Results 1 - 10 of 3785
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[en] Highlights: • The hydrophilic/hydrophobic properties hydroxyapatite can be control. • The heat of immersion, which decreases with the increasing specific surface area. • Modification of hydroxyapatite synthesis affects the specific surface area and as a consequence, the heat in water and decane. • Decrease in the heat of immersion in water and decane was measured in the J/g units.
[en] Highlights: • Nanoporous copper with high specific surface area was fabricated by dealloying method. • Cu-Ti and Cu-Ti-Ni amorphous ribbons are chosen as precursors. • The addition of a minor amount of Ni alter the resulting nanoporous structure in a large extent. • The nanoporous copper exhibits high electrocatalytic activity toward methanol oxidation.
[en] The process of the invention increases and stabilizes at high temperature the specific surface area of ceric oxide. Ceric oxide is prepared by calcination of ceric hydroxide which has undergone a thermal pretreatment in liquid media before calcination
[fr]L'invention concerne un procede pour accroitre et stabiliser a haute temperature la surface specifique d'un oxyde cerique. Le procede qui consiste a preparer un oxyde cerique par calcination d'un hydroxyde cerique est caracterise par le fait que l'hydroxide cerique est soumis a un traitement solvothermal, avant l'operation de calcination
[en] The results of studies on the electrochemical behaviour of electrodes made of nanostructured carbon (single- and multi-walled nanotubes, nanopaper, nanofibres) and of conventional electrodes modified with these nanoobjects are analysed. Specific features of electrode reactions on modified electrodes that are not associated with their high specific surface areas are revealed.
[en] Low surface areas of non-porous mineral and oxide powders have been determined by adsorption calorimetry to a precision of +-15 percent. Five standards with surface areas in the range 0.64 to 24.3 m2/g were examined to check the internal consistency of our method. Our surface area values agree within +-10 percent with supplied values, obtained by the Brunauer, Emmett and Teller (BET) nitrogen adsorption technique at -196 deg C. The present technique is less time consuming than commercial systems and requires small sample size (< 1 g per run). Also, the technique works at 25 degrees C, rather than at -196 degrees C, and can be adapted for routine operation. Finally, the technique appears preferable to a relatively tedious gas-solid chromatographic method, which uses large samples (200 to 300 g), and yields values in poor agreement with BET results
[en] Highlights: • Ionic imprinted mesoporous bilayer films (IIBFs) were prepared by dual-template docking oriented ionic imprinting (DTD-OII). • DTD-OII do not require additional steps compare with traditional imprinting. • IIBFs exhibited high selective adsorption of neodymium and dysprosium. • IIBFs can staged stripping of neodymium and dysprosium by control of temperature. - Abstract: Rare earth elements (REEs) are critical materials to many cutting-edge technologies but are difficult to separate from one another because of their chemical similarity. We present ionic imprinted mesoporous bilayer films (IIBFs) as an ideal adsorbent for selective separation of neodymium (Nd) and dysprosium (Dy) from sintered neodymium magnets. IIBFs were prepared according to dual-template docking oriented ionic imprinting (DTD-OII). Due to different imprinted compositions of bilayer films, IIBFs exhibited high specific surface area, fast binding equilibrium, and Janus properties for simultaneous selective adsorption of different rare earth ions, which made our imprinted bilayer mesoporous films a specialized adsorbent for adsorption of Nd(III) and Dy(III) at the same time. The adsorption capacities of optimized IIBFs were 17.50 mg g−1 for Dy(III) and 12.15 mg g−1 for Nd(III) at pH = 4.0. Moreover, we grafted thermo-responsive polymer on the one surface of IIBFs to realize controlled release of Nd(III) and Dy(III) by temperature. IIBFs demonstrate a high degree of reusability by cycling experiments by DTD-OII, which develop their promising applications for the REE recycling and separation industry.
[en] The main characteristics required to CeO2 (cerium oxide) be used in catalysts for purification of exhaust gases are: high specific surface area and thermal stability, more precisely specific surface about 30 m2/g after calcination at 800 deg C. In this work, the studied processes for obtain CeO2 with the above characteristics were: thermal treatment, acid treatment and precipitation. The acid treatment consisted in the leaching of the starting material with nitric acid. The starting material was cerium hydroxide (90%) originally from NUCLEMON. The studied variables were the humidity content of the raw material, nitric acid concentration and specific surface area of the starting material. The specific surface areas were determined by gaseous adsorption (BET method). The final products were characterized by X-ray diffraction, X-ray fluorescence, scanning electron microscopy and gaseous chromatography. Among the obtention methods studied, one that showed more efficient for CeO2 obtention with high specific surface area was acid treatment. By this process, it was possible to get powder with specific surface area larger than 40 m2/g, after treatment at temperature of 800 deg C for two hours. (author)
[en] The preparation of pure EUO zeolite under conventional conditions usually takes more than three days, limiting the application of the EUO zeolite. It is widely acquainted that the seed-assisted synthesis of zeolites without organotemplates is inexpensive, environmentally-friendly and lead to Al-rich products. However, synthesis with EUO seeds in the absence of organic-templates always leads to the formation of impurity phases. In this work, EUO zeolite (s-EUO) is successfully obtained by seed-directed synthesis without organotemplates. This is the first seed- directed synthesis of pure EUO zeolite with special Al source. Physicochemical characterization results show that the synthesized s-EUO zeolite exhibits high crystallinity and high specific surface area, and contains uniform crystals and plenty acidic sites. The s-EUO crystallization (by this method) occurs in a considerably shorter time (18 h) and in a more mild condition (160 °C, static state), compared to that of the conventional EUO zeolites (c-EUO, 72 h at 180 °C, at rotation) in the presence of organotemplate. Moreover, the catalytic performance of the H-form of the s-EUO zeolite is enhanced to that of the c-EUO zeolite for m-xylene isomerization, confirming the NH3-TPD results. (paper)
[en] A novel multi-layer composite (MLC) was developed consisting of a polyvinyl alcohol (PVA) film as a substrate and a drug loaded silica aerogel powder which coated by PVA nano fibers. It was tested as a controlled drug delivery system (DDS) with fluconazole as an anti-fungal drug. The hydrophilic and hydrophobic silica aerogels synthesized at ambient pressure and loaded with the fluconazole. Results of drug release showed that silica aerogels have a faster release rather than pure fluconazole because of a high specific surface area (>800 m2 g−1) and high porosity (>80%). Release rate of about 80% of the fluconazole loaded in the hydrophilic and hydrophobic silica aerogels showed an increase of 3.7-fold and 2.5-fold compare to the crystalline form of the drug, respectively. Furthermore, the PVA nano fibers help to control the fluconazole release rate. The silica aerogel/PVA composites exhibited the non-Fickian mechanism for the drug release while, the loaded silica aerogel powders follow the Fickian mechanism. The composite contains hydrophilic silica aerogel showed stronger effect on the controlled drug release compare to the hydrophobic sample. The results of the anti-fungal properties showed that the drug loaded samples have a good consequence on the fungal. (paper)