TiO2 nanoparticles were synthesized by a sol-gel process using titanium tetra isopropoxide as a precursor at room temperature. Ag-doped TiO2 nanoparticles were prepared by photoreduction of AgNO3 on TiO2 under UV light irradiation and calcinated at 400 oC. Ag-doped TiO2 nanoparticles were characterized for their structural and morphological properties by Xray diffractometry (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and transmission electron microscopy (TEM). The photocatalytic properties of the TiO2 and Ag-doped TiO2 nanoparticles were evaluated according to the degree of photocatalytic degradation of gaseous benzene under UV and visible light irradiation. To estimate the rate of photolysis under UV (λ = 365 nm) and visible (λ ≥ 410 nm) light, the residual concentration of benzene was monitored by gas chromatography (GC). Both undoped/doped nanoparticles showed about 80 % of photolysis of benzene under UV light. However, under visible light irradiation Ag-doped TiO2 nanoparticles exhibited a photocatalytic reaction toward the photodegradation of benzene more efficient than that of bare TiO2. The enhanced photocatalytic reaction of Ag-doped TiO2 nanoparticles is attributed to the decrease in the activation energy and to the existence of Ag in the TiO2 host lattice, which increases the absorption capacity in the visible region by acting as an electron trapper and promotes charge separation of the photoinduced electrons (e−) and holes (h+). The use of Ag-doped TiO2 nanoparticles preserved the option of an environmentally benign photocatalytic reaction using visible light; These particles can be applicable to environmental cleaning applications.

NaLa1-x(MoO4)2:Ho3+/Yb3+ phosphors with the correct doping concentrations of Ho3+ and Yb3+ (x = Ho3++Yb3+, Ho3+ = 0.05 and Yb3+ = 0.35, 0.40, 0.45 and 0.50) were successfully synthesized by the microwave-modified sol-gel method. Well-crystallized particles formed after heat-treatment at 900 oC for 16 h showed a fine and homogeneous morphology with particle sizes of 3-5 μm. The optical properties were examined using photoluminescence emission and Raman spectroscopy. Under excitation at 980 nm, the UC intensities of the doped samples exhibited strong yellow emissions based on the combination of strong emission bands at 545-nm and 655-nm emission bands in green and red spectral regions, respectively. The strong 545-nm emission band in the green region corresponds to the 5S2/5F4→ 5I8 transition in Ho3+ ions, while the strong emission 655-nm band in the red region appears due to the 5F5→ 5I8 transition in Ho3+ ions. Pump power dependence and Commission Internationale de L'Eclairage chromaticity of the upconversion emission intensity were evaluated in detail.

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.

The oxide films formed on etched aluminum foils play an important role as dielectric layers in aluminum electrolytic capacitors. Y2O3-doped ZrO2 (YZ) films were coated on the etched aluminum foils by sol-gel dip coating, and the electrical properties of YZ-coated Al foils were characterized. YZ films annealed at 450 oC were crystallized into a cubic phase, and as the Y2O3 doping content increased, the unit cell of ZrO2 expanded and the grain size decreased. The etch pits of Al foils were filled by YZ sol when it dried at atmospheric pressure after repeating for several times, but this step could essentially be avoided when being dried in a vacuum. YZ-coated foils indicated that the specific capacitance and dissipation factor were 2-2.5 μF/cm2 and 2-4 at 1 kHz, respectively, and the leakage current and withstanding voltage of films approximately 200 nm thick were 5 × 10−4A at 21 V and 22 V, respectively. After being anodized at 500 V, the foils exhibited a specific capacitance and dissipation factor of 0.6-0.7 μF/cm2 and 0.1-0.2, respectively, at 1 kHz, while the leakage current and withstanding voltage were 2 × 10−4 - 3 × 10−5 A at 400 V and 420-450 V, respectively. This suggests that YZ film is a promising dielectric that can be used in high voltage Al electrolytic capacitors.

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.

PTMSP[Poly(1-trimethylsilyl-1-propyne)]에 TEOS (tetraethoxysilane), TMOS (tetramethoxysilane), MTMOS (methyltrimethoxysilane), 그리고 PTMOS (phenyltrimethoxysilane)의 함량을 0, 15, 20, 30 wt%로 달리하여 졸-겔법을 이용하 여 PTMSP-silica 복합막을 제조하였다. PTMSP-silica 복합막의 알콕시실란 함량에 따른 H2, N2의 기체투과도와 N2에 대한 H2의 이상 선택도를 조사하였다. H2와 N2의 투과도는 알콕시실란 함량이 0∼20 wt% 범위에서는 증가하다가 알콕시실란 함 량이 20∼30 wt% 범위에서는 감소하였다. N2에 대한 H2의 이상 선택도는 TEOS와 PTMOS의 함량이 0∼15 wt% 범위에서 는 감소하였으며, 15∼30 wt% 범위에서는 다시 증가하였다. Robeson upper bound와 비교할 때, PTMSP-silica 복합막은 TEOS 함량이 30 wt%, MTMOS 함량이 20 wt% 그리고 PTMOS 함량이 30 wt%에서 투과도와 이상 선택도가 동시에 향상된 것으로 나타났다.

