Mechanisms for nonthermal effects on ionic mobility during microwave processing of crystalline solids

1992 ◽  
Vol 7 (2) ◽  
pp. 495-501 ◽  
Author(s):  
John H. Booske ◽  
Reid F. Cooper ◽  
Ian Dobson
Keyword(s):  
Activation Energy ◽  
Brillouin Scattering ◽  
Microwave Sintering ◽  
Microwave Frequency ◽  
Radiation Energy ◽  
Ionic Mobility ◽  
Microwave Processing ◽  
Tracer Diffusion ◽  
Crystalline Solids ◽  
Resonant Coupling

Models for nonthermal effects on ionic motion during microwave heating of crystalline solids are considered to explain the anomolous reductions of activation energy for diffusion and the overall faster kinetics noted in microwave sintering experiments and other microwave processing studies. We propose that radiation energy couples into low (microwave) frequency elastic lattice oscillations, generating a nonthermal phonon distribution that enhances ion mobility and thus diffusion rates. Viewed in this manner, it is argued that the effect of the microwaves would not be to reduce the activation energy, but rather to make the use of a Boltzmann thermal model inappropriate for the inference of activation energy from sintering-rate or tracer-diffusion data. A highly simplified linear oscillator lattice model is used to qualitatively explore coupling from microwave photons to lattice oscillations. The linear mechanism possibilities include resonant coupling to weak-bond surface and point defect modes, and nonresonant coupling to zero-frequency displacement modes. Nonlinear mechanisms such as inverse Brillouin scattering are suggested for resonant coupling of electromagnetic and elastic traveling waves in crystalline solids. The models suggest that nonthermal effects should be more pronounced in polycrystalline (rather than single crystal) forms, and at elevated bulk temperatures.

ELECTRICAL CONDUCTION IN SUBSTITUTED Li-FERRITES PREPARED BY MICROWAVE PROCESSING

2005 ◽  
Vol 19 (21) ◽  
pp. 1051-1055 ◽  
Author(s):  
MAMATA MAISNAM ◽  
SUMITRA PHANJOUBAM ◽  
H. N. K. SARMA ◽  
CHANDRA PRAKASH ◽  
L. RADHAPIYARI DEVI ◽  
...  
Keyword(s):  
Activation Energy ◽  
Lattice Constant ◽  
Electrical Conduction ◽  
Spinel Structure ◽  
Single Phase ◽  
Microwave Sintering ◽  
Microwave Processing ◽  
Conventional Sintering

Samples with representative formula Li 0.45 Ni 0.1 Mn 0.1 Fe 2.35 O 4 have been sintered by conventional sintering technique and microwave sintering technique. Both the samples showed single-phase with spinel structure. The lattice constant for the microwave sintered (MS) sample showed a lower value than the conventionally sintered (CS) sample. The density of the MS sample has been found to be higher than the CS sample. And MS sample showed a higher value of resistivity and activation energy compared to the CS sample. The possible mechanisms are discussed.

Effect of High-Frequency Microwaves on the Microhardness of Alumina Ceramic

2016 ◽  
Vol 872 ◽  
pp. 114-117 ◽  
Author(s):  
I Nyoman Sudiana ◽  
Seitaro Mitsudo ◽  
Muhammad Zamrun Firihu ◽  
Haji Aripin
Keyword(s):  
High Frequency ◽  
Microwave Sintering ◽  
Interaction Mechanism ◽  
Microwave Frequency ◽  
Microwave Processing ◽  
Conventional Heating ◽  
Physical Mechanisms ◽  
Microwave Effect ◽  
Series Of Experiments ◽  
Very High

Microwave processing of ceramics has attracted much research interest because of its significant advantages over the conventional one. Most researchers compared processes that occurred during the microwave and conventional heating at the same temperature and time. The enhancements found in the former method are indicated as a microwave effect which is usually used for explaining the phenomena in microwave processing. Numerous recent studies have been focused on the effect to elucidate the microwave interaction mechanism with materials. This paper will present effect of very high microwave frequency to hardness of sintered alumina. The sintering results were taken from a series of experiments to study the microwave effect on properties of alumina. Microwave sintering was performed by using the 300 GHz microwave sintering system. Some possible physical mechanisms are also discussed.

Lithium tracer diffusion in LiNi0.33Mn0.33Co0.33O2 cathode material for lithium-ion batteries

2021 ◽  
Vol 23 (10) ◽  
pp. 5992-5998
Author(s):  
Daniel Uxa ◽  
Helen J. Holmes ◽  
Kevin Meyer ◽  
Lars Dörrer ◽  
Harald Schmidt
Keyword(s):  
Activation Energy ◽  
Cathode Material ◽  
Lithium Ion Batteries ◽  
Lithium Ion ◽  
Tracer Diffusion ◽  
Arrhenius Law

Lithium tracer diffusivities in LiNi0.33Mn0.33Co0.33O2 cathode material for lithium-ion batteries follows the Arrhenius law with an activation energy of 0.85 eV.

