Mechanism of nucleation and precipitation in Li containing Al-Zn-Mg-Cu alloys

Investigations on the aging hardening behavior of four Al-Li-Zn-Mg-Cu alloys were carried out using differential scanning calorimetry, transmission electron microscopy and hardness measurement. It is shown that the addition of Li inhibits the formation of Zn-rich G.P. zones in Al-Zn-Mg-Cu alloys. The dominant aging hardening precipitates is delta'(Al3Li) phase. Coarse T ((AlZn)(49)Mg-32) phase, instead of MgZn2, precipitates primarily on grain boundaries, and provides little strengthening. The multi-stop aging involving plastic deformation introduces in the matrix a high concentration of structural defects. These defects play different role on the nucleation of Zn-rich G.P. zones in different alloys. For the Li free alloy, structural defects act as vacancy sinks and tend to suppress the homogeneous precipitation of G.P. zones, while for the Li containing alloys, these defects promote the heterogeneous nucleation of G.P. zones and metastable MgZn2. A significant aging hardening effect is attained in deformed Li containing alloys due to the extra precipitation of fine MgZn2 in the matrix combined with deformation hardening.

SiC颗粒对Al-Zn合金激光快凝晶粒组织的影响

Al-Zn合金和SiCp/Al-Zn复合材料的激光重熔晶粒组织的对比研究表明 ,SiC颗粒对凝固初生相的生长具有阻碍作用。在颗粒尺寸较大和颗粒含量较高的条件下 ,激光熔池中会形成非外延生长的晶粒

Influences of Al doping concentration on structural, electrical and optical properties of Zn0.95Ni0.05O powders

Nanocrystalline Zn0.95 - xNi0.05AlxO (x = 0.01, 0.02, 0.05 and 0.10) diluted magnetic semiconductors have been synthesized by an auto-combustion method. X-ray diffraction measurements indicate that all Al-doped Zn0.95Ni0.05O samples have the pure wurtzite structure. Transmission electron microscope analyses show that the as-synthesized powders are of the size 40 - 45 nm. High-resolution transmission electron microscope, energy dispersive spectrometer and X-ray photoemission spectroscope analyses indicate that Ni2+ and Al3+ uniformly substitute Zn2+ in the wurtzite structure without forming any secondary phases. The Al doping concentration dependences of cell parameters (a and c), resistance and the ratio of green emission to UV emission have the similar trends. (c) 2007 Elsevier B.V. All rights reserved.

ZnO : Zn phosphor thin films prepared by face-to-face annealing

ZnO:Zn phosphor thin films were prepared by face-to-face annealing at 450 degrees C in air. The effects of the face-to-face annealing on the structural and optical properties of the ZnO films were investigated by X-ray diffraction (XRD), photoluminescence (PL), optical transmittance and absorption measurements. Measurement results showed that the crystal quality of ZnO films was improved by face-to-face annealing. Both UV light emission and visible light emission were enhanced compared to those of open annealing films. The UV emission peak was observed to have a blueshift towards higher energy. The optical band-gap edge of as-annealed films shifted towards longer wavelength. (c) 2005 Elsevier B.V.. All rights reserved.

Zn~(2+)、Co~(2+)和Mn~(2+)对人工湿地基质生物膜的影响

研究了金属离子Zn2+,Co2+和Mn2+对复合垂直流人工湿地基质生物膜脱氢酶活性和多糖含量的影响.结果表明,在生物膜混合液中添加Zn2+能在短时间内(6h)迅速提高生物膜的酶活性,增加多糖含量,浓度为2mg/L的Zn2+可以在较长时间(72h)内保持生物膜的酶活性并且促进多糖的积累.Co2+和Mn2+对生物膜脱氢酶活性及多糖含量的影响较为相似.当Co2+浓度<1mg/L、Mn2+浓度<2mg/L条件下,6h时,对脱氢酶活性呈现了不同程度的促进作用,但随着Co2+和Mn2+离子浓度的增加,对脱氢酶活性的影

Zn~(2+)胁迫对绿球藻生长、生理特性及细胞结构的影响

Zn2+对绿球藻胁迫的实验浓度为0.1、1、10、50、100、200、400mg/L,BG11培养基作对照。实验结果表明,在特定浓度条件下,Zn2+对绿球藻的生长、生理特性以及细胞结构具有显著影响。低浓度Zn2+(0.1—1mg/L)对绿球藻生长基本没有影响;浓度在10—50mg/L时,绿球藻能维持一定的生长速率;但当Zn2+浓度大于100mg/L时,绿球藻的生长受到显著抑制。绿球藻Chla+Chlb以及Chla含量均随培养基中Zn2+浓度的升高而逐渐减少。当Zn2+浓度低于10mg/L时,绿球藻的净光

重金属Cd~(2+)、Pb~(2+)和Zn~(2+)对泥鳅DNA损伤的研究

采用单细胞凝胶电泳技术(SCGE),研究重金属Cd2+、Pb2+、Zn2+在不同暴露时间(1—35d)、单一重金属离子不同暴露浓度(0.05mg/L、0.5mg/L、5.0mg/L)或混合重金属离子(Cd2++Pb2+、Cd2++Zn2+、Pb2++Zn2+、Cd2++Pb2++Zn2+)相同浓度(0.5mg/L)条件下对泥鳅肝胰脏细胞核DNA的损伤作用。以带彗尾核DNA百分率和彗尾长度(TL)与核直径(D)比值为指标,探讨DNA损伤级别与处理浓度间的相关性。结果显示,随着处理时间的延长,带彗尾核DNA百

