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Sample records for sub-micron agglomerate-free alumina

  1. A Single Step Lapping and Polishing Process for Achieving Surfaces of Compound Semiconductors with Atomic Flatness using a Sub-micron Agglomerate-free Alumina Slurry

    SciTech Connect

    P.S. Dutta; G. Rajagopalan; J.J. Gutmann; D. Keller; L. Sweet

    2002-08-29

    A novel approach for a single step lapping and final polishing of III-V and II-VI compounds using agglomerate-free alumina slurries has been developed. The agglomerate-free nature of the sub-micron slurry leads to removal rates comparable to conventional slurries (with larger particles of tens of microns) used for semiconductor lapping. Surfaces with minimal surface damage and extremely low surface roughness have been obtained using the sub-micron slurries and a soft pad. Strategies for post polishing surface cleaning have been discussed. The new methodology has been experimented on GaSb, InAs, GaAs, InP, InSb, CdTe, GaInSb, GaInAs, AlGaAsSb, GaInAsSb and HgCdTe. Selected results of surface analyses of GaSb and GaInSb using atomic force microscopy will be presented.

  2. Deformation Behavior of Sub-micron and Micron Sized Alumina Particles in Compression.

    SciTech Connect

    Sarobol, Pylin; Chandross, Michael E.; Carroll, Jay; Mook, William; Boyce, Brad; Kotula, Paul Gabriel; McKenzie, Bonnie Beth; Bufford, Daniel Charles; Hall, Aaron Christopher.

    2014-09-01

    The ability to integrate ceramics with other materials has been limited due to high temperature (>800degC) ceramic processing. Recently, researchers demonstrated a novel process , aerosol deposition (AD), to fabricate ceramic films at room temperature (RT). In this process, sub - micro n sized ceramic particles are accelerated by pressurized gas, impacted on the substrate, plastically deformed, and form a dense film under vacuum. This AD process eliminates high temperature processing thereby enabling new coatings and device integration, in which ceramics can be deposited on metals, plastics, and glass. However, k nowledge in fundamental mechanisms for ceramic particle s to deform and form a dense ceramic film is still needed and is essential in advancing this novel RT technology. In this wo rk, a combination of experimentation and atomistic simulation was used to determine the deformation behavior of sub - micron sized ceramic particle s ; this is the first fundamental step needed to explain coating formation in the AD process . High purity, singl e crystal, alpha alumina particles with nominal size s of 0.3 um and 3.0 um were examined. Particle characterization, using transmission electron microscopy (TEM ), showed that the 0.3 u m particles were relatively defect - free single crystals whereas 3.0 u m p articles were highly defective single crystals or particles contained low angle grain boundaries. Sub - micron sized Al 2 O 3 particles exhibited ductile failure in compression. In situ compression experiments showed 0.3um particles deformed plastically, fractured, and became polycrystalline. Moreover, dislocation activit y was observed within the se particles during compression . These sub - micron sized Al 2 O 3 particles exhibited large accum ulated strain (2 - 3 times those of micron - sized particles) before first fracture. I n agreement with the findings from experimentation , a tomistic simulation s of nano - Al 2 O 3 particles showed dislocation slip and

  3. Gelcasting of sub-micron alumina, sialon, and silicon nitride powders

    SciTech Connect

    Omatete, O.O.; Strehlow, R.A.; Walls, C.A.

    1990-01-01

    Gelcasting is a near-net-shape forming technique that is applicable to various types of powders. It is accomplished by casting a concentrated suspension of a commercial ceramic powder in a solution of a polymerizable monomer and then polymerizing. A filled gel is formed, which is dried and processed further. Alumina, sialon, and silicon nitride parts of various geometries have been made and are described. Emphasis is placed on the unit-operations of the process. Because a requirement of the process is a castable suspension of more than 50 vol % solids loading, good dispersion is crucial. Drying, another key process, has been studied extensively. Shrinkage from the cast size occurs during drying and further shrinkage occurs during sintering. Data on the relationship of physical properties of products to some of the more significant processing variables is discussed. Emphasis is also placed on the machinability of the dried gelled body. Because the body at this stage is quite durable, green part machining is feasible. The monomer used in the process is acrylamide, which undergoes a vinyl polymerization. Environmental, safety and hygiene issues are summarized. 9 refs., 6 figs.

  4. Sub-micron filter

    DOEpatents

    Tepper, Frederick; Kaledin, Leonid

    2009-10-13

    Aluminum hydroxide fibers approximately 2 nanometers in diameter and with surface areas ranging from 200 to 650 m.sup.2/g have been found to be highly electropositive. When dispersed in water they are able to attach to and retain electronegative particles. When combined into a composite filter with other fibers or particles they can filter bacteria and nano size particulates such as viruses and colloidal particles at high flux through the filter. Such filters can be used for purification and sterilization of water, biological, medical and pharmaceutical fluids, and as a collector/concentrator for detection and assay of microbes and viruses. The alumina fibers are also capable of filtering sub-micron inorganic and metallic particles to produce ultra pure water. The fibers are suitable as a substrate for growth of cells. Macromolecules such as proteins may be separated from each other based on their electronegative charges.

  5. A facile approach to the synthesis of non-porous and microporous sub-micron spherical zirconia and alumina-zirconia solid solution.

    PubMed

    Ghotbi, Mohammad Yeganeh; Nasiri, Vida; Rafiee, Mehdi

    2013-01-01

    Amorphous monodisperse sub-micron spherical zirconia and alumina/zirconia solid solution particles were prepared by hydrolysis of zirconium and aluminum salts in ethanol. The heat-treatment process of the amorphous materials in air atmosphere at 500°C for 2h leaded to the production of non-porous zirconia and alumina/zirconia solid solution in tetragonal phase. The alkaline etching process of the as-prepared alumina/zirconia solid solution resulted in the formation of mono-modal microporous material with specific surface area of 125.0 m(2) g(-1) in comparison with 2. 9m(2) g(-1) for the parent material. Thermal analysis of the solid solution revealed that the incorporation of aluminum ions in the zirconia structure has decreased the phase transformation temperature from amorphous to crystalline structure. Moreover, optical study confirmed the presence of oxygen vacancy defect by substitution of tetravalent cations, Zr(4+) by trivalent cations, Al(3+) in zirconia lattice.

  6. Sub-micron particle sampler apparatus

    DOEpatents

    Gay, Don D.; McMillan, William G.

    1987-01-01

    Apparatus and method steps for collecting sub-micron sized particles include a collection chamber and cryogenic cooling. The cooling is accomplished by coil tubing carrying nitrogen in liquid form, with the liquid nitrogen changing to the gas phase before exiting from the collection chamber in the tubing. Standard filters are used to filter out particles of diameter greater than or equal to 0.3 microns; however the present invention is used to trap particles of less than 0.3 micron in diameter. A blower draws air to said collection chamber through a filter which filters particles with diameters greater than or equal to 0.3 micron. The air is then cryogenically cooled so that moisture and sub-micron sized particles in the air condense into ice on the coil. The coil is then heated so that the ice melts, and the liquid is then drawn off and passed through a Buchner funnel where the liquid is passed through a Nuclepore membrane. A vacuum draws the liquid through the Nuclepore membrane, with the Nuclepore membrane trapping sub-micron sized particles therein. The Nuclepore membrane is then covered on its top and bottom surfaces with sheets of Mylar.RTM. and the assembly is then crushed into a pellet. This effectively traps the sub-micron sized particles for later analysis.

  7. Method for sampling sub-micron particles

    DOEpatents

    Gay, Don D.; McMillan, William G.

    1985-01-01

    Apparatus and method steps for collecting sub-micron sized particles include a collection chamber and cryogenic cooling. The cooling is accomplished by coil tubing carrying nitrogen in liquid form, with the liquid nitrogen changing to the gas phase before exiting from the collection chamber in the tubing. Standard filters are used to filter out particles of diameter greater than or equal to 0.3 microns; however the present invention is used to trap particles of less than 0.3 micron in diameter. A blower draws air to said collection chamber through a filter which filters particles with diameters greater than or equal to 0.3 micron. The air is then cryogenically cooled so that moisture and sub-micron sized particles in the air condense into ice on the coil. The coil is then heated so that the ice melts, and the liquid is then drawn off and passed through a Buchner funnel where the liquid is passed through a Nuclepore membrane. A vacuum draws the liquid through the Nuclepore membrane, with the Nuclepore membrane trapping sub-micron sized particles therein. The Nuclepore membrane is then covered on its top and bottom surfaces with sheets of Mylar.RTM. and the assembly is then crushed into a pellet. This effectively traps the sub-micron sized particles for later analysis.

  8. Modeling the Combustion of a Sub-micron Aluminum Particle (PREPRINT)

    DTIC Science & Technology

    2011-05-18

    Boltzmann constant, is the emissivity of the alumina, and Nu is the convective Nusselt number . 5 Approved for public release; distribution unlimited...currently valid OMB control number . PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 1. REPORT DATE (DD-MM-YYYY) 24-05-2011 2. REPORT TYPE Journal...Article 3. DATES COVERED (From - To) 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Modeling the Combustion of a Sub-micron Aluminum Particle 5b. GRANT

  9. Sub-micron particle sampler apparatus and method for sampling sub-micron particles

    DOEpatents

    Gay, D.D.; McMillan, W.G.

    1984-04-12

    Apparatus and method steps for collecting sub-micron sized particles include a collection chamber and cryogenic cooling. The cooling is accomplished by coil tubing carrying nitrogen in liquid form, with the liquid nitrogen changing to the gas phase before exiting from the collection chamber in the tubing. Standard filters are used to filter out particles of diameter greater than or equal to 0.3 microns; however, the present invention is used to trap particles of less than 0.3 micron in diameter. A blower draws air to said collection chamber through a filter which filters particles with diameters greater than or equal to 0.3 micron. The air is then cryogenically cooled so that moisture and sub-micron sized particles in the air condense into ice on the coil. The coil is then heated so that the ice melts, and the liquid is then drawn off and passed through a Buchner funnel where the liquid is passed through a Nuclepore membrane. A vacuum draws the liquid through the Nuclepore membrane, with the Nuclepore membrane trapping sub-micron sized particles therein. The Nuclepore membrane is then covered on its top and bottom surfaces with sheets of Mylar and the assembly is then crushed into a pellet. This effectively traps the sub-micron sized particles for later analysis. 6 figures.

  10. An Advanced Wafer Stepper For Sub-Micron Fabrication

    NASA Astrophysics Data System (ADS)

    Mayer, Herbert E.; Loebach, Ernst W.

    1987-09-01

    An advanced wafer stepper is presented addressing the specific problems involved by sub-micron lithography such as alignment and focusing to multilayer resist films. New sub-systems were developed while maintaining principles well proven in a previous design. The system is described emphasizing the new sub-systems, and performance data are presented.

  11. Scanning SQUID susceptometers with sub-micron spatial resolution

    NASA Astrophysics Data System (ADS)

    Kirtley, John R.; Paulius, Lisa; Rosenberg, Aaron J.; Palmstrom, Johanna C.; Holland, Connor M.; Spanton, Eric M.; Schiessl, Daniel; Jermain, Colin L.; Gibbons, Jonathan; Fung, Y.-K.-K.; Huber, Martin E.; Ralph, Daniel C.; Ketchen, Mark B.; Gibson, Gerald W.; Moler, Kathryn A.

    2016-09-01

    Superconducting QUantum Interference Device (SQUID) microscopy has excellent magnetic field sensitivity, but suffers from modest spatial resolution when compared with other scanning probes. This spatial resolution is determined by both the size of the field sensitive area and the spacing between this area and the sample surface. In this paper we describe scanning SQUID susceptometers that achieve sub-micron spatial resolution while retaining a white noise floor flux sensitivity of ≈2μΦ0/Hz1/2. This high spatial resolution is accomplished by deep sub-micron feature sizes, well shielded pickup loops fabricated using a planarized process, and a deep etch step that minimizes the spacing between the sample surface and the SQUID pickup loop. We describe the design, modeling, fabrication, and testing of these sensors. Although sub-micron spatial resolution has been achieved previously in scanning SQUID sensors, our sensors not only achieve high spatial resolution but also have integrated modulation coils for flux feedback, integrated field coils for susceptibility measurements, and batch processing. They are therefore a generally applicable tool for imaging sample magnetization, currents, and susceptibilities with higher spatial resolution than previous susceptometers.

  12. Discovering sub-micron ice particles across Dione' surface

    NASA Astrophysics Data System (ADS)

    Scipioni, Francesca; Schenk, Pual; Tosi, Federico; Clark, Roger; Dalle Ore, Cristina; Combe, Jean-Philippe

    2015-11-01

    Water ice is the most abundant component of Saturn’s mid-sized moons. However, these moons show an albedo asymmetry - their leading sides are bright while their trailing side exhibits dark terrains. Such differences arise from two surface alteration processes: (i) the bombardment of charged particles from the interplanetary medium and driven by Saturn’s magnetosphere on the trailing side, and (ii) the impact of E-ring water ice particles on the satellites’ leading side. As a result, the trailing hemisphere appears to be darker than the leading side. This effect is particularly evident on Dione's surface. A consequence of these surface alteration processes is the formation or the implantation of sub-micron sized ice particles.The presence of such particles influences and modifies the surfaces' spectrum because of Rayleigh scattering by the particles. In the near infrared range of the spectrum, the main sub-micron ice grains spectral indicators are: (i) asymmetry and (ii) long ward minimum shift of the absorption band at 2.02 μm (iii) a decrease in the ratio between the band depths at 1.50 and 2.02 μm (iv) a decrease in the height of the spectral peak at 2.6 μm (v) the suppression of the Fresnel reflection peak at 3.1 μm and (vi) the decrease of the reflection peak at 5 μm relative to those at 3.6 μm.We present results from our ongoing work mapping the variation of sub-micron ice grains spectral indicators across Dione' surface using Cassini-VIMS cubes acquired in the IR range (0.8-5.1 μm). To characterize the global variations of spectral indicators across Dione' surface, we divided it into a 1°x1° grid and then averaged the band depths and peak values inside each square cell.We will investigate if there exist a correspondence with water ice abundance variations by producing water ice' absorption band depths at 1.25, 1.52 and 2.02 μm, and with surface morphology by comparing the results with ISS color maps in the ultraviolet, visible and infrared

  13. Separating the signal from the noise: Expanding flow cytometry into the sub-micron range.

    EPA Science Inventory

    Cytometry Part A Special Section: Separating the signal from the noise: Expanding flow cytometry into the sub-micron range. The current Cytometry Part A Special Section presents three studies that utilize cytometers to study sub-micron particles. The three studies involve the 1...

  14. Membrane fouling caused by sub-micron particles in a mixed liquor suspension of an MBR.

    PubMed

    Kimura, K; Ogyu, R; Miyoshi, T; Naruse, T; Tsuyuhara, T; Watanabe, Y

    2013-01-01

    Membrane fouling needs to be mitigated for widespread use of membrane bioreactors (MBRs). It has been pointed out that particles with small sizes found in supernatants (sub-micron particles) of mixed liquor suspensions of MBRs are important in the evolution of membrane fouling of this technology. However, information on characteristics of sub-micron particles in MBRs is still insufficient. In this study, a pilot-scale MBR treating municipal wastewater was used to investigate and characterize sub-micron particles in an MBR and to identify the size fraction(s) responsible for irreversible fouling in an MBR. It was clearly shown that characteristics of sub-micron particles in the MBR varied considerably depending on their sizes. Results of Fourier transform infrared (FTIR) analysis and monosaccharide analysis suggested that irreversible fouling in this study was mainly caused by the specific size fraction of 0.1-0.45 μm, which was close to the size of micropores of the membrane used. Pore plugging might explain this to some extent.

  15. Generating Sub-Micron Features On Rough Surfaces Using Optical Trap Assisted Nanopatterning

    NASA Astrophysics Data System (ADS)

    Tsai, Yu-Cheng; Fardel, Romain; Arnold, Craig B.

    2010-10-01

    Near-field intensity enhancement enables laser modification of materials with feature sizes below the classical diffraction limit. However, the need to maintain close distances between the objective element and the substrate typically limit demonstrations of this technology to flat surfaces, even though there are many cases where the ability to produce sub-micron features on rough or structured surfaces are needed. Here, we show the use of a new technique, optical trap assisted nanopatterning (OTAN), for the production of nanoscale features on rippled substrates. The ability to position a microbead near-field objective close to the surface without the need for active feedback and control allows one to continuously move the bead across a rough surface without sticking. Sub-micron patterning of polyimide is demonstrated on surfaces with 1.1 μm steps showing good uniformity. Finally, the enabling technology allows for straightforward parallelization where multiple patterns can be created simultaneously over surface.

  16. Preparation of sub-micron nitrocellulose particles for improved combustion behavior.

    PubMed

    Zhang, Xin; Weeks, Brandon L

    2014-03-15

    A novel method to prepare sub-micron nitrocellulose particles with spherical shape is demonstrated. The morphology of the nitrocellulose can be controlled by the solvent and the growth temperature. Using dimethylformamide (DMF) at a growth temperature is 5°C, reproducibly yielded spherical nitrocellulose particles. The final diameter of the prepared nitrocellulose particles can be further tuned by concentration. The smallest particles in this study were found to have diameters of 500nm at a concentration of 5-10mg/ml with 2 micron spheres formed at 30mg/ml. Furthermore, the thermal properties and the burn rates of the prepared materials are studied by differential scanning calorimetry and digital high-speed photography, respectively. In comparison to the bulk nitrocellulose material, the sub-micron nitrocellulose particles have lower decomposition activation energy, a 350% increase in burn rate, and a more complete combustion.

  17. A modular process for integrating thick polysilicon MEMS devices with sub-micron CMOS

    NASA Astrophysics Data System (ADS)

    Yasaitis, John A.; Judy, Michael; Brosnihan, Tim; Garone, Peter M.; Pokrovskiy, Nikolay; Sniderman, Debbie; Limb, Scott; Howe, Roger T.; Boser, Bernhard E.; Palaniapan, Moorthi; Jiang, Xuesong; Bhave, Sunil

    2003-01-01

    A new MEMS process module, called Mod MEMS, has been developed to monolithically integrate thick (5-10um), multilayer polysilicon MEMS structures with sub-micron CMOS. This process is particularly useful for advanced inertial MEMS products such as automotive airbag accelerometers where reduced cost and increased functionality is required, or low cost, high performance gyroscopes where thick polysilicon (>6um) and CMOS integration is required to increase poly mass and stiffness, and reduce electrical parasitics in order to optimize angular rate sensing. In this paper we will describe the new modular process flow, development of the critical unit process steps, integration of the module with a foundry sub-micron CMOS process, and provide test data on several inertial designs fabricated with this process.

  18. 1.55 Micrometer Sub-Micron Finger, Interdigitated MSM Photodetector Arrays with Low Dark Current

    DTIC Science & Technology

    2010-02-02

    morphology is generally smoother. These transparent conducting oxides may also be used as electrodes in solar cells and flat-panel display devices...REPORT Final Report of 1.55 UM Sub-Micron Finger, Interdigitated MSM Photodetector Arrays with Low Dark Current 14. ABSTRACT 16. SECURITY... Interdigitated MSM Photodetector Arrays with Low Dark Current Sponsored by: U. S. Army Research Office Dr. Michael D. Gerhold Contract

  19. Ordered YBCO sub-micron array structures induced by pulsed femtosecond laser irradiation.

    PubMed

    Luo, C W; Lee, C C; Li, C H; Shih, H C; Chen, Y-J; Hsieh, C C; Su, C H; Tzeng, W Y; Wu, K H; Juang, J Y; Uen, T M; Chen, S P; Lin, J-Y; Kobayashi, T

    2008-12-08

    We report on the formation of organized sub-micron YBa(2)Cu(3)O(7) (YBCO) dots induced by irradiating femtosecond laser pulses on YBCO films prepared by pulse laser deposition with fluence in the range of 0.21 approximately 0.53 J/cm(2). The morphology of the YBCO film surface depends strongly on the laser fluences irradiated. At lower laser fluence (approximately 0.21 J/cm(2)) the morphology was pattern of periodic ripples with sub-micrometer spacing. Slightly increasing the laser fluence to 0.26 J/cm(2) changes the pattern into organized sub-micron dots with diameters ranging from 100 nm to 800 nm and height of 150 nm. Further increase of the laser fluence to over 0.32 J/cm(2), however, appeared to result in massive melting and led to irregular morphology. The mechanism and the implications of the current findings will be discussed. Arrays of YBCO sub-micron dots with T(c) = 89.7 K were obtained.

  20. Oxidation of synthesized sub-micron pyrite (FeS2) in seawater

    NASA Astrophysics Data System (ADS)

    Gartman, Amy; Luther, George W.

    2014-11-01

    Synthesized sub-micron pyrite was oxidized in 0.2 μm-filtered Sargasso seawater in order to investigate the rate of oxidation and reaction end-products. Over the initial phase of the reaction, the sub-micron pyrite behaved as a soluble entity as the initial rate of oxidation was determined to be first order with respect to both pyrite and oxygen concentration, where the rate is described as -dFeS2/dt = k[FeS2][O2] and k, the rate constant, is 7.60 × 10-5 + 6.29 × 10-5 μM-1 day-1 at 25 °C. Oxidation proceeds inward from an initial surface oxidation of the pyrite and the formation of an amorphous mixed valence Fe(II)/(III) oxide surrounding the remaining pyrite core. The oxidation rates obtained through this study are up to two orders of magnitude slower than reported in previous pyrite oxidation studies using ground rather than synthesized pyrite at similar pH values. These results may be applied anywhere seawater and sub-micron pyrite are found, including hydrothermal vents, salt marshes and marine sediments.

  1. Generation of sub-micron particles and secondary pollutants from building materials by ozone reaction

    NASA Astrophysics Data System (ADS)

    Aoki, Taisuke; Tanabe, Shin-ichi

    This study reports results from two different experiments examining reactions between ozone and common building materials that can lead to the formation of secondary products and particulate-phase materials. Monitored species include sub-micron particles and volatile organic compounds (VOCs). In the first set of experiments, various building materials were placed in a 20 L stainless-steel chamber and exposed to ozone. The materials included expanded polystyrene, a natural rubber adhesive, cedar board, Japanese Cyprus board and silver fir board, as well as d-limonene, which is a known constituent of certain woods and cleaning products. The combination of ozone and either d-limonene, cedar board or cypress board produced sub-micron particles, with most of the increase occurring in the size range of 0.01- 0.5μm diameter. This was not observed for the other materials. In the case of cedar board, the consequence of ozone exposure over an extended time interval was monitored. As the exposure time elapsed, the concentration of sub-micron particles moderately decreased. In the second set of experiments, unwaxed or waxed plastic tiles were placed in the 20 L chamber and exposed to ozone. Sub-micron particles and organic compounds were measured during the course of the experiments. In the case of the waxed tile, the number of 0.01- 1.0μm size particles grew about 50×108particlesm-3; particle growth was significantly less for the un-waxed tile. For both the waxed and un-waxed tiles, the emission rates of heptane, nonane, nonanal, and decanal increased after ozone was added to the supply air. (However, it is not clear if some or all of this production was due to ozone reacting with the sorbent used for sampling or with compounds captured by the sorbent.) This study provides further evidence that ozone-initiated reactions with building materials can be a significant source of both sub-micron particles and secondary organic compounds in indoor environments.

  2. Enhanced endothelial cell density on NiTi surfaces with sub-micron to nanometer roughness.

    PubMed

    Samaroo, Harry D; Lu, Jing; Webster, Thomas J

    2008-01-01

    The shape memory effect and superelastic properties of NiTi (or Nitinol, a nickel-titanium alloy) have already attracted much attention for various biomedical applications (such as vascular stents, orthodontic wires, orthopedic implants, etc). However, for vascular stents, conventional approaches have required coating NiTi with anti-thrombogenic or antiinflammatory drug-eluting polymers which as of late have proven problematic for healing atherosclerotic blood vessels. Instead of focusing on the use of drug-eluting anti-thrombogenic or anti-inflammatory proteins, this study focused on promoting the formation of a natural antithrombogenic and anti-inflammatory surface on metallic stents: the endothelium. In this study, we synthesized various NiTi substrates with different micron to nanometer surface roughness by using dissimilar dimensions of constituent NiTi powder. Endothelial cell adhesion on these compacts was compared with conventional commercially pure (cp) titanium (Ti) samples. The results after 5 hrs showed that endothelial cells adhered much better on fine grain (< 60 microm) compared with coarse grain NiTi compacts (< 100 microm). Coarse grain NiTi compacts and conventional Ti promoted similar levels of endothelial cell adhesion. In addition, cells proliferated more after 5 days on NiTi with greater sub-micron and nanoscale surface roughness compared with coarse grain NiTi. In this manner, this study emphasized the positive pole that NiTi with sub-micron to nanometer surface features can play in promoting a natural anti-thrombogenic and anti-inflammatory surface (the endothelium) on a vascular stent and, thus, suggests that more studies should be conducted on NiTi with sub-micron to nanometer surface features.

  3. Enhanced endothelial cell density on NiTi surfaces with sub-micron to nanometer roughness

    PubMed Central

    Samaroo, Harry D; Lu, Jing; Webster, Thomas J

    2008-01-01

    The shape memory effect and superelastic properties of NiTi (or Nitinol, a nickel-titanium alloy) have already attracted much attention for various biomedical applications (such as vascular stents, orthodontic wires, orthopedic implants, etc). However, for vascular stents, conventional approaches have required coating NiTi with anti-thrombogenic or anti-inflammatory drug-eluting polymers which as of late have proven problematic for healing atherosclerotic blood vessels. Instead of focusing on the use of drug-eluting anti-thrombogenic or anti-inflammatory proteins, this study focused on promoting the formation of a natural anti-thrombogenic and anti-inflammatory surface on metallic stents: the endothelium. In this study, we synthesized various NiTi substrates with different micron to nanometer surface roughness by using dissimilar dimensions of constituent NiTi powder. Endothelial cell adhesion on these compacts was compared with conventional commercially pure (cp) titanium (Ti) samples. The results after 5 hrs showed that endothelial cells adhered much better on fine grain (<60 μm) compared with coarse grain NiTi compacts (<100 μm). Coarse grain NiTi compacts and conventional Ti promoted similar levels of endothelial cell adhesion. In addition, cells proliferated more after 5 days on NiTi with greater sub-micron and nanoscale surface roughness compared with coarse grain NiTi. In this manner, this study emphasized the positive pole that NiTi with sub-micron to nanometer surface features can play in promoting a natural anti-thrombogenic and anti-inflammatory surface (the endothelium) on a vascular stent and, thus, suggests that more studies should be conducted on NiTi with sub-micron to nanometer surface features. PMID:18488418

  4. Suppression of transient enhanced diffusion in sub-micron patterned silicon template by dislocation loops formation

    SciTech Connect

    Hu, Kuan-Kan; Woon, Wei Yen; Chang, Ruey-Dar

    2015-10-15

    We investigate the evolution of two dimensional transient enhanced diffusion (TED) of phosphorus in sub-micron scale patterned silicon template. Samples doped with low dose phosphorus with and without high dose silicon self-implantation, were annealed for various durations. Dopant diffusion is probed with plane-view scanning capacitance microscopy. The measurement revealed two phases of TED. Significant suppression in the second phase TED is observed for samples with high dose self-implantation. Transmission electron microscopy suggests the suppressed TED is related to the evolution of end of range defect formed around ion implantation sidewalls.

  5. Sub-micron alignment for nuclear emulsion plates using low energy electrons caused by radioactive isotopes

    NASA Astrophysics Data System (ADS)

    Miyamoto, S.; Ariga, A.; Fukuda, T.; Kazuyama, M.; Komatsu, M.; Nakano, T.; Niwa, K.; Sato, O.; Takahashi, S.

    2007-06-01

    Nuclear emulsion plates are employed in three-dimensional charged particle detectors that have sub-micron position resolution over 1 m2 with no dead space and no dead time. These detectors are suitable for the study of short-lived particle decays, and direct detection of neutrino interactions of all flavors. Typically emulsion plates are used in a stacked structure. Precise alignment between plates is required for physics analysis. The most accurate alignment method is to use tracks passing through the emulsion plates. The accuracy is about 0.2 μm. However, in an experiment with low track density alignment accuracy decreases to 20 μm because of plate distortion and it becomes more difficult to perform the analysis. This paper describes a new alignment method between emulsion plates by using trajectories of low energy electrons originating from environmental radioactive isotopes. As a trial emulsion plates were exposed to β-rays and γ-rays from K40. The trajectories which passed through emulsion layers were detected by a fully automated emulsion readout system. Using this method, the alignment between emulsion plates is demonstrated to be sub-micron. This method can be applied to many nuclear emulsion experiments. For example, the location of neutrino interaction vertices in the OPERA experiment can benefit from this new technique.

  6. Hybridization between nanocavities for a polarimetric color sorter at the sub-micron scale.

    PubMed

    Segal, Elad; Weissman, Adam; Gachet, David; Salomon, Adi

    2016-08-18

    Metallic hole arrays have been recently used for color generation and filtering due to their reliability and color tunability. However, color generation is still limited to several microns. Understanding the interaction between the individual elements of the whole nanostructure may push the resolution to the sub-micron level. Herein, we study the hybridization between silver nanocavities in order to obtain active color generation at the micron scale. To do so, we use five identical triangular cavities which are separated by hundreds of nanometers from each other. By tuning either the distance between the cavities or the optical polarization state of the incoming field, the transmitted light through the cavities is actively enhanced at specific frequencies. Consequently, a rainbow of colors is observed from a sub-micron scale unit. The reason for this is that the metallic surface plays a vital role in the hybridization between the cavities and contributes to higher frequency modes. Cathodoluminescence measurements have confirmed this assumption and have revealed that these five triangular cavities act as a unified entity surrounded by the propagated surface plasmons. In such plasmonic structures, multi-color tuning can be accomplished and may open the possibility to improve color generation and high-quality pixel fabrication.

  7. Kinetics of Sub-Micron Grain Size Refinement in 9310 Steel

    NASA Astrophysics Data System (ADS)

    Kozmel, Thomas; Chen, Edward Y.; Chen, Charlie C.; Tin, Sammy

    2014-05-01

    Recent efforts have focused on the development of novel manufacturing processes capable of producing microstructures dominated by sub-micron grains. For structural applications, grain refinement has been shown to enhance mechanical properties such as strength, fatigue resistance, and fracture toughness. Through control of the thermo-mechanical processing parameters, dynamic recrystallization mechanisms were used to produce microstructures consisting of sub-micron grains in 9310 steel. Starting with initial bainitic grain sizes of 40 to 50 μm, various levels of grain refinement were observed following hot deformation of 9310 steel samples at temperatures and strain rates ranging from 755 K to 922 K (482 °C and 649 °C) and 1 to 0.001/s, respectively. The resulting deformation microstructures were characterized using scanning electron microscopy and electron backscatter diffraction techniques to quantify the extent of carbide coarsening and grain refinement occurring during deformation. Microstructural models based on the Zener-Holloman parameter were developed and modified to include the effect of the ferrite/carbide interactions within the system. These models were shown to effectively correlate microstructural attributes to the thermal mechanical processing parameters.

  8. Initial Development of a sub-micron Angle Resolved Photoemission Microscope

    NASA Astrophysics Data System (ADS)

    Bostwick, Aaron; McChesney, Jessica; Rotenberg, Eli

    2007-03-01

    -abstract- We have begun initial development of a sub-micron angle resolved photoemmision microscope. The current test system consists of an SES-200 detector and a zone plate based focusing system operating at 180eV photon energy. We have measured angle resolved spectra using the SES-200 angle-dispersive collection mode at resolution of ˜500nm. We have used this to show orientational contrast on highly oriented pyrolytic graphite (HOPG). The domains on HOPG are on the order of 1-20 microns and are well orientated along the c-axis but show random azimuthal order. We are able to clearly image these domains even though they show no chemical contrast, and can measure the single crystal band structure on disordered polycrystalline sample. We believe this demonstrates the promise of such a system for the measurement of materials which cannot be found in bulk single crystals.

  9. Deep Sub Micron 65nm Program- Perspectives for the Next Generation Satellites

    NASA Astrophysics Data System (ADS)

    Hili, Laurent; Dugoujon, Laurent; Roche, Phillippe; Malou, Florence; Perdu, Phillippe

    2012-08-01

    This paper presents the recent advances in terms of European digital microelectronics technologies for space applications. This article exemplifies the case of the Deep Sub-Micron 65nm program led by ESA and CNES in partnership with semiconductor industry, ST Microelectronics. Recent programs such as Inmarsat XL (Astrium) have exacerbated the limits of the current digital ASIC (Application Specific Integrated Circuit). Those limits have been reached in all areas; transistors/gates integration, speed, power and number of available IOs. The DSM 65nm program shows how those limits will be overcome thanks to breakthrough technologies such as high speed serial links (HSSL / 6.25Gbps), high pin count flip chip package technology (1600 pins).

  10. Acoustic Emission Patterns and the Transition to Ductility in Sub-Micron Scale Laboratory Earthquakes

    NASA Astrophysics Data System (ADS)

    Ghaffari, H.; Xia, K.; Young, R.

    2013-12-01

    We report observation of a transition from the brittle to ductile regime in precursor events from different rock materials (Granite, Sandstone, Basalt, and Gypsum) and Polymers (PMMA, PTFE and CR-39). Acoustic emission patterns associated with sub-micron scale laboratory earthquakes are mapped into network parameter spaces (functional damage networks). The sub-classes hold nearly constant timescales, indicating dependency of the sub-phases on the mechanism governing the previous evolutionary phase, i.e., deformation and failure of asperities. Based on our findings, we propose that the signature of the non-linear elastic zone around a crack tip is mapped into the details of the evolutionary phases, supporting the formation of a strongly weak zone in the vicinity of crack tips. Moreover, we recognize sub-micron to micron ruptures with signatures of 'stiffening' in the deformation phase of acoustic-waveforms. We propose that the latter rupture fronts carry critical rupture extensions, including possible dislocations faster than the shear wave speed. Using 'template super-shear waveforms' and their network characteristics, we show that the acoustic emission signals are possible super-shear or intersonic events. Ref. [1] Ghaffari, H. O., and R. P. Young. "Acoustic-Friction Networks and the Evolution of Precursor Rupture Fronts in Laboratory Earthquakes." Nature Scientific reports 3 (2013). [2] Xia, Kaiwen, Ares J. Rosakis, and Hiroo Kanamori. "Laboratory earthquakes: The sub-Rayleigh-to-supershear rupture transition." Science 303.5665 (2004): 1859-1861. [3] Mello, M., et al. "Identifying the unique ground motion signatures of supershear earthquakes: Theory and experiments." Tectonophysics 493.3 (2010): 297-326. [4] Gumbsch, Peter, and Huajian Gao. "Dislocations faster than the speed of sound." Science 283.5404 (1999): 965-968. [5] Livne, Ariel, et al. "The near-tip fields of fast cracks." Science 327.5971 (2010): 1359-1363. [6] Rycroft, Chris H., and Eran Bouchbinder

  11. Chemical Mapping of Proterozoic Organic Matter at Sub-Micron Spatial Resolution

    NASA Technical Reports Server (NTRS)

    Oehler, Dorothy Z.; Robert, Francois; Mostefaoui, Smail; Meibom, Anders; Selo, Madeleine; McKay, David S.

    2006-01-01

    We have used a NanoSIMS ion microprobe to map sub-micron-scale distributions of carbon, nitrogen, sulfur, silicon, and oxygen in organic microfossils and laminae from the approximately 0.85 Ga Bitter Springs Formation of Australia. The data provide clues about the original chemistry of the microfossils, the silicification process, and biosignatures of specific microorganisms and microbial communities. Chemical maps of fossil unicells and filaments reveal distinct wall-and sheath-like structures enriched in C, N and S, consistent with their accepted biological origin. Surprisingly, organic laminae, previously considered to be amorphous, also exhibit filamentous and apparently compressed spheroidal structures defined by strong enrichments in C, N and S. By analogy to data from the well-preserved microfossils, these structures are interpreted as being of biological origin, most likely representing densely packed remnants of microbial mats. Because the preponderance of organic matter in Precambrian sediments is similarly "amorphous," our findings open a large body of generally neglected material to in situ structural, chemical, and isotopic study. Our results also offer new criteria for assessing biogenicity of problematic kerogenous materials and thus can be applied to assessments of poorly preserved or fragmentary organic residues in early Archean sediments and any that might occur in meteorites or other extraterrestrial samples.

  12. Sub-micron Hard X-ray Fluorescence Imaging of Synthetic Elements

    PubMed Central

    Jensen, Mark P.; Aryal, Baikuntha P.; Gorman-Lewis, Drew; Paunesku, Tatjana; Lai, Barry; Vogt, Stefan; Woloschak, Gayle E.

    2013-01-01

    Synchrotron-based X-ray fluorescence microscopy (SXFM) using hard X-rays focused into sub-micron spots is a powerful technique for elemental quantification and mapping, as well as microspectroscopic measurement such as μ-XANES (X-ray absorption near edge structure). We have used SXFM to image and simultaneously quantify the transuranic element plutonium at the L3 or L2 edge as well as lighter biologically essential elements in individual rat pheochromocytoma (PC12) cells after exposure to the long-lived plutonium isotope 242Pu. Elemental maps reveal that plutonium localizes principally in the cytoplasm of the cells and avoids the cell nucleus, which is marked by the highest concentrations of phosphorus and zinc, under the conditions of our experiments. The minimum detection limit under typical acquisition conditions for an average 202 μm2 cell is 1.4 fg Pu/cell or 2.9 × 10−20 moles Pu/μm2, which is similar to the detection limit of K-edge SXFM of transition metals at 10 keV. Copper electron microscopy grids were used to avoid interference from gold X-ray emissions, but traces of strontium present in naturally occurring calcium can still interfere with plutonium detection using its Lα X-ray emission. PMID:22444530

  13. Scalable Sub-micron Patterning of Organic Materials Toward High Density Soft Electronics

    NASA Astrophysics Data System (ADS)

    Kim, Jaekyun; Kim, Myung-Gil; Kim, Jaehyun; Jo, Sangho; Kang, Jingu; Jo, Jeong-Wan; Lee, Woobin; Hwang, Chahwan; Moon, Juhyuk; Yang, Lin; Kim, Yun-Hi; Noh, Yong-Young; Yun Jaung, Jae; Kim, Yong-Hoon; Kyu Park, Sung

    2015-09-01

    The success of silicon based high density integrated circuits ignited explosive expansion of microelectronics. Although the inorganic semiconductors have shown superior carrier mobilities for conventional high speed switching devices, the emergence of unconventional applications, such as flexible electronics, highly sensitive photosensors, large area sensor array, and tailored optoelectronics, brought intensive research on next generation electronic materials. The rationally designed multifunctional soft electronic materials, organic and carbon-based semiconductors, are demonstrated with low-cost solution process, exceptional mechanical stability, and on-demand optoelectronic properties. Unfortunately, the industrial implementation of the soft electronic materials has been hindered due to lack of scalable fine-patterning methods. In this report, we demonstrated facile general route for high throughput sub-micron patterning of soft materials, using spatially selective deep-ultraviolet irradiation. For organic and carbon-based materials, the highly energetic photons (e.g. deep-ultraviolet rays) enable direct photo-conversion from conducting/semiconducting to insulating state through molecular dissociation and disordering with spatial resolution down to a sub-μm-scale. The successful demonstration of organic semiconductor circuitry promise our result proliferate industrial adoption of soft materials for next generation electronics.

  14. From particle self-assembly to functionalized sub-micron protein patterns

    NASA Astrophysics Data System (ADS)

    Blättler, T. M.; Binkert, A.; Zimmermann, M.; Textor, M.; Vörös, J.; Reimhult, E.

    2008-02-01

    Biologically relevant nanopatterns are useful platforms to address fundamental questions, for example, regarding protein-protein and cell-protein interactions. For the creation of nanopatterns, complex and expensive instrumentation is often needed. We present a simple but versatile patterning method using a combination of particle and subsequent molecular self-assembly to produce ordered structures in the micron and sub-micron range. Polystyrene particles were, in a first step, assembled via dip-coating or dried in a drying cell. Silicon wafers and glass slides coated with SiO2 and a top layer of 11 nm of TiO2 were used as substrates. Large hexagonally ordered particle monolayers were formed with high reproducibility. These were subsequently shrunk in a controlled manner by exposure to a O2/N2 plasma and subsequently used as etching masks to transfer the particle pattern onto the substrate, creating TiO2 features in an SiO2 background. After removing the mask the oxide contrast was translated in three simple dip-and-rinse steps into a biochemical contrast of protein-coated features in an inert background. In short, alkane phosphates were first selectively adsorbed to the TiO2 features. Then the SiO2 background was backfilled using poly(L-lysine)-graft-poly(ethylene glycol) and finally streptavidin was adsorbed to the hydrophobic alkane phosphate SAMs, allowing subsequent binding and hybridization of biotinylated DNA.

  15. Direct femtosecond laser writing system for sub-micron and micron scale patterning

    NASA Astrophysics Data System (ADS)

    Vanagas, Egidijus; Tuzhilin, Dmitry; Zinkou, Michail; Sedunov, Alexander; Vasiliev, Nikolai; Kudryashov, Igor; Kononov, Vladimir; Suruga, Shozi

    2003-11-01

    Commercial femtosecond micromachining system (FMS) has been developed that capable to process the material in sub-micron (< 200 nm) and micron scale. Core of the system are: optical unit, controller unit and software. The other parts: fs-laser system; focusing unit; stage unit can be varied (exchangeable). Two different fs-laser systems already are compatible with core of FMS: Mira/RegA (Coherent) and Hurricane (Spectra-Physics). FMS controller unit allows to control every single fs-pulse delivery on the target. Three possible types of focusing unit are available: microscope type unit, long focal distance lens unit, and axicon lens based unit. Standard stage unit options are: three-axis piezostage, and two-axis air bearing stage combined with Z-axis piezostage. Repeatability for all dimensions is within +/-5 nm. Also, step motor stages are available. The system allows 3D scan with confocal laser-microscope (resolution δr=200nm, δz=540nm) build in optical unit. Software controls all basic functions of the system performance and writing any pattern (including 3D) on or into specimen. The results obtained by direct fs-laser writing method are presented and discussed: bits in the range of 100 - 200 nm sizes, 6 TB/cm3 density optical storage matrix, waveguides fabrication inside transparent materials, high aspect ratio (1:125) patterning of dielectric materials with Gauss-Bessel beam.

  16. Magnetic memory in a ceramic YBCO superconductor composed of sub-micron-size grains

    NASA Astrophysics Data System (ADS)

    Deguchi, Hiroyuki; Ashida, Takuya; Syudo, Mitsuhiro; Mito, Masaki; Takagi, Seishi; Hagiwara, Makoto; Koyama, Kuniyuki

    2013-06-01

    The ceramic YBa2Cu4O8 (YBCO) composed of sub-micron-size grains is considered as a random Josephson-coupled network of 0 and π junctions and shows successive phase transitions. The first transition occurs inside each grain at T c1 = 81 K, and the second transition occurs among the grains at T c2 = 47 K. A magnetic glass behavior similar to those of spin-glasses is observed at temperatures below T c2. The memory phenomena are investigated by recording the zero-fieldcooled and thermoremanent magnetizations measured on heating after the cooling process with a halt at T s = 41 K. Memory effects of the halt are imprinted in the system when the sample is re-heated. In the case without a field switch at T s , the influence of the halt is confined to a narrow temperature region near T s whereas the memory effect of the halt employing a field switch is extended over a wide temperature region below T s . The results suggest that chiral-glass ordering occurs at T c2 in the ceramic YBCO.

  17. Laser smoothing of sub-micron grooves in hydroxyl-rich fused silica

    SciTech Connect

    Shen, N; Matthews, M J; Fair, J E; Britten, J A; Nguyen, H T; Cooke, D; Elhadj, S; Yang, S T

    2009-10-30

    Nano- to micrometer-sized surface defects on UV-grade fused silica surfaces are known to be effectively smoothed through the use of high-temperature localized CO{sub 2} laser heating, thereby enhancing optical properties. However, the details of the mass transport and the effect of hydroxyl content on the laser smoothing of defective silica at submicron length scales is still not completely understood. In this study, we examine the morphological evolution of sub-micron, dry-etched periodic surface structures on type II and type III SiO{sub 2} substrates under 10.6 {micro}m CO{sub 2} laser irradiation using atomic force microscopy (AFM). In-situ thermal imaging was used to map the transient temperature field across the heated region, allowing assessment of the T-dependent mass transport mechanisms under different laser-heating conditions. Computational fluid dynamics simulations correlated well with experimental results, and showed that for large effective capillary numbers (N{sub c} > 2), surface diffusion is negligible and smoothing is dictated by capillary action, despite the relatively small spatial scales studied here. Extracted viscosity values over 1700-2000K were higher than the predicted bulk values, but were consistent with the surface depletion of OH groups, which was confirmed using confocal Raman microscopy.

  18. Preparation of multicompartment sub-micron particles using a triple-needle electrohydrodynamic device.

    PubMed

    Labbaf, Sheyda; Deb, Sanjukta; Cama, Giuseppe; Stride, Eleanor; Edirisinghe, Mohan

    2013-11-01

    Control over the size and morphology of polymeric carriers for drug delivery systems is essential to optimize their functionality. In the current study, we demonstrate the feasibility of using an electrohydrodynamic process with a triple-needle device to prepare nearly mono-dispersed, spherical, tri-layered sub-micron particles. Three biocompatible polymer solutions of poly (lactic-co-glycolic acid) (PLGA), polycaprolactone (PCL) and polymethylsilsesquioxane (PMSQ) were used to prepare particles with three distinct layers. Optimized particles were shown to be spherical with an average size ranging from 320 nm (±80 nm) to 220 (±8 nm), which varied with a change in the working distance in the electrohydrodynamic processing. The surface and internal structure and morphology were studied using confocal, transmission and scanning electron microscopy combined with focused ion beam sectioning. Cytotoxicity was shown to be negligible in an in vitro assay. The ability to fabricate such multilayered particles in a single step, under ambient conditions has considerable potential for a range of applications in particular controlled release drug delivery system.

  19. Local structure of human hair spatially resolved by sub-micron X-ray beam

    NASA Astrophysics Data System (ADS)

    Stanić, Vesna; Bettini, Jefferson; Montoro, Fabiano Emmanuel; Stein, Aaron; Evans-Lutterodt, Kenneth

    2015-11-01

    Human hair has three main regions, the medulla, the cortex, and the cuticle. An existing model for the cortex suggests that the α-keratin- based intermediate filaments (IFs) align with the hair’s axis, but are orientationally disordered in-plane. We found that there is a new region in the cortex near the cuticle’s boundary in which the IFs are aligned with the hair’s axis, but additionally, they are orientationally ordered in-plane due to the presence of the cuticle/hair boundary. Further into the cortex, the IF arrangement becomes disordered, eventually losing all in-plane orientation. We also find that in the cuticle, a key diffraction feature is absent, indicating the presence of the β-keratin rather than that of the α-keratin phase. This is direct structural evidence that the cuticle contains β-keratin sheets. This work highlights the importance of using a sub-micron x-ray beam to unravel the structures of poorly ordered, multi-phase systems.

  20. Measuring Sub-micron Size Fractionated Particulate Matter on Aluminum Impactor Disks

    SciTech Connect

    Buchholz, B A; Zermeno, P; Hwang, H; Young, T M

    2009-07-28

    Sub-micron sized airborne particulate matter is not collected well on regular quartz or glass fiber filter papers. We used a micro-orifice uniform deposit impactor (MOUDI) to size fractionate particulate matter (PM) into six size fractions and deposit it on specially designed high purity thin aluminum disks. The MOUDI separated PM into fractions 56-100 nm, 100-180 nm, 180-320 nm, 320-560 nm, 560-1000 nm, and 1000-1800 nm. Since MOUDI have low flow rates, it takes several days to collect sufficient carbon on 47 mm foil disks. The small carbon mass (20-200 microgram C) and large aluminum substrate ({approx}25 mg Al) presents several challenges to production of graphite targets for accelerator mass spectrometry (AMS) analysis. The Al foil consumes large amounts of oxygen as it is heated and tends to melt into quartz combustion tubes, causing gas leaks. We describe sample processing techniques to reliably produce graphitic targets for {sup 14}C-AMS analysis of PM deposited on Al impact foils.

  1. Conformational transitions of cytochrome c in sub-micron-sized capsules at air/buffer interface.

    PubMed

    Jaganathan, Maheshkumar; Dhathathreyan, Aruna

    2014-09-30

    This work presents the design of sub-micron-sized capsules of Cytochrome c (cyt c) in the range 300-350 nm and the conformational transitions of the protein that occur when the films of these capsules spread at the air/buffer interface are subjected to repeated compression-expansion cycles. Steady state fluorescence, time-resolved fluorescence, and circular dichroic (CD) spectra have been used to study the highly compact native conformation (70% helicity) of the protein in the capsules and its stability has been analyzed using cyclic voltammetry. The capsules have been characterized using zeta sizer and high resolution transmission electron microscopy (HRTEM). Surface concentration-surface pressure (Γ-π) isotherms of the films of the capsules spread at air/buffer interface following compression-expansion show destabilizing effect on cyt c. FTIR and CD spectra of these films skimmed from the surface show that the protein transitions gradually from its native helical to an anomalous beta sheet aggregated state. This results from a competition between stabilizing hydrated polar segments of the protein in the capsule and destabilizing nonspecific hydrophobic interactions arising at the air/buffer interface. This 2D model could further our understanding of the spatial and temporal roles of proteins in confined spaces and also in the design of new drug delivery vehicles using proteins.

  2. Scalable sub-micron patterning of organic materials toward high density soft electronics

    SciTech Connect

    Kim, Jaekyun; Kim, Myung -Gil; Kim, Jaehyun; Jo, Sangho; Kang, Jingu; Jo, Jeong -Wan; Lee, Woobin; Hwang, Chahwan; Moon, Juhyuk; Yang, Lin; Kim, Yun -Hi; Noh, Yong -Young; Yun Jaung, Jae; Kim, Yong -Hoon; Kyu Park, Sung

    2015-09-28

    The success of silicon based high density integrated circuits ignited explosive expansion of microelectronics. Although the inorganic semiconductors have shown superior carrier mobilities for conventional high speed switching devices, the emergence of unconventional applications, such as flexible electronics, highly sensitive photosensors, large area sensor array, and tailored optoelectronics, brought intensive research on next generation electronic materials. The rationally designed multifunctional soft electronic materials, organic and carbon-based semiconductors, are demonstrated with low-cost solution process, exceptional mechanical stability, and on-demand optoelectronic properties. Unfortunately, the industrial implementation of the soft electronic materials has been hindered due to lack of scalable fine-patterning methods. In this report, we demonstrated facile general route for high throughput sub-micron patterning of soft materials, using spatially selective deep-ultraviolet irradiation. For organic and carbon-based materials, the highly energetic photons (e.g. deep-ultraviolet rays) enable direct photo-conversion from conducting/semiconducting to insulating state through molecular dissociation and disordering with spatial resolution down to a sub-μm-scale. As a result, the successful demonstration of organic semiconductor circuitry promise our result proliferate industrial adoption of soft materials for next generation electronics.

  3. Scalable sub-micron patterning of organic materials toward high density soft electronics

    DOE PAGES

    Kim, Jaekyun; Kim, Myung -Gil; Kim, Jaehyun; ...

    2015-09-28

    The success of silicon based high density integrated circuits ignited explosive expansion of microelectronics. Although the inorganic semiconductors have shown superior carrier mobilities for conventional high speed switching devices, the emergence of unconventional applications, such as flexible electronics, highly sensitive photosensors, large area sensor array, and tailored optoelectronics, brought intensive research on next generation electronic materials. The rationally designed multifunctional soft electronic materials, organic and carbon-based semiconductors, are demonstrated with low-cost solution process, exceptional mechanical stability, and on-demand optoelectronic properties. Unfortunately, the industrial implementation of the soft electronic materials has been hindered due to lack of scalable fine-patterning methods. Inmore » this report, we demonstrated facile general route for high throughput sub-micron patterning of soft materials, using spatially selective deep-ultraviolet irradiation. For organic and carbon-based materials, the highly energetic photons (e.g. deep-ultraviolet rays) enable direct photo-conversion from conducting/semiconducting to insulating state through molecular dissociation and disordering with spatial resolution down to a sub-μm-scale. As a result, the successful demonstration of organic semiconductor circuitry promise our result proliferate industrial adoption of soft materials for next generation electronics.« less

  4. Scalable Sub-micron Patterning of Organic Materials Toward High Density Soft Electronics

    PubMed Central

    Kim, Jaekyun; Kim, Myung-Gil; Kim, Jaehyun; Jo, Sangho; Kang, Jingu; Jo, Jeong-Wan; Lee, Woobin; Hwang, Chahwan; Moon, Juhyuk; Yang, Lin; Kim, Yun-Hi; Noh, Yong-Young; Yun Jaung, Jae; Kim, Yong-Hoon; Kyu Park, Sung

    2015-01-01

    The success of silicon based high density integrated circuits ignited explosive expansion of microelectronics. Although the inorganic semiconductors have shown superior carrier mobilities for conventional high speed switching devices, the emergence of unconventional applications, such as flexible electronics, highly sensitive photosensors, large area sensor array, and tailored optoelectronics, brought intensive research on next generation electronic materials. The rationally designed multifunctional soft electronic materials, organic and carbon-based semiconductors, are demonstrated with low-cost solution process, exceptional mechanical stability, and on-demand optoelectronic properties. Unfortunately, the industrial implementation of the soft electronic materials has been hindered due to lack of scalable fine-patterning methods. In this report, we demonstrated facile general route for high throughput sub-micron patterning of soft materials, using spatially selective deep-ultraviolet irradiation. For organic and carbon-based materials, the highly energetic photons (e.g. deep-ultraviolet rays) enable direct photo-conversion from conducting/semiconducting to insulating state through molecular dissociation and disordering with spatial resolution down to a sub-μm-scale. The successful demonstration of organic semiconductor circuitry promise our result proliferate industrial adoption of soft materials for next generation electronics. PMID:26411932

  5. Detection, imaging, and kinetics of sub-micron organelles of chondrocytes by multiple beam interference microscopy

    NASA Astrophysics Data System (ADS)

    Joshi, Narahari V.; Medina, Honorio; Barboza, J. M.; Colantuoni, Gladys; Quintero, Maritza

    2004-07-01

    Chondrocytes, obtained from testosterone treated human articular cartilage, were examined by a recently developed Multiple Beam Interference Microscopy (MBIM) attached to a confocal set up, Video-enhanced differential interference microphotography and also by cinematography. In the MBIM, the intensity of the transmitted pattern is given by the Airy function which increases the contrast dramatically as the coefficient of the reflectance of the parallel plates increases. Moreover, in this configuration, the beam passes several times through a specific organelle and increases its optical path difference both because of the increase in the trajectory and refractive index (high density) of the organelle. The improved contrast enhances the resolving power of the system and makes visible several structural details of sub micron dimensions like nucleolus, retraction fibers, podia, etc. which are not possible to reveal with such a clarity by conventional techniques such as bright field, phase contrast or DIC. This technique permits to detect the oscillatory and rotational motions of unstained cilia for the first time. The frequency of oscillations was found to be 0.8 Hz.

  6. Scalable Sub-micron Patterning of Organic Materials Toward High Density Soft Electronics.

    PubMed

    Kim, Jaekyun; Kim, Myung-Gil; Kim, Jaehyun; Jo, Sangho; Kang, Jingu; Jo, Jeong-Wan; Lee, Woobin; Hwang, Chahwan; Moon, Juhyuk; Yang, Lin; Kim, Yun-Hi; Noh, Yong-Young; Jaung, Jae Yun; Kim, Yong-Hoon; Park, Sung Kyu

    2015-09-28

    The success of silicon based high density integrated circuits ignited explosive expansion of microelectronics. Although the inorganic semiconductors have shown superior carrier mobilities for conventional high speed switching devices, the emergence of unconventional applications, such as flexible electronics, highly sensitive photosensors, large area sensor array, and tailored optoelectronics, brought intensive research on next generation electronic materials. The rationally designed multifunctional soft electronic materials, organic and carbon-based semiconductors, are demonstrated with low-cost solution process, exceptional mechanical stability, and on-demand optoelectronic properties. Unfortunately, the industrial implementation of the soft electronic materials has been hindered due to lack of scalable fine-patterning methods. In this report, we demonstrated facile general route for high throughput sub-micron patterning of soft materials, using spatially selective deep-ultraviolet irradiation. For organic and carbon-based materials, the highly energetic photons (e.g. deep-ultraviolet rays) enable direct photo-conversion from conducting/semiconducting to insulating state through molecular dissociation and disordering with spatial resolution down to a sub-μm-scale. The successful demonstration of organic semiconductor circuitry promise our result proliferate industrial adoption of soft materials for next generation electronics.

  7. Characterization of phosphorus in organisms at sub-micron resolution using X-ray fluorescence spectromicroscopy.

    SciTech Connect

    Diaz, J.; Ingall, E; Vogt, S; Paterson, D; DeJonge, M; Rao, C; Brandes, J

    2009-01-01

    X-ray spectromicroscopy (combined X-ray spectroscopy and microscopy) is uniquely capable of determining sub-micron scale elemental content and chemical speciation in minimally-prepared particulate samples. The high spatial resolutions achievable with this technique have enabled the close examination of important microscale processes relevant to the cycling of biogeochemically important elements. Here, we demonstrate the value of X-ray microscopy to environmental and biological research by examining the phosphorus and metal chemistry of complete individual cells from the algal genera Chlamydomonas sp. and Chlorella sp. X-ray analysis revealed that both genera store substantial intracellular phosphorus as distinct, heterogeneously distributed granules whose X-ray fluorescence spectra are consistent with that of polyphosphate. Polyphosphate inclusions ranged in size from 0.3-1.4 {micro}m in diameter and exhibited a nonspecies-specific average phosphorus concentration of 6.87 {+-} 1.86 {micro}g cm{sup -2}, which was significantly higher than the average concentration of phosphorus measured in the total cell, at 3.14 {+-} 0.98 {micro}g cm{sup -2} (95% confidence). Polyphosphate was consistently associated with calcium and iron, exhibiting average P:cation molar ratios of 8.31 {+-} 2.00 and 108 {+-} 34, respectively (95% confidence). In some cells, polyphosphate was also associated with potassium, zinc, manganese, and titanium. Based on our results, X-ray spectromicroscopy can provide high-resolution elemental data on minimally prepared, unsectioned cells that are unattainable through alternative microscopic methods and conventional bulk chemical techniques currently available in many fields of marine chemistry.

  8. Grain orientation and strain measurements in sub-micron wide passivated individual aluminum test structures

    SciTech Connect

    Tamura, N.; Valek, B.C.; Spolenak, R.; MacDowell, A.A.; Celestre, R.S.; Padmore, H.A.; Brown, W.L.; Marieb, T.; Bravman, J.C.; Batterman, B.W.; Patel, J.R.

    2001-03-01

    An X-ray microdiffraction dedicated beamline, combining white and monochromatic beam capabilities, has been built at the Advanced Light Source. The purpose of this beamline is to address the myriad of problems in Materials Science and Physics that require submicron x-ray beams for structural characterization. Many such problems are found in the general area of thin films and nano-materials. For instance, the ability to characterize the orientation and strain state in individual grains of thin films allows us to measure structural changes at a very local level. These microstructural changes are influenced heavily by such parameters as deposition conditions and subsequent treatment. The accurate measurement of strain gradients at the micron and sub-micron level finds many applications ranging from the strain state under nano-indenters to gradients at crack tips. Undoubtedly many other applications will unfold in the future as we gain experience with the capabilities and limitations of this instrument. We have applied this technique to measure grain orientation and residual stress in single grains of pure Al interconnect lines and preliminary results on post-electromigration test experiments are presented. It is shown that measurements with this instrument can be used to resolve the complete stress tensor (6 components) in a submicron volume inside a single grain of Al under a passivation layer with an overall precision of about 20 MPa. The microstructure of passivated lines appears to be complex, with grains divided into identifiable subgrains and noticeable local variations of both tensile/compressive and shear stresses within single grains.

  9. Sources and characteristics of sub-micron aerosols in the San Joaquin Valley, CA

    NASA Astrophysics Data System (ADS)

    Bahreini, R.; Middlebrook, A. M.; Brioude, J.; Brock, C. A.; de Gouw, J. A.; Hall, K.; Holloway, J. S.; Neuman, J.; Nowak, J. B.; Pollack, I. B.; Ryerson, T. B.; Warneke, C.; Parrish, D. D.

    2010-12-01

    The NOAA WP-3D aircraft performed several flights in the San Joaquin Valley (SJV), California during the CalNex-2010 (California Research at the Nexus of Air Quality and Climate Change) field project in May-June 2010. SJV is generally a rural valley, with a high concentration of feedlots and agricultural sites as well as urbanized centers such as Fresno and Bakersfield. Preliminary results on size-resolved chemical composition of sub-micron aerosols measured using a compact time-of-flight aerosol mass spectrometer, measurements of trace gases affecting secondary production of aerosols, and FLEXPART back trajectory analyses are presented in order to identify sources of aerosols transported to or produced in the valley. Observed enhancements in various trace gases and aerosol species indicate a mixed influence from urban, industrial, and animal feedlots in the SJV. Three distinct observations suggest a complex transport pattern of pollutants with different origins to and within the valley: 1) CO and NOx mixing ratios were prominent downwind of the urban areas in the valley; 2) SO2, aerosol organics and sulfate were higher closer to the foothills of the Sierra Nevada Mountains on the east of the valley; 3) high concentration of aerosol phase ammonium and nitrate were observed in NH3-rich air masses, directly downwind of the feedlots in the central part of the valley. Aerosol enhancements in each of these air mass categories relative to the background determine the relative contribution and significance of different sources to aerosol loadings in the valley. Differences in VOC measurements and meteorology will be explored to investigate the observed variation in characteristics of organics on different days.

  10. Sub-micron resolution CT for failure analysis and process development

    NASA Astrophysics Data System (ADS)

    Feser, M.; Gelb, J.; Chang, H.; Cui, H.; Duewer, F.; Lau, S. H.; Tkachuk, A.; Yun, W.

