金属颗粒复合介质的光学双稳态

本文应用平均场近似和谱表示方法研究了线性金属颗粒嵌入弱非线性电介质基质的复合介质的光学双稳行为．研究结果表明,光学双稳的阈值强度与金属分量的体积浓度密切相关,并且存在着一个体积浓度的阈值,一旦超过这一阈值．双稳态将消失．本文还研究了组分的介电常数以及三阶非线性极化率对光学双稳特性的影响．     

单电子存储器存储时间的Monte Carlo模拟

建立了多隧道结单电子存储器存储时间的Monte Carlo模拟模型,重点分析了器件的工作温度、隧道结电容和隧道结数目等因素对单电子存储器存储时间的影响,给出了用Monte Carlo模拟方法模拟单电子存储器存储时间的模拟流程和方法。计算结果表明,当温度越低、隧道结电容越小、电路中隧道结的数目越多时,存储时间越长,器件工作越稳定。     

液晶盒结构和温度对液晶光学双稳态的影响

在金属膜反射镜组成的Ｆａｂｒｙ－Ｐｅｒｏｔ腔内，放置５ＣＢ或８ＣＢ液晶，当Ｈｅ－Ｎｅ激光通过时产生了光学双稳态现象。研究了液晶温度和Ｆ－Ｐ腔结构对双稳态的影响。     

高储能密度钛酸钡基复合材料

 高介电常数介电材料在储能方面的特殊作用使其在电工、电子技术领域有着重要的应用。随着电子工业的发展,高储能密度介电材料受到越来越多的关注,出现了一些新型的高储能密度介电材料。高储能密度介电材料具有高的介电常数和击穿强度,其发展的关键是提高储能密度。本文对近年来高储能密度介电材料的研究发展进行了概述,主要讨论了通过对钛酸钡的改性(即掺杂改性、表面包覆改性和复合材料制备)来提高介电材料的储能密度。分析了钛酸钡/聚合物复合材料的制备方法及其介电性能的影响因素,其中,陶瓷填料和聚合物基体2相界面的相容性是复合材料介电性能的重要影响因素。同时,指出了解决BaTiO₃粒子在聚合物基体中的分散问题、填料和聚合物基体的选择以及制备过程中工艺条件的控制都是研究兼具高介电强度和高介电常数复合材料的发展方向。     

High Resolution Acoustic Microscopy with Low Frequency and Its Applications in Analysis of Ferroelectrics

Ferroelectrics have spontaneous polarization, which can be oriented along with electric field and show high dielectric constant, high switching speed, nonvolatile memory character and large capacity memories on a given silicon wafer. Large-scale manufacturing is presently underway to incorporate ferroelectric materials as storage and bypass capacitors in IC circuitry. Nondestructive observation of domain structure of ferroelectrics, dynamic behavior under external field and related phenomena is becoming sig...     

Quantum tunnelling of the magnetization in a monolayer of oriented single-molecule magnets

A fundamental step towards atomic- or molecular-scale spintronic devices has recently been made by demonstrating that the spin of an individual atom deposited on a surface, or of a small paramagnetic molecule embedded in a nanojunction, can be externally controlled. An appealing next step is the extension of such a capability to the field of information storage, by taking advantage of the magnetic bistability and rich quantum behaviour of single-molecule magnets (SMMs). Recently, a proof of concept that the magnetic memory effect is retained when SMMs are chemically anchored to a metallic surface was provided. However, control of the nanoscale organization of these complex systems is required for SMMs to be integrated into molecular spintronic devices. Here we show that a preferential orientation of Fe(4) complexes on a gold surface can be achieved by chemical tailoring. As a result, the most striking quantum feature of SMMs-their stepped hysteresis loop, which results from resonant quantum tunnelling of the magnetization-can be clearly detected using synchrotron-based spectroscopic techniques. With the aid of multiple theoretical approaches, we relate the angular dependence of the quantum tunnelling resonances to the adsorption geometry, and demonstrate that molecules predominantly lie with their easy axes close to the surface normal. Our findings prove that the quantum spin dynamics can be observed in SMMs chemically grafted to surfaces, and offer a tool to reveal the organization of matter at the nanoscale.     

