Structural changes caused by mechanical activation of SrTiO 3 powders were investigated using a variety of methods. Average crystallite size continuously decreased with increased activation time to around 20 nm after 120 min activation, while mesopore volume and specific surface area increased accordingly. Higher activation times lead to increased agglomeration of nanoparticles to form agglomerates of around 2 µm in size, ultimately
Due to its outstanding electrical characteristics, such as the low temperature expansion coefficient, low dielectric constant and good mechanical properties, cordierite, 2MgO⋅2Al 2 O 3 ⋅ 5SiO 2 , is a very attractive high-temperature ceramic material. In order to accelerate the process of sintering, 2.50 mass% Bi 2 O 3 has been added to the starting mixtures. Liquid phase sintering caused by the presence of bismuth-oxide lowers the temperature of cordierite formation. The mechanical activation of the starting mixtures (0-56 min in vibro-mill) additionally lowers sintering temperatures. The sintering process was performed at 1200, 1300, 1350 and 1400°C, for 2 h. The particle size analysis (PSA) was employed in order to determine the changes in the particle size of the mechanically treated powders. The phase composition of the starting powders and sintered materials was analyzed by the X-ray diffraction method. Furthermore, scanning electron microscopy (SEM) was used in the analysis of the powder morphology.
Cordierite-based ceramic materials are attracting much interest for their various applications in industry, for manufacturing multilayer circuit boards, catalytic converters, filters, thermal insulation, kiln furniture, components of portable electronic devices, etc. In order to reduce production costs and modify cordierite-based materials, mechanical activation can be used. In this study, microstructural and electrical properties of mechanically activated MgO-Al 2 O 3 -SiO 2 system have been analyzed. The mixtures of MgO-Al 2 O 3 -SiO 2 powders were mechanically activated in a planetary ball mill for the time periods from 0 to 160 min. Morphological investigations have been performed on the obtained powders. The effects of activation and two-step sintering process on microstructure were investigated by scanning electron microscopy (SEM). Electrical measurements showed variations of the dielectric constant (ε r ) and loss tangent (tan δ) as a function of time of mechanical treatment.
Titanium dioxide is a photocatalyst, known not only for its ability to oxidize organic contaminants, but also for its antimicrobial properties. In this article, significant enhancement of the antimicrobial activity of TiO2 (up to 32 times) was demonstrated after its activation by ball milling. The antimicrobial activity was analyzed for one fungal and 13 bacterial ATCC strains using the microdilution method and recording the minimum inhibitory concentration (MIC) values. In order to further investigate the correlation between the mechanical activation of TiO2 and its antimicrobial activity, the structure, morphology and phase composition of the material were studied by means of Electron Microscopy, X‐ray diffraction and nitrogen adsorption‐desorption measurements. UV‐Vis diffuse reflectance spectra were recorded and the Kubelka‐Munk function was applied to convert reflectance into the equivalent band gap energy (Eg) and, consequently, to investigate changes in the Eg value. X‐ray photoelectron spectroscopy was used to analyze the influence of mechanical activation on the Ti 2p and O 1s spectra. The presented results are expected to enable the development of more sustainable and effective advanced TiO2‐based materials with antimicrobial properties that could be used in numerous green technology applications.
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