scholarly journals The importance of ionic conduction in microwave heated polyesterifications

2020 ◽  
Vol 5 (3) ◽  
pp. 495-505 ◽  
Author(s):  
George Hargreaves ◽  
Adam Buttress ◽  
Georgios Dimitrakis ◽  
Christopher Dodds ◽  
Pierre Martin-Tanchereau ◽  
...  
Keyword(s):  
Microwave Heating ◽  
Reaction Rate ◽  
Ionic Conduction ◽  
Final Conversion

Significant increases in the reaction rate and final conversion of a model polyesterification are reported by the use of microwave heating.

Synthesis of Oximes in the Microwave Oven

1992 ◽  
Vol 57 (11) ◽  
pp. 2407-2412 ◽  
Author(s):  
Monika Puciová ◽  
Štefan Toma
Keyword(s):  
Microwave Heating ◽  
Reaction Rate ◽  
Microwave Oven ◽  
Effect Of Solvents

The synthesis of a broad range of oximes has been studied. It was found that the application of microwave heating enhanced dramatically the reaction rate, and practically quantitative yields of oximes were isolated after less than 1-min heating in the most cases. The effect of solvents on the course of the reaction was also studied.

Microwave Nitrudation of Silicon Compacts Utilizing a Temperature Gradient

1992 ◽  
Vol 287 ◽  
Author(s):  
Jeffrey J. Thomas ◽  
Hamlin M. Jennings ◽  
D. Lynn Johnson
Keyword(s):  
Silicon Nitride ◽  
Temperature Gradient ◽  
Microwave Heating ◽  
Reaction Rate ◽  
Nitrogen Depletion

ABSTRACTSilicon compacts nitrided utilizing the temperature gradient inherent to microwave heating were more fully converted to silicon nitride than was possible with similar compacts nitrided isothermally. Although nitrogen depletion prevented the reaction rate in the center from exceeding that at the surface, the temperature gradient partially counteracted the effect of nitrogen depletion. Thus the microwave-heated specimens could be nitrided fully before the reduction in porosity that accompanies the reaction eliminated the diffusion of nitrogen into the compact.

Nitridation of Non-Isothermal Silicon Compacts

1992 ◽  
Vol 269 ◽  
Author(s):  
Jeffrey J. Thomas ◽  
Renee R. Jesse ◽  
D. Lynn Johnson ◽  
Hamlin M. Jennings
Keyword(s):  
Silicon Nitride ◽  
Temperature Gradient ◽  
Microwave Heating ◽  
Reaction Rate ◽  
Conventional Heating

ABSTRACTThe use of microwave heating for the processing of reaction-bonded silicon nitride offers at least two advantages over conventional heating methods. First, the reaction can be made to proceed preferentially in the interior of the reacting compact by maximizing the temperature gradient resulting from microwave heating. This helps maintain the flow of nitrogen into the compact during the later stages of the reaction, when the overall porosity is reduced. Second, the reaction rate can be controlled by changing the power, which gives better control over the processing than can be obtained using conventional heating.

Final Conversion and Reaction Rate of CaO Hydration in Different Experimental Systems

2005 ◽  
Vol 31 (4) ◽  
pp. 253-258 ◽  
Author(s):  
Shokrat Abliz ◽  
Hiranao Ogura ◽  
Hiroyuki Kage
Keyword(s):  
Reaction Rate ◽  
Final Conversion ◽  
Experimental Systems

scholarly journals Special Issue on “Microwave Applications in Chemical Engineering”

Processes ◽  
2020 ◽  
Vol 8 (4) ◽  
pp. 491
Author(s):  
Huacheng Zhu ◽  
Kama Huang ◽  
Junwu Tao
Keyword(s):  
Heating Rate ◽  
Microwave Heating ◽  
Chemical Reactions ◽  
Chemical Industry ◽  
Reaction Rate ◽  
Chemical Engineering ◽  
Special Issue ◽  
Fast Heating ◽  
Microwave Applications ◽  
By Products

Microwave heating has been widely used in the chemical industry because of its advantages, such as fast heating rate, selective and controllable heating, increasing reaction rate and reducing by-products in chemical reactions. The Special Issue contains research on microwave applications in chemical engineering.

Investigation of Selective Microwave Heating Phenomena in the Reactions of 2-Substituted Pyridines

2017 ◽  
Vol 70 (7) ◽  
pp. 776 ◽  
Author(s):  
Péter Bana ◽  
István Greiner
Keyword(s):  
Microwave Heating ◽  
Boundary Layers ◽  
Vessel Wall ◽  
Reaction Rate ◽  
Macroscopic Scale ◽  
Microwave Effect ◽  
Heating Effects ◽  
Localized Heating ◽  
Substituted Pyridines ◽  
Comparison Technique

Debated selective microwave heating effects were investigated in a rearrangement and a benzylation reaction involving 2-substituted pyridines. An accurate, reproducible comparison technique and simultaneous temperature measurement using both external infrared and internal fibre optic sensors were utilized. The experimental details of the benzylation reaction were thoroughly addressed to resolve the inconsistencies that have been discussed previously in the literature. Hidden inhomogeneities in temperature and concentration were revealed within the reaction mixtures during microwave heating, which could be prevented by the modification of the vessel wall using an inert fluoropolymer liner. Instead of the previously proposed microscopic thermal microwave effect, the enhanced reaction rate could be explained by macroscopic-scale localized heating in the boundary layers close to the vessel surface in the microwave-heated experiment.

