• Journal of Korean Society of Environmental Engineers
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• v.33 no.1
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• pp.39-46
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• 2011

NO oxidation is an important prerequisite step to assist the selective catalytic reduction (SCR) at low temperatures ($<200^{\circ}C$). Therefore, we conducted the lab- and bench-scales experiments appling the sodium chlorite powder ($NaClO_2(s)$) for the oxidation of NO to $NO_2$ and the carbon-based catalyst for the reduction of $NO_x$ and $SO_2$; the lab- and bench-scales experiments were conducted in laboratory and iron-ore sintering plant, respectively. In the lab-scale experiment, known concentrations of $NO_x$ (200 ppm), $SO_2$ (75 ppm), $H_2O$ (10%) and $NH_3$ (400 ppm) in 2.6 L/min were introduced into a packed-bed reactor containing $NaClO_2(s)$, then gases produced by the reaction with $NaClO_2(s)$ were fed into the carbon-based catalyst (space velocity = $2,000hr^{-1}$) at $130^{\circ}C$. In the bench-scale experiment, flue gases of $50Nm^3/hr$ containing 120 ppm NO and 150 ppm $SO_2$ were taken out from the duct of iron-ore sintering plant, then introduced into the flow reactor; $NaClO_2(s)$ were injected into the flow reactor using a screw feeder. Gases produced by the reaction with $NaClO_2(s)$ were introduced into the carbon-based catalyst (space velocity = $1,000hr^{-1}$). Results have shown that, in both lab- and bench-scales experiments, NO was oxidized to $NO_2$ by $NaClO_2(s)$. In addition, above 90% of $NO_x$ and $SO_2$ removal were obtained at the carbon-based catalyst. These results lead us to suggest that the combination of $NaClO_2(s)$ with the carbon-based catalyst has the potential to achieve the simultaneous removal of $NO_x$ and $SO_2$ at low temperature ($<200^{\circ}C$).

• Journal of the Korean Society of Radiology
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• v.3 no.3
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• pp.37-40
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• 2009

In this study, we made a high efficiency x-ray detecting sensor using the lead oxide(PbO) that are used in direct method of x-ray detector. PbO with nano size particles is produced by sol-gel method for high efficiency. The produced PbO with nano size is deposited on ITO(Induim Tin Oxide) glass in several temperature using the PIB(particle-in-binder) method. The thickness of the deposited PbO is about $200{\mu}m$. Through the measurement of dark current, sensitivity and SNR(Signal To Noise Ratio), an electrical properties of the produced PbO film are analyzed. Therefore, we show that an electrical properties are changed according to a temperature and that the PbO film that was treated at $500^{\circ}C$ in O2 atmosphere is the most high efficiency x-ray detecting sensor.

• Membrane Journal
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• v.22 no.2
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• pp.113-119
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• 2012

$YBaCo_2O_{5+{\delta}}$ oxide was synthesized by solid state reaction and a typical dense membrane has been prepared using as-prepared powder by unilateral pressing and sintering at $1,180^{\circ}C$. The $YBaCo_2O_{5+{\delta}}$ membraneswas analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM). XRD analysis showed the double layered perovskite structure was observed over $1,150^{\circ}C$ without impurities. Oxygen permeation was measured in the temperature range from 750 to $950^{\circ}C$ according to oxygen partial pressure difference between feed and permeation side. The oxygen permeation flux increased with increasing temperature and oxygen partial pressure and the maximum oxygen flux of $YBaCo_2O_{5+{\delta}}$ membrane with 1.0 mm thickness was about 0.15 mL/$cm^2{\cdot}min$ at $950^{\circ}C$ and $PO_2$ = 0.42 atm. The activation energy for oxygen permeation decreased with decreasing oxygen partial pressure to be 76.0 kJ/mol at the condition of $PO_2$ = 0.21 atm.

• Korean Journal of Crystallography
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• v.17 no.1
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• pp.24-32
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• 2006

The microwave dielectric properties of $Zn_3Nb_2O_8\;with\;V_2O_5$ addition were investigated. The addition of $V_2O_5$ enhanced the sinterability of $Zn_3Nb_2O_8$, which resulted in high density of $Zn_3Nb_2O_8$ ceramic greater than 95% of the theoretical value when sintered at $900^{\circ}C$ for 4 hours. X-ray diffraction analysis of sintered $Zn_3Nb_2O_8$ ceramic showed no second phase with $V_2O_5$ addition. Dielectric permittivity(${\varepsilon}_r$) and quality factor($Q{\times}f$) varied with both density at different sintering temperature and $V_2O_5$ addition. Dielectric permittivity, quality factor and temperature coefficient($T_{cf}$) of the two mole of $V_2O_5\;added\;Zn_3Nb_2O_8$ that was sintered at $900^{\circ}C$ were 21.4, 40,000, $-54ppm/^{\circ}C$, respectively.

