Advanced Materials Research Vol. 1177

Abstract: Friction stir welding is now increasingly being applied to joining aluminum alloys and other non-ferrous metals because the process has been established to be more suitable for joining soft metals. Compared with the facilities required for fusion welding, procuring friction stir welding machine is capital intensive and its utilization in the underdeveloped nations is very scanty. In this work, some experimental works were done so as determine the optimized process parameters for friction stir welding of aluminium alloys using an adapted vertical milling machine. The focus is to optimize the friction stir welding of AA1100 using an adapted vertical milling machine so as to obtain high quality weldments in terms of hardness and tensile strength. Friction stir welding of AA1100 was performed within a process window. The process parameters were optimized for improved hardness and tensile strength. The hardness property of the welded joints was measured using Brinnel hardness tester while the tensile strength was measured using Instron universal testing machine. Within the range of parameters utilized in this work, the hardness and tensile strength of the friction stir welded joint of AA1100 ranged between 15.30—35.32 BHN and 48.66 – 99.12 MPa respectively. The highest hardness value of 35.32 BHN was found at optimum parametric setting of 900 rpm rotational speed, 40 mm/min traverse speed and 2^o tilt angle while the highest tensile strength of 99.12 MPa was obtained at optimal processing parameters of 900 rpm rotational speed, 25 mm/min traverse speed and 2^o tilt angle. The ANOVA revealed that rotational speed followed by tilt angle has the most significant effect on the tensile strength of the weldment. The tilt angle and the traverse speed effects were found significant on the hardness of the weldments.

Abstract: The present work aims to understand the effect of drilling parameters (drill speed and feed rate) during the drilling of saffil fiber-reinforced Al metal matrix composite (MMC) under dry conditions. The effect of drilling parameters on individual response characteristics is evaluated and the optimum drilling parameters are also investigated using a multi-response optimization technique known as Entropy Weighted Grey Relational Analysis (EWGRA). The drilling parameter optimization has been performed with aim of minimizing the surface roughness of drilled hole, roundness error in drilled hole and feed force during drilling. Weights were assigned to individual responses with the Entropy weight method and Grey relational grades were calculated to obtain the optimal level for drilling parameters. To achieve the minimum values for all output responses the optimal value of drill speed is 22 m/min and the feed rate is 0.075 mm/rev.

Abstract: In this paper the effect of lattice friction stress on the process of dislocations annihilation is considered using dislocation dynamics method. It is shown that if dislocations of the opposite sign are located in the area where their own tension is greater than the friction stress, they annihilate. Consideration of this fact allows to connect the microscopic processes of annihilation with evolution of dislocation density in the sample under small external stresses and unloading. The area in which annihilation occurs is calculated to be proportional to the square of the friction stress/shear modulus ratio.It is also shown that the parameter responsible for the rate of dislocation annihilation depends on the cube of the ratio of the friction stress to the shear modulus, because it is inversely proportional to the number of annihilating dislocations and the time in which a dislocation pair annihilates.

Abstract: Metal organic frameworks (MOFs) are three dimensionally arranged compounds of bridged organic ligands coordinately bonded with inorganic cluster. The large surface area with large pore volume of MOFs introduces wide application in catalysis field. With accurate combination of organic and inorganic bridging units we can alter the chemical, thermal stability as well as its porosity. Luminescence is the one of the most important properties exhibited by Metal organic frameworks (MOFs). This luminescent property of MOFs is highly sensitive for guest interaction due to which they are used in the detection of various toxic substances, organic pollutants. Based on their high sensitivity and selectivity they are applied in the field of sensors, different environmental applications, various clean energies, optoelectronic devices, medical and biological applications.

Abstract: In the world of energy storage devices, Supercapacitors occupy a very unique and pivotal position. Their rapid rate of discharge gives them high power density. They have high reversibility and are robust to a large number of charging and discharging cycles. Sustained research has revealed a certain set of properties and behaviour, that every prospective candidate supercapacitor material must possess. Metal organic frameworks (MOFs) with unique textural properties, excellent specific surface area, tuneable porous structure and distinctively advantageous electrochemical behaviour are prominent candidates for the use in energy storage applications. However pristine MOF based materials are handicapped due to their low conductivity and poor mechanical stability. These inherent deficiencies can be overcome by hybridizing pristine MOFs with other materials like carbon materials (Activated Carbon, Graphene and Carbon Nano Tubes), conducting polymers, metals, and small molecules through variety of methods. This review puts the spotlight on the utilization, growth and various forms of hybrid materials based on MOFs for supercapacitor applications. It also highlights the various surface engineering techniques on the materials for high potential applications.

