$TiO_2$ 피복 석탄회의 제조와 광촉매 특성에 관한 연구

유연태,최영윤,김병규,이희정,이병택,Yu, Yeon-Tae,Choi, Young-Yoon,Kim, Byoung-Gyu,Lee, Hee-Jung,Lee, Byong-Taek 한국재료학회 2001 한국재료학회지 Vol.11 No.8

$TiO_2$ coated coal fly ash has been prepared in order to develop the low price $TiO_2$ photocatalyst and spread out its utilizing field. $TiO_2$ particles is coated on the surface of coal fly ash by precipitation method. In this method, $TiCl_4$ aqueous solution was used as a titanium stock solution and $NH_4HCO_3$ was used as a precipitant. The titanium hydroxide precipitated on the surface of coal fly ash in these neutralizing reaction process was oxidized by heat treatment in temperature ranges of $300~700^{\circ}C$. The crystal structure of the generated titanium dioxide showed anatase type. The crystal size of titanium dioxide increased with raising the temperature of heat treatment, but the removal ability of NO gas decreased. When the titanium dioxide was heated at temperature ranges of $300~ 400^{\circ}C$ for 2 hours, the crystal size of titanium dioxide appeared about 9nm, and the removal rate of NO gas showed 85~ 92%. The whiteness of $TiO_2$ coated coal fly ash increased with raising the coating rate of titanium dioxide and the temperature of heat treatment. 저가형 $TiO_2$ 광촉매의 개발과 광촉매의 활용범위를 확대하고자, 석탄회를 지지체로 이용하여 $TiO_2$ 광촉매를 제조하였다. 석탄회 표면에 $TiO_2$ 입자의 피복은 침전법에 의해서 수행되었다. $TiO_2$의 공급원으로는$ TiCl_4$수용액과 침전제로는 $NH_4$$HCO_3$가 사용되었다. 이들의 중화반응에 의해 석탄회 표면에 생성되는 Ti(OH)4$_4$는 $300~700^{\circ}C$의 열처리 과정에서 산화되었다. 여기서 생성된 $TiO_2$의 결정구조는 anatase형을 나타내었다. 피복 $TiO_2$의 결정립 크기는 열처리 온도의 상승에 따라 증가하였으나, NO가스의 제거능은 감소하는 경향을 보였다. $TiO_2$피복 석탄회를 $300~400^{\circ}C$의 온도 범위에서 2시간 동안 열처리할 경우, $TiO_2$의 결정립 크기는 약 9nm이었고, 질소산화물 제거율은 85~92%이었다. 또한, $TiO_2$피복 석탄회의 백색도는 $TiO_2$의 피복량이 증가할수록 열처리 온도가 증가할수록 상승하는 경향을 나타내었다.

WO₃ 피복 석탄회의 광촉매 특성에 미치는 TiO₂의 첨가 효과

유연태,김병규,Yu, Yeon-tae,Kim, Byoung-gyu 한국재료학회 2003 한국재료학회지 Vol.13 No.10

To improve the photocatalyticactivity of $TiO_2$-coated coal fly ash, tungsten hydroxide was doped by impregnation method and was oxidized by heat treatment in temperature ranges of $WO^{\circ}C$ for 2 hrs. The changes of crystal structure and crystal size of $TiO_2$and $WO_3$on coal fly ash were investigated by X-ray diffraction analysis. The crystal structure of titanium dioxide showed only anatase type and $TiO_2$-$WO_3$ compounds appeared in the heat treatment temperature ranges of $500∼600^{\circ}C$. By adding $V_3$in $TiO_2$coated on fly ash, the growth of crystal size of anatase was restrained and the anatase phase was stabilized in temperature ranges of $500∼<800^{\circ}C$. And $WO_3$acted as a trap site of electrons excited from anatase by irradiating UV. The maximum removal efficiency of NO gas for $TiO_2$/$WO_3$-coated coal fly ash was 84% and appeared when the ammonium tungstate of $1.3${\times}$10^{-3}$ M was doped and then heated at $600^{\circ}C$ for 2 hrs.

