• Journal of the Korean institute of surface engineering
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• v.57 no.3
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• pp.155-164
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• 2024

Physical properties of carbon nanomaterials are dependent on their nanostructures and they are modified by diverse synthesis methods. Among them, thermal plasma method stands out for synthesizing carbon nanomaterials by controlling chemical and physical reactions through various design and operating conditions such as plasma torch type, plasma gas composition, power capacity, raw material injection rate, quenching rate, kinds of precursors, and so on. The method enables the production of carbon nanomaterials with various nanostructures and characteristics. The high-energy integration at high-temperature region thermal plasma to the precursor is possible to completely vaporize precursors, and the vaporized materials are rapidly condensed to the nanomaterials due to the rapid quenching rate by sharp temperature gradient. The synthesized nanomaterials are averagely in several nanometers to 100 nm scale. Especially, the thermal plasma was validated to synthesize low-dimensional carbon nanomaterials, carbon nanotubes and graphene, which hold immense promise for future applications.

• Carbon letters
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• v.2 no.1
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• pp.72-75
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• 2001

The performance of Li-ion system based on $LiCoO_2$ and Graphite is well optimized for the 3C applications. The charge-discharge mode, the manufacturing process, the cell performance and the thermal reactions affecting safety has been explained in the engineering point of view. The energy density of the current LIB system is in the range of 300~400 Wh/l. In order to achieve the energy density higher than 500 Wh/l, the active materials should be modified or changed. Adopting new high capacity anode materials would be effective to improve energy density.

• Bulletin of the Korean Chemical Society
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• v.7 no.6
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• pp.425-428
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• 1986

A new heterocuprate containing 2-pyridyloxy ligand, lithium 2-pyridyloxy-n-butylcuprate, has shown improved thermal stability and it reacts with acid chlorides to afford the corresponding ketones in high yields. Similarly, it can be effectively utilized in conjugate addition reactions of $\alpha,\beta$-unsaturated ketones. Of synthetic significance is that the complete utilization of n-butyl group in lithium 2-pyridyloxy-n-butylcuprate has been observed.

• Analytical Science and Technology
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• v.30 no.3
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• pp.138-145
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• 2017

Microwave-assisted organic synthesis has gained a remarkable interest over the past years because of its advantages - (i) rapid energy transfer and superheating, (ii) higher yield and rapid reaction, (iii) cleaner reactions. Ionic liquids are well known for their unique properties such as negligible vapor pressure and high thermal stability. With these properties, ionic liquids have gained increasing attention as green, multi-use reaction media. Recently, ionic liquids have been applied as reaction media for biocatalysis. Lipase-catalyzed reactions in ionic liquids provide high activity and yield compared to conventional organic solvents or solvent free system. Since polar molecules are generally good absorbent to microwave radiation, ionic liquids were investigated as reaction media to improve activity and productivity. In this study, therefore, the effect of microwave irradiation in ionic liquids was investigated on lipase catalyzed reactions such as benzyl acetate synthesis and caffeic acid phenethyl ester synthesis. Comparing to conventional heating, microwave heating showed almost the same final conversion but increased initial reaction rate (3.03 mM/min) compared to 2.11 mM/min in conventional heating at $50^{\circ}C$.

• Applied Science and Convergence Technology
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• v.26 no.6
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• pp.174-178
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• 2017

The reactions of thermal hydrogen atoms H(g) with the Ge(100) surface were examined with temperature-programmed desorption (TPD) mass spectrometry. Concomitant $H_2$ and $CH_4$ TPD spectra taken from the H(g)-irradiated Ge(100) surface were distinctly different for low and high H(g) doses/substrate temperatures. Reactions suggested by our data are: (1) adsorbed mono(${\beta}_1$)-/di-hydride(${\beta}_2$)-H(a) formation; (2) H(a)-by-H(g) abstraction; (3) $GeH_3$(a)-by-H(g) abstraction (Ge etching); and (4) hydrogenated amorphous germanium a-Ge:H formation. While all these reactions occur, albeit at higher temperatures, also on Si(100), H(g) absorption by Ge(100) was not detected. This is in contrast to Si(100) which absorbed H(g) readily once the surface roughened on the atomic scale. While this result is rather against expectation from its weaker and longer Ge-Ge bond as well as a larger lattice constant, we attribute the absence of direct H(g) absorption to insufficient atomic-scale surface roughening and to highly efficient subsurface hydrogenation at moderate (>300 K) and low (${\leq}300K$) temperatures, respectively.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 1997.11a
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• pp.112-119
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• 1997

