Li1.5Al0.5Ti1.5(PO4)3 (LATP) is considered to be one of the promising solid-state electrolytes owing to its excellent chemical and thermal stability, wide potential range (~5.0 V), and high ionic conductivity (~10-4 S/cm). LATP powders are typically prepared via the sol-gel method by adding and mixing nitrate or alkoxide precursors with chelating agents. Here, the thermal properties, crystallinity, density, particle size, and distribution of LATP powders based on chelating agents (citric acid, acetylacetone, EDTA) are compared to find the optimal conditions for densely sintered LATP with high purity. In addition, the three types of LATP powders are utilized to prepare sintered solid electrolytes and observe the microstructure changes during the sintering process. The pyrolysis onset temperature and crystallization temperature of the powder samples are in the order AC-LATP > CA-LATP > ED-LATP, and the LATP powder utilizing citric acid exhibits the highest purity, as no secondary phase other than LiTi2PO4 phase is observed. LATP with citric acid and acetylacetone has a value close to the theoretical density (2.8 g/cm3) after sintering. In comparison, LATP with EDTA has a low sintered density (2.2 g/cm3) because of the generation of many pores after sintering.

K0.5Bi0.5TiO3 (KBT) thin films were prepared by sol-gel processing for future use in piezoelectric generators. It is believed that the annealing temperature of films plays an important role in the output performance of piezoelectric generators. KBT films prepared on Ni substrates were annealed at 500 ~ 700 oC. Tetragonal KBT films were formed after annealing process. As the annealing temperature increased, the grain size of KBT films increased. KBT thin films show piezoelectric constant (d33) from 23 to 41 pC/N. The increase of grain size in KBT films brought about output voltage and current in the KBT generators. Also, the increase in the displacement of specimens during bending test resulted in increases in output voltage and current. Although KBT generators showed lower output power than those of generators prepared using NBT films, as reported previously, the KBT films prepared by sol-gel method show applicability as piezoelectric thin films for lead-free nanogenerators, along with NBT films.

목적 : 소다-라임-실리카 유리(soda-lime-silica glass,SG) 기판위에 Ti, Ba-naphthenates를 출발원료로 사용하고 졸겔법으로 나노 결정질 TiO2, BaTiO3 박막을 제조하였다. 박막의 특성을 분석하기 위하여 X-선 회절 분석, 전자현미경, UV스펙트럼을 이용하여 연구하였다. 방법 : 코팅용액을 soda-lime-silica glass 기판 위에 스핀코팅하고 공기분위기에서 500℃에서 열분해시켜 박막을 제조하였다. 제조된 TiO2, BaTiO3 박막의 결정화도는 고분해능 X-선 회절분석법으로 그리고 표면미세구조와 거칠기는 전계 방출 현미경과 원자간력 현미경으로 또 자외선(200〜380 nm), 가시광선(380〜750 nm), 적외선(750〜900 nm) 영역의 투과율은 UV-Visible-NIR 분광광도계로 측정되었다. 결과 : TiO2박막은 아나타제 상이 존재하였으며, BaTiO3 박막은 최고 피크가 확인되지 않았다. 열처리한 TiO2, BaTiO3 박막의 가시광선 투과율은 80% 이상의 투과율을 나타냈으며, BaTiO3 박막은 TiO2 박막보다 자외선 및 청광 차단율이 높았다. 결론 : BaTiO3 박막은 TiO2 보다 자외선 및 청광에 대해 더 높은 차단율이 나타냈으며, 가시광선 투과율은 제조된 모든 박막에서 80% 이상의 투과율이 측정되었다.

Transition metal oxide is widely used as a water electrolysis catalyst to substitute for a noble metal catalyst such as IrO2 and RuO2. In this study, the sol-gel method is used to synthesize the CuxCo3-xO4 catalyst for the oxygen evolution reaction (OER),. The CuxCo3-xO4 is synthesized at various calcination temperatures from 250 ℃ to 400 ℃ for 4 h. The CuxCo3- xO4 synthesized at 300 ℃ has a perfect spinel structure without residues of the precursor and secondary phases, such as CuO. The particle size of CuxCo3-xO4 increases with an increase in calcination temperature. Amongst all the samples studied, CuxCo3- xO4, which is synthesized at 300?, has the highest activity for the OER. Its onset potential for the OER is 370 mV and the overpotential at 10 mA/cm2 is 438 mV. The tafel slope of CuxCo3-xO4 synthesized at 300 ℃ has a low value of 58 mV/dec. These results are mainly explained by the increase in the available active surface area of the CuxCo3-xO4 catalyst.

