Recent Innovations in Chemical Engineering - Volume 14, Issue 1, 2021

Objective: Polyethylene oxide (PEO) composed of 10 wt% ammonium bifluoride (NH4HF2) exhibited higher conductivity of 5.96x 10^-6 S/cm as compared to other concentrations of salt at room temperature. The effect of additives, i.e., nano-sized fumed silica concentration as nanofiller and propylene carbonate (PC) concentration as plasticizer on electrical, structural, as well as mechanical property studies of polymer electrolytes has been studied. Methods: The ionic conductivity, as well as dielectric studies of polymer electrolytes consisting of polyethylene oxide and different (x wt%) ammonium bifluoride (x=1, 2.5, 5, 10 and 15 wt%), have been measured using complex impedance spectroscopic technique. X-ray diffraction (XRD) and differential scanning calorimetry/thermogravimetric analysis (DSC/ TGA) studies have been conducted to observe the effect of additives on crystalline phase, crystallite size, melting temperature and weight loss of different polymer electrolytes. The effect of additives on the mechanical properties (tensile strength, modulus of elasticity and % elongation at break) of different polymer electrolytes has also been studied by Universal Testing Machine (UTM). Results: The maximum conductivity achieved was 1.55x 10^-4 S/cm in case of plasticized nanocomposite polymer electrolytes with the simultaneous presence of 3 wt% fumed silica and 0.3 ml propylene carbonate. The variation of ionic conductivity at different temperatures and activation energy values of different polymer electrolytes were also measured and observed in good correlation. Conclusion: The observed enhancement in the ionic conductivity of polymer electrolytes with additives is due to an increase in carrier concentration, amorphous content, chain flexibility, as well as the formation of more conducting pathways. Hence, this new approach led to the development of plasticized nanocomposite polymer electrolytes with high ionic conductivity and improved structural and mechanical properties.

Background: The modulation in electrical conductivity of polymer electrolyte, viz., polyethylene oxide (PEO) complexed with different concentrations of sodium iodide is studied. The role of mobility and charge concentration in the electrical conductivity of polymer electrolytes is established. Methods: The complex impedance spectroscopy (CIS) method is used to measure the electrical conductivity of film. Results: The effect on charge concentration, mobility and conductivity of PEO+NaI film by adding three different concentration of silicon is reported. Conclusion: The polarized optical microscopy (POM) is used to study the morphology of the surface of PEO, PEO+NaI films dispersed with Si.

Background: Solid polymer electrolyte (SPEs) films based on poly (vinylidene fluoride-co-hexafluoropropylene) P(VDF-HFP) and sodium thiocyanate (NaSCN) are prepared using the solution casting technique. Methods: Ionic liquid (IL; 1-ethyl-3-methyl-imidazolium tricyanomethanide ([EMIM] [TCM]) is incorporated into the prepared polymer-salt complex matrix to enhance its ionic conductivity further. Polarized optical microscopy (POM) shows a change in the surface morphology of IL doped polymer electrolyte films. The composite nature of polymer electrolyte films is confirmed using Fourier transform infrared (FT-IR) spectroscopy via studying ion-ion and ion-polymer interactions. The structural morphology of ionic liquid doped polymer electrolyte films (ILDPE) confirms the complexation between the ionic liquid ([EMIM][TCM]), salt (NaSCN) and polymer P(VDF-HFP). This is further confirmed using DSC and XRD measurements. The XRD structural analysis confirms that the intensity of crystalline peaks present in IL doped solid polymer electrolyte films decreases as compared to that of the pure polymer as well as polymer salt complex system. XRD clearly indicates the enhancement in its amorphous nature, which is necessary to increase the conductivity. Results: The incorporation of IL into polymer salt-complex matrix leads to changes in the melting of polymer electrolytes, confirmed by DSC thermograms. Polymer electrolyte films are also characterized using impedance spectroscopy (IS) to check their electrical properties. The highest ionic conductivity is found to be 7.80x10^-4 S cm^-1 for 6 wt% IL doped polymer electrolyte film. Conclusion: The Linear sweep voltammetry (LSV) analysis shows that the optimized polymer gel electrolyte is electrochemically stable up to 1.5 V. The calculated value of ionic transference number (tion) is found to be 0.985. A laboratory scale electrical double layer capacitor (EDLC) has been fabricated using this highly conducting polymer electrolyte film. The specific capacitance value is found to be 1.31 F g^-1

