Articoli di riviste: "Aluminia"

1

Feng, Chun Xia, Jing Hua Chen, Wei Guo, Bao Xiang Jiao e Hong Bin Lu. "Aluminium Titanate-Aluminia Composites Synthesized by Heterogeneous Precipitation Method". Applied Mechanics and Materials 217-219 (novembre 2012): 3–7. http://dx.doi.org/10.4028/www.scientific.net/amm.217-219.3.

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Aluminium titanate-alumina (AT-A) composites were sintered from the precursor powders prepared by two different methods: a simple sol-gel based heterogeneous precipitation method and a traditional blending method. The crystalline phase, microstructure, mechanical strength, sintering properties, and thermal expansion coefficient (TEC) of the sintered AT-A composites were investigated and compared. The heterogeneous precipitation method increases the homogeneity of the precursor powders and improves the mechanical and sintering properties of the AT-A composites. The AT-A composites with a Al:Ti ratio of 2.2 achieve the optimal performance where the bending strength is high and the TEC remains low.

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Wang, Miao, Yan Xia Guo, Fang Qin Cheng e Yao Yao Li. "A Study on the Mechanism of Aluminia Extraction from Coal Fly Ash". Advanced Materials Research 518-523 (maggio 2012): 3109–14. http://dx.doi.org/10.4028/www.scientific.net/amr.518-523.3109.

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Coal fly ash contains large amounts of aluminum, iron, silicon and other useful elements. Its utilization effectively is of significance to harmonious development of economy, society and environment. However, coal fly ash is mainly composed of mullite and other inert glassy matters with high degree of polymerization and its reactivity is poor. So the fly ash needs to be activated before utilization. This article studied the effect of activation by calcination added with NaOH additives on aluminium extraction. The results showed that the addition of NaOH could improve the aluminium extraction rate evidently. Detailed analysis and characterization was carried out by using X-ray diffraction (XRD). The results indicated that NaOH could improve the depolymerization of vitreous.

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Krampera, František, e Ludvík Beránek. "Kinetics of 1-butanol, di-(1-butyl) ether and 1-butene reactions on aluminas partially deactivated by sodium". Collection of Czechoslovak Chemical Communications 54, n. 11 (1989): 2985–97. http://dx.doi.org/10.1135/cccc19892985.

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The initial rates of six reactions taking place in 1-butanol dehydration at 260 °C in vapour phase were measured on aluminia samples differing in sodium content. The reactants were 1-butanol, di-(1-butyl) ether and 1-butene, resp. The parameters of the best fitting rate equation for each reaction were evaluated. The reaction rates as well as the rate constants and adsorption coefficients of the individual reactions show different sensitivity to datalyst acidity. Therefore, the selectivity of product formation can be influenced by sodium content of the catalyst. The selectivities (with the exception of 1-butene izomerization) strongly depend also on the partial pressure of the starting reactants. Thus, these two factors can be used to control the selectivity for preparative purposes. The results of this paper clearly demonstrate the nonseparability of the deactivation kinetics in 1-butanol dehydration on sodium poisoned aluminas.

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4

Zun, Ro Yong, Helena Davidová, Jaroslava Polednová, Květa Jirátová e Petr Schneider. "Properties of supported rhodium catalysts for steam dealkylation of toluene". Collection of Czechoslovak Chemical Communications 53, n. 3 (1988): 466–78. http://dx.doi.org/10.1135/cccc19880466.

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The effect of modification of γ-aluminia support by Cr2O3 on physical and catalytical properties of supported rhodium catalysts was investigated. Various techniques were used for characterization of catalysts: porosimetry, diffusion and permeation measurements, determination of surface OH groups, temperature-programmed reduction and catalytic behaviour in steam dealkylation of toluene. Using the transport parameters determined for pelleted catalysts the effect of internal diffusion on the reaction was predicted and compared with experiments.

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Davidová, Helena, e Petr Schneider. "Elimination of dead-volume contributions to moments of chromatographic peaks". Collection of Czechoslovak Chemical Communications 54, n. 11 (1989): 2974–84. http://dx.doi.org/10.1135/cccc19892974.

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two methods for correction of moments of peaks from packed columns were applied to experimental responses of columns packed with porous γ-aluminia in the shape of Rasching rings: 1. substraction of moments for columns of two lengths and 2. application of dead volume corrections obtained by independent measurements. It appears that both methods give identical results. An advantage of the second methods lies in increased accuracy and decreased amount of necessary measurements.

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Kočan, Anton, Alexandr Zemek e Milan Popl. "Determination of 2,3,7,8-tetrachlorodibenzo-p-dioxin in soil in the presence of large excess of chlorinated hydrocarbons". Collection of Czechoslovak Chemical Communications 56, n. 6 (1991): 1221–27. http://dx.doi.org/10.1135/cccc19911221.

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The paper describes a method of 2,3,7,8-TCDD determination in soils heavily contaminated with organic compounds ( the soil from areas of plants producing pesticides, chlorophenols, etc.). The procedure is based on a sample extraction with a hexane-acetone mixture, cleaning of the extract by washing with potassium hydroxide and sulfuric acid solution and by liquid chromatography on a multilayer modified silica column and aluminia columns, and on GC/MS determination using a labelled internal standard (13C-2,3,7,8-TCDD). The determination limit is 10 ppt and the average recovery 55%.

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Morávek, Vladimír, Miloš Kraus, L. V. Malysheva, E. A. Paukshtis e E. N. Yurchenko. "IR study of dynamic bahaviour of 2-propanol on alumina". Collection of Czechoslovak Chemical Communications 53, n. 3 (1988): 459–65. http://dx.doi.org/10.1135/cccc19880459.

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Dynamic behavior of surface complexes of 2-propanol on aluminia during adsorption and dehydration was studied using IR spectroscopy. Good agreement was found between the first-order rate constants of alkene formation in pulse-flow experiments and that of disapearance of a reactive surface complex. It was shown that the simple surface alkoxide 2-Pr-O-Al remains on the surface constant temperature, but it can be completely removed by hydrolysis, or by heating up to 200 °C. The surface carboxylates are formed very slowly and are stable even in the presence of water vapour at 300 °C.

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8

Hanika, Jiří, e Vladimíra Ehlová. "Effect of internal diffusion on kinetics of liquid phase hydrogenation and disproportionation of the cyclohexene on palladium catalysts". Collection of Czechoslovak Chemical Communications 54, n. 11 (1989): 3003–10. http://dx.doi.org/10.1135/cccc19893003.

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Kinetics of the side reactions represented by the system involving hydrogenation and disproportionation of cyclohexene on a commercial catalyst CHEROX 41-00 (3%Pd/C) and on a supported palladium catalyst prepared by impregnation of aluminia with aqueous palladium dichloride (2.15% Pd/γ-Al2O3) have been investigated. As follows from the effectiveness factors of internal diffusion for individual reactions, in the region of internal diffusion, cyclohexene hydrogenation is preferred compared to disproportionation. This finding can be related to the fact that while the rate of disproportionation is controlled by cyclohexene diffusion, the rate of hydrogenation is controlled by diffusion of hydrogen.

