• Resources Recycling
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• v.4 no.1
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• pp.52-59
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• 1995

Treating bulk superalloy scrap with molten zinc has been studled to facililate recycling and recovery- of cobalt.Superalloys investigated were the cobalt-base Mar-M-509 and X45 and the nickel-base Rene 80. Charges withZnlscrap ratlos of 1.5-6.5 were heated to 750-9002 far 1-7.5 hours in a nitrogen atmosphere. The moltenzinc dissolved superalloy scrap and zinc was removed by vacuum distillation at 850-Wk for 4-6 hours. Ithas been concluded that the optimum conditions of decomposition for Mar-M-509 and Rene 80 \"ere dissolutiontemperature of about 850k, Znlscrap ratlo of about 5, and dissalution time of about 5.5 hours. The zinc-treatedsuperalloy prouducts were friable and reacted rapidly with acid solutions. Leaching 9mm pieces of unalloyedMar-M-509 or Rene 80 with 5 times the stolchlometric amount oi 6N HCI at 90t ior 3 hours dissolved about1.5-7.270, while leachmg of the minus 20-mesh products dissolved about 89.0-93.0%.ved about 89.0-93.0%.

• Korean Journal of Environmental Agriculture
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• v.40 no.3
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• pp.149-160
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• 2021

BACKGROUND: Concerns have been raised about the impact of recent high concentrations of fine dust on human health. Ammonia(NH₃) reacts with sulfur oxides and nitrogen compounds in the atmosphere to form ultrafine ammonium sulfate and ammonium nitrate (PM2.5). There is a growing need for accurate estimates of the amount of ammonia emitted during agricultural production. Therefore, in this study, ammonia emissions generated from the cultivation of leafy perilla in plastic houses were determined. METHODS AND RESULTS: Cow manure compost, swine manure compost, and poultry manure compost each at 34.6 ton ha^-1, the amount commonly used by farmers in the field, was sprayed on the soil surface. Just after spraying cow manure compost, swine manure compost, and poultry manure compost, the ammonia was periodically measured and analyzed to be 22.5 kg ha^-1, 22.8 kg ha^-1, and 85.2 kg ha^-1, respectively. The emission factors were estimated at 70.0 kg-NH₃ ton-N, 62.8 kg-NH₃ ton-N, and 234.1 kg-NH₃ ton-N, respectively. Most ammonia was released in the two weeks after application of the compost and then the amount released gradually decreased. CONCLUSION: Therefore, it is necessary to improve the emission factor through a study on the estimation of ammonia emission by type of livestock manure and major farming types such as rice fields and uplands, and to update data on the production, distribution, and sales of livestock manure.

• Korean Journal of Agricultural Science
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• v.47 no.4
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• pp.1049-1056
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• 2020

Ultrafine dust causes asthma and respiratory and cardiovascular diseases when inhaled. Ammonia (NH3) plays a big role in ultrafine dust formation in the atmosphere by reacting with nitrogen oxides (NOx) and sulfur oxides (SOx) emitted from various sources. The agricultural sector is the single largest contributor of NH3, with the vast majority of emissions ensuing from fertilizers and livestock sector. Interest in using biochar to attenuate these NH3 emissions has grown. This experiment was conducted to study the effects of using rice hull biochar pyrolyzed at three different temperatures of 250℃ (BP 4.6, biochar pH 4.6), 350℃ (BP 6.8), and 450℃ (BP 10.3) on the emission of ammonia from soil fertilized with urea. The emissions of NH3 initially increased as the experiment progressed but decreased after peaking at the 84th hour. The amount of emitted NH3 was lower in soil with biochar amendments than in that without biochar. Emissions amongst biochar-amended soils were lowest for the BP 6.8 treatment, followed in an ascending order by BP 10.3 and BP 4.6. Since BP 6.8 biochar with neutral pH resulted in the lowest amount of NH3 emitted, it can be concluded that biochar's pH has an effect on the emissions of NH3. The results of this study, therefore, indicate that biochar can abate NH3 emissions and that a neutral pH biochar is more effective at reducing gaseous emissions than either alkaline or acidic biochar.

