Two-phase mixture of iron–nickel–silicon alloys in the Earth’s inner core

The Earth’s inner core comprises iron-nickel alloys with light elements. However, there is no clarity on the phase properties of these alloys. Here we show phase relations and equations of state of iron–nickel and iron–nickel–silicon alloys up to 186 gigapascals and 3090 kelvin. An ordered derivative of the body-centred cubic structure (B2) phase was observed in these alloys. Results show that nickel and silicon influence the stability field associated with the two-phase mixture of B2 and hexagonal close-packed phases under core conditions. The two-phase mixture can give the inner core density of the preliminary reference Earth model. The compressional wave velocity of the two-phase mixture under inner core conditions is consistent with that of the preliminary reference Earth model. Therefore, a mixture of B2 and hexagonal close-packed phases may exist in the inner core and accounts for the seismological properties of the inner core such as density and velocity deficits.

Improving the quality of bars from special alloy of the copper—nickel—silicon system

Possibilities of improving the quality of a special wear-resistant and heat-resistant alloy Cu—Ni—Si of the copper — nickel — silicon system used in the production of special-purpose electro-vacuum devices are analyzed.

Atomic Layer Deposition of Lithium–Nickel–Silicon Oxide Cathode Material for Thin-Film Lithium-Ion Batteries

Lithium nickelate (LiNiO2) and materials based on it are attractive positive electrode materials for lithium-ion batteries, owing to their large capacity. In this paper, the results of atomic layer deposition (ALD) of lithium–nickel–silicon oxide thin films using lithium hexamethyldisilazide (LiHMDS) and bis(cyclopentadienyl) nickel (II) (NiCp2) as precursors and remote oxygen plasma as a counter-reagent are reported. Two approaches were studied: ALD using supercycles and ALD of the multilayered structure of lithium oxide, lithium nickel oxide, and nickel oxides followed by annealing. The prepared films were studied by scanning electron microscopy, spectral ellipsometry, X-ray diffraction, X-ray reflectivity, X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and selected-area electron diffraction. The pulse ratio of LiHMDS/Ni(Cp)2 precursors in one supercycle ranged from 1/1 to 1/10. Silicon was observed in the deposited films, and after annealing, crystalline Li2SiO3 and Li2Si2O5 were formed at 800 °C. Annealing of the multilayered sample caused the partial formation of LiNiO2. The obtained cathode materials possessed electrochemical activity comparable with the results for other thin-film cathodes.

Guiding principles for creating new high strength-high conductivity copper alloys

Solid solution strengthened alloys such as brass and bronze have been widely used as contact materials for energisation in a range of devices due to the fact that they are relatively low cost. In more recent times precipitation strengthened alloys such as copper-beryllium, copper-titanium and copper-nickel-silicon are used due to their excellent strength and conductivity. Yet, little headway has been made in the development of precipitation hardening copper alloys due to the difficulty associated with departing from existing alloy designs and structure control methods. One team of researchers is exploring the use of over-aged material instead of the conventional peak-aged material. This is because previous studies have suggested that wires of this type may have improved strength and conductivity. But there remain many unknowns. Associate Professor Satoshi Semboshi is a researcher based at the Institute for Materials Research, Tohoku University, Japan, who is seeking to shed light on these unknowns.