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The structure and properties of the glass can be modified by introducing appropriate additives. Dolomite is one of the primary raw materials modifying the properties of glass, in which the essential component is calcium-magnesium double carbonate CaCO3∙MgCO3. The paper presents the research results on glasses obtained by smelting pure amphibolite and amphibolite modified with 10 and 20% dolomite additives. The raw material used was mined in the Poland region of Lower Silesia. The glass melting process was carried out in an electric furnace at 1450 °C for 2 h. The structure and properties of the glasses and crystallization products were determined by Differential Scanning Calorimetry (DSC), X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy—Energy Dispersive Spectroscopy (SEM-EDS). Viscosity and Vickers microhardness were also measured. It was found that the modification of amphibolite glass by adding dolomite affects the glasses' properties and structure. The research results determined the effect of dolomite addition on the properties of alumino-silicate glasses in terms of the mineral fibre products used in the construction industry. [ABSTRACT FROM AUTHOR]

The assessment of impact of incorporation of various amount of Fe2O3 at the expense of MgO and CaO on the glassy phase formation and thermal stability exhibited in P2O5–SiO2–K2O–MgO–CaO–Fe2O3 system was carried out. The characteristic temperatures for iron phosphate–silicate glasses and glass-crystalline materials were designated from associated DSC curves. Selected samples were subjected to the process of induced crystallization, and products combined with particular exothermic effects were identified. Combination of DSC, XRD and SEM–EDS methods enabled to collect invaluable data concerning the course of crystallization of not only iron phosphate–silicate glasses subjected to the process of induced crystallization, but also glass-crystalline materials obtained directly through melt-quenched technique. The amount of particular crystalline products associated with selected devitrificates was determined via Rietveld technique. Results of the conducted study indicated that Fe2O3 addition conduces to the decrease in crystallization temperatures and thermal stability which was reflected in calculated values of ΔT and KW parameters. Concomitantly, glass with 20 mol% iron (III) oxide addition exhibited significantly improved, distinctive thermal stability among the materials in the analyzed series. The connection of crystalline phases with gradual alterations in polymerization degree of glass matrix was also established. The performed study is a contribution to the knowledge of iron phosphate glasses family and associated glass-crystalline materials. [ABSTRACT FROM AUTHOR]

The sentence, "Concomitantly, glass with 20 mol% iron (III) oxide..........i N the analyzed series" should read as "Concomitantly, glass with 25 mol% iron (III) oxide ........ Correction: The glass formation and crystallization studies on iron phosphate-silicate glasses. [Extracted from the article]

The DSC, XRD and 31 P MAS NMR methods were applied to study the interactions between the transition elements (Zn, Cu, Mn, Mo) and structural components of glasses from the P 2 O 5 K 2 O CaO MgO TE (Zn/Cu/Mn/Mo) system. In order to determine the structure of domains being the result of interactions in transition elements containing silicate–phosphate glasses, the course of thermally induced crystallization of glasses was considered. To explain the different local chemical affinity of the studied transition elements to the P O TE bridging bonds formation, the crystallochemical analysis based on the ionicity of the chemical bonds was used. [ABSTRACT FROM AUTHOR]

Glasses and devitrificates from the SiO2–B2O3–P2O5–K2O–CaO–MgO system with constant contents of SiO2 and P2O5 network formers, modified by the addition of B2O3, were analyzed. All materials were synthesized by the traditional melt-quenching technique. The glass stability (GS) parameters (Krg, ∆T, KW, KH) were determined. The effect of the addition of B2O3 on the GS, liquation phenomenon, crystallization process, and the type of crystallizing phases were examined using SEM-EDS, DSC, XRD, and Raman spectroscopy imaging methods. It was observed that the addition of B2O3 increased the tendency of the glass to crystallize. Both phosphates (e.g., Ca9MgK(PO4)7, Mg3Ca3(PO4)4), and silicates (e.g., K2Mg5(Si12O30), CaMg(Si2O6), MgSiO3) crystallized in the studied system. The Raman spectrum for the orthophosphate Mg3Ca3(PO4)4 stanfieldite type was obtained. Boron ions were introduced into the structures of crystalline compounds at high crystallization temperatures. The type of crystallizing phases was found to be related to the phenomenon of liquation, and the order of their occurrence was dependent on the Gibbs free enthalpy. [ABSTRACT FROM AUTHOR]

