| Moisture-Induced Delayed Alumina Scale Spallation on a Ni(Pt)Al Coating (Preprint) |
Apr-2009 |
32 pages |
| Authors:
James L Smialek; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH GLENN RESEARCH CENTER
|
 | Delayed scale failure was examined for samples of a Ni(Pt)Al-coated CMSX4 single crystal superalloy, cyclically oxidized at 1150 degrees C for 2000 hr. One sample exhibited accentuated coating grain boundary wrinkling, initiating local alumina scale spallation to bare metal, resulting in a final weight loss of 3.3 milligrams/(square centimeter). Spallation under ambient conditions was monitored with time after cooldown and was found to continue for times up to 24 hr, ... |
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| Advanced Nanocrystalline Ceramic Matrix Composites with Improved Toughness |
09-Jan-2009 |
29 pages |
| Authors:
Amiya Mukherjee; Katherine Thomson; CALIFORNIA UNIV DAVIS DEPT OF CHEMICAL ENGINEERING AND MATERIALS SCIENCE
|
| Alumina-based nanocomposites reinforced with niobium and/or carbon nanotubes were fabricated by advanced powder processing techniques and consolidated by spark plasma sintering. Raman spectroscopy revealed that single-walled carbon nanotubes (SWCNT) begin to break down at sintering temperatures above 1150 deg C. Nuclear magnetic resonance (NMR) showed that, although thermodynamically unlikely, no Al4C3 formed in the CNT-alumina nanocomposites. Thus, the nanocomposite is purely a physical mixture and no chemical bond was formed ... |
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| Dynamic Failure Processes Under Confining Stress in AlON, a Transparent Polycrystalline Ceramic |
Dec-2008 |
9 pages |
| Authors:
B Paliwal; K T Ramesh; James W McCauley; Mingwei Chen; SANDIA NATIONAL LABS ALBUQUERQUE NM
|
| An experimental technique is developed to impose a planar lateral confinement in a prismatic specimen (with rectangular cross-section); the setup enabled a controlled and homogeneous stress state with high lateral compressive stresses. A transparent polycrystalline aluminum oxynitride (AlON) specimen was used for the study. The statically pre-compressed specimen was then subjected to axial dynamic compressive loading using a modified compression Kolsky bar setup. Experimental design was performed using 3D computational ... |
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| Protection of Polymer from Atomic-Oxygen Erosion using Al2O3 Atomic Layer Deposition Coatings |
Jan-2008 |
5 pages |
| Authors:
Russell Cooper; Timothy K Minton; Steven M George; Hari P Upadhyaya; Michael R Berman; Xiaohua Du; MONTANA STATE UNIV BOZEMAN DEPT OF CHEMISTRY AND BIOCHEMISTRY
|
| Thin films of Al2O3 grown using atomic layer deposition (ALD) techniques can protect polymers from erosion by oxygen atoms. To quantify this protection, polyimide substrates with the same chemical repeat unit as Kapton (registered trademark) were applied to quartz crystal microbalance (QCM) sensors. Al2O3 ALD films with varying thicknesses were grown on the polyimide substrates. The ALD-coated polyimide materials were then exposed to a hyperthermal atomic-oxygen beam. The mass loss ... |
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| Consolidation of A12O3 Nano-Power by Magnetic Pulsed Compaction and Sintering |
16 OCT 2007 |
13 pages |
| Authors:
Whung W. Kim; KOREA ATOMIC ENERGY RESEARCH INST DAEJEON NUCLEAR MATERIAL TECHNOLOGY DEVELOPMENT TEAM
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| Successful ulta-fine nano Al2O3 powder was consolidated and sintered using magnetic pulsed compaction. Measurements indicated that many properties in the consolidated Al2O3 bulk have been much improved over the conventional polycrystalline materials. The optimization of the compaction parameters and sintering conditions will lead to the consolidation of Al2O3 nanopowder for the higher density and even further enhanced mechanical properties. |
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| High Strain Rate Mechanical Properties of Epoxy and Epoxy-Based Particulate Composites (Preprint) |
MAY 2007 |
13 pages |
| Authors:
Jennifer L. Jordan; Wayne Richards; Brad White; Jonathan E. Spowart; AIR FORCE RESEARCH LAB EGLIN AFB FL MUNITIONS DIRECTORATE
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| Polymers and polymer-based particulate composites are becoming increasingly used in aerospace structural applications, where they experience complex, non-static loads. Correspondingly, the high strain rate mechanical properties are of increasing importance. This paper investigates the properties of epoxy - bisphenol-A/diethanolamine epoxy (Epon 826/DEA) - and epoxy-based particulate composites across strain rates from 10(exp -3) to 10(exp 5) /s. The samples were tested using Instron, traditional split Hopkinson pressure bars (SHPBs) and ... |
