查看更多>>摘要：The aim of this study was to form Fe2Ti and TiB2 phases on the steel surface in-situ using ferroalloy starting materials and to investigate the changes in the surface properties such as microstructural, hardness, wear and corrosion behavior. To this end, Fe(18?X)TiXB2 (x = 3–5) based hardfacing electrodes were produced and coated on AISI 1010 steel substrate using electric arc welding method. The development of the substrate-coating interface, solidification behavior and microstructural conditions of the samples were examined using a variety of characterization methods. In the coating microstructures, intermetallic phases such as TiB2 and Fe2Ti, α-Fe + Fe2Ti eutectic structure and trace amounts of non-equilibrium phases were detected. It has been understood that these phases formed in the microstructure have important effects on the hardness, wear and corrosion resistance of the coating. In the hardness test performed by nanoindentation method, very high hardnesses such as 3254 (± 26) HV in TiB2 phase and 1130.1 (± 13) HV in Fe2Ti phase were measured. As a result of the ball on disc reciprocal wear test performed against Al2O3 ball at different loads, it has been observed that titanium has an effect on the friction coefficient, and the wear resistance increases with the increasing amount of titanium in the electrode cover composition. In addition, according to the potentiodynamic polarization test results carried out in 3.5% NaCl solution, it has been determined that the corrosion potential increased with increasing titanium in the electrode cover composition, there was no linear change detected in the current density.
查看更多>>摘要：The effects of the stabilization conditions on the microstructure evolution in Ni-Fe-based superalloy Inconel 706 were investigated. In addition, the relationship between the microstructure and tensile and creep properties of the alloy was investigated. Stabilization at 800–840 °C resulted in the precipitation of the η phase at the grain boundaries. With an increase in the stabilization temperature, the η phase fraction increased. Non-compact γ′-γ″ co-precipitates were also formed at 800–840 °C, and their size was the largest when the stabilization was carried out at 840 °C. After double aging, the sample stabilized at 840 °C showed a cuboidal γ′ phase covered entirely with γ″ films, i.e. compact γ′-γ″ co-precipitates were observed along with a coarsened lamellae η phase. The double-aged sample stabilized at 800 °C (S80) exhibited the highest yield strength because of the presence of fine γ′ and γ″ precipitates. The double-aged samples stabilized at 810 and 840 °C (S81 and S84, respectively), exhibited similar yield strengths. Isolated stacking faults were generated in the γ′ particles of the S81 and S84 samples during the tensile deformation, indicating the high mobility of perfect dislocations in the γ-matrix. After creep at 650 °C/650 MPa, S81 and S84 exhibited higher creep strain at a given time than S80. This higher creep strain can be attributed to the synergistic effect of the increased dislocation mobility and η phase fraction, which resulted in strain accumulation at the grain boundaries. The anti-phase boundary shearing observed only in the S84 sample contributed to the strengthening of its γ-matrix and increased its creep rupture life.
查看更多>>摘要：The magnetic, structural, and thermal behaviors of the Cu-doped Heusler alloy Ni2Mn1?xCuxGa (0 ? x ? 0.4) were studied as a function of concentration x. As the Cu concentration increased, the structural transition temperatures increased, whereas the chemical order-disorder transitions and melting points decreased. The experimental results from temperature dependent X-ray diffraction reveal different crystal structures of the martensite phase at low temperatures for samples with different x, but all the samples ultimately crystallized in the L21 cubic crystal structure upon heating above their respective structural transitions. The experimental data were used to construct a comprehensive magnetic and structural phase diagram as a function of x from below their respective structural transition temperatures to their melting temperatures. The XRD analysis shows that the observed volume reduction is associated with the increasing structural transition temperature. Therefore, one of the samples was annealed under high pressure to permanently reduce its volume, and the correlation between the increasing structural transition temperatures and volumes was confirmed.
查看更多>>摘要：We have demonstrated an all-solution-processed multi-layer green phosphorescent organic light-emitting diodes(OLEDs) using zinc sulfide quantum dots (ZnS QDs) based electron injection layer (EIL) in the conventional device structure. The ZnS QDs EIL with proper work function offers efficient electron injection and retains the solvent resistance to the adjacent electron transportation layer. By inserting of a poly-ethyleneimine(PEI) interlayer between the emitting layer and electron transportation layer, solvent can be prevented from permeating through the emissive layers beneath and no additional injection barrier is formed. Thereby, the all-solution-processed OLED with a ZnS QDs EIL exhibits a highest current efficiency of 12.5 cd A?1 based on the PVK: Ir(ppy)3 emitter, achieving a 27.6% improvement in comparison to the reference without a ZnS QDs EIL. Our results provide a facile approach for the development of all-solution-processed OLEDs.
查看更多>>摘要：Long persistent luminescence (LPL) materials can be released its stored energy by various temperature induced thermal disturbance for a period of time. However, the accelerated release of trapped carriers at higher temperatures inhibits the use of LPL materials in extreme environments. In this work, a series of blue-emitting LPL phosphors Sr2MgAl22O36: Eu2+ were prepared by high temperature solid phase reaction. The investigation of photoluminescence (PL) and LPL preliminary indicated that the optimal room-temperature LPL time is 80 s, and the depth of trap was about 0.84 eV and 1.078 eV. Analyses of temperature-dependent LPL decay curves and thermoluminescence (TL) spectra show that the LPL initial brightness and duration time increase first and then decrease with the increase of temperature, and the optimal temperature is 453 K. These findings ensure the application of the discovered LPL phosphors above room temperature, including optical information storage and anti-counterfeiting among others.
