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Sample records for porous alumina ceramics

  1. 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

  2. Low-cost shape-control synthesis of porous carbon film on β″-alumina ceramics for Na-based battery application

    Science.gov (United States)

    Hu, Yingying; Wen, Zhaoyin; Wu, Xiangwei; Jin, Jun

    2012-12-01

    Porous carbon films with tunable pore structure to modify the β″-alumina electrolyte surface are fabricated through a low-cost and direct wet chemistry method with glucose and poly(methyl-methacrylate) (PMMA) as precursors. FTIR analysis confirms the effective connection between the carbohydrate and the pore-forming agent PMMA through hydrogen bonds. The experimental results indicate that the structural parameters of the porous carbon films, including mean pore size and film thickness, can be tuned simply by adjusting the amount of PMMA in the glucose/PMMA composite. This soft-template-assisted method could be readily extended to modify any other ceramic surfaces. The porous carbon films are demonstrated to greatly improve the wettability of the β″-alumina ceramics by molten sodium. Na/β″-alumina/Na cells are used to investigate the interfacial properties between sodium and the β″-alumina electrolyte. The results obtained at 350 °C reveal that the polarization behavior of the cell is alleviated by the porous coating. This work represents a successful method to coat ceramics with porous carbon and offers a promising solution to overcome the polarization problems of the sodium/β″-alumina interface in Na-based batteries.

  3. Mechanical properties of dense to porous alumina/lanthanum hexaaluminate composite ceramics

    International Nuclear Information System (INIS)

    Negahdari, Zahra; Willert-Porada, Monika; Pfeiffer, Carolin

    2010-01-01

    For development of new composite materials based on lanthanum hexaaluminate and alumina ceramics, a better understanding of the microstructure-properties relationship is essential. In this paper, attention was focused on the evaluation of mechanical properties of lanthanum hexaaluminate/alumina particulate composite. It was found out that the lanthanum hexaaluminate content plays a critical role in determination of the microstructure and mechanical properties of the composite ceramics. In situ formation of plate-like lanthanum hexaaluminate in the ceramic matrix was accompanied with formation of pores so that the microstructure shifted from dense to porous. Increasing the lanthanum hexaaluminate content up to a certain value enhanced the fracture toughness, increased the hardness, and increased the elastic modulus of the composite materials. Further increase in the lanthanum hexaaluminate content degraded the hardness as well as the elastic modulus of composite ceramics. The influence of lanthanum hexaaluminate on mechanical properties was described by means of microstructure, porosity, and intrinsic characteristics of lanthanum hexaaluminate.

  4. Engineering durable hydrophobic surfaces on porous alumina ceramics using in-situ formed inorganic-organic hybrid nanoparticles

    NARCIS (Netherlands)

    Gu, Jianqiang; Wang, Junwei; Li, Yanan; Xu, Xin; Chen, Chusheng; Winnubst, Louis

    2017-01-01

    Hydrophobic surfaces are required for a variety of applications owing to their water repellent and self-cleaning properties. In this work, we present a novel approach to prepare durable hydrophobic surfaces on porous ceramics. A polydimethylsiloxane (PDMS) film was applied to a porous alumina wafer,

  5. [Characterization of alumina adobe and sintered body of GI-infiltrated ceramic].

    Science.gov (United States)

    Wang, H; Chao, Y; Liao, Y; Liang, X; Zhu, Z; Gao, W

    2001-06-01

    This study was conducted to elucidate the mechanism of formation of porous structure by investigating the porosity of the alumina adobe and sintered body of GI-II Infiltrate Ceramic, and its role in strengthening and toughening this kind of ceramic composite. The alumina powder size-mass distribution was obtained by BI-XDC powder size analysis device; the open pore parameters of alumina adobe and sintered body were analyzed using the mercury pressure method. Their fracture surfaces were observed under scanning electronic microscope. Fine powder had two main size groups of 0.09-0.1 micron and 0.2-0.5 micron, respectively, and coarse powder, with size between 1.5 to 4.5 microns, occupied the majority of powder mass. Alumina adobe's pores became larger after sintering. The median pore radii of adobe and sintered body were 0.2531 micron and 0.3081 micron, respectively; the average pore radii changed from 0.0956 micron to 0.1102 micron. Under scanning electronic microscope, fine alumina powders were fused partially together and their surfaces were blunted, but coarse powders did not show such phenomena. The alumina size distribution contributes to the formation of porous structure of alumina sintered body. This porous structure is not only the shape skeleton but also the mechanical skeleton of GI-II Infiltrated Ceramic. It plays an important role in raising the mechanical properties of this kind of ceramic composite.

  6. 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.

  7. 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...

  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. 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.

  10. 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.

  11. 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

  12. Zirconia toughened alumina ceramic foams for potential bone graft applications: fabrication, bioactivation, and cellular responses.

    Science.gov (United States)

    He, X; Zhang, Y Z; Mansell, J P; Su, B

    2008-07-01

    Zirconia toughened alumina (ZTA) has been regarded as the next generation orthopedic graft material due to its excellent mechanical properties and biocompatibility. Porous ZTA ceramics with good interconnectivity can potentially be used as bone grafts for load-bearing applications. In this work, three-dimensional (3D) interconnected porous ZTA ceramics were fabricated using a direct foaming method with egg white protein as binder and foaming agent. The results showed that the porous ZTA ceramics possessed a bimodal pore size distribution. Their mechanical properties were comparable to those of cancellous bone. Due to the bio-inertness of alumina and zirconia ceramics, surface bioactivation of the ZTA foams was carried out in order to improve their bioactivity. A simple NaOH soaking method was employed to change the surface chemistry of ZTA through hydroxylation. Treated samples were tested by conducting osteoblast-like cell culture in vitro. Improvement on cells response was observed and the strength of porous ZTA has not been deteriorated after the NaOH treatment. The porous 'bioactivated' ZTA ceramics produced here could be potentially used as non-degradable bone grafts for load-bearing applications.

  13. Carbon nanotubes-porous ceramic composite by in situ CCVD growth of CNTs

    International Nuclear Information System (INIS)

    Mazumder, Sangram; Sarkar, Naboneeta; Park, Jung Gyu; Han, In Sub; Kim, Ik Jin

    2016-01-01

    A novel approach towards the formation of Carbon nanotubes-porous alumina ceramic composite was attempted by the application of three different reaction techniques. Porous alumina ceramics having micrometer pore dimensions were developed using the direct foaming technique. NaA zeolites were simultaneously synthesized and coated within the porous ceramics by an in situ hydrothermal process and were subjected to a simple ion exchange reaction for preparing the suitable catalyst material for Carbon nanotubes (CNTs) synthesis. The catalytic chemical vapour deposition (CCVD) technique was used to grow CNTs within the porous ceramics and the effect of growth time on the synthesized CNTs were investigated. Phase compositions of the samples were analysed by X-ray diffractometer (XRD). Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM) were used for morphology, surface quality and structural analysis. Crystallinity, defects and yield were studied by Raman spectroscopy and thermogravimetric analysis (TGA). - Highlights: • Novel processing route of MWCNTs grown on Cobalt-zeolites-porous ceramics by CCVD. • CCVD time of 120 min produced MWCNTs with most prominent tube-like structure. • 120 min produced highest yield (19.46%) of CNTs with an I_D/I_G ratio of 0.88.

  14. On the comparison of the ballistic performance of 10% zirconia toughened alumina and 95% alumina ceramic target

    International Nuclear Information System (INIS)

    Zhang, X.F.; Li, Y.C.

    2010-01-01

    Ballistic performance of different type of ceramic materials subjected to high velocity impact was investigated in many theoretical, experimental and numerical studies. In this study, a comparison of ballistic performance of 95% alumina ceramic and 10% zirconia toughened alumina (ZTA) ceramic tiles was analyzed theoretically and experimentally. Spherical cavity model based on the concepts of mechanics of compressible porous media of Galanov was used to analyze the relation of target resistance and static mechanical properties. Experimental studies were carried out on the ballistic performance of above two types of ceramic tiles based on the depth of penetration (DOP) method, when subjected to normal impact of tungsten long rod projectiles. Typical damaged targets were presented. The residual depth of penetration on after-effect target was measured in all experiments, and the ballistic efficiency factor of above two types ceramic plates were determined. Both theoretical and experimental results show that the improvement on ballistic resistance was clearly observed by increasing fracture toughness in ZTA ceramics.

  15. Carbon nanotubes-porous ceramic composite by in situ CCVD growth of CNTs

    Energy Technology Data Exchange (ETDEWEB)

    Mazumder, Sangram; Sarkar, Naboneeta; Park, Jung Gyu [Institute of Processing and Application of Inorganic Materials (PAIM), Department of Materials Science and Engineering, Hanseo University, #360 Daegok-ri, Haemi-myeon, Seosan-si, Chungnam, 356-706 (Korea, Republic of); Han, In Sub [Korea Institute of Energy Research (KIER), #152 Gajeong-gu, Daejeon 305-343 (Korea, Republic of); Kim, Ik Jin, E-mail: ijkim@hanseo.ac.kr [Institute of Processing and Application of Inorganic Materials (PAIM), Department of Materials Science and Engineering, Hanseo University, #360 Daegok-ri, Haemi-myeon, Seosan-si, Chungnam, 356-706 (Korea, Republic of)

    2016-03-01

    A novel approach towards the formation of Carbon nanotubes-porous alumina ceramic composite was attempted by the application of three different reaction techniques. Porous alumina ceramics having micrometer pore dimensions were developed using the direct foaming technique. NaA zeolites were simultaneously synthesized and coated within the porous ceramics by an in situ hydrothermal process and were subjected to a simple ion exchange reaction for preparing the suitable catalyst material for Carbon nanotubes (CNTs) synthesis. The catalytic chemical vapour deposition (CCVD) technique was used to grow CNTs within the porous ceramics and the effect of growth time on the synthesized CNTs were investigated. Phase compositions of the samples were analysed by X-ray diffractometer (XRD). Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM) were used for morphology, surface quality and structural analysis. Crystallinity, defects and yield were studied by Raman spectroscopy and thermogravimetric analysis (TGA). - Highlights: • Novel processing route of MWCNTs grown on Cobalt-zeolites-porous ceramics by CCVD. • CCVD time of 120 min produced MWCNTs with most prominent tube-like structure. • 120 min produced highest yield (19.46%) of CNTs with an I{sub D}/I{sub G} ratio of 0.88.

  16. Alumina ceramics prepared with new pore-forming agents

    Directory of Open Access Journals (Sweden)

    Zuzana Živcová

    2008-06-01

    Full Text Available Porous ceramics have a wide range of applications at all length scales, ranging from fi ltration membranes and catalyst supports to biomaterials (scaffolds for bone ingrowths and thermally or acoustically insulating bulk materials or coating layers. Organic pore-forming agents (PFAs of biological origin can be used to control porosity, pore size and pore shape. This work concerns the characterization and testing of several less common pore-forming agents (lycopodium, coffee, fl our and semolina, poppy seed, which are of potential interest from the viewpoint of size, shape or availability. The performance of these new PFAs is compared to that of starch, which has become a rather popular PFA for ceramics during the last decade. The PFAs investigated in this work are in the size range from 5 μm (rice starch to approximately 1 mm (poppy seed, all with more or less isometric shape. The burnout behavior of PFAs is studied by thermal analysis, i.e. thermogravimetry and differential thermal analysis. For the preparation of porous alumina ceramics from alumina suspensions containing PFAs traditional slip casting (into plaster molds and starch consolidation casting (using metal molds are used in this work. The resulting microstructures are investigated using optical microscopy, combined with image analysis, as well as other methods (Archimedes method of double-weighing in water, mercury intrusion porosimetry.

  17. 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.

  18. 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

  19. Obtain ceramic porous alumina-zirconia by replica method calcium phosphate coated

    International Nuclear Information System (INIS)

    Silva, A.D.R.; Rigoli, W.R.; Osiro, Denise; Pallone, E.M.J.A.

    2016-01-01

    Biomaterials used in bone replacement, including porous bioceramics, are often used as support structure for bone formation and repair. The porous bioceramics are used because present features as biocompatibility, high porosity and pore morphology that confer adequate mechanical strength and induce bone growth. In this work were obtained porous specimens of alumina containing 5% by inclusion of volume of zirconia produced by the replica method. The porous specimens had its surface chemically treated with phosphoric acid and were coated with calcium phosphate. The coating was performed using the biomimetic method during 14 days and an initial pH of 6.1. The porous specimens were characterized using the follow techniques: porosity, axial compression tests, microtomography, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and pH measurements SBF solution. The results showed specimens with suitable pore morphology for application as biomaterial, and even a reduced time of incubation favored the calcium phosphate phases formation on the material surfaces. (author)

  20. Durability of feldspathic veneering ceramic on glass-infiltrated alumina ceramics after long-term thermocycling.

    Science.gov (United States)

    Mesquita, A M M; Ozcan, M; Souza, R O A; Kojima, A N; Nishioka, R S; Kimpara, E T; Bottino, M A

    2010-01-01

    This study compared the bond strength durability of a feldspathic veneering ceramic to glass-infiltrated reinforced ceramics in dry and aged conditions. Disc shaped (thickness: 4 mm, diameter: 4 mm) of glass-infiltrated alumina (In-Ceram Alumina) and glass-infiltrated alumina reinforced by zirconia (In-Ceram Zirconia) core ceramic specimens (N=48, N=12 per groups) were constructed according to the manufacturers' recommendations. Veneering ceramic (VITA VM7) was fired onto the core ceramics using a mold. The core-veneering ceramic assemblies were randomly divided into two conditions and tested either immediately after specimen preparation (Dry) or following 30000 thermocycling (5-55 ºC±1; dwell time: 30 seconds). Shear bond strength test was performed in a universal testing machine (cross-head speed: 1 mm/min). Failure modes were analyzed using optical microscope (x20). The bond strength data (MPa) were analyzed using ANOVA (α=0.05). Thermocycling did not decrease the bond strength results for both In-Ceram Alumina (30.6±8.2 MPa; P=0.2053) and In-Ceram zirconia (32.6±9 MPa; P=0.3987) core ceramic-feldspathic veneering ceramic combinations when compared to non-aged conditions (28.1±6.4 MPa, 29.7±7.3 MPa, respectively). There were also no significant differences between adhesion of the veneering ceramic to either In-Ceram Alumina or In-Ceram Zirconia ceramics (P=0.3289). Failure types were predominantly a mixture of adhesive failure between the veneering and the core ceramic together with cohesive fracture of the veneering ceramic. Long-term thermocycling aging conditions did not impair the adhesion of the veneering ceramic to the glass-infiltrated alumina core ceramics tested.

  1. Thermal-Conductivity Studies of Macro-porous Polymer-Derived SiOC Ceramics

    Science.gov (United States)

    Qiu, L.; Li, Y. M.; Zheng, X. H.; Zhu, J.; Tang, D. W.; Wu, J. Q.; Xu, C. H.

    2014-01-01

    A three-dimensional reticular macro-porous SiOC ceramics structure, made of spherical agglomerates, has been thermally characterized using a freestanding sensor-based method. The effective thermal conductivity of the macro-porous SiOC ceramics, including the effects of voids, is found to be to at room temperature, comparable with that of alumina aerogel or carbon aerogel. These results suggest that SiOC ceramics hold great promise as a thermal insulation material for use at high temperatures. The measured results further reveal that the effective thermal conductivity is limited by the low solid-phase volume fraction for the SiOC series processed at the same conditions. For SiOC ceramics processed under different pyrolysis temperatures, the contact condition between neighboring particles in the SiOC networks is another key factor influencing the effective thermal conductivity.

  2. 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.

  3. Biomimetic Coating on Porous Alumina for Tissue Engineering: Characterisation by Cell Culture and Confocal Microscopy

    Directory of Open Access Journals (Sweden)

    Elizabeth Kolos

    2015-06-01

    Full Text Available In this study porous alumina samples were prepared and then coated using the biomimetic coating technique using a five times Simulated Body Fluid (5.0SBF as the growth solution. A coating was achieved after pre-treatment with concentrated acid. From elemental analysis, the coating contained calcium and phosphorous, but also sodium and chlorine. Halite was identified by XRD, a sodium chloride phase. Sintering was done to remove the halite phase. Once halite was burnt off, the calcium phosphate crystals were not covered with halite and, therefore, the apatite phases can be clearly observed. Cell culturing showed sufficient cell attachment to the less porous alumina, Sample B, that has more calcium phosphate growth, while the porous alumina, Sample A, with minimal calcium phosphate growth attained very little cell attachment. This is likely due to the contribution that calcium phosphate plays in the attachment of bone-like cells to a bioinert ceramic such as alumina. These results were repeated on both SEM and confocal microscopy analysis. Confocal microscopy was a novel characterisation approach which gave useful information and was a visual aid.

  4. 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

  5. Manufacturing of porous oxide ceramics by replication of plant morphologies

    Energy Technology Data Exchange (ETDEWEB)

    Sieber, H.; Rambo, C.; Cao, J.; Vogli, E.; Greil, P. [Erlangen-Nuernberg Univ., Erlangen (DE). Dept. of Materials Science (III) Glass and Ceramics

    2002-07-01

    Biomorphic oxide ceramics of alumina, mullite and zirconia with a directed pore morphology on the micrometer level were manufactured from bioorganic plant structures by sol-gel processing as well as sol-assisted nano-powder infiltrations. The inherent open porous morphology of natural grown rattan palms was used for vacuum-infiltration with aluminum isopropoxide (Al(OC{sub 3}H{sub 7}){sub 3}), zirconium oxichloride (ZrOCl{sub 2}.8H{sub 2}O) and SiO{sub 2} nano powder. Hydrolysis of the sols by adding HNO{sub 3} and pyrolysis in inert atmosphere at 800 C resulted in the formation of biocarbon/ceramic replica of the original wood morphology. The specimens were sintered in air at temperatures up to 1600 C to yield porous oxide ceramics with an unidirected pore structure similar to the original plant material. Repeated infiltration, hydrolysis and annealing steps were applied to increase the density of the ceramic materials. (orig.)

  6. Ballistic Performance of Porous-Ceramic, Thermal Protection Systems to 9 km/s

    Science.gov (United States)

    Miller, Joshua E.; Bohl, William E.; Foreman, Cory D.; Christiansen, Eric C.; Davis, Bruce A.

    2010-01-01

    Porous-ceramic, thermal protection systems are used heavily in current reentry vehicles like the Orbiter, and they are currently being proposed for the next generation of US manned spacecraft, Orion. These materials insulate the structural components and sensitive components of a spacecraft against the intense thermal environments of atmospheric reentry. These materials are also highly exposed to solid particle space environment hazards. This paper discusses recent impact testing up to 9.65 km/s on ceramic tiles similar to those used on the Orbiter. These tiles are a porous-ceramic insulator of nominally 8 lb/ft(exp 3) alumina-fiber-enhanced-thermal-barrier (AETB8) coated with a damage-resistant, toughened-unipiece-fibrous-insulation/reaction-cured-glass layer (TUFI/RCG).

  7. 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

  8. 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.

  9. 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)

  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. 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.

  12. 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

  13. A novel approach for the fabrication of carbon nanofibre/ceramic porous structures

    KAUST Repository

    Walter, Claudia

    2013-11-01

    This paper describes the fabrication of hybrid ceramic/carbon scaffolds in which carbon nanofibres and multi-walled carbon nanotubes fully cover the internal walls of a microporous ceramic structure that provides mechanical stability. Freeze casting is used to fabricate a porous, lamellar ceramic (Al2O3) structure with aligned pores whose width can be controlled between 10 and 90μm. Subsequently, a two step chemical vapour deposition process that uses iron as a catalyst is used to grow the carbon nanostructures inside the scaffold. This catalyst remains in the scaffold after the growth process. The formation of the alumina scaffold and the influence of its structure on the growth of nanofibres and tubes are investigated. A set of growth conditions is determined to produce a dense covering of the internal walls of the porous ceramic with the carbon nanostructures. The limiting pore size for this process is located around 25μm. © 2013 Elsevier Ltd.

  14. Fabrication and Characterization of Porous MgAl₂O₄ Ceramics via a Novel Aqueous Gel-Casting Process.

    Science.gov (United States)

    Yuan, Lei; Liu, Zongquan; Liu, Zhenli; He, Xiao; Ma, Beiyue; Zhu, Qiang; Yu, Jingkun

    2017-11-30

    A novel and aqueous gel-casting process has been successfully developed to fabricate porous MgAl₂O₄ ceramics by using hydratable alumina and MgO powders as raw materials and deionized water as hydration agent. The effects of different amounts of deionized water on the hydration properties, apparent porosity, bulk density, microstructure, pore size distribution and compressive strength of the samples were investigated. The results indicated that the porosity and the microstructure of porous MgAl₂O₄ ceramics were governed by the amounts of deionized water added. The porous structure was formed by the liberation of physisorbed water and the decomposition of hydration products such as bayerite, brucite and boehmite. After determining the addition amounts of deionized water, the fabricated porous MgAl₂O₄ ceramics had a high apparent porosity (52.5-65.8%), a small average pore size structure (around 1-3 μm) and a relatively high compressive strength (12-28 MPa). The novel aqueous gel-casting process with easy access is expected to be a promising candidate for the preparation of Al₂O₃-based porous ceramics.

  15. 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.

  16. 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.

  17. Ballistic Performance of Porous Ceramic Thermal Protection Systems at 9 km/s

    Science.gov (United States)

    Miller, Joshua E.; Bohl, W. E.; Foreman, C. D.; Christiansen, Eric L.; Davis, B. A.

    2009-01-01

    Porous-ceramic, thermal-protection-systems are used heavily in current reentry vehicles like the Orbiter, and they are currently being proposed for the next generation of manned spacecraft, Orion. These materials insulate the structural components and sensitive electronic components of a spacecraft against the intense thermal environments of atmospheric reentry. Furthermore, these materials are also highly exposed to space environmental hazards like meteoroid and orbital debris impacts. This paper discusses recent impact testing up to 9 km/s on ceramic tiles similar to those used on the Orbiter. These tiles have a porous-batting of nominally 8 lb/cubic ft alumina-fiber-enhanced-thermal-barrier (AETB8) insulating material coated with a damage-resistant, toughened-unipiece-fibrous-insulation (TUFI) layer.

  18. 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.

  19. 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.

  20. Separation of Hydrogen from Carbon Dioxide through Porous Ceramics

    Directory of Open Access Journals (Sweden)

    Taro Shimonosono

    2016-11-01

    Full Text Available The gas permeability of α-alumina, yttria-stabilized zirconia (YSZ, and silicon carbide porous ceramics toward H2, CO2, and H2–CO2 mixtures were investigated at room temperature. The permeation of H2 and CO2 single gases occurred above a critical pressure gradient, which was smaller for H2 gas than for CO2 gas. When the Knudsen number (λ/r ratio, λ: molecular mean free path, r: pore radius of a single gas was larger than unity, Knudsen flow became the dominant gas transportation process. The H2 fraction for the mixed gas of (20%–80% H2–(80%–20% CO2 through porous Al2O3, YSZ, and SiC approached unity with decreasing pressure gradient. The high fraction of H2 gas was closely related to the difference in the critical pressure gradient values of H2 and CO2 single gas, the inlet mixed gas composition, and the gas flow mechanism of the mixed gas. Moisture in the atmosphere adsorbed easily on the porous ceramics and affected the critical pressure gradient, leading to the increased selectivity of H2 gas.

  1. 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

  2. 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.

  3. Synthesis of aluminum oxy-hydroxide nanofibers from porous anodic alumina

    Energy Technology Data Exchange (ETDEWEB)

    Jha, Himendra; Kikuchi, Tatsuya; Sakairi, Masatoshi; Takahashi, Hideaki [Laboratory of Interface Microstructure Analysis (LIMSA), Division of Materials Science and Engineering, Graduate School of Engineering, Hokkaido University, Sapporo 060-8628 (Japan)], E-mail: himendra@eng.hokudai.ac.jp

    2008-10-01

    A novel method for the synthesis of aluminum oxy-hydroxide nanofibers from a porous anodic oxide film of aluminum is demonstrated. In the present method, the porous anodic alumina not only acts as a template, but also serves as the starting material for the synthesis. The porous anodic alumina film is hydrothermally treated for pore-sealing, which forms aluminum oxy-hydroxide inside the pores of the oxide film as well as on the surface of the film. The hydrothermally sealed porous oxide film is immersed in the sodium citrate solution, which selectively etches the porous aluminum oxide from the film, leaving the oxy-hydroxide intact. The method is simple and gives highly uniform aluminum oxy-hydroxide nanofibers. Moreover, the diameter of the nanofibers can be controlled by controlling the pore size of the porous anodic alumina film, which depends on the anodizing conditions. Nanofibers with diameters of about 38-85 nm, having uniform shape and size, were successfully synthesized using the present method.

  4. Synthesis of aluminum oxy-hydroxide nanofibers from porous anodic alumina

    International Nuclear Information System (INIS)

    Jha, Himendra; Kikuchi, Tatsuya; Sakairi, Masatoshi; Takahashi, Hideaki

    2008-01-01

    A novel method for the synthesis of aluminum oxy-hydroxide nanofibers from a porous anodic oxide film of aluminum is demonstrated. In the present method, the porous anodic alumina not only acts as a template, but also serves as the starting material for the synthesis. The porous anodic alumina film is hydrothermally treated for pore-sealing, which forms aluminum oxy-hydroxide inside the pores of the oxide film as well as on the surface of the film. The hydrothermally sealed porous oxide film is immersed in the sodium citrate solution, which selectively etches the porous aluminum oxide from the film, leaving the oxy-hydroxide intact. The method is simple and gives highly uniform aluminum oxy-hydroxide nanofibers. Moreover, the diameter of the nanofibers can be controlled by controlling the pore size of the porous anodic alumina film, which depends on the anodizing conditions. Nanofibers with diameters of about 38-85 nm, having uniform shape and size, were successfully synthesized using the present method

  5. 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.

  6. 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.

  7. 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.

  8. Porous alumina scaffold produced by sol-gel combined polymeric sponge method

    Science.gov (United States)

    Hasmaliza, M.; Fazliah, M. N.; Shafinaz, R. J.

    2012-09-01

    Sol gel is a novel method used to produce high purity alumina with nanometric scale. In this study, three-dimensional porous alumina scaffold was produced using sol-gel polymeric sponge method. Briefly, sol gel alumina was prepared by evaporation and polymeric sponge cut to designated sizes were immersed in the sol gel followed by sintering at 1250 and 1550°C. In order to study the cell interaction, the porous alumina scaffold was sterilized using autoclave prior to Human Mesenchymal Stem Cells (HMSCs) seeding on the scaffold and the cell proliferation was assessed by alamarBlue® assay. SEM results showed that during the 21 day period, HMSCs were able to attach on the scaffold surface and the interconnecting pores while maintaining its proliferation. These findings suggested the potential use of the porous alumina produced as a scaffold for implantation procedure.

  9. Topotactic preparation of textured alumina ceramics from dehydroxylation of gibbsite films

    Energy Technology Data Exchange (ETDEWEB)

    Louaer, Seif-Eddine; Wang, Yao, E-mail: yao@buaa.edu.cn; Guo, Lin, E-mail: guolin@buaa.edu.cn

    2014-11-14

    In this paper, textured alumina ceramics were prepared from dehydroxylation of gibbsite films and the pseudomorphic and topotactic nature of the dehydroxylation of textured gibbsite films has been investigated. First, the precursor film with a (001)-textured structure was obtained via vacuum filtration deposition of diluted aqueous suspensions of gibbsite nanoplatelets. Subsequently, (001)-textured α-alumina ceramics were successfully achieved by sintering of the deposited gibbsite films without addition of α-alumina seeds. The Scanning Electron Microscope (SEM) and X-ray Diffraction (XRD) results show that, during the phase transition from gibbsite to α-alumina, both layered morphology and crystal's axis orientation have been retained to a considerable extent. For the first time, a direct XRD evidence of gibbsite topotactic dehydroxylation to the α-alumina phase is presented. It is believed that the method described here exploits gibbsite's pseudomorphic and topotactic dehydroxylation, not on individual particles scale but on a bulk form. The resulting structure can be considered as inorganic scaffolds which can have applications for fabrication of dense, textured alumina-based ceramics and other layered/textured nanocomposites. - Highlights: • Gibbsite nanoplatelets were assembled on their basal plane to form (001)-textured films. • Textured alumina ceramics were prepared by sintering textured gibbsite films without addition of α-alumina seeds. • Both pseudomorphic and topotactic aspects were exploited in bulk form instead of individual nanoparticulate size. • Direct XRD evidence of the topotactic dehydroxylation from gibbsite to α-alumina is presented in this work.

  10. Topotactic preparation of textured alumina ceramics from dehydroxylation of gibbsite films

    International Nuclear Information System (INIS)

    Louaer, Seif-Eddine; Wang, Yao; Guo, Lin

    2014-01-01

    In this paper, textured alumina ceramics were prepared from dehydroxylation of gibbsite films and the pseudomorphic and topotactic nature of the dehydroxylation of textured gibbsite films has been investigated. First, the precursor film with a (001)-textured structure was obtained via vacuum filtration deposition of diluted aqueous suspensions of gibbsite nanoplatelets. Subsequently, (001)-textured α-alumina ceramics were successfully achieved by sintering of the deposited gibbsite films without addition of α-alumina seeds. The Scanning Electron Microscope (SEM) and X-ray Diffraction (XRD) results show that, during the phase transition from gibbsite to α-alumina, both layered morphology and crystal's axis orientation have been retained to a considerable extent. For the first time, a direct XRD evidence of gibbsite topotactic dehydroxylation to the α-alumina phase is presented. It is believed that the method described here exploits gibbsite's pseudomorphic and topotactic dehydroxylation, not on individual particles scale but on a bulk form. The resulting structure can be considered as inorganic scaffolds which can have applications for fabrication of dense, textured alumina-based ceramics and other layered/textured nanocomposites. - Highlights: • Gibbsite nanoplatelets were assembled on their basal plane to form (001)-textured films. • Textured alumina ceramics were prepared by sintering textured gibbsite films without addition of α-alumina seeds. • Both pseudomorphic and topotactic aspects were exploited in bulk form instead of individual nanoparticulate size. • Direct XRD evidence of the topotactic dehydroxylation from gibbsite to α-alumina is presented in this work

  11. Solid state reaction in alumina nanoparticles/LZSA glass-ceramic composites

    International Nuclear Information System (INIS)

    Montedo, O.K.; Oliveira, A.N. de; Raupp-Pereira, F.

    2016-01-01

    Full text: The aim of this work is to present results related to solid state reactions on LZSA glass-ceramic composites containing alumina reinforcement nano-particles. A LZSA (Li2O-ZrO2-SiO2-Al2O3) glass-ceramic has been prepared by sintering of powders and characterized. Composites containing 0 to 77 vol.% of alumina nanoparticles (27-43 nm APS, 35 m2.g-1 SSA) and a 16.9Li2O•5.0ZrO2•65.1SiO2•8.6Al2O3 glass-ceramic matrix have been prepared. X-ray diffractometry studies have been performed in order of investigating the solid state reactions occurring in LZSA-based composites. Results of the XRD patterns have been related to the coefficient of thermal expansion (CTE), Young modulus, and dielectric constant, showing that, in comparison with the glass-ceramic composition, the composites showed a decrease of CTE with the alumina concentration increasing, due to the increasing of beta-spodumeness formation (solid solution of beta-spodumene, Li2O.Al2O3.4-10SiO2). The performance of the glass-ceramic was improved with the alumina nano-particles addition, showing potential of using in the preparation of Low Thermal Co-fired Ceramics (LTCC). (author)

  12. Porous ceramics out of oxides

    International Nuclear Information System (INIS)

    Bakunov, V.S.; Balkevich, V.L.; Vlasov, A.S.; Guzman, I.Ya.; Lukin, E.S.; Poluboyarinov, D.N.; Poliskij, R.Ya.

    1977-01-01

    A review is made of manufacturing procedures and properties of oxide ceramics intended for high-temperature thermal insulation and thermal protection applications. Presented are structural characteristics of porous oxide refractories and their properties. Strength and thermal conductivity was shown to depend upon porosity. Described is a procedure for manufacturing porous ceramic materials from aluminium oxide, zirconium dioxide, magnesium oxide, beryllium oxide. The thermal resistance of porous ceramics from BeO is considerably greater than that of other high-refractoriness oxides. Listed are areas of application for porous materials based on oxides

  13. 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...

  14. Effect of Manganese Content on the Fabrication of Porous Anodic Alumina

    Directory of Open Access Journals (Sweden)

    C. H. Voon

    2012-01-01

    Full Text Available The influence of manganese content on the formation of well-ordered porous anodic alumina was studied. Porous anodic alumina has been produced on aluminium substrate of different manganese content by single-step anodizing at 50 V in 0.3 M oxalic acid at 15°C for 60 minutes. The well-ordered pore and cell structure was revealed by subjecting the porous anodic alumina to oxide dissolution treatment in a mixture of chromic acid and phosphoric acid. It was found that the manganese content above 1 wt% impaired the regularity of the cell and pore structure significantly, which can be attributed to the presence of secondary phases in the starting material with manganese content above 1 wt%. The pore diameter and interpore distance decreased with the addition of manganese into the substrates. The time variation of current density and the thickness of porous anodic alumina also decreased as a function of the manganese content in the substrates.

  15. Fabrication and Characterization of Porous MgAl2O4 Ceramics via a Novel Aqueous Gel-Casting Process

    Directory of Open Access Journals (Sweden)

    Lei Yuan

    2017-11-01

    Full Text Available A novel and aqueous gel-casting process has been successfully developed to fabricate porous MgAl2O4 ceramics by using hydratable alumina and MgO powders as raw materials and deionized water as hydration agent. The effects of different amounts of deionized water on the hydration properties, apparent porosity, bulk density, microstructure, pore size distribution and compressive strength of the samples were investigated. The results indicated that the porosity and the microstructure of porous MgAl2O4 ceramics were governed by the amounts of deionized water added. The porous structure was formed by the liberation of physisorbed water and the decomposition of hydration products such as bayerite, brucite and boehmite. After determining the addition amounts of deionized water, the fabricated porous MgAl2O4 ceramics had a high apparent porosity (52.5–65.8%, a small average pore size structure (around 1–3 μm and a relatively high compressive strength (12–28 MPa. The novel aqueous gel-casting process with easy access is expected to be a promising candidate for the preparation of Al2O3-based porous ceramics.

  16. Synthesis and surface characterization of alumina-silica-zirconia nanocomposite ceramic fibres on aluminium at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Mubarak Ali, M., E-mail: masterscience2003@yahoo.co.in [Advanced Materials Research Laboratory, Department of Chemistry, Periyar University, Omalur Main Road, Salem 636 011, Tamil Nadu (India); Raj, V., E-mail: alaguraj2@rediffmail.com [Advanced Materials Research Laboratory, Department of Chemistry, Periyar University, Omalur Main Road, Salem 636 011, Tamil Nadu (India)

    2010-04-01

    Alumina-silica-zirconia nanocomposite (ASZNC) ceramic fibres were synthesized by conventional anodization route. Scanning Electron Microscopy (SEM), Atomic Force microscopy (AFM), X-Ray Diffraction (XRD) and Energy Dispersive X-Ray spectroscopy (EDAX) were used to characterize the morphology and crystalloid structure of ASZNC fibres. Current density (DC) is one of the important parameters to get the alumina-silica-zirconia nanocomposite (ASZNC) ceramic fibres by this route. Annealing of the films exhibited a drastic change in the properties due to improved crystallinity. The root mean square roughness of the sample observed from atomic force microscopic analysis is about 71.5 nm which is comparable to the average grain size of the coatings which is about 72 nm obtained from X-Ray diffraction. The results indicate that, the ASZNC fibres are arranged well in the nanostructure. The thickness of the coating increased with the anodizing time, but the coatings turned rougher and more porous. At the initial stage the growth of ceramic coating increases inwards to the metal substrate and outwards to the coating surface simultaneously. Subsequently, it mainly grows towards the metal substrate and the density of the ceramic coating increases gradually, which results in the decrease of the total thickness as anodizing time increases. This new approach of preparing ASZNC ceramic fibres may be important in applications ranging from gas sensors to various engineering materials.

  17. Fabrication of mullite-bonded porous SiC ceramics from multilayer-coated SiC particles through sol-gel and in-situ polymerization techniques

    Science.gov (United States)

    Ebrahimpour, Omid

    In this work, mullite-bonded porous silicon carbide (SiC) ceramics were prepared via a reaction bonding technique with the assistance of a sol-gel technique or in-situ polymerization as well as a combination of these techniques. In a typical procedure, SiC particles were first coated by alumina using calcined powder and alumina sol via a sol-gel technique followed by drying and passing through a screen. Subsequently, they were coated with the desired amount of polyethylene via an in-situ polymerization technique in a slurry phase reactor using a Ziegler-Natta catalyst. Afterward, the coated powders were dried again and passed through a screen before being pressed into a rectangular mold to make a green body. During the heating process, the polyethylene was burnt out to form pores at a temperature of about 500°C. Increasing the temperature above 800°C led to the partial oxidation of SiC particles to silica. At higher temperatures (above 1400°C) derived silica reacted with alumina to form mullite, which bonds SiC particles together. The porous SiC specimens were characterized with various techniques. The first part of the project was devoted to investigating the oxidation of SiC particles using a Thermogravimetric analysis (TGA) apparatus. The effects of particle size (micro and nano) and oxidation temperature (910°C--1010°C) as well as the initial mass of SiC particles in TGA on the oxidation behaviour of SiC powders were evaluated. To illustrate the oxidation rate of SiC in the packed bed state, a new kinetic model, which takes into account all of the diffusion steps (bulk, inter and intra particle diffusion) and surface oxidation rate, was proposed. Furthermore, the oxidation of SiC particles was analyzed by the X-ray Diffraction (XRD) technique. The effect of different alumina sources (calcined Al2O 3, alumina sol or a combination of the two) on the mechanical, physical, and crystalline structure of mullite-bonded porous SiC ceramics was studied in the

  18. Structural analysis of anodic porous alumina used for resistive random access memory

    International Nuclear Information System (INIS)

    Lee, Jeungwoo; Nigo, Seisuke; Kato, Seiichi; Kitazawa, Hideaki; Kido, Giyuu; Nakano, Yoshihiro

    2010-01-01

    Anodic porous alumina with duplex layers exhibits a voltage-induced switching effect and is a promising candidate for resistive random access memory. The nanostructural analysis of porous alumina is important for understanding the switching effect. We investigated the difference between the two layers of an anodic porous alumina film using transmission electron microscopy and electron energy-loss spectroscopy. Diffraction patterns showed that both layers are amorphous, and the electron energy-loss spectroscopy indicated that the inner layer contains less oxygen than the outer layer. We speculate that the conduction paths are mostly located in the oxygen-depleted area.

  19. 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.

  20. Wear properties of alumina/zirconia composite ceramics for joint prostheses measured with an end-face apparatus.

    Science.gov (United States)

    Morita, Yusuke; Nakata, Kenichi; Kim, Yoon-Ho; Sekino, Tohru; Niihara, Koichi; Ikeuchi, Ken

    2004-01-01

    While only alumina is applied to all-ceramic joint prostheses at present, a stronger ceramic is required to prevent fracture and chipping due to impingement and stress concentration. Zirconia could be a potential substitute for alumina because it has high strength and fracture toughness. However, the wear of zirconia/zirconia combination is too high for clinical use. Although some investigations on composite ceramics revealed that mixing of different ceramics was able to improve the mechanical properties of ceramics, there are few reports about wear properties of composite ceramics for joint prosthesis. Since acetabular cup and femoral head of artificial hip joint are finished precisely, they indicate high geometric conformity. Therefore, wear test under flat contact was carried out with an end-face wear testing apparatus for four kinds of ceramics: alumina monolith, zirconia monolith, alumina-based composite ceramic, and zirconia based composite ceramic. Mean contact pressure was 10 MPa and sliding velocity was 40 mm/s. The wear test continued for 72 hours and total sliding distance was 10 km. After the test, the wear factor was calculated. Worn surfaces were observed with a scanning electron micrograph (SEM). The results of this wear test show that the wear factors of the both composite ceramics are similarly low and their mechanical properties are much better than those of the alumina monolith and the zirconia monolith. According to these results, it is predicted that joint prostheses of the composite ceramics are safer against break down and have longer lifetime compared with alumina/alumina joint prostheses.

  1. 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...

  2. 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

  3. 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.

  4. Photoluminescence properties of the composite of porous alumina and poly (2,5-dibutoxy-1,4 phenylenevinylene)

    International Nuclear Information System (INIS)

    Zhao Yi; Yang Deren; Zhou Chengyao; Yang Qing; Que Duanlin

    2003-01-01

    The spin coating method was used to assemble polymer (Poly (2,5-dibutoxy-1,4-phenylenevinylene)) (DBO-PPV) into the pores of porous alumina which was prepared by anodization. Four peaks in the photoluminescence (PL) spectra of the composite, with contributions from the DBO-PPV and porous alumina, were found. It was also found that the light emitting from the porous alumina could excite the photoluminescence of DBO-PPV. The nanometer effect of the porous alumina can lead to a blue shift of 90 nm of the PL peaks of DBO-PPV

  5. 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)

  6. 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

  7. Ceramic-like open-celled geopolymer foam as a porous substrate for water treatment catalyst

    Science.gov (United States)

    Kovářík, T.; Křenek, T.; Pola, M.; Rieger, D.; Kadlec, J.; Franče, P.

    2017-02-01

    This paper presents results from experimental study on microstructural and mechanical properties of geopolymer-based foam filters. The process for making porous ceramic-like geopolymer body was experimentally established, consists of (a) geopolymer paste synthesis, (b) ceramic filler incorporation, (c) coating of open-celled polyurethane foam with geopolymer mixture, (d) rapid setting procedure, (e) thermal treatment. Geopolymer paste was based on potassium silicate solution n(SiO2)/n(K2O)=1.6 and powder mixture of calcined kaolin and precipitated silica. Various types of ceramic granular filler (alumina, calcined schistous clay and cordierite) were tested in relation to aggregate gradation design and particle size distribution. The small amplitude oscillatory rheometry in strain controlled regime 0.01% with angular frequency 10 rad/s was applied for determination of rheology behavior of prepared mixtures. Thermal treatment conditions were applied in the temperature range 1100 - 1300 °C. The developed porous ceramic-like foam effectively served as a substrate for highly active nanoparticles of selected Fe+2 spinels. Such new-type of nanocomposite was tested as a heterogeneous catalyst for technological process of advanced oxidative degradation of resistive antibiotics occurring in waste waters.

  8. Fine platinum nanoparticles supported on a porous ceramic membrane as efficient catalysts for the removal of benzene.

    Science.gov (United States)

    Liu, Hui; Li, Chengyin; Ren, Xiaoyong; Liu, Kaiqi; Yang, Jun

    2017-11-29

    It would be desirable to remove volatile organic compounds (VOCs) while we eliminate the dusts using silicon carbide (SiC)-based porous ceramics from the hot gases. Aiming at functionalizing SiC-based porous ceramics with catalytic capability, we herein report a facile strategy to integrate high efficient catalysts into the porous SiC substrates for the VOC removal. We demonstrate an aqueous salt method for uniformly distributing fine platinum (Pt) particles on the alumina (Al 2 O 3 ) layers, which are pre-coated on the SiC substrates as supports for VOC catalysts. We confirm that at a Pt mass loading as low as 0.176% and a weight hourly space velocity of 6000 mL g -1 h -1 , the as-prepared Pt/SiC@Al 2 O 3 catalysts can convert 90% benzene at a temperature of ca. 215 °C. The results suggest a promising way to design ceramics-based bi-functional materials for simultaneously eliminating dusts and harmful VOCs from various hot gases.

  9. 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

  10. 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.

  11. Microstructural and Optical Properties of Porous Alumina Elaborated on Glass Substrate

    Science.gov (United States)

    Zaghdoudi, W.; Gaidi, M.; Chtourou, R.

    2013-03-01

    A transparent porous anodized aluminum oxide (AAO) nanostructure was formed on a glass substrate using the anodization of a highly pure evaporated aluminum layer. A parametric study was carried out in order to achieve a fine control of the microstructural and optical properties of the elaborated films. The microstructural and surface morphologies of the porous alumina films were characterized by x-ray diffraction and atomic force microscopy. Pore diameter, inter-pore separation, and the porous structure as a function of anodization conditions were investigated. It was then found that the pores density decreases with increasing the anodization time. Regular cylindrical porous AAO films with a flat bottom structure were formed by chemical etching and anodization. A high transmittance in the 300-900 nm range is reported, indicating a fulfilled growth of the transparent sample (alumina) from the aluminum metal. The data showed typical interference oscillations as a result of the transparent characteristics of the film throughout the visible spectral range. The thickness and the optical constants ( n and k) of the porous anodic alumina films, as a function of anodizing time, were obtained using spectroscopic ellipsometry in the ultraviolet-visible-near infrared (UV-vis-NIR) regions.

  12. Thermo-mechanical properties of mullite/zirconia reinforced alumina ceramic composites

    International Nuclear Information System (INIS)

    Wahsh, M.M.S.; Khattab, R.M.; Awaad, M.

    2012-01-01

    Highlights: ► Alumina–mullite–zirconia ceramic composites were prepared from alumina and zircon. ► Constant amount of magnesia was added as a sintering aid. ► Mechanical properties were enhanced with increasing of zircon up to 30.52 mass%. ► All of ceramic composites were achieved excellent thermal shock resistance. -- Abstract: Alumina–mullite–zirconia ceramic composites were prepared by reaction bonding of alumina and zircon mixtures after firing at different temperatures 1300°, 1400° and 1500 °C. Constant amount of magnesia was added as a sintering aid. The technological parameters of the sintered ceramic composites, i.e. the mechanical properties and densification parameter as well as thermal shock resistance, have been investigated. The phase compositions and microstructure of the sintered ceramic composites were detected by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Results indicated that alumina–mullite–zirconia ceramic composites fired at 1500 °C for 2 h were achieved a good densification parameters and mechanical properties as well as excellent thermal shock resistance. In addition, these ceramic composites were showed enhancement in Vickers’ microhardness and fracture toughness values.

  13. Characteristics of porous zirconia coated with hydroxyapatite

    Indian Academy of Sciences (India)

    However, porous hydroxyapatite bodies are mechanically weak and brittle, which makes shaping and implantation difficult. One way to solve this problem is to introduce a strong porous network onto which hydroxyapatite coating is applied. In this study, porous zirconia and alumina-added zirconia ceramics were prepared ...

  14. Characterization of the alumina-zirconia ceramic system by ultrasonic velocity measurements

    International Nuclear Information System (INIS)

    Carreon, Hector; Ruiz, Alberto; Medina, Ariosto; Barrera, Gerardo; Zarate, Juan

    2009-01-01

    In this work an alumina-zirconia ceramic composites have been prepared with α-Al 2 O 3 contents from 10 to 95 wt.%. The alumina-zirconia ceramic system was characterized by means of precise ultrasonic velocity measurements. In order to find out the factors affecting the variation in wave velocity, the ceramic composite have been examined by X-ray diffraction (XRD) and (SEM) scanning electron microscopy. It was found that the ultrasonic velocity measurements changed considerably with respect to the ceramic composite composition. In particular, we studied the behavior of the physical material property hardness, an important parameter of the ceramic composite mechanical properties, with respect to the variation in the longitudinal and shear wave velocities. Shear wave velocities exhibited a stronger interaction with microstructural and sub-structural features as compared to that of longitudinal waves. In particular, this phenomena was observed for the highest α-Al 2 O 3 content composite. Interestingly, an excellent correlation between ultrasonic velocity measurements and ceramic composite hardness was observed.

  15. Growth behavior of anodic porous alumina formed in malic acid solution

    Science.gov (United States)

    Kikuchi, Tatsuya; Yamamoto, Tsuyoshi; Suzuki, Ryosuke O.

    2013-11-01

    The growth behavior of anodic porous alumina formed on aluminum by anodizing in malic acid solutions was investigated. High-purity aluminum plates were electropolished in CH3COOH/HClO4 solutions and then anodized in 0.5 M malic acid solutions at 293 K and constant cell voltages of 200-350 V. The anodic porous alumina grew on the aluminum substrate at voltages of 200-250 V, and a black, burned oxide film was formed at higher voltages. The nanopores of the anodic oxide were only formed at grain boundaries of the aluminum substrate during the initial stage of anodizing, and then the growth region extended to the entire aluminum surface as the anodizing time increased. The anodic porous alumina with several defects was formed by anodizing in malic acid solution at 250 V, and oxide cells were approximately 300-800 nm in diameter.

  16. Method for Waterproofing Ceramic Materials

    Science.gov (United States)

    Cagliostro, Domenick E. (Inventor); Hsu, Ming-Ta S. (Inventor)

    1998-01-01

    Hygroscopic ceramic materials which are difficult to waterproof with a silane, substituted silane or silazane waterproofing agent, such as an alumina containing fibrous, flexible and porous, fibrous ceramic insulation used on a reentry space vehicle, are rendered easy to waterproof if the interior porous surface of the ceramic is first coated with a thin coating of silica. The silica coating is achieved by coating the interior surface of the ceramic with a silica precursor converting the precursor to silica either in-situ or by oxidative pyrolysis and then applying the waterproofing agent to the silica coated ceramic. The silica precursor comprises almost any suitable silicon containing material such as a silane, silicone, siloxane, silazane and the like applied by solution, vapor deposition and the like. If the waterproofing is removed by e.g., burning, the silica remains and the ceramic is easily rewaterproofed. An alumina containing TABI insulation which absorbs more that five times its weight of water, absorbs less than 10 wt. % water after being waterproofed according to the method of the invention.

  17. Electronic properties of electrolyte/anodic alumina junction during porous anodizing

    Energy Technology Data Exchange (ETDEWEB)

    Vrublevsky, I. [Department of Microelectronics, Belarusian State University of Informatics and Radioelectronics, 6 Brovka Street, Minsk 220013 (Belarus)]. E-mail: nil-4-2@bsuir.edu.by; Jagminas, A. [Institute of Chemistry, A. Gostauto 9, LT-01108 Vilnius (Lithuania); Schreckenbach, J. [Institut fuer Chemie, Technische Universitaet Chemnitz, Chemnitz D-09107 (Germany); InnoMat GmbH, Chemnitz (Germany); Goedel, Werner A. [Institut fuer Chemie, Technische Universitaet Chemnitz, Chemnitz D-09107 (Germany)

    2007-03-15

    The growth of porous oxide films on aluminum (99.99% purity), formed in 4% phosphoric acid was studied as a function of the anodizing voltage (23-53 V) using a re-anodizing technique and transmission electron microscopy (TEM) study. The chemical dissolution behavior of freshly anodized and annealed at 200 deg. C porous alumina films was studied. The obtained results indicate that porous alumina has n-type semiconductive behavior during anodizing in 4% phosphoric acid. During anodising, up to 39 V in the barrier layer of porous films, one obtains an accumulation layer (the thickness does not exceed 1 nm) where the excess electrons have been injected into the solid producing a downward bending of the conductive and valence band towards the interface. The charge on the surface of anodic oxide is negative and decreases with growing anodizing voltage. At the anodizing voltage of about 39 V, the charge on the surface of anodic oxide equals to zero. Above 39 V, anodic alumina/electrolyte junction injects protons from the electrolyte. These immobile positive charges in the surface layer of oxide together with an ionic layer of hydroxyl ions concentrated near the interface create a field, which produces an upward bending of the bands.

  18. Vapor phase versus liquid phase grafting of meso-porous alumina

    NARCIS (Netherlands)

    Sripathi, V.G.P.; Mojet, Barbara; Nijmeijer, Arian; Benes, Nieck Edwin

    2013-01-01

    Functionalization of meso-porous c-alumina has been performed by grafting of 3-Aminopropyltrimethoxysilane (3APTMS) simultaneously from either the liquid phase or from the vapor phase. In both cases, after grafting nitrogen physisorption indicates that the materials remain meso-porous with

  19. Mullite (3Al2O3·2SiO2 ceramics obtained by reaction sintering of rice husk ash and alumina, phase evolution, sintering and microstructure

    Directory of Open Access Journals (Sweden)

    M.F. Serra

    2016-03-01

    Partial densification was achieved (30% and highly converted materials were obtained. The developed microstructure consisted in a dense ceramic matrix with homogenous interconnected porosity, with a narrow pore size distribution below 20 μm. The developed material gives enough information for designing mullite ceramics materials with either porous or dense microstructures with structural, insulating or filtering applications employing RHA as silica source and calcined alumina as the only other raw material.

  20. 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)

  1. Non-contact temperature Raman measurement in YSZ and alumina ceramics

    Science.gov (United States)

    Thapa, Juddha; Chorpening, Benjamin T.; Buric, Michael P.

    2018-02-01

    Yttria-stabilized zirconia (YSZ: ZrO2 + Y2O3) and alumina (Al2O3) are widely used in high-temperature applications due to their high-temperature stability, low thermal conductivity, and chemical inertness. Alumina is used extensively in engineered ceramic applications such as furnace tubes and thermocouple protection tubes, while YSZ is commonly used in thermal barrier coatings on turbine blades. Because they are already often found in high temperature and combustion applications, these two substances have been compared as candidates for Raman thermometry in high-temperature energy-related applications. Both ceramics were used with as-received rough surfaces, i.e., without polishing or modification. This closely approximates surface conditions in practical high-temperature situations. A single-line argon ion laser at 488nm was used to excite the materials inside a cylindrical furnace while measuring Raman spectra with a fixed-grating spectrometer. The shift in the peak positions of the most intense A1g peak at 418cm-1 (room temperature position) of alumina ceramic and relatively more symmetric Eg peak at 470cm-1 (room temperature position) of YSZ were measured and reported along with a thermocouple-derived reference temperature up to about 1000°C. This study showed that alumina and YSZ ceramics can be used in high-temperature Raman thermometry with an accuracy of 4.54°C and 10.5°C average standard deviations respectively over the range of about 1000°C. We hope that this result will guide future researchers in selecting materials and utilizing Raman non-contact temperature measurements in harsh environments.

