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Sintered niobium-tantalum-aluminium anode alloys
Powder production SATELLITE ATOMIZED
FORMATION POWDERS
IN GAS
SCzbilen, (Gazi University, Ankara, Turkey.) Powder Metall., Vol 42, No 1, 1999,70-78. Satellite formation in gas atomized powders was investigated for Al, All%Li, Cu, Mg and Sn. It is shown that, to form particles with satellites, interactions between coarse and a high proportion of fine particles are required. Fine particles are formed by disintegration of coarse particles. Satellite formation is enhanced by surface roughness and is influenced by oxidation. Inhomogeneities in the oxide film affect surface roughness. VELOCITIES FREE-FALL
OF GAS FROM ATOMIZERS
D.Singh et al. (Indian Inst. of Technology, Kanpur, India.) Powder Metall., Vol42, No 1, 1999, 79-85. Gas velocities in free fall atomizers were investigated as functions of atomizer geometry and operating conditions. Wide variations in velocity were detected. Velocity increased with pressure and nozzle diameter. Empirical correlations arc established. PRODUCTION POWDERS
OF HIGH PURITY
TIN
A.D.Styrkas, D.A.Styrkas. (University of Surrey, Guildford, UK.) Powder Technol., Vol 104, No 2, 1999,164-168. Methods of producing high purity Sn with reduced %0, using the allotropic changes repeatedly, are proposed. Attrition of Sn is possible due to the 26.6% volume change between grey, c&n, and white, PSn. Electronic reconfiguration during the allotropic change, altering bonding from covalent to metallic, affects oxidation. The processing is briefly described. Powder size was 5 pm or less and the %0 was reduced to l~lO-~wt%. POLYMER ATOMIZATION ALUMINIDE
OF IRON
J.T.Strauss et al. (HJE Co, Glens Falls, USA.) Mater. Science I Engineering A, Vol 258, No l/2,1998,291-297. A method of atomizing a reactive alloy melt, Fe aluminide, with a polymeric fluid was investigated. The products are compared with gas and water atomized powders. Advantages of the
32 MPR June 2000
technique and powder properties are outlined. The powder was roll compacted and densified by a series of rollings and annealings. The material is compared with alloys made from gas and water atomized powders. PRODUCTION OF BORON BY ARC VOLATILIZATION
POWDER
‘IIHagio et al. J. Mater. Science, Letters, Vol 17, No 22, 1998, 1937-1939. Production of amorphous B powders, 0.1 to 1.0 ym in size, by volatilization from a DC arc in inert gas, between B rods preheated to 6OO”C, is described. Preheating is to induce electrical conduction. It is suggested that nitrides and carbides could be produced by appropriate selection of the operating atmosphere. PREPARATION OF NANOCOMPOSITE PARTICLES BY GAS EVAPORATION AND CONDENSATION TECHNIQUES
T.Ohno. (Gifu National Technology, Gifu, Japan.)
College of J. Jpn Sot. Powder Powder Metall., Vol 46, No 3, 1999,212-218. (In Japanese.) It is reported that nanocomposite binary (Al, Cu, Si or Gel-(In, Zn or Mg) powders had been prepared by a gas evaporation/condensation technique. Vapour of one species was condensed onto flying particles of the other, previously made by evaporationfcondensation. The powders were characterized by electron microscopy and the results are described for each binary alloy species.
Sin tering SINTERED NIOBIUM-TANTALUMALUMINIUM ANODE ALLOYS
J.N.F. de Holanda et al. (UNEF-LAMAV, Rio de Janeiro, Brazil.) Int. J. Refract. Metals Hard Mater., Vol 17, No 4, 1999, 253-257. A range of sintered Nb-Ta-Al alloys was evaluated with respect to density, morphology and electrical properties. Powders were pressed uniaxially in a steel die and vacuum sintered at 1300 to 1600°C for 15, 40 or 60 minutes. Properties are described. The materials were for anodes in electrolytic capacitors. A THERMO-OPTICAL DEVICE SZTU STUDY OF SINTERING
F.Raether Calorimetry,
et
al.
