Liquid state properties and solidification features of the pseudo binary BaS-La2S3

The high temperature thermodynamic properties of chalcogenides materials based on BaS remain elusive. Herein the pseudo binary BaS-La2S3 is investigated above 1573 K. The liquid properties of BaS-La2S3 are measured by means of high resolution in-situ visualization coupled with thermal arrest measurements in a thermal imaging furnace. This enables to report the first observation of such melts in a container-less setting. The melting points of BaS and La2S3 are revisited at 2454 K and 2004 K respectively. La2S3 demonstrates a high stability in its liquid state, in strike difference with the sublimation observed for BaS. BaS is however partially stabilized with the addition of few percents of La2S3. The remarkable chemical and thermal stability of La2S3-rich samples contrasts with the partial decomposition and high vapor pressure observed for BaS-rich samples. Observations and analysis of the solidified samples suggest three different solid solutions. Solid and liquid densities are investigated along the different compositions, supporting a first estimate of the volumetric thermal expansion coefficient for La2S3.

Highly magmatic breakup LIP centers – a revisit to the East Greenland VRM

Decompressional release of magma at continental triple rift breakup LIP centers, above mantle plume stems, result in highly magmatic settings. As a particularly well exposed example, it is proposed that the East Greenland coastal dyke swarm preserves a structural record of how dyke dilations versus tectonic extension increased upon approaching its Kangerlussuaq triple rift center. Such more magmatic breakup is reflected by how abruptly its volcanic rifted margin transitions into 100% dykes, and in this case up to 100 km farther inland than its geophysically determined continent-ocean boundary. Correspondingly high magma flux through an igneous Kap Edward Holm center sustained the lateral injection of up to 150 km-long dykes, evidenced by increased cut-off dyke thicknesses - below which there is an anomalously low abundance of thinner dykes - that conform to the cube root of their thermal arrest distance. Only the thickest and thereby longest dyke injections linked up with a more southerly located igneous Imilik center of an en echelon offset dyke swarm, the complex transition into which is also addressed. This highly magmatic central plumbing system is further compared to similar volcanic zones across Iceland and other post-Paleozoic breakup LIPs, in order to contextualize its importance.

Liquid State Properties and Solidification Features of the Pseudo Binary BaS-La2S3

The high temperature thermodynamic properties of chalcogenides materials based on BaS remain elusive, and herein the La2S3 pseudo binary system is investigated above 1573 K. The liquid properties of BaS-La2S3 are measured by means of high resolution in-situ visualization coupled with thermal arrest measurements in a thermal imaging furnace. This enables to report for the first observation of such melts in a containerless setting. The melting points of BaS and La2S3 are revisited at 2454 K and 2004 K respectively. La2S3 demonstrates a high stability in its liquid state, in strike difference with the sublimation observed for BaS. BaS is however partially stabilized with the addition of few percents of La2S3.The remarkable chemical and thermal stability of La2S3-rich samples, contrasts with the partial decomposition and high vapor pressure observed for BaS-rich samples. Observations and analysis of the solidified samples suggests three different solid solutions. Solid and liquid densities are investigated along the different compositions, supporting a first estimate of the volumetric thermal expansion coefficient for La2S3.

Semi-Solid Casting of Pure Magnesium

Semi-solid processing works on the principal of a solidification temperature interval of a substance. The substance is heated to a temperature within this interval so that there exists a related solid-liquid fraction ratio. The substance with this phase structure is then shaped by a forging or casting process. It has been stated before that it is impossible to semi-solid process and cast pure metals or eutectic alloys due to their thermodynamic temperature invariance, meaning that there is no temperature interval. It was demonstrated recently that it is possible to semi-solid casting high purity aluminium (Curle UA, Möller H, Wilkins JD. Scripta Materialia 64 (2011) 479-482) and the Al-Si binary eutectic (Curle UA, Möller H, Wilkins JD. Materials Letters 65 (2011) 1469-1472). The working principal is that there exists a time interval during thermal arrest during which solidification takes place with a solid-liquid fraction ratio until all the liquid is consumed upon cooling. The aim with this work is to demonstrate that pure magnesium can also be rheo-high pressure die cast (R-HPDC) with the system developed at the CSIR in South Africa. Magnesium is notoriously difficult to cast due to the thermal properties of magnesium. The metal was poured into a cup, processed for about 6 seconds after which it was HPDC into a plate. The microstructure of the casting consists of a structure that was solid and a structure that was liquid during thermal arrest at the time of casting.

Effective Approaches for the Improvement of Solar Energy Collector Efficiency in Town Buildings

In order to reasonably make good use of solar energy---a kind of typical and clean energy, especially increase the efficiency of solar energy usage in town buildings, this paper introduces and analyzes solar Thermal-arrest Technology by way of how to increase solar absorption efficiency and how to decrease collector heat loss, finds an effective way to increase the efficiency of present solar collectors. Solar Thermal-arrest Technology is good for being widely used in town buildings. Its reasonable development is helpful to reducing building energy consumption and the relief of present energy shortage in China.

Melting Temperatures and Thermal Conductivities of Corium Prepared from UO2 and Zircaloy-2

ABSTRACTCorium which simulates the molten core of a Boiling Water Reactor was prepared as a parameter of Zr content, and melting temperatures and thermal conductivities were measured. The melting temperatures were measured by the thermal arrest method and were 2622 oC, 2509 oC and 2540 oC, respectively, in the specimens of 24.3 at%, 49.0 at% and 73.5 at% Zr content. Thermal conductivities had low values of 2.0-3.5 W/m oC at temperatures of 400 to 1600 oC.

Two-Way Memory Effect in NiTi Shape Memory Alloys

In general, the development mechanisms of TWME have long been understood as the nucleation and growth of preferentially oriented martensite guided by the internal stress. This work extends the study by investigating the effects of martensite deformation, constrained stress and retained martensite via partial reverse transformation through thermal arrest during heating on the stress-assisted two-way memory effect (SATWME) and TWME. It was observed that the generation of maximum SATWME was caused by the development of optimum internal stress. The increase of internal stress was accompanied by the increase of martensitic strain resulting from constrained cooling. When the martensitic strain exceeded the initial pre-strain, it directly influenced on the magnitudes of SATWME and TWME. The accommodation process of stress-assisted and detwinned martensite variants as a result of partial reverse transformation caused the formation of internal forward and back stresses. TWME was promoted by the dominant internal forward stress formation, while the dominance of internal back stress decreased the TWME by decreasing the martensitic strain.

Thermal Arrest Memory Effect in Ni-Mn-Ga Alloys

Dilatation characteristics were measured to investigate the thermal arrest memory effect inNi53.6Mn27.1Ga19.3andNi54.2Mn29.4Ga16.4alloys. Interruption of the martensite-austenite phase transformation is connected with the reduction of the sample length after thermal cycle. If a total phase transformation took place in the complete thermal cycle following the interruption, then the sample length would return to its original length. Analysis of these results has shown that the thermal arrest memory effect is a consequence of a stress-focusing effect and shape memory effect. The stress-focusing effect occurs when the phase transformation propagates radially in a cylindrical sample from the surface, inward to the center. Evolution and release of the thermoelastic deformations in both alloys during heating and cooling are analyzed.