• 한국세라믹학회지
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• 제33권11호
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• pp.1195-1202
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• 1996

To prepare the dielectric thin films of (Pb1-xSrx)TiO3 (x=0.1, 0.2, 0.3, 0.35, 0.5) by the sol-gel process titanium (IV) isopropoxide (Ti[OCH(CH3)2]4) and Pb Sr, acetate were used therefore the thin films were fabricated by dip-coating method. Stability of the sol decreased with addition of Sr content thin films could be fabricated up to 35mol% Over this range precipitation of sol occured thin films couldn't be obtained. Transmittance of thin films at visible range decreased with the increase of heat-treatment temperature but exhibited transmit-tance above 60% in all case. Moreover transmittance of thin films at visible range slightly increased with of addition of Sr,. When thin film containing 30 mol% srontium was heated at 600℃ the best perovskite phase was obtained. The dielectric constant (ε) was 280 and dielectric loss factor (tan δ) was 0.021 and curie tempera-ture (Tc) decreased with the increase of addition of Sr.

• The Korean Journal of Ceramics
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• 제3권1호
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• pp.52-56
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• 1997

The Pt doped $TiO_2$ composite membranes were prepared by the sol-gel process. The Pt doped titania sol was peptized with hydrochloric acid in the pH range of 1.23 to 1.32 at 5$0^{\circ}C$. The average particle size of the Pt doped titania sol was shown to be below 15nm and well dispersed in the solution. XPS show the Pt elements continuous and homogeneous dispersed in the $TiO_2$ membrane. The mean particle size of the Pt doped $TiO_2$ composite membrane has smaller than that of the undoped $TiO_2$ composite membrane. The average pore size of the Pt doped $TiO_2$ composite membrane was increased from 58 to 193 $\AA$ with firing temperature changed from 550 to 85$0^{\circ}C$. It was observed that the Pt doped $TiO_2$ composite membranes showed crack-free and homogeneous microstructue as well as narrow particle size distribution up to above 75$0^{\circ}C$.

• 국제물리치료학회지
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• 제7권2호
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• pp.1037-1040
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• 2016

This study aims to investigate the effects of ankle foot orthosis(AFO) on the activities of tibialis anterior(TA), soleus(Sol), rectus femoris(RF) and biceps femoris(BF) during stairs descending. The activities of TA, Sol, RF and BF were initially measured while descending 4 stairs without using AFO. The activities of the same muscles were then measured again while descending 4 stairs while using AFO. Wilcoxon signed-rank tests were used to analyze the results in order to examine the differences between the with using AFO and without using AFO. Although the activities of TA, Sol and RF were relatively lower while using AFO than without using AFO, only the differences in Sol and RF activities were significant(p<0.05). The activity of BF was relatively higher while using AFO compared to the activity of BF observed without using AFO. However, difference was not significant(p>0.05). Conclusion of this study was observed since AFO's ground reaction force absorption during stairs descending reduced the need to use So and RF that is related to shock absorption. BF activity was increased with AFO than without during standing forward to correct the trunk stability.

• 한국결정성장학회지
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• 제10권3호
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• pp.271-277
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• 2000

투광성 $TiO_2$박막을 다량의 물을 사용한 티타늄알콕사이드 수용계로부터 sol-gel법으로 제조하였다. sol의 제조를 위해 각각 1 mole의 titanium(IV)iso-propoxide, acetylacetone과 8 mole의 isopropyl-alcohol로부터 킬레이트 화합물을 만들었다. 그리고 sol의 안정성을 위한 0.02~0.50 mole의 HCI과 코팅 접착성을 위한 0.3 mole의 polyethylene glycol을 함유한 50 mole의 수용액을 엄밀히 제어하여 킬레이트 화합물에 적하하였다. 제조된 sol로부터 dipping, 건조 및 $400^{\circ}C$에서 열처리하여 $TiO_2$박막을 제조하였으며, XRD, SEM, UV-visible spectrometer 등을 이용하여 특성을 검토하였다. TTIP : AcAc : IPA : $H_2$O : PEG : HCl의 몰비가 1 : 1 : 8 : 50 : 0.3 : 0.15인 조성을 갖는 중성 sol은 30일까지도 안정한 상태를 유지하였고 코팅성이 양호하였다. 30회까지 반복 침지하고 건조 및 열처리한 anatase상 $TiO_2$박막은 평활한 표면과 두께 약 2 $\mu\textrm{m}$의 치밀한 미세구조를 보였다. 제조한 $TiO_2$박막은 가시광선 영역에서 약 80%의 투과도를 나타내었다.

