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[en] Due to an oversight, the Surname of Haya Alhummiany was incorrectly spelled in the published online version. The correct surname is “Alhummiany”, instead of “Alhumminay”. The correct spelling is also shown above.
[en] Organized meso porous materials represent a class of molecular sieves because of its high potential for commercial applications in adsorption and catalysis. In this study, organized meso porous alumina was synthesized by the sol-gel method using various organic templates, i.e. cationic, neutral and anionic surfactants. Surface porosity of the synthesized alumina obtained exhibit materials in the meso pore ranges. The morphology of the samples consists of wormhole-like meso structure in the nano-region (20 - 70 nm). Sample with cetyl trimethylammonium bromide as cationic templates has the narrowest pore distribution centred at 8 nm as compared to samples synthesized with Triton X-114 (neutral) and stearic acid (anionic). All samples showed only Lewis acidity. Acidity and meso porous character present in these meso porous alumina samples showed that this material has potential as catalyst support and also used in Lewis acid catalyzed reactions. Study showed that the cationic surfactant is a better template to obtain uniform meso porous alumina that might be due to the weak interaction between the template and the surface of the alumina. (author)
[en] The phenomenon of electrostatic charge in ceramic powders takes place when the particle surfaces enter in contact between them or with the containers. The accumulation of electrostatic charge is of relevance in ceramic powders in view of their insulating character and the risk of explosions during the material handling. In this work the main factors that affect the appearance of intrinsic charge and tribo-charge in ceramic powder have been studied. In ceramic powders of alumina it has been verified that the smallest particle sizes present an increase of the electrostatic charge of negative polarity. A correlation has been observed between the nature of the OH -surface groups and the electrostatic charge. The intrinsic charge and the tribocharge in ceramic powders can be diminished by compensating the surface groups that support the charge. The dry dispersion of nanoparticles on microparticles allows surface charge compensation with a noticeable modification of the powder agglomeration. (Author) 19 refs.
[en] The method of measuring thermal assistance energy associated with photo-ionization cross-section of α-Al2O3:C has been suggested. This method involved recording of CW-OSL by stimulating simultaneously with 470 nm light and temperature using linear heating, the process termed as Thermally Assisted (TA)-OSL. The theoretical modelling has been done for the observed TA-OSL phenomenon in α-Al2O3:C phosphor. The TA-OSL signal for α-Al2O3:C has been investigated for various stimulation intensities and different heating rates. The value of thermal assistance energy (EA) associated with the dosimetry trap in α-Al2O3:C has been determined as ∼0.03 eV and temperature independent pre-exponential factor of photo-ionization cross-section as ∼4.24 x 10-18 cm2. The validity of proposed theoretical relation on temperature dependent nature of photo-ionization cross-section has been investigated using experimentally determined values of thermal assistance energy (EA) and temperature independent pre-exponential factor of photo-ionization cross-section.
[en] Standard methods of OSL measurements (CW-OSL or LM-OSL) do not allow for the direct determination of optical depth of traps. The variable energy of stimulation optically stimulated luminescence (VES-OSL) method gives such possibility. It consists in optical stimulation with the continuous increase of stimulation light energy and is analogous to the glow curve method in TL measurements. The VES-OSL curve shape and maximum position can be regulated by the stimulation photon flux, the rate of stimulation energy increase and by measurement temperature. This allows for detecting the OSL from very deep traps that give the TL signal overlapping with strong incandescence. The VES-OSL measurements carried out for Al_2O_3:C showed that traps having the optical depth between 2.0 and 2.8 eV are responsible for the OSL signal related to TL peak at about 200 °C. The OSL signal from the much deeper traps from the range 2.8–3.3 eV was also detected. The TL signal related do these traps cannot be detected below 500 °C. - Highlights: • Results of OSL measurements with the continuous increase of stimulation light energy. • Estimating the optical depths of main dosimetric traps in Al_2O_3:C. • Detecting the OSL signal from very deep traps from the range 2.8–3.3 eV.