查看更多>>摘要：Composites obtained from coal-based porous carbon (CPC)–loaded Ni-Zn ferrite often have good wave absorption properties. Here, CPC/Ni0.8Zn0.2Fe2O4 composite was innovatively prepared by microwave solid-phase reaction. The effects of microwave power and time on the sintering of the Ni-Zn ferrite precursor powder were explored, as were the effects of the CPC pore structure and the mass ratio of CPC to Ni-Zn ferrite on the wave absorption properties of the composites. Results showed that the CPC matched well with the Ni-Zn ferrite, especially at a 50% ratio at which the composite attained a maximum attenuation of ?20.8 dB at 15.2 GHz with an effective bandwidth of 4.4 GHz. The CPC broadened the wave absorption performance of Ni-Zn ferrite and the resulting composite had excellent wave absorption performance that could meet the requirements of multiple frequency bands by adjusting the coating thickness.
查看更多>>摘要：The lead-free magnetoelectric particulate composites (1-x)0.94Na0.5Bi0.5TiO3-0.06BaTiO3–x CoFe2O4 (where, x = 0, 0.15, 0.25, 0.35, 0.45) were synthesized by the solid-state sintering technique. The coexistence of piezoelectric 0.94Na0.5Bi0.5TiO3-0.06BaTiO3 (NBBT) and ferromagnetic CoFe2O4 (CFO) phases were confirmed by structural studies. The average crystallite size and the strain produced in the composites between the interface of different phases were estimated using Williamson-Hall method. The microstructural analysis indicates that the closely dense-packed CFO grains are distributed in the NBBT matrix. The ferroelectric nature of the composites was confirmed by the polarization versus electric field hysteresis loop and found to decrease with CFO content, which is attributed to the conducting nature of CFO. The observed values of saturation (Ms), remanent (Mr) magnetization, and magnetic moment (μB) in the composites are 28.46 emu/gm, 5.01 emu/gm and 1.13 μB, respectively for the higher CFO content. The dielectric relaxation phenomena in the composites have been observed, and the enhanced dielectric constant (ε′) is explained based on the electron hopping mechanism. All composites exhibit a relaxor nature which is described by the Vogel–Fulcher relation. The magnetoelectric coupling is estimated in the composites indirectly by measuring the relative change in the dielectric constant in the presence of the external magnetic field. The estimated values of magneto-capacitance at 1 kHz frequency for 25 and 35 mol% are ~ ? 5.5 and ~ ? 6%, respectively, which indicate that these materials can be useful for magneto-dielectric based devices applications.
查看更多>>摘要：The influence of high energy-ball milling (HEBM) on corrosion and hardness of age hardening aluminum alloys was investigated. Nanocrystalline age hardening (AA2024, AA6061 and AA7075) alloys were produced by HEBM of pre-alloyed powder and subsequent cold compaction under uniaxial pressure of 3 GPa. Cyclic potentiodynamic polarization and immersion tests were conducted in 0.6 M NaCl solution which revealed significantly increased pitting and protection potentials in the HEBM alloys compared to wrought alloys of same composition. X-ray diffraction analysis and transmission electron microscopy indicated grain refinement below 100 nm in the ball milled alloys which was the major strengthening mechanism in the age hardening HEBM alloys. The superior corrosion resistance and hardness of the age hardening ball milled alloys were attributed to nanocrystalline structure, extended solid solubility and homogenous microstructure- free from coarse intermetallic phases.
查看更多>>摘要：The research efforts focused on the implementation of Heusler materials into spintronic heterostructures triggered the investigations on the half-metallic and magnetic properties on Zr2CrAl ferrimagnetic compound. The theoretical investigations based on Density Functional Theory were performed on the tetragonal, orthorhombic and rhombohedral distortions of the typical inverse-Heusler cubic crystalline structure, previously reported. The compound exhibits half-metallic characteristics for all deformations considered. The slight variations in volume of the unit cell do not destroy the high spin polarization state. The band gap from minority spin channel slightly decreases in orthorhombic and rhombohedral deformations. The total magnetic moment calculated per formula unit is integer (equal to 1μB/f.u.) and follows the Slater-Pauling rule for all cases investigated. The antiferromagnetic coupling between the Zr and Cr atoms was preserved. The functionality of ferrimagnetic full-Heusler alloys to be used as overlayers in the production of epitaxially deposited heterostructures on substrates with crystalline structures other than cubic was proven.
查看更多>>摘要：Piezo catalysis has recently been considered an important technology in environmental treatment. In this study, a type II heterojunction of K2Ti6O13/TiO2 composite is successfully prepared by a hydrothermal method for the highly efficient piezo catalytic degradation of tetracycline. The factors influencing the piezo catalysis of tetracycline are systematically studied and discussed, including pH value, competition of anions/cations, ultrasonic power, ultrasonic frequency, and temperature, etc. Free radical sacrificial agents (EDTA-2Na, DMSO, AgNO3, and P-BQ, etc.) are utilized to better understand the degradation mechanism by piezo catalysis, and holes are found to play a dominant role in the catalytic process, and ·O2- comes the second. The combination of K2Ti6O13 and TiO2 constructs a type II heterojunction of the highly efficient separation of piezo electrons and holes, thus systematically increasing the piezo catalytic performance. This work provides a new idea to degrade organic pollution through piezo catalysis and the potential application of piezo catalysis in environmental treatment.
NSTL
Elsevier