• Journal of the Mineralogical Society of Korea
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• v.22 no.4
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• pp.407-415
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• 2009

The change of the nitrogen-related centers and the color change of electron beam irradiated type Ia natural diamonds were studied. The irradiation of diamond with high-energy electron beam creates lattice defects which are neutral single vacancy $V^0$. It increased with increasing electron dose density. The B aggregation seems to produce vacancies more easily than the A aggregation, because diamonds with more B aggregation have more platelets, which are sufficient breakable size by electron beam. Greenish blue color of irradiated diamond is changed to darker with increasing electron dose density. GR1 centers with a zero-phonon line at 741 nm and phonon sidebands make transmit visible light at 530 nm and it moves to 500 nm with higher intensity of GR1 centers.

• Journal of the Korean Chemical Society
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• v.22 no.3
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• pp.138-148
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• 1978

A discussion of the various theories of natural diamond formation is given. Experimental data from mass spectrometric analysis of included gases is related to theoretical data on the carbon-hydrogen-oxygen gas phase under geologic conditions.Possible temperature-pressure conditions for natural diamond formation are proposed.

• Journal of the Mineralogical Society of Korea
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• v.20 no.2 s.52
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• pp.91-96
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• 2007

Notable characteristics are found between diamond types and observed optical properties from the analysis of natural diamonds in market as a gem mineral. All of the diamond samples observed are classified into type Ia, which can be subdivided type IaA containing only A aggregates, type IaB containing only B aggregates, and type IaAB containing both A aggregates and B aggregates in detail. As B aggregates more relatively increase than A aggregates. It is possible to find out that an increase of N3 center, an enhancement of blue fluorescence reaction, and an intensification of irregularity in the strain pattern. Because the property change of diamond mentioned above are consistent with optical phenomenon caused by dislocation and with N3 center produced by changes of nitrogen aggregation process from A aggregate to B aggregate. There is a close relation between diamond type and optical properties.

• Korean Journal of Metals and Materials
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• v.50 no.1
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• pp.23-27
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• 2012

The color of a natural diamond that contains nitrogen impurities can be enhanced by a high pressure high temperature (HPHT) treatment. Type IaAB diamond samples containing nitrogen impurities were executed by HPHT process of 5.6 Gpa, 10 min by varying the annealing temperature at 1600, 1650, and $1700^{\circ}C$. Property characterization was carried out using an optical microscope, FT-IR spectrometer, low-temperature PL spectrometer, and micro Raman spectrometer. By observing optical micrographs, it can be seen that diamond sample began to alter its color to vivid yellow at $1700^{\circ}C$. In the FT-IR spectrum, there were no Type changes of the diamond samples. However, amber centers leading to brown colors lessened after $1700^{\circ}C$ annealing. In the PL spectrum, all the H4 centers became extinct, while there were no changes of yellow color center H3 before or after treatment. In the Raman spectrum, no graphite spots were detected. Consequently, diamond color enhancement can be done by higher than $1700^{\circ}C$ HPHT annealing at 5.6 GPa-10 min.

• Journal of the Mineralogical Society of Korea
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• v.10 no.1
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• pp.18-32
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• 1997

Analysis of geological data, relating to occurrence and formation of diamonds as well as host rocks, inclined author to have different outlook on the diamond genesis and to establish a proposition on their formation at pneumatolytic-hydrothermal conditions near superficial Earth zones. Based on that theoretical foundations and experimental works, the first low-pressure and low-temperature hydrothermal diamond synthesis from water solution in pressure autoclave was executed. As a result, the natural diamond seed crystal grew bigger ad coupling of the synthetic diamond single-crystalline grains were obtained. SEM documentation proofs that parallely paragenetic crystallization of quartz and diamond, and nucleation of new octahedral diamond crystals brush take place on the seed crystal surface. Forecast of none times growth of diamond industrial application at 2000 and seventeen times at 2010 with reference to 1995, needs technology of large and pure single-crystals diamond synthesis. Growth of the stable and destressed diamond single-crystals in the pseudo-metastable diamond plot, may be realized with processes going through the long time and with participation of free radicals catalysts admixtures only. Sol-gel colloidal processes are an example of environment which form stable crystals in thermodynamically unstable conditions through a long time. Paper critically discusses a whole way of studies on the diamond synthesis, from high-pressure and high-temperature processes through chemical vapour deposition up to hydrothermal experiments.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.4
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• pp.1186-1191
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• 2010

Colored cubic zirconia specimen made by skull melt process were annealed in vacuum at the temperature of $1200^{\circ}C{\sim}1400^{\circ}C$ for 10~60 minutes to enhance the color. All the seven specimen become darker and eventually be black as annealing temperature and time increase. The black samples turned into original colors when we elevated the temperature with oxy-acetylene torch for around 10 minutes in the air. Finally, we could tune the colors of cubic zirconia either anneal in vacuum or the black samples in the air to obtain the proposed colors. Our proposed new process may be appropriate to fabricate the precious synthetic colored cubic zirconia to simulate the natural colored gem quality diamonds.