• 한국세라믹학회지
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• 제49권4호
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• pp.328-332
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• 2012

Etch rates of Si and high purity SiC have been compared for various fluorocarbon plasmas. The relative plasma resistance of SiC, which is defined as the etch rate ratio of Si to SiC, varied between 1.4 and 4.1, showing generally higher plasma resistance of SiC. High resolution X-ray photoelectron analysis revealed that etched SiC has a surface carbon content higher than that of etched Si, resulting in a thicker fluorocarbon polymer layer on the SiC surface. The plasma resistance of SiC was correlated with this thick fluorocarbon polymer layer, which reduced the reaction probability of fluorine-containing species in the plasma with silicon from the SiC substrate. The remnant carbon after the removal of Si as volatile etch products augments the surface carbon, and seems to be the origin of the higher plasma resistance of SiC.

• 대한핵의학회지
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• 제24권1호
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• pp.101-107
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• 1990

To develop $^{131}I-labelled$ m-iodobeneylguanidine $(^{131}I-MIBG)$, various experiments such as synthesis of MIBG, establishment of labelling conditions, determination of radiochemical purity, and examination of stability were carried out. 1) m-Iodobenzylguanidine (MIBG) sulfate was synthesized with a total yield of 62.4% by the condensation of m-iodobenzylamine hydrochloride with cyanamide via MIBG bicarbonate. Its physical properties, IR, $^1H-NMR$, and elemental analysis data were nearly identical to those of literature. 2) Freeze-dried or vacuum-dried kit vials were prepared from the mixture so as to contain MIBG (2 mg), ascorbic acid (10 mg), copper (II) sulfate (0.14 mg), and tin (II) sulfate (0.5 mg) per vial. Copper ( I ) catalyzed radioiodination of MIBG was carried out using kit vials and 0.01 M $H_2SO_4$ as solvent at $100^{\circ}C$ for 30 min under nitrogen atmosphere (optimal conditions). Labelling yield was 98% and radiochemical purity was 99.5%, respectively. 3) Solid-phase radioiodination of MIBG was carried out at $155^{\circ}C$ for 30 min using the prepared vials to contain MIBG (2 mg) and ammonium sulfate (10 mg). Duplicate reactions under the same conditions showed labelling yield of 95% and radiochemical purity of 99.5%. 4) $^{131}I-MIBG$ prepared either by catalytic or by solid-phase exchange method showed radio-chemical purity of 99% even after 3 days storing at room temperature.

• 한국세라믹학회지
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• 제24권5호
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• pp.431-436
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• 1987

High purity Al2O3 has been extracted from serlcite of clayminerals, selicite was treated by H2SO4(2N∼18N) solution, NH4OH treatment(PH8.5∼10.0) and metallic impurities such as Fe were removed by NaOH treatment. The tendency of extraction yield of ${\alpha}$-Al2O3 have been investigated by relating reaction time, acid concentration. Reaction products were analyzed by DT-TGA, chemical analysis and X-ray diffractometer. Prepared ${\alpha}$-Al2O3 power is fired in air at 1400$^{\circ}C$, 1600$^{\circ}C$ 2hr. The results are as follows; 1. The most suitable extracting conditions of ${\alpha}$-Al2O3 from Selicite were N-H2SO4, 120 min acidtreating time. 2. The optimum pH condition was 9.0. 3. Physical properties of sintered Al2O3 bodies were as follows. Relative density is 99%. Water absorption is 0.26%. Rock well hardness is 89.

• 한국세라믹학회지
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• 제12권1호
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• pp.29-36
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• 1975

This study was conducted to research the formation, color development and application for colored glazes of the spinel solid solutions of the green pigment. On specimens prepared by calcining the oxide and basic carbonate mixture at 1250℃ for 1.5 hour, the x-ray analysis, measurement of reflectance and the test of their stabiality as a glaze pigment were carried out. The results are summarized as follows 1) Each sample is composed of single spinel and not of mixture of spinel. 2) Formation of continuous soild solution, except for a few instances, pertaining to Vegard's law was confirmed by means of the x-ray analysis. 3) The more difference between absorption and reflectance lies, the lighter colors are. When the absorption occurs at the high-reflectance, the excitation purity becomes low. On the contrary when the absorption takes place at the low-reflectance, the excitation purity becomes low. On the contrary when the absorption takes place at the low-reflectance, the excitation purity is higher. 4) Colors obtained in the CdO-MgO-Cr2O3-Al2O3 system, as the amounts of Al3+ increased, change from green through brown to pink, and the absorption peak shifts towards violet region. 5) An increase in Co2+ in the CoO-MgO-Cr2O3-Al2O3 system, changes the color from blue green to dark blue. The excitation purity is higher, and the absorption peak shifts toward regions. 6) Colors are green in the NiO-MgO-Cr2O3 and CdO-MgO-Cr2O3 systems in general, but in the ZnO-MgO-Cr2O3 system brillant hue is not obtained. 70 According to the results of the colored glaze test, the spinels turn outto be stable as brilliant glaze pigment in the calcium-magnesia glaze.

