bluuebunny/crossref_metadata_2025_split huggingface dataset:
Application of Ridged Waveguide in Microwave Sintering
Authors: Jian Zhou , Jiping Cheng , Xianjun Liu , Yuling Tang , Lei Chen 
Published: April 2011

AbstractIn this paper, a ridge rectangular waveguide is designed, and its cutoff frequency, impedance and electric field intensity are given by formulas or curves. A few ceramic samples are sintered in it by microwave energy. It is concluded that the device can be as a satisfactory microwave sintering cavity.
Fdtd Simulations And Analysis Of Thin Sample Dielectric Properties Measurements Using Coaxial Probes
Authors: Bringhurst S. , Iskander M. F. , White M. J 
Published: April 2011

AbstractA metallized ceramic probe has been designed for high temperature broadband dielectric properties measurements. The probe was fabricated out of an alumina tube and rod as the outer and inner conductors respectively. The alumina was metallized with a 3 mil layer of moly-manganese and then covered with a 0.5 mil protective layer of nickel plating. The probe has been used to make complex dielectric properties measurements over the complete frequency band from 500 MHz to 3 GHz, and for temperatures as high as 1000 °C.
Estimation Of Complex Permittivity Of Printed Circuit Board Material Using Waveguide Measurements
Authors: Reddy C. J. , Deshpande M. D. , Hanidu G. A. 
Published: April 2011

AbstractA simple waveguide measurement technique is presented to determine the complex permittivity of printed circuit board material. The printed circuit board with metal coating removed from both sides and cut into size which is the same as the cross section of the waveguide is loaded in a short X-band rectangular waveguide. Using a network analyzer, the reflection coefficient of the shorted waveguide(loaded with the sample) is measured. Using the Finite Element Method(FEM) the exact reflection coefficient of the shorted wavguide(loaded with the sample) is determined as a function of dielectric constant. Matching the measured value of the reflection coefficient with the reflection value calculated using FEM and utilizing Newton-Raphson Method, an estimate of the dielectric constant of a printed circuit board material is obtained. A comparison of estimated values of permittivity constant obtained using the present approach with the available data.
Comparison Of Finite-Difference And Analytic Microwave Calculation Methods
Authors: Friedlander F. I. , Jackson H. W. , Barmatz M. , Wagner P. 
Published: April 2011

AbstractNormal modes and power absorption distributions in microwave cavities containing lossy dielectric samples were calculated for problems of interest in materials processing. The calculations were performed both using a commercially available finite-difference electromagnetic solver and by numerical evaluation of exact analytic expressions. Results obtained by the two methods applied to identical physical situations were compared. Our studies validate the accuracy of the finite-difference electromagnetic solver. Relative advantages of the analytic and finitedifference methods are discussed.
Numerical Simulation of Resonant Cavity Microwave Systems for Materials Processing
Authors: Grotjohn Timothy A. , Asmussen Jes 
Published: April 2011

AbstractA single mode microwave resonant cavity used for materials heating is simulated using the FDTD method. The simulation includes both the resonant cavity structure and the input microwave power coupling structure. An overlapping grid method with interpolation between the conformal grid systems developed for each section of the microwave system is used to simulate geometrically complex microwave structures. Comparisons of the FDTD solution for a simplified, lossy-loaded cavity is made with a known analytical solution.
FDTD Simulation of Induction Heating of Conducting Ceramic Ware
Authors: White Mikel J , Iskander Magdy F. , Bringhurst Shane 
Published: April 2011

AbstractInduction heating for the treatment of metals has been in commercial use since the mid 1960's. Traditional advantages of induction heating over the convection or radiation processes include speed of heating, possible energy savings, and the ability to customize the coil design to optimize the heating process. In this paper we used the Finite-Difference Time-Domain (FDTD) technique to simulate and analyze the induction heating process for highly conducting ceramics. In order to analyze frequency effects, simulations were performed at 300 kHz, 2 MHz, and 25 MHz. It is found that at higher frequencies coils with a pitch of 2″ or greater became capacitive and generate a large, axial, electric-field component. This new axial electric field, in addition to the normally encountered azimuthal field, causes an improvement in the uniformity of the power deposition in the ceramic sample. If the sample occupies a large portion of the coil, uniformity may also be improved by using a variable-pitch coil, or by extending the length of the coil a few turns beyond the length of the sample. In a production-line arrangement, where multiple sample are place inside the coil, it is shown that maximum uniformity is achieved when the samples are placed coaxially.
Thermal Phenomena Under Microwave Field in the Organic Synthesis Processes: Application to the Diels Alder Reaction
Authors: Saillard R. , Poux M. , Audhuy-Peaudecerf M. 
Published: April 2011

