Browsing by Author "Khosravi F."

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    Enhancing the pull-out behavior of ribbed steel bars in CNT-modified UHPFRC using recycled steel fibers from waste tires: a multiscale finite element study
    (Nature Research, 2024) Pouraminian M.; Akbari Baghal A.E.; Andalibi K.; Khosravi F.; Arab Maleki V.
    In the current investigation, the effect of recycled steel fibers recovered from waste tires on the pull-out response of ribbed steel bars from carbon nanotube (CNT)-modified ultrahigh performance fiber reinforced concrete (UHPFRC) was considered using the multiscale finite element method (MSFEM). The MSFEM is based on three phases to simulate CNT-modified UHPC, recycled steel fibers (RSFs), and ribbed steel bars. For the first time, a bar ribbed has been simulated to make more realistic assumptions, and RSFs have been distributed in the form of curved cylinders of different lengths and with a random distribution within a concrete matrix. The interaction of the steel bar and the RSFs with the concrete is applied by the cohesive zone model (CZM). After confirming the simulation outcomes with the experimental results, the steel bar pull-out response is investigated using load-slip curves. The impact of the CNT content, RSFs and their aspect ratio on the bond strength of steel bars and CNT-modified UHPFRC was assessed. The results show that using RSFs with a lower aspect ratio (steel microfibers) significantly improves the pull-out characteristics of steel bars from concrete. Accordingly, the proposed MSFEM is considered for simulating the effects of different parameters on the pull-out response of ribbed steel bars from concrete without causing complex, time-consuming, or costly experiments. The results indicated that waste fiber or RSF can be used as a toughening component in CNT-modified ultrahigh-performance concrete and as a replacement for industrial steel fibers. © The Author(s) 2024.
  • No Thumbnail Available
    Item
    Electrochemical determination of dopamine by poly (methyl orange) shape memory alloy modified carbon paste electrode
    (Elsevier B.V., 2024) Rajendrachari S.; Altaş E.; Erdogan A.; Küçük Y.; Gök M.S.; Khosravi F.
    We have successfully prepared 50Ni-30Ti-20Hf shape memory alloy powders using a high-energy planetary ball mill for 20 h by wet milling. The fabricated shape memory alloy powders were characterized by X-ray diffraction (XRD), and scanning electron microscope (SEM) to investigate the phases present and the morphology of the powders respectively. The use of 50Ni-30Ti-20Hf (nitinol) shape memory alloy powders as electro-catalytic materials is a unique and new idea. We are the first researchers to use nitinol powders as dopamine (DA) electrochemical sensors. For better electrochemical oxidation and higher current response of DA, we have electro-polymerized the surface of nitinol-modified carbon paste electrode (MCPE) with methyl orange (MO). Using poly(MO)-NiTiHf-MCPE, we have determined the DA using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) respectively. The calculated active surface area for BCPE, NiTiHf-MCPE, and the poly(MO)-NiTiHf-MCPE were found to be 0.044, 0.089, and 0.098 cm2 respectively. The electro-polymerized nitinol MCPE not only increased the surface area but also increased the electron transfer kinetics. Our results confirmed the participation of 2 electrons and 2 protons in the electrochemical redox reaction. © 2024 Elsevier B.V.