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A dense gadolinia-doped ceria (GDC) interdiffusion barrier layer as thin as 300 nm was successfully fabricated on a rigid anode/electrolyte bilayer substrate using the chemical solution deposition (CSD) process for intermediate temperature solid oxide fuel cells (SOFCs). Drying-related macro-defects were removed by employing drying control chemical additives (DCCA), which effectively relieved drying stresses. The major process flaws caused by the constraining effects of the rigid substrate were completely eliminated by the addition of GDC nanoparticles into the chemical solution, which suppressed the generation of microstructural anisotropy by mitigating the predominant bi-axial substrate constraints. As a consequence, a thin film GDC interlayer was successfully deposited with a high volumetric density, effectively preventing the chemical interaction between the electrolyte and cathode during the fabrication process and subsequent operation. The cell test and microstructural analysis confirmed excellent electrochemical performance and structural and chemical stability. The CSD process presented in this paper is considered to be a promising technology for the practical preparation of GDC thin film barrier layers for intermediate temperature SOFCs based on the film quality, processing costs and potential for large-scale production.

A 500 nm thick thin film YSZ (yttria-stabilized zirconia) electrolyte was successfully fabricated on a conventionally processed anode substrate by spin coating of chemical solution containing slow-sintering YSZ nanoparticles with the particle size of 20 nm and subsequent sintering at 1100 °C. Incorporation of YSZ nanoparticles was effective for suppressing the differential densification of ultrafine precursor powder by mitigating the prevailing bi-axial constraining stress of the rigid substrate with numerous local multi-axial stress fields around them. In particular, adding 5 vol% YSZ nanoparticles resulted in a dense and uniform thin film electrolyte with narrow grain size distribution, and fine residual pores in isolated state. The thin film YSZ electrolyte placed on a rigid anode substrate with the GDC (gadolinia-doped ceria) and LSC (La0.6Sr0.4CoO3−δ) layers deposited by PLD (pulsed laser deposition) processes revealed that it had fairly good gas tightness relevant to a SOFC (solid oxide fuel cell) electrolyte and maintained its structural integrity during fabrication and operation processes. In fact, the open circuit voltage was 1.07 V and maximum power density was 425 mW/cm2 at 600 °C, which demonstrates that the chemical solution route can be a viable means for reducing electrolyte thickness for low- to intermediate-temperature SOFCs.

An extremely thin bilayer electrolyte consisting of yttria-stabilized zirconia (YSZ) and gadolinia-doped ceria (GDC) is successfully fabricated on a sintered NiO-YSZ substrate. Major processing flaws are effectively eliminated by applying local constraints to YSZ nanoparticles, and excellent open circuit voltage and cell performance are demonstrated in a solid oxide fuel cell (SOFC) at intermediate operating temperatures.

New dense composites comprised of a lanthanium manganite system, (La1xSrx)(Mn0.85Fe0.05Co0.05Ni0.05)O3+δ (LSMFCN, Sr2+ (x) = 0∼0.4 mole) and yttria-stabilized zirconia (YSZ) were fabricated for use as oxygen separation membranes. The densification behavior of the LSMFCN/YSZ composites were studied by sintering with different ratios of LSMFCN and YSZ at various temperatures in air. A density of about 95% was achieved for a sintering temperature of 1200°C. The electrical conductivity of the LSMFCN0/YSZ composites as a function of reciprocal absolute temperature with various YSZ contents was measured. The activation energies for conduction below and above 500°C were about 89 kJ/mol and 68 kJ/mol, respectively. The oxygen permeation flux increased until the YSZ concentration was 60 wt. %, then decreased at 80 wt. % of YSZ. The oxygen permeation flux of the 0.5 mm composite membrane was 1.06 sccm/cm2 at a 4:6 mixed ratio of LSMFCN0 /YSZ at 1200°C.

Nanocrystalline spherical particle (NP) with a dimension of 5 5.5 nm and several nanorods (NR) with different aspect ratios (diameter length: 5 8.5, 4 15, 4 18 and 3.5 22 nm) were selectively synthesized by a solvothermal process combined with non-hydrolytic sol-gel reaction. With varying the molar ratio of TTIP to oleic acid from 1:1 to 1:16, the NRs in the pure anatase phase were elongated to the c-axis direction. The prepared NP and NRs were applied for the formation of nanoporous layers in dye-sensitized solar cell (DSSC). Among them, NR2 ( nanorod with 4 15 nm) exhibited the highest cell performance: Its photovoltaic conversion efficiency () of 6.07%, with of 13.473 mA/, of 0.640 V, and FF of 70.32%, was 1.44 times that of NP with a size of 5 5.5 nm. It was observed from the transient photoelectron spectroscopy and the incident photon to current conversion efficiency (IPCE) spectra that the films derived from NR2 demonstrate the longest electron diffusion length () and the highest external quantum efficiency (EQE).

