Key Engineering Materials Vol. 875

Abstract: Titanium-Nickel pre-alloyed powder was reinforced with Nano-Silica in 2%, 4% , 6% and 8 wt. % due to effectiveness of Nanoscale ceramic Reinforcement in improving the properties of Metals and Alloys. The compositions of the Pre-Alloyed powders and Nano Silica Approximately 50 nm in diameter and spherical in shape were weighed and mixed in Planetary Ball Mill followed by compaction at 50 MPa using a Uniaxial Compaction machine The green pellets obtained were sintered in Argon Environment for 5 hrs and allowed to furnace cool. The pellets were then sectioned through their cross-section for slices 3 mm thick followed by Cold-mounting and Soldering followed by cold mounting additionally. The Samples were analyzed via X-Ray Diffraction (XRD) for phase distribution as a function of variation in nano-Silica reinforcements and Microstructural analysis was performed via Optical Microscope. The effect of Volume percentage on the densification was determined via Archimedes principle and Micro-Vickers hardness was used for mechanical Evaluation. The Electrochemical Properties were evaluated using Potentio-Dynamic Polarization and Electrochemical Impedance Spectroscopy (EIS) in neutral salt solution (3.5% NaCl). The results indicated increasing dissolution of the TiNi phase into intermetallic Titanium-rich and Ni-rich phases in the matrix and hardening due to the Nano-Silica effect of Grain Boundary impingement and phase dissolution of Equiatomic phase and mixed behavior in Corrosion properties as determined by the electrochemical techniques whereas densification decreased due to poor plasticity of Nano-Silica and hinderance in diffusion during the sintering process.

Abstract: Bulk metallic glasses (BMGs) are an important class of materials with unique set of properties. A bulk metallic glass with composition of (Fe_0.6Co_0.4)₇₁Nb₄Si₅B₂₀ was cast in the form of a 1 mm thick strip in a water cooled copper mold. The BMG produced was characterized for structure, thermal and mechanical properties. The X-ray diffraction performed on the as cast alloy has shown completely amorphous structure. The glass transition and crystallization peak temperatures obtained through differential scanning calorimetry scan were 542 °C and 588.4 °C, respectively. Some cast amorphous alloy sample was annealed below glass transition (450 °C for 30 mi93nutes) and others above glass transition (580 °C for 5 minutes) temperatures. Nano- indentation hardness of 13.3 GPa was obtained for as cast alloy while a hardness values of 12.8 and 15.84 GPa were measured for heat treated alloys at temperature of 450 °C and 580 °C, respectively. Increase in hardness was attributed to formation of crystals in an amorphous matrix whereas decrease in hardness was due to relaxation of quenching residual stresses. The maximum value of elastic modulus obtained through indentation was 255 GPa for 580 °C heat treated sample.

Abstract: Manganese bismuth alloy has gained importance due to its rare earth free elements, positive temperature coefficient and unique magnetic properties. Low temperature phase (LTP) MnBi was successfully prepared by arc melting with subsequent heat treatments and melt spinning technique followed by heat treatment for different durations. LTP MnBi formation was confirmed using XRD analysis and microstructural characterization of the samples was done using field emission scanning electron microscope. MnBi with greater LTP amount was formed by melt spinning route when compared with its counter arc melted one. Magnetic energy density of LTP MnBi formed by melt spinning technique with different heat treatment time was studied.

Abstract: Performance of the semiconductor devices is solicited by reliable metallic electrical connections. Any bad electrical connection may one of the major sources of noise and low mechanical strength, hence reducing the performance and life of the device. Apart from the successful synthesis or development of semiconductor devices or solders; the technique to carry out soldering process plays a vital role to attain reliable and reproducible electrical connections. This paper demonstrates the soldering process on gold thin films using In-3.0%Ag eutectic soldering alloys considering the three fundamental aspects of the process i.e. scavenging, wetting and aging. Scavenging and wetting behaviors of the solder were evaluated at various temperatures and different fluxes, respectively. Effect of aging was evaluated by shear testing after aging for various durations. It was observed that using the soldering temperature somewhere between 160-190 °C with 20 wt.% salicylic acid flux is favorable for better wetting and scavenging characteristics. A post solder aging (at 95 °C for 12 hours) seamed to facilitate improvement in mechanical strengths.

Abstract: The present research reports the influences of variant phenolic resin concentrations on the thermo-mechanical and ablation characteristics of ethylene propylene diene monomer (EPDM) elastomer. Backface temperature acclivity (BTA), charring rates, and insulation indexes were executed for the fabricated composite specimens. It was noticed that BTA was enhanced while linear/radial/mass ablation rates were significantly diminished with increasing concentration of phenolic resin (PR) in base matrix (elastomeric polymer). The composite (30wt%PR/EPDM) has 25% high thermal endurance compared to virgin EPDM composite. Thermal conductivity was increased with increasing PR to EPDM ratio. PR incorporation has remarkably enhanced the ultimate tensile strength of the EPDM elastomer. An efficient improvement in elastomeric hardness was also observed with increasing PR contents in EPDM matrix. Scanning Electron Microscopy (SEM) results showed the porosity generation and polymer melting during ablation.