AbstractThe influence of the microwave heating on chemical reactions were investigated. The kinetic of the Diels Alder reaction were studied under Microwave irradiation at a frequency of 2.45 GHz in a single mode cavity and were compared to the kinetic obtained by a conventional heating. Experiments were carried out in a liquid solvent in order to have a better control of the medium temperature measurement. In a second part, the presence of a catalytic solid phase was introduced. Some thermal fluctuations which are due to an heterogeneity of the electric field were detected in the medium. They reduce the precision of the results and cause problems of experimental reproducibility. A thermoluminescent material allow a good visualisation of these phenomena.In addition, the profiles of the electric field intensity were modelled by a 2D finite elements method in our reactor in the presence of a solvent. Despite the small size of the sample and the use of a monomode cavity which both limited the heterogeneities of the medium temperature, we showed a great heterogeneity of the electric field intensity and as a result the heterogeneity of the temperature in our sample.In order to avoid these phenomena which induce a lack of reproducibility, a stirring device was developed.The values of the kinetics obtained under the 2 heating modes with the introduction of the stirring device. So, it induces a good control of the medium temperature.All those investigations prompted us to the conclusion that there is no difference between microwave heating and a classical heating in the studied reaction.
Kinetics and Mechanism of the Microwave Synthesis of Barium Titanate
Authors: Zhang Hanlin , Ouyang Shixi , Liu Hanxing , Li Yongwei 
Published: April 2011

AbstractThe formation kinetics of BaTiO3from the solid-state BaCO3and TiO2powder in a microwave field was investigated. The quantitative XRD analysis and the model considered the volume change between reactant and product were used in this experiment. Results show that the formation rate of BaTiO3in a microwave field is much faster than upon conventional heating. The activation energy of the solid state reaction for BaTiO3was measured as 58 kJ/mol. This indicates the enhancement of diffusion by the microwave heating process.
Study Of Microwave-Driven Currents In Ionic Crystals
Authors: Rybakov K. I. , Semenov V. E. , Freeman S. A. , Booske J. H. , Cooper R. F. 
Published: April 2011

AbstractThe recent theory of averaged ponderomotive action of microwave E-field in solids is expanded to describe quasistationary ionic currents driven by that action. New experimental results on the dynamics of the microwave-induced currents in AgCl and NaCi are presented. Agreement between experiment and theory provides further and stronger evidence for general validity of the theoretical model.
Pulsed 35 Ghz Gyrotron with Overmoded Applicator for Sintering Experiments
Authors: Fliflet A. W. , Fischer R. P. , Kinkead A. K. , Bruce R. W. 
Published: April 2011

AbstractThe microwave sintering of nanocrystalline alumina compacts is currently under investigation at NRL. This paper will discuss an overmoded microwave furnace based on a 35 GHz pulsed gyrotron which is currently being set up to extend ongoing microwave sintering experiments at 2.45 GHz to 35 GHz. The gyrotron operates at 70 kV and currents up to 10 A. It is driven by a hard tube, variable pulse length (1–15 μs) modulator at repetition rates up to 1 kHz. The gyrotron can produce peak powers up to 100 kW at an efficiency of 20%, and average powers up to 200 W. The gyrotron output is transported via pressurized Ka-Band waveguide to an overmoded resonator containing the workpiece. In initial experiments, the resonator will consist of a piece of WR-284 waveguide. The operation of the system in preliminary sintering experiments is described.
Temperature Gradients and Residual Porosity in Microwave Sintered Zinc Oxide
Authors: Martin L. P. , Dadon D. , Rosen M. , Birman A. , Gershon D. , Calame J. P. , Levush B. , Carmel Y. 
Published: April 2011

