Crystallization study of molybdate phosphate glasses by thermal analysis (original) (raw)
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Effect of molybdenum addition on the thermal properties of silicate–phosphate glasses
Journal of Thermal Analysis and Calorimetry, 2012
Aim of the study was analysis of two groups of glasses: silicate-phosphate (41 mol.% SiO 2 -6 mol.% P 2 O 5 ) and with inverse phosphate-silicate matrix (41 mol.% P 2 O 5 -6 mol.% SiO 2 ) 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 3 in silicate-phosphate glasses is 4.4 \ [MoO 3 ] \ 5.7 mol.%, whereas in phosphate-silicate glasses MoO 3 is fully dissolved. It was found that in the case of both matrixes addition of molybdenum ions decreases the glass transition temperature (T g ), as well as the value of specific heat change (Dc p ) accompanying the glass transformation. The presence of molybdenum caused reduced the thermal stability of the studied glasses and a multi-step crystallization of silicatephosphate 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 3 in an amount C3.3 mol.% one of the crystallization product was powellite (CaMoO 4 ). 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 (DG formation).
Thermal properties of MnO2 and SiO2 containing phosphate glasses
Journal of Thermal Analysis and Calorimetry, 2015
Thermal properties of glasses from the P 2 O 5-SiO 2-K 2 O-MgO-CaO system modified by MnO 2 addition was studied by DSC, XRD and FTIR methods. It has been found that the replacement of MgO and CaO modifiers by MnO 2 in the structural network of phosphate glasses results in decrease in the glass transition temperature (T g) and thermal stability parameter (DT). The identified crystallization products proved to be diversified, including different type of polyphosphates and silicates. It was determined that the type of the crystallizing phosphate phases is consistent with the classification of phosphate glasses, based on the O/P ratio. During the crystallization in higher temperature ranges and with the content of MnO 2 over 25 mol%, a change of crystallization products was noted, including the transition of the diopside type silicate (CaMgSi 2 O 6) into the akermanite type silicate (Ca 2-MgSi 2 O 7). Simultaneously, the nature of transitions taking place during heating of the analyzed glasses was explained on the basis of crystallochemical factors (strengths of bonds) and chemical affinity of the glass components (DG of formation).
Thermal properties and crystallization of PbO–MoO3–P2O5 glasses
Journal of Materials Science, 2011
Thermal properties and crystallization of glasses from PbO-MoO 3 -P 2 O 5 ternary system were studied in three compositional series (100x)[0.5PbO-0.5P 2 O 5 ]-xMoO 3 (A), 50PbO-yMoO 3 -(50y)P 2 O 5 (B), and (50z) PbO-zMoO 3 -50P 2 O 5 (C). Glass transition temperature, crystallization temperature, coefficient of thermal expansion, and dilatation softening temperature of the studied glasses were determined by differential thermal analysis and dilatometry. Crystallization products of annealed glass samples were investigated by X-ray diffraction and Raman spectroscopy. X-ray diffraction analysis of crystallized glasses revealed the formation of PbP 2 O 6 , Pb 3 P 4 O 13 , and PbMoO 4 in the samples of the B series. In the series A and C in the samples with a high MoO 3 content, crystalline compounds of Pb(MoO 2 ) 2 (PO 4 ) 2 and (MoO 2 )(PO 3 ) 2 , respectively, were identified. Raman spectra of crystalline samples confirmed the results of X-ray diffraction measurements and provided also information on thermal stability of glasses and formation of glass-crystalline phases in the studied glass series.
Journal of Materials Science Letters, 1991
Glass ceramics of the CaO-P2Os, MgO-P205 and CaO-MgO-P205 systems are of great interest in the biomaterials field. The crystallization of phosphate glasses of these systems have already been extensively studied as a function of various factors: time, temperature, heating rate, atmosphere, etc. [1]. In particular, it has been shown that water enhances nucleation in the calcium metaphosphate system but inhibits nucleation in the magnesium metaphosphate system .
Journal of Biomedical Materials Research Part B: Applied Biomaterials, 2019
Varying formulations in the glass system of 40P2O5-(24-x)MgO-(16+x)CaO-(20-y)Na2O-yTiO2 (where 0≤x≤22 and y=0 or 1) were prepared via melt-quenching. The structure of the glasses was confirmed by X-ray diffraction (XRD), Fourier transform infrared (FTIR), micro Raman and solid-state nuclear magnetic resonance (NMR) spectroscopies. The thermal properties and the activation energy of crystallisation (Ec) were measured using thermal analysis and the Kissinger equation, respectively. The glass forming ability of the formulations investigated was seen to decrease with reducing MgO content down to 8 mol% and the glass stability region also decreased from 106 o C to 90 o C with decreasing MgO content. The activation energy of crystallisation (Ec) values also decreased from 248 (for 24 mol% MgO glass) to 229 2 kJ/mol (for the 8 mol% MgO content) with the replacement of MgO by CaO for glasses with no TiO2. The formulations containing less than 8 mol% MgO without TiO2 showed a strong tendency towards crystallisation. However, the addition of 1 mol% TiO2 in place of Na2O for these glasses with less than 8 mol% MgO content, inhibited their crystallisation tendency. Glasses containing 8 mol% MgO with 1 mol% TiO2 revealed a 12 o C higher glass transition temperature, a 14 o C increase in glass stability against crystallisation and a 38 kJ/mol increase in Ec in comparison to their non TiO2 containing counterpart. NMR spectroscopy revealed that all of the formulations contained almost equal percentages of Q 1 and Q 2 species. However, FTIR and Raman spectroscopies showed that the local structure of the glasses had been altered with addition of 1 mol% TiO2, which acted as a network modifier, impeding crystallisation by increasing the cross-linking between phosphate chains and consequently leading to increased Ec as well as their glass forming ability.
