Character of electrical resistivity variation in the sintering of ultrafine powders
As a result of oxidation of compacts from nickel and copper UFPs, their electrical resistivities may vary within a wide range. During the vacuum sintering of nickel and copper UFPs changes in electrical resistivity are recorded before densification. During heating the electrical resistivity of compacts may fall at a rate of up to half an order a minute. Measurements of γ and δL/L during repeated heating-and-cooling cycles reveal increases in the electrical resistivity and elongation of specimens, which may be linked with elastic after-effect phenomena. A small rise in electrical resistivity during heating to 100‡C may also be brought about by elastic stress relaxation. An increase in electrical resistivity accompanied by shrinkage during a rise in temperature after isothermal sintering is indicative of rupture of contacts during densification; the extent of this process, which may be linked with sliding of whole particles relative to one another, diminishes with rise in temperature.
KeywordsOxidation Copper Nickel Shrinkage Electrical Resistivity
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