• Journal of Powder Materials
• /
• v.17 no.2
• /
• pp.142-147
• /
• 2010

The ultrafine titanium carbonitride ($TiC_xN_y$) particles below 100 nm in mean size, including various carbon and nitrogen contents (x=0.55~0.9, y=0.1~0.5), were successfully synthesized by new Mg-thermal reduction process. Nanostructured sub-stoichiometric titanium carbide ($TiC_x$) particles were initially produced by the magnesium reduction of gaseous $TiCl_4+x/2C_2Cl_4$ at $890^{\circ}C$ and post heat treatments in vacuum were performed for 2 hrs to remove residual magnesium and magnesium chloride mixed with $TiC_x$. Finally, well C/N-controled $TiC_xN_y$ phases were successfully produced by nitrification heat treatment under normal $N_2$ gas atmosphere at $1150^{\circ}C$ for 2 hrs. The values of purity, mean particle size and oxygen content of produced particles were about 99.3%, 100 nm and 0.2 wt.%, respectively.

• Current Photovoltaic Research
• /
• v.8 no.2
• /
• pp.45-49
• /
• 2020

Molybdenum (Mo) thin films are widely used as back contact in copper indium diselenide (CISe) solar cells. However, despite this, there are only few published studies on the properties of Mo and characteristics of CISe solar cells formed on such Mo substrates. In this studies, we investigated the properties of sputter deposited Mo bilayer, and fabricated non-vacuum CISe solar cells using bilayer Mo substrates. The changes in surface morphology and electrical resistivity were traced by varying the gas pressure during deposition of the bottom Mo layer. In porous surface structure, it was confirmed that the electrical resistivity of Mo bilayer was increased as the amount of oxygen bonded to the Mo atoms increased. The resulting solar cell characteristics vary as the bottom Mo layer deposition pressure, and the maximum solar cell efficiency was achieved when the bottom layer was deposited at 7 mTorr with a thickness of 100 nm and the top layer deposited at 3 mTorr with a thickness of 400 nm.

• Applied Chemistry for Engineering
• /
• v.24 no.1
• /
• pp.87-92
• /
• 2013

Nonthermal plasma hybridized with photocatalysts is proven to be an effective tool to degrade toxic organics in wastewater. In this study, a specially designed dielectric barrier discharge (DBD) plasma system combined with photocatalysts was applied to decompose pestiticides such as dichlorovos, carbofuran and methidathon, which are frequently used in the golf courses and the orange plantations. The degradations of the pesticides in single and coupled systems were evaluated. The single system was used with ozone plasma which consisted of electrons, radicals, ions produced by oxygen gas and air, with and without ultra-violet (UV) irradiation, respectively. The coupled systems utilized the air-derived ozone plasma combined with zinc oxide, titanium dioxide and graphite oxide photocatalyst activated by UV. The graphite oxide was synthesized by a modified Hummer's method and characterized using FTIR spectrometer. It was elucidated that the plasma reaction with graphite oxide (0.01 g/L) brought about almost 100% of degradation degrees for dichlorovos and carbofuran in 60 min, as compared with the performances showed by no catalyst condition. The photocatalyst-hybridized plasma in the presence of UV irradiation was proven to be an effective alternative for degrading pesticides.

• Applied Chemistry for Engineering
• /
• v.27 no.6
• /
• pp.664-668
• /
• 2016

The contamination in soil, underground water and river environment became serious due to illegal waste dumping. In this study, our research group analyzed the oil species of illegally disposed oils from J City. After pretreating the mixture of oil, water and solid phases to obtain homogeneous phase components, the physical property analysis, atom analysis, and gas chromatography were performed. From the results showing 11.8% of oxygen content, $-6^{\circ}C$ of pour point and chromatogram pattern. the contaminated oil was identified as a vegetable one. High performance liquid chromatography (HPLC) analysis was also performed in order to know what kind of vegetable oil was, and the ratio of LLO, OOL and POL was found to be high indicating that the disposed oil is majorly the used soybean oil with some vegetable oil mixtures. This study can be used for identifying contaminators for oils from the illegal waste dumping.

• Economic and Environmental Geology
• /
• v.35 no.2
• /
• pp.171-177
• /
• 2002

Two piston-core sediments, obtained from the southwestern margin of the Ulleung Basin in East Sea, are analyzed to investigate the stratigraphy and sedimentary environment of the Late Quaternary. The cores consist mainly of cuddy sediments with silty sands, lapilli tephra and ash layers. The chronostratigraphic correlation with known eruption ages reveals that the core sediments contain the stratigraphic document over the past 46.1 kyr and the sedimentation rates during the last glacial period were relatively higher (12.1-14.9 cm/kyr) than those in pelagic ocean. Several sedimentary facies, mainly affected by turbidity currents, are commonly present in the core interval accumulated during the oxygen-isotope stage 2. Many of horizontal voids, which are thought to have formed by gas expansion, are observed in fore 00GHP-07. The total organic carbon (TOC) contents of the core sediments are noticeably high (average 1 .8%). Particularly, these TOC valuers increased during Termination I, suggesting that dering this time interval the sedimentary environment of the study area was changed to more anoxic.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.17 no.1
• /
• pp.137-145
• /
• 2009

