Structural,Optical, and Ferroelectric Behaviors of Cul-xLixO （0≤ x ≤ 0.09） Nanostructures

We report structural, optical, and ferroelectric behaviors of lithium-doped copper oxide （CU1-xLixO with x = 0.0, 0.05, 0.07, and 0.09） nanostructures synthesized by hydrothermal method. The XRD pattern indicates the pure phase formation of CuO without any impurity, and the crystallite size is found to be increases for x = 0-0.07 and decreases for x = 0.09. FESEM analysis shows that the average size of Cul xLixO nanostructures increases with the increasing the Li-doping concentrations up to 7% and then decreases for 9% Li doping concentration. Moreover, Raman and photoluminescence spectrum also confirm the phase formation of CuO. A significant reduction in optical band gap is observed up to x = 0.07, and then band gap increases for x ~ 0.09 due to segregation of the impurities on the surface or grain boundaries, which may suppress the grain growth and results the enhancement in optical band gap. Moreover, a weak ferroelectricity is observed in CuO nanostructures for pure and 9% Li doping through polarization versus electric field （P- E）.     

Effects of Y on mechanical properties and damping capacity of ZK60 magnesium alloys

The microstructure,mechanical properties and damping capacity of ZK60-xY(x=0,1.5%,2.5%,4.0%,mass fraction) magnesium alloys were investigated by using the optical microscope(OM),X-ray diffractometer(XRD),universal tensile testing machine and dynamic mechanical analyzer(DMA).The mechanisms for damping capacity of referred alloys were discussed by Granato-Lücke theory.The results show that Y additions remarkably reduce grain size(the average grain size is 21.6,13.0,8.6 and 4.0μm,respectively),and the tensile properties are enhanced with grain refining(the yield tensile strength increases to 292 MPa from 210 MPa and ultimate tensile strength increases to 330 MPa from 315 MPa).For the ZK60-xY(x=0,1.5%,4.0%)alloys,the damping capacity decreases with the increase of Y content.However,for the ZK60-xY(x=2.5%)alloy,the damping capacity improves abnormally,which is possibly related to the formation of Mg3Y2Zn3(W)FCC phase in this alloy.     

Strengthening and stress drop of ultrafine grain aluminum after annealing

Ultrafine grain pure aluminum was produced by equal channel angular pressing and cold rolling,the deformed aluminum was annealed at 200 °C for 1 h.The tensile curves of deformed and annealed aluminum show that yield strength of deformed aluminum increases by 100%-300% and its elongation decreases by about 20%.After low temperature annealing,strength of annealed aluminum increases by 20% and elongation decreases by over 50%,the recovery of dislocations may be the main cause of annealing strengthening.In addition,there is an abrupt stress drop in the tensile curves of annealed aluminum and the formation of shear band is responsible for it.     

Magnetic Phase Separation in Diluted Magnetic System:Zn_(1-x)Fe_xO

Single-phase diluted magnetic systems Zn_(1-x)Fe_xO have been prepared by chemical route. Structural and spectroscopic(UV–Vis and Mssbauer) studies indicate the incorporation of Fe~(3+) ions in the lattice sites. The UV–Vis results point to a systematic increase in the band gap with increasing Fe doping. The room temperature magnetization of Zn_(1-x)Fe_xO indicates a paramagnetic behavior which is in accordance with the Mssbauer results, illustrating quadrupolar doublet. At low temperature, the zero-field-cooled(ZFC) magnetization shows a cusp and this temperature increases systematically with decreasing particle size. The weak exchange bias effect manifested by a M–H loop shift is observed for x = 0.03. This shift is accompanied by the enhancement of coercivity. The dc magnetization results suggest the coexistence of ferromagnetic and antiferromagnetic exchange interactions for low doping of Fe, i.e., for x = 0.03.     