Zn~(2+)浓度对固氮鱼腥藻(Anabaena azotica Ley)光能转化特性的影响

本实验对在不同Zn2+浓度条件下培养的固氮鱼腥藻(Anabaena azoticaLey)的生长、光合放氧速率和叶绿素荧光参数Fv/Fm进行了测定.结果表明,当Zn2+浓度为1.0μmol/L时,其比生长速率(Specific growth rate)最大,光合放氧速率和Fv/Fm值最高.当Zn2+浓度大于等于5.0μmol/L时会抑制A.azotica Ley的生长和光合作用.对在0μmol/L和5.0μmol/L Zn2+浓度下生长的藻细胞藻胆体-类囊体膜复合物吸收光谱的比较和对与5.0μmol/L

Cu~(2+)、Zn~(2+)诱导稀有鮈鲫应激蛋白质的研究

以稀有鲫为材料 ,研究了应激蛋白质作为生物学指标的敏感性。结果表明 ,在无可观察效应浓度下 ,经 5d亚慢性胁迫暴露 ,以Cu2 +为胁迫因子 ,稀有鲫被诱导出约 54KDa的应激蛋白质 ;以Zn2 +为胁迫因子 ,稀有鲫被诱导出约 94KDa ,67KDa和 40KDa的应激蛋白质。应激蛋白质有可能成为一种生物学指标运用于生态风险性早期预警。

Use of microbial community to evaluate performance of a wetland system in treating Pb/Zn mine drainage

The performance of a wetland system in treating lead (Pb)/zinc (Zn) mine drainage was evaluated by using the polyurethane foam unit (PFU) microbial community (method), which has been adopted by China as a standardized procedure for monitoring water quality. The wetland system consisted of four cells with three dominant plants: Typha latifolia, Phragmites australis and Paspalum distichum. Physicochemical characteristics [pH, EC, content of total suspended solid (TSS) and metals (Pb, Zn, Cd, and Cu)] and PFU microbial community in water samples had been investigated from seven sampling sites. The results indicated that the concentrations of Pb, Zn, Cd, Cu, and TSS in the mine drainage were gradually reduced from the inlet to the outlet of the wetland system and 99%, 98%, 75%, 83%, and 68% of these metals and TSS respectively, had been reduced in concentration after the drainage passed through the wetland system. A total of 105 protozoan species were identified, the number of protozoa species and the diversity index (DI) gradually increased, while the heterotrophic index (HI) gradually decreased from the inlet to the outlet of the wetland system. The results indicated that DI, HI, and total number species of protozoa could be used as biological indicators indicating the improvement of water quality.

In(Ti,Sn)-O 与Sn(Pb)Zn-Te 的电子结构研究

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Well-Aligned Zn-Doped InN Nanorods Grown by Metal-Organic Chemical Vapor Deposition and the Dopant Distribution

We report the synthesis and characterization of Zn-doped InN nanorods by metal-organic chemical vapor deposition. Electron microscopy images show that the InN nanorods are single-crystalline structures and vertically well-aligned. Energy-dispersive X-ray spectroscopy analyses suggest that Zn ions are distributed nonhomogenously in InN nanorods. Simulations based on diffusion model show that the doping concentration along the radial direction of InN nanorod is bowl-like from the exterior to the interior, the doping concentration decreases, and Such dopant distribution result in a bimodal EDXS spectrum of Zn across the nanorod. The study of the mechanism of doping effect is useful for the design of InN-based nanometer devices. Also, high-quality Zn-doped InN nanorods will be very attractive as building blocks for nano-optoelectronic devices.'

Band-gap bowing and p-type doping of (Zn, Mg, Be)O wide-gap semiconductor alloys: a first-principles study

Using a first-principles band-structure method and a special quasirandom structure (SQS) approach, we systematically calculate the band gap bowing parameters and p-type doping properties of (Zn, Mg, Be)O related random ternary and quaternary alloys. We show that the bowing parameters for ZnBeO and MgBeO alloys are large and dependent on composition. This is due to the size difference and chemical mismatch between Be and Zn(Mg) atoms. We also demonstrate that adding a small amount of Be into MgO reduces the band gap indicating that the bowing parameter is larger than the band-gap difference. We select an ideal N atom with lower p atomic energy level as dopant to perform p-type doping of ZnBeO and ZnMgBeO alloys. For N doped in ZnBeO alloy, we show that the acceptor transition energies become shallower as the number of the nearest neighbor Be atoms increases. This is thought to be because of the reduction of p-d repulsion. The N-O acceptor transition energies are deep in the ZnMgBeO quaternary alloy lattice-matched to GaN substrate due to the lower valence band maximum. These decrease slightly as there are more nearest neighbor Mg atoms surrounding the N dopant. The important natural valence band alignment between ZnO, MgO, BeO, ZnBeO, and ZnMgBeO quaternary alloy is also investigated.