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9

Chen, Ting Yi, Wen Lu, Wei Liu, Ya Dian Xie e Ye Qi Fu. "Preparation of Purity Al₂O₃for LED Sapphire Materials by Ammonium Aluminum Sulfate and its Performance". Advanced Materials Research 1053 (ottobre 2014): 50–55. http://dx.doi.org/10.4028/www.scientific.net/amr.1053.50.

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The preparation of aluminium sulfate adopting the sulfuric acid heating method with Al (OH)3 as raw material, and join the β complexing agent in aluminium sulfate solution to remove impurities; ammonium aluminum sulfat is prepared by the reaction of the ammonium solution and aluminum sulfate, and purify ammonium aluminum sulfate to get high purity ammonium aluminum sulfate crystals containing crystal water. Purify the crystallization of ammonium aluminum sulfate with containing water treated at 1250 °C for 3 h. Then the high purity alumina was prepared. Break the high purity alumina to press, and then again process in 3 h under 1650 °C, get Al203 which is craw materials of sapphire crystal LED. The samples were characterized by atomic absorption spectrum (AAS), differential thermal analysis (TG/DTA), scanning electron microscopy, XRD and chemical analysis. The purity of high purity alumina is 99.991%, which will be applied to the LED manufacturers on sapphire artificial sapphire growth test.

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10

El, Ezzat A., Samih A. Halawy, Mohamed A. Mohamed e Mohamed I. Zaki. "Surface and Bulk Properties of Alumina Recovered Under Various Conditions from Aluminum Dross Tailings Chemical Waste Versus Bauxite Ore". Journal of Materials Research 17, n. 7 (luglio 2002): 1721–28. http://dx.doi.org/10.1557/jmr.2002.0255.

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Bauxite ore (industrial raw material) and aluminum dross tailings (a local industrial waste material of the Aluminium Company of Egypt, Egyptalum) were used as two different parent materials to produce alumina. A set of six different preparation methods was applied to aluminum extracts from both materials. X-ray powder diffractometry, thermal and chemical analyses, and surface area and charge measurements were used to characterize the alumina products. The results indicate that catalytic grade, high-purity alumina products of uniform particle sizes could be obtained in large yields, depending solely on the preparation method applied, i.e., irrespective of the raw material used. Thus, aluminum dross tailings chemical waste is proved to be a feasible parent material for specialty alumina, which is an important finding both economically and environmentally.

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Hamritha, S., M. Shilpa, M. R. Shivakumar, G. Madhoo, Y. P. Harshini e Harshith. "Study of Mechanical and Tribological Behavior of Aluminium Metal Matrix Composite Reinforced with Alumina". Materials Science Forum 1019 (gennaio 2021): 44–50. http://dx.doi.org/10.4028/www.scientific.net/msf.1019.44.

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Aluminium alloy has gained importance in the automotive and aerospace industry as it is easily available and easy in manufacturing. In the recent years, materials science has gained huge importance in the field of composites. In the field of composites metal matrix composite is playing a lead role in industrial applications. The unique combinations of properties provided by aluminum and its alloys make aluminum one of the most versatile, economical and attractive metallic materials. To enhance the properties of aluminum, it has been reinforced with alumina, silicon carbide, graphene and others. In this study, A357 aluminum has been strengthened by using different weight percent of alumina as reinforcement. Percentage of alumina used are 4%, 8% and 12% to enhance the mechanical and tribological property of A357.The fabricated samples were studied to understand the performance of the composite for mechanical and tribological characters. It was observed that the composites showed superior properties compared to the base material. Statistical analysis i.e. regression analysis has been carried out for hardness and tensile strength of alumina reinforced aluminum composite.

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Qiu, Baofu, Xiaoming Duan, Zhuo Zhang, Chen Zhao, Bo Niu, Peigang He, Delong Cai et al. "Microstructural evolution of h-BN matrix composite ceramics with La-Al-Si-O glass phase during hot-pressed sintering". Journal of Advanced Ceramics 10, n. 3 (24 marzo 2021): 493–501. http://dx.doi.org/10.1007/s40145-020-0451-0.

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AbstractBN/La-Al-Si-O composite ceramics were fabricated by hot-pressed sintering using hexagonal boron nitride (h-BN), lanthanum oxide (La2O3), aluminia (Al2O3), and amorphous silica (SiO2) as the raw materials. The effects of sintering temperature on microstructural evolution, bulk density, apparent porosity, and mechanical properties of the h-BN composite ceramics were investigated. The results indicated that La-Al-Si-O liquid phase was formed during sintering process, which provided an environment for the growth of h-BN grains. With increasing sintering temperature, the cristobalite phase precipitation and h-BN grain growth occurred at the same time, which had a significant influence on the densification and mechanical properties of h-BN composite ceramics. The best mechanical properties of BN/La-Al-Si-O composite ceramics were obtained under the sintering temperature of 1700 °C. The elastic modulus, flexural strength, and fracture toughness were 80.5 GPa, 266.4 MPa, and 3.25 MPa·m1/2, respectively.

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13

Voon, Chun Hong, M. N. Derman, U. Hashim e K. L. Foo. "Effect of Anodizing Voltage on the Formation of Porous Anodic Alumina on Al-0.5wt% Mn Alloys". Advanced Materials Research 925 (aprile 2014): 455–59. http://dx.doi.org/10.4028/www.scientific.net/amr.925.455.

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In this study, the effect of anodizing voltage on the morphologies, pore diameter and interpore distance on the porous anodic alumina formed on aluminium manganese alloy was reported. It was found that the anodizing influenced the morphologies and regularities of porous anodic alumina formed on aluminum-manganese substrate. Well ordered porous anodic alumina was obtained when anodizing voltage were 40 V and 50 V respectively. Disordered porous anodic alumina was formed when anodizing of 30 V and 70 V were applied during the anodizing process. Both pore diameter and interpore distance of porous anodic alumina increased linearly with the anodizing voltage.

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Ruiz, Andrés Felipe, Carlos Javier Peñaranda, Graciela Fuentes e María Daniela Semprun. "Análisis comparativo de resultados en el uso de la ceniza de bagazo de caña de azúcar como material sustituyente del cemento portland en el concreto". Sostenibilidad, Tecnología y Humanismo 11, n. 2 (1 luglio 2020): 8–17. http://dx.doi.org/10.25213/2216-1872.51.

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El presente artículo describe la comparación de resultados de diferentes investigaciones que se han realizado con el uso de la ceniza de bagazo de caña de azúcar como sustituyente del cemento portland en la elaboración del concreto estructural, teniendo como objetivos analizar la actividad puzolánica de las distintas muestras que se tomaron para realizar este articulo y comparar estos resultados con otras investigaciones elaboradas con otros materiales. Teniendo en cuenta aspectos importantes como la contaminación ambiental que genera este residuo, sus cantidades de sílice (SiO2) y aluminia (Al2O3) y su proceso de obtención de la caña de azúcar. Como conclusiones se puede observar el compromiso que las empresas que generan este residuo tienen con el medio ambiente desarrollando planes que permitan mitigar el impacto que este produce y también como algunos estudios analizados no recomiendan el uso de este sedimento en la elaboración de concreto estructural debido a su disminuida resistencia a la compresión y a su vez, por el contrario, como otros estudios si lo recomiendan como sustituto parcial de agregado fino, en la producción de mortero.

