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Sample records for alkalized alumina process

  1. Effect of hydrothermal process for inorganic alumina sol on crystal structure of alumina gel

    Directory of Open Access Journals (Sweden)

    K. Yamamura

    2016-09-01

    Full Text Available This paper reports the effect of a hydrothermal process for alumina sol on the crystal structure of alumina gel derived from hydrothermally treated alumina sol to help push forward the development of low temperature synthesis of α-Al2O3. White precipitate of aluminum hydroxide was prepared with a homogeneous precipitation method using aluminum nitrate and urea in aqueous solution. The obtained aluminum hydroxide precipitate was peptized by using acetic acid at room temperature, which resulted in the production of a transparent alumina sol. The alumina sol was treated with a hydrothermal process and transformed into an alumina gel film by drying at room temperature. Crystallization of the alumina gel to α-Al2O3 with 900 °C annealing was dominant for a hydrothermal temperature of 100 °C and a hydrothermal time of 60 min, as production of diaspore-like species was promoted with the hydrothermal temperature and time. Excess treatments with hydrothermal processes at higher hydrothermal temperature for longer hydrothermal time prevented the alumina gel from being crystallized to α-Al2O3 because the excess hydrothermal treatments promoted production of boehmite.

  2. Alumina Yield in the Bayer Process

    Science.gov (United States)

    Den Hond, R.

    The alumina industry has historically been able to reduce alumina production costs, by increasing the liquor alumina yield. To know the potential for further yield increases, the phase diagram of the ternary system Na2O-Al2O -H2O at various temperature levels was analysed. It was found that the maximum theorical precipitation alumina yield is 160 g/l, while that for digestion was calculated to be 675 g/l.

  3. Red mud flocculation process in alumina production

    Science.gov (United States)

    Fedorova, E. R.; Firsov, A. Yu

    2018-05-01

    The process of thickening and washing red mud is a gooseneck of alumina production. The existing automated systems of the thickening process control involve stabilizing the parameters of the primary technological circuits of the thickener. The actual direction of scientific research is the creation and improvement of models and systems of the thickening process control by model. But the known models do not fully consider the presence of perturbing effects, in particular the particle size distribution in the feed process, distribution of floccules by size after the aggregation process in the feed barrel. The article is devoted to the basic concepts and terms used in writing the population balance algorithm. The population balance model is implemented in the MatLab environment. The result of the simulation is the particle size distribution after the flocculation process. This model allows one to foreseen the distribution range of floccules after the process of aggregation of red mud in the feed barrel. The mud of Jamaican bauxite was acting as an industrial sample of red mud; Cytec Industries of HX-3000 series with a concentration of 0.5% was acting as a flocculant. When simulating, model constants obtained in a tubular tank in the laboratories of CSIRO (Australia) were used.

  4. Effects of Processing Temperatures of Nickel Plating on Capacitance Density of Alumina Film Capacitor.

    Science.gov (United States)

    Jeong, Myung-Sun; Ju, Byeong-Kwon; Lee, Jeon-Kook

    2015-06-01

    We observed the effects of nickel plating temperatures for controlling the surface morphologies of the deposited nickel layers on the alumina nano-pores. The alumina nano-channels were filled with nickel at various processing temperatures of 60-90 degrees C. The electrical properties of the alumina film capacitors were changed with processing temperatures. The electroless nickel plating (ENP) at 60 degrees C improved the nickel penetration into the alumina nano-channels due to the reduced reaction rate. Nickel layers are uniformly formed on the high aspect ratio alumina pores. Due to the uniform nickel electrode, the capacitance density of the alumina film capacitors is improved by the low leakage current, dissipation factor and equivalent series resistance. Alumina film capacitors made by ENP at 60 degrees C had a high capacitance density of 160 nF/cm2.

  5. Processing and characterization of alumina/LAS bioceramics for ...

    Indian Academy of Sciences (India)

    Administrator

    dental applications. M GUEDES1,4,*, V .... Alumina/LAS bioceramics for dental applications. 697 strength ... assessment. ... indentation load (N) and c is the median length (m) of the ... mixtures show two distinct modes, reflecting both the.

  6. Bauxite mining and alumina refining: process description and occupational health risks.

    Science.gov (United States)

    Donoghue, A Michael; Frisch, Neale; Olney, David

    2014-05-01

    To describe bauxite mining and alumina refining processes and to outline the relevant physical, chemical, biological, ergonomic, and psychosocial health risks. Review article. The most important risks relate to noise, ergonomics, trauma, and caustic soda splashes of the skin/eyes. Other risks of note relate to fatigue, heat, and solar ultraviolet and for some operations tropical diseases, venomous/dangerous animals, and remote locations. Exposures to bauxite dust, alumina dust, and caustic mist in contemporary best-practice bauxite mining and alumina refining operations have not been demonstrated to be associated with clinically significant decrements in lung function. Exposures to bauxite dust and alumina dust at such operations are also not associated with the incidence of cancer. A range of occupational health risks in bauxite mining and alumina refining require the maintenance of effective control measures.

  7. Dependence of the Stabilization of -Alumina on the Spray Process

    Czech Academy of Sciences Publication Activity Database

    Stahr, C.Ch.; Saaro, S.; Berger, L.-M.; Herrmann, M.; Dubský, Jiří; Neufuss, Karel

    2007-01-01

    Roč. 16, 5-6 (2007), s. 822-830 ISSN 1059-9630 R&D Projects: GA ČR(CZ) GA106/05/0483 Institutional research plan: CEZ:AV0Z20430508 Keywords : -Al2O3 stabilization * alumina * chromia * solid solution * X-ray diffraction Subject RIV: JK - Corrosion ; Surface Treatment of Materials Impact factor: 1.204, year: 2007

  8. THE TECHNOLOGY OF THE HYDROLYSİS PROCESS OF ALUMINA PRODUCTION FROM THE BAUXITES

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    Sami ŞAHİN

    2000-01-01

    Full Text Available The degree of growth level for many countries can be measured with their aluminum production and explatation rates. Ever though a great partion of aluminum hydroxide is turned into alumina still it has great merit. On the other hand, a large percentage of alumina is used in the aluminum production. The operation in the decomposition processes is referred to succinetly as hydrolysis process. Aluminum hydroxide is obtained from the aluminate solution. This production is named as hydrate and settled down which is proceded by filtration and finally sent to the calcination unit. Hydrolysis process is one of the most important stages in the production of alumina from bauxites. The ocovinence of hydrolysis reaction in a desirable manner is dependent on the factors that effect the reaction rate.

  9. High energy density processing of a free form nickel-alumina nanocomposite

    NARCIS (Netherlands)

    Viswanathan, V; Agarwal, A; Ocelik, V; De Hosson, J T M; Sobczak, N; Seal, S

    The development of a free form bulk Nickel reinforced Alumina matrix nano composites using Air Plasma Spray and laser processing has been presented. The process consumes less time and requires further minimal machining and therefore is cost effective. The relative differences in using APS over laser

  10. Mechanical properties correlation to processing parameters for advanced alumina based refractories

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    Dimitrijević Marija M.

    2012-01-01

    Full Text Available Alumina based refractories are usually used in metallurgical furnaces and their thermal shock resistance is of great importance. In order to improve thermal shock resistance and mechanical properties of alumina based refractories short ceramic fibers were added to the material. SEM technique was used to compare the microstructure of specimens and the observed images gave the porosity and morphological characteristics of pores in the specimens. Standard compression test was used to determine the modulus of elasticity and compression strength. Results obtained from thermal shock testing and mechanical properties measurements were used to establish regression models that correlated specimen properties to process parameters.

  11. Synthesis, extrusion processing and ionic conductivity measurements of sodium β-alumina tubes

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    Karanja Avinash

    2015-09-01

    Full Text Available Pure and Li-doped sodium β-alumina (NaMg0.67Al10.33O17 ceramics were prepared from the stoichiometric mixture of raw powders. Pellets and tubes were formed from the precursor (NBA-1S and preformed sodium β-alumina powder through compaction and extrusion processing, respectively. The obtained specimens were finally sintered to dense ceramics. The ceramics were comparatively evaluated for their density, microstructure, phase formation and electrical properties. Both tubes and pellets processed with the preformed sodium β-alumina powder (NBA-2S showed enhanced densification along with relatively better phase purity and crystallinity. The ceramics prepared from the preformed powder exhibited higher density of 94–95% TD (theoretical densities in comparison to the ceramics processed from the raw mixture (NBA-1S with a density of 85–87% TD, which are complemented well through fractographs and microstructures. The ceramics processed using the preformed sodium β-alumina (NBA-2S also exhibited high room temperature AC conductivity of 1.77×10-4 S/cm (1 MHz with an increasing trend with temperature. The higher ionic conductivity at all temperatures in NBA-2S than in NBA-1S ceramics can be attributed to the relatively high phase purity, crystallinity and higher density values of NBA-2S ceramics.

  12. Optical properties of alumina membranes prepared by anodic oxidation process

    International Nuclear Information System (INIS)

    Li Zhaojian; Huang Kelong

    2007-01-01

    The luminescence property of anodic alumina membranes (AAMs) with ordered nanopore arrays prepared by electrochemically anodizing aluminum in oxalic acid solutions have been investigated. Photoluminescence emission (PL) measurement shows that a blue PL band occurs in the wavelength ranges of 300-600 nm. The PL intensity and peak position of AAMs depend markedly on the excitation wavelength. A new peak located at 518 nm can be observed under a monitoring wavelength at 429 nm in the photoluminescence excitation (PLE) spectra. Convincing evidences have been presented that the PLE would be associated with the residual aluminum ions in the membrane. The PLE and PL of AAMs, as a function of anodizing times, have been discussed. It is found that the oxalic impurities incorporated in the AAMs would have important influences on the optical properties of AAMs in the initial stage of anodization. The PL and PLE spectra obtained show that there are three optical centers, of which the first is originated from the F + centers in AAMs, the second is correlated with the oxalic impurities incorporated in the AAMs, and the third is associated with the excess aluminum ions in the membrane

  13. Optical properties of alumina membranes prepared by anodic oxidation process

    Energy Technology Data Exchange (ETDEWEB)

    Li Zhaojian [College of Chemistry and Chemical Engineering, Central South University, Changsha 410083 (China)], E-mail: lizhaojian_lzj@hotmail.com; Huang Kelong [College of Chemistry and Chemical Engineering, Central South University, Changsha 410083 (China)], E-mail: klhuang@mail.csu.edu.cn

    2007-12-15

    The luminescence property of anodic alumina membranes (AAMs) with ordered nanopore arrays prepared by electrochemically anodizing aluminum in oxalic acid solutions have been investigated. Photoluminescence emission (PL) measurement shows that a blue PL band occurs in the wavelength ranges of 300-600 nm. The PL intensity and peak position of AAMs depend markedly on the excitation wavelength. A new peak located at 518 nm can be observed under a monitoring wavelength at 429 nm in the photoluminescence excitation (PLE) spectra. Convincing evidences have been presented that the PLE would be associated with the residual aluminum ions in the membrane. The PLE and PL of AAMs, as a function of anodizing times, have been discussed. It is found that the oxalic impurities incorporated in the AAMs would have important influences on the optical properties of AAMs in the initial stage of anodization. The PL and PLE spectra obtained show that there are three optical centers, of which the first is originated from the F{sup +} centers in AAMs, the second is correlated with the oxalic impurities incorporated in the AAMs, and the third is associated with the excess aluminum ions in the membrane.

  14. Analysis of the overall energy intensity of alumina refinery process using unit process energy intensity and product ratio method

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Liru; Aye, Lu [International Technologies Center (IDTC), Department of Civil and Environmental Engineering,The University of Melbourne, Vic. 3010 (Australia); Lu, Zhongwu [Institute of Materials and Metallurgy, Northeastern University, Shenyang 110004 (China); Zhang, Peihong [Department of Municipal and Environmental Engineering, Shenyang Architecture University, Shenyang 110168 (China)

    2006-07-15

    Alumina refinery is an energy intensive industry. Traditional energy saving methods employed have been single-equipment-orientated. Based on two concepts of 'energy carrier' and 'system', this paper presents a method that analyzes the effects of unit process energy intensity (e) and product ratio (p) on overall energy intensity of alumina. The important conclusion drawn from this method is that it is necessary to decrease both the unit process energy intensity and the product ratios in order to decrease the overall energy intensity of alumina, which may be taken as a future policy for energy saving. As a case study, the overall energy intensity of the Chinese Zhenzhou alumina refinery plant with Bayer-sinter combined method between 1995 and 2000 was analyzed. The result shows that the overall energy intensity of alumina in this plant decreased by 7.36 GJ/t-Al{sub 2}O{sub 3} over this period, 49% of total energy saving is due to direct energy saving, and 51% is due to indirect energy saving. The emphasis in this paper is on decreasing product ratios of high-energy consumption unit processes, such as evaporation, slurry sintering, aluminium trihydrate calcining and desilication. Energy savings can be made (1) by increasing the proportion of Bayer and indirect digestion, (2) by increasing the grade of ore by ore dressing or importing some rich gibbsite and (3) by promoting the advancement in technology. (author)

  15. Application of powder metallurgy and hot rolling processes for manufacturing aluminum/alumina composite strips

    Energy Technology Data Exchange (ETDEWEB)

    Zabihi, Majed, E-mail: m.zabihi@ma.iut.ac.ir [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Toroghinejad, Mohammad Reza, E-mail: toroghi@cc.iut.ac.ir [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Shafyei, Ali, E-mail: shafyei@cc.iut.ac.ir [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of)

    2013-01-10

    In this study, aluminum matrix composites (AMC) with 2, 4, 6 and 10 wt% alumina were produced using powder metallurgy (PM), mechanical milling (MM) and vacuum hot pressing (VHP) techniques; then, this was followed by the hot-rolling process. During hot rolling, AMCs with 6 and 10 wt% Al{sub 2}O{sub 3} were fractured whereas strip composites with 2 and 4 wt% Al{sub 2}O{sub 3} were produced successfully. Microstructure and mechanical properties of the samples were investigated by optical and scanning electron microscopes and tensile and hardness tests, respectively. Microscopic evaluations of the hot-rolled composites showed a uniform distribution of alumina particles in the aluminum matrix. It was found that with increasing alumina content in the matrix, tensile strength (TS) and hardness increased and the percentage of elongation also decreased. Scanning electron microscope (SEM) was used to investigate aluminum/alumina interfaces and fracture surfaces of the hot rolled specimens after tensile test. SEM observations demonstrated that the failure mode in the hot-rolled Al-2 wt% Al{sub 2}O{sub 3} composite strips is a typical ductile fracture, while the failure mode was shear ductile fracture with more flat surfaces in Al-4 wt% Al{sub 2}O{sub 3} strips.

  16. Synthesis and ceramic processing of zirconia alumina composites for application as solid oxide fuel cell electrolytes

    International Nuclear Information System (INIS)

    Garcia, Rafael Henrique Lazzari

    2007-01-01

    The global warmness and the necessity to obtain clean energy from alternative methods than petroleum raises the importance of developing cleaner and more efficient systems of energy generation, among then, the solid oxide fuel cell (SOFC). Cubic stabilized zirconia (CSZ) has been the most studied material as electrolyte in SOFC, due to its ionic conductivity and great stability at operation conditions. However, its low fracture toughness difficulties its application as a thin layer, what could lead to an improvement of cell efficiency. In this sense, the alumina addition in CSZ forms a composite, which can shift its mechanical properties, without compromising its electrical properties. In this work, coprecipitation synthesis route and ceramic processing of zirconia-alumina composites were studied, in order to establish optimum conditions to attain high density, homogeneous microstructure, and better mechanical properties than CSZ, without compromising ionic conductivity. For this purpose, composites containing up to 40 wt % of alumina, in a 9 mol % yttria-stabilized zirconia (9Y-CSZ) matrix were evaluated. In order to optimize the synthesis of the composites, a preliminary study of powder obtaining and processing were carried out, at compositions containing 20 wt % of alumina, in 9Y-CSZ. The ceramic powders were characterized by helium picnometry, X-ray diffraction, scanning electronic microscopy, transmission electronic microscopy, thermogravimetry, differential scanning calorimetry, granulometry by laser diffraction and gas adsorption (BET). The characterization of sinterized compacts were performed by X-ray diffraction, scanning electron microscopy, optical microscopy, density measurements, Vickers indentation and impedance spectroscopy. The obtained results show that the alumina addition, in the 9Y-CSZ matrix powders, raises the specific surface area, promotes deagglomeration of powders and elevates the oxides crystallization temperature, requiring higher

  17. Fabrication of porous anodic alumina films by using two-step anodization process

    International Nuclear Information System (INIS)

    Xu Zhan; Zhou Bin; Xu Xiang; Wang Xiaoli; Wu Di; Shen Jun

    2006-01-01

    This article introduces the fabrication of the porous anodic alumina films which have ordered pore arrangement by using a two-step anodization process. The films have a parallel channel structure which nanopore diameter can be 20-100 nm, and depth can reach 50 μm. The change of pore structure in the first and second anodization, moving the alumina layer, widening process was analysed. The effect of the parameters such as different electrolytes, anodization temperature and the voltage on the nanopore structure was studied. The surface and profile structure through FE-SEM (field emission scanning electron microscope), the element composition in tiny area of the anodic aluminum oxide (AAO) surface were studied. The result indicates the pore diameter of AAO which is anodized in oxalic acid solution is larger than which anodized in sulfuric acid solution. The anodization temperature and voltage can enlarge the nanopore diameter of AAO in a range. (authors)

  18. Cooling process of liquid propellant rocket by means of kerosene-alumina nanofluid

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    Mostafa Mahmoodi

    2016-12-01

    Full Text Available Heat transfer augmentation of kerosene-alumina nanofluid is studied for the possible use in the regenerative cooling channel of semi cryogenic engine. The basic partial differential equations are reduced to ordinary differential equations which are solved using differential transformation method. Velocity and temperature profiles as well as the skin friction coefficient and Nusselt number are determined. The influence of pertinent parameters such as nanofluid volume fraction, viscosity parameter and Eckert number on the flow and heat transfer characteristics is discussed. The results indicate that adding alumina into the fuel of liquid rocket engine (kerosene can be considered as the way of enhancing cooling process of chamber and nozzle walls. Nusselt number is an increasing function of viscosity parameter and nanoparticle volume fraction while it is a decreasing function of Eckert number.

  19. Studies on hydrogen separation membrane for IS process. Membrane preparation with porous α-alumina tube

    International Nuclear Information System (INIS)

    Hwang, Gab-Jin; Onuki, Kaoru; Shimizu, Saburo

    1998-01-01

    It was investigated the preparation technique of hydrogen separation membrane to enhance the decomposition ratio of hydrogen iodide in the thermochemical IS process. Hydrogen separation membranes based on porous α-alumina tubes having pore size of 100 nm and 10 nm were prepared by chemical vapor deposition using tetraethylorthosilicate (TEOS) as the Si source. In the hydrogen separation membrane, its pore was closed by the deposited silica and then the permeation of gas was affected by the hindrance diffusion. At 600degC, the selectivity ratios (H 2 /N 2 ) were 5.2 and 160 for the membranes based on porous α-alumina tube having pore size of 100 nm and 10 nm, respectively. (author)

  20. Analysis of Material Removal and Surface Characteristics in Machining Multi Walled Carbon Nanotubes Filled Alumina Composites by WEDM Process

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    Annebushan Singh Meinam

    2017-01-01

    Full Text Available The reinforcement of ceramic materials with electrically conductive particles increases the overall conductivity of the ceramic material. This allows the ceramic material to be more readily machined using wire electrical discharge machining process. The current work is an approach to identify the machinability of multi walled carbon nanotubes filled alumina composites in wire electrical discharge machining process. Alumina samples of 5 vol. % and 10 vol. % multi walled carbon nanotubes are machined and analysed for material removal rate and the surface characteristics. An increase in material removal rate is observed with increase in filler concentrations. At the same time, better surface roughness is observed. The surface characteristics of composite alumina are further compared with Monel 400 alloy. It has been observed that spalling action is the dominating material removal mechanism for alumina composites, while melting and evaporation is for the Monel 400 alloy.

  1. Investigation of the influence of the manufacturing process on the mechanical and microstructural properties of alumina

    International Nuclear Information System (INIS)

    Madruga, T.P.; Costa, C.R.C. da

    1986-01-01

    High-purity samples of alumina, without any sintering additives, were prepared using the techniques of slip casting and cold unidirectional pressing. The same sintering parameters (temperature, time and heating and cooling rates) were used for all samples. The mechanical strenght, critical flow strenght (mode I), average grain size and porosity were measured on samples manufactured using both methods. The influence of the manufaturing process on the quality of the finished pieces was inferred from the comparison and evaluation of the results for the two sets of samples. (Author) [pt

  2. A Technological Comparison of Six Processes for the Production of Reduction-Grade Alumina from Non-Bauxitic Raw Materials

    Science.gov (United States)

    Bengtson, K. B.

    The U. S. Bureau of Mines, by means of a contract with Kaiser Engineers and with Kaiser Aluminum & Chemical Corporation as a subcontractor, has sponsored a technological and an economic evaluation of six candidate processes for the manufacture of alumina from certain U. S. raw materials other than bauxite. This paper describes each process. Flow diagrams and the total energy requirement for each process are included. Important characteristics affecting the economics of producing alumina by each process are discussed, and some presently unsolved technical problems are identified. The extraction of alumina from clay via hydrochloric acid with iron separation by solvent extraction, and the crystallization of intermediate AlCl3·6H2O through the introduction of HCl gas into the pregnant mother liquor, appears to be technically feasible and the most attractive of the six raw material/process combinations.

  3. Synthesis of highly ordered nanopores on alumina by two-step anodization process

    Energy Technology Data Exchange (ETDEWEB)

    Bwana, Nicholas N. [University of Oxford, Department of Engineering Science (United Kingdom)], E-mail: Nicholas.Bwana@eng.ox.ac.uk

    2008-02-15

    Highly ordered anodic alumina was produced, on RF sputtered aluminium on a conductive glass substrate, by two step anodizing process in 0.4 M sulphuric acid at constant cell potentials of between 5 and 25 V and at a constant current density of 20 mA cm{sup -2}. The temperature was kept constant at 15 deg. C during both anodization processes. The effects of the anodizing potential, current density, and time on the pore diameters were established. Longer anodization periods result in wider irregular pores with reduced porosity for both constant potential and constant current density anodization processes. The current density increases with increasing constant anodizing potential and generally remains constant with time after a sharp rise. Potential drop during constant current density anodization behaves in a similar manner. We confirm that sulphuric acid has a self-ordering potential of 25 V above which burning occurs.

  4. Morphology of one-time coated palladium-alumina composite membrane prepared by sol-gel process and electroless plating technique

    Science.gov (United States)

    Sari, R.; Dewi, R.; Pardi; Hakim, L.; Diana, S.

    2018-03-01

    Palladium coated porous alumina ceramic membrane tube was obtained using a combination of sol-gel process and electroless plating technique. The thickness, structure and composition of palladium-alumina composite membrane were analyzed by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and atomic force microscopy (AFM). Palladium particle size was 6.18 to 7.64 nm. Palladium membrane with thickness of approximately 301.5 to 815.1 nm was formed at the outer surface of the alumina layer. EDX data confirmed the formation of palladium-alumina membrane containing 45% of palladium. From this research it shows the combination of sol-gel process and electroless plating technique with one-time coating can produce a homogeneous and smoother palladium nano layer film on alumina substrate.

  5. Influence of the anodizing process variables on the acidic properties of anodic alumina films

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    D.E. Boldrini

    Full Text Available Abstract In the present work, the effect of the different variables involved in the process of aluminum anodizing on the total surface acidity of the samples obtained was studied. Aluminum foils were treated by the electro-chemical process of anodic anodizing within the following variable ranges: concentration = 1.5-2.5 M; temperature = 303-323 K; voltage = 10-20 V; time = 30-90 min. The total acidity of the samples was characterized by two different methods: acid-base titration using Hammett indicators and potentiometric titration. The results showed that anodizing time, temperature and concentration were the main variables that determined the surface acid properties of the samples, and to a lesser extent voltage. Acidity increased with increasing concentration of the electrolytic bath, whereas the rest of the variables had the opposite effect. The results obtained provide a novel tool for variable selection in order to use synthetized materials as catalytic supports, adding to previous research based on the morphology of alumina layers.

  6. Effect of Solution Treatment Process on Hardness of Alumina Reinforced Al-9Zn Composite Produced by Squeeze Casting

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    Dwi Rahmalina

    2014-10-01

    Full Text Available Characteristics of aluminium matrix composites reinforced by alumina have been developed to improve mechanical properties. One of the determining factors in the development of this material is parameter of solution treatment process. This study discusses the performance of the composite matrix of Al-9Zn-6Mg-3Si reinforced by alumina powder of 5 % volume fraction. Composite are manufactured by squeeze casting process with the pressure of 20 Ton in the metal mould. To improve mechanical properties, the precipitation hardening process is conducted through variation of temperature of solution treatment of 450, 475 and 500 °C and holding time of solution treatment of 30, 60 and 90 minutes. Materials are characterized by hardness testing and microstructure observation. The results showed that the optimum condition of hardness was produced by solution treatment temperature of 500 °C and 90 minutes holding time of 86 HRB.

  7. Urine alkalization facilitates uric acid excretion

    Science.gov (United States)

    2010-01-01

    Background Increase in the incidence of hyperuricemia associated with gout as well as hypertension, renal diseases and cardiovascular diseases has been a public health concern. We examined the possibility of facilitated excretion of uric acid by change in urine pH by managing food materials. Methods Within the framework of the Japanese government's health promotion program, we made recipes which consist of protein-rich and less vegetable-fruit food materials for H+-load (acid diet) and others composed of less protein but vegetable-fruit rich food materials (alkali diet). Healthy female students were enrolled in this consecutive 5-day study for each test. From whole-day collected urine, total volume, pH, organic acid, creatinine, uric acid and all cations (Na+,K+,Ca2+,Mg2+,NH4+) and anions (Cl-,SO42-,PO4-) necessary for the estimation of acid-base balance were measured. Results Urine pH reached a steady state 3 days after switching from ordinary daily diets to specified regimens. The amount of acid generated ([SO42-] +organic acid-gut alkai) were linearly related with those of the excretion of acid (titratable acidity+ [NH4+] - [HCO3-]), indicating that H+ in urine is generated by the metabolic degradation of food materials. Uric acid and excreted urine pH retained a linear relationship, where uric acid excretion increased from 302 mg/day at pH 5.9 to 413 mg/day at pH 6.5, despite the fact that the alkali diet contained a smaller purine load than the acid diet. Conclusion We conclude that alkalization of urine by eating nutritionally well-designed food is effective for removing uric acid from the body. PMID:20955624

  8. Urine alkalization facilitates uric acid excretion

    Directory of Open Access Journals (Sweden)

    Seyama Issei

    2010-10-01

    Full Text Available Abstract Background Increase in the incidence of hyperuricemia associated with gout as well as hypertension, renal diseases and cardiovascular diseases has been a public health concern. We examined the possibility of facilitated excretion of uric acid by change in urine pH by managing food materials. Methods Within the framework of the Japanese government's health promotion program, we made recipes which consist of protein-rich and less vegetable-fruit food materials for H+-load (acid diet and others composed of less protein but vegetable-fruit rich food materials (alkali diet. Healthy female students were enrolled in this consecutive 5-day study for each test. From whole-day collected urine, total volume, pH, organic acid, creatinine, uric acid and all cations (Na+,K+,Ca2+,Mg2+,NH4+ and anions (Cl-,SO42-,PO4- necessary for the estimation of acid-base balance were measured. Results Urine pH reached a steady state 3 days after switching from ordinary daily diets to specified regimens. The amount of acid generated ([SO42-] +organic acid-gut alkai were linearly related with those of the excretion of acid (titratable acidity+ [NH4+] - [HCO3-], indicating that H+ in urine is generated by the metabolic degradation of food materials. Uric acid and excreted urine pH retained a linear relationship, where uric acid excretion increased from 302 mg/day at pH 5.9 to 413 mg/day at pH 6.5, despite the fact that the alkali diet contained a smaller purine load than the acid diet. Conclusion We conclude that alkalization of urine by eating nutritionally well-designed food is effective for removing uric acid from the body.

  9. Reuse of activated alumina

    Energy Technology Data Exchange (ETDEWEB)

    Hobensack, J.E. [Martin Marietta Energy Systems, Inc., Piketon, OH (United States)

    1991-12-31

    Activated alumina is used as a trapping media to remove trace quantities of UF{sub 6} from process vent streams. The current uranium recovery method employs concentrated nitric acid which destroys the alumina pellets and forms a sludge which is a storage and disposal problem. A recently developed technique using a distilled water rinse followed by three dilute acid rinses removes on average 97% of the uranium, and leaves the pellets intact with crush strength and surface area values comparable with new material. Trapping tests confirm the effectiveness of the recycled alumina as UF{sub 6} trapping media.

  10. Role of interfacial defect creation-annihilation processes at grain boundaries on the diffusional creep of polycrystalline alumina

    International Nuclear Information System (INIS)

    Ikuma, Y.; Gordon, R.S.

    1981-01-01

    It is generally assumed in the diffusional creep of a polycrystalline solid that grain boundaries act as perfect sources and sinks for lattice defects. However, if this assumption is not valid, then diffusional creep can become rate limited by interfacial defect reactions at grain boundaries. Steady state diffusional creep data will be presented at 1450 to 1500 0 C for polycrystalline alumina doped with Ti and a Mg-Ti co-dopant, which are consistent with interfacial controlled kinetics over an intermediate grain size range. A new type of creep deformation map will be presented which reveals the range of grain sizes and impurity concentrations over which interfacial defect creation and/or annihilation processes are important in the steady state creep of polycrystalline alumina

  11. Coating of diamond-like carbon nanofilm on alumina by microwave plasma enhanced chemical vapor deposition process.

    Science.gov (United States)

    Rattanasatien, Chotiwan; Tonanon, Nattaporn; Bhanthumnavin, Worawan; Paosawatyanyong, Boonchoat

    2012-01-01

    Diamond-like carbon (DLC) nanofilms with thickness varied from under one hundred to a few hundred nanometers have been successfully deposited on alumina substrates by microwave plasma enhanced chemical vapor deposition (MW-PECVD) process. To obtain dense continuous DLC nanofilm coating over the entire sample surface, alumina substrates were pre-treated to enhance the nucleation density. Raman spectra of DLC films on samples showed distinct diamond peak at around 1332 cm(-1), and the broad band of amorphous carbon phase at around 1550 cm(-1). Full width at half maximum height (FWHM) values indicated good formation of diamond phase in all films. The result of nano-indentation test show that the hardness of alumina samples increase from 7.3 +/- 2.0 GPa in uncoated samples to 15.8 +/- 4.5-52.2 +/- 2.1 GPa in samples coated with DLC depending on the process conditions. It is observed that the hardness values are still in good range although the thickness of the films is less than a hundred nanometer.

  12. Novel structure formation at the bottom surface of porous anodic alumina fabricated by single step anodization process.

    Science.gov (United States)

    Ali, Ghafar; Ahmad, Maqsood; Akhter, Javed Iqbal; Maqbool, Muhammad; Cho, Sung Oh

    2010-08-01

    A simple approach for the growth of long-range highly ordered nanoporous anodic alumina film in H(2)SO(4) electrolyte through a single step anodization without any additional pre-anodizing procedure is reported. Free-standing porous anodic alumina film of 180 microm thickness with through hole morphology was obtained. A simple and single step process was used for the detachment of alumina from aluminum substrate. The effect of anodizing conditions, such as anodizing voltage and time on the pore diameter and pore ordering is discussed. The metal/oxide and oxide/electrolyte interfaces were examined by high resolution scanning transmission electron microscope. The arrangement of pores on metal/oxide interface was well ordered with smaller diameters than that of the oxide/electrolyte interface. The inter-pore distance was larger in metal/oxide interface as compared to the oxide/electrolyte interface. The size of the ordered domain was found to depend strongly upon anodizing voltage and time. (c) 2010 Elsevier Ltd. All rights reserved.

  13. Effect of Alumina Addition to Zirconia Nano-composite on Low Temperature Degradation Process and Biaxial Strength

    Directory of Open Access Journals (Sweden)

    Moluk Aivazi

    2016-12-01

    Full Text Available Ceramic dental materials have been considered as alternatives to metals for dental implants application. In this respect, zirconia tetragonal stabilized with %3 yttrium, is of great importance among the ceramic materials for endosseous dental implant application. Because of its good mechanical properties and color similar to tooth. The aim and novelty of this study was to design and prepare Y-TZP nano-composite to reduce the degradation process at low temperature by alumina addition and maintaining submicron grain sized. Also, flexural strength of nano-composite samples was evaluated. Toward this purpose, alumina-Y-TZP nano-composites containing 0–30 vol% alumina (denoted as A-Y-TZP 0-30 were fabricated using α-alumina and Y-TZP nano-sized by sintering pressure less method. The synthesized samples were characterized using x-ray diffraction, field emission scanning electron microscopy equipped with energy dispersive x-ray spectroscopy techniques. Nano-composite samples with high density (≥96% and grain sized of ≤ 400 nm was obtained by sintering at 1270 °C for 170 min. After low temperature degradation test (LTD, A-Y-TZP20 and A-Y-TZP30 not showed monoclinic phase and the flexural strength in all of samples were higher than A-Y-TZP0. It was concluded that the grains were remained in submicron sized and A-Y-TZP20 and A-Y-TZP30 did not present biaxial strength reduction after LTD test.

  14. Synthesis and ceramic processing of alumina and zirconia based composites infiltrated with glass phase for dental applications

    International Nuclear Information System (INIS)

    Duarte, Daniel Gomes

    2009-01-01

    The interest for the use of ceramic materials for dental applications started due to the good aesthetic appearance promoted by the similarity to natural teeth. However, the fragility of traditional ceramics was a limitation for their use in stress conditions. The development of alumina and zirconia based materials, that associate aesthetic results, biocompatibility and good mechanical behaviour, makes possible the employment of ceramics for fabrication of dental restorations. The incorporation of vitreous phase in these ceramics is an alternative to minimize the ceramic retraction and to improve the adhesion to resin-based cements, necessary for the union of ceramic frameworks to the remaining dental structure. In the dentistry field, alumina and zirconia ceramic infiltrated with glassy phase are represented commercially by the In-Ceram systems. Considering that the improvement of powder's synthesis routes and of techniques of ceramic processing contributes for good performance of these materials, the goal of the present work is the study of processing conditions of alumina and/or 3 mol% yttria-stabilized zirconia ceramics infiltrated with aluminum borosilicate lanthanum glass. The powders, synthesized by hydroxide coprecipitation route, were pressed by uniaxial compaction and pre-sintered at temperature range between 950 and 1650 degree C in order to obtain porous ceramics bodies. Vitreous phase incorporation was performed by impregnation of aluminum borosilicate lanthanum powder, also prepared in this work, followed by heat treatment between 1200 and 1400 degree C .Ceramic powders were characterized by thermogravimetry, X-ray diffraction, scanning and transmission electron microscopy, gaseous adsorption (BET) and laser diffraction. Sinterability of alumina and /or stabilized zirconia green pellets was evaluated by dilatometry. Pre-sintered ceramics were characterized by apparent density measurements (Archimedes method), X-ray diffraction and scanning electron

  15. Effect of Plasma Spheroidization Process on the Microstructure and Crystallographic Phases of Silica, Alumina and Nickel Particles

    International Nuclear Information System (INIS)

    Hu Peng; Yan Shikai; Yuan Fangli; Bai Liuyang; Li Jinlin; Chen Yunfa

    2007-01-01

    During the plasma spheroidization process powders undergo different changes in their microstructures and crystal phases. In this paper, simple calculation of heat transfer between the plasma and a suspended particle was performed based on three hypotheses for the purpose of guiding experiments. Experimental investigation of the crystal phases and microstructural changes during the plasma processing was made using silica, alumina and nickel powders as starting materials. It has been revealed from the experimental results that these materials undergo different changes in crystal phases and microstructures, and these changes are essentially determined by the structures, properties and aggregate states of the starting materials

  16. Directions and prospects of using low grade process fuel to produce alumina

    Directory of Open Access Journals (Sweden)

    О. А. Дубовиков

    2016-08-01

    Full Text Available Power consumption across the globe is constantly increasing for a variety of reasons: growing population, industrialization and fast economic growth. The most widespread gaseous fuel – natural gas – has the low production cost. It is 2-3 times cheaper than liquid fuel production and 6-12 times cheaper than coal production. When natural gas is transported to distances from 1.5 to 2.5 thousand km by the pipeline, its cost with account of transportation is 1.5-2 times less than the cost of coal and the fuel storage facilities are not needed. Plants powered by natural gas have the higher efficiency as compared to the plants operating on other types of fuel. They are easier and cheaper to maintain and are relatively simple in automation, thus enhancing safety and improving the production process flow, do not require complicated fuel feeding or ash handling systems. Gas is combusted with a minimum amount of polluting emissions, which adds to better sanitary conditions and environment protection. But due to depletion of major energy resources many experts see the future of the global energy industry in opportunities associated with the use of solid energy carriers. From the environmental perspective solid fuel gasification is a preferred technology. The use of synthetic gas was first offered and then put to mass scale by English mechanical engineer William Murdoch. He discovered a possibility to use gas for illumination by destructive distillation of bituminous coal. After invention of the gas burner by Robert Bunsen, the illumination gas began to be used as a household fuel. The invention of an industrial gas generator by Siemens brothers made it possible to produce a cheaper generator gas which became a fuel for industrial furnaces. As the calorific value of generator gas produced through gasification is relatively low compared to natural gas, the Mining University studied possibilities to use different types of low grade process fuel at the

  17. Improving the sludge disintegration efficiency of sonication by combining with alkalization and thermal pre-treatment methods.

    Science.gov (United States)

    Şahinkaya, S; Sevimli, M F; Aygün, A

    2012-01-01

    One of the most serious problems encountered in biological wastewater treatment processes is the production of waste activated sludge (WAS). Sonication, which is an energy-intensive process, is the most powerful sludge pre-treatment method. Due to lack of information about the combined pre-treatment methods of sonication, the combined pre-treatment methods were investigated and it was aimed to improve the disintegration efficiency of sonication by combining sonication with alkalization and thermal pre-treatment methods in this study. The process performances were evaluated based on the quantities of increases in soluble chemical oxygen demand (COD), protein and carbohydrate. The releases of soluble COD, carbohydrate and protein by the combined methods were higher than those by sonication, alkalization and thermal pre-treatment alone. Degrees of sludge disintegration in various options of sonication were in the following descending order: sono-alkalization > sono-thermal pre-treatment > sonication. Therefore, it was determined that combining sonication with alkalization significantly improved the sludge disintegration and decreased the required energy to reach the same yield by sonication. In addition, effects on sludge settleability and dewaterability and kinetic mathematical modelling of pre-treatment performances of these methods were investigated. It was proven that the proposed model accurately predicted the efficiencies of ultrasonic pre-treatment methods.

  18. Synthesis and ceramic processing of zirconia alumina composites for application as solid oxide fuel cell electrolytes; Sintese e processamento de compositos de zirconia-alumina para aplicacao como eletrolito em celulas a combustivel de oxido solido

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, Rafael Henrique Lazzari

    2007-07-01

    The global warmness and the necessity to obtain clean energy from alternative methods than petroleum raises the importance of developing cleaner and more efficient systems of energy generation, among then, the solid oxide fuel cell (SOFC). Cubic stabilized zirconia (CSZ) has been the most studied material as electrolyte in SOFC, due to its ionic conductivity and great stability at operation conditions. However, its low fracture toughness difficulties its application as a thin layer, what could lead to an improvement of cell efficiency. In this sense, the alumina addition in CSZ forms a composite, which can shift its mechanical properties, without compromising its electrical properties. In this work, coprecipitation synthesis route and ceramic processing of zirconia-alumina composites were studied, in order to establish optimum conditions to attain high density, homogeneous microstructure, and better mechanical properties than CSZ, without compromising ionic conductivity. For this purpose, composites containing up to 40 wt % of alumina, in a 9 mol % yttria-stabilized zirconia (9Y-CSZ) matrix were evaluated. In order to optimize the synthesis of the composites, a preliminary study of powder obtaining and processing were carried out, at compositions containing 20 wt % of alumina, in 9Y-CSZ. The ceramic powders were characterized by helium picnometry, X-ray diffraction, scanning electronic microscopy, transmission electronic microscopy, thermogravimetry, differential scanning calorimetry, granulometry by laser diffraction and gas adsorption (BET). The characterization of sinterized compacts were performed by X-ray diffraction, scanning electron microscopy, optical microscopy, density measurements, Vickers indentation and impedance spectroscopy. The obtained results show that the alumina addition, in the 9Y-CSZ matrix powders, raises the specific surface area, promotes deagglomeration of powders and elevates the oxides crystallization temperature, requiring higher

  19. STUDIES ON THE EFFICIENCY OF GRUNDWATER TREATMENT PROCESS WITH ADSORPTION ON ACTIVATED ALUMINA

    Directory of Open Access Journals (Sweden)

    Ewa Szatyłowicz

    2017-07-01

    Full Text Available The one of inorganic sorbents used in water treatment technology is activated alumina. Recommended by the European Commission to remove inorganic impurities, such as arsenic, fluoride, selenium and silicates. The adsorbent is usually applied in granular form, under flow conditions. It can become absorbent material increasingly used due to the presence of arsenic beside iron and manganese in groundwater intakes. The aim of the study was to evaluate the effectiveness of groundwater treatment in the technological system containing adsorption on activated alumina. The experiment was performed on test model CE 581 manufactured by G.U.N.T. Hamburg, in which can extract four treatment stages. The first stage is used in a gravel filter of grain size 1-2 mm, in the second sand filter of grain size 0.4-0.8 mm. The third and fourth phase includes two adsorbers. The first adsorber comprises activated alumina (Al2O3 and the other comprises a granular activated carbon. The study was conducted at different speeds of filtration: 5, 10 and 15 m/h. In the raw water samples and the purified water samples after each treatment step were determined the following parameters: pH, O2 concentration, electrolytic conductivity, SO42-, concentration, NO3- concentration, PO43- concentration, Cl-concentration, color, turbidity, iron and manganese concentration, CODMn, total hardness, calcium hardness, magnesium hardness, content of dissolved substances. Conducted research indicates that optimum filtration rate for most pollution is 15 m/h. Moreover, the presence of activated alumina has contributed to increasing the efficiency of nitrate (V and phosphate (V ions removal.

  20. Ultrafiltro de alumina Alumina ultrafilter

    Directory of Open Access Journals (Sweden)

    M. F. de Souza

    1999-06-01

    Full Text Available Membranas de alumina AKP-50 foram preparadas sobre um substrato de alumina APC-SG de alta resistência mecânica. As membranas foram sinterizadas a 1000 °C e possuem uma distribuição estreita de poros de 40 a 90 nm, espessura média de 57 mm e taxa de fluxo de 0,4 m3/m2h. O filtro assim obtido é classificado como ultrafiltro sendo capaz de reter bactérias e alguns vírus. São quimicamente inertes e resistem a temperaturas inferiores a 1000 °C. A aderência entre as camadas permite a limpeza por contra-fluxo.Alumina ceramic membranes with unimodal pore size distribution in the 40 to 90 nm range were prepared on alumina porous substrates. The 57mm thickness membrane made from AKP-50 alumina shows 0,4 m3/m2h flow rate. The two layer substrate, prepared to have high mechanical strength, was made from commercially available APC-SG alumina. The filter made of three layers, membrane, intermediate layer and substrate, is classified as ultra-filter being able to retain bacteria and some viruses. Adherence between the three layers allows reverse washing. Filters are chemically inert and resistant to temperatures below 1000oC.

  1. Stress-strain effects in alumina-Cu reinforced Nb3Sn wires fabricated by the tube process

    International Nuclear Information System (INIS)

    Murase, Satoru; Nakayama, Shigeo; Masegi, Tamaki; Koyanagi, Kei; Nomura, Shunji; Shiga, Noriyuki; Kobayashi, Norio; Watanabe, Kazuo.

    1997-01-01

    In order to fabricate a large-bore, high-field magnet which achieves a low coil weight and volume, a high strength compound superconducting wire is required. For those demands we have developed the reinforced Nb 3 Sn wire using alumina dispersion strengthened copper (alumina-Cu) as a reinforcement material and the tube process of the Nb 3 Sn wire fabrication. The ductility study of the composites which consisted of the reinforcement, Nb tube, Cu, and Cu clad Sn brought a 1 km long alumina-Cu reinforced Nb 3 Sn wire successfully. Using fabricated wires measurements and evaluations of critical current density as parameters of magnetic field, tensile stress, tensile strain, and transverse compressive stress, and those of stress-strain curves at 4.2 K were performed. They showed superior performance such as high 0.3% proof stress (240 MPa at 0.3% strain) and high maximum tolerance stress (320 MPa) which were two times as large as those of conventional Cu matrix Nb 3 Sn wire. The strain sensitivity parameters were obtained for the reinforced Nb 3 Sn wire and the Cu matrix one using the scaling law. Residual stress of the component materials caused by cooling down to 4.2 K from heat-treatment temperature was calculated using equivalent Young's modulus, equivalent yield strength, thermal expansion coefficient and other mechanical parameters. Calculated stress-strain curves at 4.2 K for the reinforced Nb 3 Sn wire and the Cu matrix one based on calculation of residual stress, had good agreement with the experimental values. (author)

  2. Molybdenum adsorption by alumina and Dowex 1x8 resin for the separation and purification process of fission 99Mo

    International Nuclear Information System (INIS)

    Yamaura, M.; Damasceno, M.O.; Freitas, A.A.; Camilo, R.L.; Araujo, I.C.; Forbicini, C.A.L.G. de O.

    2011-01-01

    Molybdenum-99 is the most widely employed radioisotope in nuclear medicine, due to its decay product, Technetium-99m, a radioisotope used in over 80% of diagnostic tests. Since 2009, the production of generators 99 Mo/ 99m Tc suffers a crisis of global supply. The raw material, the 99 Mo, is produced mainly by fission of 235 U in the reactor in uranium targets. Brazilian government invests in building of a research reactor suitable for the domestic production of 99 Mo from LEU (Low Enriched Uranium) targets and the IPEN/CNEN develops the production technology. This work is part of the research for the development of production technology of 99 Mo at the IPEN/CNEN-SP. The study has evaluated the adsorption behaviour of molybdenum from the alkaline dissolution of aluminum plates by the alumina and by the anionic resin Dowex 1x8 aiming at their use in the process of separation and purification in chromatography columns. Influences of pH and of aluminum concentration in the retention of molybdenum were investigated. Results showed high performance in the wide pH range. However in strongly acid solutions containing aluminum, alumina showed higher adsorption percentage than that achieved by the resin Dowex 1x8. (author)

  3. Development of Cast Alumina-forming Austenitic Stainless Steel Alloys for use in High Temperature Process Environments

    Energy Technology Data Exchange (ETDEWEB)

    Muralidharan, Govindarajan [ORNL; Yamamoto, Yukinori [ORNL; Brady, Michael P [ORNL; Pint, Bruce A [ORNL; Pankiw, Roman [Duraloy Technologies Inc; Voke, Don [Duraloy Technologies Inc

    2015-01-01

    There is significant interest in the development of alumina-forming, creep resistant alloys for use in various industrial process environments. It is expected that these alloys can be fabricated into components for use in these environments through centrifugal casting and welding. Based on the successful earlier studies on the development of wrought versions of Alumina-Forming Austenitic (AFA) alloys, new alloy compositions have been developed for cast products. These alloys achieve good high-temperature oxidation resistance due to the formation of protective Al2O3 scales while multiple second-phase precipitation strengthening contributes to excellent creep resistance. This work will summarize the results on the development and properties of a centrifugally cast AFA alloy. This paper highlights the strength, oxidation resistance in air and water vapor containing environments, and creep properties in the as-cast condition over the temperature range of 750°C to 900°C in a centrifugally cast heat. Preliminary results for a laboratory cast AFA composition with good oxidation resistance at 1100°C are also presented.

  4. Bauxite Mining and Alumina Refining

    Science.gov (United States)

    Frisch, Neale; Olney, David

    2014-01-01

    Objective: To describe bauxite mining and alumina refining processes and to outline the relevant physical, chemical, biological, ergonomic, and psychosocial health risks. Methods: Review article. Results: The most important risks relate to noise, ergonomics, trauma, and caustic soda splashes of the skin/eyes. Other risks of note relate to fatigue, heat, and solar ultraviolet and for some operations tropical diseases, venomous/dangerous animals, and remote locations. Exposures to bauxite dust, alumina dust, and caustic mist in contemporary best-practice bauxite mining and alumina refining operations have not been demonstrated to be associated with clinically significant decrements in lung function. Exposures to bauxite dust and alumina dust at such operations are also not associated with the incidence of cancer. Conclusions: A range of occupational health risks in bauxite mining and alumina refining require the maintenance of effective control measures. PMID:24806720

  5. Synthesis and characterization of alumina-coated aluminum sponges manufactured by sintering and dissolution process as possible structured reactors

    International Nuclear Information System (INIS)

    Méndez, Franklin J.; Rivero-Prince, Sayidh; Escalante, Yelisbeth; Villasana, Yanet; Brito, Joaquín L.

    2016-01-01

    Al_2O_3–Al sponges were manufactured by sintering and dissolution process with the aim of using these materials as structured catalytic reactors. For this purpose, several synthesis conditions were examined for the design of the cellular material, such as: particle size of NaCl, weight fraction of Al, compaction pressure, and sintering temperature or time. An alumina layers was grown on top of the aluminum surfaces during both: sintering and thermal treatment. The obtained results showed that the synthesized materials could be promising as structured reactors for endothermic or exothermic reactions. - Highlights: • An efficient method for manufactured of aluminum sponges is reported. • Methods for productions of superficial Al_2O_3 are studied. • Al_2O_3–Al sponges could be used as structured reactors.

  6. Study the effect of striping in two-step anodizing process on pore arrangement of nano-porous alumina

    International Nuclear Information System (INIS)

    Rahimi, M.H.; Saramad, S.; Tabaian, S.H.; Marashi, S.P.; Zolfaghari, A.; Mohammadalinezhad, M.

    2009-01-01

    Two-step anodic oxidation of aluminum is generally employed to produce the ordered porous anodized alumina (PAA). Dissolving away (striping) the oxide film after the first anodizing step plays a key role in the final arrangement of nano-pores. In this work, different striping durations between 1 and 6 h were applied to the sample that was initially anodized at a constant voltage of 40 V at 17 deg. C for 15 h. The striping duration of 3 h was realized as the optimum time for achieving the best ordering degree for the pores. Scanning electron microscopy (SEM) was used during and at the end of the process to examine the cross section and finishing surface of the specimens. Linear-angular fast Fourier transform (LA-FFT), an in-house technique based on MATLAB software, was employed to assess the ordering degree of the anodized samples.

  7. Synthesis and characterization of alumina-coated aluminum sponges manufactured by sintering and dissolution process as possible structured reactors

    Energy Technology Data Exchange (ETDEWEB)

    Méndez, Franklin J., E-mail: fmendez@ivic.gob.ve [Centro de Química, Instituto Venezolano de Investigaciones Científicas, Apartado Postal 21827, Caracas 1020-A (Venezuela, Bolivarian Republic of); Rivero-Prince, Sayidh [Centro de Química, Instituto Venezolano de Investigaciones Científicas, Apartado Postal 21827, Caracas 1020-A (Venezuela, Bolivarian Republic of); Facultad de Ingeniería, Universidad Central de Venezuela, Caracas (Venezuela, Bolivarian Republic of); Escalante, Yelisbeth; Villasana, Yanet [Centro de Química, Instituto Venezolano de Investigaciones Científicas, Apartado Postal 21827, Caracas 1020-A (Venezuela, Bolivarian Republic of); Brito, Joaquín L., E-mail: joabrito@ivic.gob.ve [Centro de Química, Instituto Venezolano de Investigaciones Científicas, Apartado Postal 21827, Caracas 1020-A (Venezuela, Bolivarian Republic of)

    2016-03-01

    Al{sub 2}O{sub 3}–Al sponges were manufactured by sintering and dissolution process with the aim of using these materials as structured catalytic reactors. For this purpose, several synthesis conditions were examined for the design of the cellular material, such as: particle size of NaCl, weight fraction of Al, compaction pressure, and sintering temperature or time. An alumina layers was grown on top of the aluminum surfaces during both: sintering and thermal treatment. The obtained results showed that the synthesized materials could be promising as structured reactors for endothermic or exothermic reactions. - Highlights: • An efficient method for manufactured of aluminum sponges is reported. • Methods for productions of superficial Al{sub 2}O{sub 3} are studied. • Al{sub 2}O{sub 3}–Al sponges could be used as structured reactors.

  8. Study the effect of striping in two-step anodizing process on pore arrangement of nano-porous alumina

    Energy Technology Data Exchange (ETDEWEB)

    Rahimi, M.H. [Department of Mining and Metallurgical Engineering, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of); Saramad, S., E-mail: ssaramad@aut.ac.ir [Department of Physics, Amirkabir University of Technology, Hafez Avenue, Tehran (Iran, Islamic Republic of); Tabaian, S.H.; Marashi, S.P. [Department of Mining and Metallurgical Engineering, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of); Zolfaghari, A. [Chemistry and Chemical Engineering Research Centre of Iran, Tehran (Iran, Islamic Republic of); Mohammadalinezhad, M. [Department of Mining and Metallurgical Engineering, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of)

    2009-10-15

    Two-step anodic oxidation of aluminum is generally employed to produce the ordered porous anodized alumina (PAA). Dissolving away (striping) the oxide film after the first anodizing step plays a key role in the final arrangement of nano-pores. In this work, different striping durations between 1 and 6 h were applied to the sample that was initially anodized at a constant voltage of 40 V at 17 deg. C for 15 h. The striping duration of 3 h was realized as the optimum time for achieving the best ordering degree for the pores. Scanning electron microscopy (SEM) was used during and at the end of the process to examine the cross section and finishing surface of the specimens. Linear-angular fast Fourier transform (LA-FFT), an in-house technique based on MATLAB software, was employed to assess the ordering degree of the anodized samples.

  9. Study the effect of striping in two-step anodizing process on pore arrangement of nano-porous alumina

    Science.gov (United States)

    Rahimi, M. H.; Saramad, S.; Tabaian, S. H.; Marashi, S. P.; Zolfaghari, A.; Mohammadalinezhad, M.

    2009-10-01

    Two-step anodic oxidation of aluminum is generally employed to produce the ordered porous anodized alumina (PAA). Dissolving away (striping) the oxide film after the first anodizing step plays a key role in the final arrangement of nano-pores. In this work, different striping durations between 1 and 6 h were applied to the sample that was initially anodized at a constant voltage of 40 V at 17 °C for 15 h. The striping duration of 3 h was realized as the optimum time for achieving the best ordering degree for the pores. Scanning electron microscopy (SEM) was used during and at the end of the process to examine the cross section and finishing surface of the specimens. Linear-angular fast Fourier transform (LA-FFT), an in-house technique based on MATLAB software, was employed to assess the ordering degree of the anodized samples.

  10. Effects of alumina nanoparticles on the microstructure, strength and wear resistance of poly(methyl methacrylate)-based nanocomposites prepared by friction stir processing.

    Science.gov (United States)

    Aghajani Derazkola, Hamed; Simchi, Abdolreza

    2018-03-01

    In this study, alumina-reinforced poly(methyl methacrylate) nanocomposites (PMMA/Al 2 O 3 ) containing up to 20vol% nanoparticles with an average diameter of 50nm were prepared by friction stir processing. The effects of nanoparticle volume fraction on the microstructural features and mechanical properties of PMMA were studied. It is shown that by using a frustum pin tool and employing an appropriate processing condition, i.e. a rotational speed of 1600rpm/min and transverse velocity of 120mm/min, defect free nanocomposites at microscale with fine distribution of the nanoparticles can successfully been prepared. Mechanical evaluations including tensile, flexural, hardness and impact tests indicate that the strength and toughness of the material gradually increases with the nanoparticle concentration and reach to a flexural strength of 129MPa, hardness of 101 Shore D, and impact energy 2kJ/m 2 for the nanocomposite containing 20vol% alumina. These values are about 10% and 20% better than untreated and FSP-treated PMMA (without alumina addition). Fractographic studies indicate typical brittle features with crack deflection around the nanoparticles. More interestingly, the sliding wear rate in a pin-on-disk configuration and the friction coefficient are reduced up to 50% by addition of alumina nanoparticles. The worn surfaces exhibit typical sliding and ploughing features. Copyright © 2018 Elsevier Ltd. All rights reserved.

  11. Control of porosity in alumina for catalytic purposes - a review; Controle de porosidade em aluminas para fins cataliticos - uma revisao

    Energy Technology Data Exchange (ETDEWEB)

    Moure, Gustavo Torres [PETROBRAS, Rio de Janeiro, RJ (Brazil). Centro de Pesquisas (CENPES). Setor de Tecnologia de Hidrorrefino, Lubrificantes e Parafinas; Morgado Junior, Edisson [PETROBRAS, Rio de Janeiro, RJ (Brazil). Centro de Pesquisas (CENPES). Setor de Tecnologia de Craqueamento Catalitico; Figueiredo, Cecilia Maria C.

    1999-12-01

    In recent years, the Alumina Group, of the Catalysts Division of CENPES, has dedicated research to develop and characterize alumina for the catalytic processes of interest to PETROBRAS. Control of the texture of the alumina and, consequently, the alumina based catalysts, is crucially important to their adequacy and performance. Knowledge of the porosity formation mechanisms in alumina was fundamental for the development of catalysts to satisfy the demand from PETROBRAS. This comprises the scope of this review. (author)

  12. Preparation of alumina microspheres

    International Nuclear Information System (INIS)

    Santos, W.R. dos; Abrao, A.

    1980-01-01

    Inorganic exchangers are widely used for adsorption and column partition chromatography. The main difficulty of using commercial alumina (in powder) for column chromatography is related to its packing, and the operations through the column become diffcult and time-consuming; also it turns to be virtually impossible to use large dimension columns. In order to eliminate these problems, a process for the preparation of alumina micro-spheres was developed as an adaptation of a similar process used to prepare nuclear fuel microspheres (UO 2 , ThO 2 ). The flowsheet of this process is presented together with the analytical results of sphericity after calcination, granulometry, density and characterization by X-ray diffractometry. Solubility tests showed that the so-prepared microspheres are well resistant to strong acids and bases; retention tests showed their efficiency, mainly to copper. (C.L.B.) [pt

  13. High-Temperature Electrical Insulation Behavior of Alumina Films Prepared at Room Temperature by Aerosol Deposition and Influence of Annealing Process and Powder Impurities

    Science.gov (United States)

    Schubert, Michael; Leupold, Nico; Exner, Jörg; Kita, Jaroslaw; Moos, Ralf

    2018-04-01

    Alumina (Al2O3) is a widely used material for highly insulating films due to its very low electrical conductivity, even at high temperatures. Typically, alumina films have to be sintered far above 1200 °C, which precludes the coating of lower melting substrates. The aerosol deposition method (ADM), however, is a promising method to manufacture ceramic films at room temperature directly from the ceramic raw powder. In this work, alumina films were deposited by ADM on a three-electrode setup with guard ring and the electrical conductivity was measured between 400 and 900 °C by direct current measurements according to ASTM D257 or IEC 60093. The effects of film annealing and of zirconia impurities in the powder on the electrical conductivity were investigated. The conductivity values of the ADM films correlate well with literature data and can even be improved by annealing at 900 °C from 4.5 × 10-12 S/cm before annealing up to 5.6 × 10-13 S/cm after annealing (measured at 400 °C). The influence of zirconia impurities is very low as the conductivity is only slightly elevated. The ADM-processed films show a very good insulation behavior represented by an even lower electrical conductivity than conventional alumina substrates as they are commercially available for thick-film technology.

  14. Discharge Simulation and Fabrication Process of an Aluminum Electrode and an Alumina Layer in AC-PDP

    International Nuclear Information System (INIS)

    Liu Qifa; Ding Guifu; Liu Chang; Wang Yan; Yan Qun

    2013-01-01

    A larger space PDP cell with patterned aluminum as the addressing electrode and alumina as the dielectric layer was proposed. The aluminum electrode and the alumina dielectric layer formed on the aluminum electrode were prepared separately by magnetron sputtering and anodic oxidation for plasma display panel. The properties of the aluminum electrode and the alumina dielectric layer were tested and can meet the demand of PDP application. The resistivity of the aluminum electrode is about 5 × 10 −8 Ω·m, the voltage withstanding of the alumina dielectric layer exceeds 100 V/μm and the relative permittivity is about 3.5 at 1 MHz. With this structure, the manufacturing cost of PDP could be cut and the addressing discharge formative delay is reduced by 0.67%, which is proved by PIC-MCC simulation. (plasma technology)

  15. Synthesis of Alumina using the solvo thermal method

    International Nuclear Information System (INIS)

    Meor Yusoff Meor Sulaiman; Masliana Muslimin

    2007-01-01

    The paper describes work done on synthesis of α- and β-alumina by using the solvo thermal technique. Synthesis of both these aluminas involves the transition reactions of the aluminium hydroxide into alumina by a dehydroxylation process. As there are many forms of transition aluminas produced during this process, x-ray diffraction (XRD) technique was used to identify α-alumina and β-alumina. After establishing the optimum conditions for the production of a single-phase α- and β-aluminas, characteristic study on the product was performed. An important parameter in establishing nano sized powders is their crystallite size and analysis of the β-alumina shows that it is a nano sized powder with a size of 28 nm while the α-alumina has a crystallite size of 200 nm. Other properties analysed include morphology, surface area and particle size. (author)

  16. Noble gas systematics of submarine alkalic lavas near the Hawaiian hotspot

    NARCIS (Netherlands)

    Hanyu, T.; Clague, D.A.; Kaneoka, I.; Dunai, T.J.; Davies, G.R.

    2005-01-01

    Noble gas isotopic ratios were determined for submarine alkalic volcanic rocks distributed around the Hawaiian islands to constrain the origin of such alkalic volcanism and hence understand the details of mantle upwelling beneath Hawaii. Samples were collected by dredging or using submersibles from

  17. The Variscan calc-alkalic plutonism of western Corsica: mineralogy and major and trace element geochemistry

    Science.gov (United States)

    Cocherie, A.; Rossi, Ph.; Le Bel, L.

    1984-10-01

    Petrographic and structural observations on the calc-alkalic plutonism of western Corsica revealed the existence of several successively emplaced units associated with large basic bodies. The present mineralogical and geochemical study deals with the genesis, evolution and relationships of these different units. Basic plutonism is represented by three genetically linked types of rock: norites and troctolites with cumulate textures characterized by low REE contents and either no Eu anomaly or a positive Eu anomaly; gabbros with enriched LREE relatively to HREE patterns, probably close to an initial basaltic liquid; and diorites ranging up to charnockites which represent liquids evolved to varying degrees, mainly by fractional crystallization. Trace element data and studies on the evolution of pyroxene pairs demonstrate the consanguinity of these calc-alkaline basic rocks which are derived from a high alumina basaltic melt. The various granitoids (granodiorites, monzogranites and leucocratic monzogranites, i.e., adamellites) have distinct evolution trends as shown by the composition of their mafic minerals and by trace element distributions. They cannot be considered as being derivatives of the basic suite and they cannot be related by a common fractionation sequence. Rather, they represent distinctive batches of crustal anatexis. In addition, hybridization phenomena with the basic melt are noticed in granodiorites. The particular problem of the low La/Yb, Eu/Eu∗ and the high U, Th, Cs leucocratic monzogranites is discussed in detail. In addition to more conventional trace element diagrams, the simultaneous statistical treatment of all the geochemical data by correspondence factor analysis is shown to be a very use tool in distinguishing between the different units and to classify the elements according to their geochemical properties.

  18. Relationship between the catalytic activity of Pt/alumina and the relaxation process of the photoexcited electrons

    Energy Technology Data Exchange (ETDEWEB)

    Ito, Junji, E-mail: j-itou@mail.nissan.co.jp [Advanced Materials Laboratory, Nissan Research Center, NISSAN MOTOR CO., LTD., 1 Natsushima-cho, Yokosuka-shi, Kanagawa 237-8523 (Japan); Department of Applied Physics and Chemistry, The University of Electro-Communications, 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585 (Japan); Hanaki, Yasunari [Advanced Materials Laboratory, Nissan Research Center, NISSAN MOTOR CO., LTD., 1 Natsushima-cho, Yokosuka-shi, Kanagawa 237-8523 (Japan); Shen, Qing [Department of Applied Physics and Chemistry, The University of Electro-Communications, 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585 (Japan); Department of Engineering Science, The University of Electro-Communications, 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585 (Japan); PRESTO, Japan Science and Technology Agency (JST), 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan); Toyoda, Taro [Department of Applied Physics and Chemistry, The University of Electro-Communications, 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585 (Japan); Department of Engineering Science, The University of Electro-Communications, 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585 (Japan)

    2012-12-15

    Highlights: Black-Right-Pointing-Pointer We determined the decay time of photoexcited electrons of Pt/Al{sub 2}O{sub 3}. Black-Right-Pointing-Pointer Faster decay of excited electrons in Pt/Al{sub 2}O{sub 3} leads to its faster oxidation rate. Black-Right-Pointing-Pointer Decreasing excited electron lifetime in Pt/Al{sub 2}O{sub 3} may decrease Pt consumption in catalytic convertors. - Abstract: In order to decrease the consumption of precious metals used in the catalytic converters used in automobiles, we studied the relationship between the catalytic activity of Pt/alumina (Pt/Al{sub 2}O{sub 3}) and the relaxation process of photoexcited electrons. Firstly, we studied the relationship between the size of the Pt particles in Pt/Al{sub 2}O{sub 3} and catalytic performance. Secondly, the relationship between the size of the Pt particles in Pt/Al{sub 2}O{sub 3} and the decay time of the excited electrons was studied using an improved transient grating (TG) technique. The results showed that faster decay of the excited electrons leads to greater oxidation rates. The decay time obtained with the improved TG technique gives an indication of the time that the exited electrons take to return to the ground state. According to studies utilizing FT-IR, one of the processes necessary for quickly generating CO{sub 2} with Pt is that the electron in the Pt-O bond moves to the Pt side and that the Pt{sup +} becomes Pt metal. Thus, the decay time obtained with the improved TG technique corresponds to the process whereby Pt{sup +} returns to Pt metal. Thus, we found that the consumption of precious metals can be reduced by increasing the speed of the decay of the excited electrons.

  19. Relationship between the catalytic activity of Pt/alumina and the relaxation process of the photoexcited electrons

    International Nuclear Information System (INIS)

    Ito, Junji; Hanaki, Yasunari; Shen, Qing; Toyoda, Taro

    2012-01-01

    Highlights: ► We determined the decay time of photoexcited electrons of Pt/Al 2 O 3 . ► Faster decay of excited electrons in Pt/Al 2 O 3 leads to its faster oxidation rate. ► Decreasing excited electron lifetime in Pt/Al 2 O 3 may decrease Pt consumption in catalytic convertors. - Abstract: In order to decrease the consumption of precious metals used in the catalytic converters used in automobiles, we studied the relationship between the catalytic activity of Pt/alumina (Pt/Al 2 O 3 ) and the relaxation process of photoexcited electrons. Firstly, we studied the relationship between the size of the Pt particles in Pt/Al 2 O 3 and catalytic performance. Secondly, the relationship between the size of the Pt particles in Pt/Al 2 O 3 and the decay time of the excited electrons was studied using an improved transient grating (TG) technique. The results showed that faster decay of the excited electrons leads to greater oxidation rates. The decay time obtained with the improved TG technique gives an indication of the time that the exited electrons take to return to the ground state. According to studies utilizing FT-IR, one of the processes necessary for quickly generating CO 2 with Pt is that the electron in the Pt-O bond moves to the Pt side and that the Pt + becomes Pt metal. Thus, the decay time obtained with the improved TG technique corresponds to the process whereby Pt + returns to Pt metal. Thus, we found that the consumption of precious metals can be reduced by increasing the speed of the decay of the excited electrons.

  20. First principles study of the atomic layer deposition of alumina by TMA-H2O-process.

    Science.gov (United States)

    Weckman, Timo; Laasonen, Kari

    2015-07-14

    Atomic layer deposition (ALD) is a coating technology used to produce highly uniform thin films. Aluminiumoxide, Al2O3, is mainly deposited using trimethylaluminium (TMA) and water as precursors and is the most studied ALD-process to date. However, only few theoretical studies have been reported in the literature. The surface reaction mechanisms and energetics previously reported focus on a gibbsite-like surface model but a more realistic description of the surface can be achieved when the hydroxylation of the surface is taken into account using dissociatively adsorbed water molecules. The adsorbed water changes the structure of the surface and reaction energetics change considerably when compared to previously studied surface model. Here we have studied the TMA-H2O process using density functional theory on a hydroxylated alumina surface and reproduced the previous results for comparison. Mechanisms and energetics during both the TMA and the subsequent water pulse are presented. TMA is found to adsorb exothermically onto the surface. The reaction barriers for the ligand-exchange reactions between the TMA and the surface hydroxyl groups were found to be much lower compared to previously presented results. TMA dissociation on the surface is predicted to saturate at monomethylaluminium. Barriers for proton diffusion between surface sites are observed to be low. TMA adsorption was also found to be cooperative with the formation of methyl bridges between the adsorbants. The water pulse was studied using single water molecules reacting with the DMA and MMA surface species. Barriers for these reactions were found to reasonable in the process conditions. However, stabilizing interactions amongst water molecules were found to lower the reaction barriers and the dynamical nature of water is predicted to be of importance. It is expected that these calculations can only set an upper limit for the barriers during the water pulse.

  1. Improvement of In-Flight Alumina Spheroidization Process Using a Small Power Argon DC-RF Hybrid Plasma Flow System by Helium Mixture

    Science.gov (United States)

    Takana, Hidemasa; Jang, Juyong; Igawa, Junji; Nakajima, Tomoki; Solonenko, Oleg P.; Nishiyama, Hideya

    2011-03-01

    For the further improvement of in-flight alumina spheroidization process with a low-power direct-current radiofrequency (DC-RF) hybrid plasma flow system, the effect of a small amount of helium gas mixture in argon main gas and also the effect of increasing DC nozzle diameter on powder spheroidization ratio have been experimentally clarified with correlating helium gas mixture percentage, plasma enthalpy, powder in-flight velocity, and temperature. The alumina spheroidization ratio increases by helium gas mixture as a result of enhancement of plasma enthalpy. The highest spheroidization ratio is obtained by 4% mixture of helium in central gas with enlarging nozzle diameter from 3 to 4 mm, even under the constant low input electric power given to a DC-RF hybrid plasma flow system.

