Academic literature on the topic 'Silica-stabilized alumina'
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Journal articles on the topic "Silica-stabilized alumina"
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Dechézelles, Jean-François, Carmen Ciotonea, Cezar Catrinescu, Adrian Ungureanu, Sébastien Royer, and Véronique Nardello-Rataj. "Emulsions Stabilized with Alumina-Functionalized Mesoporous Silica Particles." Langmuir 36, no. 12 (March 12, 2020): 3212–20. http://dx.doi.org/10.1021/acs.langmuir.9b03900.
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Дмитриевский, А. А., Д. Г. Жигачева, А. О. Жигачев, and П. Н. Овчинников. "Прочностные свойства циркониевой керамики, упрочненной оксидом алюминия, с добавлением диоксида кремния." Физика твердого тела 63, no. 2 (2021): 259. http://dx.doi.org/10.21883/ftt.2021.02.50475.138.
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The effect of alumina and silica on strength of zirconia ceramics, stabilized with calcia, was studied. We have established the optimal concentrations of the components in the CaO-ZrO2+Al2O3+SiO2 system; these concentrations correspond to the highest flexural strength of 980±70 MPa. The optimal concentration of alumina is 5 wt.% in absence of silica. In terms of compressive strength the highest values of 2.44±0.15 MPa were obtained when concentration of alumina was 5 wt. % and content of silica was 5 mol. %. Stress-strain diagrams indicate presence of plasticity in the materials containing 4-5 mol. % SiO2 by having a yield plateau
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Lin, Yung-Jen, and Lee-Jen Chen. "Reaction synthesis of mullite–silicon carbide–yttria-stabilized zirconia composites." Journal of Materials Research 14, no. 10 (October 1999): 3949–56. http://dx.doi.org/10.1557/jmr.1999.0534.
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SiC/mullite/zirconia composites were fabricated by controlling the oxidation of powder compacts of SiC, alumina, and 3 mol% yttria-stabilized zirconia. The powder compacts were first oxidized in air at 1100 °C for various times to obtain proper amounts of amorphous silica. Subsequent reaction sintering at 1500 °C for 2 h combined the amorphous silica with alumina to form mullite with planned amounts. The incorporation of 3 mol% yttria-stabilized zirconia promoted mullite formation and enhanced the densification of the samples. With ≥10 vol% of 3 mol% yttria-stabilized zirconia in the samples, the temperature of mullite formation was lowered from 1400 to 1300 °C, and mullitization was near completion after sintering at 1500 °C for 2 h. The densification of the samples depended on the contents of SiC and 3 mol% yttria-stabilized zirconia. Samples with 20 vol% SiC and 10–20 vol% 3 mol% yttria-stabilized zirconia could be sintered to reach approximately 97% of theoretical density after sintering at 1500 °C for 2 h.
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Farooq, Ahmad, and Ali Abd El-Aty. "Novel Method of Developing Nanosilica Coated Alumina Micro Abrasives Using Silicon Nanoparticles Generated from Spark Erosion as the Source." Applied Mechanics and Materials 799-800 (October 2015): 479–82. http://dx.doi.org/10.4028/www.scientific.net/amm.799-800.479.
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Silica coated alumina abrasives, used for abrading the surface of Yttria stabilized tetragonal zirconia polycrystal ceramics, were produced in order to achieve successful bonding with resin luting cement. The source of the silica coating was from Silicon Nanoparticles (SiNPs) that were produced from spark erosion in high pressure flushing of deionized water. SEM images verified average size distribution of the SiNPs to be between 30-50nm. In contrast to the tribochemical methods that are used widely to produce such abrasives, a completely novel dry physical process was opted for this experiment. By optimization of the conditions, 2g of purified SiNPs was mixed with 20g of alumina μ-particles (approximated diameter of 100μm), in presence of 25ml ethanol, mixed thoroughly to form slurry. Heated up to 120°C for 20 minutes to evaporate the ethanol, the resultant powder mix was compacted and uploaded in furnace at temperature of 1100°C for 2hrs. This formed an oxide layer on the SiNPs which consequently formed bonding with the alumina particles. SEM/EDS results validate substantial amount of coating of silica on alumina. The paper hereby demonstrates a novel method of producing silica coated alumina abrasives, which is a dry and cleaner substitution method compared to tribochemical approach.