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Suriyana, Dadang, Liliana Sahay e Okta Meilawaty. "Kelayakan Abu Terbang PLTU Buntoi Sebagai Campuran Beton Geopolimer". Media Ilmiah Teknik Sipil 9, n. 2 (1 giugno 2021): 102–8. http://dx.doi.org/10.33084/mits.v9i2.2063.

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The main basic ingredients needed for the manufacture of this geopolymer material are materials that contain a lot of silica and aluminia elements. The 1st stage test was carried out to determine the geopolymer paste with the maximum compressive strength at the ratio of NaOH to Na2SiO3 of 1; 1.5; 2; 2.5. The second stage of testing was carried out using a geopolymer paste with the highest compressive strength, namely the ratio of NaOH to Na2SiO3 of 2.5 with a compressive strength of 22.56 MPa. Based on the results of the compressive strength test, the maximum compressive strength at the age of 28 days is 7.64 MPa. The results of the compressive strength of concrete are much lower than the compressive strength of the paste, it shows that the paste does not bind too much with the aggregate. This is evidenced by the results of the compressive strength of conventional concrete which is much higher than that of geopolymer concrete using the same aggregate. With the results of the maximum compressive strength at the age of 28 days is 29.51 MPa.

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Singh, Shivdev. "Investigating Properties of Hybrid Alumina/ Graphite Aluminium Matrix nano Composites". Journal of Advanced Research in Manufacturing, Material Science & Metallurgical Engineering 06, n. 3&4 (9 settembre 2019): 8–20. http://dx.doi.org/10.24321/2393.8315.201902.

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Ribeiro, Catarina, Lucinda Gonçalves e Francisco Delmas. "Highly Reactive Alumina Production from Spent Baths". Materials Science Forum 514-516 (maggio 2006): 1716–21. http://dx.doi.org/10.4028/www.scientific.net/msf.514-516.1716.

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Hydrated alumina Al2O3.3H2O was produced from spent alkaline baths resulting from aluminium transformation industry. Batch and continue laboratory and pilot tests were performed in order to assess technical viability of producing reactive alumina directly from the baths by a precipitation/crystallization process and at the same time of recovering and recycling the associated sodium hydroxide to the extrusion process. The influence of three parameters: time, seed quantity and dilution were evaluated using a statistical method. It was found that time and dilution are the factors which have more influence on aluminium precipitation yield, allowing to reach values greater than 45%. The hydrated aluminas obtained were characterized by granulometric analysis, scanning electron microscopy and x-ray diffraction. Therefore, apart from minimizing the environmental impact of the aluminium transformation industry by reducing a waste quantity, it is obtained a marketable sub-product and recovered a raw material (NaOH), which can be recycled within the aluminium transformation process.

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Sergeyev, D. M., e S. K. Kutshanov. "About resonance tunneling of quasiparticles through nanocontact «aluminum – aluminium oxide – aluminum» at low temperatures". Bulletin of the Karaganda University. "Physics Series" 86, n. 2 (30 giugno 2017): 21–29. http://dx.doi.org/10.31489/2017phys2/21-29.

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Li, Guang Hui, Wei Cheng, Tao Jiang, Na Sun e Ling Feng Ai. "Preparation of Porous Silica by Acid Dissociation of Thermally Activated Kaolinite". Advanced Materials Research 284-286 (luglio 2011): 1381–84. http://dx.doi.org/10.4028/www.scientific.net/amr.284-286.1381.

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Preparation of porous silica from thermally activated kaolinite was investigated by using acid dissociation process, and the relationship between structural transformation and acid dissociation properties of aluminium were elucidated. AlVI transfers into AlV and AlIV when kaolinite changes into metakaolinite during thermal activation. AlV is dissoluble in acid, while AlVI, AlIV are difficult to be dissolved into acid, therefore, the coordinations of aluminium affect acid dissociation of alumina markedly. Mesoporous silica is made by acid dissociation alumina of metakaolinite, and the specific surface area of porous silica is determined by acid dissociation ratio of alumina. The dissociation ratio of aluminum is up to 97% when kaolinite is activated at 900°C for 15 min. Specific surface area of the porous silica material is 357 m2/g, the pore volume is 0.43 cc/g, and BJH pore diameter is 2.18 nm. The pore is found to be in the worm-like shape by high resolution TEM analysis.

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Choudhary, R. K., V. Kain e R. C. Hubli. "Formation of alumina-aluminide coatings on ferritic-martensitic T91 steel". Journal of Mining and Metallurgy, Section B: Metallurgy 50, n. 2 (2014): 165–70. http://dx.doi.org/10.2298/jmmb140724022c.

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In this work, alumina-aluminide coatings were formed on ferritic-martensitic T91 steel substrate. First, coatings of aluminum were deposited electrochemically on T91 steel in a room temperature AlCl3-1-ethyl-3-methyl imidazolium chloride ionic liquid, then the obtained coating was subjected to a two stage heat treatment procedure consisting of prolonged heat treatment of the sample in vacuum at 300 ?C followed by oxidative heat treatment in air at 650 ?C for 16 hours. X-ray diffraction measurement of the oxidatively heat treated samples indicated formation of Fe-Al and Cr-Al intermetallics and presence of amorphous alumina. Energy dispersive X-ray spectroscopy measurement confirmed 50 wt- % O in the oxidized coating. Microscratch adhesion test conducted on alumina-aluminide coating formed on T91 steel substrate showed no major adhesive detachment up to 20 N loads. However, adhesive failure was observed at a few discrete points on the coating along the scratch track.

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Bocchetta, P., M. Santamaria e F. Di Quarto. "Anodic Alumina Membranes as Template for the Synthesis of 1-D Metal Oxide and Hydroxide Nanostructures". Advanced Materials Research 38 (marzo 2008): 213–28. http://dx.doi.org/10.4028/www.scientific.net/amr.38.213.

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Anodic alumina membranes with highly ordered cylindrical pores and tuneable geometry have been prepared (pore diameters=20−200 nm; pore density 1012-1014 pores/m2; thickness: 20-100 mm) by controlling the anodizing process of aluminum in phosphoric, oxalic and sulphuric acid. The influence of different parameters (initial treatment of aluminium surface, composition of electrolyte, temperature and applied potential) on the final characteristics of the membranes have been investigated. The use anodic alumina membranes as template for the electrosynthesis of some metal hydroxides and oxides 1-D nanostructures (nanowires and nanotubes) will be also proved.

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Butman, Mikhail F., Nataliya E. Kochkina, Anastasiya E. Mikhaiylova, Nikolaiy L. Ovchinnikov e Alexander V. Knotko. "BIOTEMPLATED SYNTHESIS OF ALUMINA FIBRES BY CONTROLLED HYDROLYSIS OF SALT PRECURSOR". IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENIY KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA 59, n. 5 (12 luglio 2018): 47. http://dx.doi.org/10.6060/tcct.20165905.5349.

