• Korean Journal of Metals and Materials
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• v.50 no.4
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• pp.263-270
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• 2012

This study investigates the effect of heat treatment on the mechanical properties of a forged Ni-based superalloy called Nimonic 80A. Nimonic 80A ingot samples were fabricated by vacuum spray casting to achieve a fine and homogenized microstructure. The ingot samples were subsequently hot-forged with the diameter of 220 mm at 1373 K. From the center to the surface of the forged Nimonic 80A, its average grain size decreased and its micro-Vickers hardness increased slightly. Solution treatment was carried out at 1353 K with 8 hours of air cooling followed by aging treatment, which was carried out in the range of 873-1073 K with various times from 0.5 to 256 hours. To set the optimum aging conditions, micro-Vickers hardness tests were performed. The maximum hardness value of 388.0 Hv was obtained by aging at 973 K for 32 hours. Also, tensile tests were performed for optimum aging conditions at room temperature and 873 K. The results can be used effectively to perform reasonable heat treatment of Nimonic 80A superalloy.

• Journal of Power System Engineering
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• v.21 no.5
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• pp.13-19
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• 2017

The effect of heat treatment temperature (HTT) on the mechanical properties of polyacrylonitrile (PAN)-based carbon fiber had been investigated. The heat treatment on the carbon fiber was conducted under high vacuum atmosphere of $10^{-6}mmHg$, and the range of temperature of $1,000^{\circ}C$ to $2,000^{\circ}C$. As a results, The tensile strength of carbon fiber and carbon fiber composites showed increasing tendency with the rise of heat treatment temperature. And, the shape parameter of Weibull distribution for the strength of carbon single fiber showed an increasing trend until $1,800^{\circ}C$. But the shape parameter of Weibull distribution for the strength of carbon fiber composites showed no clear tendency with the rise of heat treatment temperature. The cause of reinforcement effect of the carbon fiber by the heat treatment was regarded as the carbonization of carbon single fiber.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.322-322
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• 2010

For boron doping on n-type silicon wafer, around $1,000^{\circ}C$ doping temperature is required, because of the relatively low solubility of boron in a crystalline silicon comparing to the phosphorus case. Boron doping by fiber laser annealing and lamp furnace heat treatment were carried out for the uniformly deposited p-a-Si:H layer. Since the uniformly deposited p-a-Si:H layer by cluster is highly needed to be doped with high temperature heat treatment. Amorphous silicon layer absorption range for fiber laser did not match well to be directly annealed. To improve the annealing effect, we introduce additional lamp furnace heat treatment. For p-a-Si:H layer with the ratio of $SiH_4:B_2H_6:H_2$=30:30:120, at $200^{\circ}C$, 50 W power, 0.2 Torr for 30 min. $20\;mm\;{\times}\;20\;mm$ size fiber laser cut wafers were activated by Q-switched fiber laser (1,064 nm) with different sets of power levels and periods, and for the lamp furnace annealing, $980^{\circ}C$ for 30 min heat treatment were implemented. To make the sheet resistance expectable and uniform as important processes for the $p^+$ layer on a polished n-type silicon wafer of (100) plane, the Q-switched fiber laser used. In consequence of comparing the results of lifetime measurement and sheet resistance relation, the fiber laser treatment showed the trade-offs between the lifetime and the sheet resistance as $100\;{\omega}/sq.$ and $11.8\;{\mu}s$ vs. $17\;{\omega}/sq.$ and $8.2\;{\mu}s$. Diode level device was made to confirm the electrical properties of these experimental results by measuring C-V(-F), I-V(-T) characteristics. Uniform and expectable boron heavy doped layers by fiber laser and lamp furnace are not only basic and essential conditions for the n-type crystalline silicon solar cell fabrication processes, but also the controllable doping concentration and depth can be established according to the deposition conditions of layers.

• Land and Housing Review
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• v.11 no.3
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• pp.61-68
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• 2020

Advanced glazing systems with excellent heat transmission values (Ug-Value) have been developed to reduce the energy consumption and the greenhouse gas emission. This study proposes a triple glazing system consisting of gaps with a vacuum and a carbon dioxide gas layer which is one of greenhouse gases. As a fundamental stage, this study is focused on calculating the optimal glazing thickness and the Ug-Value via a computer simulation, Therm & Window package. As the results, it was presented that the optimal thickness of the proposed triple glazing system is 22.2 mm, and the Ug-Value is 0.273 W/㎡·K. If this glazing system is to be applied to buildings, it could not only reduce building energy consumption but could also contribute to the treatment of carbon dioxide gas which is one of greenhouse gases.