Microstructure and magnetic properties of Nd-Fe-B sintered magnets with P addition

In this paper,the effects of P doping on magnetic properties and microstructure were studied in Nd-Fe-B sintered magnets.With P doping,the grain size gets refined and the distribution of the main phase is optimized due to the reduction of the liquidus temperature.The liquidus temperature for the 0.05 wt% P-doped magnets is 1022 K,while that for the P-free magnets is 1038 K.As P content increases,the liquidus temperature significantly decreases.Clear and continuous grain boundary phases are formed in the P-containing magnets with smaller grain size.The optimized microstructure with average grain size of 8.43 μm is obtained in the 0.05 wt% P-doped magnets,which is approximately 0.69 μm smaller than that of P-free sintered magnets(9.12μm).Though P is usually thought to be an impurity element,it might be beneficial in Nd-Fe-B sintered magnets with proper addition.The coercivity of the0.05 wt% P-doped magnets could be increased to1283 kA·m~(-1),with slight changes of the remanence and the maximum magnetic energy product.NdP04 phases in the grain boundary are of hexagonal structure,while those at the triple junctions have monoclinic structure.Activated sintering is achieved by doping proper P element in the Nd-FeB sintered magnets.     

Structural,Optical, and Electrical Properties of Zn-Doped CdO Thin Films Fabricated by a Simplified Spray Pyrolysis Technique

Thin films of zinc-doped cadmium oxide with different Zn-doping levels(0, 2, 4, 6, and 8 at%) were deposited on glass substrates by employing an inexpensive, simplified spray technique using perfume atomizer at relatively low substrate temperature(375 °C) compared with the conventional spray method. The effect of Zn doping on the structural,morphological, optical, and electrical properties of the films was investigated. XRD patterns revealed that all the films are polycrystalline in nature having cubic crystal structure with a preferential orientation along the(1 1 1) plane irrespective of Zn-doping level. Zn-doping level causes a slight shift in the(1 1 1) diffraction peak toward higher angle. The crystallite size of the films was found to be in the range of 28–37 nm. The band gap value increases with Zn doping and reaches a maximum of 2.65 eV for the film coated with 6 at% Zn doping and for further higher doping concentration it decreases.Electrical studies indicate that Zn doping causes a reduction in the resistivity of the films and a minimum resistivity of15.69 X cm is observed for the film coated with 6 at% Zn.     

Preparation and characterization of Cd1−x Zn x S buffer layers for thin film solar cells

Cd1-xZnxS(x = 0, 0.1, 0.2, 0.3, 1.0) thin films have been grown successfully on soda-lime glass substrates by chemical bath deposition technique as a very promising buffer layer material for optoelectronic device applications. The composition, structural properties, surface morphology, and optical properties of Cd1-xZnxS thin films were characterized by energy dispersive analysis of X-ray technique (EDAX), X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV-Vis spectrophotometer techniques, respectively. The annealed films were observed to possess the deficient sulfur composition. The results of XRD show that the Cd1-xZnxS (x = 0.1) thin film annealed at 450 ℃ forms hexagonal (wurtzite) structure with lattice parameters a = 0.408814 nm, c = 0.666059 nm, and its average grain size is 24.9902 nm. The diffraction peaks become strong with the increasing annealing temperatures. The surface of Cd1-xZnxS (x = 0.1) thin film annealed at 450℃ is uninterrupted and homogenous as compared to other temperatures. From optical properties, it is observed that the presence of small amount of Zn results in marked changes in the optical band gap of CdS. The band gaps of the Cd1-xZnxS thin films vary from 2.42 to 3.51 eV as composition varies from x = 0.0 to 1.0.     

Effect of lithium on the casting microstructure of Cu-Li alloys

The effect of lithium on the casting microstructure of Cu-Li alloys was studied via the Wild MPS 46 Automatic camera, Deitz Diaplan, and scanning electron microscope. The result shows that trace lithium added to copper coarsens the grains of Cu-Li alloys in eqniaxed crystal area because of the excellent purification effect. With the amount of lithium increasing, the average grain size increases sharply. But when the amount of lithium increases more, the average grain size decreases instead. At the same time, the typical dentritic crystal area of copper is diminished when lithium is added to pure copper.     

