Effect of Cryogenic Treatment on Property of 14Cr2Mn2V High Chromium Cast Iron Subjected to Subcritical Treatment

Effect of cryogenic treatment on the microstructure, hardening behavior and abrasion resistance of 14Cr2Mn2V high chromium cast iron （HCCI） subjected to subcritical treatment was investigated. The results show that cryogenic treatment after subcritical treatment can obviously improve the hardness and abrasion resistance of HCCI because abundant retained austenite is transformed into martensite and fine secondary carbides E（Fe, Cr）23 C6 ] precipitate. The amount of martensite and precipitated secondary carbide in HCCI experiencing subcritical treatment followed by cryogenic treatment was more than that experiencing the subcritical treatment followed by air cooling. When the abrasion resistance of HCCI reaches the maximum, its microstructure contains about 15 % retained austenite. Cryogenic treatment can further reduce the austenite content but the retained austenite cannot be transformed in to martensite completely.

Lattice structures and electronic properties of CIGS/CdS interface:First-principles calculations

Using first-principles calculations within density functional theory, we study the atomic structures and electronic properties of the perfect and defective （2VCu＋ Incu） CulnGaSe2/CdS interfaces theoretically, especially the interface states. We find that the local lattice structure of （2VCu＋ InCu） interface is somewhat disorganized. By analyzing the local density of states projected on several atomic layers of the two interfaces models, we find that for the （2VCu＋InCu） interface the interface states near the Fermi level in CulnGaSe2 and CdS band gap regions are mainly composed of interracial Se-4p, Cu-3d and S-3p orbitals, while for the perfect interface there are no clear interface states in the CulnGaSe2 region but only some interface states which are mainly composed of S-3p orbitals in the valance band of CdS region.

First-principles calculations of 5d atoms doped hexagonal-AlN sheets: Geometry, magnetic property and the influence of symmetry and symmetry-breaking on the electronic structure

The geometry, electronic structure and magnetic property of the hexagonal A1N （h-AIN） sheet doped by 5d atoms （Lu, Hf, Ta, W, Re, Os, Ir, Pt, Au and Hg） are investigated by first-principles calculations based on the density functional theory. The influence of symmetry and symmetry-breaking is also studied. There are two types of local symmetries of the doped systems： C3v and D3h. The symmetry will deviate from exact C3,, and D3h for some particular dopants after optimization. The total magnetic moments of the doped systems are 0/-tB for Lu, Ta and It; 1 ~B for Hf, W, Pt and Hg; 2gB for Re and Au; and 3/~B for Os and Al-vacancy. The total densities of state are presented, where impurity energy levels exist. The impurity energy levels and total magnetic moments can be explained by the splitting of 5d orbitals or molecular orbitals under different symmetries.

As-cast Medium Mn Steel with Nodular Carbide Modified by Y-base Heavy RE Compound

1.IntroductionMedium Mn steel was developed be-cause the wear resistance of Hadfield steel(Mn13)is poor under low or medium im-pact and extrusion abrasion[1-4].In theforegoing investigations[2-4]we found thatwith the increase of C content,theneedle-like and network carbide in mediumMn steel increased(as shown in Fig.1(a)and(c)).Although its wear resistance was largelyimproved,its impact toughness was greatlydecreased.In order to increase toughness,along-term high temperature heat-treatmentwas needed.But the treatment caused cracks

Electron theory study on the effect of Mn on as-cast structure of Fe-C-Cr-Mn cast irons

The valence electron structure of alloying austenite of 3C-15Cr high chromium white cast iron with different Mn contents from 1% to 6% is analyzed by BLD method and EET. Results show that the addition of Mn has major influence on the valence electron structure of the alloying austenite, especially on that of Fe-C, Fe-C-Cr and Fe-C-Cr-Mn unit cells of it. The effect becomes weak when Mn content is over 4%. Based on the effect of nA, FcD, the weighting of each unit cell and the degree of undercooling on phase transition of the austenite, we can calculate the retained austenite content of as-cast structure of the high chromium white cast iron. The calculation results coincide well with those of the experiment. The phase transition characters of the austenite in high chromium white cast iron can be forecasted through valence electron structure analysis of alloying austenite by BLD method and EET on the basis of Fe-C-Cr equilibrium phase diagram.

Effects of Annealing Temperature on the Electrical Conductivity and Mechanical Property of Cu-Te Alloys

The effects of annealing temperatre on the electrical conducitivity and mechanical property of Cu-Te alloys were studied via an AG-10TA electronic universal machine, an SB2230 digital electric bridge, SEM, EDS and XPS. The results show the electrical conductivity increases while the tensile strength fluctuates when the annealing temperature becomes higher because the recrystallization occurs during the annealing process, leading to the density of dislocation decreasing, grain size growing up, but the second phase precipitating sufficiently and simultaneously.

Surface reconstruction on stishovite SiO_2,HfO_2 and rutile TiO_2 (001)

This paper systematically investigates the surface reconstruction processes and patterns on stishovite SiO2, HfO2 and rutile TiO2 （001） by using classical molecular dynamics. It is found that these three surfaces relax instead of reconstruction at 0 K, and have little possibility to reconstruct below 40 K. Above 40 K, surface reconstructions take place as collective atomic motion which can be speeded by higher temperature or compressed strain. Several reconstruction patterns with approximate surface energies are found, and electrostatic potentials on them are also provided in comparison with possible microscopic results.