  2. 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.

  3. Fiscal 1998 achievement report on regional consortium research and development project. Venture business fostering regional consortium in its 2nd year--Creation of key industries (Development of novel manufacturing technology capable of dealing with multiple types of environmental preservation oriented fine ceramic porous structures); 1998 nendo kankyoyo fine ceramics takotai no tahinshu taiogata shinseizo gijutsu no kaihatsu seika hokokusho. 2

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2000-03-01

    This effort aims to develop a technology to manufacture various types of high-temperature dust collecting porous ceramic bodies. In the development of a molding technology, guidelines regarding foam containing slurry adjustment by use of surfactant are established and, under the guidelines, an alumina body with its average porosity exceeding 80% is fabricated, with the pores structured homogenous, gradient on the surface, formed in multiple layers, and composite. As for coating, a surface reforming method is developed by which a coating that is a few tens of nanometers thick is uniformly formed on an alumina panel surface, on the exterior of a porous body, and inside a model alumina porous body. It is found that the coating enhances the anti-corrosion capability of alumina. When a titanium oxide coating with 2% silica added thereto is formed on a porous body surface by the said surface reforming method, it is found that there is a catalytic activity achieving an 80% denitrating rate at 700 degrees C. Thanks to a newly developed dust collecting performance evaluating unit, it is proved that the ceramic filter meet the purpose of a dust collector sufficiently. (NEDO)

  4. 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.

  5. Mechanical behavior of porous ceramic disks

    International Nuclear Information System (INIS)

    Pucheu, M.A; Sandoval, M.L; Tomba Martinez, A.G; Camerucci, M.A

    2008-01-01

    The mechanical behavior of green and sintered porous ceramic materials, obtained by processing control, in relation to the microstructure developed was studied. Disks in green state were prepared by direct thermal consolidation of aqueous suspensions of kaolin, talc and alumina (preliminary mixture of cordierite) with the addition of different starches as consolidating/binding agents and as formers of pores at high temperature. Commercial kaolin (C-80 washed kaolin, Piedra Grande S.A., Argentina), micronized talc (Talc 40, China), calcinated alumina (A2G ALCOA, USA) and commercial potato, manioc, modified potato and corn starches were used as raw materials. The preliminary ceramic mixture was prepared based on the composition in oxides of the ceramic raw materials, in a relationship that was as close as possible to stoichiometric cordierite. Aqueous suspensions of the powders (65% solids; 0.5% sodium naphtolenosulfonate; 1% Dolapix with 17% of each kind of starch were prepared by intensive mechanical mixing, homogenization (ball mills, 2h) and extracting the air with vacuum 20 min. Disks were prepared (diameter=20-30 mm; thickness=3-4 mm) by thermal consolidation of the suspensions in steel molds at the maximum swelling factor temperature (Tms) for each starch (75- 85 o C) for 4h and, later drying at 50 o C, 12h. The porous materials of cordierite were obtained by calcination and reaction-sintering using a controlled thermal cycle: 1 o C/min up to 650 o C, 2h; 3 o C/min up to 1330 o C, 4h and 5 o C/min to room temperature. The characterization of the porous materials in green and sintered state was done by measuring density and apparent porosity, distribution of pore sizes and SEM. The mechanical resistance of the materials in green and sintered state was evaluated in diametrical compression (Instron universal testing machine servo hydraulic model 8501), in position control (0.1-0.2 mm/min) with a statistical number of test pieces, at room air temperature. The

  6. Measurement of Emissivity of Porous Ceramic Materials

    OpenAIRE

    BÜYÜKALACA, Orhan

    1998-01-01

    In this study, measurements of spectral and total emissivities of seven different porous ceramic materials and one ceramic fibre material are reported. Measurements were made for wavelength range from 1.2 µm to 20 µm and temperature range from 200 °C to 700 °C. It was found that total emissivity increases with increase of pore size but decreases with increase of temperature. The results showed all the porous ceramic materials tested to be much better than ceramic fibre in terms of total em...

  7. Porous ceramic scaffolds with complex architectures

    Science.gov (United States)

    Munch, E.; Franco, J.; Deville, S.; Hunger, P.; Saiz, E.; Tomsia, A. P.

    2008-06-01

    This work compares two novel techniques for the fabrication of ceramic scaffolds for bone tissue engineering with complex porosity: robocasting and freeze casting. Both techniques are based on the preparation of concentrated ceramic suspensions with suitable properties for the process. In robocasting, the computer-guided deposition of the suspensions is used to build porous materials with designed three dimensional geometries and microstructures. Freeze casting uses ice crystals as a template to form porous lamellar ceramic materials. Preliminary results on the compressive strengths of the materials are also reported.

  8. Obtain ceramic porous alumina-zirconia by replica method calcium phosphate coated; Oobtencao de ceramicas porosas de alumina-zirconia pelo metodo da replica recobertas com fosfato de calcio

    Energy Technology Data Exchange (ETDEWEB)

    Silva, A.D.R.; Rigoli, W.R.; Osiro, Denise; Pallone, E.M.J.A., E-mail: adinizrs@yahoo.com.br [Universidade de Sao Paulo (FZEA/USP), Pirassununga, SP (Brazil). Faculdade de Zootecnia e Engenharia de Alimentos; Lobo, A.O. [Universidade do Vale do Paraiba (UNIVAP), Sao Jose dos Campos, SP (Brazil)

    2016-07-01

    Biomaterials used in bone replacement, including porous bioceramics, are often used as support structure for bone formation and repair. The porous bioceramics are used because present features as biocompatibility, high porosity and pore morphology that confer adequate mechanical strength and induce bone growth. In this work were obtained porous specimens of alumina containing 5% by inclusion of volume of zirconia produced by the replica method. The porous specimens had its surface chemically treated with phosphoric acid and were coated with calcium phosphate. The coating was performed using the biomimetic method during 14 days and an initial pH of 6.1. The porous specimens were characterized using the follow techniques: porosity, axial compression tests, microtomography, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and pH measurements SBF solution. The results showed specimens with suitable pore morphology for application as biomaterial, and even a reduced time of incubation favored the calcium phosphate phases formation on the material surfaces. (author)

  9. Experimentqal and analytical study on thermocracking of alumina ceramic ring in a mechanical seal

    Science.gov (United States)

    Komiya, M.; Matsuda, K.; Kaneta, M.

    1994-04-01

    A mechanism of thermocracking, which occurs in an alumina ceramic ring of a mechanical face seal, is proposed based on experimental and analytical results. Methods for its prevention are also discussed. The experiments were conducted using an external type mechanical face seal composed of a carbon ring and three kinds of alumina ceramic rings, with distilled water as the liquid to be sealed. By using a layer of gold vacuum deposited onto the surface of the ceramic ring as a part of a DC circuit, the moment of crack initiation was identified. The thermal stresses produced in the ceramic ring by frictional heating were calculated using finite element analysis.

  10. Fabrication and performance of porous lithium sodium potassium niobate ceramic

    Science.gov (United States)

    Chen, Caifeng; Zhu, Yuan; Ji, Jun; Cai, Feixiang; Zhang, Youming; Zhang, Ningyi; Wang, Andong

    2018-02-01

    Porous lithium sodium potassium niobate (LNK) ceramic has excellent piezoelectric properties, chemical stability and great chemical compatibility. It has a good application potential in the field of biological bone substitute. In the paper, porous LNK ceramic was fabricated with egg albumen foaming agent by foaming method. Effects of preparation process of the porous LNK ceramic on density, phase structure, hole size and piezoelectric properties were researched and characterized. The results show that the influence factors of LNK solid content and foaming agent addition are closely relevant to properties of the porous LNK ceramic. When solid content is 65% and foaming agent addition is 30%, the porous LNK ceramic has uniform holes and the best piezoelectric properties.

  11. Rapid fabrication of self-ordered porous alumina with 10-/sub-10-nm-scale nanostructures by selenic acid anodizing

    Science.gov (United States)

    Nishinaga, Osamu; Kikuchi, Tatsuya; Natsui, Shungo; Suzuki, Ryosuke O.

    2013-01-01

    Anodic porous alumina has been widely investigated and used as a nanostructure template in various nanoapplications. The porous structure consists of numerous hexagonal cells perpendicular to the aluminum substrate and each cell has several tens or hundreds of nanoscale pores at its center. Because the nanomorphology of anodic porous alumina is limited by the electrolyte during anodizing, the discovery of additional electrolytes would expand the applicability of porous alumina. In this study, we report a new self-ordered nanoporous alumina formed by selenic acid (H2SeO4) anodizing. By optimizing the anodizing conditions, anodic alumina possessing 10-nm-scale pores was rapidly assembled (within 1 h) during selenic acid anodizing without any special electrochemical equipment. Novel sub-10-nm-scale spacing can also be achieved by selenic acid anodizing and metal sputter deposition. Our new nanoporous alumina can be used as a nanotemplate for various nanostructures in 10-/sub-10-nm-scale manufacturing. PMID:24067318

  12. 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.

  13. Microstructure and Mechanical Properties of Heterogeneous Ceramic-Polymer Composite Using Interpenetrating Network

    OpenAIRE

    Kim, Eun-Hee; Jung, Yeon-Gil; Jo, Chang-Yong

    2012-01-01

    Prepolymer, which can be polymerized by a photo, has been infiltrated into a porous ceramic to improve the addition effect of polymer into the ceramic, as a function of the functionality of prepolymer. It induces the increase in the mechanical properties of the ceramic. The porous alumina (Al2O3) and the polyurethane acrylate (PUA) with a network structure by photo-polymerization were used as the matrix and infiltration materials, respectively. The porous Al2O3 matrix without t...

  14. 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)',.

  15. 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

  16. Tritium transport in lithium ceramics porous media

    International Nuclear Information System (INIS)

    Tam, S.W.; Ambrose, V.

    1991-01-01

    A random network model has been utilized to analyze the problem of tritium percolation through porous Li ceramic breeders. Local transport in each pore channel is described by a set of convection-diffusion-reaction equations. Long range transport is described by a matrix technique. The heterogeneous structure of the porous medium is accounted for via Monte Carlo methods. The model was then applied to an analysis of the relative contribution of diffusion and convective flow to tritium transport in porous lithium ceramics. 15 refs., 4 figs

  17. 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.)

  18. New Observations on High-Speed Machining of Hardened AISI 4340 Steel Using Alumina-Based Ceramic Tools

    Directory of Open Access Journals (Sweden)

    Mohamed Shalaby

    2018-05-01

    Full Text Available High-speed machining (HSM is used in industry to improve the productivity and quality of the cutting operations. In this investigation, pure alumina ceramics with the addition of ZrO2, and mixed alumina (Al2O3 + TiC tools were used in the dry hard turning of AISI 4340 (52 HRC at different high cutting speeds of 150, 250, 700 and 1000 m/min. It was observed that at cutting speeds of 150 and 250 m/min, pure alumina ceramic tools had better wear resistance than mixed alumina ones. However, upon increasing the cutting speed from 700 to 1000 m/min, mixed alumina ceramic tools outperformed pure ceramic ones. Scanning electron microscopy (SEM and X-ray photoelectron spectroscopy (XPS were used to investigate the worn cutting edges and analyze the obtained results. It was found that the tribo-films formed at the cutting zone during machining affected the wear resistances of the tools and influenced the coefficient of friction at the tool-chip interface. These observations were confirmed by the chip compression ratio results at different cutting conditions. Raising cutting speed to 1000 m/min corresponded to a remarkable decrease in cutting force components in the dry hard turning of AISI 4340 steel.

  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. Effect of Aluminum Purity on the Pore Formation of Porous Anodic Alumina

    International Nuclear Information System (INIS)

    Kim, Byeol; Lee, Jin Seok

    2014-01-01

    Anodic alumina oxide (AAO), a self-ordered hexagonal array, has various applications in nanofabrication such as the fabrication of nanotemplates and other nanostructures. In order to obtain highly ordered porous alumina membranes, a two-step anodization or prepatterning of aluminum are mainly conducted with straight electric field. Electric field is the main driving force for pore growth during anodization. However, impurities in aluminum can disturb the direction of the electric field. To confirm this, we anodized two different aluminum foil samples with high purity (99.999%) and relatively low purity (99.8%), and compared the differences in the surface morphologies of the respective aluminum oxide membranes produced in different electric fields. Branched pores observed in porous alumina surface which was anodized in low-purity aluminum and the size; dimensions of the pores were found to be usually smaller than those obtained from high-purity aluminum. Moreover, anodization at high voltage proceeds to a significant level of conversion because of the high speed of the directional electric field. Consequently, anodic alumina membrane of a specific morphology, i. e., meshed pore, was produced

  1. Effect of Aluminum Purity on the Pore Formation of Porous Anodic Alumina

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Byeol; Lee, Jin Seok [Sookmyung Women' s Univ., Seoul (Korea, Republic of)

    2014-02-15

    Anodic alumina oxide (AAO), a self-ordered hexagonal array, has various applications in nanofabrication such as the fabrication of nanotemplates and other nanostructures. In order to obtain highly ordered porous alumina membranes, a two-step anodization or prepatterning of aluminum are mainly conducted with straight electric field. Electric field is the main driving force for pore growth during anodization. However, impurities in aluminum can disturb the direction of the electric field. To confirm this, we anodized two different aluminum foil samples with high purity (99.999%) and relatively low purity (99.8%), and compared the differences in the surface morphologies of the respective aluminum oxide membranes produced in different electric fields. Branched pores observed in porous alumina surface which was anodized in low-purity aluminum and the size; dimensions of the pores were found to be usually smaller than those obtained from high-purity aluminum. Moreover, anodization at high voltage proceeds to a significant level of conversion because of the high speed of the directional electric field. Consequently, anodic alumina membrane of a specific morphology, i. e., meshed pore, was produced.

  2. Performance study of mullite and mullite-alumina ceramic MF membranes for oily wastewaters treatment

    DEFF Research Database (Denmark)

    Abbasi, Mohsen; Mirfendereski, Mojtaba; Fini, Mahdi Nikbakht

    2010-01-01

    In this paper, results of an experimental study on separation of oil from actual and synthetic oily wastewaters with mullite and mullite-alumina tubular ceramic membranes are presented. Mullite and mullite-alumina microfiltration (MF) symmetric membranes were synthesized from kaolin clay and α......-alumina membranes for treatment of synthetic wastewaters were investigated. In order to determine the best operating conditions, 250-3000ppm condensate gas in water emulsions was employed as synthetic oily wastewaters using mullite membrane. At the best operating conditions (3bar pressure, 1.5m/s cross flow...... velocity and 35°C temperature), performance of mullite and mullite-alumina membranes for treatment of real and synthetic wastewaters were also compared. The results for treatment of emulsions showed that the mullite ceramic membrane has the highest R (93.8%) and the lowest FR (28.97%). Also, the mullite...

  3. [Evaluation of alumina effects on the mechanical property and translucency of nano-zirconia all-ceramics].

    Science.gov (United States)

    Jiang, Li; Zhao, Yong-qi; Zhang, Jing-chao; Liao, Yun-mao; Li, Wei

    2010-06-01

    To study the effects of alumina content on sintered density, mechanical property and translucency of zirconia nanocomposite all-ceramics. Specimens of zirconia nanocomposite all-ceramics were divided into five groups based on their alumina content which are 0% (control group), 2.5%, 5.0%, 7.5% and 10.0% respectively. The sintered densities were measured using Archimedes' method. Specimens' bending strengths were measured with three-point bending test (ISO 6872). The visible light transmittances were measured with spectrophotometric arrangements and the fractured surfaces were observed using scanning electron microscope (SEM). The control group of pure zirconia could be sintered to the theoretical density under pressure-less sintering condition. The bending strength was (1100.27 ± 54.82) MPa, the fracture toughness was (4.96 ± 0.35) MPa×m(1/2) and the transmittance could reach 17.03%. The sintered density and transmittance decreased as alumina content increased from 2.5% to 10%. However, the fracture toughness only increased slightly. In all four alumina groups, the additions of alumina had no significant effect on samples' bending strengths (P > 0.05). When the content of alumina was 10%, fracture toughness of specimens reached (6.13 ± 0.44) MPa×m(1/2) while samples' transmittance declined to 6.21%. SEM results showed that alumina particles had no significant effect on the grain size and distribution of tetragonal zirconia polycrystals. Additions of alumina to yttria-tetragonal zirconia polycrystals could influence its mechanical property and translucency. Additions of the other phase to zirconia ceramics should meet the clinical demands of strength and esthetics.

  4. Effect of the local electric field on the formation of an ordered structure in porous anodic alumina

    Science.gov (United States)

    Lazarouk, S. K.; Katsuba, P. S.; Leshok, A. A.; Vysotskii, V. B.

    2015-09-01

    Experimental data and a model are presented, and the electric field that appears in porous alumina during electrochemical anodic oxidation of aluminum in electrolytes based on an aqueous solution of oxalic acid at a voltage of 90-250 V is calculated. It is found that the electric field in the layers with a porosity of 1-10% in growing alumina reaches 109-1010 V/m, which exceeds the electric strength of the material and causes microplasma patterns emitting visible light at the pore bottom, the self-organization of the structure of porous alumina, and the anisotropy of local porous anodizing. Moreover, other new effects are to be expected during aluminum anodizing under the conditions that ensure a high electric field inside the barrier layer of porous oxide.

  5. 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.

  6. 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.

  7. Fabrication of the similar porous alumina silicon template for soft UV nanoimprint lithography

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Tangyou [Wuhan National Laboratory for Optoelectronics, School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074 (China); Xu, Zhimou, E-mail: xuzhimou@mail.hust.edu.cn [Wuhan National Laboratory for Optoelectronics, School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074 (China); Zhao, Wenning; Wu, Xinghui; Liu, Sisi; Zhang, Zheng; Wang, Shuangbao; Liu, Wen [Wuhan National Laboratory for Optoelectronics, School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074 (China); Liu, Shiyuan [State Key Laboratory of Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology, Wuhan 430074 (China); Peng, Jing [College of Sciences, Wuhan University of Science and Technology, Wuhan 430081 (China)

    2013-07-01

    High density honeycombed nanostructures of porous alumina template (PAT) have been widely used to the fabrication of various electronic, optoelectronic, magnetic, and energy storage devices. However, patterning structures at sub-100 nm feature size with large area and low cost is of great importance and hardness on which semiconductor manufacture technology depends. In this paper, soft UV nanoimprint lithography (SUNIL) by using PAT as the initial mold is studied in detail. The results reveal a significant incompatibility between these two candidates. The native nonflatness of the PAT surface is about 100 nm in the range of 2–5 μm. Resist detaches from the substrate because of the mold deformation in the nonflat SUNIL. A two-inch similar porous alumina silicon (Si) template with nanopore size of 50–100 nm is fabricated. I–t curve conducted anodization and subsequent inductive coupled plasma (ICP) dry etching are applied to ensure the uniformity of the fabricated template. The surface flatness of the similar porous alumina Si template is the same as the polished Si wafer, which perfectly matches NIL.

  8. 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.

  9. Gradient porous hydroxyapatite ceramics fabricated by freeze casting method

    International Nuclear Information System (INIS)

    Zuo Kaihui; Zhang Yuan; Jiang Dongliang; Zeng Yuping

    2011-01-01

    By controlling the cooling rates and the composition of slurries, the gradient porous hydroxyapatite ceramics are fabricated by the freeze casting method. According to the different cooling rate, the pores of HAP ceramics fabricated by gradient freeze casting are divided into three parts: one is lamellar pores, another is column pore and the last one is fine round pores. The laminated freeze casting is in favour of obtaining the gradient porous ceramics composed of different materials and the ceramics have unclear interfaces.

  10. Optical, mechanical and fractographic response of transparent alumina ceramics on erbium doping

    Czech Academy of Sciences Publication Activity Database

    Drdlík, D.; Drdlíková, K.; Hadraba, Hynek; Máca, K.

    2017-01-01

    Roč. 37, č. 14 (2017), s. 4265-4270 ISSN 0955-2219 R&D Projects: GA MŠk(CZ) LQ1601; GA ČR(CZ) GA15-06390S Institutional support: RVO:68081723 Keywords : Alumina * Erbia * Fractography * Hardness * Transparency Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass OBOR OECD: Ceramics Impact factor: 3.411, year: 2016

  11. 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

  12. 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.

  13. Optimum Exploration for the Self-Ordering of Anodic Porous Alumina Formed via Selenic Acid Anodizing

    OpenAIRE

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

    2015-01-01

    Improvements of the regularity of the arrangement of anodic porous alumina formed by selenic acid anodizing were investigated under various operating conditions. The oxide burning voltage increased with the stirring rate of the selenic acid solution, and the high applied voltage without oxide burning was achieved by vigorously stirring the solution. The regularity of the porous alumina was improved as the anodizing time and surface flatness increased. Conversely, the purity of the 99.5–99.999...

  14. Influence of sintering temperature on the characteristics of a-alumina filtration tubes

    International Nuclear Information System (INIS)

    Zarina Abdul Wahid; Rafindde Ramli; Andanastuti Muchtar; Abd Wahab Mohammad

    2005-01-01

    The emerging technology of ceramic membrane filters has created a lot of impact on the materials development and separation industries. Ceramic membrane filters have been used in many separation industry applications particularly in food, dairy, beverages, biotechnology, pharmaceutical and waste treatment industries. This is due to the fact that ceramics are inert and durable and can withstand high temperatures as well as extreme chemical conditions. They also have favourable mechanical properties and lower fouling rates. In this study, ceramic filtration tubes having dimensions of 10 mm outer diameter, 6 mm inner diameter and 880 mm long were prepared from a-alumina using the extrusion technique. The effects of sintering temperature on the pore size, microstructure and porosity of the alumina tube were investigated. The optimum sintering temperature was determined based on the performance of the tubes with regards to porosity, pore size and microstructure. The alumina tubes were sintered at six different temperatures i.e. 1250 degree C, 1300 degree C, 1350 degree C, 1400 degree C, 1450 degree C and 1500 degree C. The porous structures of the alumina tubes were studied using Scanning Electron Microscope (SEM) whereas a Mercury Porosimeter was used to determine the porosity and pore size distribution. (Author)

  15. 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.

  16. Deposition and consolidation of porous ceramic films for membrane separation

    DEFF Research Database (Denmark)

    Elmøe, Tobias Dokkedal; Tricoli, Antonio; Johannessen, Tue

    The deposition of porous ceramic films for membrane separation can be done by several processes such as thermophoresis [1], dip-coating [2] and spray pyrolysis [3]. Here we present a high-speed method, in which ceramic nano-particles form a porous film by filtration on top of a porous ceramic...... substrate [4]. Ceramic nano-particles are generated in a flame, using either a premixed (gas) flame, in which a metal-oxide precursor is evaporated in an N2 stream, which is combusted with methane and air, or using a flame spray pyrolysis, in which a liquid metal-oxide precursor is sprayed through a nozzle...

  17. 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.

  18. Ballistic Performance of Porous-Ceramic, Thermal Protection Systems

    Science.gov (United States)

    Miller, J. E.; Bohl, W. E.; Christiansen, Eric C.; Davis, B. A.; Foreman, C. D.

    2011-01-01

    Porous-ceramic, thermal protection systems are used heavily in current reentry vehicles like the Orbiter, and they are currently being proposed for the next generation of US manned spacecraft, Orion. These systems insulate reentry critical components of a spacecraft against the intense thermal environments of atmospheric reentry. Additionally, these materials are highly exposed to space environment hazards like solid particle impacts. This paper discusses impact studies up to 10 km/s on 8 lb/cu ft alumina-fiber-enhanced-thermal-barrier (AETB8) tiles coated with a toughened-unipiece-fibrous-insulation/ reaction-cured-glass layer (TUFI/RCG). A semi-empirical, first principals impact model that describes projectile dispersion is described that provides excellent agreement with observations over a broad range of impact velocities, obliquities and projectile materials. Model extensions to look at the implications of greater than 10 GPa equation of state is also discussed. Predicted penetration probabilities for a vehicle visiting the International Space Station is 60% lower for orbital debris and 95% lower for meteoroids with this model compared to an energy scaled approach.

  19. 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.)

  20. Alumina Ceramics Vacuum Duct for the 3GeV-RCS of the J-PARC

    CERN Document Server

    Kinsho, Michikazu; Ogiwara, Norio; Saito, Yoshio

    2005-01-01

    It was success to develop alumina ceramics vacuum ducts for the 3GeV-RCS of J-PARC at JAERI. There are two types of alumina ceramics vacuum ducts needed, one being 1.5m-long duct with a circular cross section for use in the quadrupole magnet, the other being 3.5m-long and bending 15 degrees, with a race-track cross section for use in the dipole magnet. These ducts could be manufactured by joining several duct segments of 0.5-0.8 m in length by brazing. The alumina ceramics ducts have copper stripes on the outside surface of the ducts to reduce the duct impedance. One of the ends of each stripe is connected to a titanium flange by way of a capacitor so to interrupt an eddy current circuit. The copper stripes are produced by an electroforming method in which a stripe pattern formed by Mo-Mn metallization is first sintered on the exterior surface and then overlaid by PR-electroformed copper (Periodic current Reversal electroforming method). In order to reduce emission of secondary electrons when protons or elect...

  1. [Osteogenic activity of porous calcium phosphate ceramics fabricated by rapid prototyping].

    Science.gov (United States)

    He, Chenguang; Zhao, Li; Lin, Liulan; Gu, Huijie; Zhou, Heng; Cui, Lei

    2010-07-01

    Calcium phosphate bioceramics has a broad application prospect because of good biocompatibility, but porous scaffolds with complex shape can not be prepared by the traditional methods. To fabricate porous calcium phosphate ceramics by rapid prototyping and to investigate the in vitro osteogenic activities. The porous calcium phosphate ceramics was fabricated by rapid prototyping. The bone marrow mesenchymal stem cells (BMSCs) were isolated from bone marrow of Beagle canine, and the 3rd passage BMSCs were seeded onto the porous ceramics. The cell/ceramics composite cultured in osteogenic medium were taken as the experimental group (group A) and the cell/ceramics composite cultured in growth medium were taken as the control group (group B). Meanwhile, the cells seeded on the culture plate were cultured in osteogenic medium or growth medium respectively as positive control (group C) or negative control (group D). After 1, 3, and 7 days of culture, the cell proliferation and osteogenic differentiation on the porous ceramics were evaluated by DNA quantitative analysis, histochemical staining and alkaline phosphatase (ALP) activity. After DiO fluorescent dye, the cell adhesion, growth, and proliferation on the porous ceramics were also observed by confocal laser scanning microscope (CLSM). DNA quantitative analysis results showed that the number of BMSCs in all groups increased continuously with time. Plateau phase was not obvious in groups A and B, but it was clearly observed in groups C and D. The CLSM observation indicated that the activity of BMSCs was good and the cells spread extensively, showing good adhesion and proliferation on the porous calcium phosphate ceramics prepared by rapid prototyping. ALP quantitative analysis results showed that the stain of cells on the ceramics became deeper and deeper with time in groups A and B, the staining degree in group A were stronger than that in group B. There was no significant difference in the change of the ALP activity

  2. Study on 95 alumina ceramic metallizing and glazing technique

    International Nuclear Information System (INIS)

    Zhou Qun; Wang Wei

    2007-12-01

    Electric heater is a component of pressurizer in NPP. So the connector of heater must suit for special requirement with high reliability. It need join 95% alumina ceramic and special metal together. Traditional technique is to glazing ceramic at first, then sintering metal powder on ceramic. It result in melting glaze when metallizing at high temperature. The research on high temperature glaze hasn't got ideal result. In another way, the experiments prove low temperature metallizing couldn't get enough strength. Base on present conditions, a new technique is introduced. It is first metallizing then glazing. It can not only provide high strength with high temperature metallizing , but also avoid melting glaze at high temperature. Compared with other ways, the experiments prove it is feasible. The test data can satisfy requirement. This research has been put into production. (authors)

  3. Conversion of nuclear waste to molten glass: Formation of porous amorphous alumina in a high-Al melter feed

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Kai, E-mail: kaixu@whut.edu.cn [Pacific Northwest National Laboratory, Richland, WA 99352 (United States); Hrma, Pavel, E-mail: pavel.hrma@pnnl.gov [Pacific Northwest National Laboratory, Richland, WA 99352 (United States); Washton, Nancy; Schweiger, Michael J. [Pacific Northwest National Laboratory, Richland, WA 99352 (United States); Kruger, Albert A. [U.S. Department of Energy, Office of River Protection, Richland, WA 99352 (United States)

    2017-01-15

    The transition of Al phases in a simulated high-Al high-level nuclear waste melter feed heated at 5 K min{sup −1} to 700 °C was investigated with transmission electron microscopy, {sup 27}Al nuclear magnetic resonance spectroscopy, the Brunauer-Emmett-Teller method, and X-ray diffraction. At temperatures between 300 and 500 °C, porous amorphous alumina formed from the dehydration of gibbsite, resulting in increased specific surface area of the feed (∼8 m{sup 2} g{sup −1}). The high-surface-area amorphous alumina formed in this manner could potentially stop salt migration in the cold cap during nuclear waste vitrification. - Highlights: • Porous amorphous alumina formed in a simulated high-Al HLW melter feed during heating. • The feed had a high specific surface area at 300 °C ≤ T ≤ 500 °C. • Porous amorphous alumina induced increased specific surface area.

  4. 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.

  5. The effect of water-soluble polymers on the microstructure and properties of freeze-cast alumina ceramics

    Science.gov (United States)

    Pekor, Christopher Michael

    Porous ceramics can be divided into three separate classes based on their pore size: microporous ceramics with pores less than 2 nm, mesoporous ceramics with pores in the range of 2--50 nm and macroporous ceramics with pores that are greater than 50 nm. In particular, macroporous ceramics are used in a variety of applications such as refractories, molten metal filtration, diesel particulate filters, heterogeneous catalyst supports and biomedical scaffolds. Freeze casting is a novel method used to create macroporous ceramics. In this method growing ice crystals act as a template for the pores and are solidified, often directionally, through a ceramic dispersion and removed from the green body through a freeze drying procedure. This method has attracted some attention over the past few years due to its relative simplicity, flexibility and environmental friendliness. On top of this freeze casting is capable of producing materials with high pore volume fractions, which is an advantage over processing by packing and necking of particles, where the pore volume fraction is typically less than 50%. Many of the basic processing variables that affect the freeze cast microstructure, such as the temperature gradient, interfacial velocity and solid loading of the dispersion have been well established in the literature. On the other hand, areas such as the effect of additives on the microstructure and mechanical properties have not been covered in great detail. In this study the concept of constitutional supercooling from basic solidification theory is used to explain the effects of two water-soluble polymers, polyethylene glycol and polyvinyl alcohol, on the microstructure of freeze cast alumina ceramics. In addition, changes in the observed microstructure will be related to experimentally determined values of permeability and compressive strength.

  6. 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.

  7. 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.

  8. Manufacturing of Porous Ceramic Preforms Based on Halloysite Nanotubes (Hnts

    Directory of Open Access Journals (Sweden)

    Kujawa M.

    2016-06-01

    Full Text Available The aim of this study was to determine the influence of manufacturing conditions on the structure and properties of porous halloysite preforms, which during pressure infiltration were soaked with a liquid alloy to obtain a metal matrix composite reinforced by ceramic, and also to find innovative possibilities for the application of mineral nanotubes obtained from halloysite. The method of manufacturing porous ceramic preforms (based on halloysite nanotubes as semi-finished products that are applicable to modern infiltrated metal matrix composites was shown. The ceramic preforms were manufactured by sintering of halloysite nanotubes (HNT, Natural Nano Company (USA, with the addition of pores and canals forming agent in the form of carbon fibres (Sigrafil C10 M250 UNS SGL Group, the Carbon Company. The resulting porous ceramic skeletons, suggest innovative application capabilities mineral nanotubes obtained from halloysite.

  9. Effect of testing methods on the bond strength of resin to zirconia-alumina ceramic : microtensile versus shear test

    NARCIS (Netherlands)

    Valandro, Luiz F.; Ozcan, Mutlu; Amaral, Regina; Vanderlei, Aleska; Bottino, Marco A.

    2008-01-01

    This study tested the bond strength of a resin cement to a glass-infiltrated zirconia-alumina ceramic after three conditioning methods and using two test methods (shear-SBS versus microtensile-MTBS). Ceramic blocks for MTBS and ceramic disks for SBS were fabricated. Three surface conditioning (SC)

  10. Vapour growth of Cd(Zn)Te columnar nanopixels into porous alumina

    International Nuclear Information System (INIS)

    Sochinskii, N.V.; Abellan, M.; Martin Gonzalez, M.; Saucedo, E.; Dieguez, E.; Briones, F.

    2006-01-01

    The vapour phase growth (VPG) of CdTe and Cd 1- x Zn x Te was performed in order to investigate the formation of Cd(Zn)Te columnar nanostructures, which could serve as a basis for micropixels usable for further development of X- and gamma-ray high-resolution imaging devices. The possibility to form the 'Cd(Zn)Te-in-porous alumina' nanostructures by VPG has been demonstrated. The Cd(Zn)Te crystals integrated into nanoporous alumina have shown to have photoluminescence properties compatible with those of the bulk crystals and planar epitaxial layers. Further investigations are going on to improve the structural quality of Cd(Zn)Te nanocrystals

  11. (abstract) Experimental and Modeling Studies of the Exchange Current at the Alkali Beta'-Alumina/Porous Electrode/Alkali Metal Vapor Three Phase Boundary

    Science.gov (United States)

    Williams, R. M.; Jeffries-Nakamura, B.; Ryan, M. A.; Underwood, M. L.; O'Connor, D.; Kikkert, S.

    1993-01-01

    The microscopic mechanism of the alkali ion-electron recombination reaction at the three phase boundary zone formed by a porous metal electrode in the alkali vapor on the surface of an alkali beta'-alumina solid electrolyte (BASE) ceramic has been studied by comparison of the expected rates for the three simplest reaction mechanisms with known temperature dependent rate data; and the physical parameters of typical porous metal electrode/BASE/alkali metal vapor reaction zones. The three simplest reactions are tunneling of electrons from the alkali coated electrode to a surface bound alkali metal ion; emission of an electron from the electrode with subsequent capture by a surface bound alkali metal ion; and thermal emission of an alkali cation from the BASE and its capture on the porous metal electrode surface where it may recombine with an electron. Only the first reaction adequately accounts for both the high observed rate and its temperature dependence. New results include crude modeling of simple, one step, three phase, solid/solid/gas electrochemical reaction.

  12. The effects of sintering behavior on piezoelectric properties of porous PZT ceramics for hydrophone application

    International Nuclear Information System (INIS)

    Zeng Tao; Dong Xianlin; Chen Heng; Wang Yonglin

    2006-01-01

    Porous lead zirconate titanate (PZT) ceramics were fabricated by adding polymethyl methacrylate (PMMA) and the effects of sintering behavior on their microstructure and piezoelectric properties were investigated. The porosity of PZT ceramics decreased with an increase in the sintering temperature at a fixed PMMA addition. The dielectric constant (ε), longitudinal piezoelectric coefficient (d 33 ) and hydrostatic figures of merit (d h g h ) of 34% porous PZT ceramics increased with an increase in sintering temperature from 1050 to 1300 deg. C. When sintered at 1300 deg. C, longitudinal piezoelectric coefficient of 34% porous PZT ceramic was very close to that of 95% dense PZT ceramics, while the hydrostatic figures of merit of 34% porous PZT ceramics is about fifteen times more than that of 95% dense PZT ceramics. Compared with PZT-polymer composites, the dielectric constant of 34% porous PZT sintered at 1300 deg. C is much higher, which can be more efficient to resist the interference in receiving sensitivities caused by loading effect of the cable

  13. 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

  14. 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)

  15. Residual stress profiles in veneering ceramic on Y-TZP, alumina and ZTA frameworks: measurement by hole-drilling.

    Science.gov (United States)

    Fukushima, K A; Sadoun, M J; Cesar, P F; Mainjot, A K

    2014-02-01

    The residual stress profile developed within the veneering ceramic during the manufacturing process is an important predicting factor in chipping failures, which constitute a well-known problem with yttria-tetragonal-zirconia polycrystal (Y-TZP) based restorations. The objectives of this study are to measure and to compare the residual stress profile in the veneering ceramic layered on three different polycrystalline ceramic framework materials: Y-TZP, alumina polycrystal (AL) and zirconia toughened alumina (ZTA). The stress profile was measured with the hole-drilling method in bilayered disk samples of 19 mm diameter with a 0.7 mm thick Y-TZP, AL or ZTA framework and a 1.5mm thick layer of the corresponding veneering ceramic. The AL samples exhibited increasing compressive stresses with depth, while compressive stresses switching into interior tensile stresses were measured in Y-TZP samples. ZTA samples exhibited compressive stress at the ceramic surface, decreasing with depth up to 0.6mm from the surface, and then becoming compressive again near the framework. Y-TZP samples exhibited a less favorable stress profile than those of AL and ZTA samples. Results support the hypothesis of the occurrence of structural changes within the Y-TZP surface in contact with the veneering ceramic to explain the presence of tensile stresses. Even if the presence of Y-TZP in the alumina matrix seems to negatively affect the residual stress profiles in ZTA samples in comparison with AL samples, the registered profiles remain positive in terms of veneer fracture resistance. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  16. Processing and properties of ceramic matrix-polymer composites for dental applications

    Science.gov (United States)

    Huang, Hsuan Yao

    The basic composite structure of natural hard tissue was used to guide the design and processing of dental restorative materials. The design incorporates the methodology of using inorganic minerals as the main structural phase reinforced with a more ductile but tougher organic phase. Ceramic-polymer composites were prepared by slip casting a porous ceramic structure, heating and chemical treating the porous preform, infiltrating with monomer and then curing. The three factors that determined the mechanical properties of alumina-polymer composites were the type of polymer used, the method of silane treatments, and the type of bond between particles in the porous preforms. Without the use of silane coupling agents, the composites were measured to have a lower strength. The composite with a more "flexible" porous alumina network had a greater ability to plastically dissipate the energy of propagating cracks. However, the aggressive nature of the alumina particles on opposing enamel requires that these alumina-polymer composites have a wear compatible coating for practical application. A route to dense bioactive apatite wollastonite glass ceramics (AWGC)-polymer composites was developed. The problems associated with glass dissolution into the aqueous medium for slip casting were overcome with the use of silane. The role of heating rate and development of ceramic compact microstructure on composite properties was explored. In general, if isothermal heating was not applied, decreasing heating rate increased glass crystallinity and particle-particle fusion, but decreased pore volume. Also composite strength and fracture toughness decreased while modulus and hardness increased with decreasing heating rate. If isothermal heating was applied, glass crystallinity, pore content, and composite mechanical properties showed relatively little change regardless of the initial heating rate. The potential of AWGC-polymer composites for dental and implant applications was explored

  17. Gamma-irradiation synthesis of silver nanoparticles fixing in porous ceramic for application in water treatment

    International Nuclear Information System (INIS)

    Dang Van Phu; Nguyen Quoc Hien; Nguyen Thuy Ai Trinh; Bui Duy Du

    2013-01-01

    The Ag nanoparticles in polyvinylpyrrolidone solution with concentration of 500 mg/L and their diameter of 10-15 nm were synthesized on a large scale up to 100 L/batch by gamma irradiation route. Porous ceramic candle samples were functionalized by treatment with a 3-amino-propyltriethoxysilane coupling agent and then impregnated in Ag nanoparticles solution for fixing Ag nanoparticles. The load Ag nanoparticles content on porous ceramic was of about 200-250 mg/kg. The average pore size of porous ceramic/Ag nanoparticles was about 48.2 Å. Owing to strong bonding of silver atoms to the wall of porous ceramic functionalized by 3-amino-propyltriethoxysilane, the contents of silver released from porous ceramic/Ag nanoparticles into filtrated water by test at a flow rate of about 5 L/h were less than 10 μg/L and was far below the required standard limit (<100 μg/L) for drinking water. Thus, porous ceramic/Ag nanoparticles candles can be potentially applied for point-of-use drinking water treatment. (author)

  18. Porous ceramics achievement by soybean and corn agricultural waste insertion

    International Nuclear Information System (INIS)

    Valdameri, C.Z.; Ank, A.; Zatta, L.; Anaissi, F.J.

    2014-01-01

    Porous ceramic materials are produced by incorporating organic particles and stable foams. Generally it improves low thermal conductivity, which gives thermal comfort for buildings. The southwest region of Parana state is one of the largest producers of grains in Brazil, this causes the disposal of a large amount of waste in the agricultural processing. This paper presents the characterization of porous ceramics produced from clay minerals and agricultural waste (soybeans and corn). The precursor was characterized by X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) techniques. For the ceramic materials produced, characterizations about density, water absorption, tensile strength by diametrical compression strength and flexural strength curves was performed. The results showed high possibility of industrial/commercial application because the ceramic materials were produced from low costs precursors leading to ceramic products with properties of interest in construction. (author)

  19. Effective adsorption and collection of cesium from aqueous solution using graphene oxide grown on porous alumina

    Science.gov (United States)

    Entani, Shiro; Honda, Mitsunori; Shimoyama, Iwao; Li, Songtian; Naramoto, Hiroshi; Yaita, Tsuyoshi; Sakai, Seiji

    2018-04-01

    Graphene oxide (GO) with a large surface area was synthesized by the direct growth of GO on porous alumina using chemical vapor deposition to study the Cs adsorption mechanism in aqueous solutions. Electronic structure analysis employing in situ near-edge X-ray absorption fine structure spectroscopy and X-ray photoelectron spectroscopy measurements clarifies the Cs atoms bond via oxygen functional groups on GO in the aqueous solution. The Cs adsorption capacity was found to be as high as 650-850 mg g-1, which indicates that the GO/porous alumina acts as an effective adsorbent with high adsorption efficiency for radioactive nuclides in aqueous solutions.

  20. Porous SiC ceramics fabricated by quick freeze casting and solid state sintering

    Directory of Open Access Journals (Sweden)

    Feng Wang

    2017-06-01

    Full Text Available Porous SiC ceramics with uniform microstructure were fabricated by quick freezing in liquid nitrogen and solid state sintering. Poly (vinyl alcohol (PVA was added as binder and pore morphology controller in this work. The microstructure and mechanical properties of porous SiC ceramics could be controlled by the composition of the aqueous slurries. Both solid content of the slurries and PVA content impacted on the pore structures and mechanical properties of the porous SiC ceramics. The solid content of slurries and PVA content varied from 60 to 67.5 wt% and 2–6 wt%, respectively. Besides, the grain morphology of ceramics was also tailored by changing the sintering temperature from 2050 to 2150 °C. Porous SiC ceramics with an average porosity of 42.72%, flexural strength of 59.28 MPa were obtained at 2150 °C from 67.5 wt% slurries with 2 wt% PVA.

  1. Wear Resistance of Nano Alumina Containing SiO2-B2O3-Na2O Glass-Ceramic on Steel Substrate

    Directory of Open Access Journals (Sweden)

    A. Faeghinia

    2016-09-01

    Full Text Available The experimental study has been carried out to investigate the tribological properties of nano Alumina reinforced glass-ceramic enamel. The mixtures of (5, 10, 15 wt.% nano alumina and glass powders have been air sprayed on stainless steel substrate.. The thixotropy, wetting angle and surface tension of used slurry were increased inherently by 15-wt.% nano alumina. By heat treating at 870-640-525 ºC, the homogeneous crystalline sodium silicate phase beside nano alumina was obtained in glass –ceramic coat. According to the EDAX results, the precipitated reduced Sb and Mo particles at the interface of enamel and steel caused to reasonable adherence of coat and steel. The dry sliding wear tests were carried out using pin on disk method. Results revealed the 0.01 mg wear rate by 30N load at 100 m for nano alumina bearing coats. The wear resistance increased by a factor of 10. According to SEM micrographs, the sliding load transfer by nano alumina particles occurred.

  2. 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

  3. In vitro comparison of the biological activity of alumina ceramic and titanium particles associated with aseptic loosening

    International Nuclear Information System (INIS)

    Ding Yue; Qin Chuqiang; Xu Jie; Huang Dongsheng; Fu Yuru

    2012-01-01

    Prosthetic wear particles are thought to play a central role in the initiation and development of periprosthetic osteolysis, leading to aseptic loosening of prostheses. This study aimed to compare the biological activity of ceramic and titanium particles that are associated with particle-induced, aseptic joint loosening. Different sizes of alumina-ceramic particles and titanium particles were prepared to stimulate murine macrophage cells RAW 264.7, of which the expressions of tumor necrosis factor alpha (TNF-alpha) and receptor activator of nuclear factor-κB ligand (RANKL) were measured by qPCR and ELISA at various time points. In the presence of all particles, the expression of TNF-alpha increased in a time-dependent manner, whereas the expression of RANKL showed no regular expression patterns. Notably, particles of smaller sizes provoked significantly higher levels of TNF-alpha and RANKL than those of larger sizes. Compared to the titanium particles, the ceramic particles provoked a significantly lower production of TNF-alpha. Thus, the bioactivities of titanium and alumina ceramic particles were inversely proportional to the sizes of the particles, and the expression of RANKL was not parallel to that of TNF-alpha. The successful outcome of ceramic-on-ceramic artificial joint prostheses may be attributed to the low biological activity of ceramic particles, as evidenced here. (paper)

  4. 3D printed porous ceramic scaffolds for bone tissue engineering: a review.

    Science.gov (United States)

    Wen, Yu; Xun, Sun; Haoye, Meng; Baichuan, Sun; Peng, Chen; Xuejian, Liu; Kaihong, Zhang; Xuan, Yang; Jiang, Peng; Shibi, Lu

    2017-08-22

    This study summarizes the recent research status and development of three-dimensional (3D)-printed porous ceramic scaffolds in bone tissue engineering. Recent literature on 3D-printed porous ceramic scaffolds was reviewed. Compared with traditional processing and manufacturing technologies, 3D-printed porous ceramic scaffolds have obvious advantages, such as enhancement of the controllability of the structure or improvement of the production efficiency. More sophisticated scaffolds were fabricated by 3D printing technology. 3D printed bioceramics have broad application prospects in bone tissue engineering. Through understanding the advantages and limitations of different 3D-printing approaches, new classes of bone graft substitutes can be developed.

  5. Ceramic porous material and method of making same

    Science.gov (United States)

    Liu, Jun; Kim, Anthony Y.; Virden, Jud W.

    1997-01-01

    The invention is a mesoporous ceramic membrane having substantially uniform pore size. Additionally, the invention includes aqueous and non-aqueous processing routes to making the mesoporous ceramic membranes. According to one aspect of the present invention, inserting a substrate into a reaction chamber at pressure results in reaction products collecting on the substrate and forming a membrane thereon. According to another aspect of the present invention, a second aqueous solution that is sufficiently immiscible in the aqueous solution provides an interface between the two solutions whereon the mesoporous membrane is formed. According to a further aspect of the present invention, a porous substrate is placed at the interface between the two solutions permitting formation of a membrane on the surface or within the pores of the porous substrate. According to yet another aspect of the present invention, mesoporous ceramic materials are formed using a non-aqueous solvent and water-sensitive precursors.

  6. Surface study of nano-template anodic porous alumina pre-irradiated by ArF laser

    International Nuclear Information System (INIS)

    Jaleh, B.; Saramad, S.; Farshchi-Tabrizi, M.

    2009-01-01

    Nano-porous alumina membranes have widely used as matrix for the fabrication of nanomaterials for many applications including quantum-dot arrays, magnetic storage devices and composites for catalysis, due to their remarkable hardness, thermal and anti corrupted stability, uniform pore size and high pore density. In this experiment three sets of aluminum samples were chosen for fabrication nano-porous anodic alumina. One set has select for laser cleaning before chemical treatment and the two others with and without chemical treatment without laser irradiation. Anodic aluminum oxide (AAO) films were characterized with Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM) micrograph and the SEM results were analyzed by Linear-Angular Fast Fourier Transform (LA-FFT) technique to investigate the arrangement and ordering of pores. According to these results the laser irradiated sample has much better regularity in comparison with the usual one.

  7. 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

  8. On the variation in the electrical properties and ac conductivity of through-thickness nano-porous anodic alumina with temperature

    International Nuclear Information System (INIS)

    Tahir, Mahmood; Mehmood, Mazhar; Nadeem, Muhammad; Waheed, Abdul; Tanvir, Muhammad Tauseef

    2013-01-01

    The electrical response of self-organized through-thickness anodic alumina with hexagonal arrangement of cylindrical pores has been studied as a function of temperature. Mechanically stable thick porous anodic alumina was prepared, by through-thickness anodic oxidation of aluminum sheet in sulfuric acid, with extremely high aspect ratio pores exhibiting fairly uniform diameter and interpore distance. It was observed that the electrical properties of through-thickness anodic alumina are very sensitive to minute changes in temperature and the role of surface conductivity in governing its electrical response cannot be overlooked. At high frequencies, intrinsic dielectric response of anodic alumina was dominant. The frequency-dependent conductivity behavior at low and intermediate frequencies was explained on the basis of correlated barrier hopping (CBH) and quantum mechanical tunneling (QMT) models, respectively. Experimental data was modeled using an equivalent circuit consisting of Debye circuit, for bulk alumina, parallel to surface conduction path. The surface conduction was primarily based on two circuits in series, each with a parallel arrangement of a resistor and a constant phase element. This suggested heterogeneity in alumina pore surface, possibly related with islands of physisorbed water separated by the regions of chemisorbed water. Temperature dependence of some circuit elements has been analyzed to express different charge migration phenomena occurring in nano-porous anodic alumina

  9. The effect of α-alumina particles on the properties of EN AC-44200 Al alloy based composite materials

    OpenAIRE

    J.W. Kaczmar; A. Kurzawa

    2012-01-01

    Purpose: The unreinforced EN AC-44200 aluminium alloy is characterized by the medium mechanical properties and the purpose of performed investigations was improvement of mechanical properties of this alloy by introducing stable ceramic α-alumina particles.Design/methodology/approach: The composite materials were manufactured by squeeze casting of porous ceramic preforms characterized by the open porosities of 90%, 80%, 70% and 60% with the liquid EN AC- 44200 aluminum alloy. The composite mat...

  10. Preparation and characterization of porous alumina-zirconia composite ceramics

    Czech Academy of Sciences Publication Activity Database

    Pabst, W.; Gregorová, E.; Sedlářová, I.; Černý, Martin

    2011-01-01

    Roč. 31, č. 14 (2011), s. 2721-2731 ISSN 0955-2219. [International Conference on Ceramic Processing Science /11./. Zürich, 29.08.2010-01.09.2010] Institutional research plan: CEZ:AV0Z30460519 Keywords : sintering * slip casting * composites Subject RIV: JI - Composite Materials Impact factor: 2.353, year: 2011

  11. Pressure-induced ferroelectric to antiferroelectric phase transformation in porous PZT95/5 ceramics

    International Nuclear Information System (INIS)

    Zeng, T.; Dong, X.L.; Chen, X.F.; Yao, C.H.; He, H.L.

    2007-01-01

    The hydrostatic pressure-induced ferroelectric to antiferroelectric (FE-AFE) phase transformation of PZT95/5 ceramics was investigated as a function of porosity, pore shape and pore size. FE-AFE phase transformations were more diffuse and occurred at lower hydrostatic pressures with increasing porosity. The porous PZT95/5 ceramics with spherical pores exhibited higher transformation pressures than those with irregular pores. Moreover, FE-AFE phase transformations of porous PZT95/5 ceramics with polydisperse irregular pores were more diffuse than those of porous PZT95/5 ceramics with monodisperse irregular pores. The relation between pore structure and hydrostatic pressure-induced FE-AFE transformation was established according to stress concentration theory. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. Stiff, porous scaffolds from magnetized alumina particles aligned by magnetic freeze casting.

    Science.gov (United States)

    Frank, Michael B; Naleway, Steven E; Haroush, Tsuk; Liu, Chin-Hung; Siu, Sze Hei; Ng, Jerry; Torres, Ivan; Ismail, Ali; Karandikar, Keyur; Porter, Michael M; Graeve, Olivia A; McKittrick, Joanna

    2017-08-01

    Bone consists of a hard mineral phase and a compliant biopolymer phase resulting in a composite material that is both lightweight and strong. Osteoporosis that degrades spongy bone preferentially over time leads to bone brittleness in the elderly. A porous ceramic material that can mimic spongy bone for a one-time implant provides a potential solution for the future needs of an aging population. Scaffolds made by magnetic freeze casting resemble the aligned porosity of spongy bone. A magnetic field applied throughout freezing induces particle chaining and alignment of lamellae structures between growing ice crystals. After freeze drying to extract the ice and sintering to strengthen the scaffold, cubes from the scaffold center are mechanically compressed along longitudinal (z-axis, ice growth direction) and transverse (y-axis, magnetic field direction) axes. The best alignment of lamellar walls in the scaffold center occurs when applying magnetic freeze casting with the largest particles (350nm) at an intermediate magnetic field strength (75mT), which also agrees with stiffness enhancement results in both z and y-axes. Magnetic moments of different sized magnetized alumina particles help determine the ideal magnetic field strength needed to induce alignment in the scaffold center rather than just at the poles. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. Microstructure and Mechanical Properties of Heterogeneous Ceramic-Polymer Composite Using Interpenetrating Network

    International Nuclear Information System (INIS)

    Eun-Hee, K.; Yeon-Gil, J.; Chang-Yong, J.

    2012-01-01

    Prepolymer, which can be polymerized by a photo, has been infiltrated into a porous ceramic to improve the addition effect of polymer into the ceramic, as a function of the functionality of prepolymer. It induces the increase in the mechanical properties of the ceramic. The porous alumina (Al 2 O 3 ) and the polyurethane acrylate (PUA) with a network structure by photo-polymerization were used as the matrix and infiltration materials, respectively. The porous Al 2 O 3 matrix without the polymer shows lower values in fracture strength than the composites, since the stress is transmitted more quickly via propagation of cracks from intrinsic defects in the porous matrix. However, in the case of composites, the distribution of stress between hetero phases results in the improved mechanical properties. In addition, the mechanical properties of composites, such as elastic modulus and fracture strength, are enhanced with increasing the functionality of prepolymer attributed to the crosslinking density of polymer.

