• Korean Journal of Materials Research
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• v.2 no.5
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• pp.330-336
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• 1992

Four distinctive hot pressed and heat treated S${i_3}{N_4}$ceramics, S${i_3}{N_4}$-8%${Y_2}{O_3}$, S${i_3}{N_4}$-6% ${Y_2}{O_3}$-2% $A{l_2}{O_3}$, S${i_3}{N_4}$-4% ${Y_2}{O_3}$-3% $A{l_2}{O_3}$, 그리고 S${i_3}{N_4}$-1% MgO-1% Si$O_2$(in wt%), were prepared and characterized by X-ray diffraction, scanning electron microscopy, image analysis and mechanical tests. The fracture toughness of S${i_3}{N_4}$-8% ${Y_2}{O_3}$specimens containing large elongated grains showed the highest value of about 9.8MPa$m^{1/2}$. Two out of four S${i_3}{N_4}$, ceramics(S${i_3}{N_4}$-6% ${Y_2}{O_3}$-2% $A{l_2}{O_3}$and S${i_3}{N_4}$-4% ${Y_2}{O_3}$-3% $A{l_2}{O_3}$) heat treated at 200 $0^{\circ}C$retained the fracture strength of over 900MPa and fracture toughness of over 8.0MPa$m^{1/2}$. Large ${\beta}$-S${i_3}{N_4}$grains having a diameter larger than 1${\mu}$m appeared to contribute to increase in fracture toughness.

• Applied Chemistry for Engineering
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• v.29 no.5
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• pp.541-548
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• 2018

In this work, the $N_2O$ decomposition catalyst and reaction characteristics to control the $N_2O$ removal were described. Experiments were carried out by using Rh as an active metal catalyst on various supports and the $Rh/CeO_2$ catalyst with $CeO_2$ support showed the best activity for the $N_2O$ decomposition when it was prepared under the constant heat treatment condition ($500^{\circ}C$-4 hr). $H_2-TPR$ and XPS analyzes were performed to confirm the effect of the physical and chemical properties of the catalyst on $N_2O$ decomposition. As a result, it was found that the increase of the oxygen transfer capacity of the catalyst due to the increase of both the redox property and $Ce^{3+}$ amount affected the decomposition reaction of $N_2O$. In addition, the future work will include a treatment process capable of decomposition $N_2O$ and NO under the condition that $N_2O$ and NO are simultaneously generated and its characteristics of $N_2O$ decomposition reaction.

• Korean Journal of Soil Science and Fertilizer
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• v.44 no.6
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• pp.1207-1213
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• 2011

This study was conducted to assess $N_2O$ emissions in agricultural soils of Korea. According to 1996 and 2006 IPCC (Intergovernmental Panel on Climate Change) methodology, $N_2O$ emission was calculated the sum of direct emission ($N_2O_{DIRECT}$) and indirect emission ($N_2O_{INDIRECT}$). To calculate $N_2O$ emissions, emission factor was used default of IPCC and activity data was used the food, agricultural, forestry and fisheries statistical yearbook of MIFAFF (Ministry for Food, Agriculture, Forestry and Fisheries). It was emitted 8,608 $N_2O$ Mg resulted from direct emission by application of chemical fertilizer and animal manure, input in n-fixation crops and input of crop residues and emissions converted $N_2O$ into $CO_2$ equivalent was 2,668 $CO_2$-eq Gg. Indirect emission as $N_2O_{(G)}$ (atmospheric deposition of $NH_3$ and $NO_X$) and $N_2O_{(L)}$ (leaching and runoffs) were 4,567 and 6,013 $N_2O$ Mg and emissions converted $N_2O$ into $CO_2$ equivalent were 1,416 and 1,864 $CO_2$-eq Gg, respectively. Total $N_2O$ emission in Korea agricultural soil in 2009 was 5,948 $CO_2$-eq Gg.

• Korean Journal of Soil Science and Fertilizer
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• v.46 no.6
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• pp.463-468
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• 2013

The level of nitrous oxide ($N_2O$), a long-lived greenhouse gas, in atmosphere has increased mainly due to anthropogenic source, especially application of nitrogen fertilizers. Quantifying $N_2O$ emission from agricultural field is essential to develop national inventories of greenhouse gases (GHGs) emission. The objective of the study was to develop emission factor to estimate direct $N_2O$ emission from agricultural field in Gangwon-do, Korea by measuring $N_2O$ emissions from potato (Solanum tuberosum), red pepper (Capsicum annum L.), and Chinese cabbage (Brassica campestris L.) cultivation lands from 2009 to 2012. Accumulated $N_2O$ emission was $1.48{\pm}0.25kg$ $N_2O-N\;ha^{-1}$ for red pepper, $1.27{\pm}0.27kg$ $N_2O-N\;ha^{-1}$ for potato, $1.49{\pm}0.06kg$ $N_2O-N\;ha^{-1}$ for Chinese cabbage cultivated in spring, and $1.14{\pm}0.22kg$ $N_2O-N\;ha^{-1}$ for fall Chinese cabbage. Emission factor of $N_2O$ calculated from accumulated $N_2O$ emission, nitrogen fertilization rate, and background $N_2O$ emission was $0.0051{\pm}0.0016kg$ $N_2O-N\;ha^{-1}$ N for cropland in Gangwon province. More extensive study is deserved to be conducted to develop $N_2O$ emission factor for upland crops in Korea through examining the emission factors from various regions and crops because $N_2O$ emission is influenced by many factors including climate characteristics, soil properties, and agricultural practices.