The manganese-, nickel-, and aluminum-doped cobalt ferrite powders, Mn0.2Co0.8Fe2O4, Ni0.2Co0.8Fe2O4, and Al0.2CoFe1.8O4, are fabricated by the sol-gel method, and the crystallographic and magnetic properties of the powders are studied in comparison with those of CoFe2O4. All the ferrite powders are nano-sized and have a single spinel structure with the lattice constant increasing in Mn0.2Co0.8Fe2O4 but decreasing in Ni0.2Co0.8Fe2O4 and Al0.2CoFe1.8O4. All the Mössbauer spectra are fitted as a superposition of two Zeeman sextets due to the tetrahedral and octahedral sites of the Fe3+ ions. The values of the magnetic hyperfine fields of Ni0.2Co0.8Fe2O4 are somewhat increased in the A and B sites, while those of Mn0.2Co0.8Fe2O4 and Al0.2CoFe1.8O4 are decreased. The variation of Mössbauer parameters is explained using the cation distribution equation, superexchange interaction and particle size. The hysteresis curves of the ferrite powders reveal a typical soft ferrite pattern. The variation in the values of saturation magnetization and coercivity are explained in terms of the site distributions, particle sizes and the spin magnetic moments of the doped ions.

고분자 전해질 연료전지의 연료에 포함된 일산화탄소의 선택적 산화를 위하여, 귀금속 촉매를 대체하기 위한 CuO-CeO2 복합 산화물 촉매를 졸-겔법과 공침법으로 제조하였다. 졸-겔법으로 촉매 제조 시 Cu/Ce의 비와 가수분해 비를 변화시켰다. 제조한 촉매의 활성은 귀금속 촉매(Pt/γ-Al2O3)와 비교하였다. Cu/Ce의 비를 변화시키면서 제조한 촉매 중 Cu/Ce의 비가 4:16인 촉매가 가장 높은 CO 전환율(90%)과 선택도(60%)를 나타내었다. 촉매의 제조에서 가수분해 비가 증가할수록 촉매 표면적이 증가하였고, 아울러 촉매 활성 또한 증가하였다. 공침법으로 제조한 촉매와 1wt% Pt/γ-Al2O3 촉매의 가장 높은 CO 전환율은 각각 82% 및 81%인 반면, 졸-겔법으로 제조한 촉매의 경우는 90%가 얻어졌다. 이는 졸-겔법으로 제조한 촉매가 공침법으로 제조한 촉매나 귀금속 촉매보다 더 높은 촉매활성을 보임을 의미한다. CO-TPD 실험을 통하여, 낮은 온도(140℃)에서 CO를 탈착하는 촉매가 본 반응에서 더 높은 촉매활성을 보임을 알 수 있었다.

Nitrogen-doped titanium dioxide (N-doped TiO2) is attracting continuously increasing attention as a material for environmental photocatalysis. The N-atoms can occupy both interstitial and substitutional positions in the solid, with some evidence of a preference for interstitial sites. In this study, N-doped TiO2 is prepared by the sol–gel method using NH4OH and NH4Cl as N ion doping agents, and the physical and photocatalytic properties with changes in the synthesis temperature and amount of agent are analyzed. The photocatalytic activities of the N-doped TiO2 samples are evaluated based on the decomposition of methylene blue (MB) under visible-light irradiation. The addition of 5 wt% NH4Cl produces the best physical properties. As per the UV-vis analysis results, the N-doped TiO2 exhibits a higher visible-light activity than the undoped TiO2. The wavelength of the N-doped TiO2 shifts to the visible-light region up to 412 nm. In addition, this sample shows MB removal of approximately 81%, with the whiteness increasing to +97 when the synthesis temperature is 600℃. The coloration and phase structure of the N-doped TiO2 are characterized in detail using UV-vis, CIE Lab color parameter measurements, and powder X-ray diffraction (XRD).

This study synthesized pure anatase carbon doped TiO2 photocatalysts supported on a stainless steel mesh using a sol-gel solution of 8% polyacrylonitrile (PAN)/dimethylformamide (DMF)/TiCl4. The influence of the pyrolysis temperature and holding time on the morphological characteristics, particle sizes and surface area of the prepared catalyst was investigated. The prepared catalysts were characterized by several analytical methods: high resolution scanning electron microscopy (HRSEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), and X-ray photoelectron spectroscopy (XPS). The XRD patterns showed that the supported TiO2 nanocrystals are typically anatase, polycrystalline and body-centered tetragonal in structure. The EDS and XPS results complemented one another and confirmed the presence of carbon species in or on the TiO2 layer, and the XPS data suggested the substitution of titanium in TiO2 by carbon. Instead of using calcination, PAN pyrolysis was used to control the carbon content, and the mesoporosity was tailored by the applied temperature. The supported TiO2 nanocrystals prepared by pyrolysis at 300, 350, and 400ºC for 3 h on a stainless steel mesh were actual supported carbon doped TiO2 nanocrystals. Thus, PAN/DMF/TiCl4 offers a facile, robust sol-gel related route for preparing supported carbon doped TiO2 nanocomposites.

