• Journal of the Korean Ceramic Society
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• 제50권6호
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• pp.476-479
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• 2013

$CoSb_3$ with its high electrical conductivity, Seebeck coefficient and rather low thermal conductivity is quite a promising material for thermoelectric conversion applications. A potentially high figure of merit (ZT) can be achieved by a nanostructure evolution of thermoelectric materials. In this work, $CoSb_3$ nanoparticles were synthesized through a thermal decomposition method in cooperation with a hot injection technique. Nano-sized $CoSb_3$ particles were obtained through the thermal decomposition reaction between the pre-heated cobalt-oleate at $320^{\circ}C$ and the injected antimony oleate with room temperature. The results showed that the particle size was increased with increasing synthesis temperature and the crystallinity of particles was improved with temperature but the decomposition of $CoSb_3$ was observed at $320^{\circ}C$. The $CoSb_3$ particles synthesized at $300^{\circ}C$ showed a high purity and an homogeneous shape with average particle size of 26 nm.

• Clean Technology
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• 제15권2호
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• pp.122-129
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• 2009

The effect of calcination temperature or hydrothermal treatment of commercial Fe-beta zeolites in the range of $450{\sim}900^{\circ}C$ were examined in the direct decomposition of $N_2O$. Fe-beta zeolites used were characterized using XRD, $N_2$ sorption, $^{27}Al$ MAS NMR and XPS. Although the surface area and micropore volume of Fe-beta zeolite after calcination at $900^{\circ}C$ and hydrothermal treatment at $750^{\circ}C$ decreased ca. 30%, a larger decrease in the surface area and micropore volume by hydrothermal treatment was observed than by calcination treatment alone. However, the Al sites in frameworks of zeolite were conserved in stable tetrahedral form resulting from low degree of dealumination which was related to the adjacent Fe ions on the Al sites. This could likely be correlated with the conservation of high surface area and micropore volume of Fe-beta zeolites. The increase in the calcination or hydrothermal treatment temperature caused the increase of decomposition temperature of $N_2O$ and the severe deactivation was observed after hydrothermal treatment than calcination treatment.

• Proceedings of the Korean Vacuum Society Conference
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.163.2-163.2
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• 2014

We report catalytic decomposition of few-layer graphene on an $Au/SiO_x/Si$ surface wherein oxygen is supplied by dissociation of the native $SiO_x$ layer at a relatively low temperature of $400^{\circ}C$. The detailed chemical evolution of the graphene covered $SiO_x/Si$ surface with and without gold during the catalytic process is investigated using a spatially resolved photoelectron emission method. The oxygen atoms from the native $SiO_x$ layer activate the gold-mediated catalytic decomposition of the entire graphene layer, resulting in the formation of direct contact between the Au and the Si substrate. The notably low contact resistivity found in this system suggests that the catalytic depletion of a $SiO_x$ layer could realize a new way to micromanufacture high-quality electrical contact.

• Journal of the Korean Society of Tobacco Science
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• 제7권2호
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• pp.129-139
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• 1985

cent was carried out to study on the effect of temperature and humidity to chemical tobacco leaves during the yellowing stage. The results were follows : In the condition of high humidity and low temperature, yellowing time was delayed ; leaf color appeared lack clearness. In the higher temperature and the lower humidity during the yellowing stage : total sugar, reducing sugar and malic acid content were increased. Decomposition of nitrogenous components elevated in $38^{\circ}C$, 85%RH. Changes of total nitrogen content correlated with total curing time. Adecrease of linolenic acid with a corresponding increase of chlorogenic acid proceeded in the condition of low temperature and high humidity. In a view of tobacco quality by chemical components, the low temperature and high humidity during the yellowing stage decreased quality of tobacco leaves. It is considered to control of the proper condition of temperature and humidity during the yellowing.

• Tribology and Lubricants
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• 제14권1호
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• pp.70-78
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• 1998

Two different friction materials (organic and low-metallic pads) for automotive brakes were studied to investigate the anti-fading phenomena during stop. The anti-fading phenomena were pronounced more in the case of using low metallic friction materials than organic friction materials. The main cause of the anti-fading phenomena was the high dependence of friction coefficient on a sliding speed. The anti-fading was prominent when the initial brake temperature was high in the case of low-metallic friction materials due to the strong stick-slip event at high temperature. On the other hand, the anti-fading was not severe in organic friction materials and the effect was reduced at high braking temperature due to the thermal decomposition of organic friction materials. The strong stickslip phenomena of low metallic friction materials at high temperature induced high torque oscillations during drag test. During this experiment two different braking control modes (pressure controlled and torque controlled modes) were compared. The type of the control mode used for brake test significantly affected the friction characteristics.

