低温烧结改性PbTiO3压电陶瓷制备工艺研究

研究了添加少量低熔物SiO2作烧结促进剂的的低温烧结改性PbTiO3压电陶瓷的制备工艺,确定出能充分挖掘其优良性能的较佳工艺参数。在此工艺扌制备的陶瓷具有低烧结温度、高压电活性、大压电各向异性、高机械品质因数等优点,可应用于叠层压电降压变压器、叠层压电陶瓷滤波器等叠层压电器件方面。     

基于位移放大机构的压电快速反射镜设计

针对压电陶瓷直驱式快反镜偏转角度受到压电陶瓷伸长量较小的限制,无法实现大转角的现状,设计了一款新型压电快反镜,采用二级杠杆式放大机构实现压电陶瓷微小位移的放大,并在放大机构上粘贴电阻应变片作为反馈传感器.实验结果表明,所设计的快反镜可实现大于50 mrad的机械偏转范围,同时闭环线性度优于0.5%,能够满足大范围、高精度光束指向的需求.     

压电分流阻尼的虚拟实现

提出压电分流阻尼技术的虚拟实现方法,用主动控制的方法来真实地模拟被动压电分流阻尼器的效果。利用压电分流阻尼系统的动力学基本方程设计反馈控制器,建立相应于LR串联分支电路的反馈控制结构,整个闭环控制系统稳定或渐进稳定。虚拟实现方法避免了大电感的要求,可以在线调节电感和电阻的数值以适应环境的变化,克服了物理压电分流阻尼器的两大缺陷。数值仿真结果表明,虚拟实现方法能够有效地控制连续结构的振动。     

六维力压电天平研制与静态性能测试研究

风洞天平是空气动力学试验的重要测力装置,针对压电天平动态响应速度快、跟随特性好、结构简单、量程范围大的特点,研制了一种可应用于风洞试验中动态气动荷载测量的压电天平.对压电天平的静态校准方法进行了研究,推导出其校准公式.在风洞天平校准台上,完成了压电天平的静态单分量校准与复合加载试验,得到压电天平的标定矩阵,压电天平的非线性误差和重复性误差分别为0.06%、0.19%,最大向间干扰1.94%.对试验结果进行误差分析,给出了压电天平测试系统的不确定度.试验结果表明:压电天平主要性能指标良好,满足测试精度要求.     

大行程压电微动台的有限元分析与实验

设计了一种基于尺蠖运动原理的大行程纳米级步距压电微动台,变传统单驱动器结构为双驱动器结构,采用"推-拉"接力运动原理,实现了大的驱动力与行程.利用有限元方法对压电微动台的结构和静、动态特性进行了研究.实验结果表明,压电微动台的运动范围为11 mm,稳定性好,载物力可以达到24.5 N,最小步距小于20 nm.     

铜-压电陶瓷复合型驱动器的制备及特性

将开有空腔的黄铜片与压电陶瓷通过导电胶粘合并固化获得了一种具有大位移量和一定负载能力的铜一压电陶瓷复合型驱动器,实验得到的压电常数d33超过2000pC／N、本文系统分析了该驱动器的压电性能和位移特性;讨论了驱动器几何尺寸对驱动性能的影响,结果表明：位于金属顶盖和压电陶瓷之间的空腔可以将压电陶瓷片的径向位移转换成整个结构的轴向位移并将之放大;随着铜片厚度的降低,驱动器的谐振频率明显下降,轴向位移则明显增加。     

大各向异性锑锰改性PbTiO3压电陶瓷制备工艺研究

实验研究了以（Ｍｎ１／３Ｓｂ２／３）＾４＋Ｂ位取代Ｔｉ＾４＋为特征的大各向异性改性ＰｂＴｉＯ３压电陶瓷制备工艺,通过详细研究工艺条件对改性ＰｂＴｉＯ３陶瓷性能的影响。确定了其较佳工艺参数,在优化的工艺条件下,该陶瓷具有高压电活性,大压电各向异性,小介电常数,低机械品质因素,在多种压电超声换能器的研制方面显出良好应用前景。     

压电扬声器在温州压电元件厂试制成功

压电扬声器是一种用压电原理制成的新颖产品。它的问世能使我国广大农村的广播事业更快的发展,使广大的贫下中农都能听到毛主席、党中央的声音。由于舌簧扬声器原材料耗用大,因之用压电扬声器来取代舌簧扬声器的意义更大。压电扬声器不但价廉物美,牢固可靠,     