• 분석과학
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• 제8권4호
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• pp.553-559
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• 1995

An extraction chromatographic method of separating rare earth impurities from high purity $Nd_2O_3$, $Sm_2O_3$, $Gd_2O_3$, $Er_2O_3$, $Dy_2O_3$ and $Yb_2O_3$ was studied by using $HCl-NH_4Cl$ as moving phase and P507 as stationary phase. After the impurities were enriched from the eluate by chelant-activated carbon, the active carbon was ashed and the ignited residue was used to prepare the sample electrode for spark source mass spectrometric determination. The impurities in 99.9999% rare earth oxide can be determined by the proposed method with recovery over 80%.

• 대한수학회논문집
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• 제12권4호
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• pp.851-854
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• 1997

In this paper we will show that the pure subring R of F-rational ring S is F-rational when R is a one-dimensional ring, or S is a Gorenstein ring. And we will give a condition that a pure subring of an F-rational ring is to be F-rational.

• 반도체디스플레이기술학회지
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• 제14권4호
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• pp.8-12
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• 2015

As NMP (N-Methyl-2pyrrolidone) is becoming important in many fields, the demand for it is also rising rapidly. With its chemical property of high boiling point, low vapor pressure and high water solubility, it is easy to recover it after processing. Therefore, it is increasingly needed to develop a system that effectively recovers NMP solvent. The study produced a system modeling using AMESim software before developing high purity solvent recovery (HPSR) system to recover NMP solvent. Then, it verified reliability by comparing the simulation model with the test result.

• 한국식품위생안전성학회지
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• 제20권3호
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• pp.128-133
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• 2005

꼬막 패각 회화분을 이용하여 칼슘 보조제로서 사용 할 수 있는 젖산칼슘과 구연산칼슘을 제조하였으며, ammonium chloride process(ACP) ammonium nitrate process(ANP)법을 적용하여 이들의 순도를 높이기 위한 실험을 하였다. 꼬막 패각 회화분을 젖산용액과 구연산용액과 반응시켜 얻은 젖산칼슘과 구연산칼슘의 순도는 각 용액의 농도에 따라 각각 $94.35-96.72\%$와 $87.58-93.06\%$이었다. 꼬막 패각 회화분에 ACP법 혹은 ANP법을 적용하여 정제한 탄산칼슘으로 제조한 젖산칼슘과 구연산칼슘의 순도는 각 용액의 농도에 따라 각각 $99.53-100.34\%$와 $99.32-99.88\%$를 나타내어 꼬막 패각 회화분을 직접 이용하여 제조한 것보다 순도가 상당히 높아졌으며, 식품첨가물공전의 규격기준에 적합한 칼슘제제를 얻을 수 있었다 꼬막 패각 회화분으로 제조한 젖산칼슘과 구연산칼슘의 백색도는 각각 91.8과 92.9이었으나 ACP법 혹은 ANP법을 적용한 경우는 각각 94.8-98.5와 99.4-101.5로서 높은 값을 나타내었다. 따라서 폐기물로 버려지는 꼬막 패각 회화분에 ACP법과 ANP법을 적용하여 정제한 탄산칼슘으로 제조한 젖산칼슘과 구연산칼슘은 순도와 백색도에서 우수한 것으로 판단되었다.

• 대한방사성의약품학회지
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• 제7권2호
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• pp.147-152
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• 2021

C-11 Radiolabeled amino acid-based radiopharmaceuticals such as [¹¹C]MET for brain tumor PET imaging have limitations due to their short half-life (20 min). F-18 radiolabeled amino acid derivatives have been developed to overcome for the short half-life, one of which is [¹⁸F]FET. Brain tumor imaging using [¹⁸F]FET showed high uptake in tumor region and no non-specific uptake in inflammatory tissue, which was useful in discriminating the difference between inflammation and tumor especially. In this study, [¹⁸F]FET was synthesized using an automatic synthesis module and quality tests were carried out including enantiomeric purity analysis with reference compounds. Radiochemical yield was 50.3 ± 4.9% (n=7, decay-corrected) with molar activity of 76 ± 17 GBq/mmol. The radiochemical purity of >99%. Enantiomeric purity of [¹⁸F]FET using chiral HPLC analysis showed >99%, which was confirmed by co-injection with the L-FET and D-FET authentic standards. [¹⁸F]FET was prepared with high radiochemical yield and molar activity including no racemate mixture.

• 대한본초학회지
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• 제36권4호
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• pp.41-50
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• 2021

Objectives : This study is to check the quality of Moschus products in Korean markets using a chromatographic analysis. Methods : We collected musk products, two genuine products from Russia (A, B), two authentic products from Hong Kong (C) and Korea (D), the Ministry of Food and Drug Safety (MFDS) standard (E), and two fire ants products (E, F). Results : For identification, TLC analysis of 60% ethanol extracts of each product showed that A, B, C, and E have the suitable patterns before color development at 365 nm UV light for the MFDS regulation in Korea. A clear red spot was observed from the E at R_f 0.6 with 365 nm UV light after color development, but this spot was not found in A and B. For the purity test, a distinct violet spot with R_f 0.87 was observed from the A and B in TLC analysis of methanol extracts of each product at white light, however, this spot was not matched with the impurities of E and F. In HPLC-UV pattern analysis, a similar peak pattern was shown in A, B and E, and similar peaks were observed C, although the similarity was weaker than that of A, B, and E. The F and G showed different peak patterns compared with the peak patterns of other samples. Conclusions : Hence, it is considered that the test methods need flexibility in application for identification and purity test depending on the type of sample.