Measuring the melting curve of iron at super-Earth core conditions

Terapascal iron-melting temperature The pressure and temperature conditions at which iron melts are important for terrestrial planets because they determine the size of the liquid metal core, an important factor for understanding the potential for generating a radiation-shielding magnetic field. Kraus et al . used laser-driven shock to determine the iron-melt curve up to a pressure of 1000 gigapascals (see the Perspective by Zhang and Lin). This value is about three times that of the Earth’s inner core boundary. The authors found that the liquid metal core lasted the longest for Earth-like planets four to six times larger in mass than the Earth. —BG

Influence of the soldering paste type on optical and thermal parameters of LED modules

Purpose This paper presents the results of the investigations of LED modules soldered with the use of different soldering pastes. Design/methodology/approach The tested power LED modules are soldered using different solder pastes and soldering processes. Thermal parameters of the performed modules are tested using indirect electrical methods. The results of measurements obtained for different modules are compared and discussed. Findings It was shown that the soldering process visibly influences the results of measurements of optical and thermal parameters of LED modules. For example, values of thermal resistance of these modules and the efficiency of conversion of electrical energy into light differ between each other even by 15%. Practical implications The obtained results of investigations can be usable for designers of the assembly process of power LED modules. Originality/value This paper shows the investigations results in the area of effective assembly of power LEDs to the metal core printed circuit board (MCPCB) using different soldering pastes (REL22, REL61, LMPA-Q6, OM-5100, OM-338-PT, M8, OM-340, CVP-390). It was shown that the best thermal and optical properties of these modules are obtained for the OM5100 paste by Alpha Assembly.

A New Synthetic Methodology in the Preparation of Bimetallic Chalcogenide Clusters via Cluster-to-Cluster Transformations

A decanuclear silver chalcogenide cluster, [Ag10(Se){Se2P(OiPr)2}8] (2) was isolated from a hydride-encapsulated silver diisopropyl diselenophosphates, [Ag7(H){Se2P(OiPr)2}6], under thermal condition. The time-dependent NMR spectroscopy showed that 2 was generated at the first three hours and the hydrido silver cluster was completely consumed after thirty-six hours. This method illustrated as cluster-to-cluster transformations can be applied to prepare selenide-centered decanuclear bimetallic clusters, [CuxAg10-x(Se){Se2P(OiPr)2}8] (x = 0–7, 3), via heating [CuxAg7−x(H){Se2P(OiPr)2}6] (x = 1–6) at 60 °C. Compositions of 3 were accurately confirmed by the ESI mass spectrometry. While the crystal 2 revealed two un-identical [Ag10(Se){Se2P(OiPr)2}8] structures in the asymmetric unit, a co-crystal of [Cu3Ag7(Se){Se2P(OiPr)2}8]0.6[Cu4Ag6(Se){Se2P(OiPr)2}8]0.4 ([3a]0.6[3b]0.4) was eventually characterized by single-crystal X-ray diffraction. Even though compositions of 2, [3a]0.6[3b]0.4 and the previous published [Ag10(Se){Se2P(OEt)2}8] (1) are quite similar (10 metals, 1 Se2−, 8 ligands), their metal core arrangements are completely different. These results show that different synthetic methods by using different starting reagents can affect the structure of the resulting products, leading to polymorphism.

Seismic detection of the martian core

Clues to a planet’s geologic history are contained in its interior structure, particularly its core. We detected reflections of seismic waves from the core-mantle boundary of Mars using InSight seismic data and inverted these together with geodetic data to constrain the radius of the liquid metal core to 1830 ± 40 kilometers. The large core implies a martian mantle mineralogically similar to the terrestrial upper mantle and transition zone but differing from Earth by not having a bridgmanite-dominated lower mantle. We inferred a mean core density of 5.7 to 6.3 grams per cubic centimeter, which requires a substantial complement of light elements dissolved in the iron-nickel core. The seismic core shadow as seen from InSight’s location covers half the surface of Mars, including the majority of potentially active regions—e.g., Tharsis—possibly limiting the number of detectable marsquakes.