  2. The application of thermal solar energy to high temperature processes: case study of the synthesis of alumina from boehmite.

    Science.gov (United States)

    Padilla, Isabel; López-Delgado, Aurora; López-Andrés, Sol; Álvarez, Marta; Galindo, Roberto; Vazquez-Vaamonde, Alfonso J

    2014-01-01

    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(-2) which 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.

  3. The Application of Thermal Solar Energy to High Temperature Processes: Case Study of the Synthesis of Alumina from Boehmite

    Directory of Open Access Journals (Sweden)

    Isabel Padilla

    2014-01-01

    Full Text Available 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−2 which 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.

  4. Synthesis of nano γ-alumina by the solvothermal technique

    International Nuclear Information System (INIS)

    Meor Yusoff Meor Sulaiman; Masliana Muslimin

    2006-01-01

    The paper describes work done on synthesis of γ-alumina by using the solvo thermal technique. Synthesis of γ-alumina involves the transition reactions of the aluminium hydroxide into alumina by a dehydroxylation process. As there are many forms of transition aluminas produced during this process, a x-ray diffraction (XRD) technique was used to identify γ-alumina and the other forms of alumina. After establishing the optimum conditions for the production of a single-phase γ-alumina, characteristic study on the product was performed. An important parameter in establishing nanosized powders is their crystallite size and analysis of the γ-alumina shows that it is a nanosized powder with a size of 28 nm. Other properties analysed include morphology, surface area and particle size. (Author)

  5. alumina solid electrolyte

    Indian Academy of Sciences (India)

    -β/β -alumina ceramics come from two parent phases designated as β-alumina and β ..... Acknowledgements. This work was supported by the Energy Efficiency & ... of Trade, Industry & Energy, Republic of Korea (No. 20142010102460).

  6. Produção e caracterização de espumas de alumina pelo processo gelcasting sem controle atmosférico Production and characterization of alumina foams by the gelcasting process without atmospheric contro

    Directory of Open Access Journals (Sweden)

    E. de Sousa

    2009-06-01

    Full Text Available O processo de gelcasting, associado à aeração de suspensões cerâmicas, permite a produção de espumas cerâmicas com uma ampla faixa de porosidade (50-90vol.%. Uma das etapas críticas do processo é o enrijecimento da espuma, o qual se baseia na gelificação por meio da polimerização in situ de monômeros previamente adicionados à suspensão cerâmica. Sabidamente, tal reação é inibida pela presença de oxigênio, o que tornou usual o controle atmosférico durante a produção e gelificação da espuma. Neste trabalho, estudou-se a viabilidade de produzir espumas de alumina pelo processo de gelcasting sem controle atmosférico. Para a produção das espumas, dois diferentes agentes espumantes foram testados. As propriedades físicas e mecânicas das espumas cerâmicas, bem como a microestrutura, foram avaliadas e comparadas com resultados obtidos em condições idênticas, porém com controle atmosférico. Os resultados mostraram que ambos os processos proporcionam características semelhantes e com potencial de aplicação tecnológica.The gelcasting process with the aeration of ceramic suspensions allows the production of ceramic foams with a wide range of porosity (50-90vol.%.. One of the critical steps of the process is the setting of the foam, which is based on a gelling reaction by the in-situ polymerization of monomers previously added in the ceramic suspension. This reaction is inhibited by the presence of oxygen, which requires atmospheric control for the stabilization of the foam. In this work, the feasibility of producing alumina foams by the gelcasting process without atmospheric control was studied. For the foams production, two different foaming agents were tested. The physical and mechanical properties of ceramic foams, as well the microstructure, were evaluated and compared with those produced with the same foaming agents but with atmospheric control. The results obtained using the two procedures were similar and

  7. Dynamic tensile response of alumina-Al composites

    International Nuclear Information System (INIS)

    Atisivan, R.; Bandyopadhyay, A.; Gupta, Y. M.

    2002-01-01

    Plate impact experiments were carried out to examine the high strain-rate tensile response of alumina-aluminum (Al) composites with tailored microstructures. A novel processing technique was used to fabricate interpenetrating phase alumina-aluminum composites with controlled microstructures. Fused deposition modeling (FDM), a commercially available rapid prototyping technique, was used to produce the controlled porosity mullite ceramic preforms. Alumina-Al composites were then processed via reactive metal infiltration of porous mullite ceramics. With this approach, both the micro as well as the macro structures can be designed via computer aided design (CAD) to tailor the properties of the composites. Two sets of dynamic tensile experiments were performed. In the first, the metal content was varied between 23 and 39 wt. percent. In the second, the microstructure was varied while holding the metal content nearly constant. Samples with higher metal content, as expected, displayed better spall resistance. For a given metal content, samples with finer metal diameter showed better spall resistance. Relationship of the microstructural parameters on the dynamic tensile response of the structured composites is discussed here

  8. Porous Alumina Films with Width-Controllable Alumina Stripes

    Directory of Open Access Journals (Sweden)

    Huang Shi-Ming

    2010-01-01

    Full Text Available Abstract Porous alumina films had been fabricated by anodizing from aluminum films after an electropolishing procedure. Alumina stripes without pores can be distinguished on the surface of the porous alumina films. The width of the alumina stripes increases proportionally with the anodizing voltage. And the pores tend to be initiated close to the alumina stripes. These phenomena can be ascribed to the electric field distribution in the alumina barrier layer caused by the geometric structure of the aluminum surface.

  9. Porous Alumina Films with Width-Controllable Alumina Stripes

    Science.gov (United States)

    2010-01-01

    Porous alumina films had been fabricated by anodizing from aluminum films after an electropolishing procedure. Alumina stripes without pores can be distinguished on the surface of the porous alumina films. The width of the alumina stripes increases proportionally with the anodizing voltage. And the pores tend to be initiated close to the alumina stripes. These phenomena can be ascribed to the electric field distribution in the alumina barrier layer caused by the geometric structure of the aluminum surface. PMID:21170406

  10. Molybdenum adsorption by alumina and Dowex 1x8 resin for the separation and purification process of fission {sup 99}Mo

    Energy Technology Data Exchange (ETDEWEB)

    Yamaura, M.; Damasceno, M.O.; Freitas, A.A.; Camilo, R.L.; Araujo, I.C.; Forbicini, C.A.L.G. de O., E-mail: myamaura@ipen.b, E-mail: molidam@ipen.b, E-mail: afreitas@ipen.b, E-mail: rcamilo@ipen.b, E-mail: cruz.araujo@uol.com.b, E-mail: cforbici@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2011-07-01

    Molybdenum-99 is the most widely employed radioisotope in nuclear medicine, due to its decay product, Technetium-99m, a radioisotope used in over 80% of diagnostic tests. Since 2009, the production of generators {sup 99}Mo/{sup 99m}Tc suffers a crisis of global supply. The raw material, the {sup 99}Mo, is produced mainly by fission of {sup 235}U in the reactor in uranium targets. Brazilian government invests in building of a research reactor suitable for the domestic production of {sup 99}Mo from LEU (Low Enriched Uranium) targets and the IPEN/CNEN develops the production technology. This work is part of the research for the development of production technology of {sup 99}Mo at the IPEN/CNEN-SP. The study has evaluated the adsorption behaviour of molybdenum from the alkaline dissolution of aluminum plates by the alumina and by the anionic resin Dowex 1x8 aiming at their use in the process of separation and purification in chromatography columns. Influences of pH and of aluminum concentration in the retention of molybdenum were investigated. Results showed high performance in the wide pH range. However in strongly acid solutions containing aluminum, alumina showed higher adsorption percentage than that achieved by the resin Dowex 1x8. (author)

  11. Preparation of micro-fibrillated cellulose from sorghum fibre through alkalization and acetylation treatments

    Science.gov (United States)

    Ismojo; Simanulang, P. H.; Zulfia, A.; Chalid, M.

    2017-07-01

    Recently, the pollution due to non-degradable materials including plastics, has led to needs on the development of environmental-friendly material. Owing to its biodegradability nature, sorghum fibres are interesting to be modified with petro-polymer as a composite. These materials are also expected to reduce the impact of environmental pollution. Surface modification of sorghum through chemical treatment was aimed to enhanced crystalline part of micro-fibrillated cellulose, thus increased compatibility to petro-polymer, as mean to improve composite properties. The experiments were conducted by alkalization process (10% NaOH) followed by acetylation with acetic acid glacial and acetic anhydride (CH3CO2)2 with additions of 1 and 2 drops of 25% H2SO4. Fourier transform infra-red (FTIR) spectroscopy, field-emission scanning electron microscope (FE-SEM) and x-ray diffraction (XRD) were used to characterize the treated and untreated fibres. The results of investigation showed that the chemical treatments have effectively produced MFC with the smallest fibre size around 5.5 - 6.5 microns and reduced lignin and hemicellulose where the highest crystalline part up to 80.64% was obtained through acetate acid treatment of 17.4 M, followed acetic anhydride with 1 drop of H2SO4 addition. Based on the current results, it is promising that the synthesized composites can be improved for their compatibilities.

  12. A transitional alkalic dolerite dike suite of Mesozoic age in Southeastern New England

    Science.gov (United States)

    Hermes, O. Don; Rao, J. M.; Dickenson, M. P.; Pierce, T. A.

    1984-12-01

    Dike rocks from the New England platform of Rhode Island and adjacent Massachusetts consist of premetamorphic and post-metamorphic suites. The older group includes metamorphosed dolerite, minette, and schistose dioritic rocks. Post-metamorphic dikes consist of dolerite and sparse monchiquite. The post-metamorphic dolerites are of comparable age to the Eastern North American dolerite suite associated with the Mesozoic basins along the eastern seaboard of North America. However, the southeastern New England dolerites exhibit mineralogy and chemistry more typical of a transitional alkalic suite compared to the more subalkalic tholeiitic dolerites of the Eastern North American suite. Both suites are compatible with a rift tectonic setting, but the more alkalic dolerites may represent a deeper source of small volume melts compared to the Eastern North American dolerites. These more alkaline melts may have concentrated at local centers, or they may be typical of flank dolerites as opposed to the less alkalic varieties that occur within the central axial rift.

  13. Petrology and age of alkalic lava from the Ratak Chain of the Marshall Islands

    Science.gov (United States)

    Davis, A.S.; Pringle, M.S.; Pickthorn, L.-B.G.; Clague, D.A.; Schwab, W.C.

    1989-01-01

    Volcanic rock dredged from the flanks of four volcanic edifices in the Ratak chain of the Marshall Islands consist of alkalic lava that erupted above sea level or in shallow water. Compositions of recovered samples are predominantly differentiated alkalic basalt and hawaiite but include strongly alkalic melilitite. Whole rock 40Ar/39Ar total fusion and incremental heating ages of 87.3 ?? 0.6 Ma and 82.2 ?? 1.6 Ma determined for samples from Erikub Seamount and Ratak Guyot, respectively, are within the range predicted by plate rotation models but show no age progression consistent with a simple hot spot model. Variations in isotopic and some incompatible element ratios suggest interisland heterogeneity. -from Authors

  14. Study of the molybdenum retention in alumina

    International Nuclear Information System (INIS)

    Wilkinson, Maria V.; Mondino, Angel V.; Manzini, Alberto

    2002-01-01

    The Argentine National Atomic Energy Commission routinely produces 99 Mo by fission of highly enriched uranium contained in targets irradiated in RA-3 reactor. The current process begins with the dissolution of the irradiated target in a basic media, considering the possibility of changing the targets, it could be convenient to dissolve them in acid media. The use of alumina as a first separation step in acid dissolution processes is already known although it is necessary to determine both the type of alumina to be used and the separation conditions. The study of molybdenum retention in alumina was performed at laboratory scale, using Mo-99 as radiotracer. Different kinds of alumina were tried, varying charge solution acidity. Influence of uranium concentration in the loading solution on molybdenum retention was also studied. (author)

  15. Everlasting Dark Printing on Alumina by Laser

    Science.gov (United States)

    Penide, J.; Quintero, F.; Arias-González, F.; Fernández, A.; del Val, J.; Comesaña, R.; Riveiro, A.; Lusquiños, F.; Pou, J.

    Marks or prints are needed in almost every material, mainly for decorative or identification purposes. Despite alumina is widely employed in many different industries, the need of printing directly on its surface is still a complex problem. In this sense, lasers have largely demonstrated their high capacities to mark almost every material including ceramics, but performing dark permanent marks on alumina is still an open challenge. In this work we present the results of a comprehensive experimental analysis on the process of marking alumina by laser. Four different laser sources were used in this study: a fiber laser (1075 nm) and three diode pumped Nd:YVO4 lasers emitting at near-infrared (1064 nm), visible (532 nm) and ultraviolet (355 nm) wavelengths, respectively. The results obtained with the four lasers were compared and physical processes involved were explained in detail. Colorimetric analyses allowed to identify the optimal parameters and conditions to produce everlasting and high contrast marks on alumina.

  16. Tungsten metallizing alumina--yttria ceramics

    International Nuclear Information System (INIS)

    Cowan, R.E.; Stoddard, S.D.

    1977-03-01

    The ease with which high-alumina bodies may be metallized with tungsten is improved by additions of yttria to the alumina. Mechanisms of this bonding process were studied by use of optical and electron microscopy, electron microprobe, and tensile tests. Variables studied included yttria content of the body and the firing temperature during metallizing. The study showed that a reaction between the tungsten and the yttrogarnet grain boundary phase markedly improved adherence

  17. Bauxite Mining and Alumina Refining

    OpenAIRE

    Donoghue, A. Michael; Frisch, Neale; Olney, David

    2014-01-01

    Objective: To describe bauxite mining and alumina refining processes and to outline the relevant physical, chemical, biological, ergonomic, and psychosocial health risks. Methods: Review article. Results: The most important risks relate to noise, ergonomics, trauma, and caustic soda splashes of the skin/eyes. Other risks of note relate to fatigue, heat, and solar ultraviolet and for some operations tropical diseases, venomous/dangerous animals, and remote locations. Exposures to bauxite dust,...

  18. Fabrication of Meso-Porous Gamma-Alumina Films by Sol-Gel and Gel Casting Processes for Making Moisture Sensors

    Directory of Open Access Journals (Sweden)

    Kalyan Kumar Mistry

    2007-04-01

    Full Text Available Meso-porous g-Al2O3 film may be used as a highly sensitive trace moisture sensor. The crack-free alumina film was developed using a combination of sol-gel and tape casting processes, which produce high porosity, high surface area and small pore dimensions in the range of few nano-meter at uniform distribution. Sol-gel processes are well known in nano-technology and nano-material preparation, but it is difficult to make crack-free thick or thin films using this method. Tape cast methods are used for the fabrication of flexible crack-free thick ceramic sheets. Our objective was to develop nano-structured, crack-free, transparent Al2O3 film a few microns thick, has a highly porous and stable crystallographic nature. A metallic paste was printed by screen printing on both side of the film surface for electrodes to form a sensitive element. A silver wire (dia j=0.1mm lead was connected to a grid structure electrode using a silver paste spot for fine joining. Alumina is absorbs moisture molecules into its meso-porous layer and changes its electrical characteristics according to the moisture content, its dielectric constant increase as moisture increase. Moisture molecules can be conceived of as dipoles in random state before the application of an electric field. When the dipole orientation was changed from random to an equilibrium state under the application of external field, a large change in dielectric constant was observed. The number of water molecules absorbed determines the electrical impedance of the capacitor, which in turn is proportional to water vapor pressure.

  19. Geochemistry of tholeiitic and alkalic lavas from the Koolau Range, Oahu, Hawaii

    International Nuclear Information System (INIS)

    Roden, M.F.; Frey, F.A.

    1984-01-01

    Lavas of the post-erosional, alkalic Honolulu Volcanics have significantly lower 87 Sr/ 86 Sr and higher 143 Nd/ 144 Nd than the older and underlying Koolau tholeiites which form the Koolau shield of eastern Oahu, Hawaii. Despite significant compositional variation within lavas forming the Honolulu Volcanics, these lavas are isotopically (Sr, Nd, Pb) very similar which contrasts with the isotopic heterogeneity of the Koolau tholeiites. Among Hawaiian tholeiitic suites, the Koolau lavas are geochemically distinct because of their lower iron contents and Sr and Nd isotopic ratios which range to bulk earth values. These geochemical data preclude simple models such as derivation of the Honolulu Volcanics and Koolau tholeiites from a common source by different degrees of melting or by mixing of two geochemically distinct sources. There may be no genetic relationship between the origin and evolution of these two lava suites; however, the trend shown by Koolau Range lavas of increasing 143 Nd/ 144 Nd and decreasing 87 Sr/ 86 Sr with decreasing eruption age and increasing alkalinity also occurs at Haleakala, East Molokai and Kauai volcaneoes. A complex mixing model proposed for Haleakala lavas can account for the variations in Sr and Nd isotopic ratios and processes occurring during ascent of relatively enriched mantle through relatively depleted MORB-related lithosphere. Although two isotopically distinct components may be sufficient to explain Sr and Nd isotopic variations at individual Hawaiian volcaneoes, more than two isotopically distinct materials are required to explain variations of Sr, Nd and Pb isotopic ratios in all Hawaiian lavas. (orig.)

  20. The mineralogy of bauxite for producing smelter-grade alumina

    Science.gov (United States)

    Authier-Martin, M.; Forte, G.; Ostap, S.; See, J.

    2001-12-01

    Aluminum-producing companies rely on low-cost, high-purity, smelter-grade alumina (aluminum oxide), and alumina production utilizes the bulk of bauxites mined world-wide. The mineralogy of the bauxites has a significant impact on the operation of the Bayer process for alumina production. Typically, the Bayer process produces smelter-grade alumina of 99.5% Al2O3, starting from bauxite containing 30% to 60% Al2O3. The main objective of the Bayer process is to extract the maximum amount of aluminum from the bauxite at as high an aluminate concentration in solution as possible, while limiting any troublesome side reactions. Only with a better understanding of the chemistry of the mineral species and a strict control of the operating/processing conditions can the Bayer process produce efficiently, a low cost, high-quality alumina with minimum detrimental environmental impact.

  1. High contrast laser marking of alumina

    International Nuclear Information System (INIS)

    Penide, J.; Quintero, F.; Riveiro, A.; Fernández, A.; Val, J. del; Comesaña, R.; Lusquiños, F.; Pou, J.

    2015-01-01

    Highlights: • Laser marking of alumina using near infrared (NIR) lasers was experimentally analyzed. • Color change produced by NIR lasers is due to thermally induced oxygen vacancies. • Laser marking results obtained using NIR lasers and green laser are compared. • High contrast marks on alumina were achieved. - Abstract: Alumina serves as raw material for a broad range of advanced ceramic products. These elements should usually be identified by some characters or symbols printed directly on them. In this sense, laser marking is an efficient, reliable and widely implemented process in industry. However, laser marking of alumina still leads to poor results since the process is not able to produce a dark mark, yielding bad contrast. In this paper, we present an experimental study on the process of marking alumina by three different lasers working in two wavelengths: 1064 nm (Near-infrared) and 532 nm (visible, green radiation). A colorimetric analysis has been carried out in order to compare the resulting marks and its contrast. The most suitable laser operating conditions were also defined and are reported here. Moreover, the physical process of marking by NIR lasers is discussed in detail. Field Emission Scanning Electron Microscopy, High Resolution Transmission Electron Microscopy and X-ray Photoelectron Spectroscopy were also employed to analyze the results. Finally, we propose an explanation for the differences of the coloration induced under different atmospheres and laser parameters. We concluded that the atmosphere is the key parameter, being the inert one the best choice to produce the darkest marks

  2. Pt/Au nanoalloy supported on alumina and chlorided alumina: DFT and experimental analysis

    Science.gov (United States)

    Sharifi, N.; Falamaki, C.; Ghorbanzadeh Ahangari, M.

    2018-04-01

    Density functional theory (DFT) was used to explore the adsorption of Pt/Au nanoalloy onto a pure and chlorided γ-Al2O3(110) surface, which has been applied in numerous catalytic reactions. First, we considered the adsorption properties of Pt clusters (n ≤ 5) onto the Al2O3(110) surface to determine the most stable Pt cluster on alumina surface in reforming processes. After full structural relaxations of Pt clusters at various configurations on alumina, our computed results expressed that the minimum binding energy (‑5.67 eV) is accrued for Pt4 cluster and the distance between the nearest Pt atom in the cluster to the alumina surface is equal to 1.13 Å. Then, we investigated the binding energies, geometries, and electronic properties of adsorbed Aun clusters (n ≤ 6) on the γ-Al2O3(110) surface. Our studied showed that Au5 was the most thermodynamically stable structure on γ-Al2O3. Finally, we inspected these properties for adsorbed Au clusters onto the Pt4-decorated alumina (Aun/Pt4-alumina) system. The binding energy of the Au4/Pt4-alumina system was ‑5.01 eV, and the distance between Au4 cluster and Pt4-alumina was 1.33 Å. The Au4/Pt4alumina system was found to be the most stable nanometer-sized catalyst design. At last, our first-principles calculations predicted that the best position of embedment Cl on the Au4/Pt4-alumina.

  3. High-flux MFI-alumina hollow fibres: a membrane-based process for on-board CO2 capture from internal combustion vehicles

    International Nuclear Information System (INIS)

    Nicolas, C.H.

    2011-01-01

    This work focuses on the conception and development of a membrane-based process for an on-board CO 2 capture/storage application. In a first part, we simulate an on-board CO 2 capture unit based on a membrane process for the case study of a heavy vehicle (≥3500 kg). This study includes an energy analysis of the impact of gas separation and compression on the required membrane surface and module volume, as well the autonomy of the storage unit and the energy overconsumption involved in the process. In a second part, we study the influence of the hollow-fibre support quality on the final intergrowth level of nano-composite MFI-alumina membranes. Special attention is devoted to the influence of the isomorphic substitution of silica by boron and germanium, and replacement of the counter-cation (proton) by other elements, on the CO 2 /N 2 separation and permeance properties. Next, a complete chapter has been devoted to the evaluation of the thermodynamic (adsorption) and kinetic (diffusion) parameters in the CO 2 /N 2 separation. Finally, we analyze the influence of standard pollutants (water, NO x , hydrocarbons) on the CO 2 separation properties of the synthesized membranes. (author)

  4. [Circadian rhythms of acid production and alkalization in the stomach of healthy subjects and duodenal ulcer patients].

    Science.gov (United States)

    Kolesnikova, I Iu; Beliaeva, G S; Leint'eva, V A; Smirnova, A A

    2008-01-01

    We studied 24-h rhythms of acid production and alkalization in 30 patients with duodenal ulcer (DU) and 30 healthy subjects using upper endoscopic examination and computer intragastric pH-metry. Gastric acid production was higher in DU patients and was more intensive in the daytime than at night. Healthy subjects had low and monotonous acid production. In DU decompensation of alkalization in the antral stomach and suppression of duodenogastric reflux is total. In healthy subjects antrum alkalization is more evident and intensive at night due to, among other causes, duodenogastric reflux.

  5. Preparation of alumina-β'

    International Nuclear Information System (INIS)

    Casarini, J.R.; Souza, D.P.F.

    1984-01-01

    Alumina - (β + β') in powder, with composition of 8.85% Na 2 0 + 0.75% Li 2 0 + 90.40% Al 2 O 3 is obtained using the zeta process. The phase transformation β→β' can be seen with powder X-ray diffraction. It was observed that the efficiency of the transformation is related to the processing and purity of the raw material. Impurities as Ca and Si difficult the phase transformation β→β'. (E.G.) [pt

  6. Study on alumina-alumina brazing for application in vacuum chambers of proton synchrotron

    International Nuclear Information System (INIS)

    Yadav, D.P.; Kaul, R.; Ganesh, P.; Shiroman, Ram; Tiwari, Pragya; Sridhar, R.; Kukreja, L.M.

    2013-01-01

    The paper describes an experimental study to standardize vacuum brazing process to obtain satisfactory high purity alumina brazed joints for application in rapid cycle proton synchrotron machine. Two different brazing routes, adopted for making alumina-alumina brazed joints, included (i) multi-step Mo-Mn metallization and brazing with BVAg-8 alloy and (ii) advanced single-step active brazing with CuSil-ABA alloy. Brazed alumina specimens, prepared by both the routes, yielded ultra high vacuum compatible, helium leak tight and bakeable joints. Active-brazed specimens exhibited satisfactory strength values in tensile and four-point bend tests. Metallized-brazed specimens, although exhibited relatively lower tensile strength than the targeted value, displayed satisfactory flexural strength in four-point bend test. The results of the study demonstrated that active brazing is the simple and cost effective alternative to conventional metallization route for producing satisfactory brazed joints for application in rapid cycle proton synchrotron machine. (author)

  7. Characterization of silane coated hollow sphere alumina-reinforced

    Indian Academy of Sciences (India)

    Silane coated hollow sphere alumina ceramic particles were moulded with ultra high molecular weight polyethylene (UHMWPE) to form a series of composites with alumina weight percent in the range from 15 to 50. The composites were prepared in a cylindrical mould using powder-processing technique. The composites ...

  8. Alkalization of irrigated soils suitable for orchard growing in steppe Crimea and prospects for their use

    Science.gov (United States)

    Klimenko, O. E.

    2016-10-01

    Data of large-scale soil surveys performed by the Ukrgiprosad Institute (Ukrainian Institute for Orchard Growing) in 1997-2013 on irrigated soils of steppe Crimea reserved for orchards on the area of about 3000 ha are discussed. It is shown that all the studied soils are subjected to alkalization with the presence of soda and with an increase in concentrations of sodium and magnesium bicarbonates up to the values toxic for fruit crops. The concentrations and occurrence frequencies of alkaline salts depend on the soil type, the presence of solonetzic features, the amount of carbonates, the particular depth in the soil profile, the subsoiling, and other factors. Within the studied area, some soils are unsuitable or partly suitable for orchard growing. To improve the soil conditions for orchard growing in the areas subjected to alkalization, alkaline salts should be neutralized to nontoxic level, and the soil alkalinity should be reduced using chemical reclamation methods.

  9. High alumina refractories

    International Nuclear Information System (INIS)

    Simao, L.C.; Lopes, A.B.; Galvao Filho, N.B.; Souza, R.B. de

    1989-01-01

    High alumina refractories with 92 to 96.5% Al 2 O 3 were produced using brown and white fused as aggregate. Those refractories present only alumina-α and mullite as crystalline mineralogical phase. Other physical and chemical characteristics are similar to the ones found in refractories produced in Brazil, Japan and U.S.A. The most important physical and chemical tests used for the characterization of the raw materials and refractories, complemented by those realized at high temperatures, plus X-ray Difractometry and optical microscopy are presented, besides the refractory formulation and main parameters of production [pt

  10. Advancement of In-Flight Alumina Powder Spheroidization Process with Water Droplet Injection Using a Small Power DC-RF Hybrid Plasma Flow System

    Science.gov (United States)

    Jang, Juyong; Takana, Hidemasa; Park, Sangkyu; Nishiyama, Hideya

    2012-09-01

    The correlation between plasma thermofluid characteristics and alumina powder spheroidization processes with water droplet injection using a small power DC-RF hybrid plasma flow system was experimentally clarified. Micro-sized water droplets with a low water flow rate were injected into the tail of thermal plasma flow so as not to disturb the plasma flow directly. Injected water droplets were vaporized in the thermal plasma flow and were transported upstream in the plasma flow to the torch by the backflow. After dissociation of water, the production of hydrogen was detected by the optical emission spectroscopy in the downstream RF plasma flow. The emission area of the DC plasma jet expanded and elongated in the vicinity of the RF coils. Additionally, the emission area of RF plasma flow enlarged and was visible as red emission in the downstream RF plasma flow in the vicinity below the RF coils due to hydrogen production. Therefore, the plasma flow mixed with produced hydrogen increased the plasma enthalpy and the highest spheroidization rate of 97% was obtained at a water flow rate of 15 Sm l/min and an atomizing gas flow rate of 8 S l/min using a small power DC-RF hybrid plasma flow system.

  11. Gelcasting polycrystalline alumina

    Energy Technology Data Exchange (ETDEWEB)

    Janney, M.A. [Oak Ridge National Lab., TN (United States)

    1997-04-01

    This work is being done as part of a CRADA with Osram-Sylvania, Inc. (OSI) OSI is a major U.S. manufacturer of high-intensity lighting. Among its products is the Lumalux{reg_sign} line of high-pressure sodium vapor arc lamps, which are used for industrial, highway, and street lighting. The key to the performance of these lamps is the polycrystalline alumina (PCA) tube that is used to contain the plasma that is formed in the electric arc. That plasma consists of ionized sodium, mercury, and xenon vapors. The key attributes of the PCA tubes are their transparency (95% total transmittance in the visible region), their refractoriness (inner wall temperature can reach 1400{degrees}C), and their chemical resistance (sodium and mercury vapor are extremely corrosive). The current efficiency of the lamps is very high, on the order of several hundred lumens / watt. (Compare - incandescent lamps -13 lumens/watt fluorescent lamps -30 lumens/watt.) Osram-Sylvania would like to explore using gelcasting to form PCA tubes for Lumalux{reg_sign} lamps, and eventually for metal halide lamps (known as quartz-halogen lamps). Osram-Sylvania, Inc. currently manufactures PCA tubes by isostatic pressing. This process works well for the shapes that they presently use. However, there are several types of tubes that are either difficult or impossible to make by isostatic pressing. It is the desire to make these new shapes and sizes of tubes that has prompted Osram-Sylvania`s interest in gelcasting. The purpose of the CRADA is to determine the feasibility of making PCA items having sufficient optical quality that they are useful in lighting applications using gelcasting.

  12. Alumina Technology Roadmap

    Energy Technology Data Exchange (ETDEWEB)

    none,

    2002-02-01

    The Alumina Technology Roadmap outlines a comprehensive long-term research and development plan that defines the industry's collective future and establishes a clear pathway forward. It emphasizes twelve high-priority R&D areas deemed most significant in addressing the strategic goals.

  13. Tritium compatibility of alumina and Fosterite

    Energy Technology Data Exchange (ETDEWEB)

    Coffin, D.O.

    1979-09-01

    Many pressure measurements are required to control processing of the fuel gases associated with fusion power reactors. Since most pressure transducers respond to changes in pressure sensitive electrical parameters, insulators will be required to withstand chronic exposures to concentrated tritium. For this investigation samples of alumina and Fosterite were exposed to concentrated tritium gas for 11 weeks. Gas phase impurities were then analyzed for clues that would indicate decomposition of the exposed materials. The only gaseous impurity resulting from these tritium exposures was tritio-methane, which is always produced when tritium is stored in stainless steel containers. There was no evidence that either alumina or Fosterite decomposed in the presence of tritium.

  14. Characterization and sintering of niobium-ATR alumina

    International Nuclear Information System (INIS)

    Sibuya, N.H.; Iwasaki, H.; Suzuki, C.K.; Pinatti, D.G.

    1987-01-01

    In the niobium aluminothermy a slag is produced, composed mostly of alumina and other compounds such as niobium oxide and silica. The phase composition of this ATR alumina was characterized by X-ray powder diffractometry, and afterwards this alumina was subjected to leaching processes. It was noticed that the original content of 70% α-alumina in slag rose to 95% after the calcination. ATR alumina (leached and calcined, and without any treatment) was used to make pressed bodies which were fired in air at 1200 to 1400 0 C for 1 to 10,5 hours; and in vacuum at 1550 to 1800$0C for 2 hours. Characterization was done by density measurements, X-ray diffractometry and ultrasonic analysis. Ultrasonic analysis of some vacuum fired bodies showed londitudinal velocities close to the value found in literature. Correlation of several techniques measurements disclosed the niobium oxide interference in sintering. (Author) [pt

  15. Enhanced 400-m sprint performance in moderately trained participants by a 4-day alkalizing diet: a counterbalanced, randomized controlled trial.

    Science.gov (United States)

    Limmer, Mirjam; Eibl, Angi Diana; Platen, Petra

    2018-05-31

    Sodium bicarbonate (NaHCO 3 ) is an alkalizing agent and its ingestion is used to improve anaerobic performance. However, the influence of alkalizing nutrients on anaerobic exercise performance remains unclear. Therefore, the present study investigated the influence of an alkalizing versus acidizing diet on 400-m sprint performance, blood lactate, blood gas parameters, and urinary pH in moderately trained adults. In a randomized crossover design, eleven recreationally active participants (8 men, 3 women) aged 26.0 ± 1.7 years performed one trial under each individual's unmodified diet and subsequently two trials following either 4 days of an alkalizing (BASE) or acidizing (ACID) diet. Trials consisted of 400-m runs at intervals of 1 week on a tartan track in a randomized order. We found a significantly lower 400-m performance time for the BASE trial (65.8 ± 7.2 s) compared with the ACID trial (67.3 ± 7.1 s; p = 0.026). In addition, responses were significantly higher following the BASE diet for blood lactate (BASE: 16.3 ± 2.7; ACID: 14.4 ± 2.1 mmol/L; p = 0.32) and urinary pH (BASE: 7.0 ± 0.7; ACID: 5.5 ± 0.7; p = 0.001). We conclude that a short-term alkalizing diet may improve 400-m performance time in moderately trained participants. Additionally, we found higher blood lactate concentrations under the alkalizing diet, suggesting an enhanced blood or muscle buffer capacity. Thus, an alkalizing diet may be an easy and natural way to enhance 400-m sprint performance for athletes without the necessity of taking artificial dietary supplements.

  16. Prediction and optimization of process variables to maximize the Young's modulus of plasma sprayed alumina coatings on AZ31B magnesium alloy

    Directory of Open Access Journals (Sweden)

    D. Thirumalaikumarasamy

    2017-03-01

    Full Text Available Like other manufacturing techniques, plasma spraying has also a non-linear behavior because of the contribution of many coating variables. This characteristic results in finding optimal factor combination difficult. Subsequently, the issue can be solved through effective and strategic statistical procedures integrated with systematic experimental data. Plasma spray parameters such as power, stand-off distance and powder feed rate have significant influence on coating characteristics like Young's modulus. This paper presents the use of statistical techniques in specifically response surface methodology (RSM, analysis of variance, and regression analysis to develop empirical relationship to predict Young's modulus of plasma-sprayed alumina coatings. The developed empirical relationships can be effectively used to predict Young's modulus of plasma-sprayed alumina coatings at 95% confidence level. Response graphs and contour plots were constructed to identify the optimum plasma spray parameters to attain maximum Young's modulus in alumina coatings. A linear regression relationship was established between porosity and Young's modulus of the alumina coatings.

  17. Activated alumina preparation and characterization: The review on recent advancement

    Science.gov (United States)

    Rabia, A. R.; Ibrahim, A. H.; Zulkepli, N. N.

    2018-03-01

    Aluminum and aluminum based material are significant industrial materials synthesis because of their abandonment, low weight and high-quality corrosion resistance. The most advances in aluminum processing are the ability to synthesize it's under suitable chemical composition and conditions, a porous structure can be formed on the surface. Activated alumina particles (AAP) synthesized by the electrochemically process from aluminum have gained serious attention, inexpensive material that can be employed for water filtration due to its active surface. Thus, the paper present a review study based on recent progress and advances in synthesizing activated alumina, various techniques currently being used in preparing activated alumina and its characteristics are studied and summarized

  18. Method for nanomodulation of metallic thin films following the replica-antireplica process based on porous alumina membranes

    Energy Technology Data Exchange (ETDEWEB)

    Palma, J.L. [Departamento de Ciencias Básicas, Facultad de Ingeniería, Universidad Central de Chile, Santa Isabel 1186, 8330601 Santiago (Chile); Center for the Development of Nanoscience and Nanotechnology (CEDENNA), 9170124 Santiago (Chile); Denardin, J.C.; Escrig, J. [Departamento de Física, Universidad de Santiago de Chile (USACH), Avda. Ecuador 3493, 9170124 Santiago (Chile); Center for the Development of Nanoscience and Nanotechnology (CEDENNA), 9170124 Santiago (Chile)

    2017-03-15

    In this paper we have introduced a method for modulation of metallic thin films by sputtering of metals on anodized aluminum templates. Using a high deposition rate during deposition of the non-magnetic metal on the Al pattern, we have separated the two metallic surfaces and, thus, imprinted a pattern of nanohills on a non-magnetic metallic film, such as Au, Ag or Cu. The morphology of the nanostructured metallic films was determined by scanning electron microscopy. Thus, we have confirmed that the ordering degree of the Al template remained after the replication process. Additionally, and as an example of use of these films, we have prepared Supermalloy thin films deposited by sputtering onto these nanostructured non-magnetic metals. The room temperature magnetic behavior of these thin films is also studied. Interestingly, we have found that when the external magnetic field is applied out of plane of the substrate, the coercivity increases linearly as we increase the radius of the nanohills. These soft magnetic films can open new opportunities for magnetic field sensor applications. - Highlights: • A very soft magnetic film is investigated on ordered nanohills. • It is possible to imprint a metallic pattern directly from the etched aluminum foil. • These nanopatterned substrates add an additional degree of freedom. • A method for modulation of metallic thin films.

  19. Uranyl sorption onto alumina

    International Nuclear Information System (INIS)

    Jacobsson, A.M.M.

    1997-01-01

    The mechanism for the adsorption of uranyl onto alumina from aqueous solution was studied experimentally and the data were modeled using a triple layer surface complexation model. The experiments were carried out at low uranium concentrations (9 x 10 -11 --5 x 10 -8 M) in a CO 2 free environment at varying electrolyte concentrations (0.01--1 M) and pH (4.5--12). The first and second acid dissociation constants, pK a1 and pK a2 , of the alumina surface were determined from potentiometric titrations to be 7.2 ± 0.6 and 11.2 ± 0.4, respectively. The adsorption of uranium was found to be independent of the electrolyte concentration. The authors therefore conclude that the uranium binds as an inner sphere complex. The results were modeled using the code FITEQL. Two reactions of uranium with the surface were needed to fit the data, one forming a uranyl complex with a single surface hydroxyl and the other forming a bridged or bidentate complex reacting with two surface hydroxyls of the alumina. There was no evidence from these experiments of site heterogeneity. The constants used for the reactions were based in part on predictions made utilizing the Hard Soft Acid Base, HSAB, theory, relating the surface complexation constants to the hydrolysis of the sorbing metal ion and the acid dissociation constants of the mineral oxide surface

  20. Origin of contemporaneous tholeiitic and K-rich alkalic lavas: A case study from the northern Deccan Plateau, India

    Energy Technology Data Exchange (ETDEWEB)

    Mahoney, J.J.; Macdougall, J.D.; Lugmair, G.W. (Scripps Institution of Oceanography, La Jolla, CA (USA)); Gopalan, K. (Physical Research Lab., Ahmedabad (India)); Krishnamurthy, P. (Atomic Minerals Div., Nagpur (India))

    1985-01-01

    Concurrently erupted, alternating Deccan Trap flows of tholeiitic and potassic alkalic basalt outcrop along both banks of the Narmada River near Navgam. Nearby, around Rajpipla, early tholeiites are overlain by K-rich alkalic flows and intrusives, which are themselves cut by later tholeiitic dikes. Nd and Sr isotopic ratios of a wide variety of rocks from both areas form a single correlated array, which reflects mixing between positive epsilonsub(JUV) and negative epsilonsub(JUV) end members. There is an almost complete overlap between values for tholeiitic and alkalic samples; thus, both alkalic and tholeiitic primary magmas must have been produced that were isotopically much alike. A Rajpipla rhyolite also falls on the array, near the midpoint. For positive values of epsilonsub(JUV)(T) the array is indistinguishable from that defined by the lower group of tholeiites at Mahabaleshwar, some 450 km to the south, implying a similar or identical high epsilonsub(JUV) mantle source. The negative epsilonsub(JUV) component, apparently different from either of the two at Mahabaleshwar, may have been continental crust or enriched mantle. Both alkalic and tholeiitic groups display wide overlapping ranges in incompatible elements other than K, Rb, and Ba - particularly in Sr and Nb. This partial decoupling of incompatible elements, in conjunction with the isotopic similarity between the two classes of rocks, is strongly suggestive of an enrichment event in portions of the mantle source shortly before magmatism.

  1. Enhanced bioreduction synthesis of ethyl (R)-4-chloro-3-hydroybutanoate by alkalic salt pretreatment.

    Science.gov (United States)

    Chong, Ganggang; Di, Junhua; Ma, Cuiluan; Wang, Dajing; Wang, Chu; Wang, Lingling; Zhang, Pengqi; Zhu, Jun; He, Yucai

    2018-08-01

    In this study, biomass-hydrolysate was used for enhancing the bioreduction of ethyl 4-chloro-3-oxobutanoate (COBE). Firstly, dilute alkalic salt pretreatment was attempted to pretreat bamboo shoot shell (BSS). It was found that enzymatic in situ hydrolysis of 20-50 g/L BSS pretreated with dilute alkalic salts (0.4% Na 2 CO 3 , 0.032% Na 2 S) at 7.5% sulfidity by autoclaving at 110 °C for 40 min gave sugar yields at 59.9%-73.5%. Moreover, linear relationships were corrected on solid recovery-total delignification-sugar yield. In BSS-hydrolysates, xylose and glucose could promote the reductase activity of recombinant E. coli CCZU-A13. Compared with glucose, hydrolysate could increase the reductase activity by 1.35-folds. Furthermore, the cyclohexane-hydrolysate (10:90, v/v) biphasic media containing ethylene diamine tetraacetic acid (EDTA, 40 mM) and l-glutamine (150 mM) was built for the effective biosynthesis of ethyl (R)-4-chloro-3-hydroxybutanoate [(R)-CHBE] (94.6% yield) from 500 mM COBE. In conclusion, this strategy has high potential for the effective biosynthesis of (R)-CHBE (>99% e.e.). Copyright © 2018 Elsevier Ltd. All rights reserved.

  2. Efeito do processamento em misturas de alumina/ligantes orgânicos usadas na moldagem por injeção em baixa pressão Effect of processing variables in alumina/organic binders mixtures used in low-pressure injection molding

    Directory of Open Access Journals (Sweden)

    P . A. Ourique

    2013-03-01

    Full Text Available A moldagem por injeção em baixa pressão (MIBP é uma técnica que já vem sendo empregada na produção de peças cerâmicas com formas e geometrias complexas. A homogeneidade da mistura de ligantes orgânicos e pós cerâmicos é um fator determinante que deve ser controlado para minimizar a formação de imperfeições no processamento de feedstocks para MIBP. Defeitos típicos de processamento por MIBP, como bolhas de ar e aglomerados, geram gradientes de densidade nas misturas que, após conformação, possuem poucas possibilidades de remoção. Essas imperfeições comprometem o desempenho dos produtos obtidos por essa técnica. Este trabalho está focado na avaliação dessas heterogeneidades e como elas podem ser correlacionadas com a variação da densidade aparente e com o comportamento reológico dessas misturas. Para tanto, aluminas submicrométricas, como recebida e desaglomerada, foram adicionadas a uma mistura fundida de ligantes a base de parafinas, ceras e aditivos e processada em dois tipos diferentes de misturadores, com e sem o auxílio de vácuo. Foi observada a presença de aglomerados existentes na alumina como recebida, possivelmente gerados durante a etapa de calcinação. Também foi observado que o tipo de misturador e a aplicação ou não de vácuo durante a etapa final do processamento têm grande influência no tempo de mistura necessário para reduzir a viscosidade do feedstock para a injeção.The low-pressure injection molding (LPIM is a technique already being used in the production of ceramic parts with complex shapes and geometries. The homogeneity of the mixture of organic binder and ceramic powder is a determining factor which must be controlled to minimize defects formation while feedstock processing to LPIM. Typical defects of LPIM processing, such as air bubbles and agglomerates, generate density gradients in the mixtures, which, after shaping, have little possibility of removal. These imperfections

  3. Microstructural evolution of alumina-zirconia nanocomposites

    International Nuclear Information System (INIS)

    Ojaimi, C.L.; Chinelatto, A.S.A.; Chinelatto, A.L.; Pallone, E.M.J.A.

    2012-01-01

    Ceramic materials have limited use due to their brittleness. The inclusion of nanosized particles in a ceramic matrix, which are called nanocomposites, and ceramic processing control by controlling the grain size and densification can aid in obtaining ceramic products of greater strength and toughness. Studies showed that the zirconia nano inclusions in the matrix of alumina favors an increase in mechanical properties by inhibiting the grain growth of the matrix and not by the mechanism of the transformation toughening phase of zirconia. In this work, the microstructural evolution of alumina nanocomposites containing 15% by volume of nanometric zirconia was studied. From the results it was possible to understand the sintering process of these nanocomposites. (author)

  4. High contrast laser marking of alumina

    Science.gov (United States)

    Penide, J.; Quintero, F.; Riveiro, A.; Fernández, A.; del Val, J.; Comesaña, R.; Lusquiños, F.; Pou, J.

    2015-05-01

    Alumina serves as raw material for a broad range of advanced ceramic products. These elements should usually be identified by some characters or symbols printed directly on them. In this sense, laser marking is an efficient, reliable and widely implemented process in industry. However, laser marking of alumina still leads to poor results since the process is not able to produce a dark mark, yielding bad contrast. In this paper, we present an experimental study on the process of marking alumina by three different lasers working in two wavelengths: 1064 nm (Near-infrared) and 532 nm (visible, green radiation). A colorimetric analysis has been carried out in order to compare the resulting marks and its contrast. The most suitable laser operating conditions were also defined and are reported here. Moreover, the physical process of marking by NIR lasers is discussed in detail. Field Emission Scanning Electron Microscopy, High Resolution Transmission Electron Microscopy and X-ray Photoelectron Spectroscopy were also employed to analyze the results. Finally, we propose an explanation for the differences of the coloration induced under different atmospheres and laser parameters. We concluded that the atmosphere is the key parameter, being the inert one the best choice to produce the darkest marks.

  5. Characterization of In-Flight Processing of Alumina Powder Using a DC-RF Hybrid Plasma Flow System at Constant Low Operating Power

    Science.gov (United States)

    Nishiyama, H.; Onodera, M.; Igawa, J.; Nakajima, T.

    2009-12-01

    The aim of this study is to provide the optimum operating conditions for enhancing in-flight alumina particle heating as much as possible for particle spheroidization and aggregation of melted particles using a DC-RF hybrid plasma flow system even at constant low operating power based on the thermofluid considerations. It is clarified that the swirl flow and higher operating pressure enhance the particle melting and aggregation of melted particles coupled with increasing gas temperature downstream of a plasma uniformly in the radial direction at constant electrical discharge conditions.

  6. Grinding mechanism of zirconia toughened alumina

    International Nuclear Information System (INIS)

    Tsukuda, A.; Kondo, Y.; Yokota, K.

    1998-01-01

    In the grinding process, physical properties of ceramics affect both grinding mechanism and quality of ground surface. In this study we focused on fracture toughness of ceramics and the effect on grinding. A grinding test was carried out by single point grinding for ten different zirconia toughened alumina ceramics with different monoclinic zirconia contents. Effects of zirconia contents on the grinding mechanism and crack initiation were discussed. Copyright (1998) AD-TECH - International Foundation for the Advancement of Technology Ltd

  7. In-beam dielectric properties of alumina

    International Nuclear Information System (INIS)

    Molla, J.; Ibarra, A.; Hodgson, E.R.

    1995-01-01

    The dielectric properties (permittivity and loss tangent) of a 99.7% purity alumina grade have been measured over a wide frequency range (1 kHz-15 GHz) before and after 2 MeV electron irradiation at different temperatures. The dielectric properties at 15 GHz were measured during irradiation. Both prompt and fluence effects are observed together with permanent changes which continue to evolve following irradiation. The behaviour is complex, consistent with both radiation induced electronic effects and aggregation processes. ((orig.))

  8. Rheological Properties of Aqueous Nanometric Alumina Suspensions

    Energy Technology Data Exchange (ETDEWEB)

    Li, Chuanping [Iowa State Univ., Ames, IA (United States)

    2004-01-01

    Colloidal processing is an effective and reliable approach in the fabrication of the advanced ceramic products. Successful colloidal processing of fine ceramic powders requires accurate control of the rheological properties. The accurate control relies on the understanding the influences of various colloidal parameters on the rheological properties. Almost all research done on the rheology paid less attention to the interactions of particle and solvent. However, the interactions of the particles are usually built up through the media in which the particles are suspended. Therefore, interactions of the particle with the media, the adsorbed layers on the particle surface, and chemical and physical properties of media themselves must influence the rheology of the suspension, especially for the dense suspensions containing nanosized particles. Relatively little research work has been reported in this area. This thesis addresses the rheological properties of nanometric alumina aqueous suspensions, and paying more attention to the interactions between particle and solvent, which in turn influence the particle-particle interactions. Dense nanometric alumina aqueous suspensions with low viscosity were achieved by environmentally-benign fructose additives. The rheology of nanometric alumina aqueous suspensions and its variation with the particle volume fraction and concentration of fructose were explored by rheometry. The adsorptions of solute (fructose) and solvent (water) on the nanometric alumina particle surfaces were measured and analyzed by TG/DSC, TOC, and NMR techniques. The mobility of water molecules in the suspensions and its variation with particle volume fractions and fructose additive were determined by the 17O NMR relaxation method. The interactions between the nanometric alumina particles in water and fructose solutions were investigated by AFM. The results indicated that a large number of water layers were physically bound on the particles

  9. Submarine Alkalic Lavas Around the Hawaiian Hotspot; Plume and Non-Plume Signatures Determined by Noble Gases

    Science.gov (United States)

    Hanyu, T.; Clague, D. A.; Kaneoka, I.; Dunai, T. J.; Davies, G. R.

    2004-12-01

    Noble gas isotopic ratios were determined for submarine alkalic volcanic rocks distributed around the Hawaiian islands to constrain the origin of such alkalic volcanism. Samples were collected by dredging or using submersibles from the Kauai Channel between Oahu and Kauai, north of Molokai, northwest of Niihau, Southwest Oahu, South Arch and North Arch volcanic fields. Sites located downstream from the center of the hotspot have 3He/4He ratios close to MORB at about 8 Ra, demonstrating that the magmas erupted at these sites had minimum contribution of volatiles from a mantle plume. In contrast, the South Arch, located upstream of the hotspot on the Hawaiian Arch, has 3He/4He ratios between 17 and 21 Ra, indicating a strong plume influence. Differences in noble gas isotopic characteristics between alkalic volcanism downstream and upstream of the hotspot imply that upstream volcanism contains incipient melts from an upwelling mantle plume, having primitive 3He/4He. In combination with lithophile element isotopic data, we conclude that the most likely source of the upstream magmatism is depleted asthenospheric mantle that has been metasomatised by incipient melt from a mantle plume. After major melt extraction from the mantle plume during production of magmas for the shield stage, the plume material is highly depleted in noble gases and moderately depleted in lithophile elements. Partial melting of the depleted mantle impregnated by melts derived from this volatile depleted plume source may explain the isotopic characteristics of the downstream alkalic magmatism.

  10. Origin and evolution of the Pirituba aluminous calc-alkalic magma, state of Sao Paulo, SE Brazil

    International Nuclear Information System (INIS)

    Wernick, Eberhard

    1999-01-01

    The origin and evolution of the Late Proterozoic calc-alkalic Pirituba magmatism near the city of Sao Paulo, State of Sao Paulo, SE Brazil, are presented and discussed on the basis of geological, petrographic, mineralogical, chemical (rocks and minerals), isotopic and zircon typology data. (author)

  11. Single pyruvate intake induces blood alkalization and modification of resting metabolism in humans.

    Science.gov (United States)

    Olek, Robert A; Luszczyk, Marcin; Kujach, Sylwester; Ziemann, Ewa; Pieszko, Magdalena; Pischel, Ivo; Laskowski, Radoslaw

    2015-03-01

    Three separate studies were performed with the aim to 1) determine the effect of a single sodium pyruvate intake on the blood acid-base status in males and females; 2) compare the effect of sodium and calcium pyruvate salts and establish their role in the lipolysis rate; and 3) quantify the effect of single pyruvate intake on the resting energy metabolism. In all, 48 individuals completed three separate studies. In all the studies, participants consumed a single dose of pyruvate 0.1 g/kg 60 min before commencing the measurements. The whole blood pH, bicarbonate concentration, base excess or plasma glycerol, free fatty acids, glucose concentrations, or resting energy expenditure and calculated respiratory exchange ratio were determined. The analysis of variance for repeated measurements was performed to examine the interaction between treatment and time. The single dose of sodium pyruvate induced blood alkalization, which was more marked in the male than in the female participants. Following the ingestion of sodium or calcium pyruvate, the blood acid-base parameters were higher than in the placebo trial. Furthermore, 3-h postingestion glycerol was lower in both pyruvate trials than in placebo. Resting energy expenditure did not differ between the trials; however, carbohydrate oxidation was increased after sodium pyruvate ingestion. Pyruvate intake induced mild alkalization in a sex-dependent fashion. Moreover, it accelerated carbohydrate metabolism and delayed the rate of glycerol appearance in the blood, but had no effect on the resting energy expenditure. Furthermore, sodium salt seems to have had a greater effect on the blood buffering level than calcium salt. Copyright © 2015 Elsevier Inc. All rights reserved.

  12. Effects of Etching Time and NaOH Concentration on the Production of Alumina Nanowires Using Porous Anodic Alumina Template

    Science.gov (United States)

    Sadeghpour-Motlagh, M.; Mokhtari-Zonouzi, K.; Aghajani, H.; Kakroudi, M. Ghassemi

    2014-06-01

    In this work, two-step anodizing of commercial aluminum foil in acid oxalic solution was applied for producing alumina film. Then the anodic alumina film was etched in sodium hydroxide (NaOH) solution resulting dense and aligned alumina nanowires. This procedure leads to splitting of alumina nanotubes. Subsequently nanowires are produced. The effects of NaOH solution concentration (0.2-1 mol/L) and etching time (60-300 s) at constant temperature on characteristic of nanotubes and produced nanowires were investigated using scanning electron microscopy. The results show that an increase in NaOH solution concentration increases the rate of nanowires production and in turn the manipulation process will be more specific.

  13. Processing, adhesion and electrical properties of silicon steel having non-oriented grains coated with silica and alumina sol-gel

    International Nuclear Information System (INIS)

    Vasconcelos, D.C.L.; Orefice, R.L.; Vasconcelos, W.L.

    2007-01-01

    Silicon steels having non-oriented grains are usually coated with a series of inorganic or organic films to be used in electrical applications. However, the commercially available coatings have several disadvantages that include poor adhesion to the substrates, low values of electrical resistance and degradation at higher temperatures. In this work, silica and alumina sol-gel films were deposited onto silicon steel in order to evaluate the possibility of replacing the commercially available coatings by these sol-gel derived materials. Silica and alumina sol-gel coatings were prepared by dipping silicon steel samples into hydrolyzed silicon or aluminum alkoxides. Samples coated with sol-gel films were studied by scanning electron microscopy, energy dispersive spectroscopy and infrared spectroscopy. Adhesion between silicon steel and sol-gel films was measured by using several standard adhesion tests. Electrical properties were evaluated by the Franklin method. Results showed that homogeneous sol-gel films can be deposited onto silicon steel. Thicknesses of the films could be easily managed by altering the speed of deposition. The structure of the films could also be tailored by introducing additives, such as nitric acid and N,N-dimethyl formamide. Adhesion tests revealed a high level of adhesion between coatings and metal. The Franklin test showed that sol-gel films can produce coated samples with electrical resistances suitable for electrical applications. Electrical properties of the coated samples could also be manipulated by altering the structure of the sol-gel films or by changing the thickness of them

  14. Decomposition of silica-alumina ores of Afghanistan by sulfuric acid

    International Nuclear Information System (INIS)

    Khomidi, A.K.; Mamatov, E.D.

    2016-01-01

    Present article is devoted to decomposition of silica-alumina ores of Afghanistan by sulfuric acid. Physicochemical properties of initial silica-alumina ores were studied by means of X-ray phase, differential thermal and silicate analysis. The influence of temperature, process duration and acid concentration on extraction rate of valuable components was considered. The optimal conditions of decomposition of silica-alumina ores of Afghanistan by sulfuric acid were proposed.

  15. Interface chemistry of nanostructured materials: ion adsorption on mesoporous alumina.

    Science.gov (United States)

    Wang, Yifeng; Bryan, Charles; Xu, Huifang; Pohl, Phil; Yang, Yi; Brinker, C Jeffrey

    2002-10-01

    This paper presents a part of our work on understanding the effect of nanoscale pore space confinement on ion sorption by mesoporous materials. Acid-base titration experiments were performed on both mesoporous alumina and alumina particles under various ionic strengths. The point of zero charge (PZC) for mesoporous alumina was measured to be approximately 9.1, similar to that for nonmesoporous alumina materials, indicating that nanoscale pore space confinement does not have a significant effect on the PZC of pore surfaces. However, for a given pH deviation from the PZC, (pH-PZC), the surface charge per mass on mesoporous alumina was as much as 45 times higher than that on alumina particles. This difference cannot be fully explained by the surface area difference between the two materials. Our titration data have demonstrated that nanoscale confinement has a significant effect, most likely via the overlap of the electric double layer (EDL), on ion sorption onto mesopore surfaces. This effect cannot be adequately modeled by existing surface complexation models, which were developed mostly for an unconfined solid-water interface. Our titration data have also indicated that the rate of ion uptake by mesoporous alumina is relatively slow, probably due to diffusion into mesopores, and complete equilibration for sorption could take 4-5 min. A molecular simulation using a density functional theory was performed to calculate ion adsorption coefficients as a function of pore size. The calculation has shown that as pore size is reduced to nanoscales (<10 nm), the adsorption coefficients of ions can vary by more than two orders of magnitude relative to those for unconfined interfaces. The prediction is supported by our experimental data on Zn sorption onto mesoporous alumina. Owing to their unique surface chemistry, mesoporous materials can potentially be used as effective ion adsorbents for separation processes and environmental cleanup.

  16. Influence of alumina characteristics on glaze properties

    Directory of Open Access Journals (Sweden)

    Arrufat, S.

    2010-10-01

    Full Text Available Aluminium oxide is a synthetic raw material manufactured from bauxite by the Bayer process, whose Al2O3 content typically exceeds 99%. Four main types of alumina can be defined, depending on the processing used: hydrargillite Al(OH3, boehmite AlOOH, transition aluminas (calcined at low temperatures, 1000 °C, with an intermediary crystallographic structure between hydrates and alpha alumina, and α-Al2O3 (calcined at high temperatures, >1100 °C. In glaze manufacturing, α-Al2O3 is the main type of alumina used. This raw material acts as a matting agent: the matt effect depends on alumina particle size and content in the glaze. This study examines the effect of the degree of alumina calcination on glaze technical and aesthetic properties. For this purpose, aluminas with different degrees of calcination were added to a glaze formulated with a transparent frit and kaolin, in order to simplify the system to be studied. The results show that, depending on the degree of calcination, alumina particles can react with the glaze components (SiO2, CaO, and ZnO to form new crystalline phases (anorthite and gahnite. Both crystallisations extract CaO and ZnO from the glassy phase, increasing glassy phase viscosity. The variation in crystalline phases and glassy phase viscosity yields glazes with different technical and aesthetic properties.

    El óxido de aluminio es una materia prima sintética fabricada a partir de la bauxita por medio del proceso Bayer, cuyo contenido de Al2O3 supera, por regla general, el 99%. Se pueden definir cuatro tipos de alúmina, en función del tipo de proceso usado: hidrargilita Al(OH3, boehmita AlOOH, alúminas de transición (calcinadas a bajas temperaturas, 1000 °C, con una estructura cristalográfica intermedia entre los hidratos y la alfa alúmina, y la α-Al2O3 (calcinada a

  17. Slip cast coating of alumina crucibles

    International Nuclear Information System (INIS)

    Haroun, N.A.; El-Masry, M.A.A.

    1980-01-01

    The development of a process for coating alumina crucibles with MgO protective coat in a two-step slip casting operation is described. The best milling conditions for the alumina used were wet ball milling for 24 hr. MgO had to be calcined at 1200 0 C to minimize hydration. Optimum slip casting conditions for alumina and magnesia were found to be L/S I and pH 3-6 or 9-II for the former, and L/S 3 (alcohol) and pH 8.5-10 for the latter. Sintering of Al 2 O 3 and MgO in the temperature range 1150-500 0 C was investigated. Additions of NiO and MgO lowered the sintered densities at lower temperatures but improved the densification at 1500 0 C. Near theoretical density Al 2 O 3 and MgO crucibles were obtained. A two-step slip casting technique was developed to coat Al 2 O 3 with MgO. Certain slow firing schedules could eliminate the otherwise observed coat-crucible separation and cracks. (author)

  18. Preparation and Characterization of Activated Alumina

    Science.gov (United States)

    Rabia, A. R.; Ibrahim, A. H.; Zulkepli, N. N.

    2018-03-01

    Activated alumina is a high surface area and highly porous form of aluminum oxide that can be employed for contaminant species adsorb from ether gases or liquids without changing its form. The research in getting this material has generated huge interested. Thus, this paper presented preparation of activated alumina from chemical process. Pure aluminum (99.9% pure) reacted at room temperature with an aqueous NaOH in a reactor to produce a solution of sodium aluminate (NaAlO2). This solution was passed through filter paper and the clear filtrate was neutralized with H2SO4, to pH 6, 7 or 8, resulting in the precipitation of a white gel, Al(OH)3·XH2O. The washed gel for sulfate ions were dried at 80 °C for 6 h, a 60 mesh sieve was to separate and sort them into different sizes. The samples were then calcined (burn) for 3h in a muffle furnace, in air, at a heating rate of 2 °C min-1. The prepared activated alumina was further characterized for better understanding of its physical properties in order to predict its chemical mechanism.

  19. On the possibility of producing alumina ceramic with a slight electrical conductivity

    CERN Document Server

    Caspers, Fritz

    1989-01-01

    Antistatic alumina ceramic is desirable for certain particle accelerator applications. In general, highly insulating surface close to a charged particle beam must be avoided in order to prevent the formation of ion pockets and other unwanted electrical effects. For the AA vacuum chamber (UHV), an antistatic ferrite has been produced and successfully installed. The fabrication of antistatic alumina might be possible in a similar way. By using certain metal oxides in the cement, which holds the alumina particles together, a slight conductivity could be obtained after the firing and sintering process, without deteriorating the mechanical and outgassing properties of the alumina compound.

  20. Laser Surface Treatment of Sintered Alumina

    Science.gov (United States)

    Hagemann, R.; Noelke, C.; Kaierle, S.; Wesling, V.

    Sintered alumina ceramics are used as refractory materials for industrial aluminum furnaces. In this environment the ceramic surface is in permanent contact with molten aluminum resulting in deposition of oxidic material on its surface. Consequently, a lower volume capacity as well as thermal efficiency of the furnaces follows. To reduce oxidic adherence of the ceramic material, two laser-based surface treatment processes were investigated: a powder- based single-step laser cladding and a laser surface remelting. Main objective is to achieve an improved surface quality of the ceramic material considering the industrial requirements as a high process speed.

  1. Partial reactive crystallization of variable CO2-bearing siliceous MORB-eclogite-derived melt in fertile peridotite and genesis of alkalic basalts with signatures of crustal recycling

    Science.gov (United States)

    Mallik, A.; Dasgupta, R.

    2013-12-01

    The presence of heterogeneity in the form of recycled altered oceanic crust (MORB-eclogite) has been proposed in the source of HIMU ocean island basalts (OIBs) [1]. Partial melts of recycled oceanic crust, however, are siliceous and Mg-poor and thus do not resemble the major element compositions of alkalic OIBs that are silica-poor and Mg-rich. In an upwelling heterogenous mantle, MORB-eclogite undergoes melting deeper than volatile-free peridotite, hence, andesitic partial melt derived from eclogite will react with subsolidus peridotite. We have examined the effect of such a melt-rock reaction under volatile-free conditions at 1375 °C, 3 GPa by varying the melt-rock ratio from 8 to 50 wt.% [2]. We concluded that the reacted melts reproduce certain major element characteristics of oceanic basanites, but not nephelinites. Also, the melt-rock reaction produces olivine and garnet-bearing websteritic residue. Because presence of CO2 has been invoked in the source of many HIMU ocean islands, the effect of CO2 on such a melt-rock reaction needs to be evaluated. Accordingly, we performed reaction experiments on mixtures of 25% and 33% CO2-bearing andesitic partial melt and peridotite at 1375 °C, 3 GPa by varying the dissolved CO2 content of the reacting melts from 1 to 5 wt.% (bulk CO2 from 0.25 to 1.6 wt.%) [3, this study]. Owing to melt-rock reaction, with increasing CO2 in the bulk mixture, (a) modes of olivine and cpx decrease while melt, opx and garnet increase, (b) reacted melts evolve to greater degree of Si-undersaturation (from andesite through basanite to nephelinite), (c) enhanced crystallization of garnet take place with higher CO2 in the melt, reducing alumina content of the reacted melts, and (d) CaO and MgO content of the reacted melts increase, without affecting FeO* and Na2O contents (indicating greater propensity of Ca2+ and Mg2+ over Fe2+ and Na+ to enter silicate melt as carbonate). For a given melt-MgO, the CO2-bearing reacted melts are a better

  2. Fabrication of a novel aluminum surface covered by numerous high-aspect-ratio anodic alumina nanofibers

    Science.gov (United States)

    Nakajima, Daiki; Kikuchi, Tatsuya; Natsui, Shungo; Sakaguchi, Norihito; Suzuki, Ryosuke O.

    2015-11-01

    The formation behavior of anodic alumina nanofibers via anodizing in a concentrated pyrophosphoric acid under various conditions was investigated using electrochemical measurements and SEM/TEM observations. Pyrophosphoric acid anodizing at 293 K resulted in the formation of numerous anodic alumina nanofibers on an aluminum substrate through a thin barrier oxide and honeycomb oxide with narrow walls. However, long-term anodizing led to the chemical dissolution of the alumina nanofibers. The density of the anodic alumina nanofibers decreased as the applied voltage increased in the 10-75 V range. However, active electrochemical dissolution of the aluminum substrate occurred at a higher voltage of 90 V. Low temperature anodizing at 273 K resulted in the formation of long alumina nanofibers measuring several micrometers in length, even though a long processing time was required due to the low current density during the low temperature anodizing. In contrast, high temperature anodizing easily resulted in the formation and chemical dissolution of alumina nanofibers. The structural nanofeatures of the anodic alumina nanofibers were controlled by choosing of the appropriate electrochemical conditions, and numerous high-aspect-ratio alumina nanofibers (>100) can be successfully fabricated. The anodic alumina nanofibers consisted of a pure amorphous aluminum oxide without anions from the employed electrolyte.

  3. Microstructural evolution of alumina-zirconia nanocomposites; Evolucao microestrutural de nanocompositos alumina-zirconia

    Energy Technology Data Exchange (ETDEWEB)

    Ojaimi, C.L.; Chinelatto, A.S.A.; Chinelatto, A.L. [Universidade Estadual de Ponta Grossa (UEPG), PR (Brazil); Pallone, E.M.J.A., E-mail: christianelago@yahoo.com.br [Universidade de Sao Paulo (USP), Pirassununga, Sao Paulo, SP (Brazil). Faculdade de Zootecnia e Engenharia de Alimentos

    2012-07-01

    Ceramic materials have limited use due to their brittleness. The inclusion of nanosized particles in a ceramic matrix, which are called nanocomposites, and ceramic processing control by controlling the grain size and densification can aid in obtaining ceramic products of greater strength and toughness. Studies showed that the zirconia nano inclusions in the matrix of alumina favors an increase in mechanical properties by inhibiting the grain growth of the matrix and not by the mechanism of the transformation toughening phase of zirconia. In this work, the microstructural evolution of alumina nanocomposites containing 15% by volume of nanometric zirconia was studied. From the results it was possible to understand the sintering process of these nanocomposites. (author)

  4. Study of preparation and surface morphology of self-ordered nanoporous alumina; Estudo da preparacao e da morfologia de superficie de alumina nanoporosa auto-organizada

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, Elisa Marchezini; Martins, Maximiliano Delany, E-mail: elisamarch@gmail.com, E-mail: MG.mdm@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG. (Brazil); Silva, Ronald Arreguy, E-mail: arregsilva@yahoo.com.br [Centro Universitario de Belo Horizonte (UniBH), Belo Horizonte, MG (Brazil)

    2013-07-01

    Nanoporous alumina is a typical material that exhibits self-ordered nanochannels spontaneously organized in hexagonal shape. Produced by anodizing of metallic aluminum, it has been used as a template for production of materials at the nanoscale. This work aimed to study the preparation of nanoporous alumina by anodic anodizing of metallic aluminum substrates. The nanoporous alumina was prepared following the methodology proposed by Masuda and Fukuda (1995), a two-step method consisting of anodizing the aluminum sample in the potentiostatic mode, removing the layer of aluminum oxide (alumina) formed and then repeat the anodization process under the same conditions as the first anodization. This method produces nanoporous alumina with narrow pore diameter distribution and well-ordered structure. (author)

  5. Fabrication of asymmetric alumina membranes

    International Nuclear Information System (INIS)

    Firouzghalb, H.; Falamaki, C.

    2010-01-01

    The effect of SrO addition on the thermal stabilization of transition aluminas with the aim of producing membrane layers (supported and unsupported) has been investigated. Al 2 O 3 -x wt.% SrO composite powders (x = 1, 3, 5, 8) were synthesized by co-precipitation of the hydroxides from solutions of AlCl 3 and Sr(NO 3 ) 2 salts using NH 4 OH as a precipitating agent. Optimum SrO dopant concentration regarding the transition aluminas stabilization effect was determined to be 5 wt.% based on XRD analysis. STA analysis showed a 30 deg. C shift versus higher temperatures in the transformation of final transitional alumina (θ-Al 2 O 3 ) to stable alpha phase due to addition of 5 wt.% SrO. The mechanism of transition aluminas thermal stabilization as a result of SrO addition is thoroughly discussed. Unsupported alumina membranes were prepared by drying boehmite sols at 600, 800, 1000 and 1100 deg. C. The effect of calcination temperature on surface area, pore size distribution of unsupported membranes containing 5 wt.% SrO has been investigated. The microstructure of unsupported and supported membranes revealed quite different. Smaller grains in the supported layers were attributed to the interaction between support and membrane.

