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The feasibility of microwave dehydrating flax fiber was evaluated using a commercial domestic microwave oven at four power settings representing 200, 300, 400 and 500 Watt (W) power level. Due to the possibility of local heating and consequent fiber degradation, the changes in color of the flax fiber at different levels of temperature were also investigated. The dehydration processes at various power levels were simulated by Page model. Based on visual inspection, color analysis and scanning electron microscopy (SEM) of the fiber, it was revealed that discoloration of the fiber occurred at about 170 degrees C. At 200 and 300 W power level, after 10 minutes of dehydrating, the moisture content of the fiber reached from initial 7.9% close to 2.0 and 1.0%, respectively. For 400 W power level, the moisture content of the fiber dropped to 0. 10% in about 9.5 minutes. Major discoloration of the fiber was noticed when dehydration was proceed beyond 4.5 minutes for 500 W treatment. The Page model very well fitted the experimental data. The coefficients of determination calculated from the model and the experimental data increased with increase in applied microwave power

A parameter optimisation model is developed to find the parameters that have significant effects on homogeneous temperature distribution during microwave processing of materials. Electromagnetic, thermal and processing parameters are collected for a wide variety of materials and the heating profiles are calculated using a stationary 1D-electrothermal model. A measure of temperature homogeneity is obtained from the heating profiles by statistical calculations of normalised variance (the response variable). The processing parameters (power, temperature, size of the material sample) are optimisedfor all of these materials for a minimum normalised variance which allows maximum change of +/-3% Taverage on the T-distribution to meet most of the industrial process requirements. This mathematical model suggests a group of materials, which requires modifications in processing conditions to achieve uniform heating.

It is not rare to hear arguments against the use of thermocouples for taking temperatures in processes that are taking place under microwave fields. However, the simplicity of this device makes it attractive to consider its use. One question that arises when thermocouples are employed is whether the electric field perturbs the measurement, and if the thermocouple affects the processing. The process that was chosen for conducting this test was the synthesis of spinel (MgAl2O4) using microwaves as a power supply and hematite (Fe2O3) as an additive for both spinel formation promotion and susceptor. The alumina-based systems are very important to study because this is one of the most common ingredients in refractory materials. There are many discussions about the improvement of the process when microwaves are used, but a kinetic comparison cannot be performed if the temperature is unknown, and that is the reason for emphasizing the measurement techniques. The analysis of the obtained samples was carried out by X-ray diffraction of powders. The results of this work show that there is no difference between the products obtained when the thermocouple was inserted in the system, compared to processing without it; hence the thermocouple is appropriate for this application.

The material properties of greatest importance in microwave processing of a dielectric are the complex relative permittivity epsilon = epsilon'-jepsilon", and the loss tangent, tan delta = epsilon"/epsilon'. This paper describes two convenient laboratory based methods to obtain epsilon', epsilon" and hence tan delta of fibre-reinforced thermoplastic (FRTP) composites. One method employs a microwave network analyzer in conjunction with a waveguide transmission technique, chosen because it provides the widest possible frequency range with high accuracy. The values of the dielectric constant and dielectric loss of glass fibre reinforced (33%) low density polyethylene, LDPE/GF (33%), polystyrene, PS/GF (33%), and Nylon 66/GF (33%), were obtained. Results are compared with those obtained by another method using a high-temperature dielectric probe.

Nanocomposites of Zn/Al-layered double hydroxide(anthraquinone-2,6-disulfonate) were synthesized by spontaneous direct assembly of inorganic and organic phases from aqueous solution. Powder X-ray diffraction patterns showed that a pure, single nanocomposite phase of good crystallinity was obtained using 1.0 M antraquinone-2,6-disulfonate ion (AQ26) and aging at 80 degrees C using conventional heating for 7 days or 0.5 h under microwave radiation, and these samples are denoted as ZAAN26C or ZAAN26MH, respectively. Zn/Al-nitrate-layered double hydroxide synthesized by a conventional method (ZANLC) showed a basal spacing of 8.3 A while both the nanocomposites showed 18.8 A as a result of AQ26 intercalation. FTIR study showed that the resulting nanocomposites are free from nitrate, the co-anion present in the mother liquor, indicating that only AQ26 is preferred during intercalation for the formation of the nanocomposite. The Brunauer, Emmet and Teller (BET) and micropore surface areas for ZAAN26C decreased relative to the ZANLC from 16.2 to 4.7 and 1.6 to 1.3 m2/g, respectively. These results indicate that AQ26 can be rapidly interdcalated in layered double hydroxide using microwave-aging resulting in a nanocomposite.