AbstractZnO samples were sintered in an overmoded 2.45 GHz microwave applicator. In-situ differential temperature measurements were made to allow comparison of surface and core temperatures during heating. At intermediate temperatures, near 600°C, the sample core was measured to be more than 250°C hotter than the sample surface. As the core temperature approached 1100°C, however, the difference between the surface and core temperatures diminished. Post-sintering scanning electron microscopy (SEM) showed spatial variations in the residual porosity which were consistent with the measured temperature differential. For samples sintered to intermediate temperatures, where large temperature differences persisted, there were significant gradients in the residual porosity. For samples sintered to higher temperatures, there was little residual porosity and no observable porosity gradient. Local density versus temperature behavior was obtained by correlating porosity levels measured from the micrographs with temperature measurements made during sintering. These data demonstrate a significantly lower activation energy for microwave sintering than for conventional sintering.
High Frequency (27.12 MHz) Activation of the Radical Curing of Unsaturated Polyesters in Styrene Solution
Authors: Alazard P. , Gourdenne A. 
Published: April 2011

AbstractThe crosslinking reaction of a divinylester resin of epoxy-acrylic type in styrene solution is activated by high frequencies at 27.12 MHz. The samples to be cured are positionned betweeen two parallel steel plates used as electrodes and an electrical voltage is applied. A parametrical study is described, where the applied electrical voltage, or power, and the concentration of benzoyl peroxide, which is the radical initiator, are taken into account. The optimization of the electromagnetic curing is performed through the determination of the glassy transition temperature of the final products.
Comparative Study of Si3N4 - Based Ceramics Sintering at Frequencies 30 and 83GHz
Authors: Bykov Y. , Eremeev A. , Holoptsev V. 
Published: April 2011

AbstractThe study of microwave ceramics sintering at different frequencies of radiation has important implication for clarifying a specific effect inherent to microwave-based processes and determining the optimal conditions of sintering which yield a high-quality final product. Comparative study of Si3N4-based ceramics sintering at the frequencies of 30 and 83GHz was undertaken on retention of all the conditions but a frequency and microwave power. It is found that an increase in microwave frequency results in reduction in silicon nitride decomposition during sintering.
Microwave and Millimeter wave Processing of Polymer-Derived Silicon Nitride
Authors: Schwab S. T. , Timmons S. F. , Blanchard C. R. , Grimes M. D. , Graef R. C. , Katz J. D. , Rees D. E. , Hardek T. W. 
Published: April 2011

AbstractChemical methods of processing ceramics have the potential to overcome many of the processing-related obstacles that have hindered widespread commercialization. The Southwest Research Institute (SwRI) has focused on the development of polymeric precursors to silicon nitride (Si3N4). One such precursor, perhydropolysilazane (or PHPS), has been shown to be a useful binder for Si3N4 powder processing, a useful matrix precursor for the polymer infiltration/pyrolysis (PIP) processing of fiber-reinforced Si3N4, and a useful ceramic coating precursor for the repair of oxidation protection coatings on carbon-carbon composites. While conventional, thermal pyrolyses of these preceramnics has been sufficient to demonstrate their potential, substantial cost savings could be realized if the polymer-to-ceramic conversion could be instigated with electromagnetic energy. We have investigated the use of millimeter wave heating as a means of converting PHPS into Si3N4, and report here the results of our efforts to produce bulk compacts, coatings, and fiber-reinforced ceramics.
Microwave Plasma Sintering of Alumina
Authors: Johnson D. Lynn , Su Hunghai 
Published: April 2011

AbstractMicrowave induced plasma provides an effective heating source for sintering of ceramics without the thermal instability that occurs in microwave sintering of some materials. In the present study, small cylindrical tubes were sintered in a microwave induced oxygen plasma inside a single mode (TM012) cavity. A dilatometer and an optical fiber thermometer (OFT) black body sensor were employed to follow the changes of shrinkage and temperature during the sintering process. A similar specimen setup was built inside a conventional rapid heating furnace for comparison. The estimated activation energies were 468 ± 20 kJ/mol for plasma sintering and 488 ± 20 kJ/mol for conventional sintering. An athermal effect due to the plasma was observed. Sintering data were analyzed using the combined stage sintering model and the results suggest that the athermal effect may be ascribed to an increase of aluminum interstitial concentration during plasma sintering.
Kinetics of Intrinsic and Dopant-Enhanced Solid Phase Epitaxy in Buried Amorphous Si Layers
Authors: McCallum J. C. 
Published: April 2011

