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1.
Glass films of pure SiO 2 and TiO 2 have been prepared on sodalime silica flat slide glasses by the sol-gel process using the dip-coating technique from TEOS and Ti(OC 3H 7) 4 solutions. The various parameters such as chemicals concentrations, viscosity, type of catalyst, withdrawal speed and temperature of densification leading to the obtention of good and adherent coatings with definite film thicknesses are reported. The same technique has been used for the depositon of layers of colored films SiO 2---M xO y (M = Co, Mn, Nd and Cr). Brilliant yellow coatings have been obtained with TiO 2---CeO 2. 相似文献
2.
70Ph 2SiO·30TiO 2 coatings on slide glass and phosphate glass substrates have been prepared by the sol-gel process. Experimental results on the characterization and chemical durability of the coatings are presented. It is shown that the coatings heated at 150°C have reasonably good acid and water resistance while their alkali durability is very poor. The XPS results are used to verify the different corrosion behaviors of the coating in pure water and 1N HC1 solutions. The chemical durability of phosphate glass can be significantly improved by this coating. 相似文献
3.
Various oxide films on SiO 2 glass substrates were irradiated by a laser beam. A continuous CO 2 laser source (wavelength 10.6 μm) was used for this purpose; the composition change at the surface layer was determined by Rutherford backscattering spectrometry (RBS). All the alkaline-earth oxides as well as those of lanthanum and yttrium, entered the glass after treatment. ZrO 2 and CeO 2, however, did not enter the SiO 2 glass due to laser irradiation. It is interesting, however, that a film of ZrO 2 + Al 2O mixture easily entered into the SiO 2 glass by laser processing. The conditions and mechanism of laser-enhanced interaction of ZrO 2 or other oxide films with SiO 2 glass surfaces are discussed especially in view of their structural behaviour in glass. 相似文献
4.
The effect of the interaction between colloidal particles in SiO 2 and TiO 2 sols on the viscosity of the sols has been examined. It was found that the interaction was significantly influenced by the zeta potential of electrical double layers and terminal bonds associated with particle surfaces. Water/alkoxide mole ratio and pH affect the zeta potential and the terminal bonds and, consequently, change the interaction between the particles and the viscosity of the sols. In addition, the relationship of viscosity with the volume fraction of the colloidal particles in SiO 2 sol has been described by a Dougherty-Kreiger equation when the viscosity reached a stable value with time. 相似文献
5.
The influence of the mixed alkali effect on the chemical durability of Na 2O---TiO 2---SiO 2 glasses during substitution of K 2O for Na 2O in 21Na 2O---26TiO 2---53SiO 2 glasses was investigated. The best chemical durability was found at K 2O/Na 2O = 2.5 where the minimum was close to K + ions of larger size. It was shown that the water corrosion process of the system was predominantly controlled by both the mobility and the exchange function of K + ions resulting in the generation of a titanium-rich and silicon-rich layer at the surface. The mixed alkali effect can therefore be applied to lower the rate of water corrosion and increase chemical durability so that optical glasses with higher chemical durability can be obtained. 相似文献
6.
Yellow coatings have been prepared from titanium tetraisopropoxide and cerium chloride by the sol-gel dip-coating process, and the transmittance, chromaticity, thickness and acidic durability of the coating films produced on glass or aluminum were studied. The effects of the pH of the solution on the preparation of the transparent and homogeneous coating films were studied by adding the alkali or acid, and as a result transparent and homogeneous yellow coating films were prepared by dipping the substrate in a solution containing acetic acidic solution. The acidic durability of the aluminum foil was improved by dip-coating the brilliant yellow CeO 2-TiO 2 coating three times. 相似文献
7.
Alkoxide derived gels were prepared in the system Na 2O---B 2O 3---SiO 2. The gel compositions were situated in the liquid-liquid immiscibility area of the phase equilibrium diagram. Hydrolytic resistance tests were performed on the gels heat-treated at temperatures ranging between 120 to 850 °C. The Na2O, B2O3 and SiO2 extracted from the attack gels were analyzed. The experimental results indicate that the amount of B2O3 has a significant influence on the chemical durability of the heat-treated gels. At temperatures of 850 °C the greater the B2O3 mol% the greater are the amounts of Na2O and B2O3 extracted. Different behaviour was observed for gels heat-treated at 600 °C where the amounts of B2O3 and Na2O extracted slightly increases as the B2O3 mol% increases. Small amounts of extracted SiO2 were always observed. These results are complemented with other measurements so that an explanation of the controlling mechanism is given. 相似文献
8.
