• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.1
• /
• pp.170-178
• /
• 2019

Recently, as the interest in energy savings has increased, there has been increasing use of LED lighting, which is an eco-friendly device that replaces high energy consuming fluorescent lamps and incandescent lamps. In the case of a high output LED, however, the life time is shortened due to deterioration caused by heat generation. As a solution to this problem, this paper evaluated the LED life extension effect by increasing the convective heat transfer coefficient of the heat sink surface for LED packaging. A roughing process was carried out using sandpaper and sand blasting. The changes in surface roughness and surface area after each surface treatment process were evaluated quantitatively and the convective heat transfer coefficient was measured. When sandblasting and sandpaper were used to roughen the aluminum surface, a higher convection heat transfer coefficient was obtained compared to the untreated case, and a high heat dissipation efficiency of 82.76% was obtained in the sandblast treatment. Therefore, it is expected that the application of heat dissipation to the heat sink will extend the lifetime of the LED significantly and economically by increasing the heat efficiency.

• Proceedings of the KOSOMBE Conference
• /
• v.1998 no.11
• /
• pp.231-232
• /
• 1998

The purpose of this study was to examine whether the precipitation of calcium phosphate on titanium surface was affected by surface modification. To improve the bone conductivity, of titanium, samples were devided into 4 groups. Group 1 was immersed in 5M-NaOH solution at $60^{\circ}C$ for 24 hours. Group 2 was immersed in 5M-NaOH solution at $60^{\circ}C $ for 24 hours and heat-treated at $600^{\circ}C$ for 1 hour. Group 3 was anodized in Hanks' solution at 1V, $25^{\circ}C$ for 1 hour. Group 4 was anodized in Hanks' solution at 5V, $80^{\circ}C$ for 5 minutes. And then, all specimens were immersed in the MEM Eagle's medium whose composition was similar to that of extracellular fluid for 30 days. The precipitation of the calcium phosphate on implant surface was increased by the immersion in the NaOH solution, and more highly accelerated by heat treatment at $600^{\circ}C$. The precipitation of the calcium phosphate on titanium implant was increased with the treatment of the anodic oxidation in Hanks' solution at 5V, $80^{\circ}C$.

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

• Food Science and Preservation
• /
• v.8 no.2
• /
• pp.151-156
• /
• 2001

Acetic acid solution containing calcium (AC) was added to kimchi seasonings by 10% and 205, and heat treatment at 70$\^{C}$ for 15 min was also tried, respectively. Kimchi with treated seasonings was investigated for the quality during fermentation at 10$\^{C}$. Heat treatment with 20% AC showed a retarded decrease pH than others on 10 days, but there was no great difference after 14 days. Higher titratable acidity was revealed in kimchi with AC during the fermentation. Total microbial lead and lactic acid bacterial count were generally lower in kimchi with AC. Reducing sugar content was maximum for all samples on 5 days, and then decreased thereafter. Redness of control kimchi was steadily increased during fermentation, but was lower than those of other treatments.

• Journal of Powder Materials
• /
• v.18 no.1
• /
• pp.73-77
• /
• 2011

$Y(OH)_3$ nanowires were synthesized by a hydrothermal reaction of metallic Y with aqueous solution of LiOH. The morphology and the size of the nanowires changed with varying the volume of the LiOH solution inside the autoclave. $Y(OH)_3$ nanowires transformed to $Y_2O_3$ by a subsequent heat-treatment without morphological change. By a proper control of hydrothermal reaction parameter and heat-treatment, the yield of pure $Y_2O_3$ nanowires up to 97% was attained.

