• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.3
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• pp.50-57
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• 2013

The high temperature thermal attacks in welding can affect the residual stress of a frame for automotive assembly accompanying frame deformation. Also the residual stress can induce the negative effect on durability performance of the automobile. In order to analyze the frame deformation, the simplified test frame which had the similar shape (form) of the real automotive frame was fabricated. The contactless optical 3D scanner was used for the shape difference measurement of the frame between before and after the welding. The FE-model of the test frame was composed and the deformation and residual stress simulation were performed. The simulated results were compared with the measured results for the reference of the frame design following as the variation of welding sequency. The deformation shape of the frame by simulation was in good agreement with that by the experimental measurement. In addition, the optimized welding sequency with reduced deformation after welding could be achieved through these analyses.

• Journal of the Semiconductor & Display Technology
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• v.17 no.4
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• pp.97-100
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• 2018

$NF_3$ Plasma etching of silicon was conducted by injecting only $NF_3$ gas into reactive ion etching. $NF_3$ Plasma etching was done in intermediate pressure. Silicon etching by $NF_3$ plasma in reactive ion etching was diagnosed through residual gas analyzer and optical emission spectroscopy. In plasma etching, optical emission spectroscopy is generally used to know what kinds of species in plasma. Also, residual gas analyzer is mainly to know the byproducts of etching process. Through experiments, the results of optical emission spectroscopy during silicon etching by $NF_3$ plasma was analyzed with connecting the results of etch rate of silicon and residual gas analyzer. It was confirmed that $NF_3$ plasma etching of silicon in reactive ion etching accords with the characteristic of reactive ion etching.

• Membrane Journal
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• v.28 no.1
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• pp.37-44
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• 2018

Polysulfone composites including graphene were prepared, and their thermal characteristics in membrane states were analyzed by using a custome-made residual stress analyzer and a thermal diffusivity analyzer based on laser flash method. The residual stress analysis was carried out on the polysulfone composite films deposited on Si (100) substrates for 1 cycle of heating and cooling runs. The flat membrane of graphene-embedded polysulfone composites were prepared by the phase transfer method in distilled water and the thermal conductivity was separately measured in the out-of-plane and the in-plane directions. The residual stress of the graphene-embedded polysulfone film was gradually decreased with increasing graphene loading and the out-of-plane thermal conductivity was distinguished from the in-plane thermal conductivity in the flat membranes. These thermal characteristics are caused by the structural uniqueness of graphene and the micro-void structures formed during membrane fabrication.

• Journal of Soil and Groundwater Environment
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• v.23 no.2
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• pp.23-29
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• 2018

This study explored secondary effects of the residual hydrofluoric acid (HF) after a hypothetical acid spill accident by investigating the long-term dissolution of minerals and leaching of pre-existing arsenic (As) from two soil samples (i.e., KBS and KBM) through batch and column experiments. An increase in the HF concentration in both soil samples resulted in a dramatic increase in the release of major cations, especially Si. However, the amounts of mineral dissolved were dependent on the soil type and mineral characteristics. Compared to the KBM soil, relatively more Ca, Mg and Si were dissolved from the KBS soil. The column experiment showed that the long-term dissolution rates of the minerals are closely associated with the acid buffering capacity of the two soils. The KBM soil had relatively higher effluent pH values compared to the KBS soil. Also, more As was leached from the KBM soil, with a more amorphous hydrous oxide-bound As fraction. These results suggest that the potential of heavy metal leaching by the residual acid after an acid spill will be influenced by heavy metal speciation and mineral structure in the affected soil.

• Steel and Composite Structures
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• v.52 no.3
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• pp.377-390
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• 2024

Analyzing thermoelastic, elastoplastic, and residual stresses is pivotal for deepening our insights into material characteristics, particularly in the engineering of advanced materials like functionally graded materials (FGM). This research delves into these stress types within a thick-walled sphere composed of Al-SiC FGM, employing a detailed successive approximation method (SAM) to pinpoint stress distributions under varied loading scenarios. Our investigation centers on how the sphere's structure responds to different magnitudes of internal pressure. We discover that under various states-thermoelastic, elastoplastic, and residual-the radial stresses are adversely impacted, manifesting negative values due to the compressive nature induced by internal pressures. Notably, the occurrence of reverse yielding, observed at pressures above 410 MPa, merits attention due to its significant implications on the sphere's structural integrity and operational efficacy. Employing the SAM allows us to methodically explore the nuanced shifts in material properties across the sphere's thickness. This study not only highlights the critical behaviors of Al-SiC FGM spheres under stress but also emphasizes the need to consider reverse yielding phenomena to maintain safety and reliability in their application. We advocate for ongoing refinement of analytical techniques to further our understanding of stress behaviors in various FGM configurations, which could drive the optimized design and practical application of these innovative materials in diverse engineering fields.