A solvothermal method is described for preparing nanomaterials of titanium dioxide (TiO2) while controlling the growth of rod-shaped nanomaterials. Titanium (IV) isopropoxide (TTIP) and butyl ether were chosen as the precursor and solvent, respectively. Oleic acid and decanoic acid were used as the surfactant. TiO2 nanospherical particles and nano-rods were synthesized in mass quantities by adjusting the kind of surfactant, the concentration of the precursor, and the solvothermal reaction temperature. The synthesized TiO2 nanospherical particles and nanorods were uniform and transparent in the toluene. The TiO2 nanospherical particles were about 3.5 nm in size. The TiO2 nanospherical particles and nanorods were of a highly crystalline anatase structure. The direction of growth of the TiO2 nanorods was [001] and the band gap energy of the TiO2 nanorods, evaluated by optical absorption, was 3.34 eV.

An effect of strontium ion doping on the structural, thermal, morphological and electrical properties of a co-doped lanthanum manganite system, La1−xSrx Mn0.85Fe0.05Co0.05Ni0.05O3+i (x = 0-0.4 mole) is inves- tigated for the solid oxide fuel cell cathode application. The submicron and rhombohedral structured sample, synthesized by the Pechini method, exhibited a decrease in the unit cell volume with increasing x. The thermogravimetry study portrayed nearly fivefold weight loss for a sample with x = 0.3 mole rela- tive to the La0.75Sr0.25MnO3+i and suggested an improvement in the concentration of the oxygen vacancy for ion migration due to the co-doping effect. It also showed sufficiently high electrical conductivity (∼ 76 Sc m−1 )a t 650◦C along with a low activation energy (∼0.15 eV), a comparable coefficient of thermal expansion (∼12.1 × 10 −6 ◦ C −1 ) and a chemical compatibility with the solid electrolytes. The results were The Pechini method (15) was applied to prepare the LSMFCN. Strontium acetate hydrate (97%), lanthanum (III) acetate hydrate (99.9%), manganese (II) acetate tetrahydrate (99%), iron (II) acetate (95%), cobalt (II) acetate tetrahydrate (99%) and nickel (II) acetate tetrahydrate (99%), all from the Aldrich or Fluka Chemicals (USA), were dissolved in distilled water under stirring in an order to obtain a clear 0.3 M solution (50 ml). Ethylene glycol (99%, Aldrich; an esterification agent) and then cit- ric acid (99.5%, Aldrich; a chelating agent), both with mass equals to the total mass of cations available, were added dropwise under stirring. The continuous stirring of solution at ∼80 ◦

The oxygen stoichiometry, thermal expansion, morphology, and electrical conductivity of a co-doped perovskitetype cathode system, La1−x Sr x Mn0.85Fe0.05Co0.05Ni0.05O3+a (x = 0–0.4 mole), are studied for intermediate-temperature solid oxide fuel cell applications. Sr2+-doping led to a decrease in the unit cell volume, oxygen stoichiometry, particle size, and activation energy, and an increase in the coefficient of thermal expansion and electrical conductivity. The sample with x = 0.3 mole exhibited four to five fold weight loss with respect to La0.75Sr0.25MnO3+δ at an intermediate temperature range and suggested the availability of a large number of oxygen vacancies due to a co-doping effect. This sample also showed sufficiently high electrical conductivity (∼76 S cm−1) at 650 °C, a low activation energy (∼0.15 eV), and a coefficient of thermal expansion (∼12.1 × 10−6 °C−1) comparable to those of the adjacent components and submicron sized particles. The experimental results are explained using defect models.

Effects of solvent and chelating agent on synthesis of La{sub 0.8}Sr{sub 0.2}CrO{sub 3-{delta}} perovskite are reported. Samples are synthesized using a solvent (ethylene glycol or 2-methoxyethanol) and a chelating agent (acetylacetone, citric acid or ethylene diamine tetraacetic acid) by polymeric-gel method, and characterized by X-ray diffractometry and Fourier-transform infrared spectroscopy. Citric acid to metal cations molar ratio (Rc) is varied for ethylene glycol-citric acid system. Samples are mainly orthorhombic perovskite. SrCrO{sub 4} is appeared as a secondary phase and found to be the lowest for ethylene glycol-citric acid combination with Rc equal to 7. Crystallographic parameters of perovskite phase are determined and compared with those of LaCrO{sub 3}. A mechanism employing a partial-charge model, chelating effect and solvent-cage effect is proposed to explain the results. Effect of sintering temperature on phase, relative density and morphology of samples prepared using ethylene glycol and citric acid (Rc = 7) is also reported.

