• Journal of the Korean Ceramic Society
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• v.37 no.1
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• pp.96-101
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• 2000

Comparative studies on microstructure, and mechanical and anti-oxidation properties between TiN and Ti-Si-N films were performed. The Ti-Si-N films were deposited on high-speed steel and silicon wafer substrates by plasma-assisted chemcial vapor deposition(PACVD) technique. The Si addition to TiN film caused to change the microstructure such as grain size refinement, randomly multi-oriented microstructure, and nano-sized codeposition of silicon nitride in the TiN matrix. The Ti-Si-N film, contains Si content of ∼7 at.%, showed the micro-hardness value of ∼3400 HK, which was higher than the pure TiN film whose hardness was ∼1500HK. The Ti-Si(7 at.%)-N film also showed much improved anti-oxidation properties compared with those of the pure TiN film. These properties were also related to the microstructure of Ti-Si(7 at.%)-N film was formed and retarded further oxidation of the nitridelayer. These properties were also related to the microstructure of Ti-Si(7 at.%)-N film which was characterized by nano-sized precipitates of silicon nitride phase in the TiN matrix and randomly oriented grains.

• Journal of the Korean Society for Heat Treatment
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• v.34 no.1
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• pp.17-24
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• 2021

In this study, Ti-X (X=Mn, Fe, Mo) powder alloys were designed and manufactured by both powder metallurgy (PM) and metal powder injection molding (MIM) process to improve strength and formability compared to CP-Ti powder materials. It was found that the lamellar microstructure consisted of α and β phases was formed in PM-processed alloys. However, MIM-processed alloys showed not the lamellar microstucture but the equiaxed α + β microstructure. It was also revealed that the contents of X component and feedstock were not affected to microstructure evolution. The reason why different microstructure was appeared between PM-processed and MIM-processed alloys is not clear yet, but supposed to be the effect of intersticial elements such as C, H and N derived from feedstock during debinding process of MIM.

• Journal of Technologic Dentistry
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• v.43 no.2
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• pp.35-41
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• 2021

Purpose: This study aimed to investigate the flexural strength and surface microstructure of the zirconia crown according to the number of glazing zirconia prostheses. Methods: The specimens were made as follows. A specimen without glazing: 1ea, first glazed specimens (group B): 10ea, second glazed specimens (group C): 10ea, third glazed specimens (group D): 10ea. Three-point measuring strength equipment and electron microscopes were used for strength measurement and microstructure observation. As for statistical analysis, one-way ANOVA and t-test (level of significance level=5%) were used to determine the difference in the change in flexural strength according to the number of glazing zirconia prostheses. Results: ANOVA analysis of groups B (1st glazing), C (2nd glazing), and D (3rd glazing) revealed that the change in strength between the groups is statistically significant (p=0.023). The Mann-Whitney test for each group revealed that the difference in flexural strength between groups B and C was not statistically significant (z=-0.302, p=0.762) while that between groups C and D was statistically significant (z=-0.257, p=0.01). Microstructure observation revealed 3 changes in the microstructure of the surface of the glaze powder were observed. Conclusion: According to the number of glazing zirconia prostheses, it was found that the difference in strength between groups was statistically significant, and changes in the microstructure were observed.

• Steel and Composite Structures
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• v.38 no.5
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• pp.583-597
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• 2021

This article develops a nonclassical model to analyze bending response of squared perforated microbeams considering the coupled effect of microstructure and surface stress under different loading and boundary conditions, those are not be studied before. The corresponding material and geometrical characteristics of regularly squared perforated beams relative to fully filled beam are obtained analytically. The modified couple stress and the modified Gurtin-Murdoch surface elasticity models are adopted to incorporate the microstructure as well as the surface energy effects. The differential equations of equilibrium including the Poisson's effect are derived based on minimum potential energy. Exact closed form solution is obtained for bending behavior of the proposed model considering the classical and nonclassical boundary conditions for both uniformly distributed and concentrated loads. The proposed model is verified with results available in the literature. Influences of the microstructure length scale parameter, surface energy, beam thickness, boundary and loading conditions on the bending behavior of perforated microbeams are investigated. It is observed that microstructure and surface parameters are vital in investigation of the bending behavior of perforated microbeams. The obtained results are supportive for the design, analysis and manufacturing of perforated nanobeams that commonly used in nanoactuators, nanoswitches, MEMS and NEMS systems.

• Journal of the Korean Society for Heat Treatment
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• v.36 no.5
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• pp.277-284
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• 2023

Hardness and damping characteristics of fine discontinuous precipitates (DPs) microstructure generated by low temperature long term isothermal aging were investigated in comparison with those of T6 heat-treated microstructure composed of DPs and continuous precipitates (CPs) in Mg-9%Al alloy. In this study, T6 and fine DPs microstructures were obtained by isothermal aging at 453 K for 24 h and at 413 K for 336 h, respectively, after solution treatment at 693 K for 24 h. The DPs microstructure exhibited higher hardness than the T6 microstructure, which is related to the lower (α + β) interlamellar spacing of the DPs. The DPs microstructure possessed better damping capacity than the T6 microstructure in the strain-amplitude independent region, whereas in the strain-amplitude dependent region, the reverse behavior was observed. The damping tendencies depending on strain-amplitude were discussed based on the microstructural features of the T6 and DPs microstructures.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.31 no.3
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• pp.133-140
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• 2018

