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1.
The subliquidus miscibility gap in the system K2 O-B2 O3 -SiO2 has been determined for compositions with molar ratios SiO2 /B2 O3 <2 and T≥550°C. The shape of the miscibility gap is an elongated dome similar in form to, but less extensive than those in the lithium and sodium borosilicate systems. The consolute composition (molar) and temperature are estimated to be 4 ± 1 K2 O -30±8 B2 O3 -66±8 SiO2 and 629±5°C, respectively . 相似文献
2.
Paul Wencil Brown 《Journal of the American Ceramic Society》1990,73(11):3457-3461
A portion of the quaternary phase diagram for Na2 O-CaO-SiO2 -H2 O has been constructed. Plotting concentrations as their 10th roots allows compounds having solubilities which differ by several orders of magnitude to be represented on a single diagram. The compositional relationships among sodium-substituted calcium silicate hydrate, calcium-substituted sodium silicate hydrate, calcium bydroxide, a quaternary compound of approximate composition 0.25Na2 O · CaO · SiO2 · 3H2 O, sodium hydroxide monohydrate, and miscellaneous sodium silicate hydrates are presented. The quaternary diagram constructed shows the quaternary compound to exist in equilibrium with sodium-substituted calcium silicate hydrate and calcium hydroxide. Conditions in concrete pore solutions which favor the formation of this quaternary compound may also favor the occurrence of the alkali-silica reaction. 相似文献
3.
L. M. FOSTER G. V. CHANDRASHEKHAR J. E. SCARDEFIELD R. B. BRADFORD 《Journal of the American Ceramic Society》1980,63(9-10):509-512
A new phase diagram for the system Na2 O-Ga2 O3 (>50 mol% Ga2 O3 ) is presented. It is based on information from differential thermal analysis, X-ray examination of quenched samples, and a radiochemical technique for determining the compositions of a primary phase and a liquid in equilibrium with it. The diagram provides a guide for the growth of primary crystals of the two ionically conducting sodium gallates that are analogs of the technologically important β- and β"-aluminas. 相似文献
4.
A detailed study of the system Pb0–B2 03 –Si02 was undertaken because of the interest in lead borosilicate fluxes and the possibility of producing opaque low-melting enamels by controlled liquid-phase separations. Studies in the portion of the system containing greater than 60% PbO produced little change from previous work. The shape of the liquidus surface beneath the two-liquid region and the shape of the immiscibility dome were determined. Much of the observed immiscibility is metastable, particularly for compositions containing greater than 40% SiO2 . Using the electron microscope provided information on the way the rate of formation, stability, and texture of the immiscible liquids are affected by composition, time, and temperature. Finally, a high-temperature centrifuge was constructed to separate the immiscible liquids and thus define tie lines within the immiscibility dome. 相似文献
5.
PETER TAYLOR ALLAN B. CAMPBELL DERREK G. OWEN 《Journal of the American Ceramic Society》1983,66(5):347-351
The limits of miscibility at 650°C were determined for compositions with the mole ratio SiO2 /B2 O3 =1.07 in the systems X2 O-MO-B2 O3 -SiO2 (X = Na,K; M = Mg,Ca,Ba) and Na2 O-MgO-BaO-B2 O3 -SiO2 . The form of the miscibility gaps in the quaternary systems is similar to that previously described for the system Na2 O-ZnO-B2 O3 -SiO2 . The topography of miscibility gaps in systems of this type is discussed in detail. The extent of the miscibility gap is correlated with the polarizing power of each cation, X and M (Na > K and Zn ≅ Mg > Ca > Ba) both among the seven quaternary systems and within the single five-component system examined. The possibility of using empirical correlations observed among the quaternary systems to predict the behavior of other compositions, or of more complex systems, is explored. 相似文献
6.
BURNHAM W. KING 《Journal of the American Ceramic Society》1954,37(5):238-242
It was first shown that the enamel slips which have the best suspnding characteristics contain equal amounts of Na2 O and B2 O3 and at least a moderate amount of NaF. The solubilities of mixtures of Na2 O, NaF, and B2 O3 were then investigated. The pH of these solutions and the primary crystalline phases separating on evaporation also were determined. The solubility data obtained at room temperature were summarized. When the solutions were evaporated, NaF was the first crystalline phase to separate from a large proportion of the mixtures investigated. It was concluded that the desirable handling characteristics of enamels whose mill liquors contain the proper proportion of Na2 O, NaF, and B2 O3 are not due to the formation of complex salts but to the following combination of properties: (1) the presence of salts with a moderate solubility which changes very slightly with temperature, (2) a moderate pH of about 10 in a probably well-buffered solution, (3) a relatively stable crystalline material, NaF, as a primary phase, and (4) a secondary phase which crystallizes slowly with relatively little shrinkage. 相似文献
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8.