A novel approach to synthesize a single-phase orthorhombic perovskite, (La 0.9 Sr 0.1 ) (Cr 0.85 Fe 0.05 Co 0.05 Ni 0.05 )O 3 − δ , is reported. Samples are synthesized using two groups of precursors, metal nitrates and metal acetates by various routes of sol–gel method. The effects of the anion and synthesis route on the perovskite structure and removal of impurity phase are investigated using X-ray diffractometry and Fourier-transform infrared spectroscopy. Impurity phases, SrCrO 4 and CoCr 2 O 4 are observed only for the samples prepared using metal nitrates and ascribed due to the pH dependence of citric acid and the cation–anion bonding character, which also affect the reactivity of the mixed solvents. Variation in cell volume with route is corroborative with route-dependent high frequency stretching modes. A mechanism using a partial-charge model is proposed to explain the results.

Miniaturized solid oxide fuel cells (SOFCs) have drawn increasing interest as next generation portable and mobile power sources recently. For these applications, operation and fabrication temperature reduction along with miniaturization of SOFCs should be achieved. For these purposes, we investigated miniaturized SOFC fabrication through various processing techniques including colloidal processes. Anode- supported cells with thin electrolytes and well-controlled electrode structures are obtained by the combination of the processes such as spin-on, electrostatic spray deposition, and microwave sintering at lower fabrication temperature. The properties of cell components and the overall cell performance have been characterized and will be presented.

Porous alumina bodies were successfully prepared by spark plasma sintering of alumina powders with different amounts of graphite, and by subsequently burning out the graphite. Highly porous bodies were fabricated by spark plasma sintering at 1000°C for 3 min under a pressure of 30 MPa. The heating rate was 80°C/min, and the pulse pattern (on-off) was 12:2. For example, alumina bodies prepared by the addition of 10 ~ 30 vol% graphite showed high porosity of 50 ~ 57%. Porous alumina bodies prepared by the addition of 10 ~ 30 vol% graphite had a high compressive strength of 200 ± 55 MPa, about 35 times higher than those obtained on samples prepared by pressureless sintering, and about 2.5 times higher than those in samples prepared by hot-pressing. The significant improvement in strength relative to values obtained with conventional sintering was attributed to better sintering resulting from the rapid heating between particles.

The mechanism of apatite formation on the surface of novel PDMS modified SiO2-CaO- P2O5 hybrids is presented. The bioactive hybrids with different P2O5 content were synthesized by sol-gel method and soaked in the simulated body fluid (SBF) for different periods. The surface and the cross-section of the specimens were examined by use of Fourier transform infrared reflection spectroscopy, thin-film X-ray diffraction technique and scanning electron microscopy. The PDMS-SiO2-CaO-P2O5 hybrid containing 0.03 mole ratio of TEP(triethyl phosphate) / TEOS (tetraethoxysilane) exhibited faster apatite formation compared to P2O5-free hybrids. This composition resulted in the thickest apatite layer (~6µm) and this might be attributed to faster formation of the silica hydrogel on the surface of the P2O5-containing hybrids than on the surface of the P2O5-free hybrids. Resultingly, the apatite nucleation on the surface of the P2O5-containing hybrids is effectively induced by the hydrated silica at a lower degree of supersaturation. Changes in concentrations of the calcium, silicon and phosphorus in the SBF and the SEM-EDS line analysis depicting the variation of Si, Ca and P elements for the bulk, the interface and the apatite are reported. These were found to be quite correlative with each other. The rate of the concentration changes for the P2O5-containing hybrids is higher than that of the P2O5-free hybrids. The increases in the calcium and silicon concentrations are attributed to dissolution of the calcium and silicate ions from the hybrids, and the decrease in the phosphorus concentration is ascribed to formation of the amorphous calcium phosphate and crystalline apatite on the surface of hybrids by consuming the phosphate ion from the fluid.

