Effect of nanosilica size on physic-mechanical properties, thermal stability and weathering durability of coating based on acrylic emulsion. Nanocomposite coating formulas were filled by 2 wt.% nanosilica particles which were used in this study, namely: nanosilica from Sigma (15-20nm), nansilica from rice husk (~70-200 nm) and nanosilica from Arosil – Belgium (7-12 nm). Obtained results showed that viscosity flow of coating formula containing nanosilica from Arosil saw the highest flow-time while coating formulas filled other nanosilica and unfilled nanosilica experienced similar flow-time. In presence of nanosilica, coating properties were improved in comparison with neat coating. However, coating filled by nanosilica from rice husk indicated the best properties in studied coating formula. It may explained that size of nanosilica from rice husk was the largest in studied nanosilica particles and thus easily dispersing into coating formula.
In this study, we propose an approach using the gamma transmission technique based on the combination of the experimental and simulated data for determining the percentage concentration of the acid solution. The experiment consists of a collimated 137Cs radioactive source emitting a narrow gamma beam of 662 keV and a NaI(Tl) detector. Monte Carlo simulation data is used to construct the calibration curve of lnR versus the percentage concentration of acid solution at different temperatures (R is the ratio of the area under a transmission peak for an acid solution relative to that for water). The percentage concentration of the acid solution is determined based on the calibration curve and the experimental ratio R. The obtained results showed that this approach was feasible in which the percent concentration of 7 in total 8 samples of the sulfuric acid solution are less than 5% in comparison with one of the reference samples. There is only one sample with a relative deviation of 7.6%. These preliminary results suggest that it is possible to develop nondestructive testing for the rapid determination of the percentage concentration of acid solutions based on the gamma transmission technique.
The titania coating on phosphate surface was made by the painting method in air and at room temperature. The coatings were dried at 25°c and sintered at 15(TC, 25(FC, 350”C, 45ƠJC, 550°C for 30 minutes. X-ray diffraction, scanning electron microscopy and the cutting method (TCVN 2097-1993) were used to characterize the coatings. The results showed that the coating annealed at 350TC had the high photoactivity in the photodegradation of methylene blue.
Full spectrum analysis, FSA, has been being widely used for the identification in environmental radioactive. In this work, firstly, FSA is developed to analyze the gamma backscattering spectrum on concrete to determine the component densities. The concrete samples are mixed of Portland cement, sand, gravel and water in the different proportions. The experiments are carried out by the radioactive source Cs137 (0.5mCi) and the detector NaI(Tl) 2 inch x 2 inch. The obtained results show that FSA would be a good approach to analyze the gamma backscattering on concrete.
The TiO2/Hydroxyapatite (TiO2/HAp) nanocomposites with different ratios were prepared by precipitation of hydroxyapatite in the presence of TiO2 or TiO(OH)2. The physicochemical properties of TiO2/HAp material were characterized using the batch equilibration method and BET, XPS, DRS, FTIR analyses. The XPS result showed that binding energy of Ca-P was 347.2eV, that of P-OH was 133.3eV and the Ti 2p spectrum could be resolved into two spin-orbit pairs 2p3/2 and 2p1/2 with binding energies of 458.6 and 464.1 eV, respectively, which are the characteristics of titanium(IV) in TiO2. The FTIR result suggested that the formation of the TiO2/HAp nanocomposites have not changed the structure nor the phase of the hydroxyapatite crystals. However, the physicochemical properties of TiO2/HAp nanocomposites such as pHpzc values, band gap energy, specific surface area and pore volume were higher than those of pure TiO2 and HAp.
The effect of the diameter of the detector collimator on the saturation thickness in gamma-scattering measurements is studied using the spectrum of singly scattering. Geometric arrangement of gamma-scattering measurement includes: a gamma-ray collimated beam with the energy of 662 keV emitted from 137Cs source is irradiated on a rectangular aluminium target with incident angle of 90o, and detector NaI(Tl) 5.1cmx5.1cm with collimator is used to record the scatterd gamma rays at scattered angle of 120°. The experimental measurements are carried out to obtain scattered spectra with various target thickness and diameter of detector collimator. The profile of the singly scattering and multiply scattering in the scattered spectra are determined by a spectrum processing technique based on the least squares fitting. The experimental results showed that the saturation thickness of the counts of singly scattering increases with increasing the window diameter of the detector collimator. These results will support for the non-destructive testing research of application of gamma-scattering method to determine the thickness or the defect of the sample.
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