Papers by Keyword: Mesoporous

Abstract: Mesoporous carbonated hydroxypatite (CHA) is a promising drug delivery agent for disease treatment and could be a carrier for different types of drugs and antibiotics. It is still a challenge to introduce pores to carry drugs within the mesoporous CHA and obtain high surface area nanoparticles. This study investigates the effect of different types of nonionic surfactant and carbonate concentration on the pore characteristic of mesoporous CHA. Mesoporous CHA is synthesised through the coprecipitation technique using nonionic surfactants as pore templates i.e., P123 and F127 with different carbonate concentration. The axial view of transmission electron microscopy (TEM) images shows the pores formed within the particles are distributed randomly, while the parallel view demonstrates that nanopore channels are developed within the CHA particles. Nitrogen adsorption analysis provides the surface area and Pore Size Distribution (PSD) of the nanoparticles. The PSD shows that CHA synthesis with P123 and F127 has similar pore size, around 28.9 nm, but different surface area. The results confirm the different types of surfactant templates has a positive effect on the pore characteristic, while carbonate precursor concentration does not significantly change surface area and pore size.

Abstract: The mesoporous Ce_xZr_1-xO₂ mixed oxides with different Ce/Zr ratio were prepared via a surfactant-assisted method of nanoparticle assembly, CTAB was used as surfactant. The Ce_xZr_1-xO₂ mixed oxides were used as the supports for preparing Cr-V-O/ Ce_xZr_1-xO₂ catalysts by the wetness impregnation method, and the catalytic activities of the results catalysts for dehydrogenation of propane to propene were studied. The prepared catalysts were characterized by XRD and N₂ adsorption techniques.The Cr-V-O/ Ce_xZr_1-xO₂ catalysts exhibiting high activity and selectivity for dehydrogenation of propane to propene. The molar ratio of Ce/Zr ratio showed remarkable influence on the activity of the catalysts. The optimistic catalyst was Cr-V-O/Ce_0.5Zr_0.5O₂ the highest yield of 20.0% was obtained, the corresponding conversion of propane was 20.9% and selectivity to propene was 95.9% at 550 °C.

Abstract: Low drug water-solubility is a major challenge to overcome in the development of tablet or capsule dosage forms for a large number of promising drug candidates. Strategies to improve drug solubility and dissolution involve chemical, physical and formulation approaches. An emerging formulation approach to increase drug dissolution and solubility involves the creation of solid dispersions of drug molecules on to a high surface area inorganic carrier, such as porous silica. The combined benefits of a hydrophilic inorganic substrate, increased drug surface area and a high-energy drug form facilitate rapid drug dissolution into aqueous based media and can create supersaturated drug solutions. The work presented provides a brief overview of the silica grades investigated, processes employed to load drugs onto the silica substrates, provide some examples of the ability of silica to enhance drug dissolution and highlight some of the challenges in the development of these novel drug delivery systems.

Abstract: Mesoporous ZrO₂ with narrow mesopore size distributions has been prepared by the surfactant-assisted method of nanoparticle assembly. A series of VCrO/ZrO₂ catalysts with different V/Cr molar ratio (0.3, 0.6, 1.0, 1.3 and 1.6) were prepared by the wetness impregnation method and characterized by XRD, N₂ adsorption and TEM techniques. N₂ adsorption and TEM analysis revealed that the surfactant-assisted method prepared VCrO/ZrO₂ catalysts have wormhole-like mesoporous structure with uniform pore size distribution. VCrO/ZrO₂ catalysts have been applied for direct dehydrogenation of propane to propene. The optimistic catalyst was V/Cr-0.6 with highest yield of 41.7% the corresponding conversion of propane was 44.1% and selectivity to propene was 94.5% at 550 °C.

Abstract: Mesoporous material SBA-15 was synthesized using P123 and TEMOS as the templates. Lithium in the form of LiOH was loaded over a previously prepared SBA-15. The basic strength of the prepared samples of SBA-15 was found to increase but the mesoporous structure was severely destroyed. The mesoporous structure of the prepared SBA-15 was retained after coating it with 30 wt. % magnesium prior to LiOH loading. The stability of mesoporous structure was strongly influenced by the extent of magnesium coating. It was also noted that this structure was also affected by LiOH loading and significantly destroyed structure when magnesium coating value exceeded 20 %. These samples were thoroughly characterized for their surface area, pore volume, pore size, basic strength, SAXRD patterns and transmission electron microscopic (TEM) analysis.

