the polymers or adsorbed to the polymers' surfaces. Cell attachment was assayed after 24 hours incubation with an osteogenic cell line (ROS 17/2.8). Statistically significant differences in cell adhesion occurred between the polymers with the adsorbed peptides and the other treatment groups. Significant differences were not observed for the peptide loaded polymers and controls. These data indicate that precoating the polymer surface with a RGD-containing peptide prior to exposure to osteogenic cells increased cell attachment. For the current materials tested, the surface modification is preferred to increase osteogenic cell adhesion to degradable polyesters.
A Collagen/DBP Sponge System Designed for in Vitro Analysis of Chondroinduction
Authors: Mizuno Shuichi , Lycette Chris , Quinto Charlene , Glowacki Julie 
Published: March 2011

ABSTRACTIn response to subcutaneous implants of demineralized bone powder (DBP), cells are attracted to the DBP, are converted to chondroblasts, and produce a cartilage matrix that is resorbed and replaced by bone. In order to define the cellular mechanisms of this induction, we developed a collagen sponge model for simulating the in vivo environment and for promoting the ingrowth and viability of cells cultured in them in vitro. Reconstituted pepsin–digested type I collagen from bovine hide was neutralized. Rat DBP (75–250 εm) was added into the collagen mixture (20 mg/ml). In order to simulate the connective tissue environment, modified chondroitin sulfate, heparan sulfate, or hyaluronic acid was added into the mixture. Aliquots (0.2 ml) were placed in 3/8 inch diameter molds and freeze-dried. Human dermal fibroblasts were cultured from minced fresh tissue and inoculated at 1.5 × 105cells/sponge. Fifteen hours later, some sponges were transferred to medium which contained growth factors (PDGF or TGF-β). At intervals, samples were examined histologically. The inoculated cells attached to the collagen fibers and migrated into the sponge. Eventually the sponges contracted and acquired an oval shape. Cells on or near DBP were ovoid or stellate in shape. Cell morphology was modulated by glycosaminoglycan composition of the sponge. Increasing doses of PDGF or TGF-β promoted cellularity within the sponges. In conclusion, this system simulates the in vivo environment but allows accessibility for analysis. This three-dimensional matrix culture system will enable investigation of mechanisms of chondroinduction by morphogenic material.
Effect of Substratum Morphology on Animal Cell Adhesion and Behavior
Authors: Singhvi Rahul , Stephanopoulos Gregory N. , Wang Daniel I. C. 
Published: March 2011

ABSTRACTGlass surfaces with well defined surface morphologies have been prepared using photolithography to study the effect of surface morphology on cell adhesion and function. Using a transformed recombinant cell-line, AtT-20, as a model of shear sensitive cell, we have shown that cell-substratum adhesion strength is enhanced using a surface with uniform grooves without any loss in cellular function. Furthermore, using primary hepatocytes as a model for a cell whose function is sensitive to its shape, we have shown that surface morphology can modulate cell shape as well as its function.
Poly(Phosphoesters) as Bioabsorbable Osteosynthetic Materials
Authors: Kadiyala S. , Richards M. , Dahiyat B. , Michelson J. D. , Leong K. W. 
Published: March 2011

ABSTRACTPolymeric prosthetic devices enjoy the advantage of tailor-made properties. In particular bioabsorbable polymers possess distinct advantages. In orthopedic applications, most osteosynthesis has been achieved using metallic devices to stabilize fixation of bony fragments. The different elastic moduli of the metallic implants versus that of bone often causes cortical bone to atrophy. The theoretical advantage of gradual load transfer from the fixation device to the bone and the elimination of surgical removal after the healing of a fracture make an absorbable osteosynthetic material extremely useful. A resorbable porous coating material would also have the potential of improving fixation by promoting bony ingrowth and reducing cartilage destruction. The structural support function of a polymeric device can also be integrated with the drug-carrier function to take advantage of the recently discovered growth factors such as bone morphogenic proteins in enhancing bone union.
Tissue Engineered Growth of New Cartilage in the Shape of a Human Ear Using Synthetic Polymers Seeded with Chondrocytes
Authors: Vacanti Charles A. , Cima Linda G. , Ratkowski Dianne , Upton Joseph , Vacanti Joseph P. 
Published: March 2011

ABSTRACTThis report concerns the tissue-engineered growth of new cartilage in the shape of a human ear. Using synthetic biodegradable polyesters, a porous, three dimensional device in the shape of a human ear was fabricated. The polymer matrices were seeded with living chondrocytes isolated from a freshly sacrificed calf shoulder and implanted subcutaneously on the dorsum of athymic rats. This resulted in the formation of new cartilage in the shape of a human ear of approximately the same dimensions as the original implants. Histological analysis revealed the presence of mature cartilage in all specimens.
Sterilization Mode Effect on the Hydration Rate of Calcium Sulfate Hemihydrate
Authors: Devine T. R. 
Published: March 2011

