Structural, magnetic and dielectric properties of nickel- magnesium substituted cobalt ferrites nanoparticles and core-shell nanocomposites

Cobalt ferrite has gained great scientist interest because of its important applications in various fields of science and technology. However, the magnetic character of the particles used for many applications depends crucially on the size, shape and purity of these nanoparticles. Hence the need for developing fabrication processes that are relatively simple and yield controlled particle sizes is desired. This work involves the study of structural, magnetic, dielectric properties and morphology of Co0.5Ni0.5-xMgxFe2O4 ferrite nanoparticles (x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5), which are synthesized by chemical co-precipitation method. In addition, the core-shell nanocomposites of Co0.5Ni0.5-xMgxFe2O4/Polyaniline were successfully synthesized via chemical polymerization method. The ferrite samples were then sintered at selected temperatures of 700 °C, 800 °C, 900 °C and 1000°C for 8 hours. X-ray powder diffraction indicated that the core material is having a single phase of spinel cubic structure. The crystallite size of Co0.5Ni0.5-xMgxFe2O4 nanoparticles was found in the range of 25-40 nm. The infrared spectra of the synthesized samples displayed two absorption bands characteristic of the spinel ferrites at 585–595 cm-1 and 390–400 cm-1, which correspond to vibrations of tetrahedral and octahedral bonds, respectively. The Field Emission Scanning Electron Microscope and Transmission Electron Microscope images of ferrite nanoparticles show different aggregations at different sintering temperatures and concentrations. The combination of both Ni-, Mg- substituted cobalt ferrites showed that the substitution of Mg2+ ions for Fe made more pronounced effects on magnetic and dielectric properties at room temperature. The values of saturation magnetization (Ms) and coercivity (Hc) are enhanced by increasing of Mg concentration up to x = 0.1. By increasing Mg2+ substitution, the Ms and Hc increase from 57.35 emu/g (x = 0.0) to 61.49 emu/g (x = 0.1) and 603.26 Oe (x = 0.0) to 684.11 Oe (x = 0.1), respectively. In contrast, the Ms decreases from a maximum value 12.00 emu/g (x = 0.1) to a minimum value 5.39 emu/g (x = 0.4) when ferrites are encapsulated with Polyaniline. However, the Hc increases from a maximum value 766.94 Oe (x = 0.1) to a minimum value 646.17 Oe (x = 0.0). At 1 kHz, dielectric constant e' shows a maximum value at 86.22 for x = 0.1 and minimum value at 56.67 for x = 0.3. In addition, the dielectric loss e" shows a maximum value of 10.98 for x = 0.2 and minimum value of 9.45 for x = 0.0. For nanocomposites, e' reaches a maximum value of 68.32 (x = 0.1) and minimum value of 46.73 (x = 0.3) at 1 kHz. In addition, e" shows a maximum value of 49.42 (x = 0.2) and a minimum value of 36.33 (x = 0.3)

Graphene slurry based passive Q-switcher in erbium doped fiber laser

In this work, a Graphene slurry based passive Q-switcher fabricated from Graphene-Polylactic acid (PLA) filament which is used for 3D printing. To produce the Graphene slurry, the diameter of the filament was reduced and Tetrahydrofuran (THF) was used to dissolve the PLA. The Graphene-THF suspension was drop cast to the end of a fiber ferrule and the THF then evaporated to develop Graphene slurry based SA which is integrated in fiber laser cavity. At threshold input pump power of 30.45 mW, a Q-switched Erbium-doped fiber laser (EDFL) can be observed with the wavelength centered at 1531.01 nm and this remained stable up to a pump power of 179.5 mW. As the pump power was increased gradually, an increase in the repetition rates was recorded from 42 kHz to 125 kHz, while the pulse width was reduced to 2.58 μs from 6.74 μs. The Q-switched laser yielded a maximum pulse energy and peak power of 11.68 nJ and 4.16 mW, respectively. The proposed Graphene slurry based saturable absorber also produced a signal-to-noise ratio of 44 dB indicating a stable Q-switched pulsed laser

Improving Ag-TiO2nanocomposites’ current density by TiCl4 pretreated on FTO glass for dye-sensitised solar cells

