bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Pyrolytic Decomposition of Owens-Illinois Resin Gr650, an Organosilicon Compound
Authors: Bagley B. G. , Gallagher P. K. , Quinn W. E. , Amos L. J. 
Published: March 2011

ABSTRACTThe pyrolytic conversion of an organosilsesquioxane (Owens-Illinois resin GR650) to SiO2 is characterized by ir spectroscopy, thermogravimetry and evolved gas analysis (line-of-sight mass spectroscopy). Scanning calorimetry, ramping at 10°C/min, on the as-received (room temperature annealed) resin indicates a glass transition temperature of 67°C which decreases to 58°C for an unrelaxed sample. The ir spectra have bands which can be assigned to Si-CH3 and Si-O-Si modes. For 30 minute isothermal anneals at temperatures above 420°C there is a continuous decrease in the bands associated with the Si-CH3 groups such that after 30 minutes at 650°C the ir spectrum has evolved to that for SiO2. Evolved gas analysis indicates that there are four major components evolving. Over the temperature range (ramping at 10°C/min) ∼180 to ∼500°C we observe C2H5OH and H2O, both of which are condensation reaction products from the curing reaction. Methane is a major evolving species over the temperature range ∼500 to ∼800°C and the thermal spectrum is double peaked which we attribute to CH3+ bound to the inside and outside of the polymer cage structures. The final major component detected was H2, over the temperature range ∼600 to ∼1100°C, which was attributed to pyrolysis of the organic components, both trapped and evolving. The features of the weight loss curve can be accounted for by the measured evolving species spectra.
Micro-Raman Spectroscopy of Fresh and Aged Silica Gels
Authors: Klein L. C. , Nelson C. , Higgins K. L. 
Published: March 2011

ABSTRACTRaman spectra were obtained from fresh and aged silica gels using micro-Raman techniques. Comparison of the spectra from wet and dried gels reveals the stages of reaction in the ethanol-TEOS-water system and the gradual development of the silica structure. The steady disappearance of bands assigned to ethanol and the appearance of bands assigned to silatious species can be traced during the drying process. Increases in either acid concentration or water level increase reaction rates to give gels in a more advanced stage of polymerization. Gels tend to develop fluorescence upon aging for several months. The source of this fluorescent could not be determined, but it's development can be prevented by heating freshly dried gels to about 155°C.
Multi-Phasic Ceramic Composites made by Sol-Gel Technique
Authors: Roy Rustum , Komarneni S. , Roy D.M. 
Published: March 2011

ABSTRACTInstead of aiming to prepare homogeneous gels and xerogels, this paper reports on work done to prepare deliberately diphasic materials. This has been achieved by three different paths: (1) mixing 2 sols; (2) mixing 1 sol with 1 solution; and (3) post formation diffusion of either one or two solutions.By the last named process we have made SiO2, mullite and alumina based composites, with silver halides, BaSO4, CdS, etc., as the dispersed phase. The crystal size can be confined to the initial pores by rapid diffusion giving rise to extremely fine second phases in the submicron range. Subsequent reduction of appropriate metallic salts can be used to give finely dispersed metals (e.g. Cu, Ni) in essentially any xerogel matrix. The open porosity makes these metal atoms very accessible.By the first two processes we have made both single phase and di-phasic gels of the same composition (prototype: mullite) and shown that though they cannot be distinguished by XRD, SEM, and TEM, by DTA and thermal processing, they are radically different. Such di-phasic gels store more metastable energy than any other solids.
Formation of Glass and Amorphous Oxide Fibers from Solution
Authors: Sakka Sumio 
Published: March 2011

ABSTRACTA review has been made of our works on two types of sol-gel methods for obtaining oxide fibers through low temperature process: (1) the alkoxide method and (2) the freezing-of-gel method. In the alkoxide method, metal alkoxides in an alcoholic solution are hydrolyzed and polycondensed into chain-like polymers, drawn into gel fibers near room temperature and heated to several hundred °C. Various problems encountered in the process are discussed with SiO2-based fibers. In the freezing-of-gel method, a hydrogel is unidirectionally frozen by lowering the gel cylinder into a cold bath. Thawing of unidirectionally grown ice crystals leaves a bundle of hydroxide fibers. Factors affecting the formation of fibers are discussed with titanium and zirconium hydroxide fibers as examples.
Phase Separation In Blends of Polystyrene and Poly (P-METHYLSTYRENE) Using Thermal Analysis And Small-Angle Neutron Scattering
Authors: Xenopoulos A. , Londono J. D. , Wígnall G. D. , Wunderlich B. 
Published: March 2011

