Data for Beryllium–Hydrogen Charge Exchange in One and Two Centres Models, Relevant for Tokamak Plasmas

Data on the cross section and kinetic rate of charge exchange (CX) between the bare beryllium nucleus, the ion Be(+4) and the neutral hydrogen atom are of great interest for visible-range high-resolution spectroscopy in the ITER tokamak because beryllium is intended as the material for the first wall in the main chamber. Here an analysis of available data is presented, and the data needs are formulated. Besides the active probe signal produced by the CX of the diagnostic hydrogen neutral beam with impurity ions in plasma, a passive signal produced by the CX of impurity ions with cold edge plasma is also important, as it shows in observation data from the JET (Joint European Torus) tokamak with an ITER-like beryllium wall. Data in the range of a few eV/amu to ~100 eV/amu (amu stands for the atomic mass unit) needed for simulations of level populations for principal and orbital quantum numbers in the emitting beryllium ions Be(+3) can be obtained with the help of two-dimensional kinetic codes. The lack of literature data, especially for data resolved in orbital quantum numbers, has instigated us to make numerical calculations with the ARSENY code. A comparison of the results obtained for the one-centre Coulomb problem using an analytic approach and for the two-centre problem using numerical simulations is presented.

Hydrogen Gas Phase and Electrochemical Hydriding of LaNi5−xMx (M = Sn, Co, Al) Alloys

Hydriding/dehydriding properties of a series of LaNi5 based alloys were compared by applying both hydrogen gas phase and electrochemical hydrogen charge/discharge methods. The highest hydrogen absorption capacity of 1.4 wt.% H2 was found for LaNi4.3Co0.4Al0.3, although LaNi4.8Sn0.2 also reveals comparable hydrogen capacity (>1.3%). A significant difference in the hydriding kinetics was observed for all studied alloys before and after activation. The activated alloys (5 cycles at 65 °C, 40 atm. H2) reach their maximum capacities after less than a minute, whereas the pure LaNi5 alloy needs several minutes for complete hydriding. The electrochemical hydriding/dehydriding behavior of the alloys reveals superior performance of LaNi4.3Co0.4Al0.3 and LaNi4.8Sn0.2 compared to the other compositions studied, as the capacity of LaNi4.8Sn0.2 decreases by only 10% for 60 charge/discharge cycles at a current density of 100 mA/g. Good agreement between the hydrogen sorption kinetics of the alloys obtained electrochemically and from hydrogen gas phase has also been observed.

Electrical conductivity studies on silica phases and the effects of phase transformation

Starting with the same sample, the electrical conductivities of quartz and coesite have been measured at pressures of 1, 6, and 8.7 GPa, respectively, over a temperature range of 373–1273 K in a multi-anvil high-pressure system. Results indicate that the electrical conductivity in quartz increases with pressure as well as when the phase change from quartz to coesite occurs, while the activation enthalpy decreases with increasing pressure. Activation enthalpies of 0.89, 0.56, and 0.46 eV, were determined at 1, 6, and 8.7 GPa, respectively, giving an activation volume of –0.052 ± 0.006 cm3/mol. FTIR and composition analysis indicate that the electrical conductivities in silica polymorphs is controlled by substitution of silicon by aluminum with hydrogen charge compensation. Comparing with electrical conductivity measurements in stishovite, reported by Yoshino et al. (2014), our results fall within the aluminum and water content extremes measured in stishovite at 12 GPa. The resulting electrical conductivity model is mapped over the magnetotelluric profile obtained through the tectonically stable Northern Australian Craton. Given their relative abundances, these results imply potentially high electrical conductivities in the crust and mantle from contributions of silica polymorphs. The main results of this paper are as follows:The electrical conductivity of silica polymorphs is determined by impedance spectroscopy up to 8.7 GPa.The activation enthalpy decreases with increasing pressure indicating a negative activation volume across the silica polymorphs.The electrical conductivity results are consistent with measurements observed in stishovite at 12 GPa.

LEDs for the Implementation of Advanced Hydrogenation Using Hydrogen Charge-State Control

Light-induced degradation (LID) of p-type Cz solar cells has plagued the industry for many decades. However, in recent years, new techniques for solving this LID have been developed, with hydrogen passivation of the boron-oxygen defects appearing to be an important contributor to the solution. Advanced hydrogenation approaches involving the control of the charge state for the hydrogen atoms in silicon to enhance their diffusivity and reactivity are developed and evaluated in this work for commercial application using a prototype industrial tool in conjunction with solar cells manufactured on commercial production lines. This prototype tool, unlike the previous successful laser-based laboratory approaches, is based on the use of LEDs for controlling the charge state of the hydrogen atoms. The illumination from the LEDs is also used in this work to passivate process-induced defects and contamination from the respective production lines with significant improvements in both efficiency and stability. The results indicate that the low-cost LED-based industrial tool performs as well as the laser-based laboratory tool for implementing these advanced hydrogen passivation approaches.

Hydrogen Assisted Tempered Martensite Embrittlement of Ultra High Strength Martensitic Steel

The demand for new materials that provide excellent structural performance while reducing weight and being cost-effectively manufactured is increasing. For applications with high strength requirements, ultra-high strength steels (UHSS) have been widely used. However, with such a high strength level, UHSS are very sensitive to the hydrogen that could be ease by the tempering process. In this research, the correlation of hydrogen and tempering process on commercial UHSS 15B30 has been studied. Results show that the tensile strength (TS) of as-quenched 15B30 is about 1900MPa. After tempering treatment of the quenched 15B30, the TS decreases from 1600MPa to 1200MPa with tempering temperature increased from 200°C to 400°C. The 15B30 specimens, being subjected to hydrogen charge, exhibit the dramatic reduction of mechanical strengths.

Estimation of Fatigue Limit in Interior Inclusion Induced Fracture Mode for Bearing Steel in Rotating Bending

The fatigue life forming fine granular area (FGA) is expected to occupy a large fraction of the total fatigue life. In order to examine the commencing time of the FGA forming and estimate the fatigue limit in the interior inclusion induced fracture mode, rotating bending fatigue tests were carried out by using SUJ2 specimens with and without the hydrogen charge. Especially, the hydrogen charge time was set in the wide variety of the cyclic loadings to confirm the FGA forming process supposing the effect of the hydrogen charge on the fatigue crack propagation behavior. From experimental and analytical results, it is concluded that the FGA formation is already started at early stage as 5 % of the fatigue life. Another finding is that we have a clear correlation between the stress intensity factor range and the FGA growth ratio. Based on this aspect, the critical value of the stress intensity factor range in which the FGA is not formed around the inclusion was given as 2.65 MPa.