• Journal of the Microelectronics and Packaging Society
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• v.6 no.1
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• pp.51-58
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• 1999

The effects of glass composition on the wettability and reactivity with $ZrO_2$substrate was evaluated and fabrication variables and glass compositions was investigated. Various glass compositions was investigated. Alkaline earth silicate glass show good wettability and lower viscosity and crystallization of glass could be prevented by $B_2O_3$.The sealant glass begin to wet on $ZrO_2$substrate below $900^{\circ}C$ and porosity occurred in various glass compositions, the crystallization and porosity in the glass could be prevented by the addition of flux into glass composition. But flowability and reactivity of glass with $ZrO_2$substrate was enhanced. Processing variables should be optimized to reduce the porosity by enhancing the sintering of glass powder. Many silicate glasses were investigated for the applications of high temperature sealants. Wetting and bonding of glass was good enough to seal together between $ZrO_2$and other ceramic components of SOFC. But porosity and reaction layer were occurred in the sealant glass. It will be possible to produce glass sealant without porosity and reaction layer at the interface by optimization of processing variable and modify the glass compositions. In present study, wettability of glass-filler composite was investigated. The porosity, shape of filler and interfacial reactions of sealant glass with fillers were examined.

• Journal of the Korean Ceramic Society
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• v.39 no.10
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• pp.912-918
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• 2002

Ni-Mn-Co-Fe oxide thick films were coated on an alumina substrate by screening printing technique. The microstructure and electrical properties of the thick films, as a function of composition and sintering temperature, were investigated. The components of the NTC thick films sintered at 1150${\circ}C$ were distributed homogeneously. On the other hand, in the case of the NTC thick films sintered at 1200 and 1250${\circ}C$, Co element was distributed homogeneously, but Ni, Mn and Fe elements were distributed heterogeneously, resulting in the formation of Ni rich and Mn-Fe rich regions. All the thick film NTC thermistors prepared showed a linear relationship between log resistance (log R) and the reciprocal of absolute temperature (1/T), indicative of NTC characteristics. At a given NiO and $Mn_3O_4$ content, the resistance, B constant and activation energy of $(Ni_{1.0}Mn_{1.0}Co_{1-x}Fe_x)O_4$ (0.25${\le}$x${\le}$0.75) and $(Ni_{0.75}Mn_{1.25}Co_{1-x}Fe_x)O_4$ (0.25${\le}$x${\le}$0.75) thermistors increased with increasing $Fe_2O_3$ content.

• The Journal of Korean Academy of Prosthodontics
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• v.22 no.1
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• pp.51-68
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• 1984

The purpose of this study is primarily to test the use value of tooth ash as an alternative material of the synthetic hydroxyapatite. For this purpose the author performed the experimental study to investigate the phsyical properties of sintered tooth ash and its histocompatibility in vitro. The tooth ash was made by incinerating procedure at $650^{\circ}C,\;750^{\circ}C,\;850^{\circ}C,\;950^{\circ}C\;and\;1050^{\circ}C$ respectively. The composition of tooth ash was analyzed and X-ray diffraction was done. The experimental specimens were molded to the cylinderical form 1 cm high, 1 cm in diameter under the pressure of $1000kg/cm^2$, which were divided into two groups; the one is sintered tooth ash at $1100^{\circ}C$ and the other is fired mixture of tooth ash and dental porcelain mixed to the weight ratio of 4:6, 5:5, 6:4 and 7:3. The physical propoerties of the sintered specimens were examined and their microstructure was observed under the Scanning Electron Microscope. The results obtained were as followings: 1. The difference of the tooth ash composition depending on incinerating temperature was of no significance, but the $CO_2$ disappeared from $950^{\circ}C$. 2. X-ray diffraction showed the tooth ash was mainly composed of hydroxyapatite and a small amount of - white lockite. But phase transformation was not disclosed. 3. The microstructure of the sintered specimens of the ashed tooth powder was of no difference in the structure and grain size accompanying the ashed temperature, but sintering ability seemed to be the best in the specimen incinerated at $950^{\circ}C$. 4. There was good wettability in the mixed sintered specimens of the ashed tooth powder and the porcelain powder. 5. The compressive strength of the sintered specimens of the tooth ash incinerated at $950^{\circ}C$ was the highest with $589.75kg/cm^2$ and the porosity and the absorption were the lowest as well. 6. The mixed sintered specimens of the tooth ash and porcelain powder was good in the physical properties in the case of mixed weight ratio of 6:4. 7. The animal fibroblast cultures with porcelain showed increase in the cell number, whereas the tooth ash showed a small degree of growth inhibition. But the difference of cell multiplication efficiency between control cultures and test cultures with tooth ash was not observed.

