SILICON-CARBON EUTECTIC FIXED POINT FOR THERMOCOUPLE CALIBRATION

摘要

Three Si-SiC eutectic fixed-point cells have been constructed using electrically heated furnace for use in thermocouple thermometry. The first two cells were made from silicon powder mixed with carbon while the third was made from pure silicon. The first cell with a conventional graphite crucible was early broken during the preliminary test, so the result could not be recorded. The second cell with a modified graphite crucible, thicker and shorter than the previous one, was able to withstand until 36 melt-freeze cycles and was held above 1400 °C for about 143 h, but unfortunately this cell was also finally broken after the test. The third cell, made from pure silicon filled in the modified crucible, was successfully tested without any mechanical failure. This cell was held above 1400 °C for approximately 157 h and was subjected to 36 melt-freeze cycles, where 7 cycles of them was realized from room temperature. The melting plateau of the cell lasted about 40 min and the extreme of the measured inflection point differed by 0.1 °C. The repeatability, represented by its standard deviation, was 0.03 °C. The temperature difference between both of the last two cells was calculated to be 0.5 °C.