Abstract This study evaluates the technical potential of using silica-rich mine tailings (MTs) as a partial substitute for Portland cement in concrete. The MT was characterized using particle size analysis, inductively coupled plasma optical emission spectrometry, X-ray fluorescence, X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive spectroscopy, and sequential extraction. The material contained 25.01% silicon, 1.89% iron, and 0.21% calcium, with approximately 40% of particles smaller than 0.074 mm. XRD identified primarily quartz and moganite, two polymorphs of SiO 2 , and nearly the unique source of Si. Mixtures were prepared with 0, 2.5, 5, 10, 15, and 20% replacement. At 60 days, the mixture with 2.5% substitution reached 37.17 MPa, compared with 30.06 MPa for the reference concrete, representing a 23.7% increase; the mixture with 5% substitution reached 35.88 MPa. In contrast, the 15% and 20% substitutions reduced the strength to 25.42 and 22.14 MPa, respectively. Chloride transport exceeded 4,000 C in all mixtures, classifying them as highly permeable. The mixture with 2.5% had a value of 8,616 C, compared to 8,350 C for the control, whereas the maximum value (10,645 C) was observed at 10% substitution. The 2.5% mixture exhibited the best overall performance under the conditions studied.
Abstract The development of high-performance Fe-based alloys for structural and wear-resistant applications remains a significant challenge. This study investigates the effect of Ni, Co, and combined NiCo binders on the densification, microstructure, phase evolution, and mechanical properties of Fe 3 C–10 wt% W alloys produced by powder metallurgy. Powders containing 1.2 wt% carbon were mechanically milled for 10 h at 950 rpm, compacted at 50 MPa, and sintered at 1400°C for 2 h. X-ray diffraction and scanning electron microscopy revealed the formation of Fe–W-rich solid solutions and carbide-containing phases. The addition of Ni- and Co-enhanced diffusion-controlled densification and reduced residual porosity, while the NiCo binder promoted a finer and more homogeneous microstructure with improved interfacial cohesion. The Fe 3 C–W–NiCo alloy exhibited the best overall performance, achieving a density of 7.7 g·cm −3 , a microhardness of 885 ± 5 HV 0.1 , a flexural strength of 1620 ± 10 N·mm −2 , and an impact toughness of 2.0 J·cm −2 . These improvements are attributed to the synergistic effects of Ni and Co on diffusion, solid-solution strengthening, and phase stability during sintering.
Abstract This study investigated the direct incorporation of carbon dioxide (CO 2 ) during the mixing of alkali-activated ground granulated blast furnace slag as an alternative to traditional post-hardening carbonation. CO 2 was introduced during the final 30 s of mixing. The effects of alkali content and carbonation on CO 2 uptake, compressive strength, water absorption, and microstructure were evaluated. The results showed that CO 2 uptake increased with alkali content and exposure duration, with a maximum uptake of approximately 1.9% after 300 s of continuous CO 2 exposure. The gravimetric and thermogravimetric measurements showed strong agreement, with an R 2 of 0.99. For the selected mortar mixtures, 30 s of CO 2 exposure resulted in a 15–25% increase in 28-day compressive strength compared with non-carbonated specimens. However, water absorption showed a slight reduction. The microstructural analysis indicated carbonate-rich precipitates in pore and interparticle regions. The results demonstrate that introducing CO 2 during alkali activation can promote in situ carbonate formation while improving the later-age mechanical performance of GGBFS-based alkali-activated materials.
Abstract This study utilized siderite tailings and polypropylene as the main raw materials to prepare stone paper composites through the melt blending and hot-pressing molding process. Using characterization techniques such as scanning electron microscopy and a universal electronic testing machine, the effects of the addition amounts of four different additives – calcium stearate, maleic anhydride grafted polypropylene, silane coupling agent KH550, and polypropylene toughening agent – on the microstructure, tightness, tensile strength, smoothness, and tear resistance of the materials were systematically investigated under a fixed tailings content of 40%. The results demonstrated that an appropriate number of additives effectively improved the overall performance of the materials, whereas excessive addition not only increased costs but also potentially led to a decline in performance. In summary, the rational use of additives significantly enhanced the compatibility and dispersion between the tailings and the polypropylene matrix. Under the specific conditions of 40 wt% siderite tailings loading and the processing parameters used in this study, the optimal addition amounts for calcium stearate, maleic anhydride grafted polypropylene, KH550, and the polypropylene toughening agent were found to be 2, 2, 2, and 5%, respectively.
Abstract Material corrosion represents a significant scientific and engineering challenge. Microorganisms on material surfaces accelerate corrosion. Due to the excellent properties of graphene, bifunctional anticorrosion and antibacterial coatings were developed by incorporating graphene into epoxy resin. To mitigate the detrimental effects of agglomeration on coating performance, graphene oxide (GO) was prepared, and a silane coupling agent was used to modify the surface of GO to enhance its stability and dispersibility within the coating matrix. The properties of graphene were analyzed before and after surface modification by Fourier transform infrared spectroscopy (FTIR) and Transmission electron microscope (TEM). Epoxy/modified-GO (0.1 wt%) coating revealed the highest corrosion resistance of 9.696 × 10 7 Ω cm 2 after 144 h immersion in 3.5% NaCl solution measured by the electrochemical impedance spectroscopy (EIS) technique. Higher protection against bacteria was observed for epoxy/modified-GO (0.1 wt%) as the most efficient antibacterial composite coating. These results indicated that the coatings with modified graphene exhibited superior corrosion resistance and effectively inhibited the growth of Staphylococcus aureus .
