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Sample records for aluminia

  1. Characterization and sintering of ATR aluminia from niobium

    International Nuclear Information System (INIS)

    The characterization of resultante slag from Aluminothermic Reduction (ATR) process to obtain metallic niobium is presented. The slag was characterized for concentration and phases of aluminia by X-ray diffractometry. The results show that 70% of the slag is constituted by α aluminia. The lixiviation and calcination of the slag increased the α aluminia concentration to 95%, the slag was used for producing samples to be burning in three furnaces: electrical resistance furnace in the air, and two furnaces in the vacuum. The burned samples were characterized by microscopy, ultrasonic analysis, density measurements and X-ray diffractometry. The sintering in the vacuum is possible because the samples burned in vacuum presented major density. The formation of NbO2 and mullite was observed, by X-ray diffractometry. The data from optical microscopy, density measurements and X-ray diffractometry show high porosity. (M.C.K.)

  2. Use of emanation thermal analysis in the microstructure diagnostics of aluminia coatings

    Czech Academy of Sciences Publication Activity Database

    Balek, V.; Beneš, M.; Šubrt, Jan

    2008-01-01

    Roč. 52, č. 2 (2008), s. 85-89. ISSN 0862-5468 Institutional research plan: CEZ:AV0Z40320502 Keywords : aluminia coatings * emanation thermal analysis * SEM Subject RIV: CA - Inorganic Chemistry Impact factor: 0.644, year: 2008

  3. Influence of point defects on dosimetric properties and sintering capability of aluminia α

    International Nuclear Information System (INIS)

    This work was devoted to the study of the influence of synthesis conditions on the thermoluminescence of aluminia α for use in ionizing radiation dosimetry. Powders are synthesized by heat treatment of pure aluminia γ or doped by impregnation technique. The studied parameters are the thermal cycle, the gas atmosphere of the furnace and the nature of the dopants (Mg2+, Cr3+, Th4+, Fe3+/Fe2+). The thermoluminescence (TL) is connected with the presence of point defects. This technique consists in measuring the intensity of light emitted by a previously irradiated solid. Three TL peaks were observed. A peak around - 40 deg. C allows making evident the magnesium impurities and the oxygen vacations. The evolution of the intensity of the two peaks at 190 deg. C and 360 deg. C, is studied as a function of the oxygen partial pressure of the heat treatment and of the Mg2+, Cr3+ and Th4+ dopant concentrations. These investigations have permitted identifying the defects implied in the luminescence process of these two peaks, i.e. the aluminium vacations and the Cr3+ ions substituted to Al3+. Thus aluminia powders having a high sensitivity to ionizing radiations (X rays, UV and γ radiations) have been synthesized. Utilization in dosimetry of the peaks at 190 deg. C and 360 deg. C is suggested. The reactivity of non-doped powders containing different types of point defects was analyzed by dilatometry. Thus, the influence of the atmosphere of powder preparation upon the sintering behaviour was made evident. The differences between the removal velocities are correlated with the variations in the aluminium vacancy concentrations. These results suppose that the limiting stage in sintering these powders is the Al3+ ion diffusion

  4. Influence of point defects on dosimetric properties and sintering capability of aluminia {alpha}; Influence des defauts ponctuels sur les proprietes dosimetriques et sur l'aptitude au frittage de l'alumine {alpha}

    Energy Technology Data Exchange (ETDEWEB)

    Papin, Eric [Ecole Nationale Superieure des Mines, 42 - Saint-Etienne (France)

    1997-12-11

    This work was devoted to the study of the influence of synthesis conditions on the thermoluminescence of aluminia {alpha} for use in ionizing radiation dosimetry. Powders are synthesized by heat treatment of pure aluminia {gamma} or doped by impregnation technique. The studied parameters are the thermal cycle, the gas atmosphere of the furnace and the nature of the dopants (Mg{sup 2+}, Cr{sup 3+}, Th{sup 4+}, Fe{sup 3+}/Fe{sup 2+}). The thermoluminescence (TL) is connected with the presence of point defects. This technique consists in measuring the intensity of light emitted by a previously irradiated solid. Three TL peaks were observed. A peak around - 40 deg. C allows making evident the magnesium impurities and the oxygen vacations. The evolution of the intensity of the two peaks at 190 deg. C and 360 deg. C, is studied as a function of the oxygen partial pressure of the heat treatment and of the Mg{sup 2+}, Cr{sup 3+} and Th{sup 4+} dopant concentrations. These investigations have permitted identifying the defects implied in the luminescence process of these two peaks, i.e. the aluminium vacations and the Cr{sup 3+} ions substituted to Al{sup 3+}. Thus aluminia powders having a high sensitivity to ionizing radiations (X rays, UV and {gamma} radiations) have been synthesized. Utilization in dosimetry of the peaks at 190 deg. C and 360 deg. C is suggested. The reactivity of non-doped powders containing different types of point defects was analyzed by dilatometry. Thus, the influence of the atmosphere of powder preparation upon the sintering behaviour was made evident. The differences between the removal velocities are correlated with the variations in the aluminium vacancy concentrations. These results suppose that the limiting stage in sintering these powders is the Al{sup 3+} ion diffusion.

