R. P. Tandon

Bio: R. P. Tandon is an academic researcher from University of Delhi. The author has contributed to research in topics: Dielectric & Conductivity. The author has an hindex of 35, co-authored 225 publications receiving 4188 citations. Previous affiliations of R. P. Tandon include National Physical Laboratory & Université du Québec à Trois-Rivières.

Characterization of thick lead zirconate titanate films fabricated using a new sol gel based process

Abstract: Lead zirconate titanate (PZT) films 60 μm in thickness have been fabricated using a new sol gel based process. PZT powders are dispersed in a sol gel matrix to form a 0–3 ceramic/ceramic composite. The dielectric properties of these films have been studied as a function of powder concentration, frequency, and temperature. The characteristic Curie point is observed at 420 °C. The ferroelectric behavior measured in terms of the remanant polarization (Pr=35 μC/cm2) and coercive field (Ec=20 kV/cm) was an improvement over values quoted for thin PZT films but lower than that of bulk ceramic. The piezoelectric properties d33 (325 pC/N) and d31 (−80 pC/N) were comparable with those of the bulk ceramic.

Gas and humidity sensors based on iron oxide–polypyrrole nanocomposites

Abstract: Nanocomposites of iron oxide and polypyrrole were prepared by simultaneous gelation and polymerization process. This resulted in the formation of mixed iron oxide phase for lower polypyrrole concentration, stabilizing to a single cubic iron oxide phase at higher polypyrrole concentration. The composites in the pellet form were used for humidity and gas sensing investigations. Their sensitivity to humidity was found to increase with increasing concentration of polypyrrole. Gas sensing was performed for CO2, N2 and CH4 gases at varying pressures. The sensors showed a linear relationship between sensitivity and pressures for all the gases studied. The sensors showed highest sensitivity to CO2 gas.

Gas and humidity response of iron oxide—Polypyrrole nanocomposites

Abstract: Nanocomposites of PPY–Fe3O4 have been synthesized using an emulsion polymerization method in aqueous solution. The resulting polymer composites possessed much higher conductivity as compared to pure polypyrrole (PPY) and the conductivity decreased with increasing the PPY content. The composite exhibited fairly high sensitivity to relative humidity and some commonly used gases (N2, O2 and CO2). Changes in resistance for nitrogen and oxygen gas have also been reported. Based on these results, it is expected that these composites may furnish a simple means of humidity and gas sensing.

Insights into the structure of alkali borate glasses

Abstract: In the light of extensive new glass transition temperature (Tg) and density (ϱ) data obtained for the ternary glass system Li2O(LiCl)2B2O3 we have re-examined the well accepted structural models developed for borate glasses by Krogh-Moe and co-workers. We find that, in contrast to the conclusions of NMR, Raman and IR spectroscopy, glasses in the binary and in the ternary systems with common O/B ratios do not exhibit identical boron-oxygen networks. Rather, we find that as LiCl in the ternary is increased the network is systematically weakened and expanded to accommodate the large Cl− anion. On the basis of these observations we question the ability of spectroscopic techniques such as Raman and NMR to confirm the uniqueness of structural models based on combinations of intermediate-range units. We propose a tentative model which is qualitatively in agreement with the observed changes in Tg and ϱ upon addition of LiCl, and explains how the large Cl− ions can be accommodated without large increases in energy due to strain and electrostatic effects while maintaining BO4/BO3 constant. Recent transport results on some fast ion conducting glasses in this system are also discussed in terms of the proposed model.

Electromagnetic interference shielding with 2D transition metal carbides (MXenes)

Abstract: Materials with good flexibility and high conductivity that can provide electromagnetic interference (EMI) shielding with minimal thickness are highly desirable, especially if they can be easily processed into films. Two-dimensional metal carbides and nitrides, known as MXenes, combine metallic conductivity and hydrophilic surfaces. Here, we demonstrate the potential of several MXenes and their polymer composites for EMI shielding. A 45-micrometer-thick Ti3C2Tx film exhibited EMI shielding effectiveness of 92 decibels (>50 decibels for a 2.5-micrometer film), which is the highest among synthetic materials of comparable thickness produced to date. This performance originates from the excellent electrical conductivity of Ti3C2Tx films (4600 Siemens per centimeter) and multiple internal reflections from Ti3C2Tx flakes in free-standing films. The mechanical flexibility and easy coating capability offered by MXenes and their composites enable them to shield surfaces of any shape while providing high EMI shielding efficiency.

Gas Sensors Based on Conducting Polymers

Abstract: The gas sensors fabricated by using conducting polymers such as polyaniline (PAni), polypyrrole (PPy) and poly (3,4-ethylenedioxythiophene) (PEDOT) as the active layers have been reviewed. This review discusses the sensing mechanism and configurations of the sensors. The factors that affect the performances of the gas sensors are also addressed. The disadvantages of the sensors and a brief prospect in this research field are discussed at the end of the review.

A review on nanomaterials for environmental remediation

Abstract: This article gives an overview of the application of nanomaterials in environmental remediation. In the area of environmental remediation, nanomaterials offer the potential for the efficient removal of pollutants and biological contaminants. Nanomaterials in various shapes/morphologies, such as nanoparticles, tubes, wires, fibres etc., function as adsorbents and catalysts and their composites with polymers are used for the detection and removal of gases (SO2, CO, NOx, etc.), contaminated chemicals (arsenic, iron, manganese, nitrate, heavy metals, etc.), organic pollutants (aliphatic and aromatic hydrocarbons) and biological substances, such as viruses, bacteria, parasites and antibiotics. Nanomaterials show a better performance in environmental remediation than other conventional techniques because of their high surface area (surface-to-volume ratio) and their associated high reactivity. Recent advances in the fabrication of novel nanoscale materials and processes for the treatment of drinking water and industrial waste water contaminated by toxic metal ions, radionuclides, organic and inorganic solutes, bacteria and viruses and the treatment of air are highlighted. In addition, recent advances in the application of polymer nanocomposite materials for the treatment of contaminants and the monitoring of pollutants are also discussed. Furthermore, the research trends and future prospects are briefly discussed.