• Analytical Science and Technology
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• v.23 no.6
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• pp.511-517
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• 2010

Dissolution procedure of vanadium pentoxide, which is widely used as a catalyst for production of sulfuric acid or an oxide reaction of the numerous organic compounds, was investigated. Reagent of vanadium pentoxide was completely dissolved in aqua regia-$H_2O_2$-HF solution, but plate type of vanadium pentoxide sample was not clearly dissolved with mixed acids. Thus, in order to establish the dissolution procedure for plate type of vanadium pentoxide, the solubility of vanadium pentoxide was investigated through comparison of acid treatment-fusion and microwave digestion methods. The optimized acid for dissolution of vanadium compound was found to be mixing acids of aqua regia, $H_2O_2$ and HF. Acid-fusion and microwave digestion methods have a similar property in the solubility of vanadium compound, but the latter was more quick and convenient procedure. The content of vanadium pentoxide was found to be $97.9{\pm}0.9%$ using an inductively coupled plasma atomic emission spectrometer after dissolution of a sample with the microwave digestion system.

• Electrical & Electronic Materials
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• v.9 no.5
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• pp.470-475
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• 1996

Fiber-textured diamond films have been deposited on scratched silicon(100) substrate by micro wave .plasma enhanced chemical vapor deposition at the condition of micro wave power : 950 W, pressure : 60 torr, H$_{2}$ gas flow rate : 50 sccm, CH$_{4}$ gas flow rate : 1.5 sccm, substrate temperature : about 900.deg. C and deposition time : 20 hours. The films were characterized by mean of scanning electron microscopy, Raman spectroscopy and X-ray analysis.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.46 no.2
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• pp.185-194
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• 2020

This study was conducted to find out the optimal extraction conditions to obtain extracts with a high content of ginsenosides and antioxidant activity using the ginseng berry. After extraction by stirring, ultrasound and microwave method using 70% ethanol and distilled water as solvents, the results of considering the content of ginsenoside Re and Rb1, total polyphenol content, antioxidant activity, and whether it is an environmentally friendly manufacturing method, it was confirmed that the microwave method using distilled water is good method of extraction. The optimization of extraction conditions for microwave method were made by response surface methodology (RSM). Microwave power (50 ~ 200 W, X1), solvent and ginseng berry ratio (5 ~ 20 times, X2) and the extraction time (30 ~ 120 s, X3) were used as independent variables. The model showed a good fit having a determination coefficient of the regression equation of 0.9 or more and a p-value less than 0.05. Estimated conditions for the maximized extraction of ginsenoside contents and total polyphenols were 200 w in microwave power, 20 times in solvent and ginseng berry ratio, and 90 s in extraction time. Predicted values at the optimum conditions were total polyphenols of 6.23 mg GAE/g, ginsenoside Re of 17.69 mg/g, and ginsenoside Rb1 of 16.01 mg/g. In the verification of the actual measurement the obtained values showed 6.33 mg GAE/g, 17.79 mg/g, and 15.59 mg/g, respectively, in good agreement with predicted values.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.1
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• pp.66-72
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• 2000

The behavior of nucleation and crystallization in the $Li_2O_3-SiO_2$ glass heat-treated at different condition under the conventional and microwave processing was studied by differential thermal analysis (DTA), X-ray diffractometry (XRD), optical microscopy (OM), and electrical conductivity measurement. Nucleation temperature and temperature of maximum nucleation rate in both conventionally and microwave heat-treated samples were 460~$500^{\circ}C$ and $580^{\circ}C$, respectively. It was expected that the probability for bulk crystallization increased in microwave heat-treated sample, compared to conventionally heat-treated one. Degree of crystallization increased with increasing crystallization temperature in both conventionally and microwave heat-treated samples. However, pattern of crystallization growth under microwave processing appeared to be quite different from that under the conventional one due to its internal or volumetric heating. Electrical conductivity of conventionally and microwave heat-treated samples were 1.337~2.299, 0.281~~$0.911{\times}10^{-7}\Omega {\textrm}{cm}^{-1}$, respectively.