The type and the amount of silicate groupings existing in glassy and crystalline 2PbO·SiO 2 have been determined by direct chemical methods: paper chromatography, trimethylsilylation combined with gas-liquid partition chromatography and by the molybdate method. The results obtained by these three different methods are in good agreement and demonstrate, that glassy 2PbO·SiO 2 and each of the three main crystalline polymorphs are characterized by its own specific silicate anion distribution: the distribution in vitreous 2PbO·SiO 2 is of a polyanionic nature; in T---Pb 2SiO 4 dimetic groups [Si 2O 7] 6− prevail; M 1---Pb 2SiO 4 contains predominantly [Si 4O 12] 8− rings and H---Pb 2SiO 4 is a typical polysilicate with chain anions [SiO 32−] n. The results fit a structural model according to which glass is a random array of discrete polyatomic groupings; the gradual transition from the glassy state to the stablest crystalline structure is connected with degradation and polymerization of silicate anions. 相似文献
9.
The colorless and transparent glasses in the Al 2O 3---B 2O 3---SiO 3 system with high B 2O 3 and SiO 2 content were prepared from gels at low temperature. Their IR spectra not only revealed the evolution of the gel to glass conversion, but also showed that the formation of mixed bonds in the glasses obtained did not show any effect due to the B 2O 3 content. The accuracy of the glass composition is dependent upon the SiO 2/B 2O 3 molar ratio. The higher the ratio, the less the deviation of the analyzed compositions of the resulting glasses from their original calculated values. It is obvious that the higher the ratio, the lower the thermal expansion coefficient and the higher the transformation temperature of the glass, and the temperature at which the thermal contraction reaches an equilibrium is higher. 相似文献
10.
We investigated the dependence of the Y 2O 3 film growth on Si surface at initial growth stage. The reflection high-energy electron diffraction, X-ray scattering, and atomic force microscopy showed that the film crystallinity and morphology strongly depended on whether Si surface contained O or not. In particular, the films grown on oxidized surfaces revealed significant improvement in crystallinity and surface smoothness. A well-ordered atomic structure of Y 2O 3 film was formed on 1.5 nm thick SiO 2 layer with the surface and interfacial roughness markedly enhanced, compared with the film grown on the clean Si surfaces. The epitaxial film on the oxidized Si surface exhibited extremely small mosaic structures at interface, while the film on the clean Si surface displayed an island-like growth with large mosaic structures. The nucleation sites for Y 2O 3 were provided by the reaction between SiO 2 and Y at the initial growth stage. The SiO 2 layer known to hinder crystal growth is found to enhance the nucleation of Y 2O 3, and provides a stable buffer layer against the silicide formation. Thus, the formation of the initial SiO 2 layer is the key to the high-quality epitaxial growth of Y 2O 3 on Si. 相似文献
11.
Glasses of compositions 5ZrO 2·5SiO 2(ZS), 5ZrO 2·Al 2O 3·4SiO 2(ZAS) and 5 5ZrO 2·0.5Al 2O 3·0.5Na 2O·4SiO 2(ZANS) were prepared by the sol-gel process from metal alkoxides and sintered to make glass-ceramics. Tetragonal ZrO 2 was precipitated by heat treatment at 900 to 1300°C. The activation energy for tetragonal ZrO 2 crystal growth was extremely high in Al 2O 3 containing glasses. ZAS and ZS were sintered to the near theoretical densities above 1200°C, at which the predominant phase was tetragonal ZrO 2. On the other hand, for ZANS, high densification was not attained owing to the large pores enclosed by the glass phase. Strength and fracture toughness increased with the densification and the crystal growth of tetragonal ZrO 2, reaching 450 MPa and 9 MN/m 1.5, respectively. 相似文献
12.
