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Effects of silver on the microstructure of sintered nickel-copper-zinc ferrites
PM
m e t h o d s used. Small variations in Kk. with t e m p e r a t u r e were found in an e x p e r i m e n t a l study a n d this is a t t r i b u t e d to t h e effects of surface free energies, Young's modulus and melting point. Data for Al.~O3, SiC a n d SiaN4 are presented. PROPERTIES OF S I N T E R E D M E T A L / CERAMIC COMPACTS
M. Takada et al (University of Tokyo, Tokyo, J a p a n ) , J Japan Inst of Metals, Vol 56, No 3, 1992, 303-307, (in J a p a n e s e ) . The effect of t h e addition of Pt, Ag or Au (0.5 to l lvol%) on t h e s i n t e r i n g a n d properties of (Ba,Sr)(Ti, Sb)O3 ceramics were investigated. Sintering was in air at 1375~:C for l hour. The electrical resistivity, thermal conductivity and fracture t o u g h n e s s were all found to increase with increase in metal content.
Electric m a t e r i a l s E F F E C T S OF MECHANICAL ALLOYING ( M A ) HEAT TREATMENT ON THE MAGNETIC PROPERTIES OF SAMARIUM-IRON-NITROGEN ALLOYS
T. Itsukaichi et al (Toyahashi University of Technology, Toyohashi, J a p a n ) , ,l Japan Soc Powder and Powder Metallurgy, Vol 39, No 7, 1992, 569-574 (in J a p a n e s e ) . It is reported t h a t MA h a d been used to prepare Sm-Fe-N permanent magnet materials. MA resulted in a m o r p h i z a t i o n of the Fe over a wide range of composition a n d Sm.~Fe]7 was f o r m e d d u r i n g h e a t t r e a t m e n t of Fe-15%Sm in N at 790 to 800:C. The cocrcivity of t h e alloys is found to d e p e n d on t c m p e r a t u r e and time of heat t r e a t m e n t . The results are discussed with respect to powder particle size a n d crystal size of t h e MA powder. DIMENSIONAL STABILITY OF POROUS SINTERED COPPER U S E D AS A N O D E IN MOLTEN CARBONATE FUEL CELLS
K. H o s h i n o a n d T. K o h n o ( M i t s u b i s h i Corp, Omiya, J a p a n ) , J Japan Soc Powder and Powder Metallurgy, Vol 39, No 78, 1992, 575-578 (in J a p a n e s e ) . The performance of sintcrcd pure c o p p e r a n o d e s in molten c a r b o n a t e fuel cells is discussed with reference to e x p e r i m e n t a l and predicted results. The sintered Cu h a d a porosity of 43% a n d was p r e p a r e d from s p h e r i c a l gas a t o m i z e d p o w d e r 74 to 105 p m in size. Specimens were tested u n d e r compressive creep conditions. E F F E C T S OF SILVER ON THE MICROSTRUCTURE OF S I N T E R E D NICKEL-COPPER-ZINC F E R R I T E S
A. Nakano et al (TDK Corp, Narita, J a p a n ) , ,! J a p a n Soc P o w d e r a n d P o w d e r MetaUurgy, Vol 39, No 8, 1992, 612-617 (in J a p a n e s e ) .
50
MPR April 1993
LITERATURE
REVIEW
It is shown t h a t the addition of Ag to NiCu-Zn ferrites a c c e l e r a t e s d e n s i f i c a t i o n during low t e m p e r a t u r e sintering b u t Cu is dissociated from t h e ferrite a n d this leads to d i s c o n t i n u o u s grain growth. Lattice distortion at grain boundaries and c o n t r a c t i o n of t h e s i n t e r e d b o d i e s are reported. LIQUID PHASE SINTERING OF HIGH CRITICAL TEMPERATURE SUPERCONDUCTORS
H. Ito et al (Osaka C e m e n t Co, Kaizuka, J a p a n ) , J Japan Soc Powder and Powder Metallurgy, Vol 39, No 9, 1992, 775-778 (in J a p a n e s e ) . The use of liquid p h a s e sintering in t h e p r e p a r a t i o n of high T~. Bi-Pb-Sr-Ca-Cu-O s u p e r c o n d u c t o r s a n d t h a t high density had been attained. The liquid p h a s e is shown to be rich in Sr u n d e r t h e sintering conditions, 820 to 830::C for 16 hours. Values forT,, a n d critical c u r r e n t density are given. STABILITY OF MECHANICALLY GROUND HIGH CRITICAL TEMPERATURE S U P E R C O N D U C T O R S
J. T a k a d a et al ( O k a y a m a U n i v e r s i t y , Okayama, J a p a n ) , J Japan Soc Powder and Powder Metallurgy, Vol 39, No 9, 1992, 779-782, (in J a p a n e s e ) . Mechanical grinding of high T c Bi-Pb-SrCa-Cu-O s u p e r c o n d u c t o r powders is shown to destroy s u p e r c o n d u c t i n g ability. The s u p e r c o n d u c t i v i t y is r e s t o r e d by h e a t t r e a t m e n t a t 850~C. OPTIMIZATION OF HARD MAGNETIC PROPERTIES BY USE OF THERMAL EQUILIBRIUM DIAGRAMS
