Microstructure of Zirconia-Based Sol-Gel Glasses Studied by SANS

Zirconia-based bulk glasses were prepared for the first time by sol-gel method. Such materials are very promising for application as photochromic devices, catalytic systems, chemical sensors, lasers and other nonlinear optics devices. Obtained transparent and semi-transparent materials were studied by small and ultra-small angle neutron scattering (SANS and USANS) methods. As evidenced by SANS, morphology of zirconia glasses is very sensitive to parameters of sol-gel synthesis, e.g. temperature and concentration of reactants. SANS data correlates rather well with surface porosity data. Increasing water concentration in reaction mixtures containing zirconium propylate leads to a significant increase in fractal cluster size, while decrease of the temperature results in an increase of the fractal dimension. The obtained results indicate that parameters of the microstructure and consequently physical properties of zirconia glasses can be effectively controlled by parameters of synthesis

Structure of zirconium dioxide based porous glasses

This study is devoted to investigation of the micro- and mesostructure (including fractal properties) of porous zirconia glasses synthesized by precipitation from zirconium n-propoxide solutions in the presence of different hydrolyzing-agent (H2O) quantities at different temperatures. Analysis of small-angle neutron, ultra-small-angle neutron and X-ray scattering, scanning electron microscopy allows concluding that the synthesized glasses are complex systems with a three-level hierarchical fractal structure. It is revealed that both the temperature of synthesis and the H2O concentration in the initial solution significantly affect the structural characteristics of the glasses

Mesostructure of yttrium and aluminum basic salts coprecipitated from aqueous solutions under ultrasonic treatment

The influence of ultrasonic treatment on the micro and mesostructures and fractal characteristics of amorphous powders of yttrium and aluminum basic salts (precursors for the synthesis of neodymiumacti vated yttrium–aluminum garnet, Nd:YAG, which were coprecipitated from aqueous solutions by different precipitants, namely, aqueous solutions of ammonia and ammonium bicarbonate) is studied. It is established that ultrasonication applied during the precipitation of the aforementioned powders does not significantly change the structure of the obtained materials but always leads to the formation of structures with a less homogeneous nuclear density, i.e., a more developed surface area. Moreover, the ultrasoundassisted precip itation of the hydroxocompounds by ammonium hydrocarbonate results in a certain increase in the surface fractal dimension and the degree of aggregation for massfractal aggregates of particles

Morphological structure of Gluconacetobacter xylinus cellulose and cellulose-based organic-inorganic composite materials

Scanning electron microscopy, ultra-small-angle neutron scattering (USANS), small-angle neutron and X-ray scattering (SANS and SAXS), as well as low-temperature nitrogen adsorption, were used in the studies of micro- and mesostructure of polymer matrix prepared from air-dry preliminarily disintegrated cellulose nano-gel film (synthesized by Gluconacetobacter xylinus) and the composites based on this bacterial cellulose. The composites included ZrO$_2$ nanoparticles, Tb$^{3+}$ in the form of low molecular weight salt and of metal-polymer complex with poly(vinylpyrrolydone)-poly(methacryloyl-o-aminobenzoic acid) copolymer. The combined analysis of the data obtained allowed revealing three levels of fractal organization in mesostructure of G. xylinus cellulose and its composites. It was shown that both the composition and an aggregation state of dopants have a significant impact on the structural characteristics of the organic-inorganic composites. The composites containing Tb$^{3+}$ ions demonstrate efficient luminescence; its intensity is an order of magnitude higher in the case of the composites with the metal-polymer complex. It was found that there is the optimal content of ZrO$_2$ nanoparticles in composites resulting in increased Tb$^{3+}$ luminescence

Novel biocompatible Cu2+-containing composite hydrogels based on bacterial cellulose and poly-1-vinyl-1,2,4-triazole

