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1.
The ion-exchange mechanism between copper and alkali ions, when 20R2O · 10Al2O3· 70SiO2 (R = Li, Na, and K) glasses are immersed in divalent copper-containing molten salts in air and nitrogen at 550°C, has been investigated. In molten CuCl2, the ion-exchange behavior in both air and nitrogen was very close to that in molten CuCl in air reported previously. This is explained by assuming that CuCl2 decomposes into CuCl and Cl2 at 550°C and the Cu+ ions thus formed mainly diffuse in glasses to replace alkali ions, where Cl2 acts as an oxidizing agent just like oxygen. In the case of molten CuSO42SO4, a small amount of Cu+ which is present in the molten state plays a primary role in the Cu ⇌ R+ ion exchange process, although the contribution of direct Cu2+⇌ 2R+ ion exchange cannot be ignored.  相似文献   

2.
Simple binary alkali borate glasses of differing alkali content (alkali = Li, Na, or K) containing sulfur were prepared and their absorption spectra were measured in the range of 200 to 700 nm. The absorption bands obtained were used to determine the stable states of sulfur in these glasses by directly comparing them with published data. The following states of sulfur were identified and their ranges of stability were determined: the S2 molecule in glasses containing at least 15 mol% alkali oxide, the S3 and S2 in glasses containing 20 to 30 mol% Na2O or K2O, and the polysulfide ion (S x 2−) in glasses of 30 to 35 mol% Na2O or K2O.  相似文献   

3.
The Fe2+-Fe3+ equilibrium in binary Na2O-P2O5, glasses was studied by equilibrating glass melts at different temperatures in air. The enthalpy change (δH) of the reaction 1/2Fe2O3⇌FeO+1/4O2 was calculated for 4 glasses. The results indicate that (1) the equilibrium shifts toward the oxidized state as the Na2O content of the glass increases (plots of log ([Fe2+]/[Fe3+]) vs mol% alkali were linear) and (2) Δ H values for glasses of different composition are nearly equal but differ from the standard (calculated) value for the reaction. The experimental ΔH values were nearly equal to that for the reaction FePO4→1/3 Fe3(PO4)2+ 1/6P2O5+1/4O2, indicating that Fe forms phosphate or polyphosphate configurations in the Na2O-P2O5 glasses. In certain of the glasses studied a faint-pink solid precipitated; its X-ray diffraction pattern indicated that its principal component is crystalline Na2Fe111P3O10.  相似文献   

4.
The kinetics of the K+⇌ Na+ exchange in Na2O·3SiO2 glass at 350°C were studied. The distribution of K in the glass specimens after exchange in molten KNO3 was determined with an electron microprobe. The calculated interdiffusion coefficients, which varied with the local composition in the glass, were compared with those obtained using the Nernst-Planck equation and Fleming and Day's self-diffusion data for xNa2O. (1-x)K2O·3SiO2 glasses. Deviations of the observed interdiffusion coefficient from the Nernst-Planck formula were noted. These deviations are explained on the basis of changes in the average size of the alkali ion sites and in the strain energy that occur during ion exchange.  相似文献   

5.
Enthalpies of solution of framework aluminosilicate glasses x Ml/ n n + AlO2-(1- x )SiO2 (M = Cs, Rb, K, Na, Li, Ba, Pb, Sr, Ca, Mg) in molten 2PbO.B2O3 near 973 K were measured. The sequence above represents increasing ability of the nonframework cation M to bond to the bridging oxygen. In that sequence, the enthalpy of the substitution Si4+→+ Al3++ 1/ n M n + in the glass becomes less exothermic, the enthalpy of vitrification increases, and the tendency toward glass-glass immiscibility becomes more pronounced. These parameters correlate smoothly with the ionic potential, z/r , of the substituting cation.  相似文献   

6.
The ultraviolet absorption of vanadium(V) in R2O-B2O3 glasses (R represents Li, Na, or K) and in aqueous buffer solutions was investigated. In glasses of variable R2O:B2O3 ratio, a change in the absorption spectra similar to the [VO4]3- → [VO3(OH)]2- change in aqueous solution was observed. It is suggested that vanadium(V) in these glasses may be present as either [VO4]3- or [VO3O1/2]2- (O1/2 indicates a bridging oxygen ion), depending on the basicity of the melt. The critical R2O concentration, above which this change in vanadium(V) environment occurs with increasing alkalinity, is 24, 26, and ≅30 mol%, for K2O, Na2O, and Li2O, respectively.  相似文献   

