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Improved Grindability of Taconite Ores by Microwave Heating

Description: The 11.S. Bureau of Mines has conducted studies to utilize rapid microwave heating to stress fracture ore samples. Iron ores containing hematite, magnetite, and goethite were subjected to microwave energy in batch operations at 3 kW and heated to average maximum temperatures between 840 and 940 *C. Standard Bond grindability tests showed that microwave heating reduced the work index of iron ores by 10 to 24 pct. In a microwave chamber designed to simulate a continuous throughput operation at 3 kW, the grindability of a tacon-te ore was improved by 13 pct at a bulk temperature of 197 *C. Because stress cracking occurred at a lower temperature, less energy was consumed. To further improve the economics of microwave fracturing, higher powers up to 16 kW were used to rapidly heat samples to relatively low temperatures in a continuous, belt-fed applicator. A significant improvement of grindability was obtained with a larger rod mill feed size in comparison to a minus 6-mesh Bond feed.
Date: 1995
Creator: Walkiewicz, John W.; Lindroth, David P. & Clark, Andrea E.
Partner: UNT Libraries Government Documents Department

Microwave processing of materials. Final report

Description: A Cooperative Research and Development Agreement (CRADA) between Lockheed Martin Energy Systems, Inc. (LMES) and Lambda Technologies, Inc. (Lambda) of Raleigh, N.C., was initiated in May 1995. [Lockheed Martin Energy Research, Corp. (LMER) has replaced LMES]. The completion data for the Agreement was December 31, 1996. The purpose of this work is to explore the feasibility of several advanced microwave processing concepts to develop new energy-efficient materials and processes. The project includes two tasks: (1) commercialization of the variable-frequency microwave furnace (VFMF); and (2) microwave curing of polymer composites. The VFMF, whose initial conception and design was funded by the Advanced Industrial Concepts (AIC) Materials Program, will allow us, for the first time, to conduct microwave processing studies 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: November 1, 1997
Creator: McMillan, A.D.; Lauf, R.J. & Garard, R.S.
Partner: UNT Libraries Government Documents Department

Research on microwave joining of SiC. Final report

Description: Work on microwave joining of sintered SiC has showed that small samples could be jointed using Si interlayer (applied as pressed powder); SEM showed a smooth, homogeneous interlayer 50 {mu}m wide. Objective of this contract is to optimize these joints. Results showed that the interlayer could be reduced to 10-20 {mu}m using an oil-based slurry made from Si powder, and to less than 5 {mu}m by plasma spraying Si on one of the SiC surfaces. Direct joints were made in reaction bonded SiC, using the residual Si. Excellent joints with good mechanical properties were obtained in both small specimens and in small scale tube assemblies like in heat exchanger and radiant burner tubes. In situ reaction synthesis from powders to produce a SiC-TiC-SiC joint was demonstrated, as well feasibility of producing SiC from microwave-assisted decomposition of polymer precursors. Finally, new applicator designs, including a compound adjustable iris and a mitered bend single mode cavity, were demonstrated to provide improved heating of larger and longer specimens. This work provides the foundation for scaleup of microwave joining to SiC components for industrial applications.
Date: June 30, 1993
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

Intense high-frequency gyrotron-based microwave beams for material processing

Description: Microwave processing of materials has traditionally utilized frequencies in the 0.915 and 2.45 GHz regions. Microwave power sources are readily available at these frequencies but the relatively long wavelengths can present challenges in uniformly heating materials. An additional difficulty is the poor coupling of ceramic based materials to the microwave energy. Los Alamos National Laboratory scientists, working in conjunction with the National Center for Manufacturing Sciences (NCMS), have assembled a high-frequency demonstration processing facility utilizing gyrotron based RF sources. The facility is primarily intended to demonstrate the unique features available at frequencies as high as 84 GHz. The authors can readily provide quasi-optical, 37 GHz beams at continuous wave (CW) power levels in the 10 kW range. They have also provided beams at 84 GHz at 10 kW CW power levels. They are presently preparing a facility to demonstrate the sintering of ceramics at 30 GHz. This paper presents an overview of the present demonstration processing facility and describes some of the features they have available now and will have available in the near future.
Date: March 1, 1997
Creator: Hardek, T.W.; Cooke, W.D.; Katz, J.D.; Perry, W.L. & Rees, D.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

Temperature distribution in a flowing fluid heated in a microwave resonant cavity

