Characterization of porosity of isostatically pressed and sintered nickel-base powdered metal *

Characterization of the pore structure of compacted and sintered parts made from a nickel-base powder was accomplished using the mercury porosimetry method. The theoretical density values for the sintered specimens varied from 56.3 to 96.7% which corresponds to a porosity of 43.7 to 3.3%. A maximum interconnecting median pore diameter of 21 Μm resulted from a −80/+ 200 mesh powder compacted at 138 MN/ m 2 and sintered for 2 h at 1250°C. Photomicrographs of the same sample showed that it had a maximum pore diameter of 200 Μm. The interconnected pore volume decreased with decreasing particle size of the powder, increasing compaction pressure, and increasing sintering temperature. Mechanical properties of tensile strength, yield strength, elastic modulus and percentage elongation were correlated with the pore structure. Proper selection of particle size, compaction pressure, sintering times and sintering temperatures should permit parts with controlled porosity characteristics to be produced that possess adequate mechanical properties for application as implants.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74821/1/j.1365-2842.1976.tb00947.x.pd

Physical properties of a nickel-base alloy prepared by isostatic pressing and sintering of the powdered metal *

The physical and mechanical properties of samples of a nickel-base alloy fabricated by powder metallurgy were determined. The particle sizes of the powders used to make the samples varied from –80/+ 200 mesh to –325 mesh. The compaction pressure varied from 138 to 414 MN/m 2 and the sintering temperature varied from 1150 to 1250°C. The shrinkage during processing, the porosity, tensile strength, yield strength, elongation, and elastic modulus were used to characterize the samples. The strength of the samples generally increased with decreasing particle size of the powder and increasing compaction pressure and sintering temperatures. The porosity and strength, therefore, could be varied over a wide range by controlling the various parameters. The properties of the samples prepared by powder metallurgy were compared with those of the cast alloy and compact bone. Conditions can be selected that will yield equivalent or better properties by powder metallurgy than by casting.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74945/1/j.1365-2842.1976.tb00939.x.pd

Sintered Hydroxyapatite Ceramic for Wear Studies

A sintered hydroxyapatite (HAP) ceramic for use in wear studies was prepared from a commerical tricalcium phosphate. The sintered HAP had physical properties close to those of human enamel. The coefficient of friction and wear of the sintered HAP ceramic as characterized by tangential force, track width, and surface failure data, approximated those of human enamel.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67948/2/10.1177_00220345780570070401.pd

Wear of Composites by Abrasives of Varying Hardness

The relationship between the wear of three composite resins and the hardness of the abrasive was studied by a two-body abrasion test. The wear rates of the composites increased linearly with abrasive hardness from 530 to 2080 KHN. Measurement of the slope of the wear rate versus abrasive hardness over this range provided a sensitive method for ranking the composites.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68031/2/10.1177_00220345790580031201.pd

Adsorption of Streptococcus mutans on Chemically Treated Hydroxyapatite

Adsorption of Streptococcus mutans on hydroxyapatite and chemically treated hydroxyapatite was studied. Zeta potentials of the surfaces were measured. Chemically treated hydroxyapatite gave higher ζ potentials and lower S mutans adsorption.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67845/2/10.1177_00220345780570091601.pd

Free Surface Energy Change for Water Adsorbed on Hydroxyapatite

The free energies of immersion for three hydroxyapatite samples of different origin and method of preparation were determined from water adsorption isotherms at 20 and 25 C. The free energies varied with the temperature of the isotherm, changing linearly with the outgassing temperature in the range of 20 and 300 C. The samples outgassed at 300 C yielded free energy of immersion values of 365, 432, and 476 ergs/ cm2 for the VIC-, NBS-, and TVA-HAP, respectively. Work of adhesion and work of spreading were calculated for water on these samples.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67535/2/10.1177_00220345770560070701.pd