Transition metal-doped TiO2 powders as a photocatalyst were prepared by sol-gel process and Sb, Bi and Nb were introduced into them as dopants. The photocatalytic behaviors of the doped TiO2 powder were studied as a function of dopant, doping concentration and preparation conditions. X-ray diffraction, FT-Raman, B.E.T. and scanning electron microscopy were applied for structural and microstructural studies. Optical properties of the doped TiO2 powders were studied by UV-Visible Spectrometer and photocatalytic activity of the doped TiO2 was characterized in terms of the degradation of 1,4-dichlorobenzene. X-ray difraction analysis showed that doping with a transition metal ion suppresses anatase-to-rutile phase transition compared with the pure TiO2. The Sb and Nb-doped TiO2 powders did not exhibit any other diffraction peaks except those belonging to TiO2. On the other hand, a diffraction peak of Bi4Ti3O12 appears for 5 at.% Bi-doped samples. All of the doped TiO2 powders had higher specific surface area than undoped TiO2. Surface area increased with increasing dopant concentration depending on the dopant, from 33.9 m2/g to 55.4m2/g. The UV-visible absorption spectra of doped samples were red-shifted by 20~50nm according to the doping level. Also transition metal doped TiO2 powders exhibited better photocatalytic activity than the undoped TiO2. The increase in photoactivity is probably due to the increase in the interfacial electron transfer, red shifts, and better crystallinity.

Good optical quality Eu3+-doped silica-polyethyleneglycol (PEG) hybrid films with covalent bonds between the inorganic (silica) and organic (PEG) phases were prepared by the sol-gel process. These materials are transparent, flexible and show high Eu3+ luminescence output. Their luminescence properties, local environment around europium ion and structure have been investigated as a function of dopant concentration, molecular weight of PEG, PEG content and water content. Photoluminescence spectra of the samples prepared by different europium ion concentration showed that increasing the Eu3+ concentration induces a decrease in the intensity of the host broad band in the green-blue spectral region and an increase in the intensity of a series of Eu3+ intra 4f6 yellow-red sharp lines. However, the sample with higher Eu3+ concentration was found to exhibit concentration quenching of luminescence due to dopant clustering. Photoluminescence spectra of the samples with shorter polymer chains indicated that the distance between the hybrid’s emitting centers and the metal ions is large enough to allow efficient energy-transfer mechanisms. It was noted that luminescence intensity and sharpness were increased by increasing polymer concentration and decreasing water content.

The nanostructural and optical features of hydrogenated nanocrystalline silicon (nc-Si:H) thin films, which were prepared by plasma enhanced chemical vapor deposition (PECVD), were investigated as a function of deposition conditions. It was found that the crystallite size varied with the relative fraction of Si-H3 bonds in the films, [ ] eger n n n H Si H Si int 3 1 3 / ] [ = = ∑ − − , which was sensitively related with the flow rate of SiH4 reaction gas. The silicon nanocrystallites in the films enlarged from ~2.0 to ~8.0 nm in their size with increasing gas flow rate, while the PL emission energy varied from 2.5 to 1.8 eV; the relative fractions of the Si-H3, Si-H2, and Si-H bonds in the amorphous matrix were also varied sensitively with the SiH4 flow rate. A model for the nanostructure of the nc-Si:H films was suggested to discribe the variations in the size and chemical bonds of the nanocrystallites as well as the amorphous matrix depending on the deposition conditions.

Ceramic foams made from a wide range of ceramic materials are being considered for a whole range of applications. A promising application is electrically conducting ceramic foam which acts as current collector and air distributor at the cathode or anode side of solid oxide fuel cells (SOFC). In this work we detail a manufacturing process for electrically conducting ceramic foam by the replication of polyurethane templates.

Neodymium ion doped TiO 2 nanoparticles were prepared by sol-hydrothermal process using titanium isopropoxide as the TiO 2 precursor. The prepared neodymium ion doped TiO 2 nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The photocatalytic degradation of 1,4-dichlorobenzene (DCB) was conducted in the suspension of Nd 3+ doped TiO 2 nanoparticles. The photocatalytic behaviors and microstructure of the prepared Nd 3+ -TiO 2 nanopowder were investigated as the function of dopant content. The effect of Nd 3+ content of the doped TiO 2 nanoparticles on the DCB photodegradation reaction rate was investigated and the first order reaction rate constant (k = 0.153min -1 ) for the doped nanoparticles was found to be significantly larger than that for the undoped TiO 2 nanoparticles. The result showed the optimum value of the Nd 3+ content to be 2 mole %.

In the present study, we report the bioactivity of PDMS-CaO-SiO2-P2O5 hybrid materials prepared by a sol-gel method. The apatite formation on the surface of the specimen, after soaking in the simulated body fluid (SBF), was analyzed by thin-film X-ray diffraction (TF-XRD) and Fourier transform infrared (FT-IR) reflection spectroscopy. The structure and morphology of the surface layer were observed by FT-Raman spectroscopy, BET, and scanning electron microscopy (SEM). It was found that the bioactivity increased with decreasing PDMS content and increasing CaO content. Also, an increase in P2O5 concentration from 0 to 3 mol % decreased the induction period for apatite formation. A further increase in P2O5 content, however, increased the induction period. It was also noted that an increase in the P2O5 concentration from 0 to 3 mol % increased the surface area and micropore area and volume and decreased the pore diameter. On the other hand, the opposite trends were observed with a further increase in the P2O5 concentration. Among the various ormosil samples prepared with different compositions, the highest bioactivity was obtained from the ormosil with the composition of 20 wt % PDMS [PDMS/(TEOS + PDMS)], 15 mol % CaO [(Ca(NO3)2/TEOS) mole ratio], 3 mol % P2O5 [TEP/TEOS mole ratio].