    2008-09-01

    Many modern industrial processes and research applications place increasingly higher demands on x-ray computed tomography (CT) imaging resolution and sensitivity for low-contrast specimens with a low atomic number. The three approaches to increasing imaging resolution are (1) reduction in the x-ray spot size, (2) use of higher resolution detectors or (3) employment of x-ray optical elements. Systems that pursue one or more of these approaches are available and under continued development. The Xradia MicroXCT™ projection-type microscope described in this paper has been optimized for high-resolution x-ray CT by employing a high-resolution detector paired with a microfocus x-ray source. Large working distances in this CT system enable full tomographic data collection at micrometre resolution of large samples, such as flip-chip packages. X-ray CT instruments using x-ray optical elements for condenser optics and imaging objective lenses are a new development capable of reaching sub-50 nm resolution. These instruments find various applications, including die-level imaging in the semiconductor industry as well as the process development for fuel cells, which we describe here as one application. Sub-micron resolution CT instruments without x-ray optical elements have a large application base already; however, new instruments optimized for soft materials and low-contrast specimens, such as the Xradia nanoXCT™, offer completely new capabilities and open new applications. New developments in the area of phase contrast imaging enable unprecedented image contrast for specimens with very low absorption, which for research applications enables for the first time the imaging of many specimens in their natural state (e.g., arteries to examine calcification). Zernike phase contrast for sub-50 nm x-ray CT even enables the imaging of single cell or thin tissue slices for biological or medical applications.

  11. Sub-micron resolution high-speed spectral domain optical coherence tomography in quality inspection for printed electronics

    NASA Astrophysics Data System (ADS)

    Czajkowski, J.; Lauri, J.; Sliz, R.; Fält, P.; Fabritius, T.; Myllylä, R.; Cense, B.

    2012-04-01

    We present the use of sub-micron resolution optical coherence tomography (OCT) in quality inspection for printed electronics. The device used in the study is based on a supercontinuum light source, Michelson interferometer and high-speed spectrometer. The spectrometer in the presented spectral-domain optical coherence tomography setup (SD-OCT) is centered at 600 nm and covers a 400 nm wide spectral region ranging from 400 nm to 800 nm. Spectra were acquired at a continuous rate of 140,000 per second. The full width at half maximum of the point spread function obtained from a Parylene C sample was 0:98 m. In addition to Parylene C layers, the applicability of sub-micron SD-OCT in printed electronics was studied using PET and epoxy covered solar cell, a printed RFID antenna and a screen-printed battery electrode. A commercial SD-OCT system was used for reference measurements.

  12. A simple and wide-range refractive index measuring approach by using a sub-micron grating

    NASA Astrophysics Data System (ADS)

    Liu, Chun-Wei; Wu, Chun-Che; Lin, Shih-Chieh

    2015-04-01

    This paper presents the design and simulation results of a high-precision low-cost refractometer that demonstrates the main advantage of a wide measurement range (1 ≤ n ≤ 2). The proposed design is based on the diffractive properties of sub-micron gratings and Snell's Law. The precision and uncertainty factors of the proposed system were tested and analyzed, revealing that the proposed refractometer demonstrates a wide measurement range with sensitivity of 10-4.

  13. Prescribed 3-D Direct Writing of Suspended Micron/Sub-micron Scale Fiber Structures via a Robotic Dispensing System.

    PubMed

    Yuan, Hanwen; Cambron, Scott D; Keynton, Robert S

    2015-06-12

    A 3-axis dispensing system is utilized to control the initiating and terminating fiber positions and trajectory via the dispensing software. The polymer fiber length and orientation is defined by the spatial positioning of the dispensing system 3-axis stages. The fiber diameter is defined by the prescribed dispense time of the dispensing system valve, the feed rate (the speed at which the stage traverses from an initiating to a terminating position), the gauge diameter of the dispensing tip, the viscosity and surface tension of the polymer solution, and the programmed drawing length. The stage feed rate affects the polymer solution's evaporation rate and capillary breakup of the filaments. The dispensing system consists of a pneumatic valve controller, a droplet-dispensing valve and a dispensing tip. Characterization of the direct write process to determine the optimum combination of factors leads to repeatedly acquiring the desired range of fiber diameters. The advantage of this robotic dispensing system is the ease of obtaining a precise range of micron/sub-micron fibers onto a desired, programmed location via automated process control. Here, the discussed self-assembled micron/sub-micron scale 3D structures have been employed to fabricate suspended structures to create micron/sub-micron fluidic devices and bioengineered scaffolds.

  14. Sub-micronic capsules based on gelatin and poly(maleic anhydride-alt-vinyl acetate) obtained by interfacial condensation with potential biomedical applications.

    PubMed

    Iurea, Delia Mihaela; Peptu, Cătălina Anişoara; Chailan, Jean-François; Carriere, Pascal; Popa, Marcel

    2013-06-01

    New sub-micronic capsules based on a copolymer of maleic anhydride-alt-vinyl acetate and a natural polymer (gelatin) using an interfacial condensation method were obtained. Sub-micronic capsules were characterized by Fourier Transform infrared spectroscopy (FTIR), dynamic light scattering (DLS) method, zeta-potential, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The thermal properties were investigated by thermogravimetric analysis (TGA). According to some parameters of the synthesis reaction (polymer weight ratio, acetone/water ratio, surfactant concentration), the mean diameter of the sub-micronic capsules can be tuned from 200 to 760 nm. The sub-micronic capsules show a higher agglomeration tendency as the amount of gelatin in their composition increases. The swelling capacity in aqueous solutions is dependent on the composition and size of the sub-micronic capsules, decreasing with their diameter and gelatin composition. The drug loading and release capacity was studied using Penicillin G (sodium salt) (PG), and it has been proved that it is influenced by the sub-micronic capsules morphology induced by preparation parameters. Encapsulation and controlled release of small molecule were successfully carried out, demonstrating the potential biomedical applications of these new easily obtained sub-micronic capsules.

  15. Area- and energy-efficient CORDIC accelerators in deep sub-micron CMOS technologies

    NASA Astrophysics Data System (ADS)

    Vishnoi, U.; Noll, T. G.

    2012-09-01

    The COordinate Rotate DIgital Computer (CORDIC) algorithm is a well known versatile approach and is widely applied in today's SoCs for especially but not restricted to digital communications. Dedicated CORDIC blocks can be implemented in deep sub-micron CMOS technologies at very low area and energy costs and are attractive to be used as hardware accelerators for Application Specific Instruction Processors (ASIPs). Thereby, overcoming the well known energy vs. flexibility conflict. Optimizing Global Navigation Satellite System (GNSS) receivers to reduce the hardware complexity is an important research topic at present. In such receivers CORDIC accelerators can be used for digital baseband processing (fixed-point) and in Position-Velocity-Time estimation (floating-point). A micro architecture well suited to such applications is presented. This architecture is parameterized according to the wordlengths as well as the number of iterations and can be easily extended for floating point data format. Moreover, area can be traded for throughput by partially or even fully unrolling the iterations, whereby the degree of pipelining is organized with one CORDIC iteration per cycle. From the architectural description, the macro layout can be generated fully automatically using an in-house datapath generator tool. Since the adders and shifters play an important role in optimizing the CORDIC block, they must be carefully optimized for high area and energy efficiency in the underlying technology. So, for this purpose carry-select adders and logarithmic shifters have been chosen. Device dimensioning was automatically optimized with respect to dynamic and static power, area and performance using the in-house tool. The fully sequential CORDIC block for fixed-point digital baseband processing features a wordlength of 16 bits, requires 5232 transistors, which is implemented in a 40-nm CMOS technology and occupies a silicon area of 1560 μm2 only. Maximum clock frequency from circuit

  16. 2D-ordered dielectric sub-micron bowls on a metal surface: a useful hybrid plasmonic-photonic structure

    NASA Astrophysics Data System (ADS)

    Lan, Yue; Wang, Shiqiang; Yin, Xianpeng; Liang, Yun; Dong, Hao; Gao, Ning; Li, Jian; Wang, Hui; Li, Guangtao

    2016-07-01

    Recently, it has been demonstrated that the combination of periodic dielectric structures with metallic structures provides an efficient means to yield a synergetic optical response or functionality in the resultant hybrid plasmonic-photonic systems. In this work, a new hybrid plasmonic-photonic structure of 2D-ordered dielectric sub-micron bowls on a flat gold surface was proposed, prepared, and theoretically and experimentally characterized. This hybrid structure supports two types of modes: surface plasmon polaritons bound at the metallic surface and waveguided mode of light confined in the cavity of bowls. Optical responses of this hybrid structure as well as the spatial electric field distribution of each mode are found to be strongly dependent on the structural parameters of this system, and thus could be widely modified on demand. Importantly, compared to the widely studied hybrid systems, namely the flat metallic surface coated with a monolayer array of latex spheres, the waveguided mode with strong field enhancement appearing in the cavities of bowls is more facilely accessible and thus suitable for practical use. For demonstration, a 2D-ordered silica sub-micron bowl array deposited on a flat gold surface was fabricated and used as a regenerable platform for fluorescence enhancement by simply accommodating emitters in bowls. All the simulation and experiment results indicate that the 2D-ordered dielectric sub-micron bowls on a metal surface should be a useful hybrid plasmonic-photonic system with great potential for applications such as sensors or tunable emitting devices if appropriate periods and materials are employed.Recently, it has been demonstrated that the combination of periodic dielectric structures with metallic structures provides an efficient means to yield a synergetic optical response or functionality in the resultant hybrid plasmonic-photonic systems. In this work, a new hybrid plasmonic-photonic structure of 2D-ordered dielectric sub-micron

  17. Sub-micron resolution of localized ion beam induced charge reduction in silicon detectors damaged by heavy ions

    DOE PAGES

    Auden, Elizabeth C.; Pacheco, Jose L.; Bielejec, Edward; ...

    2015-12-01

    In this study, displacement damage reduces ion beam induced charge (IBIC) through Shockley-Read-Hall recombination. Closely spaced pulses of 200 keV Si++ ions focused in a 40 nm beam spot are used to create damage cascades within 0.25 μm2 areas. Damaged areas are detected through contrast in IBIC signals generated with focused ion beams of 200 keV Si++ ions and 60 keV Li+ ions. IBIC signal reduction can be resolved over sub-micron regions of a silicon detector damaged by as few as 1000 heavy ions.

  18. Sub-micron resolution of localized ion beam induced charge reduction in silicon detectors damaged by heavy ions

    SciTech Connect

    Auden, Elizabeth C.; Pacheco, Jose L.; Bielejec, Edward; Vizkelethy, Gyorgy; Abraham, John B. S.; Doyle, Barney L.

    2015-12-01

    In this study, displacement damage reduces ion beam induced charge (IBIC) through Shockley-Read-Hall recombination. Closely spaced pulses of 200 keV Si++ ions focused in a 40 nm beam spot are used to create damage cascades within 0.25 μm2 areas. Damaged areas are detected through contrast in IBIC signals generated with focused ion beams of 200 keV Si++ ions and 60 keV Li+ ions. IBIC signal reduction can be resolved over sub-micron regions of a silicon detector damaged by as few as 1000 heavy ions.

  19. Enhanced sub-micron colloidal particle separation with interdigitated microelectrode arrays using mixed AC/DC dielectrophoretic scheme.

    PubMed

    Swaminathan, Vikhram V; Shannon, Mark A; Bashir, Rashid

    2015-04-01

    Dielectrophoretic separation of particles finds a variety of applications in the capture of species such as cells, viruses, proteins, DNA from biological systems, as well as other organic and inorganic contaminants from water. The ability to capture particles is constrained by poor volumetric scaling of separation force with respect to particle diameter, as well as the weak penetration of electric fields in the media. In order to improve the separation of sub-micron colloids, we present a scheme based on multiple interdigitated electrode arrays under mixed AC/DC bias. The use of high frequency longitudinal AC bias breaks the shielding effects through electroosmotic micromixing to enhance electric fields through the electrolyte, while a transverse DC bias between the electrode arrays enables penetration of the separation force to capture particles from the bulk of the microchannel. We determine the favorable biasing conditions for field enhancement with the help of analytical models, and experimentally demonstrate the improved capture from sub-micron colloidal suspensions with the mixed AC/DC electrostatic excitation scheme over conventional AC-DEP methods.

  20. Fabrication and electrical characterization of sub-micron diameter through-silicon via for heterogeneous three-dimensional integrated circuits

    NASA Astrophysics Data System (ADS)

    Abbaspour, R.; Brown, D. K.; Bakir, M. S.

    2017-02-01

    This paper presents the fabrication and electrical characterization of high aspect-ratio (AR) sub-micron diameter through silicon vias (TSVs) for densely interconnected three-dimensional (3D) stacked integrated circuits (ICs). The fabricated TSV technology features an AR of 16:1 with 680 nm diameter copper (Cu) core and 920 nm overall diameter. To address the challenges in scaling TSVs, scallop-free low roughness nano-Bosch silicon etching and direct Cu electroplating on a titanium-nitride (TiN) diffusion barrier layer have been developed as key enabling modules. The electrical resistance of the sub-micron TSVs is measured to be on average 1.2 Ω, and the Cu resistivity is extracted to be approximately 2.95 µΩ cm. Furthermore, the maximum achievable current-carrying capacity (CCC) of the scaled TSVs is characterized to be approximately 360 µA for the 680 nm Cu core.

  1. Propagation characteristics of silver and tungsten subwavelength annular aperture generated sub-micron non-diffraction beams.

    PubMed

    Cheng, Tsung-Dar; Lin, Ding-Zheng; Yeh, Jyi-Tyan; Liu, Jonq-Min; Yeh, Chau-Shioung; Lee, Chih-Kung

    2009-03-30

    We examined the optical properties such as propagation modes, focal length, side lobes, etc. of metallic subwavelength annular apertures (SAA) and used finite-difference time-domain (FDTD) simulation to compare our experimental findings. Using two different metals, silver and tungsten, we examined the different optical transmission properties of the two metallic SAA structures. The far-field propagation of the silver SAA structure was found to be a type of quasi-Bessel beam when compared with a quasi-Bessel beam generated by a perfect axicon. The propagation characteristics of these two beams were found to match qualitatively. The far-field transmitted light generated by the silver SAA structure was found to possess a 390 nm sub-micron focal spot with a 24 microm depth of focus, which was much smaller than the focal spot generated by a perfect axicon. We also found that a silver SAA structure can generate a sub-micron quasi- Bessel beam that has a much lower far-field side-lobe when compared to that of non-diffraction beams generated by a tungsten SAA structure.

  2. Exploring the Role of Sub-micron-sized Dust Grains in the Atmospheres of Red L0-L6 Dwarfs

    NASA Astrophysics Data System (ADS)

    Hiranaka, Kay; Cruz, Kelle L.; Douglas, Stephanie T.; Marley, Mark S.; Baldassare, Vivienne F.

    2016-10-01

    We examine the hypothesis that the red near-infrared colors of some L dwarfs could be explained by a “dust haze” of small particles in their upper atmospheres. This dust haze would exist in conjunction with the clouds found in dwarfs with more typical colors. We developed a model that uses Mie theory and the Hansen particle size distributions to reproduce the extinction due to the proposed dust haze. We apply our method to 23 young L dwarfs and 23 red field L dwarfs. We constrain the properties of the dust haze including particle size distribution and column density using Markov Chain Monte Carlo methods. We find that sub-micron-range silicate grains reproduce the observed reddening. Current brown dwarf atmosphere models include large-grain (1-100 μm) dust clouds but not sub-micron dust grains. Our results provide a strong proof of concept and motivate a combination of large and small dust grains in brown dwarf atmosphere models.

  3. Sub-micron fracture mechanism in silica-based glass activated by permanent densification from high-strain loading

    DOE PAGES

    Wereszczak, Andrew A.; Waters, Shirley B.; Parten, Randy J.; ...

    2016-04-26

    Several silica-based glasses were fractured at high strain energy via drop-weight testing on small specimens. A cylindrical specimen geometry was chosen to promote initially simple, axisymmetric, and uniform compressive loading. The imposed uniaxial compressive strain at impact was sufficiently high to qualitatively cause permanent densification. Produced fragments were collected for postmortem and a fraction of them, for all the silica-based glasses, consistently had distinct sub-micron-sized fractures (~ 300–1000 nm), designated here as “microkernels”, on their surfaces. They would most often appear as a sub-micron pore on the fragment - apparently if the microkernel had popped out as a consequence ofmore » the local crack plane running through it, tensile-strain release, and the associated formation of the fragment it was on. No fractographic evidence was found to show the microkernels were associated with local failure initiation. However, their positioning and habit sometimes suggested they were associated with localized crack branching and that they could have influenced secondary fracturing that occurred during overall crushing and comminution and associated fragment size and shape creation. Furthermore, the size range of these microkernels is much too small to affect structural flexure strength of these glasses for most applications but are of a size and concentration that may affect their ballistic, shock, crush, and comminution responses when permanent densification is concomitantly occurring.« less

  4. Sub-micron fracture mechanism in silica-based glass activated by permanent densification from high-strain loading

    SciTech Connect

    Wereszczak, Andrew A.; Waters, Shirley B.; Parten, Randy J.; Pye, L. David

    2016-04-26

    Several silica-based glasses were fractured at high strain energy via drop-weight testing on small specimens. A cylindrical specimen geometry was chosen to promote initially simple, axisymmetric, and uniform compressive loading. The imposed uniaxial compressive strain at impact was sufficiently high to qualitatively cause permanent densification. Produced fragments were collected for postmortem and a fraction of them, for all the silica-based glasses, consistently had distinct sub-micron-sized fractures (~ 300–1000 nm), designated here as “microkernels”, on their surfaces. They would most often appear as a sub-micron pore on the fragment - apparently if the microkernel had popped out as a consequence of the local crack plane running through it, tensile-strain release, and the associated formation of the fragment it was on. No fractographic evidence was found to show the microkernels were associated with local failure initiation. However, their positioning and habit sometimes suggested they were associated with localized crack branching and that they could have influenced secondary fracturing that occurred during overall crushing and comminution and associated fragment size and shape creation. Furthermore, the size range of these microkernels is much too small to affect structural flexure strength of these glasses for most applications but are of a size and concentration that may affect their ballistic, shock, crush, and comminution responses when permanent densification is concomitantly occurring.

  5. Tracking sub-micron fluorescent particles in three dimensions with a microscope objective under non-design optical conditions

    NASA Astrophysics Data System (ADS)

    Luo, R.; Sun, Y. F.; Peng, X. F.; Yang, X. Y.

    2006-06-01

    A microscope objective designed for air medium has been used under non-design optical conditions to focus an exciting laser beam on sub-micron fluorescent particles with the emitted fluorescence received through a glass layer with a mismatched refractive index. The diffraction pattern with several clear interference fringes generated from the fluorescence emitted from a fluorescent particle changed with the particle's position along the optical axis. A scalar diffraction model developed by Gibson and Lanni (1991 J. Opt. Soc. Am. A 8 1601-13) was used to predict the diffraction patterns for various aberration conditions and to analyse the effects of the coherence properties of the fluorescence on the details of the diffraction pattern. The particle position along the optical axis, i.e. its defocus distance, could be determined based on the characteristic sizes of the particle's diffraction pattern to track the particle in three dimensions.

  6. Effects of Carbides on the Microstructural Evolution in Sub-micron Grain 9310 Steel During Isothermal Heat Treatment

    NASA Astrophysics Data System (ADS)

    Kozmel, Thomas; Tin, Sammy

    2015-07-01

    Recent interest in bulk ultra-fine-grained microstructures has given rise for the necessity to quantify their behavior during heat treatment should any subsequent thermal processing of the material be necessary after forming. The present study showed that the microstructure of 9310 steel forgings containing varying fractions of sub-micron grains retained some degree of stability after 4 hours of heat treatment between the temperatures of 522 K and 866 K (249 °C and 593 °C, respectively). The behavior of the microstructure during heat treatment was largely influenced by both the carbide volume fraction and distribution, which affected the level of Zener Drag present. This in effect controlled the type of growth behavior exhibited by the ferrite grains and the ability to retain the fine-grained structure.

  7. Impact of Device Scaling on Deep Sub-micron Transistor Reliability: A Study of Reliability Trends using SRAM

    NASA Technical Reports Server (NTRS)

    White, Mark; Huang, Bing; Qin, Jin; Gur, Zvi; Talmor, Michael; Chen, Yuan; Heidecker, Jason; Nguyen, Duc; Bernstein, Joseph

    2005-01-01

    As microelectronics are scaled in to the deep sub-micron regime, users of advanced technology CMOS, particularly in high-reliability applications, should reassess how scaling effects impact long-term reliability. An experimental based reliability study of industrial grade SRAMs, consisting of three different technology nodes, is proposed to substantiate current acceleration models for temperature and voltage life-stress relationships. This reliability study utilizes step-stress techniques to evaluate memory technologies (0.25mum, 0.15mum, and 0.13mum) embedded in many of today's high-reliability space/aerospace applications. Two acceleration modeling approaches are presented to relate experimental FIT calculations to Mfr's qualification data.

  8. Experimental and simulation studies of anti-reflection sub-micron conical structures on a GaAs substrate.

    PubMed

    Lee, Yeeu-Chang; Chang, Che-Chun; Chou, Yen-Yu

    2013-01-14

    In order to reduce surface reflection, anti-reflective (AR) coatings are widely used on the surfaces of solar cells to improve the efficiency of photoelectric conversion. This study employed colloidal lithography with a dry etching process to fabricate sub-micron anti-reflection structures on a GaAs substrate. Etching parameters, such as RF power and etching gas were investigated to determine their influence on surface morphology. We fabricated an array of conical structures 550 nm in diameter and 450 nm in height. The average reflectance of a bare GaAs wafer was reduced from 35.0% to 2.3% across a spectral range of 300 nm - 1200 nm. The anti-reflective performance of SWSs was also calculated using Rigorous Coupled Wave Analysis (RCWA) method. Both simulation and experiment results demonstrate a high degree of similarity.

  9. Analysis of functional failure mode of commercial deep sub-micron SRAM induced by total dose irradiation

    NASA Astrophysics Data System (ADS)

    Zheng, Qi-Wen; Cui, Jiang-Wei; Zhou, Hang; Yu, De-Zhao; Yu, Xue-Feng; Lu, Wu; Guo, Qi; Ren, Di-Yuan

    2015-10-01

    Functional failure mode of commercial deep sub-micron static random access memory (SRAM) induced by total dose irradiation is experimentally analyzed and verified by circuit simulation. We extensively characterize the functional failure mode of the device by testing its electrical parameters and function with test patterns covering different functional failure modes. Experimental results reveal that the functional failure mode of the device is a temporary function interruption caused by peripheral circuits being sensitive to the standby current rising. By including radiation-induced threshold shift and off-state leakage current in memory cell transistors, we simulate the influence of radiation on the functionality of the memory cell. Simulation results reveal that the memory cell is tolerant to irradiation due to its high stability, which agrees with our experimental result.

  10. Comprehensive understanding of dark count mechanisms of single-photon avalanche diodes fabricated in deep sub-micron CMOS technologies

    NASA Astrophysics Data System (ADS)

    Xu, Yux; Xiang, Ping; Xie, Xiaopeng

    2017-03-01

    The dark count noise mechanisms of single-photon avalanche diodes (SPADs) fabricated in deep sub-micron (DSM) CMOS technologies are investigated in depth. An electric field dependence of tunneling model combined with carrier thermal generation is established for dark count rate (DCR) prediction. Applying the crucial parameters provided by Geiger mode TCAD simulation such as avalanche triggering probability and electric field distribution in the SPAD avalanche region, the individual contribution of each noise source to DCR is calculated for several SPADs in DSM CMOS technologies. The model calculation results reveal that the trap-assisted tunneling is the main DCR generation source for these DSM CMOS SPADs. With the increase of doping levels in the device avalanche region, the band-to-band tunneling will be the dominant factor that could lead to the higher DCR in scaled DSM CMOS technologies.

  11. Dust Diffusion and Settling in the Presence of Collisions: Trapping (sub)micron Grains in the Midplane

    NASA Astrophysics Data System (ADS)

    Krijt, Sebastiaan; Ciesla, Fred J.

    2016-05-01

    In protoplanetary disks, the distribution and abundance of small (sub)micron grains are important for a range of physical and chemical processes. For example, they dominate the optical depth at short wavelengths and their surfaces are the sites of many important chemical reactions, such as the formation of water. Based on their aerodynamical properties (i.e., their strong dynamical coupling with the surrounding gas) it is often assumed that these small grains are well-mixed with the gas. Our goal is to study the vertical (re)distribution of grains taking into account settling, turbulent diffusion, and collisions with other dust grains. Assuming a fragmentation-limited background dust population, we developed a Monte Carlo approach that follows single monomers as they move through a vertical column of gas and become incorporated in different aggregates as they undergo sticking and fragmenting collisions. We find that (sub)micron grains are not necessarily well-mixed vertically, but can become trapped in a thin layer with a scale height that is significantly smaller than that of the gas. This collisional trapping occurs when the timescale for diffusion is comparable to or longer than the collision timescale in the midplane and its effect is strongest when the most massive particles in the size distribution show significant settling. Based on simulations and analytical considerations, we conclude that for typical dust-to-gas ratios and turbulence levels, the collisional trapping of small grains should be a relatively common phenomenon. The absence of trapping could then indicate a low dust-to-gas ratio, possibly because a large portion of the dust mass has been removed through radial drift or is locked up in planetesimals.

  12. A mass closure and PMF source apportionment study on the sub-micron sized aerosol fraction at urban sites in Italy

    NASA Astrophysics Data System (ADS)

    Vecchi, R.; Chiari, M.; D'Alessandro, A.; Fermo, P.; Lucarelli, F.; Mazzei, F.; Nava, S.; Piazzalunga, A.; Prati, P.; Silvani, F.; Valli, G.

    Sub-micron sized particles are of increasing concern owing to their effects on human health and on the environment. Up to now there are still very few studies on PM1 (i.e. particulate matter with aerodynamic diameter smaller than 1 μm) chemical characterisation; the sub-micron sized fraction is not under regulations although it is of interest because it is almost exclusively associated to anthropogenic sources. To perform the first large-scale assessment of sub-micron sized aerosol concentrations, composition and sources, two monitoring campaigns at three urban sites in Italy were carried out during the wintertime and summertime of 2004. Chemical characterisation (elements, soluble ionic fraction, elemental and organic carbon) was carried out on PM1 samples: major contributions were due to organic matter (about 30% in summer and 50% in winter) and ammonium sulphate (about 10% in winter and 40% in summer). During the cold season, nitrates also contributed up to 30% in Milan (lower contributions were registered at the other two urban sites). Chemical mass closure was achieved with an unaccounted mass in the range 14-22%. Positive Matrix Factorisation (PMF) was applied to identify the major sub-micron sized particles' sources.

  13. Exploitation of sub-micron cavitation nuclei to enhance ultrasound-mediated transdermal transport and penetration of vaccines.

    PubMed

    Bhatnagar, Sunali; Kwan, James J; Shah, Apurva R; Coussios, Constantin-C; Carlisle, Robert C

    2016-09-28

    Inertial cavitation mediated by ultrasound has been previously shown to enable skin permeabilisation for transdermal drug and vaccine delivery, by sequentially applying the ultrasound then the therapeutic in liquid form on the skin surface. Using a novel hydrogel dosage form, we demonstrate that the use of sub-micron gas-stabilising polymeric nanoparticles (nanocups) to sustain and promote cavitation activity during simultaneous application of both drug and vaccine results in a significant enhancement of both the dose and penetration of a model vaccine, Ovalbumin (OVA), to depths of 500μm into porcine skin. The nanocups themselves exceeded the penetration depth of the vaccine (up to 700μm) due to their small size and capacity to 'self-propel'. In vivo murine studies indicated that nanocup-assisted ultrasound transdermal vaccination achieved significantly (p<0.05) higher delivery doses without visible skin damage compared to the use of a chemical penetration enhancer. Transdermal OVA doses of up to 1μg were achieved in a single 90-second treatment, which was sufficient to trigger an antigen-specific immune response. Furthermore, ultrasound-assisted vaccine delivery in the presence of nanocups demonstrated substantially higher specific anti-OVA IgG antibody levels compared to other transdermal methods. Further optimisation can lead to a viable, safe and non-invasive delivery platform for vaccines with potential use in a primary care setting or personalized self-vaccination at home.

  14. Time-specific measurements of energy deposition from radiation fields in simulated sub-micron tissue volumes

    SciTech Connect

    Famiano, M.A.

    1997-07-07

    A tissue-equivalent spherical proportional counter is used with a modified amplifier system to measure specific energy deposited from a uniform radiation field for short periods of time ({approximately}1 {micro}s to seconds) in order to extrapolate to dose in sub-micron tissue volumes. The energy deposited during these time intervals is compared to biological repair processes occurring within the same intervals after the initial energy deposition. The signal is integrated over a variable collection time which is adjusted with a square-wave pulse. Charge from particle passages is collected on the anode during the period in which the integrator is triggered, and the signal decays quickly to zero after the integrator feedback switch resets; the process repeats for every triggering pulse. Measurements of energy deposited from x rays, {sup 137}Cs gamma rays, and electrons from a {sup 90}Sr/{sup 90}Y source for various time intervals are taken. Spectral characteristics as a function of charge collection time are observed and frequency plots of specific energy and collection time-interval are presented. In addition, a threshold energy flux is selected for each radiation type at which the formation of radicals (based on current measurements) in mammalian cells equals the rate at which radicals are repaired.

  15. Formation of sub-micron size carbon structures by plasma jets emitted from a pulsed capillary discharge

    NASA Astrophysics Data System (ADS)

    Bhuyan, H.; Favre, M.; Valderrama, E.; Avaria, G.; Wyndham, E.; Chuaqui, H.; Baier, J.; Kelly, H.; Grondona, D.; Marquez, A.

    2009-01-01

    We have performed an experimental investigation of the potential use of intense plasma jets produced in a repetitive pulsed capillary discharge (PCD) operating in methane gas, to irradiate Si (1 0 0) substrates. The surface modifications induced by the plasma jet using two different material inserts at the capillary end, graphite and titanium, are characterized using standard surface science diagnostic tools, such as scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) analysis and Raman spectroscopy (RS). It has been found that the application of methane plasma jet results in the formation of sub-micron size carbon structures. It is observed that the resulting plasma irradiated surface morphologies are different, depending on the different material inserts used at the capillary end, at otherwise identical operational conditions. To investigate the species responsible for the observed surface changes in different material inserts to the capillary, optical-emission spectroscopy (OES) was recorded using a 300-1000 nm spectrometer. The OES results show the presence of H, CH and C 2 Swan band in the discharge plasma, which play a significant role in the formation of the carbon structures.

  16. Prospects for sub-micron solid state nuclear magnetic resonance imaging with low-temperature dynamic nuclear polarization.

    PubMed

    Thurber, Kent R; Tycko, Robert

    2010-06-14

    We evaluate the feasibility of (1)H nuclear magnetic resonance (NMR) imaging with sub-micron voxel dimensions using a combination of low temperatures and dynamic nuclear polarization (DNP). Experiments are performed on nitroxide-doped glycerol-water at 9.4 T and temperatures below 40 K, using a 30 mW tunable microwave source for DNP. With DNP at 7 K, a 0.5 microL sample yields a (1)H NMR signal-to-noise ratio of 770 in two scans with pulsed spin-lock detection and after 80 db signal attenuation. With reasonable extrapolations, we infer that (1)H NMR signals from 1 microm(3) voxel volumes should be readily detectable, and voxels as small as 0.03 microm(3) may eventually be detectable. Through homonuclear decoupling with a frequency-switched Lee-Goldburg spin echo technique, we obtain 830 Hz (1)H NMR linewidths at low temperatures, implying that pulsed field gradients equal to 0.4 G/d or less would be required during spatial encoding dimensions of an imaging sequence, where d is the resolution in each dimension.

  17. Stable, Free-space Optical Trapping and Manipulation of Sub-micron Particles in an Integrated Microfluidic Chip.

    PubMed

    Kim, Jisu; Shin, Jung H

    2016-09-22

    We demonstrate stable, free-space optical trapping and manipulation in an integrated microfluidic chip using counter-propagating beams. An inverted ridge-type waveguide made of SU8 is cut across by an open trench. The design of the waveguide provides low propagation losses and small divergence of the trapping beam upon emergence from the facet, and the trench designed to be deeper and wider than the optical mode enables full utilization of the optical power with an automatic alignment for counter-propagating beams in a trap volume away from all surfaces. After integration with polydimethylsiloxane (PDMS) microfluidic channel for particle delivery, 0.65 μm and 1 μm diameter polystyrene beads were trapped in free space in the trench, and manipulated to an arbitrary position between the waveguides with a resolution of < 100 nm. Comparison with numerical simulations confirm stable trapping of sub-micron particles, with a 10 kBT threshold power of less than 1 mW and a stiffness that can be 1 order of magnitude larger than that of comparable fiber-based trapping methods.

  18. Stable, Free-space Optical Trapping and Manipulation of Sub-micron Particles in an Integrated Microfluidic Chip

    NASA Astrophysics Data System (ADS)

    Kim, Jisu; Shin, Jung H.

    2016-09-01

    We demonstrate stable, free-space optical trapping and manipulation in an integrated microfluidic chip using counter-propagating beams. An inverted ridge-type waveguide made of SU8 is cut across by an open trench. The design of the waveguide provides low propagation losses and small divergence of the trapping beam upon emergence from the facet, and the trench designed to be deeper and wider than the optical mode enables full utilization of the optical power with an automatic alignment for counter-propagating beams in a trap volume away from all surfaces. After integration with polydimethylsiloxane (PDMS) microfluidic channel for particle delivery, 0.65 μm and 1 μm diameter polystyrene beads were trapped in free space in the trench, and manipulated to an arbitrary position between the waveguides with a resolution of < 100 nm. Comparison with numerical simulations confirm stable trapping of sub-micron particles, with a 10 kBT threshold power of less than 1 mW and a stiffness that can be 1 order of magnitude larger than that of comparable fiber-based trapping methods.

  19. Stable, Free-space Optical Trapping and Manipulation of Sub-micron Particles in an Integrated Microfluidic Chip

    PubMed Central

    Kim, Jisu; Shin, Jung H.

    2016-01-01

    We demonstrate stable, free-space optical trapping and manipulation in an integrated microfluidic chip using counter-propagating beams. An inverted ridge-type waveguide made of SU8 is cut across by an open trench. The design of the waveguide provides low propagation losses and small divergence of the trapping beam upon emergence from the facet, and the trench designed to be deeper and wider than the optical mode enables full utilization of the optical power with an automatic alignment for counter-propagating beams in a trap volume away from all surfaces. After integration with polydimethylsiloxane (PDMS) microfluidic channel for particle delivery, 0.65 μm and 1 μm diameter polystyrene beads were trapped in free space in the trench, and manipulated to an arbitrary position between the waveguides with a resolution of < 100 nm. Comparison with numerical simulations confirm stable trapping of sub-micron particles, with a 10 kBT threshold power of less than 1 mW and a stiffness that can be 1 order of magnitude larger than that of comparable fiber-based trapping methods. PMID:27653191

  20. A method for sizing sub-micron particles using small angle diffraction of soft x-rays

    SciTech Connect

    Berkeland, D.J.; Underwood, J.H.; Perera, R.C.C.

    1988-10-01

    The purpose of this work is to develop a method of sizing sub-micron particles using small-angle soft x-ray diffraction. Solid poly-styrene spheres of known sizes were used as scattering samples, with C-K..cap alpha.. (44.8/angstrom/) and V-L..cap alpha.. (24.3/angstrom/) radiation from a conventional x-ray source. Two devices were used to diffract the x-rays. One collimates the radiation using a series of pinholes immediately preceding the sample, and directs the unfocussed radiation onto film placed far from the sample. The other utilizes radiation from a single pinhole above the source onto the sample and a spherical multilayer mirror in series, so that the radiation passes twice through the sample and is focused onto film immediately above the pinhole assembly to increase the effective sample area. Using the latter device, two types of diffraction patterns were obtained: a sharp, relatively small pattern from spheres which form a hexagonal lattice structure, and a diffuse, larger pattern from an unordered, or random, array of spheres. Both patterns are presented in this work, along with the calculations, based upon light scattering from an unordered and an ordered array of particles, of the scattering patterns. 9 refs., 32 figs., 2 tabs.

  1. Micron and sub-micron feature replication of amorphous polymers at elevated mold temperature without externally applied pressure

    NASA Astrophysics Data System (ADS)

    Mosaddegh, Peiman; Angstadt, David C.

    2008-03-01

    The focus of this study is on the ability of amorphous polymers to replicate micron and sub-micron features when molded at an elevated mold temperature without externally applied pressure. Molding was performed using three different types of amorphous polymers: cyclo-olefin copolymer (COC), polystyrene (PS) and poly (methyl methacrylate) (PMMA) on a silicon mold containing surface features as small as 700 nm in depth and aspect ratios ranging from 5 to 0.02. In this study, processing temperatures were selected in order to match the viscosity for all polymers used. Polymer viscosity was characterized via cone and plate rheometry and wettability was characterized via contact angle analysis to quantify interfacial effects. Feature replication was assessed using scanning electron microscopy (SEM) and atomic force microscopy (AFM) to compare the molded feature depth ratio. It was observed that for the features with an aspect ratio (depth/width) bigger than 2 the depth ratio of the molded parts decreases. PS shows the best replication because of high wettability behavior. PMMA shows the intermediate replication because of dipole-dipole interaction and its lower diffusion coefficient than PS. COC has the worse replication especially in low aspect ratio because of sticking to the silicon oxide layer. PS has the best surface roughness among all polymers.

  2. Sub-micron particle number size distributions characteristics at an urban location, Kanpur, in the Indo-Gangetic Plain

    NASA Astrophysics Data System (ADS)

    Kanawade, V. P.; Tripathi, S. N.; Bhattu, Deepika; Shamjad, P. M.

    2014-10-01

    We present long-term measurements of sub-micron particle number size distributions (PNSDs) conducted at an urban location, Kanpur, in India, from September 2007 to July 2011. The mean Aitken mode (NAIT), accumulation mode (NACCU), the total particle (NTOT), and black carbon (BC) mass concentrations were 12.4 × 103 cm- 3, 18.9 × 103 cm- 3, 31.9 × 103 cm- 3, and 7.96 μg m- 3, respectively, within the observed range at other urban locations worldwide, but much higher than those reported at urban sites in the developed nations. The total particle volume concentration appears to be dominated mainly by the accumulation mode particles, except during the monsoon months, perhaps due to efficient wet deposition of accumulation mode particles by precipitation. At Kanpur, the diurnal variation of particle number concentrations was very distinct, with highest during morning and late evening hours, and lowest during the afternoon hours. This behavior could be attributed to the large primary emissions of aerosol particles and temporal evolution of the planetary boundary layer. A distinct seasonal variation in the total particle number and BC mass concentrations was observed, with the maximum in winter and minimum during the rainy season, however, the Aitken mode particles did not show a clear seasonal fluctuation. The ratio of Aitken to accumulation mode particles, NAIT/NACCU, was varied from 0.1 to 14.2, with maximum during April to September months, probably suggesting the importance of new particle formation processes and subsequent particle growth. This finding suggests that dedicated long-term measurements of PNSDs (from a few nanometer to one micron) are required to systematically characterize new particle formation over the Indian subcontinent that has been largely unstudied so far. Contrarily, the low NAIT/NACCU during post-monsoon and winter indicated the dominance of biomass/biofuel burning aerosol emissions at this site.

  3. Fabrication of a high-aspect-ratio sub-micron tool using a cathode coated with stretched-out insulating layers

    NASA Astrophysics Data System (ADS)

    Zeng, Yongbin; Wang, Yufeng; Qu, Ningsong; Zhu, Di

    2013-09-01

    This paper describes a method for preparing a high-aspect-ratio sub-micron tool using a cathode coated with stretched-out insulating layers and a straight reciprocating motion applied at the anode via the liquid membrane electrochemical machining (ECM). Simulation results indicate that the application of a cathode coated with stretched-out insulating layers is beneficial for the localization of ECM. Moreover, a mathematical model was derived to estimate the final average diameter of the fabricated tools. Experiments were conducted to verify the versatility and feasibility of the proposed method and its mathematical model. It was observed that the calculated and the experimental results are in good agreement with each other. A sub-micron tool with an average diameter 140.8 nm and an aspect ratio up to 50 was fabricated using the proposed method.

  4. SiO2/ZnO Composite Hollow Sub-Micron Fibers: Fabrication from Facile Single Capillary Electrospinning and Their Photoluminescence Properties

    PubMed Central

    Song, Guanying; Li, Zhenjiang; Li, Kaihua; Zhang, Lina; Meng, Alan

    2017-01-01

    In this work, SiO2/ZnO composite hollow sub-micron fibers were fabricated by a facile single capillary electrospinning technique followed by calcination, using tetraethyl orthosilicate (TEOS), polyvinylpyrrolidone (PVP) and ZnO nanoparticles as raw materials. The characterization results of the scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) spectra indicated that the as-prepared composite hollow fibers consisted of amorphous SiO2 and hexagonal wurtzite ZnO. The products revealed uniform tubular structure with outer diameters of 400–500 nm and wall thickness of 50–60 nm. The gases generated and the directional escaped mechanism was proposed to illustrate the formation of SiO2/ZnO composite hollow sub-micron fibers. Furthermore, a broad blue emission band was observed in the photoluminescence (PL) of SiO2/ZnO composite hollow sub-micron fibers, exhibiting great potential applications as blue light-emitting candidate materials. PMID:28336887

  5. Laser Interaction with Nano-Spheres: Applications in Sub-Micron Particles Removal and Nanodot Array Fabrication

    NASA Astrophysics Data System (ADS)

    Sentis, M.; Grojo, D.; Delaporte, Ph.; Pereira, A.

    Laser-assisted nanoparticle removal processes like selective particle ablation, mechanical ejection, local substrate ablation, explosive evaporation are considered by experimental and theoretical approaches. Experiments are based on the estimation of particle removal efficiencies and thresholds depending on material and size of particles. Afterwards, a novel and efficient photonic-based method to synthesize porous alumina membranes (PAMs) and subsequent metal nano-dot arrays on various substrates, based on near laser field enhancement by nano spheres, is reported.

  6. Microscopic Strain Mapping in Nanostructured and Microstructured Alumina-Titania Coatings Under 4-point Compressive and Tensile Bending

    DTIC Science & Technology

    2010-06-01

    A & A Co. Engineering Conference International, Sub-Micron & Nanostructured Ceramics Colorado Springs, June 7-12, 2009, Colorado, USA Microscopic...Strain Mapping in Nanostructured and Microstructured Alumina-Titania Coatings Under 4-point Compressive and Tensile Bending A . Ignatov1,2, E. K. Akdogan1...provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently

  7. In situ fabrication of depth-type hierarchical CNT/quartz fiber filters for high efficiency filtration of sub-micron aerosols and high water repellency

    NASA Astrophysics Data System (ADS)

    Li, Peng; Zong, Yichen; Zhang, Yingying; Yang, Mengmeng; Zhang, Rufan; Li, Shuiqing; Wei, Fei

    2013-03-01

    We fabricated depth-type hierarchical CNT/quartz fiber (QF) filters through in situ growth of CNTs upon quartz fiber (QF) filters using a floating catalyst chemical vapor deposition (CVD) method. The filter specific area of the CNT/QF filters is more than 12 times higher than that of the pristine QF filters. As a result, the penetration of sub-micron aerosols for CNT/QF filters is reduced by two orders of magnitude, which reaches the standard of high-efficiency particulate air (HEPA) filters. Simultaneously, due to the fluffy brush-like hierarchical structure of CNTs on QFs, the pore size of the hybrid filters only has a small increment. The pressure drop across the CNT/QF filters only increases about 50% with respect to that of the pristine QF filters, leading to an obvious increased quality factor of the CNT/QF filters. Scanning electron microscope images reveal that CNTs are very efficient in capturing sub-micron aerosols. Moreover, the CNT/QF filters show high water repellency, implying their superiority for applications in humid conditions.We fabricated depth-type hierarchical CNT/quartz fiber (QF) filters through in situ growth of CNTs upon quartz fiber (QF) filters using a floating catalyst chemical vapor deposition (CVD) method. The filter specific area of the CNT/QF filters is more than 12 times higher than that of the pristine QF filters. As a result, the penetration of sub-micron aerosols for CNT/QF filters is reduced by two orders of magnitude, which reaches the standard of high-efficiency particulate air (HEPA) filters. Simultaneously, due to the fluffy brush-like hierarchical structure of CNTs on QFs, the pore size of the hybrid filters only has a small increment. The pressure drop across the CNT/QF filters only increases about 50% with respect to that of the pristine QF filters, leading to an obvious increased quality factor of the CNT/QF filters. Scanning electron microscope images reveal that CNTs are very efficient in capturing sub-micron aerosols

  8. Sub-micron-sized polyethylenimine-modified polystyrene/Fe3O4/chitosan magnetic composites for the efficient and recyclable adsorption of Cu(II) ions

    NASA Astrophysics Data System (ADS)

    Xiao, Changwei; Liu, Xijian; Mao, Shimin; Zhang, Lijuan; Lu, Jie

    2017-02-01

    A sub-micron-sized polyethylenimine(PEI)-modified polystyrene/Fe3O4/chitosan magnetic composite (PS/Fe3O4/CS-PEI) was developed as a novel adsorbent for the removal of Cu(II) ions from aqueous solutions. The PS/Fe3O4/CS-PEI microspheres with a diameter of ∼300 nm can be highly monodisperse and conveniently separated from suspensions by a magnet due to their excellent magnetism. When the PS/Fe3O4/CS-PEI microspheres were used as an absorbent for the absorption of Cu(II) ions, the adsorption isotherms and adsorption kinetics well fitted the Langmuir model and the pseudo-second-order model, respectively. The maximum adsorption capacity was about 204.6 mg g-1, which was higher than those of other chitosan adsorbents reported recently. The adsorption was considerably fast, reaching the equilibrium within 15 min. In addition, the adsorbed Cu(II) ions could be effectively desorbed using 0.1 mol L-1 NaOH solution, and the regeneration study proved that the composite microspheres could be repeatedly utilized without significant capacity loss after six cycles. All the results demonstrated that the synthesized sub-micron-sized magnetic PS/Fe3O4/CS-PEI composites can be used as an ideal adsorbent of Cu(II) ions for environmental cleanup applications.

  9. Sub-micron resolution surface plasmon resonance imaging enabled by nanohole arrays with surrounding Bragg mirrors for enhanced sensitivity and isolation.

    PubMed

    Lindquist, Nathan C; Lesuffleur, Antoine; Im, Hyungsoon; Oh, Sang-Hyun

    2009-02-07

    We present nanohole arrays in thin gold films as sub-micron resolution surface plasmon resonance (SPR) imaging pixels in a microarray format. With SPR imaging, the resolution is not limited by diffraction, but by the propagation of surface plasmon waves to adjacent sensing areas, or nanohole arrays, causing unwanted interference. For ultimate scalability, several issues need to be addressed, including: (1) as several nanohole arrays are brought close to each other, surface plasmon interference introduces large sources of error; and (2) as the size of the nanohole array is reduced, i.e. fewer holes, detection sensitivity suffers. To address these scalability issues, we surround each biosensing pixel (a 3-by-3 nanohole array) with plasmonic Bragg mirrors, blocking interference between adjacent SPR sensing pixels for high-density packing, while maintaining the sensitivity of a 50 x larger footprint pixel (a 16-by-16 nanohole array). We measure real-time, label-free streptavidin-biotin binding kinetics with a microarray of 600 sub-micron biosensing pixels at a packing density of more than 10(7) per cm(2).

  10. Morphology transformations in tetrabutyl titanate-acetic acid system and sub-micron/micron hierarchical TiO2 for dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Huang, Niu; Xie, Yanan; Sebo, Bobby; Liu, Yumin; Sun, Xiaohua; Peng, Tao; Sun, Weiwei; Bu, Chenghao; Guo, Shishang; Zhao, Xingzhong

    2013-11-01

    The concentration of tetrabutyl titanate (TBT) and H2O influence on the reaction kinetics of TBT and acetic acid (AcOH) solvothermal system are systematically studied. It is found that TBT and H2O have greatly accelerated the hydrolysis-condensation process of the TBT-AcOH system. By adjusting those concentrations with reaction time, we prepare five kinds of sub-micron/micron precursors, which are hierarchical structures consisting of different primary building blocks. The morphology of these precursors varies from noninterlaced structures composed of flower-like microsphere and ellipsoid sphere to interlaced structures composed of flower-like microsphere interlaced nanofibers, ellipsoid spheres interlaced flower-like microsphere and nanoparticles interlaced flower-like microsphere. These interlaced structures are synthesized for the first time and are not ordinary mixtures of the noninterlaced structures. After heat treatment, these precursors are transformed to anatase TiO2. Shape-dependent photovoltaic performances of dye-sensitized solar cells (DSSCs) are also discussed. DSSCs based on these hierarchical sub-micron/micron TiO2 show 7.3%-7.9% energy conversion efficiencies, and the devices based on interlaced structures have higher efficiencies (7.4%-7.9%) than those of the devices based on noninterlaced structures (7.3%-7.6%).

  11. Both improvements of the light extraction efficiency and scattered angle of GaN-LED using sub-micron Fresnel lens array

    NASA Astrophysics Data System (ADS)

    Gu, Xinyu; Chen, Linsen; Shen, Su; Wan, Wenqiang

    2015-11-01

    With the demanding requirements for light source, light emitting diodes (LED) attracts more and more attention because of its inherent advantages such as low power consumption, high reliability and longevity. However, there are two disadvantages for LED, one is the low light extraction efficiency resulting from the total internal reflection, and the other is the relative large scattered angle. In order to improve the light extraction efficiency and collimate the out-coupling light, a sub-micron Fresnel lens array is introduced and investigated in this paper. The focal length of the proposed Fresnel lens is 3μm and the minimum width of the outmost ring is about 150nm. To calculate and analyze the light extraction efficiency and the scattered angle of LED with such Fresnel lens array structure, we optimize the parameters of the Fresnel lens, such as the depth of the Fresnel lens array structure and the thickness of the p-type gallium nitride layer by using the finite difference time domain method (FDTD). By comparing the discussed patterned GaN-based LED with that traditional flat LEDs, it can be found that significant enhancement factor of the light extraction efficiency, which is improved by 3.5 times, can be obtained and the scattered angle at half maximum can be decreased 50° from 60° with this novel Fresnel lens structure. It will be expected that the proposed sub-micron structure can find wide applications in LEDs industry.

  12. Effect of epicuticular wax crystals on the localization of artificially deposited sub-micron carbon-based aerosols on needles of Cryptomeria japonica.

    PubMed

    Nakaba, Satoshi; Yamane, Kenichi; Fukahori, Mie; Nugroho, Widyanto Dwi; Yamaguchi, Masahiro; Kuroda, Katsushi; Sano, Yuzou; Wuled Lenggoro, I; Izuta, Takeshi; Funada, Ryo

    2016-09-01

    Elucidation of the mechanism of adsorption of particles suspended in the gas-phase (aerosol) to the outer surfaces of leaves provides useful information for understanding the mechanisms of the effect of aerosol particles on the growth and physiological functions of trees. In the present study, we examined the localization of artificially deposited sub-micron-sized carbon-based particles on the surfaces of needles of Cryptomeria japonica, a typical Japanese coniferous tree species, by field-emission scanning electron microscopy. The clusters (aggregates) of carbon-based particles were deposited on the needle surface regions where epicuticular wax crystals were sparsely distributed. By contrast, no clusters of the particles were found on the needle surface regions with dense distribution of epicuticular wax crystals. Number of clusters of carbon-based particles per unit area showed statistically significant differences between regions with sparse epicuticular wax crystals and those with dense epicuticular wax crystals. These results suggest that epicuticular wax crystals affect distribution of carbon-based particles on needles. Therefore, densely distributed epicuticular wax crystals might prevent the deposition of sub-micron-sized carbon-based particles on the surfaces of needles of Cryptomeria japonica to retain the function of stomata.

  13. Direct sub-micron microstructuring on cylinder using TiO2 sol-gel process and radial phase mask based lithography

    NASA Astrophysics Data System (ADS)

    Berthod, L.; Vocanson, F.; Langlet, M.; Veillas, C.; Reynaud, S.; Verrier, I.; Laukkanen, J.; Parriaux, O.; Jourlin, Y.

    2016-04-01

    Design and fabrication of a high efficiency phase mask have been performed for printing submicron period gratings along 8 mm diameter glass cylinders. In this article, the authors present the radial phase mask specially designed and manufactured for a cylindrical surface micro-structuring under UV photolithography. Its period is sub-micron (480 nm < ΛPM < 720 nm). The authors describe then the phase mask based UV lithography set-up using the interference between the transmitted beams of +1 and -1 orders generated by the phase mask. Preliminary results of printed gratings on a cylinder are described on a sol-gel TiO2 thin film layer, enabling direct photo patterning on functionalized layer. The feasibility of a grating printed with a period of Λcylin = 960 nm on an 8 mm diameter cylinder with this dedicated mask has been demonstrated.

  14. Low loss (approximately 6.45dB/cm) sub-micron polycrystalline silicon waveguide integrated with efficient SiON waveguide coupler.

    PubMed

    Fang, Q; Song, J F; Tao, S H; Yu, M B; Lo, G Q; Kwong, D L

    2008-04-28

    In this communication, the sub-micron size polycrystalline silicon (poly- Si) single mode waveguides are fabricated and integrated with SiON waveguide coupler by deep UV lithography. The propagation loss of poly-Si waveguide and coupling loss with optical flat polarization-maintaining fiber (PMF) are measured. For whole C-band (i.e., lambda approximately 1520-1565nm), the propagation loss of TE mode is measured to approximately 6.45+/-0.3dB/cm. The coupling loss with optical flat PMF is approximately 3.4dB/facet for TE mode. To the best of our knowledge, the propagation loss is among the best reported results. This communication discusses the factors reducing the propagation loss, especially the effect of the refractive index contrast. Compared to the SiO(2) cladding, poly-Si waveguide with SiON cladding exhibits lower propagation loss.

  15. Magnetic and Mössbauer characterization of the magnetic properties of single-crystalline sub-micron sized Bi₂Fe₄O₉ cubes

    SciTech Connect

    Papaefthymiou, Georgia C.; Wong, Stanislaus S.; Viescas, Arthur J.; Le Breton, Jean-Marie; Chiron, Hubert; Juraszek, Jean; Park, Tae-Jin

    2014-11-25

    Magnetic and Mössbauer characterization of single crystalline, sub-micron sized Bi₂Fe₄O₉ cubes has been performed using SQUID magnetometry and transmission Mössbauer spectroscopy in the temperature range of 4.2 K ≤ T ≤ 300 K. A broad magnetic phase transition from the paramagnetic to the anti-ferromagnetic state is observed below 250 K, with the Mössbauer spectra exhibiting a superposition of magnetic, collapsed and quadrupolar spectra in the transition region of 200 K < T < 245 K. Room temperature Mössbauer spectra obtained in transmission geometry are identical to those recorded in back-scattering geometry via conversion electron Mössbauer spectroscopy, indicating the absence of strain at the surface. A small hysteresis loop is observed in SQUID measurements at 5 K, attributable to the presence of weak-ferromagnetism arising from the canting of Fe³⁺ ion sublattices in the antiferromagnetic matrix.

  16. Rheological and filtration behavior of aqueous alumina casting slips dispersed with polyacrylate and polymethacrylate deflocculants

    NASA Astrophysics Data System (ADS)

    Shemo, David M.

    Dynamic stress-controlled rheometry methods and filtration analysis were used to characterize aluminum oxide suspensions relative to several process variables. These included dispersant molecular weight, dispersant concentration, solids concentration, alumina PSD, and aging time. It is believed that through rheological analysis, a better understanding of a slip's structure and dewatering behavior can be achieved. Based upon time- and stress-sweep data, structural models were developed for the build-up (gelation) and break-down (yielding) processes in alumina suspensions. Aqueous alumina suspensions dispersed with acrylate-based polyelectrolytes of average molecular weights of 2400, 3500, and 15000 were evaluated over an aging period of up to ten days. The aging-induced variations in their rheological, filtration, and electrochemical characteristics were quantified. These effects were related to changes in the structures of the suspensions over time. It was found that the aging effect was most pronounced for slips dispersed with higher molecular weight polyacrylate or polymethacrylate deflocculants. A mechanism was proposed to account for the aging behavior and the effect of dispersant molecular weight. Alumina slips were prepared with bimodal particle size compositions by combining two sub-micron alumina powders. Variation in rheological behavior with the composition was evaluated for slips at moderate and high solids concentration, and at fully dispersed and under dispersed states. The corresponding changes in the filtration behavior and cast density were measured. A structural model was constructed for the observed variations with alumina composition.

  17. A Fast, Versatile Nanoprobe for Complex Materials: The Sub-micron Resolution X-ray Spectroscopy Beamline at NSLS-II (491st Brookhaven Lecture)

    SciTech Connect

    Thieme, Juergen

    2014-02-06

    Time is money and for scientists who need to collect data at research facilities like Brookhaven Lab’s National Synchrotron Light Source (NSLS), “beamtime” can be a precious commodity. While scanning a complex material with a specific technique and standard equipment today would take days to complete, researchers preparing to use brighter x-rays and the new sub-micron-resolution x-ray spectroscopy (SRX) beamline at the National Synchrotron Light Source II (NSLS-II) could scan the same sample in greater detail with just a few hours of beamtime. Talk about savings and new opportunities for researchers! Users will rely on these tools for locating trace elements in contaminated soils, developing processes for nanoparticles to deliver medical treatments, and much more. Dr. Thieme explains benefits for next-generation research with spectroscopy and more intense x-rays at NSLS-II. He discusses the instrumentation, features, and uses for the new SRX beamline, highlighting its speed, adjustability, and versatility for probing samples ranging in size from millimeters down to the nanoscale. He will talk about complementary beamlines being developed for additional capabilities at NSLS-II as well.

  18. Top-Contact Self-Aligned Printing for High-Performance Carbon Nanotube Thin-Film Transistors with Sub-Micron Channel Length.

    PubMed

    Cao, Xuan; Wu, Fanqi; Lau, Christian; Liu, Yihang; Liu, Qingzhou; Zhou, Chongwu

    2017-02-28

    Semiconducting single-wall carbon nanotubes are ideal semiconductors for printed thin-film transistors due to their excellent electrical performance and intrinsic printability with solution-based deposition. However, limited by resolution and registration accuracy of current printing techniques, previously reported fully printed nanotube transistors had rather long channel lengths (>20 μm) and consequently low current-drive capabilities (<0.2 μA/μm). Here we report fully inkjet printed nanotube transistors with dramatically enhanced on-state current density of ∼4.5 μA/μm by downscaling the devices to a sub-micron channel length with top-contact self-aligned printing and employing high-capacitance ion gel as the gate dielectric. Also, the printed transistors exhibited a high on/off ratio of ∼10(5), low-voltage operation, and good mobility of ∼15.03 cm(2) V(-1)s(-1). These advantageous features of our printed transistors are very promising for future high-definition printed displays and sensing systems, low-power consumer electronics, and large-scale integration of printed electronics.

  19. Infrared-induced variation of the magnetic properties of a magnetoplasmonic film with a 3D sub-micron periodic triangular roof-type antireflection structure.

    PubMed

    Tian, Junlong; Zhang, Wang; Huang, Yiqiao; Liu, Qinglei; Wang, Yuhua; Zhang, Zhijian; Zhang, Di

    2015-01-26

    A carbon-matrix nickel composite magnetoplasmonic film with a 3D sub-micron periodic triangular roof-type antireflection structure (SPTAS) was fabricated via a simple and promising method that combines chemosynthesis with biomimetic techniques. The Troides helena (Linnaeus) forewing (T_FW) was chosen as the biomimetic template. The carbon-matrix Ni wing fabricated via electroless Ni deposition for 6 h (CNMF_6h) exhibits enhanced infrared absorption. Over a wavelength range (888-2500 nm), the enhancement of the infrared absorption of CNMF_6h is up to 1.85 times compared with the T_FW. Furthermore, infrared excitation induces a photothermal effect that results in variation in the magnetic properties of the carbon-matrix Ni wing. The magnetic properties were also confirmed using atomic force microscopy (AFM) and magnetic force microscopy (MFM). The good correlation between the AFM and MFM images demonstrates that the surface of the SPTAS of CNMF_6h exhibits strong magnetic properties. The infrared induced photothermal effect that results in magnetic variation is promising for use in the design of novel magnetoplasmonic films with potential applications in infrared information recording and heat-assisted magnetic recording.

  20. Infrared-induced variation of the magnetic properties of a magnetoplasmonic film with a 3D sub-micron periodic triangular roof-type antireflection structure

    NASA Astrophysics Data System (ADS)

    Tian, Junlong; Zhang, Wang; Huang, Yiqiao; Liu, Qinglei; Wang, Yuhua; Zhang, Zhijian; Zhang, Di

    2015-01-01

    A carbon-matrix nickel composite magnetoplasmonic film with a 3D sub-micron periodic triangular roof-type antireflection structure (SPTAS) was fabricated via a simple and promising method that combines chemosynthesis with biomimetic techniques. The Troides helena (Linnaeus) forewing (T_FW) was chosen as the biomimetic template. The carbon-matrix Ni wing fabricated via electroless Ni deposition for 6 h (CNMF_6h) exhibits enhanced infrared absorption. Over a wavelength range (888-2500 nm), the enhancement of the infrared absorption of CNMF_6h is up to 1.85 times compared with the T_FW. Furthermore, infrared excitation induces a photothermal effect that results in variation in the magnetic properties of the carbon-matrix Ni wing. The magnetic properties were also confirmed using atomic force microscopy (AFM) and magnetic force microscopy (MFM). The good correlation between the AFM and MFM images demonstrates that the surface of the SPTAS of CNMF_6h exhibits strong magnetic properties. The infrared induced photothermal effect that results in magnetic variation is promising for use in the design of novel magnetoplasmonic films with potential applications in infrared information recording and heat-assisted magnetic recording.

  1. Infrared-induced variation of the magnetic properties of a magnetoplasmonic film with a 3D sub-micron periodic triangular roof-type antireflection structure

    PubMed Central

    Tian, Junlong; Zhang, Wang; Huang, Yiqiao; Liu, Qinglei; Wang, Yuhua; Zhang, Zhijian; Zhang, Di

    2015-01-01

    A carbon-matrix nickel composite magnetoplasmonic film with a 3D sub-micron periodic triangular roof-type antireflection structure (SPTAS) was fabricated via a simple and promising method that combines chemosynthesis with biomimetic techniques. The Troides helena (Linnaeus) forewing (T_FW) was chosen as the biomimetic template. The carbon-matrix Ni wing fabricated via electroless Ni deposition for 6 h (CNMF_6h) exhibits enhanced infrared absorption. Over a wavelength range (888–2500 nm), the enhancement of the infrared absorption of CNMF_6h is up to 1.85 times compared with the T_FW. Furthermore, infrared excitation induces a photothermal effect that results in variation in the magnetic properties of the carbon-matrix Ni wing. The magnetic properties were also confirmed using atomic force microscopy (AFM) and magnetic force microscopy (MFM). The good correlation between the AFM and MFM images demonstrates that the surface of the SPTAS of CNMF_6h exhibits strong magnetic properties. The infrared induced photothermal effect that results in magnetic variation is promising for use in the design of novel magnetoplasmonic films with potential applications in infrared information recording and heat-assisted magnetic recording. PMID:25620787

  2. Magnetic and Mössbauer characterization of the magnetic properties of single-crystalline sub-micron sized Bi₂Fe₄O₉ cubes

    DOE PAGES

    Papaefthymiou, Georgia C.; Wong, Stanislaus S.; Viescas, Arthur J.; ...

