• Journal of the Korean institute of surface engineering
• /
• v.21 no.4
• /
• pp.176-182
• /
• 1988

Effects of Cr, Ni and W on the anodic polarization behavior were investigated for Fe-Cr-Ni-W alloys in deaerated 1N HCI solution. Surface films formed on the polarization were analysed using AES, SEM and EDAX. A higerconcentration of tungten was found in the surface oxide film compared to the matrix. It played an importanet role on incresing the stability of the passive film. The presence of an adequate amount of Cr was essential to increase the pitting resistance of the alloys in acid chloride media. Under 12 wt%cr,alloys containing 6wt%W did not exhidit any passivity at all. The main role of Ni was to control the microstructure rather than to modify the corrosion resistance. In 23 cr-14Ni-^W alloy, the duplex microstructure of ferrite($\delta$-phase) in an austenic matrix was developed. The reson why proferred pitting appeared in austenite and ferrite/austenite interface was that ferrite had more amount of Cr and W than austenite.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2001.06a
• /
• pp.19-20
• /
• 2001

• Journal of the Korean Society for Heat Treatment
• /
• v.32 no.3
• /
• pp.118-123
• /
• 2019

The aim of this study investigates the feasibility of scanning acoustic microscope (SAM) with high frequency transducer for material degradation. The test specimen was prepared by artificial heat treatment of Co-base superalloy. The high frequency 200 MHz acoustic lens was used to generate the leaky surface acoustic wave (LSAW) on the test specimens. The matrix precipitates coarsened with thermal aging time, and then grow up to several tens of micrometers. The velocity of LSAW decreased with increasing aging time. Also, it has a good correlation between LSAW and hardness. Consequently, V(z) curve methods of SAM using high frequency transducer is useful tool to evaluate the heat treatment effects on microstructure.

• International Journal of Concrete Structures and Materials
• /
• v.8 no.4
• /
• pp.327-333
• /
• 2014

The objective of this work was to examine the influence of carbonation on the microstructure of cement materials. Different materials, which were CEM I mortar and paste, CEM II mortar and paste, were carbonated at $20^{\circ}C$, 65 % relative humidity and 20 % of $CO_2$ concentration. The specific surface area and pore size distribution were determined from two methods: nitrogen adsorption and water adsorption. The results showed that: (1) nitrogen adsorption and water adsorption do not cover the same porous domains and thus, we observed conflicts in the results obtained by these two techniques; (2) the CEM II based materials seemed to be more sensible to a creation of mesoporosity after carbonation than the CEM I based materials. The results of this study also helped to explain why observations in the literature diverge greatly on the influence of carbonation on specific surface area.

• Korean Journal of Materials Research
• /
• v.17 no.9
• /
• pp.500-506
• /
• 2007

The effects of anisotropic surface energy on the microstructure development of porous materials have been studied through Monte Carlo simulation using a three dimensional lattice. The changes in porosity ($f_v$), mean grain diameter ($D_s$), fraction of connected pores ($f_{v,c}$) and contiguity of the solid phase (C) were examined in cases with three different ${\gamma}_{SV}$ relations and initial grain diameters ($D_{s,o}$). It has been found that larger ${\gamma}_{SV}$ enhances sintering of particles and increases C and does not change $D_s$. And Introducing anisotropic ${\gamma}_{SV}$ brought an increase in $f_v$ and $f_{v,c}$ and an decrease in $D_s$ and C, and this tendency become more marked for fine $D_{s,o}$.

• Journal of the Korean institute of surface engineering
• /
• v.26 no.5
• /
• pp.245-254
• /
• 1993

The effects of pulse current electrolysis conditions on the composition and the microstructure of Ag-Sn alloy were studied by using a pyrophosphate bath. Both cathode current efficiency and throwing power of alloy deposits formed under pulse plating conditions, decreased with increasing mean current density, and lower than those under D.C. electrolysis condition. Tin content of Ag-Sn alloy decreased noticebly with in-creasing the mean current density, while it increased with the increase of On-time from 1 to 10 ms. The pre-ferred orientation of Ag-Sn alloy changed with increasing cathode overpotential in the sequence of (100)longrightarrow(100)+(111)longrightarrow(111) at $20^{\circ}C$ and (110)longrightarrow(111)longrightarrow(111)+(100) at $30^{\circ}C$. The effective crystal grain size of the alloy was decreased by decreasing temperature from $30^{\circ}C$ to $20^{\circ}C$ and the surface structure of them was related to the preferred orientation.

