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Microwave Combustion and Sintering Without Isostatic Pressure

Description: This investigation involves a study of the influence of key processing parameters on the heating of materials using microwave energy. Selective and localized heating characteristics of microwaves will be utilized in the sintering of ceramics without hydrostatic pressure. In addition, combustion synthesis will be studied for the production of powders, carbides, and nitrides by combining two or more solids or a solid and a gas to form new materials. The insight gained from the interaction of microwaves with various materials will be utilized in the mobilization and subsequent redeposition of uranium.
Date: October 20, 1998
Creator: Ebadian, M. A. & Monroe, N. D. H.
Partner: UNT Libraries Government Documents Department

Dynamic Model for Electromagnetic Field and Heating Patterns in Loaded Cylindrical Cavities

Description: An analytical solution for the electromagnetic fields in a cylindrical cavity, partially filled with a cylindrical dielectric has been recently reported. A program based on this solution has been developed and combined with the authors` previous program for heat transfer analysis. The new software has been used to simulate the dynamic temperature profiles of microwave heating and to investigate the role of electromagnetic field in heating uniformity and stability. The effects of cavity mode, cavity dimension, the dielectric properties of loads on electromagnetic field and heating patterns can be predicted using this software.
Date: July 1, 1995
Creator: Tian, Y. L.; Black, W. M.; Sa`adaldin, H. S.; Ahmad, I. & Silberglitt, R.
Partner: UNT Libraries Government Documents Department

Investigation of interlayer materials for the microwave joining of SiC

Description: Microwave joining of ceramics has the potential for increased speed and convenience. Joints have been made in alumina, mullite and silicon nitride with flexure strength approaching, and in some cases exceeding, that of the as received material in a fraction of the time that is customarily required with conventional techniques. This paper describes the initial results of investigations aimed at applying microwave joining to SiC and other carbide ceramics. 8 refs., 5 figs.
Date: January 1, 1991
Creator: Silberglitt, R.; Palaith, D. (Technology Assessment and Transfer, Inc., Annapolis, MD (USA)); Black, W.M.; Sa'adaldin, H.S. (George Mason Univ., Fairfax, VA (USA)); Katz, J.D. & Blake, R.D. (Los Alamos National Lab., NM (USA))
Partner: UNT Libraries Government Documents Department

Ceramic matrix composites by microwave assisted CVI

Description: Chemical vapor infiltration (CVI) processes for producing continuously reinforced ceramic composites are reviewed. The potential advantages of microwave assisted CVI are noted. Recent numerical studies of microwave assisted CVI are then reviewed. These studies predict inverted thermal gradients in fibrous ceramic preforms subjected to microwave radiation and suggest processing strategies for achieving uniformly dense composites. Comparisons are made to experimental results obtained using silicon based composite systems. The importance of microwave-material interactions is stressed. In particular, emphasis is placed on the role played by the relative ability of fiber and matrix to dissipate microwave energy. Results suggest that microwave induced inverted gradients can in fact be exploited using the CVI technique to promote inside-out densification.
Date: January 1, 1993
Creator: Currier, R.P. & Devlin, D.J.
Partner: UNT Libraries Government Documents Department

Microwave sintering of large alumina bodies

Description: The application of microwaves as an energy source for materials processing of large alumina bodies at elevated temperatures has been limited to date. Most work has concerned itself with small laboratory samples. The nonuniformity of the microwave field within a cavity subjects large alumina bodies to areas of concentrated energy, resulting in uneven heating and subsequent cracking. Smaller bodies are not significantly affected by field nonuniformity due to their smaller mass. This work will demonstrate a method for microwave sintering of large alumina bodies while maintaining their structural integrity. Several alumina configurations were successfully sintered using a method which creates an artificial field or environment within the microwave cavity.
Date: January 1, 1993
Creator: Blake, R.D. & Katz, J.D.
Partner: UNT Libraries Government Documents Department

Microwave sintering of ZrO{sub 2}-12 mol% CeO{sub 2}

Description: Sintering of ZrO{sub 2}-12 mol% CeO{sub 2} was accelerated by microwave processing at 2.45 GHz as compared with conventional firing. However, the size of the ``microwave effect`` was significantly smaller than that which was previously observed for microwave sintering of ZrO{sub 2}-8 mol% Y{sub 2}O{sub 3}. The difference in the effect that the microwave field had on the two zirconia systems is interpreted in terms of their ionic conductivities.
Date: December 31, 1993
Creator: Janney, M. A.; Jackson, M. L. & Kimrey, H. D.
Partner: UNT Libraries Government Documents Department