    2014-11-25

    Magnetic and Mössbauer characterization of single crystalline, sub-micron sized Bi₂Fe₄O₉ cubes has been performed using SQUID magnetometry and transmission Mössbauer spectroscopy in the temperature range of 4.2 K ≤ T ≤ 300 K. A broad magnetic phase transition from the paramagnetic to the anti-ferromagnetic state is observed below 250 K, with the Mössbauer spectra exhibiting a superposition of magnetic, collapsed and quadrupolar spectra in the transition region of 200 K < T < 245 K. Room temperature Mössbauer spectra obtained in transmission geometry are identical to those recorded in back-scattering geometry via conversion electron Mössbauer spectroscopy, indicating the absence ofmore » strain at the surface. A small hysteresis loop is observed in SQUID measurements at 5 K, attributable to the presence of weak-ferromagnetism arising from the canting of Fe³⁺ ion sublattices in the antiferromagnetic matrix.« less

  3. Image-Guided Ultrasound Characterization of Volatile Sub-Micron Phase-Shift Droplets in the 20-40 MHz Frequency Range.

    PubMed

    Sheeran, Paul S; Daghighi, Yasaman; Yoo, Kimoon; Williams, Ross; Cherin, Emmanuel; Foster, F Stuart; Burns, Peter N

    2016-03-01

    Phase-shift perfluorocarbon droplets are designed to convert from the liquid to the gas state by the external application of acoustic or optical energy. Although droplet vaporization has been investigated extensively at ultrasonic frequencies between 1 and 10 MHz, few studies have characterized performance at the higher frequencies commonly used in small animal imaging. In this study, we use standard B-mode imaging sequences on a pre-clinical ultrasound platform to both image and activate sub-micron decafluorobutane droplet populations in vitro and in vivo at center frequencies in the range of 20-40 MHz. Results show that droplets remain stable against vaporization at low imaging pressures but are vaporized at peak negative pressures near 3.5 MPa at the three frequencies tested. This study also found that a small number of size outliers present in the distribution can greatly influence droplet performance. Removal of these outliers results in a more accurate assessment of the vaporization threshold and produces free-flowing microbubbles upon vaporization in the mouse kidney.

  4. Time-domain analysis of sub-micron transit region GaAs Gunn diodes for use in terahertz frequency multiplication chains

    NASA Astrophysics Data System (ADS)

    Amir, F.; Farrington, N.; Mitchell, C.; Missous, M.

    2010-10-01

    Simulated RF time-domain characteristics for advanced Gunn diodes with hot electron injection and sub-micron transit region lengths for use at frequencies over 100GHz are reported. The physical models used have been developed in SILVACO and are compared to measured results. The devices measured were originally fabricated to investigate the feasibility of GaAs Gunn diode oscillators capable of operating at D-band frequencies and ultimately intended for use in high power (multi-mW) Terahertz sources (~0.6THz) when used in conjunction with novel Schottky diode frequency multiplier technology. The device models created using SILVACO are described and the DC and time-domain results presented. The simulations were used to determine the shortest transit region length capable of producing sustained oscillation. The operation of resonant disk second harmonic Gunn diode oscillators is also discussed and accurate electromagnetic models created using Ansoft High Frequency Structure Simulator presented. Novel methods for combining small-signal frequency-domain electromagnetic simulations with time-domain device simulations in order to account for the significant interactions between the diode and oscillator circuit are described.

  5. Ultrasonic energy input influence οn the production of sub-micron o/w emulsions containing whey protein and common stabilizers.

    PubMed

    Kaltsa, O; Michon, C; Yanniotis, S; Mandala, I

    2013-05-01

    Ultrasonication may be a cost-effective emulsion formation technique, but its impact on emulsion final structure and droplet size needs to be further investigated. Olive oil emulsions (20wt%) were formulated (pH∼7) using whey protein (3wt%), three kinds of hydrocolloids (0.1-0.5wt%) and two different emulsification energy inputs (single- and two-stage, methods A and B, respectively). Formula and energy input effects on emulsion performance are discussed. Emulsions stability was evaluated over a 10-day storage period at 5°C recording the turbidity profiles of the emulsions. Optical micrographs, droplet size and viscosity values were also obtained. A differential scanning calorimetric (DSC) multiple cool-heat cyclic method (40 to -40°C) was performed to examine stability via crystallization phenomena of the dispersed phase. Ultrasonication energy input duplication from 11kJ to 25kJ (method B) resulted in stable emulsions production (reduction of back scattering values, dBS∼1% after 10days of storage) at 0.5wt% concentration of any of the stabilizers used. At lower gum amount samples became unstable due to depletion flocculation phenomena, regardless of emulsification energy input used. High energy input during ultrasonic emulsification also resulted in sub-micron oil-droplets emulsions (D(50)=0.615μm compared to D(50)=1.3μm using method A) with narrower particle size distribution and in viscosity reduction. DSC experiments revealed no presence of bulk oil formation, suggesting stability for XG 0.5wt% emulsions prepared by both methods. Reduced enthalpy values found when method B was applied suggesting structural modifications produced by extensive ultrasonication. Change of ultrasonication conditions results in significant changes of oil droplet size and stability of the produced emulsions.

  6. Bauxite and alumina

    USGS Publications Warehouse

    Bray, E.L.

    2009-01-01

    The article provides information on bauxite and alumina mining. U.S. states like Alabama, Arkansas and Georgia produced small amounts of bauxite and bauxitic clays for nonmetallurgical uses. Total metallurgical-grade bauxite imports in 2008 is cited. The leading suppliers of bauxite to the U.S. are Jamaica, Guinea and Brazil. The estimated domestic production of alumina in 2008 is mentioned. It also discusses consumption and prices of both bauxite and alumina.

  7. Room temperature deformation mechanisms of alumina particles observed from in situ micro-compression and atomistic simulations.

    DOE PAGES

    Sarobol, Pylin; Chandross, Michael E.; Carroll, Jay D.; ...

    2015-09-22

    Aerosol deposition (AD) is a solid-state deposition technology that has been developed to fabricate ceramic coatings nominally at room temperature. Sub-micron ceramic particles accelerated by pressurized gas impact, deform, and consolidate on substrates under vacuum. Ceramic particle consolidation in AD coatings is highly dependent on particle deformation and bonding; these behaviors are not well understood. In this work, atomistic simulations and in situ micro-compressions in the scanning electron microscope, and the transmission electron microscope (TEM) were utilized to investigate fundamental mechanisms responsible for plastic deformation/fracture of particles under applied compression. Results showed that highly defective micron-sized alumina particles, initially containingmore » numerous dislocations or a grain boundary, exhibited no observable shape change before fracture/fragmentation. Simulations and experimental results indicated that particles containing a grain boundary only accommodate low strain energy per unit volume before crack nucleation and propagation. In contrast, nearly defect-free, sub-micron, single crystal alumina particles exhibited plastic deformation and fracture without fragmentation. Dislocation nucleation/motion, significant plastic deformation, and shape change were observed. Simulation and TEM in situ micro-compression results indicated that nearly defect-free particles accommodate high strain energy per unit volume associated with dislocation plasticity before fracture. As a result, the identified deformation mechanisms provide insight into feedstock design for AD.« less

  8. Room temperature deformation mechanisms of alumina particles observed from in situ micro-compression and atomistic simulations.

    SciTech Connect

    Sarobol, Pylin; Chandross, Michael E.; Carroll, Jay D.; Mook, William M.; Bufford, Daniel Charles; Boyce, Brad L.; Hattar, Khalid Mikhiel; Kotula, Paul G.; Hall, Aaron Christopher

    2015-09-22

    Aerosol deposition (AD) is a solid-state deposition technology that has been developed to fabricate ceramic coatings nominally at room temperature. Sub-micron ceramic particles accelerated by pressurized gas impact, deform, and consolidate on substrates under vacuum. Ceramic particle consolidation in AD coatings is highly dependent on particle deformation and bonding; these behaviors are not well understood. In this work, atomistic simulations and in situ micro-compressions in the scanning electron microscope, and the transmission electron microscope (TEM) were utilized to investigate fundamental mechanisms responsible for plastic deformation/fracture of particles under applied compression. Results showed that highly defective micron-sized alumina particles, initially containing numerous dislocations or a grain boundary, exhibited no observable shape change before fracture/fragmentation. Simulations and experimental results indicated that particles containing a grain boundary only accommodate low strain energy per unit volume before crack nucleation and propagation. In contrast, nearly defect-free, sub-micron, single crystal alumina particles exhibited plastic deformation and fracture without fragmentation. Dislocation nucleation/motion, significant plastic deformation, and shape change were observed. Simulation and TEM in situ micro-compression results indicated that nearly defect-free particles accommodate high strain energy per unit volume associated with dislocation plasticity before fracture. As a result, the identified deformation mechanisms provide insight into feedstock design for AD.

  9. Microporous alumina ceramic membranes

    DOEpatents

    Anderson, M.A.; Guangyao Sheng.

    1993-05-04

    Several methods are disclosed for the preparation microporous alumina ceramic membranes. For the first time, porous alumina membranes are made which have mean pore sizes less than 100 Angstroms and substantially no pores larger than that size. The methods are based on improved sol-gel techniques.

  10. Microporous alumina ceramic membranes

    DOEpatents

    Anderson, Marc A.; Sheng, Guangyao

    1993-01-01

    Several methods are disclosed for the preparation microporous alumina ceramic membranes. For the first time, porous alumina membranes are made which have mean pore sizes less than 100 Angstroms and substantially no pores larger than that size. The methods are based on improved sol-gel techniques.

  11. Agglomeration-Free Distributor for Fluidized Beds

    NASA Technical Reports Server (NTRS)

    Ouyang, F.; Sinica, A.; Levenspiel, O.

    1986-01-01

    New gas distributor for fluidized beds prevents hot particles from reacting on it and forming hard crust. In reduction of iron ore in fluidized bed, ore particles do not sinter on distributor and perhaps clog it or otherwise interfere with gas flow. Distributor also relatively cool. In fluidized-bed production of silicon, inflowing silane does not decompose until within bed of hot silicon particles and deposits on them. Plates of spiral distributor arranged to direct incoming gas into spiral flow. Turbulence in flow reduces frequency of contact between fluidized-bed particles and distributor.

  12. Reuse of activated alumina

    SciTech Connect

    Hobensack, J.E.

    1991-12-31

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

  13. Alumina fiber strength improvement

    NASA Technical Reports Server (NTRS)

    Pepper, R. T.; Nelson, D. C.

    1982-01-01

    The effective fiber strength of alumina fibers in an aluminum composite was increased to 173,000 psi. A high temperature heat treatment, combined with a glassy carbon surface coating, was used to prevent degradation and improve fiber tensile strength. Attempts to achieve chemical strengthening of the alumina fiber by chromium oxide and boron oxide coatings proved unsuccessful. A major problem encountered on the program was the low and inconsistent strength of the Dupont Fiber FP used for the investigation.

  14. Bauxite and alumina

    USGS Publications Warehouse

    Bray, E.L.

    2011-01-01

    The article discusses the latest developments in the bauxite and alumina industry, particularly in the U.S., as of June 2011. It claims that the U.S. mainly relies on imports for its bauxite consumption. Several states, including Alabama, Arkansas and Georgia, however, produce small amounts of bauxite and bauxitic clays for nonmetallurgical purposes. The major exporters of alumina to the U.S. include Australia, Brazil and Jamaica.

  15. Alumina Technology Roadmap

    SciTech Connect

    none,

    2002-02-01

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

  16. Solid Lubricant For Alumina

    NASA Technical Reports Server (NTRS)

    Dellacorte, Christopher; Pepper, Stephen V.; Honecy, Frank S.

    1993-01-01

    Outer layer of silver lubricates, while intermediate layer of titanium ensures adhesion. Lubricating outer films of silver deposited on thin intermediate films of titanium on alumina substrates found to reduce sliding friction and wear. Films provide effective lubrication for ceramic seals, bearings, and other hot sliding components in advanced high-temperature engines.

  17. Prediction of alumina penetration

    SciTech Connect

    Mandell, D A

    1993-02-01

    The MESA hydrocode was used to predict two-dimensional tests of L/D 10 and L/D 15 tungsten rods impacting AD 90 alumina with a steel backing. The residual penetration into the steel is the measured quantity in these experiments conducted at the Southwest Research Institute (SWR). The interface velocity as a function of time between an alumina target and a lithium fluoride window, impacted by an alumina disk at velocities between 544 m/s and 2329 m/s, was also predicted. These one-dimensional flyer plate experiments were conducted at Sandia National Laboratories using Coors AD 995 alumina. The material strength and fracture models are important in the prediction of ceramic experiments. The models used in these predictions are discussed. The penetrations in the two-dimensional tests were predicted to 11.4 percent or better. In five of the six experiments, the predicted penetration depth was deeper than the measured value. This trend is expected since the calculation is based on ideal conditions. The results show that good agreement between the 1-D flyer plate data and the MESA predictions exists at the lower impact velocities, but the maximum velocity is overpredicted as the flyer plate velocity increases. At a flyer plate velocity of 2329 m/s the code overpredicted the data by 12.3 percent.

  18. Bauxite and alumina

    USGS Publications Warehouse

    Bray, E.L.

    2010-01-01

    The article reports on the global market performance of bauxite and alumina in 2009 and presents an outlook for their 2010 performance. There were only several U.S. states that could produce bauxite and bauxitic clays including Georgia, Arkansas, and Alabama. The prices for imported refractory-grade calcined bauxite ranged between 426 U.S. dollars and 554 dollars per ton.

  19. High Temperature Stability of Potassium Beta Alumina

    NASA Technical Reports Server (NTRS)

    Williams, R. M.; Kisor, A.; Ryan, M. A.

    1996-01-01

    None. From Objectives section: Evaluate the stability of potassium beta alumina under potassium AMTEC operating conditions. Evaluate the stability regime in which potassium beta alumina can be fabricated.

  20. Impact of smoking on guided tissue regeneration using a biocomposite poly (lactic-co-glycolic) acid/sub-micron size hydroxyapatite with a rubber dam as an alternative barrier.

    PubMed

    Stramazzotti, D; Coiana, C; Zizzi, A; Spazzafumo, L; Sauro, S; D'Angelo, A B; Rubini, C; Aspriello, S D

    2015-03-01

    The purpose of our study was to critically evaluate the results obtained from a guided tissue regeneration technique after 12 months using a bocomposite poly (lactic-co-glycolic) acid/sub-micron size hydroxyapatite (PLGA/HA) with a rubber dam as a barrier in smoking and non-smoking patients. We selected 36 patients (18 current smokers and 18 non-smokers) diagnosed with chronic advanced periodontitis with a periodontal site (probing depth [PD] >5) amenable to regenerative surgery. Twelve months after surgery, the periodontal parameters were found to have statistically improved, when non-smokers were compared with smokers, in: PD reduction (6.3 ± 2.1 mm vs. 3.6 ± 1.9 mm); CAL gain (4.4 ± 1.1 vs. 2.8 ± 2.2 mm); recession (1.8 ± 1.4 mm vs. 0.8 ± 0.9 mm); and hard tissue fill (4.7 ± 0.8 mm vs. 2.8 ± 2.1 mm). Furthermore, since we found PD baseline differences between groups, smoking seemed not to influence the outcomes achieved (CAL gain and ΔREC) 12 months post surgery with respect to PD baseline. The use of PLGA/HA with a rubber dam significantly improved the periodontal parameters in both smoking and non-smoking subjects. This improvement was nevertheless lower in smokers than the non-smokers, confirming the negative impact of smoking on periodontal regeneration.

  1. Removal of heavy metal ions from aqueous solution using Fe3O4-SiO2-poly(1,2-diaminobenzene) core-shell sub-micron particles.

    PubMed

    Zhang, Fan; Lan, Jing; Zhao, Zongshan; Yang, Ye; Tan, Ruiqin; Song, Weijie

    2012-12-01

    In this work, Fe(3)O(4)-SiO(2)-poly(1,2-diaminobenzene) sub-micron particles (FSPs) with high saturated magnetization of ∼60-70 emu/g were developed and utilized for the removal of As(III), Cu(II), and Cr(III) ions from aqueous solution. The isothermal results fitted well with the Freundlich model and the kinetic results fitted well with the two-site pseudo-second-order model, which indicated that multilayer adsorption of As(III), Cu(II), and Cr(III) ions on FSPs occurred at two sites with different energy of adsorption. The maximum adsorption capacities followed the order of As(III) (84±5 mg/g, pH=6.0)>Cr(III) (77±3 mg/g, pH=5.3)>Cu(II) (65±3 mg/g, pH=6.0). And the chelating interaction was considered as the main adsorption mechanism. The as-prepared materials were chemically stable with low leaching of Fe (≤1.7 wt.%) and poly(1,2-diaminobenzene) (≤4.9 wt.%) in tap water, sea water, and acidic/basic solutions. These metal-loaded FSPs could be easily recovered from aqueous solutions using a permanent magnet within 20s. They could also be easily regenerated with acid. The present work indicates that the FSPs are promising for removal of heavy metal ions in field application.

  2. Bauxite Mining and Alumina Refining

    PubMed Central

    Frisch, Neale; Olney, David

    2014-01-01

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

  3. Branchy alumina nanotubes

    NASA Astrophysics Data System (ADS)

    Zou, Jianping; Pu, Lin; Bao, Ximao; Feng, Duan

    2002-02-01

    Branchy alumina nanotubes (bANTs) have been shown to exist in aluminum oxide. Electron-beam evaporated 400 nm Al film on Si substrate is stepwise anodized in dilute sulfuric acid under the constant dc voltage 40 V at 10.0 °C. This electrochemical-anodizing route resulted in the formation of individual bANTs. Transmission electron microscopy showed that the length of the bANTs was around 450 nm, and the inner diameter was around 10-20 nm. We deduced that the bANTs, the completely detached multibranchy cells of anodic porous alumina (APA) film, should be evolved from the stagnant cells of the APA mother film. The bANTs may be used as templates in fabrication of individual branchy nanoscale cables, jacks, and heterojunctions. The proposed formation mechanisms of the bANTs and the stagnant cells should give some insights into the long-standing problem of APA film, i.e., the self-ordering mechanism of the cells arrangement in porous anodization of aluminum.

  4. Adsorptive desulfurization by activated alumina.

    PubMed

    Srivastav, Ankur; Srivastava, Vimal Chandra

    2009-10-30

    This study reports usage of commercial grade activated alumina (aluminum oxide) as adsorbent for the removal of sulfur from model oil (dibenthiophene (DBT) dissolved in n-hexane). Bulk density of alumina was found to be 1177.77 kg/m(3). The BET surface area of alumina was found to decrease from 143.6 to 66.4 m(2)/g after the loading of DBT at optimum conditions. The carbon-oxygen functional groups present on the surface of alumina were found to be effective in the adsorption of DBT onto alumina. Optimum adsorbent dose was found to be 20 g/l. The adsorption of DBT on alumina was found to be gradual process, and quasi-equilibrium reached in 24 h. Langmuir isotherm best represented the equilibrium adsorption data. The heat of adsorption and change in entropy for DBT adsorption onto alumina was found to be 19.5 kJ/mol and 139.2 kJ/mol K, respectively.

  5. Gelcasting Polycrystalline Alumina

    SciTech Connect

    Janney, M.A.; Zuk, K.J.; Wei, G.C.

    2000-01-01

    OSRAM SYLVANIA INC. is a major U.S. manufacturer of high-intensity lighting. Among its products is the Lumalux TM line of high-pressure sodium vapor arc lamps, which are used for industrial, highway, and street lighting. The key to the performance of these lamps is the polycrystalline alumina (PCA) tube that is used to contain the plasma that is formed in the electric arc. That plasma consists of ionized sodium, mercury, and xenon vapors. The key attributes of the PCA tubes are their transparency ({approximately}97% total transmittance in the visible), their refractoriness (inner wall temperature can reach l2OOC), and their chemical resistance (sodium and mercury vapor are extremely corrosive). The current efficiency of the lamps is very high, up to 100 initial lumens per watt. (Compare incandescent lamps 10-20 lumens per watt, fluorescent lamps 25-90 lumens per watt.)

  6. Alumina-Reinforced Zirconia Composites

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Bansal, Narottam P.

    2003-01-01

    Alumina-reinforced zirconia composites, used as electrolyte materials for solid oxide fuel cells, were fabricated by hot pressing 10 mol percent yttria-stabilized zirconia (10-YSZ) reinforced with two different forms of alumina particulates and platelets each containing 0 to 30 mol percent alumina. Major mechanical and physical properties of both particulate and platelet composites including flexure strength, fracture toughness, slow crack growth, elastic modulus, density, Vickers microhardness, thermal conductivity, and microstructures were determined as a function of alumina content either at 25 C or at both 25 and 1000 C. Flexure strength and fracture toughness at 1000 C were maximized with 30 particulate and 30 mol percent platelet composites, respectively, while resistance to slow crack growth at 1000 C in air was greater for 30 mol percent platelet composite than for 30 mol percent particulate composites.

  7. Gelcast zirconia-alumina composites

    SciTech Connect

    Omatete, O.O.; Bleier, A.; Westmoreland, C.G.; Young, A.C.

    1991-01-01

    Near net-shaped parts of zirconia-alumina composites have been successfully formed by gelcasting, a technique which utilizes in situ polymerization of acrylamide monomers. The high solids loading required for gelcasting ({approximately}50 vol %) was obtained by controlling the pH-dependent stability of the aqueous zirconia-alumina suspensions. A strong correspondence was found among the surface charges on the particles, colloidal stability, and the maximum solids loading. 14 refs., 3 figs., 2 tabs.

  8. Gelcasting polycrystalline alumina

    SciTech Connect

    Janney, M.A.

    1997-04-01

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

  9. Precursor decay in several aluminas

    NASA Astrophysics Data System (ADS)

    Murray, N. H.; Bourne, N. K.; Rosenberg, Z.

    1996-05-01

    Plate impact experiments were performed on three ceramics with alumina content varying from 88 to 99.9% using a 50 mm single stage gas gun. Tiles of ceramic with thicknesses varying from 2 to 12 mm were impacted above their Hugoniot Elastic Limits (HELs) and the rate dependent strength was investigated by monitoring the variation in amplitude of the elastic precursor with propagation distance. Stress levels in the target were recorded using manganin stress transducers and a 1 GS s-1 storage oscilloscope. All grades of alumina were found to exhibit some elastic precursor decay indicating strain rate sensitivity.

  10. Attrition resistant gamma-alumina catalyst support

    DOEpatents

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

    2006-03-14

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

  11. Transport properties of alumina nanofluids.

    PubMed

    Wong, Kau-Fui Vincent; Kurma, Tarun

    2008-08-27

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

  12. Gas chromatographic separation of hydrogen isotopes on columns packed with alumina, modified alumina and sol-gel alumina.

    PubMed

    Naik, Y P; Gupta, N K; Pillai, K T; Rao, G A Rama; Venugopal, V

    2012-01-06

    The stationary phase of alumina adsorbents, prepared by different chemical processes, was used to study the separation behaviour of hydrogen isotopes. Three types of alumina, obtained by conventional hydroxide route alumina coated with silicon oxide and alumina prepared by internal gelation process (IGP), were used as packing material to study the separation of HT and T(2) in a mixture at various temperatures. The conventional alumina and silicon oxide coated alumina resolved HT and T(2) at 77K temperature with different retention times. The retention times on SiO(2) coated columns were found to be higher than those of other adsorbents. However, the column filled with IGP alumina was found to be ideal for the separation of HT and T(2) at 240 K. The peaks were well resolved in less than 5 min on this column.

  13. Alumina-Enhanced Thermal Barrier

    NASA Technical Reports Server (NTRS)

    Smith, Marnell; Leiser, Dan; Goldstein, Howard

    1989-01-01

    Rigid, fibrous ceramic tile material called "alumina-enhanced thermal barrier" (AETB) extends temperature capability of insulating materials. Material has obvious potential for terrestrial use in kilns, furnaces, heat engines, and other applications in which light weight and high operating temperature are specified. Three kinds of ceramic fibers are blended, molded, and sintered to make refractory tiles.

  14. Wettability of Aluminum on Alumina

    NASA Astrophysics Data System (ADS)

    Bao, Sarina; Tang, Kai; Kvithyld, Anne; Tangstad, Merete; Engh, Thorvald Abel

    2011-12-01

    The wettability of molten aluminum on solid alumina substrate has been investigated by the sessile drop technique in a 10-8 bar vacuum or under argon atmosphere in the temperature range from 1273 K to 1673 K (1000 °C to 1400 °C). It is shown that the reduction of oxide skin on molten aluminum is slow under normal pressures even with ultralow oxygen potential, but it is enhanced in high vacuum. To describe the wetting behavior of the Al-Al2O3 system at lower temperatures, a semiempirical calculation was employed. The calculated contact angle at 973 K (700 °C) is approximately 97 deg, which indicates that aluminum does not wet alumina at aluminum casting temperatures. Thus, a priming height is required for aluminum to infiltrate a filter. Wetting in the Al-Al2O3 system increases with temperature.

  15. Alumina as a Thermoluminescent Material

    SciTech Connect

    Uzun, Erdem; Yarar, Yasemin

    2007-04-23

    Thermoluminescence dosimeters are extensively used for quantitative dose measurements in various irradiation fields. They are also important for environmental monitoring after nuclear accident and weapon tests. In this work, the principles of TLD dosimeter and characteristics of several TLD materials are presented. Besides, taken into account the importance as a raw material, the utilization of domestic alumina (Al2O3) in TLDs as a thermoluminescent material is discussed.

  16. Hypervelocity impact damage in alumina

    NASA Astrophysics Data System (ADS)

    Zhang, Cheng

    2007-12-01

    Ceramics are important engineering materials for their outstanding hardness. One of the most widely used ceramics is alumina, a candidate for armor in defense and aerospace industry. Deformation and fracture mechanisms in alpha-alumina under hypervelocity impact up to 18km/s are investigated using molecular dynamics (MD) simulations containing 540-million atoms. Impacting projectile causes melting and local amorphization of the substrate in a spherical surrounding region. Away from the impact face, a wide range of deformations emerge and disappear under the influence of local stress fields, e.g., basal and pyramidal slips, basal and rhombohedral twins, which show good agreement with the experimental and theoretical results. Furthermore, new deformation modes such as twin along {01¯11} are observed, and the relation between deformation patterns and local stress levels are probed. During unloading, micro-cracks nucleate extensively at the intersections of previous deformations. These micro-cracks grow and coalesce to form fractures under tensile stresses by the unloading wave. The substrate eventually fails along the surface of an hourglass-shaped region, when spallation ejects clusters of substrate material into the vacuum. We also carried out planar shock simulations of alpha-alumina single crystal and nanophase systems. The results show correlations between the atomistic deformation mechanisms and the elastic-plastic response of ceramic material observed in shock loading experiments.

  17. Method for preparing Pb-. beta. ''-alumina ceramic

    DOEpatents

    Hellstrom, E.E.

    1984-08-30

    A process is disclosed for preparing impermeable, polycrystalline samples of Pb-..beta..''-alumina ceramic from Na-..beta..''-alumina ceramic by ion exchange. The process comprises two steps. The first step is a high-temperature vapor phase exchange of Na by K, followed by substitution of Pb for K by immersing the sample in a molten Pb salt bath. The result is a polycrystalline Pb-..beta..''-alumina ceramic that is substantially crack-free.

  18. Structural Effects of Lanthanide Dopants on Alumina

    NASA Astrophysics Data System (ADS)

    Patel, Ketan; Blair, Victoria; Douglas, Justin; Dai, Qilin; Liu, Yaohua; Ren, Shenqiang; Brennan, Raymond

    2017-01-01

    Lanthanide (Ln3+) doping in alumina has shown great promise for stabilizing and promoting desirable phase formation to achieve optimized physical and chemical properties. However, doping alumina with Ln elements is generally accompanied by formation of new phases (i.e. LnAlO3, Ln2O3), and therefore inclusion of Ln-doping mechanisms for phase stabilization of the alumina lattice is indispensable. In this study, Ln-doping (400 ppm) of the alumina lattice crucially delays the onset of phase transformation and enables phase population control, which is achieved without the formation of new phases. The delay in phase transition (θ → α), and alteration of powder morphology, particle dimensions, and composition ratios between α- and θ-alumina phases are studied using a combination of solid state nuclear magnetic resonance, electron microscopy, digital scanning calorimetry, and high resolution X-ray diffraction with refinement fitting. Loading alumina with a sparse concentration of Ln-dopants suggests that the dopants reside in the vacant octahedral locations within the alumina lattice, where complete conversion into the thermodynamically stable α-domain is shown in dysprosium (Dy)- and lutetium (Lu)-doped alumina. This study opens up the potential to control the structure and phase composition of Ln-doped alumina for emerging applications.

  19. Physical chemistry of carbothermic reduction of alumina

    SciTech Connect

    Frank, Robert A.

    1985-09-01

    Production of aluminium, by means of carbothermic reduction of alumina, is discussed. By employing a solvent metal bath to absorb the alumina metal, carbothermic reduction of alumina was accomplished at temperatures 300/degree/C lower than the temperatures reported in the literature. Reduction occurred without the formation of intermediate compounds and without the high volatilization of aluminum bearing species. Reduction of alumina immersed in a solvent bath appeared to be rate limited by chemical reaction control. The rates seemed to be a function of the activity of aluminum in the solvent metal bath. Reduction of alumina particles, above the surface of the bath, seemed to occur via vapor transport with carbon in the particles or in the crucible walls. Mass transport in the gas phase appeared to be rate limiting. The rates seemed to be a function of the distance separating the alumina and carbon sources. With both submerged alumina and alumina particles, increasing the surface area of the alumina increased the rate of reduction. 58 refs., 65 figs., 9 tabs.

  20. Structural Effects of Lanthanide Dopants on Alumina

    DOE PAGES

    Patel, Ketan; Blair, Victoria; Douglas, Justin; ...

    2017-01-06

    Lanthanide (Ln3+) doping in alumina has shown great promise for stabilizing and promoting desirable phase formation to achieve optimized physical and chemical properties. However, doping alumina with Ln elements is generally accompanied by formation of new phases (i.e. LnAlO3, Ln2O3), and therefore inclusion of Ln-doping mechanisms for phase stabilization of the alumina lattice is indispensable. In this study, Ln-doping (400 ppm) of the alumina lattice crucially delays the onset of phase transformation and enables phase population control, which is achieved without the formation of new phases. In addition, the delay in phase transition (θ → α), and alteration of powdermore » morphology, particle dimensions, and composition ratios between α- and θ-alumina phases are studied using a combination of solid state nuclear magnetic resonance, electron microscopy, digital scanning calorimetry, and high resolution X-ray diffraction with refinement fitting. Loading alumina with a sparse concentration of Ln-dopants suggests that the dopants reside in the vacant octahedral locations within the alumina lattice, where complete conversion into the thermodynamically stable α-domain is shown in dysprosium (Dy)- and lutetium (Lu)-doped alumina. Lastly, this study opens up the potential to control the structure and phase composition of Ln-doped alumina for emerging applications.« less

  1. Structural Effects of Lanthanide Dopants on Alumina

    PubMed Central

    Patel, Ketan; Blair, Victoria; Douglas, Justin; Dai, Qilin; Liu, Yaohua; Ren, Shenqiang; Brennan, Raymond

    2017-01-01

    Lanthanide (Ln3+) doping in alumina has shown great promise for stabilizing and promoting desirable phase formation to achieve optimized physical and chemical properties. However, doping alumina with Ln elements is generally accompanied by formation of new phases (i.e. LnAlO3, Ln2O3), and therefore inclusion of Ln-doping mechanisms for phase stabilization of the alumina lattice is indispensable. In this study, Ln-doping (400 ppm) of the alumina lattice crucially delays the onset of phase transformation and enables phase population control, which is achieved without the formation of new phases. The delay in phase transition (θ → α), and alteration of powder morphology, particle dimensions, and composition ratios between α- and θ-alumina phases are studied using a combination of solid state nuclear magnetic resonance, electron microscopy, digital scanning calorimetry, and high resolution X-ray diffraction with refinement fitting. Loading alumina with a sparse concentration of Ln-dopants suggests that the dopants reside in the vacant octahedral locations within the alumina lattice, where complete conversion into the thermodynamically stable α-domain is shown in dysprosium (Dy)- and lutetium (Lu)-doped alumina. This study opens up the potential to control the structure and phase composition of Ln-doped alumina for emerging applications. PMID:28059121

  2. Perfluoropolyalkylether decomposition on catalytic aluminas

    NASA Technical Reports Server (NTRS)

    Morales, Wilfredo

    1994-01-01

    The decomposition of Fomblin Z25, a commercial perfluoropolyalkylether liquid lubricant, was studied using the Penn State Micro-oxidation Test, and a thermal gravimetric/differential scanning calorimetry unit. The micro-oxidation test was conducted using 440C stainless steel and pure iron metal catalyst specimens, whereas the thermal gravimetric/differential scanning calorimetry tests were conducted using catalytic alumina pellets. Analysis of the thermal data, high pressure liquid chromatography data, and x-ray photoelectron spectroscopy data support evidence that there are two different decomposition mechanisms for Fomblin Z25, and that reductive sites on the catalytic surfaces are responsible for the decomposition of Fomblin Z25.

  3. Formation of alumina-nickel-molybdenum catalysts

    SciTech Connect

    Erofeev, V.I.; Basov, V.G.; Vagin, A.I.; Kalechits, I.V.

    1982-06-01

    On the basis of the results obtained in physical and chemical studies of alumina-nickel-molybdenum oxide catalysts as well as binary system and the individual oxides, the conclusions show that the commercial catalyst consists mainly of nickel and aluminium molybdates, aluminium molybdates, molybdenum oxide, and the alumina support. 4 figures.

  4. Hydrogen and the structure of transition aluminas

    SciTech Connect

    Sohlberg, K.; Pennycook, S.J.; Pantelides, S.T.

    1999-08-25

    {alpha}-Alumina results from the complete dehydration of several minerals of the form Al{sub 2}O{sub 3}{center{underscore}dot}nH{sub 2}O. The ``transition'' aluminas, {gamma}-alumina, {eta}-alumina, and {delta}-alumina are known to have a spinel structure but the possibility that they contain hydrogen (H) has been the subject of debate. The authors present a series of density-functional theory calculations which, together with available experimental data, show that the spinel aluminas exist over a range of hydrogen content captured by the empirical formula H{sub 3m}Al{sub 2{minus}m}O{sub 3}, with a different greek-letter phases corresponding to different distributions of the Aluminum (Al) ions on the two cation sublattices. Calculations of densities and vibrational frequencies of bulk OH bonds are in excellent agreement with available data. The theory reconciles seemingly inconsistent data and reveals a remarkable property of the spinel aluminas: They are ``reactive sponges'' in that they can store and release water in a reactive way. This chemical activity offers a basis for understanding long-standing puzzles in the behavior of aluminas in catalytic systems.

  5. Effects of Impurities on Alumina-Niobium InterfacialMicrostructures

    SciTech Connect

    McKeown, Joseph T.; Sugar, Joshua D.; Gronsky, Ronald; Glaeser,Andreas M.

    2005-06-20

    Optical microscopy, scanning electron microscopy, and transmission electron microscopy were employed to examine the interfacial microstructural effects of impurities in alumina substrates used to fabricate alumina-niobium interfaces via liquid-film-assisted joining. Three types of alumina were used: undoped high-purity single-crystal sapphire; a high-purity, high-strength polycrystalline alumina; and a lower-purity, lower-strength polycrystalline alumina. Interfaces formed between niobium and both the sapphire and high-purity polycrystalline alumina were free of detectable levels of impurities. In the lower-purity alumina, niobium silicides were observed at the alumina-niobium interface and on alumina grain boundaries near the interface. These silicides formed in small-grained regions of the alumina and were found to grow from the interface into the alumina along grain boundaries. Smaller silicide precipitates found on grain boundaries are believed to form upon cooling from the bonding temperature.

  6. Characterization and application of electrospun alumina nanofibers

    PubMed Central

    2014-01-01

    Alumina nanofibers were prepared by a technique that combined the sol–gel and electrospinning methods. The solution to be electrospun was prepared by mixing aluminum isopropoxide (AIP) in ethanol, which was then refluxed in the presence of an acid catalyst and polyvinylpyrolidone (PVP) in ethanol. The characterization results showed that alumina nanofibers with diameters in the range of 102 to 378 nm were successfully prepared. On the basis of the results of the XRD and FT-IR, the alumina nanofibers calcined at 1,100°C were identified as comprising the α-alumina phase, and a series of phase transitions such as boehmite → γ-alumina → α-alumina were observed from 500°C to 1,200°C. The pore size of the obtained γ-alumina nanofibers is approximately 8 nm, and it means that they are mesoporous materials. The kinetic study demonstrated that MO adsorption on alumina nanofibers can be seen that the pseudo-second-order kinetic model fits better than the pseudo-first-order kinetic model. PMID:24467944

  7. Noise in Sodium Beta Alumina Crystals.

    DTIC Science & Technology

    1985-09-01

    Washington, D.C. 20375 .I- 7. 7- NOISE INI SODIUM r ALUMINA SINGLE CRYSTALS James J. Brophy and Steven W. Smith University of Utah Salt Lake City, Utah 84112...RD-Ai56 025 NOISE IN SODiUN BETA ALUMINA CRYSTALS(U) UTAH UNIV SALT II LAKE CITY DEPT OF PHYSICS J J BROPHY ET AL. SEP 85 TR-7 N88814-82-K-e603...h.0- "bf’ ; -28242 ’ITLE (andSubsist&) S. TYPE OF REPORT & PERIOD COVERED L Noise in Sodium B" Alumina Crystals Technical Report #7 CJ S. PERFORMING

  8. Fabrication of thin layer beta alumina

    NASA Technical Reports Server (NTRS)

    Tennenhouse, G. J.

    1977-01-01

    Beta alumina tubes having walls 700 microns, 300 microns, and 140 microns were processed by extrusion and sintering utilizing Ford proprietary binder and fabrication systems. Tubes prepared by this method have properties similar to tubes prepared by isostatic pressing and sintering, i.e. density greater than 98% of theoretical and a helium leak rate less than 3 x 10 to the -9th power cc/sq cm/sec. Ford ultrasonic bonding techniques were used for bonding beta alumina end caps to open ended beta -alumina tubes prior to sintering. After sintering, the bond was hermetic, and the integrity of the bonded area was comparable to the body of the tube.

  9. Dissolution Kinetics of Alumina Calcine

    SciTech Connect

    Batcheller, Thomas Aquinas

    2001-09-01

    Dissolution kinetics of alumina type non-radioactive calcine was investigated as part of ongoing research that addresses permanent disposal of Idaho High Level Waste (HLW). Calcine waste was produced from the processing of nuclear fuel at the Idaho Nuclear Technology and Engineering Center (INTEC). Acidic radioactive raffinates were solidified at ~500°C in a fluidized bed reactor to form the dry granular calcine material. Several Waste Management alternatives for the calcine are presented in the Idaho High Level Waste Draft EIS. The Separations Alternative addresses the processing of the calcine so that the HLW is ready for removal to a national geological repository by the year 2035. Calcine dissolution is the key front-end unit operation for the separations alternative.

  10. Alumina forming iron base superalloy

    DOEpatents

    Yamamoto, Yukinori; Muralidharan, Govindarajan; Brady, Michael P.

    2014-08-26

    An austenitic stainless steel alloy, consists essentially of, in weight percent 2.5 to 4 Al; 25 to 35 Ni; 12 to 19 Cr; at least 1, up to 4 total of at least one element selected from the group consisting of Nb and Ta; 0.5 to 3 Ti; less than 0.5 V; 0.1 to 1 of at least on element selected from the group consisting of Zr and Hf; 0.03 to 0.2 C; 0.005 to 0.1 B; and base Fe. The weight percent Fe is greater than the weight percent Ni. The alloy forms an external continuous scale including alumina, and contains coherent precipitates of .gamma.'-Ni.sub.3Al, and a stable essentially single phase FCC austenitic matrix microstructure. The austenitic matrix is essentially delta-ferrite-free and essentially BCC-phase-free.

  11. Joining of alumina ceramics and nickel alloy

    SciTech Connect

    Ariga, Tadashi; Nitta, Yuji; Miyazawa, Yasuyuki

    1994-12-31

    Joining of alumina ceramics to nickel alloy was made using the various types of Ag-Cu-Ti brazing filler metal. Ti-containing brazing filler metal was produced by physical vapor deposition (PVD) method on the joining area of the alumina ceramics. The joinability of the brazing filler metal was estimated by its mechanical properties. And the composition and structure of the ceramic-metal bond zone in the alumina ceramics-nickel alloy joints were analyzed by SEM, EPMA and X-ray diffraction examinations. Some of brazing filler metal achieved the highest shear strength 100 MPa at room temperature. The elemental distributions of the interface between alumina ceramics and Ag-Cu-Ti brazing filler metal was shown to form the reaction layer consisting titanium oxide.

  12. Electrical Properties of Thin Films of Alumina.

    DTIC Science & Technology

    The report consists of a literature survey on the electrical properties of alumina and aluminum oxide thin films . A bibliographic listing of reports is included along with abstracts from most of them.

  13. Loss tangent measurements on unirradiated alumina

    SciTech Connect

    Zinkle, S.J.; Goulding, R.H.

    1996-04-01

    Unirradiated room temperature loss tangent for sapphire and several commercial grades of polycrystalline alumina are complied for frequencies between 10{sup 5} and 4x10{sup 11} Hz. Sapphire exhibits significantly lower values for the loss tangent at frequencies up to 10{sup 11} Hz. The loss tangents of 3 different grades of Wesgo alumina (AL300, AL995, AL998) and 2 different grades of Coors alumina (AD94, AD995) have typical values near {approx}10{sup -4} at a frequency of 10{sup 8} Hz. On the other hand, the loss tangent of Vitox alumina exhibits a large loss peak tan d{approx} 5x10{sup -3} at this frequency.

  14. Processing of Alumina-Toughened Zirconia Composites

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Choi, Sung R.

    2003-01-01

    Dense and crack-free 10-mol%-yttria-stabilized zirconia (10YSZ)-alumina composites, containing 0 to 30 mol% of alumina, have been fabricated by hot pressing. Release of pressure before onset of cooling was crucial in obtaining crack-free material. Hot pressing at 1600 C resulted in the formation of ZrC by reaction of zirconia with grafoil. However, no such reaction was observed at 1500 C. Cubic zirconia and -alumina were the only phases detected from x-ray diffraction indicating no chemical reaction between the composite constituents during hot pressing. Microstructure of the composites was analyzed by scanning electron microscopy and transmission electron microscopy. Density and elastic modulus of the composites followed the rule-of-mixtures. Addition of alumina to 10YSZ resulted in lighter, stronger, and stiffer composites by decreasing density and increasing strength and elastic modulus.

  15. Preparation and Characterization of Electrospun Alumina Nanofibers

    NASA Astrophysics Data System (ADS)

    Pinti, Marie J.; Tacastacas, Stephen N.; Stojilovic, Nenad; O'Brien, John P.; Pischera, Anna; Espe, Matthew P.

    2008-10-01

    Alumina nanofibers are promising materials for use in high- temperature applications since they are chemically inert up to very high temperatures. Applications include use as catalyst support in high-temperature chemical reactions, fire protection materials, and as a high-temperature insulator. Electrospinning is a relatively simple and inexpensive method for obtaining nanometer-size fibers and has become a popular technique for producing metal-oxide nanofibers in recent years. The electrospinning mixture for the production of alumina nanofibers typically contains aluminum acetate stabilized with boric acid as the alumina precursor; but the observed presence of boron and sodium on the surface of these nanofibers may affect their use as catalytic supports. We have produced alumina nanofibers from an aluminum reagent devoid of the boric acid stabilizer and calcined the fibers at different temperatures to produce nanofibers with different phases of alumina. Characterization of the fibers by TGA, FE-SEM equipped with the XEDS, powder XRD, DRIFTS, and SSNMR methods to determine the fate of the precursors, fiber morphology and the composition and structure of the calcined alumina nanofibers.

  16. Synthesis of high thermally-stable mesoporous alumina particles.

    PubMed

    Song, Lee-Hwa; Park, Seung Bin

    2010-01-01

    The mesoporous undoped and Si-doped alumina were prepared with an ultrasonic spray process, and found to have well-developed mesopore structures and large surface areas. The mesoporous Si-doped alumina has a high thermal stability up to 1473 K. Its surface area and pore volume were found to slowly decrease with increasing temperature. Mesoporous undoped alumina is transformed to gamma-alumina at 1073 K, whereas the amorphous nature of the pore walls of the Si-doped alumina is maintained up to 1073 K. When heat treatment was carried out at 1473 K for 2 h, the mesopore-networks of the undoped alumina collapsed, and then all the pore walls were converted into the alpha-alumina phase. In contrast, the mesoporosity of the Si-doped alumina persisted during heat treatment, and its pore walls were transformed to gamma-alumina. The decreases in the pore volume of the undoped alumina at 1073 K and 1473 K were found to be 36% and 99% respectively, but for the Si-doped alumina were only 24% and 36% respectively. The surface area of the undoped alumina at 1473 K was found to be 11 m2/g but that of the Si-doped samples at the same temperature is higher than 100 m2/g. Thus this mesoporous Si-doped alumina can be used as a catalytic support in reactions at high temperatures.

  17. Characterization of Alumina Interfaces in TBC Systems

    SciTech Connect

    Pint, Bruce A; More, Karren Leslie

    2009-01-01

    Interfacial segregants in thermally grown {alpha}-Al{sub 2}O{sub 3} scales formed during high temperature exposure of thermal barrier coating systems reflect the oxygen-active dopants present in the bond coating and substrate, such as Y and Hf. These dopants diffuse outward and segregate to the substrate-alumina interface and the alumina grain boundaries. Related studies suggest that these segregants affect the growth and mechanical properties of the alumina-scale; however, the characterization of segregation in alumina formed on coated superalloy systems has been limited. Segregation examples evaluated using analytical transmission electron microscopy are given from traditional Pt-modified aluminide coatings and newer Pt diffusion coatings. Model systems are used to illustrate that grain boundary segregants on the columnar alumina boundaries are not because of the reverse diffusion of cations from the Y{sub 2}O{sub 3}-stabilized ZrO{sub 2} top coating, and that interstitial elements in the substrate likely affect the outward flux of cation dopants. The dynamic nature of this segregation and oxygen-potential gradient-driven diffusion is discussed in light of observations of substrate dopant and interstitial contents affecting coating performance.

  18. Dielectric Performance of a High Purity HTCC Alumina at High Temperatures - a Comparison Study with Other Polycrystalline Alumina

    NASA Technical Reports Server (NTRS)

    Chen, Liangyu

    2014-01-01

    A very high purity (99.99+%) high temperature co-fired ceramic (HTCC) alumina has recently become commercially available. The raw material of this HTCC alumina is very different from conventional HTCC alumina, and more importantly there is no glass additive in this alumina material for co-firing processing. Previously, selected HTCC and LTCC (low temperature co-fired ceramic) alumina materials were evaluated at high temperatures as dielectric and compared to a regularly sintered 96% polycrystalline alumina (96% Al2O3), where 96% alumina was used as the benchmark. A prototype packaging system based on regular 96% alumina with Au thickfilm metallization successfully facilitated long term testing of high temperature silicon carbide (SiC) electronic devices for over 10,000 hours at 500 C. In order to evaluate this new high purity HTCC alumina for possible high temperature packaging applications, the dielectric properties of this HTCC alumina substrate were measured and compared with those of 96% alumina and a previously tested LTCC alumina from room temperature to 550 C at frequencies of 120 Hz, 1 KHz, 10 KHz, 100 KHz, and 1 MHz. A parallel-plate capacitive device with dielectric of the HTCC alumina and precious metal electrodes were used for measurements of the dielectric constant and dielectric loss of the co-fired alumina material in the temperature and frequency ranges. The capacitance and AC parallel conductance of the capacitive device were directly measured by an AC impedance meter, and the dielectric constant and parallel AC conductivity of the dielectric were calculated from the capacitance and conductance measurement results. The temperature and frequency dependent dielectric constant, AC conductivity, and dissipation factor of the HTCC alumina substrate are presented and compared to those of 96% alumina and a selected LTCC alumina. Other technical advantages of this new co-fired material for possible high packaging applications are also discussed.

  19. Iron films deposited on porous alumina substrates

    NASA Astrophysics Data System (ADS)

    Yamada, Yasuhiro; Tanabe, Kenichi; Nishida, Naoki; Kobayashi, Yoshio

    2016-12-01

    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.

  20. Interface Engineering in Alumina/Glass Composites

    DTIC Science & Technology

    1992-02-29

    BN coating applied to the fibers disappeared during the fabrication process. Coating thicknesses as much as 0.3 jim was found to be assimilated during...E-200 Alumina Fiber Tin Dioxide ’ -300 - PD - 166 coating,30 -1(0.8 un) -400 00, -600 " 9.4 9.6 9.S 10.0 10.2 r ( jim ) Fig. 2. Fracture surface of...of the specimens Chemical composition’(wt.%) were polished, with 0.5 jim alumina powder, to mini- .i. 71 mize surface flaw effects. Strengih

  1. Contact Noise in Sodium Beta Alumina.

    DTIC Science & Technology

    1987-05-01

    AD-Al~i 128 CONTACT NOISE IN SODIUM BETA ALUMINA(U) UTANHUNIV SALT i/i LAKE CITY DEPT OF PHYSICS C K KUD ET AL MAY 87 UN SLR55IF IED FG 1,b2 NL UN...by Chu Kun Kuo* and James J. Brophy Physics Department University of Utah Salt Lake City, Utah 84112 ABSTRACT/ Contact noise in sodium 0alumina cells...ZIPCo*I) UNIVERSITY OF UTAH UNIVERISTY OF NEW MEXICO SALT LAKE CITY UT 84112 Bandelier Hall West Alhkq..u u. m (1 71-11 so NAME of FUNDING /SPONSORING Sb

  2. Current Noise in Sodium Beta Alumina Ceramic.

    DTIC Science & Technology

    1983-11-01

    7 ’FD-i49 549 CURRENT NOISE IN SODIUM BET ALUMINA CERAIC(U) UTAH i/iUNIV SALT LAKE CITY DEPT OF PHYSICS J J BROPHY ET AL.NOV 83 TR-5 N08814-82-K...REPORT NO. 5 CURRENT NOISE IN SODIUM 0" ALUMINA CERAMIC ID by James J. Brophy and Steven W. Smith * Prepared for Publication in the Journal of Applied...Physics D T IC ELECTE JAIN 1 Department of Physics $ ) University of Utah Salt Lake City, Utah 84112 November 1983 Reproduction in whole or in part is

  3. Chlorination of alumina in kaolinitic clay

    NASA Astrophysics Data System (ADS)

    Grob, B.; Richarz, W.

    1984-09-01

    The chlorination of alumina in kaolinitic clay with Cl2 and CO gas mixtures was studied gravimetrically. The effects of the calcination method and of NaCl addition on the reactivity of the clay were examined. Fast reaction rates were achieved only with samples previously exposed to a sulfating treatment. Optimum conditions, with maximum yield and selectivity to A1C13 and minimum SiO2 conversion, were found between 770 and 970 K. At higher temperatures the SiCl4 formed poisons the reactive alumina surface by selective chemisorption with a marked decrease of the reaction rate.

  4. REMOVING RADIUM FROM WATER BY PLAIN AND TREATED ACTIVATED ALUMINA

    EPA Science Inventory

    The research determined the feasibility of using BaSO4-impregnated activated alumina and plain activated alumina for radium removal from groundwater by fixed-bed adsorption. The major factors influencing radium adsorption onto the two types of alumina were identified. The radium ...

  5. 21 CFR 73.1010 - Alumina (dried aluminum hydroxide).

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 1 2014-04-01 2014-04-01 false Alumina (dried aluminum hydroxide). 73.1010... GENERAL LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1010 Alumina (dried aluminum hydroxide). (a) Identity. (1) The color additive alumina (dried aluminum hydroxide) is a white,...

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

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 1 2012-04-01 2012-04-01 false Alumina (dried aluminum hydroxide). 73.1010... GENERAL LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1010 Alumina (dried aluminum hydroxide). (a) Identity. (1) The color additive alumina (dried aluminum hydroxide) is a white,...

  7. 21 CFR 73.1010 - Alumina (dried aluminum hydroxide).

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 1 2011-04-01 2011-04-01 false Alumina (dried aluminum hydroxide). 73.1010... GENERAL LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1010 Alumina (dried aluminum hydroxide). (a) Identity. (1) The color additive alumina (dried aluminum hydroxide) is a white,...

  8. 21 CFR 73.1010 - Alumina (dried aluminum hydroxide).

    Code of Federal Regulations, 2010 CFR

    2010-04-01

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

  9. 21 CFR 73.1010 - Alumina (dried aluminum hydroxide).

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 1 2013-04-01 2013-04-01 false Alumina (dried aluminum hydroxide). 73.1010... GENERAL LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1010 Alumina (dried aluminum hydroxide). (a) Identity. (1) The color additive alumina (dried aluminum hydroxide) is a white,...

  10. Physics of sub-micron cosmic dust particles

    NASA Technical Reports Server (NTRS)

    Roy, N. L.

    1974-01-01

    Laboratory tests with simulated micrometeoroids to measure the heat transfer coefficient are discussed. Equations for ablation path length for electrically accelerated micrometeoroids entering a gas target are developed which yield guidelines for the laboratory measurement of the heat transfer coefficient. Test results are presented for lanthanum hexaboride (LaB sub 6) microparticles in air, argon, and oxygen targets. The tests indicate the heat transfer coefficient has a value of approximately 0.9 at 30 km/sec, and that it increases to approximately unity at 50 km/sec and above. Test results extend to over 100 km/sec. Results are also given for two types of small particle detectors. A solid state capacitor type detector was tested from 0.61 km/sec to 50 km/sec. An impact ionization type detector was tested from 1.0 to 150 km/sec using LaB sub 6 microparticles.

  11. Sub-micron scale conduction processes on clean surfaces

    SciTech Connect

    Kimberlin, K.

    1995-06-19

    Electrical conductance has been measured in-situ in two dimensions in the Ag/Si(111) system as a function of incident adatom flux rate with a 4-probe method. A conductance study in a 3-D conical structure was also made using field emission. For the 2-D study, the origin of conduction is still unclear, as transport by percolating Ag clusters and conduction through the substrate lvia electrons from the film have both been suggested. Experiments varying the flux rate were conducted to decide between the two. Smoother films are expected at lower growth rates which would result in faster drops in the 4-probe voltage; however the 4-probe voltage vs deposition time for various flux rates collapse into a universal curve which indicates that the morphology is not relevant and supports through the substrate. In the 3-D conductance study, a single, lateral micromachined W protrusion on a silica substrate is examined to identify the factors controlling emission in micromachined structures. The I-V characteristics and emission pattern indicate that miniprotrusions of a few hundred Angstroms, much smaller than the nominal radius of the tip, exist on the tip and are responsible for the emission. Adsorption-desorption events from the background environment are the cause of large fluctuations in the emitting current. Comparison of the emission of a single tip to gated arrays suggest that only a fraction of the tips in the array are emitting.

  12. Sub-Micron Long HTS Ho Electron Mixers

    NASA Technical Reports Server (NTRS)

    Harnack, 0.; Karasik, B. S.; McGrath, W. R.; Kleinsasser, A. W.; Barner, J. B.

    2000-01-01

    The hot-electron bolometer mixer made from a high-T, superconductor (HTS) was introduced recently as an alternative to a Schottky mixer at THz frequencies. The performance of the mixer depends on the total thermal conductance for heat removal from the phonon sub-system due to either length-dependent phonon diffusion or phonon escape to the substrate. We have measured both the length and temperature dependencies of the IF bandwidth of the mixers fabricated from 25-35 mn thick YBCO films on MgO and sapphire substrates. The films were grown by a laser deposition technique and electron-beam lithography was used to define bridge lengths down to 50 nm. Mixer measurements were done using signal frequencies in the range of 1-100 GHz. For 50 nm and 400 nm long devices on MgO, the 3-dB bandwidth was about 100 MHz. At temperatures below 60 K, the hot-electron plateau was clearly seen starting around 2-3 GHz. At temperatures above 70 K, the flux-flow effects begin to dominate and the IF bandwidth increases to 1-8 GHz, while the conversion efficiency drops by several dB. This temperature dependence of the IF bandwidth can account for previously reported unexpectedly high bandwidth of HTS mixers.

  13. Advanced composite applications for sub-micron biologically derived microstructures

    NASA Technical Reports Server (NTRS)

    Schnur, J. M.; Price, R. R.; Schoen, P. E.; Bonanventura, Joseph; Kirkpatrick, Douglas

    1991-01-01

    A major thrust of advanced material development is in the area of self-assembled ultra-fine particulate based composites (micro-composites). The application of biologically derived, self-assembled microstructures to form advanced composite materials is discussed. Hollow 0.5 micron diameter cylindrical shaped microcylinders self-assemble from diacetylenic lipids. These microstructures have a multiplicity of potential applications in the material sciences. Exploratory development is proceeding in application areas such as controlled release for drug delivery, wound repair, and biofouling as well as composites for electronic and magnetic applications, and high power microwave cathodes.

  14. Sub-micron surface plasmon resonance sensor systems

    NASA Technical Reports Server (NTRS)

    Glazier, James A. (Inventor); Amarie, Dragos (Inventor)

    2013-01-01

    Wearable or implantable devices combining microfluidic control of sample and reagent flow and micro-cavity surface plasmon resonance sensors functionalized with surface treatments or coatings capable of specifically binding to target analytes, ligands, or molecules in a bodily fluid are provided. The devices can be used to determine the presence and concentration of target analytes in the bodily fluids and thereby help diagnose, monitor or detect changes in disease conditions.

  15. Sub-Micron Carbon Filaments for Optical Applications

    DTIC Science & Technology

    1987-11-01

    research at this stage, t grow straight, submicroii, high aspect ratio filaments, has not yet bet achievcd. A ,ariety of groi .-th conditions have bee...however, produced very little filament groi .-th and quilt a lot of carbon deposits on the reactor walls. The deposits ranged from .ell.uwish-brown...arranged across the fiber section varies considerably from one fiber type to another. Ex- PAIN fibers are characteristically disordered in this section

  16. Sub-micron surface plasmon resonance sensor systems

    NASA Technical Reports Server (NTRS)

    Glazier, James A. (Inventor); Amarie, Dragos (Inventor)

    2011-01-01

    A sensor for detecting the presence of a target analyte, ligand or molecule in a test fluid, comprising a light transmissive substrate on which an array of surface plasmon resonant (SPR) elements is mounted is described. A multichannel sensor for detecting the presence of several targets with a single microchip sensor is described. A multichannel sensor including collections of SPR elements which are commonly functionalized to one of several targets is also described. The detectors sense changes in the resonant response of the SPR elements indicative of binding with the targets.

  17. Sub-micron surface plasmon resonance sensor systems

    NASA Technical Reports Server (NTRS)

    Glazier, James A. (Inventor); Dragnea, Bogdan (Inventor); Amarie, Dragos (Inventor)

    2010-01-01

    A sensor for detecting the presence of a target analyte, ligand or molecule in a test fluid, comprising a light transmissive substrate on which an array of surface plasmon resonant (SPR) elements is mounted is described. A multi-channel sensor for detecting the presence of several targets with a single microchip sensor is described. A multi-channel sensor including collections of SPR elements which are commonly functionalized to one of several targets is also described. The detectors sense changes in the resonant response of the SPR elements indicative of binding with the targets.

  18. Sub-micron surface plasmon resonance sensor systems

    NASA Technical Reports Server (NTRS)

    Glazier, James A. (Inventor); Amarie, Dragos (Inventor)

    2011-01-01

    A sensor for detecting the presence of a target analyte, ligand or molecule in a test fluid, comprising a light transmissive substrate on which an array of surface plasmon resonant (SPR) elements is mounted is described. A multi-channel sensor for detecting the presence of several targets with a single micro-chip sensor is described. A multi-channel sensor including collections of SPR elements which are commonly functionalized to one of several targets is also described. The detectors sense changes in the resonant response of the SPR elements indicative of binding with the targets.

  19. Sub-micron surface plasmon resonance sensor systems

    NASA Technical Reports Server (NTRS)

    Glazier, James A. (Inventor); Dragnea, Bogdan (Inventor); Amarie, Dragos (Inventor)

    2010-01-01

    A sensor for detecting the presence of a target analyte, ligand or molecule in a test fluid, comprising a light transmissive substrate on which an array of surface plasmon resonant (SPR) elements is mounted is described. A multi-channel sensor for detecting the presence of several targets with a single micro-chip sensor is described. A multi-channel sensor including collections of SPR elements which are commonly functionalized to one of several targets is also described. The detectors sense changes in the resonant response of the SPR elements indicative of binding with the targets.

  20. Sub-micron surface plasmon resonance sensor systems

    NASA Technical Reports Server (NTRS)

    Glazier, James A. (Inventor); Amarie, Dragos (Inventor)

    2012-01-01

    A sensor for detecting the presence of a target analyte, ligand or molecule in a test fluid, comprising a light transmissive substrate on which an array of surface plasmon resonant (SPR) elements is mounted is described. A multi-channel sensor for detecting the presence of several targets with a single microchip sensor is described. A multi-channel sensor including collections of SPR elements which are commonly functionalized to one of several targets is also described. The detectors sense changes in the resonant response of the SPR elements indicative of binding with the targets.

  1. Multifractal analysis of atmospheric sub-micron particle data

    NASA Astrophysics Data System (ADS)

    Arizabalo, Rubén Darío; González-Ávalos, Eugenio; Korvin, Gabor

    2015-03-01

    Multifractal analysis was used to describe air pollution by sub-micrometric atmospheric particles. Atmospheric particle concentrations were studied from March 31 to April 21, 2006, as part of the MILAGRO campaign at the Jasso Station by means of an SMPS. Sixteen campaign days were selected to carry out the multifractal analysis of the experimental data through Singularity Spectra f(α). In this work, the roughness/smoothness feature of atmospheric particle distributions was studied by means of the Hölder exponent (α), which can be associated with the intensity of particle emissions through time and the randomness of the external emission sources. Multifractal analysis has been found to be a useful tool to establish intensity fluctuations of atmospheric data.