  6. Investigating the influence of alkalization on the mechanical and water absorption properties of coconut and sponge fibers reinforced polypropylene composites

    OpenAIRE

    Okikiola Ganiu AGBABIAKA; Isiaka Oluwole OLADELE; Paul Toluwalagbara OLORUNLEYE

    2014-01-01

    Natural fibers are products made from renewable agricultural and forestry feedstock, which can include wood, grasses, and crops, as well as wastes and residues. There are two primary ways these fibers are used: to create polymers or as reinforcement and filler. Thermoplastic polymer may be reinforced or filled using natural fibers such as coir, sponge, hemp, flax, or sisal. This paper focused on the influence of alkalization (NaOH treatment) on the mechanical and water absorption properties o...

  7. Detection of novel visible-light region absorbance peaks in the urine after alkalization in patients with alkaptonuria.

    Science.gov (United States)

    Tokuhara, Yasunori; Shukuya, Kenichi; Tanaka, Masami; Mouri, Mariko; Ohkawa, Ryunosuke; Fujishiro, Midori; Takahashi, Tomoo; Okubo, Shigeo; Yokota, Hiromitsu; Kurano, Makoto; Ikeda, Hitoshi; Yamaguchi, Seiji; Inagaki, Shinobu; Ishige-Wada, Mika; Usui, Hiromi; Yatomi, Yutaka; Shimosawa, Tatsuo

    2014-01-01

    Alkaptonuria, caused by a deficiency of homogentisate 1,2-dioxygenase, results in the accumulation of homogentisic acid (2,5-dihydroxyphenylacetic acid, HGA) in the urine. Alkaptonuria is suspected when the urine changes color after it is left to stand at room temperature for several hours to days; oxidation of homogentisic acid to benzoquinone acetic acid underlies this color change, which is accelerated by the addition of alkali. In an attempt to develop a facile screening test for alkaptonuria, we added alkali to urine samples obtained from patients with alkaptonuria and measured the absorbance spectra in the visible light region. We evaluated the characteristics of the absorption spectra of urine samples obtained from patients with alkaptonuria (n = 2) and compared them with those of urine specimens obtained from healthy volunteers (n = 5) and patients with phenylketonuria (n = 3), and also of synthetic homogentisic acid solution after alkalization. Alkalization of the urine samples and HGA solution was carried out by the addition of NaOH, KOH or NH4OH. The sample solutions were incubated at room temperature for 1 min, followed by measurement of the absorption spectra. Addition of alkali to alkaptonuric urine yielded characteristic absorption peaks at 406 nm and 430 nm; an identical result was obtained from HGA solution after alkalization. The absorbance values at both 406 nm and 430 nm increased in a time-dependent manner. In addition, the absorbance values at these peaks were greater in strongly alkaline samples (NaOH- KOH-added) as compared with those in weakly alkaline samples (NH4OH-added). In addition, the peaks disappeared following the addition of ascorbic acid to the samples. We found two characteristic peaks at 406 nm and 430 nm in both alkaptonuric urine and HGA solution after alkalization. This new quick and easy method may pave the way for the development of an easy method for the diagnosis of alkaptonuria.

  8. Detection of novel visible-light region absorbance peaks in the urine after alkalization in patients with alkaptonuria.

    Directory of Open Access Journals (Sweden)

    Yasunori Tokuhara

    Full Text Available BACKGROUND: Alkaptonuria, caused by a deficiency of homogentisate 1,2-dioxygenase, results in the accumulation of homogentisic acid (2,5-dihydroxyphenylacetic acid, HGA in the urine. Alkaptonuria is suspected when the urine changes color after it is left to stand at room temperature for several hours to days; oxidation of homogentisic acid to benzoquinone acetic acid underlies this color change, which is accelerated by the addition of alkali. In an attempt to develop a facile screening test for alkaptonuria, we added alkali to urine samples obtained from patients with alkaptonuria and measured the absorbance spectra in the visible light region. METHODS: We evaluated the characteristics of the absorption spectra of urine samples obtained from patients with alkaptonuria (n = 2 and compared them with those of urine specimens obtained from healthy volunteers (n = 5 and patients with phenylketonuria (n = 3, and also of synthetic homogentisic acid solution after alkalization. Alkalization of the urine samples and HGA solution was carried out by the addition of NaOH, KOH or NH4OH. The sample solutions were incubated at room temperature for 1 min, followed by measurement of the absorption spectra. RESULTS: Addition of alkali to alkaptonuric urine yielded characteristic absorption peaks at 406 nm and 430 nm; an identical result was obtained from HGA solution after alkalization. The absorbance values at both 406 nm and 430 nm increased in a time-dependent manner. In addition, the absorbance values at these peaks were greater in strongly alkaline samples (NaOH- KOH-added as compared with those in weakly alkaline samples (NH4OH-added. In addition, the peaks disappeared following the addition of ascorbic acid to the samples. CONCLUSIONS: We found two characteristic peaks at 406 nm and 430 nm in both alkaptonuric urine and HGA solution after alkalization. This new quick and easy method may pave the way for the development of an easy method for the

  9. Comparative evaluation of alumina powders obtained from different routes for engineering applications

    International Nuclear Information System (INIS)

    Page, C.H.; Chatterjee, A.K.

    1991-01-01

    Alumina, the most versatile and widely used refractory ceramic oxide, has currently occupied the position of the most preferred material in engineering ceramic industry. Though limited to some extent, the experience so far has been that the selection of an inappropriat high alumina ceramic can lead to cost penalties and poor performance in service. With this in view, one of the studies undertaken at the research laboratories of The Associated Cement Cos.Ldt. (India) has been to synthesise alumina powders by various process routes and to compare their physico-mechanical, thermal, textural and microstructural characteristics so as to understand the effects emanating from the powder synthesis processes on the performance properties of alumina. Following this approach, the present paper deals with aluminas obtained from four process routes, viz. Sol-Gel, Controlled Precipitation, Pyrolysis and Aluminium salts and conventional alumina obtained by calcination of gibbsite. The properties of these four varieties of alumina are characterised with respect to chemical analysis, particle size, textural features, grindability, etc. Behaviour of these powders in green processing/shaping particularly in terms of compaction, density, binder requirements, etc. have been studied. The calcination characteristics as reflected in shrinkage, densification and crystal morphology have been examined. Finally, the physical and thermal properties of Aluminas obtained from various synthesis routes and their co-relation with various powder characteristics and compact microstrcture have been dealt with. (orig.)

  10. Experimental investigation of nano-alumina effect on the filling time ...

    African Journals Online (AJOL)

    In this research, by producing composite samples made of glass fibers and epoxy resin with different percentages of nanoparticles (Nano-alumina), the adding effect of nanoparticles of alumina Alpha and Gamma grade on filling time in the vacuum assistant resin transfer molding process (VARTM) is investigated. The grade ...

  11. Corrosion resistance characterization of porous alumina membrane supports

    Energy Technology Data Exchange (ETDEWEB)

    Dong Yingchao, E-mail: dongyc9@mail.ustc.edu.cn [Materials and Surface Science Institute (MSSI), University of Limerick, Limerick (Ireland); USTC Lab for Solid State Chemistry and Inorganic Membranes, Department of Materials Science and Engineering, University of Science and Technology of China (USTC) (China); Key Lab of Jiangxi Universities for Inorganic Membranes, National Engineering Research Center for Domestic and Building Ceramics, Jingdezhen Ceramic University (JCU) (China); Lin Bin [USTC Lab for Solid State Chemistry and Inorganic Membranes, Department of Materials Science and Engineering, University of Science and Technology of China (USTC) (China); Zhou Jianer [Key Lab of Jiangxi Universities for Inorganic Membranes, National Engineering Research Center for Domestic and Building Ceramics, Jingdezhen Ceramic University (JCU) (China); Zhang Xiaozhen [USTC Lab for Solid State Chemistry and Inorganic Membranes, Department of Materials Science and Engineering, University of Science and Technology of China (USTC) (China); Key Lab of Jiangxi Universities for Inorganic Membranes, National Engineering Research Center for Domestic and Building Ceramics, Jingdezhen Ceramic University (JCU) (China); Ling Yihan; Liu Xingqin; Meng Guangyao [USTC Lab for Solid State Chemistry and Inorganic Membranes, Department of Materials Science and Engineering, University of Science and Technology of China (USTC) (China); Hampshire, Stuart [Materials and Surface Science Institute (MSSI), University of Limerick, Limerick (Ireland)

    2011-04-15

    Tubular porous alumina ceramic membrane supports were fabricated by an extrusion-drying-sintering process and then characterized in detail in terms of corrosion resistance in both H{sub 2}SO{sub 4} and NaOH aqueous solutions. Variations in the properties of the alumina supports such as mass loss percent, mechanical strength, open porosity and pore size distribution were studied before and after corrosion under different conditions. In addition, the microstructures were analyzed using scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction before and after corrosion. The fabricated porous alumina supports offer possibilities for some potential applications as micro-filtration or ultra-filtration membrane supports, as well as in the pre-treatment of strongly acidic industrial waste-liquids. - Research highlights: {yields} Porous alumina membrane supports fabricated by extrusion-drying-sintering process. {yields} Corrosion resistance in 20 wt.% H{sub 2}SO{sub 4} and 1, 5, 10 wt.% NaOH aqueous solutions. {yields} Rapid mass loss and loss of flexural strength occurred in hot NaOH solution. {yields} Resistant to strong acid corrosion with low mass loss, low flexural strength loss. {yields} Porous alumina supports have potential for treatment of strong acid waste liquids.

  12. Attrition resistant gamma-alumina catalyst support

    Science.gov (United States)

    Singleton, Alan H.; Oukaci, Rachid; Goodwin, James G.

    2006-03-14

    A .gamma.-alumina catalyst support having improved attrition resistance produced by a method comprising the steps of treating a particulate .gamma.-alumina material with an acidic aqueous solution comprising water and nitric acid and then, prior to adding any catalytic material thereto, calcining the treated .gamma.-alumina.

  13. Sintering behaviour of spinel–alumina composites

    Indian Academy of Sciences (India)

    % alumina dissolves in spinel (MgAl2O4) at 1600°C. Solid solubility of alumina in spinel decreases rapidly with decreasing temperature, which causes exsolution of alumina from spinel phase. Previous work of one of the authors revealed that ...

  14. Shockless spalling damage of alumina ceramic

    Science.gov (United States)

    Erzar, B.; Buzaud, E.

    2012-05-01

    Ceramic materials are commonly used to build multi-layer armour. However reliable test data is needed to identify correctly models and to be able to perform accurate numerical simulation of the dynamic response of armour systems. In this work, isentropic loading waves have been applied to alumina samples to induce spalling damage. The technique employed allows assessing carefully the strain-rate at failure and the dynamic strength. Moreover, specimens have been recovered and analysed using SEM. In a damaged but unbroken specimen, interactions between cracks has been highlighted illustrating the fragmentation process.

  15. Transport properties of alumina nanofluids

    International Nuclear Information System (INIS)

    Wong, Kau-Fui Vincent; Kurma, Tarun

    2008-01-01

    Recent studies have showed that nanofluids have significantly greater thermal conductivity compared to their base fluids. Large surface area to volume ratio and certain effects of Brownian motion of nanoparticles are believed to be the main factors for the significant increase in the thermal conductivity of nanofluids. In this paper all three transport properties, namely thermal conductivity, electrical conductivity and viscosity, were studied for alumina nanofluid (aluminum oxide nanoparticles in water). Experiments were performed both as a function of volumetric concentration (3-8%) and temperature (2-50 deg. C). Alumina nanoparticles with a mean diameter of 36 nm were dispersed in water. The effect of particle size was not studied. The transient hot wire method as described by Nagaska and Nagashima for electrically conducting fluids was used to test the thermal conductivity. In this work, an insulated platinum wire of 0.003 inch diameter was used. Initial calibration was performed using de-ionized water and the resulting data was within 2.5% of standard thermal conductivity values for water. The thermal conductivity of alumina nanofluid increased with both increase in temperature and concentration. A maximum thermal conductivity of 0.7351 W m -1 K -1 was recorded for an 8.47% volume concentration of alumina nanoparticles at 46.6 deg. C. The effective thermal conductivity at this concentration and temperature was observed to be 1.1501, which translates to an increase in thermal conductivity by 22% when compared to water at room temperature. Alumina being a good conductor of electricity, alumina nanofluid displays an increasing trend in electrical conductivity as volumetric concentration increases. A microprocessor-based conductivity/TDS meter was used to perform the electrical conductivity experiments. After carefully calibrating the conductivity meter's glass probe with platinum tip, using a standard potassium chloride solution, readings were taken at various

  16. Enriched fluoride sorption using alumina/chitosan composite

    Energy Technology Data Exchange (ETDEWEB)

    Viswanathan, Natrayasamy, E-mail: natrayasamy_viswanathan@rediffmail.com [Department of Chemistry, Anna University Tiruchirappalli - Dindigul Campus, Dindigul 624 622, Tamil Nadu (India); Meenakshi, S., E-mail: drs_meena@rediffmail.com [Department of Chemistry, Gandhigram Rural University, Gandhigram 624 302, Tamil Nadu (India)

    2010-06-15

    Alumina possesses an appreciable defluoridation capacity (DC) of 1566 mg F{sup -}/kg. In order to improve its DC, it is aimed to prepare alumina polymeric composites using the chitosan. Alumina/chitosan (AlCs) composite was prepared by incorporating alumina particles in the chitosan polymeric matrix, which can be made into any desired form viz., beads, candles and membranes. AlCs composite displayed a maximum DC of 3809 mg F{sup -}/kg than the alumina and chitosan (52 mg F{sup -}/kg). The fluoride removal studies were carried out in batch mode to optimize the equilibrium parameters viz., contact time, pH, co-anions and temperature. The equilibrium data was fitted with Freundlich and Langmuir isotherms to find the best fit for the sorption process. The calculated values of thermodynamic parameters indicate the nature of sorption. The surface characterisation of the sorbent was performed by FTIR, AFM and SEM with EDAX analysis. A possible mechanism of fluoride sorption by AlCs composite has been proposed. Suitability of AlCs composite at field conditions was tested with a field sample taken from a nearby fluoride-endemic village. This work provides a potential platform for the development of defluoridation technology.

  17. Development and evaluation of alumina calcination

    International Nuclear Information System (INIS)

    Bennett, I.J.

    2000-01-01

    This thesis focuses on a number of aspects governing the transformation of gibbsite, via intermediate phases, to α-alumina. These aspects include the size and morphology of the gibbsite grains, the influence of additions of foreign elements, the effect of a mechanical treatment of the gibbsite prior to calcination, and combinations of these factors. The materials were characterised by scanning electron microscopy, X-ray diffraction and surface area measurements. For some of the calcined materials an attempt was made to sinter the powders to a dense body to investigate if any of the treatments during calcination had an effect on this process. The literature review covers the current state of understanding of the production of bulk alumina powder by the Bayer process and the phase changes seen on calcination of precursors to the stable α-alumina phase. A detailed description of the phase changes is given and the various routes and conditions necessary for the transformations to occur are considered. The transformations are examined in relation to the morphology of the crystals and the variables controlling the phase transformation route are discussed. Calcination in air showed that the size of the gibbsite grain governs the calcination route taken to reach oc-alumina. The standard gibbsites used in this work show a mixed calcination sequence transforming both via the boehmite phase, followed by the γ, δ and θ phases, and via the χ and κ phases. The formation of boehmite is attributed to retention of water vapour within the grain. Differences in morphology of the starting materials showed that for the range of materials seen, the morphology of the grain is less important than its size. The super fine material confirmed that a small grain size transforms via the non-boehmite route only, with the other gibbsites taking intermediate routes as for the standard gibbsites. Of the additions made prior to calcination, aluminium fluoride was found to reduce the

  18. Phase transformation of aluminium hydroxide to aα- alumina prepared from different aluminium salts

    International Nuclear Information System (INIS)

    Masliana Muslimin; Meor Yusoff Meor Sulaiman

    2006-01-01

    The study intends to look at the most suitable aluminium salt to produce a single-phase a-alumina by the hydrothermal method. In the process to produce alumina from the calcination of aluminium hydroxide (Al(OH) 3 ), three different aluminium salts namely aluminium sulfate (Al 2 (SO 4) 2), aluminium nitrate (A(NO 3 ) 3 ) and aluminium chloride (AlCl 3 ) were tried. The process involved the used of NH 4 OH as the precipitating medium. Aluminium hydroxide produced from each of these salts were characterised by x-ray diffraction (XRD) technique to identity the crystalline phase. Aluminium hydroxide produced by all the different aluminium salts is present as boehmite or pseudo-boehmite phase. Aluminium hydroxide produced from Al 2 (SO) 2 , Al(NO) 3 and AlCl 3 shows the transformation of the boehmite phase to a α-alumina phase at 500 0 C. On further heating, the α-alumina continuously formed at 800 o C followed soon at 1000 o C. But for the Al(NO3) 3 salts a different phase transitions occurs on heating especially at 1000 o C. Here it was observed not a single alumina phase is presence but the presence of both α and γ--alumina phases. At 1300 o C, the single α-alumina phase was formed. The study concluded that aluminium sulphate is recommended in order to obtain a single-phase α-alumina with the required characteristics. (Author)

  19. Energy transfer in porous anodic alumina/rhodamine 110 nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Elhouichet, H., E-mail: habib.elhouichet@fst.rnu.tn [Laboratoire de Physico-Chimie des Materiaux Mineraux et leurs Applications, Centre National de Recherches en Sciences des Materiaux, B.P. 95, Hammam-Lif 2050 (Tunisia); Departement de Physique, Faculte des Sciences de Tunis, University of Tunis Elmanar 2092 Tunis (Tunisia); Harima, N.; Koyama, H. [Hyogo University of Teacher Education, Kato, Hyogo 673-1494 (Japan); Gaponenko, N.V. [Belarusian State University of Informatics and Radioelectronics, P. Browki St. 6, 220013 Minsk (Belarus)

    2012-09-15

    We have used porous anodic alumina (PAA) films as templates for embedding rhodamine 110 (Rh110) molecules and examined their photoluminescence (PL) properties in detail. The analysis of the polarization memory (PM) of PL strongly suggests that there is a significant energy transfer from PAA to Rh110 molecules. The effect of annealing the PAA layer on the PL properties of the nanocomposite has been studied. The results show that the energy transfer becomes more efficient in annealed PAA. - Highlights: Black-Right-Pointing-Pointer Porous anodic alumina-rhodamine 110 nanocomposites are elaborated. Black-Right-Pointing-Pointer Efficient energy transfer from the host to Rh110 molecules is evidenced from measurements of photoluminescence and degree of polarization memory spectra. Black-Right-Pointing-Pointer Thermal annealing of porous anodic alumina can improve the process of excitation transfer.

  20. Synthesis of alumina powders by precipitation method and solvothermal treatment

    International Nuclear Information System (INIS)

    Politchuk, J.O.; Lima, N.B.; Lazar, D.R.R.; Ussui, V.; Yoshito, W.K.

    2012-01-01

    The improvement of alumina powders synthesis processes has been focused on the preparation of ceramic powders with well defined crystalline structure and with high specific surface area and nanometric particle size without formation of hard agglomerates. For this purpose the precipitation step should be studied and and also the temperature of alumina crystallization should be reduced. The aim of this study was to obtain alumina powders by hydroxide precipitation with ammonia in the presence of cationic surfactant, followed by solvothermal treatment and calcination. The powders were characterized by TG/DTA, X-ray diffraction, surface area measurements by gas adsorption (BET) and scanning electron microscopy. The results showed that powders produced by solvothermal treatment without surfactant have higher crystallinity. However the presence of CTAB enhances 240% the specific surface area compared with powders produced without this reagent (author)

  1. Comparative study on sintered alumina for ballistic shielding application

    International Nuclear Information System (INIS)

    Melo, Francisco Cristovao Lourenco de; Goncalves, Diniz Pereira

    1997-01-01

    This work presents a development of the armor made from special ceramic materials and kevlar. An experimental investigation was conducted to study the ballistic penetration resistance on three samples taken from sintered alumina: a commercial one and two formulations A and B made in IAE/CTA. The main differences between the two formulations was the grain size and bend resistance. The knowledge of the mechanisms during the penetration and perforation process allowed to apply a ductile composite laminate made form kevlar under the alumina to delay its rupture. The last ballistic test showed how a Weibull's modulii and other mechanical properties are able to improve ballistic penetration resistance. (author)

  2. Study of preparation and surface morphology of self-ordered nanoporous alumina

    International Nuclear Information System (INIS)

    Rodrigues, Elisa Marchezini; Martins, Maximiliano Delany; Silva, Ronald Arreguy

    2013-01-01

    Nanoporous alumina is a typical material that exhibits self-ordered nanochannels spontaneously organized in hexagonal shape. Produced by anodizing of metallic aluminum, it has been used as a template for production of materials at the nanoscale. This work aimed to study the preparation of nanoporous alumina by anodic anodizing of metallic aluminum substrates. The nanoporous alumina was prepared following the methodology proposed by Masuda and Fukuda (1995), a two-step method consisting of anodizing the aluminum sample in the potentiostatic mode, removing the layer of aluminum oxide (alumina) formed and then repeat the anodization process under the same conditions as the first anodization. This method produces nanoporous alumina with narrow pore diameter distribution and well-ordered structure. (author)

  3. Capillary condensation in porous alumina observed by positronium lifetime spectroscopy

    International Nuclear Information System (INIS)

    Ivanov, Eugeniu; Vata, Ion; Toderian, Stefan; Dudu, Dorin; Rusen, Ion; Stefan, Nitisor

    2008-01-01

    The PALS method based on time distribution measurements has been used to study capillary condensation of different gases adsorbed in microporous alumina powder. The isotherms exhibit features which are associated with a shifted gas-liquid transition. The sorption and desorption processes are irreversible presenting a hysteresis effect. Suggestions on some new aspects of the capillary condensation dynamics are made

  4. Controlled growth of single nanowires within a supported alumina template

    DEFF Research Database (Denmark)

    Vlad, A.; Mátéfi-Tempfli, M.; Faniel, S.

    2006-01-01

    A simple technique for fabricating single nanowires with well-defined position is presented. The process implies the use of a silicon nitride mask for selective electrochemical growth of the nanowires in a porous alumina template. We show that this method allows the realization of complex nanowire...

  5. Nitrate ions as cathodic alkalization promoters for the electro-assisted deposition of sol-gel thin films

    Energy Technology Data Exchange (ETDEWEB)

    Ding Shangzhi; Liu Liang [Department of Chemistry, Yuquan Campus, Zhejiang University, Hangzhou, Zhejiang 310027 (China); Hu Jiming [Department of Chemistry, Yuquan Campus, Zhejiang University, Hangzhou, Zhejiang 310027 (China)], E-mail: kejmhu@zju.edu.cn; Zhang Jianqing; Cao Chunan [Department of Chemistry, Yuquan Campus, Zhejiang University, Hangzhou, Zhejiang 310027 (China); State Key Laboratory for Corrosion and Protection, Shenyang 110016 (China)

    2008-08-15

    Nitrate was used as a promoter to prepare dodecyltrimethoxysilane thin films on aluminum substrates. With the addition of nitrate into silane sol-gel precursors, the electro-assisted formation of silane films was facilitated, as indicated by electrochemical impedance spectroscopy, scanning electron microscopy and secondary-ion mass spectroscopy, due to the promotion in cathodic alkalization. However, an extra-high concentration of nitrate would be harmful because of the salting-out effect in precursors and the soluble nitrate remaining in silane films.

  6. Synthesis and textural evolution of alumina particles with mesoporous structures

    International Nuclear Information System (INIS)

    Liu Xun; Peng Tianyou; Yao Jinchun; Lv Hongjin; Huang Cheng

    2010-01-01

    Alumina particles with mesostructures were synthesized through a chemical precipitation method by using different inorganic aluminum salts followed by a heterogeneous azeotropic distillation and calcination process. The obtained mesoporous γ-alumina particles were systematically characterized by the X-ray diffraction, transmission electron microscopy and nitrogen adsorption-desorption measurement. Effects of the aluminum salt counter anion, pH value and the azeotropic distillation process on the structural or textural evolution of alumina particles were investigated. It is found that Cl - in the reaction solution can restrain the textural evolution of the resultant precipitates into two-dimensional crystallized pseudoboehmite lamellae during the heterogeneous azeotropic distillation, and then transformed into γ-Al 2 O 3 particles with mesostructures after further calcination at 1173 K, whereas coexisting SO 4 2- can promote above morphology evolution and then transformed into γ-Al 2 O 3 nanofibers after calcination at 1173 K. Moreover nearly all materials retain relatively high specific surface areas larger than 100 m 2 g -1 even after calcinations at 1173 K. - Graphical abstract: Co-existing Cl - is beneficial for the formation of γ-alumina nanoparticles with mesostructures during the precipitation process. Interparticle and intraparticle mesopores can be derived from acidic solution and near neutral solution, respectively.

  7. Properties of Transition Metal Doped Alumina

    Science.gov (United States)

    Nykwest, Erik; Limmer, Krista; Brennan, Ray; Blair, Victoria; Ramprasad, Rampi

    Crystallographic texture can have profound effects on the properties of a material. One method of texturing is through the application of an external magnetic field during processing. While this method works with highly magnetic systems, doping is required to couple non-magnetic systems with the external field. Experiments have shown that low concentrations of rare earth (RE) dopants in alumina powders have enabled this kind of texturing. The magnetic properties of RE elements are directly related to their f orbital, which can have as many as 7 unpaired electrons. Since d-block elements can have as many as 5 unpaired electrons the effects of substitutional doping of 3d transition metals (TM) for Al in alpha (stable) and theta (metastable) alumina on the local structure and magnetic properties, in addition to the energetic cost, have been calculated by performing first-principles calculations based on density functional theory. This study has led to the development of general guidelines for the magnetic moment distribution at and around the dopant atom, and the dependence of this distribution on the dopant atom type and its coordination environment. It is anticipated that these findings can aid in the selection of suitable dopants help to guide parallel experimental efforts. This project was supported in part by an internship at the Army Research Laboratory, administered by the Oak Ridge Institute for Science and Education, along with a grant of computer time from the DoD High Performance Computing Modernization Program.

  8. Production of pure sintered alumina

    International Nuclear Information System (INIS)

    Rocha, J.C. da; Huebner, H.W.

    1982-01-01

    With the aim of optimizing the sintering parameters, the strength of a large number of alumina samples was determined which were produced under widely varying sintering conditions and with different amounts of MgO content. The strength as a function of sintering time or temperature was found to go through a maximum. With increasing time, this maximum is shifted to lower temperatures, and with decreasing temperature to longer times. Data pairs of sintering times and temperatures which yeld the strength maximum were determined. The value of the strength at the maximum remains unchanged. The strength is high (= 400 MN/m 2 , at a grain size of 3 um and a porosity of 2 per cent) and comparable to foreign aluminas produced for commercial purposes, or even higher. The increase in the sintering time from 1 h to 16 h permits a reduction of the sintering temperature from 1600 to 1450 0 C without losing strength. The practical importance of this fact for a production of sintered alumina on a large scale is emphasized. (Author) [pt

  9. A novel technique for synthesizing dense alumina nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Pancholi, A [Department of Materials Science and Engineering, University of Delaware, Newark, DE 19716 (United States); Stoleru, V G [Department of Materials Science and Engineering, University of Delaware, Newark, DE 19716 (United States); Kell, C D [Department of Chemical Engineering, University of Delaware, Newark, DE 19716 (United States)

    2007-05-30

    The formation of highly ordered nanoporous alumina membranes by anodizing high-purity aluminium under optimum conditions (i.e., anodization time, electrolyte temperature, and cell voltage) in various electrolyte solutions is a well established process. In this paper we report on the formation of a wide range of alumina nanostructures, including nanotubes/nanochannels, nanoplates, and nanofibres, by using a technique that involves anodization and etching processing steps similar to the ones that yield nanopores, under slightly modified experimental conditions. The effects of the anodization voltage, time, and temperature, as well as the effects of the etching time, on the formation and the properties of the alumina nanostructures are analysed. We propose a simple analytical model to describe the formation of different types of alumina nanostructures, as a result of irreversible breakage of the pore walls for long etching times. The geometry of the nanostructures and their dimensions, ranging between 10 and 100 nm, were found to be dependent on the pore dimensions and on the location of the cleavage/breakage of the pore walls.

  10. Evolution of extreme stomach pH in bilateria inferred from gastric alkalization mechanisms in basal deuterostomes.

    Science.gov (United States)

    Stumpp, Meike; Hu, Marian Y; Tseng, Yung-Che; Guh, Ying-Jeh; Chen, Yi-Chih; Yu, Jr-Kai; Su, Yi-Hsien; Hwang, Pung-Pung

    2015-06-08

    The stomachs of most vertebrates operate at an acidic pH of 2 generated by the gastric H(+)/K(+)-ATPase located in parietal cells. The acidic pH in stomachs of vertebrates is believed to aid digestion and to protect against environmental pathogens. Little attention has been placed on whether acidic gastric pH regulation is a vertebrate character or a deuterostome ancestral trait. Here, we report alkaline conditions up to pH 10.5 in the larval digestive systems of ambulacraria (echinoderm + hemichordate), the closest relative of the chordate. Microelectrode measurements in combination with specific inhibitors for acid-base transporters and ion pumps demonstrated that the gastric alkalization machinery in sea urchin larvae is mainly based on direct H(+) secretion from the stomach lumen and involves a conserved set of ion pumps and transporters. Hemichordate larvae additionally utilized HCO3(-) transport pathways to generate even more alkaline digestive conditions. Molecular analyses in combination with acidification experiments supported these findings and identified genes coding for ion pumps energizing gastric alkalization. Given that insect larval guts were also reported to be alkaline, our discovery raises the hypothesis that the bilaterian ancestor utilized alkaline digestive system while the vertebrate lineage has evolved a strategy to strongly acidify their stomachs.

  11. Extraction of Alumina from Red Mud for Synthesis of Mesoporous Alumina by Adding CTABr as Mesoporous Directing Agent

    Directory of Open Access Journals (Sweden)

    Eka Putra Ramdhani

    2018-05-01

    Full Text Available Mines in Bintan were producing bauxite for many years. The production process of bauxite to alumina produced much red mud. From X-ray Fluorescence (XRF, alumina content on Bintan’s red mud was 28.87 wt.%. This research was studying on the extraction alumina from red mud with reduction of hematite (Fe2O3 and desilication processes. After extraction process alumina was collected about 52.89 wt.%. Synthesis of mesoporous alumina from red mud using sol-gel method at the room temperature for 72 h with cetyltrimethylammonium bromide (CTABr as mesoporous directing agent. The CTABr/Al-salt ratio, i.e. 1.57; 4.71 and 7.85 with the sample code of AMC-1, AMC-3, AMC-5, respectively. The product was calcined at 550 °C for 6 h. The synthesized materials were characterized by X-ray Diffraction (XRD, scanning electron microscopy-energy dispersive X-ray (SEM-EDX, transmission electron microscopy (TEM, and N2 adsorption-desorption techniques. XRD pattern of AMC-1, AMC-3, and AMC-5 showed that all synthesized materials have amorphous phase. The morphology were wormhole aggregate that were showed by SEM and TEM characterization. N2 adsorption-desorption characterization showed the distribution of pore size of about 3.2 nm. The highest surface area and pore volume were obtained in solid-solid ratio CTABr/GM-AL by 1.57 (AMC-1 i.e. 241 m2/g and 0.107 cm3/g, respectively.

  12. Preparation and electrochemical performance of sulfur-alumina cathode material for lithium-sulfur batteries

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Kang [Faculty of Material Science and Chemistry, China University of Geosciences, 388 Lumo Road, 430074 Wuhan (China); Wang, Shengping, E-mail: spwang@cug.edu.cn [Faculty of Material Science and Chemistry, China University of Geosciences, 388 Lumo Road, 430074 Wuhan (China); Zhang, Hanyu; Wu, Jinping [Faculty of Material Science and Chemistry, China University of Geosciences, 388 Lumo Road, 430074 Wuhan (China)

    2013-06-01

    Highlights: ► Micron-sized alumina was synthesized as adsorbent for lithium-sulfur batteries. ► Sulfur-alumina material was synthesized via crystallizing nucleation. ► The Al{sub 2}O{sub 3} can provide surface area for the deposition of Li{sub 2}S and Li{sub 2}S{sub 2}. ► The discharge capacity of the battery is improved during the first several cycles. - Abstract: Nano-sized sulfur particles exhibiting good adhesion with conducting acetylene black and alumina composite materials were synthesized by means of an evaporated solvent and a concentrated crystallization method for use as the cathodes of lithium-sulfur batteries. The composites were characterized and examined by X-ray diffraction, environmental scanning electron microscopy and electrochemical methods, such as cyclic voltammetry, electrical impedance spectroscopy and charge–discharge tests. Micron-sized flaky alumina was employed as an adsorbent for the cathode material. The initial discharge capacity of the cathode with the added alumina was 1171 mAh g{sup −1}, and the remaining capacity was 585 mAh g{sup −1} after 50 cycles at 0.25 mA cm{sup −2}. Compared with bare sulfur electrodes, the electrodes containing alumina showed an obviously superior cycle performance, confirming that alumina can contribute to reducing the dissolution of polysulfides into electrolytes during the sulfur charge–discharge process.

  13. Preparation and electrochemical performance of sulfur-alumina cathode material for lithium-sulfur batteries

    International Nuclear Information System (INIS)

    Dong, Kang; Wang, Shengping; Zhang, Hanyu; Wu, Jinping

    2013-01-01

    Highlights: ► Micron-sized alumina was synthesized as adsorbent for lithium-sulfur batteries. ► Sulfur-alumina material was synthesized via crystallizing nucleation. ► The Al 2 O 3 can provide surface area for the deposition of Li 2 S and Li 2 S 2 . ► The discharge capacity of the battery is improved during the first several cycles. - Abstract: Nano-sized sulfur particles exhibiting good adhesion with conducting acetylene black and alumina composite materials were synthesized by means of an evaporated solvent and a concentrated crystallization method for use as the cathodes of lithium-sulfur batteries. The composites were characterized and examined by X-ray diffraction, environmental scanning electron microscopy and electrochemical methods, such as cyclic voltammetry, electrical impedance spectroscopy and charge–discharge tests. Micron-sized flaky alumina was employed as an adsorbent for the cathode material. The initial discharge capacity of the cathode with the added alumina was 1171 mAh g −1 , and the remaining capacity was 585 mAh g −1 after 50 cycles at 0.25 mA cm −2 . Compared with bare sulfur electrodes, the electrodes containing alumina showed an obviously superior cycle performance, confirming that alumina can contribute to reducing the dissolution of polysulfides into electrolytes during the sulfur charge–discharge process

  14. Nanoporous alumina as templates for multifunctional applications

    Science.gov (United States)

    Sousa, C. T.; Leitao, D. C.; Proenca, M. P.; Ventura, J.; Pereira, A. M.; Araujo, J. P.

    2014-09-01

    Due to its manufacturing and size tailoring ease, porous anodic alumina (PAA) templates are an elegant physical-chemical nanopatterning approach and an emergent alternative to more sophisticated and expensive methods currently used in nanofabrication. In this review, we will describe the ground work on the fabrication methods of PAA membranes and PAA-based nanostructures. We will present the specificities of the electrochemical growth processes of multifunctional nanomaterials with diversified shapes (e.g., nanowires and nanotubes), and the fabrication techniques used to grow ordered nanohole arrays. We will then focus on the fabrication, properties and applications of magnetic nanostructures grown on PAA and illustrate their dependence on internal (diameter, interpore distance, length, composition) and external (temperature and applied magnetic field intensity and direction) parameters. Finally, the most outstanding experimental findings on PAA-grown nanostructures and their trends for technological applications (sensors, energy harvesting, metamaterials, and biotechnology) will be addressed.

  15. Plasma sprayed alumina-titania coatings

    International Nuclear Information System (INIS)

    Steeper, T.J.; Rotolico, A.J.; Nerz, J.E.; Riggs, W.L. II; Varacalle, D.J. Jr.; Wilson, G.C.

    1992-01-01

    This paper presents an experimental study of the air plasma spraying (APS) of alumina-titania powder using argon-hydrogen working gases. This powder system is being used in the fabrication of heater tubes that emulate nuclear fuel tubes for use in thermal-hydraulic testing. Experiments were conducted using a Taguchi fractional-factorial design parametric study. Operating parameters were varied around the typical spray parameters in a systematic design of experiments in order to display the range of plasma processing conditions and their effect on the resultant coatings. The coatings were characterized by hardness and electrical tests, surface profilometry, image analysis, optical metallography, and x-ray diffraction. Coating qualities are discussed with respect to dielectric strength, hardness, porosity, surface roughness, deposition efficiency, and microstructure. attempts are made to correlate the features of the coatings with the changes in operating parameters

  16. Two steps sintering alumina doped with niobia

    International Nuclear Information System (INIS)

    Gomes, L.B.; Hatzfeld, J.; Heck, M.; Pokorny, A.; Bergmann, C.P.

    2014-01-01

    In this work, high surface area commercial alumina was doped with niobia and sintered in two steps in order to obtain dense materials with lower processing temperatures. The powders were milled and uniaxially pressed (200 MPa). The first step of sintering took place at 1100°C for 3, 6, 9 and 12 hours, followed by the second step at 1350°C for 3 hours. The relative density, porosity and water absorption of the samples were determined by the Archimedes method. The crystalline phases were analyzed by X-ray Diffraction (XRD) and the morphology of the samples after sintering, evaluated by Scanning Electron Microscopy (SEM). The results indicate that the use of niobia combined with the two steps sintering promotes an increase in the density of the material, even at lower sintering temperatures. (author)

  17. Aluminum matrix composites reinforced with alumina nanoparticles

    CERN Document Server

    Casati, Riccardo

    2016-01-01

    This book describes the latest efforts to develop aluminum nanocomposites with enhanced damping and mechanical properties and good workability. The nanocomposites exhibited high strength, improved damping behavior and good ductility, making them suitable for use as wires. Since the production of metal matrix nanocomposites by conventional melting processes is considered extremely problematic (because of the poor wettability of the nanoparticles), different powder metallurgy routes were investigated, including high-energy ball milling and unconventional compaction methods. Special attention was paid to the structural characterization at the micro- and nanoscale, as uniform nanoparticle dispersion in metal matrix is of prime importance. The aluminum nanocomposites displayed an ultrafine microstructure reinforced with alumina nanoparticles produced in situ or added ex situ. The physical, mechanical and functional characteristics of the materials produced were evaluated using different mechanical tests and micros...

  18. 1170-MW(t) HTGR-PS/C plant application-study report: alumina-plant application

    International Nuclear Information System (INIS)

    Rao, R.; McMain, A.T. Jr.; Stanley, J.D.

    1981-05-01

    This report considers the HTGR-PS/C application to producing alumina from bauxite. For the size alumina plant considered, the 1170-MW(t) HTGR-PS/C supplies 100% of the process steam and electrical power requirements and produces surplus electrical power and/or process steam, which can be used for other process users or electrical power production. Presently, the bauxite ore is reduced to alumina in plants geographically separated from the electrolysis plant. The electrolysis plants are located near economical electric power sources. However, with the integration of an 1170-MW(t) HTGR-PS/C unit in a commercial alumina plant, the excess electric power available [approx. 233 MW(e)] could be used for alumina electrolysis

  19. Ordering of Octahedral Vacancies in Transition Aluminas

    NARCIS (Netherlands)

    Wang, Yuan Go; Bronsveld, Paul M.; Hosson, Jeff Th.M. De; Djuričić, Boro; McGarry, David; Pickering, Stephen

    1998-01-01

    The microstructure of transition aluminas obtained via the dehydration of boehmite has been characterized by using transmission electron microscopy (TEM). The presence of γ-, δ-, and θ-aluminas was identified by using selected-area electron diffraction. Modifications that resulted from the

  20. Synthesis and structural evaluation of freeze-cast porous alumina

    Energy Technology Data Exchange (ETDEWEB)

    Souza, Douglas F., E-mail: souzadf@outlook.com [Department of Metallurgical and Materials Engineering, Federal University of Minas Gerais — UFMG, Avenida Presidente Antônio Carlos, 6627, Campus UFMG, Belo Horizonte, MG CEP: 31270-901, Escola de Engenharia, bloco 2, sala 2230 (Brazil); Nunes, Eduardo H.M., E-mail: eduardohmn@gmail.com [Department of Metallurgical and Materials Engineering, Federal University of Minas Gerais — UFMG, Avenida Presidente Antônio Carlos, 6627, Campus UFMG, Belo Horizonte, MG CEP: 31270-901, Escola de Engenharia, bloco 2, sala 2230 (Brazil); Pimenta, Daiana S.; Vasconcelos, Daniela C.L. [Department of Metallurgical and Materials Engineering, Federal University of Minas Gerais — UFMG, Avenida Presidente Antônio Carlos, 6627, Campus UFMG, Belo Horizonte, MG CEP: 31270-901, Escola de Engenharia, bloco 2, sala 2230 (Brazil); Nascimento, Jailton F.; Grava, Wilson [Petrobras/CENPES, Avenida Horácio Macedo 950, Cidade Universitária, Ilha do Fundão, Rio de Janeiro, RJ CEP:21941-915 (Brazil); Houmard, Manuel [Department of Materials Engineering and Civil Construction, Federal University of Minas Gerais — UFMG, Avenida Presidente Antônio Carlos, 6627, Campus UFMG, Belo Horizonte, MG CEP: 31270-901, Escola de Engenharia, bloco 1, sala 3304 (Brazil); Vasconcelos, Wander L., E-mail: wlv@demet.ufmg.br [Department of Metallurgical and Materials Engineering, Federal University of Minas Gerais — UFMG, Avenida Presidente Antônio Carlos, 6627, Campus UFMG, Belo Horizonte, MG CEP: 31270-901, Escola de Engenharia, bloco 2, sala 2230 (Brazil)

    2014-10-15

    In this work we fabricated alumina samples by the freeze-casting technique using tert-butanol as the solvent. The prepared materials were examined by scanning electron microscopy and X-ray microtomography. Next, they were coated with sol–gel silica films by dip-coating. Permeability tests were carried out in order to assess the permeation behavior of the materials processed in this study. We observed that the sintering time and alumina loading showed a remarkable effect on both the structural properties and flexural strength of the freeze-cast samples. Nitrogen adsorption tests revealed that the silica prepared in this study exhibited a microporous structure. It was observed that the presence of silica coatings on the alumina surface decreased the CO{sub 2} permeance by about one order of magnitude. Because of the similar kinetic diameters of nitrogen and carbon dioxide, the CO{sub 2}/N{sub 2} system showed a separation efficiency that was lower than that observed for the He/CO{sub 2} and He/N{sub 2} systems. We noticed that increasing the feed pressure improved the separation capacity of the obtained materials. - Highlights: • Porous alumina samples obtained by the freeze-casting technique • Microporous silica coating prepared by a simple sol–gel dip-coating methodology • Samples examined by SEM, μ-CT, and nitrogen sorption tests • Mechanical tests were carried out in the freeze-cast samples. • The presence of silica coatings on the alumina surface decreased the CO{sub 2} permeance.

  1. Preparation of alumina microspheres. Its application as in inorganic exchanger

    Energy Technology Data Exchange (ETDEWEB)

    Santos, W.R. dos; Abrao, A [Instituto de Pesquisas Energeticas e Nucleares, Sao Paulo (Brazil). Centro de Engenharia Quimica

    1980-01-01

    Inorganic exchangers are widely used for adsorption and column partition chromatography. The main difficulty of using commercial alumina (in powder) for column chromatography is related to its packing, and the operations through the column become diffcult and time-consuming; also it turns to be virtually impossible to use large dimension columns. In order to eliminate these problems, a process for the preparation of alumina microspheres was developed as an adaptation of a similar process used to prepare nuclear fuel microspheres (UO/sub 2/, ThO/sub 2/). The flowsheet of this process is presented together with the analytical results of sphericity after calcination, granulometry, density and characterization by X-ray diffractometry. Solubility tests showed that the so-prepared microspheres are well resistant to strong acids and bases; retention tests showed their efficiency, mainly to copper.

  2. Influence of the precursors on the properties of alumina supported rhodium particles

    International Nuclear Information System (INIS)

    Coq, B.; Figueras, F.; Tazi, T.

    1989-01-01

    The effect of chlorine on the properties of Rh particles supported on alumina was studied using the hydroconversion of alkanes as a molecular probe. Chloride ions on the alumina have little influence on the Rh particles. Chlorine adsorbed on the Rh particles decreases the chemisorption capacity and increases the metal-support interaction, which results in modifications of their catalytic properties. Depending on the alkane processed, specific activity can be depressed up to four orders of magnitude. (orig.)

  3. The Porgera gold deposit, Papua, New Guinea, 1: association with alkalic magmatism in a continent-island-arc collision zone

    International Nuclear Information System (INIS)

    Richards, J.P.; Chappell, B.W.; McCulloch, M.T.; McDougall, I.

    1991-01-01

    The meso thermal to epithermal Porgera gold deposit is spatially and temporally associated with shallow level (≤ 2 km emplacement depth) stocks and dykes of the Porgera Intrusive Complex (PIC). Gold mineralization immediately followed emplacement of the PIC, and is dated between 5 and 6 Ma ago. The Porgera intrusive suite is comprised of fine- to medium-grained, porphyritic to euhedral granular, volatile-rich, sodic alkali basalts/gabbros, hawaiites, and mugearites (TAS chemical classification scheme). The rocks display chemical and isotopic characteristics similar to those of intra plate alkalic basalts, but their unusually high volatile contents result in stabilization of hornblende as a phenocryst and intergranular phase in more evolved rock types. The observed order of cotectic crystallization is olivine - clinopyroxene - hornblende -plagioclase, with ubiquitous spinel (chromite/magnetite) and fluor-apatite. (author)

  4. Diffusion of Cr, Fe, and Ti ions from Ni-base alloy Inconel-718 into a transition alumina coating

    Energy Technology Data Exchange (ETDEWEB)

    Dressler, M., E-mail: martin.dressler@bam.de; Nofz, M.; Doerfel, I.; Saliwan-Neumann, R.

    2012-04-30

    Heat treating metals at high temperatures trigger diffusion processes which may lead to the formation of oxide layers. In this work the diffusion of Cr, Fe and Ti into an alumina coating applied to Inconel-718 is being investigated. Mass gain measurements, UV-vis spectroscopy and transmission electron microscopy were applied in order to study the evolution of the diffusion process. It was found that mainly Cr as well as minor amounts of Fe and Ti are being incorporated into the alumina coating upon prolonged heat treatment at 700 Degree-Sign C. It could be shown that alumina coatings being void of Cr have the same oxidation related mass gain as uncoated samples. However, incorporation of Cr into the alumina coating decreased their mass gain below that of uncoated substrates forming a Cr oxide scale only. - Highlights: Black-Right-Pointing-Pointer We investigated the diffusion of Cr into alumina coatings applied on IN-718. Black-Right-Pointing-Pointer The ingress of Cr led to the formation of mixed alumina/chromium coatings. Black-Right-Pointing-Pointer The mass gain of mixed alumina/chromium coatings was compared to uncoated IN-718. Black-Right-Pointing-Pointer The mixed alumina/chromium coatings improved the oxidation resistance of IN-718.

  5. Synthesis and characterization of alumina application in support of zeolite membrane

    International Nuclear Information System (INIS)

    Barbosa, A.S.; Rodrigues, M.G.F.

    2012-01-01

    Much interest has been aroused in process applications using zeolite membrane. The physicochemical properties of the support have a strong effect on the quality of zeolite membrane. This work is to synthesize and characterize alumina for use as a support for zeolite membrane. In this work was synthesized α-alumina: 40% alumina, 0.2% for PABA, 0.5% oleic acid and 59.3% ethyl alcohol. The mixture was ground in ball mill and placed in an oven for 24 hours at 60 °C, allowed to stand for 24h. The pressing was performed with 4 tons. The pressed material was subjected to sintering at 1400 °C/hour. The samples were characterized by EDX, XRD and SEM. The results for the media by XRD showed that they are crystalline and pure. By EDX was observed that the supports consist essentially of alumina. (author)

  6. Synthesis of ultrafine alumina powders using egg white as complexing medium

    International Nuclear Information System (INIS)

    Salem, R.E.P.; Guilherme, K. A.; Chinelatto, A.S.A.; Chinelatto, A.L.

    2011-01-01

    Synthesis of alumina powders through chemical methods has been attracting much attention of researchers in the past few years, due to the ability to produce powders in nanometric scale with high degree of purity. In this work, there were synthesized alumina powders through a chemical route, using egg white as a complexing medium and aluminium nitrate as the source of Al 3+ cations. Egg white contains ovalbumin, a protein which acts effectively on the isolation of aluminium cations during the mixing process, enabling the formation of ultrafine alumina powders in a relatively economic and environmentally friendly way. The powders obtained by calcinations of the precursor resin were characterized by X-ray diffraction, specific surface area measurements, infrared spectroscopy and scanning electron microscopy. It was observed that the egg white, present at the reaction medium, allowed obtaining transition alumina powders, with high degree of purity. (author)

  7. Oxidation of mullite-zirconia-alumina-silicon carbide composites

    International Nuclear Information System (INIS)

    Baudin, C.; Moya, J.S.

    1990-01-01

    This paper reports the isothermal oxidation of mullite-alumina-zirconia-silicon carbide composites obtained by reaction sintering studied in the temperature interval 800 degrees to 1400 degrees C. The kinetics of the oxidation process was related to the viscosity of the surface glassy layer as well as to the crystallization of the surface film. The oxidation kinetics was halted to T ≤ 1300 degrees C, presumably because of crystallization

  8. Zirconia toughened SiC whisker reinforced alumina composites small business innovation research

    Science.gov (United States)

    Loutfy, R. O.; Stuffle, K. L.; Withers, J. C.; Lee, C. T.

    1987-01-01

    The objective of this phase 1 project was to develop a ceramic composite with superior fracture toughness and high strength, based on combining two toughness inducing materials: zirconia for transformation toughening and SiC whiskers for reinforcement, in a controlled microstructure alumina matrix. The controlled matrix microstructure is obtained by controlling the nucleation frequency of the alumina gel with seeds (submicron alpha-alumina). The results demonstrate the technical feasibility of producing superior binary composites (Al2O3-ZrO2) and tertiary composites (Al2O3-ZrO2-SiC). Thirty-two composites were prepared, consolidated, and fracture toughness tested. Statistical analysis of the results showed that: (1) the SiC type is the key statistically significant factor for increased toughness; (2) sol-gel processing with a-alumina seed had a statistically significant effect on increasing toughness of the binary and tertiary composites compared to the corresponding mixed powder processing; and (3) ZrO2 content within the range investigated had a minor effect. Binary composites with an average critical fracture toughness of 6.6MPam sup 1/2, were obtained. Tertiary composites with critical fracture toughness in the range of 9.3 to 10.1 MPam sup 1/2 were obtained. Results indicate that these composites are superior to zirconia toughened alumina and SiC whisker reinforced alumina ceramic composites produced by conventional techniques with similar composition from published data.

  9. Plasma-sprayed tantalum/alumina cermets

    International Nuclear Information System (INIS)

    Kramer, C.M.

    1977-12-01

    Cermets of tantalum and alumina were fabricated by plasma spraying, with the amount of alumina varied from 0 to 65 percent (by volume). Each of four compositions was then measured for tensile strength, elastic modulus, and coefficient of thermal expansion. In general, strength and strain to failure decreased with increasing alumina content: 62 MPa for 100 percent Ta to 19 MPa for 35 v percent Ta. A maximum of 0.1 percent strain was observed for the sprayed 100 percent Ta specimens. The coefficient of thermal expansion measured for the pure Ta was 6.2 (10 -6 )/K

  10. Mullite-alumina functionally gradient ceramics

    International Nuclear Information System (INIS)

    Pena, P.; Bartolome, J.; Requena, J.; Moya, J.S.

    1993-01-01

    Cracks free mullite-alumina Functionally Gradient Ceramics (FGC) have been obtained by sequential slip casting of Mullite-alumina slurries with different mullite/alumina ratios. These slurries were prepared with 65 % solids content and viscosities ranging from 10 to 40 mPa.s. The presence of cracks perpendicular to the FGC layers have been attributed to residual stresses developed because of the mismatch in thermal expansion between layers. The microstructure of the different layers, and de residual stress value σ R in each layer was also determined. (orig.)

  11. Electrochemically grown metallic nanocomb structures on nanoporous alumina templates

    International Nuclear Information System (INIS)

    Kaya, Savas; Atar, Erdem

    2011-01-01

    Electrochemical growth of metallic nanocomb structures on anodized alumina templates is described. Nanocombs originate from the orderly growth and merger of very thin (d=15±5 nm) metallic nanowires which do not completely fill much larger pores (d∼100 nm) in the alumina template (t≤3 μm). Instead, the nanowires prefer growing along the inner corners of the hexagonal pores, coalescing into a highly ordered structure as they emerge, resulting a metallic form reminiscent of the topology of the original template. We disclose here the typical processing conditions and the microstructure of this previously unknown material as observed with a scanning electron microscope (SEM) and energy dispersive x-ray (EDX) spectroscopy. It is shown that Au nanocombs have an anomalous EDX spectra and can emit electrons at a field of ∼1 kV/cm.

  12. Removing Bacillus subtilis from fermentation broth using alumina nanoparticles.

    Science.gov (United States)

    Mu, Dashuai; Mu, Xin; Xu, Zhenxing; Du, Zongjun; Chen, Guanjun

    2015-12-01

    In this study, an efficient separation technology using Al2O3 nanoparticles (NPs) was developed for removing Bacillus subtilis from fermentation broth. The dosage of alumina nanoparticles used for separating B. subtilis increased during the culture process and remained stable in the stationary phase of the culture process. The pH of the culture-broth was also investigated for its effects on flocculation efficiency, and showed an acidic pH could enhance the flocculation efficiency. The attachment mechanisms of Al2O3 NPs to the B. subtilis surface were investigated, and the zeta potential analysis showed that Al2O3 NPs could attach to B. subtilis via electrostatic attachment. Finally, the metabolite content and the antibacterial effect of the fermentation supernatants were detected and did not significantly differ between alumina nanoparticle separation and centrifugation separation. Together, these results indicate a great potential for a highly efficient and economical method for removing B. subtilis from fermentation broth using alumina nanoparticles. Copyright © 2015 Elsevier Ltd. All rights reserved.

  13. Synthesis and textural evolution of alumina particles with mesoporous structures

    Science.gov (United States)

    Liu, Xun; Peng, Tianyou; Yao, Jinchun; Lv, Hongjin; Huang, Cheng

    2010-06-01

    Alumina particles with mesostructures were synthesized through a chemical precipitation method by using different inorganic aluminum salts followed by a heterogeneous azeotropic distillation and calcination process. The obtained mesoporous γ-alumina particles were systematically characterized by the X-ray diffraction, transmission electron microscopy and nitrogen adsorption-desorption measurement. Effects of the aluminum salt counter anion, pH value and the azeotropic distillation process on the structural or textural evolution of alumina particles were investigated. It is found that Cl - in the reaction solution can restrain the textural evolution of the resultant precipitates into two-dimensional crystallized pseudoboehmite lamellae during the heterogeneous azeotropic distillation, and then transformed into γ-Al 2O 3 particles with mesostructures after further calcination at 1173 K, whereas coexisting SO 42- can promote above morphology evolution and then transformed into γ-Al 2O 3 nanofibers after calcination at 1173 K. Moreover nearly all materials retain relatively high specific surface areas larger than 100 m 2 g -1 even after calcinations at 1173 K.

  14. On characterizing the mechanical properties of aluminum–alumina composites

    International Nuclear Information System (INIS)

    Gudlur, Pradeep; Boczek, Artur; Radovic, Miladin; Muliana, Anastasia

    2014-01-01

    The overall response of aluminum–alumina (Al–Al 2 O 3 ) composites depends strongly on their microstructural characteristics. We study the overall mechanical response of Al–Al 2 O 3 composites experimentally, using Resonant Ultrasound Spectroscopy (RUS) and uniaxial compressive testing. Microstructures of composite with 10% alumina volume content are constructed from the microstructural images of the composite obtained from scanning electron microscopy (SEM). The SEM images of the composite are converted to finite element (FE) meshes, which are used to solve the boundary value problem in order to determine the overall mechanical response of the Al–Al 2 O 3 composite. The responses generated from the micromechanical models are compared with the elastic modulus obtained from RUS and experimental stress–strain curves from uniaxial compression tests. Effects of processing, porosity, alumina content, thermal (residual) stress, and plastic deformation on the overall elastic modulus and response of the composites are also studied. We observed that slightly altering the processing method had a significant effect on the microstructural characteristics and in turn on the overall physical and mechanical properties of the composite. With changes in porosity by 2–3%, the elastic modulus was found to vary by 10–15 GPa approximately. We observed that the elastic moduli of the composites determined from the uniaxial compressive tests are close to those obtained from RUS

  15. Thermal stability and microstructure of catalytic alumina composite support with lanthanum species

    Energy Technology Data Exchange (ETDEWEB)

    Ozawa, Masakuni, E-mail: ozawa@numse.nagoya-u.ac.jp; Nishio, Yoshitoyo

    2016-09-01

    Highlights: • Thermal stability of La-modified γ-Al{sub 2}O{sub 3} with nanometer-scaled structure. • LaAlO{sub 3} particles are dispersed in the aggregated particles of alumina. • Increase of the surface basicity of La modified alumina using CO{sub 2}-TPD. - Abstract: Lanthanum (La) modified γ-alumina composite was examined for application toward thermostable catalytic support at elevated temperature. La added alumina was prepared through an aqueous process using lanthanum (III) nitrate and then characterized by surface area measurement, X-ray powder diffraction (XRD), differential thermal analysis (DTA), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoemission spectroscopy (XPS) and surface desorption of CO{sub 2}. It was found that the properties depended on the La content and heat treatment temperatures. The characterization of the surface, structural and chemical properties of La-Al{sub 2}O{sub 3} showed the existence of a strong interaction between the La species and alumina via formation of new phase and modified surface in Al{sub 2}O{sub 3} samples. LaAlO{sub 3} nanoparticle formed among alumina particles by the solid phase reaction of Al{sub 2}O{sub 3} and La{sub 2}O{sub 3}. The increase of the surface basicity of La modified alumina was demonstrated using CO{sub 2} temperature programmed desorption experiments. The controlled surface interaction between La oxide and alumina provide the unique surface and structural properties of the resulting mixed oxides as catalysts and catalytic supports.

  16. A comparative approach to synthesis and sintering of alumina/yttria nanocomposite powders using different precipitants

    Energy Technology Data Exchange (ETDEWEB)

    Kafili, G. [Department of Nanotechnology Engineering, Faculty of Advanced Sciences and Technologies, University of Isfahan, Isfahan, 81746-73441 (Iran, Islamic Republic of); Movahedi, B., E-mail: b.movahedi@ast.ui.ac.ir [Department of Nanotechnology Engineering, Faculty of Advanced Sciences and Technologies, University of Isfahan, Isfahan, 81746-73441 (Iran, Islamic Republic of); Milani, M. [Faculty of Advanced Materials and Renewable Energy Research Center, Tehran (Iran, Islamic Republic of)

    2016-11-01

    Alumina/yttria nanocomposite powder as an yttrium aluminum garnet (YAG) precursor was synthesized via partial wet route using urea and ammonium hydrogen carbonate (AHC) as precipitants, respectively. The products were characterized using X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and energy dispersive spectroscopy. The use of urea produced very tiny spherical Y-compounds with chemical composition of Y{sub 2}(CO{sub 3}){sub 3}·nH{sub 2}O, which were attracted to the surface of alumina nanoparticles and consequently, a core-shell structure was obtained. The use of ammonium hydrogen carbonate produced sheets of Y-compounds with chemical composition of Y(OH)CO{sub 3} covering the alumina nanoparticles. A fine-grained YAG ceramic (about 500 nm), presenting a non-negligible transparency (45% RIT at IR range) was obtained by the spark plasma sintering (SPS) of alumina-yttria nanocomposite synthesized in the urea system. This amount of transmission was obtained by only the sintering of the powder specimen without any colloidal forming process before sintering or adding any sintering aids or dopant elements. However, by spark plasma sintering of alumina-yttria nanocomposite powder synthesized in AHC system, an opaque YAG ceramic with an average grain size of 1.2 μm was obtained. - Highlights: • Urea proved to be an appropriate precipitant for obtaining a core-shell alumina/yttria nanocomposite. • Alumina/yttria nanocomposite powders with more appropriate morphology and highly sinterability. • A fine-grained YAG ceramic was obtained by SPS of alumina-yttria nanocomposite.

  17. Low temperature synthesis of nano alpha-alumina powder by two-step hydrolysis

    International Nuclear Information System (INIS)

    Yan, Ting; Guo, Xiaode; Zhang, Xiang; Wang, Zhixiang; Shi, Jinqiu

    2016-01-01

    Highlights: • The nano α-Al 2 O 3 with good dispersion was prepared by two-step hydrolysis. • α-Al 2 O 3 powders were added as seed particles in the hydrolysis. • This article indicated that the glucose could impel the γ-Al 2 O 3 transformed to α-Al 2 O 3 directly. • This article indicated that the addictive of α-Al 2 O 3 seed could improve the phase transformation rate of γ-Al 2 O 3 to α-Al 2 O 3 . • In this article, the pure α-Al 2 O 3 could be obtained by calcining at 1000 °C for 1.5 h. - Abstract: The ultral fine alpha-alumina powder has been successfully synthesized via two-step hydrolysis of aluminum isopropoxide. Glucose and polyvinyl pyrrolidone were used as surfactants during the appropriate processing step. The alpha-alumina powder was used as seed particles. Several synthesis parameters, such as the amount of seeds, surfactants, and calcination temperature, were studied by X-ray diffraction (XRD), Fourier transform infrared spectra (FTIR), Thermogravimetry-differential scanning calorimetry (TG-DSC), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The experimental results showed that glucose greatly lower the phase transformation temperature of alpha-alumina by impelling the gamma-alumina transformed to alpha-alumina directly, and the seed could improve the phase transformation rate of alpha-alumina, the polyvinylpyrrolidone have an effect on preventing excessive grain growth and agglomeration of alpha-alumina powder. Comparatively well dispersed alpha-alumina powder with particle size less than 50 nm can be synthesized through this method after calcinations at 1000 °C for 2 h.

  18. Sintering behaviour of spinel–alumina composites

    Indian Academy of Sciences (India)

    Administrator

    College of Engineering & Ceramic Technology, Kolkata 700 010, India. †. School of .... Chemical compositions of different batches of spinel–alumina composites. Chemistry ..... sence of magnesio–aluminate spinel, Ph D Thesis, University.

  19. 3D surface reconstruction and FIB microscopy of worn alumina hip prostheses

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, P; Inkson, B J; Rainforth, W M [Department of Engineering Materials, Mappin St., University of Sheffield, Sheffield, S1 3JD (United Kingdom); Stewart, T [School of Mechanical Engineering, University of Leeds, Leeds, LS2 9JT (United Kingdom)], E-mail: m.rainforth@sheffield.ac.uk

    2008-08-15

    Interest in alumina-on-alumina total hip replacements (THR) continues to grow for the young and active patient due to their superior wear performance and biocompatibility compared to the alternative traditional polymer/metal prostheses. While alumina on alumina bearings offer an excellent solution, a region of high wear, known as stripe wear, is commonly observed on retrieved alumina hip components that poses concern. These in-vivo stripe wear mechanisms can be replicated in vitro by the introduction of micro-separation during the simulated walking cycle in hip joint simulation. However, the understanding of the mechanisms behind the stripe wear processes is relatively poor. 3D topographic reconstructions of titled SEM stereo pairs from different zones have been obtained to determine the local worn surface topography. Focused ion beam (FIB) microscopy was applied to examine the subsurface damage across the stripe wear. The paper presents novel images of sub-surface microcracks in alumina along with 3D reconstructions of the worn ceramic surfaces and a classification of four distinct wear zones following microseparation in hip prostheses.

  20. The characterization of ceramic alumina prepared by using additive glass beads

    Science.gov (United States)

    Suprapedi; Muljadi; Sardjono, Priyo

    2018-01-01

    The ceramic alumina has been made by using additive glass bead (5 and 10 % wt.). There are two kinds of materials, such as : gamma Alumina and glass bead. Synthesis of alumina was done by ball milling for 24 hours, then the mixed powder was dried in drying oven at 100 °C for 6 hours. Furthermore, the dried powder was mixed by using 2 % of PVA and continued with compacted to form a pellet with pressure of 50 MPA. The next step is sintering process with variation temperature of 1150, 1200, 1250, 1300 and 1400 °C and holding time for 2 hours. The characterization conducted are consist of test density, hardness, shrinkage, and microstructure. The results show that ceramic alumina with addition of 10 % wt. glass bead has the higher value of density, hardness and shrinkage than addition of 5% wt. glass bead. The highest characterization of ceramic alumina with addition 10 % glass bead was achieved at sintering temperature of 1400 °C with density 3.68 g/cm3, hardness vickers 780.40 Hv and shrinkage 15.23 %. The XRD results show that it was founds a corrundum (alpha Alumina) as dominant phase and mullite as minor phase.

  1. Germania and Alumina Dopant Diffusion and Viscous Flow Effects at Preparation of Doped Optical Fibers

    Directory of Open Access Journals (Sweden)

    Jens Kobelke

    2017-01-01

    Full Text Available We report on germania and alumina dopant profile shift effects at preparation of compact optical fibers using packaging methods (Stack-and-Draw method, Rod-in-Tube (RiT technique. The sintering of package hollow volume by viscous flow results in a shift of the core-pitch ratio in all-solid microstructured fibers. The ratio is increased by about 5% in the case of a hexagonal package. The shift by diffusion effects of both dopants is simulated for typical slow speed drawing parameters. Thermodynamic approximations of surface dissociation of germania doped silica suggest the need of an adequate undoped silica barrier layer to prevent an undesired bubble formation at fiber drawing. In contrast, alumina doping does not estimate critical dissociation effects with vaporous aluminium oxide components. We report guide values of diffusion length of germania and alumina for the drawing process by kinetic approximation. The germania diffusion involves a small core enlargement, typically in the sub-micrometer scale. Though, the alumina diffusion enlarges it by a few micrometers. A drawn pure alumina preform core rod transforms to an amorphous aluminosilicate core with a molar alumina concentration of only about 50% and a non-gaussian concentration profile.

  2. Thermal stability and microstructure of catalytic alumina composite support with lanthanum species

    Science.gov (United States)

    Ozawa, Masakuni; Nishio, Yoshitoyo

    2016-09-01

    Lanthanum (La) modified γ-alumina composite was examined for application toward thermostable catalytic support at elevated temperature. La added alumina was prepared through an aqueous process using lanthanum (III) nitrate and then characterized by surface area measurement, X-ray powder diffraction (XRD), differential thermal analysis (DTA), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoemission spectroscopy (XPS) and surface desorption of CO2. It was found that the properties depended on the La content and heat treatment temperatures. The characterization of the surface, structural and chemical properties of La-Al2O3 showed the existence of a strong interaction between the La species and alumina via formation of new phase and modified surface in Al2O3 samples. LaAlO3 nanoparticle formed among alumina particles by the solid phase reaction of Al2O3 and La2O3. The increase of the surface basicity of La modified alumina was demonstrated using CO2 temperature programmed desorption experiments. The controlled surface interaction between La oxide and alumina provide the unique surface and structural properties of the resulting mixed oxides as catalysts and catalytic supports.

  3. Correlation between the mechanical property and microstructure of porcelain with high alumina contents

    International Nuclear Information System (INIS)

    Goulart, E.P.; Jordao, M.A.P.; Souza, D.D.D. de; Kiyohara, P.K.

    1989-01-01

    The substitution of quartz by a alumina in porcelain bodies produces high increase in mechanical strenght of the fired body. In the present paper, body microstruture variations caused by gradual quartz by alumina substitution have been studied and correlated to physical characteristics variations. Several bodies with quartz content varying from 22% to 0% and accordingly, the alumina content varying from 0% to 22% have been prepared. Other quartz-free bodies and the alumina content going up to 40% have been prepared. Three different alumina types have been used: two of them were of microcrystal type, the original crystal size between 1-5μm and obtained by calcining aluminum hydroxide from Bayer process; the third one is an originally macrocrystal type alumina obtained by grinding electrofused material. The sintering temperature ranged from 1250 0 C to 1400 0 C with 50 0 C of intervals between each firing. Tests on specimens covered flexural strenght, water absortion, apparent density and porosity. Microstruture variations and new mineral formation was continuously detected by scanning electron microscopy and X-ray diffraction [pt

  4. Comparative study on sintered alumina for ballistic shielding application; Estudo comparativo entre aluminas sinterizadas visando aplicacao em blindagem balistica

    Energy Technology Data Exchange (ETDEWEB)

    Melo, Francisco Cristovao Lourenco de; Goncalves, Diniz Pereira [Centro Tecnico Aeroespacial (CTA), Sao Jose dos Campos, SP (Brazil). Inst. de Aeronautica e Espaco

    1997-12-31

    This work presents a development of the armor made from special ceramic materials and kevlar. An experimental investigation was conducted to study the ballistic penetration resistance on three samples taken from sintered alumina: a commercial one and two formulations A and B made in IAE/CTA. The main differences between the two formulations was the grain size and bend resistance. The knowledge of the mechanisms during the penetration and perforation process allowed to apply a ductile composite laminate made form kevlar under the alumina to delay its rupture. The last ballistic test showed how a Weibull`s modulii and other mechanical properties are able to improve ballistic penetration resistance. (author) 3 refs.

  5. Thermal and tensile properties of alumina filled PET nanocomposites

    Science.gov (United States)

    Nikam, Pravin N.; Deshpande, Vineeta D.

