In aluminum brazing processes, corrosive flux, which is used in preventing oxidation, is currently raising environmental concerns because it generates many pollutants such as dioxin. The brazing process involving noncorrosive flux is known to encounter difficulties because the melting temperature of the flux is similar to that of the base material. In this study, a new brazing filler material is developed based on aluminum and non-corrosive flux composite powder. To minimize the interference of consolidation aluminum alloy powder by the flux, the flux is intentionally embedded in the aluminum alloy powder using a mechanical milling process. This study demonstrates that the morphology of the composite powder can be varied according to the mixing process, and this significantly affects the relative density and mechanical properties of the final filler samples.

본 연구에서는 탄소 나노재료 중 환원된 그래핀 옥사이드와 전도성 고분자중 폴리아닐린을 복합화 하여 슈퍼커패시터용 전극을 제조하였으며, 각각의 전극 재료가 가지는 단점을 서로 보완하고 장점을 극대화시킴으로써 전극의 전기화학적 특성을 크게 향상 시킬 수 있었다. 전극 물질에 사용된 폴리아닐린은 아닐린 단량체를 화학 중합법으로 제조하였고, 환원된 그래핀 옥사이드는 별도의 전 처리 과정 없이 사용 하였으며, DMF(N,N-dimethyl formamide)를 용매로 도입하여 분산용액을 제조하였다. 분산용액은 금이 코팅된PET(Polyethylene terephthalate) 기판위에 산업적 스케일로 적용이 가능한 스프레이 코팅 방법을 이용하여 전극으로 제조하였다. 환원된 그래핀 옥사이드/폴리아닐린 복합재료를 기반으로 제조된 전극의 전기화학적 특성을 비교하기 위하여 환원된 그래핀 옥사이드와 폴리아닐린 단일 전극을 제조하였으며, 동일 한 조건하에서 순환전압전류법, 임피던스 분광법, 정전류 충·방전법을 통하여 각각의 전극이 나타내는 전기 화학적 특성을 비교·분석 하였다. 그 결과로, 환원된 그래핀 옥사이드/폴리아닐린 복합재료를 기반으로 제조된 전극은 폴리아닐린, 환원된 그래핀 옥사 단일 전극에 비하여 전기 용량 값이 높게 나타났으며, 전해질 계면과의 내부 저항은 폴리아닐린, 환원된 그래핀 옥사이드 단일 전극에 비하여 각각 24 %, 58 % 감소하는 결과를 나타내었다. 이러한 결과로 미루어보아 본 연구를 통하여 제조된 환원된 그래핀 옥사이드/폴리 아닐린 복합재료 기반의 전극은 유연성 에너지 저장 매체나 웨어러블 전자기기에 적용이 가능할 것으로 판단된다.

본 연구에서는 탄소나노튜브/화이버/폴리머 복합소재 구조에 대한 재료 물성 및 강성 추정을 다룬다. 수정된 Halpin-Tsai 모델을 적용한 멀티 스케일 해석은 탄소나노튜브의 함유량 비율, CNT 두께-길이 비율, 화이버 부피 함유량, 그리고 화이버 보강각도 변화에 따라서 수행되었다. 본 연구에서 제시한 멀티-스케일 접근방법은 기존 모델을 적용하여 얻은 결과와 비교하여 검증하였다. 매개변수 해석을 통하여 CNT의 적절한 함유량은 적층된 CNTFPC 구조의 구조성능의 향상시킬 수 있는 중요한 특성을 규명하였다.

In this paper, the result of application of this simple method of vibration analysis developed by the author, to the special orthotropic plates with variable cross-section, and with a pair of opposite edges simple supported and the other pair of opposite edges free is presented. This problem represents the simple-supported single span bridge system without effective longitudinal edge beams. The effect of concentrated point mass/masses is also studied.