7.
Infrared spectroscopic studies of charge-coupled substitution in silicate glasses and crystals along the joints x MAlO2(1 – x )SiO2 (M = Li, Na, K, Rb, and Cs; 0.10 ≤ x ≤ 0.60) were carried out in the range 2000 to 200 cm−1 Three major absorption bands appeared in the 1100-, 800-, and 500-cm−1 regions. For a specific value of x, the observed changes in frequency, intensity, and bandwidth decreased in the order Li > Na > K > Rb > Cs and the apparent disorder in the glass structure caused by the substituted aluminum increased in the direction K < Na < Li. The 800-cm−1 band splits at SiO2≃ 0.75 mol, which has been interpreted in terms of the number of AlO4 tetrahedra in the structure. Most of the substituted aluminum in the glasses and the crystals was found to be in the fourfold coordination.  相似文献   

8.
The stannous-stannic equilibrium in binary alkali silicate and ternary silicate glasses was studied by equilibrating glassmelts with air at 1400°C. The Sn2+-Sn4+ equilibrium shifts more toward the oxidized state with increasing ionic radii of the alkali ions or with increasing concentration of the alkali ions in the same series of glasses. The slope of the straight lines obtained on plotting log (Sn4+)/(Sn2+)( pO2 )n/2 vs mol% R2O increased in the order Li→Na→K. In ternary silicate glasses having the base glass composition 20Na2O·10RO·70SiO2, the Sn2+-Sn4+ equilibrium shifts more toward the reduced state, with increasing bond strength between the divalent cations and the nonbridging oxygens. With increasing temperature, the equilibrium shifts more toward the reduced state.  相似文献   

9.
The third-order nonlinear optical susceptibilities χ(3) of M2O-B2O3 (M = Li, Na, K, Rb, Cs, and Ag) binary borate glasses have been measured by the third harmonic generation (THG) method. It is found that the enhancement of χ(3)by the structural change of BO3 units to BO4 units is small, while the enhancement of χ(3) due to the formation of non- bridging oxygen is rather significant. The effects of alkali cations on the χ(3) of alkali borate glasses are discussed in terms of the M-O bond character, focusing on the covalency of Li2O-B2O3 glasses. Comparison of the χ(3) values for Cs2O-B2O3 and Ag2O-B2O3 glasses which contain cations of comparable polarizability reveals that the χ(3) value is much greater for Ag2O-B2O3 glasses than for Cs2O-B2O3glasses, which is possibly due to the great contribution of Ag(4 dz2 + 5 s + 5 pz ) hybrid orbitals to the nonlinear optical response.  相似文献   

10.
Twin-roller quenching produced wide ranges of glass formation in the systems Li2O-RO-Nb2O5 (R=Ba,Ca,Mg). The glass-forming ability is improved with an increase in the ionic radius of R2+ ions. The crystallization temperature is increased as Li2O is replaced by RO or the ionic radius of R2+ ions is increased. Infrared spectra revealed that the glass LiNbO3 (=50Li2O-0Nb2O5) was composed of six-coordinated NbO6 octahedra, which were joined together by corner-sharing only. In the Li2O-RO-Nb2O5 glasses there exist edge-shared as well as corner-shared NbO6 octahedra. The edge-shared NbO6 octahedra in the glasses are increased with an increase in the content of RO or Nb2O5, and also with an increase in the ionic radius of R2+ ions.  相似文献   

11.
High-temperature neutron diffraction and Raman spectra have been obtained on M2O–2B2O3 (M=Li, Na, K) glasses and melts. Both techniques indicate a coordination change of boron atoms: the tetrahedral boron sites present in the glasses are converted into triangular boron sites. These changes of the borate network yield modifications of the alkali environment, as assessed for Li using the isotopic substitution technique. We observe that Li atoms are in a charge-compensating position in the glass and in a modifying position in the liquid. These structural modifications have important implications toward understanding the physical properties of borate melts.  相似文献   

12.
Fluoroaluminate glasses containing various concentrations of Eu2+ were prepared under a reducing atmosphere for the present study, and the wavelength dependence of the Faraday rotation angle was examined. The magnitude of the Verdet constant (Vc) increased as the concentration of Eu2+ increased. In addition, the Verdet constant of glasses containing 5 cat.% Eu2+ was larger than that of fluoroaluminate glasses containing the same concentration of Tb3+ in the wavelength region from 400 to 600 nm. The effective transition wavelength, λt, for glasses containing Eu2+ as well as those containing Tb3+ was evaluated based on the Van Vleck and Hebb theory. Factors dominating the Verdet constant of those glasses are discussed in this report.  相似文献   