Phase equilibria data, obtained both by differential thermal analysis and by quenching, are presented for the system Na2 O-Nb2 O5 . Five compounds corresponding to the formulas 3Na2 O.1Nb2 06 , lNa2 O. 1Nb2 O5 , lNa2 O 4Nb2 O6 , lNaz O.7Nb2 O5 , and lNa2 O. 10Nb2 O6 have been found. The compound 3Naz 0.lNb2 O5 melts congruently at 992°C. The compounds 1Na2 O. 4Nb2 O6 , lNa2 O.7Nb2 O, and 1Na2 O. 1Onb2 O5 melt incongruently at 1265°, 1275°, and 1290°C., respectively. The well-known perovskite structure phase NaNbO3 was found to melt congruently at 1412°C. The transition temperatures in NaNbO5 were checked by thermal analysis and only the major structural changes at 368° and 640°C. could be detected. A new disordered form of NaNbO3 could be preserved to room temperature by very rapid quenching. 相似文献
9.
HARTMUT SCHNEIDER 《Journal of the American Ceramic Society》1984,67(7):130-C
Incorporation of up to 0.4 wt% Na2 O was found in the mullites of fused-cast mullite brick. Sodium oxide incorporation probably requires very high temperatures and persists only when the material is quenched rapidly to room temperature; it may be stabilized by simultaneous entry ofZr4+ into the mullite structure. 相似文献
10.
ANTHONY R. WEST 《Journal of the American Ceramic Society》1976,59(3-4):118-121
Phase equilibria were studied for the system Na2 SiO:r Li2 SiO3 . The 2 end-member metasilicates show limited mutual solid solubility with the (Na2-χ Liχ )SiO3 solid solutions being particularly extensive at solidus temperatures (0 x 1.06). Ordering of the latter solid solution occurs at the NaLiSiO;) composition with asupercellx = 6asubcell During cooling of the solid solutions, metastable phase transformations occur; a twinned monoclinic metastable phase, low (Na, Li)2 SiO3 , has been characterized. 相似文献
11.
E. F. RIEBLING 《Journal of the American Ceramic Society》1974,57(9):373-377
Ternary Na2 O.Sb2 O3 .GeO2 glasses (with various [Na]/[Na + Sb] ratios) that contained ≥65 mol% GeO2 were prepared. Their densities (volumes), refractive indices, and infrared spectra were determined and their colors noted. The ternary glasses with ≥88 mol% GeO2 exhibit nearly additive volumes, refractivities, and frequencies for the main Ge-O vibration. Ternary glasses with lesser amounts of GeO2 exhibit a variety of behaviors, depending on the [Na]/[Na + Sb] ratio. Small amounts of Sb2 O3 cause significant volume and refraction deviations, as well as changes in νGe-O , that can be associated with gradual elimination of GeO6 octahedra. All the information supports a model for the glasses with 65 to 88 mol% GeO2 that involves a degree of depolymerization that is greater when Na2 O and Sb2 O3 are present together than when either is present alone. 相似文献
12.
W. D. JOHNSTON 《Journal of the American Ceramic Society》1965,48(4):184-190
The oxidation-reduction equilibria in molten glasses having a soda/silica ratio of 1/2 and containing small amounts of variable-valence ions of the transition elements titanium, vanadium, iron, cobalt, and nickel, the post-transition elements tin and antimony, and the rare-earth element cerium were obtained by equilibrating the melts with various atmospheres. The simple mass expression
was always applicable. In the expression, n is the number of electrons involved in the valence change of the metal M. The value of n is 1 for all systems except for the ions of antimony and tin where n is 2. The ions found are those generally accepted as existing in glass melts which are Ti3+ , Ti4+ ; Fez+, Fe3+ ; Ce3+ , Ce4+ ; Mn2+ , Mn3 ; Co2+ , Co3+ ; Ni2+ , Ni3 ; Sb3+ , Sb5+ ; and Sn2+ , Sn4+ . Two mass action expressions were needed for vanadium-containing glasses to describe the equilibria between 5+, 4+, and 3 f species. 相似文献
was always applicable. In the expression, n is the number of electrons involved in the valence change of the metal M. The value of n is 1 for all systems except for the ions of antimony and tin where n is 2. The ions found are those generally accepted as existing in glass melts which are Ti
13.
