作者：
MILLER, SFSCHOBERT, HHFuel Science Program
Department of Materials Science and Engineering Pennsylvania State University Pennsylvania 16802 University Park United States
Beulah (North Dakota) lignite was fired in both pulverized and coal-water slurry form to study the effect of fuel form and rank on ash formation processes. The fuels were burned in a down-dired pilot-scale combustor a...
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Beulah (North Dakota) lignite was fired in both pulverized and coal-water slurry form to study the effect of fuel form and rank on ash formation processes. The fuels were burned in a down-dired pilot-scale combustor at 316 MJ/h. In both of the Beulah fuels, organically bound sodium was important in the formation of micrometer and submicrometer sodium sulfate particles and coatings on larger silicate and aluminosilicate particles. The presence of sulfates indicates the importance of sulfur fixation by alkaline elements during combustion. Organically bound calcium is highly reactive within the char particle, participating in the formation of mixed aluminosilicates during char burnout;calcium is not associated with sulfur and does not appear to react outside of the char particle. The form in which the Beulah coal was fired, i.e., pulverized or as a CWSF, had no appreciable effect on the behavior of the alkalis and sulfur during combustion.
A number of equivalent exact and useful approximate equations for the liquidus of with near unity and with congruently melting end members are obtained. These are general in so far as the liquid phase is concerned, ex...
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A number of equivalent exact and useful approximate equations for the liquidus of with near unity and with congruently melting end members are obtained. These are general in so far as the liquid phase is concerned, except that the forms written for associated solution models of the liquid depend upon the species assumed. The congruent melting of the end members leads to important, usually ignored, links between the thermodynamic properties of the liquid and those of the binary compounds. It is shown that the common assumption that the heat capacity of a binary, end member, compound equals that of its supercooled liquid is generally incorrect and is unnecessary. The results are applied to a number of recent analyses of liquidus surfaces and lines.
Intensified plasma-assisted processing (IPAP), is a surface modification technique developed recently in our laboratory. Plasma intensification is accomplished by triode discharge and can be utilized for low-pressure,...
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Intensified plasma-assisted processing (IPAP), is a surface modification technique developed recently in our laboratory. Plasma intensification is accomplished by triode discharge and can be utilized for low-pressure, low-temperature diffusion treatments and synthesis of a range of advanced compounds. The energetic flux of ions and neutrals generated in IPAP can create highly favorable surface conditions producing significant improvements in properties ranging from thermal and chemical stability to wear resistance. The objective of the present study was to investigate further the role of energetic particle bombardment on the modification process. IPAP nitriding experiments were carried out on Ti-6Al-4V substrates at specific nitrogen flux levels and Bur energies. Parallel experiments were performed by low-energy, broad-beam nitrogen implantation at comparable ion energies and dose levels. Nitrogen concentrations and penetration depths were determined by depth profiling using AES and microhardness measurements. The experimental results were used to derive effective nitrogen diffusivities to assess the effect of the energetic particle bombardment on the diffusion process. For both IPAP and ion implantation, nitrogen diffusion into titanium nitride and solid solution layers is greatly accelerated compared to conventional ion nitriding. IPAP is almost as effective as low-energy ion implantation in enhancing nitrogen penetration when the two processes use ions of similar energies and dose levels. The energetic neutrals present in IPAP appear to further enhance the growth of surface nitride layers. Analysis also indicates that an optimal ion energy may exist. (C) 1997 Elsevier science S.A.
We subjected vertical boreholes drilled in cubical specimens of Cordova Cream to a 3-dimensional stress field, and increased one or both of the horizontal principal stresses until breakout failure occurred. Acoustic e...
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We subjected vertical boreholes drilled in cubical specimens of Cordova Cream to a 3-dimensional stress field, and increased one or both of the horizontal principal stresses until breakout failure occurred. Acoustic emission, borehole strain, and visual monitoring of the borehole wall during testing revealed four stages of breakout development: crack initiation, extension, breakout formation, and stabilization. Thin section analysis suggests that breakout formation in Cordova Cream is the result of shear failure mechanism. The relationships at breakout stabilization between the two horizontal principal stresses and between the span at the borehole wall and the least horizontal stress suggest a potentially simple method of estimating the far-field state of stress if 'breakouted' borehole geometry is accurately mapped.
Areas under the linear tan δ–temperature (tA) and linear loss modulus–temperature (LA) curves of the polyacrylate and polymethacrylate homologous series and their interpenetrating polymer networks (IPNs) were inves...
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Areas under the linear tan δ–temperature (tA) and linear loss modulus–temperature (LA) curves of the polyacrylate and polymethacrylate homologous series and their interpenetrating polymer networks (IPNs) were investigated. For poly(methyl acrylate), LA values are independent of crosslinking level through 25%, but tA decreases. With increasing side group length, on the other hand, tA remains nearly independent of side group length for both homologous series, having values near 50 and 65 (units of K) for the acrylate and methacrylate series, respectively. However, LA decreases steeply with increasing side group length. A phenomenological treatment of areas is presented in order to explain tA and LA behavior semiquantitatively. Both tA and LA exhibit areas characteristic of the structure of the particular polymers. The homopolymer LA areas are additive in determining the area under the corresponding curve for the IPN. This suggested a group contribution analysis for LA, where each moiety contributes specific values to the area.
