Bharti Gaur

Microbial fuel cell: technology for harvesting energy from biomass

Abstract Microbial fuel cells (MFCs) are an emerging technology that has gained considerable attention in the recent years because they provide new opportunities for sustainable production of energy from a wide range of soluble complex organic wastes and renewable biomass. The driving force for research in this field has been the apprehension over the energy climate crisis and environment pollution. MFCs are bioreactors that can convert the chemical energy present in organic compounds into electrical energy. Presently, the literature shows that current and power yields are relatively low, but improvements in the technology can enhance these parameters as well as the efficiency of these cells. Sediment MFCs in powering low-powered electronic monitoring devices is one of the practical uses of MFCs. Additionally, MFCs can be used in implantable medical devices and wastewater treatment plants. This review discusses the factors governing the performance of these cells and the maximum power density that can be obtained using various combinations of substrates and microorganisms.

Study on Mechanical and Dry Sliding Wear Characteristics of Meta-Cresol Novalac Epoxy Composites Filled with Silicon Carbide, Aluminum Oxide, and Zinc Oxide Particulates

In this article, the mechanical and dry sliding wear characteristics of synthesized m-cresol novalac epoxy composites filled with silicon carbide (SiC), aluminum oxide (Al2O3), and zinc oxide (ZnO) have been studied using a pin-on-disc apparatus. The influence of wear parameters such as applied normal load (20–40 N), sliding velocity (1.8–3.6 m/s), filler content (5–15 wt%), and sliding distance (1,000–3,000 m) on the coefficient of friction and specific wear rate of these composites have been investigated under dry sliding conditions. A design of experiment technique, response surface methodology, has been used to model the friction and wear behavior of these composites. The experimental plan for four factors at three levels using face-centered central composite design has been employed. The results showed that the hardness, tensile strength, and flexural strength of these composites increased with 5 to 10 wt% filler contents and decreased for 15 wt% filler content. The compression strength of these m-cresol novalac epoxy composites increases with an increase in the filler content from 5 to 15 wt%. The worn surfaces of these composite specimens were examined using a scanning electron microscope (SEM) to explore the wear mechanisms.

Study on the effects of nanoparticulates of SiC, Al2O3, and ZnO on the mechanical and tribological performance of epoxy-based nanocomposites

ABSTRACT In this research work, mechanical and tribological characteristics of ortho cresol novalac epoxy (OCNE)-based nanocomposites filled with nanoparticulates of SiC, Al2O3, and ZnO have been investigated. Also, in these investigations, the influence of wear parameters such as applied normal load, sliding velocity, filler contents, and sliding distance have been explored. The experimental plan for four factors at three levels using face centered composite design (CCD) has been employed by the response surface methodology (RSM) technique. The friction and wear tests were carried out using a pin on disc wear test apparatus under dry sliding conditions. The hardness and flexural strength of nano ortho cresol novalac epoxy composites filled with nano (SiC, Al2O3, and ZnO) particulates increases with an increase in the filler contents. Whereas, the tensile strength of these nanocomposites increases with an increase in the filler contents from 1 to 2 wt%, and with a further increase in filler contents the tensile strength decreases. The results of the study also showed that (2 wt%) filler contents bring superior mechanical and tribological properties. The lowest coefficient of friction and specific wear rate were found with nano Al2O3-filled composites. Also, the wear mechanisms of these nanocomposites were studied using a scanning electron microscope (SEM) equipped with an EDS analyzer.

Rheological Behavior of Vinyl Ester Resin

ABSTRACT Vinyl ester resins with varied acid values (11, 22, 32, 38, and 48 mg KOH/g solid) were prepared by reacting epoxy-novolac resin with methacrylic acid. The rheological behavior of these synthesized vinyl ester resin (VER) samples containing styrene as reactive diluent was studied using a Haake Rotovisco RV 20 viscometer. The apparent viscosity was found to be inversely proportional to the square root of the acid value in the temperature range of 25–40°C and at shear rates ranging from 100–800 sec−1. The zero-shear viscosity of these VER samples containing styrene (40% w/w) as reactive diluent decreased linearly with temperature. The activation energies for flow at constant shear stress (25–100 Pa) for a particular sample were found to be constant. The activation energy at constant shear rate decreases with the increase in the shear rate (50–400 sec−1). The activation energy at constant shear rate and shear stress decreased with the increase in the acid value. The viscosity of vinyl ester resin containing styrene as reactive diluent decreased almost 50 times with the increase in the concentration of reactive diluent from 30% to 100% (w/w of the resin).

Structure-property correlation study of bio-based multifunctional vinyl ester resin in presence of methacrylated lignin model compounds

Diels-Alder adduct of gum rosin and maleic anhydride (MPA) were treated with trimethylolpropane to obtain trimethylolpropane modified maleopimaric acid adduct (TMPA). This adduct was then epoxidized using epichlorohydrin and KOH as catalyst to synthesize an epoxy resin (TMPAE), which was further esterified using methacrylic acid in the presence of triphenyl phosphine as catalyst and hydroquinone as inhibitor to produce bio-based multifunctional vinyl ester resin (VTMPAE). This article also reports the synthesis of lignin model compounds i.e. methacrylated eugenol (ME) and methacrylated guaiacol (MG) as bio-based reactive monomers for vinyl ester resins. The chemical structures of all synthesized products were analyzed using FTIR, 1HNMR and 13C NMR spectroscopic techniques. The thermal and mechanical properties of the samples were evaluated using Differential Scanning Calorimetry (DSC), Thermogravimetric Analyzer (TGA) and Universal Testing Machine (UTM), respectively. Chemical and corrosion resistance of the above cured VTMPAE samples coated on steel panels were also evaluated as a function of % weight loss by immersing the VTMPAE samples in 1 M HCl, 1 M NaOH, and 1 M NaCl solutions for 90 days. The morphological changes that appear upon such an exposure were also studied with the help of Scanning electron microscopy (SEM).

