A new method for the measure of interparticle bonding and its correlation with other physical properties.

Thesis (Ph.D.)--Boston UniversityExpanding interest in powder technology has generated many investigations of sintering, the major step in the solidification of powder to dense material. Sintering is defined herein as the establishment of physical bonds between powder particles in mechanical contact under the influence of temperature and time. Physical properties and tests previously studied lack direct correlation with the degree of sintering. The relation between the extent of sintering and changes in surface energy of the powder system is discussed. In accordance with Gibbs-Helmholtz principles, the equivalent of the energy change with degree of sintering was measured by the electrochemical potential. The empirical nature of the practices employed in and the change in properties produced by the transition from powder to solid are reviewed. The controllable conditions governing the final properties are the powder characteristics and the treatments employed. Briquetting raises the density of the powder relative to solid density from 20 - 40% when loose to 60 - 90% when pressed. Previous explanations attribute compacted strength to localized welding of particles due to interparticle friction and adhesion between clean surfaces exposed as they undergo motion. It is suggested that the major effect of compacting is to relocate the particles, causing better mechanical packing. The strength of the green compact is considered to originate in the interparticle friction opposing the force tending to separate the particles and cause rupture. [TRUNCATED