Molybdenum is used in electrical contacts, industrial motors, and transportation materials due to its remarkable ability to resist heat and corrosion. It is also used to flame coat other metals. This study investigated, the thermal characteristics of the molybdenum sputtered material, such as electrical conductivity, and stealth effects on infrared thermal imaging cameras. To this end, molybdenum sputtered samples were prepared by varying the density of the base sample and the type of base materials used. Thereafter, the produced samples were evaluated for their surface state, electrical conductivity, electromagnetic field characteristics, thermal characteristics, stealth effect on infrared thermal imaging cameras, and moisture characteristics. As a result of infrared thermal imaging, the molybdenum layer was directed towards the outside air, and when the sample was a film, it demonstrated a greater stealth effect than the fabric. When the molybdenum layer was directed to the outside air, all of the molybdenum sputtering-treated samples exhibited a lower surface temperature than the “untreated sample.” In addition, as a result of confirming electrical properties following the molybdenum sputtering treatment, it was determined that the film exhibited better electrical conductivity than the fabric. All samples that were subjected to molybdenum sputtering exhibited significantly reduced electromagnetic and IR transmission. As a result, the stealth effect on infrared thermal imaging cameras is considered to be a better way of interpreting heat transfer than infrared transmission. These results are expected to have future applications in high-performance smartwear, military uniforms, and medical wear.

Cu matrix composites reinforced with chopped carbon fiber (CF), which is cost effective and can be well dispersed, are fabricated using electroless plating and hot pressing, and the effects of content and alignment of CF on the thermal properties of CF/Cu composites are studied. Thermal conductivity of CF/Cu composite increases with CF content in the in-plane direction, but it decreases above 10% CF; this is due to reduction of thermal diffusivity related with phonon scattering by agglomeration of CF. The coefficient of thermal expansion decreases in the in-plane direction and increases in the through-plane direction as the CF content increases. This is because the coefficient of thermal expansion of the long axis of CF is smaller than that of the Cu matrix, and the coefficient of thermal expansion of its short axis is larger than that of the Cu matrix. The thermal conductivity is greatly influenced by the agglomeration of CF in the CF/Cu composite, whereas the coefficient of thermal expansion is more influenced by the alignment of CF than the aggregation of CF.

Effective control of the heat generated from electronics and semiconductor devices requires a high thermal conductivity and a low thermal expansion coefficient appropriate for devices or modules. A method of reducing the thermal expansion coefficient of Cu has been suggested wherein a ceramic filler having a low thermal expansion coefficient is applied to Cu, which has high thermal conductivity. In this study, using pressureless sintering rather than costly pressure sintering, a polymer solution synthesis method was used to make nano-sized Cu powder for application to Cu matrix with an AlN filler. Due to the low sinterability, the sintered Cu prepared from commercial Cu powder included large pores inside the sintered bodies. A sintered Cu body with Zn, as a liquid phase sintering agent, was prepared by the polymer solution synthesis method for exclusion of pores, which affect thermal conductivity and thermal expansion. The pressureless sintered Cu bodies including Zn showed higher thermal conductivity (180 W/m·K) and lower thermal expansion coefficient (15.8×10−6/℃) than did the monolithic synthesized Cu sintered body.

Aluminum nitride (AlN) has excellent electrical insulation property, high thermal conductivity, and a low thermal expansion coefficient; therefore, it is widely used as a heat sink, heat-conductive filler, and heat dissipation substrate. However, it is well known that the AlN-based materials have disadvantages such as low sinterability and poor mechanical properties. In this study, the effects of addition of various amounts (1-6 wt.%) of sintering additives Y2O3 and Sm2O3 on the thermal and mechanical properties of AlN samples pressureless sintered at 1850oC in an N2 atmosphere for a holding time of 2 h are examined. All AlN samples exhibit relative densities of more than 97%. It showed that the higher thermal conductivity as the Y2O3 content increased than the Sm2O3 additive, whereas all AlN samples exhibited higher mechanical properties as Sm2O3 content increased. The formation of secondary phases by reaction of Y2O3, Sm2O3 with oxygen from AlN lattice influenced the thermal and mechanical properties of AlN samples due to the reaction of the oxygen contents in AlN lattice.

