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개선된 광촉매 효과를 위한 수열법에 의한 삼원계 Bi<sub>2</sub>WO<sub>6</sub>-GO-TiO<sub>2</sub> 나노복합체의 쉬운 합성 방법
조광연 ( Kwang Youn Cho ),응웬 딩 궁 디엔 ( Dinh Cung Tien Nguyen ),오원춘 ( Won-Chun Oh ) 한국공업화학회 2017 공업화학 Vol.28 No.6
독창적 물질인 Bi<sub>2</sub>WO<sub>6</sub>-GO-TiO<sub>2</sub> 나노복합체를 쉬운 수열법에 의해 성공적으로 합성하였다. 수열반응을 하는 동안, 그래핀 시트 위에 Bi<sub>2</sub>WO<sub>6</sub>와 TiO<sub>2</sub>를 도포하였다. 합성한 Bi<sub>2</sub>WO<sub>6</sub>-GO-TiO<sub>2</sub> 복합체형 광촉매는 X-선 회절법(XRD), 주사전자현미경(SEM), 에너지 분산 X-선(EDX) 분석, 투과전자현미경(TEM), 라만분광법, UV-Vis 확산반사 분광법(UV-vis-DRS), 및 X-선 광전자분광기(XPS)에 의하여 특성화하였다. Bi<sub>2</sub>WO<sub>6</sub> 나노입자는 불규칙한 dark-square block 나노 플페이트 형상을 보였으며, 이산화티탄 나노입자는 퀜텀 도트 사이즈로 그래핀 시트 위 표면을 덮고 있었다. 로다민 비의 분해는 농도감소의 측정과 함께 UV 분광법에 의하여 관찰하였다. 합성된 물질의 광촉매 반응은 Langmuir-Hinshelwood 모델과 띠 이론으로 설명하였다. A novel material, Bi<sub>2</sub>WO<sub>6</sub>-GO-TiO<sub>2</sub> composite, was successfully synthesized using a facile hydrothermal method. During the hydrothermal reaction, the loading of Bi<sub>2</sub>WO<sub>6</sub> and TiO<sub>2</sub> nanoparticles onto graphene sheets was achieved. The obtained Bi<sub>2</sub>WO<sub>6</sub>-GO-TiO<sub>2</sub> composite photo-catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM), Raman spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy (UV-vis-DRS), and X-ray photoelectron spectroscopy (XPS). The Bi<sub>2</sub>WO<sub>6</sub> nanoparticle showed an irreg-ular dark-square block nanoplate shape, while TiO<sub>2</sub> nanoparticles covered the surface of the graphene sheets with a quantum dot size. The degradation of rhodamine B (RhB), methylene blue trihydrate (MB), and reactive black B (RBB) dyes in an aque-ous solution with different initial amount of catalysts was observed by UV spectrophotometry after measuring the decrease in the concentration. As a result, the Bi<sub>2</sub>WO<sub>6</sub>-GO-TiO<sub>2</sub> composite showed good decolorization activity with MB solution under visible light. The Bi<sub>2</sub>WO<sub>6</sub>-GO-TiO<sub>2</sub> composite is expected to become a new potential material for decolorization activity. Photocatalytic reactions with different photocatalysts were explained by the Langmuir-Hinshelwood model and a band theory.
석탄계 피치에 요오드를 소량 첨가하여 제조한 탄소복합재의 치밀화 거동
조광연,류도형,신동근,주혁종,구형회,박인서,Cho, Kwang-Youn,Riu, Doh-Hyung,Shin, Dong-Geun,Joo, Heyok-Jong,Koo, Hyung-Hoi,Park, In-Seo 한국세라믹학회 2009 한국세라믹학회지 Vol.46 No.6
We investigated the viscosity behavior and the carbon yield of coal tar pitch (CTP) treated with iodine. The viscosity of iodine treated pitch showed that the fluidity of iodine treated CTP did not increase within the iodine addition of 1.4%. DTG analysis showed that cross linking was accelerated at the temperature range from $400\;to\;500{^{\circ}C}$ with iodine treatment, which is due to the accelerated dehydrogenative reaction by iodine. The iodine treatment was mainly effective for β-resin content increase of CTP. The carbon yield of CTP increased from 40 to 60% by the iodine non-treated CTP.
조광연,류도형,신동근,임경훈,진은주,김현이,하상현,최종화,Cho, Kwang-Youn,Riu, Doh-Hyung,Shin, Dong-Geun,Lim, Kyoung-Hoon,Jin, Eun-Ju,Kim, Hyoun-Ee,Ha, Sang-Hyeon,Choi, Jong-Hwa 한국세라믹학회 2009 한국세라믹학회지 Vol.46 No.6
Lithium salt have been used mainly as electrolyte of thermal battery for electricity storage. Recently, The 3phase lithium salt(LiCl-LiF-LiBr) is tried to use as electrolyte of thermal battery for high electric power. It is reported that LiCl-LiF-LiBr salt have high ion mobility due to its high lithium ion concentration. Solid lithium salt is melt to liquid state at above $500{^{\circ}C}$. The lithium ion is easily reacted with support materials. Because the melted lithium ion has small ion size and high ion mobility. For the increasing mechanical strength of electrolyte pellet, the research was started to apply ceramic filter to support of electrolyte. In this study, authors used SiOC web and glass fiber filter as ceramic mat for support of electrolyte and impregnated LiCl-LiF-LiBr salt into ceramic mat at above $500{^{\circ}C}$. The fabricated electrolyte using ceramic mat was washed with distilled water for removing lithium salt on ceramic mat. The washed ceramic mat was observed for lithium ion reaction behavior with XRD, SEM-EDS and so on.