In the present study, metal-ion-doped TiO2 powders were prepared by a sol-gel process using titanium isopropoxide as a Ti precursor and cobalt, gallium, or neodymium as a dopant. For the prepared doped TiO2 nanopowders, the photocatalytic behaviors in the decomposition of aqueous 1,4-dichlorobenzene (DCB) were investigated as a function of doping level and preparation conditions. We found that all of the metal ion doping improved the photocatalytic activity of TiO2, though Nd doping was the most effective and Co doping was least effective. XRD analyses showed that doping with Ga and Nd ions suppresses the anatase-to-rutile phase transition for TiO2, whereas doping with Co did not influence the phase transition. The UV-visible absorption spectra for these metal-ion-doped samples were red-shifted by ∼ 20–40 nm depending upon the doping level.

Fourier transform infrared (FT-IR) and FT-Raman Spectroscopy have been utilized to characterize the structure of physical and chemical bonded ORMOSILs (organically modified silicates) and to compare with the physical properties, reported earlier. The classic and sono ORMOSILs were synthesized by sol–gel method via traditional- and sono-catalysis routes, respectively. The physical and chemical bonding is established by Poly(ethylene glycol) (PEG) and Poly(dimethoxysilane) (PDMS), respectively. Existence of band at 560 cm 1 (FT-IR) and 490 cm 1 (FT-Raman) for the sono and classic gels with 5–10 wt% of PEG indicates the presence of structural defect due to the four-membered siloxane rings. Application of long molecular PEG chain and PDMS increases this defect. Modification in the intensity and peak position of siloxane (Si–O–Si) bands is found correlative with the physical properties. The xerogels with 5–10 wt% of PEG possess a large number of residual surface silanol groups than the xerogels with long molecular PEG chains and PDMS and is found related with the m(OH) band at 3470 cm 1 . These results are attributed to the way of hydro

Nanophase silica-titania particles were prepared by two different synthetic routes, namely, sol–gel and hydrothermal processing. The crystallinity and crystallographic phases, particle size and surface area of the materials were controlled by varying the calcination temperature, and/or the ratio of Si to Ti. It was determined by XRD that the crystallite sizes of SiO2-TiO2 prepared by sol–gel and hydrothermal processing decreased from 11 to 6 nm and 12 to 9 nm, respectively, as the mole fraction of silica was increased from 0.1 to 0.4. It is proposed that the presence of the amorphous silica suppresses the growth of anatase TiO2 grains and their phase transformation to rutile. The photocatalytic decomposition rate of 1,4-dichlorobenzene (DCB) in aqueous solution with the sol–gel derived SiO2-TiO2 powder prepared at 750 °C was about 10 ± 5% higher than that observed with Degussa P25, whereas the SiO2-TiO2 samples prepared by hydrothermal processing at 250 °C showed a slightly lower decomposition rate than P25.

Donor doped BaTiO3 (n-BaTiO3) ceramics were fabricated by adding polyethylene glycol (PEG) at 20 wt %. The effects of reducing and oxidizing atmospheres on the PTCR characteristics of the porous n-BaTiO3 ceramics were investigated. The PTCR characteristics of the porous n-BaTiO3 ceramics is strongly affected by chemisorbed oxygen at the grain boundaries and are recovered as the atmosphere is changed from the reducing gas to oxidizing gas. The low room-temperature resistivity of the porous n-BaTiO3 ceramics in reducing atmospheres may be caused by the decrease in potential barrier height, which originates from an increase in the number of electrons owing to the desorption of chemisorbed oxygen atoms at the grain boundaries. In addition, the high room-temperature resistivity of the porous n-BaTiO3 ceramics in oxidizing atmospheres may be caused by the increase in potential barrier height, which results from the adsorption of chemisorbed oxygen atoms at the grain boundaries.

