• 한국염색가공학회지
• /
• 제35권2호
• /
• pp.128-136
• /
• 2023

Recently, the automobile industry is developing as the demand for automo- biles increases due to industrial development and population growth. In addition, many studies are being conducted to reduce heat loss inside the automobiles in order to save energy inside the automobiles due to environmental regulations. In this study, alumina, nanosilicon, and aerogel, which are adiabatic materials, were filled in PET to manufacture yarn, identify physical and mechanical properties, and weave into fabric to confirm adiabatic performance. As the content of the adiabatic material increased, the tensile strength of the fibers filled with alumina and nanosilicon decreased greatly, and the adiabatic property slightly increased. The tensile strength of fibers filled with the aerogel decreased slightly, but the adiabatic properties were greatly increased. Therefore, it is considered to be due to the large volume fraction in the PET yarn due to the low density of the aerogel.

• 한국작물학회:학술대회논문집
• /
• 한국작물학회 2017년도 9th Asian Crop Science Association conference
• /
• pp.304-304
• /
• 2017

In semi-arid countries such as Namibia, the flooding unexpectedly happens in a rainy season, causing losses in the yield of upland-adapted cereal crop. In flooding conditions, rice roots sequentially form aerenchyma and a barrier to radial oxygen loss (ROL), and oxygen is released into the rhizosphere near the root tips. Iijima et al. (2016) and Awala et al. (2016) reported that close mixed-planting with rice can mitigate the flood stress of co-growing upland-adapted cereal crop by modifying their rhizosphere microenvironments via the oxygen released from the rice roots. Moreover, by using the model system of hydroponic culture, it was confirmed that oxygen from rice roots was transferred to co-growing upland-adapted cereal crop in close mixed planting system (Kawato et al., 2016). However, it is not sure whether the ability of oxygen release varies among rice cultivars, because Kawato et al. (2016) used only one japonica cultivar, Nipponbare (Oryza sativa). The objective of this study was to compare the ability of oxygen release in rhizosphere among rice cultivars. The experiment was conducted in a climate chamber in Kindai University. We used 10 rice cultivars from three different rice species (O. sativa (var. japonica (2), var. indica (3)), Oryza glaberrima Steud. (2) and their interspecific progenies (3)) to compare the ability of oxygen release from the roots. According to the method by Kawato et al. (2016), the dissolved oxygen concentration of phase I (with shoot) and phase II (without shoot) were measured by a fiber optic oxygen-sensing probe. The oxygen released from rice roots was calculated from the difference of the measurements between phase I and phase II. The result in this study indicated that all of the rice cultivars released oxygen from their roots, and the amount of released oxygen was significantly correlated with the above-ground biomass (r = 0.710). The ability of oxygen release (the amount of the oxygen release per fresh root weight) of indica cultivars (O. sativa) tended to be higher as compared with the other cultivars. On the other hand, that of African rice (O. glaberrima) and the interspecific progenies tended to be lower. These results suggested that the ability of oxygen release widely varies among rice cultivars, and some of indica cultivars (O. sativa) may be suitable for close mixed-planting to mitigate flood stress of upland-adapted cereal crop.

• International Journal of Precision Engineering and Manufacturing
• /
• 제8권4호
• /
• pp.38-44
• /
• 2007

Combat vehicles are frequently maneuvered in battlefields when the lives of combatants are being threatened. These vehicles are important elements that influence the consequences of a battle. Their armor must be lightweight and provide excellent protection to ensure successful operations. Ceramic composite armor has recently been developed by many countries to fulfill these requirements. We reviewed previous research to determine an effective armor design, and then fabricated a composite armor structure using $Al_2O_3$ and glass fiber-reinforced polymer. Specimens were manufactured under controlled conditions using different backing plate thicknesses and bonding methods for the ceramic layer and the backing plate. The penetration of an armor-piercing bullet was evaluated from ballistic protection tests. The bonding method between the ceramic layer and the fiber-reinforced polymer influenced the ballistic protection performance. A bonding layer using rubber provided the best protection.

• 대한기계학회논문집
• /
• 제17권7호
• /
• pp.1772-1782
• /
• 1993

The characteristics of metal matrix composite under dynamic tension at high strain rates up to the order of $10^3/sec$ is studied by using newly developed apparatus. The composite material processed in this research is aluminum-alumina metal matrix composites, arid fabricated by compocasting with the fiber volume fraction from 5 to 20%. The whisker and matrix material used in this paper were ${\delta}-Al_2O_3$ and Al-6061, respectively. The mechanical tests performed in this research are low and high strain rate tensile test. At low strain-rate tensile test, the modulus of elasticity and the ultimate tensile strength of the composites were improved about 77 pct. and 55 pct., respectively comparing with the unreinforced materials. At strain-rate from $10^{-3}\;to\;10^3/s$, the effect of strain-rate on the modulus, ultimate strength, flow stress is determined. Also the effect of strain rate on the modulus, ultimate tensile strength, flow stress and elongation to failures were investigated.

• Bulletin of the Korean Chemical Society
• /
• 제27권11호
• /
• pp.1815-1818
• /
• 2006

Imogolite which has chemical composition, $(HO)_3Al_2O_3SiOH$, was synthesized with orthosilicate acid and aluminium chloride at low pH solution. It has extremely large aspect ratio with an external diameter of 2nm and the length of a few micrometers. The high aspect ratio of the imogolite could make the material as the filler for the high strength fiber and as the wire for the electronic applications. Here, Imogolite that derives considerable microporosity from a nanometer-sized tubular structure has been modified with a conducting polymer, polypyrrole. Its bonding and wiring structure were confirmed by IR and TEM. The measured conductivity after modification with polypyrrole increased with polypyrrole thickness at various voltage conditions.

