Kyoung-Soo Kang

Ammonium fluoride-activated synthesis of cubic δ-TaN nanoparticles at low temperatures

Cubic delta-tantalum nitride (δ-TaN) nanoparticles were selectively prepared using a K2TaF7 + (5 + k) NaN3 + k NH4F reactive mixture (k being the number of moles of NH4F) via a combustion process under a nitrogen pressure of 2.0 MPa. The combustion temperature, when plotted as a function of the number of moles of NH4F used, was in the range of 850°C to 1,170°C. X-ray diffraction patterns revealed the formation of cubic δ-TaN nanoparticles at 850°C to 950°C when NH4F is used in an amount of 2.0 mol (or greater) in the combustion experiment. Phase pure cubic δ-TaN synthesized at k = 4 exhibited a specific surface area of 30.59 m2/g and grain size of 5 to 10 nm, as estimated from the transmission electron microscopy micrograph. The role of NH4F in the formation process of δ-TaN is discussed with regard to a hypothetical reaction mechanism.

Effects of Solubility of SO 2 Gas on Continuous Bunsen Reaction using HI x Solution

Abstract >> The Sulfur-Iodine thermochemical hydrogen production process (SI process) consists of the Bunsenreaction section, the H 2 SO 4 decomposition section, and the HI decomposition section. The HI x solution (I 2 -HI-H 2 O)could be recycled to Bunsen reaction section from the HI decomposition section in the operation of the integratedSI process. The phase separation characteristic of the Bunsen reaction using the HI x solution was similar to that of I 2 -H 2 O-SO 2 system. On the other hands, the amount of produced H 2 SO 4 phase was small. To investigate theeffects of SO 2 solubility on Bunsen reaction, the continuous Bunsen reaction was performed at variation of the amounts of SO 2 gas. Also, it was carried out to make sure of the effects of partial pressure of SO 2 in the conditionof 3bar of SO 2 -O 2 atmosphere. As the results, the characteristic of Bunsen reaction was improved with increasingthe amounts and solubility of SO 2 gas. The concentration of Bunsen products was changed by reverse Bunsen reaction and evaporation of HI after 12 h.Key words : Hydrogen production(수소 제조), SI process(황-요오드 공정), Bunsen reaction(분젠 반응), HIx solution(HIx 용액), Continuous reaction(연속식 반응), Pressurized reaction(가압 반응)

A Study on Characteristics of HI Decomposition Using Pt Catalysts on ZrO2-SiO2 Mixed Oxide

This work is investigated for the catalytic decomposition of hydrogen iodide (HI). Platinum was used as active material by loading on ZrO2-SiO2 mixed oxide in HI decomposition reaction. To obtain high and stable conversion of hydrogen iodide in severe condition, it was required to improve catalytic activity. For this reason, a method increasing dispersion of platinum was proposed in this study. In order to get high dispersion of platinum, zirconia was incorporated in silica by sol-gel synthesis. Incorporating zirconia influence increasing platinum dispersion and BET surface area as well as decreasing deactivation of catalysts. It should be able to stably product hydrogen for a long time because of inhibitive deactivation. HI decomposition reaction was carried out under the condition of 450℃ and 1 atm in a fixed bed reactor. Catalysts analysis methods such as N2 adsorption/desorption analysis, X-ray diffraction, X-ray fluorescence, ICP-AES and CO gas chemisorption were used to measurement of their physico-chemical properties.

Conceptual Design of Sulfur-Iodine Hydrogen Production Cycle of Korea Institute of Energy Research

The Sulfur-Iodine thermochemical cycle offers a promising approach to the high efficiency production of hydrogen from nuclear power. Several SI cycles have been proposed by several research group. General Atomic (GA) studied I2 separation by extractive distillation using H3 PO4 . RWTH introduced the concept of reactive distillation. In this process, HIx stream coming from the Bunsen reaction is fed to the column. And HIx is distillated and decomposed at the same time to obtain hydrogen. Korea Institute of Energy Research (KIER) and Japan Atomic Energy Agency (JAEA) concentrate HIx using electro-dialysis cell and concentrated HIx is fed to the column to produce HI vapor, which is decomposed to produce hydrogen. HI was separated from HIx solution by an extractive distillation using H3 PO4 . However, a large amount of electric energy was required to recycle H3 PO4 . Most of SI processes have difficulties producing hydrogen because it has excess iodine in HI decomposition Section. SI cycle with electrodialysis cell uses membrane reactor to separate H2 and HIx. The current state of the membrane technology is not compatible with the process needs. This study examined several cases of flowsheets to overcome the problems mentioned above. The flowsheets were revised by adding the iodine separator and excluding membrane reactor. The thermal efficiency of SI process was analyzed using the revised flowsheet.Copyright