The steady-state kinetics of the selective catalytic reduction (SCR) of $NO_X$ with $NH_3$ has been investigated over a commercial ${V_2}{O_5}/TiO_2$ catalyst. In order to account for the influence of transport effects the kinetics are coupled with a fully transient two-phase 1D+1D monolith channel model. The Langmuir-Hinshelwood (L-H) mechanism is adopted to describe the steady-state kinetic behavior of the ${V_2}{O_5}/TiO_2$ catalyst. The reaction rate expressions are based on previously reported papers and are modified to fit the experimental data. The steady-state chemical reaction scheme used in the present mathematical model has been validated extensively with experimental data of selective $NO_X$ reduction efficiency for a wide range of inlet conditions such as space velocity, oxygen concentrations, water concentration, and $NO_2/NO$ ratio. The parametric investigations are performed to examine how the $NH_3$ slip from a SCR $DeNO_X$ catalyst and the conversion of $NO_X$ are affected by the reaction temperature, $NH_3/NO_X$ feed ratio, and space velocity for feed gas compositions with $NO_2/NO_X$ ratios of 0 and 0.5.

• Fire Science and Engineering
• /
• v.19 no.3 s.59
• /
• pp.58-63
• /
• 2005

Experimental measurements of flames and the product properties were performed for small kerosene pool fires. which is widely used as a fire source of laboratory scale experiments with scaling modeling. The flame length and flickering frequency were investigated for the flame structures, and compared with the theory. Three measurement methods were introduced to clarify the smoke characteristics, i.e. various gas concentrations, smoke density and thermophoretic sampling with transmission electron microscopy (TEM). The yield of carbon dioxide and the consumption of oxygen were proportional to the heat release rate of pool fires, but there is no trend on carbon monoxide emission. Smoke density of turbulent flames was exponentially increased with the heat release rate. The morphology of the soot particle was investigated to address the degree of soot maturing. The results show that the similar smoke morphology between an inverse jet flame and a pool fire exists despite of different combustion controlling mechanisms.

• Transactions of the Korean hydrogen and new energy society
• /
• v.22 no.1
• /
• pp.51-59
• /
• 2011

Sulfur-Iodine (SI) cycle, which thermochemically splits water to hydrogen and oxygen through three stages of Bunsen reaction, HI decomposition, and $H_2SO_4$ decomposition, seems a promising process to produce hydrogen massively. Among them, the decomposition of $H_2SO_4$ ($H_2SO_4=H_2O+SO_2+1/2O_2$) requires high temperature heat over $800^{\circ}C$ such as the heat from concentrated solar energy or a very high temperature gas-cooled nuclear reactor. Because of harsh reaction conditions of high temperature and pressure with extremely corrosive reactants and products, there have been scarce and limited number of data reported on the pressurized $H_2SO_4$ decomposition. This work focuses whether the $H_2SO_4$ decomposition can occur at high pressure in a noble-metal reactor, which possibly resists corrosive acidic chemicals and possesses catalytic activity for the reaction. Decomposition reactions were conducted in a Pt-lined tubular reactor without any other catalytic species at conditions of $800^{\circ}C$ to $900^{\circ}C$ and 0 bar (ambient pressure) to 10 bar with 95 wt% $H_2SO_4$. The Pt-lined reactor was found to endure the corrosive pressurized condition, and its inner surface successfully carried out a catalytic role in decomposing $H_2SO_4$ to $SO_2$ and $O_2$. This preliminary result has proposed the availability of noble metal-lined reactors for the high temperature, high pressure sulfuric acid decomposition.

• Korean Chemical Engineering Research
• /
• v.43 no.1
• /
• pp.47-52
• /
• 2005

The wide use of metal dusts have been found in industrial field and many dust explosion accidents occur by fire spread of dust layer. In this study, we developed a new experimental device to examine fire and explosion characteristics of the dust layer. Aspects of the burning zone over metals(Mg, Zr, Ta, Ti, etc) and PMMA(Polymethyl methacrylate) dust layers have been investigated experimentally to clarify behaviors (Spread rate and quenching distance) and effects of $N_2$ surrounding gas on the fire spread over metal dust layers. From the experimental result, it was found that the spread rate of metal dusts is larger than PMMA, the dependability of spread rate over the thickness of dust layer is small, and the minimum oxygen concentration of spread flame over Mg dust layer is 3.6-3.7 vol%. Since high correlation between the spread rate and the reciprocal of quenching distance was seen, relative risk prediction in those inflammable parameters can be predicted.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.26 no.4
• /
• pp.589-594
• /
• 1999

There are some problems in inhalation sedation of non-cooperative pediatric patients. Usually the pediatric patients reject the nasal hood and there's no cooperation for administration of nitrous oxide gas. In mouth breathing patient, other technics of sedation such as intravenous or oral sedation or general anesthesia were recommended. Common causes of mouth breathing are common cold, allergic rhinitis, sinus problem, anatomical disorder, and habitual mouth-breathing. However in some patient not indicated the general anesthesia and high failure rate in oral and intravenous sedation. Administration of $N_2O-O_2$ with suction catheter was applied in full mouth breathing patient. Clinically effective sedation were occurred during procedure about 45 to 55 minutes. There's no any side effects by $N_2O-O_2$ inhalation sedation. The patients awoke at the end of the procedure and received 100% oxygen for 2-3 minutes. There's still some problems in use of the suction catheter such as air pollution of operation theater and elevate arterial carbon dioxide tension.