Petr Bělina

Thermal stability and colour properties of CuZr4(PO4)6

In present work, CuZr4(PO4)6, which is a complex phosphate of NASICON family, has been characterised as ceramic pigment. To this purpose, its thermal stability, colour properties and some other important pigment characteristics were studied. In order to obtain pure phase ceramic powder of CuZr4(PO4)6, several synthesis approaches were attempted. The thermal transformations in the reaction mixtures were investigated by DTA-TG and XRD analysis. Thermal stability of the obtained products was studied using heating microscopy, DTA-TG and XRD analysis. Colouring performance and lightfastness of CuZr4(PO4)6 were tested within commercial ceramic glazes, and its colour in powder and glaze is described by means of CIELAB and CIELCh systems. It is shown that CuZr4(PO4)6 ceramic powder has sufficient thermal stability and attractive colouring properties to be used as ceramic pigment.

Thermal synthesis and characterization of AlχLa1-χP3O9

New binary lanthanum-aluminum triphosphates were synthesized by thermal-condensation method from H3PO4, La2O3 and Al(OH)3. These pigments could be potentially used as special inorganic pigments; their corrosion-inhibition properties were widely studied. Synthesis conditions were determined on the basis of DTA and TG measurements. The products were also characterized by X-ray diffraction analysis. Physical properties — density by pycnometric method, particle size distribution, oil number and critical pigment volume concentration (CPVC), pH and specific conductivity of their aqueous extracts were also determined.

Thallium in spruce needles: a comparison of the analytical capabilities of spectrochemical methods

Four spectrochemical methods are employed for the determination of Tl in spruce needles: ICP-MS (inductively coupled plasma mass spectrometry), ETV-ICP-MS (electrothermal vaporisation coupled to ICP-MS) analysis of decomposed and slurry samples (SlS), and SS-HR-CS-GFAAS (solid sampling high-resolution continuum source graphite furnace atomic absorption spectrometry). The methods are compared considering practical laboratory aspects (sample pretreatment, optimisation, validation, time-consumption), as well as their analytical performance. For this specific case of Tl in spruce needles, all the methods had similar requirements regarding the time required for sample pretreatment (1–2 hours, ETV-ICP-MS, SS-HR-CS-GFAAS < ICP-MS < SlS-ETV-ICP-MS). The method optimisation can be considered as routine for ICP-MS and more complicated for slurry and solid sampling, due to the differences in the matrix of standards and samples. ICP-MS optimisation required a several dozen minutes and dozens of hours for the ETV methods, which increases operational costs. ETV-ICP-MS requires a well experienced operator, skilled in both techniques (graphite furnace and ICP-MS). The order of complexity can be classified as follows: ICP-MS < SS-HR-CS-GFAAS < ETV-ICP-MS, SlS-ETV-ICP-MS. Requirements for validation in terms of the chemicals, calibration standards, and reference and control materials are similar. Major differences were evident in time demands. The procedural LODs were found typically below 1 μg kg−1 of Tl (in μg kg−1): 0.18 ICP-MS, 0.010 ETV-ICP-MS, 0.024 SlS-ETV-ICP-MS and 1.2 SS-HR-CS-GFAAS, which are appropriate for the Tl levels found in environmental samples. The range of recoveries did not differ significantly for the different methods used (in %): ICP-MS 92–107, ETV-ICP-MS 90–114, SlS-ETV-ICP-MS 94.5–117 and SS-HR-CS-GFAAS 90–115. ICP-MS revealed better repeatabilities (1.9–6.2%) than the others (ETV-ICP-MS 5.2–19%, SlS-ETV-ICP-MS 6.3–17% and SS-HR-CS-GFAAS 0.17–15%), as expected. In practice, ICP-MS shows significant advantages for analysis of Tl in spruce needles. However, it is necessary to consider all of the factors discussed. ETV techniques may have a justified place in special routine applications, in which the difficult development and validation of methods is much more convenient than the daily preparation of highly resistant or otherwise complicated samples.

A comparative study of the influence of the method of synthesis of intermediate products in the preparation of CoNd2W2O10 and MnNd2W2O10 and their color properties in ceramic glazes

The compounds CoNd2W2O10 and MnNd2W2O10 were prepared by solid state reaction between CoWO4, resp. MnWO4 and Nd2WO6. Intermediates were prepared in laboratory by a solid state reaction and by a co-precipitation reaction. The new single-phase compounds CoNd2W2O10 and MnNd2W2O10 were prepared only from intermediates prepared by solid state reaction, as in second case the morphology of particles is inappropriate and during the reaction an unknown phase (Nd–W–O) is formed. To describe the processes during thermal reactions, the DTA/TG were used. CoNd2W2O10 and MnNd2W2O10 belong to the orthorhombic crystallographic system, their diffraction pattern were indexed. The new compounds were tested as inorganic pigments. Application of the prepared compounds in ceramic glazes did not provide technological interesting results. The reason is probably the low thermal stability of the prepared compounds CoNd2W2O10 and MnNd2W2O10. In particle form CoNd2W2O10 has blue color and MnNd2W2O10 has brown color.