  14. Porosity Dependence of Piezoelectric Properties for Porous Potassium Niobate System Ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Wada, S; Mase, Y; Shimizu, S; Maeda, K; Fujii, I; Nakashima, K; Pulpan, P; Miyajima, N, E-mail: swada@yamanashi.ac.jp [Interdisciplinary Graduate School of Medical and Engineering, University of Yamanashi, 4-4-37 Takeda, Kofu, Yamanashi 400-8510 (Japan)

    2011-10-29

    Porous potassium niobate (KNbO{sub 3}, KN) system ceramics were prepared by a conventional sintering method using carbon black (CB) nanoparticles. First, KN nanoparticles with a size of 100 nm was mixed with CB nanoparticles and binder using ball milling with ethanol. The mixture was dried, and pressed into pellets using uniaxial pressing. After binder burnout, these ceramics was sintered in air. Their piezoelectric properties were measured and discussed a relationship between porosity and piezoelectric properties. As the results, with increasing porosity, piezoelectric g33 constant increased significantly, which suggested that porous ceramics were effective for stress sensor application.

  15. Porosity Dependence of Piezoelectric Properties for Porous Potassium Niobate System Ceramics

    International Nuclear Information System (INIS)

    Wada, S; Mase, Y; Shimizu, S; Maeda, K; Fujii, I; Nakashima, K; Pulpan, P; Miyajima, N

    2011-01-01

    Porous potassium niobate (KNbO 3 , KN) system ceramics were prepared by a conventional sintering method using carbon black (CB) nanoparticles. First, KN nanoparticles with a size of 100 nm was mixed with CB nanoparticles and binder using ball milling with ethanol. The mixture was dried, and pressed into pellets using uniaxial pressing. After binder burnout, these ceramics was sintered in air. Their piezoelectric properties were measured and discussed a relationship between porosity and piezoelectric properties. As the results, with increasing porosity, piezoelectric g33 constant increased significantly, which suggested that porous ceramics were effective for stress sensor application.

  16. Preparation and Photocatalytic Property of TiO2/Diatomite-Based Porous Ceramics Composite Materials

    Directory of Open Access Journals (Sweden)

    Shuilin Zheng

    2012-01-01

    Full Text Available The diatomite-based porous ceramics was made by low-temperature sintering. Then the nano-TiO2/diatomite-based porous ceramics composite materials were prepared by hydrolysis deposition method with titanium tetrachloride as the precursor of TiO2 and diatomite-based porous as the supporting body of the nano-TiO2. The structure and microscopic appearance of nano-TiO2/diatomite-based porous ceramics composite materials was characterized by XRD and SEM. The photocatalytic property of the composite was investigated by the degradation of malachite green. Results showed that, after calcination at 550°C, TiO2 thin film loaded on the diatomite-based porous ceramics is anatase TiO2 and average grain size of TiO2 is about 10 nm. The degradation ratio of the composite for 5 mg/L malachite green solution reached 86.2% after irradiation for 6 h under ultraviolet.

  17. 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).

  18. Alumina Coating To Realize Desired Pore Characteristics Of Sintered Diatomite Membrane

    Directory of Open Access Journals (Sweden)

    Ha J.-H.

    2015-06-01

    Full Text Available Porous ceramic membranes prepared from natural materials such as diatomite, have lately attracted great interest in industrial applications due to their cost-effectiveness. In this study, we attempted to prepare an alumina coating to be deposited over a sintered diatomite-kaolin composite support layer in order to reduce the largest pore size to below 0.4 μm; such a coating could be potentially used in water treatment applications for bacterial removal.

  19. Fracture Toughness (KIC) of Lithography Based Manufactured Alumina Ceramic

    Science.gov (United States)

    Nindhia, T. G. T.; Schlacher, J.; Lube, T.

    2018-04-01

    Precision shaped ceramic components can be obtained by an emerging technique called Lithography based Ceramic Manufacturing (LCM). A green part is made from a slurry consisting of a ceramic powder in a photocurable binder with addition of dispersant and plasticizer. Components are built in a layer–by-layer way by exposing the desired cross- sections to light. The parts are subsequently sintered to their final density. It is a challenge to produce ceramic component with this method that yield the same mechanical properties in all direction. The fracture toughness (KIc) of of LCM-alumina (prepared at LITHOZ GmbH, Austria) was tested by using the Single-Edge-V-Notched Beam (SEVNB) method. Notches are made into prismatic bend-bars in all three direction X, Y and Z to recognize the value of fracture toughness of the material in all three directions. The microstructure was revealed with optical microscopy as well as Scanning Electron Microscopy (SEM). The results indicate that the fracture toughness in Y-direction has the highest value (3.10 MPam1/2) that is followed by the one in X-direction which is just a bit lower (2.90 MPam1/2). The Z-direction is found to have a similar fracture toughness (2.95 MPam1/2). This is supported by a homogeneous microstructure showing no hint of the layers used during production.

  20. Synthesis of Rh/Macro-Porous Alumina Over Micro-Channel Plate and Its Catalytic Activity Tests for Diesel Reforming.

    Science.gov (United States)

    Seong, Yeon Baek; Kim, Yong Sul; Park, No-Kuk; Lee, Tae Jin

    2015-11-01

    Macro-porous Al2O3 as the catalytic support material was synthesized using colloidal polystyrene spheres over a micro-channel plate. The colloidal polystyrene spheres were used as a template for the production of an ordered macro porous material using an alumina nitrate solution as the precursor for Al2O3. The close-packed colloidal crystal array template method was applied to the formulation of ordered macro-porous Al2O3 used as a catalytic support material over a micro-channel plate. The solvent in the mixture solution, which also contained the colloidal polystyrene solution, aluminum nitrate solution and the precursor of the catalytic active materials (Rh), was evaporated in a vacuum oven at 50 degrees C. The ordered polystyrene spheres and aluminum salt of the solid state were deposited over a micro channel plate, and macro-porous Al2O3 was formed after calcination at 600 degrees C to remove the polystyrene spheres. The catalytic activity of the Rh/macro-porous alumina supported over the micro-channel plate was tested for diesel reforming.

  1. Effect of porosity on dielectric properties and microstructure of porous PZT ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, B. Praveen [PZT Centre, Armament Research and Development Establishment, Pune 411021 (India); Kumar, H.H. [PZT Centre, Armament Research and Development Establishment, Pune 411021 (India); Kharat, D.K. [PZT Centre, Armament Research and Development Establishment, Pune 411021 (India)]. E-mail: dkkharat@rediffmail.com

    2006-02-25

    Porous piezoelectric materials are of great interest because of their high hydrostatic figure of merit and low sound velocity, which results in to low acoustic impedance and efficient coupling with medium. Porous lead zirconate titanate (PZT) ceramics with varying porosity was developed using polymethyl methacrylate by burnable plastic spheres (BURPS) process. The porous PZT ceramics were characterized for dielectric constant ({epsilon}), dielectric loss factor (tan {delta}), hydrostatic charge (d {sub h}) and voltage (g {sub h}) coefficients and microstructure. The effect of the porous microstructure on the dielectric constant and loss factor at frequencies of 10-10{sup 5} Hz are discussed in this paper.

  2. Mechanical properties of zirconia core-shell rods with porous core and dense shell prepared by thermoplastic co-extrusion

    Czech Academy of Sciences Publication Activity Database

    Kaštyl, J.; Chlup, Zdeněk; Clemen, F.; Trunec, M.

    2017-01-01

    Roč. 37, č. 6 (2017), s. 2439-2447 ISSN 0955-2219 R&D Projects: GA MŠk(CZ) LQ1601 Institutional support: RVO:68081723 Keywords : ceramic injection moldings * oxide fuel -cells * electrophoretic deposition * large pores * alumina * fabrication * behavior * tubes * bioceramics * composites * Zirconia * Co-extrusion * Core-shell * Porous structure * Mechanical properties Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass OBOR OECD: Ceramics Impact factor: 3.411, year: 2016

  3. 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.

  4. Gas phase fractionation method using porous ceramic membrane

    Science.gov (United States)

    Peterson, Reid A.; Hill, Jr., Charles G.; Anderson, Marc A.

    1996-01-01

    Flaw-free porous ceramic membranes fabricated from metal sols and coated onto a porous support are advantageously used in gas phase fractionation methods. Mean pore diameters of less than 40 .ANG., preferably 5-20 .ANG. and most preferably about 15 .ANG., are permeable at lower pressures than existing membranes. Condensation of gases in small pores and non-Knudsen membrane transport mechanisms are employed to facilitate and increase membrane permeability and permselectivity.

  5. Nano-CT study on nanostructure of porous ceramics

    International Nuclear Information System (INIS)

    Wu Wenquan; Li Wenjie; Guan Yong; Yang Yunhao; Chen Jie; Zhou Jie; Yu Xiyue; Song Xiangxia; Tian Yangchao; Li Wei; Chen Chusheng

    2010-01-01

    The porous structure of ceramic materials has a great impact on their performance. However, the existing characterization techniques fail to give 3D structure of the ceramics. In this work, nano-CT imaging technique was used to study 3D structure of a ceramic fiber tube prepared by a phase inversion technology. The results showed the shape, direction, size distribution, and 3D map of the pores inside the ceramic wall. The pore size is 0.4-1.5 μm, with a porosity of 38.31%. The data can be used to improve their preparation processes and optimize the structure parameters, for applications in chemical, energy, environmental protection and other fields. (authors)

  6. Wear Resistance of Nano Alumina Containing SiO2-B2O3-Na2O Glass-Ceramic on Steel Substrate

    OpenAIRE

    A. Faeghinia; A. Zamanian

    2016-01-01

    The experimental study has been carried out to investigate the tribological properties of nano Alumina reinforced glass-ceramic enamel. The mixtures of (5, 10, 15 wt.%) nano alumina and glass powders have been air sprayed on stainless steel substrate.. The thixotropy, wetting angle and surface tension of used slurry were increased inherently by 15-wt.% nano alumina. By heat treating at 870-640-525 ºC, the homogeneous crystalline sodium silicate phase beside nano alumina was obtained in glass ...

  7. Effect of silica fiber on the mechanical and chemical behavior of alumina-based ceramic core material

    OpenAIRE

    Weiguo Jiang; Kaiwen Li; Jiuhan Xiao; Langhong Lou

    2017-01-01

    In order to improve the chemical leachability, the alumina-based ceramic core material with the silica fiber was injected and sintered at 1100 °C/4 h, 1200 °C/4 h, 1300 °C/4 h and 1400 °C/4 h, respectively. The micrographs of ceramic core materials at sintered and leached state were characterized by scanning electron microscopy (SEM). The phase composition of ceramic core material after sintering and the leaching product after leaching were detected by X-ray diffraction (XRD). The porosity, r...

  8. 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

  9. 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)

  10. CVI-R gas phase processing of porous, biomorphic SiC-ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Sieber, H.; Vogli, E.; Mueller, F.; Greil, P. [Erlangen-Nuernberg Univ., Erlangen (DE). Dept. of Materials Science (III) Glass and Ceramics; Popovska, N.; Gerhard, H. [Univ. of Erlangen-Nuremberg, Dept. of Industrial Chemistry I, Erlangen (Germany)

    2002-07-01

    Natural pine wood was converted into biomorphic SiC-ceramics by CVI-R processing (chemical vapour infiltration - reaction). The wood samples were first pyrolyzed in inert atmosphere at temperatures of 800 C to yield biocarbon-derived template structures. Subsequently, the biocarbon preforms were infiltrated with silicon by isothermal CVI processing with MTS (methyltrichlorosilane) in excess of hydrogen at temperatures between 800 and 850 C, then converted into SiC-ceramic by annealing in inert atmosphere at temperatures between 1200-1600 C. During processing, the inherent open porous structure of the pine wood is retained down to the submicrometer level, yielding a highly porous SiC-ceramic with a unique microcellular morphology. (orig.)

  11. 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.

  12. Microstructure characterization of porous microalloyed aluminium-silicate ceramics

    Directory of Open Access Journals (Sweden)

    Purenović Jelena

    2011-01-01

    Full Text Available Kaolinite and bentonite clay powders mixed with active additives, based on Mg(NO32 and Al(NO32, sintered at high temperatures produce very porous ceramics with microcrystalline and amorphous regions and highly developed metalized surfaces (mainly with magnesium surplus. Microstructure investigations have revealed non-uniform and highly porous structure with broad distribution of grain size, specifically shaped grains and high degree of agglomeration. The ceramics samples were characterized by scanning electron microscopy (SEM, energy dispersive spectrometer (EDS, X-ray diffraction analysis (XRD and IR spectroscopy analysis, prior and after treatment in “synthetic water”, i.e. in aqueous solution of arsenic-salt. Grain size distribution for untreated and treated samples was done with software SemAfore 4. It has shown great variety in size distribution of grains from clay powders to sintered samples.

  13. Crack Growth along Interfaces in Porous Ceramic Layers

    DEFF Research Database (Denmark)

    Sørensen, Bent F.; Horsewell, Andy

    2001-01-01

    Crack growth along porous ceramic layers was studied experimentally. Double cantilever beam sandwich specimens were loaded with pure bending moments to obtain stable crack growth. The experiments were conducted in an environmental scanning electron microscope enabling in situ observations...

  14. Porous hydroxyapatite and biphasic calcium phosphate ceramics promote ectopic osteoblast differentiation from mesenchymal stem cells

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Lingli; Fan Hongsong; Zhang Xingdong [National Engineering Research Center for Biomaterials, Sichuan University, Chengdu, Sichuan 610064 (China); Hanagata, Nobutaka; Ikoma, Toshiyuki [Biomaterials Center, National Institute for Materials Science, Tsukuba, Ibaraki 305-0047 (Japan); Maeda, Megumi; Minowa, Takashi, E-mail: HANAGATA.Nobutaka@nims.go.j [Nanotechnology Innovation Center, National Institute for Materials Science, Tsukuba, Ibaraki 305-0047 (Japan)

    2009-04-15

    Because calcium phosphate (Ca-P) ceramics have been used as bone substitutes, it is necessary to investigate what effects the ceramics have on osteoblast maturation. We prepared three types of Ca-P ceramics with different Ca-P ratios, i.e. hydroxyapatite (HA), beta-tricalcium phosphate ({beta}-TCP), and biphasic calcium phosphate (BCP) ceramics with dense-smooth and porous structures. Comprehensive gene expression microarray analysis of mouse osteoblast-like cells cultured on these ceramics revealed that porous Ca-P ceramics considerably affected the gene expression profiles, having a higher potential for osteoblast maturation. In the in vivo study that followed, porous Ca-P ceramics were implanted into rat skeletal muscle. Sixteen weeks after the implantation, more alkaline-phosphatase-positive cells were observed in the pores of hydroxyapatite and BCP, and the expression of the osteocalcin gene (an osteoblast-specific marker) in tissue grown in pores was also higher in hydroxyapatite and BCP than in {beta}-TCP. In the pores of any Ca-P ceramics, 16 weeks after the implantation, we detected the expressions of marker genes of the early differentiation stage of chondrocytes and the complete differentiation stage of adipocytes, which originate from mesenchymal stem cells, as well as osteoblasts. These marker gene expressions were not observed in the muscle tissue surrounding the implanted Ca-P ceramics. These observations indicate that porous hydroxyapatite and BCP had a greater potential for promoting the differentiation of mesenchymal stem cells into osteoblasts than {beta}-TCP.

  15. Formation of self-ordered porous anodized alumina template for growing tungsten trioxide nanowires

    Science.gov (United States)

    Hussain, Tajamal; Shah, Asma Tufail; Shehzad, Khurram; Mujahid, Adnan; Farooqi, Zahoor Hussain; Raza, Muhammad Hamid; Ahmed, Mirza Nadeem; Nisa, Zaib Un

    2015-12-01

    Uniform porous anodized aluminum oxide (AAO) membrane has been synthesized by two-step anodization for fabricating tungsten trioxide (WO3) nanowires. Under assayed conditions, uniform porous structure of alumina (Al2O3) membrane with long range ordered hexagonal arrangements of nanopores was achieved. The self-assembled template possesses pores of internal diameter of 50 nm and interpore distance ( d int) of 80 nm with a thickness of about 80 µm, i.e., used for fabrication of nanostructures. WO3 nanowires have been fabricated by simple electroless deposition method inside Al2O3 nanopores. SEM images show tungsten trioxide nanowire with internal diameter of about 50 nm, similar to porous diameter of AAO template. XRD results showed that nanowires exist in cubic crystalline state with minor proportion of monoclinic phase.

  16. Effect of La2O3 content on wear resistance of alumina ceramics

    Institute of Scientific and Technical Information of China (English)

    WU Tingting; ZHOU Jian; WU Bolin; LI Wenjie

    2016-01-01

    In order to improve the wear resistance, a kind of alumina ceramic with good wear resistance was created in an Al2O3-CaCO3-SiO2-MgO-La2O3 (ACSML) system. The effects of La2O3 content on sintering temperature, bulk density, and wear rate were investigated. The wear rate of sample was as low as 0.0393‰. The wear resistance of the sample containing La2O3 has im-proved 43% than that of the sample without La2O3. Appropriate La2O3 doping could inhibit grain growth, enhance density, and purify grain boundary. La2O3 could diffuse into Al2O3 to form a solid solution and react with Al2O3 to form high-aluminum low-lanthanum complex oxides. The combination among Al2O3, the solid solution layer, and the layer of high-aluminum low-lanthanum complex oxides combined closely, which could improve grain boundary cohesion. Besides, the homogeneous distributions of elements made uniform structure. Finally, the wear resistance of alumina ceramic was improved.

  17. Preparation and Microstructure of Porous ZrB2 Ceramics Using Reactive Spark Plasma Sintering Method

    Institute of Scientific and Technical Information of China (English)

    YUAN Huiping; LI Junguo; SHEN Qiang; ZHANG Lianmeng

    2015-01-01

    Zirconium oxide (ZrO2) and boron carbide (B4C) were added to ZrB2 raw powders to prepare ZrB2 porous ceramics by reactive spark plasma sintering (RSPS). The reactions between ZrO2 and B4C which produce ZrB2 and gas (such as CO and B2O3) result in pore formation. X-Ray Diffraction results indicated that the products phase was ZrB2 and the reaction was completed after the RSPS process. The porosity could be controlled by changing the ratio of synthesized ZrB2 to raw ZrB2 powders. The porosity of porous ceramics with 20 wt% and 40 wt% synthsized ZrB2 are 0.185 and 0.222, respectivly. And dense ZrB2-SiC ceramic with a porosity of 0.057 was prepared under the same conditions for comparison. The pores were homogeneously distributed within the microstructure of the porous ceramics. The results indicate a promising method for preparing porous ZrB2-based ceramics.

  18. Thermophysical Properties of High-Frequency Induction Heat Sintered Graphene Nanoplatelets/Alumina Ceramic Functional Nanocomposites

    Science.gov (United States)

    Ahmad, Iftikhar; Subhani, Tayyab; Wang, Nannan; Zhu, Yanqiu

    2018-05-01

    This paper concerns the thermophysical properties of high-frequency induction heat (HFIH) sintered alumina ceramic nanocomposites containing various graphene nanoplatelets (GNP) concentrations. The GNP/alumina nanocomposites demonstrated high densities, fine-grained microstructures, highest fracture toughness and hardness values of 5.7 MPa m1/2 and 18.4 GPa, which found 72 and 8%, superior to the benchmarked monolithic alumina, respectively. We determine the role of GNP in tuning the microstructure and inducing toughening mechanisms in the nanocomposites. The sintered monolithic alumina exhibited thermal conductivity value of 24.8 W/mK; however, steady drops of 2, 15 and 19% were recorded after adding respective GNP contents of 0.25, 0.5 and 1.0 wt.% in the nanocomposites. In addition, a dwindling trend in thermal conductions with increasing temperatures was recorded for all sintered samples. Simulation of experimental results with proven theoretical thermal models showed the dominant role of GNP dispersions, microstructural porosity, elastic modulus and grain size in controlling the thermal transport properties of the GNP/alumina nanocomposites. Thermogravimetric analysis showed that the nanocomposite with up to 0.5 mass% of GNP is thermally stable at the temperatures greater than 875 °C. The GNP/alumina nanocomposites owning a distinctive combination of mechanical and thermal properties are promising contenders for the specific components of the aerospace engine and electronic devices having contact with elevated temperatures.

  19. Freeze-casting: Fabrication of highly porous and hierarchical ceramic supports for energy applications

    Directory of Open Access Journals (Sweden)

    Cyril Gaudillere

    2016-03-01

    The aim of this paper is to give an overview of the freeze-casting ceramic shaping method and to show how its implementation could be useful for several energy applications where key components comprise a porous scaffold. A detailed presentation of the freeze-casting process and of the characteristics of the resulting porous parts is firstly given. The characteristic of freeze-cast parts and the drawbacks of conventional porous scaffolds existing in energy applications are drawn in order to highlight the expected beneficial effect of this new shaping technique as possible substitute to the conventional ones. Finally, a review of the state of the art freeze-cast based energy applications developed up to now and expected to be promising is given to illustrate the large perspectives opened by the implementation of the freeze-casting of ceramics for energy fields. Here we suggest discussing about the feasibility of incorporate freeze-cast porous support in high temperature ceramic-based energy applications.

  20. Synthesis and photocatalytic properties of graphitic carbon nitride nanofibers using porous anodic alumina templates

    Science.gov (United States)

    Suchitra, S. M.; Udayashankar, N. K.

    2017-12-01

    In the present study, we describe an effective method for the synthesis of Graphitic carbon nitride (GCN) nanostructures using porous anodic alumina (AAO) membrane as template by simple thermal condensation of cyanamide. Synthesized nanostructure was fully analysed by various techniques to detect its crystalline nature, morphology, luminescent properties followed by the evaluation of its photocatalytic activity in the degradation of Methylene blue dye. Structural analysis of synthesized GCNNF was systematically carried out using x-ray powder diffraction (XRD) and scanning electron microscope (SEM), and. The results confirmed the growth of GCN inside the nanochannels of anodic alumina templates. Luminescent properties of GCNNF were studied using photoluminescence (PL) spectroscopy. PL analysis showed the presence of a strong emission peak in the wavelength range of 350-600 nm in blue region. GCNNF displays higher photocatalytic performance in the photodegradation of methylene blue compare to the bulk GCN. Highlights 1. In the present paper, we report the synthesis of graphitic carbon nitride nanofibers (GCNNF) using porous anodic aluminium oxide membranes as templates through thermal condensation of cyanamide at 500 °C. 2. The synthesis of Graphitic carbon nitride nanofibers using porous andic alumina template is the efficient approach for increasing crystallinity and surface area. 3. The high surface area of graphitic carbon nitride nanofibers has a good impact on novel optical and photocatalytic properties of the bulkGCN. 4. AAO templating of GCN is one of the versatile method to produce tailorable GCN nanostructures with higher surface area and less number of structural defects. 5. Towards photocatalytic degradation of dyes, the tuning of physical properties is very essential thing hence we are succeeded in achieving better catalytic performance of GCN nanostructures by making use of AAO templates.

  1. Processing of porous zirconia ceramics by direct consolidation with starch

    International Nuclear Information System (INIS)

    Garrido, Liliana B; Albano, Maria P

    2008-01-01

    Porous ceramics are used especially for those environments with high temperatures, heavy wear and in a corrosive medium. Zirconium-based materials are useful for such applications as sensors, filters, support for catalytic reactions, porous components for sofc and in biomedical applications. A conventional method for producing porous ceramics consists of the addition and later decomposition by calcination (pyrolisis) of different organic materials that act as pore formers. Several wet processing possibilities have been developed. Among these is a technique of direct consolidation with starch. This process begins with the preparation of an aqueous suspension of the ceramic with the dispersants needed to stabilize it, to which the starch is added. After casting in a waterproof mold, the suspension thermally hardens into the desired shape. The dry compacts undergo the sintering cycle to obtain pieces almost in their final form. This study aims to optimize the processing of porous zirconium ceramics using starch as a pore and binder forming agent. Zirconium with 3% yttrium molar stabilized in tetragonal phase was used. The aqueous suspensions (52-55% vol) of the zirconium-starch mixtures with different compositions were stabilized with a commercial solution of ammonium polyacrylate as a dispersant and were hardened in plastic molds at 90 o C for 30 min. The influence of added volume of starch on the physical characteristics of the pieces in green state was established while maintaining the temperature, the gelling time and the conditions of constant drying. The sintering was carried out at 1000-1500 o C-2h. The characteristics of the sintered product were evaluated by measuring density, volumetric contraction, intrusion of Hg and the evolution of the crystalline phases by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The microstructural properties of ceramic (pore volume, the relation between open and closed porosity, size distribution, morphology of

  2. 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.)

  3. 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.

  4. Microstructural and Wear Behavior Characterization of Porous Layers Produced by Pulsed Laser Irradiation in Glass-Ceramics Substrates.

    Science.gov (United States)

    Sola, Daniel; Conde, Ana; García, Iñaki; Gracia-Escosa, Elena; de Damborenea, Juan J; Peña, Jose I

    2013-09-09

    In this work, wear behavior and microstructural characterization of porous layers produced in glass-ceramic substrates by pulsed laser irradiation in the nanosecond range are studied under unidirectional sliding conditions against AISI316 and corundum counterbodies. Depending on the optical configuration of the laser beam and on the working parameters, the local temperature and pressure applied over the interaction zone can generate a porous glass-ceramic layer. Material transference from the ball to the porous glass-ceramic layer was observed in the wear tests carried out against the AISI316 ball counterface whereas, in the case of the corundum ball, the wear volume loss was concentrated in the porous layer. Wear rate and friction coefficient presented higher values than expected for dense glass-ceramics.

  5. Microstructural and Wear Behavior Characterization of Porous Layers Produced by Pulsed Laser Irradiation in Glass-Ceramics Substrates

    Directory of Open Access Journals (Sweden)

    Jose I. Peña

    2013-09-01

    Full Text Available In this work, wear behavior and microstructural characterization of porous layers produced in glass-ceramic substrates by pulsed laser irradiation in the nanosecond range are studied under unidirectional sliding conditions against AISI316 and corundum counterbodies. Depending on the optical configuration of the laser beam and on the working parameters, the local temperature and pressure applied over the interaction zone can generate a porous glass-ceramic layer. Material transference from the ball to the porous glass-ceramic layer was observed in the wear tests carried out against the AISI316 ball counterface whereas, in the case of the corundum ball, the wear volume loss was concentrated in the porous layer. Wear rate and friction coefficient presented higher values than expected for dense glass-ceramics.

  6. Overall viscoplastic behavior of non-irradiated porous nuclear ceramics

    International Nuclear Information System (INIS)

    Monerie, Yann; Gatt, Jean-Marie

    2006-01-01

    This paper deals with the overall behavior of nonlinear viscous and porous nuclear ceramics. Bi-viscous isotropic porous materials are considered: the matrix is subjected to two power-law viscosities with different exponents related to two stationary temperature-activated creeping mechanisms (scattering-creep and dislocation-creep), and this matrix contains a low porosity volume fraction. The overall behavior of these types of composite materials is obtained with the help of quadratic strain-rate potentials combined with experimental-based coupling function depending on stress and temperature. For each creeping mechanism, the hollow sphere model of [Michel, J.-C., Suquet, P., 1992. The constitutive law of nonlinear viscous and porous materials. Journal of the Mechanics and Physics of Solids 40, 783-812] is used. Mechanical parameters of the resulting model are identified and validated in the particular case of non-irradiated uranium dioxide nuclear ceramics. This model predicts, under pure thermo-mechanical loading, a variation of the material volume and a variation of the porosity volume fraction (the so-called densification or swelling). (authors)

  7. Corrosion behaviour of porous chromium carbide/oxide based ceramics in supercritical water

    International Nuclear Information System (INIS)

    Dong, Z.; Xin, T.; Chen, W.; Zheng, W.; Guzonas, D.

    2011-01-01

    Porous chromium carbide with a high density of open pores was fabricated by a reactive sintering method. Chromium oxide ceramics were obtained by re-oxidizing the porous chromium carbides formed. Some samples were added with yttria at 5 wt. %, prior to reactive sintering to form porous structures. Corrosion tests in SCW were performed at temperatures ranging from 375 o C to 625 o C with a fixed pressure at around 25∼30 MPa. The results show that chromium carbide is stable in SCW environments at temperatures up to 425 o C, above which disintegration of carbides through oxidation occurs. Porous chromium oxide samples show better corrosion resistance than porous chromium carbide, but disintegrate in SCW at around 625 o C. Among all the samples tested, chromium oxide ceramics with added yttria exhibited much better corrosion resistance compared with the pure chromium carbide/oxides. No evidence of weight change or disintegration of porous chromium oxides with 5 wt % added yttria was observed after exposure at 625 o C in SCW for 600 hours. (author)

  8. Modified Shrinking Core Model for Atomic Layer Deposition of TiO2 on Porous Alumina with Ultrahigh Aspect Ratio

    International Nuclear Information System (INIS)

    Park, Inhye; Leem, Jina; Lee, Hooyong; Min, Yosep

    2013-01-01

    When atomic layer deposition (ALD) is performed on a porous material by using an organometallic precursor, minimum exposure time of the precursor for complete coverage becomes much longer since the ALD is limited by Knudsen diffusion in the pores. In the previous report by Min et al. (Ref. 23), shrinking core model (SCM) was proposed to predict the minimum exposure time of diethylzinc for ZnO ALD on a porous cylindrical alumina monolith. According to the SCM, the minimum exposure time of the precursor is influenced by volumetric density of adsorption sites, effective diffusion coefficient, precursor concentration in gas phase and size of the porous monolith. Here we modify the SCM in order to consider undesirable adsorption of byproduct molecules. TiO 2 ALD was performed on the cylindrical alumina monolith by using titanium tetrachloride (TiCl 4 ) and water. We observed that the byproduct (i. e., HCl) of TiO 2 ALD can chemically adsorb on adsorption sites, unlike the behavior of the byproduct (i. e., ethane) of ZnO ALD. Consequently, the minimum exposure time of TiCl 4 (∼16 min) was significantly much shorter than that (∼71 min) of DEZ. The predicted minimum exposure time by the modified SCM well agrees with the observed time. In addition, the modified SCM gives an effective diffusion coefficient of TiCl 4 of ∼1.78 Χ 10 -2 cm 2 /s in the porous alumina monolith

  9. Porous (Ba,SrTiO3 ceramics for tailoring dielectric and tunability properties: Modelling and experiment

    Directory of Open Access Journals (Sweden)

    Roxana E. Stanculescu

    2017-12-01

    Full Text Available 3D Finite Element Method simulations were employed in order to describe tunability properties in anisotropic porous paraelectric structures. The simulations predicted that properties of a ceramic can be tailored by using various levels of porosity. Porous Ba0.6Sr0.4TiO3 (BST ceramics have been studied in order to investigate the influence of porosity on their functional properties. The BST ceramics with various porosity levels have been obtained by solid-state reaction. Lamellar graphite in different concentration of 10, 20 and 35 vol.% was added as sacrificial pore forming agent. The structural, microstructural, dielectric and tunability properties were investigated. By comparison with dense BST ceramic, porous samples present a fracture mode transformation from intragranular to an intergranular fracture and a decrease of grain size. Lower dielectric constants, low dielectric losses, but higher values of tunability than in the dense material were obtained in the porous BST structures as a result of local field inhomogeneity generated by the presence of air pores-ceramic interfaces.

  10. Interconnected porous hydroxyapatite ceramics for bone tissue engineering

    Science.gov (United States)

    Yoshikawa, Hideki; Tamai, Noriyuki; Murase, Tsuyoshi; Myoui, Akira

    2008-01-01

    Several porous calcium hydroxyapatite (HA) ceramics have been used clinically as bone substitutes, but most of them possessed few interpore connections, resulting in pathological fracture probably due to poor bone formation within the substitute. We recently developed a fully interconnected porous HA ceramic (IP-CHA) by adopting the ‘foam-gel’ technique. The IP-CHA had a three-dimensional structure with spherical pores of uniform size (average 150 μm, porosity 75%), which were interconnected by window-like holes (average diameter 40 μm), and also demonstrated adequate compression strength (10–12 MPa). In animal experiments, the IP-CHA showed superior osteoconduction, with the majority of pores filled with newly formed bone. The interconnected porous structure facilitates bone tissue engineering by allowing the introduction of mesenchymal cells, osteotropic agents such as bone morphogenetic protein or vasculature into the pores. Clinically, we have applied the IP-CHA to treat various bony defects in orthopaedic surgery, and radiographic examinations demonstrated that grafted IP-CHA gained radiopacity more quickly than the synthetic HA in clinical use previously. We review the accumulated data on bone tissue engineering using the novel scaffold and on clinical application in the orthopaedic field. PMID:19106069

  11. Characterization and surface treatment effects on topography of a glass-infiltrated alumina/zirconia-reinforced ceramic.

    Science.gov (United States)

    Della Bona, Alvaro; Donassollo, Tiago A; Demarco, Flávio F; Barrett, Allyson A; Mecholsky, John J

    2007-06-01

    Characterize the microstructure, composition and some physical properties of a glass-infiltrated alumina/zirconia-reinforced ceramic (IZ) and the effect of surface treatment on topography. IZ ceramic specimens were fabricated according to ISO6872 instructions and polished through 1 microm alumina abrasive. Quantitative and qualitative analyses were performed using scanning electron microscopy (SEM), backscattered imaging (BSI), electron dispersive spectroscopy (EDS) and stereology. The elastic modulus (E) and Poisson's ratio (nu) were determined using ultrasonic waves, and the density (rho) using a helium pycnometer. The following ceramic surface treatments were used: AP-as-polished; HF-etching with 9.5% hydrofluoric acid for 90 s; SB-sandblasting with 25 microm aluminum oxide particles for 15s and SC-blasting with 30 microm aluminum oxide particles modified by silica (silica coating) for 15s. An optical profilometer was used to examine the surface roughness (Ra) and SEM-EDS were used to measure the amount of silica after all treatments. The IZ mean property values were as follows: rho=4.45+/-0.01 g/cm(3); nu=0.26 and E=245 GPa. Mean Ra values were similar for AP- and HF-treated IZ but significantly increased after either SC or SB treatment (pceramic. Treating IZ with either SB or SC produced greater Ra values and the SC showed a significant increase in the surface concentration of silica, which may enhance bonding to resin via silane coupling.

  12. Alumina matrix ceramic-nickel composites formed by centrifugal slip casting

    Directory of Open Access Journals (Sweden)

    Justyna Zygmuntowicz

    2015-12-01

    Full Text Available The paper is focused on the possibility of fabricating the alumina matrix ceramic-nickel composites with gradient concentration of metal particles. Centrifugal slip casting method was chosen for the composite fabrication. This method allows fabrication of the graded distribution of nickel particles in the hollow cylinder composites. The horizontal rotation axis was applied. The samples were characterized by XRD, SEM and quantitative description of the microstructure. The macroscopic as well as SEM observations of the prepared composites confirmed the gradient concentration of Ni particles in the composite materials. The application of the centrifugal slip casting method allows for the graded distribution of metal particles in the samples.

  13. Morphological evolution of porous nanostructures grown from a single isolated anodic alumina nanochannel

    Science.gov (United States)

    Chen, Shih-Yung; Chang, Hsuan-Hao; Lai, Ming-Yu; Liu, Chih-Yi; Wang, Yuh-Lin

    2011-09-01

    Porous anodic aluminum oxide (AAO) membranes have been widely used as templates for growing nanomaterials because of their ordered nanochannel arrays with high aspect ratio and uniform pore diameter. However, the intrinsic growth behavior of an individual AAO nanochannel has never been carefully studied for the lack of a means to fabricate a single isolated anodic alumina nanochannel (SIAAN). In this study, we develop a lithographic method for fabricating a SIAAN, which grows into a porous hemispherical structure with its pores exhibiting fascinating morphological evolution during anodization. We also discover that the mechanical stress affects the growth rate and pore morphology of AAO porous structures. This study helps reveal the growth mechanism of arrayed AAO nanochannels grown on a flat aluminum surface and provides insights to help pave the way to altering the geometry of nanochannels on AAO templates for the fabrication of advanced nanocomposite materials.

  14. Morphological evolution of porous nanostructures grown from a single isolated anodic alumina nanochannel

    International Nuclear Information System (INIS)

    Chen, Shih-Yung; Wang, Yuh-Lin; Chang, Hsuan-Hao; Lai, Ming-Yu; Liu, Chih-Yi

    2011-01-01

    Porous anodic aluminum oxide (AAO) membranes have been widely used as templates for growing nanomaterials because of their ordered nanochannel arrays with high aspect ratio and uniform pore diameter. However, the intrinsic growth behavior of an individual AAO nanochannel has never been carefully studied for the lack of a means to fabricate a single isolated anodic alumina nanochannel (SIAAN). In this study, we develop a lithographic method for fabricating a SIAAN, which grows into a porous hemispherical structure with its pores exhibiting fascinating morphological evolution during anodization. We also discover that the mechanical stress affects the growth rate and pore morphology of AAO porous structures. This study helps reveal the growth mechanism of arrayed AAO nanochannels grown on a flat aluminum surface and provides insights to help pave the way to altering the geometry of nanochannels on AAO templates for the fabrication of advanced nanocomposite materials.

  15. Fabrication and characterization of nanostructured Ba-doped BiFeO3 porous ceramics

    Directory of Open Access Journals (Sweden)

    Mostafavi E.

    2016-03-01

    Full Text Available Nanostructured barium doped bismuth ferrite, Bi₀.₈Ba₀.₂FeO₃ porous ceramics with a relatively high magnetic coercivity was fabricated via sacrificial pore former method. X-ray diffraction results showed that 20 wt.% Ba doping induces a structural phase transition from rhombohedral to distorted pseudo-cubic structure in the final porous samples. Moreover, utilizing Bi₀.₈Ba₀.₂FeO₃ as the starting powder reduces the destructive interactions between the matrix phase and pore former, leading to an increase in stability of bismuth ferrite phase in the final porous ceramics. Urea-derived Bi₀.₈Ba₀.₂FeO₃ porous ceramic exhibits density of 4.74 g/cm³ and porosity of 45 % owing the uniform distribution of interconnected pores with a mean pore size of 7.5 μm. Well defined nanostructured cell walls with a mean grain size of 90 nm were observed in the above sample, which is in a good accordance with the grain size obtained from BET measurements. Saturation magnetization decreased from 2.31 in the Bi₀.₈Ba₀.₂FeO₃ compact sample to 1.85 A m²/kg in urea-derived Bi₀.₈Ba₀.₂FeO₃ porous sample; moreover, coercivity increased from 284 to 380 kA/m.

  16. 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.)

  17. High Porosity Alumina as Matrix Material for Composites of Al-Mg Alloys

    International Nuclear Information System (INIS)

    Gömze, L A; Egész, Á; Gömze, L N; Ojima, F

    2013-01-01

    The sophisticated industry and technologies require higher and higher assumptions against mechanical strength and surface hardness of ceramic reinforced metal alloys and metal matrix composites. Applying the well-known alumina powders by dry pressing technology and some special pore-forming additives and sintering technology the authors have successfully developed a new, high porosity alumina matrix material for composites of advenced Al-Mg alloys. The developed new matrix material have higher than 30% porosity, with homogenous porous structure and pore sizes from few nano up to 2–3 mm depending on the alloys containments. Thanks to the used materials and the sintering conditions the authors could decrease the wetting angles less than 90° between the high porosity alumina matrix and the Al-Mg alloys. Applied analytical methods in this research were laser granulometry, scanning electron microscopy, and X-ray diffraction. Digital image analysis was applied to microscopy results, to enhance the results of transformation

  18. Super-adiabatic combustion in Al2O3 and SiC coated porous media for thermoelectric power conversion

    International Nuclear Information System (INIS)

    Mueller, Kyle T.; Waters, Oliver; Bubnovich, Valeri; Orlovskaya, Nina; Chen, Ruey-Hung

    2013-01-01

    The combustion of ultra-lean fuel/air mixtures provides an efficient way to convert the chemical energy of hydrocarbons and low-calorific fuels into useful power. Matrix-stabilized porous medium combustion is an advanced technique in which a solid porous medium within the combustion chamber conducts heat from the hot gaseous products in the upstream direction to preheat incoming reactants. This heat recirculation extends the standard flammability limits, allowing the burning of ultra-lean and low-calorific fuel mixtures and resulting a combustion temperature higher than the thermodynamic equilibrium temperature of the mixture (i.e., super-adiabatic combustion). The heat generated by this combustion process can be converted into electricity with thermoelectric generators, which is the goal of this study. The design of a porous media burner coupled with a thermoelectric generator and its testing are presented. The combustion zone media was a highly-porous alumina matrix interposed between upstream and downstream honeycomb structures with pore sizes smaller than the flame quenching distance, preventing the flame from propagating outside of the central section. Experimental results include temperature distributions inside the combustion chamber and across a thermoelectric generator; along with associated current, voltage and power output values. Measurements were obtained for a catalytically inert Al 2 O 3 medium and a SiC coated medium, which was tested for the ability to catalyze the super-adiabatic combustion. The combustion efficiency was obtained for stoichiometric and ultra-lean (near the lean flammability limit) mixtures of CH 4 and air. - Highlights: • Design of a porous burner coupled with a thermoelectric module. • Super-adiabatic combustion in a highly-porous ceramic matrix was investigated. • Both alumina and silicon carbide ceramic surfaces were used as porous media. • Catalytic properties of Al 2 O 3 and SiC ceramic surfaces were studied

  19. Shape-dependent plasma-catalytic activity of ZnO nanomaterials coated on porous ceramic membrane for oxidation of butane.

    Science.gov (United States)

    Sanjeeva Gandhi, M; Mok, Young Sun

    2014-12-01

    In order to explore the effects of the shape of ZnO nanomaterials on the plasma-catalytic decomposition of butane and the distribution of byproducts, three types of ZnO nanomaterials (nanoparticles (NPs), nanorods (NRs) and nanowires (NWs)) were prepared and coated on multi-channel porous alumina ceramic membrane. The structures and morphologies of the nanomaterials were confirmed by X-ray diffraction method and scanning electron microscopy. The observed catalytic activity of ZnO in the oxidative decomposition of butane was strongly shape-dependent. It was found that the ZnO NWs exhibited higher catalytic activity than the other nanomaterials and could completely oxidize butane into carbon oxides (COx). When using the bare or ZnO NPs-coated ceramic membrane, several unwanted partial oxidation and decomposition products like acetaldehyde, acetylene, methane and propane were identified during the decomposition of butane. When the ZnO NWs- or ZnO NRs-coated membrane was used, however, the formation of such unwanted byproducts except methane was completely avoided, and full conversion into COx was achieved. Better carbon balance and COx selectivity were obtained with the ZnO NWs and NRs than with the NPs. Copyright © 2014 Elsevier Ltd. All rights reserved.

  20. Porous ceramic membrane with superhydrophobic and superoleophilic surface for reclaiming oil from oily water

    Science.gov (United States)

    Su, Changhong; Xu, Youqian; Zhang, Wei; Liu, Yang; Li, Jun

    2012-01-01

    A porous ceramic tube with superhydrophobic and superoleophilic surface was fabricated by sol-gel and then surface modification with polyurethane-polydimethysiloxane, and an oil-water separator based on the porous ceramic tube was erected to characterize superhydrophobic and superoleophilic surface's separation efficiency and velocity when being used to reclaim oil from oily water and complex oily water containing clay particle. The separator is fit for reclaiming oil from oily water.

  1. [In vitro drug release behavior of carrier made of porous glass ceramics].

    Science.gov (United States)

    Wang, De-ping; Huang, Wen-hai; Zhou, Nai

    2002-09-01

    To conduct the in vitro test on drug release of rifampin encapsulated in a carrier made of porous phosphate glass ceramics and to analyze main factors which affect the drug release rate. A certain quantitative of rifampin was sealed in a hollow cylindrical capsule which consisted of chopped calcium phosphate crystal fiber obtained from glass crystallization. The rifampin concentration was measured in the simulated physiological solution in which the capsule soaked. Rifampin could be released in a constant rate from the porous glass ceramic carrier in a long time. The release rate was dependent on the size of crystal fiber and the wall thickness of the capsule. This kind of calcium phosphate glass ceramics can be a candidate of the carrier materials used as long term drug therapy after osteotomy surgery.

  2. Heterocoagulação como técnica para obtenção de cerâmicas porosas Porous ceramics through heterocoagulation process

    Directory of Open Access Journals (Sweden)

    M. O. Carlos

    2005-06-01

    Full Text Available Devido ao custo da energia, tem crescido o interesse pelo uso de cerâmicas refratárias porosas como isolantes térmicos para aplicações em altas temperaturas. Isso se deve ao fato desses materiais aliarem propriedades intrínsecas das cerâmicas, como inércia química e refratariedade, à baixa condutividade térmica dos porosos. Uma das técnicas utilizadas na obtenção desses materiais consiste na adição de compostos orgânicos à matriz cerâmica, os quais volatilizam durante a queima. Essa técnica pode ter seu desempenho aprimorado (porosidade controlada pela utilização da heterocoagulação entre as partes inorgânicas e orgânicas. O objetivo desse trabalho foi avaliar o impacto da heterocoagulação na fabricação de cerâmicas porosas utilizando PVC ou amido como aditivo orgânico e alumina como componente inorgânico. Foram definidas as condições mais favoráveis à heterocoagulação para os dois incorporadores. Independente do tipo de incorporador, o aumento do teor utilizado resultou em cerâmicas mais porosas. Entretanto, um teor máximo de 50vol% do material orgânico foi escolhido, uma vez que maiores teores resultam em uma resistência mecânica insatisfatória. Verificou-se ainda que, em comparação com o processo convencional, as cerâmicas produzidas por heterocoagulação apresentaram maior homogeneidade microestrutural e resistência mecânica.The crisis faced by the energy sector has led to a growing interest in the use of refractory porous ceramics as high temperature insulators, due to their unique combination of properties: chemical inertia, refractoriness and low thermal conductivity. Among the several techniques employed in the production of these materials, the addition of organic particles, which volatilize during the first heat-up, to the ceramic matrix is one of the most promising techniques. This procedure can be optimized in order to attain a better control over the porosity using the

  3. 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.

  4. Superplastically foaming method to make closed pores inclusive porous ceramics

    International Nuclear Information System (INIS)

    Kishimoto, Akira; Hayashi, Hidetaka

    2011-01-01

    Porous ceramics incorporates pores to improve several properties including thermal insulation maintaining inherenet ceramic properties such as corrosion resistance and large mechanical strength. Conventional porous ceramics is usually fabricated through an insufficient sintering. Since the sintering accompanies the exclusion of pores, it must be terminated at the early stage to maintain the high porosity, leading to degraded strength and durability. Contrary to this, we have innovated superplastically foaming method to make ceramic foams only in the solid state. In this method, the previously inserted foam agent evaporates after the full densification of matrix at around the sintering temperature. Closed pores expand utilizing the superplastic deformation driven by the evolved gas pressure. The typical features of this superplastically foaming method are listed as follows, 1. The pores are introduced after sintering the solid polycrystal. 2. Only closed pores are introduced, improving the insulation of gas and sound in addition to heat. 3. The pore walls are fully densified expecting a large mechanical strength. 4. Compared with the melt foaming method, this method is practical because the fabrication temperature is far below the melting point and it does not need molds. 5. The size and the location pores can be controlled by the amount and position of the foam agent.

  5. Gas permeability of ice-templated, unidirectional porous ceramics

    Science.gov (United States)

    Seuba, Jordi; Deville, Sylvain; Guizard, Christian; Stevenson, Adam J.

    2016-01-01

    We investigate the gas flow behavior of unidirectional porous ceramics processed by ice-templating. The pore volume ranged between 54% and 72% and pore size between 2.9 ?m and 19.1 ?m. The maximum permeability (?? m?) was measured in samples with the highest total pore volume (72%) and pore size (19.1 ?m). However, we demonstrate that it is possible to achieve a similar permeability (?? m?) at 54% pore volume by modification of the pore shape. These results were compared with those reported and measured for isotropic porous materials processed by conventional techniques. In unidirectional porous materials tortuosity (?) is mainly controlled by pore size, unlike in isotropic porous structures where ? is linked to pore volume. Furthermore, we assessed the applicability of Ergun and capillary model in the prediction of permeability and we found that the capillary model accurately describes the gas flow behavior of unidirectional porous materials. Finally, we combined the permeability data obtained here with strength data for these materials to establish links between strength and permeability of ice-templated materials.

  6. 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)

  7. 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)

  8. Obtaining of dense and highly porous ceramic materials from metallurgical slag

    OpenAIRE

    Fidancevska E.; Mangutova B.; Milosevski D.; Milosevski M.; Bossert J.

    2003-01-01

    Glass-ceramics in a dense and highly porous form can be obtained from metallurgical slag and waste glass of TV monitors. Using polyurethane foam as pore creator, a highly porous system with porosity of 65 ± 5 %, E-modulus and flexural strength of 8 ± 3 GPa and 13 ± 3.5 MPa respectively can be obtained. This porous material had durability (mass loss) of 0.03 % in 0.1 M HCl that is identical with the durability of a dense composite.

  9. Fracture strength of three all-ceramic systems: Top-Ceram compared with IPS-Empress and In-Ceram.

    Science.gov (United States)

    Quran, Firas Al; Haj-Ali, Reem

    2012-03-01

    The purpose of this study was to investigate the fracture loads and mode of failure of all-ceramic crowns fabricated using Top-Ceram and compare it with all-ceramic crowns fabricated from well-established systems: IPS-Empress II, In-Ceram. Thirty all-ceramic crowns were fabricated; 10 IPS-Empress II, 10 In-Ceram alumina and 10 Top-Ceram. Instron testing machine was used to measure the loads required to introduce fracture of each crown. Mean fracture load for In-Ceram alumina [941.8 (± 221.66) N] was significantly (p > 0.05) higher than those of Top-Ceram and IPS-Empress II. There was no statistically significant difference between Top-Ceram and IPS-Empress II mean fracture loads; 696.20 (+222.20) and 534 (+110.84) N respectively. Core fracture pattern was highest seen in Top- Ceram specimens.

  10. Mechanical reliability of current alumina and beryllia ceramics used in microwave windows for gyrotrons

    International Nuclear Information System (INIS)

    Becher, P.F.; Ferber, M.K.

    1983-02-01

    The mechanical reliability was evaluated for the alumina and beryllia ceramics now used as microwave windows in the high-power (greater than or equal to 200 kW) high-frequency (greater than or equal to 60 GHz) gyrotron tubes being developed for plasma heating in fusion systems. Analysis of the stresses generated in the various window configurations and tube operating conditions indicated that significant tensile stresses are generated in the ceramic window by dielectric heating. As a result, we characterized the static and dynamic fatigue behavior and the inert strength distributions for these two ceramics (i.e., fatigue studies included the behavior in the fluorocarbon fluid used for window cooling at 22 and 48 0 C and in both air (65% relative humidity) and distilled water at 22 0 C. These data were then analyzed in order to construct reliability diagrams for these materials

  11. 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.

  12. Synthesis and characterization of ceramic membranes for micro filtration

    International Nuclear Information System (INIS)

    Mohammad Idrees; Lim Yan Ne; Hamdani Saidi

    1996-01-01

    This paper presents the results of a preliminary research work in the development of ceramic membranes by moulding process. The two major objectives were to determine the effect of operating parameters ori- the membrane sheet and membrane characterization. The starting material for the membrane was powdered aluminum oxide and alumina granules. Alumina granules were obtained by spray drying of mixture of alumina with additives and binders under specific conditions. The membrane sheet was produced by mould pressing at various pressures and then sintering at different temperatures. Membrane characterization was done based on microstructure using SEM, pore size distribution, density, and porosity. Strong and porous membranes were produced at pressing force of 120 -140 kN and sintering temperature of 1400 -1500 'C. Pore size and porosity obtained was in the range of 2 -10 μ m, and 13 - 48% respectively. These membranes can be used for, microfiltration at elevated temperature and under extreme environmental condition. They can also be used as porous support for the production qf composite asymmetric UF/hyperfiltration, and gas separation membranes. Further work in the refinement of' pore-size and permeation studies is envisaged

  13. Properties of Ni and Ni–Fe nanowires electrochemically deposited into a porous alumina template

    Directory of Open Access Journals (Sweden)

    Alla I. Vorobjova

    2016-11-01

    Full Text Available The comparative analysis of the electrochemical deposition of Ni and Ni–Fe nanowires (NWs into ordered porous alumina templates is presented. The method developed allows for obtaining NWs of 50 ± 5 nm in diameter and 25 μm in length, i.e., with an aspect ratio of 500. XRD data demonstrate the polycrystalline nature of Ni and Ni–Fe in a face-centered cubic close-packed lattice. Both fabricated materials, Ni and Ni–Fe, have shown ferromagnetic properties. The specific magnetization value of Ni–Fe NWs in the alumina template is higher than that of the Ni sample and bulk Ni, also the Curie temperature of the Ni–Fe sample (790 K is higher than that of the Ni sample one or bulk Ni.

  14. Study and characterization of porous ceramic obtained via gelatinization

    International Nuclear Information System (INIS)

    Storion, A.G.; Campos, M.G.N.; Mariano, N.A.; Maestrelli, S.C.; Mariano, W.A.

