bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reaction Injection Molding of Silica-Alumina Mixtures Using Heterocoagulation
Authors: Pujar Vijay V. , Cawley James D. , Hu Ping , Lee L. James 
Published: March 2011

ABSTRACTA colloidal processing technique based on the heterocoagulation of selected ceramic oxide systems, and analogous to reaction injection molding of polymers, is described. Commercial colloidal silica and boehmite sols, which have oppositely charged particles in the pH range 2.0-9.0, and mixtures of these suspensions with micron sized oxide powders, have been used to determine whether a liquid to solid transformation could be induced when the two materials are simultaneously injected at high velocities into a mold cavity. Rheological changes have been measured as a function of relative flow rates of the two suspensions, solids loading and oscillatory frequency. Viscosity is observed to increase by as much as six orders of magnitude under optimized conditions.
Binder Design for Fabricating Internal Crack-Free Injection-Molded Si3N4-Based Ceramics
Authors: Su Sophia R. 
Published: March 2011

ABSTRACTBinder design is an important issue in ceramic injection molding technology. The binder decomposition mechanism, which involves thermodynamics, kinetics, as well as heat and mass transfer, controls the binder removal process. This process, in turn, is governed by the thermal and physical characteristics of the organic waxes used, and is the most critical step in injection molding ceramics. In this paper, we present the binder design philosophy and the method of binder selection. A systematic binder removal study focusing on heating rate, setter powder, and sublimable materials was carried out with the selected compositions. As a result of this study, we concluded that the fluid wicking controls the binder removal at the molten temperature of the binder, and the diffusion and permeation-controlled mechanism dominate at the decomposition temperature range of the binder. With the right binder selection, it is feasible to produce internal and external crack-free large cross-section injection-molded ceramic parts.
Combined Stage Sintering Model: Review and Applications
Authors: Rusin R.P. , Hansen J.D. , Teng M.-H. , Johnson D. Lynn 
Published: March 2011

ABSTRACTIn the combined stage sintering model previously introduced[l], a single equation was derived that quantifies sintering as a continuous phenomenon from beginning to end. The microstructure is characterized by two separate parameters representing the geometry (Γ) and the scale (G). Calculations of Γ from experimental data show the effect of surface diffusion and microstructural geometry on Γ. The model is reviewed and discussed with respect to the sintering of alumina and spherical nickel powder.
Cellular Automaton Simulations of Surface Mass Transport Due to Curvature Gradients: Simulations of Sintering in 3-D.
Authors: Bentz D.P. , Pimienta P.J.P. , Garboczi E.J. , Carter W.C. 
Published: March 2011

ABSTRACTA cellular automaton algorithm is described that simulates the evolution of a surface driven by the reduction of chemical potential differences on the surface. When the surface tension is isotropic, the chemical potential is proportional to the curvature at the surface. This process is important in the development of microstructure during the sintering of powders. The algorithm is implemented in two and three dimensions in a digital image mode, using discrete pixels to represent continuum objects. The heart of the algorithm is a pixel-counting-based method for computing the potential at a pixel located in a digital surface. This method gives an approximate measure of the curvature at the given surface pixel. The continuum version of this method is analytically shown to give the true curvature at a point on a continuum surface. The digital version of the curvature computation method is shown to obey the scaling laws derived for the continuum version. The evolution of the surface of a three dimensional loosely packed powder, along with the percolation characteristics of its pore space, are computed as an example of the algorithm.
Liquid Phase Sintering in the Glass-Cordierite System - Effect of Melt Infiltration Distance
Authors: Jean Jau-Ho , Gupta Tapan K. 
Published: March 2011

ABSTRACTEffect of glass infiltration distance, controlled by particle sizes of glass and ceramic filler, and green density, on densification kinetics of glass-filled ceramics has been studied using borosilicate glass-cordierite as the model system. Within the particle size range investigated, the densification is found to be significantly enhanced by increasing cordierite size, reducing glass size and increasing green density. The above results are attributed to both increased driving force of densification by reducing glass particle size, and decreased glass redistribution distance by either increasing green density of compacts or increasing the particle size ratio between cordierite and glass powders.
Additive Sintering Process in Aluminum Nitride Ceramics
Authors: Makihara H. , Kamehara N. 
Published: March 2011

