Influence of stabilization heat treatment temperature on microstructure and stress rupture properties of Inconel 706 superalloy

Although the stabilizing heat treatment between solution treatment and aging treatment in Inconel 706 alloy is important to improve its stress rupture life, the influence of stabilization heat treatment temperature on the microstructure and stress rupture properties has not been well understood. In this study, heat treatments consisting of three stabilization temperatures (800 °C, 845 °C, and 880 °C) were performed in Inconel 706 alloy. The results showed that the stress rupture properties were improved with the increase of stabilization temperature. When compared with stabilization at 800 °C, the alloy stabilized at 880 °C exhibited a 96% increase in stress rupture life and a 110% increase in elongation. Furthermore, increasing the stabilization temperature led to the increased amount of η phase at grain boundaries. The η phase appeared in granular, rod-shaped or needle-shaped morphology. The microstructure in the grain interior exhibited compact γ'/γ'' coprecipitates in the samples stabilized at 800 °C and 845 °C, while that showed noncompact γ'/γ'' coprecipitates in the sample stabilized at 880 °C. The formation of 2.34 vol% η phase was found to be beneficial for the stress rupture properties. The improvement in stress rupture properties was ascribed to the presence of η phase and the associated precipitate-free zones at grain boundaries

Identification and Characterization of miR164-NAC Regulatory Modules in Banana

【Objective】This study aims to understand the roles of MIR164, NAC gene families and miR164-NAC regulatory modules in banana ripening and response to low temperature stress, so as to provide a theoretical basis for banana variety improvement and molecular breeding.【Method】'Brazil banana' was used as test material. Through high-throughput sequencing and bioinformatics analysis using miRBase, NCBI database and Clustal, TBtools, MCScanX and iTOL softwares, miR164 and NAC family members in banana were characterized, including their chromosomal location, structure, physical/ chemical properties, phylogenetic relationships, etc. Multiple miR164-NAC regulatory modules in bananas were identified through degradome sequencing and experimental validation combining transcriptome data. Next, the expression patterns of miR164-NAC regulatory modules during ripening and under cold stress were analyzed by small RNA northern blot and qRT-PCR.【Result】A total of six miR164 family members were identified in banana, of which four were located within the coding genes and two in the intergenic region. Phylogenetic analysis showed that several banana MIR164 precursors with high abundance were clustered together with papaya, suggesting that the origin of banana MIR164 gene family was closer to dicotyledonous plants. The banana genome encodes a total of 222 NAC members, unevenly distributed across all 11 chromosomes. A total of 134 homologous gene pairs were identified in these banana NACs, including 4 tandem repeats and 130 segment-replicating repeats, indicating that the main driving force of banana NAC genes evolution came from segmentreplicating events. Comparative phylogenetic analysis of all NAC proteins in banana, Arabidopsis thaliana and Oryza sativa divided this family into 23 subgroups, and transcriptome data revealed extensive redundancy and expression specificity of banana NAC genes. Physicochemical analysis showed that almost all banana NAC proteins were hydrophilic, and less than 15% were stable proteins. The miR164-NAC176/165 regulatory module in banana was verified, and the accumulation of miR164 in banana was induced by ethylene and gradually increased with fruit ripening, while the expression of MaNAC176/165 negatively regulated by miR164 in this module was gradually decreased during fruit ripening. Under the cold stress, miR164 was also obviously induced, resulting in the downregulation of its targets MaNAC176 and MaNAC165.【Conclusion】This study suggested that MaNAC176 and MaNAC165 may be transcriptional repressors of banana fruit ripening, while miR164 promotes ripening by negatively regulating MANAC176/165. This module may also be a key regulatory pathway of banana chilling injury. This study identified key miR164-NAC candidate modules in banana fruit ripening and cold stress response, which laid a foundation for subsequent gene cloning and functional analysis

Tuning electronic structure of the carbon skeleton to accelerate electron transfer for promoting the capture of gold

The efficient and selective recovery of gold from secondary sources is key to sustainable development. However, the complexity of the recovery environment can significantly complicate the compositions of utilized sorbents. Here, we report a straw-derived mesoporous carbon as an inexpensive support material. This mesoporous carbon is modified by anions (sulfur modulation, C-S-180) to improve its electron-transfer efficiency and tune the electronic structure of its skeleton toward enhanced gold reduction. The high surface area of C-S-180 (989.4 m2/g), as well as the presence of abundant C–S in the porous structure of the adsorbent, resulted in an outstanding Au3+-uptake capacity (3422.75 mg/g), excellent resistance to interference, and favorable Au3+ selectivity. Dissimilar to most existing carbon-based adsorbents, electrochemistry-based studies on the electron-transfer efficiencies of adsorbents reveal that sulfur modulation is crucial to optimizing their adsorption performances. Furthermore, the density functional theory reveals that the optimization mechanism is attributable to the adjustment of the electronic structure of the carbon skeleton by C–S, which optimizes the band-gap energy for enhanced Au3+ reduction. These findings offer a strategy for constructing green and efficient adsorbents, as well as a basis for extending the applications of inexpensive carbon materials in gold recovery from complex environments