• Journal of the Korean institute of surface engineering
• /
• v.37 no.1
• /
• pp.58-63
• /
• 2004

The oxidation behavior of Ti-Nb alloys was studied in dry atmosphere. After vacuum arc melting and hot rolling treatment, Ti-Nb alloys were oxidized at $450^{\circ}C$∼$750^{\circ}C$. The oxidation behaviors between matrix and oxide scale were analyzed by SEM, XPS and XRD. Ti-Nb alloys had higher oxidation resistance than pure Ti at $750^{\circ}C$. XPS analysis of oxide film revealed that $TiO_2$ oxide was formed on the top of surface. The weight gains during the oxidation increase rapidly at temperature above $600^{\circ}C$ which obey the parabolic law.

• Journal of Periodontal and Implant Science
• /
• v.37 no.2
• /
• pp.251-263
• /
• 2007

The present study was performed to evaluate the effects of Tetracycline-HCI on the microstructure change of SLA implant surface according to application time. In the Tetracycline-HCI group, 6 implants were rubbed with sponges soaked $50mg/m{\ell}$ Tetracycline-HCI solution for O.5min., lmin., 1. 5min., 2min., 2.5min. and 3min. In the saline group. another 6 implants conditioned with sponges soaked saline using same methods. One implant wasn't conditioned anything. Then, the changes of surface roughness values were evaluated by optical interferometer & specimens were processed for scanning electron microscopic observation. The results of this study were as follows: 1. In both Tetracycline-HCI group & saline group, there are no significant differences between surface roughness values before & after surface detoxification. And in scanning electron microscopic observation. there are slightly changes of implant surface structures but this changes were not significant by comparison with no treatment implant surface. 2. In the changes of surface roughness values & the scanning electron microscopic observation, there were no significant differences between saline & Tetracycline-HCI groups. In conclusion, the detoxification with $50mg/m{\ell}$ Tetracycline-HCI within 3 minutes can be applied for treatment of peri-implantitis in SLA surface implants. without surface microstructure changes.

• Journal of the Korean institute of surface engineering
• /
• v.25 no.2
• /
• pp.90-96
• /
• 1992

Thed effects of sputter gas pressure and substrate surface micro-roughness on the microstructure and surface topography have been investigated in the Cu thin films sputter deposited onto polyimide substrates. The surface roughness of polyimide was controlled by oxygen rf plasma treatment. In the Cu film deposited at the pressure of 5 mtorr, the surface is smooth and the columnar structure is not visible regardless of polyimide surface more open boundaries. The polyimide surface roughness enhances these effects, These phenomena can be explained in therm of atomic shadowing effect.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.26 no.11
• /
• pp.1691-1698
• /
• 1989

Gas sensing effects produced by adsorptive reaction between specimen surface and gases are expected to be influenced greatly by the state of the speimen surface. In this study, Co1-xMgxO ceramics oxygen sensors were prepared by pressing at 0.3-1.5ton/cm\ulcornerwith or without binder, intending to change porosity and average grain size on the surface purposely. The composition ratio of CoO to MgO was fixed at 1:1(mol.%). Microstructure of prepared Co0.5Mg0.5O ceramics were observed, the electrical properties and the sensitivity characteristics for oxygen gas were investigated in the device temperature range of 700-1000\ulcorner and for oxygen partical pressure range of 1-10**-4 atm. Temperature dependence of the resistivity of the specimen showed NTC behavior, average grain size increased and porosity decreased with increasing compaction pressure. The slope of the resistivity of the specimen on the oxygen partial pressure decreased with increasing average grain size and with decreasing porosity. Particularly, specimen pressed by 0.3 and 0.5 ton/cm\ulcornershowed the highest sensitivity to oxygen gas.