Application of Lanthanum in High Strength and High Conductivity Copper Alloys

China is quite poor in argent resource. Roughly 80% of this industrial argent is imported every year. In order to improve the situation, we took advantage of rare earth (RE) mineral resource and successfully developed the non-argent Lanthanum-tellurium-copper alloy as a substitute for industry argent-copper. In our research, we were able to successfully apply rare earth lanthanum to copper alloy. The defects as porosity, inclusion, etc. originating from nonvacuum melting processing were controlled. Fine grain was obtained. Meanwhile, the comprehensive properties of the copper alloy, such as strength, conductivity and thermal conductivity were improved. The research results in increasing conductivity and thermal conductivity by 5% and 15%, respectively, while the tensile strength is increased by 6% higher than Ag-Cu alloy. The anti-electric corrosion property is good, and there is no argent-cadmium steam population originating from the electric arc effect. The addition of lanthanum further reduces the content of oxygen and hydrogen. The optimum quantity of the addition of RE lanthanum in the copper alloy is 0.010% - 0.020% .

Experimental Study on the Electrical Conductivity of Orthopyroxene at High Temperature and High Pressure under Different Oxygen Fugacities

At presure 1.0-4.0 GPa and temperature 1073-1423 K and under oxygen partial pressure conditions, a YJ-3000t multi-anvil solid high-pressure apparatus and Sarltron-1260 Impedance/Gain-Phase analyzer were employed to conduct an in-situ measurement of the electrical conductivity of orthopyroxene. The buffering reagents consist of Ni＋NiO, Fe＋Fe3O4, Fe＋FeO and Mo＋MoO2 in order to control the environmental oxygen fugacity. Experimental results made clear that： （1） within the measuring frequency range from 10-1 to 106 Hz, the complex impedance （R） is of intensive dependence on the frequency; （2） The electrical conductivity （a） tends to increase along to the rise of temperature （T）, and Log a vs. 1/ T fit the Arrenhius linear relations; （3） Under the control of oxygen buffer Fe＋Fe3O4, with the rise of pressure, the activation enthalpy tends to increase whereas the electrical conductivity tends to decrease. The activation energy and activation volume of the main current carders of orthopyroxene have been obtained, which are （1.715±0.035） eV and （0.03±0.01） cm^3/mol, respectively; （4） Under given pressure and temperature, the electrical conductivity tends to increase with increasing oxygen fugacity, while under given pressure the activation enthalpy tends to decrease with increasing oxygen fugacity; and （5） The sample＇s small polarons mechanism has provided a reasonable explanations to the conduction behavior at high temperature and high pressure.

Fuzzy neural network analysis on gray cast iron with high tensile strength and thermal conductivity

To develop a high performance gray cast iron with high tensile strength and thermal conductivity, multivariable analysis of microstructural effects on properties of gray cast iron was performed. The concerned parameters consisted of graphite content, maximum graphite length, primary dendrite percentage and microhardness of the matrix. Under the superposed influence of various parameters, the relationships between thermal conductivity and structural characteristics become irregular, as well as the effects of graphite length on the strength. An adaptive neuro-fuzzy inference system was built to link the parameters and properties. A sensitivity test was then performed to rank the relative impact of parameters. It was found that the dominant parameter for tensile strength is graphite content, while the most relative parameter for thermal conductivity is maximum graphite length. The most effective method to simultaneously improve the tensile and thermal conductivity of gray cast iron is to reduce the carbon equivalent and increase the length of graphite flakes.

The Electrical Conductivity of Gabbro at High Temperature and High Pressure

The electric conductivity of gabbro has been measured at 1.0-2.0 GPa and 320-700℃, and the conduction mechanism has been analyzed in terms of the impedance spectra. Experimental results indicated that the electric conductivity depends on the frequency of alternative current. Impedance arcs representing the conduction mechanism of grain interiors are displayed in the complex impedance plane, and the mechanism is dominated at high pressure. These arcs occur over the range of 10\+2-k×10\+5 Hz (k is the positive integer from 1 to 9). On the basis of our results and previous work, it is concluded that gabbro cannot form any high conductivity layer (HCL) in the middle\|lower crust.