In order to expand the application of oxide dispersion-strengthened (ODS) steel, a composite material is manufactured by adding mechanically alloyed ODS steel powder to conventional steel and investigated in terms of microstructure and wear properties. For comparison, a commercial automobile part material is also tested. Initial microstructural observations confirm that the composite material with added ODS steel contains i) a pearlitic Fe matrix area and ii) an area with Cr-based carbides and ODS steel particles in the form of a Fe-Fe3C structure. In the commercial material, various hard Co-, Fe-Mo-, and Cr-based particles are present in a pearlitic Fe matrix. Wear testing using the VSR engine simulation wear test confirms that the seatface widths of the composite material with added ODS steel and the commercial material are increased by 24% and 47%, respectively, with wear depths of 0.05 mm and 0.1 mm, respectively. The ODS steel-added composite material shows better wear resistance. Post-wear-testing surface and cross-sectional observations show that particles in the commercial material easily fall off, while the ODS steel-added material has an even, smooth wear surface.

최근 전세계적으로 이산화탄소 분리기술에 관한 연구가 활발하게 이루어지고 있다. 그 중 특히 분리막을 이용한 이산화탄소 분리는 타 방식에 비해 다양한 장점으로 광범위하게 연구되고 있다. 본 연구에서는 고선택성을 지닌 Polyhedral oligomeric silsesquioxane(POSS)과 고투과성을 지닌 Poly(ethylene glycol)으로 이산화탄소 포집에 우수한 성능을 나타내는 POSS-PEG를 합성하고 특성평가하는 것에 중점을 두었다. 1H-NMR스펙트럼과 FT-IR 스펙트럼을 활용 하여 합성의 유무를 확인하였고 PAN지지체에 코팅하는 방식으로 복합막을 제조하였다. 기체특성평가를 실시하기 위해 기체투과에 필요한 실험모듈을 제작하였고 이산화탄소 투과특성을 평가하였다.

Al/expanded graphite was successfully synthesized through a facile method including ultrasonic and heat treatment. In the well-designed three dimensional structure, expanded graphite(EG) works as a conductive matrix to support coated Al particles. The effects of the fabrication parameters on the microstructures and thermal conductivities of these composites were investigated. As a result, it was found that composites with graphite volume fraction of 17.4-69.4% sintered at 600 oC/45 MPa exhibit in-plane thermal conductivities of 380-940 W/mK, over 90 % of the predictions by rule of mixture. According to the non-destructive analysis results, the synergistic enhancement was caused by the formation of efficient thermally conductive pathways due to the hybrid of the differently sized EG. The structure integrates the advantages of expanded graphite as a conductive support, preserving the electrode activity and integrity and improving the electrochemical performance.

본 연구에서는 라포나이트계 무기물 소재를 이온교환방법을 이용하여 실리케이트 층내에 술폰산기를 도입시켰으며 이를 이용하여 복합막을 제조한 후 특성 평가를 진행하였다. 층상구조를 가지는 라포나이트의 도입을 통하여 메탄올 투 과도가 감소하는 것을 확인할 수 있었으며, 동시에 술폰산기의 도입을 통하여 프로톤 전도도가 향상됨을 확인 할 수 있었다.

복합재는 높은 비강도와 비강성을 가지고 있어 자동차, 항공기 등 전반적인 산업분야에서 널리 사용되는 재료이다. 우주선의 노즐 부분과 같이 높은 온도뿐만 아니라 높은 압력이 작용하는 환경에서 사용하기 위한 재료로 복합재가 필요하다. 복합재의 물성치를 아는 것은 매우 중요한데 모재(matrix)와 강화섬유(fiber) 각각의 물성치를 수치적으로 대입해 얻는 결과는 실험값과의 오차가 커 예측하는데 있어 더 정확한 방법이 필요할 것이다. 본 연구에서는 유한요소법을 이용한 EDISON용 CASAD solver 프로그램을 활용해 분석하였다. matrix와 fiber의 물성치를 대입해 복합재의 물성치를 구해 실험으로 측정된 물성치, 경험식으로 계산된 물성치와 비교를 하였다.

The filler was one of the structural parts using composite material. The filler manufacturing machine was effectively developed based on the principles of usability by HCI. This machine consisted of an ultrasonic cutter, heater, forming rollers and drawing motor. It applied to separate the disk-shape cutter of ultrasonic cutter in order to remove burning the knife edge of ultrasonic cutter. And the developed machine had the two-stage forming rollers for improved formability which maintained accurately the filler shape.

