• Corrosion Science and Technology
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• 제17권1호
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• pp.30-36
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• 2018

The high rate of corrosion of magnesium alloys makes it limited for industrial applications. Therefore, surface treatment is required to enhance their corrosion resistance. In our study, a chemical conversion coating for protecting the corrosion of the magnesium alloy, AZ31B, was prepared by using a phosphate-permanganate solution. The chemical conversion coating had a limited protection ability due to defects arising from cracks and pores in the coating layer. The sol-gel coating was prepared by using trimethoxymethylsilane (MTMS) and 3-glycidoxypropyltrimethoxysilane (GPTMS) as precursors, and aluminum acetyl acetonate as a ring opening agent. The corrosion protection properties of sol-gel and conversion coatings in 0.35wt% NaCl solution were measured by the electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization test. The EIS results indicated that the resistance of the chemical conversion coating with the sol-gel coating was significantly improved through the sol-gel sealed phosphate-permanganate conversion coating. The results of the potentiodynamic polarization test revealed that the sol-gel coating decreased the corrosion current density ($I_{corr}$). The SEM image showed that the sol-gel coating sealed conversion coating and improved corrosion protection.

• Corrosion Science and Technology
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• 제20권4호
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• pp.175-182
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• 2021

Magnesium alloy is limited in the industrial field because its standard electrode potential is -2.363 V vs. NHE (Normal Hydrogen Electrode) at 25 ℃. This high electrochemical activity causes magnesium to quickly corrode with oxygen in air; chemical conversion coating prevents corrosion but causes surface defects like cracks and pores. We have examined the anti-corrosion effect of sol-gel coating sealed on the defected conversion coating layer. Sol-gel coatings produced higher voltage current and smaller pore than the chemical conversion coating layer. The conversion coating on magnesium alloy AZ31 was prepared using phosphate-permanganate solution. The sol-gel coating was designed using trimethoxymethylsilane (MTMS) and (3-Glycidyloxypropyl) trimethoxysilane (GPTMS) as precursors, and aluminum acetylacetonate as a ring-opening agent. The thermal shock resistance was tested by exposing specimens at 140 ℃ in a convection oven; the results showed changes in the magnesium alloy AZ31 surface, such as oxidization and cracking. Scanning electron microscope (FE-SEM) analysis confirmed a sealed sol-gel coating layer on magnesium alloy AZ31. Electrochemical impedance spectroscopy (EIS) measured the differences in corrosion protection properties by sol-gel and conversion coatings in 0.35 wt% NaCl solution, and the potentiodynamic polarization test and confirmed conversion coating with the sol-gel coating show significantly improved resistance by crack sealing.

• E2M - 전기 전자와 첨단 소재
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• 제7권6호
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• pp.496-503
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• 1994

In recent years Sol-Gel processing provides an interesting alternative method for the fabrication of ferroelectric thin layers and powder. PZT powder was prepared from an alkoxide-based solution by a Sol-Gel method. Gelation of synthesized complex solutions, microstructure, thermal analysis and crystallization behaviors of the calcined powder were studied in accordance with a water content and a catalyst. Especially gelation and crystallization behavior were analysed with the change of pH. The gelation time decreased as the pH of the mixed solution increased. For PZT powder with 650.deg. C heat treatment, 100% perovskite phase was formed by using either acidic or basic catalyst. By using either acidic or basic catalyst, we were able to get very fine powders of uniform shape with an average particle size of 0.8-1.mu.m.

• 한국표면공학회지
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• 제38권4호
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• pp.167-173
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• 2005

Surface characteristics of HA(hydroxyapatite) coated dental implant alloy by Sol-Gel method were investigated using potentiostat, ICP, SEM, EDX, EPMA and surface roughness tester. Surface roughness of HA coated specimen by Sol-Gel showed higher than that of PVD coated specimen. Corrosion resistance increased in the order of $1\%$ lactic acid, artificial saliva, $0.5\%$ HCI and $0.9\%$ NaCl solution. Amount of Ca element release was higher than that of V and P in the $0.5\%$ HCI and $0.9\%$ NaCl solution.

• Bulletin of the Korean Chemical Society
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• 제17권2호
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• pp.158-162
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• 1996

The steady-state emission and fluorescence lifetimes of 1,3-dipyrenylpropane were measured in silicate sol-gel and xerogel matrices. In sol solution, the fluorescence emission spectra of monomer and excimer resemble those in hydrocarbon solvents. In gel and xerogel condition, however, the fluorescence spectra exhibit significant change, largely confirming the intramolecular motions in gel pores are influenced by microviscosity. The rate constants for intramolecular excimer formation were obtained from the measured fluorescence lifetimes and the rate processes for excimer forming in silicate sol-gel are described by a simple kinetic scheme.

