2005/06/11 | 金刚石[Diamond]
类别(℃〖化学〗) | 评论(0) | 阅读(27) | 发表于 16:42
Diamond consists of elemental carbon in a framework structure. It forms only at very high pressures; at lower pressures carbons instead forms graphite. Diamond is the hardest substance known, as well as the best heat conductor. Natural diamonds may be yellow (due to N impurities), blue (due to B), or pink (due to ?).
In 1797, diamonds were burned and shown to produce CO2,proving they are made of carbon. In 1880, Hanney claimed to have synthesized diamonds by sealing lithium, bone oil, and hydrocarbons in a steel pipe, firing it in a furnace, and examining the contents. In the few instances where the pipe did not explode, Hanney found a substance with density 3.5, which he concluded was diamond. However, the highest pressures he could have possibly achieved were [img]http://scienceworld.wolfram.com/chemistry/dimg16.gif[img] 2000 atm which are much to low to produce diamonds. The material he observed was most likely SiC (silicon carbide).
In 1890, another experimenter placed Fe and C in a crucible, which he then heated a quenched. He claimed that the contraction of the crucible had compressed the carbon and formed diamond. However, the diamonds he submitted for analysis showed a trace element content suspiciously similar to African diamonds. In 1917, Parsons repeated the crucible experiment and claimed to have found diamonds. However, on his deathbed, he admitted that the diamonds he had "made" were actually purchased. Apparently, he had grown tired of performing an experiment which always failed, and so purchased some diamonds in order to give them to his superior so that he could stop repeating the experiment.

Diamond consists of elemental carbon in a framework structure. It forms only at very high pressures; at lower pressures carbons instead forms graphite. Diamond is the hardest substance known, as well as the best heat conductor. Natural diamonds may be yellow (due to N impurities), blue (due to B), or pink (due to ?).

In 1797, diamonds were burned and shown to produce CO2, proving they are made of carbon. In 1880, Hanney claimed to have synthesized diamonds by sealing lithium, bone oil, and hydrocarbons in a steel pipe, firing it in a furnace, and examining the contents. In the few instances where the pipe did not explode, Hanney found a substance with density 3.5, which he concluded was diamond. However, the highest pressures he could have possibly achieved were 2000 atm which are much to low to produce diamonds. The material he observed was most likely SiC (silicon carbide).

In 1890, another experimenter placed Fe and C in a crucible, which he then heated a quenched. He claimed that the contraction of the crucible had compressed the carbon and formed diamond. However, the diamonds he submitted for analysis showed a trace element content suspiciously similar to African diamonds. In 1917, Parsons repeated the crucible experiment and claimed to have found diamonds. However, on his deathbed, he admitted that the diamonds he had "made" were actually purchased. Apparently, he had grown tired of performing an experiment which always failed, and so purchased some diamonds in order to give them to his superior so that he could stop repeating the experiment.

In the late 1940s, Druckemer constructed an apparatus which reached 425 kbar at room temperature. He also tried 70 kbar at , but only made graphite. In the late 1950s, the General Electric belt apparatus created 1000 kbar of pressure ar for hours. Only graphite was produced. This was curious, since thermodynamics predicted that diamonds should have been formed. After an extensive search, GE found a catalyst of Mn, Ni, and Cr. They are now able to make diamonds at every attempt. Presently, synthetic diamonds for abrasives are one of G. E.'s most profitable enterprises.
0

评论Comments

日志分类
首页[1408]
∑〖数学〗[349]
Ω〖物理〗[357]
¤〖天文〗[343]
℃〖化学〗[359]