In this paper, optical infrared thermography simulation using thermal wave imaging technique is performed to analyze the thermal characteristics of delamination defects. In this study, lock-in thermography(LIT) and pulsed thermography(PT) simulation was performed to analyze the samples of european traditional tiles with delamination defects, and the analytical modeler was developed through the ANSYS 19.2 transient thermal analysis tool. Applied sinusoidal heating with modulation frequency according to pulse heating and phase locking technique. The thermal response of the sample surface by heating was recorded and then data analysis was performed. The temperature gradient characteristics of each technique were compared, and phase angle was calculated for the LIT to analyze the parameters for the experiment setting. The simulation model was developed as a useful data for practical optical infrared thermography tests.

In order to enhance the utilization of underground heat including underground water, the comparison between the existing high density polyethylene underground heat exchanger and the newly developed metal heat exchanger was conducted to suggest the potential use of geothermal energy corresponding to the geological characteristics of Jeju Island. When the acquired heat of the underground loop system test condition of the KS B 8292 water-water geothermal heat pump unit was compared by installing heat exchanger of HDPE material and the heat exchanger of STS material under the same bore hole condition, the total heat area of the heat exchanger of STS material was about 15% less than HDPE, but the acquired heat was estimated to be about 4 times or more.

The electromagnetic and thermal properties of a heavy fermion CeNi2Ge2 are investigated using first-principle methods with local density approximation (LDA) and fully relativistic approaches. The Ce f-bands are located near the Fermi energy EF and hybridized with the Ni-3d states. This hybridization plays important roles in the characteristics of this material. The fully relativistic approach shows that the 4f states split into 4f7/2 and 4f5/2 states due to spin-orbit coupling effects. It can be found that within the LDA calculation, the density of states near the Fermi level are mainly of Ce-derived 4f states. The Ni-derived 3d states have high peaks around -1.7eV and spreaded over wide range around the Fermi level. The calculated magnetic of CeNi2Ge2 with LDA method does not match with that of experimental result because of strong correlation interaction between electrons in f orbitals. The calculations show that the specific heat coefficient underestimates the experimental value by a factor of 19.1. The discrepancy between the band calculation and experiment for specific heat coefficient is attributed to the formation of a quasiparticle. Because of the volume contraction, the exchange interaction between the f states and the conduction electrons is large in CeNi2Ge2, which increases the quasiparticle mass. This will result in the enhancement of the specific hear coefficient.

Infiltration is a popular technique used to produce valve seat rings and guides to create dense parts. In order to develop valve seat material with a good thermal conductivity and thermal expansion coefficient, Cu-infiltrated properties of sintered Fe-Co-M(M=Mo,Cr) alloy systems are studied. It is shown that the copper network that forms inside the steel alloy skeleton during infiltration enhances the thermal conductivity and thermal expansion coefficient of the steel alloy composite. The hard phase of the CoMoCr and the network precipitated FeCrC phase are distributed homogeneously as the infiltrated Cu phase increases. The increase in hardness of the alloy composite due to the increase of the Co, Ni, Cr, and Cu contents in Fe matrix by the infiltrated Cu amount increases. Using infiltration, the thermal conductivity and thermal expansion coefficient were increased to 29.5 W/mK and 15.9 um/moC, respectively, for tempered alloy composite.

In this study, the thermal behavior of adaptor housing was analyzed by the numerical method. The boundary conditions used to die casting process were the temperature of molten metal and injection time. As the temperature of the molten metal increased, the tensile strength of the product decreased by the blow hole generated in the molten metal, and the decreasing tendency was gradually decreased. As the injection time of the molten metal increased, the heat flux rose, but the degree of the increase was very small. So, the injection time of the molten metal had little effect on the thermal behavior and diffusion of the adapter housing. As a result, the heat of the molten metal was transferred into the housing and the thermal behavior spread widely.

PVA 부직포의 방염성을 향상시키기 위하여 POCl3로 방염처리하였다. POCl3로 처리한 PVA 부직포의 물리적 및 열적 특성을 측정하고 분석하였다. 개질한 PVA 부직포는 대부분 물에 용해하지 않았으나 수축과 스웰링 특성을 보 였다. POCl3로 방염처리한 PVA 부직포의 열적 특성이 우수하고 방염특성이 원시료 보다 많이 우수한 것을 확인하였다. 그라프트 비와 염색성 사이의 선형관계는 PVA 부직포의 히드록시기와 POCl3가 공유결합으로 연결된 것에 기인하는 것 으로 분석되었다.