  2. Peltier Effect in Sub-micron-Size Metallic Junctions

    NASA Astrophysics Data System (ADS)

    Fukushima, Akio; Yagami, Kojiro; Tulapurkar, Ashwin A.; Suzuki, Yoshishige; Kubota, Hitoshi; Yamamoto, Atsushi; Yuasa, Shinji

    2005-01-01

    Resistance (R)-current (I) curves in trilayer CPP-GMR (current perpendicular to plane-giant magnetoresistance) elements show a parabolic baseline because of Joule heating, and abrupt jumps due to magnetization reversals. The bottom of the parabolic baseline shifts in one current direction for reasons that were previously unclear. Our study of the R-I characteristics of CPP elements with various structures showed (i) the shift in the R-I curve originates from Peltier cooling in the CPP elements; (ii) the cooling power per unit area of the CPP elements (˜105 W/cm2) is much greater than that of conventional thermoelectric materials (˜5 W/cm2).

  3. Fabrication of biodegradable elastomeric scaffolds with sub-micron morphologies

    PubMed Central

    Stankus, John J.; Guan, Jianjun; Wagner, William R.

    2010-01-01

    The native extracellular matrix (ECM) of elastic tissues is strong and flexible and supports cell adhesion and enzymatic matrix remodeling. In an attempt to convey these ECM properties to a synthetic scaffold appropriate for soft tissue engineering applications, a biodegradable, elastomeric poly(ester urethane)urea (PEUU) was combined with type I collagen at various ratios (2.5, 5, 10, 20, 50, 60, 70, 80, and 90 wt% collagen) and electrospun to construct elastic matrices. Randomly orientated fibers in the electrospun matrices ranged in diameter from 100–900 nm, dependent on initial polymer concentration. Picrosirius red staining of matrices and CD spectroscopy of released collagen confirmed collagen incorporation and preservation of collagen structure at the higher collagen mass fractions. Matrices were strong and distensible possessing strengths of 2–13 MPa with breaking strains of 160–280% even with low PEUU content. Collagen incorporation significantly enhanced smooth muscle cell adhesion onto electrospun scaffolds. An approach has been demonstrated that mimics elastic extracellular matrices by using a synthetic component to provide mechanical function together with a biomacromolecule, collagen. Such matrices may find application in engineering soft tissue. PMID:15307165

  4. Thermal Conductivity of Alumina-Toughened Zirconia Composites

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Zhu, Dong-Ming

    2003-01-01

    10-mol% yttria-stabilized zirconia (10YSZ)-alumina composites containing 0 to 30 mol% alumina were fabricated by hot pressing at 1500 C in vacuum. Thermal conductivity of the composites, determined at various temperatures using a steady-state laser heat flux technique, increased with increase in alumina content. Composites containing 0, 5, and 10-mol% alumina did not show any change in thermal conductivity with temperature. However, those containing 20 and 30-mol% alumina showed a decrease in thermal conductivity with increase in temperature. The measured values of thermal conductivity were in good agreement with those calculated from simple rule of mixtures.

  5. Dielectric Performance of High Purity HTCC Alumina at High Temperatures - A Comparison Study with Other Polycrystalline Alumina

    NASA Technical Reports Server (NTRS)

    Chen, Liang-Yu

    2012-01-01

    A very high purity (99.99+) high temperature co-fired ceramic (HTCC) alumina has recently become commercially available. The raw material of this HTCC alumina is very different from conventional HTCC alumina, and more importantly there is no glass additive in this co-fired material. Previously, selected HTCC and LTCC (low temperature co-fired ceramic) alumina materials were evaluated at high temperatures as dielectric and compared to a regularly sintered 96 polycrystalline alumina (96 Al2O3), where 96 alumina was used as the benchmark. A prototype packaging system based on regular 96 alumina with Au thick-film metallization successfully facilitated long term testing of high temperature silicon carbide (SiC) electronic devices for over 10,000 hours at 500C. In order to evaluate this new HTCC alumina for possible high temperature packaging applications, the dielectric properties of this HTCC alumina substrate were measured and compared with those of 96 alumina and a LTCC alumina from room temperature to 550C at frequencies of 120 Hz, 1 KHz, 10 KHz, 100 KHz, and 1 MHz. A parallel-plate capacitive device with dielectric of the HTCC alumina and precious metal electrodes were used for measurements of the dielectric constant and dielectric loss of the co-fired alumina material in the temperature and frequency ranges. The capacitance and AC parallel conductance of the capacitive device were directly measured by an AC impedance meter, and the dielectric constant and parallel AC conductivity of the dielectric were calculated from the capacitance and conductance measurement results. The temperature and frequency dependent dielectric constant, AC conductivity, and dissipation factor of the HTCC alumina substrate are presented and compared to those of 96 alumina. Other technical advantages of this new co-fired material for possible high packaging applications are also discussed.

  6. Rheological Properties of Aqueous Nanometric Alumina Suspensions

    SciTech Connect

    Li, Chuanping

    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

  7. Microwave joining of high-purity alumina

    SciTech Connect

    Cozzi, A.D.; Clark, D.E.; Ferber, M.K.

    1996-12-31

    Microwave hybrid heating (MHH) was used to join 99.5% pure alumina pieces 25 mm diameter and 25 mm long using 94% pure alumina as the interlayer material. The interlayer material was cut from a rod into discs approximately 2 mm thick. Joining was performed in a home model microwave oven. Temperatures for joining ranged from 1450{degrees}C to 1550{degrees}C and pressures from 1-3 MPa. For comparison, similar joints were made in a conventional furnace. Joined specimens were tested using four-point bend at room temperature. Statistical analysis was utilized to determine the relative effect of the different processing parameters on the strength of the joint.

  8. Li + ion diffusion in nanoscale alumina coatings

    NASA Astrophysics Data System (ADS)

    Johannes, Michelle; Bernstein, Noam

    Nanoscale coatings of alumina are used to stabilize surfaces for a variety of technologies. Diffusion of ions through these coatings is of primary importance: in some cases, diffusion is unwanted (e.g. corrosion) and in others (e.g. electrode materials), it is necessary. In this work DFT and AIMD calculations are used to investigate Li+ ion diffusion through a nano-layer of alumina, examining the phase (alpha, gamma, and amorphous), ion concentration, and electron count dependence. We look at the role of the surface itself in promoting diffusion. One of our main findings is that as the number of ions or charge increases, the diffusivity rises. We show how our data can explain electrochemical data from coated LiCoO2 cathodes and may point toward better and more efficient coatings for stabilizing electrodes.

  9. Silica containing highly porous alumina ceramic

    NASA Astrophysics Data System (ADS)

    Svinka, R.; Svinka, V.; Zake, I.

    2011-04-01

    Porous alumina ceramic were produced by slip casting of aqueous alumina slurry with added small amount of metallic aluminium powder. Pores form in result of chemical reaction of aluminum with water by hydrogen gas evolution reaction and solidification of suspension. Porosity of such materials sintered at a temperature of 1600 - 1750°C varies from 60 to 90%. Pore size distribution and mechanical strength of these materials depend largely on the grain size of used raw materials. The major part of pores in the materials produced without additive of silica are larger than 10 ±m, but with 5 - 10 wt.% additive of silica in the raw mix pore size decreases considerably. The sintering shrinkage decreases to 2.5%. Coefficient of thermal expansion equally decreases from 8.9-10-6 K-1 to 7.1 10-6 K-1 and classification temperature increases to 1600°C, while deformation at high temperature decreases considerably.

  10. Activation of consolidation processes of alumina ceramics

    NASA Astrophysics Data System (ADS)

    Matrenin, S. V.; Zenin, B. S.; Tayukin, R. V.

    2016-02-01

    The methods for activating sintering ceramics based on Al2O3 by mechanical activation in the planetary mill, by adding in the mixture of nanopowders (NP) Al, Al2O3, and submicron powder TiO2, and by applying the technology of spark plasma sintering (SPS) are developed. It has been shown that adding the nanopowder up to 20 wt. % Al2O3 in a coarse powder α-Al2O3 activates the sintering process resulting in increased density and hardness of the sintered alumina ceramics. Substantial effect of increasing density of alumina ceramics due to adding the submicron powder TiO2 in the compound of initial powder mixtures has been established.

  11. Mesoscale Modelling of the Response of Aluminas

    SciTech Connect

    Bourne, N. K.

    2006-07-28

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

  12. Tribology of alumina-graphite composites

    NASA Astrophysics Data System (ADS)

    Yu, Chih-Yuan

    Alumina-graphite composites, which combine high wear resistance and self-lubricity, are a potential and promising candidate for advanced tribological applications. The processing, mechanical properties and tribology of alumina-graphite composites are discussed. Full density is difficult to achieve by a pressureless sintering route. Porosity of the composites increases with graphite content which causes the strength, modulus of elasticity, and hardness of the composites to decrease. The increased porosity does cause the fracture toughness to slightly increases. Tribology of alumina-graphite composites was studied with a pin-on-disk tribometer with emphasis on the following aspects: the graphite content in both pin and disk, the graphite flake size and the orientation of the graphite flakes. Scan electronic microscopy (SEM) and X-ray diffraction are utilized to examine and characterize the wear debris and the worn surface. Results confirmed that it is necessary to optimize the structure and the supply of lubricant to improve the tribological behavior and that the arrangements of sliding couples also affect the tribology of self-lubricated ceramic composites. Continuous measurements of the friction coefficients were collected at high frequency in an attempt to correlate the tribology of alumina-graphite composites to vibrations introduced by friction. While these measurements indicate that the time frequency behavior of tribology is an important area of study, conclusions regarding the frequency response of different sliding couples could not be definitively stated. Finally, a new concept connecting instantaneous wear coefficient and instantaneous contact stress is proposed for prediction of wear behavior of brittle materials.

  13. Decay of elastic waves in alumina

    NASA Astrophysics Data System (ADS)

    Marom, H.; Sherman, D.; Rosenberg, Z.

    2000-11-01

    The dynamic response of alumina under shock compression was studied using planar impact experiments with different tile thicknesses. Stress-time measurements were made with manganin gauges backed by different backing materials in order to optimize gauge response. The results show an apparent decay in the Hugoniot elastic limit with propagation distance. However, further analysis reveals that this phenomenon is probably a measurement artifact, resulting from the relatively slow response times of manganin gauges.

  14. Luminescence of Cu+ Beta’ Alumina.

    DTIC Science & Technology

    1987-07-01

    the ion exchange procedure using melts of pure cuprous salts often resulted in crystals which were discolored and which lumi- nesced only weakly...importance is the stabil- ity of the cuprous ions in the fil-alumina host. We have begun to explore some of these questions. Very high intensity UV radia...SCHEDULE dis tribut ion is unlimited 4. PERFORMING ORGANIZATION REPORT NUMBER(S) S. MONITORING ORGANIZATION REPORT NUMBER(S) Technical Report No. 12 Ga

  15. Compression Testing of Alumina Fiber Insulation

    NASA Technical Reports Server (NTRS)

    Vaughn, Wallace L.

    2006-01-01

    A series of tests were conducted to measure the response of alumina fiber insulation to compression loading. The alumina fiber insulation is a candidate gasket material for the Space Shuttle Government Furnished Equipment (GFE) Tile Overlay Repair. Tests were conducted at room temperature and 2300 F. The alumina fiber insulation is a fibrous insulation blanket which was supplied to Langley in two forms, a nominal 3 lb/ft3 version and a nominal 9 lb/ft3 version. The 3 lb/ft3 material was tested as sheets 0.15 and 0.25 inches thick and the 9 lb/ft3 material in sheets 1 inch thick. The material showed very non-linear compression behavior with the compressive resistance of the material increasing as the material was compressed. The 3 lb/ft3 0.15-inch thick material required 4.1 psi to reach the nominal installation thickness of 0.045 inches and retain a load of 2.1 lbs during unloading. Testing at 2300 F resulted in a stiffer more board-like material. The 3 lb/ft3 0.15-inch thick material retained 1 psi of compressive resistance after a 10 minute hold at 2300 F and 0.045 inches thickness.

  16. High contrast laser marking of alumina

    NASA Astrophysics Data System (ADS)

    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.

  17. Role of alumina phase and size in tungsten CMP

    SciTech Connect

    STEIN,DAVID J.; HER,ROBERT Y.-S.

    2000-02-01

    The role of the alumina particle phase and size on polish rate and process temperature was studied to elucidate removal mechanisms involved in tungsten CMP using potassium iodate-based slurries. Additional work including polishing of blanket PETEOS and titanium films, and polishing of M1 to V1 to M2 electrical test structures was performed to determine the performance of the various aluminas in production CMP. The polish rate of tungsten was highest with alpha alumina. Delta/theta and gamma alumina showed lower polish rates. Tungsten and PETEOS polish rates increased with particle size. Only alpha alumina was able to clear the titanium barrier stack. The size of the alpha alumina did not effect the electrical characteristics of short loop electrical test structures.

  18. A simple procedure to prepare spherical {alpha}-alumina powders

    SciTech Connect

    Liu Hongyu; Ning Guiling Gan Zhihong; Lin Yuan

    2009-04-02

    Spherical {alpha}-alumina powders were prepared by the controlled hydrolysis of aluminum isopropoxide in a hydrolysis system consisting of octanol and acetonitrile. Diverse solvents to dissolve reactant formed diverse hydrolysis systems and affected particle shape of {alpha}-alumina powders. The precursors crystallized to {gamma}-alumina at 1000 deg. C and converted to {alpha}-alumina at 1150 deg. C without intermediate phases. The particle morphology of precursor was retained after it crystallized to {alpha}-alumina. The heating rate influenced the particle shape and the state of agglomeration during calcination process. The thermal properties of the precursors were characterized by thermal gravimetric and differential thermal analysis. X-ray diffraction technique was used to confirm the conversion of crystalline phase of alumina powders from amorphous to {alpha}-phase. Transmission electron microscopy was used to investigate the morphologies and size of the precursors and products.

  19. Free-standing alumina nanobottles and nanotubes pre-integrated into nanoporous alumina membranes

    NASA Astrophysics Data System (ADS)

    Fang, Jinghua; Levchenko, Igor; (Ken Ostrikov, Kostya

    2014-08-01

    A novel interfacial structure consisting of long (up to 5 μm), thin (about 300 nm), highly-ordered, free-standing, highly-reproducible aluminum oxide nanobottles and long tubular nanocapsules attached to a rigid, thin (less than 1 μm) nanoporous anodic alumina membrane is fabricated by simple, fast, catalyst-free, environmentally friendly voltage-pulse anodization. A growth mechanism is proposed based on the formation of straight channels in alumina membrane by anodization, followed by neck formation due to a sophisticated voltage control during the process. This process can be used for the fabrication of alumina nanocontainers with highly controllable geometrical size and volume, vitally important for various applications such as material and energy storage, targeted drug and diagnostic agent delivery, controlled drug and active agent release, gene and biomolecule reservoirs, micro-biologically protected platforms, nano-bioreactors, tissue engineering and hydrogen storage.

  20. Free-standing alumina nanobottles and nanotubes pre-integrated into nanoporous alumina membranes

    PubMed Central

    Fang, Jinghua; Levchenko, Igor; Ostrikov, Kostya (Ken)

    2014-01-01

    A novel interfacial structure consisting of long (up to 5 μm), thin (about 300 nm), highly-ordered, free-standing, highly-reproducible aluminum oxide nanobottles and long tubular nanocapsules attached to a rigid, thin (less than 1 μm) nanoporous anodic alumina membrane is fabricated by simple, fast, catalyst-free, environmentally friendly voltage-pulse anodization. A growth mechanism is proposed based on the formation of straight channels in alumina membrane by anodization, followed by neck formation due to a sophisticated voltage control during the process. This process can be used for the fabrication of alumina nanocontainers with highly controllable geometrical size and volume, vitally important for various applications such as material and energy storage, targeted drug and diagnostic agent delivery, controlled drug and active agent release, gene and biomolecule reservoirs, micro-biologically protected platforms, nano-bioreactors, tissue engineering and hydrogen storage. PMID:27877705

  1. Method for preparing Pb-.beta."-alumina ceramic

    DOEpatents

    Hellstrom, Eric E.

    1986-01-01

    A process is disclosed for preparing impermeable, polycrystalline samples of Pb-.beta."-alumina ceramic from Na-.beta."-alumina ceramic by ion exchange. The process comprises two steps. The first step is a high-temperature vapor phase exchange of Na by K, followed by substitution of Pb for K by immersing the sample in a molten Pb salt bath. The result is a polycrystalline Pb-.beta."-alumina ceramic that is substantially crack-free.

  2. Plasma sintering of beta″-alumina

    NASA Astrophysics Data System (ADS)

    Henrichsen, Matthew

    Sintering and phase conversion of beta″-alumina were investigated with static and ultra-rapid passthrough plasma firing. Ultra-rapid passthrough induction firing was used to differentiate the effects of rapid heating rates from plasma effects. Static plasma sintering at low pressures resulted in excessive sodium loss which prohibited the use of dilatometry. Sintering was characterized using the diameter profiles of partially fired tubes. Phase conversion was examined with x-ray diffraction of powdered sections of partially fired tubes. Ultra-rapid passthrough firing speeds ranged from 8 to ˜240 mm/min. Instantaneous shrinkage rates as large as 8%/sec were measured. Phase conversion and sintering were both rapid, and were complete in seconds. Tubes with densities above 97%, beta″-phase content above 98%, and ionic resistivity as low as 13.8 Ocm were produced. Two modes of cracking were identified for tubes in ultra-rapid firing. Both were related to the thickness of the tube wall and sinterability of the powder being fired. A finite element model of sintering and heat transfer was developed to aid in determining the causes of cracking. Cracks formed because of mechanical stress rather than thermal shock. Low levels of cobalt in the precursor materials greatly reduced specimen heating in the plasma. The surface of beta″-alumina, like that of alpha-alumina, is catalytic for recombination of ions and radical components from the plasma. Induction furnace firing produced heating rates lower than those in plasma heating. Fired tubes were oversintered and had duplex microstructures. Some specimens fired in the induction furnace were contaminated by carbon from the graphite susceptor. Two peaks were observed in shrinkage rate profiles of some tubes. A model of dimensional change from simultaneous sintering and phase conversion was constructed. The model produced shrinkage rate profiles similar to those observed in both plasma and induction firing. The multiple peaks

  3. Sintering of beta-type alumina bodies using alpha-alumina encapsulation

    DOEpatents

    McEntire, Bryan J.; Virkar, Anil V.

    1981-01-01

    A method of sintering a shaped green, beta-type alumina body comprising: (A) inserting said body into an open chamber prepared by exposing the interior surface of a container consisting essentially of at least about 50 weight percent of alpha-alumina and a remainder of other refractory material to a sodium oxide or sodium oxide producing environment; (B) sealing the chamber; and heating the chamber with the shaped body encapsulated therein to a temperature and for a time necessary to sinter said body to the desired density. The encapsulation chamber prepared as described above is also claimed.

  4. Samarium and europium beta”-alumina derivatives characterized by XPS

    DOE PAGES

    Myhre, Kristian; Meyer, Harry; Du, Miting

    2017-01-04

    Characterization of sodium, samarium and europium beta -alumina derivatives has been carried out using X-ray photoelectron spectroscopy. Beta -alumina has been widely studied as a material capable of incorporating many different cations into its lattice structure, such as sodium and many of the lanthanide elements. The X-ray photoelectron spectra of samarium and europium in the beta -alumina structure are reported here. Additionally, the spectra of the precursor sodium beta -alumina as well as the europium and samarium trichloride starting materials are presented.

  5. Effect of Impurities on O and Al Boundary Diffusion in Alumina: Application Alumina Scale Growth in Alloys

    DTIC Science & Technology

    2012-01-24

    uniform dispersion of Ni marker particles (0.5 vol%). The extent of the alumina spinel oxidation layer was measured as a function of the wedge...of Ni alone enhances transport by approximately a factor of 2 relative to undoped alumina. The diffusive transport of chromium in both pure and Y...doped fine-grained alumina has been investigated over the temperature range 1250 -1650 C. From a quantitative assessment of the chromium diffusion

  6. The effect of different powder particle size on mechanical properties of sintered alumina, resin- and glass-infused alumina.

    PubMed

    Chaiyabutr, Yada; Giordano, Russell; Pober, Richard

    2009-02-01

    In this study, the compaction and sintering behavior of fine alumina powders of different particle sizes and the effect of matrix particle size on biaxial strength and fracture toughness of infused matrices were investigated. Three different alumina powders, In-Ceram alumina, A16SG, and RC172 were selected, representing a range of particle size and shape. RC172 and A16SG were dry-pressed. In-Ceram alumina was slip-cast following manufacturer's recommendations. Dry-pressed ceramic blocks were sectioned into disks with a thickness of 1.5-mm. Uninfused disks were sintered at four temperatures between 1250 degrees C and 1400 degrees C. For glass or resin infused specimens, alumina disks were sintered at 1250 degrees C for 2 h and separated into two groups for glass infusion and resin (UDMA/TEGDMA) infusion. Disks were tested for biaxial flexural strength with a universal testing machine (Instron) at 0.5-mm/min crosshead speeds. One-way ANOVA and Duncan's multiple range tests revealed that alumina disks with different smaller particle sizes have significantly higher biaxial strength (p < 0.05). The strength of the alumina matrix was greatly increased by glass and resin infusion. The biaxial strength of resin-infused alumina increased as particle size decreased, whereas strength of glass-infused alumina was constant.

  7. Improved Synthesis Of Potassium Beta' '-Alumina

    NASA Technical Reports Server (NTRS)

    Williams, Roger M.; Jeffries-Nakamura, Barbara; Ryan, Margaret A.; O'Connor, Dennis E.; Kisor, Adam; Underwood, Mark

    1996-01-01

    Improved formulations of precursor materials synthesize nearly-phase-pure potassium beta' '-alumina solid electrolyte (K-BASE) powder. Materials are microhomogeneous powders (or, alternatively, gels) containing K(+,) Mg(2+), and Al(3+). K-BASE powder produced used in potassium-working-fluid alkali-metal thermal-to-electric conversion (K-AMTEC), in which heat-input and heat-rejection temperatures lower than sodium-working-fluid AMTEC (Na-AMTEC). Additional potential use lies in purification of pottassium by removal of sodium and calcium.

  8. On the inelastic shock profile in alumina

    NASA Astrophysics Data System (ADS)

    Marom, H.; Sherman, D.; Rosenberg, Z.; Murray, N.

    2002-11-01

    The dynamic response of alumina specimens, above their elastic limits, was studied using planar impact experiments with different tile thickness. Stress-time measurements with manganin gauges show a steady spreading of the inelastic portion of the shock profile with increasing tile thickness. Such behavior is typical of elastic waves moving at a constant speed that depends on their amplitude. This finding supports recent interpretations of the failure ramp, by which the elastic response of these materials should be extended to higher stresses than the initial jump. However, further analysis of these profiles raises some questions regarding the exact determination of the Hugoniot elastic limit.

  9. Laser Surface Treatment of Sintered Alumina

    NASA Astrophysics Data System (ADS)

    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.

  10. Anisotropic shrinkage characteristics of tape cast alumina

    NASA Astrophysics Data System (ADS)

    Patwardhan, Jaideep Suresh

    Dimensional control during sintering is a major issue in ceramics processing to avoid high post-sintering costs associated with machining of the fired ceramic part to desired tolerances and dimensions. Ceramic forming processes such as tape casting, injection molding, and extrusion involve shear of anisotropic particles resulting in preferential alignment of the particles in the green body. This preferential alignment causes directionality in mechanical, electrical, optical, and magnetic properties and most importantly warpage or distortion during sintering. A large effort has been devoted to synthesizing ceramic green bodies with minimal density gradients and uniform packing and modeling the sintering behavior evolution but little effort has been devoted to characterizing orientation of particles and the effect of preferential alignment on sintering shrinkage anisotropy. A systematic study was initiated to study the effect of processing variables such as shear rate, solids loading, temperature, and binder content on aqueous tape cast alumina. Three different alumina systems: A16-SG, Baikowski RC-UFX DBM and RC-LS DBM were investigated. Aqueous tapes of high solids loading alumina (56 vol. %) were tape cast at various speeds and thicknesses and assuming plane Couette flow a shear rate regime of 21--270 s-1 was investigated. Higher shear rates and high solids loading resulted in higher in-plane anisotropy whereas the anisotropy in the thickness direction was higher for low solids loading systems. The anisotropy was found to be fairly constant above a certain critical shear rate (˜100 s-1) irrespective of the temperature and the solids loading and this correlated with the viscosity-shear rate relationship of the cast slips. The higher shrinkage anisotropy in the thickness direction for the low solids loading systems (35 and 45 vol. %) was attributed to the higher amount of organics in the slip required to sustain the suitable viscosity for tape casting and

  11. Intercalation of water into lithium. beta. -alumina

    SciTech Connect

    Dudney, N J; Bates, J B; Wang, J C; Brown, G M; Larson, B C; Engstrom, H

    1981-01-01

    Infrared absorption, neutron diffraction and weight loss techniques have been used to investigate the hydration of single crystals of Li ..beta..-alumina. The hydration is a reversible intercalation reaction. Up to approximately two water molecules per formula unit can penetrate the conduction plane. Other protonated species are formed from the dissociation of the molecular water. The rate of hydration is controlled by the diffusion of water in the conduction plane. A likely diffusion mechanism requires dissociation of the water and an interstitialcy motion of the oxygen.

  12. Quantum dots confined in nanoporous alumina membranes

    NASA Astrophysics Data System (ADS)

    Xu, Jun; Xia, Jianfeng; Wang, Jun; Shinar, Joseph; Lin, Zhiqun

    2006-09-01

    CdSe /ZnS core/shell quantum dots (QDs) were filled into porous alumina membranes (PAMs) by dip coating. The deposition of QDs induced changes in the refractive index of the PAMs. The amount of absorbed QDs was quantified by fitting the reflection and transmission spectra observed experimentally with one side open and freestanding (i.e., with two sides open) PAMs employed, respectively. The fluorescence of the QDs was found to be retained within the cylindrical nanopores of the PAMs.

  13. Conduction mechanism of single-crystal alumina

    NASA Technical Reports Server (NTRS)

    Will, Fritz G.; Delorenzi, Horst G.; Janora, Kevin H.

    1992-01-01

    The fully guarded three-terminal technique was used to perform conductivity measurements on single-crystal alumina at temperatures of 400-1300 C. The conductivity was also determined as a function of time at various temperatures and applied fields. Further, the fractions of the current carried by Al and O ions (ionic transference numbers) were determined from long-term transference experiments in the temperature range 1100-1300 C. A mathematical model of the conduction mechanism is proposed, and model predictions are compared with experimental results.

  14. Microstructural and Mechanical Characterization of Actively Brazed Alumina Specimens

    SciTech Connect

    Hosking, F.M.; Cadden, C.H.; Stephens, J.J.; Glass, S.J.; Yang, N.Y.C.; Vianco, P.V.; Walker, C.A.

    1999-08-26

    Alumina (94 and 99.8% grade compositions) was brazed directly to itself with gold-based active brazing alloys (ABA's) containing vanadium additions of 1,2 and 3 weight percent. The effects of brazing conditions on the joint properties were investigated. Wetting behavior, interfacial reactions, microstructure, hermeticity and tensile strength were determined. Wetting was fair to good for the ABA and base material combinations. Microanalysis identified a discontinuous Al-V-O spinel reaction product at the alumina-braze interface. Tensile strength results for 94% alumina were uniformly good and generally not sensitive to the vanadium concentration, with tensile values of 85-105 MPa. There was more variability in the 99.8% alumina strength results, with values ranging from 25-95 MPa. The highest vanadium concentration (3 wt. %) yielded the highest joint strength for the brazed 99.8% alumina. Failures in the 99.8% alumina samples occurred at the braze-alumina interface, while the 94% alumina specimens exhibited fracture of the ceramic substrate.

  15. Dynamic compressive and tensile strengths of spark plasma sintered alumina

    SciTech Connect

    Girlitsky, I.; Zaretsky, E.; Kalabukhov, S.; Dariel, M. P.; Frage, N.

    2014-06-28

    Fully dense submicron grain size alumina samples were manufactured from alumina nano-powder using Spark Plasma Sintering and tested in two kinds of VISAR-instrumented planar impact tests. In the first kind, samples were loaded by 1-mm tungsten impactors, accelerated to a velocity of about 1 km/s. These tests were aimed at studying the Hugoniot elastic limit (HEL) of Spark Plasma Sintering (SPS)-processed alumina and the decay, with propagation distance, of the elastic precursor wave. In the tests of the second kind, alumina samples of 3-mm thickness were loaded by 1-mm copper impactors accelerated to 100–1000 m/s. These tests were aimed at studying the dynamic tensile (spall) strength of the alumina specimens. The tensile fracture of the un-alloyed alumina shows a monotonic decline of the spall strength with the amplitude of the loading stress pulse. Analysis of the decay of the elastic precursor wave allowed determining the rate of the irreversible (inelastic) strains in the SPS-processed alumina at the initial stages of the shock-induced inelastic deformation and to clarify the mechanisms responsible for the deformation. The 1-% addition of Cr{sub 2}O{sub 3} decreases the HEL of the SPS-processed alumina by 5-% and its spall strength by 50% but barely affects its static properties.

  16. Process for the recovery of alumina from fly ash

    DOEpatents

    Murtha, M.J.

    1983-08-09

    An improvement in the lime-sinter process for recovering alumina from pulverized coal fly ash is disclosed. The addition of from 2 to 10 weight percent carbon and sulfur to the fly ash-calcium carbonate mixture increase alumina recovery at lower sintering temperatures.

  17. 40 CFR 721.10120 - Siloxane modified alumina nanoparticles (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... nanoparticles (generic). 721.10120 Section 721.10120 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.10120 Siloxane modified alumina nanoparticles (generic). (a) Chemical... as siloxane modified alumina nanoparticles (PMN P-05-687) is subject to reporting under this...

  18. Dynamic compressive and tensile strengths of spark plasma sintered alumina

    NASA Astrophysics Data System (ADS)

    Girlitsky, I.; Zaretsky, E.; Kalabukhov, S.; Dariel, M. P.; Frage, N.

    2014-06-01

    Fully dense submicron grain size alumina samples were manufactured from alumina nano-powder using Spark Plasma Sintering and tested in two kinds of VISAR-instrumented planar impact tests. In the first kind, samples were loaded by 1-mm tungsten impactors, accelerated to a velocity of about 1 km/s. These tests were aimed at studying the Hugoniot elastic limit (HEL) of Spark Plasma Sintering (SPS)-processed alumina and the decay, with propagation distance, of the elastic precursor wave. In the tests of the second kind, alumina samples of 3-mm thickness were loaded by 1-mm copper impactors accelerated to 100-1000 m/s. These tests were aimed at studying the dynamic tensile (spall) strength of the alumina specimens. The tensile fracture of the un-alloyed alumina shows a monotonic decline of the spall strength with the amplitude of the loading stress pulse. Analysis of the decay of the elastic precursor wave allowed determining the rate of the irreversible (inelastic) strains in the SPS-processed alumina at the initial stages of the shock-induced inelastic deformation and to clarify the mechanisms responsible for the deformation. The 1-% addition of Cr2O3 decreases the HEL of the SPS-processed alumina by 5-% and its spall strength by 50% but barely affects its static properties.

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

    PubMed

    Sarkar, Sudipta; Gupta, Anirban

    2003-01-01

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

  20. Experimental study of 248nm excimer laser etching of alumina

    NASA Astrophysics Data System (ADS)

    Hu, Hongtao; Shao, Jingzhen; Wang, Xi; Fang, Xiaodong

    2016-10-01

    The 248 nm excimer laser etching characteristic of alumina ceramic and sapphire had been studied using different laser fluence and different number of pulses. And the interaction mechanism of 248 nm excimer laser with alumina ceramic and sapphire had been analyzed. The results showed that when the laser fluence was less than 8 J/cm2, the etching depth of alumina ceramic and sapphire were increased with the increase of laser fluence and number of pulses. At the high number pulses and high-energy, the surface of the sapphire had no obvious melting phenomenon, and the alumina ceramic appeared obvious melting phenomenon. The interaction mechanism of excimer laser with alumina ceramics and sapphire was mainly two-photon absorption. But because of the existence of impurities and defects, the coupling between the laser radiation and ceramic and sapphire was strong, and the thermal evaporation mechanism was also obvious.

  1. Thermal Conductivity of Alumina-reinforced Zirconia Composites

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.

    2005-01-01

    10-mol% yttria-stabilized zirconia (10SZ) - alumina composites containing 0-30 mol% alumina were fabricated by hot pressing at 1500 C in vacuum. Thermal conductivity was determined at various temperatures using a steady-state laser heat flux technique. Thermal conductivity of the composites increased with increase in alumina content. Composites containing 0, 5, and 10-mol% alumina did not show any change in thermal conductivity with temperature. However, those containing 20 and 30-mol% alumina showed a decrease in thermal conductivity with increase in temperature. The measured values of thermal conductivity were in good agreement with those calculated from the Maxwell-Eucken model where one phase is uniformly dispersed within a second major continuous phase.

  2. Adsorption of carboxymethyl cellulose on alumina particles.

    PubMed

    Zhivkov, Alexandar M; Hristov, Rosen P

    2015-06-01

    The polyelectrolyte adsorption on colloid particles is often used for stabilization or flocculation of water suspensions. The aim of this work is to study the adsorption of carboxymethyl cellulose (CMC) on alumina (γ-Al2O3) colloid particles. The particles and polymer are chosen because of the capability of the metal-oxide ampholyte surface and the weak polyelectrolytes to alter their charge by pH. The measurements are done at pH 6.0 where the CMC carboxylic gropes are almost fully dissociated and the alumina surface is positively charged. The high linear charge density of the polyelectrolyte chain provides Na(+) counterions condensation on the COO(-) groups. The main employed method is the electric light scattering based on particle orientation in sinusoidal electric field. The electric polarizability and the relaxation time after field switching off (both depending on the particle charge and size) are used as criteria for polymer adsorption and particle aggregation. Micro-electrophoresis is applied as additional techniques indicating the sign and density of the surface charge. The results obtained give the conditions (time dependence, particle and polymer concentrations) where the CMC adsorption is complete and the suspension is stable.

  3. Combination for electrolytic reduction of alumina

    DOEpatents

    Brown, Craig W.; Brooks, Richard J.; Frizzle, Patrick B.; Juric, Drago D.

    2002-04-30

    An electrolytic bath for use during the electrolytic reduction of alumina to aluminum. The bath comprises molten electrolyte having the following ingredients: AlF.sub.3 and at least one salt selected from the group consisting of NaF, KF, and LiF; and about 0.004 wt. % to about 0.2 wt. %, based on total weight of the molten electrolyte, of at least one transition metal or at least one compound of the metal or both. The compound is, a fluoride; oxide, or carbonate. The metal is nickel, iron, copper, cobalt, or molybdenum. The bath is employed in a combination including a vessel for containing the bath and at least one non-consumable anode and at least one dimensionally stable cathode in the bath. Employing the instant bath during electrolytic reduction of alumina to aluminum improves the wetting of aluminum on a cathode by reducing or eliminating the formation of non-metallic deposits on the cathode.

  4. Properties of Transition Metal Doped Alumina

    NASA Astrophysics Data System (ADS)

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

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

  5. Parsing abnormal grain growth in specialty aluminas

    NASA Astrophysics Data System (ADS)

    Lawrence, Abigail Kremer

    Grain growth in alumina is strongly affected by the impurities present in the material. Certain impurity elements are known to have characteristic effects on abnormal grain growth in alumina. Specialty alumina powders contain multiple impurity species including MgO, CaO, SiO2, and Na 2O. In this work, sintered samples made from alumina powders containing various amounts of the impurities in question were characterized by their grain size and aspect ratio distributions. Multiple quantitative methods were used to characterize and classify samples with varying microstructures. The grain size distributions were used to partition the grain size population into subpopulations depending on the observed deviation from normal behavior. Using both grain size and aspect ratio a new visual representation for a microstructure was introduced called a morphology frequency map that gives a fingerprint for the material. The number of subpopulations within a sample and the shape of the distribution on the morphology map provided the basis for a classification scheme for different types of microstructures. Also using the two parameters a series of five metrics were calculated that describe the character of the abnormal grains in the sample, these were called abnormal character values. The abnormal character values describe the fraction of grains that are considered abnormal, the average magnitude of abnormality (including both grain size and aspect ratio), the average size, and variance in size. The final metric is the correlation between grain size and aspect ratio for the entire population of grains. The abnormal character values give a sense of how different from "normal" the sample is, given the assumption that a normal sample has a lognormal distribution of grain size and a Gaussian distribution of aspect ratios. In the second part of the work the quantified measures of abnormality were correlated with processing parameters such as composition and heat treatment conditions. A

  6. Fabrication of Alumina Nanowires from Porous Alumina Membranes by Etching in Phosphoric Acid Solution

    NASA Astrophysics Data System (ADS)

    Wang, Xuehua; Li, Chengyong; Ma, Lianjiao; Cao, Hong; Zhang, Baohua

    Alumina nanowires (ANWs) with high aspect ratios were synthesized by the chemical etching of porous alumina membranes (PAMs) in phosphoric acid solution. The morphology and structure of ANWs were analyzed by SEM and XRD, respectively. The results showed that the typical features of ANWs are around 35 nm in diameter and around 20 μm in length, the crystalline structure of the ANWs was amorphous, which was in accordance with that of the PAMs. Furthermore, the morphology of the PAMs was characterized by AFM and SEM in detail. On the basis of AFM and SEM observations, a possible formation mechanism of ANWs was discussed, and the inhomogeneous of the dissolution between the triple points and the side walls was considered to be the essential factor deciding the formation of ANWs.

  7. Terbium luminescence in alumina xerogel fabricated in porous anodic alumina matrix under various excitation conditions

    SciTech Connect

    Gaponenko, N. V.; Kortov, V. S.; Orekhovskaya, T. I.; Nikolaenko, I. A.; Pustovarov, V. A.; Zvonarev, S. V.; Slesarev, A. I.; Prislopski, S. Ya.

    2011-07-15

    Terbium-doped alumina xerogel layers are synthesized by the sol-gel method in pores of a porous anodic alumina film 1 {mu}m thick with a pore diameter of 150-180 nm; the film is grown on a silicon substrate. The fabricated structures exhibit terbium photoluminescence with bands typical of trivalent terbium terms. Terbium X-ray luminescence with the most intense band at 542 nm is observed for the first time for such a structure. Morphological analysis of the structure by scanning electron microscopy shows the presence of xerogel clusters in pore channels, while the main pore volume remains unfilled and pore mouths remain open. The data obtained confirm the promising applications of fabricated structures for developing matrix converters of X-rays and other ionizing radiations into visible light. The possibilities of increasing luminescence intensity in the matrix converter are discussed.

  8. Deformation Behaviour of Coarse Grain Alumina under Shock Loading

    NASA Astrophysics Data System (ADS)

    Gupta, Satish

    2013-06-01

    To develop better understanding of the shock wave induced deformation behavior of coarse grain alumina ceramics, and for measurement of its Hugoniot Elastic Limit (HEL), in-situ and recovery gas gun experiments have been carried out on coarse grain alumina (grain size ~ 10 μm), prepared in the form of discs (>99.9% TMD) by pressure-less sintering of alpha alumina powder at 1583 K. The HEL value of 1.9 GPa has been determined from the kink in the pressure history recorded using piezoresistance gauge and also from the free surface velocity history of the sample shocked to 9 GPa. The nano-indentation measurements on the alumina samples shocked to 6.5 GPa showed hardness value 15% lower than 21.3 GPa for unshocked alumina, and strong Indentation Size Effect (ISE); the hardness value was still lower and the ISE was stronger for the sample shocked to 12 GPa. The XRD measurements showed reduced particle size and increased microstrains in the shocked alumina fragments. SEM, FESEM and TEM measurements on shock treated samples showed presence of grain localized micro- and nano-scale deformations, micro-cleavages, grain-boundary microcracks, extensive shear induced deformations, and localized micro-fractures, etc. These observations led to the development of a qualitative model for the damage initiation and its subsequent growth mechanisms in shocked alumina. The work performed in collaboration with K.D. Joshi of BARC and A.K. Mukhopadhyay of CGCRI.

  9. Processing and mechanical characterization of alumina laminates

    NASA Astrophysics Data System (ADS)

    Montgomery, John K.

    2002-08-01

    Single-phase ceramics that combine property gradients or steps in monolithic bodies are sought as alternatives to ceramic composites made of dissimilar materials. This work describes novel processing methods to produce stepped-density (or laminated) alumina single-phase bodies that maintain their mechanical integrity. One arrangement consists of a stiff, dense bulk material with a thin, flaw tolerant, porous exterior layer. Another configuration consists of a lightweight, low-density bulk material with a thin, hard, wear resistant exterior layer. Alumina laminates with strong interfaces have been successfully produced in this work using two different direct-casting processes. Gelcasting is a useful near-net shape processing technique that has been combined with several techniques, such as reaction bonding of aluminum oxide and the use of starch as a fugative filler, to successfully produced stepped-density alumina laminates. The other direct casting process that has been developed in this work is thermoreversible gelcasting (TRG). This is a reversible gelation process that has been used to produce near-net shape dense ceramic bodies. Also, individual layers can be stacked together and heated to produce laminates. Bilayer laminate samples were produced with varied thickness of porous and dense layers. It was shown that due to the difference in modulus and hardness, transverse cracking is found upon Hertzian contact when the dense layer is on the exterior. In the opposite arrangement, compacted damage zones formed in the porous material and no damage occurred in the underlying dense layer. Flaw tolerant behavior of the porous exterior/dense underlayer was examined by measuring biaxial strength as a function of Vickers indentation load. It was found that the thinnest layer of porous material results in the greatest flaw tolerance. Also, higher strength was exhibited at large indentation loads when compared to dense monoliths. The calculated stresses on the surfaces

  10. Fabrication of alumina films with laminated structures by ac anodization.

    PubMed

    Segawa, Hiroyo; Okano, Hironaga; Wada, Kenji; Inoue, Satoru

    2014-02-01

    Anodization techniques by alternating current (ac) are introduced in this review. By using ac anodization, laminated alumina films are fabricated. Different types of alumina films consisting of 50-200 nm layers were obtained by varying both the ac power supply and the electrolyte. The total film thickness increased with an increase in the total charge transferred. The thickness of the individual layers increased with the ac voltage; however, the anodization time had little effect on the film thickness. The laminated alumina films resembled the nacre structure of shells, and the different morphologies exhibited by bivalves and spiral shells could be replicated by controlling the rate of increase of the applied potentials.

  11. Porous alumina based ordered nanocomposite coating for wear resistance

    NASA Astrophysics Data System (ADS)

    Yadav, Arti; Muthukumar, M.; Bobji, M. S.

    2016-08-01

    Uniformly dispersed nanocomposite coating of aligned metallic nanowires in a matrix of amorphous alumina is fabricated by pulsed electrodeposition of copper into the pores of porous anodic alumina. Uniform deposition is obtained by controlling the geometry of the dendritic structure at the bottom of pores through stepwise voltage reduction followed by mild etching. The tribological behaviour of this nanocomposite coating is evaluated using a ball on flat reciprocating tribometer under the dry contact conditions. The nanocomposite coating has higher wear resistance compared to corresponding porous alumina coating. Wear resistant nanocomposite coating has wide applications especially in protecting the internal surfaces of aluminium internal combustion engines.

  12. Self-diffusion of oxygen in single crystal alumina

    NASA Astrophysics Data System (ADS)

    Oishi, Y.; Ando, Ken; Kubota, Y.

    1980-08-01

    The self-diffusion coefficient of oxygen in (polished slices of a Verneuil) single-crystal alumina was determined in the temperature range 1500-1770 °C by means of the gas-solid isotope exchange technique. The results were represented by D=1.12×103 exp (-155×103/RT) cm2/s. The activation energy was interpreted to be for intrinsic diffusion. By comparison of the results with the oxygen self-diffusion coefficients previously reported for crushed particles of a Verneuil alumina and a vapor-grown alumina, the extrinsic diffusion exhibited by the crushed particles was confirmed to be due to a dislocation enhancement process.

  13. Fabrication of alumina films with laminated structures by ac anodization

    NASA Astrophysics Data System (ADS)

    Segawa, Hiroyo; Okano, Hironaga; Wada, Kenji; Inoue, Satoru

    2014-02-01

    Anodization techniques by alternating current (ac) are introduced in this review. By using ac anodization, laminated alumina films are fabricated. Different types of alumina films consisting of 50-200 nm layers were obtained by varying both the ac power supply and the electrolyte. The total film thickness increased with an increase in the total charge transferred. The thickness of the individual layers increased with the ac voltage; however, the anodization time had little effect on the film thickness. The laminated alumina films resembled the nacre structure of shells, and the different morphologies exhibited by bivalves and spiral shells could be replicated by controlling the rate of increase of the applied potentials.

  14. Processing of silicon nitride and alumina nanosize powders

    SciTech Connect

    Gonzalez, E.J.; Piermarini, G.; Hockey, B.; Malghan, S.G.

    1995-08-01

    The effects of pressure on the compaction and subsequent processing of nanosize {gamma} alumina powders were studied. A 3 mm diameter piston/cylinder die was used to compact the nanosize powders to pressures of 1 and 2.5 GPa. The green bodies were sintered at temperatures up to 1600{degrees}C. Results show that green body density can be increased by higher compaction pressures. It appears that as a result of the {gamma}-to-{alpha} transformation in alumina, higher green density does not necessarily produce a higher density sintered alumina body. The microstructures of the sintered bodies are described in terms of porosity and phase content.

  15. Effects of long term inhalation of alumina fibres in rats.

    PubMed Central

    Pigott, G. H.; Gaskell, B. A.; Ishmael, J.

    1981-01-01

    Groups of rats were exposed by inhalation to atmospheres containing a refractory alumina fibre (Saffil Fibres, I.C.I.) either as manufactured or in a thermally aged form. Similar groups were exposed to UICC chrysotile A asbestos or clean air to serve as positive and negative controls respectively. Exposures continued for 86 weeks after which the animals were maintained to 85% mortality. Pulmonary reaction to both forms of alumina fibre was minimal; chrysotile asbestos provoked the expected progressive fibrosis. Pulmonary tumours (both benign and malignant) were confined to rats dosed with asbestos. The results support the predicted inert nature of these alumina fibres. Images Fig. 2 PMID:7248173

  16. Boria modified alumina probed by methanol dehydration and IR spectroscopy

    NASA Astrophysics Data System (ADS)

    de Farias, Andréa M. Duarte; Esteves, Angela M. Lavogade; Ziarelli, Fabio; Caldarelli, Stefano; Fraga, Marco A.; Appel, Lucia G.

    2004-04-01

    Al 2O 3·B 2O 3 catalysts were synthesized by co-precipitation and impregnation methods applying two calcination temperatures and boria loadings. Catalysts were analyzed by IR spectroscopy of pyridine and CO 2 adsorption and were evaluated in methanol dehydration. Results showed that boron addition to alumina causes a decrease of the number of basic and Lewis acid sites on alumina surface. It could also be observed an enhancement in acid strength of Lewis sites for impregnated samples. The results of methanol dehydration show that strong Brönsted sites are not formed on borate alumina.

  17. Alumina Paste Sublimation Suppression Barrier for Thermoelectric Device

    NASA Technical Reports Server (NTRS)

    Paik, Jong-Ah (Inventor); Caillat, Thierry (Inventor)

    2014-01-01

    Alumina as a sublimation suppression barrier for a Zintl thermoelectric material in a thermoelectric power generation device operating at high temperature, e.g. at or above 1000K, is disclosed. The Zintl thermoelectric material may comprise Yb.sub.14MnSb.sub.11. The alumina may be applied as an adhesive paste dried and cured on a substantially oxide free surface of the Zintl thermoelectric material and polished to a final thickness. The sublimation suppression barrier may be finalized by baking out the alumina layer on the Zintl thermoelectric material until it becomes substantially clogged with ytterbia.

  18. Preparation ways and photoluminescence of mesoporous alumina

    NASA Astrophysics Data System (ADS)

    Zhang, P.; Liu, J.; Zhao, X.; Wu, G.

    2010-12-01

    High specific surface area (SSA) mesoporous alumina (MA) is synthesized by a sol-gel method using pelagic clay as the raw material. The MA synthesized with a (1-hexadecyl) trimethylammonium bromide (CTAB): utea mixed template shows a SSA of 385.56 m2/g and a mean pore size of 3.6 nm. And the SSA of the MA synthesized with the mixed template is increased compared with the MA synthesized with a CTAB single template. Simultaneously, the MA exhibits a blue photoluminescence which come from the defect F+ and F centers, and the higher PL emission of the MA synthesized with a CTAB: utea mixed template is attributed to the high defect center density in the MA.

  19. Tensile creep behavior of polycrystalline alumina fibers

    NASA Technical Reports Server (NTRS)

    Yun, H. M.; Goldsby, J. C.

    1993-01-01

    Tensile creep studies were conducted on polycrystalline Nextel 610 and Fiber FP alumina fibers with grain sizes of 100 and 300 nm, respectively. Test conditions were temperatures from 800 to 1050 C and stresses from 60 to 1000 MPa. For both fibers, only a small primary creep portion occurred followed by steady-state creep. The stress exponents for steady-state creep of Nextel 610 and Fiber FP were found to be about 3 and 1, respectively. At lower temperatures, below 1000 C, the finer grained Nextel 610 had a much higher 0.2 percent creep strength for 100 hr than the Fiber FP; while at higher temperatures, Nextel 610 had a comparable creep strength to the Fiber FP. The stress and grain size dependencies suggest Nextel 610 and Fiber FP creep rates are due to grain boundary sliding controlled by interface reaction and Nabarro-Herring mechanisms, respectively.

  20. Crystallography of Alumina-YAG-Eutectic

    NASA Technical Reports Server (NTRS)

    Farmer, Serene C.; Sayir, Ali; Dickerson, Robert M.; Matson, Lawrence E.

    2000-01-01

    Multiple descriptions of the alumina-YAG eutectic crystallography appear in the ceramic literature. The orientation between two phases in a eutectic system has direct impact on residual stress, morphology, microstructural stability, and high temperature mechanical properties. A study to demonstrate that the different crystallographic relationships can be correlated with different growth constraints was undertaken. Fibers produced by Laser-Heated Float Zone (LHFZ) and Edge-defined Film-fed Growth (EFG) were examined. A map of the orientation relationship between Al2O3 and Y3Al5O12 and their relationship to the fiber growth axis as a function of pull rate are presented. Regions in which a single orientation predominates are identified.

  1. Optimized alumina coagulants for water treatment

    DOEpatents

    Nyman, May D [Albuquerque, NM; Stewart, Thomas A [Albuquerque, NM

    2012-02-21

    Substitution of a single Ga-atom or single Ge-atom (GaAl.sub.12 and GeAl.sub.12 respectively) into the center of an aluminum Keggin polycation (Al.sub.13) produces an optimal water-treatment product for neutralization and coagulation of anionic contaminants in water. GaAl.sub.12 consistently shows .about.1 order of magnitude increase in pathogen reduction, compared to Al.sub.13. At a concentration of 2 ppm, GaAl.sub.12 performs equivalently to 40 ppm alum, removing .about.90% of the dissolved organic material. The substituted GaAl.sub.12 product also offers extended shelf-life and consistent performance. We also synthesized a related polyaluminum chloride compound made of pre-hydrolyzed dissolved alumina clusters of [GaO.sub.4Al.sub.12(OH).sub.24(H.sub.2O).sub.12].sup.7+.

  2. Electrostatic-based model for alumina surfaces

    NASA Astrophysics Data System (ADS)

    Streitz, F. H.; Mintmire, J. W.

    1994-12-01

    As most technologically important metals will form oxides readily, any complete study of adhesion at real metal surfaces must include the metal-oxide interface. The role of this ubiquitous oxide layer cannot be overlooked, as the adhesive properties of the oxide or oxide-metal system can be expected to differ profoundly from the adhesive properties of a bare metal surface. We report on the development of a novel computational method for molecular dynamics simulations which explicitly includes variable charge transfer between anions and cations. This method is found to be capable of describing the elastic properties, surface energies, and surface relaxation of crystalline metal-oxides accurately. We discuss in detail results using this method of alpha-alumina and several of its low index faces.

  3. Compositional characterization of atomic layer deposited alumina

    SciTech Connect

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

    2014-01-28

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

  4. Microstructure and creep properties of alumina.

    SciTech Connect

    Moreno, J. M. C.; Lopez, A. R.; Rodriguez, A. D.; Routbort, J. L.; Materials Science Division; Univ. of Seville

    1995-01-01

    High temperature creep of two zirconia toughened alumina ceramics, fabricated by powder processing and sol-gel precursors processing, has been studied in order to determine plastic deformation mechanisms. Compressive creep tests were carried out between 1300 and 1450 C, under stresses from 10 to 150 MPa. For the sample fabricated from powders, a stress exponent of 1.4 and an activation energy of 580 kJ/mol were found below a critical stress of 40 MPa. For larger stresses, accelerated creep rates developed. In the specimens processed from precursors, values of 1.8 for the stress exponent and 540 kJ/mol for the activation energy, over the entire range of stresses have been determined. Creep parameters and microstructural evolution of the samples during the experiments have been correlated with models to establish the dominant creep mechanism.

  5. Quantum Dots Confined in Nanoporous Alumina Membranes

    NASA Astrophysics Data System (ADS)

    Xu, Jun; Xia, Jianfeng; Wang, Jun; Shinar, Joseph; Lin, Zhiqun

    2007-03-01

    Precise control over the dispersion and lateral distribution of quantum dots (QDs) within nanoscopic porous media provides a unique route to manipulate the optical and/or electronic properties of QDs in a very simple and controllable manner for applications related to light emitting, optoelectronic, and sensor devices. Here we filled nanoporous alumina membranes (PAMs) with CdSe/ZnS core/shell QDs by dip coating. The deposition of QDs induced changes in the refractive index of PAMs. The amount of absorbed QDs was quantified by fitting the reflection and transmission spectra observed experimentally with one side open and freestanding (i.e., with two sides open) PAMs employed, respectively. The fluorescence of the QDs was found to be retained within the cylindrical nanopores of PAMs.

  6. Nanoporous alumina as templates for multifunctional applications

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  7. Aluminum-Alloy-Matrix/Alumina-Reinforcement Composites

    NASA Technical Reports Server (NTRS)

    Kashalikar, Uday; Rozenoyer, Boris

    2004-01-01

    Isotropic composites of aluminum-alloy matrices reinforced with particulate alumina have been developed as lightweight, high-specific-strength, less-expensive alternatives to nickel-base and ferrous superalloys. These composites feature a specific gravity of about 3.45 grams per cubic centimeter and specific strengths of about 200 MPa/(grams per cubic centimeter). The room-temperature tensile strength is 100 ksi (689 MPa) and stiffness is 30 Msi (206 GPa). At 500 F (260 C), these composites have shown 80 percent retention in strength and 95 percent retention in stiffness. These materials also have excellent fatigue tolerance and tribological properties. They can be fabricated in net (or nearly net) sizes and shapes to make housings, pistons, valves, and ducts in turbomachinery, and to make structural components of such diverse systems as diesel engines, automotive brake systems, and power-generation, mining, and oil-drilling equipment. Separately, incorporation of these metal matrix composites within aluminum gravity castings for localized reinforcement has been demonstrated. A composite part of this type can be fabricated in a pressure infiltration casting process. The process begins with the placement of a mold with alumina particulate preform of net or nearly net size and shape in a crucible in a vacuum furnace. A charge of the alloy is placed in the crucible with the preform. The interior of the furnace is evacuated, then the furnace heaters are turned on to heat the alloy above its liquidus temperature. Next, the interior of the furnace is filled with argon gas at a pressure about 900 psi (approximately equal to 6.2 MPa) to force the molten alloy to infiltrate the preform. Once infiltrated, the entire contents of the crucible can be allowed to cool in place, and the composite part recovered from the mold.

  8. The Effect of Fine Alumina Type on Composition of in Situ Spinel Formation in Alumina-Magnesia Castables

    NASA Astrophysics Data System (ADS)

    Paghandeh, M.; Monshi, A.; Emadi, R.

    Three types of low cement castables (LCC) were prepared from 5% reactive alumina (R5), 5% calcined alumina (A5) and equal proportions of 2.5% (AR). The nest of the composition was fine bauxite (0-1 mm, 57%), coarse bauxite (1-3 mm, 20%), calcined magnesia (5%), secar 71 refractory cemet (7%) and microsilica (1%). By the addition of 5% water, castables were moulded, aged, dried and fired to 1400°C for 2 h. XRD studies showed higher amount of in situ spinel formation in A5. The lattice constants of spinels in A5, AR and R5 were, respectively, 8.0348, 8.0688 and 8.0847 Å. This accounted for respectively alumina rich, stochiometry and magnesia rich spinels. Since calcined alumina is cheaper, produce higher amounts of spinel with the aid of alumina from the aggregate of bauxite and the binder of cement, and alumina rich spinel has better corrosion resistance properties, use of calcined alumina is recommended in LCC.

  9. Effects of ball milling and sintering on alumina and alumina-boron compounds

    NASA Astrophysics Data System (ADS)

    Cross, Thomas

    Alumina has a wide variety of applications, but the processing of alumina based materials can be costly. Mechanically milling alumina has been shown to enhance the sintering properties while decreasing the sintering temperature. Additions of boron have also proven to increase sintering properties of alumina. These two processes, mechanical milling and boron additions, will be combined to test the sintering properties and determine if they are improved upon even further compared to the individual processes. Multiple samples of pure alumina, 0.2 weight percent boron, and 1.0 weight percent boron are batched and processed in a ball mill for different time intervals. These samples are then characterized to observe the structure and properties of the samples after milling but before sintering. Pellets are dry pressed from the milled powders, sintered at 1200°C for one to 10 hours, and characterized to determine the impact of processing. X-ray diffractometry (XRD) was used on each sample to determine crystallite size and lattice parameters at different stages throughout the experiment. XRD was also used to identify any samples with an aluminum borate phase. Scanning electron microscopy (SEM) was used to observe the powder and pellet morphology and to measure bulk chemical composition. Samples were sputter coated with an Au-Pd coating observed in the SEM to characterize the topography as a function of variables such as milling time, boron composition, and sintering time. Additionally, porosity and change in diameter were measured to track the sintering process. Milling sample for longer periods of time would be unnecessary due to the crystallite size leveling off between 10 and 12 hours of milling time. Samples of alumina with 0.2 weight percent boron prove to have very little effect on the sintering properties. At 1.0 weight percent boron, there are changes in diffraction patterns and topography after being sintered for one hour. The porosities of all of the sintered

  10. Alumina Inlay Failure in Cemented Polyethylene-backed Total Hip Arthroplasty

    PubMed Central

    Iwaki, Hiroyoshi; Minoda, Yukihide; Ohashi, Hirotsugu; Takaoka, Kunio

    2008-01-01

    Alumina-on-alumina bearings for THA have markedly improved in mechanical properties through advances in technology; however, alumina fracture is still a concern. We retrospectively reviewed 77 patients (82 hips) with cemented alumina-on-alumina THAs to identify factors relating to alumina failure. The mean age of the patients at surgery was 63 years. The prostheses had a cemented polyethylene-backed acetabular component with an alumina inlay and a 28-mm alumina head. Revision surgery was performed because of alumina inlay failure in four hips (three fractures and one dissociation; 5.6%), deep infection in two, and recurrent dislocation in one. The 8-year survival rate was 90.7% with revision for any reason and 94.4% with revision for alumina failure as the end point. There were no differences in age, body mass index, gender, mobility, function, abduction angle, or size of component among the four hips with alumina failure and the remaining 68 hips without it; however, radiolucent lines in the sockets were more apparent in four cases with alumina inlay failure. This alumina-on-alumina THA thus yielded unsatisfactory medium-term results because we observed a high rate of catastrophic alumina inlay failure. Level of Evidence: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence. PMID:18288546

  11. Removing Fluoride Ions with Continously Fed Activated Alumina.

    ERIC Educational Resources Information Center

    Wu, Yeun C.; Itemaking, Isara Cholapranee

    1979-01-01

    Discussed is the mathematical basis for determining fluoride removal during water treatment with activated alumina. The study indicates that decreasing particle size decreases the pore diffusion effect and increases fluoride removal. (AS)

  12. Growth of Zircone on Nanoporous Alumina Using Molecular Layer Deposition

    NASA Astrophysics Data System (ADS)

    Hall, Robert A.; George, Steven M.; Kim, Yeongae; Hwang, Woonbong; Samberg, Meghan E.; Monteiro-Riviere, Nancy A.; Narayan, Roger J.

    2014-04-01

    Molecular layer deposition (MLD) is a sequential and self-limiting process that may be used to create hybrid organic/inorganic thin films from organometallic precursors and organic alcohol precursors. In this study, films of a zirconium-containing hybrid organic/inorganic polymer known as zircone were grown on nanoporous alumina using MLD. Scanning electron microscopy data showed obliteration of the pores in zircone-coated nanoporous alumina. An in vitro cell viability study indicated that the growth of human epidermal keratinocytes was the greatest on zircone-coated nanoporous alumina than on uncoated nanoporous alumina. Our results suggest that MLD may be used to create biocompatible coatings for use in many types of medical devices.

  13. Potassium Beta-Alumina/Molybdenum/Potassium Electrochemical Cells

    NASA Technical Reports Server (NTRS)

    Williams, R.; Kisor, A.; Ryan, M.; Nakamura, B.; Kikert, S.; O'Connor, D.

    1994-01-01

    potassium alkali metal thermal-to-electric converter (K-AMTEC) cells utilizing potassium beta alumina solid electrolyte (K-BASE) are predicted to have improved properties for thermal to electric conversion at somewhat lower temperatures than sodium AMTEC's.

  14. Fabrication method produces high-grade alumina crucibles

    NASA Technical Reports Server (NTRS)

    Palmour, H.

    1965-01-01

    Alumina-binder mixture, which has been dry pressed in a die using a mating punch, forms crucibles of various configurations and after firing results in a ceramic structure for use in diffusion experiments.

  15. Voltage Fluctuations at Sodium Beta Alumina/Mercury Electrodes.

    DTIC Science & Technology

    1987-06-01

    008 VOLTAGE FLUCTUATIONS AT SODIUM 0" ALUMINA/MERCURY ELECTRODES by Chu Kun Kuo* and James J. Brophy Physics Department University of Utah Salt Lake...ADDRESS (Cty. State, and ZIP Code) 7b. ADDRESS (City. State, and ZIP Code) UNIVERSITY OF UTAH UNIVERSITY OF NEW MEXICO SALT LAKE CITY, UTAH 84112...Include Security Classification) VOLTAGE FLUCTUATIONS AT SODIUM BETA" ALUMINA/MERCURY ELECTRODES -, J l.. 0 12 PERSONAL AUTHOR(S) Chu Kun Kuo and James

  16. The microstructure and mechanical reliability of alumina scales and coatings

    SciTech Connect

    Alexander, K.B.; Pruessner, K.; Tortorelli, P.F.

