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Study of flooding of fine powders
Sintering SINTERING OF CERAMICS BY PULSED HIGH CURRENT MILLIMETRE WAVELENGTH MICROWAVE RADIATION S.Myake. (Osaka University, Ibaraki, Japan.) J. Jpn Sot. Powder Powder Metall.,Vol 45, No 11, 1998, 1045-1049. (In Japanese.) Studies of microwave sintering of ceramic materials are reviewed. Investigations of sintering Al,O,-ZrO,, and TiN-Cr,N materials are Si,N, described. Sintering mechanisms at mm wavelengths, 28 GHz and with pulsed currents are discussed with reference to electromagnetic phenomena in particles and at grain boundaries.
Fundamentals USE OF WAVE THEORY TO CALCULATE PARTICLE SIZE IN ROTATING DISC ATOMIZATION H.Li, P.Tsakiropoulos. Surrey, Guildford,
Non-Equlib. 55-70.
(University of UK.) Int. J. Process., Vol 11, No 1, 1998,
Disintegration of molten metal at edges of rotating discs is analysed and a model for calculation of mean particle size is proposed. Good agreement between prediction and experiment is reported. Atomization and material parameters are taken into account. It is shown that particle size can be reduced by increase in disc speed or diameter. Particle size is also shown to be influenced by the ratio of density to surface tension, high ratios giving fine powders. RELATIONSHIP BETWEEN PARTICLES IN A FOIL AND THE PLANAR PROJECTED IMAGE I.Kohutek, M.Besterci. Wstav Materialoveho Vyskumu SAV, Kosice, Slovak Republic.) Pokroky Praskove Metal., Vol 36, No 4, 1998, 29-34. (In Czech.) The relationship between the volume fraction of particles in an electron microscope thin foil and the plane image projected from them is evaluated using models of the particle arrangement in space. Two particle shapes are considered, an ellipsoid and a rectangular parallelopiped.
36 MPR March 2000
THREE DIMENSIONAL SIMULATION OF BALL MOTION IN A TUMBLING BALL MILL H.Hashimoto, T.Abe. (Tohoku National Industrial Research Inst, Sendai, Japan.) J. Jpn Sot. Powder Powder Metall., Vol45, No 10, 1998,986-989. (In Japanese.) It is noted that there may be poor reproducibility in mechanical alloying and that indices for mathematical description may be inadequate. A attempting to trace threestudy, dimensional ball movement in a mill, is described. Factors in the model include collisions, distribution of ball impact energy and ball:fill ratio. It is deduced efficient particle that the most deformation occurs when the mill is half full of balls. PACKING DENSITY OF PERFECT BINARY MIXTURES S.M.K.Rassouly. (Int. Atomic Energy Agency, Vienna, Austria.) Powder Technol., Vol 103, No 2, 1999, 145-150. Models are constructed for packing of mixtures of spherical particles of two sizes. Trapping of the smaller in the interstices larger, between the homogeneity of the mixture and consequent expansion are considered. An equation is deduced and is shown to be valid for all proportions of the components for particle size ratios of less than 0.3. A simpler relationship is derived for all size ratios. Results for the two expressions are similar for size ratios less than 0.6. The models were verified experimentally. FINE GRINDING CHARACTERISTICS OF HARD MATERIALS IN AN ATTRITION MILL K.Shinohara et al. (Hokkaido University, Sapporo, Japan.) Powder Technol., Vol 103, No 3, 1999,292-296. Grinding characteristics of hard materials, such as synthetic diamond and Also,, were investigated in a stirred water cooled ball mill. Particle size distribution was measured for a range of process conditions. Grinding rate was increased by larger ball size, faster rotational speed and increased amount of feed in the mill. Comparison was made with a relatively soft material, SiO,, The mill was part filled with liquid and there was an optimum amount for milling Also,.
STUDY OF FLOODING OF FINE POWDERS S.Jing, H.Li. (Tsinghua University, Beijing, China.) Powder Technol., Vol 103, No 3,1999,297-299. Flooding of fine powders, where the powder behaves more like a liquid and flows, was studied experimentally. This may arise due to entrainment of air in the powder. In order to observe the phenomenon glass apparatus was used. A quantitative measure, the flooding number, is derived, to describe the tendency of a powder to flood.
Aluminium EFFECT OF EXTRUSION RATIO AND TEMPERATURE ON STRUCTURE AND PROPERTIES OF ALUMINIUM ALLOY L.Hu et al. (Harbin Inst. of Technology, Harbin, China.) Powder Metall., Vol 42, No 2,1999, 153-156. A12024 alloys were prepared from rapidly solidified and milled nanocrystalline powder, less than 50 nm, by hot hydrostatic extrusion. Structure and properties determined with reference to extrusion ratio and temperature. The results are discussed are made for and suggestions rationalization of process conditions. EFFECTS OF VARIABLES ON SIZE AND CHARACTERISTICS OF GAS ATOMIZED ALUMINIUM POWDERS T.J.Davies et al. WMIST, Manchester, UK.) Powder Metall., Vol42, No 2, 1999, 156-163. Al powder was atomized in a free fall liquid metal delivery system to a Mannesmann type nozzle. The effects of process parameters on particle size, shape and cooling rate were determined. Powders with a mean particle size down to 20 pm were produced. Particles above 20 ,um were irregular in shape and had a cellular dendritic structure. Particles below 20 pm were smooth and spherical. CREEP OF PARTICLE REINFORCED ALUMINIUM ALLOY C.Broeckmann, A.Packeisen. (Ruhr University, Bochum, Germany.) Metal, Vol 52, No 12, 1998, 701-711. (In German.) Creep properties of A16061 alloy, with A&O, particle reinforcements, were investigated. The particles are shown to affect minimum creep rate and the creep
Fundamentals USE OF WAVE THEORY TO CALCULATE PARTICLE SIZE IN ROTATING DISC ATOMIZATION H.Li, P.Tsakiropoulos. Surrey, Guildford,
Non-Equlib. 55-70.
