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Sample records for beryllia

  1. Investigation of the beryllia ceramics molding process by the hot casting method

    Science.gov (United States)

    Zhapbasbaev, U. K.; Ramazanova, G. I.; Sattinova, Z. K.

    2013-03-01

    Results of mathematical simulation of the ceramics molding process by the hot casting method are presented. The mathematical model describes the motion of beryllia liquid thermoplastic slurry in a form-building cavity subject to solidification. Velocity and temperature profiles providing homogeneous properties of the beryllia ceramics in the process of molding by the hot casting method are obtained.

  2. Texture study of divided solids by gas adsorption: application to beryllia, alumina and to gels and oxides; Contribution a l'etude, par adsorption gazeuse, de la texture des solides divises. Application a l'alumine, a la glucine et a differents gels et oxydes

    Energy Technology Data Exchange (ETDEWEB)

    Rouquerol, F. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1965-12-01

    A certain number of porous materials have been studied in an adsorption apparatus developed by us and leading to a measurement of the surface area with a reproducibility as good as 1/1 000. We have shown that this is only obtained at the cost of a number necessary precautions in the measurement of the gaseous volume adsorbed in a monomolecular layer (especially in the case of microporous solids). It also appears convenient to substitute argon to nitrogen, the latter being sensitive to chemical or electrical interactions with the adsorbent. Calculation methods of the pore size distribution are analyzed and discussed. The experimental data shows that the thickness of the multi-molecular layer must be estimated from the number of layers given by Shull using a layer thickness of 3.6 angstrom. A new method of analysis of the desorption curve is also given. We have also shown that a certain number of lamellar, non porous, systems, such as Be(OH){sub 2} present a hysteresis branch on the adsorption isotherm of type I or II. Using the numerical data obtained by our method together with the information provided by the electronic microscope, we have been able to conclude that this hysteresis can be ascribed to the lack of rigidity of the solid. On the contrary, samples of microporous texture (r < 20 A) of the type of beryllia, provide the case, which we have been able to characterize, of porous materials which do not exhibit a hysteresis phenomenon. The above conclusions have allowed us to describe the evolution of the texture during their progressive dehydration (thermal treatment from 150 to 1100 C) of two series of samples, namely beryllia and alumina. (author) [French] A l'aide d'un appareil d'adsorption que nous avons mis au point, et qui permet d'atteindre Une reproductibilite de 1/1000 dans la mesure des surfaces specifiques, nous avons etudie de nombreux solides divises. Nous montrons qu'il est indispensable, de prendre des precautions (en

  3. High modulus invert analog glass compositions containing beryllia

    Science.gov (United States)

    Bacon, J. F. (Inventor)

    1974-01-01

    Glass compositions having a Young's modulus of at least 15 million psi and a specific modulus of at least 110 million inches consisting essentially of, in mols, 10-45% SiO2, 2-15% Li2O, 3-34% BeO, 12-36% of at least one bivalent oxide selected from the group consisting of CaO, ZnO, MgO and CuO, 10-39% of at least one trivalent oxide selected from the group consisting of Al2O3, B2O3, La2O3, Y2O3 and the mixed rare earth oxides, the total number of said bivalent and trivalent oxides being at least three, and up to 10% of a tetravalent oxide selected from the group consisting of ZrO2, TiO2 and CeO2.

  4. Thermal Conductivity of Composites of Beryllia and Lithium Titanate

    Science.gov (United States)

    Rath, B. N.; Ghanwat, S. J.; Kaity, Santu; Danani, Chandan; Kulkarni, R. V.; Alur, V. D.; Sathiyamoorthy, D.; Anantharaman, S.

    2013-11-01

    The International Thermonuclear Experimental Reactor (ITER) is designed to demonstrate the scientific and technological feasibility of fusion power for energy purposes. Wide varieties of solid breeders and multiplier materials have been proposed for fusion blankets. Beryllium and lithium titanate (Li2TiO3) have been accepted as neutron multiplier and breeder materials, respectively. However, swelling of beryllium due to helium and tritium permeation through metallic beryllium and low thermal conductivity of lithium titanate have caused serious limitations when ITER is in the demo version. It has been well established that BeO due its highest thermal conductivity among the known ceramics, low neutron absorption cross section, and high neutron reflection cross section is a good neutron multiplier. In the present investigation, a novel ceramic single compound of BeO-Li2TiO3 was synthesized, keeping the BeO content to Li2TiO3 in the volume ratio of 80:20, 75:25, 65:35, and 55:45 with the aim of maintaining the tritium breeding ratio as more than one, and characterized for phases present by x-ray diffraction and scanning electron microscopy.

