Journal of Nano Research Vol. 58

Abstract: Nanostructured (Fe_0.6Al_0.4)_100-xSi_x powders with x= 0, 5, 10, 15 and 20 at.% were elaborated by means of mechanical alloying for a fixed milling time of 72 h. We have investigated the effect of silicon addition on the microstructure and magnetic properties of these ternary alloys. X-ray diffraction experiments reveal that these powders are single-phase disordered solid solutions with body centered cubic crystal structure. The lattice parameter diminishesalmost linearly as the Si content increases. The mean crystallite size,<D(nm)>, is around three times smaller for the samples with higher amount of Si (≈ 10 nm) compared with that of the binary alloy (27 nm). Moreover, the volume fraction of grain boundaries (fgb) seems to be higher with increasing the Si content, as well as both dislocation density (ρ) and lattice microstrain (<ε>),that follow alinear trend. The SEM images show that the Si helps in refining the shape and size of the powder particles, leading to a nearly homogeneous small particles.The addition of Si strongly affects the value of the saturation magnetization, Ms, that falls nearly an order of magnitude for the sample with 20 at.% Si, while the coercivity remains almost unchanged. The Mössbauer spectra show the presence of a sextet (ferromagnetic phase) and a singlet or a doublet (non ferromagnetic phase), except for the sample corresponding to x = 10, where only one singlet is observed in the spectrum.

Abstract: Porous, phosphate-silicate glass with high-conductivity and nano-size pores was synthesized through a xero-gel route, using non-ionic surfactant polyethylene glycol monocetyl ether (Brij 56) to control pore size. The influences of Brij 56 concentration on pore size and conductivity under different humidity were studied by measuring conductivity and calculating the volume ratio of adsorbed-water to pore volume. Samples prepared with 0.1 wt% Brij 56 had 5.2 nm pore size, 0.91 volume ratio, and narrower pore size distribution than other samples. The nano-size pores were filled with water, which in pores of 5.2 nm is mostly chemically bonded with the hydroxyl groups on the pore surfaces, resulting in higher conductivity than other samples in high relative humidity (over 55%).

Abstract: This research investigates the pH value of stainless steel (SS) 316L/ deionised water (DIW), alumina (Al₂O₃)/DIW, and copper (I) oxide (Cu₂O)/DIW nanofluids prepared using a two-step controlled sonication temperature approach of 10°C to 60°C. The nanoparticles volumetric concentration of each family of as-prepared nanofluid ranged from 0.1 to 1.0 vol%, using as-received nanopowders, of 18 – 80 nm average particles size. Furthermore, the pH measuring apparatus and the measurement procedure were validated by determining the pH of commercially supplied calibration fluids, of pH 4, 7, and 10. Following the validation, pH correlations were obtained from the experimental measurements of the 0.1, 0.5, and 1.0 vol% nanofluids in terms of varied sonication bath temperatures and volumetric concentrations. Those correlations were then combined into one robust pH_nf correlation and validated using the pH data of the 0.3 and 0.7 vol% nanofluids. The new proposed correlation was found to have a 2.18%, 0.92%, and 0.63%, average deviation from the experimental pH measurements of SS 316L, Al₂O₃, and Cu₂O nanofluids, respectively, with an overall prediction accuracy of ~ 92%.

Abstract: For many high voltage transmission lines, lightning is the first cause of outages. Different alternatives have been used to diminish these outages, like the use of counterpoise wires, installation of surge arresters, and the improvement of the grounding system using ground enhancers or chemical enhancers. In this paper, graphene nanoparticles were used to reformulate commercial ground enhancers. The results of this research end up in an improvement factor of up to 100 times the reduction in resistivity, when graphene nanoparticles are used. After lightning current impulse tests done on both types of samples, the performance of the un-reformulated ground enhancer samples shows a faster deterioration than the graphene reinforced ground enhancer samples. In order to establish a criterion to quantitatively rank the chemical ground enhancers ́ performance after the lightning impulse current tests, a neural network model was developed.

Abstract: In this article, the analyses of free vibration of nanoplates, such as single-layered graphene sheets (SLGS), lying on an elastic medium is evaluated and analyzed via a novel refined plate theory mathematical model including small-scale effects. The noteworthy feature of theory is that the displacement field is modelled with only four unknowns, which is even less than the other shear deformation theories. The present one has a new displacement field which introduces undetermined integral variables, the shear stress free condition on the top and bottom surfaces of the plate is respected and consequently, it is unnecessary to use shear correction factors. The theory involves four unknown variables, as against five in case of other higher order theories and first-order shear deformation theory. By using Hamilton’s principle, the nonlocal governing equations are obtained and they are solved via Navier solution method. The influences played by transversal shear deformation, plate aspect ratio, side-to-thickness ratio, nonlocal parameter, and elastic foundation parameters are all examined. From this work, it can be observed that the small-scale effects and elastic foundation parameters are significant for the natural frequency.