14.
K. Nakanishi J. Acocella J. Molinelli; and M. Tomozawa 《Journal of the American Ceramic Society》1982,65(5):c71-c71
Up to 5.75 WHO of concentrated (49 wt%) HF solution was placed in Nazo.3SiO2 glass under hydrothermal conditions. Electrical conductivity of the resulting glasses was primarily determined by the water content. 相似文献
15.
J. D. HODGE 《Journal of the American Ceramic Society》1984,67(3):183-185
A subsolidus phase diagram for the system Li2 O-Na2 O-Al2 O3 at 1500°C is presented. Unlike the analogous system MgO-Na2 O-Al2 O3 , β" was the only ternary compound observed in the section of the lithia-based system examined in this study. A fairly extensive region of β solid solution was found. In contrast, the range of compositions where β" exists is small and does not extend into the Na2 O-Al2 O3 binary. 相似文献
16.
ANTHONY R. WEST 《Journal of the American Ceramic Society》1976,59(3-4):124-127
Ternary phase relations have been studied and several modifications made to Kracek's phase equilibrium diagram. These include location of the primary phase fields of Na6 Si8 O19 and Li2 Si2 O5 . Metastable phases and polymorphs were often encountered, notably a primary phase, δ-Na2 Si2 O5 , and a new polymorph of Li2 Si2 O5 . 相似文献
17.
The molecular dynamics computer simulation technique was used to determine the short-time dynamics behavior and resultant structures of ions at the surface of Li2 0·3SiO2 and Na2 O-3SiO2 glasses. Room temperature and elevated temperatures were used. Results are compared with similar studies of the K2 O·3SiO2 glass surface and with recent experimental ion-scattering-spectroscopy data. The simulations indicate that a localized surface rearrangement occurs within picoseconds after formation of the free surface, creating a surface excess of alkali in the Na (and K) case, but not in the Li case. Elevated temperatures, even for brief times, enhance the observed surface excess of Na and K. The results correspond to those obtained from the ion-scattering-spectroscopy studies. 相似文献
18.
The chemical resistance of mixed-alkali glasses to water was measured by determining the sodium, potassium, calcium, and silicon ions extracted instead of evaluating it from the alkalinity of the mixed-alkali extracts. In glasses of the composition K2 O and Na2 O 18, CaO 10, and SiO2 72% the minimum extraction of alkali (maximum durability) occurred for a K2 O/-Na2 O ratio of 2.6/1.0 (by weight). Based on an ionic-composition analysis of the results, an empirical index is suggested for determining the relative degree of ion-exchange and network-breakdown modes of reactions that occur when such mixed-alkali glasses are attacked by water. 相似文献
19.
Alumina and gallia were substituted separately for Na2 O in amounts of 0.2, 0.5, 1.0, 1.5, 2.0, and 3.0 wt% in three Na2 O-SiO2 glass compositions (82, 84, and 86 wt% SiO2 ) within the immiscibility region. The immiscibility regions for each system extend to ∼1.5 mol% of the added oxide. In general, the addition reduced the immiscibility temperature ( T m ), but at the edge of the immiscibility region (82% SiO2 ) the Na2 O loss effect initially increased T m . A structural model of the miscibility of Al2 O3 added to silicate glasses is presented. 相似文献
20.
CECIL M. JONES II 《Journal of the American Ceramic Society》1971,54(7):347-349
A technique for growing α-Al2 O3 crystals is described in which Na2 O·11Al2 O3 is dissolved in a liquid of composition Na2 O·4TiO2 ·3Al2 O3 . Alpha Al2 O3 is precipitated as Na2 O evaporates from the system; Na2 O·11Al2 O3 serves as a source of Al2 O3 , and Na2 O in the liquid. The content of solids in the mixture is always such that it does not melt completely. The size of the α-Al2 O3 crystals grown is related to the Na2 O content of the composition. Crystals as large as 4000 by 3000 μm in the α-axis direction and 500 μm in the c -axis direction have been grown. 相似文献