Miroslav Trojan

Study of the thermal preparation and stability of tetrametaphosphates of bivalent metals

Abstract The dehydration and condensation reactions during the thermal preparation of tetrametaphosphates (cyclotetraphosphates) of bivalent metals have been followed by thermal analyses under quasi-isothermal, quasi-isobaric conditions. These analyses permitted a more detailed assessment of important factors (reaction temperatures and times, water vapour pressure) that play decisive roles from the technological point of view. A significant favourable influence of increased vapour pressure on the yields of the condensation reactions has been observed. High-temperature differential thermal analysis at various precisely defined conditions of the atmosphere was used to follow the conditions of melting of tetrametaphosphates. Conditions were established for their congruent melting and of their non-congruent melting connected with the formation of higher linear phosphates of vitreous character. Thermal analysis has also been used to evaluate the recrystallization of these polyphosphate glasses with reversible transformation into tetrametaphosphates.

Synthesis of Ce1−xPrxO2 pigments with other lanthanides

The synthesis of some new inorganic pigments has been investigated, with particular respect to the preparation of high-temperature colour pigments which can be used for colouring ceramic glazes. The synthesis of these pigments is based on high-temperature calcination of the starting oxides. The optimum conditions for the syntheses of these pigments have been estimated and the pigments prepared have been evaluated from the standpoint of their structure, colour hue and ability to colour ceramic glazes.

Cerium Dioxide Fluorite Type Pigments

Abstract Pigments of cerium-praseodymium type have not been well known. They are of interest with respect to their colour hues in ceramic glazes, and are based on the incorporation of praseodymium ions into the host lattice of cerium dioxide. We have now studied possibilities for the preparation of Ce 1- x Pr x O 2 pigments, their properties, structure, quality and possible applications for ceramic glazes.

Study of Ce1-xPrxO2 pigments

Abstract The synthesis of new compounds based on CeO 2 , which can be used as pigments for colouring of ceramic glazes, is investigated in our laboratory. The optimum conditions for the syntheses of these compounds have been estimated and the pigments prepared have been evaluated from the standpoint of their structure. The first information about the temperature region of the formation of the pigments investigated is provided by thermal analysis. The synthesis of these compounds is followed by thermal analysis using STA 449C Jupiter (NETZSCH, Germany).

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.

Reaction of formation of c-Co2P4O12, a study using thermalanalysis methods

Abstract The thermal behaviour of Co(H 2 PO 4 )2·2H 2 O and reaction of formation of c-Co 2 P 4 O 12 is described in this paper. Increasing temperature evolves the hydrate water at first, then follows the constitute water and the condensation reactions of the phosphate anions. It was found that this water vapour pressure has a great influence on the course of these condensation reactions, on the temperature and velocity of the reactions and their result too. According to the vapour pressure there occurs a partial splitting of the first condensation product - dihydrogendiphosphate.

Binary Cu(II)–Mn(II) cyclo-tetraphosphates

Abstract Cyclo-tetraphosphates of the type Cu 2− x Mn x P 4 O 12 have been synthesised as new binary compounds. The synthesis is based on a thermal procedure involving the reversible transformation of cyclo-tetraphosphates to higher linear phosphates. The compounds prepared have been evaluated from the standpoint of their structure, density and thermal stability.

New green pigments; ZnO–CoO

A zinc oxide pigment with an admixture of cobalt oxide has been prepared as a new green pigment for colouring plastics and paints. The effect of the CoO content in the starting mixture on the colour hue of the pigment has been evaluated and calcination conditions of the pigment synthesis have been established. The optimum conditions for the synthesis of pigments and the properties of the products (colour hue and structure) have been estimated.

The synthesis of the Ce0.95−yPr0.05LayO2-y/2 pigments

Abstract The synthesis of some new inorganic pigments has been investigated. In this regard, emphasis was placed on the preparation of heat-resistant pigments. The synthesis of the title pigments is based on high-temperature calcination of CeO 2 and Pr 6 O 11 , and the optimum conditions for pigment formation have been determined The pigments were evaluated from the standpoint of their structure, colour and ability to dye ceramic glazes.

A study of condensation reactions during formation of c-Cu2P4O12 by means of quasi-isothermal-isobaric thermal analyses

Abstract Calcination of a mixture of copper (II) oxide and phosphoric acid (mol. ratio CuO/P2O5 = 1) produces dicopper (II) cyclo-tetraphosphate as the main product. At first, various intermediates of the type of simple copper (II) phosphates are formed. Then, at higher temperatures, condensation of phosphate anions takes place. Temperature and rate of the individual reactions as well as yields of the main product are distinctly affected by water vapour pressure in the calcinate.