N. A. Niaz

Structural, electrical, and magnetic properties of polypyrrole–Zn0.5Ni0.45Mn0.05Fe2O4 nanocomposites prepared by in situ chemical polymerization

Polypyrrole–Zn0.5Ni0.45Mn0.05Fe2O4 nanocomposites are conducting polymer-ferrites with useful properties and new functions. The ferrite and polypyrrole–ferrite nanocomposites were synthesized by wow sol gel and in situ chemical polymerization respectively. The structures, morphology, electrical and magnetic properties of the samples were characterized by various instruments. The results of X-ray diffraction (XRD) patterns, Fourier transform infrared (FTIR) spectra and field emission scanning electron microscopy (FE-SEM) showed the presence of the two intended phases. FE-SEM results show that phase separation was found to increase with increase of ferrite contents. The crystallite size measured by XRD was found to be in the range 40.9–88.6 nm. Possible bonding effect between metal cations and Polypyrrole (PPy) made the electronic density of the polymer chain reduce and hence resulted in the decrease of the conductivity. The room temperature dielectric measurements were performed in the frequency range 0.1 kHz–1 MHz. The dielectric constant followed the Maxwell–Wagner interfacial polarization. The frequency dependent conductivity obeyed a power law of frequency. Incorporation of ferrites in the conducting polypyrrol matrix leads to higher values of dielectric constant and dielectric loss. The loss tangent was found to have high values for composite materials as compared to pure samples. Under applied magnetic field, the Hysteresis measurements revealed that the saturation magnetization increased with increase in ferrite content. Anisotropy constant K values showed that grains were not single domains and anisotropy contribution is not uniaxial. In general the different variety of the results obtained by just changing the relative percentage of PPy–Zn,Ni,Mn ferrites nanocomposites, made the present studied samples to be useful in radiation absorption and shielding applications.

ab intio study of points defects in 2D graphene layer

With a hexagonal (honeycomb) network of mono-layered carbon atoms, graphene has demonstrated outstanding electronic properties. This work describes the impact of deliberately introduced single, double and triple carbon vacancies in grapheme monolayer. In addition, these carbon vacancies were then substituted with gold atoms and their influence on the electronic properties of the two-dimensional (2D) graphene layers was investigated. In this regard, a first principle calculation was performed to examine electronic properties and formation energy of 2D graphene layer by applying density functional theory (DFT). Introduction of such defects appeared to increase the stability of the graphene sheet as confirmed by formation energy calculations. Moreover, decrease of formation energy was noticed to be significant with an increase in the number of defects. Band structure calculations described the shifting of localized states from valance to conduction bands which caused the transformation of semiconducting beha...

Structural, Electrical, and Magnetic Properties of Ferrite–Polymer Composites

Six samples consisting of polypyrrole (PPy), pure NiFe2O4 ferrite, and their composites at ratio of 1:4 (PF1), 1:2 (PF2), 3:4 (PF3), and 1:1 (PF4) have been prepared by a coprecipitation method and their structural, electrical, dielectric, and magnetic properties measured experimentally. The direct-current (DC) resistivity was enhanced with increasing ferrite content, while the dielectric constant and loss decreased. The magnetic properties of all the composites and the ferrite revealed a narrow loop, confirming their soft nature. The saturation magnetization, remanence, and coercivity values increased with increasing ferrite content. The obtained parameter values suggest that such materials might be suitable for use in high-frequency applications.

Magnetic, Electrical and Thermal Studies of Polypyrrole-Fe2O3 Nanocomposites

This research paper comprises of the synthesis of polypyrrole (PPy)-Fe2O3 nanocomposites by employing the in situ chemical oxidative polymerization method. The concentration of the filler material was adjusted between 10–50 wt % of PPy. The synthesized nanocomposites were characterized by using X-ray diffraction (XRD). Magnetic analysis and DC electrical conductivity of the samples were carried out using vibrating sample magnetometer (VSM) and two probe DC conductivity method, point towards magnetically active and electrically conductive samples. The magnetic parameters under applied magnetic field demonstrated that the values of coercivity (H c ), saturation magnetization (M s ) and remanence (M r ) can be tailored by carefully controlling the amount of dopant material into the nanocomposites indicating their suitability for controllable switching devices and microwave absorption applications. The DC electrical conductivity showed an increase up to 20 wt % of filler material and thereafter a decrease in the conductivity of nanocomposites with increase in filler content is observed. Thermogravimetric analysis (TGA) showed an increase in thermal stability with an increase in ferrite content in nanocomposites.

Effect of ZnNiCrFe2O4 content on structural and dielectric properties of polyaniline based nanocomposites, synthesized via in-situ chemical polymerization

Zn0.5Ni0.4Cr0.1Fe2O4 nanopowder and its composite with polyaniline were successfully prepared by using wow sol-gel and in situ chemical polymerization respectively. The samples were characterized by X-ray diffraction and field emission scanning electron microscopy. Dielectric properties were investigated as function of frequency by using impedance analyzer. The results showed the presence of the two intended phases. The ac conductivity was found to obey Jonscher’s universal power law. The dielectric constant and loss showed dispersion in low frequency region. Impedance analysis revealed the semiconducting behavior of the investigated samples.

Study on conductivity and dielectric behavior of chemically synthesized polypyrrol dodecylbenzene sulfonic acid blended with poly(methyl methacrylate)

Polypyrrole (PPy) doped with dodecylbenzene sulfonic acid was synthesized and was blended with compatible polymer PMMA in chloroform. Flexible and free-standing films with compositions PPy: PMMA = 10: 90, 20: 80, 30: 70, and 50: 50 were obtained. The percentage of crystallinity and particle size of synthesized polymers were estimated from X-rays diffraction studies. Scanning Electron Micrographs showed that phase separation was observed and compatibility of the mixture decreased with increase of PMMA content. The dielectric measurements were performed in the frequency range 0.1 kHz–1 MHz in temperature range 303–473 K. The frequency dependent conductivity (σac) obeyed a power law of frequency with an exponent s < 1. Electric modulus formalism exhibits a peak in frequency. The peak of conductivity relaxation shifted towards higher frequencies and the magnitude of relaxation decreased with the increase of PMMA content in the composites.