    2016-01-01

    Conventional processes for manufacturing porous ceramic sometimes provide bodies with low mechanical strength, showing cracks and macro defects, in addition to the high complexity or cost. This work proposes a new porous ceramic processing route called cold gelatinization, using as raw material a clay with low plasticity, water and gelatin. At first, the characterization of the clay was carried out and then specimens of various compositions were produced by varying clay content (40, 50, 55 and 60% of solids) and keeping the water and gelatin content constant in the formulation. After cold forming the samples were and fired under various conditions: initial temperature of 300 or 600 °C; maximum firing temperature of 800, 900, 1000, 1100 or 1350 °C. After firing, it was obtained water absorption, apparent density, apparent porosity, linear shrinkage and mechanical resistance via 3 points bending test. The best results were for samples fired in temperatures lower than 1100 °C and 50% and 55 % of solid content. (author)

  15. 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

  16. Obtaining of dense and highly porous ceramic materials from metallurgical slag

    Directory of Open Access Journals (Sweden)

    Fidancevska E.

    2003-01-01

    Full Text Available Glass-ceramics in a dense and highly porous form can be obtained from metallurgical slag and waste glass of TV monitors. Using polyurethane foam as pore creator, a highly porous system with porosity of 65 ± 5 %, E-modulus and flexural strength of 8 ± 3 GPa and 13 ± 3.5 MPa respectively can be obtained. This porous material had durability (mass loss of 0.03 % in 0.1 M HCl that is identical with the durability of a dense composite.

  17. Report on achievements in fiscal 1999. Research and development of synergy ceramics (research and development of ultra-high temperature gas turbine for power generation); 1999 nendo synergy ceramics no kenkyu kaihatsu seika hokokusho. Hatsuden'yo chokoon gas turbine no kenkyu kaihatsu

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2000-03-01

    This research and development has been performed on the following themes: (1) high-temperature energy materials, (2) high-function active materials, (3) fundamental member material design technologies, (4) materials to activate specific environmental gases, (5) energy materials having high resistance to silicon groups, (6) porous multi-layer ceramic materials, (7) micro and macro applied analytic technologies, and (8) microscopically destructive analysis technologies. In Item 1, investigations were performed on the relationship of micro columnar particle structure of porous silicon nitride bodies with strength and destruction energy to identify the mechanism for manifestation of these characteristics. In Item 2, catalyst and electrode materials having the selectively separating and cleaning functions were developed, and materials to convert oxides thermo-electrically having high characteristics were discussed. In Item 3, polycrystalline alumina, polycrystalline zirconia, and zirconia particle dispersed alumina were fabricated on the trial basis to give them microscopic and macroscopic evaluations. In Item 4, crystalline hexa-aluminates in single phase were synthesized successfully. In Item 5, a synthesizing experiment was carried out on Ca-{alpha} sialon powder to evaluate and analyze the configuration phase of the product and the particle patterns. In Item 7, the homogenizing method was used to develop a three-dimensional program to analyze the correlation between the microscopic non-homogeneous structure and the macroscopic properties of synergy ceramics. In Item 8, the basic dimensions of porous alumina bodies were discussed based on energy density. (NEDO)

  18. Y-TZP ceramic processing from coprecipitated powders: a comparative study with three commercial dental ceramics.

    Science.gov (United States)

    Lazar, Dolores R R; Bottino, Marco C; Ozcan, Mutlu; Valandro, Luiz Felipe; Amaral, Regina; Ussui, Valter; Bressiani, Ana H A

    2008-12-01

    (1) To synthesize 3mol% yttria-stabilized zirconia (3Y-TZP) powders via coprecipitation route, (2) to obtain zirconia ceramic specimens, analyze surface characteristics, and mechanical properties, and (3) to compare the processed material with three reinforced dental ceramics. A coprecipitation route was used to synthesize a 3mol% yttria-stabilized zirconia ceramic processed by uniaxial compaction and pressureless sintering. Commercially available alumina or alumina/zirconia ceramics, namely Procera AllCeram (PA), In-Ceram Zirconia Block (CAZ) and In-Ceram Zirconia (IZ) were chosen for comparison. All specimens (6mmx5mmx5mm) were polished and ultrasonically cleaned. Qualitative phase analysis was performed by XRD and apparent densities were measured on the basis of Archimedes principle. Ceramics were also characterized using SEM, TEM and EDS. The hardness measurements were made employing Vickers hardness test. Fracture toughness (K(IC)) was calculated. Data were analyzed using one-way analysis of variance (ANOVA) and Tukey's test (alpha=0.05). ANOVA revealed that the Vickers hardness (pceramic materials composition. It was confirmed that the PA ceramic was constituted of a rhombohedral alumina matrix, so-called alpha-alumina. Both CAZ and IZ ceramics presented tetragonal zirconia and alpha-alumina mixture of phases. The SEM/EDS analysis confirmed the presence of aluminum in PA ceramic. In the IZ and CAZ ceramics aluminum, zirconium and cerium in grains involved by a second phase containing aluminum, silicon and lanthanum were identified. PA showed significantly higher mean Vickers hardness values (H(V)) (18.4+/-0.5GPa) compared to vitreous CAZ (10.3+/-0.2GPa) and IZ (10.6+/-0.4GPa) ceramics. Experimental Y-TZP showed significantly lower results than that of the other monophased ceramic (PA) (pceramics (pceramic processing conditions led to ceramics with mechanical properties comparable to commercially available reinforced ceramic materials.

  19. 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.

  20. Permeability optimization and performance evaluation of hot aerosol filters made using foam incorporated alumina suspension.

    Science.gov (United States)

    Innocentini, Murilo D M; Rodrigues, Vanessa P; Romano, Roberto C O; Pileggi, Rafael G; Silva, Gracinda M C; Coury, José R

    2009-02-15

    Porous ceramic samples were prepared from aqueous foam incorporated alumina suspension for application as hot aerosol filtering membrane. The procedure for establishment of membrane features required to maintain a desired flow condition was theoretically described and experimental work was designed to prepare ceramic membranes to meet the predicted criteria. Two best membranes, thus prepared, were selected for permeability tests up to 700 degrees C and their total and fractional collection efficiencies were experimentally evaluated. Reasonably good performance was achieved at room temperature, while at 700 degrees C, increased permeability was obtained with significant reduction in collection efficiency, which was explained by a combination of thermal expansion of the structure and changes in the gas properties.

  1. Report on achievements in fiscal 1999. Research and development of synergy ceramics (research and development of ultra-high temperature gas turbine for power generation); 1999 nendo synergy ceramics no kenkyu kaihatsu seika hokokusho. Hatsuden'yo chokoon gas turbine no kenkyu kaihatsu

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2000-03-01

    This research and development has been performed on the following themes: (1) high-temperature energy materials, (2) high-function active materials, (3) fundamental member material design technologies, (4) materials to activate specific environmental gases, (5) energy materials having high resistance to silicon groups, (6) porous multi-layer ceramic materials, (7) micro and macro applied analytic technologies, and (8) microscopically destructive analysis technologies. In Item 1, investigations were performed on the relationship of micro columnar particle structure of porous silicon nitride bodies with strength and destruction energy to identify the mechanism for manifestation of these characteristics. In Item 2, catalyst and electrode materials having the selectively separating and cleaning functions were developed, and materials to convert oxides thermo-electrically having high characteristics were discussed. In Item 3, polycrystalline alumina, polycrystalline zirconia, and zirconia particle dispersed alumina were fabricated on the trial basis to give them microscopic and macroscopic evaluations. In Item 4, crystalline hexa-aluminates in single phase were synthesized successfully. In Item 5, a synthesizing experiment was carried out on Ca-{alpha} sialon powder to evaluate and analyze the configuration phase of the product and the particle patterns. In Item 7, the homogenizing method was used to develop a three-dimensional program to analyze the correlation between the microscopic non-homogeneous structure and the macroscopic properties of synergy ceramics. In Item 8, the basic dimensions of porous alumina bodies were discussed based on energy density. (NEDO)

  2. 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

  3. Application of porous ceramic as soil moisture sensor in controlled environment

    International Nuclear Information System (INIS)

    Oliveira, R.M.; Nono, M.C.A.; Mineiro, S.L.

    2009-01-01

    In this work, the behavior of ZrO 2 -TiO 2 porous ceramic as soil water content sensor element at different climatic conditions is presented. The analysis of the sensor element was carried out correlating the results of electrical properties, through the measurement of capacitance and impedance variation in function of the soil water content, with the microstructure of the ZrO 2 -TiO 2 ceramic. The ceramic sensor was studied in a sandy clay soil type at different climatic conditions characterized by temperature and relative humidity. The microstructural characterization of the ceramic sensor included scanning electron microscopy observations, X-ray diffraction patterns and pore size distribution using mercury porosimetry. (author)

  4. Development and sintering of alumina based mixed oxide ceramic products for sensor applications in petroleum industries

    Energy Technology Data Exchange (ETDEWEB)

    Yadava, Y.P.; Muniz, L.B.; Aguiar, L.A.R.; Sanguinetti Ferreira, R.A. [Departamento de Engenharia Mecanica, Universidade Federal de Pernambuco, CEP 50741-530, Recife-PE (Brazil); Albino Aguiar, J. [Departamento de Fisica, Universidade Federal de Pernambuco, CEP 50670-901 Recife-PE (Brazil)

    2005-07-01

    In petroleum production, different types of sensors are required to monitor temperature, pressure, leakage of inflammable gases, etc. These sensors work in very hostile environmental conditions and frequently suffer from abrasion and corrosion problems. Presently perovskite oxide based ceramic materials are increasingly being used for such purposes, due to their highly inert behavior in hostile environment. In the present work, we have developed and characterized alumina based complex perovskite oxide ceramics, Ba{sub 2}AlSnO{sub 5.5}. These ceramics were prepared by solid state reaction process and produced in the form of circular discs by uniaxial pressure compaction technique. Green ceramic bodies were sintered at different sintering temperatures (1200 to 1500 deg. C) in air atmosphere. Structural and microstructural characteristics of sintered Ba{sub 2}AlMO{sub 5.5} were studied by XRD and SEM techniques. Mechanical properties were tested by Vickers microhardness tests. Ceramics sintered in the temperature range 1300 deg. C 1400 deg. C presented best results in terms of microstructural characteristics and mechanical performance. (authors)

  5. Porous biomorphic silicon carbide ceramics coated with hydroxyapatite as prospective materials for bone implants

    Energy Technology Data Exchange (ETDEWEB)

    Gryshkov, Oleksandr, E-mail: gryshkov@imp.uni-hannover.de [Institute for Multiphase Processes, Leibniz Universität Hannover, 30167 Hannover (Germany); Klyui, Nickolai I., E-mail: klyuini@ukr.net [College of Physics, Jilin University, 130012 Changchun (China); V. Lashkaryov Institute of Semiconductor Physics, National Academy of Science of Ukraine, 03028 Kyiv (Ukraine); Temchenko, Volodymyr P., E-mail: tvp@isp.kiev.ua [V. Lashkaryov Institute of Semiconductor Physics, National Academy of Science of Ukraine, 03028 Kyiv (Ukraine); Kyselov, Vitalii S., E-mail: kyselov@isp.kiev.ua [V. Lashkaryov Institute of Semiconductor Physics, National Academy of Science of Ukraine, 03028 Kyiv (Ukraine); Chatterjee, Anamika, E-mail: chatterjee@imp.uni-hannover.de [Institute for Multiphase Processes, Leibniz Universität Hannover, 30167 Hannover (Germany); Belyaev, Alexander E., E-mail: belyaev@isp.kiev.ua [V. Lashkaryov Institute of Semiconductor Physics, National Academy of Science of Ukraine, 03028 Kyiv (Ukraine); Lauterboeck, Lothar, E-mail: lauterboeck@imp.uni-hannover.de [Institute for Multiphase Processes, Leibniz Universität Hannover, 30167 Hannover (Germany); Iarmolenko, Dmytro, E-mail: iarmolenko.dmytro@isp.kiev.ua [V. Lashkaryov Institute of Semiconductor Physics, National Academy of Science of Ukraine, 03028 Kyiv (Ukraine); Glasmacher, Birgit, E-mail: glasmacher@imp.uni-hannover.de [Institute for Multiphase Processes, Leibniz Universität Hannover, 30167 Hannover (Germany)

    2016-11-01

    Porous and cytocompatible silicon carbide (SiC) ceramics derived from wood precursors and coated with bioactive hydroxyapatite (HA) and HA-zirconium dioxide (HA/ZrO{sub 2}) composite are materials with promising application in engineering of bone implants due to their excellent mechanical and structural properties. Biomorphic SiC ceramics have been synthesized from wood (Hornbeam, Sapele, Tilia and Pear) using a forced impregnation method. The SiC ceramics have been coated with bioactive HA and HA/ZrO{sub 2} using effective gas detonation deposition approach (GDD). The surface morphology and cytotoxicity of SiC ceramics as well as phase composition and crystallinity of deposited coatings were analyzed. It has been shown that the porosity and pore size of SiC ceramics depend on initial wood source. The XRD and FTIR studies revealed the preservation of crystal structure and phase composition of in the HA coating, while addition of ZrO{sub 2} to the initial HA powder resulted in significant decomposition of the final HA/ZrO{sub 2} coating and formation of other calcium phosphate phases. In turn, NIH 3T3 cells cultured in medium exposed to coated and uncoated SiC ceramics showed high re-cultivation efficiency as well as metabolic activity. The recultivation efficiency of cells was the highest for HA-coated ceramics, whereas HA/ZrO{sub 2} coating improved the recultivation efficiency of cells as compared to uncoated SiC ceramics. The GDD method allowed generating homogeneous HA coatings with no change in calcium to phosphorus ratio. In summary, porous and cytocompatible bio-SiC ceramics with bioactive coatings show a great promise in construction of light, robust, inexpensive and patient-specific bone implants for clinical application. - Highlights: • Synthesis and characterization of porous biomorphic SiC ceramics derived from wood • Successful deposition of bioactive calcium phosphate coatings using gas detonation deposition • Porosity and pore size of Si

  6. Porous biomorphic silicon carbide ceramics coated with hydroxyapatite as prospective materials for bone implants

    International Nuclear Information System (INIS)

    Gryshkov, Oleksandr; Klyui, Nickolai I.; Temchenko, Volodymyr P.; Kyselov, Vitalii S.; Chatterjee, Anamika; Belyaev, Alexander E.; Lauterboeck, Lothar; Iarmolenko, Dmytro; Glasmacher, Birgit

    2016-01-01

    Porous and cytocompatible silicon carbide (SiC) ceramics derived from wood precursors and coated with bioactive hydroxyapatite (HA) and HA-zirconium dioxide (HA/ZrO 2 ) composite are materials with promising application in engineering of bone implants due to their excellent mechanical and structural properties. Biomorphic SiC ceramics have been synthesized from wood (Hornbeam, Sapele, Tilia and Pear) using a forced impregnation method. The SiC ceramics have been coated with bioactive HA and HA/ZrO 2 using effective gas detonation deposition approach (GDD). The surface morphology and cytotoxicity of SiC ceramics as well as phase composition and crystallinity of deposited coatings were analyzed. It has been shown that the porosity and pore size of SiC ceramics depend on initial wood source. The XRD and FTIR studies revealed the preservation of crystal structure and phase composition of in the HA coating, while addition of ZrO 2 to the initial HA powder resulted in significant decomposition of the final HA/ZrO 2 coating and formation of other calcium phosphate phases. In turn, NIH 3T3 cells cultured in medium exposed to coated and uncoated SiC ceramics showed high re-cultivation efficiency as well as metabolic activity. The recultivation efficiency of cells was the highest for HA-coated ceramics, whereas HA/ZrO 2 coating improved the recultivation efficiency of cells as compared to uncoated SiC ceramics. The GDD method allowed generating homogeneous HA coatings with no change in calcium to phosphorus ratio. In summary, porous and cytocompatible bio-SiC ceramics with bioactive coatings show a great promise in construction of light, robust, inexpensive and patient-specific bone implants for clinical application. - Highlights: • Synthesis and characterization of porous biomorphic SiC ceramics derived from wood • Successful deposition of bioactive calcium phosphate coatings using gas detonation deposition • Porosity and pore size of SiC ceramics depend on wood

  7. Progress in Treatment of Oily Wastewater by Inorganic Porous Ceramic Membrane

    Directory of Open Access Journals (Sweden)

    Dai Xiaoyuan

    2017-01-01

    Full Text Available The composition and complexity of oily wastewater contains many solid particles, free oil, emulsified oil and so on.It brought about a series of environmental pollution problems when oily wastewater was directly discharged into rivers, lakes and other water bodies. Therefore, researchers are committed to study how to deal with oily wastewater to deal with oily wastewater to apply it to meet the requirements of water injection.Inorganic porous ceramic membrane has excellent properties among many filtering methods. For example, high temperature and high pressure resistance, resistance to acid and alkali, low energy consumption, no pollution to the environment and has a good prospect in the field of oily wastewater treatment, which has attracted the attention of many scholars not only at home but also on abroad. This article describes the present situation of the research on the treatment of oily wastewater by ceramic membrane in recent years, and expounded the significance of the treatment of oily wastewater to people’s lives and makes an expectation for the development of inorganic porous ceramic membrane in the future.

  8. [Ceramic-on-ceramic bearings in total hip arthroplasty (THA)].

    Science.gov (United States)

    Sentürk, U; Perka, C

    2015-04-01

    The main reason for total hip arthroplasty (THA) revision is the wear-related aseptic loosening. Younger and active patients after total joint replacement create high demands, in particular, on the bearings. The progress, especially for alumina ceramic-on-ceramic bearings and mixed ceramics have solved many problems of the past and lead to good in vitro results. Modern ceramics (alumina or mixed ceramics containing alumina) are extremely hard, scratch-resistant, biocompatible, offer a low coefficient of friction, superior lubrication and have the lowest wear rates in comparison to all other bearings in THA. The disadvantage of ceramic is the risk of material failure, i.e., of ceramic fracture. The new generation of mixed ceramics (delta ceramic), has reduced the risk of head fractures to 0.03-0.05 %, but the risk for liner fractures remains unchanged at about 0.02 %. Assuming a non-impinging component implantation, ceramic-on-ceramic bearings have substantial advantages over all other bearings in THA. Due to the superior hardness, ceramic bearings produce less third body wear and are virtually impervious to damage from instruments during the implantation process. A specific complication for ceramic-on-ceramic bearings is "squeaking". The high rate of reported squeaking (0.45 to 10.7 %) highlights the importance of precise implant positioning and the stem and patient selection. With precise implant positioning this problem is rare with many implant designs and without clinical relevance. The improved tribology and the presumable resulting implant longevity make ceramic-on-ceramic the bearing of choice for young and active patients. Georg Thieme Verlag KG Stuttgart · New York.

  9. Conversion of nuclear waste to molten glass: Formation of porous amorphous alumina in a high-Al melter feed

    Science.gov (United States)

    Xu, Kai; Hrma, Pavel; Washton, Nancy; Schweiger, Michael J.; Kruger, Albert A.

    2017-01-01

    The transition of Al phases in a simulated high-Al high-level nuclear waste melter feed heated at 5 K min-1 to 700 °C was investigated with transmission electron microscopy, 27Al nuclear magnetic resonance spectroscopy, the Brunauer-Emmett-Teller method, and X-ray diffraction. At temperatures between 300 and 500 °C, porous amorphous alumina formed from the dehydration of gibbsite, resulting in increased specific surface area of the feed (∼8 m2 g-1). The high-surface-area amorphous alumina formed in this manner could potentially stop salt migration in the cold cap during nuclear waste vitrification.

  10. Preparation and properties of porous PMN-PZT ceramics doped with strontium

    International Nuclear Information System (INIS)

    Zeng Tao; Dong Xianlin; Mao Chaoliang; Chen Shutao; Chen Heng

    2006-01-01

    The piezoelectric and dielectric properties of lead magnesium niobate-lead zirconate titanate (PMN-PZT) ceramics were investigated as a function of density for transducer applications. A decrease in density increased elastic compliance and improved acoustic impedance matching between PMN-PZT ceramics and ambient media. The reduced dielectric constant (ε 33 ) and enhanced hydrostatic figure of merit (d h g h ) of PMN-PZT were observed with decreased density. The results showed the d h g h of PMN-PZT ceramic with density of about 5.4 g/cm 3 reached 4000 x 10 -15 m 2 /N, and the ε 33 was very close to 2000, which demonstrates that porous PMN-PZT ceramic is a promising material for transducer applications. Moreover, the low density PMN-PZT ceramics exhibited lower dielectric loss than high density PMN-PZT ceramics during the temperature from 250 deg. C to 500 deg. C

  11. Compressive Creep Behavior of NEXTEL(TradeMark) 720/Alumina Ceramic Matrix Composite at 1200 Degrees C in Air and in Steam Environment

    National Research Council Canada - National Science Library

    Szymczak, Neil R

    2006-01-01

    ...) 720/Alumina ceramic matrix composite at 1200 deg. C in air and 100% steam environments. The effects of creep loading history on the tensile and compressive material behavior will also be examined...

  12. Effect of yttria addition on the stability of porous chromium oxide ceramics in supercritical water

    International Nuclear Information System (INIS)

    Dong Ziqiang; Chen Weixing; Zheng Wenyue; Guzonas, Dave

    2013-01-01

    Porous chromium oxide (Cr 2 O 3 ) ceramics were prepared by oxidizing highly porous chromium carbides that were obtained by a reactive sintering method, and were evaluated at temperatures ranging from 375 °C to 625 °C in supercritical water (SCW) environments with a fixed pressure of 25–30 MPa. Reactive element yttrium was introduced to the porous oxide ceramic by adding various amounts of yttria of 5, 10 and 20 wt.%, respectively, prior to reactive sintering. The exposure in SCW shows that the porous chromium oxide is quite stable in SCW at 375 °C. However, the stability decreased with increasing temperature. It is well known that chromium oxide can be oxidized to soluble chromium (VI) species in SCW when oxygen is present. Adding yttria increases the stability of chromium oxide in SCW environments. However, adding yttria higher than 5 wt.% increased the weight loss of porous chromium oxide samples because of the direct dissociation of Y 2 O 3 in SCW.

  13. Formation and disruption of current paths of anodic porous alumina films by conducting atomic force microscopy

    International Nuclear Information System (INIS)

    Oyoshi, K.; Nigo, S.; Inoue, J.; Sakai, O.; Kitazawa, H.; Kido, G.

    2010-01-01

    Anodic porous alumina (APA) films have a honeycomb cell structure of pores and a voltage-induced bi-stable switching effect. We have applied conducting atomic force microscopy (CAFM) as a method to form and to disrupt current paths in the APA films. A bi-polar switching operation was confirmed. We have firstly observed terminals of current paths as spots or areas typically on the center of the triangle formed by three pores. In addition, though a part of the current path showed repetitive switching, most of them were not observed again at the same position after one cycle of switching operations in the present experiments. This suggests that a part of alumina structure and/or composition along the current paths is modified during the switching operations.

  14. Formation and disruption of current paths of anodic porous alumina films by conducting atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Oyoshi, K., E-mail: oyoshi.keiji@nims.go.jp [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan); Nigo, S.; Inoue, J.; Sakai, O.; Kitazawa, H.; Kido, G. [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan)

    2010-11-15

    Anodic porous alumina (APA) films have a honeycomb cell structure of pores and a voltage-induced bi-stable switching effect. We have applied conducting atomic force microscopy (CAFM) as a method to form and to disrupt current paths in the APA films. A bi-polar switching operation was confirmed. We have firstly observed terminals of current paths as spots or areas typically on the center of the triangle formed by three pores. In addition, though a part of the current path showed repetitive switching, most of them were not observed again at the same position after one cycle of switching operations in the present experiments. This suggests that a part of alumina structure and/or composition along the current paths is modified during the switching operations.

  15. Determination of distribution function of refraction index and anion diffusion depth in porous alumina photonic crystals

    Directory of Open Access Journals (Sweden)

    H. Kaviani

    2007-09-01

    Full Text Available   Band structure of porous alumina photonic crystal in the Γ X direction was calculated using order-N method . In a comparison of calculated results with experimental data of reflective and absorptive index, the variation of refractive index of alumina in the external region of oxide layer, around the pores were studied. A Gaussian distribution function was adopted for phosphate anions in the external oxide layer and the variation of refractive index and diffusion depth were determined. The structure of the first four bands was calculated using the obtained distribution of refractive index in the external oxide layer for both TE and TM mode. This results show a narrow full band gap in the TM mode.

  16. 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.

  17. Ultrafast excited state deactivation of doped porous anodic alumina membranes

    International Nuclear Information System (INIS)

    Makhal, Abhinandan; Sarkar, Soumik; Pal, Samir Kumar; Yan, Hongdan; Wulferding, Dirk; Cetin, Fatih; Lemmens, Peter

    2012-01-01

    Free-standing, bi-directionally permeable and ultra-thin anodic aluminum oxide (AAO) membranes establish attractive templates (host) for the synthesis of nano-dots and rods of various materials (guest). This is due to their chemical and structural integrity and high periodicity on length scales of 5–150 nm which are often used to host photoactive nano-materials for various device applications including dye-sensitized solar cells. In the present study, AAO membranes are synthesized by using electrochemical methods and a detailed structural characterization using FEG-SEM, XRD and TGA confirms the porosity and purity of the material. Defect-mediated photoluminescence quenching of the porous AAO membrane in the presence of an electron accepting guest organic molecule (benzoquinone) is studied by means of steady-state and picosecond/femtosecond-resolved luminescence measurements. Using time-resolved luminescence transients, we have also revealed light harvesting of complexes of porous alumina impregnated with inorganic quantum dots (Maple Red) or gold nanowires. Both the Förster resonance energy transfer and the nano-surface energy transfer techniques are employed to examine the observed quenching behavior as a function of the characteristic donor–acceptor distances. The experimental results will find their relevance in light harvesting devices based on AAOs combined with other materials involving a decisive energy/charge transfer dynamics. (paper)

  18. Ultrafast excited state deactivation of doped porous anodic alumina membranes

    Science.gov (United States)

    Makhal, Abhinandan; Sarkar, Soumik; Pal, Samir Kumar; Yan, Hongdan; Wulferding, Dirk; Cetin, Fatih; Lemmens, Peter

    2012-08-01

    Free-standing, bi-directionally permeable and ultra-thin anodic aluminum oxide (AAO) membranes establish attractive templates (host) for the synthesis of nano-dots and rods of various materials (guest). This is due to their chemical and structural integrity and high periodicity on length scales of 5-150 nm which are often used to host photoactive nano-materials for various device applications including dye-sensitized solar cells. In the present study, AAO membranes are synthesized by using electrochemical methods and a detailed structural characterization using FEG-SEM, XRD and TGA confirms the porosity and purity of the material. Defect-mediated photoluminescence quenching of the porous AAO membrane in the presence of an electron accepting guest organic molecule (benzoquinone) is studied by means of steady-state and picosecond/femtosecond-resolved luminescence measurements. Using time-resolved luminescence transients, we have also revealed light harvesting of complexes of porous alumina impregnated with inorganic quantum dots (Maple Red) or gold nanowires. Both the Förster resonance energy transfer and the nano-surface energy transfer techniques are employed to examine the observed quenching behavior as a function of the characteristic donor-acceptor distances. The experimental results will find their relevance in light harvesting devices based on AAOs combined with other materials involving a decisive energy/charge transfer dynamics.

  19. Ultrafast excited state deactivation of doped porous anodic alumina membranes

    Energy Technology Data Exchange (ETDEWEB)

    Makhal, Abhinandan; Sarkar, Soumik; Pal, Samir Kumar [Department of Chemical, Biological and Macromolecular Sciences, S N Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700 098 (India); Yan, Hongdan; Wulferding, Dirk; Cetin, Fatih; Lemmens, Peter [Institute for Condensed Matter Physics, TU Braunschweig, Mendelssohnstrasse 3, 38106 Braunschweig (Germany)

    2012-08-03

    Free-standing, bi-directionally permeable and ultra-thin anodic aluminum oxide (AAO) membranes establish attractive templates (host) for the synthesis of nano-dots and rods of various materials (guest). This is due to their chemical and structural integrity and high periodicity on length scales of 5-150 nm which are often used to host photoactive nano-materials for various device applications including dye-sensitized solar cells. In the present study, AAO membranes are synthesized by using electrochemical methods and a detailed structural characterization using FEG-SEM, XRD and TGA confirms the porosity and purity of the material. Defect-mediated photoluminescence quenching of the porous AAO membrane in the presence of an electron accepting guest organic molecule (benzoquinone) is studied by means of steady-state and picosecond/femtosecond-resolved luminescence measurements. Using time-resolved luminescence transients, we have also revealed light harvesting of complexes of porous alumina impregnated with inorganic quantum dots (Maple Red) or gold nanowires. Both the Foerster resonance energy transfer and the nano-surface energy transfer techniques are employed to examine the observed quenching behavior as a function of the characteristic donor-acceptor distances. The experimental results will find their relevance in light harvesting devices based on AAOs combined with other materials involving a decisive energy/charge transfer dynamics. (paper)

  20. Fabrication of Porous Ceramic-Geopolymer Based Material to Improve Water Absorption and Retention in Construction Materials: A Review

    Science.gov (United States)

    Jamil, N. H.; Ibrahim, W. M. A. W.; Abdullah, M. M. A. B.; Sandu, A. V.; Tahir, M. F. M.

    2017-06-01

    Porous ceramic nowadays has been investigated for a variety of its application such as filters, lightweight structural component and others due to their specific properties such as high surface area, stability and permeability. Besides, it has the properties of low thermal conductivity. Various formation techniques making these porous ceramic properties can be tailored or further fine-tuned to obtain the optimum characteristic. Porous materials also one of the good candidate for absorption properties. Conventional construction materials are not design to have good water absorption and retention that lead to the poor performance on these criteria. Temperature is a major driving force for moisture movement and influences sorption characteristics of many constructions materials. The effect of elevated temperatures on the water absorption coefficient and retention remain as critical issue that need to be investigated. Therefore, this paper will review the process parameters in fabricating porous ceramic for absorption properties.

  1. 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.

  2. CVD of solid oxides in porous substrates for ceramic membrane modification

    NARCIS (Netherlands)

    Lin, Y.S.; Lin, Y.S.; Burggraaf, Anthonie; Burggraaf, A.J.

    1992-01-01

    The deposition of yttria-doped zirconia has been experimented systematically in various types of porous ceramic substrates by a modified chemical vapor deposition (CVD) process operating in an opposing reactant geometry using water vapor and corresponding metal chloride vapors as reactants. The

  3. Preparation and properties of highly porous, biomorphic YSZ ceramics

    International Nuclear Information System (INIS)

    Rambo, C.R.; Cao, J.; Sieber, H.

    2004-01-01

    Highly porous, biomorphic YSZ (yttria-stabilized zirconia) ceramics were manufactured by infiltration of zirconium-oxychloride (ZrOCl 2 ·8H 2 O) sol into biological template structures derived from rattan and pine wood. 3-5 mol% yttrium nitrate (Y(NO 3 ) 3 ·5H 2 O) was added to the sol to stabilize the tetragonal ZrO 2 phase. After vacuum-assisted infiltration, the specimens were pyrolysed at 800 deg. C in N 2 atmosphere. Repeated infiltrations and subsequent annealing in air at temperatures up to 1550 deg. C yields the burn out of the biocarbon template and resulted in the formation of biomorphous YSZ ceramics, which maintained the microstructural features of the biological preform. Depending on the type of the biological template as well as the processing parameters, biomorphic ZrO 2 ceramics with an unidirected pore morphology and a large variety of microstructures can be obtained

  4. Fabrication of porous anodic alumina using normal anodization and pulse anodization

    Science.gov (United States)

    Chin, I. K.; Yam, F. K.; Hassan, Z.

    2015-05-01

    This article reports on the fabrication of porous anodic alumina (PAA) by two-step anodizing the low purity commercial aluminum sheets at room temperature. Different variations of the second-step anodization were conducted: normal anodization (NA) with direct current potential difference; pulse anodization (PA) alternate between potential differences of 10 V and 0 V; hybrid pulse anodization (HPA) alternate between potential differences of 10 V and -2 V. The method influenced the film homogeneity of the PAA and the most homogeneous structure was obtained via PA. The morphological properties are further elucidated using measured current-transient profiles. The absent of current rise profile in PA indicates the anodization temperature and dissolution of the PAA structure were greatly reduced by alternating potential differences.

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

    Directory of Open Access Journals (Sweden)

    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.

  6. Structured Ni catalysts on porous anodic alumina membranes for methane dry reforming: NiAl 2 O 4 formation and characterization

    KAUST Repository

    Zhou, Lu

    2015-06-29

    This communication presents the successful design of a structured catalyst based on porous anodic alumina membranes for methane dry reforming. The catalyst with a strong Ni-NiAl2O4 interaction shows both excellent activity and stability. This journal is © The Royal Society of Chemistry.

  7. Structured Ni catalysts on porous anodic alumina membranes for methane dry reforming: NiAl 2 O 4 formation and characterization

    KAUST Repository

    Zhou, Lu; Guo, Y.; Basset, Jean-Marie; Kameyama, H.

    2015-01-01

    This communication presents the successful design of a structured catalyst based on porous anodic alumina membranes for methane dry reforming. The catalyst with a strong Ni-NiAl2O4 interaction shows both excellent activity and stability. This journal is © The Royal Society of Chemistry.

  8. Linear Coefficient of Thermal Expansion of Porous Anodic Alumina Thin Films from Atomic Force Microscopy

    OpenAIRE

    Zhang, Richard X; Fisher, Timothy; Raman, Arvind; Sands, Timothy D

    2009-01-01

    In this article, a precise and convenient technique based on the atomic force microscope (AFM) is developed to measure the linear coefficient of thermal expansion of a porous anodic alumina thin film. A stage was used to heat the sample from room temperature up to 450 K. Thermal effects on AFM probes and different operation modes at elevated temperatures were also studied, and a silicon AFM probe in the tapping mode was chosen for the subsequent measurements due to its temperature insensitivi...

  9. Three-dimensional printing of porous ceramic scaffolds for bone tissue engineering.

    Science.gov (United States)

    Seitz, Hermann; Rieder, Wolfgang; Irsen, Stephan; Leukers, Barbara; Tille, Carsten

    2005-08-01

    This article reports a new process chain for custom-made three-dimensional (3D) porous ceramic scaffolds for bone replacement with fully interconnected channel network for the repair of osseous defects from trauma or disease. Rapid prototyping and especially 3D printing is well suited to generate complex-shaped porous ceramic matrices directly from powder materials. Anatomical information obtained from a patient can be used to design the implant for a target defect. In the 3D printing technique, a box filled with ceramic powder is printed with a polymer-based binder solution layer by layer. Powder is bonded in wetted regions. Unglued powder can be removed and a ceramic green body remains. We use a modified hydroxyapatite (HA) powder for the fabrication of 3D printed scaffolds due to the safety of HA as biocompatible implantable material and efficacy for bone regeneration. The printed ceramic green bodies are consolidated at a temperature of 1250 degrees C in a high temperature furnace in ambient air. The polymeric binder is pyrolysed during sintering. The resulting scaffolds can be used in tissue engineering of bone implants using patient-derived cells that are seeded onto the scaffolds. This article describes the process chain, beginning from data preparation to 3D printing tests and finally sintering of the scaffold. Prototypes were successfully manufactured and characterized. It was demonstrated that it is possible to manufacture parts with inner channels with a dimension down to 450 microm and wall structures with a thickness down to 330 microm. The mechanical strength of dense test parts is up to 22 MPa. Copyright 2005 Wiley Periodicals, Inc.

  10. A self-setting particle-stabilized porous ceramic panel prepared from commercial cement and loaded with carbon for potential radar'absorbing applications

    Directory of Open Access Journals (Sweden)

    Jang-Hoon Ha

    2018-03-01

    Full Text Available Porous ceramic materials are in a current research focus because of their outstanding thermal stability, chemical stability and lightweight. Recent research has widened the range of applications to radar absorption to utilize the advantages of porous ceramic materials. There has been long-standing interest in the development of lightweight radar-absorbing materials for military applications such as camouflaging ground-based facilities against airborne radar detection. Therefore, in this study, a novel lightweight radar-absorbing material for X-band frequencies was developed using a self-setting particle-stabilized porous ceramic panel composited with carbon. The panel was prepared using a commercial calcium aluminate cement (as a self-setting matrix, zeolite 13X particles with propyl gallate (as a particle-stabilized pore former and carbon (as a radar-absorbing material. The panel contained macropores approximately 200 to 400 µm in size formed by zeolite 13X particles that are irreversibly adsorbed at liquid-gas interfaces. The self-setting particle-stabilized porous ceramic panels were characterized by scanning electron microscopy, mercury porosimetry, physisorption analysis, capillary flow porosimetry and network analysis. When 0.2 wt.% carbon was added to a self-setting particle-stabilized porous ceramic panel to fabricate a composite 7 mm thick, the maximum reflection loss was −11.16 dB at 12.4 GHz. The effects of the amount of added carbon and the thickness variation of a self-setting particle-stabilized porous ceramic panel on the radar-absorbing properties remain important issues for further research.

  11. Preparation and properties of highly porous, biomorphic YSZ ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Rambo, C.R.; Cao, J.; Sieber, H

    2004-10-15

    Highly porous, biomorphic YSZ (yttria-stabilized zirconia) ceramics were manufactured by infiltration of zirconium-oxychloride (ZrOCl{sub 2}{center_dot}8H{sub 2}O) sol into biological template structures derived from rattan and pine wood. 3-5 mol% yttrium nitrate (Y(NO{sub 3}){sub 3}{center_dot}5H{sub 2}O) was added to the sol to stabilize the tetragonal ZrO{sub 2} phase. After vacuum-assisted infiltration, the specimens were pyrolysed at 800 deg. C in N{sub 2} atmosphere. Repeated infiltrations and subsequent annealing in air at temperatures up to 1550 deg. C yields the burn out of the biocarbon template and resulted in the formation of biomorphous YSZ ceramics, which maintained the microstructural features of the biological preform. Depending on the type of the biological template as well as the processing parameters, biomorphic ZrO{sub 2} ceramics with an unidirected pore morphology and a large variety of microstructures can be obtained.

  12. Preparation and biocompatibility evaluation of apatite/wollastonite-derived porous bioactive glass ceramic scaffolds

    International Nuclear Information System (INIS)

    Zhang Hua; Ye Xiaojian; Li Jiashun

    2009-01-01

    An apatite/wollastonite-derived (A/W) porous glass ceramic scaffold with highly interconnected pores was successfully fabricated by adding a plastic porosifier. The morphology, porosity and mechanical strength were characterized. The results showed that the glass ceramic scaffold with controllable pore size and porosity displayed open macropores. In addition, good in vitro bioactivity was found for the scaffold obtained by soaking it in simulated body fluid. Mesenchymal stem cells (MSCs) were cultured, expanded and seeded on the scaffold, and the adhesion and proliferation of MSCs were determined using MTT assay and environmental scanning electron microscopy (ESEM). The results revealed that the scaffold was biocompatible and had no negative effects on the MSCs in vitro. The in vivo biocompatibility and osteogenicity were investigated by implanting both the pure scaffold and the MSC/scaffold construct in rabbit mandibles and studying histologically. The results showed that the glass ceramic scaffold exhibited good biocompatibility and osteoconductivity. Moreover, the introduction of MSCs into the scaffold observably improved the efficiency of new bone formation, especially at the initial stage after implantation. However, the glass ceramic scaffold showed the same good biocompatibility and osteogenicity as the hybrid one at the later stage. These results indicate that porous bioactive scaffolds based on the original apatite-wollastonite glass ceramic fulfil the basic requirements of a bone tissue engineering scaffold.

  13. CAD/CAM Zirconia vs. slip-cast glass-infiltrated Alumina/Zirconia all-ceramic crowns: 2-year results of a randomized controlled clinical trial

    Directory of Open Access Journals (Sweden)

    Murat Cavit Çehreli

    2009-02-01

    Full Text Available The aim of this randomized controlled clinical trial was to compare the early clinical outcome of slip-cast glass-infiltrated Alumina/Zirconia and CAD/CAM Zirconia all-ceramic crowns. A total of 30 InCeram® Zirconia and Cercon® Zirconia crowns were fabricated and cemented with a glass ionomer cement in 20 patients. At baseline, 6-month, 1-year, and 2-year recall appointments, Californian Dental Association (CDA quality evaluation system was used to evaluate the prosthetic replacements, and plaque and gingival index scores were used to explore the periodontal outcome of the treatments. No clinical sign of marginal discoloration, persistent pain and secondary caries was detected in any of the restorations. All InCeram® Zirconia crowns survived during the 2-year period, although one nonvital tooth experienced root fracture coupled with the fracture of the veneering porcelain of the restoration. One Cercon® Zirconia restoration fractured and was replaced. According to the CDA criteria, marginal integrity was rated excellent for InCeram® Zirconia (73% and Cercon® Zirconia (80% restorations, respectively. Slight color mismatch rate was higher for InCeram® Zirconia restorations (66% than Cercon® Zirconia (26% restorations. Plaque and gingival index scores were mostly zero and almost constant over time. Time-dependent changes in plaque and gingival index scores within and between groups were statistically similar (p>0.05. This clinical study demonstrates that single-tooth InCeram® Zirconia and Cercon® Zirconia crowns have comparable early clinical outcome, both seem as acceptable treatment modalities, and most importantly, all-ceramic alumina crowns strengthened by 25% zirconia can sufficiently withstand functional load in the posterior zone.

  14. 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

  15. 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)

  16. Relationship between microstructure and optical properties of a novel perovskite C12PbI4 embedded in matrix of porous alumina

    Science.gov (United States)

    Zaghdoudi, W.; Bardaoui, A.; Khalifa, N.; Chtourou, R.

    2013-01-01

    In this study, organic-inorganic hybrid perovskite multiple quantum wells (PbI QWs) embedded in porous anodic alumina (PAA) thin films on glass and aluminum substrates are investigated in detail. The pore height and diameter of the nanoscale structure of porous anodic alumina (PAA) film produced by the anodization technique are controllable. The synthesized films are characterized morphologically using the atomic force microscopy (AFM). Scanning electron microscopy (SEM) study showed granular surface. The structural and optical properties were investigated by X-ray diffraction (XRD), photoluminescence (PL) and UV-Vis-NIR spectrophotometer. The effect of the two different substrates on the impregnation of the PbI QW in the PAA is presented. Both PL and AFM studies show a better penetration of the PbI QW in the case of the Al substrate providing a wider pore diameter. Remarkable enhancement of quantum confinement is demonstrated.

  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. A study of the bending resistance of implant-supported reinforced alumina and machined zirconia abutments and copies.

    Science.gov (United States)

    Sundh, Anders; Sjögren, Göran

    2008-05-01

    The purpose of the present study was to evaluate the bending resistance of implant-supported CAD/CAM-processed restorations made out of zirconia or manually shaped made out of reinforced alumina. Units of abutments and copies made of (i) a prefabricated hot isostatic pressed (HIPed) yttrium oxide partially-stabilized zirconia (Y-TZP) (Denzir), (ii) a prefabricated densely-sintered magnesia partially stabilized zirconia (Mg-PSZ) (Denzir-M) or, copies made of (iii) a prefabricated partially-sintered, porous reinforced alumina ceramic (RN synOcta-In-Ceram) were subjected to static loading perpendicularly at the long axis. The abutments were attached to either stainless steel analogs or titanium implant fixtures. The Y-TZP and Mg-PSZ copies were bonded onto the ceramic abutments with a dual-cured resin composite (Rely-X Unicem). Units of titanium abutment attached to a titanium implant fixtures were used as reference. The units comprising Denzir abutments as delivered (pstainless steel analogs exhibited significantly higher bending resistance than the control. The heat-treated Denzir copies bonded to the heat-treated Denzir M abutments attached to titanium implant fixtures and the In-Ceram specimens attached to stainless steel analogs showed significantly (pstainless steel analogs. No statistically significant (p>0.05) differences were seen among the other groups studied. All the ceramic abutments and copies exhibited values that were equal or superior to that of the control and exceeded the reported value, up to 300 N, for maximum incisal bite forces. To assess the clinical behavior long-term clinical studies should be conducted.

  19. 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.

  20. Composite reinforced alumina ceramics with titan and lantana for use in coating storage tanks and transport of crude oil

    International Nuclear Information System (INIS)

    Mendes, C.E.; Rego, S.A.B.C.; Oliveira, J.C.S.; Ferreira, R.A. Sanguinetti; Yadava, Y.P.

    2011-01-01

    The objective of this work is to use ceramics to improve the performance of the tanks that store and transport crude oil and which use metallic materials for their manufacture. These tanks in contact with crude oil undergo a process of degradation on their surfaces, since crude oil is a highly corrosive substance. And in turn ceramic materials have good stability in hostile environments. However, they are inherently fragile for display little plastic deformation. Therefore, the choice of a ceramic composite alumina-titania-lantana has high mechanical strength and high toughness which were produced by thermo-mechanical processing. These composites were sintered at 1350 ° C for 36 hours, and it was held Vickers hardness testing and microstructural characterization to assess their surfaces before and after the attack by crude to use such material as ceramic coating. These results will be presented at the congress. (author)

  1. Adição de grafite na conformação de substratos cerâmicos porosos processados por rolos a frio Addition of graphite in the conformation of ceramic porous substrates processed by cold roll pressing

    Directory of Open Access Journals (Sweden)

    L. Koshimizu

    2012-12-01

    Full Text Available O desenvolvimento de substratos cerâmicos porosos de fina espessura (The development of porous ceramic substrates with thickness less than 1 mm presents a great technology interesting for electro-electronic or catalytic applications. Among all the techniques of ceramic conformation, the viscoplastic processing shows great advantages decreasing the amount of liquids and the particles agglomeration from an intensive shearing of the ceramic paste. This process allows the conformation of ceramic samples in a simple way and without toxic additives, the opposite of tape casting, which is the method often applied. The substrates were conformed by cold roll pressing in a thickness between 400 and 700 µm, and with the rotation of rollers of 15 rpm. Theses were dried before the firing at 1600 ºC for 1 h. As a pore-forming agent it was studied the graphite powder which was added to the alumina plastic paste in two different concentrations, 9 and 18 wt%, which results in an apparent porosity of 21 and 52%, respectively.

  2. 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

  3. NUMERICAL SIMULATION OF METAL MELT FLOWS IN MOLD CAVITY WITH CERAMIC POROUS MEDIA

    Directory of Open Access Journals (Sweden)

    Changchun Dong

    2016-05-01

    Full Text Available Process modeling of metal melt flow in porous media plays an important role in casting of metal matrix composites. In this work, a mathematical model of the metal melt flow in preform ceramic particles was used to simulate the flow behavior in a mold cavity. The effects of fluid viscosity and permeability (mainly affected by porosity of ceramic preforms on the flow behavior were analyzed. The results indicate that ceramic porous media have a significant effect on the flow behavior by contributing to a low filling velocity and sharp pressure drop in the cavity. The pressure drop has a linear relationship with the fluid velocity, and a nonlinear relationship with porosity. When the porosity is relatively small, the pressure drop is extremely large. When porosity exceeds a certain value, the pressure drop is independent of porosity. The relationship between viscosity and porosity is described, and it is shown that the critical porosity changes when the viscosity of the melt changes. However, due to the limited viscosity change, the critical porosity changes by less than 0.043.

  4. Properties of porous FeAlOy/FeAlx ceramic matrix composite ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 36; Issue 7. Properties of porous FeAlO/FeAl ceramic matrix composite influenced by mechanical activation of FeAl powder. V Usoltsev S Tikhov A Salanov V Sadykov G Golubkova O Lomovskii. Volume 36 Issue 7 December 2013 pp 1195-1200 ...

  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. 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.

  7. Porosity determination of alumina and boron carbide ceramic samples by gamma ray transmission

    International Nuclear Information System (INIS)

    Moreira, Anderson Camargo; Appoloni, Carlos Roberto

    2009-01-01

    The aim of this work is to apply the Gamma Ray Transmission (GRT), a non destructive technique, for structural characterization of ceramic samples. With this technique, the porosity of Alumina (Al 2 O 3 ) and Boron Carbide (B 4 C) ceramic samples, in tablet format, was determined. The equipment employed is constituted by a 241 Am gamma ray source (59.6 keV and 100mCi), a 2''x2'' diameter NaI (Tl) scintillation detector coupled to a standard gamma ray transmission electronic and a micrometric and automated table for sample movement. The porosity profile of the samples shows a homogeneous porosity distribution, within the spatial resolution of the employed transmission system. The mean porosity determined for Al 2 O 3 and B 4 C were 17.8±1.3% and 3.87±0.43%, respectively. A statistical treatment of these results was performed and showed that the mean porosity values determinate by the GRT are the same as those supplied by the manufacturer. (author)

  8. 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.)

  9. 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.

  10. Effect of heat treatment on the structure of incorporated oxalate species and photoluminescent properties of porous alumina films formed in oxalic acid

    Science.gov (United States)

    Vrublevsky, I.; Jagminas, A.; Hemeltjen, S.; Goedel, W. A.

    2008-09-01

    The present work focuses on the use of IR spectroscopy and photoluminescence spectral measurements for studying the treatment temperature effect on the compositional and luminescent properties of oxalic acid alumina films. In line with the recent researches we have also found that heat treatment of porous alumina films formed in oxalic acid leads to considerable changes in their photoluminescence properties: upon annealing the intensity of photoluminescence (PL) increases reaching a maximum at the temperature of around 500 °C and then decreases. IR spectra of as-grown and heat-treated films have proved that PL emission in the anodic alumina films is related with the state of 'structural' oxalate species incorporated in the oxide lattice. These results allowed us to conclude that PL behavior of oxalic acid alumina films can be explained through the concept of variations in the bonding molecular orbitals of incorporated oxalate species including σ- and π-bonds.

  11. Porous biomorphic silicon carbide ceramics coated with hydroxyapatite as prospective materials for bone implants.

    Science.gov (United States)

    Gryshkov, Oleksandr; Klyui, Nickolai I; Temchenko, Volodymyr P; Kyselov, Vitalii S; Chatterjee, Anamika; Belyaev, Alexander E; Lauterboeck, Lothar; Iarmolenko, Dmytro; Glasmacher, Birgit

    2016-11-01

    Porous and cytocompatible silicon carbide (SiC) ceramics derived from wood precursors and coated with bioactive hydroxyapatite (HA) and HA-zirconium dioxide (HA/ZrO2) composite are materials with promising application in engineering of bone implants due to their excellent mechanical and structural properties. Biomorphic SiC ceramics have been synthesized from wood (Hornbeam, Sapele, Tilia and Pear) using a forced impregnation method. The SiC ceramics have been coated with bioactive HA and HA/ZrO2 using effective gas detonation deposition approach (GDD). The surface morphology and cytotoxicity of SiC ceramics as well as phase composition and crystallinity of deposited coatings were analyzed. It has been shown that the porosity and pore size of SiC ceramics depend on initial wood source. The XRD and FTIR studies revealed the preservation of crystal structure and phase composition of in the HA coating, while addition of ZrO2 to the initial HA powder resulted in significant decomposition of the final HA/ZrO2 coating and formation of other calcium phosphate phases. In turn, NIH 3T3 cells cultured in medium exposed to coated and uncoated SiC ceramics showed high re-cultivation efficiency as well as metabolic activity. The recultivation efficiency of cells was the highest for HA-coated ceramics, whereas HA/ZrO2 coating improved the recultivation efficiency of cells as compared to uncoated SiC ceramics. The GDD method allowed generating homogeneous HA coatings with no change in calcium to phosphorus ratio. In summary, porous and cytocompatible bio-SiC ceramics with bioactive coatings show a great promise in construction of light, robust, inexpensive and patient-specific bone implants for clinical application. Copyright © 2016 Elsevier B.V. All rights reserved.

  12. Using mathematical modelling of the changes in the characteristics of the bodies during SHS-process for porous ceramic filters manufacture

    Directory of Open Access Journals (Sweden)

    Юлія Славоміровна Повстяна

    2016-11-01

    Full Text Available Porous ceramic materials possess great lifetime, high mechanical strength, are resistant to household effects and easy to use. The binder volume fraction and normalized pressure as a function of the temperature in the SHS process in the ceramic body have been studied in this work. Basing on theoretical calculations the temperature range of the binder burnout has been determined. The theoretical results can be used to predict and obtain porous ceramic filters with predetermined characteristics. The theoretical calculations were used in the manufacture of experimental samples of porous ceramic bodies obtained on the basis of 18H2N4MA steel scale and the saponite. Pressing in a hydraulic press was used to manufacture ceramic pieces. Unilateral press mould made of stainless steel was used to form the samples. Pressing was carried out in the pressure range of 10-25 MPa. The resulting pieces were formed in cylinders of 30mm in diameter and 40 mm height. Sintering of the samples was conducted in the modernized reactor for the SHS process. Mathematical justification of SHS process made it possible to avoid the formation of cracks in the ceramic bodies and crumble areas

  13. Study of the influence of micro-structures and porosity of pellets alumina in the ultrasonic pulse in the frequency domain

    International Nuclear Information System (INIS)

    Costa, Antonio Mario Leal Martins

    2009-01-01

    This work is part of a study to the applicability of ultrasonic technique in the frequency domain for non-destructive characterization of ceramic pellets fuel, which is of great interest because of concern about the safety and efficacy in the nuclear industry. In this work it was analysed if there were changes in frequency spectrum, generated by the traveling of an ultrasonic pulse through ceramic pellets of aluminum oxide (Al 2 O 3 ). Using the ultrasonic technique in the frequency domain, together with micro-structural analysis of pellets by scanning electron microscope, it was possible to associate the characteristics of the material inspected with its respective frequency spectrum. The characterization was performed on 40 pellets alumina sintered in the temperatures of 1150, 1400, 1480, 1540 and 1580 deg C with porosities, as measured by the Archimedes method, ranging from 5.09% to 37.3%. The results show that the ultrasonic technique is effective in determining the micro-structure of ceramic alumina pellets and can be applied in the characterization of other porous materials in a production line, where the format of the frequency spectrum generated by the structure of the material may determine if the pellets belong the required specifications. (author)

  14. Method of preparing porous, rigid ceramic separators for an electrochemical cell. [Patent application

    Science.gov (United States)

    Bandyopadhyay, G.; Dusek, J.T.

