Showing papers on "Aluminium powder published in 1999"

Process optimisation and numerical modelling of powder metallurgical aluminium matrix composites

Abstract: The present research focuses on optimisation of a novel application of the cold uniaxial pressing and liquid phase sintering powder metallurgical method to the processing of ceramic particulate reinforced aluminium matrix composites and the numerical modelling of these advanced materials. The investigated process areas include material selection, powder mixing and powder heat treatment, lubrication type, quantity and method, compaction and ejection, green sample conditioning, sintering time, temperature and atmosphere, and sintered compact heat treatment. The methods of analysis used include particle size, shape and H20 content analysis, powder compressibility testing, ejection stress analysis, green strength testing, green compact and sintered material density measurement, macrohardness, compression and tensile testing, and both optical and scanning electron microscopy. The present numerical modelling work involves the development and use of a new geometrically versatile continuum mechanics based finite element analysis model capable of allowing the isolation of particulate volume fraction, size, and distribution variations and simulating the constitutive response of a specific composite material. The process investigations have elucidated many of the factors affecting the mechanical properties of the final material and have found that small to medium sized net shape and near net shape aluminium matrix composite components may be produced by this conventional powder metallurgical processing method. It has been identified that the success of this process is strongly dependent on factors including aluminium powder and reinforcement particle size, powder heat treatment and component sintering conditions. Also, the present numerical model provides a method of predicting the response of these composite materials to thermal and mechanical loading, and allows for independent adjustment of the constitutive material properties and geometric model form to aid in the design of these versatile composites. The modelling investigations carried out indicate that internal stress development within a discontinuously reinforced metal matrix composite depends primarily on the proximity of particles, the relative orientation of particles in close proximity and the directionality of loading.

Method of preparing heat-insulating sheet wollastoniti- based material

Abstract: FIELD: manufacture of heat-insulating sheet materials based on natural stock such as wollastonite, quartz, and lime. SUBSTANCE: method comprises combined grinding of highly pure burned lime, quartz sand and moistening of mixture in order to slave lime, intensive stirring of mixture of burned lime, quartz sand and highly needle-shaped wollastonite as pore-forming agent or aqueous suspension of aluminium powder or aqueous surfactant solution as foaming agent, molding mixture in moist heat-insulating sheet material, autoclave treatment, drying, calibration and roasting. Preparation of finely porous structure and highly strong material involves using highly needle-shaped wollastonite in amount of 50-70 % based on weight of dry components containing at least 50% elementary needles at needle length to diameter ratio of 5-20 including needle content of at least 15% at needle length to diameter ratio of 10- 20, molding of moist mixture to form sheet material is carried out by nibromethod. Drying is carried at 250-300 C to maintain mixture for 1.5-3 hours, and roasting is carried out at 850-900 C for 4-6 hours. Finally porous asbestos-free heat-insulating material is used at temperature not higher than 1000 C for contact with liquid aluminium. EFFECT: more efficient preparation method. 5 ex

Aluminium powder for blowing agent for light weight (foamed) concrete, and its aqueous paste composition

Abstract: PROBLEM TO BE SOLVED: To improve the quality of products as ALC materials by adopting flaky aluminium powder having a specific particle diameter and a specific sieve residue to control its reaction with mortar slurry and to improve its water dispersibility and storage stability, and by adjusting foaming efficiency. SOLUTION: The purpose of this invention is achieved by adopting aluminium powder with an average particle diameter of 15-35 μm and the 74 μm sieve residue of /g, and that a higher fatty acid, a fatty acid alkanolamide and a nonionic surfactant are added to this alminium powder in respective preferred quantities.

Production method of flux for aluminum welding and method of welding

Abstract: PURPOSE: A method for producing flux for aluminum welding that need not cladding treatment is provided to save production cost and product reliability. CONSTITUTION: The production method of flux for aluminum welding includes the steps of (i) melting 87-89wt.% of 40 series aluminum and 5-13wt.% of silica in an electric furnace, followed by stabilization for 30 minutes; (ii) charging the liquid metal in an electric furnace having a lid, and elevating the temperature of the liquid metal to a temperature higher than the melting point thereof by 150 to 200deg.C; (iii) stabilizing the flow of liquid metal; and (iv) mixing 30-55wt.% of aluminium powder that is manufactured by nitrogen gas spraying, 8-15wt.% of KAlF4 that is manufactured with aluminium hydroxide, fluoric acid, and potassium carbonate, 40-60wt.% of a fixing agent that comprises 5-20wt.% of resin and 80-95wt.% of solvent.