J.
FOR IN
Therm.
Anal.
Vol53, No 3,1998,717-735.
It is reported that a thermo-optical device had been developed for in situ study of thermal and optical properties during sintering. Shrinkage was measured by a non-contact dilatometer. The objective was to optimize time-temperature-atmosphere of sintering cycles. It is shown that there is good resolution in identification of sintering states. References are made to Fe and Al,O,.
Fundamentals ESTIMATION OF PARTICLE SIZE DISTRIBUTION FROM A NETWORK MODEL OF POROUS MEDIA
G.P.Mathews et al. (University of Plymouth, Devon, UK.) Powder Tech., Vol 104, No 2, 1999, 169-179. A method of measuring particle size distribution in consolidated porous media, using Hg porosimetry and a network model of the void structure, is described. The technique is shown to compare favourably with that of Meyer and Stowe. RING TESTS
FOR PM MATERIALS
R.E.Dutton et Science/Engineering,
al.
J.
Vol
Manuf:
120,
No 4, 1998,764-769. Use of a ring test to assess friction in PM materials at the work piece/die interface during powder forging was investigated by measuring the change in diameter as a function of reduction in height, Finite element simulation was carried out. Validation was by isothermal compression tests on ol,Ti aluminide with initial densities of 75%, 85% or full density. Friction for the porous samples was slightly higher than for full density materials in lubricated and un-lubricated conditions. Good agreement was shown between predicted and measured values of density distribution.
Copper STRUCTURAL PARAMETERS DISPERSION STRENGTHENED COPPER-ALUMINA
J.Zrnik Kosice,
IN
(Technical University, Republic.) Pokroky Praskove Metal., Vol 37, No 1, 1999, 3237. (In Czech.) Image analysis was used to investigate structural parameters in Cu-(3 to 1O)nominal vol%Al,O,, prepared by et
al.
Czech
FORMATION POWDERS
IN GAS
SCzbilen, (Gazi University, Ankara, Turkey.) Powder Metall., Vol 42, No 1, 1999,70-78. Satellite formation in gas atomized powders was investigated for Al, All%Li, Cu, Mg and Sn. It is shown that, to form particles with satellites, interactions between coarse and a high proportion of fine particles are required. Fine particles are formed by disintegration of coarse particles. Satellite formation is enhanced by surface roughness and is influenced by oxidation. Inhomogeneities in the oxide film affect surface roughness. VELOCITIES FREE-FALL
OF GAS FROM ATOMIZERS
D.Singh et al. (Indian Inst. of Technology, Kanpur, India.) Powder Metall., Vol42, No 1, 1999, 79-85. Gas velocities in free fall atomizers were investigated as functions of atomizer geometry and operating conditions. Wide variations in velocity were detected. Velocity increased with pressure and nozzle diameter. Empirical correlations arc established. PRODUCTION POWDERS
OF HIGH PURITY
TIN
A.D.Styrkas, D.A.Styrkas. (University of Surrey, Guildford, UK.) Powder Technol., Vol 104, No 2, 1999,164-168. Methods of producing high purity Sn with reduced %0, using the allotropic changes repeatedly, are proposed. Attrition of Sn is possible due to the 26.6% volume change between grey, c&n, and white, PSn. Electronic reconfiguration during the allotropic change, altering bonding from covalent to metallic, affects oxidation. The processing is briefly described. Powder size was 5 pm or less and the %0 was reduced to l~lO-~wt%. POLYMER ATOMIZATION ALUMINIDE
OF IRON
J.T.Strauss et al. (HJE Co, Glens Falls, USA.) Mater. Science I Engineering A, Vol 258, No l/2,1998,291-297. A method of atomizing a reactive alloy melt, Fe aluminide, with a polymeric fluid was investigated. The products are compared with gas and water atomized powders. Advantages of the
32 MPR June 2000
technique and powder properties are outlined. The powder was roll compacted and densified by a series of rollings and annealings. The material is compared with alloys made from gas and water atomized powders. PRODUCTION OF BORON BY ARC VOLATILIZATION
POWDER
‘IIHagio et al. J. Mater. Science, Letters, Vol 17, No 22, 1998, 1937-1939. Production of amorphous B powders, 0.1 to 1.0 ym in size, by volatilization from a DC arc in inert gas, between B rods preheated to 6OO”C, is described. Preheating is to induce electrical conduction. It is suggested that nitrides and carbides could be produced by appropriate selection of the operating atmosphere. PREPARATION OF NANOCOMPOSITE PARTICLES BY GAS EVAPORATION AND CONDENSATION TECHNIQUES
T.Ohno. (Gifu National Technology, Gifu, Japan.)
