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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

Microwave-assisted pyrolysis of SiC and its application to joining

Description: Microwave energy has been used to pyrolyze silicon carbide from commercially available polycarbosilane precursor. The pyrolysis was performed on SiC surfaces having various surface treatments, to identify conditions which improve the wetting and adherence. Grinding and etching of the surfaces in hydrofluoric (HF) acid promotes the bonding of precursor derived ceramic to the SiC ceramic. Finally, the polycarbosilane precursor mixed with fine silicon carbide powder was used as the interlayer material to join silicon carbide specimens.
Date: July 1995
Creator: Ahmad, I.; Silberglitt, R. & Shan, T. A.
Partner: UNT Libraries Government Documents Department

THE 110 GHz MICROWAVE HEATING SYSTEM ON THE DIII-D TOKAMAK

Description: OAK-B135 Six 110 GHz gyrotrons in the 1 MW class are operational on DIII-D. Source power is > 4.0 MW for pulse lengths {le} 2.1 s and {approx} 2.8 MW for 5.0 s. The rf beams can be steered poloidally across the tokamak upper half plane at off-perpendicular injection angles in the toroidal direction up to {+-} 20{sup o}. measured transmission line loss is about -1 dB for the longest line, which is 92 m long with 11 miter bends. Coupling efficiency into the waveguide is {approx} 93% for the Gaussian rf beams. The transmission lines are evacuated and windowless except for the gyrotron output window and include flexible control of the elliptical polarization of the injected rf beam with remote controlled grooved mirrors in two of the miter bends on each line. The injected power can be modulated according to a predetermined program or controlled by the DIII-D plasma control system using real time feedback based on diagnostic signals obtained during the plasma pulse. Three gyrotrons have operated at 1.0 MW output power for 5.0 s. Peak central temperatures of the artificially grown diamond gyrotron output windows are < 180 C at equilibrium.
Date: July 2003
Creator: Lohr, J.; Callis, R. W.; Doane, J. L.; Ellis, R. A.; Gorelov, Ya; Kajiwara, K. et al.
Partner: UNT Libraries Government Documents Department

Novel Direct Steelmaking by Combining Microwave, Electric Arc, and Exothermal Heating Technologies

Description: Steel is a basic material broadly used by perhaps every industry and individual. It is critical to our nation's economy and national security. Unfortunately, the American steel industry is losing competitiveness in the world steel production field. There is an urgent need to develop the next generation of steelmaking technology for the American steel industry. Direct steelmaking through the combination of microwave, electric arc, and exothermal heating is a revolutionary change from current steelmaking technology. This technology can produce molten steel directly from a shippable agglomerate, consisting of iron oxide fines, powdered coal, and ground limestone. This technology is projected to eliminate many current intermediate steelmaking steps including coking, pellet sintering, blast furnace (BF) ironmaking, and basic oxygen furnace (BOF) steelmaking. This technology has the potential to (a) save up to 45% of the energy consumed by conventional steelmaking; (b) dramatically reduce the emission of CO{sub 2}, SO{sub 2}, NO{sub x}, VOCs, fine particulates, and air toxics; (c) substantially reduce waste and emission control costs; (d) greatly lower capital cost; and (e) considerably reduce steel production costs. This technology is based on the unique capability of microwaves to rapidly heat steelmaking raw materials to elevated temperature, then rapidly reduce iron oxides to metal by volumetric heating. Microwave heating, augmented with electric arc and exothermal reactions, is capable of producing molten steel. This technology has the components necessary to establish the ''future'' domestic steel industry as a technology leader with a strong economically competitive position in world markets. The project goals were to assess the utilization of a new steelmaking technology for its potential to achieve better overall energy efficiency, minimize pollutants and wastes, lower capital and operating costs, and increase the competitiveness of the U.S. steel industry. The objectives associated with this goal were to (a) generate a solid base ...
Date: March 28, 2005
Creator: Huang, Dr. Xiaodi & Hwang, Dr. J. Y.
Partner: UNT Libraries Government Documents Department

Extrapolation of the Dutch 1 MW tunable free electron maser to a 5 MW ECRH source

