Tensoresistive effect in thin metal films in the range of elastic and plastic strain

The tensoresistive effect in single-layer Cr, Fe, Mo, Ni, and Pd films and double-layer Fe/Cr, Cu/Cr, Ni/Cr, and Pd/Fe films is studied in the range of elastic and plastic strain. The influence of the surface and grain-boundary scatterings of electrons on strain sensitivity S ^ρ of the single-layer films is analyzed. Sensitivities Sρ of the single- and double-layer films to elastic and plastic strains are compared. It is found that the volume and grain-boundary scatterings of electrons are main contributors to S ^ρ in the Fe/Cr film system. Grain-boundary scattering is equally effective under elastic and plastic strain, as judged by a high coefficient of electron grain-boundary scattering (R ≌ 0.36–0.41).     

Preparation of hard magnetic materials in thin film form

We report on the preparation, by means of pulsed laser ablation deposition, of trilayers of nominal composition Cr/SmCo₅/Cr//Si with thicknesses in the order of 250/240/125 nm, respectively. According to the results of the structural, chemical and magnetic characterizations performed in our as-deposited samples, the Sm–Co layer was structurally amorphous, exhibited abrupt compositional interfaces with the capping and buffering layers, and coercivities of a few hundreds of Oe. Magnetic hardness was developed upon submitting the samples to current anneals under vacuum at temperatures in the range of 540–670 °C. The hardening process was followed in detail by correlating the phase distribution, the nature of the interlayer atomic diffusion processes, the occurrence of textures and the temperature dependence of the coercive force. From our results we conclude about (i) the occurrence of a large degree of Co diffusion/segregation, which results in the detection, from the diffraction and magnetometric results, of the presence of CoCr alloys in the treated samples, and (ii) the close correlation, evidenced from the fits of the temperature dependence of the coercive force to the micromagnetic model, between the coercivity optimization and the crystallinity enhancement of the SmCo₅ grains.     

塑料光学元件的清洗、镀膜和胶合

各种塑料光学元件在光学系统中的应用越来越广泛。作为光学元件,必然涉及清洗、镀膜和胶合等工艺技术问题。本文就塑料光学元件的这三个技术作一介绍。     

Al-Cu多晶锯齿形屈服现象中的尺度效应

对Al-Cu多晶合金锯齿形屈服现象中各特征物理量(应力跌幅、跌落时间和再加载时间)随应变演化的规律进行了系统研究，讨论了不同厚度试件演化结果的区别.同时，这种尺度效应还表现为相同加载条件下1，2mm厚度试件与3mm厚度试件的Portevin-Le Chrtelier (PLC)类型的差异.利用非线性时间序列分析的方法对前者在相空间中吸引子的几何特性进行了描述，并通过主分量分析的方法初步判定其中存在着混沌行为.后者演化过程中应力跌落事件按跌落幅度统计分布符合幂律规律，具有自组织临界性特征.最后，借助自组织 关键词： 锯齿形屈服 尺度效应 Al-Cu合金     

Molecular dynamic study of temperature dependence of mechanical properties and plastic inception of CoCrCuFeNi high-entropy alloy

Molecular dynamics simulations are performed to study mechanical characteristics and homogeneous plastic inception of CoCrCuFeNi high-entropy alloy at various temperatures under uniaxial tension. It is found that the elastic modulus and ultimate tensile strength increase with temperature decreasing. A notable softening effect is observed at the elastic deformation stage caused by the decrease of the interatomic force gradient. Extrinsic stacking faults and deformation twins are extensively observed, which are formed via intrinsic stacking faults overlap.     