조광연,류도형,허승헌,신동근,김현이,최종화,정해원,Cho, Kwang-Youn,Riu, Doh-Hyung,Huh, Seung-Hun,Shin, Dong-Geun,Kim, Hyoun-Ee,Choi, Jong-Hwa,Cheong, Hae-Won 한국세라믹학회 2008 한국세라믹학회지 Vol.45 No.7
Ceramic Fiber separator is the promising material for thermal battery system because it reduces the production cost and offers the potential to a new application compared to a pellet type electrolyte. The molten salt electrolytes for thermal battery were prepared by the impregnation of the commercial glass filters such as GF-A, C and F (Whatman, USA) with two types of molten-lithium salts, LiCl-KCl and LiK-LiBr-LiF. The wetting properties were evaluated by wetting balance test and wetting angle measurement. The wetting behaviors were strongly affected by the composition of the molten salts and the pore structure of the glass separators. The optimum wetting conditions for maximum loading and effective retention of the molten electrolyte were also studied.
SiOC 매트(Mat)를 이용한 열전지용 전해질 격리판 제조 및 특성
임경훈,조광연,류도형,신동근,진은주,김현이,정해원,이홍림,Lim, Kyoung-Hoon,Cho, Kwang-Youn,Riu, Doh-Hyung,Shin, Dong-Geun,Jin, Eun-Ju,Kim, Hyoun-Ee,Cheong, Hae-Won,Lee, Hong-Lim 한국세라믹학회 2009 한국세라믹학회지 Vol.46 No.6
Ceramic fiber separator is the promising material for thermal battery system because it reduces the production cost and offers the potential to a new application compared to a pellet type electrolyte. The electrolyte separator for thermal battery should be easily handled and loaded a large amount of the molten lithium salt. Ceramic fibers were used as an electrolyte separator and the lithium based molten salts were infiltrated into the ceramic filters. Leakage of molten salt (several lithium salts) leads to short-circuit during the thermal battery operation. In this study, a uniform and fine SiOC mat with fibers ranging from 1 to 3 ${\mu}m$ was obtained by electrospinning of polycarbosilane and pyrolysis. The optimum spinning conditions for obtaining fine diameters of SiOC fiber were controlled by the solution composition and concentration, applied voltage and spinning rate, release rate by porosity. The pore structures of the ceramic filter and the melting properties of the lithium salts affected to the electrolyte loading and leakage. The importance of the fiber size and porosity and their control was discussed and the mechanical properties were also discussed.
Infusiblization of Iodine Doped Polycarbosilane for Silicon Carbide Fiber Fabrication
서정민,허서에르딘키싱바야르,조광연,Seo, Jung-Min,Khishigbayar, Khos-Erdene,Cho, Kwang-Youn The Korean Fiber Society 2016 한국섬유공학회지 Vol.53 No.6
Low molecular polycarbosilane (PCS) is used as raw material in the fabrication of continuous silicon carbide (SiC) fiber at a relatively low temperature using a low pressure stabilization method with iodine vapor. The low stabilization temperature provides a good environment to use the low molecular PCS for the melt-spun process, which has good spinnability, but also has many difficulties with the conventional oxidation curing method due to the low softening point of PCS. However, SiC fibers fabricated from the low molecular PCS have shown poor mechanical properties. In this study, we are aiming to improve those mechanical properties and fabricate high strength SiC fibers from low molecular PCS using the low pressure stabilization method. The ceramic yield of iodine doped PCS was increased in proportion to the iodine content after stabilization according to thermogravimetric analysis, and exhibits more than twice the tensile strength than fibers fabricated from as-received PCS.
