• Bulletin of the Korean Chemical Society
• /
• 제28권12호
• /
• pp.2333-2337
• /
• 2007

Nanoporous TiO2 and ZrO2 thin films were spin-coated using a surfactant-templated approach from Pluronic P123 (EO20PO70EO20) as the templating agent, titanium alkoxide (Ti(OC4H9)4) as the inorganic precursor, and butanol as a the solvent. The control of the electronic structure of TiO2 is crucial for its various applications. We found that the band gap of the hybrid nanoporous thin films can be easily tuned by adding an acetylacetonestabilized Zr(OC4H9)4 precursor to the precursor solution of Ti(OC4H9)4. Pores with a diameter of 5 nm-10 nm were randomly dispersed and partially connected to each other inside the films. TiO2 and ZrO2 thin films have an anatase structure and tetragonal structure, respectively, while the TiO2-ZrO2 hybrid film exhibited no crystallinity. The refractive index was significantly changed by varying the atomic ratio of titanium to zirconium. The band gap for the nanoporous TiO2 was estimated to 3.43 eV and that for the TiO2-ZrO2 hybrid film was 3.61 eV.

• 한국분말재료학회지
• /
• 제10권5호
• /
• pp.337-343
• /
• 2003

Nanostructured Cu-$Al_2O_3$ composite powders were synthesized by thermochemical process. The synthesis procedures are 1) preparation of precursor powder by spray drying of solution made from water-soluble copper and aluminum nitrates, 2) air heat treatments to evaporate volatile components in the precursor powder and synthesis of nano-structured CuO + $Al_2O_3$, and 3) CuO reduction by hydrogen into pure Cu. The suggested procedures stimulated the formation of the gamma-$Al_2O_3$, and different alumina formation behaviors appeared with various heat treating temperatures. The mean particle size of the final Cu/$Al_2O_3$ composite powders produced was 20 nm, and the electrical conductivity and hardness in the hot-extruded bulk were competitive with Cu/$Al_2O_3$ composite by the conventional internal oxidation process.

• 한국진공학회지
• /
• 제20권3호
• /
• pp.182-188
• /
• 2011

탄소가 없는 폴리실라잔 계와 탄소가 함유된 폴리메틸 실라잔 계 전구체를 실리콘 기판에 스핀코팅하고 $150^{\circ}C$, $400^{\circ}C$, $850^{\circ}C$에서 열처리하여 형성된 박막의 물리적 화학적 특성을 평가하였다. 프리에 변환 적외선 분광, 수축 율, 갭-충진, 식각속도 등을 평가하여 박막형성과 형성된 박막의 물리화학적 특성에 미치는 탄소의 영향을 고찰하였다. 탄소함유 전구체는 (탄소가 없는 전구체보다) $400^{\circ}C$에서 질소, 수소, 탄소의 휘발량이 더 적고 산소 흡수량이 더 적어서 (15.6%)보다 낮은 14.5% 두께 수축을 나타내었으나, $800^{\circ}C$에서는 휘발 량이 더 많고 산소 흡수량도 더 많아져 (19.4%)보다 높은 37.4% 두께 수축을 나타냈다. 프리에 변환 적외선 분광분석결과, 전구체내의 탄소는 Spin-on dielectric (SOD) 박막으로 하여금 Si-O 결합형성을 적게, 박막특성을 불균일하게, 그리고 화학 용액에 더 빨리 식각되도록 만들었다.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.2
• /
• pp.732-734
• /
• 2003

A solvothermal synthetic method to $BaTiO_3$ nanoparticle has been investigated in toluene solution with $BaTi(OR)_6$ as precursor. A precursor prepared from barium metal with toluene, isopropanol and titanium isopropoxide was used as a starting material. Weight ratio of precursor to solvent prepared in the mixture are 5/100, 10/100, 20/100 and 50/100wt%. At the weight ratio of 50/100wt%, $BaTiO_3$ butterfly twin crystalline(${\fallingdotseq}100nm$) was obtained after synthesis at $250^{\circ}C$ for 20hrs in an autoclave. X-ray diffraction and transmission electron microscopy showed that the product of 50/100wt% has crystallization. At 5/100, 10/100, and 20/100wt%, however, red colloidal solution was obtained after synthesis and crystalline phase of $BaTiO_3$ was not produced.

