Xiaona Ren

Lignocellulosic residues accumulate worldwide, and cadmium (Cd)-contaminated farmland threatens crop safety. Converting biomass waste into a soil amendment for Cd-contaminated land would combine waste management with remediation. Iron-based catalysts promote artificial humification of biomass, but how iron speciation controls the process and the environmental function of the products remains unclear. In this study, four iron catalysts (FeCl3, Fe(NO3)3, Fe2(SO4)3, and Fe2O3) were compared for catalytic pyrolysis-assisted humification of bamboo powder. Iron addition shifted thermal decomposition to 200 – 300 °C, and humic-like substances reached their maximum yield at 250 °C. Catalyst phase and coordination environment defined the pathway selectivity. Ionic Fe3+ salts behaved as homogeneous Lewis acids, cleaving ether bonds and accumulating carboxylic acids and esters. Solid Fe2O3 mediated heterogeneous radical coupling and aromatic condensation, extending the humification from depolymerization to aromatic assembly. Fe2O3 achieved the highest humic acid (HA) content (16.05 wt%), humification index (43.29%), and carbon enrichment efficiency (28.15%). Control experiments confirmed that iron cations (particularly Fe3+ rather than anions) dictated pathway directionality, with the Fe3+ valence state critical for carboxyl generation and structural maturation. Additionally, the HA generated with Fe2O3 reduced bioavailable Cd in contaminated soil by 75.97% and promoted wheat growth, highlighting its potential for soil management. These results provide a speciation-driven framework for iron-catalyzed humification and a practical strategy for converting biomass waste into soil amendments that remediate heavy-metal contamination.

Pyrolytic remediation of petroleum-contaminated soil (PCS) often requires high temperatures, which increase energy demand, limit resource recovery, and impair post-treatment soil functionality. This high-temperature dependence reflects not only the cracking resistance of heavy hydrocarbons, but also strong oil–soil interfacial locking that restricts their release and conversion. Here, we tested whether targeted interfacial regulation could lower remediation severity in PCS by using functionalized artificial humic acid (FAHA) as an interface-active mediator. Potassium citrate and lignin directed the molecular evolution of artificial humic acid, while Fe complexation introduced additional reactivity during pyrolysis. Under optimal conditions, FAHA2 at 0.5 wt % lowered the remediation threshold from 480 to 390 °C. Multiscale analyses suggested that FAHA reorganized the oil–mineral interface, weakened direct mineral–petroleum interactions, and facilitated lower-temperature release of interfacially constrained petroleum fractions. During pyrolysis, FAHA-bound Fe likely evolved from Fe–S-associated with Fe–O-rich coordination environments that could further facilitate hydrocarbon conversion. Compared with direct high-temperature pyrolysis, the FAHA-assisted pathway better preserved soil functionality and showed a lower estimated gross process-carbon burden under the defined accounting boundary. These results highlight sequential interfacial–thermochemical coupling as a design principle for more sustainable remediation of interface-dominated contaminated matrices.

Si₃N₄ ceramics with a YF₃-MgSiN₂ binary additive system were fabricated by hot pressing (HP) and spark plasma sintering (SPS) at 1500–1700 °C, followed by annealing at 1850 °C for 6 h. The effects of sintering route and temperature on phase transformation, microstructure evolution, thermal conductivity, and mechanical properties were systematically investigated. SPS significantly accelerated the α→β phase transformation compared with HP, and the β-Si₃N₄ content in SPS samples exceeded 94% at 1600 °C. After annealing, all samples were completely transformed into β-Si₃N₄, accompanied by obvious grain growth. Thermal conductivity was closely related to both grain size and relative density. Grain growth reduced grain-boundary phonon scattering, whereas density loss and residual porosity deteriorated heat transport. The mechanical properties were jointly governed by β-Si₃N₄ content, grain morphology, and porosity. Elongated β-Si₃N₄ grains promoted crack deflection and crack bridging, thereby improving fracture toughness, while excessive porosity reduced flexural strength. These results demonstrate that optimizing the balance between phase transformation, grain growth, and densification is essential for tailoring the thermal and mechanical performance of Si₃N₄ ceramics containing non-oxide sintering additives.