Description: A Free Electron Maser (FEM) is now under construction at the FOM Institute (Rijnhuizen) Netherlands with the goal of producing 1 MW long pulse to CW microwave output in the range 130 GHz to 250 GHz with wall plug efficiencies of 50% (Verhoeven, et al EC-9 Conference). An extrapolated version of this device is proposed which by scaling up the beam current, would produce microwave power levels of up to 5 MW CW in order to reduce the cost per watt and increase the power per module, thus providing the fusion community with a practical ECRH source.
Date: April 1, 1995
Creator: Caplan, M.; Nelson, S.; Kamin, G.; Antonsen, T. Levush, B.; Urbanus, W. & Tulupov, A.
Partner: UNT Libraries Government Documents Department

Development of A Microwave Assisted Particulate Filter Regeneration System

Description: The need for active regeneration of diesel particulate filters and the advantages of microwave assisted regeneration are discussed. The current study has multiple objectives, which include developing a microwave assisted particulate filter regeneration system for future generation light-duty diesel applications, including PNGV type applications. A variable power 2.0 kW microwave system and a tuned waveguide were employed. Cavity geometry is being optimized with the aid of computational modeling and temperature measurements during microwave heating. A wall-flow ceramic-fiber filter with superior thermal shock resistance, high filtration efficiency, and high soot capacity was used. The microwave assisted particulate filter regeneration system has operated for more than 100 hours in an engine test-cell with a 5.9-liter diesel engine with automated split exhaust flow and by-pass flow capabilities. Filter regeneration was demonstrated using soot loads up to 10 g/liter and engine exhaust at idling flow rates as the oxygen source. A parametric study to determine the optimal combination of soot loading, oxidant flow rate, microwave power and heating time is underway. Preliminary experimental results are reported.
Date: August 5, 2001
Creator: Popuri, Sriram
Partner: UNT Libraries Government Documents Department

Microwave heating for production of a glass bonded ceramic high-level waste form.

Description: Argonne National Laboratory has developed a ceramic waste form to immobilize the salt waste from electrometallurgical treatment of spent nuclear fuel. The process is being scaled up to produce bodies of 100 Kg or greater. With conventional heating, heat transfer through the starting powder mixture necessitates long process times. Coupling of 2.45 GHz radiation to the starting powders has been demonstrated. The radiation couples most strongly to the salt occluded zeolite powder. The results of these experiments suggest that this ceramic waste form could be produced using microwave heating alone, or by using microwave heating to augment conventional heating.
Date: July 30, 2002
Creator: O'Holleran, T. P.
Partner: UNT Libraries Government Documents Department

Decontamination of Radionuclides from Concrete During and After Thermal Treatment

Description: The objective was to clarify from the theoretical viewpoint the mechanical, diffusional, thermodynamic and electromagnetic aspects of the decontaminations problem, by means of developing a powerful computational model to evaluate the effect of a very rapid heating regime on the on the contaminated concrete walls or slabs. The practical objective was to assess the feasibility of the microwave heating scheme envisaged and determine its suitable parameters such as power and duration. This objective was complementary to, but separate from, the chemical and nuclear aspects of long-time processes that led to the contamination and various conceivable alternative methods of decontamination which were investigated by Dr. Brian Spalding of Oak Ridge National Laboratory, with whom the start-up phase of this project was coordinated.
Date: September 15, 1998
Creator: Bazant, Z. P.
Partner: UNT Libraries Government Documents Department

Technical and Engineering Feasibility Study of the Vitrification of Plutonium-Bearing Sludges at the Krasnoyarsk Mining and Chemical Combine by Means of Microwave Heating

Description: This engineering feasibility study compared three possible technical options and their economic viability of processing plutonium-bearing sludges containing 0.6 MT of weapons-grade Pu accumulated at the Mining and Chemical Combine (MCC) at Krasnoyarsk. In Option 1, the baseline, the sludges are processed by extraction and purification of plutonium for storage using existing technologies, and the non-soluble radioactive residues generated in these processes undergo subsequent solidification by cementation. Options 2 and 3 involve the direct immobilization of plutonium-bearing sludges into a solid matrix (without any Pu extraction) using a microwave solidification process in a metal crucible to produce a glass, which is boron-silicate in Option 2 and phosphate glass in Option 3. In all three options, the solid radioactive waste end products will be placed in storage for eventual geologic disposal. Immobilization of residual plutonium into glass-like matrices provides both safer storage over the lifetime of the radionuclides and greater security against unauthorized access to stored materials than does the extraction and concentration of PuO{sub 2}, supporting our efforts toward non-proliferation of fissile materials. Although immobilization in boron-silicate glass appears now to be marginally preferable compared to the phosphate glass option, a number of technical issues remain to be assessed by further study to determine the preferable immobilization option.
Date: March 3, 2000
Creator: Revenko, Y.A.; Kudinov, K.G.; Tretyakov, A.A.; Vassilyev, A.V.; Borisov, G.B.; Nazarov, A.V. et al.
Partner: UNT Libraries Government Documents Department

