• Bulletin of the Korean Chemical Society
• /
• v.23 no.2
• /
• pp.184-188
• /
• 2002

Unsaturated $Cr(CO)_x(1{\leq}x{\leq}5)$molecules were generated in the gas phase from photolysis of $Cr(CO)_6$vapor in He using an unfocussed weak UV laser pulse and their reactions with $O_2$ and $N_2O$ have been studied. The formation and disappearance of the ground state CrO molecules were identified by monitoring laser-induced fluorescence(LIF) intensities vs delay time between the photolysis and probe pulses. The photolysis laser power dependence as well as the delay time dependence of LIF intensities from the CrO orange system showed different behavior as those from ground state Cr atoms, suggesting that the ground state CrO molecules were generated from the reaction between $O_2/N_2O$ and photo-fragments of $Cr(CO)_6$ by one photon absorption. The depletion rate constants for the ground state CrO by $O_2$ and $N_2O$ are $5.4{\pm}0.2{\times}10^{-11}$ and $6.5{\pm}0.4{\times}10^{-12}cm^3molecule^{-1}s^{-1}$, respectively.

• Journal of Korean Ophthalmic Optics Society
• /
• v.7 no.2
• /
• pp.19-25
• /
• 2002

Ternary $xSrO-yB_2O_3-0.1Al_2O_3$ and $xSrO-yB_2O_3-0.1SiO_2$ glasses were prepared as a function of R(${\equiv}x/y$). The fraction of four-coordinated brans ($N_4$), symmetric three-coordinated barons ($N_{3S}$), and asymmetric three-coordinated barons ($N_{3A}$) were determined quantitatively to study the structures of these glasses by $^{11}B$ NMR. The values of $Q_{cc}$ and ${\eta}$ for $BO_3$ unit in the glasses were 2.74MHz and 0.22, those for $BO_3{^-}$ unit were 2.54MHz and 0.55, and those for $BO_4$ unit 0.60~0.75MHz and 0.00, respectively. The structure of SrBAl glass at $R_{1st}$ consisted of tetraborate ($[B_8O_{13}]^{-2}$) units and 1st-modified diborate ($[B_2Al_2O_7]^{-2}$) units, and those for the glass at $R_{max}$consisted of diborate ($[B_4O_7]^{-2}$) units, metaborate ($[BO_2^{-1}]$), 1st-modified diborate units, and 2nd-modified diborate ($[B_2Al_2O_8]^{-4}$) units. Due to the oxygens introduced from the strontium oxide. $AlO_4$ units were preferably formed rather than $BO_4$ units. And, the structure of SrBSi glasses in the region $R{\leq}0.5$ could be viewed as binary $SrO-B_2O_3$ glasses structure diluted by silicate oxide: therefore, the Si atoms of the glasses did not contributed to the change the configuration around the boron atoms. The silicate oxide was formed the $SiO_4{^-}$ units rather than the $BO_3{^-}$ units by the oxygens introduced from the storntium oxide in the region of $R{\geq}R_{max}$, and structure of those glass at $R_{max}$ consisted of diborate units, metaborate units loose $BO_4([BO_2]^{-1})$, and $SiO_4{^-}([SiO_{2.5}]^{-1})$ units.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.07b
• /
• pp.1096-1099
• /
• 2004

The principal problems in development of dielectric paste materials for PDP(plasma display panel)are PbO free paste and low melting temperature. We prepared PbO free paste from glasses in the system BaO-ZnO-$B_2O_3$-$V_2O_5$. DTA, and XRD were used to characterize BaO-ZnO-$B_2O_3$-$V_2O_5$ glasses. In this present study, PbO free paste had thermal expansion of $74\times10^{-7}/^{\circ}C$, DTA softening point of $460^{\circ}C$, and firing condition of $520^{\circ}C$, 20min

• Bulletin of the Korean Chemical Society
• /
• v.35 no.11
• /
• pp.3239-3243
• /
• 2014

