Microwave Ignition Research Articles

Morphology and Phase Evolution in Microwave Synthesized Al/Fe3O4 System

Thermite reaction between Al/Fe3O4 raised by microwave (MW) heating under N2 atmosphere has been investigated, and compared with that by the electric furnace. In addition to the stoichiometric ratio for the production of metallic iron and alumina, mixture with slightly lower in Al content is also studied. As thermite reaction is highly exothermic, melting of reaction product and destruction of microstructure may occur, which corresponds to the enthalpy and adiabatic temperature of the reaction. Hence, to avoid this problem, reaction coupled with a smaller driving force by controlling the MW ignition condition at low temperature exotherm has been investigated. The phase and microstructure evolution during the reaction were analyzed by differential thermal analysis (DTA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Thermogram of the DTA analysis, irrespective of their mole ratio, recorded two exothermic peaks, one at ~ 1310oC and another one at ~ 1370oC. When heated by microwave at 955oC, the main products were identified as Al, FeO and Fe, minor amount of Fe3O4 and some Fe and alumina were detected. When heating to 1155oC, Al and Fe3O4 peaks disappeared, formation of Fe-Al alloy was observed. For sample heated at 1265°C, a porous body was obtained. Micron sized metal particles with complex morphology, irregular in size and shapes were formed, uniformly distributed within the spinel hercynite and/or alumina matrix. In contrast, conventional heating produced no porous products. Formation of alumina is also observed around the metal particles. Controlling of the reaction progress was possible while heating the sample by MW around the low temperature exotherm region, whereas the combustion wave could not be self-propagated.

Space Ignition Method Using Microwave Radiation

Highest efficiency in fuel consumption — a target the Micro Wave Ignition AG faced by developing its new microwave ignition of combustion engines. This space ignition method can be utilised to save up to 30 % fuel consumption and prevents up to 80 % of pollutant emissions.

Emission Properties of Compact Antenna-Excited Super-High Pressure Mercury Microwave Discharge Lamps

A compact high-intensity microwave discharge lamp and ignition system have been investigated using a couple of antennas and a solid-state microwave generator. It is found that the antenna-excited microwave discharge lamps can sustain mercury discharges at pressures higher than 100 atm with 2.45 GHz microwave power lower than 80 W, and that a stable plasma column is generated isolated from the lamp wall. The radial radiant profile is much different from that of conventional microwave discharge lamps without electrodes.

Microwave-Assisted Ignition

AbstractThe microwave heating and ignition of a combustible material is modeled and analyzed in the small Biot number and large activation energy regimes. Both the temporal and spatial evolution of the temperature within the material are described. The ignition characteristics are determined by a localized equation for the perturbation to the inert temperature, which is shown to exhibit thermal runaway behavior. Analysis of this local equation provides explicit ignition conditions in terms of the physical parameters in the problem.

Microwave ignition and combustion synthesis of composites

Microwave processing and combustion synthesis have been united to fabricate composite materials. The internal heating with microwave energy initiates the ignition in the center of the sample and the combustion wave font propagates radially outward. Under suitable processing conditions the wave front can be controlled in contrast with the self-propagation in conventional combustion synthesis. The exothermic energy released during the combustion reaction assists in microwave heating (microwave absorption increases with increasing temperature). Thus microwave ignition, controlled combustion and sintering of dense compacts allows fabrication of composites which are difficult to obtain with conventional self-propagating high-temperature synthesis.

Unique Application of Microwave Energy to the Processing of Ceramic Materials

Microwave energy has been used to internally ignite combustible materials, resulting in a relatively uniform combustion wavefront propagating radially outward. Since microwave heating and combustion synthesis assist each other, samples of Ti + C reactants having compact density greater than 80 percent of theoretical values have been ignited successfully. Internal heating by microwave radiation has also been utilized to control propagation of the combustion wavefront in high density compacts of TiO2 + Al + C reactants. Microwave ignition and controlled combustion of dense compacts followed by sintering has allowed fabrication of A12031TiC composites without significant expansion usually observed with conventional self-propagating high-temperature synthesis (SHS).

Computer Controlled Microwave VVaveguide for Sample Heating and Dissolution

Microwave energy has been used to internally ignite combustible materials, resulting in a relatively uniform combustion wavefront propagating radially outward. Since microwave heating and combustion synthesis assist each other, samples of Ti + C reactants having compact density greater than 80 percent of theoretical values have been ignited successfully. Internal heating by microwave radiation has also been utilized to control propagation of the combustion wavefront in high density compacts of TiO2 + Al + C reactants. Microwave ignition and controlled combustion of dense compacts followed by sintering has allowed fabrication of A12031TiC composites without significant expansion usually observed with conventional self-propagating high-temperature synthesis (SHS).