  5. Fabrication and properties of yttria, ceria doped zirconia-aluminia ceramic composites

    International Nuclear Information System (INIS)

    At present, zirconia-based ceramics are gaining popularity in dentistry, particularly in fixed prosthodontics. clinically, it is important that ceramic restorations reproduce the translucency and color of natural teeth. Zirconia based ceramics is a high performance material with excellent biocompatibility and mechanical properties, which suggest its suitability for posterior fixed partial dentures. Y2O3-stabilized tetragonal zirconia polycrystalline (YTZ/Al2O3) and CeO2-stabilized tetragonal zirconia polycrystalline (CZA) ceramics with high-performance were prepared for dental application by use the wet chemical route, consolidated by cold isostatic pressing, and two-step sintering method. Physical and mechanical properties test results show that the bending strength, fracture toughness, and the density of full sintered ceramics suggest that the material is relatively suitable for dental restoration.

  6. Study of plutonium sorption in aluminia column in the system HNO3-HF

    International Nuclear Information System (INIS)

    The column chromatographic method using alumina has been applied successfully to study the sorption-desorption behavior of plutonium traces in HNO3-HF and HNO3-HF-UO2(NO3)2 systems, aiming to elaborate a process for recovering plutonium traces from reprocessing wastes, mainly in existing solutions where uranium is presented in macro quantities. Basically, the method consists in the sorption of plutonium by percolating a solution containing HNO3(0,1 to 0,8M) or uranyl nitrate (1-50 gU/l) and HF(0,1 to 0,3M) through an Al2O3 collumn. The plutonium is fixed on Al2O3 whereas the uranyl ions is collected in the efluent. The adsorption of Pu-III, Pu-IV and Pu-VI in the presence of HF was determined and Pu-IV can be almost completely sorbed. The Pu-IV is eluted by reduction to Pu-III in the column using 3 M HNO3-0,005M FeSO4 at 500C as elutrient. This method is very simple and can be applied for separation and purification of plutonium (traces) from uranyl nitrate or others coming solutions from wet chemistry of irradiated fuels

  7. Synthesis by Sol-gel and characterization of catalysts Ag/Al2O3-CeO2

    International Nuclear Information System (INIS)

    Aluminia, cerium and mixed oxides Al2O3-CeO2 with different relationship Al/Ce (0.75, 0.50 and 0.25) were prepared by sol-gel and used as support for the Ag. The samples were characterized by XRD, DRIFT, TPR and adsorption of N2 to temperature of liquid nitrogen. The surface area BET showed that the materials that contain aluminia present near values among them. XRD allowed to identify to the cerianite in the oxides that whose support contains cerium and to the α-aluminia. A mixture of phases was observed in the aluminia. Vibration bands attributed to the bond Al-O and Ce-O were observed by DRIFT in the catalytic materials. TPR showed differences in the reducibility of the Ag precursor in the indicative catalysts of a different interaction with the support. (Author)

  8. Synthesis by Sol-gel and characterization of catalysts Ag/Al{sub 2}O{sub 3}-CeO{sub 2}; Sintesis por Sol-gel y caracterizacion de catalizadores Ag/Al{sub 2}O{sub 3}-CeO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Zayas, M.L.; Perez H, R. [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico); Rubio, E. [BUAP, Centro de Vinculacion, 72000 Puebla (Mexico); Velasco, A. [BUAP, Facultad de Quimica, 72000 Puebla (Mexico)

    2004-07-01

    Aluminia, cerium and mixed oxides Al{sub 2}O{sub 3}-CeO{sub 2} with different relationship Al/Ce (0.75, 0.50 and 0.25) were prepared by sol-gel and used as support for the Ag. The samples were characterized by XRD, DRIFT, TPR and adsorption of N{sub 2} to temperature of liquid nitrogen. The surface area BET showed that the materials that contain aluminia present near values among them. XRD allowed to identify to the cerianite in the oxides that whose support contains cerium and to the {alpha}-aluminia. A mixture of phases was observed in the aluminia. Vibration bands attributed to the bond Al-O and Ce-O were observed by DRIFT in the catalytic materials. TPR showed differences in the reducibility of the Ag precursor in the indicative catalysts of a different interaction with the support. (Author)

  9. Market analysis of shale oil co-products. Appendices

    Energy Technology Data Exchange (ETDEWEB)

    1980-12-01

    Data are presented in these appendices on the marketing and economic potential for soda ash, aluminia, and nahcolite as by-products of shale oil production. Appendices 1 and 2 contain data on the estimated capital and operating cost of an oil shales/mineral co-products recovery facility. Appendix 3 contains the marketing research data.

