Search Results (3)

In this work, a novel method for the disposal of ladle furnace slag (LFS) and soda residue (SR) was proposed. By applying geopolymer technology, LFS and SR were used as precursors to manufacture a geopolymer with sufficient fresh and mechanical properties that can be used in construction works, such as in non-structural components like lightweight partition walls. The effects of raw material ratios and Na₂O equivalents on the fresh properties, mechanical properties, microstructure and environmental impact of LFS-SR geopolymer (LSG) were analyzed by rheology, compressive strength, XRD, TG/DTG, SEM, and calculation of embodied carbon. The results showed that the compressive strength of LSGs increased when the SR content decreased or Na₂O equivalent increased, and the maximum compressive strength could reach 12.0 MPa at 28 d. The hydration products of LSG were mainly C-(A)-S-H gel, C₃AH₆, and AFt. Notably, the C-(A)-S-H gels formed a stable cross-linked structure, and the extremely fine granular C₃AH₆ further filled the pores. Furthermore, AFt was generated from the interaction between LFS and CaSO₄ rich in SR during the hydration process. The carbon calculation results indicated that the embodied carbon of LSGs was significantly lower than that of traditional cement, and the LSG containing 20% SR and 12% Na₂O equivalent had the highest sustainability. This study proposed strategies for mitigating the environmental hazards of alkaline solid waste and improving its resource utilization, thereby promoting sustainable development in the construction industry. Full article

Nickel-rich cathode materials have emerged as ideal candidates for electric vehicles due to their high energy density; however, polycrystalline materials are prone to microcrack formation and unavoidable side reactions with electrolytes during cycling, leading to structural instability and capacity degradation. Herein, an Sr-doped single-crystalline nickel-rich LiNi_0.88Co_0.05Mn_0.07O₂/Sr cathode material is synthesized, with Sr doping levels controlled at x = 0.3%, 0.5%, 1 mol%. The nickel-rich LiNi_0.88Co_0.05Mn_0.07O₂/Sr cathode features particle sizes of approximately 2 μm, at a relatively low temperature. It inhibits the microcrack formation, prevents electrolyte penetration into the particle interior, and reduce side reactions, thereby enhancing structural stability. This enables the cathode to deliver a high initial discharge capacity of 205.3 mAh g⁻¹at 0.1 C and 170.8 mAh g⁻¹ at 10 C, within the voltage range of 2.7 V–4.3 V, and an outstanding capacity retention of 96.61% at 1 C after 100 cycles. These improvements can be attributed to the Sr-doping, which reduces the single-crystal growth temperature, effectively mitigating Li⁺/Ni²⁺ cation mixing. Moreover, the incorporation of Sr expands the interlayer spacing, thereby facilitating Li⁺ diffusion. The doping strategy employed in this work provides a new insight for low-temperature single-crystal materials synthesis, significantly improving the electrochemical performance of nickel-rich cathode materials. Full article

This work concerns the hydration mechanism of calcium zirconium aluminate as a ternary compound appearing in the CaO-Al₂O₃-ZrO₂ diagram besides the calcium aluminates commonly used as the main constitutes of calcium aluminate cements (CACs). Moreover, a state-of-the-art approach towards significant changes in hydraulic properties was implemented for the first time in this work, where the effect of structural modification on the hydration behavior of calcium zirconium aluminate was proved by XRD, ²⁷Al MAS NMR and SEM-EDS. The substitution of Sr²⁺ for Ca²⁺ in the Ca₇ZrAl₆O₁₈ lattice decreases the reactivity of Sr-substituted Ca₇ZrAl₆O₁₈ in the presence of water. Since the original cement grains remain unhydrated up to 3 h (Ca₇ZrAl₆O₁₈) or 72 h (Sr_1.25Ca_5.75ZrAl₆O₁₈) of curing period in the hardened cement paste structures, strontium can be considered as an inhibition agent for cement hydration. The complete conversion from anhydrous ²⁷Al^IV to hydrated ²⁷Al^VI species was achieved during the first 24 h (Ca₇ZrAl₆O₁₈) or 7 d(Sr_1.25Ca_5.75ZrAl₆O₁₈) of hydration. Simultaneously, the chemical shift in the range of octahedral aluminum from ca. 4 ppm to ca. 6 ppm was attributed to the transformation of the hexagonal calcium aluminate hydrates and Sr-rich (Sr,C)₃AH₆ hydrate into the cubic phase Ca-rich (Sr,C)₃AH₆ or pure C₃AH₆ in the hardened Sr-doped cement paste at the age of 7 d. The same ²⁷Al NMR chemical shift was detected at the age of 24 h for the reference hardened undoped Ca₇ZrAl₆O₁₈ cement paste. Full article