    2018-05-01

    In the present investigation, nanocomposites of poly(ethylene terephathalate)(PET) with different content (0 to 5 wt.%) of alumina nanoparticles (n-Al2O3) were prepared by melt-extrusion technique. Morphological characterization of samples was examined by transmission electron microscopy (TEM). Morphological analysis revealed that degree of dispersion of alumina nanoparticles (ANPs) was increased at lower content (i.e. upto 2 wt.%), which observed by TEM. Thermal and tensile measurements were carried out using and differential scanning calorimetry (DSC) and universal testing machine (UTM). The thermal analysis showed that the glass transition termperature (Tg), melting temperature (Tm), crystallization temperature (Tc) of PET/alumina nanocomposites (PNCs) were higher than neat PET (PET0). The heat enthalpy (ΔHm) of crystallization for PNCs was increased compared to PET0, which indicates that degree of crystallinity of PNCs also increased compared to PET0. The half-time (t0.5) of crystallization of PNCs were decreased compared to PET0 which indicates that the incorporation of ANPs nucleate the PET molecular chains and allowing the easily crystallization during nonisothermal process. The tensile analysis revealed that the tensile elastic modulus (i.e. Young's modulus) of PNCs increased almost linearly with increasing the content of ANPs while tensile elongation at break decreased nonlinearly. The tensile strength of PNCs increased with a 1 wt.% of ANPs whereas the higher content of ANPs decreased the tensile strength.

  6. Environmental Sustainability of the Alumina Industry in Western Europe

    Directory of Open Access Journals (Sweden)

    Valentina Dentoni

    2014-12-01

    Full Text Available The implementation of European policies on environmental protection is enforcing some substantial modifications in the processing methods and technologies traditionally adopted in the alumina industry and, in particular, in the management of the alumina residue produced. The article analyses the evolution of the alumina production and the residue disposal practices in Western Europe. Some critical aspects regarding the legal implementation of the EU Directive on the landfill of waste are highlighted and discussed. With reference to the requirements established for the landfill of non-hazardous waste, a key point is represented by the possibility of reducing the deposit protection measures if the collection and treatment of leachate is not necessary. The flexibility introduced by the Directive is not incorporated into the Italian law; this fact may represent a major issue in the prospect of disposal conversion from wet to dry methods for companies operating in Italy, as it may endanger the economic sustainability of the plants’ upgrade, as well as the opportunity to attract outside investments.

  7. Results of recent KROTOS FCI tests. Alumina vs. corium melts

    Energy Technology Data Exchange (ETDEWEB)

    Huhtiniemi, I.; Magallon, D.; Hohmann, H. [Commission of the European Communities, Ispra (Italy). Joint Research Center

    1998-01-01

    Recent results from KROTOS fuel-coolant interaction experiments are discussed. Five tests with alumina were performed under highly subcooled conditions, all of these tests resulted in spontaneous steam explosions. Additionally, four tests were performed at low subcooling to confirm, on one hand, the suppression of spontaneous steam explosions under such conditions and, on the other hand, that such a system is still triggerable using an external initiator. The other test parameters in these alumina tests included the melt superheat and the initial pressure. All the tests in the investigated superheat range (150 K - 750 K) produced a steam explosion and no evidence of the explosion suppression by the elevated initial pressure (in the limited range of 0.1 - 0.375 MPa) was observed in the alumina tests. The corium test series include a test with 3 kg of melt under both subcooled and near saturated conditions at ambient pressure. Two additional tests were performed with subcooled water; one test was performed at an elevated pressure of 0.2 MPa with 2.4 kg of melt and another test with 5.1 kg of melt at ambient pressure. None of these tests with corium produced a propagating energetic steam explosion. However, propagating low energy (about twice the energy of the trigger pulse) events were observed. All corium tests produced significantly higher water level swells during the mixing phase than the corresponding alumina tests. Present experimental evidence suggests that the water depletion in the mixing zone suppresses energetic steam explosions with corium melts at ambient pressure and in the present pour geometry. Processes that could produce such a difference in void generation are discussed. (author)

  8. Ion irradiation effect of alumina and its luminescence

    Energy Technology Data Exchange (ETDEWEB)

    Aoki, Yasushi; Yamamoto, Shunya; Naramoto, Hiroshi [Japan Atomic Energy Research Inst., Takasaki, Gunma (Japan). Takasaki Radiation Chemistry Research Establishment; My, N T

    1997-03-01

    The luminescence spectra of single crystalline alpha-alumina and ruby which has 0.02% of Cr{sub 2}O{sub 3} as a impurity, induced by 200 keV He{sup +} and Ar{sup +} irradiation were measured at room temperature as a function of irradiation dose. The analysis of the measured spectra showed the existence of three main luminescence features in the wavelength region of 250 to 350 nm, namely anionic color centers, F-center at 411 nm and F{sup +}-center at 330 nm and a band observed around 315 nm. As alpha-alumina was irradiated with He{sup +}, F-center and F{sup +}-center luminescence grew and decayed, but the behaviors of those were different from each other. It seems that a concentration quenching occurred on the F-center luminescence in the dose range above 1x10{sup 14} He/cm{sup 2}. Furthermore, F-center luminescence was strongly suppressed in ruby, compared with that in alumina. On the other hand, the luminescence band around 315 nm appeared only in the early stage of irradiation and did not show its growth part. The dose dependent behavior was similar to that of Cr{sup 3+} emission at 695 nm (R-line) in ruby in both cases of He{sup +} and Ar{sup +} irradiation. Based on the experimental results mentioned above, the processes of defect formation and excitation in alumina in the early stage of ion irradiation will be discussed. (author)

  9. Shock diffraction in alumina powder

    International Nuclear Information System (INIS)

    Venz, G.; Killen, P.D.; Page, N.W.

    1996-01-01

    In order to produce complex shaped components by dynamic compaction of ceramic powders detailed knowledge of their response under shock loading conditions is required. This work attempts to provide data on release effects and shock attenuation in 1 μm and 5 μm α-alumina powders which were compacted to between 85 % and 95 % of the solid phase density by the impact of high velocity steel projectiles. As in previous work, the powder was loaded into large cylindrical dies with horizontal marker layers of a contrasting coloured powder to provide a record of powder displacement in the recovered specimens. After recovery and infiltration with a thermosetting resin the specimens were sectioned and polished to reveal the structure formed by the passage of the projectile and shock wave. Results indicate that the shock pressures generated were of the order of 0.5 to 1.4 GPa and higher, with shock velocities and sound speeds in the ranges 650 to 800 m/s and 350 to 400 m/s respectively

  10. The structure-directed effect of Al-based metal–organic frameworks on fabrication of alumina by thermal treatment

    International Nuclear Information System (INIS)

    Liu, Dandan; Dai, Fangna; Tang, Zhe; Liu, Yunqi; Liu, Chenguang

    2015-01-01

    Highlights: • We use Al-MOFs as precursor in the fabrication process of mesoporous alumina by thermal treatment. • The obtained mesoporous alumina has dual pore system and five-fold aluminum. • The aluminum building units in the precursor show structure-directed effect on the formation of alumina. - Abstract: In this work, the block-shaped Al-based metal–organic frameworks (Al-MOFs) MIL-53 have been synthesized by hydrothermal method. To detect the correlation between the structure of Al-MOFs and the formation of alumina, the ligands are eliminated by thermal treatment. MIL-53 and the calcination products were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), transmission electron microscopy (TEM), nitrogen adsorption–desorption and solid-state 27 Al nuclear magnetic resonance ( 27 Al NMR). It was found that after calcination, the block-shaped Al-MOFs precursor turns into high-crystallinity mesoporous alumina nanosheets, and the thermal treatment product γ-alumina possesses a dual pore system and a large surface area (146 m 2 /g), with five-fold aluminum. During the thermal treatment process, the structure of MIL-53 and its secondary building units have structure-directed effect in the formation of alumina

  11. Investigating the influence of alkalization on the mechanical and water absorption properties of coconut and sponge fibers reinforced polypropylene composites

    Directory of Open Access Journals (Sweden)

    Okikiola Ganiu AGBABIAKA

    2014-11-01

    Full Text Available Natural fibers are products made from renewable agricultural and forestry feedstock, which can include wood, grasses, and crops, as well as wastes and residues. There are two primary ways these fibers are used: to create polymers or as reinforcement and filler. Thermoplastic polymer may be reinforced or filled using natural fibers such as coir, sponge, hemp, flax, or sisal. This paper focused on the influence of alkalization (NaOH treatment on the mechanical and water absorption properties of selected natural fibers (coconut and sponge fibers reinforced polypropylene composites. In this study, coconut and sponge fiber were extracted from its husk by soaking them in water and was dried before it was cut into 10mm length. Those fibers were chemically treated with sodium hydroxide (NaOH in a shaking water bath before it was used as reinforcement in polypropylene composite. The reinforced polypropylene composite was produced by dispersing the coconut fibers randomly in the polypropylene before it was fabricated in a compression molding machine where the composite was produced. The fiber content used were; 2%wt, 4%wt, 6%wt, 8%wt and 10%wt. Tensile and flexural properties was observed from universal testing machine while water absorption test was carried out on the samples for seven (7 days. It was observed that the influence of NaOH treatment highly enhanced the Flexural and water absorption properties of sponge fiber reinforced polypropylene composites than coconut fiber reinforced composite samples.

  12. Tunable alumina 2D photonic-crystal structures via biomineralization of peacock tail feathers

    Science.gov (United States)

    Jiang, Yonggang; Wang, Rui; Feng, Lin; Li, Jian; An, Zhonglie; Zhang, Deyuan

    2018-04-01

    Peacock tail feathers with subtle periodic nanostructures exhibit diverse striking brilliancy, which can be applied as natural templates to fabricate artificial photonic crystals (PhCs) via a biomineralization method. Alumina photonic-crystal structures are successfully synthesized via an immersion and two-step calcination process. The lattice constants of the artificial PhCs are greatly reduced compared to their natural matrices. The lattice constants are tunable by modifying the final annealing conditions in the biomineralization process. The reflection spectra of the alumina photonic-crystal structures are measured, which is related to their material and structural parameters. This work suggests a facile fabrication process to construct alumina PhCs with a high-temperature resistance.

  13. Severe wear behaviour of alumina balls sliding against diamond ...

    Indian Academy of Sciences (India)

    study, alumina ball was chosen as the counter body material to show better performance of the ... Tribology is a relatively new science that considers ... The science is applied in ... for example, in hip prosthesis, instead of existing alumina.

  14. Challenges and Strategies in the Synthesis of Mesoporous Alumina Powders and Hierarchical Alumina Monoliths

    Directory of Open Access Journals (Sweden)

    Anne Galarneau

    2012-02-01

    Full Text Available A new rapid, very simple and one-step sol-gel strategy for the large-scale preparation of highly porous γ-Al2O3 is presented. The resulting mesoporous alumina materials feature high surface areas (400 m2 g−1, large pore volumes (0.8 mL g−1 and the ��-Al2O3 phase is obtained at low temperature (500 °C. The main advantages and drawbacks of different preparations of mesoporous alumina materials exhibiting high specific surface areas and large pore volumes such as surfactant-nanostructured alumina, sol-gel methods and hierarchically macro-/mesoporous alumina monoliths have been analyzed and compared. The most reproducible synthesis of mesoporous alumina are given. Evaporation-Induced Self-Assembly (EISA is the sole method to lead to nanostructured mesoporous alumina by direct templating, but it is a difficult method to scale-up. Alumina featuring macro- and mesoporosity in monolithic shape is a very promising material for in flow applications; an optimized synthesis is described.

  15. Electrochemically produced alumina as TL detector

    International Nuclear Information System (INIS)

    Osvay, M.

    1996-01-01

    The goal of this work was to compare the TL properties of various electrochemically produced alumina layers (E-AIO) in order to investigate the effect of the electrolyte and the Mg content on the alloys. It has been found that the TL sensitivity of oxidised layers is more influenced by the type of electrolyte, than by the composition of alloy. Hard oxide layer evolved in reduction electrolyte has rather different character compared to other alumina production investigated. The effect of reducing media seems to be very important during preparation of alumina layer. One of the advantages properties of E-AIO is, that it serve a promising method to increase the measuring range of TL method above 10 kGy as well. (author)

  16. Iron films deposited on porous alumina substrates

    Energy Technology Data Exchange (ETDEWEB)

    Yamada, Yasuhiro, E-mail: yyasu@rs.kagu.tus.ac.jp; Tanabe, Kenichi; Nishida, Naoki [Tokyo University of Science (Japan); Kobayashi, Yoshio [The University of Electro-Communications (Japan)

    2016-12-15

    Iron films were deposited on porous alumina substrates using an arc plasma gun. The pore sizes (120 – 250 nm) of the substrates were controlled by changing the temperature during the anodic oxidation of aluminum plates. Iron atoms penetrated into pores with diameters of less than 160 nm, and were stabilized by forming γ-Fe, whereas α-Fe was produced as a flat plane covering the pores. For porous alumina substrates with pore sizes larger than 200 nm, the deposited iron films contained many defects and the resulting α-Fe had smaller hyperfine magnetic fields. In addition, only a very small amount of γ-Fe was obtained. It was demonstrated that the composition and structure of an iron film can be affected by the surface morphology of the porous alumina substrate on which the film is grown.

  17. Hydrogen diffusion in Pb β''-alumina

    International Nuclear Information System (INIS)

    Bates, J.B.; Dudney, N.J.; Wang, J.C.

    1985-01-01

    The mobile Na + ions in Na β''-alumina can be completely exchanged with Pb 2+ ions by treatment in molten PbCl 2 . When this exchange was carried out in the presence of air, protons in the form of OH - were introduced into the conduction layers along with lead ions. Although the concentration of OH - was low, on the order of 5 x 10 -3 per formula unit of Pb/sub 0.84/Mg/sub 0.67/Al/sub 10.33/O_1_7, the distribution of OH - after ion exchange indicated that the proton mobility in Pb β''-alumina is high. The potential use of Pb β''-alumina as a fast proton conductor that is stable at 400 0 C motivated further studies of hydrogen diffusion. In this report, the results of tracer diffusion measurements by isotope exchange will be presented

  18. Electron-irradiation-induced phase transformation in alumina

    International Nuclear Information System (INIS)

    Chen, C.L.; Arakawa, K.; Lee, J.-G.; Mori, H.

    2010-01-01

    In this study, electron-irradiation-induced phase transformations between alumina polymorphs were investigated by high-resolution transmission electron microscopy. It was found that the electron-irradiation-induced α → κ' phase transformation occurred in the alumina under 100 keV electron irradiation. It is likely that the knock-on collision between incident electrons and Al 3+ cations is responsible for the occurrence of electron-irradiation-induced phase transformation from α-alumina to κ'-alumina.

  19. Blocking of grain reorientation in self-doped alumina materials

    International Nuclear Information System (INIS)

    Suarez, M.; Fernandez, A.; Menendez, J.L.; Ramirez-Rico, J.; Torrecillas, R.

    2011-01-01

    Alumina nanoparticles 10-20 nm in diameter were nucleated on alumina particles, 150 nm average diameter, by a colloidal route followed by calcination. It is shown that after sintering, the final grain size is up to 20% smaller due to the addition of the alumina nanoparticles. Electron backscattered diffraction analysis shows that whereas a correlation in the relative crystalline orientations between neighbouring grains exists in the pure materials, the addition of alumina nanoparticles results in a random crystalline orientation.

  20. A hybrid approach to the surface biofunctionalization of nanostructured porous alumina

    Energy Technology Data Exchange (ETDEWEB)

    Silvan, Miguel Manso; Ruiz, Josefa Predestinacion Garcia [Departamento de Fisica Aplicada y Departamento de Biologia Molecular, Facultad de Ciencias, Universidad Autonoma de Madrid, Unidad Asociada GMNF (ICMM-CSIC), 28049 Madrid (Spain); Centro de Investigaciones Biomedicas en Red, Bioingenieria Biomateriales y Nanomedicina (CIBERbbn) (Spain); Gonzalez, Ruy Sanz [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas, 28049 Madrid (Spain); Velez, Manuel Hernandez [Departamento de Fisica Aplicada y Departamento de Biologia Molecular, Facultad de Ciencias, Universidad Autonoma de Madrid, Unidad Asociada GMNF (ICMM-CSIC), 28049 Madrid (Spain)

    2010-02-15

    The application of nanostructured porous alumina templates as a solid support in biomedical assays requires a surface biofunctionalization process that has been addressed in this work by an hybrid aminopropyl-triethoxysilane/tetraisopropyl-orthotitanate (APTS/ TIPT) self assembled film. The nanostructured porous alumina templates are activated in a peroxide solution before immersion in the biofunctionalizing APTS/TIPT solution. The biofunctionalization process was followed up by UV-vis spectroscopy, which confirmed the modification of the dielectric structure of the alumina surface. The influence of the biofunctionalization step in an immunological assay was carried out by fluorescence microscopy. Results confirm the gain in activity after the immobilization of an FITC labelled mouse Igg. Specific biological recognition in a bovine serum albumin (BSA)-antiBSA assay is proved afterwards by shifts observed in the reflectance interferograms thus providing a fast biosensing transducer platform. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  1. Studies of alumina additions in zirconia - magnesia

    International Nuclear Information System (INIS)

    Muccillo, R.

    1987-01-01

    Ionic conductivity measurements have been carried out in the 500 0 C - 1000 0 C temperature range in Mg - PSZ (Partially Stabilized Zirconia) with 0.5 to 10 mol % alumina additions. All specimens were prepared by pressing followed by pre - and sintering at 1000 0 C/2h and1450 0 C/4h, respectively. Thermal histerysis of the ionic conductivity have been detected, probably due to phase changes in the Mg-PSZ samples. The results show that alumina additions up to 2.1% enhances densification with no major variations in electrical resistivity values. (Author) [pt

  2. Delayed Failure in a Shock Loaded Alumina

    International Nuclear Information System (INIS)

    Cooper, G. A.; Millett, J. C. F.; Bourne, N. K.; Dandekar, D. P.

    2006-01-01

    Manganin stress gauges have been used to measure the lateral stress in a shock-loaded alumina. In combination with known longitudinal stresses, these have been used to determine the shear strength of this material, behind the shock front. The two-step nature of the lateral stress traces shows a slow moving front behind the main shock, behind which shear strength undergoes a significant decrease. Results also show that this front decreases markedly in velocity as the HEL is crossed, suggesting that limited plasticity occurs during inelastic deformation. Finally, comparison of measured shear strengths with other aluminas shows a high degree of agreement

  3. Fabrication of Ceramic Matrix Composite Tubes Using a Porous Mullite/Alumina Matrix and Alumina/Mullite Fiber

    National Research Council Canada - National Science Library

    Radsick, Timothy

    2001-01-01

    ... or from inadequate oxide-based ones. A porous mullite/alumina matrix combined with alumina/mullite fiber reinforcement eliminates the need for an interface coating while producing a strong, tough and oxidation resistant composite...

  4. Rapid Nuclear Exclusion of Hcm1 in Aging Saccharomyces cerevisiae Leads to Vacuolar Alkalization and Replicative Senescence

    Directory of Open Access Journals (Sweden)

    Ata Ghavidel

    2018-05-01

    Full Text Available The yeast, Saccharomyces cerevisiae, like other higher eukaryotes, undergo a finite number of cell divisions before exiting the cell cycle due to the effects of aging. Here, we show that yeast aging begins with the nuclear exclusion of Hcm1 in young cells, resulting in loss of acidic vacuoles. Autophagy is required for healthy aging in yeast, with proteins targeted for turnover by autophagy directed to the vacuole. Consistent with this, vacuolar acidity is necessary for vacuolar function and yeast longevity. Using yeast genetics and immunofluorescence microscopy, we confirm that vacuolar acidity plays a critical role in cell health and lifespan, and is potentially maintained by a series of Forkhead Box (Fox transcription factors. An interconnected transcriptional network involving the Fox proteins (Fkh1, Fkh2 and Hcm1 are required for transcription of v-ATPase subunits and vacuolar acidity. As cells age, Hcm1 is rapidly excluded from the nucleus in young cells, blocking the expression of Hcm1 targets (Fkh1 and Fkh2, leading to loss of v-ATPase gene expression, reduced vacuolar acidification, increased α-syn-GFP vacuolar accumulation, and finally, diminished replicative lifespan (RLS. Loss of vacuolar acidity occurs about the same time as Hcm1 nuclear exclusion and is conserved; we have recently demonstrated that lysosomal alkalization similarly contributes to aging in C. elegans following a transition from progeny producing to post-reproductive life. Our data points to a molecular mechanism regulating vacuolar acidity that signals the end of RLS when acidification is lost.

  5. Characterization of alumina using small angle neutron scattering (SANS)

    International Nuclear Information System (INIS)

    Megat Harun Al Rashidn Megat Ahmad; Abdul Aziz Mohamed; Azmi Ibrahim; Che Seman Mahmood; Edy Giri Rachman Putra; Muhammad Rawi Muhammad Zin; Razali Kassim; Rafhayudi Jamro

    2007-01-01

    Alumina powder was synthesized from an aluminium precursor and studied using small angle neutron scattering (SANS) technique and complemented with transmission electron microscope (TEM). XRD measurement confirmed that the alumina produced was high purity and highly crystalline αphase. SANS examination indicates the formation of mass fractals microstructures with fractal dimension of about 2.8 on the alumina powder. (Author)

  6. 21 CFR 73.1010 - Alumina (dried aluminum hydroxide).

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Alumina (dried aluminum hydroxide). 73.1010... GENERAL LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1010 Alumina (dried aluminum hydroxide). (a) Identity. (1) The color additive alumina (dried aluminum hydroxide) is a white, odorless...

  7. Ionic and molecular transport in beta- and beta''-alumina

    International Nuclear Information System (INIS)

    Bates, J.B.

    1984-03-01

    Investigations of rapid transport of cations and water molecules in the β- and β''-alumina family of superionic conductors are reviewed. Particular topics that are discussed include the Haven ratio and mixed-ion effects in β-alumina, and the influence of superlattice ordering on ionic transport in β''-alumina

  8. Fabrication of a segmented composite stainless steel-alumina discharge tube for a theta-pinch coil

    International Nuclear Information System (INIS)

    Dickinson, J.M.; Stoddard, S.D.; Muller, J.F.

    1975-11-01

    An 80-mm-diam segmented discharge tube that simulated in a simplified way the blanket and first wall of the Reference Theta-Pinch Reactor (RTPR) has been constructed. The segments were fabricated by plasma-arc spraying an alumina coating on tubular stainless steel trapezoids. These were laid up to form a cylinder that was contained in a fully dense alumina vacuum tube. The fabrication processes are discussed in detail

  9. Techniques for detection of transition phases in calcined alumina

    International Nuclear Information System (INIS)

    Pandolfelli, V.C.; Folgueras-Dominguez, S.

    1987-01-01

    Detection of transition phases in alumina, is very important in the receiving control and calcination of aluminium hydroxide. The non alfa or transition phases difficults the processability and causes localized shrinkage on sintering compromising the dimensional and mechanical aspects of the product. In this research using refraction index, absorption of dyes, specific density, X-ray diffraction and scanning electron microscopy, analyses, are done in calcined hydroxides submited to different thermal treatments. The limits and facilities of each technique are discussed and compared. (Author) [pt

  10. Effects of Starch on Properties of Alumina-based Ceramic Cores

    Directory of Open Access Journals (Sweden)

    LI Fengguang

    2016-12-01

    Full Text Available In order to improve the poor leachability of alumina-based ceramic cores, different amount of starch was added to the specimens as pore former. Alumina-based ceramic cores were prepared by hot injection technology using corundum powder as base material, paraffin wax and beeswax as plasticizer, silica powder and magnesium oxide powder as mineralizing agent, wherein the parameters of the hot injection process were as follows:temperature of the slurry was 90℃, hot injection pressure was 0.5 MPa and holding time was 25 s. The effects of starch content on the properties of alumina-based ceramic cores were studied and discussed. The results indicate that during sintering period, the loss of starch in the specimens makes porosity of the alumina-based ceramic cores increase. When starch content increases, the room-temperature flexural strength of the ceramic cores reduces and the apparent porosity increases; the volatile solvent increases and the bulk density decreases. After being sintered at 1560℃ for 2.5 h, room-temperature flexural strength of the alumina-based ceramic cores with starch content of 8%(mass fraction is 24.8 MPa, apparent porosity is 47.98% when the volatile solvent is 1.92 g/h and bulk density is 1.88 g/cm3, the complex properties are optimal.

  11. Designing robust alumina nanowires-on-nanopores structures: superhydrophobic surfaces with slippery or sticky water adhesion.

    Science.gov (United States)

    Peng, Shan; Tian, Dong; Miao, Xinrui; Yang, Xiaojun; Deng, Wenli

    2013-11-01

    Hierarchical alumina surfaces with different morphologies were fabricated by a simple one-step anodization method. These alumina films were fabricated by a new raw material: silica gel plate (aluminum foil with a low purity of 97.17%). The modulation of anodizing time enabled the formation of nanowires-on-nanopores hybrid nanostructures having controllable nanowires topographies through a self-assembly process. The resultant structures were demonstrated to be able to achieve superhydrophobicity without any hydrophobic coating layer. More interestingly, it is found that the as-prepared superhydrophobic alumina surfaces exhibited high contrast water adhesion. Hierarchical alumina film with nanowire bunches-on-nanopores (WBOP) morphology presents extremely slippery property which can obtain a sliding angle (SA) as low as 1°, nanowire pyramids-on-nanopores (WPOP) structure shows strongly sticky water adhesion with the adhesive ability to support 15 μL inverted water droplet at most. The obtained superhydrophobic alumina surfaces show remarkable mechanical durability even treated by crimping or pressing without impact on the water-repellent performance. Moreover, the created surfaces also show excellent resistivity to ice water, boiling water, high temperature, organic solvent and oil contamination, which could expand their usefulness and efficacy in harsh conditions. Copyright © 2013 Elsevier Inc. All rights reserved.

  12. Mantle to surface degassing of alkalic magmas at Erebus volcano, Antarctica

    Science.gov (United States)

    Oppenheimer, C.; Moretti, R.; Kyle, P.R.; Eschenbacher, A.; Lowenstern, J. B.; Hervig, R.L.; Dunbar, N.W.

    2011-01-01

    Continental intraplate volcanoes, such as Erebus volcano, Antarctica, are associated with extensional tectonics, mantle upwelling and high heat flow. Typically, erupted magmas are alkaline and rich in volatiles (especially CO2), inherited from low degrees of partial melting of mantle sources. We examine the degassing of the magmatic system at Erebus volcano using melt inclusion data and high temporal resolution open-path Fourier transform infrared (FTIR) spectroscopic measurements of gas emissions from the active lava lake. Remarkably different gas signatures are associated with passive and explosive gas emissions, representative of volatile contents and redox conditions that reveal contrasting shallow and deep degassing sources. We show that this unexpected degassing signature provides a unique probe for magma differentiation and transfer of CO2-rich oxidised fluids from the mantle to the surface, and evaluate how these processes operate in time and space. Extensive crystallisation driven by CO2 fluxing is responsible for isobaric fractionation of parental basanite magmas close to their source depth. Magma deeper than 4kbar equilibrates under vapour-buffered conditions. At shallower depths, CO2-rich fluids accumulate and are then released either via convection-driven, open-system gas loss or as closed-system slugs that ascend and result in Strombolian eruptions in the lava lake. The open-system gases have a reduced state (below the QFM buffer) whereas the closed-system gases preserve their deep oxidised signatures (close to the NNO buffer). ?? 2011 Elsevier B.V.

  13. Feasibility study of use alumina waste in compositions containing clay for the mullite synthesis; Estudo da viabilidade do uso de residuo de alumina em composicoes contendo argilas destinadas a sintese de mulita

    Energy Technology Data Exchange (ETDEWEB)

    Silva, V.J.; Dias, G.; Goncalves, W.P.; Santana, L.N.L., E-mail: valmir_jspb@yahoo.com.br [Universidade Federal de Campina Grande (UFCG), PB (Brazil). Unidade Academica de Engenharia de Materiais

    2016-07-01

    The reuse of alumina residue in addition to reducing environmental impacts can be used as raw material in ceramic masses to mullite produce. This study aims to obtain mullite from compositions containing clays and alumina residue used heating in a conventional oven. The raw materials were processed and characterized. Subsequently, these compositions were formulated containing precursors in appropriate proportions based on the stoichiometry of the mullite 3:2. Then, heat treatment was performed at temperatures of 1300 to 1400°C and 5°C rate/min. The products obtained were characterized by XRD, analyzing qualitatively and quantitatively the phases formed. The results showed that is possible, from compositions containing clays and alumina residue to obtain mullite as major phase (>70%) and high crystallinity (> 80%) The percentage of mullite approached the values obtained with the compositions containing alumina and clays. (author)

  14. Fast femtosecond laser ablation for efficient cutting of sintered alumina substrates

    Science.gov (United States)

    Oosterbeek, Reece N.; Ward, Thomas; Ashforth, Simon; Bodley, Owen; Rodda, Andrew E.; Simpson, M. Cather

    2016-09-01

    Fast, accurate cutting of technical ceramics is a significant technological challenge because of these materials' typical high mechanical strength and thermal resistance. Femtosecond pulsed lasers offer significant promise for meeting this challenge. Femtosecond pulses can machine nearly any material with small kerf and little to no collateral damage to the surrounding material. The main drawback to femtosecond laser machining of ceramics is slow processing speed. In this work we report on the improvement of femtosecond laser cutting of sintered alumina substrates through optimisation of laser processing parameters. The femtosecond laser ablation thresholds for sintered alumina were measured using the diagonal scan method. Incubation effects were found to fit a defect accumulation model, with Fth,1=6.0 J/cm2 (±0.3) and Fth,∞=2.5 J/cm2 (±0.2). The focal length and depth, laser power, number of passes, and material translation speed were optimised for ablation speed and high quality. Optimal conditions of 500 mW power, 100 mm focal length, 2000 μm/s material translation speed, with 14 passes, produced complete cutting of the alumina substrate at an overall processing speed of 143 μm/s - more than 4 times faster than the maximum reported overall processing speed previously achieved by Wang et al. [1]. This process significantly increases processing speeds of alumina substrates, thereby reducing costs, making femtosecond laser machining a more viable option for industrial users.

  15. LOW TEMPERATURE SINTERING OF ALUMINA BIOCERAMIC UNDER NORMAL PRESSURE

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Superfine alumina powder with high purity (mean particle size is less than 0. 35μm) were used as main starting material for sintering alumina ceramic. A multiple additive MgO-ZrO2 (Y2O3) was homogeneously added into the batch by the chemical coprecipitation method. Sintering of alumina bioceramic at low tempera ture (<1600C) was achieved resulting in a dense and high strength alumina ceramic with the bending strength up to 382 MPa and an improved fracture toughness. Mechanism that the multiple additives promote the sintering of alumina ceramic is discussed on the base of XRD and SEM analysis.

  16. Investigating the property profile of polyamide-alumina nanocomposite materials

    International Nuclear Information System (INIS)

    Sarwar, Muhammad Ilyas; Zulfiqar, Sonia; Ahmad, Zahoor

    2009-01-01

    Transparent sol-gel-derived nanocomposites were prepared by incorporating an alumina network into a polyamide matrix. Different amounts of aluminum butoxide were hydrolyzed and condensed to produce the alumina network. Thin composite films were characterized in terms of their optical, morphological, mechanical and thermomechanical properties. Tensile modulus, stress at both yield and break points, improved for alumina loadings of 5-10 wt.%. The glass transition temperature increased to 140 o C for nanocomposites containing 15 wt.% alumina. Scanning electron microscopy investigations indicated a uniform distribution of alumina in the polyamide matrix.

  17. Mechanical Properties of Plasma Sprayed Alumina Coatings

    Czech Academy of Sciences Publication Activity Database

    Kovářík, O.; Nohava, Jiří; Siegel, J.

    2003-01-01

    Roč. 48, č. 2 (2003), s. 129-145 ISSN 0001-7043 R&D Projects: GA ČR GA106/01/0094 Institutional research plan: CEZ:AV0Z2043910 Keywords : plasma sprayed alumina coatings, fatigue test, metalography, fractography, residual stress, microhardness, Young's modulus , four-point bending Subject RIV: BL - Plasma and Gas Discharge Physics

  18. Yield stress of alumina-zirconia suspensions

    International Nuclear Information System (INIS)

    Ramakrishnan, V.; Pradip; Malghan, S.G.

    1996-01-01

    The yield stress of concentrated suspensions of alumina, zirconia, and mixed alumina-zirconia powders was measured by the vane technique as a function of solids loading, relative amounts of alumina and zirconia, and pH. At the isoelectric point (IEP), the yield stress varied as the fourth power of the solids loading. The relative ratio of alumina and zirconia particles was important in determining the yield stress of the suspension at the IEP. The yield stress of single and mixed suspensions showed a marked variation with pH. The maximum value occurred at or near the IEP of the suspension. The effect of electrical double-layer forces on the yield stress can be described on the basis of the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. A normalized yield stress--that is, the ratio of the yield stress at a given pH to the yield stress at the IEP predicted by this model--showed good correlation with experimental data

  19. Minimum and Full Fluidization Velocity for Alumina Used in the Aluminum Smelter

    Directory of Open Access Journals (Sweden)

    Paulo Douglas S. de Vasconcelos

    2011-11-01

    Full Text Available Fluidization is an engineering unit operation that occurs when a fluid (liquid or gas ascends through a bed of particles, and these particles get a velocity of minimum fluidization enough to stay in suspension, but without carrying them in the ascending flow. As from this moment the powder behaves as liquid at boiling point, hence the term “fluidization”. This operation is widely used in the aluminum smelter processes, for gas dry scrubbing (mass transfer and in a modern plant for continuous alumina pot feeding (particles’ momentum transfer. The understanding of the alumina fluoride rheology is of vital importance in the design of fluidized beds for gas treatment and fluidized pipelines for pot feeding. This paper shows the results of the experimental and theoretical values of the minimum and full fluidization velocities for the alumina fluoride used to project the state of the art round non‐metallic air‐fluidized conveyor of multiples outlets.

  20. Wear of alumina on alumina total hip prosthesis - effect of lubricant on hip simulator test

    Energy Technology Data Exchange (ETDEWEB)

    Ueno, M.; Amino, H. [Kyocera Corp., Fushimi, Kyoto (Japan). Bioceram Div.; Oonishi, H. [Dept. of Orthopaedic Surgery, Artificial Joint Sect. and Biomat. Res. Lab., Osaka Minami National Hospital, Osaka (Japan); Clarke, I.C.; Good, V. [Dept. of Orthopaedic Surgery, Loma Linda Univ. Medical Center, CA (United States)

    2001-07-01

    The complex wear-friction-lubrication behavior of alumina on alumina combination in total hip prostheses (THP) was investigated using a hip joint simulator. The objectives of this study were to evaluate the effect of the ball/cup clearance and of the lubricant conditions. Alumina bearings were categorized in three diametrical clearances, 20-30, 60-70 and 90-100 micrometer, three each and wear tests were carried out with 90% bovine serum. There was no significant difference between three groups. Volumetric wear in the run-in phase for all tested nine ceramic liners averaged 0.27mm{sup 3}/million cycles and in the steady-state phase averaged 0.0042mm{sup 3}/million cycles. In addition to the 90% serum, 27% serum and saline were used as the lubricant for evaluate the effect of serum concentration on alumina on alumina wear couples. The wear test results showed that in all tested conditions the wear trends of alumina BEARING were bi-phasic and wear volume could be affected by the serum concentration. Both ''Run-in'' and ''Steady-state'' wear rates in 90% bovine serum were three times higher than those in saline. (orig.)

  1. Preparation of alumina - β'. 2. Effects of the impurities in the ionic conductivity

    International Nuclear Information System (INIS)

    Casarini, J.R.; Souza, D.P.F.

    1984-01-01

    Sinterized samples of alumina - β' with 98% of theoretical density are obtained from alumina powder (β + β') with composition of 8.85% Na 2 O + 0.75% Li 2 O + 90.40% Al 2 O 3 . The concentration of this impurities is controled by the carbothermic reduction at 1300 0 C of aluminium hydroxide used as raw material. The final product of the reduction process is aluminium oxide. The conductivity measurement of the sodium beam is done in samples with (2.5 x 1.0 x 0.3) cm using synchronous phase amplificator. (E.G.) [pt

  2. Combustion chemical vapor deposition (CCVD) of LaPO4 monazite and beta-alumina on alumina fibers for ceramic matrix composites

    International Nuclear Information System (INIS)

    Hwang, T.J.; Hendrick, M.R.; Shao, H.; Hornis, H.G.; Hunt, A.T.

    1998-01-01

    This research used the low cost, open atmosphere combustion chemical vapor deposition (CCVD SM ) method to efficiently deposit protective coatings onto alumina fibers (3M Nextel TM 610) for use in ceramic matrix composites (CMCs). La-monazite (LaPO 4 ) and beta-alumina were the primary candidate debonding coating materials investigated. The coated fibers provide thermochemical stability, as well as desired debonding/sliding interface characteristics to the CMC. Dense and uniform La-phosphate coatings were obtained at deposition temperatures as low as 900-1000 C with minimal degradation of fibers. However, all of the β-alumina phases required high deposition temperatures and, thus, could not be applied onto the Nextel TM 610 alumina fibers. The fibers appeared to have complete and relatively uniform coatings around individual filaments when 420 and 1260 filament tows were coated via the CCVD process. Fibers up to 3 feet long were fed through the deposition flame in the laboratory of MicroCoating Technologies (MCT). TEM analyses performed at Wright-Patterson AFB on the CCVD coated fibers showed a 10-30 nm thick La-rich layer at the fiber/coating interface, and a layer of columnar monazite 0.1-1 μm thick covered with sooty carbon of <50 nm thick on the outside. A single strength test on CCVD coated fibers performed by 3M showed that the strength value fell in the higher end of data from other CVD coated samples. (orig.)

  3. Effect of alumina sol addition to micro-arc oxidation electrolyte on the properties of MAO coatings formed on magnesium alloy AZ91D

    International Nuclear Information System (INIS)

    Laleh, M.; Rouhaghdam, A. Sabour; Shahrabi, T.; Shanghi, A.

    2010-01-01

    Oxide coatings were formed on AZ91D magnesium alloy using micro-arc oxidation process in alkaline electrolyte without and with addition of alumina sol. The microstructures and compositions of the MAO coatings were analyzed by scanning electron microscope (SEM) and X-ray diffraction (XRD). Corrosion behaviors of the coatings were evaluated with electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests in 3.5%NaCl solution. Porosities of the coatings were measured by potentiodynamic polarization tests. It was found that the coating produced in the electrolyte with alumina sol has more compact and uniform morphology than that produced in the electrolyte without alumina sol. The results of corrosion tests showed that the coating formed in electrolyte with alumina sol enhances the corrosion resistance of the substrate significantly. XRD patterns showed that the coating produced in the electrolyte with alumina sol has more MgAl 2 O 4 phase than MgO.

  4. Isotope geochemistry of brasiliano age, coarsely porphyritic, K-calc-alkalic granitoids and associated K-diorites, northeast Brazil

    International Nuclear Information System (INIS)

    Sial, A.N.; Mariano, G.; Ferreira, V.P.

    1989-01-01

    Several porphyritic, K-calc-alkalic were syntectonically intruded in NE Brazil during the Brasiliano orogeny. They show bi-(qz) diorite and coarsely porphyritic granodiorite to qz monzonite ('Itaporanga-type') in commingling zones on a scale of cm to m irrespective of whether plutons are at the margins of the NE-trending Cachoeirinha-Salgueiro Fold Belt (CSF) or intruded metasediments of the Serido Fold Belt (SFB). The bi(qz) diorites are found in magmatic or stromatic structures and narrow dikes wich intruded the felsic facies. SiO 2 in the porphyritic facies ranges from 61 to 72% with K 2 O usually > Na 2 O. K-diorities exhibit SiO 2 from 50 to 58%, MgO from 2 to 10% and K 2 O from 2 to 5%. Both facies are usually Ba and Sr-enriched, with similar, highly fractionated REE patterns, lacking free of Eu anomaly. Quartz 180 values are considered homogeneous on the scale of these intrusions in the CSF, (8 to 10 per milSMOW). Bi-(qz) diorites exhibit slightly higher 180 (9.5 to 10.5 per milSMOW). In the SFB both facies are lower than 180. The oxygen isotope data for the porphyritic facies are compatible with I-type source with some metasedimentary component of variable proportion. As bi(qz) diorites were formed pre- to post-porphyritic facies intrusion, their high LREE, K and 180 reflect their source rather than the interaction with the potassic felsic magma. Preliminarly sulfur isotope values suggest that porphyritic facies of granitoids in the SBF are lower in 34S than those in the CSF. Rb and Sr isotopes reflect source heterogeneity, complicated by mixing relations. Ages span from 510 to 630 Ma suggesting that the Itaporanga-type association was formed during uplift and cooling of the Pan-African I and onset of the Pan-African II orogenies, recognized in West Africa. (author) [pt

  5. Magnetic properties of ferromagnetic nanowires embedded in nanoporous alumina membranes

    International Nuclear Information System (INIS)

    Kroell, M.; Blau, W.J.; Grandjean, D.; Benfield, R.E.; Luis, F.; Paulus, P.M.; Jongh, L.J. de

    2002-01-01

    Iron, nickel and cobalt nanowires are prepared within the pores of nanoporous alumina membranes using an electrochemical AC plating procedure. Nanowires produced in this way can be easily varied in diameter (5-250 nm) and length (up to several hundred microns). The magnetisation curves for these nanowire/alumina composites can then be determined not only as a function of the temperature but also as a function of the wire diameter and length. Conclusions regarding the magnetisation reversal processes that take place in the wires can be drawn. For Fe and Ni nanowires, we show that the magnetisation process in wires with a diameter smaller than the domain wall width is independent of the wire length and probably takes place via the formation of a small magnetic domain at the end of the wires and a subsequent propagation of the domain wall along the wire. For Co nanowires a competition between the shape anisotropy and the temperature- and size-dependent magnetocrystalline anisotropy could be observed

  6. Improvement of mechanical properties of zirconia-toughened alumina by sinter forging

    NARCIS (Netherlands)

    He, Y.; Winnubst, Aloysius J.A.; Verweij, H.; Burggraaf, Anthonie; Burggraaf, A.J.

    1994-01-01

    ZTA powder with a composition of 85 wt% alumina/15 wt% zirconia was prepared by a gel precipitation method. Sinter forging was performed with this powder to enhance the mechanical properties of ZTA materials. The influence of processing flaws on mechanical properties of sinter forged materials and

  7. Adhesion of electrolessly deposited nickel-phosphorus on alumina ceramic : an assessment of the current status

    NARCIS (Netherlands)

    Severin, J.W.; With, de G.

    1993-01-01

    Literature data on the adhesion of electrolessly deposited Ni(P) films on alumina ceramic substrates are reviewed in this paper. The influences of conditions of successive etching, nucleation and metallization processes on adhesion are discussed as well as the effect of subsequent annealing

  8. Electroless Fabrication of Cobalt Alloys Nanowires within Alumina Template

    Directory of Open Access Journals (Sweden)

    Nazila Dadvand

    2007-01-01

    Full Text Available A new method of nanowire fabrication based on electroless deposition process is described. The method is novel compared to the current electroless procedure used in making nanowires as it involves growing nanowires from the bottom up. The length of the nanowires was controlled at will simply by adjusting the deposition time. The nanowires were fabricated within the nanopores of an alumina template. It was accomplished by coating one side of the template by a thin layer of palladium in order to activate the electroless deposition within the nanopores from bottom up. However, prior to electroless deposition process, the template was pretreated with a suitable wetting agent in order to facilitate the penetration of the plating solution through the pores. As well, the electroless deposition process combined with oblique metal evaporation process within a prestructured silicon wafer was used in order to fabricate long nanowires along one side of the grooves within the wafer.

  9. Defluoridation of water using activated alumina in presence of natural organic matter via response surface methodology.

    Science.gov (United States)

    Samarghandi, Mohammad Reza; Khiadani, Mehdi; Foroughi, Maryam; Zolghadr Nasab, Hasan

    2016-01-01

    Adsorption by activated alumina is considered to be one of the most practiced methods for defluoridation of freshwater. This study was conducted, therefore, to investigate the effect of natural organic matters (NOMs) on the removal of fluoride by activated alumina using response surface methodology. To the authors' knowledge, this has not been previously investigated. Physico-chemical characterization of the alumina was determined by scanning electron microscope (SEM), Brunauer-Emmett-Teller (BET), Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence (XRF), and X-ray diffractometer (XRD). Response surface methodology (RSM) was applied to evaluate the effect of single and combined parameters on the independent variables such as the initial concentration of fluoride, NOMs, and pH on the process. The results revealed that while presence of NOM and increase of pH enhance fluoride adsorption on the activated alumina, initial concentration of fluoride has an adverse effect on the efficiency. The experimental data were analyzed and found to be accurately and reliably fitted to a second-order polynomial model. Under optimum removal condition (fluoride concentration 20 mg/L, NOM concentration 20 mg/L, and pH 7) with a desirability value of 0.93 and fluoride removal efficiency of 80.6%, no significant difference was noticed with the previously reported sequence of the co-exiting ion affinity to activated alumina for fluoride removal. Moreover, aluminum residual was found to be below the recommended value by the guideline for drinking water. Also, the increase of fluoride adsorption on the activated alumina, as NOM concentrations increase, could be due to the complexation between fluoride and adsorbed NOM. Graphical abstract ᅟ.

  10. Characterization of metallized alumina: properties. [Diamonite P-3142-1, Wesgo Al-500 alumina ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Swearengen, J.C.; Burchett, O.L., Gieske, J.H.

    1976-12-01

    The effects of metallizing and brazing on the mechanical properties of Diamonite P-3142-1 and Wesgo A1-500 alumina ceramics were evaluated. The information was required for analytical prediction of the performance of ceramic-to-metal joints formed by the metallize-braze process. Residual stresses and fracture strengths were monitored before and after metallizing treatments; micromechanical modelling and surface acoustic wave experiments were utilized to determine density, thermal expansion and elastic moduli within the metallized region of the ceramics. It was observed that the metallizing elements penetrate the ceramics to a depth of about 005 ..mu..m and measurably modify the properties to a depth of about 300 ..mu..m. The moduli and density are increased approximately five percent within the penetration zone. The thermal expansion coefficients are not modified significantly by metallizing; the warping which occurs during metallizing results from microstructural changes within the ceramics and not differential thermal contraction. Fracture toughness of the Diamonite ceramic is greater than that of the Wesgo, although the metallizing treatments increase the toughness of each. Fracture strength of the Diamonite was degraded on the metallized surface, whereas the strength of the Wesgo was essentially unchanged by metallizing. Macroscopic compressive residual stresses, which exist at the surfaces of the ceramics, do not significantly affect the fracture strengths. The implications of these results for calculations of joint performance are discussed.

  11. Characterization of glassy phase at the surface of alumina ceramics substrate and its effect on laser cutting

    Energy Technology Data Exchange (ETDEWEB)

    Fu Renli [School of Mechanical-Electronic and Materials Engineering, China Univ. of Mining and Technology, Xuzhou, JS (China); Dept. of Ceramics and Glass Engineering, CICECO, Univ. of Aveiro, Aveiro (Portugal); Li Yanbo [School of Mechanical-Electronic and Materials Engineering, China Univ. of Mining and Technology, Xuzhou, JS (China); Xu Xin; Ferreira, J.M.F. [Dept. of Ceramics and Glass Engineering, CICECO, Univ. of Aveiro, Aveiro (Portugal)

    2004-07-01

    Nowadays alumina ceramic substrates are widely used for high precision applications in electronic devices, such as hybrid integrated circuits (HIC). Usually, the alumina ceramic substrates are shaped through tape casting method and sintered in continuous slab kilns. The sintering aids used to enhance densification during sintering give rise to the formation of an alumino-silicate liquid phase, which is of crucial importance in pressureless and low-temperature sintering (<1600 C) of alumina ceramics. The preferential migration of liquid phase to the surface of alumina substrates under the capillary action and its transformation into glassy phase during cooling affects the subsequent processing steps of HIC. A smoothening effect on surface with its enrichment in glassy phase is accompanied by a decrease of the surface toughness. On the other hand, the accumulated glassy phase onto the surface has a great effect on laser cutting. The high temperatures developed during laser cutting turn the superficial glassy phase into liquid again, while rapid solidification will occur after removing laser beam. The fast cooling of the liquid phase causes formation of extensive network of cracks on the surface of alumina substrate. Apparently, the presence of such faults degrades mechanical strength and thermal shock resistance of alumina substrates. Meanwhile, the recast layers and spatter deposits at the periphery of the hole has been observed. (orig.)

  12. Agentes ligantes e seus efeitos em concretos refratários alumina-magnésia Binders and their effects on alumina-magnesia refratory castables

    Directory of Open Access Journals (Sweden)

    M. A. L. Braulio

    2010-12-01

    Full Text Available Concretos refratários alumina-magnésia são comumente ligados por cimentos de aluminato de cálcio. Estes materiais apresentam, em temperaturas elevadas, uma reação de caráter expansivo decorrente da espinelização in-situ (MgAl2O4. Quando ligados por cimentos, reações adicionais (formação de CA2 e CA6 contribuem para a expansão. Uma alternativa para controlar a estabilidade volumétrica é a substituição do cimento tipicamente utilizado (~30%-p CaO por outro de menor teor de cálcio (~20%-p CaO ou por alumina hidratável. Tais substituições podem afetar as propriedades dos concretos, como a resistência mecânica a frio, a hidratação da magnésia e as propriedades durante e após a sinterização. Deste modo, o objetivo deste trabalho é avaliar o impacto destes ligantes no processamento de concretos alumina-magnésia. Sendo assim, pretende-se utilizar a fonte de ligante como uma ferramenta para a obtenção de concretos refratários com expansão engenheirada, visando-se aumentar a flexibilidade na seleção de materiais aplicados em panelas de siderurgia.The usual binder of alumina-magnesia castables is the calcium aluminate cement. Due to in-situ spinel (MgAl2O4 formation at high temperatures, these materials present an expansive behavior. When bonded with cement, further reactions (CA2 and CA6 formation also contribute to the overall expansion. Changing the most common cement used (~ 30 wt.% CaO for other containing less calcia (~ 20 wt.% CaO or for hydratable alumina are suitable alternatives for controlling the castables' volumetric stability. Nevertheless, the binder replacement may affect castables properties, such as cold mechanical strength, MgO hydration degree and properties during and after sintering. Therefore, the objective of the present paper is to analyze the effects of these binders on the alumina-magnesia castables processing. As a result, the binder systems can be used as a tool for designing the alumina

  13. Control of the γ-alumina to α-alumina phase transformation for an optimized alumina densification

    Energy Technology Data Exchange (ETDEWEB)

    Lamouri, S.; Hamidouche, M.; Bouaouadja, N.; Belhouchet, H.; Garnier, V.; Fantozzi, G.; Trelkat, J.F.

    2017-07-01

    In this work, we studied the aptitude to sintering green bodies using γ-Al2O3 transition alumina as raw powder. We focused on the influence of the heating rate on densification and microstructural evolution. Phase transformations from transition alumina γ→δ→θ→α-Al2O3 were studied by in situ X-rays diffraction from the ambient to 1200°C. XRD patterns revealed coexistence of various phase transformations during the heating cycle. DTA and dilatometry results showed that low heating rate leads to a significant reduction of the temperature of the α-Al2O3 alumina formation. Around 1190, 1217 and 1240°C were found when using 5, 10 and 20°C/min of heating rate, respectively. The activation energy for θ-Al2O3→α-Al2O3 transformation calculated by Kissinger and JMA equations using dilatometry method were 464.29 and 488.79kJ/mol, respectively and by DTA method were 450.72 and 475.49kJ/mol, respectively. In addition, the sintering of the green bodies with low heating rate promotes the rearrangement of the grains during θ-Al2O3→α-Al2O3 transformation, enhancing the relative density to 95% and preventing the development of a vermicular structure. (Author)

  14. Oxidation of Alumina-Forming MAX Phases in Turbine Environments

    Science.gov (United States)

    Smialek, James; Garg, Anita; Harder, Bryan; Nesbitt, James; Gabb, Timothy; Gray, SImon

    2017-01-01

    Protective coatings for high temperature turbine components are based on YSZ thermal barriers and oxidation resistant, alumina-forming NiAl or NiCoCrAlY bond coats. Ti2AlC and Cr2AlC MAX phases are thus of special interest because of good oxidation resistance and CTE that can match Al2O3 and YSZ. Their alumina scales grow according to cubic kinetics due to grain growth in the scale, with initial heating dominated by fast TiO2 growth. Protective cubic kinetics are also found in high pressure burner rig tests of MAXthal 211 Ti2AlC, but with reduced rates due to volatile TiO(OH)2 formation in water vapor. YSZ-coatings on bulk Ti2AlC exhibit remarkable durability up to 1300C in furnace tests and at least a 25x life advantage compared to superalloys. At another extreme, Cr2AlC is resistant to low temperature Na2SO4 hot corrosion and exhibits thermal cycling stability bonded to a superalloy disk material. Accordingly, sputtered Cr2AlC coatings on disk specimens prevented hot corrosion detriments on LCF. Breakaway oxidation (Ti2AlC), scale spallation (Cr2AlC), interdiffusion, and processing as coatings still present serious challenges. However the basic properties of MAX phases provide some unusual opportunities for use in high temperature turbines.

  15. Wet chemical synthesis of nickel supported on alumina catalysts

    International Nuclear Information System (INIS)

    Freire, Ranny Rodrigues; Costa, Talita Kenya Oliveira; Morais, Ana Carla da Fonseca Ferreira; Costa, Ana Cristina Figueiredo de Melo; Freitas, Normanda Lino de

    2016-01-01

    Heterogenic catalysts are those found to be in a different phase on the reaction when compared to the reactants and products. Preferred when compared to homogeneous catalysts due to the easiness on which the separation is processed. The objective of this study is to obtain and characterize Alumina based catalysts impregnated with Nickel (Al_2O_3), by wet impregnation. The alumina was synthesized by combustion reaction. Before and after the impregnation the catalysts were characterized by X-ray diffraction (XRD), granulometric analysis, the textural analysis will be held by nitrogen adsorption (BET), energy-dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM). The results show a presence of a stable crystalline phase of Al2O3 in all the studied samples and after the impregnation the second phase formed was of NiO and NiAl_2O_4. The Al_2O_3 e Ni/Al_2O_3 catalysts resulted in clusters with a medium diameter of 18.9 and 14.2 μm, respectively. The catalysts show a medium-pore characteristic (medium pore diameter between 2 and 50 nm), the superficial area to Al_2O_3 and Ni/Al_2O_3 catalysts were 8.69 m"2/g and 5.56 m"2/g, respectively. (author)

  16. Alkalization of steam and condensate with 2-amino-1-butanol and hydrazine; Alkalisering av aanga och kondensat med butanolamin och hydrazin

    Energy Technology Data Exchange (ETDEWEB)

    Falk, I [Studsvik Material AB, Nykoeping (Sweden)

    1996-04-01

    To maintain a low corrosion level in steam- and condensate systems at power and industrial plants, an alkalization of the steam is needed. A low corrosion level lowers the risk of operation disturbances and reduces the cost of the condensate clean up. A better knowledge in the behavior of the alkalis will improve the possibilities to avoid the corrosion attacks. In this work experimental measurements have been carried out during steam boiler conditions as temperature, continuous steam generation and condensation. It has been found that the volatility of 2-amino-1-butanol is very low during stationary dynamic conditions at 250 deg C and 120 deg C. To achieve a high ph-value in the final condensate a very high concentration of 2-amino-1-butanol is thus needed especially when the steam contains acidic compounds. The alkalization effect is obtained from ammonia which is created by thermal decomposition of hydrazine in the boiler water. It is necessary to carry out experimental investigations showing the thermal stability of organic compounds in boiler water before it is possible to recommend them as better volatile alkalis than ammonia and hydrazine. 6 refs, 13 figs

  17. Mechanical properties of ion-implanted alumina

    International Nuclear Information System (INIS)

    Pope, S.G.

    1988-01-01

    Monolithic oxide ceramics are being proposed as structural materials in continuously more-demanding applications. The demands being placed on these materials have caused concern pertaining to the continued growth of oxide structural ceramics due to limited toughness. The realization that ceramic strength and toughness can be affected by surface conditions has led to many surface-modification techniques, all striving to improve the mechanical properties of ceramics. Along these lines, the effects of ion implantation as a surface modification technique for improvement of the mechanical properties of alumina were studied. Initially, sapphire samples were implanted with elemental ion species that would produce oxide precipitates within the sapphire surface when annealed in an oxygen-containing atmosphere. Optimum conditions as determined from implantation into sapphire were then used to modify a polycrystalline alumina. Specific modifications in microhardness, indentation fracture toughness and flexure strength are reported for the parameters studied. Microstructure and phase relationships related to modified surfaces properties are also reported

  18. Mesoscale Modelling of the Response of Aluminas

    International Nuclear Information System (INIS)

    Bourne, N. K.

    2006-01-01

    The response of polycrystalline alumina to shock is not well addressed. There are several operating mechanisms that only hypothesized which results in models which are empirical. A similar state of affairs in reactive flow modelling led to the development of mesoscale representations of the flow to illuminate operating mechanisms. In this spirit, a similar effort is undergone for a polycrystalline alumina. Simulations are conducted to observe operating mechanisms at the micron scale. A method is then developed to extend the simulations to meet response at the continuum level where measurements are made. The approach is validated by comparison with continuum experiments. The method and results are presented, and some of the operating mechanisms are illuminated by the observed response

  19. Performance characteristics of porous alumina ceramic structures

    International Nuclear Information System (INIS)

    Latella, B.A.; Liu, T.

    2000-01-01

    Porous ceramics have found a wide range of applications as filters for liquids and gases. The suitability of materials for use in these types of applications depends on the microstructure (grain size, pore size and pore volume fraction) and hence the mechanical and thermal properties. In this study alumina ceramics with different levels of porosity and controlled pore sizes were fabricated and the surface damage and fracture properties were examined. Copyright (2000) The Australian Ceramic Society

  20. Separation of tungsten and rhenium on alumina

    Directory of Open Access Journals (Sweden)

    MILOVAN SM. STOILJKOVIC

    2004-09-01

    Full Text Available The conditions for the efficient separation of tungsten(VI and rhenium (VII on alumina were established. The distribution coefficients Kd for tungstate and perrhenate anions, as well as the separation factors a (a = KdWO42-/Kd ReO4- were determined using hydrochloric or nitric acid as the aqueous media. A solution of sodium chloride in the pH range 2–6 was also examined. Under all the tested experimental conditions, alumina is a much better adsorbent for tungsten than for rhenium. The obtained results indicated that the best separation of these two elements is achieved when 0.01– 0.1 mol dm-3 HCl or 1.0 mol dm-3 HNO3 are used as the aqueous media. If NaCl is used as the aqueous phase, the best separation is achieved with 0.20 mol dm-3 NaCl, pH 4–6. Under these experimental conditions, the breakthrough and saturation capacities of alumina for tungsten at pH 4 are 17 and 26 mg W/g Al2O3, respectively. With increasing pH, these values decrease. Thus, at pH 6 they are only 4 and 13 mg W/g Al2O3, respectively.

  1. Surface preparation for high purity alumina ceramics enabling direct brazing in hydrogen atmospheres

    Science.gov (United States)

    Cadden, Charles H.; Yang, Nancy Yuan Chi; Hosking, Floyd M.

    2001-01-01

    The present invention relates to a method for preparing the surface of a high purity alumina ceramic or sapphire specimen that enables direct brazing in a hydrogen atmosphere using an active braze alloy. The present invention also relates to a method for directly brazing a high purity alumina ceramic or sapphire specimen to a ceramic or metal member using this method of surface preparation, and to articles produced by this brazing method. The presence of silicon, in the form of a SiO.sub.2 -containing surface layer, can more than double the tensile bond strength in alumina ceramic joints brazed in a hydrogen atmosphere using an active Au-16Ni-0.75 Mo-1.75V filler metal. A thin silicon coating applied by PVD processing can, after air firing, produce a semi-continuous coverage of the alumina surface with a SiO.sub.2 film. Room temperature tensile strength was found to be proportional to the fraction of air fired surface covered by silicon-containing films. Similarly, the ratio of substrate fracture versus interface separation was also related to the amount of surface silicon present prior to brazing. This process can replace the need to perform a "moly-manganese" metallization step.

  2. Optimizing the Synthesis of Alumina Inserts Using Hot Isostatic Pressing (HIP)

    Science.gov (United States)

    Ariff, T. F.; Azhar, A. Z.; Sariff, M. N.; Rasid, S. N.; Zahari, S. Z.; Bahar, R.; Karim, M.; Nurul Amin, AKM

    2018-01-01

    Alumina or Aluminium Oxide (Al2O3) is well known for its high strength and hardness. Its low heat retention and low specific heat characteristics make it attractive to be used widely as a cutting tool for grinding, milling and turning processes. Various synthesis methods have been used for the purpose of enhancing the properties of the alumina inserts. However, the optimization process using Hot Isostatic Pressing (HIP) has not been performed. This research aims in finding the optimum parameters in synthesizing the alumina inserts (98Al2O3 1.6ZrO2 0.4MgO, 93Al2O3 6.4ZrO2 0.6MgO and 85Al2O3 14.5ZrO2 0.5MgO) using HIP at different temperatures (1200, 1250 and 1300°C) and sintering time (10, 30 and 60 minutes). Hardness, density, shrinkage and microstructure using SEM were analysed. The optimum sintering condition for the alumina insert was found in 98Al2O3 1.6ZrO2 0.4MgO sintered at 1300°C for 60 minutes for it exhibited the highest values of hardness (1917HV), density (3.95g/cm3), shrinkage (9.6%).

  3. Wet chemical synthesis of nickel supported on alumina catalysts; Sintese de catalisadores de niquel suportado em alumina por via umida

    Energy Technology Data Exchange (ETDEWEB)

    Freire, Ranny Rodrigues; Costa, Talita Kenya Oliveira; Morais, Ana Carla da Fonseca Ferreira; Costa, Ana Cristina Figueiredo de Melo; Freitas, Normanda Lino de, E-mail: normanda@ufcg.edu.br [Universidade Federal de Campina Grande (UFCG), PB (Brazil)

    2016-07-01

    Heterogenic catalysts are those found to be in a different phase on the reaction when compared to the reactants and products. Preferred when compared to homogeneous catalysts due to the easiness on which the separation is processed. The objective of this study is to obtain and characterize Alumina based catalysts impregnated with Nickel (Al{sub 2}O{sub 3}), by wet impregnation. The alumina was synthesized by combustion reaction. Before and after the impregnation the catalysts were characterized by X-ray diffraction (XRD), granulometric analysis, the textural analysis will be held by nitrogen adsorption (BET), energy-dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM). The results show a presence of a stable crystalline phase of Al2O3 in all the studied samples and after the impregnation the second phase formed was of NiO and NiAl{sub 2}O{sub 4}. The Al{sub 2}O{sub 3} e Ni/Al{sub 2}O{sub 3} catalysts resulted in clusters with a medium diameter of 18.9 and 14.2 μm, respectively. The catalysts show a medium-pore characteristic (medium pore diameter between 2 and 50 nm), the superficial area to Al{sub 2}O{sub 3} and Ni/Al{sub 2}O{sub 3} catalysts were 8.69 m{sup 2}/g and 5.56 m{sup 2}/g, respectively. (author)

  4. Cold Spray Aluminum–Alumina Cermet Coatings: Effect of Alumina Content

    Science.gov (United States)

    Fernandez, Ruben; Jodoin, Bertrand

    2018-04-01

    Deposition behavior and deposition efficiency were investigated for several aluminum-alumina mixture compositions sprayed by cold spray. An increase in deposition efficiency was observed. Three theories postulated in the literature, explaining this increase in deposition efficiency, were investigated and assessed. Through finite element analysis, the interaction between a ceramic particle peening an impacting aluminum particle was found to be a possible mechanism to increase the deposition efficiency of the aluminum particle, but a probability analysis demonstrated that this peening event is too unlikely to contribute to the increment in deposition efficiency observed. The presence of asperities at the substrate and deposited layers was confirmed by a single-layer deposition efficiency measurement and proved to be a major mechanism in the increment of deposition efficiency of the studied mixtures. Finally, oxide removal produced by the impact of ceramic particles on substrate and deposited layers was evaluated as the complement of the other effects and found to also play a major role in increasing the deposition efficiency. It was found that the coatings retained approximately half of the feedstock powder alumina content. Hardness tests have shown a steady increase with the coating alumina content. Dry wear tests have revealed no improvement in wear resistance in samples with an alumina content lower than 22 wt.% compared to pure aluminum coatings. Adhesion strength showed a steady improvement with increasing alumina content in the feedstock powder from 18.5 MPa for pure aluminum coatings to values above 70 MPa for the ones sprayed with the highest feedstock powder alumina content.

  5. Tribological and stability investigations of alkylphosphonic acids on alumina surface

    International Nuclear Information System (INIS)

    Cichomski, M.; Kośla, K.; Grobelny, J.; Kozłowski, W.; Szmaja, W.

    2013-01-01

    Alumina substrates are commonly used for various micro-/nanoelectromechanical systems (MEMS/NEMS). For efficient and lifetime longevity of these devices, lubricant films of self-assembled monolayers (SAMs) with nanometer thickness are increasingly being employed. In the present paper, we report preparation, tribological and stability investigations of alkylphosphonic acids on the alumina surface. The alkylphosphonic acids were prepared on the alumina surface using the liquid phase deposition method. The effectiveness of modification of the alumina surface by alkylphosphonic acids was investigated using water contact angle measurements, secondary ion mass spectrometry, X-ray photoelectron and infrared spectroscopy. Frictional behavior in milinewton load range was studied by microtribometry. It is shown that surface modification of the alumina surface by alkylphosphonic acids reduces the coefficient of friction values compared to the unmodified alumina. In comparison to the non-modified alumina surface, all tested alkylphosphonic acids cause a decrease in the friction coefficients in friction tests for counterparts made from different materials, such as steel, zirconia and silicon nitride. It is also found that the alumina surface modified by alkylphosphonic acids with longer chain has a higher degree of hydrophobicity and lower coefficient of friction. The best frictional properties are obtained for the system consisting of the alumina surface modified by n-octadecylphosphonic acid and silicon nitride counterpart. Stability tests in different environmental conditions: laboratory, acidic and alkaline solutions were also monitored.

  6. Dynamical stability of the alpha and theta phases of alumina

    DEFF Research Database (Denmark)

    Lodziana, Zbigniew; Parlinski, K.

    2003-01-01

    Using density functional calculations the phonon dispersion relations, phonon density of states, and free energy of theta and alpha phases of alumina are investigated. The temperature dependence of the free energy indicates that entropy contributes to the destabilization of the alpha phase...... cations in alumina, and suggest that some other than entropic mechanism exists, which stabilizes transition aluminas up to 1400 K. The present calculations go beyond the ground state energy calculations [C. Wolverton and K.C. Hass, Phys. Rev. B 63, 24102 (2001)], and give an additional understanding...... of the stability of transition alumina at finite temperatures....

  7. Comparative study between yeasts immobilized on alumina beads and on membranes prepared by two routes

    Directory of Open Access Journals (Sweden)

    Kiyohara Pedro K.

    2003-01-01

    Full Text Available Alumina channeled beads and rough surface membranes prepared from aqueous sols of fibrillar pseudoboehmite are able to immobilize yeasts for ethanol fermentation of sugar solutions. This paper describes comparative results of assays carried out with yeasts immobilized onto alpha-alumina beads and membranes prepared under two different conditions of processing and firing. The fermentation tests evaluated by the decrease of fermentable sugars, referred as Brix degrees per hour, indicated that the yeasts immobilized on beads had similar performance, probably because their surfaces, even being morphologically different, presented the same value of open porosity. One type of membrane (asymmetrical; precursor: pseudoboehmite; firing temperature 1,150ºC; crystal structure; alpha-alumina had better performance than the other type (asymmetrical; precursor: fibrillar pseudoboehmite plus aluminum hydroxiacetate mixture; 1,150ºC; alpha-alumina because the yeast cells entered into their porous interior through the surface slits, were immobilized and their growth was easier than on the external surface.

  8. Investigation of Removal Possibilities of Colloidal Alumina from Aqueous Solution by the Use of Anionic Polyacrylamide

    International Nuclear Information System (INIS)

    Wisniewska, M.; Chibowski, S.; Urban, T.

    2016-01-01

    Purification of drinking and industrial water required usage of high molecular weight polymer to cause flocculation process of dispersed suspension of contaminants. Poly electrolytes, including ionic polyacrylamide are especially appropriate for these purposes, because in this case the suspension stability can be controlled by both steric and electrostatic forces. Thus the influence of solution p H and hydrolysis degree (carboxyl groups content) of anionic polyacrylamide (PAM) on the alumina (Al_2O_3) suspension stability were studied. The turbidimetry was applied for determination of the examined systems stability. The mechanism of suspension stabilization or destabilization in the polymer presence was proposed on the basis of determined parameters: adsorbed amount of PAM, its adsorption layer thickness, linear dimensions of macromolecules in the solution and zeta potential of alumina particles covered with the polyacrylamide layer. The greatest decrease of the alumina suspension stability in the polymer presence in comparison to that without the polymer was obtained at p H 6 after the addition of PAMs with higher molecular weight (i.e. 14 000 0000) and hydrolysis degrees 20 and 30% (efficient neutralization of solid surface charge). In turn, the most unstable alumina system proved to be that prepared at p H 9 containing PAM with the highest molecular weight and the greatest hydrolysis degree (causing the most effective bridging flocculation).

  9. Beryllium Adsorption at Transition Aluminas: Implications for Environmental Science and Oxidation of Aluminum Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Sergey N. Rashkeev; Michael V. Glazoff

    2010-08-01

    It is demonstrated that?gamma- and?eta- aluminas (transition Al2O3 polytypes with defect spinel structure) can effectively capture beryllium atoms. Although the bulk crystal structures of these two oxides are characterized only by slight differences in cation vacancy distributions, the interaction of Be with the two polytypes are different. For gamma- Al2O3, the Be adsorption energy is high (~ 5 eV per atom), and all Be atoms are captured and trapped at the surface - all attempts to move Be in the subsurface region result in its expulsion back to the surface. On the other hand, for ?eta- alumina Be atoms can be captured both at the surface and in octahedrally-coordinated subsurface cation vacancies. This result implies that both alumina oxides could be successfully used for Be capture out of wastewater streams related to industrial processes of aluminum and alumina production. Also, the surface adsorption mechanism of Be at?gamma- Al2O3 explains why very small additions of Be (of the order of several ppm) to Al-Mg and Al-Mg-Si casting and wrought alloys prevent run-away oxidation of these materials in molten state, as well as ingot cracking. We also discuss possibilities to use other additives (e.g., Ca and Sr) yielding the same protective effect for aluminum alloys but which are less toxic than beryllium.