Thermal properties and crystallization of BaO–MoO3–P2O5 glasses
Journal of Thermal Analysis and Calorimetry, 2017
The thermal behavior and crystallization of barium molybdate-phosphate glasses were studied in two compositional series, namely A: (100x)Ba(PO 3) 2-xMoO 3 (with x = 0-70 mol%) and B: 50BaO-yMoO 3-(50y)P 2 O 5 (with y = 0-15 mol% MoO 3). Thermal properties were studied with differential thermal analysis and dilatometry. Glass transition temperature increases in series A in the range of 0-40 mol% MoO 3 and then decreases with a further increase in MoO 3 content, whereas the thermal expansion coefficient in series A reveals a minimum at 50 mol% MoO 3. These trends are not observed in series B, where the glass transition temperature increases in the range of 0-15 mol% MoO 3 and the thermal expansion coefficient almost does not change. Crystallization of these glasses was studied by X-ray diffraction analysis, Raman and 31 P MAS NMR spectroscopy. Large thermal stability of glass with a composition 35BaO-30MoO 3-35P 2 O 5 toward crystallization was demonstrated. Crystallization of glasses resulted in the formation of the compound Ba(MoO 2) 2 (PO 4) 2 in this ternary system. Raman spectroscopy also provided information on the formation of glasscrystalline samples in some studied compositions. Keywords Barium molybdate-phosphate glasses Á Thermal analysis Á Crystallization Á XRD Á Raman spectra & Ladislav Koudelka
Thermal study of Mn-containing silicate–phosphate glasses
Journal of Thermal Analysis and Calorimetry, 2012
Silicate-phosphate glasses of SiO 2 -P 2 O 5 -K 2 O-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 g ) and heat capacity change (Dc p ) accompanying the glass transformation. Simultaneously, thermal stability of the glasses increased. Products of multistage crystallization of glasses containing up to 8 mol% of MnO 2 were: marokite (CaMn 2 O 4 ), phosphate of Ca 9 MgK(PO 4 ) 7 type, and diopside (CaMgSi 2 O 6 ). Product of crystallization of glasses containing higher amount of manganese was braunite (Mn 7 O 8 SiO 4 ). This was accompanied by change of structure of magnesium calcium silicates from diopsidetype structure to akermanite-type silicates (Ca 2 MgSi 2 O 7 ). The data interpretation was based on bonds and chemical interactions of the individual components forming the glass structure.
Thermal properties and crystallization of MgO–FeOx–P2O5 glasses
Journal of Thermal Analysis and Calorimetry, 2018
Differential scanning calorimetry (DSC), dilatometry and X-ray diffraction have been used to study thermal behavior and stability of glasses prepared simultaneously in Al 2 O 3 or Pt crucibles in compositional series (40x)MgO-xFe 2 O 3-60P 2 O 5 within the concentration range of x = 0-40 mol% Fe 2 O 3. Mössbauer spectra showed that all glasses with Fe 2 O 3 contained both Fe(II) and Fe(III) ions. The contamination glasses from alumina crucibles ranged from 0.3 to 0.9 mol% Al 2 O 3. The replacement of MgO by Fe 2 O 3 resulted in a gradual decrease in glass transition temperature and dilatometric softening temperature, whereas thermal expansion coefficient did not change significantly. The DSC curves showed that all glasses crystallize on heating in the broad temperature range & 560-900°C. Crystallization temperature decreases with increasing Fe 2 O 3 content. The highest tendency toward crystallization was found for the glass containing 40 mol% Fe 2 O 3. X-ray diffraction measurements showed that the major compounds formed by glass crystallization were Mg(PO 3) 2 , Fe(PO 3) 3 , Fe 3 (P 2 O 7) 2 and FePO 4. All thermoanalytical studies showed differences in thermal behavior of glasses prepared in Al 2 O 3 or Pt crucibles.
Elaboration and structural characterization of phosphate glasses with composition 37.5Na2O-25[(1-x)MgO-xNiO]-37.5P2O5 (0≤x≤1), 2019
Phosphate glasses, with molar compositions 37.5Na2O-25[(1-x)MgO-xNiO]-37.5P2O5 (0 ≤ x ≤ 1), have been prepared using the conventional melt quenching technique. The free nickel glass is colorless while the glasses containing nickel are yellow. The effect of Ni 2+ ions on structural and physico-chemical properties of these glasses has been investigated by XRD, DTA, EPR, Raman, FTIR spectroscopies and by density and chemical durability measurements. Substitution of Ni 2+ for Mg 2+ strengthens the glass network, as shown by the decrease of the molar volume, the increase of the glass transition temperature, and the improvement of the chemical durability. This behavior is a consequence of the replacement of Mg-O bonds by more covalent Ni-O bonds. The glass structure consists of tri-phosphate (P3O10) 5-and di-phosphate (P2O7) 4-groups, and Mg/NiO6 octahedra, with Mg-O-P and Ni-O-P linkages.