B. Grieb et al (Magnctfabrik S c h r a m b e r g GmbH, G e r m a n y ) , Powder Metallurgy, Vol 35, No 3, 1992, 221-227. The magnetic properties of Fe-Nd-B and related sTstems are discussed a n d it is pointed o u t t h a t the properties at elevated temperatures require significant e n h a n c e m e n t . The relationships between magnetic properties and the phases p r e s e n t are considered. It is suggested that to obtain the improvements knowledge of t h e p h a s e relationships a n d m i c r o s t r u c t u r e s is important. Composition, including additives, liquid p h a s e sintering, and h e a t t r e a t m e n t are taken into account in respect of the Fe-Nd-B, Fe-(Dy, Tb)-B, Fe-Nd-C, Fe-Nd-Al a n d Fe-Nd-(Dy, Tb)-B .systems. SHOCK CONSOLIDATION OF RAPIDLY SOLIDIFIED NEODYMIUM BASE RARE EARTH MAGNET POWDERS
M.W. Petrie a n d N.W. Page (University of Q u e e n s l a n d , Brisbane, A u s t r a l i a ) , Acta Metall Mater, Vol 40, No 11, 1992, 31953203. The use of shock consolidation of RS FeNd-B powders is d e ~ r i b e d . M e a s u r e m e n t s
on the c o m p a c t e d materials are in close a g r e e m e n t with prediction. Hardness a n d m i c r o s t r u c t u r e s were studied. Values of h a r d n e s s were said to show considerable evidence of work hardening. Quasi-static pressing produced cracked parts but dynamically c o m p a c t e d material is shown to be essentially free from defects due to cold welding. PREPARATION OF ULTRA-FINE BARIUM TITANATE POWDERS BY CO-PRECIPITATION
H.K. S u n g ct al ( C h u n g n a m N a t i o n a l University, Daejon, Korea), J Korean Inst of Metals, Vol 30, No 1, 1992, 7-12 (in Korean). Production of BaTiO3 powders by coprecipitation from BaClz a n d TiCl4 solution by oxalic acid is described. Effects of process conditions of powder characteriztics are outlined, means particle size being 0.16 ~m a n d specific surface 6.091 m~/g. POWDER CHARACTERIZTICS AND E F F E C T S OF COMPOSITION ON MAGNETIC P R O P E R T I E S OF B O N D E D MAGNETS
S.D. Choi et al (Inst. of Industrial Science and Technology, Pohang, Korea), J Korean Inst of Metals, Vol 30, No 2, 1992, 186-195 (in Korean). q~c a d d i t i o n of 1.5 at% Zr to Fe-Nd-Co-B powders is reported to result in increased green density because of more favourable powder packing. A relationship between green density a n d compaction p r e s s u r e is s u g g e s t e d . T h e g r a i n size of t h e Zr c o n t a i n i n g alloy was larger t h a n in the alloy w i t h o u t Zr. The magnetic properties are described.
Hard materials CUTTING T E S T OF S I N T E R E D SAWBLADE USING COPPER COATED SYNTHETIC DIAMOND POWDER
T. Fujimori et al ( C h i b a Inst. of Technology, Narashino, J a p a n ) , J Japan Soc Powder and Powder Metallurgy, Vol 39, No 7, 1992, 597-583 (in J a p a n e s e ) . It is n o t e d t h a t t h e addition of .synthetic d i a m o n d powder to cutting tool materials r e s u l t s in a r e d u ( ' t i o n o f e l e v a t e d t e m p e r a t u r e strength. It is shown t h a t by precoating t h e d i a m o n d powders with Cu this loss is reduced. This is a t t r i b u t e d to reduction of fracture rate of t h e diamond. A D H E S I O N B E T W E E N TITANIUM CARBIDE-NICKEL AND T U N G S T E N CARBIDE-COBALT C E R M E T S
O. Terada et al (Fuji Die Co, Tokyo, J a p a n ) , J J a p a n Soc P o w d e r and P o w d e r Metallurgy, Vol 39, No 7, 1992, 584-589
m e t h o d s used. Small variations in Kk. with t e m p e r a t u r e were found in an e x p e r i m e n t a l study a n d this is a t t r i b u t e d to t h e effects of surface free energies, Young's modulus and melting point. Data for Al.~O3, SiC a n d SiaN4 are presented. PROPERTIES OF S I N T E R E D M E T A L / CERAMIC COMPACTS
M. Takada et al (University of Tokyo, Tokyo, J a p a n ) , J Japan Inst of Metals, Vol 56, No 3, 1992, 303-307, (in J a p a n e s e ) . The effect of t h e addition of Pt, Ag or Au (0.5 to l lvol%) on t h e s i n t e r i n g a n d properties of (Ba,Sr)(Ti, Sb)O3 ceramics were investigated. Sintering was in air at 1375~:C for l hour. The electrical resistivity, thermal conductivity and fracture t o u g h n e s s were all found to increase with increase in metal content.