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| Stoichiometry and Characterization of Aluminum Oxynitride Thin Films by Ion-Beam-Assisted Pulsed Laser Deposition (Preprint) |
JAN 2007 |
23 pages |
| Authors:
J. S. Zabinski; J. J. Hu; J. E. Bultman; N. A. Pierce; A. A. Voevodin; DAYTON UNIV OH RESEARCH INST
|
| Oxides are inherently stable in air at elevated temperatures and may serve as wear resistant matrices for solid lubricants. Aluminum oxide is a particularly good candidate for a matrix because it has good diffusion barrier properties and modest hardness. Most thin film deposition techniques that are used to grow alumina require high temperatures to impart crystallinity. Crystalline films are about twice as hard as amorphous ones. Unfortunately, the mechanical properties ... |
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| Global Mechanical Response and its Relation to Deformation and Failure Modes at Various Length Scales under Shock Impact in Alumina AD995 Armor Ceramic |
01 NOV 2006 |
40 pages |
| Authors:
D. P. Dandekar; J. W. McCauley; W. H. Green; N. K. Bourne; M. W. Chen; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
|
| Polycrystalline aluminum oxide (Al2O3) based materials have both personnel and ground vehicle armor applications. However, as their ballistic performance can vary significantly it is important to identify the fundamental macro and micro mechanisms of deformation and failure in the ballistic event. This has proven elusive over the years. Using a newly developed soft recovery plate impact experiment, a multidisciplinary, multi-national collaboration has, for the first time, determined micro and macro ... |
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| Template-Growth of Highly Ordered Carbon Nanotube Arrays on Silicon POSTPRINT |
SEP 2006 |
5 pages |
| Authors:
Aijun Yin; Marian Tzolov; David Cardimona; Jimmy Xu; BROWN UNIV PROVIDENCE RI DEPT OF ENGINEERING
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| This paper reports on the success in and the key conditions for direct growth or carbon nanotubes or unprecedented uniformity on silicon. The uniformity is ensured through the growth within the highly ordered nanopores or an alumina oxide template, which is in turn formed on silicon through anodization of aluminum of unprecedented thickness evaporated on silicon. The formation of highly ordered nanopore array by anodization of thick aluminum evaporated on ... |
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| Effect of Environment on Creep Behavior of an Oxide/Oxide CFCC with 45 deg. Fiber Orientation |
JUN 2006 |
145 pages |
| Authors:
Gregory T. Siegert; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING AND MANAGEMENT
|
| Aerospace applications require materials capable of maintaining superior mechanical properties while operating at high temperatures and oxidizing environments. Nextel(trademark) 720/A (N720/A), an oxide/oxide ceramic matrix composite (CMC) with a porous alumina matrix was developed specifically to provide improved long-term properties and performance at 1200 deg C. This research evaluated the creep behavior of N720/A with a plus or minus 45 deg fiber orientation at 1200 deg C in: laboratory air, ... |
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| Effects of Frequency and Environment on Fatigue Behavior of an Oxide-Oxide Ceramic Matrix Composite at 1200 Deg. C |
JUN 2006 |
118 pages |
| Authors:
Griffin Hetrick; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING AND MANAGEMENT
|
| Advances in aeronautical engineering in the 21st century depend upon materials that can perform well in extreme environments such as high temperatures and oxidizing conditions. Nextel(Trademark)720/Alumina (N720/A) is an oxide/oxide ceramic matrix composite with a porous alumina matrix that has been identified as a candidate material for such applications. This research investigated the effects of frequency on fatigue response of N720/A at 1200C in both air and steam environment. Prior ... |
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| In Vitro Toxicity of Aluminum Nanoparticles in Rat Alveolar Macrophages |
MAR 2006 |
10 pages |
| Authors:
Andrew Wagner; Charles Bleckmann; E. England; Krista Hess Saber /Hussain; John J. Schlager; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH HUMAN EFFECTIVENESS DIRECTORATE
|
| The purpose of this research was to investigate and characterize the in vitro cellular effects of exposing rat lung macrophages to aluminum oxide nanoparticles (30 and 40nm average size) compared to aluminum metal nanoparticles (50, 80, and 120nm). This study used toxicity endpoints involving cell viability, mitochondrial function, phagocytotic ability, and inflammatory response. Results indicated none to minimal toxicological effects occurred with exposure of macrophages as high as 500 microg/ml ... |