College of J. Jpn Sot. Powder Powder Metall., Vol 46, No 3, 1999,212-218. (In Japanese.) It is reported that nanocomposite binary (Al, Cu, Si or Gel-(In, Zn or Mg) powders had been prepared by a gas evaporation/condensation technique. Vapour of one species was condensed onto flying particles of the other, previously made by evaporationfcondensation. The powders were characterized by electron microscopy and the results are described for each binary alloy species.
Sin tering SINTERED NIOBIUM-TANTALUMALUMINIUM ANODE ALLOYS
J.N.F. de Holanda et al. (UNEF-LAMAV, Rio de Janeiro, Brazil.) Int. J. Refract. Metals Hard Mater., Vol 17, No 4, 1999, 253-257. A range of sintered Nb-Ta-Al alloys was evaluated with respect to density, morphology and electrical properties. Powders were pressed uniaxially in a steel die and vacuum sintered at 1300 to 1600°C for 15, 40 or 60 minutes. Properties are described. The materials were for anodes in electrolytic capacitors. A THERMO-OPTICAL DEVICE SZTU STUDY OF SINTERING
F.Raether Calorimetry,
et
al.
J.
FOR IN
Therm.
Anal.
Vol53, No 3,1998,717-735.
It is reported that a thermo-optical device had been developed for in situ study of thermal and optical properties during sintering. Shrinkage was measured by a non-contact dilatometer. The objective was to optimize time-temperature-atmosphere of sintering cycles. It is shown that there is good resolution in identification of sintering states. References are made to Fe and Al,O,.
Fundamentals ESTIMATION OF PARTICLE SIZE DISTRIBUTION FROM A NETWORK MODEL OF POROUS MEDIA
G.P.Mathews et al. (University of Plymouth, Devon, UK.) Powder Tech., Vol 104, No 2, 1999, 169-179. A method of measuring particle size distribution in consolidated porous media, using Hg porosimetry and a network model of the void structure, is described. The technique is shown to compare favourably with that of Meyer and Stowe. RING TESTS
FOR PM MATERIALS
R.E.Dutton et Science/Engineering,
al.
J.
Vol
Manuf:
120,
No 4, 1998,764-769. Use of a ring test to assess friction in PM materials at the work piece/die interface during powder forging was investigated by measuring the change in diameter as a function of reduction in height, Finite element simulation was carried out. Validation was by isothermal compression tests on ol,Ti aluminide with initial densities of 75%, 85% or full density. Friction for the porous samples was slightly higher than for full density materials in lubricated and un-lubricated conditions. Good agreement was shown between predicted and measured values of density distribution.
Copper STRUCTURAL PARAMETERS DISPERSION STRENGTHENED COPPER-ALUMINA
J.Zrnik Kosice,
IN
(Technical University, Republic.) Pokroky Praskove Metal., Vol 37, No 1, 1999, 3237. (In Czech.) Image analysis was used to investigate structural parameters in Cu-(3 to 1O)nominal vol%Al,O,, prepared by et
al.
Czech