Electric m a t e r i a l s E F F E C T S OF MECHANICAL ALLOYING ( M A ) HEAT TREATMENT ON THE MAGNETIC PROPERTIES OF SAMARIUM-IRON-NITROGEN ALLOYS
T. Itsukaichi et al (Toyahashi University of Technology, Toyohashi, J a p a n ) , ,l Japan Soc Powder and Powder Metallurgy, Vol 39, No 7, 1992, 569-574 (in J a p a n e s e ) . It is reported t h a t MA h a d been used to prepare Sm-Fe-N permanent magnet materials. MA resulted in a m o r p h i z a t i o n of the Fe over a wide range of composition a n d Sm.~Fe]7 was f o r m e d d u r i n g h e a t t r e a t m e n t of Fe-15%Sm in N at 790 to 800:C. The cocrcivity of t h e alloys is found to d e p e n d on t c m p e r a t u r e and time of heat t r e a t m e n t . The results are discussed with respect to powder particle size a n d crystal size of t h e MA powder. DIMENSIONAL STABILITY OF POROUS SINTERED COPPER U S E D AS A N O D E IN MOLTEN CARBONATE FUEL CELLS
K. H o s h i n o a n d T. K o h n o ( M i t s u b i s h i Corp, Omiya, J a p a n ) , J Japan Soc Powder and Powder Metallurgy, Vol 39, No 78, 1992, 575-578 (in J a p a n e s e ) . The performance of sintcrcd pure c o p p e r a n o d e s in molten c a r b o n a t e fuel cells is discussed with reference to e x p e r i m e n t a l and predicted results. The sintered Cu h a d a porosity of 43% a n d was p r e p a r e d from s p h e r i c a l gas a t o m i z e d p o w d e r 74 to 105 p m in size. Specimens were tested u n d e r compressive creep conditions. E F F E C T S OF SILVER ON THE MICROSTRUCTURE OF S I N T E R E D NICKEL-COPPER-ZINC F E R R I T E S
A. Nakano et al (TDK Corp, Narita, J a p a n ) , ,! J a p a n Soc P o w d e r a n d P o w d e r MetaUurgy, Vol 39, No 8, 1992, 612-617 (in J a p a n e s e ) .
50
MPR April 1993
LITERATURE
REVIEW
It is shown t h a t the addition of Ag to NiCu-Zn ferrites a c c e l e r a t e s d e n s i f i c a t i o n during low t e m p e r a t u r e sintering b u t Cu is dissociated from t h e ferrite a n d this leads to d i s c o n t i n u o u s grain growth. Lattice distortion at grain boundaries and c o n t r a c t i o n of t h e s i n t e r e d b o d i e s are reported. LIQUID PHASE SINTERING OF HIGH CRITICAL TEMPERATURE SUPERCONDUCTORS
H. Ito et al (Osaka C e m e n t Co, Kaizuka, J a p a n ) , J Japan Soc Powder and Powder Metallurgy, Vol 39, No 9, 1992, 775-778 (in J a p a n e s e ) . The use of liquid p h a s e sintering in t h e p r e p a r a t i o n of high T~. Bi-Pb-Sr-Ca-Cu-O s u p e r c o n d u c t o r s a n d t h a t high density had been attained. The liquid p h a s e is shown to be rich in Sr u n d e r t h e sintering conditions, 820 to 830::C for 16 hours. Values forT,, a n d critical c u r r e n t density are given. STABILITY OF MECHANICALLY GROUND HIGH CRITICAL TEMPERATURE S U P E R C O N D U C T O R S
J. T a k a d a et al ( O k a y a m a U n i v e r s i t y , Okayama, J a p a n ) , J Japan Soc Powder and Powder Metallurgy, Vol 39, No 9, 1992, 779-782, (in J a p a n e s e ) . Mechanical grinding of high T c Bi-Pb-SrCa-Cu-O s u p e r c o n d u c t o r powders is shown to destroy s u p e r c o n d u c t i n g ability. The s u p e r c o n d u c t i v i t y is r e s t o r e d by h e a t t r e a t m e n t a t 850~C. OPTIMIZATION OF HARD MAGNETIC PROPERTIES BY USE OF THERMAL EQUILIBRIUM DIAGRAMS
