Mg - ZSM -22 촉매상에서 1- 부텐의 골격이성화 반응 특성에 관한 연구

백성현,최영헌,이화영 ( Sung Hyeon Baeck,Young Heon Choe,Wha Young Lee ) 한국화학공학회 1995 화학공학의이론과응용 Vol.1 No.2

이온 교환된 ZSM -22 촉매상에서 1- 부텐의 골격이성화 반응 특성에 관한 연구

백성현,이화영 ( Sung Hyeon Baeck,Wha Young Lee ) 한국화학공학회 1995 화학공학의이론과응용 Vol.1 No.1

BiOCl이 첨가된 Li2CO3-Sm2O3 촉매상에서 메탄의 Oxidative Coupling 반응

백성현 ( Sung Hyeon Baeck ),정진석 ( Jin Suk Chung ),이화영 ( Wha Young Lee ) 한국화학공학회 1998 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.36 No.3

환원법에 의한 직접 메탄올 연료전지(DMFC)용 Pt-Bi/Carbon 전극제조

김관성 ( Kwan Sung Kim ),김민경 ( Min Kyung Kim ),노동균 ( Dong Kyun Noh ),탁용석 ( Yong Sug Tak ),백성현 ( Sung Hyeon Baeck ) 한국공업화학회 2011 공업화학 Vol.22 No.5

다양한 비율의 Pt와 Bi를 carbon black (Vulcan XC-72R)에 담지시킨 Pt-Bi/C 촉매를 환원법을 이용하여 합성하였다. Pt와 Bi의 전구체로는 염화백금산(H2PtCl6 ·xH2O)과 비스무스트리질산(Bi(NO3)3 ·5H2O) 수용액을 각각 사용하였으며, 금속을 carbon에 담지하기 전, 금속물질의 분산도를 높여주기 위해 열처리와 산처리를 수행한 carbon black을 사용하였다. XRD (X-ray Diffraction) 분석과 XPS (X-ray Photoelectron Spectroscopy) 분석을 통하여 Pt-Bi/C 촉매 내에 Pt와 Bi가 소성 시키기 전에는 BiPt 혹은 Bi2Pt로 존재하지만 500 ℃에서 소성을 한 후에는 Pt 격자구조 안으로 Bi가 침투하여 alloy을 형성하는 것을 확인하였다. 합성한 전극의 메탄올 산화반응은 전기화학분석장치(Potentiostat; Princeton applied research, VSP)를 사용하여 0.5 M CH3OH와 0.5 M H2SO4의 혼합수용액에서 순환전압법(cyclic voltammetry, CV)을 이용해 측정하였다. 메탄올 산화에 대한 전기화학적 촉매 활성을 평가한 결과 적절한 양의 Bi를 첨가한 경우, 메탄올 산화반응에 대한 높은 촉매활성을 나타냄을 확인하였다. 메탄올 산화에 대한 활성은 전극과 전해질 사이의 안정성과 밀접한 관련이 있다. 정전압법(Chronoamperometry, CA)을 이용하여 전극의 안정성을 평가한 결과 메탄올 산화반응에 높은 활성을 나타내는 촉매일수록 전극의 안정성도 높은 것을 확인하였다. Pt-Bi/C catalysts supported on carbon black with various Pt/Bi ratios were synthesized by a reduction method. Chloroplatinic acid hydrate (H2PtCl6 ·xH2O) and bismuth (III) nitrate pentahydrate (Bi(NO3)3 ·5H2O) were used as precursors for Pt and Bi, respectively. Before loading metal on carbon, heat treatment and pretreatment of carbon black in an acidic solution was conducted to enhance the degree of dispersion. The physical property of the synthesized catalysts was investigated by X-ray diffraction and X-ray photoelectron spectroscopy. The XRD pattern of untreated Pt-Bi/C catalyst showed BiPt and Bi2Pt peaks in addition to Pt peaks. These results imply that Bi atoms were incorporated into the Pt crystal lattice by Pt-Bi alloy formation. The catalytic activity for methanol oxidation was measured using cyclic voltammetry in a mixture of 0.5 M H2SO4 and 0.5 M CH3OH aqueous solution. The addition of proper amount of Bi was found to significantly improve catalytic activity for methanol oxidation. The catalytic activity for methanol oxidation was closely related to the stability between electrode and electrolyte. In order to investigate the stability of catalysts, chronoamperometry analysis was carried out in the same solution at 0.6 V.