ABSTRACTPlaster bandages have been found to support bacteria. The sterilization of plaster (calcium sulfate hemihydrate) for use as an implant biomaterial is, therefore, a primary concern. Heat sterilization can significantly alter material properties and the kinetics of plaster hydration. A study has been done of the effects of sterilization by gamma radiation and by ethylene oxide on the hydration rate of plaster. Three hemihydrate bases with differing water requirements and hydration rates were sterilized by each method. Adiabatic temperature rise was used to follow hydration. Five outcomes were measured and analyzed. These outcomes include the induction period, maximum rate of temperature rise (MRR), time to MRR, total temperature rise, and time to maximum temperature. Neither sterilization mode was found to significantly alter the hydration process of any of the plaster bases. From a material property standpoint, either gamma radiation or ethylene oxide treatment is preferred to heat sterization of calcium sulfate hemihydrate.
Effects of Non-Collagenous Matrix Proteins, Fatty Acid Derivatives, Etc. on the Nucleation and Growth of Calcium Phosphate on Hydroxyapatite
Authors: Wong A. T.-C. , Czernuszka J. T. 
Published: March 2011

ABSTRACTThe effects of various non-collagenous bone matrix bio-chemicals on the deposition of calcium phosphate on hydroxyapatite surfaces have been studied. Guanidine-HCI bone extract, guanidine-EDTA bone extract and phosphatidylserine all showed an overall inhibitory effect on calcification. Phosphoserine promoted secondary nucleation but hindered crystal growth. Serum albumin altered the lattice structure of the crystals, thus inducing a significant calcium deficiency. This structural change also resulted in a different fracture behaviour.
Multiple Scattering Theory, A Successful Approach Towards Electromigration
Authors: Ek J. Van , Lodder A. 
Published: March 2011

ABSTRACTBoth the electromigration wind valence and the residual resistivity for hydrogen in all row 5 (Y,….Ag) and row 6 (La,….Au) transition metals were calculated. Host metals with a hexagonal lattice have been treated in the FCC or BCC structure. The KKR-Green function method used to describe the multiple scattering of Bloch electrons, accounts for charge transfer and lattice deformation around the interstitial hydrogen.
Implications and Applications of Relativistic Spin-Polarized Multiple Scattering
Authors: Hörmandinger G. , Weinberger P. 
Published: March 2011

ABSTRACTThe consideration of spin-orbit coupling in spin-polarized electronic structure calculations leads to magnetic anisotropies and reduces the symmetry of the problem. The theory of magnetic groups is required to make full use of the remaining symmetry, which in turn then is applied to the Green's function method.
The Muffin-Tin-Orbital Point of View
Authors: Andersen O. K. , Postnikov A. V. , Savrasov S. Yu. 
Published: March 2011

ABSTRACTWe review the interpretation of multiple-scattering theory in terms of muffin-tin orbitals. The use of slightly overlapping muffin-tin wells is justified rigorously. It is shown that the structure constants may be screened for a useful range of positive and negative energies, and that the screening may be chosen to yield desirable properties of the KKR matrix. Energy linearization and the linear muffin-tin-orbital method are discussed.
Wave Propagation in Dispersed Random Media
Authors: Sheng Ping , Jing Xiaodun , Zhou Minyao 
Published: March 2011

ABSTRACTWe present a generalized coherent potential approximation for the identification of quasi propagating modes in dispersed random media and the calculation of their dispersion relations. The validity of this approach is supported by multiple-scattering calculations, numerical simulation, and comparison with experimental data on acoustic excitations in colloidal suspensions. Our theory yields excellent quantitative agreement with the measured dispersion relations and provides an explanation for the observed frequency gaps in the excitations spectra.
Complex Geometry and Electric Double Layers
Authors: Duplantier Bertrand 
Published: March 2011

ABSTRACTThe properties of electric double layers near curved surfaces of arbitrary shape and genus are obtained exactly within the Debye-Hückel theory by means of multiple-scattering expansion. For smooth membranes, geometric and topological feature of the electrostatic free energy then emerge through convergent expansions in inverse powers of the principal radii of curvature. Some consequences for the electrostatic stability of various membrane shapes are considered. We also study the effects of surface singularities, e.g., wedges, on the thermodynamics of electric double layers near a rough colloid. Each wedge yields an additive contribution to the free energy that is a functionof the angle. A probabilistic Brownian representation of is given, which is entirely similar to that of vibration eigenmodes given by M. Kac long ago in “Canone hear the shape of a drum?” [Amer. Math. Monthly 73S, 1 (1966)]. The analysis yields a universal scaling law for the free energy of a rough colloid with its fractal Minkowski dimension.
Optical Response of Rough Metal Surfaces and Island Films
Authors: Urbakh M. 
Published: March 2011