Materials processing using a variable frequency microwave furnace

Description: We describe a materials processing system that uses a high power traveling wave tube (TWT) as the microwave source. The TWT provides approximately one octave bandwidth and variable power levels up to 2 kW into a multimode cavity. By controlling the frequency, efficient coupling to the load can be maintained even as the load`s dielectric properties change. Alternatively, can be used as a means of mode stirring at rates far beyond those attainable through mechanical stirring. The system has been tested for sintering alumina ceramics, annealing a tungsten penetrator alloy, curing epoxy resin, and depositing diamond films from a microwave plasma.
Date: December 31, 1993
Creator: Lauf, R. J.; Bible, D. W.; Maddox, S. R.; Everleigh, C. A.; Espinosa, R. J. & Johnson, A. C.
Partner: UNT Libraries Government Documents Department

Y-12 development organization technical progress report period ending February 1, 1994. Part 7, Lithium and uranium chemical processing

Description: Microwave energy was used successfully to consolidate small lots of uranium powder. Factors varied were max power, hold time, heating rate, gas pressure, batch composition, crucible material, insulation configuration. Results indicate that that the microwave consolidation process was rugged against all 7 factors for their respective parameters.
Date: March 8, 1994
Creator: Smith, W. E.
Partner: UNT Libraries Government Documents Department

Experimental observations of thermal spikes in microwave processing of ceramic oxide fibers

Description: Microwave heating of alumina/silica fiber tows in a single-mode microwave cavity at 2.45 GHz have produced a surprising thermal spike behavior on the fiber bundles. During a thermal spike, a ``hot spot`` on the tow brightens rapidly, persists for a few seconds, and rapidly extinguishs. A hot spot can encompass the entire tow in the cavity or just a localized portion of the tow. Some local hot spots propagate along the fiber. Thermal spikes are triggered by relatively small (<15%) increases in power, thus having obvious implications for the development of practical microwave fiber processing systems. A tow can be heated through several successive thermal spikes, after which the tow is left substantially cooler than it was originally, although the applied microwave electric field is much larger. X-ray diffraction studies show that after each temperature spike there is a partial phase transformation of the tow material into mullite. After several excursions the tow has been largely transformed to the new, less lossy phase and is more difficult to heat. Heating experiments with Nextel 550 tows are examined for a pausible explanation of this microwave heating behavior.
Date: April 1, 1994
Creator: Vogt, G. J.; Unruh, W. P. & Thomas, J. R. Jr.
Partner: UNT Libraries Government Documents Department

Temperature distribution in microwave sintering of alumina cylinders

Description: Small cylinders of high-purity alumina were encased in a `casket` of low-density zirconia insulation and heated to sintering temperature in a large multi-mode microwave oven. Optical fiber sensors were used to monitor the temperature at several locations in the system. It was found that the alumina samples heat faster than the zirconia insulation at temperatures above 1000 C, and that the temperature distribution in the sample is essentially uniform during the heating process. A two-dimensional mathematical model of the heat transfer process was developed which reproduces the essential features of the observed phenomena. Literature data for all temperature-dependent properties were incorporated into the model. The model suggests that the alumina samples absorb a significant fraction of the microwave energy.
Date: April 1, 1994
Creator: Thomas, J. R. Jr.; Katz, J. D. & Blake, R. D.
Partner: UNT Libraries Government Documents Department

Microwave sintering of multiple aritcles

Description: Disclosed are apparatus and method for producing articles of alumina and of alumina and silicon carbide in which the articles are sintered at high temperatures using microwave radiation. The articles are placed in a sintering container which is placed in a microwave cavity for heating. The rates at which heating and cooling take place is controlled.
Date: December 31, 1992
Creator: Blake, R. D. & Katz, J. D.
Partner: UNT Libraries Government Documents Department

Microwave hybrid heating of alumina filaments

Description: Low loss oxide ceramics filaments are not readily heated to sintering temperatures (>900{degrees}C) by direct microwave heating at 2.45 GHz. Use of high power levels typically yields thermal runaway with catastrophic melting. In other studies, hybrid, or indirect, heating has been successfully applied to processing bulk oxide ceramics. In this work, commercial alumina-based filaments have been indirectly heated to 700{degrees}--900{degrees}C through a lossy carbon coating on the filament tow. Specific filaments can reach higher temperatures by direct coupling after preheating with a lossy coating. The results of microwave hybrid heating in a single mode TE{sub 102} cavity will be described for commercial alumina-based filaments.
Date: May 1, 1993
Creator: Vogt, G. J. & Unruh, W. P.
Partner: UNT Libraries Government Documents Department

