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Technique for Measuring the Dielectric Properties of Minerals as a Function of Temperature and Density At Microwave Heating Frequencies.

Paper in Materials Research Soc Symp Proceedings Volume 189 Mater Res Soc PP 509-515 :509-515
As part of the research effort on investigating the effects of microwave energy absorption on the chemical and physical properties of minerals and ores, the U.S. Bureau of Mines Tuscaloosa Research Center has developed a technique of measuring the dielectric constant and loss tangent of minerals at the common microwave heating frequencies. The objective was to establish a reliable data base to aid in predicting the effects of microwave heating on minerals. In this phase of microwave research, the Bureau measured the dielectric properties of powdered minerals with medium to high electrical conductivities (o >/= 0.02 Mho/m) in the frequency range of 300 mhz to 3 ghz using an open-ended coaxial line probe connected to an hp 8753a network analyzer. Since the minerals were prepared as powders, techniques were used to relate the measured dielectric properties of the powdered minerals to the dielectric properties of the mineral at its theoretical or natural density. Also, these measurements were performed as a function of temperature, from 25 to 325 deg c. The measured values of the dielectric constants and loss tangents using this method were accurate within +/-5 pct. This report describes the method of measurement and discusses the results of the Bureau's investigations into dielectric properties of minerals.
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OP 243-91
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Paper in Materials Research Soc. Symp. Proceedings Volume 189. Mater Res. Soc., PP. 509-515