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[en] The gradient (“transient”) systems are required for many biomedical applications, especially if the materials with different properties are to be joined without strong internal stresses. In this paper one step, radiation-induced synthesis of thermo-responsive hydrogels based on 2-(2-methoxyethoxy)ethyl methacrylate with gradient in crosslink density, has been presented. The influence of the monomer composition and synthesis procedure (irradiation dose and conditioning temperature) on the general properties of prepared gels has been discussed. It has been found that the properties of particular sections of the gel sample do not result from the differences in chemical structure, but from significantly different morphology. The explanation of the mechanism leading to gradient behavior of obtained gels has been proposed. The chemical structure of obtained products and morphology of synthesized hydrogels as well as general properties of products have been analyzed. - Highlights: • Thermo-sensitive hydrogels with gradient of cross-link density. • Analysis of parameters describing network formation. • Synthesis of hydrogels with various morphologies depending on post-irradiation procedure
[en] An appropriate filler is a key component required to achieve an useful composite with expected properties. Not only sophisticated types of filler, like graphene are popular, but also more common ones, like silica flour or fly ash because of their low costs. Besides production costs, adequate size and possibility of functionalization of particles surface to create stable bonds with a matrix are essential in filler selection. To create an useful filler for epoxy resin based composites with use of a waste material, namely fly ash, two-step procedure was proposed. In the first part, raw material was sieved and five different ranges of the filler size were obtained. After mechanical tests with fracture toughness, tensile strength and Young Modulus, as well thermal conductivity, the best size of the fly ash was chosen for further modification. During the second step, filler was modified with coupling agent [3-(2-aminoethylamino)propyl]trimethoxysilane in order to enhance the coupling between particular components of composite. Presence of the silane layer was confirmed with infrared spectroscopy and scanning electron microscopy measurements, whilst prepared epoxy composite filled with silanized fly ash was examined similarly as previous composites. Obtained results have proved the significant influence of size of a filler and bonding to the matrix on mechanical and thermal properties of fly ash-epoxy resin composite. Proposed simple method of fly ash modification is an environmentally friendly way for utilization of the fly ash. Moreover, it creates an alternative material applicable in electrical devices as functional composite.
[en] Highlights: • Stability of electrostatically stabilized aqueous dispersions of Ag NPs is studied. • Ag NPs were annealed or irradiated by laser or by electron beam. • Post radiation effect was found for Ag NPs treated with low doses (≤ 100 Gy). • Both thermal and radiation treatments lead to narrower distribution of Ag NPs sizes. • Ag NPs photostability depends on relation of plasmonic absorption to light energy. - Abstract: The stability of silver nanoparticles (Ag NPs) attracts an increasing attention because of the broadening field of their application, especially in catalysis, medicine and pharmacy, electronics and optoelectronics, sensors, environment protection technologies, textronics and many others. In this article, the stability of electrostatically stabilized aqueous dispersions of Ag NPs with different sizes under irradiation and thermal treatment is discussed. The UV–Vis spectrophotometry supported by Atomic Force Microscopy (AFM), Dynamic Light Scattering (DLS) and Transmission Electron Microscopy (TEM) were used to monitor the changes induced in Ag NPs by temperature, laser and electron-beam irradiation. It was found that the nature and mechanism of size and shape changes in Ag NPs treated by elevated temperature and radiation are different. KBr added to the reacting mixture as a size-control agent determines also the stability of investigated Ag NPs. The higher KBr content, the lower Ag NPs size, but surprisingly the highest thermal and photostability. Both thermal and radiation treatments lead to narrower distribution of Ag NPs sizes. The effects induced by laser light strongly depend on the relationship between the maximum of the plasmonic absorption band and wavelength of laser light. Small doses of electron beam radiation (≤ 100 Gy) does not change the NPs immediately. However a strong post radiation effect was found. The lower applied dose, the stronger effect observed.
[en] The influence of high-energy electron beam, (EB), treatment, in the dose range of 100–1000 kGy, on the physicochemical properties of silica-supported TiO_2 was examined. TiO_2/SiO_2 supported oxides were obtained by impregnation of commercial silica gel (2–4 mm) with titanium (IV) n-butoxide. Surface and optical properties of prepared TiO_2/SiO_2 systems were analyzed using SEM, BET, XRD, Raman and UV–vis spectroscopy. The photoactivity under visible light was tested in discoloration of azo dye solution. No significant structural changes of the TiO_2/SiO_2 surface were detected as a result of EB treatment. Effect of EB irradiation was observed as an increase of photocatalytic activity in dye decomposition under visible light for TiO_2/SiO_2 samples containing ca. 23 wt% TiO_2. The enhancement of activity was assigned to EB-induced defects and C-modification of TiO_2 particles. - Highlights: • Titanium (IV) n-butoxide and silica were used for synthesis of TiO_2/SiO_2 samples. • Preparation conditions affected surface and optical properties of TiO_2/SiO_2 samples. • Electron beam red shifted light absorption of TiO_2/SiO_2 samples. • Electron beam enhanced the photoactivity of TiO_2/SiO_2 in azo dye discoloration
[en] Highlights: • Magnetite particles, after separation from reaction mixture and drying, were irradiated using electron beam (EB). • After EB irradiation bare Fe3O4 nanoparticles aggregated in aqueous dispersion. • Surface of uncoated Fe3O4 particles was oxidized during EB irradiation. • EB irradiation caused disaggregation of citrate-coated Fe3O4 particles. - Abstract: Influence of electron beam (EB) irradiation on surface properties of magnetite was investigated using XRD, TEM, DLS, zeta-potential, FTIR and Raman spectroscopy. Fe3O4 particles were synthesized by alkaline hydrolysis of ferrous ions and stabilized with sodium citrate. Dry samples of bare and citrate- coated Fe3O4 particles were EB-irradiated with doses up to 300 kGy. The crystallite sizes of uncoated and citrate-coated magnetite were found to be in the range of 25–27 nm and 30–32 nm, respectively. EB- irradiation did not result in phase and size change of Fe3O4 nanoparticles. Using DLS and TEM analysis, it has been found, that EB-irradiated bare Fe3O4 nanoparticles have aggregated in aqueous dispersion. Traces of hematite and maghemite were identified on the surface of EB-irradiated bare particles by Raman spectroscopy. Radiation-induced oxidation of magnetite was probably involved to radiolysis of water molecules adsorbed onto particle surface and formation of hydroxyl radicals which are strong oxidize species. Disaggregation of citrate-coated particles in water dispersion after EB irradiation has been assigned to disruption of Fe-citrate bonds.