• Carbon letters
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• v.4 no.4
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• pp.180-184
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• 2003

The role of KOH in the one-stage KOH-activation of rice straws was studied using FTIR, XPS, TGA, and DTG techniques. It was found that at the impregnation, KOH extracts to some extent the lignin component from rice straw and reacts with hydroxyl groups. On heat-treatment, the impregnated KOH facilitates intermolecular condensation reaction on one hand but retards the thermal degradation of cellulose molecules on the other hand. The oxygen-containing surface functional groups newly created by oxidation of KOH may facilitate the bulk, not controlled, consumption of carbon atoms so that the effective porosities may not be able to be developed by the one-stage activation process.

• Nuclear Engineering and Technology
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• v.48 no.2
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• pp.299-303
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• 2016

Prompt gamma activation analysis using a thermal neutron-guided beam at Japan Atomic Energy Agency JRR-3M was applied for the precise determination of Si in silicon nitride ceramic reference materials [Japan Ceramic Reference Material (JCRM) R 003]. In this study, the standard addition method coupled with internal standard was used for the nondestructive determination of Si in the sample. Cadmium was used as internal standard to obtain the linear calibration curves and to compensate for the neutron beam variability. The analytical result of determining Si in JCRM R 003 silicon nitride fine powder ceramic reference materials using prompt gamma activation analysis was in good agreement with that obtained by classical gravimetric analysis. The relative expanded measurement uncertainty (k = 2) associated with the determined value was 2.4%.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.140-140
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• 2010

Non-mass analyzed ion shower doping (ISD) technique with a bucket-type ion source or mass-analyzed ion implantation with a ribbon beam-type has been used for source/drain doping, for LDD (lightly-doped-drain) formation, and for channel doping in fabrication of low-temperature poly-Si thin-film transistors (LTPS-TFT's). We reported an abnormal activation behavior in boron doped poly-Si where reverse annealing, the loss of electrically active boron concentration, was found in the temperature ranges between $400^{\circ}C$ and $650^{\circ}C$ using isochronal furnace annealing. We also reported reverse annealing behavior of sequential lateral solidification (SLS) poly-Si using isothermal rapid thermal annealing (RTA). We report here the importance of implantation conditions on the dopant activation. Through-doping conditions with higher energies and doses were intentionally chosen to understand reverse annealing behavior. We observed that the implantation condition plays a critical role on dopant activation. We found a certain implantation condition with which the sheet resistance is not changed at all upon activation annealing.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.149.1-149.1
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• 2005

• Proceedings of the Materials Research Society of Korea Conference
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• 1996.11a
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• pp.177-177
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• 1996

• Journal of the Korean Society of Safety
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• v.17 no.2
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• pp.39-44
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• 2002

This study was investigated the thermal decomposition characteristics of azo type sponge blowing agent azodicarbonamide(ADCA) using differential scanning calorimeter(DSC). The experimental results showed that the exothermic onset $temperatures(T_{o})$ for ADCA were about $201{\sim}206^{\circ}C$ and evolution heats(Q) were about $144{\sim}150cal/g$. The exothermic onset $temperatures(T_{o})$, exothermic maximum $temperature(T_{m})$ and exothermic final $temperature(T_{f})$ were decreased by decreasing particle size of ADCA and evolution heats(Q) were increased with it. $T_{o}$ and Q for $6.1{\sim}7.2{\mu}m$ ADCA were increased by increasing heating rate at constant sample weight and activation energy was about 37.29kcal/mol. A positive gas pressure was employed in the elucidation of the decomposition behavior of ADCA because it sublimes during linear heating at atmospheric pressure. $T_{o}$ and Q of ADCA tended to increase with a pressure in air or nitrogen. In the case of azo dye, experimental results showed that $T_{o}$ were about $280{\sim}420^{\circ}C$ and Q were about $2{\sim}30cal/g$.

