硅酸钾和硅酸钠灌浆型防火玻璃的研究

对硅酸钾和硅酸钠两种灌浆型防火玻璃进行耐火性能、透光率和耐候性能对比研究,分别进行了透光率测试、耐辐照测试、红外光谱测试(FTIR)、热重测试(TG)、发泡测试、SEM测试。结果表明,同摩尔比条件下硅酸钾灌浆玻璃具有更好的透光率,硅酸钠灌浆防火玻璃耐火性能更好,硅酸钠凝胶的发泡性能要好于硅酸钾凝胶。两种灌浆玻璃都具有很好的耐候性。     

Continuous dissolution of sodium and potassium silicate glass in a tower dissolver

Sodium and potassium silicate glass was continuously dissolved in a tower dissolver operated at atmospheric pressure. In pilot experiments the rate, controlled by the dissolution process occurring at the glass/liquor interface, was dependent on surface area, temperature, type, and chemical composition of the glass, but was independent of concentration and flowrate. Activation energies for the dissolution process lay in the range 22-48 kJ/mol, while typical rates of dissolution were 26 and 21 kg m^?3 h^?1 for 2.0 and 3.2 SiO₂/Na₂O weight ratio sodium silicate glass at 99°C. The corresponding rate for potassium silicate glass of SiO₂/K₂O weight ratio 2.0was 195 kgm^?3h^?1 at 80°C. Loss of potassium silicate due to the formation of insoluble compounds was prevented by operating below 93°C. Tower dissolvers warrant further consideration as an alternative to conventional digestors, having the advantages of continuous operation and uniform product density.     

Pulsed cathodoluminescence of two-alkali sodium potassium silicate glasses

Alkali silicate glasses of variable composition 22xNa₂O · 22(1?x)K₂O · 3CaO · 75SiO₂ with equimolecular replacement of sodium ions by potassium ions are investigated using pulsed cathodoluminescence. It is revealed that localized electronic states interact with vibrations of two types, namely, polarization vibrations of the silicon-oxygen network with the frequency v₀ = 820 cm^?1 and bending vibrations of the modifier sublattice. At low concentrations of one of the alkali components (x < 0.1), bending vibrations are observed at two frequencies. These frequencies coincide with those of the corresponding vibrations in one-alkali systems containing Na (530 cm^?1) and K (520 cm^?1). At higher concentrations (x in the range ～0.14–0.86), there occur bending vibrations of the cationic sublattice with a frequency of 420 cm^?1. This can be interpreted as a luminescence analog of two-alkali (mixed-alkali) effect.     

Superior scintillation property of Tb3+-doped sodium silicate glass

The ability of a scintillator to absorb and convert the high-energy X-ray photons to low-energy visible photons is crucial for the application of X-ray in medical tests, security checks and scientific research. However, traditional scintillation crystals are synthesized by complex preparation process with high cost, hindering the wide development in practical applications. Here, Tb³⁺ doped sodium silicate glass, which exhibits remarkable scintillation property and recoverability to X-ray irradiation, was successfully prepared by an exercisable melt-quenching method. The obtained scintillator shows intense radioluminescence, which is about 1.5 times higher than that of the reference of Bi₄Ge₃O₁₂. The damaged glass to X-ray irradiation can be returned to the original state after heat treatment again, indicating excellent recovery. Moreover, the scintillator displays wonderful thermal stability with the fluorescence intensity at 573 K still remaining 96% at room temperature. These results demonstrate that the obtained scintillating glass has potential application towards the real world.     

Field-assisted diffusion of K<Superscript>+</Superscript>, Rb<Superscript>+</Superscript>, Cs<Superscript>+</Superscript>, Ag<Superscript>+</Superscript>, and Tl<Superscript>+</Superscript> ions in sodium silicate glass

The composition of the diffusion zone formed during the interaction between 20Na₂O · 80SiO₂ glass and molten silver, rubidium, cesium, and thallium nitrates with and without imposition of a constant electric field was determined using X-ray microanalysis. The interdiffusion coefficients and values of electrical mobility were calculated, and the parameters of temperature dependence were determined. The electrical mobility was almost independent of the size and chemical nature of a cation and was determined by the mobility of the cation included into the initial glass.     

Absorption spectral properties of Cu2 ions in sodium potassium sulphate

This short note reports the results concerning electron paramagnetic resonance (EPR) and optical absorption spectra of Cu²⁺ ions doped in sodium potassium sulphate both at 300K and 77K.     