피복제 적하법에 의한 Ag 피복 Cu 미립자의 제조 및 광학적 특성

유연태,Yu, Yeon-tae 한국재료학회 2003 한국재료학회지 Vol.13 No.9

Ag-coated Cu particles were prepared by dropping method of coating agent and were evaluated by scanning electron microscope and color difference meter. The shape of Cu particles having obvious crystal plan and edge was changed spherically according to the increase of Ag coating amount. When the Ag coating amount was 50 wt% to Cu particles, the whiteness of Ag-coated Cu particles was almost similar to that of pure Ag particles. Adding $NH_4$OH in reductant solution could increase effectively the whiteness of the Ag-coated particles. The Ag-coated particles having the highest whiteness was obtained when the content of hydrazine in reductant solution was 0.48 M.

페복제 적하법에 의한 나노 결정 TiO₂ 피복 석탄회의 제조와 광촉매 특성

유연태,최영윤,김병규,Yu, Yeon-Tae,Choe, Yeong-Yun,Kim, Byeong-Gyu 한국재료학회 2002 한국재료학회지 Vol.12 No.5

$TiO_2$-coated fly ash was synthesized by dropping method of coating agent in order to get $TiO_2$ coating layer with high photocatalytic activity on the surface of coal fly ash. The properties of the $TiO_2$ coating layer such as morphology, crystal structure, crystal size and photocatalytic activity were compared with those of the $TiO_2$-coated fly ash prepared by the traditional method of precipitation. $TiCl_4$ aqueous solution was used as a titanium stock solution and $NH_4HCO_3$ was used as a precipitant. The $TiO_2$ coating layer obtained by dropping method of coating agent was more uniform than that coated by precipitation. However, the crystal of $TiO_2$ coated by dropping method of coating agent was easy to grow by heat treatment because of the small primary particle size and bulky morphology, and its photocatalytic activity was consequently lower than that of the $TiO_2$ coated by precipitation. The $TiO_2$ coating layer obtained by both methods had a crystal structure of anatase, and the temperature of phase transformation into rutile was 90$0^{\circ}C$. The minimum crystal size of $TiO_2$ for the highest photocatalytic activity was found to be about 10nm.

Au/TiO₂ core-shell 나노입자의 합성에 있어서 Au 나노입자의 분산특성에 미치는 Mercaptoundecanoic acid (MUA)의 피복 효과

유연태,김병규,Yu, Yeon-Tae,Kim, Byoung-Gyu 한국재료학회 2006 한국재료학회지 Vol.16 No.12

Mercaptoundecanoic acid (MUA) has been used to enhance the dispersity of Au nanoparticles in organic solvent and the affinity between the Au nanoparticles surface and titanium dioxide shell in the synthesis of $Au/TiO_2$ core-shell composite nanoparticles. The dispersity of the MUA-coated Au nanoparticles in ethanol aqueous solution with different concentration of $H_2O$ was investigated by UV-Vis. absorption spectrum and the coating amount of MUA was varied from 0.02 mM to 1.0 mM. The MUA-coated Au nanoparticles were highly dispersed in pure $H_2O$ in the wide range of the coating amount of MUA. On the contrary, the MUAcoated Au nanoparticles showed an enhanced stability in the ethanol/$H_2O$=8/2 mixed solution only when the coating amount of MUA was 0.05 mM, and in the ethanol/$H_2O$=7/3 mixed solution when the coating amount of MUA was in the range from 0.02 mM to 0.17 mM. From this systematic study, it can be inferred that the stability and the dispersibility of Au nanoparticles in organic solvents are highly sensitive towards the amount of MUA coating.

