• 한국분말재료학회지
• /
• 제26권5호
• /
• pp.395-404
• /
• 2019

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 $Y_2O_3$ and $Sm_2O_3$ on the thermal and mechanical properties of AlN samples pressureless sintered at $1850^{\circ}C$ in an $N_2$ 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 $Y_2O_3$ content increased than the $Sm_2O_3$ additive, whereas all AlN samples exhibited higher mechanical properties as $Sm_2O_3$ content increased. The formation of secondary phases by reaction of $Y_2O_3$, $Sm_2O_3$ 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.

• Advances in materials Research
• /
• 제8권2호
• /
• pp.137-154
• /
• 2019

In this study, thermal effects on the mechanical properties of cement mortars with some types of fibers is investigated. The replaced fibers were made of polypropylene (PP), aramid, glass and basalt. In other words, the main goal of this paper is to study the effects of different fibers on the mechanical properties of cement mortars after subjecting to normal and sub-elevated temperatures. The experimental tests used for investigating these effects were compressive, splitting tensile, and four-point bending tests at 20, 100 and $300^{\circ}C$, respectively. Moreover, the microstructures of the specimens in different temperatures were investigated using scanning electron microscope (SEM). Based on the experimental results, the negative effects of sub-elevated temperatures on four-point bending tests were much more than the others. Moreover, using the fibers with higher melting points could not improve the qualities of the samples in sub-elevated temperatures.

• Fibers and Polymers
• /
• 제6권2호
• /
• pp.169-173
• /
• 2005

Low temperature plasma (LTP) treatment was applied to wool fabric with the use of a non-polymerizing gas, namely oxygen. After the LTP treatment, the fabric properties including low-stress mechanical properties, air permeability and thermal properties, were evaluated. The low-stress mechanical properties were evaluated by means of Kawabata Evaluation System Fabric (KES-F) revealing that the tensile, shearing, bending, compression and surface properties were altered after the LTP treatment. The changes in these properties are believed to be related closely to the inter-fiber and inter-yam frictional force induced by the LTP. The decrease in the air permeability of the LTP-treated wool fabric was found to be probably due to the plasma action effect on increasing in the fabric thickness and a change in fabric surface morphology. The change in the thermal properties of the LTP-treated wool fabric was in good agreement with the above findings and can be attributed to the amount of air trapped between the yams and fibers. This study suggested that the LTP treatment can influence the final properties of the wool fabric.

• 폴리머
• /
• 제29권5호
• /
• pp.481-485
• /
• 2005

본 연구에서는 2관능성 에폭시 수지에 기상성장 탄소나노섬유(VGCNFs)를 0, 0.1, 0.5, 1.0 그리고 $2wt\%$ 함량 비로 첨가하여, 제조한 VGCNFs/에폭시 복합재료의 열적 및 기계적 특성을 고찰하고자 하였다. VGCNFs/에폭시 나노복합재료의 열적 특성은 TMA와 DMA로 알아보았으며, 기계적 특성은 만능 시험기와 낙하 충격 시험기 및 마찰$\cdot$마모 시험기를 통하여 관찰하였다. 실험 결과. VGCNFs의 함량이 증가할수록 열적 및 기계적 특성이 향상됨을 확인할 수 있었는데, 이는 현재의 복합재료 시스템에 있어서 VGCNFs와 에폭시 사이의 기계적 얽힘 현상의 향상을 가져오는 복합재료의 가교구조의 증가 때문이라 판단된다.

• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2003년도 추계학술발표대회 논문집
• /
• pp.221-224
• /
• 2003

Polyvinyl chloride (PVC)/gypsum Polymer blend materials were prepared by melt blending of PVC with gypsum and additives. Effect of gypsum content on the properties of PVC/gypsum Polymer blend material was studied by investigating physico-mechanical properties, thermal properties and morphology development. It was found that the replacement of gypsum for methylene-butadiene-sarene (MBS) component in PVC/gypsum polymer blend material enhanced the tensile strength, but gradually decreased its impact strength. Besides, with the increase of gypsum content, the elongation at break of material gradually decreased. The Presence of the different gypsum contents made a shift of g1ass transition temperature and increased the thermal stability as well as the processing temperature range of polymer blends. The observation of morphology, the results of the physico-mechanical properties and thermal properties proved simultaneously that PVC/gypsum Polymer blend material with the gypsum content of 22.56 wt.% reached the optimum results among five kinds of PVC/gypsum Polymer blend materials investigated.

