bluuebunny/crossref_metadata_2025_split huggingface dataset:
Are Gel-Derived Glasses Different from Ordinary Glasses?
Authors: Weinberg M. C. 
Published: March 2011

ABSTRACTA review is presented of some of the previously reported differences and similarities between comparable gel glasses (and gels) and ordinary glasses. In this regard, considerations are made with respect to such factors as structure, physical and thermal properties, and phase transformation behavior. A variety of silicate lass compositions are used for illustrative purposes. The discussion is roughly ivided into two sections; low and high temperature behavior. At low temperatures one anticipates that differences between gel and conventional glasses will exist, but such dissimilarities are not expected to persist to high temperatures. However, experimental evidence is presented which indicates the perpetuation of such differences to very high temperatures. A partial resolution for this anomalous behavior is offered.
Electron-Spin Resonance and other Spectroscopies used in Characterizing Sol-Gel Processing
Authors: Klein L. C. , Kordas G. 
Published: March 2011

ABSTRACTThe molecular structure of sol-gel processed silica can be studied using electron-spin resonance (ESR) spectroscopy. Spectra reveal changes in structure from sol to gel and from gel to glass. Gels prepared under various conditions contain intrinsic and extrinsic defects. Other spectroscopies that have been used to investigate gels are nuclear magnetic resonance (NMR), Raman, and visible.
The Need for Controlled Heterogeneous Nucleation in Ceramic Processing
Authors: Messing Gary L. , Mcardle James L. , Shelleman Richard A. 
Published: March 2011

ABSTRACTThe principles underlying controlled heterogeneous nucleation are reviewed. The application of these principles for the preparation of ceramic powders with equiaxed morphology and narrow size distribution is illustrated with examples from the literature and our recent work on alumina. It is concluded that controlled heterogeneous nucleation will be an important factor in fully realizing the benefits of chemically derived polycrystalline ceramics.
Comparison of Clay-Water Systems With Aluminum Hydroxide Gels Prepared in Acidic Media
Authors: Pierre A. C. , Uhlmann D. R. 
Published: March 2011

ABSTRACTAlumina sols made by the hydrolysis of aluminum sec-butoxide in an acidic medium have been found to show behavior during drying and aging which appears similar to that reported for gels in a number of clay-water systems. Structural and phenomenological characteristics of these two classes of materials are compared. The extension to aluminum hydroxide systems of the models proposed to explain the gelation of clay sols are discussed, and a model is presented to describe the gelation behavior of aluminum hydroxide sols.
Molecular Dynamics Modeling of the Structural Failure of Glass
Authors: Simmons Joseph H. , Montrose Charles J. 
Published: March 2011

ABSTRACTMolecular Dynamics (MD) methods for modeling the structure and kinetic behavior of ceramics and glasses are reviewed and discussed while emphasizing the effect of various potential functions on the structure developed and the relevance of model calculations. Two dynamic experiments from the authors’ research are used as examples of modeling technique and interpretation of results. In the first, a Lennard-Jones force function is used to model the behavior of viscous liquids under large deformations. In the second, the brittle response of amorphous SiO2 modeled with an ionic Born-Mayer-Huggins interparticle potential is investigated at very high deformation rates. A comparison of results with experiment show the limitations and the great promise of the MD approach.
Ceramic Microstructure-Property Fractal-Diffractal Calculus : Static Synergetics Yield Optimization During Processing Via Real–Time Q.A.and Interactive Q.C
Authors: Siegel Edward 
Published: March 2011

