Shear Bond Strength to Enamel, Mechanical Properties and Cellular Studies of Fiber-Reinforced Composites Modified by Depositing SiO2 Nanofilms on Quartz Fibers via Atomic Layer Deposition

Abstract

Introduction: Poor interfacial bonding between the fibers and resin matrix in fiber-reinforced composites (FRCs) is a significant drawback of the composites. To enhance the mechanical properties of FRC, fibers were modified by depositing SiO₂ nanofilms via the atomic layer deposition (ALD) technique. This study aims to evaluate the effect of ALD treatment of the fibers on the mechanical properties of the FRCs.

Methods: The quartz fibers were modified by depositing different cycles (50, 100, 200, and 400) of SiO₂ nanofilms via the ALD technique and FRCs were proposed from the modified fibers. The morphologies, surface characterizations of nanofilms, mechanical properties, and cytocompatibility of FRCs were systematically investigated. Moreover, the shear bond strength (SBS) of FRCs to human enamel was also evaluated.

Results: The SEM and SE results showed that the ALD-deposited SiO₂ nanofilms have good conformality and homogeneity. According to the results of FTIR and TGA, SiO₂ nanofilms and quartz fiber surfaces had good chemical combinations. Three-point bending tests with FRCs showed that the deposited SiO₂ nanofilms effectively improved FRCs' strength and Group D underwent 100 deposition cycles and had the highest flexural strength before and after aging. Furthermore, the strength of the FRCs demonstrated a crescendo-decrescendo tendency with SiO₂ nanofilm thickness increasing. The SBS results also showed that Group D had outstanding performance. Moreover, the results of cytotoxicity experiments such as cck8, LDH and Elisa, etc., showed that the FRCs have good cytocompatibility.

Conclusion: Changing the number of ALD reaction cycles affects the mechanical properties of FRCs, which may be related to the stress relaxation and fracture between SiO₂ nanofilm layers and the built-up internal stresses in the nanofilms. Eventually, the SiO₂ nanofilms could enhance the FRCs' mechanical properties and performance to enamel by improving the interfacial bonding strength, and have good cytocompatibility.

Keywords: SiO2 nanofilms; atomic layer deposition; interfacial bonding; surface modification.