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Alumina fibres were obrained by impregnation of the cellulose biotemplate with precursor solutions in which the hydrolysis ratio [OH-]/[Al3+] is varied and in which different aluminium oligo- and polycations content. The biotemplates and alumina fibres were studied by X-ray, TG/DSC, electrophoretic light scattering, SEM, and N2 adsorption/desorption. It was shown that the infiltration with the precursor did not affect the cellulose structure. The possibility to vary the surface area, pore size and pore volume of the ceramic fibres by controlled hydrolysis of aluminum was demonstrated.

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Uribe, R., e C. Baudín. "Formación de titanato de aluminio por reacción en estado sólido de alúmina y titania". Boletín de la Sociedad Española de Cerámica y Vidrio 39, n. 2 (30 aprile 2000): 221–28. http://dx.doi.org/10.3989/cyv.2000.v39.i2.867.

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Sooksaen, Pat, e Pathompong Puathawee. "Conversion of Aluminum Dross Residue into Value-Added Ceramics". Key Engineering Materials 690 (maggio 2016): 71–75. http://dx.doi.org/10.4028/www.scientific.net/kem.690.71.

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This study utilized aluminum dross residue obtained from secondary process of aluminum production as the main component in the fabrication of ceramic refractories. The amount of residue varied in the range 60-90 wt% and other components in the ceramic formulations were a combination of alumino-silicate based clays. Alpha-alumina, a-Al2O3 was the main crystalline phase found in all sintered samples according to x-ray diffraction analysis. Mullite phase, Al6Si2O13 was also found in all the sintered refractories. It appeared as the main second phase which gave high strength and refractoriness. All the synthesized refractories had excellent heat-resistant characteristics when tested for thermal shock resistance. Samples were heated at 1200°C and subsequently quenched to cold water and ambient air. Refractories produced from aluminum dross residue in this study are advantageous for various applications such as high alumina bricks, high duty firebricks for steel and glass melting industry.

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Choux, Céline, Sébastien Chevalier e Yannik Cadoret. "Elaboration of Nickel Aluminide Diffusion Coatings: Application to Oxidation Resistance". Materials Science Forum 595-598 (settembre 2008): 41–49. http://dx.doi.org/10.4028/www.scientific.net/msf.595-598.41.

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Aluminide diffusion coatings are widely used in aeronautic domain. Nickel based superalloys present good mechanical properties and creep resistance at high temperature but their corrosion resistance is somewhat poor. In order to enhance their lifetime at high temperature, aluminide coatings can be applied on alloy surface. Aluminium present on material surface can form, at high temperature, alumina scale which is a protective oxide scale. In the present study, nickel aluminide coatings were carried out by aluminisation in a single step pack cementation process on nickel based superalloys 600 and AM1. Ni-Al intermetallic was obtained in each case. Oxidation tests were carried out at 900°C in air under atmospheric pressure. At this temperature, transient alumina as γ-Al2O3 and θ-Al2O3 appear on surface and are less protective than the stable α- Al2O3. Reactive elements can enhance α-Al2O3 nucleation and change diffusion mechanism during oxidation leading to a better adherence of alumina scale. In the present work, yttria was introduced by Metal-Organic Chemical Vapour Deposition (MOCVD) prior to the aluminisation. Yttria doped and undoped sample behaviours were compared under oxidising atmospheres.

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Valeev, Dmitry, Andrei Shoppert, Alexandra Mikhailova e Alex Kondratiev. "Acid and Acid-Alkali Treatment Methods of Al-Chloride Solution Obtained by the Leaching of Coal Fly Ash to Produce Sandy Grade Alumina". Metals 10, n. 5 (29 aprile 2020): 585. http://dx.doi.org/10.3390/met10050585.

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Sandy grade alumina is a valuable intermediate material that is mainly produced by the Bayer process and used for manufacturing primary metallic aluminum. Coal fly ash is generated in coal-fired power plants as a by-product of coal combustion that consists of submicron ash particles and is considered to be a potentially hazardous technogenic waste. The present paper demonstrates that the Al-chloride solution obtained by leaching coal fly ash can be further processed to obtain sandy grade alumina, which is essentially suitable for metallic aluminum production. The novel process developed in the present study involves the production of amorphous alumina via the calcination of aluminium chloride hexahydrate obtained by salting-out from acid Al-Cl liquor. Following this, alkaline treatment with further Al2O3 dissolution and recrystallization as Al(OH)3 particles is applied, and a final calcination step is employed to obtain sandy grade alumina with minimum impurities. The process does not require high-pressure equipment and reutilizes the alkaline liquor and gibbsite particles from the Bayer process, which allows the sandy grade alumina production costs to be to significantly reduced. The present article also discusses the main technological parameters of the acid treatment and the amounts of major impurities in the sandy grade alumina obtained by the different (acid and acid-alkali) methods.

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Wittenburg, Christine, e Jean Ellen Duckworth. "Comparison of aluminum toxicology and homeopathic Alumina: a mixed methods study". International Journal of High Dilution Research - ISSN 1982-6206 17, n. 1 (22 luglio 2021): 08–09. http://dx.doi.org/10.51910/ijhdr.v17i1.897.

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Toxicology forms part of homeopathy. The founder of homeopathy, Samuel Hahnemann, incorporated many toxicological symptoms in his Materia Medica. These symptoms are part of the information homeopathic practitioners relay on to choose the appropriate medication for their patients. This medication is administered in form of ultra-high dilutions. Hahnemann also developed Materia Medica on the base of provings done with high diluted substances only â€“ simply because these substances did not have a known toxicology at his time. Alumina is one of these substances. Today we possess a reliable toxicology of aluminum and its compounds. The objective of this study was to determine the grade of concordance between homeopathic (highly diluted) Alumina and aluminum toxicology. A striking concordance will add to evidence of homeopathically potentized substances. The present was a literature-based investigation conducted from a phenomenologist stance. The design is a novel one. Symptoms of aluminum intoxication were obtained from case reports published in scholarly journals. 70 original research articles containing case-reports of 5 aluminum-induced diseases served for the extraction of over 300 symptoms. These symptoms were compared to HahnemannÂ´s Alumina proving symptoms. A review of modern investigations of the toxic effects of aluminum showed that the conventional medical paradigm and basic science are just starting to explore the huge number of noxious effects the metal has on human, animal and plant health. Qualitative explorations of the relevant homeopathic literature (toxicology in homeopathy and Alumina in randomized controlled trials) resulted in the finding that toxicology plays a minor role in modern homeopathy and that Alumina has been poorly investigated. The result of the quantitative part of this study â€“ the comparison of proving and toxicology obtained from clinical cases â€“ shows an uneven picture. It leads to only partly significant concordances between symptoms from both sources which are strong in core areas of AluminaÂ´s remedy action while the overall comparison shows a coincidence of 50.76% (39.76% for symptoms probably produced by UHDs). This study has to be seen as a pilot for a literature-based proof of the evidence of homeopathic potencies. There remains much to be done, especially in the realm of homeopathic proving and its design. HahnemannÂ´s procedure â€“ to rely on sensible provers â€“ should be reconsidered. The reproving of Alumina should be envisaged. Keywords: Homeopathy, proving, toxicology, homeopathic pathogenetic trial (HPT), Alumina, aluminum

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28

Kim, Sung Wook, Shinji Iwamoto e Masashi Inoue. "Pore Structure of Alumina Derived from the Alkyl Derivatives of Boehmite". Advances in Science and Technology 45 (ottobre 2006): 2153–58. http://dx.doi.org/10.4028/www.scientific.net/ast.45.2153.

