• 한국분말재료학회지
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• 제24권4호
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• pp.321-325
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• 2017

In this study, we investigate the optical properties of InP/ZnS core/shell quantum dots (QDs) by controlling the synthesis temperature of InP. The size of InP determined by the empirical formula tends to increase with temperature: the size of InP synthesized at $140^{\circ}C$ and $220^{\circ}C$ is 2.46 nm and 4.52 nm, respectively. However, the photoluminescence (PL) spectrum of InP is not observed because of the formation of defects on the InP surface. The growth of InP is observed during the deposition of the shell (ZnS) on the synthesized InP, which is ended up with green-red PL spectrum. We can adjust the PL spectrum and absorption spectrum of InP/ZnS by simply adjusting the core temperature. Thus, we conclude that there exists an optimum shell thickness for the QDs according to the size.

• 청정기술
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• 제4권1호
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• pp.6-23
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• 1998

반도체 산업은 각종 전자지기의 발달로 급격히 성장하였으며 현재는 우리 나라에서도 반도체 산업이 경제에서 큰 비중을 차지하고 있다. 국내외의 환경규제와 환경에 대한 대중의 관심이 높아지면서, 반도체 공정의 안전한 관리와 환경유해성 물질의 배출억제를 위하여 반도체 산업에서의 청정기술의 개발이 시급한 과제가 되고 있다. 청정기술이란 근본적으로 환경유해성 오염물질을 배출하지 않는 기술을 의미하나 이는 지금까지 개발된 기술로는 거의 불가능하다. 따라서 공정 내에서부터 환경유해물질의 배출을 최소화하는 기술도 청정기술의 범위에 포함시킨다. 반도체 공정은 연속적인 화학공정들로 구성되어 있으며 그 과정에서 많은 종류의 환경유해성 오염물질이 배출될 수 있다. 반도체 공정에서 발생하는 오염물질들은 기상 형태의 배가스, 액상 형태의 폐수, 폐기물의 세 가지 형태로 나누어 볼 수 있다. 기상의 오염물질을 억제하기 위한 기술로는 오염물질만을 선택적으로 파괴하거나 오염물질만을 농축하여 공정 내에서 재활용하는 방법, 또는 오염을 유발하는 물질 대신 이를 대체할 수 있는 환경에 안전한 물질을 개발하는 방법 등이 있다. 액상의 오염물질을 저감시키는 기술로는 공정의 최적화를 통하여 오염물질의 양을 최소화하는 방법과 유독한 물질로 구성된 원료를 대체하는 방법 등이 있다. 또한 근본적인 오염원을 제거하기 위하여 화학물질의 사용량 자체를 줄이거나 기상을 이용한 세정 시스템 등의 방법을 사용하는 것도 연구중이다.

• 한국진공학회지
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• 제4권S2호
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• pp.40-48
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• 1995

$TiB_2$-TiN double-layer coating have been prepared by ion beam enhanced deposition. AES, XRD, TEM and HRTEM were employed to characterize the $TiB_2$ layer. The microhardness of the coatings was evaluated by an ultra low-load microhardness indenter system, and the tribological behavior was examined by a ball-on-disc tribology wear tester. It was found that in a single titanium diboride layer, the composition is uniform along the depth of the film, and it is mainly composed of nanocrystalline $TiB_2$ with hexagonal structure, which resulted from the ion bombardment during the film growth. The hardness of the $TiB_2$ films increases with increasing ion energy, and approaches a maximum value of the $TiB_2$ films increases with increasing ion energy, and approaches a maximum value of 39 Gpa at ion energy of 85 keV. The tribological property of the TiB2 films is also improved by higher energy of 85keV. The tribological property of the $TiB_2$ films is also improved by higher energy ion beam bombardment. There is no major disparity in the mechanical properties of double-layer $TiB_2$/TiN coatings and TiN/$TiB_2$ coatings. Both show an improved wear resistance compared with single-layer $TiB_2$ films. The adhesion of double-layer coatings is also superior to that of single-layer films.

