Corrosion resistance and thermal stability of sputtered Fe44Al34Ti7N15 and Al61Ti11N28 thin films for prospective application in oil and gas industry

Fe-and Al-based thin-film metallic glass coatings (Fe44Al34Ti7N15 and Al61Ti11N28) were fabricated using magnetron co-sputtering technique, and their corrosion performances compared against wrought 316L stainless steel. The results of GI-XRD and XPS analyses demonstrated amorphous structure and oxide layer formation on the surface of the fabricated thin films, respectively. The potentiodynamic (PD) polarization test in chloride-thiosulfate (NH4Cl ​+ ​Na2S2O3) solution revealed lower corrosion current (Icorr) (0.42 ​± ​0.02 ​μA/cm2 and 0.086 ​± ​0.001 ​μA/cm2 Vs. 0.76 ​± ​0.05 ​μA/cm2), lower passivation current (Ipass) (1.45 ​± ​0.03 ​μA/cm2 and 1.83 ​± ​0.07 ​μA/cm2 Vs. 1.98 ​± ​0.04 ​μA/cm2), and approximately six-fold higher breakdown potential (Ebd) for Fe- and Al-based coatings than those of wrought 316L stainless steel. Electrochemical Impedance Spectroscopy (EIS) of both films showed 4- and 2-fold higher charge transfer resistance (Rct), 7- and 2.5-times higher film resistance (Rf), lower film capacitance values (Qf) (10 ​± ​2.4 ​μS-sacm-2, and 5.41 ​± ​0.8 ​μS-sacm-2 Vs. 18 ​± ​2.21 ​μS-sacm-2), and lower double-layer capacitance values (Qdl) (31.33 ​± ​4.74 ​μS-sacm-2, and 15.3 ​± ​0.48 ​μS-sacm-2 Vs. 43 ​± ​4.23 ​μS-sacm-2), indicating higher corrosion resistance of the thin films. Cyclic Voltammetry (CV) scan exhibited that the passive films formed on the Fe- and Al-based coatings were more stable and less prone to pitting corrosion than the wrought 316L stainless steel. The surface morphology of both films via SEM endorsed the CV scan results, showing better resistance to pitting corrosion. Furthermore, the thermal analysis via TGA and DSC revealed the excellent thermal stability of the thin films over a wide temperature range typically observed in oil-gas industries

Deformation characteristics and stress-strain response of nanotwinned copper via molecular dynamics simulation

In this research parallel molecular dynamics (MD) simulations have been performed to study the deformation behavior of nanocrystalline copper samples with embedded nanotwins under approximately uniaxial tensile load. Simulation results reveal that twin boundaries (TBs) act as obstacles to dislocation movements that lead to the strengthening of nanotwinned structures. However, easy glide of dislocations parallel to the TBs contribute primarily to the plastic strain or ductility of these materials. At higher deformation stages, the strengthening effects reach a maximum when abundant dislocations begin crossing the TBs. Due to this highly anisotropic plastic response of the grains, a random polycrystalline sample will show combined properties of ductility and strength. The strengths of the nanotwinned models are found to exhibit an inverse relationship with the twin width and temperature. We also investigate the relation between the deformation behavior in different grains, their orientation with respect to the loading direction, and ultimately the observed response of nanotwinned structures

Design and Development of an Interdisciplinary Nanotechnology Courses for STEM Education

