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Using the sol-gel auto combustion approach, nanoferrites of the CoCrxFe2−xO4 series (x = 0.00, 0.05, 0.10, 0.15, 0.20) are fabricated. Lattice constants are computed within the range of 8.312–8.375 Å, while crystallite size, estimated using Scherrer method yields ranges from 55.20 to 34.79 nm. Using Fourier transform infrared (FTIR) spectroscopy, different functional groups are found to correlate to different absorption bands. Five active modes are identified by Raman spectroscopy, revealing O2−ion vibrations at both tetrahedral and octahedral locations. Throughout the series, ferromagnetic hysteresis loop is observed which is explained by Neel's model. When the doping concentration increases in the Fe2+ site the ac conductivity are found to decrease with increase in Cr3+ doping content. With increasing frequency, both the dielectric constant and dielectric loss increase. In addition, with an increase in Cr3+ doping, saturation magnetization (Ms), remnant magnetization (Mr), and coercivity (Hc) show declining trends. For applications involving microwave devices, the sample CoCr0.2Fe1.8O4shows the most promising magnetic behavior, with Ms ranging from 73.12 to 39.71 emu/g, Mr from 37.77 to 20.64 emu/g, and Hc from 1939 Oe to 1200Oe throughout the series. [ABSTRACT FROM AUTHOR]

The interest in BiFeO3 perovskite for photostable applications is rapidly rising, owing to its efficient single photon emitter behavior. A detailed analysis of the structural, optical and electrochemical behavior of BiFeO3 perovskite synthesized by different synthesis techniques viz. sol–gel and solid-state synthesis techniques, divulging that 30–40-nm-sized-prepared BiFeO3 have well-grown grains but the grain size is non-uniform. The major problem faced in these materials is their photostability under optical excitation. Sol–gel-assisted synthesis procedure exhibited enhanced photostability. Remarkable magnetic and impedance properties of the synthesized material satisfy the competitiveness and also pave a way for the development of perovskite photovoltaics. Hence, the enhancement in the magnetic and impedance properties of BiFeO3 clearly focuses on the importance of sintering atmosphere and also paves a way for BFO thin film for applications in optoelectronics. [ABSTRACT FROM AUTHOR]

Electrical, mechanical, and thermal properties of the poly(methyl methacrylate) (PMMA) composites containing functionalized multiwalled carbon nanotubes (f-MWCNTs) and reduced graphene oxide (rGO) hybrid nanofillers have been investigated. The observed electrical percolation threshold of FHC is 0.8 wt% with maximum conductivity of 1.21 x [10.sup.-3] S/cm at 4 wt% of f-MWCNTs. The electrical transport mechanism and magneto resistance studied of hybrid composites have also been investigated. Progressive addition of f-MWCNTs in rGO/PMMA composite results increase in mechanical (tensile strength and Young's modulus) and thermal (thermal stability) properties of f-MWCNTs-rGO/PMMA hybrid nanocomposites (FHC). The increased mechanical properties are due to the efficient load transfer from PMMA matrix to f-MWCNTs and rGO through better chemical interaction. The strong interaction between PMMA and f-MWCNTs-rGO in FHC is the main cause for improved thermal stability., INTRODUCTION Due to increasing demand of high quality multifunctional materials for various applications, there are tremendous research efforts on the advanced nanostructured composites with interesting properties. Due to exciting physical [...]

Bi-doped CoFe2O4 (CFO) nanoparticles with different contents of Bi (x = 0.0, 0.05, 0.1, 0.15, and 0.2) were prepared via sol–gel auto-combustion method. The structural characteristics of the prepared samples were characterized using room-temperature X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM). Moreover, the electrical conductivity and magnetic properties of the nanoferrites were investigated using impedance analyzer and vibrating sample magnetometer (VSM). Pure CFO and Bi-doped CFO showed spinel crystalline structure with the presence of secondary phase at higher doping content of Bi. The FESEM micrographs of the nanoferrites showed different aggregations for the different Bi contents and reduction in particle size was obtained with increasing Bi content. With Bi substitution, saturation magnetization was found to increase rapidly. The frequency (100 Hz–1 MHz) and temperature (30–450 °C)-dependent dielectric properties show that the dielectric constant is T-independent and at a certain point increasing trend overcomes. Magnetodielectric (MD) studies revealed the magnetic ordering of Bi-doped CFO consequences in the increase in number of polar domains thereby improving the magnetodielectric effect. The high MD property outcome of this work established the unification of the synthesized samples for multifunctional device applications. [ABSTRACT FROM AUTHOR]

