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Sample records for aluminia

  1. 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

  2. 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.

  3. 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

  4. 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)

  5. 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.

  6. 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)

  7. 分光光度仪比较四种常用全瓷冠在三种基底表面的色度学参数%Spectrophotometric comparison of the colorimetric data of three dark color abutments overlaid by four types of all-ceramic crowns

    Institute of Scientific and Technical Information of China (English)

    陈奕帆; 李晓敏; 张琳; 王剑

    2015-01-01

    AIM:To evaluate the colorimetric parameter of 3 dark color abutments overlaid by 4 all-ceramic crowns using a digital dental spectrophotometer. METHODS: Abutments of Co-Cr alloys, Au-Pt alloys and ND8 (n=10) were made and were respectively tried in 4 groups of all-ceramic crowns (Procera aluminia, Procera zirconi-a, Lava zirconia and IPS E. max glass-ceramic lithium disilicate-reinforced monolithic crown) (n=10) respectively. The colorimetric data of the cervical, body and incisal sites of the samples were recorded and analyzed by a spectropho-tometer. The CIE L∗a∗b∗ values were measured again after veneer. The unglazed A2 ( Vitapan Classical) shade tab was used as the control. The L∗a∗b∗values and the color difference between the samples and control were calculated and statistically analyzed. RESULTS: There was significant difference of the lightness and saturation among 3 abut-ments. But after all-ceramic copings were tried in, the difference of the L∗values of the Pro-Alu copings and E. max HO copings decreased greatly. TheΔE value of the Pro-Alu copings was the smallest among all ceramic copings. And the ΔE value of the copings on the ND8 abutment was smallest among 3 abutments. After veneer, the consistency of the L∗ a∗b∗ values of all the copings increased, the IPS E. max HO crowns had very close L∗ values and the Pro-Zir crowns had similar a∗b∗ values in 3 groups of abutments. CONCLUSION:4 ceramic copings can promote the light-ness and hue of the dark abutments. All the copings on the ND8 abutment had small ΔE values. Veneering porcelain can increase the colorimetric match between the abutments to some extent. IPS E. max HO crowns have little difference of lightness and Procera zirconia has little difference of saturation among the abutmens.%目的::采用分光光度比色仪比较3种深色基底表面4种全瓷冠各部分的色度学参数。方法:制作钴铬合金、金铂合金及ND8色基牙预备体,分别戴

  8. A study of colorimetric characteristics of the gold-platinum alloys substructure covered by different all-ceramic crowns before and after veneered application%不同全瓷冠在金铂合金基核表面颜色变化的分析

    Institute of Scientific and Technical Information of China (English)

    陈奕帆; 刘红春; 孟玉坤; 巢永烈; 杨晓喻

    2015-01-01

    Objective   To evaluate the optical data of the different sites of the gold-platinum alloys substructures covered by four different all-ceramic crowns, as well as the color difference between the crowns and target tab by using a digital dental spectrophotometer. Methods  Ten gold-platinum alloy substructures were made and were respectively tested on four different groups of all-ceramic crowns(Procera aluminia, Procera zirconia, Lava zirconia, and IPS E.max glass-ceramic lithium disilicate-reinforced monolithic crown). The color data of the cervical, body, incisal sites of the specimens were recorded and analyzed by a spectrophotometer. The L*, a*, b* values were measured again after veneered application. The color difference between the substructures covered by all-ceramic crowns and target A2 dentine shade tab was evaluated. Results  The L* values of the substructures can be increased by all four groups of all-ceramic copings and were higher than that of the A2 tab, but a* values were decreased and lower than A2 tab. The b* values showed inconsistent tendency of change. A statistical difference was found among four groups of copings. After veneered application, the L* values of all the copings declined and were lower than that of the control group. The values of a* and b* increased significantly, but the a* of the specimens was lower than that of the control. When compared with A2 dentine shade tab, the ΔΕ of the crowns was small, but the color difference was still clinically perceptible by human eyes.