• 한국수소및신에너지학회논문집
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• 제19권4호
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• pp.299-304
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• 2008

Thermal decomposition of Ammonia Borane have been investigated with various analytical methods including TGA, TP-MS, DSC. By-products such as aminoborane and borazine were identified during hydrogen release by TGA, TP-MS analysis. $H_2$ release amount was measured at each temperature isothermally, which resulted in 7 wt% $H_2$ release at 130$^{\circ}C$. Moreover, higher temperature enhanced hydrogen release kinetics leading to shortened induction period from 20 min at 95$^{\circ}C$ to 0 min at 130$^{\circ}C$. Melting and decomposition at close temperature (4$^{\circ}C$ difference) caused the formation of thin foam during hydrogen release. Suppression of by-products and thin foam formation during hydrogen release is suggested as critical issues to realize chemical hydrogen storage system with ammonia borane.

• 한국수소및신에너지학회논문집
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• 제30권1호
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• pp.1-7
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• 2019

The preparation and catalytic activities of various transition metal carbide crystallites (VC, MoC, WC) were examined in this study. In particular, the effect of different kinds of transition metal crystallites were scrutinized on the ammonia decomposition reaction. The experimental results showed that BET surface areas ranged from $8.3m^2/g$ to $36.3m^2/g$ and oxygen uptake values varied from $9.1{\mu}mol/g$ to $25.4{\mu}mol/g$. Amongst prepared transition metal carbide crystallites, tungsten compounds (WC) were observed to be most active for ammonia decomposition reaction. The main reason for these results were considered to be related to the extent of electronegativity between these materials. Most of transition metal carbide crystallites were exceeded by Pt/C crystallite. However, the steady state reactivities for some of transition metal carbide crystallites (WC) were comparable to or even higher than that determined for the Pt/C crystallite.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2014년도 제49회 KOSCO SYMPOSIUM 초록집
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• pp.235-236
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• 2014

An experimental study has been carried out to investigate a thermal decomposition of urea solution at relative low temperature with a lab-scaled exhaust pipe. The conversion efficiency of reductant considered with both ammonia and HNCO related with the urea injection quantity, inflow gas velocity and temperature. The conversion efficiency of ammonia was larger than that of HNCO under all experimental conditions unlike the theoretical thermolysis reaction.

• Elastomers and Composites
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• 제34권4호
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• pp.350-359
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• 1999

초임계유체로써 물, 28% 암모니아 수용액, 암모니아에 대한 폐타이어의 전환율과 오일수율을 비교하였다. 같은 온도와 압력에서 초임계암모니아에 의한 전환율이 가장 높았다. 본 논문에서는 전환율이 가장 높은 초임계암모니아를 주용매로 사용하였고 오일수율을 극대화할 수 있는 공용매로서 수소공여체 물질인 테트라린을 사용하였다. 테트라린의 함량이 증가할수록 오일의 수율은 증가하였다. 초임계암모니아 단독으로 폐타이어를 추출했을 때, 오일의 수율은 $280^{\circ}C$, 22.3MPa에서 48.8%인 반면에 폐타이어에 대한 테트라린의 무게비(데트라린무게/폐타이어무게)가 5일 때 오일의 수율은 $280^{\circ}C$, 22.3MPa에서 61.2%였다. 이런 현상은 초임계상태의 열분해에서 생성된 라디칼이 수소공여체물질에 의해 안정화되어 생성물의 고분자화 또는 이차분해가 억제되는 것으로 보여진다. 테트라린에 팽윤시킨 폐타이어는 적은 데트라린 소모로도 높은 오일수율을 얻을 수 있었다.

• 신재생에너지
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• 제9권1호
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• pp.51-59
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• 2013

Tantalum carbide crystallites which is to be used for $H_2$ fuel cell has been synthesized via a temperature-programmed reduction of $Ta_2O_5$ with pure $CH_4$. The resultant Ta carbide crystallites prepared using two different heating rates and space velocity exhibit the different surface areas. The $O_2$ uptake has a linear relation with surface area, corresponding to an oxygen capacity of $1.36{\times}10^{13}\;O\;cm^{-2}$. Tantalum carbide crystallites are very active for hydrogen production form ammonia decomposition reaction. Tantalum carbides are as much as two orders of magnitude more active than Pt/C catalyst (Engelhard). The highest activity has been observed at a ratio of $C_1/Ta^{{\delta}+}=0.85$, suggesting the presence of electron transfer between metals and carbon in metal carbides.