ABSTRACTCalcium compounds and yttrium compounds are frequently used as additives to densify AlN ceramics[l,2]. They react with oxygen impurities, such as A1203 in the raw AlN powder and in aluminate forms. A phase diagram is helpful in deciding the amount of additives to add, but the AlN sintering process doesn't come to equilibrium. We investigated the differences between sintering AlN with CaCO3 and with Y2O3.With CaCO3 added, the calcium-aluminate liquid phase evaporates from the sintered AlN body at high sintering temperatures. The AlN thermal conductivity doesn't increase above a sintering temperature of 1700°C because residual oxygen substitutes into the AlN grains. With Y2O3 added, AlN sinters below 1850°C, as predicted by a phase diagram. With a large amount of Y2O3 added, 5 wt%, thermal conductivity doesn't depend on residual oxygen. This is because yttrium doesn't evaporate from the sintered AlN body and residual oxygen substitutes into AlN grains at an early stage of the AlN sintering.
Fundamental Issues in the Sintering of Ceramic Particulate Composites
Authors: Rahaman Mohamed N. 
Published: March 2011

ABSTRACTThe sintering rate of a ceramic powder matrix can be reduced significantly by the presence of rigid inclusions. The factors that lead to this reduced sinterability have been the subject of much debate in the last 5–10 years. Recent work indicate that the reduction in the matrix sinterability is a processing-related problem. The main factors that control the sinterability of ceramic particulate composites include the packing of the matrix immediately surrounding the inclusions and interactions between the inclusions which constrain the matrix. A processing method which avoids the difficulties associated with these two factors is outlined. The method involves the synthesis of coated inclusion particles. Composites containing up to 40 volume percent inclusions can be freely sintered in the solid state to full density.
Modeling Refractory Material Production by Self-Propagating High Temperature Synthesis (SHS)
Authors: Crane Thomas F. , Gutierrez-Miravete Ernesto 
Published: March 2011

ABSTRACTSelf-propagating high temperature synthesis (SHS) can be used to prepare near net refractory shapes which are difficult to produce by other methods. In SHS, green compacts capable of strong exothermal reaction are ignited at one end and transformed into the desired products by a self-propagating reaction. Physical processes involved in SHS include chemical kinetics, macroscopic transport phenomena and phase transformations. This paper describes a simplified mathematical model of the SHS process derived by combining the heat equation with the chemical reaction rate equation. The model equations are solved numerically to obtain representation of the SHS process. Parametric studies have been performed to investigate the relative importance of the physical parameters in the model.
From Minierals to Materlals: A Facile Synthetic Route to Preceraic Polymers for Aluminum Oxide
Authors: Apblett Allen W. , Landry Christopher C. , Mason Mark R. , Barron Andrew R. 
Published: March 2011

ABSTRACTReaction of boehmite, [AI(O)(OH)]n, with an excess of carboxylic acid (HO2CR) results in the formation of the carboxy substituted alumoxanes, [AI(O)x(OH)y(O2CR)z)]n where 2x + y + z = 3 and R = alkyl substituents. The alumoxanes have been fully characterized by SEM, elemental analysis, IR and multinuclear NMR spectroscopy. The physical properties of the alumoxanes are highly dependent on the identity of R, and range from insoluble crystalline powders, e.g. R = CH3, to powders which readily form solutions or gels in hydrocarbon solvents, e.g. R = C5H11. All of the alumoxanes decompose under mild thermolysis to yield γ-alumina.
Advanced Hydrothermal ZrO2 Powder
Authors: Sōmiya Shigeyuki , Hishinuka Kazumitsu , Nakai Zenjiro , Abe Notoshi , Akiba Tokuji 
Published: March 2011

ABSTRACTWell-crystallized Y2O3 -ZrO2 powder of 12nm crystallite size was synthesized by RoAogenious precipitation under hydrothermal condition at 180°C for 1 hour. This powder consisted of tetragonal zirconia. After calcination and ball milling, the crystiilite size was 22 nm and the tetragonal phase was reduced to 55% by ball milling. The average grain size was 0.5 µm and specific: surface area was 20 m /g. Highly dense TZP(> 99%) with a homogeneous microstructure was obtained by sintering this powder at 1400°C for 2 hours.
Oxygen Effect and Redistribution in Cobalt Silicide Formation
Authors: Lien Chuen-Der , Nicolet Marc-A. 
Published: March 2011