Abstract: Conducting polymer blends Polyaniline-Dodecylbenzene sulfonic acid (Pani.DBSA) and thermoplastic polyurethane (TPU) were prepared using in-situ emulsion polymerization method by dissolving both components in DMF. Ani.DBSA/TPU blends were prepared with different compositions 20/80, 30/70, 40/60 and 50/50 wt%. Theses blends have good conducting and mechanical properties. Blends were characterized by Potentiostate, Thermogravimetric analysis (TGA), Infrared spectroscopy (FTIR) and Dynamic mechanical thermal analyzer (DMTA). The electrical conductivity increases up to 30 wt% loading of aniline.DBSA after that it decreases gradually. The uniform dispersion of aniline.DBSA showed in SEM images which is the indication of a strong connection between aniline.DBSA and TPU which increase the conductivity. These blends can be used as strain sensors.

Abstract: Over the next half decade, significant changes expected in global carbon structures, carbon products and applications. Technological advances that improve the structure-property relationship of advanced carbon materials and breakthrough in manufacturing processes resulting in lower cost, leads to availability of carbon nano materials for applications in the metallurgical industry with a reference to electrodes for the metallurgical industry.In the current work we synthesized pitch-based C/C nano composite lab scale electrodes, partially replacing petroleum coke with nanofibers, by using a ball milling dispersion and high energy milling technique. The effect of different processing variables including the amount of binder and dispersants as well as mixing conditions is investigated. Low vacuum -SEM analyses of green pitch and dispersant samples show the pitch coating on dispersants. Field emission gun (FEG)-SEM is used to analyse dispersants, baked pitch/dispersant system as well baked electrodes. Transmission electron microscope (TEM) is applied to investigate in detail the primary structure of the dispersants, as well as the fiber/matrix interface and the alignment of binder with the fibres in graphitized and un-graphitized electrodes.

Abstract: In this study, the effect of SBR concentration (10 Phr, 20 Phr & 30 Phr ) on the thermal behavior of EPDM/SBR blends was studied. Thermogravimetric analysis (TGA) was used to check weight loss of samples as function of temperature by heating upto 600^°C. X-ray diffraction (XRD) was performed to determine quality and % crystallinity of the elastomer blends. It was seen that % crystallinity improved with an increase in the content of SBR in EPDM/SBR blends. TGA revealed that the thermal stability of EPDM/SBR blends has improved by 17% than neat EPDM. Carbon nano-coatings produced by sputtering have no beneficial influence on thermal behaviour of elastomers.

Abstract: This research examines the mechanical properties of graphene-based polymer composites and Nomex honeycomb sandwich using a new strain sensing technique. Sandwich panels are fabricated individually with glass fibre reinforced polymers (GFRP) and face-sheets having different filler ratios of graphene nanoparticles (GNPs). These graphene nanoparticles are oxidized with (UV-O3) ozone to get graphene oxide (GO) which in turn improves resin matrix interfacial strength. Filler ratios of GO 0.0%, 0.2%, 0.6% and 1.0% by weight of poly-epoxy are fabricated for the face-sheets of composite sandwich panels. Graphene-based strain sensors are synthesized having a concentration of GNPs 5% by weight of polystyrene (PS). The strain sensors are pasted on the sandwich panels and four-point bending of the sandwich beams is performed to predict its flexural strength. The response of composite under different filler ratios of graphene oxide on mechanical properties is inspected during mechanical testing of sandwich panels and the results of (PS-GNPs) strain sensors will be compared with the strains produced during mechanical testing.

Abstract: Graphene as a wonder material has received great attention and importance due to its fascinating properties. Here in this study, we also demonstrate a simple two step process to prepare graphene sheets (GSs) from the electrochemical exfoliated graphene oxide (EE-GO) followed by microwave irradiation reduction. The properties and structure of the resulted product samples were studied by Ultraviolet spectroscopy (UV), Fourier-transform infrared spectroscopy (FTIR), Thermogravimetric analysis (TGA), X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy-dispersive X-ray (EDX or EDS), Raman spectroscopy and Atomic force microscopy (AFM) for validation of their distinguishing characteristics. UV spectra of microwave irradiation reduced graphene oxide (MI-RGO) and EE-GO exhibited an intense and sharp absorption peak concentrated at wavelengths of 236 and 266nm, respectively. The elimination of oxygen functionalities present in the EE-GO plane was illustrated by FTIR as a result of microwave irradiation treatment. The relative layer structures of MI-RGO and EE-GO were confirmed by XRD. Similarly, the Raman spectra revealed the difference in between the EE-GO and MI-RGO characteristic reflection bands. The thin, crumpled and curved type morphology of the obtained graphene sheets (GSs) was also displayed by SEM while the composition of a few layer graphene sheets with atomic mass percents of carbon (75%) and oxygen (25%) was established by EDX. The Synthesis procedure is simple, rapid and eco-friendly with high yield.