• Journal of the Korean Magnetics Society
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• v.18 no.2
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• pp.58-62
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• 2008

$Ni_{0.4}Zn_{0.4}Cu_{0.2}Fe_2O_4$ ferrite was fabricated by solid stat reaction method and sol-gel method. Because of the drawbacks of each method, we combined these two methods together. We proposed and experimentally verified that nanocrystalline ferrite additive was effective on improving the densification behavior and magnetic properties of NiZnCu ferrites for multilayer chip inductors. The initial permeability of the toroidal core Sample with 20 wt% nanocrystalline ferrite increased from 78.1 to 178.2 as annealing temperature is increased from $880^{\circ}C$ to $920^{\circ}C$. The density, shrinkage and saturation magnetization were increased with increasing annealing temperature, which was attributed to the decrease of additive grain size and increase of sintering density.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.5
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• pp.392-397
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• 2012

In the $(La_{0.8}Ca_{0.2})(Cr_{0.9}Co_{0.1})O_3$ (LCCC), which has been using as interconnector materials in SOFC, Al ions were substituted for Co because ionic radius of Al is similar to that of Co. Because of the almost identical ionic radius of Al and Co, the substitution was not thought to be affect the tolerance factor of LCCC, and the densification behavior, high temperature electrical conductivity and thermal expansion coefficient were examined as a function of Al concentration. In the cases of the x= 0 and x= 0.02 in $(La_{0.8}Ca_{0.2})(Cr_{0.9}Co_{0.1-x}Al_x)O_3$ (x= 0~0.1), the samples showed the relative densities above ${\geq}95%$ when those were sintered at ${\geq}1,350^{\circ}C$. In the case of the $x{\geq}0.06$ the sintered density deteriorated greatly at lower sintering temperatures. High temperature electrical conductivity of the samples decreased as the content of Al increased. Since the valence state of Al ion is unchangeable, while Cr or Co ions contribute to the electrical conduction by changing those valence states, Al substitution resulted in the decreased electrical conductivity. Al doping of LCCC was an effective way of decreasing the thermal expansion coefficient (TEC).

• Korean Journal of Materials Research
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• v.22 no.1
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• pp.35-41
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• 2012

Presently, the most promising family of lead-free piezoelectric ceramics is based on $K_{0.5}Na_{0.5}NbO_3$(KNN). Lithium, silver and antimony co-doped KNN ceramics show high piezoelectric properties at room temperature, but often suffer from abnormal grain growth. In the present work, the $(Ba_{0.85}Ca_{0.15})(Ti_{0.88}Zr_{0.12})O_3$ component, which has relaxor ferroelectric characteristics, was doped to suppress the abnormal grain growth. To investigate this effect, Lead-Free $0.95(K_{0.5}Na_{0.5})_{0.95}Li_{0.05}NbO_3-(0.05-x)AgSbO_3-x(Ba_{0.85}Ca_{0.15})(Ti_{0.88}Zr_{0.12})O_3$[KNLN-AS-xBCTZ] piezoelectric ceramics were synthesized by ball mill and nanosized-milling processes in lead-Free $0.95(K_{0.5}Na_{0.5})_{0.95}Li_{0.05}NbO_3-(0.05-x)AgSbO_3$ in order to suppress the abnormal grain growth. The nanosized milling process of calcined powders enhanced the sintering density. The phase structure, microstructure, and ferroelectric and piezoelectric properties of the KNLN-AS ceramics were systematically investigated. XRD patterns for the doped and undoped samples showed perovskite phase while tetragonality was increased with increasing BCZT content, which increase was closely related to the decrease of TO-T. Dense and uniform microstructures were observed for all of the doped BCZT ceramics. After the addition of BCTZ, the tetragonal-cubic and orthorhombic-tetragonal phase transitions shifted to lower temperatures compared to those for the pure KNNL-AS. A coexistence of the orthorhombic and tetragonal phases was hence formed in the ceramics with x = 0.02 mol at room temperature, leading to a significant enhancement of the piezoelectric properties. For the composition with x = 0.02 mol, the piezoelectric properties showed optimum values of: $d_{33}$ = 185 pC/N, $k_P$ = 41%, $T_C=325^{\circ}C$, $T_{O-T}=-4^{\circ}C$.