• Journal of the Korean Society for Nondestructive Testing
• /
• v.23 no.4
• /
• pp.372-379
• /
• 2003

The problems encountered by ultrasonic testing of austenitic stainless steel weld joints are discussed in the paper. Due to low thermal conductivity and the occurrence of single phase between the melting point and the room temperature, coarse and oriented grains are formed in such weld metals more in thick sections. This leads to higher scattering at the grain boundaries and low signal to noise ratio, and extensive beam skewing. Experimental results to understand these problem are explained.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2003.11a
• /
• pp.497-500
• /
• 2003

The propose of this study is to discover the extrusion lightweight concrete panel mixing by admixture. The standard of water ratio 50% and weight substitution 0%, 10% by Fly-ash. When the products are manufactured, it is used to maintain its form weight substitution and addition among the viscosity agent each Silica-fume and Hydroxy propyl methyl cellulose. The study is basic properties and performances of extrusion lightweight concrete panels. Testing methods was specific gravity, water absorption, resistance to impact, thermal conductivity, and sound insulation.

• Journal of the Korean Ceramic Society
• /
• v.15 no.3
• /
• pp.135-139
• /
• 1978

Sintering oxide which was prepared by sintering at $1200^{\circ}C$ the mixture of ${\gamma}$-$Fe_2O_3$ and $Sb_2O_3$ in 2 : 1 mol ratio, showed 1st electrical switching and stable 2nd switching when D.C. voltage was applied. This electrical switching mechanism was known to be thermal mechanism from dependence of environmental temperature of threshold Voltage(Vm), Current(Im) and the conductivity of the current filament of the sintering oxide.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2000.04a
• /
• pp.93-96
• /
• 2000

In this paper, physical properties of planting concrete using Recycled aggregates made with demolished concrete and construction wastes are investigated. According to the test results. It shows that recycled aggregates made with demolished concrete and construction wastes have low physical properties compared with crushed stone. But, recycled aggregates made with construction wastes shows better performance in absorption ratio, unit weight and thermal conductivity than crushed stone. According it is thought that they are available for being applied to planting concrete considering the sides of efficient recycling of construction wastes and saving the manufacturing cost.

• Journal of Ceramic Processing Research
• /
• v.13 no.spc2
• /
• pp.428-432
• /
• 2012

Polyamidimide (PAI)-colloidal silica (CS) nanohybrid films were synthesized by an advanced sol-gel process. The synthesized PAI-CS hybrid films have a uniform and stable chemical bonding and there is no interfacial defects observed by TEM. The thermal degradation ratio of PAI-CS (10 wt%) hybrid films is delayed by 100 ℃ compared with pure PAI sample determined by on set temperature range in TGA. The dielectric constant of PAI-CS (10 wt%) hybrid films decreases with increasing CS content up to about 5 wt% but increases at higher CS content, which is not explained simply by effective medium therories (EMT). The duration time of PAI-CS (10 wt%) hybrid coil is 38 sec, which is very longer than that of pure PAI coil sample. The PAI-CS (10 wt%) hybrid film has a higher breakdown voltage resistance than the pure PAI film at surge environment and exhibits superior heat resistance. The PAI-CS (10 wt%) sample shows the advanced and stable thermal emission properties in transformer module compared with the pure PAI sample. This result illustrates that the advanced thermal conductivity and expansion properties of PAI-CS sample in the case of appropriate sol-gel processes brings the stable thermal emission in transformer system. Therefore, new PAI-CS hybrid samples with such stable thermal emission properties are expected to be used as a high functional coating application in ET, IT and electric power products.

• Advanced Composite Materials
• /
• v.16 no.3
• /
• pp.195-206
• /
• 2007

Carbon nanofiber (CNF)/unsaturated polyester resin (UPR) was prepared by a solvent evaporation method, and the temperature dependency of electrical conductivity was investigated. The CNF/UPR composites had quite a low percolation threshold due to CNF having a larger aspect ratio and being well dispersed in the UPR matrix. The positive temperature coefficient (PTC) was found in the CNF/UPR composites and it showed stronger effect around the percolation threshold. The electrical resistance of the CNF/UPR composites decreased and had lower temperature dependency with increasing numbers of thermal cycles.