• 접착 및 계면
• /
• 제15권1호
• /
• pp.14-21
• /
• 2014

본 연구에서는 이축압출기와 사출기를 사용하여 폴리유산(PLA)와 폴리부틸렌숙시네이트(PBS) 수지의 함량비를 달리하여 PLA/PBS 블랜드를 제조하고, 그들의 기계적, 열적 특성 및 모폴로지를 조사하였다. PLA/PBS 블랜드의 굴곡강도, 굴곡탄성률, 인장강도 및 인장탄성률과 같은 기계적 특성, 그리고 용융거동, 동역학적 열특성 및 열안정성과 같은 열적 특성이 PLA와 PBS 함량비에 크게 의존하였다. 그러나 PLA/PBS 블랜드의 열변형온도는 PLA 또는 PBS 함량 변화에 크게 영향을 받지 않았다. 또한 PLA/PBS 블랜드의 파단면은 PBS 함량이 증가함에 따라 brittle 양상으로부터 ductile 양상으로 변화되었다.

• 한국응용과학기술학회지
• /
• 제25권1호
• /
• pp.15-22
• /
• 2008

The effects of fillers on the mechanical and thermal properties of glass/novolac composites have been studied. The matrix polymer and reinforcement were novolac type phenolic resin and milled glass fiber, respectively. Three different fillers, such as calcium carbonate, aluminum oxide, and wood powder were used for glass fiber reinforced plastic(GFRP) manufacture. Gravity, moisture content, tensile and flexural strength were measured to analyze the mechanical properties of GFRP and the final composites was burned in the electronic furnace at $1000^{\circ}C$ to confirm thermal properties GFRP containing aluminium oxide shows the highest thermal stability with 32% of weight loss at $1000^{\circ}C$ for one hour. GFRP containing calcium carbonate shows the maximum flexural strength (146 MPa), but that containing wood powder dose the highest tensile strength (65 MPa). Conclusively, we found that the characteristics of final composites strongly depend on several factors, such as types of materials, contents and chemical affinity of fillers. Therefore, it is very important to set up the combination of fillers for GFRP manufacturing to improve both mechanical and thermal properties at the same time.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2005년도 춘계학술대회 논문집
• /
• pp.391-396
• /
• 2005

Salt water spray test and salt water immersion test were experimentally conducted in order to investigate the durability of fiber reinforced composites under salt water environment. The specimens were made of glass fabric reinforcement and phenolic resin. Mechanical test was performed to obtain mechanical properties such as tensile properties, flexural properties, and shear properties by varying with exposure times. Also dynamic mechanical test and FTIR were conducted to investigate a change in chemical structure as well as thermal analysis properties such as storage shear modulus, loss shear moduls, and tan ${\delta}$. According to the results, salt water environment has effected on mechanical properties and thermal analysis properties and especially the durability of glass fabric/phenolic composites were severely affected on salt water immersion environment rather than salt water spray environment.

• 감성과학
• /
• 제5권3호
• /
• pp.47-52
• /
• 2002

직물의 태는 손으로 만져 보았을 때 느껴지는 감촉, 육안으로 느껴지는 감각, 그리고 직물의 물리적 역학적 성질 등이 함께 어울어져 이루어지는 것이다. 따라서 본 연구에서는 폴리에스테르 원형사와 삼각사로 제직된 직물의 태와 온/냉감 및 광택도를 측정하였다. 삼각단면사로 제직된 직물이 원형단면사로 제직된 직물보다 더 좋은 태를 보였으며 열전달계수가 크게 나타나 냉감을 느낄 수 있었으며 높은 반사율을 보였다.

• Advances in concrete construction
• /
• 제14권3호
• /
• pp.215-225
• /
• 2022

Thermal comfort and energy conservation are critical issues in the building sector. Energy consumption in the building sector should be reduced whilst enhancing the thermal comfort of occupants. Concrete is the most widely used construction material in buildings. Its thermal conductivity (k-value) has a direct effect on thermal comfort perception. This study aims to find the optimum value of replacing the normal aggregate with lightweight expanded clay aggregate (LECA) under high strengths and low thermal conductivity, density and water absorption. The k-value of the LECA concrete and its physical and mechanical properties have varying correlations. Results indicate that the oven-dry density, compressive strength, splitting tensile strength and k-value of concrete decrease when normal coarse aggregates are replaced with LECA. However, water absorption (initial and final) increases. Thermal conductivity and the physical and mechanical properties have a strong correlation. The statistical optimisation of the experimental data shows that the 39% replacement of normal coarse aggregate by LECA is the optimum value for maximising the compressive and splitting tensile strengths whilst maintaining the k-value, density and water absorption at a minimum.