Influence of Metals on Diamond to Graphite Phase Transformation

Transformation of diamond into graphite was investigated in the region of diamond metastability under the action of media chemically active to carbon in the temperature range from 770 K up to 2200 K and pressure range from 10(exp -3) Pa up to 3Gpa. I Y - III Y group metals of periodic system and oxygen were used as media chemically active relative to diamond. Methods of electron diffraction, chemical analyses, emission spectroscopy and X-ray phase analyses were used for determination of the reaction products. It was found that in the region of diamond metastability the stage of catalytic phase transformation of diamond into graphite took place during the Interaction between diamond and metal. Metals reduce activation energy for transition of diamond into graphite from 109.4kcal/mole to 77.4kcal/mole. Kinetic of phase transformation of diamond into graphite was investigated. Pressure does not considerably influence on the rate of phase transformation of diamond into graphite in the presence of transition metals. It is established that catalytic action of transition metals and silicon considerably increases in the presence of oxygen during into graphite. Action energy is maximal for silicon (40 kcal/mole) and minimal for manganese (13 kcal/mole).