초음파를 이용한 PVA에 의한 다중벽 탄소나노튜브의 수상 그래프팅

김영선(Yeong Seon Kim),백성현(Sung Hyeon Baeck),심상은(Sang Eun Shim) 한국고분자학회 2014 폴리머 Vol.38 No.3

초음파를 이용한 수중 반응을 통하여 친수성 고분자인 poly(vinyl alcohol) (PVA)를 다중벽 탄소나노튜브 표면에 개질하였다. 초음파 인가 시 PVA는 라디칼을 지닌 상태로 절단되며 탄소나노튜브는 일반적으로 라디칼 스캐빈저 역할을 하므로 생성된 PVA 라디칼과 반응하여 PVA 사슬이 탄소나노튜브 표면에 그래프트 된다. PVA의 그래프트 반응을 조절하기 위하여 초음파 인가 조건을 300과 500 W로 선택하였으며, 인가 시간은 최대 50분으로 하였다. 탄소나노튜브 표면에 그래프트된 PVA는 FTIR, TGA, SEM, 및 TEM을 통하여 분석하였다. 또한 PVA로 개질된탄소나노튜브의 분산안정성을 분석하였다. 그래프트된 PVA의 양은 초음파의 인가 출력과 인가 시간에 비례하여 증가하였으며, PVA로 개질된 탄소나노튜브는 물 속에서 매우 안정적인 분산성을 보였다. Multiwall carbon nanotubes (MWCNTs) were modified with a water soluble polymer, poly(vinyl alcohol),PVA, using a simple ultrasonic wave in water. Under the irradiation of ultrasound, PVA chains were severed as macroradicalsand instantly grafted onto the surface of MWCNTs due to the radical scavenging effect of MWCNTs. To controlthe grafting PVA onto MWCNTs, the ultrasonication power and irradiation time were changed from 300 to 500 Wand from 10 to 50 min, respectively. The grafted PVA onto MWCNTs was confirmed by FTIR, TGA, SEM, and TEM. Dispersion stability of the modified MWCNTs was monitored by Turbiscan. The amount of grafted PVA on MWCNTsincreased with the increase in the sonication power and irradiation time. The grafted PVA on MWCNTs induced theimproved dispersion stability of the modified MWCNTs in water. These findings exhibit that ultrasound can be readilyused for the grafting polymer chains on MWCNTs.

고효율의 리튬/공기 이차전지 공기전극용 Mn_1+XCo_2-XO₄ 고용체 촉매 합성 및 분석

박인영,장재용,임동욱,김태우,심상은,박석훈,백성현,Park, Inyeong,Jang, Jaeyong,Lim, Dongwook,Kim, Taewoo,Shim, Sang Eun,Park, Seok Hoon,Baeck, Sung-Hyeon 한국전기화학회 2015 한국전기화학회지 Vol.18 No.4

$Mn_{1+X}Co_{2-X}O_4$ solid solutions with various Mn/Co ratios were synthesized by a combustion method, and used as cathode catalysts for lithium/air secondary battery. Their electrochemical and physicochemical properties were investigated. The morphology was examined by transmission electron microscopy (TEM), and the crystallinity was confirmed by X-ray diffraction (XRD) analyses. For the measurement of electrochemical properties, charge and discharge measurements were carried out at a constant current density of $0.2mA/cm^2$, monitoring the voltage change. Electrochemical impedance spectroscopy (EIS) analyses were also employed to examine the change in charge transfer resistance during charge-discharge process. $Mn_{1+X}Co_{2-X}O_4$ solid solutions showed enhanced cycleability as a cathode of Li/air secondary battery, and the performance was found to be strongly dependent on Mn/Co ratio. Among synthesized catalysts, $Mn_{1.5}Co_{1.5}O_4$ exhibited the best performance and cycleability, due to high charge transfer rate.

