• Journal of Ocean Engineering and Technology
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• v.22 no.1
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• pp.58-63
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• 2008

The effect of alkaline environmental condition on durability of GFRP composites according to additives was investigated. Additives used were polyvinyl alcohol(PVA), kaolin and alumina powder. Weight gains increased with immersion time in all GFRP composites at $80^{\circ}C$. But weight gain of specimen added PVA did not differ through the wlwle immersion time in both tap water and alkaline solution at 20 and $80^{\circ}C$. Tensile strength decreased with immersion time in all environment conditions. Tensile strength of GFRP composites regardless of additives decreased rapidly up to 5 days of immersion and then decreased slowly up to 30 days in alkaline solution environment at $80^{\circ}C$. Weight gains had not. much difference in both tap water and alkaline solution at $20^{\circ}C$. And weight gain of GFRP composites added polyvinyl alcohol had smaller than the others through the whole immersion time in both tap water and alkaline solution at $20^{\circ}C$ and $80^{\circ}C$. Tensile strength of GFRP composites added polyvinyl alcohol had higher than the others through the whole immersion time in both tap water and alkaline solution at $20^{\circ}C$ and $80^{\circ}C$.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.909-912
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• 2008

Fiber is an important ingredient in strain-hardening cementitious composite (SHCC), which can control fracture of cementitious composite by bridging action. The properties of reinforcing fiber, as tensile strength, aspect ratio and elastic modulus, have great effect on the fracture behavior of SHCC. But SHCC has serious problem as drying shrinkage because silica powder is used to make SHCC in order to improve bond strength between reinforcing fibers and cement matrix. Therefore, curing method (period and temperature) is very important for SHCC to show high tensile performance. a variety of experiments have being performed to access the performance of SHCC recently. This research emphasis is on the mechanical properties of SHCC made in Polyvinyl alcohol (PVA), Polyethylene (PE) fibers and steel cord (SC), and how curing method affects the composite property, and ultimately its strain-hardening performance.

• Composites Research
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• v.25 no.5
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• pp.159-163
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• 2012

The coating of metal surface with carbon nanotubes(CNTs) has been studied for the heat transfer enhancement of the boiling and condensation of refrigerant. The multiwalled carbon nanotube/copper oxide(CuO) composite powder, which has been surface modified by dispersant and polyvinyl alcohol solution, was ultrasonically sprayed and sintered on a copper wafer. In this paper, experiments were performed to assess the characterization and comparison of the carbon nanotube before and after sinterning and the morphology changes of the CNT/CuO-coated surface by using different dispersants. The dispersants used are THF (Tetrahydrofuran), SDBS(Dodecylbenzenesulfonic acid sodium salt), SDS(Sodium dodecy sulfate). The samples were examined by scanning electron microscopy(SEM), thermogravimetric analysis(TGA), differential scanning calorimeter(DSC) and Raman spectroscopy.

• Journal of the Korean Ceramic Society
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• v.42 no.11 s.282
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• pp.729-736
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• 2005

HTGR (High Temperature Gas-cooled Reactor) is spotlighted to next generation nuclear power plant for producing the clean hydrogen gas and the electricity. In this study, the spherical $UO_3$ gel particles were prepared by the external gelation process, and the characteristics of these particles were analyzed the particle shape, composition of precipitate, and thermal decomposition characteristics with the Streoscope, FT-IR, and X-ray diffractometer. Raw material of the ADUN (Acid Deficient Uranyl Nitrate) solution, which has [$NO_3$]/[U] mole ratio = 1.75, was obtained from dissolution of the $U_{3}O_{8}$ powder with concentrated $HNO_3$, and its concentration is 3.5 M-U/l. The broth solution is prepared with the ADUN, urea, PVA, and THFA solution. The droplets of the broth solution was made through a nozzle system. From this study, we obtained the following results; 1) an externel chemical gelation process is a suitable method in the spherical $UO_3$ particle production, 2) the particle shape are changed by an urea mixing time, THFA volume, and the viscosity of the broth solution, 3) the amorphous $UO_3$ particles obtained from these experiments was converted to $U_{3}O_{8}$ and then $UO_2$ by heat treatment in hydrogen atmosphere at $600^{\circ}C$.