ABSTRACTDifferential scanning calorimetry (DSC) was used to study blends of polystyrene (PS) and poly (p-Methylstyrene) (PpmS). The presence of two glass transitions on heating after quenching was interpreted as evidence of phase separation at the temperature of the liquid before quenching. The small difference between the glass transitions of the homopolymers in the PS/PpmS system of “13 K limits the reliable detection of double glass transitions for blends to concentrations between 30 and 70%. The results of the DSC technique are supported by comparison with small angle neutron scattering (SANS) data.
Simulation Studies Of Titanium And Zirconium Wadeite Glasses
Authors: Vessal Behnam , Dickinson James E. 
Published: March 2011

ABSTRACTMolecular dynamics simulations of the structure of crystalline and glassy titanium and zirconium wadeites have been undertaken to study the microscopic origin of the striking difference between these two systems in terms of nucleation and surface crystallization. The results of simulation are in accord with Raman and EXAFS spectroscopy as well as neutron scattering and DTA scans on the same structures.
Nucleation and medium Range Order in Silicate Liquids: Inferences From NMR Spectroscopy
Authors: Stebbins Jonathan R. , Sen Sabyasachi 
Published: March 2011

ABSTRACTNMR spectroscopy is beginning to provide quantitative information on short- and medium-range structure in silicate glasses and liquids, and on molecular-scale dynamics in the liquids. Data on coordination numbers, second and higher neighbor connectivities, and larger scale heterogeneities, as determined by NMR at ambient and high temperatures, are potentially very useful in models of nucleation and growth of immiscible liquid and crystalline phases. New techniques such as dynamic angle spinning (DAS), high temperature magic angle spinning (MAS) are especially promising. Detailed studies of paramagnetic nuclear spin relaxation can characterize compositional heterogeneity in glasses to distance scales of at least several nanometers.
Amorphous-to-crystalline transition in Tb33Fe66 films studied via EXAFS
Authors: Hams V. G. , Das B. N. , Elam W. T. , Koon N. C. 
Published: March 2011

AbstractThe amorphous-to-crystalline transition in sputter-deposited amorphous Tb33Fe66 films has been studied using a conversion-electron extended X-ray absorption (EXAFS) technique. Modeling of the EXAFS data using theoretical and empirical standards allowed the quantitative measurement of coordination, radial distance, and disorder of local atom shells around the Fe sites after varying degrees of heat treatments.
Transient Nucleation in Devitrification
Authors: Greer A. L. 
Published: March 2011

ABSTRACTA review is given of transient crystal nucleation in glassy or amorphous solids. The types of behaviour are surveyed. It is shown that the kinetics can be quantitatively modelled and that the matching of experiment and theory provides an important test of the classical theory. Examples are considered of homogeneous nucleation (affecting glass formation), heterogeneous nucleation, and nucleation at an interphase interface. While the emphasis is on transient effects of the kind implicit in the classical theory, it is shown that transients can arise for other reasons as well, thus potentially complicating the interpretation of experiments.
The Elastic Strain Energy of Coherent Ellipsoidal Precipitates in Anisotropic Crystalline Solids: Applications to the Aragonite-Calcite Transformation
Authors: Liu Ming 
Published: March 2011

ABSTRACTEshelby's theory has been applied to the aragonite-calcite transformation in order to calculate the elastic strain energy of coherent ellipsoidal precipitates in anisotropie solids. Using a quasiNewton's Method and a finite-difference gradient, the elastic strain energy was incorporated in order to calculate the activation energy ΔG* for homogeneous nucleation under hydrostatic and non-hydrostatic conditions.
Analysis of Crystal Nucleation and Growth in Amorphous Cobalt Disilicede.
Authors: Smith D. A. , Evans P. V. , Koppikar S. R. 
Published: March 2011

ABSTRACTExtensive in situ investigations of the crystallization of amorphous cobalt disilicide have been conducted using a transmission electron microscope with a hot stage. Thermodynamic and kinetic parameters describing the heterogeneous transformation have been evaluated. The angle of contact betwen crystalline and amorphous material was determined from tilting experiments to be 76°. Nucleation rates in samples 40 nm thick were evaluated at various temperatures and compared with thermodynamic models to deduce an interfacial energy between amorphous and crystalline COSi2 (σca) of 121 mJ/m2 and an activation energy for crystallization of 1.27 eV. Johnson-Mehl-Avrami analysis of the observed continuous nucleation and steady state isotropie growth in 100 nm thick samples points to a gradual transition of the crystallization mode from 3-dimensional (n=4) to 2-dimensional (n=3) growth as might be expected. Comparison of the nucleation and growth rates in 40 nm and 100 nm thick samples demonstrated the influence of surfaces on crystallization phenomena in thin films.
Crystallization Kinetics In A Ni24Zr76 Amorphous Alloy
Authors: Ghosh G. , Chen F.-R. 
Published: March 2011