夹层式压电换能器开路电压影响因素

为探明压电换能器开路电压随各影响因素的变化规律,从而为提高压电路面能量收集效果提供理论依据,采用压电陶瓷晶片PZT-5H及聚氨酯基板制备了夹层式压电换能器。通过室内振动加载试验,研究压电换能器开路电压在不同荷载水平、荷载频率、压电陶瓷晶片并联数量下的变化规律。在此基础上,制备了小尺寸压电路面结构模型,并通过移动加载试验分析面层类型和面层温度对埋置在结构内部的压电换能器开路电压的影响。结果表明:开路电压与荷载水平和荷载频率正相关,但开路电压增长速度随荷载水平和荷载频率的提高逐渐变缓,荷载水平直接影响压电陶瓷晶片应力大小,当施加荷载为5kN,加载频率为4Hz时,压电换能器开路电压稳定在9.44V;开路电压随压电换能器中压电陶瓷晶片并联个数增加而减小,压电陶瓷晶片个数增加,单个压电陶瓷晶片承受荷载变小,当并联个数由1个增加到3个时,开路电压下降了26.6%;不同类型的沥青混合料力学性能不同,AC-13面层下开路电压较AC-10和OGFC-13大,AC-13面层与压电换能器匹配效果较好;温度不仅影响沥青混合料的结构性能还影响压电陶瓷晶片工作性能,温度升高,沥青混合料结构性能变差,压电陶瓷晶片工作性能降低,开路电压降低。     

点缺陷正方晶格声子晶体的大尺寸压电陶瓷复合换能器

为了保证大尺寸夹心式压电陶瓷复合换能器的纵向工作效率,减少纵、横振动之间的强烈耦合,改善换能器前辐射端面的纵向位移分布均匀度,本文在大尺寸夹心式压电陶瓷复合换能器的前盖板上,加工了3行3列与换能器轴向平行的按正方晶格排列的二维空气圆柱孔,并通过改变3×3超元胞中心空气圆柱孔的半径来引入点缺陷,构造基于半径异常型点缺陷的二维正方晶格近周期声子晶体.该设计不仅可以利用晶体在径向的不完全带隙对大尺寸压电陶瓷复合换能器的横向振动进行抑制;还可以利用点缺陷的Anderson局域化特性,调控局域声场的强度和相位,进一步改善前盖板辐射面的位移分布均匀度;另外,本文分析了点缺陷空气圆柱孔的结构参数对换能器纵向共振频率以及纵向振动位移分布的影响规律.仿真结果表明,基于点缺陷声子晶体的大尺寸压电陶瓷复合换能器能够有效抑制换能器轴向的杂散模态、大幅优化辐射面纵向位移分布,改善大尺寸压电陶瓷复合换能器的性能.     

各向异性对非对称薄膜中的自旋波的影响

采用界面重标度(IR)方法〔1〕,研究了非周期性边界条件下,双层非对称铁磁薄膜中自旋波的本征值问题,并计入体单轴各向异性,讨论了其对非对称铁磁薄膜中自旋波色散关系以及其波形的影响.结果表明:体单轴各向异性对非对称铁磁薄膜中的自旋波的影响很大,情况也较复杂.具体来说,随着两层薄膜中某一层的体各向异性常数的增加,体模和相应层内的禁闭模均有所变化(包括数目和数值),在整个变化过程中,光学-光学界面模的数目不变,本征模能量随DA(体各向异性)的增加而线性减小,而且,体单轴各向异性对各种自旋波本征模的波形影响也很大.     

Global azimuthal seismic anisotropy and the unique plate-motion deformation of Australia

Differences in the thickness of the high-velocity lid underlying continents as imaged by seismic tomography, have fuelled a long debate on the origin of the 'roots' of continents. Some of these differences may be reconciled by observations of radial anisotropy between 250 and 300 km depth, with horizontally polarized shear waves travelling faster than vertically polarized ones. This azimuthally averaged anisotropy could arise from present-day deformation at the base of the plate, as has been found for shallower depths beneath ocean basins. Such deformation would also produce significant azimuthal variation, owing to the preferred alignment of highly anisotropic minerals. Here we report global observations of surface-wave azimuthal anisotropy, which indicate that only the continental portion of the Australian plate displays significant azimuthal anisotropy and strong correlation with present-day plate motion in the depth range 175-300 km. Beneath other continents, azimuthal anisotropy is only weakly correlated with plate motion and its depth location is similar to that found beneath oceans. We infer that the fast-moving Australian plate contains the only continental region with a sufficiently large deformation at its base to be transformed into azimuthal anisotropy. Simple shear leading to anisotropy with a plunging axis of symmetry may explain the smaller azimuthal anisotropy beneath other continents.     

不同衬底温度下Tb/Fe/Dy纳米多层膜超磁致伸缩性能研究

采用多靶磁控溅射仪在室温和衬底温度为300 ℃的条件下制备Tb/Fe/Dy纳米多层膜,研究其磁性能和超磁致伸缩性能.结果表明该纳米多层膜较TbDyFe单层膜有更明显的垂直磁各向异性和更大的矫顽力.尽管纳米多层膜样品具有垂直各向异性,但仍具有超磁致伸缩性能.特别是衬底温度为300 ℃的纳米多层膜样品,具有Laves相结构的TbDyFe纳米晶体析出,使得低磁场下磁致伸缩性能有了显著的提高.     

