共查询到20条相似文献,搜索用时 53 毫秒
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通过基于密度泛函理论的第一性原理计算方法,研究了Pt-M(M=Fe,Co,Ni)各金属间化合物的结构、能量、电子结构和弹性性质。首先对Pt-M(M=Fe,Co,Ni)金属间化合物进行几何优化,对其能带结构、总态密度、分态密度、键合特征和弹性性质进行研究,并计算各金属间化合物的结合能与生成焓。计算所得晶格参数与实验值和文献计算值吻合。PtFe_3的生成焓最小,结合能最大,说明PtFe_3较其他合金相更稳定、键合力更强。通过对Pt-M(M=Fe,Co,Ni)的能带结构和电子态密度进行计算,分析了其结构稳定性的物理本质。PtFe_3-t中Pt-Fe和Fe-Fe键相比其他合金相键长较短且电荷密度较高,说明PtFe_3-t中Pt-Fe和Fe-Fe键的键能比其他合金相大,所以PtFe_3-t合金相的结构稳定性最好。对Pt-M(M=Fe,Co,Ni)弹性性质的研究表明PtFe_3为脆性相,PtFe、Pt3Fe、PtCo、Pt_3Co、PtNi和PtNi3为延性相,其中Pt_3Co的塑性最好,PtFe_3-t有较高的弹性模量,其原子间结合力相对较强,材料的强度较大。 相似文献
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采用离子束溅射技术制备不同Pt/Ru比PtRu合金纳米载体薄膜材料.研究了薄膜中形成PtRu合金的结构特点和组分差异.结果表明该薄膜材料在成膜过程中既有Ru渗入Pt晶格之中又有Pt渗入Ru的晶格之中,属于(Pt) (Ru)两相区的合金化过程. 相似文献
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介绍了在聚乙烯醇缩甲醛(PVF或Formvar)膜上蒸镀Au,Pd和Ag金属膜,用XPS研究其表面与界面的化学组分与价态。实验发现,在PVF膜上蒸镀Au,Pd和Ag后,三种不同价态的C1s相对含量均发生了变化。表明金属原子在PVF膜上的沉积是化学吸附。 相似文献
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金/银合金纳米颗粒的制备及光学吸收特性 总被引:4,自引:1,他引:3
以柠檬酸盐为还原剂,通过共还原氯金酸和硝酸银的混合溶液制备出Au/Ag合金纳米颗粒,用透射电子显微镜(TEM)对颗粒的形貌和尺寸进行了表征。300-800nm范围的吸收光谱研究发现,Au/Ag合金纳米颗粒具有单峰等离子体吸收特征,且随着反应液中氯化金和硝酸银的摩尔比的减少,吸收峰将产生蓝移。实验结果表明,Au-Ag合金纳米颗粒的光学吸收特性具有组分可裁剪性,使其在纳米尺度的光学领域具有潜在的应用价值。 相似文献
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We have synthesized a variety of alkali-metal and ammonium fluorosulfatometallates (titanates, zirconates, and hafnates). The alkali fluorosulfatozirconates and fluorosulfatohafnates have been shown to exhibit efficient roentgenoluminescence (RL) in the UV through visible spectral region, with a maximum at 390–440 nm. Their RL spectra depend significantly on their composition (cation, anion, and water content), coordination of KF and K2SO4, and relative amounts of fluorine and SO4 groups. We have examined the effect of heat treatment on the RL of these compounds. The rubidium and cesium fluorosulfatozirconates Rb3Zr2F9SO4 · 2H2O, Cs2ZrF2(SO4)2 · 2H2O, Cs8Zr4F2(SO4)11 · 16H2O, and Cs2ZrF4SO4 offer the most efficient RL. 相似文献
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A. M. Grishin 《Journal of Engineering Physics and Thermophysics》2001,74(4):895-903
Basic definitions and concepts of the physicomathematical theory of natural catastrophes are given. Possibilities of mathematical modeling of natural and technogenic catastrophes are discussed in the context of the theory of heat and mass transfer and the mechanics of reacting media. The importance of taking into account conjugate heat and mass exchange in modeling catastrophes is emphasized. A formula for evaluating the probability of a collisional catastrophe is given. 相似文献
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Velev JP Jaswal SS Tsymbal EY 《Philosophical transactions. Series A, Mathematical, physical, and engineering sciences》2011,369(1948):3069-3097
The existence of multiple ferroic orders in the same material and the coupling between them have been known for decades. However, these phenomena have mostly remained the theoretical domain owing to the fact that in single-phase materials such couplings are rare and weak. This situation has changed dramatically recently for at least two reasons: first, advances in materials fabrication have made it possible to manufacture these materials in structures of lower dimensionality, such as thin films or wires, or in compound structures such as laminates and epitaxial-layered heterostructures. In these designed materials, new degrees of freedom are accessible in which the coupling between ferroic orders can be greatly enhanced. Second, the miniaturization trend in conventional electronics is approaching the limits beyond which the reduction of the electronic element is becoming more and more difficult. One way to continue the current trends in computer power and storage increase, without further size reduction, is to use multi-functional materials that would enable new device capabilities. Here, we review the field of multi-ferroic (MF) and magnetoelectric (ME) materials, putting the emphasis on electronic effects at ME interfaces and MF tunnel junctions. 相似文献
