Biplab Kumar Paul

Significant enhancement of dielectric and conducting properties of electroactive polymer polyvinylidene fluoride films: An innovative use of Ferrum metallicum at different concentrations

Background: There are experimental evidences of nanoparticle aspect of homoeopathic medicine. It has also been established that the size of these nanoparticles (NPs) decrease with increase in potency. Aim: We have used this aspect of homoeopathic medicines in some technical applications. Here, to improve the electrical properties of an electroactive polymer, poly (vinylidene fluoride-hexa-fluoropropylene) (PVDF-HFP), we have incorporated in the polymer film, a very novel and unique probe Ferrum metallicum (FeM), a homoeopathic medicine, the size of which can be changed by dilution, followed by controlled agitation. Settings and Design: The composite film was synthesized by solution-casting technique. Using standard procedures, the characterization studies by X-ray diffraction, field-emission scanning electron microscope, and Fourier transform infrared spectroscopy were performed to check the incorporation of the NPs in the film. Material and Method: Each sample was freshly prepared 2 times by doping FeM in PVDF-HFP matrix using solution-casting technique, and the experiment was repeated with each sample for 5 times. Statistical Analysis: This being a continuous data recording, error bars cannot be shown. We have presented the graphs which have been repeated maximum number of times. Result and Conclusion: Our result shows that the electrical properties such as dielectric constant, tangent loss, and electrical conductivity of these polymer films get significantly modified due to incorporation of this homoeopathic nanomedicine and the effect increases with the increase in concentration of the probe up to a critical value. These FeM-incorporated PVDF-HFP films will have potential applications as high-energy storage devices such as multilayered high-charge storage device.

Enhanced dielectric properties and conductivity of triturated copper and cobalt nanoparticles-doped PVDF-HFP film and their possible use in electronic industry

We have synthesised a novel nanocomposite film by incorporating copper and cobalt nanoparticles, prepared by the method of trituration, in the poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) films by simple solution-casting technique. Fourier transform infrared spectroscopy (FTIR) study of these nanocomposite films detected presence of α- and β-phases. Scanning electron micrographs showed spherulitic crystal structure of PVDF-HFP in the nanocomposite film and study of dielectric properties over broadband frequency of these doped nanocomposite film showed that these films have higher dielectric permittivity and significantly lower dissipation factor (tanδ) at room temperature compared to the pure PVDF-HFP. The incorporation of metallic nanoparticles in the polymer matrix activates the transition of phase between α and β and provides the nanocomposites higher mobile charge carriers which participate in the interfacial polarisation. The room temperature dielectric constant of the pure PVDF-HFP at 20 Hz frequency increases with increase in concentration of the metal nanoparticles and reaches a maximum almost four times the value of the pure one. At higher concentrations, the effect reduces, perhaps due to agglomeration of the nanoparticles. The metal nanoparticles, obtained by the method of trituration, are inexpensive, easy to fabricate and environment friendly. Thus, their incorporation in polymer matrix to get enhanced electrical properties will have a significant contribution to the present day research.

Abrupt change of dielectric properties in mullite due to titanium and strontium incorporation by sol-gel method

Highly crystallized mullite has been achieved at temperatures of 1100 °C and 1400 °C by sol-gel technique in presence of titanium and strontium ions of different concentrations: G0 = 0 M, G1 = 0.002 M, G2 = 0.01 M, G3 = 0.02 M, G4 = 0.1 M, G5 = 0.2 M and G6 = 0.5 M. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), LCR meter characterized the samples. Mullite formation was found to depend on the concentration of the ions. The dielectric properties (dielectric constant, loss tangent and AC conductivity) of the composites have been measured, and their variation with increasing frequency and concentration of the doped metals was investigated. All the experiments were performed at room temperature. The composites showed maximum dielectric constants of 24.42 and 37.6 at 1400 °C of 0.01 M concentration for titanium and strontium ions at 2 MHz, respectively. Due to the perfect nature of the doped mullite, it can be used for the fabrication of high charge storing capacitors and also as ceramic capacitors in the pico range.