基于CoFe／Pd的自旋阀底电极中增强的垂直磁各向异性

采用磁控溅射方法制备了Pd（3nm）／CoFe（0．8nm）／纳米氧化层／CoFe（fnm）／Cu（4nm）／Pd（5nm）自旋阀底电极薄膜,并用振动样品磁强计对样品的磁性能进行了测量．研究结果表明：纳米氧化层的引入可以使电极薄膜的磁各向异性在退火后从面内转到垂直膜面方向,并且这种强烈的垂直磁各向异性在CoFe有效厚度为2nm时仍能保持．这种具有非多层膜结构、铁磁层较厚、热稳定性较高的底电极有利于基于自旋转移矩的垂直磁各向异性全金属赝自旋阀的发展．     

具有单离子各向异性场的键稀疏混合横向伊辛自旋系统的相图(英文)

本文在有效场理论的框架内研究了具有单离子各向异性场的键稀疏混合横向伊辛自旋系统的相图。重点给出了蜂窝晶格的相图。如果负单离子各向异性场参数不大且横场值较小,我们观察到在目前的系统中重入相变可能发生。横场对重入相变行为的影响在本文中也进行了讨论。     

V型件翻边成形的数值模拟

将Mindlin曲壳单元引入基于逐级更新的虚功率增率型原理，考虑板材的厚向各向异性，建立了大变形弹塑性有限元模型．对V型零件翻边成形进行了模拟，模拟和实验结果的比较证实了本模型的有效性．基于此模型，研究了零件张角、翻边部分初始长度以及材料各向异性参数和应变硬化指数对V型零件翻边的影响．结果表明，几何形状，尤其是零件张角，对V型零件翻边成形性具有决定性的影响．     

Anisotropy of thermal diffusivity in the upper mantle.

Heat transfer in the mantle is a key process controlling the Earth's dynamics. Upper-mantle mineral phases, especially olivine, have been shown to display highly anisotropic thermal diffusivity at ambient conditions, and seismic anisotropy data show that preferred orientations of olivine induced by deformation are coherent at large scales (>50 km) in the upper mantle. Thus heat transport in the upper mantle should be anisotropic. But the thermal anisotropy of mantle minerals at high temperature and its relationship with deformation have not been well constrained. Here we present petrophysical modelling and laboratory measurements of thermal diffusivity in deformed mantle rocks between temperatures of 290 and 1,250 K that demonstrate that deformation may induce a significant anisotropy of thermal diffusivity in the uppermost mantle. We found that heat transport parallel to the flow direction is up to 30 per cent faster than that normal to the flow plane. Such a strain-induced thermal anisotropy implies that the upper-mantle temperature distribution, rheology and, consequently, its dynamics, will depend on deformation history. In oceans, resistive drag flow would result in lower vertical diffusivities in both the lithosphere and asthenosphere and hence in less effective heat transfer from the convective mantle. In continents, olivine orientations frozen in the lithosphere may induce anisotropic heating above mantle plumes, favouring the reactivation of pre-existing structures.     

Inner-core shear-wave anisotropy and texture from an observation of PKJKP waves

Since the discovery of the Earth's core a century ago, and the subsequent discovery of a solid inner core (postulated to have formed by the freezing of iron) seismologists have striven to understand this most remote part of the deep Earth. The most direct evidence for a solid inner core would be the observation of shear-mode body waves that traverse it, but these phases are extremely difficult to observe. Two reported observations in short-period data have proved controversial. Arguably more successful have been studies of longer-period data, but such averaging limits the usefulness of the observations to reported sightings. We present two observations of an inner-core shear-wave phase at higher frequencies in stacked data from the Japanese High-Sensitivity Array, Hi-Net. From an analysis of timing, amplitude and waveform of the 'PKJKP' phase we derive constraints on inner-core compressional-wave velocity and shear attenuation at about 0.3 Hz which differ from standard isotropic core models. We can explain waveform features and can partially reconcile the otherwise large differences between core wavespeed and attenuation models that our observations apparently suggest if we invoke shear-wave anisotropy in the inner core. A simple model of an inner core composed of hexagonal close-packed iron with its c axis aligned perpendicular to the rotation axis yields anisotropy that is compatible with both the shear-wave anisotropy that we observe and the well-established 3 per cent compressional-wave anisotropy.     

Dynamical Suppression of Magnetic Tunneling

Introduction　　Macroscopicquantumphenomena(MQP)havebeeninvestigatedintensivelyformanyyears.AccordingtothepioneeringworksofCaldeiraandLeggett[1,2],ifthedissipationinteractionwiththeenvironmentwassmallenough,quantumtunnelingcouldtakeplaceonthemacroscopicscale.Overthelastfifteenyears,alotofexperimentalandtheoreticalworkhavebeendevotedtothisfield.Recently,owingmainlytothedevelopmentsoftechnologyinnanostructurephysics,manystudieshavefocusedonthenanometer-scalemagneticsystemswhichexhibitmacroscop…