ABSTRACTCeramic microstructure-property relationships dominate any and all attempts at“better ceramics through chemistry”. Required is some universal calculus to allow analytic, universal, reversible scalable computation of one from the other. Static Synergetics universality-principle provides such a flexible versatile tool, heretofore not available. It is a reexpression of the very basic three laws of thermodynamics into r-,k-,and w-domainsthe equivalence of(symmetry-breaking/defect) Pattern-recognition(the “structure”) to signal-processing(the frequency-dependent FM) properties/ Functions. More basically, it is a manifestation of Noether's theoremthe basis of mechanics and orgin of the energy continuity equation that is the thermodynamic first law. Such an algorithm, the”software”of yield optimization(quality and quantity) real-time Q.A. and(in parallel with a specificity dominated process- model)interactive Q.C.requires as “hardware”produced input the small-angle-scattering(SAS)dominated diffraction-pattern/static structure factor SSAS(k) or Fourier transform r-domain Pattern/ photomicrograph-recognition imaging(of processing-introduced property-detrimental defects(heterogeneity heirarchy)). Output are universal FM:I/f flicker(voltage and/or current)noise power spectrum, signal-to-noise ratio over dynamic rangemulti-level system dominated anomalous low temperature/frequency thermalracoustic. properties, and 1/f relaxation response susceptibility polarization catastrophe derived dielectric, electrical, optical, noise, viscoelastic/mechanicalmagnetic,...property Functions. Input can be the ubiquitous,...universal Mandelbrot fractals,dominating ceramics;output(and internal)Functions are Berry-Nye-Jakeman wdomain diffractals,dominating all properties universally.How and Why it works are detailed exactly;universality, reversibility and scalability are analytically insured for self-similar(or selfaffine) fractal scaling-relation Pattern-recognition input;approximate. deviations from universal Functions output obtains from less than perfect mathematically ideal fractal scaling-relation Pattern-recognition input.Static Synergetics provides a new practical use for external radiation small-angle-scattering(SAS) diffraction-pattern/static structure factor measurements in ceramic material microstructure-property relationships during processing
Ceramics From Hydridopolysilazane
Authors: Legrow Gary E. , Lim Thomas F. , Lipowitz J. , Reaoch Ronald S. 
Published: March 2011

ABSTRACTThe Advanced Ceramics Based on Polymer Processing Program is sponsored by the Defense Advanced Research Projects Agency (Materials Science Division). The objectives of the program include development of a family of Si-C, Si-N, and Si-C-N ceramic fibers which may be used for reinforcement in ceramic, metal and plastic matrices, and development of economical process technology for fabricating ceramic matrix composites with high fracture toughness, high temperature performance and no inherent limitations to forming complex shapes. Attainment of these objectives would circumvent two limitations of existing ceramic material technology - lack of design reliability due largely to catastrophic failure related to brittleness, and inability to fabricate complex shapes [1].
29Si NMR, Sec and Ftir Studies of The Hydrolysis and Condensation of Si(OC2H5 )4 and Si2O(OC2H5)6
Authors: Lin Chia-Cheng , Basil John D. 
Published: March 2011

ABSTRACTThe hydrolysis and initial condensation reactions of Si(OC2H5)4 and low order polyethoxysiloxanes have been studied with high resolution 29Si NMR and size exclusion chromatography/FTIR spectroscopy. The effects of various parameters such as H2O/TEOS mole ratio, catalyst, pH, solvent, temperature and aging have been observed in the different nature of the reaction products. The products include partially hydrolyzed and unhydrolyzed Si(OC2H5)4, Si2O(CH2H5)6, and Si3O2(OC2H5)8. The rate of formation and concentration of each product obtained under different conditions provides information about the reactivity of various silanol-containing species and the factors that affect the overall reaction scheme.
Zirconia Characterization by Perturbed Angular Correlation Spectroscopy
Authors: Jaeger Herbert , Gardner John A. , Haygarth Ohn C. , Rasera Robert L. 
Published: March 2011

ABSTRACTPerturbed Angular Correlation spectroscopy of 181Ta nuclei occupying cation sites has been used to investigate microscopic structural properties of several pure and stabilized zirconia materials. The PAC spectra are used to derive the electric field gradients at the tracer nucleus. Thse are compared with calculations based on a simple point-ion model. Agreement between experiment and theory is good for stabilized material and qualitatively reasonable for pure zirconia.
EPR of Cu(II) in Sol-Gel Prepared SiO2 Glass
Authors: Dave S. , Maccrone R. K. 
Published: March 2011

ABSTRACTSiO2 glass has been prepared by the hydrolysis of TEOS in alcohol using HCl and NH4OH to control the pH. Copper ions were incorporated from the acetate to act as structural probe ions during the process of gellation and calcination. The local structure of copper ions was investigated using EPR determined at 300 K and 10 K.It was found that the pH of the solution had a profound effect on the EPR spectra of the copper in the gels and glasses, indicating differences in the local structure.
Microporous Layers from Sol-Gel Techniques
Authors: Larbot A. , Alary J. A. , Fabre J. P. , Guizard C. , Cot L. 
Published: March 2011

ABSTRACTIn separative process, the use of mineral membranes instead of organic ones is more interesting for it offers numerous advantages as follows :- High temperature and pressure resistant (no compression of the membrane).- Corrosion and abrasion resistant.- Not sensitive to bacterial action.- Steam sterilisable.- Longer life time.
Effects of Hydrolysis On Metallo-Organic Solution Deposition of PZT FILMS
Authors: Lipeles Russell A. , Coleman Dianne J. , Leung Martin. S. 
Published: March 2011