The sol-gel method is the simplest method for synthesizing monodispersed silica particles. The purpose of this study is to synthesize uniform, monodisperse spherical silica nanoparticles using tetraethylorthosilicate (TEOS) as the silica precursor, ethanol, and deionized water in the presence of ammonia as a catalyst. The reaction time and temperature and the concentration of the reactants are controlled to investigate the effect of the reaction parameters on the size of the synthesized particles. The size and morphology of the obtained silica particles are investigated using transmission electron microscopy and particle size analysis. The results show that monodispersed silica particles over a size range of 54-504 nm are successfully synthesized by the sol-gel method without using any additional process. The nanosized silica particles can be synthesized at higher TEOS/H2O ratios, lower ammonia concentrations, and especially, higher reaction temperatures.

고분자 전해질 막의 성능을 개선하고자 사용된 대표적인 무기물인 solid acid가 첨가된 복합막의 경우 고온에서 높은 열안정성을 나타내며 친수성이 강해지는 장점을 나타내지만 물에 녹는 단점을 가지고 있다. 그러므로 본 연구에서는 phosphotungstic acid(PWA)의 이온전도성을 증가시키며 물에 용해되는 성질을 제거하기 위하여 실리카 입자를 sol-gel법을 이용하여 술폰산기와 아민그룹을 도입시킨 입자를 제조한 후 sulfonated poly(arylene ether sulfone)(SPAES) 고분자에 첨가하여 복합막을 제조하였으며 특성평가가 이루어졌다.

Tungsten trioxide thin films are successfully synthesized by a sol-gel method using tungsten hexachlorideas precursors. The structural, chemical, and optical properties of the prepared films are characterized by scanning elec-tron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and UV-Vis spectrophotometry. The electrochem-ical and electrochromic properties of the films before and after heat treatment are also investigated by cyclicvoltammetry, chronoamperometry, and in situ transmittance measurement system. Compared to as-prepared films, heat-treated tungsten trioxide thin films exhibit a higher electrochemical reversibility of 0.81 and superior coloration effi-ciency of 65.7 cm2/C, which implies that heat treatment at an appropriate temperature is a crucial process in a sol-gelmethod for having a better electrochromic performance.

Pb1-xMoO4:Er3+/Yb3+ phosphors with various doping concentrations of Er3+ and Yb3+ (x = Er3++Yb3+, Er3+ = 0.05, 0.1, 0.2, and Yb3+ = 0.2, 0.45) are successfully synthesized using a microwave sol-gel method, and the up-conversion photoluminescence properties are investigated. Well-crystallized particles, which are formed after heat treatment at 900 oC for 16 h, exhibit a fine and homogeneous morphology with particle sizes of 2-5 μm. Under excitation at 980 nm, the Pb0.7MoO4: Er0.1Yb0.2 and Pb0.5MoO4:Er0.05Yb0.45 particles exhibit a strong 525 nm emission band, a weak 550 nm emission band in the green region, and a very weak 655 nm emission band in the red region. The Raman spectra of the doped particles indicate the presence of strong peaks at higher and lower frequencies induced by the disordered structures of Pb1-xMoO4 through the incorporation of the Er3+ and Yb3+ ions into the crystal lattice, which results in the unit cell shrinkage accompanying the new phase formation of the MoO4-x group.

Anti-reflection coating films have used to increase the transmittance of displays and enhance the efficiency of solar cells. Hydrophobic anti-reflection coating films were fabricated on a glass substrate by sol-gel method. To fabricate an anti-reflection film with a high transmittance, poly ethylene glycol (PEG) was added to tetraethyl orthosilicate (TEOS) solution. The content of PEG was changed from 1 to 4 wt% in order to control the morphology, thickness, and refractive index of the SiO2 thin films. The reflectance and transmittance of both sides of the coated thin film fabricated with PEG 4 wt% solution were 0.3% and 99.4% at 500 nm wavelength. The refractive index and thickness of the thin film were n = 1.29 and d = 105 nm. Fluoro alkyl silane (FAS) was used for hydrophobic treatment on the surface of the anti-reflection thin film. The contact angle was increased from 13.2˚ to 113.7˚ after hydrophobic treatment.

The sol-gel method was used to prepare binary metal oxide (IrO2-RuO2) pH sensor. The electrodes that mole percent compositions (mol%) of IrO2 and RuO2 were 70:30 and 30:70 were selected. The characterizations of Nernstian response over pH range, response rate, interference on alkaline metals and reproducibility were investigated. Also the electroanalytical properties of these electrodes were evaluated in comparison with a commercial glass pH electrode. The composition of IrO2:RuO2 70:30 mol% was chosen as better electrode formulation. The electrode was not susceptible to the action of interfering ions such as Li+, Na+ and K+.

