• Journal of the Korean Wood Science and Technology
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• v.42 no.6
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• pp.682-690
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• 2014

In order to improve the thermal stability of wood plastic composites (WPC), thermal degradation behavior of WPC in this study was investigated by the addition of wood flour and fire retardant after hybridization of wood flour and ammonium polyphosphate (APP) into polypropylene (PP) matrix. Thermal degradation behavior of all formulations was analyzed with thermogravimetric analyzer under nitrogen environment at heating rate of $10^{\circ}C/min$. As the thermal degradation temperature of wood flour is lower than that of PP, char layer formed by the wood flour decreases the speed of heat transfer to PP. In addition, the char layer increases the 2nd thermal degradation temperature and decreases the 2nd thermal degradation speed. The WPC treated with APP increases the 1st and 2nd degradation temperatures. In the case of WPC with high loading level of wood flour, the 1st thermal degradation temperature and 2nd thermal degradation rate were increased by the addition of APP, and then the amount of remnants at high temperature was increased by the increase of the APP loading level. In the case of WPC treated with APP, the amount of the remnants at high temperature was increased with the increase of wood flour content from 10 wt% to 50 wt%, indicating that char formation of the APP and wood flour occurred at the same time, resulting in high thermal stability effect by the increase of wood flour content.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.03b
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• pp.41-41
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• 2010

We present facile chemical route stabilizing dispersion of carboxylated single-walled carbon nanotubes (SWCNTs) in ZnOsol prepared by using diethanolamine as a stabilizer. The dispersion was stabilized via capping of carboxyl groups on the SWCNT surface by a titania layer. We also demonstrated that the conductivity of the films prepared P3/$TiO_2$/ZnO as enhanced by therml treatment, and thethermal stbility of the film improved hybridization with ZnO sol pristine P3, P3/$SiO_2$ and P3/$TiO_2$ hybrid films.

• Nuclear Engineering and Technology
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• v.35 no.1
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• pp.45-54
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• 2003

A hyperbolic two-phase, two-fluid equation system developed in the previous work has been implemented in an existing nuclear safety analysis code, MARS. Although the implicit treatment of interfacial pressure force term introduced in momentum equation of the hyperbolic equation system is required to enhance the numerical stability, it is very difficult to implement in the code because it is not possible to maintain the existing numerical solution structure. As an alternative, two-step approach with stabilizer momentum equations has been selected. The results of a linear stability analysis by Von-Neumann method show the equivalent stability improvement with fully-implicit solution method. To illustrate the applicability, the new solution scheme has been implemented into the best-estimate thermal-hydraulic analysis code, MARS. This paper also includes the comparisons of the simulation results for the perturbation propagation and water faucet problems using both two-step method and the original solution scheme.

• Elastomers and Composites
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• v.47 no.2
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• pp.168-173
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• 2012

Polystyrene-polyimide core-shell microsphere was prepared by dispersion polymerization using poly(amic acid) as the stabilizer. Iron oxide was formed at the microsphere by thermal decomposition of iron pentacarbonyl impregnated in the microsphere. The magnetic polystyrene-polyimide microsphere was monodisperse and the size was about 500 nm. The magnetic polystyrene-polyimide microsphere had 40% of iron oxide, which was identified as $Fe_3O_4$ by X-ray diffraction.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.497-499
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• 2007

전력연구원은 한국남동발전(주) 삼천포화력 발전소의 요청에 따라 삼천포 화력 6호기 계획예방정비공사 기간(07.03.14-04.19) 중 발전기 여자시스템의 계통안정화 장치의 시간영역(Time Domain)과 주파수영역(Frequency Domain)에서의 Step 시험을 통하여 건전성을 평가하였다. 본 논문에서는 전력계통의 동요를 안정시키기 위한 삼천포 화력 발전기 여자시스템의 계통 안정화 장치(GE사 3S7932LA300)의 개요, 구성 및 건전성 평가 결과를 기술하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.5
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• pp.3286-3291
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• 2014

A study on the crack protection and thermal insulation properties of the expanded perlite inorganic composites was performed. Mixed expanded perlite with a water glass was stabilized for 24 hrs at room temperature in the mold and, thereafter, converted into a massive foamed body through complete drying process at $150^{\circ}C$. Aluminum phosphate and micron size mica powder were used as a reaction accelerator and a stabilizer for thermal crack, respectively. Especially, use of mica exhibited a remarkable effect on the protection of thermal crack at higher temperature over $500^{\circ}C$, and thermal conductivity of the composites was enhanced with higher perlite contents, showing ca. 0.09 W/mK for the sample of 100/200/10/1.5 water glass/perlite/mica/Al phosphate by weight. A severe dimensional deformation of the composite materials was observed over $600^{\circ}C$, however, showing a temperature limitation for a practical application. The facts were considered as the results from the glass transition temperature of the water glass, of which main component is sodium silicate.

