bluuebunny/crossref_metadata_2025_split huggingface dataset:
Formation of End-of-Range Defects in Silicon at Low Temperatures
Authors: Seibt M. , Imschweiler J. , Heftier H. -A. 
Published: March 2011

ABSTRACTWe have used high resolution transmission electron microscopy to study the formation of end- of- range defects after pre- amorphization due to Ge+ - implantation and subsequent furnace annealing at temperatures below 550 C. It is shown that depending on the annealing conditions two types of extrinsic stacking faults (SFs) are formed, i.e. {113}- defects or Frank- type {111} SFs. We present a scheme allowing the controlled deposition of Si self- interstitials into {113}- defects, which can be removed more easily than Frank type SFs during subsequent RTA under constraints of low thermal budget.
Ion Implantation Defect Characterization by High-Resolution X-Ray Diffraction
Authors: Klappe Jos G.E. , Bársony István , Ryan Tom W. 
Published: March 2011

ABSTRACTHigh-energy ion-implantation is one of the roost critical processing steps regarding the formation of defects in mono-crystalline silicon. High- as well as low-doses implanted at various energies can result in relatively high residual defect concentrations after post-implantation annealing.Before annealing, the crystal lattice strain is mainly caused by the point defects. After annealing, the accommodation of substitutional impurities is the main origin of the residual lattice strain. High-Resolution X-ray Diffraction (HRXD) has been frequently used for the characterization of these structures. Dislocation loops formed during the high temperature step, however, cause enhanced diffuse X-ray scattering, which can dominate the measured X-ray intensity in conventional HRXD.Triple axis diffractometry is used in this study to analyze the size, type and location of defects in a boron implanted and rapid thermally annealed silicon sample.
Uniform Low-Temperature Deposition of Optical Layers by Plasma-Activated CVD
Authors: Lydtin Hans , Ritz Arnd 
Published: March 2011

ABSTRACTPlasma activated CVD in a remote operation mode is applied to the deposition of dielectric layers on extended substrates. Layer thickness uniformity of ±1% over areas of 80mm diameter is demonstrated. The microwave applicator sustaining the plasma source of condensable species is compared in its deposition characteristic to conventional evaporation sources. Deposition efficiencies up to 70% are reached. The layer materials used are SiO2 and TiO2. Multilayer structures are prepared and optically characterized.
Measurement of Microwave Induced Forces
Authors: Watkins John L. , Jackson H. W. , Barmatz M. 
Published: March 2011

ABSTRACTElectrically polarizable materials in an inhomogeneous electric field experience a dielectrophoretic force which is proportional to the gradient of the square of the electric field. For high frequency radiation, the time averaged electromagnetic field provides a dc force. The force exerted on a sapphire and a metal sphere by the microwave field in a single mode resonant cavity has been measured. The force measurements have been made at equally spaced points along three orthogonal axes centered in a cylindrical cavity operating in the TE111 mode using 20 watts of microwave power at about 4.84 GHz. These data are compared to the simple theory of dielectrophoresis on a small sphere and verify that, for this mode and in the absence of other forces, there is a unique and stable equilibrium position at the center of the cavity. Measurements of the quality factor of the cavity provide a means of making an absolute check to the theory. The TE111 mode is one of an infinite set of modes predicted to have stable equilibrium positions that exist away from the cavity walls. It is proposed that dielectrophoresis in a microwave resonant cavity can be used to position samples for material processing applications in a microgravity environment. Knowledge of these forces may also be important for interpreting thermogravimetric measurements made in a microwave oven.
Interaction between Gyrotron Radiation and Powder Materials
Authors: Sklyarevich V. , Detkov A. , Shevelev M. , Decker R. 
Published: March 2011

ABSTRACTTo capitilize on the special advantages of gyrotron radiation for fast and continuous materials processing, surface and interface layers are ‘alloyed’ with lossy chemicals and fine-disperse powders. The principles and practical uses are described herein.
Fabrication of Hydroxyapatite Ceramics by Microwave Processing
Authors: Agrawal Dinesh. K. , Fang Y. , Roy D. M. , Roy R. 
Published: March 2011