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Zhao, Xiangyun, Yu Cong, Yanqiang Huang, Shuang Liu, Xiaodong Wang, and Tao Zhang. "Rhodium Supported on Silica-Stabilized Alumina for Catalytic Decomposition of N2O." Catalysis Letters 141, no. 1 (November 2, 2010): 128–35. http://dx.doi.org/10.1007/s10562-010-0472-3.
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Carvalho, Cristiane Fonseca, Cláudio Luis Melo-Silva, Claudinei Santos, and Jefferson Fabricio Cardoso Lins. "Effect of Surface Treatment of Yttria Stabilized Zirconia for Dental Prostheses." Materials Science Forum 727-728 (August 2012): 831–36. http://dx.doi.org/10.4028/www.scientific.net/msf.727-728.831.
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When it comes to providing reliable adhesion of low silica content alumina ceramic, hydrofluoric acid etching along with silanization has not shown sufficient efficacy because the microstructure of high-alumina content ceramics is unable to degrade them. The objective of this study was to analyze the effect of surface sandblasting of zirconia-based ceramic stabilized by yttria as used in dental prostheses, using a SEM and roughness average. The samples were divided in control, no surface treatment; Al2O3sandblasting; Al2O3sandblasting and Al2O3+ SIC particles 110 µm average sized; Al2O3sandblasting and Al2O3+ SIC particles 110 µm average sized milled for 2 hours; Al2O3sandblasting and Al2O3+ SIC particles 110 µm average sized milled for 6 hours. The Al2O3sandblasting and the 2-hour milled Al2O3+ SIC particles showed better results and better characterization of roughness in SEM with the silica deposition on the samples surface.
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Melo-Silva, C. L., C. F. Carvalho, T. C. F. Melo-Silva, R. X. Freitas, F. R. F. Silva, and J. F. C. Lins. "Analysis of the Y-TZP Ceramic Substucture in Blasting with Aluminum Oxide before and after Sintering." Materials Science Forum 805 (September 2014): 576–80. http://dx.doi.org/10.4028/www.scientific.net/msf.805.576.
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The objective of this study was to evaluate the microstructure of a ceramic based on yttria stabilized zirconia (Y-TZP) in blasting with aluminum oxide and its effect on the sintering. 25 pre-sintered Y-TZP blocks were obtained. Ten samples were blasted with alumina, and then all samples were sintered and divided into the groups: Control-no treatment; alumina G1-blasted with alumina and sintered; alumina and Rocatec G1-blasted, sintered, and Rocatec; alumina G2-sintered, alumina blasting; alumina and Rocatec G2-sintering, alumina blasting, and Rocatec. The samples were evaluated by a scanning electron microscopy. The qualitative analysis showed that the treated samples had an increase in the surface texture and that group 1– alumina and Rocatec– presented the silica incorporation to be regular and homogeneous. It was concluded that the treatment of pre-sintered surfaces is a good alternative in the bonding strength between the Y-TZP and the resin cements.
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Ma, Xianzheng, Katarzyna Janowska, Vittorio Boffa, Debora Fabbri, Giuliana Magnacca, Paola Calza, and Yuanzheng Yue. "Surfactant-Assisted Fabrication of Alumina-Doped Amorphous Silica Nanofiltration Membranes with Enhanced Water Purification Performances." Nanomaterials 9, no. 10 (September 24, 2019): 1368. http://dx.doi.org/10.3390/nano9101368.
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Surfactant-templated 5 mol% Al2O3-doped silica membranes nanofiltration membranes were synthesized via the sol-gel method, and afterward, were optimized, and tested with respect to the permeability and rejection rate. The disordered silica network was stabilized by doping 5 mol% alumina. Tetraethyl orthosilicate and aluminum isopropoxide were used as the silica and alumina precursors, respectively. Cetyltrimethylammonium bromide (CTAB) was used not only as a pore-forming agent, but also to control the reaction rate of the aluminum isopropoxide, thus obtaining highly homogeneous materials. The results about filtration of model solutions showed that the optimized membranes are featured by both a relatively high water permeability (1.1–2.3 L·m−2·h−1 ·bar−1) and a high rejection for salts (74% for NaCl, and >95% for MgSO4 and Na2SO4) and organic pollutants (e.g., about 98% for caffeine). High rejection of divalent ions and organic molecules was also observed when a real wastewater effluent was filtered. The influence of the synthesis conditions on the membrane performance is discussed.