• Korean Chemical Engineering Research
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• v.51 no.2
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• pp.279-284
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• 2013

The phenolic beads in macrosize range were obtained by suspension polymerization at $98^{\circ}C$ from phenol and formaldehyde in the presence of basic catalyst with a phenol to formaldehyde (P/F) range of 1:1~1:4, and they were carbonized to spherical carbon beads under nitrogen at $700^{\circ}C$. Thermal analysis on spherical phenolic beads obtained by suspension polymerization showed that the postcuring process is essential. In order to optimize the suspension polymerization, the effects of the P/F molar ratio, the pH of catalyst, and the molecular weight of stabilizer on the size distribution and yield of spherical phenol beads were examined separatively. The particle size was increased whereas the yield was decreased with P/F molar ratio. The increasing basicity of catalyst made the particle size to increase, while the molecular weight of stabilizer had more effect on the yield rather than on the particle size distribution. The thermal stability of the spherical phenolic beads obtained through postcure was also examined by TGA. The phenol beads of high P/F ratio still showed the weight loss at $220^{\circ}C$ even after postcure due to the high possibility of dibenzyl ether, while those of low P/F ratio showed the steady decrease in weight during $220^{\circ}C$ to $400^{\circ}C$, which showed that the optimal P/F ratio was 1:2.

• Korean Membrane Journal
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• v.9 no.1
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• pp.34-42
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• 2007

A perovskite-type ($La_{0.6}Sr_{0.4}Ti_{0.2}Fe_{0.8}O_{3-{\delta}}$) dense ceramic membrane was prepared by polymerized complex method, using citric acid as a chelating agent and ethylene glycol as an organic stabilizer. Effect of Ti addition on lanthanum-strontium ferrite mixed conductor was investigated by evaluating the thermal expansion coefficient, the oxygen flux, the electrical conductivity, and the phase stability. The thermal expansion coefficient in air was $21.19\;{\times}\;10^{-6}/K$ at 473 to 1,223 K. At the oxygen partial pressure of 0.21 atm ($20%\;O_2$), the electrical conductivity increased with temperature and then decreased after 973 K. The decrement in electrical conductivity at high temperatures was explained by a loss of the lattice oxygen. The oxygen flux increased with temperature and was $0.17\;mL/cm^2{\cdot}min$ at 1,223 K. From the temperature-dependent oxygen flux data, the activation energy of oxygen ion conduction was calculated and was 80.5 kJ/mol at 1,073 to 1,223 K. Also, the Ti-added lanthanum-strontium ferrite mixed conductor was structurally and chemically stable after 450 hours long-term test at 1,173 K.

• Journal of the Korean institute of surface engineering
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• v.34 no.5
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• pp.486-493
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• 2001

Partially stabilized zirconia (PSZ) is an attractive material for thermal barrier coating. Zirconia exists in three crystallographic phases: cubic, tetragonal and monoclinic. Especially, the phase transformation of tetragonal phase to monoclinic phase accompanies significant volume expansion, so this transition generally results in cracking and contributes to the failure of the TBC system. Both the plasma sprayed ZrO$_2$-8Y$_2$O$_3$ (YSZ) coat and the ZrO$_2$,-25CeO$_2$,-2.5Y$_2$O$_3$ (CYSZ) coat are isothermally heat -treated at 130$0^{\circ}C$ and 150$0^{\circ}C$ for 100hr and cooled at different cooling rates. The monoclinic phase is not discovered in all the CYSZ annealed at 130$0^{\circ}C$ and 150$0^{\circ}C$. In the 150$0^{\circ}C$ heat-treated specimens, the YSZ contains some monoclinic phase while none exists in the 130$0^{\circ}C$ heat-treated YSZ coat. For the YSZ, the different phase transformation behaviors at the two temperatures are due to the stabilizer concentration of high temperature phases and grain growth. For the YSZ with 150$0^{\circ}C$-100hr annealing, the amount of monoclinic phase increased with the slower cooling rate. The extra oxygen vacancy, thermal stress, and c to t'phase transformation might suppress the t to m martensitic phase transformation.

• Journal of the Korean Ceramic Society
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• v.40 no.4
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• pp.385-392
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• 2003

Sol-gel preparation technique using a chemical reaction of metal alkoxides has been widely used for the fabrication of various materials including ceramics. However, its mechanism has been studied till now because a number of chemical ways are possible from various alkoxides and additives. In this study, the mechanism of hydrolysis, condensation, and polymerization of alkoxides were investigated from the fabrication of lead-zirconate-titanate (PbZr$\_$x/Ti$\_$l-x/O$_3$; PZT) thin film that is used as various micro-actuator, transducer, and sensor because of its high electro-mechanical coupling factors and thermal stability. Furthermore, the fabrication process and characteristics of self-patternable PZT film using photosensitive stabilizer were studied in order to resolve the problem of physical damage and properties degradation during dry etching for device fabrication. Using an optimum condition to prepare the self-patternable PZT film, more than 5000 ${\AA}$ thick self-patternable PZT film could be fabricated by three times coating. The PZT film showed 28.4 ${\mu}$c/cm$^2$ of remnant polarization (Pr) and 37.0 kV/cm of coercive field (E$\_$c/).