• 한국정밀공학회지
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• 제29권1호
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• pp.109-113
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• 2012

The LED failure rate greatly depends on the physical properties of packaging materials (epoxy). The glass transitions temperature (Tg) of the epoxy is one of the most important physical properties. Therefore, in the present study, various epoxies with high Tg were prepared and their failure shapes were analyzed. In addition, the failure shapes depending on the amount of epoxy and the wire bonding structure were measured. As a consequence, the lower failure rate was obtained with the smaller amount of epoxy. The safety of LED was improved with increasing the Tg of the epoxy.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.695-698
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• 2002

Induction heating process is one of the most efficient heating process in terms of temperature control accuracy and heating time saving. In the past study, fabrication process of cellular 6061 alloys by powder metallurgical route and induction heating process was studied. To supplement the framing conditions that studied in past study, effect of induction heating capacity and holding time at foaming temperature were investigated. Under the achieved framing conditions, teamed 6061 alloys were fabricated for variation of foaming temperature, and porosities(%)-foaming temperature curves were obtained by try-error experimental method. Uniaxial compression tests were performed to investigate the relationship between porosities(%) and stress-strain curves of framed 6061 alloy. Also, energy absorption capacity and efficiency were calculated from stress-strain curves to investigated. Moreover, dependence of plateau stress on strain rate was investigated in case of cellular 6061 alloy with low porosities(%)

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.1369-1375
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• 2004

For many years and primarily for economical reasons, Dissimilar Metal Welds have been used as transition joints in a variety of equipment and applications. But Dissimilar Metal Welds have several fabrication and metallurgical drawbacks that can often lead to in-service failures. For example, the most pronounced fabrication faults are hot cracks. Laser welding techniques have been characterised for various materials. In this paper, the laser weldability of STS304 stainless steel and SM45C at dissimilar metal welds using a continuous wave Nd：YAG laser are experimentally investigated. An experimental study was conducted to determine effects of welding parameters, on eliminating or reducing the extent welding zone formation at dissimilar metal welds and to optimize those parameters that have the most influence parameters such as focus length, power, beam speed, shielding gas, and wave length of laser were tested

• 한국전기전자재료학회논문지
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• 제31권2호
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• pp.107-111
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• 2018

In this study, we designed the temperature coefficient of resistance (TCR) and heat radiation properties of shunt fixed resistors by adjusting the atomic composition of a metal alloy resistor, and fabricated a resistor that satisfied the designed properties. Resistors with similar atomic composition of copper and nickel showed low TCR and excellent shunt fixed resistor properties such as short-time overload, rated load, humidity load, and high temperature load. Finally, we expect that improved sensor accuracy will be obtained in current-distribution-type shunt fixed resistor for IoT sensors by designing the atomic composition of the metal alloy resistor proposed in this work.

• 열처리공학회지
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• 제4권4호
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• pp.44-52
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• 1991

The effect of deformation temperature and manganes contents on the tensile properties of duplex stainless steels with the structure of both ferrite and austenite were investigate. For this investigation, Fe-19% Cr-5% Ni-4~8% Mn alloys were prepared. The result obtained from this experiment are summerized as follows. With decreasing deformation temperature, tensile strengths of duplex stainless steel increased. Elongation showd to be increased and then decreased after representing the highest value at specific temperature. Tensile properties of duplex stainless steel were controlled by TRIP behavior in this experimental range of austenite contents. Tensile strengths decreased with increasing Mn contents. With increasing Mn contents, elongation decreased in the high temperature region, but increased in the low temperature region. The peak temperature representing the maximum elongation were changed to low temperature and the width of peak appeared to be broaden with increasing Mn contents.

• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.281-281
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• 2006

In this study, the polyurethane which has versatile applications has been reinforced with the natural clay, hectorite. The hectorite has better properties than montmorillonite. There are studies on polyurethane and montmorillonite but polyurethane and hectorite composite is published first time. Polyurethane is industrial polyurethane which makes the study to be applicable to the industry. Exfoliated structure has been obtained without using organic modifiers due to the hydrophilic nature of the polymer matrix and the mineral clay. Mechanical properties have been improved as well.

• 고문화
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• 56호
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• pp.147-180
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• 2000

이 연구는 김해 양동리 고분에서 출토된 2800 여점의 철제유물 중 6점에 대한 금속학적인 검토를 통해 고고학과 문화재보존과학의 기초자료로서 활용하고자 하였다. 1 김해 양동리 고분군 출토 철제유물은 원로로서 적철광을 사용하였고, 연료는 목탄을 이용한 것으로 추정된다. 2. 주조유물 중 철복은 C함량이 $4.6\%$의 과공정백주철이고 주조철부는 C함량이 $3.58\%$의 아공정백주철 임을 알 수 있었다. 이들 유물이 백주철인 것으로 보아 주조 후 바로 급랭하여 제작된 것으로 보인다. 3. 단조유물은 C함량이 $0.08\%,\;0.11\%$의 아공석강으로 대부분의 기지조직이 pearlite와 ferrite이며, 제작시 괴련철을 단조한 후 공랭하여 철기를 제작한 것으로 사료된다.

• 한국주조공학회지
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• 제16권2호
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• pp.149-157
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• 1996

Several aluminum based alloys were fabricated by a twin roll strip casting mill. As-cast microstructures and microsegregations of these aluminum alloys were investigated by means of optical microscope, scanning electron microscope and electron probe micro analysis. Clear distinction on microsegregation among the alloy systems was observed, that is, A1235 and A8011 alloys showed diffused segregation in the middle of the strip, while A3003 and A5086 alloys revealed a centerline segregation consisted of lamellar structure. Above center line segregation was resulted from enrichment of the alloying elements such as Mn, Fe, Cu, Si and eutictic reaction in central region of the alloy strip.

• Journal of Electrochemical Science and Technology
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• 제7권2호
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• pp.115-131
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• 2016

Though battery chemistry and technology had been developed for over a hundred years back, increase in demand for storage energy, in the computer accessories, cell phones, automobile industries for future battery car and uninterrupted power supply, has made, the development of existing and new battery, as an emerging areas of research. With innovation of high energetic inexpensive Nano structure materials, a more energy efficient battery with lower cost can be competitive with the present primary and rechargeable batteries. Materials electrochemistry of electrode materials, their synthesis and testing have been explained in the present paper to find new high efficient battery materials. The paper discusses fundamental of electrochemistry in finding true cell potential, overvoltages, current, specific energy of various combinations of anode-cathode system. It also describes of finding the performance of new electrode materials by various experiments viz. i. Cyclic Voltammetry ii. Chronoamperometry iii. Potentiodynamic Polarization iv. Electrochemical Impedance Spectroscopy (EIS). Research works of different battery materials scientists are discussed for the development of existing battery materials and new nano materials for high energetic electrodes. Problems and prospects of a few promising future batteries are explained.

• Tribology and Lubricants
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• 제25권4호
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• pp.250-255
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• 2009

Oxidation characteristics of Zirlo and Zircaloy-4 tubes, which are widely used as nuclear power fuel cladding, are studied in steam environment up to $1200^{\circ}C$. Oxidation resistances are compared in terms of the mass increase due to the absorption of oxygen. The evolution of microscopic structure accompanied with the oxidation process is investigated. Also, the influence of oxidation on the fretting wear characteristics of the tubes is studied. Piezo-electrically actuated rig is employed to fret the tubes with cross-contacting arrangement. Wear scar is observed and measured, by using microscopes and a 3D-profiler. The results of fretting wear are quantified in terms of scar size, wear volume and wear coefficient, and compared for the three different tube materials of oxidated Zirlo, virgin Zirlo and Zircaloy-4.