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| In Vitro Toxicity of Aluminum Nanoparticles in Rat Alveolar Macrophages |
MAR 2006 |
111 pages |
| Authors:
Andrew J. Wagner; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING AND MANAGEMENT
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| The purpose of this research is to characterize the in vitro cellular effects of rat lung macrophages to exposure to aluminum oxide nanoparticles (Al2O3-NP) (30 and 40nm) compared to aluminum nanoparticles (Al-NP) (50, 80, and 120nm). This study concentrates on cell viability, mitochondrial function, phagocytosis ability, and cytokine response. Results indicate no to minimal toxicological effects on macrophages exposed as high as 500 μg/ml for 24 hours with Al2O3-NP. However, ... |
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| Effects of Machining on the Uniaxial and Equibiaxial Flexure Strength of CAP3 AD-995 Al2O3 |
SEP 2005 |
70 pages |
| Authors:
Andrew A. Wereszczak; Jeffrey J. Swab; Reuben H. Kraft; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
|
| The effect of surface condition on the uniaxial and equibiaxial flexure strength of CoorsTek's CAP3 AD-995 alumina was examined. (Note that this material was found not to be the same as CoorsTek's AD-955 alumina-a comparison and discussion of the differences are provided in this report.) The following four surface conditions were considered: as-fired (i.e., unmachined) surfaces; the condition produced by CoorsTek's standard surface-grinding procedures (i.e., the condition they will provide ... |
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| The Influence of Particulates on Thruster Plume / Shock Layer Interaction at High Altitudes |
JAN 2005 |
13 pages |
| Authors:
Sergey F. Gimelshein; Alina A. Alexeenko; Dean C. Wadsworth; Natalia E. Gimelshein; UNIVERSITY OF SOUTHERN CALIFORNIA LOS ANGELES
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| A two-phase plume flow from a small aluminized propellant side thruster interacting with rarefied atmosphere at 120 km has been examined numerically. A three step continuum-kinetic approach has been used, with the Navier-Stokes equations solved inside the nozzle, and a 2D/3D DSMC method employed to compute the plume nearfield and then the plume-atmosphere interaction region. At each of these steps, a two-way gas-particulate coupling has been used. The DSMC implementation ... |
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| Adsorption of Soluble Silica Species on Alumina Powders and Vice Versa |
06 MAY 2004 |
8 pages |
| Authors:
Biao Liu; Xiaojun Liu; Carl D. Meinhart; Fred F. Lange; CALIFORNIA UNIV SANTA BARBARA DEPT OF MATERIALS
|
| In an effort to texture a glass surface with alumina particles, we found that positively charged alumina particles were only attracted to the negatively charged silica substrates in aqueous solution for a very short period although the pH was between the iso-electric-point (IEP) of alumina and silica. Instead, experiments show that the glass surface attracted the dissolved species of alumina, which made the surface repel the alumina particles. It was ... |
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| Oxidation Processes on Aluminum and Rhodium |
17 MAR 2004 |
9 pages |
| Authors:
Andrew M. Rappe; PENNSYLVANIA UNIV PHILADELPHIA DEPT OFCHEMISTRY
|
| During the reporting period, we have made new discoveries in the areas of oxide-supported nanocatalysts, quantum Monte Carlo methodlolgy, subsurface vacancies in metals, fundamental understanding of chemisorption, and self-assembled monolayers. We have completed the first major theoretical study of Pt chemisorbed on alumina. We contrast Pt nanoparticle and layer adsorption, focusing on how oxide defects influence the Pt growth, and the CO chemisorption properties on the nanoparticles. We have completed ... |
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| Evaluation of Materials for Rapid Runway Repair |
2004 |
6 pages |
| Authors:
Michael Riley; CERATECH INC BALTIMORE MD
|
| While the goals of this effort are to improve the strength and thermal resistance characteristics of PaveMend products, ultimate cost will also be kept as a determining factor. The metal oxides currently used in PaveMend products are magnesia/alumina based, but are irregular shaped ground particulates. To add stiffness and additional compressive strength to the product, we will investigate the role of chopped ceramic fibers as low weight additives to the ... |
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| High Temperature Materials Simulations on Parallel Computers |
30 APR 2003 |