Li1+xAlxTi2-x(PO4)3(LATP) is a promising solid electrolyte for all-solid-state Li ion batteries. In this study, LATP isprepared through a sol-gel method using relatively the inexpensive reagents TiCl4. The thermal behavior, structuralcharacteristics, fractured surface morphology, ion conductivity, and activation energy of the LATP sintered bodies areinvestigated by TG-DTA, X-ray diffraction, FE-SEM, and by an impedance method. A gelation powder was calcined at 500oC.A single crystalline phase of the LiTi2(PO4)3(LTP) system was obtained at a calcination temperature above 650oC. The obtainedpowder was pelletized and sintered at 900oC and 1000oC. The LTP sintered at 900~1000oC for 6 h had a relatively low apparentdensity of 75~80%. The LATP(x=0.3) pellet sintered at 900oC for 6 h was denser than those sintered under other conditionsand showed the highest ion conductivity of 4.50×10−5S/cm at room temperature. However, the ion conductivity of LATP(x=0.3) sintered at 1000oC decreased to 1.81×10−5S/cm, leading to Li volatilization and abnormal grain growth. For LATPsintered at 900oC for 6 h, x=0.3 shows the lowest activation energy of 0.42eV in the temperature range of room temperatureto 300oC.

The sol-gel technique has been studied to fabricate a homogeneous Fe-Mo/MgO catalyst. Ambient effects (air, Ar, and H2) on thermal decomposition of the citrate precursor have been systematically investigated to fabricate an Fe-Mo/MgO catalyst. Severe agglomeration of metal catalyst was observed under thermal decomposition of citrate precursor in air atmosphere. Ar/H2 atmosphere effectively restricted agglomeration of bimetallic catalyst and formation of highly-dispersed Fe-Mo/MgO catalyst with high specific surface-area due to the formation of Fe-Mo nanoclusters within MgO support. High-quality thin-multiwalled carbon nanotubes (t-MWCNTs) with uniform diameters were achieved on a large scale by catalytic decomposition of methane over Fe-Mo/MgO catalyst prepared under Ar-atmosphere. The produced t-MWCNTs had outer diameters in the range of 4-8 nm (average diameter ~6.6 nm) and wall numbers in the range of 4-7 graphenes. The as-synthesized t-MWCNTs showed product yields over 450% relative to the utilized Fe-Mo/MgO catalyst, and indicated a purity of about 85%.

Carbon nanotube(CNT) plays an essential role in various fields of nano based science and technology. Recently, silica coated CNT composites are interested because they are useful for the optical, magnetical, and catalytic applications. In this report, carboxyl groups were introduced on the MWCNT using nitric acid. In order to maximize the silica encapsulation efficiency, carboxyl groups of MWCNT reacted with a silane coupling agent were used to prepare silica coated MWCNT. Due to their strong interaction between modified MWCNT and TEOS. Silica layer with a controllable thickness was achieved. Silica coated MWCNT were further utilized as the template for the synthesis of hollow silica nanotubes after 800℃ calcination.

Titanium dioxide (), which is one of the most basic materials in our daily life, plays a key role for environment purification. We synthesized nanoparticles by the hydrolysis reactions of titanium tetraisopropoxide using as a peptizing agent or as a chelating agent in the sol-gel method. The powder consisted of a rod shape or a spherical shape according to the concentration and kind of acid. The physical properties of nanoparticles were investigated with X-ray diffraction, SEM, BET analysis, and UV-Vis spectrophotometer.

In this study, the silica-based hybrid material with high barrier property was prepared by incorporating ethylene-vinyl alcohol (EVOH) copolymer, which has been utilized as packaging materials due to its superior gas permeation resistance, during sol-gel process. In preparation of this EVOH/SiO2 hybrid coating materials, the (3-glycidoxy-propyl)-trimethoxysilane (GPTMS) as a silane coupling agent was employed to promote interfacial adhesion between organic and inorganic phases. As confirmed from FT-IR analysis, the physical interaction between two phases was improved due to the increased hydrogen bonding, resulting in homogeneous microstructure with dispersion of nano-sized silica particles. However, depending on the range of content of added silane coupling agent (GPTMS), micro-phase separated microstructure in the hybrid could be observed due to insufficient interfacial attraction or possibility of polymerization reaction of epoxide ring in GPTMS. The oxygen barrier property of the mono-layer coated BOPP (biaxially oriented polypropylene) film was examined for the hybrids containing various GPTMS contents. Consequently, it is revealed that GPTMS should be used in an optimum level of content to produce the high barrier EVOH/SiO2 hybrid material with an improved optical transparency and homogeneous phase morphology.