We have developed a simple method for tuning the morphologies of $Cu_2O$ microcrystals. $Cu_2O$ microcrystals were prepared by precipitation at room temperature from a mixture of $Cu(CH_3COO)_2{\cdot}H_2O$, N,N,N',N'-tetramethyl ethylenediamine (TMEDA), ascorbic acid, and polyethylene glycol (PEG). TMEDA was used to promote the formation of copper-TMEDA complexes. A variety of $Cu_2O$ microcrystal morphologies were obtained simply by varying the concentrations of TMEDA and ascorbic acid. Aggregated $Cu_2O$ microspheres are formed at higher concentrations of ascorbic acid in the absence of TMEDA. Aggregated $Cu_2O$ microcubes are formed at lower concentrations of ascorbic acid and higher concentrations of TMEDA. The crystal growth mechanism of these $Cu_2O$ morphologies is explained.

• Bulletin of the Korean Chemical Society
• /
• v.31 no.4
• /
• pp.925-928
• /
• 2010

Nitrogen-doped $TiO_2$ ($TiO_2$:N) nano-particles with a pure anatase crystalline structure were successfully synthesized through the hydrolysis of $TiCl_4$ in an ammonia aqueous solution. The samples were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), $N_2$-sorption, and UV-vis diffuse reflectance spectra (UV-vis DRS) techniques. The absorption edge of nitrogen-doped $TiO_2$ shifted into the visible wavelength region. The photoelectrochemical (PEC) performances were investigated for the $TiO_2$ mesoporous electrodes doped with different nitrogen concentrations. The $TiO_2$:N electrodes exhibited much higher PEC responses compared to the pure $TiO_2$ electrode because of the significantly enhanced visible-photoresponsibility of the $TiO_2$:N electrodes.

• Journal of the Korean Chemical Society
• /
• v.67 no.5
• /
• pp.333-338
• /
• 2023

In this study, the H₂O reaction with SiO clusters was investigated using ab initio Monte Carlo simulations and density functional theory calculations. Three chemistry models, PBE1/DGDZVP (Model 1), PBE1/DGDZVP (Si atom), and aug-cc-pVDZ (O and H atoms), (Model 2) and PBE1/aug-cc-pVDZ (Model 3), were used. The average bond lengths, as well as the relative and reaction energies, were calculated using Models 1, 2, and 3. The average bond lengths of Si-O and O-H are 1.67-1.75 Å and 0.96-0.97 Å, respectively, using Models 1, 2, and 3. The most stable structures were formed by the H transfer from an H₂O molecule except for Si₃O₃-H₂O-1 cluster. The Si₃O₃ cluster with H₂O exhibited the lowest reaction energy. In addition, the Bader charge distributions of the Si_nO_n and (SiO)_n-H₂O clusters with n = 1-7 were calculated using Model 1. We determined that the reaction sites between H₂O and the SiO clusters possessed the highest fraction of electrons.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.07a
• /
• pp.54-57
• /
• 2003

[ $HfO_xN_y$ ] films using a hafnium tertiary-butoxide $(Hf[OC(CH_3)_3]_4)$ in plasma and $N_2$ ambient were prepared to improve the thermal stability of hafnium-based gate dielectrics. A 10% nitrogen incorporation into $HfO_2$ films showed a smooth surface morphology and a crystallization temperature as high as $200^{\circ}C$ compared with pure $HfO_2$ films. The $TaN/HfO_xN_y/Si$ capacitors showed a stable capacitance-voltage characteristics even at post-metal annealing temperature of $1000^{\circ}C$ in $N_2$ ambient and a constant value of 1.6 nm EOT (equivalent oxide thickness) irrespective of an increase of PDA and PMA temperature. Leakage current densities of $HfO_xN_y$ capacitors annealed at PDA temperature of 800 and $900^{\circ}C$, respectively were approximately one order of magnitude lower than that of $HfO_2$ capacitors.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1998.05b
• /
• pp.186-191
• /
• 1998