B. Grieb et al (Magnctfabrik S c h r a m b e r g GmbH, G e r m a n y ) , Powder Metallurgy, Vol 35, No 3, 1992, 221-227. The magnetic properties of Fe-Nd-B and related sTstems are discussed a n d it is pointed o u t t h a t the properties at elevated temperatures require significant e n h a n c e m e n t . The relationships between magnetic properties and the phases p r e s e n t are considered. It is suggested that to obtain the improvements knowledge of t h e p h a s e relationships a n d m i c r o s t r u c t u r e s is important. Composition, including additives, liquid p h a s e sintering, and h e a t t r e a t m e n t are taken into account in respect of the Fe-Nd-B, Fe-(Dy, Tb)-B, Fe-Nd-C, Fe-Nd-Al a n d Fe-Nd-(Dy, Tb)-B .systems. SHOCK CONSOLIDATION OF RAPIDLY SOLIDIFIED NEODYMIUM BASE RARE EARTH MAGNET POWDERS
M.W. Petrie a n d N.W. Page (University of Q u e e n s l a n d , Brisbane, A u s t r a l i a ) , Acta Metall Mater, Vol 40, No 11, 1992, 31953203. The use of shock consolidation of RS FeNd-B powders is d e ~ r i b e d . M e a s u r e m e n t s
on the c o m p a c t e d materials are in close a g r e e m e n t with prediction. Hardness a n d m i c r o s t r u c t u r e s were studied. Values of h a r d n e s s were said to show considerable evidence of work hardening. Quasi-static pressing produced cracked parts but dynamically c o m p a c t e d material is shown to be essentially free from defects due to cold welding. PREPARATION OF ULTRA-FINE BARIUM TITANATE POWDERS BY CO-PRECIPITATION
H.K. S u n g ct al ( C h u n g n a m N a t i o n a l University, Daejon, Korea), J Korean Inst of Metals, Vol 30, No 1, 1992, 7-12 (in Korean). Production of BaTiO3 powders by coprecipitation from BaClz a n d TiCl4 solution by oxalic acid is described. Effects of process conditions of powder characteriztics are outlined, means particle size being 0.16 ~m a n d specific surface 6.091 m~/g. POWDER CHARACTERIZTICS AND E F F E C T S OF COMPOSITION ON MAGNETIC P R O P E R T I E S OF B O N D E D MAGNETS
S.D. Choi et al (Inst. of Industrial Science and Technology, Pohang, Korea), J Korean Inst of Metals, Vol 30, No 2, 1992, 186-195 (in Korean). q~c a d d i t i o n of 1.5 at% Zr to Fe-Nd-Co-B powders is reported to result in increased green density because of more favourable powder packing. A relationship between green density a n d compaction p r e s s u r e is s u g g e s t e d . T h e g r a i n size of t h e Zr c o n t a i n i n g alloy was larger t h a n in the alloy w i t h o u t Zr. The magnetic properties are described.
Hard materials CUTTING T E S T OF S I N T E R E D SAWBLADE USING COPPER COATED SYNTHETIC DIAMOND POWDER
T. Fujimori et al ( C h i b a Inst. of Technology, Narashino, J a p a n ) , J Japan Soc Powder and Powder Metallurgy, Vol 39, No 7, 1992, 597-583 (in J a p a n e s e ) . It is n o t e d t h a t t h e addition of .synthetic d i a m o n d powder to cutting tool materials r e s u l t s in a r e d u ( ' t i o n o f e l e v a t e d t e m p e r a t u r e strength. It is shown t h a t by precoating t h e d i a m o n d powders with Cu this loss is reduced. This is a t t r i b u t e d to reduction of fracture rate of t h e diamond. A D H E S I O N B E T W E E N TITANIUM CARBIDE-NICKEL AND T U N G S T E N CARBIDE-COBALT C E R M E T S
O. Terada et al (Fuji Die Co, Tokyo, J a p a n ) , J J a p a n Soc P o w d e r and P o w d e r Metallurgy, Vol 39, No 7, 1992, 584-589