X-ray photoelectron spectroscopic investigation of nanocrystalline calcium silicate hydrates synthesised by reactive milling

X-ray photoelectron spectroscopy (XPS) has been used to analyse a series of mechanochemically synthesised, nanocrystalline calcium silicate hydrates (C-S-H). The samples, with Ca/Si ratios of 0.2 to 1.5, showed structural features of C-S-H(I). XPS analysis revealed changes in the extent of silicate polymerisation. Si 2p, Ca 2p and O 1s spectra showed that, unlike for the crystalline calcium silicate hydrate phases studied previously, there was no evidence of silicate sheets (Q³) at low Ca/Si ratios. Si 2p and O 1s spectra indicated silicate depolymerisation, expressed by decreasing silicate chain length, with increasing C/S. In all spectra, peak narrowing was observed with increasing Ca/Si, indicating increased structural ordering. The rapid changes of the slope of FWHM of Si 2p, Δ_Ca-Si and Δ_NBO-BO as function of C/S ratio indicated a possible miscibility gap in the C-S-H-solid solution series between C/S 5/6 and 1. The modified Auger parameter (α′) of nanocrystalline C-S-H decreased with increasing silicate polymerisation, a trend already observed studying crystalline C-S-H. Absolute values of α′ were shifted about − 0.7 eV with respect to crystalline phases of equal C/S ratio, due to reduced crystallinity.     

Morphology of silicate glasses with lead sulfide nanocrystals

The specific features in the structure of nanostructured glass-ceramic materials based on sodium zinc silicate glasses doped with lead sulfide are investigated using small-angle X-ray scattering and X-ray powder diffraction. It is established that a close-to-monodisperse size distribution of PbS nanocrystals is an important structural feature of the system under investigation. An analysis of the X-ray powder diffraction data demonstrates that the shape of the lead sulfide nanocrystals precipitated depends on the heat treatment conditions and can differ from a spherical shape.     

X-ray photoelectron spectroscopic investigation of coal

X-ray photoelectron spectroscopy (XPS) has been used to study the carbon, oxygen and sulphur content of several coking coals, a series of sink—float fractions from a high-volatile coking coal, and several inorganic minerals that are commonly found in coals. Single carbon and oxygen peaks were obtained that corresponded to carbon 1s orbital and oxygen 1s orbital electron binding energies which are expressed in units of electron volts (eV). Two sulphur 2p (S 2p) peaks were found. The 169–171 eV S 2p peak corresponded to the sulphates resulting from the oxidation of pyrite (FeS₂), while the 163–164 eV S 2p peak was assigned to the iron sulphide compounds such as pyrite or marcasite. No separate organic sulphur peaks were found for coal, because the majority of the organic sulphur peaks are probably overlapped by the inorganic sulphide line at 163–164 eV. The total carbon and sulphur determined using the XPS peak height correlated with the chemical analysis, although the accuracy of the XPS determinations seems to be lower. A possible direct quantitative method for determining the organic sulphur in coal by XPS is discussed.     

X-ray investigation of thin films of lead-silicate glasses

The methods of x-ray and electron spectroscopy are used to investigate films of quartz and lead-silicate glasses with a thickness of 200–3000 Å. The composition of the films differs from that of massive specimens used for spray-coating. The films are depleted of PbO and the depletion is higher the greater the thickness of the film.Translated from Steklo i Keramika, No. 12, pp. 9–10, December, 1995.     

Properties of lead borosilicate glasses: The effect of the structure

A study of the structure and physicochemical properties of lead borosilicate glasses is reported. Consideration is given to the coordination transitions in the glasses and their effect on the properties. A pattern of changes is established in the properties depending on the chemical and phase composition of the glasses.     

Investigation of the structural transformations in nitrided layers of optical lead silicate glasses by infrared reflection spectroscopy

The IR reflection spectra of nitrided layers of the TF10, TF5, and TF8 glasses are analyzed. It is shown that thermal nitridation of the surface layers of the glass samples at a temperature of 375–495°C and a pressure of 0.1–1.0 MPa for 1–20 h brings about the breaking of the Si-O-Si bonds and the formation of the Si-N-Si and Si-N bonds. The degree of structural transformation in the surface layer depends on the conditions of thermal nitridation and on the chemical composition of the glass.     