This paper is concerned with the 2-D micostructure generation for $Ni-A{\ell}_2O_3$ dual-phase composite materials and the numerical analysis of mechanical characteristic of hierarchical models of microstructure which are defined in terms of the scale of microstructure. The microstructures of dual-phase composite materials were generated by applying the mathematical RMDF(random morphology description functions) technique to a 2-D RVE of composite materials. And, the hierarchical models of microstructure were defined by the number of Gaussian points. Meanwhile, the volume fractions of metal and ceramic particles were set by adjusting the level of RMD functions. The microstructures which were generated by RMDF technique are definitely random even though the total number of Gaussian points is the same. The randomly generated microstructures were applied to a 2-D beam model, and the variation of normal and shear stresses to the scale of microstructure was numerically investigated. In addition, through the crack analyses, the influence of RMDF randomness and Gauss point number on the crack-tip stress is investigated.

• Korean Journal of Materials Research
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• v.17 no.9
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• pp.453-457
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• 2007

Interest in use of ink-jet printing for pattern-on-demand fabrication of metal interconnects without complicated and wasteful etching process has been on rapid increase. However, ink-jet printing is a wet process and needs an additional thermal treatment such as an annealing process. Since a metal ink is a suspension containing metal nanoparticles and organic capping molecules to prevent aggregation of them, the microstructure of an ink-jet printed metal interconnect 'as dried' can be characterized as a stack of loosely packed nanoparticles. Therefore, during being treated thermally, an inkjet-printed interconnect is likely to evolve a characteristic microstructure, different from that of the conventionally vacuum-deposited metal films. Microstructure characteristics can significantly affect the corresponding electrical and mechanical properties. The characteristics of change in microstructure and electrical resistivity of inkjet-printed silver (Ag) films when annealed isothermally at a temperature between 170 and $240^{\circ}C$ were analyzed. The change in electrical resistivity was described using the first-order exponential decay kinetics. The corresponding activation energy of 0.44 eV was explained in terms of a thermally-activated mechanism, i.e., migration of point defects such as vacancy-oxygen pairs, rather than microstructure evolution such as grain growth or change in porosity.

• Journal of Powder Materials
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• v.22 no.1
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• pp.21-26
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• 2015

In this study, the control of microstructure for increasing surface roughness of Al with an electro-chemical reaction and a post treatment is systematically investigated. The Al specimen is electro-chemically treated in an electrolyte. In condition of the post treatment at $100^{\circ}C$ for 10 min, a change of the surface microstructure occur at 50V (5 min), and a oxidized layer is at 400V, to which lead a decreasing surface roughness. The minimum temperature of the post treatment for a change of microstructure is $80^{\circ}C$. Moreover, in the condition of 300V (5 min), the electro-chemical reaction is followed by the post treatment at $100^{\circ}C$, the critical enduring time for the change of microstructure is 3 min. The longer post treatment time leads to the rougher surface. The treated Al specimen demonstrate better heat release ability owing to the higher surface roughness than the non-treated Al.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.216-216
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• 2009

This paper describes a novel processing technique for the fabrication of polymer-derived SiCN (silicone carbonitride) microstructures for extreme microelectromechanical system (MEMS) applications. A polydimethylsiloxane (PDMS) mold was formed on an SU-8 pattern using a standard UV photolithographic process. Next, the liquid precursor, polysilazane, was injected into the PDMS mold to fabricate free-standing SiCN microstructures. Finally, the solid polymer SiCN microstructure was cross-linked using hot isostatic pressure at $400^{\circ}C$ and 205 bar. The optimal pyrolysis and annealing conditions to form a ceramic microstructure capable of withstanding temperatures over $1400^{\circ}C$ were determined. Using the optimal process conditions, the fabricated SiCN ceramic microstructure possessed excellent characteristics includingshear strength (15.2 N), insulation resistance ($2.163{\times}10^{14}\;{\Omega}$, and BDV (1.2 kV, minimum). Since the fabricated ceramic SiCN microstructure has improved electrical and physical characteristics compared to bulk Si wafers, it may be applied to harsh environments and high-power MEMS applications such as heat exchangers and combustion chambers.

• Journal of the Korean Ceramic Society
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• v.34 no.12
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• pp.1240-1246
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• 1997

Silicon carbides with self-reinforced microstructure which hore a small grain matrix and dispersed large grains with rod-like type were prepared by the liquid-phase sintering and the control of starting phases of raw materials. The specimens with self-reinforced microstructure could be obtained from the compacts with mixed compositions of $\alpha$-SiC and 10-50 % $\beta$-SiC powders and by the pressureless sintering at 185$0^{\circ}C$ for 5h. Large grains with rod or plate-like types were 4H-SiC and small grains with equi-axed type were 6H-SiC. Fracture grains with rod or plate-like types were 4h-SiC and small grains with equi-axed type were 6H-SiC. Fracture toughness of specimens with self-reinforced microstructure was increased by the crack deflection and formation of microcracking due to the existence of rod-like large grains during crack propagation.