Dielectric relaxation of some aliphatic ketones in dilute solutions

1976 ◽  
Vol 54 (7) ◽  
pp. 794-799 ◽  
Author(s):  
M. P. Madan
Keyword(s):  
Free Energy ◽  
Relaxation Time ◽  
Dielectric Relaxation ◽  
Relaxation Mechanism ◽  
Relaxation Data ◽  
Nonpolar Solvents ◽  
Aliphatic Ketones ◽  
Entropy Of Activation ◽  
Enthalpy And Entropy ◽  
Dielectric Relaxation Behavior

The dielectric relaxation behavior of 2-butanone, 2-pentanone, 2-heptanone, and 3-nonanone in dilute nonpolar solvents, n-heptane, cyclohexane, benzene, and carbon tetrachloride has been studied in the microwave region at a number of temperatures. The relaxation data have been used to estimate the free energy, enthalpy, and entropy of activation for the relaxation mechanism. The values of the relaxation time for those solutions for which there are available known data agree well with other determinations. The results have been discussed in terms of dipole reorientation by intramolecular and overall molecular rotation and compared, wherever possible, with other similar studies on aliphatic molecules.

Effect of ZnO Nano-Particles on The Dielectric Relaxation Behavior and Thermal Stability of Polycarbonate Host

2011 ◽  
Vol 24 (6) ◽  
pp. 837-852 ◽  
Author(s):  
A.A. Al Jaafari ◽  
A.S. Ayesh
Keyword(s):  
Thermal Stability ◽  
Relaxation Time ◽  
Dielectric Relaxation ◽  
Zno Nanoparticles ◽  
Relaxation Behavior ◽  
Nano Particles ◽  
Effect Of Temperature ◽  
Frequency Range ◽  
Dielectric Relaxation Behavior ◽  
Thermal Stability Of

The influence of ZnO nanoparticles on the dielectric properties, dielectric relaxation behavior, and thermal stability of PC host was investigated at different ZnO nanoparticles concentration. The dielectric study was carried out over a frequency range from 500 Hz up to 1 MHz as a function of ZnO concentration. Results obtained from the best fitting of relative permittivity data with Yan and Rhodes model reveal that the dielectric relaxation is not a single relaxation process and there are two values of relaxation time for each nanocomposite at room temperature and domain frequency range. Furthermore, addition of ZnO nanoparticles to PC host changes the dielectric properties of PC, mainly, increases relative permittivity, dielectric loss, and AC conductivity while decreases the impedance values of PC host. Moreover, effect of temperature on AC conductivity of ZnO-PC nanocomposites at 1 kHz was also considered. Besides, dielectric relaxation behavior of PC was investigated at 165°C (above the glass transition temperature of PC) in the domain frequency range. At this elevated temperature (165°C), dielectric loss data shows a single relaxation peak (α-relaxation) in the domain frequency range and was successfully fitted with Debye equation. Also, it was found that as the content of ZnO nanoparticles increases in the PC host the frequency of the peak maximum ( fmax) shifts toward higher frequency value and as a result decreases the value of relaxation time. Additionally, this study shows that the isothermal effect of ZnO nano particles on the α-relaxation of PC host is similar to the effect of temperature. Both of them have a linear dependence with ln( fmax). Furthermore, addition of ZnO nanoparticles to PC host will decrease the thermal stability and glass transition temperature of PC host. Finally, there is a strong evidence from the obtained dielectric and thermal results that addition of ZnO nanoparticles to PC host will highly enhance the chain mobility and also increase the polar character of PC host.

