Radio Frequency Induction Heating Research Articles

Silicide Film Formation in the Ta/Ti/Si System by RF Induction Heating

AbstractSilicidation of Ta-Ti-Si film on Si (111) and Si (100) substrates was investigated by a new radio frequency (RF) heating in order to evaluate the progress of reaction and establish whether the substrate orientation influence on the rate of reaction prevails. Substrate orientation was observed notwithstanding the high temperatures applied and the very short duration of RF. It was observed that while the reaction on Si (111) goes to completion, on Si (100) substrates under the same conditions intermediate phases remained. A qualitative analysis of the RF treatment of a conductor film on the silicon substrate is presented. It is done for the first time using the mathematical approach of the heat explosion theory. According to the analysis the specimens might experience either heating at constant temperature or by a sudden temperature increase. The relation between the parameters for the heat explosion regime is presented in simple analytical form. Measurable quantities such as sheet resistance and the magnetic field applied determine the stage of the process. The value of the resulting sheet resistance indicates whether the progress of the RF occurred by heating in the slow growth temperature regime or in the heat explosion stage where reactions of a conductor film occur within a fraction of a second.

Reactive Flow in Halide Chemical Vapor Deposition of Silicon Carbide Epitaxial Films

Halide chemical vapor deposition emerges as a potent technique for growing silicon carbide epitaxial films at high deposition rates. Experimental studies suggest that thermal environment and fluid flow in the reactor are important factors that control the gas-phase and surface chemistry and therefore have a profound influence on the deposition rate, quality, and properties of the as-deposited films. In this study, a comprehensive transport model that includes gas dynamics, heat and mass transfer, gas-phase and surface chemistry, and radio-frequency induction heating is employed to study the complex heterogeneous chemical reactions as well as transport of multiple chemical species in a high-temperature environment Simulations are performed over a wide range of operational parameters in a horizontal hot-wall reactor using Sicl 4 /C 3 H 8 /H 2 as the precursors. The results show that deposition temperature and the flow rate of carrier gas are important factors determining the processing conditions and deposition rate. The model can be further used to improve reactor design and to optimize the processing conditions.

Ex-situ tritium removal from JET tiles using RF inductive heating

Radio-frequency (RF) inductive heating has been successfully used as an ex-situ technique for the detritiation of entire tiles retrieved from JET. The assessment of the detritiation process used three different techniques, namely autoradiography, calorimetry and full combustion assisted by the liquid scintillation analysis. Autoradiography showed that using the RF technique more than 99% of the total surface tritium inventory can be efficiently removed from a tile after several heating cycles at the average temperature of only 490 °C. On the other hand, a comparison of the combustion measurements obtained before and after RF heating has shown that the bulk tritium activity decreased significantly (95% of the bulk tritium was released), while at the same time more than 99% of the surface tritium was liberated. The three methods used to assess the RF detritiation process have their advantages and disadvantages. Calorimetry allows a rough estimation of the tritium content of the complete tile, whilst IP imaging allows an approximate estimation of the content before and after detritiation but only for the surface tritium. On the other hand, full combustion associated with scintillation analysis allows very accurate measurements but only for specific samples with reduced dimensions, therefore extrapolation is needed to estimate the tritium content of an entire tile.

An integrated model for halide chemical vapor deposition of silicon carbide epitaxial films

Halide chemical vapor deposition emerges as a potent technique for growing silicon carbide epitaxial layers with a high deposition rate in the range of 50–300 μm/h. Experimental studies suggest that the gas composition in the reactor has profound influence on the deposition rate, the quality, and the properties of the as-deposited films. In this study, a comprehensive model was developed for halide chemical vapor deposition process including gas dynamics, heat and mass transfer, gas phase and surface chemistry, and radio-frequency induction heating. Numerical simulations of the deposition process in a horizontal hot-wall reactor using silicon tetrachloride, propane, and hydrogen as precursors were performed over a wide range of operational parameters to quantify the effects of deposition temperature, precursor flow rate, and reactor configuration. Special attention was directed to the etching of silicon carbide films by hydrogen chloride and its impact on the film deposition rate at different processing conditions. Improved gas delivery method was proposed for controlling the formation of hydrogen chloride and the associated etching effect.