Composition for thermostable coating

Abstract: FIELD: paint and varnish materials. SUBSTANCE: invention describes a new composition for thermostable coating containing polyphenylsiloxane resin, acrylate copolymer, aluminium powder and an organic solvent characterized in that it has additionally a filling agent and a rheological addition at the following ratio of components, wt.-%: polyphenylsiloxane resin 30-35; acrylate copolymer 4.5-10; aluminium powder 8-12; filling agent 2.5-6.5; rheological addition 0.5-1.5 and an organic solvent - the rest. Invention can be used in machine engineering for protection of metallic surfaces working at increased temperatures, under conditions of high corrosion aggression of medium. EFFECT: improved physico-mechanical properties of the composition. 2 cl, 2 tbl

Thermal insulation elastic waterproof coating for building surface and its preparation method

Abstract: An insulating and elastic water-proof paint is prepared from the waste polyester bottles as raw material through putting waste polyester bottles into mixed solvent, radiating it by Co-60, addition ofassistant to become radiated resin, and mixing it with toluene diisocyanate and aluminium powder, and features high thermal insulating and water-proofing effect.

Studies of post-production ageing effects in atomised aluminium powder

Abstract: The evolution of hydrogen gas from the reaction between a series of atomised aluminium powder samples and 2.5 M HCl was monitored over time. The pattern of hydrogen evolution in each case was similar in that after an initial period of slow gas production there was a rapid increase followed by slow gas production again. These studies also showed differences in the time taken to reach maximum hydrogen evolution for similarly aged powders. Lower purity aluminium powder (99.7 vs. 99.93%) or samples with a higher proportion of smaller particles reached the maximum rate of hydrogen evolution more quickly. Changes in the time taken to reach maximum gas evolution were also noted for all the powders as they aged; the time to reach a maximum generally increasing with time after atomisation. However, for each powder a short regression occurred between ca. 21 and 35 d. This suggests that changes continue to take place in the surface layer of the aluminium particulates long after atomisation has taken place.

A preliminary investigation into preparation and characterisation of a Raney titanium catalyst

Abstract: A preliminary investigation is carried out into the preparation and characterisation of a Raney-type titanium catalyst. Titanium-40 wt % aluminium powder is used as the precursor alloy and caustic leaching as the preparation method. Leaching in 25 wt % NaOH solutions at both 50°C and 80°C results in preferential removal of aluminium and formation of a highly porous layer containing almost complete titanium. The thickness and the surface roughness of the leached layer increases with leaching time and to a less degree with higher solution temperature. The combined morphological and kinetic measurements suggest that a diffusion barrier built up in the solution/metal interphas plays a key role in the leaching process. Electrochemical tests performed with the leached powder show a significantly reduced overpotential towards cathodic hydrogen evolution reaction, thus a potentially promising catalyst. Further work is needed to establish optimal leaching parameters to increase its electrochemical activity.

Low-temp technology for smelting aluminium by wet method

Abstract: A low-temp technology for smelting aluminium by wet method, that is, directly producing aluminium includes such technological steps as crushing raw bauxite to a certain granularity, calcining in solution of sulfide for decomposing, removing dregs, baking the liquid containin decomposed aluminium, low-temp chemical treating in said solution of sulfide to obtain metallic aluminium powder, heating to a certain temp to obtain molten aluminium and moulding to obtain aluminium ingots. Its advantages include less investment, low cost, low consumption of energy, no pollution and recoverable by-product.

Low-Valent Titanium-Induced Reactions of Substituted Nitrobenzenes.

Abstract: Aluminium powder has been used to reduce titanium tetrachloride to generate the Low-valent Titanium reagent (LVT); the reactions of substituted nitrobenzenes induced by LVT are described and the reaction mechanism is briefly discussed.

Aluminium nitride granules

Abstract: not available for EP0828688Abstract of corresponding document: WO9615982A method for preparing partially or completely nitrided aluminium granules that are shelf-stable and coated with a passivating layer of calcium carbonate (CaCO3), wherein aluminium powder mixed with a suitable amount of powdered CaCO3 is reacted with nitrogen under continuous stirring by heating the reaction medium to a suitable temperature.

Recrystallization of Cold-Pressed Aluminium Powder

Abstract: Second phase particles in metal matrix may have a considerable influence on deformation and recrystallization behaviour. The recrystallization of metals containing a dispersion of hard particles may be accelerated or retarded, depending primary on the diameter of particles1–4. However, the most of related studies were concentrated on the alloys produced by ingot metallurgy, where the second phase particles precipitate through heat treatment processes. Such processes bear some limitations, mainly through solubility, volume fraction and diameter of particles. On the contrary, powder metallurgy techniques of consolidation do not depend on such limitations and enable admixing various particles in a metal matrix.