ABSTRACTThe effects of hydrolysis on the degree of polymerization during metallo-organic solution deposition of lead zirconate titanate (PZT) films have been investigated. The reaction of lead 2-ethylhexanoate, zirconium n-tetrapropoxide, and titanium tetrabutoxide in isopropanol with water were studied using thermogravimetry, specular reflectance Fourier transform infrared spectroscopy (FTIR) and optical and electron microscopy.Films prepared from coating solutions having varying amounts of water exhibited dramatic differences in morphology. The films were spin-coated on platinum coated fused silica substrates and annealed at 525°C for 30 minutes. Unhydrolyzed coating solutions and solutions with a mole ratio of water to total metal of 0.5 yielded perovskite films with 0.5–5μm grains. A mole ratio of 1.5 (the amount of water required to completely hydrolyze the metallo–organics in the solution) formed amorphous, porous films. The stability of the prepolymerized films inhibits crystallization and densification at moderate temperatures.
Iron-Oxide and Yttrium-Iron-Oxide Thin Films a Test of the Feasibility of Producing and Measuring Micro- and Millimeter-Wave Materials
Authors: Bruce Ralph W. , Kordas George 
Published: March 2011

ABSTRACTTin-oxide/iron-oxide and yttrium-iron-oxide thin-films have been produced with the sol-gel method. Film thicknesses from 50 to 155 nm were deposited by the sol-to-gel transformation onto borosilicate substrates. The dielectric losses of the films were deduced by the complex reflection coefficient of these materials in the range from 2 GHz to 18GHz using an HP network analyzer.Samples of 5 cm × 5 cm were centered on the waveguide flange and a shorting plate (12.2 cm × 15.2 cm) of brass centered over the sample. Measurements were automatically made using the HP software provided.In the X-Band region, three absorption bands at 8.3, 9.4, and 11.5 GHz were detected for the substrate, with losses (absorption peaks) ranging from 13.5, 11.9, and 9.9, respectively. For the tin-oxide/iron-oxide sol-gel coated substrate, three bands at 8.4, 9.5, and 11.6 GHz were observed having losses of 16.2 to 13.4, 12.9 to 11.4. and 11.3 to 9.7, respectively, depending upon thickness and orientation. For the yttrium-iron-oxide sol-gel coated substrate, three bands at 8.4, 9.5, and 11.6, with losses depending upon solgel thickness and orientation.
Siloxane Modified Sio2-TiO2 Glasses Via Sol-Gel
Authors: Parkhurst C. S. , Doyle W. F. , Silverman L. A. , Singh S. , Andersen M. P. , McClurg D. , Wnek G. E. , Uhlmann D. R. 
Published: March 2011

ABSTRACTPolydimethylsiloxane [PDMS]-modified SiO2-TiO2, glasses have been prepared via the sol-gel route. Polymer compositions varied between 17 and 67 wt% PDMS, using PDMS of molecular weights 1,700 and 36,000. Also varied was the Si/Ti ratio for a given polymer content and the nature of the Ti alkoxide.A general synthetic procedure was found which made optically clear samples. Dense monolithic structures were obtained at room temperature for all compositions. The room temperature densification is attributed to relaxation and flow in the sample due to the presence of the polymer. The effects on properties of the overall composition and molecular weight of the polymer are reported, and implications in terms of structural models are considered.
Oxide -Non-Oxide Composites By Sol-Gel
Authors: Pope Edward J. A. , Mackenzie J. D. 
Published: March 2011

ABSTRACTIn this paper, three types of composites prepared using the sol-gel process are examined. Porous composites, based upon the dispersion of solid, oxide and non-oxide ceramic particles in a sol-gel derived matrix are described. A transparent composite, prepared by the impregnation of a polymer phase into a porous gel matrix is presented. Light-weight, “triphasic” composites, possessing good abrasion resistance and high fracture ductility, can also be fabricated by the polymer impregnation of a porous gel composite.
Raman Studies of Carrier Activation in Laser Annealed GaAs Capped with Silicon Nitride
Authors: Compaan A. , Abbi S. C. , Yao H. D. , Bhat A. , Hashmi F. 
Published: March 2011

