• Progress in Superconductivity
• /
• 제7권2호
• /
• pp.145-151
• /
• 2006

Nickel and nickel-tungsten alloy were electroplated on a cold rolled and heat treated copper(Cu) substrate. 4 mm-thick high purity commercial grade Cu was rolled to various thicknesses of 50, 70, 100 and 150 micron. High reduction ratio of 30% was applied down to 150 micron. Rolled texture was converted into cube texture via high temperature heat treatment at $400-800^{\circ}C$. Grain size of Cu was about 50 micron which is much smaller compared to >300 micron for the Cu prepared using smaller reduction pass of 5%. 1.5 km-long 150 micron Cu was fabricated with a rolling speed of 33 m/min and texture of Cu was uniform along length. Abnormal grain growth and non-cube texture appeared for the specimen anneal above $900^{\circ}C$. 1-10 micron thick Ni and Ni-W film was electroplated onto an annealed cube-textured Cu or directly on a cold rolled Cu. Both specimens were annealed and the degree of texture was measured. For electroplating of Ni on annealed Cu, Ni layer duplicated the cube-texture of Cu substrate and the FWHM of in plane XRD measurement for annealed Cu layer and electroplated layer was $9.9^{\circ}\;and\;13.4^{\irc}$, respectively. But the FWHM of in plane XRD measurement of the specimen which electroplated Ni directly on cold rolled Cu was $8.6^{\circ}$, which is better texture than that of nickel electroplated on annealed Cu and it might be caused by the suppression of secondary recrystallization and abnormal grain growth of Cu at high temperature above $900^{\circ}C$ by electroplated nickel.

• 대한전자공학회논문지TE
• /
• 제37권2호
• /
• pp.83-90
• /
• 2000

본 논문에서는 IMT2000 중계기용으로 1.88-1.98 ㎓ 대역 전력증폭기를 저 가격, 소형으로 개발하였다. 이 전력증폭기는 두 단으로 구성되어 있으며 초단은 P-HEMT (ATF-34143, 800 micron gate width, Agilent Technologies)를 사용하였으며, 종단은 GaAs FET(EFA240D-SOT89, 2400 micron gate width, Excelics Semiconductor)를 사용하였다. 개발된 전력 증폭기는 전체 주파수 대역인 1880-1980 ㎒에서 이득이 29.5㏈, 1㏈ gain compression point는 29.5dBm, 3rd order intercept point(OIP3)는 42dBm 그리고 입출력 return loss는 -10㏈/-l2㏈ 이다. 본 연구에서는 이 전력 증폭기를 설계하기 위하여 각 소자의 비선형 모델을 사용하여 전력증폭기의 여러 가지 비선형 특성을 설계할 수 있었으며, 이 전력 증폭기의 크기는 42(L) x 34(W) mm으로 소형화가 가능하였다.

• 한국진공학회지
• /
• 제8권4A호
• /
• pp.456-460
• /
• 1999

Experimental studies of laser micromachining on Mo diaphragm using piezo Q-switched Nd:YAZ laser have been performed. Application of miniaturized micorcolumn electron gun arrays as a potential electron beam lithography or portable mini-scanning electron microscope (SEM) application have recently extensively examined. The conventional microcolumn fabrication technique would give a limitation on the minimization of aberration, In this paper, we obtained 20~30 $\mu \textrm m$aperture of laser micromachining on Mo diaphragm using piezo Q-swithed Nd:YAG laser. The geometrical figures, such as the diameter and the preciseness of the drilled aperture are dependent upon the total energy of the laser pulse train, laser pulse width, and the diameter of laser spot in addition to the materials-dependent parameters.

• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2003년도 International Meeting on Information Display
• /
• pp.791-794
• /
• 2003

To synthesize $Gd_{2}O_{3}:Eu$ phosphor powder of nano size and high luminescence efficiency under UV (ultraviolet) and VUV (vacuum ultraviolet) light, organic additives such as citric acid and ethylene glycol and $Na_{2}CO_{3}$ flux were introduced in large-scale spray pyrolysis and critical conditions for forming nano-sized particles were investigated. The $Gd_{2}O_{3}:Eu$ phosphor particles prepared from solutions with organic additives such as citric acid and ethylene glycol had micron size and spherical shape. However, the particles prepared from polymeric precursor solution with $Na_{2}CO_{3}$ flux had nano size and non-aggregation characteristics. The as-prepared spherical particles with micron size turned into nano-sized particles during post-treatment by recrystallization process. The nano-sized $Gd_{2}O_{3}:Eu$ phosphor particles showed higher brightness than the commercial $Y_2O_3:Eu$ phosphor product under both UV light of 254nm and VUV light of 147 nm.