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Abstract (sommario):

Solvothermal reaction of aluminum alkoxides in various alcohols at 250-300 oC yielded alkyl derivatives of boehmite (alkoxyalumoxanes; AlO(OH)1-x(OR)x) in which alkyl groups were incorporated between the boehmite layers through the covalent bondings. In the present work, pore textures of aluminas prepared by calcination of the products were examined. The alumina obtained from the ethyl derivative of boehmite had a broad pore-size distribution, while the pore-size of the alumina obtained from the dodecyl derivative of boehmite distributed in a narrow range in the mesopore region. The mode pore diameter of the latter alumina increased with the increase in calcination temperature (600 oC, 39 Å; 800 oC, 54 Å; 1000 oC, 74 Å), but narrow pore-size distribution was maintained even after calcination at high temperatures.

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29

Mallik, B., K. Sikdar e D. Roy. "Synthesis and Characterization of Aluminium Base in situ Metal Matrix Composites by Spark Plasma Sintering". Journal of Materials Science Research 7, n. 1 (29 dicembre 2017): 14. http://dx.doi.org/10.5539/jmsr.v7n1p14.

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Abstract (sommario):

Fe-aluminide and alumina reinforced in-situ aluminium based metal matrix composite was prepared by spark plasma sintering (SPS) of aluminium and nanosized Fe2O3 powder mixture. In-situ reinforcements were formed during SPS by exothermal reaction between aluminium and nano-size Fe2O3 particle. The thermal characteristics of the in-situ reaction were studied by differential scanning calorimetry (DSC). Field Emission Scanning Electron Microscopy (FESEM) along with the Energy Dispersive Spectroscopy (EDS) and X-ray diffraction (XRD) techniques were used to study the microstructural architecture of the composites as a function of SPS temperature and the volume fraction of reinforcement. Microhardness measurement of the composite shows significant increase in hardness with increase in SPS temperature and volume fraction of secondary phase.

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30

Saidin, Nur Ubaidah, Kuan Ying Kok, Inn Khuan Ng e Suhaila Hani Ilias. "Fabrication of Nanoporous Aluminum Oxide via a Two-Step Anodisation Process". Advanced Materials Research 620 (dicembre 2012): 464–68. http://dx.doi.org/10.4028/www.scientific.net/amr.620.464.

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Abstract (sommario):

In this study, we report the fabrication of nanoporous aluminum oxide film from high purity aluminium foil via a two-step anodisation process controlled by a constant direct current potential ranging from 40 60 V from a DC power supply. The anodisation process was conducted at 20˚C in an electrochemical cell with the Al foil acting as anode, Pt as cathode and an acidic bath as electrolyte. Porous aluminium oxide films of pore diameters ranging between 30 90 nm were successfully fabricated. The morphologies and phase compositions of the anodized porous alumina films were investigated using scanning electron microscopy (SEM) and x-ray diffraction (XRD) for characterizations.

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31

Feret, Frank R. "Selected applications of Rietveld-XRD analysis for raw materials of the aluminum industry". Powder Diffraction 28, n. 2 (2 maggio 2013): 112–23. http://dx.doi.org/10.1017/s088571561300016x.

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Abstract (sommario):

In the last few decades, X-ray diffraction (XRD) systems have been paramount and irreplaceable in controlling bauxite exploration, as well as Bayer and reduction processes. XRD quantitative phase analysis in the aluminum industry witnessed a steady deployment of the Rietveld method, which at present progressively replaces existing methodologies in research and plant laboratories. Rietveld analysis not only helped to surpass traditional XRD calibration methods, it also opened the door for new applications previously not possible. The use of the Rietveld method to characterize selected materials unique to the aluminum industry, such as bauxite, red mud, and alumina is demonstrated and discussed. This paper also presents how synchrotron-based diffractograms obtained for bauxite and red mud samples allowed a much better understanding of mineralogical representation, and made it possible to leverage their Rietveld quantification. Despite clear advantages, the Rietveld method also has limitations that are revealed. For alumina phase quantification, a dedicated Rietveld analytical program was built with structure data for eight alumina mineralogical phases: alpha, beta (β-Al2O3 = Na2O•11Al2O3), delta, gamma (2), kappa, sigma, and theta. The paper gives unique examples of phase quantification in aluminas of various origins and phase composition.

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32

Gromov, Nalivaiko, Ambaryan, Vlaskin, Buryakovskaya, Kislenko, Zhuk et al. "Aluminum–Alumina Composites: Part Ⅰ: Obtaining and Characterization of Powders". Materials 12, n. 19 (27 settembre 2019): 3180. http://dx.doi.org/10.3390/ma12193180.

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Abstract (sommario):

The process of advanced aluminum-alumina powders production for selective laser melting was studied. The economically effective method of obtaining aluminum–alumina powdery composites for further selective laser melting was comprehensively studied. The aluminum powders with 10–20 wt. % alumina content were obtained by oxidation of aluminum in water. Aluminum oxidation was carried out at ≤200 °C. The oxidized powders were further dried at 120 °C and calcined at 600 °C. Four oxidation modes with different process temperatures (120–200 °C) and pressures (0.15–1.80 MPa) were investigated. Parameters of aluminum powders oxidation to obtain composites with 10.0, 14.5, 17.4, and 20.0 wt. % alumina have been determined. The alumina content, particle morphology, and particle size distribution for the obtained aluminum–alumina powdery composites were studied by XRD, SEM, laser diffraction, and volumetric methods. According to the obtained characteristics of aluminum–alumina powdery composites, they are suitable for the SLM process.

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33

Li, Xin Hao, Xing Yong Gu, Wei Xia Dong e Ting Luo. "In Situ Growth of Mullite Whisker Using Different Aluminium Source and Properties of Mullite-Corundum Lightweight Refractory". Materials Science Forum 848 (marzo 2016): 328–32. http://dx.doi.org/10.4028/www.scientific.net/msf.848.328.

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Abstract (sommario):

In-situ growth of mullite whisker from waste coal gangue and different aluminium source mixtures by dry pressing were investigated aiming at the preparation of mullite - corundum lightweight refractory by controlling mullite whisker precursor pseudo particle size and quantity in corundum matrix. The phase composition and microstructure were studied using X-ray diffraction (XRD) and scanning electron microscope (SEM) techniques. Apparent porosity and bending strength were also measured. The samples exhibited characteristic alumina and mullite phases. The formation mechanism and influence factors for mullite whiskers materials were discussed. The experimental results showed that the whisker of the obtained sample changed from the accumulated short column to mesh cross acicular whisker shape, and the length to diameter ratio increases. When the aluminium source was aluminium hydroxide, the length to diameter ratio and apparent porosity reached the maximum of 17.6 and the minimum of 2.15%. The bending strength of all the samples was similar, that of the sample prepared by calcined bauxite was the largest (84 MPa), that of the sample prepared by calcined alumina was inferior, and the sample prepared by aluminum hydroxide was the lowest.