ABSTRACTVarious hydroxyapatite (HAp) ceramics were fabricated by microwave processing. By carefully selecting the starting material and controlling the processing conditions, regular HAp ceramics with density up to 97% of the theoretical density, porous HAp ceramics with porosity up to 76%, and fully densified transparent HAp ceramics were obtained by using a 2.45 GHz, 500W microwave oven. These ceramics were characterized for density, microstructure, strength, and phase composition, and the results were compared with the conventionally processed ceramics.
Microwave Sintering of Oxide Ceramics
Authors: Brandon J.R. , Samuels J. , Hodgkins W.R. 
Published: March 2011

ABSTRACTThe activities of EA Technology in microwave processing of oxide ceramics are reviewed. Comparative sintering rate measurement techniques have been used to demonstrate microwave enhanced densification of oxide ceramics. Temperature distributions within microwave and conventionally heated ceramics are simulated. Based on these simulations a method for firing large components has been developed which achieves uniform microstructures and low thermal stresses by careful control of temperature distribution.
Processing Aerosols and Filaments in a TM010 Microwave Cavity at 2.45 GHz
Authors: Vogt Gerald J. , Unruh Wesley P. 
Published: March 2011

ABSTRACTAs part of the development of generic microwave processes for spray-drying of homogeneous complex metal oxide powders and for inorganic fiber processing, we have investigated the use of 2.45 GHz microwaves in a high-Q single-mode TM010 cavity coupled directly to aerosols and fibers. Aqueous and ethanol aerosols of ferric nitrate solutions have been successfully dried at 1.8 kW of cavity power for a loaded Q greater than 6000 in flowing nitrogen gas. Similarly, we have observed extremely rapid heating rates in the TM0l0 cavity for small-diameter confined cylinders of water and lossy inorganic fibers. These observations suggest using 2.45 GHz microwave power for drying, calcining, and sintering extruded ceramic filaments. Droplet modeling indicates that the large dielectric shielding for spherical droplets can significantly limit the coupling of 2.45 GHz microwave with spherical aerosols, but not with fibers. Experimental observations on the microwave interactions with ferric nitrate aerosols and with ceramic filaments in the TM010 cavity are described.
Nitridation of Non-Isothermal Silicon Compacts
Authors: Thomas Jeffrey J. , Jesse Renee R. , Johnson D. Lynn , Jennings Hamlin M. 
Published: March 2011

ABSTRACTThe use of microwave heating for the processing of reaction-bonded silicon nitride offers at least two advantages over conventional heating methods. First, the reaction can be made to proceed preferentially in the interior of the reacting compact by maximizing the temperature gradient resulting from microwave heating. This helps maintain the flow of nitrogen into the compact during the later stages of the reaction, when the overall porosity is reduced. Second, the reaction rate can be controlled by changing the power, which gives better control over the processing than can be obtained using conventional heating.
Characterization of Sintered Reaction-Bonded Silicon Nitride Processed by Microwave Heating
Authors: Kiggans J. O. , Tiegs T. N. 
Published: March 2011

ABSTRACTSintered reaction-bonded silicon nitride (SRBSN) tiles were fabricated using microwave and conventional heating. Materials from both processes were analyzed at various stages in their fabrication. Microwave processing resulted in a SRBSN material of higher density and strength than the conventionally processed material.
Mechanica and Physical Properties of Microwave Sintered Si3N4
Authors: Patterson M.C.L. , Apte P.S. , Kimber R.M. , Roy R. 
Published: March 2011

ABSTRACTMicrowave energy at 2.45 GHz has been used to sinter silicon nitride in times of between 30 and 120 minutes to form a dense product with an average grain size of 0.35 μm and substantially improved uniformity of properties over all commercial silicon nitrides and sialons investigated.A comparison between microwave and conventionally sintered parts of the same density showed the average mechanical properties to be the same for both sintering techniques, but revealed an improvement in the uniformity of mechanical properties of the microwave sintered products.Silicon nitride components with 5% Al2O3 and 5% Y2O3 as sintering aids, has been sintered to a density of approximately 97% of theoretical. Hipping of these components at 1800 °C for 60 minutes, resulted in the complete removal of residual porosity. Dense components were evaluated in machining tests against commercial ceramic cutting tools. The results show a reduction in wear rate of batter than 10% for microwave sintered Sl3N4 in turning and milling operations on cast iron at a cutting speed of 2000 surface feet per minute.
Microwave Sintering of Si3N4 Ceramics
Authors: Zhang Jinsong , Cao Lihua , Xia Fei 
Published: March 2011

