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계단형 텅스텐 결정면의 질소 흡착에 관한 연구 : Ⅱ. W(210) 및 W(310)면
최대선(D. S. Choi),한종훈(J. H. Han),백선목(S. M. Paik),박노길(N. G. Park),김욕욱(Y. W. Kim),황정남(C. N. Whang) 한국진공학회(ASCT) 1996 Applied Science and Convergence Technology Vol.5 No.4
장전자 방출법으로 텡스텐 (210)면 및 (310)면(100)면의 질소 흡착에 의한 일함수의 변화에 heat of desorption을 측정하였으며 Thermal Desortion Spectra(TDS) 결과로부터 adsorption site를 예측하였다. 텅스텐 (210)면 및 (310)면에 에 질소가 흡착될 때 흡착율에 따라 일함수는 증가하다가 각 면에 대하여 흡착율 5 Langmuir일때 최대 변화량 0.29 eV및 0.20 eV에서 포화되었다. TDS 결과는 이 면들은 낮은 dose의 영역에서 각각 3개의 흡착 site가 있음을 보였으며 이 흡착 site들 중 α₁state의 spectrum의 강도는 (210)면에서 보다 (310)면에서 상대적으로 강해짐을 보였다. 또한 (210)와 (310)면의 α₁ 과 β₂ state의 흡착 site에 흡착된 질소의 dipole moment의 방향은 이 흡착 site들에 대응되는 (100)면의 α₁ 과 β₂state의 흡착 site에 흡착된 질소의 dipole moment의 방향과 반대 방향으로 측정되었으며 이 현상으로부터 질소의 상대적인 흡착 위치를 예측하였다. The heat of desorption and the work function change induced by nitrogen adsorption on the stepped tungstein surface planes, W(210) and W(310), are measured using the Field Electron Emission Microscope(FEM). The adsoption sites are predicted from the Thermal Desortion Spectra(TDS). The work function change of both W(210) and W(310) planes increase as increasing the nitrogen dose and saturates at the nitrogen dose about 5 Langmuir to 0.29 eV and 0.20 ev respectively. We find three adsorption site on each plane for the low dose range. The TDS result shows that the intensity of α₁, state on W(310) is much stronger than that of α₁ state on W(210), and the direction of nitrogen dipole moment adsorbed on the sites correspond to α₁, and β₂ states on W(210) and W(310) planes are in the opposite direction to that of the equivalent states on W(100) plane. From this observation we can predict the relative atomic position in the zdirection (perpendicular direction to the surface) of nitrogen molecules/atoms adsorbed on these sites.
LIGA-like 공정을 이용한 마이크로 부품 복제용 Ni과 Ni-W 금형 제조 및 특성
황완식,박준식,강영철,조진우,박순섭,이인규,강성군,Hwang, W.S.,Park, J.S.,Kang, Y.C.,Cho, J.W.,Park, S.S.,Lee, I.G.,Kang, S.G. 한국재료학회 2003 한국재료학회지 Vol.13 No.1
Electroplated Ni and Ni-W micro-molds using LIGA-like process for replication of micro-components such as microfluidic parts and micro optical parts have been investigated. In general, it is hard to produce micro-parts using conventional mechanical processes. Micro-mold formed by LIGA-like process could fabricate micro-parts with high aspect ratio. In this paper, fabrication and properties of electroplated Ni molds with varying applied current types as well as those of Ni-W molds were investigated. Ni molds fabricated under pulse-reverse current showed the highest hardness value of about 160 Hv. Ni-W molds showed the hardness of about 500 Hv which was much harder than that of Ni electroplated molds. The above results suggested that high quality micro-molds could be fabricated by using Ni electroplating of pulse-reverse type for core molds and sequential Ni-W alloys coating.