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Shyu, Jiin-Jyh, and Yuan-Chieh Chen. "Zirconia-mullite ceramics made from composite particles coated with amorphous phase: I. Effect of zirconia addition." Journal of Materials Research 10, no. 1 (January 1995): 63–70. http://dx.doi.org/10.1557/jmr.1995.0063.
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Mullite-based ceramics added with 0–20 vol % stabilized zirconia have been prepared by alumina/zirconia particles coated with an amorphous silica layer. All samples can be densified through the viscous flow of the amorphous silica layer in the typical temperature range of 1100–1310 °C. For the ZrO2-free mullite ceramics, the viscous densification kinetics is inhibited by increasing the content of the alumina inclusion particles and by crystallization of the amorphous silica layer. However, for the zirconia-mullite ceramics, the addition of the zirconia inclusion particles accelerates the viscous densifcation kinetics. Mullitization kinetics is also enhanced by the addition of zirconia. As the sintering temeperature is high, a porous, duplex microstructure is observed in samples with or without zirconia. Zirconia addition enhances the development of this microstructure. As the sintering temperature and/or zirconia content is increased, ZrO2 particles tend to coarsen, resulting in a decreased tetragonal to monoclinic ratio. Fracture toughness KlC increases with the zirconia content. Mullite-20 vol % ZrO2 composite sintered at 1600 °C has a KlC of 3.8 MPa · m1/2.
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Hatmoko, John Tri, and Hendra Suryadharma. "Fundamental factors on the behaviour of bagasse ash stabilized organic soil." MATEC Web of Conferences 258 (2019): 01019. http://dx.doi.org/10.1051/matecconf/201925801019.
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A series of experimental programs was undertaken to investigate mechanical behaviour of bagasse ash stabilized organic soil. Preliminary experiment was done to verify the chemical and physical characteristics of bagasse ash and organic soil. The following experiment was then performed to study the improvement of unconfined compression strength of bagasse ash stabilized organic soil. In this research, three different organic soils and four different bagasse ashes were used. The soil was mixed with 10, 20 and 30% bagasse ash, then a set of unconfined compression tests were performed. In general, the results indicate that the unconfined compression strength of stabilized soil improve proportional to the percentage of bagasse ash. And, the quick lime content (CaO), ratio between quick lime and silica (CaO/SiO2), and ratio between quick lime and the sum of silica and alumina {CaO/(SiO2+Al2O3)} were the fundamental factors affecting the improvement of bagasse ash stabilized soil unconfined compression strength. The significant improvement occurs on 0.25 < (CaO/SiO2) < 1.00, and 0.20< (CaO/(SiO2+Al3O3) < 0.67. In contrast, organic content decreased unconfined compression, and maximum dry density (MDD) of stabilized soil. The addition of bagasse to the organic soil, however, does not significantly improve the unconfined compression strength, then addition of 6, 8, and 10% calcium carbide residue (CCR) was performed to the bagasse ash stbilized organic soil to get better engineering performance of stabilized soil. For 9% CCR, qu improve from 93 to 208 kPa.
Dissertations / Theses on the topic "Silica-stabilized alumina"
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Keyvanloo, Kamyar. "Preparation of Active, Stable Supported Iron Catalysts and Deactivation by Carbon of Cobalt Catalysts for Fischer-Tropsch Synthesis." BYU ScholarsArchive, 2014. https://scholarsarchive.byu.edu/etd/5705.