• 한국광학회:학술대회논문집
• /
• 한국광학회 2004년도 제15회 정기총회 및 동계학술발표회
• /
• pp.304-305
• /
• 2004

• 전기화학회지
• /
• 제14권3호
• /
• pp.184-190
• /
• 2011

다공성 중공형태의 $LiMn_2O_4$는 실리카 템플레이트과 침전법에 의해 합성되었다. 합성한 $LiMn_2O_4$는 나노사이즈의 1차입자를 가지며 다공성 중공형태를 가지고 있었다. 실리카 템플레이트의 제거는 NaOH를 이용하여 화학적 에칭법이 사용되었다. NaOH의 농도를 높여줌에 따라 망간산화물 입자 크기가 증가 하며 다공성의 중공구가 형성되었다. X-선 회절 분석을 통하여 합성된 $LiMn_2O_4$는 Fd3m의 공간 그룹을 가지는 스피넬 구조가 형성된 것을 확인 할 수 있었다. 실리카와 망간염의 비율을 높여주었을 경우 합성된 $LiMn_2O_4$는 1차입자의 크기는 감소한다. 실리카와 망간염의 비율이 1 : 9 이상인 경우에서 마이크론 단위의 정방정계의 $LiMn_2O_4$가 합성되었다. 다공성 중공형태의 $LiMn_2O_4$의 전기화학적 특성을 평가하기 위하여 2032형태의 코인셀을 제작하여 충/방전 테스트를 하였다. 나노사이즈의 1차입자를 가진 시료의 경우에는 마이크론 사이즈의 1차입자를 가진 시료보다 용량은 낮았지만 용량유지율은 향상되는 것 확인 할 수 있었다.

• 천문학회보
• /
• 제44권1호
• /
• pp.44.3-44.3
• /
• 2019

Massive stars, supernovae, and kilonovae are among the most luminous radiation sources in the universe. Observations usually show near- to mid-infrared (NIR-MIR, 1-5~micron) emission excess from H II regions around young massive star clusters (YMSCs) and anomalous dust extinction and polarization towards Type Ia supernova (SNe Ia). The popular explanation for such NIR-MIR excess and unusual dust properties is the predominance of small grains (size a<0.05micron) relative to large grains (a>0.1micron) in the local environment of these strong radiation sources. The question of why small grains are predominant in these environments remains a mystery. Here we report a new mechanism of dust destruction based on centrifugal stress within extremely fast rotating grains spun-up by radiative torques, namely the RAdiative Torque Disruption (RATD) mechanism, which can resolve this question. We find that RATD can destroy large grains located within a distance of ~ 1 pc from a massive star of luminosity L~ 10^4L_sun and a supernova. This increases the abundance of small grains relative to large grains and successfully reproduces the observed NIR-MIR excess and anomalous dust extinction/polarization. We show that small grains produced by RATD can also explain the steep far-UV rise in extinction curves toward starburst and high redshift galaxies, as well as the decrease of the escape fraction of Ly-alpha photons observed from HII regions surrounding YMSCs.

• 분석과학
• /
• 제24권6호
• /
• pp.429-434
• /
• 2011

본 연구에서는 마이크로 크기의 입자(안료, 대기입자, 등)를 수집과 동시에 물에 분산된 상태로 분획가능한 장치를 개발하였다. 이 장치에서는 물을 넣은 입자수집용 실린더 세 개를 직렬로 연결하여 공기를 통과하게 하였다. 그럼으로써 크기가 다른 입자들이 다른 실린더에 모아지도록 하였고, 수집과 동시에 분획이 가능하도록 하였다. 이 장치의 중요한 특징은 막필터(membrane filter)를 사용하지 않는다는 점이다. 즉, 필터를 사용하지 않고 마이크로 크기의 입자를 직접 시료 수집용 실린더에 수집되도록 하였다. 또한 수집된 시료는 수집되는 동안 물에 분산된 상태로 장치 내에서 동시분획이 가능하다. 이 장치를 에어본 입자의 수집에 응용하였다. 수집된 에어본 입자는 침강 장-흐름 분획법(sedimentation field-flow fractionation, SdFFF)을 이용하여 입자 크기별로 분획하였고, 광학현미경(optical microscopy, OM)을 이용하여 입자 크기와 모양을 관찰하였다. 또한 AAS와 ICP-AES를 이용하여 에어본 입자들의 조성을 분석하였다. 본 연구를 통하여 개발한 입자 수집 및 분획장치는 다양한 종류의 입자의 수집 및 크기분포 분석에 활용이 가능할 것으로 기대한다.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2001년도 The 6th International Symposium of East Asian Resources Recycling Technology
• /
• pp.633-637
• /
• 2001

Oil fly ash is known as one source of raw materials from which vanadium and nickel metals can be recovered. The current recovery process of valuable metals from oil fly ash is mainly the hydrormetallurgy one. Nevertheless, a great amount about 50~80%, of unburned carbon remains as byproduct after hydrormetallursy process. In Taiwan, if hydrormetallursy processes have proceeded, it can be estimated that the annual production of unburned carbon is 25 thousand tons. From the viewpoint of resource recycling, this study is a preliminary study and investigates in recovery of sub micron- graphitized carbon from unburned carbon by a designed process. The designed process included the following steps: 1.selecting a portion with +400mesh size from unburned carbon; 2.treating the selected in ultrasonic waves; 3.using a 400mesh sieve to obtain the product which is under 400mesh; 4.Removal ash from the product. In regard to treatment by ultrasonic waves in the designed process, treating time of ultrasonic waves is a simple and only variance in this study. The results indicate that the production yields increase with the treating time of ultrasonic waves; the production yield in specific conditions of this study can reach about 23%, in which ash content in product is about 2.5%. According to results of SEM, TEM and XRD, the products from the designed process are flakes in shape, several microns in size and graphitized carbon in carbon crystal phase. Except to graphitized carbon, there are a little carbon blacks, which are graphite 2H in carbon crystal phase in the products. Conclusively, the designed process is possibly applicable, by which comes to the recovery of micron- graphitized carbon.

• 한국대기환경학회:학술대회논문집
• /
• 한국대기환경학회 2006년도 춘계학술대회 논문집
• /
• pp.224-225
• /
• 2006