    Porous, rigid separators for electrochemical cells are prepared by first calcining particles of ceramic material at temperatures above about 1200/sup 0/C for a sufficient period of time to reduce the sinterability of the particles. A ceramic powder that has not been calcined is blended with the original powder to control the porosity of the completed separator. The ceramic blend is then pressed into a sheet of the desired shape and sintered at a temperature somewhat lower than the calcination temperature. Separator sheets of about 1 to 2.5 mm thickness and 30 to 70% porosity can be prepared by this technique. Ceramics such as yttria, magnesium oxide, and magnesium-aluminium oxide have advantageously been used to form separators by this method.

  15. Stereo-selective hydrolytic reaction of toxic compounds by enzyme immobilized on porous ceramics; Takoshitsu ceramics kotaika koso ni yoru dokusei kagobutsu no rittai sentakuteki kasui bunkai hanno

    Energy Technology Data Exchange (ETDEWEB)

    Kato, K.; Saito, T. [National Industrial Research Institute of Nagoya, Nagoya (Japan)

    2000-08-25

    Experiment was made on stereo-selective hydrolytic reaction of trifluoroethyl ester of ketoprophene by various kinds of lipase. In addition, study was made on the stability of lipase simply immobilized on porous ceramics under the existence of organic solvent. In the experiment, the hydrolytic activity of 8 kinds of lipase was studied for ketoprophene monochloroethyl ester (1a) and trifluoroethyl ester (1b). The experiment result showed that lipase M originating in mold (Mucor Javanicus) shows a high reactivity and stereo-selectivity for the compound (1a). The lipase immobilized on porous ceramics was easily obtained by a very simple method composed of only throwing carriers into enzyme suspension, agitation and refrigerated drying. The lipase immobilized on porous ceramics 'Toyonite 200-A' synthesized from kaolinite retained the residual activity of nearly 50%, original selectivity and considerable stability after 5 times of repetitive uses. This study result is useful for bio- reactors and bio-sensors for synthesis or decomposition of compounds. (NEDO)

  16. 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 ...

  17. Effect of Organic Vapour on Porous Alumina Based Moisture Sensor in Dry Gases

    Directory of Open Access Journals (Sweden)

    Saakshi DHANEKAR

    2009-08-01

    Full Text Available A capacitive porous alumina based trace moisture sensor in the range of 50 to 500 ppm (V was fabricated by low cost sol-gel technique. The cross-sensitivities due to the presence of organic vapours like ethanol, methanol, acetone and benzene were studied. The change in response and recovery time with ppm for moisture sensing was also calculated. The experimental results conclude that moisture sensor is responsive to the polar organic vapours but has almost negligible response to the nonpolar molecules like benzene. Response of the sensor to the organic vapours as compared to the moisture sensitivity is very less. The effect of ambient temperature was found to be negligible.

  18. Porous Materials from Thermally Activated Kaolinite: Preparation, Characterization and Application

    Directory of Open Access Journals (Sweden)

    Jun Luo

    2017-06-01

    Full Text Available In the present study, porous alumina/silica materials were prepared by selective leaching of silicon/aluminum constituents from thermal-activated kaolinite in inorganic acid or alkali liquor. The correlations between the characteristics of the prepared porous materials and the dissolution properties of activated kaolinite were also investigated. The results show that the specific surface area (SSA of porous alumina/silica increases with silica/alumina dissolution, but without marked change of the BJH pore size. Furthermore, change in pore volume is more dependent on activation temperature. The porous alumina and silica obtained from alkali leaching of kaolinite activated at 1150 °C for 15 min and acid leaching of kaolinite activated at 850 °C for 15 min are mesoporous, with SSAs, BJH pore sizes and pore volumes of 55.8 m2/g and 280.3 m2/g, 6.06 nm and 3.06 nm, 0.1455 mL/g and 0.1945 mL/g, respectively. According to the adsorption tests, porous alumina has superior adsorption capacities for Cu2+, Pb2+ and Cd2+ compared with porous silica and activated carbon. The maximum capacities of porous alumina for Cu2+, Pb2+ and Cd2+ are 134 mg/g, 183 mg/g and 195 mg/g, respectively, at 30 °C.

  19. Conversion of wood flour/SiO2/phenolic composite to porous SiC ceramic containing SiC whiskers

    Directory of Open Access Journals (Sweden)

    Li Zhong

    2013-01-01

    Full Text Available A novel wood flour/SiO2/phenolic composite was chosen to be converted into porous SiC ceramic containing SiC whiskers via carbothermal reduction. At 1550°C the composite is converted into porous SiC ceramic with pore diameters of 10~40μm, and consisting of β-SiC located at the position of former wood cell walls. β-SiC wire-like whiskers of less than 50 nm in diameter and several tens to over 100 μm in length form within the pores. The surface of the resulting ceramic is coated with β-SiC necklace-like whiskers with diameters of 1~2μm.

  20. Comparative study on in vivo response of porous calcium carbonate composite ceramic and biphasic calcium phosphate ceramic

    Energy Technology Data Exchange (ETDEWEB)

    He, Fupo, E-mail: fphebm@126.com [School of Electromechanical Engineering, Guangdong University of Technology, Guangzhou 510006 (China); Ren, Weiwei [School of Electromechanical Engineering, Guangdong University of Technology, Guangzhou 510006 (China); Tian, Xiumei [Department of Biomedical Engineering, School of Basic Sciences, Guangzhou Medical University, Guangzhou 510182 (China); Liu, Wei; Wu, Shanghua [School of Electromechanical Engineering, Guangdong University of Technology, Guangzhou 510006 (China); Chen, Xiaoming, E-mail: xmchenw@126.com [Department of Biomedical Engineering, School of Basic Sciences, Guangzhou Medical University, Guangzhou 510182 (China)

    2016-07-01

    In a previous study, robust calcium carbonate composite ceramics (CC/PG) were prepared by using phosphate-based glass (PG) as an additive, which showed good cell response. In the present study the in vivo response of porous CC/PG was compared to that of porous biphasic calcium phosphate ceramics (BCP), using a rabbit femoral critical-size grafting model. The materials degradation and bone formation processes were evaluated by general observation, X-ray radiography, micro-computed tomography, and histological examination. The results demonstrated excellent biocompatibility and osteoconductivity, and progressive degradation of CC/PG and BCP. Although the in vitro degradation rate of CC/PG was distinctly faster than that of BCP, at 4 week post-implantation, the bone generation and material degradation of CC/PG were less than those of BCP. Nevertheless, at postoperative week 8, the increment of bone formation and material degradation of CC/PG was pronouncedly larger than that of BCP. These results show that CC/PG is a potential resorbable bone graft aside from the traditional synthetic ones. - Highlights: • A calcium carbonate composite ceramic (CC/PG) was acquired. • The in vivo response of CC/PG and biphasic calcium phosphate (BCP) was compared. • CC/PG showed faster in vitro degradation rate compared to BCP. • CC/PG showed less in vivo degradation and bone formation than BCP at week 4. • CC/PG had larger increment of degradation and bone formation than BCP at week 8.

  1. Comparative study on in vivo response of porous calcium carbonate composite ceramic and biphasic calcium phosphate ceramic

    International Nuclear Information System (INIS)

    He, Fupo; Ren, Weiwei; Tian, Xiumei; Liu, Wei; Wu, Shanghua; Chen, Xiaoming

    2016-01-01

    In a previous study, robust calcium carbonate composite ceramics (CC/PG) were prepared by using phosphate-based glass (PG) as an additive, which showed good cell response. In the present study the in vivo response of porous CC/PG was compared to that of porous biphasic calcium phosphate ceramics (BCP), using a rabbit femoral critical-size grafting model. The materials degradation and bone formation processes were evaluated by general observation, X-ray radiography, micro-computed tomography, and histological examination. The results demonstrated excellent biocompatibility and osteoconductivity, and progressive degradation of CC/PG and BCP. Although the in vitro degradation rate of CC/PG was distinctly faster than that of BCP, at 4 week post-implantation, the bone generation and material degradation of CC/PG were less than those of BCP. Nevertheless, at postoperative week 8, the increment of bone formation and material degradation of CC/PG was pronouncedly larger than that of BCP. These results show that CC/PG is a potential resorbable bone graft aside from the traditional synthetic ones. - Highlights: • A calcium carbonate composite ceramic (CC/PG) was acquired. • The in vivo response of CC/PG and biphasic calcium phosphate (BCP) was compared. • CC/PG showed faster in vitro degradation rate compared to BCP. • CC/PG showed less in vivo degradation and bone formation than BCP at week 4. • CC/PG had larger increment of degradation and bone formation than BCP at week 8.

  2. Elaboration of porous gehlenite and anorthite based ceramics using low price raw materials

    Directory of Open Access Journals (Sweden)

    F. Zenikheri

    Full Text Available Abstract Porous ceramics of good quality cost a lot in the world market, which has limited their use in developing countries. This is why this work was mainly devoted to prepare low-cost and good quality ceramics, using kaolin (DD2 type and calcite (CaCO3 available in abundance in Algeria. Based on previous results, 28 wt% CaCO3 ceramic was selected. The presence of CaCO3 favors to achieve porous samples characterized by a high percentage of porosity due to the CO2 release and CaO formation during its calcination at about 700 °C. The choice of these raw materials is based on their natural abundance (low price. It has been found that the samples had interesting characteristics: average pore size between 2.87 and 6.50 μm and porosity between 53 and 57%. It has also been found that the manufactured membrane supports are mainly constituted of gehlenite and anorthite phases. Moreover, the pore size distribution was mono-modal type. The surface and cross-section morphologies observed through a scanning electron microscope were also homogeneous and do not present any possible macro-defects (cracks, etc..

  3. 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

  4. Influence of Water Activated by Far infrared Porous Ceramics on Nitrogen Absorption in the Pig Feed.

    Science.gov (United States)

    Meng, Junping; Liu, Jie; Liang, Jinsheng; Zhang, Hongchen; Ding, Yan

    2016-04-01

    Under modern and, intensive feeding livestock and poultry density has increased, and brought a deterioration of the farm environment. The livestock and their excrement generate harmful gases such as ammonia, etc. which restricted the sustainable development and improvement of production efficiency of animal husbandry. In this paper, a new kind of far infrared porous ceramics was prepared to activate, the animal drinking water. The activated water and common water were then supplied to pigs, and the fresh pig feces of experimental group and:control group were collected on a regular basis. The residual protein content in feces was tested by Kjeldahl nitrogen method to study the influence law of the porous ceramics on absorbing nitrogen element in animal feces. The results showed that compared with the control group, the protein content in the experimental group decreased on average by 39.2%. The activated drinking water was conducive to the absorption of nitrogen in pig feed. The clusters of water molecules became smaller under the action of the porous ceramics. Hence, they were easy to pass through the water protein channel on the cell membrane for speeding up the metabolism.

  5. Compressive deformation of liquid phase-sintered porous silicon carbide ceramics

    Directory of Open Access Journals (Sweden)

    Taro Shimonosono

    2014-12-01

    Full Text Available Porous silicon carbide ceramics were fabricated by liquid phase sintering with 1 wt% Al2O3–1 wt% Y2O3 additives during hot-pressing at 1400–1900 °C. The longitudinal strain at compressive fracture increased at a higher porosity and was larger than the lateral strain. The compressive Young's modulus and the strain at fracture depended on the measured direction, and increased with the decreased specific surface area due to the formation of grain boundary. However, the compressive strength and the fracture energy were not sensitive to the measured direction. The compressive strength of a porous SiC compact increased with increasing grain boundary area. According to the theoretical modeling of the strength–grain boundary area relation, it is interpreted that the grain boundary of a porous SiC compact is fractured by shear deformation rather than by compressive deformation.

  6. 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.

  7. Physico-chemical study of coating plasma duplex alumina/hydroxyapatite for medical applications relation elaboration/structure/properties(dissolution/adherence/residual constraints)

    International Nuclear Information System (INIS)

    Demonet, N.

    1998-01-01

    The physico-chemical behavior of porous ceramics depositing is studied in order to use them to favour the biological fixing of hip prosthesis fixed without cement. Alumina depositing, hydroxyapatite depositing and duplex (the both together) have been realized by plasma projection on a substrate in Ti-6Al-V. Tests of dissolution have been made. An original method of sound followed by radioactive tracers has allowed to establish an order of phases degradation and to consider the kinetics of calcium ions in function of several parameters of tests. (N.C.)

  8. 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.

  9. Variation of nanopore diameter along porous anodic alumina channels by multi-step anodization.

    Science.gov (United States)

    Lee, Kwang Hong; Lim, Xin Yuan; Wai, Kah Wing; Romanato, Filippo; Wong, Chee Cheong

    2011-02-01

    In order to form tapered nanocapillaries, we investigated a method to vary the nanopore diameter along the porous anodic alumina (PAA) channels using multi-step anodization. By anodizing the aluminum in either single acid (H3PO4) or multi-acid (H2SO4, oxalic acid and H3PO4) with increasing or decreasing voltage, the diameter of the nanopore along the PAA channel can be varied systematically corresponding to the applied voltages. The pore size along the channel can be enlarged or shrunken in the range of 20 nm to 200 nm. Structural engineering of the template along the film growth direction can be achieved by deliberately designing a suitable voltage and electrolyte together with anodization time.

  10. Planar, Polysilazane-Derived Porous Ceramic Supports for Membrane and Catalysis Applications.

    Science.gov (United States)

    Konegger, Thomas; Williams, Lee F; Bordia, Rajendra K

    2015-10-01

    Porous, silicon carbonitride-based ceramic support structures for potential membrane and catalysis applications were generated from a preceramic polysilazane precursor in combination with spherical, ultrahigh-molecular weight polyethylene microparticles through a sacrificial filler approach. A screening evaluation was used for the determination of the impact of both porogen content and porogen size on pore structure, strength, and permeability characteristics of planar specimens. By optimizing both the composition as well as cross-linking parameters, maximum characteristic biaxial flexural strengths of 65 MPa and porosities of 42% were achieved. The evolution of an interconnected, open-pore network during thermal porogen removal and conversion of the preceramic polymer led to air permeabilities in the order of 10 -14 m 2 . The materials were further exposed to long-term heat treatments to demonstrate the stability of properties after 100 h at 800°C in oxidizing, inert, and reducing environments. The determined performance, in combination with the versatile preparation method, illustrates the feasibility of this processing approach for the generation of porous ceramic support structures for applications at elevated temperatures in a variety of fields, including membrane and catalysis science.

  11. 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.

  12. Synthesis and characterization of biomorphic ceramics

    International Nuclear Information System (INIS)

    Rambo, Carlos Renato

    2001-01-01

    Biotemplating represents a recently developed technology for manufacturing of biomorphous ceramics from naturally grown plant structures. This approach allows the production of ceramic materials with cellular structure, where the microstructural features of the ceramic product are similar to the native plant. After processing, the biomorphic ceramic exhibits directed pore morphology in the micrometer range. Biomorphic SiC fibers were produced from bamboo by carbothermal reduction of SiO 2 originally present in the bamboo structure. Bamboo pieces were heated up to 1500 deg C in argon to promote the reaction between carbon and silica. Biomorphic alumina, mullite and zirconia ceramics were manufactured via the sol-gel route by repeated infiltration of low viscous oxide precursors (sols) into rattan, pine and bamboo structures. The raw samples were pyrolyzed at 800 deg C in nitrogen for 1h and subsequently annealed at 1550 deg C in air. The microstructure and physical properties of the biomorphic ceramics were characterized by X-ray diffraction (XRD) and high temperature-XRD, scanning electron microscopy (SEM), porosimetry and picnometry. Thermal analysis (TGA/DTA) was performed on the infiltrated samples in order to evaluate the reactions and the total weight loss during the thermal process. The mechanical properties were evaluated by compressive strength tests. In contrast to conventional processed ceramic foam of similar porosity, the microstructure highly porous biomorphic ceramics shows uniaxial pore morphology with anisotropic properties. These properties are favorable for applications in catalyst support, filters or low-density heat insulation structures, or as biomaterials. (author)

  13. Preparation and Characteristics of Porous Ceramics by a foaming Technology at Low Temperature

    Science.gov (United States)

    Zhang, H. Q.; Wang, S. P.; Wen, J.; Wu, N.; Xu, S. H.

    2017-12-01

    Recycling and converting coal gangue and red mud into porous ceramics with good performance is a feasible disposal route. In this present work, porous foam ceramics was prepared using coal gangue and red mud as main raw materials at low sintering temperature, The amount of coal gangue and red mud were up to 70 wt%. To regulate the forming and sintering performance of the product, quartz sands and clay material were added to the formula. The green body was formed by a foaming technology using aluminum powders as foaming agents at room temperature. After foamed, the specimens were dried at 60-80 °C, and then calcined at 1060°C. Effects of concentration of NaOH and amount of aluminum powders on the phase, mechanical properties and microstructure were investigated here. Such study is expected to provide a new utilization route of the coal gangue and red mud, and brings both intensive environmental and economic benefits.

  14. Planar, Polysilazane?Derived Porous Ceramic Supports for Membrane and Catalysis Applications

    OpenAIRE

    Konegger, Thomas; Williams, Lee F.; Bordia, Rajendra K.

    2015-01-01

    Porous, silicon carbonitride?based ceramic support structures for potential membrane and catalysis applications were generated from a preceramic polysilazane precursor in combination with spherical, ultrahigh?molecular weight polyethylene microparticles through a sacrificial filler approach. A screening evaluation was used for the determination of the impact of both porogen content and porogen size on pore structure, strength, and permeability characteristics of planar specimens. By optimizin...

  15. Synthesis and structure of porous alumina precursors derived from n-alkylamine-AlCl3 system; Chokusa alkylamine-AlCl{sub 3} kei wo mochiiru takoshitsu alumina zenkutai no gosei to kozo

    Energy Technology Data Exchange (ETDEWEB)

    Yoshimura, M.; Machida, M.; Kijima, T. [Miyazaki Univ. (Japan)

    1998-06-01

    Alumina precursors have been prepared from AlCl3 by using n-alkylamines (C{sub n}H{sub 2n+1}NH2) as precipitant at pH 9.6 and pH 6.2, and the structure, composition, microstructure, and thermal decomposition behavior are investigated. The effects of the structure of the precursor on the decomposition behavior and on the surface area of porous alumina are also investigated. When alkylamines n{>=}6 are used, long periodicity phases are produced corresponding to larger than d=2.0nm spacing which can not be attributed to bayerite or pseudo-boehnite. Long periodicity phase is formed uniquely near the water content of about 50mass% (H2O/Al=4.5), and the spacing varies depending on the alkyl chainlength of amine. When the precipitate prepared at pH 6.2 is heated, water is desorbed at near 100degC, pseudo-baehnite phase is pyrolyzed at 300degC, and the precipitate changed into {gamma}-alumina at temperatures higher than 500degC. 16 refs., 9 figs.

  16. Vertical single- and double-walled carbon nanotubes grown from modified porous anodic alumina templates

    International Nuclear Information System (INIS)

    Maschmann, Matthew R; Franklin, Aaron D; Amama, Placidus B; Zakharov, Dmitri N; Stach, Eric A; Sands, Timothy D; Fisher, Timothy S

    2006-01-01

    Vertical single-walled and double-walled carbon nanotube (SWNT and DWNT) arrays have been grown using a catalyst embedded within the pore walls of a porous anodic alumina (PAA) template. The initial film structure consisted of a SiO x adhesion layer, a Ti layer, a bottom Al layer, a Fe layer, and a top Al layer deposited on a Si wafer. The Al and Fe layers were subsequently anodized to create a vertically oriented pore structure through the film stack. CNTs were synthesized from the catalyst layer by plasma-enhanced chemical vapour deposition (PECVD). The resulting structure is expected to form the basis for development of vertically oriented CNT-based electronics and sensors

  17. Review. Freeze-casting: Fabrication of highly porous and hierarchical ceramic supports for energy applications

    Energy Technology Data Exchange (ETDEWEB)

    Gaudillere, C.; Serra, J. M.

    2016-05-01

    The manufacture of structured ceramic porous support knows an important boom since more than a decade with the development of new shaping techniques. Among the most promising ones, the freeze-casting also called Ice-Tem plating allows the fabrication of ceramic parts exhibiting high porosity (>50%) and vertically aligned and hierarchically organized pores. Such structures were firstly conceived for biomedical applications like bone substitute and tissue engineering, but the distinctive features of freeze-cast structures have attracted the attention of diverse scientific fields, especially in high temperature ceramic-based energy production systems. Indeed, technologies like (a) Solid Oxide Fuel Cell (SOFC) and Electrolyser Cell (SOEC), (b) gas separation (O{sub 2}, H{sub 2}) by asymmetric supported membranes based on mixed ionic and electronic conductors (MIEC) or hydrogen-permeable metals, and (c) Catalytic Membrane Reactor (CMR) systems present a porous component in their physical structure. This latest, presenting a tortuous pathway for gas access and as a consequence, a high transport limitation, is known to be a limiting component for the operation at high flow streams that would enable to reach industrial target. (Author)

  18. Nanoscale electrochemical metallization memories based on amorphous (La, Sr)MnO3 using ultrathin porous alumina masks

    International Nuclear Information System (INIS)

    Liu, Dongqing; Zhang, Chaoyang; Wang, Nannan; Cheng, Haifeng; Wang, Guang; Shao, Zhengzheng; Zhu, Xuan

    2014-01-01

    Nanoscale electrochemical metallization (ECM) memories based on amorphous La 1−x Sr x MnO 3 (a-LSMO) were fabricated using ultrathin porous alumina masks. The ultrathin alumina masks, with thicknesses of about 200 nm and pore diameters of about 80 nm, were fabricated through a typical two-step anodization electrochemical procedure and transferred onto conductive Pt/Ti/SiO 2 /Si substrates. Resistive switching (RS) properties of the individual Ag/a-LSMO/Pt ECM cell were directly measured using a conductive atomic force microscope. The cells exhibited typical RS characteristics and the OFF/ON resistance ratio is as high as 10 2 . Reproducible RS behaviours on the same ECM cell and the I–V cycles obtained from different ECM cells ensured that the RS properties in nanoscale Ag/a-LSMO/Pt cells are reproducible and reliable. This work provides an effective approach for the preparation of nanostructured large-scale ordered ECM memories or memristors. (paper)

  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. Tailoring thermal conductivity via three-dimensional porous alumina.

    Science.gov (United States)

    Abad, Begoña; Maiz, Jon; Ruiz-Clavijo, Alejandra; Caballero-Calero, Olga; Martin-Gonzalez, Marisol

    2016-12-09

    Three-dimensional anodic alumina templates (3D-AAO) are an astonishing framework with open highly ordered three-dimensional skeleton structures. Since these templates are architecturally different from conventional solids or porous templates, they teem with opportunities for engineering thermal properties. By establishing the mechanisms of heat transfer in these frameworks, we aim to create materials with tailored thermal properties. The effective thermal conductivity of an empty 3D-AAO membrane was measured. As the effective medium theory was not valid to extract the skeletal thermal conductivity of 3D-AAO, a simple 3D thermal conduction model was developed, based on a mixed series and parallel thermal resistor circuit, giving a skeletal thermal conductivity value of approximately 1.25 W·m -1 ·K -1 , which matches the value of the ordinary AAO membranes prepared from the same acid solution. The effect of different filler materials as well as the variation of the number of transversal nanochannels and the length of the 3D-AAO membrane in the effective thermal conductivity of the composite was studied. Finally, the thermal conductivity of two 3D-AAO membranes filled with cobalt and bismuth telluride was also measured, which was in good agreement with the thermal model predictions. Therefore, this work proved this structure as a powerful approach to tailor thermal properties.

  1. Tailoring thermal conductivity via three-dimensional porous alumina

    Science.gov (United States)

    Abad, Begoña; Maiz, Jon; Ruiz-Clavijo, Alejandra; Caballero-Calero, Olga; Martin-Gonzalez, Marisol

    2016-01-01

    Three-dimensional anodic alumina templates (3D-AAO) are an astonishing framework with open highly ordered three-dimensional skeleton structures. Since these templates are architecturally different from conventional solids or porous templates, they teem with opportunities for engineering thermal properties. By establishing the mechanisms of heat transfer in these frameworks, we aim to create materials with tailored thermal properties. The effective thermal conductivity of an empty 3D-AAO membrane was measured. As the effective medium theory was not valid to extract the skeletal thermal conductivity of 3D-AAO, a simple 3D thermal conduction model was developed, based on a mixed series and parallel thermal resistor circuit, giving a skeletal thermal conductivity value of approximately 1.25 W·m−1·K−1, which matches the value of the ordinary AAO membranes prepared from the same acid solution. The effect of different filler materials as well as the variation of the number of transversal nanochannels and the length of the 3D-AAO membrane in the effective thermal conductivity of the composite was studied. Finally, the thermal conductivity of two 3D-AAO membranes filled with cobalt and bismuth telluride was also measured, which was in good agreement with the thermal model predictions. Therefore, this work proved this structure as a powerful approach to tailor thermal properties. PMID:27934930

  2. 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

  3. The thermal stability of sodium beta'-Alumina solid electrolyte ceramic in AMTEC cells

    International Nuclear Information System (INIS)

    Williams, Roger M.; Ryan, Margaret A.; Homer, Margie L.; Lara, Liana; Manatt, Ken; Shields, Virgil; Cortez, Roger H.; Kulleck, James

    1999-01-01

    A critical component of alkali metal thermal-to electric converter (AMTEC) devices for long duration space missions is the beta'-alumina solid electrolyte ceramic (BASE), for which there exists no substitute. The temperature and environmental conditions under which BASE remains stable control operational parameters of AMTEC devices. We have used mass loss experiments in vacuum to 1573K to characterize the kinetics of BASE decomposition, and conductivity and exchange current measurements in sodium vapor filled exposure cells to 1223K to investigate changes in the BASE which affect its ionic conductivity. There is no clear evidence of direct thermal decomposition of BASE below 1273K, although limited soda loss may occur. Reactive metals such as Mn or Cr can react with BASE at temperatures at least as low as 1223K

  4. [Cytocompatibility of two porous bioactive glass-ceramic in vitro].

    Science.gov (United States)

    Zhang, Yan; Jiang, Xinquan; Zhang, Xiuli; Wang, Deping; Zhen, Lei

    2013-06-01

    To compare the cytocompatibility of two kinds porous bioactive glass-ceramic made by same raw materials. Apatite/wollastonite bioactive glass-ceramic (4006) were prepared by sol-gel method, and bioactive glass (45S5) were prepared by melting method. Bone marrow stromal cells (BMSCs) were cultivated, differentiated and proliferated into osteoblasts, from a rabbit's marrow in the differentiatiofn culture medium with active function. The viability of BMSCs cultivated with extraction of these two kinds of biomaterial, which could represent the cytotoxicity effect of 4006 and 45S5 against BMSCs, was evaluated by the MTp assay. BMSCs were seeded and cocultivated with two kinds of biomaterial scaffolds respectively in vitro. The proliferation and biological properties of cells adhered to scaffolds were observed by inverted phase contrast microscope, scanning electron microscope (SEM), and environmental scanning electron microscope (ESEM), and a suitable cell amount for seeding on the scaffold was searched. There was no difference on the viability of BMSCs only cultured for one day by complete extract of 4006 and culture medium (P>0.05), but there was significant difference between them when the cells had been cultured for 3 days(Pglass-ceramic has good bioactivity and cytocompatibility. Therefore, it may have the potential to be a new cell vehicle for bone tissue engineering. And the suitable seeding cell amount of apatite/wollastonite bioactive glass-ceramic should be 2x10(7) cells.mL-1 or even more than that.

  5. 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.

  6. Design and Fabrication of Porous Yttria-Stabilized Zirconia Ceramics for Hot Gas Filtration Applications

    Science.gov (United States)

    Shahini, Shayan

    Hot gas filtration has received growing attention in a variety of applications over the past few years. Yttria-stabilized zirconia (YSZ) is a promising candidate for such an application. In this study, we fabricated disk-type porous YSZ filters using the pore forming procedure, in which poly methyl methacrylate (PMMA) was used as the pore-forming agent. After fabricating the pellets, we characterized them to determine their potential for application as gas filters. We investigated the effect of sintering temperature, polymer particle size, and polymer-to-ceramic ratio on the porosity, pore size, gas permeability, and Vickers hardness of the sintered pellets. Furthermore, we designed two sets of experiments to investigate the robustness of the fabricated pellets--i.e., cyclic heating/cooling and high temperature exposure. This study ushers in a robust technique to fabricate such porous ceramics, which have the potential to be utilized in hot gas filtration.

  7. Effects of SiC and MgO on aluminabased ceramic foams filters

    Directory of Open Access Journals (Sweden)

    CAO Da-li

    2007-11-01

    Full Text Available Alumina-based foam ceramic filters were fabricated by using alumina, SiC, magnesia powder as major materials. It has been found that this ceramic filter has a uniform macrostructure for filtering molten metals. The influences of SiC and magnesia content, the sintering temperatures on ceramic properties were discussed. Aluminabased foam ceramic filters containing 2.2 mass% magnesia and 7.6 mass% SiC has a compressive strength of 1.36 MPa and a thermal shock resistance of 5 times. Its main phases after 1 hour sintering at 1 500 consist of alumina, silicon carbide, spinel and mullite.

  8. Surface oxidation of porous ZrB2-SiC ceramic composites by continuous-wave ytterbium fibre laser

    International Nuclear Information System (INIS)

    Mahmod, Dayang Salyani Abang; Glandut, Nicolas; Khan, Amir Azam; Labbe, Jean-Claude

    2015-01-01

    Highlights: • Surface oxidation of ZrB 2 -SiC ceramic composites by Yb-fibre laser. • Round spiral laser pattern created for the surface oxidation. • Presence of laser-formed oxide scale and unaffected beneath regions. • Crazed but uncracked surface oxide. • A dense glassy SiO 2 -rich layer exhibited enhances oxidation resistance. - Abstract: Surface treatment of ceramic substrates by a laser beam can allow to incorporate interesting properties to these ceramics. In the present work, surface oxidation of ca. 30% porous ZrB 2 -SiC ceramic composites by using an ytterbium fibre laser was conducted. Oxidation of ceramic substrates through this process under ambient conditions has certain advantages compared to the classical oxidation method. A particular spiral laser pattern was created in order to produce an oxidized structure on ZrB 2 -SiC porous substrates. The laser parameters were as follows i.e., laser power of 50, 60 and 70 W, a beam diameter of 1.25 mm, velocity of 2 mm/s, acceleration and deceleration of 1 mm/s 2 . The microstructural and morphological changes in the laser-treated region was examined using scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction. At laser power of 70 W, the sample exhibits uniform oxidation. It revealed that the very porous bulk beneath remained unaffected and unoxidized because this laser-formed oxide scale protects the substrate from oxidation. The presence of oxidized and unaffected regions indicated a high degree of heat localization. The dense glassy SiO 2 -rich layer prevents the inward oxygen diffusion into the inner bulk hence enhances the oxidation resistance.

  9. 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.

  10. A uranium bed with ceramic body for tritium storage

    Energy Technology Data Exchange (ETDEWEB)

    Khapov, A.S.; Grishechkin, S.K.; Kiselev, V.G. [' All Russia Research Institute of Automatics' - FSUE VNIIA, Moscow (Russian Federation)

    2015-03-15

    It is widely recognized that ceramic coatings provide an attractive solution to lower tritium permeation in structural materials. Alumina based ceramic coatings have the highest permeation reduction factor for hydrogen. For this reason an attempt was made to apply crack-free low porous ceramics as a structural material of a bed body for tritium storage in a setup used for hydrogenating neutron tube targets at VNIIA. The present article introduces the design of the bed. This bed possesses essentially a lower hydrogen permeation factor than traditionally beds with stainless steel body. Bed heating in order to recover hydrogen from the bed is suggested to be implemented by high frequency induction means. Inductive heating allows decreasing the time necessary for tritium release from the bed as well as power consumption. Both of these factors mean less thermal power release into glove box where a setup for tritium handling is installed and thus causes fewer problems with pressure regulations inside the glove box. Inductive heating allows raising tritium sorbent material temperature up to melting point. The latter allows achieving nearly full tritium recovery.

  11. Low-friction arthroplasty of the hip using alumina ceramic and cross-linked polyethylene. A 17-year follow-up report.

    Science.gov (United States)

    Wroblewski, B M; Siney, P D; Fleming, P A

    2005-09-01

    We report the results of our continued review of 11 total hip arthroplasties using 22.225 mm alumina ceramic femoral heads on a Charnley flanged stem, articulating with chemically cross-linked polyethylene. There was an initial bedding-in of up to 0.41 mm at the articular surface in the first two years. This had not progressed further, at a minimum follow-up of 15 years. Radiographically no femoral or acetabular component showed loosening or osteolysis.

  12. Reliability Estimation for Single-unit Ceramic Crown Restorations

    Science.gov (United States)

    Lekesiz, H.

    2014-01-01

    The objective of this study was to evaluate the potential of a survival prediction method for the assessment of ceramic dental restorations. For this purpose, fast-fracture and fatigue reliabilities for 2 bilayer (metal ceramic alloy core veneered with fluorapatite leucite glass-ceramic, d.Sign/d.Sign-67, by Ivoclar; glass-infiltrated alumina core veneered with feldspathic porcelain, VM7/In-Ceram Alumina, by Vita) and 3 monolithic (leucite-reinforced glass-ceramic, Empress, and ProCAD, by Ivoclar; lithium-disilicate glass-ceramic, Empress 2, by Ivoclar) single posterior crown restorations were predicted, and fatigue predictions were compared with the long-term clinical data presented in the literature. Both perfectly bonded and completely debonded cases were analyzed for evaluation of the influence of the adhesive/restoration bonding quality on estimations. Material constants and stress distributions required for predictions were calculated from biaxial tests and finite element analysis, respectively. Based on the predictions, In-Ceram Alumina presents the best fast-fracture resistance, and ProCAD presents a comparable resistance for perfect bonding; however, ProCAD shows a significant reduction of resistance in case of complete debonding. Nevertheless, it is still better than Empress and comparable with Empress 2. In-Ceram Alumina and d.Sign have the highest long-term reliability, with almost 100% survivability even after 10 years. When compared with clinical failure rates reported in the literature, predictions show a promising match with clinical data, and this indicates the soundness of the settings used in the proposed predictions. PMID:25048249

  13. 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

  14. Grinding damage assessment on four high-strength ceramics.

    Science.gov (United States)

    Canneto, Jean-Jacques; Cattani-Lorente, Maria; Durual, Stéphane; Wiskott, Anselm H W; Scherrer, Susanne S

    2016-02-01

    The purpose of this study was to assess surface and subsurface damage on 4 CAD-CAM high-strength ceramics after grinding with diamond disks of 75 μm, 54 μm and 18 μm and to estimate strength losses based on damage crack sizes. The materials tested were: 3Y-TZP (Lava), dense Al2O3 (In-Ceram AL), alumina glass-infiltrated (In-Ceram ALUMINA) and alumina-zirconia glass-infiltrated (In-Ceram ZIRCONIA). Rectangular specimens with 2 mirror polished orthogonal sides were bonded pairwise together prior to degrading the top polished surface with diamond disks of either 75 μm, 54 μm or 18 μm. The induced chip damage was evaluated on the bonded interface using SEM for chip depth measurements. Fracture mechanics were used to estimate fracture stresses based on average and maximum chip depths considering these as critical flaws subjected to tension and to calculate possible losses in strength compared to manufacturer's data. 3Y-TZP was hardly affected by grinding chip damage viewed on the bonded interface. Average chip depths were of 12.7±5.2 μm when grinding with 75 μm diamond inducing an estimated loss of 12% in strength compared to manufacturer's reported flexural strength values of 1100 MPa. Dense alumina showed elongated chip cracks and was suffering damage of an average chip depth of 48.2±16.3 μm after 75 μm grinding, representing an estimated loss in strength of 49%. Grinding with 54 μm was creating chips of 32.2±9.1 μm in average, representing a loss in strength of 23%. Alumina glass-infiltrated ceramic was exposed to chipping after 75 μm (mean chip size=62.4±19.3 μm) and 54 μm grinding (mean chip size=42.8±16.6 μm), with respectively 38% and 25% estimated loss in strength. Alumina-zirconia glass-infiltrated ceramic was mainly affected by 75 μm grinding damage with a chip average size of 56.8±15.1 μm, representing an estimated loss in strength of 34%. All four ceramics were not exposed to critical chipping at 18 μm diamond grinding. Reshaping a

  15. Bond strength of the porcelain repair system to all-ceramic copings and porcelain.

    Science.gov (United States)

    Lee, Sang J; Cheong, Chan Wook; Wright, Robert F; Chang, Brian M

    2014-02-01

    The purpose of this study was to investigate the shear bond strength of the porcelain repair system on alumina and zirconia core ceramics, comparing this strength with that of veneering porcelain. Veneering ceramic (n = 12), alumina core (n = 24), and zirconia core (n = 24) blocks measuring 10 × 5 × 5 mm(3) were fabricated. Veneering ceramic blocks were used as the control. Alumina and zirconia core blocks were divided into 2 groups (n = 12 each), and a slot (2 × 2 × 4 mm(3)) filled with veneering ceramics was prepared into one of the alumina and zirconia core groups (n = 12). Followed by surface treatments of micro-abrasion with 30 μm alumina particles, etching with 35% phosphoric acid and silane primer and bond, composite resin blocks (2 × 2 × 2 mm(3)) were built up and light polymerized onto the treated surfaces by 3 configurations: (a) composite blocks bonded onto veneering ceramic surface alone, (b) composite blocks bonded onto alumina core or zirconia core surfaces, (c) a 50% surface area of the composite blocks bonded to veneering ceramics and the other 50% surface area of the composite blocks to alumina core or zirconia core surfaces. The shear bond strength of the composite to each specimen was tested by a universal testing machine at a 0.5 mm/min crosshead speed. The shear bond strength was analyzed by unpaired t-tests for within the configuration groups and ANOVA for among the different configuration groups. When the mean shear bond strength was compared within groups of the same configuration, there were no statistically significant differences. Comparison of the shear bond strength among groups of different configurations revealed statistically significant differences. The mean shear bond strength of composite onto 100% veneering ceramic surface and composite onto 50% veneering 50% all-ceramic cores was statistically higher than that of composite onto 100% all-ceramic cores; however, the differences of the shear bond strength of composite bonded

  16. Influence of corn flour as pore forming agent on porous ceramic material based mullite: Morphology and mechanical properties

    Directory of Open Access Journals (Sweden)

    Ayala-Landeros J.G.

    2016-01-01

    Full Text Available Porous material was processed by the mixing, molding and pressing the ceramic material, afterward burnout and sintering; through the forming porous, using corn flour at different concentration (10, 15 and 20 wt.% as a pore forming agent; in order to determinate the influence of porous on the mechanical, morphological and structural properties. The effect of the volume fraction of corn flour in the mullite matrix, at various sintering temperature from 1100, 1200, 1300 and 1500°C were tested by Diffraction X ray, showing changes in crystalline phases of mullite (3Al2O3-2SiO2, as result of sintered temperatures. Presence of talcum powder in formula, also cause the formation of the cordierite and cristobalite crystalline phases, giving stability and adhesion to the structure of ceramic material. When sintering at temperatures between 1300 to 1500°C, and it was used the concentration of corn flour 15-20 wt.% as forming agent porous, it was found the better mechanical properties. The scanning electron microscopy analysis shows the presence of open porosity and anisotropy.

  17. 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.

  18. 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

  19. Ceramic Parts for Turbines

    Science.gov (United States)

    Jones, R. D.; Carpenter, Harry W.; Tellier, Jim; Rollins, Clark; Stormo, Jerry

    1987-01-01

    Abilities of ceramics to serve as turbine blades, stator vanes, and other elements in hot-gas flow of rocket engines discussed in report. Ceramics prime candidates, because of resistance to heat, low density, and tolerance of hostile environments. Ceramics considered in report are silicon nitride, silicon carbide, and new generation of such ceramic composites as transformation-toughened zirconia and alumina and particulate- or whisker-reinforced matrices. Report predicts properly designed ceramic components viable in advanced high-temperature rocket engines and recommends future work.

  20. Surface oxidation of porous ZrB{sub 2}-SiC ceramic composites by continuous-wave ytterbium fibre laser

    Energy Technology Data Exchange (ETDEWEB)

    Mahmod, Dayang Salyani Abang, E-mail: dygsalyani@gmail.com [Department of Mechanical and Manufacturing Engineering, Faculty of Engineering, Universiti Malaysia Sarawak, 94300 Kota Samarahan, Sarawak (Malaysia); Glandut, Nicolas [SPCTS, UMR 7315, CNRS, University of Limoges, European Ceramic Center, 12 Rue Atlantis, 87068 Limoges (France); Khan, Amir Azam [Department of Mechanical and Manufacturing Engineering, Faculty of Engineering, Universiti Malaysia Sarawak, 94300 Kota Samarahan, Sarawak (Malaysia); Labbe, Jean-Claude [SPCTS, UMR 7315, CNRS, University of Limoges, European Ceramic Center, 12 Rue Atlantis, 87068 Limoges (France)

    2015-12-01

    Highlights: • Surface oxidation of ZrB{sub 2}-SiC ceramic composites by Yb-fibre laser. • Round spiral laser pattern created for the surface oxidation. • Presence of laser-formed oxide scale and unaffected beneath regions. • Crazed but uncracked surface oxide. • A dense glassy SiO{sub 2}-rich layer exhibited enhances oxidation resistance. - Abstract: Surface treatment of ceramic substrates by a laser beam can allow to incorporate interesting properties to these ceramics. In the present work, surface oxidation of ca. 30% porous ZrB{sub 2}-SiC ceramic composites by using an ytterbium fibre laser was conducted. Oxidation of ceramic substrates through this process under ambient conditions has certain advantages compared to the classical oxidation method. A particular spiral laser pattern was created in order to produce an oxidized structure on ZrB{sub 2}-SiC porous substrates. The laser parameters were as follows i.e., laser power of 50, 60 and 70 W, a beam diameter of 1.25 mm, velocity of 2 mm/s, acceleration and deceleration of 1 mm/s{sup 2}. The microstructural and morphological changes in the laser-treated region was examined using scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction. At laser power of 70 W, the sample exhibits uniform oxidation. It revealed that the very porous bulk beneath remained unaffected and unoxidized because this laser-formed oxide scale protects the substrate from oxidation. The presence of oxidized and unaffected regions indicated a high degree of heat localization. The dense glassy SiO{sub 2}-rich layer prevents the inward oxygen diffusion into the inner bulk hence enhances the oxidation resistance.

  1. Porous ceramics achievement by soybean and corn agricultural waste insertion; Obtencao de ceramicas porosas pela insercao de residuos agricolas de soja e milho

    Energy Technology Data Exchange (ETDEWEB)

    Valdameri, C.Z.; Ank, A., E-mail: cledison@unipar.br [Universidade Paranaense (UNIPAR), Francisco Beltrao, PR (Brazil). Departamento de Engenharia Civil; Zatta, L. [Universidade Tecnologica Federal do Parana (UTFPR), Pato Branco, PR (Brazil). Departamento de Quimica; Anaissi, F.J. [Universidade Estadual do Centro-Oeste (UNICENTRO), Guarapuava, PR (Brazil). Departamento de Quimica

    2014-07-01

    Porous ceramic materials are produced by incorporating organic particles and stable foams. Generally it improves low thermal conductivity, which gives thermal comfort for buildings. The southwest region of Parana state is one of the largest producers of grains in Brazil, this causes the disposal of a large amount of waste in the agricultural processing. This paper presents the characterization of porous ceramics produced from clay minerals and agricultural waste (soybeans and corn). The precursor was characterized by X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) techniques. For the ceramic materials produced, characterizations about density, water absorption, tensile strength by diametrical compression strength and flexural strength curves was performed. The results showed high possibility of industrial/commercial application because the ceramic materials were produced from low costs precursors leading to ceramic products with properties of interest in construction. (author)

  2. 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.)

  3. Obtenção e propriedades de cerâmicas porosas pela técnica de incorporação de espuma Production and properties of porous ceramics obtained by foam addition technique

    Directory of Open Access Journals (Sweden)

    R. C. O. Romano

    2006-06-01

    Full Text Available Cerâmicas porosas, em geral, associam baixa condutividade térmica, alta área superficial, alta permeabilidade e resistência a ataques químicos. Essas características despertam grande interesse do setor de refratários para sua utilização como filtros em altas temperaturas e/ou como isolantes térmicos, quando sua porosidade é fechada. Diversas técnicas foram reportadas para obtenção desses materiais, tais como a queima de partículas orgânicas, a réplica e o gelcasting de espumas cerâmicas. No entanto, com as técnicas convencionais utilizadas até o momento, ainda não é possível o adequado controle da porosidade e da homogeneidade microestrutural. Por isso, no presente trabalho é proposta uma nova forma de obtenção de materiais porosos, onde uma espuma estável, produzida independentemente, é adicionada em uma suspensão de alumina, gerando materiais com elevada porosidade e estrutura homogênea (com estreita população de poros. Além disso, algumas propriedades, como resistência mecânica e módulo de Weibull são apresentadas e os resultados indicam que essa nova rota de processamento pode vir a ser utilizada para desenvolvimento de novos produtos.Porous ceramics materials, usually, associate low thermal conductivity, high superficial area, high permeability and high resistance to chemical corrosion. These are interesting features for refractory applications such as filters for high temperatures or thermal insulating purposes. Several techniques have been reported to obtain porous ceramics: organic particle burn-out, replica technique and gelcasting of ceramic foams. However, these processing routes generally result heterogeneous materials with a broad of pore size distribution. Therefore, in this work a novel technique is used in order to produce porous ceramics, where a stable foam, prepared independently, is mixed to a Al2O3 suspension, producing materials with high porosity and homogeneous microstructure (narrow

  4. 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.

  5. A novel processing approach for free-standing porous non-oxide ceramic supports from polycarbosilane and polysilazane precursors

    OpenAIRE

    Konegger, Thomas; Patidar, Rajesh; Bordia, Rajendra K.

    2015-01-01

    In this contribution, a low-pressure/low-temperature casting technique for the preparation of novel free-standing macrocellular polymer-derived ceramic support structures is presented. Preceramic polymers (polycarbosilane and poly(vinyl)silazane) are combined with sacrificial porogens (ultra-high molecular weight polyethylene microbeads) to yield porous ceramic materials in the Si?C or Si?C?N systems, exhibiting well-defined pore structures after thermal conversion. The planar-disc-type speci...

  6. Ceramic foams porous microstructure characterization by X-ray microtomography

    Directory of Open Access Journals (Sweden)

    Carlos Roberto Appoloni

    2004-12-01

    Full Text Available Knowledge of the porous structure of amorphous materials is of fundamental importance in calculating geometrical parameters such as total porosity, pore size distribution and physical parameters relating to fluid flow inside void space. The present work deals with the measurement of the microstructural parameters of porous ceramic filters. Microtomographic measurements of samples were taken using an X-ray tube. Bremsstrahlung radiation was filtered in transmission mode with a Sn filter at 58.5 and 28.3 keV and the images analyzed in two ways. The first method consisted in analyzing transepts of the images in order to calculate total porosity based on the average particle size and media linear attenuation coefficients. The second method involved a study of the images using an image analysis software, called Imago, which allows one to calculate total porosity and pore size distribution. The total measured porosity of the filter C90 was 73.8%, 71.1%, 74.4% and 71.5% by, respectively, the Arquimedes method, simple gamma ray transmission, transept analysis and analysis of the microtomographic images at 28.3 keV.

  7. Elaboration and characterization of mullite-anorthite-albite porous ceramics prepared from Algerian kaolin

    International Nuclear Information System (INIS)

    Rouabhia, F.; Nemamcha, A.; Moumeni, H.

    2018-01-01

    Mullite-anorthite-albite porous ceramic materials were successfully prepared by a solid-state reaction between kaolin clay and two different additives (CaCO 3 and Na 2 CO 3 ). The starting raw material was characterized by X-ray fluorescence, X-ray diffraction (XRD) and dynamic light scattering techniques. The effect of CaCO 3 and Na 2 CO 3 concentration (10 to 70 wt%) on structure, morphology and thermal properties of the obtained ceramics was investigated by XRD, scanning electron microscopy and differential scanning calorimetry (DSC) techniques. The XRD patterns showed that mullite (3Al 2 O 3 .2SiO 2 ), anorthite (CaO.Al 2 O 3 .2SiO 2 ) and albite (Na 2 O.Al 2 O 3 .6SiO 2 ) were the main crystalline phases present in the materials. The morphology investigation revealed the porous texture of obtained ceramics characterized by the presence of sponge-like structure mainly due to the additive decomposition at high temperatures. The DSC results confirm the presence of four temperature regions related to the kaolin thermal transformations and the formation of minerals. The temperature and enthalpy of mineral formation are additive concentration dependent. As a result, the optimal content of additives which allowed the coexistence of the three phases, a spongelike morphology, and high porosity without cracks corresponded to 15 wt% CaCO 3 , 15 wt% Na 2 CO 3 , and 70 wt% kaolin. (author)

  8. Ceramic protective coatings applied by sol-gel or electrophoresis

    International Nuclear Information System (INIS)

    Stoch, A.

    1993-01-01

    Sol-gel and electrophoresis are the complementary techniques which may be used for obtaining the ceramic coatings. The composition of such a coatings depends on the composition of electrophoresis bath or sol solution. Thermal treatment is used for densifying the coating and promoting the adherence of coating to the substrate. In presented work silica, silica-alumina or alumina coatings are applied by sol-gel dip coating procedure on steel, aluminium or ceramic substrates. Electrophoresis is employed for obtaining zirconia, alumina or hydroxyapatite coatings on stainless steel. (author). 7 refs

  9. Mechanical properties of hybrid composites prepared by ice-templating of alumina

    Czech Academy of Sciences Publication Activity Database

    Roleček, J.; Salamon, D.; Chlup, Zdeněk

    2017-01-01

    Roč. 37, č. 14 (2017), s. 4279-4286 ISSN 0955-2219 R&D Projects: GA MŠk(CZ) LQ1601 Institutional support: RVO:68081723 Keywords : fracture-toughness * ceramic s * matrix * laminate * behavior * fibers * Ice-templating * Alumina * Epoxide * Hybrid composites * Strength Subject RIV: JH - Ceramic s, Fire-Resistant Materials and Glass OBOR OECD: Ceramic s Impact factor: 3.411, year: 2016

  10. Ceramic hot-gas filter

    Science.gov (United States)

    Connolly, E.S.; Forsythe, G.D.; Domanski, D.M.; Chambers, J.A.; Rajendran, G.P.

    1999-05-11

    A ceramic hot-gas candle filter is described having a porous support of filament-wound oxide ceramic yarn at least partially surrounded by a porous refractory oxide ceramic matrix, and a membrane layer on at least one surface thereof. The membrane layer may be on the outer surface, the inner surface, or both the outer and inner surface of the porous support. The membrane layer may be formed of an ordered arrangement of circularly wound, continuous filament oxide ceramic yarn, a ceramic filler material which is less permeable than the filament-wound support structure, or some combination of continuous filament and filler material. A particularly effective membrane layer features circularly wound filament with gaps intentionally placed between adjacent windings, and a filler material of ceramic particulates uniformly distributed throughout the gap region. The filter can withstand thermal cycling during back pulse cleaning and is resistant to chemical degradation at high temperatures.

  11. Ceramic hot-gas filter

    Science.gov (United States)

    Connolly, Elizabeth Sokolinski; Forsythe, George Daniel; Domanski, Daniel Matthew; Chambers, Jeffrey Allen; Rajendran, Govindasamy Paramasivam

    1999-01-01

    A ceramic hot-gas candle filter having a porous support of filament-wound oxide ceramic yarn at least partially surrounded by a porous refractory oxide ceramic matrix, and a membrane layer on at least one surface thereof. The membrane layer may be on the outer surface, the inner surface, or both the outer and inner surface of the porous support. The membrane layer may be formed of an ordered arrangement of circularly wound, continuous filament oxide ceramic yarn, a ceramic filler material which is less permeable than the filament-wound support structure, or some combination of continuous filament and filler material. A particularly effective membrane layer features circularly wound filament with gaps intentionally placed between adjacent windings, and a filler material of ceramic particulates uniformly distributed throughout the gap region. The filter can withstand thermal cycling during backpulse cleaning and is resistant to chemical degradation at high temperatures.

  12. Multiscale modeling of porous ceramics using movable cellular automaton method

    Science.gov (United States)

    Smolin, Alexey Yu.; Smolin, Igor Yu.; Smolina, Irina Yu.

    2017-10-01

    The paper presents a multiscale model for porous ceramics based on movable cellular automaton method, which is a particle method in novel computational mechanics of solid. The initial scale of the proposed approach corresponds to the characteristic size of the smallest pores in the ceramics. At this scale, we model uniaxial compression of several representative samples with an explicit account of pores of the same size but with the unique position in space. As a result, we get the average values of Young's modulus and strength, as well as the parameters of the Weibull distribution of these properties at the current scale level. These data allow us to describe the material behavior at the next scale level were only the larger pores are considered explicitly, while the influence of small pores is included via effective properties determined earliar. If the pore size distribution function of the material has N maxima we need to perform computations for N-1 levels in order to get the properties step by step from the lowest scale up to the macroscale. The proposed approach was applied to modeling zirconia ceramics with bimodal pore size distribution. The obtained results show correct behavior of the model sample at the macroscale.

  13. Effects of SiC and MgO on aluminabased ceramic foams filters

    OpenAIRE

    CAO Da-li; ZHOU Jing-yi; JIN Yong-ming

    2007-01-01

    Alumina-based foam ceramic filters were fabricated by using alumina, SiC, magnesia powder as major materials. It has been found that this ceramic filter has a uniform macrostructure for filtering molten metals. The influences of SiC and magnesia content, the sintering temperatures on ceramic properties were discussed. Aluminabased foam ceramic filters containing 2.2 mass% magnesia and 7.6 mass% SiC has a compressive strength of 1.36 MPa and a thermal shock resistance of 5 times. Its main phas...