Natural and expandable graphites were chemically treated in acidic aqueous solutions such as acetic acid or mixtures of acetic acid and nitric acid. Structures and thermal conductivities of the as-treated graphites were characterized in detail. Both graphites were significantly oxidized in the mixed acidic solution of H2SO4 and HNO3, which condition was generally used for the oxidation of carbon nanotubes. This considerable oxidation of graphites caused a depression of their thermal conductivity. The structural characteristics, obtained by XRD and XPS, show that the graphites treated in the relatively weak acidic conditions (acetic acid or mixture of acetic acid and nitric acid) were quite similar to the untreated graphites. However, the thermal conductivities of both acidic-treated graphites were remarkably increased.

Geopolymers have many advantages over Portland cement, including energy efficiency, reduced greenhouse gas emissions, high strength at early age and improved thermal resistance. Alkali activated geopolymers made from waste materials such as fly ash or blast furnace slag are particularly advantageous because of their environmental sustainability and low cost. However, their durability and functionality remain subjects for further study. Geopolymer materials can be used in various applications such as fire and heat resistant fiber composites, sealants, concretes, ceramics, etc., depending on the chemical composition of the source materials and the activators. In this study, we investigated the thermal properties and microstructure of fly ash and blast furnace slag based geopolymers in order to develop eco-friendly construction materials with excellent energy efficiency, sound insulation properties and good heat resistance. With different curing times, specimens of various compositions were investigated in terms of compressive strength, X-ray diffraction, thermal property and microstructure. In addition, we investigated changes in X-ray diffraction and microstructure for geopolymers exposed to 1,000 oC heat.

This study analyzed the thermal properties of a thermal conductive polymer polyethylene terephthalate(PET) to make it into a heat sink and evaluated the temperature properties of 10W COB(chip on board) LED(Ligth Emitting Diode) as a heat sink. This study confirmed the composition and content of inorganic compounds in PET. As a result, carbon filler content of Samples A and B accounted for 73.93 and 61.46%, respectively. Sample B included 10% more inorganic filler(Al, Mg, Si, Ca), and its thermal conductivity was 10.9 W/mk higher than Sample A. Based on the material properties, this study compared the heat dissipation properties of 10W COB LED between PET and aluminum heat sinks. As a result, the maximum temperature of PET heat sink was 4.4℃ higher than that of aluminum heat sink, and the minimum temperature outside PET heat sink was 13.6℃ lower than that of aluminum heat sink. Based on these results, PET heat sinks are inferior to aluminum heat sinks in thermal properties. However, it is considered possible to realize various designs because they have excellent formability and lightweight properties due to the lower melting point and specific gravity

Ohmic heating uses electric resistance heat which occurs equally and rapidly inside food when the electrical current is transmitted into. Prior to the study, we have researched the potato starch’s thermal property changes during ohmic heating. Comparing with conventional heating, the gelatinization temperature and the range of potato starch treated by ohmic heating are increased and narrowed respectively. Herein, we have studied thermal property changes of wheat, corn, potato and sweet potato starch by ohmic heating as well as conventional heating. And then we measure the water holding capacity of starches. Annealing of starch is a heat treatment method heated at 3~4% below the gelatinization point. This treatment changes the starch’s thermal property. In the DSC analysis of this study, the To, Tp, Tc of all starch levels have increased, and the Tc－To narrowed. In the ohmic heating, the treatment sample is extensively changed but not with the conventional heating. From the ohmic treatment, increases from gelatinization temperature are potato (8.3℃) > wheat (5.3℃) > corn (4.9℃) > sweet potato (4.5℃), and gelatinization ranges are potato (7.9℃), wheat (7.5℃), corn (6.1℃) and sweet potato (6.8℃). In the case of conventional treatment, water holding capacity is not changed with increasing temperature but the ohmic heating is increased. Water holding capacity is related to the degree of gelatinization for starch. This result show that when treated with below gelatinization temperature, the starches are partly gelatined by ohmic treatment. When viewing the results of the above, ohmic treatment is enhanced by heating and generating electric currents to the starch structure.

This paper presents that hybrid cooler of vapor compression type and natural refrigerant circulation type is energy saving cooler using R-410a for indoor mobile telecommunication station. Its performance and operation characterists are done experimently about receiver tank, piping and heat exchanger designs for natural circulation of refrigeration and use of R-410a for fixed height location difference of indoor and outdoor cooler.