Preparation and characterization of FeZrB amorphous ferrofluids as magnetic sizing agents for basalt fibers coating

In this paper, FeZrB amorphous nanoparticles were prepared and used to obtain a magnetic fluid which can be used as a magnetic sizing agent for basalt fibers. Unmodified FeZrB nanoparticles (Unmodified FeZrB), citric acid-modified FeZrB nanoparticles (FeZrB@CA) and sodium oleate-modified FeZrB nanoparticles (FeZrB@NaOL) were synthesised by chemical reduction. Three kinds of FeZrB magnetic sizing agents were obtained by dispersing nanoparticles into the mixture consisting of PVA and KH-550. The magnetic basalt fibers were prepared by spraying the magnetic sizing agents in the process of drawing basalt fibers. The structure, morphology, surface state and magnetic properties of unmodified and modified FeZrB amorphous nanoparticles were characterized by XRD, SEM, TEM, FT-IR and VSM. The properties of magnetic basalt fibers were investigated by SEM, VSM and EDS. The results showed that the XRD spectra showed sharp diffraction peaks in both Unmodified FeZrB and FeZrB@NaOL nanoparticles, and the two groups of samples had different degrees of crystallinity. Only a single broad peak can be observed at around 45° in FeZrB@CA, which confirms the amorphous structure of FeZrB@CA. SEM and TEM images show that the FeZrB amorphous nanoparticles exhibit spherical with sizes ranging from 7 nm to 25 nm. Electron diffraction patterns showed that FeZrB@CA had a diffraction halo typical of an amorphous structure, and the remaining two samples displayed diffraction rings, indicating some degree of crystallinity. The FT-IR spectra confirm the formation of CO bonds in both FeZrB@CA and FeZrB@NaOL nanoparticles, suggesting the successful modification of FeZrB nanoparticles. The saturation magnetization of Unmodified FeZrB, FeZrB@CA, and FeZrB@NaOL nanoparticles were determined as 83.4 emu/g, 98.9 emu/g, and 60.3 emu/g, respectively. The SEM images showed that the surface of fibers was completely covered by the magnetic sizing agents. Moreover, the saturation magnetization of BF-Unmodified FeZrB, BF-FeZrB@CA, BF-FeZrB@NaOL (magnetic basalt fibers) could reach 47.9 emu/g, 63.5 emu/g, and 28.9 emu/g, respectively. The formation mechanism of magnetic basalt fibers was elucidated, which is attributed to the Si O bonds between basalt fibers and KH-550, as well as CONH bonds between KH-550 and FeZrB@CA. Consequently, the FeZrB magnetic sizing agents could adhere to the fiber surface. This study provides a simple method for developing magnetic sizing agents and offers a new perspective for imparting magnetism to basalt fibers and preparing magnetic fibers.