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Microwave heating technology is becoming a successful technique used for sintering ceramic materials. However, various aspects of sintering experiments, such as the use of process stimulus and the preparation of sample arrangements, depend mainly on human expertise. The Transmission Line Matrix (TLM) method is first used to solve the combined electromagnetic and thermal equations modeling microwave heating of dielectric materials. It is then used to simulate microwave sintering of a low-loss ceramic material in a multimode microwave cavity. To enhance the microwave sintering process, Silicon Carbid (SiC) was first used as a susceptor and in a picket fence arrangement. As multiple samples may be processed in a microwave oven, the TLM was used to model such a process, and the introduction of SiC as a stimulus was also examined. Results show the importance of the stimulus thickness and configuration on the uniformity and density of the electromagnetic field distribution and, therefore, on the power dissipation within the ceramic load. 相似文献
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Iskander M.F. Smith R.L. Andrade A.O.M. Kimrey H. Jr. Wal L.M. 《Microwave Theory and Techniques》1994,42(5):793-800
Microwave 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 profess such as preparation of 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 an improved 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 ceramic loading plate placed at the base of the cavity 相似文献
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Steven Bradshaw Willem Louw Cariné van der Merwe Howard Reader Sam Kingman Ma?gorzata Celuch Weronika Kijewska 《The Journal of microwave power and electromagnetic energy》2007,40(4):228-240
Microwave heating of mineral ores had previously been shown to result in process benefits such as reduced strength and improved mineral liberation, but the economics of the process were not attractive and no attention was given to feasible scale-up. This paper provides an overview of the multi-disciplinary approach that has been required to address these failings and develop the technology to pilot scale. Thermal stress simulations show that the operation at high power densities and short residence times is the optimal operating strategy. Experiments using high power densities (approximately 10(9) W/m3 absorbing phase) and short residence times (approximately 0.1 s) were used to confirm that the benefits can now be achieved at economically viable microwave energy inputs (approximately 1 kWh/t). In order to design applicators, reliable measurement of effective microwave properties of crushed ores is required. A method has been developed to extract dielectric properties when the sample thickness is a multiple of half a guide wavelength at some point in the measurement band. Finite difference time domain modeling has been used to design and simulate applicators. A transverse E field applicator with a reflection compensating step has been developed, and a unit with a capacity of > 10 tons/h is being tested. Preliminary economic analysis shows that the overall cost of the process will be between US $0.16 - 0.85 per ton of ore. 相似文献
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This paper presents results on the development of an automatic feedback control system for controlling the temperature of ceramic samples being heated by microwave energy. Design of the temperature controller is presented, and experimental results from heating experiments are given. The temperature control system is evaluated in terms of its robustness to parameter variations in the linearized model and in terms of its performance in actual experiments 相似文献
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Ohmi T. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1993,81(5):716-729
The importance of ultraclean processing in establishing advanced process technologies for deep submicron ULSI fabrication is discussed. The most essential requirement for the process technologies is the simultaneous fulfilment of the three principles of ultraclean technology: ultraclean wafer surface, ultraclean processing environment, and perfect process-parameter control. The growth of high-crystallinity silicon epitaxial layers at temperatures as low as 250°C with accompanying in situ impurity doping as a result of optimizing pertinent process parameters in a low-kinetic-energy particle process is described. Advanced copper metallization for large-current driving interconnect formation is discussed. Ultraclean oxidation, which is characterized by native-oxide-free and surface-microroughness-free oxidation, is confirmed to form high-quality very thin oxide films ranging from 5 to 10 nm with complete uniformity. A low-temperature annealing ion implantation that makes practical a metal gate self-aligned MOS LSI, which is crucial for high-speed CMOS having high current driving capability, is described 相似文献
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John Harper Duncan Price Jie Zhang 《The Journal of microwave power and electromagnetic energy》2007,40(4):219-227