  14. 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.

  15. All-ceramic posts and cores: the state of the art.

    Science.gov (United States)

    Koutayas, S O; Kern, M

    1999-06-01

    Metal posts used to restore endodontically treated teeth may shine through all-ceramic crowns and thin gingival tissue. When nonprecious alloys are used, corrosion products may lead to discoloration. All-ceramic posts and cores can be used in combination with all-ceramic crowns to prevent these problems. All-ceramic posts and cores are highly biocompatible and will almost always increase the translucency of an all-ceramic restoration. The purpose of this article is to describe the fabrication of all-ceramic posts and cores, using high-toughness ceramic materials such as alumina or zirconia ceramics, through 4 different techniques: the slip-casting technique; the copy-milling technique; the 2-piece technique, which involves a prefabricated zirconia ceramic post and a copy-milled alumina or zirconia ceramic core; and the heat-press technique, which involves a prefabricated zirconia ceramic post and a heat-pressed glass-ceramic core. Indications, contraindications, advantages, and disadvantages of the different techniques are compared.

  16. Highly porous polymer-derived wollastonite-hydroxycarbonate apatite ceramics for bone regeneration.

    Science.gov (United States)

    Fiocco, L; Li, S; Bernardo, E; Stevens, M M; Jones, J R

    2016-04-12

    A novel strategy was employed to synthesize highly porous wollastonite-hydroxycarbonate apatite ceramic scaffolds for bone regeneration. A commercial liquid preceramic polymer filled with micro-CaCO3 powders was foamed at low temperature (at 350 °C), using the decomposition of a hydrazine additive, and then converted into ceramic by a treatment at 700 °C. Hydroxycarbonate apatite was later developed by a phosphatization treatment of ceramized foams, in a P-rich solution, while wollastonite was obtained by a second firing, at 900 °C. The effectiveness of the method was proven by x-ray diffraction analysis, showing the presence of the two expected crystalline phases. Porosity, interconnect size distribution and mechanical strength were in the range that is thought to be suitable for bone regeneration in non-load bearing sites (compressive strength ≈ 3 MPa, porosity ≈ 90%, modal interconnect diameter ≈ 130-160 μm). In addition, bioactivity and ion release rate were assessed in simulated body fluid (SBF). MC3T3 osteoblast precursor cells were able to colonize the material in vitro through the pore architecture and expressed osteogenic markers.

  17. Obtaining of ceramics biphasic dense and porous

    International Nuclear Information System (INIS)

    Pallone, E.M.J.A.; Rigo, E.C.S.; Fraga, A.F.

    2010-01-01

    Among the bioceramic hydroxyapatite (HAP) and beta-tricalcium phosphate (beta-TCP) are materials commonly used in biomedical field. Their combined properties result in a material with absorbable and at the same time with bioactive surface. Called biphasic ceramics such materials respond more quickly when exposed to physiological environment. In this work, powders of HAP/beta-TCP were obtained by chemical precipitation. After obtaining the post-phase was added at a ratio of 0, 15% and 30w% aqueous solutions of corn starch in order to obtain porous bodies. After mixing the resulting solutions were dried, resigned in tablet form and sintered at 1300 deg C. The initial powder was characterized by X-ray diffraction with Rietveld refinement to quantify the phases present. Bodies-of-evidence has been characterized by calculating the bulk density, X-ray diffraction (XRD), scanning electron microscopy and diametral compression. (author)

  18. 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.

  19. Electrochemical growth of nanowires in anodic alumina templates: the role of pore branching

    International Nuclear Information System (INIS)

    Noyan, Alexey A.; Leontiev, Alexey P.; Yakovlev, Maxim V.; Roslyakov, Ilya V.; Tsirlina, Galina A.; Napolskii, Kirill S.

    2017-01-01

    Highlights: • The model of metal growth inside the anodic alumina with branched pores is developed. • Model predicts the dependence of anodic alumina filling on deposition regime. • Branched pores affect the uniformity of anodic alumina filling with electrodeposits. • Branched pores make growth front of metal nanowires inside template multimodal. - Abstract: A comparative study of electrochemical growth of nanowires in the anodic alumina templates with various degree of porous structure ordering is performed. Scanning electron microscopy and coulometric analysis are used for experimental evaluation of the average filling of pores with metal. The theoretical model of metal growth inside anodic alumina templates is proposed. The model takes into account the presence of branched channels in the real structure of anodic alumina and operates with completeness of template filling achieved at the moment when metal reaches the external surface of the oxide film. In case of the diffusion-controlled regime the strong dependence of the pore filling factor on the thickness of porous film and the degree of its structure ordering is predicted theoretically and observed experimentally. The influence of the nature of limiting current on the homogeneity and completeness of template filling is discussed.

  20. Ballistic Performance of Porous-Ceramic, Thermal-Protection-Systems

    Science.gov (United States)

    Christiansen, E. L.; Davis, B. A.; Miller, J. E.; Bohl, W. E.; Foreman, C. D.

    2009-01-01

    Porous-ceramic, thermal protection systems are used heavily in current reentry vehicles like the Space Shuttle and are currently being proposed for the next generation of manned spacecraft, Orion. These materials insulate the structural components of a spacecraft against the intense thermal environments of atmospheric reentry. Furthermore, these materials are also highly exposed to space environmental hazards like meteoroid and orbital debris impacts. This paper discusses recent impact testing up to 9 km/s, and the findings of the influence of material equation-of-state on the simulation of the impact event to characterize the ballistic performance of these materials. These results will be compared with heritage models1 for these materials developed from testing at lower velocities. Assessments of predicted spacecraft risk based upon these tests and simulations will also be discussed.

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

    Directory of Open Access Journals (Sweden)

    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.

  2. 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

  3. Development of an oxidation resistant glass-ceramic composite coating on Ti-47Al-2Cr-2Nb alloy

    Science.gov (United States)

    Li, Wenbo; Zhu, Shenglong; Chen, Minghui; Wang, Cheng; Wang, Fuhui

    2014-02-01

    Three glass-ceramic composite coatings were prepared on Ti-47Al-2Cr-2Nb alloy by air spraying technique and subsequent firing. The aim of this work is to study the reactions between glass matrix and inclusions and their effects on the oxidation resistance of the glass-ceramic composite coating. The powders of alumina, quartz, or both were added into the aqueous solution of potassium silicate (ASPS) to form slurries used as the starting materials for the composite coatings. The coating formed from an ASPS-alumina slurry was porous, because the reaction between alumina and potassium silicate glass resulted in the formation of leucite (KAlSi2O6), consuming substantive glass phase and hindering the densification of the composite coating. Cracks were observed in the coating prepared from an ASPS-quartz slurry due to the larger volume shrinkage of the coating than that of the alloy. In contrast, an intact and dense SiO2-Al2O3-glass coating was successfully prepared from an ASPS-alumina-silica slurry. The oxidation behavior of the SiO2-Al2O3-glass composite coating on Ti-47Al-2Cr-2Nb alloy was studied at 900 °C. The SiO2-Al2O3-glass composite coating acted as an oxygen diffusion barrier, and prevented the inward diffusion of the oxygen from the air to the coating/alloy interface, therefore, decreasing the oxidation rate of the Ti-47Al-2Cr-2Nb alloy significantly.

  4. 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.

  5. Ceramic on ceramic arthroplasty of the hip: new materials confirm appropriate use in young patients.

    Science.gov (United States)

    Sentuerk, U; von Roth, P; Perka, C

    2016-01-01

    The leading indication for revision total hip arthroplasty (THA) remains aseptic loosening owing to wear. The younger, more active patients currently undergoing THA present unprecedented demands on the bearings. Ceramic-on-ceramic (CoC) bearings have consistently shown the lowest rates of wear. The recent advances, especially involving alumina/zirconia composite ceramic, have led to substantial improvements and good results in vitro. Alumina/zirconia composite ceramics are extremely hard, scratch resistant and biocompatible. They offer a low co-efficient of friction and superior lubrication and lower rates of wear compared with other bearings. The major disadvantage is the risk of fracture of the ceramic. The new composite ceramic has reduced the risk of fracture of the femoral head to 0.002%. The risk of fracture of the liner is slightly higher (0.02%). Assuming that the components are introduced without impingement, CoC bearings have major advantages over other bearings. Owing to the superior hardness, they produce less third body wear and are less vulnerable to intra-operative damage. The improved tribology means that CoC bearings are an excellent choice for young, active patients requiring THA. ©2016 The British Editorial Society of Bone & Joint Surgery.

  6. Advanced ceramics reinforced with carbon nanotubes for ballistic application

    International Nuclear Information System (INIS)

    Couto, Carlos Alberto de Oliveira; Passador, Fabio Roberto

    2016-01-01

    Full text: The carbon nanotubes have excellent mechanical properties, the elastic modulus is around 1TPa, next to the diamond and the mechanical strength is 10 to 100 times higher than steel, moreover they are self-lubricating, which facilitates the ceramic composites compression process. The insertion of carbon nanotubes tends to improve the fracture toughness of ceramic composites, but is necessary to obtain a good dispersion in the ceramic matrix. The objective of this work is to develop a tough and tenacious ceramics for ballistic application, using structural ceramics of alumina and tetragonal zirconia and evaluate the influence of the addition of carbon nanotubes (multilayer) on the mechanical properties of the composite. The carbon nanotubes were functionalized with carboxylic groups by nitric acid oxidation reaction. To ensure a homogeneous distribution of the carbon nanotubes in the matrix of alumina/zirconia, surfactants were used: sodium dodecyl sulphate + gum arabic in the amount of 50% by mass of carbon nanotubes. Ceramic powders were prepared with pure alumina and alumina + 20% by mass of tetragonal zirconia/yttria, with and without addition of carbon nanotubes at concentrations of 0.1 and 0.5% by mass. The samples were uniaxially and isostatically pressed at 300 MPa and sintered in a conventional oven at 1500 °C for two hours and a heating rate of 5 °C/min, aimed at commercial application. The morphology of ceramic powders were characterized by SEM and XRD. The mechanical properties of the sintered samples were evaluated by flexural bending at three points, Vickers microhardness and fracture toughness by single edge-notched beam (SENB). The use of carbon nanotubes in the ceramic composite caused a decrease in hardness and an increase in fracture toughness, with great potential for ballistic applications. (author)

  7. Advanced ceramics reinforced with carbon nanotubes for ballistic application

    Energy Technology Data Exchange (ETDEWEB)

    Couto, Carlos Alberto de Oliveira; Passador, Fabio Roberto, E-mail: carlos.couto.sjc@gmail.com [Universidade Federal de Sao Paulo (UNIFESP), Sao Jose dos Campos, SP (Brazil)

    2016-07-01

    Full text: The carbon nanotubes have excellent mechanical properties, the elastic modulus is around 1TPa, next to the diamond and the mechanical strength is 10 to 100 times higher than steel, moreover they are self-lubricating, which facilitates the ceramic composites compression process. The insertion of carbon nanotubes tends to improve the fracture toughness of ceramic composites, but is necessary to obtain a good dispersion in the ceramic matrix. The objective of this work is to develop a tough and tenacious ceramics for ballistic application, using structural ceramics of alumina and tetragonal zirconia and evaluate the influence of the addition of carbon nanotubes (multilayer) on the mechanical properties of the composite. The carbon nanotubes were functionalized with carboxylic groups by nitric acid oxidation reaction. To ensure a homogeneous distribution of the carbon nanotubes in the matrix of alumina/zirconia, surfactants were used: sodium dodecyl sulphate + gum arabic in the amount of 50% by mass of carbon nanotubes. Ceramic powders were prepared with pure alumina and alumina + 20% by mass of tetragonal zirconia/yttria, with and without addition of carbon nanotubes at concentrations of 0.1 and 0.5% by mass. The samples were uniaxially and isostatically pressed at 300 MPa and sintered in a conventional oven at 1500 °C for two hours and a heating rate of 5 °C/min, aimed at commercial application. The morphology of ceramic powders were characterized by SEM and XRD. The mechanical properties of the sintered samples were evaluated by flexural bending at three points, Vickers microhardness and fracture toughness by single edge-notched beam (SENB). The use of carbon nanotubes in the ceramic composite caused a decrease in hardness and an increase in fracture toughness, with great potential for ballistic applications. (author)

  8. Fabrication and characterization of fine ceramic based on alumina, bentonite, and glass bead

    Science.gov (United States)

    Sebayang, P.; Nurdina; Simbolon, S.; Kurniawan, C.; Yunus, M.; Setiadi, E. A.; Sitorus, Z.

    2018-03-01

    Fabrication of fine ceramics based on alumina, bentonite and glass bead has been carried out by powder metallurgy. The preparation of powder has been performed using High Energy Milling (HEM) with wet milling process and using toluene as medium for 2 hours. The powder milling result was dried in oven at 100 °C for 24 hours. After that, the powder was compacted into pellet by using hydraulic press with 80 kgf/cm2 pressure at room temperature. Then, the pellet was sintered at 900 °C for 4 hours. Materials characterization such as physical properties (true density, bulk density, porosity, and water absorption), average particle diameter, hardness, microstructure and phase were measured by Archimedes method, Particle Size Analyzer (PSA), Hardness Vickers (HV), Scanning Electron Microscope (SEM-EDX) and X-Ray Diffraction (XRD). From the result, the optimum condition is sample D (with addition of 30 wt.% γ-Al2O3) with sintering temperature of 900 °C for 4 hours. At this condition, these properties were measured: average particle diameter of 4.27 μm, true density of 2.32 g/cm3, porosity of 5.57%, water absorption of 2.46%, bulk density of 2.39 g/cm3, and hardness of 632 HV. The fine ceramic has four phases with albite (Al2NaO8Si3) and quartz (SiO2) as dominant phases and corundum (Al2O3) and nepheline (AlNaO4Si) as minor phases.

  9. Transmission Electron Microscopy Specimen Preparation Method for Multiphase Porous Functional Ceramics

    DEFF Research Database (Denmark)

    Zhang, Wei; Kuhn, Luise Theil; Jørgensen, Peter Stanley

    2013-01-01

    An optimum method is proposed to prepare thin foil transmission electron microscopy (TEM) lamellae of multiphase porous functional ceramics: prefilling the pore space of these materials with an epoxy resin prior to focused ion beam milling. Several advantages of epoxy impregnation are demonstrated...... by successful preparation of TEM specimens that maintain the structural integrity of the entire lamella. Feasibility of the TEM alignment procedure is demonstrated, and ideal TEM analyses are illustrated on solid oxide fuel cell and solid oxide electrolysis cell materials. Some potential drawbacks of the TEM...

  10. A combined SEM, CV and EIS study of multi-layered porous ceramic reactors for flue gas purification

    DEFF Research Database (Denmark)

    He, Zeming; Andersen, Kjeld Bøhm; Nygaard, Frederik Berg

    2013-01-01

    The effect of sintering temperature of 12-layered porous ceramic reactors (comprising 5 cells) was studied using scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The difference in microstructures of the reactors was evaluated by SEM...

  11. 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

  12. Forming of superplastic ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Lesuer, D.R.; Wadsworth, J.; Nieh, T.G.

    1994-05-01

    Superplasticity in ceramics has now advanced to the stage that technologically viable superplastic deformation processing can be performed. In this paper, examples of superplastic forming and diffusion bonding of ceramic components are given. Recent work in biaxial gas-pressure forming of several ceramics is provided. These include yttria-stabilized, tetragonal zirconia (YTZP), a 20% alumina/YTZP composite, and silicon. In addition, the concurrent superplastic forming and diffusion bonding of a hybrid ceramic-metal structure are presented. These forming processes offer technological advantages of greater dimensional control and increased variety and complexity of shapes than is possible with conventional ceramic shaping technology.

  13. Microwave performance of photoresist-alumina microcomposites for batch fabrication of thick polymer-based dielectric structures

    International Nuclear Information System (INIS)

    Rashidian, Atabak; Klymyshyn, David M; Aligodarz, Mohammadreza Tayfeh; Boerner, Martin; Mohr, Jürgen

    2012-01-01

    The goal of this paper is to investigate the electrical properties of photoresist-alumina microcomposites with different portions of ceramic content. Substrates of photoresist-alumina microcomposites are fabricated and a comprehensive analysis is performed to characterize their dielectric constant and dielectric loss tangent at microwave frequencies up to 40 GHz. To evaluate the performance of these materials for microwave applications, the properties of various lithographically fabricated antenna elements are examined and analysed based on the measured electrical properties. The experimental results show that the electrical properties of the photoresist composite are nonlinearly affected by ceramic content and also a minimum percentage of ceramic portion is required to improve the electrical properties of the photoresist composite. For instance, comparison of 0 wt% with 23 wt% SU8-alumina shows that no reduction is achieved for the dielectric loss tangent. Comparison of 38 wt% with 48 wt% SU8-alumina microcomposite shows that the dielectric loss tangent is improved from 0.03 to 0.01 and the dielectric constant is increased from 3.8 to 5.0 at 25 GHz. These improvements can result in superior performance for the photoresist-based microwave components. (paper)

  14. Microwave performance of photoresist-alumina microcomposites for batch fabrication of thick polymer-based dielectric structures

    Science.gov (United States)

    Rashidian, Atabak; Klymyshyn, David M.; Tayfeh Aligodarz, Mohammadreza; Boerner, Martin; Mohr, Jürgen

    2012-10-01

    The goal of this paper is to investigate the electrical properties of photoresist-alumina microcomposites with different portions of ceramic content. Substrates of photoresist-alumina microcomposites are fabricated and a comprehensive analysis is performed to characterize their dielectric constant and dielectric loss tangent at microwave frequencies up to 40 GHz. To evaluate the performance of these materials for microwave applications, the properties of various lithographically fabricated antenna elements are examined and analysed based on the measured electrical properties. The experimental results show that the electrical properties of the photoresist composite are nonlinearly affected by ceramic content and also a minimum percentage of ceramic portion is required to improve the electrical properties of the photoresist composite. For instance, comparison of 0 wt% with 23 wt% SU8-alumina shows that no reduction is achieved for the dielectric loss tangent. Comparison of 38 wt% with 48 wt% SU8-alumina microcomposite shows that the dielectric loss tangent is improved from 0.03 to 0.01 and the dielectric constant is increased from 3.8 to 5.0 at 25 GHz. These improvements can result in superior performance for the photoresist-based microwave components.

  15. Formation of Flower-Like Crystals of Tris(8-hydroxyquinolinealuminum from 8-Hydroxyquinoline on Anodic Porous Alumina

    Directory of Open Access Journals (Sweden)

    Shohei Yamaguchi

    2017-01-01

    Full Text Available The treatment of anodic porous alumina (APA plates in heated water containing 8-hydroxyquinoline (HQ produces crystalline tris(8-hydroxyquinolinealuminum (Alq3 microbelts about 5–10 μm wide and 5–20 μm long. These microbelts were found to aggregate to form flower-like structures on the surface. X-ray diffraction studies indicated that the Alq3 microbelts are composed of an α-phase having a meridional structure. The Alq3 microbelts exhibited green photoluminescence with a peak at around 520 nm. Scanning electron microscope images and energy dispersive X-ray spectra showed that this reaction is induced at the APA surface by the reaction between the HQ and amorphous Al2O3 species.

  16. Preparation of porous ceramics from nanocrystalline zirconia and its microstructure

    International Nuclear Information System (INIS)

    Nikitin, D.S.; Zhukov, V.A.; Kul'kov, S.N.; Perkov, V.V.; Buyakova, S.P.

    2004-01-01

    The behaviour of ZrO 2 (Y) nanocrystalline powder under pressing, the effect of forming pressure, the temperature and the time of sintering on the structure of the sintered porous ceramics are under study. It is shown that on pressing the fracturing of powder particles and their agglomerates takes place even at low pressures (≅50 MPa). The change of densification mechanisms is revealed - from quasi-liquid displacement of powder particles at the beginning of mechanical action to fracture of coarse structural elements. It is established that a strong skeleton responsible for needed porosity is formed even at the initial stage of sintering [ru

  17. Large ceramics for fusion applications

    International Nuclear Information System (INIS)

    Hauth, W.E.; Stoddard, S.D.

    1979-01-01

    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. Ceramic-to-ceramic sealing has applications for several technologies that require large and/or complex vacuum-tight ceramic shapes. Information is provided concerning the assembly of complex monolithic ceramic shapes by bonding of subassemblies at temperatures ranging from 450 to 1500 0 C. Future applications and fabrication techniques for various materials are presented

  18. 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.

  19. 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.

  20. 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.

  1. Multiscale Simulation of Porous Ceramics Based on Movable Cellular Automaton Method

    Science.gov (United States)

    Smolin, A.; Smolin, I.; Eremina, G.; Smolina, I.

    2017-10-01

    The paper presents a model for simulating mechanical behaviour of multiscale porous ceramics based on movable cellular automaton method, which is a novel particle method in computational mechanics of solid. The initial scale of the proposed approach corresponds to the characteristic size of the smallest pores in the ceramics. At this scale, we model uniaxial compression of several representative samples with an explicit account of pores of the same size but with the random unique position in space. As a result, we get the average values of Young’s modulus and strength, as well as the parameters of the Weibull distribution of these properties at the current scale level. These data allow us to describe the material behaviour at the next scale level were only the larger pores are considered explicitly, while the influence of small pores is included via the effective properties determined at the previous scale level. If the pore size distribution function of the material has N maxima we need to perform computations for N - 1 levels in order to get the properties from the lowest scale up to the macroscale step by step. The proposed approach was applied to modelling zirconia ceramics with bimodal pore size distribution. The obtained results show correct behaviour of the model sample at the macroscale.

  2. Radiation degradation in the mechanical properties of Polyetheretherketone–alumina composites

    International Nuclear Information System (INIS)

    Lawrence, Falix; Mallika, C.; Kamachi Mudali, U.; Natarajan, R.; Ponraju, D.; Seshadri, S.K.; Sampath Kumar, T.S.

    2012-01-01

    Polyetheretherketone (PEEK) is extensively employed in corrosive and radiation environments. To improve the radiation tolerance of PEEK in the presence of high energetic radiation, PEEK was reinforced with micron sized alumina powder (5–25% by weight) and PEEK–alumina composite sheets fabricated were irradiated to 10 MGy. Mechanical properties of the irradiated composites revealed significant reduction in the degradation of PEEK with addition of alumina as the polymer reinforced with ceramic additives is expected to increase the interface area of the constituents in the system resulting in an improvement in the performance of the reinforced material.

  3. Interface mechanics and histomorphometric analysis of hydroxyapatite-coated and porous glass-ceramic implants in canine bone

    DEFF Research Database (Denmark)

    Nimb, L; Jensen, J S; Gotfredsen, K

    1995-01-01

    A canine study was performed to make a histological and biomechanical evaluation of the interface between bone and two different bioceramic implants. A newly developed glass-ceramic formed by P2O5, CaO, SiO2, and Al2O3, giving a crystal phase composed of CaP2O6-AlPO4-SiP2O7, was compared...... analysis. The ultimate shear strength for the HA-coated implants was significantly higher than in the glass-ceramic group. When these values were related to the histomorphometric measurements, the difference could be explained by the tissue-to-implant contact. The glass-ceramic showed direct contact only...... with nonmineralized, osteoid bone. The HA-coated implants, however, were integrated into the bone. The study indicated that porous glass-ceramic containing AlPO4 causes local osteomalacia and might not be suitable for clinical purposes....

  4. Porous ZrO_2-TiO_2 ceramics for applications as sensing elements in the air humidity monitoring

    International Nuclear Information System (INIS)

    Oliveira, Rodrigo de Matos; Nono, Maria do Carmo de Andrade

    2011-01-01

    The environmental monitoring requires versatile, reliable and lower cost instruments. The chemical superficial absorption/adsorption capability of water molecules by several ceramic oxides makes them excellent candidates for this application. In this way, many efforts have been made for the development of porous ceramics, manufactured from mechanical mixture of ZrO_2 and TiO_2 powders, for application as air humidity sensing elements. The sintered ceramics were characterized as for crystalline phases (X-ray diffraction) and pores structure (scanning electron microscopy and mercury porosimetry). The relative humidity curves for the ceramics were obtained from measurements with RLC bridge in climatic chamber. The behavior of these curves were comparatively analyzed with the aid of pores sizes distribution curves, obtained through mercury porosimetry. The results evidenced that the air humidity ceramic sensing elements are very promising ones. (author)

  5. Ion conductivity of nasicon ceramics

    International Nuclear Information System (INIS)

    Hoj, J.W.; Engell, J.

    1989-01-01

    The Nasicon ss ,Na 1 + X Zr 2 Si X P 3 - X O 12 o , X , 3, includes some of the best solid state sodium conductors known today. Compositions in the interval 1.6 , X , 2.6 show conductivities comparable to the best β double-prime-alumina ceramics. It is well known that the ion conductivity of β-alumina is strongly dependent on the texture of the ceramic. Here a similar behavior is reported for Nasicon ceramics. Ceramics of the bulk composition Na 2.94 Zr 1.49 Si 2.20 P 0.80 O 10.85 were prepared by a gel method. The final ceramics consist of Nasicon crystals with x = 2.14 and a glass phase. The grain size and texture of the ceramics were controlled by varying the thermal history of the gel based raw materials and the sintering conditions. The room temperature resistivity of the resulting ceramics varies from 3.65*10 3 ohm cm to 1.23*10 3 ohm cm. Using the temperature comparison method and estimates of the area of grain boundaries in the ceramics, the resistivity of the Nasicon phase is estimated to be 225 ohm cm at 25 degrees C. B 2 O 3 - or Al 2 O 3 -doping of the glass bearing Nasicon ceramic lower the room temperature resistivity by a factor 2 to 5. The dopants do not substitute into the Nasicon phase in substantial amounts

  6. Influence of Material Properties on the Ballistic Performance of Ceramics for Personal Body Armour

    OpenAIRE

    Kaufmann, Christian; Cronin, Duane; Worswick, Michael; Pageau, Gilles; Beth, Andre

    2003-01-01

    In support of improved personal armour development, depth of penetration tests have been conducted on four different ceramic materials including alumina, modified alumina, silicon carbide and boron carbide. These experiments consisted of impacting ceramic tiles bonded to aluminum cylinders with 0.50 caliber armour piercing projectiles. The results are presented in terms of ballistic efficiency, and the validity of using ballistic efficiency as a measure of ceramic performance was examined. In...

  7. Numerical simulation of diametral compression tests for the evaluation of porous ceramic disks; Simulacion numerica de ensayos de compresion diametral para la evaluacion de discos ceramicos porosos

    Energy Technology Data Exchange (ETDEWEB)

    Sandoval, M. L.; Tomba Martinez, A. G.; Camerucci, M. A.

    2012-11-01

    The mechanical behavior of porous cordierite materials was studied by diametral compression tests. The analytical solution allowing the indirect measuring of the tensile mechanical strength in this load configuration is formulated under certain assumption which may be not satisfied in practice. With the aim to analyze deviations of the ideal conditions, the test was simulated using computational techniques. Porous cordierite disks were prepared by firing (650 degree centigrade, 2h) and reaction-sintering (1330 degree centigrade, 4h) of green disks shaped by thermo gelling the aqueous suspensions of a cordierite precursor mixture (kaolin, talc and alumina) with native potato starch as a consolidator/binder of ceramic particles and a pore former by burn-out at high temperature. The mechanical tests were carried out in displacement control (0.2 mm/min) using a servo hydraulic testing machine. From the apparent stress-strain ratio, the following parameters were determined: mechanical strength, apparent Young modulus and yield stress. Fracture features of tested disks were also analyzed. The influence of the geometrical deviations more usually identified in practice (deviation of the circularity and no parallelism between the plane surfaces of the disk) on the stress distribution was studied by means of the simulation by finite element method, considering the Hertzs equation for contact problems as reference. (Author) 20 refs.

  8. Composite reinforced alumina ceramics with titan and lantana for use in coating storage tanks and transport of crude oil; Composito de ceramica alumina reforcada com titania e lantana para a utilizacao em revestimento de tanques de armazenamento e transporte de petroleo cru

    Energy Technology Data Exchange (ETDEWEB)

    Mendes, C.E.; Rego, S.A.B.C.; Oliveira, J.C.S.; Ferreira, R.A. Sanguinetti; Yadava, Y.P., E-mail: cata_esposito@hotmail.com [Universidade Federal de Pernambuco (UFPE), PE (Brazil). Centro de Tecnologia e Geociencia. Departamento de Engenharia Mecanica

    2011-07-01

    The objective of this work is to use ceramics to improve the performance of the tanks that store and transport crude oil and which use metallic materials for their manufacture. These tanks in contact with crude oil undergo a process of degradation on their surfaces, since crude oil is a highly corrosive substance. And in turn ceramic materials have good stability in hostile environments. However, they are inherently fragile for display little plastic deformation. Therefore, the choice of a ceramic composite alumina-titania-lantana has high mechanical strength and high toughness which were produced by thermo-mechanical processing. These composites were sintered at 1350 ° C for 36 hours, and it was held Vickers hardness testing and microstructural characterization to assess their surfaces before and after the attack by crude to use such material as ceramic coating. These results will be presented at the congress. (author)

  9. Combinatorial Production and Processing of Oxide Nanopowders for Transparent, Ceramic Lasers

    National Research Council Canada - National Science Library

    Laine, Richard M; Rand, Stephen C

    2007-01-01

    Since the discovery of transparent polycrystalline alumina by Coble in 1962, transparent and translucent alumina and yttria based ceramics have achieved a significant presence in our everyday lives...

  10. Formation of nanocomposite alumina-zirconia-silica ceramics

    Czech Academy of Sciences Publication Activity Database

    Chráska, Tomáš; Klementová, Mariana; Hostomský, Jiří

    2007-01-01

    Roč. 52, č. 4 (2007), s. 331-341 ISSN 0001-7043 R&D Projects: GA AV ČR KAN300430651 Institutional research plan: CEZ:AV0Z20430508; CEZ:AV0Z40320502 Keywords : TEM * sample preparation * plasma spraying * ceramic s Subject RIV: JH - Ceramic s, Fire-Resistant Materials and Glass

  11. Interfacial characterization of ceramic core materials with veneering porcelain for all-ceramic bi-layered restorative systems.

    Science.gov (United States)

    Tagmatarchis, Alexander; Tripodakis, Aris-Petros; Filippatos, Gerasimos; Zinelis, Spiros; Eliades, George

    2014-01-01

    The aim of the study was to characterize the elemental distribution at the interface between all-ceramic core and veneering porcelain materials. Three groups of all-ceramic cores were selected: A) Glass-ceramics (Cergo, IPS Empress, IPS Empress 2, e-max Press, Finesse); B) Glass-infiltrated ceramics (Celay Alumina, Celay Zirconia) and C) Densely sintered ceramics (Cercon, Procera Alumina, ZirCAD, Noritake Zirconia). The cores were combined with compatible veneering porcelains and three flat square test specimens were produced for each system. The core-veneer interfaces were examined by scanning electron microscopy and energy dispersive x-ray microanalysis. The glass-ceramic systems showed interfacial zones reach in Si and O, with the presence of K, Ca, Al in core and Ca, Ce, Na, Mg or Al in veneer material, depending on the system tested. IPS Empress and IPS Empress 2 demonstrated distinct transitional phases at the core-veneer interface. In the glassinfiltrated systems, intermixing of core (Ce, La) with veneer (Na, Si) elements occurred, whereas an abrupt drop of the core-veneer elemental concentration was documented at the interfaces of all densely sintered ceramics. The results of the study provided no evidence of elemental interdiffusion at the core-veneer interfaces in densely sintered ceramics, which implies lack of primary chemical bonding. For the glass-containing systems (glassceramics and glass-infiltrated ceramics) interdiffusion of the glass-phase seems to play a critical role in establishing a primary bonding condition between ceramic core and veneering porcelain.

  12. Morphological and Structural Study of a Novel Porous Nurse’s A Ceramic with Osteoconductive Properties for Tissue Engineering

    Directory of Open Access Journals (Sweden)

    Ruben Rabadan-Ros

    2016-06-01

    Full Text Available The characterization process of a new porous Nurse’s A ceramic and the physico chemical nature of the remodeled interface between the implant and the surrounding bone were studied after in vivo implantation. Scaffolds were prepared by a solid-state reaction and implanted in New Zealand rabbits. Animals were sacrificed on days 15, 30, and 60. The porous biomaterial displayed biocompatible, bioresorbable, and osteoconductive capacity. The degradation processes of implants also encouraged osseous tissue ingrowths into the material’s pores, and drastically changed the macro- and microstructure of the implants. After 60 healing days, the resorption rates were 52.62% ± 1.12% for the ceramic and 47.38% ± 1.24% for the residual biomaterial. The elemental analysis showed a gradual diffusion of the Ca and Si ions from the materials into the newly forming bone during the biomaterial’s resorption process. The energy dispersive spectroscopy (EDS analysis of the residual ceramic revealed some particle categories with different mean Ca/P ratios according to size, and indicated various resorption process stages. Since osteoconductive capacity was indicated for this material and bone ingrowth was possible, it could be applied to progressively substitute an implant.

  13. Joining Dental Ceramic Layers With Glass

    Science.gov (United States)

    Saied, MA; Lloyd, IK; Haller, WK; Lawn, BR

    2011-01-01

    Objective Test the hypothesis that glass-bonding of free-form veneer and core ceramic layers can produce robust interfaces, chemically durable and aesthetic in appearance and, above all, resistant to delamination. Methods Layers of independently produced porcelains (NobelRondo™ Press porcelain, Nobel BioCare AB and Sagkura Interaction porcelain, Elephant Dental) and matching alumina or zirconia core ceramics (Procera alumina, Nobel BioCare AB, BioZyram yttria stabilized tetragonal zirconia polycrystal, Cyrtina Dental) were joined with designed glasses, tailored to match thermal expansion coefficients of the components and free of toxic elements. Scanning electron microprobe analysis was used to characterize the chemistry of the joined interfaces, specifically to confirm interdiffusion of ions. Vickers indentations were used to drive controlled corner cracks into the glass interlayers to evaluate the toughness of the interfaces. Results The glass-bonded interfaces were found to have robust integrity relative to interfaces fused without glass, or those fused with a resin-based adhesive. Significance The structural integrity of the interfaces between porcelain veneers and alumina or zirconia cores is a critical factor in the longevity of all-ceramic dental crowns and fixed dental prostheses. PMID:21802131

  14. 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.

  15. Wonderland of ceramics superplasticity; Ceramics chososei no sekai

    Energy Technology Data Exchange (ETDEWEB)

    Wakai, F. [National Industrial Research Inst. of Nagoya, Nagoya (Japan)

    1995-07-01

    It has been ten years since it was found that ceramics, which is strong and hard at room temperatures and does not deform at all, may exhibit a superplasticity phenomenon at high temperatures that it endlessly elongates when pulled as if it were chewing gum. This phenomenon is one of peculiar behaviours which nano-crystal ceramics, pulverized to an extent that the crystalline particle size is on the order of nanometers, show. The application of superplasticity made the material engineers`s old dream come true that hard ceramics are arbitrarily deformed and machined like metal. Using as models materials such as silicone nitride, alumina and zirconia, this paper describes the history and deformation mechanism of ceramics superplasticity, material design aiming at superplasticization and application of ceramics superplasticity to the machining technology. Furthermore, it describes the trend and future development of international joint researches on the basic surveys on ceramics superplasticity. 25 refs., 11 figs.

  16. Ultrasonic technique for measuring porosity of plasma-sprayed alumina coatings

    Science.gov (United States)

    Parthasarathi, S.; Tittmann, B. R.; Onesto, E. J.

    1997-12-01

    Porosity is an important factor in plasma-sprayed coatings, especially ceramic coatings. Excessive poros-ity can adversely affect the performance of the coated component in various ways. An ultrasonic nonde-structive measurement technique has been developed to measure porosity in plasma-sprayed alumina coatings. The technique is generic and can be extended to other ceramic coating systems. To test the tech-nique, freestanding alumina coatings with varying levels of porosity were fabricated via plasma spray. Samples with varying porosity, obtained through innovative fabrication techniques, were used to gener-ate a calibration curve. The ultrasonic velocity in the low-frequency range was found to be dependent on the density of freestanding coatings (measured via Archimedian techniques). This dependence is the basis of the development of a technique to measure the density of coatings.

  17. Ceramic nanostructures and methods of fabrication

    Science.gov (United States)

    Ripley, Edward B [Knoxville, TN; Seals, Roland D [Oak Ridge, TN; Morrell, Jonathan S [Knoxville, TN

    2009-11-24

    Structures and methods for the fabrication of ceramic nanostructures. Structures include metal particles, preferably comprising copper, disposed on a ceramic substrate. The structures are heated, preferably in the presence of microwaves, to a temperature that softens the metal particles and preferably forms a pool of molten ceramic under the softened metal particle. A nano-generator is created wherein ceramic material diffuses through the molten particle and forms ceramic nanostructures on a polar site of the metal particle. The nanostructures may comprise silica, alumina, titania, or compounds or mixtures thereof.

  18. Synthesis and characterization of biomorphic ceramics; Sintese e caracterizacao de ceramicas biomorficas

    Energy Technology Data Exchange (ETDEWEB)

    Rambo, Carlos Renato

    2001-07-01

    Biotemplating represents a recently developed technology for manufacturing of biomorphous ceramics from naturally grown plant structures. This approach allows the production of ceramic materials with cellular structure, where the microstructural features of the ceramic product are similar to the native plant. After processing, the biomorphic ceramic exhibits directed pore morphology in the micrometer range. Biomorphic SiC fibers were produced from bamboo by carbothermal reduction of SiO{sub 2} originally present in the bamboo structure. Bamboo pieces were heated up to 1500 deg C in argon to promote the reaction between carbon and silica. Biomorphic alumina, mullite and zirconia ceramics were manufactured via the sol-gel route by repeated infiltration of low viscous oxide precursors (sols) into rattan, pine and bamboo structures. The raw samples were pyrolyzed at 800 deg C in nitrogen for 1h and subsequently annealed at 1550 deg C in air. The microstructure and physical properties of the biomorphic ceramics were characterized by X-ray diffraction (XRD) and high temperature-XRD, scanning electron microscopy (SEM), porosimetry and picnometry. Thermal analysis (TGA/DTA) was performed on the infiltrated samples in order to evaluate the reactions and the total weight loss during the thermal process. The mechanical properties were evaluated by compressive strength tests. In contrast to conventional processed ceramic foam of similar porosity, the microstructure highly porous biomorphic ceramics shows uniaxial pore morphology with anisotropic properties. These properties are favorable for applications in catalyst support, filters or low-density heat insulation structures, or as biomaterials. (author)

  19. Thermal Response of Whipox-Type All-Oxide Ceramic Matrix Composites during Reentry Simulation in the Dlr-Lbk Arc-Heated Facility

    Science.gov (United States)

    Mechnich, P.; Braue, W.; Schneider, H.; Koch, U.; Esser, B.; Gülhan, A.

    2005-02-01

    All-oxide ceramic matrix composites (CMCs) such as WHIPOXTM (wound highly porous oxide) exhibit excellent damage tolerance and thermal stability up to 1400°C. Due to their low density and thermal conductivity these new ceramic materials are considered promising candidates for thermal protection systems (TPS) of spacecrafts. The performance of WHIPOX-type CMCs was evaluated during reentry simulations in the L2K leg of the arc-heated LBK facility of DLR, Cologne. The application of reaction-bonded alumina (RBAO) coatings provides significant CMC surface protection and decreased gas permeability, which are key issues for reentry applications. Since emittance and catalycity of the RBAO-coatings limit the performance of CMCs in a reentry environment, binary SiC/RBAO coatings providing higher emittance and/or lower catalycity proved to be a promising approach.

  20. 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.

  1. Ceramic injection molding

    International Nuclear Information System (INIS)

    Agueda, Horacio; Russo, Diego

    1988-01-01

    Interest in making complex net-shape ceramic parts with good surface finishing and sharp tolerances without machining is a driving force for studying the injection molding technique. This method consists of softhening the ceramic material by means of adding some plastic and heating in order to inject the mixture under pressure into a relatively cold mold where solidification takes place. Essentially, it is the same process used in thermoplastic industry but, in the present case, the ceramic powder load ranges between 80 to 90 wt.%. This work shows results obtained from the fabrication of pieces of different ceramic materials (alumina, barium titanate ferrites, etc.) in a small scale, using equipments developed and constructed in the laboratory. (Author) [es

  2. 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.

  3. Deformation of a dental ceramic following adhesive cementation.

    LENUS (Irish Health Repository)

    2010-01-01

    Stress-induced changes imparted in a \\'dentin-bonded-crown\\' material during sintering, annealing, pre-cementation surface modification, and resin coating have been visualized by profilometry. The hypothesis tested was that operative techniques modify the stressing pattern throughout the material thickness. We polished the upper surfaces of 10 ceramic discs to remove surface imperfections before using a contact profilometer (40-nm resolution) to measure the \\'flatness\\'. Discs were re-profiled after annealing and after alumina particle air-abrasion and resin-coating of the \\'fit\\' surface. Polished surfaces were convex, with a mean deflection of 8.4 + or - 1.5 microm. Mean deflection was significantly reduced (P = 0.029) following alumina particle air-abrasion and increased (P < 0.001) on resin-coating. Polishing induced a tensile stress state, resulting in surface convexity. Alumina particle air-abrasion reduced the relative tensile stress state of the contralateral polished surface. Resin-polymerization generated compression within the resin-ceramic \\'hybrid layer\\' and tension in the polished surface and is likely to contribute to the strengthening of ceramics by resin-based cements.

  4. 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

  5. Waste-to-resource preparation of a porous ceramic membrane support featuring elongated mullite whiskers with enhanced porosity and permeance

    NARCIS (Netherlands)

    Zhu, Li; Dong, Yingchao; Hampshire, Stuart; Cerneaux, Sophie; Winnubst, Aloysius J.A.

    2015-01-01

    Different from traditional particle packing structure, a porous structure of ceramic membrane support was fabricated, featuring elongated mullitewhiskers with enhanced porosity, permeance and sufficient mechanical strength. The effect of additives (MoO3and AlF3) and sintering procedureon open

  6. Influence of Material Properties on the Ballistic Performance of Ceramics for Personal Body Armour

    Directory of Open Access Journals (Sweden)

    Christian Kaufmann

    2003-01-01

    Full Text Available In support of improved personal armour development, depth of penetration tests have been conducted on four different ceramic materials including alumina, modified alumina, silicon carbide and boron carbide. These experiments consisted of impacting ceramic tiles bonded to aluminum cylinders with 0.50 caliber armour piercing projectiles. The results are presented in terms of ballistic efficiency, and the validity of using ballistic efficiency as a measure of ceramic performance was examined. In addition, the correlation between ballistic performance and ceramic material properties, such as elastic modulus, hardness, spall strength and Hugoniot Elastic Limit, has been considered.

  7. Defect production in ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Zinkle, S.J. [Oak Ridge National Lab., TN (United States); Kinoshita, C. [Kyushu Univ. (Japan)

    1997-08-01

    A review is given of several important defect production and accumulation parameters for irradiated ceramics. Materials covered in this review include alumina, magnesia, spinel silicon carbide, silicon nitride, aluminum nitride and diamond. Whereas threshold displacement energies for many ceramics are known within a reasonable level of uncertainty (with notable exceptions being AIN and Si{sub 3}N{sub 4}), relatively little information exists on the equally important parameters of surviving defect fraction (defect production efficiency) and point defect migration energies for most ceramics. Very little fundamental displacement damage information is available for nitride ceramics. The role of subthreshold irradiation on defect migration and microstructural evolution is also briefly discussed.

  8. A review on chemical methodologies for preparation of mesoporous silica and alumina based materials.

    Science.gov (United States)

    Naik, Bhanudas; Ghosh, Narendra Nath

    2009-01-01

    The discovery of novel family of molecular sieves called M41S aroused a worldwide resurgence in the field of porous materials. According to IUPAC definition inorganic solids that contain pores with diameter in the size range of 20-500 A are considered mesoporous materials. Mesoporous silica and alumina based materials find applications in catalysis, adsorption, host- guest encapsulation etc. This article reviews the current state of art and outline the recent patents in mesoporous materials research in three general areas: Synthesis, various mechanisms involved for porous structure formation and applications of silica and alumina based mesoporous materials.

  9. Report on achievements in fiscal 1999. Research and development of synergy ceramics (research and development of technologies to prevent corrosion in petroleum production systems); 1999 nendo synergy ceramics no kenkyu kaihatsu seika hokokusho. Sekiyu seisan system fushoku boshi gijutsu kenkyu kaihatsu

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2000-03-01

    This research and development has been performed on the following themes: 1. Material realizing technology, and advanced evaluation and design technology (1-(1) ultra precision materials, 1-(2) high-temperature energy materials, 1-(3) basic member design technology, 1-(4) materials having function to detect stresses and micro destruction, 1-(5) porous materials to control gas hole patterns, and 1-(6) materials having self-restoring/self-lubricating function); 2. Application technology (2-(1) materials having substance and light selecting function, 2-(2) high wear resistant and easy-to-process materials, 2-(3) high-performance resistance materials for electric power devices, and 2-(4) flexible sliding materials); 3. Formation of common base technologies. 4. Report on achievements in countries making joint researches. In Item 1-(1), micro destruction mechanisms were analyzed, and the directionality of material structure control was clarified. In Item 1-(2), controlled closing holes were introduced. In Item 1-(3), polycrystalline alumina, polycrystalline zirconia, and zirconia particle dispersed alumina were evaluated microscopically and macroscopically. In Item (4), Y-TZP/Ni nano-compound materials were fabricated successfully. In Item 1-(5), destruction behavior of porous ceramics was studied. In Item 1-(6), characteristics were investigated on Fe(Al)Al2O3 which was fabricated on the trial basis. (NEDO)

  10. A method for the densification of ceramic layers, especially ceramic layers within solid oxide cell (SOC) technology, and products obtained by the method

    DEFF Research Database (Denmark)

    2013-01-01

    A ceramic layer, especially for use in solid oxide cell (SOC) technology, is densified in a method comprising (a) providing a multilayer system by depositing the porous ceramic layer, which is to be densified, onto the selected system of ceramic layers on a support, (b) pre-sintering the resulting......(s) in the porous layer surface and (e) performing a thermal treatment at a temperature T2, where T2 > ?1, to obtain densification of and grain growth in the porous layer formed in step (b). The method makes it possible to obtain dense ceramic layers at temperatures, which are compatible with the other materials...... present in a ceramic multilayer system....

  11. Reaction-sintered porous mineral-based mullite ceramic membrane supports made from recycled materials.

    Science.gov (United States)

    Dong, Yingchao; Zhou, Jian-Er; Lin, Bin; Wang, Yongqing; Wang, Songlin; Miao, Lifeng; Lang, Ying; Liu, Xingqin; Meng, Guangyao

    2009-12-15

    Bulk porous mullite supports for ceramic membranes were prepared directly using a mixture of industrial waste fly ash and bauxite by dry-pressing, followed by sintering between 1200 and 1550 degrees C. The effects of sintering temperature on the phase composition and shrinkage percent of porous mullite were studied. The XRD results indicate that secondary mullitization reaction took place above 1200 degrees C, and completed at 1450 degrees C. During sintering, the mixture samples first shrunk, then expanded abnormally between 1326 and 1477 degrees C, and finally shrunk again above 1477 degrees C. This unique volume self-expansion is ascribed to the secondary mullitization reaction between bauxite and fly ash. More especially, the micro-structural variations induced by this self-expansion sintering were verified by SEM, porosity, pore size distribution and nitrogen gas permeation flux. During self-expansion sintering, with increasing temperature, an abnormal increase in both open porosity and pore size is observed, which also results in the increase of nitrogen gas flux. The mineral-based mullite supports with increased open porosity were obtained. Furthermore, the sintered porous mullite membrane supports were characterized in terms of thermal expansion co-efficient and mechanical strength.

  12. Contribution to the study of porous or very finely divided alumina; Contribution a l'etude des alumines poreuses ou tres finement divisees

    Energy Technology Data Exchange (ETDEWEB)

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

    1961-12-15

    An amorphous porous alumina having a large surface area can be made non-stoichiometric by a treatment at 500 - 700 deg C in a vacuum. The oxygen deficit after a treatment at 500 deg C, and the aluminium deficit after a treatment at 700 deg C, give rise to semiconductor properties successively of type n and of the type p. A crystallized {delta}-alumina in the form of non-porous spherical grains compressed at a pressure of 1 to 5 metric tons/cm{sup 2} is also non-stoichiometric with a deficit of oxygen or of aluminium. None of these phenomena could be observed with a sample which had not been compressed. The favorable influence of oxygen on the recrystallization process of amorphous alumina, and on the {delta}-{alpha}, transformation of crystallized alumina has been demonstrated. Furthermore, the strains produced by the compression of the {delta}-alumina make possible its transformation in air into a at a temperature lower than the temperature necessary to observe this phenomenon with non-compressed {delta}-alumina. Amorphous alumina undergoes an intergranular sintering at 500 deg C and an intergranular sintering at 1 000 deg C. Only the latter occurs in the case of spherical alumina grains. For these, the strains brought about by the compression cause a lowering of 100 deg C in the threshold sintering temperature, with respect to the temperature required to produce the phenomena in a non-compressed sample. The amount of sintering in a crystallized alumina pellet depends, as well, on the rate of rise of temperature. This study tends to show that new properties, or at least unusual solid-state properties, can be observed on disorganised solids or on solids which are crystallized but which have a large surface area and a certain amount of strain. (author) [French] Une alumine poreuse amorphe de grande surface specifique peut etre rendue non-stoechiometrique par traitement sous vide pousse a 500-700 deg C. Le deficit en oxygene apres chauffage a 500 deg C, puis le

  13. Mesoporous Alumina Microfibers In Situ Transformation from AACH Fibers and the Adsorption Performance

    Directory of Open Access Journals (Sweden)

    Xiaoqin Shi

    2014-01-01

    Full Text Available Well-dispersed mesoporous γ-alumina microfibers with high surface were prepared by thermal decomposition of the ammonium aluminum carbonate hydroxide (AACH precursors. The as-synthesized alumina retained the morphology of its precursor and exhibited memory effect. The structural, morphological, porous, and adsorptive properties of the samples were investigated by XRD, FTIR, TGA-DSC, SEM, TEM, and UV-vis spectroscopy. The prepared γ-alumina microfibers exhibited excellent ability to remove organic pollutants from waste water because of their mesoporous structures. The γ-alumina in situ converted from AACH synthesized without surfactant exhibited adsorption ability for Congo red as good as that synthesized with PEG2000 and better than PEG20000 that provided a facile method without surfactant to synthesize γ-alumina with excellent adsorption performance.

  14. Advanced ceramic materials and their potential impact on the future

    International Nuclear Information System (INIS)

    Laren, M.G.M.

    1989-01-01

    This article reviews the types of advanced ceramic materials that are being used today and their potential for even greater utilization in the future. Market analysis and projections have been developed from a number of sources both foreign and domestic are referenced and given in the text. Projection on the future use of advanced ceramics to the year 2000 indicate a potential growth of the total world market approaching 187 billion dollars. This paper describes advanced ceramic materials by their functionality, i.e. structural, electronic, chemical, thermal, biological, nuclear, etc. It also refers to specific engineering uses of advanced ceramics and include automotive ceramic materials with physical data for the most likely ceramic materials to be used for engine parts. This family of materials includes silicon carbides, silicon nitride, partially stabilized zirconia and alumina. Fiber reinforced ceramic composites are discussed with recognition of the research on fiber coating chemistry and the compatibility of the coating with the fiber and the matrix. Another class of advanced ceramics is toughened ceramics. The transformation toughened alumina is recognized as an example of this technology. The data indicate that electronic ceramic materials will always have the largest portion of the advanced ceramic market and the critical concepts of a wide range of uses is reviewed. (Auth.)

  15. The study of the volume expansion of aluminum during porous oxide formation at galvanostatic regime

    Energy Technology Data Exchange (ETDEWEB)

    Vrublevsky, I.; Parkoun, V.; Sokol, V.; Schreckenbach, J.; Marx, G

    2004-01-30

    The volume expansion factor of porous alumina, formed by through anodizing of an Al foil of thickness 11.5 {mu}m in the range of current densities of 4-35 mA cm{sup -2} in oxalic and sulfuric acid at 18-24 deg. C has been studied. The microstructure of anodizing samples has been observed using scanning electron microscopy. The thickness of obtained porous alumina films was measured by a mechanical profilometer with a computer signal-processing. The volume expansion factor of porous alumina varied from 1.35 to 1.65. Linear dependences were obtained for the volume expansion factor of porous alumina versus the anodizing voltage and the ionic current-density logarithm versus the inverse volume expansion factor. Unlike oxide formation in sulfuric acid, these dependences have two subsequential rectilinear regions in oxalic acid. This peculiarity of the dependences in oxalic acid was explained by formation of a region of the immobile negative space charge in the barrier Al oxide layer and its influence on the ionic transport.

  16. Fabrication of low thermal expansion SiC/ZrW{sub 2}O{sub 8} porous ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Poowancum, A; Matsumaru, K; Juarez-Ramirez, I; Ishizaki, K [Department of Mechanical Engineering, Nagaoka University of Technology, 1603-1 Kamitomioka, Nagaoka, Niigata 940-2188 (Japan); Torres-Martinez, L M [Universidad Autonoma de Nuevo Leon, Av. Universidad s/n, San Nicolas de los Garza, NL, C.P. 66451 (Mexico); Fu, Z Y [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, Hubei, 430070 (China); Lee, S W, E-mail: anurat@ishizaki.nagaokaut.ac.jp [Department of Environment Engineering, Sun Moon University, 100, Kalsan-ri, Tangjeong-myeon, Asan, Chungnam 336-708 (Korea, Republic of)

    2011-03-15

    Low or zero thermal expansion porous ceramics are required for several applications. In this work near zero thermal expansion porous ceramics were fabricated by using SiC and ZrW{sub 2}O{sub 8} as positive and negative thermal expansion materials, respectively, bonded by soda lime glass. The mixture of SiC, ZrW{sub 2}O{sub 8} and soda lime glass was sintered by Pulsed Electric Current Sintering (PECS, or sometimes called Spark Plasma Sintering, SPS) at 700 deg. C. Sintered samples with ZrW{sub 2}O{sub 8} particle size smaller than 25 {mu}m have high thermal expansion coefficient, because ZrW{sub 2}O{sub 8} has the reaction with soda lime glass to form Na{sub 2}ZrW{sub 3}O{sub 12} during sintering process. The reaction between soda lime glass and ZrW{sub 2}O{sub 8} is reduced by increasing particle size of ZrW{sub 2}O{sub 8}. Sintered sample with ZrW{sub 2}O{sub 8} particle size 45-90 {mu}m shows near zero thermal expansion.