  10. Preparation of palladium nanoparticles on alumina surface by chemical co-precipitation method and catalytic applications

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Avvaru Praveen; Kumar, B. Prem; Kumar, A.B.V. Kiran; Huy, Bui The [Department of Chemistry, Changwon National University, Changwon 641-773 (Korea, Republic of); Lee, Yong-Ill, E-mail: yilee@changwon.ac.kr [Department of Chemistry, Changwon National University, Changwon 641-773 (Korea, Republic of)

    2013-01-15

    Highlights: Black-Right-Pointing-Pointer Facile synthesis of palladium nanoparticles on alumina surface. Black-Right-Pointing-Pointer The surface morphology and properties of the nanocrystalline powders were characterized. Black-Right-Pointing-Pointer The catalytic activities of palladium nanoparticles were investigated. - Abstract: The present work reports a chemical co-precipitation process to synthesize palladium (Pd) nanoparticles using alumina as a supporting material. The optimized temperature for the formation of nanocrystalline palladium was found to be 600 Degree-Sign C. The X-ray diffraction (XRD) and Raman spectroscopy were used to study the chemical nature of the Pd in alumina matrix. The surface morphology and properties of the nanocrystalline powders were examined using thermogravimetric analysis (TG-DTA), XRD, Raman spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The calcinations in different atmospheres including in the inert medium forms the pure nano Pd{sup 0} while in the atmospheric air indicates the existence pure Pd{sup 0} along with PdO nanoparticles. The catalytic activities of the as-synthesized nanocrystalline Pd nanoparticles in the alumina matrix were investigated in Suzuki coupling, Hiyama cross-coupling, alkene and alkyne hydrogenation, and aerobic oxidation reactions.

  11. Synthesis and characterization of α-alumina col-gel nanometric: elaboration of biomaterials nanostructured for biomedical applications

    International Nuclear Information System (INIS)

    Passoni, L.S.; Feit, G.; Camargo, N.H.A.

    2010-01-01

    The production of nanostructured biomaterials are research themes for these present new characteristics of biocompatibility and bioactivity. The sol-gel process allows obtaining α-alumina nanometric with purity 99.99%. The use of nanoparticles of Al 2 O 3 -α, SiO 2 and TiO 2 are being employed as a second stage in the development of nanocomposites biomaterials. The presence of the second phase within a ceramic matrix leads to obtaining nanomaterials with micropores in micro and nanostructures interconnected, what contributes within the processes of osseous integration, osseous induction. The goal of this work focused on synthesis and characterization of an α- alumina by sol-gel process. Characterization studies were conducted using the various techniques: X-ray diffraction, scanning electron microscopy, exploratory differential scanning calorimetry and infrared spectrometry by Fourier transforms. The preliminary results showed the attainment the nanometric α-alumina powder. (author)

  12. Zirconia dispersion as a toughening agent in alumina - Influence of the cerium oxide

    International Nuclear Information System (INIS)

    Gritti, Olivier

    1987-01-01

    The improvement of mechanical properties of alumina can be obtained by fine dispersion of zirconia particles. The addition of cerium oxide as a stabilizer of the tetragonal phase has been examined. Different powder preparations, based on impregnation of the alumina powder by zirconium and cerium precursor salts, have been studied. Parameters, such as properties of alumina powder and cerium oxide content, for the production of reactive powders have been determined by two laboratory processes. The sintering of these powders in air at 1600 deg. C has resulted in dense materials with homogeneous microstructure. The mechanical properties, in particular the biaxial flexure strength and the toughness, have been determined in the temperature range 20 deg. C-900 deg. C. A reinforcement of about 80 pc in comparison with alumina is achieved. The optimal composition is (Al 2 O 3 ) 0.8 (ZrO 2 ) 0.18 (CeO 2 ) 0.02 . In the other hand, powder preparation by spray drying has been chosen for an approach to a larger scale process. The sintered ceramics made with these powders present a double microstructure which does not affect the mechanical properties. The presence of cerium oxide produces the following improvements: - increased mobility of the intergranular zirconia inclusions which results in a faster densification; - stabilization of a tetragonal phase without prohibiting the stress induced transformation; - increase of the critical sizes of the tetragonal → monoclinic transformation; - a large decrease in the transformation kinetic in water at 300 deg. C in comparison with that observed for alumina-zirconia doped with yttrium oxide. (author) [fr

  13. Non-isothermal kinetics of phase transformations in magnetron sputtered alumina films with metastable structure

    International Nuclear Information System (INIS)

    Zuzjaková, Š.; Zeman, P.; Kos, Š.

    2013-01-01

    Highlights: • Non-isothermal kinetics of phase transformations in alumina films was investigated. • The structure of alumina films affects kinetics of the transformation processes. • Kinetic triplets of all transformation processes were determined. • The KAS, FWO, FR and IKP methods for determination of E a and A were used. • The Málek method for determination of the kinetic model was used. - Abstract: The paper reports on non-isothermal kinetics of transformation processes in magnetron sputtered alumina thin films with an amorphous and γ-phase structure leading ultimately to the formation of the thermodynamically stable α-Al 2 O 3 phase. Phase transformation sequences in the alumina films were investigated using differential scanning calorimetry (DSC) at four different heating rates (10, 20, 30, 40 °C/min). Three isoconversional methods (Kissinger–Akahira–Sunose (KAS), Flynn–Wall–Ozawa (FWO) and Friedman (FR) method) as well as the invariant kinetic parameters (IKP) method were used to determine the activation energies for transformation processes. Moreover, the pre-exponential factors were determined using the IKP method. The kinetic models of the transformation processes were determined using the Málek method. It was found that the as-deposited structure of alumina films affects kinetics of the transformation processes. The film with the amorphous as-deposited structure heated at 40 °C/min transforms to the crystalline γ phase at a temperature of ∼930 °C (E a,IKP = 463 ± 10 kJ/mol) and subsequently to the crystalline α phase at a temperature of ∼1200 °C (E a,IKP = 589 ± 10 kJ/mol). The film with the crystalline γ-phase structure heated at 40 °C/min is thermally stable up to ∼1100 °C and transforms to the crystalline α phase (E a,IKP = 511 ± 16 kJ/mol) at a temperature of ∼1195 °C. The empirical two-parameter Šesták–Berggren kinetic model was found to be the most adequate one to describe all transformation processes

  14. Fabrication and characteristics of alumina-iron functionally graded materials

    DEFF Research Database (Denmark)

    He, Zeming; Ma, J.; Tan, G.E.B.

    2009-01-01

    . The microstructure and the composition of the prepared component were studied, and its flexural strength, fracture toughness, and fracture energy were tested and evaluated. The relative density and the Vickers hardness of each layer in the graded material were also measured. The correlation between microstructure...... and composition and mechanical properties was discussed. Flat, crack-free, and relatively high-density gradient components were obtained from this work. Compared to monolithic alumina ceramic, the remarkable improvement on fracture toughness and fracture energy of the investigated graded material system......In the present work, five-layered alumina–iron functionally graded materials (FGMs) were fabricated via a simple route of die pressing and pressureless sintering. The shrinkage differences among the layers in the FGM were minimized by particle size selection and processing control...

  15. Titanium nitride stamps replicating nanoporous anodic alumina films

    International Nuclear Information System (INIS)

    Navas, D; Sanchez, O; Asenjo, A; Jaafar, M; Baldonedo, J L; Vazquez, M; Hernandez-Velez, M

    2007-01-01

    Fabrication of nanostructured TiN films by magnetron sputtering using nanoporous anodic alumina films (NAAF) as substrates is reported. These hard nanostructured films could be used for pre-patterning aluminium foils and to obtain nanoporous films replicating the starting NAAF over a wide range of pore diameters and spacings. Pre-patterned Al foils are obtained by compression with pressures lower than those previously reported, then a new NAAF can be fabricated by means of only one anodization process. As an example, one of the TiN stamps was used for pre-patterning an Al foil at a pressure of 200 kg cm -2 and then it was anodized in oxalic acid solution obtaining the corresponding replica of the starting NAAF

  16. Cathodoluminescence study of anodic nanochannel alumina

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Q.X. [Department of Electrical and Electronic Engineering, Saga University, Honjo-1, Saga, 840-8502 (Japan)]. E-mail: guoq@cc.saga-u.ac.jp; Hachiya, Y. [Department of Electrical and Electronic Engineering, Saga University, Honjo-1, Saga, 840-8502 (Japan); Tanaka, T. [Department of Electrical and Electronic Engineering, Saga University, Honjo-1, Saga, 840-8502 (Japan); Nishio, M. [Department of Electrical and Electronic Engineering, Saga University, Honjo-1, Saga, 840-8502 (Japan); Ogawa, H. [Department of Electrical and Electronic Engineering, Saga University, Honjo-1, Saga, 840-8502 (Japan)

    2006-07-15

    Nanochannel alumina (NCA) templates with highly ordered pore arrays were prepared by anodizing pure aluminum foil in acid solutions. Cathodoluminescence measurements reveal that a blue emission band appears at around 2.8 eV and its energy position depends on measurement temperature and pore size of NCA. The shift of the blue emission band energy with temperature is ascribed to the variations of electron-phonon interactions. X-ray absorption near-edge fine structure results show that the blue emission band shift with pore size is due to the local environment change of atoms in NCA.

  17. Creep cavitation effects in polycrystalline alumina

    International Nuclear Information System (INIS)

    Porter, J.R.; Blumenthal, W.; Evans, A.G.

    1981-01-01

    Fine grained polycrystalline alumina has been deformed in creep at high temperatures, to examine the evolution of cavities at grain boundaries. Cavities with equilibrium and crack-like morphologies have been observed, distributed nonuniformly throughout the material. The role of these cavities during creep has been described. A transition from equilibrium to crack-like morphology has been observed and correlated with a model based on the influence of the surface to boundary diffusivity ratio and the local tensile stress. The contribution of cavitation to the creep rate and total creep strain has been analyzed and excluded as the principal cause of the observed non-linear creep rate

  18. Characterization of the porous anodic alumina nanostructures with a metal interlayer on Si substrates

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Chia-Hui; Chen, Hung-Ing; Hsiao, Jui-Ju; Wang, Jen-Cheng; Nee, Tzer-En, E-mail: neete@mail.cgu.edu.tw

    2014-04-15

    Porous anodic alumina (PAA) films produced by the anodization technique have made possible the mass production of porous nano-scale structures where the pore height and diameter are controllable. A metal interlayer is observed to have a significant influence on the characteristics of these PAA nanostructures. In this study, we investigate in-depth the effect of the current density on the properties of porous anodic alumina nanostructures with a metal interlayer. A thin film layer of tungsten (W) and titanium (Ti) was sandwiched between a porous anodic alumina film and a silicon (Si) substrate to form PAA/W/Si and PAA/Ti/Si structures. The material and optical characteristics of the porous anodic alumina nanostructures, with and without a metal interlayer, on silicon substrates were studied using the scanning electron microscopy, X-ray diffraction (XRD), and temperature-dependent photoluminescence (PL) measurements. The current densities of the porous anodic alumina nanostructures with the metal interlayer are higher than for the PAA/Si, resulting in an increase of the growth rate of the oxide layer. It can be observed from the X-ray diffraction curves that there is more aluminum oxide inside the structure with the metal interlayer. Furthermore, it has been found that there is a reduction in the photoluminescence intensity of the oxygen vacancy with only one electron due to the formation of oxygen vacancies inside the aluminum oxide during the re-crystallization process. This leads to competition between the two kinds of different oxygen-deficient defect centers (F+ and F centers) in the carrier recombination mechanism from the PL spectra of the porous anodic alumina nanostructures, with and without a metal interlayer, on silicon substrates. -- Highlights: • Study of porous anodic alumina (PAA) films with metal interlayers on silicon. • The highly ordered PAA film with a fairly regular nano-porous structure. • The luminescence properties of PAA films were

  19. Investigations on thermoluminescent dosimetry (TLD) with doped alumina ceramics

    International Nuclear Information System (INIS)

    Janas, R.; Huebner, K.

    1976-01-01

    Alumina ceramics doped and burned under various conditions have been investigated with regard to their suitability for thermoluminescent dosimetry. The production of ceramics is described. The properties essential for dosimetric purposes, such as glow curve, energy dose characteristics, fading, recoverability, lower detection limit and energy dependence, are indicated. The advantages and disadvantages of alumina ceramics are compared. (author)

  20. Cavity cutting efficiency of a Bioglass and alumina powder ...

    Indian Academy of Sciences (India)

    1531–1536. c Indian Academy of Sciences. ... conical in shape, whereas cavities produced by alumina and alumina + 45S5 were more ... any other material having good cutting properties is highly .... Saw, Buehler Ltd, IL, USA) at a blade speed of 3500 r.p.m. ... and the machine was run for 1min to remove any residual.

  1. Treatment of chrome plating wastewater (Cr+6) using activated alumina.

    Science.gov (United States)

    Sarkar, Sudipta; Gupta, Anirban

    2003-01-01

    Suitability of activated alumina for removal of hexavalent chromium from electroplating wastewater has been investigated. Activated alumina exhibited good sorption capacity for hexavalent chromium and pH has no pronounced effect on the sorption capacity. Both batch and column adsorption studies have been carried out and an adsorption column design indicated reasonable depth of column for practical application.

  2. Near net-shape fabrication of alumina glass composites

    NARCIS (Netherlands)

    Zhu, Q.; With, de G.; Dortmans, L.J.M.G.; Feenstra, F.

    2005-01-01

    The purpose of the present study is to fabricate alumina glass composites by melt infiltration with better dimensional control through reducing both the presintering and infiltration temperature. Main efforts were put to develop glasses that are chemically compatible with alumina. After extensive

  3. Synthesis of Gamma-Alumina from Kankara Kaolin as Potential ...

    African Journals Online (AJOL)

    Engr Solomn Gajere

    Large specific surface area gamma-alumina (γ-Al2O3) was synthesized by hydrothermal method using Kankara kaolin as starting material. Thermal treatment of ammonium alum prepared from the filtrate of the dealuminated metakaolin was employed to obtain the alumina. Crystalline aluminum sulfate with 39 wt% Al2O3 ...

  4. Synthesis of Nano Crystalline Gamma Alumina from Waste Cans

    Directory of Open Access Journals (Sweden)

    Nada Sadoon Ahmedzeki

    2018-03-01

    Full Text Available In the present study waste aluminium cans were recycled and converted to produce alumina catalyst. These cans contain more than 98% aluminum oxide in their structure and were successfully synthesized to produce nano sized gamma alumina under mild conditions. A comprehensive study was carried out in order to examine the effect of several important parameters on maximum yield of alumina that can be produced. These parameters were reactants mole ratios (1.5, 1.5, 2, 3, 4 and 5, sodium hydroxide concentrations (10, 20, 30, 40, 50 and 55% and weights of aluminum cans (2, 4, 6, 8 and 10 g. The compositions of alumina solution were determined by Atomic absorption spectroscopy (AAS; and maximum yield of alumina solution was 96.3% obtained at 2 mole ratios of reactants, 40% sodium hydroxide concentrations and 10g of aluminum cans respectively. Gamma alumina was acquired by hydrothermal treatment of alumina solution at pH 7 and calcination temperature of 550 ºC. The prepared catalyst was characterized by X-ray diffraction (XRD, N2 adsorption/ desorption isotherms, X-ray fluorescence (XRF and atomic force microscopy (AFM. Results showed good crystallinity of alumina as described by XRD patterns, with surface area of 311.149 m2/g, 0.36 cm3/g pore volume, 5.248 nm pore size and particle size of 68.56 nm respectively.

  5. Characterization of the microporous HDPE film with alpha alumina

    International Nuclear Information System (INIS)

    Park, Jong Seok; Sung, Hae Jun; Gwon, Hui Jeong; Lim, Youn Mook; Nho, Young Chang

    2010-01-01

    The effects of the addition of the alpha alumina on the properties of the microporous high density polyethylene (HDPE) films were investigated. The particle size and the specific surface area of alpha alumina were 400 nm and 7.3 m 2 g -1 . The HDPE and the alpha alumina were mixed to obtain the precursor film in the twin extruder. The precursor films were uni-axially stretched up to 600% in oven 120 .deg. C and then the stretched HDPE films were irradiated by gamma rays. The pore volume of the microporous HDPE films was increased with an increasing content of the alpha alumina. The mechanical characteristics of the microporous HDPE films were increased with a content of alpha alumina up to 15%, but decreased at 20%. The electrochemical stability of the microporous HDPE film containing alpha alumia was increased with an increased irradiation dose up ti 50 kGy

  6. Thermal shock behavior of rare earth modified alumina ceramic composites

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Junlong; Liu, Changxia [Ludong Univ., Yantai (China). School of Transportation

    2017-05-15

    Alumina matrix ceramic composites toughened by AlTiC master alloys, diopside and rare earths were fabricated by hot-pressing and their thermal shock behavior was investigated and compared with that of monolithic alumina. Results showed that the critical thermal shock temperature (ΔT) of monolithic alumina was 400 C. However, it decreased to 300 C for alumina incorporating only AlTiC master alloys, and increased with further addition of diopside and rare earths. Improvement of thermal shock resistance was obtained for alumina ceramic composites containing 9.5 wt.% AlTiC master alloys and 0.5 wt.% rare earth additions, which was mainly attributed to the formation of elongated grains in the composites.

  7. Morphology and transmittance of porous alumina on glass substrate

    Energy Technology Data Exchange (ETDEWEB)

    Guo Peitao, E-mail: guopeitao@hotmail.com [Wuhan University of Technology. Wuhan (China); Xia Zhilin [Wuhan University of Technology. Wuhan (China); Key Laboratory of Low Dimensional Materials and Application Technology, Xiangtan University, Ministry of Education, Xiangtan (China); Xue Yiyu [Wuhan University of Technology. Wuhan (China); Huang Caihua [China Three Gorges University, Yichang (China); Zhao Lixin [Wuhan University of Technology. Wuhan (China)

    2011-02-01

    The porous optical film has higher threshold of laser-induced damage than densified films, for the study of mechanism of laser-induced damage of porous optical film with ordered pore structure. Porous anodic alumina (PAA) film with high transmittance on glass substrate has been prepared. Aluminum film was deposited on glass substrate by means of resistance and electron beam heat (EBH) evaporation. Porous alumina was prepared in oxalic acid solution under different anodizing conditions. At normal incidence, the optical transmittance spectrum over 300-1000 nm spectra region was obtained by spectrophotometer. SEM was introduced to analysis the morphology of the porous alumina film. The pore aperture increased with the increase of anodizing voltage, which resulted in a rapid decrease of the pore concentration and the optical thickness of porous alumina film. Damage morphology of porous alumina film is found to be typically defects initiated, and the defect is the pore presented on the film.

  8. Stability, rheology and thermal analysis of functionalized alumina- thermal oil-based nanofluids for advanced cooling systems

    International Nuclear Information System (INIS)

    Ilyas, Suhaib Umer; Pendyala, Rajashekhar; Narahari, Marneni; Susin, Lim

    2017-01-01

    Highlights: • Alumina nanoparticles are functionalized with oleic acid. • Functionalization of alumina nanoparticles gives better dispersion in thermal oil. • Thermophysical properties of nanofluids are experimentally measured. • TGA confirms the improvement in life of nanofluids. - Abstract: Thermal oils are widely used as cooling media in heat transfer processes. However, their potential has not been utilised exquisitely in many applications due to low thermal properties. Thermal oil-based nanofluids are prepared by dispersing functionalized alumina with varying concentrations of 0.5–3 wt.% to enhance thermal properties of oil for advanced cooling systems. The oleic acid coated alumina is prepared and then dispersed in the oil to overcome the aggregation of nanoparticles in base fluid. The surface characterizations of functionalized nanoparticles are performed using different analysis such as XRD, EDS, SEM, TEM and FTIR. Dispersion behaviour and agglomeration studies are conducted at natural and functionalized conditions using different analysis to ensure long-term stability of nanofluids. In addition, rheological behaviour of non-Newtonian nanofluids is studied at high shear rates (100–2000 s"−"1). Effective densities and enhancement in thermal conductivities are measured for different nanofluids concentrations. Specific heat capacity is measured using Differential Scanning Calorimetry. The correlations are developed for thermophysical properties of nanofluids. Thermogravimetric analysis is performed with respect to temperature and time to exploit the effect of the addition of nanoparticles on the degradation of nanofluids. Significant improvement in the thermal properties of oil is observed using highly stable functionalized alumina nano-additives.

  9. Sol-gel synthesized of nanocomposite palladium-alumina ceramic membrane for H{sub 2} permeability: Preparation and characterization

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, A.L.; Mustafa, N.N.N. [School of Chemical Engineering, Engineering Campus, Universiti Sains Malaysia, Seri Ampangan, 14300 Nibong Tebal, Penang (Malaysia)

    2007-08-15

    Palladium-alumina membrane with mesopore and narrow pore size distribution was prepared by the sol-gel method. Effect of the finely dispersed metal on the microstructure and the characteristic properties of the palladium-alumina membrane were investigated. Observations were made on membrane weight loss, morphology, pore structure, pore size, surface area, pore surface fractal and membrane's crystal structure. Autosorb analysis, X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Fourier Transform Infrared (FTIR) analysis were employed in the membrane characterization. Autosorb analysis found that, BET surface area decreased and pore size of the membrane increased with the increasing of calcinations temperature (500-1100{sup o}C) and with the increasing of palladium amount in the membrane. FTIR and TG/DTA analysis show that the suitable temperature for calcinations of palladium-alumina membrane is at 700{sup o}C. Palladium metals are highly dispersed at calcinations temperature of 700{sup o}C as observed by TEM analysis. The fine crystallinity of the palladium and {gamma}-alumina phase was obtained after calcined at 700{sup o}C. The SEM morphology shows a smooth and free crack layer of palladium-alumina membrane after repeating the process of dipping, drying and calcinations at temperature of 700{sup o}C. The membrane also successfully coated with a good adhesion on support. The thickness of the final membrane layer was estimated as 9{mu} m. (author)

  10. Pore surface fractal analysis of palladium-alumina ceramic membrane using Frenkel-Halsey-Hill (FHH) model.

    Science.gov (United States)

    Ahmad, A L; Mustafa, N N N

    2006-09-15

    The alumina ceramic membrane has been modified by the addition of palladium in order to improve the H(2) permeability and selectivity. Palladium-alumina ceramic membrane was prepared via a sol-gel method and subjected to thermal treatment in the temperature range 500-1100 degrees C. Fractal analysis from nitrogen adsorption isotherm is used to study the pore surface roughness of palladium-alumina ceramic membrane with different chemical composition (nitric acid, PVA and palladium) and calcinations process in terms of surface fractal dimension, D. Frenkel-Halsey-Hill (FHH) model was used to determine the D value of palladium-alumina membrane. Following FHH model, the D value of palladium-alumina membrane increased as the calcinations temperature increased from 500 to 700 degrees C but decreased after calcined at 900 and 1100 degrees C. With increasing palladium concentration from 0.5 g Pd/100 ml H(2)O to 2 g Pd/100 ml H(2)O, D value of membrane decreased, indicating to the smoother surface. Addition of higher amount of PVA and palladium reduced the surface fractal of the membrane due to the heterogeneous distribution of pores. However, the D value increased when nitric acid concentration was increased from 1 to 15 M. The effect of calcinations temperature, PVA ratio, palladium and acid concentration on membrane surface area, pore size and pore distribution also studied.

  11. Mesoporous silica materials modified with alumina polycations as catalysts for the synthesis of dimethyl ether from methanol

    Energy Technology Data Exchange (ETDEWEB)

    Macina, Daniel; Piwowarska, Zofia; Tarach, Karolina; Góra-Marek, Kinga [Jagiellonian University, Faculty of Chemistry, Ingardena 3, 30-060 Kraków (Poland); Ryczkowski, Janusz [Maria Curie Skłodowska University, Faculty of Chemistry, Maria Curie-Skłodowska 2, 20-031 Lublin (Poland); Chmielarz, Lucjan, E-mail: chmielar@chemia.uj.edu.pl [Jagiellonian University, Faculty of Chemistry, Ingardena 3, 30-060 Kraków (Poland)

    2016-02-15

    Highlights: • Deposition of alumina ologoctaions on mesoporous silicas modified with surface −SO{sub 3}H groups. • Alumina aggregates generated acid properties in the silica supports. • Alumina modified SBA-15 and MCF were active and selective catalysts in DME synthesis. - Abstract: Mesoporous silica materials (SBA-15 and MCF) were used as catalytic supports for the deposition of aggregated alumina species using the method consisting of the following steps: (i) anchoring 3-(mercaptopropyl)trimethoxysilane (MPTMS) on the silica surface followed by (ii) oxidation of −SH to−SO{sub 3}H groups and then (iii) deposition of aluminum Keggin oligocations by ion-exchange method and (iv) calcination. The obtained samples were tested as catalysts for synthesis of dimethyl ether from methanol. The modified silicas were characterized with respect to the ordering of their porous structure (XRD), textural properties (BET), chemical composition (EDS, CHNS), structure ({sup 27}Al NMR, FTIR) and location of alumina species (EDX-TEM), surface acidity (NH{sub 3}-TPD, Py-FTIR) and thermal stability (TGA). The obtained materials were found to be active and selective catalysts for methanol dehydration to dimethyl ether (DME) in the MTD process (methanol-to-dimethyl ether).

  12. La3+-modified activated alumina for fluoride removal from water

    International Nuclear Information System (INIS)

    Cheng, Jiemin; Meng, Xiaoguang; Jing, Chuanyong; Hao, Jumin

    2014-01-01

    Graphical abstract: - Highlights: • A La 3+ -modified activated alumina adsorbent was prepared for effective removal F − . • SEM/EDS and EXAFS analyses determined the formation of La(OH) 3 coating on the AA. • The La-AA had much high adsorption rate and capacity than the AA. • The La-AA was promising adsorbent for effective removal of F − from water. - Abstract: A La 3+ -modified activated alumina (La-AA) adsorbent was prepared for effective removal of fluoride from water. The surface properties of adsorbent were characterized with zeta potential analysis, SEM-EDS and EXAFS. Batch and column experiments were conducted to evaluate improvement of F − removal by the La-AA. SEM/EDS and EXAFS analyses determined the formation of La(OH) 3 coating on the AA and strong bonding interactions between La 3+ and the Al atoms. The points of zero charge (pH PZC ) of AA and La-AA were at pH 8.94 and 9.57, respectively. Batch experimental results indicated that the La-AA had much higher adsorption rate and capacity than the AA. The F − adsorption processes on La-AA and AA followed the pseudo-second-order kinetics and the Langmuir isotherm. Column filtration results shows that the La-AA and AA treated 270 and 170 bed volumes of the F − -spiked tap water, respectively, before F − breakthrough occurred. The results demonstrated that the La-AA was a promising adsorbent for effective removal of F − from water

  13. Development of ceramic composites from mixture of alumina and ceramic precursor polymer poly (silsesquioxane))

    International Nuclear Information System (INIS)

    Machado, Glauson Aparecido Ferreira

    2009-01-01

    Processing of ceramics materials, by polymer precursors pyrolysis, has been intensively researched over the past decades, due to advantages that this path provides, such as: lower temperature process compared to conventional techniques; structure control at molecular level; synthesis possibility of a wide range of ceramic compounds; obtaining parts with dimensions of the final product etc. The active filler controlled polymer pyrolysis (AFCOP) process, enables the synthesis of ceramic composites, by reaction between added filler (oxides, metals, intermetallic etc.) and solid and gaseous products, from polymer decomposition. In this study, based on this process, samples of alumina, with addition of 10 and 20 mass% of poly silsesquioxane polymer precursor, were manufactured. These samples were pyrolyzed at 900 degree C and thermal treated at temperatures of 1100, 1300 and 1500 degree C. The samples were characterized for bulk density, porosity and hardness, after each stage of thermal treatment. Structural transformations were analyzed by X-ray diffraction, scanning electron microscopy and infrared spectroscopy. Samples treated until 1300 degree C resulted in composites of alumina and silicon oxycarbide, while those treated at 1500 degree C, formed composites of mullite and alumina. The samples with 20% of polymer added started to density around 800 degree C and high retraction rate was observed at 1400 degree C. (author)

  14. Change in organic molecule adhesion on α-alumina (Sapphire) with change in NaCl and CaCl2 solution salinity

    DEFF Research Database (Denmark)

    Juhl, Klaus; Bovet, Nicolas Emile; Hassenkam, Tue

    2014-01-01

    We investigated the adhesion of two functional groups to α-alumina as a model for the adsorption of organic molecules on clay minerals. Interactions between organic compounds and clay minerals play an important role in processes such as drinking water treatment, remediation of contaminated soil...... the growth of bones, teeth, and shells. Adhesion of carboxylic acid, -COO(H), and pyridine, -C5H5N(H+), on the {0001} plane of α-alumina wafers has been investigated with atomic force microscopy (AFM) in chemical force mapping (CFM) mode. Both functional groups adhered to α-alumina in deionized water at p...... in surface properties, controlling surface tension (i.e., contact angle) and adsorption affinity on α-alumina and, by analogy, on clay minerals....

  15. Ball Milling Treatment of Black Dross for Selective Dissolution of Alumina in Sodium Hydroxide Leaching

    OpenAIRE

    Thi Thuy Nhi Nguyen; Man Seung Lee; Thi Hong Nguyen

    2018-01-01

    A process consisting of ball milling followed by NaOH leaching was developed to selectively dissolve alumina from black dross. From the ball milling treatment, it was found that milling speed greatly affected the leaching behavior of silica and the oxides of Ca, Fe, Mg, and Ti present in dross. The leaching behavior of the mechanically activated dross was investigated by varying NaOH concentration, leaching temperature and time, and pulp density. In most of the leaching conditions, only alumi...

  16. Evaluation of technological properties of alumina refractory systems-zirconia and zirconia-silica-alumina

    International Nuclear Information System (INIS)

    Marinho, A.R.O.; Carvalho, T.U.S.; Fagury Neto, E.; Rabelo, A.A.

    2014-01-01

    Alumina-zirconia refractories are noted for being products of excellent cost-effective, however, zirconia may limit its use due to decreasing resistance to thermal shock. This study aims to evaluate these refractories with the addition of microsilica, which can greatly improve their properties. Were used the following starting materials: calcined alumina, zirconia (stabilized and monoclinic) in amounts of 2%, 4% and 6% by weight, plus microsilica (5%w.). The powders were milled together with binder and lubricant for conformation bodies by uniaxial pressing. The samples were dried, calcined and sintered at 1400 °C/2h were characterized using the methods of Archimedes, and scanning electron microscopy (SEM), chemical analysis using energy dispersive X-ray (EDS), and mechanical flexural strength tests at room temperature. Formulations with the presence of microsilica showed satisfactory results and optimized properties. (author)

  17. Microstructural evaluation of alumina-niobium and alumina- niobium-zircon ceramics for ballistic application

    International Nuclear Information System (INIS)

    Mota, Juliana Machado da; Lopes, Cristina Moniz Araujo; Melo, Francisco Lourenco Cristovao de

    2009-01-01

    This study aimed to evaluate the microstructural of Alumina- Niobium and Alumina- Niobium-Zircon ceramics. Samples with 3.5 x 4.5 x 34 mm dimensions were prepared by uniaxial pressure (50 MPa) followed by isostatic pressure (300 MPa). The samples were sintered at 1500 ° C for 1 hour. The ceramics obtained were characterized by scanning electron microscopy (SEM) and X-ray diffraction, to evaluate the phases and microstructures. In order to analyze the microstructure, by SEM the samples were prepared using two techniques: heat treatment (1350 ° C for 5 minutes) and thermochemical treatment (500 ° C for 8 minutes in a solution of NaOH and KOH) on polished and fractured surfaces. The results showed that despite differences between the two etchings, both were effective to analyze the microstructure. (author)

  18. Dissolution kinetics for alumina in cryolite melts. Distribution of alumina in the electrolyte of industrial aluminium cells

    Energy Technology Data Exchange (ETDEWEB)

    Kobbeltvedt, Ove

    1997-12-31

    This thesis contributes to the understanding of which factors determine the rate of dissolution of alumina added to the bath in alumina reduction cells. Knowing this may help reduce the occurrences of operation interruptions and thus make it possible to produce aluminium using less energy. When alumina powder was added to a stirred cryolite melt, the alumina dissolved in two distinct main stages. In the first stage, the dissolution rate was very high, which reflects dissolution of single alumina grains that are being dispersed in the bath upon addition. In the second stage, lumps of alumina infiltrated with bath dissolved at a rate considerably slower than that of the first stage. The formation of these alumina agglomerates is the most important contributor to slow dissolution. The parameters varied in the experiments were convection, batch size, and temperature of the bath and of the added alumina. Increased gas stirring of the bath speeded up dissolution in both stages but the size of the batch was of little significance. Increasing the bath temperature had no effect in the first stage but speeded up dissolution considerably in the second stage. Compared to adding alumina at room temperature, preheating it to a high temperature (600 {sup o}C) increased the dissolution rate in the first stage while preheating to lower temperatures (100-300 {sup o}C) decreased the dissolution rate. In the second stage, preheating slowed the dissolution. The two latter phenomena of reduced dissolution rates are ascribed to the removal of moisture from the alumina upon preheating. The bath flow and the distribution of alumina in the bath were measured in four different types of cells. It was found that if a certain asymmetry of the magnetic field traverse to the cell was present, due to the presence of risers, then loops of high velocity bath flow occurred near the short ends of the cell. Thus, alumina added near the short ends is effectively transferred away from the feeding

  19. Adsorption decontamination of radioactive waste solvent by activated alumina and bauxites

    International Nuclear Information System (INIS)

    Hassan, N.M.; Marra, J.C.; Kyser, E.A.

    1994-01-01

    An adsorption process utilizing activated alumina and activated bauxite adsorbents was evaluated as a function of operating parameters for the removal of low level radioactive contaminants from organic waste solvent generated in the fuel reprocessing facilities and support operations at Savannah River Site. The waste solvent, 30% volume tributyl phosphate in n-paraffin diluent, was degraded due to hydrolysis and radiolysis reactions of tributyl phosphate and n-paraffin diluent, producing fission product binding degradation impurities. The process, which has the potential for removing these activity-binding degradation impurities from the solvent, was operated downflow through glass columns packed with activated alumina and activated bauxite adsorbents. Experimental breakthrough curves were obtained under various operating temperatures and flow rates. The results show that the adsorption capacity of the activated alumina was in the order 10 4 dpm/g and the capacity of the activated bauxite was 10 5 dpm/g. The performance of the adsorption process was evaluated in terms of dynamic parameters (i.e. adsorption capacity, the height and the efficiency of adsorption zone) in such a way as to maximize the adsorption capacity and to minimize the height of the mass transfer or adsorption zone

  20. Mechanical behavior of alumina and alumina-feldspar based ceramics in an acetic acid (4%) environment

    International Nuclear Information System (INIS)

    Stumpf, Aisha S.G.; Bergmann, Carlos P.; Vicenzi, Juliane; Fetter, Rebecca; Mundstock, Karina S.

    2009-01-01

    This study investigates the mechanical properties of alumina-feldspar based ceramics when exposed to an aggressive environment (acetic acid 4%). Alumina ceramics containing different concentrations of feldspar (0%, 1%, 5%, 10%, or 40%) were sintered at either 1300, 1600, or 1700 o C. Flaws (of width 0%, 30%, or 50%) were introduced into the specimens using a saw. Half of these ceramic bodies were exposed to acetic acid. Their flexural strength, K IC , and porosity were measured and the fractured samples were evaluated using scanning electronic- and optical microscopy. It was found that in the ceramic bodies sintered at 1600 o C, feldspar content up to 10% improved flexural strength and K IC, and reduced porosities. Generally, it was found that acetic acid had a weakening effect on the flexural strength of samples sintered at 1700 o C but a beneficial effect on K IC of ceramics sintered at 1600 o C. It was concluded that alumina-based ceramics with feldspar content up to 10% and sintered at higher temperatures would perform better in an aggressive environment similar to oral cavity.

  1. Master sintering curves of two different alumina powder compacts

    Directory of Open Access Journals (Sweden)

    Vaclav Pouchly

    2009-12-01

    Full Text Available Concept of Master Sintering Curve is a strong tool for optimizing sintering schedule. The sintering behaviour can be predicted, and sintering activation energy can be calculated with the help of few dilatometric measurements. In this paper an automatic procedure was used to calculate Master Sintering Curves of two different alumina compacts. The sintering activation energies were determined as 640 kJ/mol for alumina with particle size of 240 nm, respective 770 kJ/mol for alumina with particle size of 110 nm. The possibility to predict sintering behaviour with the help of Master Sintering Curve was verified.

  2. Effect of alumina on the dissolution rate of glasses

    International Nuclear Information System (INIS)

    Palavit, G.; Montagne, L.

    1997-01-01

    Small alumina addition to silicate glasses improves their chemical durability, but a large amount of alumina can also be beneficial to obtain a high dissolution rate. This paper describes the effect of Al 3+ on the early stage of glass alteration, in relation with its coordination in the glass and also with the reactions involved (hydrolysis and ionic exchange). We describe briefly nuclear magnetic resonance tools available to characterize the aluminum environments in the glasses. The rote of alumina on the dissolution rate of phosphate glasses is also discussed in order to show that the effect of Al 3+ is dependant upon the nature of the glass matrix. (author)

  3. Alumina strength degradation in the elastic regime

    International Nuclear Information System (INIS)

    Furnish, Michael D.; Chhabildas, Lalit C.

    1998-01-01

    Measurements of Kanel et al. [1991] have suggested that deviatoric stresses in glasses shocked to nearly the Hugoniot Elastic Limit (HEL) relax over a time span of microseconds after initial loading. 'Failure' (damage) waves have been inferred on the basis of these measurements using time-resolved manganin normal and transverse stress gauges. Additional experiments on glass by other researchers, using time-resolved gauges, high-speed photography and spall strength determinations have also lead to the same conclusions. In the present study we have conducted transmitted-wave experiments on high-quality Coors AD995 alumina shocked to roughly 5 and 7 GPa (just below or at the HEL). The material is subsequently reshocked to just above its elastic limit. Results of these experiments do show some evidence of strength degradation in the elastic regime

  4. Compositional characterization of atomic layer deposited alumina

    Energy Technology Data Exchange (ETDEWEB)

    Philip, Anu; Thomas, Subin; Kumar, K. Rajeev [Department of Instrumentation, Cochin University of Science and Technology, Cochin-22, Kerala (India)

    2014-01-28

    As the microelectronic industry demands feature size in the order of few and sub nanometer regime, the film composition and other film properties become critical issues and ALD has emerged as the choice of industry. Aluminum oxide is a material with wide applications in electronic and optoelectronic devices and protective and ion barrier layers. Al{sub 2}O{sub 3} is an excellent dielectric because of its large band gap (8.7eV), large band offsets with silicon. We have deposited thin layers of alumina on silicon wafer (p-type) for gate dielectric applications by ALD technique and compositional characterizations of the deposited thin films were done using EDS, XPS and FTIR spectra.

  5. Compositional characterization of atomic layer deposited alumina

    International Nuclear Information System (INIS)

    Philip, Anu; Thomas, Subin; Kumar, K. Rajeev

    2014-01-01

    As the microelectronic industry demands feature size in the order of few and sub nanometer regime, the film composition and other film properties become critical issues and ALD has emerged as the choice of industry. Aluminum oxide is a material with wide applications in electronic and optoelectronic devices and protective and ion barrier layers. Al 2 O 3 is an excellent dielectric because of its large band gap (8.7eV), large band offsets with silicon. We have deposited thin layers of alumina on silicon wafer (p-type) for gate dielectric applications by ALD technique and compositional characterizations of the deposited thin films were done using EDS, XPS and FTIR spectra

  6. Rheological properties of alumina injection feedstocks

    Directory of Open Access Journals (Sweden)

    Vivian Alexandra Krauss

    2005-06-01

    Full Text Available The rheological behavior of alumina molding feedstocks containing polyethylene glycol (PEG, polyvinylbutyral (PVB and stearic acid (SA and having different powder loads were analyzed using a capillary rheometer. Some of the feedstocks showed a pseudoplastic behavior of n < 0, which can lead to the appearance of weld lines on molded parts. Their viscosity also displayed a strong dependence on the shear rate. The slip phenomenon, which can cause an unsteady front flow, was also observed. The results indicate that the feedstock containing a lower powder load displayed the best rheological behavior. The 55 vol. % powder loaded feedstock presented the best rheological behavior, thus appearing to be more suitable than the formulation containing a vol. 59% powder load, which attained viscosities exceeding 10³ Pa.s at low shear rates, indicating its unsuitability for injection molding.

  7. Characterization of alumina suspensions by electroacoustics

    Energy Technology Data Exchange (ETDEWEB)

    Galassi, C.; Roncari, E.; Greenwood, R.; Piancastelli, A. [CNR, Faenza (Italy). Research Inst. for Ceramics Technology

    1997-12-31

    Using the acoustophoresis technique three different dispersants were selected to investigate the effect of the volume fraction of the suspension on the minimum amount of dispersant required to give the maximum zeta potential. No effect was detected over a volume fraction range 0.11 to 0.35. The acoustosizer was used to screen many dispersants for alumina in a relatively short time. From the viewpoint that the most stable suspensions are those with the greatest zeta potentials, then the following dispersants can be recommended: Reotan LA (0.25 mg/m{sup 2}) Dolapix CA (0.20 mg/m{sup 2}) and Dolapix PC33 (0.30 mg/m{sup 2}). Vanisperse and Borresperse are poor. Polyacrylic acid and polymethacrylic acid were better than some commercially available products. (orig.) 2 refs.

  8. The local strength of microscopic alumina reinforcements

    International Nuclear Information System (INIS)

    Žagar, Goran; Pejchal, Václav; Mueller, Martin G.; Rossoll, Andreas; Cantoni, Marco; Mortensen, Andreas

    2015-01-01

    We measure, using an adaptation of a method designed for ceramic ball bearings, the local strength of a brittle second phase that serves to reinforce a metal. The method uses focused ion beam milling and a nanoindentation device, and is free of artifacts commonly present in micromachined specimens. It is demonstrated on Nextel 610™ nanocrystalline alumina fibers embedded in an aluminum matrix composite. Results reveal a size effect that does not follow, across size scales, usual Weibull statistics: the fiber strength distribution differs between measurements at the microscale and macroscopic tensile testing. This implies that, in micromechanical analysis of multiphase materials, highly localized events such as the propagation of internal damage require input data that must be measured at the same, local, microscale as the event; the present work opens a path to this end.

  9. Glass transition temperature of PMMA/modified alumina nanocomposite: Molecular dynamic study

    OpenAIRE

    Mohammadi, Maryam; Davoodi, Jamal; Javanbakht, Mahdi; Rezaei, Hamidreza

    2017-01-01

    In this study, the effect of alumina and modified alumina nanoparticles in a PMMA/alumina nanocomposite was investigated. To attain this goal, the glass transition behavior of poly methyl methacrylate (PMMA), PMMA/alumina and PMMA/hydroxylated alumina nanocomposites were investigated by molecular dynamic simulations (MD). All the MD simulations were performed using the Materials Studio 6.0 software package of Accelrys. To obtain the glass transition temperature, the variation of density vs. t...

  10. The nature of the potassium compound acting as a promoter in iron-alumina catalysts for ammonia synthesis

    NARCIS (Netherlands)

    van Ommen, J.G.; Bolink, W.J.; Prasad, J.; Mars, P.

    1975-01-01

    The chemical form of the potassium promoter on an iron-alumina catalyst during ammonia synthesis has been studied by two methods, viz, (i) the measurement of the equilibrium constant of the process KNH2 + H2 KH + NH3, and (ii) chemical analysis of the used catalyst. The equilibrium constant

  11. Synthesis of alumina nano-sheets via supercritical fluid technology with high uranyl adsorptive capacity

    International Nuclear Information System (INIS)

    Jing Yu; Jun Wang; Zhanshuang Li; Qi Liu; Milin Zhang; Hongbin Bai; Caishan Jiao; Jun Wang; Lianhe Liu

    2012-01-01

    Supercritical carbon dioxide is beneficial to the synthesis of superior ultrafine and uniform materials due to its high chemical stability, low viscosity, high diffusivity, and 'zero' surface tension. γ-Alumina nano-sheets were obtained by a simple hydrothermal route in the presence of supercritical carbon dioxide. XRD, FTIR, SEM, TEM and nitrogen sorption isotherm were employed to characterize the samples. Alumina as-prepared has a high specific surface area of up to 200 ± 6 m 2 g -1 , which presents a high adsorption capacity (4.66 ± 0.02 mg g -1 ) for uranyl ions from aqueous solution. Furthermore, the adsorption process was found to be endothermic and spontaneous in nature. (authors)

  12. The influence of preparation methodology on high voltage behaviour of alumina insulators in vacuum

    CERN Document Server

    Goddard, B; Tan, J

    1998-01-01

    The flashover characteristics of an insulator bridged high voltage vacuum gap can play an important role in the overall performance of a high voltage device, for example in the extreme environments of high energy particle accelerators. The detailed preparation of the insulators is, at present, governed by the commercial production methods and by standard bulk cleaning processes, which for a particular application may be far from optimum. The influence of particular cleaning technique have been investigated for commercially available alumina samples, with measurement of surface characteristics by scanning electron microscopy and laser diffraction and fields up to 200 kV/cm. The results of the different measurements are discussed in the overall context of the problems encountered in the full sized high voltage devices, and suggestions are made as to how the performance of alumina insulators could be improved by modification of the production and preparation specification.

  13. Ultra-thin alumina and silicon nitride MEMS fabricated membranes for the electron multiplication

    Science.gov (United States)

    Prodanović, V.; Chan, H. W.; Graaf, H. V. D.; Sarro, P. M.

    2018-04-01

    In this paper we demonstrate the fabrication of large arrays of ultrathin freestanding membranes (tynodes) for application in a timed photon counter (TiPC), a novel photomultiplier for single electron detection. Low pressure chemical vapour deposited silicon nitride (Si x N y ) and atomic layer deposited alumina (Al2O3) with thicknesses down to only 5 nm are employed for the membrane fabrication. Detailed characterization of structural, mechanical and chemical properties of the utilized films is carried out for different process conditions and thicknesses. Furthermore, the performance of the tynodes is investigated in terms of secondary electron emission, a fundamental attribute that determines their applicability in TiPC. Studied features and presented fabrication methods may be of interest for other MEMS application of alumina and silicon nitride as well, in particular where strong ultra-thin membranes are required.

  14. Effect of alumina strengthening particles on brazed joints of GlidCop Al-15 copper alloy

    International Nuclear Information System (INIS)

    Chen, S.; Liu, J.Y.; Chin, B.A.

    1994-01-01

    Brazed joints of the alumina dispersion-strengthened copper alloy were developed using resistance heating brazing with BCuP-3 braze alloy. Experimental results show that tensile strength and fatigue properties are a function of the brazing process temperature cycle. Maximum tensile and fatigue properties can be obtained by choice of an optimal braze time and temperature. However, in both tensile and fatigue tests the brazed joints exhibited low ductility. Metallography of the fractured tensile and fatigue samples showed that cracks always initiated in and propagated along the interface between the transition layer and the braze metal. EDS analysis across the joint showed that P diffused very quickly into base metal along grain boundaries. A strong Al peak (associated with the detection of Al 2 O 3 ) was found that corresponded with the transition layer. Fractography showed an intergranular fracture pattern across this transition zone indicating that the observed segregation of alumina particles reduces the ductility of this region. ((orig.))

  15. Synthesis and Thermal Conductivity of Exfoliated Hexagonal Boron Nitride/Alumina Ceramic Composite

    Science.gov (United States)

    Hung, Ching-cheh; Hurst, Janet; Santiago, Diana; Lizcano, Maricela; Kelly, Marisabel

    2017-01-01

    Exfoliated hexagonal boron nitride (hBN)/alumina composite can be fabricated by following the process of (1) heating a mixture of hBN, AlCl3, and NaF in nitrogen for intercalation; (2) heating the intercalated product in air for exfoliation and at the same time converting the intercalate (AlCl3) into Al2O3, (3) rinsing the oxidized product, (4) coating individual exfoliated hBN platelets that contain Al2O3 with new layers of aluminum oxide, and finally, (5) hot pressing the product into the composite. The composite thus obtained has a composition of approximately 60 percent by weight hBN and 40 percent by weight alumina. Its in-plane and through-plane thermal conductivity were measured to be 86 and 18 watts per meter Kelvin, respectively, at room temperature.

  16. A Reliable Method for the Preparation of Multiporous Alumina Monoliths by Ice-Templating

    Directory of Open Access Journals (Sweden)

    Jérémy Dhainaut

    2016-03-01

    Full Text Available Alumina supports presenting a bimodal porosity are generally advantageous for the conversion of bulky molecules such as found in biomass, refining, and petrochemistry. However, shaping of such materials, while controlling pores size and orientation, proves to be hard. This problem can be tackled by using a simple method involving sol-gel chemistry, surfactant self-assembly, and ice-templating. Herein, a systematic study of the formulation and process parameters’ influence on the final material properties is presented. This protocol results in the repeatable preparation of centimeter-sized alumina monoliths presenting a uni-directional macroporosity and structured mesopores. These monoliths should be of particular interest in high flow rate catalytic applications.

  17. Poly(Butylene Terephthalate Based Composites Containing Alumina Whiskers: Influence of Filler Functionalization on Dielectric Properties

    Directory of Open Access Journals (Sweden)

    Pietro Russo

    2014-01-01

    Full Text Available Poly(butylene terephthalate (PBT is one of the most widely used semicrystalline thermoplastics polyester because of its superior thermal and mechanical properties, high dimensional stability and excellent processability. In this research PBT-based nanocomposites, including various amounts (up to 10 wt% of commercial alumina whiskers, have been prepared by using a Brabender internal chamber mixer and analysed in terms of morphological features and dielectric properties. Specific attention has been focused on the effect of the filler functionalization considering 3-glycidoxy propylmethoxysilane (GPS or 3-methacryloxypropyltrimethoxysilane (MPS as coupling agents. Tests, performed on compounds filled with neat and functionalized alumina whiskers, show a clear dependence of relative dielectric permittivity εr, invariance of dissipation factor (tgδ, and a sensible increase of volume electrical resistivity (ρv with the filler’s content and are encouraging for a future introduction of such composites in many electrical applications.

  18. Removal of Cadmium from Aqueous Solution by Nano Structured γ-Alumina

    Directory of Open Access Journals (Sweden)

    Seyed Hassan Zavar Mousavi

    2012-01-01

    Full Text Available In this study the use of nano structured γ-alumina as a new and convince adsorbent for removal of cadmium ions from aqueous solution was investigated. The equilibrium adsorption level was determined as a function of the solution pH, temperature, contact time, initial adsorbate concentration and adsorbent doses. Adsorption isotherms of Cd(II on adsorbents were determined and correlated with common isotherm equations such as Langmuir, Freundlich and Tempkin models. The isotherm data fitted well to the Langmuir isotherm. The maximum adsorption capacity for Cd(II on nano structured γ-alumina was 76.92 mg g-1. The adsorption kinetics was investigated and the best fit was achieved by a second-order equation. The thermodynamic parameters such as free energy (ΔG0, enthalpy (ΔH0 and entropy changes (ΔS0 for the adsorption of Cd(II were computed to predict the nature of adsorption process.

  19. Chemical treatment and biomimetic coating evaluating in zirconia-alumina ceramics; Avaliacao de tratamentos quimicos e recobrimento biomimetico em ceramicas de alumina-zirconia

    Energy Technology Data Exchange (ETDEWEB)

    Aguiar, Amanda Abati

    2007-07-01

    Ceramic materials, as alumina and zirconia have been explored along the years as biomaterials application. The bio inert nature has been stimulating the development of new alternatives, as chemical treatments to improve the biological application of these ceramics. The biomimetic process of bio inert ceramics for coating apatite is based on soaking the implant in a simulated body fluid, SBF, with ion concentrations nearly equal to those of human blood plasma. The bioactivity of the material is related with the formation of a layer constituted of hydroxyapatite low crystalline, similar to the biological apatite. The biocompatibility associated to the structural properties of the alumina and zirconia has been stimulating the clinical use of these materials, mainly in areas of larger mechanical requests, places not recommended for bioactive hydroxyapatite, for instance. In this work samples of alumina, zirconia doped with Yttria (3% mol) and composites of alumina and zirconia doped with Yttria (3% mol) were prepared by co-precipitation method, calcinate, sintered, chemically treated with solutions of acid phosphoric and sodium hydroxide and them immersed in 1.0 M and 1.5 M SBF. The calcinate powders were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), gas adsorption (BET) and laser diffraction. The XRD results indicate that the samples are low crystalline. It was observed for BET that the samples present high specific surface area. The results of laser diffraction and SEM showed that the powders are agglomerates. The sintered samples were analyzed by XRD, SEM and X-ray fluorescence (XRF). The phases quantified by Rietveld method were: cubic, tetragonal and monoclinic of the zirconia, besides the phase alpha of the alumina. The chemical treatment with phosphoric acid didn't present a tendency of larger apatite formation in relation to the samples no chemically treated. The treatment with sodium hydroxide provoked accentuated transformation

  20. Grazing incidence x-ray diffraction analysis of zeolite NaA membranes on porous alumina tubes.

    Science.gov (United States)

    Kyotani, Tomohiro

    2006-07-01

    Zeolite NaA-type membranes hydrothermally synthesized on porous alumina tubes, for dehydration process, were characterized by grazing incidence 2 theta scan X-ray diffraction analysis (GIXRD). The fine structure of the membrane was studied fractionally for surface layer and for materials embedded in the porous alumina tube. The thickness of the surface layer on the porous alumina tube in the membranes used in this study was approximately 2-3 microm as determined from transmission electron microscopy with focused ion beam thin-layer specimen preparation technique (FIB-TEM). To discuss the effects of the membrane surface morphology on the GIXRD measurements, CaA-type membrane prepared by ion exchange from the NaA-type membrane and surface-damaged NaA-type membrane prepared by water leaching were also studied. For the original NaA-type membrane, 2 theta scan GIXRD patterns could be clearly measured at X-ray incidence angles (alpha) ranging from 0.1 to 2.0 deg in increments of 0.1 deg. The surface layers of the 2 - 3 microm on the porous alumina tube correspond to the alpha values up to ca. 0.2 deg. For the CaA-type and the surface-damaged NaA-type membranes, however, diffraction patterns from the surface layer could not be successfully detected and the others were somewhat broad. For all the three samples, diffraction intensities of both zeolite and alumina increased with depth (X-ray incidence angle, alpha) in the porous alumina tube region. The depth profile analysis of the membranes based on the GIXRD first revealed that amount of zeolite crystal embedded in the porous alumina tube is much larger than that in the surface layer. Thus, the 2 theta scan GIXRD is a useful method to study zeolite crystal growth mechanism around (both inside and outside) the porous alumina support during hydrothermal synthesis and to study water permeation behavior in the dehydration process.

  1. Catalytic fast pyrolysis of durian rind using silica-alumina catalyst: Effects of pyrolysis parameters.

    Science.gov (United States)

    Tan, Y L; Abdullah, A Z; Hameed, B H

    2018-05-18

    Silica-alumina catalyst was prepared and used in the catalytic fast pyrolysis of durian rind in a drop-type two-stage reactor. The effects of catalytic temperature (400 °C-600 °C) and catalyst-to-durian rind ratio (1:30-3:30) were evaluated. Bio-oil yield was increased with increased catalytic temperature due to considerable dehydration process, but it was reduced with high catalyst loading due to the overcracking of organics into light gases. Silica-alumina catalyst possessed good selectivity and the products changed according to the temperature. The major components in bio-oil were hydrocarbons, furan derivatives, and aromatic compounds at 400 °C, 500 °C, and 600 °C, respectively. The hydrogen and carbon contents of bio-oil were reduced with high catalyst loading due to the overcracking of organics, and the deoxygenation process became unfavorable. The silica-alumina catalyst worked well in catalytic fast pyrolysis of durian rind, and the condition may be adjusted based on the desired products. Copyright © 2018 Elsevier Ltd. All rights reserved.

  2. Influence of alumina on mineralogy and environmental properties of zinc-copper smelting slags

    Science.gov (United States)

    Mostaghel, Sina; Samuelsson, Caisa; Björkman, Bo

    2013-03-01

    An iron-silicate slag, from a zinc-copper smelting process, and mixtures of this slag with 5wt%, 10wt%, and 15wt% alumina addition were re-melted, semi-rapidly solidified, and characterized using scanning electron microscopy equipped with energy dispersive spectroscopy, and X-ray diffraction. The FactSage™6.2 thermodynamic package was applied to compare the stable phases at equilibrium conditions with experimental characterization. A standard European leaching test was also carried out for all samples to investigate the changes in leaching behaviour because of the addition of alumina. Results show that the commonly reported phases for slags from copper and zinc production processes (olivine, pyroxene, and spinel) are the major constituents of the current samples. A correlation can be seen between mineralogical characteristics and leaching behaviours. The sample with 10wt% alumina addition, which contains high amounts of spinels and lower amounts of the other soluble phases, shows the lowest leachabilities for most of the elements.

  3. Immersion Freezing of Aluminas: The Effect of Crystallographic Properties on Ice Nucleation

    Science.gov (United States)

    King, M.; Chong, E.; Freedman, M. A.

    2017-12-01

    Atmospheric aerosol particles serve as the nuclei for heterogeneous ice nucleation, a process that allows for ice to form at higher temperatures and lower supersaturations with respect to ice. This process is essential to the formation of ice in cirrus clouds. Heterogeneous ice nucleation is affected by many factors including the composition, crystal structure, porosity, and surface area of the particles. However, these factors are not well understood and, as such, are difficult to account for in climate models. To test the effects of crystal structure on ice nucleation, a system of transition aluminas (Al2O3) that differ only in their crystal structure, despite being compositionally similar, were tested using immersion freezing. Particles were immersed in water and placed into a temperature controlled chamber. Freezing events were then recorded as the chamber was cooled to negative 30 °. Alpha-alumina, which is a member of the hexagonal crystal system, showed a significantly higher temperature at which all particles froze in comparison to other samples. This supports the hypothesis that, since a hexagonal crystal structure is the lowest energy state for ice, hexagonal surface structures would best facilitate ice nucleation. However, a similar sample of hexagonal chi-alumina did not show the same results. Further analysis of the samples will be done to characterize surface structures and composition. These conflicting data sets raise interesting questions about the effect of other surface features, such as surface area and porosity, on ice nucleation.

  4. Strengthening of Aluminum Wires Treated with A206/Alumina Nanocomposites

    Directory of Open Access Journals (Sweden)

    David Florián-Algarín

    2018-03-01

    Full Text Available This study sought to characterize aluminum nanocomposite wires that were fabricated through a cold-rolling process, having potential applications in TIG (tungsten inert gas welding of aluminum. A206 (Al-4.5Cu-0.25Mg master nanocomposites with 5 wt % γAl2O3 nanoparticles were first manufactured through a hybrid process combining semi-solid mixing and ultrasonic processing. A206/1 wt % γAl2O3 nanocomposites were fabricated by diluting the prepared master nanocomposites with a monolithic A206 alloy, which was then added to a pure aluminum melt. The fabricated Al–γAl2O3 nanocomposite billet was cold-rolled to produce an Al nanocomposite wire with a 1 mm diameter and a transverse area reduction of 96%. Containing different levels of nanocomposites, the fabricated samples were mechanically and electrically characterized. The results demonstrate a significantly higher strength of the aluminum wires with the nanocomposite addition. Further, the addition of alumina nanoparticles affected the wires’ electrical conductivity compared with that of pure aluminum and aluminum–copper alloys. The overall properties of the new material demonstrate that these wires could be an appealing alternative for fillers intended for aluminum welding.

  5. Strengthening of Aluminum Wires Treated with A206/Alumina Nanocomposites.

    Science.gov (United States)

    Florián-Algarín, David; Marrero, Raúl; Li, Xiaochun; Choi, Hongseok; Suárez, Oscar Marcelo

    2018-03-10

    This study sought to characterize aluminum nanocomposite wires that were fabricated through a cold-rolling process, having potential applications in TIG (tungsten inert gas) welding of aluminum. A206 (Al-4.5Cu-0.25Mg) master nanocomposites with 5 wt % γAl₂O₃ nanoparticles were first manufactured through a hybrid process combining semi-solid mixing and ultrasonic processing. A206/1 wt % γAl₂O₃ nanocomposites were fabricated by diluting the prepared master nanocomposites with a monolithic A206 alloy, which was then added to a pure aluminum melt. The fabricated Al-γAl₂O₃ nanocomposite billet was cold-rolled to produce an Al nanocomposite wire with a 1 mm diameter and a transverse area reduction of 96%. Containing different levels of nanocomposites, the fabricated samples were mechanically and electrically characterized. The results demonstrate a significantly higher strength of the aluminum wires with the nanocomposite addition. Further, the addition of alumina nanoparticles affected the wires' electrical conductivity compared with that of pure aluminum and aluminum-copper alloys. The overall properties of the new material demonstrate that these wires could be an appealing alternative for fillers intended for aluminum welding.

  6. Alumina-on-Polyethylene Bearing Surfaces in Total Hip Arthroplasty.

    Science.gov (United States)

    Jung, Yup Lee; Kim, Shin-Yoon

    2010-02-11

    The long-term durability of polyethylene lining total hip arthroplasty (THA) mainly depends on periprosthetic osteolysis due to wear particles, especially in young active patients. In hip simulator study, reports revealed significant wear reduction of the alumina ceramic-on-polyethylene articulation of THA compared with metal-on-polyethylene bearing surfaces. However, medium to long-term clinical studies of THA using the alumina ceramic-on-polyethylene are few and the reported wear rate of this articulation is variable. We reviewed the advantages and disadvantages of ceramicon- polyethylene articulation in THA, hip simulator study and retrieval study for polyethylene wear, in vivo clinical results of THA using alumina ceramic-on-polyethylene bearing surfaces in the literature, and new trial alumina ceramic-onhighly cross linked polyethylene bearing surfaces.

  7. Synthesis of beta alumina from aluminum hydroxide and oxyhydroxide precursors

    CSIR Research Space (South Africa)

    Van Zyl, A

    1993-02-01

    Full Text Available Two aluminium oxyhydroxides, boehmite and pseudoboehmite, and two aluminium hydroxides, bayerite and gibbsite, have been investigated as precursors for the synthesis of the solid electrolyte, beta alumina. Reaction pathways and products have been...

  8. Significance of structure–property relationship in alumina based ...

    Indian Academy of Sciences (India)

    Unknown

    adverse environmental conditions and mechanical vibra- tions. Most ceramic ... However, even alumina insulators manufactured (for use in 25 kV railway traction ..... early showed plastic deformation and large cracks in and around the indents.

  9. Ceramic joining through reactive wetting of alumina with calcium ...

    Indian Academy of Sciences (India)

    phase analysis of the fractured joint surface clearly indicate reactive wetting of the alumina ceramics. This wetting enhances ... ally considered oxide materials for many applications. .... three cases but is more pronounced in the case of C12A7.

  10. Failure Analysis of Alumina Reinforced Aluminum Microtruss and Tube Composites

    Science.gov (United States)

    Chien, Hsueh Fen (Karen)

    The energy absorption capacity of cellular materials can be dramatically increased by applying a structural coating. This thesis examined the failure mechanisms of alumina reinforced 3003 aluminum alloy microtrusses and tubes. Alumina coatings were produced by hard anodizing and by plasma electrolytic oxidation (PEO). The relatively thin and discontinuous oxide coating at the hinge acted as a localized weak spot which triggered a chain reaction of failure, including oxide fracture, oxide spallation, oxide penetration to the aluminum core and severe local plastic deformation of the core. For the PEO microtrusses, delamination occurred within the oxide coating resulting in a global strut buckling failure mode. A new failure mode for the anodized tubes was observed: (i) axisymmetric folding of the aluminum core, (ii) longitudinal fracture, and (iii) alumina pulverization. Overall, the alumina coating enhanced the buckling resistance of the composites, while the aluminum core supported the oxide during the damage propagation.

  11. Characterization of the Uptake of Nitrogen Oxides on Alumina Adsorbents

    National Research Council Canada - National Science Library

    Pocengal, David

    1999-01-01

    ...) to quantify nitrate and nitrite (NOx) in aqueous solutions that contained NOx exposed alumina and to correlate the quantities of these surface NOx species with the quantity of gaseous NOx sorbed...

  12. Surface chloride salt formation on Space Shuttle exhaust alumina

    Science.gov (United States)

    Cofer, W. R., III; Pellett, G. L.; Sebacher, D. I.; Wakelyn, N. T.

    1984-01-01

    Aluminum oxide samples from the exhaust of Space Shuttle launches STS-1, STS-4, STS-5, and STS-6 were collected from surfaces on or around the launch pad complex and chemically analyzed. The results indicate that the particulate solid-propellant rocket motor (SRM) alumina was heavily chlorided. Concentrations of water-soluble aluminum (III) ion were large, suggesting that the surface of the SRM alumina particles was rendered soluble by prior reactions with HCl and H2O in the SRM exhaust cloud. These results suggest that Space Shuttle exhaust alumina particles are good sites for nucleation and condensation of atmospheric water. Laboratory experiments conducted at 220 C suggest that partial surface chloriding of alumina may occur in hot Space Shuttle exhaust plumes.

  13. Synthesis of α-Alumina (Corundum) and its Application

    International Nuclear Information System (INIS)

    Nay Thwe Kyi; Kyaw Myo Naing; Tin Tin Aye; Nyunt Wynn

    2005-09-01

    This paper described the preparation of aluminium isopropoxide from aluminium sheet at different heating times.Aluminium sheet is found to have a reaction with absolute isopropyl alcohol and mercury (II) chloride as a catalyst under nitrogen atmosphere. Aluminium isopropoxide was characterized by NMR, XRD and IR. Aluminium isopropoxide serves as a molecular precursor to derive pure alumina gel by hydrolysis under both homogeneous and heterogeneous conditions. Pyrolysis to this alumina gel transforms it into -aluminia (corundum) at 1200'C. The phase transformation during pyrolysis was characterized by XRD, SEM and TEM. The alumina (corundum) has porous crystalline nature with high surface aera, which may be used as efficient adsorbent packing material in coloumn chromatography for the seperation of vitamin A from the leaves. -alumina can be also used in catalysis

  14. Effect of chemical composition and alumina content on structure and ...

    Indian Academy of Sciences (India)

    porcelain types (Morrell 1985; Vazquez and Mejia Velasquez. 1998). By increasing ... Orlova et al found that, in alumina porcelains, opti- mum mechanical ... of high mobility of ions, acceptable electrical performance may be achieved with ...

  15. Characterization and mechanical testing of alumina-based nanocomposites reinforced with niobium and/or carbon nanotubes fabricated by spark plasma sintering

    International Nuclear Information System (INIS)

    Thomson, K.E.; Jiang, D.; Yao, W.; Ritchie, R.O.; Mukherjee, A.K.

    2012-01-01

    Alumina-based nanocomposites reinforced with niobium and/or carbon nanotubes (CNT) were fabricated by advanced powder processing techniques and consolidated by spark plasma sintering. Raman spectroscopy revealed that single-walled carbon nanotubes (SWCNT) begin to break down at sintering temperatures >1150 °C. Nuclear magnetic resonance showed that, although thermodynamically unlikely, no Al 4 C 3 formed in the CNT–alumina nanocomposites, such that the nanocomposite can be considered as purely a physical mixture with no chemical bond formed between the nanotubes and ceramic matrix. In addition, in situ single-edge notched bend tests were conducted on niobium and/or CNT-reinforced alumina nanocomposites to assess their toughness. Despite the absence of subcritical crack growth, average fracture toughness values of 6.1 and 3.3 MPa m 1/2 were measured for 10 vol.% Nb and 10 vol.% Nb–5 vol.% SWCNT–alumina, respectively. Corresponding tests for the alumina nanocomposites containing 5 vol.% SWCNT, 10 vol.% SWCNT, 5 vol.% double-walled-CNT and 10 vol.% Nb yielded average fracture toughnesses of 3.0, 2.8, 3.3 and 4.0 MPa m 1/2 , respectively. It appears that the reason for not observing improvement in fracture toughness of CNT-reinforced samples is because of either damage to CNTs or possibly non-optimal interfacial bonding between CNT-alumina.

  16. Radiological assessment for bauxite mining and alumina refining.

    Science.gov (United States)

    O'Connor, Brian H; Donoghue, A Michael; Manning, Timothy J H; Chesson, Barry J

    2013-01-01

    Two international benchmarks assess whether the mining and processing of ores containing Naturally Occurring Radioactive Material (NORM) require management under radiological regulations set by local jurisdictions. First, the 1 Bq/g benchmark for radionuclide head of chain activity concentration determines whether materials may be excluded from radiological regulation. Second, processes may be exempted from radiological regulation where occupational above-background exposures for members of the workforce do not exceed 1 mSv/year. This is also the upper-limit of exposure prescribed for members of the public. Alcoa of Australia Limited (Alcoa) has undertaken radiological evaluations of the mining and processing of bauxite from the Darling Range of Western Australia since the 1980s. Short-term monitoring projects have demonstrated that above-background exposures for workers do not exceed 1 mSv/year. A whole-of-year evaluation of above-background, occupational radiological doses for bauxite mining, alumina refining and residue operations was conducted during 2008/2009 as part of the Alcoa NORM Quality Assurance System (NQAS). The NQAS has been guided by publications from the International Commission on Radiological Protection (ICRP), the International Atomic Energy Agency (IAEA) and the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA). The NQAS has been developed specifically in response to implementation of the Australian National Directory on Radiation Protection (NDRP). Positional monitoring was undertaken to increase the accuracy of natural background levels required for correction of occupational exposures. This is important in view of the small increments in exposure that occur in bauxite mining, alumina refining and residue operations relative to natural background. Positional monitoring was also undertaken to assess the potential for exposure in operating locations. Personal monitoring was undertaken to characterise exposures in Similar

  17. Alumina-on-Polyethylene Bearing Surfaces in Total Hip Arthroplasty

    OpenAIRE

    Jung, Yup Lee; Kim, Shin-Yoon

    2010-01-01

    The long-term durability of polyethylene lining total hip arthroplasty (THA) mainly depends on periprosthetic osteolysis due to wear particles, especially in young active patients. In hip simulator study, reports revealed significant wear reduction of the alumina ceramic-on-polyethylene articulation of THA compared with metal-on-polyethylene bearing surfaces. However, medium to long-term clinical studies of THA using the alumina ceramic-on-polyethylene are few and the reported wear rate of th...

