• Proceedings of the Korean Ceranic Society Conference
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• 2002.10a
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• pp.174.2-174
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• 2002

• Applied Chemistry for Engineering
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• v.3 no.1
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• pp.88-99
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• 1992

For the development of semiconducting photoelectrode to be more stable and efficient in the process of photoelectrolysis of the water, pure titanium rods were oxidized by anodic oxidation, furance oxidation and flame oxidation and used as electrodes. The Indium islands were formed by electrodeposition of "In" thin film on $TiO_2$ and Ti by electrodeposition. Also $A1_2O_3$ and NiO islands were coated on Ti by the electron-beam evaporation technique. The maximum photoelectrochemical conversion efficiency(${\eta}$) was 0.98% for flame oxidized electrode($1200^{\circ}C$ for 2min in air). Anodically oxidized electrodes have photoelectrochemical conversion efficiency of 0.14%. Furnace oxidized electrode($800^{\circ}C$ for 10min in air) has 0.57% of photoelectrochemical efficiency and shows a band-gap energy of about 2.9eV. The $In_2O_3$ coated $TiO_2$ exhibits 0.8% of photoelectrochemical efficiency but much higher value of ${\eta}$ was obtained with the Increase of applied blas voltage. However, $Al_2O_3$ or NiO coated $TiO_2$ shows much low value of ${\eta}$. The efficiency was dependent on the presence of the metallic interstitial compound $TiO_{0+x}$(x<0.33) at the metal-semiconductor interface and the thickness of the suboxide layer and the external rutile scale.

• Korean Journal of Materials Research
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• v.29 no.5
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• pp.328-335
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• 2019

Nb-doped $TiO_2$(NTO) coated NiCrAl alloy foam for hydrogen production is prepared using ultrasonic spray pyrolysis deposition(USPD) method. To optimize the size and distribution of NTO particles based on good physical and chemical stability, we synthesize particles by adjusting the weight ratio of the Nb precursor solution(5 wt%, 10 wt% and 15 wt%). The morphological, chemical bonding, and structural properties of the NTO coated NiCrAl alloy foam are investigated by X-ray diffraction(XRD), X-ray photo-electron spectroscopy(XPS), and Field-Emission Scanning Electron Microscopy(FESEM). As a result, the samples of controlled Nb weight ratio exhibit a common diffraction pattern at ${\sim}25.3^{\circ}$, corresponding to the(101) plane, and have chemical bonding(O-Nb=O) at 534 eV. The NTO particles with the optimum weight ratio of N (10 wt%) show a uniform distribution with a size of ~18.2-21.0 nm. In addition, they exhibit the highest corrosion resistance even in the electrochemical stability estimation. As a result, the introduction of NTO coated NiCrAl alloy foam by USPD improves the chemical stability of the NiCrAl alloy foam by protecting the direct electrochemical reaction between the foam and the electrolyte. Thus, the optimized NTO coating can be proposed for excellent protection of NiCrAl alloy foam for hydrocarbon-based steam methane reforming(SMR).

• Korean Journal of Materials Research
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• v.14 no.11
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• pp.813-820
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• 2004

The electrolytic reduction of spent oxide fuel involves the liberation of oxygen in a molten LiCl electrolyte, which is a chemically aggressive environment that is very corrosive for typical structural materials. So, it is essential to choose the optimum material for the process equipment handling molten salt. In this study, corrosion behavior of Haynes 263, 75, and Inconel X-750, 718 in molten salt of $LiCl-Li_{2}O$ under oxidation atmosphere was investigated at $650^{\circ}C\;for\;72\sim360$ hours. At $3\;wt\%\;of\;Li_{2}O$, Haynes 263 alloy showed the highest corrosion resistance among the examined alloys, and up to $8\;wt\%\;of\;Li_{2}O$, Haynes 75 exhibited the highest corrosion resistance. Corrosion products were formed $Li(Ni,Co)O_2,\;LiNiO_2\;and\;LiTiO_2\;and\;Cr_{2}O_3$ on Haynes 263, $Cr_{2}O_3,\;NiFe_{2}O_4,\;LiNiO_2,\;Li_{2}NiFe_{2}O_4,\;Li_{2}Ni_{8}O_10$ and Ni on Haynes 75, $Cr_{2}O_3,\;(Al,Nb,Ti)O_2,\;NiFe_{2}O_4,\;and\;Li_{2}NiFe_{2}O_4$ on Inconel X-750 and $Cr_{2}O_3,\;NiFe_{2}O_4\;and\;CrNbO_4$ on Inconel 718, respectively. Haynes 263 showed local corrosion behavior and Haynes 75, Inconel X-750, 718 showed uniform corrosion behavior.

