• 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 $2{\sim}30cal/g$.

• Journal of the Mineralogical Society of Korea
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• v.12 no.1
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• pp.11-22
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• 1999

Thermal behavior of dickite was studied by thermal analysis, X-ray diffraction analysis, electron microprobe analysis, and scanning electron microscopy, Dickite has an endothermic peak at about$ 650^{\circ}C$ and an exothermic one at $960^{\circ}C$ in the differential thermal analysis. The endothermic reaction is assigned to the decomposition of dickite to meta-dickite. Hydroxyl radicals are removed from dickite structure by the reaction, resulting in the weight loss about 10.5~14.5% and appearance of a 14$\AA$ phase different from other kaolin minerals. The reaction slowly proceed in the range of $200^{\circ}C$. As the completion of decomposition, aciclular mullite forms at the expense of meta-dickite plates with random crystallographic relationship. Mullites have diverse silica versus alumina ratio. The exothermic reaction without weight loss seems to be due to the formation of spinel and amorphous silica. The spinel phase shows cryptocrystalline globular morphology accompanying a little amount of silica. From spinel phase shows cryptocrystalling globular morphology accompanying a little amount of silica. From this work, it is suggested that mullite is formed from meta-dickite much lower temperature than the reported one in the previous works.

• Proceedings of the Materials Research Society of Korea Conference
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• 1996.05a
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• pp.124-124
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• 1996

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.2
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• pp.61-66
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• 2003

The electromagnetic properties and thermal behavior of Mn-Zn ferrite cores used for the blocking filter in he Power Line Communication(PLC) application were investigated as the function of additives. The highest density and permeability of 4.98 g/㎤) and 8,221 respectively were obtained to the specimen with composition of MnO 24 mol%, ZnO 25 mol% and Fe$_2$O$_3$ 51 mol% added MnO$_3$ 400 ppm, SiO$_2$ 100 ppm and CaO 200 ppm since the uniform grains were organized and the microstructures were compacted through reduction of pores. The permeability was increased up to 13,904 as temperature of specimen increased to 11$0^{\circ}C$, however, it was decreased precipitously under 100 over 11$0^{\circ}C$. The exothermic behavior was observed in the frequency range from 1 kHz to 1 MHz that the maximum temperature of specimens became 102$^{\circ}C$ at 1 MHz. In the consequence, the Mn-Zn ferrite core developed by this research will maintain the stable electromagnetic properties since the temperature of ferrite core rose to 93$^{\circ}C$ in the range of 10 kHz to 450 kHz bandwidth qualified for PLC.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.04a
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• pp.68-71
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• 2002

The electromagnetic properties and thermal behavior of ferrite cores used in the blocking filter for PLC were investigated as a function of additives. The highest density of 4.98 $g/cm^2$ and permeability of 8221 were obtained to the specimen added $MoO_3$ 400 ppm, $SiO_2$ 100 ppm and CaO 200 ppm since the microstructures were compacted through reduction of pores in the specimen. The permeability was increased up to 13094 at $110^{\circ}C$ with increasing temperature of specimen, however, it was decreased precipitously to under 100 over $110^{\circ}C$. The exothermic behavior was observed that the temperature of specimens became $102^{\circ}C$ at 1MHz. In the consequence, the ferrite core developed by this research will maintain the stable electromagnetic properties since the temperature of ferrite core rose to $93^{\circ}C$ in the range of 10kHz to 450kHz bandwidth qualified for PLC.

• Journal of Powder Materials
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• v.3 no.1
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• pp.42-48
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• 1996

To investigate the phase transformation behaviors of mechanically alloyed Nb-25 at%Al powders, the mixed Nb-25 at%Al powders were mechanically alloyed in SPEX 8000 Mixer/Mill. Mechanical alloying(MA) time was varied between 0.5 hour and 72 hours. The phase formation behaviors of these mechanically alloyed powders were examined using X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM), and differential thermal analysis(DTA). Appreciable amorphization started from 6 hours of MA. The powders mechanically alloyed for 10 hours were in almost amorphous phase. DTA results showed that the powders mechanically alloyed for 12 hours had a strong exothermic peak about$600^{\circ}C$, whereas the powders mechanically alloyed for 6 hours had two exothermic peaks. The first peak was found to be due to the stress relief effect and the second one due to the formation of$Nb_{3}Al,Nb_{2}Al and Nb_{2}C$phases by crystallization.

