• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.87-92
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• 2001

In this paper, high strength pressure vessel steels having the same chemical compositions were manufactured by the two different steel-making processes, such as vacuum degassing(VD) and electro-slag remelting(ESR) methods. After the steel-making process, they were normalized at $955^{\circ}C$, quenched at $843^{\circ}C$, and finally tempered at $550^{\circ}C$ or $450^{\circ}C$, resulting in tempered martensitic microstructures with different yielding strengths depending on the tempering conditions. Low-cycle fatigue(LCF) tests, fatigue crack growth rate(FCGR) tests, and fracture toughness tests were performed to investigate the fatigue and fracture behaviors of the pressure vessel steels. In contrast to very similar monotonic, LCF, and FCGR behaviors between VD and ESR steels, a quite difference was noticed in the fracture toughness. Fracture toughness of ESR steel was higher than that of VD steel, being attributed to the removal of impurities in steel-making process.

• 분석과학
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• 제21권6호
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• pp.487-494
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• 2008

극미량 우라늄시료에 대한 열이온화 질량분석기를 이용하여 우라늄 동위원소 비 측정 및 정량과 관련하여 고순도(zone refined) 레늄필라멘트와 일반 레늄필라멘트로부터 오는 바탕값(background) 특성을 비교하였다. 두 종류 필라멘트에서 가벼운 알칼리금속원소들의 클러스터(cluster)인 $(^{39}K_6)^+$, $(^{39}K_5+^{41}K)^+$ 및 금속산화물($PbO_2$)로 추측되는 우라늄 동중원소영향(isobaric effect)을 확인하였다. 고순도 레늄필라멘트를 < $10^{-7}$ torr에서 약 $2000^{\circ}C$로 1.5 시간 이상 degassing 함으로 불순물들을 완전히 제거할 수 있었으나 일반 레늄필라멘트의 경우 5시간 이상 degassing을 하여도 약 3 pg-U이 남아있었다. 일반 레늄필라멘트에 대한 불순물 제거(degassing) 실험결과 5 A, 30 분이 불순물제거의 최소조건이었다. U-233을 spike로 사용, 동위원소희석 질량분석법으로 일반 레늄필라멘트 중 불순물로 포함된 우라늄 양을 측정한 결과 degassing을 하지 않은 필라멘트에서는 0.31 ng-U이 측정되었고, degassing (5.5 A, 1 hr.)을 한 것은 약 3 pg-U 이 측정되었다. 즉, 일반필라멘트의 경우, degassing을 하더라도 1 ng-U 시료에 대하여 0.3% 오차를 근본적으로 갖는 것을 알 수 있었다. 따라서 환경급 극미량 우라늄시료 측정에는 고순도 필라멘트를 degassing하여 사용해야 함을 알 수 있었다. 우라늄 측정 시 필라멘트 전류를 5.5 A로 하였을 때보다 6.0 A로 했을 때 불순물 우라늄 량이 1.5 배 더 크게 나타났다. 따라서 필라멘트 전류를 5.5 A 이상 올리지 않는 것이 바탕값 영향이 작음을 알 수 있었다. 우라늄 표준물질(KRISS 표준물질/NIST U-005, 030)을 사용하여 우라늄 동위원소 함량을 측정한 후 인증 값과 비교한 결과 U-235 는 0.04%, U-234, U-236는 2% 이내에서 각각 일치하였다.

• E2M - 전기 전자와 첨단 소재
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• 제7권1호
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• pp.64-72
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• 1994

본 고는 현재 전기적 응용을 위한 수지 절연물의 진공/가압 수지-주형처리 분야에서 가장 앞선 기술과 연구개발력을 보유하고 있는 스위스의 Ciba-Geigy사와 최신의 진공성형 시스템을 개발, 생산하고 있는 독일의 Hedrich사 및 진공주형/자동가압 성형장비를 생산하는 스위스의 Vogel사 등을 최근에 방문하여 Epoxy, Polyurethane, Polyester 및 Silicone 수지 등의 수지절연시스템을 가지고 구조적으로 기포가 없으며 전기적, 기계적, 열적특성이 매우 우수하고 매끄러운 표면이 요구되는 수지 mold제품을 생산하는데 적용되고 있는 진공 수지-주형처리기술의 현황과 아울러 경화시간을 크게 단축시켜 생산자동화가 가능한 최신의 자동가압겔화(Automatic pressure gelation)/주입몰드공정(Injection molding process)의 특징 및 기술개발현황에 대해 파악한 내용을 소개하고자 한다.

• 대한금속재료학회지
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• 제48권5호
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• pp.424-429
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• 2010

In the RH process, it is possible to obtain quicker processing times by enhancing the decarburization rates at a low carbon range of steel melt through Ar gas injection into the vacuum vessel. The RH decarburization reaction was simulated through a dissolved oxygen removal reaction by injecting nitrogen into a 1/8 scale RH water model system. The gas nozzles for the N$_{2}$ injection into the vacuum vessel were located at the lowest level of the vessel's outer wall. The nitrogen bubbling in the vacuum vessel resulted in an increase in the reaction rate constant, which rose in accordance with an increase in the bubbling flow rate and number of nozzles used. However, there was almost no variation in the reaction rate constant, which depended on the horizontal positions of the bubbling nozzles.

