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Effects of particle size on sintering of porous tantalum
Tantalum EFFECTS OF PARTICLE SIZE ON SINTERING OF POROUS TANTALUM
F.Hanada et ~2. (Suzuka National College of Technology, Suzuka, Japan.) Jpn. Sot. Powder Powder Metall., Vo145, No 8,1998, 721-726. (In Japanese.) Sintering of Ta powder, with particle sizes of 1.7 and 3.5 pm, in vacuum or by HIP, is discussed and an investigation is described. The density of the sintered Ta is shown to be independent of particle size and increased with increase in sintering temperature. Grain coarsening was more apparent in the materials with the smaller starting particle size.
7hgsten DISTORTION AND SOLID/LIQUID SEGREGATION DURING LIQUID PHASE SINTERING IN MICROGRAVITY
R.M.German et al. (Pennsylvania State University, USA.) Metall. Mater. Tram B, Vol29B, No 8,1998,857-866. It is reported that W heavy alloys, with 78 to 98wt%W had been liquid phase sintered in microgravity at 1507°C for two hours. The sintered microstructures were quantitatively measured. Microstructural parameters were analysed and compared with empirical Macroand equations. microstructures are correlated. Critical values of solids volume fraction, contiguity and connectivity needed for freestanding structural rigidity are defined. The extent of solid-liquid segregation, due to differences in specific gravity between liquid and solid could be predicted.
Ceramic materials EFFECT OF BALL CONTENT OF BALL MILL ON GRINDING SPEED IN WET ROTARY GRINDING
K.Yokota et al. (Kagawa Industrial Technology Centre, Takamatsu, Japan.) Jpn. Sot. Powder Powder Metall., Vol45, No 7,1998,680-684. (In Japanese.) Wet ball milling of A&O, was investigated to determine effects of ball:powder ratio, speed of rotation, proportion of mill volume filled. The rate of size reduction increased with mill. When over half the mill space was filled there was a critical mill speed for minimum particle size. Above this speed the balls were car34 MPR January 2000
ried round by the mill and the powder was not ground. The critical mill speed depended on the filled volume. STUDIES OF WATER SLIP-CASTING OF FINE HIGH PURITY a ALUMINA
(National Industrial Y.Shibasaki. Research Inst. of Nagoya, Nagoya, Japan.) J. Jpn Sot. Powder Powder Metall., Vol 45, No 9, 1998, 839-848. (In Japanese.) The high cost of organic binders and solvents for slip casting of fine ceramic powders is noted. Studies to develop low cost water based slips are described. Fine, high purity AlaO, was used. INFLUENCE REACTMTY
OF PARTICLE SIZE ON OF QUARTZ POWDER
J.C.Benezet, A.Benhassaine. (Ecole des Mines d’Al&s, Ales, France.) Powder Technol., Vol 103, No 1,1999,26-29. Reactivity of quartz powder was investigated with consideration of the vitreous state. The pozzolanic reaction was studied. Quartz is considered to have low reactivity, The reaction is influenced by several factors and is shown to proceed by a solution/precipitation mechanism. ESTIMATION OF SIMPLE AND MIXED OXIDES BY MASS TITRATION USING POINT OF ZERO CHARGE F.Kolenda. (UMR CRNSVernaison, France.) Powder Technol., Vol 103, No 1,1999,30-36. A method of evaluating simple and mixed oxides by means of the point of zero charge is described. Proposals are made for alterations to Schwarz’s method of mass titration and these are evaluated. Use of solutions of electrolytes is shown to give good agreement with published data. The method is reported to be applicable to determination of impurity content of oxide materials.
