جستجوی مقالات مرتبط با کلیدواژه « porous » در نشریات گروه « علوم پایه »

This study explores the incorporation of aqueous methylene blue (MB+) into a specially prepared metal oxide host.  Derived from the chemical exfoliation of KTiNbO5 into nanosheet colloids, the host material was synthesized in water using acid to restack the colloids into aggregates of nanosheets.  The metal oxide host has a large open pore, disordered, and turbostratic layered structure.  When exposed to aqueous solutions of MB+, within minutes the novel host rapidly intercalated MB+ to saturation, to produce an organic-inorganic composite with an MB+ loading of 226 mg/g.  Well-rinsed composites exhibited a deep purple color, indicative of the high internal content of MB+.  The MB+ loading was quantified using EDX and UV-Vis spectrophotometry.  Small-angle x-ray scattering (SAXS) measurements were carried out and analyzed using a unified exponential/power-law (UEP) model to describe the composite’s nanostructure.  SAXS analyses indicated that intercalated material is composed of two phases, each with different layer spacings for the restacked sheets.  Compared to transmission spectra of aqueous MB+, diffuse reflectance UV-Vis absorption spectra of composite revealed changes in the absorbance maxima of the intercalated MB+, indicating that the MB+ molecules were interacting strongly with each other and with the oxide host.  Raman and IR spectra also revealed significant host-guest interactions.  As determined by x-ray diffraction, the measured layer spacing between restacked nanosheets in the composite is consistent with a molecular orientation of MB+ standing on the end but tilted 40.4° away from the plane of the sheets.  Electron microscopy analysis showed that there were no significant morphological changes occurred in the porous host aggregates during the intercalation of MB+.  From an electrostatics evaluation, the new organic-inorganic composite materials were found to contain 40 % of the theoretical maximum of MB+, which resulted in an empirical formula of (MB)0.4H0.6TiNbO5.

Among the various phases of alumina, two phases γ and α are the most widely used in various industries. In this paper, γ-Al2O3 porous nanoparticles have been successfully synthesized from a simple aqueous sol–gel method using inexpensive material such as: sodium aluminate liquor, HCl, NaOH, Polyethylene glycol (PEG) and polyvinyl alcohol (PVA). Sodium aluminate liquor was extracted from Bayer liquor of alumina product processed in the Jajarm alumina factory. PEG and PVA were used as structure-stabilizing agents. The structures and properties of samples calcined at 800 ºC, were performed utilizing X-ray diffraction (XRD), infrared spectroscopy (FTIR), scanning electronmicroscopy (SEM), termogeravimetery analysis (TG/DTA), and N2 adsorption/desorptiontechniques. Prepared sample of γ-Al2O3 with polyethylene glycol surfactant has an average crystallite size of 2.313 nm, average particle size of 20 nm, specific surface area (SSA) of 138.8 m2/g, and pore volume of ∼ 0.166 cm3/g. The average crystallite size of 2.063 nm, average particle size of 46 nm, specific surface area of 201.1 m2/g, and pore volume of ∼ 0.246 cm3/g, were achieved using polyvinyl alcohol surfactant.

Polyacrylonitrile (PAN) membranes with nano-porous surface and high hydrophilicity were fabricated by addition of polyoxyethylene (40) nonylphenyl ether (IGEPAL) as an additive in the casting solution. The membranes were prepared from PAN/IGEPAL/1-Methyl-2-pyrrolidone (NMP) via phase inversion induced by immersion precipitation technique. Pure water was used as coagulation medium. The effects of adding IGEPAL and the PAN concentration on the morphology, wettability, and permeability of the prepared membranes were studied. The morphological studies were investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). In addition, the wettability and permeability of membranes were examined by contact angel measurements and permeation experiments. The contact angle measurements indicate that the hydrophilicities of membrane enhanced by the addition of IGEPAL surfactant and decreasing the PAN concentration in the casting solution. According to SEM and AFM analysis, it was found that the addition of IGEPAL and change concentration of polymer have a significant influence on structure of the membrane top surface and the sub-layer. In addition, it was found that decreasing the PAN concentration and addition of IGEPAL resulted in the formation of membranes with high permeability.