• Korean Journal of Metals and Materials
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• v.47 no.11
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• pp.716-721
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• 2009

The major drive for the application of low-temperature plasma treatment in nitrocarburizing of austenitic stainless steels lies in improved surface hardness without degraded corrosion resistance. The low-temperature plasma nitrocarburizing was performed in a gas mixture of $N_{2}$, $H_{2}$, and carbon-containing gas such as $CH_{4}$ at $450^{\circ}C$. The influence of the processing time (5~30 h) and $N_{2}$ gas composition (15~35%) on the surface properties of the nitrocarburized layer was investigated. The resultant nitrocarburized layer was a dual-layer structure, which was comprised of a N-enriched layer (${\gamma}_N$) with a high nitrogen content on top of a C-enriched layer (${\gamma}_C$) with a high carbon content, leading to a significant increase in surface hardness. The surface hardness reached up to about $1050HV_{0.01}$, which is about 4 times higher than that of the untreated sample ($250HV_{0.01}$). The thickness of the hardened layer increased with increasing treatment time and $N_{2}$ gas level in the atmosphere and reached up to about $25{\mu}m$. In addition, the corrosion resistance of the treated samples without containing $Cr_{2}N$ precipitates was enhanced than that of the untreated samples due to a high concentration of N on the surface. However, longer treatment time (25% $N_{2}$, 30 h) and higher $N_{2}$ gas composition (35% $N_{2}$, 20 h) resulted in the formation of $Cr_{2}N$ precipitates in the N-enriched layer, which caused the degradation of corrosion resistance.

• Journal of Powder Materials
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• v.27 no.6
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• pp.498-502
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• 2020

We investigate the effects of Yb2O3 and calcium aluminosilicate (CAS) glass as sintering additives on the sintering behavior of AlN. The AlN specimens are sintered at temperatures between 1700℃ and 1900℃ for 2 h in a nitrogen atmosphere. When the Yb2O3 content is low (within 3 wt.%), an isolated shape of secondary phase is observed at the AlN grain boundary. In contrast, when 3 wt.% Yb2O3 and 1 wt.% CAS glass are added, a continuous secondary phase is formed at the AlN grain boundary. The thermal conductivity decreases when the CAS glass is added, but the sintering density does not decrease. In particular, when 10 wt.% Yb2O3 and 1 wt.% CAS glass are added to AlN, the flexural strength is the highest, at 463 MPa. These results are considered to be influenced by changes in the microstructure of the secondary phase of AlN.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.4 no.4
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• pp.370-377
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• 1994

DC plasma torch which is a non-transferred type was constructed and silicon nitride powders were produced. Ar gas is used as a plasma gas and gas reactants with the carrier gas are introduced beneath the plasma ignition part. Two slits are attached and a reactive quenching gas is introduced through them. Using $SiCl_4 and NH_3$ as starting materials, silicon nitride powders were produced. As-produced powders were amorphous and crystalline silicon nitrides were obtained by heating at $1420^{\circ}C$ for two hours under nitrogen atmosphere. Silicon nitride phase was identified in the XRD patterns and IR spectrum, and the image of the powders before and after heating was observed from the TEM analysis.

• Korean Journal of Materials Research
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• v.33 no.10
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• pp.430-438
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• 2023

In this study, we synthesized pH-controlled resorcinol-formaldehyde (RF) gels through the polymerization of two starting materials: resorcinol and formaldehyde. The prepared RF gels were dried using an acetone substitution method, and they were subsequently carbonized under nitrogen atmosphere to obtain carbon xerogels (CX_Y) prepared at different pH (Y). The carbon xerogels were utilized as active materials for coin-type organic supercapacitor electrodes to investigate the influence of pH on the electrochemical properties of the carbon xerogels. The carbon xerogels prepared at lower pH (CX_9.5 and CX_10) exhibited sufficient particle growth, with a three-dimensional network of particles during the RF gel formation, resulting in the development of abundant mesopores. Conversely, the carbon xerogels prepared at higher pH (CX_11 and CX_12) retained densely packed structures of small particles, leading to pore collapse and low specific surface areas. Consequently, CX_9.5 and CX_10 showed high specific surface areas, and provided ample adsorption sites for the formation of electric double layers with electrolyte ions. Moreover, the three-dimensional particle network in CX_9.5 and CX_10 significantly enhanced electrical conductivity. The presence of well-developed mesopores in these materials further facilitated the effective transport of electrolyte ions, contributing to their superior performance as organic supercapacitor electrodes. This study confirmed that pH-controlled carbon xerogels are one of the promising active materials for organic supercapacitor electrodes. Furthermore, we concluded that pH during RF gel formation is a crucial factor determining the electrode performance of the carbon xerogels, highlighting the need for precise pH control to obtain high-performance carbon xerogel electrodes.