  18. Novel Translucent and Strong Submicron Alumina Ceramics for Dental Restorations.

    Science.gov (United States)

    Zhao, M; Sun, Y; Zhang, J; Zhang, Y

    2018-03-01

    An ideal ceramic restorative material should possess excellent aesthetic and mechanical properties. We hypothesize that the high translucency and strength of polycrystalline ceramics can be achieved through microstructural tailoring. The aim of this study is to demonstrate the superior optical and mechanical properties of a new class of submicron grain-sized alumina ceramics relative to the current state-of-the-art dental ceramic materials. The translucency, the in-line transmission ( T IT ) in particular, of these submicron alumina ceramics has been examined with the Rayleigh-Gans-Debye light-scattering model. The theoretical predictions related very well with the measured T IT values. The translucency parameter ( TP) and contrast ratio ( CR) of the newly developed aluminas were measured with a reflectance spectrophotometer on a black-and-white background. For comparison, the T IT , TP, and CR values for a variety of dental ceramics, mostly measured in-house but also cited from the literature, were included. The flexural strength of the aluminas was determined with the 4-point bending test. Our findings have shown that for polycrystalline alumina ceramics, an average grain size ceramic and zirconias, including the most translucent cubic-containing zirconias. The strength of these submicron grain-sized aluminas was significantly higher than that of the cubic-containing zirconia (e.g., Zpex Smile) and lithia-based glass-ceramics (e.g., IPS e.max CAD HT). A coarse-grained alumina could also reach a translucency level comparable to that of dental porcelain. However, the relatively low strength of this material has limited its clinical indications to structurally less demanding applications, such as orthodontic brackets. With a combined high strength and translucency, the newly developed submicron grain-sized alumina may be considered a suitable material for dental restorations.

  19. Self-ordered Porous Alumina Fabricated via Phosphonic Acid Anodizing

    OpenAIRE

    Akiya, Shunta; Kikuchi, Tatsuya; Natsui, Shungo; Sakaguchi, Norihito; Suzuki, Ryosuke O.

    2016-01-01

    Self-ordered periodic porous alumina with an undiscovered cell diameter was fabricated via electrochemical anodizing in a new electrolyte, phosphonic acid (H3PO3). High-purity aluminum plates were anodized in phosphonic acid solution under various operating conditions of voltage, temperature, concentration, and anodizing time. Phosphonic acid anodizing at 150-180 V caused the self-ordering behavior of porous alumina, and an ideal honeycomb nanostructure measuring 370-440 nm in cell diameter w...

  20. 11C-radioisotope study of methanol co-reaction with ethanol over Ni-MCM-41 silica-alumina and Ni-alumina

    International Nuclear Information System (INIS)

    Sarkadi-Priboczki, E.; Kovacs, Z.; Tsoncheva, T.; Kumar, N.; Murzin, D.Yu.

    2009-01-01

    Complete text of publication follows. The Ni modifies the properties of acidic alumina and light acidic MCM-41 silica-alumina supports. The radioisotopic method is a suitable tool for distinction of the 11 Cradioisotopic methanol and its co-derivates from derivates of non-radioactive ethanol on these catalysts. Experimental. The Ni/A l 2O 3 (5 wt % Ni) is commercially available while H-MCMN-41 (Si/Al=20) and Ni-ion-exchanged MCM-41 silica-alumina (5 wt % Ni) were prepared and characterized in previous works. Before catalysis the Ni/Al 2 O 3 and Ni-MCM-41 were pre-reduced. The 11 C-methanol was formed by a radiochemical process from 11 C-carbon dioxide produced at cyclotron (T 1/2 = 20.4 min). The mixture of equivalent volume of radioactive methanol and non-radioactive ethanol was introduced into glass tube micro-flow reactor at ambient temperature. After adsorption, the valves were closed and the catalyst was heated up to the required temperatures. The desorption rate of the remaining 11 C-derivatives on catalysts were continuously followed by radiodetectors and the derivatives of methanol with ethanol were analyzed by Radio/FID-gas chromatography (FID is coupled on-line with a radiodetector). The ethanol and its derivates were identified by FID while the 11 C-methanol and its co-derivates (with ethanol) were detected by both of FID and radiodetector. Results The 11 C-dimethyl ether was the common product of the single 11 C-methanol transformation on H-MCM-41, Ni-MCM-41 and Ni- Al 2 O 3 at low temperature (200-280 degC) due to middle strong acid sites. At higher temperature (280-350 degC), the dimethyl ether and hydrocarbons were the dominant products on H-MCM-41 while dimethyl ether selectivity decreased on Ni-alumina and Ni-MCM-41 in favor of methane. The selectivities of methanol to formaldehyde and methane were the highest on Ni-MCM-41. During co-reaction of 11 C-methanol with non-radioactive ethanol, the 11 C-labeled coethers, namely 11 C-methyl ethyl ether

  1. Alumina Concentration Detection Based on the Kernel Extreme Learning Machine.

    Science.gov (United States)

    Zhang, Sen; Zhang, Tao; Yin, Yixin; Xiao, Wendong

    2017-09-01

    The concentration of alumina in the electrolyte is of great significance during the production of aluminum. The amount of the alumina concentration may lead to unbalanced material distribution and low production efficiency and affect the stability of the aluminum reduction cell and current efficiency. The existing methods cannot meet the needs for online measurement because industrial aluminum electrolysis has the characteristics of high temperature, strong magnetic field, coupled parameters, and high nonlinearity. Currently, there are no sensors or equipment that can detect the alumina concentration on line. Most companies acquire the alumina concentration from the electrolyte samples which are analyzed through an X-ray fluorescence spectrometer. To solve the problem, the paper proposes a soft sensing model based on a kernel extreme learning machine algorithm that takes the kernel function into the extreme learning machine. K-fold cross validation is used to estimate the generalization error. The proposed soft sensing algorithm can detect alumina concentration by the electrical signals such as voltages and currents of the anode rods. The predicted results show that the proposed approach can give more accurate estimations of alumina concentration with faster learning speed compared with the other methods such as the basic ELM, BP, and SVM.

  2. Antibacterial activity of zinc oxide-coated nanoporous alumina

    Energy Technology Data Exchange (ETDEWEB)

    Skoog, S.A. [Joint Department of Biomedical Engineering, University of North Carolina and North Carolina State University, Box 7115, Raleigh, NC 27695-7115 (United States); Bayati, M.R. [Department of Materials Science and Engineering, North Carolina State University, Box 7907, Raleigh, NC 27695-7907 (United States); Petrochenko, P.E. [Joint Department of Biomedical Engineering, University of North Carolina and North Carolina State University, Box 7115, Raleigh, NC 27695-7115 (United States); Division of Biology, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, U.S. Food and Drug Administration, Silver Spring, MD 20993 (United States); Stafslien, S.; Daniels, J.; Cilz, N. [Center for Nanoscale Science and Engineering, North Dakota State University, 1805 Research Park Drive, Fargo, ND 58102 (United States); Comstock, D.J.; Elam, J.W. [Energy Systems Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Narayan, R.J., E-mail: roger_narayan@msn.com [Joint Department of Biomedical Engineering, University of North Carolina and North Carolina State University, Box 7115, Raleigh, NC 27695-7115 (United States); Department of Materials Science and Engineering, North Carolina State University, Box 7907, Raleigh, NC 27695-7907 (United States)

    2012-07-25

    Highlights: Black-Right-Pointing-Pointer Atomic layer deposition was used to deposit ZnO on nanoporous alumina membranes. Black-Right-Pointing-Pointer Scanning electron microscopy showed continuous coatings of zinc oxide nanocrystals. Black-Right-Pointing-Pointer Activity against B. subtilis, E. coli, S. aureus, and S. epidermidis was shown. - Abstract: Nanoporous alumina membranes, also known as anodized aluminum oxide membranes, are being investigated for use in treatment of burn injuries and other skin wounds. In this study, atomic layer deposition was used for coating the surfaces of nanoporous alumina membranes with zinc oxide. Agar diffusion assays were used to show activity of zinc oxide-coated nanoporous alumina membranes against several bacteria found on the skin surface, including Bacillus subtilis, Escherichia coli, Staphylococcus aureus, and Staphylococcus epidermidis. On the other hand, zinc oxide-coated nanoporous alumina membranes did not show activity against Pseudomonas aeruginosa, Enterococcus faecalis, and Candida albicans. These results suggest that zinc oxide-coated nanoporous alumina membranes have activity against some Gram-positive and Gram-negative bacteria that are associated with skin colonization and skin infection.

  3. Antimicrobial Properties of Chitosan-Alumina/f-MWCNT Nano composites

    International Nuclear Information System (INIS)

    Masheane, M.; Nthunya, L.; Malinga, S.; Masheane, M.; Nthunya, L.; Nxumalo, E.; Mhlanga, S.; Barnard, T.

    2016-01-01

    Antimicrobial chitosan-alumina/functionalized-multi walled carbon nano tube (f-MWCNT) nano composites were prepared by a simple phase inversion method. Scanning electron microscopy (SEM) analyses showed the change in the internal morphology of the composites and energy dispersive spectroscopy (EDS) confirmed the presence of alumina and f-MWCNTs in the chitosan polymer matrix. Fourier transform infrared (FTIR) spectroscopy showed the appearance of new functional groups from both alumina and f-MWCNTs, and thermogravimetric analysis (TGA) revealed that the addition of alumina and f-MWCNTs improved the thermal stability of the chitosan polymer. The presence of alumina and f-MWCNTs in the polymer matrix was found to improve the thermal stability and reduced the solubility of chitosan polymer. The prepared chitosan-alumina/f-MWCNT nano composites showed inhibition of twelve strains of bacterial strains that were tested. Thus, the nano composites show a potential for use as a biocides in water treatment for the removal of bacteria at different environmental conditions.

  4. Superhydrophobic surfaces fabricated by surface modification of alumina particles

    Science.gov (United States)

    Richard, Edna; Aruna, S. T.; Basu, Bharathibai J.

    2012-10-01

    The fabrication of superhydrophobic surfaces has attracted intense interest because of their widespread potential applications in various industrial fields. Recently, some attempts have been carried out to prepare superhydrophobic surfaces using metal oxide nanoparticles. In the present work, superhydrophobic surfaces were fabricated with low surface energy material on alumina particles with different sizes. It was found that particle size of alumina is an important factor in achieving stable superhydrophobic surface. It was possible to obtain alumina surface with water contact angle (WCA) of 156° and a sliding angle of Superhydrophobicity of the modified alumina is attributed to the combined effect of the micro-nanostructure and low surface energy of fatty acid on the surface. The surface morphology of the alumina powder and coatings was determined by FESEM. The stability of the coatings was assessed by conducting water immersion test. Effect of heat treatment on WCA of the coating was also studied. The transition of alumina from hydrophilic to superhydrophobic state was explained using Wenzel and Cassie models. The method is shown to have potential application for creating superhydrophobic surface on cotton fabrics.

  5. Influence of additives on the stability of the phases of alumina; Influencia de aditivos na estabilidade das fases da alumina

    Energy Technology Data Exchange (ETDEWEB)

    Rosario, D.C.C.; Gouvea, D., E-mail: deisedorosario@usp.br [Universidade de Sao Paulo (USP), SP (Brazil). Departamento de Engenharia Metalurgica e de Materiais. Laboratorio de Processos Ceramicos

    2011-07-01

    Problems with the stability of gamma alumina in catalytic reactions have been solved with the inclusion of additives during the synthesis of alumina. These additives stabilize the temperature of phase transition allowing the use of metastable alumina at high temperatures, but the mechanisms of action of additives are not well defined. It is known that each family of additive or additives behaves in different ways for this stabilization. This work aimed to study the performance of MgO and ZrO{sub 2}, respectively at different concentrations in alumina synthesized via Pechini. The samples were analyzed by DSC, X-ray diffraction, measurement of specific surface area by BET analysis, and infrared analysis. The results showed an increase in transition temperature for both additives, and a different changes for specific surface area, showing that MgO and ZrO{sub 2} work on improving the stability but with distinct mechanisms. (author)

  6. Nano or micro grained alumina powder? A choose before sintering

    Directory of Open Access Journals (Sweden)

    Román, R.

    2008-12-01

    Full Text Available Two different wet routes have been used to synthesize alumina powders in order to compare the characteristics of the final product and its behaviour during sintering. The Homogeneous Precipitation (HP gives rise to nanoparticulated powders of about 2 nm. However, such particles quickly aggregate and grow with calcination temperature. The Polymerized Organic-Inorganic Synthesis (POI produces homogeneous particle size powders (about 1 micron after resin charring. The characterization of the powder surface is the basis of an efficient process control. Particle characterization parameters (morphology, crystallinity and degree of aggregation are characterized by different techniques, such as DTA/TG, IR, XRD, SEM and TEM, and compared between these synthesis methods. The results show the evolution from the amorphous to the corundum alumina phase for both processes and their ability for sintering, as well discuses the beneficial of nanoparticles obtained by HP during sintering.

    Se han utilizado dos diferentes síntesis por vía húmeda para la preparación de polvos de alúmina con el fin de comparar las características de los productos finales y su comportamiento durante la sinterización. La Precipitación Homogénea (HP da lugar a polvos nanoparticulados de unos 2nm. Se observa sin embargo, como estas partículas se agregan rápidamente y crecen con la temperatura de calcinación. La Síntesis por Polimerización Orgánica-Inorgánica (POI produce polvos de tamaño de partícula homogéneo (en torno a 1 micra después de la descomposión de la resina. La caracterización de la superficie de los polvos es la base de un control eficiente del proceso. Los parámetros de caracterización de las partículas obtenidas (morfología, cristalinidad y grado de agregación se obtienen por diferentes técnicas como DTA/TG, IR, XRD, SEM y TEM, y se comparan entre estos métodos de síntesis. Los resultados muestran la evolución desde el amorfo a la fase

  7. [Phenotypic plasticity and its regulation of tillers prolonged reproductive growth of Puccinellia tenuiflora population on alkalized meadow in Songnen Plains of China].

    Science.gov (United States)

    Sun, Ju; Yang, Yun-Fei

    2007-04-01

    Puccinellia tenuiflora is a salt-tolerant plant of grass family. By the method of random sampling, big samples of reproductive tillers of P. tenuiflora population on the alkalized meadow in the Songnen Plains of China were collected at early heading, heading, flowering, and milky stages, respectively, and the plasticity of their quantitative characters was analyzed. The results showed that except some fluctuations at flowering stage, the tiller height, tiller biomass, spike length and spike biomass of the reproductive tillers at other three growth stages increased significantly every five days with the increasing time of reproductive growth. At each growth stage, tiller height had a significant positive correlation with spike biomass, but a negative correlation with reproductive allocation. With the time of reproductive growth prolonged, the increasing rate of spike biomass at early heading, flowering and milky stages increased in power function with the increase of tiller height. The reproductive allocation decreased linearly by 43.2% and 44.31% at early heading and heading stages, respectively when the reproductive growth time increased ten days, and by 130% at milky stage when the time increased five days. The regulation of the tiller phenotypic plasticity of P. tenuiflora population at its reproductive growth stage followed definite patterns.

  8. Effective enzymatic in situ saccharification of bamboo shoot shell pretreated by dilute alkalic salts sodium hypochlorite/sodium sulfide pretreatment under the autoclave system.

    Science.gov (United States)

    Chong, Gang-Gang; He, Yu-Cai; Liu, Qiu-Xiang; Kou, Xiao-Qin; Huang, Xiao-Jun; Di, Jun-Hua; Ma, Cui-Luan

    2017-10-01

    In this study, dilute alkali salts (0.6% NaClO, 0.067% Na 2 S) pretreatment at 10% sulfidity under the autoclave system at 120°C for 40min was used for pretreating bamboo shoot shell (BSS). Furthermore, FT-IR, XRD and SEM were employed to characterize the changes in the cellulose structural characteristics (porosity, morphology, and crystallinity) of the pretreated BSS solid residue. After 72h, the reducing sugars and glucose from the enzymatic in situ hydrolysis of 50g/L pretreated BSS in dilute NaClO/Na 2 S media could be obtained at 31.11 and 20.32g/L, respectively. Finally, the obtained BSS-hydrolysates containing alkalic salt NaClO/Na 2 S resulted in slightly negative effects on the ethanol production. Glucose in BSS-hydrolysates was fermented from 20.0 to 0.17g/L within 48h, and an ethanol yield of 0.41g/g glucose, which represents 80.1% of the theoretical yield, was obtained. This study provided an effective strategy for potential utilization of BSS. Copyright © 2017 Elsevier Ltd. All rights reserved.

  9. Preparation of a Pd-Pt alloy on alumina and its application for a gas chromatography

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Minsoo [Korea Atomic Energy Research Institute, 150 Deokjin-dong, Yuseong, Daejeon 305-353 (Korea, Republic of)]. E-mail: minm@kaeri.re.kr; Paek, Seungwoo [Korea Atomic Energy Research Institute, 150 Deokjin-dong, Yuseong, Daejeon 305-353 (Korea, Republic of); Ahn, Do-Hee [Korea Atomic Energy Research Institute, 150 Deokjin-dong, Yuseong, Daejeon 305-353 (Korea, Republic of); Kim, Kwang-Rag [Korea Atomic Energy Research Institute, 150 Deokjin-dong, Yuseong, Daejeon 305-353 (Korea, Republic of); Yim, Sung-Paal [Korea Atomic Energy Research Institute, 150 Deokjin-dong, Yuseong, Daejeon 305-353 (Korea, Republic of); Chung, Hongsuk [Korea Atomic Energy Research Institute, 150 Deokjin-dong, Yuseong, Daejeon 305-353 (Korea, Republic of)

    2007-08-30

    In this study we attempted to obtain a Pd-Pt alloy on alumina (PPA) by using an impregnation and alcohol reduction method for the purpose of a hydrogen isotopes separation, in which {alpha}-alumina powder was impregnated into an ethanol water (1/1, w/w) solution containing PdCl{sub 2}, PtCl{sub 2}, and polyvinylpyrrolidone (PVP, MW = 10,000). The sample was dried, reduced by hydrogen, and thermally treated at 1073 K. Thus, two kinds of PPA (Pd content 17 and 29 wt%) were achieved. The produced PPA showed a good crystallinity from the XRD analysis and it exhibited an adequate hydrogen desorption isotherm as a packing material for the separation of hydrogen isotopes. GC columns packed with PPA and Cu powder were used for the separation of a 29.2% D{sub 2}-H{sub 2} gas mixture at 303 and 343 K. The experimental result showed a good separation efficiency of the hydrogen isotopes for the GC process. Consequently, the suggested technique for the production of a Pd-Pt alloy on alumina was proven to be successful.

  10. Mechanical and physical properties of calcium silicate/alumina composite for biomedical engineering applications.

    Science.gov (United States)

    Shirazi, F S; Mehrali, M; Oshkour, A A; Metselaar, H S C; Kadri, N A; Abu Osman, N A

    2014-02-01

    The focus of this study is to investigate the effect of Al2O3 on α-calcium silicate (α-CaSiO3) ceramic. α-CaSiO3 was synthesized from CaO and SiO2 using mechanochemical method followed by calcinations at 1000°C. α-CaSiO3 and alumina were grinded using ball mill to create mixtures, containing 0-50w% of Al2O3 loadings. The powders were uniaxially pressed and followed by cold isostatic pressing (CIP) in order to achieve greater uniformity of compaction and to increase the shape capability. Afterward, the compaction was sintered in a resistive element furnace at both 1150°C and 1250°C with a 5h holding time. It was found that alumina reacted with α-CaSiO3 and formed alumina-rich calcium aluminates after sintering. An addition of 15wt% of Al2O3 powder at 1250°C were found to improve the hardness and fracture toughness of the calcium silicate. It was also observed that the average grain sizes of α-CaSiO3 /Al2O3 composite were maintained 500-700nm after sintering process. © 2013 Published by Elsevier Ltd.

  11. Effect of surface finishing and heat treatments on the mechanical strength of sintered alumina

    International Nuclear Information System (INIS)

    Lino, U.R.A.

    1982-04-01

    The effect of surface finishing on the mechanical strength of two pure aluminas, one of self-production and another a commercial one, is studied. Three types of finishings: as-sintered, as machined and as-machined with thermal treatment were studied. It was verified that the as-machined alumina is about 50 percent stronger than the as-sintered one, and that a thermal treatment increases even more the mechanical strength of the sintered alumina. The effect of the volume and pressing direction on mechanical strength was studied. The kinetics of crack healing was determined from a series of systematically selected thermal treatments with annealing temperatures between 1200 0 C and 1600 0 C. It was verified that a recently developed theoretical model for crack healing can describe the experimental results; using this model a value for the activation energy of the process of 715 kJ/mcl was obtained, which suggests that crack healing is promoted by volume diffusion. The material behavior under subcritical crack growth action was also studied, and a value of about 40 for the subcritical crack growth exponent N from dynamic loading tests in water was found. A fractographic study intended to localize and measure the flaws that originated the fracture of the tested specimens was performed; the measured flaw sizes were compared with the flaw size calculated from the values of the measured mechanical strength; in this comparison an excellent agreement was observed. (Author) [pt

  12. Role of metal ion impurities in generation of oxygen gas within anodic alumina

    Energy Technology Data Exchange (ETDEWEB)

    Shimizu, K. [Keio Univ., Yokohama (Japan). Chemical Lab.; Habazaki, H. [Hokkaido Univ., Sapporo (Japan). Graduate School of Engineering; Skeldon, P.; Thompson, G.E.; Wood, G.C. [University of Manchester Inst. of Science and Technology (United Kingdom). Corrosion and Protection Centre

    2002-07-01

    The generation of oxygen gas within an amorphous anodic alumina film is reported. The film was formed by anodizing aluminum, which was first electropolished and then chemically polished in CrO{sub 3}-H{sub 3}PO{sub 4} solution, in sodium tungstate electrolyte. The procedure results in incorporation of mobile Cr{sup 3+} species, from the chemical polishing film, and mobile W{sup 6+} species, from the electrolyte, into the amorphous structure. The tungsten species are present in the outer 27% of the film thickness, while Cr{sup 6+} species occupy a thin layer within the tungsten-containing region. Above the Cr{sup 3+} containing layer, a band develops that contains oxygen bubbles of a few nanometres size. The oxygen is generated by oxidation of O{sup 2-} ions of the alumina. A mechanism of oxygen generation within the alumina is proposed based on the electronic band structure of the oxide, modified by the Cr{sup 3+} and W{sup 6+} species, and on the ionic transport processes during oxide growth. (author)

  13. Interaction of alumina with liquid Pb{sub 83}Li{sub 17} alloy

    Energy Technology Data Exchange (ETDEWEB)

    Jain, Uttam, E-mail: uttamj@barc.gov.in [Fusion Reactor Materials Section, Bhabha Atomic Research Centre, Mumbai 400085 (India); Mukherjee, Abhishek; Sonak, Sagar; Kumar, Sanjay [Fusion Reactor Materials Section, Bhabha Atomic Research Centre, Mumbai 400085 (India); Mishra, Ratikant [Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Krishnamurthy, Nagaiyar [Fusion Reactor Materials Section, Bhabha Atomic Research Centre, Mumbai 400085 (India)

    2014-11-15

    Highlights: • The role of oxygen in the interaction of alumina with Pb{sub 83}Li{sub 17} alloy was studied. • Li of Pb{sub 83}Li{sub 17} alloy undergoes oxidation even in flowing high pure argon atmosphere. • It was seen that alumina reacts with Pb{sub 83}Li{sub 17} alloy at 550 °C to form LiAlO{sub 2} compound. • The reaction is rapid in the presence of oxygen and happens more slowly in the presence of flowing argon. - Abstract: Eutectic lead lithium (Pb{sub 83}Li{sub 17}) alloy is being considered a coolant, neutron multiplier and tritium breeder for International Thermonuclear Experimental Reactor (ITER) and Fusion Power Reactors (FPR). In order to reduce the magneto-hydrodynamic drag (MHD) and to prevent corrosion of structural materials due to the flow of lead lithium (Pb{sub 83}Li{sub 17}) alloy, alumina (Al{sub 2}O{sub 3}) is proposed as a candidate ceramic coating material. Interaction of liquid Pb{sub 83}Li{sub 17} alloy with Al{sub 2}O{sub 3} at the operating temperature of these reactors is therefore an important issue. The present paper deals with the characterization of Pb{sub 83}Li{sub 17} alloy and its interaction with Al{sub 2}O{sub 3} at the reactor operating temperature. The interaction was studied using EPMA, XRD and thermal analysis technique. The result indicates that alumina can interact with Pb{sub 83}Li{sub 17} alloy at 550 °C even in high purity argon atmosphere. The role of oxygen in the interaction process has also been discussed.

  14. Improvements in nanoscale zero-valent iron production by milling through the addition of alumina

    Energy Technology Data Exchange (ETDEWEB)

    Ribas, D. [Fundació CTM Centre Tecnològic de Manresa (Spain); Cernik, M. [Technical University of Liberec, Institute for Nanomaterials, Advanced Technologies and Innovation (Czech Republic); Martí, V.; Benito, J. A., E-mail: josep.a.benito@upc.edu [Fundació CTM Centre Tecnològic de Manresa (Spain)

    2016-07-15

    A new milling procedure for a cost-effective production of nanoscale zero-valent iron for environmental remediation is presented. Conventional ball milling of iron in an organic solvent as Mono Ethylene Glycol produces flattened iron particles that are unlikely to break even after very long milling times. With the aim of breaking down these iron flakes, in this new procedure, further milling is carried out by adding an amount of fine alumina powder to the previously milled solution. As the amount of added alumina increases from 9 to 54 g l{sup −1}, a progressive decrease of the presence of flakes is observed. In the latter case, the appearance of the particles formed by fragments of former flakes is rather homogeneous, with most of the final nanoparticles having an equivalent diameter well below 1 µm and with an average particle size in solution of around 400 nm. An additional increase of alumina content results in a highly viscous solution showing worse particle size distribution. Milled particles, in the case of alumina concentrations of 54 g l{sup −1}, have a fairly large specific surface area and high Fe(0) content. These new particles show a very good Cr(VI) removal efficiency compared with other commercial products available. This good reactivity is related to the absence of an oxide layer, the large amount of superficial irregularities generated by the repetitive fracture process during milling and the presence of a fine nanostructure within the iron nanoparticles.

  15. The role of powder preparation method in enhancing fracture toughness of zirconia ceramics with low alumina amount

    International Nuclear Information System (INIS)

    Danilenko, I.; Konstantinova, T.; Volkova, G.; Burkhovetski, V.; Glazunova, V.

    2015-01-01

    In most cases zirconia-alumina composites for scientific investigations and industry are prepared by means of mechanical mixing of powders, compaction and sintering. In our opinion, this is one of the reasons for the low values for fracture toughness of the sintered materials. In this study, we investigated the effect of nanopowder synthesis methods on the structure and mechanical properties of 3Y-TZP/alumina ceramic composites and determined the mechanisms involved in composite toughening. We show that the addition of a small amount of alumina (1 - 2 wt%) to zirconia ceramics has the potential to increase the fracture toughness of zirconia ceramics. The starting powders were obtained by means of co-precipitation and ball milling. It turned out that at equal density, bending strength and hardness values, the fracture toughness in ceramic composites sintered from co-precipitated nanopowders is higher in comparison with fracture toughness values in matrix material and traditional 3Y-TZP/alumina composites. We believed that the role of the crack deflection process in ceramic composites sintered from co-precipitated nanopowders increased significantly. This can be conditioned by means of a series of processes for composite structure formation during precipitation, crystallization, and sintering of nanopowders.

  16. The role of powder preparation method in enhancing fracture toughness of zirconia ceramics with low alumina amount

    Energy Technology Data Exchange (ETDEWEB)

    Danilenko, I.; Konstantinova, T.; Volkova, G.; Burkhovetski, V.; Glazunova, V. [NAS of Ukraine, Donetsk (Ukraine). Donetsk Inst. for Physics and Engineering

    2015-07-01

    In most cases zirconia-alumina composites for scientific investigations and industry are prepared by means of mechanical mixing of powders, compaction and sintering. In our opinion, this is one of the reasons for the low values for fracture toughness of the sintered materials. In this study, we investigated the effect of nanopowder synthesis methods on the structure and mechanical properties of 3Y-TZP/alumina ceramic composites and determined the mechanisms involved in composite toughening. We show that the addition of a small amount of alumina (1 - 2 wt%) to zirconia ceramics has the potential to increase the fracture toughness of zirconia ceramics. The starting powders were obtained by means of co-precipitation and ball milling. It turned out that at equal density, bending strength and hardness values, the fracture toughness in ceramic composites sintered from co-precipitated nanopowders is higher in comparison with fracture toughness values in matrix material and traditional 3Y-TZP/alumina composites. We believed that the role of the crack deflection process in ceramic composites sintered from co-precipitated nanopowders increased significantly. This can be conditioned by means of a series of processes for composite structure formation during precipitation, crystallization, and sintering of nanopowders.

  17. Recovery of alumina from khushab bauxite by leaching with sulphuric acid and removal of iron impurity by ethanol

    International Nuclear Information System (INIS)

    Tariq, M.; Iqbal, M.M.; Shafiq, M.; Aziz, A.

    2014-01-01

    Bauxite is heterogeneous material principally composed of aluminum oxide minerals and found in all continents. It is being used in chemical, cement, refractory, abrasive, fertilizer, steel and other industries. In order to extract the alumina, the calcined samples of bauxite of Khushab area were ground to -710 meum. Sulphuric acid of purity 40% was used as leaching agent and slurry of pulp density 14% was prepared by dissolving 60 ml acid in 20 gm sample. The leaching was carried out at 90 degree C for 2 hours. The iron impurity was removed by ethanol of purity 68%. The drying, dehydration and desulphurization temperatures were kept 105 degree C, 450 degree C and 850 degree C respectively in all the stages of the process. Alumina recoveries from four samples of Sultan Mehdhi, Chamil More, Niaz Mine and Nadi locations were 20.8%, 9.81%, 15.47% and 7.78% respectively. Iron was almost completely removed as the analysis shows that the Fe/sub 2/O/sub 3/ removal was from 97.8% to 99.6%. It is concluded that leaching efficiency was quite encouraging except Nadi ore sample. However the iron free alumina recoveries were low as the analysis of Fe/sub 2/O/sub 3/ processed residue shows that it contains 72.72% to 92.94% of leached alumina in all the four experiments. (author)

  18. A Quantitative Tunneling/Desorption Model for the Exchange Current at the Porous Electrode/Beta - Alumina/Alkali Metal Gas Three Phase Zone at 700-1300K

    Science.gov (United States)

    Williams, R. M.; Ryan, M. A.; Saipetch, C.; LeDuc, H. G.

    1996-01-01

    The exchange current observed at porous metal electrodes on sodium or potassium beta -alumina solid electrolytes in alkali metal vapor is quantitatively modeled with a multi-step process with good agreement with experimental results.

  19. Properties of single crystal beta''-aluminas

    International Nuclear Information System (INIS)

    Bates, J.B.; Brown, G.M.; Kaneda, T.; Brundage, W.E.; Wang, J.C.; Engstrom, H.

    1979-01-01

    Large single crystals of sodium beta''-alumina were grown by slow evaporation of Na 2 O at 1690 0 C from a mixture of Na 2 CO 3 , MgO, and Al 2 O 3 . Polarized Raman measurements were made on the Na β'' single crystals and on single crystals of Li, K, Rb, and Ag β'' prepared by ion exchange of Na β''. The low frequency Raman spectra of Na, K, Rb, and Ag β'' contained four or more bands due to vibrations of the mobile cations. These results were analyzed by assuming the spectra to be due to the normal modes of a defect cluster consisting of a cation vacancy surrounded by three cations. From model calculations, the Raman band of Na β'' at 33 cm -1 is assigned to the attempt mode for diffusion of Na + ions. The structure of a Ag β'' single crystal was investigated by neutron diffraction, and 20% of the Ag + ion sites were found to be vacant

  20. Coprecipitated nickel-alumina methanation catalysts

    International Nuclear Information System (INIS)

    Kruissink, E.C.

    1981-01-01

    In the last few years there has been a renewed interest in the methanation reaction CO+3H 2 =CH 4 +H 2 O. The investigations described in this thesis were performed in relation to the application of this reaction, within the framework of the so-called 'NFE' project, also called 'ADAM' and 'EVA' project. This project, which has been under investigation in West Germany for some years, aims at the investigation of the feasibility of transporting heat from a nuclear high temperature reactor by means of a chemical cycle. A promising possibility to realize such a cycle exists in applying the combination of the endothermic steam reforming of methane and the exothermic methanation reaction. This thesis describes the investigations into a certain type of methanation catalyst, viz. a coprecipitated nickel-alumina catalyst, with the aim to give more insight into the interrelationship between the preparation conditions on the one hand and catalyst properties such as activity and stability on the other hand. (Auth.)

  1. Influence of coprecipitation and mechanical mixture methods on the characteristics of nickel oxide-alumina composites; Influencia dos metodos de coprecipitacao e mistura mecanica nas caracteristicas de compositos oxido de niquel-alumina

    Energy Technology Data Exchange (ETDEWEB)

    Cordeiro, G.L.; Yoshito, W.K.; Ussui, V.; Lima, N.B. de; Lazar, D.R.R., E-mail: gcordeiro@usp.br [Instituto de Pesquisas Energeticas e Nucleares (CCTM/IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Centro de Ciencia e Tecnologia de Materiais

    2014-07-01

    Alumina-supported nickel catalysts are currently used in the reforming process due to low cost and high activity for hydrogen production from alcohols. In this work, the effect of preparation methods on nickel oxide-alumina based materials has been investigated. Nickel content was fixed at 15 wt%. Ceramic powders were obtained by coprecipitation in ammonia medium and mechanical mixture. Coprecipitated materials were calcined in air at 750 deg C to obtain the corresponding oxides. Materials obtained by mechanical mixture were prepared by wet milling of nickel oxide and alumina powders, both synthesized by precipitation and calcination in air at 450 and 750 deg C, respectively. Powders were characterized by X-ray diffraction, nitrogen gas sorption by applying the BET method, laser diffraction, scanning electron microscopy, electrophoretic mobility measurements for zeta potential determination and infrared spectroscopy. The results showed that coprecipitation method allowed the production of mixed oxides with high surface area (232,7 ± 3,2 m{sup 2}.g{sup -1}) and normal granulometric distribution while mechanical mixture led to the formation of materials constituted by gamma alumina and nickel oxide phases, with low surface area (136,2 ± 0,5 m{sup 2}.g{sup -1}) and bimodal granulometric distribution. (author)

  2. Microstructure and interfacial behaviour of Alumina/Inconel 600 joints prepared by brazing route

    International Nuclear Information System (INIS)

    Laik, A.; Mishra, P.; Bhanumurthy, K.; Kashyap, B.P.

    2010-01-01

    Joining of metals to ceramics remains a technological challenge due to the wide difference in the physical and mechanical properties of the two classes of materials. Attempt was made to produce leak tight joints between Inconel-600 and alumina using the brazing route with Au-Ni brazing alloy. Alumina tubes were metallised following the Mo-Mn route and then coated with Ni. The metallised alumina tubes were brazed to Inconel-600 ferrules using Au-18%Ni brazing alloy under vacuum, at optimised process parameters. In order to study the effect of prolong annealing on the microstructural stability and the micro-chemistry of the brazing zone, brazed joints were subjected to prolong annealing at 400 deg C and 560 deg C for 8000 hrs each. Detailed analysis of the interfacial structure of the brazing zones was done using an electron probe microanalyser (EPMA). X-ray maps of the elements Fe, Ni, Cr, Al, Au, Mo and Mn along with BSE images of the brazing zone are given. These X-ray maps precisely reveal the micro-chemistry of the brazing zones. The various phases formed were identified. The distribution of the various elements across the interfaces was also obtained, which helps to reveal the chemical behaviour of the individual elements during the process of brazing. Two phases appear very distinctly in the brazement, one is rich in Au and the other is rich in Ni. Depending upon their affinity, rest of the elements shows a partitioning in these two phases. While Fe, Cr and Mo get dissolved in the Ni-rich phase, Mn seems to partition in the Au-rich phase. The microstructure and the X-ray maps of the couple annealed at 400 deg C shows that the spatial variation in the composition throughout the brazing zone gets homogenised due to diffusion at high temperatures. This effect is even more pronounced on annealing at 560 deg C. Moreover, the transport of Cr from the Inconel side to the surface of alumina is very evident. On annealing at 560 deg C, a region rich in Cr, was found to

  3. Effect of humic acid on sorption of technetium by alumina

    International Nuclear Information System (INIS)

    Kumar, S.; Rawat, N.; Kar, A.S.; Tomar, B.S.; Manchanda, V.K.

    2011-01-01

    Highlights: → Tc sorption on alumina has been studied under aerobic as well anaerobic condition over pH 3-10. → Effect of humic acid on sorption of Tc by alumina has been investigated. → Linear additive modeling and surface complexation modeling were carried out to delineate the role of humic acid in Tc(IV) sorption in ternary system of Tc(IV)-humic acid-alumina. → Sorption of humic acid onto alumina and strong complexation of Tc(IV) with humic acid were found to govern the sorption of Tc(IV) in the ternary system. - Abstract: Sorption of technetium by alumina has been studied in absence as well as in presence of humic acid using 95 Tc m as a tracer. Measurements were carried out at fixed ionic strength (0.1 M NaClO 4 ) under varying pH (3-10) as well as redox (aerobic and reducing anaerobic) conditions. Under aerobic conditions, negligible sorption of technetium was observed onto alumina both in absence and in presence of humic acid. However, under reducing conditions (simulated with [Sn(II)] = 10 -6 M), presence of humic acid enhanced the sorption of technetium in the low pH region significantly and decreased at higher pH with respect to that in absence of humic acid. Linear additive as well as surface complexation modeling of Tc(IV) sorption in presence of humic acid indicated the predominant role of sorbed humic acid in deciding technetium sorption onto alumina.

  4. Understanding improved osteoblast behavior on select nanoporous anodic alumina

    Science.gov (United States)

    Ni, Siyu; Li, Changyan; Ni, Shirong; Chen, Ting; Webster, Thomas J

    2014-01-01

    The aim of this study was to prepare different sized porous anodic alumina (PAA) and examine preosteoblast (MC3T3-E1) attachment and proliferation on such nanoporous surfaces. In this study, PAA with tunable pore sizes (25 nm, 50 nm, and 75 nm) were fabricated by a two-step anodizing procedure in oxalic acid. The surface morphology and elemental composition of PAA were characterized by field emission scanning electron microscopy and X-ray photoelectron spectroscopy analysis. The nanopore arrays on all of the PAA samples were highly regular. X-ray photoelectron spectroscopy analysis suggested that the chemistry of PAA and flat aluminum surfaces were similar. However, contact angles were significantly greater on all of the PAA compared to flat aluminum substrates, which consequently altered protein adsorption profiles. The attachment and proliferation of preosteoblasts were determined for up to 7 days in culture using field emission scanning electron microscopy and a Cell Counting Kit-8. Results showed that nanoporous surfaces did not enhance initial preosteoblast attachment, whereas preosteoblast proliferation dramatically increased when the PAA pore size was either 50 nm or 75 nm compared to all other samples (Paluminum by modifying surface nano-roughness alone (and not changing chemistry) through an anodization process to improve osteoblast density, and, thus, should be further studied as a bioactive interface for orthopedic applications. PMID:25045263

  5. Understanding focused ion beam guided anodic alumina nanopore development

    International Nuclear Information System (INIS)

    Chen Bo; Lu, Kathy; Tian Zhipeng

    2011-01-01

    Graphical abstract: Display Omitted Highlights: → We study the effect of FIB patterning on pore evolution during anodization. → FIB patterned concaves with 1.5 nm depth can effectively guide nanopore growth. → The edge effect of FIB guided patterns causes nanopores to bend. → Anodization window is enlarged to 50-80 V for 150 nm interpore distance hexagonal arrays. - Abstract: Focused ion beam (FIB) patterning in combination with anodization has shown great promise in creating unique pore patterns. This work is aimed to understand the effect of the FIB patterned sites in guiding anodized pore development. Highly ordered porous anodic alumina has been created with the guidance of FIB created patterns on electropolished aluminum followed by oxalic acid anodization. Shallow concaves created by the FIB with only 1.5 nm depth can effectively guide the growth of ordered nanopore patterns. With the guidance of the FIB pattern, the anodization rate is much faster and the nanopore growth direction bends at the boundary of the FIB patterned and un-patterned regions. FIB patterning also enlarges the anodization window; ordered nanopore arrays with 150 nm interpore distances can be produced under an applied potential from 50 V to 80 V. The fundamental understanding of these unique processes is discussed.

  6. Optimization of Nd: YAG Laser Marking of Alumina Ceramic Using RSM And ANN

    International Nuclear Information System (INIS)

    Peter, Josephine; Doloi, B.; Bhattacharyya, B.

    2011-01-01

    The present research papers deals with the artificial neural network (ANN) and the response surface methodology (RSM) based mathematical modeling and also an optimization analysis on marking characteristics on alumina ceramic. The experiments have been planned and carried out based on Design of Experiment (DOE). It also analyses the influence of the major laser marking process parameters and the optimal combination of laser marking process parametric setting has been obtained. The output of the RSM optimal data is validated through experimentation and ANN predictive model. A good agreement is observed between the results based on ANN predictive model and actual experimental observations.

  7. An evaluation of the effects of PEO/PEG molecular weights on extruded alumina rods

    Science.gov (United States)

    Bolger, Nancy Beth

    1998-12-01

    Alumina rods were piston extruded from bodies containing polyethylene glycols (PEGs) and polyethylene oxides (PEOs) with molecular weights ranging from 1,300 to 3,800,000 g/mol. A blend of aluminas possessing different particle size distributions was evaluated with regard to its extrusion pressure by varying the amount of PEG/PEO addition. Behavior exhibited by the alumina blend was dependent upon the additive that was used. The higher molecular weight binders with average molecular weight of 200,000 g/mol and 3,350,000 g/mol displayed the most severe behaviors of near dilatant and dilatant respectively. Physical properties of the green and fired states, as well as the binder burnout, were investigated with the changing additions. Correlation between the green and fired strengths and the changing molecular weights were examined. The additive present influenced the surface properties of the rods, which affected the green strengths. The highest average molecular weight polyethylene glycols showed higher green strengths, while the lowest green strengths were observed for the high molecular weight polyethylene oxides. Fired strengths generally ranged from approximately 12,000 psi to 16,000 psi for additive batches. Alumina pellets containing twelve separate combinations of polyethylene glycol with polyethylene oxide were dry pressed. Physical properties of the green and fired states were examined. Statistical analysis was performed upon the data and seven combinations of polyethylene glycol with polyethylene oxide were deemed significant. These combinations in conjunction with the same alumina blend were then piston extruded. The addition of polyethylene glycol reduced the near dilatant behavior exhibited by the 200,000 g/mol average molecular weight polyethylene oxide. Dilatant behavior was completely eliminated from the 3,350,000 g/mol average molecular weight polyethylene oxide batches. Physical properties of the green and fired states were again investigated with

  8. Chemical treatment and biomimetic coating evaluating in zirconia-alumina ceramics

    International Nuclear Information System (INIS)

    Aguiar, Amanda Abati

    2007-01-01

    Ceramic materials, as alumina and zirconia have been explored along the years as biomaterials application. The bio inert nature has been stimulating the development of new alternatives, as chemical treatments to improve the biological application of these ceramics. The biomimetic process of bio inert ceramics for coating apatite is based on soaking the implant in a simulated body fluid, SBF, with ion concentrations nearly equal to those of human blood plasma. The bioactivity of the material is related with the formation of a layer constituted of hydroxyapatite low crystalline, similar to the biological apatite. The biocompatibility associated to the structural properties of the alumina and zirconia has been stimulating the clinical use of these materials, mainly in areas of larger mechanical requests, places not recommended for bioactive hydroxyapatite, for instance. In this work samples of alumina, zirconia doped with Yttria (3% mol) and composites of alumina and zirconia doped with Yttria (3% mol) were prepared by co-precipitation method, calcinate, sintered, chemically treated with solutions of acid phosphoric and sodium hydroxide and them immersed in 1.0 M and 1.5 M SBF. The calcinate powders were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), gas adsorption (BET) and laser diffraction. The XRD results indicate that the samples are low crystalline. It was observed for BET that the samples present high specific surface area. The results of laser diffraction and SEM showed that the powders are agglomerates. The sintered samples were analyzed by XRD, SEM and X-ray fluorescence (XRF). The phases quantified by Rietveld method were: cubic, tetragonal and monoclinic of the zirconia, besides the phase alpha of the alumina. The chemical treatment with phosphoric acid didn't present a tendency of larger apatite formation in relation to the samples no chemically treated. The treatment with sodium hydroxide provoked accentuated transformation of

  9. Bulk rock and mineral chemistries and ascent rates of high-K calc-alkalic epidote-bearing magmas, Northeastern Brazil

    Science.gov (United States)

    Brasilino, R. G.; Sial, A. N.; Ferreira, V. P.; Pimentel, M. M.

    2011-12-01

    A manifestation of the Pan-African-Brasiliano orogeny (700-550 Ma) in northeastern Brazil was the emplacement of widespread Neoproterozoic granitoids in diverse tectonic terranes. Among these plutons are the magmatic epidote-bearing Conceição das Creoulas, Caldeirão Encantado, Murici, and Boqueirão plutons, located close to the boundary between the Alto Pajeú and Cachoeirinha-Salgueiro terranes. The plutons are high-K calc-alkalic granodiorites to monzogranites, with tabular K-feldspar megacrysts. Pistacite [atomic Fe+ 3/(Fe3++ Al)] in epidote in these granitoids ranges from 21 to 27%. High oxygen fugacity (log fO2 - 19 to - 13) and the preservation of epidote suggest that the magma was oxidized. Al-in-hornblende barometry indicates hornblende solidification between 6 and 8 kbar, at 620 to 780 °C according to the hornblende-plagioclase thermometer. Zircon saturation thermometry attests to a near-liquidus temperature range from 794 to 853 °C. Partial corrosion of magmatic epidote in these four plutons occurred during an interval of no more than 10-30 years, which corresponds to maximum magma ascent rates of 650-1000 m/year. Diking, associated with regional shearing, probably facilitated rapid transport of granitic magma through hot continental crust at peak metamorphism, and permitted survival of epidote that was out of equilibrium at the low pressure of final emplacement. Similarities between mineralogical composition, chemistry, and isotopic compositions (εNd(0.60Ga) between - 2 and - 5,TDM from 1.2 to 1.3 Ga, δ18O values > 10‰, V-SMOW) of these four plutons and Neoproterozoic magmatic epidote-bearing plutons elsewhere in northeastern Brazil, argue for similar metabasaltic/mafic sources that had previously experienced low-temperature alteration.

  10. Hidratação do óxido de magnésio em presença de alumina hidratável Magnesium oxide hydration in presence of hydratable alumina

    Directory of Open Access Journals (Sweden)

    R. Salomão

    2010-07-01

    Full Text Available Aluminas hidratáveis são compostos obtidos a partir da calcinação incompleta da gibsita Al(OH3, que podem reagir com água e possuem ação ligante em suspensões cerâmicas. A substituição do cimento de aluminato de cálcio pelas aluminas hidratáveis em concretos refratários contendo óxido de magnésio (MgO pode gerar diversos benefícios em relação às propriedades termomecânicas e refratariedade. No entanto, os efeitos da combinação desses materiais e suas conseqüências para a hidratação do MgO ainda não foram investigados sistemicamente. Neste trabalho, quatro fontes de MgO e aluminas hidratáveis foram combinadas em diferentes proporções e hidratados simultaneamente. Após investigações utilizando difração de raios X, termogravimetria e expansão volumétrica aparente, verificou-se que a relação MgO/Al2O3 e as diferenças de reatividade de cada matéria prima podem afetar significativamente o processo de hidratação. Além disso, foi observado que essa combinação pode ser utilizada como uma interessante técnica anti-hidratação para o MgO.The substitution of calcium aluminate cement by hydratable aluminas in MgO-containing refractory castables can afford several benefits for these materials mechanical properties and refractoriness. Nevertheless, the way that hydratable aluminas affects MgO hydration and its consequences were not yet systemically explored. In the present work, four sources of magnesia and alumina were combined at different ratios and hydrated simultaneously. They were investigated by X-ray diffraction, thermogravimetry and apparent volumetric expansion measurements. It was found that the magnesia/alumina ratio and the differences of reactivity of each raw material can greatly affect both hydration processes, generating different hydrated compounds. It was also verified that this combination can be suitably used as powerful MgO anti-hydration technique.

  11. Digestion of Alumina from Non-Magnetic Material Obtained from Magnetic Separation of Reduced Iron-Rich Diasporic Bauxite with Sodium Salts

    Directory of Open Access Journals (Sweden)

    Guanghui Li

    2016-11-01

    Full Text Available Recovery of iron from iron-rich diasporic bauxite ore via reductive roasting followed by magnetic separation has been explored recently. However, the efficiency of alumina extraction in the non-magnetic materials is absent. In this paper, a further study on the digestion of alumina by the Bayer process from non-magnetic material obtained after magnetic separation of reduced iron-rich diasporic bauxite with sodium salts was investigated. The results indicate that the addition of sodium salts can destroy the original occurrences of iron-, aluminum- and silicon-containing minerals of bauxite ore during reductive roasting. Meanwhile, the reactions of sodium salts with complex aluminum- and silicon-bearing phases generate diaoyudaoite and sodium aluminosilicate. The separation of iron via reductive roasting of bauxite ore with sodium salts followed by magnetic separation improves alumina digestion in the Bayer process. When the alumina-bearing material in bauxite ore is converted into non-magnetic material, the digestion temperature decreases significantly from 280 °C to 240 °C with a nearly 99% relative digestion ratio of alumina.

  12. Thermal and Electrical Characterization of Alumina Substrate for Microelectronic Applications

    International Nuclear Information System (INIS)

    Ahmad, S.; Ibrahim, A.; Alias, R.; Shapee, S. M.; Ambak, Z.; Zakaria, S. Z.; Yahya, M. R.; Mat, A. F. A.

    2010-01-01

    This paper reports the effect of sintering temperature on thermal and electrical properties of alumina material as substrate for microelectronic devices. Alumina materials in the form of green sheet with 1 mm thickness were sintered at 1100 deg. C, 1300 deg. C and 1500 deg. C for about 20 hours using heating and cooling rates of 2 deg. C/min. The densities were measured using densitometer and the microstructures of the samples were analyzed using SEM micrographs. Meanwhile thermal and electrical properties of the samples were measured using flash method and impedance analyzer respectively. It was found that thermal conductivity and thermal diffusivity of the substrate increases as sintering temperature increases. It was found also that the dielectric constant of alumina substrate increases as the sintering temperature increases.

  13. Thermal and Electrical Characterization of Alumina Substrate for Microelectronic Applications

    Science.gov (United States)

    Ahmad, S.; Ibrahim, A.; Alias, R.; Shapee, S. M.; Ambak, Z.; Zakaria, S. Z.; Yahya, M. R.; Mat, A. F. A.

    2010-03-01

    This paper reports the effect of sintering temperature on thermal and electrical properties of alumina material as substrate for microelectronic devices. Alumina materials in the form of green sheet with 1 mm thickness were sintered at 1100° C, 1300° C and 1500° C for about 20 hours using heating and cooling rates of 2° C/min. The densities were measured using densitometer and the microstructures of the samples were analyzed using SEM micrographs. Meanwhile thermal and electrical properties of the samples were measured using flash method and impedance analyzer respectively. It was found that thermal conductivity and thermal diffusivity of the substrate increases as sintering temperature increases. It was found also that the dielectric constant of alumina substrate increases as the sintering temperature increases.

  14. Alumina composites for oxide/oxide fibrous monoliths

    International Nuclear Information System (INIS)

    Cruse, T. A.; Polzin, B. J.; Picciolo, J. J.; Singh, D.; Tsaliagos, R. N.; Goretta, K. C.

    2000-01-01

    Most work on ceramic fibrous monoliths (FMs) has focused on the Si 3 N 4 /BN system. In an effort to develop oxidation-resistant FMs, several oxide systems have recently been examined. Zirconia-toughened alumina and alumina/mullite appear to be good candidates for the cell phase of FMs. These composites offer higher strength and toughness than pure alumina and good high-temperature stability. By combining these oxides, possibly with a weaker high-temperature oxide as the cell-boundary phase, it should be possible to product a strong, resilient FM that exhibits graceful failure. Several material combinations have been examined. Results on FM fabrication and microstructural development are presented

  15. Retrospective dosimetry with alumina substrate from electronic components

    International Nuclear Information System (INIS)

    Ekendahl, D.; Judas, L.

    2012-01-01

    Alumina substrate can be found in electronic components used in portable electronic devices. The material is radiation sensitive and can be applied in dosimetry using thermally or optically stimulated luminescence. Electronic portable devices such as mobile phones, USB flash discs, mp3 players, etc., which are worn close to the body, can represent personal dosemeters for members of the general public in situations of large-scale radiation accidents or malevolent acts with radioactive materials. This study investigated dosimetric properties of alumina substrates and aspects of using mobile phones as personal dosemeters. The alumina substrates exhibited favourable dosimetry characteristics. However, anomalous fading had to be properly corrected in order to achieve sufficient precision in dose estimate. Trial dose reconstruction performed by means of two mobile phones proved that mobile phones can be used for reconstruction of personal doses. (authors)

  16. Conductivity variations in composites of. alpha. -zirconium phosphate and alumina

    Energy Technology Data Exchange (ETDEWEB)

    Slade, R.C.T.; Knowles, J.A. (Dept. of Chemistry, Exeter Univ. (UK))

    Composite proton-conducting solid electrolytes have been formed from {alpha}-zirconium hydrogen phosphate ({alpha}-Zr(HPO{sub 4}){sub 2}.H{sub 2}O, {alpha}-ZrP) and aluminas (Al{sub 2}O{sub 3}) in varying mole ratios. Conductivity variations as a function of temperature have been characterised and compared to that for a delaminated {alpha}-ZrP (no alumina). There are no appreciable conductivity enhancements on composite formation, but conductivity for materials ca. 50 mole% in alumina can be comparable to the delaminated materials. Differential scanning calorimetry shows the composites to have different thermal properties to simple admixtures. High resolution {sup 31}P NMR studies show reaction to form aluminium phosphate at the interface between components. (orig.).

  17. Radiation silver paramagnetic centers in a beta-alumina crystal

    International Nuclear Information System (INIS)

    Badalyan, A.G.; Zhitnikov, R.A.

    1985-01-01

    Silver paramagnetic centers in a β-alumina crystal, formed after X-ray radiation at 77 K, are investigated by the EPR method. Silver enters the β-alumina crystal, substituting sodium and potassium ions in a mirror plane. Crystals with substitution from 0.1 to 100% of alkali metal ions by Ag + ions are investigated. Silver atomic centers (Ag 0 -centers), formed by electron capture with the Ag + ion, are firstly detected and investigated in the β-alumina. Hole Ag 2+ -centers are investigated and detected in crystals with high concentration of Ag + . By studying the orientation dependence of a g-factor it is established that hole capture by the Ag + ion is accompanied by Ag 2+ ion displacement from the position, Ag + being primarity taken up (Beavers-Roth or anti- Beavers-Roth) to the position between two oxygen ions in the mirror plane

  18. Pressureless sintering behavior of injection molded alumina ceramics

    Directory of Open Access Journals (Sweden)

    Liu W.

    2014-01-01

    Full Text Available The pressureless sintering behaviors of two widely used submicron alumina (MgOdoped and undoped with different solid loadings produced by injection molding have been studied systematically. Regardless of the sinterability of different powders depending on their inherent properties, solid loading plays a critical role on the sintering behavior of injection molded alumina, which greatly determines the densification and grain size, and leads to its full densification at low temperatures. As compared to the MgO-doped alumina powder, the undoped specimens exhibit a higher sinterability for its smaller particle size and larger surface area. While full densification could be achieved for MgO-doped powders with only a lower solid loading, due to the fact that MgO addition can reduce the detrimental effect of the large pore space on the pore-boundary separation.

  19. PENGARUH REGENERASI KOLOM ALUMINA ASAM TERHADAP RECOVERY DAN KUALITAS 99mTc HASIL EKSTRAKSI PELARUT MEK DARI 99Mo HASIL AKTIVASI NEUTRON

    Directory of Open Access Journals (Sweden)

    Adang H G

    2017-01-01

    radiopharmaceutical kit. In this study, the used of acidic alumina column for 99mTc purification was tried more than once by regeneration using 0.1N HNO3 solution after purification process is completed. Parameters observed in this study are the percent recovery, elution profile, pH, radiochemical purity and radionuclida purity. The results of observational studies conducted over 5 days has been obtained pH ~ 5,% recovery > 60%, radiochemical purity of > 95% and 99Mo leakage not detected. The treatment of acidic alumina column with 0,1 N HNO3 solution concluded that acidic alumina column does not need to be replaced every day. Keywords: 99mTc, 99Mo, MEK, acidic alumina column, radiochemical purity.

  20. On the physical and chemical details of alumina atomic layer deposition: A combined experimental and numerical approach

    International Nuclear Information System (INIS)

    Pan, Dongqing; Ma, Lulu; Xie, Yuanyuan; Yuan, Chris; Jen, Tien Chien

    2015-01-01

    Alumina thin film is typically studied as a model atomic layer deposition (ALD) process due to its high dielectric constant, high thermal stability, and good adhesion on various wafer surfaces. Despite extensive applications of alumina ALD in microelectronics industries, details on the physical and chemical processes are not yet well understood. ALD experiments are not able to shed adequate light on the detailed information regarding the transient ALD process. Most of current numerical approaches lack detailed surface reaction mechanisms, and their results are not well correlated with experimental observations. In this paper, the authors present a combined experimental and numerical study on the details of flow and surface reactions in alumina ALD using trimethylaluminum and water as precursors. Results obtained from experiments and simulations are compared and correlated. By experiments, growth rate on five samples under different deposition conditions is characterized. The deposition rate from numerical simulation agrees well with the experimental results. Details of precursor distributions in a full cycle of ALD are studied numerically to bridge between experimental observations and simulations. The 3D transient numerical model adopts surface reaction kinetics and mechanisms based on atomic-level studies to investigate the surface deposition process. Surface deposition is shown as a strictly self-limited process in our numerical studies. ALD is a complex strong-coupled fluid, thermal and chemical process, which is not only heavily dependent on the chemical kinetics and surface conditions but also on the flow and material distributions

  1. Modification of Alumina and Spinel Inclusions by Calcium in Liquid Steel

    Science.gov (United States)

    Verma, Neerav

    2011-12-01

    Steel Cleanliness plays a crucial role in determining steel properties such as toughness, ductility, formability, corrosion resistance and surface quality. The production of clean steel often involves the elimination or chemical and morphological modification of oxide and sulfide inclusions. Along with deteriorating the steel properties, solid inclusions can affect steel castability through nozzle clogging. Nozzle clogging occurs when solid inclusions accumulate in the caster pouring system such as the ladle shroud or submerged entry nozzle (SEN). Thus, it is important to understand how to achieve desired inclusion characteristics (shape, size and chemistry) through the steelmaking process. Among the various practices adopted in industries to counteract the effect of solid inclusions, modification of solid inclusions to liquid or partially liquid state through calcium treatment is one of the methods. Calcium can be used because it has a strong ability to form oxides and sulfides. In Al-killed steels, the most common inclusions are alumina (Al2O3) inclusions, which are solid at steelmaking temperatures. On calcium treatment, solid alumina inclusions are converted to calcium aluminates, which have liquidus temperatures lower than steelmaking temperature (1600°C) [14]. It has been found that alumina inclusions may contain some MgO and such inclusions are termed alumina magnesia spinels (Al2O3.xMgO) [18]. These spinels are more stable than alumina and it has been suggested that they might be more difficult to modify [18]. But, some authors have proposed that MgO can actually help in the liquefaction of inclusions, and have demonstrated successful modification of spinels by Ca treatment [20, 21]. In the present research, the mechanism of transformation of alumina and spinel inclusions upon calcium treatment was studied by characterizing transient evolution of inclusions. A vacuum induction was used for melting, making additions (Al, Al-Mg and CaSi2) and sampling. The

  2. Cylindrical Three-Dimensional Porous Anodic Alumina Networks

    Directory of Open Access Journals (Sweden)

    Pedro M. Resende

    2016-11-01

    Full Text Available The synthesis of a conformal three-dimensional nanostructure based on porous anodic alumina with transversal nanopores on wires is herein presented. The resulting three-dimensional network exhibits the same nanostructure as that obtained on planar geometries, but with a macroscopic cylindrical geometry. The morphological analysis of the nanostructure revealed the effects of the initial defects on the aluminum surface and the mechanical strains on the integrity of the three-dimensional network. The results evidence the feasibility of obtaining 3D porous anodic alumina on non-planar aluminum substrates.

  3. Fabrication of Anodic Porous Alumina by Squaric Acid Anodizing

    OpenAIRE

    Kikuchi, Tatsuya; Yamamoto, Tsuyoshi; Natsui, Shungo; Suzuki, Ryosuke O.

    2014-01-01

    The growth behavior of anodic porous alumina formed via anodizing in a new electrolyte, squaric acid (3,4-dihydroxy-3-cyclobutene-1,2-dione), is reported for the first time. A high-purity aluminum foil was anodized in a 0.1 M squaric acid solution at 293 K and a constant applied potential of 100-150 V. Anodic oxides grew on the aluminum foil at applied potentials of 100-120 V, but a burned oxide film was formed at higher voltage. Anodic porous alumina with a cell size of approximately 200-400...

  4. Behaviour modelling of two aluminas in divergent spherical pyrotechnical experiments

    International Nuclear Information System (INIS)

    Malaise, F.; Tranchet, J.Y.; Collombet, F.

    1997-01-01

    Two pure aluminas of different characteristics have been subjected to the propagation of a longitudinal divergent spherical shock wave through pyrotechnical experiments. An approach combining a phenomenological analysis and numerical 1D-calculations is proposed to study the behaviour of these aluminas submitted to that type of wave loading. The modelling, proposed in a previous paper, is refined and gives satisfying experimentation-calculation correlations. An analysis of the influence exerted by the various encountered phenomena (plastic activity, pore closure, microcracking) is performed. The significant consequence of the activation of damage with an extension criterion is also underlined. (orig.)

  5. Synthesis and Optical Investigations of the Guest-Host Nanostructures Alumina-SiC and Alumina-In{sub 2}O{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Bouifoulen, A; Kassiba, A; Edely, M [Laboratoire de Physique de l' Etat Condense, UMR-CNRS 6087, Institut de recherche IRIM2F-FR-CNRS 2575-Universite du Maine, Avenue Olivier Messiaen, 72085 Le Mans Cedex 9 (France); Outzourhit, A; Oueriagli, A [Laboratoire de Physique du Solide et Couches Minces, Faculte des Sciences Semlalia, Universite Cadi Ayyad, B. P. 2390, Marrakech 40000, Maroc (Morocco); Makowska-Janusik, M [Institute of Physics, Al. Armii.Krajowej, 13/15, J. Dlugosz University, 42-200 Czestochowa (Poland); Szade, J, E-mail: kassiba@univ-lemans.fr [A.Chelkowski Institute of Physics - University Slaski in Katowice - 40-219 Katowice (Poland)

    2011-04-01

    Several strategies were developed to synthesise two classes of nanostructured thin films with nanocrystals of SiC (nc-SiC) or In{sub 2}O{sub 3} (nc-In{sub 2}O{sub 3}) confined in alumina. The syntheses were performed by using Rf-sputtering and co-pulverisation process of the suitable reactants. Thus, Al{sub 2}O{sub 3}/nc-SiC and Al{sub 2}O{sub 3}/nc-In{sub 2}O{sub 3} composite thin films were obtained and their structural and optical features analyzed respectively by XRD, XPS and UV-VIS absorption. The deposition conditions and the post-synthesis treatments were optimized in order to improve the crystalline character of confined nanocrystals. The optical properties were compared in the range 200 nm-1200 nm for bare alumina films or nanostructured ones with the semiconducting nanocrystals. The direct and indirect band band gaps were evaluated and discussed with regard to the stoechiometry and morphologies of the nanocomposite films

  6. Physicochemical study of zirconium oxides and of the alumina-zirconia dispersoid

    International Nuclear Information System (INIS)

    Orlans, Patrick

    1987-01-01

    This research thesis reports the physicochemical characterization of different zirconium oxides, but also their synthesis in laboratory by using a gel precipitation method. Various techniques are used to characterize gels and powders: electro-kinetic potential measurement, study of rheological properties, granulometry, chemical analysis, X-ray diffraction, thermo-luminescence, differential thermal analysis, specific surface measurements, scanning electronic microscopy. This process is then extended to the synthesis of an alumina-zirconia dispersoid. The measurement of mechanical properties allowed the synthesis to be modulated in order to obtain powders with properties as close as possible to defined properties [fr

  7. Hemispherical Shell Nanostructures from Metal-Stripped Embossed Alumina on Aluminum Templates

    DEFF Research Database (Denmark)

    Nielsen, Peter; Albrektsen, Ole; Simonsen, Adam Cohen

    2011-01-01

    aluminum/ alumina (Al/Al2O3) templates as a novel and versatile nanofabrication procedure, and we demonstrate explicitly how to exploit the technique for developing large-area hexagonally close-packed hemispherical shell nanostructures by stripping noble metal layers from embossed templates fabricated from...... anodized Al. Utilizing for this process the linear relationship between anodization voltage and the resulting interpore distance in the formed oxide, it is possible to tune the radius of curvature of the resulting hemispherical shells continuously, which in turn results in tunable optical properties...

  8. Distribution and occurrence of lithium in high-alumina-coal fly ash

    DEFF Research Database (Denmark)

    Hu, Pengpeng; Hou, Xinjuan; Zhang, Jianbo

    2018-01-01

    the generalized gradient approximation (GGA) method indicated that Li occurred in Q3(0Al) and Q3(1Al) structures by reacting with Q4(0Al) and Q4(1Al). Based on the experimental and simulation results, we propose extracting Li during the pre-desilication process by dissolving the glass phase.......High-alumina-coal fly ash (HAFA) with a high Li content is regarded as a potential resource for Li production. To support the development of Li recovery technology from HAFA, the distribution and modes of occurrence of Li in HAFA were investigated. HAFA was separated into magnetic particles, glass...

  9. Low Concentration Fe-Doped Alumina Catalysts Using Sol-Gel and Impregnation Methods: The Synthesis, Characterization and Catalytic Performance during the Combustion of Trichloroethylene

    Directory of Open Access Journals (Sweden)

    Carolina Solis Maldonado

    2014-03-01

    Full Text Available The role of iron in two modes of integration into alumina catalysts was studied at 0.39 wt% Fe and tested in trichloroethylene combustion. One modified alumina was synthesized using the sol-gel method with Fe added in situ during hydrolysis; another modification was performed using calcined alumina, prepared using the sol-gel method and impregnated with Fe. Several characterization techniques were used to study the level of Fe modification in the γ-Al2O3 phase formed and to correlate the catalytic properties during trichloroethylene (TCE combustion. The introduction of Fe in situ during the sol-gel process influenced the crystallite size, and three iron species were generated, namely, magnetite, maghemite and hematite. The impregnated Fe-alumina formed hematite and maghemite, which were highly dispersed on the γ-Al2O3 surface. The X-ray photoelectron spectra (XPS, FT-IR and Mössbauer spectroscopy analyses revealed how Fe interacted with the γ-Al2O3 lattice in both catalysts. The impregnated Fe-catalyst showed the best catalytic performance compared to the catalyst that was Fe-doped in situ by the sol-gel method; both had better catalytic activity than pure alumina. This difference in activity was correlated with the accessibility of the reactants to the hematite iron species on the surface. The chlorine poisoning for all three catalysts was less than 1.8%.

  10. Low Concentration Fe-Doped Alumina Catalysts Using Sol-Gel and Impregnation Methods: The Synthesis, Characterization and Catalytic Performance during the Combustion of Trichloroethylene.

    Science.gov (United States)

    Maldonado, Carolina Solis; De la Rosa, Javier Rivera; Lucio-Ortiz, Carlos J; Hernández-Ramírez, Aracely; Barraza, Felipe F Castillón; Valente, Jaime S

    2014-03-12

    The role of iron in two modes of integration into alumina catalysts was studied at 0.39 wt% Fe and tested in trichloroethylene combustion. One modified alumina was synthesized using the sol-gel method with Fe added in situ during hydrolysis; another modification was performed using calcined alumina, prepared using the sol-gel method and impregnated with Fe. Several characterization techniques were used to study the level of Fe modification in the γ-Al₂O₃ phase formed and to correlate the catalytic properties during trichloroethylene (TCE) combustion. The introduction of Fe in situ during the sol-gel process influenced the crystallite size, and three iron species were generated, namely, magnetite, maghemite and hematite. The impregnated Fe-alumina formed hematite and maghemite, which were highly dispersed on the γ-Al₂O 3 surface. The X-ray photoelectron spectra (XPS), FT-IR and Mössbauer spectroscopy analyses revealed how Fe interacted with the γ-Al₂O₃ lattice in both catalysts. The impregnated Fe-catalyst showed the best catalytic performance compared to the catalyst that was Fe-doped in situ by the sol-gel method; both had better catalytic activity than pure alumina. This difference in activity was correlated with the accessibility of the reactants to the hematite iron species on the surface. The chlorine poisoning for all three catalysts was less than 1.8%.

  11. Treatment of alumina refinery waste (red mud) through neutralization techniques: A review.

    Science.gov (United States)

    Rai, Suchita; Wasewar, K L; Agnihotri, A

    2017-06-01

    In the Bayer process of extraction of alumina from bauxite, the insoluble product generated after bauxite digestion with sodium hydroxide at elevated temperature and pressure is known as 'red mud' or 'bauxite residue'. This alumina refinery waste is highly alkaline in nature with a pH of 10.5-12.5 and is conventionally disposed of in mostly clay-lined land-based impoundments. The alkaline constituents in the red mud impose severe and alarming environmental problems, such as soil and air pollution. Keeping in view sustainable re-vegetation and residue management, neutralization/treatment of red mud using different techniques is the only alternative to make the bauxite residue environmentally benign. Hence, neutralization techniques, such as using mineral acids, acidic waste (pickling liquor waste), coal dust, superphosphate and gypsum as amenders, CO 2 , sintering with silicate material and seawater for treatment of red mud have been studied in detail. This paper is based upon and emphasizes the experimental work carried out for all the neutralization techniques along with a comprehensive review of each of the processes. The scope, applicability, limitations and feasibility of these processes have been compared exhaustively. Merits and demerits have been discussed using flow diagrams. All the techniques described are technically feasible, wherein findings obtained with seawater neutralization can be set as a benchmark for future work. Further studies should be focused on exploring the economical viability of these processes for better waste management and disposal of red mud.

