57 research outputs found
Temperatureâdependent mechanical and oxidation behavior of in situ formed ZrN/ZrOââcontaining SiâNââbased composite
In this work, SiâNâ and Zr(NOâ)â were used as raw materials to prepare ZrN/ZrOââcontaining SiâNââbased 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(NOâ)â was transformed into tetragonal ZrOâ, which further reacted with SiâNâ, resulting in the formation of ZrN. The introduction of ZrN enhanced the highâtemperature mechanical properties of the composite, and its hardness and fracture toughness reached 13.4 GPa and 6.1 MPa¡mš/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 highâtemperature 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 SiâNâ in the temperature range of 100°Câ1000°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 BuildingâCoal 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
Controllable selfâtransport of bouncing droplets on ultraslippery surfaces with wedgeâshaped grooves
Abstract Preventing the accretion of droplets on surfaces is vital and slippery liquidâinfused porous surfaces (SLIPS) have promising application prospects, such as surface selfâcleaning and droplet transportation. In this work, controllable selfâtransport of bouncing droplets on ultraslippery surfaces with wedgeâshaped grooves is reported. The impact behaviors of droplets on SLIPS under various impact velocities and diameters are explored, which can be classified as hover, total bounce, partial bounce, Worthington jet, and crush. SLIPS with wedgeâshaped grooves were designed to transport accreted droplets. An energy and transport model is established to explain the impact and selfâtransport mechanism, where the Laplace pressure and moving resistance between droplets play a key role. Finally, SLIPS with branched wedgeâshaped grooves were designed for droplet selfâtransport and demonstrated advantages. This work provides a general reference for spontaneous motion control of sessile droplets, droplets with initial impacting velocity, or even liquid films
- âŚ