| Budget Amount *help |
¥7,600,000 (Direct Cost: ¥7,600,000)
Fiscal Year 1996: ¥2,900,000 (Direct Cost: ¥2,900,000)
Fiscal Year 1995: ¥4,700,000 (Direct Cost: ¥4,700,000)
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| Research Abstract |
Synthesis of a diamond beater, that is, a substance harder than diamond is one of the most important challenges in the field of solid state chemistry. Extremely low compressibility or extremely high hardness has been found in covalent substances made of light elements : Diamond and c-BN are the most typical examples. In 1989 Liu and Cohen raised a theoretical possibility that a covalent C-N compound, which is beta-C_3N_4 crystallizing in the beta-Si_3N_4 structure, might have a lower compressibility than that of diamond. More recently Teter and Hemley suggested that cubic C_3N_4 might be even harder and that it would be stabilized under high pressure.
Following these theoretical predictions, much work has been done to obtain these hypothetical, if ever metastable, substances mainly in the form of thin films by using sputtering, CVD,and other methods.
The subject of the present research project is, on the other hand, the synthesis in its bulk form of a superhard C-N compound by the use of a high pressure technique. The use of high pressure has been expected to be effective to confine volatile nitrogen in a solid product. Organic substances like tetrazole, tetracyanoethlene, and polycyanogene were treated with/without a nitrogen generator (Na_3N,Fe_3N,or Cu_3N) at 6GPa and 1000 C for 30min., typically.
Fortunately, some new carbon nitrides were found in the course of the present study, though we did not obtain neither beta-C_3N_4 nor cubic C_3N_4 unfortunately. The characterization of these new compounds including strucure analysis by means of powder X-ray diffraction, electron diffraction, high resolution electron microscopy, and FT-IR and measurements of their compressibilities are in progress.
Some important know-hows concerning treatment of reactive organic carbon nitrides at high pressure and high temperature were collected in the course of the present research, which will be of great use in our future researches.
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