ABSTRACTThis study treats the optical properties of different two-dimensional inhomogeneous systems in which localized and delocalized surface modes excited by incident light can exist. The optical response is described with the use of kinetic equations linking together different types of surface and bulk modes. It is important that both electromagnetic interactions between local modes and the dependence of the optical characteristics of centers on the local geometrical structure are taken into account.It is shown that the behavior of experimentally observable quantities (enhancement ratioof the electric field at the surface, surface absorption, etc.) as functions of the frequency and concentration of local centers depends essentially on the excitation mechanismof local modes.
Applications of Multiple Scattering Theory to Electron Spectroscopy
Authors: Durham P J 
Published: March 2011

ABSTRACTBecause it gives direct and convenient access to the Green's function, multiple scattering theory (MST) provides a powerful machinery for the calculation of I particle observables in general and electron spectroscopies in particular.The two techniques in which multiple scattering methods have made the biggest impact areangle-resolved photoemission and x-ray spectroscopy (absorption and emission); here the essential point is that MST allows experimental data to be analysed and modelled on the same footing as calculations of the underlying electronic structure, for both ordered and disordered systems. Applications in these areas are briefly reviewed, drawing attention to the two outstanding current deficiencies of the methodology (the use of density functional theory to describe excited states and the approximate — muffin-tin — form of the effective 1—electron potential) as well as its successes.Current developments, particularly the treatment of relativistic and magnetic systems, the possibilities opened up by third-generation synchrotron radiation sources, and the use of parallel computing techniques, are mentioned.
Charge and Spin Selfconsistent Kkr-Cpa Methodology for Complex Multi-Component Alloys
Authors: Bansil A. , Kaprzyk S. , Tobola J. 
Published: March 2011

ABSTRACTWe have developed the charge and spin selfconsistent KKR-CPA approach for a first-principles parameter free treatment of disorder effects in complex multi-component alloys. Thenature of the KKR-CPA Green's function in the complex energy plane is discussed. A generalized Lloyd formula for the density of states is obtained and some subtle features of the formalism are pointed out. We illustrate our KKR-CPA methodology by giving a number of examples of magnetic as well as non-magnetic systems. The non-magnetic cases considered are the simple cubic perovskites BaxK1−0BiO3 and BaPb—1BixO3, and the high-Te superconductor La2—xSrxCuO4 for the body-centeredtetragonal phase. The examples of magnetic systems discussed are, the the Heusler alloys Co2—xFexMnSi (L21 structure), and the semi-magnetic semiconductor Cdl—xMnxTe in the zincblende structure.
Mechanical Behavior of Hierarchical Synthetic Composites
Authors: Mayer George 
Published: March 2011

AbstractDiverse microstructures observed in rigid natural composites have been linked to mechanical properties that are equal to and, at times, superior to those which have been designed into synthetic composite materials comprised of organic, metallic, and ceramic constituents. The constitution, properties, and microstructures of the natural and synthetic materials are described, along with what is known and what is unknown about the constituent components, and interfaces. Hierarchical approaches to designing with and the mechanical analyses of both natural and synthetic composites will be described.
The Influence of Reinforcing Fibers on the Morphology and Crystallization of Thermoplastic Polymer Composites
Authors: Rebenfeld Ludwig , Desio Glenn P. , Reinsch Veronika E. 
Published: March 2011

AbstractSemi-crystalline thermoplastic polymers are being used increasingly as matrices in high performance fiber reinforced composites. The crystallization kinetics and morphology of these polymers have been studied extensively, but relatively little attention has been given to the effects of the reinforcing fibers on the crystallization process.We have studied the effects of glass, carbon and aramid fibers on the rates of crystallization, the degree of crystallinity, and the glass transition temperature of such typical thermoplastics as poly(phenylene sulfide) and poly(ethylene terephthalate). Based on the isothermal crystallization studies using DSC, we find that, in general, reinforcing fibers increase the rates of crystallization and decrease the degree of crystallinity, the extent of these effects being dependent on the weight fraction of fiber in the composite, the specific type of fiber, and the nature of surface finishes (sizes) that may have been applied.The spherulitic morphology that develops in these polymers during the crystallization process, as characterized by polarized light microscopy, is also affected by the reinforcing fibers. In many cases, transcrystalline regions develop near the fiber surface due to nucleation effects.