• Journal of the Semiconductor & Display Technology
• /
• v.3 no.2
• /
• pp.11-15
• /
• 2004

Scales, accumulated on some parts of semiconductor equipments such as sputters and CVD during the device fabrication processes, often lower the lifetime of the equipments and production yields. Thus, many equipment parts have be cleaned regularly. In this study, an attempt to establish an effective process to remove scales on the sidewall of collimators located inside the chamber of the sputter was made. The EDX analysis revealed that the scales were composed of Ti and TiN with the columnar structure. Through the trial-and-error experiments, it was found that the etching in the $HNO_3$:$H_2SO_4$:$H_2O$=4:2:4 solution for 5.5 hrs at $67^{\circ}C$, after the oxide removal in the HF solution, and the heat-treatment at $700^{\circ}C$ for 1 min., was the most effective process for the scale removal.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2007.10a
• /
• pp.254-257
• /
• 2007

In this paper, anisotropic tensile properties of the AZ31B Mg-alloy sheet are obtained with the tensile test at elevated temperatures. Change of microscopic structures and the hardness is inspected after the solution heat treatment process in order to confirm the micro-structural stability of the used sheet metal. Results obtained from tensile tests show that it is very difficult to apply the conventional modeling scheme with the assumption of strain hardening to the forming analysis of the magnesium alloy sheet which shows the strain-softening behavior at the elevated temperature.

• Journal of the Korean Society for Heat Treatment
• /
• v.33 no.6
• /
• pp.290-295
• /
• 2020

In this study, Electro spinning was carried out using Cabon nanotube 0.1%-Polyacrylonitrile 3%-Dimethylformamide 17% agitation solution. It was investigated the solute and solvent correlations according to the electro spinning voltages ranging form 5 to 40 kV, based on the SEM image. Except voltage 25 kV, electro spinning was failed due to the lack of electro spinning (less than 60%). Voltage 25 kV was showed excellent properties, and was confirmed Cabon nanotube 58.1 nm and diameter of Cabon nanotube + Polyacrylonitrile 1.76 ㎛ as shown SEM image. Also, the tensile test results were showed that SK Chemical prepreg electro spinning angle of 0 and 90 degrees were 137 MPa and 60 MPa, respectively.

• Korean Journal of Food Science and Technology
• /
• v.21 no.6
• /
• pp.845-850
• /
• 1989

Effect of high temperature soaking in salt solution and short time microwave heat treatment on quality of Korean pickled cucumbers during fermentation was investigated. The Korean pickled cucumbers were fermented at $25^{\circ}C$ for 10 days in 10% salt solution. The physicochemical properties measured were pH, the total acidity, hardness and the sensory properties of odor, taste and texture were also evaluated. The result showed that the effect of soaking cucumber in $80-90^{\circ}C$ hot salt solution significantly reduced the fermentation rate and softening rate of texture while a rather rapid fermentation was found for those soaked in $60-70^{\circ}C$. The effect of microwave treatment inhenced fermentation a little for short treatment but it was significantly reduced softening rate of texture by 3 minutes heating. The sensory evaluation of Korean pickled cucumber was found that heat treatments with hot solution and microwave heating had a possitive effect for reduction of softening of cucumber tissue, however odor and taste were not significantly affected.

• The Journal of the Convergence on Culture Technology
• /
• v.9 no.3
• /
• pp.593-599
• /
• 2023

Nickel oxide (NiO) nanoparticles were successfully synthesized by a simple liquid phase process for producing ceramics powder using a precursor impregnated with a nickel(II) nitrate hexahydrate aqueous solution in an industrial pulp. The microfibrile structure of the precursor impregnated with nickel nitrate hexahydrate aqueous solution was confirmed by scanning electron microscope (SEM), and the crystal structure and particle size of nickel oxide (NiO) particles produced as the heat treatment temperature of the precursor were analyzed by X-ray diffraction (XRD) and SEM. As a result, it was confirmed through XRD and SEM analysis that the temperature at which the organic material of the precursor is completely thermally decomposed was 495-500℃, and the size and crystallinity of the nickel oxide particles produced increased as the heat treatment temperature increased. The size of the nickel oxide particles obtained by heat treatment at 500-800℃ for 1 hour was 50-200 nm. It was confirmed by XRD and SEM analysis that a NiO crystal phase was formed at a heat treatment temperature of 380℃, only a single NiO phase existed until 800℃.