NaLa1-x(MoO4)2:Eu3+/Yb3 phosphors with doping concentrations of Eu3+ and Yb3+ (x=Eu3++Yb3+, Eu3+=0.05, 0.1,0.2 and Yb3+=0.2, 0.45) were successfully synthesized by the microwave-modified sol-gel method, and the upconversion andspectroscopic properties were investigated. Well-crystallized particles showed a fine and homogeneous morphology with particlesizes of 2-5µm. Under excitation at 980nm, NaLa0.5(MoO4)2:Eu0.05Yb0.45 particles exhibited a strong 525-nm emission bandand a weak 550-nm emission band in the green region, and a very weak 665-nm emission band in the red region. The strong525-nm emission in the green region corresponds to the 7F1→5D1 transition and the weak 550-nm emission in the green regioncorresponds to the 7F0→5D2 transition, while the very weak emission 665-nm band in the red region corresponds to the5D0→7F3 transition. The Raman spectra of the doped particles indicated the domination of strong peaks at higher frequenciesof 762, 890, 1358 and 1430cm−1 and weak peaks at lower frequencies of 323, 388 and 450cm−1 induced by the disorder ofthe [MoO4]2− groups with the incorporation of the Eu3+ and Yb3+ elements into the crystal lattice or by a new phase formation.

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+.

ZrO2 films were coated on aluminum etching foil by the sol-gel method to apply ZrO2 as a dielectric material in an aluminum(Al) electrolytic capacitor. ZrO2 films annealed above 450˚C appeared to have a tetragonal structure. The withdrawal speed during dip-coating, and the annealing temperature, influenced crack-growth in the films. The ZrO2 films annealed at 500˚C exhibited a dielectric constant of 33 at 1 kHz. Also, uniform ZrO2 tunnels formed in Al etch-pits 1μm in diameter. However, ZrO2 film of 100-200 nm thickness showed the withstanding voltage of 15 V, which was unsuitable for a high-voltage capacitor. In order to improve the withstanding voltage, ZrO2-coated Al etching foils were anodized at 300 V. After being anodized, the Al2O3 film grew in the directions of both the Al-metal matrix and the ZrO2 film, and the ZrO2-coated Al foil showed a withstanding voltage of 300 V. However, the capacitance of the ZrO2-coated Al foil exhibited only a small increase because the thickness of the Al2O3 film was 4-5 times thicker than that of ZrO2 film.

The Mg-enriched magnesium aluminum silicate (MAS) glass is known for its higher mechanical strength and chemical resistance. Among such glasses, cordierite (Mg2Al4Si5O18) is well known to have a low thermal expansion and low melting point. Polycrystalline engineering ceramics such as alumina can be strengthened by a surface modification with low thermal expansion materials. The present study involves the synthesis of cordierite by a sol-gel process and investigates the effect of glass penetration on the surface of alumina. The cordierite powders were prepared from Al(OC3H7)3, Mg(OC2H5)2 and tetraethyl orthosilicate by hydrolysis and condensation reaction. The cordierite powders were characterized by X-ray diffraction (XRD, Rigaku), scanning electron microscope (SEM, JEOL: JSM-5610), energy dispersive spectroscopy (EDS, JEOL: JSM-5610), and universal testing machine (UTM, INSTRON). The X-ray diffraction patterns showed that the synthesized particles were μ-cordierite calcined at 1100˚C for 1 h. The shape of synthesized cordierite was changed from μ-cordierite to α-cordierite with increasing calcination temperature. Synthesized cordierite was used for surface modification of alumina. Cordierite powders penetrated deeply into the alumina sample along grain boundaries with increasing temperature. The results of surface modification tests showed that the strength of the prepared alumina sample increased after surface modification. The strength of a surface modified with synthesized cordierite increased the most, to about 134.6MPa.

Nanocomposites comprised of graphene oxide (GO) nanosheets and magnesium oxide (MgO) nanoparticles were synthesized by a sol-gel process. The synthesized samples were studied by X-ray powder diffraction, atomic force microscopy, transmission electron microscopy, and energy-dispersive X-ray analysis. The results show that the MgO nanoparticles, with an average diameter of 70 nm, are decorated uniformly on the surface of the GOs. By controlling the concentration of the MgO precursors and reaction cycles, it was possible to control the loading density and the size of the resulting MgO particles. Because the MgO particles are robustly anchored on the GO structure, the MgO/GOs nanocomposites will have future applications in the fields of adsorption and chemical sensing.

There is increasing interest in zirconia as a dental material due to its aesthetics, as well as the exceptionally high fracture toughness and high strength that are on offer when it is alloyed with certain oxides like yttria. In recent years, many solution based chemical synthesis methods have been reported for synthesis of zirconia, of which the sol-gel method is considered to be best. Here, we synthesize zirconia by a sol gel assisted precipitation method using either PEG or PVA as a stabilizing agent. Zirconia sol is first synthesized using the hydrothermal method. We used NaOH as the precipitating agent in this method because it is easy to remove from the final solution. Zirconium and yttrium salts are used as precursors and PEG or PVA are used as stabilizers to separate the metal ions. The resulting amorphous zirconia powder is calcined at 900˚C for 2 h to get crystallized zirconia. XRD analysis confirmed the partially stabilized zirconia synthesis in all the synthesized powders. SEM was taken to check the morphology of the powder synthesized using either PEG or PVA as a stabilizing agent and finally the transparency was calculated. The results confirmed that the powder synthesized with 10 % PVA as the stabilizing agent had highest percentage of transparency among all the synthesized powder.