Titanium tetrachloride (TiCl4) pretreatment on the fluorine-doped tin oxide (FTO) is one of the alternative techniques to enhance short-circuit current density (Jsc) and efficiency of dye-sensitised solar cells (DSSC) by improving the inter-particle bonding between FTO grain and nanoporous titanium dioxide (TiO2). The present study investigbrkates the effect of TiCl4 pretreatment on the surface of FTO glass to enhance the Jsc and efficiency of silver-titanium dioxide (Ag-TiO2) nanocomposites. The pretreatment process was prepared by immersing FTO glass into TiCl4 solution at 70°C for 30 min, and then sintered at 500°C for 30 min. Morphological and elemental characteristics were done to observe the structure and composition of pretreatment on the FTO glass. The results showed that the Ag-TiO2 with TiCl4 pretreatment achieved high efficiency of 7.27% with Jsc of 18.95 mA/cm2. The proposed method shows that the pretreatment can improve the efficiency by improving the inter-particle bonding between nanoporous TiO2 and FTO grain, which can enhance the electron transfer. Also, the presence of Ag in the nanocomposites as a solar concentrator can increase the light absorption by TiO2 nanoparticles and also increase the DSSC efficiency

Synthesis of silver nanoparticles using chemical reduction techniques for Q-switcher at 1.5 µm region

This research investigated the generation of passively Q-switched erbium (Er)-doped fibre laser using silver nanoparticles/poly (vinyl alcohol) (Ag/PVA) as a saturable absorber (SA). The Ag nanoparticles were synthesised via the chemical reduction technique. The Ag/PVA film based SA was fabricated by blending Ag nanoparticles powder into the PVA suspension, then left to dry at ambient to develop a free-standing SA film. Next, the Ag/PVA film was sandwiched in between two FC/PC fibre ferrules and integrated into the laser cavity for Q-switched pulse generation. The result shows that the Q-switched pulsed laser achieved pulse energy and peak power of 128.04 nJ and 21.34 mW at the maximum pump power of 107.1 mW. A signal-to-noise ratio (SNR) value of 66.23 dB was obtained at a frequency of 66.23 kHz proving that it is an excellent candidate as a SA material for Q-switched generation in future large-scale manufacturing

Rheological, mechanical, morphological and thermal properties ofr ecycled poly (ethylene terephthalate)- polythylene filled montmorillonite

The objective of this research is to investigate the effect of incorporating nanofiller, montmorillonite (MMT) on mechanical, morphology, rheological and thermal properties of recycled poly(ethylene terephthalate) (rPET) and High density polyethylene (HDPE) nanocomposites. The MMT contents in 90:10 rPET/HDPE and 70:30 rPET/PE ranged from 1 to 5 wt.%. Blends based on rPET/HDPE nanocomposites were made through single extrusion and injection-molded into tensile and impact test samples. Samples underwent rheological test by using capillary rheometer, and the morphology of the nanocomposites was investigated by scanning electron microscopy (SEM). Thermal stability of organoclays and nanocomposites was tested by thermogravimetric analysis (TGA). The results pointed out that MMT displayed a higher compatibilizing act giving rise to a neat improvement of phase dispersion and interfacial adhesion in the blends. The maximum tensile strength was at 3 wt. % and 1 wt. % of MMT for 90:10 and 70:30 rPET/HDPE blends. However, tensile modulus decreased significantly with the incorporation of MMT. Impact strength for both blending 90:10 and 70:30 reached a maximum point at 3 wt. % and started to decrease beyond 3 wt. %. The incorporation of MMT increased the shear viscosity of 90:10 and 70:30 which reached a maximum value at 3 wt. % and 1 wt. %

Effect of Cu-Al substitution on the structural and magnetic properties of Co ferrites

In this work copper aluminum substituted cobalt nanocrystalline spinel ferrites having general formula Co1-xCuxFe2-x AlxO4, with 0.0=0.8 have been synthesized by using a co-precipitation method. The Cu-Al substituted samples were annealed at 600 °C and characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM) and vibrating sample magnetometer (VSM). XRD analysis confirmed a single phase spinel structure and the crystalline size calculated using Scherre

Synthesis, structural and magnetic behavior studies of Zn-Al substituted cobalt ferrite nanoparticles

A series of nano-sized Zn-Al substituted cobalt ferrite Co(1- x )Zn( x )Fe2- xAlxO4 with 0.0=x=1.0 have been synthesized by chemical co-precipitation technique. The XRD spectra revealed the single phase spinel structure of Co(1- x )Zn( x )Fe2- xAlxO4 with average size of nanoparticles are estimated to be 17-30 nm. These are small enough to achieve the suitable signal to noise ratio, which is important in the high-density recording media. The FTIR spectra show the characteristic of two strong absorption bands at 560-600 cm-1 corresponds to the intrinsic stretching vibrations of the metal at the tetrahedral site and lowest band is observed at 370-410 cm-1 corresponds to octahedral site. The crystalline structures of nanoparticles composite were characterized by Field Emission Scanning Electron Microscopy (FE-SEM). The magnetic properties such as saturation magnetization, remanence magnetization, and coercivity were calculated from the hysteresis loops. Saturation magnetization were found to increase up to x = 0.4 while remanence magnetization and coercivity continuously decrease with increasing Zn-Al concentration. The stability in coercivity while increase in saturation magnetization confirms that the Co0.6Zn0.4Fe1.6Al0.4O4 ferrite sample is suitable for applications in high-density recording media