ABSTRACT18O was implanted in the Si substrate or in the Co overlayer to study the effect of oxygen and its redistribution during Co silicides formation. Implanted and unimplanted samples were annealed in vacuum at 450°C for different durations. Over the investigated dose range of 0.5 to 2 × 101618O/cm2 in the Co film, the phases formed upon annealing are Co2Si and CoSi, as for the unimplanted samples. The kinetics of the silicide growth is changed little by the presence of oxygen in the Co film. Oxygen accumulates at the Co2Si/Co interface. When the oxygen is implanted in the Si substrate, the higher the oxygen dose is, the slower (fasteil the growth rate of CoSi(Co2Si) becomes. Below 1 × 1016 O/cm, both phases (i.e. CoSi and Co2Si) still form; above 2 × 1016 O/cm2 , only Co2Si formsWhen two phases form, the oxygen moves deep into the Si substrate; when only Co2Si forms, the oxygen moves toward the surface.
A Comparison of Electron Energy Loss Spectroscopy and Electron Diffraction for Polycrystalline and Xe+ Irradiated Nickel Silicides
Authors: Barbour J.C. , Grunes L.A. , Mayer J.W. 
Published: March 2011

ABSTRACTVariations in the valence and core level electron energy loss spectroscopy (EELS) peaks are studied as a function of nickel silicide composition.Analysis of the EELS spectra in comparison with the electron diffraction patterns show the plasmon energies fingerprint the silicide phases. The EELS core level spectra reflect the Si bonding and the electronic density of states in each phase.Irradiated Ni 2Si becomes amorphous causing a change in the plasmon peak energy and the Si L23peaks.
The Morphology of the Polysilicon - SiO2 Interface
Authors: Bravman J.C. , Sinclair R. 
Published: March 2011

ABSTRACTA systematic TEM study of the morphology of the polysilicon - SiO2 interface has been performed. LPCVD films were deposited on thermally oxidized silicon substrates, doped via diffusion or ion implantation, and oxidized in pyrogenic steam. Several aspects of the interface have been investigated as a function of dopant species, dopant concentration, oxidation time and oxidation temperature.
Thermal behavior of Metal-Metal-Silicon or Metal-Silicide-Silicon Structures for Pt, Ni, and Cr
Authors: Barcz A. J. , Bartur M. 
Published: March 2011

ABSTRACTWe report on a study of thermal interactions between pairs of Ni, Cr, and Pt films and their silicides on a Si substrate. For each pair of metals M1, M2, four systems were investigated: Si−M1 −2, Si−M2 −M2, Si−M1 Si−M2 and Si−M2Si−M1 giving altogether twelve initial combinations. Samples were annealed in the temperature range of 300−700°C and the analysis was made by Backscattering Spectrometry (BS). It is found that double layers of uniform silicides can be grown when the Cr silicide is the top layer. The rate of CrSi2 formation in this case is less then that reported for CrSi2 growth on Si substrate. In all other cases we find some intermixing. Impurities are found to effect the growth kinetics and the layer morphology.
The Early Stages of Silicide Formation on Metal and Silicon Surfaces, Time-of-Flight Atom-Probe Studies of Atomic Structures and Compositions
Authors: Tsong T. T. 
Published: March 2011

ABSTRACTThe early stages of silicide formation on metal and silicon surfaces have been studied in the atom-probe FIM. Precursors to silicide formation are low temperature diffusion of single Si atoms, their interactions, and adsorption layer superstructure formation. These phenomena have been studied quantitatively. At high temperatures, silicide films can be formed. Four distinctive stages of silicide formation on tungsten surfaces have been observed from the atomically resolved FIM images. Formation of silicide layers on platinum, nickel, and silicon surfaces have also been studied. From both the atom-probe compositional depth profiling and the FIM observation one can conclude that the interface formed at low temperature is sharp. At high temperature, Si atoms can diffuse deep into a Pt matrix and Ni atoms into a Si matrix. Conclusions drawn from these atom-probe studies are summarized, and future directions suggested.
Structural Effects in the Initial Stages of Epitaxy
Authors: Pimbley J. M. , Lu T.-M. 
Published: March 2011

