单颗粒稀土纳米晶的三基色上转换发光

可调谐发光颜色的上转换荧光纳米粒子具有广阔的应用前景。本文设计并成功合成了结构紧凑的多层核-壳纳米颗粒。在不同波段激光的泵浦下,该颗粒中不同壳层分别产生红、绿、蓝3种颜色的上转换荧光。光谱测试结果表明,样品三基色发光的颜色纯度较好,并且可以实现全色域的颜色实时调节。此外,还测试了样品发光强度与泵浦功率之间的依赖关系,用于研究其中的上转换发光机理。这种在单颗粒水平上具有全色域可调发光的紧凑核-壳结构纳米晶体在多通道生物检测及成像、超高分辨率显示器件、高端防伪应用等领域显示出巨大的潜力。     

铁基纳米药物的研究现状与发展趋势

铁基纳米药物是目前屈指可数的临床用无机金属纳米材料,已成功用于磁共振影像增强、静脉补铁及磁致热疗等医疗领域.由于该类药物特殊的纳米属性与磁学功能,随着现代生物医学研究的不断深入,铁基纳米药物的生产工艺及质量标准需要更为严格和系统地制定.测试技术,尤其是对铁基组分的分析检测方法,需要革新并建立该类产品的质量控制体系.与此同时,新型铁基纳米药物的研发以及多项针对新适应症的临床试验也在积极进行中.本文总结了铁基纳米药物的分类、用途、主要制备技术及产品标准的研究现状,展望了新型铁基纳米药物的发展趋势.     

石墨烯基单原子催化剂的合成、表征及分析

单原子催化剂具有配位数低、配位环境特殊、原子利用率极高和催化位点高度均一等优点,是沟通均相和异相催化剂之间的桥梁,有助于更好地认识催化反应的本质。本文综述了近年来国内外石墨烯基单原子催化剂的多种合成方法,包括原子层沉积法、浸渍-煅烧法、缺陷捕获法、配位锚定法和其他新颖方法的制备过程、合成原理和表征。在此基础上,本文对石墨烯基金属单原子催化剂在催化方面的性能进行阐述和分析,以期为单原子催化剂制备提供指导和参考。     

Glass-Forming Ability of an Iron-Based Alloy Enhanced by Co Addition and Evaluated by a New Criterion

A new Fe-based alloy that can be cast into a fully amorphous rod with a diameter of at least 16mm by the conventional copper-mould casting technique is obtained by partially replacing Fe with Co in a previously reported Fe-based bulk metallic glass. The preliminary thermodynamic analysis indicates that the Co-containing alloy has a significantly lower Gibbs free energy difference between the undercooled melt and the corresponding crystalline solid, compared to the Co-free alloy, reflecting the dramatic role of the Co addition in stabilizing the supercooled melt and facilitating glass formation in iron-based alloys. Here, a new criterion, derived from the classical nucleation and growth theory, is introduced to evaluate the glass-forming ability of Fe-based bulk metallic glasses.     

磁场退火对Co基熔体抽拉丝巨磁阻抗效应的影响

对Co基熔体抽拉非晶丝进行了普通炉内退火和不同磁场强度（500 Oe,1600 Oe,4000 Oe）下的横向和纵向磁场退火,利用HP4192阻抗分析仪和Lakeshore7407VSM分析了退火态样品的巨磁阻抗（GMI）效应和软磁性能.研究结果表明,纵向磁场降低了环向各向异性,纵向磁场退火样品GMI效应降低且GMI曲线为单峰,最大阻抗变化率ΔZ/Z为131%,磁场响应灵敏度为7%/Oe;而横向磁场提高了环向畴体积,增加了环向各向异性场,导致退火样品GMI曲线随频率升高由单峰转 关键词： 非晶丝 巨磁阻抗效应 退火     

A New Model for Microstructure of Liquid Metals

A nanocrystalline model for microstructures of liquid metals is constructed. According to the nanocrystalline model, the intensity curves of x-ray diffraction (XRD) on liquid Cu, A1 and Al65Cu20Fe15 alloy are derived by broadening the XRD peaks of these metals in some crystal structures. These broadening intensity curves are     

The Kinetic Theory of Growth of Zr-Sn Diffusion Layers on Zr55Cua0Al10Ni5 Metallic Glass

The growth kinetics of the intermetallic compound layer between molten pure Sn and Zr55Cu30AlloNi5 bulk metallic glass （BMG） is mainly controlled by the diffusion mechanism at stage I at which the value of the time exponent is approximately 1/2, also there is unusual or unique stage Ⅱ whose time exponent of the growth is suppressed to 1/3. It is deduced that phase transition such as nucleation, coalescence occurring in the vicinity of the interface of the diffusion layer within the BMG and the average size growing as one-third power of time, called the Lifshitz-Slezov law. A more elegant means of attack is based upon the Fokker-Planck approach, which permits us to calculate directly the probability of the distribution of steady-state thickness fluctuations. Physical implications of the analytical results also give the one-third power of time of distance scale. The transmission of Sn particles through a disorder system of the BMG, scattered by the local fluctuation levels, is the source of the time exponent from 1/2 to 1/3 as a macroscopic cumulative effect.     

Influence of the distance between two voltage contacts on giant magneto-impedance of Co-based amorphous wires

The Co₇₅ Fe_4.2Si₈B₁₂Nb_0.8 amorphous wires of 30 μ m in diameter are produced by melt extraction and annealing at 450 oC for 20 min in vacuum with a longitudinal or transverse field of 40 kA/m. Distances between the two voltage contacts of 6, 5, 4 and 2 mm are obtained by moving the two voltage contacts towards the centre of the sample at the same time. Results indicate that magneto-impedance response is dependent on the distance significantly. As distance decreases from 6 to 2 mm, △Z/Z reduces from 609% to 95% and giant magneto-impedance (GMI) profiles change from two-peak to single-peak. Besides, field sensitivity improves from 0.47%/(A/m) to 0.76%/(A/m) when the single-peak GMI just appears. It is therefore concluded that actual measurements can be made comparable only by taking into account the influence of distance between two voltage contacts for a magneto-impedance measurement.