• 한국세라믹학회지
• /
• 제40권4호
• /
• pp.365-370
• /
• 2003

The phase development process of $Ba_2$ $Ti_{9}$ $O_{20}$ ceramics is not clearly known and frequently accompanies second phases which deteriorate dielectric properties. In synthesizing $Ba_2$ $Ti_{9}$ $O_{20}$ ceramics, in order to trace the reaction sequence during conventional solid-state reaction in BaO-Ti $O_2$ system, different barium sources of BaC0$_3$ and BaTi0$_3$ precursor were used as starting materials. From the analysis of XRD patterns, different secondary phases could be identified depending on the barium source used, which might mean that the equilibrium phases in BaO-Ti $O_2$ system are very difficult to be synthesized. Because the BaTi0$_3$ precursor provides short diffusion paths of ions, the system revealed less secondary phases during solid state reaction. In synthesizing BaO-xSm$_2$0$_3$-4.5Ti0$_2$ system using different barium sources, different secondary phases were developed also. Microstructure and dielectric properties were examined and discussed in terms of secondary phase development.

• 한국재료학회지
• /
• 제13권3호
• /
• pp.180-184
• /
• 2003

Ce-doped $Y_2$SiO$_{5}$ phosphor particles of spherical morphology, fine size, high crystallinity and high photoluminescence (PL) intensity were prepared by spray pyrolysis. When nitrate precursor solution is adopted, hollow particles were formed by uneven drying rate between surface and inside of droplet. Citric acid and ethylene glycol were introduced as polymeric precursor to control the morphology of particles. When polymeric solution is adopted, polymeric chain is formed by the esterification reaction between carboxyl and hydroxy groups of citric acid and ethylene glycol, and considered as controlling the drying characteristics of droplet. $Y_2$$SiO_{5}$ :Ce phosphor particles prepared from polymeric precursor solution were spherical, filled, fine size and not agglomerate before and after post heat treatment. The optimum doping concentration of cerium was 0.5 mol% of overall solution concentration. The optimum amount of TBOS of high PL intensity and pure crystallinity of X2-type $Y_2$$SiO _{5}$ was 105% of stoichiometric amount. The PL intensity of $Y_2$X$/_{5}$ :Ce phosphor particles prepared using the polymeric precursor solution was 164% of that of the nitrate precursor solution due to homogeneous composition and good morphology.y.

• 분석과학
• /
• 제21권2호
• /
• pp.123-128
• /
• 2008

졸-겔법에 의한 코디어라이트계 전구체(precursor) 제조 시 마그네슘 에톡사이드를 사용하면 황금색을 띠는 불투명한 전구체 용액이 되고, 조핵제인 5%-$Zr(OC_3H_7)_4$ 첨가 시에는 투명한 코디어라이트를 얻을 수 있다. 적외선 흡수 분광 분석에서 $SiO_2$ 성분은 $1045cm^{-1}$에서 흡수 피크를 확인 할 수 있었으며, 동시에 $1140cm^{-1}$과 $940cm^{-1}$의 두 개 피크 분리는 열처리 한 겔체인 $SiO_4$ 신축 진동이고, $Al_2O_3$ 성분은 $580cm^{-1}$과 $680cm^{-1}$의 흡수 피크로 보아 $Al_2O_6$ 망목 구조이고, MgO 성분은 $575cm^{-1}$에서 MgO 신축 진동 임을 알 수 있었다. X-선 회절 분석에서 코디어라이트계 전구체 : 물 몰비 1:5의 경우 반응 소결 온도 $1000^{\circ}C$ 이상에서는 ${\mu}$-cordierite 결정상이 나타남을 알 수 있었고, 코디어라이트계 전구체 : 암모니아 몰비 1:5 건조 겔체의 경우 $1050^{\circ}C$에서는 ${\mu}$-cordierite와 ${\alpha}$-cordierite가 공존 하다가 $1100^{\circ}C$에서는 ${\alpha}$-cordierite만이 존재함을 알 수 있었다.

