• Carbon letters
• /
• v.7 no.3
• /
• pp.196-200
• /
• 2006

Graphite has hexagonal closed packing structure with two bonding characteristics of van der Waals bonding between the carbon layers at c axis, and covalent bonding in the carbon layer at a and b axis. Graphite has high tolerant to the extreme conditions of high temperature and neutron irradiations rather than any other materials of metals and ceramics. However, carbon elements easily react with oxygen at as low as 400C. Considering the increasing production of today of hydrogen and electricity with a nuclear reactor, study of oxidation characteristics of graphite is very important, and essential for the life evaluation and design of the nuclear reactor. Since the oxidation behaviors of graphite are dependent on the shapes of testing specimen, critical care is required for evaluation of nuclear reactor graphite materials. In this work, oxidation rate and amounts of the isotropic graphite (IG-110, Toyo Carbon), currently being used for the Koran nuclear reactor, are investigated at various temperature. Oxidation process or principle of graphite was figured out by measuring the oxidation rate, and relation between oxidation rate and sample shape are understood. In the oxidation process, shape effect of volume, surface area, and surface to volume ratio are investigated at $600^{\circ}C$, based on the sample of ASTM C 1179-91.

• Journal of the Korean Ceramic Society
• /
• v.55 no.5
• /
• pp.498-503
• /
• 2018

Using the thermal ablation method, the oxidation behavior of $SiC_f/SiC$ composites was investigated in air and in the temperature range of $1,300^{\circ}C$ to $2,000^{\circ}C$. At the relatively low temperature of $1,300^{\circ}C$, passive oxidation, which formed amorphous phase, predominantly occurred in the thermal ablation test. When the oxidation temperature increased, SiO (g) and CO (g) were formed by active oxidation and the dense oxide layer changed to a porous one by vaporization of gas phases. In the higher temperature oxidation test, both active oxidation due to $SiO_2$ decomposition on the surface of the oxide layer and active/passive oxidation transition due to interfacial reaction between oxide and base materials such as SiC fiber and matrix phase simultaneously occurred. This was another cause of high temperature degradation of $SiC_f/SiC$ composites.

• Journal of the Korean Ceramic Society
• /
• v.33 no.7
• /
• pp.816-822
• /
• 1996

Dependence of graphitic structure on oxidation of carbon materials was discussed using furan resin-derived carbon with inorganic compounds such as SiC and TiO2 Oxidation of carbon was governed by active site. I. e surface area regardless of the degree of graphitization. When oxidation was considered for not unit weight but unit area graphitization was important factor for oxidation so that the degree of graphitization increased the oxidation rate was delayed. Graphite (tiO2 addition) and turbostratic graphite(SiC addition) were oxidized through the same mechanism. In carbon materials with different structure components more than 2 oxidation of each component was different and amorphous component without the influence of additives on the surface was selectively oxidized in the intial oxidation stage.

• Journal of Environmental Health Sciences
• /
• v.26 no.4
• /
• pp.29-37
• /
• 2000

Fenton’s oxidation process is one of the most commonly applied processes to the wastewater which cannot be treated by conventional biological treatment processes. However, it is necessary to minimize the cost of Fenton’s oxidation treatment by modifying the treatment processes or other means of chemical treatment. So, as a method for the chemical oxidation of biorefractory or nonbiodegradable organic pollutants, the Photo-Fenton-Reaction which utilizes iron(11)salt. $H_2O$$_2$ and UV-light simultaneously has been proprosed. Therfore, the purpose of this study is to test a removal efficiency of dye-wastewater and treatment cost with Fenton’s and Photo-Fenton’s oxidation process. The Fe(11)/$H_2O$$_2$ reagent is referred to as the fenton’s reagent. which produces hydroxy radicals by the interaction of Fe(11) with $H_2O$$_2$. In this exoeriment, the main results are as followed; 1. The Fenton oxidation was most efficient in the pH range of 3-5. The optimal condition for initial reaction pH was 3.5 for the high CO $D_{Cr}$ & TOC-removal efficiency. 2. The removal efficiency of TOC and CO $D_{Cr}$ increased up to the molar ration between ferrate and hydrogen peroxide 0.2:1, but above that ratio removal efficiency hardly increased. 3. The highest removal efficiency of TOC and CO $D_{Cr}$ were showed when the mole ration of ferrate to hydrogen peroxide was 0.2:3.4. 4. Without pretreatment process, photo-fenton oxidation which was not absorbed UV light was not different to fenton oxidation. 5. And Fenton oxidtion with pretreatment process was similar to Fenton oxidation in the absence of coagulation, the proper dosage of F $e^{2+}$: $H_2O$$_2$ was 0.2:1 for the optimal removal efficiency of TOC or CO $D_{Cr}$ .6. Also, TOC & CO $D_{Cr}$ removal efficiency in the photo-fenton oxidation with pretreatment was increased when UV light intensity enhanced.7. Optimum light intensity in the range from 0 to 1200 W/$m^2$ showed that UV-intensity with 1200W/$m^2$ was the optimum condition, when F $e_{2+}$:$H_2O$$_2$ ratio for the highest decomposition was 0.2:2.5.EX>$_2$ ratio for the highest decomposition was 0.2:2.5.

• Applied Chemistry for Engineering
• /
• v.25 no.5
• /
• pp.474-480
• /
• 2014

In this study, NO oxidation reaction using $Mn/TiO_2$ catalysts was investigated. NO oxidation results revealed that the different trend was observed upon physicochemical properties of $TiO_2$ and interactions between Mn and $TiO_2$ support. $Mn/TiO_2(A)$ catalyst has a superior NO oxidation activity, which increased with decreased space velocity and increased Mn amounts from 10 to 30 wt%. The results indicated that the SCR activity could increase by the fast SCR reaction process using the $Mn/TiO_2(A)$ catalyst located in front of the SCR unit.

