Hakan Colak
材料科学技术（英文）
This paper reported the synthesis, crystal structure and electrical conductivity properties of Ni-doped ZnO powders (i.e. Zn1-XNiXObinary system, X=0, 0.0025, 0.005, 0.0075 and in the range 0.01≤X≤0.15). I-phase samples, which were indexed as single phase with a hexagonal (wurtzite) structure in the Zn1-XNiXObinary system, were determined by X-ray diffraction (XRD). The widest range of the I-phase was determined as 0≤X≤0.03 at 1200°C; above this range the mixed phase was observed. The impurity phase was determined as NiO when compared with standard XRD data, using the PDF program. We focused on single I-phase ZnO samples which were synthesized at 1200°C because of the widest range of solubility limit at this temperature. It was observed that the lattice parameters a and c of the I-phase decreased with Ni doping concentration. The morphology of the I-phase samples was analyzed with a scanning electron microscope. The electrical conductivity of the pure ZnO and single I-phase samples were studied by using the four-probe dc method at temperatures between 100 and 950°C in air atmosphere. The electrical conductivity values of pure ZnO and 3 mol% Ni-doped ZnO samples at 100°C were 2×10-6 and 4.8×10-6Ω-1?cm-1, and at 950°C they were 1.8 and 3.6Ω-1?cm-1, respectively. In other words, electrical conductivity increased with Ni doping concentration.
关键词:
II-VI semiconductors
Journal of Materials Science
In this paper, Portevin-Le Chatelier (PLC) effect of LA41 magnesium alloy is reported. With increasing strain rate, both ultimate tensile stresses (sigma(b)) and 0.2% proof (sigma(0.2)) stresses increase, while serrations become less severe. Major acoustic emission (AE) peaks appear at the end of elastic region, and transform to burst type signals in the plastic range. In another alloy containing less Li (LA11), serrations are absent and major AE peak values are considerably lowered. Additionally, PLC effect disappears in LA41 after annealing. The role of twins is discussed in details. Actual causes for AE activity during deformation are also proposed.
关键词:
tensile deformation;magnesium alloys;bands;az31
Journal of Materials Research
The morphology of the dark and bright regions observed by transmission electron microscopy for the Zr(64.13)Cu(15.75)Ni(10.12)Al(10) bulk metallic glass strongly depends on the ion beam parameters used for ion milling. This indicates that the ion beam could introduce surface fluctuation to metallic glasses during ion milling.
关键词:
room-temperature
Yongli Huang
材料科学技术（英文）
The reverse analysis provides a convenient method to determine four elastic-plastic parameters through an indentation curve such as Young's modulus E, hardness H, yield strength σy and strain hardening exponent n. In this paper, mathematical analysis on a reverse algorithm from Dao model (Dao et al., Acta Mater., 2001, 49, 3899) was carried out, which thought that only when 20≤E*/σ0:033≤26and 0.3<n≤0.5, the reverse algorithm would yield two solutions of n by dimensionless function Π2. It is shown that, however, there are also two solutions of n when 20≤E*/σ0:033≤26 and 0≤n<0.1. A unique n can be obtained by dimensionless function Π3 instead of Π2 in these two ranges. E and H can be uniquely determined by a full indentation curve, and σy can be determined if n is unique. Furthermore, sensitivity analysis on obtaining n from dimensionless function Π3 or Π22 has been made.
关键词:
Elastic-plastic properties
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Yongli Huang
材料科学技术（英文）
The reverse analysis provides a convenient method to determine four elastic-plastic parameters through an indentation curve such as Young's modulus E, hardness H, yield strength σy and strain hardening exponent n. In this paper, mathematical analysis on a reverse algorithm from Dao model (Dao et al., Acta Mater., 2001, 49, 3899) was carried out, which thought that only when 20≤E*/σ0:033≤26and 0.3<n≤0.5, the reverse algorithm would yield two solutions of n by dimensionless function Π2. It is shown that, however, there are also two solutions of n when 20≤E*/σ0:033≤26 and 0≤n<0.1. A unique n can be obtained by dimensionless function Π3 instead of Π2 in these two ranges. E and H can be uniquely determined by a full indentation curve, and σy can be determined if n is unique. Furthermore, sensitivity analysis on obtaining n from dimensionless function Π3 or Π22 has been made.
关键词:
Elastic-plastic properties
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