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34

Chan, K. S., N. S. Cheruvu e G. R. Leverant. "Coating Life Prediction Under Cyclic Oxidation Conditions". Journal of Engineering for Gas Turbines and Power 120, n. 3 (1 luglio 1998): 609–14. http://dx.doi.org/10.1115/1.2818189.

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Abstract (sommario):

The hot gas path section components of land based turbines require materials with superior mechanical properties and good hot corrosion and oxidation resistance. These components are generally coated with either a diffusion coating (aluminide or platinum aluminide) or with an overlay coating (MCrAlY) to provide additional hot corrosion and/or oxidation protection. These coatings degrade due to inward and outward diffusion of elements during service. Outward diffusion of aluminum results in formation of a protective oxide layer on the surface. When the protective oxide spalls, Aluminum in the coating diffuses out to reform the oxide layer. Accelerated oxidation and failure of coating occur when the Al content in the coating is insufficient to reform a continuous alumina film. This paper describes development of a coating life predictions model that accounts for both oxidation and oxide spallation under thermal mechanical loading as well as diffusion of elements that dictate the end of useful life. Cyclic oxidation data for aluminide and platinum aluminide coatings were generated to determine model constants. Applications of this model for predicting cyclic oxidation life of coated materials are demonstrated. Work is underway to develop additional material data and to qualify the model for determining actual blade and vane coating refurbishment intervals.

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35

ADIVI, HAMID GHANBARI, IMAN EBRAHIMZADEH, MORTEZA HADI e MORTEZA TAYEBI. "THE EFFECT OF ALUMINA NANOPARTICLES ADDITION ON HIGH-TEMPERATURE WEAR BEHAVIOR OF INTERMETALLIC IRON ALUMINIDE PRODUCED BY THE SPARK PLASMA SINTERING PROCESS". Surface Review and Letters 27, n. 11 (25 giugno 2020): 2050004. http://dx.doi.org/10.1142/s0218625x20500043.

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Abstract (sommario):

The pure iron and aluminum powders were milled with 3[Formula: see text]wt.% and 7[Formula: see text]wt.% of alumina nanoparticles in planetary ball mill in order to produce iron aluminide by mechanical alloying technique. The resulting powder mixture was sintered after the formation of iron aluminide by spark plasma sintering (SPS) method to achieve specimens with the highest densification. SPS technique was utilized on specimens under the condition of 40[Formula: see text]MPa pressure at 950∘C for 5[Formula: see text]min. The microstructures were analyzed after sintering using scanning electron microscopy and EDS analysis. The results indicated that the aluminide iron phase has been produced at high purity. The sintered specimens were treated under hardness and density tests, and it was characterized that the specimen included 3[Formula: see text]wt.% of alumina nanoparticles had the highest microhardness. Likewise, it was revealed that the unreinforced sample had a maximum relative density. The wear behavior of specimens was performed at 600∘C. The results of weight loss showed after 1000[Formula: see text]m of wear test, the weight loss of unreinforced specimen was reduced up to 0.21[Formula: see text]g while the specimen with 3[Formula: see text]wt.% of alumina nanoparticle indicated the lowest weight loss about 0.02[Formula: see text]g. The worn surfaces were evaluated by scanning electron microscopy which indicated that the main wear mechanism at high temperature included adhesive wear and delamination.

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36

Sooksaen, Pat, e Pathompong Puathawee. "Properties of Unglazed Ceramics Containing Aluminum Dross as a Major Component". Solid State Phenomena 266 (ottobre 2017): 182–86. http://dx.doi.org/10.4028/www.scientific.net/ssp.266.182.

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Abstract (sommario):

Aluminum dross residue is a by-product produced at secondary re-melt plants where aluminum scraps are recycled. In this study, aluminum dross residue was utilized as a major component in the fabrication of unglazed ceramics for wall tile applications. The use of this by-product can reduce the landfill and environmental problems. The amount of aluminum dross residue used in the ceramic compositions varied in the range 50-90 wt.%. Other components utilized in the ceramic compositions included recycled glass alumino-silicate based clays. Firing was carried out between 1140 and 1200°C with 4h holding time which resulted in strong ceramic samples. Alpha-alumina, α-Al2O3 was the main crystalline phase found in all sintered ceramic samples. The appearance of mullite phase, Al6Si2O13 was evident in all fired samples. Overall, the synthesized ceramics had excellent densification characteristics when the amount of aluminum dross residue was less than 70 wt% in the ceramic composition.

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37

Kobayashi, Yoshio, Yusuke Mabuchi, Masachika Hama, Katsumi Yamamura, Yusuke Yasuda e Toshiaki Morita. "Effects of Seeding with Nanocrystallites and Addition of Inorganic Alumina Sol on Crystallization of Alkoxide Alumina Gel". Key Engineering Materials 697 (luglio 2016): 12–17. http://dx.doi.org/10.4028/www.scientific.net/kem.697.12.

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Abstract (sommario):

This paper reports a method for producing α-Al2O3 at low temperature from aluminum alkoxide using a combination of seeding of α-Al2O3 nanocryatallites and adding of inorganic alumina sol. An alkoxide alumina sol was obtained by hydrolyzing aluminum isopropoxide in water at 80°C and then peptizing the hydrolyzed aluminum isopropoxide using acetic acid at 80°C. An inorganic alumina sol was obtained by producing aluminum compound with a homogeneous precipitation method using aluminum nitrate and urea in aqueous solution and then peptizing the aluminum compound using acetic acid at room temperature. α-Al2O3 nanocrystallites were added to the alkoxide alumina sol containing the inorganic alumina sol. The addition of inorganic alumina sol provided successful fabrication of a crack-free α-Al2O3-seded alumina film by a spin-coating technique. The sol containing α-Al2O3 nanocrystallites was transformed to an α-Al2O3-seeded alumina gel by drying the sol at room temperature. The non-seeded alumina gel was crystallized into γ-Al2O3 at a temperature below 900°C. In contrast, the alumina seeded at 1% α-Al2O3 nanocrystallites content began to be transformed to α-Al2O3 by annealing at the temperature. The seeding and the adding promoted crystallization of the alumina gel into α-Al2O3. The promotion of crystallization was significant with an increase in α-Al2O3 nanocrystallites content by weight in the final seeded alumina gel.

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38

Nor, Nor Hafiez Mohamad, Ismail Muhammad Hussain, Nur Atikah Abu Kasim, Wan Dung Teng e M. K. Idham. "Sintering of Alumina-AIN System for Heat Sink". Applied Mechanics and Materials 465-466 (dicembre 2013): 76–80. http://dx.doi.org/10.4028/www.scientific.net/amm.465-466.76.