• Journal of Korean Society on Water Environment
• /
• v.23 no.3
• /
• pp.319-323
• /
• 2007

The Advanced Oxidation Process (AOP) is being increasingly used to oxidize complex organic constituents in treated effluents from domestic wastewater treatment plants. Generally, ${NO_3}^--N$ concentrations ranges between 5 and 8 mg/L for biologically well-treated effluents. However, nitrate ions, ${NO_3}^-$, affects on oxidation as not only a well-known strong absorber of UV light below 250 nm of wavelength but also as an OH radical scavenger. The objective of this study was to evaluate the AOP systems for degradation of 2,4-DCP, and to delineate the effect of nitrate ions on UV oxidation of 2,4-DCP by conducting a bench-scale operation at various reaction times and initial concentrations of $H_2O_2$. The experimental results indicated that 2,4-DCP could be completely oxidized by $UV/H_2O_2$ process with an initial $H_2O_2$ concentration of 20 mg/L at a retention time of 1.0 min or longer. Nitrate ions did not show any adverse effect on 2,4-DCP oxidation at this high $H_2O_2$ concentration, and the practical initial $H_2O_2$ concentration and reaction time for the 80% oxidation turned out to be 5 mg/L and 1.0 min, respectively.

• Journal of the Korean Chemical Society
• /
• v.24 no.3
• /
• pp.183-192
• /
• 1980

Oxidation reactions of carbon monoxide on $SnO_2$, Sb-doped $SnO_2$, and Pt catalyst were studied. The oxidation reaction was found to be first order with respect to both CO and O$_2$ on $SnO_2$ and Sb-doped $SnO_2$ catalysts, and to be of half order on Pt catalyst. A small addition of Sb to $SnO_2$ (depant composition: 0.05∼0.1 mol %) increased the rate of oxidation. On the contrary, a large addition decreased the rate. From the rate expression of oxidation on Pt catalyst, the inhibition effect of carbon monoxide on the rate of oxidation was deduced. The experimentally obtained activatio energies were 5.7 kcal for the Sb doped $SnO_2$ catalyst (dopant composion: 0.05 mole%), and 6.4 kcal for the Pt catalyst. A possible reaction mechanism was proposed from the experimentally obtained kinetic data.

• Korean Chemical Engineering Research
• /
• v.51 no.4
• /
• pp.432-437
• /
• 2013

The CO preferential oxidation reaction (PROX) has been done using Cu catalytic active species supported on some of mesoporous silica materials which can facilitate the diffusion of the reactants in order to prevent the poisoning of anode active materials by CO molecules during driving polymer electrolyte fuel cells (PEMFC) in this study. As a result when SBA-15 with large pore used as a support showed excellent CO oxidation activity, especially the activity increased in proportion to the amount of supported Cu. Ti components which was inserted to increase the degree of dispersion of Cu, contributed to improving the performance for CO oxidation at low-temperature. The degree of dispersion of Cu ingredients was the best in the catalyst inserted 20 mol-% Ti into the framework of SBA-15, and CO oxidation activity was also improved.

• Journal of the Korean Chemical Society
• /
• v.29 no.2
• /
• pp.111-120
• /
• 1985

The oxidation reaction of CO on the catalysts 4 mol%, 8 mol%, and 12 mol% Cd-doped ${\alpha}-Fe_2O_3$ is individually investigated. Regardless of Cd doping level, over-all reaction order for the oxidation of CO is 1.5; the first order with respect to CO and the one-half order with respect to $O_2$. Over the temperature range of 350∼$460^{\circ}C$, the activation energy for CO oxidation is 10.10∼11.30Kcal/mol. From the agreement between the kinetic data and conductivity measurements, the reaction mechanism is suggested. Especially from the effect of Cd doping, the fact that catalytic activity of ${\alpha}-Fe_2O_3$ is due to the excitation of electrons which are traped on oxygen vacancy is found, and the adsorption sites for reactant molecules are found.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.14 no.3
• /
• pp.229-234
• /
• 1985

The effect of packaging on the quality of dried anchovy was investigated, when packed with various materials and stored at different conditions. In cases of nitrogen gas substitution or addition of antioxidant, the reaction rates of lipid oxidation, the loss of available lysine and browning of the samples sealed in aluminum laminated film bag were lower than those packed in kraft paper or polyethylene film bag while the samples without gas substitution did not reveal any great differences in the rate of the reactions. The shelf-lives of the samples computed as a function of lipid oxidation were 90, 98 and 137 days at the storage of $35^{\circ}C$ for the packages of kraft paper, polyethylene and aluminum film respectively. And those at $55^{\circ}C$ storage for the same samples were 47, 51 and 77 days. The half-lives of available lysine loss were 227, 209 and 312 days at $35^{\circ}C$: 83, 83 and 147 days at $55^{\circ}C$ for the samples respectively. And the shelf-lives determined as a function of browning reaction were 26, 27 and 49 days at $55^{\circ}C$. The predicted shelf-lives at $25^{\circ}C$ as a function of lipid oxidation were 130, 140, and 189 days for kraft paper, polyethylene and aluminum laminated film packaging: 207, 229 and 246 days for the browning reaction, and 363, 339 and 415 days for the loss of available lysine. The results suggest that the protective effect of packaging on the reactions of lipid oxidation and browning could not be aided unless the air was expelled or replaced to inert gas.