  17. Highly sensitive room temperature ammonia gas sensor based on Ir-doped Pt porous ceramic electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Wenlong [College of pharmacy and biological engineering, Chengdu University, Chengdu, 610106 (China); Department of chemical and materials engineering, National Chin-Yi University of Technology, Taichung 411, Taiwan (China); Liu, Yen-Yu [Department of chemical and materials engineering, Tunghai University, Taichung 407, Taiwan (China); Do, Jing-Shan, E-mail: jsdo@ncut.edu.tw [Department of chemical and materials engineering, National Chin-Yi University of Technology, Taichung 411, Taiwan (China); Li, Jing, E-mail: lijing@cdu.edu.cn [College of pharmacy and biological engineering, Chengdu University, Chengdu, 610106 (China)

    2016-12-30

    Highlights: • Water vapors seem to hugely improve the electrochemical activity of the Pt and Pt-Ir porous ceramic electrodes. • The gas sensors based on the Pt and Pt-Ir alloy electrodes possess good sensing performances. • The reaction path of the ammonia on platinum has been discussed. - Abstract: Room temperature NH{sub 3} gas sensors based on Pt and Pt-Ir (Ir doping Pt) porous ceramic electrodes have been fabricated by both electroplating and sputtering methods. The properties of the gaseous ammonia sensors have been examined by polarization and chronoamperometry techniques. The influence of humidity on the features of the resulting sensors in the system has also been discussed, and the working potential was optimized. Water vapors seem to hugely improve the electrochemical activity of the electrode. With increasing the relative humidity, the response of the Pt-Ir(E)/Pt(S)/PCP sensor to NH{sub 3} gas could be enhanced remarkably, and the sensitivity increases from 1.14 to 12.06 μA ppm{sup −1} cm{sup −2} .Then we have also discussed the sensing mechanism of the Pt-Ir sensor and the result has been confirmed by X-ray photoelectron spectroscopy of the electrode surface before and after reaction in the end.

  18. Determination of the slow crack growth susceptibility coefficient of dental ceramics using different methods.

    Science.gov (United States)

    Gonzaga, Carla Castiglia; Cesar, Paulo Francisco; Miranda, Walter Gomes; Yoshimura, Humberto Naoyuki

    2011-11-01

    This study compared three methods for the determination of the slow crack growth susceptibility coefficient (n) of two veneering ceramics (VM7 and d.Sign), two glass-ceramics (Empress and Empress 2) and a glass-infiltrated alumina composite (In-Ceram Alumina). Discs (n = 10) were prepared according to manufacturers' recommendations and polished. The constant stress-rate test was performed at five constant stress rates to calculate n(d) . For the indentation fracture test to determine n(IF) , Vickers indentations were performed and the crack lengths were measured under an optical microscope. For the constant stress test (performed only for d.Sign for the determination of n(s) ) four constant stresses were applied and held constant until the specimens' fracture and the time to failure was recorded. All tests were performed in artificial saliva at 37°C. The n(d) values were 17.2 for Empress 2, followed by d.Sign (20.5), VM7 (26.5), Empress (30.2), and In-Ceram Alumina (31.1). In-Ceram Alumina and Empress 2 showed the highest n(IF) values, 66.0 and 40.2, respectively. The n(IF) values determined for Empress (25.2), d.Sign (25.6), and VM7 (20.1) were similar. The n(s) value determined for d.Sign was 31.4. It can be concluded that the n values determined for the dental ceramics evaluated were significantly influenced by the test method used. 2011 Wiley Periodicals, Inc.

  19. Effect of Ceramic Surface Treatments After Machine Grinding on the Biaxial Flexural Strength of Different CAD/CAM Dental Ceramics.

    Science.gov (United States)

    Bagheri, Hossein; Hooshmand, Tabassom; Aghajani, Farzaneh

    2015-09-01

    This study aimed to evaluate the effect of different ceramic surface treatments after machining grinding on the biaxial flexural strength (BFS) of machinable dental ceramics with different crystalline phases. Disk-shape specimens (10mm in diameter and 1.3mm in thickness) of machinable ceramic cores (two silica-based and one zirconia-based ceramics) were prepared. Each type of the ceramic surfaces was then randomly treated (n=15) with different treatments as follows: 1) machined finish as control, 2) machined finish and sandblasting with alumina, and 3) machined finish and hydrofluoric acid etching for the leucite and lithium disilicate-based ceramics, and for the zirconia; 1) machined finish and post-sintered as control, 2) machined finish, post-sintered, and sandblasting, and 3) machined finish, post-sintered, and Nd;YAG laser irradiation. The BFS were measured in a universal testing machine. Data based were analyzed by ANOVA and Tukey's multiple comparisons post-hoc test (α=0.05). The mean BFS of machined finish only surfaces for leucite ceramic was significantly higher than that of sandblasted (P=0.001) and acid etched surfaces (P=0.005). A significantly lower BFS was found after sandblasting for lithium disilicate compared with that of other groups (Pceramics was affected by the type of ceramic material and surface treatment method. Sandblasting with alumina was detrimental to the strength of only silica-based ceramics. Nd:YAG laser irradiation may lead to substantial strength degradation of zirconia.

  20. Porous hydroxyapatite composite with alumina for bone repair

    International Nuclear Information System (INIS)

    Rusnah Mustaffa; Mohd Reusmaazran Mohd Yusof; Idris Besar

    2010-01-01

    Porous fabrications, a number of techniques were investigated using polyurethane foam as the scaffold. These techniques involve dipping of the foam into a slurry prepared by mixing of HA+Al 2 O 3 powder with PVA and Sago as binder and subjecting to burn off procedure to get the porous products. Sintering parameter was studied at 1100, 1200 and 1300 degree Celsius. Initially HA powder was prepared by the sol-gel precipitation method using calcium hydroxide and ortho-phosphoric acid meanwhile Al 2 O 3 powder from supplier (MERK). The fine HA powder, measuring 2 O 3 . These techniques also produce the uniformity pore shape. Characterization of the physical analysis, porosity, surface morphology by Scanning Electron Microscopy analysis (SEM) and compression strength were studied. Mechanical properties showing that the composite of porous HA+Al 2 O 3 gives higher maximum compression strength compared to the porous hydroxyapatite itself. Observation from this studied the increasing of temperature will increase the strength. (author)

  1. Effects of pore shape and porosity on the properties of porous LNKN ceramics as bone substitute

    International Nuclear Information System (INIS)

    Wang Qi; Chen Qiang; Zhu Jianguo; Huang Chunpeng; Darvell, Brian W.; Chen Zhiqing

    2008-01-01

    A porous lead-free piezoelectric ceramic is investigated as direct bone substitute. Porous lithium sodium potassium niobate (Li 0.06 Na 0.5 K 0.44 )NbO 3 specimens were prepared by pore-forming method. Different volume fraction of ammonium oxalate monohydrate and poly(methyl methacrylate) were used as porogens to obtain different pore shape and porosity. Scanning electron microscopy showed a bicontinuous 3-3 structure of interconnected pores 150-250 μm in size. The piezoelectric constants and electromechanical coupling coefficients may be controlled by both size and shape of the porogens to tune for the best biological response. Such materials show promise for use as a piezoelectric composite bone substitute

  2. A novel processing approach for free-standing porous non-oxide ceramic supports from polycarbosilane and polysilazane precursors.

    Science.gov (United States)

    Konegger, Thomas; Patidar, Rajesh; Bordia, Rajendra K

    2015-09-01

    In this contribution, a low-pressure/low-temperature casting technique for the preparation of novel free-standing macrocellular polymer-derived ceramic support structures is presented. Preceramic polymers (polycarbosilane and poly(vinyl)silazane) are combined with sacrificial porogens (ultra-high molecular weight polyethylene microbeads) to yield porous ceramic materials in the Si-C or Si-C-N systems, exhibiting well-defined pore structures after thermal conversion. The planar-disc-type specimens were found to exhibit biaxial flexural strengths of up to 60 MPa. In combination with their observed permeability characteristics, the prepared structures were found to be suitable for potential applications in filtration, catalysis, or membrane science.

  3. 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.

  4. Sintered glass ceramic composites from vitrified municipal solid waste bottom ashes

    International Nuclear Information System (INIS)

    Aloisi, Mirko; Karamanov, Alexander; Taglieri, Giuliana; Ferrante, Fabiola; Pelino, Mario

    2006-01-01

    A glass ceramic composite was obtained by sinter-crystallisation of vitrified municipal solid waste bottom ashes with the addition of various percentages of alumina waste. The sintering was investigated by differential dilatometry and the crystallisation of the glass particles by differential thermal analysis. The crystalline phases produced by the thermal treatment were identified by X-ray diffraction analysis. The sintering process was found to be affected by the alumina addition and inhibited by the beginning of the crystal-phase precipitation. Scanning electron microscopy was performed on the fractured sintered samples to observe the effect of the sintering. Young's modulus and the mechanical strength of the sintered glass ceramic and composites were determined at different heating rates. The application of high heating rate and the addition of alumina powder improved the mechanical properties. Compared to the sintered glass ceramic without additives, the bending strength and the Young's modulus obtained at 20 deg. C/min, increased by about 20% and 30%, respectively

  5. Thermal shock resistance of ceramic fibre composites characterized by non-destructive methods

    Directory of Open Access Journals (Sweden)

    M. Dimitrijević

    2008-12-01

    Full Text Available Alumina based ceramic fibres and alumina based ceramic were used to produce composite material. Behaviour of composite ceramics after thermal shock treatments was investigated. Thermal shock of the samples was evaluated using water quench test. Surface deterioration level of samples was monitored by image analysis before and after a number of quenching cycles. Ultrasonic measurements were done on samples after quench tests. Dynamic Young modulus of elasticity and strength degradation were calculated using measured values of ultrasonic velocities. Strengths deterioration was calculated using the non-destructive measurements and correlated to degradation of surface area and number of quenches. The addition of small amount of ceramic fibres improves the strengths and diminishes the loss of mechanical properties of samples during thermal shock experiments.

  6. Flexural resistance of Cerec CAD/CAM system ceramic blocks. Part 2: Outsourcing materials.

    Science.gov (United States)

    Sedda, Maurizio; Vichi, Alessandro; Del Siena, Francesco; Louca, Chris; Ferrari, Marco

    2014-02-01

    To test different Cerec CAD/CAM system ceramic blocks, comparing mean flexural strength (sigma), Weibull modulus (m), and Weibull characteristic strength (sigma0) in an ISO standardized set-up. Following the recent ISO Standard (ISO 6872:2008), 11 types of ceramic blocks were tested: IPS e.max CAD MO, IPS e.max CAD LT and IPS e.max CAD HT (lithium disilicate glass-ceramic); In-Ceram SPINELL, In-Ceram Alumina and In-Ceram Zirconia (glass-infiltrated materials); inCoris AL and In-Ceram AL (densely sintered alumina); In-Ceram YZ, IPS e.max Zir-CAD and inCoris ZI (densely sintered zirconia). Specimens were cut out from ceramic blocks, finished, crystallized/infiltrated/sintered, polished, and tested in a three-point bending test apparatus. Flexural strength, Weibull characteristic strength, and Weibull modulus were obtained. A statistically significant difference was found (P ceramic (sigma = 272.6 +/- 376.8 MPa, m = 6.2 +/- 11.3, sigma0 = 294.0 +/- 394.1 MPa) and densely sintered alumina (sigma = 441.8 +/- 541.6 MPa, m = 11.9 +/- 19.0, sigma0 = 454.2 +/- 565.2 MPa). No statistically significant difference was found (P = 0.254) in glass infiltrated materials (sigma = 376.9 +/- 405.5 MPa, m = 7.5 +/- 11.5, sigma0 = 393.7 +/- 427.0 MPa). No statistically significant difference was found (P = 0.160) in densely sintered zirconia (sigma = 1,060.8 +/- 1,227.8 MPa, m = 5.8 +/- 7.4, sigma0 = 1,002.4 +/- 1,171.0 MPa). Not all the materials tested fulfilled the requirements for the clinical indications recommended by the manufacturer.

  7. About a new preparation method for non-stoichiometric colored alumina

    International Nuclear Information System (INIS)

    Arghiropoulos, Basile; Elston, Jean; Juillet, Francois; Teichner, Stanislas

    1960-01-01

    Non-porous, 150 A diameter alumina spherules (δ variety), initially compressed at a pressure of 1 to 5 t/cm 2 , are colored in black after a vacuum treatment (10 -6 mm Hg) at 500 deg. C. Coloration is linked with oxygen loss. The non-stoichiometry of black alumina is demonstrated using a Mc Bain balance and electric conductivity measurements. Reprint of a paper published in Comptes rendus des seances de l'Academie des Sciences, t. 249, p. 2549-2551, sitting of 9 December 1959 [fr

  8. Structural and Chemical Analysis of the Zirconia-Veneering Ceramic Interface.

    Science.gov (United States)

    Inokoshi, M; Yoshihara, K; Nagaoka, N; Nakanishi, M; De Munck, J; Minakuchi, S; Vanmeensel, K; Zhang, F; Yoshida, Y; Vleugels, J; Naert, I; Van Meerbeek, B

    2016-01-01

    The interfacial interaction of veneering ceramic with zirconia is still not fully understood. This study aimed to characterize morphologically and chemically the zirconia-veneering ceramic interface. Three zirconia-veneering conditions were investigated: 1) zirconia-veneering ceramic fired on sandblasted zirconia, 2) zirconia-veneering ceramic on as-sintered zirconia, and 3) alumina-veneering ceramic (lower coefficient of thermal expansion [CTE]) on as-sintered zirconia. Polished cross-sectioned ceramic-veneered zirconia specimens were examined using field emission gun scanning electron microscopy (Feg-SEM). In addition, argon-ion thinned zirconia-veneering ceramic interface cross sections were examined using scanning transmission electron microscopy (STEM)-energy dispersive X-ray spectrometry (EDS) at high resolution. Finally, the zirconia-veneering ceramic interface was quantitatively analyzed for tetragonal-to-monoclinic phase transformation and residual stress using micro-Raman spectroscopy (µRaman). Feg-SEM revealed tight interfaces for all 3 veneering conditions. High-resolution transmission electron microscopy (HRTEM) disclosed an approximately 1.0-µm transformed zone at sandblasted zirconia, in which distinct zirconia grains were no longer observable. Straight grain boundaries and angular grain corners were detected up to the interface of zirconia- and alumina-veneering ceramic with as-sintered zirconia. EDS mapping disclosed within the zirconia-veneering ceramic a few nanometers thick calcium/aluminum-rich layer, touching the as-sintered zirconia base, with an equally thick silicon-rich/aluminum-poor layer on top. µRaman revealed t-ZrO2-to-m-ZrO2 phase transformation and residual compressive stress at the sandblasted zirconia surface. The difference in CTE between zirconia- and the alumina-veneering ceramic resulted in residual tensile stress within the zirconia immediately adjacent to its interface with the veneering ceramic. The rather minor chemical

  9. Characterization and evaluation of ceramic properties of clay used in structural ceramics

    International Nuclear Information System (INIS)

    Reis, A.S.; Oliveira, J.N.; Della-Sagrillo, V.P.; Valenzuela-Diaz, F.R.

    2014-01-01

    The clay used in the manufacture of structural ceramic products must meet quality requirements that are influenced by their chemical, physical, mineralogical and microstructural characteristics, which control the ceramic properties of the final products. This paper aims to characterize the clay used in the manufacture of ceramic roof tiles and bricks. The clay was characterized through XRF, XRD, thermogravimetry and differential thermal analysis, Atterberg limits and particle size distribution. Specimens were shaped, dried at 110°C, and burned at 900 deg C in an industrial kiln. After that, they were submitted to tests of water absorption, apparent porosity, bulk density and flexural strength. The results show that the chemical composition of clay has significant amount of silica and alumina and adequate levels of kaolinite for use in structural ceramic. The ceramic properties evaluated in the specimens partially meet the requirements of the Brazilian standard-clays for structural ceramics. (author)

  10. Physico-chemical study of coating plasma duplex alumina/hydroxyapatite for medical applications relation elaboration/structure/properties(dissolution/adherence/residual constraints); Etude physico-chimique de depots plasma duplex alumine/hydroxyapatite pour applications medicales relations elaboration/structure/proprietes (dissolution/adherence/contraintes residuelles)

    Energy Technology Data Exchange (ETDEWEB)

    Demonet, N

    1998-11-19

    The physico-chemical behavior of porous ceramics depositing is studied in order to use them to favour the biological fixing of hip prosthesis fixed without cement. Alumina depositing, hydroxyapatite depositing and duplex (the both together) have been realized by plasma projection on a substrate in Ti-6Al-V. Tests of dissolution have been made. An original method of sound followed by radioactive tracers has allowed to establish an order of phases degradation and to consider the kinetics of calcium ions in function of several parameters of tests. (N.C.)

  11. Tubular solid oxide fuel cells with porous metal supports and ceramic interconnections

    Science.gov (United States)

    Huang, Kevin [Export, PA; Ruka, Roswell J [Pittsburgh, PA

    2012-05-08

    An intermediate temperature solid oxide fuel cell structure capable of operating at from 600.degree. C. to 800.degree. C. having a very thin porous hollow elongated metallic support tube having a thickness from 0.10 mm to 1.0 mm, preferably 0.10 mm to 0.35 mm, a porosity of from 25 vol. % to 50 vol. % and a tensile strength from 700 GPa to 900 GPa, which metallic tube supports a reduced thickness air electrode having a thickness from 0.010 mm to 0.2 mm, a solid oxide electrolyte, a cermet fuel electrode, a ceramic interconnection and an electrically conductive cell to cell contact layer.

  12. Application of gamma irradiation method to synthesize silver nanoparticle and fix them on porous ceramics for water treatment

    International Nuclear Information System (INIS)

    Nguyen Thuy Ai Trinh; Phan Dinh Tuan; Ngo Manh Thang; Dang Van Phu; Le Anh Quoc; Nguyen Quoc Hien

    2013-01-01

    The colloidal silver nanoparticles (AgNPs) solution with the AgNPs diameter of 10-15 nm was synthesized by gamma irradiation method using polyvinylpyrrolidone as stabilizer. Porous ceramic samples were functionalized by treatment with an aminosilane (AS) agent (3-aminopropyltriethoxysilane) and then impregnated in colloidal silver nanoparticles solution for fixing through coordination bonds between - NH 2 groups of the aminosilane and the silver atoms. The AgNPs content attached in porous ceramic (AgNPs/PC) was of about 200-250 mg/kg. The contents silver release from AgNPs/PC into filtrated water by flowing test with the rate of about 5 litters/h were less than 10 μg/L analyzed by neutron activation analysis method, it is satisfactory to the WHO guideline of 100 μg/L for drinking water. The antimicrobial effect of AgNPs/PC for E. coli was carried out by flowing test with an inoculated initial contamination of E.coli in water of about 10 6 CFU/100 ml. Results showed that the contamination of E. coli in filtrated water through AgNPs/PC (up to 500 litters) was less than 1 CFU/100 ml compared to 2.5x10 4 CFU/100 ml for base porous ceramic (only up to 60 litters). The antimicrobial effect of AgNPs/PC is in accordance with the TCVN 6096-2004 for bottled drinking. Thus, AgNPs/PC with the silver content of 200-250 mg/kg and the specific surface area of 1.51 m 2 /g, average pore size of 48.2 Å and pore volume of 1.8x10 -3 cm 3 /g has highly antimicrobial effect that can be applied for point-of-use drinking water treatment. (author)

  13. Study on the Synthesis of Silver Nanoparticles by Gamma Irradiation for Fixing in Porous Ceramics for Water Treatment

    International Nuclear Information System (INIS)

    Nguyen Quoc Hien; Dang Van Phu; Le Anh Quoc; Nguyen Ngoc Duy; Vo Thi Kim Lang; Bui Duy Du

    2013-01-01

    The colloidal silver nanoparticles (AgNPs) solution with the AgNPs diameter of 10 - 15 nm was synthesized by gamma irradiation method using polyvinylpyrrolidone as stabilizer. Porous ceramic samples were functionalized by treatment with an aminosilan (AS) agent (3-aminopropyltriethoxysilane) and then impregnated in colloidal silver nanoparticles solution for fixing through coordination bonds between (-NH 2 ) groups of the aminosilan and the silver atoms. The AgNPs content attached in porous ceramic (AgNPs/PC) was of about 200-250 mg/kg. The contents of silver release from AgNPs/PC into filtrated water by flowing test with the rate of about 5 litters/h were less than 10 µg/L analyzed by neutron activation analysis method, it is satisfactory to the WHO guideline of 100 µg/L for drinking water. The antimicrobial effect of AgNPs/PC for E. coli was carried out by flowing test with an inoculated initial contamination of E. coli in water of about 10 6 CFU/100 ml. Results showed that the contamination of E. coli in filtrated water through AgNPs/PC (up to 500 litters) was less than 1 CFU/100 ml compared to 2.5x10 4 CFU/100 ml for bare porous ceramic (only up to 60 litters). The antimicrobial effect of AgNPs/PC is in accordance with the TCVN 6096-2004 for bottled drinking water. Thus, AgNPs/PC with the silver content of 200-250 mg/kg and the specific surface area of 1.51 m 2 /g, average pore size of 48.2 Å and pore volume of 1.8x10 -3 cm 3 /g has highly antimicrobial effect that can be applied for point-of-use drinking water treatment. (author)

  14. Uniformly Porous Nanocrystalline CaMgFe1.33Ti3O12 Ceramic Derived Electro-Ceramic Nanocomposite for Impedance Type Humidity Sensor

    Science.gov (United States)

    Tripathy, Ashis; Pramanik, Sumit; Manna, Ayan; Shasmin, Hanie Nadia; Radzi, Zamri; Abu Osman, Noor Azuan

    2016-01-01

    Since humidity sensors have been widely used in many sectors, a suitable humidity sensing material with improved sensitivity, faster response and recovery times, better stability and low hysteresis is necessary to be developed. Here, we fabricate a uniformly porous humidity sensor using Ca, Ti substituted Mg ferrites with chemical formula of CaMgFe1.33Ti3O12 as humidity sensing materials by solid-sate step-sintering technique. This synthesis technique is useful to control the grain size with increased porosity to enhance the hydrophilic characteristics of the CaMgFe1.33Ti3O12 nanoceramic based sintered electro-ceramic nanocomposites. The highest porosity, lowest density and excellent surface-hydrophilicity properties were obtained at 1050 °C sintered ceramic. The performance of this impedance type humidity sensor was evaluated by electrical characterizations using alternating current (AC) in the 33%–95% relative humidity (RH) range at 25 °C. Compared with existing conventional resistive humidity sensors, the present sintered electro-ceramic nanocomposite based humidity sensor showed faster response time (20 s) and recovery time (40 s). This newly developed sensor showed extremely high sensitivity (%S) and small hysteresis of humidity sensors. PMID:27916913

  15. Electron beam treatments of electrophoretic ceramic coatings

    International Nuclear Information System (INIS)

    De Riccardis, M.F.; Carbone, D.; Piscopiello, E.; Antisari, M. Vittori

    2008-01-01

    In this work a method to densify ceramic coating obtained by electrophoresis and to improve its adhesion to the substrate is proposed. It consists in irradiating the coating surface by electron beam (EB). Alumina and alumina-zirconia coatings were deposited on stainless steel substrates and treated by low power EB. SEM, XRD and TEM characterizations demonstrated that the sintering occurred. Moreover, it is shown that on alumina-zirconia coating the EB irradiation produced a composite material consisting principally of tetragonal zirconia particles immersed in an amorphous alumina matrix. The adhesion stress of EB treated coating was estimated by stud pull test and it was found to be comparable to that of plasma-sprayed coatings

  16. Systematic approach to preparing ceramic-glass composites with high translucency for dental restorations.

    Science.gov (United States)

    Yoshimura, Humberto N; Chimanski, Afonso; Cesar, Paulo F

    2015-10-01

    Ceramic composites are promising materials for dental restorations. However, it is difficult to prepare highly translucent composites due to the light scattering that occurs in multiphase ceramics. The objective of this work was to verify the effectiveness of a systematic approach in designing specific glass compositions with target properties in order to prepare glass infiltrated ceramic composites with high translucency. First it was necessary to calculate from literature data the viscosity of glass at the infiltration temperature using the SciGlass software. Then, a glass composition was designed for targeted viscosity and refractive index. The glass of the system SiO2-B2O3-Al2O3-La2O3-TiO2 prepared by melting the oxide raw materials was spontaneously infiltrated into porous alumina preforms at 1200°C. The optical properties were evaluated using a refractometer and a spectrophotometer. The absorption and scattering coefficients were calculated using the Kubelka-Munk model. The light transmittance of prepared composite was significantly higher than a commercial ceramic-glass composite, due to the matching of glass and preform refractive indexes which decreased the scattering, and also to the decrease in absorption coefficient. The proposed systematic approach was efficient for development of glass infiltrated ceramic composites with high translucency, which benefits include the better aesthetic performance of the final prosthesis. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  17. 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

  18. Dilatometric study of anisotropic sintering of alumina/zirconia laminates with controlled fracture behaviour

    Czech Academy of Sciences Publication Activity Database

    Maca, K.; Pouchlý, V.; Drdlík, D.; Hadraba, Hynek; Chlup, Zdeněk

    2017-01-01

    Roč. 37, č. 14 (2017), s. 4287-4295 ISSN 0955-2219 R&D Projects: GA ČR(CZ) GA15-06390S; GA MŠk(CZ) LQ1601 Institutional support: RVO:68081723 Keywords : Alumina/zirconia laminate * Crack deflection * Master sintering curve * Sintering shrinkage Subject RIV: JH - Ceramic s, Fire-Resistant Materials and Glass OBOR OECD: Ceramic s Impact factor: 3.411, year: 2016

  19. 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 ...

  20. Development and characterization of ceramic composites alumina-titania based reinforced with lanthanum oxide for fabrication of inert coatings for metallic tanks of the oil industry

    International Nuclear Information System (INIS)

    Bandeira, J.M.; Yadava, Y.P.; Silva, N.D.G.; Ferreira, R.A.S.

    2016-01-01

    Crude petroleum is highly corrosive causing superficial degradation in metallic tanks used for storage and transportation of this material, which causes a serious problem in the oil industry. An alternative to solve this problem is to use some kind of coating that is inert to this kind of corrosion. Alumina and titania are interesting materials for several engineering applications because, when compared with other ceramic materials, they present superior mechanical properties, e.g. high mechanical strength, good chemical stability and high fracture toughness combined with good wear resistance and a coefficient of thermal expansion close to the iron's, which makes them fit to use in ceramic hardening process and coating. In this paper, alumina-titania ceramic composites with 5%, 10%, 15% and 20% of titania (TiO2) and reinforced with 2% of lanthanum oxide of were produced by thermo-mechanical processing and sintering techniques at 1350 deg C. In these composites, microstructure and mechanical properties were analyzed using X-ray spectroscopy, optical microscopy, scanning electron microscopy and Vickers hardness in order to evaluate their applicability. X-ray spectroscopy showed the formation of composite without the presence of other phases. Optical microscopy and scanning electron microscopy showed a homogeneous microstructure in terms of particle size and distribution. Vickers hardness test showed a gradual decrease in hardness with the addition of titania. The composite with 5% of titania and 2% of lanthanum oxide is the best choice for structural applications. The composites were submerged in crude petroleum for 30 days to study their stability in such environment. Through the analysis of X-ray spectroscopy, optical microscopy and Vickers hardness before and after the submersion in crude petroleum, it was not observed structural or microstructural degradation nether alterations in mechanical properties. This way, it was concluded that these composites have good

  1. Rheological properties of ceramic nanopowders in aqueous and nonaqueous suspensions

    International Nuclear Information System (INIS)

    Tomaszewski, H.; Loiko, E.M.

    2003-01-01

    The potential for ceramic nanocomposites to offer significantly enhanced mechanical properties is generally known since the first work of Niihara published in 1991. However achieving these properties needs carefully done colloidal processing, because ceramic nanopowders are naturally prone to agglomeration. The work presented here is concerned with the processing of zirconia/alumina nanocomposites via aqueous and alumina silicon carbide nanocomposites via nonaqueous colloidal route. The effect of pH of aqueous alumina and zirconia suspensions on properties of suspension and centrifuged green bodies was studied. A correlation between surface electric charge of grains (zeta potential)and agglomerate size, viscosity of suspension and porosity of green compacts was found. In the case of nonaqueous route alumina and silicon carbide suspensions in iso-propanol were investigated. Electrostatic surface charge of grains was changed by addition of chloroacetic acid and determined indirectly by the mass of powder deposited on electrode during electrophoresis. Different behaviour of SiC nanopowder than of alumina was observed and mechanism of charge creation is proposed on the base of DLVO theory. The effect of grain charge on preventing agglomeration on the silicon carbide powder is presented on micrographs of sintered nanocomposites. (author)

  2. 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.

  3. 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.

  4. Zirconia toughened ceramics for heat engine applications

    International Nuclear Information System (INIS)

    Rossi, G.A.; Blum, J.B.; Manwiller, K.E.; Knapp, C.E.

    1986-01-01

    Three classes of zirconia toughened ceramics (ZTC) were studied, i.e. Mg-PSZ (MgO-partially stabilized zirconia), Y-TZP (Y/sub 2/O/sub 3/-tetragonal zirconia polycrystals) and ZTA (zirconia toughened alumina). The main objective was to improve the high temperature strength and toughness, which are not satisfactory in the ''state of the art'' ZTC materials. Powders prepared by melting/rapid solidification and by chemical routes were used. The green parts were made by both dry and wet shape forming methods. Fine grained Mg-PSZ ceramics with unique microstructures were produced using the rapidly solidified powders. The Y-TZP materials were improved mainly through microstructure control and by addition of alpha alumina as a dispersed phase. Preliminary results on ZTA ceramics made with the rapidly solidified powders were also obtained. It is concluded that the Al/sub 2/O/sub 3//Y-TZP composites offer a good chance of meeting the program objectives

  5. Thickness dependence of light transmittance, translucency and opalescence of a ceria-stabilized zirconia/alumina nanocomposite for dental applications.

    Science.gov (United States)

    Shiraishi, Takanobu; Watanabe, Ikuya

    2016-05-01

    This study was conducted to investigate thickness dependence of light transmittance, translucency and opalescence of a commercially available fully-sintered ceria-stabilized zirconia/alumina nanocomposite for dental all-ceramic restorations. Three disk samples of 16 mm in diameter and thickness ranging from 0.2 to 0.6 mm with 0.1 mm increment each were cut from a fully-sintered rod-shaped Ce-TZP/alumina nanocomposite (NANOZR, Panasonic Healthcare, Japan) and polished flat by using diamond slurry. Spectral light transmittance data under the CIE standard illuminant D65 were recorded at 10nm intervals from 360 to 740 nm using a computer-controlled spectrophotometer. Average transmittance, translucency and opalescence parameters were determined as a function of sample thickness. Optical properties of a fully-sintered yttria-stabilized tetragonal zirconia polycrystals (Cercon(®) base, DeguDent GmbH, Germany) were also investigated as a reference. Two-way ANOVA was performed to determine the significant differences in various optical parameters among types of ceramic and thicknesses at α=0.05. Results of the two-way ANOVA showed that the average transmittance, translucency and opalescence parameters of both ceramic materials were significantly influenced by the type of ceramic and thickness (popalescence parameters exceeding 20 CIE units when the sample thickness was nearly 0.3 mm. The prominent characteristics of high opalescence and low transmittance of light in the NANOZR was considered to be caused by its specific very fine interpenetrated intragranular microstructure and by a large difference of refractive indices of Ce-TZP and alumina components. High opalescence and low transmittance of light of the ceria-stabilized zirconia/alumina nanocomposite (NANOZR) are attractive properties for use as a substructure in fabricating porcelain-veneering-type esthetic all-ceramic restorations. Copyright © 2016 Academy of Dental Materials. Published by Elsevier Ltd. All

  6. All-ceramic or metal-ceramic tooth-supported fixed dental prostheses (FDPs)? A systematic review of the survival and complication rates. Part II: Multiple-unit FDPs.

    Science.gov (United States)

    Pjetursson, Bjarni Elvar; Sailer, Irena; Makarov, Nikolay Alexandrovich; Zwahlen, Marcel; Thoma, Daniel Stefan

    2015-06-01

    To assess the 5-year survival of metal-ceramic and all-ceramic tooth-supported fixed dental prostheses (FDPs) and to describe the incidence of biological, technical and esthetic complications. Medline (PubMed), Embase and Cochrane Central Register of Controlled Trials (CENTRAL) searches (2006-2013) were performed for clinical studies focusing on tooth-supported FDPs with a mean follow-up of at least 3 years. This was complemented by an additional hand search and the inclusion of 10 studies from a previous systematic review [1]. Survival and complication rates were analyzed using robust Poisson's regression models to obtain summary estimates of 5-year proportions. Forty studies reporting on 1796 metal-ceramic and 1110 all-ceramic FDPs fulfilled the inclusion criteria. Meta-analysis of the included studies indicated an estimated 5-year survival rate of metal-ceramic FDPs of 94.4% (95% CI: 91.2-96.5%). The estimated survival rate of reinforced glass ceramic FDPs was 89.1% (95% CI: 80.4-94.0%), the survival rate of glass-infiltrated alumina FDPs was 86.2% (95% CI: 69.3-94.2%) and the survival rate of densely sintered zirconia FDPs was 90.4% (95% CI: 84.8-94.0%) in 5 years of function. Even though the survival rate of all-ceramic FDPs was lower than for metal-ceramic FDPs, the differences did not reach statistical significance except for the glass-infiltrated alumina FDPs (p=0.05). A significantly higher incidence of caries in abutment teeth was observed for densely sintered zirconia FDPs compared to metal-ceramic FDPs. Significantly more framework fractures were reported for reinforced glass ceramic FDPs (8.0%) and glass-infiltrated alumina FDPs (12.9%) compared to metal-ceramic FDPs (0.6%) and densely sintered zirconia FDPs (1.9%) in 5 years in function. However, the incidence of ceramic fractures and loss of retention was significantly (p=0.018 and 0.028 respectively) higher for densely sintered zirconia FDPs compared to all other types of FDPs. Survival rates of all

  7. Mathematical modeling of sustainability of porous Al2O3 growth during two-stage anodization process

    Science.gov (United States)

    Aryslanova, Elizaveta M.; Alfimov, Anton V.; Chivilikhin, Sergey A.

    2015-06-01

    Currently, due to the development of nanotechnology and metamaterials, it has become important to obtain regular nanoporous structures with different parameters, such as porous anodic alumina films that are used for synthesis of various nanocomposites. In this work we consider the motion of the interfaces between electrolyte and alumina layers, and between alumina and aluminum layers. We also took into account the dynamics of moving boundaries and the change of small perturbations of these boundaries. Each area under Laplace's equation is solved for the potential of the electric field. The growth of porous alumina is described with the theory of small perturbations. Small perturbations of the interface are considered, which lead to small changes in potential and current in the boundaries. As a result of the developed model we obtained the minimum distance between centers of aluminum oxide pores in the beginning of anodizing process and the wavelength of porous structure irregularities.

  8. Understanding and control of optical performance from ceramic materials

    International Nuclear Information System (INIS)

    Barbour, J.C.; Knapp, J.A.; Potter, B.G.; Jennison, D.R.; Verdozzi, C.A.; Follstaedt, D.M.; Bendale, R.D.; Simmons, J.H.

    1998-06-01

    This report summarizes a two-year Laboratory-Directed Research and Development (LDRD) program to gain understanding and control of the important parameters which govern the optical performance of rare-earth (RE) doped ceramics. This LDRD developed the capability to determine stable atomic arrangements in RE doped alumina using local density functional theory, and to model the luminescence from RE-doped alumina using molecular dynamic simulations combined with crystal-field calculations. Local structural features for different phases of alumina were examined experimentally by comparing their photoluminescence spectra and the atomic arrangement of the amorphous phase was determined to be similar to that of the gamma phase. The luminescence lifetimes were correlated to these differences in the local structure. The design of both high and low-phonon energy host materials was demonstrated through the growth of Er-doped aluminum oxide and lanthanum oxide. Multicomponent structures of rare-earth doped telluride glass in an alumina and silica matrix were also prepared. Finally, the optical performance of Er-doped alumina was determined as a function of hydrogen content in the host matrix. This LDRD is the groundwork for future experimentation to understand the effects of ionizing radiation on the optical properties of RE-doped ceramic materials used in space and other radiation environments

  9. 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)

  10. Experimental analysis of the strength of silver-alumina junction elaborated at solid state bonding

    International Nuclear Information System (INIS)

    Serier, B.; Bachir Bouiadjra, B.; Belhouari, M.; Treheux, D.

    2011-01-01

    Highlights: → The adhesion strength is closely related to the plastic deformation of the metal joint. → It is possible to transform a system with weak energy of adhesion into a system with strong energy. → The adhesion strength depends on Silver diffusion in the ceramic grains boundaries. -- Abstract: The mechanisms of ceramics-metal assemblies, particularly silver and alumina, can be better understood by studying the strength of their adhesion. These two materials are a priori non-reactive, their thermodynamic work of adhesion is low and the difference between their thermal coefficients of expansion in very considerable. In this study, the strength of silver-alumina junctions elaborated at solid state by thermo-compression is tested by an indirect tensile test and shearing one. The effects of several parameters such as: the pressure of bonding, the time of bonding, the temperature, and the oxygen dissolve in metal solid solution on the strength of the junction are analyzed. The obtained results show that the resistance of the junction is affected by all this parameters and it is essential to optimize these different parameters in order to increase the durability of the junction. It was also shown that the diffusion of the silver in alumina could be the cause of the damage of alumina near the interface.

  11. 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

  12. 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.

  13. 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.

  14. 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.

  15. A study on improving mechanical properties of porous HA tissue engineering scaffolds by hot isostatic pressing

    International Nuclear Information System (INIS)

    Zhao Jing; Xiao Suguang; Lu Xiong; Wang Jianxin; Weng Jie

    2006-01-01

    Various interconnected porous hydroxyapatite (HA) ceramic scaffolds are universally used to induct the tissue growth for bone repair and replacement, and serve to support the adhesion, transfer, proliferation and differentiation of cells. Impregnation of polyurethane sponges with a ceramic slurry is adopted to produce highly porous HA ceramic scaffolds with a 3D interconnected structure. However, high porosity always accompanies a decrease in the strength of the HA ceramic scaffolds. Therefore, it is significant to improve the strength of the HA ceramic scaffolds with highly interconnected porosity so that they are more suitable in clinical applications. In this work, highly porous HA ceramic scaffolds are first produced by the polymer impregnation approach, and subsequently further sintered by hot isostatic pressing (HIP). The phase composition, macro- and micro-porous structure, sintering and mechanical properties of the porous HA scaffolds are investigated by x-ray diffraction (XRD), scanning electron microscopy (SEM), nanoindentation analysis and compressive test. The experimental results show that the nanohardness and compressive strength of HIP-sintered porous HA ceramics are higher than those of commonly sintered HA scaffolds. The HIP technique can effectively improve the sintering property and densification of porous HA ceramic scaffolds, so inducing an increase in the compression strength

  16. An Experimental Study on Mechanical Modeling of Ceramics Based on Microstructure

    Directory of Open Access Journals (Sweden)

    Ya-Nan Zhang

    2015-11-01

    Full Text Available The actual grinding result of ceramics has not been well predicted by the present mechanical models. No allowance is made for direct effects of materials microstructure and almost all the mechanical models were obtained based on crystalline ceramics. In order to improve the mechanical models of ceramics, surface grinding experiments on crystalline ceramics and non-crystalline ceramics were conducted in this research. The normal and tangential grinding forces were measured to calculate single grit force and specific grinding energy. Grinding surfaces were observed. For crystalline alumina ceramics, the predictive modeling of normal force per grit fits well with the experimental result, when the maximum undeformed chip thickness is less than a critical depth, which turns out to be close to the grain size of alumina. Meanwhile, there is a negative correlation between the specific grinding energy and the maximum undeformed chip thickness. With the decreasing maximum undeformed chip thickness, the proportions of ductile removal and transgranular fracture increase. However, the grinding force models are not applicable for non-crystalline ceramic fused silica and the specific grinding energy fluctuates irregularly as a function of maximum undeformed chip thickness seen from the experiment.

  17. 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...

  18. The Effect of Plasma Surface Treatment on a Porous Green Ceramic Film with Polymeric Binder Materials

    International Nuclear Information System (INIS)

    Yun Jeong Woo

    2013-01-01

    To reduce time and energy during thermal binder removal in the ceramic process, plasma surface treatment was applied before the lamination process. The adhesion strength in the lamination films was enhanced by oxidative plasma treatment of the porous green ceramic film with polymeric binding materials. The oxygen plasma characteristics were investigated through experimental parameters and weight loss analysis. The experimental results revealed the need for parameter analysis, including gas material, process time, flow rate, and discharge power, and supported a mechanism consisting of competing ablation and deposition processes. The weight loss analysis was conducted for cyclic plasma treatment rather than continuous plasma treatment for the purpose of improving the film's permeability by suppressing deposition of the ablated species. The cyclic plasma treatment improved the permeability compared to the continuous plasma treatment.

  19. Nano-oxides to improve the surface properties of ceramic tiles

    International Nuclear Information System (INIS)

    Rambaldi, E.; Tucci, A.; Esposito, L.; Naldi, D.; Timellini, G.

    2010-01-01

    The aim of the present work is to realise ceramic tiles with superior surface mechanical characteristics and chemical resistance, by the addition of nano-oxides, such as zirconia and alumina, since such advanced ceramics oxides are well known for their excellent mechanical properties and good resistance to chemical etching. In order to avoid any dangerousness, the nanoparticles were used in form of aqueous suspension and they were sprayed, by airbrush, directly onto the dried ceramic support, before firing. To observe the distribution of the nanoparticles and to optimise the surface treatment, SEM-EDS analyses were carried out on the fired samples. XRD analysis was conducted to assess the phases evolution of the different materials during the firing step. The surface mechanical characteristics of the samples have been evaluated by Vickers hardness and scratch test. In addition, also chemical resistance tests were performed. Microstructural observations allowed to understand how alumina and zirconia nanoparticles acted to improve the surface performances of the modified ceramic tiles. (Author) 20 refs.

  20. Hydroxyapatite additive influenced the bioactivity of bioactive nano-titania ceramics and new bone-forming capacity

    Energy Technology Data Exchange (ETDEWEB)

    Li Zhensheng [Third Military Medical University, College of Biomedical Engineering and Medical Imaging (China); Yang Xiaozhan [Chongqing University of Technology, School of Optoelectronic Information (China); Guo Hongfeng [Third Military Medical University, Tissue Engineering Research Center of Chongqing, Department of Anatomy, College of Basic Medical Sciences (China); Yang Xiaochao; Sun Lili [Third Military Medical University, College of Biomedical Engineering and Medical Imaging (China); Dong Shiwu, E-mail: shiwudong@gmail.com [Third Military Medical University, Tissue Engineering Research Center of Chongqing, Department of Anatomy, College of Basic Medical Sciences (China)

    2012-09-15

    Bioceramics plays an important role in bone-substitutes. In this study, titania porous ceramics with excellent bioactivity were prepared using hydroxyapatite (HA, 10 vol.% contents) as a grain growth inhibitor. The pure TiO{sub 2} porous ceramics were also prepared as a control. After sintered at 1,000 Degree-Sign C with a pressureless sintering method, the particle size of the pure TiO{sub 2} and TiO{sub 2}/HA (10 vol.%) porous ceramics were 450 and 310 nm, respectively. Each of the porous ceramics presented numerous pores, which were cross-connected. The size of the pores ranged from 100 to 300 {mu}m. There were also profuse micropores inside the pore wall and between the particles. A SBF soaking experiment demonstrated that the HA additive played an important role in promoting apatite formation. The cell proliferation demonstrated that osteoblasts on the TiO{sub 2}/HA (10 vol.%) porous ceramics proliferated faster than that on the pure TiO{sub 2} ceramics. The histological sections and EDX assay results of the two porous ceramics also illustrated that TiO{sub 2}/HA (10 vol.%) composite ceramics combined with Ca and P elements induced much better apatite formation than that of the pure TiO{sub 2} ceramics. These results indicated that titania ceramics combined with HA holds great promise for bone-substitutes.

  1. Simulation of a porous ceramic membrane reactor for hydrogen production

    Energy Technology Data Exchange (ETDEWEB)

    Yu, W.; Ohmori, T.; Yamamoto, T.; Endo, A.; Nakaiwa, M.; Hayakawa, T. [National Inst. of Advanced Industrial Science and Technology, Tsukuba (Japan); Itoh, N. [National Inst. of Advanced Industrial Science and Technology, Tsukuba (Japan); Utsunomiya Univ. (Japan). Dept. of Applied Chemistry

    2005-08-01

    A systematic simulation study was performed to investigate the performance of a porous ceramic membrane reactor for hydrogen production by means of methane steam reforming. The results show that the methane conversions much higher than the corresponding equilibrium values can be achieved in the membrane reactor due to the selective removal of products from the reaction zone. The comparison of isothermal and non-isothermal model predictions was made. It was found that the isothermal assumption overestimates the reactor performance and the deviation of calculation results between the two models is subject to the operating conditions. The effects of various process parameters such as the reaction temperature, the reaction side pressure, the feed flow rate and the steam to methane molar feed ratio as well as the sweep gas flow rate and the operation modes, on the behavior of membrane reactor were analyzed and discussed. (author)

  2. 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)

  3. Development of physical and mathematical models for the Porous Ceramic Tube Plant Nutrification System (PCTPNS)

    Science.gov (United States)

    Tsao, D. Teh-Wei; Okos, M. R.; Sager, J. C.; Dreschel, T. W.

    1992-01-01

    A physical model of the Porous Ceramic Tube Plant Nutrification System (PCTPNS) was developed through microscopic observations of the tube surface under various operational conditions. In addition, a mathematical model of this system was developed which incorporated the effects of the applied suction pressure, surface tension, and gravitational forces as well as the porosity and physical dimensions of the tubes. The flow of liquid through the PCTPNS was thus characterized for non-biological situations. One of the key factors in the verification of these models is the accurate and rapid measurement of the 'wetness' or holding capacity of the ceramic tubes. This study evaluated a thermistor based moisture sensor device and recommendations for future research on alternative sensing devices are proposed. In addition, extensions of the physical and mathematical models to include the effects of plant physiology and growth are also discussed for future research.

  4. A porous ceramic membrane tailored high-temperature supercapacitor

    Science.gov (United States)

    Zhang, Xin; He, Benlin; Zhao, Yuanyuan; Tang, Qunwei

    2018-03-01

    The supercapacitor that can operate at high-temperature are promising for markedly increase in capacitance because of accelerated charge movement. However, the state-of-the-art polymer-based membranes will decompose at high temperature. Inspired by solid oxide fuel cells, we present here the experimental realization of high-temperature supercapacitors (HTSCs) tailored with porous ceramic separator fabricated by yttria-stabilized zirconia (YSZ) and nickel oxide (NiO). Using activated carbon electrode and supporting electrolyte from potassium hydroxide (KOH) aqueous solution, a category of symmetrical HTSCs are built in comparison with a conventional polymer membrane based device. The dependence of capacitance performance on temperature is carefully studied, yielding a maximized specific capacitance of 272 F g-1 at 90 °C for the optimized HTSC tailored by NiO/YSZ membrane. Moreover, the resultant HTSC has relatively high durability when suffer repeated measurement over 1000 cycles at 90 °C, while the polymer membrane based supercapacitor shows significant reduction in capacitance at 60 °C. The high capacitance along with durability demonstrates NiO/YSZ membrane tailored HTSCs are promising in future advanced energy storage devices.

  5. Study on the potential of water/oil of tubular alumina ceramics through flux and turbidity analysis; Estudo do potencial de separacao agua/oleo de membranas ceramicas tubulares de alumina atraves da analise das medidas de fluxo e turbidez

    Energy Technology Data Exchange (ETDEWEB)

    Silva, A.A; Melo, K.S. [Universidade Federal, Campina Grande, PB (Brazil)]. E-mail: adrianasilva_cg@yahoo.com.br; Maia, J.B.N.; Franca, R.V.; Silva, R.A.V.; Lira, H.L.; Carvalho, L.H. [Universidade Federal, Campina Grande, PB (Brazil). Dept. de Engenharia de Materiais]. E-mail: helio@dema.ufpb.br; Franca, K.B.; Rodrigues, M.G.F [Universidade Federal, Campina Grande, PB (Brazil). Dept. de Engenharia Quimica]. E-mail: kepler@labdes.ufpb.br

    2003-07-01

    In the last years, a considerable attention was given to the effluents composed by contaminated water with oil and the impact on the environment . The water pollution by oleaginous hydrocarbon is specially harmful to the aquatic life, decreasing the transmission of light and disturb the normal mechanism of oxygen transfer. So, to remove oil from water is an important aspect to control the pollution from several industries. The ceramic membranes act as a barrier for the emulsified oil. It has been studied enough as a medium to separate oil/ water from stable emulsions. The objective of this work is to present an evaluation of the separation potential of a tubular alumina ceramic membrane made in laboratory from Materials Engineering Department, Federal University of Campina Grande (UFCG). It was done test of flux and concentration of oil the permeate. The results showed that the membranes can be satisfactorily used in the oil/water separation. (author)

  6. A Comparative Analysis of the Flow Properties between Two Alumina-Based Dry Powders

    Directory of Open Access Journals (Sweden)

    Milene Minniti de Campos

    2013-01-01

    Full Text Available We measured and compared the flow properties of two alumina-based powders. The alumina powder (AP is irregularly shaped and has a smooth surface and moisture content of 0.16% (d.b., and the ceramic powder (CP, obtained after atomization in a spray dryer, is spherical and has a rough surface and moisture content of 1.07%. We measured the Hausner ratio (HR, the static angle of repose (AoR, the flow index (FI, the angle of internal friction, and the wall's friction angle. The properties measured using aerated techniques (AoR and HR demonstrated that AP presents true cohesiveness (and therefore a difficult flow, while CP presents some cohesiveness and its flow might be classified as half way between difficult and easy flow. Their FI values, which were obtained using a nonaerated technique, enable us to classify the alumina as cohesive and the ceramic powder as an easy-flow powder. The large mean diameter and morphological characteristics of CP reduce interparticle forces and improve flowability, in spite of the higher moisture content of their granules. The angles of internal friction and of wall friction were not significantly different when comparing the two powders.

  7. In Vitro Comparison of the Bond Strength between Ceramic Repair Systems and Ceramic Materials and Evaluation of the Wettability.

    Science.gov (United States)

    Kocaağaoğlu, Hasan; Manav, Taha; Albayrak, Haydar

    2017-04-01

    When fracture of an all-ceramic restoration occurs, it can be necessary to repair without removing the restoration. Although there are many studies about the repair of metal-ceramic restorations, there are few about all-ceramic restorations. The aim of this study was to evaluate the shear bond strength between ceramic repair systems and esthetic core materials and to evaluate the wettability of all-ceramic core materials. Disk-like specimens (N = 90) made of three dental ceramic infrastructure materials (zirconia ceramic, alumina ceramic, glass ceramic) were polished with silicon carbide paper, prepared for bonding (abrasion with 30 μm diamond rotary cutting instrument). Thirty specimens of each infrastructure were obtained. Each infrastructure group was divided into three subgroups; they were bonded using 3 repair systems: Bisco Intraoral Repair Kit, Cimara & Cimara Zircon Repair System, and Clearfil Repair System. After 1200 thermocycles, shear bond strength was measured in a universal testing machine at a 0.5 mm/min crosshead speed. In addition, the contact angle values of the infrastructures after surface treatments were examined for wettability. Data were analyzed by using ANOVA and Tukey post hoc tests. Although there were no significant differences among the repair systems (p > 0.05) in the glass ceramic and zirconia groups, a significant difference was found among the repair systems in alumina infrastructure (p 0.05); however, a statistically significant difference was found among the repair systems (p < 0.05). No difference was found among the infrastructures and repair systems in terms of contact angle values. Cimara & Cimara Zircon Repair System had higher bond strength values than the other repair systems. Although no difference was found among the infrastructures and repair systems, contact wettability angle was decreased by surface treatments compared with polished surfaces. © 2015 by the American College of Prosthodontists.

  8. Impeded solid state reactions and transformations in ceramic catalysts supports and catalysts

    Directory of Open Access Journals (Sweden)

    Ernő E. Kiss

    2012-12-01

    Full Text Available Impeded chemical reactions and impeded polymorphous transformation in materials are discussed, as desired effects, for stabilization of ceramic catalyst supports and ceramic based catalysts. This paper gives a short overview about the possibilities of slowing down the aging processes in ceramic catalyst supports and catalysts. Special attention is given to alumina and titania based catalysts.

  9. Extraction of diagnostic parameters from the transient response of a porous electro ceramic gas sensor

    International Nuclear Information System (INIS)

    Hossein-Babaei, F.; Orvatinia, M.