锂离子电池研究进展以及重庆市的发展现状和前景

锂离子电池与其他二次电池相比,具有比能量大、自放电小、质量轻、无记忆效应和环境友好等优点,因此决定了其在电动汽车、存储电源等方面极具发展前景;通过对锂离子电池正极和负极材料等关键性技术的研究进展进行综述,进而分析了重庆市锂离子电池行业现状;指出了目前重庆市锂离子电池行业存在的问题并提出了解决问题的建议;最后阐述了重庆市发展锂电产业的优势和前景。     

原位聚合-热膨胀制备聚苯胺/膨胀石墨复合物及导电性能研究

以-100目(孔径0.254 mm)低温可膨胀石墨为石墨固体膨胀剂,采用原位聚合-热膨胀技术制备了聚苯胺/膨胀石墨复合物,并对聚苯胺/膨胀石墨复合物进行了形貌和结构表征.同时,对聚苯胺/膨胀石墨复合物的导电性能进行了研究.结果显示,聚苯胺/膨胀石墨复合物颗粒具有蠕虫状形貌和聚苯胺包覆在膨胀石墨上的结构,其膨胀体积为10.0 mL/g;实验结果表明,反应时间和反应温度对聚苯胺/膨胀石墨复合物的导电率有影响.     

Unusual phase transitions in ferroelectric nanodisks and nanorods

Bulk ferroelectrics undergo structural phase transformations at low temperatures, giving multi-stable (that is, multiple-minimum) degenerate states with spontaneous polarization. Accessing these states by applying, and varying the direction of, an external electric field is a key principle for the operation of devices such as non-volatile ferroelectric random access memories (NFERAMs). Compared with bulk ferroelectrics, low-dimensional finite ferroelectric structures promise to increase the storage density of NFERAMs 10,000-fold. But this anticipated benefit hinges on whether phase transitions and multi-stable states still exist in low-dimensional structures. Previous studies have suggested that phase transitions are impossible in one-dimensional systems, and become increasingly less likely as dimensionality further decreases. Here we perform ab initio studies of ferroelectric nanoscale disks and rods of technologically important Pb(Zr,Ti)O3 solid solutions, and demonstrate the existence of previously unknown phase transitions in zero-dimensional ferroelectric nanoparticles. The minimum diameter of the disks that display low-temperature structural bistability is determined to be 3.2 nm, enabling an ultimate NFERAM density of 60 x 10(12) bits per square inch-that is, five orders of magnitude larger than those currently available. Our results suggest an innovative use of ferroelectric nanostructures for data storage, and are of fundamental value for the theory of phase transition in systems of low dimensionality.     

外电场作用下向列相液晶的光学双稳态

将Ｈｅ－Ｎｅ激光和外电场同时作用在Ｆａｂｒｙ－Ｐｅｒｏｔ腔内的向列相液晶（８ＣＢ，５ＣＢ）上，实现光学双稳态。获得双稳的最大输出光强，开启光强与外电场强度关系，同时首次获得双稳特性与电场频率的关系。     

应变调控柔性电子器件磁电性质的研究进展

柔性电子器件具有独特的形状可塑性,因而引起了人们极大的研究热情.柔性电子器件在未来或将成为下一代电子器件的重要分支,在电子显示、二极管、生物医疗器件、太阳能电池等领域有着广阔的发展前景.近些年,许多研究人员将柔性技术与自旋电子学相结合,开始探索应变对于生长在柔性衬底上的磁电异质结磁电性质的影响,通过改变柔性衬底的曲率等手段调控器件的磁电效应.相关基础研究为磁存储器、磁传感器、非易失性阻变存储器等电子器件的研究开辟了新思路.     

电化学体系中非连续型振荡的诱发

根据非连续型振动与慢流型，双稳态现象之间的内在联系，讨论了演化机制可出现多定态分支的电极反应体系，因外控状态参量慢变化导致非连续型电化学振荡的可能性。模型研究表明，适当的外电路阻抗或反应体系温度控制的热补偿机制的存在，可能诱发该类振荡，从而为抑制或诱发利用该类振荡提供了一条可能的途径。     

多铁性异质结研究进展

多铁异质结中的磁电耦合效应是凝聚态物理和材料物理的研究热点之一.相比单相的多铁材料,多铁异质结中界面处的自旋、电荷、轨道以及晶格之间存在着复杂的相互作用,导致出现一些新的物理现象,使得其在新一代的存储器、传感器、微波等领域中具有重要的应用前景.文章介绍近年来在多铁异质结方向取得的进展,着重介绍实现电场对磁性控制的场效应、应变效应、交换偏置效应等,以及磁场对多铁性的调控,从而获得很大的磁电耦合效应;分析了多铁隧道结及其磁电耦合效应,其集成了传统铁电隧道结和铁磁隧道结的优势,可大幅度提高单个存储单元存储状态,从而提高存储密度.最后提出当前面临的问题和对未来的展望.     

