11:00
Microwave and high frequency material interaction (1)
11:00
15 mins
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NEW DEVICE FOR CONTROLLING THE EVOLUTION OF THE MATERIAL UNDER A MICROWAVE FIELD USING THE DOPPLER EFFECT
Tan-Hoa VUONG
Abstract: The use of microwaves as a source of energy in material processing procedures has brought advantages and disadvantages, in particular difficulties in measuring the physical quantities of the material (eg temperature). Indeed, the usual sensors (apart from those using an optical fiber) cause disturbances and create microwave leaks during the emission phase of the microwave power source. For example, a problem often encountered concerns the measurement by metal thermocouples of the temperature of the product to be treated during the microwave heating. In addition, when chemicals (eg acids) are to be treated, measurements at the core of the product by contact are virtually impossible.
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11:15
15 mins
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MICROWAVE-ACCELARATED RUTHENIUM COMPLEXE SYNTEHSIS: REACTION MODELING USING DIELECTRIC MEASUREMENT AND DENSITY FUNCTION THEORY
Takeko Matsumura
Abstract: Platinum metal complexes are important functional materials as phosphor illuminants.
These metals, rarely occurring in nature, are very hard against chemical reaction.
That means, it is hard process to dissociate M-Cl bond of MCl3 (M; Ir or Ru) to form
new N-M or C-M bonds with organic ligands.
Microwave dielectric effect was focused to dielectric property of reaction media.
The dielectric loss factor, ε”, and conductivity, σ, of metal ions take important roles
of microwave thermal effect. The microwave chemical effect on these platinum metal
complexes are discussed in view of molecular orbital theory with density function
theory.
Fig.1. Real-time monitoring of MW synthesis for Ru(II) complex
References
1. T.Matsumura-Inoue,M.Tanabe, Chem. Lett.,1994,443
2. T. Matsumura-Inoue, Y. Yamamoto, N. Yoshikawa, M. Terashima, Y. Yoshida, A. Fujii ,
K. Yoshino, Optical Materials, ,27（2004）187-191
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11:30
15 mins
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PERMITTIVITY IN MICROWAVE FIRING OF CARBONATES: CALCITE
Angel M. López-Buendía, Beatriz García-Baños, Joaquín Bastida, Joaquín Bastida, M. Mar Urquiola, José M. Catalá-Civera
Abstract: Carbonate minerals are used as raw materials in products requiring firing process in many industrial sectors, e.g. lime, cement, ceramic. Calcium carbonate (calcite, aragonite) is the major component used, with secondary contribution of dolomite (calcium-magnesium carbonate). During heating calcite (CaCO3) is decomposed in CO2 and CaO (lime) at temperatures starting around 600ºC.
Calcite and dolomite show very low loss factor, traditionally considered in the order of magnitude of the materials transparent to the microwaves. However, several factors are involved in the dielectric properties of the carbonates, such as chemical composition, texture or crystallinity.
A study of dielectric properties of carbonates, centered in calcite, has been done to evaluate the microwave properties under different conditions. High purity spar calcite has been used to evaluate the effect of the particular size, mechanical treatment and crystallinity over the dielectric properties. Mechanically treated samples were measured using a powdered sample method in a dielectric kit for vials device at room temperatures. Kinetic of thermal decomposition of calcite was monitored by using a dielectric thermal analysis during microwave (MW-DETA).
X-ray powder diffraction was used several temperature of treatment. Dielectric constant (ε’) and loss factor (ε”) during heating was correlated with the mineralogical changes.
The sensitiveness of the dielectric properties to the nature and pre-treatments of the calcite shows the ability of use of microwave heating for the calcination of carbonates.
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11:45
15 mins
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COMPUTATIONAL VERIFICATION OF RADIO AND MW FREQUENCY HEATINGS USING DENSITY FUNCTIONAL THEORY
Shozo Yanagida, Takeko Matsumura
Abstract: Cyclohexanol solution was reported to heat up under irradiance of radio frequency wave, 0.235, 1.36, 3.22, 4.53, 10.1 NHz.1) The heating was explained as due to entropy change of the solution. On the other hand, density functional theory (DFT) is the most appropriate for molecular modeling (DFT/MM) of aggregated molecular systems that are induced by van der Waals and Coulomb interactions (vdW&Clmb). Hydrogen bonding is the most important vdW&Clmb, and cyclohexanol should hydrogen-bonded in solution. For theoretical understanding of the above-mentioned radio frequency heating, DFT-based molecular modeling (DFT/MM) of cyclohexanol hydrogen-bonded trimer is carried out using computational software “Spartan” (Wavefunction, Inc.) in PC. Figure 1 shows that cyclohexanol trimer forms exothermically (ΔE=-18.6 kcal/mol), having dipole moment of 3.12debye. Interestingly, broad absorption in FIR spectrum (200cm-1~radio-frequency) can be assigned to cyclohexane ring vibration, and then we verify that heating-up phenomena is as due to thermo-upconversion. The same thermo-upconversion is true for microwave (MW)-driven heating. MW-thermal catalytic reaction and Matsumura’s MW quick synthesis of transient metal complexes will be discussed in view of thermo-upconversion.
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