bluuebunny/crossref_metadata_2025_split huggingface dataset:
The use of Microwave-Assisted Processing for the Production of High Tc Superconductors
Authors: Rowley A. T. , Wroe F. C. R. 
Published: April 2011

AbstractHigh critical temperature superconducting (HTcS) bulk ceramics with the high values of critical current densities (Jc) necessary for practical applications, are only achieved through careful control of the material microstructure. Consequently, many stages in the production of HTcSs are extremely time consuming; often taking a number of days to proceed to completion, and usually requiring precise control of sample temperature.The volumetric nature of microwave heating will clearly have an impact on the processing of large quantities of these materials, particularly when it is balanced with the simultaneous application of radiant heating. In this way, the production of thermal gradients can be avoided, even when relatively fast heating rates (for these materials) are used.Perhaps more interesting, is the possibility of non-thermal microwave effects (due to the presence of an electric field) enhancing the processing times and even the material properties of HTcSs.This work assesses the impact of microwave-assisted processing on a number of stages involved in the production of bulk pieces of Bi-2212 and Y-123 based superconductors, and demonstrates quite clearly that non-thermal as well as thermal microwave effects are relevant to these materials.
In—Line Measurement Of High Temperature Dielectric Constant In The Process Of Sintering
Authors: Jian Zhou , Jiping Cheng , Yuling Tang , Jinyu Qiu 
Published: April 2011

AbstractIn this paper, a resonant cavity method is developed and some experimental results for measuring dielectric constants of ceramic samples (e. g. Al2O3) under different sintering temperatures are reported. The experiments show that this method has higher precision and good prospects of in—line monitoring the high temperature dielectric constant in the process of raising the temperature of the samples. These results provide some scientific experimental basis for physical research of ceramic materials.
The Dielectric Properties Of Porous Zinc Oxide Ceramics
Authors: Calame J. P. , Carmel Y. , Gershon D. , Birman A. , Martin L. P. , Dadon D. , Rosen M. 
Published: April 2011

AbstractMeasurements of the complex dielectric constant of microwave sintered, porous ZnO at 2.45 GHz are presented. The dielectric properties as a function of porosity do not obey the standard Maxwell-Garnet dielectric mixing law with the ceramic material as the major phase, but instead behave as if the ceramic grains always remain in relatively poor electrical contact even at very high densities. Electromagnetic simulations, carried out for a variety of microstructure geometries, are performed to explore this observation. A model which treats the ceramic as an array of grains and pores, with the grains separated from each other by nonor slightly-percolating, fractal-geometry surfaces, provides a good description of the experimental results.
FDTD Simulation of Microwave Sintering in Large (500/4000 Liter) Multimode Cavities
Authors: Subirats Marta , Iskander Magdy F. , White Mikel J , Kiggans Jim 
Published: April 2011

AbstractTo help develop large-scale microwave-sintering processes and to explore the feasibility of the commercial utilization of this technology, we used the recently developed multi-grid 3D Finite-Difference Time-Domain (FDTD) code and the 3D Finite-Difference Heat-Transfer (FDHT) code to determine the electromagnetic (EM) fields, the microwave power deposition, and temperature-distribution patterns in layers of samples processed in large-scale multimode microwave cavities.This paper presents results obtained from the simulation of realistic sintering experiments carried out in both 500 and 4000 liter furnaces operating at 2.45 GHz. The ceramic ware being sintered is placed inside a cubical crucible box made of rectangular plates of various ceramic materials with various electrical and thermal properties. The crucible box can accommodate up to 5 layers of ceramic samples with 16 to 20 cup-like samples per layer. Simulation results provided guidelines regarding selection of crucible-box materials, cruciblebox geometry, number of layers, shelf material between layers, and the fraction volume of the load vs. that of the furnace.Results from the FDTD and FDHT simulations will be presented and various tradeoffs involved in designing an effective microwave-processing system will be compared graphically.
Open Applicator Analysis For Material Joining And Dielectric Measurements
Authors: Chen S. P. , Tinga W. R. , Vermeulen F. E. 
Published: April 2011

