• Journal of Adhesion and Interface
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• v.15 no.1
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• pp.14-21
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• 2014

In the present work, PLA/PBS blends with poly(lactic acid) (PLA) and poly(butylene succinate) (PBS) at different contents were processed by using a twin-screw extruder and an injection molding machine, and then their mechanical, thermal and morphological properties were investigated. The mechanical properties such as flexural strength, flexural modulus, tensile strength and tensile modulus and thermal properties such as melting behavior, dynamic mechanical thermal properties and thermal stability significantly depended on the contents of PLA and PBS. However, the heat deflection temperature of the blends was not significantly influenced by the contents of PLA and PBS. Also, the fracture surfaces of PLA/PBS blends were changed from a brittle pattern to a ductile pattern with increasing the PBS contents.

• Advances in materials Research
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• v.6 no.1
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• pp.1-12
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• 2017

The aim of the work was to evaluate the effect of ultraviolet-ozone ($UV-O_3$) irradiation with different times on the structure and thermal properties of hydroxypropyl methylcellulose (HPMC) in the form of a thin film to be used as bioequivalent materials according to their important broad practical and medical applications. HPMC thin films were exposed to $UV-O_3$ radiation in air at a wavelength of 184.9 nm.The beneficial effects of this treatment on the crystallinity and amorphousity regions were followed by X-ray diffraction technique and FTIR spectroscopy. Differential scanning calorimetry, thermogravimetric and differntial thermal analyses were used in order to study the thermal properties of HPMC samples following the process of photodegradation. The obtained results indicated that the rate of degradation process was increased with increasing the exposure time. Variations in shape and area of the thermal peaks were observed which may be attributed to the different degrees of crystallinity after exposing the treated HPMC samples. This meant a change in the amorphousity of the treated samples, the oxidation of its chemical linkages on its surface and its bulk, and the formation of free radical species as well as bond formation.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.1231-1238
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• 2010

Recently, the utilization of recycled aggregates for backfilling a power transmission pipeline trench has been increasing due to the issues of eco-friendly construction and shortage of natural aggregate resource. It is important to investigate the physical and thermal properties of the recycled aggregates that can be used as a backfill material. This study presents the thermal properties of two types of recycled aggregates with various particle size distributions. The thermal properties of the recycled aggregate were measured using the transient hot wire method and the probe method after performing the standard compaction test using an automatic compactor. Similar to silica sand, the thermal resistivity of the recycled aggregates decreased when the water content increased. This study shows that the recycled aggregate can be a promising backfill material substituting for natural aggregate when backfilling the power transmission pipeline trench.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.8
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• pp.893-897
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• 2004

In this paper, we studied the mechanical and thermal properties on slice XLPE sheet from 22 kV and 154 kV power cables. Interface structures are XLPE/semiconductor and XLPE/water/semiconductor. We evaluated mechanical property, thermal analysis, moisture analysis. Based on mechanical and thermal properties of the 22 kV XLPE sheet, elongation, mechanical strength, and melting point were evaluated to be 485.48 %, 1.74 kgf/$\textrm{mm}^2$ and $102.48^{\circ}C$, respectively. It was also evaluated from the mechanical and thermal properties of 154 kV XLPE sheet that elongation, mechanical strength, and melting point are 507.81 %, 1.8 kgf/$\textrm{mm}^2$, $106.9^{\circ}C$, respectively. A region shows a rapid increase in tension strength, and B region only shows increase in elongation under 1.0 kgf/$\textrm{mm}^2$, C region shows increase in both elongation and tension strength. Difference of melting point came from the chain of XLPE polymer and the difference of crystallization. Moisture density of semiconductor showed 800 ∼ 1200 ppm before extrude, 14000 ∼24000 ppm after extrude. These values were higher than the moisture density of XLPE (300∼560) ppm.

• Journal of Sensor Science and Technology
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• v.32 no.1
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• pp.39-43
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• 2023

Microscale thermophysical property measurements of liquids have been developed considering the increasing interest in the thermal management of cooling systems and energy storage/transportation systems. To accurately predict the heat transfer performance, information on the thermal conductivity, heat capacity, and density is required. However, a simultaneous analysis of the thermophysical properties of small-volume liquids has rarely been considered. Recently, we proposed a new methodology to simultaneously analyze the aforementioned three intrinsic properties using heater-integrated fluidic resonators (HFRs) in an atmospheric pressure environment comprising a microchannel, resistive heater/thermometer, and mechanical resonator. Typically, the thermal conductivity and volumetric heat capacity are measured based on a temperature response resulting from heating using a resistive thermometer, and the specific heat capacity can be obtained from the volumetric heat capacity by using a resonance densitometer. In this study, we analyze methods to improve the thermophysical property measurement performance using HFRs, focusing on the effect of the ambience around the sensor. The analytical method is validated using a numerical analysis, whose results agree well with preliminary experimental results. In a vacuum environment, the thermal conductivity measurement performance is enhanced, except for the thermal conductivity range of most gases, and the sensitivity of the specific heat capacity measurement is enhanced owing to an increase in the time constant.

