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High Specific Surface Area (high + specific_surface_area)
Selected AbstractsSelf-Assembling of Er2O3,TiO2 Mixed Oxide Nanoplatelets by a Template-Free Solvothermal RouteCHEMISTRY - A EUROPEAN JOURNAL, Issue 45 2009Beatriz Julián-López Dr. Abstract An easy solvothermal route has been developed to synthesize the first mesoporous Er2O3,TiO2 mixed oxide spherical particles composed of crystalline nanoplatelets, with high surface area and narrow pore size distribution. This synthetic strategy allows the preparation of materials at low temperature with interesting textural properties without the use of surfactants, as well as the control of particle size and shape. TEM and Raman analysis confirm the formation of nanocrystalline Er2O3,TiO2 mixed oxide. Mesoscopic ordered porosity is reached through the thermal decomposition of organic moieties during the synthetic process, thus leading to a template-free methodology that can be extended to other nanostructured materials. High specific surface areas (up to 313,m2,g,1) and narrow pore size distributions are achieved in comparison to the micrometric material synthesized by the traditional sol,gel route. This study opens new perspectives in the development, by solvothermal methodologies, of multifunctional materials for advanced applications by improving the classical pyrochlore properties (magnetization, heat capacity, catalysis, conductivity, etc.). In particular, since catalytic reactions take place on the surface of catalysts, the high surface area of these materials makes them promising candidates for catalysts. Furthermore, their spherical morphology makes them appropriate for advanced technologies in, for instance, ceramic inkjet printers. [source] ZnO Hierarchical Micro/Nanoarchitectures: Solvothermal Synthesis and Structurally Enhanced Photocatalytic Performance,ADVANCED FUNCTIONAL MATERIALS, Issue 7 2008Fang Lu Abstract A novel ZnO hierarchical micro/nanoarchitecture is fabricated by a facile solvothermal approach in an aqueous solution of ethylenediamine (EDA). This complex architecture is of a core/shell structure, composed of dense nanosheet-built networks that stand on a hexagonal-pyramid-like microcrystal (core part). The ZnO hexagonal micropyramid has external surfaces that consist of a basal plane (000) and lateral planes {011}. The nanosheets are a uniform thickness of about 10,nm and have a single-crystal structure with sheet-planar surfaces as {20} planes. These nanosheets interlace and overlap each other with an angle of 60° or 120°, and assemble into a discernible net- or grid-like morphology (about 100,nm in grid-size) on the micropyramid, which shows a high specific surface area (185.6,m2,g,1). Such a ZnO micro/nanoarchitecture is new in the family of ZnO nanostructures. Its formation depends on the concentration of the EDA solution as well as on the type of zinc source. A two-step sequential growth model is proposed based on observations from a time-dependent morphology evolution process. Importantly, such structured ZnO has shown a strong structure-induced enhancement of photocatalytic performance and has exhibited a much better photocatalytic property and durability for the photodegradation of methyl orange than that of other nanostructured ZnO, such as the powders of nanoparticles, nanosheets, and nanoneedles. This is mainly attributed to its higher surface-to-volume ratio and stability against aggregation. This work not only gives insight into understanding the hierarchical growth behaviour of complex ZnO micro/nanoarchitectures in a solution-phase synthetic system, but also provides an efficient route to enhance the photocatalytic performance of ZnO, which could also be extended to other catalysts, such as the inherently excellent TiO2, if they are of the same hierarchical micro/nanoarchitecture with an open and porous nanostructured surface layer. [source] Synthesis of Nanophased Metal Oxides in Supercritical Water: Catalysts for Biomass ConversionINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 5 2006Caroline Levy Nanoparticles of zinc oxide-based materials (ZnO, ZnAl2O4) with various morphologies were synthesized in supercritical water (SCW) with a flow-type apparatus and in sub- and supercritical water with a batch reactor. In the flow-type apparatus, smaller particles were obtained. Depending on the precursors, the morphology of crystallites is rod, hexagonal, or rectangular shaped. ZnAl2O4 was synthesized with a high specific surface area (SBET) reaching 210 m2/g and nanocrystallite sizes ,10 nm. The KOH concentration played a major role in the formation of ZnO and ZnAl2O4 phases. Then, the synthesized materials were used as catalysts for the biomass conversion by the oxidation process to produce hydrogen. [source] Preparation and characterization of UV-grafted ion-exchange textiles in continuous electrodeionizationJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 12 2004Kyeong-Ho Yeon Abstract Ion-exchange textiles (IETs) suitable for use in continuous electrodeionization (CEDI) stacks were prepared using the ultraviolet (UV)-induced grafting of acrylic acid and sodium styrene sulfonate for cation-exchange textiles, or 2-hydroxyethyl methacrylate and vinylbenzyl