• Korean Chemical Engineering Research
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• v.60 no.3
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• pp.439-445
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• 2022

In this study, Silicon and petroleum pitch were coated on the surface of Si/C fiber manufactured using electrospinning to improve the electrochemical performances. SiO₂/PAN fiber was prepared by electrospinning with TEOS and PAN at various ratios dissolved in DMF. The characteristics of carbonization, reduction, and pitch coating processes were investigated for the optimal process of the pitch coated Si/C fiber anode composite. Anode composite prepared with TEOS/PAN = 4/6 (CR-46) after carbonization and reduction process has a capacity of 657 mAh/g. To improve capacity and stability, Si powder and PFO pitch were coated at the surface of CR-46. When the pitch composition was fixed at 10 wt%, it was found that the capacity increased as the weight ratio of silicon increased, but the stability decreased. The pitch coated Si/C fiber composite with 10 wt% silicon has high capacity of 982.4 mAh/g and capacity retention of 86.1%. In the test to evaluate rate performance, the rate capability was 80.2% (5C/0.1C).

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.3
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• pp.131-135
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• 2008

This study is to establish the coating technique for synthetic mica and to prepare synthetic mica with the non-aqueous property. The surface coating of synthetic mica is prepared with stearic acid using the high speed stirrer. The characterizations for mica powders coated the stearic acid are carried out by the deposition test, XRD and SEM. The results of research could be coated the stearic acid on the mica by 1600 rpm/min at $70^{\circ}C$ for 10 min. From the observation of SEM was found that the non-aqueous property mica could obtained by mixture ratios for stearic acid and mica, the inner temperature and rotation speed of the stirrer but treated time be unrelated.

• Journal of Ocean Engineering and Technology
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• v.23 no.6
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• pp.99-104
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• 2009

PTFE has good mechanical and chemical stability at a wide range of temperatures and demonstrates a low friction coefficient value. PTFE is being used for self-lubricating parts in industry. But it shows a high wear rate. Thus, PTFE and nano-diamond powder were mixed into a composite and the wear properties of a PTFE coating layer on Al6061 was investigated. A ball-on-disk type of wear tester was used under a dry condition and different temperatures of oil. After the wear test, the wear track wasexamined by optical microscope. The PTFE-diamond showed the lowest friction coefficient (0.02) of all the lubricants in the experiments. The friction coefficient was shown to be directly related to the diamond powder in the PTFE coating. Adhesion estimations were performed by a scratch test, which is mainly used for coatings. The critical load between the coating and substrate was defined through analyses of the friction load, normal load curve, and acoustic emissions, along with optical microscope observations. The scratch test results showed that an import item (SWISS) gave the highest critical load values.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.10
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• pp.1333-1339
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• 2014

As the demand for petroleum resources increases, and oilfields on lands and in shallow-sea become exhausted, the areas for oil production are expanding to the deep sea and therefore technologies for flow assurance are coming into the highlight. In low temperature environment such as the deep sea, wax is accumulated and prevents stable oil production. Therefore, the development of flow assurance technologies is required. Wax is precipitated in crystalline form when the oil temperature decreases below the wax appearance temperature; it then accumulates on the inner walls of pipelines causing blockages. In particular, in subsea pipelines, which have a large surface contact area with the surrounding seawater, wax deposition problems are frequent. The internal tubular coating can effectively reduce wax deposition without pausing oil production when the coating is appropriately designed. This study carried out wax deposition tests on a number of internal tubular coatings under single flow conditions. The results were analyzed for the effects that the physical properties of the coatings had on wax deposition.

• Journal of Welding and Joining
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• v.31 no.3
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• pp.66-75
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• 2013

In this study, the effect of coating thickness($20{\mu}m$ and $30{\mu}m$) on microstructure and tensile properties in Yb:YAG disk laser welds of Al-Si-coated boron steel (1.2mmt) was investigated. In the case of as welds, the quantity of ferrite was found to be higher in base metal than that in HAZ (Heat Affected Zone) and fusion zone, indicating, fracture occurrs in base metal, and the fracture position is unrelated to the coating thickness. Furthermore, yield strength, tensile strength of base metal and welded specimens showed similar behavior whereas elongation was decreased. On the other hand, base metal and HAZ showed existence of martensite after heat treatment, the fusion zone indicated the presence of full ferrite or austenite and ferrite during heat treatment ($900^{\circ}C$, 5min), After water cooling, austenite was transformed to martensite, and the quantity of ferrite in fusion zone was higher as compared with in base metal, resulting in sharply decrease of yield strength, tensile strength and elongation, which leads to fracture occured at fusion zone. In particular, results showed that because the concentration of Al was higher in 30um coating layer specimen than that of 20um coating specimen, after heat treatment, producing a higher quantity of ferrite was higher after heat treatment in the fusion zone; howevers, it leads to a lower tensile property.

