白釉还原焰烧成的研究

氧化焰白釉技术已经非常成熟,但对于还原焰来说,单纯通过提高釉中锆的含量,也不一定实现白釉可以完全遮盖住坯体,并呈现较高的白度。所以,研究是否可以通过改变乳浊剂的颗粒粒径来实现白釉的还原焰烧成。乳白釉配方的釉用乳浊剂种类较多,有氧化锡、氧化锌、锆英砂、氧化锆等等。鉴于氧化锆受气氛影响较小,乳浊效果较好,是较稳定的乳浊剂。本次试验选择氧化锆和硅酸锆作为乳浊剂。硅酸锆的粒度不同,可以对釉配方性能产生较大的影响。     

无氟乳浊玻璃

氟化物是常用的玻璃乳浊剂,但污染环境。阐述了无氟乳浊玻璃如磷酸盐乳浊玻璃、氧化物乳浊玻璃、分相乳浊玻璃的成分和制备工艺,并指出存在的问题和发展方向。     

LOW-LEAD,BRIGHT OPAQUE GLAZES AT CONES 08 TO 06*

This investigation covered several systematic fields of opaque fritted glazes for cones 08 to 06 (1733° to 1841°F.) in which lead oxide was replaced by barium, strontium, and zinc oxides. All glaze ingredients except the kaolin and the Ultrox zirconium opacifier were incorporated in the frits. Glazes of low-lead content as well as some lead-free compositions were obtained which possessed excellent gloss and opacity on wall tile of low and of medium tale content. Barium oxide was the best substitute for lead oxide from the standpoint of gloss, although moderate amounts of strontium and zinc oxides can be used to advantage. The whitest and most opaque glazes were obtained with the use of zinc oxide.     

Effects of Zirconium-Type Opacifiers on Properties of Glazes

The use of various zirconium-type opacifiers such as zircon, zirconia, and the alkaline-earth silicates of zirconium in fritted and raw glazes maturing in the range cones 06 to 04 and cones 9 to 11, respectively, and the properties of the resulting slips and fired glazes were investigated. Substitution of the various opacifiers was in each instance based on the molecular glaze composition. In the fritted glazes maturing at cones 06 to 04 where the use of all types of zirconium opacifiers was not possible without altering the molecular composition, optimum properties were obtained with zircon. In the raw type of glaze maturing at cones 9 to 11, in which a greater variety of opacifier substitutions could be made, combinations of the alkaline-earth silicates of zirconium as opacifiers produced a marked improvement in slip properties and a definite reduction in opacifier segregation compared with glazes opacified with zircon or with zirconia. Use of the alkaline-earth silicates of zirconium did not impair other fired properties such as opacity, gloss, texture, and finish.     

Volatilization of components from zirconia ceramics

Conclusions We investigated volatilization in isothermal conditions of solid solutions of oxides of calcium and yttrium in ZrO₂.The calcium oxide is intensely sublimited from the solid solution of zirconium dioxide, stabilized with CaO at 2000–2100°C. However, during soaking and rapid cooling, destabilization does not occur, even during sublimation of 70–75% CaO. With rise in temperature to 2400–2500°C and a 4 h soak, only 0.5% CaO is preserved in the solid solution, which leads to destabilization and conversion of a large part of the cubic form of ZrO₂ with calcium oxide by fusion, we note sublimation of part of the CaO, and the remaining quantity (3%) is adequate for complete conversion of the zirconia into the stable cubic form.Volatilization of the stabilizing additive occurs in the form of YO at substantially higher temperatures than volatilization of the calcium oxide from the solid solution of zirconium dioxide, stabilized with yttrium oxide. Simultaneously with this we note volatilization of zirconium dioxide in the form of ZrO and ZrO₂.For the use of zirconium dioxide at elevated service temperatures, we would recommend yttrium oxide as a stabilizing additive.Translated from Ogneupory, No. 1, pp. 49–52, January, 1968.     

Oxyfluoronitride Glasses with High Elastic Modulus and Low Glass Transition Temperatures

The preparation and properties of novel calcium aluminosilicate glasses containing both nitrogen and fluorine are reported. Nitrogen increases Young's modulus and microhardness of oxide glasses by ∼25%. However, one of the major disadvantages of the use of oxynitride glasses for high-stiffness applications is the fact that nitrogen also increases glass viscosity. Melting temperatures of the order of ∼1700°C are required to achieve sufficiently low viscosities for glass forming and drawing processes. Fluorine substitution for oxygen in Ca–Si–Al–O–N glasses yields significant decreases in glass transition temperature and glass melting temperature as well as increasing nitrogen solubility to levels much higher than that previously reported for glasses made by melting CaO, SiO₂, Si₃N₄, and Al₂O₃ powder mixtures. The important effect that N results in increased elastic modulus is not diminished by the addition of fluorine. Thus, it is possible to produce novel oxyfluoronitride glasses with a high elastic modulus but melting and working can be carried out at more conventional glass processing temperatures.     

