• 한국세라믹학회지
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• 제25권5호
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• pp.473-478
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• 1988

In order to obtain the high purity $\beta$-SiC powder that possesses the excellent sinterability and is close to the spherical shape, the carbon black was mixed into the composition of Si(OC2H5)4-H2O-NH3-C2H5OH which the monodispersed spherical fine particles is formed the hydrolysis of Ethylsilicate and the mixture was carbonized under an argon atmosphere. Particle shpae, size and the yield of $\beta$-SiC powder were investigated according to the molar ratio of carbon/alkoxide and variations of reaction temperature and reaction time. The results of this study are as follow ; 1) The yield of $\beta$-SiC gained from the reaction for one hour at 150$0^{\circ}C$ almost got near 100% and the particle size of $\beta$-SiC from the reaction for 15 hrs at 150$0^{\circ}C$ was 0.2${\mu}{\textrm}{m}$ on the average and close to the spherical shape agglomerate state. 2) When the molar ratio carbon/alkoxide is over 3.1 and the reaction occurs at 145$0^{\circ}C$ for 5hrs, the carbon content has not an effect on the kind of crystal of product.

• 환경위생공학
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• 제16권3호
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• pp.34-41
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• 2001

It is well known that bioassay on the low organic matters in water have developed from the two methods. One is assimilable organic carbon(AOC) that makes use of the maximum growth biomass of the pure strains for the standard substrates, the other is biodegradable dissolved organic carbon(BDOC) that determines the fraction of dissolved organic carbon(DOC) available for microbial utilization. The purpose of this study was to upgrade the measurement method of BDOC in natural water or drinking water. BBOC was determined by means of the bacterial growth and the DOC decrease at the same time. The origin inoculums were used to the suspended bacteria from Han River water, The initial optimum biomass and incubation time for initial DOC were induced by variation of nutrient repression and inoculums. The time reached to minimum DOC was selected as incubation time. The initial optimum biomass for Han river water was about 1000~5000 CFU/mL, respectively. In a sufficient biomass, suitable incubation time was about 3~5 day. It was indirectly calculated BDOC on maximum growth rate by measuring growth yield of indigenous bacteria. But it was difficult to adapt growth yield coefficient because of irregular bacterial growth. The measured 3 day BDOC was close to BDOC calculated with our proposed experimental equation between DOC and BDOC. It shows that the quantification of BDOC with this experimental equation can be used indirectly.

• Carbon letters
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• 제25권
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• pp.78-83
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• 2018

Pyrolyzed fuel oil (PFO) and coal tar was blended in the feedstock to produce pitch via thermal reaction. The blended feedstock and produced pitch were characterized to investigate the effect of the blending ratio. In the feedstock analysis, coal tar exhibited a distinct distribution in its boiling point related to the number of aromatic rings and showed higher Conradson carbon residue and aromaticity values of 26.6% and 0.67%, respectively, compared with PFO. The pitch yield changed with the blending ratio, while the softening point of the produced pitch was determined by the PFO ratio in the blends. On the other hand, the carbon yield increased with increasing coal tar ratio in the blends. This phenomenon indicated that the formation of aliphatic bridges in PFO may occur during the thermal reaction, resulting in an increased softening point. In addition, it was confirmed that the molecular weight distribution of the produced pitch was associated with the predominant feedstock in the blend.

• Journal of Microbiology and Biotechnology
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• 제31권3호
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• pp.429-438
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• 2021

Bacterial cellulose (BC) is widely used in the food industry for products such as nata de coco. The mechanical properties of BC hydrogels, including stiffness and viscoelasticity, are determined by the hydrated fibril network. Generally, Komagataeibacter bacteria produce gluconic acids in a glucose medium, which may affect the pH, structure and mechanical properties of BC. In this work, the effect of pH buffer on the yields of Komagataeibacter hansenii strain ATCC 53582 was studied. The bacterium in a phosphate and phthalate buffer with low ionic strength produced a good BC yield (5.16 and 4.63 g/l respectively), but there was a substantial reduction in pH due to the accumulation of gluconic acid. However, the addition of gluconic acid enhanced the polymer density and mechanical properties of BC hydrogels. The effect was similar to that of the bacteria using glycerol in another carbon metabolism circuit, which provided good pH stability and a higher conversion rate of carbon. This study may broaden the understanding of how carbon sources affect BC biosynthesis.

• 한국버섯학회지
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• 제18권2호
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• pp.135-140
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• 2020

산느타리 배지재료별 적정 혼합비율을 구명하기 위하여 1 kg 봉지재배를 통해 배지의 화학성과 2주기까지의 버섯 수량간 관계를 분석한 결과, 1주기 버섯 수확량은 총 질소량과 상관을 보였는데, 총 질소량 1.1% 부근에서 최대의 수량을 보였고 그보다 질소량이 적거나 많은 경우 수량이 적어지는 경향을 보였다. 또한 2주기 버섯 수확량은 총질소, 총탄소, C/N율 등 여러 가지 화학성과 높은 상관을 보였는데, 질소함량 1% 이상의 구간에서 질소함량이 높을수록, 탄소함량 13% 이상의 구간에서 탄소함량이 높을수록 수량이 증가되는 양상을 보였다. 따라서 산느타리 재배시 혼합배지의 질소함량이 1.1% 정도인 경우 1주기 버섯수량이 가장 높았고, 2주기 수량은 질소와 탄소의 함량이 높은 배지에서 높은 경향을 보였다. 다만, 면실피가 다량 첨가된 배지에서 대두박과 케이폭박이 합계 20% 첨가되면 버섯 발생에 문제가 생길 수 있으므로 주의해야 할 것이다.