ABSTRACTIsothermal crystallization kinetics of Ni24Zr76 amorphous alloy has been studied by differential scanning calorimetry (DSC). Theoretically estimated transient times are found to be consistent with the experimentally observed incubation periods. The crystallization kinetics has been analyzed in terms of Kolmogorov-Johnson-Mehl-Avrami (KJMA) Model and significant departure from the linear KJMA behavior was observed. Such non-linearity is due to the surface-induced crystallization, anisotropie growth of the crystals, impingement effects and variation of the nucleation rate during crystallization etc. By applying high-resolution electron Microscopy (HREM), it has been shown that the nucleation and growth of the crystals do not take place at a constant state of disorder.
Amorphous/Crystalline Structure And Phase Transformations In Metastable Semiconducting Ge1−xSnx
Authors: Lee Susanne M. , Barmak Katayun 
Published: March 2011

ABSTRACTThe semiconducting crystalline alloys, Ge1−xSnx, are of interest due to theoretical predictions about their electronic band structures which make them useful in infrared photodetectors. However the composition region where these alloys have the desired properties is greater than the equilibrium solid solubility limit of Sn in Ge (x<0.01). We have circumvented the solubility limits and produced thin (2000Å) and thick (4–8Μm) films of Gei.xSnx (x<0.31) by rf sputtering. Differential scanning calorimetry (DSC) Measurements were performed to study grain growth and crystallization processes in these highly metastable semiconductors. X-ray and electron diffraction measurements indicated the materials were amorphous, but the fact that some of the films were fine grained polycrystalline samples only became apparent in their DSC spectra. We present models that describe quantitatively the transformation behavior in both sets of films.
Heterogeneous Nucleation of Superparamagnetic Phases in “Fe-Bearing Cordierite-Glasses
Authors: Abs-Wurmbach Irmgard , Boberski Cornelia 
Published: March 2011

ABSTRACTGlasses of stoichiometric cordierite composition Mg2(Al1−xFex)4Si5O18, containing very low iron contents (x=0.015 and 0.005) have been investigated by 57Fe Mössbauer spectroscopy. At higher Fe concentrations spinel exsolution has been observed in X-ray powder patterns. To allow Mössbauer spectroscopy at very low Fe-concentrations (<0.8 weight* Fe2O), starting materials were doped with 100% 57Fe. Glasses prepared in air at 1560°C were also oxidized In water saturated O2 stream. Glasses were crystallized to cordierite by heating In air at 1100 to 1400°C. 57Fe-Mössbauer spectra of all samples are governed by a doublet typical for Fe2+ in octahedral coordination (IS: 1.09–1.15, QS: 2.00–2.31 in MM/s relative to metallic iron). X-ray powder patterns exhibit no additional phases. But, the 295 K and 5 K Mössbauer spectra of treated and untreated glasses and of cordierltes exhibit broad lines, which have been fitted by applying internal magnetic hyperfine fields H of ca. 500 kG. These lines are attributed to heterogeneously nucleated, superparamagnetic (MgFe) (AlFe)2O4 spinels of complex compositions. From the calculated subspec-tra one may conclude that 35 to 65% of the total iron, depending on preparation conditions, is incorporated in the spinels.
Stability And Precipitation Kinetics In Si1-yCy/Si and Si1-x-yGexC/Si Heterostructures Prepared by Solid Phase Epitaxy
Authors: Strane J. W. , Picraux S. T. , Stein H. J. , Lee S. R. , Candelaria J. , Theodore D. , Mayer J. W. 
Published: March 2011

