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在自制的高温物性综合测定仪上,测定了难熔金属(钨、钼、钽)的熔点、膨胀系数和电阻率。采用直接通电的方法加热试样;用显微光学高温计测定试样的温度。熔化是以黑体腔底的突然变黑为准。以穿透试样的小孔作为测定膨胀系数时的长度标记,用垂高计测定有效区段在每一温度下的精确长度。用交流电位差计测定通过试样的电流及有效区段的电压降,以便算得电阻。测定了钨的熔点,钨、钼的膨胀系数和钽、钼的电阻率。钨的熔点值为3401℃,相对标准误差0.9%;膨胀系数测定的相对标准误差不大于4%;电阻率测定的相对标准误差不大于2%。
The melting point, coefficient of thermal expansion and resistivity of refractory metals (tungsten, molybdenum, tantalum) were measured on a self-made high-temperature pyrometer. The method of direct power is used to heat the sample; the temperature of the sample is measured with a micro-optical pyrometer. Melting is based on the sudden darkening of the black cavity bottom prevail. The length of the effective section of the effective section at each temperature is determined by measuring the length of the hole through which the sample penetrates when the coefficient of thermal expansion is measured. The AC potentiometer was used to determine the current through the sample and the voltage drop across the active section to calculate the resistance. The melting points of tungsten, the expansion coefficients of tungsten and molybdenum, and the resistivities of tantalum and molybdenum were determined. The melting point of tungsten is 3401 ℃, the relative standard error of 0.9%; the relative standard deviation of the determination of the coefficient of expansion of not more than 4%; the relative standard deviation of the determination of resistivity of not more than 2%.