Uniform bulk Material Processing using Multimode Microwave Radiation

Description: An apparatus for generating uniform heating in material contained in a cylindrical vessel is described. TE{sub 10}-mode microwave radiation is coupled into a cylindrical microwave transition such that microwave radiation having TE{sub 11}-, TE{sub 01}- and TM{sub 01}-cylindrical modes is excited therein. By adjusting the intensities of these modes, substantially uniform heating of materials contained in a cylindrical drum which is coupled to the microwave transition through a rotatable choke can be achieved. The use of a poor microwave absorbing insulating cylindrical insert, such as aluminum oxide, for separating the material in the container from the container walls and for providing a volume through which air is circulated is expected to maintain the container walls at room temperature. The use of layer of highly microwave absorbing material, such as SiC, inside of the insulating insert and facing the material to be heated is calculated to improve the heating pattern of the present apparatus.
Date: June 18, 1999
Creator: Varma, Ravi & Vaughan, Worth E.
Partner: UNT Libraries Government Documents Department

Microwave combustion and sintering without isostatic pressure

Description: In recent years interest has grown rapidly in the application of microwave energy to the processing of ceramics, composites, polymers, and other materials. Advances in the understanding of microwave/materials interactions will facilitate the production of new ceramic materials with superior mechanical properties. One application of particular interest is the use of microwave energy for the mobilization of uranium for subsequent redeposition. Phase III (FY98) will focus on the microwave assisted chemical vapor infiltration tests for mobilization and redeposition of radioactive species in the mixed sludge waste. Uranium hexachloride and uranium (IV) borohydride are volatile compounds for which the chemical vapor infiltration procedure might be developed for the separation of uranium. Microwave heating characterized by an inverse temperature profile within a preformed ceramic matrix will be utilized for CVI using a carrier gas. Matrix deposition is expected to commence from the inside of the sample where the highest temperature is present. The preform matrix materials, which include aluminosilicate based ceramics and silicon carbide based ceramics, are all amenable to extreme volume reduction, densification, and vitrification. Important parameters of microwave sintering such as frequency, power requirement, soaking temperature, and holding time will be investigated to optimize process conditions for the volatilization of uranyl species using a reactive carrier gas in a microwave chamber.
Date: January 1, 1998
Creator: Ebadian, M.A.
Partner: UNT Libraries Government Documents Department

Soil sample preparation using microwave digestion for uranium analysis

Description: A new sample preparation procedure has been developed for digestion of soil samples for uranium analysis. The technique employs a microwave oven digestion system to digest the sample and to prepare it for separation chemistry and analysis. The method significantly reduces the volume of acids used, eliminates a large fraction of acid vapor emissions, and speeds up the analysis time. The samples are analyzed by four separate techniques: Gamma Spectrometry, Alpha Spectroscopy using the open digestion method, Kinetic Phosphorescence Analysis (KPA) using open digestion, and KPA by Microwave digestion technique. The results for various analytical methods are compared and used to confirm the validity of the new procedure. The details of the preparation technique along with its benefits are discussed.
Date: April 5, 2000
Creator: MOHAGHEGHI,AMIR H.; PRESTON,ROSE; AKBARZADEH,MANSOOR & BAKHTIAR,STEVEN
Partner: UNT Libraries Government Documents Department

Microwave versus conventional sintering of silicon carbide tiles

Description: Silicon carbide is being evaluated as an armor material because of its lightweight, high-hardness, and excellent armor efficiency. However, one of the problems associated with silicon carbide is the high cost associated with achieving fully dense tiles. Full density requires either hot pressing and sintering or reaction bonding. Past efforts have shown that hot pressed tiles have a higher armor efficiency than those produced by reaction bonded sintering. An earlier stuy showed that the acoustic properties of fully-dense silicon carbide tiles were enhanced through the use of post-sintered microwave heat treatments. One of the least expensive forming techniques is to isostatically press-and-sinter. In this study, the authors have used microwave energy to densify silicon carbide green bodies. Microwave sintering has been demonstrated to be a very quick way to sinter ceramics such as alumina to exceptionally high densities. Previous work has shown that microwave post treatment of fully-dense reaction bonded silicon carbide tiles significantly improves the acoustic properties of the tiles. These properties include Poisson`s ratio, Young`s modulus, shear modulus, and bulk modulus.
Date: May 7, 1997
Creator: Kass, M. D.; Caughman, J. B. O.; Forrester, S. C. & Akerman, A.
Partner: UNT Libraries Government Documents Department