AbstractThe kinetics of intrinsic and dopant-enhanced solid phase epitaxy (SPE) have been measured in buried amorphous Si (a-Si) layers produced by ion implantation. Buried a-Si layers formed by self-ion implantation provide a suitable environment for studies of the intrinsic growth kinetics of amorphous Si, free from the rate-retarding effects of H. For the first time, dopant-enhanced SPE rates have been measured under these H-free conditions. Buried a-Si layers containing uniform As concentration profiles ranging from 1–16.1 × 1019 As.cm−3 were produced by multiple-energy ion implantation and time resolved reflectivity was used to measure SPE rates over the temperature range 480–660°C. In contrast to earlier studies, the dopant-enhanced SPE rate is found to depend linearly on the As concentration over the entire concentration range measured. The SPE rate can be expressed in the form, v/vi(T) = 1 + N/[No exp(-ΔE/kT)], where vi(T) is the intrinsic SPE rate, N is the dopant concentration and No = 1.2 × 1021 cm−3, ΔE = 0.21 eV.
Amorphization Mechanisms in AlxGa1-xAs
Authors: Lagow B. W. , Turkot B. A. , Robertson I. M. , Rehn L. E. , Baldo P. M. , Roh S. D. , Forbes D. V. , Coleman J. J. 
Published: April 2011

AbstractBulk ion implantations of AlxGa1-xAs (x = 0.6 or 0.85) were performed at 77 K with 1.5 MeV Kr+, 1 MeV Ar+ or 1.5 MeV++ ions, and the resulting damage state examined by using Rutherford backscattering spectrometry-channeling at 77 K and 293 K and transmission electron microscopy at 300 K. Amorphization of a portion of the AlxGa1-x As layer occurred at 77 K only for the 1.5 MeV Kr+ implantation, although the dose required to cause amorphization was higher for the higher Al content alloy. TRIM calculations[10–11 ] show that with this implantation the density of high energy density cascades varies as a function of depth through the layer and that these are superimposed on a high, uniform density of defects. Comparison of the ion channeling spectra at 77 K and 293 K shows that recovery occurs over a portion of the layer in the Al0.6Ga0.4As but is not detected in the Al0.85Ga0.15As layer. In both alloys, the room temperature microstructure consists of an amorphous and a crystalline region. The amorphous region extends from the deeper AlxGa1-xAs/GaAs interface into the layer, and is separated from the crystalline material by a crystalline region containing planar defects. The difference between the alloys is in the extent of this latter region, which decreases in width with increasing Al content. These results will be used to examine current models for amorphization in the AlxGa1-xAs system.
Germanium Redistribution Phenomena in the Synthesis of SiGe Layers
Authors: Patel C. J. , Butcher J. B. 
Published: April 2011

AbstractA unique germanium redistribution phenomenon occurs in the synthesis of SiGe by 74Ge+, ion implantation. A number of silicon samples were implanted with 74Ge+ ion using a range of substrate temperatures (R.T. to 600°C) with different germanium fluences (1.5 × 1016 cm-2 to 4 × 1016 cm-2) and implantation energies (100keV - 180KeV). Samples were germanium profiled using Rutherford backscattering spectrometry (RBS) and secondary ion mass spectrometry (SIMS).The experimental results show that the peak range of the germanium implant increases progressively above 150°C and a shift of 40nm in the peak germanium range was measured for a sample implanted at 600°C. The ‘hot’ implants have an extended tail profile contrary to the Debye model for root-mean-square deviations of the lattice atoms from their equilibrium sites which should ideally contribute to dechanneling. The data suggest strongly that dynamic annealing related diffusion (DARD) processes exist, whereby mobile non-equilibrium point defects influence diffusion to take place at the elevated implantation temperature. The SIMS spectra of samples implanted with high Ge fluences at elevated temperature show “uphill” diffusion.
X-Ray Photoelectron Spectroscopy Investigation of the Interaction of NF3 with Silicon
Authors: Little T. W. , Ohuchi F. S. 
Published: April 2011