The modelling of carbon substances obtaining, for instance, carbon fibers which have high fire resistance, has been realized on the example of the polyacrylonitrile pyrolysis modelling. The pyrolysis is considered as a double step process when the formation of a liquid phase and the oxidation of substance are excluded. Three main reactions are considered: a) with the evolution of ammonia; b) with the evolution of hydrogen cyanide; c) with the evolution of hydrogen. Reactions b) and c) are sequential, and a) and b) are parallel. The problem is formulated as one-dimensional. The equations of energy, masses or concentrations, porosity and thermal conductivity are proposed. The mathematical model of the carbonization process is designed using tile kinetic characteristics of the above reactions and the thermodynamic parameters of reagents and products in these reactions. The equations received are calculated by Runge-Cutta method and by Adams method of the fourth order accuracy.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.17 no.2
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• pp.1-10
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• 2021

Lithium-ion batteries with high energy density, long cycle life and other advantages, have been widely used to energy storage systems(ESS). But as ESS fires frequently occur, the safety concern has become the main obstacle that hinders the large-scale applications of lithium-ion batteries. Especially, thermal runaway is the key scientific problem in battery safety research. Therefore, in this study, we performed a numerical analysis on the thermal runaway phenomenon of NCM111, NCM523 and NCM622 batteries using a two-dimensional analysis model. The results show that the two-dimensional simulation results are generally matched with three-dimensional simulation. Also, In the case of NCM111 with a low Ni content in the temperature range used in this study, thermal runaway phenomenon does occurred very slowly, but as the Ni content is increased, the thermal runaway phenomenon occurs rapidly and the thermal stability tends to be decreased. And, in NCM523 and NCM622 batteries, chain reactions occur almost simultaneously, but in the case of NCM111 battery, it is found that after the SEI(Solid Electrolyte Interface) layer decomposition reaction, the cathode-electrolyte reaction is appeared sequentially. After that, the anodic decomposition reaction is increased and leads to the thermal runaway reaction.

• Macromolecular Research
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• v.15 no.6
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• pp.587-594
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• 2007

Well defined amphiphilic diblock copolymers of poly(styrene-b-vinylbenzylphosphonic acid) (PS-b-PVBPA) were prepared by controlled radical polymerization technique, two-step hydrolysis reactions using trime-thylsilyl bromide from the corresponding phosphonic ethyl ester. By indirect, backward pH titration of the block copolymer, a good titration curve of a dibasic acid was observed. The IEC values obtained from both backward pH titration and volumetric back titration were almost identical. Thermal gravimetric analysis (TGA) of the phosphonic acid containing block copolymer showed a high thermal stability up to $400^{\circ}C$.

• Journal of Welding and Joining
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• v.24 no.2
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• pp.57-63
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• 2006

In this study, the curing kinetics and thermal degradation of underfill were investigated using differential scanning calorimetry (DSC) and thermo gravimetry analysis (TGA). The mechanical and thermal properties of underfill were characterized using dynamic mechanical analysis (DMA) and thermo-mechanical analysis (TMA). Also, we presented on underfill dispensing process using Prostar tool. The non-isothermal DSC scans at various heating rates, the exothermic reaction peak became narrower with increasing the heating rate. The thermal degradation of underfill was composed of two processes, which involved chemical reactions between the degrading polymer and oxygen from the air atmosphere. The results of fluidity phenomena were simulated using Star CD program, the fluidity of the underfills with lower viscosity was faster.

• 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.