Effect of cooling rate and forced convection on as-cast structure of 2205 duplex stainless steel

To forecast the as-cast structure and ferrite-austenite phase ratio of 2205 duplex stainless steel(DSS), the effects of cooling rate and forced convection were observed in a high-vacuum resistance furnace in which the forced convection was created by the rotation of the crucible. The as-cast structure of all 2205 DSS samples is full equiaxed grains, and the microstructure consists of a great amount of desirable intra-granular austenite inside the continuous ferrite grain matrix, besides Widmanstatten austenite and grain boundary austenite. The ferrite grain size decreases gradually with the increase in the cooling rates(20 to 60 oC·min-1) or the forced convection, while the ferrite grains of the samples solidified with a strong convection are barely changed when the cooling rate is below 50 oC·min-1. Moreover, a small grain size is beneficial for the austenite formation but the influence is not very obvious under the cooling rates in the range of 5 to 50 oC·min-1. Compared with grain size, the cooling rate has a greater influence on the final ferrite content. A model based on the experimental results is established to predict the ferrite content, which could be approximated by δ(%) = 20.5·exp(c/80.0) + 0.34 d +34.1, where cis the cooling rate in oC·min-1 and d is the grain size in mm. By using this model, the dependence of the final ferrite content on cooling rate and grain size is well described.     

Effects of Zr Content on the Microstructures and Tensile Properties of Ti-3Al-8V-6Cr-4Mo-xZr Alloys

The microstructural evolution and tensile properties of Ti-3Al-8V-6Cr-4Mo-xZr(x = 0,2,4 and 6) titanium alloys were investigated.The precipitated phases and tensile fracture morphologies were observed using scanning electron microscopy and transmission electron microscopy.Experimental results show that the presence of trace impurity Si and the addition of Zr induce the formation of(TiZr)_6Si_3 silicides.The quantity of silicides increases with Zr content increasing.The dispersed silicides refined the grain size of β Zr-containing alloys,and the grain size decreases significantly with Zr content increasing.Accompanying these microstructural changes,the strength of the alloys is enhanced gradually with the increase of Zr content,which is attributed to the combination of precipitation strengthening and grain refinement.     

Microstructures and tensile properties of as-extruded Mg-Sn binary alloys

The microstructure and mechanical properties of Mg-xSn(x=3,7 and 14,mass fraction,%) alloys extruded indirectly at 300℃ were investigated by means of optical microscopy,scanning electron microscopy and tensile test.The grain size of theα-Mg matrix decreases from 220,160 and 93μm after the homogenization treatment to 28,3 and 16μm in the three alloys after extrusion,respectively.The results show that the grain refinement is most remarkable in the as-extruded Mg-7Sn alloy.At the same time,the amount of the Mg2Sn particles remarkably increases in the Mg-7Sn alloy with very uniform distribution in theα-Mg matrix.In contrast,the Mg2Sn phase inherited from the solidification with a large size is mainly distributed along grain boundary in the Mg-14Sn alloy.The tensile tests at room temperature show that the ultimate tensile strength of the as-extruded Mg-7Sn alloy is the highest,i.e.,255 MPa,increased by 120%as compared with that of as-cast samples.     

Thermally and Optical-Induced Effect on Optical and Electrical Parameters of Ag-Doped CdSe Thin Films

Thin films of Ag-doped Cd Se are deposited on the glass substrates by thermal evaporation technique using inert gas condensation method. The elemental composition of the prepared thin film is confirmed by EDX spectra. SEM analysis reveals the uniform distribution of the grains over the substrate. TEM analysis reveals the spherical nature of nanoparticles having size in the range of 25–30 nm. X-ray diffraction study indicates an increase in the grain size after thermal annealing and the decrease in the grain size after light soaking treatment. Transmittance spectra are found to decrease with corresponding red shift after annealing and light soaking of as-deposited thin films. The value of the band gap is found to decreases and refractive index increases, after annealing and light soaking treatment. The dispersion of refractive index is described using the Wemple–Di Domenico single oscillator model and the effects of the annealing and the light soaking on the dispersion parameters are studied. The dark conductivity is found to change from 2.24 9 10-8to 1.54 9 10-7and1.45 9 10-9X-1cm-1after annealing and light soaking of thin films, respectively. Hall effect measurement reveals n-type behavior of as-deposited, annealed and light-soaked thin films.     

