Petr Mošner

Lead borophosphate glasses doped with titanium dioxide

Abstract Glasses of the compositional series of 50PbO–yB2O3–(50−y)P2O5–xTiO2 (with x=0–16) have been prepared and characterized by the determination of density, molar volume, glass transition temperature, dilatation softening temperature, thermal and chemical durability. Structural changes were evaluated from the studies by 31P and 11B MAS NMR, Raman and infrared spectroscopy. Molar volume of the glasses decreases and the glass transition temperature increases with increasing additions of TiO2. 31P MAS NMR spectra revealed that titanate units enter phosphate chains decreasing the number of Q2 units and increasing the number of Q1 units. This result is confirmed by the observed changes in the Raman and infrared spectra of the TiO2-doped glasses.

Study of the structure and properties of Pb-Zn borophosphate glasses

Abstract Multicomponent oxide glasses of composition 25PbO–25ZnO–xB2O3–(50−x)P2O5, series A, and yPbO–(50−y)ZnO–20B2O3–30P2O5, series B, are investigated. The role of compositional changes on their density, chemical durability, thermomechanical properties and Raman scattering is examined. Structural changes are found to be more pronounced in the series A glasses affecting most thermomechanical properties of the glasses. Raman spectra reveal a continuous shift in frequency of the main vibrational band from 1170 cm −1 at x=0, to 960 cm −1 at x=40, explained in terms of a successive transformation of metaphosphate (Q2) units into pyrophosphate (Q1) and orthophosphate (Q0) units. In the series B of glasses, results show that mixed Pb–Zn borophosphate glasses (y=25) have better chemical durability than end point (y=0, y=50) composition single-cation glasses. With an increasing PbO content, Tg is found to slowly decrease and the thermal expansion coefficient to increase. The frequency shift of the main Raman band from 1092 cm −1 (at y=0) to 1011 cm −1 (at y=50) is ascribed to differences in chemical bonding, coordination numbers and field strength of both cations.

The synthesis of binary zinc(II)–nickel(II) cyclo-tetraphosphates as new special pigments

The synthesis of new inorganic pigments has been investigated, with the goal of preparing heat stable and anticorrosive pigments. The synthesis of the title pigments is based on temperature calcination of the starting materials, and the optimum reaction conditions for this process have been assessed. The pigments have been evaluated from the standpoint of their structure, colour hue and ability to dye ceramic glazes. New binary condensed phosphates were synthesised based on results of thermal analyses. These new compounds were developed with environmentally friendly special pigments in mind.

Anticorrosion properties of SrO–ZnO–B2O3–P2O5 pigments

Seven compositions of anticorrosion pigments of zinc‐strontium borophosphates were prepared and then characterized by X-ray diAraction analysis, solubility measurements, particle size distribution, and the pH of their aqueous extracts. The pigments were dispersed in an alkyd resin formulation, and used in paints. Following application of the paints to steel sheets, they were subjected to standard anticorrosion tests, to assess their anticorrosive‐inhibitory properties. Test results showed that 14.6SrO‐43.7ZnO‐8.3B2O3‐33.3P2O5 and 37.5SrO‐37.5ZnO‐25B2O3 compositions surpassed the anticorrosive properties of standard pigments based on zinc orthophosphate and calcium metaborate. # 2000 Elsevier Science Ltd. All rights reserved.

Study of structure and properties of modified borophosphate glasses

A review on the investigation of the structure and properties of zinc and lead borophosphate glasses is given. Structural studies with the application of Raman and infrared spectroscopy and 31P and 11B MAS NMR spectroscopy are manifested on several borophosphate glasses. Structural studies were realized in several compositional series and thus compositional dependencies and the evolution of basic structural units in the glasses was established. The modification of phosphate and borophosphate glasses with other oxides e.g. Sb2O3 and transition metal oxides like TiO2 and Nb2O5 is presented.