ABSTRACTThis study investigates the stability of Metastable Si1-yCy/Si heterostructures during rapid thermal annealing (RTA) over a temperature range of 1000 – 1150° C Heterostructures of Si1-yCy/Si and Si1-x-yGexCy/Si (x=0.077, y ≤ .0014) were formed by solid phase epitaxy from C implanted, preamorphized substrates using a 30 Minute 700° C anneal in N2. The occupancy of C in substitution lattice sites was monitored by Fourier Transform Infrared Absorption spectroscopy. The layer strain was monitored by rocking curve x-ray diffraction and the structural changes in the layers were determined using plan-view and X-sectional transmission electron Microscopy (TEM). For anneals of 1150° C or above, all the substitutional C was lost from the Si lattice after 30 seconds. TEM verified that the strain relaxation was the result of C precipitating into highly aligned βSiC particles rather than by the formation of extended defects. No nucleation barrier was observed for the loss of substitutional C Preliminary results will also be discussed for Si1-x-yGexCy/Si heterostructures where there is the additional factor of the competition between strain energy and the chemical driving forces.
Crystallization Processes In Poly (Ethylene Terephthalate) / Polycarbonate Blends
Authors: Reinsch Veronika E. , Rebenfeld Ludwig 
Published: March 2011

ABSTRACTBlends of poly (ethylene terephthalate), or PET, and polycarbonate (PC) over a range of compositions were studied in isothermal crystallizations from the melt using differential scanning calorimetry (DSC). Both crystallization rate and degree of crystallinity of PET depend on blend composition. The glass transition temperature, Tg, of PET and PC in blends and pure polymer were also measured by DSC. Elevation of the Tg of PET and depression of the Tg of PC are observed upon blending. In cooling scans, dynamic crystallization from the melt was observed. In PET/PC blends with high PC content, a novel dual-peak crystallization of PET was observed. The effects of thermal history on crystallization kinetics and degree of crystallinity were also determined in isothermal crystallization studies. For Melt processing times between 1 and 30 Min and for processing temperatures between 280 and 300 °C, Melt processing temperature was seen to have a stronger effect than processing time.
The Evolution of Sol-Gel Films in the Environmental Scanning Electron Microscope.
Authors: Mckernan Stuart , Wright John , Francis Lorraine F. 
Published: March 2011

ABSTRACTThe ability to study the surface texture of a sol-gel film of lead titanate as it is heated in-situ in an environmental scanning electron microscope is demonstrated. Measurements of the shrinkage of the film at cracks and around delaminations of several microns have been Made. Grain sizes of the final crystalline microstructure were determined to be ∼ 0.2 μm. The formation of bumps in the film 1–5 μm in size was observed. The presence of these features may correlate with the onset of crystallization.
The Pyrolytic Conversion of Perhydropolysilazane into Si3N4: X-Ray Diffraction Analysis
Authors: Blanchard Cheryl R. , Schwab Stuart T. 
Published: March 2011

ABSTRACTX-ray diffraction analysis was used to study the pyrolytic conversion of a preceramic polysilazane into Si3N4. Quantitative data for crystallite size, phase composition, and degree of crystallinity versus pyrolysis temperature and atmosphere (N2 and NH3) are presented. Pyrolytic products produced under N2 and NH3 atmospheres consist of microcrystals of silicon and a- and β-Si3N4. Under both atmospheres, a majority of the char is crystalline at ∼ 1270°C, and the entire char is crystallized at 1400°C. Pyrolysis under an NH3 atmosphere produces near stoichiometric Si3N4, while pyrolysis under N2 produces a silicon-rich material.
Crystallization Process and Chemical Disorder in Flash Evaporated Amorphous Gallium Antimonide Films
Authors: Dias Da Silva J. H. , Cisneros I. , Cardoso L. P. 
Published: March 2011

ABSTRACTIn this work we describe a flash evaporation system specially built to produce Amorphous films of III-V compounds and characterize GaSb films using optical, electrical and X-Ray diffraction Measurements. Changes in the composition of the GaSb samples were obtained by the use of different crucible temperatures. In such samples, consequently, the optical absorption edge and the DC electrical conductivity were Modified. The departure from stoichiometry in GaSb films is analyzed on the basis of these results which can be used as an evidence of the chemical disorder. This kind of disorder is represented by either wrong bonds or sites with different coordination.Thermal annealing with a sequence of increasing temperatures first induced detectable variations in the optical absorption edge and in the vibrational properties of the Amorphous GaSb. These variations are compatible with the GaSb local ordering and were observed by Raman scattering and infrared absorption spectra. The annealing at higher temperatures allowed the crystallization of the material confirmed by X-Ray diffraction. From these experimental results a crystallization mechanism based on the segregation of Sb excess coming from the crystallized regions toward the Amorphous tissue is proposed.
Lateral Grain Growth in the Excimer Laser Crystallization of Poly-Si
Authors: Kuriyama H. , Sano K. , Ishida S. , Nohda T. , Aya Y. , Kuwahara T. , Noguchi S. , Kiyama S. , Tsuda S. , Nakano S. 
Published: March 2011