20 pages |
| Authors:
Priya Vashishta; Rajiv K. Kalia; Aiichiro Nakano; LOUISIANA STATE UNIV BATON ROUGE
|
| Final Progress (1 May 99 - 30 Apr 03): This project deals with properties and processes in high-temperature materials (HTMs) that are vital to the DoD technology base. In this project, molecular-dynamics (MD) simulations have been performed to investigate: i) sintering of nanostructured SiC and high- pressure structural transformation in SiC; ii) dynamic fracture in nanostructured systems; iii) structure of amorphous Al2O3; and iv) reactive wetting of Al2O3 surface by ... |
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| AB Initio Propagator Theory of Clusters |
12 FEB 2003 |
15 pages |
| Authors:
J. V. Ortiz; KANSAS STATE UNIV MANHATTAN DEPT OF CHEMISTRY
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| Oxidative processes involving aluminum lead to the creation of many intermediates whose structure and reactivity stimulate intense study. Aluminum- rich species are especially pertinent to the growth and structure of interfaces between bulk Al2O3 and metallic Al phases. Ceramics, minerals, reactive surfaces and catalytic supports often consist of oxides of aluminum. This project aims to improve understanding of the basic interactions between atoms of oxygen and aluminum at the atomic ... |
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| Microstructure and Dynamic Behavior Correlation in Two-Phase TiB2+Al2O3 Ceramic |
OCT 2002 |
104 pages |
| Authors:
Naresh N. Thadhani; Min Zhou; GEORGIA INST OF TECH ATLANTA SCHOOL OFMATERIALS SCIENCE AND ENGINEERING
|
| The high-strain-rate deformation and damage response of four types of microstructurally-biased two-phase (nominally 30:70) TiB2+Al2O3 ceramics, produced by SHS or mechanical milling techniques, have been investigated in this work. The microstructural-bias includes differences in phase (grain) size and phase distribution, such that in one case a continuous (interconnected) TiB2 network surrounds the Al2O3 phase (qualitatively termed TA'), and in the other case the TiB2 and Al2O3 phases are interdispersed and ... |
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| Preliminary Shock Wave Studies in Alumina and Tungsten Carbide |
DEC 2001 |
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| Authors:
N. K. Bourne; J. C. Millett; CRANFIELD UNIV (UNITED KINGDOM) ROYAL MILITARY COLLEGE OF SCIENCE
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 | The present report describes the results of shock wave investigations conducted to determine shear strengths of two materials: an alumina (Al203), commercially produced by Coors as AD995, and pressure assisted densified tungsten carbide (WC) manufactured by Cercom. In addition, an effort was made to recover shock compressed AD995 in order to determine the change in the initial microstructure of AD995 due to shock and release wave propagation. The shear strength ... |
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| Novel Synthesis of Aluminium Oxide Nanofibers |
NOV 2001 |
|
| Authors:
Huai Y. Zhu; Gao Q. Lu; QUEENSLAND UNIV BRISBANE (AUSTRALIA)
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| This report presents a novel synthesis method of alumina nanofibers at moderate conditions in aqueous systems through a surfactant-directed crystal growth process. In the presence of polyethylene oxide (PEO) surfactants, boehmite nanofibers of about 3 nm thick and 30-60 nm long formed from aluminium hydrate colloids. During the subsequent heating, the surfactant was evaporated and boehmite nanofibers were converted into gamma-alumina nanofibers. The function of the PEO surfactant and the ... |
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| Preparation of Copper Aluminium Oxide by Spray Pyrolysis |
NOV 2001 |
4 pages |
| Authors:
Ji-Youn Rim; Shin-Ae Song; Seung-Bin Park; KOREA ADVANCED INST OF SCIENCE AND TECHNOLOGY DAEJON DEPT OF CHEMICAL ENGINEERING
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| Copper aluminium oxide(CuAlO2) particles a promissing p-type TCO(transparent conducting oxide), were prepared by spray pyrolysis. Delafossite phase of CuAlO2 was obtained when copper nitrate, copper acetate and copper sulfate, divalent copper precursors, were used as copper precursor and aluminium nitrate as aluminium precursors. However, when copper chloride (CuCl, a monovalent copper precursor) was used, the delafossite phase was not obtained regardless of the type of aluminium precursor. The O2-doped CuAlO2 ... |
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| Magnetization Reversal and Magnetic Anisotropy of Fe, Ni and Co Nanowires in Nanoporous Alumina Membranes |
APR 2001 |
6 pages |
| Authors:
M. Kroell; L. J. de Jongh; F. Luis; P. Paulus; G. Schmid; TRINITY COLL DUBLIN (IRELAND) DEPT OF PHYSICS