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The first half of this dissertation reports the development of supported Fe FT catalysts including the effects of various, carefully chosen preparation methods on the performance of alumina-supported iron/copper/potassium (FeCuK/Al2O3); it was determined that non-aqueous slurry impregnation and co-impregnation yielded catalysts with activities as high as any reported in the literature. Furthermore, the effects of support properties including pore size, hydroxyl group concentration, and support stabilizer were investigated for FeCuK/Al2O3 catalysts containing 20 or 40% Fe. For the first time, we report the performance of a supported Fe FT catalyst that is not only more active and stable than any supported Fe catalyst previously reported, but also has activity equivalent to that of the most active, unsupported catalysts. More importantly, the catalyst is extremely stable as evidenced by the fact that after 700 h on stream, its activity and productivity are still increasing. These catalyst properties result from the use of a novel γ-alumina support material doped with silica and pretreated at 1100°C. This unique support has a high pore volume, large pore diameter, and unusually high thermal stability. The ability to pretreat this support at 1100°C enables preparation of a material having a low number of acid sites and weak metal oxide-support interactions, all desirable properties for an FT catalyst. The second half of this dissertation investigates the effects of operating conditions including the partial pressures of CO and H2 and temperature on the deactivation by carbon of 25 wt% Co/ 0.25 wt% Pt/Al2O3 catalyst. It also reports the kinetics of the main FT reaction on this catalyst. As temperature increases, the H2 and CO orders for the main reaction (in the absence of deactivation) become more positive and more negative, respectively. A new mechanism was proposed to account for the inhibition effect of CO at high reaction temperatures, which includes H-assisted dissociation of CO to C* and OH*. Further, twelve samples of the CoPt/Al2O3 catalyst were tested over a period of 800 hours and XCO < 24%, each at a different set of CO and H2 partial pressures and temperature (220-250°C). At reaction temperature of 230°C, increasing PCO or PH2 increases the deactivation rate; possibly due to formation of polymeric carbons. The H2 and CO partial pressure orders for the deactivation rate at 230°C were found to be 1.12 and 1.43, respectively using a generalized-power-law-expression (GPLE) with limiting activity of 0.7 and 1st order deactivation. For a H2/CO of 2 (PH2 = 10 bar and PCO = 5 bar) the deactivation rate increases as process temperature increases from 220 to 250°C with an activation energy of 81 kJ/mol. However, at higher CO partial pressure (PCO = 10 bar) the deactivation rate for the Co catalyst of this study decreases with increasing temperature; this can possibly be attributed to the formation of more active cobalt sites at higher temperatures due to surface reconstruction.
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"Synthesis of Mesoporous Metal Oxide Materials." Doctoral diss., 2012. http://hdl.handle.net/2286/R.I.15165.
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abstract: Nanoporous crystalline oxides with high porosity and large surface areas are promising in catalysis, clean energy technologies and environmental applications all which require efficient chemical reactions at solid-solid, solid-liquid, and/or solid-gas interfaces. Achieving the balance between open porosity and structural stability is an ongoing challenge when synthesizing such porous materials. Increasing porosity while maintaining an open porous network usually comes at the cost of fragility, as seen for example in ultra low density, highly random porous aerogels. It has become increasingly important to develop synthetic techniques that produce materials with these desired properties while utilizing low cost precursors and increasing their structural strength. Based on non-alkoxide sol-gel chemistry, two novel synthetic methods for nanoporous metal oxides have been developed. The first is a high temperature combustion method that utilizes biorenewable oil, affording gamma alumina (Al2O3) with a surface area over 300 cm3/g and porosity over 80% and controllable pore sizes (average pore width 8 to 20 nm). The calcined crystalline products exhibit an aerogel-like textural mesoporosity. To demonstrate the versatility of the new method, it was used to synthesize highly porous amorphous silica (SiO2) which exhibited increased mechanical robustness while achieving a surface area of 960 m2/g and porosity of 85%. The second method utilizes sequential gelation of inorganic and organic precursors forming an interpenetrating inorganic/organic gel network. The method affords yttria-stabilized zirconia with surface area over 90 cm3/g and porosity over 60% and controllable pore sizes (average pore width 6 to 12 nm). X-ray diffraction, gas sorption analysis, Raman spectroscopy, nuclear magnetic resonance spectroscopy and electron microscopy were all used to characterize the structure, morphology, and the chemical structure of the newly afforded materials. Both novel methods produce products that show superior pore properties and robustness compared to equivalent commercially available and currently reported materials.Dissertation/Thesis
Ph.D. Chemistry 2012
Book chapters on the topic "Silica-stabilized alumina"
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Jolivet, Jean-Pierre. "Nanomaterials: Specificities of Properties and Synthesis." In Metal Oxide Nanostructures Chemistry. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780190928117.003.0004.
