Fe-Ga磁致伸缩合金相结构及其制备工艺研究进展

与已商业化的Terfenol-D磁致伸缩材料相比,新型磁致伸缩Fe-Ga合金以其高强度、良好韧性、低磁场高磁致伸缩和低成本等优势成为目前凝聚态物理和材料科学领域的研究热点。Fe-Ga合金的磁致伸缩性能取决于合金的微结构,特别是该类合金的相结构。而Fe-Ga合金的微结构又密切相关于合金的制备工艺。从Fe-Ga二元合金的基本相结构出发,在详细分析平衡态和亚稳态Fe-Ga二元合金相图的基础上,重点综述了Fe-Ga合金的相结构对其磁致伸缩性能的影响;之后,详细综述了各种制备工艺下Fe-Ga合金的相结构和磁致伸缩性能;最后展望了该类合金未来发展方向。     

深海走航抛弃式测量仪器时变信道对传输性能的影响

由于环境的要求,深海走航抛弃式测量仪器信号传输大多使用有线信道,然而,信道的电阻抗随放线长度不断变化,严重影响了深海走航抛弃式测量仪器信道传输的稳定性.本文以国家海洋技术中心自主研发的走航抛弃式温度、盐度、湿度(XCTD)剖面仪的传输信道为原型,提出了一种动态分析有线信道对传输信号幅值和相位影响的方法.首先推导出各电路参数随信道长度变化的规律,建立简化的传输电路模型和该模型的传输函数.通过定性分析得出传输频率、分布电容和缠绕电感对信号相位的影响.利用MATLAB软件分析XCTD在动态放线过程中信道对信号幅值和相位的影响.研究结果可进一步指导抛弃式走航测量系统的电路设计,提高测量数据的精度和信号传输的稳定性.     

Label-free tungsten disulfide quantum dots as a fluorescent sensing platform for highly efficient detection of copper(Ⅱ) ions

A fluorescent probe for the sensitive and selective determination of copper ion(Cu~(2+)) is presented. It is based on the use of tungsten disulfide quantum dots(WS_2 QDs) which is independent of the p H of solution and emits strong blue fluorescence. Copper ions could cause aggregation of the WS_2 QDs and lead to fluorescence quenching of WS_2 QDs. The change of fluorescence intensity is proportional to the concentration of Cu~(2+), and the limit of detection is 0.4 μM. The fluorescent probe is highly selective for Cu~(2+) over some potentially interfering ions. These results indicate that WS_2 QDs,as a fluorescent sensing platform, can meet the selective requirements for biomedical and environmental application.     

Facilitative effect of graphene quantum dots in MoS_2 growth process by chemical vapor deposition

The substrate treatment with seeding promoter can promote the two-dimensional material lateral growth in chemical vapor deposition(CVD) process. Herein, graphene quantum dots(GQDs) as a novel seeding promoter were used to obtain uniform large-area MoS_2 monolayer. The obtained monolayer MoS_2 films were confirmed by optical microscope,scanning electron microscope, Raman and photoluminescence spectra. Raman mapping revealed that the MoS_2 monolayer was largely homogeneous.     

In situ growth of different numbers of gold nanoparticles on MoS_2 with enhanced electrocatalytic activity for hydrogen evolution reaction

Producing hydrogen through a hydrogen evolution reaction(HER) by splitting water at the suitable overpotential is a great alternative to solving the problems of environmental pollution and the energy crisis. Molybdenum sulfide(MoS_2)has attracted extensive attention as one of the most promising catalytic materials for HER. In this work, we design a facile method to in situ grow gold nanoparticles(Au NPs) on MoS_2. Different numbers of Au NPs with MoS_2 are used to find the best catalytic activity. Due to the larger active surface area and higher conductivity of the Au–MoS_2 composites, all the Au–MoS_2 composites exhibit more enhanced HER electroactivity than pure MoS_2. In brief, the new material architecture exhibits optimized HER activity with a low onset overpotential of 0.12 V, low Tafel slope of 0.163 V·dec~(-1), and an excellent stability in acidic solution.     

Facile and controllable synthesis of molybdenum disulfide quantum dots for highly sensitive and selective sensing of copper ions

Molybdenum disulfide quantum dots(MoS_2QDs) were synthesized via a hydrothermal method using sodium molybdate and cysteine as molybdenum and sulfur sources, respectively. The optimal hydrothermal time was studied. Furthermore, the as synthesized water-soluble MoS_2QDs were used as a fluorescence probe for the sensitive and selective detection of copper ions. The fluorescence of the MoS_2QDs was quenched after the addition of copper ions; the reason may be that the transfer of the excited electron from QDs to copper ions leads to the reduction of the radiative recombination.The fluorescence quenching of MoS_2QDs is linearly dependent on the copper ions concentration ranging from 0.1 μM to600 μM, the limit of detection is 0.098 μM, which is much lower than that of existing methods. Moreover, the MoS_2QDs show highly selectivity towards the detection of copper ions.