热膨胀动态过程的直接观测及其机制

DIRECT OBSERVATION AND MECHANISM STUDY OF THE DYNAMIC PROCESS OF THERMAL EXPANSION

本文采用 0.1μs脉冲 CO_2激光快速加热厚度为微米量级的铝箔、康铜箔、氮化硼片样品,井使用参考激光束造成单缝衍射。然后,通过光电转换装置,实现长度、光强、电压的转化过程,来观测物体被快速加热时,热膨胀量随时间的变化情况。首次直接观测到了热膨胀的动态过程并摄下了膨胀的驰豫曲线。在此基础上就铝样品考察了驰豫时间与样品长度的关系。最后,对热膨胀动态过程的机制进行了讨论。

In this work, CO2 laser pulse of 0. 1μs was used to heat instantly the thin specimens of Al. constantan , BN with the thickness of 20-100μm. and a system of the slit diffraction using He-Ne laser was also adopted. By a photoelectric converting device, the change of the specimen length was transferred to the change of light strength, then to that of voltage. Using above method, we have observed and measured the changing process of the ther-mal expansion amount of the specimen with time during the specimen was heated instantly. For the first time, the dynamic-process of thermal expansion was observed directly and the oscillograms of the relaxation curves of thermal expansion were obtained. On the basis of above experiment, we have examed the relation between the relaxation time and the specimen length for Al. The mechanism of the dynamic-process of thermal expansion has also beendiscussed.