Effects of Annealing on Microstructure, Mechanical and Electrical Properties of AlCrCuFeMnTi High Entropy Alloy

The multi-component A1CrCuFeMnTi high entropy alloy was prepared using a vacuum arc melting process. Serial annealing processes were subsequently performed at 590 ℃, 750 ℃, 955 ℃ and 1 100 ℃ respectively with a holding time of 4 h at each temperature. The effects of annealing on microstructure, mechanical and electrical properties of as-cast alloy were investigated by using differential thermal analysis （DTA）, X-ray diffraction （XRD）, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The experimental results show that two C14 hexagonal structures remain unchanged after annealing the as-cast A1CrCuFeMnTi alloy specimens being heated to 1 100℃. Both annealed and as-cast microstructures show typical cast-dendrite morphology and similar elemental segregation. The hardness of alloys declines as the annealing temperature increases while the strength of as-cast alloy improves obviously by the annealing treatment. The electrical conductivities of annealed and as-cast alloys are influenced by the distribution of interdendrite re^ions which is rich in Cu element.

The effect of nitrogen on the compressibility and conductivity of iron at high pressure

Although nitrogen in the Earth’s interior has attracted significant attention recently,it remains the most enigmatic of the light elements in the Earth’s core.In this work,synchrotron X-ray diffraction(XRD)and electrical conductivity experiments were conducted on iron nitrides(Fe_(2)N and Fe_(4)N)in diamond anvil cells(DACs)up to about 70 GPa at ambient temperature.These results show that iron nitrides are stable up to at least 70 GPa.From the equation of state(EOS)parameters,iron nitrides are more compressible than iron carbides.Moreover,using the van der Pauw method and Wiedemann-Franz law,the electrical and thermal conductivity of samples were determined to be much lower than that of iron carbides.The conductivities of Fe_(2)N and Fe_(4)N were similar at 20–70 GPa,suggesting no evident effects by varying the N stoichiometries in iron nitrides.Iron nitrides are less dense and conductive but more compressible than carbides at 0–70 GPa.This study indicates that less nitrogen than carbon can explain geophysical phenomena in the deep Earth,such as the density deficit.

Studies of electrical properties of rocks under high temperature and pressure

Studies of the rocks′ electrical properties under high temperature and pressure have found favors in the geophysicist′s eyes, because those studies are becoming to be the important methods to understand the earth′s interior materials, their migration and evolution. This article introduces the development and significant of those studies from the measurements, instruments and affections, etc .

Electrical properties of dry polycrystalline olivine mixed with various chromite contents: Implications for the high conductivity anomalies in subduction zones

Chromite,a crucial high-conductivity mineral phase of peridotite in ophiolite suites,has a significant effect on the electrical structure of subduction zones.The electrical conductivities of sintered polycrystalline olivine containing various volume percents of chromite(0,4,7,10,13,16,18,21,23,100 vol.%)were measured using a complex impedance spectroscopic technique in the frequency range of 10^(−1)-10^(6) Hz under the conditions of 1.0-3.0 GPa and 873-1223 K.The relationship between the conductivities of the chromite-bearing olivine aggregates and temperatures conformed to the Arrhenius equation.The positive effect of pressure on the conductivities of the olivine-chromite systems was much weaker than that of temperature.The chromite content had an important effect on the conductivities of the olivine-chromite systems,and the bulk conductivities increased with increasing volume fraction of chromite to a certain extent.The inclusion of 16 vol.%chromites dramatically enhanced the bulk conductivity,implying that the percolation threshold of interconnectivity of chromite in the olivine-chromite systems is-16 vol.%.The fitted activation enthalpies for pure polycrystalline olivine,polycrystalline olivine with isolated chromite,polycrystalline olivine with interconnected chromites,and pure polycrystalline chromite were 1.25,0.78-0.87,0.48-0.54,and 0.47 eV,respectively.Based on the chemical compositions and activation enthalpies,small polaron conduction was proposed to be the dominant conduction mechanism for polycrystalline olivine with various chromite contents.Furthermore,the conductivities of polycrystalline olivine with interconnected chromite(10-1.5-100.5 S/m)provides a reasonable explanation for the high conductivity anomalies in subduction-related tectonic environments.