In this work, we report a simple solvothermal method to fabricate CoFe2O4-graphene nanocomposites. X-ray powder diffraction pattern, Fourier-transform infrared spectroscopy spectra and RAMAN spectra confirmed the pure-phase of CoFe2O4 as well as CoFe2O4-graphene nanocomposites. Micrographical images revealed a reduction in CoFe2O4 particles when blended with graphene. The complex impedance and modulus spectroscopy have been investigated as a function of frequency in regime of 102–106 Hz in the temperature range of 30–300 °C. Activation energies obtained from the Arrhenius plots of the grain and the grain boundary conductions are ascribed to the hopping of charge carriers. The dielectric constant was found to increase massively with graphene incorporation and further increased with increase in graphene content. Present work is focussed to increase the dielectric constant with low loss so as to exploit it in the field of high frequency based devices. Magnetization measurement reveals CoFe2O4-graphene nanocomposites possess affluence in magnetisation and demagnetisation which makes these materials to be possibly used in high frequency devices, data storage devices and erasable memories. [ABSTRACT FROM AUTHOR]

Electrical and thermal properties of the hybrid composites, prepared using reduced graphene oxide (rGO), multi-walled carbon nanotubes (MWCNTs), and Poly (methyl methacrylate) (PMMA) have been investigated. In this hybrid composite, the effect of rGO wt.% in MWCNTs/PMMA composite has been investigated. The investigation demonstrates that the rGO-MWCNTs/PMMA hybrid composite achieved considerable improvements in electrical properties compared to the MWCNTs/PMMA and rGO/PMMA composites. The hybrid nanocomposite exhibits a percolation threshold of around 0.743 wt.% which is less than that of MWCNTs/PMMA (pc = 0:838wt:%) and rGO/PMMA (pc = 1wt:%) composites and has a maximum conductivity of 1.546-10-1S cm-1 with a filler content of 6 wt.% rGO. The experimentally observed improved electrical and thermal properties as a result of increased rGO wt.% in MWCNTs/PMMA are attributed to a synergistic effect of MWCNTs and rGO. The experimentally observed physical properties of the rGO-MWNTs/PMMA nanocomposite suggest it as potential material for future applications. [ABSTRACT FROM AUTHOR]

The influence of water absorption on the mechanical and thermo-mechanical behaviour of carbon nanofibre (CNF) doped epoxy composites was investigated. When immersed in seawater for a long interval of 6 months, all the composite specimens endured saturation whilst weight change of composites was periodically monitored after removal of travelling specimens from a water-beaker. The equilibrium water content and the diffusion coefficient of all composites were evaluated with the help of Fick’s law of diffusion. The results demonstrated a general reduction in flexural modulus and strength, hardness, storage modulus and glass transition temperature (Tg) for seawater exposed specimens due to absorption of seawater as compared to their unexposed specimens. After-effects of water absorption such as plasticisation, swelling of epoxy polymer, interfacial damages and micro-cracks, were marked as the main reasons behind the deterioration of properties. However, among all, the least degradation in properties was observed in the nanocomposite with 0.75 wt.% CNFs loading. Such trivial degradation in properties is due to formation of strong interface of CNFs with the epoxy polymer. The experimental findings were further confirmed by the microstructures of fractured specimens using field emission scanning electron microscopy. [ABSTRACT FROM AUTHOR]

The study of mechanical properties of carbon nanotube reinforced polymeric materials under different environmental conditions are very much essential as this material possesses potential for using it in structural parts, automobiles, marine field and so on. This study deals with the effect of moisture absorption on the mechanical and thermal properties of carbon nanotube/epoxy composites by immersing it in sea and distilled water at 30℃ temperature and at 75% Relative Humidity (RH) humidity. Composite specimens containing different wt.% of carbon nanotubes were prepared, tested and subjected to water immersion test. The flexural properties, hardness and glass transition temperature (Tg) of water-immersed specimens were evaluated and compared with unexposed specimens as per the American Society for Testing and Material (ASTM) standard. It is concluded that the water absorption brought certain loss in the mechanical properties and reduction in Tg of the composites. It was also found that moisture uptake affected both sea and distilled water samples in different ways. [ABSTRACT FROM AUTHOR]

Hygrothermic aging of epoxy and carbon nanotube (CNT)/epoxy composites (0.5, 0.75, and 1 wt.%) was studied for their application suitability in seawater environments. The specimens were emerged in seawater and kept at constant temperature of 30°C for a maximum duration of 180 days. The specimens were periodically weighed for water absorption study and tested for mechanical as well as thermal properties. All aged samples were showing some amount of degradation owing to their moistureabsorption rates. CNT composites absorbed less moisture than pure epoxy because of the presence of nanofillers. C0.75 was found to be hygrothermally more stable reflecting minimum reduction in flexural properties and glass transition temperature value, which was due to least moisture/water absorption. Deterioration of properties was significant in C1, though it was better than pure epoxy. Fractographic analysis by scanning electron microscopy (SEM) revealed interfacial debonding as the dominant failure mechanism, resulting in pull out of nanotubes. [ABSTRACT FROM AUTHOR]