• Current Research on Agriculture and Life Sciences
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• v.30 no.1
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• pp.41-50
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• 2012

As a part of abating formaldehyde emission of urea-formaldehyde resin, this study was conducted to investigate the rmalcure kinetics of both neat and modified urea-formaldehyde resins using differential scanning calorimetry. Neat urea-formaldehyde resins with three different formaldehyde/urea mol ratios (1.4, 1.2 and 1.0) were modified by adding three different additives (sodium bisulfite, sodium hydrosulfite and acrylamide) at two different levels (1 and 3wt%). An isoconversional method at four different heating rates was employed to characterize thermal cure kinetics of these urea-formaldehyde resins to obtain activation energy ($E{\alpha}$) dependent on the degree of conversion (${\alpha}$). The $E{\alpha}$ values of neat urea-formaldehyde resins (formaldehyde/urea = 1.4 and 1.2) consistently changed as the ${\alpha}$ increased. Neat and modified urea-formaldehyde resins of these two F/U mol ratios did show a decrease of the $E{\alpha}$ at the final stage of the conversion while the $E{\alpha}$ of neat urea-formaldehyde resin (formaldehyde/urea = 1.0) increased as the ${\alpha}$ increased, indicating the presence of incomplete cure. However, the change of the $E{\alpha}$ values of all urea-formaldehyde resins was consistent to that of the Ea values. The isoconversional method indicated that thermal cure kinetics of neat and modified urea-formaldehyde resins showed a strong dependence on the resin viscosity as well as diffusion control reaction at the final stage of the conversion.

• Advances in materials Research
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• v.1 no.4
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• pp.245-268
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• 2012

Results of isothermal torsional oscillation tests are reported on melts of linear low density polyethylene and isotactic polypropylene. Prior to rheological tests, specimens were annealed at various temperatures ranging from $T_a$ = 180 to $310^{\circ}C$ for various amounts of time (from 30 to 120 min). Thermal treatment induced degradation of the melts and caused pronounced decreases in their molecular weights. With reference to the concept of transient networks, constitutive equations are developed for the viscoelastic response of polymer melts. A melt is treated as an equivalent network of strands bridged by junctions (entanglements and physical cross-links). The time-dependent response of the network is modelled as separation of active strands from and merging of dangling strands with temporary nodes. The stress-strain relations involve three adjustable parameters (the instantaneous shear modulus, the average activation energy for detachment of active strands, and the standard deviation of activation energies) that are determined by matching the dependencies of storage and loss moduli on frequency of oscillations. Good agreement is demonstrated between the experimental data and the results of numerical simulation. The study focuses on the effect of molecular weight of polymer melts on the material constants in the constitutive equations.

• Journal of the Korean Society of Safety
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• v.21 no.6 s.78
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• pp.38-45
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• 2006

Polymeric floorings mainly consisted of PVC are easily decomposed by many kinds of hot environmental factors, then generate hazardous asphyxiate gases and/or toxic gases etc. Therefore the mechanism of decomposition and quantitative toxic indices of products are very important for preventing safety and health disasters, especially in case of confined area. So we have investigated decomposition kinetics, numbers of process involved, toxicity indices of product and so on, using DSC, TGA, FT-IR and Pyrolyzer-GC/MS. The thermal decomposition process of polymeric floorings can be mainly divided by dehydrochlorinated reaction and polyene decomposition step, and activation energies of those are approximately $53.93{\sim}62.42kcal/mol$. Especially lethal concentration($LC_{50}$), fractional effective dose (FED) are calculated by measuring the amount of decomposition product. The values on $LC_{50}$ of sample G are ranged $2,003{\sim}2,019(mg/m^{3})$ in case of sample K and H are $1,877,\;1,998(g/m^{3})$ respectively. Even if the results are estimated by calculation method without animal test and/or clinical demonstration, these values could be very useful data for occupational health, hygiene and safety control.

• Macromolecular Research
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• v.14 no.4
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• pp.416-423
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• 2006

The dynamic mechanical thermal properties of poly(hexamethylene terephthalate) (PHT), poly(1,4-cyclohexylenedimethylene terephthalate) (PCT) and their P(HT-co-CT) random copolymers in the amorphous state were examined as a function of temperature and frequency. All the samples exhibited two main relaxation processes in the plot of tan ${\delta}$ versus temperature: the primary ${\alpha}$-relaxation associated with the glass transition and the secondary ${\beta}$-relaxation attributed to the local segmental motions of mostly cyclohexylene rings for PCT and to cooperative motions of methylene, carboxyl, and phenylene groups for PHT. Both ${\alpha}$- and ${\beta}$-relaxation temperatures increased with increasing CT content. The activation energy of the ${\alpha}$-relaxation increased with increasing CT content, whereas that of the ${\beta}$-relaxation decreased. The sub-glassy secondary ${\beta}$-relaxation processes of PCT and PHT were investigated in terms of the cooperativity of main-chain segmental motions.