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Microwave Processing (microwave + processing)
Selected AbstractsDesign and Construction of Insulation Configuration for Ultra-High-Temperature Microwave Processing of CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2003Geng-fu Xu A multilayer insulation configuration suitable for microwave sintering of ceramics up to 2100°C was designed and tested successfully. The configuration is based on porous, granular BN/ZrO2 fiber composite powder for packed beds and spacer cylinders. This insulation allows stable, controlled microwave sintering and can be modified to microwave process materials with different thermal, dielectric properties with improved properties. [source] Effect of resin compositions on microwave processing and thermophysical properties of benzoxazine-epoxy-phenolic ternary systems filled with silicon carbide (SiC) whiskerPOLYMER ENGINEERING & SCIENCE, Issue 5 2009Chanchira Jubsilp Microwave processing of silicon carbide (SiC) whisker filled ternary systems based on benzoxazine, epoxy, and phenolic resins has been investigated using an industrial microwave apparatus at a fixed frequency of 2.45 GHz. The low viscosity molding compound and void-free cured specimens can easily be obtained from the resin mixtures. Increasing of epoxy mass fraction in the ternary systems provided a better microwave coupling, therefore, a faster curing time and higher conversion under microwave irradiation. However, the greater amount of epoxy resin in the mixture was observed to retard the traditional thermal cure process as seen in the shifting of the exothermic curing peaks to higher temperature. The higher dielectric constant of epoxy resin comparing with the benzoxazine resin can be attributed to the observed phenomenon. Additionally, benzoxazine fraction was found to render a reduction in linear thermal expansion coefficient of the ternary systems. The development of ternary systems yields the polymer systems with high flexibility in resin-curing agent mixing ratios with relatively high Tg in the broader range of mixing ratios i.e., BEP451-BEP811. Synergism in glass transition temperature of the ternary systems is also observed with the maximum Tg up to 160°C in BEP721. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers [source] Role of various elliptical shapes for efficient microwave processing of materialsAICHE JOURNAL, Issue 6 2007Tanmay Basak Abstract A detailed theoretical analysis has been carried out to assess the role of various elliptical shapes/cross sections on microwave heating of 2-D cylinders for beef and oil samples. Two types of elliptical cross sections are considered as type A (ellipse with major axis along the horizontal plane), and type B (ellipse with minor axis along the horizontal plane.) A preliminary analysis on microwave heating of samples has been shown via average power within a sample vs. sample radius of circular cross section for beef and oil samples. Several regimes (I,III) based on small and large radius for circular cross sections have been selected. The effect of elliptical shapes for type A and B configurations has been studied initially via average power vs. aspect ratio distributions for various regimes. The grayscale images of power absorption have been analyzed further for elliptical cross section with varying aspect ratios for regimes I,III where aspect ratio and types of configuration are shown to influence spatial power absorptions. The detailed temperature profiles have also been shown to illustrate the role of elliptical shapes on uniform heating and thermal runaway. Depending on the material dielectric properties and sample dimension, either type A or B or both configuration has been recommended. © 2007 American Institute of Chemical Engineers AIChE J, 2007 [source] Dielectric properties of pharmaceutical materials relevant to microwave processing: Effects of field frequency, material density, and moisture contentJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 2 2010Paul W.S. Heng Abstract The rising popularity of microwaves for drying, material processing and quality sensing has fuelled the need for knowledge concerning dielectric properties of common pharmaceutical materials. This article represents one of the few reports on the density and moisture content dependence of the dielectric properties of primary pharmaceutical materials and their relevance to microwave-assisted processing. Dielectric constants and losses of 13 pharmaceutical materials were measured over a frequency range of 1,MHz,1,GHz at 23,±,1°C using a parallel-electrode measurement system. Effects of field frequency, material density and moisture content on dielectric properties were studied. Material dielectric properties varied considerably with frequency. At microwave frequencies, linear relationships were established between cube-root functions of the dielectric parameters ( and ) and density which enabled dielectric properties of materials at various densities to be estimated by regression. Moisture content was the main factor that contributed to the disparities in dielectric properties and heating capabilities of the materials in a laboratory microwave oven. The effectiveness of a single frequency density-independent dielectric function for moisture sensing applications was explored and found to be suitable within low ranges of moisture contents for a model material. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99:941,957, 2010 [source] Nanosized PbZrO3 Powder from Oxalate Precursor: Microwave-Aided Synthesis and Thermal CharacterizationJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2009Yuvraj S. Malghe Nanosized lead zirconate (PbZrO3) powder was synthesized from its oxalate precursor, namely lead zirconyl oxalate (LZO). LZO heated in a microwave heating system for 1 h yielded the PbZrO3 at 600°C. The same precursor (LZO), when heated in a resistance-heated furnace at 850°C for 3 h, does not give a pure product. Thermogravimetry, differential thermal analysis, and X-ray diffraction techniques were used to characterize the precursor and optimize the conditions for microwave processing. The particle size of PbZrO3 powder prepared at 600°C using microwave heating was measured using transmission electron microscopy (TEM). The TEM images show that the particles of PbZrO3 are spherical in shape and that the particle size varies between 20 and 22 nm. [source] Synthesis of Hydrated Aluminum Sulfate from Kaolin by Microwave ExtractionJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2000Seong Soo Park The feasibility of extracting alumina from kaolin via a microwave extraction process was investigated by comparing reaction times, reaction temperatures, and acid concentrations under microwave treatment with the same factors under conventional thermal extraction. The maximum amount of alumina extracted from kaolin under conventional processing at 90°C for 240 min with 1M H2SO4 was 99.9%; the same amount of alumina was extracted under microwave processing at 90°C for 120 min with 1M H2SO4. [source] Effect of resin compositions on microwave processing and thermophysical properties of benzoxazine-epoxy-phenolic ternary systems filled with silicon carbide (SiC) whiskerPOLYMER ENGINEERING & SCIENCE, Issue 5 2009Chanchira Jubsilp Microwave processing of silicon carbide (SiC) whisker filled ternary systems based on benzoxazine, epoxy, and phenolic resins has been investigated using an industrial microwave apparatus at a fixed frequency of 2.45 GHz. The low viscosity molding compound and void-free cured specimens can easily be obtained from the resin mixtures. Increasing of epoxy mass fraction in the ternary systems provided a better microwave coupling, therefore, a faster curing time and higher conversion under microwave irradiation. However, the greater amount of epoxy resin in the mixture was observed to retard the traditional thermal cure process as seen in the shifting of the exothermic curing peaks to higher temperature. The higher dielectric constant of epoxy resin comparing with the benzoxazine resin can be attributed to the observed phenomenon. Additionally, benzoxazine fraction was found to render a reduction in linear thermal expansion coefficient of the ternary systems. The development of ternary systems yields the polymer systems with high flexibility in resin-curing agent mixing ratios with relatively high Tg in the broader range of mixing ratios i.e., BEP451-BEP811. Synergism in glass transition temperature of the ternary systems is also observed with the maximum Tg up to 160°C in BEP721. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers [source] | |||||||||||||