Studies on the decomposition of tetra-alkylammonium salts in solution. Part II. Dependence of the activation parameters on the structure of the substrate

1969 ◽  
Vol 47 (20) ◽  
pp. 3725-3728 ◽  
Author(s):  
J. T. Burns ◽  
K. T. Leffek
Keyword(s):  
Free Energy ◽  
Nitrogen Atom ◽  
Tertiary Amine ◽  
Chloroform Solution ◽  
Activation Parameters ◽  
Decomposition Reaction ◽  
Energy Correlation ◽  
Entropy Of Activation ◽  
Alkylammonium Salts ◽  
Enthalpy And Entropy

The enthalpy and entropy of activation for the decomposition reaction of seven tetra-alkylammonium iodides in chloroform solution have been measured. All the salts contained the benzyl group attached to the nitrogen atom and decomposed to yield benzyl iodide and a tertiary amine as the only products.A Hammett free energy correlation is made and used to deduce the nature of the transition state, and a rationalization of the variation of the enthalpy and entropy of activation with the structure of the substrate is given.

Dielectric relaxation of some aliphatic ester molecules in solutions

1979 ◽  
Vol 57 (7) ◽  
pp. 1035-1038 ◽  
Author(s):  
M. P. Madan
Keyword(s):  
Relaxation Time ◽  
Dielectric Relaxation ◽  
Relaxation Times ◽  
Activation Parameters ◽  
Dielectric Absorption ◽  
Aliphatic Ketones ◽  
Dielectric Data ◽  
Aliphatic Ester ◽  
Aliphatic Esters ◽  
Intramolecular Rotation

The dielectric absorption of several aliphatic esters has been examined in the microwave region over a range of temperatures in n-heptane, cyclohexane, and benzene. The relaxation times and the thermodynamic parameters have been determined using the measured dielectric data. The values of the relaxation time for those solutions for which there are available known data agree well with other determinations. The relaxation times and the various molar activation parameters have been discussed in terms of dipole reorientation by molecular and intramolecular rotation. It would appear that the relaxation behavior of aliphatic esters is similar to that for other aliphatic molecules, such as aliphatic ketones studied previously.

Correlating Blocking Temperatures in Single Molecule Magnets with Raman Relaxation

2018 ◽  
Author(s):  
Marcus J. Giansiracusa ◽  
Andreas Kostopoulos ◽  
George F. S. Whitehead ◽  
David Collison ◽  
Floriana Tuna ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Single Molecule ◽  
Energy Barrier ◽  
Thermal Relaxation ◽  
Relaxation Mechanism ◽  
Blocking Temperature ◽  
Single Molecule Magnets ◽  
Single Molecule Magnet ◽  
Key Parameter

We report a six coordinate DyIII single-molecule magnet<br>(SMM) with an energy barrier of 1110 K for thermal relaxation of<br>magnetization. The sample shows no retention of magnetization<br>even at 2 K and this led us to find a good correlation between the<br>blocking temperature and the Raman relaxation regime for SMMs.<br>The key parameter is the relaxation time (𝜏<sub>switch</sub>) at the point where<br>the Raman relaxation mechanism becomes more important than<br>Orbach.

Relaxation processes of some simple aliphatic molecules in dilute solutions

1977 ◽  
Vol 55 (4) ◽  
pp. 297-301 ◽  
Author(s):  
M. P. Madan
Keyword(s):  
Carbon Tetrachloride ◽  
Dielectric Relaxation ◽  
Thermodynamic Parameters ◽  
Relaxation Times ◽  
Relaxation Processes ◽  
Dilute Solutions ◽  
Microwave Region ◽  
Nonpolar Solvents ◽  
Dielectric Data ◽  
Intramolecular Rotation

The dielectric relaxation processes of acetone, cyclohexanone, 4-methyl-2-pentanone, and 4-heptanone in dilute nonpolar solvents, n-heptane, cyclohexane, benzene, and carbon tetrachloride have been studied in the microwave region over a temperature range 10 to 60 °C. The relaxation times and the thermodynamic parameters for the activated states have been determined using the measured dielectric data. The results have been discussed in terms of dipole reorientation by molecular and intramolecular rotation and compared, wherever possible, with other similar studies on aliphatic molecules.

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