Evolution of gettering technologies for vacuum tubes to getters for MEMS

Getter materials are technically proven and industrially accepted practical ways to maintain vacuum inside hermetically sealed tubes or devices to assure high reliability and long lifetime of the operating devices.The most industrially proven vacuum tube is the cathode rays tubes (CRTs), where large surfaces are available for the deposition of an evaporated barium film by a radio frequency inductive heating of a stainless steel container filled with a BaAl4 powder mixed to Ni powder. The evolution of the CRTs manufacturing technologies required also new types of barium getters able to withstand some thermal process in air without any deterioration of the evaporation characteristics.In other vacuum tubes such as traveling waves tubes, the space available for the evaporation of a barium film and the sorption capacity required to assure the vacuum for the lifetime of the devices did not allow the use of the barium film, prompting the development of sintered non evaporable getter pills that can be activated during the manufacturing process or by flowing current through an embedded resistance. The same sintered non evaporable getter pills could find usage also in evacuated parts to thermally isolate the infrared sensors for different final applications.In high energy physics particle accelerators, the getter technology moved from localized vacuum getter pumps or getter strips to a getter coating over the surface of vacuum chambers in order to guarantee a more uniform pumping speed.With the advent of solid state electronics, new challenges faced the getter technology to assure long life to vacuum or inert gas filled hermetical packages containing microelectronic devices, especially in the telecommunication and military applications. A well known problem of GaAs devices with Pd or Pt metalization is the H2 poisoning of the metal gate: to prevent this degradation a two layer getter film has been develop to absorb a large quantity of H2 per unit of getter surface.The development of Micro Electro Mechanical Systems (MEMS) with moving parts in a vacuum environment required the development of a new generation of getter film, few microns thick, that can be selectively patterned onto a silicon or glass wafer (usually 4″ or 8″). This wafer with patterned getter film can be used directly as the cap wafer of a wafer to wafer bonded MEMS structure, assuring long life and reliability to the moving MEMS structure especially in automotive applications where thermal cycles are required for qualification.

Floating-zone growth of CrB 2 single crystals

Single crystals of CrB 2 up to 2.4 cm in diameter were prepared by the floating-zone method with radio-frequency induction heating. The electromagnetic coupling between the work coil and the sample, i.e. the heating efficiency, was improved by 40% by preparing the thick crystal rod at a higher feed rate of the feed sintered rod. Under these improved growth conditions, the heating power was proportional to the crystal diameter. The CrB 2 crystal was used as a substrate for epitaxial growth of gallium nitride and aluminum nitride.

A Novel Nano-Carbon Rapid Growth Method in Liquid Alcohol Using Radiofrequency Induction Heating

Carbon nanotubes have been grown on both sides of a nickel−chromium substrate in methanol using radiofrequency induction heating. Hollow multiwalled carbon nanotubes were obtained that stood unifor...

Transient numerical study of temperature gradients during sublimation growth of SiC: Dependence on apparatus design

Using transient and stationary mathematical heat transfer models including heat conduction, radiation, and radio frequency (RF) induction heating, we numerically investigate the time evolution of temperature gradients in axisymmetric growth apparatus during the sublimation growth of silicon carbide (SiC) bulk single crystals by physical vapor transport (PVT) (modified Lely method). Temperature gradients in the bulk and on the surface of the growing crystal can cause defects. Here, the evolution of these gradients is studied numerically during the heating, growth, and cooling stages, varying the apparatus design, namely the amount of the source powder charge as well as the size of the upper blind hole used for cooling of the seed. Our results show that a smaller upper blind hole can reduce the temperature gradients both in the bulk and on the surface of the crystal without reducing the surface temperature itself.

Optimizing the Temperature Profile during Sublimation Growth of SiC Single Crystals: Control of Heating Power, Frequency, and Coil Position

We use a numerical optimization method to determine the control parameters frequency, power, and coil position for the radio frequency (RF) induction heating of the growth apparatus during sublimation growth of SiC single crystals via physical vapor transport (PVT) (also called the modified Lely method). The control parameters are determined to minimize a functional, tuning the radial temperature gradient on the single-crystal surface as well as the vertical temperature gradient between SiC source and seed, both being crucial for high-quality growth. The optimization is subject to constraints with respect to a required temperature difference between source and seed, a required temperature range at the seed, and an upper bound for the temperature in the entire apparatus. The numerical computations use a stationary mathematical model for the heat transport, including heat conduction, radiation, and RF heating to solve the forward problem, and a Nelder−Mead method for optimization. In agreement with published experimental results, a minimal radial temperature gradient is found to coincide with a minimal temperature at the single-crystal surface. A maximal temperature gradient between source and seed is found to coincide with a low coil position.

Illuminated spot technique—a novel method for the determination of solid–liquid phase transition temperatures

It was demonstrated, for the first time, that the conventional ‘spot technique’ (a method based on optical pyrometry) could be extended to lower temperatures using an external illumination procedure. Based on this observation a new technique, called the ‘illuminated spot technique’, was developed for the measurement of solid to liquid transition temperatures in metals and alloys. In order to validate this technique the melting points of pure metals in the temperature range 430–1358 K were measured. The suitability of two different modes of heating (viz. radiofrequency (RF) induction and resistance heating) for the present technique was examined. A new experimental technique called the ‘spot DTA’ technique was devised, by means of which the solidus and liquidus temperatures could be simultaneously determined by both the illuminated spot method as well as differential thermal analysis (DTA).