[SiO2]x[TiO2]1-x(x = 0.1, 0.2, 0.3, 0.4) powders were prepared by hydrothermal reaction of titanium isopropoxide (TIP) and tetraethyl-orthosilicate (TEOS) stabilized in acidic ethanol/water solution. The size and phase of TiO2 particles were controlled by adjusting the SiO2 content and the composition of the solvent system. The microstructure and photocatalytic activity of the prepared SiO2-TiO2 nanoparticles were characterized by XRD, TEM, BET, Raman and UV visible spectroscopic techniques. The major phase for all the prepared samples was anatase. The particle size of 0.3SiO2-0.7TiO2 powders prepared with excess amount of ethanol (REtOH = EtOH/alkoxide molar ratio = 120) was about 8.7 nm, while that of the sample prepared with small amount of ethanol (REtOH = 4) was 9.9 nm. The photocatalytic activity of these composite powders under excess ethanol was 1.5 times higher than that of pure TiO2 with respect to the decomposition of 1,4-dichlorobenzene (DCB).

Porous (Ba,Sr)(Ti,Sb)O 3 ceramics were fabricated by adding corn-starch (1–20 wt.%) and effect of sintering condition on the PTCR characteristics of the porous ceramics was investigated. The room-temperature electrical resistivity of the (Ba,Sr)(Ti,Sb)O 3 ceramics was decreased and increased with increasing sintering temperature and sintering time, respectively. The former was attributed mainly to the increase of grain size as well as the partial decrease of the porosity, and the latter was due to the increase of the electrical barrier height of grain boundaries. The sample sintered at 1450 °C for 1 h showed the excellent PTCR characteristics, i.e. the lowest room-temperature resistivity (8.4×10 Ω cm) with the high ratio of maximum resistivity to minimum resistivity (6.3×10 5 ).

mole), are reported. BET, UV-visible spectroscopy and SEMwere used for characterizations. The increase in acid or base concentration increased the size of pores andaggregated silica particles. The samples with pH ≤ 2.5 were transparent and attributed to the small size of pores(~20 A) and silica particles. The samples with pH > 2.5 were translucent or opaque due to non-uniform poresystem formed by voids and large aggregated silica particles. The surface area was found a key factorcontrolling the interactions between the gel matrix and the dye. The OS samples with the highest dyeconcentration exhibited the minimal values of pore size, surface area and silica particle size, resulting in theconcentration-quenching phenomenon. Key Words : Physical properties, Microstructure, Organic dye, ORMOSILIntroductionThe organic dye doped ORMOSILs (organically modifiedsilicates) attract widespread interests in recent years due totheir wide application as gain media in laser materials, non-linear optical materials, photochemical hole burning,luminescence solar concentrator, chemical sensor, pH sensor,etc.

Poly(dimethylsiloxane) (PDMS) modified silica xerogels were prepared by two-step acid/base catalyzed sol-gel process. By keeping the acid amount and hydrolysis period in acidic environment fixed, and adding different amounts of base to the sol afterwards, attempts had been made to study the effect of the different amounts of base catalyst on the micro-structure and physical properties of the prepared ORMOSILs. DTA, SEM, BET, FTIR were performed to characterize the derived specimens. The microstructure and physical properties are greatly influenced by the amount of base added to the sol. With increasing base content the crystallite size and porosity increase and the pore size distribution takes a broad spectrum. Whereas, the glass transition temperature seems to decrease with increasing of base catalyst amount. This is explained in terms of the change in the relative amounts of hydrolysis and condensation reactions due to the addition of different amount of base catalyst, which predominantly influences the condensation reactions. The results are reported in this communication along with possible explanations behind the observations.

Organically modified silicates (ORMOSIL) have been prepared by incorporating poly(dimethylsiloxane) (PDMS) into silica xerogels, with tetraethyl orthosilicate (TEOS) as the starting inorganic material, by (i) one-step acid- or base-catalyzed process and (ii) two-step acid/base-catalyzed sol–gel process. The condensation between PDMS and TEOS have been studied to get an idea how experimental parameters control them by using thermal analysis (differential thermal analysis (DTA) and thermal gravimetric analysis (TGA)). It has been found that a base environment enhances the co-condensation between the PDMS and TEOS, whereas an acidic environment has more influence on the hydrolysis reactions. The results are reported in this communication along with possible explanations behind the observations.

†The formation temperature for the perovskite lead zirconate titanate [Pb(Zr,Ti)O 3, PZT] derived from sol-gel route was lowered by more than 100 o C with the addition of crystallographically suitable seed particles, such as barium titanate (BT) or PZT. We investigated the effect of seeding on the crystallization of perovskite phase and on the microstructure of the sol-gel derived PZT powder by varying the concentration, size and chemical species of seed particles. The phase transition as a function of temperature was monitored by DTA, XRD, and Raman spectroscopy, and the interface between the seed particle and grown PZT layer was analyzed by SEM and high resolution TEM techniques. It was found that both the heterogeneous and homogeneous nucleation contributes competitively in the formation of perovskite PZT grains.