Copper Ion Doped Mullite Composite in Poly (vinylidene Fluoride) Matrix: Effect on Microstructure, Phase Behavior and Electrical Properties

Highly crystallized copper ion doped mullite composites have been synthesized at 1100°C and 1400°C via sol-gel technique with five different strengths of copper ion and was incorporated in poly-vinylidene fluoride (PVDF) to make doped mullite composite/polymer films. We have studied the effects of this dopant on microstructure, phase transformation, and electrical properties of the polymer films over a wide range of frequency from 1.0 KHz to 2.0 MHz. Characterizations were done by various analytical tools at room temperature. Prominent mullite phases were observed from XRD, FTIR spectroscopy and FESEM characterization of composite polymer. The concentration of the dopant and the sintering temperature were found to be the two basic factors which affect the phase transition of the polymer. The composite film showed maximum dielectric constant of 19.96 at 1 KHz for 1.2M concentration of copper ion doped mullite sintered at 1400°C, compared to 3.09 for the pure polymer. Furthermore, both dielectric constant and electrical conductivity of the composite were found to be highly frequency and temperature dependent. After doping, the A.C. conductivity of the composite was found to increase with increasing temperature following Jonscher’s power law and the electrical resistivity reduced too. Moreover, the results revealed that the phase behaviors and micro structural changes of the copper ion doped mullite composite/polymer film affected its electrical properties with possible impact on its applications.

Segmentation of three phase micrograph: an automated approach

Quantitative description of micro-structure of the materials enables the analysis of material characteristics. Material under study undergoes heat and cool treatment and micro-structures thereby get revealed. Image processing has enormous potential in the analysis of microscopic images of the processed materials. Thus, the extraction of microstructures/phases present in the material forms the fundamental step towards material description. In this work, we present an automated scheme for segmenting the phases namely Ferrite, Martensite and Bainite present in the microscopic image of HSLA steel. First of all, region contours are obtained using topological watershed. Each region is then characterized as Ferrite, Martensite and Bainite based on average intensity and white grain concentration of the region. Finally, a refinement process is carried out to merge the adjacent regions of same type. As no state of the art technique is readily available, the segmentation output has been validated by the domain expert.

Tungsten doped hydroxyapatite processed at different temperature: dielectric behaviour and anti-microbial aspects

Hydroxyapatite is regarded as one of the most significant emerging biomaterials owing to its biocompatibility with bone/enamel. In the present study, tungsten doped hydroxyapatite (W-HAp) nanoparticles have been synthesized via chemical precipitation followed by annealing at different temperatures (800, 1000 and 1200 °C) and characterized with XRD and FESEM, along with EDS, TEM, XPS and DTA-TGA. Morphological changes as well as newly formed phases arise in each sample, and the samples also exhibit high mechanical strength and better Young’s modulus as a result of the effects of annealing temperature. The maximum dielectric constant/electric polarization is observed for the W-HAp10 composite, whereas the frequency dependent tangent loss and frequency dependent capacitance are similar for the W-HAp8 and W-HAp12 samples. The anti-bacterial activity of W-HAp10 against Gram-negative (E. coli) and Gram-positive (S. aureus) bacteria has been explored through a mortality assay, MIC (minimum inhibitory concentration), MBC (minimum bactericidal concentration), ROS (reactive oxygen species) generation, fluorescence microscopy, and cell wall degradation under FESEM. The bioactivity of W-HAp10 has been monitored in simulated body fluid (SBF) and is attributable to the formation of apatite on its surface. These significant results suggest that the influence of temperature (at 1000 °C) along with tungsten doping in hydroxyapatite will be beneficial for the advancement of pathogen-free biomaterials with dielectric activity for medicinal applications.