Aim of the study was analysis of two groups of glasses: silicate-phosphate (41 mol.% SiO-6 mol.% PO) and with inverse phosphate-silicate matrix (41 mol.% PO-6 mol.% SiO) modified by the addition of molybdenum ions. Their effect on glass forming ability, glass transition effect, crystallization process, and kind of crystallizing phases was examined using such methods as DSC, XRD, and SEM. It was found that the solubility limit of MoO in silicate-phosphate glasses is 4.4 < [MoO] < 5.7 mol.%, whereas in phosphate-silicate glasses MoO is fully dissolved. It was found that in the case of both matrixes addition of molybdenum ions decreases the glass transition temperature ( T), as well as the value of specific heat change (∆ c) accompanying the glass transformation. The presence of molybdenum caused reduced the thermal stability of the studied glasses and a multi-step crystallization of silicate-phosphate glasses. It was found that the crystallizing phases were silicates and phosphates in both groups of glasses. Only in the case of silicate-phosphate glasses containing MoO in an amount ≥3.3 mol.% one of the crystallization product was powellite (CaMoO). The nature of transitions taking place during heating of the analyzed glasses was in accordance with crystallochemical factors (strengths of bonds) and chemical affinity of the glass components (∆ G formation). [ABSTRACT FROM AUTHOR]

Silicate-phosphate glasses of SiO-PO-KO-MgO-CaO system containing manganese cations were investigated to obtain information about the influence of manganese ions on the thermal behavior of such glasses. Amorphous state of glasses and the course of phase transformation and crystallization taking place during their heating were investigated by DSC, XRD, and FTIR methods. It was shown that an increasing content of manganese replacing calcium and magnesium in the structure of analyzed glasses causes decrease of glass transition temperature ( T) and heat capacity change (Δ c) accompanying the glass transformation. Simultaneously, thermal stability of the glasses increased. Products of multistage crystallization of glasses containing up to 8 mol% of MnO were: marokite (CaMnO), phosphate of CaMgK(PO) type, and diopside (CaMgSiO). Product of crystallization of glasses containing higher amount of manganese was braunite (MnOSiO). This was accompanied by change of structure of magnesium calcium silicates from diopside-type structure to akermanite-type silicates (CaMgSiO). The data interpretation was based on bonds and chemical interactions of the individual components forming the glass structure. [ABSTRACT FROM AUTHOR]

Glasses of the SiO2–P2O5–K2O–MgO–CaO–B2O3 system acting as nutrients carriers in the soil environment were synthesised by the melt-quenching technique. Thermal properties were studied using DTA/DSC methods and the influence of B2O3 and P2O5 content on thermal stability and crystallization process of these glasses was examined. The structure of the glass network was characterized by FTIR, 31P, and 11B MAS NMR. The chemical activity of the glasses in the 2 mass% citric acid solution was measured by the ICP-AES method. The analysis indicated that the formation of P–O–B units with chemically stable tetrahedral borate groups decreases the glass solubility in conditions simulating the soil environment. [ABSTRACT FROM AUTHOR]

The structure of silicate-phosphate glass containing the different amounts of phosphorus, magnesium and calcium cations, acting as macroelements was examined by FTIR, XRD and thermal (DTA/DSC) methods. It has been found that in the structure of silicate-phosphate glass modified by an addition of Mg2+ and Ca2+ there are formed domains characterized by certain degree of ordering of the units present in their composition, while the structure of the newly formed domains is similar to the structure of the crystal compounds formed during crystallization of these glasses. The changing character of domains structure may be the reason of different chemical activity of glass acting as glassy fertilizers. [ABSTRACT FROM AUTHOR]

Abstract: Silico-phosphate glasses of XCaPO4–SiO2 (X=Na+ and/or K+) system have been the subject of the presented investigations. One of the most important problems is to ensure proper biomaterial mechanical resistance. This can be achieved by introduction of proper additions, usually Al3+, into glass structure or/and partial glass devitrification. To design direct crystallization process properly it is necessary to know the texture and structure of the glassy precursor. Microscopic investigations have made it possible to find out that in all the glasses studied liquation takes place. A small addition of Al3+ influences homogeneity of the glass texture. It has been established (EDX investigations) that addition of aluminium dramatically changes the composition of the matrix and inclusions. Spectroscopic investigations (FTIR, NMR) have shown that both, the matrix and the inclusions exhibit domain composition whose structure is close to that of the corresponding crystalline phases. Domains can be considered as the specific ‘‘crystallization nuclei’’ which have a decisive impact on the process of directed glass crystallization. Based on DTA examinations it has been found out that crystallization of the glasses from XCaPO4–SiO2 system is a multistep process while the crystallization of glasses from XCaPO4–SiO2–AlPO4 system is a one step process. [Copyright &y& Elsevier]