Microwave Athermal Effects in Chemistry: A Myth’s Autopsy: Part II: Orienting effects and thermodynamic consequences of electric field.

Stuerga, D.; Gaillard, P.

doi:10.1080/08327823.1996.11688300

Cited by 88 publications

(83 citation statements)

References 7 publications

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“…Figure 1.11 gives the three-dimensional curves depicting the dependence dielectric properties on frequency and temperature [70]. Depending on the values of the working frequency and the relaxation frequency, three general cases can be observed: case 1, where the real and imaginary parts of the dielectric permittivity decrease with temperature (working frequency lower than relaxation frequency); case 2, where the real and imaginary parts of the dielectric permittivity increase with temperature (working frequency higher than relaxation frequency); and case 3, where the real and/or imaginary part of the dielectric have a maximum (working frequency very close to relaxation frequency).…”

Section: Thermal Dependency Of Dielectric Permittivitymentioning

confidence: 99%

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Microwave‐Material Interactions and Dielectric Properties, Key Ingredients for Mastery of Chemical Microwave Processes

Stuerga¹

2006

Microwaves in Organic Synthesis

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The main focus of the revised edition of this first chapter is essentially the same as the original -to explain in a chemically intelligible fashion the physical origin of microwave-matter interactions and, especially, the theory of dielectric relaxation of polar molecules. This revised version contains approximately 60% new material to scan a large range of reaction media able to be heated by microwave heating. The accounts presented are intended to be illustrative rather than exhaustive. They are planned to serve as introductions to the different aspects of interest in comprehensive microwave heating. In this sense the treatment is selective and to some extent arbitrary. Hence the bibliography contains historical papers and valuable reviews to which the reader anxious to pursue particular aspects should certainly turn.It is the author's conviction, confirmed over many years of teaching experience, that it is much safer -at least for those who rate not trained physicists -to deal intelligently with an oversimplified model than to use sophisticated methods which require experience before becoming productive. Because of comments about the first edition, however, the author has included more technical material to enable better understanding of the concepts and ideas. These paragraphs could be omitted, depending on the level of comprehension of the reader. They are preceded by two different symbols -k for TOOLS and j for CONCEPTS.After consideration of the history and position of microwaves in the electromagnetic spectrum, notions of polarization and dielectric loss will be examined. The orienting effects of electric fields and the physical origin of dielectric loss will be analyzed, as also will transfers between rotational states and vibrational states within condensed phases.Dielectric relaxation and dielectric losses of pure liquids, ionic solutions, solids, polymers and colloids will be discussed. Effect of electrolytes, relaxation of defects within crystals lattices, adsorbed phases, interfacial relaxation, space charge polarization, and the Maxwell-Wagner effect will be analyzed. Next, a brief overview of 1 thermal conversion properties, thermodynamic aspects, and athermal effects will be given.

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Section: Thermal Dependency Of Dielectric Permittivitymentioning

confidence: 99%

“…1.11. Change of the complex dielectric permittivity with frequency and temperature (e 0 is the real part and e 00 is the imaginary part of the dielectric loss) [70].…”

Section: Thermal Dependency Of Dielectric Permittivitymentioning

confidence: 99%

Microwave‐Material Interactions and Dielectric Properties, Key Ingredients for Mastery of Chemical Microwave Processes

Stuerga¹

2006

Microwaves in Organic Synthesis

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“…[19][20][21][22][23][24][25][26][27][28][29] The impact of microwaves on the reaction can be due to a thermal effect 20,23,26 or to an influence on the electronic structure of the reactants, [27][28][29] but this is still a matter of debate. 30,31 A new tool for studying surface chemistry under microwave irradiation can help understanding.…”

Section: Introductionmentioning

confidence: 99%

Infrared and microwaves at 5.8 GHz in a catalytic reactor

Séguin

Thomas

Bazin

et al. 2009

Phys. Chem. Chem. Phys.

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An improved micro-reactor cell for IR spectroscopic studies of heterogeneous catalysis was built around a 5.8 GHz microwave cavity. The reactor can operate at 20 bars and with conventional heating up to 720 K, with reactant gas flows velocities (GHSV) from 25 000 to 50 000 h À1 . The temperature of the sample under microwave irradiation was measured by time resolved IR emission spectroscopy. The first experiment performed was the IR monitoring of the desorption of carbonates induced by irradiating an alumina sample by microwaves at 5.8 GHz.

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“…For example, it has been hypothesised that molecules align with the microwaves to make collisions more efficient, or even that microwaves trigger reactions directly. Currently, there is a large body of evidence suggesting these effects do not exist [133,134,129] but direct effects have not been completely disproven and the debate continues.…”

Section: Microwave Assisted Catalysismentioning

confidence: 99%