Journal of Nano Research Vol. 29

Abstract: This work is concerned with the preparation of samarium iron garnet (Sm₃Fe₅O₁₂) nanoparticles via an improved technique named: Modified Conventional Mixing Oxides (MCMO) method. This material was characterized by XRD, FESEM, EDX and TEM. Metal oxides and ethanol solution were used as raw materials to prepare Sm₃Fe₅O₁₂ (SmIG) material. Single-phase SmIG nanoparticles with an average particle value of 25 nm and average crystallite size value of 44 nm have been synthesized at 1350 °C via the MCMO method. SmIG powders with grain sizes below 1 μm and high purity have been presented by FESEM and EDX results, respectively. Lattice constant value of 12.535 Å and density value of 6.221 g.cm^-3, were calculated for the SmIG sample. The latter has reached around 99% of its theoretical density. The MCMO method appears to be an attractive route due to the enhancement of structural properties of the interested sample with high yield in the nanoscale product as compared to other preparation techniques.

Abstract: Fe‒Si alloys are widely used as transformer magnets and magnetic cores because of their excellent soft magnetic properties. Fe60Si40 powders were milled in a high energy planetary ball mill (Rctsch PM400) under argon atmosphere at different time of milling. The metal powders obtained have an average diameter d50 of 2.5 to 6 um. The introduction of Si into Fe can result in a decrease of magnetic anisotropy (therefore leading to a decrease of coercivity). The nanocomposite magnetic cores were made from the Fe60Si40 powder obtained by high energy ball milling for different milling time. The particles of powder were mixed with unsaturated polyester (UP) to obtain toroidal cores. The polymerization process was made under a magnetic field H-500 Am. and ensured a preferential orientation of powder particles. Influences of the metallic powder fraction on soft magnetic properties as well as thermal increase under isothermal conditions were investigated along with the possibility to control these properties with the size and amount of powder fraction. It was also found that the soft magnetic properties of the polymer composites can be controlled in a wide range and depends on the mass fraction of the metallic powder Fe60Si40 in the composite, on shape and size of the powder particles and their orientation in the composite.

Abstract: Polymer-clay nanocomposites (PCNC) offer better properties at very low volume fraction of the nanofiller compared to conventional polymer composites, thus minimizing the effect on other favored properties of the polymer. The mechanism by which clay platelets, which have thicknesses of a few nanometers in size compared with several hundred nanometers in the other two dimensions, introduce mechanical and other properties improvement can be attributed to their high efficiency in introducing a discontinuity to flows through the bulk matrix polymer material. The extent of this improvement depends on the success of intercalation or separation of the clay platelets through the bulk matrix. This paper contains a general overview of polymer-clay nanocomposites in terms of properties and processing. The improvements in gas barrier properties are discussed in detail; and a model to represent the effect of introduction of nanofillers on the permeability is proposed. The model builds on previous models to explain the improvements in the gas barrier properties due to the presence of clay nanoparticles and by assuming a proper distribution of these particles.

Abstract: Perfect and spiral configurations of carbon nanotubes (CNTs) were modeled by a commercial finite element package and their tensile behavior was studied. Computational tests with cantilevered boundary conditions were performed to evaluate their Young’s modulus. It was concluded that the existence of any imperfection, spiral shape in particular, in the structure of perfect CNTs results in a remarkable reduction in the stiffness. It was also revealed that the Young’s modulus of perfect CNTs decreases by introducing spiral distortion.

Abstract: This study deals with the investigation of the tensile and shear behavior of connected carbon nanotubes (CNTs) with parallel longitudinal axes by performing several computational tests. In particular, the effect of imperfections on the mechanical properties, i.e. Young’s modulus and shear modulus, of these nanoconfigurations was analyzed. For this purpose, straight hetero-junctions were simulated in their perfect form and different boundary conditions were considered. In the second phase the three most likely atomic defects, i.e. impurities (doping with Si atoms), vacant sites (carbon vacancy) and introduced perturbations of the ideal geometry in different amounts to the perfect models, were simulated. Finally, the mechanical properties of imperfect hetero-junctions were numerically evaluated and compared with the behavior of perfect ones. It was concluded that the existence of any type of imperfections in the structure of connected CNTs leads to a reduction in the Young’s modulus as well as the shear modulus, and as a result, lower stiffness of these straight nanostructures.

Abstract: Usage of magnetic materials is not unusual in oil and gas research, specifically in enhanced oil recovery (EOR) where various magnetic micro-and nanoparticles were used to enhance sweep efficiency, reducing interfacial tension and heat generation. Magnetic nanoparticles which are activated by a magnetic field are anticipated to have the ability to travel far into the oil reservoir and assist in the displacement of the trapped oil. In this work, magnetic Fe₂O₃-Al₂O₃ nanocomposite was synthesized and characterized for its morphological, structural and magnetic properties. At an annealing temperature of 900°C, this nanomaterial starts to exhibit magnetization as the composite structure crystallizes to the stable Fe₂O₃ and Al₂O₃. Subsequently, dispersion of the 0.01 wt% Fe₂O₃-Al₂O₃ nanocomposite in distilled water was used for displacement tests to validate its feasibility to be applied in EOR. In the displacement test, the effect of electromagnetic waves on the magnetization of Fe₂O₃-Al₂O₃ nanofluid was also investigated by irradiating a 13.6 MHz square wave to the porous medium while nanofluid injection is taking place. In conclusion, an almost 20% increment in the recovery of oil was obtained with the application of electromagnetic waves in 2.4 pore volumes (PV) injection of Fe₂O₃-Al₂O₃ nanofluid.

Abstract: Integration of nanoparticles in enhanced oil recovery (EOR) has been intensively studied in recent years due to their unique properties owing to the nanoscale dimensions, rendering them to have different properties in comparison with its bulk material. Application of magnetic nanoparticles such as ferrites was able to exploit their rheological properties as a chain-like structure formed due to dipole-dipole alignment with the applied magnetic field. Ferromagnetic nanoparticles had shown an increment in the oil recovery under the irradiation of an EM wave. In this research, the influence of magnetic nanoparticles nickel-zinc-ferrite, Ni_1-xZn_xFe₂O₂ in the form of nanofluids on the recovery efficiency in EOR was studied. Nickel-zinc-ferrite magnetic nanoparticles with various values of x were synthesized to observe the effect of nickel to zinc ratio on recovery efficiency. The nanoparticles were characterized using X-ray Diffraction (XRD) and Vibrating Sample Magnetometer (VSM). Coreflooding experiments were conducted where the nanofluids were injected into the compacted sand saturated with crude oil under EM irradiation. The amount of oil recovered from the core was evaluated. VSM tests shows that the sample with x = 0.5 had the highest magnetization of 52.6 emu/g. The nanofluids prepared from the sample also achieved the highest crude oil recovery of 26.07% of the residual oil in place (ROIP).

Abstract: Nanostructured Ba-Cu-Si clathrate powders were synthesized by mechanical milling using different amounts of process control agent (PCA). We investigated systematically the effects of PCA on the phase constitution and crystallite size of nanopowders using X-ray diffraction (XRD) as well as the particle size and morphology by scanning electron microscopy (SEM). The PCA increases the powder yield by reducing the powder agglomeration. No detectable reaction occurred between the PCA and the clathrate phase, and thus the composition of the clathrate phase is unchanged after milling. Compared to the powders milled without PCA, the crystalline size of powders with PCA is reduced from about 70 to about 50 nm.