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Si3N4/Cu-Ag-Ti-Al 계 브레이징 합금계면에 형성된 반응생성물의 규명
강춘식,이우천 대한금속재료학회(대한금속학회) 1992 대한금속·재료학회지 Vol.30 No.6
Joining of 304 stainless steel to Si₃N₄ ceramic using Cu-Ag-Ti-Al braze alloy was made in vacuum furnace. For the joint showing shear strength value of more than 202 ㎫, reaction products formed at the interface between Si₃N₄ and brazing alloy were investigated by O. M., SEM, EDS, WDS, XRD and X-AEM. The redox reaction of Si₃N₄ with Ti results in the formation of particulate TiN and continuous Ti_5Si₄ layers at the nearest interface. For a Cu-Ag-Ti alloy the FeTiSi on those layers was uniformly formed by solid-state reaction of Ti_5Si₄ with Fe segregated/diffused from stainless steel. But for a Cu-Ag-Ti-Al alloy the M_(1.5)Ti(M : Fe, Cr, Fe/Cr=6.4) compounds were locally formed on the Ti_5Si₄ layer and in the brazement. Titanium irregularly erodes the Si₃N₄ surface, resulting in the formation of local intrusions of TiN particles into the substrate. EDAX analyses showed that Fe and Cr diffused through the glassy phase of Si₃N₄ in the neighborhood of interface.
Protease-activated Receptor 2 is Associated with Activation of Human Macrophage Cell Line THP-1.
강춘식,이영미,김병수,문우성,김대기,태진 대한면역학회 2005 Immune Network Vol.5 No.4
Background: Protease-activated receptor 2 (PAR2) belongs to a family of G protein- coupled receptors activated by proteolytic cleavage. Trypsin-like serine proteases interact with PAR2 expressed by a variety of tissues and immune cells. The aim of our study was to investigate whether PAR2 stimulation can lead to the activation of human macrophages. Methods: PAR2-mediated proliferation of human macrophage cell line THP-1 was measured with MTT assay. We also examined the extracellular regulated kinase (ERK) phosphorylation and cytokine production induced by trypsin and PAR2-agonist using western blot and enzyme-linked immunosorbent assay (ELISA), respectively. Results: Treatment of trypsin or PAR2-activating peptide increased cell proliferation in a dose-dependent manner, and induced the activation of ERK1/2 in THP-1 cells. In addition, trypsin-induced cell proliferation was inhibited by pretreatment of an ERK inhibitor (PD98059) or trypsin inhibitor (SBTI). Moreover, PAR2 activation by trypsin increased the secretion of TNF-α in THP-1 cells. Conclusion: There results suggest that PAR2 activation by trypsin-like serine proteases can induce cell proliferation through the activation of ERK in human macrophage and that PAR2 may play a crucial role in the cell proliferation and cytokine secretion induced by trypsin-like serine proteases.
B 를 삽입재로 사용한 STS 304 강의 등온응고확산접합
강춘식,정재필,이충도 대한금속재료학회(대한금속학회) 1993 대한금속·재료학회지 Vol.31 No.3
A new diffusion bonding method (named as Melting Induced Diffusion(MID) bonding) which aimed to make better Transient Liquid Phase(TLP) bonding was developed and applied to the bonding of 304/304 stainless steel. In this research boron powder was used as a insert metal. The width of reacted layer of the bonded joint had linear relationship with square root of bonding time. And the bonded ratio of the joint increased with bonding time. As a result of tension test, tensile strength far room temperature were about 200㎫.
마그네슘합금의 부식거동에 미치는 석출상의 Chunk Breakage
강춘식,신광선,이충도 대한금속재료학회(대한금속학회) 2001 대한금속·재료학회지 Vol.39 No.1
In present study, the chunk breakage of precipitate and the negative difference effect which is a typical electrochemical behavior of Mg-alloy was investigated. In order to estimate the effect of precipitate, the calibration curves were obtained by XRD analyses(internal standard method). The chunk breakage of precipitate was observed under open circuit potential and maintained its original morphology. And, it revealed that the fraction of precipitate in corrosion products was approximately same as the fraction of precipitate in as-cast alloy. This is because of the corrosion behavior which the Mg-rich matrix is preferentially dissolved against the precipitate. Therefore, it was considered that the fraction of precipitate has a role of fixed factor on the corrosion rate of as-cast alloy. Also, the negative difference effect is arisen because the corrosion behavior of Mg-rich matrix is varied by the Al content, e. g. corrosion behavior of surface protective film. And, it reveals that the chunk breakage of precipitate operates only as a factor for the variation of the degree of difference effect(Δ).
Si3N4-304 스테인리스강 접합체의 계면조직과 접합강도에 대한 Ag-Cu 기 브레이징 합금내 첨가원소의 영향 (1) : Mo 첨가 영향 Effect of Mo Addition
강춘식,이우천 대한금속재료학회(대한금속학회) 1991 대한금속·재료학회지 Vol.29 No.10
Joinning of 304 stainless steel to Si₃N₄, ceramic using Cu-48%Ag-3.8%Ti brazing alloy was made in vacuum furnace. Effect of Mo addition in Cu-Ag-Ti alloy, brazing temperature, and brazing time on interfacial reactions and banding strength of Si₃N₄-304 joints were investigated. Bonding strength was determined by fracture shear loading and high shear strength value of more than 180 ㎫ were obtained for joints brazed with Cu-Ag-Ti- Mo alloy at 1083 K for 1.2 ks. The strong bonding is attritutable to the formation of FeTiSi and TO_5Si₄ by redox reaction between Si₃N₄ and Ti at Si+3N₄ ceramic interface. Thickness of interfacial reaction layer was increased and bonding strength was decreased as brazing temperature and brazing time were increased. It was found that interfacial reaction was retarded by Mo addition.