An inorganic-organic hybrid system, silica-poly(ethylene glycol) songel is reported. This system was prepared via sol-gel method by varying varous processing variables. e.g. ultrasonic radiation time, gelling temperanture, PEG content and its molecular weight. Various experimental techniques wee employed to analyze the morphological, mechanical and optical properties of the system. The results were discussed in the light of existing theories. The sonogel system exhibited the common features of inorganic-organic hybrids. wt% PEG sonogel exhibited the morphological and optical properties superior to those reported earlier for the classic gels and found suitable for device applications.

Inorganic–organic hybrids or organically modified silicates (ORMOSILs), with tailorable optical and electrical properties depending on the inorganic and organic components chosen, processing conditions, etc., offer many new exciting properties that lead to different applications. In this study, tetraethoxysilane (TEOS) and poly(dimethylsiloxane) (PDMS) were chosen as the inorganic and organic components respectively, to prepare ORMOSIL matrix. Silanol-terminated PDMS can condense with oxide precursors to produce metal–O–Si bond and is known for its superior relaxation. The effects of H 2 O/TEOS ratio, PDMS molecular weight and different reaction schemes (i.e. reaction order) on the microstructures and mechanical properties of the SiO 2 –PDMS ORMOSILs have been studied. Attempts are made to explain the results in the light of presently available theories.

Doping of classical silicate glass prepared by sol–gel technique by Ag or other nanometer size metal particles have made a major stride in past decade. But studies of metallic particle incorporated organically modified silicates (ORMOSIL) are quite scarce. The present work attempts to study the effects of Ag doping on the structural and physical properties of poly(dimethylsiloxane) (PDMS) modified silica xerogels. The choice of tetraethoxysilane (TEOS) and PDMS as the starting inorganic and organic components, respectively, for the preparation of ORMOSIL was dictated by the similarity in their backbone structure (SiO). Ag nano particles were incorporated by two routes: (i) directly into the sol by adding calculated amount of AgNO 3 prior to gelation, and (ii) in this case preformed porous matrix was obtained first and then Ag doping was done by immersion of that matrix in AgNO 3 solution for several days and subsequent heat treatment. Microstructures (SEM, TEM, XRD), particle size distribution, infrared response (FTIR) and density have been studied. It was found that the Ag particles in the sample prepared by the second route were less prone to aggregation compared with that prepared using first route. The merits and demerits of the two methods have been discussed. It was observed that when exposed to humid air, the samples changed the optical state from transparency to opacity to various degrees depending on the amount of Ag incorporation. However, transparency could be brought back by treating the sample at a temperature above 300 °C. This phenomenon exhibits its potential to be used as humidity sensor and/or optical switches.

The transport properties of a new fast Li+ ion-conducting sol–gel-derived ormolyte, (SiO2–10 wt% PEG)–[Li/O] LiCF3SO3, with [Li/O] = 0–0.1 (mol/mol), is reported. The composition with [Li/O] = 0.04 exhibited the highest conductivity (σ25 °C = 1 × 10−4 S cm−1), with an enhancement of 103 over the host matrix (SiO2–10 wt% PEG xerogel), and has been found to be the ‘optimum conducting composition’. Direct determination of Li+ ion mobility (μ) and mobile ion concentration (n) revealed that the enhancement was due to the increase in both μ and n. Studies of the variation of σ, μ, and nversus temperature indicated that the system shows Arrhenius-type behavior. The activation energy and energies of migration and formation were evaluated from their respective Arrhenius plots. Measurement of the ion transference number (tion) confirmed that the ions are the sole charge carriers in the system. These results are discussed in the light of existing theories.

The effect of ultrasonic radiation is reported for silica-poly(ethylene glycol) system prepared without the solvent using sol-gel processing by varying various parameters such as ultrasonic irradiation time, PEG content and HCl/TEOS molar ratio. The property of sonogel is compared with classic gel which has been prepared with ethanol as a solvent by traditional sol-gel processing. SEM, BET, DTA-TGA, density and Vickers hardness measurements are carried out for analyzing the samples. The gelation time is found strongly dependent on radiation time, PEG content and pH value, and has been discussed on the basis of existing theories. The SiO₂-10 &20 wt% PEG sonogel exhibited superior optical, physical and gel properties as compared to the classic gel, hence, found suitable for device applications. The ultrasonic radiation increased the density and surface area, and also reduced the pore size which is well supported by the shift in the peak of DTA curve. The DTA thermogram was found similar to that of pure silica gel.

