Sintering Studies Project.
Abstract
A new concept explains the factors which influence the sinterability of ceramic (and metal) powders. This theory, based on the thermodynamics consideration of pore disappearance, is centered on the coordination number of distributon of pores within the initial powder compact and on the changes in the pore coordination number during sintering. Thermodynamic arguments show that only pores with a coordination number less than a critical value (R > R sub c) can disappear by diffusion. The coordination number of a pore is the number of touching particles that surround and the pore size). This concept suggested the following phenomena: (1) Consolidation forces (e.g., iso-pressing) that increase bulk density will eliminate pores with high coordination numbers and thus increase the sinterability of the powder compact. (2) Multiple-particle packing units containing pores with low coordination (R < R sub c) will first densify during sintering to increase the size and coordination number of pores between the densifying packing units. (3) Grain growth, supported by dense packing units, will decrease the coordination number of pores enlarged by local densification. i.e. normal grain growth is advantageous to sinterability. (4) Compressive stress produced by either surface tension effects or hot-pressing cause the dense regions to deform, thus closing pores between the dense regions and reducing their coordination number.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 13, 1985
- Accession Number
- ADA154750
Entities
People
- F. F. Lange
- W. J. Knapp
Organizations
- University of California, Los Angeles