Title: Design and Development of an Interdisciplinary Nanotechnology Courses for STEM Education Mujibur Rahman Khan1*, Ishraq Shabib2, Rafael Quirino3, Aniruddha Mitra4 1,4Assistant Professor; Department of Mechanical Engineering, Georgia Southern University 2 Department of Engineering; Central Michigan University 3 Department of Chemistry; Georgia Southern University The purpose of this project is to design and introduce interdisciplinary nanotechnology courses for STEM education. The planned courses are: a first year experience course and an applied studio laboratory course. Inclusion of a first-year-experience (FYE) module (title: Introduction to Nanoscale Science and Engineering) will expose freshmen to nanotechnology, serving as a recruitment tool for the more advanced senior-level courses. The courses will be cross-listed in other colleges for additional cross-talk between disciplines and is meant to develop interest and excitement about nanotechnology. The 2nd course (Title: Nanomaterials and Nonmanufacturing) will be a four hours studio (lecture and Lab) course. Lecture modules e will be divided into four modules where fundamental knowledge on nanoscale matter and nanotechnology will be taught, integrating engineering, chemical, physical, biological, manufacturing, environmental health, and economic aspects. The integrated laboratory section is designed to provide students with hands-on experience with fabrication and testing of a nanoscale materials, devices and characterization tools. The lab will also incorporate simulation and modeling at nanoscale to engage students in design of nanomaterials and devices. Empirically defensible educational techniques will be used to deliver an innovative, interdisciplinary curriculum. The lecture and studio course teach not just engineering, but chemistry, biology, physics, environmental science, and economics, each delivered by experts in the various fields. The intellectual merit of this project is that it will provide an important initial model for how to approach interdisciplinary nanotechnology education at the post-secondary level. The newly designed courses and laboratory modules will implement the best practices in education to integrate nanotechnology into the existing curriculum. The course modules incorporate real world experiences and future vision to excite and enrich first-year experience and enhance engagement opportunities for upper level students. The project is designed to produce intellectual fusion across the academic spectrum allowing students to engage outside of the traditional silos of education. Key words: Nanotechnology, Interdisciplinary, STEM, Nanomaterla

A Coupled Atomistic-continuum Study of Bi-layer Nanoindentation of Ni-Al Alloy

Peer reviewed: YesNRC publication: Ye

Elastic Properties of UHMWPE-SWCNT Nanocomposites’ Fiber: An Experimental, Theoretic, and Molecular Dynamics Evaluation

Ultrahigh molecular weight polyethylene (PE) filaments were reinforced with 2 wt.% of single-walled carbon nanotubes (SWCNTs). The solution spinning method was used to produce both neat and reinforced PE filaments. Tensile tests and strain hardening through repeated loading-unloading cycles of the filaments revealed a spectacular contribution of the SWCNTs in enhancing the elastic properties, e.g., strength and modulus. The theoretic strength and modulus of the reinforced PE were predicted using the shear lag model and micromechanics-based model, respectively, and verifying with experimental results. It was observed that the predicted strength and modulus were comparable only with those obtained after strain hardening. In the next step, a molecular dynamic simulation was conducted by simulating a unit cell containing a SWCNT surrounded by PE matrix subjected to uniaxial tensile strain. The strength and modulus of the simulated structure showed an agreement, to certain extent, with experimental observations of strain-hardened nanocomposites

Investigation of Mechanical Properties and Morphology of Multi-Walled Carbon Nanotubes Reinforced Cellulose Acetate Fibers

Cellulose acetate (CA) fibers were reinforced with multi-walled carbon nanotubes (MWCNTs) at 0.5%, 1.0%, 1.5% and 2.0%. Yield strength, ultimate tensile strength, fracture strain and toughness of the nanocomposite fiber increased up to 1.5 wt. % of the carbon nanotube (CNT) loading, however, further inclusion (2.0%) of MWCNTs in CA decreased the mechanical properties. Experimental properties were also compared with analytical predictions using a Shear lag model for strength and the rule of mixture for modulus. A solution spinning process, coupled with sonication, mixing, and extrusion, was used to process the CNT-reinforced composite fiber. Scanning electron microscopy (SEM) images of the cross sections of neat CA and CA-MWCNT fibers showed the formation of voids and irregular features. The enhanced interconnected fibrillation in the CNT-reinforced CA samples resulted in improved mechanical properties, which were observed by tensile testing. Fourier transform infrared spectroscopy (FTIR) spectra showed the area under the curve for C–H bonding after the inclusion of CNT. There was no significant shift of wavenumber for the inclusion of MWCNT in the CA matrix, which indicates that the sonication process of the CNT-loaded solution did not degrade the CA bonding structure