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排序方式: 共有370条查询结果,搜索用时 93 毫秒
1.
《Calphad》2021
Diffusion behaviors in Mg–Sc hcp and bcc solid solutions between 773 and 873 K were investigated using both single-phase and multi-phase diffusion couple techniques. The EPMA detected composition-distance profiles were smoothed and fitted using the error function expansion (ERFEX). The interdiffusion coefficients were extracted using Sauer–Freise integral. The interdiffusion coefficients in hcp phase showed a slightly parabolic composition dependence at the Mg-rich part and the maximum value was around 2–3 at. % Sc. However, the interdiffusion coefficients in the bcc phase monotonously decreased with the increase of solubility of Sc. The determined inter- and impurity diffusion coefficients in the hcp Mg–Sc alloys were assessed to develop the atomic mobility database, and their validity was justified by reproducing the composition profiles and diffusion fluxes obtained in this diffusion couple experiment. Meanwhile, the development of bcc atomic mobility was realized via the Maclaurin approximation, extrapolation, and optimization. The results make up for the missing data of Mg–Sc diffusion kinetics. 相似文献
2.
P204对Sc有很好的分离选择性和分离能力,但由于反萃困难限制了其在Sc纯化中的应用。本工作研究了从裂变产物中分离纯化Sc的方法,建立流程如下:首先利用P204树脂对Sc的强萃取能力,将Sc与大量裂变产物分离,再通过灰化方法破坏树脂官能团,解决了吸附在P204树脂上的Sc难以解吸的问题,最后通过阳离子交换树脂实现Sc与残留Zr和Mo的分离,从而实现了Sc与裂变产物的分离。该方法对样品体积和酸度要求低,流程步骤操作简单。通过对模拟样品进行分析,Sc的回收率大于65%,对主要裂变产物的去污因子大于103,适用于Sc与裂变产物的分离。 相似文献
3.
采用光学显微镜(OM)、扫描电镜(SEM)、电子探针显微分析(EPMA)、X射线衍射(XRD)以及扫描透射电镜(STEM),研究了一种高Cu含量Al-2.35Cu-4.6Li-0.12Sc(at%)合金在均匀化热处理过程中微观组织演变以及W(Al8Cu4Sc)相的形成机制。结果表明:铸态时,合金中的主要凝固相为TB(Al7Cu4Li)相,Sc主要以过饱和固溶体的形式存在于基体中;均匀化后,TB相完全溶解,基体中的Cu含量增加,Sc含量减少,稳定的W相形成。分析表明,由于TB相与基体界面是非共格的,W相优先在此界面形核将有利于其形核能的降低。W相形核后通过不断消耗其附着的TB相上的Cu原子和Al基体中的过饱和Sc原子而逐渐长大,直至形成尺寸1 μm左右的稳定粒子。 相似文献
4.
《Ceramics International》2022,48(14):19971-19977
Molybdenum diboride is unique among transition metal diborides because it exists in both hexagonal (AlB2-type) and rhombohedral structures. However, it is difficult to stabilize the superconducting AlB2-type phase, which requires either extreme synthesis condition or suitable chemical doping. Here we report the structural and physical properties of Sc-doped nonstoichiometric molybdenum diborides (Mo0.95Sc0.05)1-xB2 and (Mo1-yScy)0.71B2 prepared by the common arc melting method. The AlB2-type phase is found to form over wide ranges of 0 ≤ x ≤ 0.29 and 0.025 ≤ y ≤ 0.30 for the first time, and bulk superconductivity with Tc up to 7.9 K is observed. Tc increases with increasing x in the (Mo0.95Sc0.05)1-xB2 series, but evolves nonmonotonically with varying y in the (Mo1-yScy)0.71B2 series. Despite this contrast, Tc of both borides follows nearly the same linear dependence on the electron-phonon coupling constant, suggesting that it is mainly controlled by the electron-phonon interaction. In addition, the stabilization of AlB2-type structure is attributed to the decrease in the number of d electrons as a consequence of Sc doping, which suggests that a similar effect may be achieved by substituting Mo with other d electron-poorer metal elements. 相似文献
5.
