In this study, we designed and manufactured a large angular contact ball bearing (LACBB) with low deformation using JIS-SUJ2 steel and analyzed changes in its structural characteristics and chemical composition upon heat treatment. The bearing was produced by hot forging and heat treatment including a quenching and tempering (Q/T) process, and its properties were analyzed using 4 mm thick specimens. A difference in the size distribution of the carbide in the outer and inner parts of the bearing was observed and it was confirmed that large and non-uniform carbide was distributed in the inner part of the bearing. After heat treatment, the hardness value of the outer part increased from 13.4 HRC to 61 HRC and the inner part increased from 8.0 HRC to 59.7 HRC. As a result of X-ray diffraction (XRD) measurements, the volume fraction of the retained austenite contained in the outer part was calculated to be 3.5~4.8 % and the inner part was calculated to be 3.6~5.0 %. The surface chemical composition and the content of chemical bonds were quantified through X-ray photoelectron spectroscopy (XPS), and a decrease in C=C bonds and an increase in Fe-C bonds were confirmed.

This study explores reducing the oxygen content of a commercial Ti-48Al-2Cr-2Nb powder to less than 400 ppm by deoxidation in the solid state (DOSS) using Ca vapor, and investigates the effect of Ca vapor on the surface chemical state. As the deoxidation temperature increases, the oxygen concentration of the Ti-48Al-2Cr-2Nb powder decreases, achieving a low value of 745 ppm at 1100oC. When the deoxidation time is increased to 2 h, the oxygen concentration decreases to 320pp m at 1100oC, and the oxygen reduction rate is approximately 78% compared to that of the raw material. The deoxidized Ti-48Al-2Cr-2nb powder maintains a spherical shape, but the surface shape changes slightly owing to the reaction of Ca and Al. The oxidation state of Ti and Al on the surface of the Ti-48Al-2Cr-2Nb powder corresponds to a mixture of TiO2 and Al2O3. As a result, the peaks of metallic Ti and Ti suboxide intensify as TiO2 and Al2O3 in the surface oxide layer are reduced by Ca vapor deposition

Using lanthanum zinc oxide (LZO) film with the ion-beam irradiation, uniform and homogeneous liquid crystal (LC) alignment was achieved. To fabricate the LZO thin film on glass substrate, solution process was conducted as a deposition method. Cross-polarized optical microscopy (POM) and the crystal rotation method reveal the state of LC alignment on the ion-beam irradiated LZO film. Between orthogonally placed polarizers, POM image showed constant black color with regular transmittance. Furthermore, collected incidence angle versus transmittance curve from the crystal rotation method revealed that the LC molecules on the ion-beam irradiated LZO film were aligned homogeneously. Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were conducted to reveal the relationship between the ion-beam irradiation and the LC alignment. The ion-beam irradiation changed the LZO film surface to rougher than before by etching effect. Numerical roughness values from AFM analysis supported this phenomenon specifically. XPS analysis showed the chemical composition change due to the ion-beam irradiation by investigation of O 1s, La 3d and Zn 2p spectra. The ion-beam irradiation induced the breakage of chemical bonds in the LZO film surface and this occurred surface chemical anisotropic characteristics for uniform LC alignment.

CFRP materials are one of the excellent lightweight materials of the next generation. Also, the CFRP materials are attracting materials form the global automotive industry. However, CFRP material is made at a high cost of carbon fiber as raw material, so research of production cost reduction into the development of molding equipment and molding process technology related to mass production for the automotive industry is actively administered. Generally, CFRP is known as a high corrosion-resistant material in which no corrosion occurs. However, the investigation of the relationship with corrosion behavior on the roughness of CFRP's conditions according to is rarely studied. In this paper, the surface roughness has conducted three surface roughness conditions given arbitrarily, and the electrochemical evaluation has performed under the electrolysis conditions of 5 wt.% NaCl, which is the salt-water test condition of vehicle parts in automotive industries. Moreover, the samples were analyzed with changes of microstructures by FE-SEM and chemical composition's variation by EDS before and after electrochemical evaluation.

