Accession Number : ADA262340


Title :   DN Hard Materials Laser Assisted Formation of Dense Phases


Descriptive Note : Final technical rept. for 1989-90


Corporate Author : PENNSYLVANIA STATE UNIV UNIVERSITY PARK MATERIALS RESEARCH LAB


Personal Author(s) : Rustum, Roy


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a262340.pdf


Report Date : 14 Jan 1991


Pagination or Media Count : 36


Abstract : Diamond and other high-pressure phases of carbon were synthesized in air by exposing fine particles of carbon black to carbon dioxide and Nd-YAG laser radiation. The high-pressure phases were separated from the carbon black by selective oxidation and were characterized by electron and x-ray diffraction. Formation of cubic diamond, chaoite, and graphite was confirmed. Exposure of a falling stream of 1 um average size a-quartz particles to a continuous wave or pulsed C02 laser beam in air resulted in the formation of a complete series of high-pressure phases of silica: coesite, stishovite, and apparently even denser forms with a-PbO2 and Fe2N structures. Since the laser exposure technique works with the carbon black to diamond transition, the technique is confirmed as a simple and generally applicable means to achieve the same effects as exposure to several hundred kilobars pressure. High-pressure phases of CaCO3, namely aragonite, calcite II, and possibly calcite III, were synthesized in air by exposing 10- to 20-um-size particles of CaCO3 (calcite I phase) to a C02 laser radiation at short pulse lengths (O.l ms). The system B-0 was explored at high pressures and some very interesting new materials prepared near the composition B120-B220. The properties were not reproducible.... Diamond synthesis via laser pulses, Novel hard BxO phases.


Descriptors :   *PHASE TRANSFORMATIONS , *DIAMONDS , YAG LASERS , RADIATION , SILICON DIOXIDE , MATERIALS , SYNTHESIS(CHEMISTRY) , STRUCTURES , CONTINUOUS WAVES , X RAY DIFFRACTION , GRAPHITE , HIGH PRESSURE , LASER BEAMS , ELECTRONS , LASER APPLICATIONS , QUARTZ , DIFFRACTION , OXIDATION , ARAGONITE , CALCITE , PHOTONS , CRYSTAL GROWTH , CARBON BLACK , SHORT PULSES , STREAMS


Subject Categories : Lasers and Masers
      Crystallography


Distribution Statement : APPROVED FOR PUBLIC RELEASE