Temperature‐dependent mechanical and oxidation behavior of in situ formed ZrN/ZrO₂‐containing Si₃N₄‐based composite

In this work, Si₃N₄ and Zr(NO₃)₄ were used as raw materials to prepare ZrN/ZrO₂‐containing Si₃N₄‐based ceramic composite. The processing, phase composition, and microstructure of the composite were investigated. Hardness and fracture toughness of the ceramics were evaluated via Vickers indentation in Ar at 25°C, 300°C, 600°C, and 900°C. During spark plasma sintering, Zr(NO₃)₄ was transformed into tetragonal ZrO₂, which further reacted with Si₃N₄, resulting in the formation of ZrN. The introduction of ZrN enhanced the high‐temperature mechanical properties of the composite, and its hardness and fracture toughness reached 13.4 GPa and 6.1 MPa·m¹/² at 900°C, respectively. The oxidation experiment was carried out in air at 1000°C, 1300°C, and 1500°C for 5 h. It was shown that high‐temperature oxidation promoted the formation and growth of porous oxide layers. The microstructure and phase composition of the formed oxide layers were investigated in detail. Finally, it was identified that the obtained composite exhibited a higher thermal diffusivity than that of monolithic Si₃N₄ in the temperature range of 100°C–1000°C

Manipulating the 3D organization of the largest synthetic yeast chromosome

Whether synthetic genomes can power life has attracted broad interest in the synthetic biology field. Here, we report de novo synthesis of the largest eukaryotic chromosome thus far, synIV, a 1,454,621-bp yeast chromosome resulting from extensive genome streamlining and modification. We developed megachunk assembly combined with a hierarchical integration strategy, which significantly increased the accuracy and flexibility of synthetic chromosome construction. Besides the drastic sequence changes, we further manipulated the 3D structure of synIV to explore spatial gene regulation. Surprisingly, we found few gene expression changes, suggesting that positioning inside the yeast nucleoplasm plays a minor role in gene regulation. Lastly, we tethered synIV to the inner nuclear membrane via its hundreds of loxPsym sites and observed transcriptional repression of the entire chromosome, demonstrating chromosome-wide transcription manipulation without changing the DNA sequences. Our manipulation of the spatial structure of synIV sheds light on higher-order architectural design of the synthetic genomes. </p

Carbon Nanotube Fabrication at Industrial Scale: Opportunities and Challenges

Careful research on different materials reveals that the material properties are mostly affected by the size of it. Material size down to nanometer scale exhibits some remarkable properties, resulting in unique physical and chemical characteristics. In todays world of nanotechnology, carbon nanotubes (CNTs) have become a high priority material because of their exclusive structure, novel characteristics with enormous potential in many technological applications. Till date chemical vapor deposition (CVD) is the preferred and widely used technique among different CNT growth methods, because of its potential advantage to produce CNTs of high purity, large yield with ease of scale up and low setup cost. This article provides an overview of different CVD methods for industrial scale fabrication of CNTs. The influence of material aspect, viz. catalyst type, catalyst support, and growth control aspect, viz. process temperature, pressure, catalyst concentration, are discussed. Additionally, possible growth mechanisms concerning CNT formation are described. Finally, the key challenges of the process are addressed with future perspective.Comment: carbon nanotubes, chemical vapor depositio

Fragility Analysis of the Main Building–Coal Conveyor Trestle Interaction System of a Thermal Power Plant

Thermal power plants play a crucial role in the power system as critical lifeline infrastructure. In order to meet the production process requirements, the main building of a thermal power plant is often connected to a coal conveyor trestle. This study focuses on investigating the seismic interaction between the common three-row reinforced concrete frame-bent main building and the steel trestle in a circulating fluidized bed (CFB) unit. The objective is to assess the influence of the trestle on the main building and understand the failure mode of the trestle structure. The seismic interaction is analyzed through fragility analysis based on Incremental Dynamic Analysis (IDA). The results indicate that the trestle has minimal influence on the main building, except during the large deformation stage. The study identifies the failure mode of the coal conveyor trestle as excessive relative displacement along the longitudinal direction at the connection points, leading to collisions or falls. A seismic demand model based on longitudinal relative displacement is developed to obtain the fragility curve for the trestle structure. These findings offer valuable insights for assessing the seismic performance of thermal power plants