Abstract: In this work, gamma–MnO2 nanostructure was used as a sorbent to remove Zn (II) ion from aqueous solution. The influence of pH, sorption time and Zn (II) ion initial concentration were examined. The results showed that equilibrium adsorption was obtained after 60 minutes with 240 rpm of shaking speed at pH = 4.0. The experimental data were analyzed using five non-linear isotherm models: Langmuir, Freundlich, Sips, Tempkin and Dubinin – Radushkevich. The adsorption capacity (qm) from the Langmuir isotherm model for Zn (II) is founded as 55.23 mg/g. The heat of sorption process and the mean free energy were estimated from Temkin and Dubinin – Redushkevich isotherm models to be less than 8 kj/mol which vividly proved that the adsorption experiment followed a physical process. Kinetic studies have shown that although the adsorption data partially followed pseudo-first-order and pseudo-second-order equation for different time, it was well expressed by pseudo-second-order model.
Abstract: The dielectric properties of ZnO and Al2O3 are dependent upon various factors such as chemical composition, method of synthesis, grain size, particle size distribution and porosity. A low dielectric constant is often desirable for several applications, whilst for enhanced oil recovery application, high loss dielectrics is required rendering the particles as surface-active agent. In this study, the dependence of the dielectric properties on the calcination temperature of ZnO and Al2O3 nanoparticles is determined as a function of two applied radio frequencies of 18.82 MHz and 167.32 MHz. The experimental results indicate that the nanoparticles of different phases can significantly improve the densification and their dielectric properties. Detailed analysis of the results showed that rotational polarization is the major contributor to the enhanced dielectric behavior of the nanoparticles at the applied frequencies.
Abstract: Nano size (2 - 10 nm) metal particles were formed and accumulated on powder substrate by conventional physical vapor deposition (PVD) process, in which the powder were a non-volatile in vacuum, such as Al2O3 powder. The neutral nuclei which were formed on the substrates from vaporized or sputtered metal atoms at an initial thin film growth were not grown up to coalescence and island stage with arrival atoms and ad-atom migration in the continuous deposition process, when the powder in vessel were continuously stirred during the deposition. Nano sized particles on the polymer chips (diameter: 1-2mm) easily dispersed into the polymer matrix by heating the chips, and on non-soluble powder, g-Al2O3, were stuck on the supporters stably in air. The nanoparticles on sucrose directly formed colloid with water solvents without dispersive agents. Most of the nano sized particles appear their own characteristic colors due to plasmon effect. Concentration and size of the nanoparticles are controlled by physical parameters in the PVD and the stirring speed of the powder. Surface phenomena on the substrate have been discussed with TEM, SEM, EDX, UV spectroscopy, etc. comparing with the conventional thin film growth.
Abstract: The effect of drying techniques on the crystallinity and thermal stability nanocrystalline cellulose (NCC) prepared from oil palm empty fruit bunch (OPEFB) via the TEMPO-oxidation process was investigated. NCC was subjected to three separate drying techniques viz. oven drying (OD), freeze drying (FD) and solvent exchange (SE). The crystallinity and thermal properties were investigated for all samples using DSC and X-ray diffraction (XRD). There is no significant difference in the degree of crystallinity for both OD-NCC and FD-NCC as compared to the starting material of unbleached pulp (UP) (72% vs 76%), however SE-NCC showed a tremendous reduction with the crystallinity of only 40%. Both OD-NCC and FD-NCC have almost similar thermal behavior but the SE-NCC showed a significant difference. For the application of NCC in non-polar bionanocomposites, both OD-NCC and FD-NCC is recommended due to its relatively superior thermal stability and a higher crystallinity index.
Abstract: A new carbon material viz. graphene has been attracted an increasing research interest owing to its unique electrical and mechanical properties that is useful for the various device applications. The synthesis of graphene from graphene oxide usually involves harmful chemical reducing agents that are toxic and undesirable to human and the environment. By avoiding the use of toxic and environmentally harmful reductants, we report a green approach to effectively reduce graphene oxide to graphene in glucose solution at room temperature. Graphite oxide was synthesized from graphite powder using modified Hummers’ method. Graphite oxide then further exfoliated to graphene oxide by using ultrasonic irradiation. The mild reduction of graphene oxide is carried out by mixing graphene oxide solution with glucose. The reduction time is varied with 15, 30, 45 and 60 minutes. TEM images provide clear evidence for the formation of few layer graphene. Characterization of theresulting glucose reduced graphene oxide by FTIR indicates the partial removal of oxygen-containing functional groups from the surface of graphene oxide and formation of graphene with defects.
Abstract: A theoretical approach is developed to describe creation of space-periodical modulation of microstructure by means irradiation and influence of this modulation on properties of the irradiated material. It has considered nonlinear dynamics of development of radiation-induced defects. The structure of defects drives microstructure and changes material properties. It is found that nanoscale space-periodical distribution is results of interaction of radiation-induced defects both with each other and with elements of microstructure. It is shown that homogenous defect distribution become instable and bifurcation happen with respect to development of space-periodical distribution. Thus change of microstructure and material properties become space-periodical. Period of inhomogeneity and bifurcation values of parameters have been obtained.
Abstract: In this paper, the effect of substitution of Co by d-valent elements such as Ag and Pt on electronic structure and magnetic properties of full Heusler type Co2FeSi alloys was investigated. Structural study reveals the presence of a small gap in the minority band structure around the vicinity of the Fermi level on Co2FeSi resulting to half-metallic behaviour. However, CoFeSiAg and CoFeSiPt cannot preserved the half-metalicity due to disappearing of the gap in the minority band structure due to the creation of new states around the Fermi level in the minority density of states. The variation in the magnetic moment of Co2FeSi with change of the atoms was attributed to the change in the local magnetic moment of atoms.
Abstract: In this study, first principles calculations based on density functional theory were used to evaluate optimized sructures and the total energy of the La doped PbTiO3 tetragonal (P4mm phase group). The calculations were conducted using local density approximation (LDA) functional as implemented in Cambridge Serial Total Energy Package (CASTEP) computer code. The different composition of Lanthanum (x) were doped on PbTiO3 resulting Pb1-xLaxTiO3 and its effect on the structural of Pb1-xLaxTiO3 were investigated. The different composition of La changed the lattice parameter and the volume of Pb1-xLaxTiO3. The total energy also were calculated and x= 0.2 is suitable composition of dapant to doped with PbTiO3 which is more stable compared with the other composition. The results are compared with experimental and other theoretical data.
Abstract: To achieve sustainability in construction, the rehabilitation of existing concrete structures is vital in ensuring its structural integrity and longevity. Therefore, an experimental investigation on the shear strengthening of 2-span continuous reinforced concrete (RC) beams wrapped with carbon fiber reinforced polymer (CFRP) strips were conducted. The beam specimens were subjected to four point bending test and loaded incrementally until failure occurs. Different wrapping schemes and layers of CFRP strips were externally bonded within the shear span of the beams. The failure load, modes of failure, its crack patterns, deflection profile were recorded and presented for discussion. From observation, the experimental results indicated good improvement as the shear strengthened beams shows enhanced failure load and shear strength capacity. An improved stiffness and ductility behaviour was also observed compared to the control beam. Comparison with ACI 440 (2008) design provisions for shear strength shows that the prediction values underestimated its experimental results. This indicates that the enhanced shear performances of the 2-span continuous RC beams prove the reliability of CFRP as a strengthening material. Hence, the shear strengthening technique allows the rehabilitation process of existing structural members to improve its structural integrity, longevity and sustainability.