Vibration of Nano Beam Induced by Ramp Type Heating

The non-Fourier effect in heat conduction and the coupling effect between temperature and strain rate, became the most significant effects in the nano-scale beam. In the present study, a generalized solution for the generalized thermoelastic vibration of a bounded nano-beam resonator induced by ramp type of heating is developed and the solutions take into account the above two effects. The Laplace transforms and direct method are used to determine the lateral vibration, the temperature, the displacement, the stress and the energy of the beam. The effects of the relaxation time and the ramping time parameters have been studied with some comparisons.

State-space approach to vibration of gold nano-beam induced by ramp type heating

In the nanoscale beam,two effects become domineering.One is the non-Fourier effect in heat conduction and the other is the coupling effect between temperature and strain rate.In the present study,a generalized solution for the generalized thermoelastic vibration of gold nano-beam resonator induced by ramp type heating is developed.The solution takes into account the above two effects.State-space and Laplace transform methods are used to determine the lateral vibration,the temperature,the displacement,the stress and the strain energy of the beam.The effects of the relaxation time and the ramping time parameters have been studied.

Bending of small-scale Timoshenko beams based on the integral/differential nonlocal-micropolar elasticity theory: a finite element approach

A novel size-dependent model is developed herein to study the bending behavior of beam-type micro/nano-structures considering combined effects of nonlocality and micro-rotational degrees of freedom. To accomplish this aim, the micropolar theory is combined with the nonlocal elasticity. To consider the nonlocality, both integral (original) and differential formulations of Eringen’s nonlocal theory are considered. The beams are considered to be Timoshenko-type, and the governing equations are derived in the variational form through Hamilton’s principle. The relations are written in an appropriate matrix-vector representation that can be readily utilized in numerical approaches. A finite element (FE) approach is also proposed for the solution procedure. Parametric studies are conducted to show the simultaneous nonlocal and micropolar effects on the bending response of small-scale beams under different boundary conditions.

Dynamic modeling of preloaded size-dependent nano-crystalline nano-structures

The vibration behavior of size-dependent nano-crystalline nano-beams is investigated based on nonlocal, couple stress and surface elasticity theories. A nano- crystalline nano-beam is composed of three phases which are nano-grains, nano-voids, and interface. Nano-voids or porosities inside the material have a stiffness-softening impact on the nano-beam. A Eringen＇s nonlocal elasticity theory is applied in the analysis of nano-crystalline nano-beams for the first time. Residual surface stresses which are usually neglected in modeling nano-crystalline nano-beams are incorporated into nonlocal elasticity to better understand the physics of the problem. Also, a modified couple stress theory is used to capture rigid rotations of grains. Applying a differential transform method （DTM） satisfying various boundary conditions, the governing equations obtained from the Hamilton＇s principle are solved. Reliability of the proposed approach is verified by comparing the obtained results with those provided in the literature. The effects of the nonlocal parameter, surface effect, couple stress, grain size, porosities, and interface thickness on the vibration characteristics of nano-crystalline nano-beams are explored.

Road Performances of Mesoporous Nano-silica Modified Asphalt Binders

The objective of this paper was to find new modifier to improve the aging resistance and low temperature cracking resistance of asphalt. To investigate the aging resistance of modified asphalt binders, mesoporous nano-silica（doping Ti^（4＋）） was used as a asphalt modifier. Some physical properties including penetration, ductility, and softening point of asphalt were analyzed with RTFO（Rotating thin film oven） aging and ultraviolet aging. Moreover, the performances of high and low temperature of modified asphalt binders with pressure aging were tested by dynamic shear rheometer（DSR） test and bending beam rheometer（BBR） test. These results showed that the penetration decreased, low temperature ductility, and softening point increased when adding mesoporous nano-silica to base asphalt. After ultraviolet radiation aging, the penetration loss and ductility loss of modified asphalt decreased than that of original asphalt, the increase of softening point was also significantly reduced than that of base asphalt. Furthermore, The test results of DSR and BBR showed that the G＊sinδ and creep modulus‘s＇ of pressure aged asphalt decreased, but the creep rate ‘m＇ increased. It can be concluded that the aging resistance and cracking resistance of modified asphalt are improved by adding mesoporous nano-silica, especially the doping of Ti^（4＋） could improve the aging resistance obviously.

Research on the Adsorption of Methylene Blue with Rice Husk Ash Aided by Ion Beam Etching Technique

[Objective] The aim was to study the mechanism of the removal effect of methylene blue(MB) by rice husk ash(RHA).[Method] The effects of contact time and pH on the adsorption of MB by rice husk ash were investigated,and the mechanism was discussed.[Result] RHA exhibited a remarkable ability on the adsorption of MB.The process of adsorption reached the equilibrium after 30 min,at about pH 9.The adsorption effect was explored with the aid of ion beam etching technique,which displayed that there were two main adsorption manners.One was the electrostatic interactions,through which the negatively charged RHA could adsorb the positively charged MB,the other was the porous effect due to the huge specific surface area of the micro/nano-scale porous silica in RHA,and MB could be adsorbed and deposited into the pores.[Conclusion] RHA could be used in the treatment of textile wastewater.Ion beam technology might be used as an effective way to investigate the adsorption effect.

