Methods and apparatus are disclosed for generating an electromagnetic field inside a reactor to trigger an exothermic reaction. The design and implementation of the electromagnetics are based on the requirements of a particular exothermic reaction or reactor. For example, the triggering mechanism of a particular exothermic reaction or reactor may require a magnetic field with a specific magnitude, polarity, and/or orientation.

Provided are multi-phase heating systems for bidispersed and polydispersed particle applications. Provided is a multi-phase reactor comprising a reaction chamber for containing a catalyst wherein the catalyst reacts with a fluid material. A heating system arranged around the reaction chamber comprises a first heater for heating a core of the chamber and a second heater for heating a periphery of the chamber, where combined heating from the first and second heaters provide the reaction chamber at a temperature for clustering of the fluid material for reaction with the catalyst. Also provided is an additive manufacturing printer comprising a first heater for heating a core of the chamber and a second heater for heating a periphery of the chamber, wherein combined heating from the first and second heaters provide the chamber at a temperature for clustering of printable material for extrusion through a nozzle.