Abstract: Present study reports the enhanced photoluminescence properties of Ti incorporated Zr networked 4-{formyl (Hydroxymethylidine)-4-Sulfanyl] Benzoic Acid. The as-synthesized metal organic framework (MOF) was synthesized by solvothermal process and was analyzed by SEM (scanning electron microscopy), XRD (X-ray diffraction spectroscopy) and photoluminescence spectroscopy. The as-synthesized MOFs are well crystalline with average particle size of 35 to 56 nm. From XRD data X-ray diffraction patterns which illustrated the well maintained topological structure during the cation exchange process. From scanning electron microscopy study it shows irregular shape of MOFs.

Abstract: In the present research work, carbon nanosphere (5 wt. %, 10 wt. % and 15 wt. %)/Zr- based metal organic frame works (CNS: Zr (II)-MOFs) with different molar ratios of the legend 4-{[(1E)-1-Hydroxy-3-Oxoprop-1-En-2-yl] Sulfanyl} Benzoic Acid (HOSBA) have been successfully synthesized by hydrothermal method. Studies using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA) have validated certain structural, optical, and morphological features. The supercapacitance performance of the synthesized MOFs was investigated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). At a current density of 0.5 A g^-1 and at a scan rate of 10 mV/s, the 15% CNS doped Zr-MOF demonstrated highest specific capacitance (C_s) of 239.4 F g^-1. 15 wt.% CNS doped Zr-MOF proven power density of 2100 W kg^-1 and maximum energy density of 14.82 Wh Kg^-1 with capacitive retention of 77.63 % following 2000 cycles mark this combination a good for supercapacitors (SCs) material. Regardless of the synthetic conditions, we achieved MOFs which exhibited hetero structure formation with spherical morphologies. The results open us new and energy approach for the supercapacitor of the Zr-metal based MOFs and applications in the photonics, optoelectronics, and promising electrode material for electrochemical energy storage systems.

Abstract: K₂Gd_0.97Zr (PO₄)₃:3mol% Eu³⁺ were prepared by the solid-state diffusion method and under a vacuum ultra-violet (VUV) region, photoluminescence properties of the phosphor were examined. The phenomenon of visible quantum harvesting via DC was observed in synthesized phosphor for the Gd³⁺–Eu³⁺ pair. In the process of quantum harvesting, the two visible light photons are emitted per absorbed VUV photon. This phenomenon occurred upon the 190 nm excitation of Gd³⁺ at the ⁶G_J level through a two-step energy transfer from Gd³⁺ to Eu³⁺ by cross-relaxation and sequential transfer of the remaining excitation energy. The consequences are that the quantum efficiency of the K₂Gd_0.97Zr (PO₄)₃:3mol% Eu³⁺ phosphor in the energy transfer process from Gd³⁺ to Eu³⁺ could reach 233%. The quantum efficiency goes to more than 200% (i.e., 233%) at just low concentration Eu³⁺ ions (i.e. 3% only). This novelty was found in the prepared phosphor. Therefore, the phosphor K₂Gd_0.97Zr (PO₄)₃:3mol% Eu³⁺ was a potential quantum harvester and potential candidate for mercury free fluorescent lamp and plasma display panel.

Abstract: The transporting of sediments across watershed systems and their placement in reservoirs causes expensive issues for the operators of dams in many different nations throughout the world. In addition to the reservoir's functional capacity steadily decreasing as sediment settles in it, silt removal is a sensitive and challenging process that frequently necessitates taking the reservoir out of service, which is practically unachievable in dry and semi-arid regions. De-silting by hydraulic dredging has recently become a necessity to increase their longevity. But during this operation there are load loss exists so it is necessary to find solutions to reduce it. The present paper revealed that use the Sodium Tripolyphosphate as a reducing agent of the friction factor during the hydraulic dredging of dams. To carry out this study, a rheumatic characterization of dams sediments and dams sediments -sodium tripolyphosphate mixtures was carried out using a torque controlled rheometer (Discovery Hybrid Rheometer DHR2 from TA instrument). The flow curves as a function of dose of sodium tripolyphosphate added to dam sediments were analysed by the modified Cross model. It is clearly shown, in this work, when the quantity of sodium tripolyphosphate is less than of 0.4 % causes a decrease in the yield stress, the zero shear rate viscosity (lower Newtonian plateau) and the infinite shear rate viscosity (upper Newtonian plateau). However, when dose of sodium tripolyphosphate is greater than the critical dose, the the yield stress, the zero shear rate viscosity (lower Newtonian plateau) and the infinite shear rate viscosity (upper Newtonian plateau) are increased. As a result, this study find that the increase on thixotropic behavior of dams sediments is occurred by the addition of sodium tripolyphosphate in a concentration ranging between 0.2 wt% and 0.8 wt% to 40 wt% and 45 wt% of dams sediments. The study also demonstrated that adding of 0.4 wt% of sodium tripolyphosphate to 40 wt% and 45 wt% dam sediments decreased the friction factor by 96% and 25% respectively.