Topic
Chaoite
About: Chaoite is a research topic. Over the lifetime, 39 publications have been published within this topic receiving 1390 citations. The topic is also known as: IMA1968-019.
Papers
TL;DR: Current issues and problems in the chemical vapor deposition (CVD) of diamond are those which relate to its characterization, its nucleation on foreign surfaces, the question of its formation in preference to the other phases of solid carbon, and why different morphologies and crystallographic orientations (textures) are seen in different experiments.
Abstract: Current issues and problems in the chemical vapor deposition (CVD) of diamond are those which relate to its characterization, its nucleation on foreign surfaces, the question of its formation in preference to the other phases of solid carbon (for example, graphite, chaoite, or lonsdaleite), why different morphologies and crystallographic orientations (textures) are seen in different experiments or with different parameters in the same experiment, and finally whether well-crystallized metastable phases can be obtained by CVD in other material systems or are only a peculiarity of carbon chemistry. Whether a given carbon coating is justly described as diamond has been such an issue, and coatings should clearly show evidence for diamond by x-ray diffraction and Raman spectroscopy before the claim of diamond is made. Experimental results have not been consistent in many cases, and much work remains to be done before an accurate assessment can be made of the technological impact of the development.
708 citations
TL;DR: A new allotropic form of carbon occurs in shock-fused graphite gneisses in the Ries Crater, Bavaria, and electron-probe analyses indicate that the new phase is pure carbon.
Abstract: A new allotropic form of carbon occurs in shock-fused graphite gneisses in the Ries Crater, Bavaria. The assemblage in which it occurs consists of hexagonal graphite, rutile, pseudobrookite, magnetite, nickeliferous pyrrhotite, and baddeleyite. Electron-probe analyses indicate that the new phase is pure carbon. It is opaque and much more strongly reflecting than hexagonal graphite. Measurement of x-ray diffraction powder patterns leads to cell dimensions a = 8.948 ± 0.009, c = 14.078 ± 0.017 angstroms, with a primitive hexagonal lattice.
253 citations
TL;DR: Evidence for a new polymorphic form of carbon, similar to but distinct from chaoite, has been discovered in graphitic carbons under free-vaporization conditions at low pressures, with temperatures above approximately 2550�K.
Abstract: Evidence for a new polymorphic form of carbon, similar to but distinct from chaoite, has been discovered It is trigonal, with a 0 = 533 angstroms and c 0 = 1224 angstroms It is produced along with chaoite on the surfaces of graphitic carbons under free-vaporization conditions at low pressures, with temperatures above approximately 2550°K
67 citations
TL;DR: Based on its mineral composition and structure, the Havero meteorite is a ureilite, the sixth meteorite in this rare group as mentioned in this paper, which is represented by diamond, lonsdaleite, graphite and chaoite microcrystals in the intergrowths.
Abstract: Based on its mineral composition and structure the Havero meteorite, which fell on August 2, 1971, in Finland, is a ureilite, the sixth meteorite in this rare group. Elementary carbon in this meteorite is represented by diamond, lonsdaleite, graphite and chaoite microcrystals in the intergrowths. The presence of lonsdaleite and chaoite indicates that diamonds were formed in the Havero meteorite due to the action of strong shock waves
47 citations
TL;DR: A hexagonal polymorph of diamond has been synthesized by relatively weak shock loading (in a range of projectile velocity 0.655 to 1.88 km sec−1) with a recovery technique as mentioned in this paper.
Abstract: A hexagonal polymorph of diamond has been synthesized by relatively weak shock loading (in a range of projectile velocity 0.655 to 1.88 km sec−1) with a recovery technique. Four mixtures of copper with spectroscopic graphite, amorphous carbon, glassy carbon and graphite fluoride, with densities of 4.8 to 7.8 g cm−3, were used to control the shock temperature rise and to quench efficiently. Spectroscopic graphite gave the maximum yield of diamond (8%). Chaoite was also observed in the shocked amorphous carbon and glassy carbon. A local temperature rise during shock was inferred from the temperature of some spherical particles, indicative of superheating of the particles to near or above the melting point.
43 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2016 | 2 |
| 2010 | 1 |
| 2009 | 1 |
| 2008 | 2 |
| 2007 | 1 |
| 2005 | 1 |