原子力显微镜-扫描电子显微镜共定位表征系统的研发与应用

微纳加工过程中,常有样品需要进行聚焦离子束(FIB)溅射、切割,扫描电子显微镜(SEM)以及原子力显微镜(AFM)表征,而这三类仪器都需要将样品固定在样品台上才可测试,固定不佳会影响表征结果.但固定好的样品在不同仪器之间转移、拆卸、再固定的过程中极易受到破坏.基于以上问题,设计了AFM-SEM-FIB样品共定位系统,可实现样品在此三种仪器之间的无损转移及共定位,避免珍贵样品破坏及目标丢失,以及解决AFM扫描无法控制方向、迅速调整位点等问题.在微纳表征中有优异的表现,系统已被开发成产品并量产销售.

纳米隔热材料在板坯加热炉水梁中的应用研究

针对新型纳米绝热保温材料在高温板坯加热炉的应用,开展了传统水梁包扎方式与新型纳米隔热包扎方式的对比研究。通过数值仿真分析对不同方案隔热效果及温度分布进行了预测,并搭建水冷实验系统对采用不同包扎方式的水梁散热量进行测试分析。测试结果表明随着炉温逐步升高,纤维隔热材料的导热系数快速上升,常规纤维隔热水梁散热快速增加,而纳米隔热材料的导热系数增加较小,故此纳米隔热水梁的散热增加较为缓慢,两种方案散热量的差距随着炉温升高而逐渐增大。在此基础上开展了工程应用,应用效果与数值仿真及实验研究数据吻合良好。工程应用对比结果表明,纳米隔热水梁相对传统水梁包扎方案可实现水梁区域能耗降低25%,具有较好的经济和生态效益。

矢量涡旋光场在激光微纳加工中的应用

矢量光场领域在过去20年出现了众多重要进展。考虑到多篇综述介绍了矢量光场产生方法以及调控技术,作者仅以矢量涡旋光场为线索总结了其在激光减材、改性以及增材等微纳加工领域的典型应用,回顾了矢量涡旋光在材料表面和内部的微纳结构加工、光存储以及立体微结构光刻等应用中的部分关键进展。详细介绍了基于定制光场的图案化光致表面周期结构以及立体微结构快速双光子光刻的原理与技术。最后,总结了矢量涡旋光场在激光微纳加工中的优势与挑战,展望了其在未来将赋能更多复杂应用。

一维纳米准晶层合梁的非局部振动、屈曲与弯曲研究

基于非局部理论,建立了一维纳米准晶层合简支深梁模型,研究了其自由振动、屈曲行为及其弯曲变形问题.采用伪Stroh型公式,导出了纳米梁的控制方程,并通过传递矩阵法获得简支边界条件下纳米准晶层合梁固有频率、临界屈曲载荷及弯曲变形广义位移和广义应力的精确解.通过数值算例,分析了高跨比、层厚比、叠层顺序及非局部效应对一维纳米准晶层合简支梁固有频率、临界屈曲载荷和弯曲变形的影响.结果表明:固有频率和临界屈曲载荷随着非局部参数增大而减小;外层准晶弹性常数更高时,固有频率和临界屈曲载荷更大;叠层顺序对纳米准晶梁的力学行为有较大影响.所得的精确解可为纳米尺度下梁结构的各种数值方法和实验结果提供参考.

采集人体能量的压电能量收集器研究进展

采集人体能量的压电能量收集器具有可持续性、便携性、环保型和经济性等优势,已引起了人们的广泛关注。该文综述了压电能量收集器在人体能量采集领域的最新研究进展,包括用于人体能量采集的压电能量收集器的设计、更适用于穿戴或植入的压电材料的选择、以及新工艺对人体压电能量收集器性能的改善等。在传统能源日益匮乏的今天,人们对能量收集器的环保性以及可自供能的穿戴设备提出了更高的要求,未来的人体用压电能量收集器将面临更多的机遇与挑战,应着眼于新材料、新技术、新工艺的开发,推动压电能量收集器的发展,使其能更好地适应不同的应用,提高人体能量收集效率。

波形梁钢护栏纳米锌合金防腐涂层评测研究

热镀锌因其优秀的抗腐蚀性能、广泛的环境适应性和良好的经济性被广泛用于交通工程钢构件的防腐蚀处理,但该技术存在高能耗、高污染、镀件尺寸受限、工人劳动环境差等缺点。本研究采用理论分析、试验室测试及工程现场评测相结合的方法,对新型纳米锌合金防腐涂层材料的防腐性能进行评估、测试,并在外观质量、与金属基体附着性、耐盐雾性能方面与传统热镀锌涂层进行比较,结果表明:新型纳米锌合金涂层外观质量良好、成膜致密、涂层厚度均匀,具有优秀的抗腐蚀能力,在国家“双碳”政策背景下,有望成为替代热镀锌涂层最具潜力的新型防腐处理技术。

