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闪光法测量材料的导温系数、比热和导热系数由W.J.Parker等于1961年首次提出。由于该方法在测量导温系数方面具有许多优点,因此至今仍被广泛采用。但所提出的比热测量方法不仅精度低操作复杂,而且需要两次试验才能得到比热数据,因此无法实现快速综合测试。本文提出的测量比热新方法是基于空腔原理,其要点是在一个密闭的空腔上开一小孔,激光通过该小孔进入空腔内经多次反射后几乎全部被空腔吸收,因此可把空腔看成是一个对光的绝对吸收体。应用空腔原理实现对比热测量的要点是:首先应用一个比热为已知的壳体与样品共同组成一个空腔,二者之间相互绝热,当具有已知能量的激光进入空腔后,经过在腔内的多次反射,该能量最终将被壳体和样品吸收,壳体吸收的能量可通过测定壳体温升求得,因此样品吸收的能量及比热也可随之得到。由于激光是经过聚焦后进入空腔的,因此壳体上的小孔可以做得很小,从而大大减小了把空腔视为绝对吸收体所带来的误差。样品的导温系数可与比热同时测得,导热系数可通过比热、导温系数及密度计算出来。应用本方法测得了Fe、Ni、Cu、Mo等金属的室温比热、导温系数和导热系数,这些数据与有关文献一致。本方法与传统方法比较有如下特点; 1.能在单次激光脉冲作用下,同时获得比热、导温系数、导热系数三个热物理量。 2.样品表面无需特殊加工和处理。 3.比热测量的精度及可靠性高。
Flash method for measuring the material’s thermal conductivity, specific heat and thermal conductivity by W. J. Parker was first proposed in 1961. Since this method has many advantages in the measurement of thermal conductivity, it is still widely used. However, the proposed specific heat measurement method not only has the advantages of low precision and complex operation, but also requires two experiments to obtain the specific heat data, so that rapid comprehensive testing can not be achieved. The new method proposed in this paper is based on the principle of cavity. The key point is to open a small hole in a closed cavity. When the laser passes through the small hole and enters into the cavity, it is almost completely absorbed by the cavity after multiple reflections. Think of the cavity as an absolute absorber of light. The principle of using the cavity to achieve contrast thermal measurement points are: first, a specific heat for the known shell and the sample together to form a cavity, the two mutually adiabatic, when a laser with known energy into the cavity, After multiple reflections in the cavity, the energy will eventually be absorbed by the shell and the sample. The energy absorbed by the shell can be determined by measuring the temperature rise of the shell, so that the energy and specific heat absorbed by the sample can be obtained. Since the laser is focused into the cavity, the holes in the housing can be made small, greatly reducing the error associated with viewing the cavity as an absolute absorber. The temperature coefficient of the sample can be measured simultaneously with the specific heat, and the thermal conductivity can be calculated by the specific heat, the temperature coefficient and the density. Measured by this method Fe, Ni, Cu, Mo and other metal room temperature specific heat, thermal conductivity and thermal conductivity coefficient, the data consistent with the literature. Compared with the traditional method, this method has the following characteristics: 1. It can simultaneously obtain three thermal physical quantities of specific heat, thermal conductivity coefficient and thermal conductivity under the action of a single laser pulse. 2. The sample surface without special processing and handling. 3. Specific heat measurement accuracy and reliability.