Kinetics of the Ostwald ripening in lithium aluminosilicate glasses containing TiO2 and ZrO2

A structural investigation is undertaken on lithium aluminosilicate glasses containing a titanium oxide or titanium and zirconium oxides. The structural transformations in the course of Ostwald ripening observed after the increase in temperature of the glasses preliminarily heat-heated to the attainment of a stable two-phase structure (catalyst phase) are studied by the small-angle X-ray scattering (SAXS) technique. In all the cases, an increase in temperature leads to the loss of stability and a partial dissolution of the phase precipitated at a lower temperature. The low-temperature heat treatment (660°C) of lithium aluminosilicate glasses containing TiO₂ and ZrO₂ brings about the precipitation of aluminotitanate phase that reaches the stable state upon prolonged heat treatments for 5000–6000 h. As the temperature increases, this phase becomes unstable, which results in its dissolution and the precipitation of a new phase containing titanium and zirconium oxides in the form of zirconium titanate microcrystals. Changes in the phase composition in the course of Ostwald ripening upon isothermal treatments of glasses containing TiO₂ and ZrO₂ are associated with different mobilities of structural elements involving titanium or zirconium ions.     

Kinetics of the Ostwald ripening in lithium aluminosilicate glasses containing TiO2 and ZrO2

A structural investigation is undertaken on lithium aluminosilicate glasses containing a titanium oxide or titanium and zirconium oxides. The structural transformations in the course of Ostwald ripening observed after the increase in temperature of the glasses preliminarily heat-heated to the attainment of a stable two-phase structure (catalyst phase) are studied by the small-angle X-ray scattering (SAXS) technique. In all the cases, an increase in temperature leads to the loss of stability and a partial dissolution of the phase precipitated at a lower temperature. The low-temperature heat treatment (660°C) of lithium aluminosilicate glasses containing TiO₂ and ZrO₂ brings about the precipitation of aluminotitanate phase that reaches the stable state upon prolonged heat treatments for 5000–6000 h. As the temperature increases, this phase becomes unstable, which results in its dissolution and the precipitation of a new phase containing titanium and zirconium oxides in the form of zirconium titanate microcrystals. Changes in the phase composition in the course of Ostwald ripening upon isothermal treatments of glasses containing TiO₂ and ZrO₂ are associated with different mobilities of structural elements involving titanium or zirconium ions.     

Hydrogen Dissolution in and Release from Nonmetals: III, Tetragonal Zirconia

The solubility and release kinetics of hydrogen in single-crystal zirconia were investigated by the infusion–extraction method. Equilibration in hydrogen at pressures between 1.4 and 11 atm (0.14 and 1.1 MPa) and at temperatures from 1300° to 1600°C produced H/Zr ratios varying from 4 × 10⁻⁵ to 1.3 × 10⁻⁴. Dissolution was exothermic with an enthalpy of solution of 6.6 kcal/mol (28 kJ/mol). The solubility increased with the extent of substoichiometry of the oxide caused by exposure to hydrogen. The solubility behavior and the kinetics of release indicated that hydrogen in the solid forms defect clusters consisting of a hydrogen atom, two trivalent cations, and a doubly charged oxygen vacancy. The trivalent ions were either impurities or reduced zirconium ions. Rate constants for first-order detrapping were determined. Diffusion was shown not to be a rate-limiting process in hydrogen release.     

复合日用瓷乳白釉的研制

通过调整ＲＯ，ＳｉＯ２和Ａｌ２Ｏ３的含量，研制成功了以锆英石为主要乳浊剂、氧化锡为辅助乳浊剂的日用瓷复合生料乳浊釉．探索了各主要组分对釉面质量的影响。     

EFFECT OF COMPOSITION AND TEMPERATURE ON SOLUBILITY OF IRON OXIDE IN GROUND-COAT ENAMEL GLASS*

The solubility of iron oxide in ground-coat enamel glasses at various temperatures was studied by adding varying amounts of ferric oxide to the milled enamel and giving the mixture a heat-treatment to acquire uniformity without devitrification at the desired temperature. The iron oxide solubility was obtained by finding the breaking point in the curve for iron oxide versus index of refraction. The frit solubilities were obtained at 1400°, 1600°, 1800°, and 2000°F. with variations in Na₂O, B₂O₃, A1₂O₃, CaF₂, CaO, F₂, SiO₂, COO, NiO, MnO₂, BaO, and MoO₃. Data are given on a number of commercial frits.     

A Limited Review of Water Diffusivity and Solubility in Glasses and Melts

A limited review of the literature dealing with water solubility and diffusion in oxide glasses and melts is presented, with an emphasis on simple and commercial compositions and on work during the past decade. Several methods for determination of water solubilities and diffusivities are discussed. Experimental results are presented for silicate, borate, and germanate glasses and melts. Water diffusivities always increase with increasing temperature and modifier oxide content in these melts. Variations in water solubility and diffusivity with alkali and alkaline earth identity for otherwise identical compositions are small, while variations with the identity of the glass-forming oxide are large. Water solubility increases with increasing modifier oxide content in alkali silicate melts, but decreases with increasing modifier oxide content in alkali borate and germanate melts.     