The structure and thermal stability of ZrO 2 films grown on Si (1 0 0) substrates by metalorganic chemical vapor deposition have been studied by high-resolution transmission electron microscopy, selected area electron diffraction and X-ray energy dispersive spectroscopy. As-deposited films consist of tetragonal ZrO 2 nanocrystallites and an amorphous Zr silicate interfacial layer. After annealing at 850°C, some monoclinic phase is formed, and the grain size is increased. Annealing a 6 nm thick film at 850°C in O 2 revealed that the growth of the interfacial layer is at the expense of the ZrO 2 layer. In a 3.0 nm thick Zr silicate interfacial layer, there is a 0.9 nm Zr-free SiO 2 region right above the Si substrate. These observations suggest that oxygen reacted with the Si substrate to grow SiO 2, and SiO 2 reacted with ZrO 2 to form a Zr silicate interfacial layer during the deposition and annealing. Oxygen diffusion through the tetragonal ZrO 2 phase was found to be relatively easier than through the monoclinic phase. 相似文献
13.
Chemical durability of the Si 3N 4 doped (up to 0.5 wt%) chalconitride glasses was evaluated by weight losses of glass samples after immersion in deionized water, H 2SO 4, HCl and NaOH solutions. IR spectra and SEM were used as an aid to examine the surface structure of corroded glass samples. Weight loss measurements showed a poorer stability of non-oxide glasses in basic solution than in acid solution, and the Si 3N 4 doping was found to improve chemical durability. Comparison of IR spectra of samples exposed to the basic solution with their original ones suggested the higher content of OH − in its reaction layers, indicating that the corrosion of the present non-oxide glasses in the basic solution may result from the breakdown of the bridging Se due to an attack launched by OH −. The SEM evidence confirmed that Si 3N 4 doping did hinder the OH − attacks on Ge and/or As, which is most likely related to incorporation of the three-coordinated N into the glass network, as supported by a comparison of the IR transmitting spectrum between uncorroded chalconitride glass and undoped chalcogenide glass. 相似文献
14.
Tellurite containing vanadate (50− x)V 2O 5– xBi 2O 3–50TeO 2 glasses with different bismuth ( x=0, 5, 10, 15, 20 and 25 wt%) contents have been prepared by rapid quenching method. Ultrasonic velocities (both longitudinal and shear) and attenuation (for longitudinal waves only) measurements have been made using a transducer operated at the fundamental frequency of 5 MHz in the temperature range from 150 to 480 K. The elastic moduli, Debye temperature, and Poisson’s ratio have been obtained both as a function of temperature and Bi 2O 3 content. The room temperature study on ultrasonic velocities, attenuation, elastic moduli, Poisson’s ratio, Debye temperature and glass transition temperature show the absence of any anomalies with addition of Bi 2O 3 content. The observed results confirm that the addition of Bi 2O 3 modifier changes the rigid formula character of TeO 2 to a matrix of regular TeO 3 and ionic behaviour bonds (NBOs). A monotonic decrease in velocities and elastic moduli, and an increase in attenuation and acoustic loss as a function of temperature in all the glass samples reveal the loose packing structure, which is attributed to the instability of TeO 4 trigonal bipyramid units in the network as temperature increases. It is also inferred that the glasses with low Bi 2O 3 content are more stable than with high Bi 2O 3 content. 相似文献
15.
The preparation of glass-lined coating mould from gels in the ternary system of SiO 2–ZrO 2–B 2O 3 has been investigated. The crystallization characterization and high temperature structure stability of this coating mould are demonstrated. We can find that the crystallization of t-ZrO 2 as well as the tetragonal to monoclinic phase transformation are, respectively, retarded and impeded owing to the encasement of SiO 2 matrix. While the inhibitive effect of B 2O 3 on crystallization of the SiO 2–ZrO 2–B 2O 3 coating mould is explained. Finally, DD3 single crystal superalloy melt can realize highly undercooled rapid solidification by adopting this coating mould, which further evinces that SiO 2–ZrO 2–B 2O 3 coating mould has an ideal nucleation inhibition for superalloy. 相似文献
16.