• Journal of Sensor Science and Technology
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• v.26 no.5
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• pp.360-365
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• 2017

In this study, a heat treatment process was applied to ZnS nano-powder to improve the optical properties of ZnS ceramic, and the characteristics of heat treatment time were studied. The ZnS nano-powders were synthesized by hydrothermal synthesis. The heat treatment was carried out at $550^{\circ}C$ for 0.5, 1, 2, and 4 hours in a vacuum atmosphere ($10^{-2}torr$). X-ray diffraction and scanning electron microscope analyzes confirmed the change of crystal phase and grain size to confirm the structural change with heat treatment time. The heat treated ZnS nano-powder was sintered by hot pressing, and the change of optical properties of the ZnS ceramic was analyzed by infrared spectroscopy.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.1
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• pp.129-138
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• 2001

This study examined the effects of the annealing heat treatments on the mechanical properties of the Invar(Fe-36%Ni Alloy) materials. Invar materials were annealed at various temperatures range 900~120$0^{\circ}C$ in vacuum(10-4Torr) and hydrogen atmospheres. And annealing conditions were changed by cooling rate and holding time at 110$0^{\circ}C$. The grain size of rolled Invar materials was very fine but those of annealed Invar materials at 900~120$0^{\circ}C$ in vacuum and hydrogen atmosphere increased with increasing annealing temperature. The micro-vickers hardness values of annealed Invar materials were decreased about 15% that of the rolled Invar materials, regardless of the various of annealing temperatures, atmosphere(vacuum, hydrogen) and annealing conditions. The tensile strength and yield strength of annealed Invar materials at 900~120$0^{\circ}C$ in vacuum and hydrogen atmosphere were decreased 10.0~14.4% and 34.6~39.1% those of the rolled Invar materials, respectively. The strength ratio(tensile strength/ yield strength) of annealed Invar materials was improved to 1.7~1.8 from the value of 1.2~1.3 of rolled Invar materials. The degree of spring back of annealed Invar materials was about 50% of the rolled Invar materials, regardless of the various of annealing temperatures, atmosphere(vacuum, hydrogen) and annealing conditions.

• Journal of the Korean Wood Science and Technology
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• v.37 no.6
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• pp.487-496
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• 2009

The sapwood of yellow poplar is very bright while its heartwood is usually greenish which changes to dark brown with weathering. This difference in color value between sapwood and heartwood causes difficulty in using yellow poplar as higher value added materials such as interior finish and furniture part. In this study, hot-water treatment, vacuum-heat treatment and oven-heat treatment were carried out to reduce the difference in color value between heartwood and bright sap wood and to increase durability. FT-IR analysis, contact angle measurement and decay test were carried out to find out the mechanism of functional group change and the increment of durability by heat treatment. The result of decrement ratio of color difference were 45.7% by hot-water treatment, 26.8% by vacuum-heat treatment, and 60.2%, 87.8%, and 88.8% by $180^{\circ}C$, $200^{\circ}C$ and $220^{\circ}C$ oven-heat treatments respectively. Furthermore, it has been found that oven-heat treatment causes decrement of mass loss by decay in this study. It is suggested that oven-heat treatment could be environmentally friendly preservative treatment without chemicals.

• Journal of the Korean Society for Heat Treatment
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• v.3 no.3
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• pp.13-20
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• 1990

SCM 21 and D.P steel were carburized in vacuum using prophane at a temperature ranging from 1228k to 1308k under a gas pressure ranging from 21.3kpa to 61.8kpa, and the following results were obrained. 1) D.P. steel has considerable efficiency in depressing the grain growth during the high temperature carburizing and it has fine structure even at 1268k for 14.4ks when carburizied. Therefore this steel is expected to be suitable for vacuum carburizing at a high temperature. 2) Case depth was increased as the carburizing temperature increases and it was 3.2mm at max, temperature of 1308k, for max, time of 14.4ks and under max, pressure of 61.8kpa. Thus vacuum-carburizing was considered effective for the materials which need case depth, which is necessary for machine structure use. 3) The rate of case depth of SCM 21 was faster than D.P. steel under same carburizing conditions and the increasing rate of the case depth was constant. 4) Case depth was increased as the gas pressure becomes high under same carburizing temperature. 5) Case carbon concentration, $C_s$, of SCM 21 obeys to a formula, $$C_s=kt^{1/2}+C_0$$ Where k is $2.15{\times}10^{-2}$($wt%.S^{-1/2}$) and this value is a little bit lower than that of SNCM 815.

• Korean Journal of Materials Research
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• v.11 no.12
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• pp.1057-1062
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• 2001

We investigated the change of mechanical properties for TiNi shape memory alloy by heat treatment. 6061Al matrix composites with TiNi shape memory alloy as reinforcement were fabricated by vacuum casting. TiNi alloy has the maximum tensile strength at 673K treated and there is no change of tensile strength and hardness at 448K treated. The composites, prepared by vacuum casting, showed good interface bonding by vacuum casting. It was about 3$\mu\textrm{m}$ of thickness of the diffusion layer. Tensile strength of the composite was in higher than that of 6061Al alloy as increased value of about 70MPa at room temperature and about 110MPa at 363K. We thought that the increase of the tensile strength at 363K was due to reverse transformation of the TiNi shape memory alloy.

• Journal of the Korean Society for Heat Treatment
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• v.27 no.4
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• pp.175-179
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• 2014

IGZO thin films were prepared by radio frequency (RF) magnetron sputtering on glass substrates and then annealed in vacuum for 30 minutes at 100, 200 and $300^{\circ}C$, respectively. The thickness of films kept at 100 nm by controlling the deposition rate. While the optical transmittance and sheet resistance of as deposited films were 91.9% and $901{\Omega}/{\Box}$, respectively, the films annealed at $300^{\circ}C$ show the optical transmittance of 95.4% and the sheet resistance of $383{\Omega}/{\Box}$. The experimental results indicate that vacuum-annealed IGZO film at $300^{\circ}C$ is an attractive candidate for the transparent thin film transistor (TTFT) in large area electronic applications.