Novel composite hydrogels representing interpenetrating polymeric networks (IPN) have been synthesized and consisted of Gluconacetobacter xylinus cellulose (GxC) and poly-1-vinyl-1,2,4-triazole (PVT) with Cu2⁺. The composite hydrogels’ mesostructure has been studied from 1.6 ​nm to 2.5 ​μm by small-angle and ultra-small-angle neutron scattering methods. It has been found that IPN complexes have three types of inhomogeneities: GxC, PVT, and PVT complex with Cu2⁺. The amount of the absorbed ions can be tuned as confirmed by electron paramagnetic spectroscopy. Besides, three hierarchy levels of GxC remained in the supramolecular structure of composite hydrogels. Reveling structure formation in these composite hydrogels is essential in fabricating hybrid polymeric materials for regenerative medicine, involving antibacterial or antifungal applications

Morphological structure of Gluconacetobacter xylinus cellulose and cellulose-based organic-inorganic composite materials

Scanning electron microscopy, ultra-small-angle neutron scattering (USANS), small-angle neutron and X-ray scattering (SANS and SAXS), as well as low-temperature nitrogen adsorption, were used in the studies of micro- and mesostructure of polymer matrix prepared from air-dry preliminarily disintegrated cellulose nano-gel film (synthesized by Gluconacetobacter xylinus) and the composites based on this bacterial cellulose. The composites included ZrO2 nanoparticles, Tb3+ in the form of low molecular weight salt and of metal-polymer complex with poly(vinylpyrrolydone)-poly(methacryloyl-o-aminobenzoic acid) copolymer. The combined analysis of the data obtained allowed revealing three levels of fractal organization in mesostructure of G. xylinus cellulose and its composites. It was shown that both the composition and an aggregation state of dopants have a significant impact on the structural characteristics of the organic-inorganic composites. The composites containing Tb3+ ions demonstrate efficient luminescence; its intensity is an order of magnitude higher in the case of the composites with the metal-polymer complex. It was found that there is the optimal content of ZrO2 nanoparticles in composites resulting in increased Tb3+ luminescence

Composite Hydrogels Based on Bacterial Cellulose and Poly-1-vinyl-1,2,4-triazole/Phosphoric Acid: Supramolecular Structure as Studied by Small Angle Scattering

New composite hydrogels (CH) based on bacterial cellulose (BC) and poly-1-vinyl-1,2,4-triazole (PVT) doped with orthophosphoric acid (oPA), presenting interpenetrating polymeric networks (IPN), have been synthesized. The mesoscopic study of the supramolecular structure (SMS) of both native cellulose, produced by the strain Komagataeibacter rhaeticus, and the CH based on BC and containing PVT/oPA complex were carried out in a wide range of momentum transfer using ultra- and classical small-angle neutron scattering techniques. The two SMS hierarchical levels were revealed from 1.6 nm to 2.5 μm for the objects under investigation. In addition, it was shown that the native BC had a correlation peak on the small-angle scattering curves at 0.00124 Å−1, with the correlation length ξ being equal to ca. 510 nm. This motive was also retained in the IPN. The data obtained allowed the estimation of the fractal dimensions and ranges of self-similarity and gave new information about the BC mesostructure and its CH. Furthermore, we revealed them to be in coincidence with Brown’s BC model, which was earlier supported by Fink’s results

Mesostructure of yttrium and aluminum basic salts coprecipitated from aqueous solutions under ultrasonic treatment

The influence of ultrasonic treatment on the micro and mesostructures and fractal characteristics of amorphous powders of yttrium and aluminum basic salts (precursors for the synthesis of neodymiumacti vated yttrium–aluminum garnet, Nd:YAG, which were coprecipitated from aqueous solutions by different precipitants, namely, aqueous solutions of ammonia and ammonium bicarbonate) is studied. It is established that ultrasonication applied during the precipitation of the aforementioned powders does not significantly change the structure of the obtained materials but always leads to the formation of structures with a less homogeneous nuclear density, i.e., a more developed surface area. Moreover, the ultrasoundassisted precip itation of the hydroxocompounds by ammonium hydrocarbonate results in a certain increase in the surface fractal dimension and the degree of aggregation for massfractal aggregates of particles