Mössbauer absorption measurements have been made at room temperature on 57Fe in iron sodium silicate glasses containing 3–15 mol% Fe 2O 3 and various iron alkali silicate crystals in order to study the state of iron in these glasses. The spectra of all the glasses gave one doublet with a quadrupole splitting varying from 0.73–0.78 mm s −1, while those of Na 2O · Fe 2O 3 · 4 SiO 2 and 5 Na 2O · Fe 2O 3 · 8 SiO 2 crystals showed much smaller quadrupole splitting, 0.28 mm s −1 and 0.10 mm s −1, respectively, and an asymmetrical doublet of much narrower linewidth. When sodium was replaced by other alkali metals of larger size, such as K and Cs, in MFeSi 2O 6 and MFeSi 3O 8 crystals, the quadrupole splitting became wider and approached to 0.73 mm s −1. Such a variation was not observed for glasses. These results suggest that a larger number of non-identical sites exist in iron sodium silicate glasses than in the corresponding crystals. 相似文献
17.
We obtained the chemical shielding constants of 29Si in Li 2S–SiS 2 glass system on the basis of molecular orbital calculations. The relative chemical shieldings calculated at the HF/6-31G* level is −16.1 and −23.8 ppm for E(1) and E(0), respectively. These calculations are in good agreement with the previous NMR study: σ( E(2))>σ( E(1))>σ( E(0)). It is found theoretically that incorporation of Li 2S into SiS 2 does not influence the 29Si chemical shift, while incorporation of Li 2O into SiO 2 does to a significant extent. It is also found that the existence of oxygen in Li 2S–SiS 2 glasses increases the chemical shielding of 29Si by about 25 ppm, which is in good agreement with the experimental result. 相似文献
18.
The structure of Li 2O·SiO 2 glass has been determined by the pair-function analysis of the radial distribution function (RDF) obtained by X-ray and neutron diffraction measurements. The structure models were constructed by the molecular dynamics method (MD). The calculated RDFs, the summation of the pair-functions of the model, were compared with the observed RDFs while varying the MD parameters. Taking advantage of the negative scattering length of Li for neutron diffraction, the glass structure was investigated in detail, and it was found that the chains of SiO 4 tetrahedra bend at 20 °, which is a little less than for the crystal (23.48 °). It is known that the larger the size of the alkali ions (Na + → K + → Cs +), the smaller the bending angle of the chains. It was found that this rule also applies to Li +. 相似文献
19.
The La L 1 and L 3 XANES and L 3 EXAFS have been investigated for the series of glasses 10K 2O---50SiO 2--- x La 2O 3 ( x = 1, 5, 10) and (10 − x)K 2O---40SiO 2−( x/3)La 2O 3 ( x = 7.5, 5, 2.5) and model compounds La 2O 3, LaAlO 3, LaPO 4, La 2NiO 4, La 2CuO 4 and La(OH) 3. An edge resonance at 25 eV above the L 1 edge in the glass spectra is concentration-dependent, decreasing in intensity with increasing lanthanum concentration. The 2s → nd forbidden transition increases with La 2O 3 concentration, indicating a reduction in the ‘average’ site symmetry of the first coordination shell of La. Mapping X( k) space, which is a new and promising technique, was employed to extract bond distance, coordination number and thermal parameters from the EXAFS. By this method, one calculates the complete X( k) space a function of all physically reasonable values of the adjusted parameters in all possible combinations. The advantage in this method is the assurance of a global minimum. Bond lengths were comparable to those obtained by Fourier transforming the phase corrected EXAFS. The values are 2.42 Å (± 0.03 Å) for La---O. The coordination numbers ( N ≤ 7 ± 1.5) were derived by mapping and comparison to the published structures for other La compounds. X( k) mapping is compared with least-squares fitting the data, and the correlation between the Debye-Waller factor and coordination number is also discussed. 相似文献
20.
V 2O 5 gels containing up to 18 mol% of TiO 2 were obtained through the simultaneous hydrolysis of alkoxides in ethanol solution. V 2O 5 gels containing Na 2O or Li 2O were obtained through the ion exchange method. The crystallization temperature, Tcr, of the gels increased and the H 2O content of the gels decreased by the addition of TiO 2 or Na 2O. These additives seem to stabilize the amorphous state of the gels. On the other hand, Tcr and the H 2O-content slightly varied with the addition of Li 2O. No ionic polarization was observed in coating films of the gels dried at temperatures below Tcr. The dc conductivity of the films was anisotropic, and increased with the addition of Li 2O or Na 2O. However, it decreased with increasing TiO 2 content. The fiber-like structure of gels was observed by TEM. The gels obtained from alkoxides were thin and short in comparison with the gels obtained through the ion exchange method. 相似文献
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