Interaction of microwaves with organic and inorganic matter

Microwaves interact with matter and they give rise to different phenomena to those induced by conventional heating. This is what gives rise to speculations about the possible existence of a “microwave effect”. The objective of the work reported here has been to investigate the possibility of a microwave effect being responsible for microwave-induced solid state transformations in a variety of inorganic and bacterial materials.

This work consists of four parts. In the first part a theoretical explanation for the way in which microwaves interact with cellular materials is attempted, in which the cells are described by the Japanese model of multistratified shells. Unfortunately, the link between that model and the microwave effect is not achieved in this work.

In the second, the interaction of microwaves with bacteria is investigated experimentally, using a single mode cavity. Significantly, cases are found in the work when bacteria are quite probably killed at sub-lethal temperatures. Attempts are made to explain experimental results in which three different types of bacteria were irradiated namely Salmonella Poona, Escherichia Coli and Staphylococcus Aureus. The interactions of microwaves with bacteria are investigated through an extensive literature review. In the third, the interactions of microwaves with bacteria are investigated through an extensive literature review. In the fourth part, thermally-induced solid state transformations in which layered double hydroxides are converted to mixed metal oxides are investigated, again in a single mode cavity, in this case using a temperature/power feedback mechanism to control the sample temperature during the process. The most basic layered double hydroxide is hydrotalcite which contains magnesium (II) and aluminium (III). While hydrotalcite interacts with microwaves to some extent, it is found in this work that incorporation of certain transition metals, copper (II) for instance, enhances the interactions of the mixed hydroxides with microwaves, and, for materials incorporating these transition metal ions, significantly different transformations are induced in the microwave field compared to those induced in a conventional furnace at the same nominal temperature. These structural differences in the products of calcination of layered double hydroxides may have implications for the applications of these materials in catalysis and other fields.