Synthesis of Alumina-coated Graphite Using Polyvinylpyrrolidone via Sol-Gel Reaction

Jeonghoon Nam(남정훈),Yeongseon Kim(김영선),Kyunghee Kim(김경희),Sung Hyeon Baeck(백성현),Dong Wha Park(박동화),Sang Eun Shim(심상은) 한국고분자학회 2016 폴리머 Vol.40 No.1

흑연은 200~800 W/mK의 우수한 열전도성을 지니고 있으나, 인쇄회로기판의 코팅 재료, 반도체 실장용 접착제의 충전제, 열확산 쉬트와 같은 열전도성 복합재료로 사용하기에 한계가 있다. 이는 전기 전도성에 기인한 것으로, 흑연에 전기 절연성을 부여하기 위하여 폴리비닐피롤리돈(PVP)을 접착력 향상제로 사용하여 알루미나 층을 코팅하였다. 알루미늄 이소프로폭사이드(AIP)를 알루미나의 전구체로 사용하였다. 알루미나 코팅은 염기성 촉매하에서 졸-젤 반응을 통하여 이루어졌다. 제조된 결과물의 모폴로지 변화, 코팅된 알루미나의 양 및 전기 절연성이 조사되었으며, 최적의 알루미나@PVP@흑연의 합성 조건을 찾기 위하여 AIP와 PVP의 양을 변화시켰다. 합성된 알루미나가 코팅된 흑연은 면저항이 1012 ohm/sq으로 전기 절연성을 보유하였다. Although graphite has excellent thermal conductivity of 200-800 W/mK, there are definite limits when applying graphite to thermally conductive materials, such as a coating material for printed circuit boards (PCB), an additive to the adhesive for the assembly of electronic chips, and a filler for thermal spreader pads. The problems are largely attributed to the electrically conductive property. To endow graphite with an electrically insulating property, graphite was coated with a well-grown alumina layer using polyvinylpyrrolidone (PVP) as a cohesive promotor. Aluminum isopropoxide (AIP) was used as the alumina precursor and PVP was used to improve the cohesion between graphite and alumina. An alumina-coating on graphite was conducted by a base-catalyzed sol-gel reaction. The changes in the morphology and the amounts of coated alumina, as well as the electrically insulating properties were investigated. An optimized condition to make alumina@PVP@graphite was determined by changing the amounts of AIP and PVP. The synthesized alumina@PVP@graphite was categorized as an electrical insulator with a high surface resistivity of about 10<SUP>12</SUP> ohm/sq.

무기계 내화 필러로 충전된 실리콘 고무 복합체의 열적, 물리적 특성

류현준(Hyun Jun Ryu),조선태(Sun Tae Cho),김영선(Young Seon Kim),백성현(Sung-Hyeon Baeck),진성훈(Sung Hoon Jin),심상은(Sang Eun Shim) 한국고분자학회 2017 폴리머 Vol.41 No.3

무기계 내화 필러는 실리콘 고무의 내화 성능 보강재로서 많은 관심을 받고 있다. 본 연구에서는 실리콘 고무 내화 필러로서 잘 알려진 수산화마그네슘(MDH), 수산화알루미늄(ATH)과 미네랄 울 2종의 실리콘 복합체를 제작해 열적, 물리적 특성을 비교 분석하였다. 가스토치 화염시험, 콘칼로리미터, TGA 분석을 통해 미네랄 울 2종의 내화 성능이 기존의 내화 필러 복합체보다 우수함을 확인하였다. 주사전자현미경(SEM), 만능재료시험기(UTM)를 통해 필러의 표면적이 큰 MDH를 실리콘 고무에 효과적으로 분산시킨 MDH/실리콘 고무 복합체가 인장, 인열, 신장율에서 우수한 특성을 나타냈고, 미네랄 울/실리콘 고무 복합체는 (MDH, ATH)/실리콘 고무 복합체에 비해 압축강도, 경도에서 우수한 특성을 확인하였다. Inorganic fillers have attracted a great deal of interest as reinforcing materials for fire-proof performance in silicone rubber (SR). In this study, magnesium hydroxide (MDH) and aluminium hydroxide (ATH)/SR composites, well known fire-proof materials, and mineral wool/SR composites were analyzed for thermal and physical properties. It was confirmed that mineral wool/SR composites have an improved fire-proof performance than the (MDH, ATH)/SR composites through gas torch flame test, cone calorimeter, and thermogravimetric analysis (TGA). MDH/SR shows great tensile, tear strength and elongation at break through SEM and UTM due to the fine dispersion of MDH in SR. Also, mineral wool/SR composites show compressive strength and hardness properties higher than those of (MDH, ATH)/SR composites.

