Hongchuan Jiang Chaojie Wang Wanli Zhang Xu Si Yanrong Li
材料科学技术（英）
TaNx thin films were deposited on commercial polished Al2O3 ceramic substrates by reactive dc magnetron sputtering. The influences of the film thickness on the electrical properties of the samples were examined in detail. It is found that the film thickness does not influence the phase structures of the TaNx thin films. The sheet resistances of the samples shift from 173 Ω/sq. to 7.5 Ω/sq. with the film thickness shifting from 30 nm to 280 nm. With the increase of the film thickness from 30 nm to 280 nm, the temperature coefficient of resistance (TCR) of the samples shifts from negative value to positive value. When the film thickness is about 100 nm, TaNx thin films exhibits a near-zero TCR value (approximately -15×10-6/°C). This fact implies that TaNx thin films with a null TCR can be obtained by adjusting the film thickness. The variation in the electrical properties of the TaNx thin films with the film thickness can be qualitatively explained by the parallel connection of surface layer with high resistivity and negative TCR and TaNx layer with low resistivity and positive TCR.
关键词:
TaNx thin films
,
Film thickness
,
TCR
,
Sheet resistance
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
Journal of Physics and Chemistry of Solids
The layered ternary ceramics Ti3SiC2 and Ti3AlC2 are isostructural and can form Ti3Si1-xAlxC2 solid solutions combining the advanced properties of both compounds [H.B. Zhang, Y.C. Zhou, Y.W. Bao, M.S. Li, Improving the oxidation resistance of Ti3SiC2 by forming a Ti3Si0.90Al0.1C2 solid solution, Acta Mater. 52 (2004) 3631-3637; E.D. Wu, J.Y. Wang, H.B. Zhang, Y.C. Zhou, K. Sun, Y.J. Xue, Neutron diffraction studies of Ti3Si0.9Al0.1C2 compound, Mater. Lett. 59 (2005) 2715-2719; J.Y. Wang, Y.C. Zhou, First-principles study of equilibrium properties and electronic structure of Ti3Si0.75Al0.25C2 solid solution, J. Phys.: Condens. Matter 15 (2003) 5959-5968; Y.C. Zhou, J.X. Chen, J.Y. Wang, Strengthening of Ti3AlC2 by incorporation of Si to form Ti3Al1-xSixC2 solid solutions, Acta. Mater. 54 (2006) 1317-1322]. In the present work, the solid solutions of Ti3Si1-xAlxC2 (x = 0, 0.25, 0.33, 0.5, 0.67, 0.75, 1) are investigated by first-principle calculations based on pseudo-potential plan-wave method within the density functional theory framework. The results show that as Al content increases in the solid solution, all the bonds have weakened to certain extents, which lead to an unstable structure both energetically and geometrically. The calculated results are compared and discussed with the reported data for the Ti3Si1-xAlxC2 solid solutions. (c) 2007 Elsevier Ltd. All rights reserved.
关键词:
ceramics;ab initio calculations;electronic structure;electrical;conductivity;oxidation behavior;mechanical-properties;ti3sic2;temperature;ti3alc2;air;si
陈荣
,
黄正
,
张永刚
,
陈昌麒
,
沈剑韵
材料研究学报
doi:10.3321/j.issn:1005-3093.2000.03.009
分析了Li加入Al-Mg-Si体系后相的析出和组织变化,计算了几个典型的相图截面,并对三种典型合金进行了TEM观测验证.相图计算表明,Li加入Al-Mg-Si体系后,在平衡状态下,δ为主要析出相,还形成富Si相AlLiSi和Mg2Si;在非平衡的实际析出状态下,亚稳相δ'成为主要析出相.δ'相的析出抑制Mg2Si的形成,增加Mg含量可在一定程度上促进Mg2Si的析出.
关键词:
相图计算
,
Al-Li-Mg-Si合金
,
显微结构
Journal of the European Ceramic Society
Dense Si2N2O was successfully synthesized using 2 mol% Li2O as an additive by a hot-pressing method at 1500 degrees C. Compared to other metal oxide additives, Li2O can significantly decrease the sintering temperature of Si2N2O, which is ascribed to the lower melting point of Li2O-SiO2 and the formation of less viscous liquid phase. Increasing Li2O content has no apparent influence on the mechanical and dielectric properties of dense Si2N2O, which is due to the easy evaporation of Li2O at sintering temperature. The mechanical properties of Si2N2O with Li2O additive are comparable to those of Si2N2O synthesized with other additives. The as-prepared bulk Si2N2O with 2 mol% Li2O additive exhibits both low dielectric constant (6.17 at 1 MHz) and loss tangent (0.0008 at 1 MHz) and combines good mechanical performance, indicating it is a potential high-temperature structural/functional material. (C) 2007 Elsevier Ltd. All rights reserved.
关键词:
Si2N2O;sintering;mechanical properties;dielectric properties;silicon oxynitride ceramics;thermal-conductivity;nitride;densification;toughness;strength;yttria;system
侯贤华
,
胡社军
,
汝强
,
张志文
稀有金属材料与工程
采用基于密度泛函理论的第一性原理平面波论调势方法计谋了Li-Si各种合金相的物理性质和电化学性能.结果表明:除了在反应过程中生成传统的固态电解持SEI膜之外形成的Li12Si7合金相也是部分导致首次不可逆容量损失的重要原因.另外,采用射频磁控溅射制备了纯Si薄膜电极,并运用XRD、徨伏安CV、恒流充放电CC表征和测试了材料的结构和电化学性能,结果表明首次不可逆容量损失非常大,无定型结构能有交抑制体积膨胀和改善徨性能.
关键词:
锂离子电池
,
嵌锂形成能
,
容量损失
,
第一性原理
卢庆亮
,
于化顺
,
闵光辉
,
王常春
,
冯刚
稀有金属材料与工程
通过液态原位反应合成制备MgO/Mg2Si增强Mg-Li基复合材料,利用TEM对增强相形态及界面结构进行了观察.实验结果表明,复合材料中增强粒子与基体界面结合良好,无反应物生成.确定了增强粒子与基体的界面取向关系,MgO与基体α相的晶体学关系为[100]MgO//[40(4)3]α,(011)MgO//((1)2(1)0)α;Mg2Si与基体β相的晶体学关系为 [310]MgSi//[411]β,(1(3)(1))MgSi//(001)β.
关键词:
Mg-Li基复合材料
,
粒子增强
,
界面结构
