Low-Temperature Oxidation, Hydrothermal Corrosion, and Their Effects on Properties of SiC (Tyranno) Fibers

The effects of oxidation in air and corrosion in high-temperature, high-pressure water on the mechanical properties of three commercially available amorphous Si-Ti-C-O (Tyranno) fibers with different oxygen contents (12%–18%) and diameters (8–11 μm) were investigated. The fibers were exposed to isothermal treatments at elevated temperatures and subsequently tested at room temperature. Structural changes in the fibers after oxidation and corrosion were also studied in order to understand better the degradation mechanisms of the fibers. Oxidation resulted in the formation of vitreous silica films and decreases of strength and Young's modulus of the fibers. Hydrothermal corrosion under 100 MPa water pressure started above 300°C and resulted in the formation of a carbon layer on the surface of the fibers. Dissolution of silica in water during the treatment was observed. Corrosion at temperatures above 400°C led to the formation of relatively thick carbon films which delaminated easily. It caused a decrease of strength and Young's modulus of the fibers. The hydrothermal method can be used for producing carbon coatings with thickness up to 2 μm on the surface of silicon carbide fibers. The degrading of the mechanical properties after oxidation and corrosion was controlled by the thickness of the oxide or carbon layer. Based on this fact, it is possible to predict changes in the mechanical properties from the oxidation data.     

The determination of the energy barrier for phase slips in superfluid4He

The velocity dependence of the energy barrier for vortex creation in microscopic apertures is determined. When compared to results from other laboratories, the energy barrier seems to be a universal function of velocity. This universality suggests that the vortex nucleation process is independent of the microscopic surface structure of the aperture. In DC flow experiments, the vortices are nucleated at rates up to 700kHz. In single phase slip experiments, the rate of nucleation is on the order of 10 Hz. Each of these types of experiments gives the energy barrier in a different velocity regime. The energy barrier has more curvature, as a function of velocity, than can be accounted for by the half-ring model of vortex nucleation.     

Retrospective Individual Dosimetry at a Populated Point with a High Degree of Radioactive Contamination

The results of a reconstruction of the individual accumulated absorbed dose of internal and external whole-body irradiation (from 1986 to 2000) for the residents in the village of Zabor'e in the Krasnogorsk rayon of Bryansk oblast – the most highly contaminated populated point in Russia as a result of the Chernobyl accident (4329 kBq/m^{2 137}Cs) – are presented. The total individual accumulated absorbed dose is 50–490 mGy. For 18 of the 42 individuals examined, the dose exceeds 200 mGy. It is found that the protective countermeasure (elimination of the family milk cows) taken in 1986 was ineffective, since in 1987 the villagers began to reacquire family cows. Measures are proposed for limiting the consumption of local contaminated food products. The computational methodology adopted, based on questioning the population and assessing the running radiation conditions, is verified by comparing with data from individual EPR dosimetry on tooth enamel for some of the individuals examined (10 samples). The agreement with the EPR data is good.     

Effects of rolling texture on fatigue failure in 07Kh13N4AG20 steel

Notched circular cylindrical specimens have been cut in the plane of the sheet from 07Kh13N4AG20 steel along and transverse to the rolling fibers and have been tested in bending with rotation, with the determination of the fatigue ridge step (fatigue crack microgrowth rate) together with the stress intensity coefficients K. It is concluded that there is a substantial effect from the rolling texture in the plane of the sheet on the kinetics of the fatigue failure.Translated from Problemy Prochnosti, No. 12, pp. 26–31, December, 1992.     

Stamping of Flexible,Coplanar Micro‐Supercapacitors Using MXene Inks

The fast growth of portable smart electronics and internet of things have greatly stimulated the demand for miniaturized energy storage devices. Micro‐supercapacitors (MSCs), which can provide high power density and a long lifetime, are ideal stand‐alone power sources for smart microelectronics. However, relatively few MSCs exhibit both high areal and volumetric capacitance. Here rapid production of flexible MSCs is demonstrated through a scalable, low‐cost stamping strategy. Combining 3D‐printed stamps with arbitrary shapes and 2D titanium carbide or carbonitride inks (Ti₃C₂T_x and Ti₃CNT_x, respectively, known as MXenes), flexible all‐MXene MSCs with controlled architectures are produced. The interdigitated Ti₃C₂T_x MSC exhibits high areal capacitance: 61 mF cm^?2 at 25 µA cm^?2 and 50 mF cm^?2 as the current density increases by 32 fold. The Ti₃C₂T_x MSCs also showcase capacitive charge storage properties, good cycling lifetime, high energy and power densities, etc. The production of such high‐performance Ti₃C₂T_x MSCs can be easily scaled up by designing pad or cylindrical stamps, followed by a cold rolling process. Collectively, the rapid, efficient production of flexible all‐MXene MSCs with state‐of‐the‐art performance opens new exciting opportunities for future applications in wearable and portable electronics.