IR spectroscopic study of water in the structure of binary alkali borate glasses

The influence of the synthesis conditions and composition of binary sodium and potassium borate glasses on the spectral absorption in the wavelength range 2.5–4 µm due to the presence of structurally bound water is investigated. It is demonstrated that water in the structure of alkali borate glasses, as in the structure of alkali silicate glasses, can exist in the form of so-called free and bound hydroxyl groups that are incorporated into the glass network in different ways. The ratio between the numbers of these forms of structural water in borate glasses is determined by the synthesis conditions and composition of the glass. The synthesis under different conditions makes it possible to prepare glasses not only with different water contents but also with different ratios between the numbers of free and bound hydroxyl groups.Original Russian Text Copyright © 2005 by Fizika i Khimiya Stekla, Golubeva, Pavinich.     

Crystallization kinetics of sodium-niobium silicate glasses

The crystallization of glasses in the Na₂O-Nb₂O₅-SiO₂ system in the temperature range 690–750°C is investigated by measuring the material density and X-ray powder diffraction analysis. It is found that the kinetics of precipitation of the NaNbO₃ crystalline phase can be described by the Avrami equation with the Avrami exponentn ≈ 1. The model describing the crystallization kinetics is proposed. The crystallization of amorphous inhomogeneity regions, which are formed as a result of phase separation, is considered in the model. The consideration refers to the crystallization process governed by the nucleation of crystals in these regions. The calculated Avrami exponents are close to unity. The proposed model does not contradict the available data on the X-ray small-angle scattering that have been obtained upon crystallization of the samples and qualitatively explains a nonmonotonic variation in the material transparency during crystallization.     

Crystallization kinetics of sodium-niobium silicate glasses

The crystallization of glasses in the Na₂O-Nb₂O₅-SiO₂ system in the temperature range 690–750°C is investigated by measuring the material density and X-ray powder diffraction analysis. It is found that the kinetics of precipitation of the NaNbO₃ crystalline phase can be described by the Avrami equation with the Avrami exponentn ≈ 1. The model describing the crystallization kinetics is proposed. The crystallization of amorphous inhomogeneity regions, which are formed as a result of phase separation, is considered in the model. The consideration refers to the crystallization process governed by the nucleation of crystals in these regions. The calculated Avrami exponents are close to unity. The proposed model does not contradict the available data on the X-ray small-angle scattering that have been obtained upon crystallization of the samples and qualitatively explains a nonmonotonic variation in the material transparency during crystallization.     

Structure aspects of the crystallization of silicate glasses

Translated from Steklo i Keramika, No. 6, pp. 34–35, June, 1989.     

IR spectroscopic investigation of interaction between sodium aluminosilicate electrode glasses and aqueous solutions

The effect of introduction of aluminum oxide into the composition of sodium silicate glasses has been studied by IR absorption and reflection spectroscopy. The change in the spectroscopic characteristics of glasses after their treatment with HNO₃ and AgNO₃ aqueous solutions is analyzed. The concentration profiles of Na₊ and Ag₊ ions in the surface layers of these glasses are determined by the HF-sectioning technique. It is found that silver ions predominantly interact with the [AlO_4/2]^- groups in the glass. The leaching of sodium ions, formation of amorphous silica in the surface layers of the treated glass samples, and exchange of sodium ions by hydrogen ions are revealed from changes in the spectra.     

IR spectroscopic investigation of interaction between sodium aluminosilicate electrode glasses and aqueous solutions

The effect of introduction of aluminum oxide into the composition of sodium silicate glasses has been studied by IR absorption and reflection spectroscopy. The change in the spectroscopic characteristics of glasses after their treatment with HNO₃ and AgNO₃ aqueous solutions is analyzed. The concentration profiles of Na₊ and Ag₊ ions in the surface layers of these glasses are determined by the HF-sectioning technique. It is found that silver ions predominantly interact with the [AlO_4/2]^- groups in the glass. The leaching of sodium ions, formation of amorphous silica in the surface layers of the treated glass samples, and exchange of sodium ions by hydrogen ions are revealed from changes in the spectra.     

A soft X-ray microscope investigation into the effects of calcium chloride on tricalcium silicate hydration

Calcium chloride (CaCl₂) is one of the most recognized and effective accelerators of hydration, setting, and early strength development in portland cement and tricalcium silicate (C₃S) pastes. The mechanisms responsible for this acceleration, as well as the microstructural consequences, are poorly understood. Soft X-ray transmission microscopy has recently been applied to the study of cementitious materials and allows the observation of hydration in situ over time. This technique was applied to the examination of tricalcium silicates hydrating in a solution containing CaCl₂. It appears that CaCl₂ accelerates the formation of “inner product” calcium silicate hydrate (C-S-H) with a low-density microstructure.