Rheological properties of Mg substituted cobalt nickel ferrite nanoparticles as an additive in magnetorheological elastomer

Additive has been used widely in magnetorheological elastomer (MRE) fabrication in order to enhance the magnetic, electrical and rheological properties. In this study, the ferrite nanoparticles namely Magnesium (Mg) substituted Cobalt Nickel Ferrite is introduced as an additive in order to enhance the magnetic and rheological properties of MRE. The conventional co-precipitation method is used to synthesize the Mg substituted Cobalt Nickel Ferrite nanoparticles. The 1 wt% of spherical Mg substituted Cobalt Nickel Ferrite nanoparticles with a range size of 50 nm are then sonicated using ultrasonication before mixing with 70 wt% carbonyl iron particles (CIPs) and silicon-rubber (SR) as a matrix. Two prepared samples of MRE with and without Mg substituted Cobalt Nickel Ferrite nanoparticles are characterized using Vibrating Sample Magnetometer (VSM). Meanwhile, the rheological properties related to the frequency and magnetorheological (MR) effect in off- and on-state condition are determined by using rotational rheometer. The result depicted that the magnetic saturation of MRE with Mg substituted Cobalt Nickel Ferrite nanoparticles increased by 2%. Meanwhile, the maximum storage modulus of MRE with Mg substituted Cobalt Nickel Ferrite nanoparticles enhanced up to 13% as compared to conventional MRE. In the case of energy dissipation, the MRE + S1, exhibit higher energy dissipation as compared to conventional MRE. In the meantime, the relative MR effect of MRE with 1 wt% Mg substituted Cobalt Nickel Ferrite nanoparticles can reach up to 215%, as compared to conventional MRE. The enhancement of magnetic and rheological properties of MRE with Mg substituted Cobalt Nickel Ferrite nanoparticles suggest that the nanoparticles additive fill the void and improved the interaction between CIPs resulted in increment of storage modulus

Enhancing photocurrent performance based on photoanode thickness and surface plasmon resonance using Ag-TiO2 nanocomposites in dye-sensitized solar cells

This study investigated the different thicknesses of TiO2 photoanode films and the effect of surface plasmon resonance (SPR) of Ag-TiO2 nanocomposites on the current-voltage (I–V) performance of dye-sensitized solar cells (DSSC). The TiO2 layer was deposited using the doctor blade technique and the thickness of the TiO2 films was controlled by using a different number of Scotch tape layers. The silver nanoparticles (AgNP) were synthesised using a chemical reduction method and the concentration of sodium citrate as a reducing agent was varied from 4 to 12 mM to study the effect of citrate ion on the size of the nanoparticles. Ag-TiO2 nanopowder was prepared by adding pure anatase TiO2 powder into AgNP colloidal solution. The mixture was left to dry for 24 h to obtain Ag-TiO2 powder for paste preparation. The three-layer Scotch tape, with thickness of 14.38 µm, achieved a high efficiency of 4.14%. This results showed that three layers was the optimal thickness to improve dye loading and to reduce the charge recombination rate. As for the Ag-TiO2 nanocomposites, 10 mM of AgNP, with a mean diameter of 65.23 nm and high efficiency of 6.92%, proved that SPR can enhance the absorption capability of dye and improve the photon-to-electron generation

Synthesis of silver nanoparticles using chemical reduction techniques for Q-switcher at 1.5 μm region

This research investigated the generation of passively Q-switched erbium (Er)-doped fibre laser using silver nanoparticles/poly (vinyl alcohol) (Ag/PVA) as a saturable absorber (SA). The Ag nanoparticles were synthesised via the chemical reduction technique. The Ag/PVA film based SA was fabricated by blending Ag nanoparticles powder into the PVA suspension, then left to dry at ambient to develop a free-standing SA film. Next, the Ag/PVA film was sandwiched in between two FC/PC fibre ferrules and integrated into the laser cavity for Q-switched pulse generation. The result shows that the Q-switched pulsed laser achieved pulse energy and peak power of 128.04 nJ and 21.34 mW at the maximum pump power of 107.1 mW. A signal-to-noise ratio (SNR) value of 66.23 dB was obtained at a frequency of 66.23 kHz proving that it is an excellent candidate as a SA material for Q-switched generation in future large-scale manufacturing