Yazar "Bhethanabotla, Venkat" seçeneğine göre listele

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    Crosslinked polyethyleneimine-based structures in different morphologies as promising CO2 adsorption systems: A comprehensive study
    (Wiley, 2024) Demirci, Şahin; Inger, Erk; Bhethanabotla, Venkat; Şahiner, Nurettin
    Although there are many studies on CO2 adsorption via PEI-modified carbon particles, metal-organic frameworks, zeolitic imidazolate frameworks, and silica-based porous structures, only a limited number of studies on solely cross-linked PEI-based structures. Here, the CO2 adsorption capacities of PEI-based microgels and cryogels were investigated. The effects of various parameters influencing the CO2 adsorption capacity of PEI-based structures, for example, crosslinker types, PEI types (branched [bPEI] or linear [lPEI]), adsorbent types (microgel or cryogel), chemical-modification including their complexes were examined. NaOH-treated glycerol diglycidyl ether (GDE) crosslinked lPEI microgels exhibited higher CO2 adsorption capacity among other microgels with 0.094 +/- 0.006 mmol CO2/g at 900 mm Hg, 25 degrees C with 2- and 7.5-fold increase upon pentaethylenehexamine (PEHA) modification and Ba(II) metal ion complexing, respectively. The CO2 adsorption capacity of bPEI and lPEI-based cryogels were compared and found that lPEI-GDE cryogels had higher adsorption capacity than bPEI-GDE cryogels with 0.188 +/- 0.01 mmol CO2/g at 900 mm Hg and 25 degrees C. The reuse studies revealed that NaOH-treated GDE crosslinked bPEI and lPEI microgels and cryogels showed promising potential, for example, after 10-times repeated use >50% CO2 adsorption capacity was retained. The results affirmed that PEI-based microgels and cryogels are encouraging materials for CO2 capture and reuse applications.
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    Modifying wetting properties of PI Film: The impact of surface texturing and CF4 and O2 plasma treatment
    (Elsevier, 2024) Aktaş, Cihan; Bhethanabotla, Venkat; Ayyala, Ramesh S.; Şahiner, Nurettin
    Polyimide (PI) is a versatile polymer widely used in various industries because of its excellent heat and chemical resistance, and structural properties. This study presents an effective method for modifying the surface properties of PI films using a combination of laser -induced surface texturing and low-pressure CF4 and O2 plasma treatments. Post plasma treatment and surface texturing, the polyimide (PI) films exhibited enhanced hydrophobicity, as indicated by an increased contact angle from 82.4 +/- 0.8 degrees to 143.6 +/- 2.2 degrees, and a reduced surface free energy from 45.0 +/- 0.3 mN/m to 1.4 +/- 0.3 mN/m. The friction force between water droplets and the treated PI films decreased by approximately 30 %, indicating a significant improvement in the wetting properties. Surface characterization with X-ray photoelectron spectroscopy (XPS) analysis confirmed the successful introduction of new fluorine -containing groups and an increase in the extent of C = O bonds. Importantly, the plasma gas treatment resulted in a significant decrease in bacterial attachment, demonstrating its potential for reducing biofouling.