• Korean Journal of Mineralogy and Petrology
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• 제36권2호
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• pp.95-106
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• 2023

Quartz (SiO₂) is among the major rock-forming minerals in the earth's crust. The atomistic structures of SiO₂ may evolve during diverse frictional processes. The reduction of friction of quartz-rock accompanied by its amorphization, hydration, and formation of silica gel provides mineralogical insights into earthquakes and related phenomena. Ball milling, together with rotary shear experiments have been useful to infer the atomic origins of such processes. In this study, optimal experimental conditions for ball milling for amorphization of SiO₂ were determined by taking into account various process variables. The crystallinity of SiO₂ gradually decreased and became amorphous as the ball milling time increased at a high milling speed. The degree of wear of the milling media and its effect on the amorphization of SiO₂ were analyzed using distinct milling materials (zirconia, stainless steel). The amount of ball wear increased with increasing milling time. Furthermore, the worn stainless steel particles from balls tend to interact with amorphized SiO₂ to form Si-O-Cr. These results aid in understanding the process of atomistic structural changes caused by ball milling of divserse materials with relatively high hardness, such as SiO₂, and understanding various geological friction processes.

• Proceedings of the Korean Magnestics Society Conference
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• 한국자기학회 2005년도 동계학술연구발표회 및 2차 아시안포럼
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• pp.7-7
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• 2005

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 한국표면공학회 2016년도 추계학술대회 논문집
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• pp.189-189
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• 2016

In this study, the Al-rich AlTiSiN thin films that consisted of TiN/AlSiN nano-multilayers were deposited on the steel substrate by magnetron sputtering, and their high-temperature oxidation behavior was investigated, which has not yet been adequately studied to date. Since the oxidation behavior of the films depends sensitively on the deposition method and deposition parameters which affect their crystallinity, composition, stoichiometry, thickness, surface roughness, grain size and orientation, the oxidation studies under various conditions are imperative. AlTiSiN nano-multilayer thin films were deposited on a tool steel substrate, and their oxidation behavior of was investigated between 600 and $1000^{\circ}C$ in air. Since the amount of Al which had a high affinity for oxygen was the largest in the film, an ${\alpha}-Al_2O_3-rich$ scale formed, which provided good oxidation resistance. The outer surface scale consisted of ${\alpha}-Al_2O_3$ incoporated with a small amount of Ti, Si, and Fe. Below this outer surface scale, a thin ($Al_2O_3$, $TiO_2$, $SiO_2$)-intermixed scale formed by the inwardly diffusing oxygen. The film oxidized slower than the $TiO_2-forming$ kinetics and TiN films, but faster than ${\alpha}-Al_2O_3-forming$ kinetics. During oxidation, oxygen from the atmosphere diffused inwardly toward the reaction front, whereas nitrogen and the substrate element of iron diffused outwardly to a certain extent.

• Journal of Korea Foundry Society
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• 제30권2호
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• pp.76-82
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• 2010

Effect of reaction time and sludge formation on the thickness of die soldering reaction layer has been studied in Al-9Si-0.3Mg casting alloy. Ternary ${\alpha}_{bcc}-Al_8Fe_2Si$ and ${\alpha}_{hcp}-Al_8Fe_2Si$ intermetallic compounds formed at the interface of SKD61 tool steel by interaction diffusion of Al, Fe and Si atoms after 0.5hr and 6hr immersion time, respectively. Binary ${\eta}-Fe_2Al_5$ additionally formed at the interface of SKD61 tool steel after 10hr immersion time. Thickness of soldering reaction layer in die surface increased as immersion time increased from 0.5hr to 24hr. Sludge formation was ascertained in the samples which were immersed in the melts more than 10hr. Reaction of die soldering after sludge formation was more accelerated than that of before sludge formation due to a decrease in Fe content, followed by higher diffusion rate of Al in the melt by sludge formation.

• Applied Science and Convergence Technology
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• 제26권6호
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• pp.208-213
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• 2017

Flexible opto-electronic devices are developed on the insulating layer deposited stainless steel (STS) substrates. The silicon dioxide ($SiO_2$) material as the diffusion barrier of Fe and Cr atoms in addition to the electrical insulation between the electronic device and STS is processed using the plasma enhanced chemical vapor deposition method. Noble silver (Ag) films of approximately 100 nm thickness have been formed on $SiO_2$ deposited STS substrates by E-beam evaporation technique. The films then were annealed at $650^{\circ}C$ for 20 min using the rapid thermal annealing (RTA) technique. It was investigated the variation of the surface morphology due to the interaction between Ag films and $SiO_2$ layers after the RTA treatment. The results showed the movement of Si atoms in silver film from $SiO_2$. In addition, the structural investigation of Ag annealed at $650^{\circ}C$ indicated that the Ag film has the material property of p-type semiconductor and the bandgap of approximately 1 eV. Also, the films annealed at $650^{\circ}C$ showed reflection with sinusoidal oscillations due to optical interference of multiple reflections originated from films and substrate surfaces. Such changes can be attributed to both formation of $SiO_2$ on Ag film surface and agglomeration of silver film between particles due to annealing.