  12. High-frequency characteristics of glass/ceramic composite and alumina multilayer structures

    International Nuclear Information System (INIS)

    Niwa, K.; Suzuki, H.; Yokoyama, H.; Kamechara, N.; Tsubone, K.; Tanisawa, H.; Sugiki, H.

    1990-01-01

    This paper reports the transmission characteristics of glass/ceramic composite (borosilicate glass/alumina) and alumina multilayer structures examined. The triplate stripline formed in the glass/ceramic multilayer shows low conductor and dielectric loss. Alumina multilayer, however, has twice the transmission loss at 10 GHz, because the resistivity of W in the alumina multilayer is higher than the Cu in the glass/ceramic multilayer. Crosstalk between striplines in the glass/ceramics is less than -80 dB up to 11 GHz and 9 GHz for alumina

  13. Microwave-assisted brazing of alumina ceramics for electron tube ...

    Indian Academy of Sciences (India)

    Vickers microhardness measurement indicated reliable joint performance for the microwave-assisted brazed joints during ... Alumina ceramics are used in wide range of applications due to their .... temperature were recorded by DAQSOFT software in a sep- .... Tubes: Design and Development Capabilities (MTDDC)',.

  14. State of the art: alumina ceramics for energy applications

    International Nuclear Information System (INIS)

    Hauth, W.E.; Stoddard, S.D.

    1978-01-01

    Prominent ceramic raw materials and products manufacturers were surveyed to determine the state of the art for alumina ceramic fabrication. This survey emphasized current capabilities and limitations for fabrication of large, high-density, high-purity, complex shapes. Some directions are suggested for future needs and development

  15. Multifunctional substrates of thin porous alumina for cell biosensors

    KAUST Repository

    Toccafondi, Chiara; Thorat, Sanjay B.; La Rocca, Rosanna; Scarpellini, Alice; Salerno, Marco; Dante, Silvia; Das, Gobind

    2014-01-01

    We have fabricated anodic porous alumina from thin films (100/500 nm) of aluminium deposited on technological substrates of silicon/glass, and investigated the feasibility of this material as a surface for the development of analytical biosensors aiming to assess the status of living cells. To this goal, porous alumina surfaces with fixed pitch and variable pore size were analyzed for various functionalities. Gold coated (about 25 nm) alumina revealed surface enhanced Raman scattering increasing with the decrease in wall thickness, with factor up to values of approximately 104 with respect to the flat gold surface. Bare porous alumina was employed for micro-patterning and observation via fluorescence images of dye molecules, which demonstrated the surface capability for a drug-loading device. NIH-3T3 fibroblast cells were cultured in vitro and examined after 2 days since seeding, and no significant (P > 0.05) differences in their proliferation were observed on porous and non-porous materials. The effect on cell cultures of pore size in the range of 50–130 nm—with pore pitch of about 250 nm—showed no significant differences in cell viability and similar levels in all cases as on a control substrate. Future work will address combination of all above capabilities into a single device.

  16. Grafting of alumina on SBA-15: Effect of surface roughness

    Czech Academy of Sciences Publication Activity Database

    Zukal, Arnošt; Šiklová, Helena; Čejka, Jiří

    2008-01-01

    Roč. 24, č. 17 (2008), s. 9837-9842 ISSN 0743-7463 R&D Projects: GA AV ČR KAN100400701 Institutional research plan: CEZ:AV0Z40400503 Keywords : alumina-grafted materials * SBA-15 * Nitrogen adsorption Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.097, year: 2008

  17. Macroporous silica–alumina composites with mesoporous walls

    Indian Academy of Sciences (India)

    Macroporous silica–alumina composites with mesopores have been prepared by employing polymethylmethacrylate beads as templates in the presence of the cationic surfactant, N-cetyl-N,N,N-trimethylammonium bromide. The Si/Al ratio in the composites has been varied between 4.5 and 48 and the occurrence of ...

  18. Improving subcritical crack growth resistance for alumina glass dental composite

    NARCIS (Netherlands)

    Zhu, Q.; With, de G.

    2005-01-01

    The improvement of subcritical crack growth (SCG) resistance for alumina glass dental composites was explored in this study. The addition of nitrogen to the glass phases in the composite was found to increase the SCG resistance, where the SCG exponent n increases from 22 for the oxide glass

  19. Electrochemical impedance spectroscopy of nanoporous anodic alumina template

    International Nuclear Information System (INIS)

    Shahzad, K.

    2010-01-01

    Room temperature EIS characterization of nanoporous anodic alumina prepared at 40 V and 60 V has been done in 0.3 M oxalic acid solution. Rapid decrease in impedance was observed for the template prepared at 40 V. EIS study of porous anodic alumina template prepared in 0.3 M oxalic acid has been done in different electrolytes. Templates prepared in 0.3 M sulfuric acid solution were also characterized for comparison. Rapid decrease in the thickness of nonporous anodic film was observed with an increase of aggressiveness of electrolyte. Temperature based systematic study of EIS measurement has been done for porous anodic alumina template at different temperatures. Formation of micropores was observed in the nanoporous anodic alumina film formed on aluminum in 0.3 M oxalic acid solution which accelerates the dissolution rate with increase of measurement temperature. In addition to these, electropolishing behavior of pure aluminum has also been studied in different electrolytes and it was observed that electropolishing conditions prior to anodization are extremely important. (author)

  20. Indentation fatigue in silicon nitride, alumina and silicon carbide ...

    Indian Academy of Sciences (India)

    Unknown

    carbide ceramics. A K MUKHOPADHYAY. Central Glass and Ceramic Research Institute, Kolkata 700 032, India. Abstract. Repeated indentation fatigue (RIF) experiments conducted on the same spot of different structural ceramics viz. a hot pressed silicon nitride (HPSN), sintered alumina of two different grain sizes viz.

  1. Synthesis and characterization of hydroxyapatite/alumina ceramic ...

    Indian Academy of Sciences (India)

    39

    In the present work, nano crystalline hydroxyapatite/alumina (HAp-Al2O3) composite was .... powder was dried in hot air oven at 80 °C for 24 hours. ... weekly, and the culture medium was changed twice in a week. 4. Results and Discussion.

  2. Dielectric properties of carbon nanofibre/alumina composites

    Czech Academy of Sciences Publication Activity Database

    Fernandez-Garcia, L.; Suarez, M.; Menéndez, J.L.; Pecharromán, C.; Nuzhnyy, Dmitry; Bovtun, Viktor; Savinov, Maxim; Kempa, Martin; Petzelt, Jan

    2013-01-01

    Roč. 57, JUN (2013), s. 380-387 ISSN 0008-6223 R&D Projects: GA ČR GAP204/12/0232; GA MŠk LD12025 Institutional support: RVO:68378271 Keywords : alumina * carbon nanofibre * dielectric and THz spectroscopy * infrared spectroscopy * percolation threshold Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 6.160, year: 2013

  3. Synthesis of Gamma-Alumina from Kankara Kaolin as Potential ...

    African Journals Online (AJOL)

    In compounded zeolite catalyst it serves as the active matrix which aids the conversion of the bulkiest molecules in the feed owing to its larger pore size than zeolite. Large specific surface area gamma-alumina (γ-Al2O3) was synthesized by hydrothermal method using Kankara kaolin as starting material. Thermal treatment ...

  4. Multifunctional substrates of thin porous alumina for cell biosensors

    KAUST Repository

    Toccafondi, Chiara

    2014-02-27

    We have fabricated anodic porous alumina from thin films (100/500 nm) of aluminium deposited on technological substrates of silicon/glass, and investigated the feasibility of this material as a surface for the development of analytical biosensors aiming to assess the status of living cells. To this goal, porous alumina surfaces with fixed pitch and variable pore size were analyzed for various functionalities. Gold coated (about 25 nm) alumina revealed surface enhanced Raman scattering increasing with the decrease in wall thickness, with factor up to values of approximately 104 with respect to the flat gold surface. Bare porous alumina was employed for micro-patterning and observation via fluorescence images of dye molecules, which demonstrated the surface capability for a drug-loading device. NIH-3T3 fibroblast cells were cultured in vitro and examined after 2 days since seeding, and no significant (P > 0.05) differences in their proliferation were observed on porous and non-porous materials. The effect on cell cultures of pore size in the range of 50–130 nm—with pore pitch of about 250 nm—showed no significant differences in cell viability and similar levels in all cases as on a control substrate. Future work will address combination of all above capabilities into a single device.

  5. Indentation fatigue in silicon nitride, alumina and silicon carbide ...

    Indian Academy of Sciences (India)

    Repeated indentation fatigue (RIF) experiments conducted on the same spot of different structural ceramics viz. a hot pressed silicon nitride (HPSN), sintered alumina of two different grain sizes viz. 1 m and 25 m, and a sintered silicon carbide (SSiC) are reported. The RIF experiments were conducted using a Vicker's ...

  6. Fabrication of an alumina torus for thermonuclear fusion containment

    International Nuclear Information System (INIS)

    Hauth, W.E.; Blake, R.D.; Dickinson, J.M.; Rutz, H.L.; Stoddard, S.D.

    1978-05-01

    A 235-cm-diam torus has been fabricated for plasma containment during thermonuclear fusion experiments. This 30-cm-diam torus consists of sixty 99.5%-alumina segments, 80% of which are assembled by forming vacuum-tight ceramic-to-ceramic seals. Selection of sealing materials and techniques are discussed

  7. Luminescence evolution from alumina ceramic surface before flashover under direct and alternating current voltage in vacuum

    Energy Technology Data Exchange (ETDEWEB)

    Su, Guo-Qiang; Wang, Yi-Bo; Song, Bai-Peng; Mu, Hai-Bao, E-mail: haibaomu@xjtu.edu.cn, E-mail: gjzhang@xjtu.edu.cn; Zhang, Guan-Jun, E-mail: haibaomu@xjtu.edu.cn, E-mail: gjzhang@xjtu.edu.cn [State Key Laboratory of Electrical Insulation and Power Equipment, School of Electrical Engineering, Xi’an Jiaotong University, Xi’an, Shaanxi 710049 (China); Li, Feng; Wang, Meng [Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang, Sichuan 621900 (China)

    2016-06-15

    The luminescence evolution phenomena from alumina ceramic surface in vacuum under high voltage of direct and alternating current are reported, with the voltage covering a large range from far below to close to the flashover voltage. Its time resolved and spatial distributed behaviors are examined by a photon counting system and an electron-multiplying charge-coupled device (EMCCD) together with a digital camera, respectively. The luminescence before flashover exhibits two stages as voltage increasing, i.e., under a relative low voltage (Stage A), the luminescence is ascribed to radiative recombination of hetero-charges injected into the sample surface layer by Schottky effect; under a higher voltage (Stage B), a stable secondary electron emission process, resulting from the Fowler-Nordheim emission at the cathode triple junction (CTJ), is responsible for the luminescence. Spectrum analysis implies that inner secondary electrons within the surface layer of alumina generated during the SSEE process also participate in the luminescence of Stage B. A comprehensive interpretation of the flashover process is formulated, which might promote a better understanding of flashover issue in vacuum.

  8. Application of various types of alumina and nano--alumina sulfuric acid in the synthesis of α-aminonitriles derivatives: comparative study

    Directory of Open Access Journals (Sweden)

    A. Teimouri

    2014-09-01

    Full Text Available An efficient and green protocol for the synthesis of α-aminonitrile derivatives by one-pot reaction of different aldehydes with amines and trimethylsilyl cyanide has been developed using natural alumina, alumina sulfuric acid (ASA, nano-g-alumina, nano-g-alumina sulfuric acid (nano-g-ASA under microwave irradiation and solvent-free conditions. The advantages of methods are short reaction times, high yields, milder conditions and easy work up. The catalysts can be recovered for the subsequent reactions and reused without any appreciable loss of efficiency. DOI: http://dx.doi.org/10.4314/bcse.v28i3.13

  9. Superhydrophilicity of novel anodic alumina nanofibers films and their formation mechanism

    Science.gov (United States)

    Peng, Rong; Yang, Wulin; Fu, Licai; Zhu, Jiajun; Li, Deyi; Zhou, Lingping

    2017-06-01

    A novel anodic alumina nanofibers structure, which is different from the traditional porous anodic structure, has been quickly fabricated via anodizing in a new electrolyte, pyrophosphoric acid. The effects of the solution concentration and the anodizing time on the formation of the anodic alumina nanofibers were analyzed. The results show that the nanostructure of anodic alumina can change to the nanofiber oxide from the porous oxide by increasing the solution concentration. Prolonging the anodizing time is beneficial to obtain alumina nanofibers at high solution concentration. Growth behavior of the alumina nanofibers was also discussed by scanning electron microscopy observations. Owing to the unique hexagonal structure of anodic alumina as well as the preferential chemical dissolution between the porous anodic alumina and the anodic alumina nanotips, the slightly soluble anodic alumina nanotips could form novel alumina nanofibers during anodizing. The results show that the nanofibers-covered aluminum surface exhibits superhydrophilic property, with a near-zero water contact angle. Such alumina nanofibers with superhydrophilic property could be used for various potential applications.

  10. Nanostructural characterization of large-scale porous alumina fabricated via anodizing in arsenic acid solution

    Energy Technology Data Exchange (ETDEWEB)

    Akiya, Shunta; Kikuchi, Tatsuya, E-mail: kiku@eng.hokudai.ac.jp; Natsui, Shungo; Suzuki, Ryosuke O.

    2017-05-01

    Highlights: • Anodic porous alumina was formed in an arsenic acid solution. • Potential difference (voltage) anodizing at 340 V was achieved. • The porous alumina was slightly ordered under the appropriate conditions. • Pore sealing behavior was not observed in boiling distilled water. • The porous alumina exhibits a white photoluminescence emission under UV irradiation. - Abstract: Anodizing of aluminum in an arsenic acid solution is reported for the fabrication of anodic porous alumina. The highest potential difference (voltage) without oxide burning increased as the temperature and the concentration of the arsenic acid solution decreased, and a high anodizing potential difference of 340 V was achieved. An ordered porous alumina with several tens of cells was formed in 0.1–0.5 M arsenic acid solutions at 310–340 V for 20 h. However, the regularity of the porous alumina was not improved via anodizing for 72 h. No pore sealing behavior of the porous alumina was observed upon immersion in boiling distilled water, and it may be due to the formation of an insoluble complex on the oxide surface. The porous alumina consisted of two different layers: a hexagonal alumina layer that contained arsenic from the electrolyte and a pure alumina honeycomb skeleton. The porous alumina exhibited a white photoluminescence emission at approximately 515 nm under UV irradiation at 254 nm.

  11. Optical performance of hybrid porous silicon-porous alumina multilayers

    Science.gov (United States)

    Cencha, L. G.; Antonio Hernández, C.; Forzani, L.; Urteaga, R.; Koropecki, R. R.

    2018-05-01

    In this work, we study the optical response of structures involving porous silicon and porous alumina in a multi-layered hybrid structure. We performed a rational design of the optimal sequence necessary to produce a high transmission and selective filter, with potential applications in chemical and biosensors. The combination of these porous materials can be used to exploit its distinguishing features, i.e., high transparency of alumina and high refractive index of porous silicon. We assembled hybrid microcavities with a central porous alumina layer between two porous silicon Bragg reflectors. In this way, we constructed a Fabry-Perot resonator with high reflectivity and low absorption that improves the quality of the filter compared to a microcavity built only with porous silicon or porous alumina. We explored a simpler design in which one of the Bragg reflectors is replaced by the aluminium that remains bound to the alumina after its fabrication. We theoretically explored the potential of the proposal and its limitations when considering the roughness of the layers. We found that the quality of a microcavity made entirely with porous silicon shows a limit in the visible range due to light absorption. This limitation is overcome in the hybrid scheme, with the roughness of the layers determining the ultimate quality. Q-factors of 220 are experimentally obtained for microcavities supported on aluminium, while Q-factors around 600 are reached for microcavities with double Bragg reflectors, centred at 560 nm. This represents a four-fold increase with respect to the optimal porous silicon microcavity at this wavelength.

  12. Advanced morphological analysis of patterns of thin anodic porous alumina

    Energy Technology Data Exchange (ETDEWEB)

    Toccafondi, C. [Istituto Italiano di Tecnologia, Department of Nanophysics, Via Morego 30, Genova I 16163 (Italy); Istituto Italiano di Tecnologia, Department of Nanostructures, Via Morego 30, Genova I 16163 (Italy); Stępniowski, W.J. [Department of Advanced Materials and Technologies, Faculty of Advanced Technologies and Chemistry, Military University of Technology, 2 Kaliskiego Str., 00-908 Warszawa (Poland); Leoncini, M. [Istituto Italiano di Tecnologia, Department of Nanostructures, Via Morego 30, Genova I 16163 (Italy); Salerno, M., E-mail: marco.salerno@iit.it [Istituto Italiano di Tecnologia, Department of Nanophysics, Via Morego 30, Genova I 16163 (Italy)

    2014-08-15

    Different conditions of fabrication of thin anodic porous alumina on glass substrates have been explored, obtaining two sets of samples with varying pore density and porosity, respectively. The patterns of pores have been imaged by high resolution scanning electron microscopy and analyzed by innovative methods. The regularity ratio has been extracted from radial profiles of the fast Fourier transforms of the images. Additionally, the Minkowski measures have been calculated. It was first observed that the regularity ratio averaged across all directions is properly corrected by the coefficient previously determined in the literature. Furthermore, the angularly averaged regularity ratio for the thin porous alumina made during short single-step anodizations is lower than that of hexagonal patterns of pores as for thick porous alumina from aluminum electropolishing and two-step anodization. Therefore, the regularity ratio represents a reliable measure of pattern order. At the same time, the lower angular spread of the regularity ratio shows that disordered porous alumina is more isotropic. Within each set, when changing either pore density or porosity, both regularity and isotropy remain rather constant, showing consistent fabrication quality of the experimental patterns. Minor deviations are tentatively discussed with the aid of the Minkowski measures, and the slight decrease in both regularity and isotropy for the final data-points of the porosity set is ascribed to excess pore opening and consequent pore merging. - Highlights: • Thin porous alumina is partly self-ordered and pattern analysis is required. • Regularity ratio is often misused: we fix the averaging and consider its spread. • We also apply the mathematical tool of Minkowski measures, new in this field. • Regularity ratio shows pattern isotropy and Minkowski helps in assessment. • General agreement with perfect artificial patterns confirms the good manufacturing.

  13. Al2O3 - TiO2-A simple sol-gel strategy to the synthesis of low temperature sintered alumina-aluminium titanate composites through a core-shell approach

    International Nuclear Information System (INIS)

    Jayasankar, M.; Ananthakumar, S.; Mukundan, P.; Wunderlich, W.; Warrier, K.G.K.

    2008-01-01

    A simple sol-gel based core-shell approach for the synthesis of alumina-aluminium titanate composite is reported. Alumina is the core and titania is the shell. The coating of titania has been performed in aqueous medium on alumina particle by means of heterocoagulation of titanyl chloride. Further heat treatment results in low temperature formation of aluminium titanate as well as low temperature sintering of alumina-aluminium titanate composites. The lowering of the reaction temperature can be attributed to the maximisation of the contact surface between the reactants due to the core-shell approach involving nanoparticles. The mechanism of formation of aluminium titanate and the observations on densification features in the present process are compared with that of mixture of oxides under identical conditions. The sintered alumina-aluminium titanate composite has an average grain size of 2 μm. - Graphical abstract: The article presents a simple sol-gel process through core-shell approach to the synthesis of low temperature sintered alumina-aluminium titanate. The lowering of the reaction temperature can be attributed to the maximisation of the contact surface between the reactant due to the core-shell approach. This material showed the better microstructure control compared to the standard solid-state mixing route

  14. Highly active Pd–In/mesoporous alumina catalyst for nitrate reduction

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Zhenwei; Zhang, Yonggang; Li, Deyi [State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, Shanghai 200092 (China); Werth, Charles J. [Civil, Architectural and Environmental Engineering, University of Texas at Austin, 301 East Dean Keeton St., Stop C1786, Austin, TX 78712 (United States); Zhang, Yalei, E-mail: zhangyalei2003@163.com [State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, Shanghai 200092 (China); Zhou, Xuefei, E-mail: zhouxuefei@tongji.edu.cn [State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, Shanghai 200092 (China)

    2015-04-09

    Highlights: • Pd–In nanoparticles (6–7 nm) uniformly form in the mesopores of alumina (4 nm). • Pd–In nanoparticles aggregation is prevented during the synthesis process. • The reduction rate of nitrate is efficient by using the obtained catalyst. • The selectivity toward N{sub 2} is ideal by using the obtained catalyst. - Abstract: The catalytic reduction of nitrate is a promising technology for groundwater purification because it transforms nitrate into nitrogen and water. Recent studies have mainly focused on new catalysts with higher activities for the reduction of nitrate. Consequently, metal nanoparticles supported on mesoporous metal oxides have become a major research direction. However, the complex surface chemistry and porous structures of mesoporous metal oxides lead to a non-uniform distribution of metal nanoparticles, thereby resulting in a low catalytic efficiency. In this paper, a method for synthesizing the sustainable nitrate reduction catalyst Pd–In/Al{sub 2}O{sub 3} with a dimensional structure is introduced. The TEM results indicated that Pd and In nanoparticles could efficiently disperse into the mesopores of the alumina. At room temperature in CO{sub 2}-buffered water and under continuous H{sub 2} as the electron donor, the synthesized material (4.9 wt% Pd) was the most active at a Pd–In ratio of 4, with a first-order rate constant (k{sub obs} = 0.241 L min{sup −1} g{sub cata}{sup −1}) that was 1.3× higher than that of conventional Pd–In/Al{sub 2}O{sub 3} (5 wt% Pd; 0.19 L min{sup −1} g{sub cata}{sup −1}). The Pd–In/mesoporous alumina is a promising catalyst for improving the catalytic reduction of nitrate.

  15. Study on the bound water of several high specific surface-area oxides (beryllia, alumina, silica-alumina)

    International Nuclear Information System (INIS)

    Rouquerol, J.

    1964-11-01

    This study is concerned with the bound water of several oxides (beryllia, alumina, silica-alumina) at different steps of their dehydration (heating temperatures between 150 and 1100 deg. C). The following techniques have been used simultaneously: Thermal analysis (a new method has been developed), nitrogen adsorption (study of the texture), Diborane hydrolysis (qualitative and quantitative analysis of surface water), Infra-red spectrography (in the absorption range of water), Nuclear magnetic resonance (in the resonance range of protons). Thanks to these different techniques, five kinds of bound water have been observed. Attention is called on the great influence of the thermal treatment conditions on the evolution of the products resulting from the decomposition of alumina α-trihydrate Al(OH) 3 and beryllium α-hydroxide, in the course of the dehydration. Moreover, the author emphasizes the peculiar properties of the two kinds of oxides (alumina and beryllia) prepared through a new method of treatment under low pressure and constant speed of decomposition. Such particular features concern mainly texture, bound water, and consequently, also catalytic activity. (author) [fr

  16. EFFECTIVE ELASTIC PROPERTIES OF ALUMINA-ZIRCONIA COMPOSITE CERAMICS - PART 4. TENSILE MODULUS OF POROUS ALUMINA AND ZIRCONIA

    Directory of Open Access Journals (Sweden)

    W. Pabst

    2004-12-01

    Full Text Available In this fourth paper of a series on the effective elastic properties of alumina-zirconia composite ceramics the influence of porosity on the effective tensile modulus of alumina and zirconia ceramics is discussed. The examples investigated are alumina and zirconia ceramics prepared from submicron powders by starch consolidation casting using two different types of starch, potato starch (median size D50 =47.2 µm and corn starch (median size D50 =13.7 µm. The dependence of effective tensile moduli E, on the porosity f, measured for porosities in the ranges of approx. 19-55 vol.% and 10-42 vol.% for alumina and zirconia, respectively, using a resonant frequency technique, was evaluated by fitting with various model relations, including newly developed ones. A detailed comparison of the fitting results suggests the superiority of the new relation E/E0 = (1 - f·(1 - f/fC, developed by the authors (with the tensile modulus of the dense ceramic material E0 and the critical porosity fC, over most other existing fit models. Only for special purposes and well-behaved data sets the recently proposed exponential relation E/E0 = exp [-Bf/(1 - f] and the well-known Phani-Niyogi relation E/E0 = (1 - f/fCN might be preferable.

  17. Pemanfaatan serat silicon carbon dan partikel alumina pada matrik aluminium untuk meningkatkan sifat mekanis material komposit

    Directory of Open Access Journals (Sweden)

    Ketut Suarsana

    2017-03-01

    previous treatment. Indonesia has the potential of naturalresources potential, especially as fiber from plant sources also include metals aluminum (bauxite from fossils. This material canbe used for the needs of the industry as the manufacture of composite base Aluminium and as a reinforcement in the form offibers or particles of alumina. The method of making Aluminum Matrix Composites (AMC with a powder metallurgy process atthe compression force / compaction 2.5 tons using a hydraulic press equipment, holding time 15 minutes, and the treatmentprocess in the variation of the composition by weight (%wt. Variations in the composition of the fiber reinforcement SiliconCarbon (SiC and Al2O3 (alumina on a matrix Aluminium is: 30% SiC + 0% Al203, 27% SiC + 3% Al203, 24% SiC + 6% Al203 and21% SiC + 9% Al203 with a matrix of 70% Al, on condition tempertaur 500oC, 550oC and 600oC. After the composite material isformed, tested for mechanical properties due to the influence of variations in composition between matrix and reinforcement incomposites. Characteristics test performed in the laboratory to knowing strength and hardness properties of composite materials.Furthermore sought the relationship between the nature of each composition fiber reinforcement and an Al2O3 forming SiCcomposites made to know the benefits of reinforcing fibers and particles of alumina.Keywords: Strength, hardness, SiC fibers and Al2O3

  18. Effects of a magnetic field on growth of porous alumina films on aluminum

    Energy Technology Data Exchange (ETDEWEB)

    Ispas, Adriana; Bund, Andreas [Technische Universitaet Dresden, Physikalische Chemie und Elektrochemie, 01062 Dresden (Germany); Vrublevsky, Igor, E-mail: vrublevsky@bsuir.edu.b [Belarusian State University of Informatics and Radioelectronics Minsk, Department of Micro and Nanoelectronics, 220013 Minsk (Belarus)

    2010-05-01

    The effects induced by a magnetic field on the oxide film growth on aluminum in sulfuric, oxalic, phosphoric and sulfamic acid, and on current transients during re-anodizing of porous alumina films in the barrier-type electrolyte, were studied. Aluminum films of 100 nm thickness were prepared by thermal evaporation on Si wafer substrates. We could show that the duration of the anodizing process increased by 33% during anodizing in sulfuric acid when a magnetic field was applied (0.7 T), compared to the process without a magnetic field. Interestingly, such a magnetic field effect was not found during anodizing in oxalic and sulfamic acid. The pore intervals were decreased by ca. 17% in oxalic acid. These findings were attributed to variations in electronic properties of the anodic oxide films formed in various electrolytes and interpreted on the basis of the influence of trapped electrons on the mobility of ions migrating during the film growth. The spin dependent tunneling of electrons into the surface layer of the oxide under the magnetic field could be responsible for the shifts of the current transients to lower potentials during re-anodizing of heat-treated oxalic and phosphoric acid alumina films.

  19. Synthesis and characterization of mesoporous ceria/alumina nanocomposite materials via mixing of the corresponding ceria and alumina gel precursors.

    Science.gov (United States)

    Khalil, Kamal M S

    2007-03-01

    Mesoporous ceria/alumina, CeO(2)/Al(2)O(3), composites containing 10, 20 and 30% (w/w) ceria were prepared by a novel gel mixing method. In the method, ceria gel (formed via hydrolysis of ammonium cerium(IV) nitrate by aqueous ammonium carbonate solution) and alumina gel (formed via controlled hydrolysis of aluminum tri-isopropoxide) were mixed together. The mixed gel was subjected to subsequent drying and calcination for 3 h at 400, 600, 800 and 1000 degrees C. The uncalcined (dried at 110 degrees C) and the calcined composites were investigated by different techniques including TGA, DSC, FTIR, XRD, SEM and nitrogen adsorption/desorption isotherms. Results indicated that composites calcined for 3 h at 800 degrees C mainly kept amorphous alumina structure and gamma-alumina formed only upon calcinations at 1000 degrees C. On the other hand, CeO(2) was found to crystallize in the common ceria, cerinite, phase and it kept this structure over the entire calcination range (400-1000 degrees C). Therefore, high surface areas, stable surface textures, and non-aggregated nano-sized ceria dispersions were obtained. A systematic texture change based on ceria ratio was observed, however in all cases mesoporous composite materials exposing thermally stable texture and structure were obtained. The presented method produces composite ceria/alumina materials that suit different applications in the field of catalysis and membranes technology, and throw some light on physicochemical factors that determine textural morphology and thermal stability of such important composite.

  20. BaxSr1-xTi1.02O3 metal-insulator-metal capacitors on planarized alumina substrates

    NARCIS (Netherlands)

    Tiggelman, M.P.J.; Reimann, K.; Klee, M.; Mauczok, R.; Keur, W.; Hueting, Raymond Josephus Engelbart

    2010-01-01

    Nanocrystalline barium strontium titanate (BaxSr1−xTi1.02O3) thin films with a barium content of x=0.8, 0.9 and 1 have been fabricated in a metal–insulator–metal configuration on glass-planarized alumina substrates. Cost-effective processing measures have been utilized by using poly-crystalline

  1. Properties of alumina films prepared by metal-organic chemical vapour deposition at atmospheric pressure in hte presence of small amounts of water

    NARCIS (Netherlands)

    Haanappel, V.A.C.; Haanappel, V.A.C.; van Corbach, H.D.; Rem, J.B.; Fransen, T.; Gellings, P.J.

    1995-01-01

    Thin alumina films were deposited on stainless steel, type AISI 304. The deposition process was carried out in nitrogen with low partial pressures of water (0–2.6 × 10−2 kPa (0−0.20 mmHg)) by metal-organic chemical vapour deposition (MOCVD) with aluminium-tri-sec-butoxide (ATSB) as the precursor.

  2. Effect of friction time on the properties of friction welded YSZ‐alumina composite and 6061 aluminium alloy

    Directory of Open Access Journals (Sweden)

    Uday M. Basheer

    2012-03-01

    Full Text Available The aim of this work was to study the effect of friction time on the microstructure and mechanical properties of alumina 0, 25, 50 wt% yttria stabilized zirconia (YSZ composite and 6061 aluminium alloy joints formed by friction welding. The alumina-YSZ composites were prepared through slip casting in plaster of Paris molds (POP and subsequently sintered at 1600°C, while the aluminium rods were machined down using a lathe machine to the dimension required. The welding process was carried out under different rotational speeds and friction times, while friction force (0.5 ton-force was kept constant. Scanning electron microscopy was used to characterize the interface of the joints structure. The experimental results showed that the friction time has a significant effect on joint structure and mechanical properties.

  3. Density control of electrodeposited Ni nanoparticles/nanowires inside porous anodic alumina templates by an exponential anodization voltage decrease.

    Science.gov (United States)

    Marquardt, B; Eude, L; Gowtham, M; Cho, G; Jeong, H J; Châtelet, M; Cojocaru, C S; Kim, B S; Pribat, D

    2008-10-08

    Porous alumina templates have been fabricated by applying an exponential voltage decrease at the end of the anodization process. The time constant η of the exponential voltage function has been used to control the average thickness and the thickness distribution of the barrier layer at the bottom of the pores of the alumina structure. Depending on the η value, the thickness distribution of the barrier layer can be made very uniform or highly scattered, which allows us to subsequently fine tune the electrodeposition yield of nickel nanoparticles/nanowires at low voltage. As an illustration, the pore filling percentage with Ni has been varied, in a totally reproducible manner, between ∼3 and 100%. Combined with the ability to vary the pore diameter and repetition step over ∼2 orders of magnitude (by varying the anodization voltage and electrolyte type), the control of the pore filling percentage with metal particles/nanowires could bring novel approaches for the organization of nano-objects.

  4. Numerical performance study of paraffin wax dispersed with alumina in a concentric pipe latent heat storage system

    Directory of Open Access Journals (Sweden)

    Valan Arasu Amirtham

    2013-01-01

    Full Text Available Latent heat energy storage systems using paraffin wax could have lower heat transfer rates during melting/freezing processes due to its inherent low thermal conductivity. The thermal conductivity of paraffin wax can be enhanced by employing high conductivity materials such as alumina (Al2O3. A numerical analysis has been carried out to study the performance enhancement of paraffin wax with nanoalumina (Al2O3 particles in comparison with simple paraffin wax in a concentric double pipe heat exchanger. Numerical analysis indicates that the charge-discharge rates of thermal energy can be greatly enhanced using paraffin wax with alumina as compared with a simple paraffin wax as PCM.

  5. Step-by-step seeding procedure for preparing HKUST-1 membrane on porous α-alumina support.

    Science.gov (United States)

    Nan, Jiangpu; Dong, Xueliang; Wang, Wenjin; Jin, Wanqin; Xu, Nanping

    2011-04-19

    Metal-organic framework (MOF) membranes have attracted considerable attention because of their striking advantages in small-molecule separation. The preparation of an integrated MOF membrane is still a major challenge. Depositing a uniform seed layer on a support for secondary growth is a main route to obtaining an integrated MOF membrane. A novel seeding method to prepare HKUST-1 (known as Cu(3)(btc)(2)) membranes on porous α-alumina supports is reported. The in situ production of the seed layer was realized in step-by-step fashion via the coordination of H(3)btc and Cu(2+) on an α-alumina support. The formation process of the seed layer was observed by ultraviolet-visible absorption spectroscopy and atomic force microscopy. An integrated HKUST-1 membrane could be synthesized by the secondary hydrothermal growth on the seeded support. The gas permeation performance of the membrane was evaluated. © 2011 American Chemical Society

  6. Preparation, characterization and microstructural optimization of a thin {gamma}-alumina membrane on a porous stainless steel substrate

    Energy Technology Data Exchange (ETDEWEB)

    Abedini, Sanam [Department of Mining and Metallurgical Engineering, Amirkabir University of Technology (Tehran Polytechnic), Hafez Street, Tehran (Iran, Islamic Republic of); Parvin, Nader, E-mail: naderparvin@yahoo.com [Department of Mining and Metallurgical Engineering, Amirkabir University of Technology (Tehran Polytechnic), Hafez Street, Tehran (Iran, Islamic Republic of); Ashtari, Parviz [Nuclear Science and Technology Research Institute, Tehran (Iran, Islamic Republic of)

    2012-01-30

    Highlights: Black-Right-Pointing-Pointer A mesoporous {gamma}-Al{sub 2}O{sub 3} membrane was synthesized on conventional {alpha}-Al{sub 2}O{sub 3} substrates. Black-Right-Pointing-Pointer {gamma}-Al{sub 2}O{sub 3} membrane was potential for CO{sub 2} separation at high pressure test conditions. Black-Right-Pointing-Pointer Thus, it was required to provide the membrane layer with more strength. Black-Right-Pointing-Pointer {alpha}-Alumina substrate was substituted with porous stainless steel. Black-Right-Pointing-Pointer A stainless steel supported {alpha}-Al{sub 2}O{sub 3} membrane with better properties was synthesized. - Abstract: In this work, a supported mesoporous (MEP) {gamma}-Al{sub 2}O{sub 3} membrane was synthesized on conventional {alpha}-Al{sub 2}O{sub 3} substrates by sol-gel dip coating process. In the following, the preparation of a novel metallic-ceramic composite membrane was studied, which incorporated desirable properties of both ceramic membrane and porous metallic substrate. For this purpose, mesoporous alumina membrane layer was developed on a porous 316L stainless steel substrate. The substrate was prepared by loose powder sintering and modified by soaking-rolling and fast drying method. The prepared membranes were characterized using scanning electron microscope (SEM), field emission scanning electron microscope (FESEM), X-ray diffractometer (XRD) and N{sub 2}-adsorption/desorption measurements (BET analyses). The results revealed that a defect-free {gamma}-alumina membrane with 2.1 nm average pore size can be produced. Permeation tests with N{sub 2} gas revealed that the stainless steel substrate had 40 times more permeability than conventionally used alumina support. Additionally, single gas permeation of {gamma}-alumina membrane for CO{sub 2} and N{sub 2} was compared. It was observed that CO{sub 2} could be separated from N{sub 2} by the MEP {gamma}-Al{sub 2}O{sub 3} membrane in high pressure permeation condition, where stainless steel

  7. The concentration of the coolant 7Li in Kozloduy Nuclear Power Plant operating with potassium hydroxide as an alkalizing reagent (possible impact on the occurrence of axial offset anomaly)

    International Nuclear Information System (INIS)

    Dobrevski, I.D.; Minkova, K.F.; Ivanova, R.A.

    2003-01-01

    The phenomenon of axial offset anomaly (AOA) has occurred in a number of PWRs operating with extended fuel cycles and high boiling duty cores. Up to now AOA has been observed in PWRs operating with lithium hydroxide and the alkalizing reagent used for pH adjustment in boric acid water solutions. Since AOA is connected with the LiBO 2 precipitation in porous corrosion product deposits on the fuel cladding surfaces, we could presume that the replacement of lithium hydroxide with potassium hydroxide will avoid AOA. Nowadays there is a lack of observed AOA in VVER, i.e., a lack of formation of lithium metaborate (LiBO 2 ) deposits on the fuel element surfaces by coolant alkalization with potassium hydroxide. Nevertheless, the concentrations of 7 Li appear in the coolant, as a product of the neutron reaction with boron: 10 B (n,α) → 7 Li (n, α). As a consequence the possibility it is not excluded of LiBO 2 formation in VVERs with potassium hydroxide water chemistry. The aim of this study is to inform the reader about the development of the concentration of the coolant lithium concentration during the fuel cycles of VVERs and to discuss the possibility of LiBO 2 formation under VVER operation conditions. (orig.)

  8. Controlling the number of walls in multi walled carbon nanotubes/alumina hybrid compound via ball milling of precipitate catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Nosbi, Norlin [School of Materials and Mineral Resources Engineering, Engineering Campus, Universiti Sains Malaysia (USM), 14300 Nibong Tebal, Seberang Perai Selatan, Pulau Pinang (Malaysia); Akil, Hazizan Md, E-mail: hazizan@usm.my [School of Materials and Mineral Resources Engineering, Engineering Campus, Universiti Sains Malaysia (USM), 14300 Nibong Tebal, Seberang Perai Selatan, Pulau Pinang (Malaysia); Cluster for Polymer Composite (CPC), Science and Engineering Research Centre, Engineering Campus, Universiti Sains Malaysia (USM), 14300 Nibong Tebal, Seberang Perai Selatan, Pulau Pinang (Malaysia)

    2015-06-15

    Graphical abstract: - Highlights: • We report that, to manipulate carbon nanotubes geometry and number of walls are by controlling the precipitate catalyst size. • Number of walls and geometry effects depend on the milling time of the precipitate catalyst. • Increasing milling of time will decrease the carbon nanotubes number of walls. • Increasing milling of time will increase the carbon nanotubes thermal conductivity. - Abstract: This paper reports the influence of milling time on the structure and properties of the precipitate catalyst of multi walled carbon nanotubes (MWCNT)/alumina hybrid compound, produced through the chemical vapour deposition (CVD) process. For this purpose, light green precipitate consisted of aluminium, nickel(II) nitrate hexahydrate and sodium hydroxide mixture was placed in a planetary mill equipped with alumina vials using alumina balls at 300 rpm rotation speed for various milling time (5–15 h) prior to calcinations and CVD process. The compound was characterized using various techniques. Based on high-resolution transmission electron microscopy analysis, increasing the milling time up to 15 h decreased the diameter of MWCNT from 32.3 to 13.1 nm. It was noticed that the milling time had a significant effect on MWCNT wall thickness, whereby increasing the milling time from 0 to 15 h reduced the number of walls from 29 to 12. It was also interesting to note that the carbon content increased from 23.29 wt.% to 36.37 wt.% with increasing milling time.

  9. Optimal factor evaluation for the dissolution of alumina from Azaraegbelu clay in acid solution using RSM and ANN comparative analysis

    Directory of Open Access Journals (Sweden)

    P.E. Ohale

    2017-12-01

    Full Text Available Artificial neural network (ANN and Response Surface Methodology based on a 25−1 fractional factorial design were used as tools for simulation and optimisation of the dissolution process for Azaraegbelu clay. A feedforward neural network model with Levenberg–Marquard back propagating training algorithm was adapted to predict the response (alumina yield. The studied input variables were temperature, stirring speed, clay to acid dosage, leaching time and leachant concentration. The raw clay was characterized for structure elucidation via FTIR, SEM and X-ray diffraction spectroscopic techniques and the result indicates that the clay is predominantly kaolinite. Leachant concentration and dosage ratio were found to be the most significant process parameter with p-value of 0.0001. The performance of the ANN and RSM model showed adequate prediction of the response, with AAD of 11.6% and 3.6%, and R2 of 0.9733 and 0.9568, respectively. A non-dominated optimal response of 81.45% yield of alumina at 4.6 M sulphuric acid concentration, 214 min leaching time, 0.085 g/ml dosage and 214 rpm stirring speed was established as a viable route for reduced material and operating cost via RSM. Keywords: Alumina dissolution, ANN modelling, Azaraegbelu, Clay, RSM

  10. Highly efficient and large-scale fabrication of superhydrophobic alumina surface with strong stability based on self-congregated alumina nanowires.

    Science.gov (United States)

    Peng, Shan; Tian, Dong; Yang, Xiaojun; Deng, Wenli

    2014-04-09

    In this study, a large-area superhydrophobic alumina surface with a series of superior properties was fabricated via an economical, simple, and highly effective one-step anodization process, and subsequently modified with low-surface-energy film. The effects of the anodization parameters including electrochemical anodization time, current density, and electrolyte temperature on surface morphology and surface wettability were investigated in detail. The hierarchical alumina pyramids-on-pores (HAPOP) rough structure which was produced quickly through the one-step anodization process together with a low-surface-energy film deposition [1H,1H,2H,2H-perfluorodecyltriethoxysilane (PDES) and stearic acid (STA)] confer excellent superhydrophobicity and an extremely low sliding angle. Both the PDES-modified superhydrophobic (PDES-MS) and the STA-modified superhydrophobic (STA-MS) surfaces present fascinating nonwetting and extremely slippery behaviors. The chemical stability and mechanical durability of the PDES-MS and STA-MS surfaces were evaluated and discussed. Compared with the STA-MS surface, the as-prepared PDES-MS surface possesses an amazing chemical stability which not only can repel cool liquids (water, HCl/NaOH solutions, around 25 °C), but also can show excellent resistance to a series of hot liquids (water, HCl/NaOH solutions, 30-100 °C) and hot beverages (coffee, milk, tea, 80 °C). Moreover, the PDES-MS surface also presents excellent stability toward immersion in various organic solvents, high temperature, and long time period. In particular, the PDES-MS surface achieves good mechanical durability which can withstand ultrasonication treatment, finger-touch, multiple fold, peeling by adhesive tape, and even abrasion test treatments without losing superhydrophobicity. The corrosion resistance and durability of the diverse-modified superhydrophobic surfaces were also examined. These fascinating performances makes the present method suitable for large

  11. A study on heat transfer characteristics of spherical and fibrous alumina nanofluids

    International Nuclear Information System (INIS)

    Kim, Chang Kyu; Lee, Gyoung-Ja; Rhee, Chang Kyu

    2012-01-01

    Highlights: ► Spherical and fibrous alumina nanoparticles were prepared by pulsed wire evaporation and hydrolysis methods. ► Fibrous alumina nanofluid exhibited higher thermal conductivity enhancement than spherical one due to entangled structure of nanofibers with high aspect-ratio. ► Decreasing rate of viscosity with temperature for fibrous alumina nanofluid was much larger than that for spherical one. - Abstract: Ethylene glycol based nanofluids containing spherical/fibrous alumina nanoparticles were synthesized by pulsed wire evaporation and hydrolysis methods. The crystallographic and morphological properties of the prepared nanoparticles were analyzed by X-ray diffraction, nitrogen gas adsorption and transmission electron microscopy. The average diameter of spherical alumina nanoparticles was about 80 nm and the alumina nanofibers exhibited a high aspect ratio (length/width). The viscosity and thermal conductivity of the spherical/fibrous alumina nanofluids were experimentally measured in the temperature range from 25 to 80 °C. For the fibrous alumina nanofluid, the increase of temperature raised thermal conductivity but lowered viscosity. On the other hand, for the spherical alumina nanofluid, both thermal conductivity and viscosity were decreased with increasing temperature. In particular, the fibrous alumina nanofluid exhibited a higher enhancement of thermal conductivity than the spherical one due to the well-connected structure between entangled nanofibers with high aspect ratio.

  12. Deuterium permeation of amorphous alumina coating on 316L prepared by MOCVD

    International Nuclear Information System (INIS)

    Li Shuai; He Di; Liu Xiaopeng; Wang Shumao; Jiang Lijun

    2012-01-01

    Highlights: ► Deuterium permeation behavior of alumina coating by MOCVD is investigated. ► The as-prepared alumina is amorphous. ► The alumina coating is dense and well adherent to substrate. ► Deuterium permeation rate of alumina coating is 2–3 orders of magnitude lower than martensitic steels. - Abstract: The deuterium permeation behavior of the alumina coating on 316L stainless steel prepared by metal organic chemical vapor deposition (MOCVD) was investigated. The alumina coating was also characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscope (SEM). It was found that the as-prepared coating consisted of amorphous alumina. This alumina coating had a dense, crack-free and homogeneous morphology. Although the alumina coating was amorphous, effective suppression of deuterium permeation was demonstrated. The deuterium permeability of the alumina coating was 51–60 times less than that of the 316L stainless steel and 153–335 times less than that of the referred low activation martensitic steels at 860–960 K.

  13. An electrochemical investigation on the dissolution of bilayered porous anodic alumina

    International Nuclear Information System (INIS)

    Liao, Jinfu; Ling, Zhiyuan; Li, Yi; Hu, Xing

    2015-01-01

    Highlights: • Pulse polarization was introduced to investigate the dissolution of PAA. • Electric field within the bilayers was estimated. • The formation of the barrier layer involves mainly solid-state processes. • The structure should be the determining factor in the dissolution of the bilayers. - Abstract: Anodic alumina attracts much research interest in many disciplines for its versatility. Meanwhile, some aspects regarding its growth are still not well-understood, such as the formation and properties of its bilayer structure. In this paper, along with capacitance measurement, pulse polarization is introduced to study the dissolution of bilayered porous anodic alumina (PAA). Combined with electron microscope observation, the electric field in the outer layer is estimated to be slightly higher than that in the inner layer. By comparing with (oxy-)hydroxide layers, the electric field distribution within barrier layer of PAA confirms that the bilayers are compact and are formed mainly by solid-state ionic migration. The changes of dissolution rates after annealing and application of electric pulses suggest that structure may be a determining factor for the dissolution behaviors of the bilayers.

  14. Fabrication of TiO2 Nanotanks Embedded in a Nanoporous Alumina Template

    Directory of Open Access Journals (Sweden)

    C. Massard

    2015-01-01

    Full Text Available The feasibility of surface nanopatterning with TiO2 nanotanks embedded in a nanoporous alumina template was investigated. Self-assembled anodized aluminium oxide (AAO template, in conjunction with sol gel process, was used to fabricate this nanocomposite object. Through hydrolysis and condensation of the titanium alkoxide, an inorganic TiO2 gel was moulded within the nanopore cavities of the alumina template. The nanocomposite object underwent two thermal treatments to stabilize and crystallize the TiO2. The morphology of the nanocomposite object was characterized by Field Emission Scanning Electron Microscopy (FESEM. The TiO2 nanotanks obtained have cylindrical shapes and are approximately 69 nm in diameter with a tank-to-tank distance of 26 nm. X-ray diffraction analyses performed by Transmission Electron Microscopy (TEM with selected area electron diffraction (SAED were used to investigate the TiO2 structure. The optical properties were studied using UV-Vis spectroscopy.

  15. Synthesis of alumina powder with seeds by Pechini Method using O2 as calcination atmosphere

    International Nuclear Information System (INIS)

    Salem, R.E.P.; Guilherme, K.A.; Chinelatto, A.S.A.; Chinelatto, A. L.

    2012-01-01

    Alumina is a very investigated material due to its excellent refractory characteristics and mechanical properties. Its alpha phase, the most stable one, has a formation temperature of about 1200 ° C. Due to its high temperature of formation, many researches have been trying to reduce it through addition of seeds of alpha phase in chemical processes of synthesis. This work aims to synthesize ultrafine powders of alpha-alumina by the Pechini method with seeding, and using an O 2 atmosphere in the pre-calcination (500 ° C) and calcination (1000 ° C and 1100° C) steps. The resulting powders were characterized through X-ray diffractometry, infrared spectroscopy and scanning electron microscopy. The results were compared with samples calcined on ai. It was verified that the presence of oxygen in the calcination atmosphere favored the elimination of residual carbon from the precursor powders, forthcoming from the great amount of organic material used on the synthesis, modifying its morphology and favoring reduction of particle size. (author)

  16. Facile SILAR approach to air-stable naked silver and gold nanoparticles supported by alumina.

    Science.gov (United States)

    Stamplecoskie, Kevin G; Manser, Joseph S

    2014-10-22

    A synthetically convenient and scalable SILAR (successive ion layer adsorption and reaction) method is used to make air-stable films of silver and gold nanoparticles supported on alumina scaffolds. This solution-based deposition technique yields particles devoid of insulating capping agents or ligands. The optical properties of the nanoparticle films were investigated using femtosecond transient absorption spectroscopy. A linear absorption arising from intraband excitation (775 nm laser pulse) is seen only for Au nanoparticles at low intensity. However, both Au and Ag particles exhibit plasmon resonance responses at high excitation intensity via two photon absorption of the 775 nm pump pulse. The difference in optical response to near-IR laser excitation is rationalized based on the known density of states for each metal. To demonstrate the potential applications of these films, alumina-supported Ag nanoparticles were utilized as substrates for surface enhanced Raman spectroscopy, resulting in a 65-fold enhancement in the Raman signal of the probe molecule rhodamine 6G. The exceptional stability and scalability of these SILAR films opens the door for further optical and photocatalytic studies and applications, particularly with ligand-free Ag nanoparticles that typically oxidize under ambient conditions. Additionally, isolating plasmonic and interband electronic excitations in stable AgNP under visible light irradiation could enable elucidation of the mechanisms that drive noble metal-assisted photocatalytic processes.

  17. The Use of Activated Alumina and Magnetic Field for the Removal Heavy Metals from Water

    Directory of Open Access Journals (Sweden)

    Ewa Szatyłowicz

    2018-05-01

    Full Text Available The objective of this work was to verify the granular activated alumina (AA sorption properties, during the process of removing copper, lead and cadmium from water, and to monitor the impact of magnetic field (MF on the effectiveness of removing copper, lead and cadmium from water. Activated alumina adsorption is known to be an effective and inexpensive technology for the removal of selenium and arsenic from water and was suggested by EPA as a BAT for point-of-use applications. The removal of copper, lead and cadmium from water using AA and impact of magnetic field was less reported. Pilot tests showed that the use of AA sorption materials with MF impact could possibly decrease the copper, lead and cadmium content in the model water. The MF had also a positive effect on the efficiency of removal copper, lead and cadmium on AA. Increasing the efficiency of heavy metals removal in the samples had been exposed magnetic field varied from 1.9% to 8.2% compared to the control samples.

  18. The investigation of efficient conditions for alumina production from diasporic bauxites

    International Nuclear Information System (INIS)

    Alp, A.; Aydin, A.O.

    2002-01-01

    The main objective of this study was to investigate the leach conditions of diasporic bauxites in the region of Mugla-Milas for alumina production. The chemical composition was 57.91% Al 2 O 3 , 21.33% Fe 2 O 3 , 3.84% SiO 2 , 2.20% TiO 2 , 2.10% CaO, 1.02% FeS 2 , 1.65% CO 2 , and 0.52% other. The effects of alkaline (CaO and/or Na 2 CO 3 ) additives, precalcination temperature, calcination time, leaching time, solution concentration, liquid/bauxite ratio and particle size on the efficiency of alumina and silica dissolution were investigated. The optimum conditions of the process were the addition of alkaline in 0.5 mole fraction, 900 o C precalcination temperature, 2 hours of calcination time, 3 hours of leaching time, 1.5 molar Na 2 O of caustic concentration and liquid/bauxite ratio of 30 at the boiling temperature of leach solution under continuous stirring. Although the highest extraction efficiency of Al 2 O 3 was found to be 81.77% with precalcination at 1200 o C, 900 o C was preferred as an optimum calcination temperature. (author)

  19. Nanostructured thin films of indium oxide nanocrystals confined in alumina matrixes

    International Nuclear Information System (INIS)

    Bouifoulen, A.; Edely, M.; Errien, N.; Kassiba, A.; Outzourhit, A.; Makowska-Janusik, M.; Gautier, N.; Lajaunie, L.; Oueriagli, A.

    2011-01-01

    Nanocrystals of indium oxide (In 2 O 3 ) with sizes below 10 nm were prepared in alumina matrixes by using a co-pulverization method. The used substrates such as borosilicate glasses or (100) silicon as well as the substrate temperatures during the deposition process were modified and their effects characterized on the structural and physical properties of alumina-In 2 O 3 films. Complementary investigation methods including X-ray diffraction, optical transmittance in the range 250-1100 nm and transmission electron microscopy were used to analyze the nanostructured films. The crystalline order, morphology and optical responses were monitored as function of the deposition parameters and the post-synthesis annealing. The optimal conditions were found and allow realizing suitable nanostructured films with a major crystalline order of cubic phase for the In 2 O 3 nanocrystals. The optical properties of the films were analyzed and the key parameters such as direct and indirect band gaps were evaluated as function of the synthesis conditions and the crystalline quality of the films.

  20. Compaction study of particulate iron-chromium matrix composite reinforced with alumina

    International Nuclear Information System (INIS)

    Saidatulakmar Shamsuddin; Shamsul Baharin Jamaludin; Zuhailawati Hussain; Zainal Arifin Ahmad

    2007-01-01

    Recently, a sharper focus on cost reduction in producing advanced composites systems has increased and leads to an interest in ferrous matrix composite which is cheaper compared to Cobalt, Nickel and their alloys that are scarce, expensive and their dust is especially harmful. In the present investigation, Fe-Cr-Al 2 O 3 composite was prepared using conventional powder metallurgy technique; mixing, compaction and sintering. Consolidation of particulate materials is dependent on the compaction process. As load is increased, the number of contacting asperities increases and they flatten and grow to form a planar contact surface. These asperities eventually merge to form bonding surfaces between particles. This paper focused on finding the optimum compaction parameter in a uniaxial pressing. Six different pressure were studied; (250, 375, 500, 625, 750 and 875)MPa. experimental results show that the optimum compaction parameter is 750 MPa that produced highest linear shrinkage, highest bulk density, lowest porosity and highest hardness value. Every sample has formed binary alloy of Fe-Cr alloy, confirmed by XRD and alumina are homogeneously distributed in the Fe-Cr matrix revealed by optical micrograph and SEM. from EDX, the composites consist of iron, chromium and alumina. (author)

  1. Fine tuning of optical signals in nanoporous anodic alumina photonic crystals by apodized sinusoidal pulse anodisation.

    Science.gov (United States)

    Santos, Abel; Law, Cheryl Suwen; Chin Lei, Dominique Wong; Pereira, Taj; Losic, Dusan

    2016-11-03

    In this study, we present an advanced nanofabrication approach to produce gradient-index photonic crystal structures based on nanoporous anodic alumina. An apodization strategy is for the first time applied to a sinusoidal pulse anodisation process in order to engineer the photonic stop band of nanoporous anodic alumina (NAA) in depth. Four apodization functions are explored, including linear positive, linear negative, logarithmic positive and logarithmic negative, with the aim of finely tuning the characteristic photonic stop band of these photonic crystal structures. We systematically analyse the effect of the amplitude difference (from 0.105 to 0.840 mA cm -2 ), the pore widening time (from 0 to 6 min), the anodisation period (from 650 to 950 s) and the anodisation time (from 15 to 30 h) on the quality and the position of the characteristic photonic stop band and the interferometric colour of these photonic crystal structures using the aforementioned apodization functions. Our results reveal that a logarithmic negative apodisation function is the most optimal approach to obtain unprecedented well-resolved and narrow photonic stop bands across the UV-visible-NIR spectrum of NAA-based gradient-index photonic crystals. Our study establishes a fully comprehensive rationale towards the development of unique NAA-based photonic crystal structures with finely engineered optical properties for advanced photonic devices such as ultra-sensitive optical sensors, selective optical filters and all-optical platforms for quantum computing.

  2. A nanoporous alumina microelectrode array for functional cell–chip coupling

    International Nuclear Information System (INIS)

    Wesche, Manuel; Hüske, Martin; Yakushenko, Alexey; Brüggemann, Dorothea; Mayer, Dirk; Offenhäusser, Andreas; Wolfrum, Bernhard

    2012-01-01

    The design of electrode interfaces has a strong impact on cell-based bioelectronic applications. We present a new type of microelectrode array chip featuring a nanoporous alumina interface. The chip is fabricated in a combination of top-down and bottom-up processes using state-of-the-art clean room technology and self-assembled generation of nanopores by aluminum anodization. The electrode characteristics are investigated in phosphate buffered saline as well as under cell culture conditions. We show that the modified microelectrodes exhibit decreased impedance compared to planar microelectrodes, which is caused by a nanostructuring effect of the underlying gold during anodization. The stability and biocompatibility of the device are demonstrated by measuring action potentials from cardiomyocyte-like cells growing on top of the chip. Cross sections of the cell–surface interface reveal that the cell membrane seals the nanoporous alumina layer without bending into the sub-50 nm apertures. The nanoporous microelectrode array device may be used as a platform for combining extracellular recording of cell activity with stimulating topographical cues. (paper)

  3. Alpha alumina synthesis by laser treatment of bi-phasic nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Aktas, Cenk, E-mail: cenk.aktas@inm-gmbh.de [Leibniz Institute for New Materials, D2 2 Campus, 66123 Saarbrücken (Germany); Lee, Juseok; Míro, Marina Martinez [Leibniz Institute for New Materials, D2 2 Campus, 66123 Saarbrücken (Germany); Barnoush, Afrooz [Norwegian University of Science and Technology, Trondheim (Norway); Saarland University, D2 2 Campus, 66123 Saarbrücken (Germany); Veith, Michael [Leibniz Institute for New Materials, D2 2 Campus, 66123 Saarbrücken (Germany)

    2013-08-01

    Al/Al{sub 2}O{sub 3} bi-phasic nanowires (Al-core/Al{sub 2}O{sub 3} shell) are prepared by chemical vapor deposition (CVD) using single source precursor (SSP) approach. Such bi-phasic nanostructures were heat-treated using an argon laser operating at visible wavelengths. Al core seems to act as an active binder, which might decrease the inhomogeneous heating and thermal gradients. Nanoindentation method is used to estimate the hardness of the laser treated surfaces. Hardness values and pop-in behaviour in loading-curve indicate a formation of α-Al{sub 2}O{sub 3} with very low defect density. It is believed that Al/Al{sub 2}O{sub 3} bi-phasic layers exhibit a dynamic change by transforming into alumina after the laser irradiation and this leads to alteration of the optical absorption especially in the visible wavelength region. Following the full transformation to alumina, the surface reflects back the laser light which hinders inhomogeneous and excessive heating. In this context, laser treatment of Al/Al{sub 2}O{sub 3} bi-phasic nanowires provides a controlled sintering process which can open up various applications in different fields.

  4. Health monitoring technology for alumina-fiber-reinforced plastic

    International Nuclear Information System (INIS)

    Aoyama, Hiroshi; Watanabe, Hiroyuki; Terai, Motoaki

    1998-01-01

    Formally, we developed new load-support systems that consists of a biconical, alumina-fiber-reinforced plastic (ERP) structure for the superconducting magnet. Safe operation of the superconducting magnet will be jeopardized if the mechanical condition of the load-support system begins to degrade. One of the factors that evaluate the soundness of the superconducting magnet is the stiffness of the load-support system. Here, it is important to know the relation between the degradation of the stiffness and the growth of defects. For this purpose, firstly, a fatigue test of the load-support system was carried out, and the various defects (matrix cracking and delamination of FRP laminates) were observed during this fatigue testing. Finally, we proposed the application of two non-destructive-evaluation (NDE) methods for the health monitoring of alumina/epoxy load-support systems. (author)

  5. Long-term results of uncemented alumina acetabular implants.

    Science.gov (United States)

    Boehler, M; Knahr, K; Plenk, H; Walter, A; Salzer, M; Schreiber, V

    1994-01-01

    We report the clinical and tribological performance of 67 ceramic acetabular prostheses implanted between 1976 and 1979 without bone cement. They articulated with ceramic femoral heads mounted on mental femoral stems. After a mean elapsed period of 144 months, 59 sockets were radiographically stable but two showed early signs and six showed late signs of loosening. Four of the loose sockets have been revised. Histological analysis of the retrieved tissue showed a fibrous membrane around all the implants, with fibrocartilage in some. There was no bone ingrowth, and the fibrous membrane was up to 6 mm thick and infiltrated with lymphocytes, plasma cells, and macrophages. Intra- and extracellular birefringent wear particles were seen. Tribological analysis showed total wear rates in two retrieved alumina-on-alumina joints of 2.6 microns per year in a stable implant and 68 microns in a loose implant. Survival analysis showed a revision rate of 12.4% at 136 months.

  6. Evaluation of technological properties of alumina refractory systems-zirconia and zirconia-silica-alumina; Avaliacao das propriedades tecnologicas de refratarios dos sistemas alumina-zirconia e alumina-zirconia-silica

    Energy Technology Data Exchange (ETDEWEB)

    Marinho, A.R.O.; Carvalho, T.U.S.; Fagury Neto, E.; Rabelo, A.A., E-mail: adriano@unifesspa.edu.br [Universidade Federal do Sul e Sudeste do Para (UFSSPA), Maraba, PA (Brazil)

    2014-07-01

    Alumina-zirconia refractories are noted for being products of excellent cost-effective, however, zirconia may limit its use due to decreasing resistance to thermal shock. This study aims to evaluate these refractories with the addition of microsilica, which can greatly improve their properties. Were used the following starting materials: calcined alumina, zirconia (stabilized and monoclinic) in amounts of 2%, 4% and 6% by weight, plus microsilica (5%w.). The powders were milled together with binder and lubricant for conformation bodies by uniaxial pressing. The samples were dried, calcined and sintered at 1400 °C/2h were characterized using the methods of Archimedes, and scanning electron microscopy (SEM), chemical analysis using energy dispersive X-ray (EDS), and mechanical flexural strength tests at room temperature. Formulations with the presence of microsilica showed satisfactory results and optimized properties. (author)

  7. MICROWAVE JOINING OF ALUMINA CERAMIC AND HYDROXYLAPATITE BIOCERAMIC

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    Microwave joining is a rapid developmental new techniqu e in recent years.This paper introduces a new microwave joining equipment which was made by our lab,succeeds in alumina ceramic-hydroxylapatite bioceramic j o in in the equipment, and analyzes the join situation of join boundary by using s canni ng electron microscope(SEM),this paper analyzes the mechanism of microwave joini ng also.

  8. Porous Alumina and Zirconia Ceramics With Tailored Thermal Conductivity

    Czech Academy of Sciences Publication Activity Database

    Gregorová, E.; Pabst, W.; Sofer, Z.; Jankovský, O.; Matějíček, Jiří

    2012-01-01

    Roč. 395, č. 1 (2012), 012022-012022 ISSN 1742-6588. [European Thermal Sciences Conference (Eurotherm)/6./. Poitiers, 04.09.2012-07.09.2012] Institutional support: RVO:61389021 Keywords : Ceramics * alumina * zirconia * porosity * thermal conductivity * pore-forming agent * oxide ceramics * starch * porosity Subject RIV: JK - Corrosion ; Surface Treatment of Materials http://iopscience.iop.org/1742-6596/395/1/012022/pdf/1742-6596_395_1_012022.pdf

  9. On the thermally activated crack propagation in alumina

    International Nuclear Information System (INIS)

    Devezas, T.C.

    1983-01-01

    Subcritical crack growth was studied in the temperature 25-100 0 C in two commercial aluminas containing different amounts of a glassy phase. The experimental method employed was that of double torsion under constant load, using a device specially built to carry out mechanical tests at constant compressive load and high temperatures. Activation enthalpies of subcritical crack growth were determined for the two materials. (Author) [pt

  10. Antibacterial Activity of Zinc Oxide-Coated Nanoporous Alumina

    Science.gov (United States)

    2012-05-17

    made nanoporous alumina membranes, which were created by means of anodic oxidation of aluminum in an oxalic acid electrolyte, for treatment of skin...this study. All of the solutions were prepared using 18 M de-ionized water (lab supply) and trace metal grade nitric acid (Thermo Fisher Scientific...low production cost, repro- ducible reproduction, and facile reproduction approach for these materials. Using in vitro studies, keratinocytes (HaCaT

  11. Efective infrared reflectivity and dielectric function of polycrystalline alumina ceramics

    Czech Academy of Sciences Publication Activity Database

    Nuzhnyy, Dmitry; Petzelt, Jan; Borodavka, Fedir; Vaněk, Přemysl; Šimek, Daniel; Trunec, D.; Maca, K.

    2017-01-01

    Roč. 254, č. 5 (2017), s. 1-8, č. článku 1600607. ISSN 0370-1972 R&D Projects: GA ČR GA15-08389S Institutional support: RVO:68378271 Keywords : alumina * ceramics * effective dielectric function * effective medium approximation * geometrical resonances * infrared reflectivity Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 1.674, year: 2016

  12. Glass properties in the yttria-alumina-silica system

    Science.gov (United States)

    Hyatt, M. J.; Day, D. E.

    1987-01-01

    The glass formation region in the yttria-alumina-silica system was investigated. Properties of glasses containing 25 to 55 wt pct yttria were measured and the effect of the composition was determined. The density, refractive index, thermal-expansion coefficient, and microhardness increased with increasing yttria content. The dissolution rate in 1N HCl increased with increasing yttria content and temperature. These glasses were also found to have high electrical resistivity.

  13. Proton adsorption onto alumina: extension of multisite complexation (MUSIC) theory

    Energy Technology Data Exchange (ETDEWEB)

    Nagashima, K.; Blum, F.D.

    1999-09-01

    The adsorption isotherm of protons onto a commercial {gamma}-alumina sample was determined in aqueous nitric acid with sodium nitrate as a background electrolyte. Three discrete regions could be discerned in the log-log plots of the proton isotherm determined at the solution pH 5 to 2. The multisite complexation (MUSIC) model was modified to analyze the simultaneous adsorption of protons onto various kinds of surface species.

  14. Vitrification of high-level alumina nuclear waste

    International Nuclear Information System (INIS)

    Brotzman, J.R.

    1979-01-01

    Borophosphate glass compositions have been developed for the vitrification of a high-alumina calcined defense waste. The effect of substituting SiO 2 , P 2 O 5 and CuO for B 2 O 3 on the viscosity and leach resistance was measured. The effect of the alkali to borate ratio and the Li 2 O:Na 2 O ratio on the melt viscosity and leach resistance was also measured

  15. Organized Mesoporous Alumina: Synthesis, Structure and Potential in Catalysis

    Czech Academy of Sciences Publication Activity Database

    Čejka, Jiří

    2003-01-01

    Roč. 254, - (2003), s. 327-338 ISSN 0926-860X R&D Projects: GA AV ČR IAA4040001; GA ČR GA104/02/0571; GA MŠk ME 404 Institutional research plan: CEZ:AV0Z4040901 Keywords : organized mesoporous alumina * mesoporous molecular sieves * synthesis Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.825, year: 2003

  16. The effect of alumina particles on the microstructural and mechanical properties of copper foams fabricated by space-holder method

    Science.gov (United States)

    Salvo, C.; Aguilar, C.; Lascano, S.; Pérez, L.; López, M.; Mangalaraja, R. V.

    2018-05-01

    The copper foam is an interesting field of research because of its several advantages as an engineering material. Powder metallurgy presents an alternative route to obtain a porous structure with high strength to weight ratio and functional properties. The viability of processing copper foam separately with two different space-holders such as ammonium hydrogen carbonate (NH4HCO3) and sodium chloride (NaCl) of 50 vol% was studied. The green compacts obtained under 200 MPa were sintered at different cycles for the complete removal of space-holder. The sintered foams were characterized by optical microscopy (OM), scanning electron microscopy (SEM) and uniaxial testing machine (UTM) to study their structural features and compressive strength, respectively. The results showed that NaCl particles were the best alternative to obtain a porous structure, hence two different sizes (1 and 0.01 μm) of alumina (Al2O3) particles with 2, 4 and 6 vol% were used to fabricate copper foams. As a result, a bimodal structure consisting of macro and micropores with a highly interconnected porosity was achieved. In addition, the smaller size alumina particles promoted a higher density of pores, however, the compressive strength was reduced for the higher volume fraction of alumina particles.

  17. Preparation and characterization of 6-layered functionally graded nickel-alumina (Ni-Al2O3) composites

    Science.gov (United States)

    Latiff, M. I. A.; Nuruzzaman, D. M.; Basri, S.; Ismail, N. M.; Jamaludin, S. N. S.; Kamaruzaman, F. F.