FACTORS INFLUENCING FLUXING ACTION OF VARIOUS OXIDES IN LOW-TEMPERATURE BOROSILICATE GLASSES*

Strontium, barium, and lead oxides were studied as fluxes in low-temperature borosilicate glasses by using the button-flow method. It was found that strontia may be superior to lead oxide as a flux in glasses high in fluorides and low in alumina. This result was explained by the greater solubility of fluorides in strontia glasses, in which case the two fluxes, strontia and fluorspar, are acting together.     

Strengthening by Ion Exchange

This paper is a brief review of the physical and chemical methods of strengthening glass, in particular that due to the large for small ion exchange resulting from treatment in molten salt at temperatures below the annealing range for the glass. Abrasion of treated glass is shown to reduce markedly the strength of experimental alkali-lime-silica glasses as well as commercial glasses of this and other types. Treated alkali-alumina-silica and alkali-zirconia-silica glasses, however, are less affected by abrasion. Strength after abrasion increases with alumina or zirconia content, reaching 117,000 psi for cane of a 35% alumina glass. The explanation for the aluminum or zirconium effect may involve an unusual ionic environment caused by their presence in the lattice.     

Internal Friction of Simple Alkali Silicate Glasses Containing Alkaline-Earth Oxides: I, Experimental Results

The internal friction of simple alkali silicate glasses to which systematic alkaline-earth oxide additions were made was investigated. These additions produced two significant results: (1) The two peaks previously reported in alkali silicate glasses were shifted to higher temperatures and decreased in height and (2) a third peak was found in some glasses which became more pronounced with increasing alkaline-earth oxide content. Internal friction measurements of alkali-free silicate and phosphate glasses also are described. In these glasses, peaks were present which closely resembled those found in glasses containing alkali.     

Evidence of Tin Oxide Recrystallization in Opacified Lead Glazes

Tin oxide (SnO₂) particles that are a few hundred nanometers in size and are embedded in a lead glaze act as a white opacifier. The insolubility of SnO₂ particles in a lead glaze is responsible for this microstructure. Although it is assumed that SnO₂ particles do not react during the glaze formation, we demonstrate that the development of metastable phases prior to the fusion of the PbO-SiO₂-SnO₂ mixture allows the SnO₂ particles to react and then recrystallize subsequent to the fusion of the mixture. The recrystallization of SnO₂ occurs during heating and/or cooling until the temperature is sufficiently low and/or the tin supply is exhausted.     

Nature and Thermal Evolution of Amorphous Hvdrated Zirconium Oxide

The thermal behavior of amorphous hydrated zirconium oxide and its coprecipitates with other oxides was studied. Solid solution with a limit of solubility seems to exist in the amorphous coprecipitates. A relation with the high-temperature solid solution was established. The structure of the amorphous zirconia was studied by X-ray and neutron diffraction; a thin plate model related to the structure of tetragonal zirconia is proposed. Heating the precipitates in an oxygen-free atmosphere produced a black nonstoichiometric oxide and stabilization of the tetragonal form.     

Nonstoichiometry of ZrO2 and Its Relation to Tetragonal-Cubic Inversion in ZrO2

The system Zr-O was studied in the composition range 50 to 66.7 at.% O by metallographic analysis, high-temperature X-ray analysis, and lattice parameter determinations at room temperature. The solubility of zirconium in zirconia was determined from 1200° to 2000°C, and the cubic-tetragonal inversion temperature of ZrO₂ was shown to be lowered to approximately 1490°C for samples containing α-Zr and oxide phase. Alpha zirconium has greater solubility in the cubic phase than in the tetragonal phase, and the inversion is revealed, in samples quenched from the cubic field, by the exsolution of α-Zr, which is metallographically characterized as striations. At room temperature, the striations are oriented with the 111 and 11° planes of monoclinic zirconia.     

FUNCTION AND ACTION OF OPACIFIERS1

The causes of opacification and the function of opacifiers in white ware glazes are discussed briefly. The relative covering power of tin oxide is shown to be greater than that of zircon oxide under the same conditions. The fluidity of the glaze is affected by the amount of opacifier used and can be controlled in commercial practice by the use of a simple inclined testing block.     

Total Heat-Transmission Coefficients of Amber and Green Glasses in Temperatures of Melting Range

Measurements of an over-all heat-transmission coefficient for several commercial amber glasses were carried out in a pilot-scale furnace at temperatures of the melting range. The data obtained were used in deciding depth and insulation of tank furnaces. It appears that the transmission of light of amber glasses in the near-infrared range gives a practical indication of these heat-transmission properties. The same pilot-scale furnace was used to investigate the effect of chromium oxide, nickel oxide, and iron oxide on the over-all heat-transmission coefficients of green glasses. An empirical equation was derived, relating the heat-transmission coefficient to the concentration of the coloring oxides. Of the three oxides, the effect of the nickel oxide on heat transmission is the strongest and the effect of the iron oxide is the weakest.