• Journal of Korean Society for Atmospheric Environment
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• 제21권E2호
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• pp.57-65
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• 2005

An experimental study was performed on the decomposition of gaseous ammonia and two selected volatile organic compounds (VOCs: toluene and acetone) in a combined nonthermal plasma reactor with corona and glow discharges. A lab pilot scale reactor (206 liter) equipped with a high electric power pack was used to determine the decomposition efficiency in relation with the inlet concentration and applied voltage. Three different types of discharging electrode such as wired rack, wire strings for corona discharge, and thin plate for glow discharge were put in order in the reactor. While decomposition of ammonia decreased with an increase in the initial concentration, acetone showed an opposite result. In the case of toluene however no explicit tendency was found in toluene and aceton. Negative discharge resulted in high decomposition efficiency than the positive one for all gases. A better removal of gas phase element could be achieved when fume dust were present simultaneously.

• 한국대기환경학회지
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• 제24권5호
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• pp.512-522
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• 2008

Ammonia is a major compound of odor in livestock house. To enhance the performance of ammonia oxidation (decomposition). the gas-liquid, two phase photocatalytic oxidation system was designed and prepared in this study. Commercial P-25 as $TiO_2$ catalyst was used for ammonia decomposition. V/P-25 catalyst prepared by sol gel method was also used for the removal of by-producted $NO_x$ in $NH_3$ oxidation reaction. When $TiO_2$ was used as a photocatalyst, the conversion to $N_2$ in ammonia decomposition reached above 90% until 200hr (The air flow rate of 4L/min with the ammonia concentration up to 25ppm.). However, considerable amounts of NO and $NO_2$ were formed as a result of $NH_3$ oxidation (as a by-product). Therefore, we added Vanadia impregnated $TiO_2$(P-25) catalyst for the removal of $NO_x$ at the end of reaction trail. The results of a pilot-scale operation were successful to achieve the simultaneous removal of $NH_3\;and\;NO_x$ about 81 and 87%, respectively.

• Elastomers and Composites
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• 제34권3호
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• pp.239-246
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• 1999

폐타이어에서 보강실과 고무로 배합된 부분(side wall)을 아임계와 초임계 상태의 세가지 용매, 물, 28% 암모니아수, 암모니아를 사용하여 용매의 분해와 추출능을 비교하였다. 6mm 입방체로 만든 폐타이어의 초임계물에 의한 분해와 추출속도는 140 kJ/mol의 활성화에너지를 갖는 1차 속도식을 잘 만족하였다. 초임계상태에서 28% 암모니아용액은 압력이 감소할수록 초기추출에서 초임계물보다 추출능이 높게 나타났다. 이 현상은 초임계물에 용해되어 있는 암모니아의 영향 때문이라고 추측된다.

• 대한화학회지
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• 제7권1호
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• pp.1-5
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• 1963

The thermal decomposition process of ammonium paratungstate $5(NH_4)_2O{\cdot}12WO_3{\cdot}5H_2O$ was analysed by the methods of thermogravimetric analysis, differential thermal analysis, quantitative analysis of the ammonia which is released during heating and X-ray powder diffraction in air and in vacuo. There are several endothermic peaks which indicate release of ammonia and exothermic peaks which indicate crystal growth and oxidation of decomposed prodects in air. After water is driven off the ammonia is released at intervals corresponding to the endothermic peaks. The highest temperature at which ammonia is released is about $420^{\circ}C$ in air and $480^{\circ}C$ in vacuo. In air the crystal structure of paratungstate is conserved up to a temperature of $300^{\circ}C$ at which the remaining ammonia is about 4 mols. At $320^{\circ}C$ the remaining ammonia becomes less than 2 mols and the paratungstate structure changes into the amorphous state. After that ${\gamma}$ oxide is produced and is oxidized to ${\alpha}$ oxide in the temperature range of 400-$500^{\circ}C$ in air. In vacuo however the endothermic peaks and structural changes occur at lower temperatures and the structure of ${\gamma}$ oxide is conserved up to temperatures higher than $500^{\circ}C$.

• Journal of Advanced Marine Engineering and Technology
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• 제28권5호
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• pp.818-826
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• 2004

The spray-induced mixing characteristics and thermal decomposition of aqueous urea solution into ammonia have been studied to design optimum sizes and geometries of the mixing chamber in SCR(Selective Catalytic Reduction) system. The cold flow tests about the urea-injection nozzle were performed to clarify the parameters of spray mixing characteristics such as mean diameter and velocity of drops and spray width determined from the interactions between incoming air and injected drops. Discrete particle model in Fluent code was adopted to simulate spray-induced mixing process and the experimental results on the spray characteristics were used as input data of numerical calculations. The simulation results on the spray-induced mixing were verified by comparing the spray width extracted from the digital images with the simulated Particle tracks of injected drops. The single kinetic model was adopted to predict thermal decomposition of urea solution into ammonia and solved simultaneously along with the verified spray model. The hot air generator was designed to match the flow rate and temperature of the exhaust gas of the real engines The measured ammonia productions in the hot air generator were compared with the numerical predictions and the comparison results showed good agreements. Finally, we concluded that the design capabilities for sizing optimum mixing chamber were established.