The experimental studies on electrical con-ductivities and P-wave velocities of anortho-site at high pressure and high temperature

Results of P-wave velocity (vP) and electrical conductivity measurements on anorthosite are presented from room temperature to 880 C at 1.0 GPa using ultrasonic transmission technique and impedance spectra technique respec-tively. The experiments show that the P-wave velocities in anorthosite decrease markedly above 680 C following the dehydration of hydrous minerals in the rock, and the complex impedances collected from 12 Hz to 105 Hz only indicate the grain interior conduction mechanism at 1.0 GPa, from 410 C to 750 C. Because the fluids in the rock have not formed an interconnected network, the dehydration will not pronouncedly enhance the electrical conduc-tivity and change the electrical conduction mechanism. It is concluded that the formation and evolution of the low-velocity zones and high-conductivity layers in the crust may have no correlations, and the dehydration can result in the formation of the low-velocity zones, but cannot simultaneously result in the high-conductivity layers.

New Type of Nitrides with High Electrical and Thermal Conductivities

The nitrogen dimer as both a fundamental building unit in designing a new type of nitrides, and a material gene associated with high electrical and thermal conductivities is investigated by first principles calculations.The results indicate that the predicted Si N4 is structurally stable and reasonably energy-favored with a striking feature in its band structure that exhibits free electron-like energy dispersions. It possesses a high electrical conductivity（5.07 × 10^5 S/cm） and a high thermal conductivity（371 W/m·K） comparable to copper. The validity is tested by isostructural Al N4 and Si C4. It is demonstrated that the nitrogen dimers can supply a high density of delocalized electrons in this new type of nitrides.

Facile synthesis of high electrical conductive CoP via solid-state synthetic routes for supercapacitors

Co-P precursor was prepared by a mechanical alloying method and then is controlled to synthesis of CoP phase through an annealing method. The optimal conditions of ball milling and annealing temperature are investigated. The CoP exhibits higher electrical conductivity than graphite and cobalt oxide, showing excellent pseudocapacitive properties due its high electrical conductivity which can result in a fast electron transfer in high rate charge-discharge possess. The as-obtained CoP electrode achieves a high specific capacitance of 447.5 Fig at 1 Aug, and displays an excellent rate capability as well as good cycling stability. Besides, the asymmetric supercapacitor (ASC) based on the CoP as the positive electrode and activated carbon (AC) as the negative electrode was assembled and displayed a high rate capability (60% of the capacitance is retained when the current density increased from 1 Aug to 12 Aug), excellent cycling stability (96.7% of the initial capacitance is retained after 5000 cycles), and a superior specific energy of 19 Wh/kg at a power density of 350.8 W/kg. The results, suggest that the CoP electrode materials have a great potential for developing high-performance electrochemical energy storage devices. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.

Stability of fiber laser-MIG hybrid welding of high strength aluminum alloy

The effect of fiber laser on MIG arc was investigated with 8 mm 7075-T6 high strength aluminum alloy as base material.The arc shape,droplet transfer form and electrical signal in the process of MIG welding and laser-MIG hybrid welding were analyzed.The stability of the hybrid welding process was evaluated by standard deviation analysis.The results show that with the increase of laser power,a large number of laser-induced plasma enters the arc column area,providing more conductive channels,which makes the heat of MIG arc more concentrated and the short circuit transition disappear.Due to the continuous effect of laser,the keyhole becomes a continuous electron emission source,and a stable cathode spot will be formed near the keyhole,which enhances the stability of MIG arc at the base current state.By using the method of standard deviation analysis,the voltage standard deviation of single MIG welding arc and laser-MIG hybrid arc within 4 seconds was calculated.The standard deviation of single MIG arc voltage was 1.05,and the standard deviation of MIG arc voltage in laser-MIG hybrid welding was 0.71–0.86,so the hybrid welding process was more stable.