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| The magnetization reversal and magnetic anisotropy of Fe, Ni and Co nanowires is studied at low temperatures. All nanowires show a strong shape anisotropy with the easy axis being parallel to the long axis of the wires. Co nanowires additionally show a temperature dependent magnetocrystalline anisotropy along the hexagonal c-axis, which is directed nearly perpendicular to the long axis of the wires, as is confirmed by X-Ray diffraction measurements and ... |
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| Zirconia-Alumina-ITO Nanolaminates for Transparent, Conducting, Transformation-Toughening Coatings |
15 NOV 2000 |
71 pages |
| Authors:
Carolyn R. Aita; WISCONSIN UNIV-MILWAUKEE
|
| The revised objective of the proposed research was investigate room temperature interface alloy and compound formation in zirconia-bearing pseudobinary nanolaminate systems. Two model systems with the same nominal architecture but extremes in chemical reactivity between constituents were compared: zirconia-alumina (immiscible) and zirconia-yttria (completely miscible). The results showed that in zirconia-alumnina nanolaminates, layers were separate entity and with incoherent interfaces. The phase present in the zirconia layers was governed by the ... |
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| Characterization of Nanometer- to Micron-Sized Aluminum Powders by Thermogravimetric Analysis |
24 JUL 2000 |
29 pages |
| Authors:
Curtis E. Johnson; Stephen Fallis; Thomas J. Groshens; Kelvin T. Higa; Ismail M. Ismail; NAVAL AIR WARFARE CENTER WEAPONS DIV CHINA LAKE CA
|
| The reactivity of aluminum powders was studied by thermogravimetric analysis in air, oxygen, and nitrogen. Weight gains from complete oxidation of the aluminum were used to calculate particle sizes in the range of 30 nm to 500 nm. These particle sizes correlated well with particle sizes derived from surface area measurement. Particle size was also examined by scanning electron microscopy and atomic force microscopy, and compared to crystallite size determined ... |
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| Thermomechanical Behavior of Functionally Graded Materials |
09 MAY 2000 |
31 pages |
| Authors:
A. Almajid; S. Hudnut; M. Taya; UNIV OF WASHINGTON SEATTLE DEPT OF MECHANICAL ENGINEERING
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| Functionally graded materials are studied with emphasis on fracture resistance behavior and piezoelectric performance. Several types of metal/ ceramic FGM plates are processed and their fracture resistance, Kr as a function of crack length was examined experimentally. The Kr behavior of the FGM plates are explained by two models successfully. Then, a new type of piezoelectric FGM plates are designed by using several models, classical lamination ... |
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| Single Particle Studies of Heterogeneous Atmospheric Chemistry on Aluminum Oxide Particles in a Quadrupole Trap |
MAR 2000 |
89 pages |
| Authors:
A. J. Hunter; D. M. Sonnenfroh; D. B. Oakes; W. T. Rawlins; PHYSICAL SCIENCES INC ANDOVER MA
|
| This report documents a research program consisting of laboratory and field measurements investigating the atmospheric chemistry and aerosol microphysics of the impacts of rocket motor exhausts on upper atmospheric chemical cycles and ozone. The experimental investigation employs a laboratory quadrupole trap electrodynamic levitation apparatus to study heterogeneous processes on single aluminum oxide particles representative of those exhausted into the atmosphere by solid rocket motors. We ... |
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| The Effects of Colloidal Processing on the Densification of Titanium Diboride (TiB2) - Alumina (Al2O3) Composites |
MAR 2000 |
25 pages |
| Authors:
Lisa P. Franks; Melissa J. Crimp; Ernest Chin; Gary Gilde; ARMY TANK-AUTOMOTIVE COMMAND WARREN MI
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| Titanium diboride/Alumina (TiB2/Al2O3) powders produced using self-propagating high-temperature synthesis (SHS) can be hot pressed into armor tiles that exhibit superior resistance to penetration as compared to TiB2, SiC, B4C or Al2O3. As with other advanced ceramics however, difficulties in processing TiB2/Al2O3 arise from the inability to reproduce specimens having identical microstructure and properties. Since the SHS powders are available commercially, the interactions between TiB2 and Al2O3 have been analyzed with ... |
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| Processing and Deposition of Nanocrystalline Oxide Composites for Thermal Barrier Coatings |
31 DEC 1999 |
6 pages |
| Authors:
Jackie Y. Ying; Justin T. McCue; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMICAL ENGINEERING
|
| This report describes the synthesis, thermal stability and coating of nanocrystalline oxide composites for thermal barrier coating applications. The composites consisted of alumina-zirconia and alumina-yittria stabilized zirconia. The effect of alumina and yittria content on zirconia phase stability was examined. It was found that alumina-zirconia composites underwent phase transformation upon heat treatment at 950-1100 C. A small amount of yttria additive (1%) prevented zirconia phase ... |
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| Effects of pH, Surface Area, and Background Matrices on the Removal of Lead from Aqueous Solutions Using Activated Alumina |
05 DEC 1999 |
129 pages |
| Authors:
Patrick Wootton; AUBURN UNIV AL
|
| The metallic compound lead poses a human health risk and is environmentally toxic. The removal of lead from drinking and waste waters is therefore of great importance. To ensure that the lead concentration is reduced to safe levels, conventional treatment procedures for the removal of lead such as chemical precipitation and ion exchange have been used. These methods often do not yield sufficient removal of ... |
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| Laboratory Studies of Al(2)O(3)-NO(x) Aerosols |
30 SEP 1999 |
13 pages |
| Authors:
Robert Disselkamp; John R. Edwards; Daniel Pilson; Tyrrel W. Smith Jr.; TRW SPACE AND ELECTRONICS GROUP REDONDOBEACH CA
|
| Laboratory experiments were performed to investigate the chemistry of aluminum oxide (gamma Al(2)0(3)) aerosol samples upon exposure to NO(x) (NO(x) is NO, NO(2), etc.,) gases. Static aerosol samples were generated in an aerosol chamber and studied at temperatures ranging from 298 to 183 K. Fornier-transform infrared (FTIR) absorption spectroscopy was used to study the aerosol samples over time. Each aerosol was created using the same procedure. First, a reactant gas ... |
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| Characterization of the Uptake of Nitrogen Oxides on Alumina Adsorbents |
MAY 1999 |
162 pages |
| Authors:
David A. Pocengal; FLORIDA UNIV GAINESVILLE DEPT OF ENVIRONMENTAL ENGINEERING SCIENCES
|
| The objective of this research was to develop a method that employed ion-specific electrodes (ISEs) to quantify nitrate and nitrite (NOx) in aqueous solutions that contained NOx exposed alumina and to correlate the quantities of these surface NOx species with the quantity of gaseous NOx sorbed. The final objective was to obtain material balances of NOx sorbed to nitrate and nitrite formed and to observe indicative relationships between the surface ... |
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| Solid Sorbent Control of Nitrogen Oxides (NOx) |
18 JAN 1999 |
272 pages |
| Authors:
Maxwell R. Lee; FLORIDA UNIV GAINESVILLE COLL OF ENGINEERING
|
| Solid materials have demonstrated applicable control of combustion- source NOx. A support material of (gamma)-alumina can provide improved NOx sorption in comparison to a previously applied sorbent, magnesia-coated vermiculite. NOx sorption of treated (gamma)-alumina correlates with the ionization potential of the group-1 element. General mechanisms of NOx sorption have been developed for untreated, K2CO3-treated and KOH-treated (gamma)- alumina. Sorption of NO appears to increase formation of nitrine. Untreated (gamma)-alumina formed ... |
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| Laboratory Studies of the Stratospheric Effects of Rocket Exhaust |
DEC 1998 |
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| Authors:
M. J. Molina; M. Haider; Y. Mantz; L. Gutzwiller; L. T. Molina; MASSACHUSETTS INST OF TECH CAMBRIDGE
|
| The most important chlorine activation reaction that takes place in the stratosphere is the heterogeneous reaction of chlorine nitrate with hydrogen chloride to produce molecular chlorine and nitric acid. The reaction is catalytic, promoted by surfaces that are not themselves affected by the reaction. This process was investigated in the laboratory: the reaction probability was found to have a value of about 0.02 on glass, on laboratory alumina, and on ... |
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| Modeling of Multiphase Alumina-Loaded Jet Flow Fields. AIAA/ASME/SAE/ ASEE Joint Propulsion Conference (34th) and Exhibit Held in Cleveland, OH on July 13-15, 1998 |
15 JUL 1998 |
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| Authors:
A. V. Rodionov; Yu. A. Plastinin; J. A. Drakes; M. A. Simmons; R. S. Hiers III; AMERICAN INST OF AERONAUTICS AND ASTRONAUTICS NEW YORK
|