• Bulletin of the Korean Chemical Society
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• 제27권1호
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• pp.65-70
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• 2006

An amperometric glucose biosensor has been developed based on the use of the nanoporous composite film of sol-gel-derived zirconia and perfluorosulfonated ionomer, Nafion, for the encapsulation of glucose oxidase (GOx) on a platinized glassy carbon electrode. Zirconium isopropoxide (ZrOPr) was used as a sol-gel precursor for the preparation of zirconia/Nafion composite film and the performance of the resulting glucose biosensor was tuned by controlling the water content in the acid-catalyzed hydrolysis of sol-gel stock solution. The presence of Nafion polymer in the sol-gel-derived zirconia in the biosensor resulted in faster response time and higher sensitivity compared to those obtained at the pure zirconia- and pure Nafion-based biosensors. Because of the nanoporous nature of the composite film, the glucose biosensor based on the zirconia/Nafion composite film can reach 95% of steady-state current less than 5 s. In addition, the biosensor responds to glucose linearly in the range of 0.03-15.08 mM with a sensitivity of 3.40 $\mu$A/mM and the detection limit of 0.037 mM (S/N = 3). Moreover, the biosensor exhibited good sensor-to-sensor reproducibility (~5%) and long-term stability (90% of its original activity retained after 4 weeks) when stored in 50 mM phosphate buffer at pH 7 at 4 ${^{\circ}C}$.

• 폴리머
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• 제29권3호
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• pp.242-247
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• 2005

콜로이드 실리카 종류, 콜로이드 실리카/실란의 함량비, 반응시간 등의 반응조건에 따라 두 종류의 콜로이드 실리카/실란 솔을 합성하였다. 이러한 졸을 이용하여 솔-젤 코팅막을 제조하여 물리적 화학적 특성을 조사하였다. 그 결과 1034A콜로이드 실리카계로부터 얻어진 솔-젤 코팅막의 접촉각과 표면균질성은 HSA계 솔-젤 코팅막에 비하여 우수하였다. 그리고 1034A 콜로이드 실리카계로부터 얻어진 솔-젤 코팅막은 $550^{circ}C$까지 열분해없이 안정하였고 methyltrimeth-oxysilane(MTMS) 함량이 증가할수록 코팅막의 두께가 두꺼워 졌다. 1034A 콜로이드 실리카계 솔-젤 코팅막의 경도는 MTMS의 함량 증가에 따라 감소하였으나 HSA계는 큰 영향을 받지 않았다. 표면에너지는 MTMS 함량 증가와 더불어 전반적으로 감소하는 경향을 보였다.

• Food Science and Biotechnology
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• 제16권5호
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• pp.817-821
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• 2007

The effect of acetylated rice (AR) starch at different concentrations (0, 4, 6, and 8%) on rheological properties of surimi sols and gels was studied. Dynamic frequency sweeps of surimi-AR starch sols at $10^{\circ}C$ showed that the magnitudes of storage moduli (G') decreased with an increase in starch concentration while those of tan ${\delta}$ increased, indicating that the effect of AR starch on the viscoelastic properties of surimi sols depended on starch concentration. In general, the G' thermograms of surimi sols showed the similar sol-gel transition pattern and they were also influenced by the addition of AR starch. The presence of AR starch in the surimi gel system reduced the gel strength and expressible moisture content (EMC). Surimi-AR starch gels showed better freeze-thaw stability compared to the control (0% starch concentration). The effect of AR starch on the rheological properties of surimi sols and gels appeared to be related to the swelling ability of starch granules in the presence of limited water available for starch.