    1997-09-01

    Alumina scales on iron-aluminides (Fe{sub 3}Al-based) and NiCrAl- based alloys were characterized in order to develop the knowledge to control the oxidation performance of alloys by controlling the microstructure and microchemistry of their scales. Plasma-deposited amorphous alumina coatings on iron-aluminides were used to study phase transformations, transport processes in the scales, and S segregation to the scale/metal interface. It was found that during heat treatment in absence of oxidation, amorphous coatings first transform to {gamma}-Al{sub 2}O{sub 3} and eventually {alpha}-Al{sub 2}O{sub 3} nucleates at the scale/metal interface. Sulfur from the Zr- free alloy segregates to the scale/metal interface during heat treatment. Thermally grown scales on Zr-doped iron-aluminides were compared to those formed after oxidation of a specimen with an alumina coating. Microstructural and gravimetric results showed that the primarily amorphous alumina coating promoted the nucleation and growth of metastable alumina phases, which resulted in more rapid oxidation. The thermally grown oxide was found on top of the coating. The NiCrAl-based alloys formed columnar alumina scales underneath a layer of mixed oxides. Segregation of alloying elements like Y, Hf, and At was found at both oxide grain boundaries and scale/metal interfaces.

  17. Superhydrophobic surfaces fabricated by surface modification of alumina particles

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

    The fabrication of superhydrophobic surfaces has attracted intense interest because of their widespread potential applications in various industrial fields. Recently, some attempts have been carried out to prepare superhydrophobic surfaces using metal oxide nanoparticles. In the present work, superhydrophobic surfaces were fabricated with low surface energy material on alumina particles with different sizes. It was found that particle size of alumina is an important factor in achieving stable superhydrophobic surface. It was possible to obtain alumina surface with water contact angle (WCA) of 156° and a sliding angle of <2°. Superhydrophobicity of the modified alumina is attributed to the combined effect of the micro-nanostructure and low surface energy of fatty acid on the surface. The surface morphology of the alumina powder and coatings was determined by FESEM. The stability of the coatings was assessed by conducting water immersion test. Effect of heat treatment on WCA of the coating was also studied. The transition of alumina from hydrophilic to superhydrophobic state was explained using Wenzel and Cassie models. The method is shown to have potential application for creating superhydrophobic surface on cotton fabrics.

  18. Carbon dioxide pressure swing adsorption process using modified alumina adsorbents

    DOEpatents

    Gaffney, T.R.; Golden, T.C.; Mayorga, S.G.; Brzozowski, J.R.; Taylor, F.W.

    1999-06-29

    A pressure swing adsorption process for absorbing CO[sub 2] from a gaseous mixture containing CO[sub 2] comprises introducing the gaseous mixture at a first pressure into a reactor containing a modified alumina adsorbent maintained at a temperature ranging from 100 C and 500 C to adsorb CO[sub 2] to provide a CO[sub 2] laden alumina adsorbent and a CO[sub 2] depleted gaseous mixture and contacting the CO[sub 2] laden adsorbent with a weakly adsorbing purge fluid at a second pressure which is lower than the first pressure to desorb CO[sub 2] from the CO[sub 2] laden alumina adsorbent. The modified alumina adsorbent which is formed by depositing a solution having a pH of 3.0 or more onto alumina and heating the alumina to a temperature ranging from 100 C and 600 C, is not degraded by high concentrations of water under process operating conditions. 1 fig.

  19. Carbon dioxide pressure swing adsorption process using modified alumina adsorbents

    DOEpatents

    Gaffney, Thomas Richard; Golden, Timothy Christopher; Mayorga, Steven Gerard; Brzozowski, Jeffrey Richard; Taylor, Fred William

    1999-01-01

    A pressure swing adsorption process for absorbing CO.sub.2 from a gaseous mixture containing CO.sub.2 comprising introducing the gaseous mixture at a first pressure into a reactor containing a modified alumina adsorbent maintained at a temperature ranging from 100.degree. C. and 500.degree. C. to adsorb CO.sub.2 to provide a CO.sub.2 laden alumina adsorbent and a CO.sub.2 depleted gaseous mixture and contacting the CO.sub.2 laden adsorbent with a weakly adsorbing purge fluid at a second pressure which is lower than the first pressure to desorb CO.sub.2 from the CO.sub.2 laden alumina adsorbent. The modified alumina adsorbent which is formed by depositing a solution having a pH of 3.0 or more onto alumina and heating the alumina to a temperature ranging from 100.degree. C. and 600.degree. C., is not degraded by high concentrations of water under process operating conditions.

  20. Production and characterization of alumina-titania biocomposite

    NASA Astrophysics Data System (ADS)

    Cetiner, B. N.; Erkmen, Z. E.

    2015-03-01

    Alumina is a biomaterial of choice for more than 20 years due to its high hardness accompanied by low friction, wear and inertness to in vivo environment. It has been reported that titanium oxidized to the rutile phase is bioactive. This is a property discovered for certain ceramics such as Bioglass and sintered hydroxylapatite (HA). But the combination of alumina and titania forming tialite (Aluminium titanate-50 mol % Al2O3 and 50 mol % TiO2) is a new challenge. In this work we made firstly the beneficiation of the Seydişehir alumina by leaching it in the acidic solution "the Aqua Regia" followed by preparation of batches containing 2,5 wt %, 3,5 wt % and 4,5 wt % of MgO as the sintering aid, 1 wt % of SiO2 and the balance; the alumina and titania powder mixture (1:1 mole). After sintering these batches at 1600°C for about 12 h, their mechanical properties (the compression and hardness testings) and phase ratios (the XRD analysis) were analyzed and compared with the control group containing the laboratory scale alumina instead of the Seydişehir alumina. Following the characterization (the SEM and the EDS analysis) of the substrate material, the comparison of two different materials was carried out.

  1. Porous alumina and zirconia ceramics with tailored thermal conductivity

    NASA Astrophysics Data System (ADS)

    Gregorová, E.; Pabst, W.; Sofer, Z.; Jankovský, O.; Matějíček, J.

    2012-11-01

    The thermal conductivity of porous ceramics can be tailored by slip casting and uniaxial dry pressing, using either fugitive pore formers (saccharides) or partial sintering. Porous alumina and zirconia ceramics have been prepared using appropriate powder types (ungranulated for casting, granulated for pressing) and identical firing regimes (but different maximum temperatures in the case of partial sintering). Thermal diffusivities have been measured by the laser- and xenon-flash method and transformed into relative thermal conductivities, which enable a temperature-independent comparison between different materials. While the porosity can be controlled in a similar way for both materials when using pore formers, partial sintering exhibits characteristic differences between alumina and zirconia (for alumina porosities below 45 %, full density above 1600 °C, for zirconia porosities below 60 %, full density above 1300 °C). The different compaction behavior of alumina and zirconia (porosity after pressing 0.465 and 0.597, respectively) is reflected in the fact that for alumina the relative conductivity data of partially sintered materials are below the exponential prediction, while for zirconia they coincide with the latter. Notwithstanding these characteristic differences, for both alumina and zirconia it is possible to tailor the thermal conductivity from 100 % down to approx. 15 % of the solid phase value.

  2. Dynamic yield and tensile strengths of spark plasma sintered alumina

    NASA Astrophysics Data System (ADS)

    Girlitsky, I.; Zaretsky, E.; Kalabukhov, S.; Dariel, M.; Frage, N.

    2014-05-01

    Fully dense alumina samples with 0.6 μm grain size were produced from alumina powder using Spark Plasma Sintering and tested in two types of VISAR-instrumented planar impact tests. In the tests of the first type the samples of 0.28 to 6-mm thickness were loaded by 1-mm tungsten impactors accelerated up to a velocity of about 1 km/s. These tests were aimed to study the Hugoniot elastic limit (HEL) of the SPS-processed alumina and the decay of the elastic precursor wave with propagation distance. In the second type of test the samples of ~3-mm thickness were loaded by 1-mm copper impactors accelerated up to velocities 100-1000 m/s. These tests were aimed to study the dynamic tensile (spall) strength of the alumina. The data on tensile fracture of the alumina demonstrate a monotonic decline of the spall strength with the amplitude of the loading stress pulse. The data on the decay of the elastic precursor wave allows for determining the rates of the irreversible (inelastic) strains in the SPS-processed alumina at the initial stages of shock-induced inelastic deformation and, thus, to derive some conclusions concerning the mechanisms responsible of the deformation.

  3. Dynamic yield and tensile strengths of spark plasma sintered alumina

    NASA Astrophysics Data System (ADS)

    Girlitsky, Inna; Zaretsky, E.; Kalabukhov, S.; Dariel, M.; Frage, N.

    2013-06-01

    Fully dense alumina samples with 0.6- μ grain size were produced from alumina powder using Spark Plasma Sintering and tested in two types of VISAR-instrumented planar impact tests.. In the tests of the first type the samples of 0.28 to 6-mm thickness were loaded by 1-mm tungsten impactors accelerated up to velocity of about 1 km/s. These tests were aimed to study of the Hugoniot elastic limit (HEL) of the SPS-processed alumina and the decay of the elastic precursor wave with the propagation distance. In the second type of the tests the samples of ~ 3-mm thickness were loaded by 1-mm copper impactors accelerated up to velocities 100-1000 m/s was. These tests were aimed to the study of the dynamic tensile (spall) strength of the alumina. The data on the decay of the elastic precursor wave allow determining the rates of the irreversible (inelastic) strains in the SPS-processed alumina at the initial stages of the shock-induced plastic deformation and, thus, to derive some conclusions concerning the mechanisms responsible of the deformation. The data on the tensile fracture of the alumina demonstrate a monotonous decline of the spall strength with the amplitude of the loading stress pulse.

  4. Wetting and strength issues at Al/alpha-alumina interfaces

    SciTech Connect

    Saiz, Eduardo; Tomsia, Antoni P.; Suganuma, Katsuaki

    2003-04-15

    The wetting behavior and strength at aluminum/alumina interfaces has been an active subject of research. Al/alumina applications include ceramic-metal composites and several applications for electronic industries. In this paper the interface strength and microstructure of Al/alpha-alumina was investigated. We discovered that in a solid-state joining, the strength of the joint increases with increasing joining temperature. In a liquid-state joining, the strength of the joint gradually decreases due to the formation of unbonded areas. The strength, sigma sub b, is expressed by the following equation as a function of unbonded area, A: sigma sub b = 2.22 A + 143 (70 percent {le} A {le} 100 percent). The highest strength reached 400 MPa when the interface was formed at around the melting temperature of aluminum. An aluminum layer close to the interface became a single crystal when it was bonded to a sapphire. The following crystallographic orientation relationship is established: (1{bar 1}1){sub Al}//(001){sub {alpha}}-Al{sub 2} O{sub 3}, (110){sub Al}//<100>{sub {alpha}}-Al{sub 2}O{sub 3}. Amorphous alumina islands were formed at the interface. In the amorphous alumina, gamma-alumina nanocrystals grew from the sapphire, with the same orientation relationship to sapphire as above.

  5. Edge-defined film-fed growth of beta-alumina and Mg-substituted beta-alumina

    NASA Technical Reports Server (NTRS)

    Morrison, A. D.; Stormont, R. W.; Cocks, F. H.

    1975-01-01

    High Na vapor pressure, peritectic decomposition, and high reactivity of the melt complicate the growth of beta-alumina crystals. These difficulties were overcome by using a high-pressure (300 psig) growth chamber, Na2O-rich melts, and Ir for all surfaces in contact with the melt. These procedures were combined with the edge-defined film-fed growth technique to produce single-crystal beta-alumina tubes and ribbons.

  6. Effect of alumina composition and surface integrity in alumina/epoxy composites on the ultrasonic attenuation properties.

    PubMed

    Cho, Eikhyun; Park, Gwanwoo; Lee, Jae-Wan; Cho, Sung-Min; Kim, Taekyung; Kim, Joongeok; Choi, Wonjoon; Ohm, Won-Suk; Kang, Shinill

    2016-03-01

    We report a method of fabricating backing blocks for ultrasonic imaging transducers, using alumina/epoxy composites. Backing blocks contain scatterers such as alumina particles interspersed in the epoxy matrix for the effective scattering and attenuation of ultrasound. Here, the surface integrity can be an issue, where the composite material may be damaged during machining because of differences in strength, hardness and brittleness of the hard alumina particles and the soft epoxy matrix. Poor surface integrity results in the formation of air cavities between the backing block and the piezoelectric element upon assembly, hence the increased reflection off the backing block and the eventual degradation in image quality. Furthermore, with an issue of poor surface integrity due to machining, it is difficult to increase alumina as scatterers more than a specific mass fraction ratio. In this study, we increased the portion of alumina within epoxy matrix by obtaining an enhanced surface integrity using a net shape fabrication method, and verified that this method could allow us to achieve higher ultrasonic attenuation. Backing blocks were net-shaped with various mass fractions of alumina to characterize the formability and the mechanical properties, including hardness, surface roughness and the internal micro-structure, which were compared with those of machined backing blocks. The ultrasonic attenuation property of the backing blocks was also measured.

  7. Microstructure evolution and densification of alumina in liquid phase sintering

    NASA Astrophysics Data System (ADS)

    Dong, Weimin

    The microstructure evolution and densification of alumina during liquid phase sintering were quantified. Quantification included the evolution of pore-size distribution, the redistribution of liquid phase, the densification kinetics, and the fraction of closed and open pores. The results revealed that the small and large pores were filled simultaneously. This is inconsistent with Shaw's model in which liquid fills preferentially the smaller low-coordination-number pores in order to reach a low-energy configuration. The results also recommended that the pressure build-up of the trapped gases in pores due to the closure of open pores might have a significantly negative contribution to the driving force, and consequently cause the termination of the densification of alumina. To demonstrate whether the trapped gases played an important role in the microstructure evolution and the densification of alumina during liquid phase sintering, the following two experiments have been conducted. First, alumina preforms containing artificial pores were penetrated by glass. The results indicated that the trapped gases in pores had a considerable influence on the pore filling process, and ultimately caused the termination of the densification of the alumina preforms. Second, alumina compacts containing different amount of glass were sintered in vacuum. The alumina compact containing 20 vol. % reached full density during vacuum sintering, indicating that the pressure build-up of the trapped gases in pores was the main factor causing the termination of the densification of alumina in the final stage of liquid phase sintering. The limiting relative densities of compacts were calculated theoretically on the basis of a comprehensive analysis of the variation of the capillary pressure and gas pressure in pores with pore size and pore number. The capillary pressure and gas pressure in alumina compact during liquid phase sintering were analyzed on the basis of the above theoretical models

  8. Joining of alumina by vacuum brazing

    NASA Astrophysics Data System (ADS)

    Heikinheimo, Liisa; Siren, Mika; Kauppinen, Pentti

    1993-08-01

    The active brazing method for diffusion bonding of ceramics to metals is addressed. This method is very flexible compared to the traditional Mo-manganese coating with subsequent brazing that includes four process steps: in active brazing the process is done in one step. The joint properties are favorable, the residual stress build up is limited if the braze is correctly selected and the thermal cycle is controlled, and the resulting strength and leak tightness are good. In experimental work the joinability of alumina to titanium and Ni superalloys was studied by wetting experiments, nondestructive test and shear strength measurements. The spreading of the braze is affected not only by the surface conditions of mating materials but also by the type of the brazing alloy. The Ag-Cu base alloys give better wetting, strength and leak tightness properties than the Ag base alloys. A shear test method was developed for the mechanical testing of metal-ceramic joints. However, the sample geometry affects the measured values, namely a smaller specimen size provides better results. The correlation between the C-SAM results, which describe the ratio between the true bonded area and unbonded area, and measured shear strength values is presented. The dependence between the measured strength and the area of the joint defects becomes obvious and should be studied in more detail.

  9. Thermal Conductivity of Alumina and Silica Nanofluids

    NASA Astrophysics Data System (ADS)

    Castellanos, Julian G. Bernal

    This thesis studies the effects of the base fluid, particle type/size, and volumetric concentration on the thermal conductivity of Alumina and Silica nanofluids. The effects of base fluid were observed by preparing samples using ethylene glycol (EG), water, and mixtures of EG/water as the base fluid and Al2O3 (10 nm) nanoparticles. The particles type/size and volumetric concentration effects were tested by preparing samples of nanofluids using Al2O3 (10nm), Al2O3 (150nm), SiO2 (15 nm), and SiO2 (80 nm) nanoparticles and ionized water as base fluid at different volumetric concentrations. All samples were mixed using a sonicator for 30 minutes and a water circulator to maintain the sample at room temperature. The thermal conductivity was measured using a Thermtest Transient Plane Source TPS 500S. The effects of gravity, Brownian motion and thermophoresis were also studied. EG produced the highest thermal conductivity enhancement out of all base fluids tested. Smaller particle size produced a higher enhancement of thermal conductivity, while the volumetric concentration did not have a significant effect in the thermal conductivity enhancement. Finally, gravity, Brownian diffusion and thermophoresis effects played a role in the total enhancement of the thermal conductivity. The nanoparticles were observed to settle rapidly after sonication suggesting gravity effects may play a significant role.

  10. Cast alumina forming austenitic stainless steels

    DOEpatents

    Muralidharan, Govindarajan; Yamamoto, Yukinori; Brady, Michael P

    2013-04-30

    An austenitic stainless steel alloy consisting essentially of, in terms of weight percent ranges 0.15-0.5C; 8-37Ni; 10-25Cr; 2.5-5Al; greater than 0.6, up to 2.5 total of at least one element selected from the group consisting of Nb and Ta; up to 3Mo; up to 3Co; up to 1W; up to 3Cu; up to 15Mn; up to 2Si; up to 0.15B; up to 0.05P; up to 1 total of at least one element selected from the group consisting of Y, La, Ce, Hf, and Zr; <0.3Ti+V; <0.03N; and, balance Fe, where the weight percent Fe is greater than the weight percent Ni, and wherein the alloy forms an external continuous scale comprising alumina, and a stable essentially single phase FCC austenitic matrix microstructure, the austenitic matrix being essentially delta-ferrite free and essentially BCC-phase-free. A method of making austenitic stainless steel alloys is also disclosed.

  11. Annealing Would Improve beta" - Alumina Solid Electrolyte

    NASA Technical Reports Server (NTRS)

    Williams, Roger; Homer, Margie; Ryan, Margaret; Cortez, Roger; Shields, Virgil; Kisor, Adam

    2003-01-01

    A pre-operational annealing process is under investigation as a potential means of preventing a sudden reduction of ionic conductivity in a Beta"-alumina solid electrolyte (BASE) during use. On the basis of tests, the sudden reduction of ionic conductivity, followed by a slow recovery, has been found to occur during testing of the solid electrolyte and electrode components of an alkali metal thermal-to-electric converter (AMTEC) cell. At this time, high-temperature tests of limited duration have indicated the superiority of the treated BASE, but reproducible tests over thousands of hours are necessary to confirm that microcracking has been eliminated. The ionic conductivity of the treated BASE is also measured to be higher than untreated BASE at 1,073 K in low-pressure sodium vapor. Microcracking resulting in loss of conductivity was not observed with treated BASE in one high-temperature experiment, but this result must be duplicated over very long testing times to be sure of the effect. Shorter annealing times (10 to 20 hours) were found to result in significantly less loss of mass; it may be necessary for the packed powder mixture to evolve some Na2O before the Na2O can leave the ceramic.

  12. Mechanical properties of alumina porcelain during heating

    NASA Astrophysics Data System (ADS)

    Šín, Peter; Podoba, Rudolf; ŠtubÅa, Igor; Trník, Anton

    2014-11-01

    The mechanical strength and Young's modulus of green alumina porcelain (50 wt. % of kaolin, 25 wt. % of Al2O3, and 25 wt. % of feldspar) were measured during heating up to 900 °C and 1100 °C, respectively. To this end, we used the three point-bending method and modulated force thermomechanical analysis (mf-TMA). The loss liberation - of the physically bound water (20 - 250 °C) strengthens the sample and Young's modulus increases its values significantly. The dehydroxylation that takes place in the range of 400 - 650 °C causes a slight decrease in Young's modulus. On the other hand, the mechanical strength slightly increases in this temperature range, although it has a sudden drop at 420 °C. Beyond the dehydroxylation range, above 650 °C, both Young's modulus and mechanical strength increase. Above 950 °C, a sharp increase of Young's modulus is caused by the solid-state sintering and the new structure created by the high-temperature reactions in metakaolinite.

  13. Ion polarization behavior in alumina under pulsed gate bias stress

    NASA Astrophysics Data System (ADS)

    Liu, Yu; Diallo, Abdou Karim; Katz, Howard E.

    2015-03-01

    Alkali metal ion incorporation in alumina significantly increases alumina capacitance by ion polarization. With high capacitance, ion-incorporated aluminas become promising high dielectric constant (high-k) gate dielectric materials in field-effect transistors (FETs) to enable reduced operating voltage, using oxide or organic semiconductors. Alumina capacitance can be manipulated by incorporation of alkali metal ions, including potassium (K+), sodium (Na+), and lithium (Li+), having different bond strengths with oxygen. To investigate the electrical stability of zinc tin oxide-based transistors using ion incorporated alumina as gate dielectrics, pulsed biases at different duty cycles (20%, 10%, and 2% representing 5 ms, 10 ms, and 50 ms periods, respectively) were applied to the gate electrode, sweeping the gate voltage over series of these cycles. We observed a particular bias stress-induced decrease of saturation field-effect mobility accompanied by threshold voltage shifts (ΔVth) in potassium and sodium-incorporated alumina (abbreviated as PA and SA)-based FETs at high duty cycle that persisted over multiple gate voltage sweeps, suggesting a possible creation of new defects in the semiconductor. This conclusion is also supported by the greater change in the mobility-capacitance (μC) product than in capacitance itself. Moreover, a more pronounced ΔVth over shorter times was observed in lithium-incorporated alumina (abbreviated as LA)-based transistors, suggesting trapping of electrons in existing interfacial states. ΔVth from multiple gate voltage sweeps over time were fit to stretched exponential forms. All three dielectrics show good stability using 50-ms intervals (20-Hz frequencies), corresponding to 2% duty cycles.

  14. Ion polarization behavior in alumina under pulsed gate bias stress

    SciTech Connect

    Liu, Yu; Diallo, Abdou Karim; Katz, Howard E.

    2015-03-16

    Alkali metal ion incorporation in alumina significantly increases alumina capacitance by ion polarization. With high capacitance, ion-incorporated aluminas become promising high dielectric constant (high-k) gate dielectric materials in field-effect transistors (FETs) to enable reduced operating voltage, using oxide or organic semiconductors. Alumina capacitance can be manipulated by incorporation of alkali metal ions, including potassium (K{sup +}), sodium (Na{sup +}), and lithium (Li{sup +}), having different bond strengths with oxygen. To investigate the electrical stability of zinc tin oxide-based transistors using ion incorporated alumina as gate dielectrics, pulsed biases at different duty cycles (20%, 10%, and 2% representing 5 ms, 10 ms, and 50 ms periods, respectively) were applied to the gate electrode, sweeping the gate voltage over series of these cycles. We observed a particular bias stress-induced decrease of saturation field-effect mobility accompanied by threshold voltage shifts (ΔV{sub th}) in potassium and sodium-incorporated alumina (abbreviated as PA and SA)-based FETs at high duty cycle that persisted over multiple gate voltage sweeps, suggesting a possible creation of new defects in the semiconductor. This conclusion is also supported by the greater change in the mobility-capacitance (μC) product than in capacitance itself. Moreover, a more pronounced ΔV{sub th} over shorter times was observed in lithium-incorporated alumina (abbreviated as LA)-based transistors, suggesting trapping of electrons in existing interfacial states. ΔV{sub th} from multiple gate voltage sweeps over time were fit to stretched exponential forms. All three dielectrics show good stability using 50-ms intervals (20-Hz frequencies), corresponding to 2% duty cycles.

  15. Corrosion resistance characterization of porous alumina membrane supports

    SciTech Connect

    Dong Yingchao; Lin Bin; Zhou Jianer; Zhang Xiaozhen; Ling Yihan; Liu Xingqin; Meng Guangyao; Hampshire, Stuart

    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.

  16. The mechanical reliability of alumina scales and coatings

    SciTech Connect

    Alexander, K.B.; Pruebner, K.; Tortorelli, P.F.

    1996-08-01

    The mechanical integrity of oxide scales ultimately determines their ability to protect materials from corrosion and other environmental effects arising from deleterious reactions with gases and condensable products. The microstructure and mechanical behavior of alumina products thermally grown or deposited on Fe-28 at.% Al intermetallic alloys are being characterized in order to develop the knowledge and means to control the mechanical reliability of alumina scales by microstructural manipulation through design and processing. Mechanical characterization involved gravimetric data from cyclic oxidation experiments, in-situ observation of oxidized specimens undergoing flexural loading in a scanning electron microscope, and measurements of hardness, elastic modulus and cracking resistance by nanoindentation. Values of cracking thresholds for Al{sub 2}O{sub 3} scales were consistent with other measurements for surface and bulk alumina. The oxidation behavior of Fe{sub 3}Al alloys coated with a thin (0.5 - 1 {mu}m) alumina film deposited by plasma synthesis has been studied. During exposure in the oxidizing environment, new oxide was formed between the coating and the substrate. The presence of the deposited amorphous oxide inhibited the subsequent thermal oxidation of the metal. Because the thermally grown alumina forms under the deposit, the adherence of the coating is controlled by the strength of the metal/oxide interface that develops during oxidation.

  17. Enriched fluoride sorption using alumina/chitosan composite.

    PubMed

    Viswanathan, Natrayasamy; Meenakshi, S

    2010-06-15

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

  18. Biocompatibility of atomic layer-deposited alumina thin films.

    PubMed

    Finch, Dudley S; Oreskovic, Tammy; Ramadurai, Krishna; Herrmann, Cari F; George, Steven M; Mahajan, Roop L

    2008-10-01

    Presented in this paper is a study of the biocompatibility of an atomic layer-deposited (ALD) alumina (Al2O3) thin film and an ALD hydrophobic coating on standard glass cover slips. The pure ALD alumina coating exhibited a water contact angle of 55 degrees +/- 5 degrees attributed, in part, to a high concentration of -OH groups on the surface. In contrast, the hydrophobic coating (tridecafluoro-1,1,2,2-tetrahydro-octyl-methyl-bis(dimethylamino)silane) had a water contact angle of 108 degrees +/- 2 degrees. Observations using differential interference contrast microscopy on human coronary artery smooth muscle cells showed normal cell proliferation on both the ALD alumina and hydrophobic coatings when compared to cells grown on control substrates. These observations suggested good biocompatibility over a period of 7 days in vitro. Using a colorimetric assay technique to assess cell viability, the cellular response between the three substrates can be differentiated to show that the ALD alumina coating is more biocompatible and that the hydrophobic coating is less biocompatible when compared to the control. These results suggest that patterning a substrate with hydrophilic and hydrophobic groups can control cell growth. This patterning can further enhance the known advantages of ALD alumina, such as conformality and excellent dielectric properties for bio-micro electro mechanical systems (Bio-MEMS) in sensors, actuators, and microfluidics devices.

  19. The nature of hydrogen in γ-alumina

    SciTech Connect

    Li, Yunguo Lousada, Cláudio M. Korzhavyi, Pavel A.

    2014-05-28

    Gibbs free energy models are derived from the calculated electronic and phonon structure of two possible models of γ-alumina, a defective spinel phase and a hydrogenated spinel phase. The intrinsic vacancies and hydrogen in the two structural models give rise to a considerable configurational (residual) entropy and significantly contribute to thermodynamic stability and physical-chemical properties of γ-alumina, which was neglected in previous studies but considered in this work. The electronic densities of states, calculated using a hybrid functional for the two structural models of γ-alumina, are presented. The dynamic stability of the two phases is confirmed by full-spectrum phonon calculations. The two phases share many similarities in their electronic structure, but can be distinguished by their vibrational spectra and specific heat. The defective spinel is found to be the ground state of γ-alumina, while the hydrogenated spinel to be a metastable phase. However, dehydration of the metastable phase into the ground state is expected to be slow due to the low diffusion rate of H, which leaves hydrogen as a locked-in impurity in γ-alumina.

  20. Effect of humic acid on sorption of technetium by alumina.

    PubMed

    Kumar, S; Rawat, N; Kar, A S; Tomar, B S; Manchanda, V K

    2011-09-15

    Sorption of technetium by alumina has been studied in absence as well as in presence of humic acid using (95)Tc(m) as a tracer. Measurements were carried out at fixed ionic strength (0.1M NaClO(4)) under varying pH (3-10) as well as redox (aerobic and reducing anaerobic) conditions. Under aerobic conditions, negligible sorption of technetium was observed onto alumina both in absence and in presence of humic acid. However, under reducing conditions (simulated with [Sn(II)] = 10(-6)M), presence of humic acid enhanced the sorption of technetium in the low pH region significantly and decreased at higher pH with respect to that in absence of humic acid. Linear additive as well as surface complexation modeling of Tc(IV) sorption in presence of humic acid indicated the predominant role of sorbed humic acid in deciding technetium sorption onto alumina.

  1. The surface reaction kinetics of salicylate on alumina

    SciTech Connect

    Wang, Z.; Ainsworth, C.C.; Friedrich, D.M.; Joly, A.G.; Gassman, P.L.

    1997-12-31

    The kinetics of reaction of salicylate with colloidal alumina in aqueous suspension and with Al(III) in homogeneous aqueous solution were studied by stopped-flow laser fluorescence spectroscopy. The emission spectra confirmed the formation of both monodentate complexes and more stable bidentate chelates. Temporal evolution of the spectra indicated that the reaction was fast (within first few minutes) for both the homogeneous and heterogeneous reactions but slowed down afterwards for the latter. Reactions completed within 10 minutes in homogeneous phase at pH 3.3 but took more than 12 hours in alumina suspension. Analysis of the fluorescence intensity within first four minutes showed that in homogeneous phase the reaction followed a single pseudo-first-order kinetics. In alumina suspension log plots were nonlinear and characteristic of multiple heterogeneous reaction paths. The kinetics are interpreted in terms of the simultaneous formation of multiple species as well as subsequent conversion between species.

  2. Alumina composites for oxide/oxide fibrous monoliths

    SciTech Connect

    Cruse, T. A.; Polzin, B. J.; Picciolo, J. J.; Singh, D.; Tsaliagos, R. N.; Goretta, K. C.

    2000-03-01

    Most work on ceramic fibrous monoliths (FMs) has focused on the Si{sub 3}N{sub 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.

  3. Origin of High-Alumina Basalt, Andesite, and Dacite Magmas.

    PubMed

    Hamilton, W

    1964-10-30

    The typical volcanic rocks of most island arcs and eugeosynclines, and of some continental environments, are basalt, andesite, and dacite, of high alumina content. The high-alumina basalt differs from tholeiitic basalt primarily in having a greater content of the components of calcic plagioclase. Laboratory data indicate that in the upper mantle, below the level at which the basaltic component of mantle rock is transformed by pressure to eclogite or pyroxenite, the entire basaltic portion probably is melted within a narrow temperature range, but that above the level of that transformation plagioclase is melted selectively before pyroxene over a wide temperature range. The broad spectrum of high-alumina magmas may represent widely varying degrees of partial melting above the transformation level, whereas narrow-spectrum tholeiite magma may represent more complete melting beneath it.

  4. Plastic deformation and sintering of alumina under high pressure

    SciTech Connect

    Liu, Fangming; Liu, Pingping; Wang, Haikuo; Xu, Chao; Yin, Shuai; Yin, Wenwen; Li, Yong; He, Duanwei

    2013-12-21

    Plastic deformation of alumina (Al{sub 2}O{sub 3}) under high pressure was investigated by observing the shape changes of spherical particles, and the near fully dense transparent bulks were prepared at around 5.5 GPa and 900 °C. Through analyzing the deformation features, densities, and residual micro-strain of the Al{sub 2}O{sub 3} compacts prepared under high pressures and temperatures (2.0–5.5 GPa and 600–1200 °C), the effects of plastic deformation on the sintering behavior of alumina have been demonstrated. Under compression, the microscopic deviatoric stress caused by grain-to-grain contact could initiate the plastic deformation of individual particles, eliminate pores of the polycrystalline samples, and enhance the local atomic diffusion at the grain boundaries, thus produced transparent alumina bulks.

  5. Molecular dynamics studies of interfacial water at the alumina surface.

    SciTech Connect

    Argyris, Dr. Dimitrios; Ho, Thomas; Cole, David

    2011-01-01

    Interfacial water properties at the alumina surface were investigated via all-atom equilibrium molecular dynamics simulations at ambient temperature. Al-terminated and OH-terminated alumina surfaces were considered to assess the structural and dynamic behavior of the first few hydration layers in contact with the substrates. Density profiles suggest water layering up to {approx}10 {angstrom} from the solid substrate. Planar density distribution data indicate that water molecules in the first interfacial layer are organized in well-defined patterns dictated by the atomic terminations of the alumina surface. Interfacial water exhibits preferential orientation and delayed dynamics compared to bulk water. Water exhibits bulk-like behavior at distances greater than {approx}10 {angstrom} from the substrate. The formation of an extended hydrogen bond network within the first few hydration layers illustrates the significance of water?water interactions on the structural properties at the interface.

  6. Fabrication of alumina films with laminated structures by ac anodization

    PubMed Central

    Segawa, Hiroyo; Okano, Hironaga; Wada, Kenji; Inoue, Satoru

    2014-01-01

    Anodization techniques by alternating current (ac) are introduced in this review. By using ac anodization, laminated alumina films are fabricated. Different types of alumina films consisting of 50–200 nm layers were obtained by varying both the ac power supply and the electrolyte. The total film thickness increased with an increase in the total charge transferred. The thickness of the individual layers increased with the ac voltage; however, the anodization time had little effect on the film thickness. The laminated alumina films resembled the nacre structure of shells, and the different morphologies exhibited by bivalves and spiral shells could be replicated by controlling the rate of increase of the applied potentials. PMID:27877636

  7. Modifying alumina red mud to support a revegetation cover

    NASA Astrophysics Data System (ADS)

    Xenidis, A.; Harokopou, A. D.; Mylona, E.; Brofas, G.

    2005-02-01

    Alumina red mud, a fine-textured, iron-rich, alkaline residue, is the major waste product of bauxite digestion with caustic soda to remove alumina. The high alkalinity and salinity as well as the poor nutrient status are considered to be the major constraints of red mud revegetation. This research was conducted to evaluate the ameliorating effect of gypsum, sewage sludge, ferrous sulfate, ammonium sulfate, ammonium nitrate, and calcium phosphate on alumina red mud. The effectiveness of the mixtures was evaluated by applying extraction tests and performing experiments using six plant species. Gypsum amendment significantly reduced the pH, electrical conductivity, and sodium and aluminum content of red mud. Sewage sludge application had an extended effect in improving both the soil structure and the nutrient status of the gypsum-amended red mud. Together with the gypsum and sewage sludge, calcium phosphate application into red mud enhanced plant growth and gave the most promising results.

  8. Characteristics of alumina particles in dispersion-strengthened copper alloys

    NASA Astrophysics Data System (ADS)

    Zhang, Xue-hui; Li, Xiao-xian

    2014-11-01

    Two types of alumina dispersion-strengthened copper (ADSC) alloys were fabricated by a novel in-situ reactive synthesis (IRS) and a traditional internal oxidation (IO) process. The features of alumina dispersoids in these ADSC alloys were investigated by X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy. It is found that nano-sized γ-Al2O3 particles of approximately 10 nm in diameter are homogeneously distributed in the IRS-ADSC composites. Meanwhile, larger-sized, mixed crystal structure alumina with rod-shaped morphology is embedded in the IO-ADSC alloy. The IRS-ADSC composites can obtain better mechanical and physical properties than the IO-ADSC composites; the tensile strength of the IRS-ADSC alloy can reach 570 MPa at room temperature, its electrical conductivity is 85% IACS, and the Rockwell hardness can reach 86 HRB.

  9. Factors contributing to the breakdown of sodium beta-alumina

    SciTech Connect

    Buechele, A.C.

    1982-05-01

    Clarification of the breakdown process occurring during charge transfer in sodium beta alumina solid electrolytes was derived from: (1) studying the effects of molten sodium contact at 350/sup 0/C on single crystal sodium beta alumina and polycrystalline sodium beta alumina; (2) determination of critical current density by monitoring acoustic emissions accompanying crack growth in sodium/sodium beta alumina/sodium cells subjected to linear current ramping at 1 mA cm/sup -2/ sec/sup -1/; (3) failure analysis conducted on cycled electrolytes, some from commercial sodium/sulfur cells, which had been subjected to up to 703 Ahr cm/sup -2/ of charge transfer. Gray coloration developing in beta aluminas in contact with molten sodium was found to be a consequence of formation, through reduction by sodium, of oxygen vacancies charge compensated by electrons. Electronic conductivity of the electrolyte increases as a result. No second phase formation was detected. Colored electrolytes from sodium/sulfur cells show evidence of a newly recognized degradation mechanism in which fracture occurs when sodium is reduced and deposited internally under pressure as metal in regions where an electronic conductivity gradient exists. Heating colored beta aluminas in air produces reoxidation and bleaching. Kinetics and other properties of the coloration and bleaching processes were determined. Critical current density was found to bear an inverse relation to average electrolyte grain size. Evidence was found in the cycled electrolytes for a slow crack growth mechanism and a progressive mode of degradation advancing from the sulfur electrode interface. Implications of the findings for the construction and operation of sodium/sulfur battery systems are discussed.

  10. Effects of atmospheres on bonding characteristics of silver and alumina

    SciTech Connect

    Kim, Jin Yong; Engelhard, Mark H.; Choi, Jung-Pyung; Weil, K. Scott

    2008-03-12

    Joints prepared using a silver-copper oxide based reactive air brazing (RAB) technique is known to experience a significant decrease in joint strength when exposed in a reducing atmosphere at high temperature. To investigate the effects of atmospheres on the bonding characteristics of ceramic joints brazed with Ag-CuO braze filler metals, alumina joints prepared using a series of Ag-CuO compositions were exposed to a reducing atmosphere in hydrogen and also reoxidized in air at 800°C. All the brazed joints exposed to hydrogen revealed significant reduction in flexural strength and exhibited debonding of the interface between the braze filler and the alumina substrate. In the case of the joints brazed with a braze filler containing a high copper content of 8 mol%, the formation of interfacial porosity caused by the reduction of interfacial oxide phases led to an extremely weak interface, which was not recovered after subsequent reoxidation in air at 800°C. However, no significant microstructural change or interfacial porosity formation was observed in the braze filler metals containing no or low copper contents, and the interface remained intact even though interfacial strength was weak. Subsequent reoxidation of the joints with these filler materials resulted in the recovery of interfacial strength and flexural strength. This result clearly indicates that the bonding characteristics of the silver/alumina interface are by and large influenced by atmospheres of high temperature exposure. XPS analysis conducted on the in-situ¬ fractured surfaces of as-brazed and hydrogen-treated samples prepared using a braze filler with 2 mol% Cu indicated that oxygen in the silver matrix plays a critical role in bond strength between silver and alumina. The sample exposed in inert atmosphere also revealed low flexural strength and debonding of the silver/alumina interface, confirming the role of oxygen on the bond strength between silver and alumina.

  11. Current Noise in Sodium Beta Alumina Ceramics and Single Crystals.

    DTIC Science & Technology

    1986-08-01

    AD-Ai7O 412 CURRENT NOISE IN SODIUM BETA ALUMINA CERAMICS AIND t/l SINGLE CRYSTALS(U) UTAH UNIV SALT LAKE CITY DEPT OF PHYSICS J J BROPHY’ 81 AUG 86...ZIP C-0- UNIVERSITY OF UTAH UNIVERSITY OF NEW MEXICO SALT LAKE CITY, UTAH 84112 Bandelier Hall West Albuquerque, NM 87131 go NAME OF FUNDING...bloeS nIumbe Conductivity fluctuations and contact noise observed in ceramic and single crystal silver 811 alumina are very pilar to those in sodium 8

  12. Atomistic force field for alumina fit to density functional theory

    SciTech Connect

    Sarsam, Joanne; Finnis, Michael W.; Tangney, Paul

    2013-11-28

    We present a force field for bulk alumina (Al{sub 2}O{sub 3}), which has been parametrized by fitting the energies, forces, and stresses of a large database of reference configurations to those calculated with density functional theory (DFT). We use a functional form that is simpler and computationally more efficient than some existing models of alumina parametrized by a similar technique. Nevertheless, we demonstrate an accuracy of our potential that is comparable to those existing models and to DFT. We present calculations of crystal structures and energies, elastic constants, phonon spectra, thermal expansion, and point defect formation energies.

  13. Fabrication and characterization of alumina tube by thermal spray forming

    NASA Astrophysics Data System (ADS)

    Mohammed, M. A.; Zaidan, Sh. A.; Smich, H. E.

    2017-02-01

    In the present study spray forming of alumina tube with a wall thickness of 0.4-0.6 mm and the diameter of 38-62 mm on graphite substrate with two different sizes of alumina feedstock powders was used for flame spraying to form matrix of Al2O3 structures which have been fabricated. A detailed characterization of the spray-formed Al2O3 structure has been performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), (AFM) and Micro Hardness measurements. This study proves that a variety of structured materials and their combinations can be fabricated to near net shapes.

  14. The influence of aluminum grain size on alumina nanoporous structure

    SciTech Connect

    Feil, A. F.; Costa, M. V. da; Amaral, L.; Teixeira, S. R.; Migowski, P.; Dupont, J.; Machado, G.; Peripolli, S. B.

    2010-01-15

    An approach to control the interpore distances and nanopore diameters of 150-nm-thick thin aluminum films is reported here. The Al thin films were grown by sputtering on p-type silicon substrate and anodized with a conventional anodization process in a phosphoric acid solution. It was found that interpore distance and pore diameter are related to the aluminum grain size and can be controlled by annealing. The grain contours limit the sizes of alumina cells. This mechanism is valid for grain sizes supporting only one alumina cell and consequently only one pore.

  15. Mechanical properties of tricalcium phosphate-alumina composites

    NASA Astrophysics Data System (ADS)

    Sakka, S.; Ben Ayed, F.; Bouaziz, J.

    2012-02-01

    Tricalcium phosphate and alumina powder were mixed in order to elaborate biphasic ceramics composites. This study deals to produce bioceramics composites sintered at various temperatures for differents times. The characterization of samples, before and after the sintering process was investigated, using X-Ray diffraction, scanning electronic microscopy, 31P and 27Al nuclear magnetic resonance and differential thermal analysis. Mechanical properties of biphasic composites were studied using Brazilian test. The tricalcium phosphate - 75 wt% alumina composites mechanical resistance increased with sintered temperature. The mechanical resistance reach it's optimum value (8.6 MPa) at 1550°C for two hours.

  16. Study on surface properties of gamma-alumina catalytic membrane

    SciTech Connect

    Mengchenu Lu; Guoxing Xiong; Bauser, H.

    1994-12-31

    In recent years, preparation and separation applications of gamma-alumina membranes have been extensively studied. In catalysis research field, this membrane can be used not only as a separating medium but also as a catalyst or catalyst support. In this paper, a gamma-alumina catalytic membrane was prepared by a sol-gel technique, then special attention was paid to its surface properties related to catalysis, its surface acidity, hydroxyl, microstructure and pore properties was studied by IR with pyridine adsorption, XRD and N{sub 2} adsorption at low temperature, 1-butanol dehydration as a probe reaction was used to study its reaction property.

  17. Structure factor changes in supercooled yttria-alumina

    SciTech Connect

    Wilding, Martin C.; Greaves, G. Neville; Quang Vu Van; Majerus, Odile; Hennet, Louis

    2009-01-29

    Changes in the structure factor of yttria-alumina liquids have been identified in the supercooled range. Different inter-polyhedral configurations between AlO{sub 4} and YO{sub 6} groups distinguish low density and high density liquid phases. The coexistence of phases at high temperatures have been identified in simultaneous measurements of small angle x-ray scattering.

  18. Formation of {gamma}-alumina nanorods in presence of alanine

    SciTech Connect

    Dabbagh, Hossein A.; Rasti, Elham; Yalfani, Mohammad S.; Medina, Francesc

    2011-02-15

    Graphical abstract: Nanorod aluminas with a possible hexagonal symmetry, high surface area and relatively narrow pore size distribution were obtained. Research highlights: {yields} Research highlights {yields} Boehmite was prepared using a green sol-gel process in the presence of alanine. {yields} Nanorod aluminas with a high surface area were obtained. {yields} Addition of alanine would shape the size of the holes and crevices. {yields} The morphologies of the nanorods were revealed by transmission electron microscope. -- Abstract: Boehmite and alumina nanostructures were prepared using a simple green sol-gel process in the presence of alanine in water medium at room temperature. The uncalcined (dried at 200 {sup o}C) and the calcined materials (at 500, 600 and 700 {sup o}C for 4 h) were characterized using XRD, TEM, SEM, N{sub 2} physisorption and TGA. Nanorod aluminas with a possible hexagonal symmetry, high surface area and relatively narrow pore size distribution were obtained. The surface area was enhanced and crystallization was retarded as the alanine content increased. The morphologies of the nanoparticles and nanorods were revealed by a transmission electron microscope (TEM).

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

    SciTech Connect

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

    2010-06-15

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

  20. Nanocomposite formed by titanium ion implantation into alumina

    SciTech Connect

    Spirin, R. E.; Salvadori, M. C. Teixeira, F. S.; Sgubin, L. G.; Cattani, M.; Brown, I. G.

    2014-11-14

    Composites of titanium nanoparticles in alumina were formed by ion implantation of titanium into alumina, and the surface electrical conductivity measured in situ as the implantation proceeded, thus generating curves of sheet conductivity as a function of dose. The implanted titanium self-conglomerates into nanoparticles, and the spatial dimensions of the buried nanocomposite layer can thus be estimated from the implantation depth profile. Rutherford backscattering spectrometry was performed to measure the implantation depth profile, and was in good agreement with the calculated profile. Transmission electron microscopy of the titanium-implanted alumina was used for direct visualization of the nanoparticles formed. The measured conductivity of the buried layer is explained by percolation theory. We determine that the saturation dose, φ{sub 0}, the maximum implantation dose for which the nanocomposite material still remains a composite, is φ{sub 0} = 2.2 × 10{sup 16 }cm{sup −2}, and the corresponding saturation conductivity is σ{sub 0} = 480 S/m. The percolation dose φ{sub c}, below which the nanocomposite still has basically the conductivity of the alumina matrix, was found to be φ{sub c} = 0.84 × 10{sup 16 }cm{sup −2}. The experimental results are discussed and compared with a percolation theory model.

  1. Tritiated alumina serves as reagent for self-labeling analysis

    NASA Technical Reports Server (NTRS)

    Erenrich, E. H.; Klein, P. D.

    1967-01-01

    Tritiated alumina, prepared by exchange of the surface hydroxyl groups with tritiated water, is a suitable reagent for exchange-labeling of specific compounds in low concentrations prior to chromatographic analysis. In a chromatographic column, it detects and measures submicrogram quantities of material.

  2. Osseointegration of alumina bioceramic granules: A comparative experimental study

    NASA Astrophysics Data System (ADS)

    Rerikh, V. V.; Avetisyan, A. R.; Zaydman, A. M.; Anikin, K. A.; Bataev, V. A.; Nikulina, A. A.; Sadovoy, M. A.; Aronov, A. M.; Semantsova, E. S.

    2016-08-01

    To perform a comparative analysis of osseointegration of bioceramic alumina-based granules, hydroxyapatite-based granules, and deproteinized bone granules. The experiment was conducted on 52 adult male Kyoto-Wistar rats weighing 350 to 520 g. The animals were divided into five matched groups that differed only in the type of an implanted material. The granules were implanted in the lumbar vertebral bodies and in the distal right femur of each laboratory animal. Two months after surgery, the animals were euthanized, followed by tissue sampling for morphological studies. An examination of specimens from the groups with implanted alumina granules revealed the newly formed trabecular bone with remodeling signs. The bone tissue filled the intragranular space, tightly adhering to the granule surface. There was no connective tissue capsule on the border between bone tissue and alumina granules. Cylindrical bioceramic alumina-based granules with an open internal channel have a higher strength surpassing than that of analogs and the osseointegration ability close to that of hydroxyapatite and deproteinized bone granules.

  3. Template synthesis of gold nanotubes in an anodic alumina membrane.

    PubMed

    Kohli, Punit; Wharton, John E; Braide, Otonye; Martin, Charles R

    2004-07-01

    Nanotube-containing membranes prepared by the template method show promise for use as highly selective filters for membrane-based chemical and biological separations. Most of the work to date has been done on gold nanotubes prepared by electroless deposition of Au within the pores of polymeric filtration membranes. These polymeric filters have very low porosities (< 1%), and, as a result, the flux through Au nanotube membranes based on these templates is very low. In contrast, the other popular template membranes-anodic aluminas-have high porosities-30% to 50%. In spite of this potential advantage of anodic alumina templates, there have been no reports of electrolessly plated Au nanotubes within the pores of these templates. This is because the electroless plating method used to deposit Au nanotubes in polymeric templates does not work in aluminas. We have developed a modified electroless plating strategy that can be used to deposit high-quality Au nanotubes within the pores of the alumina templates. We describe this new plating method here.

  4. On the electrical conductivity of Ti-implanted alumina

    SciTech Connect

    Salvadori, M. C.; Teixeira, F. S.; Cattani, M.; Nikolaev, A.; Savkin, K. P.; Oks, E. M.; Park, H.-K.; Phillips, L.; Yu, K. M.; Brown, I. G.

    2012-03-15

    Ion implantation of metal species into insulators provides a tool for the formation of thin, electrically conducting, surface layers with experimenter-controlled resistivity. High energy implantation of Pt and Ti into alumina accelerator components has been successfully employed to control high voltage surface breakdown in a number of cases. In the work described here we have carried out some basic investigations related to the origin of this phenomenon. By comparison of the results of alumina implanted with Ti at 75 keV with the results of prior investigations of polymers implanted with Pt at 49 eV and Au at 67 eV, we describe a physical model of the effect based on percolation theory and estimate the percolation parameters for the Ti-alumina composite. We estimate that the percolation dose threshold is about 4 x 10{sup 16} cm{sup -2} and the maximum dose for which the system remains an insulator-conductor composite is about 10 x 10{sup 16} cm{sup -2}. The saturation electrical conductivity is estimated to be about 50 S/m. We conclude that the observed electrical conductivity properties of Ti-implanted alumina can be satisfactorily described by percolation theory.

  5. Viscosity of alumina nanoparticles dispersed in car engine coolant

    SciTech Connect

    Kole, Madhusree; Dey, T.K.

    2010-09-15

    The present paper, describes our experimental results on the viscosity of the nanofluid prepared by dispersing alumina nanoparticles (<50 nm) in commercial car coolant. The nanofluid prepared with calculated amount of oleic acid (surfactant) was tested to be stable for more than 80 days. The viscosity of the nanofluids is measured both as a function of alumina volume fraction and temperature between 10 and 50 C. While the pure base fluid display Newtonian behavior over the measured temperature, it transforms to a non-Newtonian fluid with addition of a small amount of alumina nanoparticles. Our results show that viscosity of the nanofluid increases with increasing nanoparticle concentration and decreases with increase in temperature. Most of the frequently used classical models severely under predict the measured viscosity. Volume fraction dependence of the nanofluid viscosity, however, is predicted fairly well on the basis of a recently reported theoretical model for nanofluids that takes into account the effect of Brownian motion of nanoparticles in the nanofluid. The temperature dependence of the viscosity of engine coolant based alumina nanofluids obeys the empirical correlation of the type: log ({mu}{sub nf}) = A exp(BT), proposed earlier by Namburu et al. (author)

  6. Experiments on individual alumina-supported adatoms and clusters

    NASA Astrophysics Data System (ADS)

    Nilius, N.; Cörper, A.; Bozdech, G.; Ernst, N.; Freund, H.-J.

    2001-08-01

    To contribute to an understanding of growth conditions and electronic properties of metal clusters on technologically relevant oxides we have examined the mobility of individual, alumina-supported Pt-adatoms and the optical properties of single supported Ag-clusters. Using field-ion microscopy (FIM) we have prepared and imaged an individual Pt-adatom at approximately 40 K, both on the apex plane of a [1 1 0]-oriented NiAl tip and on a thin alumina film, grown on the same NiAl specimen by oxidation. On the alumina film, the onset temperature for Pt surface diffusion approaches 100 K being distinctively lower than the value 165 K measured on NiAl(1 1 0). Employing the tip of a scanning tunneling microscope (STM) as a local electron source, photon emission from individual, alumina-supported Ag-clusters was spectroscopically analyzed. The occurrence of a distinct emission line is explained by the decay of a collective electron oscillation (Mie-plasmon resonance). For decreasing Ag-cluster diameter, the emission lines (i) shift to higher energies and (ii) their widths increase. To explain these observations, we discuss (i) the reduced screening of the plasmon oscillation due to the Ag 4d electrons and (ii) an enhanced electron surface scattering rate in small clusters.

  7. Development of Cast Alumina-Forming Austenitic Stainless Steels

    NASA Astrophysics Data System (ADS)

    Muralidharan, G.; Yamamoto, Y.; Brady, M. P.; Walker, L. R.; Meyer, H. M., III; Leonard, D. N.

    2016-11-01

    Cast Fe-Ni-Cr chromia-forming austenitic stainless steels with Ni levels up to 45 wt.% are used at high temperatures in a wide range of industrial applications that demand microstructural stability, corrosion resistance, and creep strength. Although alumina scales offer better corrosion protection at these temperatures, designing cast austenitic alloys that form a stable alumina scale and achieve creep strength comparable to existing cast chromia-forming alloys is challenging. This work outlines the development of cast Fe-Ni-Cr-Al austenitic stainless steels containing about 25 wt.% Ni with good creep strength and the ability to form a protective alumina scale for use at temperatures up to 800-850°C in H2O-, S-, and C-containing environments. Creep properties of the best alloy were comparable to that of HK-type cast chromia-forming alloys along with improved oxidation resistance typical of alumina-forming alloys. Challenges in the design of cast alloys and a potential path to increasing the temperature capability are discussed.

  8. Influence of Alumina Additions on the Physical and Chemical Properties of Lithium-iron-phosphate Glasses

    NASA Astrophysics Data System (ADS)

    Liu, Huali; Yang, Ruijuan; Wang, Yinghui; Liu, Shiquan

    Alumina improves the properties and depresses the devitrification of soda-lime-silicate glasses. Herein, the influence of alumina on the glass transition temperature, density, chemical durability, crystallization of lithium-iron-phosphate (LIP) glass has been investigated. As alumina was added to replace the iron oxide in a base LIP glass with the molar composition of Li2O:Fe2O3:P2O5=30:20:50, the alumina-containing glasses have increased Tg, densities and chemical stabilities than the base glass. When the amount of alumina is increased from 2 to 6 mol, the Tg value slightly increases, whereas the density decreases. However, the smallest weight loss is shown for the glass containing 3.2 mol of alumina. The variations of the properties with alumina are explained based on the infrared structure analysis results. In addition, it is found the either the base or the alumina-containing glasses have surface crystallization upon heat-treatments. Under the same treatment conditions, the base glass exhibits a thin layer of crystallization with LiFeP2O7 as the main phase. In contrast, alumina-containing glasses show much higher degree of crystallization, which is further increased with the amount of alumina. This trend is opposite to that of silicate glass. Besides the LiFeP2O7 main phase, Fe7(PO4) phase is also identified in the crystallized alumina-containing glasses.

  9. Processing and Mechanical Properties of Various Zirconia/Alumina Composites for Fuel Cell Applications

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Bansal, Narottam P.

    2002-01-01

    Various electrolyte materials for solid oxide fuel cells were fabricated by hot pressing 10 mol% yttria-stabilized zirconia (10-YSZ) reinforced with two different forms of alumina, particulates and platelets, each containing 0 to 30 mol% alumina. Flexure strength and fracture toughness of both particulate and platelet composites at ambient temperature increased with increasing alumina content, reaching a maximum at 30 mot% alumina. For a given alumina content, strength of particulate composites was greater than that of platelet composites, whereas, the difference in fracture toughness between the two composite systems was negligible. No virtual difference in elastic modulus and density was observed for a given alumina content between particulate and platelet composites. Thermal cycling up to 10 cycles between 200 to 1000 C did not show any effect on strength degradation of the 30 mol% platelet composites, indicative of negligible influence of CTE mismatches between YSZ matrix and alumina grains.

  10. Advanced morphological analysis of patterns of thin anodic porous alumina

    SciTech Connect

    Toccafondi, C.; Stępniowski, W.J.; Leoncini, M.; Salerno, M.

    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.

  11. Unoxidized Graphene/Alumina Nanocomposite: Fracture- and Wear-Resistance Effects of Graphene on Alumina Matrix

    PubMed Central

    Kim, Hyo Jin; Lee, Sung-Min; Oh, Yoon-Suk; Yang, Young-Hwan; Lim, Young Soo; Yoon, Dae Ho; Lee, Changgu; Kim, Jong-Young; Ruoff, Rodney S.

    2014-01-01

    It is of critical importance to improve toughness, strength, and wear-resistance together for the development of advanced structural materials. Herein, we report on the synthesis of unoxidized graphene/alumina composite materials having enhanced toughness, strength, and wear-resistance by a low-cost and environmentally benign pressure-less-sintering process. The wear resistance of the composites was increased by one order of magnitude even under high normal load condition (25 N) as a result of a tribological effect of graphene along with enhanced fracture toughness (KIC) and flexural strength (σf) of the composites by ~75% (5.60 MPa·m1/2) and ~25% (430 MPa), respectively, compared with those of pure Al2O3. Furthermore, we found that only a small fraction of ultra-thin graphene (0.25–0.5 vol%, platelet thickness of 2–5 nm) was enough to reinforce the composite. In contrast to unoxidized graphene, graphene oxide (G-O) and reduced graphene oxide (rG-O) showed little or less enhancement of fracture toughness due to the degraded mechanical strength of rG-O and the structural defects of the G-O composites. PMID:24898792

  12. Alumina lightweight ceramics modified with plasma synthesized nanopowders

    NASA Astrophysics Data System (ADS)

    Zake, I.; Svinka, R.; Svinka, V.; Palcevskis, E.

    2011-12-01

    The aim of this study is to clarify possibilities of using plasma synthesized Al2O3 and SiC nanopowders as additives in alumina lightweight ceramics prepared by slip casting. Each plasma synthesized nanopowder (PSNP) was incorporated in the material by a different method, because of their diverse influence on the properties of slip. Al2O3 PSNP was introduced in the matrix in form of aqueous suspension. SiC nanopowder was added directly to raw materials. Bending strength, bulk density, apparent porosity and thermal shock resistance were determined to evaluate the influence of these additives. The effect of Al2O3 PSNP addition on the properties of material depends on the initial sintering temperature. SiC particles during sintering oxidize into SiO2 and then in the reaction with alumina form mullite. Addition of SiC considerably improves bending strength and thermal shock resistance.

  13. Measurements of prompt radiation induced conductivity of alumina and sapphire

    SciTech Connect

    Hartman, E. Frederick; Zarick, Thomas Andrew; Sheridan, Timothy J.; Preston, Eric F.

    2011-04-01

    We performed measurements of the prompt radiation induced conductivity in thin samples of Alumina and Sapphire at the Little Mountain Medusa LINAC facility in Ogden, UT. Five mil thick samples were irradiated with pulses of 20 MeV electrons, yielding dose rates of 1E7 to 1E9 rad/s. We applied variable potentials up to 1 kV across the samples and measured the prompt conduction current. Analysis rendered prompt conductivity coefficients between 1E10 and 1E9 mho/m/(rad/s), depending on the dose rate and the pulse width for Alumina and 1E7 to 6E7 mho/m/(rad/s) for Sapphire.

  14. Adsorption of copper on a γ-alumina support

    NASA Astrophysics Data System (ADS)

    Papas, Brian N.; Whitten, Jerry L.

    2016-09-01

    The interaction of a Cu atom with two model γ-alumina surfaces was examined using configuration interaction theory. These two surfaces are centered on Td and Oh coordinated Al atoms near the surface, with both surfaces fully hydroxylated. Copper was found to bind to non-hydrogenated oxygen atoms in the surface by 25 kcal/mol, with the possibility that an under coordinated aluminum site may bind copper much more strongly. Vacancies formed by the removal of hydrogen atoms, or by removal of OH groups, were found to bind Cu by values ranging from 40 to 98 kcal/mol. The interaction of a planar Cu7 particle with an exposed Td coordinated Al atom at an OH vacancy site was found to lead to decomposition of the particle and partial absorption of the Cu into the alumina surface.

  15. Deterministic processing of alumina with ultra-short laser pulses

    SciTech Connect

    Furmanski, J; Rubenchik, A M; Shirk, M D; Stuart, B C

    2007-06-27

    Ultrashort pulsed lasers can accurately ablate materials which are refractory, transparent, or are otherwise difficult to machine by other methods. The typical method of machining surfaces with ultrashort laser pulses is by raster scanning, or the machining of sequentially overlapping linear trenches. Experiments in which linear trenches were machined in alumina at various pulse overlaps and incident fluences are presented, and the dependence of groove depth on these parameters established. A model for the machining of trenches based on experimental data in alumina is presented, which predicts and matches observed trench geometry. This model is then used to predict optimal process parameters for the machining of trenches for maximal material removal rate for a given laser.

  16. Conduction in alumina with atomic scale copper filaments

    SciTech Connect

    Xu, Xu; Liu, Jie; Anantram, M. P.

    2014-10-28

    The conductance of atomic scale filaments with three and seven Cu atoms in α-alumina are calculated using ab initio density functional theory. We find that the filament with 3 Cu atoms is sufficient to increase the conductance of 1.3 nm thick alumina film by more than 10{sup 3} times in linear response. As the applied voltage increases, the current quickly saturates and differential resistance becomes negative. Compared to the filament with three Cu atoms, while the conductance of the filament with seven Cu atoms is comparable in linear response, they carry as much as twenty times larger current at large biases. The electron transport is analyzed based on local density of states, and the negative differential resistance in the seven Cu filaments occurs due to their narrow bandwidth.

  17. Real-time polarimetric biosensing using macroporous alumina membranes

    NASA Astrophysics Data System (ADS)

    Álvarez, Jesús; Sola, Laura; Platt, Geoff; Cretich, Marina; Swann, Marcus; Chiari, Marcella; Hill, Daniel; Martínez-Pastor, Juan

    2013-05-01

    We report the first demonstration of real-time biosensing in free standing macroporous alumina membranes. The membranes with their 200 nm diameter pores are ideal candidates for biosensing applications where fast response times for small sample volumes are needed as they allow analytes to flow through the pores close to the bioreceptors immobilized on the pores walls. A bulk refractive index sensitivity of 5.2x10-6 refractive index units was obtained from signal responses to different concentrations of NaCl solutions flowing through the pores. Finally, after functionalizing the alumina pore surfaces with an epoxysilane and then spotting it with β-Lactoglobulin protein, the interactions between the β-lactoglobulin and rabbit anti-β-lactoglobulin, as well as the interaction between the rabbit anti-β-lactoglobulin and a secondary antibody anti-rabbit Immunoglobulin G were monitored in real-time.

