The internal structure of both natural and synthesized diamonds can be revealed in great detail by electrostatic charging in the electron beam in a SEM. Closely spaced growth rings can be resolved by this simple technique which should be useful for characterizing diamonds for several applications.

The high pressure thermal stability of hydronium beta alumina and ammonium beta alumina have been investigated from 5 to 50 Kb pressure and from room temperature to 550°C. Both phases are stable at 400°C to 50 Kb pressure. At 50 Kb and 450°C, ammonium beta alumina decomposes into α-Al2O3 and hydronium beta alumina decomposes into H2O.5Al2O3 (Tohdite) and α-Al2O3. A tentative phase diagram is suggested for the stability range of hydronium beta alumina in the Al2O3-H2O system.

Extensive plastic deformation of diamond crystals can be accomplished by squeezing diamond embedded in diamond powder at high pressures and temperatures. By inhibiting brittle fracture, deformation takes place at temperatures as low as 900°C at 60kb. The {111} deformation lamellae have a higher abrasion resistance than even the {111} plane of diamond.

Platinum aluminide layers were formed on Pt by the diffusion of Al from a pack-aluminiding process. Metallographic, microprobe and X-ray characterization of these layers indicate good agreement with most of the subsolidus equilibria depicted by the currently-accepted phase diagram, with the exception of the region around the nominal composition, Pt2Al. The system appears to demonstrate the usefulness of the diffusion-couple approach for studying subsolidus equilibria in refractory systems.

Relief-polished striations have been found within grains in polished sections of framesite, a naturally occurring polycrystalline diamond. Because the narrow zones represented by these surface striations are harder than any orientation of the matrix (as revealed by abrasion resistance) and because they etch preferentially, they have been interpreted as representing oriented deformation bands within the grains. It is concluded that the microstructure of framesite is the result of plastic deformation of diamond grains probably under conditions such that brittle fracture was inhibited.

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation M. J. Moore, D. B. Sorensen, R. C. DeVries; A Simple Heating Device for Diamond Anvil High Pressure Cells. Rev. Sci. Instrum. 1 November 1970; 41 (11): 1665–1666. https://doi.org/10.1063/1.1684375 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioReview of Scientific Instruments Search Advanced Search |Citation Search

PbO·PbCrO4 is a paint pigment with interesting semiconductor and thermochromic properties. Preparatory to crystal growth and property measurements of this material, phase equilibria studies were made in the systems PbO·PbCrO4-PbO·PbMoO4, PbO·PbCrO4-PbO·PbWO4 and PbO·PbCrO4-PbO·PbSO4. In each case complete miscibility in the solid and liquid states was found. The small separation between solidus and liquidus in each system and rapid attainment of equilibrium permits the growth of large homogeneous crystals by pulling from the melt.

The system Li3BN2 was studied over the pressure and temperature range from 10 to 65 kb and 300–1900°C, respectively. The stability region of a quenchable high pressure modification, Li3BN2(W), was defined, and the data also suggest the possibility of another nonquenchable high pressure modification. Li3BN2(W) is the phase which appears to be in equilibrium with borazon (cubic BN) during growth of this phase from the system Li3N-BN, and the P-T data obtained on the melting of Li3BN2(W) are useful for defining the growth conditions for borazon.

An investigation of the decomposition of CrO2 to Cr2O3 from 800° to 1580°C and 15 to 65 kb was made in the “belt” apparatus. CrO2 can be held for at least 10 minutes without decomposition at temperatures to above 1500°C at pressures of 60 to 65 kb. These results indicate the feasibility of reacting other oxides with CrO2 for the formation of new compounds.

PbCrO3 has been synthesized in the high-pressure ``belt'' apparatus from PbO and CrO2 at 1150°C and a pressure in excess of 50 kbar. Single-crystal and powder x-ray diffraction at room temperature show the compound has the cubic perovskite structure with a0=4.00 Å. No deformation of the cubic structure was discerned in neutron diffraction patterns at 77° and 4.2°K. At low temperature the magnetic moments of the chromium atoms are ordered in the antiferromagnetic G-type structure in which the spins on each Cr are antiparallel to those of the six nearest neighbors. Assuming the magnetic form factor of chromium can be approximated by that of Cr3+, the magnetic intensities give a moment of 1.9 μB per chromium atom, approximately the spin value for Cr4+ (3d2). The temperature dependence of the (111) magnetic peak was measured and the results fitted to a Brillouin function with TN≈240°K. The magnetic susceptibility does not show a maximum at the Néel point but does obey a Curie-Weiss law above TN, consistent with the neutron-diffraction results.

Oriented layers of CrO2 have been grown epitaxially on {100}, {110}, {210} and {001} surfaces of single crystal TiO2 (rutile) and on the {0001} planes of single crystal Al2O3 and Fe2O3 by the decomposition of CrO3 on the substrate contained in a pressure vessel. The area of these layers is limited primarily by the size of the single crystal substrates. Beside meeting structural requirements the substrate must not form stable compounds with molten CrO3 or the other chromium oxides resulting from CrO3 decomposition. The CrO2 layer begins to form during the decomposition of Cr2O5 by nucleation of oriented CrO2 at many sites on the substrate surface. Defects on the surface of the substrates limit the perfection of the oriented layer. Characterization of the films by both chemical analysis and x-ray techniques indicate that the epitaxial CrO2 is identical in all respects to the bulk material. The oriented layers have been used for magnetic measurements.