• Journal of Surface Science and Engineering
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• v.50 no.6
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• pp.486-491
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• 2017

Silver nanowire (AgNW) transparent electrode is one of next generations of flexible and transparent electrode. The electrode shows high conductivity and high transparency comparable to ITO. However, the electrode is weak against heat. The wires are separated into nanodots at temperature above $200^{\circ}C$. It causes the electrical resistance increase. Moreover, it is vulnerable to oxygen and moisture in the atmosphere. The improvement of thermal and moisture resistance of silver nanowire transparent electrode is the most important for commercializing. We proposed silver nanowires transparent electrode which is capped with very thin nickel oxide layer. The nickel oxide layer is five nanometers of thickness, but the heat and moisture resistance of the transparent electrode is effectively improved. The AgNW/NiO electrode can endure at $300^{\circ}C$ of temperature for 30 minutes, and resistance is not increased for 180 hours at $85^{\circ}C$ of temperature and 85% of relative humidity. We showed an applications of transparent and flexible heater using the electrode, the heater is operated more than $180^{\circ}C$ of temperature.

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

• Structural Engineering and Mechanics
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• v.91 no.6
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• pp.627-642
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• 2024

In the present work, the deformation and stresses induced in a functionally graded disk have been reported for different loading conditions. The governing differential equation is solved using the classical method namely Navier's method by considering thermal and mechanical boundary conditions at the surface of the disk. To simplify solving the second-order differential equation, a plane stress condition was assumed. Following validation using a one-dimensional steady-state heat condition problem, temperature variations were computed for constant heat generation and varying conductivity. The research aims to investigate both the individual and combined effects of rotation, gravity, and temperature with constant heat generation on a hollow disk operating under complex loading conditions. The results demonstrated a high degree of accuracy when compared with those in existing literature. Material properties, such as Young's modulus, density, conductivity, and thermal expansion coefficient, were modeled using a power law variation along the disk's radius by considering aluminum as a base material. The proposed analytical method is straightforward, providing valuable insights into the behavior of disks under various loading conditions. This method is particularly useful for researchers and industries in selecting appropriate loading conditions and grading parameters for engineering applications, including aerospace components, energy systems, and rotary machinery parts.

• Journal of Powder Materials
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• v.11 no.2
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• pp.158-164
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• 2004

W-Cu composite has been used for the applications requiring both high strength, good thermal and electrical conductivity. A graded combination of W and Cu will reduce thermal stress concerned with heat conduction, maintaining good thermal conductivity and high mechanical strength. In the present work, an attempt was made to fabricate continuous W-Cu FGM by preparing the graded porous structure of W skeleton using spark plasma sintering (SPS) process followed by infiltrating Cu. The graded porous structure was prepared at 150$0^{\circ}C$ for 60s under pressure of 15MPa by SPS process using a graphite mold with varying crr)ss section in the longitudinal direction. Infiltration of Cu was performed at 115$0^{\circ}C$ for 1 hour under $H_2$. W-Cu composite with graded Cu composition of 14 to 27 wt％ was finally prepared. In this process the gradient of composition could be conveniently controlled by varying the gradient of cross sectional area of graphite mold, temperature and pressure.

• Korean Journal of Materials Research
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• v.29 no.9
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• pp.567-577
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• 2019

Aluminum nitride (AlN) has versatile and intriguing properties, such as wide direct bandgap, high thermal conductivity, good thermal and chemical stability, and various functionalities. Due to these properties, AlN thin films have been applied in various fields. However, AlN thin films are usually deposited by high temperature processes like chemical vapor deposition. To further enlarge the application of AlN films, atomic layer deposition (ALD) has been studied as a method of AlN thin film deposition at low temperature. In this mini review paper, we summarize the results of recent studies on AlN film grown by thermal and plasma enhanced ALD in terms of processing temperature, precursor type, reactant gas, and plasma source. Thermal ALD can grow AlN thin films at a wafer temperature of $150{\sim}550^{\circ}C$ with alkyl/amine or chloride precursors. Due to the low reactivity with $NH_3$ reactant gas, relatively high growth temperature and narrow window are reported. On the other hand, PEALD has an advantage of low temperature process, while crystallinity and defect level in the film are dependent on the plasma source. Lastly, we also introduce examples of application of ALD-grown AlN films in electronics.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.12
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• pp.1022-1030
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• 2009

Numerical analysis was carried out to investigate the effect of GDL (Gas diffusion layer) porosity on the performance of PEMFC (proton exchange membrane fuel cell). A complete three-dimensional model was chosen for single straight channel geometry including cooling channel. Main emphasis is placed on the heat and mass transfer through the GDL with different porosity. The present numerical results show that at high current densities, the cell voltage is influenced by the GDL porosity while the cell performance is nearly the same at low current densities. At high current densities, low value of GDL porosity results in decrease of the fuel cell performance since the diffusion of reactant gas through GDL becomes slow with decreasing porosity. On the other hand, for high GDL porosity, the effective thermal conductivity becomes low and the heat generated in the cell is not removed rapidly. This causes the temperature of fuel cell to increase and gives rise to dehydration of the membrane, and ultimately increase of the ohmic loss.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.06a
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• pp.140-141
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• 2020

