ABSTRACT
The alumina and zirconia surfaces were pretreated with chemical etching using alkaline mixtures of ammonia, hydrogen peroxide and sodium hydroxide, and followed with application of the powder layer of Ca-deficient hydroxyapatite (CDH). The influence of etching bath conditions time and concentration on surface development, chemical composition and morphology of medicinal ceramic powders were studied. The following analyses were performed: morphology (scanning electron microscopy), phase composition (X-ray diffraction analysis), changes in binding interactions and chemical composition (FT-Infrared and Energy dispersive spectroscopies). Both types of etchants did not expose the original phase composition changes or newly created phases for both types of ceramics. Subsequent decoration of the surface with hydroxyapatite revealed differences in the morphological appearance of the layer on both ceramic surfaces. The treated zirconia surface accepted CDH as a flowing layer on the surface, while the alumina was decorated with individual CDH aggregates. The goal of this study was to focus further on the ceramic fillers for polymer-ceramic composites used as a biomaterial in dental prosthetics.
ABSTRACT
Organically modified vermiculites can be used as nanostructured adsorbents of organic compounds from waters or gaseous phases similarly as organically modified smectites or bentonites. There is a large amount of research data focused on adsorption properties of organoclays, however only a little information is about their post-sorption treatment. This work is focused on study of two possible ways of subsequent processing of organovermiculite after its use as sorbent for heavily polluted waste water. At first, the vermiculite modified with hexadecylpyridinium ions was used in batch static sorption against phenol ammonium water from the coke industry to get highly contaminated sorption material, especially containing organic hydrocarbons and their derivatives. The sorbent is known to have excellent sorption properties; however ecotoxicological characteristics of original material showed that sorbent had hazardous properties even before its utilization. For that reason, it was necessary to design a post-sorption treatment. Two possible methods of treatment were investigated, specifically solvent treatment (with dichloromethane) and thermal treatment (thermodesorption) at temperatures of 300 and 1100 °C, respectively. The treated materials were studied using infrared spectroscopy, X-ray diffraction and carbon phase analyses. The solvent treatment confirmed that it is possible to reuse modified vermiculite as adsorbent several times, although adsorption capacity after each extraction decreases. The thermal treatment at 300 °C was not sufficient to remove all organic compounds from the vermiculite structure; however at 1100 °C the only presence of magnesium silicate, magnesium aluminate and ferric oxide confirmed the formation of an inert material convenient for an environmentally harmless disposal of used adsorbent.
ABSTRACT
The present article describes a method of the preparation of erbium oxide nanocrystallites (nano Er2O3) via thermal decomposition of a transient complex formed in situ from Er(NO3)3·5H2O and glycine. Decomposition of the complex occurred at about of (250±10) °C. Ultra-fine light pink powder of erbium oxide nanocrystallites was obtained via this method. The resulting nanocrystallites were characterized using X-ray powder diffraction analysis, which showed the nanocrystallites having the crystallite size equal to 10 nm. Morphology of the nanocrystallites was examined by scanning and transmission electron microscopy. Electron diffraction observed in transmission electron microscopy corresponds to the results obtained from X-ray diffraction analysis. The elemental composition of the product was confirmed by EDS analysis.
ABSTRACT
The hybrid nanocomposite materials based on the vermiculite/zinc oxide-chlorhexidine were prepared in two steps. In the first step the vermiculite/zinc oxide nanocomposite was prepared by the mechanochemical method followed by a heat treatment at 650 °C for 90 min. In the second step the chlorhexidine dihydrochloride was intercalated to the vermiculite/zinc oxide nanocomposite in weight ratio 1:1, 1:2, 1:4, 2:1 and 4:1 (wt%) thereby vermiculite/zinc oxide-chlorhexidine nanocomposites were prepared. Phase analysis, crystal structure, phase transformation, chemical composition and particle size of the prepared hybrid nanocomposite materials were using X-ray diffraction methods, energy dispersive X-ray fluorescence spectroscopy, carbon phase analysis, Fourier transforms infrared spectroscopy and particle size analysis. Antibacterial activity of hybrid nanocomposite materials was investigated on Gram negative (E. coli, P. aeruginos.) and the Gram positive (S. aureus, E. faecalis) bacterial strain and against yeast Candida a. by finding the minimum inhibitory concentration. The hybrid nanocomposite materials exhibit high antibacterial activity after 30 minutes with a long-lasting effect persisting up to 5 days. Dependence of the zinc oxide and chlorhexidine concentration in vermiculite structure on the antibacterial activity was observed.