J.P.Reymond,
IFP,
at 1750°C. Densities of 96% were attained. The sintering aid gave a more and microstructure homogeneous YaAlsO,, was detected. NbC restrained grain growth. FRACTURE TOUGHNESS OF ZIRCON&ALUMINA MATERIALS
et aZ. (Polytechnic University of Catalonia, Barcelona, Spain.) Int. J. Refractory Metals Hard Mater., Vol 17 No 1,1999,11-20. The influence of microstructural coarsening, induced by heat treatment at 16OO”C,on the fracture toughness of A&0,-(5, 15 and 30)%ZrO, was investigated. Fracture toughness was evaluated by using a Vickers hardness indentor to produce small surface cracks and through thickness cracks. It is shown that fracture toughness increases with increase in %ZrO, and with ZrO, particle coarsening. The effects are attributed to effects of microstructural parameters and a stress induced phase change. D.Casellas
Electrical and magnetic materials SINTER JOINING MAGNETS
OF FERRITE
et al. (Setsunan University, Neyagawa, Japan.) J. Jpn Sot. Powder Powder Metall., Vol 45, No 8, 1998, 763768. (In Japanese.) An investigation of sinter joining of sub-parts of ferrite magnets, with differing magnetic orientations, to form a complex magnet, is described. The two components of the part were pressed, assembled and sintered. The strength of the joint was measured. 0.75wt% CaO was added to the ferrite powders. K.Okimoto
Hard materials and tool steels
SINTERING OF ALUMINA-NIOBIUM CARBIDE COMPOSITES
SHRINKAGE OF TUNGSTEN CARBIDE-COBALT BARDMETALS
et al. (Inst. Pesq. Energeticas e Nucleares, Sao Paulo, Brazil.) Int. J. Refractory Metals Hard Mater., Vol 16, No 4-6,1998,423-427. Studies of the sintering of A&O,NbC, with Y,O, added as a sintering enhancer, are described. Compositions were A&0,-(0, lo,20 and 4O)wt%NbC-(0 and 3)%Y,O,. Pressureless sintering was 30 minutes at 1650°C or 15 minutes
G.Gille
R.M.R.Pasotti
et al. (Fraunhofer Inst. for Ceramics and Sintered Materials, Dresden Germany.) 2. Metallkd., Vo189, No 2,1998,73-76. (In German.) Degassing and sintering of WClOwt%Co was investigated. It is noted that solid state sintering contributes 75% of the densification and depends on powder properties and process conditions. A model for solid state sintering is
F.Hanada et ~2. (Suzuka National College of Technology, Suzuka, Japan.) Jpn. Sot. Powder Powder Metall., Vo145, No 8,1998, 721-726. (In Japanese.) Sintering of Ta powder, with particle sizes of 1.7 and 3.5 pm, in vacuum or by HIP, is discussed and an investigation is described. The density of the sintered Ta is shown to be independent of particle size and increased with increase in sintering temperature. Grain coarsening was more apparent in the materials with the smaller starting particle size.
7hgsten DISTORTION AND SOLID/LIQUID SEGREGATION DURING LIQUID PHASE SINTERING IN MICROGRAVITY
R.M.German et al. (Pennsylvania State University, USA.) Metall. Mater. Tram B, Vol29B, No 8,1998,857-866. It is reported that W heavy alloys, with 78 to 98wt%W had been liquid phase sintered in microgravity at 1507°C for two hours. The sintered microstructures were quantitatively measured. Microstructural parameters were analysed and compared with empirical Macroand equations. microstructures are correlated. Critical values of solids volume fraction, contiguity and connectivity needed for freestanding structural rigidity are defined. The extent of solid-liquid segregation, due to differences in specific gravity between liquid and solid could be predicted.