Nano-sized β-SiC nanoparticles were synthesized combined with a sol-gel process and a carbothermal process. TEOS and carbon black were used as starting materials for the silicon source and carbon source, respectively. SiO2 nanoparticles were synthesized using a sol-gel technique (Stober process) combined with hydrolysis and condensation. The size of the particles could be controlled by manipulating the relative rates of the hydrolysis and condensation reactions of tetraethyl orthosilicate (TEOS) within the micro-emulsion. The average particle size and morphology of synthesized silicon dioxide was about 100nm and spherical, respectively. The average particles size and morphology of the used carbon black powders was about 20nm and spherical, respectively. The molar ratio of silicon dioxide and carbon black was fixed to 1:3 in the preparation of each combination. SiO2 and carbon black powders were mixed in ethanol and ball-milled for 12 h. After mixing, the slurries were dried at 80˚C in an oven. The dried powder mixtures were placed in alumina crucibles and synthesized in a tube furnace at 1400~1500˚C for 4 h with a heating rate of 10˚C/min under flowing Ar gas (160 cc/min) and furnace cooling down to room temperature. SiC nanoparticles were characterized by XRD, TEM, and SAED. The XRD results showed that high purity beta silicon carbide with excellent crystallinity was synthesized. TEM revealed that the powders are spherical shape nanoparticles with diameters ranging from 15 to 30 nm with a narrow distribution.

(Na, K) NbO3 thick film was successfully achieved using a sol-gel coating process with the addition of polyvinylpyrrolidone (PVP) to a metal alkoxide solution. The transparent coating solution, mixed with Nb:PVP = 1:1 in a molar ration, was synthesized by evaporating the solvent to over 62.5 wt%. Additive PVP increased the viscosity of the solution so that the coating thickness could be enhanced. The thickness of the (Na, K) NbO3 film assisted by PVP was ca. 320 nm at the time of deposition; this value is four times thicker than that of the sample fabricated without PVP. Also, due to PVP binding with the OH groups of the metal alkoxide, the condensation reaction in the film was suppressed. The crystalline size of the (Na, K) NbO3 films assisted by PVP was ca. 15 nm smaller than that of the film fabricated without PVP. After the sintering process at 700˚C, the (Na, K) NbO3 films were mainly composed of randomly oriented (Na, K) NbO3 phase of perovskite crystal structure, including a somewhat secondary phase of K2Nb4O11. However, by adding PVP, the content of the secondary phase became quite smaller than that of the sample without PVP. It was thought that the addition of PVP might have the effect of restraining the loss of potassium and that PVP could hold metalloxane by strong hydrogen bonding before complete decomposition. Therefore, the film thickness of the (Na, K) NbO3 films could be considerably advanced and made more crack-free by the addition of PVP.

This paper describes the spherical ammonium diuranate gel particles which are the intermediated material of the microsphere for an VHTR(very high temperature reactor) nuclear fuel. The characteristics of the intermediate-ADU gel particles prepared by AWD(ageing, washing, and drying) and FB(fluidized-bed) apparatus were examined and compared in a sol-gel fabrication process. The electrical conductivity of washing filtrate from the FB treating and the surface area of dried-ADU gel particles were higher than those of AWD treating. Also, an internal pore volume in dried-ADU gel particles showed a more decrease in AWD treatment than FB treatment because of decomposition of PVA affected by the washing time. However, the internal microstructures of ADU gel particles were similar regardless of the process variation.

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.

Fe/SiO2 core-shell type composite nanoparticles have been synthesized using a reverse micelle process combined with metal alkoxide hydrolysis and condensation. Nano-sized SiO2 composite particles with a core-shell structure were prepared by arrested precipitation of Fe clusters in reverse micelles, followed by hydrolysis and condensation of organometallic precursors in micro-emulsion matrices. Microstructural and chemical analyses of Fe/SiO2 core-shell type composite nanoparticles were carried out by TEM and EDS. The size of the particles and the thickness of the coating could be controlled by manipulating the relative rates of the hydrolysis and condensation reaction of TEOS within the micro-emulsion. The water/surfactant molar ratio influenced the Fe particle distribution of the core-shell composite particles, and the distribution of Fe particles was broadened as R increased. The particle size of Fe increased linearly with increasing FeNO3 solution concentration. The average size of the cluster was found to depend on the micelle size, the nature of the solvent, and the concentration of the reagent. The average size of synthesized Fe/SiO2 core-shell type composite nanoparticles was in a range of 10-30 nm and Fe particles were 1.5-7 nm in size. The effects of synthesis parameters, such as the molar ratio of water to TEOS and the molar ratio of water to surfactant, are discussed.

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%.