  5. Ab-initio investigations of the electronic properties of bulk wurtzite Beryllia and its derived nanofilms

    KAUST Repository

    Goumri-Said, Souraya

    2010-08-01

    In this Letter we investigate the electronic properties of the bulk and the nanofilm BeO in wurtzite structure. We performed a first-principles pseudo-potential method within the generalized gradient approximation. We will give more importance to the changes in band structure and density of states between the bulk structure and its derived nanofilms. The bonding characterization will be investigated via the analysis Mulliken population and charge density contours. It is found that the nanofilm retains the same properties as its bulk structure with slight changes in electronic properties and band structure which may offer some unusual transport properties. © 2010 Elsevier B.V. All rights reserved.

  6. Thermal-shock Resistance of a Ceramic Comprising 60 Percent Boron Carbide and 40 Percent Titanium Diboride

    Science.gov (United States)

    Yeomans, C M; Hoffman, C A

    1953-01-01

    Thermal-shock resistance of a ceramic comprising 60 percent boron carbide and 40 percent titanium diboride was investigated. The material has thermal shock resistance comparable to that of NBS body 4811C and that of zirconia, but is inferior to beryllia, alumina, and titanium-carbide ceramals. It is not considered suitable for turbine blades.

  7. Radio frequency heating of ceramic windows in fusion applications

    Energy Technology Data Exchange (ETDEWEB)

    Fowler, J.D. Jr.

    1981-11-01

    Ceramic windows will be used as material barriers for radio frequency plasma heating in fusion reactors. This report examines the theory behind rf heating phenomena. Heating calculations are presented for various window materials, thicknesses, wavelengths, and power densities. The most pertinent material properties are loss tangent, thermal conductivity, dielectric constant, strength, and radiation resistance. Calculations indicate that among candidate materials, beryllium oxide offers the most promise because of its large thermal conductivity and relatively low loss tangent and dielectric constant. On the other hand, beryllia is susceptible to neutron damage, and this may adversely affect its electrical properties. Another promising candidate is sapphire, particularly at lower temperatures where the thermal conductivity is high. Fused silica suffers from low thermal conductivity and large positive temperature coefficient for loss tangent, but it may be useful under some conditions. In summary, calculations of heating can lead to elimination of some candidate materials and selection of others for further study.

  8. Thick silicon growth techniques

    Science.gov (United States)

    Bates, H. E.; Mlavsky, A. I.; Jewett, D. N.

    1973-01-01

    Hall mobility measurements on a number of single crystal silicon ribbons grown from graphite dies have shown some ribbons to have mobilities consistent with their resistivities. The behavior of other ribbons appears to be explained by the introduction of impurities of the opposite sign. Growth of a small single crystal silicon ribbon has been achieved from a beryllia dia. Residual internal stresses of the order of 7 to 18,000 psi have been determined to exist in some silicon ribbon, particularly those grown at rates in excess of 1 in./min. Growth experiments have continued toward definition of a configuration and parameters to provide a reasonable yield of single crystal ribbons. High vacuum outgassing of graphite dies and evacuation and backfilling of growth chambers have provided significant improvements in surface quality of ribbons grown from graphite dies.

  9. Oxide Fiber Targets at ISOLDE

    CERN Document Server

    Köster, U; Carminati, D; Catherall, R; Cederkäll, J; Correia, J G; Crepieux, B; Dietrich, M; Elder, K; Fedosseev, V; Fraile-Prieto, L M; Franchoo, S; Fynbo, H O U; Georg, U; Giles, T; Joinet, A; Jonsson, O C; Kirchner, R; Lau, C; Lettry, Jacques; Maier, H J; Mishin, V I; Oinonen, M; Peräjärvi, K; Ravn, H L; Rinaldi, T; Santana-Leitner, M; Wahl, U; Weissman, L

    2003-01-01

    Many elements are rapidly released from oxide matrices. Some oxide powder targets show a fast sintering, thus losing their favorable release characteristics. Loosely packed oxyde fiber targets are less critical since they may maintain their open structure even when starting to fuse together at some contact points. The experience with various oxyde fiber targets (titania, zirconia, ceria and thoria) used in the last years at ISOLDE is reviewed. For short-lived isotopes of Cu, Ga and Xe the zirconia and ceria targets respectively provided significantly higher yields than any other target (metal foils, oxide powders, etc.) tested before. Titania fibers, which were not commercially available, were produced in a relic process by impregnation of a rayon felt in a titanium chloride solution and subsequent calcination by heating the dried felt in air. Thoria fibers were obtained either by the same process or by burning commercial gas lantern mantle cloth. In the future a beryllia fiber target could be used to produce...

