Journal of Nano Research Vol. 78

Abstract: Nanostructured FeNi and FeNiGr alloys were successfully synthesized by the mechanical alloying technique. The alloys formation and different magnetic properties were studied as a function of milling time in the range of 0 to 30h by X-ray diffraction (XRD) technique, Scanning Electron Microscope (SEM) analysis and a Vibrating Sample Magnetometer (VSM) process. The X-ray diffraction study confirmed the apparition of the α-FeNi alloy after 5h of milling with an average crystallite size of 26.80nm. The crystallite size obtained after 30h of milling is 10.13nm, While, the lattice deformation increases from 0.431 to 0.935%. in addition, the analysis of the magnetization curves of the Fe-Ni alloys revealed original magnetic properties: super paramagnetic behavior, and especially saturation magnetization and significant coercivity. ​​​​​​​ Furthermore, the addition of graphene into FeNi alloy, reduced its crystallite size from 11.56 to 6.65 nm, and increases the lattice strain and lattice parameter from 0.631 to 0.748% and from 0.28686 to 0.28704nm, respectively. Which, enhanced these magnetic properties, by increasing its coercivity (Hc) from 16. 07 to 135.42 Oe and Mr from 1.73 to 5.87 emu/g, while the magnetization saturation is decreased from 153.25 to 123.06 emu/g.

Abstract: The present work aims at the preparation and characterization of ceramic layered composite prepared from fine submicron-sized Al₂O₃ with the addition of electrospun graphene-coated Al₂O₃ fibers (Al₂O₃/G-Fs) by Spark Plasma Sintering with double pressure sintering process. A layered composite containing 2.5 wt. % of Al₂O₃/G fibers in three homogeneous layers was prepared and compared with the pure monolithic Al₂O₃ material obtained under the same conditions. The microstructures of the samples were studied by optical microscopy, scanning, and transmission electron microscopy. The presence of graphene after the sintering in the final composite was proved by Raman spectroscopy. The effect of the graphene-coated fibers on the composite`s microstructure and mechanical properties was described along with the fractographic analysis. Graphene on the surface of the electrospun Al₂O₃ fibers suppressed the grain growth which dominantly takes place during the sintering of the composite, which significantly influenced the character of the fracture. While predominantly intergranular fracture occurs in the monolithic fracture surface, the fracture character becomes transgranular with the addition of layers of Al₂O₃/G-Fs. Fracture toughness improvement took place because of the presence of small pores, in order of a few nanometers, which showed high energy absorption and provided self-induced crack propagation inhibition.

Abstract: The ultrafine fibers of Poly Vinyl Alcohol (PVA) /Graphene Oxide (GO) composite were prepared by using a homemade electrospinning set-up at 12.5 kV and 12 cm with different concentrations of GO (1g/L, 0.75g/L, and 0.5g/L) in PVA. The effect of GO concentrations in 10% PVA solution on the diameter of fibers was investigated. Fourier Transform Infrared (FTIR) Spectroscopy was used to analyze the functional groups. Ultraviolet (UV)-visible spectra of GO suspension showed the absorption peak at 232 nm. The morphology of the nanofibers was analyzed by Scanning Electron Microscopy (SEM). The X-ray diffraction (XRD) technique was used to analyze the crystalline nature of this material. The diameter of nanofibers decreased with improved crystallinity, thus, increasing the concentration of GO in PVA.

