Results 1 - 10 of 4321
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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] The work studies the applicability of dunite rocks from Inagli massif (South Yakutia) for the production of mixed (composite) cement. The paper reviews the implementation of dunite for manufacturing materials and products. The chemical and mineral compositions of Inagli massif dunite rocks are presented, which relegate the rocks to magnesia-silicate rocks of low-quality in terms of its application as refractory feedstock due to appreciable serpentinization of dunite. The work presents the results of dunite study in terms of its applicability as an additive to Portland cement. The authors have established that dunite does not feature hydraulicity and can be used as a filling additive to Portland cement in the amount of up to 40%. It was unveiled that the mixed grinding of Portland cement and dunite sand with specific surface area of 5500 cm2/g yields the cement that complies with GOST 31108-2016 for CEM II and CEM V normal-cured cements with strength grades of 32.5 and 42.5. The work demonstrates the benefits of the studies of dunite as a filling additive for producing both Portland cement with mineral component and composite (mixed) cement. (paper)
[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] An experimental study on the characteristics of aluminum wire explosion in ambient gas is carried out. A compact experimental device is built to study the electrical parameters, morphology and size distribution of nanoparticles generated by wire explosion. The typical characteristics are obtained and the influence of the type and pressure of the ambient gas is investigated. The explosion process in argon indicates a longer time for breakdown development and larger deposited energy compared with those in helium. It is proposed that these differences are mainly due to different barrier effects on the formation of plasma channel. The nanoparticles formed in helium have a smaller average diameter, a more concentrated size distribution and a larger specific surface area. It is found that there exists a pressure of about 80 kPa, at which both the peak voltage and deposited energy possess the maximum values. (paper)
[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] This work reports the biological evaluation of nanosized hydroxyapatite (HAp) previously synthesized by continuous-flow precipitation in a scaled-up meso oscillatory flow reactor (meso-OFR). Physico-chemical characterization of the synthesized HAp suggests high surface reactivity namely because of its high specific surface area and low crystallinity. On the other hand, in vitro biomineralization assays demonstrated the apatite-forming activity of the prepared HAp and their higher surface reactivity when compared to a commercial HAp. Furthermore, human osteoblastic-like (Saos-2) cells culture evidenced that the synthesized HAp stimulated cell proliferation, especially when applied at lower concentrations (30 and 50 μ g ml−1), although its cellular uptake behavior. Therefore, the prepared HAp shows immense potential as biomedical material, as well as drug and gene delivery vehicle. The results are also very promising regarding further scaling up of the process, as the designed methodology allow for the preparation in a continuous mode of nanosized HAp with controlled physico-chemical properties. (paper)