용존 6가 우라늄은 다양한 화학종으로 존재하며, 화학종의 분포는 수용액의 pH에 의존한다. 산성 및 중성 근처의 pH 환경 에서는 대표적으로 UO2 2+, UO2OH+, (UO2)2(OH)2 2+, (UO2)3(OH)5 + 화학종이 공존한다. 수용액 속에 비결정성 실리카가 콜로이드 성질의 부유입자 상태로 존재할 때 용존 화학종은 실리카 표면에 쉽게 흡착된다. 이 연구에서는 표면 흡착 화학종의 분 포가 용존 화학종의 분포를 따르는지 조사하였다. 시료의 pH 값이 3.5-7.5인 조건에서 3종의 용존 화학종(UO2 2+, UO2OH+, (UO2)3(OH)5 +)과 2종의 표면 흡착 화학종(≡SiO2UO2, ≡SiO2(UO2)OH‐ 또는 ≡SiO2(UO2)3(OH)5 ‐)의 시간 분해 발광(luminescence) 스펙트럼을 측정하였다. pH 변화에 따른 각 화학종의 스펙트럼 변화 양상을 비교한 결과로 표면 흡착 U(VI) 화학종의 분포는 용존 U(VI) 화학종의 분포와 다르다는 것을 확인하였다.

리튬 덴드라이트의 효과적인 억제를 위해 유/무기 복합체를 리튬메탈 전극의 보호층으로 사용하였다. 유기물로는 PVDF-HFP가 사용되었으며 무기물로는 TiO2가 사용되었다. 유기물로 사용된 PVDF-HFP는 높은 유연성을 가지는 고분자로서 무기물의 matrix 역할을 하며, 무기물로 사용된 TiO2 나노입자는 보호막의 기계적 강도와 이온전도성을 향상시켜주는 역할을 하였다. 합성된 보호막은 SEM, AFM, XRD를 통하여 PVDF-HFP matrix에 TiO2가 잘 분산되어 있는 형태인 것을 확인할 수 있 었다. 또한 전기화학적 분석 결과, 향상된 기계적 물성과 이온전도성으로 인해 polymer-inorganic composite은 비교 샘플(untreated 와 PVDF-HFP 보호층) 대비 100번째 사이클까지 80%의 높은 쿨롱 효율 및 20 mV 미만의 낮은 과전압을 나타내었다.

In this study, the surface passivation process for InP-based quantum dots (QDs) is investigated. Surface coating is performed with poly(methylmethacrylate) (PMMA) and thioglycolic acid. The quantum yield (QY) of a PMMA-coated sample slightly increases by approximately 1.3% relative to that of the as-synthesized InP/ZnS QDs. The QYs of the uncoated and PMMA-coated samples drastically decrease after 16 days because of the high defect state density of the InP-based QDs. PMMA does not have a significant effect on the defect passivation. Thioglycolic acid is investigated in this study for the effective surface passivation of InP-based QDs. Surface passivation with thioglycolic acid is more effective than that with the PMMA coating, and the QY increases from 1.7% to 11.3%. ZnS formed on the surface of the InP QDs and S in thioglycolic acid show strong bonding property. Additionally, the QY is further increased up to 21.0% by the photochemical reaction. Electron–hole pairs are formed by light irradiation and lead to strong bonding between the inorganic and thioglycolic acid sulfur. The surface of the InP core QDs, which does not emit light, is passivated by the irradiated light and emits green light after the photochemical reaction.

Surface morphology and optical properties such as transmittance and haze effect of glass etched by physical and chemical etching processes were investigated. The physical etching process was carried out by pen type sandblasting process with 15~20 μm dia. of Al2O3 media; the chemical etching process was conducted using HF-based mixed etchant. Sandblasting was performed in terms of variables such as the distance of 8 cm between the gun nozzle and the glass substrate, the fixed air pressure of 0.5bar, and the constant speed control of the specimen stage. The chemical etching process was conducted with mixed etching solution prepared by combination of BHF (Buffered Hydrofluoric Acid), HCl, and distilled water. The morphology of the glass surface after sandblasting process displayed sharp collision vestiges with nonuniform shapes that could initiate fractures. The haze values of the sandblasted glass were quantitatively acceptable. However, based on visual observation, the desirable Anti-Glare effect was not achieved. On the other hand, irregularly shaped and sharp vestiges transformed into enlarged and smooth micro-spherical craters with the subsequent chemical etching process. The curvature of the spherical crater increased distinctly by 60 minutes and decreased gradually with increasing etching time. Further, the spherical craters with reduced curvature were uniformly distributed over the etched glass surface. The haze value increased sharply up to 55 % and the transmittance decreased by 90 % at 60 minutes of etching time. The ideal haze value range of 3~7 % and transmittance value range of above 90 % were achieved in the period of 240 to 720 minutes of etching time for the selected concentration of the chemical etchant.

