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Alumina Powders Prepared by Emulsion Evaporation
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Abstract
In order to prepare fine alumina powders, an emulsion was prepared under optimum conditions. The emulsion was examined by optical microscopy and the prepared fine alumina powders were characterised by electron microscopy. The particles were formed of porous spheres and their sizes were between 1 and 10 µm. The powder samples were sintered by varying the temperature between 700 and 1600°C. The adsorption and desorption of nitrogen on these samples were investigated. By using the adsorption data, the specific surface areas were calculated according to different procedures and the correlation between them was discussed. The specific micropore and mesopore volumes were calculated from the desorption data. Some kinetic and thermodynamic estimations about the intra-particle sintering were made according to the variation of the specific micropore-mesopore volumes as a function of the sintering temperature. © 2000 TUBITAK
Key Words: Alumina powder, calcination, pore volume, sintering, surface area, thermal analysis.
Yuksel SARIKAYA, Ismet SEVINC, Muserref ONAL, Tulay ALEMDAROGLU
Ankara University, Faculty of Science, Department of Chemistry, Tandogan, 06100 Ankara-TURKEY
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Ductility & Malleability of Metals
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In material sciences the term ductility refers to a materials ability to deform under tensile stress while malleability refers to a materials ability to deform under compressive stress. While the terms are commonly used interchangeably, the relationship between the two is such that there is not a direct correlation.
In general terms, the ductility of metals ranges from (most to least) Gold to Lead, while malleability goes from Gold to Nickel. A good example of the variation within a metal is Lead which fractures quickly when bent while at the same time it can easily be hammered into shape. Alloys such as steel will vary dramatically in ductility & malleability depending on the chemistry and conditions employed in the metallurgy process.1
Particle size also plays an important role in the ductile and malleable strength of metals. For example the tensile stength and elongativeness of extruded FeAlZrB increases as the particle size distribution decreases and narrows.2
1 Rich, Jack C. (1988), The Materials and Methods of Sculpture, Courier Dover Publications, p. 129
2 Strothers, Susan D, (1991), Processing/Microstructue/Mechanical Property Relationships in FeAlZrB, Case Western Reserve University PhD Thesis.
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Effect of surfactant on Zeta Potential & Distribution of Nanoparticles
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Effect of surfactant on the co-electrodeposition of the nano-sized ceria particle in the nickel matrix
Abstract
The nickel–ceria (Ni–CeO2) nanocomposite coatings have been pulse electrodeposited from a Watts-type electrolyte containing nano-sized CeO2 particles produced by high-energy ball milling technique (HEBM). Sodium Lauryl Sulphate (SLS) has been added in the electrolyte as a cationic surfactant. The effects of the surfactant on the zeta potential, co-deposition and distribution of ceria particles in the nickel matrix and hardness of composite coatings have been investigated. Experimental results show that the addition of SLS up to 0.10 g/l increases the amount of co-deposited ceria particles in the nickel matrix and microhardness of the nanocomposite. However, when the amount of SLS in the electrolyte is more than 0.1 g/l, there is a tendency to form agglomerates of ceria particles in the nickel matrix resulting no further increase in hardness of the Ni–CeO2 nanocomposite coatings. ©2009 Elsevier B.V.
Keywords: Ball milling; Pulse co-electrodeposition; Surfactant; Hardness; Composite materials
Ranjan Sena, Sumit Bhattacharyaa, Siddhartha Dasa and Karabi Das
Department of Metallurgical and Materials Engineering, Indian Institute of Technology, Kharagpur 721302, India
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Iron Sulfide in Lithium Cells
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Abstract
Chemical composition, physical characteristics and structural features of a natural FeS2 powder and a synthetic FeS2 sample were correlated with their specific discharge capacities in lithium cells. The levels of impurity elements, primarily present as second-phase oxides and sulfides, were significantly higher in the natural FeS2 than in the synthetic sample. These impure second-phases were electrochemically inactive, and they did not have any significant effects on the discharge of Li/FeS2 cells. Trace amounts of impurity elements were detected in solid solution of FeS2 pyrite and the pyrite structure was nearly ideal for both the natural and synthetic samples. A sulfur-deficient pyrrhotite FeS1.3 phase was found in the center of some large synthetic FeS2 particles, which was electrochemically active at 1.5 V versus lithium. Optical microscopy showed that the grain sizes within synthetic FeS2 particles were significantly smaller than those within natural FeS2 particles. The superior rate capability of Li/synthetic FeS2 cells was attributed primarily to the smaller grain sizes within synthetic FeS2 particles in comparison to the natural FeS2 sample. © 2001 Elsevier Science Ltd.
Keywords: Pyrite; Lithium batteries; X-ray diffraction; Sulfide; Electron microscopy
Yang Shao-Horn and Quinn C. Horn, Energizer Inc., 25225 Detroit Road, Westlake, OH 44145, USA
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Material Issues of the Metal Printing Process
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Abstract
The metal printing process, MPP; is a novel Rapid Manufacturing process under development at SINTEF and NTNU in Trondheim, Norway. The process, which aims at the manufacturing of end-use products for demanding applications in metallic and CerMet materials, consists of two separate parts; The layer fabrication, based on electrostatic attraction of powder materials, and the consolidation, consisting of the compression and sintering of each layer in a heated die. This approach leads to a number of issues regarding the interaction between the process solutions and the materials. This paper addresses some of the most critical material issues at the current development stage of MPP, and the present solutions to these. ©2006 RMPlatform.com
K. Boivie¹, R. Karlsen², and C. Van der Eijk³
¹Department of Production and Quality Engineering, Norwegian University of Science and Technology, NTNU, Trondheim, Norway
²SINTEF Technology and Society, Product and Production, Trondheim, Norway
³ SINTEF Materials and Chemistry, Metallurgy, Trondheim, Norway
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Titanium in Medical Implants
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Titanium Powder and its Alloys for Medical Applications
Abstract
Titanium and its alloys are used extensively for coating the surface of implantable medical devices to accelerate bone growth and the healing process. Different coating process equipment and process routes require unique powder particle size distributions (PSD) in order that the powder correctly bonds with the underlying implant surface. Medical coating users take great care in specifying the morphology and PSD requirements for their process, and in many cases will have as many as five or more PSD specifications depending on the medical device being treated. Control of the finished particle size distribution is another critical powder parameter. Many medical coating users specify sieving screen analysis using US screen sizes (mesh or microns) for powders. For finer powder grades, laser PSD measurement is preferred which significantly increases the PSD resolution below 75um (200 mesh). © Reading Alloys, Inc.
Dr Colin McCracken, Reading Alloys, PO Box 53, Robesonia, PA 19551
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| Applications & Industries
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