• Journal of Surface Science and Engineering
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• 제47권2호
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• pp.75-80
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• 2014

Nanocrystalline diamond(NCD) films on steel(SKH51) has been investigated using SiC interlayer film. SiC was deposited on SKH51 or Si wafer by RF magnetron sputter. NCD was deposited on SiC at $600^{\circ}C$ for 0.5~4 h employing microwave plasma CVD. Film morphology was observed by FESEM and FIB. Film adherence was examined by Rockwell C adhesion test. The growth rate of NCD on SiC/Si substrate was much higher than that on SiC/SKH51. During particle coalescence, NCD growth rate was slow since overall rate was determined by the diffusion of carbon on SiC surface. After completion of particle coalescence, NCD growth became faster with the reaction of carbon on NCD film controlling the whole process. In the case of SiC/SKH51 substrate, a complete NCD film was not formed even after 4 h of deposition. The adhesion test of NCD/SiC/SKH51 samples revealed a delamination of film whereas that of SiC/SKH51 showed a good adhesion. Many voids of less than 0.1 ${\mu}m$ were detected on NCD/SiC interface. These voids were believed as the reason for the poor adhesion between NCD and SiC films. The origin of voids was due to the insufficient coalescence of diamond particles on SiC surface in the early stage of deposition.

• Transactions of Materials Processing
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• 제20권8호
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• pp.540-547
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• 2011

Recent years have seen advent of hot stamped parts made from laser-welded blanks of boron steels for structures requiring high crash energy absorption. However, the presence of Al-Si coating interfered with satisfactory mechanical characterizations after laser butt welding. In this study, laser ablation technology was considered in order to facilitate adequate mechanical characterization of the final hot-stamped panels.

• Journal of Surface Science and Engineering
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• 제30권4호
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• pp.248-254
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• 1997

The sulfidation behavior of a sputter-deposited amorphous coating of 69.0%Nb-16.9Ni-11.9%Al-2.2%Si (at.%) has been investigated as a funtion of temperature.(973-1173K) in pure sulfur pressure of 0.01atm. The sulfidation kinetics of the casting obyed the parabolic rate low over the whole temperature ranges studied. The stlfidation rate increased with the temperature, as expected. The sulfide scale, the composition of which was $Al_2S_3,\;NbS_2,\;Ni_{3-x}S_2\;and\;FeCrS_4$, formed on the amorphous coating was primarily bilayered. Both the outer fastgrowing non-protective 4Al_2S_3$scale and the inner slowly-growing protective $NbS_2$,/TEX> scale and the inner slowly-growing protective $NbS_2$ scale had some Fe and Cr dissolution, which evidently came from the base substrate alloy of stainless steel type 304. Belows the coating, Kirkendall void formation was noticed. Nevertheless, a dramatic improvement of sulfidation resistance was achieved by sputter-depositing Nb-2 Ni-Al-Si layer on the stainless steel 304.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 한국표면공학회 2013년도 춘계학술대회 논문집
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• pp.109-110
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• 2013

Medium carbon steel was aluminized by hot dipping into molten Al or Al-1%Si baths. After hot-dipping in these baths, a thin Al-rich topcoat and a thick alloy layer rich in $Al_5Fe_2$ formed on the surface. A small a mount of FeAl and $Al_3Fe$ was incorporated in the alloy layer. Silicon from the Al-1%Si bath was uniformly distributed throughout the entire coating. The hot dipping increased the microhardness of the steel by about 8 times. Heating at $700-1000^{\circ}C$ however decreased the microhardness through interdiffusion between the coating and the substrate. The oxidation at $700-1000^{\circ}C$ in air formed a thin protective ${\alpha}-Al_2O_3$ layer, which provided good oxidation resistance. Silicon was oxidized to amorphous silica, exhibiting a glassy oxide surface.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• 제16권2호
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• pp.233-242
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• 2018

To overcome the low mechanical strength and corrosion behavior of a carbon steel canister at high temperature condition of a deep borehole, SiC ceramics were studied as an alternative material for the disposal canister. In this paper, a design concept for a SiC canister, along with an outer stainless steel container, was proposed, and its manufacturing feasibility was tested by fabricating several 1/3 scale canisters. The proposed canister can contain one PWR assembly. The outer container was also prepared for the string formation of SiC canisters. Thermal conductivity was measured for the SiC canister. The canister had a good thermal conductivity of above $70W{\cdot}m^{-1}{\cdot}K^{-1}$ at $100^{\circ}C$. The structural stability was checked under KURT environment, and it was found that the SiC ceramics did not exhibit any change for the 3 year corrosion test at $70^{\circ}C$. Therefore, it was concluded that SiC ceramics could be a good alternative to carbon steel in application to deep borehole disposal canisters.