Glass-forming region and enhanced Bi NIR emission in sodium tantalum silicate laser glass

Bismuth (Bi)-doped glasses and fibers are of current interest as promising active media for new fiber lasers and amplifiers due to their 800-1700 nm near-infrared (NIR) emission. However, the optically active Bi centers in silica are easily volatilized during high-temperature fiber drawing, which results in low Bi doping concentration and low gain NIR luminescence. Here, we explored the glass-forming region in a model glass system of sodium tantalum silicate (Na₂O-Ta₂O₅-SiO₂) glass and attained suitable glass host for enhancing Bi NIR emission, right followed by detailed analysis on optical and structural characterization. Glass-forming region roughly lies in where Ta₂O₅ ≤ 30 mol%, SiO₂ ≥ 40 mol%, and Na₂O ≤ 40 mol%. Not only is glass-forming ability improved but also Bi NIR emission is enhanced (~60 times) by the introduction of Ta into glass network. Dissociated Na cations are restricted beside Ta, the high-field-strength element, so that the negative impacts of Na cations on glass formation and Bi NIR emission are weakened, which is responsible for the highly enhanced Bi NIR emission. This work helps us understand the glass-forming of tantalum silicate glass systems and luminescent behaviors of Bi. Hopefully, it could contribute to designing the Bi-doped laser glasses and high gain fibers with stable luminescent properties in future.     

Spectral-kinetic analysis of the photoinduced recombination of radiation-induced color centers in the sodium silicate glass

A technique for the spectral-kinetic analysis of the photoinduced recombination of radiation-induced color centers in glasses is developed. This technique is used to investigate the sodium silicate glass. The photoinduced absorption spectra of color centers are decomposed into individual Gaussian profiles, and the kinetic dependences of the intensities of these profiles are determined. The absorption spectrum associated with the radiation-induced color centers stable to optical radiation in the spectral range used in this study is separated from the total absorption spectrum of color centers. It is demonstrated that the absorption bands with maxima in the vicinity of 2.0, 2.8, and 4.0 eV are attributed to intrinsic hole centers of different types.     

Atomistic understanding of surface wear process of sodium silicate glass in dry versus humid environments

Understanding surface reactions of silicate glass under interfacial shear is critical as it can provide physical insights needed for rational design of more durable glasses. Here, we performed reactive molecular dynamics (MD) simulations with ReaxFF potentials to study the mechanochemical wear of sodium silicate glass rubbed with amorphous silica in the absence and presence of interfacial water molecules. The effect of water molecules on the shear-induced chemical reaction at the sliding interface was investigated. The dependence of wear on the number of interfacial water molecules in ReaxFF-MD simulations was in reasonable agreement with the experimental data. Confirming this, the ReaxFF-MD simulation was used to find further details of atomistic reaction dynamics that cannot be obtained from experimental investigations only. The simulation showed that the severe wear in the dry condition is due to the formation of interfacial Si_substrate–O–Si_{counter_surface} bond that convey the interfacial shear stress to the subsurface and the presence of interfacial water reduces the interfacial bridging bond formation. The leachable sodium ions facilitate surface reactions with water-producing hydroxyl groups and their key role in the hydrolysis reaction is discussed.     

The structure of sodium silicate glass from neutron diffraction and modeling of oxygen-oxygen correlations

It is shown that modeling the first oxygen-oxygen peak in the neutron correlation function of a glass enables structural information about other correlations to be obtained, and the method is illustrated by application to a sodium silicate glass. The first O–O coordination number can be calculated from network theory, and sodium silicate crystal structures show that the mean O–O distance can be calculated from the Si–O distance, despite the distortion of the SiO₄ tetrahedra. Modeling the O–O peak for a sodium silicate glass allows the Na-O bond length distribution to be determined. For a binary glass with 42.5 mol% Na₂O, it is found that the Na–O coordination number is 4.8(2) with an average bond length of 2.45 Å, and the Na–O bond lengths are more widely distributed than in sodium silicate crystal structures. Sodium ions are bonded mostly to non-bridging oxygens (NBOs), and the Na–NBO coordination number may be four as in crystals. Sodium ions are also bonded to a smaller number of bridging oxygens (BOs). Contrary to previous reports, it is not concluded that Na–NBO bonds are shorter than Na–BO bonds, but instead that the Na–BO distribution is relatively narrow, whilst the Na–NBO distribution extends to both shorter and longer distance. The broad distribution of Na–O bond lengths arises from a relatively broad distribution of Na–NBO bond valences, subject to the overall requirement of charge balance.     

Drying of sodium silicate solutions

Sodium silicate solutions with a silicon dioxide:sodium monoxide mole ratio of 3.41:1 were dried gently to give amorphous solids. These solids, together with the products obtained by heating them at various temperatures up to ～ 200°c, were studied by differential thermal analysis, solubility tests and other techniques. The resultant data give some insight into the structural changes which occur in the solid during the drying process.     

