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

Rights to Land, Forests and Carbon in REDD+ : Insights from Mexico, Brazil and Costa Rica

Land tenure and carbon rights constitute critical issues to take into account in achieving emission reductions, ensuring transparent benefit sharing and determining non-permanence (or non-compliance) liabilities in the context of REDD+ strategies and projects. This is so because tenure systems influence who becomes involved in efforts to avoid deforestation and improve forest management, and that land tenure, carbon rights and liabilities may be linked or divorced with implications for rural development. This paper explores these issues by looking at tenure regimes and carbon rights issues in Mexico, Brazil and Costa Rica. It is effectively shown that complex bundles of rights over forest resources have distinct implications for REDD+ design and implementation, and that REDD+ strategies in selected countries have to date failed in procedurally addressing land-use conflicts and carbon rights entitlements and liabilities

A Study of Gold Platinum Alloys with the Addition of Small Amounts of Iron

Previous investigators have shown gold rich Au-Pt alloys with the addition of small amounts of iron exhibit a definite change in mechanical properties as a function of iron content and heat treatment . However, the literature reveals little information concerning the mechanism by which these alloys harden. The object of this investigation was to observe the change in hardness values in gold rich Au-Pt-Fe alloys as a function of composition, aging time, and aging temperature. In addition, electron microscopy techniques have been employed in an attempt to explain the hardening characteristics in the gold-platinum-iron system

Isostatic Pressing Of Nickel Base Powder Metallurgy Parts For Potential Bio-engineering Applications.

PhDMetallurgyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/186977/2/7214869.pd

The Chloride Corrosion Behavior of Silver-base Casting Alloys

The chloride corrosion behavior of five silver-palladium dental casting alloys was investigated in a 1% NaCl solution through the use of electrochemical hysteresis technique. The corrosion mechanism has been interpreted in terms of the microstructure of these alloys and their possible electrochemical reactions. </jats:p

The Chloride Corrosion of Low-Gold Casting Alloys

Potentiodynamic polarization measurements have indicated that the so-called 'low-gold' casting alloys are characterized by decreased chloride corrosion resistance, when compared with ADA Type III and Type IV gold alloys. This decrease in chloride corrosion resistance results apparently from the presence of Ag-rich microsegregations with a possible minor contribution from Curich segregations or precipitates. </jats:p

Research into Practice: Concept Learning in Geometry

How well do primary students understand such geometric concepts as angle, rectangle, and cube? How might your students show that they understand them? These are important questions, since the geometry strand for K–4 programs contains a host of concepts involving two- and three-dimensional shapes.</jats:p