• 한국분말재료학회지
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• 제25권5호
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• pp.395-401
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• 2018

The improvement of dispersion stability for the primary polishing slurry in a CMP process is achieved to prevent defects produced by agglomeration of the slurry. The dispersion properties are analyzed according to the physical characteristics of each silica sol sample. Further, the difference in the dispersion stability is confirmed as the surfactant content. The dispersibility results measured by Zeta potential suggest that the dispersion properties depend on the content and size of the abrasive in the primary polishing slurry. Moreover, the optimum ratio for high dispersion stability is confirmed as the addition content of the surfactant. Based on the aforementioned results, the long-term stability of each slurry is analyzed. Turbiscan analysis demonstrates that the agglomeration occurs depending on the increasing amount of surfactant. As a result, we demonstrate that the increased particle size and the decreased content of silica improve the dispersion stability and long-term stability.

• 한국재료학회지
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• 제31권1호
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• pp.8-15
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• 2021

Transparent, photocatalytic, and self-cleaning TiO2 thin film is developed by TiO2 sol-gel coating on glass and polycarbonate (PC) substrates. Acetyl acetone (AcAc) suppresses the precipitation of TiO2 by forming a yellowish (complex) transparent sol-gel. XPS analysis confirms the presence of Ti2p and O1s in the thin films on glass and PC substrates. The TiO2-sol is prepared by stabilizing titanium (IV) isopropoxide (TTIP) with diethylamine and methyl alcohol. The addition of AcAcsilane coupling solution to the TiO2-sol instantaneously turns to yellowish color owing to the complexing of titanium with AcAc. The AcAc solution substantially improves the photocatalytic property of the TiO2 coating layer in MB solutions. The coated TiO2 film exhibits super hydrophilicity without and with light irradiation. The TiO2 thin film stabilized by adding 8.7 wt% AcAc shows the highest photo-degradation for methylene blue (MB) solution under UV light irradiation. Also, the optimum photocatalytic activity is obtained for the 8.7 wt% AcAc-stabilized TiO2 coating layer calcined at 450 ℃. The thin-films on glass exhibit fast self-cleaning from oleic acid contamination within 45 min of UV-light irradiation. The appropriate curing time at 140 ℃ improves the anti-fogging and thermal stability of the TiO2 film coated on PC substrate. The watermark-free PC substrate is particularly beneficial to combat fogging problems of transparent substrates.

• 한국세라믹학회지
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• 제40권4호
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• pp.385-392
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• 2003

Sol-gel preparation technique using a chemical reaction of metal alkoxides has been widely used for the fabrication of various materials including ceramics. However, its mechanism has been studied till now because a number of chemical ways are possible from various alkoxides and additives. In this study, the mechanism of hydrolysis, condensation, and polymerization of alkoxides were investigated from the fabrication of lead-zirconate-titanate (PbZr$\_$x/Ti$\_$l-x/O$_3$; PZT) thin film that is used as various micro-actuator, transducer, and sensor because of its high electro-mechanical coupling factors and thermal stability. Furthermore, the fabrication process and characteristics of self-patternable PZT film using photosensitive stabilizer were studied in order to resolve the problem of physical damage and properties degradation during dry etching for device fabrication. Using an optimum condition to prepare the self-patternable PZT film, more than 5000 ${\AA}$ thick self-patternable PZT film could be fabricated by three times coating. The PZT film showed 28.4 ${\mu}$c/cm$^2$ of remnant polarization (Pr) and 37.0 kV/cm of coercive field (E$\_$c/).