No abstract

No abstract

No abstract

No abstract

No abstract

No abstract

This study describes an experimental investigation of the degradation of the tensile properties of basalt fibers and epoxy-based composites in various corrosive environments, including alkaline, acid, salt and water solutions, and clarifies the corresponding degradation mechanisms. Carbon and glass fibers and their composites are adopted as references. Accelerated experiments were conducted at temperatures of 25℃ and 55℃ and the variation in tensile properties was studied by means of tension testing, mass loss weighing, scanning electron microscope imaging and energy spectrum analysis. The experimental results show that basalt fibers posses relatively strong resistance to water and salt corrosion, moderate resistance to acid corrosion and severe degradation in an alkaline solution. The tensile properties of basalt FRP composites are much better than those of basalt fibers. The degradation mechanism of basalt fibers involves damage by etching in salt, water and alkaline solutions and by change in the chemical composites in an acid solution. The fracture properties of basalt FRP composites are controlled by the failure of corroded interfaces between the fibers and the resin, making the interface the critical factor, rather than the fiber itself.

N-doped TiO 2 (anatase) with high visible light photoactivity was obtained by the thermal treatment of nanotube titanic acid (denoted as NTA) in an NH 3 flow and investigated by means of X-ray diffraction (XRD), transmission electronic microscopy (TEM), diffuse reflectance spectra (DRS), X-ray photoelectron spectroscopy (XPS), electron spin resonance (ESR), and photoluminescence (PL). With increasing NH 3 treatment temperature at T = 400 to 600 1C, the anatase crystallinity of the N-NTA(400-600) samples was gradually enhanced, while at 700 1C a new phase, TiN, appeared in the N-NTA(700) sample. XPS results show that the doped N atoms incorporated into anatase TiO 2 exist in the form of NO. A revised explanation for the triplet ESR signals obtained from the N-NTA(500-700) samples was put forward, i.e. the g = 2.004 main peak is contributed by single-electron-trapped oxygen vacancies (denoted as V o ), while two weak peaks (g = 2.023, 1.987) are contributed by chemisorbed NO in well-crystallized anatase TiO 2 .The visible light photoactivity is proportional to the height of the g = 2.004 main peak, which suggests that the photoactive centers are V o -NO-Ti. The adsorbed NO molecule can effectively suppress the photoluminescence of V o defects, which facilitates photogenerated charge transfer to the surface reactive centers to conduct redox reactions. The higher the V o -NO-Ti concentration, the better the visible light photoactivity. The highest photoactivity was obtained for the catalyst, NH 3 -treated at 600 1C. But the formation of TiN at T = 700 1C can readily destruct V o -NO-Ti photoactive centers, and thus readily decreases photoactivity efficiency.