Structure and magnetic properties of Ni Cu Zn ferrite materials with La doping

Ni_(0.3)Cu_(0.07)Zn_(0.63)Fe_(2-x)La_xO_4 ferrites were prepared by solid phase method and sintered at 1,150 ℃ for6 h.The phase formation,micro structure,and magnetic properties of samples were investigated.With doping of La~(3+),the samples contain two phases:LaFeO_3 and NiCuZn ferrites.Scanning electron microscope(SEM) image shows that La doping constrains the growth of NiCuZn ferrite,which is more uniform.La doping improves magnetic properties of NiCuZn ferrite when x=0.03.The saturation magnetization(M_s) increases first;when x=0.03,the highest value is 75.35 A·m~2·kg~(-1).The permeability increases to the maximum value with frequency and then decreases with the concentration of La~(3+) increasing.When x=0.03,the maximum value of real permeability at 1 MHz is 333.5,and the loss angle tangent(tanδ) is not more than 0.02.La doping improves the properties of NiCuZn ferrite,which can be applied to low-frequency filters.     

Effect of Thermal Annealing on the Physical Properties of Zn1-xCuxSe Thin Films Deposited by Close Spaced Sublimation Technique

Thin films of Zn1-xCuxSe （x= 0.00, 0.05, 0.10, 0.15, 0.20） were grown on glass substrates by closed space sublimation technique. The deposited films were annealed at 200 ~C and 400 ~C in air for 1 h. The annealed samples have been investigated through Rutherford backscattering spectroscopy （RBS）, X-ray diffraction （XRD）, spectroscopic ellipsometer, spectrophotometer and Raman spectroscopy. Through RBS, the composition of the films was calculated and compared with the initial concentration. Structural characteriza- tion including crystal structure, crystal orientation, lattice parameter, grain size, strain and dislocation density were carried out using XRD data. From XRD spectra it was revealed that the as-deposited and annealed films were polycrystalline in nature with zinc-blende structure. However, the crystallinity and the grain size were improved with the increase of annealing temperature. According to Raman spectroscopy, it was observed that as deposited and annealed samples have the same characteristic vibrational modes of ZnSe at low and high frequency optical phonon modes while another mode was observed for 400 ℃ annealed samples at 745 cm-1. Spectroscopic ellipsometer has been used to found annealing effect on the optical properties of ZnSe. The band gap energy has been determined using transmission spectra. It was found that the band gap energy of the film increased with the increase of annealing temperature.     

Reheating microstructure of refined AZ91D magnesium alloy in semi-solid state

By means of equal channel angular extrusion (ECAE) test, upsetting test and metalloseope, reheating mierostruetures of raw casting ingots, materials prepared by SIMA and materials extruded by ECAE in semi-solid state were investigated. The results show that compared with those of raw casting ingots and materials prepared by SIMA, reheating microstrueture of materials extruded by ECAE is the best and the final grain size is the finest. With increasing holding time, a growing phenomenon occurs in reheating microstrueture of materials extruded by ECAE, which can be described by Ostwald ripening law. The average grain size increases firstly, subsequently decreases and the shape factor of grains approaches to 1 as the reheating temperature increases. With increasing equivalent strain, the average grain size decreases. This demonstrates that reheating material extruded by ECAE technology is a good method to prepare AZ91D magnesium alloy semi-solid billets.     