Microwave assisted chemical vapor infiltration

Description: A microwave assisted process for production of continuous fiber reinforced ceramic matrix composites is described. A simple apparatus combining a chemical vapor infiltration reactor with a conventional 700 W multimode oven is described. Microwave induced inverted thermal gradients are exploited with the ultimate goal of reducing processing times on complex shapes. Thermal gradients in stacks of SiC (Nicalon) cloths have been measured using optical thermometry. Initial results on the ``inside out`` deposition of SiC via decomposition of methyltrichlorosilane in hydrogen are presented. Several key processing issues are identified and discussed. 5 refs.
Date: December 31, 1991
Creator: Devlin, D. J.; Currier, R. P.; Barbero, R. S.; Espinoza, B. F. & Elliott, N.
Partner: UNT Libraries Government Documents Department

Microwave processing of ceramics

Description: Recent work in the areas of microwave processing and joining of ceramics is briefly reviewed. Advantages and disadvantages of microwave processing as well as some of the current issues in the field are discussed. Current state and potential for future commercialization of this technology is also addressed.
Date: April 1, 1993
Creator: Katz, J. D.
Partner: UNT Libraries Government Documents Department

Design of a tunable 4-MW Free Electron Maser for heating fusion plasmas

Description: There is an ongoing program at the FOM institute, The Netherlands, to develop a 1-MW, long-pulse, 200-Ghz Free Electron Maser (FEM) using a DC accelerator system with depressed collector. We present an extrapolation of this design to more than 4MW of output microwave power in order to reduce the cost per kW and increase the power per module in a plasma heating system.
Date: September 1, 1993
Creator: Caplan, M.; Kamin, G.; Shang, C. C. & Lindquist, W.
Partner: UNT Libraries Government Documents Department

Advanced Industrial Materials Program. Annual progress report, FY 1993

Description: Mission of the AIM program is to commercialize new/improved materials and materials processing methods that will improve energy efficiency, productivity, and competitiveness. Program investigators in the DOE national laboratories are working with about 100 companies, including 15 partners in CRDAs. Work is being done on intermetallic alloys, ceramic composites, metal composites, polymers, engineered porous materials, and surface modification. The program supports other efforts in the Office of Industrial Technologies to assist the energy-consuming process industries. The aim of the AIM program is to bring materials from basic research to industrial application to strengthen the competitive position of US industry and save energy.
Date: June 1, 1994
Creator: Stooksbury, F.
Partner: UNT Libraries Government Documents Department

Metal recovery from porous materials

Description: The present invention relates to recovery of metals. More specifically, the present invention relates to the recovery of plutonium and other metals from porous materials using microwaves. The United States Government has rights in this invention pursuant to Contract No. DE-AC09-89SR18035 between the US Department of Energy and Westinghouse Savannah River Company.
Date: January 1, 1991
Creator: Sturcken, E. F.
Partner: UNT Libraries Government Documents Department

Thermal Wadis in Support of Lunar Exploration: Concept Development and Utilization

Description: Thermal wadis, engineered sources of heat, can be used to extend the life of lunar rovers by keeping them warm during the extreme cold of the lunar night. Thermal wadis can be manufactured by sintering or melting lunar regolith into a solid mass with more than two orders of magnitude higher thermal diffusivities compared to native regolith dust. Small simulant samples were sintered and melted in the electrical furnaces at different temperatures, different heating and cooling rates, various soaking times, under air, or in an argon atmosphere. The samples were analyzed with scanning electron microscopy and energy dispersive spectroscopy, X-ray diffraction, a laser-flash thermal diffusivity system, and the millimeter-wave system. The melting temperature of JSC-1AF simulant was ~50°C lower in an Ar atmosphere compared to an air atmosphere. The flow of Ar during sintering and melting resulted in a small mass loss of 0.04 to 0.1 wt% because of the volatization of alkali compounds. In contrast, the samples that were heat-treated under an air atmosphere gained from 0.012 to 0.31 wt% of the total weight. A significantly higher number of cavities were formed inside the samples melted under an argon atmosphere, possibly because of the evolution of oxygen bubbles from iron redox reactions. The calculated emissivity of JSCf-1AF simulant did not change much with temperature, varying between 0.8 and 0.95 at temperatures from 100 to 1200°C. The thermal diffusivities of raw regolith that was compressed under a pressure of 9 metric tons ranged from 0.0013 to 00011 in the 27 to 390°C temperature range. The thermal diffusivities of sintered and melted JSC-1AF simulant varied from 0.0028 to 0.0072 cm2/s with the maximum thermal diffusivities observed in the samples that were heated up 5°C/min from RT to 1150°C under Ar or air. These thermal diffusivities are high enough for the rovers ...
Date: October 12, 2009
Creator: Matyas, Josef; Wegeng, Robert S. & Burgess, Jeremy M.
Partner: UNT Libraries Government Documents Department