Low-temperature luminescence of lead silicate glass

The temperature quenching of intrinsic luminescence of a lead silicate glass of the 20PbO · 80SiO₂ composition has been investigated in the temperature range 7–200 K. It has been found that the temperature behavior of the intensity of intrinsic luminescence does not obey the well-known Mott’s law for intracenter quenching of luminescence but is adequately described by the empirical Street’s formula. It has been demonstrated that, with allowance made for the disorder of the atomic structure, the experimental temperature dependence of the luminescence intensity of the glass can be represented as a superposition of Mott’s dependences for an ensemble of local luminescence centers. The obtained distribution of luminescence centers over the activation energies of quenching has an asymmetric form with prevailing low-energy states. It has been assumed that this feature has a general character and, at low temperatures, determines the specificity of the processes of nonradiative relaxation of the electronic subsystem for many oxide glasses.     

Differences in molecular species present in aqueous potassium silicate solutions and their efficiency as adhesives for phosphors on glass

Potassium silicate liquors of very similar composition (SiO₂/K₂O ratios approximately 3.mD4:1) prepared from Aerosil, acid-washed silica-gel fines or potash glass have been examined by (a) light scattering, (b) reaction with molybdate and (c) use of the metachromatic effect with pinacyanol chloride. Definite differences between the molecular weights of the samples were obtained from the light-scattering results. These differences correlated well with the interaction observed between the silicate and pinacyanol chloride and the wet adhesion shown by the silicate; the samples containing more of the very high molecular weight polysilicate showing poor adhesion. The actual molecular weights have been estimated, but the determination of these involved dilutions of the silicate liquors and, over the range of dilution used, the reaction with molybdate showed that rapid depolymerisation of the silicate polyanion occurred on dilution. The results indicate that liquors prepared from potash glass contain more high-molecular-weight material than liquors prepared from silica gel or Aerosil.     

层状结晶硅酸钠的制备

就层状结晶硅酸钠的制备条件进行了探讨。发现采用KCl作为晶型转化剂，其加量为5％，在温度800℃下转化10min，δ晶型转化最完全，可以得到钙、镁离子交换量大的层状结晶硅酸钠。     

The hydrothermal preparation of sodium silicate

A comparatively high steam pressure should be used to give complete sodium silicate formation from the starting materials. Moreover, a higher steam pressure is required in the case of using sodium carbonate than on using sodium hydroxide. Sodium metasilicate hydrate prepared under a low steam pressure (2.5 atm)^a appears to be amorphous in nature while that prepared from sodium hydroxide or sodium carbonate at a higher steam pressure is crystalline and very similar to the metasilicate hydrate with the formula Na₂SiO₃. 9H₂O. However, the metasilicate prepared from sodium carbonate appears to be poorly crystalline due to the presence, in the prepared material, of an appreciable amount of sodium carbonate.     

Complexometeic determination of rare-earth elements in sodium-potassium-calcium silicate glass

Glass and Ceramics -     

Mechanism of aventurine formation in copper-containing alkali-lead silicate glass

The mechanism of aventurine formation in copper-containing sodium-lead silicate glass is investigated. The methods of electron and optical microscopy are used to establish the role of iron monoxide in the stages of formation of a colloidal suspension of microdrops of metallic copper in the glass and the transformation of the latter into aventurine crystals.     

Enhanced energy storage and discharge-charge performance by changing glass phase content in potassium sodium niobate glass-ceramics

(1-x) (K₂O–Na₂O–2Nb₂O₅)-x (2BaO–Nb₂O₅–2SiO₂) glass-ceramics with x = 0.10, 0.15, 0.20, 0.25 have been successfully prepared by traditional melting method. XRD and microstructure analysis demonstrate that all glass-ceramics are crystallized into uniform Na_0.9K_0.1NbO₃ and K₂(NbO)₂(Si₄O₁₂) ferroelectric crystalline phase. Increasing x promotes the formation of Ba₂NaNb₅O₁₅ phase with a tungsten bronze structure. Raman and complex impedance data confirmed that Ba²⁺ is introduced to repair the disruption of the glass network and make carrier migration difficult when x = 0.15. Thus, the x = 0.15 glass-ceramic sample possesses a maximum calculated energy storage density of 2.32 J/cm³ under 820 kV/cm because of a high degree of polymerization (DOP) glass network structure. Moreover, the pulsed discharge-charge tests are carried out to evaluate actual energy storage performance.