• S K SIT

Articles written in Bulletin of Materials Science

• Investigation of dielectric relaxation in tributyl phosphate from susceptibility and conductivity measurement under microwave field

Susceptibility (${\chi}$$_{ij}’s) and conductivity ({\sigma}$$_{ij}$’s) measurement techniques are proposed to determine dielectric behaviour in terms of relaxation time ${\tau}$ and dipole moment ${\mu}$ of tributyl phosphate (TBP, $j$) dissolved in various non-polar solvent ($i$) ($p$-xylene, cyclohexane and $n$-heptane) under S-band, C-band, X-band and Ku-band microwave field at different temperatures (25, 30 and 35$^{\circ}$C) within Debye’s dielectric model. The possibility of double relaxation times(${\tau}$$_2 and {\tau}$$_1$) for inter- and intra-molecular rotation of the polar molecule TBP is predicted from measured data of ${\chi}$'$_{ij}$ (= ${\varepsilon}$'$_{ij}$-${\varepsilon}_{\infty}{ij}$), ${\chi}$"$_{ij}$ (= ${\varepsilon}$"$_{ij}$) and ${\chi}$$_{0ij} (= {\varepsilon}$$_{0ij}$ – ${\varepsilon}$$_{\infty}{ij}) at different weight fractions w_j’s of solute, applying slope and intercept of \frac{{\chi}_{0ij} - {\chi}'_{ij}}{{\chi}'_{ij}}against \frac{{\chi}"_{ij}}{{\chi}'_{ij}} linear equation to confirm mono relaxation behaviour {\tau}$$_2$ only. ${\tau}$ ’s are measured from individual variation of real and imaginary parts of ${\chi}$$_{ij} and {\sigma}$$_{ij}$ with w$_j$’s as well as linear relation of imaginary against real. The dipole moments ${\mu}$$_j$’s are measured from both the measurement techniques under S-band (3.2 GHz), C-band (6.8 GHz),X-band (11.2 GHz) and Ku-band (16.5 GHz) microwave field at 25, 30 and 35$^{\circ}$C temperatures. Various molecular associations are determined in terms of relaxation time ${\tau}$ and dipole moment ${\mu}$ in polar–non-polar liquid mixture.Thermodynamic energy parameters are also calculated from Eyring rate theory to predict molecular dynamics or natureof molecular environment surrounding the polar molecule TBP. Debye relaxation mechanism in all the systems under observation is validated by the estimated Debye factor from both the measurement methods. A new simple microwave sensor is proposed to design for determination of TBP concentration from measured penetration depth at different temperatures under microwave field.

• Investigation of dielectric relaxation in dipolar liquids from conductivity measurement

Conductivity (σ$_{ijk}$’s) measurement method is proposed to investigate dielectric relaxation in ternary polar–nonpolar mixture of N,N-dimethyl formamide (DMF)(j) with pyridine(k) or acetonitrile(k) dissolved in p-xylene (i) at various weight fractions (w$_{jk}$’s) and temperature under different bands (S, C, X and Ku) of microwave field applying Debye’s dielectric model. Ratio of slopes of imaginary σ$_{ijk}$″ vs. w$_{jk}$ with real σ$_{ijk}$′ vs. w$_{jk}$ of complex conductivity σ$_{ijk}$* as well as linear slope of σ$_{ijk}$″ vs. σ$_{ijk}$′ are used to predict τ$_{jk}$’s (relaxation time) and μ$_{jk}$’s (dipole moments). Variousmolecular associations are also identified from the meaningful interactions among polar–nonpolar molecules in terms of τ$_{jk}$ and μ$_{jk}$. Molecular dynamics or molecular environment surrounding the polar molecules DMF, pyridine or acetonitrileis extensively studied with the help of estimated thermodynamic energy parameters. The existence of Debye relaxation mechanism in polar–nonpolar mixture is authenticated by the estimated Debye factor. Microwave sensor development is also ascertained from various dielectric parameters like permittivity, conductivity and penetration depth under microwave field.

• # Bulletin of Materials Science

Volume 46, 2023
All articles
Continuous Article Publishing mode

• # Dr Shanti Swarup Bhatnagar for Science and Technology

Posted on October 12, 2020

Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
Chemical Sciences 2020