$Eu^{2+}, Dy^{3+}$를 도핑한 $SrAl_2O_4$축광성 형광체 합성에 있어서 $B_2O_3$의 첨가 효과

유연태,김병규,남철우,Yu, Yeon-Tae,Kim, Byeong-Gyu,Nam, Cheol-U 한국재료학회 1998 한국재료학회지 Vol.8 No.11

$SrAl_2O_4$:$Eu^{2+}, Dy^{3+}$ 축광성 형광체의 합성에 있어서 $B_2O_3$는 일반적으로 고상반응의 촉진을 위한 플럭스로서 첨가된다. 본 연구에서는 플럭스로 첨가되는 $B_2O_3$가 $SrAl_2O_4$:$Eu^{2+}, Dy^{3+}$ 형광체의 결정구조 및 잔광 특성에 미치는 영향을 조사하였다. 합성된 $SrAl_2O_4$:$Eu^{2+}, Dy^{3+}$ 형광체는 520nm에서 최대 피크를 갖는 폭넓은 발광 스펙트럼을 나타내었고, $B_2O_3$ 첨가량의 5wt%일 때 최대값을 나타내었다. $B_2O_3$의 첨가에 의해 $SrAl_2O_4$:$Eu^{2+}, Dy^{3+}$ 결정 내부에는 균일 변형(uniform strain)이 발생하였고 이 결과로 결정격자의 a축과 c축의 길이 및 $\beta$각이 감소하여다. 그리고 $SrAl_2O_4$ 결정내부의 균일 변형은 $Eu^{2+}$이온의 여기과정에서 발생하는 정공(hole)의 포획 사이트인 음이온 결함(negative defect)을 다량 발생시키는 원인이 되고, 결과적으로 $SrAl_2O_4$:$Eu^{2+}, Dy^{3+}$ 결정의 잔광 특성을 향상시키는 것으로 생각되었다.

증기급속응축법 제조 귀금속 나노분말의 결정학적 특성 연구

유연태,Yu, Yeon-Tae 한국재료학회 2003 한국재료학회지 Vol.13 No.5

The nanosized silver and gold particles are prepared by ERC method in which metal vapors with high temperature is rapidly quenched by coolants such as liquid nitrogen or liquid argon. In order to monitor the crystal structural changes on the internal and the surface of the nanosized noble metal particles, lattice parameter, internal strain and Debye-Waller factor are investigated, and the calculation of X-ray diffraction scattering intensity is performed. The lattice parameters of silver and gold particles agree with those of bulk materials, and crystal internal strain of the metal particles is not changed by rapid cooling. The Debye-Waller factor of gold particles is increased with decreasing particle size because of the surface softening phenomenon of nanosized particles, but the crystal structural change on the surface of the particles is not detected from the comparison the calculated X-ray diffraction profile with the experimental profile on gold particles with the particle size of 4 nm.

$\textrm{TiOSO}_4$ 및 $\textrm{TiO(\textrm{SO}_4)_2$용액으로부터 촉매 담체용 $\textrm{TiO}_2$합성에 관한 연구

유연태,최영윤,김병규,남철우,안병국,Yu, Yeon-Tae,Choe, Yeong-Yun,Kim, Byeong-Gyu,Nam, Cheol-U,An, Byeong-Guk 한국재료학회 1999 한국재료학회지 Vol.9 No.11

고정원으로부터 배출되는 질소산화물의 저감 기술 중에서 선택적 촉매 환원법(SCR법)은 가장 경제적이고 효율적인 방법으로 알려져 있다. 이 SCR 촉매의 탈질능을 향상시키기 위하여,$ TiOSO_4$ 및 Ti($SO_4$)$_2$용액으로부터 비표면적이 넓은 $TiO_2$의 비표면적 및 결정구조에 미치는 영향과 이들의 상관관계에 대하여 조사하였다. $TiOSO_4$용액으로부터 합성한 $TiO_2$의 최대 비표면적은 $382\m^2$/g이었고, Ti($SO_4$)$_2$용액으로부터 합성한 $TiO_2$의 최대 비표면적은 $335\m^2$/g이었으며, $TiO_2$는 비정질 형태의 결정구조를 보였다. 하소처리에 의해 비정질 $TiO_2$는 결정화되었고, 결정 중에 함유되어 있는 불순물은 $TiO_2$의 결정화를 억제하였다.