• 한국초전도ㆍ저온공학회논문지
• /
• 제13권2호
• /
• pp.17-20
• /
• 2011

Superconducting magnetic energy storage (SMES) has attracted a great deal of interest from the viewpoint of energy saving. The magnet of conduction-cooled high temperature superconducting (HTS) SMES is cooled down by a cryocooler. One of the most important problems to be assured the protection of magnet and cryocooler is breakdown at cryogenic temperature. In this study, we investigated insulation materials such as Kapton, Aluminum Nitride(AIN), Alumina($Al_2O_3$), glass fiber reinforced plastics(GFRP) and vacuum in cryogenic temperature. Also, we analyzed statistically the Weibull distribution of breakdown voltage.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2008년도 추계학술대회A
• /
• pp.234-238
• /
• 2008

The efficiency of fiber reinforced CMC(ceramic matrix composite) on the SiC materials have been investigated, in conjunction with the fabrication process by liquid phase sintering and the characterization. LPS-$SiC_f$/SiC composites was studied with the detailed analysis such as the microstructure, sintered density, flexural strength and fracture behavior. The applicability of carbon interfacial layer has been also investigated in the LPS process. Submicron SiC powder with the constant total amount and composition ratio of $Al_2O_3,\;Y_2O_3$ as sintering additives was used in order to promote the performance of the SiC matrix material. LPS-$SiC_f$/SiC composites were fabricated with hot press under the sintering temperature and applied pressure of $1820^{\circ}C$ and 20MPa for 1hr. The typical property of monolithic LPS-SiC materials was compared with LPS-$SiC_f$/SiC composites.

• 접착 및 계면
• /
• 제21권1호
• /
• pp.27-33
• /
• 2020

유리섬유강화 복합재료 (GFRC)의 표면거칠기에 따른 에폭시 접착제의 접착강도를 평가하였고 최적의 표면거칠기를 선정하였다. 서로 다른 입자크기의 알루미나 (Al2O3) 입자를 GFRC의 표면에 분사하였고 이를 통하여 서로 다른 표면거칠기를 부여하였다. 표면거칠기를 정량화 하였고 표면거칠기에 따른 표면관찰을 진행하였다. 각 표면거칠기에 따른 접촉각을 측정하였고 이를 통하여 표면에너지를 계산하였으며, 에폭시 접착제와의 접착일을 계산 및 비교하여 접착력을 예측하였다. 단일랩전단 시험을 통해 접착강도를 평가하였고 거칠기에 따라 접착강도가 증가된다는 것을 확인하였다. 박리 후 표면을 관찰해 보았을 때 기지재인 GFRC의 박리 정도가 다른 것을 확인하였고 최종적으로 표면거칠기의 최적조건을 확인할 수 있었다.

• 한국결정성장학회지
• /
• 제23권1호
• /
• pp.44-50
• /
• 2013

E-glass 섬유는 항공기, 자동차, 레져기구의 복합재료 보강용으로 가장 널리 사용되는 유리섬유이다. 그러나 최근 E-glass 섬유의 원재료비 상승, 환경문제 및 화학적 저항성과 기계적 특성을 향상시키기 위해 산화붕소 함량을 8 %에서 0(제로)까지 감소시키는(소위 'Boron free E-glass'라고 불리는) 연구가 진행되고 있다. 본 연구에서는 'BF(Boron free E-glass)' 조성의 벌크유리와 섬유유리를 제조하고, 열적특성 및 광학적특성을 평가하였다. 5~10 %의 서로 다른 알루미나 함량을 갖는 배치를 $1550^{\circ}C$에서 2시간 용융하여 'BF(Boron free E-glass)'가 얻어졌고, 81~86 %의 높은 가시광투과율, $4.2{\sim}4.9{\times}10^{-6}/^{\circ}C$의 낮은 열팽창계수, $907{\sim}928^{\circ}C$의 연화점을 갖는 투명하고 맑은 유리가 얻어졌다. 'BF' 섬유 시편에 대한 화학적내구성 시험에 있어서는 알루미나 함량이 높아질수록 더 좋은 침식저항성을 나타냄을 확인할 수 있었다.

• 한국세라믹학회지
• /
• 제55권6호
• /
• pp.527-555
• /
• 2018

High-temperature thermal insulation materials challenge extensive oxide candidates such as porus $SiO_2$, $Al_2O_3$, yttria-stabilized zirconia, and mullite, due to the needs of good mechanical, thermal, and chemical reliabilities at high temperatures simultaneously. Recently, porous rare earth (RE) silicates have been revealed to be excellent thermal insulators in harsh environments. These materials display attractive properties, including high porosity, moderately high compressive strength, low processing shrinkage (near-net-shaping), and very low thermal conductivity. The current critical challenge is to balance the excellent thermal insulation property (extremely high porosity) with their good mechanical properties, especially at high temperatures. Herein, we review the recent developments in processing techniques to achieve extremely high porosity and multiscale strengthening strategy, including solid solution strengthening and fiber reinforcement methods, for enhancing the mechanical properties of porous RE silicate ceramics. Highly porous RE silicates are highlighted as emerging high-temperature thermal insulators for extreme environments.