AbstractCarrier concentrations exceeding 1019/cm3 in GaAs implanted with Si (2 × 1014/cm2 @ 140 keV) have been obtained by pulsed laser annealing with either a dye laser (λ = 728 nm) or a XeCl excimer laser (λ = 308 nm). Carrier concentrations were measured by plasmon Raman scattering over a wide range of anneal energy densities. Compared with capless laser annealing, much higher carrier activations were achieved when the annealing laser pulse was incident through a Si3N4 cap.
Reactive Quenching at Liquid-Solid Interface Induced by Pulsed Ruby Laser Treatment: Aqueous Oxidation of Iron.
Authors: Ogale S. B. , Patil P. P. , Phase D. M. , Kulkarni S. A. , Ghaisas S. V. , Bhide V. G. 
Published: March 2011

AbstractThis paper demonstrates that metastable compounds can be synthesized on solid surface via pulsed laser induced processes at the liquid solid interface. Specifically, it is shown that the metastable oxides of iron can be obtained when an iron foil immersed in water is treated with Ruby Laser pulses [ λ =693.4 nm, pulse width 30 ns, energy density 10 J/cm2].The oxide has been characterized by using the techniques of conversion electron Mössbauer spectroscopy, X-ray diffraction and Rutherford Backscattering Spectrometry. The oxygen concentration near the surface as well as the depth scale over which it falls to zero can be varied by changing the laser treatment parameters such as pulse to pulse overlap, energy per pulse etc. A near-surface composition of ∼50 at.% and a depth scale of oxygen incorporation of a few thousand A° can be easily achieved. The phase transformation of a metastable oxide under thermal treatment is also explored. The mechanisms which could be responsible for the observed effects are commented upon. Some iron foils have been treated in air using comparable laser pulse parameters to obtain a comparision between treatment in air and liquid. Interestingly these foils show presence of √-Fe, which is a high temperature phase of iron known to be unstable at room temperature when pure. Other possible applications of laser processing of solids in liquid media are also discussed.
Pulsed Laser Induced Melt and Phase Transformation of Ni Silicide Layers on Si Substrate
Authors: Baeri P. , Grimaldi M. G. , Priolo F. , Rimini E. , Cullis A. G. , Chew N. C. 
Published: March 2011

AbstractThermally grown Ni2 Si and NiSi2 layers on <111> Si substrates were irradiated by 40 ns Nd laser pulses in the energy density range 0.3–2.0 J/cm2. The samples were analyzed by time-resolved reflectivity, 2.0 MeV He+ Rutherford backscattering in combination with channeling and by transmission electron microscopy. In the NiSi2/Si system the melt starts at the free surface (1280 K) and propagates towards the inside. Dissolution of substrate silicon atoms occurs when the silicon temperature reaches the liquidus temperature (1400 K). In the Ni2Si/Si samples the melt starts instead at the interface when it reaches the eutectic temperature (1250 K). The subsequent propagation towards the surface is limited by the mass transport of silicon atoms to maintain a composition near that of the eutectic. In some cases the surface may melt also at the congruent melting temperature (1570 K), giving rise after solidification to a quite complex structure. The different behaviour of the two silicides/silicon systems is explained in terms of phase diagram.
A Hydrodynamic Study of Laser-Induced Vaporization of Aluminum in Vacuum
Authors: Brost G. A. , Bohn C. L. , Crawford M. L. , Mullins B. W. 
Published: March 2011

AbstractThe three-dimensional hydrodynamics of laser-induced, steady state vaporization of aluminum (2024) in vacuim was investigated with the aid of both a hydrodynamic computer code and a Mach-Zender interferometer. Provided the laser beam is sufficiently intense, a vapor plasma forms, resulting in a sustained region of high pressure near the target. The pressure is distributed asymmetrically over the footprint in the case of oblique incidence.
Time-Resolved Crystallization of GeTe
Authors: Huber E. , Marinero E. E. 
Published: March 2011

AbstractAmorphous thin films of GeTe were irradiated with excimer laser pulses and the subsequent crystallization was investigated utilizing simultaneous transient reflectivity and conductivity measurements. Below a threshold fluence of 15 mJ/cm2 pure thermal behaviour was found. Above that value, nucleation and growth are observed during the cooldown process. Above a fluence of 22 mJ/cm2 the films crystallize to a large degree within 200ns. Between 15 and 22 mJ/cm2 crystallite nuclei are formed (“frustrated crystallization”), and application of a subsequent pulse over areas exposed to this fluence regime leads to extremely fast crystallization (50 ns).
Analysis of Picosecond Pulsed Laser Melted Graphite
Authors: Steinbeck J. , Braunstein G. , Speck J. , Dresselhaus M. S. , Huang C. Y. , Malvezzi A. M. , Bloembergen N. 
Published: March 2011