Song, K.J.,Ko, R.K.,Kim, H.S.,Ha, H.S.,Ha, D.W.,Oh, S.S.,Park, C.,Yoo, S.-I.,Kim, M.W.,Kim, C.J.,Joo, J.H. Institute of Electrical and Electronics Engineers 2007 IEEE transactions on applied superconductivity Vol.17 No.2
<P>The degree of ferromagnetism of Ni-W<SUB>y</SUB> alloys decreases as W-content y increases. Both the saturation magnetization <I>M</I> <SUB>sat</SUB> and Curie temperature <I>T</I> <SUB>c</SUB> decrease linearly with W-content y, and both <I>M</I> <SUB>sat</SUB> and <I>T</I> <SUB>c</SUB> go to zero at critical concentration of y<SUB>c</SUB> ~9.50 at.% W. To compare with Ni-W alloys, the magnetic properties of a series of both as-rolled (non-textured) and annealed (biaxially textured) [Ni<SUB>97at.%</SUB>-W<SUB>3at.%</SUB>]<SUB>100-x</SUB>-Cu<SUB>x</SUB> alloy tapes with compositions x = 0, 1, 3, 5, and 7 at.%, were studied. Characterization methods included XRD analyses to investigate the biaxial texturing of the annealed [Ni-W]-Cu alloy tapes and studies of the magnetization for both as-rolled and annealed [Ni-W]-Cu alloy tapes. Both the isothermal mass magnetizations <I>M</I>(<I>H</I>) of a series of samples at different fixed temperatures and <I>M</I>(<I>T</I>) in fixed field, were measured. The effect of Cu addition on both the saturation magnetization and Curie temperature T<SUB>c</SUB> of the Ni<SUB>97at.%</SUB>-W<SUB>3at.%</SUB> alloy was investigated.</P>
확산펌프 기반의 BCl<SUB>3</SUB> 축전결합 플라즈마를 이용한 GaAs와 AlGaAs의 건식 식각
이성현,박주홍,노호섭,최경훈,송한정,조관식,이제원,Lee, S.H.,Park, J.H.,Noh, H.S.,Choi, K.H.,Song, H.J.,Cho, G.S.,Lee, J.W. 한국진공학회 2009 Applied Science and Convergence Technology Vol.18 No.4
본 논문은 확산펌프 기반의 축전 결합형 $BCl_3$ 플라즈마를 사용하여 GaAs와 AlGaAs를 건식 식각한 연구에 관한 것이다. 실험에서 사용한 압력 범위는 $50{\sim}180$ mTorr, CCP 파워는 $50{\sim}200\;W$, $BCl_3$ 가스 유량은 $2.5{\sim}10$ sccm 이었다. 식각 후에 GaAs와 AlGaAs의 식각 속도와 표면 거칠기분석은 표면 단차 측정기를 이용하여 하였다. GaAs의 식각 벽면과 표면 상태는 전자현미경으로 분석하였다. 식각 중 플라즈마의 광 특성 분석은 광학 발광 분석기를 이용하였다. 본 실험을 통하여 5 sccm의 소량의 $BCl_3$ 가스 유량으로 공정 압력이 130 mTorr이내인 경우에는, 100 W CCP 파워의 조건에서 GaAs는 약 $0.25{\mu}m$/min 이상의 우수한 식각 속도를 얻을 수 있었다. AlGaAs의 경우는 GaAs의 식각 속도보다 조금 낮았다. 그러나 같은 유량에서 공정압력이 180 mTorr로 높아지면 GaAs와 AlGaAs의 식각 속도가 급격히 감소하여 거의 식각되지 않는 것을 알 수 있었다. 또한 CCP 파워의 경우에는 50 W의 파워에서는 GaAs와 AlGaAs 모두 거의 식각되지 않았다. 그러나 $100{\sim}200\;W$의 조건에서는 $0.3{\mu}m$/min 이상의 높은 식각 속도를 주었다. 두 결과를 보았을 때 축전결합형 $BCl_3$ 플라즈마 식각에서 GaAs와 AlGaAs의 식각 속도는 CCP 파워가 $100{\sim}200\;W$ 범위에 있으면 그 값에 비례하지 않고 거의 일정한 값이 된다는 사실을 알았다. 75mTorr, 100 W의 CCP 파워 조건에서 $BCl_3$의 유량 변화에 따른 GaAs와 AlGaAs의 식각 속도의 경우, $BCl_3$의 유량이 2.5 sccm의 소량일 때는 GaAs는 식각 속도가 높았지만 AlGaAs는 거의 식각되지 않는 흥미로운 결과를 얻었다. 플라즈마 발광 특성을 보면 $BCl_3$ 축전 결합 플라즈마는 주로 $500{\sim}700\;mm$ 범위를 가지는 넓은 분자 피크만 만든다는 것을 알 수 있었다. 전자 현미경 사진 결과에서는 5 sccm과 10 sccm의 $BCl_3$ 플라즈마 모두 식각 중에 GaAs의 벽면을 언더컷팅 하였으며, 10 sccm의 $BCl_3$유량을 사용하였을 때 언더컷팅이 더 심했다. We report the etch characteristics of GaAs and AlGaAs in the diffusion pump-based capacitively coupled $BCl_3$ plasma. Process variables were chamber pressure ($50{\sim}180$ mTorr), CCP power ($50{\sim}200\;W$) and $BCl_3$ gas flow rate ($2.5{\sim}10$ sccm). Surface profilometry was used for etch rate and surface roughness measurement after etching. Scanning electron microscopy was used to analyze the etched sidewall and surface morphology. Optical emission spectroscopy was used in order to characterize the emission peaks of the $BCl_3$ plasma during etching. We have achieved $0.25{\mu}m$/min of GaAs etch rate with only 5 sccm $BCl_3$ flow rate when the chamber pressure was in the range of 50{\sim}130 mTorr. The etch rates of AlGaAs were a little lower than those of GaAs at the conditions. However, the etch rates of GaAs and AlGaAs decreased significantly when the chamber pressure increased to 180 mTorr. GaAs and AlGaAs were not etched with 