  10. Aluminium nitride: from the powder to the substrate. Le nitrure d'aluminium: de la poudre au substrat

    Energy Technology Data Exchange (ETDEWEB)

    Jarrige, J. (Lab. de Ceramiques Nouvelles, Limoges (France)); Mexmain, J. (Lab. de Ceramiques Nouvelles, Limoges (France)); Oumaloul, M. (Lab. de Ceramiques Nouvelles, Limoges (France)); Bachelard, R. (CRRA ELF ATOCHEM, Pierre Benite (France)); Disson, J.P. (CRRA ELF ATOCHEM, Pierre Benite (France))

    1993-04-01

    The aluminium nitride is a material which should replace alumina or beryllia as substrate for power electronic applications. The powder, prepared by carbothermal nitridation, is dispersed in a butanone-2-ethanol azeotrop solvent with a phosphate ester. Electrical conductivity, sedimentation, viscosity have been used to determine which phenomena take place in the defloculation of the suspension. The stability of AlN suspensions is due mainly to an electrostatic mechanism, with a steric contribution. The aluminium nitride tape-casting slip has been sintered at 1850 C in a nitrogen atmosphere. Removing of the binder and plasticizer can be performed in the same oven at 650 C, due to their nature and low concentration. The thermal conductivity of the substrates has been measured and is in the 160 to 200 W/m.K range. (orig.).

  11. Oxide fiber targets at ISOLDE

    Energy Technology Data Exchange (ETDEWEB)

    Koester, U. E-mail: ulli.koster@cern.ch; Bergmann, U.C.; Carminati, D.; Catherall, R.; Cederkaell, J.; Correia, J.G.; Crepieux, B.; Dietrich, M.; Elder, K.; Fedoseyev, V.N.; Fraile, L.; Franchoo, S.; Fynbo, H.; Georg, U.; Giles, T.; Joinet, A.; Jonsson, O.C.; Kirchner, R.; Lau, Ch.; Lettry, J.; Maier, H.J.; Mishin, V.I.; Oinonen, M.; Peraejaervi, K.; Ravn, H.L.; Rinaldi, T.; Santana-Leitner, M.; Wahl, U.; Weissman, L

    2003-05-01

    Many elements are rapidly released from oxide matrices. Some oxide powder targets show a fast sintering, thus losing their favorable release characteristics. Loosely packed oxide fiber targets are less critical since they may maintain their open structure even when starting to fuse together at some contact points. The experience with various oxide fiber targets (titania, zirconia, ceria and thoria) used in the last years at ISOLDE is reviewed. For short-lived isotopes of Cu, Ga and Xe the zirconia and ceria targets respectively provided significantly higher yields than any other target (metal foils, oxide powders, etc.) tested before. Titania fibers, which were not commercially available, were produced in a relic process by impregnation of a rayon felt in a titanium chloride solution and subsequent calcination by heating the dried felt in air. Thoria fibers were obtained either by the same process or by burning commercial gas lantern mantle cloth. In the future a beryllia fiber target could be used to produce very intense {sup 6}He beams (order of 10{sup 13} ions per second) via the {sup 9}Be(n,{alpha}) reaction using spallation neutrons.

  12. Machining risk of beryllium disease and sensitization with median exposures below 2 micrograms/m3.

    Science.gov (United States)

    Kreiss, K; Mroz, M M; Newman, L S; Martyny, J; Zhen, B

    1996-07-01

    We examined the prevalence of beryllium sensitization in relation to work process and beryllium exposure measurements in a beryllia ceramics plant that had operated since 1980. We interviewed 136 employees (97.8% of the workforce), ascertained beryllium sensitization with the beryllium lymphocyte proliferation blood test, and reviewed historical industrial hygiene measurements. Of eight beryllium-sensitized employees (5.9%), six (4.4% of participating employees) had granulomatous disease on transbronchial lung biopsy. Machinists had a sensitization rate of 14.3% compared to a rate of 1.2% among other employees. Machining had significantly higher general area and breathing zone measurements than did other processes in the time period in which most beryllium-sensitized cases had started machining work. Daily weighted average (DWA) estimates of exposure for matching processes also exceeded estimates for other work processes in that time period, with a median DWA of 0.9 microgram/m3. Machining process DWAs accounted for the majority of DWAs exceeding the 2.0 micrograms/m3 OSHA standard, with 8.1% of machining DWAs above the standard. We conclude that lowering machining process-related exposures may be important to lowering risk of beryllium disease.