Stress-Induced Ordering in Y203-Stabilized Tetragonal Zr02

1985 ◽  
Vol 43 ◽  
pp. 222-223
Author(s):  
J. Y. Koo ◽  
M. P. Anderson
Keyword(s):  
Electron Diffraction ◽  
Ionic Conduction ◽  
Electron Diffraction Study ◽  
Ceramic Materials ◽  
Bright Field Image ◽  
Transformation Toughening ◽  
Ion Milling ◽  
Thin Foils ◽  
Carbon Coated ◽  
Convergent Beam

Tetragonal Zr02 has been used as a toughening phase in a large number of ceramic materials. In this system, complex diffraction phenomena have been observed and an understanding of the origin of the diffraction effects provides important information on the nature of transformation toughening, ionic conduction, and phase destabilization. This paper describes the results of an electron diffraction study of Y203-stabilized, tetragonal Zr02 polycrystals (Y-TZP).Thin foils from the bulk Y-TZP sample were prepared by careful grinding and cryo ion-milling. They were carbon coated and examined in a Philips 400T/FEG microscope. Fig. 1 shows a typical bright field image of the 100% tetragonal(t) Zr02. The tetragonal structure was identified by both bulk x-ray diffraction and convergent beam electron diffraction (Fig. 2. A local region within a t-Zr02 grain was subjected to an intense electron beam irradiation which caused partial martensitic transformation of the t-Zr02 to monoclinic(m) symmetry, Fig. 3 A.

A transmission electron microscopic study of structural transitions in fast ionic conductors

1987 ◽  
Vol 45 ◽  
pp. 156-157
Author(s):  
R. B. Queenan ◽  
P. K. Davies
Keyword(s):  
Optical Properties ◽  
Ionic Conduction ◽  
Recent Observation ◽  
Ionic Conductivities ◽  
Sodium Aluminate ◽  
Two Dimensions ◽  
Ionic Conductors ◽  
Electron Microscopic ◽  
Transmission Electron ◽  
Trivalent Cations

Na ß“-alumina (Na1.67Mg67Al10.33O17) is a non-stoichiometric sodium aluminate which exhibits fast ionic conduction of the Na+ ions in two dimensions. The Na+ ions can be exchanged with a variety of mono-, di-, and trivalent cations. The resulting exchanged materials also show high ionic conductivities.Considerable interest in the Na+-Nd3+-ß“-aluminas has been generated as a result of the recent observation of lasing in the pulsed and cw modes. A recent TEM investigation on a 100% exchanged Nd ß“-alumina sample found evidence for the intergrowth of two different structure types. Microdiffraction revealed an ordered phase coexisting with an apparently disordered phase, in which the cations are completely randomized in two dimensions. If an order-disorder transition is present then the cooling rates would be expected to affect the microstructures of these materials which may in turn affect the optical properties. The purpose of this work was to investigate the affect of thermal treatments upon the micro-structural and optical properties of these materials.

Locating Al in the DABCO catalyst before and after Al extraction

1990 ◽  
Vol 48 (4) ◽  
pp. 265-267
Author(s):  
Kathleen B. Reuter
Keyword(s):  
Active Site ◽  
Inverse Relationship ◽  
Transverse Direction ◽  
Reaction Rate ◽  
Acid Phosphate ◽  
Fracture Surfaces ◽  
Al Content ◽  
Before And After ◽  
Relationship Of

The reaction rate and efficiency of piperazine to 1,4-diazabicyclo-octane (DABCO) depends on the Si/Al ratio of the MFI topology catalysts. The Al was shown to be the active site, however, in the Si/Al range of 30-200 the reaction rate increases as the Si/Al ratio increases. The objective of this work was to determine the location and concentration of Al to explain this inverse relationship of Al content with reaction rate.Two silicalite catalysts in the form of 1/16 inch SiO2/Al2O3 bonded extrudates were examined: catalyst A with a Si/Al of 83; and catalyst B, the acid/phosphate Al extracted form of catalyst A, with a Si/Al of 175. Five extrudates from each catalyst were fractured in the transverse direction and particles were obtained from the fracture surfaces near the center of the extrudate diameter. Particles were also obtained from the outside surfaces of five extrudates.

Sign in / Sign up

Export Citation Format

Share Document