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Item Corrosion resistance and thermal stability of sputtered Fe44Al34Ti7N15 and Al61Ti11N28 thin films for prospective application in oil and gas industry(Elsevier, 2021-10-01) Maruf, Mahbub Alam; Rizvi, Syed Muhammad Mujtaba; Noor-A-Alam, Mohammed; Shin, Donghyun; Haider, Waseem; Shabib, Ishraq; Mechanical and Energy Engineering, School of Engineering and Technology, IUPUCFe-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.Item Enhancing controlled and uniform degradation of Fe by incorporating Mg and Zn aimed for bio-degradable material applications(Elsevier, 2022-06-01) Maruf, Mahbub Alam; Noor-A-Alam, Mohammed; Haider, Waseem; Shabib, Ishraq; IUPUC Mechanical EngineeringIn this study, combinatorial development of three nanostructured thin film systems, i.e., Fe87Mg9Zn4 (FMZ-1), Fe74Mg19Zn7 (FMZ-2), and Fe60Mg30Zn10 (FMZ-3), are employed via magnetron sputtering and their degradation pattern is studied in Phosphate Buffered Saline (PBS) solution. Controlled and uniform degradation of Fe is observed with the addition of Mg and Zn, which are crucial for temporary biodegradable implants. The structural characterization of the three samples demonstrates a crystalline structure of Fe87Mg9Zn4, a partially amorphous structure of Fe74Mg19Zn7, and a substitutional solid solution of bcc-Fe-Mg in Fe60Mg30Zn10 sample. Potentiodynamic polarization test reveals higher degradation tendency with the addition of Mg and Zn in the samples compared to pure Fe, as validated by more negative corrosion potentials and higher corrosion current densities. Samples with higher Mg and Zn contents (FMZ-2 and FMZ-3) exhibiting lower charge transfer resistance, as extracted from electrochemical impedance spectroscopy (EIS), also indicates higher corrosion rate compared to Pure Fe. Time-dependent EIS demonstrates gradual decrease in impedance values, representing controlled degradation of the samples upon exposure in PBS solution. Scanning Electron Microscopy (SEM) confirms uniform degradation pattern of FMZ-2 and FMZ-3 samples compared to FMZ-1 after 12 h and 24 h immersion in PBS solution. Finally, the X-ray Photoelectron Spectroscopy (XPS) depicts the formation of oxides, hydroxides, and phosphates of Fe, Mg, and Zn as corrosion products. The higher degradation tendency of the co-sputtered samples is ascribed to the combined role of chemical composition and non-equilibrium nanostructures.