Crystallization and Thermal Stability of the P-Doped Basaltic Glass Fibers

Abstract

The present research focuses on the influence of phosphorus oxide additives on the structure and thermal properties of the basalt glasses, produced in the form of fibers, i.e. at very high quenching speed. Basaltic glass fibers with various P2O5 contents were produced in two stages. In the first stage, the bulk glasses were prepared by adding variable amounts of (NH4)4P2O7 to milled natural andesitic basalt in order to obtain samples containing 2, 4, and 6 wt % P2O5. In the second stage, the glass fibers were obtained using a laboratory-scale system. Basalt glass fibers were characterized by Raman spectroscopy to obtain information on the structure of the obtained fibers, and by DSC-TG and XRD analyses to determine the change in crystallization mechanism of basaltic fibers. The hydrostatic weighing was used for the determination of glasses density. An increase in the content of P2O5 to 6 wt % leads to a decrease in the density of glass fibers due to the polymerizing effect of phosphorus oxide. The obtained X-ray diffraction patterns indicate that all samples are X-ray amorphous. The Raman results show that the decrease in the intensity of the line corresponding to vibrations of the structural units Q2 (about 920 cm–1) with respect to the line corresponding to Q3 (about 1125 cm–1) is related to an increase of P2O5 content. This also indicates the increase in polymerization degree of glass structure. DSC and XRD data also found out the change of phase transformations order with an increase of phosphorus oxide. The crystallization in natural and modified basalt glass fibers begins with spontaneous spinel-like phase formations that become nucleation sites for the precipitation of monoclinic pyroxene as a major phase. With an increase in the P2O5 content, there is a tendency to a decrease in the pyroxene at higher temperature, as a result of which, the hematite crystallizes at lower temperatures. That is associated with the activation of liquation processes, accompanied by the formation of amorphous phases with different viscosities with an increase in the concentration of P2O5. In conclusion, all the obtained data indicate the prospect of using the proposed approach to obtain basalt glass fibers with enhanced thermal and mechanical stability.

The effects of aggressive environments on the mechanical properties of basalt plastics

“…An example of a comparative assessment of effects of aqueous acid solutions on the properties of BP and GP is given in [44], which proves the need to control reversible and irreversible transformations in an epoxy matrix. The high resistance of BF and BP to effects of acid solutions are also noted by other authors, for example in [9,10,17,21].…”

“…A series of informative reviews are presented in the scientific and technical literature, in which effects of the chemical composition of BF on their mechanical properties are analyzed, and a comparison is made with properties of GF. For example, in [3,8,9,10], the content of oxides in BF is compared with the three types of GF (E-glassaluminoborosilicate glasses with less alkaline elements and with replacement of sodium and potassium by boron oxide, S-glassaluminosilicate glass with a high magnesium content of increased strength, ZrO 2 -glass is chemically resistant glass containing zirconium oxide). The presence of Fe 2 O 3 is the reason for the gray-brown color of BF.…”

“…The first line shows data [3,8], the second line gives data [9,10]. The authors in [24] believe that heat treatment improves the crystal structure of biologically active BF.…”

“…Over the past two decades, application of basalt fibers (BF), as an alternative to glass fibers (GF), has been expanding rapidly [1,2,3,4,5,6,7,8,9,10]. BF is obtained from various rocks containing an eight-component system of oxides Na 2 O-K 2 O-MgO-CaO-FeO-Fe 2 O 3 --SiO 2 -Al 2 O 3 , with a small content of titanium oxide (up to 1 wt.%) [9,10].…”

“…Over the past two decades, application of basalt fibers (BF), as an alternative to glass fibers (GF), has been expanding rapidly [1,2,3,4,5,6,7,8,9,10]. BF is obtained from various rocks containing an eight-component system of oxides Na 2 O-K 2 O-MgO-CaO-FeO-Fe 2 O 3 --SiO 2 -Al 2 O 3 , with a small content of titanium oxide (up to 1 wt.%) [9,10]. The major purpose of BF is related to development of basalt plastics (BP), which reinforcing elements are strong and rigid bundles of fibers, threads, fabrics, nets for manufacture of a large range of various cheap structural elements: (rods for concrete reinforcement [1,2], road structures [3], pipes [4], bridge elements [4,5], details of transport products, sports equipment, wind turbines [6], offshore structures [7], etc.…”