• 한국입자에어로졸학회지
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• 제9권1호
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• pp.31-36
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• 2013

In this study, Mo metal powder was prepared by hydrogen reduction of Mo trioxides with different purity of 2N and 3N grades. We have obtained Mo metal powder with oxygen content of 1450 ppm by hydrogen reduction and subsequent heat treatment for degassing. Using the Mo metal powder, a low-oxygen Mo ingot was prepared by repetitive vacuum arc melting. The oxygen content of the obtained Mo ingot was less than 70 ppm after vacuum arc melting for 30 min. The purity of the Mo metal powder and the ingot was evaluated using glow discharge mass spectrometry. The purity of the respective Mo ingots was increased to 3N and 4N grades from the Mo powder of 2N and 3N grades after the repetitive vacuum arc melting. The low oxygen Mo ingot thus can be used as a raw material for sputtering targets.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 C
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• pp.1823-1826
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• 2002

The purpose of this experiment was to develope Triggered Vacuum Switch (TVS) for the high voltage and high current. The TVS has an array of rods of alternate polarity in which a fixed gap spacing is maintained between the rods. The cross section of each rod has trapezoidal shape. It consists of electrode, ceramic chamber, getter and trigger. Currently, triggered vacuum switch (TVS) with seal-off has been designed and fabricated at PAL. An experimentation and trigger devices for TVS were designed for testing characteristics of electricity. For making the prototype of TVS, it is developed of fabrication process and fined of electrode material. The fabrication of the TVS is a lot of process which have manufacturing of part, chemical clean, ceramic brazing and metal welding. The fabricated TVS is tested of leak for vacuum, hold-off voltage and conditioning of trigger system. The TVS has pinch-off after it is removed of gas in the TVS and activated of getter in degassing furnace. The prototype TVS tested about 20 kV, 75 kA, 83 ${\mu}s$ with 100 kJ capacitor bank and inductance 5 ${\mu}H$. This paper describes the results of tests and the characteristics of the switch.

• 한국분말재료학회지
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• 제5권4호
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• pp.340-344
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• 1998

Along with the growth of conventional ferrous powder metallurgy (PM), PM of aluminum alloys has been intensively investigated in Japan. Although rapidly solidified aluminum alloy powder was first used in the USA,/sup 1)/ commercialization for consumer market was first realized in Japan./sup 2)/ In order to achieve the viable cost-performance including Near Net Shape (NNS) formability, we developed three processes, powder extrusion, powder forging and sintering. The new powder extrusion process does not use either capsulation or vacuum degassing. The new powder forging does not need lateral flow. The new sintering process does not use liquid phase. The performance achieved by the processes is outstanding mechanical or physical properties that has potential to substitute cast iron, steel, titanium Metal Matrix Composite (MMC) or Ingot Metallurgy (IM) aluminum alloys. Cooperation with customers, powder suppliers and research associations contributed to the advancement of PM aluminum alloys in Japan.

• International Journal of Aerospace System Engineering
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• 제5권2호
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• pp.8-15
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• 2018

For small earth observation satellites, alignment between the optical components is important for precise observation. However, satellite cameras are structurally subject to misalignment in the launch environment where vibration excitations and impacts apply, and in space environments where zero gravity, vacuum, radiant heat and degassing occur. All of these variables can cause misalignment among the optical components. The misalignment among optical components results in degradation of image quality, and a re-alignment process is needed to compensate for the misalignment. This process of re-alignment between optical components is referred to as a refocusing process. In this paper, we proposed a 3 - axis focusing mechanism to perform the refocusing process. This mechanism is attached to the back of the secondary mirror and consists of three piezoelectric inertia-friction actuators to compensate the x-axis, y-axis tilt, and de-space through three-axis motion. The fabricated focus mechanism demonstrated excellent servo performance by experimenting with PD servo control.

• 한국진공학회지
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• 제12권4호
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• pp.201-206
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• 2003

스테인레스 스틸 304 재료로 가공된 진공용기의 온도를 $235 ^{\circ}C$까지 올린 후 다시 상온까지 내리는 굽기 과정에서와 세 개의 열음극 전리 진공게이지를 켜거나 탈기체 시켰을 때 이탈하는 기체의 양과 조성을 잔류기체분석기로 측정하여 분석하였다. 굽기 과정에서 이탈된 기체는 주로 $H_2,\; CO,\; H_2O$ 등이었으나 상온에서의 잔류기체는 $H_2$와 CO가 대부분이었다. 게이지를 켜거나 탈가스 시킨 후 용기내의 잔류가스는 $H_2$와 $H_2O$가 대부분이었고 이탈된 기체의 양과 종류는 게이지마다 조금씩 차이가 있음을 알 수 있었다.

• 대한치과기공학회지
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• 제21권1호
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• pp.15-26
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• 1999

This study was carried out by observing to composition of oxide on the surface of dental porcelain low gold alloy with various Indium additions according to the degassing and analysing the change composition of additional elements In on diffusion behaviors of Porcelain-matal surface. The specimens used were Au-Pd-Ag alloys by small indium addition. These specimens were treated for 10min at $1000^{\circ}C$ in vacuum condition. To investigate the microsturcture of oxidized alloy surface, SEM and EDAX were used, and EPMA were used to investigate the diffusion behaviors of porcelain-metal surface. X-ray diffraction were used to observe the morphological changes in the oxidation zone. The results of this study were obtained as follows ; 1) The hardness of alloy increased with increasing amount of In addition. 2) The formation of oxidation increased with increasing In content after heat treatment. 3) Diffusion of indium elements increased with increasing In content in metal-porcelain surface after firing. 4) The oxidations of alloy surface were mainly $In_2O_3$.