ABSTRACTStructural effects of sub-monolayer epitaxial films are described by the pair correlation function of surface atoms. We have developed a new scheme to evaluate this atomic pair correlation function analytically and exactly for the combined overlayer and substrate system during the first stages of epitaxy. We employ this correlation function to calculate electron diffraction profiles from model surfaces and compare these calculations to recent LEED measurements of Si/Si(111) and W/W(110) epitaxy.
Resonance between Channeled Particle Wavelengths and Periodicity of Strained-Layer Superlattices
Authors: Chu W. K. , Picraux S. T. , Biefeld R. M. , Osbourn G. C. , Ellison J. A. 
Published: March 2011

ABSTRACTRecent studies of the resonance effect between the wavelength of planar channeled ions and the periodicity of strained-layer superlattices are summarized for MeV 4He ions backscattering from GaAsxP1-X/GaP superlattices. When the incident beam energy is adjusted so the half-wavelength matches the thickness of the layers, a catastrophic dechanneling effect is observed. A simple phase rotation analysis has been developed to calculate the dechanneling in each layer and good agreement is obtained with the observed dechanneling per interface. This resonance effect is used to measure the amount of strain in the GaAsxP1-x/GaP strained-layer superlattice.
Electromigration in Al And Al-Alloy Thin-Film Conductors
Authors: Pasco R.W. , Felton L.E. , Schwarz J.A. 
Published: March 2011

ABSTRACTTemperature-ramp Resistance Analysis to Characterize Electromigration (TRACE) has been applied to thin-film Al and Al-alloy conductors. Results have yielded activation energies in agreement with literature values. The TRACE technique has been used to determine the effect of H2on the kinetics of electromigration damage (EMD) for both Al and Al-2%Cu thin-film conductors.
Barrier Properties of Tasi2 in Contact With Al-Metallization
Authors: Neppl F. , Schwabe U. 
Published: March 2011

ABSTRACTThe reaction between cosputtered amorphous and polycrystalline tantalum silicide with Al-Si-metallization was investigated by means of Schottky and ohmic contacts on Si. Diffusson of Al and Si across the silicide was impeded up to 475 °C, as long as the silicide films contained excess Ta with respect to the TaSi2 stoichiometry. The results show that Al-Si with a thin Ta-rich tantalum silicide underlayer provides a VLSI-metallization with considerably reduced contact resistance, particularly for small contacts, and low Schottky barrier to n-Si without significant Si consumption from the substrate
Formation of Titanium Disilicide by Electron Beam Irradiation Under Non Steady State Conditions
Authors: Maydell-Ondrusz E A , Harper R E , Abid A , Hemment P L F , Stephens K G 
Published: March 2011

ABSTRACTTitanium disilicide was formed by multiply-scanned electron beam irradiation of titanium films of nominal thickness 1200Å on silicon substrates. Samples were annealed at power densities of 2 to 52.5Wcm−2 using times in the range of 1 to a few hundreds seconds. Rutherford backscattering analysis was used to study the metal redistribution and to estimate the approximate compositions and thicknesses of the films. Compounds were identified by X-ray and electron diffraction. Sheet resistance was measured by the four probe technique and surface topography inspected by scanning electron microscopy.The silicide thickness achieved depends only on annealing time for power densities in the range of 20 to 50Wcm−2 and hence is independent of heating rate and peak temperature during the heating cycle.
3d C/C Processing with High Gas Pressure
Authors: Hsu S. E. , Chen C. I. , Chou S. T. 
Published: March 2011

ABSTRACTCarbon/Carbon composite is densified by Hipping infiltrated pitch. The pore size in matrix decreased as processing pressure increases. The porosity decreasing rate is defined as (Vi−Vi+ 1)/Vi, and is proportional to the applied gas pressure, where Vi and Vi+1 are the pore volume before and after hipping respectively. The bonding strength also increases with the applied gas pressure and with densification cycle. The density of a 67% porosity fiber preform can reach up to 1.9 g/cm3 in less than 6 hipping cycles with maximum gas pressure of 103 Mpa.
Elastic Deformation in Hardness Test and Young's Modulus of Hipped Si3N4
Authors: Hamasaki Toyohiro , Ishizaki K. 
Published: March 2011