ABSTRACTThe Si3N4 ceramics(91wt%Si3N4+5wt%Y2O3+4wt%Al2O3) of room temperature strength 620--760 MPa and fracture toughness 7 MPa-m½ were prepared by microwave sintering and their microstructure and mechanical properties were studied.The experiment results show that the higher N2 pressure (>4atm) is very necessary for microwave sintering of Si3N4 ceramics; microwave sintering can greatly decrease the sintering temperature to 1500* C, and increase the transformation rate of α to β-Si3N4,and reduce the total sintering time to about 1 hour. The mechanical properties of the Si3N4 ceramics sintered by microwave are better than that by conventional pressureless sintering.
Polymethyl Methacrylate Binder Removal from an Alumina Compact: Microwave Versus Conventional Heating
Authors: Moore Edmund H. , Clark David E. , Hutcheon Ronald 
Published: March 2011

ABSTRACTCompact samples of alumina and polymethyl methacrylate have been heated in a 2.45 GHz microwave cavity and by conventional heating in an electric furnace. Various heating schedules have been used to effect the removal of the polymeric binder by thermal decomposition. Dielectric properties, porosity and other physical properties have been investigated in order to better understand the binder removal process in a microwave field. Results of the study emphasize the amount of carbon residuals remaining in the bulk.
Surface Modification of Ceramics Using Microwave Energy
Authors: Fathi Z. , Clark D.E. , Hutcheon R. 
Published: March 2011

ABSTRACTSodium alumino-silicate glasses having a constant concentration of alkali ions (15mol%) were prepared. The interdiffusion of potassium ions, K+, for sodium ions, Na+, in the glass composition having AI/Na= 1 was investigated in the presence and absence of a microwave field. Characterization consisted of dielectric loss measurements, electron microprobe analysis (EMP), and microhardness indentation.
Electron Microscopy Study on Zirconia and Alumina Ceramic Powders Synthesized by Microwave Plasma Pyrolysis
Authors: Sickafus Kurt E. , Vollath Dieter , Varma Ravi 
Published: March 2011

ABSTRACTMorphology, chemistry and microstructure of zirconia and alumina based ceramic powders synthesized by microwave plasma pyrolysis were studied by transmission electron microscopy. Electron diffraction was used to determine the phases present, while conventional bright field and dark field imaging were used to characterize grain size and density variations. Materials analyzed in this study were either pure zirconia, pure alumina, or a ternary zirconia-yttria-alumina oxide. Solid spheres, hollow spheres, and fragments of hollow spheres were observed. All three modifications of zirconia were observed in the pure zirconia powder. In alumina, the predominant phase was cubic, gamma alumina. In the ternary oxide, most structures exhibited cubic zirconia diffraction patterns. Energy dispersive x-ray spectroscopy revealed chemical inhomogeneities in the ternary oxide powder.
Microwave Processing of Aluminum-Silicon Carbide Cermets
Authors: Bescher Eric P. , Sarkar Urmimala , MacKenzie John D. 
Published: March 2011

ABSTRACTElectromagnetic radiation in the microwave range has been utilized for the fabrication of SiC particulates-reinforced aluminum matrix cermets. Powder mixtures with compositions ranging from 70 wt% Al - 30wt% SiC to 100 wt% Al were placed and processed under protective nitrogen atmosphere in a 750 W multimode cavity operating at 2.45 GHz. Temperatures larger than 800°C have been achieved in a time varying with the mixture composition. Microstructures and some physical properties of the composites are presented.
Synthesis of Nanocrystalline Powders for Oxide Ceramics by Microwave Plasma Pyrolysis
Authors: Vollath Dieter , Varma Ravi , Sickafus Kurt E. 
Published: March 2011

