Eva Bartoníčková

SYNTHESIS AND PROCESSING OF InVO4 CERAMICS

Indium vanadates for severe applications as photocatalysts, anodes for Li rechargeable batteries or electrochromic devices were prepared via conventional and non-conventional preparation methods. The conventional high temperature solid state reaction was performed at 800°C for 25 hours and the non-conventional microwave-assisted synthesis was performed at 220°C for different reaction times under hydrothermal conditions. The as-prepared powders were characterized in terms of phase composition by X-Ray diffraction analysis (XRD) and infrared spectroscopy (IR) and of powder morphology by scanning electron microscopy (SEM) and BET method. Nanosized indium vanadate powders were successfully synthesized by non-conventional microwave-assisted hydrothermal method. The dense ceramic bodies suitable for electrical conductivity measurements with 96% t.d. were obtained by sintering of powders prepared by high-temperature solid state reaction at 1100°C for 4 h with admission of oleic acid as a binder additive.

Determination of critical parameters of drug substance influencing dissolution: a case study.

The purpose of this study was to specify critical parameters (physicochemical characteristics) of drug substance that can affect dissolution profile/dissolution rate of the final drug product manufactured by validated procedure from various batches of the same drug substance received from different suppliers. The target was to design a sufficiently robust drug substance specification allowing to obtain a satisfactory drug product. For this reason, five batches of the drug substance and five samples of the final peroral drug products were analysed with the use of solid state analysis methods on the bulk level. Besides polymorphism, particle size distribution, surface area, zeta potential, and water content were identified as important parameters, and the zeta potential and the particle size distribution of the drug substance seem to be critical quality attributes affecting the dissolution rate of the drug substance released from the final peroral drug formulation.

Utilization of By-Pass Cement Kiln Dust in Alkali-Activated Materials

This paper deals with the mechanical properties and phase study of alkali activated blast furnace slag and by-pass cement kiln dust mixture. The by-pass cement kiln dust (CKD) solves the problem with significant shrinkage of alkali activated materials which is considerably limiting their practical applications. The mechanism of action of CKD in alkali activated matrix has been investigated as well as its optimal dosage in the means of mechanical properties. The reaction products during the hydration process were characterized by X-ray powder diffraction.

The influence of starting materials´ solubility on tobermorite structure formation under the hydrothermal conditions

Overall, the tobermorite mineral crystallises under the hydrothermal conditions from the CaO-SiO2-H2O system. The system of calcium hydrosilicates species is extremely complex and many factors play an important role. The solubility of starting materials belongs to one of the most important factors. Dissolution rates of SiO2 source are significantly affected by their particle size distribution. Also the starting cation ́s concentration in the aqueous solution affects the yield of the hydrothermal reaction. The main aim of this contribution is to study the influence of water-to-solid ratio on tobermorite crystallization. The effect of particle size of various sources of SiO2 was also studied. The cost effective Ca and Si sources was primarily favoured. The C/S ratio of the experiments was set to 0.83. All syntheses were performed at 180 °C in laboratory steel autoclaves. The prepared powdered samples were characterized in order to determine the phase composition by using of X-Ray diffractometry. The thermal behaviour of prepared samples was studied by TG-DTA analyser. Morphology and particle size of synthetized powdered products was studied by scanning electron microscopy.

The effect of amorphous and crystal sodium warfarin and its content uniformity on bioequivalence of tablets

&NA; Warfarin is intensively discussed in terms of generic substitution due to particular cases of bleeding, which are attributable to fluctuations in API content or the substitution of crystalline (WSC) for amorphous (WSA) warfarin. The aim of this study was to assess to what extent the in vitro release was affected by the form of API depending on the composition and technology. Bioequivalent tablets containing 5 mg of WSA or WSC prepared by wet granulation or direct compression were used. Furthermore, tablets of the same composition with WSC or WSA prepared by direct compression were evaluated. Raman spectroscopy was used to confirm the presence of WSA or WSC. The dissolution was more influenced by the technology than by the form of API but even tablets with dissimilar profiles were bioequivalent. This is probably due to the precipitation of WSA and WSC in the stomach on a poorly soluble acidic form, which subsequently dissolves in the neutral environment of the small intestine. Recrystallization was demonstrated in the in vitro assay at a pH of 1.2 and 4.5 using Raman spectroscopy and X‐ray diffraction. In summary, the content uniformity appears to be the main factor affecting the safety of the treatment.

TiO2 Surface Coating of Mn-Zn Dopped Ferrites Study

This study deals with TiO2 coating of powder Mn-Zn ferrite in order to recieve photocatalytic layer on the top of these particles, forming core-shell catalyst. Powder catalysts are of great advance over the world due to the high surface area, considering the kinetics proceeds through heterogenous phase boundary catalysis. However their withdrawal from cleaning systems often requires energetically and economically demanding processes such as filtration and ultrafiltration. Since the ferrite is magnetic, the advantage of such formed core-shell photocatalyst is easibility of removing from photocatalytic decomposition system using external magnetic field. In this study the surface coating is performed, using Ti alkoxides mixtures with nanosized TiO2 particles and C and Au coating to form film layer of TiO2 on the surface of ferrite. XRD, SEM – EDS analyses are employed to study surface coating.

Synthesis of Layered Calcium Cobaltites Intended for Thermolectric Application

Layered misfit cobaltites exhibit adequate combination of electrical and thermal properties under the high temperatures. Cobaltites are due to these properties and appropriate costs optimal candidates for thermoelectric industrial applications [1]. Calcium cobaltites were prepared via conventional and less conventional synthesizing methods. Wet citric and glycine/nitrate combustion syntheses were compared with conventional solid state reaction. Prepared powders were studied in terms of phase and chemical composition, morphology, size of particles/agglomerates and thermoelectric properties. Particle size of prepared powders was varied from nano to micro size with different level of agglomeration. The lowest values of particle size (~ 160 nm) with low agglomeration were obtained with the citric combustion method. The influence of the preparation method on the properties of final bulk product was evaluated within this work.