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

• Korean Journal of Materials Research
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• v.33 no.10
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• pp.422-429
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• 2023

High-strength low-alloy steel is one of the widely used materials in onshore and offshore plant engineering. We investigated the alloying effect of solute atoms in α-Fe based alloy using ab initio calculations. Empirical equations were used to establish the effect of alloying on the Vicker's hardness, screw energy coefficient, and edge dislocation energy coefficient of the steel. Screw and edge energy coefficients were improved by the addition of V and Cr solute atoms. In addition, the addition of trace quantities of V, Cr, and Mn enhanced abrasion resistance. Solute atoms and contents with excellent mechanical properties were selected and their thermal conductivity and thermal expansion behavior were investigated. The addition of Cr atom is expected to form alloys with low thermal conductivity and thermal expansion coefficient. This study provides a better understanding of the state-of-the-art research in low-alloy steel and can be used to guide researchers to explore and develop α-Fe based alloys with improved properties, that can be fabricated in smart and cost-effective manners.

• Journal of Powder Materials
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• v.17 no.2
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• pp.148-153
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• 2010

Thermal barrier systems have been widely investigated over the past decades, in order to enhance reliability and efficiency of gas turbines at higher temperatures. Yttria-stabilized zirconia (YSZ) is one of the most leading materials as the thermal barriers due to its low thermal conductivity, thermodynamic stability, and thermal compatibility with metal substrates. In this work, rare-earth oxides with pyrochlore phases for thermal barrier systems were investigated. Pyrochlore phases were successfully formed via solid-state reactions started from rare-earth oxide powders. For the heat-treated samples, thermo-physical properties were examined. These rare-oxide oxides showed thermal expansion of $9{\sim}12{\times}10^{-6}/K$ and thermal conductivity of 1.2~2.4 W/mK, which is comparable with the thermal properties of YSZ.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.7
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• pp.627-633
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• 2003

The effects of alloying-element additions to Ag sheath on thermal conductivity and mechanical properties of Bi-2223 superconductor tapes have been evaluated. In order to evaluate the effects of sheath alloys and their configuration on the properties of tape, various combinations of Ag and Ag alloys were selected as the inner and outer sheath. Thermal conductivity of the tapes was evaluated by using thermal integral method at 10 ∼120 K. It was observed that the addition of Mg, Sb, and Au to Ag sheath significantly decreased the thermal conductivity at low temperature probably due to the alloying effect. Specifically, the thermal conductivity of AgMg, AgSb, and AgAu at 40 K were 411.4, 142.3, and 109.7 W/(m·K), respectly, which is about 2∼9 times lower than that of Ag (1004.6 W/(m·K)). In addition, the thermal conductivity of alloy-sheathed tape was significantly dependent on their thermal conductivities of constituent sheath materials. The mechanical properties of alloy-sheathed tapes were also evaluated. Yield strength and tensile strength were improved but workability decreased for alloy-sheathed tapes.

• Korean Journal of Materials Research
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• v.20 no.2
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• pp.104-110
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• 2010

The characteristics of all polymer composites containing carbon materials are determined by four factors: component properties, composition, structure and interfacial interactions. The most important filler characteristics are particle size, size distribution, specific surface area and particle shape. As a consequence, in this paper we discuss the aspects of the mechanical, electrical and thermal properties of composites with different fillers of carbon black, carbon nanotube (CNT), graphene and graphite and focus on the relationship between factors and properties, as mentioned above. Accordingly, we fabricate rubber composites that contain various carbon materials in carbon black-based and silica based-SBR matrixes with dual phase fillers and use scanning electron microscopy, Raman spectroscopy, a rhometer, an Instron tensile machine, and a thermal conductivity analyzer to evaluate composites' mechanical, fatigue, thermal, and electronic properties. In mechanical properties, hardness and 300%-modulus of graphene-composite are sharply increased in all cases due to the larger specific surface. Also, it has been found that the thermal conductivity of the CNT-composite is higher than that of any of the other composites and that the composite with graphene has the best electrical properties.