• 한국전기전자재료학회논문지
• /
• 제19권12호
• /
• pp.1092-1098
• /
• 2006

The influence of the concentration of precursor solution and the number of solution coatings on the densification of the $Pb(Zr_xTi_{1-x})O_3$ (PZT) thick films was studied. PZT powder and PZT precursor solution were prepared by3 sol-gel method and PZT thick films were fabricated by the screen-printing method on the alumina substrates. The composition of powder and precursor solution were PZT(70/30) and PZT(30/70), respectively. The PZT precursor solution was spin-coated on the PZT thick films. A concentration of a coating solution was 0.5 to 2.0 mol/L[M] and the number of coating was repeated from 0 to 6. The XRD patterns of all PZT thick films shelved typical perovskite polycrystalline structure. The porosity of the thick films was decreased with increasing the number of coatings and 6-time coated films with 1.5 M showed the dense microstructure and thickness of about $60{\mu}m$. The relative dielectric constant of the PZT thick film was increased with increasing the number of solution coatings and the thick films with 1.5 M, 6-time coated showed the 698. The remanent polarization the 1.5 M and 6-time coated PZT thick films was $38.3{\mu}C/cm^2$.

• 한국진공학회지
• /
• 제8권4A호
• /
• pp.425-431
• /
• 1999

$Pb(Zr_{0.52}, Ti_{0.48})O_3$ (PZT) thick films as an actuating material with conducting oxides, $(La_{0.5}Sr_{0.5}) CoO_3$ (LSCO), have been fabricated by sol-gel method for Optical Micro-Electro-Mechanical System (MEMS) devices, in which PZT/LSCO/SiO2 structures were used. In order to improve the adhesion to LSCO solution in order to enhance the wetting behavior of a water-based LSCO precursor solution and further to improve the adhesion between LSCO and $SiO_2$ layers. PZT films were made using 1-3 propanediol based precursor solution which has a high viscosity and a boiling point appropriate for thick film fabrication. In the precursor solution, Ti-propoxied and Zr-propoxied are partially substituted with acetylacetone to achieve the solution stability while maintaining reactivity. Crack free PZT films (0.8~1$\mu\textrm{m}$) have been successfully fabricated at crystallization temperatures above $700^{\circ}C$. Dielectric constants and dielectric losses of the PZT films were 900~1200and 2~5%, respectively. Piezoelectric constant $d_{33}$ of the PZT films constrained by a substrate were 200pm/V at 100kV/cm.

• 한국식품영양과학회지
• /
• 제32권8호
• /
• pp.1390-1393
• /
• 2003

동위 원소를 이용하여 골조직 collagen과 같이 대사속도가 느린 단백질의 합성 속도를 측정 할 때 가장 중요한 점은 전구체 공급원의 비균일성 및 복잡한 대사경로로 인한 해석상의 제한점을 극복하기 위하여 동위원소가 함유된 전구체를 지속적으로 투여하여 동위원소공급원의 항상성을 유지하는 것이다. 이 경우 precursor-product kinetics를 적용하여 $k_{s}$값을 정확하게 측정할 수 있다. $^2$$H_2O$는 저렴한 안정동위 원소 추적자로서 독성이나 부작용 없이 장기간 공급 가능하고 공급방법 또한 간단하다. 본 연구에서는 골조직 collagen 합성속도를 아미노산에 $^2$$H_2O$를 치환하는 precursor-product 방법으로 측정하였으며, 골조직 collagen으로부터 분리한 아미노산의 동위 원소함량을 GC/MS로 분석하였다. 실험 기간동안 체액의 $^2$$H_2O$는 2.7 ∼ 3.0% 수준으로 일정하게 유지되었고 성장기 흰쥐 골조직의 collagen 합성속도는 $k_{s}$(OH-pro) = 0.066$\pm$0.049 w $k^{-1}$였다. 동위원소를 연속적으로 공급해야하는 precursor product방법은 교체율이 느린 단백질에 적용하는데 기술적인 어려움이 있었지만, 안정하고 저렴한 $^2$$H_2O$ 특성으로 인하여 precursor-product방법을 교체율이 느린 단백질에 적용하는 것이 가능하게 되었다..