Effects of Zr on crystallization kinetics of Pr—Fe—B amorphous alloys

The effects of Zr on crystallization kinetics of Pr-Fe-B amorphous alloys have been investigated by DTA and XRD methods.It was found that for Pr8Fe86-xZrxB6(x=0,1,2)amorphous alloys,the final crystallized mixture is α-Fe and Pr2Fe14B,and the metastable Pr2Fe23B3 phase occurs during crystallization of Pr8Fe86B6 amorphous alloy,not during crystallization of Pr8Fe86-xZrxB6(x=1,2)amorphous alloys,By analyzing the activation energy of crystallization,the formation of an α-Fe/Pr2Fe14B composite microstructure with a coarse grain size in annealed Pr8Fe86B6 alloy,is attributed to a difficult nucleation and an easy growth for both the α-Fe and Pr2Fe14B in the alloy.The addition of Zr can be used to change the crystallization behavior of the α-Fe phase in Pr-Fe-B amorphous alloy,which is helpful to reduce the grain size for the α-Fe phase.     

Electronical and thermoelectric properties of half-Heusler ZrNiPb under pressure in bulk and nanosheet structures for energy conversion

The pressure dependence of structural,electronic and thermoelectric properties of half-Heusler ZrNiPb was investigated in the bulk and nanosheet structures.In order to obtain the accurate results,the full-potential(linearized) augmented plane-wave(FP(L)APW)calculations were performed with the Perdew-BurkeErnzerhof generalized gradient approximation(PBE-GGA)and modified Becke-Johnson(mBJ) plus spin-orbit coupling(SOC).Obtained band gap values are in close agreement with the experimental results(0.5 eV).The variations of the thermoelectric properties of the ZrNiPb were studied under different temperatures,carrier concentrations and the hydrostatic pressures.The results show that the hydrostatic pressure decreases the lattice constant value.The band structure calculations display that the band gap increases with pressure for the bulk state and it is 0 for the nanosheet of ZrNiPb [010].The highest value of figure of merit(ZT)=0.95 is found at 9.378 GPa at a carrier concentration of n=1 × 10~(18) cm~(-3) at 250 K for p-type of ZrNiPb.     

Microstructure and magnetostrictive properties of Tb doped Fe–Ga bulk alloys prepared by melt quenching

The microstructure and magnetostrictive properties were investigated in the Tb doped Fe83Ga17-xTbx(x = 0.05, 0.10, 0.20, 0.30, 0.40, 0.50) bulk rods prepared by melt rapidly quenching. The partial solid solubility of Tb in the Fe–Ga matrix was preliminary detected by the lattice parameters and SEM observation. The matrix keeps A2 structure and the second phase appears surround the grain boundary as x C 0.1. h100 i preferred orientation is also observed for x = 0.1 sample along the axis of the quenched rod. The saturation magnetostriction first increases and maximum value reaches at x = 0.1, and then decreases with Tb addition increasing. The initial increase of the magnetostriction should be associated with the partial solution of Tb in the matrix, the maximum value at x = 0.1 should be attributed to the h100 i preferred orientation, and the decrease of the magnetostriction is correlated with the appearance of the second phase along the grain boundary.     

Solidification structure simulation and casting process optimization of GCr15 bloom alloy

Based on the solidification heat transfer model and CAFémodel,the solidification structure of GCr15 bloom alloy was studied.Using nail shooting and acid etching experiments,the solidification models were verified.The secondary dendrite arm spacing(SDAS)model of GCr15 was obtained by simulation calculation and metallographic observation.With the increase of casting speed,the SDAS,equiaxed crystal ratio(ECR)and average grain size increase.With the rise of superheat,the SDAS increases in the 20-70 mm of thickness and decreases in the 80-160 mm of thickness.The ECR decreases and the average grain size increases with the increase of superheat.With the increase of specific water flow,both the SDAS and ECR decrease.The minimum average grain size is obtained when the specific water flow is 0.20 L·kg^-1.The central carbon segregation index is reduced from 1.11 to 1.075.