| A computer program for simulating coupled phenomena of propulsion- generated, chemically reacting, two-phase jet flow fields is described in detail. A sample calculation is performed using typical solid-propellant rocket motor operating conditions as input. The model contains approximations for turbulence, particle drag, chemistry, and particle supercooling. The particle phase change is simulated kinetically and includes two solid Al2O3 crystalline structures: meta stable gamma and ... |
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| Low Power GaAs Enhancement - Depletion Technology using Native Al2O3 as an Insulator |
11 MAY 1998 |
16 pages |
| Authors:
Brian Thibeault; WIDEGAP TECHNOLOGY WESTLAKE VILLAGE CA
|
| The WiTech phase I objectives were to explore the feasibility of Al2O3 as a buffer layer insulator for GaAs-on-insulator (GOI) technology and as a gate insulator for GaAs-based MISFETs. specifically, we have: (1) investigated the oxidation process and its effect on active device layers, showing the very little or no detrimental effect of the oxidation on the active region can be achieved by using LT-AlGaAs buffer layers. (2) fabricated an ... |
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| Method of Preparing Monoclinic BaO.Al2O3.2SiO2 |
09 DEC 1997 |
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| Authors:
Inna G. Talmy; Deborah A. Haught; PATENT OFFICE WASHINGTON DC
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| Monoclinic celsian (BaO.Al2O3.2SiO2) is produced by heating a stoichiometric, powder mixture of BaCO3 (or BaC2O4), Al2O3, and SiO2 (preferably SiO2 gel) with monoclinic celsian seeds at from 1250 deg C to 1500 deg C. |
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| A.S.E. Source at 1550nm for IFOG Applications |
05 DEC 97 |
3 pages |
| Authors:
Annand Gopinath; William Berglund; Ben Ellerbusch; MINNESOTA UNIV MINNEAPOLIS DEPT OF ELECTRICAL ENGINEERING
|
| We performed annealing studies for the Al2O3 guides, and we have identified the best annealing temperatures in terms of lifetimes and luminescence. For example a 0.1% Er doped film is best annealed at 500 C for a period of 1 hour in an oxygen ambient atmosphere. The lifetimes measured with 0. 1% Er is around 4 ms, which is a factor of two less than as seen in fiber for ... |
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| Measurement and Correlation of Water Adsorption Equilibria on Silica Gel, Sorbead, and Alumina Using a Novel Experimental Isotherm Apparatus |
DEC 97 |
41 pages |
| Authors:
Scott M. Maurer; David T. Croft; David K. Friday; GUILD ASSOCIATES INC BALTIMORE MD
|
| The design and operation of a novel, experimental volumetric isotherm apparatus is discussed. Water adsorption equilibria in nitrogen is measured over three adsorbents: silica gel 40, alumina F-200, and sorbead RF. This work concentrated on the adsorption behavior of water at low partial pressures ranging from 1 - 1000 Pa. The isotherm data for all adsorbents studied were measured over three orders of magnitude in both loading and partial pressure ... |
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| New Approaches to Aluminum Passivation for Corrosion Prevention |
10 OCT 97 |
27 pages |
| Authors:
John T. Yates Jr; PITTSBURGH UNIV PA DEPT OF CHEMISTRY
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| A new method has been discovered for producing a corrosion-resistant aluminum oxide film on aluminum surfaces. The method employs the electronic activation of adsorbed water molecules on the aluminum surface, using electron- bombardment. The artificial oxide film, so produced, exhibits about 25 times higher electrical impedance using electrochemical measurements compared to aluminum oxide films made by conventional oxidation. |
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| Tailoring of Grain Boundary Chemistry for the Development of Highly Creep Resistant Alumina |
29 AUG 97 |
151 pages |
| Authors:
M. P. Harmer; H. M. Chan; J. Rickman; J. Bruley; J. Cho; LEHIGH UNIV BETHLEHEM PA WHITAKER LAB
|
| Research has demonstrated that the controlled doping of ultra-high purity alumina with small amounts (<1000ppm) of rare earth elements, such as La and Y, dramatically lowers the sintering and creep rate. Due to the large ionic radius of the rare earth elements, rare earth elements have a low solubility in alumina and segregate strongly to the grain boundaries. Chemical composition (STEM) profiles indicate that segregation of Y and La is ... |
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| Free Form Fabrication of Ceramics by Stereolithography |
25 AUG 97 |
41 pages |
| Authors:
John W. Halloran; MICHIGAN UNIV ANN ARBOR DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| During this grant we showed that stereolithography can directly fabricate ceramic green bodies from ultraviolet (UV) curable solutions which contain dispersed ceramic powders. We demonstrated SLA of silica, a model refractory for metal casting molds, and SLA of alumina, which is promising for structural ceramics. Viscosity control for these highly concentrated suspensions and cure depth behavior were the main issues for fabricating a ceramic using stereolithography techniques. These ceramic SLA ... |
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| Processing of A12O3-ZrO2 Nanocomposites for Thermal Barrier Coatings |
30 JUN 97 |
8 pages |
| Authors:
Jackie Y. Ying; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMICAL ENGINEERING
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| Nanocrystalline composites of Al2O3-ZrO2 have been synthesized through four different processes and evaluated in terms of their densification and ability to retain the metastable tetragonal zirconia phase. The physical stabilization of the tetragonal phase is dependent primarily on the microstructure of the material which is a strong function of the powder preparation method. Significant stabilization of the tetragonal phase after thermal treatments at 1200 deg C was achieved with the ... |
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| CrB2-NbB2//A12O3 and CrB2-NbB2/SiC Ceramic Composite Materials. |
18 FEB 1997 |
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| Authors:
Inna G. Talmy; Eric J. Wuchina; James A. Zaykoski; Mark M. Opeka; DEPARTMENT OF THE NAVY WASHINGTON DC
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| A composite with a reinforcing material that is Al2O3, SiC, or mixtures thereof in a matrix that is a ceramic material based on a solid solution of CrB2 and NbB2. |
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| Phase Stabilization of Zirconia. |
30 JAN 1997 |
13 pages |
| Authors:
Virgil Provenzano; Ronald L. Holtz; David Lewis; DEPARTMENT OF THE NAVY WASHINGTON DC
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| Stabilized zirconia containing sintered particles of alumina and zirconia in tetragonal phase is prepared by mixing alumina particles of less than 30 nanometers with zirconia particles of less than 30 nanometers in, presence of a liquid to form a suspension, drying the suspension at a temperature up to about 600 deg C to remove the liquid and products thereof to form a dried suspension composed of agglomerated alumina and zirconia ... |
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| Effective Medium Theory Characterization of Au/Ag Nanoalloy-Porous Alumina Composites |
30 SEP 96 |
9 pages |
| Authors:
G. L. Hornyak; C. J. Patrissi; C. R. Martin; J. C. Valmalette; L. Lemaire; COLORADO STATE UNIV FORT COLLINS DEPT OF ANIMAL SCIENCE
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| The optical constants n sub Al and k sub Al of a 50/50 volume fraction Au / Ag alloy were derived synthetically by application of a Bruggeman (BG) effective medium expression. The alloy data base was then input into a Maxwell-Garnett (MG) effective medium expression to determine the absorption maximum of the nano-alloy/insulator composite (the volume fraction of the nano- alloy was equal to 5%). The absorption maximum (lambda max) ... |
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| Effect of Processing Parameters on the High Temperature Creep of SiC whisker-Reinforced Alumina |
27 SEP 96 |
8 pages |
| Authors:
Terence G. Langdon; UNIVERSITY OF SOUTHERN CALIFORNIA LOS ANGELES
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| This program investigated the role of processing on the high temperature creep behavior of polycrystalline alumina reinforced with SiC whiskers or particulates. Three types of tests were conducted. First, creep data were obtained on monolithic unreinforced alumina and on alumina composites reinforced with SiC whiskers or SiC particulates. Second, the effect of processing was investigated by testing conventionally processed composites and composites produced using a dispersion processing procedure. Third, the ... |
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| Surface Modification of Structural Ceramics by Ion Implantation Annealing: Al2O3 and Si3N4 |
06 SEP 96 |
7 pages |
| Authors:
Alan J. Ardell; CALIFORNIA UNIV LOS ANGELES DEPT OF MATERIALS SCIENCE AND ENGINEERING
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| The near-surface regions of polycrystalline Si3N4 were modified by ion implantation and post-implantation annealing. Metallographically polished bars and disks 3 mm in diameter and ranging in thickness from 250 to 500 micrometers were implanted of co-implanted with Al(+) ,B(+) and N(+) to fluences up to 2 x 10(exp 16) ions//sq cm, using implantation energies up to 300 keV. Some of the implanted material was post-implantation annealed at temperatures in the ... |
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