Microwave temperature measurement method

Solvent-free conditions can be employed according to three main methods (a) using only neat reactants (b) reactants adsorbed onto solid supports or (c) reactants in the presence of phase transfer catalysts (in the case of anionic reactions). Besides the apparent potential benefits in solvent usage, reactions can be conducted conveniently and rapidly, often without temperature measurement in domestic microwave ovens. However, they now are often carried out under more precisely controlled conditions using monomode reactors initially introduced by the former French manufacturer Prolabo. Nowadays, several systems are available that provide facilities for the accurate measurement and monitoring of temperature throughout the reaction by modulation of emitted power with an infrared detector or an optical fibre. 

The specific heat of InN was measured using InN microcrystals obtained by the microwave nitrogen plasma method [20]. The specific heat was obtained using differential scanning calorimeter Setaram DSC 92 with a precision better than 1% for the entire temperature range the results of these measurements are listed in TABLE 3. 

Reliable temperature measurement in a microwave reaction presents a considerable challenge to the experimentalist, as the microwave field directly affects conventional instruments such as thermometers and thermocouples. Although thermocouples may be used if they are suitably shielded and earthed, there is an inevitable perturbation to the microwave field pattern. A number of other methods are available that are appropriate to use at moderate temperatures. A gas pressure thermometer, or a microwave-transparent liquid thermometer, may be used as inexpensive options, whilst thermal imaging and fluoro-optic thermometry, although expensive, provide more reliable, higher precision information. 

Here we would like to remark that correct and/or complete description of the setup used, the method of temperature measurement, the reaction size, and the energy input are especially important in a microwave procedure [20, 76). 

To show an application of the method of linear least squares to data collected in a laboratory, a procedure has been developed in which a beaker containing water was heated in a domestic microwave oven, and the water temperature measured as a function of time and power. Students obtained a regression line for each power level screened and determined the intercept and slope of the line. They then compared and contrasted the values obtained for initial temperature and power input using the linear regression with those set experimentally, outlining sources of error. 

Abstract— Hypothermic brain treatment for newborn babies are currently hindered by the lack of appropriate techniques for continuous and non-invasive measurement of deep brain temperature. Microwave radiometry (MWR) is one of the promising methods that is completely passive and inherently safe. Five-band microwave radiometer system and its feasibility were reported with a confidence interval level of the temperature estimation of about 1.6 °C at 5 cm depth from the surface. This result was not good enough for clinical application because clinical requirement is less than 1 °C for both accuracy and stability. This paper describes the improved result of temperature resolutions of the five radiometer receivers, and shows the new confidence interval obtained form temperature measurement experiment using an agar phantom based on a water-bath. Temperature resolutions were 0.103, 0.129, 0.138, 0.105 and 0.111 °C for 1.2, 1.65, 2.3, 3.0 and 3.6 GHz receiver, respectively, and new confidence interval was 0.51 °C at 5 cm from surface. We believe that the system takes a step closer to the clinical hypothermic treatment. 

The microwave irradiation was generated using a reactor setup that allowed accurate measurements of internal reaction temperature using fiber-optic probes. Experiments were carried out under at least two different power values, and also with simultaneous external cooling when a higher power of microwave radiation was applied. The same method of temperature measurement was also used in experiments with conventional heating. 

Figure 39. Light-off curves of methane conversion as a function of temperature measured with (a) MLC-60 (microwave-assisted method), (b) CLC-60 (eonventional method), and (c) bulk LaCoOs perovskites. The inset shows the corresponding Arrhenius plot[39].

These results provide clear evidence for the existence of selective heating effects in MAOS involving heterogeneous mixtures. It should be stressed that the standard methods for determining the temperature in microwave-heated reactions, namely with an IR pyrometer from the outside of the reaction vessel, or with a fiber-optic probe on the inside, would only allow measurement of the average bulk temperature of the solvent, not the true reaction temperature on the surface of the solid reagent. 

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