SiCp/ZL102复合材料及其压铸件耐磨性能研究

该文针对制约颗粒增强铝基复合材料应用的关键问题，提出运用压力铸造使其近终成型。在成功制备SiCp／ZL102压铸件的基础上，系统研究了基体合金、复合材料铸锭及其压铸件的耐磨性能。研究结果表明，复合材料的耐磨性能优于基体合金，压铸成型后，压铸件的耐磨性能显著优于复合材料铸锭，将压铸工艺应用于金属基复合材料的成型，能够有效扩大颗粒增强金属基复合材料的应用范围。     

Fe-C-MoS2/CuSn合金基复合材料的研究

应用粉末冶金技术制备了烧结Fe-C-MoS2/CuSn合金基减摩复合材料,对其组织结构和机械物理性能进行了研究.结果表明以CuSn合金为基体保证了材料的导电性.CuSn合金的强度大于混合同种金属元素烧结材料的强度.CuSn合金与Fe润湿性好,促进了烧结合金化,因而大幅度提高了材料的强度、硬度、冲击韧性.C以游离状态存在于基体中,其膨胀系数大于基体材料,起到了减摩作用.MoS2均匀分布在基体中,明显地起到了高温减摩作用.其中当Fe(质量分数)增加到15%时,冲击韧性达20.6 J/cm2,抗拉伸强度为163.2 MPa,布氏硬度为53.8,达到和超过了TB/T1842.1-2002电力机车粉末冶...     

碳纳米管表面电荷电分布及尖端电场研究

碳纳米管具有一些特殊的物理性质，其中潜藏着重要的技术价值。从理论上具体研究了金属型碳纳米管周围的电势分布、纳米管表面电荷分布及其尖端附近的电场强度等静电特性，结果显示长径比小的碳纳米管尖端处所集聚电荷密度的相对值大，而长径比大的碳纳米管尖端处所集聚电荷密度的绝对值大，并且碳纳米管的尖端电场强度有很大的加强。这对理论上进一步探索碳纳米管的场发射机制有积极意义。     

新戊二醇/海泡石复合贮热材料的性能测定

用熔融法制备了贮热用新戊二醇／海泡石复合材料，并采用DSC和DTA－TG热分析手段测定了样品的各种热化学性能。实验数据表明，复合贮热材料和纯新戊二醇有着相同的贮热功能，并降低了新戊二醇的挥发性，复合贮热材料在充当填料的同时，兼有贮热功能。     

具有分子双稳性的一维自由基磁相变材料的研究

具有分子双稳性的化合物是实现分子集合体作为新的光开关和信息存储元件的理想分子体系。本文合成苄基吡啶衍生物,研究其分子构象与堆积的关系,并研究了构建—维分子基磁体以及常温常压下的电学、磁学等性质。     

Current-induced domain-wall switching in a ferromagnetic semiconductor structure

Magnetic information storage relies on external magnetic fields to encode logical bits through magnetization reversal. But because the magnetic fields needed to operate ultradense storage devices are too high to generate, magnetization reversal by electrical currents is attracting much interest as a promising alternative encoding method. Indeed, spin-polarized currents can reverse the magnetization direction of nanometre-sized metallic structures through torque; however, the high current densities of 10(7)-10(8) A cm(-2) that are at present required exceed the threshold values tolerated by the metal interconnects of integrated circuits. Encoding magnetic information in metallic systems has also been achieved by manipulating the domain walls at the boundary between regions with different magnetization directions, but the approach again requires high current densities of about 10(7) A cm(-2). Here we demonstrate that, in a ferromagnetic semiconductor structure, magnetization reversal through domain-wall switching can be induced in the absence of a magnetic field using current pulses with densities below 10(5) A cm(-2). The slow switching speed and low ferromagnetic transition temperature of our current system are impractical. But provided these problems can be addressed, magnetic reversal through electric pulses with reduced current densities could provide a route to magnetic information storage applications.     

天然橡胶/杜仲胶复合材料的制备及其阻尼性能研究

在天然橡胶(NR)中引入杜仲胶(EUG),以环氧化天然橡胶(ENR)/受阻酚AO-80(质量比为25∶20)为阻尼相,制备了NR/EUG/ENR/AO-80复合材料,并测定了复合材料的硫化特性、力学性能、结晶性能与动态力学性能。结果表明：复合材料在常温范围内具有较高的损耗因子与较宽的阻尼温域,当NR与EUG的质量比为60∶40时复合材料具有最大的损耗因子峰值,并且随着EUG含量的增加,总体上复合材料在常温范围内的储能模量逐渐增大;复合材料的玻璃化转变温度出现在-60℃附近,并且随着EUG含量的增加,复合材料开始出现EUG结晶的熔融峰,结晶度和熔融温度逐渐增大。扫描电子显微镜(SEM)测试结果表明复合材料的断面较为平整,ENR改善了两相的相容性;透射电子显微镜(TEM)测试结果表明NR与EUG两相之间具有明显的分界。复合材料在低应变下表现出高柔性的特点,同时具有较高的拉伸强度和拉断伸长率。