$UO_2$-5wt%CeO$_2$ 분말에서 소결온도(1600, 1$700^{\circ}C$), 소결분위기(H$_2$, $N_2$-7vol.%H$_2$) 및 Li$_2$O 첨가량(0.05-2wt%)에 따른 소결성의 변화를 관찰하였다. $UO_2$-5wt%CeO$_2$를 attrition mill에서 2 시간까지 분쇄한 후, 1$700^{\circ}C$에서 H$_2$, N2-7vol.%H$_2$ 분위기에서 소결하면 소결밀도가 각각 10.46, 10.36 g/㎤이지만, 각 분위기에서 소결체내의 결경립크기가 일정하지 않고 Ce agg1omerate도 소결체내의 여러 곳에 분포되어 있어 분말처리만으로 소결성을 개선하는데는 한계가 있었다. 반면에, $UO_2$-5wt%CeO$_2$에 0.lwt%Li$_2$O를 첨가하여 1 시간동안 분쇄란 후, 1$600^{\circ}C$에서 H$_2$$N_2$-7vol.%H$_2$ 분위기로 소결하면 밀도는 각각 10.51, 10.48 g/㎤이었고, 결정립크기는 각각 8.9, 42.1 $\mu\textrm{m}$이었다. 즉, Li$_2$O의 첨가에 의해 밀도와 결정립크기가 모두 증가했으며, H$_2$ 분위기보다는 $N_2$-7vol.%H$_2$ 분위기에서 결정립이 더 크게 성장하였고, 1$700^{\circ}C$에서도 유사한 경향을 나타내었다. $UO_2$-5wt%CeO$_2$와 이 조성에 0.lwt%Li$_2$O를 첨가한 분말들을 H$_2$ 및 $N_2$-7vol.%H$_2$ 분위기에서 소결하여 기공크기 및 기공부피의 변화를 관찰한 결과, H2 분위기에서 소결하였을 때는 Li$_2$O의 첨가에 의해 치밀화가 주로 일어났고, 반면에 $N_2$-7vol.%H$_2$ 분위기에서 소결하면 Li$_2$O의 첨가에 의해 작은 기공은 소멸되고 큰 기공이 생성되었다.

• Journal of Industrial Technology
• /
• v.31 no.B
• /
• pp.119-125
• /
• 2011

N-doped Titanium oxides were prepared by using urea as a source of nitrogen. The photoactivities of the doped $TiO_2$ were evaluated on the basis of degradation of humic acid in aqueous solutions with different light sources, ultraviolet lamp, fluorescent lamp and solar light. XRD analysis was conducted to identify the crystal structure of the synthesized photocatalysts. N-doped $TiO_2$ and $pure-TiO_2$ was anatase type. SEM results showed that spherical particles were formed, which are the characteristics of the anatase form. N doped $TiO_2$ showed higher $UV_{254}$ decrease ratio and DOC removal ratio compared to $pure-TiO_2$. The humic acid degradation reaction using the UV-A lamp and UV-C lamp was assigned to pseudo-first order reaction. For solar light, only $pure-TiO_2$ and $N-TiO_2$ exhibited the pseudo-first order reaction.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
• /
• 2004.05a
• /
• pp.67-71
• /
• 2004

400~450nm 파장 범위의 청색광을 검출하는 Si 포토다이오드에서 $SiO_2$, $Si_{3}N_{4}$, $SiO_{2}/Si_{3}N_{4}$를 광반사 방지막으로 사용하는 경우 광반사 방지막의 두께에 따른 표면 광반사 손실을 이론적으로 계산하였다. 400~450nm 청색 파장에서 $SiO_2$, $Si_{3}N_{4}$ 단일막에 대한 최소 광반사 손실은 각각 $d(SiO_2)=700~750{\AA}$ 와 $d(Si_{3}N_{4})=500${\AA}$에서 나타났으며, $SiO_{2}/Si_{3}N_{4}$ 이중막에 대한 최소 광반사 손실은 $d(SiO_{2}/Si_{3}N_{4})=750{\AA}/(180~200){\AA}$에서 나타났다.