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전기화학적 분석을 통해 산출된 코팅 결함율이 트라이볼로지적 특성에 미치는 영향 평가
김우중(Woo-Jung Kim),안승호(Seung-Ho Ahn),김호건(Ho-Gun Kim),김정구(Jung-Gu Kim),조정우(Chung-Woo Cho),이영제(Young-Ze Lee) 한국트라이볼로지학회 2004 한국트라이볼로지학회 학술대회 Vol.38 No.-
Recently, many of the current development in surface modification engineering are focused on multilayered coatings. Multilayered coatings have the potential to improve the tribological properties. Four different multilayered coatings were deposited on AISI D2 steel. The prepared samples are designed as WC-Ti0.6Al0.4N, WC-Ti0.6Al0.4N, WC-Ti0.53Al0.47N and WC-Ti0.43Al0.57N. The multilayered coatings were investigated with respect to coating surface and cross-sectional morphology, roughness, adhesion, hardness, porosity and tribological behavior. Especially, wear tests of four multilayered coatings were performed by using a ball-on-disc configuration with a linear sliding speed of 0.017 m/sec, 5.38 N load. The tests were carried out at room temperature in air by employing AISI 52100 steel ball (HR = 66) having a diameter of 10 ㎜. The surface morphology, and topography of the wear scars of samples and balls have been determined by using scanning electron spectroscopy (SEM). Also, wear mechanism was determined by using SEM coupled with EDS. Results have showed an improved wear resistance of the WC-Ti1-xAlxN coatings with increasing of Al concentration.
전기화학적 분석을 통해 산출된 코팅 결함율이 트라이볼로지적 특성에 미치는 영향 평가
김우중(Woo-Jung Kim),안승호(Seung-Ho Ahn),김호건(Ho-Gun Kim),김정구(Jung-Gu Kim),조정우(Chung-Woo Cho),이영제(Young-Ze Lee) 한국트라이볼로지학회 2004 한국윤활학회지(윤활학회지) Vol.20 No.6
Many of the current development in surface modification engineering are focused on multilayered coatings, which have the potential to improve the tribological properties. Four different multilayered coatings were deposited on AISI D2 steel in this study. The prepared samples are designed as WC-Ti_(0.6)Al_(0.4)N, WCTi_(0.53)Al_(0.47)N, WC-Ti_(0.5)Al_(0.5)N and WC-Ti_(0.43)Al_(0.57)N. The multilayered coatings were investigated with respect to coating surface and cross-sectional morphology, roughness, adhesion, hardness, porosity and tribological behaviors. Especially, wear tests of four multilayered coatings were performed by using a ball-on-disc configuration with a linear sliding speed of 0.017 m/sec and a normal load of 5.38 N load. The tests were carried out at room temperature in air by employing AISI 52100 steel ball (H_R = 66) having a diameter of 10 ㎜. The surface morphology, and topography of the wear scars of samples and balls have been determined by using scanning electron spectroscopy (SEM). Also, wear mechanism was determined by using SEM coupled with energy-dispersive spectroscopy (EDS). Results have showed an improved wear resistance of the WC- Ti_(1-x)AlxN coatings with increasing of Al (aluminum) concentration.