• Journal of the Korean Solar Energy Society
• /
• v.35 no.2
• /
• pp.53-62
• /
• 2015

Boiling heat transfer characteristic is very important in the various industries such as solar thermal system, power generation, heat exchangers, cooling of high-power electronics components and cooling of nuclear reactors. Therefore, in this study, boiling heat transfer characteristics such as critical heat flux (CHF) and heat transfer coefficient under the pool boiling state were tested using graphene nanofluids. Graphene used in this study, which have the same thermal conductivity but with different sizes. The experimental results showed that the highest the CHF and boiling heat transfer coefficient increase ratio for graphene nanofluids was at the 0.01 vol.%. At the present juncture, the CHF and boiling heat transfer coefficient increase ratio of the small-sized graphene nanofluids was higher than the large-sized graphene nanofluids.

• Journal of the Semiconductor & Display Technology
• /
• v.21 no.1
• /
• pp.148-154
• /
• 2022

As the 4th industrial age approaches, the demand for semiconductors is increasing enough to be used in all electronic devices. At the same time, semiconductor technology is also developing day by day, leading to ultraprecision and low power consumption. Semiconductors that keep getting smaller generate heat because the energy density increases, and the generated heat changes the shape of the semiconductor package, so it is important to manage. The temperature change is not only self-heating of the semiconductor package, but also heat generated by external damage. If the package is deformed, it is necessary to manage it because functional problems and performance degradation such as damage occur. The package burn in test in the post-process of semiconductor production is a process that tests the durability and function of the package in a high-temperature environment, and heat dissipation performance can be evaluated. In this paper, we intend to review a new material formulation that can improve the performance of the adapter, which is one of the parts of the test socket used in the burn-in test. It was confirmed what characteristics the basic base showed when polyamide, a high-molecular material, and alumina, which had high thermal conductivity, were mixed for each magnification. In this study, functional evaluation was also carried out by injecting an adapter, a part of the test socket, at the same time as the specimen was manufactured. Verification of stiffness such as tensile strength and flexural strength by mixing ratio, performance evaluation such as thermal conductivity, and manufacturing of a dummy device also confirmed warpage. As a result, it was confirmed that the thermal stability was excellent. Through this study, it is thought that it can be used as basic data for the development of materials for burn-in sockets in the future.

• Journal of the Korean Applied Science and Technology
• /
• v.37 no.6
• /
• pp.1591-1596
• /
• 2020

The solid-state electrolyte based on polymer has great attention to develop its ionic conductivity from conventional polymer electrolyte by using wide range of ionic liquids with remarkable processability, flexibility and is applicable to various electrochemical devices including batteries, supercapacitor. Polymer electrolyte based on Ionic liquid with high conductivity, wide electrochemical stability, thermal stability is used in various electronic devices. In this work, we have investigated and developed solid-state electrolyte based on ionic liquid and polymer with enhanced ionic conductivity and electrochemical performances to conduct to various electronic devices including secondary battery. The ionic conductivity of polymer based solid state electrolyte with optimized ratio of the ionic liquid was 1.46-2 S/cm. The ionic liquid and polymer based electrolyte with enhanced ionic conductivity is promising candidates to utilize in wide range of secondary batteries.

• Journal of environmental and Sanitary engineering
• /
• v.12 no.3
• /
• pp.73-79
• /
• 1997

This research was intended as an investigation of applying Reduced Pressure Evaporation as efficient treatment method for landfill leachate. According to the variance of time, temperature, pressure and pH in experiments, the properties of leachate treatment are follows. The removal efficiencies of COD, NH$_{3}$-N, TOC, Conductivity and SS on the basis of reaction time was 96.4%-97.5%, -1.4%-53.7%, 81.7%-89.0%, 92.0%-95.3% and 99.86%-99.97%, respectively. When the pH of Influent was 7.5, the pH of effluent was increased to 10-11 with time elapse. It is concluded that the orgin of pH increase may be ammonia. When the properties of concentrate were investigated at the concentration ratio 90%(V/V), concentration difficiency represented in the ratio of experimental value/calculated value had following orders ; COD>TOC>NH$_{3}$-N>Conductivity>SS. Concentrate had good precipitation because of additive thermal treatment in the process. When evaporation experiments with pH adjustment of 4.0, 6.0, 7.5, 9.0 and 10.0 were performed ; Acidic evaporation experiments(pH 4.0, 6.0) showed low removal efficiency(81.6, 87.6%) of COD and high removal efficiency (97.5%. 84.6%) of NH$_{3}$-N at initial evaporation. Basic evaporation(pH 9.0, 10.0) showed high removal efficiency (97.2%, 98.9%) of COD and very low removal efficiency (-7.4%, -27.2%) of NH$_{3}$-N at initial evaporation.