• Fibers and Polymers
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• v.5 no.1
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• pp.1-5
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• 2004

The ability of inherently conducting polymer (ICP) coated textiles to recover gold metal from aqueous solutions containing $[AuCl_4]^-$ was investigated. Nylon-lycra, nylon, acrylic, polyester and cotton were coated with a layer of polypyrrole (PPy) doped with 1,5-naphthalenedisulfonic acid (NDSA), 2-anthraquinonesulfonic acid (AQSA) or p-toluenesulfonic acid (pTS). Textiles coated with polyaniline (PAn) doped with chloride were also used. The highest gold capacity was displayed by PPy/NDSA/nylon-lycra, which exhibited a capacity of 115 mgAu/g coated textile, or 9700 mgAu/g polymer. Varying the underlying textile substrate or the ICP coating had a major effect on the gold capacity of the composites. Several ICP coated textiles recovered more than 90 % of the gold initially present in solutions containing 10 ppm $[AuCl_4]^-$ and 0.1 M HCl in less than 1 min. Both PPy/NDSA/nylon-lycra and PAn/Cl/nylon-lycra recovered approximately 60 % of the gold and none of the iron present in a solution containing 1 ppm $[AuCl_4]^-$, 1000 ppm $Fe^{3+}$ and 0.1 M HCl. The spontaneous and sustained recovery of gold metal from aqueous solutions containing $[AuCl_4]^-$ using ICP coated textiles has good prospects as a potential future technology.

• Composites Research
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• v.32 no.3
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• pp.127-133
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• 2019

Although carbon nanotubes(CNTs) have outstanding theoretical mechanical and electrical properties, CNT fibers(CNTFs) have not yet reached that level. Particularly, tensile strength is only about 10% or less, so studies for making up for it are being actively conducted. As a way for improving mechanical strength, methods such as synthesizing long CNT, orientation, chemical cross-linking, hydrogen bonding and polymer infiltration are being studied. In this review paper, we report preparation methods for highly conductive and strong CNTF/Carbon composites through coating and infiltration followed by carbonization of carbon precursor polymers such as polyacrylonitrile (PAN) and polydopamine (PDA) on CNTFs.

• Korean Journal of Soil Science and Fertilizer
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• v.40 no.5
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• pp.377-382
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• 2007

Porous mineral coating have been fabricated and applied for basic research on their slow release action to a fertilizer. Feldspar was selected as raw mineral for the coating and two different particle sizes of powder were prepared. Slow-release action was estimated by using a potassium sulfate fertilizer. Spherical pellets were prepared with a pan-type pelletizer and then screened into sizes ranging 1.4 to 2.35mm. While the fertilizer pellets were rotated in the pelletizer again, the feldspar powder and 0.5% polyvinyl alcohol solution were simultaneously sprayed on the pellets. The fertilizer pellets coated with feldspar powder were fabricated. The pellets were heated to increase their strength and screened to sort by coating thickness. Potassium releasing tests were conducted for 40 days and the performance for slow-release action was estimated as functions of the heating temperature, coating thickness and raw mineral powder size. The Burst effect caused high initial releasing rate. Releasing kinetics was proportional to concentration of potassium in pellets. The pellet that was fabricated with $27.4{\mu}m$-sized feldspar and heated at $1050^{\circ}C$ showed a releasing rate of 43% on the 40th day.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.17 no.4
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• pp.172-178
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• 2007

Mica (muscovite) powders were synthesized by hydrothermal method (horizontal turning method). The hydrothermal conditions for the synthesis of mica were prepared by the ratio of $K_2O : Al(OH)_3 : SiO_2$ = 1 : 3 : 3 mol% as the starting materials with KOH (8 mol%) solution as the hydrothermal solvent and reaction temperature at $260^{\circ}C$ for 72hrs. The synthetic powder used for preparation of nano silver coated mica by vertical hydrothermal treatment. The hydrothermal conditions for the treated as nano silver coating were prepared by the synthetic powder as raw materials, triple distilled water ($0.5{\ell}$) solution as the hydrothermal solvent with nano silver sol (1,000 ppm) as the material of nano silver coating and reaction temperature at $160{\sim}260^{\circ}C$ for 72 hrs. After hydrothermal treatment, structural, judgment of nano silver coating and character of nano silver coated mica were examined by XRD, SEM, TEM-EDX and shake plask method.

• Proceedings of the Membrane Society of Korea Conference
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• 1995.04a
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• pp.42-43
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• 1995

현재 에탄올 분리공정에서 사용하고 있는 투과증발분리 공정은 7-10%의 fermentation broths로 부터 나온 feed를 재래식 증류법으로 약 95%의 등비 혼합물까지 농축한 후 가교 polyvinylalcohol(PVA)를 사용하여 투과증발을 행하여 99.5%의 에탄올을 제조하고 있다. 현재 세계적으로 가장 많이 쓰이고 있느느 투과증발막으로는 독일의 GFT사로부터 개발되었고 PVA막을 PAN 부직포에 coating하여 제조하고 plate and frame type의 module을 써서 pervatporation unit를 생산하고 있다. 이러한 PVA 막보다 우수하며 여러 유기물 범위에서 사용가능한 막을 제조하기 위하여 많은 노력이 이루어지고 있다. 이같은 개량된 투과증발막을 제조하기 위하여 본 연구에서는 천연에 풍부히 존재하는 천연고분자인 키토산을 이용하였다.