Direct Observation of Inherent Atomic‐Scale Defect Disorders responsible for High‐Performance Ti1−xHfxNiSn1−ySby Half‐Heusler Thermoelectric Alloys

Structural defects often dominate the electronic‐ and thermal‐transport properties of thermoelectric (TE) materials and are thus a central ingredient for improving their performance. However, understanding the relationship between TE performance and the disordered atomic defects that are generally inherent in nanostructured alloys remains a challenge. Herein, the use of scanning transmission electron microscopy to visualize atomic defects directly is described and disordered atomic‐scale defects are demonstrated to be responsible for the enhancement of TE performance in nanostructured Ti_1?x Hf_x NiSn_1?y Sb_y half‐Heusler alloys. The disordered defects at all atomic sites induce a local composition fluctuation, effectively scattering phonons and improving the power factor. It is observed that the Ni interstitial and Ti,Hf/Sn antisite defects are collectively formed, leading to significant atomic disorder that causes the additional reduction of lattice thermal conductivity. The Ti_1?x Hf_x NiSn_1?y Sb_y alloys containing inherent atomic‐scale defect disorders are produced in one hour by a newly developed process of temperature‐regulated rapid solidification followed by sintering. The collective atomic‐scale defect disorder improves the zT to 1.09 ± 0.12 at 800 K for the Ti_0.5Hf_0.5NiSn_0.98Sb_0.02 alloy. These results provide a promising avenue for improving the TE performance of state‐of‐the‐art materials.     

轻量级分组密码Pyjamask的不可能差分分析

Pyjamask是美国国家技术标准研究院征选后量子时代轻量级密码算法中进入第二轮的候选分组密码,对其抵抗现在流行的不可能差分分析分析为未来在实际系统中使用起到重要的作用.提出一些2.5轮不可能差分链并分析它们的结构特点和攻击效率,在一些最有效的不可能差分链的前后各接1轮和半轮,形成4轮Py-jamask多重不可能差分攻击路径.攻击结果表明Pyjamask的行混淆运算扩散性比较强,能较好地抵抗不可能差分分析,此结果是对Pyjamask安全性分析的一个重要补充.     

Effects of doping on the high-temperature thermoelectric properties of IrSb3 skutterudite compounds

The IrSb₃-based skutterudite compounds have a potential for thermoelectric applications because of high Hall mobility, Seebeck coefficient, and relatively low thermal conductivity. In the present study, polycrystalline p- and n-type IrSb₃ compounds are prepared by powder metallurgy techniques. The effect of doping on thermoelectric properties has been investigated in binary and ternary IrSb₃ compounds using Ru, Ge, Pd, or Pt as a dopant. It is shown that the electrical properties depend strongly not only on the kinds of doping impurities but also their levels. Our theoretical analysis suggests that the effective mass is significantly affected by doping impurities and the levels.     

邮电工业CIMS发展战略初探

当前国际上制造业自动化总趋势是由单元自动化发展成由信息技术，网络技术和计算机技术支撑的计算机集成制造系统ＣＩＭＳ，本文简略地介绍了ＣＩＭＳ的概念及国内、国外发展概况，并以邮电工业如何发展ＣＩＭＳ作一些初步的探讨。     

高压氨分离器A—FA601设计和制造特点分析

介绍了利用多层板夹紧式技术制造大直径设备及设备开孔处边缘应力的分析和测定。     

Thermoelectric Properties of Ruddlesden–Popper Phase n-Type Semiconducting Oxides: La-, Nd-, and Nb-Doped Sr3Ti2O7

We report herein on Ruddlesden–Popper-type doped Sr _{n +1}Ti _n O_{3 n +1} ( n =2) as a potential candidate for n -type thermoelectric (TE) oxides. The TE properties of 5 at.% La-, Nd-, and Nb-doped Sr₃Ti₂O₇ polycrystalline ceramics were investigated and the origin of Seebeck coefficient was discussed from the viewpoint of the symmetry of TiO₆ octahedra. A significant reduction in the lattice thermal conductivity was observed by the enhancement of phonon scattering at SrO/(SrTiO₃) _n interfaces originating from the inherent superlattice structure, and the maximum dimensionless figure of merit, ZT ∼0.15, at a 1000 K value was obtained in 5 at.% La-doped Sr₃Ti₂O₇.     

磁控射频溅射法制备光波导薄膜研究

采用磁控射频溅射法制备了用作光波导器件的玻璃薄膜。通过选取不同的溅射材料,在不同溅射条件下制备的玻璃薄膜的光学参数进行的测量、比较,并对其作为光波导的性能进行研究,通过理论上推导与计算,得出了在１,５５ｕｍ窗口下制备光波导器件的玻璃薄膜所应具备的溅射条件。     

Topotactic Metal–Insulator Transition in Epitaxial SrFeOx Thin Films

Topotactic phase transformation enables structural transition without losing the crystalline symmetry of the parental phase and provides an effective platform for elucidating the redox reaction and oxygen diffusion within transition metal oxides. In addition, it enables tuning of the emergent physical properties of complex oxides, through strong interaction between the lattice and electronic degrees of freedom. In this communication, the electronic structure evolution of SrFeO_x epitaxial thin films is identified in real‐time, during the progress of reversible topotactic phase transformation. Using real‐time optical spectroscopy, the phase transition between the two structurally distinct phases (i.e., brownmillerite and perovskite) is quantitatively monitored, and a pressure–temperature phase diagram of the topotactic transformation is constructed for the first time. The transformation at relatively low temperatures is attributed to a markedly small difference in Gibbs free energy compared to the known similar class of materials to date. This study highlights the phase stability and reversibility of SrFeO_x thin films, which is highly relevant for energy and environmental applications exploiting the redox reactions.     

Lowering the Schottky Barrier Height by Graphene/Ag Electrodes for High‐Mobility MoS2 Field‐Effect Transistors

2D transition metal dichalcogenides (TMDCs) have emerged as promising candidates for post‐silicon nanoelectronics owing to their unique and outstanding semiconducting properties. However, contact engineering for these materials to create high‐performance devices while adapting for large‐area fabrication is still in its nascent stages. In this study, graphene/Ag contacts are introduced into MoS₂ devices, for which a graphene film synthesized by chemical vapor deposition (CVD) is inserted between a CVD‐grown MoS₂ film and a Ag electrode as an interfacial layer. The MoS₂ field‐effect transistors with graphene/Ag contacts show improved electrical and photoelectrical properties, achieving a field‐effect mobility of 35 cm² V^?1 s^?1, an on/off current ratio of 4 × 10⁸, and a photoresponsivity of 2160 A W^?1, compared to those of devices with conventional Ti/Au contacts. These improvements are attributed to the low work function of Ag and the tunability of graphene Fermi level; the n‐doping of Ag in graphene decreases its Fermi level, thereby reducing the Schottky barrier height and contact resistance between the MoS₂ and electrodes. This demonstration of contact interface engineering with CVD‐grown MoS₂ and graphene is a key step toward the practical application of atomically thin TMDC‐based devices with low‐resistance contacts for high‐performance large‐area electronics and optoelectronics.