Effects of Melt Thermal Treatment on A356 Alloy

To increase the casting quality of hypoeutectic Al-Si alloys, the effects of melt thermal treatment on the solidification structure of the A356 alloy were analyzed by a factorial experiment, in which the overheated melt was mixed with the low temperature melt. Experimental results show that the elongation ratio and strength of the treated samples increase remarkably compared with the control sample. The primary dendrite size reduces dramatically and the dendrite changes from columnar to equiaxed, with a little change of the secondary dendrite arm spacing (SDAS). Combined with the measurement of the nucleation undercooling, it is concluded that the solidification structure and refining effect are dependent primarily on the low temperature melt. The refining mechanism is believed as a result of the multiplication of the nuclei in the melt thermal treatment procedure.

Evidences of the expanding Earth from space-geodetic data over solid land and sea level rise in recent two decades

According to the space-geodetic data recorded at globally distributed stations over solid land spanning a period of more than 20-years under the International Terrestrial Reference Frame 2008,our previous estimate of the average-weighted vertical variation of the Earth＇s solid surface suggests that the Earth＇s solid part is expanding at a rate of 0.24 ± 0.05 mm/a in recent two decades.In another aspect,the satellite altimetry observations spanning recent two decades demonstrate the sea level rise（SLR） rate 3.2 ± 0.4 mm/a,of which1.8 ± 0.5 mm/a is contributed by the ice melting over land.This study shows that the oceanic thermal expansion is 1.0 ± 0.1 mm/a due to the temperature increase in recent half century,which coincides with the estimate provided by previous authors.The SLR observation by altimetry is not balanced by the ice melting and thermal expansion,which is an open problem before this study.However,in this study we infer that the oceanic part of the Earth is expanding at a rate about 0.4 mm/a.Combining the expansion rates of land part and oceanic part,we conclude that the Earth is expanding at a rate of 0.35 ± 0.47 mm/a in recent two decades.If the Earth expands at this rate,then the altimetry-observed SLR can be well explained.

Thermophysical properties of iridium at finite temperature

The bulk properties of materials in an extreme environment such as high temperature and high pressure can be understood by studying anharmonic effects due to the vibration of lattice ions and thermally excited electrons.In this spirit,in the present paper,anharmonic effects are studied by using the recently proposed mean-field potential（MFP） approach and Mermin functional which arise due to the vibration of lattice ions and thermally excited electrons,respectively.The MFP experienced by a wanderer atom in the presence of surrounding atoms is constructed in terms of cold energy using the local form of the pseudopotential.We have calculated the temperature variation of several thermophysical properties in an extreme environment up to melting temperature.The results of our calculations are in excellent agreement with the experimental findings as well as the theoretical results obtained by using first principle methods.We conclude that presently used conjunction scheme（MFP＋pseudo potential） is simple computationally,transparent physically,and accurate in the sense that the results generated are comparable and sometimes better than the results obtained by first principle methods.Local pseudopotential used is transferable to extreme environment without adjusting its parameters.

In-situ investigation of melting characteristics of waste selective catalytic reduction catalysts during harmless melting treatment

Selective catalytic reduction(SCR) catalyst waste is a hazardous solid waste that seriously threatens the environment and public health.In this study,a thermal melting technology is proposed for the treatment of waste SCR catalysts.The melting characteristics and mineral phase transformation of waste SCR catalysts blended with three different groups of additives were explored by heating stage microscopy,thermogravimetric analysis/differential scanning calorimetry(TG/DSC) analysis,thermodynamic simulation,and X-ray diffraction(XRD) analysis;heavy metal leaching toxicity was tested by inductively coupled plasma-atomic emission spectrometry(I CP-AES) analysis.The results indicated that the melting point of waste SCR catalysts can be effectively reduced with proper additives.The additive formula of 39.00% Fe2 O3(in weight),6.50% CaO,3.30% SiO2,and 1.20% Al2 O3 achieves the optimal fluxing behavior,significantly decreasing the initial melting temperature from 1223℃ to1169℃.Furthermore,the whole heating process of waste SCR catalysts can be divided into three stages:the solid reaction stage,the sintering stage,and the primary melting stage.The leaching concentrations of V,As,Pb,and Se are significantly reduced,from 10.64,1.054,0.195,and 0.347 mg/L to 0.178,0.025,0.048,and 0.003 mg/L,respectively,much lower than the standard limits after melting treatment,showing the strong immobilization capacity of optimal additives for heavy metals in waste SCR catalysts.The results demonstrate the feasibility of harmless melting treatments for waste SCR catalysts with relatively low energy consumption,providing theoretical support for a novel method of disposing of hazardous waste SCR catalysts.

Design and application of copper/lithium composite anodes for advanced lithium metal batteries

Lithium(Li)is a promising candidate for nextgeneration battery anode due to its high theoretical specific capacity and low reduction potential.However,safety issues derived from the uncontrolled growth of Li dendrite and huge volume change of Li hinder its practical application.C onstructing dendrite-free composite Li anodes can significantly alleviate the above problems.Copper(Cu)-based materials have bee n widely used as substrates of the composite electrodes due to their chemical stability,excellent conductivity,and good mechanical strength.Copper/lithium(Cu/Li)composite anodes significantly regulate the local current density and decrease Li nucleation overp otential,realizing the uniform and dendrite-free Li deposition.In this review,Cu/Li composite methods including electrodeposition,melting infusion,and mechanical rolling are systematically summarized and discussed.Additionally,design strategies of Cu-based current collectors for high performance Cu/Li composite anodes are illustrated.General challenges and future development for Cu/Li composite anodes are presented and postulated.We hope that this review can provide a comprehensive understanding of Cu/Li composite methods of the latest development of Li metal anode and stimulate more research in the future.

Liquid metal as energy transportation medium or coolant under harsh environment with temperature below zero centigrade

The current highly integrated electronics and energy systems are raising a growing demand for more sophisticated thermal management in harsh environments such as in space or some other cryogenic environment. Recently, it was found that room temperature liquid metals （RTLM） such as gallium or its alloys could significantly reduce the electronics temperature compared with the conventional coolant, like water, oil or more organic fluid. However, most of the works were focused on RTLM which may subject to freeze under low temperature. So far, a systematic interpretation on the preparation and thermal properties of liquid metals under low temperature （here defined as lower than O^C） has not yet been available and related applications in cryogenic field have been scarce. In this paper, to promote the research along this important direction and to overcome the deficiency of RTLM, a comprehensive evaluation was proposed on the concept of liquid metal with a low melting point below zero centigrade, such as mercury, alkali metal and more additional alloy candidates. With many unique virtues, such liquid metal coolants are expected to open a new technical frontier for heat transfer enhancement, especially in low temperature engineering. Some innovative ways for making low melting temperature liquid metal were outlined to provide a clear theoretical guideline and perform further experiments to discover new materials. Further, a few promising applied situations where low melting temperature liquid metals could play irreplaceableroles were detailed. Finally, some main factors for optimization of low temperature coolant were summarized. Overall, with their evident merits to meet various critical requirements in modem advanced energy and power industries, liquid metals with a low melting temperature below zero centigrade are expected to be the next- generation high-performance heat transfer medium in thermal managements, especially in harsh environment in space.