• Journal of the Korean Ceramic Society
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• v.35 no.10
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• pp.1078-1084
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• 1998

lanthanum chromite(LaCrO3) powder was synthesized by the combustion of a solution of metal nitrates La(NO3).6H2O and Cr(NO3)3.9H2O and urea. The pH of solution affected a yield of the combustion products but did not influence the morphology of the products. When the pH of the solution was in the range of 0.7-4, the yield of the combustion products was more than 90% The morphology of the combustion products was af-fected by heating methods for the solution. The hot-plate induced heating of the solution yielded powders hav-ing two-dimensionally interconnected agglomerates whereas microwave-induced heating produced a fine and non-agglomerated powders. The specific surface area(BET) of the combustion products using microwave-in-non-agglomerated powders. The specific surface area(BET) of the combustion products using microwave-in-duced heating method were larger(25~32m2/g) than that of hot plate heating method(10-14m2/g)

• Clean Technology
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• v.21 no.3
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• pp.178-183
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• 2015

Lead molybdate (PbMoO₄) oxides were successfully synthesized using a conventional hydrothermal method and a microwave-assisted hydrothermal method. They were characterized by XRD, DRS, BET, Raman, SEM and PL. We also investigated the photocatalytic activity of these materials for the decomposition of Rhodamine B under UV-light irradiation. From XRD and Raman results, well-crystallized PbMoO₄ crystals have been successfully synthesized regardless of preparation method and had 42~59 nm particle size. The PbMoO₄ catalysts prepared using microwave-assisted process had the similar particle size and enhanced the photocatalytic activity when compared to that prepared by hydrothermal method. The PbMoO₄ catalysts prepared under the irradiation of microwave for 75 min showed the highest photocatalytic activity. The PL peaks appears at about 530 nm at all catalysts and it was also shown that the excitonic PL signal is proportional to the photocatalytic activity for the decomposition of Rhodamine B.

• Journal of the Korean Ceramic Society
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• v.41 no.9
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• pp.684-689
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• 2004

Hexagonal sheet typed $\alpha$-Al$_2$O$_3$ nano particles were synthesized successfully at various conditions with the aluminum sulfate solution extracted from kaolin through the conventional and microwave assisted polyacrylamide (PAA) gel methods. Shorter gel time and higher yield were obtained in the microwave assisted PAA gel method, compared to conventional method. the size of nano particles was not changed by increasing the concentration of aluminum sulfate, but decreased with increasing the concentration of cross-linking agent in both the conventional and microwave samples. Above 0.01M concentration of cross-linking agent, the sizes of nano particles in the microwave samples were relatively larger than those in the conventional samples.

• Journal of the Korea Institute of Building Construction
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• v.11 no.2
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• pp.162-170
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• 2011

As the result of implementing a treated material test and durability test after quickly drying S.P.F. species, a type of softwood structural material, within a short period time, soaking it in liquid phosphate flame proof agent for an hour, microwave heating it, and compressing it from 3.8cm to 1cm, when setting the appropriate heating time of microwave heating at 7 minutes at 5kW, it is observed that it satisfies the target water content (4~5%). It is shown that in a water content measurement of the wood that is compressed after being softened by soaking in the flame proof agent, drying and heating at 3kW for 9 minutes, all specimens satisfied 12~14%, the appropriate water content for exterior wood. Also, it is shown that in terms of the flame performance obtained through a flame resistance treatment of the compressed wood and a treated material test, the specimen soaked in flame proof agent for 30 minutes was the most excellent, and that the performance test result of the compressed wood in all areas, such as nail withdrawal resistance, compression, bending strength, and shearing strength, were all improved in their mechanical features to twice to three times better performances.

• Korean Journal of Microbiology
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• v.54 no.2
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• pp.140-145
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• 2018

The most energy-intensive processes in lipids extraction were the disruption of the cell wall of microalgae. Here, we tried to extract lipids through lysis using virus-infecting microalgae, to compare with those by the other two methods using microwave or ultrasonication. The lipids yield using viral infection was not significantly different from those using ultrasonication and microwave oven. This suggests that the same amount of lipids can be obtained with low energy and costs, as well as that microalgal lipids extraction by chlorella virus infection might provide the price competitiveness in biodiesel production even if it will be applied to mass production facilities.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2000.11a
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• pp.130-134
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• 2000

본 논문에서는 확장된 시간영역 유한차분법(Extended finite difference time domain method)을 이용하여 마이크로파 중폭기를 해석하였다. 회로에 포함되어 있는 능동 소자는 고주파 등가 회로를 이용하여 모델링 하였다. 고주파 등가 회로를 통하여 계산한 게어트와 드레인의 전류를 FDTD의 전계 계산식에 첨가향으로개 마이크로스트립 회로의 전자기파와 능동 소자와의 상호 작용을 특성 지었다. 해석 결과는 주파수 영역 회로 해석법(Frequency-domain circuit analysis)을 이용한 결과와의 비교를 통하여 정확성을 입증했다.