Sulfonated poly (arylene ether sulfone) proton exchange membranes for fuel cell applications

Abstract Sulfonated poly (arylene ether sulfone) membranes were synthesized by direct copolymerization of 4,4-bis (4-hydroxyphenyl) valeric acid, 4,4′-difluorodiphenyl sulfone and synthesized sulfonated 6F-bisphenol-A/bisphenol-A as novel proton exchange membranes for fuel cell applications. Prepared membranes were subsequently crosslinked with synthesized 6F-bisphenol-A based epoxy resin (EFN) by thermal curing reaction keeping in view the resilience and toughness of the membranes. The structural characterization was done by using Fourier transform infrared (FTIR), 1H nuclear magnetic resonance (NMR) and 13C NMR techniques. Proton conductivity of the membranes was determined by a four-point probe technique. Methanol permeability was determined by using a diffusion cell in which concentration of the liquids was determined by UV-spectroscopic technique. The enhancement in mechanical properties determined by a universal testing machine and also a better oxidative stability were observed for the crosslinked membranes. However, a decrease in their water and methanol absorption, ion exchange capacity, proton conductivity and methanol permeability was observed. This was due to the reduction in the numbers of ionic channels in case of crosslinked membranes which was confirmed by carrying out morphological analysis of the membranes using atomic force microscopy. In addition, X-ray diffraction measurement by XPERT-PRO diffractometer was also used for structural characterization. Crosslinked membranes showed better thermal stability as determined by thermogravimetric analysis and differential scanning calorimetry.

New trends in vinyl ester resins

Abstract Vinyl ester resins (VERs) are high-performance unsaturated resins derived by the addition reaction of various epoxide resins with α-β unsaturated carboxylic acids. These resins have always been classified under unsaturated polyester resins. However, VERs have remarkable corrosion resistance and superior physical properties as compared with these conventional polyester resins, which make VERs a class of their own and hallmark of today’s resin industries. Hence, there is a need to review the available literature on this important class of thermosetting resins separately. In this article, an attempt is made to review the state of the art of VERs, including synthesis, characterization, curing, thermal, chemical, oxidative properties, and applications. The main focus is on the latest developments in this area.

Effect of Microsize Particulates on Tribological Characteristics of Vinylester Composites under Dry and Lubricated Conditions

In this paper the friction wear characteristics of vinylester and vinylester composites have been investigated under dry and water lubricated sliding conditions, under different applied normal load and sliding speed. The experiments have been carried on a pin on disc arrangement at normal temperature conditions. The results showed that with increase in the applied normal load and sliding speed the coefficient of friction and specific wear rate decreases under both dry and water lubricated sliding conditions. It is also found that a thin film formed on the counterface seems to be effective in improving the tribological characteristics. The worm surface examined by SEM showed that more of the fiber exposure and fiber breakage for vinylester composite resulting higher wear rate.

Curing and thermal behavior of epoxy resins of hexafluoro - bisphenol –A and bisphenol-A

This paper describes the synthesis and characterization of epoxy resins based on (hexafluoroisopropylidene)diphenol (EFN) and p,p’-isopropylidenebisphenol (EBN), respectively and 4, 4’- (hexafluoroisopropylidene)dipthalic-imideamine (IMAM), a curing agent. The synthesized epoxy resins and IMAM curing agent were characterized by Fourier Transform Infrared (FTIR) and 1H Nuclear Magnetic Resonance (NMR) spectroscopy.13C NMR technique was also used to characterize IMAM. Study of curing behavior of EFN and EBN with stoichiometric amount of aromatic 4,4’-diaminodiphenylmethane (DDM), 4,4’-diaminodiphenylsulfone (DDS) and IMAM by using Differential Scanning Calorimetery (DSC) indicated that IMAM was least reactive curing agent towards both epoxy resins as compared to DDS and DDM. The investigation of thermal decomposition of the cured compounds by thermogravimetric analyzer (TGA) indicated the higher thermal stability of EFN and EBN resins initially with DDS and at elevated temperatures with IMAM. It was also observed that EFN resins were thermally more stable than EBN resins cured with corresponding curing agents.

Study on the effects of nano-aluminum-oxide particulates on mechanical and tribological characteristics of chopped carbon fiber reinforced epoxy composites:

An experimental study has been carried out to investigate the mechanical and tribological characteristics of chopped carbon fiber (CCF) reinforced epoxy composites filled with nano-Al2O3 particulates, as a function of fiber and filler contents. The experiments were conducted using a pin-on-disc wear test apparatus under dry sliding conditions. The coefficient of friction and specific wear rate of these composites was determined as a function of applied normal load, sliding velocity, sliding distance, and reinforcement content. The tensile, flexural, and compression strengths of ortho cresol novalac epoxy and chopped carbon fiber (OCNE/CCF) filled composites are found to be within the ranges of 48–58.54 MPa, 115–156.56 MPa, and 48–61.15 MPa. Whereas the tensile, flexural, and compression strengths of OCNE/CCF/Al2O3-filled composites are found to be within the ranges of 96–110 MPa, 176–204.66 MPa, and 72–85.65 MPa, respectively. It has been observed that the coefficient of friction decreases and specific wear rate increases with increase in the applied normal loads. Further increases in the fiber (6 wt%) and particle (3 wt%) contents in the epoxy matrix resulted in a decrease of both the mechanical and tribological properties, but remains above that of the CCF reinforced epoxy composites. The worn surfaces of composites were examined with scanning electron microscopy equipped with energy dispersion X-ray analyzer and X-ray diffraction analysis technique to investigate the wear mechanisms.