AbstractResonant internal and radiated external electromagnetic fields of an open coaxial structure are analyzed using FDTD. These fields are characterized for two structures, with and without a quarter-wave choke. Techniques utilized to obtain a steady state solution are discussed. Good agreement with field measurements is obtained. This moveable open applicator is convenient for creating intense hot zones as required in ceramic joining. It is also suitable for the measurement of surface dielectric properties of planar materials at room or elevated temperatures.
Scale-Up of the Nitridation and Sintering of Silicon Preforms Using Microwave Heating
Authors: Kiggans J. O. , Tiegs T. N. , Davisson C. C. , Morrow M. S. , Garvey G. J. 
Published: April 2011

AbstractScale-up studies were performed in which microwave heating was used to fabricate reactionbonded 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. 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.
Development Of A Multi-Grid Fdtd Code For Three-Dimensional Simulation Of Large Microwave Sintering Experiments
Authors: White Mikel J , Iskander Magdy F. , Kimrey Hal D. 
Published: April 2011

AbstractThe Finite-Difference Time-Domain (FDTD) code available at the University of Utah has been used to simulate sintering of ceramics in single and multimode cavities, and many useful results have been reported in literature [1–4]. More detailed and accurate results, specifically around and including the ceramic sample, are often desired to help evaluate the adequacy of the heating procedure. In electrically large multimode cavities, however, computer memory requirements limit the number of the mathematical cells, and the desired resolution is impractical to achieve due to limited computer resources. Therefore, an FDTD algorithm which incorporates multiple-grid regions with variable-grid sizes is required to adequately perform the desired simulations. In this paper we describe the development of a three-dimensional multi-grid FDTD code to help focus a large number of cells around the desired region. Test geometries were solved using a uniform-grid and the developed multi-grid code to help validate the results from the developed code. Results from these comparisons, as well as the results of comparisons between the developed FDTD code and other available variable-grid codes are presented. In addition, results from the simulation of realistic microwave sintering experiments showed improved resolution in critical sites inside the three-dimensional sintering cavity. With the validation of the FDTD code, simulations were performed for electrically large, multimode, microwave sintering cavities to fully demonstrate the advantages of the developed multi-grid FDTD code.
Numerical Simulation and Experimental Validation of RF Drying
Authors: Bringhurst S. , White M. J , Iskander M. F. 
Published: April 2011

AbstractThe Finite-Difference Time-Domain (FDTD) method has been used by our group to simulate a wide variety of Radio Frequency (RF) and induction-drying processes and realistic, microwave-sintering experiments. Many results were presented and some guidelines towards the effective use of the microwave and RF heating technologies of ceramic ware were developed.In this paper we describe an experimental effort which was used to validate the FDTD simulation results. Specifically an experimental RF dryer, Thermax Model No. T3GB operating at 25 MHz, was used to dry ceramic ware of various materials, sizes, and shapes and the temperature distribution pattern was monitored using six fiber-optic temperature probes. The measured heating patterns were then compared with the FDTD simulation results. Many of the guidelines developed using the numerical simulations were confirmed experimentally.Results from various comparisons between simulation and experimental data will be presented. Additional results from the simulation efforts illustrating possible procedures for improving the efficiency and the uniformity of RF drying will also be described
Application of the 50 Ω Radio Frequency Technology in the Automotive Industry: Fast Bonding of Composite Materials: Rear Doors of the Citroen Zx and Citroen Xantia Cars
Authors: Bernard J. P. , Sabran Mr. , Collet L. 
Published: April 2011