  18. Melt processing of Bi--2212 superconductors using alumina

    DOEpatents

    Holesinger, Terry G.

    1999-01-01

    Superconducting articles and a method of forming them, where the superconducting phase of an article is Bi.sub.2 Sr.sub.2 CaCu.sub.2 O.sub.y (Bi-2212). Alumina is combined with Bi-2212 powder or Bi-2212 precursor powder and, in order to form an intimate mixture, the mixture is melted and rapidly cooled to form a glassy solid. The glassy solid is comminuted and the resulting powder is combined with a carrier. An alternative to melting is to form the mixture of nanophase alumina and material having a particle size of less than about 10 microns. The powder, with the carrier, is melt processed to form a superconducting article.

  19. Diffusion bonding of titanium-titanium aluminide-alumina sandwich

    SciTech Connect

    Wickman, H.A.; Chin, E.S.C.; Biederman, R.R.

    1995-12-31

    Diffusion bonding of a metallic-intermetallic-ceramic sandwich is of interest for potential armor applications. Low cost titanium, titanium diboride reinforced titanium aluminide (Ti-48at.%Al), and aluminum oxide are diffusion bonded in a vacuum furnace between 1,000 C and 1,400 C. Metallographic examination of the prior bonding interface showed excellent metallurgical coupling between the Ti-48at.%Al composite and the low cost Ti. A series of microstructures representative of phases consistent with a hypothetical Ti-Al-B phase diagram is visible. The alumina-Ti-48at.%Al interfacial bond is achieved through penetration of titanium-aluminum phases into the existing alumina porosity. A detailed microstructural analysis identifying mechanisms of interfacial bonding will be presented for each interfacial zone.

  20. A sodium/beta-alumina/nickel chloride secondary cell

    NASA Astrophysics Data System (ADS)

    Galloway, R. C.

    1987-01-01

    Nickel chloride has been studied in a cell system, sodium/beta alumina/sodium tetrachloroaluminate/nickel chloride, which is analogous to two existing rechargeable high energy density cells based on iron chloride and sodium sulfur. The cell reaction can be written as: 2Na + NiCl2 yields on discharge Ni + 2NaCl. The positive electrode, conveniently assembled in the discharged state, was a nickel/sodium choride sinter. Molten sodium tetrachloroaluminate electrolyte (NaAlCl4) acted as intermediate between electrode and beta alumina tube. Encouraging results were obtained in terms of low resistances and rates of discharge for cells up to 20-Ah capacity. Cells were operated over the temperature range from 230 to 400 C where the OCV of the cell reaction varied from 2.60 V to 2.56 V.

  1. Strain-Induced Deformation in Magnesia-Alumina Layered Composites

    SciTech Connect

    Kim, Chang Soo; Lombardo, Stephen J; Winholtz, Robert A

    2008-06-18

    Ceramic beams are induced in situ to form complex shapes at elevated temperature without the application of an external stress. This process has been demonstrated for thin alumina substrates coated with a layer of magnesia. The internal strain causing the substrates to deform at elevated temperature arises as a consequence of strain mismatch accompanying the penetration of the coating into the substrate. The magnitude of the deformation depends on the amount of coating applied, on the thickness of the substrate, on the density of the substrate, and on the temperature. During exposure of the beams to elevated temperature, the magnesia coating reacts with the alumina substrate to form the spinel phase; the resulting volume change accompanying the phase transformation is likely the predominant driving force for deformation.

  2. Process for High-Rate Fabrication of Alumina Nanotemplates

    NASA Technical Reports Server (NTRS)

    Myung, Nosang; Fleurial, Jean-Pierre; Yun, Minhee; West, William; Choi, Daniel

    2007-01-01

    An anodizing process, at an early stage of development at the time of reporting the information for this article, has shown promise as a means of fabricating alumina nanotemplates integrated with silicon wafers. Alumina nanotemplates are basically layers of alumina, typically several microns thick, in which are formed approximately regular hexagonal arrays of holes having typical diameters of the order of 10 to 100 nm. Interest in alumina nanotemplates has grown in recent years because they have been found to be useful as templates in the fabrication of nanoscale magnetic, electronic, optoelectronic, and other devices. The present anodizing process is attractive for the fabrication of alumina nanotemplates integrated with silicon wafers in two respects: (1) the process involves self-ordering of the holes; that is, the holes as formed by the process are spontaneously arranged in approximately regular hexagonal arrays; and (2) the rates of growth (that is, elongation) of the holes are high enough to make the process compatible with other processes used in the mass production of integrated circuits. In preparation for fabrication of alumina nanotemplates in this process, one first uses electron-beam evaporation to deposit thin films of titanium, followed by thin films of aluminum, on silicon wafers. Then the alumina nanotemplates are formed by anodizing the aluminum layers, as described below. In experiments in which the process was partially developed, the titanium films were 200 A thick and the aluminum films were 5 m thick. The aluminum films were oxidized to alumina, and the arrays of holes were formed by anodizing the aluminum in aqueous solutions of sulfuric and/or oxalic acid at room temperature (see figure). The diameters, spacings, and rates of growth of the holes were found to depend, variously, on the composition of the anodizing solution, the applied current, or the applied potential, as follows: In galvanostatically controlled anodizing, regardless of the

  3. Protective coating for alumina-silicon carbide whisker composites

    DOEpatents

    Tiegs, Terry N.

    1989-01-01

    Ceramic composites formed of an alumina matrix reinforced with silicon carbide whiskers homogenously dispersed therein are provided with a protective coating for preventing fracture strength degradation of the composite by oxidation during exposure to high temperatures in oxygen-containing atmospheres. The coating prevents oxidation of the silicon carbide whiskers within the matrix by sealing off the exterior of the matrix so as to prevent oxygen transport into the interior of the matrix. The coating is formed of mullite or mullite plus silicon oxide and alumina and is formed in place by heating the composite in air to a temperature greater than 1200.degree. C. This coating is less than about 100 microns thick and adequately protects the underlying composite from fracture strength degradation due to oxidation.

  4. Capillarity in isothermal infiltration of alumina fiber preforms with aluminum

    SciTech Connect

    Michaud, V.J.; Mortensen, A. . Dept. of Materials Science); Compton, L.M. )

    1994-10-01

    Models derived in petroleum engineering and soil science for flow of two immiscible fluids in a porous medium are extended to the infiltration of ceramic preforms by a liquid metal. SAFFIL alumina fiber preforms are infiltrated with an aluminum matrix in a series of interrupted unidirectional and isothermal experiments at various low applied pressures, to measure profiles of the volume fraction of metal along the length of the preforms. Comparison of experimental data with theory reveals the existence of a pressure-dependent incubation time for wetting of the alumina preforms by molten aluminum at 973 K. If this incubation time is taken into account, experimental curves of metal distribution are well predicted by theory, confirming the validity of the models after initiation of flow.

  5. Interfacial characterization of alumina-to-alumina joints fabricated using silver–copper–titanium interlayers

    SciTech Connect

    Lin, Kun-Lin; Singh, Mrityunjay; Asthana, Rajiv

    2014-04-01

    Two Ag–Cu–Ti interlayers with different compositions (Ag–35.3Cu–1.75Ti and Ag–26.7Cu–4.5Ti) were used to join sintered polycrystalline Al{sub 2}O{sub 3} having different amounts of porosity to investigate the effect of titanium and porosity contents on evolution of interfacial chemistry and microstructures. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive spectroscopy (EDS) were used to characterize the interfacial microstructure. Two reaction layers, Ti{sub 2}O and Cu{sub 3}Ti{sub 3}O, were found at the interface of Ag–Cu–Ti interlayers and Al{sub 2}O{sub 3} using a series of simulated and experimental selected area diffraction patterns (SADP) of TEM and EDS. The total thickness of Ti{sub 2}O and Cu{sub 3}Ti{sub 3}O reaction layers at the interfaces increases with increasing amounts of Ti in the Ag–Cu–Ti interlayers but is independent of the porosity content in the Al{sub 2}O{sub 3}. Two possible formation mechanisms of Ti{sub 2}O and Cu{sub 3}Ti{sub 3}O reaction layers at the interface of Ag–Cu–Ti interlayers and Al{sub 2}O{sub 3} have been proposed based on the interfacial characterization performed in the present study. - Highlights: • Effect of alumina porosity and % Ti in interlayer on interface structure delineated • SEM, EDS, XRD, TEM with SADP used to delineate phases, compositions, crystallography • Ti{sub 2}O and Cu{sub 3}Ti{sub 3}O reaction layers identified and their formation mechanisms proposed.

  6. The multiple applications of hydrocyclones in alumina production

    SciTech Connect

    Oeberg, N.; Kelton, G.P.; Rawlins, C.H.

    1996-10-01

    Hydrocyclones are used in many alumina refineries to enhance efficiency. A partial list of applications includes bauxite grinding, bauxite refinement sands separations from red muds, sand washing, hydrate classification and product size control, seed size control, hydrate thickening and deliquoring, agglomeration, preferential separation/reduction of oxalates, spent liquor solids recovery, cooling tower water clean-up, and lime slurry degritting. This paper reviews these applications including viable flowsheets and operating experience; and summarizes basic hydrocyclone selection including the main factors affecting performance.

  7. Increasing productivity during grinding of high-alumina ceramics

    SciTech Connect

    Belous, K.P.; Leptukha, V.P.

    1984-01-01

    The grinding of high-alumina ceramics involves specific problems as the effectiveness of the grinding is affected by the rate of material removal to ensure high productivity, the surface roughness, and the wear of the diamond tool. This study of the cutting processes in cylindrical and internal grinding was done to determine the optimum cutting parameters and specifications of the diamond grinding wheels, and the results helped increase productivity and reduce wheel consumption.

  8. Probing the improbable: imaging carbon atoms in alumina

    SciTech Connect

    Marquis, E A; Yahia, Noor; Larson, David J.; Miller, Michael K; Todd, Richard

    2010-01-01

    Atom-probe tomography has proven very powerful to analyze the detailed structure and chemistry of metallic alloys and semiconductor structures while ceramic materials have remained outside its standard purview. In the current work, we demonstrate that bulk alumina can be quantitatively analyzed and microstructural features observed. The analysis of grain boundary carbon segregation - barely achievable by electron microscopy - opens the possibility of understanding the mechanistic effects of dopants on mechanical properties, fracture and wear properties of bulk oxides.

  9. Conditions to obtain reliable high strength alumina via centrifugal casting

    SciTech Connect

    Huisman, W.; Graule, T.; Gauckler, L.J.

    1995-09-01

    Electrostatically stabilized alumina suspensions with high solids content of up to 58 vol% were consolidated into near-net-shape parts via centrifugal casting. High density green bodies showed excellent sintering kinetics leading to {ge} 99.5% of theoretical density (TD) at lowered temperatures compared to isostatic pressing. Four point bend strengths of 540 MPa with Weibull moduli of up to 24 were achieved using commercial {alpha}-alurnina powders.

  10. Directional solidification of the alumina-zirconia ceramic eutectic system

    SciTech Connect

    Boldt, Christopher

    1994-07-27

    It is possible to produce alumina-zirconia ceramic samples through existing solidification techniques. The resulting microstructures typically consist of rods of zirconia in an alumina matrix, although a lamellar structure has been noted in some cases. In nearly all cases, colony growth was present which may possibly result from grain size, repeated nucleation events, and lamellar oscillations. In the same vein, it appears that the amount of impurities within the system might be the underlying cause for the colony growth. Colony growth was diminished through impurity control as the higher purity samples exhibited colony free behavior. In addition to colony formations, faceted alumina dendrites or nonfaceted zirconia dendrites may result in the ceramic if the sample is solidified out of the coupled zone. In all cases, for larger-sized Bridgman samples, a lower limit in the eutectic spacing was noted. The solidification model which includes the kinetic effect has been developed, although the effect appears to be negligible under present experimental conditions. A spacing limit might also occur due to the result of heat flow problems. Heat flow out of the ceramic is difficult to control, often causing radial and not axial growth. This behavior is exaggerated in the presence of impurities. Thus, higher purity powders should always be used. Higher purity samples, in addition to yielding a more microstructurally uniform ceramic, also showed increased directionality. In the future, the kinetic model needs to be examined in more detail, and further research needs to be accomplished in the area of molten ceramics. Once better system constants are in place, the kinetic model will give a better indication of the behavior in the alumina-zirconia system.

  11. Proton adsorption onto alumina: extension of multisite complexation (MUSIC) theory

    SciTech Connect

    Nagashima, K.; Blum, F.D.

    1999-09-01

    The adsorption isotherm of protons onto a commercial {gamma}-alumina sample was determined in aqueous nitric acid with sodium nitrate as a background electrolyte. Three discrete regions could be discerned in the log-log plots of the proton isotherm determined at the solution pH 5 to 2. The multisite complexation (MUSIC) model was modified to analyze the simultaneous adsorption of protons onto various kinds of surface species.

  12. Single Crystal Structure Determination of Alumina to 1 Mbar

    NASA Astrophysics Data System (ADS)

    Dong, H.; Zhang, L.; Prakapenka, V.; Mao, H.

    2014-12-01

    Aluminum oxide (Al2O3) is an important ceramic material and a major oxide in the earth. Additionally, alumina is a widely used pressure standard in static high-pressure experiments (Cr3+-bearing corundum, ruby). The changes of its crystal structure with pressure (P) and temperature (T) are important for its applications and understanding its physical properties in the deep Earth. There have been numerous reports on the high P-T polymorphs of alumina. Previous theoretical calculations and experiments suggest that the crystal structure of Al2O3 evolves greatly at high P-T. In this study, we used the newly developed multigrain crystallography method combined with single-crystal x-ray diffraction analysis technique for the structure determination of alumina at high P-T to provide single-crystal structure refinement for high-pressure phases of Al2O3. Alumina powder was mixed with ~10% Pt and Ne was used as both pressure transmitting media and thermal insulating layers during laser-heating. Coarse-grained aggregates of Al2O3 were synthesized in a laser-heated diamond anvil cell. The structure change of Al2O3 was monitored by in situ x-ray diffraction at ~1 Mbar and 2700 K. The results allow us to distinguish the structural differences between the Rh2O3 (II) structure (space group Pbcn) and perovskite structure (space group Pbnm) for the first high-pressure phase of Al2O3. More detailed results will be discussed in the later work.

  13. Moisture-Induced Alumina Scale Spallation: The Hydrogen Factor

    NASA Technical Reports Server (NTRS)

    Smialek, James L.

    2010-01-01

    For some time the oxidation community has been concerned with interfacial spallation of protective alumina scales, not just upon immediate cool down, but as a time-delayed phenomenon. Moisture-induced delayed spallation (MIDS) and desktop spallation (DTS) of thermal barrier coatings (TBCs) refer to this process. It is most apparent for relatively adherent alumina scales that have survived initial cool down in a dry environment, have built up considerable thickness and strain energy, and have been somewhat damaged, such as by cyclic oxidation cracking. Indeed, a "sensitive zone" can be described that maximizes the observed effect as a function of all the relevant factors. Moisture has been postulated to serve as a source of interfacial hydrogen embrittlement. Hydrogen is derived from reaction with aluminum in the alloy at an exposed interface. The purpose of this monograph is to trace the close analogy of this phenomenon to other hydrogen-induced effects, such as embrittlement of aluminides and blistering of alloys and anodic alumina films. A formalized, top-down, logic-tree structure is presented as a guide to this discussion. A theoretical basis for interfacial weakening by hydrogen is first cited, as are demonstrations of hydrogen detection as a reaction product or interfacial species. Further support is provided by critical experiments that recreate the moisture effect, but by isolating hydrogen from other potential causative factors. These experiments include tests in H 2-containing atmospheres or cathodic hydrogen charging. Accordingly, they strongly indicate that interfacial hydrogen, derived from moisture, is the key chemical species accounting for delayed alumina scale spallation.

  14. Advances in Zirconia Toughened Alumina Biomaterials for Total Joint Replacement

    PubMed Central

    Kurtz, Steven M.; Kocagöz, Sevi; Arnholt, Christina; Huet, Roland; Ueno, Masaru; Walter, William L.

    2014-01-01

    The objective of this article is to provide an up-to-date overview of zirconia-toughened alumina (ZTA) components used in total hip arthroplasties. The structure, mechanical properties, and available data regarding the clinical performance of ZTA are summarized. The advancements that have been made in understanding the in vivo performance of ZTA are investigated. This article concludes with a discussion of gaps in the literature related to ceramic biomaterials and avenues for future research. PMID:23746930

  15. Alumina Based 500 C Electronic Packaging Systems and Future Development

    NASA Technical Reports Server (NTRS)

    Chen, Liang-Yu

    2012-01-01

    NASA space and aeronautical missions for probing the inner solar planets as well as for in situ monitoring and control of next-generation aeronautical engines require high-temperature environment operable sensors and electronics. A 96% aluminum oxide and Au thick-film metallization based packaging system including chip-level packages, printed circuit board, and edge-connector is in development for high temperature SiC electronics. An electronic packaging system based on this material system was successfully tested and demonstrated with SiC electronics at 500 C for over 10,000 hours in laboratory conditions previously. In addition to the tests in laboratory environments, this packaging system has more recently been tested with a SiC junction field effect transistor (JFET) on low earth orbit through the NASA Materials on the International Space Station Experiment 7 (MISSE7). A SiC JFET with a packaging system composed of a 96% alumina chip-level package and an alumina printed circuit board mounted on a data acquisition circuit board was launched as a part of the MISSE7 suite to International Space Station via a Shuttle mission and tested on the orbit for eighteen months. A summary of results of tests in both laboratory and space environments will be presented. The future development of alumina based high temperature packaging using co-fired material systems for improved performance at high temperature and more feasible mass production will also be discussed.

  16. Liquid permeation and chemical stability of anodic alumina membranes

    PubMed Central

    Buldakov, Dmitrii A; Tishkin, Alexey A; Lukashin, Alexey V; Eliseev, Andrei A

    2017-01-01

    A study on the chemical stability of anodic alumina membranes and their performance in long-term water and organic solvent permeation experiments is reported. Anodic alumina possesses high stability for both protonic and aprotonic organic solvents. However, serious degradation of the membrane occurs in pure water, leading to a drastic decrease of permeance (over 20% of the initial value after the passing of 0.250 m3/m2 of pure water). The drying of the membrane induces further permeance drop-off. The rate of membrane degradation strongly depends on the pH of the penetrant solution and increases in basic media. According to 27Al NMR and thermogravimetry results, the degradation of the membranes is associated with the dissolution of water-soluble [Al13O4(OH)24(H2O)12]7+ polyhydroxocomplexes and their further redeposition in the form of [Al(OH)4]−, resulting in channels blocking. This process intensifies in basic pH due to the high positive charge of the anodic alumina surface. An approach for improving anodic aluminum oxide stability towards dissolution in water by carbon CVD coating of the membrane walls is suggested. PMID:28382245

  17. Thermochemical Analysis of Molybdenum Thin Films on Porous Alumina.

    PubMed

    Lee, Kyoungjin; de Lannoy, Charles-François; Liguori, Simona; Wilcox, Jennifer

    2017-01-12

    Molybdenum (Mo) thin films (thickness <100 nm) were physically deposited by e-beam evaporation on a porous alumina substrate and were analyzed for their stability and reactivity under various thermal and gas conditions. The Mo thin-film composites were stable below 300 °C but had no reactivity toward gases. Mo thin films showed nitrogen incorporation on the surface as well as in the subsurface at 450 °C, as confirmed by X-ray photoelectron spectroscopy. The reactivity toward nitrogen was diminished in the presence of CO2, although no carbon species were detected either on the surface or in the subsurface. The Mo thin films have a very stable native oxide layer, which may further oxidize to higher oxidation states above 500 °C due to the reaction with the porous anodized alumina substrate. The oxidation of Mo thin films was accelerated in the presence of oxidizing gases. At 600 °C in N2, the Mo thin film on anodized alumina was completely oxidized and may also have been volatilized. The results imply that choosing thermally stable and inactive porous supports and operating in nonoxidizing conditions below 500 °C will likely maintain the stability of the Mo composite. This study provides key information about the chemical and structural stability of a Mo thin film on a porous substrate for future membrane applications and offers further insights into the integrity of thin-film composites when exposed to harsh conditions.

  18. EFFECT OF GRAIN SIZE ON DYNAMIC SCRATCH RESPONSE IN ALUMINA

    SciTech Connect

    Wang, Hong; Wereszczak, Andrew A; Lance, Michael J

    2006-01-01

    The machining and wear of ceramics and ceramic components are obviously influenced by abrasive damage. One parameter that can affect the abrasion process is the grain size of the ceramic material. To investigate this, single-grit pendulum scratch testing was used to investigate the dynamic scratch response in three 99.9% aluminas that each had a tight size distribution about mean grain sizes of 2, 15, or 25 m, respectively. The scratch speeds generated had an order of magnitude of ~ 1 m/s and the maximum scratch depths were several tens of micrometers. Tangential and normal scratch forces were monitored during each test and interpreted in conjunction with postmortem SEM and profilometry results. It was observed that both plastic deformation and brittle fracture participated in the scratching process and the relative activity of each was dependent on depth of penetration. At a specific depth of penetration, the material removal of alumina prevailingly relies on the generation and interaction of oblique radial and lateral cracks. Chip formation is greatly enhanced when the created cracks interact and that interaction itself depends on grain size. Larger grain size gives rise to larger lateral cracks, more severe fracture at the groove's bottom, and larger amplitude of scratch force oscillation. Lastly, the cutting pressure and the scratch hardness of alumina exhibit sensitivity to both grain size and the groove depth.

  19. Moisture-Induced Alumina Scale Spallation: The Hydrogen Factor

    NASA Technical Reports Server (NTRS)

    Smialek, James L.

    2009-01-01

    For some time our community has been concerned with interfacial spallation of protective alumina scales, not just upon immediate cooldown, but as a time-delayed phenomenon. Moisture-induced delayed spallation (MIDS) and desktop spallation (DTS) of TBC's refer to this process. It is most apparent for relatively adherent alumina scales that have survived cool down in a dry environment, built up considerable thickness and strain energy, and have been somewhat damaged, such as by cyclic oxidation cracking. Indeed, a "sweet zone" can be defined that maximizes the observed effect as a function of all the relevant factors. Moisture has been postulated to serve as a source of interfacial hydrogen embrittlement derived from reaction with aluminum in the alloy at an exposed interface. The purpose of this monograph is to trace the close analogy of this phenomenon to other hydrogen effects, such as embrittlement of aluminides and blistering of alloys and anodic alumina films. A formalized, top-down, logic tree structure is presented as a guide to this discussion. A theoretical basis for interfacial weakening by hydrogen is first cited, as are demonstrations of hydrogen as a reaction product or detected interfacial species. Further support is provided by critical experiments that produce the same moisture effect, but by isolating hydrogen from other potential causative factors. These experiments include tests in H2-containing atmospheres or cathodic hydrogen charging.

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

    PubMed

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

    2015-12-01

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

  1. Mechanics in alumina ceramics modified by ultradispersed diamonds

    NASA Astrophysics Data System (ADS)

    Kireitseu, Maksim V.; Yerakhavets, Sergey G.; Basenuk, Vladimir L.; Jornik, Victor

    2003-10-01

    Alumina coating modified by ultra-dispersed diamonds (UDD) have been produced by combination of thermal flame spraying and micro arc oxidizing technologies on sprayed aluminum substrate was. Structures of alumina-based ultra dispersed diamond particles composite coatings were investigated in detail by transmission electron microscopy and SEM imaging. The particles were deposited with alumina layer on aluminum substrates under various conditions and have different levels of strength, hardness and internal stresses. It was revealed that by UDD strengthening the coating is to have high microhardness of 22 - 26 GPa, fine structure and smooth surface. Diamonds was found to be conglomerated in clusters along the interface obtained with high current density, but it disappeared when deposited with lower current regimes of alternating pulse current. On the other hand, the failure of crystal diamonds became smaller with decreasing current density concentrations. From the correspondence between the structures and the hardness of the composite, it was suggested that the effect of ultra dispersed diamonds resulted in the complicated trend of hardness, strength and fine structure with respect to current density and diamonds concentration in the electrolyte. In view of technological setup pulse current regime at high current frequency improve microhardness and roughness of the coatings. Potential application of the coating is sliding bearings, insulators, aerospace units.

  2. Zirconia-alumina-nanodiamond composites with gemological properties

    NASA Astrophysics Data System (ADS)

    Díaz, Luis A.; Montes-Morán, Miguel A.; Peretyagin, Pavel Y.; Vladimirov, Yuriy G.; Okunkova, Anna; Moya, José S.; Torrecillas, Ramón

    2014-02-01

    Nanodiamonds have excellent mechanical and optical properties with a wide range of potential applications as a filler material for nanocomposites. Here, we present a new family of zirconia-alumina-nanodiamond composites using two main processing routes: (1) a colloidal method, and (2) power mixing homogenization. Composites with detonation nanodiamonds quantities ranging within 0.3-5 vol.% followed by a pulsed electrical current sintering at a temperature range from 1,200 to 1,500 °C have been analyzed, and a significant enhancement in mechanical properties, i.e., indentation hardness (16.17 GPa), fracture toughness (15.5 MPa m1/2), and bending strength (1,600 MPa), could be observed. To support these excellent properties, TEM, color, reflectivity, and Raman spectroscopy measurements were also carried out. The microstructure of the composites is very homogeneous with average grain sizes between 200 and 500 nm depending on the processing temperature. Two morphologies are present: (a) intergranular dispersion of alumina grains and nanodiamonds distributed along the grain boundaries of the ZrO2 matrix, and (b) intragranular nano-dispersion of ZrO2 particles with sizes 20-80 nm located inside the alumina grains. In the present article, we show, for the first time in the scientific literature, a continuous palette of gray color gradation of new ceramic materials of metalized colors (white index L* 98-40) for gemological applications.

  3. Development of Alumina-Forming Austenitic Stainless Steels

    SciTech Connect

    Brady, Michael P; Yamamoto, Yukinori; Bei, Hongbin; Santella, Michael L; Maziasz, Philip J

    2009-01-01

    This paper presents the results of the continued development of creep-resistant, alumina-forming austenitic (AFA) stainless steel alloys, which exhibit a unique combination of excellent oxidation resistance via protective alumina (Al2O3) scale formation and high-temperature creep strength through the formation of stable nano-scale MC carbides and intermetallic precipitates. Efforts in fiscal year 2009 focused on the characterization and understanding of long-term oxidation resistance and tensile properties as a function of alloy composition and microstructure. Computational thermodynamic calculations of the austenitic matrix phase composition and the volume fraction of MC, B2-NiAl, and Fe2(Mo,Nb) base Laves phase precipitates were used to interpret oxidation behavior. Of particular interest was the enrichment of Cr in the austenitic matrix phase by additions of Nb, which aided the establishment and maintenance of alumina. Higher levels of Nb additions also increased the volume fraction of B2-NiAl precipitates, which served as an Al reservoir during long-term oxidation. Ageing studies of AFA alloys were conducted at 750 C for times up to 2000 h. Ageing resulted in near doubling of yield strength at room temperature after only 50 h at 750 C, with little further increase in yield strength out to 2000 h of ageing. Elongation was reduced on ageing; however, levels of 15-25% were retained at room temperature after 2000 h of total ageing.

  4. Formation process of a strong water-repellent alumina surface by the sol-gel method

    NASA Astrophysics Data System (ADS)

    Feng, Libang; Li, Hui; Song, Yongfeng; Wang, Yulong

    2010-03-01

    A novel strong water-repellent alumina thin film is fabricated by chemically adsorbing stearic acid (STA) layer onto the porous and roughened aluminum film coated with polyethyleneimine (PEI). The formation process and the structure of the strong water-repellent alumina film are investigated by means of contact angle measurement and atomic force microscope (AFM). Results show that the water contact angles for the alumina films increase with the increase of the immersion time in the boiling water, and meanwhile, the roughness of the alumina films increases with the dissolution of the boehmite in the boiling water. Finally, the strong water-repellent film with a high water contact angle of 139.1° is obtained when the alumina films have distinct roughened morphology with some papillary peaks and porous structure. Moreover, both the roughened structure and the hydrophobic materials of the STA endow the alumina films with the strong water-repellence.

  5. Role of metal oxides in chemical evolution: interaction of ribose nucleotides with alumina.

    PubMed

    Arora, Avnish Kumar; Kamaluddin

    2009-03-01

    Interaction of ribonucleotides--namely, 5'-AMP, 5'-GMP, 5'-CMP, and 5'-UMP--with acidic, neutral, and basic alumina has been studied. Purine nucleotides showed higher adsorption on alumina in comparison with pyrimidine nucleotides under acidic conditions. Adsorption data obtained followed Langmuir adsorption isotherm, and X(m) and K(L) values were calculated. On the basis of infrared spectral studies of ribonucleotides, alumina, and ribonucleotide-alumina adducts, we propose that the nitrogen base and phosphate moiety of the ribonucleotides interact with the positive charge surface of alumina. Results of the present study may indicate the importance of alumina in concentrating organic molecules from dilute aqueous solutions in primeval seas in the course of chemical evolution on Earth.

  6. Divalent Beta’ Aluminas: High Conductivity Solid Electrolytes for Divalent Cations.

    DTIC Science & Technology

    1982-10-13

    results indicated that divalent ions diffuse very slowly in beta alumina, they discouraged interest in its divalent derivatives. After their work...using polycrystalline Na+ beta alumina to separate two NiCl2-NaCl melts at 800-10000C. After several days’ exposure, they found that the beta alumina...samples were exchanged in a nitrogen or argon atmosphere. After exchange, crystals were soaked in a suitable solvent (usually methanol), washed in

  7. Lifetime of Sodium Beta-Alumina Membranes in Molten Sodium Hydroxide

    DTIC Science & Technology

    2008-07-01

    Report 3. DATES COVERED (From – To) 1 April 2007 – 01 April 2008 4. TITLE AND SUBTITLE Lifetime of Sodium Beta-alumina Membranes in Molten Sodium ...ABSTRACT Summary: Sodium metal can be made by electrolysis of molten sodium hydroxide in sodium beta-alumina membrane electrolysis cells...However, there are some uncertainties about the lifetime of the sodium beta-alumina membranes in contact with molten sodium hydroxide. The main objective

  8. The Effect of Alumina Dispersant Powder on the Workability of Chromia Based Refractory for IGCC Application

    NASA Astrophysics Data System (ADS)

    Ming, Zhao Jing; Xun, Yang Zheng; Hong, Hwang Kyu; Hwan, Park Sang

    2011-10-01

    The quality of refractory applied on IGCC is a key factor that affects the cost of production. The workability and microstructure of chromia based castable are varied by introducing different type of alumina dispersant powder, such as active alumina powder. In this study, three types of active alumina powder are added to improve the workability. It's proved that the specific surface area and particle size distribution of fine powders in matrix part greatly affect the flow values and microstructures.

  9. Structural and Acidic Properties of Niobia-Silica and Niobia-Alumina Aerogels

    DTIC Science & Technology

    1991-05-06

    objective is to develop a comparative set of samples of known structure for chemical characterization . Bulk oxide aerogels of niobia, alumina, and silica ...objective is to develop a comparative set of samples of known structure for chemical characterization . Bulk oxide aerogels of niobia, alumina, and silica were...properties and the developed structures caused by the thermal treatment or increased concentration of niobia on the silica and alumina aerogel

  10. Effects of particle size and coating on decomposition of alumina-extracted residue from high-alumina fly ash.

    PubMed

    Wang, Zehua; Ma, Shuhua; Tang, Zhenhua; Wang, Xiaohui; Zheng, Shili

    2016-05-05

    The effective removal of alkali in the alumina-extracted reside (AER) obtained by extracting alumina from high-alumina fly ash is the premise for realizing the utilization of the silicon component in the fly ash. Sodium was removed from the AER by a decomposition reaction. The effects of the particle size and reactant coating on the decomposition reaction of AER were studied, and the results showed that by decreasing the particle size, the decomposition reaction rate of AER could be enhanced obviously and the Na2O content of the products could be decreased effectively. In addition, the process and mechanism of the decomposition reaction of AER and the reaction kinetics were investigated. The results revealed that the decomposition reaction of AER started from the outer surface of the AER particles. The reaction kinetics corresponded with shrinking unreacted core models. Furthermore, the decomposition reaction rate of AER could be enhanced obviously by decreasing the particle size because the effect of product layer diffusion was weakened when the particle size of AER was decreased.

  11. Viscosity of aqueous and cyanate ester suspensions containing alumina nanoparticles

    SciTech Connect

    Lawler, Katherine

    2009-01-01

    The viscosities of both aqueous and cyanate ester monomer (BECy) based suspensions of alumina nanoparticle were studied. The applications for these suspensions are different: aqueous suspensions of alumina nanoparticles are used in the production of technical ceramics made by slip casting or tape casting, and the BECy based suspensions are being developed for use in an injection-type composite repair resin. In the case of aqueous suspensions, it is advantageous to achieve a high solids content with low viscosity in order to produce a high quality product. The addition of a dispersant is useful so that higher solids content suspensions can be used with lower viscosities. For BECy suspensions, the addition of nanoparticles to the BECy resin is expected to enhance the mechanical properties of the cured composite. The addition of saccharides to aqueous suspensions leads to viscosity reduction. Through DSC measurements it was found that the saccharide molecules formed a solution with water and this resulted in lowering the melting temperature of the free water according to classic freezing point depression. Saccharides also lowered the melting temperature of the bound water, but this followed a different rule. The shear thinning and melting behaviors of the suspensions were used to develop a model based on fractal-type agglomeration. It is believed that the structure of the particle flocs in these suspensions changes with the addition of saccharides which leads to the resultant viscosity decrease. The viscosity of the BECy suspensions increased with solids content, and the viscosity increase was greater than predicted by the classical Einstein equation for dilute suspensions. Instead, the Mooney equation fits the viscosity behavior well from 0-20 vol% solids. The viscosity reduction achieved at high particle loadings by the addition of benzoic acid was also investigated by NMR. It appears that the benzoic acid interacts with the surface of the alumina particle which may

  12. Oxidation behavior in reaction-bonded aluminum-silicon alloy/alumina powder compacts

    SciTech Connect

    Yokota, S.H.

    1992-12-01

    Goal of this research is to determine the feasibility of producing low-shrinkage mullite/alumina composites by applying the reaction-bonded alumina (RBAO) process to an aluminum-silicon alloy/alumina system. Mirostructural and compositional changes during heat treatment were studied by removing samples from the furnace at different steps in the heating schedule and then using optical and scanning electron microscopy, EDS and XRD to characterize the powder compacts. Results suggest that the oxidation behavior of the alloy compact is different from the model proposed for the pure Al/alumina system.

  13. Method to produce alumina aerogels having porosities greater than 80 percent

    DOEpatents

    Poco, John F.; Hrubesh, Lawrence W.

    2003-09-16

    A two-step method for producing monolithic alumina aerogels having porosities of greater than 80 percent. Very strong, very low density alumina aerogel monoliths are prepared using the two-step sol-gel process. The method of preparing pure alumina aerogel modifies the prior known sol method by combining the use of substoichiometric water for hydrolysis, the use of acetic acid to control hydrolysis/condensation, and high temperature supercritical drying, all of which contribute to the formation of a polycrystalline aerogel microstructure. This structure provides exceptional mechanical properties of the alumina aerogel, as well as enhanced thermal resistance and high temperature stability.

  14. The Effect of Novel Synthetic Methods and Parameters Control on Morphology of Nano-alumina Particles

    NASA Astrophysics Data System (ADS)

    Xie, Yadian; Kocaefe, Duygu; Kocaefe, Yasar; Cheng, Johnathan; Liu, Wei

    2016-05-01

    Alumina is an inorganic material, which is widely used in ceramics, catalysts, catalyst supports, ion exchange and other fields. The micromorphology of alumina determines its application in high tech and value-added industry and its development prospects. This paper gives an overview of the liquid phase synthetic method of alumina preparation, combined with the mechanism of its action. The present work focuses on the effects of various factors such as concentration, temperature, pH, additives, reaction system and methods of calcination on the morphology of alumina during its preparation.

  15. Electromotive force measurements on cells involving beta-alumina solid electrolyte

    NASA Technical Reports Server (NTRS)

    Choudhury, N.

    1973-01-01

    Open circuit emf measurements have been made to demonstrate that a two-phase, polycrystalline mixture of beta- alumina and alpha-alumina could be used as a solid electrolyte in galvanic cells with reversible electrodes fixing oxygen or aluminum chemical potentials. These measurements indicate that such a two phase solid electrolyte can be used to monitor oxygen chemical potentials as low as that corresponding to Al, Al2O3 coexistence. The activity of Na2O in beta-alumina in coexistence with alpha-alumina was also determined by emf measurements.

  16. Alumina-alumina artificial hip joints. Part II: characterisation of the wear debris from in vitro hip joint simulations.

    PubMed

    Tipper, J L; Hatton, A; Nevelos, J E; Ingham, E; Doyle, C; Streicher, R; Nevelos, A B; Fisher, J

    2002-08-01

    Until recently it was not possible to reproduce clinically relevant wear rates and wear patterns in in vitro hip joint simulators for alumina ceramic-on-ceramic hip prostheses. The introduction of microseparation of the prosthesis components into in vitro wear simulations produced clinically relevant wear rates and wear patterns for the first time. The aim of this study was to characterise the wear particles generated from standard simulator testing and microseparation simulator testing of hot isostatically pressed (HIPed) and non-HIPed alumina ceramic-on-ceramic hip prostheses, and compare these particles to those generated in vivo. Standard simulation conditions produced wear rates of approximately 0.1 mm3 per million cycles for both material types. No change in surface roughness was detected and very few wear features were observed. In contrast, when microseparation was introduced into the wear simulation, wear rates of between 1.24 (HIPed) and 1.74 mm3 per million cycles (non-HIPed) were produced. Surface roughness increased and a wear stripe often observed clinically on retrieved femoral heads was also reproduced. Under standard simulation conditions only nanometre-sized wear particles (2-27.5 nm) were observed by TEM, and it was thought likely that these particles resulted from relief polishing of the alumina ceramic. However, when microseparation of the prosthesis components was introduced into the simulation, a bi-modal distribution of particle sizes was observed. The nanometre-sized particles produced by relief polishing were present (1-35nm). however, larger micrometre-sized particles were also observed by both transmission electron microscopy (TEM) (0.021 microm) and scanning electron microscopy (SEM) (0.05-->10 microm). These larger particles were thought to originate from the wear stripe and were produced by trans-granular fracture of the alumina ceramic. In Part I of this study, alumina ceramic wear particles were isolated from the periprosthetic

  17. Interaction of hydrogen chloride with alumina. [atmospheric effluent concentrations and interaction of solid rocket propellants used in space shuttle

    NASA Technical Reports Server (NTRS)

    Bailey, R. R.; Wightman, J. P.

    1978-01-01

    The influence of temperature, pressure, and outgas conditions on the absorption of hydrogen chloride and water vapor on both alpha and gamma alumina was studied. Characterization of the adsorbents was performed using X-ray powder diffraction, scanning electron microscopy (SEM), low temperature nitrogen adsorption desorption measurements, BET nitrogen surface area measurements and electron spectroscopy for chemical analysis (ESCA). Water vapor adsorption isotherms at 30, 40, and 50 C were measured on alpha and gamma alumina after outgassing at 80, 200, and 400 C. Both outgas temperature and adsorption temperature influenced the adsorption of water vapor on the aluminas. The water vapor adsorption was completely reversible. Alpha alumina absorbed more water per unit area than gamma alumina. Differences in the adsorption capacity for water vapor of the two aluminas were explained on the basis of ideal surface models of alpha and gamma alumina. Isosteric heats of adsorption for water vapor on the aluminas were determined over a limited range of surface coverage.

  18. Intermetallic strengthened alumina-forming austenitic steels for energy applications

    NASA Astrophysics Data System (ADS)

    Hu, Bin

    In order to achieve energy conversion efficiencies of >50 % for steam turbines/boilers in power generation systems, materials required are strong, corrosion-resistant at high temperatures (>700°C), and economically viable. Austenitic steels strengthened with Laves phase and Ni3Al precipitates, and alloyed with aluminum to improve oxidation resistance, are potential candidate materials for these applications. The creep resistance of these alloys is significantly improved through intermetallic strengthening (Laves-Fe 2Nb + L12-Ni3Al precipitates) without harmful effects on oxidation resistance. This research starts with microstructural and microchemical analyses of these intermetallic strengthened alumina-forming austenitic steels in a scanning electron microscope. The microchemistry of precipitates, as determined by energy-dispersive x-ray spectroscopy and transmission electron microscope, is also studied. Different thermo-mechanical treatments were carried out to these stainless steels in an attempt to further improve their mechanical properties. The microstructural and microchemical analyses were again performed after the thermo-mechanical processing. Synchrotron X-ray diffraction was used to measure the lattice parameters of these steels after different thermo-mechanical treatments. Tensile tests at both room and elevated temperatures were performed to study mechanical behaviors of this novel alloy system; the deformation mechanisms were studied by strain rate jump tests at elevated temperatures. Failure analysis and post-mortem TEM analysis were performed to study the creep failure mechanisms of these alumina-forming austenitic steels after creep tests. Experiments were carried out to study the effects of boron and carbon additions in the aged alumina-forming austenitic steels.

  19. Functionally graded alumina-based thin film systems

    DOEpatents

    Moore, John J.; Zhong, Dalong

    2006-08-29

    The present invention provides coating systems that minimize thermal and residual stresses to create a fatigue- and soldering-resistant coating for aluminum die casting dies. The coating systems include at least three layers. The outer layer is an alumina- or boro-carbide-based outer layer that has superior non-wettability characteristics with molten aluminum coupled with oxidation and wear resistance. A functionally-graded intermediate layer or "interlayer" enhances the erosive wear, toughness, and corrosion resistance of the die. A thin adhesion layer of reactive metal is used between the die substrate and the interlayer to increase adhesion of the coating system to the die surface.

  20. Screen-Cage Ion Plating Of Silver On Polycrystalline Alumina

    NASA Technical Reports Server (NTRS)

    Spalvins, Talivaldis; Sliney, Harold E.; Deadmore, Daniel L.

    1995-01-01

    Screen-cage ion plating (SCIP) cost-effective technique offering high throwing power for deposition of adherent metal films on ceramic substrates. Applies silver films to complexly shaped substrates of polycrystalline alumina. Silver adheres tenaciously and reduces friction. SCIP holds promise for applying lubricating soft metallic films to high-temperature ceramic components of advanced combustion engines. Other potential uses include coating substrates with metal for protection against corrosion, depositing electrical conductors on dielectric substrates, making optically reflective or electrically or thermally conductive surface layers, and applying decorative metal coats to ceramic trophies or sculptures.

  1. Preparation Of Strong, Dense Potassium Beta''-Alumina Ceramic

    NASA Technical Reports Server (NTRS)

    Williams, Roger M.; Jeffries-Nakamura, Barbara; Ryan, Margaret A.; O'Connor, Dennis E.; Kisor, Adam; Kikkert, Stanley J.; Losey, Robert; Suitor, Jerry W.

    1995-01-01

    Improved process for making mechanically strong, dense, phase-pure potassium beta''-alumina solid electrolyte (K-BASE) results in material superior to all previous K-BASE preparations and similar to commercial Na-BASE in strength, phase purity and high-temperature ionic conductivity. Potassium-based alkali-metal thermal-to-electric conversion (AMTEC) cells expected to operate efficiently at lower heat-input temperatures and lower rejection temperatures than sodium-based AMTEC cells, making them appropriate for somewhat different applications.

  2. Fractal dimension of alumina aggregates grown in two dimensions

    NASA Technical Reports Server (NTRS)

    Larosa, Judith L.; Cawley, James D.

    1992-01-01

    The concepts of fractal geometry are applied to the analysis of 0.4-micron alumina constrained to agglomerate in two dimensions. Particles were trapped at the bottom surface of a drop of a dilute suspension, and the agglomeration process was directly observed, using an inverted optical microscope. Photographs were digitized and analyzed, using three distinct approaches. The results indicate that the agglomerates are fractal, having a dimension of approximately 1.5, which agrees well with the predictions of the diffusion-limited cluster-cluster aggregation model.

  3. Method for thermal processing alumina-enriched spinel single crystals

    DOEpatents

    Jantzen, Carol M.

    1995-01-01

    A process for age-hardening alumina-rich magnesium aluminum spinel to obtain the desired combination of characteristics of hardness, clarity, flexural strength and toughness comprises selection of the time-temperature pair for isothermal heating followed by quenching. The time-temperature pair is selected from the region wherein the precipitate groups have the characteristics sought. The single crystal spinel is isothermally heated and will, if heated long enough pass from its single phase through two pre-precipitates and two metastable precipitates to a stable secondary phase precipitate within the spinel matrix. Quenching is done slowly at first to avoid thermal shock, then rapidly.

  4. Method for thermal processing alumina-enriched spinel single crystals

    DOEpatents

    Jantzen, C.M.

    1995-05-09

    A process for age-hardening alumina-rich magnesium aluminum spinel to obtain the desired combination of characteristics of hardness, clarity, flexural strength and toughness comprises selection of the time-temperature pair for isothermal heating followed by quenching. The time-temperature pair is selected from the region wherein the precipitate groups have the characteristics sought. The single crystal spinel is isothermally heated and will, if heated long enough pass from its single phase through two pre-precipitates and two metastable precipitates to a stable secondary phase precipitate within the spinel matrix. Quenching is done slowly at first to avoid thermal shock, then rapidly. 12 figs.

  5. Room-temperature ferromagnetism observed in alumina films

    NASA Astrophysics Data System (ADS)

    Zheng, Y. L.; Zhen, C. M.; Wang, X. Q.; Ma, L.; Li, X. L.; Hou, D. L.

    2011-08-01

    We have prepared alumina thin films on Si substrates using a radio frequency (RF) sputtering method, and have observed room-temperature ferromagnetism (RTFM) in the thin films. When the thin films were annealed in vacuum, the saturation magnetization (Ms) increased, while annealing the sample in the air contributed to a decrease in the value of Ms. The Ms of the thin film also decreased as the thickness increased. We confirm that the unpaired electron spins responsible for ferromagnetism (FM) in Al 2O 3-δ thin films have their origin in the oxygen vacancies, especially at the interface of the Al 2O 3-δ thin film and the Si substrate.

  6. Tilted Liquid Crystal Alignment on Asymmetrically Grooved Porous Alumina Film

    NASA Astrophysics Data System (ADS)

    Maeda, Tsuyoshi; Hiroshima, Kohki

    2005-06-01

    This paper reports the achievement of tilted liquid crystal (LC) alignment on an anodic porous alumina (APA) film using microgrooves with asymmetric shapes and dozens of minute pores. The microgrooves with asymmetric shapes were formed by a rubbing technique. The minute pores were then produced by anodization. The LC pretilt angle was controlled by the shapes of the microgrooves and pores. The LC director was orientated in the same inclining direction as that of a rubbed polyimide (PI) film. The pretilt angle was in the range of 20 to 90°. This tilted LC alignment remains very stable against external forces such as thermal shock and intense light.

  7. Silicon carbide whisker-zirconia reinforced mullite and alumina ceramics

    DOEpatents

    Becher, Paul F.; Tiegs, Terry N.

    1987-01-01

    The flexural strength and/or fracture toughness of SiC whisker-reinforced composites utilizing mullite or alumina as the matrix material for the composite are increased by the addition of zirconia in a monoclinic or tetragonal phase to the matrix. The zirconia addition also provides for a lower hot-pressing temperature and increases the flexural strength and/or fracture toughness of the SiC whisker-reinforced composites over SiC whisker-reinforced composites of the similar matrix materials reinforced with similar concentrations of SiC whiskers.

  8. Optical properties of porous anodic alumina embedded Cu nanocomposite films

    NASA Astrophysics Data System (ADS)

    Liu, Huiyuan; Sun, Huiyuan; Liu, Lihu; Hou, Xue; Jia, Xiaoxuan

    2015-06-01

    Porous anodic alumina embedded Cu with iridescent colors were fabricated in copper sulfate electrolyte. The films display highly saturated colors after being synthesized by an ac electrodeposition method. Tunable color in the films is obtained by adjusting anodization time, and can be adjusted across the entire visible range. Theoretical results of the changes in the structural color according to the Bragg-Snell formula are consistent with the experimental results. The films could be used in many areas including decoration, display and multifunctional anti-counterfeiting applications.

  9. Measurement of the radiative transport properties of reticulated alumina foams

    SciTech Connect

    Hale, M.J.; Bohn, M.S.

    1992-12-01

    This paper presents a method for determining radiative transport properties of reticulated materials. The method has both experimental and analytical components. A polar nephelometer is used to measure the scattering profile of a sample of the reticulated material. The results of a Monte Carlo simulation of the experiment are then combined with the experimental results to give the scatter albedo and extinction coefficient. This paper presents the results of using this method to determine the radiative transport properties of four different porosities (10, 20, 30, 65 pores per inch) of cylindrical reticulated alumina samples ranging in thickness form 0.5 inches to 2. 5 inches.

  10. Luminescent properties of alumina ceramics doped with chromium oxide

    NASA Astrophysics Data System (ADS)

    Kortov, V.; Kiryakov, A.; Pustovarov, V.

    2016-08-01

    Ceramics doped with chromium oxide were synthesized from alumina nanopowder at high heating and cooling rates. XRD analysis of the obtained samples shows that they consist mainly of Al2O3 α-phase. Photoluminescence (PL) spectra in the visible spectral region and thermoluminescence (TL) curves were measured. An effect of the dopant concentration on the intensity and shape of the PL bands as well as on the TL yield was found. Annealing of the quenching defects which emerged during the synthesis changed the PL spectra. The centers responsible for PL and TL in the synthesized ceramics were identified.

  11. Design Manual: Removal of Fluoride from Drinking Water Supplies by Activated Alumina

    EPA Science Inventory

    This document is an updated version of the Design Manual: Removal of Fluoride from Drinking Water Supplies by Activated Alumina (Rubel, 1984). The manual is an in-depth presentation of the steps required to design and operate a fluoride removal plant using activated alumina (AA)...

  12. Improving the voltage holdoff performance of alumina insulators in vacuum by quasimetallizing or doping

    SciTech Connect

    Miller, H.C.

    1980-08-11

    Treatment of the surface of an alumina insulator with coatings incorporating varying amounts of Cr, Mn, and Ti can significantly increase the vacuum voltage holdoff capability of the insulator (up to 25 percent). During processing (quasimetallizing) the coating penetrates into the alumina, so it is insensitive to mechanical damage. This quasimetallize treatment is also compatible with subsequent metallizing and brazing of the alumina insulator. Quasimetallizing with appropriate formulations has been shown to change the surface characteristics of alumina in two ways: it decreases both the surface resistivity of the alumina and the secondary electron emission yield of the alumina. Each change improves the voltage holdoff characteristics of the alumina. Similar improvements in voltage holdoff capability can be obtained by doping the plain alumina to the 5 percent (by weight) level with additives of 4 parts Mn/1 part Ti or 2 Mn/1 Ti/1 Cr. Such doped ceramics have the advantage of requiring fewer processing steps than do the quasimetallized ceramics. Both doped and quasimetallized ceramics are suitable for use in ultrahigh vacuum apparatus.

  13. Measurement of Elastic Modulus of Alumina and Barium Strontium Titanate Wafers Produced by Tape Casting Method

    DTIC Science & Technology

    2014-02-01

    UNCLASSIFIED AD-E403 481 Technical Report ARMET-TR-12039 MEASUREMENT OF ELASTIC MODULUS OF ALUMINA AND BARIUM STRONTIUM ...DATES COVERED (From – To) 4. TITLE AND SUBTITLE MEASUREMENT OF ELASTIC MODULUS OF ALUMINA AND BARIUM STRONTIUM TITANATE WAFERS PRODUCED BY...configuration testing method. Samples of barium strontium titanate (BST) were made using a regular powder pressing, sintering, pelletizing, and

  14. Faceted Surface Grain Morphology of Rapidly Solidified Alumina: Characterization and Potential Applications

    SciTech Connect

    Harimkar, Sandip; Kenik, Edward A; Shim, Sanghoon; Dahotre, Narendra B

    2009-01-01

    This communication reports on the characterization of novel surface microstructure formed in rapidly solidified porous alumina ceramic. Advanced characterization techniques such as Orientation Imaging Microscopy (OIM) and Atomic Force Microscopy (AFM) are used to understand the crystallographic and morphological aspects of the resultant microstructure. Potential applications of laser surface modified alumina ceramics are presented.

  15. A Review of Alumina Feeding and Dissolution Factors in Aluminum Reduction Cells

    NASA Astrophysics Data System (ADS)

    Lavoie, Pascal; Taylor, Mark P.; Metson, James B.

    2016-08-01

    Modern aluminum reduction cells use point feeding technology to replenish alumina as it is consumed by the electrolytic process. The dissolution of alumina has become increasingly difficult to control as the cell sizes and electrolysis intensity have increased. The mass of alumina added per unit time is now much higher than a decade ago, and must take place within a smaller electrolyte mixing volume. In order to replenish the alumina concentration evenly, the alumina needs to be delivered, dispersed, dissolved, and distributed throughout the reduction cell. The dissolution itself follows a 4-step process that can be limited by a multitude of factors. The status of the research on each of these factors is reviewed in the present paper. Although research in laboratory cells has been conducted many times, and the impact of many factors on dissolution has been measured, published observations of alumina feeding on industrial cells are very sparse, especially regarding the dissolution dynamics in the space-time domain and the impact of the feeder hole condition. The present paper therefore presents a qualitative model of the factors governing alumina dissolution in industrial cells and offers the hypothesis that maintenance of the feeder hole condition is central to ensuring alumina dissolution and prevention of sludging.

  16. Effects of Variable Aspect-Ratio Inclusions on the Electrical Impedance of an Alumina Zirconia Composite at Intermediate Temperatures

    NASA Technical Reports Server (NTRS)

    Goldsby, Jon C.

    2010-01-01

    A series of alumina-yttria-stabilized zirconia composites containing either a high aspect ratio (5 and 30 mol%) hexagonal platelet alumina or an alumina low aspect ratio (5 and 30 mol%) spherical particulate was used to determine the effect of the aspect ratio on the temperature-dependent impedance of the composite material. The highest impedance across the temperature range of 373 to 1073 K is attributed to the grain boundary of the hexagonal platelet second phase in this alumina zirconia composite.

  17. Dissolution of carbon from alumina-carbon mixtures into liquid iron: Influence of carbonaceous materials

    NASA Astrophysics Data System (ADS)

    Khanna, Rita; Sahajwalla, Veena; Rodgers, Brenton; McCarthy, Fiona

    2006-08-01

    Due to their excellent thermal shock and wear resistance at high temperatures, alumina-carbon based refractories are used extensively in the steel industry. A clear understanding of factors affecting the dissolution of carbon from refractories is of crucial importance, as carbon depletion from the refractory can significantly deteriorate refractory performance and metal quality. Atomistic simulations on the alumina-graphite/liquid iron system have shown that nonwetting between alumina and liquid iron is an important factor inhibiting the penetration of liquid metal in the refractory matrix and limiting carbon dissolution. This study investigates the role played by the carbonaceous material in the dissolution of carbon from the refractory composite. Two carbonaceous materials, namely, petroleum coke and natural graphite, respectively, containing 0.35 and 5.26 pct ash, were used in this study. Substrates were prepared from mixtures of alumina and carbon over a wide concentration range. Using a sessile drop arrangement, carbon pickup by liquid iron from alumina-carbon mixtures was measured at 1550 °C and was compared with the carbon pickup from alumina-synthetic graphite mixtures. These studies were supplemented with wettability measurements and microscopic investigations on the interfacial region. For high alumina concentrations (>40 wt pct), carbon dissolution from refractory mixtures was found to be negligible for all carbonaceous materials under investigation. Significant differences however were observed at lower alumina concentrations. Carbon dissolution from alumina-petroleum coke mixtures was much lower than the corresponding dissolution from alumina synthetic graphite-mixtures and was attributed to poor wettability of petroleum coke with liquid iron, its structural disorder, and the presence of sulfur. Very high levels of carbon dissolution, however, were observed from alumina-natural graphite mixtures, with carbon pickup by liquid iron from mixtures with up

  18. Interactions of L-alanine with alumina as studied by vibrational spectroscopy.

    PubMed

    Garcia, Ana R; de Barros, Ricardo Brito; Fidalgo, Alexandra; Ilharco, Laura M

    2007-09-25

    The interactions of L-alanine with gamma- and alpha-alumina have been investigated by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). L-alanine/alumina samples were dried from aqueous suspensions, at 36.5 degrees C, with two amino acid concentrations (0.4 and 0.8 mmol g-1) and at different pH values (1, 6, and 13). The vibrational spectra proved that the nature of L-alanine interactions with both aluminas is the same (hydrogen bonding), although the groups involved depend on the L-alanine form and on alumina surface groups, both controlled by the pH. For samples prepared at pH 1, cationic L-alanine [CH3CH(NH3+)COOH] displaces physisorbed water from alumina, and strong hydrogen bonds are established between the carbonyl groups of alanine, as electron donors, and the surface Al-OH2+ groups of alumina. This occurs at the expense of alanine dimer dissociation and breaking of intramolecular bonds. When samples are prepared at pH 6, the interacting groups are Al-OH2+ and the carboxylate groups of zwitterionic L-alanine [CH3CH(NH3+)COO-]. The affinity of L-alanine toward alumina decreases, as the strong NH3+...-OOC intermolecular hydrogen bonds prevail over the interactions with alumina. Thus, for a load of 0.8 mmol g-1, phase segregation is observed. On alpha-alumina, crystal deposition is even observed for a load of 0.4 mmol g-1. At pH 13, the carboxylate groups of anionic L-alanine [CH3CH(NH2)COO-] are not affected by alumina. Instead, hydrogen bond interactions occur between NH2 and the Al-OH surface groups of the substrate. Complementary N2 adsorption-desorption isotherms showed that adsorption of L-alanine occurs onto the alumina pore network for samples prepared at pH 1 and 13, whereas at pH 6 the amino acid/alumina interactions are not strong enough to promote adsorption. The mesoporous structure and the high specific surface area of gamma-alumina make it a more efficient substrate for adsorption of L-alanine. For each alumina, however, it is

  19. Final report on DSA methods for monitoring alumina in aluminum reduction cells with cermet anodes

    NASA Astrophysics Data System (ADS)

    Windisch, C. F., Jr.

    1992-04-01

    The Sensors Development Program was conducted at the Pacific Northwest Laboratory (PNL) for the US Department of Energy, Office of Industrial Processes. The work was performed in conjunction with the Inert Electrodes Program at PNL. The objective of the Sensors Development Program in FY 1990 through FY 1992 was to determine whether methods based on digital signal analysis (DSA) could be used to measure alumina concentration in aluminum reduction cells. Specifically, this work was performed to determine whether useful correlations exist between alumina concentration and various DSA-derived quantification parameters, calculated for current and voltage signals from laboratory and field aluminum reduction cells. If appropriate correlations could be found, then the quantification parameters might be used to monitor and, consequently, help control the alumina concentration in commercial reduction cells. The control of alumina concentration is especially important for cermet anodes, which have exhibited instability and excessive wear at alumina concentrations removed from saturation.

  20. Rare earth modified silica-aluminas as supports for bifunctional catalysis

    SciTech Connect

    Soled, S.L.; McVicker, G.; Miseo, S.

    1996-12-31

    We have explored rare earth oxide-modified amorphous silica-aluminas as {open_quotes}permanent{close_quotes} intermediate strength acids used as supports for bifunctional catalysts. The addition of well dispersed weakly basic rare earth oxides {open_quotes}titrates{close_quotes} the stronger acid sites of amorphous silica-alumina and lowers the acid strength to the level shown by halided aluminas. Physical and chemical probes, as well as model olefin and paraffin isomerization reactions show that acid strength can be adjusted close to that of chlorided and fluorided aluminas. Metal activity is inhibited relative to halided alumina catalysts, which limits the direct metal-catalyzed dehydrocyclization reactions during paraffin reforming but does not interfere with hydroisomerization reactions.

  1. Micromechanics of deformation in porous liquid phase sintered alumina under hertzian contact

    SciTech Connect

    DIGIOVANNI,ANTHONY A.; CHAN,HELEN M.; HARMER,MARTIN P.; NIED,HERMAN F.

    2000-05-15

    A series of fine-grained porous alumina samples, with and without a liquid phase, were fabricated in compositions matched closely to commercially available alumina used as a microelectronic substrates. Hertzian indentation on monolithic specimens of the glass-containing samples produced a greater quasi-ductile stress-strain response compared to that observed in the pure alumina. Maximum residual indentation depths, determined from surface profilometry, correlated with the stress-strain results. Moreover, microstructural observations from bonded interface specimens revealed significantly more damage in the form of microcracking and under extreme loading, pore collapse, in the glass-containing specimens. The absence of the typical twin faulting mechanism observed for larger-grained alumina suggests that the damage mechanism for quasi-ductility in these fine-grained porous alumina derived from the pores acting as a stress concentrator and the grain boundary glass phase providing a weak path for short crack propagation.

  2. Improved mechanical properties of HDPE/nano-alumina composite through silane coupling agent

    NASA Astrophysics Data System (ADS)

    Akmil, N.; Luqman, C. A.; Ahmad, M.; Zaman, K.

    2012-11-01

    The effect of silane coupling agent to mechanical properties of HDPE/nano-alumina composite was investigated. Nano-alumina used in this study was produced by using sol-gel method. The shape and size of nano-alumina were determined by using TEM. Prior to the usage of nano alumina as a filler in the polymer matrix, (3-methacryloxypropyl) trimethoxysilane (MPS) was used to functionalize the nanoparticles due to its bifunctional nature: hydrolysable group (-Si(OCH3)3) and unsaturated carbon-carbon double bond. The XRD result shows diffraction spectrum of the synthesized nano-alumina. In order to improve the mechanical properties of the composite, nanoalumina was treated with (3-methacryloxypropyl) trimethoxysilane (MPS). A high tensile strength, is achieved at 4 wt% of MPS.

