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讨论了一种用于微波化学反应器中的微波辐射器的一体化设计与优化方法。辐射器在工作过程中温度变化剧烈,由此产生的热应力可能造成辐射器破裂,导致反应器不能正常工作,甚至出现爆炸。为避免出现上述现象,基于有限元方法,首先根据电磁场边界条件,对辐射器的传输特性进行分析,初步优化其结构参数,保证辐射器的反射系数尽可能小,以减小微波能量在传输过程中的损耗,然后采用多物理场耦合分析方法,对辐射器进行优化设计,降低了辐射器工作过程中产生的热应力,并避免了在结构突变以及衔接部位产生过大的热应力,改善了辐射器的结构稳定性。 相似文献
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《Journal of the European Ceramic Society》2006,26(10-11):1845-1851
Low-temperature dielectric properties of BaZn1/3Nb2/3O3-based ceramics, CeO2-based ceramics and Ruddlesden–Popper Srn+1TinO3n+1 (n = 1–4) ceramics has been studied in microwave, THz and infrared frequency range down to 10 K. Extrinsic dielectric losses originating probably from diffusion of charged defects are observed in two families of compounds by a minimum in the temperature dependence of microwave quality Q. The rise of microwave permittivity and dielectric losses at low temperatures in Srn+1TinO3n+1 (n = 2–4) ceramics was explained by softening of an optical polar mode in SrTiO3, which is in the Srn+1TinO3n+1 (n = 3, 4) ceramics contained as a second phase. 相似文献
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微波技术与煤热解技术结合而成的煤微波热解技术可高效地治理传统煤热解技术中环境污染高和资源利用效率低的难题,为低变质煤的清洁高效利用和分级提质利用提供了新的思路。煤催化微波热解技术能有效改善热解升温特性和产物分布,从而受到较多学者的关注。本文从低变质煤催化微波热解技术发展历程着手,概述了国内外煤催化微波热解研究技术进展,通过加入Fe、Co、Ni和Cu等金属化合物或焦炭、活性炭等碳材料作为吸波剂,能显著增强煤对微波的吸收能力,提高热解升温速率、产物收率及产物质量,而有些金属化合物在微波热解反应中不仅起到吸波作用,还具有催化作用。碳基吸波催化剂作为一种性能优越的煤微波热解催化剂,具有优越的电磁和吸波性能、较好的催化性能和高经济性等优点,本文在煤催化微波热解技术研究现状的基础上,对碳基吸波催化剂进行了较为详细地分析,概述了碳基吸波催化剂的碳基体和催化活性组分的研究进展,对比了3种常见碳基吸波催化剂制备方法的优劣势。最后,总结了碳基吸波催化剂在研发过程中存在的难题,并展望了低变质煤催化微波热解技术的应用前景。 相似文献
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微波吸收剂辅助吸波快速热解稻壳的气化特性 总被引:1,自引:0,他引:1
以稻壳为研究对象,采用碳化硅、残炭为微波吸收剂,运用新型微波辅助催化气化技术以及微波吸附剂辅助加热技术,研究微波吸收剂辅助吸波快速热解稻壳气化特性,通过气相色谱等手段对裂解气体进行分析。结果表明,微波吸收剂辅助吸波快速热解稻壳产物以气体为主,最高达53%,热解气体产物主要成分为H2、CO2、CO、CH4,占到纯热解气总量的97%以上,氢气体积分数最高,均高于38%。稻壳与残炭添加量质量比为1:1时,氢气体积分数可达48.12%,合成气(H2+CO)含量大于60%。研究结果证明了微波吸收剂辅助吸波快速热解稻壳气化制备富氢燃气的可行性。 相似文献
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《Journal of the European Ceramic Society》2022,42(12):4969-4973
Low-temperature-fired microwave ceramics are key to realizing the integration and miniaturization of microwave devices. In this study, a facile wet chemical method was applied to synthesize homogenous nano-sized CaF2 powders for simultaneously achieving low-temperature sintering and superior microwave dielectric properties. Pure CaF2 ceramics sintered at 950 °C for 6 h with good microwave dielectric properties (εr = 6.22, Q×f = 36,655 GHz, and τf = ?102 ppm/°C) was achieved. The microwave dielectric properties of the CaF2 ceramics were further improved by introducing LiF as a sintering aid. The sintering temperature of CaF2-based ceramics was effectively lowered from 950 °C to 750 °C with 10 wt% LiF doping, and excellent microwave dielectric properties (εr = 6.37, Q×f = 65,455 GHz, and τf = ?71 ppm/°C) were obtained. 相似文献
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Charles Manière Geuntak Lee Elisa Torresani John F. Gerling Vadim V. Yakovlev Darold Martin Eugene A. Olevsky 《Journal of the American Ceramic Society》2020,103(8):4110-4121
Microwave Pressing is a promising way to reduce microwave sintering temperatures and stabilize microwave powder materials processing. A multiphysics simulation was conducted of the regulated pressure-assisted microwave cavity. This simulation took into consideration resonance phenomena and the nonlinear temperature-dependent material parameters of zirconia. The intrinsic behaviors of microwave systems and zirconia make the regulation of the microwave pressing difficult. However, the same phenomena can be used to activate flash sintering. Flash microwave sintering uses high electric fields of the resonant microwave profile, the Negative Temperature Behavior (NTC) of zirconia resistivity, and the mechanical pressure applied to the powder via a die compaction configuration. The resulting flash microwave pressing still needs improvement in terms of the processed material structure homogeneity, but it has the capacity to become the fastest sintering treatment as it allows room temperature activation where the total process time only takes a few seconds. In addition, this 10-20 seconds processing technique has shown good potential for improving the transparency of alumina presintered specimens. 相似文献