• 한국표면공학회지
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• 제37권5호
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• pp.253-262
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• 2004

Calcareous deposits are the consequence of pH increase of the electrolyte adjacent to metal surface affected by cathodic current in seawater. It obviously has several advantages over conventional coatings, since the calcareous deposit coating is formed from coating (Mg$^{2+}$, $Ca^{2+}$) naturally existing in seawater. In consideration of this respect, environment friendly calcareous deposit films were formed by an electro deposition technique on steel substrates submerged in 48$^{\circ}C$ natural seawater. And the influence of current density, coating time and attachment of steel mesh on composition ratio, structure and morphology of the electrodeposited films were investigated by Scanning Electron Microscopy(SEM), Energy Dispersive Spectroscopy(EDS) and X-Ray Diffractor(XRD), respectively. Accordingly, this study provides a better understanding of the composition between the growth of $Mg(OH)_2$ and $CaCO_3$ during the formation of electro deposit films on steel substrate under cathodically electrodeposition in $48^{\circ}C$ natural seawater. The Mg compositions, in general, are getting decreased regardless of current density but Ca compositions are getting increased as electrodeposition time runs. That is, $Mg(OH)_2$ compounds of brucite structure shaped as flat type is formed at the initial stage of electrodeposition, but CaCO$_3$ compounds of aragonite structure shaped as flower type is formed in large scale. Besides, $Mg(OH)_2$ compounds were much formed at 5 A/$\m^2$ environment condition compared to the 3 A/$\m^2$ and 4 A/$\m^2$ environment conditions. This is because that OH- which was comparatively largely generated at the metal surface is preferably combined with $Mg^{2+}$TEX>.

• 한국재료학회지
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• 제29권1호
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• pp.1-6
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• 2019

Recent industrialization has led to a high demand for the use of fossil fuels. Therefore, the need for producing hydrogen and its utilization is essential for a sustainable society. For an eco-friendly future technology, photoelectrochemical water splitting using solar energy has proven promising amongst many other candidates. With this technique, semiconductors can be used as photocatalysts to generate electrons by light absorption, resulting in the reduction of hydrogen ions. The photocatalysts must be chemically stable, economically inexpensive and be able to utilize a wide range of light. From this perspective, cuprous oxide($Cu_2O$) is a promising p-type semiconductor because of its appropriate band gap. However, a major hindrance to the use of $Cu_2O$ is its instability at the potential in which hydrogen ion is reduced. In this study, gold is used as a bottom electrode during electrodeposition to obtain a preferential growth along the (111) plane of $Cu_2O$ while imperfections of the $Cu_2O$ thin films are removed. This study investigates the photoelectrochemical properties of $Cu_2O$. However, severe photo-induced corrosion impedes the use of $Cu_2O$ as a photoelectrode. Two candidates, $TiO_2$ and $SnO_2$, are selected for the passivation layer on $Cu_2O$ by by considering the Pourbaix-diagram. $TiO_2$ and $SnO_2$ passivation layers are deposited by atomic layer deposition(ALD) and a sputtering process, respectively. The investigation of the photoelectrochemical properties confirmed that $SnO_2$ is a good passivation layer for $Cu_2O$.

• Tribology and Lubricants
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• 제38권6호
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• pp.235-240
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• 2022

Atomically-thin 2D nanomaterials can be easily deformed and have surface corrugations which can influence the frictional characteristics of the 2D nanomaterials. Chemical vapor deposition (CVD) graphene can be grown in a wafer scale, which is suitable as a large-area surface coating film. The CVD growth involves cooling process to room temperature, and the thermal expansion coefficients mismatch between graphene and the metallic substrate induces a compressive strain in graphene, resulting in the surface corrugations such as wrinkles and atomic ripples. Such corrugations can induce the friction anisotropy of graphene, and therefore, accurate imaging of the surface corrugation is significant for better understanding about the friction anisotropy of CVD graphene. In this work, the combinatorial analysis using friction force microscopy (FFM) and transverse shear microscopy (TSM) was implemented to unveil the friction anisotropy of CVD bi-layer graphene. The periodic friction anisotropy of the wrinkles was measured following a sinusoidal curve depending on the angles between the wrinkles and the scanning tip, and the two domains were observed to have the different friction signals due to the different directions of the atomic ripples, which was confirmed by the high-resolution FFM and TSM imaging. In addition, we revealed that the atomic ripples can be easily suppressed by ironing the surface during AFM scans with an appropriate normal force. This work demonstrates that the friction anisotropy of CVD bilayer graphene is well-correlated with the corrugated structures and the local friction anisotropy induced by the atomic ripples can be controllably removed by simple AFM scans.

