• Journal of the Microelectronics and Packaging Society
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• v.28 no.1
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• pp.31-37
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• 2021

Sn-3wt%Ag-0.5wt%Cu (SAC305) solder is most popular solder in electronics industry. However, SAC305 has also drawbacks such as growth of β-Sn phase, intermetallic compounds (IMCs) of Ag3Sn, Cu6Sn5 and Cu3Sn which can result in deterioration of solder joints in terms of metallurgically, mechanically and electrically. Thus, improvement of SAC305 solders have been investigated continuously by addition of alloying elements, nano-particles and etc. In this paper, recent improvements of SAC solders including nano-composite alloys and related solderabilty and metallurgical and mechanical properties are investigated.

• Bulletin of Food Technology
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• v.23 no.2
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• pp.205-211
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• 2010

• Food Science and Industry
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• v.47 no.1
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• pp.46-49
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• 2014

• Air Cleaning Technology
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• v.33 no.2
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• pp.1-9
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• 2020

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.169.1-169.1
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• 2013

산업 및 기술의 발전에 의해 많은 신소재들이 개발되고 있다. 그 중에서 SiC는 고온재료, LED, 반도체 등의 우주선 표면재료, 핵융합로 구조재료, 고온 씰, 히터 등 여러 산업분야에서 관심을 가지면서 다양한 가스를 이용한 합성법이 개발되어 있다. 최근에는 분말의 형태 및 크기를 용도에 맞게 개발해서 사용하고 있는 상황이다. 그런데 각 합성법에 따른 합성원리에 대해서는 여러 가지 주장이 있다. 그 중에서 몇 가지 합성법에 대해서 고찰하고 합성의 원리를 추론한다. 그리고 그 중의 한 가지인 CH3SiCl3 가스를 이용한 SiC 나노분말 합성과 SiC의 결정성장 과정에서 나타나는 whisker의 형성을 확인했다. 정교한 SiC 분말합성은 일반적으로 sol-gel, 플라즈마(DC, AC 및 ICP 등) 등을 이용한 방법이 개발되어 있다. 이와 같이 정교한 SiC 나노분말 등은 실리콘 유기 화합물 중합체(trichloromethylsilane, polycarbosilane 등)의 열분해를 통해 합성 할 수 있으며, 열분해 는 약 1,000{\sim}1,500^{\circ}C의 온도 영역에서 일어난다. 이 과정에서 고분자의 열분해 및 재결합 이 동반되고 부산물로서 HCl, CH4 등의 유해가스를 같이 생성한다. 합성된 SiC 나노분말은 전형적인 ${\beta}-SiC$로 XRD의 관찰결과 (111), (220), (311)의 방향성을 갖는 것을 확인했으며 평균입자의 크기는 약 30 nm 정도다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.5
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• pp.81-86
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• 2019

Metal oxide/graphene composites have been known as promising functional materials for advanced applications such as high sensitivity gas sensor, and high capacitive secondary battery. In this study, tin dioxide ($SnO_2$) nanostructures were grown on chemically synthesized graphene nanosheets using a two-zone horizontal furnace system. The large area graphene nanosheets were synthesized on Cu foil by thermal chemical vapor deposition system with the methane and hydrogen gas. Chemically synthesized graphene nanosheets were transferred on cleaned $SiO_2$(300 nm)/Si substrate using the PMMA. The $SnO_2$ nanostuctures were grown on graphene nanosheets at $424^{\circ}C$ under 3.1 Torr for 3 hours. Raman spectroscopy was used to estimate the quality of as-synthesized graphene nanosheets and to confirm the phase of as-grown $SnO_2$ nanostructures. The surface morphology of as-grown $SnO_2$ nanostructures on graphene nanosheets was characterized by field-emission scanning electron microscopy (FE-SEM). As the results, the synthesized graphene nanosheets are bi-layers graphene nanosheets, and as-grown tin oxide nanostructures exhibit tin dioxide phase. The morphology of $SnO_2$ nanostructures on graphene nanosheets exhibits complex nanostructures, whereas the surface morphology of $SnO_2$ nanostructures on $SiO_2$(300 nm)/Si substrate exhibits simply nano-dots. The complex nanostructures of $SnO_2$ on graphene nanosheets are attributed to functional groups on graphene surface.

• Korean Journal of Metals and Materials
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• v.49 no.2
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• pp.161-166
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• 2011

The aim of this study was to determine the effect of high-energy mechanical milling (HEMM) time and sintering temperature on microstructure and mechanical properties of the TiAl composite fabricated by pulse current activated sintering. TiAl intermetallic powders were milled by HEMM for 1h, 4h, and 8h respectively. Thermal analysis was used to observe the phase transformation of the milled TiAl powders. The sintering time decreased with increase of milling time. The hardness and fracture toughness of the sintered specimens also was improved with increasing milling time. The grain size of the sintered specimens which was milled for 4h was in the range of 50~100 nm.

• Journal of Adhesion and Interface
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• v.22 no.4
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• pp.144-152
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• 2021

Understanding charge transfer across the interface between organic semiconductor and gate insulator gives insight into the development of high-performance organic memory as well as highly stable organic field-effect transistors (OFETs). In this work, we firstly unveil a novel interfacial charge transfer mechanism, in which hole transfer from organic semiconductor to polymer insulator was nonlinearly boosted by localized states coupling. For this, OFETs based on rubrene single crystal semiconductor and Mylar gate insulator were fabricated via vacuum lamination, which allows stable repetition of lamination and delamination between semiconductor and gate insulator. The surfaces of rubrene single crystal and Mylar film were selectively degraded by photo-induced oxygen diffusion and UV-ozone treatment, respectively. Consequently, we found that the interfacial charge transfer and resultant bias-stress effect were nonlinearly boosted by coupling between localized states in rubrene and Mylar. In particular, the small number of localized states in rubrene single crystal provided fluent pathway for interfacial charge transport.

• Journal of Adhesion and Interface
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• v.22 no.3
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• pp.106-110
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• 2021

Recently, research using waste among eco-friendly materials has been attracting attention. In this study, we investigated the physical properties of blends in which high density polyethylene (HDPE) was filled with waste gypsum (CaSO₄) generated during fertilizer manufacturing. Composites were prepared by adding the gypsum content 0~20 wt% using a twin screw extruder. The mechanical, rheological, and thermal properties of the composites were evaluated. It was found that the tensile strength of the composites was less than 4.1% compared to that of unfilled HDPE, so there is no significant deterioration in physical properties. The thermal stability of the composites was improved as the gypsum content increased and the gypsum content had little effect on the viscosities of the composites.

• Membrane Journal
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• v.31 no.2
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• pp.133-144
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• 2021

Alkaline water electrolysis system is the oldest technology among various hydrogen production processes to produce green hydrogen with the least amount of greenhouse gas generated. Alkaline water electrolysis (AWE) system is used in alkaline atmosphere condition. In comparison to polymer electrolyte membrane water electrolysis (PEMWE), this system can utilize stable transition metals such as nickel, cobalt, and silver, as electrode catalysts. AWE is relatively inexpensive, and can easily be scaled up to large scale. The system is a mature technology, as it has been in operation since the beginning of the 20th century in MW-scale for hydrogen generation, and there are currently more than 20 commercial manufacturers. In this review, the basic principles of AWE, along with catalysts, electrodes, and diaphragm membranes, are summarized. Particularly, the research and development trends of the diaphragm membrane unit, which is the core component of an AWE, are discussed in detail.