Low VOC drying of lumber and wood panel products. Progress report No. 8

Description: This study was initiated by an Institute of Paper Science and Technology finding that heating softwood in a low-headspace environment removed much of the VOCs without removing the water. This offered the possibility of removing VOCs from wet wood, capturing them as a product, and then drying the VOC-depleted wood conventionally with little or no VOC controls. Two means of low-headspace heating were explored: steam and radiofrequency (RF). It was found in the previous year, that while both steam and RF were able to drive out VOCs, steam was impracticably slow for lumber. Hence the effect of RF or microwave on wood was the principal focus of the work reported here. Finally, in order to understand the mechanism of VOC release, the transport of the VOCs in wood was studied, together with the seasonal effects that influence VOC concentration in trees.
Date: July 1, 1998
Creator: Su, W.; Yan, H.; Hooda, U.; Wild, M.P.; Banerjee, S.; Shmulsky, R. et al.
Partner: UNT Libraries Government Documents Department

Low VOC drying of lumber and wood panel products. Progress report number 9

Description: This project is based on the finding that brief microwave or RF-treatment of wood under low-headspace conditions leads to the release of VOCs. On occasion the authors have found that prolonged irradiation increases turpentine yield much more than anticipated from a simple mass balance; i.e., more pinene appeared to be released than was present in the wood in the first place. If taken at face value, this suggests that brief low-headspace irradiation removes VOCs, while prolonged exposure creates it. While seemingly improbable, this could follow if dielectric heating exposed regions of wood that were otherwise inaccessible to the solvent used for extraction (unlikely), or if the irradiation induced depolymerization of terpene dimers or higher polymers. In this report the authors attempt to identify the conditions that lead to this apparent enhancement of terpene yield, by constructing relationships between yield and irradiation parameters. The tentative conclusions are that this enhancement only occurs with relatively wet heartwood, and only under prolonged irradiation. An additional conclusion is that continuing analyses of twelve trees in the MSU forest confirm that the absence of a significant seasonal influence on turpentine content. An apparatus for permeability testing has been constructed, and work is underway.
Date: October 1, 1998
Creator: Hooda, U.; Banerjee, S.; Ingram, L. & Conners, T.
Partner: UNT Libraries Government Documents Department

Variable frequency microwave (VFM) curing, processing of thermoset prepreg laminates. Final report

Description: The objective of this work was to investigate the beneficial effect of the variable frequency microwave (VFM) technology to cure thermosetting prepreg laminates. Further, it was to investigate the interrelationship and effect on the curing process of frequency, band width, and curing time with different types of laminates. Previous studies of microwave-assisted curing of neat resins (epoxy) and unidirectional glass and carbon fiber laminates with a fixed frequency of 2.45 GHz, have shown that a substantial reduction in the curing time was obtained. Results of this earlier work indicate that the microwave-assisted curing of multidirectional glass fiber laminates also show a substantial reduction of the required curing time. This may be explained by the penetration of microwave energy directly and throughout the laminate with enhancement of the kinetics of the chemical reaction. The fixed frequency microwave radiation of 2.45 GHz has been demonstrated to be a partially acceptable method to cure unidirectional carbon fiber laminates. Multidirectional carbon fiber/epoxy laminates demonstrate a lack of coupling during the curing process. A direct curing of these laminates was not possible by microwave radiation with the experimental approach used in agreement with previous work. In addition to this short coming, the unidirectional laminate samples cured with the fixed frequency are visually nonuniform. Localized areas of darker colors (burn, hot spots, overheating) are attributed to the formation of standing waves within the microwave cavity. For this reason, the laminates are subject to proper rotation while curing through fixed frequency. The present research indicates that variable frequency microwave technology is a sound and acceptable processing method to effectively cure uni-, bi- or multi-directional thermosetting glass fiber laminates. Also, this methodology will effectively cure unidirectional thermosetting carbon fiber laminates. For all these cases, this technology yielded a substantial reduction in the required cure time of these laminates. ...
Date: September 30, 1996
Creator: Paulauskas, F. L.
Partner: UNT Libraries Government Documents Department

