10/06/2024


The excellent physical and chemical properties of metallic glasses and the absence of crystal defects make them ideal materials for the preparation of microelectrodes. A vertical liquid membrane electrochemical etching method is proposed here for the fabrication of microelectrodes from the Fe-based metallic glass Fe77.5B15Si7.5. With this method, insoluble electrolysis products are kept away from the processing area, and the nonuniformity of the diffusion layer that occurs in traditional transverse liquid membrane electrochemical etching is reduced. Simulations of the potential distribution and the current density distribution are carried out in COMSOL software, and the simulation results are verified by experiments. The passivation characteristics of the Fe77.5B15Si7.5 metallic glass in H2SO4 and H3PO4 electrolytes are studied. The effects of processing voltage on electrode morphology and surface quality are studied experimentally. Micropins with good tip size can be prepared in the active dissolution stage in 0.1M H2SO4 solution, and high-aspect-ratio cylindrical microtool electrodes with high surface quality can be fabricated in the transpassivation stage in 80% H3PO4 electrolyte with high machining stability.This study presents a new method for measuring the Seebeck coefficient under high pressure in a multi-anvil apparatus. The application of a dual-heating system enables precise control of the temperature difference between both ends of the sample in a high-pressure environment. Two pairs of W-Re thermocouples were employed at both ends of the sample to monitor and control the temperature difference, and independent probes were arranged to monitor the electromotive force (emf) produced by temperature oscillation at a given target temperature. The temperature difference was controlled within 1 K during the resistivity measurements to eliminate the influence of the emf owing to a sample temperature gradient. The Seebeck measurement was successfully measured from room temperature to 1400 K and was obtained by averaging the two measured values with opposite thermal gradient directions (∼20 K). Thermoelectric properties were measured on disk-shaped p-type Si wafers with two different carrier concentrations as a reference for high Seebeck coefficients. This method is effective to determine the thermoelectric power of materials under pressure.This paper numerically confirms that in the ideal case, the form of cone with 16 ribs benefits the reduction in impedance and the promotion (about 20%-30%) on transmission efficiency of a magnetically insulated transmission line, in comparison with the traditional form of cone. Magnetically insulated transmission lines in the form of cone, cone with 4, 8, 12, and 16 ribs, are first designed by using CREO and then imported to COMSOL for obtainment of their circuit parameters. Two codes based on the wave process and wave process coupled with RLC circuits, respectively, simulating the propagation of external waves through non-uniform transmission lines are analyzed and presented in detail. The obtained parameters are then used in these codes for deriving the designed transmission lines' transmission efficiency of peak power. As a comparison, the obtained data are also employed in PSpice for derivation of the transmission efficiency. These derived results consistently verify that the form cone with ribs may effectively promote the transmission efficiency of magnetically insulated transmission lines.A movable Allison type emittance scanner is being developed to characterize the phase-space distribution of the beamlets of spectral phase interferometry for direct electric-field reconstruction, the prototype RF negative ion source of the ITER heating neutral beam injector. To test the electronics and verify the capability of the device to resolve nearby beamlets, a compact RF ion source prototype has been set up, capable of accelerating 1 mA of helium ions up to a voltage of 2 kV. A commercial 100 W RF generator creates a plasma inside a Pyrex tube, with a density between 1015 and 1016 m-3 and an electron temperature up to 15 eV. Three multi-aperture grids in accel-decel configuration extract and accelerate the ions, which are measured with a Faraday cup. We present in this paper the characterization of the ion source and its first operation, showing that it is suitable for the commissioning of the Allison scanner.The full-wave analysis was applied for a coaxial line (i.e., transmission line) that has a "short-circuited" discontinuity. The discontinuity has a radius less than or equal to the inner radius of the coaxial line. The "sample region" can be considered as a partially filled circular waveguide. Such a structure is very practical and is of particular interest for the dielectric spectroscopy applications. It takes into account the inhomogeneous field distribution, which is the limiting factor for the determination of high dielectric permittivity values at microwave frequencies. https://www.selleckchem.com/products/GDC-0980-RG7422.html The direct problem was solved by using the mode-matching technique, and the relationship between the complex reflection coefficient and the dielectric permittivity of the cylindrical sample was obtained. By solving the inverse problem, it is possible to obtain the complex dielectric permittivity from the experimental values of the scattering matrix. The results were verified by the finite element modeling of the system and applied for particular materials. The correspondence between these approaches is excellent. This method is very suitable for the determination of permittivity, which exceeds several thousands (it is applicable for any type of material). It extends the frequency range where the permittivity can be determined reliably. There is no necessity to prepare samples with different geometries (i.e., surface area and thickness).A sample holder for a suite of synchrotron radiation measurements on extraterrestrial materials, which are fragile and irregularly shaped, was developed using carbon nanotubes and polyimide. The holder enables investigation of such samples with multiple analytical instruments, which means that we can reduce the number of sample transfers between holders. The holder developed in our study also enables investigation of such samples without exposure to the terrestrial atmosphere, which contains abundant contaminants, such as water vapor and organic substances. The stability of the samples in the holder during the measurements and disturbance of the analysis result by the holder were evaluated, which showed that sample drift motion and image disturbance due to x-ray attenuation and scattering of the holder materials are insignificant.