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Garny A Nickerson DP Cooper J Weber dos Santos R Miller AK McKeever S Nielsen PM Hunter PJ 《Philosophical transactions. Series A, Mathematical, physical, and engineering sciences》2008,366(1878):3017-3043
We have, in the last few years, witnessed the development and availability of an ever increasing number of computer models that describe complex biological structures and processes. The multi-scale and multi-physics nature of these models makes their development particularly challenging, not only from a biological or biophysical viewpoint but also from a mathematical and computational perspective. In addition, the issue of sharing and reusing such models has proved to be particularly problematic, with the published models often lacking information that is required to accurately reproduce the published results. The International Union of Physiological Sciences Physiome Project was launched in 1997 with the aim of tackling the aforementioned issues by providing a framework for the modelling of the human body. As part of this initiative, the specifications of the CellML mark-up language were released in 2001. Now, more than 7 years later, the time has come to assess the situation, in particular with regard to the tools and techniques that are now available to the modelling community. Thus, after introducing CellML, we review and discuss existing editors, validators, online repository, code generators and simulation environments, as well as the CellML Application Program Interface. We also address possible future directions including the need for additional mark-up languages. 相似文献
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Wiwanitkit V 《Hemodialysis international. International Symposium on Home Hemodialysis》2012,16(1):116; author reply 116-116; author reply 117
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热交换器是将不同温度介质之间的热量通过热传导的形式,由高温介质传递给低温介质,使介质达到生产所需温度的工艺设备,也可作为一种节能设备使用.通过对不同热交换器的结构分析,总结不同热交换器的优缺点、适用环境,为生产工艺设计人员及设备制造单位在选择可降低能耗、提高效率的设备上提供参考. 相似文献
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Yongkang Chen Mike Bacich Cory Nardin Albert Sitorus Mark M. Weislogel 《Microgravity science and technology》2005,17(4):14-24
The behavior of wall-bound drops and bubbles is fundamental to many natural and industrial processes. Key characteristics
of such capillary systems include interface shape and stability for a variety of gravity levels and orientations. Significant
solutions are in hand for axisymmetric pendent drops for a variety of uniform boundary conditions along the contact line with
gravity acting normal to a planar wall. The special case of a wall-bound drop or bubble that is also pinned at an edge (i.e.
a ‘wall-edge-bound’ drop) is considered here where numerical solutions are obtained for interface shape and stability as functions
of drop volume, contact angle, fluid properties, and uniform gravity vector. For a semi-infinite zero-thickness planar wall
(plate), a critical contact angle is identified below which wall-edge-bound drops are always stable. The critical contact
angle is computed as a function of the gravity vector. The numerical procedure, which makes no account for contact angle hysteresis,
predicts that such wall-edge-bound drops are unconditionally unstable for any gravity field with a component that is tangent
to the wall while inwardly normal to the edge. Select experiments are conducted that support the conclusions drawn from the
numerical results. 相似文献