Abstract: Micro-mesoporous mixed oxides containing nickel, cobalt and aluminum have been synthesized using conventional coprecipitation method. FESEM and HRTEM analyses demonstrated the flower and hexagonal plate-like nanostructured of mixed oxides. Different mixed oxide formation, homogenous metal dispersion, textural properties were investigated using XRD, ICP-MS and BET (N₂ adsorption-desorption) techniques. nanostructured mixed oxides exhibited 2.6 wt% hydrogen adsorption that were studied using temperature programmed reduction-adsorption-desorption (H₂-TPR/TPD) and thermogravimetric and differential thermal analysis (TGA-DTA) techniques. Investigation corresponds that morphologies, textural properties and surface energy of mixed oxides are important in hydrogen adsorption.

Abstract: HZSM-5 catalysts with SiO₂/Al₂O₃ molar ratio of 80 were treated with 0.4 mol/L Na₂CO₃ solution at 80°C for 2 h to improve diffusion properties. Further, some of these catalysts were modified by impregnation of La (NO₃)₃. These catalysts characterized by XRD and BET were evaluated in a fixed bed reactor for conversion of methanol to gasoline (MTG) reaction. The Na₂CO₃ treatment results in formation of mesoporous structure in ZSM-5 zeolite. Meanwhile, LaZSM-5/AT catalyst exhibits significantly enhancement in catalytic lifetime and liquid hydrocarbons yield as well as selectivity of isoparaffin and olefin. The conversion of methanol remains above 80 % over 125 h on LaZSM-5/AT catalyst under atmospheric pressure, 380°C and weight hourly space velocities (WHSV) of 1.5 h^-1.

Abstract: Graphene-NiO nanocomposites were prepared via a solvothermal method. The nanostructure and morphology of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). SEM and TEM results indicated that NiO nanoplates distributed homogeneously on graphene sheets. The electrochemical properties of the samples as active anode materials for lithium-ion batteries were examined by constant current charge-discharge cycling. With graphene as conductive matrix, homogeneous distribution of NiO nanoplates can be ensured and volume changes of thenanocomposite during the charge and discharge processes can be accomodated effectively, which results in good electrochemical performance of the composites.

Abstract: Mesoporous titanium dioxide/graphitic carbon microspheres were synthesized by a simple nanocasting route using monodisperse silicon dioxide microspheres as the template. The characterize and the morphology of the titanium dioxide/graphitic carbon microspheres have been analyzed by means of XRD, N₂-sorption, SEM, TEM, TG-DTA and EDAX. Indicated by the experimental results and the theoretical analysis, the anatase titanium dioxide nanoparticles of 8-14 nm in diameter were highly dispersed in the graphitic carbon microspheres. The obtained material can be used as catalyst or battery material. Key words: titanium dioxide/graphitic carbon; Microspheres; Nanocasting route;Mesoporous

Abstract: Hybrid silica xerogel mesoporous composite was synthesized by a mild temperature acid catalysed sol-gel route where a natural copolymer; sodium alginate (Na-COOH) together with calcium oxide (CaO) powder were incorporated into silica sol precursor prior to gel formation. For this study, bulk xerogels samples were prepared with the amount of silica precursor and the natural copolymer was fixed meanwhile the loading of calcium oxide was varied at 10 and 20 wt%. The monolith silica was also synthesized as control parameter. The preliminary properties were investigated using XRD, FTIR and SEM together with EDS for elemental analysis. The calcium oxide powder used in this study was prepared from calcium hydroxide, CaOH compound, which was previously calcined at 1000°C for 3 hours in normal air. The component of calcium oxide and sodium alginate were found to be uniformly dispersed in matrixes without affecting the cross-linked silica formation. As the presence of the components in the silica matrixes, the synthesized hybrid xerogels were found to be crack-free, structurally amorphous and physically opaque. Furthermore, the hybrid xerogels samples were found to have denser bodies, smoother surface, and decreased in particle sizes and thus might produced less brittleness in nature compared to the monolith xerogels.