Production of high charge state ions with the Advanced Electron Cyclotron Resonance ion source at LBNL

Description: Production of high charge state ions with the Advanced Electron Cyclotron Resonance ion source (AECR) at Lawrence Berkeley National Laboratory (LBNL) has been significantly improved by application of various new techniques. Heating the plasma simultaneously with microwaves of two frequencies (10 and 14 GHz) has increased the production of very high charge state heavy ions. The two-frequency technique provides extra electron cyclotron resonance heating zone as compared to the single-frequency heating and improves the heating of the plasma electrons. Aluminum oxide on the plasma chamber surface improves the production of cold electrons at the chamber surfaces and increases the performance of the AECR. Fully stripped argon ions, {gt} 5 enA, were produced and directly identified by the source charge state analyzing system. High charge state ion beams of bismuth and uranium, such as {sup 209}Bi{sup 51+} and {sup 238}U{sup 53+}, were produced by the source and accelerated by the 88-Inch Cyclotron to energies above 6 MeV/nucleon for the first time. To further increase the production of high charge state ions to support the nuclear science research programs at the 88-Inch Cyclotron, an upgrade is taking place to increase the AECR magnetic field strengths and mirror ratios to improve the plasma confinement. Conceptual design is underway for a 3rd Generation ECR that uses superconducting magnets to reach higher magnetic field strengths and higher mirror ratios, high secondary emission chamber walls to increase the yield of cold electrons at the chamber surfaces and microwaves of multiple frequencies to improve plasma heating.
Date: September 1, 1995
Creator: Xie, Zu Qi & Lyneis, C.M.
Partner: UNT Libraries Government Documents Department

Adsorption and desorption of sulfur dioxide on novel adsorbents for flue gas desulfurization. Final report, September 1, 1994--February 29, 1996

Description: A sol-gel granulation method was developed to prepare spherical {gamma}-alumina granular supports and supported CuO granular sorbents for flue gas desulfurization. The prepared {gamma}-alumina supported CuO sorbents exhibit desirable pore structure and excellent mechanical properties. The sorbents contain higher loading (30-40 wt. %) of CuO dispersed in the monolayer or sub-monolayer form, giving rise to a larger SO{sub 2} sorption capacity ({gt}20 wt.%) and a faster sorption rate as compared to similar sorbents reported in the literature. With these excellent sulfation and mechanical properties, the sol-gel derived {gamma}-alumina supported CuO granular sorbents offer great potential for use in the dry, regenerative flue gas desulfurization process. Research efforts were also made to prepare DAY zeolite supported sorbents with various CuO contents by the microwave and conventional thermal dispersion methods at different conditions. Monolayer or sub-monolayer coating of Cu(NO{sub 3})sub 2 or CuO was achieved on several DAY supported sorbents by the microwave heating method but not by the conventional thermal dispersion method. The DAY zeolite supported CuO sorbents prepared by the microwave heating method can adsorb up to 15 wt.% of SO{sub 2}. The results obtained have demonstrated the feasibility of effective preparation of zeolite supported CuO sorbents by the microwave heating method.
Date: August 5, 1996
Creator: Lin, Y.S. & Deng, S.G.
Partner: UNT Libraries Government Documents Department

[A variable frequency microwave furnace]. CRADA final report for CRADA Number ORNL91-0055