고분자 전해질 막의 성능을 개선하고자 사용된 대표적인 무기물인 solid acid가 첨가된 복합막의 경우 고온에서 높은 열안정성을 나타내며 친수성이 강해지는 장점을 나타내지만 물에 녹는 단점을 가지고 있다. 그러므로 본 연구에서는 phosphotungstic acid(PWA)의 이온전도성을 증가시키며 물에 용해되는 성질을 제거하기 위하여 실리카 입자를 sol-gel법을 이용하여 술폰산기와 아민그룹을 도입시킨 입자를 제조한 후 sulfonated poly(arylene ether sulfone)(SPAES)고분자에 첨가하여 복합막을 제조하였으며 특성평가가 이루어졌다.

Compared to steel of the same weight in steel concrete structures, fiber reinforced polymer (FRP) is known to have greater strength and better resistance to corrosion. As such, it is being proposed as an effective structural material. Despite its many advantages, FRP has not been rapidly adopted in civil structures. This is because it is more expensive, prone to brittle fracture, and has weak fire resistance. To examine changes in the mechanical properties of FRP and the effectiveness of fire resistant coating, this study conducted tensile tests on coated and uncoated specimens over varying temperature. Glass fiber has excellent fire resistance since it does not melt or burn at high temperatures. However, epoxy is unable to withstand exposure to temperatures exceeding the transition temperature, thus leading to unsatisfactory structural performance and fire resistance. This study investigated the behavioral changes in FRP by exposing the specimens to temperatures ranging from room temperature (approx. 25℃) to 300℃, so as to improve the fire resistance of epoxy.

The composite of porous silicon (Si) and amorphous carbon (C) is prepared by pyrolysis of a nano-porous Si + pitch mixture. The nano-porous Si is prepared by mechanical milling of magnesium powder with silicon monoxide (SiO) followed by removal of MgO with hydrochloric acid (etching process). The Brunauer-Emmett-Teller (BET) surface area of porous Si (64.52 m2g−1) is much higher than that before etching Si/MgO (4.28 m2g−1) which indicates pores are formed in Si after the etching process. Cycling stability is examined for the nano-porous Si + C composite and the result is compared with the composite of nonporous Si + C. The capacity retention of the former composite is 59.6% after 50 charge/discharge cycles while the latter shows only 28.0%. The pores of Si formed after the etching process is believed to accommodate large volumetric change of Si during charging and discharging process.

Silicon-carbon composite was prepared by the magnesiothermic reduction of mesoporous silica and subsequent impregnation with a carbon precursor. This was applied for use as an anode material for high-performance lithium-ion batteries. Well-ordered mesoporous silica(SBA-15) was employed as a starting material for the mesoporous silicon, and sucrose was used as a carbon source. It was found that complete removal of by-products (Mg2Si and Mg2SiO4) formed by side reactions of silica and magnesium during the magnesiothermic reduction, was a crucial factor for successful formation of mesoporous silicon. Successful formation of the silicon-carbon composite was well confirmed by appropriate characterization tools (e.g., N2 adsorption-desorption, small-angle X-ray scattering, X-ray diffraction, and thermogravimetric analyses). A lithium-ion battery was fabricated using the prepared silicon-carbon composite as the anode, and lithium foil as the counter-electrode. Electrochemical analysis revealed that the silicon-carbon composite showed better cycling stability than graphite, when used as the anode in the lithium-ion battery. This improvement could be due to the fact that carbon efficiently suppressed the change in volume of the silicon material caused by the charge-discharge cycle. This indicates that silicon-carbon composite, prepared via the magnesiothermic reduction and impregnation methods, could be an efficient anode material for lithium ion batteries.

This paper shows the feasibility on the application of E-glass fiber/epoxy(GFRP) composite materials to an automotive leaf spring. In order to keep much lighter weight by replacing the steel with the composite material, it is important to optimize the material parameters and design variables consisting of the structure. This paper focused on the effects of material compositions and its fiber orientations for estimating the static behaviors of leaf spring. First of all, basic material properties of GFRP composite were measured by five types of coupon specimens from ASTM standard test. The reverse implementation was also done to obtain the complete set of in-situ fiber and matrix properties from ply test results. Finally, the static spring rates was examined for the variation of thickness and material parameters such as fiber angles and resin contents of composite leaf spring.