1. Enhanced Sintering Rate and Reduction of Grain Size by Application of a Small AC Electric FieldHans Conrad, North Carolina State University, DMR 1002751 Ceramics are significant components in a variety of products including insulators, gas turbines, microelectronics, fuel cells, nuclear rods, body armor, heat shields and other high-temperature structural materials. The ceramic parts are usually produced by sintering, in which fine particles of the material are compacted and then heated to a high temperature during which the particles bond to form a dense body essentially free of porosity. It was discovered that the application of a 60 Hz AC electric field applied during the sintering of zirconia (3Y-TZP) significantly enhanced the sintering rate, which increased with the strength of the field; see figure on right. The enhancement with the AC field was greater than with the equivalent DC field. Theoretical calculations and scanning electron microscopy observations gave that a major factor in the enhancement of the sintering rate by the field was a retardation of the grain growth which normally occurs during the sintering operation. Of interest in future work is: (a) the effect of electric field frequency, (b) the heating rate and (c) other ceramics. Effect of the strength of 60 Hz AC electric field on the sintering rate of zirconia (3Y-TZP). Dashed lines indicate the relative densities where theoretical calculations were made to determine grain size.

2. Enhanced Sintering Rate and Reduction of Grain Size by Application of a Small AC Electric Field Hans Conrad, North Carolina State University, DMR 1002751 Because of the high temperatures required in the sintering of ceramics, appreciable energy is consumed, making it a costly process. Hence, reduction in the final temperature, Tf, required to attain full density which results from the application of an electric field (see figure on left) can lead to a significant reduction in energy and, in turn, in cost. Moreover, the reduction in grain size which concurrently occurs (see figure on left) is expected to give higher strength and toughness to the product. Our results also suggest that the enhanced sintering rate and finer grain size which have been reported in microwave, high-frequency induction and so-called “spark plasma” sintering may be due in part to the associated electric field. Discussions with industry are underway on the application of an electric field in commercial practice. The influence of the strength of a 60 Hz electric field, E, on the temperature, Tf, required to attain full density in zirconia (3Y-TZP) and the corresponding observed(scanning electron microscopy) reduction in grain size at E = 14 V per cm.