ABSTRACTThe relationship between sintering conditions and mechanical properties were examined for fully densified Si3N4 with different, β phase fractions (0.2 to 1). The samples were sintered by a capsule-HIP method with Y2O3 and Al2O3 additives (6 mol% in total) at temperatures between 1823 to 2023 K, under 60 MPa for 1 hour. The elastic deformation was calculated by Vickers indentation recovery. The Vickers hardness reached the maximum value for a β phase fraction of about 0.5, while fracture toughness, elastic deformation, and Young's modulus increased as the β phase content augmented.
Direct Evidence on the Elimination of Pore by the Applied Pressure in Hot Isostatic Pressing of Alumina
Authors: Fukai Seiki , Uchida Nozomu , Kato Zenji , Uematsu Keizo 
Published: March 2011

ABSTRACTRemoval of natural pore during capsule hot isostatic pressing (HIP) and normal sintering were examined directly with the novel liquid immersion technique, which can reveal details of micro-structure and characterize flaw-forming defects of microns-size in lightly densified specimens. The results were supplemented by the pore size measurement with the mercury porosimetry, microstructural examination with SEM as well as microstructural examination of specimens after final densification. The behaviors in both pore size and shape changes were different in HIP and normal sintering. Removal of large pores of microns-size started from the beginning of densification in HIP. Whereas large pores grow with densification in normal sintering. Large pores changes their shape drastically in HIP, but hardly changes in normal sintering. The behavior of pore in the early stage of densification is closely related to the microstructure of densified specimen; without HIP, large defects of processing origin are present in near-fully dense specimen. These observations were discussed in terms of current sintering theory.
Hot Isostatic Forging of Materials at Pressures up to 60,000 Psi
Authors: Tavenner Robert F. , Hodge Edwin S. 
Published: March 2011

ABSTRACTThis paper will discuss the role of Hot Isostatic Forging (HIF) of partially dense powder preforms to full density at greatly reduced temperatures at pressures to 60,000 psi. The floor to floor cycle times are minutes compared to hours for more conventional Hot Isostatic Processing (HIP) of materials. The process greatly reduces energy consumption and labor costs. Materials that would normally require temperatures of 1225°C to achieve full densification by HIP canbe densified at temperatures as low as 800 to 850°C. Composite materials can be processed rapidly enough at much lower temperatures by HIF to greatly reduce the potential for reaction between the matrix and the reinforcement material. In addition, composites can also be fabricated by a combination of SHS (Self- Propagating High Temperature Synthesis) and HIF to further reduce the reaction between the matrix and the reinforcement material. This permits going from a CIP'ed (Cold Isostatic Pressing) blend of Nickel, Aluminum, and Aluminum Oxide whiskers to final density in about 5 to 10 minutes. The process is amenable to the fabrication of near-net finished shapes by this rapid integrated cycle.
Materials Processing through Levitation in High Gas Pressure
Authors: Nanko Makoto , Ishizaki K. 
Published: March 2011

ABSTRACTNew levitation materials processing on the ground was developed using high gas pressure. Conventional levitation materials processes are carried out in microgravity fields, such as in space or in free-falling, or by applying aerodynamic force, electromagnetic force etc.. This innovated method is based on buoyancy by very high density of high pressure gas. Advantages of this new method are not only as a containerless processing which is able to prepare high purity materials, to produce perfect spheres, but also the possibility to use normal HIP techniques. It is expected that the new processing is applicable in many fields and easy to commercialize.
Oxidation of Si1−xGex Alloys at Elevated Pressure
Authors: Caragianis Christine , Paine David C. , Schwartzman Alan F. , Shigesato Yuzo 
Published: March 2011

ABSTRACTThermal passivation of Si1−xGex (x=10 at.%) using dry high pressure (>700 atm) and hydrothermal (>500 atm) oxidation (HPO) was studied. Alloys of Si1−xGex approximately 200 nm thick were oxidized using three processes: (i) dry oxygen at 700 atm and at a temperature of 550°C, (ii) hydrothermal at 510 atm and 550°C, and (iii) conventional 1 atm at 800°C. Auger sputter depth profiling (AES), X-ray photoelectron spectroscopy (XPS), and Raman Spectroscopy were used to characterize the oxides. AES and Raman studies reveal that both dry high pressure and hydrothermal oxidizing conditions produce compositionally congruent oxides from Si90Ge10, multicomponent alloys. XPS studies were used to establish that the Ge in these oxides is chemically incorporated. Thermodynamic and kinetic considerations of the Si-Ge-O system are discussed for both HPO and conventional oxidation. The metastable nature of the HPO oxides is confirmed by examining the microstructure of annealed oxides.