Advanced Materials Research Vol. 1155

Abstract: Bulk metallic glasses (BMGs) and their composites (BMGMCs) have emerged as competitive materials for structural engineering applications exhibiting superior tensile strength, hardness along with very large elastic strain limit. However, they suffer from lack of ductility and subsequent low toughness due to the inherent brittleness of the glassy structure which makes them amenable to failure without appreciable yielding. Various mechanisms and methods have been proposed to counter this effect out of which, recently Additive Manufacturing has gained widespread attention. It is proposed that additive manufacturing can overcome these difficulties in single step due to inherent existence of very high cooling rate in the process which is essential for glass formation. This, when coupled with careful selection of alloy chemistry is proposed to be the best solution to fabricate near net shape parts in a single step with excellent properties. In this report, an effort has been made to describe one possible route to achieve this. Solidification processing employing carefully selected inoculants based on edge to edge matching technique along with the carefuly controlled inoculation procedure is proposed to reflect upon enhanced mechanical properties. It is hypothesized that number density, size and distribution of ductile crystalline phase would best be able to improve microstructure and hence properties. This is meant to be controlled by manipulating type, size and the amount of inoculants. The proposed methodology is claimed to bear maximum potential.

Abstract: In this experimental studies, three types of fabric such as Jute, Okra and Pineapple Leaf Fiber (PALF) were selected and matrix material such as polypropylene (PP) was selected to manufacture composites. Jute/PP, Okra/PP, and PALF/PP based composites were prepared successfully by a conventional compression molding technique. The objective of this study is to compare the mechanical such as tensile strength (TS), tensile modulus (TM), bending strength (BS), bending modulus (BM), elongation at break (Eb%) and interfacial properties of the composites. Jute fiber (hessian cloth)-reinforced polypropylene matrix composites (45wt% fiber) were fabricated by compression molding. TS, TM, BS, BM, and IS of the composites were found to be 45 MPa, 2.2 GPa, 54 MPa, 4.1 GPa, and 16 kJ/m², respectively. Then Okra and PALF fiber reinforced polypropylene-based composites (45 wt% fiber) were fabricated and the mechanical properties were compared with those of the jute-based composites. The result revealed that mechanical properties of PALF composite higher than jute and Okra fiber reinforced composites. Water absorption and elongation percentage at break showed different scenario and it was noticed from the experimental study that water absorption and elongation at break (%) of jute fabric was higher than other composites. Fracture sides of the composites were studied by scanning electron microscope (SEM), and the results revealed poor fiber-matrix adhesion for jute fiber-based composites compared to that of the other fiber-based composites (OF/PP and PALF/PP). KEY WORDS: Polypropylene, Jute Fiber, Okra Fiber, Pineapple Fiber, Mechanical Properties, Interfacial Properties, Composites. *Corresponding Address: dr.ruhul_khan@yahoo.com

Abstract: This paper examines and present the findings of the physical and mechanical properties of concrete containing rice husk ash (RHA), and the blend of rice husk ash with calcium carbide waste (RHA-CCW). Concrete cubes, cylindrical and beam specimens containing different percentages of RHA and RHA-CCW by weight of cement (5, 10, 15 and 20 %) were cast. Compressive strength test was carried out after the specimens were cured in water for 7, 14, 28 and 56 days. Test for tensile and flexural strength was carried out after 28 days curing. Initial and final setting time test was carried out on mortar specimens with the same percentage of RHA and RHA-CCW. Bogues model was used to determine the elemental and compound composition of cement when blended with the RHA and RHA-CCW. From the results obtained, the compressive strength of RHA-CCW concrete increases as cement is partially replaced with RHA-CCW content, with the maximum strength attained at 5 % replacement. RHA concrete attains it maximum strength at 10 % replacement. The maximum compressive strength results obtained for both RHA and RHA-CCW concrete were higher than the strength of plain concrete (0 % replacement) by 1.1 % and 14.7 % respectively. Interestingly, results obtained for the tensile strength also shows a similar pattern of strength development with that of compressive strength. The flexural strength properties of concrete was improved upon when RHA-CCW was used in concrete compared to RHA. The results of setting time test for RHA mortar showed a decrease in setting time, while the reverse was the case for RHA-CCW mortar. In conclusion, provided adequate curing is maintained, the used of RHA-CCW gives a better performance in concrete than RHA. However, they both perform better in concrete than the plain, and can be used as additives in concrete production.

Abstract: The platinum (Pt) degradation, poisoning and carbon corrosion in acidic fuel cell has led to explore the research in alkaline fuel cell. However, the high cost of Pt has brought a lot of studies to find replacement for Pt catalyst. Due to that, silver metal is selected as non-Pt catalyst and supported by the nitrogen and phosphorus-doped on graphene for oxygen reduction reaction in alkaline medium. The adsorption energy and mechanism of the oxygen reduction reaction is studied by using density functional theory (DFT) calculation. The support catalyst of graphene is doped with three atom nitrogen and phosphorus namely as N3 and P3, respectively. The Ag supported on N3 and P3 are tested on O₂, OOH, O and OH species. There are two types adsorption of O2 on N3 and P3 which is side and end-on adsorption configuration. The N3-Ag has similar adsorption energy for both configurations, but P3-Ag has low adsorption energy by end-on adsorption configuration. The effect of doped atoms on graphene also have been tested on O₂, OOH, O and OH species. The result shows that increasing nitrogen doping atom has decreased the adsorption energy of O2 and vice versa on phosphorus atoms. A single phosphorus doping atom on graphene has shown the lowest adsorption energy, but the end-on configuration of P3-Ag has shown most stable adsorption. The schematic free energy profile shows that both N3-Ag and P3-Ag have high possibilities to be followed in oxygen reduction reaction mechanism but P3-Ag has advantage due to stable adsorption as non-Pt catalyst. The Ag metal supported on nitrogen and phosphorus-doped graphene show promising result to be a catalyst in alkaline fuel cell.

Abstract: This study focuses on the role of Mo addition on the mechanical properties of an Al-Si-Cu-Mg alloy in as-cast and heat-treated condition at ambient and elevated temperature. Addition of 0.4 to 0.6 wt.% Mo forms Mo-bearing dispersoid particles which have a relatively high melting point and improve high temperature tensile strength. Ductility suffered in the presence of Mo-bearing particles. Trace addition of Mo up to 0.6 wt.% has a negligible influence on the yield strength and hardness of Al-Si-Cu-Mg alloy in as-cast and heat-treated conditions at ambient temperature and 250 °C.

Abstract: Functionally graded material (FGM) has a unique design in which material properties vary smoothly and continuously which leads to having better thermal and mechanical performance. Functionally graded material has a wide area of application from the pressure vessel to aerospace due to its tailoring properties. The main emphasis has been made here, to present a structural mechanical and steady-state thermal analysis of functionally graded flat plate made up of aluminum and ceramic. The flat plate is subjected to various boundary and loading condition. Material properties of FGM is calculated across the thickness using power law with the help of MATLAB programming. An analysis is performed for various volume gradation using MACROS in ANSYS APDL. The analysis results for functionally graded materials are compared with a composite sandwich plate for the same boundary conditions. It was found that von-Mises stress generated in FGM is 14.6% less than compared to sandwich structure, the stress in x and y-direction is 16.5% less, XY-Shear is 13.5% less and deflection is 33% less than a sandwich plate of aluminum and ceramic.