• The Journal of the Acoustical Society of Korea
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• v.6 no.4
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• pp.55-63
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• 1987

Modified $PbTiO_3$ piezoelectric ceramics added with 0.2, 0.25, 0.3 mol of $CaCO_3$ and 0.04 mol of $(Co_{\frac{1}{2}}W_{\frac{1}{2}})$ and 0.05 mol of $MnO_2$ and NiO have been fabricated. These ceramics can be poled sufficiently within 10 minutes at $100^{\circ}C$ under about d.c. field of 40 kv/cm. Detailed measurement was performed on dielectric constants, cutie temperatures, elastic and piezoelectric properties and coupling factors for the fabricated ceramics. The most value of the piezoelectric coupling factors was coupling factor of thickness mode kt and its value for 0.25 mol of Ca was about $45\%$. Dielectric constants of $\varepsilon_{33}^T$ and $\varepsilon_{11}^T$ for 0.25 mol of Ca were 242 and 260, and coupling factor ratio (kt/Kp) and Qm were 6 and 357 respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.894-897
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• 2004

Sodum bismuth titanate $(Na_{0.5}Bi_{0.5}TiO_3$ or NBT) thin films coated on the $LaNiO_3$ (LNO) electrode by sol-gel methode and rapid thermal annealing (RTA) technique. The NBT (NBT/LNO/Si) thin films examined by x-ray diffraction (XRD). The orientation of NBT was observed for films coated at $900^{\circ}C$, 5 min and $600^{\circ}C$, 60 min. Filed emission scanning electron microscopy (FE-SEM) showed uniform surface composed of grains. The grain size of NBT thin films increased with increasing annealing temperature.

• Korean Chemical Engineering Research
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• v.51 no.4
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• pp.518-522
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• 2013

Cyclohexanone is important intermediate for the manufacture of caprolactam which is monomer of nylron. Cyclohexanone is generally produced by dehydrogenation reaction of cyclohexanol. In this study, highly mesoporous metal oxides such as meso-$WO_3$, meso-$TiO_2$, meso-$Fe_2O_3$, meso-CuO, meso-$SnO_2$ and meso-NiO were synthesized using mesoporous silica KIT-6 as a hard template via nano-replication method for dehydrogenation of cyclohexanol. The overall conversion of cyclohexanol followed a general order: meso-$WO_3$ >> meso-$Fe_2O_3$ > meso-$SnO_2$ > meso-$TiO_2$ > meso-NiO > meso-CuO. In particular, meso-$WO_3$ significantly showed higher activity than the other mesoporous metal oxides. Therefore, the meso-$WO_3$ has wide range of application possibilities for dehydrogenation of cyclohexanol.

• Journal of the Korean Society for Heat Treatment
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• v.22 no.1
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• pp.3-7
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• 2009

Variation in oxidation behavior with heat treatment temperature is investigated for a Ni-Ti alloy using X-ray diffraction, DSC (differential scanning calorimetry) and Auger electron spectroscopy. And the effect of oxidation on transformation behavior and superelasticity is characterized. A cold-worked 50.6Ni-Ti alloy is oxidized at 300-$700^{\circ}C$ for 1 hr in the air atmosphere. With an increase in heating temperature, the structure of $TiO_2$ changes from amorphous (300 and $400^{\circ}C$) to anatase ($500^{\circ}C$), and to rutile ($700^{\circ}C$). Activation energy of oxidation for NiTi is measured to be 51 Kcal/mol when heating temperature is $500^{\circ}C$ or above. Since Ti reacts preferably with oxygen, Ni content increases between matrix and oxide, forming $Ni_{3}Ti$ compounds. The resultant of oxidation decreases significantly $M_s$ and $A_s$ temperature in the specimen oxidized at $900^{\circ}C$ with $B_2{\rightarrow}M$ transformation path. An extra is found on cooling between two peaks in the specimen with $B_2{\rightarrow}R{\rightarrow}M$ one which is oxidized at $900^{\circ}C$ and aged at $500^{\circ}C$. Oxidation deteriorates superelasticity due to formation of Ni-rich compound.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.10
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• pp.935-941
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• 2006

In this paper, the dielectric and piezoelectric properties of $0.4Pb(Ni_{1/3}Nb_{2/3})O_3+0.6Pb(Zr_{405}Ti_{595})O_3+X\;wt%\;Fe_2O_3$ ceramics were investigated with the addition of $Fe_2O_3$ and sintering temperature. Dielectric constant and piezoelectric constant increased with amount of $Fe_2O_3$ to 0.25 wt% and then decreased the further addition of $Fe_2O_3$. It seems that $Fe_2O_3$ acts as a sintering aid at the sintering temperature of $1150^{\circ}C$. By the addition of $Fe_2O_3$., sintering temperature of the system was lowered from $1250^{\circ}C\;to\;1100^{\circ}C$. The piezoelectric properties showed the maximum value of ${\varepsilon}r=4669,\;d_{33}=810(10^{-12}m/V)$, kp = 77 %, Qm = 55, in $0.4Pb(Ni_{1/3}Nb_{2/3})O_3\;-0.6Pb(Zr_{0.405}Ti_{0.595})O_3+0.25wt%\;Fe_2O_3$ ceramics having composition near the morphotropic phase boundary. The composition may be appropriate for actuator materials because of high piezoelectric constant and electromechanical coupling factor.

• Korean Journal of Materials Research
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• v.11 no.1
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• pp.44-47
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• 2001

Effects of $Er_2O_3$ addition on the dielectric properties of non-reducible $BaTi_3$-based X7R dielectrics with Ni electrode have been studied in reducing atmosphere. X7R with moderate temperature-dependence was developed after addition of $Er_2O_3$ with $MnO_2-MgO$; room-temperature dielectric constant and dissipation factor were >2900 and < 1.0%, respectively. The addition of $Er_2O_3$ greater than 3.0 mol% improved the temperature dependence of dielectric properties, but a significant decrease of the dielectric constant at room-temperature was observed. The TCC curves rebated clockwise with increasing MnO$_2$ content at a given additive system, 1.5 mol% $Er_2O_3$ and 2.0 mol% MgO.