A new range of laboratory furnaces that combine radiant and microwave heating was launched by the UK furnace manufacturer Carbolite at Achema 2006 in Frankfurt.
Carbolite has developed the MAT furnaces in collaboration with C-Tech Innovation Ltd, based near Chester, UK, a leading specialist in microwave-assisted heating technology. The first two models are chamber furnaces with 1200°C and 1600°C maximum operating temperatures and 23 litre and 16 litre capacities respectively. In addition to the conventional radiant heat generated by the furnace elements, up to 1.8kW of power is generated in each model by an industrial 2450 MHz magnetron.
Unlike radiant heat, which is conducted from the outer surface of a sample to the interior, microwaves generate heat immediately within the body of the material. This combined approach produces faster processing rates than both radiant-only and microwave-only systems, which reduces energy usage, throughput times and emissions. More consistent properties can also be achieved in some materials, including greater strength, improved yield and reduced formation of undesirable phases. Processors can also take advantage of the selective heating characteristic of microwaves.
The design of the furnaces combines the controllability of the radiant elements with the thermal equalising effect of the microwave heating system. The controller allows 20-segment programming of both the radiant and the microwave heating, giving users a high degree of flexibility. Over-temperature protection is also included.
Successful applications for microwave-assisted heating include precious metals assaying, burning off wax castings moulds and sintering high-performance ceramics such as zirconia, where benefits include very consistent grain size.
While scaling up microwave-only systems from laboratory to production capacities can be difficult because of the problem of maintaining high power densities over a large area, MAT heating furnaces can be scaled up relatively easily, according to Carbolite.
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