소성블릭 제조를 위한 무연탄 석탄회의 특성 연구

유연태,김병규,최영윤,남철우,이용석,김천순,Yu Yeon-Tae,Kim Byoung-Gyu,Choi Young-Yoon,Nam Chul-Woo,Lee Yeng-Seok,Kim Cheon-Sun 한국자원리싸이클링학회 2004 資源 리싸이클링 Vol.13 No.2

To increase the recycling rate of anthracite fly ash, the properties of anthracite fly ash were compared to that of bituminous fly ash. Especially, the high temperature properties of the fly ash are investigated by using thermal analysis, high temperature microscope and X-ray diffraction analysis for utilizing anthracite fly ash to prepare the calcinated bricks. The average ratio of $A1_2$$O_3$/$SiO_2$ for anthracite is 0.62 and the ratio for bituminous is 0.34. The content of $SiO_2$ in anthracite fly ash was higher than that of bituminous fly ash. The $A1_2$$O_3$ of anthracite fly ash reacted with the $A1_2$$O_3$ in the fly ash and formed new mullite crystal at over $1000^{\circ}C$, so anthracite fly ash showed high fire resistance. And, the fly ash mixtures having kaolin were prepared, and then extruded in vacuum to evaluate the extruding property of anthracite fly ash mixture. The extruding velocity was decrease with increasing the addition amount of fly ash in the mixture, and the maximum addition amount of fly ash that could be extruded was 60 wt%. 무연탄 석탄회의 재활용 향상을 위하여, 무연탄 석탄회의 특성을 유연탄 석탄회의 특성과 비교하였다. 특히, 무연탄 석탄회를 소성블릭의 원료로 활용하기 위하여, 무연탄 석탄회의 고온 특성이 열분석, 고온현미경 및 X선 회절 분석에 의해 조사되었다. 무연탄석탄회의 $A1_2$$O_3$/SiO$_2$ 비는 평균 0.62이고 유연탄 석탄회는 $A1_2$$O_3$/$SiO_2$ 비가 0.34로 무연탄 석탄회 중 A1$_2$$O_3$ 성분의 조성이 높았다. 무연탄 석탄회 중 $SiO_2$는 석탄회 중의 $A1_2$$O_3$와 반응하여 $1000^{\circ}C$의 고온에서 새로운 뮬라이트 결정을 형성하였고, 그 결과 우수한 내화도를 나타내었다. 또한, 무연탄 석탄회의 첨가량 변화에 따른 혼합시료의 압출 성형 특성을 평가하기 위하여 고령토와의 혼합시료가 제조되었고, 무연탄 석탄회 첨가 성형 벽돌의 압출속도는 혼합시료 중 석탄회의 첨가량이 증가할수록 감소하였으며, 압출 성형가능한 무연탄 석탄회의 최대 첨가량은 60wt%이었다.

황산동 수용액으로부터 hydrazine 환원에 의한 Cu 미립자의 합성

유연태,최영윤,Yu, Yeon-tae,Choi, Young-yoon 한국재료학회 2003 한국재료학회지 Vol.13 No.8

In order to prepare the uniform copper particles from copper sulfate solution by using hydrazine as a reduction agents, the reduction behavior of copper particles from copper sulfate was investigated in detail at room temperature by the observation of reaction products. The effects of $NH_4$OH and $Na_4$$P_2$$O_{7}$ on the formation of uniform copper particles were discussed. ($NHCu_3$)$_4$$SO_4$was completely formed at over pH 11 by adding $NH_4$OH in copper sulfate solution. The fine $Cu_2$O with the particle size of 50 nm was produced in the initial reduction process of (NH$Cu_3$)$_4$$SO_4$solution with $Na_4$$P_2$$O_{ 7}$ and then the Cu$_2$O was converted into copper particles by inserting additional hydrazine. When Cu(NH$_3$)$_4$SO$_4$solution with $Na_4$$P_2$$O_{ 7}$ was reduced at $80^{\circ}C$ by hydrazine, the highly dispersed copper particles with the particle size of about 0.8 $\mu\textrm{m}$ was obtained.