Employing NaYF4: Yb, Tm upconversion particles (UCPs) in combination with rGO and PANI nanomaterials for the fabrication of radiation-curable anticorrosion composites/coatings

Upconversion particles (UCPs) able to emit photons from the ultraviolet to near-infrared (NIR) region of the electromagnetic spectrum when excited by a NIR laser may be used as internal radiation sources for the manufacture of thick composites with uniform and deep polymerization. In this work, NaYF4: Yb, Tm-based UCPs were synthesized and employed to cure composites using a dual curing method via UV and blue light produced from the UCPs to activate the photo-initiators (PIs), and the resulting cure depth and degree of double bond conversion (DC) were measured. In addition, the influence of UCP content and laser power on cure depth and DC was investigated. The emission rate of the UCPs demonstrated a non-linear, wavelength-specific relationship with increasing laser power and exposure time. Using optimal conditions, 62 % DC with a 2.5 cm cure depth was achieved. For the first time, the ability of UCPs to cure composites in the presence of reduced graphene oxide (rGO) and polyaniline (PANI) nanoparticles was studied. Results indicated that DC was almost consistent across samples (except the sample containing 1 wt% rGO), although the addition of nanomaterials decreased DC and cure depth. The addition of 0.5-0.5 wt% rGO-PANI increased the nanocomposites' compressive strength and strain at failure by 66 and 37 %, respectively. The nanocomposite formulations were applied to steel and the anti-corrosion properties were also investigated. The findings revealed low-frequency impedance (|Z|10 mHz) numbers higher than 1010 omega.cm2 up to 4 w immersion duration, proving this coating's exceptional barrier anti-corrosion capabilities.