폴리카보실란으로부터 제조된 탄화규소 중공사의 미세구조제어
신동근,공은배,조광연,권우택,김영희,김수룡,홍준성,류도형,Shin, Dong-Geun,Kong, Eun-Bae,Cho, Kwang-Youn,Kwon, Woo-Tek,Kim, Younghee,Kim, Soo-Ryong,Hong, Jun-Sung,Riu, Doh-Hyung 한국세라믹학회 2013 한국세라믹학회지 Vol.50 No.4
SiC hollow fiber was fabricated by curing, dissolution and sintering of Al-PCS fiber, which was melt spun the polyaluminocarbosilane. Al-PCS fiber was thermally oxidized and dissolved in toluene to remove the unoxidized area, the core of the cured fiber. The wall thickness ($t_{wall}$) of Al-PCS fiber was monotonically increased with an increasing oxidation curing time. The Al-PCS hollow fiber was heat-treated at the temperature between 1200 and $2000^{\circ}C$ to make a SiC hollow fibers having porous structure on the fiber wall. The pore size of the fiber wall was increased with the sintering temperature due to the decomposition of the amorphous $SiC_xO_y$ matrix and the growth of ${\beta}$-SiC in the matrix. At $1400^{\circ}C$, a nano porous wall with a high specific surface area was obtained. However, nano pores grew with the grain growth after the thermal decomposition of the amorphous matrix. This type of SiC hollow fibers are expected to be used as a substrate for a gas separation membrane.
Silicon Carbide Fibers Derived from Polycarbosilane Doped with Iodine as Oxygen Inducer
허서에르딘키싱바야르,서정민,조광연,Khishigbayar, Khos-Erdene,Seo, Jung-Min,Cho, Kwang-Youn The Korean Fiber Society 2016 한국섬유공학회지 Vol.53 No.6
Silicon oxycarbides (SiOxCy) fabricated at $1300^{\circ}C$ from iodine-doped polycarbosilane (PCS) have been shown to have high tensile strength. Iodine doping of PCS can induce oxygen atoms into the molecular structure of PCS, which forces it to start cross-linking at a relatively low temperature of $180^{\circ}C$. The mechanical properties of fabricated SiC fibers strongly depend on the degree of cross-linking during stabilization. In this study, the role of oxygen in the cross-linking reaction of PCS was investigated by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TG), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) analysis.
Cyclohexene을 첨가한 PIP 공정 사용 Cf/SiC 복합재의 고밀도화
배진철 ( Jin Cheol Bae ),조광연 ( Kwang Youn Cho ),김정일 ( Jun Il Kim ),임동원 ( Dong Won Im ),박종규 ( Jong Kyu Park ),이만영 ( Man Young Lee ),이재열 ( Jae Yeol Lee ) 한국복합재료학회 2013 Composites research Vol.26 No.5
탄소섬유강화 SiC기지상 복합재는 우수한 산화저항성과 우수한 열충격저항성을 가진다. 그리고 이런 특성들은 탄소섬유강화복합재가 고온구조재로서 응용케하였다. 본 연구에서는 Cf/SiC 복합재가 전구체 함침과 액상 함침이 동반된 열분해공정, Cyclohexene을 사용한 화학기상 경화공정을 통해 제조되었다. 최종 제조된 Cf/SiC 복합재는 5회 함침을 통해 0.43 g/cm3 밀도를 갖는 탄소섬유 프리폼에서 1.76 g/cm3의 밀도값을 나타내고 있다. 그리고 산화저항성 특성면에서 Cf/SiC 복합재의 무게가 공기중 1400oC에서 6시간 유지 후에 81%가 남았다. 결과적으로 Cyclohexene을 사용한 화학기상 경화공정은 효과적으로 높은 치밀화와 증가된 산화저항성을 보이고 있다. Carbon fiber-reinforced SiC matrix composites have good oxidation resistance and thermal shock resistance. These properties have allowed the composites to be applied to high-temperature structures. In this study, Cf/SiC composites were fabricated via precursor infiltration and pyrolysis (PIP) process, including liquid phase infiltration and chemical vapor curing using cyclohexene. The final Cf/SiC composites, which have gone through the PIP process five times, showed a density of 1.79 g/cm3, as compared to a density of 0.43 g/cm3 for pre-densified bare carbon fiber preform. As for the oxidation resistance characteristics, the weight of Cf/SiC composite was maintained at 81% at 1400oC in air for 6 hours. Chemical vapor curing (CVC) using cyclohexene has shown to be an effective method to achieve high densification, leading to increased oxidation resistance.
The Characteristics of Modified Polycarbosilane by Different Organic Solvents
주영준,허서에르딘키싱바야르,김철진,조광연,Joo, Young Jun,Khishigbayar, Khos-Erdene,Kim, Cheol Jin,Cho, Kwang Youn The Korean Fiber Society 2017 한국섬유공학회지 Vol.54 No.5
Silicon carbide (SiC) fiber with a high tensile strength and heat resistance was synthesized using polycarbosilane (PCS) precursor. The many research have been progressed to improve the spinnability and handling strength of PCS green fiber due to its brittle property by a low molecular weight. However, the study for the effect of various solvents, which is used to synthesize the PCS or to modify the PCS structure using additive is insufficient. Therefore, PCS modified by polymer blend method using various organic solvents such as para-xylene, meta-xylene, ortho-xylene, and cyclohexane. The thermal properties and GPC profile for the modified PCSs show the different interaction between PCS and solvent. The spinnability of PCSs was confirmed through apparent activation energy, calculated by Andrade equation, and spinning process. SiC fiber that is converted from blended PCS fibers with para-xylene and ortho-xylene show the same morphology containing the clean and smooth surface.