A framework for statistical modelling of plastic yielding initiated cleavage fracture of structural steels

The well established consensus that cleavage fracture is preceded by plastic deformation in structural steels implies that plastic yielding is the threshold stress state for a volume element to incur cleavage fracture. An accurate compliance with this consensus underlies the normalisation of cumulative cleavage fracture probability and the justification of constraint effect on cleavage fracture. These understandings lead to the proposal of a framework for statistical modelling of cleavage fracture in structural steels. The framework takes the spatial microcrack distribution into account to formulate the cumulative failure probability model that allows for a pertinent physical interpretation of Weibull statistics, and derives the fracture probability of an elemental volume in conformity with the yielding condition from a set of commonly adopted microcrack size or strength distributions. Alternative approaches to calibrating model parameters are suggested based on frequency analysis of brittle particles as cleavage initiators and on statistical analysis of cleavage fracture stress. The strict adherence to plastic yielding as a prerequisite to cleavage fracture also reveals the probabilistic nature of notch brittleness and ductile-to-brittle transition behaviour.     

塑料微球表面制备聚乙烯醇涂层研究进展

在聚苯乙烯（PS）-聚乙烯醇（PVA）-碳氢聚合物（CH）三层球的设计中制备PVA涂层的方法主要包括乳液微封装法、炉内成球涂层法、浸(旋)涂法、界面缩聚法及喷涂法等,前三种方法目前最为常用。总结了前三种制备PVA涂层方法的优缺点及目前的研究和制备现状。乳液微封装法适合于500 m以下小尺寸双层球的制备,具有微球成活率高、产品质量较好等优点,但制备过程受人为因素影响较大,且不易制备大直径双层球。炉内成球涂层法也适用于小尺寸双层球的制备,其制备周期短,但液滴发生器的设计苛刻,PVA层的均匀性差,且不易制得较大尺寸的双层球。浸（旋）涂法可制备1000 m以上的大直径双层球,但该方法中影响PVA涂层铺展的因素较多,得到的PVA涂层均匀性较差,且涂层很薄。     

塑料微球表面制备聚乙烯醇涂层研究进展

在聚苯乙烯（PS）-聚乙烯醇（PVA）-碳氢聚合物（CH）三层球的设计中制备PVA涂层的方法主要包括乳液微封装法、炉内成球涂层法、浸(旋)涂法、界面缩聚法及喷涂法等,前三种方法目前最为常用。总结了前三种制备PVA涂层方法的优缺点及目前的研究和制备现状。乳液微封装法适合于500 m以下小尺寸双层球的制备,具有微球成活率高、产品质量较好等优点,但制备过程受人为因素影响较大,且不易制备大直径双层球。炉内成球涂层法也适用于小尺寸双层球的制备,其制备周期短,但液滴发生器的设计苛刻,PVA层的均匀性差,且不易制得较大尺寸的双层球。浸（旋）涂法可制备1000 m以上的大直径双层球,但该方法中影响PVA涂层铺展的因素较多,得到的PVA涂层均匀性较差,且涂层很薄。     

Nanoindentation of a hard ceramic coating formed on a soft substrate

The hardness and Young’s modulus of the thin hydroxyapatite-based coatings deposited by RF magnetron sputtering onto magnesium alloy, titanium, and steel substrates are studied. As the penetration depth increases, the hardness and Young’s modulus of these coatings are found to tend toward the values that are characteristic of the substrates. It is shown that the difference between the values of hardness and Young’s modulus at small penetration depths (h < 80–100 nm) can be caused by the difference between the physicomechanical properties inside the coatings and that this difference at large penetration depths (h > 100 nm) can be induced by an additional effect of the strength properties of the substrate material.     

Imperfect antireflection coating effect reduction schemes for birefringent interleaver and optical communication systems

Chromatic dispersion (CD) caused by an imperfect antireflection coating is a great concern for optical engineers, and different techniques have been proposed to reduce CD in optical devices. In this article, we investigate two popular CD reduction techniques used in birefringent interleaver manufacturing and their effects on performance improvement of optical communication systems. Our results show that some CD reduction scheme bringing about a smaller CD ripple amplitude does not necessarily guarantee better system performance. This result can be used as a guideline for optical engineers working on reducing CD caused by an imperfect antireflection coating.     