Detection of Thermophysical Properties for High Strength Concrete after Exposure to High Temperature

Using the detection principle of infrared thermal imaging technique and the detection principle of DRH thermal conductivity tester laboratory,we investigated the infrared thermal image inspection,coefficient of thermal conductivity,apparent density,and compressive strength test on C80 high-strength concrete（HSC） in the presence and absence of polypropylene fibers under completely heated conditions.Only slight damages were detected below 400 ℃,whereas more and more severe deterioration events were expected when the temperature was above 500 ℃.The results show that the elevated temperature through infrared images generally exhibits an upward trend with increasing temperature,while the coefficient of thermal conductivity and apparent density decrease gradually.Additionally,the addition of polypropylene fibers with appropriate length,diameter,and quantity contributes to the improvement of the high-temperature resistance of HSC.

Study on the Electrical Conductivity of 0.025 mol NaCl Solution at 0.25-3.75 GPa and 20-370℃

The electrical conductance of 0.025 mol NaCl solution was measured at0.25-3.75 GPa and 20-370℃. As shown by the results, the conductance increases with temper-ature, and there is a liner relation between the reciprocal of temperature and the logarithm ofthe conductance but their slopes are different at different pressures. The relations between theconductance and pressure is rather complex and there are some discontinuities: in the range of2.25-3.75 GPa, the conductance increases with the pressure; in the range of 1.25-2.0 GPa, theconductance is not related to the pressure; and at a pressure of 0.75 GPa, the conductance ishigher than that at the pressures nearby. This reflects that the NaCl solution has rather differentproperties of electronic chemistry at various pressures, and probably is an important cause forthe existence of the layers with high electrical conductance and low velocity in the Earth's crustand mantle.

High-pressure investigations on the isostructural phase transition and metallization in realgar with diamond anvil cells

The high-pressure structural,vibrational and electrical properties for realgar were investigated by in-situ Raman scattering and electrical conductivity experiments combined with first-principle calculations up to~30.8 GPa.It was verified that realgar underwent an isostructural phase transition at~6.3 GPa and a metallization at a higher pressure of~23.5 GPa.The isostructural phase transition was well evidenced by the obvious variations of Raman peaks,electrical conductivity,crystal parameters and the As–S bond length.The phase transition of metallization was in closely associated with the closure of bandgap rather than caused by the structural phase transition.And furthermore,the metallic realgar exhibited a relatively low compressibility with the unit cell volume V_(0)=718.1.4Å^(3)and bulk modulus B_(0)=36.1 GPa.

Effect of Plastic Deformation on Microstructure and Properties of Cu-(1 wt%-6 wt%) Ag Alloy

In the present study,the Cu-(1 wt%-6 wt%)Ag alloys were prepared by melting,forging and wire drawing.The effects of plastic deformation on microstructure evolution and properties of the alloys were investigated.The results show that non-equilibrium eutectic colonies exist in the Cu-(3 wt%-6 wt%)Ag alloy and no eutectic colonies in the 1 wt%-2 wt%Ag containing alloys.These eutectic colonies are aligned along the drawing direction and refined with the increase of draw ratio.Attributed to the refinement of eutectic colonies,the Cu-Ag alloy exhibits higher strength with the increase of draw ratio.The Cu-6Ag alloy exhibits excellent comprehensive properties with a strength of 930 MPa and a conductivity of 82%IACS when the draw ratio reaches 5.7.

Evolution of electrical conductivity and semiconductor to metal transition of iron oxides at extreme conditions

Iron oxides are widely found as ores in Earth's crust and are also important constituents of its interiors.Their polymorphism,composition changes,and electronic structures play essential roles in controlling the structure and geodynamic properties of the solid Earth.While all-natural occurring iron oxides are semiconductors or insulators at ambient pressure,they start to metalize under pressure.Here in this work,we review the electronic conductivity and metallization of iron oxides under high-pressure conditions found in Earth's lower mantle.We summarize that the metallization of iron oxides is generally controlled by the pressure-induced bandgap closure near the Fermi level.After metallization,they possess much higher electrical and thermal conductivity,which will facilitate the thermal convection,support a more stable and thicker D′′layer,and formulate Earth's magnetic field,all of which will constrain the large-scale dynamos of the mantle and core.