Concrete has a lower thermal conductivity or thermal diffusion coefficient compared to other building materials, so it is widely used as fireproof compartment material or refractory material for structures. However, in the event of thermal damage such as fire, cement curing agents and aggregates act differently, resulting in heat generation or deterioration of tissue due to dehydration, resulting in deterioration of physical properties and fire resistance. Therefore, in this study, the processing structure of cement paste is measured through nitrogen absorption method. The test specimen is a cement paste of 40% W/C and is set at 1000 ℃ under heating temperature conditions. As the temperature rose, the micro-pore mass below was reduced based on about 0.01 감소m, but the air gap above that was increased.Thus, in the range of pores measured in nitrogen adsorption, the air mass tended to decrease under high temperature conditions.

• Asian Journal of Turfgrass Science
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• v.23 no.2
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• pp.229-240
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• 2009

The high temperature and water content in soil profile probably affect the physiological disorder especially on cool-season turfgrasses in warm and humid weather of Korean summer. The purpose of this research was to analyze the effect of soil temperature and water content on the growth and stress response of creeping bentgrass(Agrostis palustris Huds.) under a humid and warm temperature. USGA(United State of Golf Association) green profile in laboratory test, Daily temperature changes were tested under a dried sand, 70% water content of field capacity, and saturated condition at $34^{\circ}C$ of the USGA green in lab. In this test, the dried sand reached to $80^{\circ}C$, however, the surface temperature decrease of $10^{\circ}C$ on the saturated condition. In the thermal properties test in field, thermal conductivity, thermal diffusivity, and soil temperature were increased followed by irrigation practise. In the water-deficient condition, the highest soil temperature was reached temporally right after irrigation, however, the excessive soil water content higher than field water holding capacity showed the highest soil temperature after a while. This result indicated that a heat damage to root system was caused from the thermal conductivity of a high surface soil temperature. The excessive irrigation when a high turf surface temperature should occur a negative result on tufgrass growth, moreover, it would be fatal to root growth of creeping bentgrass, especially when associated with a poor draining system on USGA sand green. Overall, this study shows that high soil temperature with water-excessive condition negatively affects on cool-season grass during the summer season, suggesting that excessive irrigation, over 70% field capacity of soil condition, does not help to reduce soil temperature for summer season in Korea. In the study that cool-season grass were treated with different water content of soil, The soil had higher temperature and more water holding capacity when treatment rate of soil conditioner was increased. The best growth at the normal water condition and the worst state of growth at thee water-excessive condition were observed.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2750-2753
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• 2008

This paper introduce the CFD analysis for predicting the heat transfer at the Ultrasonic horn. Approximately Ultrasonic horn separates two part. One is preheating part and the other is cooling part. Temperature of preheating part rise up by $260^{\circ}C$ that make it possible to attach a chip to a semiconductor. Also there is a piezo material in the cooling part. When piezo work, it generates heat of $100^{\circ}C$. It can stand by $150^{\circ}C$. But the high temperature conducted from the preheating part has a bad affect on the piezo. These situation make it necessary cooling at piezo. Previously except of the piezo, all of them are composed of the SUS440c that has good thermal conductivity. This study shows way that not only cooling the piezo but also cutting off the conduction between preheating part and cooling part by using the Ti and Duralumin that have low thermal conductivity compare with the SUS440c. Conclusion of CFD analysis that the heat coming from the piezo can't be transferred the horn cause of the Ti and Duralumin.

• Journal of Powder Materials
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• v.29 no.6
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• pp.468-476
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• 2022

Yttria-stabilized zirconia (YSZ) has a low thermal conductivity, high thermal expansion coefficient, and excellent mechanical properties; thus, it is used as a thermal barrier coating material for gas turbines. However, during long-time exposure of YSZ to temperatures of 1200℃ or higher, a phase transformation accompanied by a volume change occurs, causing the YSZ coating layer to peel off. To solve this problem, YSZ has been doped with trivalent and tetravalent oxides to obtain coating materials with low thermal conductivity and suppressed phase transformation of zirconia. In this study, YSZ is doped with trivalent oxides, Nd₂O₃, Yb₂O₃, Al₂O₃, and tetravalent oxide, TiO₂, and the thermal conductivity of the obtained materials is analyzed according to the composition; furthermore, the relative density change, microstructure change, and m-phase formation behavior are analyzed during long-time heat treatment at high temperatures.