Observation of plastic deformation in TiAlCN/a -C ceramic nanocomposite coating

Extensive plastic deformation of titanium aluminum carbonitride/amorphous carbon nanocomposite coating at room temperature was observed in this study. Nanoindentation measurement showed that the coating hardness was 24.4 GPa with the plasticity of 57.6%. The critical load of 1.3 m coating in scratch test was beyond 100 N. The depth of the 100 N scratch track identified by microstylus profilometer was 6.7 m, while the thickness of the coating in the center of the scratch track observed by scanning electron microscopy was 0.4 m, which is only about one third of that for the as-deposited coating. The amorphous carbon with sp² hybrid and -bonding is proposed to account for this unique plasticity. PACS 81.15.Gh; 81.07.Bc     

Rotations of material in the shearing plastic deformation of thin layers

A study was made of the profile of the middle layer of three-layer zinc-silver-zinc specimens after plastic deformation of the specimens on a Bridgman shear-testing machine under pressure. Kinks and folds are formed in the middle layer as a result of the deformation due to the development of rotational motions in the deformed material. The angle of rotation may amount to several tens of degrees. The reasons for the rotations are internal nonuniformities associated with the structure of the specimens and external nonuniformities due to a difference in the frictional forces on local sections of the specimen-die contact surfaces.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 78–82, February, 1989.     

The CIDNP effect in plastic crystals

The CIDNP effects in the photolysis reactions of some aldehydes and ketones (including linear, aromatic and cyclic) in plastic crystals of cyclohexane have been discovered and studied. In going from liquid to solid solutions, the change of polarization sign is observed for some substances investigated. The CIDNP effect for a simple model for a relative motion of atoms of radicals possessing spin density (translational diffusion in a restricted volume) has been calculated. The results observed are interpreted in the framework of the radical pair mechanism of CIDNP effect formation.     

基于塑料镜片防水加硬抗老化光学薄膜的研制

为了解决现有光学塑料镜片表面易划伤、高温时容易发生膜裂的问题,选取机械性能稳定的Ti₃O₅、SiO₂作为高、低折射率材料,依据光学薄膜理论,采用TFCalc软件设计膜系,通过电子束加热蒸发和离子源辅助沉积薄膜,在膜系的最外层用电阻加热法镀制防水膜。通过选择新材料SV-55作为连接层,增强了塑料镜片与膜层的附着力,解决了膜系与塑料镜片膨胀系数不匹配的问题,提高了塑料镜片的抗温能力。通过优化工艺参数,得到400 nm~700 nm反射率R≤1%的绿色减反膜。测试结果显示,研制的薄膜具有耐摩擦、抗老化、防水和防油污的特性。     

Ground states in classical lattice systems with hard core

In this paper we prove the existence of translation invariant ground states in an infinite classical lattice system with hard core and give a characterization of their support. Some examples are discussed.     

Nanoscale morphology for high hydrophobicity of a hard sol-gel thin film

It is challenging to obtain a hydrophobic smooth coating with high optical and mechanical properties at the same time because the hydrophobic additives are soft in nature resulting in reduced hardness and durability. This paper reports a durable hydrophobic transparent coating on glass fabricated by sol-gel technology and a low volume medium pressure (LVMP) spray process. The sol-gel formula consists of a pre-linked hydrophobic nano-cluster from hydroxyl-terminated polydimethylsiloxane, titanium tetraisopropoxide and a silica-based sol-gel matrix with silica hard fillers. Polydimethylsiloxane (PDMS) is uniformly distributed throughout the coating layer providing durable hydrophobic property. Mechanical properties are achieved by the hard matrix and hard fillers with the nano-structures. Due to the surface nano-morphology, a high degree of hydrophobicity was maintained with only 10 vol.% PDMS, while the hardness and abrasion resistance of the coatings were not significantly compromised. Chemical analyses by FTIR confirmed the uniform distribution of the PDMS and surface morphology analyses by atomic force microscopy (AFM) displayed the nano-surface structures that enhanced the hydrophobicity. The special surface nanostructures can be quantified using surface Kurtosis and ratio between asperity peak height to distance between peaks. The LVMP process influences the spray droplet size resulting in different surface structures.     

The memory of thin polymer films generated by spin coating

The European Physical Journal E - The interstitial tumor microenvironment is composed of heterogeneously organized collagen-rich porous networks as well as channel-like structures and interfaces...