微量钪对Al-Zn-Mg-Cu-Zr铝合金组织与性能的影响 总被引:5,自引:0,他引:5
采用铸锭冶金法制备了Al 7.6Zn 2 .2Mg 1.2 4Cu 0 .13Zr和Al 7.8Zn 2 .2Mg 1.3 0Cu 0 .3 0Sc 0 .14Zr合金 ,测试了不同热处理状态下合金的力学性能和电导率 ,利用金相显微镜和透射电子显微镜研究了 2种合金不同处理态的显微组织 ,利用扫描电镜观察铝合金的拉伸断口。结果表明 :添加微量的Sc可以明显细化合金的铸态晶粒 ,显著提高Al Zn Mg Cu Zr合金的力学性能和电导率 ,其作用机理主要为Al3 (Sc ,Zr)引起的细晶强化、亚结构强化和弥散强化。 相似文献
6.
采用溶胶-凝胶法合成了Sc掺杂La0.6Sr0.4Co0.2Fe0.8-xScxO3-δ(LSCFScx,x=0,0.04,0.08)阴极粉体,系统分析了LSCFSc阴极材料的晶体结构、表面元素化学形态、催化活性及电化学性能。XRD结果表明,LSCF为立方结构,Sc3+掺杂后LSCFSc阴极材料由立方相向六方结构转变。LSCFSc阴极材料的电导率随着Sc3+的掺杂而降低,在300~800℃温度范围内LSCFSc0.08阴极样品的电导率仍大于100 S/cm。XPS结果表明Sc3+掺杂提高了LSCFSc阴极材料表面吸附氧(OAds)的含量,LSCFSc0.08阴极材料在800℃测得的极化面电阻RASR为0.026Ω·cm2,相比LSCF阴极材料RASR降低了约87.7%,显著改善了LSCFSc阴极材料对氧气... 相似文献
7.
《Calphad》2016
Thermodynamic optimization of the Au–Sc and Fe–Sc systems was carried out by means of the CALPHAD (CALculation of PHAse Diagram) method on the basis of the available experimental data in literature. Redlich–Kister polynomials were used to describe the excess Gibbs energy of solution phases, and all the compounds are treated as stoichiometric ones. The Au–Sc system was described thermodynamically for the first time, and the Fe–Sc system was re-optimized by considering the new experimental data about enthalpies of mixing of the liquid phase. A set of self-consistent parameters was obtained for each of these two binary systems, respectively. 相似文献
8.
《Materials Science & Technology》2013,29(2):144-150
AbstractThe microstructures of silicon alloyed γ-Ti–Al alloys containing silicide particles have been studied after thermomechanical treatments to investigate microstructural evolution. Important parameters including temperature, forging strain, and sequence of thermomechanical treatments were systematically studied. Isothermal forging below the eutectoid temperature resulted in inhomogeneous dynamic recrystallisation with fine equiaxed grains in recrystallised areas and residual α2 + γ lamellae elsewhere. Eutectic silicides play an important role in destruction of the as cast structure by promoting dynamic recrystallisation during deformation and static recrystallisation on subsequent annealing. There is evidence that silicon, in solution, also enhances recrystallisation. The presence of fine silicides produced by precipitation in the solid state restricts the size of grains produced by both dynamic and static recrystallisation. Silicon also alters significantly the phase equilibrium between the α and γ phases. 相似文献
9.
Valentina V Zhurikhina Pavel N Brunkov Vladimir G Melehin Tommi Kaplas Yuri Svirko Victoria V Rutckaia Andrey A Lipovskii 《Nanoscale research letters》2012,7(1):676
We demonstrate that silver nanoisland film self-assembled on the surface of silver-containing glass in the course of thermal processing in hydrogen is capable to detect 10−7 M concentration of rhodamine 6G in water using surface enhanced Raman spectroscopy (SERS) technique. The film can be multiply restored on the same glass substrate via annealing of the glass in hydrogen. We showed that the film can be self-assembled after as much as ten circles of the substrate cleaning followed by annealing. The proposed technique of the silver nanoisland film formation enables multiple usage of the same glass substrate in SERS experiments. 相似文献
10.