• Journal of the Korean Ceramic Society
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• v.26 no.1
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• pp.31-36
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• 1989

In order to synthesize AlN-polytypes from AlN-SiO2-Al2O3 system, composition A (AlN/SiO2/Al2O3=1/0.3/0.05, mole ratio) and composition B(AlN-SiO2-Al2O3=1/0.2/0.05, mole ratio) were used. AlN-polytypes were produced by nitriding the mixture at 175$0^{\circ}C$~190$0^{\circ}C$ under N2 atmosphere. For lower reaction temperature, 15R phase was produced and in the case of higher reaction temperature, AlN phase was only produced. As each composition was heated at 185$0^{\circ}C$ in N2 atmosphere, produced main phases were 15R phase for composition A and 21R phase for composition B respectively. The fracture surfaces of produced reactants showed porous skeleton structure.

• Journal of the Korean Chemical Society
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• v.54 no.1
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• pp.120-124
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• 2010

$TiO_2$ and N-substituted $TiO_{2-x}N_x$ were synthesized by using precipitation method. $TiO_{2-x}N_x$ compound absorbed whole UV light as well as long wavelength of visible light (400 - 700 nm) because of the change of band gap from 3.2 eV to 1.77 eV. Results obtained revealed that $TiO_{2-x}N_x$ showed higher activity than pure $TiO_2$ or P-25 for visible-photocatalytic degradation of 1,4-dichlorobenzene.

• Clean Technology
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• v.17 no.2
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• pp.134-141
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• 2011

The effects of the compounds and concentrations of nitrogenous electron acceptor, the ratio of electron donor/electron acceptor (C/N), and the complexity of electron donor on the emission of $N_2O$ during wastewater denitrification were quantitatively investigated in this study. The higher ${NO_3}^-$ and ${NO_2}^-$ concentrations, the more $N_2O$ emission was observed. ${NO_2}^-$ has strong effect on $N_2O$ emission as it emitted morc $N_2O$ than ${NO_3}^-$, 50 mg/L of ${NO_2}^-$-N gave the highest conversion (9.3%) and yield (9.8%) of $N_2O$ while ${NO_3}^-$-N (50 mg/L) gave 5.6% conversion and 11.0% yield. Lower C/N ratio decreases nitrogen removal efficiency, but it increases the conversion of $N_2O$ because of the incomplete denitrification by the limited organic carbon. When real domestic wastewater is used as the electron donor of the denitrification, $N_2O$ emission is reduced to 1/10 of the emission when single carbon (acetate) is used. It is thought that multiple carbon source utilizes many denitrification pathways and it seems to be helpful for the reduction of $N_2O$ emission.

• Journal of Korean Society for Atmospheric Environment
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• v.20 no.6
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• pp.749-758
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• 2004

Nitrous oxide ($N_2$O) has been known as an important trace gas due to the greenhouse gas and the major source of stratospheric oxide of nitrogen (NO). Soil is the major source of $N_2$O in nature. The physicochemical characteristics of soils affect the emission of $N_2$O from soil. These physicochemical parameters are soil moisture, soil temperature, and soil N content. Since these parameters are correlated to the flux of $N_2$O from soil individually and compositely, there still remain many unknowns in the mechanism to produce $N_2$O in soil and the roles of such physicochemical parameters which affect the soil $N_2$O emission. Soil $N_2$O fluxes were measured at different levels in water filled pore space (WFPS), soil temperature and soil N contents from the same amounts of soils which were sampled from agriculturally managed upland field in a depth of ～30 cm at Kunsan. The soil $N_2$O flux measurements were conducted in a laboratory with a closed flux chamber system. The optimum soil moisture and soil temperature were observed at 60% of WFPS and ～13$^{\circ}C$. The soil $N_2$O flux increased as soil N contents increases during the whole experimental hours (up to 48 hours). However, average $N_2$O flux decreased after ～30 hours when organic carbon was mixed with nitrogen in the sample soils. It is suggested that organic carbon could be important for the emission of $N_2$O, and that the ratio of N to C needs to be identified in the process of $N_2$O soil emission.

• Journal of the Korean Chemical Society
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• v.22 no.5
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• pp.295-303
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• 1978

The dipole moments for octahedral [Co(III)-$O_3N_3$], tetrahedral [M(II)-$O_2N_2$] and square planar [M(II)-$O_2N_2$] types complexes are calculated by the expansion method for spherical harmonics using the valence basis sets for the central metal ion and the single basis set orbital ($2p_z$) for ligands. The calculated dipole moments for these complexes are in agreement with the experimental values.

• Electrical & Electronic Materials
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• v.7 no.1
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• pp.25-31
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• 1994

Properties of oxynitride films reoxidized by $N_2{O}$ gas after thermal oxidation and $N_2{O}$ oxide films directly oxidized by using $N_2{O}$ gas on the bare silicon wafer have been studied. From the AES analysis, nitrogen pile-up at the interface of Si/oxynitride and Si/$N_2{O}$ oxide has observed. $N_2{O}$ oxide and oxynitride films have the self-limited characteristics. Therefore, it will be possible to obtain ultra-thin films. Nitrogen pile-up at the interfaces of Si/oxynitride and Si/$N_2{O}$ oxide strengthens film structure and improves dielectric reliability. Although fixed charge densities and interface trap densities of N20 oxide and oxynitride films have somewhat higher than those of thermal $SiO_2{O}$, $N_2{O}$ oxide and oxynitride films showed improved I-V characteristics and constant current stress.