Transient temperature phenomena during sublimation growth of silicon carbide single crystals

In this article, we use numerical simulation to investigate transient temperature phenomena during sublimation growth of SiC single crytals via physical vapor transport (also called the modified Lely method). We consider the evolution of temperatures at the SiC source and at the SiC seed crystal, which are highly relevant to the quality of the grown crystals, but inaccessible to direct measurements. The simulations are based on a transient mathematical model for the heat transport, including heat conduction, radiation, and radio frequency (RF) induction heating. Varying the position of the induction coil as well as the heating power, it is shown that the measurable temperature difference between the bottom and the top of the growth apparatus can usually not be used as a simple indicator for the respective temperature difference between SiC source and seed. Moreover, it is shown that there can be a time lag of 1.5 h between the heating of the temperature measuring points and the heating of the interior of the SiC source.

Ti-Cu-TiB<SUB>2</SUB>混合粉末の高周波誘導加熱によるチタン基材へのTiB<SUB>2</SUB>-Ti<I><SUB>x</SUB></I>Cu<I><SUB>y</SUB></I>化合物層の形成

Radio frequency (R.F.) induction heating was applied to Ti, TiB2 and Cu mixed powder on a pure titanium substrate in vacuum. This method enabled the formation of a surface layer of TixCuy compounds (TiCu2 and Ti2Cu3) containing titanium di-boride (TiB2) particles. The layer with highest hardness (HV=8.0 GPa) and flat surface was obtained at a mixing ratio of Ti:TiB2:Cu=30:20:50(mol)%. The layer formation was completed in a shorter time by R.F. heating than normal electric furnace heating in vacuum. In case of R.F. heating up to 1170 K or 1220 K, TiB2 particles were distributed in lines in the TixCuy matrix, while TiB2 particles were homogenously distributed in case of electric furnace heating at 1223 K. Mixed powder initially melted at a temperature higher than 1170 K, and solidified by increasing the temperature to a higher value than 1240 K or with continuous holding at 1220 K. The reason for the solidification will be due to the decomposition of TiB2 and increase in melting point by the solution of boron into the melt.

Monitoring Density and Temperature in C/C Composites Processing by CVI with Induction Heating

Carbon/carbon composites are processed by chemical vapor infiltration (CVI) with radio-frequency inductive heating, which leads to inside-out temperature gradients, suitable for the production of homogeneously densified pieces if properly controlled throughout the whole processing. We present here a 2D axisymmetrical case where a comprehensive numerical model is tested against experimental runs. The numerical thermal model takes into account induction heating, radiative, conductive, and convective effects, intermediate regime diffusion and densification reactions in the pores, and the evolution of the porous medium. The results are the time evolution of the temperature, concentration, and composite material density field, as well as the input power necessary to ensure a given maximal temperature in the preform. Experimental data are measurements of the temperature and density fields at various infiltration stages. Comparison between experience and simulation, yielding an useful agreement, shows that porosity becomes trapped inside the preform as densification proceeds, because of the progressive lowering of the temperature gradient steepness. The discrepancies between computations and experimental data rely on the only approximate knowledge of some quantities, principally the reaction kinetics, which are currently under investigation.

Vacuum processing technique for development of primary standard blackbodies

Blackbody sources with nearly unity emittance that are in equilibrium with a pure freezing metal such as gold, silver, or copper are used as primary standard sources in the International Temperature Scale of 1990 (ITS-90). Recently, a facility using radio-frequency induction heating for melting and filling the blackbody crucible with the freeze metal under vacuum conditions was developed at the National Institute of Standards and Technology (NIST). The blackbody development under a vacuum environment eliminated the possibility of contamination of the freeze metal during the process. The induction heating, compared to a resistively heated convection oven, provided faster heating of crucible and resulted in shorter turn-around time of about 7 h to manufacture a blackbody. This paper describes the new facility and its application to the development of fixed-point blackbodies.

Numerical simulation of heat transfer in floating zone single crystal growth process with radio frequency induction heating

Analysis of heat transfer in the floating zone (FZ) crystal growth system with a radio-frequency (RF) induction heating is carried out, using the hybrid finite element and boundary element method for calculation of the electromagnetic and temperature fields, and applying the coordinate transformation method to represent exactly the unknown shapes of phase boundaries in the system. The effects of processing parameters, such as the RF current frequency, on FZ growth is investigated numerically, and a diagram for the upper and lower limits of the current density in the RF coil between which the molten zone can be stable is proposed.