The purpose of the present work is to study the effect of silver (Ag) incorporation on the structural and physical properties of poly(dimethylsiloxane) (PDMS) modified silica xerogels. PDMS was chosen as the organic component because of its similarity of backbone structure (–Si–O–) with tetraethyl orthosilicate, the inorganic component of organically modified silicates. In the present work silver was incorporated by two routes: (i) directly in the sol and (ii) silver doping was done after preformed porous matrix was obtained. The microstructures, particle size distribution, infrared spectra, and optical coloration have been studied. The utility of two methods has been discussed. It was found that the particle size was much smaller compared with that of classical gels with dispersed Ag particles. For the indirect method of silver doping the particle size distribution was found to follow log-normal distribution function. Upon exposure to humid air the samples change optical state from transparency to opacit...

Nd-doped Bi4Ge3O12 (Nd:BGO) crystals were successfully grown in the auto-diameter control system equipped with a frequency weighing sensor with the Czochralski method. The Nd3+ ion doping level was varied from 0.25 to 2.5 at.%. The crystals were transparent and of light purple color, with a typical size of about 20 mm in diameter and 50 mm in length. The effective distribution coefficient (keff) of Nd3+ ion was about 0.957 irrespective of concentration, and the Nd3+ ions were distributed homogeneously throughout the crystal. The doping concentration (pi) of active ion in Nd:BGO crystal was 2.54x1020 ions/cm3, which is higher than that in the Nd:YAG crystal. Therefore, the Nd:BGO crystal was judged to be more suitable for the laser diode pumping microchip laser material where size reduction was desirable.

A promising candidate material for a H 2 permeable membrane is SiC due to its many unique properties. Ahydrogen-selective SiC membrane was successfully fabricated on the outer surface of an intermediate multilayer γ-Al 2 O 3 witha graded structure. The γ-Al 2 O 3 multilayer was formed on top of a macroporous α-Al 2 O 3 support by consecutively dipping intoa set of successive solutions containing boehmite sols of different particle sizes and then calcining. The boehmite sols wereprepared from an aluminum isopropoxide precursor and heated to 80 o C with high speed stirring for 24 hrs to hydrolyze theprecursor. Then the solutions were refluxed at 92 o C for 20 hrs to form a boehmite precipitate. The particle size of the boehmitesols was controlled according to various experimental parameters, such as acid types and acid concentrations. The topmost SiClayer was formed on top of the intermediate γ-Al 2 O 3 by pyrolysis of a SiC precursor, polycarbosilane, in an Ar atmosphere. Theresulting amorphous SiC-on-Al

Mechanical, electrical and micro-structural properties of new electronic conducting ceramic foams are reported. Ceramic foams are prepared using the slurry of La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) by the polymeric sponge method, which is followed by spray coating for increasing the number of coatings?sinterings on polyurethane foams of 30, 45 and 60?ppi (pores per linear inch). An increase in the number of coatings?sinterings and ppi improved the compressive strength, density and electrical conductivity by decreasing the porosity to ~76%, as also observed by the SEM study. The three-times coated?sintered ceramic foams (60?ppi) exhibited optimum values of compressive strength of ~1.79?MPa and relative density of ~0.24 at 25??C and electrical conductivity of ~22?S?cm?1 at 600??C with an activation energy of ~0.22?eV indicating its suitability as a solid oxide fuel cell current collector. The experimental results are discussed in terms of the Gibson and Ashby theoretical model.

The effect of composition on the structure of the new solid oxide fuel cell (SOFC) perovskite (La1−x Srx )(Cr0.85Fe0.05Co0.05Ni0.05)O3−δ is studied using x-ray diffractometry, pycnometry, and Fourier-transform infrared and Raman spectroscopy. Samples were synthesized using the Pechini method via doping the La site with Sr 2+ , to a composition with x = 0‐0.4 mole fraction, and at the Cr site with 0.05 mol of Co 2+ , Fe 2+ and Ni 2+ , and the structural results were compared with those for orthorhombic LaCrO3 .T he samples were orthorhombic perovskite of the Pnma space group. A second phase, monoclinic SrCrO4, was also observed, whose content increased linearly with increasing x. A large decrease in the lattice and hence volume was observed for the sample with x = 0.1, which was accompanied by a sharp decrease in the Cr−O bond length, tilt angle and crystallite size. The structural parameters were almost invariant for x = 0.1‐0.4, probably due to an increase in content of the high valence cations of smaller ionic radii, as suggested by an increase in the intensity of the defect band (∼515 cm −1 , IR). The octahedral CrO6 stretching, bending and tilting modes were found shifted accordingly. A mechanism employing a partial-charge model was proposed to explain the results. (Some figures in this article are in colour only in the electronic version)