점막하 침윤 조기위암 환자에서 VEGF-C와 COX-2 발현의 임상적 의의
조윤정,이정의,이관주,박조현,박승만,전해명,안창준,김정구,이동호,이상철,Cho, Yun-Jung,Lee, Jung-Uee,Lee, Kwan-Ju,Park, Cho-Hyun,Park, Seung-Man,Jeon, Hae-Myung,Ahn, Chang-Joon,Kim, Jeong-Goo,Lee, Dong-Ho,Lee, Sang-Chul 대한위암학회 2009 대한위암학회지 Vol.9 No.3
목적: Vascular endothelial growth factor (VEGF)-C와 -D 및 Cyclooxygenase (COX)-2는 위암에서 림프절 전이와 연관이 있다고 알려져 있다. 이에 저자들은 점막하 침윤 조기위암에서 VEGF-C와 -D 및 COX-2의 발현과 림프절 전이 등을 포함하는 다양한 임상병리학적 인자와의 관련성을 알아 보고자 하였다. 대상 및 방법: 1991년 1월부터 2007년 10월까지 본원에서 점막하 침윤 조기위암으로 수술을 시행 받은 85명의 환자를 대상으로 VEGF-C, -D 및 COX-2와 VEGF-C에 대한 면역 조직화학 염색을 시행하였다. 염색의 결과에 따라 환자군을 나누어 다양한 임상병리학적 인자와의 연관성을 조사하였고, 또 이 세 가지 인자들 상호 간의 연관 관계를 분석하였다. 결과: 전체 85명의 환자 중 16명이 림프절 전이가 있었다(18.8%). VEGF-C는 34.1% VEGF-D는 22.3% 그리고 COX-2는 37.6%가 양성으로 판정되었다. 이 중 VEGF-C와 COX-2 모두 림프절 전이와 유의한 상관관계를 보였고(P<0.001, P=0.023). VEGF-D와 연관성을 보이는 인자는 확인하지 못하였다. 또 VEGF-C와 COX-2의 발현은 밀접한 상관관계를 보였다(P=0.001). 결론: 점막하 침윤 조기위암에서 VEGF-C와 COX-2는 림프절 전이와 연관이 있고, 따라서 이 두 인자가 점막하 침윤 조기위암의 림프절 전이를 예측하는 인자로서의 가능성이 있다고 할 수 있겠다. Purpose: Lymph node metastasis is an important factor in determining prognosis and therapeutic options for early gastric cancer (EGC) patients. Vascular endothelial growth factor (VEGF)-C and D are known as lymphangiogenic factors, and cyclooxygenase (COX)-2 is thought to play a role in lymph node metastasis in gastric carcinoma. This study was designed to determine whether the expression of VEGF-C, VEGF-D, and COX-2 is associated with clinicopathologic factors, especially lymph node metastasis in EGCs invading the submucosa. Materials and Methods: Tissue samples were obtained from 85 Patients undergoing standard gastrectomy with lymph node dissection between 1991 and 2007 in the Department of Surgery of Daejeon St. Mary's Hospital in Daejeon, Korea. All patients were diagnosed with gastric cancers and submucosal invasion. We examined the expression of VEGF-C, VEGF-D, and COX-2 using immunohistochemical methods. Results: Of the 85 patients, 16 (18.8%) had lymph node metastasis. VEGF-C, VEGF-D, and COX-2 were positively expressed in 34.1% (29/85), 22.3% (19/85), and 37.6% (32/85) of the patients. VEGF-C and COX-2 expression was significantly correlated with lymph node metastasis (P<0.05). A positive correlation existed between VEGF-C and COX-2 expression (P< 0.001). Conclusion: VEGF-C and COX-2 expression is associated with lymph node metastasis in gastric cancer with submucosal invasion. VEGF-C and COX-2 may thus be predictive markers for lymph node metastasis in EGC patients with submucosal invasion.
AISI D2강 위에 다층으로 증착된 WC-Ti_(1-X)Al_(X)N 코팅의 국부부식 거동에 관한 연구
안승호,이정호,김호건,김정구,한전건 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.9
Multilayered WC-Ti_(1-x)Al_(x)N coatings are characterized by periodically repeated structures of lamellae of WC-Ti/WC-Ti_(1-x)Al_(x)N. WC-Ti_(1-x)Al_(x)N coatings of changing Al concentration were deposited on AISI D2 steel by high-ionization sputtered plasma vapor deposition (PVD). The Al concentration could be controlled by using evaporation source for Al and fixing the evaporating rate of other metals. Four kinds of WC-Ti_(1-x)Al_(x)N coatings were prepared: WC-Ti_(0.6)Al_(0.4)N, WC-Ti_(0.53)Al_(0.47)N, WC-Ti_(0.5)Al_(0.5)N and WC-Ti_(0.43)Al_(0.57)N. The corrosion behavior of WC-Ti_(1-x)Al_(x)N coatings was investigated using electrochemical techniques in deaerated 3.5% NaCl electrolyte (galvanic corrosion test, potentiodynamic polarization test, electrochemical impedance spectroscopy and Mott-Schottky method) and surface analyses (GDOES, SEM and EDS). Particular attention was paid to the effect of growth defects on the coating properties related to the corrosion behavior. The results of the coating and substrate galvanic corrosion test showed low galvanic current densities. In the potentiodynamic polarization test and EIS measurement, the corrosion current density of WC-Ti_(0.5)Al_(0.5)N was lower than others and presented higher R_(ct) values than others after 240 h immersion time. This could be attributed to the formation of a Ti oxide, which promotes partial closing of the defects. Capacitance values obtained from EIS as a function of different potentials (C^(-2) vs E) showed that the oxide layer exhibited an n-type semiconductor behavior.
