Using B4C nanoparticles to enhance thermal and mechanical response of aluminum

In this work, Al-B4C nanocomposites were produced by microwave sintering and followed by hot extrusion processes. The influence of ceramic reinforcement (B4C) nanoparticles on the physical, microstructural, mechanical, and thermal characteristics of the extruded Al-B4C nanocomposites was investigated. It was observed that the density decreased and porosity increased with an increase in B4C content in aluminum matrix. The porosity of the composites increased whereas density decreased with increasing B4C content. Electron microscopy analysis reveals the uniform distribution of B4C nanoparticles in the Al matrix. Mechanical characterization results revealed that hardness, elastic modulus, compression, and tensile strengths increased whereas ductility decreases with increasing B4C content. Al-1.0 vol. % B4C nanocomposite exhibited best hardness (135.56 Hv), Young's modulus (88.63 GPa), and compression/tensile strength (524.67/194.41 MPa) among the materials investigated. Further, coefficient of thermal expansion (CTE) of composites gradually decreased with an increase in B4C content.Scopu

Highly ordered mesoporous silica and halloysite nanotubes loaded with diethylenetriamine DETA for smart anti corrosion coatings

The development of nanoscience and technology has devoted significant attention to conducting studies on hollow particles. Among the available materials, mesoporous silica nanoparticles have recently gained attention as potential nanocontainers due to their high stability, large surface area, controllable pore diameter and easy surface functionalization as they can store and release organic or inorganic molecules of different sizes and functionalities. The aim of this work is to study the use of mesoporous silica as a potential reservoir for corrosion inhibitor for active corrosion protection of carbon steel and using epoxy encapsulated halloysite nanotubes for the self healing process of the epoxy based coatings. The synthesized mesoporous silica particles were characterized by using XRD, FTIR and SEM. Mesoporous silica particles loaded with diethylenetriamine (DETA) were embedded into the epoxy polymer along with the halloysite nanotubes (HNTs) encapsulated with epoxy monomer and amine immobilized in mesoporous silica with a weight ratio of 5 wt% of mesoporous silica. Kinetics of release of corrosion inhibitor was evaluated by electrochemical impedance (EIS) measurements in 3.5 wt% NaCl solution. The EIS analysis confirms that the release of inhibitor during the corrosion process has significantly improved the anticorrosion properties when compared to the epoxy coated sample without any corrosion inhibitor. The self healing phenomenon in the scratched epoxy coated sample was monitored by SEM during different time intervals. The SEM results showed that that the epoxy pre-polymer was slowly released into the crack.Upon release, the epoxy pre-polymer came into contact with the amine immobilized in mesoporous silica and cross-linked to heal the scratch over the sample surface. This study suggests that these novel coatings may have some potential applications in the oil and gas industry.qscienc

A comparative study of structural and mechanical properties of Al–Cu composites prepared by vacuum and microwave sintering techniques

In this paper, the aluminum metal matrix composite reinforced with copper particulates (3, 6 and 9 vol.%) were fabricated by high energy ball milling, followed by vacuum sintering (VS) and microwave sintering techniques (MS) separately. The effects of Cu content and preparation methods on the microstructure and compression mechanical behavior of Al–Cu matrix composites were investigated. The microstructural characterizations revealed a homogeneous distribution of Cu particles in the Al matrix and also fine microstructures of microwave sintered samples. The microwave sintered specimen exhibited the highest hardness and better mechanical properties compared to vacuum sintered specimens. Furthermore, the hardness and compressive strength increased 137.2% and 30.3% for the microwave sintered Al–9 vol.% Cu composite, respectively. The increase in mechanical properties with the increasing volume fraction of Cu particulates can be ascribed to the presence of harder Cu particles reinforcement. The developed materials of the microwave sintered Al–Cu composite in this investigation could be successfully used for industrial applications due to improved mechanical properties. Keywords: Al matrix composites, Microwave sintering, Microstructure, Mechanical behavio

Synergistic Behavior of Polyethyleneimine and Epoxy Monomers Loaded in Mesoporous Silica as a Corrosion-Resistant Self-Healing Epoxy Coating

Corrosion is a significant problem and is, to a large extent, responsible for the degradation of metallic parts. In this direction, mesoporous silica particles (MSPs) were synthesized by a sol–gel technique and had an average pore diameter of ∼6.82 nm. The MSPs were loaded with polyethyleneimine (PEI) and epoxy monomers and, after that, carefully mixed into the epoxy matrix to formulate new modified polymeric coatings. The microstructural, compositional, structural, and thermal properties were investigated using various characterizing tools [Transmission electron microscopy, Fourier transform infrared spectroscopy, hermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy]. TGA confirms the loading of mesoporous silica with a corrosion inhibitor, and its estimated loading amount is ∼8%. The electrochemical impedance spectroscopy properties of the reference and modified coated samples confirm the promising anti-corrosive performance of the synthesized polymeric smart coatings. Localized electrochemical tests (scanning vibrating electrode technique and scanning ion-selective electrode technique) evidence the corrosion inhibition ability of the coating, and its self-healing was also observed during 24 h of immersion. The decent anti-corrosion performance of the modified coatings can be credited to the efficient synergistic effect of the PEI and epoxy monomer.This work was performed with NPRP grant 11S-1226-170132 from the Qatar National Research Fund (a member of the Qatar Foundation). R. A. Shakoor would like to acknowledge the Core Laboratories, QEERI, for their TEM and SEM imaging. In addition, the authors acknowledge Prof. M. F. Montemor and Dr. M. G. Taryba (Instituto Superior Técnico) for conducting SVET and SEIT tests. The publication of this article was funded by Qatar National Library. Statements made herein are solely the responsibility of the authors.Scopu