    2004-01-01

    A novel concept for the diagnosis of a pure target gas in air is presented. The method employs a resistive gas sensor with a mm-thick highly porous electro ceramic gas sensitive body. The diagnosis is based on the fact that the diffusion time of the target gas through the porous body would depend on its molecular properties. The transient response of the device was analyzed based on a diffusion reaction equation. The solutions of the equation were shown to be of diagnostic merits. Such a device was fabricated by partial sintering of a Zn O body formed by low pressure pressing. The transient responses of the device to methanol, ethanol, poropanol and butanol were recorded. The analytical data, and the diagnostic parameters were resulted as the fitting parameters. Comparison of the parameters obtained with those available from the calibration experiments afforded target gas identification

  10. 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.

  11. Status quo of ceramic material for metal halide discharge lamps

    International Nuclear Information System (INIS)

    Kappen, Theo G M M

    2005-01-01

    Polycrystalline alumina is an excellent ceramic material for use as the envelope for metal halide discharge lamps. Although this material was introduced in the mid-1960s, and is thus already known for several decades, recent years have seen considerable effort aimed at further development of these ceramic envelope materials. Developments are not only in the field of ceramic shaping technologies, but are also concentrated on the material properties of the ceramic material itself. Optical, mechanical as well as the chemical properties of the ceramic envelope are strongly controlled by the shape as well as the microstructure of the ceramics used

  12. Correlation between the bending strength and the thickness interlayer of alumina-mild steel friction welded at lower rotational speed

    International Nuclear Information System (INIS)

    Mohamad Zaky Noh; Luay Bakir Hussain; Zainal Arifin Ahmad

    2007-01-01

    The joining of ceramic-metal could be done through a few techniques: brazing, diffusion bonding, friction welding etc. However, the mechanism of ceramic-metal joining was still not properly understood. In this study, alumina rod was bonded to mild steel rod via friction welding technique by using Al 1100 sheet as interlayer. The diameter of the rods was 10 mm. Friction pressure of 20 MPa and forging pressure of 40 MPa were used. Rotational speeds were maintained at 900 rpm and friction times of 2 to 20 seconds were applied. The joining strength was determined through four point bending test. The maximum bending strength, 240 MPa was obtained at the friction times of 20 seconds. Under optical microscope and SEM observation, the deformation of the aluminum interface was clearly obtained. Mechanical interlocking and close contact between the alumina aluminum and aluminum-mild steel were observed at magnifications of 3000X. The strength of alumina-steel bonding is much dependent on the wettability of the alumina surface by the molten aluminum and the existing of mechanical interlocking between interlayer and sample materials. (Author)

  13. Evaluation of interfacial bonding in dissimilar materials of YSZ-alumina composites to 6061 aluminium alloy using friction welding

    International Nuclear Information System (INIS)

    Uday, M.B.; Ahmad Fauzi, M.N.; Zuhailawati, H.; Ismail, A.B.

    2011-01-01

    Research highlights: → Friction-welding process. → Joining between ceramic composite and metal alloy. → Slip casting of the yttria stabilized zirconia/alumina composite samples. - Abstract: The interfacial microstructures characteristics of alumina ceramic body reinforced with yttria stabilized zirconia (YSZ) was evaluated after friction welding to 6061 aluminum alloy using optical and electron microscopy. Alumina rods containing 25 and 50 wt% yttria stabilized zirconia were fabricated by slip casting in plaster of Paris (POP) molds and subsequently sintered at 1600 deg. C. On the other hand, aluminum rods were machine down to the required dimension using a lathe machine. The diameter of the ceramic and the metal rods was 16 mm. Rotational speeds for the friction welding were varied between 900 and 1800 rpm. The friction pressure was maintained at 7 MPa for a friction time of 30 s. Optical and scanning electron microscopy was used to analyze the microstructure of the resultant joints, particularly at the interface. The joints were also examined with EDX line (energy dispersive X-ray) in order to determine the phases formed during the welding. The mechanical properties of the friction welded YSZ-Al 2 O 3 composite to 6061 alloy were determined with a four-point bend test and Vickers microhardness. The experimental results showed the degree of deformation varied significantly for the 6061 Al alloy than the ceramic composite part. The mechanical strength of friction-welded ceramic composite/6061 Al alloy components were obviously affected by joining rotational speed selected which decreases in strength with increasing rotational speed.

  14. Bioactive type glass-ceramics within incorporated aluminium

    International Nuclear Information System (INIS)

    Volzone, C.; Stabile, F.M.; Ortiga, J.

    2012-01-01

    Bioactive glass-ceramics are used as biomaterials for the reparation of bone tissue. They are prepared, generally, by bioglass of specific composition for each particular use. The aluminium addition in the formulation at very small quantities influences on the structural properties. Two glass-ceramics obtained by P 2 O 5 -Na 2 O-CaO-SiO 2 formulation within aluminium (0.5 % in Al 2 O 3 base) added through a reactive alumina and purified feldspar were analyzed. The results showed structural differences between both glass-ceramics. (author)

  15. Synthesis of ZSM-5 on the Surface of Foam Type Porous SiC Support

    International Nuclear Information System (INIS)

    Jung, Eunjin; Lee, Yoon Joo; Won, Ji Yeon; Kim, Younghee; Kim, Soo Ryong; Shin, Dong-Geun; Kwon, Woo Teck; Lee, Hyun Jae

    2015-01-01

    ZSM-5 crystals grew by hydrothermal synthesis method on the surface of foam type porous silicon carbide ceramics which fabricated by polymer replica method. Oxide layer was developed on the surface of the porous silicon carbide ceramics to induce growth of ZSM-5 from the surface. In this study, hydrothermal synthesis was carried out for 7 h at 150 .deg. C using TEOS, Al(NO 3 )•9H 2 O and TPAOH as raw materials in the presence of the porous silicon carbide ceramics. X-ray Powder Diffraction (XRD) and Scanning Electron Microscope (SEM) analyses were confirmed 1-3 μm sized ZSM-5 crystals have grown on the surface of porous silicon carbide ceramics. BET data shows that small pores about 10Å size drastically enhanced and surface area increased from 0.83 m 2 /g to 30.75 m 2 /g after ZSM-5 synthesis on the surface of foam type porous silicon carbide ceramics.

  16. Analysis and measurement of residual stress distribution of vanadium/ceramics joints for fusion reactor applications

    International Nuclear Information System (INIS)

    Nemoto, Y.; Ueda, K.

    1998-01-01

    Vanadium alloys are considered as candidate structural materials for fusion reactor system. When vanadium alloys are used in fusion reactor system, joining with ceramics for insulating is one of material issues to be solved to make component of fusion reactor. In the application of ceramics/metal jointing and coating, residual stress caused by difference of thermal expansion rate between ceramics and metals is an important factor in obtaining good bonding strength and soundness of coating. In this work, residual stress distribution in direct diffusion bonded vanadium/alumina joint (jointing temperature: 1400 C) was measured by small area X-ray diffraction method. And the comparison of finite element method (FEM) analysis and actual stress distribution was carried out. Tensile stress concentration at the edge of the boundary of the joint in alumina was observed. The residual stress concentration may cause cracks in alumina, or failure of bonding. Actually, cracks in alumina caused by thermal stress after bonding at 1500 C was observed. The stress concentration of the joint must be reduced to obtain good bonded joint. Lower bonding temperature or to devise the shape of the outer surface of the joint will reduce the stress concentration. (orig.)

  17. Synthesis of silver nanoparticles deposited in porous ceramic by γ-irradiation

    International Nuclear Information System (INIS)

    Nguyen Thuy Ai Trinh; Ngo Manh Thang; Nguyen Thi Kim Lan; Dang Van Phu; Nguyen Quoc Hien; Bui Duy Du

    2015-01-01

    Silver nanoparticles (Ag nano) were deposited in porous ceramic (PC) that was functionalized with aminosilane (AS) agent (PC-AS-Ag nano) by gamma Co-60 irradiation of the PC-AS/Ag"+ mixture using polyvinylpyrrolidone (PVP) as stabilizer. Effect of dose on the formation of Ag nano was investigated. Characteristics of the nanocomposite material (PC-AS-Ag nano) were determined by ultraviolet visible spectroscopy (UV-Vis), X-ray diffraction (XRD), transmission electron microscopy (TEM) and inductively coupled plasma-atomic emission spectroscopy (ICP-AES). Results indicated that Ag nano size was ⁓ 9 nm and the Ag nano content in PC-AS-Ag nano material was about of 341 ± 51 mg/kg at dose of 14-20 kGy. Thus, gamma Co-60 irradiation method has the advantage of creation of small Ag nanoparticles with fairly homogenous distribution in PC material. (author)

  18. Diffusion in ceramics

    CERN Document Server

    Pelleg, Joshua

    2016-01-01

    This textbook provides an introduction to changes that occur in solids such as ceramics, mainly at high temperatures, which are diffusion controlled, as well as presenting research data. Such changes are related to the kinetics of various reactions such as precipitation, oxidation and phase transformations, but are also related to some mechanical changes, such as creep. The book is composed of two parts, beginning with a look at the basics of diffusion according to Fick's Laws. Solutions of Fick’s second law for constant D, diffusion in grain boundaries and dislocations are presented along with a look at the atomistic approach for the random motion of atoms. In the second part, the author discusses diffusion in several technologically important ceramics. The ceramics selected are monolithic single phase ones, including: A12O3, SiC, MgO, ZrO2 and Si3N4. Of these, three refer to oxide ceramics (alumina, magnesia and zirconia). Carbide based ceramics are represented by the technologically very important Si-ca...

  19. 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)

  20. Pressureless sintering and gas flux properties of porous ceramic membranes for gas applications

    Directory of Open Access Journals (Sweden)

    David O. Obada

    Full Text Available The preparation and characterization of kaolin based ceramic membranes using styrofoam (STY and sawdust (SD as pore formers have been prepared by mechano-chemical synthesis using pressureless sintering technique with porogen content between (0–20 wt% by die pressing. Pellets were fired at 1150 °C and soaking time of 4 h. The membranes cast as circular disks were subjected to characterization studies to evaluate the effect of the sintering temperature and pore former content on porosity, density, water absorption and mechanical strength. Obtained membranes show effective porosity with maximum at about 43 and 47% respectively for membranes formulated with styrofoam and sawdust porogens but with a slightly low mechanical strength that does not exceed 19 MPa. The resultant ceramic bodies show a fine porous structure which is mainly caused by the volatilization of the porogens. The fabricated membrane exhibited high N2 gas flux, hence, these membranes can be considered as efficient for potential application for gas separation by reason of the results shown in the gas flux tests. Keywords: Porosity, Pore formers, Kaolin, Physico-mechanical properties, Gas separation, Gas flux

  1. Environment-oriented low-cost porous mullite ceramic membrane supports fabricated from coal gangue and bauxite

    Energy Technology Data Exchange (ETDEWEB)

    Lü, Qikai [Institute of Urban Environment, Chinese Academy of Sciences, Xiamen (China); Ningbo Urban Environment Observation and Research Station-NUEORS, Chinese Academy of Sciences, Ningbo (China); School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou (China); Dong, Xinfa [School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou (China); Zhu, Zhiwen [Institute of Urban Environment, Chinese Academy of Sciences, Xiamen (China); Ningbo Urban Environment Observation and Research Station-NUEORS, Chinese Academy of Sciences, Ningbo (China); Dong, Yingchao, E-mail: ycdong@iue.ac.cn [Institute of Urban Environment, Chinese Academy of Sciences, Xiamen (China); Ningbo Urban Environment Observation and Research Station-NUEORS, Chinese Academy of Sciences, Ningbo (China)

    2014-05-01

    Highlights: • Coal gangue was recycled to fabricate low-cost porous mullite membrane supports. • A unique volume-expansion occurred due to a mullitization-crystal-growth process. • A porous structure consists of glassy particles and embedded mullite crystals. - Abstract: Porous mullite ceramic supports for filtration membrane were successfully fabricated via recycling of coal gangue and bauxite at sintering temperatures from 1100 to 1500 °C with corn starch as pore-forming agent. The dynamic sintering behaviors, phase evolution, shrinkage, porosity and pore size, gas permeation flux, microstructure and mechanical property were systematically studied. A unique volume-expansion stage was observed at increased temperatures from 1276 to 1481 °C caused by a mullitization-crystal-growth process. During this stage, open porosity increases and pore size distributions broaden, which result in a maximum of nitrogen gas flux at 1400 °C. The X-ray diffraction results reveal that secondary mullitization took place from 1100 °C and the major phase is mullite with a content of ∼84.7 wt.% at 1400 °C. SEM images show that the as-fabricated mullite supports have a porous microstructure composed of sintered glassy particles embedded with inter-locked mullite crystals, which grew gradually with increasing temperature from rod-like into blocky-like morphologies. To obtain mullite membrane supports with sufficient porosity and acceptable mechanical strength, the relationship between porosity and mechanical strength was investigated, which was fitted using a parabolic equation.

  2. Hardness and electrochemical behavior of ceramic coatings on Inconel

    Directory of Open Access Journals (Sweden)

    C. SUJAYA

    2012-03-01

    Full Text Available Thin films of ceramic materials like alumina and silicon carbide are deposited on Inconel substrate by pulsed laser deposition technique using Q-switched Nd: YAG laser. Deposited films are characterized using UV-visible spectrophotometry and X-ray diffraction. Composite microhardness of ceramic coated Inconel system is measured using Knoop indenter and its film hardness is separated using a mathematical model based on area-law of mixture. It is then compared with values obtained using nanoindentation method. Film hardness of the ceramic coating is found to be high compared to the substrates. Corrosion behavior of substrates after ceramic coating is studied in 3.5% NaCl solution by potentiodynamic polarization and electrochemical impedance spectroscopy measurements. The Nyquist and the Bode plots obtained from the EIS data are fitted by appropriate equivalent circuits. The pore resistance, the charge transfer resistance, the coating capacitance and the double layer capacitance of the coatings are obtained from the equivalent circuit. Experimental results show an increase in corrosion resistance of Inconel after ceramic coating. Alumina coated Inconel showed higher corrosion resistance than silicon carbide coated Inconel. After the corrosion testing, the surface topography of the uncoated and the coated systems are examined by scanning electron microscopy.

  3. Synthesis of boehmite by hydrothermal treatment used as inorganic binder for alumina powder

    International Nuclear Information System (INIS)

    Lima, M.B.; Tercini, M.B.; Yoshimura, H.N.

    2012-01-01

    Presently, due to the concerns with the environment, it has been developed studies to replace the organic binder by an inorganic binder for forming of ceramic powders, in order to avoiding the generation of polluting gases during sintering (firing). A potential alternative is the use of boehmite, produced by hydrothermal treatment on the surfaces of the alumina powder, previously ground in a ball mill using zirconia milling media to produce hydrated phases on alumina powder which are converted to boehmite. In the treated alumina powders, it was observed the formation of boehmite phase by X-ray diffraction analysis and Fourier transformed infrared (FTIR) spectroscopy, demonstrating the efficiency of boehmite formation during the hydrothermal treatment at 150°C for 3 hours.(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. Effect of anodizing voltage on the sorption of water molecules on porous alumina

    Energy Technology Data Exchange (ETDEWEB)

    Vrublevsky, I., E-mail: vrublevsky@bsuir.edu.by [Belarusian State University of Informatics and Radioelectronics, Department of Micro and Nanoelectronics, 220013 Minsk (Belarus); Chernyakova, K. [Belarusian State University of Informatics and Radioelectronics, Department of Micro and Nanoelectronics, 220013 Minsk (Belarus); Bund, A.; Ispas, A.; Schmidt, U. [Fachgebiet Elektrochemie und Galvanotechnik, Technische Universitaet Ilmenau, 98693 Ilmenau (Germany)

    2012-05-01

    The amount of water adsorbed on different centers on the surface of oxalic acid alumina films is a function of the anodizing voltage. It is decreased with increasing the anodizing voltage from 20 up to 50 V, came up to maximum value at 20-30 V and slightly increased at voltages above 50 V. Water adsorption by oxide films formed at voltages below 50 V can be due to the negative surface charge that is present on the alumina surface. The negative surface charge disappears in the films formed at voltages higher than 50 V, and thus, the water is adsorbed on aluminum ions in a tetrahedral and octahedral environment. The correlation between anodizing conditions of aluminum in oxalic acid and the structure and composition of anodic alumina was established by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), thermogravimetric and differential thermal analyses (TG/DTA).

  6. Microtensile bond strength of a resin cement to glass infiltrated zirconia-reinforced ceramic: The effect of surface conditioning

    NARCIS (Netherlands)

    Amaral, R.; Ozcan, M.; Bottino, M.A.; Valandro, L.F.

    2006-01-01

    Objectives. This study evaluated the effect of three surface conditioning methods on the microtensile bond strength of resin cement to a glass-infiltrated zirconia-reinforced alumina-based core ceramic. Methods. Thirty blocks (5 x 5 x 4 mm) of In-Ceram Zirconia ceramics (In-Ceram Zirconia-INC-ZR,

  7. Microtensile bond strength of a resin cement to glass infiltrated zirconia-reinforced ceramic : The effect of surface conditioning

    NARCIS (Netherlands)

    Amaral, R; Ozcan, M; Bottino, MA; Valandro, LF

    Objectives. This study evaluated the effect of three surface conditioning methods on the microtensile bond strength of resin cement to a glass-infiltrated zirconia-reinforced alumina-based core ceramic. Methods. Thirty blocks (5 x 5 x 4 mm) of In-Ceram Zirconia ceramics (In-Ceram Zirconia-INC-ZR,

  8. Fabrication and Characterization of Single Phase α-Alumina Membranes with Tunable Pore Diameters

    Science.gov (United States)

    Masuda, Tatsuya; Asoh, Hidetaka; Haraguchi, Satoshi; Ono, Sachiko

    2015-01-01

    Nanoporous and single phase α-alumina membranes with pore diameters tunable over a wide range of approximately 60–350 nm were successfully fabricated by optimizing the conditions for anodizing, subsequent detachment, and heat treatment. The pore diameter increased and the cell diameter shrunk upon crystallization to α-alumina by approximately 20% and 3%, respectively, in accordance with the 23% volume shrinkage resulting from the change in density associated with the transformation from the amorphous state to α-alumina. Nevertheless, flat α-alumina membranes, each with a diameter of 25 mm and a thickness of 50 μm, were obtained without thermal deformation. The α-alumina membranes exhibited high chemical resistance in various concentrated acidic and alkaline solutions as well as when exposed to high temperature steam under pressure. The Young’s modulus and hardness of the single phase α-alumina membranes formed by heat treatment at 1250 °C were notably decreased compared to the corresponding amorphous membranes, presumably because of the nodular crystallite structure of the cell walls and the substantial increase in porosity. Furthermore, when used for filtration, the α-alumina membrane exhibited a level of flux higher than that of the commercial ceramic membrane. PMID:28788005

  9. Fabrication and Characterization of Single Phase α-Alumina Membranes with Tunable Pore Diameters

    Directory of Open Access Journals (Sweden)

    Tatsuya Masuda

    2015-03-01

    Full Text Available Nanoporous and single phase α-alumina membranes with pore diameters tunable over a wide range of approximately 60–350 nm were successfully fabricated by optimizing the conditions for anodizing, subsequent detachment, and heat treatment. The pore diameter increased and the cell diameter shrunk upon crystallization to α-alumina by approximately 20% and 3%, respectively, in accordance with the 23% volume shrinkage resulting from the change in density associated with the transformation from the amorphous state to α-alumina. Nevertheless, flat α-alumina membranes, each with a diameter of 25 mm and a thickness of 50 μm, were obtained without thermal deformation. The α-alumina membranes exhibited high chemical resistance in various concentrated acidic and alkaline solutions as well as when exposed to high temperature steam under pressure. The Young’s modulus and hardness of the single phase α-alumina membranes formed by heat treatment at 1250 °C were notably decreased compared to the corresponding amorphous membranes, presumably because of the nodular crystallite structure of the cell walls and the substantial increase in porosity. Furthermore, when used for filtration, the α-alumina membrane exhibited a level of flux higher than that of the commercial ceramic membrane.

  10. Tomography based determination of permeability, Dupuit-Forchheimer coefficient, and interfacial heat transfer coefficient in reticulate porous ceramics

    International Nuclear Information System (INIS)

    Petrasch, Joerg; Meier, Fabian; Friess, Hansmartin; Steinfeld, Aldo

    2008-01-01

    A computer tomography based methodology is applied to determine the transport properties of fluid flow across porous media. A 3D digital representation of a 10-ppi reticulate porous ceramic (RPC) sample was generated by X-ray tomographic scans. Structural properties such as the porosity, specific interfacial surface area, pore-size distribution, mean survival time, two-point correlation function s 2 , and local geometry distribution of the RPC sample are directly extracted from the tomographic data. Reference solutions of the fluid flow governing equations are obtained for Re = 0.2-200 by applying finite volume direct pore-level numerical simulation (DPLS) using unstructured, body-fitted, tetrahedral mesh discretization. The permeability and the Dupuit-Forchheimer coefficient are determined from the reference solutions by DPLS, and compared to the values predicted by selected porous media flow models, namely: conduit-flow, hydraulic radius theory, drag models, mean survival time bound, s 2 -bound, fibrous bed correlations, and local porosity theory-based models. DPLS is further employed to determine the interfacial heat transfer coefficient and to derive a corresponding Nu-correlation, which is compared to empirical correlations

  11. Hard tissue formation in a porous HA/TCP ceramic scaffold loaded with stromal cells derived from dental pulp and bone marrow.

    NARCIS (Netherlands)

    Zhang, W.; Walboomers, X.F.; Osch, G.J.V.M. van; Dolder, J. van den; Jansen, J.A.

    2008-01-01

    The aim of this study was to compare the ability of hard tissue regeneration of four types of stem cells or precursors under both in vitro and in vivo situations. Primary cultures of rat bone marrow, rat dental pulp, human bone marrow, and human dental pulp cells were seeded onto a porous ceramic

  12. [Interface bond and compatibility between GI-II glass/alumina composite and Vitadur alpha veneering porcelain].

    Science.gov (United States)

    Meng, Yukun; Chao, Yonglie; Liao, Yunmao

    2002-01-01

    Multiple layer techniques were commonly employed in fabricating all-ceramic restorations. Bond and compatibility between layers were vitally important for the clinical success of the restorations. The purposes of this study were to investigate the bond of the interface between the GI-II glass/alumina composite and Vitadur alpha veneering porcelain, and to study the thermal compatibility between them. Prepared a bar shaped specimen of GI-II glass/alumina composite 25 mm x 5 mm x 1 mm in size, with bottom surface pre-notched. The upper surface was veneered with Vitadur alpha veneering porcelain (0.2 mm opaque dentin and 0.6 mm dentin porcelain), then fractured and the fracture surface were examined under scanning electron microscope (SEM) and electron microprobe analyzer (EMPA) with electron beam of 10 micrometer in diameter; ten all-ceramic single crowns for an upper right central incisor were fabricated and the temperatures of thermal shock resistance were tested. SEM observation showed tight bond between the composite and the porcelain; The results of EMPA showed that penetration of Na, Al elements from glass/alumina into veneering porcelain and Si, K, Ca elements from veneering porcelain into glass/alumina occurred after sintering baking; The temperature of thermal shock resistance for anterior crowns in this study was 158 +/- 10.3 degrees C, cracks were mainly distributed in veneering porcelain with thicker layer. Chemical bond exists between the GI-II glass/alumina composite and Vitadur alpha veneering porcelain, and there is good thermal compatibility between them.

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

    Directory of Open Access Journals (Sweden)

    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.

  14. Mirror-backed Dark Alumina: A Nearly Perfect Absorber for Thermoelectronics and Thermophotovotaics

    Science.gov (United States)

    Farhat, Mohamed; Cheng, Tsung-Chieh; Le, Khai. Q.; Cheng, Mark Ming-Cheng; Bağcı, Hakan; Chen, Pai-Yen

    2016-01-01

    We present here a broadband, wide-angle, and polarization-independent nearly perfect absorber consisting of mirror-backed nanoporous alumina. By electrochemically anodizing the disordered multicomponent aluminum and properly tailoring the thickness and air-filling fraction of nanoporous alumina, according to the Maxwell-Garnet mixture theory, a large-area dark alumina can be made with excellent photothermal properties and absorption larger than 93% over a wide wavelength range spanning from near-infrared to ultraviolet light, i.e. 250 nm-2500 nm. The measured absorption is orders of magnitude greater than other reported anodized porous alumina, typically semi-transparent at similar wavelengths. This simple yet effective approach, however, does not require any lithography, nano-mixture deposition, pre- and post-treatment. Here, we also envisage and theoretically investigate the practical use of proposed absorbers and/or photothermal converters in integrated thermoelectronic and/or thermophotovoltaic energy conversion devices, which make efficient use of the entire spectrum of ambient visible to near-infrared radiation.

  15. Mirror-backed Dark Alumina: A Nearly Perfect Absorber for Thermoelectronics and Thermophotovotaics

    KAUST Repository

    Farhat, Mohamed

    2016-01-28

    We present here a broadband, wide-angle, and polarization-independent nearly perfect absorber consisting of mirror-backed nanoporous alumina. By electrochemically anodizing the disordered multicomponent aluminum and properly tailoring the thickness and air-filling fraction of nanoporous alumina, according to the Maxwell-Garnet mixture theory, a large-area dark alumina can be made with excellent photothermal properties and absorption larger than 93% over a wide wavelength range spanning from near-infrared to ultraviolet light, i.e. 250 nm–2500 nm. The measured absorption is orders of magnitude greater than other reported anodized porous alumina, typically semi-transparent at similar wavelengths. This simple yet effective approach, however, does not require any lithography, nano-mixture deposition, pre- and post-treatment. Here, we also envisage and theoretically investigate the practical use of proposed absorbers and/or photothermal converters in integrated thermoelectronic and/or thermophotovoltaic energy conversion devices, which make efficient use of the entire spectrum of ambient visible to near-infrared radiation.

  16. Resistance to bond degradation between dual-cure resin cements and pre-treated sintered CAD-CAM dental ceramics

    Science.gov (United States)

    Osorio, Raquel; Monticelli, Francesca; Osorio, Estrella; Toledano, Manuel

    2012-01-01

    Objective: To evaluate the bond stability of resin cements when luted to glass-reinforced alumina and zirconia CAD/CAM dental ceramics. Study design: Eighteen glass-infiltrated alumina and eighteen densely sintered zirconia blocks were randomly conditioned as follows: Group 1: No treatment; Group 2: Sandblasting (125 µm Al2O3-particles); and Group 3: Silica-coating (50 µm silica-modified Al2O3-particles). Composite samples were randomly bonded to the pre-treated ceramic surfaces using different resin cements: Subgroup 1: Clearfil Esthetic Cement (CEC); Subgroup 2: RelyX Unicem (RXU); and Subgroup 3: Calibra (CAL). After 24 h, bonded specimens were cut into 1 ± 0.1 mm2 sticks. One-half of the beams were tested for microtensile bond strength (MTBS). The remaining one-half was immersed in 10 % NaOCl aqueous solution (NaOClaq) for 5 h before testing. The fracture pattern and morphology of the debonded surfaces were assessed with a field emission gun scanning electron microscope (FEG-SEM). A multiple ANOVA was conducted to analyze the contributions of ceramic composition, surface treatment, resin cement type, and chemical challenging to MTBS. The Tukey test was run for multiple comparisons (p ceramic interfacial longevity depended on cement selection rather than on surface pre-treatments. The MDP-containing and the self-adhesive resin cements were both suitable for luting CAD/CAM ceramics. Despite both cements being prone to degradation, RXU luted to zirconia or untreated or sandblasted alumina showed the most stable interfaces. CAL experimented spontaneous debonding in all tested groups. Key words:CAD/CAM ceramic, alumina, zirconia, resin cement, surface pre-treatment, sandblasting, silica-coating, chemical aging, bond degradation, microtensile bond strength. PMID:22322517

  17. Significant room-temperature ferromagnetism in porous ZnO films: The role of oxygen vacancies

    Energy Technology Data Exchange (ETDEWEB)

    Hou, Xue; Liu, Huiyuan [College of Physics Science & Information Engineering, Hebei Normal University, Shijiazhuang 050024 (China); Key Laboratory of Advanced Films of Hebei Province, Shijiazhuang 050024 (China); Sun, Huiyuan, E-mail: huiyuansun@126.com [College of Physics Science & Information Engineering, Hebei Normal University, Shijiazhuang 050024 (China); Key Laboratory of Advanced Films of Hebei Province, Shijiazhuang 050024 (China); Liu, Lihu; Jia, Xiaoxuan [College of Physics Science & Information Engineering, Hebei Normal University, Shijiazhuang 050024 (China); Key Laboratory of Advanced Films of Hebei Province, Shijiazhuang 050024 (China)

    2015-10-15

    Graphical abstract: - Highlights: • Porous ZnO films were deposited on porous anodic alumina substrates. • Significant ferromagnetism (FM) has been observed in porous ZnO films (110 emu/cm{sup 3}). • The strong magnetic anisotropy was observed in the porous ZnO films. • The origin of FM is attributed to the oxygen vacancy with a local magnetic moment. - Abstract: Pure porous ZnO films were prepared by direct current reactive magnetron sputtering on porous anodic alumina substrates. Remarkably large room-temperature ferromagnetism was observed in the films. The highest saturation moment along the out-of-plane direction was about 110 emu/cm{sup 3}. Experimental and theoretical results suggested that the oxygen vacancies and the unique porous structure of the films are responsible for the large ferromagnetism. There are two modes of coupling between oxygen vacancies in the porous ZnO films: (i) exchange interactions directly between the oxygen vacancies and (ii) with the mediation of conduction electrons. In addition, it was found that the magnetic moment of ZnO films can be changed by tuning the concentration of oxygen vacancies. These observations may be useful in the development of ZnO-based spintronics devices.

  18. Characterization of the Sol-Gel Transition for Zirconia-Toughened Alumina Precursors

    Science.gov (United States)

    Moeti, I.; Karikari, E.; Chen, J.

    1998-01-01

    High purity ZTA ceramic powders with and without yttria were produced using metal alkoxide precursors. ZTA ceramic powders with varying volume percents of zirconia were prepared (7, 15, and 22%). Aluminum tri-sec butoxide, zirconium propoxide, and yttrium isopropoxide were the reagents used. Synthesis conditions were varied to control the hydrolysis and the aging conditions for the sol to gel transition. FTIR analysis and theological characterization were used to follow the structural evolution during the sol to gel transition. The greater extent of hydrolysis and the build-up of structure measured from viscoelastic properties were consistent. Heat treatment was conducted to produce submicron grain fully crystalline ZTA ceramic powders. In all experimental cases a-alumina and tetragonal zirconia phases were confirmed even in the absence of yttria.

  19. The use of ceramic in prosthetic hip surgery. The state of the art.

    Science.gov (United States)

    Toni, A; Terzi, S; Sudanese, A; Tabarroni, M; Zappoli, F A; Stea, S; Giunti, A

    1995-01-01

    The authors review current knowledge regarding the use of ceramic materials in prosthetic hip surgery, both as constituents of prosthetic components, and as materials used to coat metallic surfaces. A review of the literature defines the advantages and disadvantages to using ceramic-polyethylene or ceramic-ceramic combinations, based on the possibility that alumina coating may favor localized bone demineralization, and on the first promising clinical results of the use of hydroxyapatite coating.

  20. ZIF-8 Membranes with Improved Reproducibility Fabricated from Sputter-Coated ZnO/Alumina Supports

    KAUST Repository

    Yu, Jian; Pan, Yichang; Wang, Chongqing; Lai, Zhiping

    2015-01-01

    for reproducible fabrication of high-quality membranes. In this study, high-quality ZIF-8 membranes were prepared through hydrothermal synthesis under the partial self-conversion of sputter-coated ZnO layer on porous α-alumina supports. The reproducibility

  1. Room temperature H{sub 2}S gas sensing characteristics of platinum (Pt) coated porous alumina (PoAl) thick films

    Energy Technology Data Exchange (ETDEWEB)

    More, P.S., E-mail: p_smore@yahoo.co.in [Department of Physics, Institute of Science, Mumbai 400 032 (India); Raut, R.W. [Department of Botany, Institute of Science, Mumbai 400 032 (India); Ghuge, C.S. [Department of Physics, Institute of Science, Mumbai 400 032 (India)

    2014-02-14

    The study reports H{sub 2}S gas sensing characteristics of platinum (Pt) coated porous alumina (PoAl) films. The porous alumina (PoAl) thick layers were formed in the dark on aluminum substrates using an electrochemical anodization method. Thin semitransparent platinum (Pt) films were deposited on PoAl samples using chemical bath deposition (CBD) method. The films were characterized using energy dispersive X-ray analysis (EDAX) and scanning electron microscopy (SEM). The thicknesses of coated and bare films were measured using ellipsometry. The sensing properties such as sensitivity factor (S.F.), response time, recovery time and repeatability were measured using a static gas sensing system for H{sub 2}S gas. The EDAX studies confirmed the purity of Pt–PoAl film and indicated the formation of pure platinum (Pt) phase. The ellipsometry studies revealed the thickness of PoAl layer of about 15–17 μm on aluminum substrates. The SEM studies demonstrated uniform distribution of spherical pores with a size between 0.250 and 0.500 μm for PoAl film and nearly spherical platinum particles with average particle size ∼100 nm for Pt–PoAl film. The gas-sensing properties of these samples were studied in a home-built static gas characterization system. The H{sub 2}S gas sensing properties of Pt–PoAl at 1000 ppm of H{sub 2}S gave maximum sensitivity factor (S.F.) = 1200. The response time and recovery time were found to be 2–3 min and ∼1 min respectively. Further, the measurement of H{sub 2}S gas sensing properties clearly indicated the repeatability of gas sensing response of Pt–PoAl film. The present study indicated the significant potential of Pt coated PoAl films for H{sub 2}S gas sensing applications in diverse areas. - Highlights: • Electrochemical anodization, cheap and effective method for fabrication of PoAl. • Chemical bath deposition, a simple and effective method for deposition of Pt on PoAl. • A nano-composite film sensor with high sensitivity

  2. Fracture-dissociation of ceramic liner.

    Science.gov (United States)

    Hwang, Sung Kwan; Oh, Jin-Rok; Her, Man Seung; Shim, Young Jun; Cho, Tae Yeun; Kwon, Sung Min

    2008-08-01

    The use of BIOLOX delta ceramic (CeramTec AG, Plochingen, Germany) has been increasing. This ceramic prevents cracking by restraining the phase transformation due to the insertion of nano-sized, yttria-stabilized tetragonal zirconia into the alumina matrix. This restrains the progress of cracking through the formation of platelet-like crystal or whiskers due to the addition of an oxide additive. We observed a case of BIOLOX delta ceramic liner (CeramTec AG) rim fracture 4 months postoperatively. Radiographs showed that the ceramic liner was subluxated from the acetabular cup. Scratches on the acetabular cup and femoral neck were seen, and the fracture was visible on the rim of the liner. Under electron microscope, metal particle coatings from the ceramic liner were identified. The ceramic liner, fracture fragments, and adjacent tissues were removed and replaced with a ceramic liner and femoral head of the same size and design. We believe the mechanism of the fracture-dissociation of the ceramic liner in this case is similar to a case of separation of the ceramic liner from the polyethylene shell in a sandwich-type ceramic-ceramic joint. To prevent ceramic liner fracture-dissociation, the diameter of the femoral neck needs to be decreased in a new design, while the diameter of the femoral head needs to be increased to ensure an increase in range of motion.

  3. Flame assisted synthesis of catalytic ceramic membranes

    DEFF Research Database (Denmark)

    Johansen, Johnny; Mosleh, Majid; Johannessen, Tue

    2004-01-01

    technology it is possible to make supported catalysts, composite metal oxides, catalytically active surfaces, and porous ceramic membranes. Membrane layers can be formed by using a porous substrate tube (or surface) as a nano-particle filter. The aerosol gas from the flame is led through a porous substrate...

  4. Variation of the dimensions and the strength of electrical ceramics during irradiation

    International Nuclear Information System (INIS)

    Blaunshtein, I.M.; Kishinevskaya, M.B.; Muminov, M.I.

    1988-01-01

    Changes were studied in the linear dimensions and the ultimate bend strength of a wide range or ceramic materials (MK and GB7 high-alumina ceramics, the UF-46 mullite-corundum ceramic, SNTs and SK-1 steatite ceramics, and the glasses that have the same chemical composition as that of the glass phase of the GB-7 and UF-46 ceramics) following irradiation with a gamma beam from a Co 60 source and in the field of mixed gamma-neutron radiation from a VVR-SM reactor up to the maximum doses

  5. Relative translucency of six all-ceramic systems. Part I: core materials.

    Science.gov (United States)

    Heffernan, Michael J; Aquilino, Steven A; Diaz-Arnold, Ana M; Haselton, Debra R; Stanford, Clark M; Vargas, Marcos A

    2002-07-01

    All-ceramic restorations have been advocated for superior esthetics. Various materials have been used to improve ceramic core strength, but it is unclear whether they affect the opacity of all-ceramic systems. This study compared the translucency of 6 all-ceramic system core materials at clinically appropriate thicknesses. Disc specimens 13 mm in diameter and 0.49 +/- 0.01 mm in thickness were fabricated from the following materials (n = 5 per group): IPS Empress dentin, IPS Empress 2 dentin, In-Ceram Alumina core, In-Ceram Spinell core, In-Ceram Zirconia core, and Procera AllCeram core. Empress and Empress 2 dentin specimens also were fabricated and tested at a thickness of 0.77 +/- 0.02 mm (the manufacturer's recommended core thickness is 0.8 mm). A high-noble metal-ceramic alloy (Porc. 52 SF) served as the control, and Vitadur Alpha opaque dentin was used as a standard. Sample reflectance (ratio of the intensity of reflected light to that of the incident light) was measured with an integrating sphere attached to a spectrophotometer across the visible spectrum (380 to 700 nm); 0-degree illumination and diffuse viewing geometry were used. Contrast ratios were calculated from the luminous reflectance (Y) of the specimens with a black (Yb) and a white (Yw) backing to give Yb/Yw with CIE illuminant D65 and a 2-degree observer function (0.0 = transparent, 1.0 = opaque). One-way analysis of variance and Tukey's multiple-comparison test were used to analyze the data (P In-Ceram Spinell > Empress, Procera, Empress 2 > In-Ceram Alumina > In-Ceram Zirconia, 52 SF alloy.

  6. 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

  7. Ceramic core–shell composites with modified mechanical properties prepared by thermoplastic co-extrusion

    Czech Academy of Sciences Publication Activity Database

    Kaštyl, J.; Chlup, Zdeněk; Clemens, F.; Trunec, M.

    2015-01-01

    Roč. 35, č. 10 (2015), s. 2873-2881 ISSN 0955-2219 R&D Projects: GA MŠk(CZ) ED1.1.00/02.0068 Institutional support: RVO:68081723 Keywords : Alumina * Zirconia toughened alumina * Co-extrusion * Composite * Mechanical properties1 Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 2.933, year: 2015

  8. Obtenção e análise de cerâmicas porosas com a incorporação de produtos orgânicos ao corpo cerâmico Obtaining and analysis of porous ceramic with the incorporation of organic products to the ceramic body

    Directory of Open Access Journals (Sweden)

    R. P. S. Dutra

    2002-12-01

    Full Text Available As cerâmicas porosas possuem um elevado potencial para serem usadas em diversas aplicações importantes. Combinando adequadamente matérias-primas e técnicas de processamento, é possível obter cerâmicas porosas com elevados valores de resistência mecânica, resistência ao ataque químico, elevada refratariedade e elevada uniformidade estrutural. Entre os vários métodos de obtenção de cerâmica porosa, o método de incorporação de produtos orgânicos ao corpo cerâmico é bastante utilizado quando se deseja trabalhar com a porosidade do produto. No entanto, muitas variáveis devem ser analisadas, a começar pela quantidade de material orgânico adicionado ao corpo cerâmico. Este trabalho tem como objetivo a elaboração de cerâmicas porosas com a incorporação do pó-de-madeira ao corpo cerâmico e a análise das propriedades físicas e mecânicas deste material com a variação da temperatura de processamento. Os resultados indicaram que o método é viável, constatando um aumento da fração de poros com a adição do material orgânico e boa resistência mecânica do material.The porous ceramic have a high potential to be used in several important applications. Combining raw materials with processing techniques appropriately is possible to obtain porous ceramic with high values of mechanical resistance, resistance to the chemical attack, high refratariety and high structural uniformity. Among the several methods of obtaining porous ceramic, the method of incorporation organic products of the ceramic body is very used when wish work with the porosity of the product. However, many variety should be analyzed, to begin the amount of organic material added to the ceramic body. This work has as objective the elaboration of porous ceramic with the incorporation of the wood powder to the ceramic body and the analysis of the physical and mechanical properties of this material with the variation of the processing temperature. The

  9. Preparation of biomorphic SiC ceramic by carbothermal reduction of oak wood charcoal

    International Nuclear Information System (INIS)

    Qian Junmin; Wang Jiping; Jin Zhihao

    2004-01-01

    Highly porous silicon carbide (SiC) ceramic with woodlike microstructure has been prepared at 1400-1600 deg. C by carbothermal reduction reaction of charcoal/silica composites in static argon atmosphere. These composites were fabricated by infiltrating silica sol into a porous biocarbon template from oak wood using a vacuum/pressure infiltration process. The morphology of resulting porous SiC ceramic, as well as the conversion mechanism of wood to porous SiC ceramic, have been investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques. Experimental results show that the biomorphic cellular morphology of oak wood charcoal is remained in the porous SiC ceramic with high precision that consists of β-SiC with traces of α-SiC. Silica in the charcoal/silica composites exists in the cellular pores in form of fibers and rods. The SiC strut material is formed by gas-solid reaction between SiO (g) and C (s) during the charcoal-to-ceramic conversion. The densification of SiC strut material may occur at moderate temperatures and holding time

  10. Preparation of biomorphic SiC ceramic by carbothermal reduction of oak wood charcoal

    Energy Technology Data Exchange (ETDEWEB)

    Qian Junmin; Wang Jiping; Jin Zhihao

    2004-04-25

    Highly porous silicon carbide (SiC) ceramic with woodlike microstructure has been prepared at 1400-1600 deg. C by carbothermal reduction reaction of charcoal/silica composites in static argon atmosphere. These composites were fabricated by infiltrating silica sol into a porous biocarbon template from oak wood using a vacuum/pressure infiltration process. The morphology of resulting porous SiC ceramic, as well as the conversion mechanism of wood to porous SiC ceramic, have been investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques. Experimental results show that the biomorphic cellular morphology of oak wood charcoal is remained in the porous SiC ceramic with high precision that consists of {beta}-SiC with traces of {alpha}-SiC. Silica in the charcoal/silica composites exists in the cellular pores in form of fibers and rods. The SiC strut material is formed by gas-solid reaction between SiO (g) and C (s) during the charcoal-to-ceramic conversion. The densification of SiC strut material may occur at moderate temperatures and holding time.

  11. Erosion resistance and adhesion of composite metal/ceramic coatings produced by plasma spraying

    OpenAIRE

    Ramm , D.; Hutchings , I.; Clyne , T.

    1993-01-01

    Ceramic coatings can exhibit greater erosion resistance than most metallic coatings. Such coatings are conveniently produced by thermal spraying. Unfortunately, thermally sprayed ceramic coatings often exhibit poor adhesion, partly as a consequence of the development of residual stresses during spraying and subsequent cooling. Composite coatings have been studied using aluminium/alumina deposits on steel substrates. The incorporation of ceramics within a ductile matrix has potential for sharp...

  12. THE USE OF POROUS CERAMICS FOR EVAPORATIVE AND EVAPORATIVE – VAPOR –COMPRESSION SYSTEMS

    Directory of Open Access Journals (Sweden)

    Cheban D.N.

    2013-04-01

    Full Text Available The use of natural evaporative cooling is one of technical solutions of problem of energy efficiency in air conditioning systems. The use of evaporative cooling in the first combined cooling stage allows reducing the load on the condenser of the cooling machine due to reducing of the condensing temperature. This combination allows the use of this type of system in any climatic conditions, including regions with small water resources. Multi-porous ceramic structure is used in evaporative air coolers and water coolers in this case. The objective of this paper is to show advantages of the using of porous ceramic as a working attachment, and to show advantages of the proposed scheme of compression-evaporation systems in comparison with standard vapor compression systems. Experimental research proved the fact, that in the film mode cooling efficiency of air flow is between EA=0,6÷0,7 and is slightly dependent of water flow. For countries with hot and dry climate where reserves of water are limited, it is recommended to use cyclical regime with EA≈0,65 value, or to use channel regime with a value of EA≈0,55. This leads to considerable energy savings. It has been determined, that combined air conditioning system is completely closed on the consumption of water at the parameters of the outside air equal to tA =32ºC and XA>13g/kg (in system with direct evaporative cooling machine, and tA=32ºC and XA>12g/kg (in system with indirect evaporative cooling machine. With these parameters, the cost of water in evaporative cooling stage can be fully compensated by condensate from the evaporator chiller.

  13. Anisotropic and Hierarchical Porosity in Multifunctional Ceramics

    Science.gov (United States)

    Lichtner, Aaron Zev

    The performance of multifunctional porous ceramics is often hindered by the seemingly contradictory effects of porosity on both mechanical and non-structural properties and yet a sufficient body of knowledge linking microstructure to these properties does not exist. Using a combination of tailored anisotropic and hierarchical materials, these disparate effects may be reconciled. In this project, a systematic investigation of the processing, characterization and properties of anisotropic and isotropic hierarchically porous ceramics was conducted. The system chosen was a composite ceramic intended as the cathode for a solid oxide fuel cell (SOFC). Comprehensive processing investigations led to the development of approaches to make hierarchical, anisotropic porous microstructures using directional freeze-casting of well dispersed slurries. The effect of all the important processing parameters was investigated. This resulted in an ability to tailor and control the important microstructural features including the scale of the microstructure, the macropore size and total porosity. Comparable isotropic porous ceramics were also processed using fugitive pore formers. A suite of characterization techniques including x-ray tomography and 3-D sectional scanning electron micrographs (FIB-SEM) was used to characterize and quantify the green and partially sintered microstructures. The effect of sintering temperature on the microstructure was quantified and discrete element simulations (DEM) were used to explain the experimental observations. Finally, the comprehensive mechanical properties, at room temperature, were investigated, experimentally and using DEM, for the different microstructures.

  14. Ultrasonic Welding of Thin Alumina and Aluminum Using Inserts

    Science.gov (United States)

    Ishikuro, Tomoaki; Matsuoka, Shin-Ichi

    This paper describes an experimental study of ultrasonic welding of thin ceramics and metals using inserts. Ultrasonic welding has enable the joining of various thick ceramics, such as Al2O3 and ZrO2, to aluminum at room temperature quickly and easily as compared to other welding methods. However, for thin ceramics, which are brittle, welding is difficult to perform without causing damage. In this study, aluminum anodized oxide with different anodizing time was used as thin alumina ceramic. Vapor deposition of aluminum alloys was used to create an effective binder layer for welding at a low pressure and within a short duration in order to prevent damage to the anodic oxide film formed with a short anodizing time. For example, ultrasonic welding of thin Al2O3/Al was accomplished under the following conditions: ultrasonic horn tip amplitude of 30µm, welding pressure of 5MPa, and required duration of 0.1s. However, since the vapor deposition film tends to exfoliate as observed in the anodic oxide film formed with a long anodizing time, welding was difficult.

  15. Porous SiO_2 nanofiber grafted novel bioactive glass–ceramic coating: A structural scaffold for uniform apatite precipitation and oriented cell proliferation on inert implant

    International Nuclear Information System (INIS)

    Das, Indranee; De, Goutam; Hupa, Leena; Vallittu, Pekka K.

    2016-01-01

    A composite bioactive glass–ceramic coating grafted with porous silica nanofibers was fabricated on inert glass to provide a structural scaffold favoring uniform apatite precipitation and oriented cell proliferation. The coating surfaces were investigated thoroughly before and after immersion in simulated body fluid. In addition, the proliferation behavior of fibroblast cells on the surface was observed for several culture times. The nanofibrous exterior of this composite bioactive coating facilitated homogeneous growth of flake-like carbonated hydroxyapatite layer within a short period of immersion. Moreover, the embedded porous silica nanofibers enhanced hydrophilicity which is required for proper cell adhesion on the surface. The cells proliferated well following a particular orientation on the entire coating by the assistance of nanofibrous scaffold-like structural matrix. This newly engineered composite coating was effective in creating a biological structural matrix favorable for homogeneous precipitation of calcium phosphate, and organized cell growth on the inert glass surface. - Highlights: • Fabricated porous SiO_2 nanofibers grafted composite bioactive glass–ceramic coating on inert glass. • The newly engineered coating facilitates uniformly dense apatite precipitation. • Embedded porous silica nanofibers enhance hydrophilicity of the coated surface. • Cells proliferate well on the entire coating following a particular orientation by the assistance of nanofibers. • The coatings have potential to be used as biological scaffold on the surface of implants.

  16. Synthesis and separation properties of an α-alumina-supported high-silica MEL membrane

    NARCIS (Netherlands)

    Kosinov, N.; Hensen, E.J.M.

    2013-01-01

    A thin high-silica MEL membrane was synthesized on a porous a-alumina hollow fiber support by a secondary growth approach. The membrane quality was evaluated by permporometry, single-gas permeation and butane isomer separation. Comparison of the pervaporation performance of MEL membranes with a MFI

  17. Planar ceramic membrane assembly and oxidation reactor system

    Science.gov (United States)

    Carolan, Michael Francis; Dyer, legal representative, Kathryn Beverly; Wilson, Merrill Anderson; Ohm, Ted R.; Kneidel, Kurt E.; Peterson, David; Chen, Christopher M.; Rackers, Keith Gerard; Dyer, deceased, Paul Nigel

    2007-10-09

    Planar ceramic membrane assembly comprising a dense layer of mixed-conducting multi-component metal oxide material, wherein the dense layer has a first side and a second side, a porous layer of mixed-conducting multi-component metal oxide material in contact with the first side of the dense layer, and a ceramic channeled support layer in contact with the second side of the dense layer. The planar ceramic membrane assembly can be used in a ceramic wafer assembly comprising a planar ceramic channeled support layer having a first side and a second side; a first dense layer of mixed-conducting multi-component metal oxide material having an inner side and an outer side, wherein the inner side is in contact with the first side of the ceramic channeled support layer; a first outer support layer comprising porous mixed-conducting multi-component metal oxide material and having an inner side and an outer side, wherein the inner side is in contact with the outer side of the first dense layer; a second dense layer of mixed-conducting multi-component metal oxide material having an inner side and an outer side, wherein the inner side is in contact with the second side of the ceramic channeled layer; and a second outer support layer comprising porous mixed-conducting multi-component metal oxide material and having an inner side and an outer side, wherein the inner side is in contact with the outer side of the second dense layer.

  18. Ion Transport in Organic Electrolyte Solution through the Pore Channels of Anodic Nanoporous Alumina Membranes

    International Nuclear Information System (INIS)

    Fukutsuka, Tomokazu; Koyamada, Kohei; Maruyama, Shohei; Miyazaki, Kohei; Abe, Takeshi

    2016-01-01

    Highlights: • Ion transport in organic electrolyte solution in macro- and meso-pores was focused. • Anodic nanoporous alumina membrane was used as a porous material. • The specific ion conductivities drastically decreased in macro- and meso-pores. - Abstract: For the development of high energy density lithium-ion batteries with the high rate performance, the enhancement of the ion transport in the electrolyte solutions impregnated in the porous electrodes is a key. To study the ion transport in porous electrodes, anodic nanoporous alumina (APA) self-standing membranes with macro- or meso-pores were used as model porous materials. These membranes had nearly spherical pore channels of discrete 20–68 nm in diameters. By using the geometric shape of the pores, we attempted to evaluate the specific ion conductivities of the organic electrolyte solution dissolving lithium salt simply. AC impedance spectroscopy measurement of a four-electrode cell with membranes showed one depressed semi-circle in the Nyquist plots and this semi-circle can be assigned as the ion transport resistance in the pores. The specific ion conductivities evaluated from the ion transport resistances and the geometric parameters showed very small values, even in the macro-pores, as compared with that of the bulk electrolyte solution.

  19. Usefulness of ceramic implants in neurosurgery.

    Science.gov (United States)

    Kobayashi, S; Hara, H; Okudera, H; Takemae, T; Sugita, K

    1987-11-01

    The authors have designed various implants made of alumina ceramic for neurosurgical use. They were used for reconstruction of the sellar floor and orbital wall and for cranioplasty to repair bone defects in both the convexity and the suboccipital region. Burr hole and sphenoid buttons were made to prevent postoperative dents in the skin. A ceramic-silicon sponge was developed as a marker prosthesis for neurovascular decompression. There were no untoward side effects such as infection or rejection by recipient tissue in humans or dogs. The advantages and disadvantages of the material are discussed.

  20. Preparation and Characterization of Nano-structured Ceramic Powders Synthesized by Emulsion Combustion Method

    International Nuclear Information System (INIS)

    Takatori, Kazumasa; Tani, Takao; Watanabe, Naoyoshi; Kamiya, Nobuo

    1999-01-01

    The emulsion combustion method (ECM), a novel powder production process, was originally developed to synthesize nano-structured metal-oxide powders. Metal ions in the aqueous droplets were rapidly oxidized by the combustion of the surrounding flammable liquid. The ECM achieved a small reaction field and a short reaction period to fabricate the submicron-sized hollow ceramic particles with extremely thin wall and chemically homogeneous ceramic powder. Alumina, zirconia, zirconia-ceria solid solutions and barium titanate were synthesized by the ECM process. Alumina and zirconia powders were characterized to be metastable in crystalline phase and hollow structure. The wall thickness of alumina was about 10 nm. The zirconia-ceria powders were found to be single-phase solid solutions for a wide composition range. These powders were characterized as equiaxed-shape, submicron-sized chemically homogeneous materials. The powder formation mechanism was investigated through the synthesis of barium titanate powder with different metal sources