Ceramic materials EFFECT OF BALL CONTENT OF BALL MILL ON GRINDING SPEED IN WET ROTARY GRINDING
K.Yokota et al. (Kagawa Industrial Technology Centre, Takamatsu, Japan.) Jpn. Sot. Powder Powder Metall., Vol45, No 7,1998,680-684. (In Japanese.) Wet ball milling of A&O, was investigated to determine effects of ball:powder ratio, speed of rotation, proportion of mill volume filled. The rate of size reduction increased with mill. When over half the mill space was filled there was a critical mill speed for minimum particle size. Above this speed the balls were car34 MPR January 2000
ried round by the mill and the powder was not ground. The critical mill speed depended on the filled volume. STUDIES OF WATER SLIP-CASTING OF FINE HIGH PURITY a ALUMINA
(National Industrial Y.Shibasaki. Research Inst. of Nagoya, Nagoya, Japan.) J. Jpn Sot. Powder Powder Metall., Vol 45, No 9, 1998, 839-848. (In Japanese.) The high cost of organic binders and solvents for slip casting of fine ceramic powders is noted. Studies to develop low cost water based slips are described. Fine, high purity AlaO, was used. INFLUENCE REACTMTY
OF PARTICLE SIZE ON OF QUARTZ POWDER
J.C.Benezet, A.Benhassaine. (Ecole des Mines d’Al&s, Ales, France.) Powder Technol., Vol 103, No 1,1999,26-29. Reactivity of quartz powder was investigated with consideration of the vitreous state. The pozzolanic reaction was studied. Quartz is considered to have low reactivity, The reaction is influenced by several factors and is shown to proceed by a solution/precipitation mechanism. ESTIMATION OF SIMPLE AND MIXED OXIDES BY MASS TITRATION USING POINT OF ZERO CHARGE F.Kolenda. (UMR CRNSVernaison, France.) Powder Technol., Vol 103, No 1,1999,30-36. A method of evaluating simple and mixed oxides by means of the point of zero charge is described. Proposals are made for alterations to Schwarz’s method of mass titration and these are evaluated. Use of solutions of electrolytes is shown to give good agreement with published data. The method is reported to be applicable to determination of impurity content of oxide materials.
J.P.Reymond,
IFP,
at 1750°C. Densities of 96% were attained. The sintering aid gave a more and microstructure homogeneous YaAlsO,, was detected. NbC restrained grain growth. FRACTURE TOUGHNESS OF ZIRCON&ALUMINA MATERIALS
et aZ. (Polytechnic University of Catalonia, Barcelona, Spain.) Int. J. Refractory Metals Hard Mater., Vol 17 No 1,1999,11-20. The influence of microstructural coarsening, induced by heat treatment at 16OO”C,on the fracture toughness of A&0,-(5, 15 and 30)%ZrO, was investigated. Fracture toughness was evaluated by using a Vickers hardness indentor to produce small surface cracks and through thickness cracks. It is shown that fracture toughness increases with increase in %ZrO, and with ZrO, particle coarsening. The effects are attributed to effects of microstructural parameters and a stress induced phase change. D.Casellas
Electrical and magnetic materials SINTER JOINING MAGNETS
OF FERRITE
et al. (Setsunan University, Neyagawa, Japan.) J. Jpn Sot. Powder Powder Metall., Vol 45, No 8, 1998, 763768. (In Japanese.) An investigation of sinter joining of sub-parts of ferrite magnets, with differing magnetic orientations, to form a complex magnet, is described. The two components of the part were pressed, assembled and sintered. The strength of the joint was measured. 0.75wt% CaO was added to the ferrite powders. K.Okimoto
Hard materials and tool steels
SINTERING OF ALUMINA-NIOBIUM CARBIDE COMPOSITES
SHRINKAGE OF TUNGSTEN CARBIDE-COBALT BARDMETALS
et al. (Inst. Pesq. Energeticas e Nucleares, Sao Paulo, Brazil.) Int. J. Refractory Metals Hard Mater., Vol 16, No 4-6,1998,423-427. Studies of the sintering of A&O,NbC, with Y,O, added as a sintering enhancer, are described. Compositions were A&0,-(0, lo,20 and 4O)wt%NbC-(0 and 3)%Y,O,. Pressureless sintering was 30 minutes at 1650°C or 15 minutes
G.Gille
R.M.R.Pasotti
et al. (Fraunhofer Inst. for Ceramics and Sintered Materials, Dresden Germany.) 2. Metallkd., Vo189, No 2,1998,73-76. (In German.) Degassing and sintering of WClOwt%Co was investigated. It is noted that solid state sintering contributes 75% of the densification and depends on powder properties and process conditions. A model for solid state sintering is