  10. Biocompatible composites for orthopedics applications

    International Nuclear Information System (INIS)

    The paper presents the results of the experimental research on the laminated composites and on that with the microconcretes structure destined for medical applications. These composites were based on the porous aluminia ceramics. Many materials with very different physicomechanical features were obtained. They may serve as the implants for filling bone cavities, and some of them even in the places where act the considerable forces. (author)

  11. Methods for detection of fused alumina powder, used as a tracer aerosol, on air sample filters

    International Nuclear Information System (INIS)

    Graded fused aluminia dusts (Aloxite) of mean particle sizes of 6 μm upwards are useful for measuring the effects of particle size on aerosol sampling systems and in dust experiments. Methods are described for the determination of filter loading with Aloxite aerosol using thermoluminescence (TL) and x-ray fluorescence (XRF). The XRF method was found to be almost as precise as direct weighing with a precision microbalance, and presents a useful method of detection where other contaminants are present in the sampled airstream. (author)

  12. Luminescence in region 1.54 μm of erbium for two-dimensional and three-dimensional mesoscopic structures

    International Nuclear Information System (INIS)

    We have investigated the photoluminescence and photoluminescence excitation spectra of erbium in the region 1.54 μm in xerogels of titanium oxides and silicon oxide, which are formed in mesoscopic pores of three-dimensional synthetic opals and two-dimensional structures of porous anodic aluminia. For films of titanium oxide doped with erbium and formed in opal, unlike similar films based on porous anodic alumina, an intense wide band is revealed which has a maximum in a region of about 360 nm. A possible nature of this band is discussed. (authors)

  13. Heterogeneous phase gamma irradiation of ethylene-hydrogen mixtures

    International Nuclear Information System (INIS)

    Experiments of radioinduced ethylene hydrogenation were performed. The G yield of volatile saturated hydrocarbons was 0,49 for silica-gel with simultaneous irradiation and 0,09-0,05 for the other solids (silica-alumina and molecular sieve 5A). The highest yield corresponds to 4,5% of saturated products in relation to initial ammount of ethylene (silica-gel). Polymerization was the most important reaction, with yields as high as 95%. Changes in color and appearance of silica-aluminia in contact with moisture was observed, after the irradiation process. (author)

  14. The 1989 progress report: Fine chemistry

    International Nuclear Information System (INIS)

    The 1989 progress report of the laboratory of Fine Chemistry of the Polytechnic School (France) is presented. The investigations are focused on the following subjects: nuclear magnetic resonance study of adsorbates, origin of claid inflating phenomena, models on water-claid thin films interaction, re-orientation of benzene adsorbed on aluminia, oxydation of cyclohexene, kaolinites, obtention of acrylates, recognition of molecules, biological chloration, distribution of addition products of N-benzylidene aniline and end ethers, epistemological reflection about representations in chemistry. The published papers, the conferences and Laboratory staff are listed

  15. Methods of fabricating cermet materials and methods of utilizing same

    Science.gov (United States)

    Kong, Peter C.

    2006-04-04

    Methods of fabricating cermet materials and methods of utilizing the same such as in filtering particulate and gaseous pollutants from internal combustion engines having intermetallic and ceramic phases. The cermet material may be made from a transition metal aluminide phase and an aluminia phase. The mixture may be pressed to form a green compact body and then heated in a nitrogen-containing atmosphere so as to melt aluminum particles and form the cermet. Filler materials may be added to increase the porosity or tailor the catalytic properties of the cermet material. Additionally, the cermet material may be reinforced with fibers or screens. The cermet material may also be formed so as to pass an electrical current therethrough to heat the material during use.

  16. Experimental study of the deposition of iodine and other fission products in the coolant circuit of a CAGR

    International Nuclear Information System (INIS)

    In a continuing programme, iron oxide particles of 0.6, 2 and 5 μm diameter, 17 μm aluminia particles and methyl iodide vapour have each been injected into the CO2 coolant of a reactor at Hinkley Point, England. Subsequent changes of concentration provide information on the rate of deposition. Initially, rapid deposition occurred for all the tracers. Methyl iodide was removed with an initial half-life of 12 s. The corresponding half-life was about 20 s for the particles up to 5 μm diameter, and 120 s for 17 μm particles. After the first few minutes the removal became slower, but concentrations fell by factors of several hundred to some tens of thousands during a period of 3 h following each injection. The potential escape of fission products in an accident could be reduced several hundred times by deposition. In one experiment, 17 μm particles were injected with the reactor shut down and the coolant flow rate reduced. The particles deposited more rapidly than at full flow. On increasing the flow rate to full flow most of the particles were resuspended into the gas stream. The results imply that the metal-oxide particles deposit onto, but also bounce and blow off, the internal surfaces of the coolant circuit. Methyl iodide is converted, at least in part, into one or more chemical forms of iodine, which also disappear rapidly from the gas stream. Although the mechanisms for removal are not fully understood, the benefit of deposition in reducing the amount of circulating activity is clearly very great. (orig./HP)