Recent progress in ceramic joining

Description: Both fundamental and practical aspects of ceramic joining are understood well enough for many, if not most, applications requiring moderate strengths at room temperature. This paper argues that the two greatest needs in ceramic joining are for techniques to join buried interfaces by selective heating, and methods for joining ceramics for use at temperatures of 800 to 1,200 C. Heating with microwave radiation or with high-energy electron beams has been used to join buried ceramic interfaces, for example SiC to SiC. Joints with varying levels of strength at temperatures of 600 to 1,000 C have been made using four techniques: (1) transient liquid phase bonding; (2) joining with refractory braze alloys; (3) joining with refractory glass compositions; and (4) joining using preceramic polymers. Joint strengths as high as 550 MPa at 1,000 C have been reported for silicon nitride-silicon nitride bonds tested in four-point flexure.
Date: September 1, 1998
Creator: Loehman, R.E.
Partner: UNT Libraries Government Documents Department

Quasi-optical gyrotron materials processing at Los Alamos

Description: Los Alamos has recently obtained and installed quasi-optical gyrotrons of 37 and 84 GHz with power outputs up to 35 kW. A quasi-optical gyrotron is unique in that the output is a Gaussian beam which can be focused and manipulated using mirrors. The Gaussian beam output is ideally suited for one and two dimensional materials processing applications such as joining and surface treatment. Working with the National Center for Manufacturing Sciences (NCMS) we have formed a consortium of companies to investigate several materials processing applications.
Date: May 1, 1995
Creator: Katz, J.D. & Rees, D.E.
Partner: UNT Libraries Government Documents Department

Phase 2 microwave concrete decontamination results

Description: The authors report on the results of the second phase of a four-phase program at Oak Ridge National Laboratory to develop a system to decontaminate concrete using microwave energy. The microwave energy is directed at the concrete surface through the use of an optimized wave guide antenna, or applicator, and this energy rapidly heats the free water present in the interstitial spaces of the concrete matrix. The resulting steam pressure causes the surface to burst in much the same way popcorn pops in a home microwave oven. Each steam explosion removes several square centimeters of concrete surface that are collected by a highly integrated wave guide and vacuum system. The authors call this process the microwave concrete decontamination, or MCD, process. In the first phase of the program the principle of microwaves concrete removal concrete surfaces was demonstrated. In these experiments, concrete slabs were placed on a translator and moved beneath a stationary microwave system. The second phase demonstrated the ability to mobilize the technology to remove the surfaces from concrete floors. Area and volume concrete removal rates of 10.4 cm{sup 2}/s and 4.9 cm{sup 3}/S, respectively, at 18 GHz were demonstrated. These rates are more than double those obtained in Phase 1 of the program. Deeper contamination can be removed by using a longer residence time under the applicator to create multiple explosions in the same area or by taking multiple passes over previously removed areas. Both techniques have been successfully demonstrated. Small test sections of painted and oil-soaked concrete have also been removed in a single pass. Concrete with embedded metal anchors on the surface has also been removed, although with some increased variability of removal depth. Microwave leakage should not pose any operational hazard to personnel, since the observed leakage was much less than the regulatory standard.
Date: April 1, 1995
Creator: White, T.L.; Foster, D. Jr.; Wilson, C.T. & Schaich, C.R.
Partner: UNT Libraries Government Documents Department

Microwave processing of Tantalum capacitors. CRADA final report

Description: A Cooperative Research and Development Agreement (CRADA) between Lockheed Martin Energy Systems, Inc. (LMES) and AVX Tantalum Corporation (AVX) of Biddeford, Maine, was initiated in October 1991. [Lockheed Martin Energy Research Corp. (LMER) has replaced LMES]. The completion date for the Agreement was March 1996. The purpose of this work is to explore the feasibility of an advanced microwave processing concept to develop higher capacitance tantalum anodes. Tantalum capacitors are used where high reliability is needed (e.g., pacemakers, hearing aids, and military devices). Two types of tantalum powder are used: sodium-reduced powder and electron beam-refined powder. Sodium-reduced powder has higher surface area, but lower purity; electron beam-refined powder has higher purity for working voltages, but somewhat lower surface area. The powder is pressed into pellets using traditional methods and then placed in the microwave furnace for processing. It is of interest to determine if variable-frequency microwave sintering can increase quality while decreasing processing time and decreasing or eliminating surface contamination; these issues must be addressed while retaining the maximum surface area of the anode. Meeting each of these needs will result in a higher quality anodic film, which will thereby increase the dielectric strength. Additionally, microwave sintering might enable the authors to develop a strong sintered anode without excessive grain growth. The variable-frequency microwave furnace (VFMF), located at the Y-12 Plant, allows the authors to study the effects of sintering over a wide frequency range. This novel design uses a high-power traveling wave tube (TWT), originally developed for electronic warfare. By using this microwave source, one can not only select individual microwave frequencies for particular experiments, but also achieve uniform power densities over a large area by the superposition of many different frequencies.
Date: March 1, 1998
Creator: McMillan, A.D.; Lauf, R.J. & Vierow, W.F.
Partner: UNT Libraries Government Documents Department

