• Journal of the Korean Ceramic Society
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• v.49 no.3
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• pp.221-225
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• 2012

It is possible to enhance the color of the natural diamond with a high pressure high temperature(HPHT) process. We employed a pyrophyllite tube cell and cubic press apparatus for HPHT treatment on the brown colored Type II (5.6 GPa/ $1700^{\circ}C$/ 52 min), and Type I aB(5.6 GPa/ $1650^{\circ}C$/ 30 min) diamond samples. We investigated the microstructure, Types, fluorescence, properties of the diamonds with an optical microscopy, FT-IR, photoluminescence(PL) spectroscopy, Diamond-View, and micro-Raman spectroscopy. Two tinted brown diamonds changed into colorless just after the HPHT process. Optical microscopy showed that no crack and significant inclusion evolution occurred during the HPHT process except the small graphite spot appeared in Type I aB sample. FTIR spectrum confirmed that no Type, amber center, and platelet defect change with the HPHT treatment. Diamond-View could not distinguish the HPHT treated diamonds from the naturals. PL spectroscopy showed that N3 and H3 color centers remained even after HPHT process. Consequently, we successfully changed the color of diamonds into colorless by 5.6 GPa HPHT process.

• 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 Korean Ceramic Society
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• v.49 no.6
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• pp.614-619
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• 2012

We investigated color and graphite layer formation on the surface of Type I tinted brown diamonds exposed for 5 minutes under a high-pressure high-temperature (HPHT) condition in a stable graphite regime. We executed the HPHT processes of Process I, varying the temperature from $1600^{\circ}C$ to $2300^{\circ}C$ under 5.2 GPa pressure for 5 minutes, and Process II, varying the pressure from 4.2 to 5.7 GPa at $2150^{\circ}C$ for 5 minutes. Optical microscopy and micro-Raman spectroscopy were used to check the microstructure and surface layer phase evolution. For Process I, we observed a color change to vivid yellow and greenish yellow and the growth of a graphite layer as the temperature increased. For Process II, the graphite layer thickness increased as the pressure decreased. We also confirmed by 531 nm micro-Raman spectroscopy that all diamonds showed a $1440cm^{-1}$ characteristic peak, which remained even after HPHT annealing. The results implied that HPHT-treated colored diamonds can be distinguished from natural stones by checking for the existence of the $1440cm^{-1}$ peak with 531 nm micro-Raman spectroscopy.

• Korean Journal of Materials Research
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• v.20 no.5
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• pp.278-288
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• 2010

High Pressure High Temperature (HPHT) treatment can significantly change the color of diamonds. We studied the variation of the optical properties according to the nitrogen arrangement in natural brown diamonds of various types (type IaAB, type IaB, type IaA > B, type IaA < B, IaA = B) after HPHT treatment. The diamonds with different arrangements of nitrogen were annealed at temperatures in the range $1700-1800^{\circ}C$ under a stabilizing pressure of 5 GPa. HPHT treated samples were analyzed using UV-Vis-NIR, FT-IR, and PL spectroscopy. The absorption and luminescence spectra were measured to compare the variations of nitrogen arrangement in the natural brown diamonds before and after HPHT treatment. After HPHT treatment, the brown coloration in all types of diamonds was reduced and a decrease in the peaks related to the A-aggregate of nitrogen was more predominant than the B-aggregate. Furthermore, the peaks related to N3 (415.4 nm), H4 (496.4 nm), and platelet decreased and the peaks related to H3 (503.2 nm) and G-band increased after HPHT treatment. In conclusion, spectroscopic analysis of natural brown diamonds after HPHT treatment showed that a yellow color was produced by absorption in the H3 centers and a green color was generated by interaction between absorptions of the H3 and H2 centers.

• Korean journal of applied entomology
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• v.31 no.4
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• pp.452-460
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• 1992

To establish the economical and reliable routine bioassay system for developing new insecticidal compounds, effects of leaf-dipping time, application methods, insect species and their developmental stages on susceptibilities of insects to insecticides were studied. The stable insecticidal activity appeared at the dipping time for 30-60 seconds in leaf-dipping method, and the most effective application methods were leaf-dipping method for apterous green peach aphid adults, and third instars of diamond-back moth and tobacco cutworm, whereas seedling+insect spray method for adults or third instars of brown planthoppers. For two-spotted spider mite, leaf-dipping or intact plant spray method was favorable. In the bioassay for chitin synthesis inhibitors, the inoculation of third instars of brown planthopper, diamond-back moth, tobacco cutworm and green peach aphid, and larvae of two-spotted spider mite to the young host plants treated by spray method were adequate bioassay methods.