• Food Science of Animal Resources
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• v.43 no.6
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• pp.1170-1182
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• 2023

The aim of this study was to determine the effect of chitosan (CH)-based nanocomposite coating applications [chitosan+TiO₂ (CHT) and chitosan+TiO₂+rosmarinic acid (CHTRA)] on changes in quality attributes of rainbow trout fillets during cold storage (4℃). Fish fillets were randomly divided into four groups and subjected to treatments (CH, CHT, CHTRA, and control). After treatments, the groups were packaged under a modified atmosphere (40% CO₂+30% O₂+30% N₂) and stored at 4℃ for 18 days. During cold storage, the samples were subjected to physico-chemical and microbiological analyses. During storage, CH, CHT, and CHTRA treatments showed lower aerobic mesophilic and psychrotrophic bacteria counts than the control. However, the differences between coating treatments were not significant. The highest mean pH value was determined in the control group. As the storage time increased, the thiobarbituric acid reactive substances value increased. At the end of the storage period, no significant differences were observed between the treatments, including in the control group. The total volatile basic nitrogen (TVB-N) level in the control group was above 25 mg/100 g on day 15 of storage. However, the TVB-N level in the treatment groups was below 20 mg/100 g on day 18. It was also determined that coating application×storage period interaction had a significant effect on all color parameters (p<0.01). At the end of storage, the highest CIE L* was observed in CHTRA treatment. However, the value of this treatment did not differ from that of the CH treatment.

• Journal of The Korean Society of Grassland and Forage Science
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• v.36 no.4
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• pp.318-324
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• 2016

In order to study the effect of barley, Italian ryegrass (IRG), and legume mixture on nitrogen fixation and transfer to grasses on spring paddy field, an experiment was carried out from Oct. 2006 to June 2007 in Naju, Korea. A split plot design with three replications was used for the experiment. One reference plot was assigned for each treatment to determine nitrogen fixation. Main plots consisted of Chinese milk vetch, crimson clover, forage pea, and hairy vetch with barley, respectively. Subplot treatment were barley or IRG with four seeding ratio of legumes (50:50, 60:40, 70:30, and 80:20). To estimate N fixation by legumes, $^{15}N$ isotope dilution technique was used. $^{15}N$ fertilizer [$(^{15}NH_4)_2SO_4$ solution at 99.8 atom N] was uniformly applied to $600cm^2$ in the middle of each plot on April 15, 2007. Plots were harvest by hand on June 8, 2007. Dried sample were ground to a fine power and analyzed for total N isotope N. $^{15}N$ was determined using elemental analyzer-isotope ratio mass spectrometry. The calculation of N transfer was determined with the isotope dilution method. The content of N was higher in legumes than that in barley or Italian ryegrass. Nitrogen level in forage pea was significantly higher than that of other legumes. There were significantly differences in N content between legumes in IRG mixture. Atom % $^{15}N$ excess was significantly different in legumes with barley. The 60:40 sub plot had higher (p<0.05) atom % $^{15}N$ than other seeding ratio treatments. The enrichment ranged from 0 to 0.58. Compared to barley, the enrichment of IRG with its accompanied legumes was higher, ranging from 0.38 to 1.0. The N derived from the atmosphere (Ndfa) ranged from 0% to 49.5% with barley-legume mixture. It ranged from 0 to 60.5% in IRG-legume plots. N transfer from legumes to neighboring grasses was 12.3 to 90.9 kg/ha for barley-legume mixture and 31.7 to 107.8 kg/ha for IRG plots. IRG plots showed higher N transfer for IRG-legume mixture in general based on difference method. Based on $^{15}N$ dilution method, the N transfer was 0 to 36.1 kg/ha for barley-legume mixture and 0 to 50.6 kg/ha for IRG plots. There was a tendency toward higher N transfer on the difference method than that of the $^{15}N$ dilution method.

• Korean Journal of Food Science and Technology
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• v.29 no.1
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• pp.57-64
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• 1997

The research was investigated to determine the effect of organic acids or packaging methods (PA) either alone or in combination on the quality of Aster scaber during storages. The Aster scaber was treated with organic acids and PA, and stored at different temperature $(1\;and\;5^{\circ}C)$. Total plate counts, weight loss, color change, and sensory evaluation were evaluated. Both organic acid treatments, PA, and combined treatment had little effect on the inhibition of total plate counts compared to the control (non-treatment). Organic acid treatments showed less weight reduction compared to the control and nitrogen treated package had the least weight reduction, but the combined treatments showed less weight reduction than organic acid treatments or packaging method alone. Organic acid treatments were little different from the control on color change, but nitrogen packages had the least color change, whereas combined treatments were a little reduced, but little different compared to the control or nitrogen packages. The nitrogen packages showed better effects on the sensory evaluation compared to other treatments and the results of sensory evaluation were consistent with that of weight reduction and color change, but not in total counts. All these results showed better effects in $5^{\circ}C$ rather than $1^{\circ}C$.