이 연구의 목적은 폴리머의 물리적 혼합 또는 화학적 합성 방법을 통해 막증류 법에 사용되는 막의 소수성을 변화시킴으로써 막증류법의 수투과도 변화를 측정 하고자 한다. 막의 소수성을 향상시키기 위해, 물리적 혼합 방법으로 PTFE 을 섞어 준비하였고, 화학적 결합 방법으로는 Styrene, pentafluorostyrene 등을 ATRP 방법을 통해 합성하여 막을 준비하고, 그에 따른 화학적 구조를 FT-IR로 확인하였다. 두 방법을 통해 준비된 중공사 막을 MD에 적용하였을 때 순수 막과 비교하여 소수성 및 성능의 향상 여부를 확인하였다.

수처리용 MF 막의 소재로 널리 쓰이는 PVDF는 높은 소수성으로 인해 막 오염현상 등의 문제점을 발생시킨다. 본 연구에서는 이러한 현상을 해결하기 위해 PVDF 중공사막 표면과 기공 내부에 defluorination을 시켜 hydroxyl기를 형성하고 epoxy, aldehyde functional PEG를 grafting하여 기공 내부와 막 표면의 친수화를 달성하고자한다. 이를 통해 막 오염현상을 감소시킴은 물론 수투과도 향상 또한 기대할 수 있다. PVDF 중공사 표면에 grafting된 functional PEG를 확인하고, 개질된 막의 친수화 정도와 anti-fouling 특성을 평가하고자 한다.

수처리용 MF 막의 소재로 널리 쓰이는 PVDF는 높은 소수성으로 인해 막 오염현상 등의 문제점을 발생시킨다. 본 연구에서는 이러한 현상을 해결하기 위해 PVDF 중공사막 표면과 기공 내부에 defluorination을 시켜 hydroxyl기를 형성하고 epoxy, aldehyde functional PEG를 grafting하여 기공 내부와 막 표면의 친수화를 달성하고자한다. 이를 통해 막 오염현상을 감소시킴은 물론 수투과도 향상 또한 기대할 수 있다. PVDF 중공사 표면에 grafting된 functional PEG를 확인하고, 개질된 막의 친수화 정도와 장기운전 성능을 평가하고자 한다.

Physical and chemical changes in a polished wafer and in 2.5μm & 4μm epitaxially grown Si layer wafers (Epilayer wafer) after surface treatment were investigated. We characterized the influence of surface treatment on wafer properties such as surface roughness and the chemical composition and bonds. After each surface treatment, the physical change of the wafer surface was evaluated by atomic force microscopy to confirm the surface morphology and roughness. In addition, chemical changes in the wafer surface were studied by X-ray photoemission spectroscopy measurement. Changes in the chemical composition were confirmed before and after the surface treatment. By combined analysis of the physical and chemical changes, we found that diluted hydrofluoric acid treatment is more effective than buffered oxide etching for SiO2 removal in both polished and Epi-Layer wafers; however, the etch rate and the surface roughness in the given treatment are different among the polished 2.5μm and 4μm Epi-layer wafers in spite of the identical bulk structural properties of these wafers. This study therefore suggests that independent surface treatment optimization is required for each wafer type, 2.5μm and 4μm, due to the meaningful differences in the initial surface chemical and physical properties.

목적: 플라즈마 표면처리가 불화규소 아크릴레이트 재질의 RGP 콘택트렌즈의 물리화학적 특성에 미치는 영향을 분석하였다. 방법: RGP 렌즈 표면의 플라즈마 처리는 공기 중 상온에서 200 W로 수행하였으며, 처리시간은 0∼250초로 다르게 하였다. 습윤성을 평가하기 위해 접촉각을 측정하였다. 표면 성분은 X-선광전자분광분석기(XPS)로 관찰하고, 플라즈마 처리에 의한 실리케이트의 형성을 분석하였다. 표면의 형상과 거칠기는 원자현미경(AFM)으로 관찰하였다. 산소침투성의 변화는 전기분해 분석법으로 얻은 렌즈의 투과 전류값과 중심두께를 측정하여 비교하였다. 결과: 플라즈마로 표면 처리되면 초기에 접촉각이 급격히 감소하였으며, 처리되지 않은 표면에 비해 30%까지 감소하였다. 표면 성분의 탄소와 불소는 70% 이하로 감소했으나, 산소와 실리콘은 150% 이상 증가하였다. 표면에서 탄소가 감소하는 형태는 접촉각의 변화와 직접적으로 관계가 있었다. 플라즈마 표면처리에 의해 표면의 탄소와 불소는 휘발하고, 유리된 실리콘이 산소와 결합하여 표면에 친수성 실리케이트(SiOx, x=1.5∼2.0)가 형성되며, 실리케이트는 50% 이상 크게 증가하였다. 플라즈마 처리된 표면에서 원형이나 직각형의 돌출부가 관찰되고, 거칠기(RMS)는 40% 이상 증가하였다. 결론: RGP 콘택트렌즈를 공기 중에서 플라즈마 처리하면 표면에 친수성인 실리케이트가 형성되어 습윤성은 개선되지만 산소침투성에는 영향을 주지 않았다. 습윤성의 증가는 표면형상의 변화보다는 실리케이트의 형성이 더 큰 영향을 준 것으로 판단되었다. 또한 플라즈마 처리에 의해 표면에 국한되어 형성된 실리케이트가 열린 구조를 갖고 있어 산소침투성에 유의한 변화가 없었던 것으로 생각된다.