A quasicrystalline model of a binary liquid in which two sublattices containing randomly distributed vacancies is developed via statistical thermodynamics. The relative partial molar quantities are obtained. The const...
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A quasicrystalline model of a binary liquid in which two sublattices containing randomly distributed vacancies is developed via statistical thermodynamics. The relative partial molar quantities are obtained. The constraints imposed upon the adjustable model parameters to ensure that the Schottky constant increases with increasing temperature but never exceeds unity are developed, as well as the constraints entering upon application to a AC system forming a congruently melting, narrow homogeneity-range compound AC (s). The model is an extension of an earlier version for liquids and of analogous models for narrow homogeneity-range compounds, AC (s), in that the excess Gibbs energies of vacancy creation are cubic functions of the atomic fraction. The model is also an alternative to associated solution models which would assume a single equiatomic associated species. The model is then applied to systems of varying polarity but all forming a narrow homogeneity-range crystalline compound whose stoichiometric composition is 50 at. pct. Quantitatively good fits are obtained for the Hg-Te, Cd-Te, Zn-Te, and Pb-Te systems and, for the first three systems, are comparable to fits obtained with the associated solution model using the same experimental data. Quantitatively good fits are also obtained for the less polar In-Sb and Ga-Sb systems, and these are comparable to those obtained by us with a Margules-type model in which the enthalpy of mixing for the liquid is a quartic function of atom fraction and a quadratic function of temperature. Finally, the predictions for the enthalpy of mixing at temperatures above the present range of experimental data are given and discussed for the various systems and models. It appears the model given here is appropriate for the type of systems tested.
High-energy mechanical attrition of Ag powders was conducted at the liquid nitrogen temperature without using process control agents. This process improves the milling efficiency and yields powders with truly nanocrys...
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High-energy mechanical attrition of Ag powders was conducted at the liquid nitrogen temperature without using process control agents. This process improves the milling efficiency and yields powders with truly nanocrystalline grain structure. The microhardness and grain growth behavior at different storage temperatures, as well as the excess enthalpy introduced by milling, have been studied and compared with the results for nanophase Ag prepared using other methods.
Classical spin liquids (CSLs) are intriguing states of matter that do not exhibit long-range magnetic order and are characterized by an extensive ground-state degeneracy. Adding quantum fluctuations, which induce dyna...
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Stretchable energy storage devices,maintaining the capability of steady operation under large mechanical strain,have become increasing more important with the development of stretchable electronic *** supercapacitors(...
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Stretchable energy storage devices,maintaining the capability of steady operation under large mechanical strain,have become increasing more important with the development of stretchable electronic *** supercapacitors(SSCs),with high power density,modest energy density,and superior mechanical properties are regarded as one of the most promising power supplies to stretchable electronic *** polymers,such as polyaniline(PANI),polypyrrole(PPy),polythiophene(PTh)and poly(3,4-ehtylenedioxythiophene)(PEDOT),are among the well-studied electroactive materials for the construction of SSCs because of their high specific theoretical capacity,excellent electrochemical activity,light weight,and high *** effort has been devoted to developing stretchable,conductive polymer-based SSCs with different device structures,such as sandwich-type and fiber-shaped type *** review summarizes the material and structural design for con ductive polymer-based SSCs and discusses the challenge and importa nt di recti ons in this emergi ng field.
The gasification reactivity of an Illinois No. 6 bituminous coal char was determined in oxygen and carbon dioxide using thermogravimetric analysis (TGA). Extensive tests were carried out to ensure the absence of diffu...
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The gasification reactivity of an Illinois No. 6 bituminous coal char was determined in oxygen and carbon dioxide using thermogravimetric analysis (TGA). Extensive tests were carried out to ensure the absence of diffusional limitations. Measurements of chemically controlled rates were verified by analysing the activation energies for reactions of the char at various conversion levels. The effect of stable carbon-oxygen complex formation on TGA reactivity profiles was investigated. For disordered carbons (e.g. coal chars) gasified in oxygen, the results showed that the observed differences between reactivity profiles obtained by TGA and those obtained by product gas analysis (e.g. non-dispersive infrared spectroscopy, i.r.) can be attributed to significant amounts of stable complex being formed during the initial stages of reaction. The fact that TGA reactivity profiles become equivalent to i.r. reactivity profiles, when corrected to account for stable complex formation, suggests that the former may not be accurate representations of the variations in intrinsic reaction rates and should be used with caution when attempting to validate proposed models of char gasification kinetics. The extent to which stable complex forms during char gasification was used to explain the observed differences in the reactivity profiles obtained for reactions of char in oxygen and carbon dioxide.
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