(University of UK.) Int. J. Process., Vol 11, No 1, 1998,
Disintegration of molten metal at edges of rotating discs is analysed and a model for calculation of mean particle size is proposed. Good agreement between prediction and experiment is reported. Atomization and material parameters are taken into account. It is shown that particle size can be reduced by increase in disc speed or diameter. Particle size is also shown to be influenced by the ratio of density to surface tension, high ratios giving fine powders. RELATIONSHIP BETWEEN PARTICLES IN A FOIL AND THE PLANAR PROJECTED IMAGE I.Kohutek, M.Besterci. Wstav Materialoveho Vyskumu SAV, Kosice, Slovak Republic.) Pokroky Praskove Metal., Vol 36, No 4, 1998, 29-34. (In Czech.) The relationship between the volume fraction of particles in an electron microscope thin foil and the plane image projected from them is evaluated using models of the particle arrangement in space. Two particle shapes are considered, an ellipsoid and a rectangular parallelopiped.
36 MPR March 2000
THREE DIMENSIONAL SIMULATION OF BALL MOTION IN A TUMBLING BALL MILL H.Hashimoto, T.Abe. (Tohoku National Industrial Research Inst, Sendai, Japan.) J. Jpn Sot. Powder Powder Metall., Vol45, No 10, 1998,986-989. (In Japanese.) It is noted that there may be poor reproducibility in mechanical alloying and that indices for mathematical description may be inadequate. A attempting to trace threestudy, dimensional ball movement in a mill, is described. Factors in the model include collisions, distribution of ball impact energy and ball:fill ratio. It is deduced efficient particle that the most deformation occurs when the mill is half full of balls. PACKING DENSITY OF PERFECT BINARY MIXTURES S.M.K.Rassouly. (Int. Atomic Energy Agency, Vienna, Austria.) Powder Technol., Vol 103, No 2, 1999, 145-150. Models are constructed for packing of mixtures of spherical particles of two sizes. Trapping of the smaller in the interstices larger, between the homogeneity of the mixture and consequent expansion are considered. An equation is deduced and is shown to be valid for all proportions of the components for particle size ratios of less than 0.3. A simpler relationship is derived for all size ratios. Results for the two expressions are similar for size ratios less than 0.6. The models were verified experimentally. FINE GRINDING CHARACTERISTICS OF HARD MATERIALS IN AN ATTRITION MILL K.Shinohara et al. (Hokkaido University, Sapporo, Japan.) Powder Technol., Vol 103, No 3, 1999,292-296. Grinding characteristics of hard materials, such as synthetic diamond and Also,, were investigated in a stirred water cooled ball mill. Particle size distribution was measured for a range of process conditions. Grinding rate was increased by larger ball size, faster rotational speed and increased amount of feed in the mill. Comparison was made with a relatively soft material, SiO,, The mill was part filled with liquid and there was an optimum amount for milling Also,.
STUDY OF FLOODING OF FINE POWDERS S.Jing, H.Li. (Tsinghua University, Beijing, China.) Powder Technol., Vol 103, No 3,1999,297-299. Flooding of fine powders, where the powder behaves more like a liquid and flows, was studied experimentally. This may arise due to entrainment of air in the powder. In order to observe the phenomenon glass apparatus was used. A quantitative measure, the flooding number, is derived, to describe the tendency of a powder to flood.
Aluminium EFFECT OF EXTRUSION RATIO AND TEMPERATURE ON STRUCTURE AND PROPERTIES OF ALUMINIUM ALLOY L.Hu et al. (Harbin Inst. of Technology, Harbin, China.) Powder Metall., Vol 42, No 2,1999, 153-156. A12024 alloys were prepared from rapidly solidified and milled nanocrystalline powder, less than 50 nm, by hot hydrostatic extrusion. Structure and properties determined with reference to extrusion ratio and temperature. The results are discussed are made for and suggestions rationalization of process conditions. EFFECTS OF VARIABLES ON SIZE AND CHARACTERISTICS OF GAS ATOMIZED ALUMINIUM POWDERS T.J.Davies et al. WMIST, Manchester, UK.) Powder Metall., Vol42, No 2, 1999, 156-163. Al powder was atomized in a free fall liquid metal delivery system to a Mannesmann type nozzle. The effects of process parameters on particle size, shape and cooling rate were determined. Powders with a mean particle size down to 20 pm were produced. Particles above 20 ,um were irregular in shape and had a cellular dendritic structure. Particles below 20 pm were smooth and spherical. CREEP OF PARTICLE REINFORCED ALUMINIUM ALLOY C.Broeckmann, A.Packeisen. (Ruhr University, Bochum, Germany.) Metal, Vol 52, No 12, 1998, 701-711. (In German.) Creep properties of A16061 alloy, with A&O, particle reinforcements, were investigated. The particles are shown to affect minimum creep rate and the creep