Description: The goals of this CRADA were to: (1) development and demonstrate a highly frequency-agile microwave furnace; (2) explore applications of the furnace for materials processing; and (3) develop control systems and packaging that are robust, user-friendly, and suitable for sale as a turnkey system. Microwave Laboratories, Inc. (MLI) designed, built, and successfully brought to market a benchtop Variable Frequency Microwave Furnace (VFMF). The concept has demonstrated advantages in polymer curing, waste remediation, and diamond (CVD). Through experimentation and modeling, the VFMF approach has gained credibility within the technical community.
Date: December 8, 1994
Creator: Lauf, R. J.
Partner: UNT Libraries Government Documents Department

Non-fusion applications of RF and microwave technology

Description: The processing of materials using rf and/or microwave power is a broad area that has grown significantly in the past few years. The authors have applied rf and microwave technology in the areas of ceramic sintering, plasma processing, and waste processing. The sintering of ceramics in the frequency range of 50 MHz-28 GHz has lead to unique material characteristics compared to materials that have been sintered conventionally. It has been demonstrated that sintering can be achieved in a variety of materials, including alumina, zirconia, silicon carbide, and boron carbide. In the area of plasma processing, progress has been made in the development and understanding of high density plasma sources, including inductively coupled plasma (ICP) sources. The effects of processing conditions on the ion energy distribution at the substrate surface (a critical processing issue) have been determined for a variety of process gases. The relationship between modeling and experiment is being established. Microwave technology has also been applied to the treatment of radioactive and chemical waste. The application of microwaves to the removal of contaminated concrete has been demonstrated. Details of these programs and other potential application areas are discussed.
Date: December 1, 1995
Creator: Caughman, J.B.O.; Baity, F.W.; Bigelow, T.S.; Gardner, W.L.; Hoffman, D.J.; Forrester, S.C. et al.
Partner: UNT Libraries Government Documents Department

Application of microwave solidification technology to radioactive waste

Description: The EPA has declared vitrification to be the Best Available Demonstrated Technology (BDAT) for High Level Radioactive Waste (40 CFR 268.42). Vitrification has been chosen as the method of choice for treating a number of radioactive residues and wastes in the DOE complex. Vitrification offers advantages of waste volume reduction, the ability to handle changing waste forms, and a stable, nonleachable final waste form. Microwave heating is a superior method for vitrification of radioactive wastes. Advantages of microwave heating include: (1) direct waste heating, eliminates need for electrodes, refractories and other consumables; (2) ``in-can`` processing allows for treatment of the material in its final container, (3) a mechanically simple system where the microwaves are generated away from the treatment area and transmitted to the treatment applicator by a wave guide, thus minimizing worker exposure to radiation; (4) easier equipment maintenance; and (5) a high degree of public acceptance.
Date: September 28, 1995
Creator: Harris, M.; Sprenger, G.; Roushey, B.; Fenner, G. & Nieweg, R.
Partner: UNT Libraries Government Documents Department

The use of solid-state NMR techniques for the analysis of water in coal and the effect of different coal drying techniques on the structure and reactivity of coal; Quarterly report, September 1--November 30, 1993

Description: For the research program reported here, different methods of drying are being investigated to determine if drying can be accomplished without destroying coal reactivity toward liquefaction. In an effort to understand the mechanism of water for enhancing coal liquefaction yield, the reactions of D{sub 2}O with the molecular constituents of coal during coal liquefaction are being investigated. This study involves the use of solution-state deuterium NMR, as well as, conventional solution-state {sup 1}H and {sup 13}C NMR analyses of the coal, and the coal liquids and residue from a coal liquefaction process. These D{sub 2}O transfer reactions will be conducted on coals which have been dried by various methods and rehydrated using D{sub 2}O and by successive exchange of H{sub 2}O associated with the coals with D{sub 2}O. The drying methods include thermal, microwave, and chemical dehydration of the coal. The overall objectives of this study are to develop a nuclear magnetic resonance (NMR) method for measuring the water in coal, to measure the changes in coal structure that occur during coal drying, to determine what effect water has on retrograde/condensation reactions, to determine the mechanism by which water may impact coal reactivity toward liquefaction, and to conduct D{sub 2}O exchange studies to ascertain the role of water in coal liquefaction. The objectives for this quarterly report period were (1) to measure the volumetric swelling ratio for thermally- and microwave-dried coals and (2) to conduct preliminary experiments concerning the exchange of water in coal with deuterium oxide (D{sub 2}O).
Date: December 31, 1993
Creator: Netzel, D.A.
Partner: UNT Libraries Government Documents Department