Improved properties of Al-Si3N4 nanocomposites fabricated through a microwave sintering and hot extrusion process

In this study, nano-sized Si3N4 (0, 0.5, 1.0 and 1.5 vol%)/Al composites were fabricated using a powder metallurgy method involving microwave sintering technique followed by hot extrusion. The influence of Si3N4 content on the structural, mechanical and thermal behaviour of Al–Si3N4 nanocomposites was systematically investigated. Electron microscopy examination reveals the uniform distribution of hard Si3N4 nanoparticles in the soft Al matrix. The compressive and tensile strengths of Al composites increased with the increase of Si3N4 content while the ductility decreased. The thermal expansion coefficient of the Al composite decreased with the progressive addition of hard Si3N4 nanoparticles. Overall, hot extruded Al–1.5 vol% Si3N4 nanocomposites exhibited the best combination of tensile, compressive, hardness, Young's modulus and thermal properties of 191 ± 4 MPa, 412 ± 3 MPa, 16.3 ± 0.8 GPa, 94 ± 2 GPa and 19.3 μ K−1, respectively. Tensile tests performed at 200 °C revealed that the tensile strength reduced by ∼35% when compared to the strength at room temperature. The strength, however, was still higher compared to that of the pure Al at 200 °C. The major enhancement in the strength of the nanocomposites is primarily attributed to the presence of uniformly distributed nano-sized Si3N4 nanoparticles in the Al matrix.Scopu

Corrosion behavior of high strength low alloy HSLA steel in 35 wt% NaCl solution containing diethylenetriamine DETA as corrosion inhibitor

High strength low alloy (HSLA) steels demonstrate improved mechanical and anticorrosion properties when compared to plain carbon steels. HSLA steels have succeeded to find their major applications in industries such as defense (gun barrel, turret), food, component manufacturing, wind tunnels, power generation, and water jet cutting, etc. There are significant economic benefits to develop novel materials to mitigate the harmful effects of corrosion. At the same time, the corrosion challenges have also been addressed using various kinds of inhibitors. The corrosion inhibitors are commonly added to the corrosive medium in order to reduce their aggressive attack on the materials to improve their inhibition performance. The smart corrosion protection leads to secure our natural resources, time, efforts, energy and will also ensure a safe operation. The aim of this research work is to study the corrosion behavior of high strength low alloy steel (APIX120) in 3.5 wt.% NaCl solution containing different concentrations of diethylenetriamine (DETA). The electrochemical behavior of HSLA steel was investigated at room temperature using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and weight loss techniques. In addition, the adsorption isotherm, activation energy and other thermodynamic parameters were calculated from the electrochemical results. The corrosion products formed on the surface of the steel were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Furthermore, surface topography and surface roughness of un-corroded and rusted samples were studied by atomic force microscopy (AFM) to elucidate the effect of the aggressive media on the corrosion performance of HSLA steel. Our study discloses that the inhibition efficiency of HSLA steel increases with increasing concentration of DETA in 3.5% NaCl solution.qscienc

Synthesis and properties of polyelectrolyte multilayered microcapsules reinforced smart coatings

The present research work focuses on the synthesis, characterization and properties of novel polyelectrolyte multilayered microcapsules used as smart additives in organic coatings for corrosion protection of steel parts. Urea formaldehyde microcapsules encapsulated with linalyl acetate (UFMCs), sensitive to mechanical stimulus, were synthesized by in situ emulsion polymerization technique. In the next step, dodecylamine, working as a pH stimulus corrosion inhibitor, was loaded into layers of polyelectrolyte molecules, polyethylenimine (PEI) and sulfonated polyether ether ketone (SPEEK). These were applied layer-by-layer over the microcapsules to form inhibitor containing multilayered urea formaldehyde microcapsules (MLUFMCs). In the next step, MLUFMCs (5.0 wt%) and UFMCs (5.0 wt%) were thoroughly dispersed into the epoxy resin and coated on cleaned steel. A comparison of the structural, thermal and anticorrosive properties indicates that coatings modified with multilayered capsules (PMLSCs) demonstrate good thermal stability, improved self-healing characteristics and higher corrosion resistance compared to the coating modified with urea formaldehyde microcapsules. The improved properties of PMLSCs can be attributed to efficient release of the encapsulated self-healing agent and corrosion inhibitor from the MLUFMCs. Therefore, epoxy coatings modified with the novel multilayered capsules may be attractive for corrosion protection of steel parts used in oil and gas and related industries.Other Information Published in: Journal of Materials Science License: https://creativecommons.org/licenses/by/4.0See article on publisher's website: http://dx.doi.org/10.1007/s10853-019-03761-9</p