A.D. Vyas

Dielectric relaxation study of mixtures of 1-propanol with aniline, 2-chloroaniline and 3-chloroaniline at different temperatures using time domain reflectometry

Abstract Complex permitivity spectra of the mixtures of 1-propanol with aniline, 2-chloroaniline and 3-chloroaniline at different temperatures have been measured in the frequency range between 10 MHz to 20 GHz using time domain reflectometry. Dielecric parameters viz, static dielectric constant, relaxation time were obtained from complex permittivity spectra using nonlinear least squares fir method. Using these parameters excess dielectric properties, Kirkwood correlation factor and thermodynamical parameters were determined. Strong molecular association through hydrogen bonding was observed between the pola-polar constituents of the mixtures. Molecular association between aniline and alcohol mixture is found to be affected by substitution of −Cl group at 2- and 3-positions.

Dielectric dispersion and relaxation mechanism of associative + non-associative (rigid) polar molecules at microwave frequencies

Abstract The dielectric behaviour of mixtures of chlorobenzene with methyl alcohol, ethyl alcohol, n-propyl alcohol and tert-butyl alcohol has been measured at microwave frequencies 8.98 GHz and 19.64 GHz and also at 10 kHz and optical frequency at 30°C in dilute solutions of benzene. The permittivity and dielectric loss at different frequencies have been plotted against concentration (weight fraction). The slopes a have been plotted against a in a complex plane. The plots are semicircles indicating a single relaxation mechanism in these mixtures.

Dielectric relaxation studies of some fluoro, chloro, bromo substituted anilines and their mixtures in benzene

Abstract The dielectric absorption of six polar molecules, viz; 2-fluoroaniline, 4-fluroaniline, 2-chloroaniline, 3-chloraniline, 2-bromoaniline, 3-bromoaniline and their binary mixtures in dilute solutions of benzene has been studied at 3 cm microwave region over the temperature range 20–50°C. The relaxation time and thermodynamical parameters, viz; free energy, enthalpy and entropy of activation have been determined using the measured dielectric data. The relaxation times of single component solutions agree well with literature values. The relaxation time of polar mixtures compares reasonably well with the computed values obtained from a relation proposed by M.P. Madan [Can. J. Phys., 58 (1980) 20].

Dielectric relaxation studies of some aliphatic alcohols and their mixtures in benzene solutions

Abstract Dielectric absorption of four aliphatic alcohols, viz., methyl alcohol, ethyl alcohol, n-propyl alcohol, tert-butyl alcohol and their binary mixtures, mixtures of these alcohols with dimethyl formamide and 2-fluoroaniline has been studied in the 3 cm microwave region at a temperature of 30°C in benzene. In alcohols and their mixtures the tan σ - concentration curve shows a marked increase in the concentration range 0.02 – 0.05 weight fraction. This behaviour has been explained as due to the formation of complex via self and hetero-association. The alcohols + DMF systems show complex formation at a very low concentration range. The study of systems alcohols + 2 - fluoroaniline indicate that the 2-fluoroaniline produces dissociating effects in these alcohols.

Microwave absorption and dielectric behaviour of some rigid polar molecules and their mixtures

Abstract The dielectric absorption of four rigid polar molecules, viz., benzotrichloride, benzotrifluoride, chlorobenzene, fluorobenzene and their binary mixtures in dilute solutions of benzene has been studied in the 3 cm microwave region over the temperature range 30–60°C. The relaxation time and the thermodynamical parameters, viz., free energy, enthalpy and entropy of activation have been determined using the measured dielectric data. The relaxation times for single component solutions agree well with literature values. The relaxation times of polar mixtures compares reasonably well with the computed values obtained from a relation proposed by M.P. Madan [Can. J. Phys., 58 (1980) 20.].

Dielectric relaxation in mixtures of 1-heptanol and phenol at lower microwave frequencies

Complex permittivity spectra of mixtures of 1-heptanol and phenol over a range of concentration are obtained in the frequency range 30 MHz to 3.0 GHz using Vector Network Analyzer (VNA). Obtained complex permittivity data points at different frequencies were fitted into Debye model to evaluate dielectric relaxation parameters like, a relaxation time (tau), static permittivity (isin0) and permittivity at high frequency (isininfin). These parameters were used to interpret the molecular interaction between the molecular species of the mixtures.

Dielectric relaxation mechanism in mixtures of 1-Butanol and fluorobenzene at lower microwave frequencies

Complex permittivity of 1-butanol and its mixtures with fluorobenzene over a range of concentration were obtained in the radio and lower microwave frequency range at constant temperature. Vector network analyzer (VNA) operating in the frequency range 0.03 MHz to 3.0 GHz was used to obtain complex permittivity spectra. Complex permittivity data points at different frequencies were fitted into Debye model to evaluate dielectric relaxation parameters like, a relaxation time (tau), static permittivity (isin0) permittivity at high frequency (isininfin). Various dielectric parameters like excess inverse relaxation time (1/tau)E, excess permittivity (isin0 E) and Kirkwood correlation factor (g) were also evaluated. These parameters were used to interpret the molecular interaction between the molecular species of the liquid mixtures.