• Transactions on Electrical and Electronic Materials
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• v.11 no.5
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• pp.234-237
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• 2010

Nanoenergetic materials were synthesized and the thermite reaction between the CuO nanowires and the deposited nano-Al by Joule heating was studied. CuO nanowires were grown by thermal annealing on a glass substrate. To produce nanoenergetic materials, nano-Al was deposited on the top surface of CuO nanowires. The temperature of the first exothermic reaction peak occurred at approximately $600^{\circ}C$. The released heat energy calculated from the first exothermic reaction peak in differential scanning calorimetry, was approximately 1,178 J/g. The combustion of the nanoenergetic materials resulted in a bright flash of light with an adiabatic frame temperature potentially greater than $2,000^{\circ}C$. This thermite reaction might be utilized to achieve a highly reliable selective area crystallization of amorphous silicon films.

• 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 the Mineralogical Society of Korea
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• v.11 no.1
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• pp.32-44
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• 1998

The transformation sequence of kaolinite to mullite is examined with new electron diffraction data obtained mainly by an energy filtering transmission electron microscope. Kaolinite is transformed finally into mullite and cristobalite through several steps of continuous reactions by heating, which result in metakaolinite, microcrystalline spinel-type phase and amorphous silica. Metakaolinite maintains a short-range order in its structure ven at $920^{\circ}C$. Spinel phase results from a topotactictransformation of metakaolinite apart from the breakdown of metakaolinite structure. the first strong exothermic peak on DTA curve is mainly due to the extraction of amorphous silica from metakaolinite and the gradual nucleation of mullite. Metakaolinite decomposes around$ 940^{\circ}C$ to mullite that doesn't show a clear crystallographic relationship to the parent metakaolinite structure. However, spinel phase produced previously is maintained. The initially formed spinel and mullite phases are suggested to be Al-rich, but progressively gain Si in their structures at higher temperatures. Spinel phase decomposes completely through a second weak exothermic reaction promoting the growth of mullite, and crystallization of amorphous silica to cristobalite.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.509-512
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• 2004

This research is targeting that estimate the effect on cement concrete pavement with type of chloride deicers. In order to this study objective, when chloride deicers were spread on road surface, thermal characteristics test was conducted. Also, skid resistance test according to types and concentration of chloride deicier, road surface conditions were investigated. As a test results, thermal characteristics with kind of chloride deicier could know that sodium chloride(NaCl) is exothermic reactive material, calcium chloride$(CaCl_2)$ is endothermic reactive material. And, in case of mixed salt of the calcium and sodium chloride, it could know that can change to the exothermic or endothermic reaction according to dosage ratios. Skid value by British Pendulum Tester(BPT) has shown that it is seldom difference between the types($CaCl_2$, NaCl, mixed salt) and solution concentrations(0.5, 0.8, 1.0, 4.0, $10\%$) of chloride deicier comparing with tap water except mixed salt($10\%$ solution concentration).

• Journal of the Korean Ceramic Society
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• v.40 no.9
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• pp.837-841
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• 2003

Duplex microstructure of zirconia and alumina has been achieved via an organic-inorganic solution technique. Zirconium 2,4-pentanedionate, aluminum nitrate and polyethylene glycol were dissolved in ethyl alcohol without any precipitation. The organicinorganic precursor gels were turned to porous powders having volume expansion through explosive, exothermic reaction during drying process. The volume expansion was caused by abrupt decomposition of the organic groups in the gels during the vigorous exothermic reaction. The volume expanded, porous powders were crystallized and densified at 1500$^{\circ}C$ for 1 h. At the optimum amount of the PEG polymer, the metal cations were well dispersed in the solution and a homogeneous polymeric network was formed. The polymer content also affected on the specific surface area of the synthesized powder and the grain size of the sintered composite.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.11 no.3
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• pp.7-20
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• 2007

We examined the steady state solution for a strongly exothermic mixtures in some class A geometries subjected to different boundary conditions under Arrhenius, Bimolecular and Sensitised reactions. The solution of the governing nonlinear reaction diffusion equation was obtained using the variational method formulation executed in Mathematica package. The paper elucidates the influence of geometry, boundary conditions and types of reaction on the thermal ignition of the reactive mixture. Apart from validating known results in literature, the solution gave further insight into the influence of material properties and conditions on the occurrence of thermal ignition.

• Nuclear Engineering and Technology
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• v.54 no.9
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• pp.3580-3585
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• 2022

The thermal stability of carbohydrazide, hydrazine nitrate, acetohydroxamic acid in nitric acid solutions has been studied at atmospheric pressure and above atmospheric pressure. The volumes of gaseous products of thermolysis and the maximum rate of gas evolution have been determined at atmospheric pressure. It has been shown that, despite the high rate of gas evolution and large volumes of evolved gases, the conditions for the development of autocatalytic oxidation are not created. Exothermic processes are observed in a closed vessel in the temperature range of 50-250 ℃. With an increase in the concentration of nitric acid, the temperatures of the onset of exothermic effects for all mixtures decrease, and the values of the total thermal effects of reactions increase, to the greatest extent for solutions with carbohydrazide.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.3
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• pp.15-22
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• 1995

This paper presents the effects of assistant gas pressure on laser cutting. To investigate the effects of assistant gas pressure, pressure measuring system was constructed with good handling and precision at low price. The measured results discussed compare with that of laser cutting of STS304. The assistant gas pressure varied with the variation of distance between nozzle and workpiece. The peak pressure existed at some distance and could be known by using the deviced pressure measuring system. The higher assistant gas pressure helps to remove the dross and the exothermic energy out of the material. The quantity of dross beneath the workpiece decreases and the kerf width narrows at measured peak pressure.

• 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

• Fire Science and Engineering
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• v.34 no.1
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• pp.66-71
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• 2020

The process of discharging batteries using salt water, when used for the disposal of a lithium-ion (Li-ion) batteries, is likely to cause a fire. However, there is a dearth of studies in the literature on the risk of fire while discharging mobile phone batteries in salt water. In order to investigate the possibility of fire by elucidating the discharge characteristics and the generation of heat, we conducted experiments by varying the concentration of the salt water, number of overlapping batteries, and type of the mobile phone batteries used as experimental specimen. The discharging voltage and the temperature of the batteries were measured, and the fire risk was predicted by analyzing the data. The results of the experiment showed that the higher the salt water concentration, the greater the discharge value of the mobile phone battery and the higher the exothermic temperature. Moreover, the exothermic temperatures of the overlapping batteries were higher than that of the single battery submerged in salt water. The highest exothermic temperature points of the battery occurred at the positive and negative poles.