Microwave heating has a number of advantages over conventional heating due to the ability to heat specimens directly through specific interaction of electromagnetic radiation with the material. Thus it is possible to consider highly localised, rapid melting of thermoplastics using microwave radiation as a means of forming and welding. However, most polymers exhibit very low dielectric losses in the GHz region, which means that it is difficult to heat them efficiently by this means. We have therefore studied the use of fillers such as talc, zinc oxide and carbon black as a way of increasing the susceptibility of common polymers to microwave processing. Carbon black was found to be the most effective susceptor for high density polyethylene and its efficiency was directly proportional to its surface area and loading. 相似文献
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sol-gel法制备微波介质陶瓷材料 总被引:10,自引:1,他引:9
以Zr(NO3)4·5H2O、Ti(OC4H9)4、SnCl4·5H2O为原料,用溶胶-凝胶法制备了Zr-Ti-Sn系微波介质超微粉料。实验表明:温度、湿度、溶液浓度、pH值等是影响形成溶胶、凝胶的主要因素。采用合适的工艺参数能制备出高Q值的微波介质陶瓷微粉。 相似文献
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Adam J.D. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1988,76(2):159-170
The main performance advantage that analog signal-processing devices have over their digital competitors is the ability to operate with wide instantaneous bandwidths and moderately high dynamic ranges at microwave frequencies. Here, applications of magnetostatic wave (MSW) devices that capitalize on these advantages are reviewed. The first area is broadband microwave receivers, which includes frequency channelizers, dispersive delay lines for compressive receivers, delay lines for pulse storage, and frequency-selective limiters. The second area is beamsteering of phased-array antennas by variable time delays. In both cases, the MSW device approaches and applications are discussed with emphasis on the device characteristics and their systems utilization. Where possible, comparisons with other analog signal-processing approaches are given 相似文献
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R Akarapu B Q Li Y Huo J Tang F Liu 《The Journal of microwave power and electromagnetic energy》2004,39(3-4):153-165
This paper presents an integrated electromagnetic and thermal model for the microwave processing offood packages. The model is developed by combining the edge finite element formulation of the 3-D vector electromagnetic field in the frequency domain and the node finite element solution of the thermal conduction equation. Both mutual and one-way coupling solution algorithms are discussed. Mutual coupling entails the iterative solution of the electromagnetic field and the thermal field, because the physical properties are temperature-dependent. The one-way coupling is applicable when the properties are temperature independent or this dependence is weak. Mesh sensitivity and shape regularity for the edge element based formulation for computational electromagnetics are discussed in light of available analytical solutions for a simple wave guide. The integrated model has been used to study the electromagnetic and thermal phenomena in a pilot scale microwave applicator with and without the food package immersed in water. The calculated results are compared with the experimentally measured data for the thermal fields generated by the microwave heating occurring in a whey protein gel package, and reasonably good agreement between the two is obtained. 相似文献
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In this paper,a multirate processing approach for microwave imaging is presented.This approach has the advantages of largely compressing the raw spectral data for imaging,greatly reducing the storage requirement and enhancing the processing efficiency.To demonstrateits applicability,the proposed approach is tested on both simulated and experimental data. 相似文献
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Guoyun Tian Yueli Liu Johnson R.W. Lall P. Palmer M. Islam M.N. Crane L. 《Electronics Packaging Manufacturing, IEEE Transactions on》2005,28(3):231-240
The use of chip-scale packages (CSPs) has expanded rapidly, particularly in portable electronic products. Many CSP designs will meet the thermal cycle or thermal shock requirements for these applications. However, mechanical shock (drop) and bending requirements often necessitate the use of underfills to increase the mechanical strength of the CSP-to-board connection. Capillary flow underfills processed after reflow provide the most common solution to improving mechanical reliability. However, capillary underfill dispense, flow, and cure steps and the associated equipment add cost and complexity to the assembly process. Corner bonding provides an alternate approach. Dots of underfill are dispensed at the four corners of the CSP site after solder paste print but before CSP placement. During reflow, the underfill cures, providing mechanical coupling between the CSP and the board at the corners of the CSP. Since only small areas of underfill are used, board dehydration is not required. This paper examines the manufacturing process for corner bonding including dispense volume, CSP placement, and reflow. Drop test results are then presented. A conventional, capillary process was used for comparison of drop test results. Test results with corner bonding were intermediate between complete capillary underfill and nonunderfilled CSPs. Finite-element modeling results for the drop test are also included. 相似文献
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It is demonstrated that an irregularity in a microwave array can be diagnosed optically from its microwave hologram with the aid of a complex spatial filter which stores the elemental far-field pattern. This process yields information about the original object which may not be readily apparent in the direct optical image and far-field pattern. 相似文献