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The concept of material concerns matter in solid state that is endowed with usable properties for practical applications. It is indeed in the solid state that matter exhibits the highest mechanical strength and chemical inertness, providing solidity and sustainability because the solid is based on an extended stiff crystalline framework. It is also in the solid state that many properties exist, including optical, electrical, and magnetic properties, providing great technological progress. A typical example is electronics which owes its enormous development to doped silicon. A material may therefore be defined as a useful solid. The properties of a solid depend directly on its chemical composition, crystalline and electronic structures, texture, as well as morphology and casting. This last point, which is often neglected, is illustrated by amorphous silica glass, which is used largely for its properties such as chemical inertness, mechanical strength, optical transparency, and low thermal and electrical conductivities. These various properties are highlighted through the many possibilities of casting and shaping: flat glass (optical transparency for glazing); hollow glass (chemical inertness and mechanical strength for bottling); short fibers (glass wool for heat insulation) and long fibers (optical fibers); massive pieces (insulators for electric power lines); and thin films (insulating layers for miniaturized electronics). Metal oxides exhibit a wide range of exploitable properties useful for innumerable applications. Silica, SiO2, as flat glass, has excellent optical properties, but other oxides such as LiNbO3 and KTiOPO4 exhibit interesting nonlinear optical properties, allowing changes in the wavelength of the transmitted light. Certain oxides are good electrical insulators (SiO2), but others are true electronic conductors (VO2, NaxWO3), ionic conductors (β-alumina NaAl11O17, NaSiCON Na3Zr2PSi2O12, yttria-stabilized cubic zirconia Zr1–xYxO2–x/ 2), and also superconductors (cuprates such as YBa2Cu3O7–x and Bi4Sr3Ca3Cu4O16+x). Compounds such as BaTiO3, PbZr1–xTixO3, and PbMg1/3Nb2/3O3 are ferroelectric solids used largely as miniaturized electronic components, whereas spinel ferrite γ-Fe2O3, barium hexaferrite BaFe12O19, and garnet Y3Fe5O12 are more or less coercive ferrimagnetic solids used in magnetic recording or as permanent magnets.
Conference papers on the topic "Silica-stabilized alumina"
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Dubsky, J., K. Neufuss, and B. Kolman. "Phase Composition Changes in Annealed Plasma-Sprayed Zircon-Alumina Coatings." In ITSC 1997, edited by C. C. Berndt. ASM International, 1997. http://dx.doi.org/10.31399/asm.cp.itsc1997p0473.
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Abstract Phase transformations and/or decomposition of deposited compounds have an indisputable influence on materials properties of plasma sprayed deposits. Using water stabilized plasma, free-standing parts were manufactured from a mechanical mixture of zircon and alumina powders and annealed. The phase composition was determined by X-ray diffraction and the chemical composition was checked by x-ray microanalysis. ZrSiO4 during plasma spraying decomposes into ZrO2 and SiO2. In the as-sprayed condition, after a relatively fast quenching, the following phases can be found: a very fine eutectic mixture of tetragonal and monoclinic ZrO2, amorphous SiO2 and a spinel phase of Al2O3. On annealing for 2 hours at 1300 and 1500 °C the spinel Al2O3 transformed to corundum. At the same time, amorphous silica crystallized. Tetragonal ZrO2 transformed to the monoclinic modification and together with SiO2 formed again ZrSiO4. At the highest annealing temperature Al2O3 and SiO2 partialy reacted to form a small amount of mullite (3Al2O3.2SiO2).
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John, G., and T. Troczynski. "Surface Modification of Thermal Sprayed Coatings." In ITSC 1996, edited by C. C. Berndt. ASM International, 1996. http://dx.doi.org/10.31399/asm.cp.itsc1996p0483.
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Abstract Thermal sprayed coatings are frequently used in corrosive environments, even when their major purpose is to provide wear or thermal resistance, rather than corrosion resistance. This includes Thermal Barrier Coatings (TBC), where high porosity is a desired feature to give good thermal protection. However, as this proves to be a limiting factor in the corrosion protection, a trade off is involved. This is because the interconnected porosity in TBCs allows the corrosive media to reach the coating-substrate interface, which eventually leads to delamination of the coatings. This work addresses the problem of permeability of TBCs which can lead to premature delamination due to interfacial corrosion. The coatings studied were yttria-stabilized zirconia TBCs. A simple infiltration technique has been proposed using sol-gel ceramic precursors. The precursors studied include aluminum isopropoxide or pre-hydrolyzed ethyl silicate, which decomposed to alumina and silica respectively, at surface heat treatment temperatures as low as 550°C. In addition to sealing the surface, it is believed that some level of compressive stress is generated on the surface of TBCs on cooling from the processing temperature. Electrochemical tests in 3.0% NaCl have been carried out to study the effectiveness of the sealant. These potentiodynamic tests as well as permeability tests show a considerable decrease in interconnected porosity with sol-gel modifications of the coatings.