Microwave Assisted Firing

Conventional ceramic firing processes rely on surface heating to raise the temperature, and consequently cause temperature gradients to form within the components during firing. In extreme cases these gradients can limit the fired density and even cause shrinkage related stresses and cracking. The use of dwell periods both during the heating cycle and at the firing temperature can serve to dissipate the temperature gradients as well as allowing rate limiting processes such as diffusion to occur throughout the fired item.
Extending the firing period in this way to overcome the effects of temperature gradients leads to increased grain growth with potential consequences for material properties.

In contrast, microwaves are absorbed by materials and their effect is to generate heat within the component.

Combining microwaves with conventional (radiative) heating leads to a reduction in the temperature gradient within the component. As a consequence the temperature required to achieve sintering can be reduced and the dwell shortened with a significant impact on the energy used. Energy savings as high as 35% have been claimed for microwave assisted firing though the actual saving will depend on the materials being fired and the temperature. Binner et al ⁽¹⁾ have also shown benefits in terms of grain size reduction which cannot be explained purely in terms of improving the temperature distribution, and speculate on the existence of a 'microwave effect'.

A furnace is available at CERAM for trials with customers' materials on a one to one basis. The results of such trials will be confidential to the client only.

¹REF - Evidence for the Microwave Effect During Hybrid Sintering
J. Wang, J. Binner, B. Vaidhyanathan, N. Joomun, J. Kilner, G. Dimitrakis and T.E. Cross
Journal of the American Ceramic Society, Volume 89, Issue 6: 1977-1984.