Definitive experimental evidence for <i>Microwave Effects</i>: radically new effects of separated E and H fields, such as decrystallization of oxides in seconds

Roy, Rustum; Peelamedu, Ramesh; Hurtt, Larry; Cheng, Jiping; Agrawal, Dinesh Kumar

doi:10.1007/s10019-002-0199-x

Cited by 183 publications

(106 citation statements)

References 9 publications

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“…29,30 FeCo@Fe is a soft magnetic material with good microwaveabsorbing properties. The microwave solvent used in this study, ethylene glycol (EG), gives the highest 'loss tangent' (tan d > 0.5; i.e., the ability of a material to convert electromagnetic energy into heat energy at a given frequency and temperature) compared to other common solvents such as alcohols, water, DMSO or DMF.…”

Section: Sem Tem and Xrd Characterisationmentioning

confidence: 99%

Enhanced methanol oxidation and oxygen reduction reactions on palladium-decorated FeCo@Fe/C core–shell nanocatalysts in alkaline medium

Fashedemi

Ozoemena

2013

Phys. Chem. Chem. Phys.

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Palladium based nano-alloys are well known for their unique electrocatalytic properties. In this work, a palladium-decorated FeCo@Fe/C core-shell nanocatalyst has been prepared by a new method called microwave-induced top-down nanostructuring and decoration (MITNAD). This simple, yet efficient technique, resulted in the generation of sub-10 nm sized FeCo@Fe@Pd nanocatalysts (mainly 3-5 nm) from a micron-sized (0.21-1.5 mm) FeCo@Fe/C. The electrocatalytic activities of the core-shell nanocatalysts were explored for methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR) in alkaline medium. A negative shift of 300 mV in the onset potential for MOR was observed, with a current thrice that of the Pd/C catalysts. A very low resistance to electron transfer (R ct ) was observed while the ratio of forward-to-backward oxidation current (I f /I b ) was doubled. The overpotential of ORR was significantly reduced with a positive shift of about 250 mV and twice the reduction current density was observed in comparison with Pd/C nanocatalysts with the same mass loading. The kinetic parameters (in terms of the Tafel slope (b) = À59.7 mV dec À1 (Temkin isotherm) and high exchange current density ( j o ) = 1.26 Â 10 À2 mA cm À2) provide insights into the favorable electrocatalytic performance of the catalysts in ORR in alkaline media. Importantly, the core-shell nanocatalyst exhibited excellent resistance to possible methanol cross-over during ORR, which shows excellent promise for application in direct alkaline alcohol fuel cells (DAAFCs).

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Section: Sem Tem and Xrd Characterisationmentioning

confidence: 99%

Enhanced methanol oxidation and oxygen reduction reactions on palladium-decorated FeCo@Fe/C core–shell nanocatalysts in alkaline medium

Fashedemi

Ozoemena

2013

Phys. Chem. Chem. Phys.

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“…A mixture of Ni 52:5 Zr 15 Nb 10 Ti 15 Pt 7:5 glassy alloy powders and Sn powders failed to show noticeable response in E-field like other metals, 13,20) but could couple with MW and be heated up rapidly to appointed temperatures in H-field. As heating was performed by manipulating the three stubs manually, all heating curves are not smooth.…”

Section: Resultsmentioning

confidence: 98%

Microwave Sintering of Ni-Based Bulk Metallic Glass Matrix Composite in a Single-Mode Applicator

Xie

Louzguine-Luzgin

et al. 2008

Mater. Trans.

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Microwave (MW) heating and sintering of Ni-based bulk metallic glass matrix composite, consisting of gas-atomized Ni 52:5 Zr 15 Nb 10 Ti 15 Pt 7:5 glassy alloy and tin powders, was performed without external pressure by using a single-mode applicator. These powders could be heated well in the magnetic field maximum, but not heated enough in the electric field maximum. A bulk sintered body with the retention of the amorphous phase was obtained below 783 K in an inert atmosphere. The addition of Sn particles promoted the densification of the sintered Ni 52:5 Zr 15 Nb 10 Ti 15 Pt 7:5 glassy specimen. The results suggest that the MW sintering of metallic glasses offers a flexibility of fabricating bulk metallic glasses and metallic glass matrix composites.