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Abstract (sommario):

Aluminium alloys is widely applied in heat sink but its application of heat absorption is still unsatisfied. While, Aluminum Nitride (AIN) was discovered as another option for heat sink application because of its great thermal conductivity and it also has high electrical conductivity at high temperature. Thus, the mechanical and chemical properties of a sintered mixed powder of Alumina and AIN are investigated experimentally. There are five different compositions of mixed powder of Alumina-AIN and sintered at three different sintering temperatures which are 1400°C, 1500°C and 1600°C. As applying a high sintering temperature on samples inducted great flexural strength and increase it modulus of rupture. High sintering temperature (1600°C) also affected the materials microstructure as the particle was arranged closely between each other and reduces the amount of porosity. The application of high temperature in the mixture of AIN with Alumina reduces the occurrence of flaws like cracking and accordingly improves the strength. These combination of Alumina-AIN brought acceptable result in thermal conductivity value analysis and as well enhancing the thermal conductivity.

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39

Jabbarnia, A., e Saeed Heshmati-Manesh. "Effect of Milling Time on Crystallite Size and Morphology of Nickel Aluminde Based Composite Powder Prepared by Mechanical Assisted SHS Route". Advanced Materials Research 83-86 (dicembre 2009): 940–44. http://dx.doi.org/10.4028/www.scientific.net/amr.83-86.940.

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Abstract (sommario):

Mechanical alloying technique was used to produce an intermetallic based composite powder. Mechanical activation of aluminum and nickel oxide powder mixture using a high energy ball mill resulted in a self-propagating high temperature synthesis through which nickel oxide was reduced by metallic aluminum and produced nickel aluminide and alumina composite powder. Effect of milling time on crystallite sizes of the product phases was investigated. The synthesized product was characterized by scanning electron microscope and X-ray diffraction. It was shown that increased milling time resulted in crystallite size reduction and peak broadening in XRD patterns. Calculation of the mean crystallite sizes of the product phases indicated that they are in nano scale. The results were further confirmed by transmission electron microscopy.

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40

Abdulkader, Niveen J., Payman Sahbah Ahmed e Mohammed Mahdy Jabar. "Study Corrosion Behavior of Alumina Particulate / (AA6061) Aluminum Metal Matrix Composite In Marine Environment". Sulaimani Journal for Engineering Sciences 3, n. 3 (1 aprile 2016): 30–36. http://dx.doi.org/10.17656/sjes.10034.

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41

Yin, Jian Jun, Min Li, Zhong Dong Zhang, Dong Wang, Shuai Shao e Xiong Hou Gao. "The Preparation of High Alumina Content Alumina Sol". Applied Mechanics and Materials 528 (febbraio 2014): 118–26. http://dx.doi.org/10.4028/www.scientific.net/amm.528.118.

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Abstract (sommario):

The alumina sol with high content of Al2O3 was prepared by peptizing aluminum hydroxide powder. The properties of the alumina sol were characterized by Fourier transform-infrared (FT-IR) spectrum, zeta potential analyzer, X-ray diffraction (XRD) and Transmission electron microscope (TEM). The results show that the sol with high content of Al2O3 can be easily prepared by peptizing the soluble aluminum hydroxide powder, the smaller of the size of aluminum hydroxide powder, the higher of the aluminum content of the alumina sol. Two-step peptization process is optimum, the effect of peptization aluminum hydroxide powder using AlCl3 :HCl=1:4 solution as peptizer is best, the alumina sol sample with pH value of 2.5 and alumina content 11% had good stability. A great application potential of the high alumina content sol has been displayed in preparing FCC catalysts.

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42

Takano, H., Takafumi Kusunose, Tohru Sekino, Rajagopalan Ramaseshan e Koichi Niihara. "Development of Low Machining Cost Materials by Using Aluminum Borate". Key Engineering Materials 317-318 (agosto 2006): 335–38. http://dx.doi.org/10.4028/www.scientific.net/kem.317-318.335.

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Abstract (sommario):

6061 aluminum alloy composite reinforced with α-alumina and aluminum borate is fabricated by casting method. The above mentioned composite has been compared to a similar composite without aluminum borate reinforcement for their machinability. The aluminum borate filler was controlled up to (2.5, 5.0 and 30vol %) on the surface of α-alumina. The reaction zone between alumina and the matrix in both the systems are analyzed with the help of TEM micrographs as well as X-ray diffraction profiles. At the reaction zone between alumina and the aluminum alloys, some spinel-like compounds (MgAl2O4) are identified. Finally, machinability was analyzed with the single point tool machining.

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43

Sjaifudin, Achmad. "FABRIKASI DAN KARAKTERISASI BEBERAPA PADUAN ALUMINIUM - ALUMINA PARTIKULAT KOMPOSIT MELALUI PENGECORAN". Jurnal Teknologi Bahan dan Barang Teknik 2, n. 2 (31 dicembre 2012): 51. http://dx.doi.org/10.37209/jtbbt.v2i2.23.

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Abstract (sommario):

Paduan aluminium-partikulat keramik komposit meningkatkan sifat mekanik dan fisik paduan aluminium tersebut. Namun kesulitan terbesar adalah masalah mampu membasahi (wettability) dari matriks aluminium (Al) terhadap partikel keramik dan reaksi antar muka antara maktriks dengan partikel. Oleh karena itu telah dilakukan percobaan pembuatan paduan aluminium yang diperkuat oleh partikulat alumina (alumina particulate reinforced aluminium alloys) melalui proses pengecoran konvensional untuk mengetahui dan dikarekterisasi dengan Scanning Electron Microscope (SEM). Prosesnya adalah dengan cara mencampur logam cair paduan Al dengan partikulat alumina, kemudian diaduk sebelum dituangkan ke dalam cetakan besi cor. Matriksnya adalah Al murni, Al-1,5 wt% Mg, Al-4,5 wt % Cu dan Al-18 wt% Ni. Hasil dari beberapa percobaan, setelah dikarakterisasi dengan menggunakan SEM ini tidak terlalu sempurna karena permasalahan rendahnya mampu basah dan perbedaan masa jenis antara partikel alumina dengan matriks sehingga menghasilkan penguatan sebagian saja.Kata kunci : Aluminium komposit, partikulat alumina, mampu basah, pengecoran, karakterisasi

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44

Wu, Dao Ji, Ding Li, Li Rui Weng, Wei Jie Zheng e Xiao Yan Qu. "The Regenerative Experiment of Activated Alumina Granules". Advanced Materials Research 201-203 (febbraio 2011): 2649–52. http://dx.doi.org/10.4028/www.scientific.net/amr.201-203.2649.

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Abstract (sommario):

Activated alumina granules is a primary sorption media . The intention of this experiment is to get out of the difference between the different regenerate medias, caustic soda and alumina sulfate . Experimental result shows the renewal adsorption capacity of activated alumina using caustic soda regenerate is more than using aluminum sulfate .Under the same experiment condition ,aluminum sulfate can regain 13.27mg/g adsorption capacity while using 0.8 per cent caustic soda to regenerate alumina and 5.36mg/g using 4 per cent aluminum sulfate .The intensity of activated alumina granules reduces when we use caustic soda as regenerate media .The mass wastage of activated alumina granules is between 12% and 14% using caustic soda as regenerate media and between 6% and 8%uing aluminum sulfate .It is needed to neutralized by hydrochloric acid or aluminum sulfate after regenerated by caustic soda .Without neutralized, the concentration of treated water is over 1.0mg/l in the beginning.And neutralized with hydrochloric acid or aluminum sulfate, the efficacious run time can achieve 23 hours and 31hours .