Abstract: In this study, silver-silica (Ag/SiO₂) was synthesized using the sol-gel method by silica from rice husks. Silica derived from rice husk waste was previously synthesized using the sol gel method. In addition, the Ag material used in this study was also performed into silver nanoparticles (AgNPs). This method was chosen to obtain an Ag/SiO₂ composite with nano size and high purity. AgNPs were synthesized using silver nitrate (AgNO₃) by reduction method at 90 °C. The reducing agent and stabilizer used is trisodium citrate. UV-Vis, FTIR, XRD, and SEM-EDX were used for the analysis Ag/SiO₂ composites. Uv-Vis analysis results Ag/SiO₂ has an absorption peak at a wavelength of 412 nm with a bandgap energy of 2.25 eV. These peaks indicate that AgNPs have formed in the SiO₂ membrane. The FTIR results revealed the Si-O-Si bonds which indicated the presence of silica and the Ag-O functional group, and the presence of AgNPs. The results of XRD analysis showed that the silica structure formed was cristobalite and silver crystals in the face center cubic (fcc) shape. The results of the SEM-EDX morphological analysis showed that the Ag/SiO₂ nanocomposite was shaped like sharp stone chips and the presence of small granules (granules) with different particle sizes and shapes, slightly porous and the composition of the compounds in the Ag/SiO₂ nanocomposite indicated the presence of various chemical elements in the sample, including carbon, oxygen, sodium, silica, and silver.

Abstract: Cellulose acetate (CA) composite membranes are tailored for potential gas-transportation and antibacterial activity by incorporating various ratios (0-8wt. %) of zeolite-CuO (10:1, ZC) composite. The aim behind this is to develop an anti-biofouling membrane with enhanced CO₂ permeation and selection properties. In situ coprecipitation route is adopted to synthesize ZC that imparted morphological, structural, thermal, and performance characteristics of membranes synthesized by solution casting mechanism. FESEM analysis revealed, pores size transformed from 1µm to 1.4 nm as observed in M0 (virgin) and M4 (8wt. % ZC) membranes, respectively. The existence and linkages of impregnated ZC in the developed membranes are verified by FTIR investigations. TGA-tested thermally endured membranes are tested for gas permeation/selectivity. In comparison to virgin CA membrane, three folds enhancements in CO₂ permeation and two folds in CO₂/N₂ selectivity are observed. Membranes are also evaluated for antibacterial test against ‘gram-negative bacteria’ elucidates that increasing ZC content in composite membranes exhibit remarkable results.

Abstract: Herein, we report for the first time the thermal diffusivity of zinc ferrite/ silver/ silver chloride nanocomposite with a four-fold enhancement in comparison with the base fluid. A systematic analysis of the dependence of calcination temperature and synthesis routes on the crystallinity of nanocomposites of zinc ferrite with silver and silver chloride suiting it for diverse applications was done. Synthesized via the co-precipitation method, the samples were characterized using X-ray diffraction, Field emission scanning electron microscopy, Energy dispersive X-ray, Vibration sample magnetometer, ultraviolet-visible Diffusive Reflective spectroscopy and Photoluminescence studies. A zeta potential of -31.1mV was obtained for the sample showing good colloidal stability. The thermal diffusivity of the samples as nanofluids was analyzed using the dual beam thermal lens method. The study also envisages the magnetically retrievable and visible light-active nature of the synthesized samples indicating their suitability for photocatalytic degradation of toxic dyes. The work on photocatalytic degradation of methylene blue stands out in attaining rapid, efficient dye degradation of 98% within 90 minutes of sunlight exposure in comparison with unblended zinc ferrite nanoparticles even without any oxidizing agent.

Abstract: This paper reports on the successful synthesis of fine nanoparticles of nickel-substituted lithium-iron ferrites of composition Li_0.5-x/2Ni_xFe_2.5-x/2O₄ (0.2≤ x ≤1.0) by the sol-gel autocombustion method. It has been found that the alternating current (AC) and direct current (DC) conductivity is preferably tuned due to its dependence on temperature and nickel doping. Analysis of the Arrhenius dependences also confirms the appearance of more than one conduction mechanism upon substitution. The predominance of one type of conductivity over another depends on the concentration of the substituting element. Measurement of the magnetic properties has shown that the substitution of Ni²⁺ can significantly change the saturation and residual magnetization. Samples of composition Li_0.4Ni_0.2Fe_2.4O₄ have the highest saturation magnetization (84.08 emu/g), residual magnetization (15.85 emu/g), and the lowest coercive force (0.18 kOe). All the obtained results indicate a significant effect of the substitution of Ni²⁺ ions on the structure and properties of Li_0.5-x/2Ni_xFe_2.5-x/2O₄ ferrite nanoparticles.Photocatalytic properties have been obtained by the degradation of Methylene Blue dye under illumination with a halogen lamp. It is shown that an increase in the content of nickel ions leads to a change in the type of conductivity: from n-type (unsubstituted lithium pentaferrite) to p-type (with substitution x = 0.8 and higher). These systems are characterized by hopping conduction realized by octa-positions according to the mechanisms Fe³⁺+e^-↔Fe²⁺, and Ni³⁺↔Ni²⁺+h⁺. The predominance of one or another mechanism depends on the content of nickel ions. The optical band gap ranges from 1.4 to 2.25 eV. Samples with nickel content x = 0.4 and x = 0.8 have shown the best degradation ability, which is 97% within 160 min for Methylene Blue.