Al-based alloys have recently attracted considerable interest as structural materials and light weight materials due to their excellent physical and mechanical properties. For the investigation of the potential of Al-based alloys, a surface porous Al88Cu6Si6 eutectic alloy has been fabricated through a chemical leaching process. The formation and microstructure of the surface porous Al88Cu6Si6 eutectic alloy have been investigated using X-ray diffraction and scanning electron microscopy. The Al88Cu6Si6 eutectic alloy is composed of an α-Al dendrite phase and a single eutectic phase of Al2Cu and α-Al. We intended to remove only the α-Al phase and then the Al2Cu phase would form a porous structure on the surface with open pores. Both acidic and alkaline aqueous chemical solutions were used with various concentrations to modify the influence on the microstructure and the overall chemical reaction was carried out for 24 hr. A homogeneous open porous structure on the surface was revealed via selective chemical leaching with a H2SO4 solution. Only the α-Al phase was successfully leached while the morphology of the Al2Cu phase was maintained. The pore size was in a range of 1~5μm and the dealloying depth was nearly 3μm. However, under an alkaline NaOH, aqueous solution, an inhomogeneous porous structure on the surface was formed with a 5 wt% NaOH solution and the morphology of the Al2Cu phase was not preserved. In addition, the sample that was leached by using a 7 wt% NaOH solution crumbled. Al extracted from the Al2Cu phase as α-Al phase was dealloyed, and increasing concentration of NaOH strongly influenced the morphology of the Al2Cu phase and sample statement.

Single-walled carbon nanotubes (SWNTs)를 320 ℃에서 90분 동안 가열하여 비정질 탄소를 제거하고 남아 있는 금속 촉매를 제거하기 위해 염산에 24시간 처리하였다. 정제된 SWNT 표면에 산화반응을 통해 카복실기를 도입하였으며, 가혹한 환경으로 인해 길이가 짧아진 SWNT를 얻었다. 세정된 실리콘 웨이퍼를 3-aminopropyldiisopropylethoxysilane (3-APDIPES)의 톨루엔 용액에 담가 표면에 3-APDIPES의 자기 조립 단층막을 형성시켰다. SWNT의 카복실기와 3-APDIPES의 아미노기 사이의 산-염기 반응을 통해 생성되는 이온 사이의 정전기적 인력을 이용하여 실리콘 웨이퍼 표면에 SWNT를 배열하였다. Atomic Force Microscopy (AFM) 분석을 통해 반응시간과 농도에 따른 효과를 확인하였고, Transmission Electron Microscopy (TEM)을 이용해 산 처리 시간에 따른 효과를 확인하였다.

Multi-walled carbon nanotube (MWNT)를 황산과 질산의 혼산(3:1)에 넣고 상온에서 ultrasonication 을 가해주어 MWNT의 표면에 산화반응을 통하여 카복실기를 도입하였다. 세정된 실리콘 웨이퍼를 3-aminopropylethoxysilane (3-APDIPES)의 톨루엔 용액에 담그어 실리콘 웨이퍼 표면에 3-APDIPES의 자기 조립 단층막을 형성하였다. 이 과정에서 실리콘 웨이퍼 표면에 형성된 3-APDIPES 자기 조립 단층막의 두께는 8 Å 이며, 이 단층막이 매우 견고하게 실리콘 웨이퍼 표면에 결합되어져 있음을 확인하였다. MWNT의 카복실기와 3-APDIPES의 아미노기 사이의 산-염기 반응을 통하여 생성되는 이온 사이의 정전기적 인력을 이용하여 실리콘 웨이퍼 표면에 MWNT를 배열하였다. 이 때 얻어지는 MWNT의 배향은 수직 배향이 아니라 수평 배향임을 atomic force microscopy (AFM)와 field emission-scanning electron microscopy (FE-SEM) 분석을 통하여 확인하였다.