Eluent Jet Interface for Combining Capillary Liquid Flows with Electron Impact Mass Spectrometry

A new interface based on an eluent jet in combination with a conventional gas chromatography momentum separator for use with electron impact mass spectrometry is described. The formation of the eluent jet is based on radio frequency inductive heating. The aerosol formation in the interface is discussed in relation to commercial particle beam (PB) interfaces. The interface is tested in combination with electron impact mass spectrometry using flow injection analysis at flow rates in the range of 5-15 μL/min commonly encountered in microcolumn liquid chromatography. Electron impact spectra at 1-10-ng levels are found to be comparable with reference spectra. In the single-ion mode, 50 pg of caffeine is detectable with a signal-to-noise ratio of 3 :1. Contrary to many other PB systems, linear calibration plots are obtained in the tested range of 3-200 ng of caffeine.

Numerical Simulation of Fz Single Crystal Growth Process with Radio-Frequency Induction Heating

ABSTRACTAnalyses of a floating zone (FZ) crystal growth system with a radio frequency (RF) induction heating are carried out. The electromagnetic and temperature fields, and surface interfaces are solved for numerically. Finite element methods are used for the calculation of the temperature fields and interfaces and the hybrid finite element and boundary element methods are used for the calculation of the electromagnetic field. The calculation domain is divided into eleven regions, each of which, except for the RF coil region, require a coordinate transformation. In the present study, the silicon FZ growth system ,where the diameter of both feed-rod and single crystal were set to be 1cm was computed. The Lorentz force is found to play an important role in determining the melt free surface shape and the molten zone length. The effect of the current density, frequency of RF coil and crystal growth rate are investigated.

A windowless 13N production target for use with low energy deuteron accelerators

The recent development of low energy accelerators for positron emission tomography has necessitated the development of new targets for 13N production. 12C(d,n) 13N reaction yields in graphite at low deuteron beam energies (0.8–3.2 MeV) are presented and a new technique for the in situ extraction of 13N activity from solid graphite and subsequent conversion to [ 13N] ammonia is described. The target is windowless and is reusable for multiple isotope production runs. This technique utilizes radio frequency induction heating to rapidly heat the graphite to combustion temperatures in an O 2 gas stream. The conversion of activity induced in the target to [ 13N] ammonia in under 10 min with an overall decay-corrected efficiency of 45% is reported.

A preliminary investigation of shape memory alloys in the surgical correction of scoliosis.

Nitinol, a shape memory alloy, is flexible at low temperatures but retains its original shape when heated. This offers interesting possibilities for scoliosis correction. Of the shape memory alloys, nitinol is the most promising medically because of biocompatibility and the ability to control transition temperature. In vivo: Six goats with experimental scoliosis were instrumented with 6-mm nitinol rods. The rods were transformed, and the scoliosis corrected, in the awakened goats by 450-kHz radio frequency induction heating. The curves averaged 41 degrees before instrumentation, 33 degrees after instrumentation, and 11 degrees after rod transformation. The animals tolerated the heating without discomfort, neurologic injury, or evidence of thermal injury to the tissues or the spinal cord. In vitro: Nitinol rods were tested under both constant deflection and constant loading conditions and plotted temperature versus either force or displacement. The 6-mm rod generated forces of 200 N. The 9-mm rod generated up to 500 N. We safely coupled shape memory alloy transformation to the spine and corrected an experimental spinal deformity in awake animals. The forces generated can be estimated by the rod's curvature and temperature. The use of shape memory alloys allows continuous neurologic monitoring during awake correction, true rotational correction by rod torsion, and the potential option of periodic correction to take advantage of spinal viscoelasticity and the potential of true rotational correction by rod torsion.

Interfacial crack propagation induced by scraper action on ice

This paper is concerned with the problem of interfacial crack propagation between a layer of ice and its substrate induced by a scraper action on the ice. We consider a layer of ice of uniform thickness bonded to a flat surface. There exists an initial crack generated by radio-frequency induction heating at the ice-substrate interface. The ice is treated as an elastic medium. Two types of loading condition are considered, namely, the longitudinal compression due to a flat head scraper moving with constant speed and the transverse lift due to the penetration of a sharp blade with constant speed. In this analysis, the effect of the propagation of stress wave is neglected. However, the kinetic energy induced by a growth in crack length and the application of an end displacement is included. A nonlinear initial value problem is formulated based on the principle of balance of energy. Numerical results are obtained by the Runge-Kutta method. The buckling and crushing of ice due to longitudinal compressive stress brought on by the action of a flat head scraper and the flexural stress at the crack tip due to penetration of a sharp blade at the interface are investigated. An analogous problem of crack propagation due to an indentation of a wedge on a large specimen is also discussed.