• Journal of the Korean institute of surface engineering
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• v.52 no.4
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• pp.227-232
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• 2019

Mo-N based coatings have been studied for enhancing mechanical characteristics of thin films. In the case of Mo-X-N coatings, the microstructure and mechanical properties can be affected by the addition of the third element. In this work, Mo-Cu-N coatings were successfully fabricated with varying the Cu content from 4.5 at% to 31 at% by the co-sputtering method. Thus, properties of the coatings were analyzed by EDS, SEM, XRD, AFM, nano indentation and scratch test techniques. From observed results, MoxN bonds were made in a nitrogen atmosphere and Cu elements were present at grain boundaries. In addition, coatings with the Cu content above 14 at% had a Cu3N peak in the XRD results. Thus, it is suggested that the formation of Cu3N phase affected the microstructure and mechanical properties of Mo-Cu-N coatings. Mechanical properties of Mo-Cu-N coatings were found to be relatively better at Cu content of about 12 at%.

• Nuclear Engineering and Technology
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• v.49 no.3
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• pp.576-580
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• 2017

A dynamic nanoindentation method was applied to study an Fe-18 at.% Gd alloy as a neutron-absorbing material prepared by vacuum arc-melting and cast in a mold. The Fe-18 at.% Gd cast alloy had a microstructure with matrix phases and an Fe-rich primary dendrite of $Fe_9Gd$. Rietveld refinement of the X-ray spectra showed that the Fe-18 at.% Gd cast alloy consisted of 35.84 at.% $Fe_3Gd$, 6.58 at.% $Fe_5Gd$, 16.22 at.% $Fe_9Gd$, 1.87 at.% $Fe_2Gd$, and 39.49 at.% ${\beta}-Fe_{17}Gd_2$. The average nanohardness of the primary dendrite phase and the matrix phases were 8.7 GPa and 9.3 GPa, respectively. The fatigue limit of the matrix phase was approximately 37% higher than that of the primary dendrite phase. The dynamic nanoindentation method is useful for identifying local phases and for analyzing local mechanical properties.

• Journal of the Korean institute of surface engineering
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• v.54 no.6
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• pp.357-364
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• 2021

In this study, DLC films deposited by PECVD were evaluated to the properties of super-hydrophobic by CF₄ treatment. The structure of DLC films were confirmed by Raman Spectra whether or not mixed sp³ (like diamond) peak and sp² (like graphite) peak. And the hydrogen contents in the DLC films (F-DLC) were measured by RBS analysis. In addition, DLC films were analyzed by scratch test for adhesion, nano-indentation for hardness and tribo-meter of Ball-on-disc type for friction coefficient. In the result of analysis, DLC films had traditional structure regardless of variation of hardness at constant conditions. Also adhesion of DLC film was increased as higher material hardness. Otherwise, friction coefficient was increased as lower material hardness. The DLC films were treated by CF₄ plasma treatment to enhance the properties of super-hydrophobic. And the DLC films were measured by ESEM(Enviromental Scanning Electron Microscope) for water condensation.

• Journal of Adhesion and Interface
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• v.22 no.2
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• pp.47-56
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• 2021

Steel plates coated by self-healable polymer still can be rusted since it takes time to be healed. In this study, dual self-healing coating material is developed using corrosion inhibitor (DTBEDA) which can form hindered urea (HUB) as reversible cross-linking bond at the same time. Developed dual self-healing polymer is coated on steel plate, and scratch healing property was investigated by surgical blades and nano/micro indentation tester. The anticorrosion effect of DTBEDA was investigated by electrochemical impedance spectroscopy (EIS).

• Korean Journal of Metals and Materials
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• v.46 no.7
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• pp.464-470
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• 2008

Metallic nanostructures have great potential for bio-chemical sensor applications due to the excitation of localized surface plasmon and its sensitive response to environmental change. Unlike the commonly explored absorption-based sensing, the optical scattering provides single particle detection scheme. For the localized surface plasmon resonance spectroscopy, the metallic nanostructures with controlled shape and size have been usually fabricated on adhesion-layer pre-coated transparent glass substrates. In this study, we calculated the optical scattering properties of plasmonic Au nanodisc using a discrete dipole approximation method and analyzed the effect of adhesion layer on them. Our result also indicates that there is a trade-off between the surface plasmon damping and the capability of supporting nanostructures in determining the optimal thickness of adhesion layer. Marginal thickness of Ti adhesion layer for supporting Au nanostructures fabricated on a silica glass substrate was experimentally analyzed by an adhesion strength test using a nano-indentation technique.