13.
The kinetics of copper-potassium ion exchange of potassium aluminosilicate glass have been investigated in molten CuCl at 550°C in air and nitrogen. The presence of oxygen dissolved in molten CuCl has a great effect on the Cu-K ion-exchange kinetics, i.e. ion exchange in nitrogen is controlled by the interdiffusion process of Cu+ and K+ in the glass, whereas ion exchange in air seems to be controlled by the Cu+→Cu2+ oxidation reaction.  相似文献   

14.
The mixed alkali effect on electrical conductivity, that is, the reduction of conductivity due to alkali mixing, was observed in Na2O–K2O–Ga2O3–TiO2 glasses, which are nonconventional in the sense that glass-forming oxides defined by Zachariasen are not involved. The magnitude of the reduction in conductivity of the present glasses due to alkali mixing was similar to that of corresponding mixed alkali silicate and phosphate glasses. The activation energy for electrical conduction showed a maximum around the composition Na/(Na + K) = 0.5, where the conductivity was at a minimum.  相似文献   

15.
Effect of Corrosion Processes on Subcritical Crack Growth in Glass   总被引:3,自引:0,他引:3  
Crack-growth studies were conducted on soda-lime-silica, soda borosilicate, and two binary soda-silica glasses immersed in solutions of 1 M Li+, 1 M Cs+, or deionized water at different pH values. A definite effect of the Li+ and Cs+ was observed on the V-K1 curves in all but the soda-lime glass. A plateau in crack velocity in the range 10-8 to 10-10 m/s was measured on the binary soda-silica glasses for K1<0.35 MPa.m1/2. These data are analyzed in terms of both the ion exchange and SiO2 dissolution steps of the corrosion process. A model of crack growth in corrosive conditions is proposed.  相似文献   

16.
The optical absorption spectra of 22R2O.13Al2O3.65B2O3 (mol%) glasses contain ing uranium indicate the presence of U6+, U5+, and U4+. The presence of U6+ in the uranyl group is favored as alkali ion (R) is replaced in the direction Li6+ coordinated diflerently from that in uranyl groups (possibly 4-coordinated). A suggestion for making use of such findings in estimating the uranium content of a sample is given.  相似文献   

17.
Experimental studies were made on the compositional dependence of the redox equilibrium of Eu in synthetic silicate liquids, together with an empirical model describing the observed compositional dependence. Electron paramagnetic resonance (EPR) was used to measure the concentration ratio of Eu2+ to Eu3+ in various glasses formed by rapidly quenching silicate liquids. The compositional field studied comprised mixtures of SiO2, TiO2, Al2O3, CaO, MgO, and Na2O. The proposed model describes the Eu2+/Eu3+ ratio over the entire compositional field in terms of parameters easily related to each glass composition. The general applicability and utility of the model is further demonstrated by its application to the Fe2+-Fe3+, Ce3+-Ce4+, and Cr3+-Cr6+ redox reactions in binary alkali oxide silicate glasses of Li, Na, and K.  相似文献   

18.
Controlled melting conditions for Cu-containing solder glasses yielded a variety of Cu+/Cu2+ ratios from a single glass starting composition. Measurements of softening point, thermal expansion, chemical durability, plus chemical analysis revealed that the well-known viscosity effect of adding copper oxide to solder glasses is caused primarily by the Cu+ ion; Cu2+ plays a minor role, if any.  相似文献   

19.
The glass-forming regions in the ternary systems M2O-In2O3-GeO2 (M = Li,Na,K) were determined. The region in each of the three ternaries is less extensive than in either of the analogous systems M2O-Al2O3-GeO2 and M2O-Ga2O3-GeO2; this behavior reflects the restrictive coordination requirements of the larger In ion. The In2O3-containing glasses exhibit higher densities and refractive indices than the corresponding Al2O3 and Ga2O3-containing glasses. Refractive index and density maxima are observed along lines of constant In2O3 in each of the three alkali indogermanate systems.  相似文献   

20.
The energy relations existing between the congruently melting compounds Li2O -2B2O3, Na2O–2B2O3, Na2O-4B2O3, and K2O-4B2O3 and their glasses have been determined for the temperature range 25° to 1100°C. High-temperature heat-content, entropy, and heat of solution data are given for both the glasses and the corresponding devitrified materials. A comparison of the heats of fusion of the alkali borates on a gram atom of oxygen basis shows that they follow the order Li > Na > K. The entropy differences between the glass and the corresponding crystalline material have been determined at 25°C. The free-energy change at 25°C. for the reaction crystal → glass has been calculated for the four compounds.  相似文献   

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