AbstractIn the field of plastic and composite materials the radio frequency dielectric heating is more and more used. Compared to traditional techniques such as conduction and convection heating, the radio frequency technology is interesting, because it allows fast heating of thick materials and heat insulation materials.As bonding techniques are more and more integrated in production lines, the polymerization of glues must be realized in a very short time. The 50 use of the Ω radio frequency technology makes this heating process possible.The authors describe the industrial application of this technology to the CITROEN ZX and CITROEN XANTIA cars. Steps involved in implementing this industrial process (laboratory - pilot -industrial equipment) are presented and analysis the technical and economic results of this application.
Spread Spectrum Microwave Power Generation for Improving Efficiency
Authors: Van Loock W. M. 
Published: April 2011

AbstractMicrowave power for heating applications is normally generated in the designated ISM frequency bands which occupy a band of 4%. Actual microwave generators, such as are used in domestic ovens utilise only a small fraction of this bandwidth. It is being demonstrated that spreading the power uniformly over the full ISM band by controlled frequency modulation dramatically reduces all levels of potential electromagnetic interference. With such controlled modulation telecommunication channels can operate within the ISM bands without serious problems because the leakage levels are reduced by 20 to 30 dB with no additional shielding costs. One simple (though not optimum) modulating waveform is a large ripple voltage on the magnetron power supply. Frequency modulation that spreads the energy over the full ISM band also improves the overall energy efficiency in multimode heating applications.
Microwave Process Control Through A Traveling Wave Tube Source
Authors: Vogt G. J. , Regan A. , Rohlev A. , Curtin M. 
Published: April 2011

AbstractA rapid feedback control system was designed to operate with a traveling wave tube amplifier for regulating the sintering temperature of tows and tubes in a single mode microwave cavity. The control system regulated the microwave frequency and power absorbed by the sample in order to maintain the sample temperature. Testing with NICALON tows and mullite tubes demonstrated that the control scheme worked well for stationary and slowly moving (<10mi/min) samples, but failed for fast moving samples. Difficulty with measuring sample temperatures was resolved by using a light sensor to measure the emitted light intensity and to gauge the relative degree of heating. This work was supported by the Department of Energy, Office of Industrial Technologies, Advanced Industrial Materials Program.
Control of Microwave Process for Polymer Curing by Dielectric Property Measurements in a Broad Frequency Range, 1 MHz-10 GHz
Authors: Meyer O. , Belhadj-Tahar N. , Fourrier-Lamer A. 
Published: April 2011

AbstractLet us present a new automatic system which couples a high power circuit (2.45 GHz) for heating with a low power one, for broad frequency band measurements of dielectric permittivity (1 MHz-10 GHz). The sample under microwave curing consists in an epoxy resin + hardener complex (DGEBA+DDS). The broad band spectra shows the existence of a dielectric relaxation. This absorption is used as a marker to describe the evolution of the reaction in relation with time and temperature, in terms of conversion ratio, kinetic velocity and quality. The phenomenum of microwave activation and interactions between permanent molecular dipoles and electromagnetic waves form the subject of this study. We also try to establish the specificity of microwave curing from a microscopic point of view. This work emphasizes new concepts which concern microwave chemistry.
Use of Microwaves for Nondestructive Material Inspection
Authors: Hokkanen B. R. , Lindsey J. F. 
Published: April 2011

AbstractWideband S-parameter measurements have been used to investigate the properties of electrically non-conductive materials using a vector network analyzer. Using S21 scattering parameters, amplitude and phase shift measurements were taken for a variety of both homogeneous and heterogeneous materials. With these initial S-parameter measurements as a reference, surface defects were modeled on the test samples and the S-parameter measurements were reevaluated. The effect of varying levels of moisture absorption in certain materials was also investigated. The results of this study indicate that there is indeed potential for the use of a vector network analyzer as a nondestructive testing tool to evaluate the structural integrity and/or moisture content of electrically non-conductive materials through the transmission of microwave energy.
Mask-Edge Distributions Produced by 80 KeV As+ Ion Implantation Into Si
Authors: Danailov D. , Karpuzov D. , Almazouzi A. , Almeida P.De , Victoria M. 
Published: April 2011