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45

Galusková, Dagmar, Miroslav Hnatko, Jozef Kraxner, Dušan Galusek e Pavol Šajgalík. "Influence of Calcium Addition on the Chemical Durability of the Model Alumino-Silicate Glasses in Aqueous Solutions". Key Engineering Materials 512-515 (giugno 2012): 1009–14. http://dx.doi.org/10.4028/www.scientific.net/kem.512-515.1009.

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Abstract (sommario):

The corrosion resistance of liquid phase sintered (LPS) alumina ceramics in aqueous environments strongly depends on composition and chemistry of grain boundary glass formed during sintering. The chemical durability of model alumino-silicate glasses with various contents of CaO in aqueous solutions was therefore evaluated. Prepared glasses were corroded under hydrothermal conditions in deionized water under static conditions. The examination of surface morphology of corroded specimens after the contact with deionized water, together with the analysis of corrosion solution provided information on mechanism of dissolution of grain boundary glasses in LPS aluminas and confirmed that dissolution process is hindered due to saturation of solution with respect to leached elements. The initial dissolution rates for studied glasses were determined. The results are applicable for optimization and enhancement of corrosion resistance of LPS alumina under hydrothermal conditions.

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46

Becker, Lillian C., Ivan Boyer, Wilma F. Bergfeld, Donald V. Belsito, Ronald A. Hill, Curtis D. Klaassen, Daniel C. Liebler et al. "Safety Assessment of Alumina and Aluminum Hydroxide as Used in Cosmetics". International Journal of Toxicology 35, n. 3_suppl (novembre 2016): 16S—33S. http://dx.doi.org/10.1177/1091581816677948.

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Abstract (sommario):

This is a safety assessment of alumina and aluminum hydroxide as used in cosmetics. Alumina functions as an abrasive, absorbent, anticaking agent, bulking agent, and opacifying agent. Aluminum hydroxide functions as a buffering agent, corrosion inhibitor, and pH adjuster. The Food and Drug Administration (FDA) evaluated the safe use of alumina in several medical devices and aluminum hydroxide in over-the-counter drugs, which included a review of human and animal safety data. The Cosmetic Ingredient Review (CIR) Expert Panel considered the FDA evaluations as part of the basis for determining the safety of these ingredients as used in cosmetics. Alumina used in cosmetics is essentially the same as that used in medical devices. This safety assessment does not include metallic or elemental aluminum as a cosmetic ingredient. The CIR Expert Panel concluded that alumina and aluminum hydroxide are safe in the present practices of use and concentration described in this safety assessment.

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47

Padilla, Isabel, Aurora López-Delgado, Sol López-Andrés, Marta Álvarez, Roberto Galindo e Alfonso J. Vazquez-Vaamonde. "The Application of Thermal Solar Energy to High Temperature Processes: Case Study of the Synthesis of Alumina from Boehmite". Scientific World Journal 2014 (2014): 1–7. http://dx.doi.org/10.1155/2014/825745.

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Abstract (sommario):

The aim of this paper is to evaluate the feasibility of obtaining alumina from boehmite using a free, clean, and unlimited power source as the solar energy. Boehmite was obtained by hydrothermal treatment of a hazardous waste coming from aluminum slag milling. The waste is considered as a hazardous substance because of it releasing toxic gases (hydrogen, ammonia, methane, and hydrogen sulfide) in the presence of water. The as-obtained boehmite was transformed into alumina, in air atmosphere, using a solar energy concentrator (Fresnel lens). The solar installation provides a power density of 260 W·cm−2which allows reaching temperatures upper than 1000°C at few minutes of exposure. Tests were performed at different periods of time that ranged between 5 and 90 min. The percentage of transformation of boehmite into alumina was followed by the water content of samples after solar radiation exposure. Samples were characterized by X-ray diffraction, infrared spectroscopy, and thermogravimetry. Metastable aluminas started to appear at 5 min and the crystalline and stable phase corundum at 10 min of solar radiation exposure.

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48

Zhou, Tian Pei. "Application of Intelligent Characteristic Model in Alumina Concentration Control System". Advanced Materials Research 328-330 (settembre 2011): 1837–40. http://dx.doi.org/10.4028/www.scientific.net/amr.328-330.1837.

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Abstract (sommario):

In electrolytic aluminum production processing, the measurement and control of alumina density is one of the three most important control aims. However, due to alumina density can not be measured directly and continuously online, and electrolytic aluminum production process is nonlinear, time-varying and large delay, which can not be described through the mathematical analysis model. Therefore, efficient and reliable development of alumina density control method is very important. In this paper, alumina density is controlled by single neural adaptive PID controller in electrolytic aluminum production processing, and alumina density based on intelligent characteristic model is established by using the intelligent characteristic model method, takes the model as the control model, alumina density is controlled combination of the two advantage, which achieve a good control effect.

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49

Senthilkumar, R., N. Arunkumar e M. Manzoor Hussian. "Effects of Micro and Nano-Size Al₂O₃ Particle Reinforcement on Mechanical Behaviour of Extruded Aluminum Alloy Matrix Composite". Applied Mechanics and Materials 787 (agosto 2015): 617–21. http://dx.doi.org/10.4028/www.scientific.net/amm.787.617.

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Abstract (sommario):

Aluminum alloy (AA2014) matrix composites reinforced by different weight percentage of aluminum oxide (Al2O3) in micro and nano sizes were fabricated through powder metallurgy route followed by hot extrusion process. Seven different aluminium composites with varying percentages of nano and micron sized alumina particles varying from 1% to 10% were evaluated in addition to monolithic alloy. The microstructure of nano-composite and monolithic alloys were examined by optical microscope and scanning electron microscope (SEM) equipped with an energy dispersive X-ray analysis (EDAX). In addition, the effects of weight fraction of the reinforcement matrix on mechanical properties were evaluated. The results have indicated that, a significant improvement in hardness of the nano composite was found in case of nano-composite with 8% of micro Al2O3 and 2% of nano Al2O3 particles by the addition of reinforcement.

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Cao, Hui Qin, Ji Luo e Wei Wei Yang. "Preparation of Dispersion Strengthened Aluminum Alloy by High Energy Ball Milling". Advanced Materials Research 602-604 (dicembre 2012): 598–601. http://dx.doi.org/10.4028/www.scientific.net/amr.602-604.598.

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Abstract (sommario):

In order to develop a high-strength aluminum alloy, alumina dispersion strengthened aluminum alloy was prepared by high energy ball milling on 2024 aluminum alloy powder in ethanol. The microstructure, particle size and distribution of the Al2O3 particles in the alloy were analyzed by FE-SEM; the mechanical properties were investigated. Results showed that alumina dispersion strengthened aluminum alloy was prepared successfully by high energy ball milling, the Al2O3 particles of several tens of nm in diameter were homogeneously distributed in the matrix grain and the spatial distance between particles was about 50-100nm. The yield strength and elongation of alumina oxide dispersion strengthened aluminum alloy were 489MPa and 7.9%.

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