Description: This paper presents results of an analytical study of microwave heating of a fluid flowing through a tube situated along the axis of a cylindrical microwave applicator. The interaction of the microwave field pattern and the fluid velocity profiles is illustrated for both laminar and turbulent flow. Resulting temperature profiles are compared with those generated by conventional heating through a surface heat flux. It is found that microwave heating offers several advantages over conventional heating.
Date: April 1, 1996
Creator: Thomas, J.R. Jr.; Nelson, E.M.; Kares, R.J. & Stringfield, R.M.
Partner: UNT Libraries Government Documents Department

Studies on the scale-up of the microwave-assisted nitridation and sintering of reaction-bonded silicon nitride

Description: Studies using laboratory test samples have shown that microwave heating produces sintered reaction-bonded silicon nitride materials with improved properties. The final challenge for processing this material by microwave heating is the development of a technology for processing larger batch-size quantities of these materials. Initial microwave scale-up experiments were performed using powder compacts of a bucket tappet geometry. In experiments using microwave-transparent boron nitride sample crucibles, temperature gradients within some crucibles led to larger variations in the sample densities than were obtained with the conventionally processed samples. The use of a microwave-suscepter type crucible made of silicon carbide and boron nitride resulted in an improved temperature uniformity and in density variations comparable to those obtained for the control groups.
Date: May 1, 1996
Creator: Kiggans, J.O.: Tiegs, T.N. & Kimrey, H.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 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

Adhesive bonding via exposure to microwave radition and resulting mechanical evaluation

Description: Adhesive bonding/joining through microwave radiation curing has been evaluated as an alternative processing technology. This technique significantly reduces the required curing time for the adhesive while maintaining equivalent physical characteristics as the adhesive material is polymerized (crosslinked). This results in an improvement in the economics of the process. Testing of samples cured via microwave radiation for evaluation of mechanical properties indicated that the obtained values from the single lap-shear test are in the range of the conventionally cured samples. In general, the ultimate tensile strength, {sigma}{sub B}, for the microwave processed samples subjected to this single lap-shear test was slightly higher than for conventionally cured samples. This technology shows promise for being applicable to a wide range of high volume, consumer goods industries, where plastics and polymer composites will be processed.
Date: April 1, 1996
Creator: Paulauskas, F.L.; Warren, C.D. & Meek, T.T.
Partner: UNT Libraries Government Documents Department

Scale-up of microwave nitridation of sintered reaction bonded silicon nitride parts. Final report

Description: Scale-up were performed in which microwave heating was used to fabricate reaction-bonded silicon nitride and sintered reaction-bonded silicon nitride (SRBSN). Tests were performed in both a 2.45 GHz, 500 liter and a 2.45 GHz, 4000 liter multimode cavities. The silicon preforms processed in the studies were clevis pins for diesel engines. Up to 230 samples were processed in a single microwave furnace run. Data were collected which included weight gains for nitridation and sintering studies were performed using a conventional resistance-heated furnace.
Date: October 1, 1997
Creator: Tiegs, T.N.; Kiggans, J.O. & Garvey, G.A.
Partner: UNT Libraries Government Documents Department

Scale-up of the nitridation and sintering of silicon preforms using microwave heating

Description: Scale-up studies were performed in which microwave heating was used to fabricate reaction-bonded silicon nitride and sintered reaction-bonded silicon nitride (SRBSN). Tests were performed in both a 2.45 GHz, 500 liter and a 2.45 GHz, 4,000 liter multimode cavities. A variety of sizes, shapes, and compositions of silicon preforms were processed in the studies, including bucket tappets and clevis pins for diesel engines. Up to 230 samples were processed in a single microwave furnace run. Data were collected which included weight gains for nitridation experiments, and final densities for nitridation and sintering experiments. For comparison, nitridation and sintering studies were performed using a conventional resistance-heated furnace.
Date: May 1, 1996
Creator: Kiggans, J.O. Jr.; Tiegs, T.N.; Davisson, C.C.; Morrow, M.S. & Garvey, G.J.
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

Y-12 development organization technical progress report. Part 5 -- Polymers, ceramics and solvents, period ending January 1, 1996

Description: Microwave sintering studies with boron carbide (B{sub 4}C) are being evaluated to compare properties of unidirectionally pressed and sintered microwaved pellets with gelcasting of B{sub 4}C. The particle blend is a 50/50 blend of 1-{micro}m and 0.1-{micro}m using 5 wt% carbon (Thermax{reg_sign}) addition. The large, dual-frequency microwave furnace was used to determine that scaleup of a large number of parts can be processed simultaneously using a microwave furnace. Microwave heat treatment of commercial silicon carbide (SiC) resulted in minimal densification, which is thought to result from the exclusion of liquid-phase eutectic, producing sintering aids.
Date: April 15, 1996
Creator: Northcutt, W.G. Jr.
Partner: UNT Libraries Government Documents Department