    2018-04-01

    The present research study deals with the preparation of 6-layered functionally graded (FG) metal-ceramic composite materials through powder metallurgy technique. Using a cylindrical die-punch set made of steel, the nickel-alumina (Ni-Al2O3) graded composite structure was fabricated. The samples consist of four gradual inter layers of varied nickel composition (80wt.%, 60wt.%, 40wt.%, 20wt.%) sandwiched with pure Ni and Al2O3 powders at the ends (100wt.% and 0wt.% nickel) were fabricated under 30 ton compaction load using a hydraulic press. After that, two-step sintering was carried out at sintering temperature 1200ºC and soaking time 3 hours was maintained in a tube furnace. The properties of the prepared samples were characterized by radial shrinkage, optical microscopy and hardness testing. Results showed that larger shrinkage occurred within the ceramic phase which proves that more porosities were eliminated in the ceramic rich layers. From the microstructural analysis, it was observed that alumina particles are almost uniformly distributed in nickel matrix, so as nickel particles in the ceramic matrix of alumina-dominant layers. From interfacial analyses, it was observed that a smooth transition in microstructure from one layer to the next confirms a good interfacial solid state bonding between metal-ceramic constituents and good compaction process. On the other hand, microhardness test results suggest that there might be increasing percentage of porosities in the graded structure as the ceramic content rises.

  18. An investigation on the compressibility of aluminum/nano-alumina composite powder prepared by blending and mechanical milling

    International Nuclear Information System (INIS)

    Razavi Hesabi, Z.; Hafizpour, H.R.; Simchi, A.

    2007-01-01

    The densification response of aluminum powder reinforced with 5 vol.% nanometric alumina particles (35 nm) during uniaxial compaction in a rigid die was studied. The composite powder was prepared by blending and mechanical milling procedures. To determine the effect of the reinforcement nanoparticles on the compressibility of aluminum powder, monolithic Al powder, i.e. without the addition of alumina, was also examined. It was shown that at the early stage of compaction when the rearrangement of particles is the dominant mechanism of the densification, disintegration of the nanoparticle clusters and agglomerates under the applied load contributes in the densification of the composite powder prepared by blending method. As the compaction pressure increases, however, the load partitioning effect of the nanoparticles decreases the densification rate of the powder mixture, resulting in a lower density compared to the monolithic aluminum. It was also shown that mechanical milling significantly impacts the compressibility of the unreinforced and reinforced aluminum powders. Morphological changes of the particles upon milling increase the contribution of particle rearrangement in densification whilst the plastic deformation mechanism is significantly retarded due to the work-hardening effect of the milling process. Meanwhile, the distribution of alumina nanoparticles is improved by mechanical milling, which in fact, affects the compressibility of the composite powder. This paper addresses the effect of mechanical milling and reinforcement nanoparticles on the compressibility of aluminum powder

  19. Investigating the effect of sputtering conditions on the physical properties of aluminum thin film and the resulting alumina template

    Science.gov (United States)

    Taheriniya, Shabnam; Parhizgar, Sara Sadat; Sari, Amir Hossein

    2018-06-01

    To study the alumina template pore size distribution as a function of Al thin film grain size distribution, porous alumina templates were prepared by anodizing sputtered aluminum thin films. To control the grain size the aluminum samples were sputtered with the rate of 0.5, 1 and 2 Å/s and the substrate temperature was either 25, 75 or 125 °C. All samples were anodized for 120 s in 1 M sulfuric acid solution kept at 1 °C while a 15 V potential was being applied. The standard deviation value for samples deposited at room temperature but with different rates is roughly 2 nm in both thin film and porous template form but it rises to approximately 4 nm with substrate temperature. Samples with the average grain size of 13, 14, 18.5 and 21 nm respectively produce alumina templates with an average pore size of 8.5, 10, 15 and 16 nm in that order which shows the average grain size limits the average pore diameter in the resulting template. Lateral correlation length and grain boundary effect are other factors that affect the pore formation process and pore size distribution by limiting the initial current density.

  20. Corrosion performance of atmospheric plasma sprayed alumina coatings on AZ31B magnesium alloy under immersion environment

    Directory of Open Access Journals (Sweden)

    D. Thirumalaikumarasamy

    2014-12-01

    Full Text Available Plasma sprayed ceramic coatings are successfully used in many industrial applications, where high wear and corrosion resistance with thermal insulation are required. The alumina powders were plasma sprayed on AZ31B magnesium alloy with three different plasma spraying parameters. In the present work, the influence of plasma spray parameters on the corrosion behavior of the coatings was investigated. The corrosion behavior of the coated samples was evaluated by immersion corrosion test in 3.5 wt% NaCl solution. Empirical relationship was established to predict the corrosion rate of plasma sprayed alumina coatings by incorporating process parameters. The experiments were conducted based on a three factor, five-level, central composite rotatable design matrix. The developed relationship can be effectively used to predict the corrosion rate of alumina coatings at 95% confidence level. The results indicate that the input power has the greatest influence on corrosion rate, followed by stand-off distance and powder feed rate.

  1. Low-temperature α-alumina thin film growth: ab initio studies of Al adatom surface migration

    International Nuclear Information System (INIS)

    Wallin, E; Helmersson, U; Muenger, E P; Chirita, V

    2009-01-01

    Investigations of activation energy barriers for Al surface hopping on α-Al 2 O 3 (0 0 0 1) surfaces have been carried out by means of first-principles density functional theory calculations and the nudged elastic band method. Results show that surface diffusion on the (most stable) Al-terminated surface is relatively fast with an energy barrier of 0.75 eV, whereas Al hopping on the O-terminated surface is slower, with barriers for jumps from the two metastable positions existing on this surface to the stable site of 0.31 and 0.99 eV. Based on this study and on the literature, the governing mechanisms during low-temperature α-alumina thin film growth are summarized and discussed. Our results support suggestions made in some previous experimental studies, pointing out that limited surface diffusivity is not the main obstacle for α-alumina growth at low-to-moderate temperatures, and that other effects should primarily be considered when designing novel processes for low-temperature α-alumina deposition.

  2. The removal of Tartrazine dye by modified Alumina with sodium dodecyl sulfate from aqueous solutions: equilibrium and thermodynamic studies

    Directory of Open Access Journals (Sweden)

    A. Parchebaf Jadid

    2017-11-01

    Full Text Available Edible colors are materials which in the case of adding to food and drinks cause transferring color to them. Most of these colors are not acceptable in terms of applying in human food and underlies various diseases like gastrointestinal disorders, renal, liver and blood toxicity. The goal of this study was investigating the efficiency of improved alumina by sodium dodecyl sulfate (SDS in eliminating Tartrazine from aqueous environments. In this research, the impact of effective parameters such as initial concentration of Tartrazine, time, pH, alumina dose and SDS value were studied in order to approach an optimal condition for eliminating the color. Also, absorption behavior was evaluated by Freundlich and Langmuir isotherms. The highest efficiency of Tartrazine elimination in the solution resulted in optimal pH of 2, the amount of adsorbent 1.5 g/L, 16 min duration and value 0.04 SDS g/l which was obtained for dye concentration 5 mg/L about 94.13%. Also, results suggested that Tartrazine absorption follows Langmuir isotherm (R2 = 0.9867. Obtained results from thermodynamic studies such as Gibbs free energy (-5.728 Kj/mol and enthalpy (-85.86 Kj/mol and entropy (-271.102 J/mol.K also suggested that the absorption process was exothermic. The results of this research suggested that improved alumina by sodium dodecyl sulfate had a relative good capability in Tartrazine elimination from aqueous environments. Thus

  3. Near-field radiative heat transfer in mesoporous alumina

    International Nuclear Information System (INIS)

    Li Jing; Feng Yan-Hui; Zhang Xin-Xin; Huang Cong-Liang; Wang Ge

    2015-01-01

    The thermal conductivity of mesoporous material has aroused the great interest of scholars due to its wide applications such as insulation, catalyst, etc. Mesoporous alumina substrate consists of uniformly distributed, unconnected cylindrical pores. Near-field radiative heat transfer cannot be ignored, when the diameters of the pores are less than the characteristic wavelength of thermal radiation. In this paper, near-field radiation across a cylindrical pore is simulated by employing the fluctuation dissipation theorem and Green function. Such factors as the diameter of the pore, and the temperature of the material are further analyzed. The research results show that the radiative heat transfer on a mesoscale is 2∼4 orders higher than on a macroscale. The heat flux and equivalent thermal conductivity of radiation across a cylindrical pore decrease exponentially with pore diameter increasing, while increase with temperature increasing. The calculated equivalent thermal conductivity of radiation is further developed to modify the thermal conductivity of the mesoporous alumina. The combined thermal conductivity of the mesoporous alumina is obtained by using porosity weighted dilute medium and compared with the measurement. The combined thermal conductivity of mesoporous silica decreases gradually with pore diameter increasing, while increases smoothly with temperature increasing, which is in good agreement with the experimental data. The larger the porosity, the more significant the near-field effect is, which cannot be ignored. (paper)

  4. Nanocarbon-Coated Porous Anodic Alumina for Bionic Devices

    Directory of Open Access Journals (Sweden)

    Morteza Aramesh

    2015-08-01

    Full Text Available A highly-stable and biocompatible nanoporous electrode is demonstrated herein. The electrode is based on a porous anodic alumina which is conformally coated with an ultra-thin layer of diamond-like carbon. The nanocarbon coating plays an essential role for the chemical stability and biocompatibility of the electrodes; thus, the coated electrodes are ideally suited for biomedical applications. The corrosion resistance of the proposed electrodes was tested under extreme chemical conditions, such as in boiling acidic/alkali environments. The nanostructured morphology and the surface chemistry of the electrodes were maintained after wet/dry chemical corrosion tests. The non-cytotoxicity of the electrodes was tested by standard toxicity tests using mouse fibroblasts and cortical neurons. Furthermore, the cell–electrode interaction of cortical neurons with nanocarbon coated nanoporous anodic alumina was studied in vitro. Cortical neurons were found to attach and spread to the nanocarbon coated electrodes without using additional biomolecules, whilst no cell attachment was observed on the surface of the bare anodic alumina. Neurite growth appeared to be sensitive to nanotopographical features of the electrodes. The proposed electrodes show a great promise for practical applications such as retinal prostheses and bionic implants in general.

  5. Dielectric properties of alumina/zirconia composites at millimeter wavelengths

    International Nuclear Information System (INIS)

    Molla, J.; Heidinger, R.; Ibarra, A.; Link, G.

    1994-01-01

    Alumina-zirconia composites with ZrO 2 contents up to 20% and negligible porosity were investigated at millimeter (mm) wavelengths to determine the changes appearing in the dielectric properties of pure alumina ceramics when unstabilized or partially stabilized ZrO 2 is added to improve the mechanical strength. It is demonstrated that it essential to distinguish between the contributions of the monoclinic and the tetragonal phase of zirconia (m-ZrO 2 , t-ZrO 2 ). Permittivity is raised with increasing content of either phases; the effective permittivity can be assessed by the rule of mixtures (Maxwell-Garnett formulation of the generalized Clasussius-Mossotti relation) using permittivity values of 10 for Al 2 O 3 , 14-21 for m-ZrO 2 and 40-45 for t-ZrO 2 . The permittivity data show only a small variation in the investigated range of 9-145 GHz. For the dielectric loss, there is evidence of a predominant contribution of m-ZrO 2 ; in addition, the marked increase in loss with frequency becomes sharper. The t-ZrO 2 , which is responsible for strengthening, does not show any significant influence on losses. It is therefore concluded, that ZrO 2 strengthening of alumina is feasible without affecting mm-wave losses at room temperature as long as the presence of m-ZrO 2 is avoided

  6. Synthesis of zeolite membrane (Y / α-alumina)

    International Nuclear Information System (INIS)

    Araujo, Ana Paula; Silva, Valmir Jose da; Crispin, Alana Carolyne; Rodrigues, Meiry Glaucia F.; Menezes, Romualdo R.

    2009-01-01

    The general aim of this study was to develop materials of the type: Y zeolite (hydrothermal synthesis), ceramic support (forming of powder) and zeolite membrane (rubbing). The preparation of the Y zeolite was conducted in accordance with the hydrothermal synthesis method, the time of crystallization was one day. The ceramic support was prepared by means of the forming of powder technique and subsequently subjected to sintering at a temperature of 1400 deg C/1h. The zeolite membrane (Y/α- alumina) was prepared by secondary growth method (rubbing). These materials were characterized by XRD and SEM. Obtaining Y zeolite could be confirmed by X ray diffractograms. From the images obtained by SEM, it was possible to derive from analysis that the Y zeolite is composed of a homogeneous morphology, where the particles are crowded, with uniform size. The results obtained for the ceramic support (α-alumina) showed that it displays characteristics peaks of aluminum oxide. By using micrographs it was possible to observe a heterogeneous microstructure with a compact form, without cracks upon the layers. According to the XRD, for the method of secondary growth (rubbing), it was observed that the Y zeolite which had been synthesized on the ceramic support displayed a crystalline structure. The micrography of the zeolite membrane (Y/α-alumina) showed the formation of a layer of zeolite on the ceramic support. (author)

  7. Investigation of vapor explosions with alumina droplets in sodium

    International Nuclear Information System (INIS)

    Zimmer, H.J.

    1991-02-01

    Within the analysis of severe hypothetical fast breeder accidents the consequence of a fuel-coolant interaction has to be considered i.e. the thermal interaction between hot molten fuel and sodium. Experiments have been performed to study the thermal fragmentation of a molten alumina droplet in sodium. Alumina temperatures up to 3100 K and sodium temperatures up to 1143 K were used. For the first time film boiling of alumina drops in sodium was achieved. With some droplets undergoing film boiling, the fragmentation was triggered by an externally applied pressure wave. The trigger was followed promptly by a strong reaction pressure wave if and only if a contact temperature threshold of T I =2060±160 K was exceeded. In agreement with similar experiments in which other materials were studied this threshold corresponds to an interfacial temperature close to the homogeneous nucleation temperature of the vaporising liquid. Based on the present and previous experimental results a model concept of thermal fragmentation is developed. (orig.) [de

  8. Intermetallic Strengthened Alumina-Forming Austenitic Steels for Energy Applications

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Bin [Dartmouth College, Hanover, NH (United States); Baker, Ian [Dartmouth College, Hanover, NH (United States)

    2016-03-31

    In order to achieve energy conversion efficiencies of >50 % for steam turbines/boilers in power generation systems, the materials required must be strong, corrosion-resistant at high temperatures (>700°C), and economically viable. Austenitic steels strengthened with Laves phase and L12 precipitates, and alloyed with aluminum to improve oxidation resistance, are potential candidate materials for these applications. The creep resistance of these alloys is significantly improved through intermetallic strengthening (Laves-Fe2Nb + L12-Ni3Al precipitates) without harmful effects on oxidation resistance. Microstructural and microchemical analyses of the recently developed alumina-forming austenitic (AFA) steels (Fe-14Cr-32Ni-3Nb-3Al-2Ti-based) indicated they are strengthened by Ni3Al(Ti) L12, NiAl B2, Fe2Nb Laves phase and MC carbide precipitates. Different thermomechanical treatments (TMTs) were performed on these stainless steels in an attempt to further improve their mechanical properties. The thermo-mechanical processing produced nanocrystalline grains in AFA alloys and dramatically increased their yield strength at room temperature. Unfortunately, the TMTs didn’t increase the yield strengths of AFA alloys at ≥700ºC. At these temperatures, dislocation climb is the dominant mechanism for deformation of TMT alloys according to strain rate jump tests. After the characterization of aged AFA alloys, we found that the largest strengthening effect from L12 precipitates can be obtained by aging for less than 24 h. The coarsening behavior of the L12 precipitates was not influenced by carbon and boron additions. Failure analysis and post-mortem TEM analysis were performed to study the creep failure mechanisms of these AFA steels after creep tests. Though the Laves and B2-NiAl phase precipitated along the boundaries can improve the creep properties, cracks were

  9. Understanding improved osteoblast behavior on select nanoporous anodic alumina

    Directory of Open Access Journals (Sweden)

    Ni S

    2014-07-01

    Full Text Available Siyu Ni,1 Changyan Li,1 Shirong Ni,2 Ting Chen,1 Thomas J Webster3,4 1College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, Shanghai, People’s Republic of China; 2Department of Pathophysiology, Wenzhou Medical University, Wenzhou, People’s Republic of China; 3Department of Chemical Engineering, College of Engineering, Northeastern University, Boston, MA, USA; 4Center of Excellence for Advanced Materials Research, King Abdulaziz University, Jeddah, Saudi Arabia Abstract: The aim of this study was to prepare different sized porous anodic alumina (PAA and examine preosteoblast (MC3T3-E1 attachment and proliferation on such nanoporous surfaces. In this study, PAA with tunable pore sizes (25 nm, 50 nm, and 75 nm were fabricated by a two-step anodizing procedure in oxalic acid. The surface morphology and elemental composition of PAA were characterized by field emission scanning electron microscopy and X-ray photoelectron spectroscopy analysis. The nanopore arrays on all of the PAA samples were highly regular. X-ray photoelectron spectroscopy analysis suggested that the chemistry of PAA and flat aluminum surfaces were similar. However, contact angles were significantly greater on all of the PAA compared to flat aluminum substrates, which consequently altered protein adsorption profiles. The attachment and proliferation of preosteoblasts were determined for up to 7 days in culture using field emission scanning electron microscopy and a Cell Counting Kit-8. Results showed that nanoporous surfaces did not enhance initial preosteoblast attachment, whereas preosteoblast proliferation dramatically increased when the PAA pore size was either 50 nm or 75 nm compared to all other samples (P<0.05. Thus, this study showed that one can alter surface energy of aluminum by modifying surface nano-roughness alone (and not changing chemistry through an anodization process to improve osteoblast density, and, thus, should be

  10. Simulator of Non-homogenous Alumina and Current Distribution in an Aluminum Electrolysis Cell to Predict Low-Voltage Anode Effects

    Science.gov (United States)

    Dion, Lukas; Kiss, László I.; Poncsák, Sándor; Lagacé, Charles-Luc

    2018-04-01

    Perfluorocarbons are important contributors to aluminum production greenhouse gas inventories. Tetrafluoromethane and hexafluoroethane are produced in the electrolysis process when a harmful event called anode effect occurs in the cell. This incident is strongly related to the lack of alumina and the current distribution in the cell and can be classified into two categories: high-voltage and low-voltage anode effects. The latter is hard to detect during the normal electrolysis process and, therefore, new tools are necessary to predict this event and minimize its occurrence. This paper discusses a new approach to model the alumina distribution behavior in an electrolysis cell by dividing the electrolytic bath into non-homogenous concentration zones using discrete elements. The different mechanisms related to the alumina distribution are discussed in detail. Moreover, with a detailed electrical model, it is possible to calculate the current distribution among the different anodic assemblies. With this information, the model can evaluate if low-voltage emissions are likely to be present under the simulated conditions. Using the simulator will help the understanding of the role of the alumina distribution which, in turn, will improve the cell energy consumption and stability while reducing the occurrence of high- and low-voltage anode effects.

  11. A Study on the Effect of Nano Alumina Particles on Fracture Behavior of PMMA

    Directory of Open Access Journals (Sweden)

    Arezou Sezavar

    2015-04-01

    Full Text Available In the current research, the role of nano-sized alumina on deformation and fracture mechanism of Poly Methyl Methacrylate (PMMA was investigated. For this purpose, PMMA matrix nanocomposite reinforced with different wt% of alumina (i.e., 5, 10 and 15 were fabricated using the compression molding technique. Tensile properties of produced nanocomposites were studied using Zwick Z250 apparatus at cross head speed of about 5 mm/min. In order to specify the role of alumina nanoparticles on deformation and fracture mechanism of PMMA, microscopic evaluation was performed using scanning electron microscope (SEM. The achieved results prove that tensile properties of PMMA depend on alumina wt%. For example, addition of 15 wt% alumina to PMMA causes an increase of about 25% modulus of elasticity. Micrographs taken from the fracture surface of PMMA and its nanocomposites show deformation and fracture mechanism of PMMA changes as alumina is added to it.

  12. Deuterium permeation of amorphous alumina coating on 316L prepared by MOCVD

    Science.gov (United States)

    Li, Shuai; He, Di; Liu, Xiaopeng; Wang, Shumao; Jiang, Lijun

    2012-01-01

    The deuterium permeation behavior of the alumina coating on 316L stainless steel prepared by metal organic chemical vapor deposition (MOCVD) was investigated. The alumina coating was also characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscope (SEM). It was found that the as-prepared coating consisted of amorphous alumina. This alumina coating had a dense, crack-free and homogeneous morphology. Although the alumina coating was amorphous, effective suppression of deuterium permeation was demonstrated. The deuterium permeability of the alumina coating was 51-60 times less than that of the 316L stainless steel and 153-335 times less than that of the referred low activation martensitic steels at 860-960 K.

  13. Role of Metal Oxides in Chemical Evolution: Interaction of Ribose Nucleotides with Alumina

    Science.gov (United States)

    Arora, Avnish Kumar; Kamaluddin

    2009-03-01

    Interaction of ribonucleotides—namely, 5‧-AMP, 5‧-GMP, 5‧-CMP, and 5‧-UMP—with acidic, neutral, and basic alumina has been studied. Purine nucleotides showed higher adsorption on alumina in comparison with pyrimidine nucleotides under acidic conditions. Adsorption data obtained followed Langmuir adsorption isotherm, and Xm and KL values were calculated. On the basis of infrared spectral studies of ribonucleotides, alumina, and ribonucleotide-alumina adducts, we propose that the nitrogen base and phosphate moiety of the ribonucleotides interact with the positive charge surface of alumina. Results of the present study may indicate the importance of alumina in concentrating organic molecules from dilute aqueous solutions in primeval seas in the course of chemical evolution on Earth.

  14. Experimental research on HEL and failure properties of alumina under impact loading

    Directory of Open Access Journals (Sweden)

    Xiao-wei Feng

    2016-06-01

    Full Text Available A series of plate impact experiments on alumina was conducted using a light gas gun in order to further investigate Hugoniot elastic limit (HEL and failure properties of alumina under shock compression. The velocity interferometer system for any reflector (VISAR was used to record the rear-free surface velocity histories of the alumina samples. According to the experimental results, the HELs of tested alumina samples with different thicknesses were measured, and the decay phenomenon of elastic wave in shocked alumina was studied. A phenomenological expression between HEL and thickness of sample was presented, and the causes of the decay phenomenon were discussed. The propagation of failure wave in shocked alumina was probed. The velocity and delayed time of failure wave propagation were obtained. The physical mechanism of the generation and propagation of failure was further discussed.

  15. Heterogeneous burnable poisons. Sinterability study in oxidizing atmosphere of alumina-gadolinia and alumina-boron carbide compounds

    International Nuclear Information System (INIS)

    Agueda, H.C.; Leiva, S.F.; Russo, D.O.

    1990-01-01

    Solid burnable poisons are used in reactors cooled by pressure light water (PLWR) with the purpose of controlling initial reactivity in the first reactor's core. The burnable poisons may be uniformly mixed with the fuel -known as 'homogeneous' poisons-; or constituting separate elements -known as heterogeneous poisons-. The purpose of this work is to present the results of two sinterability studies, performed on Al 2 O 3 -Gd 2 O 3 and Al 2 O 3 -B 4 C, where alumina acts as inert matrix, storing the absorbing elements as Gd 2 O 3 or B 4 C. The elements were sintered at an air atmosphere and additives permitting the obtention of a greater density alumina were tested at lower temperatures than the characteristic for this material, in order to determine its compatibility with the materials dealt with herein. (Author) [es

  16. Fabrication of a novel aluminum surface covered by numerous high-aspect-ratio anodic alumina nanofibers

    OpenAIRE

    Nakajima, Daiki; Kikuchi, Tatsuya; Natsui, Shungo; Sakaguchi, Norihito; Suzuki, Ryosuke O.

    2015-01-01

    The formation behavior of anodic alumina nanofibers via anodizing in a concentrated pyrophosphoric acid under various conditions was investigated using electrochemical measurements and SEM/TEM observations. Pyrophosphoric acid anodizing at 293 K resulted in the formation of numerous anodic alumina nanofibers on an aluminum substrate through a thin barrier oxide and honeycomb oxide with narrow walls. However, long-term anodizing led to the chemical dissolution of the alumina nanofibers. The de...

  17. Removal of Arsenic from Drinking Water Using Modified Activated Alumina

    Directory of Open Access Journals (Sweden)

    Mohammad Mosaferi

    2005-09-01

    Full Text Available Considering contamination of drinking water to arsenic in some villages ofIran. In order to develop a simple method for household water treatment in rural areas, efficiency of  modified activated alumina with iron compounds- a product of Alcan Company with trade name of AAFS-50- was studied Equilibrium batch experiments were carried out using shaker incubator and arsenic was analyzed with SDDC method. Effects of initial concentration of arsenic, adsorbent dose, oxidation state of arsenic, pH and oxidation with chlorine on adsorption were studied. Correlation coefficient of Freundlich and Laungmuier  isotherms  for As(V and As(III were 0.964 , 0.991 and 0.970, 0.978 respectively . These results show that adsorption of arsenic on modified activated alumina is compatible with both models specially Laungmuier models. Removal efficiency of As(V at 0.5 ,1 and 2 hr increased with doubling the adsorbent dose from 44.8 to 72%, 69.6 to 90.8 and 92.4 to 98% ; respectively. Experiments using different concentrations of arsenic showed that adsorption of arsenic on activated alumina are a first order reaction that is, rate of reaction is dependent on intial; concentration of arsenic. Removal efficiency for concentration of 0.250 mg/L of arsenic, with increasing of reaction time from 15 min to 60 min, increased 1.54 times and reached from 61% to 94%. During 2hrs, removal of As(V and As(III were 96% and 16% respectively. Using 1.5 mg/L Chlorine as oxidant agent, removal of As(III was increased to 94%. In the case of pH effect, rate of adsorption increased for arsenite, with increasing of pH to 8 and decreased with more increasing, so that adsorption at pH 14 was equal to pH 2. For arsenate, the most adsorption was observed at pH between 6 to 8 . These results show that by using the studied activated alumina, there will not be need for adjustment of pH and the activated alumina used in this study could have application as a safe adsorbent for removal of

  18. Laser-induced reaction alumina coating on ceramic composite

    Science.gov (United States)

    Xiao, Chenghe

    Silicon carbide ceramics are susceptible to corrosion by certain industrial furnace environments. It is also true for a new class of silicon carbide-particulate reinforced alumina-matrix composite (SiCsb(P)Alsb2Osb3) since it contains more than 55% of SiC particulate within the composite. This behavior would limit the use of SiCsb(P)Alsb2Osb3 composites in ceramic heat exchangers. Because oxide ceramics corrode substantially less in the same environments, a laser-induced reaction alumina coating technique has been developed for improving corrosion resistance of the SiCsb(P)Alsb2Osb3 composite. Specimens with and without the laser-induced reaction alumina coating were subjected to corrosion testing at 1200sp°C in an air atmosphere containing Nasb2COsb3 for 50 ˜ 200 hours. Corroded specimens were characterized via x-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectrometer (EDS). The uncoated SiCsbP/Alsb2Osb3 composite samples experienced an initial increase in weight during the exposure to Nasb2COsb3 at 1200sp°C due to the oxidation of residual aluminum metal in the composite. There was no significant weight change difference experienced during exposure times between 50 and 200 hours. The oxidation layer formed on the as-received composite surface consisted of Si and Alsb2Osb3 (after washing with a HF solution). The oxidation layer grew outward and inward from the original surface of the composite. The growth rate in the outward direction was faster than in the inward direction. The formation of the Si/Alsb2Osb3 oxidation layer on the as-received composite was nonuniform, and localized corrosion was observed. The coated samples experienced very little mass increase. The laser-induced reaction alumina coating effectively provided protection for the SiCsbP/Alsb2Osb3 composite by keeping the corrodents from contacting the composite and by the formation of some refractory compounds such as Nasb2OAlsb2Osb3SiOsb2 and Nasb2Alsb{22}Osb

  19. Highly fluorescent silver nanoclusters in alumina-silica composite optical fiber

    Energy Technology Data Exchange (ETDEWEB)

    Halder, A.; Chattopadhyay, R.; Majumder, S.; Paul, M. C.; Das, S.; Bhadra, S. K., E-mail: skbhadra@cgcri.res.in [Fiber Optics and Photonics Division, CSIR-Central Glass and Ceramic Research Institute, 196, Raja S. C. Mullick Road, Kolkata 700032 (India); Bysakh, S.; Unnikrishnan, M. [Material Characterization Division, CSIR-Central Glass and Ceramic Research Institute, 196, Raja S. C. Mullick Road, Kolkata 700032 (India)

    2015-01-05

    An efficient visible fluorescent optical fiber embedded with silver nanoclusters (Ag-NCs) having size ∼1 nm, uniformly distributed in alumina-silica composite core glass, is reported. Fibers are fabricated in a repetitive controlled way through modified chemical vapour deposition process associated with solution doping technique. Fibers are drawn from the transparent preforms by conventional fiber drawing process. Structural characteristics of the doped fibers are studied using transmission electron microscopy and electron probe micro analysis. The oxidation state of Ag within Ag-NCs is investigated by X-ray photo electron spectroscopy. The observed significant fluorescence of the metal clusters in fabricated fibers is correlated with electronic model. The experimentally observed size dependent absorption of the metal clusters in fabricated fibers is explained with the help of reported results calculated by ab-initio density functional theory. These optical fibers may open up an opportunity of realizing tunable wavelength fiber laser without the help of rare earth elements.

  20. Low-pressure injection molding of alumina ceramics using a carnauba wax binder: preliminary results

    Energy Technology Data Exchange (ETDEWEB)

    Quevedo Nogueira, R.E.F.; Bezerra, A.C.; Santos, F.C. dos [Dept. de Engenharia Mecanica, Centro de Tecnologia-UFC, Fortaleza, CE (Brazil); Sousa, M.R. de; Acchar, W. [Dept. de Engenharia Mecanica, Univ. Federal do Rio Grande do Norte, UFRN-Campus Univ., Natal, RN (Brazil)

    2001-07-01

    Carnauba wax, a natural product from Northeastern Brazil, has found application in the processing of ceramics. However, the use of pure carnauba wax is not recommended due to its narrow melting range and poor mechanical properties. In the present work carnauba wax based organic vehicles with the addition of low-density polyethylene and stearic acid were developed for use in the low-pressure injection molding of alumina ceramics. Viscosimetric testing was employed for the determination of optimal composition of the organic vehicle. The optimal content of ceramic powder in the mixture was also determined. All the materials used are easily available in the Brazilian market. A simple ceramic part was injected at low pressures (0.6 MPa) using a semi-automatic injection molding machine. For this purpose a double cavity mold was designed and built. Preliminary results demonstrate the technical viability of the process using the organic vehicle developed. (orig.)

  1. Thermally induced structural evolution and performance of mesoporous block copolymer-directed alumina perovskite solar cells.

    KAUST Repository

    Tan, Kwan Wee

    2014-04-11

    Structure control in solution-processed hybrid perovskites is crucial to design and fabricate highly efficient solar cells. Here, we utilize in situ grazing incidence wide-angle X-ray scattering and scanning electron microscopy to investigate the structural evolution and film morphologies of methylammonium lead tri-iodide/chloride (CH3NH3PbI(3-x)Cl(x)) in mesoporous block copolymer derived alumina superstructures during thermal annealing. We show the CH3NH3PbI(3-x)Cl(x) material evolution to be characterized by three distinct structures: a crystalline precursor structure not described previously, a 3D perovskite structure, and a mixture of compounds resulting from degradation. Finally, we demonstrate how understanding the processing parameters provides the foundation needed for optimal perovskite film morphology and coverage, leading to enhanced block copolymer-directed perovskite solar cell performance.

  2. Thermally induced structural evolution and performance of mesoporous block copolymer-directed alumina perovskite solar cells.

    KAUST Repository

    Tan, Kwan Wee; Moore, David T; Saliba, Michael; Sai, Hiroaki; Estroff, Lara A; Hanrath, Tobias; Snaith, Henry J; Wiesner, Ulrich

    2014-01-01

    Structure control in solution-processed hybrid perovskites is crucial to design and fabricate highly efficient solar cells. Here, we utilize in situ grazing incidence wide-angle X-ray scattering and scanning electron microscopy to investigate the structural evolution and film morphologies of methylammonium lead tri-iodide/chloride (CH3NH3PbI(3-x)Cl(x)) in mesoporous block copolymer derived alumina superstructures during thermal annealing. We show the CH3NH3PbI(3-x)Cl(x) material evolution to be characterized by three distinct structures: a crystalline precursor structure not described previously, a 3D perovskite structure, and a mixture of compounds resulting from degradation. Finally, we demonstrate how understanding the processing parameters provides the foundation needed for optimal perovskite film morphology and coverage, leading to enhanced block copolymer-directed perovskite solar cell performance.

  3. The Conversion and Sustainable Use of Alumina Refinery Residues: Global Solution Examples

    Science.gov (United States)

    Fergusson, Lee

    This paper introduces current industry best practice for the conversion of alumina refinery residues (or "red mud") from hazardous waste to benign, inert material. The paper will examine four neutralization methods and Basecon Technology, a sustainable conversion process. The paper will consider ways through which this converted material can be combined and processed for sustainable applications in the treatment of hazardous waste streams (such as industrial wastewater and sludges, biosolids, and CCA wastes), contaminated brownfield sites, and mine site wastes. Recent discoveries and applications, such as the successful treatment of high levels of radium in drinking water in the USA, will also be discussed. Examples of global solutions and their technical merits will be assessed.

  4. Thermally Induced Structural Evolution and Performance of Mesoporous Block Copolymer-Directed Alumina Perovskite Solar Cells

    Science.gov (United States)

    2015-01-01

    Structure control in solution-processed hybrid perovskites is crucial to design and fabricate highly efficient solar cells. Here, we utilize in situ grazing incidence wide-angle X-ray scattering and scanning electron microscopy to investigate the structural evolution and film morphologies of methylammonium lead tri-iodide/chloride (CH3NH3PbI3–xClx) in mesoporous block copolymer derived alumina superstructures during thermal annealing. We show the CH3NH3PbI3–xClx material evolution to be characterized by three distinct structures: a crystalline precursor structure not described previously, a 3D perovskite structure, and a mixture of compounds resulting from degradation. Finally, we demonstrate how understanding the processing parameters provides the foundation needed for optimal perovskite film morphology and coverage, leading to enhanced block copolymer-directed perovskite solar cell performance. PMID:24684494

  5. Absorption of Ethylene on Membranes Containing Potassium Permanganate Loaded into Alumina-Nanoparticle-Incorporated Alumina/Carbon Nanofibers.

    Science.gov (United States)

    Tirgar, Ashkan; Han, Daewoo; Steckl, Andrew J

    2018-06-06

    Ethylene is a natural aging hormone in plants, and controlling its concentration has long been a subject of research aimed at reducing wastage during packaging, transport, and storage. We report on packaging membranes, produced by electrospinning, that act as efficient carriers for potassium permanganate (PPM), a widely used ethylene oxidant. PPM salt loaded on membranes composed of alumina nanofibers incorporating alumina nanoparticles outperform other absorber systems and oxidize up to 73% of ethylene within 25 min. Membrane absorption of ethylene generated by avocados was totally quenched in 21 h, and a nearly zero ethylene concentration was observed for more than 5 days. By comparison, the control experiments exhibited a concentration of 53% of the initial value after 21 h and 31% on day 5. A high surface area of the alumina nanofiber membranes provides high capacity for ethylene absorption over a long period of time. In combination with other properties, such as planar form, flexibility, ease of handling, and lightweight, these membranes are a highly desirable component of packaging materials engineered to enhance product lifetime.

  6. Viscosity of aqueous and cyanate ester suspensions containing alumina nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Lawler, Katherine [Iowa State Univ., Ames, IA (United States)

    2009-01-01

    The viscosities of both aqueous and cyanate ester monomer (BECy) based suspensions of alumina nanoparticle were studied. The applications for these suspensions are different: aqueous suspensions of alumina nanoparticles are used in the production of technical ceramics made by slip casting or tape casting, and the BECy based suspensions are being developed for use in an injection-type composite repair resin. In the case of aqueous suspensions, it is advantageous to achieve a high solids content with low viscosity in order to produce a high quality product. The addition of a dispersant is useful so that higher solids content suspensions can be used with lower viscosities. For BECy suspensions, the addition of nanoparticles to the BECy resin is expected to enhance the mechanical properties of the cured composite. The addition of saccharides to aqueous suspensions leads to viscosity reduction. Through DSC measurements it was found that the saccharide molecules formed a solution with water and this resulted in lowering the melting temperature of the free water according to classic freezing point depression. Saccharides also lowered the melting temperature of the bound water, but this followed a different rule. The shear thinning and melting behaviors of the suspensions were used to develop a model based on fractal-type agglomeration. It is believed that the structure of the particle flocs in these suspensions changes with the addition of saccharides which leads to the resultant viscosity decrease. The viscosity of the BECy suspensions increased with solids content, and the viscosity increase was greater than predicted by the classical Einstein equation for dilute suspensions. Instead, the Mooney equation fits the viscosity behavior well from 0-20 vol% solids. The viscosity reduction achieved at high particle loadings by the addition of benzoic acid was also investigated by NMR. It appears that the benzoic acid interacts with the surface of the alumina particle which may

  7. Reduction in Friction and Wear of Alumina Surfaces as Assisted with Surface-Adsorbing Polymers in Aqueous Solutions

    DEFF Research Database (Denmark)

    Røn, Troels; Lee, Seunghwan

    2016-01-01

    We have investigated the aqueous lubricating effects of various polymers for the sliding contacts of self-mated alumina surfaces in neutral aqueous environment. Given that isoelectric point (IEP) of alumina is ca. pH 9, polyanions can readily adsorb onto alumina surface at neutral pH via electros......We have investigated the aqueous lubricating effects of various polymers for the sliding contacts of self-mated alumina surfaces in neutral aqueous environment. Given that isoelectric point (IEP) of alumina is ca. pH 9, polyanions can readily adsorb onto alumina surface at neutral pH via...

  8. The effect of alumina nanofillers size and shape on mechanical behavior of PMMA matrix composite

    Directory of Open Access Journals (Sweden)

    Ben Hasan Somaya Ahmed

    2014-01-01

    Full Text Available Composites with the addition of alumina nanofillers show improvement in mechanical properties. The PMMA polymer was used as a matrix and two different types of nanofillers, having extremely different shapes were added in the matrix to form the composite. Reinforcements were based on alumina nanoparticles having either spherical shape or whiskers having the length to diameter ratio of 100. The influence of alumina fillers size, shape and fillers loading on mechanical properties of prepared composite were studied using the nanoindentation measurements and dynamic mechanical analysis. It was observed that both alumina whiskers and alumina spherical nanoparticles added in the PMMA matrix improved the mechanical properties of the composite but the improvement was significantly higher with alumina whisker reinforcement. The concentration of the reinforcing alumina spherical nanoparticles and alumina whiskers in PMMA matrix varied up to 5 wt. %. The best performance was obtained by the addition of 3 wt. % of alumina whiskers in the PMMA matrix with regard to mechanical properties of the obtained composite.

  9. Determination of calcium and magnesium in nuclear grade alumina by ion chromatography technique

    International Nuclear Information System (INIS)

    Hespanhol, E.C.B.; Pires, M.A.F.; Atalla, L.T.

    1987-07-01

    A simple method for solubilization of alumina and separation of magnesium and calcium from alumina matrix was developed by initial coprecipitation of those elements with iron(III) hydroxide. Calcium and magnesium were later separated from iron chloride anionic complex in a Dowex 1-X 10 anionic exchange resin. The ion chromatography tecnnique was employed for the analysis of calcium and magnesium. One hundred percent recovery for calcium and magnesium was obtained in their separation from alumina. A precision of 6% and 10% for magnesium and calcium, respectively, was obtained in alumina samples analysis which contain less than 0,02% of magnesium and less than 0,08% of calcium. (Author) [pt

  10. Surface area, crystal morphology and characterization of transition alumina powders from a new gibbsite precursor

    Directory of Open Access Journals (Sweden)

    Antonio Carlos Vieira Coelho

    2007-06-01

    Full Text Available A new procedure was used to prepare a microcrystalline powder constituted by thin euhedral hexagonal gibbsite plates, 0.2 to 0.6 µm in diameter and 32 nm thick. The powder, fired between 200 and 1000 °C, produced chi and kappa transition aluminas. Alpha-alumina is formed from 1000 °C and recrystallized up to 1500 °C. At 1000 °C, kappa- and alpha-alumina coexisted, but kappa-alumina could only be characterized by SAED. The details of the internal organization of the transition alumina pseudomorphs were clearly observable in TEM due to the great thinness of the I-gibbsite plates. The specific surface area varied from pristine I-gibbsite (24.9 m².g-1 to chi- and kappa transition aluminas (25.4 m².g-1 at 1000 °C to alpha-alumina (4.0 m².g-1 at 1500 °C. The maximum value of specific surface area is 347 m².g-1 in chi-alumina powder at 300 °C, a difference from Bayer gibbsite, in which the chi-alumina highest surface area is 370 m².g-1 at 400 °C.

  11. Synthesis and characterization of platinum supported on alumina doped with cerium catalyst

    International Nuclear Information System (INIS)

    Yusof Abdullah; Abd Fatah Awang Mat; Mohd Ali Sufi; Sarimah Mahat; Razali Kassim; Nurhaslinda Abdullah.

    1996-03-01

    The synthesis and characterization of gamma-alumina doped with cerium as platinum support for the automobile exhaust catalyst are described. Platinum/alumina/ceria catalyst were prepared by impregnation of hexachloroplatinic acid and sintered at 500 degree Celsius to obtain metal dispersions of 1.0 wt%. Catalyst distribution inside the powder and the effects of the addition of cerium to alumina were analyzed by the scanning electron microscopy (SEM) and x-ray fluorescence spectroscopy (XRF). The results showed that the alumina - supported catalysts contained well dispersion of the noble metal

  12. Metallorganic routes to nanoscale iron and titanium oxide particles encapsulated in mesoporous alumina: formation, physical properties, and chemical reactivity.

    Science.gov (United States)

    Schneider, J J; Czap, N; Hagen, J; Engstler, J; Ensling, J; Gütlich, P; Reinoehl, U; Bertagnolli, H; Luis, F; de Jongh, L J; Wark, M; Grubert, G; Hornyak, G L; Zanoni, R

    2000-12-01

    towards formation of carbon nanotubes by a CVD process. Depending on the reaction conditions, the formation of smaller carbon nanotubes inside the interior of larger carbon nanotubes within the alumina pores can be achieved. This behavior can be understood by means of selectively turning on and off the iron catalyst by adjusting the flow rate of the gaseous carbon precursor in the CVD process.

  13. The microwave effects on the properties of alumina at high frequencies of microwave sintering

    Energy Technology Data Exchange (ETDEWEB)

    Sudiana, I. Nyoman, E-mail: sudiana75@yahoo.com; Ngkoimani, La Ode; Usman, Ida [Department of Physics, Faculty of Mathematic and Natural Science, Halu Oleo University, Kampus Bumi Tridharma Anduonohu, Kendari 93232 (Indonesia); Mitsudo, Seitaro; Sako, Katsuhide; Inagaki, Shunsuke [Research Center for Development of Far-Infrared Region, University of Fukui, 3-9-1 Bunkyo, Fukui-shi 910-8507 (Japan); Aripin, H. [Center for Material Processing and Renewable Energy, Faculty of Learning Teacher and Education Science, Siliwangi University, Jl. Siliwangi 24 Tasikmalaya 46115, West Java (Indonesia)

    2016-03-11

    Microwave sintering of materials has attracted much research interest because of its significant advantages (e.g. reduced sintering temperatures and soaking times) over the conventional heating. Most researchers compared processes that occurred during the microwave and conventional heating at the same temperature and time. The enhancements found in the former method are indicated as a 'non-thermal effect' which is usually used for explaining the phenomena in microwave processing. Numerous recent studies have been focused on the effect to elucidate the microwave interaction mechanism with materials. Moreover, recent progress on microwave sources such as gyrotrons has opened the possibility for processing materials by using a higher microwave frequency. Therefore, the technology is expected to exhibit a stronger non-thermal effect. This paper presents results from a series of experiments to study the non-thermal effect on microwave sintered alumina. Sintering by using a wide rage of microwave frequencies up to 300 GHz as well as a conventional furnace was carried out. The linear shrinkages of samples for each sintering method were measured. Pores and grains taken from scanning electron microstructure (SEM) images of cut surfaces were also examined. The results of a comparative study of the shrinkages and microstructure evolutions of the sintered samples under annealing in microwave heating systems and in an electric furnace were analyzed. A notably different behavior of the shrinkages and microstructures of alumina after being annealed was found. The results suggested that microwave radiations provided an additional force for mass transports. The results also indicated that the sintering process depended on microwave frequencies.

  14. The microwave effects on the properties of alumina at high frequencies of microwave sintering

    International Nuclear Information System (INIS)

    Sudiana, I. Nyoman; Ngkoimani, La Ode; Usman, Ida; Mitsudo, Seitaro; Sako, Katsuhide; Inagaki, Shunsuke; Aripin, H.

    2016-01-01

    Microwave sintering of materials has attracted much research interest because of its significant advantages (e.g. reduced sintering temperatures and soaking times) over the conventional heating. Most researchers compared processes that occurred during the microwave and conventional heating at the same temperature and time. The enhancements found in the former method are indicated as a 'non-thermal effect' which is usually used for explaining the phenomena in microwave processing. Numerous recent studies have been focused on the effect to elucidate the microwave interaction mechanism with materials. Moreover, recent progress on microwave sources such as gyrotrons has opened the possibility for processing materials by using a higher microwave frequency. Therefore, the technology is expected to exhibit a stronger non-thermal effect. This paper presents results from a series of experiments to study the non-thermal effect on microwave sintered alumina. Sintering by using a wide rage of microwave frequencies up to 300 GHz as well as a conventional furnace was carried out. The linear shrinkages of samples for each sintering method were measured. Pores and grains taken from scanning electron microstructure (SEM) images of cut surfaces were also examined. The results of a comparative study of the shrinkages and microstructure evolutions of the sintered samples under annealing in microwave heating systems and in an electric furnace were analyzed. A notably different behavior of the shrinkages and microstructures of alumina after being annealed was found. The results suggested that microwave radiations provided an additional force for mass transports. The results also indicated that the sintering process depended on microwave frequencies.

  15. Low-cost fabrication and polar-dependent switching uniformity of memory devices using alumina interfacial layer and Ag nanoparticle monolayer

    Directory of Open Access Journals (Sweden)

    Peng Xia

    2017-11-01

    Full Text Available A facile and low-cost process was developed for fabricating write-once-read-many-times (WORM Cu/Ag NPs/Alumina/Al memory devices, where the alumina passivation layer formed naturally in air at room temperature, whereas the Ag nanoparticle monolayer was in situ prepared through thermal annealing of a 4.5 nm Ag film in air at 150°C. The devices exhibit irreversible transition from initial high resistance (OFF state to low resistance (ON state, with ON/OFF ratio of 107, indicating the introduction of Ag nanoparticle monolayer greatly improves ON/OFF ratio by four orders of magnitude. The uniformity of threshold voltages exhibits a polar-dependent behavior, and a narrow range of threshold voltages of 0.40 V among individual devices was achieved upon the forward voltage. The memory device can be regarded as two switching units connected in series. The uniform alumina interfacial layer and the non-uniform distribution of local electric fields originated from Ag nanoparticles might be responsible for excellent switching uniformity. Since silver ions in active layer can act as fast ion conductor, a plausible mechanism relating to the formation of filaments sequentially among the two switching units connected in series is suggested for the polar-dependent switching behavior. Furthermore, we demonstrate both alumina layer and Ag NPs monolayer play essential roles in improving switching parameters based on comparative experiments.

  16. Low-cost fabrication and polar-dependent switching uniformity of memory devices using alumina interfacial layer and Ag nanoparticle monolayer

    Science.gov (United States)

    Xia, Peng; Li, Luman; Wang, Pengfei; Gan, Ying; Xu, Wei

    2017-11-01

    A facile and low-cost process was developed for fabricating write-once-read-many-times (WORM) Cu/Ag NPs/Alumina/Al memory devices, where the alumina passivation layer formed naturally in air at room temperature, whereas the Ag nanoparticle monolayer was in situ prepared through thermal annealing of a 4.5 nm Ag film in air at 150°C. The devices exhibit irreversible transition from initial high resistance (OFF) state to low resistance (ON) state, with ON/OFF ratio of 107, indicating the introduction of Ag nanoparticle monolayer greatly improves ON/OFF ratio by four orders of magnitude. The uniformity of threshold voltages exhibits a polar-dependent behavior, and a narrow range of threshold voltages of 0.40 V among individual devices was achieved upon the forward voltage. The memory device can be regarded as two switching units connected in series. The uniform alumina interfacial layer and the non-uniform distribution of local electric fields originated from Ag nanoparticles might be responsible for excellent switching uniformity. Since silver ions in active layer can act as fast ion conductor, a plausible mechanism relating to the formation of filaments sequentially among the two switching units connected in series is suggested for the polar-dependent switching behavior. Furthermore, we demonstrate both alumina layer and Ag NPs monolayer play essential roles in improving switching parameters based on comparative experiments.

  17. PENGARUH PERBEDAAN SIFAT PENYANGGA ALUMINA TERHADAP SIFAT KATALIS HYDROTREATING BERBASIS NIKEL-MOLIBDENUM

    Directory of Open Access Journals (Sweden)

    Maria Ulfah

    2012-11-01

    Full Text Available EFFECT OF ALUMINA SUPPORT PROPERTIES ON THE NICKEL-MOLIBDENUM BASE HYDROTREATING CATALYST. Effect of surface characteristics of three species of synthesized γ-alumina (alumina-1, alumina-2 and alumina-3 on characteristics NiMo catalysts has been studied. Those aluminas are derived from boehmite Catapal B by varying rasio mol nitric acid to boehmite. A sol-gel method is used to synthesize γ-Al2O3 support. The Nitrogen adsorption, X-ray diffraction (XRD, Temperature Programmed Reduction (TPR of H2, Temperature Programmed Desorption (TPD of NH3, and mechanical strength are used to characterize the supports and catalysts. The results showed that the surface area alumina affects the formation of crystalline MoO3 in the NiMo catalyst, while γ-Al2O3-3 support which has the highest surface area (about 195 m2/g compared to the other two types of alumina (>195 m2/g does not have a crystalline MoO3. The formation of crystalline MoO3 is not influenced by the acidity alumina. Based on the results of XRD, it is  indicated that the supported alumina-3 NiMo catalyst (having the highest acid strength shows that there is no presence of crystalline MoO3. Pore size distribution of support did not change significantly after the deposition of Ni and Mo oxides. Mechanical strength of support also affects the strength NiMo catalyst. Support alumina-3 which has the highest mechanical strength gives the mechanical strength of the highest NiMo catalyst. Pengaruh sifat penyangga γ-alumina hasil pengembangan (alumina-1, alumina-2 dan alumina-3 pada karakter katalis hydrotreating nikel-molibdenum (NiMo telah dipelajari. Ketiga jenis γ-alumina diturunkan dari boehmite “Catapal B” dengan menvariasikan nisbah mol asam nitrat terhadap boehmite. Pembuatan γ-alumina menggunakan metoda sol-gel. Adsorpsi Nitrogen, X-ray difraksi (XRD, Temperature Programmed Reduction (TPR H2, Temperature Programmed Desorption (TPD NH3, dan kekuatan mekanik digunakan untuk

  18. Chemical elimination of alumina in suspension in nuclear reactors heavy water

    International Nuclear Information System (INIS)

    Ledoux, A.

    1967-02-01

    Corrosion of aluminium in contact with moderating water in nuclear reactor leads to the formation of an alumina hydrosol which can have an adverse effect on the operation of the reactor. Several physical methods have been used in an attempt to counteract this effect. The method proposed here consists in the elimination of the aluminium by dissolution and subsequent fixation in the ionic form on mixed-bed ion-exchange resin. In order to do this, the parameters and the values of these parameters most favorable to the dissolution process have been determined. If the moderator is heavy water, the deuterated acid can be prepared by converting a solution in heavy water to a salt of the acid using a deuterated cationic resin. (author) [fr

  19. Formation and characterization of nanotubes of La(OH)3 obtained using porous alumina membranes

    International Nuclear Information System (INIS)

    Gonzalez-Rovira, L; Sanchez-Amaya, J M; Botana, F J; Lopez-Haro, M; Hungria, A B; Boukha, Z; Bernal, S

    2008-01-01

    An electrodeposition process is used to synthesize nanotubes of a lanthanum-containing phase, employing porous alumina membranes as templates. This method should lead to the formation of La(OH) 3 nanowires, according to the previous results presented by Bocchetta et al (2007 Electrochem. Commun. 9 683-8), which can be decomposed to La 2 O 3 , as the latter shows more interest for different applications. The results obtained by means of different electron microscopy techniques indicate that this method leads to the formation of nanotubes of about 200 nm in diameter and 30-40 μm in length, instead of the nanowires proposed in the literature. Additionally, the chemical characterization demonstrates that the material synthesized is composed of lanthanum hydroxycarbonate. The presence of carbonates is found to be crucial in determining the conditions for the preparation of La 2 O 3 from the nanotubes here obtained.

  20. Enhancing the platinum atomic layer deposition infiltration depth inside anodic alumina nanoporous membrane

    Energy Technology Data Exchange (ETDEWEB)

    Vaish, Amit, E-mail: anv@udel.edu; Krueger, Susan; Dimitriou, Michael; Majkrzak, Charles [National Institute of Standards and Technology (NIST) Center for Neutron Research, Gaithersburg, MD 20899-8313 (United States); Vanderah, David J. [Institute for Bioscience and Biotechnology Research, NIST, Rockville, Maryland 20850 (United States); Chen, Lei, E-mail: lei.chen@nist.gov [NIST Center for Nanoscale Science and Technology, Gaithersburg, Maryland 20899-8313 (United States); Gawrisch, Klaus [Laboratory of Membrane Biochemistry and Biophysics, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, Maryland 20892 (United States)

    2015-01-15

    Nanoporous platinum membranes can be straightforwardly fabricated by forming a Pt coating inside the nanopores of anodic alumina membranes (AAO) using atomic layer deposition (ALD). However, the high-aspect-ratio of AAO makes Pt ALD very challenging. By tuning the process deposition temperature and precursor exposure time, enhanced infiltration depth along with conformal coating was achieved for Pt ALD inside the AAO templates. Cross-sectional scanning electron microscopy/energy dispersive x-ray spectroscopy and small angle neutron scattering were employed to analyze the Pt coverage and thickness inside the AAO nanopores. Additionally, one application of platinum-coated membrane was demonstrated by creating a high-density protein-functionalized interface.

  1. Shape induced magnetic vortex state in hexagonal ordered cofe nanodot arrays using ultrathin alumina shadow mask

    Science.gov (United States)

    Sellarajan, B.; Saravanan, P.; Ghosh, S. K.; Nagaraja, H. S.; Barshilia, Harish C.; Chowdhury, P.

    2018-04-01

    The magnetization reversal process of hexagonal ordered CoFe nanodot arrays was investigated as a function of nanodot thickness (td) varying from 10 to 30 nm with fixed diameter. For this purpose, ordered CoFe nanodots with a diameter of 80 ± 4 nm were grown by sputtering using ultra-thin alumina mask. The vortex annihilation and the dynamic spin configuration in the ordered CoFe nanodots were analyzed by means of magnetic hysteresis loops in complement with the micromagnetic simulation studies. A highly pinched hysteresis loop observed at 20 nm thickness suggests the occurrence of vortex state in these nanodots. With increase in dot thickness from 10 to 30 nm, the estimated coercivity values tend to increase from 80 to 175 Oe, indicating irreversible change in the nucleation/annihilation field of vortex state. The measured magnetic properties were then corroborated with the change in the shape of the nanodots from disk to hemisphere through micromagnetic simulation.

  2. Estudio de la formacion de los complejos intermedios durante la sintesis de alumina

    Directory of Open Access Journals (Sweden)

    Rodríguez-Páez J.E.

    2001-01-01

    Full Text Available One of the most important compounds that are used in structural ceramics is alumina. During the last years, a variety of synthesis methods have been developed to obtain raw materials with suitable characteristics in terms of particle composition, size and shape. Controlled precipitation method (CP allows to reach these demands and with this method is possible to control the synthesis to guarantee characteristics of the ceramic powder. One stage of the CPM is the formation of intermediate complexes of cations whose oxide derives to obtain. In this work the results of study of the formation of aluminum intermediate complexes are presented. We used potentiometric and conductimetric titration to follow the advance of the process. We utilized UV-visible and IR spectroscopies to characterize the liquid phase present in the system.

  3. Formation and characterization of nanotubes of La(OH)3 obtained using porous alumina membranes

    Science.gov (United States)

    González-Rovira, L.; Sánchez-Amaya, J. M.; López-Haro, M.; Hungria, A. B.; Boukha, Z.; Bernal, S.; Botana, F. J.

    2008-12-01

    An electrodeposition process is used to synthesize nanotubes of a lanthanum-containing phase, employing porous alumina membranes as templates. This method should lead to the formation of La(OH)3 nanowires, according to the previous results presented by Bocchetta et al (2007 Electrochem. Commun. 9 683-8), which can be decomposed to La2O3, as the latter shows more interest for different applications. The results obtained by means of different electron microscopy techniques indicate that this method leads to the formation of nanotubes of about 200 nm in diameter and 30-40 µm in length, instead of the nanowires proposed in the literature. Additionally, the chemical characterization demonstrates that the material synthesized is composed of lanthanum hydroxycarbonate. The presence of carbonates is found to be crucial in determining the conditions for the preparation of La2O3 from the nanotubes here obtained.

  4. Alumina-zirconium ceramics synthesis by selective laser sintering/melting

    International Nuclear Information System (INIS)

    Shishkovsky, I.; Yadroitsev, I.; Bertrand, Ph.; Smurov, I.

    2007-01-01

    In the present paper, porous refractory ceramics synthesized by selective laser sintering/melting from a mixture of zirconium dioxide, aluminum and/or alumina powders are subjected to optical metallography and X-ray analysis to study their microstructure and phase composition depending on the laser processing parameters. It is shown that high-speed laser sintering in air yields ceramics with dense structure and a uniform distribution of the stabilizing phases. The obtained ceramic-matrix composites may be used as thermal and electrical insulators and wear resistant coating in solid oxide fuel cells, crucibles, heating elements, medical tools. The possibility to reinforce refractory ceramics by laser synthesis is shown on the example of tetragonal dioxide of zirconium with hardened micro-inclusion of Al 2 O 3 . By applying finely dispersed Y 2 O 3 powder inclusions, the type of the ceramic structure is significantly changed

  5. Microencapsulation of silicon nitride particles with yttria and yttria-alumina precursors

    International Nuclear Information System (INIS)

    Garg, A.K.; De Jonghe, L.C.

    1990-01-01

    Procedures are described to deposit uniform layers of yttria and yttria-alumina precursors on fine powders and whiskers of silicon nitride. The coatings were produced by aging at elevated temperatures aqueous systems containing the silicon nitride core particles, yttrium and aluminum nitrates, and urea. Optimum concentrations of the core particles, in relation to the reactants, were established to promote surface deposition of the oxide precursors. Polymeric dispersants were used effectively to prevent agglomeration of the solids during the microencapsulation process. The morphology of the powders was characterized using scanning and transmission electron microscopy. The mechanisms for the formation of the coated layers are discussed. A description is provided that allows qualitative assessment of the experimental factors that determine microencapsulation by a slurry method

  6. Microwave sintering of zirconia toughened alumina at 28GHz

    International Nuclear Information System (INIS)

    Samandi, M.; Ji, H.; Miyake, S.

    1998-01-01

    Microwave radiation from a 10 kW, CW gyrotron operating at 28 GHz was employed to sinter 10% zirconia toughened alumina (ZTA) ceramic samples. It has been established that the use of millimetre wave radiation circumvents the difficulties encountered during the sintering of ceramics, i e. formation of hot spot, by radiation at industrially permissible frequency of 2.45GHz. Further, careful density measurement and microstructural characterisation of mm- wave and conventionally sintered samples by XRD, SEM and TEM has unequivocally demonstrated the effectiveness of mm-wave radiation for obtaining high density ceramics at lower sintering temperatures. Copyright (1998) Australasian Ceramic Society

  7. Liquid-film assisted formation of alumina/niobium interfaces

    OpenAIRE

    Sugar, Joshua D.; McKeown, Joseph T.; Marks, Robert A.; Glaeser, Andreas M.

    2002-01-01

    Alumina has been joined at 1400 degrees C using niobium-based interlayers. Two different joining approaches were compared: solid-state diffusion bonding using a niobium foil as an interlayer, and liquid-film assisted bonding using a multilayer copper/niobium/copper interlayer. In both cases, a 127-(mu)m thick niobium foil was used; =1.4-(mu)m or =3-(mu)m thick copper films flanked the niobium. Room-temperature four-point bend tests showed that the introduction of a copper film had a significa...

  8. Electrochemically replicated smooth aluminum foils for anodic alumina nanochannel arrays

    International Nuclear Information System (INIS)

    Biring, Sajal; Tsai, K-T; Sur, Ujjal Kumar; Wang, Y-L

    2008-01-01

    A fast electrochemical replication technique has been developed to fabricate large-scale ultra-smooth aluminum foils by exploiting readily available large-scale smooth silicon wafers as the masters. Since the adhesion of aluminum on silicon depends on the time of surface pretreatment in water, it is possible to either detach the replicated aluminum from the silicon master without damaging the replicated aluminum and master or integrate the aluminum film to the silicon substrate. Replicated ultra-smooth aluminum foils are used for the growth of both self-organized and lithographically guided long-range ordered arrays of anodic alumina nanochannels without any polishing pretreatment

  9. Adhesion of silver films to ion-bombarded alumina

    International Nuclear Information System (INIS)

    Erck, R.A.; Fenske, G.R.

    1990-01-01

    This paper reports on silver films deposited on alumina substrates using ion bombardment. Adhesion strength was measured as a function of deposition conditions, sputter-cleaning time, and bombarding ion species, using a pull-type adhesion tester. Argon- and argon/oxygen-ion sputtering produced large increases in adhesion strength, with the greatest increases occurring for oxygen-ion bombardment. Adhesion strength increased monotonically as a function of ion sputtering time. At a given deposition rate, further enhancement of adhesion is seen with concurrent ion bombardment

  10. Diffusion and flow of water vapours in chromatographic Alumina gel

    International Nuclear Information System (INIS)

    Khan, M.; Shah, H. U.

    2005-01-01

    The kinetics of sorption of water vapours in chromatographic alumina gel was studied. Water vapours are adsorbed on the gel at temperature (15 degree C) at different constant relative pressure from 0.1-0.93 p/p. Rate constant, Effective diffusivities, Knudsen diffusivities and bulk diffusivities were determined through Fick type equation. Total pore volume is 0.498 cc g-1 and specific surface area comes to be 465 m2 g-1 as obtained by Gurvitsch rule and Kieselve's quantities respectively. An average pore radius (hydraulic) is 1.1x10/sub -7/ cm. The study of these quantities provide a strong basis for evaluating surface properties. (author)

  11. Thermal diffusivity of alumina-zirconia sintered with niobium additions

    International Nuclear Information System (INIS)

    Santos, W.N. dos; Paulin Filho, P.I.; Taylor, R.

    1994-01-01

    The effect of niobium oxide addition on the alumina-zirconia thermal diffusivity was investigated from 100 0 C to 1000 0 C by the laser flash method. It was observed that 4 to 6% addition of niobium oxide increases the thermal diffusivity when samples were sintered at 1450 0 C. This effect was due to elimination of porosity by formation of liquid please above 1420 0 C in the Al 2 O 3 - Nb 2 O 5 system. (author). 7 refs., 3 figs

  12. Preparation of 11C-labelled methanol on alumina column

    International Nuclear Information System (INIS)

    Sarkadi, E.; Kovacs, Z.; Horvath, G.

    1998-01-01

    The [ 11 C]methyl iodide is an important intermedia to synthesize 11 C-labelled radiopharmaceuticals for medical diagnostics in positron emission tomography. Recently a new method has been developed to produce [ 11 C]methanol intermedia. The advantage of this method of radiomethanol preparation is the application of an alumina column at room temperature instead of a complicated cooling unit used with the conventional reaction vessel. The yield and purity of radiomethanol was the same as in the previous methods. (K.A.)

  13. Selective etching of injection molded zirconia-toughened alumina: Towards osseointegrated and antibacterial ceramic implants.

    Science.gov (United States)

    Flamant, Quentin; Caravaca, Carlos; Meille, Sylvain; Gremillard, Laurent; Chevalier, Jérôme; Biotteau-Deheuvels, Katia; Kuntz, Meinhard; Chandrawati, Rona; Herrmann, Inge K; Spicer, Christopher D; Stevens, Molly M; Anglada, Marc

    2016-12-01

    Due to their outstanding mechanical properties and excellent biocompatibility, zirconia-toughened alumina (ZTA) ceramics have become the gold standard in orthopedics for the fabrication of ceramic bearing components over the last decade. However, ZTA is bioinert, which hampers its implantation in direct contact with bone. Furthermore, periprosthetic joint infections are now the leading cause of failure for joint arthroplasty prostheses. To address both issues, an improved surface design is required: a controlled micro- and nano-roughness can promote osseointegration and limit bacterial adhesion whereas surface porosity allows loading and delivery of antibacterial compounds. In this work, we developed an integrated strategy aiming to provide both osseointegrative and antibacterial properties to ZTA surfaces. The micro-topography was controlled by injection molding. Meanwhile a novel process involving the selective dissolution of zirconia (selective etching) was used to produce nano-roughness and interconnected nanoporosity. Potential utilization of the porosity for loading and delivery of antibiotic molecules was demonstrated, and the impact of selective etching on mechanical properties and hydrothermal stability was shown to be limited. The combination of injection molding and selective etching thus appears promising for fabricating a new generation of ZTA components implantable in direct contact with bone. Zirconia-toughened alumina (ZTA) is the current gold standard for the fabrication of orthopedic ceramic components. In the present work, we propose an innovative strategy to provide both osseointegrative and antibacterial properties to ZTA surfaces: we demonstrate that injection molding allows a flexible design of surface micro-topography and can be combined with selective etching, a novel process that induces nano-roughness and surface interconnected porosity without the need for coating, avoiding reliability issues. These surface modifications have the

  14. Development of tungsten coatings for the corrosion protection of alumina-based ceramics

    International Nuclear Information System (INIS)

    Arons, R.M.; Dusek, J.T.; Hafstrom, J.W.

    1979-01-01

    A means of applying tungsten coatings to an alumina based ceramic is described. A slurry of pure tungsten was prepared and applied by brush coating or slip casting on the alumina-3 wt % Yt small crucible. The composite was fired and a very dense ceramic crucible with a crack free tungsten coating was produced

  15. A High-Purity Alumina for Use in Studies of Shock Loaded Samples

    Science.gov (United States)

    Lacina, David; Neel, Christopher

    2017-06-01

    We report the results of plate impact experiments on a potential new ``standard'' material, Coorstek Plasmapure-UC (99.9% purity) polycrystalline alumina, for use in non-conduction, impact environment, shock loading studies. This work was motivated by a desire to find a 99.9% purity alumina to replace the now unavailable Coors Vistal (99.9%) alumina, as it was hoped the Hugoniot elastic limit (HEL) of the new standard would match the 9-11 GPa value of Vistal. Shock response data, including the HEL, Hugoniot particle velocities, Hugoniot shock velocities, stress vs volume, and release wave speeds, was obtained up to 14 GPa. This data will be compared with Hugoniot curve data for other high purity alumina to contrast differences in the shock response, and is intended to be useful in impedance matching calculations. We will show that the HEL of Plasmapure-UC alumina is 5.5 GPa and speculate on causes for this lower than expected value. We will also explore why the elastic-plastic response for Plasmapure-UC alumina differs from what has been observed from other high purity alumina. The final result of this work is to recommend a well-characterized, lower purity alumina (Coorstek AD-995) as a potential new ``standard'' material.

  16. Polyethyleneglycol grafting of γ-alumina membranes for solvent resistant nanofiltration

    NARCIS (Netherlands)

    Tanardi, Cheryl; Catana, Romina; Barboiu, Mihai; Ayral, André; Vankelecom, Ivo F.J.; Nijmeijer, Arian; Winnubst, Aloysius J.A.

    2016-01-01

    A method is presented for grafting mesoporous g-alumina (pore size 5 nm), supported on an a-alumina ceramic membrane, with polyethylene glycols (PEG). The grafting performance of g-Al2O3 powders with various PEG grafting agents, having different molecular weights, alkoxy groups, and ureido

  17. Factors influencing the transport rate of short-chain alcohols through mesoporous y-alumina membranes

    NARCIS (Netherlands)

    Roy Chowdhury, Sankhanilay; Roy Chowdhury, S.; Blank, David H.A.; ten Elshof, Johan E.

    2005-01-01

    The pressure-driven transport of water, ethanol, and 1-propanol through supported -alumina membranes with different pore diameters is reported. Water and alcohols had similar permeabilities when they were transported through y-alumina membranes with average pore diameters of 4.4 and 6.0 nm, and the

  18. Morphology and thermal properties of compatibilized PA12/PP blends with boehmite alumina nanofiller inclusions

    CSIR Research Space (South Africa)

    Ogunniran, ES

    2011-12-01

    Full Text Available -1 Morphology and Thermal Properties of Compatibilized PA12/PP Blends with Boehmite Alumina Nanofiller Inclusions 1. Elijah Soba Ogunniran1, 2. Rotimi Sadiku1, 3. Suprakas Sinha Ray2,*, 4. Nyambeni Luruli3 Keywords: ? boehmite alumina; ? morphology...

  19. All cause mortality and incidence of cancer in workers in bauxite mines and alumina refineries

    NARCIS (Netherlands)

    Fritschi, Lin; Hoving, Jan Lucas; Sim, Malcolm R.; del Monaco, Anthony; Macfarlane, Ewan; McKenzie, Dean; Benke, Geza; de Klerk, Nicholas

    2008-01-01

    Bauxite is a reddish clay that is refined to produce alumina, which is then reduced to aluminium. There have been studies examining the health of workers in aluminium smelters, but not workers in bauxite mining and alumina refining. A cohort of employees of 1 large aluminium company since 1983 was

  20. Studies on the promotion of nickel—alumina coprecipitated catalysts: I. Titanium oxide

    NARCIS (Netherlands)

    Lansink Rotgerink, H.G.J.; Mercera, P.D.L.; van Ommen, J.G.; Ross, J.R.H.

    1988-01-01

    A series of TiO2-promoted nickel—alumina catalysts has been prepared and characterized. The promoter was added in various proportions to a calcined coprecipitated nickel—alumina material by adsorption of the acetylacetonate complex of titanium, followed by further calcination and reduction. The