考虑非局部效应的纳米梁非线性振动

以弹性理论为基础,建立考虑非局部效应和轴向非线性伸长的两端固支纳米梁物理模型,推导其动力学方程,计算得到考虑非局部效应和轴向非线性纳米梁的固有频率,研究考虑非局部效应的纳米梁主谐波共振响应。数值结果表明,非局部效应对两端固支纳米梁固有频率和幅频关系均有影响。

聚焦离子束系统原理、应用及进展

聚焦离子束纳米加工系统,具有传统加工工具无可比拟的优势而逐渐成为新一代微纳分析、加工的工具,在微纳米加工、操纵以及器件的研制等方面具有重要应用。本文介绍了聚焦离子束系统的内部结构和工作原理,探讨了该系统的扩展功能、应用及发展前景。

基于电子隧道效应的纳米梁非线性振动控制

以Euler-Bornoulli梁为振动模型,提出了基于电子隧道效应的纳米梁非线性振动控制方法。隧道效应电流具有高灵敏性、高精确性的特点,可用于检测纳米梁的振动信号。应用位移和速度电压反馈控制器,考虑时滞反馈影响,建立基于隧道效应的纳米梁时滞非线性振动控制方程,应用多尺度方法得到纳米梁主共振的幅频响应方程。研究了直流和交流激励电压、控制增益和时滞等参数与纳米梁振动非线性之间的关系,分析了减弱系统非线性、增强系统稳定性的影响因素。研究结果表明,通过选择合适的控制增益和时滞,适当减小直流和交流激励电压幅值可以降低振动的非线性,提高系统的稳定性。

电子束辐照制备纳米银(英文)

在水溶液中,常温常压下不加入任何催化剂,用电子加速器辐照作为一种新的方法可以成功制备出纳米银。我们利用XRD、TEM、UV、DSC来分别表征材料的结构、形貌、大小、光学特性以及材料的熔点。TEM图像证明颗粒大小为30nm,这与XRD实验通过Scherer理论公式计算的结果相一致。

纳米二氧化钒薄膜的制备及红外光学性能

采用双离子束溅射方法在Si3N4/SiO2/Si基底表面沉积氧化钒薄膜,在氮气气氛下热处理获得二氧化钒薄膜.利用X射线衍射(XRD)、扫描电子显微镜(SEM)和X射线光电子能谱(XPS)研究了热处理温度对氧化钒薄膜晶体结构、表面形貌和组分的影响,利用傅里叶变换红外光谱(FT-IR)对二氧化钒薄膜的红外透射性能进行了测试分析.结果表明,所制备的氧化钒薄膜以非晶态V2O5和四方金红石结构VO2为主,经400℃、2h热处理后获得了(011)择优取向的单斜金红石结构纳米VO2薄膜,提高热处理温度至450℃,纳米结构VO2薄膜的晶粒尺寸减小.FT-IR结果显示,纳米VO2薄膜透射率对比因子超过0.99,高温关闭状态下透射率接近0.小晶粒尺寸纳米VO2薄膜更适合在热光开关器件领域应用.

扫描电镜测量纳米尺度的影响因素

本文从纳米尺度测量、长度标准器选择、扫描电镜参数选取入手,在不同的试验条件下,根据GB/T20307-2006对纳米级尺度进行测量,系统地研究了加速电压、束斑大小、工作距离以及象限位置对纳米级TiO2、ZnO、C纳米管测量结果的影响。通过分析讨论,提出了提高纳米尺度测量精度的最佳方案。

带孔纳米单晶铜悬臂梁弯曲的分子动力学模拟

应用分子动力学方法模拟了带孔纳米单晶铜悬臂梁的弯曲过程。通过一端固定另一端施加横向作用力驱使原子运动,得到纳米单晶铜悬臂梁弯曲的变形图。对其不同于宏观连续介质理论的位移-载荷曲线进行分析,给出了合理的解释。结果表明:纳米尺度下的微缺陷对纳米单晶铜悬臂梁的性能具有明显的影响;尺寸效应和表面效应的影响,以及位错滑移和弛豫的综合作用,使得纳米单晶铜悬臂梁在纳米尺度下表现出与宏观尺度下不同的力学特性。

电子束辐照诱发纳米Al/Al_2O_3复合颗粒中Al非晶化的纳米束斑原位分析

在 ＨＦ－２０００场发射电镜上完成了Ａｌ／Ａｌ２Ｏ３颗粒的辐照诱发Ａｌ非晶化转变和原位观察。