• Journal of the Korean Electrochemical Society
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• 제15권1호
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• pp.19-26
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• 2012

SEI (solid electrolyte interphase) layers are generated on a graphite negative electrode from three different electrolytes and low-temperature ($-30^{\circ}C$) charge/discharge performance of the graphite electrode is examined. The electrolytes are prepared by adding 2 wt% of vinylene carbonate (VC) and fluoroethylene carbonate (FEC) into a standard electrolyte solution. The charge-discharge capacity of graphite electrode shows the following decreasing order; FEC-added one>standard>VC-added one. The polarization during a constant-current charging shows the reverse order. These observations illustrate that the SEI film resistance and charge transfer resistance differ according to the used additives. This feature has been confirmed by analyzing the chemical composition and thickness of three SEI layers. The SEI layer generated from the standard electrolyte is composed of polymeric carbon-oxygen species and the decomposition products ($Li_xPF_yO_z$) of lithium salt. The VC-derived surface film shows the largest resistance value even if the salt decomposition is not severe due to the presence of dense film comprising C-O species. The FEC-derived SEI layer shows the lowest resistance value as the C-O species are less populated and salt decomposition is not serious. In short, the FEC-added electrolyte generates the SEI layer of the smallest resistance to give the best low-temperature performance for the graphite negative electrode.

• Journal of Forest and Environmental Science
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• 제32권4호
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• pp.323-328
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• 2016

Thermal stability and rheological behaviors of Ricinodendron heudelotii wood were investigated. Thermogravimetric analysis conducted at a heating rate of $10^{\circ}C/min$ from 20 to $600^{\circ}C$ in a nitrogen atmosphere indicated that there was no variation in the decomposition of the onset and final temperature for all the polymers. The thermal behaviours were investigated at a temperature range from 130 to $0^{\circ}C$ at $3^{\circ}C/min$, multi-frequencies of 0.1-10 Hz using dynamic mechanical analysis. N-methyl-2-pyrolidone saturated specimens were tested while submerged under the same solvent. Polymers decomposition pattern during thermogravimetric analysis are similar in the radial position of the wood. The glass transition temperature (Tg) of R. heudelotii is $45{\pm}1^{\circ}C$ at 0.1 Hz. The Tg differs from the innerwood to outerwood. The Tg showed that N-methyl-2-pyrolidone saturated R. heudelotii would require low energy consumption during chemi-thermomechanical pulping.

• Journal of Korea Foundry Society
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• 제23권5호
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• pp.268-275
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• 2003

The mechanism of the hydrogen gas pore formation was investigated in Lost Foam Casting of Al-alloy by reduced pressure test and real casting. The hydrogen gas pick-up was affected by the formed gas during the decomposition of polystyrene in addition to the liquid product. It depended on pouring temperature and a proper temperature of metal front gave the minimum hydrogen pick-up. At a low pouring temperature, the hydrogen went into the melt mainly from entrapped liquid product of polystyrene but pores were formed from the gas as well as the liquid product at a high pouring temperature. The mold flask evacuation down to 710torr decreased the gas porosity down by around 0.4% vol%. The entrapped decomposition product of polystyrene in the melt was observed through the visualization of filling behavior of Al alloy-melt with the high speed camera.

• Journal of Ecology and Environment
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• 제38권4호
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• pp.517-528
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• 2015

Litter decomposition is an important process in terrestrial ecosystem. However, studies on decomposition are rare, especially in evergreen broadleaf trees. We collected the leaf litter of five evergreen broadleaf trees (Daphniphyllum macropodum, Dendropanax morbifera, Castanopsis cuspidata var. thunbergii, Machilus thunbergii and Quercus acuta), and carried out a decomposition experiment using the litterbag method in Ju-do, Wando-gun, Korea for 731 days from December 25, 2011 to December 25, 2013. Among the five experimental tree species, C. cuspidata var. thunbergii distribution was limited in Jeju Island, and D. macropodum was distributed at the highest latitude at Mt. Baekyang (N 35°40′). About 2% of the initial litter mass of D. macropodum and D. morbifera remained, while 20.9% remained for C. cuspidata var. thunbergii, 30.4% for M. thunbergii, and 31.6% for Q. acuta. D. macropodum litter decayed four times faster (k = 2.02 yr^-1) than the litter of Q. acuta (k = 0.58 yr^-1). The decomposition of litter was positively influenced by thermal climate such as accumulated mean daily air temperature (year day index) and precipitation, as well as by physical characteristics such as thickness (R²=0.939, P = 0.007) and specific leaf area (SLA) (R² = 0.964, P = 0.003). The characteristics of chemical composition such as lignin (R² = 0.939, P = 0.007) and water-soluble materials (R² = 0.898, P = 0.014) showed significant correlations with litter decomposition. However, the nutrients in litter showed complicated species-specific trends. The litter of D. macropodum and D. morbifera had fast decomposition despite their low nitrogen concentration and high C/N ratio. This means that the litter decomposition was more strongly affected by physical characteristics than chemical composition and nutrient content. On the other hand, the litter of Q. acuta which had the slowest decay rate had a high amount of N and low C/N ratio. Thus, the decomposition of Q. acuta litter was more affected by the P content of the litter than the N content, although all litter had similar physical characteristics.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 한국농업기계학회 1993년도 Proceedings of International Conference for Agricultural Machinery and Process Engineering
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• pp.526-537
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• 1993

The development of composting techniques is essential to the low input sustainable agriculture. This paper resents an evaluation of composting system, compost materials, aeration & temperature effects, compost maturity , and operational concerns for compost utilization. The composting of organic waste is markedly affected by the nature of the feedstock and the operational temperature employed for the process. These two major parameters are critically examined in this paper, with references to the decomposition of the organic waste. Future research should concentrate on the indications of stability and environmental problems.