Thermomechanical properties and stability of mixed strontium-zinc borophosphate glasses

Borophosphate glasses of the SrO-ZnO-B2O3-P2O5 system were prepared in 3 compositional series of 25ZnO-25SrO-xB2O3-(50 − x)P2O5, (58.3 − x) ZnO-xSrO-16.6B2O3-33.33P2O5 and (50 − x)ZnO-20B2O3-30P2O5 and the changes in their thermomechanical and thermal properties with changes in their composition were investigated. The thermal expansion coefficient α decreases with increasing B2O3 content, whereas the values of glass transformation temperature Tg and dilatation softening temperature Td increase. The replacement of ZnO by SrO increases both Tg and Td. From the DSC results the value of the the Hrubys criterion Kgl was calculated and changes in the glass-forming tendency with changes in glass composition were discussed.

Electrical mobility of silver ion in Ag2O-B2O3-P2O5-TeO2 glasses.

The effect of adding TeO(2) into (100 - x)[0.5Ag(2)O - 0.1B(2)O(3) - 0.4P(2)O(5)] - xTeO(2), with 0-80 mol % TeO(2) glass, on the structural changes and electrical properties has been investigated. DSC and thermodilatomery were used to study their thermal behavior, structure was studied by Raman spectroscopy, and electrical properties have been studied by impedance spectroscopy over a wide temperature and frequency range. The introduction of TeO(2) as a third glass former to the glass network causes the structural transformation from TeO(3) (tp) to TeO(4) (tbp) which contributes to the changes in conductivity. The glasses with low TeO(2) content show only a slow decrease in dc conductivity with addition of TeO(2) due to the increase of the number of nonbridging oxygens, which increases the mobility of Ag(+) ions. The steep decrease in conductivity for glasses containing more than 40 mol % TeO(2) is a result of decrease of the Ag(2)O content and stronger cross-linkage in glass network through the formation of more Te-(eq)O(ax)-Te bonds in TeO(4) tbp units. The glasses obey ac conductivity scaling with respect to temperature, implying that the dynamic process is not temperature dependent. On the other hand, the scaling of the spectra for different glass compositions showed the deviations from the Summerfield scaling because of the local structural disorder which occurs as a result of the structural modifications in the tellurite glass network.

Investigation of the Non-isothermal Kinetics of the Formation of ZnFe2O4 and ZnCr2O4

The kinetics of ZnFe2 O4 and ZnCr2 O4 formation under non-isothermal conditions using DTA is discussed. It was determined activation energy and kinetic model for studied reactions in the case of used various sources of starting materials (ferric pigments, chromic oxides). The activation energies for ZnFe2 O4 are positioned in a range of 200–475 kJ mol−1 (in dependence of used ferric pigments) and in case of ZnCr2 O4 in a range of 130–160 kJ mol−1 . The autocatalytic kinetic model (Šesták-Berggren) was found to be the most convenient description of the studied processes.

Preparation and study of Ca1 − xMgx(PO3)2 glassy and crystalline phases

The structure of Ca1 − xMgx(PO3)2 crystalline and glassy samples was investigated in the whole concentration region of x = 0–1.0. From X-ray diffraction data it was found that, in the crystalline samples, solid solutions are formed for x < 0.3 on the calcium-side of the system, with the structure of β-Ca(PO3)2, and for x > 0.6 on its magnesium-side, with the structure of Mg2P4O12. Similar results were obtained from the study of their infrared and Raman spectra. In the glassy state, homogeneous glasses were formed within the whole concentration region. The values of their transformation temperatures, Tg, and crystallization temperature, Tc, change slightly with the composition and lie within the region of Tg = 529–544 °C and Tc = 631–677 °C.

The effects of the mode of preparation on the anticorrosion properties of Ca‐Zn and Mg‐Zn borophosphates

Twelve pigment compositions derived from the xCaO·(50−x)ZnO·20B2O3·30P2O5·(x=10, 20, 30) and yMgO·(50−y)ZnO·20B2O3·30P2O5·(y=10, 20, 30) systems were prepared. The synthesis was carried out either by the medium‐temperature process or by the high‐temperature process followed by cooling in air and an isothermal crystallisation of the glass obtained. The pigments prepared by the medium‐temperature process achieved better corrosion results in styrene‐acrylate coating formulations, whereas those prepared by the high‐temperature process achieved better results in alkyd‐resin coating formulations. The anti‐corrosion results for the Ca‐Zn pigments were better than those for the Mg‐Zn pigments.