AbstractThe 2D-dopant and defect distributions resulting from 80 keV ion implantation of As+ ions into Si through a high-edge mask are presented. The distributions are obtained by means of an efficient computer procedure using the results of Monte Carlo simulation. Two versions of the computer code TRIM are used. The 2D-target atom redistribution is obtained as a result of cascade collisions. The simulation reveals the effect of near-mask-edge target atom depletion. This effect is related to the recoil phenomena and can be explained on the basis of simple model.
Dose Rate Effects During Damage Accumulation in Silicon
Authors: Caturla M. -J. , Rubia T. Diaz de la 
Published: April 2011

AbstractWe combine molecular dynamics and Monte Carlo simulations to study damage accumulation and dose rate effects during irradiation of Silicon. We obtain the initial stage of the damage produced by heavy and light ions using classical molecular dynamics simulations. While heavy ions like As or Pt induce amorphization by single ion impact, light ions like B only produce point defects or small clusters of defects. The amorphous pockets generated by heavy ions are stable below room temperature and recrystallize at temperatures below the threshold for recrystallization of a planar amorphous-crystalline interface. The damage accumulation during light ion irradiation is simulated using a Monte Carlo model for defect diffusion. In this approach, we study the damage in the lattice as a function of dose and dose rate. A strong reduction in the total number of defects left in the lattice is observed for lower dose rates.
Annealing Properties of Defects in Bf2+ Implanted Silicon
Authors: Kitano T. , Watanabe M. , Yaoita A. , Oguro S. , Uedono A. , Moriya T. , Tanigawa S. , Kawano T. , Suzuki R. , Ohdaira T. , Mikado T. 
Published: April 2011

AbstractThe annealing properties of defects in BF2+ implanted silicon were investigated using positron annihilation, TEM and SIMS techniques. For the as-implanted specimens, the major species of defects was identified to be divacancies. After thermal annealing, vacancy-fluorine complexes were formed. The size of open volume in the vacancy-fluorine complexes became larger with increasing annealing temperature. Even after 1100 °C, the vacancy-fluorine complexes were still stable with the size of open volume close to V5. The depth profile of vacancy-fluorine complexes was not largely changed after re-crystallization. In this way, the fluorine atoms played an important role in forming the defects with a large size of open volume. After 1100°C annealing, the fluorine atoms piled up at two regions; the projected range of fluorine and the original amorphous/crystalline interface, where bubbles were observed by TEM. The vacancy-fluorine complexes detected by positron annihilation might be precursors of the bubbles observed by TEM.
Competition Between Gettering by Implantation-Induced Cavities in Silicon and Internal Gettering Associated with SiO2 Precipitation
Authors: McHugo S. A. , Weber E. R. , Myers S. M. , Petersen G. A. 
Published: April 2011

AbstractThe gettering behavior of Cu and Fe was investigated in CZ silicon containing both internal-gettering sites in the bulk due to SiO2 precipitation and a device-side layer of cavities formed by He ion implantation and annealing. The objective was to quantify the effectiveness of impurity gettering at cavities relative to the widely used internal-gettering process. Both rapid thermal anneals and furnace anneals were used during the gettering sequences to reveal transient effects as well as the final, thermodynamically-equilibrated condition. For temperatures of 700, 800 and 850°C, the cavity gettering was observed to dominate the internal gettering as indicated both by the number of gettered atoms in the cavities and the residual solution concentration in the device region. The results are interpreted in detail by numerically solving the diffusion equation with sink-related source terms based on earlier, fundamental studies of the underlying mechanisms of internal and cavity gettering.
Secondary Defect Formation And Gettering in Mev Self-Implanted Silicon
Authors: Brown R. A. , Kononchuk O. , Radzimski Z. , Rozgonyi G. A. , Gonzalez F. 
Published: April 2011