• Journal of Adhesion and Interface
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• v.7 no.1
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• pp.16-22
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• 2006

In this work, the effect of cure temperature and time on the thermal stability and the exothermic cure reaction peak of a waterborne resol-type phenol-formaldehyde resin, which may be used for preparing phenolic sheet molding compounds (SMC), has been investigated using a thermogravimetric analyzer and a differential scanning calorimeter. The weight loss of waterborne phenol-formaldehyde resin was mainly occurred at three temperature stages: near $200^{\circ}C,\;400^{\circ}C$, and $500^{\circ}C$. The carbon yield at $750^{\circ}C$ for the cured resin was about 62%~65%. Their thermal stability increased with increasing cure temperature and time. Upon cure, the exothermic reaction was taken placed in the range of $120^{\circ}C{\sim}190^{\circ}C$ and the maximum peak was found in between $165^{\circ}C$ and $170^{\circ}C$. The shape and the maximum of the exothermic curves depended on the given cure temperature and time. To remove $H_2O$ and volatile components, the uncured resin needed a heat-treatment at $100^{\circ}C$ for 60 min at least prior to cure or molding. Curing at $130^{\circ}C$ for 120 min made the exothermic peak of waterborne phenol-formaldehyde resin completely disappeared. And, post-curing at $180^{\circ}C$ for 60 min further improved the thermal stability of the cured resin.

• KIEE International Transactions on Electrophysics and Applications
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• v.12C no.4
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• pp.220-224
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• 2002

The electromagnetic properties and thermal behavior of Mn-Zn ferrite cores for the blocking filter of PLC application were investigated as the function of additives. The highest density and permeability were 4.98 g/㎤ and 8,221, respectively and were obtained to the specimen with composition of MnO 24 mol%, ZnO 25 mol% and Fe$_2$O$_3$51 mol%, added MoO$_3$ of 400 ppm, SiO$_2$ of 100 ppm, and CaO of 200 ppm. The uniform grains were organized, and the microstructures were compacted due to reduction of pores in the specimen. The permeability was increased up to 13,904 as the temperature of specimen increased to 110。C. However, it was decreased precipitously under 100 over 110。C. The exothermic behavior was observed in the frequency range from 1 kHz to 1 MHz, and the maximum temperature of specimen was 102。C at 1 MHz. In the consequence, the Mn-Zn ferrite core developed in this research will maintain the stable electromagnetic properties since the temperature of ferrite core rose to 93 。C in the range of 100 kHz to 450 kHz bandwidth qualified for PLC. The blocking filters were designed for single phase and three phases using the in-line and non-contact core. The best attenuation ratios of -46.46 dB and -73.9 dB were measured in the range of 100 kHz to 450 kHz bandwidth, respectively.

• Bulletin of the Korean Chemical Society
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• v.32 no.7
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• pp.2267-2273
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• 2011

A novel energetic material, 1-amino-1-(2,4-dinitrophenylhydrazinyl)-2,2-dinitroethylene (APHDNE), was synthesized by the reaction of 1,1-diamino-2,2-dinitroethylene (FOX-7) and 2,4-dinitrophenylhydrazine in N-methyl pyrrolidone (NMP) at 110 $^{\circ}C$. The theoretical investigation on APHDNE was curried out by B3LYP/6-311+$G^*$ method. The IR frequencies analysis and NMR chemical shifts were performed and compared with the experimental results. The thermal behavior of APHDNE was studied by DSC and TG/DTG methods, and can be divided into two crystal phase transition processes and three exothermic decomposition processes. The enthalpy, apparent activation energy and pre-exponential factor of the first exothermic decomposition reaction were obtained as -525.3 kJ $mol^{-1}$, 276.85 kJ $mol^{-1}$ and $10^{26.22}s^{-1}$, respectively. The critical temperature of thermal explosion of APHDNE is 237.7 $^{\circ}C$. The specific heat capacity of APHDNE was determined with micro-DSC method and theoretical calculation method, and the molar heat capacity is 363.67 J $mol^{-1}K^{-1}$ at 298.15 K. The adiabatic time-to-explosion of APHDNE was also calculated to be a certain value between 253.2-309.4 s. APHDNE has higher thermal stability than FOX-7.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.6
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• pp.490-495
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• 2003

The electromagnetic properties and thermal behavior of Mn-Zn ferrite cores for the blocking filter of Power Line Communication(PLC) application were investigated as a function of additives. The highest density and permeability were 4.98 g/$\textrm{cm}^2$ and 8,221, respectively and were obtained to the specimen with composition of MnO 24 mol%, ZnO 25 mol% and Fe$_2$O$_3$ mol%, added MoO$_3$ of 400 ppm, SiO$_2$ of 100 ppm, and CaO of 200 ppm. The uniform grains were organized, and the microstructures were densified due to reduction of pores in the specimen. The permeability was increased up to 13,904 as the temperature of specimen increased to 110$^{\circ}C$. However, it was decreased precipitously under 100 over 110$^{\circ}C$. The exothermic behavior was observed in the frequency range from 1 kHz to 1 MHz, and the maximum temperature of specimen was 102$^{\circ}C$ at 1 MHz. In the consequence, the Mn-Zn ferrite core developed in this research will maintain the stable electromagnetic properties since the temperature of ferrite core rose to 93$^{\circ}C$ in the range of 100 kHz to 450 kHz bandwidth qualified for PLC. The blocking filters were designed for single phase and three phases using the in-line and non-contact core. The best attenuation ratios of -46.46 dB and -73.9 dB were measured in the range of 100 kHz to 450 kHz bandwidth, respectively.