Molecular Beam Epitaxial Growth of Pb_(1-x)Eu_xSe_yTe_(1-y) Double Heterostructure

A Pb_(1-x)Eu_xSe_yTe_(1-y) double heterostructure was grown successfully on a p-type (100)_oriented PbTesubstrate by molecular beam epitaxy.In order to obtain semiconductor laser emitting at 2～4 μm,the band gapof the active region can be adjusted by controlling Eu composition (x value) in the active region.It was obtainedthat x=0.012,y=0.016 for the active region and x=0.030,y=0.016 for the confinement layers.The resultsmeasured from SEM and electrical properties show that the Pb_(1-x)Eu_xSe_yTe_(1-y) double heterostructure has ahomogeneous morphology and an obvious junction character.     

Compositional characterization of Cu-rich phase particles present in as-cast Al-Cu-Mg(-Li) alloys containing Ag

The effects of small additions of Ag on the aging of wrought Al-Cu-Mg(-Li) alloys, involving widespread nucleation of Cu-rich Ω (and T₁) phase precipitates, are known. This article examines the influence of small additions of Ag on the nature of Cu-rich θ-Al₂Cu, S-Al₂CuMg, and T₁-Al₂CuLi phases present in appropriate as-cast Al-Cu, Al-Cu-Mg, and Al-Cu-Li-Mg alloys. Using a combination of light microscopy, scanning electron microscopy (SEM), and electron probe microanalysis (EPMA), it is shown that neither independent nor combined additions of Ag and Mg to the binary Al-Cu alloy alter the composition of the θ phase; however, there are differences in the ways the θ phase is evolved in Al-Cu-Mg alloys with and without Ag. Ag additions to the Al-Cu-Mg alloy result in the formation of an Al-Cu-Mg-based ternary phase, having a Cu content similar to that of the θ phase and containing small amounts of Mg; rapid rates of cooling cause the retention of this phase in the as-cast alloy. Relatively large amounts of both Ag and Mg are always located in the peripheral regions of such a phase. This phase is readily replaced by θ phase upon annealing at 450 °C. The S phase of the ternary Al-Cu-Mg system is identified in this alloy and is found to dissolve small amounts of Ag. In the case of the Al-Cu-Li-Mg-Ag alloy, two major changes are observed: both Ag and Mg are always present in relatively large amounts in the peripheral regions of the T₁ phase, and the S-phase particles are once again found to dissolve small amounts of Ag. These results are discussed in light of the known compositional features of the precipitates formed in the artificially aged Al-Cu-Mg(-Li)-Ag alloys, to reveal that examination of phases present in the as-cast microstructure is a contributory step toward determining the locations of trace alloy additions in the phase precipitates of interest.     

An investigation of the lattice parameters of α-(Fe,P) alloys

In this investigation the lattice parameters of α-(Fe, P) alloys are measured very accurately. By comparison with literature it is concluded that the distribution of P-atoms in Fe is not always random and varies with heat treatment.     

Macroporous perovskite-type complex oxide catalysts of La_(1-x)K_xCo_(1-y)Fe_yO_3 for diesel soot combustion

A facile procedure was carried out to prepare macroporous perovskite-type complex oxide catalysts of La1-xKxCo1-yFeyO3(x=0,0.1,y=0,0.1) by using the combined method of organic ligation and solution combustion.This method could ensure the formation of the desired macroporous structures and the desired crystal phases of the prepared catalysts.It was found that the macroporous catalysts showed higher catalytic activities for soot combustion than that of the corresponding nanometric samples,and the macroporous ...     

Synthesis and characterization of Co_(1-2x)Ni_xMn_xCe_yFe_(2-y)O_4 nanoparticles

Spinel ferrite Co_(1-2 x)Ni_xMn_xFe_(2-y)Ce_yO_4(0.0≤x=y≤0.3) nanoparticles(NPs) were prepared by sol-gel auto-combustion method.The synthesized NPs were examined using several techniques such as X-ray diffraction(XRD),field emission scanning electron microscopy(FE-SEM) coupled with EDX and elemental mapping,transmission electron microscopy(TEM),Fourier-transform infrared spectroscopy(FT-IR),and a vibrating sample magnetometer(VSM).The analysis of the crystal structure and the phase identification of samples indicates the formation of spinel cubic phase with the occurrence of CeO_2 as secondary phase when the content of Ce substitution element increases.In addition,all produced samples exhibit cubic symmetry with space group Fd3m.TEM confirms the presence of two phases,i.e.,the cubic spinel ferrite and the cubic cerium oxide(CeO_2).The characteristics of hysteresis loops reveal the soft ferrimagnetic nature of the different synthesized samples.The saturation(M_s) and remanent(M_r) magnetizations fall on increasing the content of substituting elements.Compared with pure CoFe_2O_4 NPs,the value of coercive field(H_c) slightly increases for x=y=0.1 and x=y=0,2 NPs.Then,H_c reduces with further increasing the x and y contents.The squareness ratio is found to be in the 0.528-0.400 interval,indicating the single domain NPs with uniaxial anisotropy for the different produced NPs.The magneto crystalline anisotropy constant(K_(eff)),anisotropy field(H_a),magneton number(n_B) and the demagnetizing field(N) were also determined and discussed.