  3. Cellulose extraction from Zoysia japonica pretreated by alumina-doped MgO in AMIMCl.

    PubMed

    Liu, Le; Ju, Meiting; Li, Weizun; Jiang, Yang

    2014-11-26

    In this study, alumina-doped MgO was produced as a solid alkali for lignocellulose pretreatment. Pretreatment with alumina-doped MgO disrupted the lignocellulose structure and significantly reduced the lignin content of the Z. japonica. After pretreatment, Z. japonica showed significant solubility in 1-allyl-3-methylimidazolium chloride (AMIMCl). The similar high solubility of pretreated Z. japonica samples by original alumina-doped MgO and used alumina-doped MgO also proved that alumina-doped MgO had strong stability, which can be recycled and used repeatedly. The regenerated cellulose was similar to microcrystalline cellulose according to FTIR and NMR analyses. Compared to microcrystalline cellulose, only the crystallinity of the regenerated cellulose decreased.

  4. Extraction and characterization of alumina nanopowders from aluminum dross by acid dissolution process

    NASA Astrophysics Data System (ADS)

    Sarker, Md. Saifur Rahman; Alam, Md. Zahangir; Qadir, Md. Rakibul; Gafur, M. A.; Moniruzzaman, Mohammad

    2015-04-01

    A significant amount of aluminum dross is available as a waste in foundry industries in Bangladesh. In this study, alumina was extracted from aluminum dross collected from two foundry industries situated in Dhamrai and Manikgang, near the capital city, Dhaka. Aluminum dross samples were found to approximately contain 75wt% Al2O3 and 12wt% SiO2. An acid dissolution process was used to recover the alumina value from the dross. The effects of various parameters, e.g., temperature, acid concentration, and leaching time, on the extraction of alumina were studied to optimize the dissolution process. First, Al(OH)3 was produced in the form of a gel. Calcination of the Al(OH)3 gel at 1000°C, 1200°C, and 1400°C for 2 h produced γ-Al2O3, (α+γ)-Al2O3, and α-alumina powder, respectively. Thermal characterization of the Al(OH)3 gel was performed by thermogravimetric/differential thermal analysis (TG/DTA) and differential scanning calorimetry (DSC). The phases and crystallite size of the alumina were determined by X-ray diffraction analysis. The dimensions of the alumina were found to be on the nano level. The chemical compositions of the aluminum dross and alumina were determined by X-ray fluorescence (XRF) spectroscopy. The microstructure and morphology of the alumina were studied with scanning electron microscopy. The purity of the alumina extracted in this study was found to be 99.0%. Thus, it is expected that the obtained alumina powders can be potentially utilized as biomaterials.

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

    NASA Technical Reports Server (NTRS)

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

    2017-01-01

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

  6. Stress-rupture behavior of small diameter polycrystalline alumina fibers

    NASA Technical Reports Server (NTRS)

    Yun, Hee Mann; Goldsby, Jon C.; Dicarlo, James A.

    1993-01-01

    Continuous length polycrystalline alumina fibers are candidates as reinforcement in high temperature composite materials. Interest therefore exists in characterizing the thermomechanical behavior of these materials, obtaining possible insights into underlying mechanisms, and understanding fiber performance under long term use. Results are reported on the time-temperature dependent strength behavior of Nextel 610 and Fiber FP alumina fibers with grain sizes of 100 and 300 nm, respectively. Below 1000 C and 100 hours, Nextel 610 with the smaller grain size had a greater fast fracture and rupture strength than Fiber FP. The time exponents for stress-rupture of these fibers were found to decrease from approximately 13 at 900 C to below 3 near 1050 C, suggesting a transition from slow crack growth to creep rupture as the controlling fracture mechanism. For both fiber types, an effective activation energy of 690 kJ/mol was measured for rupture. This allowed stress-rupture predictions to be made for extended times at use temperatures below 1000 C.

  7. Bath for electrolytic reduction of alumina and method therefor

    SciTech Connect

    Brown, Craig W.; Brooks, Richard J.; Frizzle, Patrick B.; Juric, Drago D.

    2002-11-26

    An electrolytic bath for use during the electrolytic reduction of alumina to aluminum. The bath comprises a molten electrolyte having the following ingredients: (a) AlF.sub.3 and at least one salt selected from the group consisting of NaF, KF, and LiF; and (b) about 0.004 wt. % to about 0.2 wt. %, based on total weight of the molten electrolyte, of at least one transition metal or at least one compound of the metal or both. The compound may be, for example, a fluoride, oxide, or carbonate. The metal can be nickel, iron, copper, cobalt, or molybdenum. The bath can be employed in a combination that includes a vessel for containing the bath and at least one non-consumable anode and at least one dimensionally stable cathode in the bath. Employing the bath of the present invention during electrolytic reduction of alumina to aluminum can improve the wetting of aluminum on a cathode by reducing or eliminating the formation of non-metallic deposits on the cathode. Removing sulfur from the bath can also minimize cathode deposits. Aluminum formed on the cathode can be removed directly from the cathode.

  8. Bath for electrolytic reduction of alumina and method therefor

    SciTech Connect

    Brown, Craig W.; Brooks, Richard J.; Frizzle, Patrick B.; Juric, Drago D.

    2001-07-10

    An electrolytic bath for use during the electrolytic reduction of alumina to aluminum. The bath comprises a molten electrolyte having the following ingredients: (a) AlF.sub.3 and at least one salt selected from the group consisting of NaF, KF, and LiF; and (b) about 0.004 wt. % to about 0.2 wt. %, based on total weight of the molten electrolyte, of at least one transition metal or at least one compound of the metal or both. The compound may be, for example, a fluoride, oxide, or carbonate. The metal can be nickel, iron, copper, cobalt, or molybdenum. The bath can be employed in a combination that includes a vessel for containing the bath and at least one non-consumable anode and at least one dimensionally stable cathode in the bath. Employing the bath of the present invention during electrolytic reduction of alumina to aluminum can improve the wetting of aluminum on a cathode by reducing or eliminating the formation of non-metallic deposits on the cathode.

  9. Mechanical properties of tricalcium phosphate-fluorapatite-alumina composites

    NASA Astrophysics Data System (ADS)

    Bouslama, N.; Ben Ayed, F.; Bouaziz, J.

    2009-11-01

    This study deals to produce tricalcium phosphate - fluorapatite composites sintering at various temperatures (1300∘ C, 1350∘ C and 1400∘ C) and with different alumina additives amounts (2.5 wt%, 5 wt%, 7.5 wt%, 10 wt% and 20 wt%). The characterization of samples before and after sintering was investigated, using X-ray diffraction, infrared spectroscopy, scanning electronic microscopy and by analysis using 31P and 27Al nuclear magnetic resonance. Mechanical properties have been measured by Brazilian test. The evolution of composite rupture strength was studied as a function of sintering temperature. The effect of sintering on the mechanical properties was measured with the change in composition and microstructure of the composite. The mechanical resistances of composites were increased with the temperatures and with concentrations of alumina. At 1350∘ C, the mechanical resistance reaches its maximum value with 5 wt% Al2O3 (13.6 MPa) whereas the optimum density is about 90% with 2.5 wt% Al2O3.

  10. Modeling of chemisorption on copper oxide supported on alumina

    NASA Astrophysics Data System (ADS)

    Hao, Y. G.; Cooper, B. R.

    1994-06-01

    Transition metals supported on alumina are widely used as catalysts, and over the last few decades a large amount of experimental work has been done to characterize such systems. While it is generally believed that the catalytic reactions occur on and near the surface, knowledge of the reactions and the adsorption sites on the surface and related energetics is seriously lacking, especially at the atomic structure level. We have used a combination of the film linearized muffin-tin orbital (FLMTO) method and an ab initio molecular quantum cluster method to model the use of the system of CuO/-γ-Al 2O 3 as a regenerable adsorbent of SO 2 (of interest for flue-gas cleanup). The modeling and calculations with the FLMTO method show that the copper atoms are adsorbed at the surface octahedral vacant sites of the alumina. The modeling and calculations with the ab initio cluster method rule out the adsorption of the SO 2 molecule with sulfur-copper bonding and indicate that the SO 2 molecule is adsorbed via oxygen-copper bonding; and accordingly we investigate some pertinent geometrical configurations including "bridge" arrangements providing bonding between the oxygen atoms of the SO 2 molecule and the surface copper or aluminum atoms.

  11. On the Hugoniot elastic limit in polycrystalline alumina

    NASA Astrophysics Data System (ADS)

    Bourne, N. K.; Millett, J. C. F.; Chen, M.; McCauley, J. W.; Dandekar, D. P.

    2007-10-01

    The use of polycrystalline ceramics in engineering applications requires a better knowledge of microstructural response than exists at present. The continuum response of the alumina AD995 to shock loading has been extensively investigated. This work aims to connect microstructural response with continuum observations. Over recent years, workers have reported failure in various polycrystalline ceramics occurring behind a propagating front running behind the shock. These phenomena have been investigated using embedded stress sensors and a recovery technique that has allowed the observation of the microstructure above and below the Hugoniot elastic limit (HEL). These results are brought together here to explain the observed behavior. The failure front velocity is found to change with the applied stress, in particular, it slows markedly as the HEL is exceeded. Further, the curvature of histories recorded by sensors may be related to the observed response. The evidence in the microstructure shows that the response below HEL is dominated by the intergranular failure, while above it by plasticity in grains (including twinning), which alters the deformation and failure characteristics. These microstructural features are combined with the continuum observations to review the response of the alumina.

  12. Evaluation of Alumina-Forming Austenitic Foil for Advanced Recuperators

    SciTech Connect

    Pint, Bruce A; Brady, Michael P; Yamamoto, Yukinori; Santella, Michael L; Maziasz, Philip J; Matthews, Wendy

    2011-01-01

    A corrosion- and creep-resistant austenitic stainless steel has been developed for advanced recuperator applications. By optimizing the Al and Cr contents, the alloy is fully austenitic for creep strength while allowing the formation of a chemically stable external alumina scale at temperatures up to 900 C. An alumina scale eliminates long-term problems with the formation of volatile Cr oxy-hydroxides in the presence of water vapor in exhaust gas. As a first step in producing foil for primary surface recuperators, three commercially cast heats have been rolled to 100 m thick foil in the laboratory to evaluate performance in creep and oxidation testing. Results from initial creep testing are presented at 675 C and 750 C, showing excellent creep strength compared with other candidate foil materials. Laboratory exposures in humid air at 650 800 C have shown acceptable oxidation resistance. A similar oxidation behavior was observed for sheet specimens of these alloys exposed in a modified 65 kW microturbine for 2871 h. One composition that showed superior creep and oxidation resistance has been selected for the preparation of a commercial batch of foil. DOI: 10.1115/1.4002827

  13. Synthesis of magnesium aluminate spinel by periclase and alumina chlorination

    SciTech Connect

    Orosco, Pablo; Barbosa, Lucía; Ruiz, María del Carmen

    2014-11-15

    Highlights: • Use of chlorination for the synthesis of magnesium aluminate spinel. • The reagents used were alumina, periclase and chlorine. • Isothermal and non-isothermal assays were performed in air and Cl{sub 2}–N{sub 2} flows. • The chlorination produced magnesium aluminate spinel at 700 °C. • Selectivity of the chlorination reaction to obtain spinel is very high. - Abstract: A pyrometallurgical route for the synthesis of magnesium aluminate spinel by thermal treatment of a mechanical mixture containing 29 wt% MgO (periclase) and 71 wt% Al{sub 2}O{sub 3} (alumina) in chlorine atmosphere was developed and the results were compared with those obtained by calcining the same mixture of oxides in air atmosphere. Isothermal and non-isothermal assays were performed in an experimental piece of equipment adapted to work in corrosive atmospheres. Both reagents and products were analyzed by differential thermal analysis (DTA), X-ray diffraction (XRD) and X-ray fluorescence (XRF). Thermal treatment in Cl{sub 2} atmosphere of the MgO–Al{sub 2}O{sub 3} mixture produces magnesium aluminate spinel at 700 °C, while in air, magnesium spinel is generated at 930 °C. The synthesis reaction of magnesium aluminate spinel was complete at 800 °C.

  14. Development of Alumina-Forming Austenitic Stainless Steels

    SciTech Connect

    Yamamoto, Yukinori; Brady, Michael P; Santella, Michael L; Bei, Hongbin; Maziasz, Philip J; Pint, Bruce A

    2008-01-01

    Work in fiscal year 2008 focused on the development of creep-resistant, alumina-forming austenitic (AFA) stainless steel alloys, which exhibit a unique combination of an excellent oxidation resistance via protective alumina (Al2O3) scale formation and high-temperature creep strength through the formation of stable nano-scale MC carbides [1-8]. High levels of Nb additions (> 1 wt.% Nb) and/or Ni additions (25-30 wt.%), at Al levels of 2.5-4 wt.%, were found to correlate with increased upper-temperature limit for Al2O3 scale formation in air ( 900 aC) and air with 10% water vapor ( 800 aC). Creep resistance also showed a strong dependence on the level of Nb additions, and was correlated with volume fraction of MC-type carbides using thermodynamic computational tools. A trial heat of a 50 lb AFA alloy ingot was made using conventional single-melt vacuum techniques, and the alloy was successfully hot-rolled without any cracking [2]. This heat showed good weldability, using filler material of the same alloy.

  15. Rheological behavior or bauxite- and alumina-based castables

    NASA Astrophysics Data System (ADS)

    Ye, Fangbao

    In this cooperative work between Ecole Polytechnique, Canada and Zhengzhou University, China initiated in 2000, the following subjects have been studied: (1) the rheological properties of the matrix part of bauxite-based castables; (2) the rheological properties of SiC containing bauxite-based castables; (3) the high temperature mechanical properties of the SiC containing bauxite-based castables; (4) the rheological behavior of low cement alumina-based castable with and without graphite addition; (5) the rheological behavior of zero cement alumina-based castable with and without MgO and/or graphite addition. At first it was intended to optimize the factors affecting the rheological behaviour of a slurry containing up to 80% solids (such as super-fine silica and alumina addition, water/cement ratio, type and content of dispersants and powder particle-size), to use them in later work on the rheology of castables. The second and third subjects were tackled to understand the relationship between rheological behavior and high temperature properties and to optimize these properties for conventional castable used in iron making industry. The fourth and fifth subjects were initiated to contribute to the understanding of rheological properties of new alumina-based castables, containing magnesia and carbon. The goals in each case are to identify the parameters which influence the most shear thinning or the shear thickening of mixes by measuring the rheological characteristics, torque viscosity and yield stress (from rheometer) for self-flow and pumpable castables, and to assess the optimal conditions in the formulation of different mixes, including these newly developed carbon-containing castables, yet to be commercialized, at least those containing graphite. In total, more than 200 different mixes have been prepared and their rheological behaviour studied. For this purpose, three methods have been used: (1) Rotational viscometer---for study on rheology of matrix slurry; (2

  16. MSTAR: an absolute metrology sensor with sub-micron accuracy for space-based applications

    NASA Technical Reports Server (NTRS)

    Peters, Robert D.; Lay, Oliver P.; Dubovitsky, Serge; Burger, Johan P.; Jeganathan, Muthu

    2004-01-01

    The MSTAR sensor is a new system for measuring absolute distance, capable of resolving the integer cycle ambiguity of standard interferometers, and making it possible to measure distance with subnanometer accuracy.

  17. Sub-micron resolution rf cavity beam position monitor system at the SACLA XFEL facility

    NASA Astrophysics Data System (ADS)

    Maesaka, H.; Ego, H.; Inoue, S.; Matsubara, S.; Ohshima, T.; Shintake, T.; Otake, Y.

    2012-12-01

    We have developed and constructed a C-band (4.760 GHz) rf cavity beam position monitor (RF-BPM) system for the XFEL facility at SPring-8, SACLA. The demanded position resolution of the RF-BPM is less than 1 μm, because an electron beam and x-rays must be overlapped within 4 μm precision in the undulator section for sufficient FEL interaction between the electrons and x-rays. In total, 57 RF-BPMs, including IQ demodulators and high-speed waveform digitizers for signal processing, were produced and installed into SACLA. We evaluated the position resolutions of 20 RF-BPMs in the undulator section by using a 7 GeV electron beam having a 0.1 nC bunch charge. The position resolution was measured to be less than 0.6 μm, which was sufficient for the XFEL lasing in the wavelength region of 0.1 nm, or shorter.

  18. Cathepsin K-targeted sub-micron particles for regenerative repair of vascular elastic matrix.

    PubMed

    Jennewine, Brenton; Fox, Jonathan; Ramamurthi, Anand

    2017-04-01

    Abdominal Aortic Aneurysms (AAA) involve slow dilation and weakening of the aortic wall due to breakdown of structural matrix components, such as elastic fibers by chronically overexpressed matrix metalloproteinases (MMPs), primarily, MMPs-2 and -9. Auto-regenerative repair of disrupted elastic fibers by smooth muscle cells (SMCs) at the AAA site is intrinsically poor and together with chronic proteolysis prevents restoration of elastin homeostasis, necessary to enable AAA growth arrest or regression to a healthy state. Oral doxycycline (DOX) therapy can inhibit MMPs to slow AAA growth, but has systemwide side-effects and inhibits new elastin deposition within AAA tissue, diminishing prospects for restoring elastin homeostasis preventing the arrest/regression of AAA growth. We have thus developed cationic amphiphile (DMAB)-modified submicron particles (SMPs) that uniquely exhibit pro-elastogenic and anti-proteolytic properties, separate from similar effects of the encapsulated drug. These SMPs can enable sustained, low dose DOX delivery within AAA tissue to augment elastin regenerative repair. To provide greater specificity of SMP targeting, we have conjugated the DOX-SMP surface with an antibody against cathepsin K, a lysosomal protease that is highly overexpressed within AAA tissue. We have determined conditions for efficient cathepsin K Ab conjugation onto the SMPs, improved SMP binding to aneurysmal SMCs in culture and to injured vessel walls ex vivo, conjugation did not affect DOX release from the SMPs, and improved pro-elastogenic and anti-proteolytic effects due to the SMPs likely due to their increased proximity to cells via binding. Our study results suggest that cathepsin K Ab conjugation is a useful targeting modality for our pro-regenerative SMPs. Future studies will investigate SMP retention and biodistribution following targeting to induced AAAs in rat models through intravenous or catheter-based aortal infusion and thereafter their efficacy for regenerative elastic matrix repair in the AAA wall.

  19. A biological sub-micron thickness optical broadband reflector characterized using both light and microwaves.

    PubMed

    Vukusic, P; Kelly, R; Hooper, I

    2009-04-06

    Broadband optical reflectors generally function through coherent scattering from systems comprising one of three designs: overlapped; chirped; or chaotic multilayer reflectors. For each, the requirement to scatter a broad band of wavelengths is met through the presence of a variation in nanostructural periodicity running perpendicular to the systems' outer surfaces. Consequently, the requisite total thickness of the multilayer can often be in excess of 50 mum. Here, we report the discovery and the microwave-assisted characterization of a natural system that achieves excellent optical broadband reflectivity but that is less than 1 mum thick. This system, found on the wing scales of the butterfly Argyrophorus argenteus, comprises a distinctive variation in periodicity that runs parallel to the reflecting surface, rather than perpendicular to it. In this way, the requirement for an extensively thick system is removed.

  20. Mechanoresponsive system based on sub-micron chitosan-functionalized ferromagnetic disks.

    SciTech Connect

    Kim, D-H.; Karavayev, P.; Rozhkova, E. A.; Pearson, J.; Yefremenko, V.; Bader, S. D.; Novosad, V.

    2011-01-01

    We report a doxorubicin loaded chitosan biopolymer-ferromagnetic disks hybrid system capable of on-demand magnetomechanically induced release of drug molecules. Gold covered ferromagnetic disks were encapsulated into the polymer scaffold through the assembly of the thiolated chitosan on the disk's gold surface followed by entrapping of the doxorubicin drug within a cross-linked polymer matrix. We demonstrate that the release process can be effectively tuned and controlled by varying the magnetic field characteristics: orientation, amplitude, frequency and duration.

  1. Openstage: A Low-Cost Motorized Microscope Stage with Sub-Micron Positioning Accuracy

    PubMed Central

    Campbell, Robert A. A.; Eifert, Robert W.; Turner, Glenn C.

    2014-01-01

    Recent progress in intracellular calcium sensors and other fluorophores has promoted the widespread adoption of functional optical imaging in the life sciences. Home-built multiphoton microscopes are easy to build, highly customizable, and cost effective. For many imaging applications a 3-axis motorized stage is critical, but commercially available motorization hardware (motorized translators, controller boxes, etc) are often very expensive. Furthermore, the firmware on commercial motor controllers cannot easily be altered and is not usually designed with a microscope stage in mind. Here we describe an open-source motorization solution that is simple to construct, yet far cheaper and more customizable than commercial offerings. The cost of the controller and motorization hardware are under $1000. Hardware costs are kept low by replacing linear actuators with high quality stepper motors. Electronics are assembled from commonly available hobby components, which are easy to work with. Here we describe assembly of the system and quantify the positioning accuracy of all three axes. We obtain positioning repeatability of the order of in X/Y and in Z. A hand-held control-pad allows the user to direct stage motion precisely over a wide range of speeds ( to ), rapidly store and return to different locations, and execute “jumps” of a fixed size. In addition, the system can be controlled from a PC serial port. Our “OpenStage” controller is sufficiently flexible that it could be used to drive other devices, such as micro-manipulators, with minimal modifications. PMID:24586468

  2. Limits of miniaturization: assessing ITP performance in sub-micron and nanochannels.

    PubMed

    Janssen, Kjeld G H; Li, Jiajie; Hoang, Hanh T; Vulto, Paul; van den Berg, Richard J B H N; Overkleeft, Herman S; Eijkel, Jan C T; Tas, Niels R; van der Linden, Heiko J; Hankemeier, Thomas

    2012-08-21

    The feasibility of isotachophoresis in channels of sub micrometer and nanometer dimension is investigated. A sample injection volume of 0.4 pL is focused and separated in a 330 nm deep channel. The sample consists of a biomatrix containing the fluorescently-labeled amino acids glutamate and phenylalanine, 20 attomoles of each. Isotachophoretic focusing is successfully demonstrated in a 50 nm deep channel. Separation of the two amino acids in the 50 nm deep channel however, could not be performed as the maximum applicable voltage was insufficient. This limit is imposed by bubble formation that we contribute to cavitation as a result of the mismatch in electro-osmotic flow, so called electrocavitation. This represents an unexpected limit on the miniaturization of ITP. Nonetheless, we report the smallest isotachophoretic separation and focusing experiment to date, both in terms of controlled sample injection volume and channel height.

  3. Characterization and recovery of Deep Sub Micron (DSM) technologies behavior under radiation

    NASA Technical Reports Server (NTRS)

    Stoica, Adrian; Wang, Xiao

    2005-01-01

    This paper serves a twofold purpose: characterize the behavior of a reconfigurable chip exposed to radiation; and demonstrate a method for functionality recovery due to Total Ionizing Dose (TID) effects. The experiments are performed using a PL developed reconfigurable device, a Field Programmable Transistor Array (FPTA). The paper initially describes experiments on the characterization of the NMOS transistor behavior for TID values up to 300krad. The behavior of analog and digital circuits downloaded onto the FPTA chip is also assessed for TID effects. This paper also presents a novel approach for circuit functionality recovery due to radiation effects based on Evolvable Hardware. The key idea is to reconfigure a programmable device, in-situ, to compensate, or bypass its degraded or damaged components. Experiments with total radiation dose up to 300kRad show that while the functionality of a variety of circuits, including digital gates, a rectifier and a Digital to Analog Converter implemented on a FPTA-2 chip is degraded/lost at levels before 200kRad, the correct functionality can be recovered through the proposed evolutionary approach and the chips are able to survive higher radiation, for several functions in excess of total radiation dose of 250kRad.

  4. Detection of Sub-Micron Radiation from the Surface of Venus by Cassini/VIMS

    USGS Publications Warehouse

    Baines, K.H.; Bellucci, G.; Bibring, J.-P.; Brown, R.H.; Buratti, B.J.; Bussoletti, E.; Capaccioni, F.; Cerroni, P.; Clark, R.N.; Coradini, A.; Cruikshank, D.P.; Drossart, P.; Formisano, V.; Jaumann, R.; Langevin, Y.; Matson, D.L.; McCord, T.B.; Mennella, V.; Nelson, R.M.; Nicholson, P.D.; Sicardy, B.; Sotin, C.; Hansen, G.B.; Aiello, J.J.; Amici, S.

    2000-01-01

    We report the first detection and profile characterization of thermal emission from the surface of Venus at 0.85 and 0.90 ??m, observed in the first planetary spectrum acquired by the Visual-Infrared Mapping Spectrometer onboard the Cassini spacecraft en route to the Saturn system. The strength and shape of these two newly observed nightside emissions agree with theoretical predictions based on the strength of the strong emission observed at 1.01 ??m. These emissions, together with previously-reported surface emission features at 1.01, 1.10, and 1.18 ??m, potentially provide a new technique for remotely mapping the mineralogical composition of the venusian surface. ?? 2000 Academic Press.

  5. Seasonality of ultrafine and sub-micron aerosols and the inferences on particle formation processes

    NASA Astrophysics Data System (ADS)

    Cheung, H. C.; Chou, C. C.-K.; Chen, M.-J.; Huang, W.-R.; Huang, S.-H.; Tsai, C.-Y.; Lee, C. S.-L.

    2015-08-01

    The aim of this study is to investigate the seasonal variations in the physicochemical properties of atmospheric ultrafine particles (UFPs, d ≤ 100nm) and submicron particles (PM1, d ≤ 1 μm) in an East-Asian urban area, which are hypothesized to be affected by the interchange of summer and winter monsoons. An observation experiment was conducted at the TARO, an urban aerosol station in Taipei, Taiwan, from October 2012 to August 2013. The measurements included the mass concentration and chemical composition of UFPs and PM1, as well as the particle number concentration (PNC) and size distribution (PSD) with size range of 4-736 nm. The results indicate that the mass concentration of PM1 was elevated during cold seasons with peak level of 18.5 μg m-3 in spring, whereas the highest UFPs concentration was measured in summertime with a seasonal mean of 1.62 μg m-3. Moreover, chemical analysis revealed that the UFPs and PM1 were characterized by distinct composition; UFPs were composed mostly of organics, whereas ammonium and sulfate were the major constituents in PM1. The seasonal median of total PNCs ranged from 13.9 × 103 cm-3 in autumn to 19.4 × 103 cm-3 in spring. The PSD information retrieved from the corresponding PNC measurements indicates that the nucleation mode PNC (N4-25) peaked at 11.6 × 103 cm-3 in winter, whereas the Aitken mode (N25-100) and accumulation mode (N100-736) exhibited summer maxima at 6.0 × 103 and 3.1 × 103 cm-3, respectively. The shift in PSD during summertime is attributed to the enhancement in the photochemical production of condensable organic matter that, in turn, contributes to the growth of aerosol particles in the atmosphere. In addition, remarkable photochemical production of particles was observed in spring and summer seasons, which was characterized with averaged particle growth and formation rates of 4.3 ± 0.8 nm h-1 and 1.6 ± 0.8 cm-3 s-1, respectively. The prevalence of new particle formation (NPF) in summer is suggested as a result of seasonally enhanced photochemical oxidation of SO2, which contributes to the production of H2SO4, and low level of PM10 (d ≤ 10 μm) that serves as the condensation sink. Regarding the sources of aerosol particles, correlation analysis upon the PNCs against NOx revealed that the local vehicular exhaust was the dominant contributor of the UFPs throughout a year. On the contrary, the Asian pollution outbreaks can have significant influence in the PNC of accumulation mode particles during the seasons of winter monsoons. The results of this study underline the significance of secondary organic aerosols in the seasonal variations of UFPs and the influences of continental pollution outbreaks in the downwind areas of Asian outflows.

  6. Measurements of Sub-Micron AL203 Particles in Rocket Plumes

    DTIC Science & Technology

    1992-12-01

    aluminum oxide particles were a Sauter mean diameter of 0.30 + /- .02 microns, an index of refraction of 1.64 + /- .04 and standard deviation of 1.52...motor geometries. The average values obtained for the aluminum oxide particles were a Sauter mean diameter of 0.30+/-.02 microns, an index of...region were dominated by small particles which had an index of refraction of 1.63+8%, and a Sauter mean diameter of 0.15g+4 %. Recommended improvements

  7. Heavy ion acceleration driven by the Interaction between ultraintense Laser pulse and sub-micron foils

    NASA Astrophysics Data System (ADS)

    Yu, Jinqing; McGuffey, C.; Beg, F. N.; High Energy Density Group Team

    2015-11-01

    For ion acceleration at the intensity exceeding 1021W/cm2, Radiation Pressure Acceleration (RPA) could offer advantages over Target Normal Sheath Acceleration (TNSA) and Break-Out Afterburner (BOA). In this ultra-relativistic regime, target electrons become highly relativistic and the results are sensitive to many parameters. Especially for heavy ions acceleration, the understanding of the most important parameter effects is limited due to the lack of experiments and modeling. To further understand the key parameters and determine the most suitable regimes for efficient acceleration of heavy ions, we have carried out two-dimensional Particle-in-Cell simulations with the epoch code. In the simulations, effects of preplasma and optimal targets thicknesses for different laser pulse have been studied in detail. Based on the understanding of ion RPA, we propose some new target parameters to achieve higher ion energy. This work was performed with the support of the Air Force Office of Scientific Research under grant FA9550-14-1-0282.

  8. Free-Standing Organic Transistors and Circuits with Sub-Micron Thicknesses

    PubMed Central

    Fukuda, Kenjiro; Sekine, Tomohito; Shiwaku, Rei; Morimoto, Takuya; Kumaki, Daisuke; Tokito, Shizuo

    2016-01-01

    The realization of wearable electronic devices with extremely thin and flexible form factors has been a major technological challenge. While substrates typically limit the thickness of thin-film electronic devices, they are usually necessary for their fabrication and functionality. Here we report on ultra-thin organic transistors and integrated circuits using device components whose substrates that have been removed. The fabricated organic circuits with total device thicknesses down to 350 nm have electrical performance levels close to those fabricated on conventional flexible substrates. Moreover, they exhibit excellent mechanical robustness, whereby their static and dynamic electrical characteristics do not change even under 50% compressive strain. Tests using systematically applied compressive strains reveal that these free-standing organic transistors possess anisotropic mechanical stability, and a strain model for a multilayer stack can be used to describe the strain in this sort of ultra-thin device. These results show the feasibility of ultimate-thin organic electronic devices using free-standing constructions. PMID:27278828

  9. An Examination of the Shrinking-Core Model of Sub-Micron Aluminum Combustion

    DTIC Science & Technology

    2012-09-14

    steady, at best an approximation; and that apart from the aluminum/oxide transformation, the geometry is fixed. Provided these approximations only lead...ingredients has significant mechanical consequences in the context of the spherical geometry , and therefore it is important to consider it. Because of the...mechanical consequences, an analytical treatment in the spherical geometry is not possible, and yet analytical treatments are of great value in revealing

  10. Sub-micron scale patterning of fluorescent silver nanoclusters using low-power laser.

    PubMed

    Kunwar, Puskal; Hassinen, Jukka; Bautista, Godofredo; Ras, Robin H A; Toivonen, Juha

    2016-04-05

    Noble metal nanoclusters are ultrasmall nanomaterials with tunable properties and huge application potential; however, retaining their enhanced functionality is difficult as they readily lose their properties without stabilization. Here, we demonstrate a facile synthesis of highly photostable silver nanoclusters in a polymer thin film using visible light photoreduction. Furthermore, the different stages of the nanocluster formation are investigated in detail using absorption and fluorescence spectroscopy, fluorescence microscopy, and atomic force microscopy. A cost-effective fabrication of photostable micron-sized fluorescent silver nanocluster barcode is demonstrated in silver-impregnated polymer films using a low-power continuous-wave laser diode. It is shown that a laser power of as low as 0.75 mW is enough to write fluorescent structures, corresponding to the specifications of a commercially available laser pointer. The as-formed nanocluster-containing microstructures can be useful in direct labeling applications such as authenticity marking and fluorescent labeling.

  11. Sub-micron scale patterning of fluorescent silver nanoclusters using low-power laser

    NASA Astrophysics Data System (ADS)

    Kunwar, Puskal; Hassinen, Jukka; Bautista, Godofredo; Ras, Robin H. A.; Toivonen, Juha

    2016-04-01

    Noble metal nanoclusters are ultrasmall nanomaterials with tunable properties and huge application potential; however, retaining their enhanced functionality is difficult as they readily lose their properties without stabilization. Here, we demonstrate a facile synthesis of highly photostable silver nanoclusters in a polymer thin film using visible light photoreduction. Furthermore, the different stages of the nanocluster formation are investigated in detail using absorption and fluorescence spectroscopy, fluorescence microscopy, and atomic force microscopy. A cost-effective fabrication of photostable micron-sized fluorescent silver nanocluster barcode is demonstrated in silver-impregnated polymer films using a low-power continuous-wave laser diode. It is shown that a laser power of as low as 0.75 mW is enough to write fluorescent structures, corresponding to the specifications of a commercially available laser pointer. The as-formed nanocluster-containing microstructures can be useful in direct labeling applications such as authenticity marking and fluorescent labeling.

  12. Engineering design of sub-micron topographies for simultaneously adherent and reflective metal-polymer interfaces

    NASA Technical Reports Server (NTRS)

    Brown, Christopher A.

    1993-01-01

    The approach of the project is to base the design of multi-function, reflective topographies on the theory that topographically dependent phenomena react with surfaces and interfaces at certain scales. The first phase of the project emphasizes the development of methods for understanding the sizes of topographic features which influence reflectivity. Subsequent phases, if necessary, will address the scales of interaction for adhesion and manufacturing processes. A simulation of the interaction of electromagnetic radiation, or light, with a reflective surface is performed using specialized software. Reflectivity of the surface as a function of scale is evaluated and the results from the simulation are compared with reflectivity measurements made on multi-function, reflective surfaces.

  13. Low loss coupling to sub-micron thick rib and nanowire waveguides by vertical tapering.

    PubMed

    Madden, S; Jin, Z; Choi, D; Debbarma, S; Bulla, D; Luther-Davies, B

    2013-02-11

    Highly nonlinear planar glass waveguides have been shown to be useful for all optical signal processing. However, the typical SMF-28 fiber to waveguide coupling loss of ~5dB/end remains a barrier to practical implementation. Low loss coupling to a fiber using vertical tapering of the waveguide film is analyzed for rib and nanowire waveguides and experimentally demonstrated for ribs showing polarization and wavelength independence over >300nm bandwidth. Tapers with essentially zero excess loss led to total losses from the waveguide to fiber core of 1.1dB per facet comprising only material absorption (0.75dB) and mode overlap loss (0.36dB), both of which can be eliminated with improvements to processing and materials.

  14. Sub-micron period metal lattices fabricated by interfering ultraviolet femtosecond laser processing

    NASA Astrophysics Data System (ADS)

    Nakata, Yoshiki; Matsuba, Yoshiki; Miyanaga, Noriaki

    2016-05-01

    The interference pattern of a femtosecond laser has been utilized to fabricate nanostructures in the lattice. In this paper, SH (second-harmonic) waves (λ = 392.5 {{nm}}) of a femtosecond laser were applied to four beams interfering laser processing using a demagnification system as a beam correlator. The lattice constant of the resultant matrix was shortened to 760 nm. The unit structures fabricated on gold thin films were nanoholes, nanobumps, nanodrops or nanowhiskers, and their unit size was minimized compared to the case with a greater lattice constant formed by fundamental wavelengths. The radius of a nanoball on top of a nanodrop was between 42 and 76 nm, and the radius of metallic hole arrays (MHA) was 220 nm. The energy efficiency of the laser increased by 4.79 times due to better absorption coefficient of gold at ultraviolet wavelengths. In addition, the smallest lattice constant was estimated with the use of a commercial plano-convex fused-silica lens and a NIR (near-infrared) achromatic lens.

  15. Sub-micron mapping of GHz magnetic susceptibility using scanning transmission x-ray microscopy

    NASA Astrophysics Data System (ADS)

    Cheng, Cheng; Bailey, William E.

    2012-10-01

    We report submicron imaging (˜0.75 μm resolution) of complex magnetic susceptibility in a micron-size ferromagnetic heterostructure using time-resolved scanning transmission x-ray microscopy. The real and imaginary parts of the susceptibility are extracted from the phase and amplitude of the small-angle (<20°) rotational response of the local magnetization under microwave excitation. Frequency-dependent response patterns were observed in an incompletely saturated bilayer element. The technique is extensible to higher frequencies (to ˜10 GHz), better spatial resolution, and layer-specific measurement.

  16. Fabrication of large area gratings with sub-micron pitch using mold micromachining

    SciTech Connect

    Fleming, J.G.; Barron, C.C.; Stallard, B.; Kaushik, S.

    1997-03-01

    In this work, the authors have applied mold micromachining and standard photolithographic techniques to the fabrication of parts integrated with 0.4 micron pitch diffraction gratings. In principle, the approach should be scaleable to considerably finer pitches. They have achieved this by relying on the thickness of deposited or grown films, instead of photolithography, to determine the grating pitch. The gratings can be made to extend over large areas and the entire process is compatible with batch processing. Literally thousands of parts can be batch fabricated from a single lot of six inch wafers. In the first stage of the process they fabricate a planarized silicon dioxide pad over which the silicon nitride wave guide runs. The grating is formed by first patterning and etching single crystalline silicon to form a series of trenches with well defined pitch. The silicon bounding the trenches is then thinned by thermal oxidation followed by stripping of the silicon dioxide. The trenches are filled by a combination of polysilicon depositions and thermal oxidations. Chemical mechanical polishing (CMP) is used to polish back these structures resulting in a series of alternating 2000 {angstrom} wide lines of silicon and silicon dioxide. The thickness of the lines is determined by the oxidation time and the polysilicon deposition thickness. The silicon lines are selectively recessed by anisotropic reactive ion etching, thus forming the mold for the grating. The mold is filled with low stress silicon nitride deposited by chemical vapor deposition. A wave guide is then patterned into the silicon nitride and the mold is locally removed by a combination of deep silicon trench etching and wet KOH etching. This results in a suspended diffraction grating/membrane over the KOH generated pit.

  17. The deformation of gum metal under nanoindentation and sub-micron pillar compression

    NASA Astrophysics Data System (ADS)

    Withey, Elizabeth Ann

    Reaching ideal strength has proven to be difficult in most materials. Dislocation slip, phase transformations, twinning, and fracture all tend to occur at stresses well below the ideal strength of a material. Only on very small scales has it been possible to approach ideal strength. Thus, it was of great interest when a set of beta-Ti alloys, Gum Metal, were found to have a bulk yield strength close to half of its ideal strength. However, some recent studies have questioned the reliability of this claim. Several studies have suggested Gum Metal deforms by dislocation slip. Others have suggested the possibility of transformation-induced plasticity. The present study was undertaken in order to help clarify if and how Gum Metal can reach ideal strength. Two different experiments, ex situ nanoindentation and quantitative in situ nanopillar compression in a transmission electron microscope to correlate real-time deformation behavior, were performed on a single composition of Gum Metal, Ti-23Nb-0.7Ta-2Zr-1.20 at. %, obtained from Toyota Central R&D Laboratories. Nanoindented specimens were thinned from the bottom surface until the pits of multiple indentations became electron-transparent allowing for qualitative analysis of the deformation microstructure in both fully cold-worked and solution-treated specimens. Real-time load-displacement behavior from the nanopillar compression tests was correlated with real-time video recorded during each compression to determine both the compressive strength of each pillar and the timing and strengths of different deformation behaviors observed. Combining the results from both experiments provided several important conclusions. First, Gum Metal approaches and can attain ideal strength in nanopillars regardless of processing condition. While dislocations exist in Gum Metal, they can be tightly pinned by obstacles with spacing less than ˜20 nm, which should inhibit their motion at strengths below the ideal shear strength. The plastic deformation of Gum Metal is not controlled by giant faults or by stress-induced phase transformations. Both of these phenomena, while active, are not the source of plasticity in Gum Metal.

  18. Research investigation of the physical interactions and phenomena associated with hypervelocity sub-micron particles

    NASA Technical Reports Server (NTRS)

    Roy, N. L.

    1975-01-01

    Signals from impact ionization plasmas were studied as a means of performing microparticle composition analysis. Impact ionization signal response was measured in a time-of-flight (TOF) system for lanthanum hexaboride, carbonyl iron, and aluminum microparticle impacts on a tantalum target, primarily in the 1 - 8 km/s velocity range. Oscilloscope photographs of representative ion TOF signal response are given for each material studied. Graphs and histograms are presented of the total charge collected as well as the charge collected in each observed ion mass group. Data show that ion signals consist primarily of the lower ionization potential elements over the 1 - 8 km/s range.

  19. Sub-micron scale patterning of fluorescent silver nanoclusters using low-power laser

    PubMed Central

    Kunwar, Puskal; Hassinen, Jukka; Bautista, Godofredo; Ras, Robin H. A.; Toivonen, Juha

    2016-01-01

    Noble metal nanoclusters are ultrasmall nanomaterials with tunable properties and huge application potential; however, retaining their enhanced functionality is difficult as they readily lose their properties without stabilization. Here, we demonstrate a facile synthesis of highly photostable silver nanoclusters in a polymer thin film using visible light photoreduction. Furthermore, the different stages of the nanocluster formation are investigated in detail using absorption and fluorescence spectroscopy, fluorescence microscopy, and atomic force microscopy. A cost-effective fabrication of photostable micron-sized fluorescent silver nanocluster barcode is demonstrated in silver-impregnated polymer films using a low-power continuous-wave laser diode. It is shown that a laser power of as low as 0.75 mW is enough to write fluorescent structures, corresponding to the specifications of a commercially available laser pointer. The as-formed nanocluster-containing microstructures can be useful in direct labeling applications such as authenticity marking and fluorescent labeling. PMID:27045598

  20. Uptake of nitric acid by sub-micron-sized ice particles

    NASA Astrophysics Data System (ADS)

    Arora, O. P.; Cziczo, D. J.; Morgan, A. M.; Abbatt, J. P. D.; Niedziela, R. F.

    The uptake of gas phase nitric acid by half-micron-diameter ice crystals has been studied at 230 K by measuring the nitrate content of ice particles which have been exposed to 5 × 10-6 torr of nitric acid in a low temperature flow tube. A cold NaOH-coated denuder is used to distinguish gas-phase nitric acid from adsorbed nitric acid. Ice particle diameters were determined by fitting measured aerosol infrared extinction spectra to spectra calculated via Mie theory, and their number density is measured directly with a CN counter. Under conditions in which the surface is saturated and not all the gas-phase nitric acid adsorbs, the measured uptakes are 1.2 × 1014 molecules/cm² where the surface area is the geometric area of the particles. Within experimental uncertainties, this surface coverage is the same as that measured on thin films of ice formed by freezing liquid water. These results are the first quantitative study of the nitric acid uptake capacity of ice particles, and they provide additional support to the suggestion that ice and snow provide a route for the efficient scavenging of nitric acid from the atmosphere.

  1. Characterization and source identification of sub-micron particles at the HKUST Supersite in Hong Kong.

    PubMed

    Cheung, K; Ling, Z H; Wang, D W; Wang, Y; Guo, H; Lee, B; Li, Y J; Chan, C K

    2015-09-15

    Particle size distribution measurements were conducted continuously at a 30-second interval using the Fast Mobility Particle Sizer (FMPS) in August, September, November and December of 2011 at a coastal background site in Hong Kong. Concurrent measurements of CO, NOx, O3, SO2 and volatile organic compounds (VOCs) were used to determine the causes of high particle number concentration (PNC) events. In all sampling months, PNC were usually higher in the evening, likely resulting from the arrival of upwind air pollutants as wind direction changed in the late afternoon. On the more polluted days, the PNC were usually higher around noon, particularly in August, similar to the diurnal trend of O3. The mode diameter at noon was smaller than in other time periods in all sampling months, further highlighting the role of secondary formation at this urban background site. A prolonged period of pollution episode occurred in late August. High PNC resulted from the arrival of pollution laden air from the PRD region or super regions. In December, new particle formation followed by subsequent growth accounted for most of the polluted days. Overall, meteorology was the most important parameter affecting particle concentrations and formation at this Hong Kong background site.

  2. Sub micron area Nb/AlO(x)/Nb tunnel junctions for submillimeter mixer applications

    NASA Technical Reports Server (NTRS)

    Leduc, Henry G.; Bumble, B.; Cypher, S. R.; Judas, A. J.; Stern, J. A.

    1992-01-01

    In this paper, we report on a fabrication process developed for submicron area tunnel junctions. We have fabricated Nb/AlO(x)/Nb tunnel junctions with areas down to 0.1 sq micron using these techniques. The devices have shown excellent performance in receiver systems up to 500 GHz and are currently in use in radio astronomy observatories at 115, 230, and 500 GHz.

  3. Characterization of Sub-Micron Sized Carbon Electrodes Insulated with a Phenol-Allylphenol Copolymer

    DTIC Science & Technology

    1992-01-15

    phosphate buffer. This solution consisted of 0 O099 M citric acid (Aldrich Chemical), and 0.181 M sodium phosphate, dibasic (Baker Scientific). Dopamine...potentiostat, and recorded on a Hewlett Packard X-Y recorder. The potentiostat was operated in the two electrode mode with a saturated sodium calomel...decade) (mV vs SSCE) Dopamine 163 ± 14 75 ± 11 12 4-methylcatechol 188 ± 14 126 ± 9 12 3,4-dihydroxy- phenylacetate 327 ± 24 155 ± 9 10 Ferrocyanide

  4. Dynamics of Sub-Micron Bubbles Growing in a Wedge in the Low Capillary Number Regime

    NASA Astrophysics Data System (ADS)

    Norton, Michael; Park, Jeung; Kodambaka, Suneel; Ross, Frances; Bau, Haim

    2014-11-01

    Using a hermetically-sealed liquid cell, we observed the growth and migration of bubbles (tens to hundreds of nanometers in diameter) with a transmission electron microscope. The internal pressure of the liquid caused the thin silicon nitride membranes that comprise the cell's observation windows to bow outward, creating spatial gradients in the liquid cell's height. As a result, growing bubbles migrated in the direction of increasing cell height. To better understand the migration dynamics, we developed a simple, two-dimensional model to predict the translational velocity of a bubble that makes contact with both wedge surfaces as a function of the bubble growth rate and wedge opening angle. The model is valid in the asymptotic limit of zero capillary number and relies on a phenomenological relationship between the contact line velocity and the dynamic contact angle. The theoretical predictions are compared with experimental observations. MN was supported, in part, by the Nano/Bio Interface Center through the National Science Foundation NSEC DMR08-32802. HHB and FR were supported, in part, by Grants 1129722 and 1066573 from the National Science Foundation.

  5. Free-Standing Organic Transistors and Circuits with Sub-Micron Thicknesses

    NASA Astrophysics Data System (ADS)

    Fukuda, Kenjiro; Sekine, Tomohito; Shiwaku, Rei; Morimoto, Takuya; Kumaki, Daisuke; Tokito, Shizuo

    2016-06-01

    The realization of wearable electronic devices with extremely thin and flexible form factors has been a major technological challenge. While substrates typically limit the thickness of thin-film electronic devices, they are usually necessary for their fabrication and functionality. Here we report on ultra-thin organic transistors and integrated circuits using device components whose substrates that have been removed. The fabricated organic circuits with total device thicknesses down to 350 nm have electrical performance levels close to those fabricated on conventional flexible substrates. Moreover, they exhibit excellent mechanical robustness, whereby their static and dynamic electrical characteristics do not change even under 50% compressive strain. Tests using systematically applied compressive strains reveal that these free-standing organic transistors possess anisotropic mechanical stability, and a strain model for a multilayer stack can be used to describe the strain in this sort of ultra-thin device. These results show the feasibility of ultimate-thin organic electronic devices using free-standing constructions.

  6. Multidisciplinary Approach to the Science and Technology of Sub-Micron Electronics.

    DTIC Science & Technology

    1987-03-10

    made (Drs. Schwank and Fogler (Task 1)). In the latter project the presence of the metal is found to strongly influence the structural stability of...research results in each of the three subtasks. TASK 1: PREPARATION AND CHARACTERIZATION OF ULTRASMALL METAL CLUSTERS J. Schwank and H.S. Fogler ...Director of institute of Science and Technology R. Clarke Associate Professor of Physics and Director of Ultra-small Structures Research Office H.S. Fogler

  7. Suspension Plasma Spraying of Sub-micron Silicon Carbide Composite Coatings

    NASA Astrophysics Data System (ADS)

    Mubarok, F.; Espallargas, N.

    2015-06-01

    Thermal spraying of silicon carbide (SiC) material is a challenging task since SiC tends to decompose during atmospheric spraying process. The addition of metal or ceramic binders is necessary to facilitate the bonding of SiC particles, allowing SiC composite coating to be deposited. In the conventional procedures, the binders are added through mechanical mixing of powder constituents, making it difficult to achieve homogeneous distribution. In the new procedure proposed in this work, the binder is delivered as a nano-film of the surface of the individual SiC particles through co-precipitation treatment. Suspension plasma spray (SPS) coating technique has been used with the aim at avoiding the decomposition of SiC typically expected with atmospheric techniques, such as atmospheric plasma spray. The deposited SiC coatings by SPS showed identical SiC phase peak as identified in the suspension feedstock, indicating that the nano-film binder was able to protect SiC particles from decomposition. Further analysis by XPS revealed that SiC particles underwent some minor oxidation. Unfortunately, all the SiC coatings exhibited poor mechanical performance due to low cohesive strength, high porosity, and powdery structure making the coatings vulnerable to grain pull-out. This was due to the absence of sintering process during the spraying process contributing to the low performance of SiC SPS coatings.

  8. Properties of micro-nano particle size admixtures of alumina at different sintering condition

    NASA Astrophysics Data System (ADS)

    Sifat, Rahin; Akter, Manira; Rashid, A. K. M. Bazlur

    2016-07-01

    Among various ceramic materials, alumina is mostly used material for its hardness and strength. There is a difference between the properties of alumina due to their different particle size. Also different holding time in the sintering temperature has effect on the sintering of alumina of different particle size. In this study, micro alumina and nano alumina were mixed in different ratios and sintered at different sintering condition to compare their mechanical properties that varied due to their different particle size distribution. In this work, conventional solid state sintering route was followed to prepare final samples. Six different particle size ratio of alumina (micro:nano= 100:0, 95:5, 90:10, 10:90, 5:95, 0:100) with a doping of 0.1% MgO were used. The sintering temperature was 1500° C but sintering condition was different. After comparing the mechanical properties, it has been observed that relatively improved properties can be obtained by increasing nano particle percentages in the micro alumina than the reverse mixture.

  9. Effect of surface acidity and basicity of aluminas on asphaltene adsorption and oxidation.

    PubMed

    Nassar, Nashaat N; Hassan, Azfar; Pereira-Almao, Pedro

    2011-08-01

    This study investigates the effect of surface acidity and basicity of aluminas on asphaltene adsorption followed by air oxidation. Equilibrium batch adsorption experiments were conducted at 25°C with solutions of asphaltenes in toluene at concentrations ranging from 100 to 3000 g/L using three conventional alumina adsorbents with different surface acidity. Data were found to better fit to the Freundlich isotherm model showing a multilayer adsorption. Results showed that asphaltene adsorption is strongly affected by the surface acidity, and the adsorption capacities of asphaltenes onto the three aluminas followed the order acidic>basic and neutral. Asphaltenes adsorbed over aluminas were subjected to oxidation in air up to 600°C in a thermogravimetric analyzer to study the catalytic effect of aluminas with different surface acidity. A correlation was found between Freundlich affinity constant (1/n) and the catalytic activity. Basic alumina that has the lowest 1/n value, depicting strongest interactions, has the highest catalytic activity, followed by neutral and acidic aluminas, respectively.

  10. Fabrication of nanosized alumina powders by a simple polymer solution route.

    PubMed

    Lee, Sang-Jin; Chun, Sung-Yong; Lee, Choong-Hyo; Yoon, Young-Soo

    2006-11-01

    Nanosized alumina (Al2O3) powders had been successfully fabricated by a simple polymer solution route employing polyvinyl alcohol (PVA) as an organic carrier. The fabricated alumina powders had an average particle size of 6.1 nm with a high specific surface area of 99.5 m2/g. As well, the alumina powders were fully crystallized to alpha phase at a relatively low temperature of 1000 degrees C. The PVA polymer contributed to a soft and porous microstructure of the calcined alumina powders, and ball-milling process with the porous powders was effective in making nanosized alumina powders. In addition, the content and degree of polymerization of the PVA affected the development of crystallization and powder properties. In this study, the simple polymer technique and milling process for the fabrication of nanosized alumina powders are introduced, and the effects of PVA on the property of the synthesized alumina powders are observed. For the study, the characterizations of the synthesized powders are conducted by using XRD, TEM, particle size analyzer, and nitrogen gas adsorption.

  11. Preparation of Micro-Porous Alumina Sheet Support for Ceramic Membrane by Extrusion

    NASA Astrophysics Data System (ADS)

    Hemra, Khanthima; Atong, Duangduen; Aungkavattana, Pavadee

    Among several types of ceramic membrane developed for a half of century, alumina is the most extensive advantage. In this study, many types of alumina with different particle size distributions were used as a starting material for fabrication of support sheet ceramic membrane using extrusion process. The investigation focused on the alumina dough components composed of some organic binders and water. The organic binder of about 12 wt. % was required in order for dough to be easily extruded, while the amount of water added to the dough depended on the particle size of alumina powder. The particle size and size distribution of starting powder showed strong effects on pore size of sintered alumina support. The pore size decreased when smaller particle size of starting powder was used. In addition, the pore volume of the sintered alumina decreased with increasing the sintering temperature due to improvement in densification, while pore size remained the same. The mechanical strength of alumina supports was also influenced by the particle size of starting powder; the finer particle size resulted in the higher mechanical strength. However, in order to obtain a good flux for the membrane, a high mechanical strength of the support along with its effective porosity is critical concerns. In this work, the support sintered at 1450°C provided a proper porosity of approximately 40% with an acceptable mechanical strength of 30-45MPa.

  12. Ultraviolet scattering properties of alumina particle clusters at three phase states in aircraft plume

    NASA Astrophysics Data System (ADS)

    Li, Jingying; Bai, Lu; Wu, Zhensen; Guo, Lixin; Gong, Yanjun

    2017-04-01

    We simulate the clusters of alumina particles using the parallel diffusion limited aggregation algorithm (DLA), and solve the scattering matrixes of the alumina particles in different phase states (alpha phase, gamma phase and liquid) through the multiple sphere T matrix method in UV. The effect of the number of monomers, fractal dimension and incident wavelength to the scattering phase function of the clusters of alumina particles is discussed. The results show that the different of the number of monomers, fractal dimensions and incident wavelengths have significant effect on the scattering properties of the clustered alumina particle. The researchers used to make the alumina particle equivalent to the alpha phase spherical particle, but it is too simplistic. We compare the scattering phase functions of the equivalent volume sphere (EVS), the equivalent surface sphere (ESS) and the clusters of alumina particles in three kinds of phase states. The results show that the backward scattering would be overestimated if the alumina particle is equivalent to the alpha phase spherical particle. Accurate phase function calculation in different phase states is very helpful to study the radiation propagation characteristics of aircraft plume.

  13. Strength, Fracture Toughness, and Slow Crack Growth of Zirconia/alumina Composites at Elevated Temperature

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Bansal, Narottam P.

    2003-01-01

    Various electrolyte materials for solid oxide fuel cells were fabricated by hot pressing 10 mol% yttria-stabilized zirconia (10-YSZ) reinforced with two different forms of alumina particulates and platelets each containing 0 to 30 mol% alumina. Flexure strength and fracture toughness of platelet composites were determined as a function of alumina content at 1000 C in air and compared with those of particulate composites determined previously. In general, elevated-temperature strength and fracture toughness of both composite systems increased with increasing alumina content. For a given alumina content, flexure strength of particulate composites was greater than that of platelet composites at higher alumina contents (greater than or equal to 20 mol%), whereas, fracture toughness was greater in platelet composites than in particulate composites, regardless of alumina content. The results of slow crack growth (SCG) testing, determined at 1000 C via dynamic fatigue testing for three different composites including 0 mol% (10-YSZ matrix), 30 mol % particulate and 30 mol% platelet composites, showed that susceptibility to SCG was greatest with SCG parameter n = 6 to 8 for both 0 and 30 mol% particulate composites and was least with n = 33 for the 30 mol% platelet composite.

  14. Infrared radiative properties of alumina up to the melting point: A first-principles study

    NASA Astrophysics Data System (ADS)

    Yang, J. Y.; Xu, M.; Liu, L. H.

    2016-11-01

    The high thermal emission of alumina dominates the radiative heat transfer of rocket exhaust plume. Yet numerous experimental measurements on radiative properties of alumina at high temperatures vary considerably from each other and cannot provide physical insight into the underlying mechanism. In this work, the ab initio molecular dynamics (AIMD) method and ab initio parameterized Drude model are combined to predict the radiative properties of alumina for temperatures up to 2327 K (the melting point) in the spectral range 1-12 μm. Contributed by different microscopic processes, the optical absorption of alumina in the spectral range 1-4 and 4-12 μm is described by two distinct methods. In the spectral range 4-12 μm, the multi-phonon process mainly contributes to optical absorption and can be simulated by the AIMD method based on the linear response theory. While in the spectral range 1-4 μm, the optical absorption is mainly caused by intrinsic carriers and can be effectively described by the ab initio parameterized Drude model. The first-principles calculations can successfully predict the infrared radiative properties of alumina at high temperatures and well reproduce the literature experiments. Moreover, the theoretical simulations verify that alumina can retain its semiconducting character even in the liquid phase and there emerges sharp increase in the near-infrared optical absorption of alumina upon melting.

  15. Sintering and mechanical properties of the alumina-tricalcium phosphate-titania composites.

    PubMed

    Sakka, Siwar; Bouaziz, Jamel; Ben Ayed, Foued

    2014-07-01

    The objective of this study was to determine the effect of the content of titania and the sintering process on the transformation phase, the densification, the rupture strength and the microstructures of the alumina-10 wt.% tricalcium phosphate composites. After the sintering process, the samples were examined by using (31)P and (27)Al magic angle scanning nuclear magnetic resonance, X-ray powder diffraction and scanning electron microscopy analysis. The Brazilian test was used to measure the rupture strength of the samples. The present results provide new information about solid-state reactivity in the ternary system α-alumina-β-tricalcium phosphate-anatase-titania. The differential thermal analysis of the α-alumina-β-tricalcium phosphate-titania composites shows two endothermic peaks, at 1360 °C and at 1405 °C, which are caused by the reactions between titania/alumina and titania/tricalcium phosphate, respectively. Thus, the presence of titania in the alumina-10 wt.% tricalcium phosphate leads to the formation of β-Al2TiO5 at 1360 °C. At 1600 °C, the alumina-10 wt.% tricalcium phosphate-5 wt.% titania composites displayed the highest rupture strength (74 MPa), compared to the alumina-10 wt.% tricalcium phosphate composites (13.5 MPa). Accordingly, the increase of the rupture strength is due to the formation of the new β-Al2TiO5 phase.

  16. Morphology-controlled electrochemical sensing amaranth at nanomolar levels using alumina.

    PubMed

    Zhang, Yuanyuan; Gan, Tian; Wan, Chidan; Wu, Kangbing

    2013-02-18

    Different-shaped aluminas were readily prepared via hydrothermal reaction. It was found that the morphology and the electrochemical sensing properties of alumina were heavily dependent on the reaction time. When extending the reaction time from 6 h to 24 h, the obtained alumina samples changed from amorphous bumps to regular microfibers in diameter of 200 nm, as confirmed by scanning electron microscopy. Transmission electron microscopy observation revealed that longer reaction time was beneficial for the formation of porous and uniform fiber-like structures. Electrochemical tests proved that alumina microfibers were more active for the oxidation of amaranth and exhibited much higher enhancement effect, compared with alumina bumps. On the surface of alumina microfibers, the oxidation peak currents of amaranth increased remarkably. The influences of pH value, amount of alumina microfibers, and accumulation time on the signal enhancement of amaranth were discussed. As a result, a novel electrochemical method was developed for the detection of amaranth. The linear range was from 1 to 150 nM, and the detection limit was 0.75 nM after 1-min accumulation. The analytical application in drink samples was investigated, and the results consisted with the values that obtained by high-performance liquid chromatography.

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

    SciTech Connect

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

    2013-06-01

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

  18. Metastable zirconia-yttria-alumina ceramics: Structure, processing and properties

    NASA Astrophysics Data System (ADS)

    Zhou, Xinzhang

    2002-09-01

    Metastable phases of zirconia-yttria-alumina produced by atmospheric plasma spray and subsequent quenching were studied. Two kinds of quenching methods were used: water quenching and splat quenching. Quenching rates were estimated to be 104°C/s for water quenching and between 105--107°C/s for splat quenching. Five compositions of sprayed dried powders (pure alumina, TZ3Y20A, TZ3Y57A, TZ3Y80A and pure zirconia) were plasma sprayed and quenched. The phases and microstructures of the plasma sprayed powders and thin films were investigated by XRD and FESEM. It was found that at different compositions and quenching rates, different high temperature phases formed. These phases are metastable at room temperature and can be in the form of an extended solid solution phase, an intermediate phase, or an amorphous structure. The grain sizes of the metastable phases are below 50 nm, as determined by XRD peak broadening. At the eutectic composition, zirconia-rich fibers (50 nm in diameter) uniformly distributed in an alumina-rich matrix were observed. 2-D and 3-D metastable phase diagrams were constructed to explain the metastable phase formation. Plasma spraying can be used to fabricate ceramic nanocomposites either by pressure-assisted sintering or spray forming of the metastable powders. Mechanical properties of TZ3Y20A specimens produced by plasma spray forming on steel substrates were studied. The dependence of the 4-point bend strength on plasma spray parameters was studied by a 26-2 statistical experimental design. It was found that the bend strength was sensitive to both standoff distance and scanning speed. The results of study show much promise in applications of the metastable ceramics. Firstly, homogeneous nucleation and growth of stable phases during sintering and high creep rate at elevated temperatures will result in uniformly dense nanoceramic composites. Secondly, extended solid solutions of rare earth elements in glass will greatly enhance the optical

  19. Contact fatigue response of porcelain-veneered alumina model systems.

    PubMed

    Stappert, Christian F J; Baldassarri, Marta; Zhang, Yu; Stappert, Dina; Thompson, Van P

    2012-02-01

    Fatigue damage modes and reliability of hand-veneered (HV) and over-pressed (OP) aluminum-oxide layer structures were compared. Influence of luting cement thickness on mechanical performance was investigated. Sixty-four aluminum-oxide plates (10 × 10 × 0.5 mm) were veneered with hand built-up or pressed porcelain (0.7 mm) and adhesively luted (50- or 150-μm cement thickness) to water-aged composite resin blocks (12 × 12 × 4 mm). Single-load-to-failure and fatigue tests were performed with a spherical tungsten carbide indenter (d = 6.25 mm) applied in the center of the veneer layer. Specimens were inspected with polarized-reflected-light and scanning electron microscopy. Use-level probability Weibull curves were plotted with two-sided 90% confidence bounds, and reliability at 75,000 cycles and 250 N load was calculated. For all specimens but two OP with 50-μm cement thickness, failure was characterized by flexural radial cracks initiating at the bottom surface of the alumina core and propagating into the veneering porcelain before cone cracks could extend to the porcelain/alumina interface. HV specimens showed higher reliability compared to OP. Those with 50-μm cement thickness were more reliable relative to their 150-μm counterparts (HV_50 μm: 95% (0.99/0.67); HV_150 μm: 55% (0.92/0.01); OP_50 μm: 69% (0.84/0.48); OP_150 μm: 15% (0.53/0.004)). Similar failure modes were observed in HV and OP specimens. Radial cracks developing in the core and spreading into the veneer are suggested to cause bulk fracture, which is the characteristic failure mode for alumina core crowns. However, the highest resistance to fatigue loading was found for the HV specimens with thin cement thickness, while the lowest occurred for the OP with thick cement layer.

