Search results for "engineer"
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Savaime sklindančios aukštatemperatūrinės sintezės būdu gautų aliuminio oksinitrido miltelių ir jų keramikų optinės savybės
2021
The reported study was funded by RFBR according to the Research Project No. 19-08-00655. V.P. acknowledges the State Research Program ‘Aug-stas enerģijas fizika un paātrinātāju tehnoloģijas’ (Projekta Nr. VPP-IZM-CERN-2020/1-0002). The Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the H2020-WIDESPREAD-01-2016-2017-Teaming Phase2 under Grant Agreement No. 739508, Project CAMART2.
Migration kinetics of ion-implanted beryllium in glassy carbon
2008
Abstract Migration kinetics of low-concentration implanted 7 Be in glassy carbon has been studied by the modified radiotracer technique at temperatures 1285 °C and 1340 °C. The annealed sample concentration profiles show two distinctive components: (i) Main profile broadening assigned to beryllium trapping in defects during annealing. (ii) Tail parts on both sides of the profile maximum related to faster migration. Of the latter the profile representing bulk diffusion lies on the region free of defect influence and is well described by concentration-independent diffusivity. The features of the concentration profile broadening towards the sample surface indicate partial Be trapping in defect…
Evolution of the microstructure of sputter deposited TaAlON thin films with increasing oxygen partial pressure
2021
Abstract Recently, quaternary oxynitrides of transition metals and aluminum have attracted increasing interest due to their tunable properties. Within the present work, a series of TaAl(O)N films was sputter deposited using constant nitrogen and varying oxygen partial pressures. The films were grown from single element Ta and Al targets. The deposition parameters were adjusted to obtain a Ta/Al atomic ratio of ~50/50 for the oxygen-free film and were held constant for the following depositions, with the exception of the increasing oxygen partial pressure and compensatory decreasing argon partial pressure. Elastic recoil detection analysis revealed oxygen contents of up to ~26 at.%, while th…
Plastic yielding of glass in high-pressure torsion apparatus
2018
International audience; Hardness measurements performed at room temperature have demonstrated that glass can flow under elevated pressure, whereas the effect of high pressure on glass rheology remains poorly quantified. Here, we applied a high-pressure torsion (HPT) apparatus to deform SCHOTT SF6 â glass and attempted to quantify the effect of pressure and temperature on the shear deformation of glass subjected to pressures from 0.3 GPa to 7 GPa and temperatures from 25 ℃ to 496 ℃. Results show that the plastic yield deformation was occurring during the HPT experiments on the SF6 glass at elevated temperature from 350 ℃ to 496 ℃. The yield stress of SF6 glass decreases with increasing tempe…
Structural characterization and electrochemical hydrogen storage properties of Ti2LxZrxNi (x [ 0, 0.1, 0.2) alloys prepared by mechanical alloying
2013
International audience; Nominal Ti2Ni was synthesized under argon atmosphere at room temperature using a planetary high-energy ball mill. The effect of milling time and Zr substitution for Ti on the microstructure was characterized by XRD, SEM and TEM, and the discharge capacities of Ti2xZrxNi (x 1/4 0, 0.1, 0.2) were examined by electrochemical measurements at galvanostatic conditions. XRD analysis shows that amorphous phase of Ti2Ni can be elaborated by 60 h of milling, whereas Zr substitution hinders amorphization process of the system. The products of ball milling nominal Ti2xZrxNi (x 1/4 0.1, 0.2) were austenitic (Ti, Zr)Ni and partly TiO, despite the fact that the operation was carrie…
Optimum Design and Performance of an Electron Gun for a Ka-Band TWT
2019
This paper deals with optimum design and development of a thermionic electron gun to meet specified beam requirements within defined electric and geometric constraints for a Ka -band traveling wave tube (TWT) for space applications. The electron gun design is based on the Pierce method and carried out according to the iterative process indicated by Vaughan. The design of a periodic permanent magnet (PPM) beam focusing system for the stability of the beam is also required. A sensitivity analysis, by varying electric parameters and geometric parameters, is presented and taken into account as a fundamental role to the aim of optimizing the design of the Pierce gun. A cathode current value of 5…
Design and analysis of non-linear circuit with tunnel diode for hybrid control systems
2018
Electric circuits with tunnel diode's represent a classical example of dynamic systems with nonlinearities, which feature piecewise negative damping and multiple equilibria and, as consequence, nontrivial trajectories in the state-space. In this paper, we describe the experimental design and analysis of an electrical circuit, including a tunnel diode, allowing for a storage behavior with bistable output voltage states - low and high. The system is modeled for simulation and an experimental setup is designed and implemented in order to run a formal verification on different tools, applying a variety of hybrid control methods. The nonlinear diode's characteristic curve is experimentally deter…
Batch-to-Melt Conversion Kinetics in Sodium Aluminosilicate Batches Using Different Alumina Raw Materials
2016
The batch-to-melt conversion in batches of sand, soda ash and corundum (C), alumina spinel (A), boehmite (B), or gibbsite (G) as Al2O3 carrier are studied using thermal analysis, X-ray diffraction, and 27Al nuclear magnetic resonance spectroscopy. Laboratory-scaled batches are either heated continuously or quenched from 1600°C in a series of increasing dwell times. The results show that the conversion from the raw materials to the fresh melt proceeds in two kinetic stages. During the first stage (3–5 min), fast conversion of nearly 95% by mass occurs and the conversion coefficient increases in the order G < C ≈ A < B. The second stage is controlled by the slow dissolution of intermediate cr…
Photoluminescence-Based Spatially Resolved Temperature Coefficient Maps of Silicon Wafers and Solar Cells
2020
In this article, we present a method to obtain implied open-circuit voltage images of silicon wafers and cells at different temperatures. The proposed method is then demonstrated by investigating the temperature coefficients of various regions across multicrystalline silicon wafers and cells from different heights of two bricks with different dislocation densities. Interestingly, both low and high temperature coefficients are found in dislocated regions on the wafers. A large spread of temperature coefficient is observed at regions with similar performance at 298 K. Reduced temperature sensitivity is found to be correlated with the increasing brick height and is exhibited by both wafers and…
A Novel Method for Characterizing Temperature Sensitivity of Silicon Wafers and Cells
2019
In this paper, we present a novel method to obtain temperature dependent lifetime and implied-open-circuit voltage (iV OC ) images of silicon wafers and solar cells. First, the method is validated by comparing the obtained values with global values acquired from lifetime measurements (for wafers) and current-voltage measurements (for cells). The method is then extended to acquire spatially resolved images of iV OC temperature coefficients of silicon wafers and cells. Potential applications of the proposed method are demonstrated by investigating the temperature coefficients of various regions across multi-crystalline silicon wafers and cells from different heights of two bricks with differe…