• Journal of The Korean Society of Grassland and Forage Science
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• v.34 no.4
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• pp.240-246
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• 2014

The present study was conducted to evaluate the productivity of $Sorghum{\times}sudangrass$ (SX17) hybrid and BMR (brown mid rib) $Sorghum{\times}sudangrass$ hybrid and silage quality of these forages with corn grain supplementation. The effect of corn grain supplementation on the quality of silages was also investigated. No remarkable differences at growth characteristics and productivities in two hybrids were found. Sugar content, however, in stem of BMR hybrid showed significantly great (p<0.05) and the difference between two hybrids was about $2B^{\circ}$. Ratio of lactic acid in total organic acid in BMR hybrid (82.8%) was significantly greater than the control (SX17 hybrid) (78.5%) (p<0.05). Ratio of butyric acid in total organic acid in SX17 hybrid (18.5%) was significantly greater than BMR hybrid (9.8%) (p<0.05). According to the result of organic acid ratio, it could be assumed that the use of BMR hybrid can improve silage quality. NDF and ADF contents in both SX17 and BMR hybrids were significantly declined with increased corn grain supplementation (p<0.05). Different TDN values in SX17 (56.2) and BMR (57.1) hybrids were detected. However, TDN values of both SX17 and BMR hybrid silages were significantly elevated by increasing the proportion of ground corn (p<0.05).

• The Journal of the Korea Contents Association
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• v.10 no.11
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• pp.154-161
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• 2010

With Jewelry industry is becoming active with gradual increase of transactions of pearl and diamond. The pearl market of recent times the size of that market was magnified because the pearls of various type are imported. The necessity of new design development and grasps properties of pearl is demanded clearly because like that. This research analyzed the cultivated brown pearl and black pearl which is sold from market with gemological Analysis. As result, it is ascertained the dyed fresh water pearl. I suggest the design which uses the chocolate brown color pearl beads which the consumers prefer and another pearl design which is concept of wedding gift through CAD/CAM works.

• The Plant Pathology Journal
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• v.19 no.4
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• pp.203-204
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• 2003

Decayed samples of marketed mungbean sprout were collected from Sacheon, Suncheon, and Dangjin cities in Korea. Initial symptom on hypocotyls was dark-brown diamond speck, which developed into enlarged sunken brownish-black spot with irregular margin, followed by softening yellowish decay. Brown speck on cotyledon further developed into irregular lesions. This study isolated the fungus Colletotrichum sp. The fungal colony was pale orange, which turned greenish gray after 1 week at $25^{\circ}C$. Colony of reverse side in a petri dish was pink. Neither conidiomata nor setae were present in the culture. Typical fusiform conidia sized 7.5-15.0$\times$2.5-2.9 $\mu\textrm$were hyaline, aseptate, smooth, and had salmon color in mass. Conidiogenous cells were phialidic, hyaline, smooth, and cylindrical with terminal distinct collarette. Basedon these mycological characteristics, the casual organism was identified as Colletotrichum acutatum. This is first report of Colletotrichum acutatum in Korea.

• Applied Biological Chemistry
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• v.45 no.1
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• pp.37-41
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• 2002

Seven organophosphorus compounds and three carbamates of some monoterpenoids were synthesized and tested for insecticidal activity to five insects, brown plant happer (BPH, Nilaparvata lugens), green peach aphid (GPA, Myzus persicae), diamond bark moth (DBM, Plutella xylostella), tobacco cut worm (TCW, Spodoptera litura), and two spotted spider mite (TSSM, Tetranychus urticae). With the administration of 500 mg/l concentration thiophosphates of carveol and geraniol showed motality of from 95% to 100% to BPH and DBM. On the other hand, phosphates of menthol, thymol, and borneol had also good to moderate activity to BPH and TSSM insects at the same concentration.

• Korean journal of applied entomology
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• v.31 no.2
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• pp.182-189
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• 1992

The influnces of 9 kinds of solvents on the toxicities against several insect species, phytotoxicity and solubility of compounds were evaluated by means of leaf dipping and spray methods. In case of the spray application, density and vapor pressure seemed to be a contributing factor to lethal toxicity against brown planthopper and diamond-back moth, respectively; the bigger the property of density and the smaller the vapor pressure gave the stronger toxicity. It appeared that the toxicity of solvents was not correlated with anyone of physical properties such as boiling point, dipole moment, dielectric constant, surface tension and viscosity. Spray treatment gave more toxicity to insects than leaf dipping treatment. Although dielectric constant and dipole moment seemed to be contributing factors to phytotoxic damage to rice seedling and bean plants, respectively, no general correlation between phytoxicity and the other physical properties was found. Leaf dipping application caused stronger phytotoxicity than spray application. It is concluded that 5% acetone solution may be most suitable to test chemicals because of its favorable solubility of compounds, lower toxicity to insects, and lower phytotoxicity.