trimethyl ammonium chloride for anion-exchange textiles, onto nonwoven polypropylene fabric using benzophenone as photoinitiator. Although the ion-exchange capacity (2.2 meq g,1) of the prepared strong acid cation-exchange textile was lower than that of IRN77 strong acid cation-exchange resin (4.2 meq g,1), the overall rate constant of IET was very high due to its low crosslinking and high specific surface area. There was no significant difference between the two different media in terms of the Co(II) removal rate. Furthermore, the current efficiency for IETs was higher than that of IRN77 cation-exchange resin during a CEDI operation, with efficiencies of 60% and 20%, respectively. The IET also showed the faster exchange kinetics. Therefore, IETs prepared in this study proved to have desirable ion-conducting characteristics within the CEDI systems. Also this study revealed that the primary removal mechanism in CEDI is the transport of ions through a medium and not the ionic capacity of a medium. Copyright © 2004 Society of Chemical Industry [source] Relevance of Osteoinductive Biomaterials in Critical-Sized Orthotopic DefectJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 5 2006Pamela Habibovic Abstract Several publications have shown the phenomenon of osteoinduction by biomaterials to be real. However, whether the ability of a biomaterial to initiate bone formation in ectopic implantation sites improves the performance of such osteoinductive biomaterial in clinically relevant orthotopic sites remains unclear. No studies have been published in which osteoinductive potential of a biomaterial is directly related to its performance orthotopically. In this study, we compared osteoinductive and nonosteoinductive biphasic calcium,phosphate (BCP) ceramics ectopically and in a clinically relevant critical-sized orthotopic defect in goats. The two materials, BCP1150 and BCP1300, had similar chemical compositions, crystallinities, and macrostructures, but their microstructures differed significantly. BCP1150, sintered at a lower temperature, had a large amount of micropores, small average crystal size, and hence a high specific surface area. In contrast, BCP1300, with few micropores, had a significantly lower specific surface area as compared to BCP1150. Twelve-week intramuscular implantation in goats (n,=,10) showed that bone was induced in all BCP1150 implants, while no signs of bone formation were found in any of the BCP1300 implants. After 12 weeks of implantation in a bilateral critical-sized iliac wing defect in the same goats, BCP1150 showed significantly more bone than BCP1300. In addition, the analysis of fluorochrome markers, which were administered to the animals 4, 6, and 8 weeks after implantation to follow the bone growth dynamics, showed an earlier start of bone formation in BCP1150 as compared to BCP1300. Significantly better performance of an osteoinductive ceramic in a critical-sized orthotopic defect in a large animal model in comparison to a nonosteoinductive ceramic suggests osteoinduction to be clinically relevant. Further improvement of material osteoinductive properties is thus a significant step forward in the search for alternatives for autologous bone graft. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res [source] Precipitation of Carbonated Calcium Phosphate Powders from a Highly Supersaturated Simulated Body Fluid SolutionJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2007Ingo Hofmann Carbonated hydroxy apatite (CHA) powders were prepared by precipitation from a modified simulated body fluid (5 × M-SBF). The ionic concentrations were five times higher than in human blood plasma with the exception of Mg2+ and HCO3, concentrations that were reduced in order to accelerate crystal growth. Spheroaggregates of CHA platelets with molar (Ca+Mg)/P ratios ranging from 1.44 to 1.56 were obtained after precipitation at 50°C. The crystallite size in the c direction was approximately 31 nm and depending on the precipitation time, a CO32, content of 1.8,5.2 wt% was determined. Using this low-temperature precipitation method, CHA powders with a high specific surface area of 83 m2/g and a composition and crystallite size close to those of the mineral phase of human bone were obtained. [source] Aqueous Combustion Synthesis of Strontium-Doped Lanthanum Chromite CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2003Kishori Deshpande An aqueous combustion synthesis is used to produce powders of La0.8Sr0.2CrO3 perovskite. It is shown that interaction between chromium nitrate and glycine controls the process. In addition, it is suggested that glycine reacts with products of nitrate decomposition to yield an intermediate compound, which decomposes exothermically providing high-temperature conditions for complex oxide formation. It is remarkable that although reaction temperature is high (up to 800°C) and characteristic time is small (,1 s) for synthesis under the self-propagating high-temperature mode, the produced perovskites have high specific surface area (,40 m2/g) and well-defined crystalline structure. As a result, ceramics sintered by using these powders are dense (,96% of theoretical) and possess high electronic and low ionic conductivities, important for interconnect