Mechanical Properties of Silica-coated Multi-walled Carbon Nanotube/Epoxy Composites

Kyunghee Kim(김경희),Yeongseon Kim(김영선),Jeonghoon Nam(남정훈),Sung-Hyeon Baeck(백성현),Dong Wha Park(박동화),Sang Eun Shim(심상은) 한국고분자학회 2016 폴리머 Vol.40 No.1

다중벽 탄소 나노튜브(MWCNTs)/에폭시 복합체의 기계적 강도와 전기 절연성을 증가시키기 위하여, tetraethyl orthosilicate(TEOS)를 전구체로 사용한 1 단계 졸-젤 반응을 통하여 다중벽 탄소 나노튜브(MWCNTs)를 실리카 층으로 코팅하였다. MWCNTs 표면을 화학적으로 개질하지 않고 폴리에틸렌이민을 커플링제로 사용하여 실리카로 균일하게 코팅하였다. 실리카 코팅된 MWCNTs 및 순수한 MWCNTs를 충전제로 사용하여 제조된 복합체의 기계적 특성, 열적 특성, 전기적 성질을 관찰하였다. 에폭시 사슬들은 MWCNTs 표면의 실리카 층에 강하게 속박되어, 실리카 층은 MWCNTs에 전기 절연막을 형성하였다. 결과적으로, 실리카 코팅된 MWCNTs가 충전된 에폭시 복합체의 기계적 물성 및 전기저항이 증가하였다. Multi-walled carbon nanotubes (MWCNTs) were coated with silica layers via a one-step sol-gel process with tetraethyl orthosilicate (TEOS) as a silica precursor to enhance the mechanical strength and electrical resistivity of MWCNTs-filled epoxy composites. The MWCNTs were coated uniformly with silica using polyethyleneimine as a coupling agent without chemical modification of the surface of the MWCNTs. The silica-coated MWCNTs were used as a filler in the epoxy. The epoxy composites filled with the raw and silica-coated MWCNTs were prepared and their properties were examined in terms of mechanical, thermal and electrical properties. The epoxy chains were bound strongly to the silica layer on the surface of the MWCNTs, and the silica layer provided the MWCNTs with electrically insulating barriers. As a result, the silica-coated MWCNTs-filled epoxy composites showed improved mechanical strength and electrical resistivity.

전사법으로 제조한 SOFC용 YSZ 전해질 전사지의 치밀화 및 전기화학적 특성

조해란 ( Hae Ran Cho ),최병현 ( Byung Hyun Choi ),안용태 ( Yong Tae An ),백성현 ( Sung Hyeon Baeck ),노광철 ( Kwang Chul Roh ),박선민 ( Sun Min Park ) 대한금속재료학회(구 대한금속학회) 2012 대한금속·재료학회지 Vol.50 No.9

Decalcomania is a new method for SOFCs (solid oxide fuel cells) unit cell fabrication. A tight and dense 5 ㎛Yttria-stabilized zirconia (8YSZ) electrolyte layer on anode substrate was fabricated by the decalcomania method. After 8YSZ as the electrolyte starting material was calcined at 1200℃, the particle size was controlled by the attrition mill. The median particle size (D50) of each 8YSZ was 39.6 ㎛, 9.30 ㎛, 6.35 ㎛, and 3.16 ㎛, respectively. The anode substrate was coated with decalcomania papers which were made by using 8YSZ with different median particle sizes. In order to investigate the effect of median particle sizes and sintering conditions on the electrolyte density, each sample was sintered for 2, 5 and 10 h, respectively. 8YSZ with a median particle size of 3.16 ㎛which was sintered at 1400℃ for 10 had the highest density. With this 8YSZ, a SOFCs unit cell was manufactured with a 5 ㎛layer by the decalcomania method. Then the unit cell was run at 800℃. The Open Circuit Voltage (OCV) and Maximum power density (MPD) was 1.12 V and 650 mW/cm2, respectively.