ABSTRACTPyrolytically prepared ceramic powders usually exhibit excellent homogeneity and small grain sizes. The energy efficiency of those methods for synthesis is, particularly in systems heated electrically, very poor. The situation can be improved drastically using a microwave plasma as a source of energy. This has been confirmed by the synthesis of alumina- and zirconia-based ceramic powders for which an efficiency of more than 80% was found. Aqueous solutions of nitrates of zirconium, yttrium, and aluminum were used as starting materials. Electron microscopy revealed that, through proper selection of the experimental conditions, it is possible to obtain nanocrystalline powders with cubic structure. Because of the extreme conditions during synthesis, it is possible to prepare solid solutions in systems without solubility.
RF Processing of Thermoset and Thermoplastic Composites
Authors: Pearce John A. , Faulkner Carl M. 
Published: March 2011

ABSTRACTGraphite fiber-thermoset epoxy resin composite materials are frequently used in aerospace and related industries. Electromagnetic heating may have some advantages over the present autoclave techniques, especially for large objects. However, the loss factor of graphite composites at microwave frequencies (915 MHz and 2.45 GHz) is so high that the depth of penetration is no more than about 0.1 mm. Arcing may be encountered at high heating rates due to strong transverse E-fields. Also, since the curing process is exothermic and the surface is at elevated temperature, thermal runaway may be encountered in the interior spaces and result in over-cured (thermally damaged) material.We have investigated the heating obtained at radio frequency (nominal 27 MHz) in magnetic induction fields in both experiments and numerical models. Inductive coupling has the advantage that arcing is virtually eliminated, even at high heating rates, for typical cylindrical geometries. Also, induction heating easily accomplishes lap seam welds in thermoplastic composites owing to favorable electric field boundary conditions. Transient temperatures were recorded during heating by optical fiber probes and heating distribution was measured, where possible, using thermographic imaging. Finite difference electrical and thermal model results illustrate the dominance of conduction heat transfer in these materials.
Microwave Dynamic Dielectric Analysis of Curing Neat Resins
Authors: King Ray J. , Werner Michael J. , Mayorga Guillermo D. 
Published: March 2011

ABSTRACTMicrowave reflection resonator sensors have been developed to monitor the dynamic, in situ real and imaginary dielectric components (ε′, ε″) of thermoset polymer matrix composites and thermoplastics. These reusable and noninvasive sensors are conformably mounted in the autoclave mold in such a manner that the EM fields are strongly coupled to the resin. Tracking of (ε′, ε″) during the cure provides information about the chemical kinetics such as timing the point of minimum viscosity and monitoring the relative cure index. The sensor is readily adjustable for optimum coupling to the type of material being tested and is rated for temperatures up to 250°C (480*F). The technique is complementary to other analysis techniques such as Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA). A prototype software and electronics package has been developed to support the sensor.
Preliminary Comparison of Microwave Heating of Complex-Shaped Composites Reinforced with Conductive and Nonconductive Fibers
Authors: Fellows Larry A. , Travis Susannah , Hawley Martin C. 
Published: March 2011

ABSTRACTThe microwave heating of composites with complex shapes has been studied. A V-shaped mold was used to fabricate samples which do not lie parallel to the electric field produced in a 7-in. cylindrical microwave applicator operating at 2.45 GHz.A polyester/glass composite and a polyester/graphite fiber composite were produced for comparison. Heating profiles were made more uniform by applying mode-switching techniques to the processing. Mode-switching is the application of more than one electromagnetic mode to achieve uniform heating.The samples were tested for heating patterns in different geometric and fiber orientations within a single-frequency, cylindrical microwave applicator operating at 2.45 GHz. The temperature profile for each mode was recorded. Mode-switching provided better temperature profiles than single modes. Modeswitching techniques were more successful with the graphite fiber reinforcement.
Finite-Difference Time-Domain (FDTD) Simulation of Microwave Sintering in Multimode Cavities
Authors: Smith Ray L. , Iskander Magdy F. , Andrade Octavio , Kimrey Hal 
Published: March 2011