• 자원환경지질
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• 제26권1호
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• pp.41-54
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• 1993

경상분지 남동부에 위치한 울산광산은 석회암을 교대한 전형적인 calcareous skarn강상으로 Fe W광화작용 이외에도 Cu, Pb, Zn, As, Bi, Ni, Co, Cr, Ag, Sn, In, Te, Sb 등이 수반되는 다금속광화작용의 특성을 보여주고 있다. 본 광상은 직립에 가까운 파이프상 광체로 산출되며, 자철석과 함께 북측의 혼펠스와의 경계부근에 회중석이 부분적으로 광염되어 있다. 본 광상의 스카른대는 석회암 및 혼펠스를 교대한 괴상 스카른과 양자를 각기 절단하는 맥상스카른으로 구분된다. 괴상스카른은 석회암 기원의 스카른이 주체를 이루며, 이러한 스카른대는 규회석 스카른, 석류석 스카른, 단사휘석-석류석 스카른, 단사휘석 스카른으로 분류되며, 부분적으로 스카른대 주변부를 따라 거정질 방해석대가 존재하고 있다. 스카른 진화과정은 초기스카른 및 후기스카른의 두 시기로 분류되며, 초기스카른은 prograde한 스카른 생성시기로 초기에는 규회석, Mg-rich 단사휘석, Al-rich garnet가 주로 정출되며 광석광물은 거의 불모한 시기이나, 초기스카른의 말기로 진행됨에 따라 자철석과 회중석이 정출된다. 그리고, 후기스카른의 전반기까지는 Fe-rich 단사휘석, Fe-rich garnet와 함께 자철석 회중석이 연속적으로 정출되었으나, 후기스카른의 중기부터는 Ni, Co, As, Cu, Zn, Fe, Bi 등의 황화광물이 정출되는 다금속광화 작용의 특정을 보인다. 또한, 최후기 열수작용시기에는 섬아연석과 방연석 등의 Base-metal 황화광물이 주로 정출되는 연 아연 광화작용의 양상을 나타낸다. 이러한 각 광화시기별 스카른 광물과 광석광물의 변화양상은 고온의 열수용액이 천부로 유출되는 과정에서 광화용액의 온도가 급격히 떨어진 결과 (telescope)에 기인된 것으로 사료된다.

• 한국습지학회지
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• 제20권3호
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• pp.235-242
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• 2018

운전시간이 경과함에 따라 공극폐색 문제로 인하여 수직 흐름형 습지의 기능은 저하되는데 이와 같은 문제는 폰딩(ponding)이나 월류 현상에 의하여 쉽게 관측할 수 있다. 공극폐색 잠재성을 조사하기 위하여 도로주변에 설치된 파일럿 규모의 습지 운전자료를 분석하였다. 습지에는 각각 우드칩과 마사(부석), 그리고 화산석을 충진하였다. 약 7개월 동안 도로 강우유출수 처리시험을 수행한 후 충진된 여재를 비운 후 여재 층별로 분류하여 여재에 의해 포획된 고형물 입자의 양과 특성을 분석하였다. 분석결과 대부분의 포획물질은 외부기인 부유물질 이었으며 다음으로 여재표면에 증식한 생물막인 것으로 나타났다. 특히 다른 여재와 비교하여 유기성 여재인 우드칩에서 생물막의 증식이 왕성하였다. 또한 전체 포획량 중 30% 이상이 상부 20cm 이내에 집중되어 있어 폐색으로 인한 폰딩 발생시 이 부분의 여재를 우선적으로 교체하여야 할 것으로 판단된다. 또한 모델계산 결과 우드칩 충진 습지에서 폐색에 도달하는데 약 2달 정도가 소요될 것으로 산출되었으나 실제로는 전혀 폐색 기미는 발생하지 않았는데 이는 강우시에만 운영되는 특성상 강우활동이 없는 무강우 기간 동안 포획된 유기물질이나 생물막이 자연적으로 분해되어 일정기간이 경과되면 공극이 회복되었다.