• 한국세라믹학회지
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• 제40권4호
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• pp.380-384
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• 2003

The effects of the mole concentrations of precursor solution on the microstructure and dielectric properties of sol-gel deposited $Ba_{0.85}$S $r_{0.15}$Ti $O_3$(BST) thin films have been investigated. The films were of single perovskite phase with strong (100) preferred orientation when grown on LaNi0$_3$ buffered Pt/Ti/ $SiO_2$Si substrates using a diluted precursor solution. Variation of the precursor solution concentration resulted in a different microstructure and, in turn, affected the tunability of the sol-gel deposited films. It was observed that leakage currents increased asymmetrically for the negative and positive bias voltage with decreasing thickness. Overall results suggest that those BST films have acceptable properties f3r applications as room-temperature tunable elements.

• 상하수도학회지
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• 제13권3호
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• pp.101-106
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• 1999

This research aims to compare immobilized catalysts prepared by various methods and determine suitable $TiO_2$ catalyst for water purification. Sol-gel method by Anderson and powder coation method by Tanaka ate famous in the methods to immobilize catalyst. Therefore, the $TiO_2$ catalyst for this research was prepared by sol-gel method and powder coating method. Its structure was tested by X-ray diffractometer (XRD), Scanning electron microseope (SEM). Durability of a catalyst-support couple in an solution was investigated. too. Experimental results were summarized as following; i) Optimum ratio of Ti : $H_2O$ : $H^+$ to obtain stable sol was 1 : 10 : 0.1 and the XRD patterns of $TiO_2$ film immobilized by sol-gel method which were fired at $700^{\circ}C$ showed that the catalyst had an anatase structure. ii) The particle size of $TiO_2$ prepared by sol-gel method was less than $5{\mu}$, but it was observed that coated side was not unifiom. iii) Sol-gel method was very effective to obtain $TiO_2$ catalyst of thin film, but spreadability and durability of a catalyst-support couple in a solution were than $TiO_2$ film immobilized by powder coating method. iv) The particle size of $TiO_2$ immobilized by powder coating method was a little larger than it prepared by sol-gel method, but spreadability and uniformity of $TiO_2$ film and durability of a catalyst-support couple in a solution were better than it immobilized by sol-gel method.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2012년도 추계총회 및 학술대회 논문집
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• pp.137-138
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• 2012

ZnO 박막을 Sol-gel용액을 이용한 스핀코팅 방법으로 석영기판 위에 성장하였고 Sol-gel 용액의 온도 변화에 따른 구조적, 광학적 특성을 분석하였다. ZnO 박막의 구조적, 광학적 특성을 조사하기 위해 field-emission scanning electron microscopy, X-ray diffraction (XRD), photoluminescence (PL), 그리고 ultraviolet-visible (UV) spectroscopy을 사용하였다. PL 분석에서 ZnO 박막은 orange 계열의 발광을 하였으며, PL spectra는 3.3 eV 부근의 near-band edge emission (NBE) 피크와 2.0 eV 부근의 deep-level emission (DLE) 피크로 이루어져있다. 모든 sol-gel 용액 온도에서, DLE 피크가 NBE 피크보다 더 우세하고 이 DLE 피크는 sol-gel 용액의 온도가 증가함에 따라 점점 증가하다가 감소하는 것을 알 수 있다. 이런 DLE 피크는 산소 공공, 아연 공공, 침입형 산소, 침입형 아연 등과 같은 결함에 의한 것이며, ZnO 박막은 sol-gel 용액의 온도에 따라 결함의 특성이 변화하였다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2007년도 추계학술발표대회 및
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• pp.52.1-52.1
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• 2007

• 자원리싸이클링
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• 제18권6호
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• pp.30-37
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• 2009

소디움실리케이트 수용액으로부터 나트륨이온이 제거된 핵생성 산화실리케이트 수용액과 실리케이트 수용액을 pH 10~11로 조절하여 혼합한 다음, $20{\sim}80^{\circ}C$에서 솔-젤 반응하여 실리카 솔 입자를 제조하였다. 이 때 yellow silicomolybdate method를 이용하여 소디움실리케이트와 나트륨이온이 제거된 실리케이트 수용액의 특성과 이들 출발용액으로부터 솔-젤 반응에 의해 제조된 실리카 솔의 입자특성에 대하여 고찰하였다. $SiO_2$를 2 wt% 함유한 소디움실리케이트 수용액은 약 95% 이상의 반응성 실리케이트를 함유하며, 솔-젤 반응에 참여하는 반응성 실리케이트는 전체 실리카 기준 약 50% 정도이다. 반응온도가 증가함에 따라 silanol(Si-OH) 결합구조의 흡수피크 세기는 감소하고, siloxane(Si-O-Si) 결합구조의 흡수피크 세기가 증가하였다. 반응조건별로 제조된 실리카 솔 수용액의 zeta potential은 -40~-60 mV 범위로 분산성이 좋은 상태를 유지하였다. 실리카 솔 입자크기는 5~10 nm로 반응온도 증가에 따라 크기가 약간 감소하였다. 실리카 솔 제조 후, 2차 입자 성장을 위하여 실리케이트 수용액을 재 첨가하였을 경우에 실리카 솔입자 크기가 약 20 nm로 증가하였다.