Microwave dissolution of plant tissue and the subsequent determination of trace lanthanide and actinide elements by inductively coupled plasma-mass spectrometry

Description: Recently there has been much concern with the ability of plants to uptake heavy metals from their surroundings. With the development of instrumental techniques with low detection limits such as inductively coupled plasma-mass spectrometry (ICP-MS), attention is shifting toward achieving faster and more elegant ways of oxidizing the organic material inherent in environmental samples. Closed-vessel microwave dissolution was compared with conventional methods for the determination of concentrations of cerium, samarium, europium, terbium, uranium and thorium in a series of samples from the National Institute of Standards and Technology and from fields in Idaho. The ICP-MS technique exhibited detection limits in parts-per-trillion and linear calibration plots over three orders of magnitude for the elements under study. The results obtained by using nitric acid and hydrogen peroxide in a microwave digestion system for the analysis of reference materials showed close agreement with the accepted values. These values were compared with results obtained from dry- and wet-ashing procedures. The findings from an experiment comparing radiometric techniques for the determination of actinide elements to ICP-MS are reported.
Date: August 1, 1997
Creator: Alvarado, J.S.; Neal, T.J.; Smith, L.L. & Erickson, M.D.
Partner: UNT Libraries Government Documents Department

Microwave processing of silicon carbide. CRADA final report

Description: A Cooperative Research and Development Agreement (CRADA) between Lockheed Martin Energy Systems, Inc. (LMES) and Dow Chemical Company was initiated on May 3, 1993. (Lockheed Martin Energy Research Inc. (LMER) replaced LMES). The completion date for the Agreement was December 1996. The purpose of this project is to develop microwave processing techniques to produce superior silicon carbide. Sintered silicon carbide is an attractive material for use in high-stress, high-temperature, high-wear, or highly corrosive applications. However, use in these applications has been hampered by a lack of consistency in strength, density, and other physical properties. It is proposed that the enhanced sintering that has been achieved using microwaves in oxide and halide systems be applied to the sintering of these materials to produce a more highly controlled density and microstructure. This will, in turn, increase the strength and Weibull modulus of the sintered body. The use of microwave energy to anneal for a moderate temperature (1,400--1,600 C) anneal in a high vacuum (< 10{sup {minus}4} Torr) results in an improvement in the sintered density and density distribution. These changes in turn result in improved properties of the sintered compacts. Further, scale up of the process has resulted in the routine production of 3 kg components in excess of 4 cm in thickness.
Date: February 1, 1998
Creator: Kimrey, H.D.; Kiggans, J.O.; Ness, E.A. & Rafaniello, W.
Partner: UNT Libraries Government Documents Department

Microwave processing improvements for methane conversion to ethylene

Description: This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The project`s objective was to investigate microwave enhanced catalysis. Published work by others had demonstrated improved selectivity in microwave-driven catalytic conversion of 2-methylpentane to its isomers. We reproduced their experiment, discovering that there is no improvement in selectivity using microwaves. The selectivity at a given conversion was the same for both microwave heated and conventionally heated catalyst beds. Meetings with the authors of the previously published work led to the conjecture that their catalyst was not being prepared properly, leading to anomalously low selectivity for their conventional heating runs. An optical temperature diagnostic suitable for use on a microwave applicator was developed and characterized in this project. This pyrometer can measure the temperature of small scale features on the catalyst bed, and it has a fast response that can follow the rapid heating often encountered in a microwave processing system. The behavior of the microwave applicator system was studied, and theoretical models were developed to yield insight about the stability and control of the system.
Date: August 1, 1997
Creator: Stringfield, R.; Ott, K.; Nelson, E.; Anderson, G.; Chen, Dye-Zone; Dyer, T. et al.
Partner: UNT Libraries Government Documents Department