  20. Microwave behavior of silicon carbide/high alumina cement composites

    NASA Astrophysics Data System (ADS)

    Leiser, Kristie Sue

    2001-09-01

    Microwave susceptors have been fabricated from composites of silicon carbide/high alumina cement. These composites are very useful for microwave processing other materials. By using these composites for microwave hybrid heating, both ordinary and unique materials have the potential to be fabricated. The use of the susceptors can help to produce a more even temperature distribution across a material being microwave heated. This composite of silicon carbide particles embedded in high alumina cement only needed to be better characterized to enhance its applicability to more systems. This goal was accomplished in this study. During the course of the study, the factors affecting the heating rate of the composites were identified. These factors included silicon carbide particle size, weight percent silicon carbide in the composite, silicon carbide phase, processing atmosphere, and the maximum temperature experienced by the composite. A systematic study was designed to examine the importance of factors such as these and their effects upon the heating rate of high alumina cement/silicon carbide composites. Statistical design was employed to determine the significance of the factors of interest. The effects of these factors on the heating rate of the composites were determined. As the amount of silicon carbide in the composite increased, the heating rate tended to increase. The effects observed were explained by a combination of dielectric mixing equations, a heat transfer model and percolation theory. The silicon carbide particle size also affected the heating rate of the composites. Mathematical modeling showed that the particle size effect was a geometric effect that was dependent upon imperfect thermal contact between the silicon carbide particle and the cement matrix. The silicon carbide particle size also affected the percolation threshold of the composites. The heating rate of the composites increased when calcium carbonate present in the cement was pyrolyzed to form

  1. Contribution of Aluminas and Aluminosilicates to the Formation of PCDD/Fs on Fly Ashes

    PubMed Central

    Potter, Phillip M.; Dellinger, Barry; Lomnicki, Slawomir M.

    2015-01-01

    Chlorinated aromatics undergo surface-mediated reactions with metal oxides to form Environmentally Persistent Free Radicals (EPFRs) which can further react to produce polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Previous work using laboratory-made fly ash surrogates composed of transition metal oxides deposited on silica powder has confirmed their ability to mimic fly ash in the production of PCDD/Fs. However, little is known about the propensity of aluminas and aluminosilicates, other components of fly ash, to form PCDD/Fs. A fly ash sample containing both alumina and mullite, an aluminosilicate, was tested for PCDD/F formation ability and compared to PCDD/F yields from the thermal degradation of 2-monochlorophenol (2-MCP) precursor over γ-alumina, α-alumina, and mullite. A packed-bed flow reactor was used to investigate the thermal degradation of 2-MCP over the various catalysts at 200–600 °C. Fly ash gave similar PCDD/F yields to surrogates made with similar transition metal content. γ-alumina, which is thermodynamically unfavorable, was very catalytically active and gave low PCDD/F yields despite a high destruction of 2-MCP. Mullite and α-alumina, the thermodynamically favorable form of alumina, yielded higher concentrations of dioxins and products with a higher degree of chlorine substitution than γ-alumina. The data suggest that certain aluminas and aluminosilicates, commonly found in fly ash, are active catalytic surfaces in the formation of PCDD/Fs in the post-flame cool zones of combustion systems and should be considered as additional catalytic surfaces active in the process. PMID:26615490

  2. Degradation in Thermal Properties and Morphology of Polyetheretherketone-Alumina Composites Exposed to Gamma Radiation

    NASA Astrophysics Data System (ADS)

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

    2012-07-01

    Sheets of polyetheretherketone (PEEK) and PEEK-alumina composites with micron-sized alumina powder with 5, 10, 15, 20, and 25% by weight were fabricated, irradiated with gamma rays up to 10 MGy and the degradation in their thermal properties and morphology were evaluated. The radicals generated during irradiation get stabilized by chain scission and crosslinking. Chain scission is predominant on the surface and crosslinking is predominant in the bulk of the samples. Owing to radiation damage, the glass transition temperature, T g increased for pure PEEK from 136 to 140.5 °C, whereas the shift in T g for the composites decreased with increase in alumina content and for PEEK-25% alumina, the change in T g was insignificant, as alumina acts as an excitation energy sink and reduces the crosslinking density, which in turn decreased the shift in T g towards higher temperature. Similarly, the melting temperature, T m and enthalpy of melting, Δ H m of PEEK and PEEK-alumina composites decreased on account of radiation owing to the restriction of chain mobility and disordering of structures caused by crosslinks. The decrease in T m and Δ H m was more pronounced in pure PEEK and the extent of decrease in T m and Δ H m was less for composites. SEM images revealed the formation of micro-cracks and micro-pores in PEEK due to radiation. The SEM image of irradiated PEEK-alumina (25%) composite showed negligible micro-cracks and micro-pores, because of the reinforcing effect of high alumina content in the PEEK matrix which helps in reducing the degradation in the properties of the polymer. Though alumina reduces the degradation of the polymer matrix during irradiation, an optimum level of ceramic fillers only have to be loaded to the polymer to avoid the reduction in toughness.

  3. NO{sub 2} and NO adsorption properties of KOH-treated {gamma}-alumina

    SciTech Connect

    Lee, M.R.; Allen, E.R.; Wolan, J.T.; Hoflund, G.B.

    1998-08-01

    A method to control nitrogen oxide (NO{sub x}) emissions from combustion sources by adsorption of NO{sub 2} and NO on {gamma}-alumina before and after KOH treatments has been evaluated. Compared to previously studied sorbents consisting of magnesium-oxide-coated vermiculite, untreated {gamma}-alumina exhibits a 6-fold increase in activity in tubular flow system tests. XPS analyses of the adsorbent surfaces before and after exposure to NO{sub x} indicate that potassium influences the NO{sub x}-sorption process. Subsequent treatment of {gamma}-alumina with KOH by impregnation or precipitation improves the adsorptive properties of {gamma}-alumina toward both NO{sub 2} and NO, with the precipitated samples performing better than impregnated samples. This research confirms previous findings that sorption of 3 mol of NO{sub 2} on {gamma}-alumina results in the catalytic formation of 1 mol of NO. However, treatment with KOH delays and reduces the formation of NO while increasing 5-fold the amount of NO{sub 2} adsorbed. Formation of nitrate and nitrite species is observed by XPS analysis of KOH-precipitated {gamma}-alumina exposed to NO{sub x}. A 40% loss of BET surface area occurs due to KOH precipitation on {gamma}-alumina followed by a further 56% loss in surface area after saturation with NO{sub x}. The addition of water vapor (3 vol %) to the feed gas stream significantly enhances the adsorption properties of the KOH-treated {gamma}-alumina. Washing the {gamma}-alumina pellets exposed to NO{sub x} with water essentially removes all of the potassium nitrates and nitrites formed. This harmless solution can be disposed of safely or used as fertilizer, and the pellets can be regenerated.

  4. From alumina nanopores to nanotubes: dependence on the geometry of anodization system.

    PubMed

    Feil, Adriano F; da Costa, Marlla V; Migowski, Pedro; Dupont, Jaïrton; Teixeira, Sérgio R; Amaral, Lívio

    2011-03-01

    The Conventional anodization of commercial aluminum sheets with a phosphoric acid electrolyte was employed for the preparation of alumina nanopore and/or nanotube structures. Modifying the system geometry (the ratio of platinum to aluminum electrode areas) controlled the nature of the anodization process (mild to hard). Nanotube formation was observed after low temperature preferential chemical etching of the defective corners of the hexagonal alumina cells using the same solution from the anodization process. Electrode geometry can be used to combine mild and hard anodization with low temperature etching to tune the alumina morphology from 100% nanopores to 100% nanotubos coverage.

  5. Fabrication and evaluation of low fiber content alumina fiber/aluminum composites

    NASA Technical Reports Server (NTRS)

    Hack, J. E.; Strempek, G. C.

    1980-01-01

    The mechanical fabrication of low volume percent fiber, polycrystalline alumina fiber reinforced aluminum composites was accomplished. Wire preform material was prepared by liquid-metal infiltration of alumina fiber bundles. The wires were subsequently encapsulated with aluminum foil and fabricated into bulk composite material by hot-drawing. Extensive mechanical, thermal and chemical testing was conducted on preform and bulk material to develop a process and material data base. In addition, a preliminary investigation of mechanical forming of bulk alumina fiber reinforced aluminum composite material was conducted.

  6. Introduction of bridging and pendant organic groups into mesoporous alumina materials.

    PubMed

    Grant, Stacy M; Woods, Stephan M; Gericke, Arne; Jaroniec, Mietek

    2011-11-01

    Incorporation of organic functionalities into soft-templated mesoporous alumina was performed via organosilane-assisted evaporation induced self-assembly using aluminum alkoxide precursors and block copolymer templates. This strategy permits one to obtain mesoporous alumina-based materials with tailorable adsorption, surface and structural properties. Isocyanurate, ethane, mercaptopropyl, and ureidopropyl-functionalized mesoporous alumina materials were synthesized with relatively high surface area and large pore volume with uniform and wormhole-like mesopores. The presence of organosilyl groups within these hybrid materials was confirmed by IR or Raman spectroscopy and their concentration was determined by elemental analysis.

  7. Densification characteristics of chromia/alumina castables by particle size distribution

    PubMed Central

    2012-01-01

    The quality of the refractories applied on integrated gasification combined cycle should be a key factor that affects both the reliability and the economics of gasifier operation. To enhance the workability of chromia/alumina castables, three types of ultrafine alumina powder were added to improve the workability. Densification behavior of such castables in the presence of ultrafine alumina was assessed through the measurement of parameters like flow value, viscosity, bulk density, apparent porosity, and microstructure evaluation by an SEM study. It's proved that the specific surface area and particle size distribution of ultrafine powders in matrix parts greatly influence the densification behavior of these castables. PMID:22221548

  8. Densification characteristics of chromia/alumina castables by particle size distribution

    NASA Astrophysics Data System (ADS)

    Zhao, Jingming; Kim, Taesuk; Kim, Gichul; Hwang, Kyuhong; Bae, Dongsik

    2012-01-01

    The quality of the refractories applied on integrated gasification combined cycle should be a key factor that affects both the reliability and the economics of gasifier operation. To enhance the workability of chromia/alumina castables, three types of ultrafine alumina powder were added to improve the workability. Densification behavior of such castables in the presence of ultrafine alumina was assessed through the measurement of parameters like flow value, viscosity, bulk density, apparent porosity, and microstructure evaluation by an SEM study. It's proved that the specific surface area and particle size distribution of ultrafine powders in matrix parts greatly influence the densification behavior of these castables.

  9. Interaction of hydrogen chloride with alumina. [influence of outgas and temperature conditions on adsorption

    NASA Technical Reports Server (NTRS)

    Bailey, R. R.; Wightman, J. P.

    1975-01-01

    The influence of outgas conditions and temperature on the adsorptive properties of two aluminas Alon-c and Al6sG were studied using adsorption isotherm measurements. Alon-C and Al6SG were characterized using X-ray powder diffraction, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and BET nitrogen surface areas. Some of these techniques were applied to two other aluminas but no isotherm data was obtained. Isotherm data and techniques applied to each alumina are summarized in tabular form.

  10. The Future of Alumina-Forming Alloys: Challenges and Applications for Power Generation

    SciTech Connect

    Pint, Bruce A

    2011-01-01

    Alumina-forming alloys have been studied for over 50 years and are now needed for high efficiency power generation applications operating at higher temperatures. Especially in the presence of water vapor, alumina-forming alloys outperform conventional chromia-forming alloys above 1000 C. However, alloy mechanical behavior is a significant issue and alumina-forming alloy development has been limited. The opportunity for alloy development is discussed as well as the factors that limit oxidation resistance, including alloy thermal expansion and optimizing reactive element additions. Finally, lifetime modeling is discussed for thick section components together with the need to address performance in more complex environments.

  11. Influence of Alumina Reaction Tube Impurities on the Oxidation of Chemically-Vapor-Deposited Silicon Carbide

    NASA Technical Reports Server (NTRS)

    Opila, Elizabeth

    1995-01-01

    Pure coupons of chemically vapor deposited (CVD) SiC were oxidized for 100 h in dry flowing oxygen at 1300 C. The oxidation kinetics were monitored using thermogravimetry (TGA). The experiments were first performed using high-purity alumina reaction tubes. The experiments were then repeated using fused quartz reaction tubes. Differences in oxidation kinetics, scale composition, and scale morphology were observed. These differences were attributed to impurities in the alumina tubes. Investigators interested in high-temperature oxidation of silica formers should be aware that high-purity alumina can have significant effects on experiment results.

  12. Preparation of silica or alumina pillared crystalline titanates

    SciTech Connect

    Udomsak, S.; Nge, R.; Dufner, D.C.; Anthony, R.G.; Lott, S.E.

    1994-05-01

    Layered crystalline titanates (CT) [Anthony and Dosch, US Patent 5 177 045 (1993)] are pillared with tetraethyl orthosilicate, 3-aminopropyltrimethoxysilane, and aluminum acetylacetonate to prepare porous and high surface area supports for sulfided NiMo catalyst. Tetra-ethyl orthosilicate or aluminum acetylacetonate intercalated CT are prepared by stepwise intercalation. First, the basal distance is increased by n-alkylammonium ions prior to intercalation with inorganic compounds. However, an aqueous solution of 3-aminopropyltrimethoxysilane could directly pillar CT without first swelling the titanate with n-alkylamine. The catalytic activities for hydrogenation of pyrene of sulfided NiMo supported silica or alumina pillared CT were higher than those of commercial catalysts (Shell324 and Amocat1C). The silicon and aluminum contents of the pillared CT, used as supports, have a considerable effect on the catalytic activities and physical properties of the supports.

  13. Synthesis and Characterization of Silica Alumina Supported Heteropolyoxometallets

    NASA Astrophysics Data System (ADS)

    Dangwal, A.; Singhal, S.; Semwal, S.; Shukla, S.

    2014-04-01

    Novel acid catalysts for alkane isomerization were synthesized with silica alumina supported heteropolyoxometallets by wet incipient method. Two series of catalysts were prepared by dispersing TPA or MPA. Characterization of catalysts was done by BET and TPD methods. Objective was to find high surface and acidity catalysts and to see the effect of synthesis parameter as loading or impregnation time on catalyst physicochemical properties as surface area, pore size, pore volume and acidity of HPA based oxide Seralox-5. TPA or MPA loading affected acidity and pore volume of catalysts, however no effect of impregnation time has been revealed. Surface area of catalysts was found in the range of 154-198 m2/g and acidity 10.1-17.7 ml/g of NH3 at STP. Among all the catalysts optimum characteristic catalysts were found from both the series, selecting one from each. These two catalysts exhibit high surface area, mesopore structure and high acidity.

  14. Ordered Nanomaterials Thin Films via Supported Anodized Alumina Templates

    NASA Astrophysics Data System (ADS)

    Es-Souni, Mohammed; Habouti, Salah

    2014-10-01

    Supported anodized alumina template films with highly ordered porosity are best suited for fabricating large area ordered nanostructures with tunable dimensions and aspect ratios. In this paper we first discuss important issues for the generation of such templates, including required properties of the Al/Ti/Au/Ti thin film heterostructure on a substrate for high quality templates. We then show examples of anisotropic nanostructure films consisting of noble metals using these templates, discuss briefly their optical properties and their applications to molecular detection using surface enhanced Raman spectroscopy. Finally we briefly address the possibility to make nanocomposite films, exemplary shown on a plasmonic-thermochromic nanocomposite of VO2-capped Au-nanorods.

  15. SCOPING MELTING STUDIES OF HIGH ALUMINA WASTE GLASS COMPOSITIONS

    SciTech Connect

    Kroll, Jared O.; Schweiger, Michael J.; Vienna, John D.

    2015-09-04

    Glass property models will be used at the Hanford Tank Waste Treatment and Immobilization Plant to formulate durable high-level waste glasses for disposal. A major effort is focused on expanding glass property models to cover a broader range of wastes and higher waste-loaded glasses. As a part of this effort, a statistically designed matrix of high-alumina glass compositions was developed. Forty five compositions were selected from the matrix to evaluate glass properties. Of these compositions, thirty three produced homogeneous glasses. The other twelve compositions contained segregated phases and high crystallinity; these were iteratively modified in an attempt to produce homogeneous glass samples while altering the original composition as little as possible. This paper focuses on the characterization of the twelve inhomogeneous compositions and their modifications using X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy.

  16. Semimetal nanowires and their superlattices in anodic alumina membranes.

    PubMed

    Li, Liang; Dou, Xincun; Li, Guanghai

    2010-11-01

    Semimetal Bi and Sb are important thermoelectric materials. Since theoretical calculation predicted that thermoelectric efficiency can be improved as the dimension of materials decreases, the synthesis and physical properties of Bi-based nanostructures (nanowires, nanotubes, nanobelts, nanoplates) have attracted great interests. This review begins with a survey of the patents and reports on the recent developments of Bi-based nanowires. We focus on Bi-based nanowires fabricated by pulsed electrodeposition in anodic alumina membranes, which are main achievements in our group. Based on the literatures and patents, from synthesis of Bi-based nanowires and their alloys and superlattices, to physical properties including electronic transport, thermal expansion, and thermoelectricity will be demonstrated.

  17. Reactive Spreading of a Lead-Free Solder on Alumina

    SciTech Connect

    Gremillard, L.; Saiz, E.; Radmilovic, V.R.; Tomsia, A.P.

    2005-12-01

    The wetting of Sn3Ag-based alloys on Al{sub 2}O{sub 3} has been studied using the sessile-drop configuration. Small additions of Ti decrease the contact angle of Sn3Ag alloys on alumina from 115 to 23 degrees. Adsorption of Ti-species at the solid-liquid interface prior to reaction is the driving force for the observed decrease in contact angle, and the spreading kinetics is controlled by the kinetics of Ti dissolution into the molten alloy. The addition of Ti increases the transport rates at the solid-liquid interface, resulting in the formation of triple-line ridges that pin the liquid front and promote a wide variability in the final contact angles.

  18. Evaporation of sessile droplets on nano-porous alumina surfaces

    NASA Astrophysics Data System (ADS)

    Singh, Sanchit K.; Pratap, Dheeraj; Ramakrishna, S. Anantha; Khanderkar, Sameer

    2013-07-01

    An experimental investigation of evaporation of sessile droplets is presented on nano-porous alumina surfaces with different pore distribution morphologies and pore sizes. Evaporation can be considered as a quasi-steady-state process, such that the vapor concentration distribution above the droplet satisfies the Laplace equation, but with a timevarying droplet surface. For benchmarking, the evaporation of sessile water and ethanol droplets is also investigated on standard borosilicate glass and Teflon surfaces respectively, and results are compared with the previous work. Contact angle variation with time is also recorded and high speed videos showing the spreading process of droplets on nanoporous surfaces are taken. The results clearly show that nano-structuring is an effective tool to control wettability as well as the diffusive evaporation process.

  19. Removal of mercury from an alumina refinery aqueous stream.

    PubMed

    Mullett, Mark; Tardio, James; Bhargava, Suresh; Dobbs, Charles

    2007-06-01

    Digestion condensate is formed as a by-product of the alumina refinery digestion process. The solution exhibits a high pH and is chemically reducing, containing many volatile species such as water, volatile organics, ammonia, and mercury. Because digestion condensate is chemically unique, an innovative approach was required to investigate mercury removal. The mercury capacity and adsorption kinetics were investigated using a number of materials including gold, silver and sulphur impregnated silica and a silver impregnated carbon. The results were compared to commercial sorbents, including extruded and powdered virgin activated carbons and a sulphur impregnated mineral. Nano-gold supported on silica (88% removal under batch conditions and 95% removal under flow conditions) and powdered activated carbon (91% under batch conditions and 98% removal under flow conditions) were the most effective materials investigated. The silver and sulphur impregnated materials were unstable in digestion condensate under the test conditions used.

  20. Development of alumina ceramic bipolar hip prosthesis and clinical application.

    PubMed

    Asada, K; Yoshida, K; Shimazu, A; Yunoki, H; Ishida, N

    1987-02-01

    The concept of the bipolar type prosthesis is that the articular motion is observed primarily between the HDP bearing insert and the inner head, thereby avoiding the greater frictional shear force between the prosthetic head and acetabulum found with the traditional one piece endoprosthesis. A newly developed ceramic bipolar hip prosthesis utilizes an outer head composed of bio-inert fine alumina ceramic rather than a metal head. The mechanical strength of this prototype bipolar hip prosthesis was tested with static load and impact force, and the dynamic fatigue strength was also tested with repeated loads. Results were judged to show that the device has strength adequate for clinical use. The hip prostheses has been clinically applied in replacement of the femoral head of a neck fracture, femoral head necrosis and osteoarthritic hip. Finally, using a mathematical model, the so-called self-centering effect due to center offset between outer and inner heads is discussed.

  1. Sodium-Beta Alumina Batteries: Status and Challenges

    SciTech Connect

    Lu, Xiaochuan; Lemmon, John P.; Sprenkle, Vincent L.; Yang, Zhenguo

    2010-09-05

    Sodium-beta alumina batteries, have been extensively developed for a few decades and encouraging progress has been achieved so far. The anode is typically molten sodium while the cathode can be molten sulfur (Na-S battery) or solid transition metal halides plus a liquid phase secondary electrolyte (e.g., ZEBRA battery). The electrolyte typically used is a β"-Al2O3 solid membrane. The issues prohibiting broad commercialization of this type of technology are dependent on the materials used, but can be broadly described as relatively high cost, safety (particularly for the Na-S couple), and low power. This paper offers a review on materials and designs for the batteries and discusses the challenges ahead for further technology improvement.

  2. Fatigue strength testing of LTCC and alumina ceramics bonds

    NASA Astrophysics Data System (ADS)

    Dąbrowski, A.; Matkowski, P.; Golonka, L.

    2012-12-01

    In this paper the results of fatigue strength tests of ceramic joints are presented. These tests have been performed on the samples subjected to thermal and vibration fatigue as well as on the reference samples without any additional loads. The main goal of the investigation was to determine the strength of hybrid ceramics joints using tensile testing machine. The experiment enabled evaluation of fatigue effects in the mentioned joints. Geometry of test samples has been designed according to FEM simulations, performed in ANSYS FEM environment. Thermal stress as well as the stress induced by vibrations have been analyzed in the designed model. In the experiments two types of ceramics have been used — LTCC green tape DP951 (DuPont) and alumina ceramic tape. The samples have been prepared by joining two sintered ceramic beams made of different types of material. The bonds have been realized utilizing low temperature glass or a layer of LTCC green tape.

  3. Adsorption of chromium onto activated alumina: kinetics and thermodynamics studies.

    PubMed

    Marzouk, Ikhlass; Dammak, Lassaad; Hamrouni, Béchir

    2013-02-01

    In this study, the removal of chromium (VI) by adsorption on activated alumina was investigated and the results were fitted to Langmuir, Freundlich, Dubinin-Redushkevich, and Temkin adsorption models at various temperatures. The constants of each model were evaluated depending on temperature. Thermodynamic parameters for the adsorption system were determined at 10, 25 and 40 degrees C. (deltaH degrees = -21.18 kJ x mol(-1); deltaG degrees = -8.75 to -7.43 kJ x mol(-1) and deltaS degrees = -0.043 kJ x K(-1) x mol(-1)). The obtained values showed that chromium (VI) adsorption is a spontaneous and exothermic process. The kinetic process was evaluated by first-order, second-order and Elovich kinetic models.

  4. Ferromagnetic nanotubes by atomic layer deposition in anodic alumina membranes

    NASA Astrophysics Data System (ADS)

    Daub, M.; Knez, M.; Goesele, U.; Nielsch, K.

    2007-05-01

    In this paper, two methods for the synthesis of magnetic nanotubes inside the pores of anodic alumina membranes by atomic layer deposition (ALD) are compared. The precursors were nickelocene or cobaltocene, and H2O or O3. The first method consists of a three-step ALD cycle: First, the sample is exposed to the metal-organic precursor, subsequently to water, and finally, to hydrogen. In the second method, metal oxide is deposited by a conventional two-step ALD cycle. After the ALD process, the sample is reduced under hydrogen atmosphere. The magnetic nanotubes obtained by the second method have a smaller grain size and improved magnetic properties. The magnetic nanotubes with diameters ranging from 35to60nm exhibit a preferential magnetization direction along the nanowire axis. The Ni or Co nanotubes with larger diameters (around 160nm) show a nearly isotropic magnetic behavior, with the magnetic moments arranged in a vortex state at zero field.

  5. Corrosion performance of alumina scales in coal gasification environments

    SciTech Connect

    Natesan, K.

    1997-02-01

    Corrosion of metallic structural materials in complex gas environments of coal gasification is a potential problem. The corrosion process is dictated by concentrations of two key constituents: sulfur as H{sub 2}S and Cl as HCl. This paper examines the corrosion performance of alumina scales that are thermally grown on Fe-base alloys during exposure to O/S mixed-gas environments. The results are compared with the performance of chromia-forming alloys in similar environments. The paper also discusses the available information on corrosion performance of alloys whose surfaces were enriched with Al by the pack-diffusion process, by the electrospark deposition process, or by weld overlay techniques.

  6. AFM, SEM and TEM Studies on Porous Anodic Alumina

    PubMed Central

    2010-01-01

    Porous anodic alumina (PAA) has been intensively studied in past decade due to its applications for fabricating nanostructured materials. Since PAA’s pore diameter, thickness and shape vary too much, a systematical study on the methods of morphology characterization is meaningful and essential for its proper development and utilization. In this paper, we present detailed AFM, SEM and TEM studies on PAA and its evolvements with abundant microstructures, and discuss the advantages and disadvantages of each method. The sample preparation, testing skills and morphology analysis are discussed, especially on the differentiation during characterizing complex cross-sections and ultrasmall nanopores. The versatility of PAAs is also demonstrated by the diversity of PAAs’ microstructure. PMID:20672104

  7. Tailorable advanced blanket insulation using aluminoborosilicate and alumina batting

    NASA Technical Reports Server (NTRS)

    Calamito, Dominic P.

    1989-01-01

    Two types of Tailorable Advanced Blanket Insulation (TABI) flat panels for Advanced Space Transportation Systems were produced. Both types consisted of integrally woven, 3-D fluted core having parallel faces and connecting ribs of Nicalon yarns. The triangular cross section flutes of one type was filled with mandrels of processed Ultrafiber (aluminoborosilicate) stitchbonded Nextel 440 fibrous felt, and the second type wall filled with Saffil alumina fibrous felt insulation. Weaving problems were minimal. Insertion of the fragile insulation mandrels into the fabric flutes was improved by using a special insertion tool. An attempt was made to weave fluted core fabrics from Nextel 440 yarns but was unsuccessful because of the yarn's fragility. A small sample was eventually produced by an unorthodox weaving process and then filled with Saffil insulation. The procedures for setting up and weaving the fabrics and preparing and inserting insulation mandrels are discussed. Characterizations of the panels produced are also presented.

  8. The mechanical behavior of an alumina carbon/epoxy laminate

    SciTech Connect

    Sherman, D.; Leckie, F.A.; Lemaitre, J.

    1995-12-01

    An experimental study has been made of a laminate consisting of monolithic thin alumina plates alternating with unidirectional carbon/epoxy (C/E) prepreg tapes. The main advantages of this system over the traditional means of reinforcing ceramics, are the avoidance of large flaws due to processing, which occur in fiber reinforced brittle matrix composites, and the nearly isotropic behavior under biaxial loading. In addition, the multiple fracture mechanism occurring in the system gives rise to pseudo ductile behavior and enhanced strain energy dissipation.The mechanical behavior of the laminate is explored. The effects of the number of layers, volume fraction and transverse properties are also investigated. The loss of stiffness with increase of the applied strain is estimated using a simple shear lag theory, which includes the plastic behavior of the interface.

  9. Acoustic phonon spectrum and thermal transport in nanoporous alumina arrays

    DOE PAGES

    Kargar, Fariborz; Ramirez, Sylvester; Debnath, Bishwajit; ...

    2015-10-28

    We report results of a combined investigation of thermal conductivity and acoustic phonon spectra in nanoporous alumina membranes with the pore diameter decreasing from D=180 nm to 25 nm. The samples with the hexagonally arranged pores were selected to have the same porosity Ø ≈13%. The Brillouin-Mandelstam spectroscopy measurements revealed bulk-like phonon spectrum in the samples with D = 180 nm pores and spectral features, which were attributed to spatial confinement, in the samples with 25 nm and 40 nm pores. The velocity of the longitudinal acoustic phonons was reduced in the samples with smaller pores. As a result, analysismore » of the experimental data and calculated phonon dispersion suggests that both phonon-boundary scattering and phonon spatial confinement affect heat conduction in membranes with the feature sizes D < 40 nm.« less

  10. Acoustic phonon spectrum and thermal transport in nanoporous alumina arrays

    SciTech Connect

    Kargar, Fariborz; Ramirez, Sylvester; Debnath, Bishwajit; Malekpour, Hoda; Lake, Roger; Balandin, Alexander A.

    2015-10-28

    We report results of a combined investigation of thermal conductivity and acoustic phonon spectra in nanoporous alumina membranes with the pore diameter decreasing from D=180 nm to 25 nm. The samples with the hexagonally arranged pores were selected to have the same porosity Ø ≈13%. The Brillouin-Mandelstam spectroscopy measurements revealed bulk-like phonon spectrum in the samples with D = 180 nm pores and spectral features, which were attributed to spatial confinement, in the samples with 25 nm and 40 nm pores. The velocity of the longitudinal acoustic phonons was reduced in the samples with smaller pores. As a result, analysis of the experimental data and calculated phonon dispersion suggests that both phonon-boundary scattering and phonon spatial confinement affect heat conduction in membranes with the feature sizes D < 40 nm.

  11. Multi-Objective Optimization for Alumina Laser Sintering Process

    NASA Astrophysics Data System (ADS)

    Fayed, E. M.; Elmesalamy, A. S.; Sobih, M.; Elshaer, Y.

    2016-09-01

    Selective laser sintering processes has become one of the most popular additive manufacturing processes due to its flexibility in creation of complex components. This process has many interacting parameters, which have a significant influence on the process output. In this work, high purity alumina is sintered through a pulsed Nd:YAG laser sintering process. The aim of this work is to understand the effect of relevant sintering process parameters (laser power and laser scanning speed) on the quality of the sintered layer (layer surface roughness, layer thickness and vector/line width, and density). Design of experiments and statistical modeling techniques are employed to optimize the process control factors and to establish a relationship between these factors and output responses. Model results have been verified through experimental work and show reasonable prediction of process responses within the limits of sintering parameters.

  12. Abrasive wear of alumina fibre-reinforced aluminium

    NASA Astrophysics Data System (ADS)

    Axen, N.; Alahelisten, A.; Jacobson, S.

    1994-04-01

    The friction and abrasive wear behaviour of an Al-Si1MgMn aluminium alloy reinforced with 10, 15 and 30 vol.% of alumina fibers has been evaluated. The influence of fiber content, matrix hardness, applied load as well as the hardness and size of the abrasive grits was investigated. The tests were performed with a pin-on-drum two-body abrasion apparatus. The wear mechanisms were studied using scanning electron microscopy. It is shown that fiber reinforcement increases the wear resistance in milder abrasive situations, i.e. small and soft abrasives and low loads. However, in tougher abrasive situations, meaning coarse and hard abrasives and high loads, the wear resistance of the composites is equal to or, in some cases, even lower than that of the unreinforced material. It is also shown that the coefficient of friction decreases with increasing fiber content and matrix hardness of the composites.

  13. AFM, SEM and TEM Studies on Porous Anodic Alumina

    NASA Astrophysics Data System (ADS)

    Zhu, Yuan Yuan; Ding, Gu Qiao; Ding, Jian Ning; Yuan, Ning Yi

    2010-04-01

    Porous anodic alumina (PAA) has been intensively studied in past decade due to its applications for fabricating nanostructured materials. Since PAA’s pore diameter, thickness and shape vary too much, a systematical study on the methods of morphology characterization is meaningful and essential for its proper development and utilization. In this paper, we present detailed AFM, SEM and TEM studies on PAA and its evolvements with abundant microstructures, and discuss the advantages and disadvantages of each method. The sample preparation, testing skills and morphology analysis are discussed, especially on the differentiation during characterizing complex cross-sections and ultrasmall nanopores. The versatility of PAAs is also demonstrated by the diversity of PAAs’ microstructure.

  14. Amorphous and crystalline phases in thermal quench simulations of alumina.

    PubMed

    Rosen, J; Warschkow, O; McKenzie, D R; Bilek, M M M

    2007-05-28

    The authors report molecular dynamics simulations of alumina (Al2O3) during crystallization from the melt. Using liquid quench methods, they investigate the effect of cooling rate on the structural evolution of the alpha, kappa, and the bixbyite phases. A critical temperature window is identified, where the time spent in this window is crucial in determining the extent to which the systems approach crystallinity. A strong dependence is observed between the final structure and the quench rate, which is most pronounced for the alpha phase and to lesser extent for the other phases. The results show that the different phases have different tendencies to crystallize that are determined by energetics, complexity of crystal structure, and the number of metastable states.

  15. Effects of precracking methods on the fracture properties of alumina

    NASA Technical Reports Server (NTRS)

    Salem, Jonathan A.; Shannon, John L., Jr.; Jenkins, Michael G.; Ferber, Mattison K.

    1991-01-01

    Fracture toughness values were compared for quasi-statically cracked, rapidly precracked, and fatigue precracked specimens of the same 96 percent alumina. The quasi-statically cracked specimens exhibited a rising R-curve and crack length dependent fracture toughness values. The rising R-curve resulted from grain bridging in the crack wake. Tension and compression fatigue precracked specimens did not exhibit crack length dependence, but did produce consistent fracture toughness values from fast fracture tests. Specimens that were rapidly precracked with the bridge indentation method also did not exhibit crack length dependence. These results imply that the measured fracture toughness and observed crack growth resistance of some brittle ceramics are dependent on loading history, crack extension and environment.

  16. Porosity estimation of alumina samples based on resonant backscattering spectrometry

    NASA Astrophysics Data System (ADS)

    Mokhles Gerami, F.; Kakuee, O.; Mohammadi, S.

    2016-04-01

    In this work, columnar porous alumina samples were investigated using the 16O(α,α)16O resonance scattering at 3.045 MeV. If the incident energy is slightly above the resonance energy, a resonance peak appears in the energy spectra of the backscattered ions. The position and width of this peak for non-porous samples are mainly determined by the experimental setup, whilst for porous materials, the peak position shifts towards higher energies under certain conditions. This effect can be explained by the lower amount of material which the ions encounter along the backscattered trajectories. The energy shift of the resonance peak towards higher energies was revealed experimentally and discussed theoretically. The estimated porosities of the samples based on this energy shift were compared with those evaluated from the graphical analysis of the images obtained by field emission scanning electron microscopy.

  17. Preparation and Various Characteristics of Epoxy/Alumina Nanocomposites

    NASA Astrophysics Data System (ADS)

    Kozako, Masahiro; Ohki, Yoshimichi; Kohtoh, Masanori; Okabe, Shigemitsu; Tanaka, Toshikatsu

    Epoxy/ alumina nanocomposites were newly prepared by dispersing 3, 5, 7, and 10 weight (wt) % boehmite alumina nanofillers in a bisphenol-A epoxy resin using a special two-stage direct mixing method. It was confirmed by scanning electron microscopy imaging that the nanofillers were homogeneously dispersed in the epoxy matrix. Dielectric, mechanical, and thermal properties were investigated. It was elucidated that nanofillers affects various characteristics of epoxy resins, when they are nanostructrued. Such nano-effects we obtained are summarized as follows. Partial discharge resistance increases as the filler content increases; e.g. 7 wt% nanofiller content creates a 60 % decrease in depth of PD-caused erosion. Weibull analysis shows that short-time electrical treeing breakdown time is prolonged to 265 % by 5 wt% addition of nanofillers. But there was more data scatter in nanocomposites than in pure epoxy. Permittivity tends to increase from 3.7 to 4.0 by 5 wt% nanofiller addition as opposed to what was newly found in the recent past. Glass transition temperature remains unchanged as 109 °C. Mechanical properties such as flexural strength and flexural modulus increase; e.g. flexural strength and flexural modulus are improved by 5 % and 8 % with 5 wt% content, respectively. Excess addition causes a reverse effect. It is concluded from permittivity and glass transition temperature characteristics that interfacial bonding seems to be more or less weak in the nanocomposite specimens prepared this time, even though mechanical strengths increase. There is a possibility that the nanocomposites specimens will be improved in interfacial quality.

  18. Damping Behavior of Alumina Epoxy Nano-Composites

    NASA Astrophysics Data System (ADS)

    Katiyar, Priyanka; Kumar, Anand

    2016-10-01

    Polymer nano composites, consisting of a polymer matrix with nanoparticle filler, have been predicted to be one of the most beneficial applications of nanotechnology. Addition of nano particulates to a polymer matrix enhances its performance by capitalizing on the nature and properties of the nano-scale fillers. The damping behavior of composites with nano structured phases is significantly different from that of micro structured materials. Viscoelastic homopolymer exhibit a high material damping response over a relatively narrow range of temperature and frequencies. In many practical situations, a polymeric structure is required to possess better strength and stiffness properties together with a reasonable damping behavior. Viscoelastic polymers show higher loss factor beyond the glassy region which comes with a significant drop in the specific modulus. Addition of nano alumina particles to epoxy leads to improved strength and stiffness properties with an increase in glass transition temperature while retaining its damping capability. Experimental investigations are carried out on composite beam specimen fabricated with different compositions of alumina nano particles in epoxy to evaluate loss factor, tan δ. Impact damping method is used for time response analysis. A single point Laser is used to record the transverse displacement of a point on the composite beam specimen. The experimental results are compared with theoretical estimation of loss factor using Voigt estimation. The effect of inter phase is included in theoretical estimation of loss factor. The result reveals that the study of interface properties is very important in deriving the overall loss factor of the composite since interface occupies a significant volume fraction in the composite.

  19. Static fracture behavior of multilayered alumina-zirconia composites

    NASA Astrophysics Data System (ADS)

    Moon, Robert John

    The techniques for evaluating the static fracture behavior of monolithic materials are well established. Applying these same techniques to evaluate the fracture behavior of multilayered and/or gradient composites requires consideration of the changing microstructural influence on fracture. In the current study, single-edge-V-notched-beam (SEVNB) testing was used to evaluate the R-curve behavior of multilayered gradient alumina-zirconia composites. Crack initiation and extension from the V-notch tip were observed via in situ optical microscopy. The V-notch tip was positioned near specific microstructural features within the composite and during loading short cracks (5 to 75 mum) were initiated from the V-notch tip and extended stably in ˜10 mum increments. The influence of gradient microstructures, layer-layer interfaces, platelike alumina additions, residual stresses, and the direction of crack propagation on the resulting R-curves were investigated. The fracture mechanics weight function was used to estimate the fracture behavior based on the stress distribution (applied bending stress and residual stresses). The results were compared to the measured R-curves and the weight function analysis was observed to underestimate the measured KR. These differences were likely due to bridging stresses within the samples that were not accounted for in the weight function analysis. Initial attempts to account for bridging stress within the weight function analysis were in good agreement with the measured R-curves for the monolithic sample and for the samples having a step-wise change in residual stress. However, the same bridging function was not applicable for the samples having a composition gradient within each layer.

  20. Optical Basicity and Nepheline Crystallization in High Alumina Glasses

    SciTech Connect

    Rodriguez, Carmen P.; McCloy, John S.; Schweiger, M. J.; Crum, Jarrod V.; Winschell, Abigail E.

    2011-02-25

    The purpose of this study was to find compositions that increase waste loading of high-alumina wastes beyond what is currently acceptable while avoiding crystallization of nepheline (NaAlSiO4) on slow cooling. Nepheline crystallization has been shown to have a large impact on the chemical durability of high-level waste glasses. It was hypothesized that there would be some composition regions where high-alumina would not result in nepheline crystal production, compositions not currently allowed by the nepheline discriminator. Optical basicity (OB) and the nepheline discriminator (ND) are two ways of describing a given complex glass composition. This report presents the theoretical and experimental basis for these models. They are being studied together in a quadrant system as metrics to explore nepheline crystallization and chemical durability as a function of waste glass composition. These metrics were calculated for glasses with existing data and also for theoretical glasses to explore nepheline formation in Quadrant IV (passes OB metric but fails ND metric), where glasses are presumed to have good chemical durability. Several of these compositions were chosen, and glasses were made to fill poorly represented regions in Quadrant IV. To evaluate nepheline formation and chemical durability of these glasses, quantitative X-ray diffraction (XRD) analysis and the Product Consistency Test were conducted. A large amount of quantitative XRD data is collected here, both from new glasses and from glasses of previous studies that had not previously performed quantitative XRD on the phase assemblage. Appendix A critically discusses a large dataset to be considered for future quantitative studies on nepheline formation in glass. Appendix B provides a theoretical justification for choice of the oxide coefficients used to compute the OB criterion for nepheline formation.

  1. Lightweight alumina refractory aggregate. Phase 2, Pilot scale development

    SciTech Connect

    Swansiger, T.G.; Pearson, A.

    1994-11-01

    Kilogram quantities of refractory aggregate were prepared from both a paste and a pelletized form of extruder feed material in both bench and pilot-scale equipment. The 99{sup +} % alumina aggregate exhibited a bulk density approaching 2.5 g/cm{sup 3} and a fired strength slightly lower than fused alumina. Based on initial evaluation by two refractory manufacturers in brick or castable applications, the new aggregate offered adequate strength with thermal conductivity reductions up to 34%, depending on the temperature and application of the new aggregate in these initial trials. The new aggregate was simply substituted for Tabular{trademark} in the refractory formulation. Thus, there is room for improvement through formulation optimization with the lightweight aggregate. The new aggregate offers a unique combination of density, strength, and thermal properties not available in current aggregate. To this point in time, technical development has led to a pelletized formulation with borderline physical form leaving the Eirich mixer. The formulation requires further development to provide more latitude for the production of pelletized material without forming paste, while still reducing the bulk density slightly to reach the 2.5 g/cm{sup 3} target. The preferred, pelletized process flowsheet was outlined and a preliminary economic feasibility study performed based on a process retrofit into Alcoa`s Arkansas tabular production facilities. Based on an assumed market demand of 20,000 mt/year and an assumed selling price of $0.65/lb (25% more than the current selling price of Tabular{trademark}, on a volume basis), economics were favorable. Decision on whether to proceed into Phase 3 (full- scale demonstration) will be based on a formal market survey in 1994 October.

  2. Iron migration from the anode surface in alumina electrolysis

    NASA Astrophysics Data System (ADS)

    Zhuravleva, Elena N.; Drozdova, Tatiana N.; Ponomareva, Svetlana V.; Kirik, Sergei D.

    2013-01-01

    Corrosion destruction of two-component iron-based alloys used as an anode in high-temperature alumina electrolysis in the melt of NaF/KF/AlF3 electrolyte has been considered. Ni, Si, Cu, Cr, Mn, Al, Ti in the amount of up to 10% have been tested as the dopants to an anode alloys. The composition of the corrosion products has been studied using X-ray diffraction, scanning electron microscopy and electron microprobe analysis. It has been established that the anode corrosion is induced by a surface electrochemical polarization and iron atom oxidation. Iron ions come into an exchange interaction with the fluoride components of the melted electrolyte, producing FeF2. The last interacts with oxyfluoride species transforming into the oxide forms: FeAl2O4, Fe3O4, Fe2O3. Due to the low solubility, the iron oxides are accumulated in the near-electrode sheath. The only small part of iron from anode migrates to cathode that makes an production of high purity aluminum of a real task. The alloy dopants are also subjected to corrosion in accordance with electromotive series resulting corrosion tunnels on the anode surface. The oxides are final compounds which collect in the same area. The corrosion products form an anode shell which is electronic conductor at electrolysis temperature. The electrolysis of alumina occurs beyond the corrosion shell. The rate limiting step in the corrosion is the electrolyte penetration through corrosion shell to the anode surface. The participation of the released oxygen in the corrosion has not been observed.

  3. Rational engineering of nanoporous anodic alumina optical bandpass filters

    NASA Astrophysics Data System (ADS)

    Santos, Abel; Pereira, Taj; Law, Cheryl Suwen; Losic, Dusan

    2016-08-01

    Herein, we present a rationally designed advanced nanofabrication approach aiming at producing a new type of optical bandpass filters based on nanoporous anodic alumina photonic crystals. The photonic stop band of nanoporous anodic alumina (NAA) is engineered in depth by means of a pseudo-stepwise pulse anodisation (PSPA) approach consisting of pseudo-stepwise asymmetric current density pulses. This nanofabrication method makes it possible to tune the transmission bands of NAA at specific wavelengths and bandwidths, which can be broadly modified across the UV-visible-NIR spectrum through the anodisation period (i.e. time between consecutive pulses). First, we establish the effect of the anodisation period as a means of tuning the position and width of the transmission bands of NAA across the UV-visible-NIR spectrum. To this end, a set of nanoporous anodic alumina bandpass filters (NAA-BPFs) are produced with different anodisation periods, ranging from 500 to 1200 s, and their optical properties (i.e. characteristic transmission bands and interferometric colours) are systematically assessed. Then, we demonstrate that the rational combination of stacked NAA-BPFs consisting of layers of NAA produced with different PSPA periods can be readily used to create a set of unique and highly selective optical bandpass filters with characteristic transmission bands, the position, width and number of which can be precisely engineered by this rational anodisation approach. Finally, as a proof-of-concept, we demonstrate that the superposition of stacked NAA-BPFs produced with slight modifications of the anodisation period enables the fabrication of NAA-BPFs with unprecedented broad transmission bands across the UV-visible-NIR spectrum. The results obtained from our study constitute the first comprehensive rationale towards advanced NAA-BPFs with fully controllable photonic properties. These photonic crystal structures could become a promising alternative to traditional optical

  4. Atomic layer deposition of TiO2 thin films on nanoporous alumina templates: Medical applications

    NASA Astrophysics Data System (ADS)

    Narayan, Roger J.; Monteiro-Riviere, Nancy A.; Brigmon, Robin L.; Pellin, Michael J.; Elam, Jeffrey W.

    2009-06-01

    Nanostructured materials may play a significant role in controlled release of pharmacologic agents for treatment of cancer. Many nanoporous polymer materials are inadequate for use in drug delivery. Nanoporous alumina provides several advantages over other materials for use in controlled drug delivery and other medical applications. Atomic layer deposition was used to coat all the surfaces of a nanoporous alumina membrane in order to reduce the pore size in a controlled manner. Neither the 20 nm nor the 100 nm TiO2-coated nanoporous alumina membranes exhibited statistically lower viability compared to the uncoated nanoporous alumina membrane control materials. Nanostructured materials prepared using atomic layer deposition may be useful for delivering a pharmacologic agent at a precise rate to a specific location in the body. These materials may serve as the basis for “smart” drug delivery devices, orthopedic implants, or self-sterilizing medical devices.

  5. Interfacial Reactions between Alumina and Carbon Refractories and Molten Iron at 1,823 K

    NASA Astrophysics Data System (ADS)

    Ikram-ul-Haq, Muhammad; Khanna, Rita; Sahajwalla, Veena

    2016-10-01

    High temperature interactions of alumina-carbon refractories with molten iron were investigated at 1,823 K in argon atmosphere. These studies were specifically focussed on the decomposition of alumina in the simultaneous presence of carbon and iron, and associated refractory degradation. Refractory mixtures were prepared by blending 90 wt% alumina with 10 wt% synthetic graphite; 5-15 wt% iron powder was then mixed with the refractory mixture. Using phenol formaldehyde as a binder, pellets were prepared from various blends; these were heat treated at 1,823 K for 30 min in Ar atmosphere. The presence of molten iron significantly enhanced the decomposition of alumina resulting in an enhanced refractory degradation as well as the formation of a new reactant product. This product was identified as a Fe-Al intermetallic phase from SEM/EDS (scanning electron microscopy/energy-dispersive spectroscopy) and x-ray microdiffraction investigations.

  6. Alumina Volatility in Water Vapor at Elevated Temperatures: Application to Combustion Environments

    NASA Technical Reports Server (NTRS)

    Opila, Elizabeth J.; Myers, Dwight L.

    2003-01-01

    The volatility of alumina in high temperature water vapor was determined by measuring weight loss of sapphire coupons at temperatures between 1250 and 1500 C, water vapor partial pressures between 0.15 and 0.68 atm in oxygen, at one atmosphere total pressure, and a gas velocity of 4.4 centimeters per second. The variation of the volatility with water vapor partial pressure was consistent with Al(OH)3(g) formation. The enthalpy of reaction to form Al(OH)3(g) from alumina and water vapor was found to be 210 plus or minus 20 kJ/mol. Surface rearrangement of ground sapphire surfaces increased with water vapor partial pressure, temperature and volatility rate. Recession rates of alumina due to volatility were determined as a function of water vapor partial pressure and temperature to evaluate limits for use of alumina in long term applications in combustion environments.

  7. Effect of low-dimensional alumina structures on viability of L 929 cells

    SciTech Connect

    Fomenko, Alla N. Korovin, Matvey S. Bakina, Olga V. Kazantsev, Sergey O. Glazkova, Elena A. Svarovskaya, Natalia V. Lozhkomoev, Aleksandr S.

    2015-10-27

    In the study, we estimated the cytotoxicity of alumina nanoparticles differing in shape (nanofibers, nanoplates, nanosheets, agglomerates of nanosheets) and close in physicochemical properties (particle size, specific surface area, phase composition, and zeta potential). The alumina structures were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) data, low-temperature nitrogen adsorption, and dynamic light scattering (DLS). The cytotoxicity was estimated on fibroblast cells of the L929 line. It was found that a more adverse effect on the cells was exerted by alumina nanofibers and nanosheets. The action of nanosheets on the cells was inhibitory and was of about the same level, irrespective of the observation period. The effect of alumina nanosheet agglomerates and nanoplates on the cell proliferation was weak even at an exposure time of 72 h.

  8. Theoretical and phenomenological analogies between flash sintering and dielectric breakdown in α-alumina

    NASA Astrophysics Data System (ADS)

    Biesuz, Mattia; Luchi, Piero; Quaranta, Alberto; Sglavo, Vincenzo M.

    2016-10-01

    α-alumina pre-sintered samples were subjected to flash sintering at 1200 °C under differing electric field strengths. The analysis of the relation between the incubation time and pre-sintering temperature clearly shows that the presence of pores and surfaces within the sample plays a central role in field-assisted sintering behavior of the material. The observed behavior is accounted for by the strong non-linear electrical conductivity shown by porous alumina at high field strength. The observed non-ohmic conductivity can also be related to the "pre-breakdown" behavior previously described by Frenkel. Literature results suggest that the field involved in flash sintering of alumina is comparable with the dielectric strength at high temperature. We can also state that dielectric breakdown and flash sintering in alumina are associated with similar physical phenomena.

  9. World bauxite and alumina production capacity in the mid-1990`s

    SciTech Connect

    Sehnke, E.D.

    1996-10-01

    A comprehensive review indicates that total worldwide in place capacity for the production of bauxite and bauxite-alternative ores currently is approximately 133 million metric tons per year. This includes the annual capacity to produce 123 million metric tons of metallurgical grade bauxite, 7 million metric tons of bauxite used for nonmetal applications, and 3 million metric tons of alumina equivalent non-bauxitic materials (alunite and nepheline) for alumina production. Current total world alumina production capacity amounts to about 51 million metric tons per year. This includes the annual capacity to provide approximately 47 million metric tons per year of smelter-grade alumina for the production of primary aluminum metal and nearly 4 million metric tons for nonmetal specialty applications.

  10. Laser ultrasonic surface wave inspection of alumina ceramics of varying density

    PubMed

    Kehoe; Coyle; Murray; Flannery; Crean

    2000-03-01

    In this paper, the surface acoustic wave velocity results acquired from the inspection of specially manufactured and characterised alumina ceramic materials are presented. Ultrasonic velocity data of alumina-based ceramics in the range 60-100% theoretical density was generated utilising non-contacting laser-ultrasonic measurements based on laser generation and detection of surface acoustic waves with the objective of creating a routine technique for industrial advanced alumina inspection. With linear fitting the surface acoustic wave velocity data serves as a calibration graph for using laser ultrasonics for routine monitoring of alumina. A second laser ultrasonic technique based on the laser generation and foil transducer detection of surface acoustic waves was used to validate the surface acoustic wave velocities measured by the laser generation/detection technique.

  11. Development of polysilane-supported palladium/alumina hybrid catalysts and their application to hydrogenation.

    PubMed

    Oyamada, Hidekazu; Naito, Takeshi; Miyamoto, Shinpei; Akiyama, Ryo; Hagio, Hiroyuki; Kobayashi, Shū

    2008-01-07

    Novel immobilized Pd catalysts, polysilane-supported palladium/alumina hybrid catalysts, have been developed. The catalysts showed high catalytic activity for hydrogenation, and could be used in an organic solvent or under solvent-free conditions.

  12. Relationship Between Liquor Yield, Plant Capacity Increases, and Energy Savings in Alumina Refining

    NASA Astrophysics Data System (ADS)

    Ter Weer, Peter-Hans

    2014-09-01

    The mechanisms of alumina trihydrate precipitation and controlling parameters, and the methods and technologies affecting liquor yield/productivity in alumina refining, have been described in several publications [e.g., Refs. Alamdari et al. ( Light Metals 1998, pp. 133-137, 1998), Moretto and Power ( Proc. 1990 Alumina Quality Workshop, Perth, Australia, pp. 154-165, 1990)]. However, the relationship between increasing liquor yield, on the one hand, and plant production capacity increases and related energy savings, on the other, has been under-emphasized. This article addresses this issue and provides estimates of plant production capacity increases and steam and power energy savings as a function of precipitation yield increases resulting from the implementation of plant adaptations. Conclusions are that increasing precipitation yield in an alumina refinery results overall in a significant improvement of project economics and interestingly improves a refinery's direct and indirect environmental performance, thus, addressing two of the three "pillars" of sustainable development (economic, environmental, and social).

  13. Characterisation of dynamic behaviour of alumina ceramics: evaluation of stress uniformity

    NASA Astrophysics Data System (ADS)

    Wang, Zhiyong; Li, Peifeng

    2015-10-01

    Accurate characterisation of dynamic behaviour of ceramics requires the reliable split-Hopkinson pressure bar (SHPB) technique and the condition of uniaxial homogeneous specimen deformation. In this study, an experimentally validated 3D finite element model of the full scale SHPB experiment was developed to quantitatively evaluate the wave propagation in the bars and the stress distribution/evolution in the alumina specimen. Wave signals in both the SHPB experiments and the finite element model were analysed to characterise the dynamic behaviour of alumina. It was found that the equilibrium of both stresses within the specimen and forces at the specimen ends can be established in the intermediate stage of deformation. The validity of stress uniformity in the alumina specimen supports the assumption of uniaxial homogeneous specimen deformation in the SHPB and validates the characterisation of dynamic behaviour of alumina ceramics.

  14. Mechanical Properties of a Graded Alumina-Zirconia Composite Prepared by Centrifugal Slip Casting

    SciTech Connect

    Hara, Yasuyuki; Onda, Tetsuhiko; Hayakawa, Motozo

    2008-02-15

    Compositionally graded composite of alumina-20 vol%zirconia was fabricated by using centrifugal casting incorporated with relatively thin slip. An EPMA analysis exhibited a nearly linear variation of the alumina/zirconia ratio along the centrifugal direction; zirconia tended to accumulate in the bottom section, while alumina in the top section. Such a graded structure exhibited a considerably higher flexural strength when the alumina rich surface was subjected to a tensile stress than compositionally uniform composite of the same average composition. Fracture toughness measurement across the specimen thickness by indentation method revealed that the crack lengths along the vertical and horizontal directions were different. The anisotropy of the fracture toughness was accounted for by the variation of the residual stress across the specimen thicknesss.

  15. Stability of trapped charges in sapphires and alumina ceramics: Evaluation by secondary electron emission

    NASA Astrophysics Data System (ADS)

    Zarbout, K.; Si Ahmed, A.; Moya, G.; Bernardini, J.; Goeuriot, D.; Kallel, A.

    2008-03-01

    The stability of trapped charges in sapphires and alumina ceramics is characterized via an experimental parameter expressing the variation of the secondary electron emission yield between two electron injections performed in a scanning electron microscope. Two types of sapphires and polycrystalline alumina, which differ mainly by their impurity content, are investigated in the temperature range 300-663K. The stable trapping behavior in sapphires is attributed to trapping in different defects, whose nature depends on the purity level. In alumina ceramics, the ability to trap charges in a stable way is stronger in samples of high impurity content. In the low impurity samples, stable trapping is promoted when the grain diameter decreases, whereas the reverse is observed in high impurity materials. These behaviors can stem from a gettering effect occurring during sintering. The strong dependence of the variation of the secondary electron emission yield on the grain diameter and impurities enables a scaling of the stable trapping ability of alumina materials.

  16. Atomic layer deposition of TIO{sub 2} thin films on nanoporous alumina templates : medical applications.

    SciTech Connect

    Narayan, R. J.; Monteiro-Riviere, N. A.; Brigmon, R. L.; Pellin, M. J.; Elam, J.W.; Energy Systems; Univ. of North Carolina; North Carolina State Univ.; SRL

    2009-06-01

    Nanostructured materials may play a significant role in controlled release of pharmacologic agents for treatment of cancer. Many nanoporous polymer materials are inadequate for use in drug delivery. Nanoporous alumina provides several advantages over other materials for use in controlled drug delivery and other medical applications. Atomic layer deposition was used to coat all the surfaces of a nanoporous alumina membrane in order to reduce the pore size in a controlled manner. Neither the 20 nm nor the 100 nm TiO{sub 2}-coated nanoporous alumina membranes exhibited statistically lower viability compared to the uncoated nanoporous alumina membrane control materials. Nanostructured materials prepared using atomic layer deposition may be useful for delivering a pharmacologic agent at a precise rate to a specific location in the body. These materials may serve as the basis for 'smart' drug delivery devices, orthopedic implants, or self-sterilizing medical devices.

  17. Stabilized Alumina/Ethanol Colloidal Dispersion for Seeding High Temperature Air Flows

    NASA Technical Reports Server (NTRS)

    Wernet, Judith H.; Wernet, Mark P.

    1994-01-01

    Seeding air flows with particles to enable measurements of gas velocities via laser anemometry and/or particle image velocimetry techniques can be quite exasperating. The seeding requirements are compounded when high temperature environments are encountered and special care must be used in selecting a refractory seed material. The pH stabilization techniques commonly employed in ceramic processing are used to obtain stable dispersions for generating aerosols of refractory seed material. By adding submicron alumina particles to a preadjusted pH solution of ethanol, a stable dispersion is obtained which when atomized produces a high quality aerosol. Commercial grade alumina powder is used with a moderate size distribution. The technique is not limited to alumina/ethanol and is also demonstrated with an alumina/H2O system. Other ceramic powders in various polar solvents could also be used once the point of zero charge (pH(sub pzc)) of the powder in the solvent has been determined.

  18. Preparation and characterization of Rh catalyst supported on nanoporous alumina for the ethylene hydroformylation.

    PubMed

    Kim, You Jung; Joo, Ji Bong; Kim, Hui Chan; Yi, Jongheop

    2010-01-01

    Nanoporous gamma-aluminas were prepared by a sol-gel method with and without surfactant, and characterized by nitrogen adsorption-desorption, transmission electron microscopy (TEM), X-ray diffraction (XRD) and temperature programmed reduction (TPR). The resulting materials were applied to Rh catalyst supports for the ethylene hydroformylation. The ordered nanoporous alumina (A-1) which was prepared using surfactant, showed well-developed pore structures with high surface area. Rh catalyst supported on A-1 alumina (Rh/A-1) exhibited higher catalytic activity in the ethylene hydroformylation than other Rh catalysts. It is believed that the high catalytic performance of Rh/A-1 resulted from the well-developed pore structure with high surface area of ordered nanoporous A-1 and consequently finely dispersed Rh particle on the surface of gamma-alumina support.

  19. Sodium lignosulfonate as a renewable stabilizing agent for aqueous alumina suspensions.

    PubMed

    Megiatto, Jackson D; Cerrutti, Bianca M; Frollini, Elisabete

    2016-01-01

    The macromolecule sodium lignosulfonate (SL) has been investigated as dispersing agent for aqueous alumina colloids as a renewable alternative to usual petrochemical stabilizing agents. Optimization of the SL concentration necessary to stabilize the alumina suspension at different pH values was determined by viscometer. The results showed that addition of 250 ppm of the total suspension mass led to about 70% viscosity reduction of the suspension, whereas zeta potential analysis revealed negative values for the SL suspensions throughout the pH range investigated, suggesting that the alumina particles were covered by negatively charged SL molecules. Particle size investigation informed that the average particle diameter of the SL suspensions was smaller compared to that of the pristine particles. Sedimentation time for the SL suspensions was dramatically longer than that for the pristine one. The reported data strongly corroborated that SL is a suitable renewable dispersing agent for aqueous alumina colloids.

  20. Optical Properties of Amorphous Alumina Dust in the Envelopes around O-Rich AGB Stars

    NASA Astrophysics Data System (ADS)

    Suh, Kyung-Won

    2016-08-01

    We investigate optical properties of amorphous alumina (Al_2O_3) dust grains in the envelopes around O-rich asymptotic giant branch (AGB) stars using laboratory measured optical data. We derive the optical constants of amorphous alumina over a wide wavelength range that satisfy the Kramers-Kronig relation and reproduce the laboratory data. Using the amorphous alumina and silicate dust, we compare the radiative transfer model results with the observed spectral energy distributions. Comparing the theoretical models with observations on various IR two-color diagrams for a large sample of O-rich AGB stars, we find that the amorphous alumina dust (about 10-40%) mixed with amorphous silicate better models the observed points for the O-rich AGB stars with thin dust envelopes.