| Abstrakt: |
Results of investigating the emissivity of metals of group II of the Periodic Table in the interval of temperatures "solid body–liquid" have been presented. Selection of the objects of investigation, i.e., metallic beryllium, magnesium, and calcium, has been argued by the absence, in practice, of data on the emissivity of these elements in a broad temperature range from periodic and reference literature. The measurement method was radiative, and the technique of heating of a metal specimen, resistive. A structure of a cylindrical model of an ideal black body with an emissivity factor no lower than 0.99 has been presented. The material of the equilibrium-radiation source was metallic tantalum. The estimate of experimental uncertainty amounted to 5–8%. Graphic illustrations of experimental results on each investigated element have been presented. The obtained complex experimental data on normal integral emissivity within the limits of each phase of state of the metals grew monotonically. In the region of phase transition of the first kind, the characteristic abrupt change in the emissivity of the metals was observed. Investigation results have been discussed and compared with the literature data of other authors. A theoretical calculation of the emissivity of these metals from the classical electromagnetic theory has been carried out with the Foot approximation. The conclusion has been drawn on the disagreement between the theoretical calculations on emissivity and the experimental data. [ABSTRACT FROM AUTHOR] |
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