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Oxygen-affected cracking commonly presents on thin Ni-based single crystal superalloy components serving in high temperature and oxidizing environments. This study uses a newly developed in-situ thermal-stress environmental transmission electron microscope to investigate the oxidation and fracture behaviors of Ni-based single crystal superalloy at 650°C under stress. The in-situ oxidation was found to change the tensile fracture mode from the close-packed {111} planes of plastic fracture to $ \{001\} $ planes adjacent to γ/γ′ interfaces of brittle fracture. The microanalysis also revealed that the γ′ cuboids, γ phase, and γ/γ interface exhibit different oxidation behavior, thus underscoring the thickness debit effect.

Porous SiC ceramics were prepared by a new approach combination of carbothermal reduction and subsequent recrystallization sintering. Firstly, micro-sized SiC particles were used as the skeleton, and SiC spherical nanocrystals were in-situ synthesized by the vapor-solid reaction between carbon nanoparticles and silicon monoxide vapor. The shape and diameter of SiC nanocrystals are related to the pristine carbon nanoparticles, showing a shape memory effect. After recrystallization sintering, high purity α-SiC porous ceramics with tailored necking area were obtained by the evaporation-condensation of SiC nanocrystals. A linear relation was revealed between the flexural strength and the value of d/d0 of porous recrystallized SiC (RSiC) ceramics (the neck diameter to coarse micron-sized grains diameter ratio). The necking area and d/d0 value increased with the SiC nanocrystals content, due to the higher saturated vapor pressure resulted in high mass mobility to neck area of SiC nanoparticles. As a result, a remarkable value of d/d0 ~ 99% and outstanding flexural strength of 75.7 MPa could be achieved for the porous RSiC ceramics with ~42% porosity by adding 20 wt.% nano-sized SiC sintered at 1950°C for 2 h.

Revealing the atomistic mechanisms for the high-temperature mechanical behavior of materials is important for optimizing their properties for service at high-temperatures and their thermomechanical processing. However, due to materials microstructure’s dynamic recovery and the absence of available in situ techniques, the high-temperature deformation behavior and atomistic mechanisms of materials are difficult to evaluate. Here, we report the development of a microelectromechanical systems-based thermomechanical testing apparatus that enables mechanical testing at temperatures reaching 1556 K inside a transmission electron microscope for in situ investigation with atomic-resolution. With this unique technique, we first uncovered that tungsten fractures at 973 K in a ductile manner via a strain-induced multi-step body-centered cubic (BCC)-to-face-centered cubic (FCC) transformation and dislocation activities within the strain-induced FCC phase. Both events reduce the stress concentration at the crack tip and retard crack propagation. Our research provides an approach for timely and atomic-resolved high-temperature mechanical investigation of materials at high-temperatures., High-temperature deformation of materials is challenging to evaluate. Here the authors develop a novel device that allows atomic resolved in situ high temperature mechanical tests inside a transmission electron microscope and reveal ductile fracture of a single crystal tungsten deformed at 973 K.

Routing mechanism is a key issue in Wireless Sensor Networks, and rumor routing protocol can reduce energy consumption and extend the lifecycle of network with unicast mechanism. However, in Rumor Routing protocol, the transmission path of event message is not optimal and random forwarding mechanism will lead to routing loop. In this paper, we investigate Rumor Routing protocol, and propose an improved rumor routing protocol based on optimized intersection angle theory. Localization technology and vector intersection angle mechanism are brought into the new protocol as two metrics of route selection. The new mechanism can reduce the energy consumption of data transmission. We compare Rumor Routing protocol, GPSR protocol, a Rumor Routing-based protocol, and the improved protocol. Results of simulation experiments indicate that the improved routing protocol can reduce the energy consumption of routing path and extend the lifecycle of network.

M23C6 carbide is a common precipitate phase present in Ni-based superalloys. The carbide is generally an alloy carbine and often contains more than one metallic element. In this study, the site preference of metallic elements in M23C6 carbide in a Ni-based single crystal was determined by means of aberration-corrected High-Angle Annular Dark Field Scanning Transmission Electron Microscopy (HAADF-STEM) technique and quantitative STEM (QSTEM)-based image simulation method. The carbide was found to contain mostly Cr and Re, with a small amount of Mo. The HAADF-STEM and QSTEM-based simulation analyses indicate that heavy atoms prefer to substitute Cr at 8c sites. Keywords: Ni-based superalloy, Creep, Carbides, Rhenium, Aberration-corrected HAADF-STEM

In this article, the Ni-46.1Al-7.8Mo (at.%) alloy was directionally solidified at different growth rates ranging from 15 μm/s to 1000 μm/s under a constant temperature gradient (334 K/cm). The dependence of microstructural length scales on the growth rate was investigated. The results show that, with the growth rate increasing, the primary dendritic arm spacings (PDAS) and secondary dendritic arm spacings (SDAS) decreased. There exists a large distribution range in PDAS under directional solidification conditions at a constant temperature gradient. The average PDAS and SDAS as a function of growth rate can be given as λ1 = 848.8967 V−0.4509 and λ2 = 64.2196 V−0.4140, respectively. In addition, a comparison of our results with the current theoretical models and previous experimental results has also been made.

Survival classification on time-to-event clinical data is useful in clinical research. Survival analysis techniques are widely used to predict the survival probability over time that a particular event occurs. It is crucial to identify the risk of experiencing the event for patients, which can be achieved by classifying risk groups of patients. However, the existing classification methods, such as logistic regression, support vector machines and artificial neural network, cannot be applied to clinical data directly, due to the context of censoring. To address this problem, we propose a new two-tied labeling approach for reformulating the clinical data and make classifiers available to process such data. We perform such labeling on real-life clinical data and the good performances achieved by the classification methods reveal the great promise of our approach for risk group classification.

In this work, we designed a micro-electromechanical systems (MEMS) device that allows simultaneous direct measurement of mechanical properties during deformation under external stress and characterization of the evolution of nanomaterial microstructure within a transmission electron microscope. This MEMS device makes it easy to establish the correlation between microstructure and mechanical properties of nanomaterials. The device uses piezoresistive sensors to measure the force and displacement of nanomaterials qualitatively, e.g., in wire and thin plate forms. The device has a theoretical displacement resolution of 0.19 nm and a force resolution of 2.1 μN. The device has a theoretical displacement range limit of 5.47 μm and a load range limit of 55.0 mN.