• 한국광학회지
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• 제14권1호
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• pp.23-32
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• 2003

타원법(ellipsometry)을 사용하여 광기록 매체용 Ge$_2$ Sb$_2$ Te$^{5}$ (GST) 박막의 성장과정에 따른 타원상수 Ψ와 $\Delta$를 측정하여. GST 박막의 최적성장조건을 연구하였다. 아르곤기체압력과 DC 출력 그리고 기판의 온도를 변화시키면서 GST 박막을 성장시켰다. 제작된 시료들의 분광타원 데이터를 모델링 분석하여 GST박막의 밀도분포를 구하고 한편으로는 GST 박막이 성장하는 동안 측정한 in situ 타원 성장곡선을 분석하여 박막의 밀도분포의 변화를 추적하였다. 아르곤기체압력이 7 mTorr일 때 박막의 상대적인 밀도분포가 고르게 되었고 DC출력이 증가함에 따라 그리고 기판의 온도가 증가함에 따라 GST 박막의 밀도 균일성은 크게 향상되었다. 주사형전자현미경(SEM)을 사용하여 최적 밀도 균일성을 가지는 성장조건(7 mTorr, 45 W, 15$0^{\circ}C$)에서 제작된 GST 시료가 가장 균일한 구조를 보여줌을 확인하였다. 균일한 밀도 분포를 가지는 GST 박막의 성장조건 확립을 통하여 여러번 기록/재생할 때 광기록 박막의 안정성을 유지하는데 크게 기여할 것이다.

• Asian-Australasian Journal of Animal Sciences
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• 제21권12호
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• pp.1785-1793
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• 2008

Fifty-four PIC barrows were used to evaluate the effects of lower dietary lysine content and energy level on carcass characteristics and meat quality in slaughter pigs. Pigs were allotted to one of three treatments by body weight with six replicate pens in each treatment. The dietary treatments for body weights of 20-50 kg, 50-80 kg and 80-90 kg were as follows, respectively: control diet (digestible energy 14.22 MJ/kg, lysine/DE 0.67 g/MJ, 0.53 g/MJ and 0.42 g/MJ); a low lysine group (digestible energy 14.22 MJ/kg, lysine/DE 0.49, 0.38 and 0.30 g/MJ); and a low lysine-low energy group or low nutrient group (digestible energy 13.11 MJ/kg, lysine/DE 0.49, 0.38 and 0.30 g/MJ). The daily weight gain, daily feed intake and feed efficiency were calculated in the overall growth period (nearly 12 weeks). Meanwhile, carcass characteristics and meat quality were evaluated at 60 and 90 kg body weight respectively. During the overall growth trial, lowering dietary lysine and nutrient level both decreased weight gain (p<0.05) and feed efficiency (p<0.01). At 60 kg body weight, decreasing dietary lysine and nutrient level noticeably decreased dressing percentage (p<0.01) and back fat depth at last rib of PIC pigs (p<0.01), but enhanced marbling scores (p<0.10), intramuscular fat content (p<0.10) and water loss rate (p<0.01) of the longissimus dorsi muscle. At 90 kg body weight, lean percentage (p<0.01) was evidently reduced by both lowering lysine content and nutrient level in the diet. However, the shoulder back fat depth (p<0.05) and marbling scores of the loin eye muscle (p<0.05) were increased; Lowering dietary nutrient level could improve back fat depth of 10th rib (p<0.01) and last rib (p<0.01), intramuscular fat content (p<0.10), redness (p<0.01) and water loss rate of the loin eye muscle (p<0.05), but decrease loin area (p<0.05). Finally, when comparing the 60 kg and 90 kg slaughter weights, it was found that the shoulder back fat depth (p<0.01, p<0.10), 6th-7th rib (p<0.01, p<0.01), 10th-rib (p<0.01, p<0.01) and last rib back fat depth (p<0.01, p<0.01) of the low lysine and low nutrient group were all obviously increased comparing with the control group. Taken together, the results showed that decreasing dietary lysine content and nutrient level increased intramuscular fat content and water loss rate of longissimus dorsi muscle; On the other hand, both lowering dietary lysine and nutrient level markedly compensated to increase back fat deposition in the later finishing period (body weight from 60 to 90 kg) in contrast to the control group.