다층박막 WC-Cr_(1-x)Al_(x)N의 Al 함량에 따른 부식특성에 관한 연구
이정호,안승호,김정구 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.11
Multilayered WC-Cr_(1-x)Al_(x)N coatings were deposited on AISI D2 steel by cathodic arc ion plating process (CAIP). The Al concentration was controlled by using evaporation source for Al and fixing the evaporation rate of the other metals (WC alloy and Cr). Five types of WC-Cr_(1-x)Al_(x)N were deposited, i.e., WC-Cr_(0.6)Al_(0.4)N, WC-Cr_(0.57)Al_(0.43)N, WC-Cr_(0.53)Al_(0.47)N, WC-Cr_(0.48)Al_(0.52)N, and WC-Cr_(0.45)Al_(0.55)N. The corrosion behavior in deaerated 3.5 wt.% NaCl solution for the prepared samples was investigated by electrochemical tests (potentiodynamic polarization test, galvanic corrosion test, electrochemical impedance spectroscopy (EIS)) and surface analyses (scanning electron microscopy (SEM), X-ray diffractometry (XRD), glow discharge optical emission spectroscopy (GDOES), and electron probe micro analyzer (EPMA)). The results from potentiodynamic polarization test showed that the WC-Cr_(0.48)Al_(0.52)N coating with the lower porosity (0.144) enhanced the corrosion resistance. Galvanic corrosion test was accomplished using the galvanic couple between the substrate and the WC-Cr_(1-x)Al_(x)N coating. The WC-Cr_(0.6)Al_(0.4)N showed a higher galvanic current density. In EIS measurements, the WC-Cr_(0.48)Al_(0.52)N coating showed an increased charge transfer resistance (R_(ct)). The measured electrochemical tests indicated that the WC-Cr_(0.48)Al_(0.52)N coating with the lower corrosion current density (3.023 μA/㎠) and higher charge transfer resistance (158.7 kΩ㎠) enhanced corrosion resistance.
인공고관절용 스테인리스강 316L에 증착된 다이아몬드상 카본 필름의 전기화학적 특성에 관한 연구
김호건,안승호,김정구,박세준,이광렬 대한금속재료학회 2004 대한금속·재료학회지 Vol.42 No.4
Diamond-like carbon (DLC) films have several advantages in applications such as high hardness, chemical inertness, low friction and electrical insulation. Furthermore, DLC-coated STS 316L films have been reported to have a good biocompatibility, such as the absence of inflammatory response. Thus, corrosion resistance is the first consideration for the biomaterials to be used in the body. DLC films have been deposited onto substrates of STB 316L for artificial hip joints using r.f PACVD (plasma-assisted chemical vapor deposition) with C_(6)H_(6) and mixture of C_(6)H_(6) and SiH_(4) as the process gases. Three kinds of DLC-coated films were prepared as a function of diverse bias voltage and Si incorporation. Corrosion behavior of DLC films was investigated by electrochemical techniques (potentiodynamic polarization test and electrochemical impedance spectroscopy) and surface analyses (atomic force microscopy and scanning electron microscopy). The electrolyte used in his test was a 0.89%NaCl solution of pH 7.4 at temperature 37℃. Electrochemical measurements showed that DLC films with higher bias voltage and Si incorporation could improve corrosion resistance in the simulated body fluid environment. (Received December 5, 2003)
Cu-6Ni-4Sn 합금에서 Cr 첨가에 따른 전기화학적 특성에 관한 연구
박창규,김정구,안승호,한승전 대한금속재료학회 2005 대한금속·재료학회지 Vol.43 No.3
Corrosion characteristics of Cu-6%Ni-4%Sn-x%Cr alloys in a acid-chloride solution (0.1M H₂SO₄+ 0.0056M NaCl) at pH = 6, were studied as a function of chromium addition. Three kinds of Cu-6%Ni-4%Sn-x%Cr alloys were prepared by melting, and casting, followed by thermomechanical treatments. The corrosion behavior of Cu-6%Ni-4%Sn-x%Cr alloys was investigated by electrochemical corrosion tests (potentiodynamic polarization test, electrochemical impedance spectroscopy) and surface analyses (optical microscopy, electron probe micro analysis, scanning electron microscopy). Cr additions were found to prevent the localized corrosion behavior. This is the reason that the small addition of Cr promoted the decomposition behaviors of the supersaturated solid solution a in Cu-6%Ni-4%Sn alloy, i.e., the number of like-Sn-rich carbide impurities (LCI), which increased the galvanic effect between the matrix and the LCI, decreased with increasing the Cr addition. (Received September 8, 2004)