• Korean Journal of Materials Research
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• v.33 no.9
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• pp.353-359
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• 2023

This study investigated the growth behavior and characteristics of compounds formed at the interface between a liquid Al-Si-Cu alloy and solid cast iron. Through microstructural analyses, it was observed that various AlFe and AlFeSi phases are formed at the interface, and the relative proportion of each phase changes when small amounts of strontium are added to the Al alloy. The results of the microstructural analysis indicate that the primary phases of the interfacial compounds in the Al-Si-Cu base alloy are Al₈Fe₂Si and Al_4.5FeSi. However, in the Sr-added alloys, significant amounts of binary AlFe intermetallic compounds such as Al₅Fe₂ and Al₁₃Fe₄ formed, in addition to the AlFeSi phases. The inclusion of Sr has a slight diminishing effect on the rate at which the interfacial compounds layer thickens during the time the liquid Al alloy is in contact with the cast iron. The study also discusses the nano-indentation hardness and micro-hardness of the interfacial phases.

• Archives of Metallurgy and Materials
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• v.67 no.4
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• pp.1535-1538
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• 2022

MoO₃ thick film was manufactured by using a thermal spray process (Atmospheric Plasma Spray, or APS) and its microstructure, phase composition and properties of the coating layer were investigated. Initial powder feedstock was composed of an orthorhombic α-MoO₃ phase, and the average powder particle size was 6.7 ㎛. As a result of the APS coating process, a MoO₃ coating layer with a thickness of about 90 ㎛ was obtained. Phase transformation occurred during the process, and the coating layer consisted of not only α-MoO₃ but also β-MoO₃, MoO₂. Phase transformation could be due to the rapid cooling that occurred during the process. The properties of the coating layer were evaluated using a nano indentation test. Hardness and reduced modulus were obtained as 0.47 GPa and 1.4 GPa, respectively. Based on the above results, the possibility of manufacturing a MoO₃ thick coating layer using thermal spray is presented.

• Tribology and Lubricants
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• v.33 no.3
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• pp.106-111
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• 2017

Sapphire is an anisotropic material with excellent physical and chemical properties and is used as a substrate material in various fields such as LED (light emitting diode), power semiconductor, superconductor, sensor, and optical devices. Sapphire is processed into the final substrate through multi-wire saw, double-side lapping, heat treatment, diamond mechanical polishing, and chemical mechanical polishing. Among these, chemical mechanical polishing is the key process that determines the final surface quality of the substrate. Recent studies have reported that the material removal characteristics during chemical mechanical polishing changes according to the crystal orientations, however, detailed analysis of this phenomenon has not reported. In this work, we carried out chemical mechanical polishing of C(0001), R($1{\bar{1}}02$), and A($11{\bar{2}}0$) substrates with different sapphire crystal planes, and analyzed the effect of crystal orientation on the material removal characteristics and their correlations. We measured the material removal rate and frictional force to determine the material removal phenomenon, and performed nano-indentation to evaluate the material characteristics before and after the reaction. Our findings show that the material removal rate and frictional force depend on the crystal orientation, and the chemical reaction between the sapphire substrate and the slurry accelerates the material removal rate during chemical mechanical polishing.

• Journal of Powder Materials
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• v.23 no.5
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• pp.384-390
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• 2016

Tri-isotropic (TRISO) coatings on zirconia surrogate beads are deposited using a fluidized-bed vapor deposition (FB-CVD) method. The silicon carbide layer is particularly important among the coated layers because it acts as a miniature pressure vessel and a diffusion barrier to gaseous and metallic fission products in the TRISO-coated particles. In this study, we obtain a nearly stoichiometric composition in the SiC layer coated at $1400^{\circ}C$, $1500^{\circ}C$, and $1400^{\circ}C$ with 20 vol.% methyltrichlorosilane (MTS), However, the composition of the SiC layer coated at $1300-1350^{\circ}C$ shows a difference from the stoichiometric ratio (1:1). The density decreases remarkably with decreasing SiC deposition temperature because of the nanosized pores. The high density of the SiC layer (${\geq}3.19g/cm^2$) easily obtained at $1500^{\circ}C$ and $1400^{\circ}C$ with 20 vol.% MTS did not change at an annealing temperature of $1900^{\circ}C$, simulating the reactor operating temperature. The evaluation of the mechanical properties is limited because of the inaccurate values of hardness and Young's modulus measured by the nano-indentation method.

• Journal of Electrical Engineering and Technology
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• v.12 no.5
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• pp.2007-2013
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• 2017

In order to give hydrophobic surface properties on carbon steel, the fluorinated amorphous carbon films were prepared by using linear 2.45GHz microwave PECVD device. Two different process approaches have been tested. One is direct deposition of a-C:H:F films using admixture of $Ar/CH_4/CF_4$ working gases and the other is surface treatment using $CF_4$ plasma after deposition of a-C:H film with $Ar/CH_4$ binary gas system. $Ar/CF_4$ plasma treated surface with high $CF_4$ gas ratio shows best hydrophobicity and durability of hydrophobicity. Nanometer scale surface roughness seems one of the most important factors for hydrophobicity within our experimental conditions. The properties of a-C:H:F films and $CF_4$ plasma treated a-C:H films were investigated in terms of surface roughness, hardness, microstructure, chemical bonding, atomic bonding structure between carbon and fluorine, adhesion and water contact angle by using atomic force microscopy (AFM), nano-indentation, Raman analysis and X-ray photoelectron spectroscopy (XPS).