Research on microwave joining of SiC

Description: Results: identification of optimum joining temperature range for reaction bonded Si carbide at 1420-1500 C; demonstration that specimens joined within this range have fracture roughness greater than as-received material; and demonstration of ability to use SiC formed in situ from the decomposition of polycarbosilane as a joining aid for sintered Si carbide. In the latter case, the interlayer material was also shown to fill any pores in the joining specimens near the interlayer. Together with the demonstration of leaktight joints between tube sections of reaction bonded and sintered SiC under the previous contract, these results provide the foundation for scaleup to joining of the larger and longer tubes needed for radiant burner and heat exchanger tube assemblies. The formation of SiC in situ is important because maintaining roundness of these large tubes is a technical challenge for the tube manufacturer, so that formation of a leaktight joint may require some degree of gap filling.
Date: July 31, 1995
Creator: Silberglitt, R.
Partner: UNT Libraries Government Documents Department

R and D 100 market assessment

Description: The microwave solidification system can be used for treating a variety of waste materials. The principal application is for treating solid and liquid nuclear waste in the form of residue oxides and salts, sludges, contaminated materials used in processing or handling nuclear materials and combustion residues.
Date: December 31, 1998
Partner: UNT Libraries Government Documents Department

High intensity production of high and medium charge state uraniumand other heavy ion beams with VENUS

Description: The next generation, superconducting ECR ion source VENUS(Versatile ECR ion source for NUclear Science) started operation with 28GHzmicrowave heating in 2004. Since then it has produced world recordion beam intensities. For example, 2850 e mu A of O6+, 200 e mu A of U33+or U34+, and in respect to high charge state ions, 1 e mu A of Ar18+, 270e mu A of Ar16+, 28 e mu A of Xe35+ and 4.9 e mu A of U47+ have beenproduced. A brief overview of the latest developments leading to theserecord intensities is given and the production of high intensity uraniumbeams is discussed in more detail.
Date: November 15, 2007
Creator: Leitner, Daniela; Galloway, Michelle L.; Loew, Timothy J.; Lyneis, Claude M.; Rodriguez, Ingrid Castro & Todd, Damon S.
Partner: UNT Libraries Government Documents Department

BIOASSAY VESSEL FAILURE ANALYSIS

Description: Two high-pressure bioassay vessels failed at the Savannah River Site during a microwave heating process for biosample testing. Improper installation of the thermal shield in the first failure caused the vessel to burst during microwave heating. The second vessel failure is attributed to overpressurization during a test run. Vessel failure appeared to initiate in the mold parting line, the thinnest cross-section of the octagonal vessel. No material flaws were found in the vessel that would impair its structural performance. Content weight should be minimized to reduce operating temperature and pressure. Outer vessel life is dependent on actual temperature exposure. Since thermal aging of the vessels can be detrimental to their performance, it was recommended that the vessels be used for a limited number of cycles to be determined by additional testing.
Date: September 22, 2008
Creator: Vormelker, P
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

Commissioning of the long-pulse fast wave current drive antennas for DIII-D

Description: Two new four-element fast wave current drive antennas have been installed on DIII-D. These antennas are designed for 10-s pulses at 2 MW each in the frequency range of 30 to 120 MHz. Each element comprises two poloidal segments fed in parallel in order to optimize plasma coupling at the upper end of the frequency range. The antennas are mounted on opposite sides of the vacuum vessel, in ports designated 0{degrees} and 180{degrees} after their toroidal angle. Each antenna array is fed by a single transmitter. The power is first split two ways by means of a 3-dB hybrid coupler, then each of these lines feeds a resonant loop connecting a pair of array elements. The power transfer during asymmetric phasing is shunted between resonant loops by a decoupler. The resonant loops are fitted with line stretchers so that multiple frequencies of operation are possible without reconfiguring the transmission line. Commissioning of these antennas has been underway since June 1994. Several deficiencies in the transmission line system were uncovered during initial vacuum conditioning, including problems with the transmission line insulators and with the drive rods for the variable elements. The former was solved by replacing the original alumina insulators, and the latter has been avoided during operation to date by positioning the tuners to avoid high voltage appearing on the drive rods. A modified design for the drive rods will be implemented before RF operations resume operation June 1995. New transmitters were procured from ABB for the new antennas and were installed in parallel with the antenna installation. During initial vacuum conditioning of the antenna in the 180{degree} port a fast digital oscilloscope was used to try to pinpoint the location of arcing by a time-of-flight technique and to develop an understanding of the typical arc signature in the system.
Date: September 1, 1995
Creator: Baity, F.W.; Barber, G.C.; Goulding, R.H.; Hoffman, D.J.; DeGrassie, J.S.; Pinsker, R.I. et al.
Partner: UNT Libraries Government Documents Department