Microwave frequency combs source based on Brillouin scattering

2015 ◽  
pp. 579-582
Author(s):  
Peng Zhang ◽  
Tianshu Wang ◽  
Wanzhuo Ma ◽  
Lizhong Zhang ◽  
Shoufeng Tong ◽  
...  
Keyword(s):  
Brillouin Scattering ◽  
Microwave Frequency ◽  
Frequency Combs

Oxygen diffusion in amorphous and partially crystalline gallium oxide

2019 ◽  
Vol 21 (8) ◽  
pp. 4268-4275 ◽  
Author(s):  
Alexandra von der Heiden ◽  
Manuel Bornhöfft ◽  
Joachim Mayer ◽  
Manfred Martin
Keyword(s):  
Activation Energy ◽  
Diffusion Coefficients ◽  
Low Temperatures ◽  
Oxygen Diffusion ◽  
Gallium Oxide ◽  
Tracer Diffusion ◽  
Tof Sims ◽  
Tracer Diffusion Coefficients ◽  
Oxygen Tracer

We established a TTT diagram of crystallisation of gallium oxide. Determination of oxygen tracer diffusion coefficients by IEDP/ToF-SIMS allowed us to access the activation energy for amorphous GaO1.5 at low temperatures.

Microwave Processing of Silicon Nitride

1990 ◽  
Vol 189 ◽  
Author(s):  
T. N. Tiegs ◽  
J. O. Kiggans ◽  
H. D. Kimrey
Keyword(s):  
Silicon Nitride ◽  
Grain Boundary ◽  
Microwave Heating ◽  
Grain Growth ◽  
Microwave Power ◽  
Microwave Sintering ◽  
Microwave Processing ◽  
Microwave Furnace

ABSTRACTMicrowave sintering of Si3N4—based materials showed improved densification as compared to samples heated conventionally under similar conditions. Accelerated nitridation of Si in the microwave furnace to produce Si3N4 was also observed. Dense Si3N4, annealed by microwave heating, exhibited enhanced grain growth; however preferential coupling of the microwave power to the grain—boundary phases in the present experiments resulted in their degradation.

Elastic After-Effect Due to Oxygen Relaxation in Yba2Cu3O7−δAbove Tc

1990 ◽  
Vol 209 ◽  
Author(s):  
J. R. Cost ◽  
P. E. Armstrong ◽  
R. B. Poeppel ◽  
J. T. Stanley
Keyword(s):  
Activation Energy ◽  
Relaxation Time ◽  
Internal Friction ◽  
Relaxation Times ◽  
Tracer Diffusion ◽  
Induced Motion ◽  
Arrhenius Temperature Dependence ◽  
After Effect ◽  
Friction Measurements ◽  
Arrhenius Temperature

ABSTRACTIsothermal elastic after-effect measurements to obtain relaxation times for the stress-induced motion of oxygen in YBa2Cu3O7−δ have been made from 50°C to 110°C. These results extend our previous internal friction measurements of the same oxygen relaxation to lower temperatures. The combined results, which cover nine orders of magnitude in relaxation time, show a classical Arrhenius temperature dependence, activation energy Q−1.13±0.01 eV and attempt frequency τ0−1.6×10−13 s (log τ0−.12.79±0.13). The mechanism of the relaxation is considered to be stress-induced ordering of oxygen atoms on theCuO basal plane. Diffusivities obtained from these results are compared with those from tracer diffusion of oxygen.

Microwave Processing and Sintering of PZT and PLZT Ceramics

1988 ◽  
Vol 124 ◽  
Author(s):  
W. B. Harrison ◽  
M. R. B. Hanson ◽  
B. G. Koepke
Keyword(s):  
Lead Titanate ◽  
Microwave Sintering ◽  
Ferroelectric Properties ◽  
Lead Zirconate ◽  
Microwave Processing ◽  
High Density ◽  
Pzt Ceramics ◽  
Conventional Sintering ◽  
Processing Techniques ◽  
Fast Firing

ABSTRACTMicrowave processing techniques were established for all of the thermal treatment steps necessary to prepare high density PZT and PLZT. The microstructure and ferroelectric properties of the microwave processed materials were compared to conventionally sintered and fast fired PZT. Unique high density, small grain size, PZT and PLZT were obtained by microwave sintering either conventionally or fully microwave processed powders. It was estimated that microwave sintering would use only five percent of the energy used by conventional sintering.The suitability of microwave processing for the production of two modifications (Sr and La) of lead zirconate - lead titanate (PZT) ceramics was investigated in this program. A commercial microwave oven was used to evaluate drying, calcining, binder burnoff, and sintering. These materials were then compared to those produced by fast-firing and conventional sintering methods.

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