Thermal properties of high-k Hf_(1-x)Si_xO_2

Classical atomistic simulations based on the lattice dynalnics theory and the Born core-shell model are performed to systematically study the crystal structure and thermal properties of high-k Hfl-xSixO2. The coefficients of thermal expansion, specific heat, Griineisen parameters, phonon densities of states and Debye temperatures are calculated at different temperatures and for different Si-doping concentrations. With the increase of the Si-doping concentration, the lattice constant decreases. At the same time, both the coefficient of thermal expansion and the specific heat at a constant volume of Hf1-mSixO2 also decreases. The Griineisen parameter is about 0.95 at temperatures less than 100 K. Compared with Si-doped HfO2, pure HfO2 has a higher Debye temperature when the temperature is less than 25 K, while it has lower Debye temperature when the temperature is higher than 50 K. Some simulation results fit well with the experimental data. We expect that our results will be helpful for understanding the local lattice structure and thermal properties of Hf1-mSixO2.

Phase-, shape- and size-controlled synthesis of NaYF_4:Yb^(3+),Er^(3+) nanoparticles using rare-earth acetate precursors

Hexagonal-phase NaYF4：Yb3＋,Er3＋ upconversion nanoparticles（UCNPs） with a uniform size distribution were synthesized using rare-earth acetates as precursors. The effects of reaction temperature and time on the phase transition process of the UCNPs were systematically studied. Based on the evolution of particle morphology and phase with temperature and time, it could be concluded that the transition from cubic phase to hexagonal phase for NaYF4：Yb3＋,Er3＋ UCNPs was consistent with a dissolution/recrystallization process. In addition, the shape and size of the UCNPs could be controlled by adjusting the solvent ratio and the precursor ratio, respectively.

Improving the performance of all-solid-state supercapacitors by modifying ionic liquid gel electrolytes with graphene nanosheets prepared by arc-discharge

Ionic liquid gel polymers have widely been used as the electrolytes in all-solid-state supercapacitors, but they suffer from low ionic conductivity and poor electrochemical performance. Arc discharge is a fast, low-cost and scalable method to prepare multi-layered graphene nanosheets, and as-made graphene nanosheets （denoted as ad-GNSs） with few defects, high electrical conductivity and high thermal stability should be favorable conductive additive materials. Here, a novel ionic liquid gel polymer electrolyte based on an ionic liquid （EM1MNTF2） and an copolymer （P（VDF-HFP）） was modified by the addition of ad-GNSs as an ionic conducting promoter. This modified gel electrolyte shows excellent thermal stability up to 400 ℃ and a wide electrochemical window of 3 V. An all-solid-state supercapacitor based on commercial activated carbon was fabricated using this modified ionic liquid gel polymer electrolyte, which shows obviously improved electrochemical behaviors compared with those of the corresponding all-solid-state supercapacitor using pure ionic liquid gel polymer electrolyte. Specially, smaller internal resistance, higher specific capacitance, better rate performance and cycling stability are achieved. These results indicate that the ionic liquid gel polymers modified by ad-GNSs would be promising and suitable gel electrolytes for high performance all-solid-state electrochemical devices.

Effects of defect states on the performance of CuInGaSe_2 solar cells

Device modeling has been carried out to investigate the effects of defect states on the performance of ideal CulnGaSe2 （CIGS） thin film solar cells theoretically. The varieties of defect states （location in the band gap and densities） in absorption layer CIGS and in buffer layer CdS were examined. The performance parameters： open-circuit voltage, short-circuit current, fill factor, and photoelectric conversion efficiency for different defect states were quantitatively analyzed. We found that defect states always harm the performance of CIGS solar cells, but when defect state density is less than 10 14 cm-3 in CIGS or less than 10 18 cm-3 in CdS, defect states have little effect on the performances. When defect states are located in the middle of the band gap, they are more harmful. The effects of temperature and thickness are also considered. We found that CIGS solar cells have optimal performance at about 170 K and 2 μm of CIGS is enough for solar light absorption.

Development of RuS_(2) for near-infrared photodetector by atomic layer deposition and post-sulfurization

The chalcogenides of platinum-group metals(PGMs)have been known to be present in minerals and the intermediate products of refining.Over recent years,their applications in various fields,including catalysis,have been explored.Given that certain PGM chalcogenides behave as compound semiconductors,they can be used as materials for photodetectors.In this study,RuS_(2),featuring a bandgap suitable for near-infrared photodetectors,was prepared by forming Ru on a SiO_(2)/Si substrate via the atomic layer deposition method using[Ru(TMM)(CO)_(3)]as the precursor.Annealing was conducted at 800℃ for 1 h under H_(2)S flow.High-resolution transmission electron microscopy(HRTEM)and X-ray diffraction(XRD)analysis clearly confirmed that the as-deposited hexagonal close-packed(hcp)Ru transformed to cubic RuS_(2) after post-annealing.The surface morphologies,chemical states,and electrical and optical properties of RuS_(2) were investigated.The influence of the metallic Ru surface morphology prior to sulfurization on the reaction between Ru and H_(2)S was also discussed.To evaluate the potential of using RuS_(2) as a photodetector,a photodetector was fabricated by forming electrodes on RuS_(2) to measure its photocurrent under near-infrared light.Thus,RuS_(2) was proven to exhibit a short response time(59μs)and generate a photocurrent of 84 nA under near-infrared light at 940 nm.

THE EFFECT OF HEATING RATE ON CURIE TEMPERATURE OF MAGNETIC AMORPHOUS ALLOYS

Ⅰ.INTRODUCTION Amorphous alloys will transfer from metastability state into stable state on given conditions. When the Curie temperature, T_c, of amorphous magnetic alloys is measured in heating, amorphous magnetic alloys are hastened to transfer into a