AbstractA Raman microprobe and TEM have been used to analyze the resolidified region of liquid carbon generated by picosecond pulse laser radiation. From the relative intensities of the zone center Raman-allowed mode for graphite at 1582cm−1 and the disorder-induced mode at 1360cm−1 , the average graphite crystallite size in the resolidified region is determined as a function of incident pulse energy density. By comparing with Rutherford backscattering spectra and Raman spectra from nanosecond pulsed laser melting experiments, additional information about the disorder depth in picosecond pulsed laser melted graphite is obtained. Comparisons of TEM micrographs for nanosecond and picosecond pulsed laser melting experiments show that the structure of the laser disordered regions in graphite are similar and exhibit similar behavior with increasing laser pulse fluence. The similarities in the resolidified regions under both irradiation schemes discourages a determination of the properties of liquid carbon after the liquid has resolidified.
Effects of Impurities on the Kinetics of Nucleation and Growth in Amorphous Silicon
Authors: Roth J. A. , Olson G. L. 
Published: March 2011

AbstractThe effects of intentionally introduced impurities on the crystallization time, nucleation rate and crystallite growth velocity during solid phase random crystallization of amorphous Si thin films have been determined. Films deposited in UHV onto oxidized Si wafers were subjected to multiple energy ion implantation to introduce uniform distributions of P, B, As, O or F at 0.1–1.0 at.%. Crystallization times and growth velocities were determined over the temperature range 650 to 850°C from time-resolved reflectivity measurements, and nucleation rates were determined from these data using a classical, steady state nucleation and growth model. Strong impurity effects are observed: P, B and As all decrease the nucleation rate but accelerate the growth of crystallites, whereas both 0 and F retard growth while enhancing nucleation. The largest effects are for P, which reduces the nucleation rate more than 100 times at 1% concentration, and F, which increases the rate by roughly the same amount.
Surface Alloys of Icosahedral AlMnSi with Phason Distortions
Authors: Follstaedt D. M. , Knapp J. A. 
Published: March 2011

AbstractThe microstructures produced by electron-beam melting and by ion-beam mixing Al/Mn and Al/Mn/Si layers on Si substrates are examined. The treatments were found to incorporate Si from the substrate into the surface alloy. Several phases formed, depending on treatment, including α- and β-AlMnSi, μ-AlMn (epitaxial on Si{111}), and amorphous and icosahedral AlMnSi. The observed microstructures relate the novel icosahedral phase to other phases and elucidate its formation kinetics. Diffraction patterns from large icosahedral grains (up to 5 μm) show distortions in the position and shape of weak (but not strong) reflections, as predicted for phason defects in a quasicrystalline lattice, one of the structures proposed for icosahedral phases.
Ion Implantation and Annealing of Oxides
Authors: White C. W. , Boatner L. A. , Sklad P. S. , Mchargue C. J. , Pennycook S. J. , Aziz M. J. , Farlow G. C. , Rankin J. 
Published: March 2011

AbstractIon implantation damage and annealing results are presented for a number of crystalline oxides. In A12 O3, the amorphous phase produced by ion bombardment of the pure material first crystallizes in the (crystalline) γ phase. This is followed by the transformation of γ-Al2 O3 to α-A12O3 at a well defined interface. The activation energy for the growth of α alumina from γ is 3.6 eV/atom. In CaTiO3, the implantation-induced amorphous phase transforms to the crystalline phase by solid-phase epitaxy (SPE). ZnO is observed to remain crystalline even after high implantation doses at liquid nitrogen temperatures. The near surface of KTaO3 is transformed to a polycrystalline state after implantation at room temperature or liquid nitrogen temperature.
Mg Implantation and Characterization of Sapphire Surfaces
Authors: Jardine A. P. , Mukhopadhyay S. Mitra , Blakely J. M. 
Published: March 2011

AbstractMg ion-implantation of A12O3 wafers followed by air annealing at high temperatures was investigated as a way to provide bulk doped samples for studies of Mg surface segregation and its effect on surface mass transport. SIMS was used to analyse Mg concentrations in implanted and unimplanted near-surface regions and in the bulk. It was found that the concentration of Mg decreases dramatically with depth from both surfaces of an annealed wafer and is also observed in the bulk. These observations are attributed to bulk diffusion of the Mg combined with equilibrium surface segregation. Surface mass transport associated with the (1120) surface of an A12 O3 single crystal wafer doped and equilibrated by such a method was studied by the grating decay method; the Mg doped sample showed a decay rate in air higher than that in the undoped wafer by a factor of ∼ 2.4 at 1500°C.