SCIENCE CHINA Materials•2026•DOI: 10.1007/s40843-025-3927-9
The mechanical properties of as-cast TiAl alloys are severely limited by their coarse as-cast microstructure. This study proposes a low-temperature pre-deformation heat treatment to refine the microstructure of an as-cast Ti-47Al-2Nb-2Cr alloy. The process involves pre-deformation below the eutectoid temperature followed by heat treatment in the α+γ phase field, yielding two distinct microstructures: duplex (DP) and nearly lamellar (NL). The average lamellar colony size was reduced to 5.3% and 20% of the as-cast size for DP and NL structures, respectively. Microstructural evolution analysis reveals that the decomposition of coarse lamellar colonies and the formation of fine grains are governed by γ recrystallization, γ→α phase transformation, and α recrystallization. Remnant colonies after deformation are completely eliminated by subsequent heat treatment, enhancing microstructural homogeneity and mechanical properties. The DP alloy exhibits an ultimate tensile strength (UTS) of 537 MPa and an elongation (EI) of 6.8% at 800°C, representing increases of 44.7% and 518.2% over the as-cast alloy, respectively. Analysis of crack propagation and deformation mechanisms indicates that grain refinement and lamellar structure refinement contribute to improved deformation ability. This work provides a viable pathway for optimizing as-cast TiAl alloys for high-temperature applications.
Chinese Journal of Environmental Engineering•2026•DOI: 10.12030/j.cjee.202509020
The AAOA-MBR (anaerobic-anoxic-oxic-anoxic membrane bioreactor) process is widely used in municipal wastewater treatment, but its multi-stage internal recirculation complicates sludge retention time (SRT) and carbon source distribution. This study systematically regulated three reflux ratios (R1: membrane tank to oxic tank; R2: oxic tank to anoxic I tank; R3: anoxic II tank to anaerobic tank) in a pilot-scale system (0.24 m3·d−1) to reveal their effects on nutrient removal and membrane fouling. When R1:R2:R3 = 300%:200%:100%, effluent COD, TN, TP, and NH3-N met discharge standards. Reducing R1 and R2, thereby decreasing total reflux ratio from R=6 to R=3, shortened SRT, which suppressed nitrifier accumulation and increased effluent COD and TN, but decreased TP. High-throughput sequencing of anoxic I and oxic tanks showed that denitrifying bacteria (Thauera and Ottowia) relative abundances decreased from 0.68% to 0.42% and 0.51% to 0.24%, respectively, while the phosphorus-accumulating organism Candidatus_Accumulibacter increased from 0.78% to 1.12%, enhancing phosphorus removal. Additionally, lowering R1 to 200% caused sludge accumulation in the membrane tank, exacerbating membrane fouling. Thus, internal recirculation ratios must be adjusted based on influent characteristics to balance nutrient removal and membrane performance.
Journal of Fuel Chemistry and Technology•2026•DOI: 10.1016/S1872-5813(26)60663-9
The catalytic hydrogenation of biomass-derived dimethyl succinate (DMS) to 1,4-butanediol (BDO) is a pivotal route for producing high-value C4 chemicals in green chemistry. Cu/SiO2 catalysts are known for high selectivity in hydrogenating ester groups, with performance correlated to copper species microstructure. Although calcination critically defines this active structure, systematic influence of calcination atmosphere remains underexplored. Here, Cu/SiO2 catalysts were prepared via urea-assisted hydrothermal method and calcined under different atmospheres to elucidate effects on physicochemical properties and hydrogenation performance. Comprehensive characterization (N2 physisorption, FT-IR, H2-TPR, XRD, TEM, N2O pulse chemisorption, XPS, NH3-TPD) revealed that calcination atmosphere profoundly alters metal-support interaction, regulating dispersion and chemical state of copper species. Specifically, air calcination promoted stronger metal-support interaction, enhancing copper dispersion and increasing proportion of key active Cu+ species. Consequently, air-calcined catalyst achieved 92.37% DMS conversion and 64.15% BDO yield under optimized conditions (210 °C, 5.0 MPa, WHSV 0.6 h−1, H2/DMS molar ratio 100). This work underscores calcination atmosphere engineering as potent strategy for optimizing metal-support interactions in heterogeneous catalysts for efficient hydrogenation.