Sintering additives play a crucial role in the phase transformation, microstructure evolution, and properties of Si3N4 ceramics. In this work, Si₃N₄ ceramics containing a fixed total content of Y2O3 and MgB2 sintering additives with different Y2O3/MgB2 ratios were fabricated by spark plasma sintering and post-annealing. The influence of the additive ratio on phase evolution, microstructure, mechanical properties, and thermal conductivity was systematically investigated. Decreasing the Y2O3/MgB2 ratio markedly suppressed the α→β phase transformation during spark plasma sintering, leading to pronounced variations in grain morphology and mechanical properties. After post-annealing, all α-Si3N4 transformed completely into β-Si3N4, whereas the final grain morphology remained strongly dependent on the additive ratio. The highest flexural strength (1170 ± 26 MPa), fracture toughness (9.17 ± 0.42 MPa·m1/2), and Vickers hardness (19.7 ± 0.6 GPa) were obtained at 2, 3, and 6 mol% MgB2, respectively. Despite significant differences in oxygen content and microstructure, the thermal conductivity remained within 53–58 W/(m·K). Localized boron enrichment was observed in individual Si3N4 grains, indicating that the distribution and chemical state of boron deserve further investigation. These results provide insights into the role of Y2O3/MgB2 additive ratio in controlling phase evolution, microstructure, and the resulting properties of Si3N4 ceramics.

Yttrium oxide (Y₂O₃), as a rare-earth oxide nanoparticle, has potential toxicity that remains unresolved. By bridging the gap between nanomaterial development and safety assessment, this work aimed to evaluate the biodistribution of Y₂O₃ using a novel radiolabeling approach with technetium-99m (^99mTc) for real-time tracking. Different concentrations (0.4, 4, and 8 mg/mL) of Y₂O₃ were used for ^99mTc labeling and were intravenously administered to mice. In vivo organ biodistribution was measured via dynamic planar imaging and micro single-photon emission computed tomography/computed tomography (micro-SPECT/CT). Biodistribution and inductively coupled plasma mass spectrometry (ICP-MS) were conducted to quantitative tissue uptake of ^99mTc-Y₂O₃, and hematoxylin-eosin (H&E) staining were performed for histopathological evaluation. Different concentrations of ^99mTc-Y₂O₃ were successfully synthesized with a high radiochemical purity and stability. In vivo imaging revealed different distribution patterns with 0.4, 4, and 8 mg/mL of ^99mTc-Y₂O₃. Low-dose ^99mTc-Y₂O₃ nanoparticles rapidly cleared from pulmonary circulation, shifting to predominant hepatic-splenic accumulation. In contrast, medium and high doses demonstrated prolonged lung retention with partial redistribution to the spleen and liver. These biodistribution patterns were validated by ICP-MS, which showed a strong correlation with the ^99mTc-Y₂O₃ tracking. Histopathology revealed dose-related alveolar wall thickening and splenic white pulp expansion. This study demonstrated that ^99mTc-Y₂O₃ could be a robust tool for nanoparticle in vivo tracking, providing the organ distribution information for long-term toxicity studies and chronic exposure effects.

The main method for large-scaled preparing powder superalloys in the production process is inert gas atomization, particularly vacuum-induced gas atomization (VIGA). A novel technique called electrode-induced gas atomization (EIGA) with a crucible-free electrode was proposed to prepare non-inclusion superalloy powders. In this study, a Ni-based superalloy of FGH4096 powder was prepared using both the VIGA and EIGA methods, while blanks were prepared through direct hot isostatic pressing (as-HIPed) near-net-forming method. The particle size, morphology, microstructure, and mechanical properties of the powders and blanks were compared via a laser particle size analyzer, SEM, TEM, and room-temperature and 650 °C tensile tests. The results indicated that EIGA-prepared powders exhibited a finer particle size and better surface quality than the one prepared via VIGA, which showed reduced satellite powders. However, the as-HIPed blank of EIGA-prepared powders had a lower secondary γ’ ratio and slightly reduced strength compared to the as-HIPed blank of VIGA-prepared powders due to its slightly lower secondary γ’ phase ratio and less effective inhibition of dislocation movement. Furthermore, the overall performance of the two samples did not differ significantly due to the similar microstructural characteristics of the powders. However, the variation in particle size affects heat conduction during the HIP process, resulting in slight differences in blanks’ properties.