Design of the 3rd generation ECR ion source

Description: Development of the 3rd Generation ECR ion source has progressed from a concept described in the last ECR Ion Source Workshop to the fabrication of a full scale prototype superconducting magnet structure. The prototype consists of three solenoid coils and six race track coils with iron poles forming the sextupole. The design calls for mirror fields of 4 T at injection and 3 T at extraction and for a radial field strength at the wall of 2.4 T. The prototype magnet will be tested this spring in an existing vertical cryostat to determine its operating characteristics including maximum operating values, training characteristics and to study the interaction between the solenoid and sextupole coils. Design of the ECR plasma chamber includes aluminum walls to provide an enhanced source of cold electrons, up to three separate microwave feeds to allow simultaneous heating of the plasma electrons at 10, 14 and 18 GHz or at 6, 10 and 14 GHz. Water cooling of the plasma chamber walls and the injection and extraction plates is planned so that up to 10 kW of microwave power can be used without excessive heating of the chamber components. Experience with the AECR-U at LBNL shows that increasing the magnetic fields and using two frequency heating allows operation at lower neutral pressures and higher microwave power density. Both of these conditions are needed to produce very high charge states from elements with masses greater than xenon and the resulting higher energy, more intense heavy beams from the 88-Inch Cyclotron would provide new research opportunities.
Date: February 1, 1997
Creator: Lyneis, C.M.; Xie, Z.Q. & Taylor, C.E.
Partner: UNT Libraries Government Documents Department

Optimization of microwave heating in an existing cubicle cavity by incorporating additional wave guide and control components

Description: The use of microwave energy to thermally treat Low Level (LLW), Transuranic (TRU), and mixed waste has been under development at the Rocky Flats Environmental Technology Site (Site) since 1986. During that time, the technology has progressed from bench-scale tests, through pilot-scale tests, and finally to a full-scale demonstration unit. Experimental operations have been conducted on a variety of non-radioactive surrogates and actual radioactive waste forms. Through these studies and development efforts, the Microwave Vitrification Engineering Team (MVET) at Rocky Flats has successfully proven the application of microwave energy for waste treatment operations. In the microwave solidification process, microwave energy is used to heat a mixture of waste and glass frit to produce a vitrified product that meets all the current acceptance criteria at the final disposal sites. All of the development to date has utilized a multi-mode microwave system to provide the energy to treat the materials. Currently, evaluations are underway on modifications to the full-scale demonstration system that provide a single-mode operation as a possible method to optimize the system. This poster presentation describes the modifications made to allow the single-mode operation.
Date: April 1, 1995
Creator: Erle, R.R.; Eschen, V.G. & Sprenger, G.S.
Partner: UNT Libraries Government Documents Department

Treatment options for low-level radiologically contaminated ORNL filtercake

Description: Water softening sludge (>4000 stored low level contaminated drums; 600 drums per year) generated by the ORNL Process Waste Treatment Plant must be treated, stabilized, and placed in safe storage/disposal. The sludge is primarily CaCO{sub 3} and is contaminated by low levels of {sup 90}Sr and {sup 137}Cs. In this study, microwave sintering and calcination were evaluated for treating the sludge. The microwave melting experiments showed promise: volume reductions were significant (3-5X), and the waste form was durable with glass additives (LiOH, fly ash). A commercial vendor using surrogate has demonstrated a melt mineralization process that yields a dense monolithic waste form with a volume reduction factor (VR) of 7.7. Calcination of the sludge at 850-900 C yielded a VR of 2.5. Compaction at 4500 psi increased the VR to 4.2, but the compressed form is not dimensionally stable. Addition of paraffin helped consolidate fines and yielded a VR of 3.5. In conclusion, microwave melting or another form of vitrification is likely to be the best method; however for immediate implementation, the calculation/compaction/waxing process is viable.
Date: April 1, 1996
Creator: Lee, Hom-Ti & Bostick, W.D.
Partner: UNT Libraries Government Documents Department