Background: Thin films of PbS were prepared onto glass substrates by using a simple and cost-effective CBD method. Methods: The influence of deposition time on structural, morphology and optical properties have been investigated systematically. The XRD analysis revealed that PbS films are polycrystalline with preferred orientation in (200) direction. Enhancement in crystallinity and PbS crystallite size has been observed with an increase in deposition time. The formation of single-phase PbS thin films has been further confirmed by Raman spectroscopy. The surface morphology analysis revealed the formation of prismatic and pebble-like PbS particles and with an increase in deposition time, these PbS particles are separated from each other without secondary growth. The data obtained from the EDX spectra show the formation of high-quality but slightly sulfur-rich PbS thin films over the entire range of deposition time studied. Results and Conclusion: All films show an increase in absorption with an increase in deposition time and strong absorption in the visible and sub-bandgap regime of the NIR range of the spectrum with red-shift in band edge. The optical band gap shows a decreasing trend, as deposition time increases but it is higher than the bandgap of bulk PbS.

Objective: Phosphorus doped hydrogenated nano-crystalline silicon (nc-Si:H) thin films were synthesized by catalytic chemical vapor deposition (Cat-CVD) method. Methods: The effect of deposition pressure on opto-electronic and structural properties was studied using various analysis techniques such as low angle XRD analysis, FTIR spectroscopy, Raman spectroscopy, UV-Visible spectroscopy, dark conductivity, etc. Results: From low angle XRD and Raman spectroscopy analysis, it is observed that an increase in deposition pressure causes Si:H films to transform and transit from amorphous to the crystalline phase. At optimized deposition pressure (300 mTorr), phosphorous doped nc- Si:H films having a crystallite size of ~29 nm and crystalline volume fraction of ~58% along with high deposition rate (~29.7 Å/s) have been obtained. The band gap was found to be ~1.98 eV and hydrogen content was as low as (~1.72 at.%) for these films. Conclusion: The deposited films can be useful as an n-type layer for Si:H based p-i-n, tandem and c-Si hetero-junction solar cells.

Objective: Herein, we report the effect of variation of hydrogen flow rate on the properties of Si:H films synthesized using PE-CVD method. Raman spectroscopy analysis show an increase in crystalline volume fraction and crystallite size implying that hydrogen flow in PE-CVD promotes the growth of crystallinity in nc-Si:H films with an expense of a reduction in deposition rate. Methods: FTIR spectroscopy analysis indicates that hydrogen content in the film increases with an increase in hydrogen flow rate and hydrogen is predominantly incorporated in Si-H2 and (Si-H2)n bonding configuration. The optical band gap determined using E04 method and Tauc method (ETauc) show an increasing trend with an increase in hydrogen flow rate and E04 is found higher than ETauc over the entire range of hydrogen flow rate studied. Results and Conclusion: We found that the defect density and Urbach energy increases with an increase in hydrogen flow rate. Photosensitivity (σPhoto σDark) decreases from ~10^-3 to ~1 when hydrogen flow rate is increased from 30 sccm to 100 sccm and can be attributed to amorphous-to-nanocrystallization transition in Si:H films. The results obtained from the present study demonstrated that hydrogen flow rate is an important deposition parameter in PECVD to synthesize nc-Si:H films.

Background and Objective: Zwitterionic polymer electrolyte has been successfully synthesized using NH4PF6 salt. The conductivity of the synthesized polymer membrane is found to be of the order of 10^-3 Scm^-1. Dielectric and Modulus properties of the polymer electrolyte have also been studied which shows well relaxation peaks with both temperature and salt concentrations. Results: Debye type relaxation behavior has observed from the electric modulus. Conclusion: Frequency dependent conductivity data (fitted with Jonscher's power law equation) confirmed the presence of NCL/SLPL type behavior in the studied frequency range.

The present review presents the most commonplace vegetable-based feedstock for biodiesel production. It focuses on biodiesel production with an emphasis on the most recent studies and innovations. Transesterification of plant oil or animal fat is the most common process for the production of biodiesel. Several techniques are utilized for this transesterification reaction, such as batch processes, ultrasonic, microwave and other methods. Many conditions are usually studied, including temperature, pressure, solvent and catalysis. Furthermore, we aim to provide an investigation of the different processes and technologies applicable to the production of second-generation biodiesel, with special attention paid to the development of innovative catalysts as well as new reactor concepts.