AbstractThe interaction of nitrogen trifluoride (NF3) with silicon (Si) surfaces has been investigated by x-ray photoelectron spectroscopy (XPS). Si (100) surfaces were subjected to NF3 ion bombardment as a means of approximating plasma processing under controlled conditions. Samples were also exposed to actual NF3 DC plasmas and the results compared to ion beam and plasma processing using nitrogen (N2). The results indicate that nitridation of silicon is possible using NF3 although it seems to be limited by simultaneous etching. Additionally, results suggest bonding between both Si-F and Si-N species and perhaps F-N-Si moieties. NF3 plasma processing has lead to curious results for F 1s spectra which are not fully understood at present.
Effect of Energy and Dose on Transient-Enhanced Diffusion and Defect Microstructure in Low Energy High Dose As+ Implanted Si
Authors: Krishnamoorthy V. , Venables D. , Moeller K. , Jones K. S. , Freer B. 
Published: April 2011

Abstract(001) CZ silicon wafers were implanted with arsenic (As+) at energies of 10–50keV to doses of 2x 1014 to 5x1015/cm2. All implants were amorphizing in nature. The samples were annealed at 700°C for 16hrs. The resultant defect microstructures were analyzed by XTEM and PTEM and the As profiles were analyzed by SIMS. The As profiles showed significantly enhanced diffusion in all of the annealed specimens. The diffusion enhancement was both energy and dose dependent. The lowest dose implant/annealed samples did not show As clustering which translated to a lack of defects at the projected range. At higher doses, however, projected range defects were clearly observed, presumably due to interstitials generated during As clustering. The extent of enhancement in diffusion and its relation to the defect microstructure is explained by a combination of factors including surface recombination of point defects, As precipitation, As clustering and end of range damage.
In-Situ Irradiation Studies on the Effects of Helium on the Microstructural Evolution of V-3.8Cr-3.9Ti
Authors: Doraiswamy N. , Kestel B. , Alexander D. E. 
Published: April 2011

AbstractThe role of helium on the microstructural evolution of V-3.8Cr-3.9Ti has been investigated by in-situ transmission electron microscopy observations of as-prepared and He implanted (<10 appm) samples subjected to 200keV He irradiation at room temperature. Quantitative analysis of the defects showed an increase in the defect density and size with irradiation in both types of samples. The unimplanted sample showed a defect density consistent with electron irradiation experiments. In comparison, the He preimplanted sample had slightly larger defects and a substantially greater increase in the number density of defects. This result is consistent with a mechanism of He trapping by the formation of He-vacancy-X (X= C, N, O) complexes.
Microstructural Kinetics in Alloys Undergoing Transmutations: Application to Aic Neutron Absorbers
Authors: Desgranges C. , Martin G. , Defoort F. 
Published: April 2011

AbstractWhenever an alloy changes composition because of metal to metal transmutations, as is the case in Ag-In-Cd alloys undergoing (n, −) actions in the control rods of Pressurised Water Reactors, unique features may develop.A simple model shows that in a two components alloy more than two phases can coexist under appropriate irradiation conditions i.e. temperature, which scales diffusivities and solubilities, and flux, which scales the transmutations rate; because second phase precipitation occurs at the grain boundaries, the grain size in the underlying matrix is found to be one important parameter of the process.The above ideas are illustrated on a multicomponent alloy, the thermodynamics and the kinetics of which are treated at the same level of sophistication in a mean field approximation.
Ion-Beam Mixing and Solid-State Reaction in Zr-Fe Multilayers
Authors: Paesano A. , Motta A. T. , Birtcher R. C. , Ryan E. A. , Teixeira S. R. , Bruckmann M. E. , Amaral L. 
Published: April 2011

AbstractVapor-deposited Zr-Fe multilayered thin films with various wavelengths and of overall composition either 50% Fe or Fe-rich up to 57 % Fe were either irradiated with 300 keV Kr ions at temperatures from 25K to 623 K to fluences up to 2 × 1016 cm−2, or simply annealed at 773K in-situ in the Intermediate Voltage Electron Microscope at Argonne National Laboratory. Under irradiation, the final reaction product is the amorphous phase in all cases studied, but the dose to amorphization depends on the temperature and on the wavelength. In the purely thermal case (annealing at 773 K), the 50–50 composition produces the amorphous phase but for the Fe-rich multilayers the reaction products depend on the multilayer wavelength. For small wavelength, the amorphous phase is still formed, but at large wavelength the Zr-Fe crystalline intermetallic compounds appear. These results are discussed in terms of existing models of irradiation kinetics and phase selection during solid state reaction.