applications in solid oxide fuel cells. [source] Novel Method for Obtaining Corundum Layers of High Surface Area on Ceramic Supports for High-Temperature CatalysisJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2002Alejandro Souto The surface of an aluminosilicate ceramic was transformed to a corundum layer of high specific surface area by heating at 1300°,1450°C in a controlled reducing atmosphere. This procedure selectively reduced and volatilized the silica of the glass and mullite, and the alumina of the mullite formed a layer of corundum crystals with a thickness of ,20 ,m and a specific surface area of ,16 m2/g. Specific surface area remained stable at 10.5 m2/g after prolonged heating at 1300°C in air, and at 8.5 m2/g at 1450°C. These materials are well suited for use as catalyst supports in applications such as catalytic combustion at temperatures in this range. [source] Biological treatment of milk processing wastewater in a sequencing batch flexible fibre biofilm reactorASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2009Mohamed Abdulgader Abstract Biological treatment of dairy wastewater was investigated using a laboratory scale aerobic sequencing batch flexible fibre biofilm reactor (SBFFBR). The SBFFBR system was modified from a typical sequencing batch reactor system by using eight flexible fibre bundles with a very high specific surface area, which served as support for microorganisms. The reactor was operated under different influent chemical oxygen demand (COD) concentrations (610, 2041 and 4382 mg l,1) and constant hydraulic retention times of 1.6 days. The results have shown successful applicability of the SBFFBR system to treat this dairy wastewater. High COD removal efficiencies between 89.7 and 97% were achieved at average organic loading rates of 0.4 and 2.74 kg COD m,3 d,1, respectively. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Nanobiomaterials and Nanoanalysis: Opportunities for Improving the Science to Benefit Biomedical Technologies,ADVANCED MATERIALS, Issue 5 2008W. Grainger Abstract Nanomaterials advocated for biomedical applications must exhibit well-controlled surface properties to achieve optimum performance in complex biological or physiological fluids. Dispersed materials with extremely high specific surface areas require as extensive characterization as their macroscale biomaterials analogues. However, current literature is replete with many examples of nanophase materials, most notably nanoparticles, with little emphasis placed on reporting rigorous surface analysis or characterization, or in formal implementation of surface property standards needed to validate structure-property relationships for biomedical applications. Correlations of nanophase surface properties with their stability, toxicity and biodistributions are essential for in vivo applications. Surface contamination is likely, given their processing conditions and interfacial energies. Leaching adventitious adsorbates from high surface area nanomaterials is a possible toxicity mechanism. Polydimethylsiloxane (PDMS), long known as a ubiquitous contaminant in clean room conditions, chemical synthesis and microfabrication, remains a likely culprit in nanosystems fabrication, especially in synthesis, soft lithography and contact molding methods. New standards and expectations for analyzing the interfacial properties of nanoparticles and nano-fabricated technologies are required. Surface science analytical rigor similar to that applied to biomedical devices, nanophases in microelectronics and heterogeneous catalysts should serve as a model for nanomaterials characterization in biomedical technologies. [source] Structure of nanoporous zirconia-based powders synthesized by different gel-combustion routesJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2007Jorge R. Casanova Zirconia-based ceramics that retain their metastable tetragonal phase at room temperature are widely studied due to their excellent mechanical and electrical properties. When these materials are prepared from precursor nanopowders with high specific surface areas, this phase is retained in dense ceramic bodies. In this work, we present a morphological study of nanocrystalline ZrO2,2.8 mol% Y2O3 powders synthesized by the gel-combustion method, using different organic fuels , alanine, glycine, lysine and citric acid , and calcined at temperatures ranging from 873 to 1173,K. The nanopore structures were investigated by small-angle X-ray scattering. The experimental results indicate that nanopores in samples prepared with alanine, glycine and lysine have an essentially single-mode volume distribution for calcination temperatures up to 1073,K, while those calcined at 1173,K exhibit a more complex and wider volume distribution. The volume-weighted average of the nanopore radii monotonically increases with increasing calcination temperature. The samples prepared with citric acid exhibit a size distribution much wider than the others. The Brunauer,Emmett,Teller technique was used to determine specific surface area and X-ray diffraction, environmental scanning electron microscopy and transmission electron microscopy were also employed for a complete characterization of the samples. [source] | |||||||||||||||||||||||||