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“…Whether the acceleration of ceramic reactions is simply the result of more effective heat transfer or whether there are effects of the microwave field itself remains an open question. Recent experiments with ferrites suggest that there is more to microwave reactions than heat transfer [10][11][12] .…”

Section: Referencesmentioning

confidence: 99%

Reaction Mechanisms of Magnesium Silicates With Carbon Dioxide in Microwave Fields

White¹,

Silsbee²,

Kearns³

2004

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The objective of the investigation was to determine whether microwave fields would enhance the reactions of CO 2 with silicates that are relevant to the sequestration of carbon dioxide. Three sets of experiments were conducted. (1) Serpentine and CO 2 were reacted directly at one atmosphere pressure in a microwave furnace. Little reaction was observed. (2) Serpentine was dehydroxylated in a microwave furnace. The reaction was rapid, reaching completion in less than 30 minutes. A detailed investigation of this reaction produced an S-shaped kinetics curve, similar to the kinetics from dehydroxylating serpentine in a resistance furnace, but offset to 100 ˚C lower temperature. This set of experiments clearly demonstrates the effect of microwaves for enhancing reaction kinetics. (3) Reactions of serpentine with alkaline carbonates and in acid solution were carried out in a microwave hydrothermal apparatus. There was a greatly enhanced decomposition of the serpentine in acid solution but, at the temperature and pressure of the reaction chamber (15 bars; 200 ˚C) the carbonates did not react. Overall, microwave fields, as expected, enhance silicate reaction kinetics, but higher CO 2 pressures are needed to accomplish the desired sequestration reactions. These reactions are thermodynamically favorable but suffer from exceeding slow reaction rates. Research by others has shown that reaction rates can be accelerated by use of aqueous carbonate solutions and high CO 2 pressures. The proposed research offers an alternative rate enhancement mechanism through the use of microwave fields. Scope of Work and Task ListThe Scope of Work and list of tasks are taken directly from the original proposal. Progress and accomplishments on the tasks are then summarized in the sections that follow.Two series of experiments were proposed. In series (1) a gas stream of CO 2 containing variable amounts of water vapor would be reacted directly with the magnesium silicates at modest temperatures in a microwave cavity. The objective would be to determine the rate of reaction as a function of temperature, water vapor partial pressure, magnesium silicate particle size, and microwave power. In series (2) experiments, aqueous solutions would be reacted with CO 2 under pressures up to 80 bars and temperatures up to 200 C in a Teflon high pressure reactor in a microwave field. One objective of this portion of the research would be to compare the efficacy of microwave processing with similar compositions, temperatures and pressures without microwaves. Task 1. Adapt existing microwave equipment for continuous gas stream reaction.Task 2. React magnesium silicates with wet CO 2 at a sequence of water contents, temperatures, and microwave power levels.Task 3. Characterize products from Task 2 experiments and determine rates of reaction.Task 4. Construct equipment for microwave hydrothermal experiments.Task 5. React silicates in aqueous alkali carbonate solutions at autogeneous steam pressures in the microwave field.Task 6. React silicates in aqueous...

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Definitive experimental evidence for Microwave Effects: radically new effects of separated E and H fields, such as decrystallization of oxides in seconds

Cited by 183 publications

References 9 publications

Enhanced methanol oxidation and oxygen reduction reactions on palladium-decorated FeCo@Fe/C core–shell nanocatalysts in alkaline medium

Enhanced methanol oxidation and oxygen reduction reactions on palladium-decorated FeCo@Fe/C core–shell nanocatalysts in alkaline medium

Microwave Sintering of Ni-Based Bulk Metallic Glass Matrix Composite in a Single-Mode Applicator

Reaction Mechanisms of Magnesium Silicates With Carbon Dioxide in Microwave Fields

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