ABSTRACTMicrowave sintering of ceramics in multimode cavities, particularly the use of picket-fence arrangements, has recently received considerable attention. Various types of ceramics have been successfully sintered and, in some cases, a desirable and unique “microwave effect” has been observed.At present, various aspects of the sintering process such as sample sizes and shapes, types of insulations, and the desirability of including a process stimulus such as SiC rods are considered forms of art and highly dependent on human expertise. The simulation of realistic sintering experiments in a multimode cavity may provide a better understanding of critical parameters involved and allow for the development of guidelines towards the optimization of the sintering process.In this paper, we utilize the FDTD technique to model various geometrical arrangements and material compatibility aspects in multimode microwave cavities and to simulate realistic sintering experiments. The FDTD procedure starts with the simulation of a field distribution in multimode microwave cavities that resembles a set of measured data using liquid crystal sheets. Also included in the simulation is the waveguide feed as well as a dielectric loading plate placed at the base of the cavity. The FDTD simulation thus provides realistic representation of a typical sintering experiment. Aspects that have been successfully simulated include types of insulation, role of SiC rods on the uniformity of the resulting fields, problems that may result from presence of thermocouples, and the possible shielding effects that may result from excessive use of SiC. These results as well as others showing the electromagnetic fields and power-deposition patterns in multiple ceramic samples are presented.
Immobilization of ASH by Microwave Melting
Authors: Morita Kazuki , Nguyen Vinh Q. , Nakaoka Ron , Mackenzie John D. 
Published: March 2011

ABSTRACTNon-radioactive ash was immobilized via microwave melting. The ash composed mainly of silica (SiO2), titania (TiO2), calcia (CaO), alumina (Al2O3), and carbon (C). The ash was melted with various additives, such as magnetite (Fe3O4), lithium carbonate (Li2CO3), sodium carbonate (Na2CO3), and boron oxide (B2O3) by using a 2.45 GHz, 750 W microwave oven. Samples with different ash and additive concentrations were melted when subjected to microwave radiation. Ease of melting was dependent on the carbon and magnetite concentrations. Melted samples were characterized by X-ray diffraction and scanning electron microscopy (SEM), and subjected to the Toxicity Characteristic Leaching Procedure in regard to lead (Pb) immobilization. Melted samples with more than 30 wt% additives has an undetectable leaching rate of less than 0.1 ppm of lead for TCLP test, which was found to be due to the reduction and evaporation of the lead during melting. More than 80 % of the lead was lost through evaporation leaving less than 0.1 wt% Pb in the melted glass.
High Temperature Broadband Dielectric Properties Measurement Techniques
Authors: Andrade Octavio M. , Iskander Magdy F. , Bringhurst Shane 
Published: March 2011

ABSTRACTThis paper discusses theoretical and practical aspects of the development and implementation of various measurement techniques for high-temperature broadband microwave characterization of materials at the University of Utah. Objectives include materials measurements in the frequency range from 45 MHz to 12 GHz and for temperatures as high as 1000°C.
General Purpose High Temperature Microwave Measurement of Electromagnetic Properties
Authors: Batt John A. , Rukus Robert , Gilden Meyer 
Published: March 2011

ABSTRACTAn efficient general purpose method has been developed for implementing a variety of broad band microwave measurement techniques at high temperature. Central to these techniques has been the development of a “dual-waveguide” test fixture. These techniques have been selected, out of necessity, to cover a variety of material types and geometries such as slabs, posts and sheets. These include measurement of complex permittivity and permeability using a modified Nicolson-Ross technique for slabs and Marcuwitz' algorithm for posts. In the implementation of the dual-waveguide, two adjacent and symmetric X-band waveguides are machined from a single block of Inconel alloy 601*, one serving as a test waveguide, the other as a reference waveguide. The dual-waveguide is surrounded by a programmable clam-shell furnace. The reference waveguide provides data which is used to compensate for electrical and dimensional thermal changes in the test section. Combined with commonly used HP 8510 Network Analyzer methods, automated test procedures have been developed to accommodate the various measurement types and sample shapes. Prototypical data will be presented illustrating the effectiveness of some of these techniques. The methods discussed are most useful for rapid data generation over temperatures ranging from room temperature to 2000 degrees F (1093 degrees C) and at frequencies defined by the waveguide dimensions. This paper highlights developments in the dual waveguide system since its construction over one year ago.
Microwave Heating and Characterization of Machinable Ceramics
Authors: Xi Weiguo , Tinga W.R. 
Published: March 2011

ABSTRACTThe dielectric properties of three types of machinable ceramics have been investigated using an automatic microwave dielectrometer system from 300°C to 1600°C at 3GHz. The system setup and techniques are described, and results are presented.