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Organosolv lignin from olive tree pruning was subjected to liquefaction under microwave heating and modifying the experimental conditions (time, temperature, and concentration of catalyst) according to an experimental design. The organosolv lignin and obtained polyols were characterized using attenuated‐total reflection infrared spectroscopy (ATR‐IR), thermogravimetric analysis (TGA), gel permeation chromatography, and another parameter such as the hydroxyl number (IOH). The ATR‐IR and the TGA results showed that the solvents (polyethylene glycol #400 and glycerol) reacted with the lignin being present in the final product. The optimal polyol showed a liquefaction yield of 99.07% that was obtained in 5 min of reaction at 155°C with 1% of sulphuric acid. The liquefaction product showed a hydroxyl number of 811.8 mg KOH/g, suitable to be used as a precursor in polyurethane foam synthesis. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3292–3298, 2013 相似文献
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《Journal of the European Ceramic Society》2014,34(12):2925-2932
Barium strontium titanate (BST) is a promising material for passive tunable microwave devices such as phase shifters, tunable filters or tunable matching networks. This publication covers the preparation of BST thick-films for microwave applications through inkjet printing. A Ba0.6Sr0.4TiO3 ink was prepared, printed on alumina substrates and sintered at temperatures between 1100 °C and 1200 °C. The microstructure of the thick-films reveals the evolution of grain growth and porosity with increasing sintering temperature. Furthermore, a reaction with the substrate was observed for T ≥ 1175 °C. A maximum tunability of 36% was observed at temperatures right below the onset of the substrate reactions. This process conditions were used for the preparation of a loaded line phase shifter, which successfully shows the capability of the inkjet printing process for future microwave device fabrication. 相似文献
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Chai Liu Chenghai Liu Hongkun Xue Yu Sun Zhen Lin Haijun Liu 《Drying Technology》2017,35(11):1388-1397
ABSTRACTMicrowave foam drying (MFD) is a novel drying technology particularly for the drying of agricultural products with high viscosity and thermal-sensitive components. The effect of dissipation of microwave energy on the drying process of berry puree was investigated in MFD conditions. The results show that the dissipation of microwave energy induces the vapor pressure inside the berry puree to improve the formation of bubbles. The changes of pressure inside bubbles of berry puree follow Sine equations. The favorable conditions of bubbles formation inside berry puree are the temperature of 70–80°C with the corresponding viscosity of 70–80?pa?s and moisture content of 80–85% (wb). The dissipation of microwave energy in berry puree tends to decaying trend due to the changes of dielectric properties. Moisture content has the most significant positive effect on both dielectric constant and dielectric loss factor of berry puree, followed by the density, and the drying temperature has the least but significant effect on both indicators. The focusing phenomenon of microwave irradiation depended on the dielectric properties determines the distribution of temperature of berry puree. The findings in current work contribute to a better understanding the MFD behavior of berry puree and will help to optimize the drying conditions of MFD for enhancing energy efficiency and drying quality. 相似文献
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微波在化学反应中的应用 总被引:2,自引:0,他引:2
针对微波加热在纳米材料制备、有机化学反应、高分子化学反应以及新型炭(碳)材料的制备和加工,特别是在无机纳米粒子改性、聚合物微球合成中的应用进展进行了综述。 相似文献
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S. Ghosh K.S. PalN. Dandapat A.K. MukhopadhyayS. Datta D. Basu 《Ceramics International》2011,37(3):1115-1119
Commercial Al powder was exposed to microwave radiation for 45 min. The as received and microwave heated Al powders were characterized by X-ray diffraction analysis (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis and transmission electron microscopy (TEM). XRD of the microwave treated Al powder confirmed the formation of Al-Al2O3 composite. FTIR studies and EDX analysis indicated the transformation of Al powder into Al-Al2O3 core-shell composite powder after microwave processing. SEM showed that the morphology of the microwave processed Al powder was quite different from that of the as-received Al powder. TEM image of the microwave treated Al powder supported the FTIR and EDX data. 相似文献
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在微波辐射下,以2,4-二硝基酚、KOH和氯化苄为原料,KI为催化剂,聚乙二醇200为溶剂合成了标题化合物。通过测定熔点和红外光谱对产物进行了确证。采用单因素实验法,考察了反应物的物质的量比、微波功率和辐射时间等因素对收率的影响,结果表明:在聚乙二醇200存在下,当n(2,4-二硝基酚)∶n(KOH)∶n(氯化苄)∶n(KI)=1∶1∶1.17∶0.81、微波功率为320 W、辐射时间为3 min时,收率89.28%。 相似文献
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香菇多糖微波降解反应动力学研究 总被引:2,自引:0,他引:2
文中建立了微波降解后香菇多糖特性黏度[η]变化的反应动力学方程。通过测定微波功率对[η]的影响,可得到不同功率下[η]t-1/α-[η]0-1/α随微波处理时间t的变化关系及降解速率常数kn随[η]n的变化关系。结果表明:香菇多糖微波降解速率常数随反应时间发生变化;在微波功率为195,385,575 W时,降解速率常数kn与特性黏度[η]n之间呈正相关性,表明kn和[η]n的线性关系服从一级动力学;微波功率上升至765 W时,kn和[η]n之间呈负相关性,表明kn和[η]n的线性关系偏离了一级动力学。 相似文献