• 한국응용과학기술학회지
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• 제21권2호
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• pp.174-181
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• 2004

Multi-walled carbon nanotubes (CNTs) were prepared by thermal chemical vapor deposition (CVD) and microwave plasma chemical vapor deposition (MPCVD) using various combination of binary catalysts with four transition metals such as Fe, Co, Cu, and Ni. In the preparation of CNTs from acetylene precursor by thermal CVD, the CNTs with very high yield of 43.6 % was produced over $Fe-Co/Al_2O_3$. The highest yield of CNTs was obtained with the catalyst reduced for 3 hr and the yield was decreased with increasing reduction time to 5 hr, due to the formation of $FeAl_2O_4$ metal-aluminate. On the other hand, the CNTs prepared by acethylene plasma CVD had more straight, smaller diameter, and larger aspect ratio(L/D) than those prepared by thermal CVD, although their yield had lower value of 27.7%. The degree of graphitization of CNTs measured by $I_d/I_g$ value and thermal degradation temperature were 1.04 and $602^{\circ}C$, respectively.

• 한국토양비료학회지
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• 제28권3호
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• pp.287-294
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• 1995

본 논문에서는 철 이외에 사이데로포 생성에 관여하는 요인을 연구하였다. 약산성(pH6)에서 세포의 양은 감소하는 반면에 세포당 사이데로포의 생성은 증가하였다. 사이데로포 생성의 적정온도는 7NSK2 균주가 $12^{\circ}C$이고 ANP15은 $19^{\circ}C$였다. 배지의 C : N 비율에 따른 사이데로포 생성력을 보면 C : N율이 낮은 배지에서는 사이데로포 생성과 세포생장은 감소됐다. 서로 다른 배지에서 사이데로포 생성을 조사한 바에 의하면 citrate를 탄소원으로 했을 경우 세포의 철 흡수능력이 증가했으며 사이데로포 생성도 감소되었다. 그러나 Glucose나 Succiuate에 비해서 citrate 배치의 세포량에는 별 차이가 나타나지 않았다. 이상의 결과로 보아 환경요인으로 작용할 수 있는 pH나 온도, 탄소원 등은 철분 외에도 사이데로포의 생성에 영향을 미칠 수 있음을 확인하게 되었다.

• Carbon letters
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• 제3권4호
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• pp.210-218
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• 2002

Electrostatic spinnings were performed with the solutions of PAN/DMF to be nanofiber webs. The diameter of the fibers ranged from 200 nm to 1000 nm depending on the PAN concentration and on the applied DC voltage. The nanofibers were oxidatively stabilized and subsequently carbonized up to $1000^{\circ}C$ with carbonization yield of 40%. The bulk electric conductivity of the carbonized web increased form $6.8{\times}10^{-3}S/cm$ to 1.96 S/cm while the carbonizaton temperature increased from $700^{\circ}C$ to $1000^{\circ}C$.

• KSBB Journal
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• 제6권4호
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• pp.407-412
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• 1991

The extraction of indole alkaloids from Catharanthus roseus using the supercritital carbon dioxide with ethanol was performed in various temperature and pressure conditions. The contents of vindoline in the extracts were determined by HPLC. In this study, the flow rate of cosolvent ehtanol was 20.4$\mu$l/min, about 3 wt.% of flow rate of supercritical carbon dioxide. However the effect of ethanol on the yield of extracted vindoline was not significant.

• 한국재료학회지
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• 제24권6호
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• pp.293-300
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• 2014

Coal-tar pitch, a feedstock which can be heat-treated to create graphite, is composed of very complex molecules. Coal-tar pitch is a precursor of many useful carbon materials (e.g., graphite, carbon fibers, electrodes and matrices of carbon/carbon composites). Modified coal-tar pitch (MCTP) was prepared using two different heat-treatment methods and their properties were characterized and compared. One was prepared using heat treatment in nitrogen gas; the other was prepared under a pressure of 350 mmHg in air. The MCTPs were investigated to determine several properties, including softening point, C/H ratio, coke yield, formation of anisotropic mesophase and viscosity. The MCTPs were subject to considerable changes in chemical composition due to condensation and polymerization in the used-as-received coal-tar pitch after heat-treatment under different conditions. The MCTPs showed considerable increases in softening point, C/H ratio, and coke yield, compared to those of as-received coal-tar pitch. The MCTP formed by heat-treatment in nitrogen showed isotropic phases below $350^{\circ}C$ for 1 h of soaking time. However, MCTP heat-treated under high pressure (350 mmHg) showed isotropic phases below $300^{\circ}C$, and showed anisotropic phases above $350^{\circ}C$, for 1 h of soaking time. The viscosity of the MCTPs increased with increase in their softening points.