• Journal of the Korean Ceramic Society
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• v.51 no.5
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• pp.459-465
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• 2014

In this study, Si-SiC composites were fabricated using a Si melt infiltration method using ${\beta}$-SiC/C composite powders synthesized by the carbothermal reduction of $SiO_2-C$ precursors made from a TEOS and a phenol resin. The purity of the synthesized SiC-C composite powders was higher than 99.9993 wt% and the average particle size varied from 4 to $6{\mu}m$ with increasing carbon contents of the $SiO_2-C$ precursors. It was found that the Si-SiC composites fabricated in this study consist of ${\beta}$-SiC and residual Si, without any trace of ${\alpha}$-SiC. The 3-point bending strengths of the fabricated Si-SiC composites were measured and found to be higher than 550 MPa, although the density of the fabricated Si-SiC composite was less than $2.9g/cm^3$. The bending strengths and the densities of the fabricated Si-SiC composites were found to decrease with increasing C/Si mole ratios in the SiC-C composite powders. The specific resistivities of the Si-SiC composites fabricated using the SiC-C composite powders were less than $0.018{\Omega}cm$. With increasing C content in the SiC-C composite powders used for the fabrication of Si-SiC composites, the specific resistivity of the Si-SiC composites was found to slightly increase from 0.0157 to $0.018{\Omega}cm$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.1
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• pp.16-22
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• 2008

We fabricated thermally-evaporated 10 nm-Ni/30 nm and 70 nm Poly-Si/200 nm-$SiO_2/Si$ structures to investigate the thermal stability of nickel silicides formed by rapid thermal annealing(RTA) of the temperature of $300{\sim}1100^{\circ}C$ for 40 seconds. We employed for a four-point tester, field emission scanning electron microscope(FE-SEM), transmission electron microscope(TEM), high resolution X-ray diffraction(HRIXRD), and scanning probe microscope(SPM) in order to examine the sheet resistance, in-plane microstructure, cross-sectional microstructure evolution, phase transformation, and surface roughness, respectively. The silicide on 30 nm polysilicon substrate was stable at temperature up to $900^{\circ}C$, while the one on 70 nm substrate showed the conventional $NiSi_2$ transformation temperature of $700^{\circ}C$. The HRXRD result also supported the existence of NiSi-phase up to $900^{\circ}C$ for the Ni silicide on the 30 nm polysilicon substrate. FE-SEM and TEM confirmed that 40 nm thick uniform silicide layer and island-like agglomerated silicide phase of $1{\mu}m$ pitch without residual polysilicon were formed on 30 nm polysilicon substrate at $700^{\circ}C\;and\;1000^{\circ}C$, respectively. All silicides were nonuniform and formed on top of the residual polysilicon for 70 nm polysilicon substrates. Through SPM analysis, we confirmed the surface roughness was below 17 nm, which implied the advantage on FUSI gate of CMOS process. Our results imply that we may tune the thermal stability of nickel monosilicide by reducing the height of polysilicon gate.

• Journal of Environmental Impact Assessment
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• v.28 no.6
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• pp.549-555
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• 2019

The purpose of this study is to ensure optimal operating conditions for improving the removal efficiency of phosphorus (P) and nitrogen (N) that are the causative agents of eutrophication by utilizing functional media. The main ingredients of the functional media used in this study are Si, Al, and Fe, SiO₂, KAlSiO₃O₈, Al₂O₂·2SiO₂O, H₃Al₂Si₂O₉, Fe₃O₄O), and berylite. To identify the maximum efficiency of the filtration process, the processing efficiency experiment was carried out according to flow method, velocity, and thickness of residual media. The flow method carried out two experiments, 50 m/day, 100 m/day, 150 m/day, 200 m/day, 250 m/day, and 20 cm, 40 cm, 50 cm, 60 cm, 80 cm of lead depth. Experiments have shown that SS, T-N, and T-P all showed higher elimination efficiency of the upflow current conditions than the downflow current conditions, and that the processing efficiency of the linearity is the highest at SS 50 m/day, T-N 150 m/day and T-P 100 m/day. In addition, the analysis of the removal efficiency according to the residual thickness showed that SS, T-N, and T-P all showed the highest efficiency at 60 cm. In addition, the analysis of the removal efficiency according to the residual thickness showed that SS, T-N, and T-P all showed the highest efficiency at 60 cm. It is considered desirable to set the top-down flow conditions and residual thickness of 60 cm and adjust the velocity of the line according to the target media for removal.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.159-160
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• 2002

To investigate the humidity effect on tribological behaviors of Si-DLC/DLC multi-layers, the samples were prepared using a system consisted of an ion-gun for deposition DLC films and a balanced magnetron sputter for introducing silicon atoms to Si-DLC films. The Si-DLC/DLC multi-layers were composed of pure DLC films and Si-incorporated DLC films alternatively and had different bilayer numbers. Hardness and residual stress were drastically decreased through the formation of Si-DLC/DLC multi-layers compared to those of the pure and Si-incorporated DLC films. Wear results obtained under the various humidity conditions (<10%, $40{\sim}50%$, and >85%) showed that the pure DLC film was largely depended on the humidity while the Si-DLC and the Si-DLC/DLC multi-layers were little affected by the environmental humidity. Although friction coefficients of all samples were increased with the relative humidity, the multi-layer films showed relatively lower friction coefficients that those of the single films.

• Journal of the Korean Ceramic Society
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• v.30 no.4
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• pp.316-324
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• 1993

Three types of dispersed, coated and mechanically mixed SiC reinforced Al2O3 composite powders were used to investigate the effect of composite powder type on sintering characteristics and properties of Al2O3-SiC composites. Sinterability of coated type composite powders was superior to that of other composite powders when they were pressureless sintered at 1500~1$700^{\circ}C$ for 2h in Ar atmosphere. However, sinterabilities (>98% TD) of each type of composite powders were similar when they were hot pressed at 180$0^{\circ}C$ for 1h under 30MPa in N2 atmosphere. SiC powders were randomly distributed in the specimen prepared from dispersed type composite powders, whereas homogeneously distributed for coated type specimens. It was found that SiC powders inhibited the grain growth of Al2O3, and fracture toughness was increased by the increment of crack growth resistance due to residual stress by secondary SiC particles within Al2O3 grains.