ABSTRACTWe have succeeded in obtaining nondoped, thin poly-Si film (thickness ∼500Å) with excellent crystallinity and large grain size (Maximum grain size ∼4.5 μ m) by an excimer laser annealing Method, which offers the features of low-temperature processing and a short processing time. The grain size distribution shrinks in the region around 1.5 μ m and this poly-Si film exhibits a strong (111) crystallographic orientation. Poly-Si thin film transistors using these films show quite a high field effect mobility of 440cm2/V · s below 600°C process.
Excimer Laser Crystallization of Amorphous Silicon Films for Poly-Si TFT Fabrication
Authors: Tanabe Hiroshi , Sera Kenji , Nakamura Ken-Ichi , Hirata Kazumi , Yuda Katsuhisa , Okumura Fujio 
Published: March 2011

ABSTRACTExcimer laser crystallized silicon films have been studied as a function of the number of laser shots, and the influence of the use of such polycrystalline films in thin film transistors (TFTs) has also been investigated. It is found that electron Mobility, one of the most important of all TFT characteristics, increases monotonically with the number of irradiations, with maximum mobility being obtained at about 20 shots. This result is not due to grain size, since transmission electron microscopy indicates that the number of laser shots does not affect grain size in polycrystalline silicon films. Raman studies and TFT carrier transport analysis, on the other hand, suggest that this increase in electron mobility may be explained by the decrease in grain boundary defects and defects inside grains.
Compamson in the Growth and Properties of rf Sputtered μc-Si:H and Glow Discharge-Chemical Vapor Deposited μc-Si:H Films
Authors: Lin J. Y. , Tseng B. H. , Hsu K. C. , Hwang H. L. 
Published: March 2011

ABSTRACTProperties of μc-Si:H films grown by rf sputtering and by glow discharge-chemical vapor deposition (GD-CVD) using diluted-hydrogen and hydrogen-atom-treatment method were compared employing TEM, X-ray diffraction, Raman scattering and FT-IR. The films deposited by both methods all exhibited comparable grain sizes in the range of 10–18 nm. and showed the same tendency in almost all the Measurements.
The Sensitivity of Small Molecule Sorption to Annealing in Glassy Liquid Crystalline Polymers
Authors: Morisato Atsushi , Miranda N. R. , Willits J. T. , Cantrell G. R. , Freeman B. D. , Hopfenberg H. B. , Makhija S. , Haider I. , Jaffe M. 
Published: March 2011

ABSTRACTThe sorption of organic penetrants is found to be sensitive to thermal annealing conditions in a series of glassy, nematic, thermotropic, random copolyesters. Controlled thermal annealing of two polymers in this series permitted a systematic variation of chain packing and, presumably, higher order molecular suprastructure, ranging from a disordered amorphous morphology to More ordered nematic liquid crystalline and semi-crystalline morphologies. The development of liquid crystalline order appears to reduce or preclude small molecule solubility in nematically ordered forms of these polymers.
Mechanical Properties of Plated Copper
Authors: Korhonen M. A. , Brown D. D. , Li C.-Y. , Steinwall J. E. 
Published: March 2011

AbstractBoth electrodeposited and electroless copper are widely used in the electronics industry to form signal lines and plated-through holes in printed circuit cards and boards. Because of widely differing thermal expansion coefficients of copper and of the ceramic and polymeric substrates, large mechanical stresses develop in the metallization during thermal cycles, as e.g. during solder reflow. To safeguard against premature fracture it is imperative that the metallization is sufficiently ductile. Plated thin foil copper of poor ductility is known to be susceptible to cracks in plated-through holes which, besides causing problems in the manufacture, poses a threat to device reliability in service. In this paper we show that such cracks arise as a combination of reduced ductility due to presence of initial porosity in copper and due to grain boundary sliding and diffusional cavity growth during the soldering cycle. We emphasize that there exists strong interactions between these ductility reducing effects, such that their coupled action may exceed the effect when each mechanism operates independently. We review recent research on deformation and fracture of bulk and plated copper between RT and 300°C. Finally, we briefly discuss approaches to improve mechanical properties of plated thin foil copper.
Models for the Thermomechanical Behavior of Metal/Ceramic Laminates
Authors: Spearing S. M. , Tenhover M. A. , Lukco D. B. , Viswanathan L. , Hollen D. K. 
Published: March 2011

AbstractMetal/ceramic bilayers fracture by one of three failure modes; crazing, spalling or interfacial failure. Models for these failure modes are developed. The results are presented as maps that can be used in the design and failure analysis of electronic packages. Examples are presented for several material systems, including A1N.