The spectral emissivities, at an effective wavelength of 0.65 microns, and total normal emissivities, were determined for machined and polished surfaces of the graphites Great Lakes Carbon H1LM and H3LM, and Speer 7100. The spectral emissivities were investigated within 1000 to 3000 C. For machined surfaces, the spectral emissivity decreased with increasing temperature from 0.87 to 0.81 for H1LM; from 0.87 to 0.83 for H3LM; and from 0.87 to 0.78 for Speer. For polished surfaces, the spectral emissivity remained constant with increasing temperature and the mean value was 0.855 for H1LM; 0.777 for H3LM; and 0.820 for Speer 7100. The total normal emissivities were investigated from 1600 to 3000 C. For machined surfaces, the mean value of the total normal emissivity was 0.852 for H1LM; 0.852 for H3LM; and 0.847 for Speer 7100. For polished surfaces, the mean value of the total normal emissivity was 0.802 for H1LM; 0.808 for H3LM; and 0.800 for Speer 7100. (Author).

Proceedings of the Fifth Conference on Carbon

The emissometer is an extension of the multiproperty apparatus which is a powerful and unique tool for simultaneously measuring ten thermophysical properties on the same sample of an electrically-conducting solid and of studying its behavior under various environmental conditions. The apparatus features rapid time-to-temperature and data acquisition under minicomputer control yielding state-of-the-art accuracy. Performance evaluation tests of the emissometer are presented. These tests deal with veiling glare, blackbody cavity quality, and temperature distribution in the heating tube and sample. In addition spectral emissivity measurements to at least 10 micrometers have been made on tantalum (reference material), SiC, Si3N4, graphite and carbon-carbon composites from 1500 to 2400 K or their respective degradation temperatures. The new data on the ceramics provides some understanding on their high temperature behavior including the effect of fabrication process and impurities.

This book deals with the properties and behavior of carbon at high temperatures. It presents new methods and new ways to obtain the liquid phase of carbon. Melting of graphite and the properties of liquid carbon are presented under stationary heat and pulse methods. Metal like properties of molten graphite at high initial density are indicated. A new possible transition of liquid carbon from metal to nonmetal behavior much above the melting point is mentioned. Methodical questions of pulse heating, in particular the role of pinch-pressure in receiving a liquid state of carbon, are discussed. The reader finds evidence about the necessity of applying high pressure (higher than 100 bar) to melt graphite (melting temperature 4800±100 K). The reader can verify the advantage of volume pulse electrical heating before surface laser heating to study the physical properties of carbon, including enthalpy, heat capacity, electrical resistivity and temperature. The advantages of fast heating of graphite by pulsed electric current during a few microseconds are shown. The data obtained for the heat capacity of liquid carbon under constant pressure and constant volume were used to estimate the behavior at temperatures much higher 5000 K.