Abstract: Magnetic-bead separation or purification serves as a technique for effective isolation of biomolecules. In presented work we prepared and characterized core-shell magnetic nanoparticle samples consisted of Fe₃O₄ core coated with SiO₂ shell. Samples were subsequently coated with ligands MPTMS (3-(mercaptopropyl)trimethoxysilane), CPTMS (3-(chloropropyl)trimethoxysilane) and MMSP (3-(trimethoxysilyl)propyl methacrylate) with aim to increase the number of active centers for specific binding with RNA. Such samples were further investigated for their magnetic properties, size, and morphology. Magnetic properties were studied in DC field up to 5 T in temperature range 5 – 300 K. Size and morphology were determined from SEM micrographs and elemental compositions of the samples were investigated using EDX analysis. Modification of nanoparticle surface with different ligands leads to modification of active centers on the SiO₂ surface on which the DNA and RNA molecules can be bounded. It also causes the change in magnetic and structural properties of nanoparticles.

Abstract: Hydrogen evolution reactions (HER) are important in a variety of electrochemical devices, such as electrolysers and fuel cells. To reduce the reaction overpotential and reduce energy consumption, efficient, low-cost, and durable electrocatalysts must be developed. Needle-less electrospinning (NLE) technique was used to prepare the fibrous electrocatalyst. NLE is a user-friendly and adaptable technique for large-scale low-cost fiber production. NLE created transition metal phosphides carbon fibers (TMP CF). The precursor foam was folded between two Al₂O₃ ceramic plates. The heat treatment was carried out in a tube furnace at 1200 °C in an Ar atmosphere, followed by a reduction in an H₂ atmosphere at 780 °C. The electrolyser's membrane electrode assembly can be immediately submerged in the final TMP CF in the form of plates. The created NiCoP catalytic plates could be directly used in electrolyser's membrane electrode assembly of PEM electrolysers. In a three-electrode system, the electrochemical activity of the produced electrocatalysts was evaluated using linear sweep voltammetry. The electrochemical activity of the produced electrocatalysts were evaluated using linear sweep voltammetry. The catalyst's stability and endurance in acidic and alkaline environments were investigated.

Abstract: This present study is intended for a CFD analysis of hydrodynamic and thermal characteristics of water-based fluid containing TiO₂ or CuO nanoparticles flowing in laminar regime in a 3D uniformly heated horizontal annulus utilizing several. Four distinct models have been developed using various combinations (A, B, C and D) of the available theorical-based and experimental-based thermal conductivity and viscosity correlations. A CFD-Fortran code based on the finite volume technique was elaborated for the numerical solution of the mathematical model of the problem. The implications of Grashof number, volume fraction, and type of nanoparticle on isovelocity, isotherms, mean and wall temperatures, Nusselt number, heat transfer coefficient, pressure drop, and thermal performance evaluation criteria are explored using these different models. The results demonstrate that the Nusselt number and heat transfer coefficient of all developed models improve with the addition of nanoparticles. For 2% of nanoparticles’ concentration, the largest enhancement was reached for model D by about 23.5% with respect to the based liquid, while the smallest enhancement was obtained for model B by about 1.16%. The highest Performance Evaluation Criteria (PEC) are attained by employing model D by about 1.263, followed by model C by about 1.074.