50 W CCP power. With $100{\sim}200\;W$ CCP power, etch rates of the materials increased over $0.3{\mu}m$/min. It was found that the etch rates of GaAs and AlGaAs were not always proportional to the increase of CCP power. We also found the interesting result that AlGaAs did not etched at 2.5 sccm $BCl_3$ flow rate at 75 mTorr and 100 W CCP power even though it was etched fast like GaAs with more $BCl_3$ gas flow rates. By contrast, GaAs was etched at ${{\sim}}0.3{\mu}m$/min at the 2.5 sccm $BCl_3$ flow rate condition. A broad molecular peak was noticed in the range of $500{\sim}700\;mm$ wavelength during the $BCl_3$ plasma etching. SEM photos showed that 10 sccm $BCl_3$ plama produced more undercutting on GaAs sidewall than 5 sccm $BCl_3$ plasma.
Park, J.W.,Suh, J.Y.,Kang, S.W.,Shin, S.E.,Bae, D.H. MPR Pub. Services 2014 International journal of refractory metals & hard Vol.43 No.-
In the present work, we investigate the effects of the size and volumetric fraction of Zr<SUB>2</SUB>Cu on the density and mechanical strength of liquid-reactive sintered W/MWCNTs/ Zr<SUB>2</SUB>Cu composites. Composite powders are formed by mechanical ball-milling and are sintered into a high density composite at 1400<SUP>o</SUP>C. During sintering, two major reactions occur: 1) C atoms in the MWCNTs reacted with the W matrix to form WC; 2) Zr in the Zr<SUB>2</SUB>Cu liquid phase, which flows through the capillaries between particles, reacts with WC in the W matrix to form ZrC. Based on our results, higher density composites with finer ZrC reinforcements are successfully produced using sub-micron size Zr<SUB>2</SUB>Cu powders. In addition, the amount of Zr<SUB>2</SUB>Cu is varied, and the optimal volumetric fraction of Zr<SUB>2</SUB>Cu that maximizes the hardness of the composite (1180Hv) is equal to 30vol.%. When the Zr<SUB>2</SUB>Cu content is less than the critical value, and the density of the composite is too low due to an insufficient amount of liquid. The hardness of the composite decreases when the Zr<SUB>2</SUB>Cu content is greater than 30vol.%, because excess liquid yields a network structure of WC, ZrC, and Zr. The experimental results also reveal that the sintering time required to reach the maximum hardness (1180Hv) significantly decreases as the size of Zr<SUB>2</SUB>Cu is reduced from micron-scale to nano-scale.
Comparison of essential oil composition between Angelica gigas and Angelica acutiloba
Park,C,H,Juliani,H,R,Park,H,W,Yu,H,S,Simon,J,E 한국자원식물학회 2003 Plant Resources Vol.6 No.3
Two kinds of Angelica belong to Umbelliferae collected, the one is Angelica gigas that is inhabitant in Korea and the other is Angelica acutiloba that is indigenous in Japan at the field of Snyder Research and Extension Farm Rutgers University, New Jersey and was analyszed by GC and GC/MS. The composition of the essential oil of the different aerial parts of the Angelica has been studied. The oil yields obtained upon hydrodistillation were 0.18% (v/w) in Korean Angelica and 0.44% (v/w) in Japanese Angelica on dry root weight basis. By the growing stage in the Rutgers greenhouse condition, leaf and root of essential oil content a little decreased on 9 months later than 4 months later except for Angelica gigas leaf. Both of Angelica showed that amounts of essential oil content presented in order of leaf > petiole > root according to different plant part. The analysis of the essential oil from Angelica root led to the identification of 14 constituents totaling 64% in Korean Angelica and 13 constituents totaling 68% in Japanese Angelica. The major constituents of the Angelica root essential oil were ligustilide (47 %) and gamma terpi (14 %) in Korean Angelica, and alpha pinei (32 %) and nonane (25 %) in Japanese Angelica