AbstractSecondary defect and impurity distributions in MeV self-implanted Czochralski (Cz) and float-zone (FZ) silicon have been investigated by transmission electron microscopy, optical microscopy with preferential chemical etching, and secondary ion mass spectroscopy. We found that the ion fluence and the oxygen content of the implanted wafers affect the number and depth distribution of extended defects remaining after annealing. Intrinsic oxygen also redistributes during annealing of Cz wafers, producing two regions of relatively high oxygen concentration: one at extended defects near the ion projected range, and another, shallower region, which correlates with the distribution of vacancy-type defects. Both of these regions are also able to getter metallic impurities, depending on the implantation and annealing conditions. These defect issues may adversely affect the quality of the near surface device region, and must be controlled for successful gettering by ion implantation.
Ion Beam Synthesis of SiC/Si Heterostructures by Mevva Implantation
Authors: Wong S. P. , Ho L. C. , Cihen Djhu , Guo W. S. , Yan H. , Kwok R. W. M. 
Published: April 2011

AbstractIon beam synthesis of SiC/Si heterostructures was performed by MIEVVA (metal vapor vacuum arc) implantation under various implantation and annealing conditions. The implanted SiC/Si heterostructures were characterized by various techniques. Carbon redistribution in overstoichiometrically implanted samples during annealing to form a stoichiometric SiC layer has been observed for the first time. The FTIR spectra were found to be composed of two components, one attributed to amorphous SiC and the other to ß-SiC. It was also found that there are critical dose and critical energy at which the crystalline fraction increases abruptly. Other results on electrical and optical characterization are also presented and discussed.
SiC Precipitate Formation During High Dose Carbon Implantation Into Silicon
Authors: Lindner J. K. N. , Volz K. , Stritzker B. 
Published: April 2011

AbstractThe formation of SiC precipitates during the high-dose implantation of carbon ions into Si(100) is studied by means of TEM for implantation conditions, which are suitable for the ion beam synthesis of buried SiC layers in silicon. It is observed that in crystalline silicon nm-sized epitaxially oriented 3C-SiC precipitates are formed which are almost identical in size, nearly independent of the depth and dose (4 – 9 ×1017 C+/cm2). With increasing dose, it is mainly the density of precipitates which increases. Amorphization of the silicon host lattice leads to depth intervals with a strongly decreased density of oriented crystalline SiC precipitates. The irradiation induced formation of larger randomly oriented SiC crystallites is observed to occur in amorphized regions after prolonged implantation. Both the irradiation induced destruction and formation of SiC precipitates contribute to the generation of a nearly box-shaped precipitate density distribution at doses near the stoichiometry dose.
Formation and Characteristics of CoSi2 Layers Synthesized by Mevva Implantation
Authors: Wong S. P. , Peng Qicai , Cheung W. Y. , Guo W. S. , Xu J. B. , Wilson I. H. , Hark S. K. , Morton R. , Lau S. S. 
Published: April 2011

AbstractIon beam synthesis of CoSi2 layers in Si by NIEVVA (Metal Vapor Vacuum Arc) implantation has been performed under various conditions. The formation and characteristics of these CoSi2 layers have been studied by XTEM, RBS, AFM, X-ray diffraction, ellipsometry, electrical and Hall effect measurements. It was found that a higher substrate temperature during implantation results in an as-implanted Co distribution closer to the surface and hence the formation of a shallower CoSi2 layer after annealing. Buried CoSi2 layers of good crystal quality and low resistivity CoSi2 can be formed by MEVVA implantation and annealing under appropriate conditions. A strong temperature dependence of the Hall coefficient showing a large peak at around 100K was observed for the CoSi2 layers formed in p-type Si substrates but not in n-type substrates. The properties and their dependence on the processing conditions, in particular, the substrate temperature during implantation, are presented and discussed.