强激光辐照下纳米晶体铜薄膜层裂破坏的实验研究

采用强激光辐照加载技术和激光速度干涉(VISAR)测试技术,对纳米晶体铜薄膜的层裂特性进行实验测量和分析.基于VISAR实测的自由面速度波形,计算得到纳米晶体铜薄膜在超高拉伸应变率下的层裂强度高达3 GPa,明显高于多晶铜的层裂强度, 其原因归咎于纳米晶体材料中存在大量晶界阻碍了位错运动. 关键词： 纳米晶体铜薄膜 层裂 激光辐照     

强激光辐照下纳米晶体铜薄膜层裂破坏的实验研究

采用强激光辐照加载技术和激光速度干涉(VISAR)测试技术，对纳米晶体铜薄膜的层裂特性进行实验测量和分析.基于VISAR实测的自由面速度波形，计算得到纳米晶体铜薄膜在超高拉伸应变率下的层裂强度高达3 GPa，明显高于多晶铜的层裂强度, 其原因归咎于纳米晶体材料中存在大量晶界阻碍了位错运动.     

CdS0.1Se0.9纳米晶体共振电吸收谱的线形分析

采用电调制技术在室温下测量了 Cd S0 .1 Se0 .9纳米晶体的电吸收谱 ,并对电吸收谱线形进行了分析。纳米晶体与第一个吸收峰有关的电吸收谱结构具有吸收系数对能量的二阶微商特征 ,表明第一激发态在电场作用下以吸收谱线的宽化为主 ,而纳米晶体尺寸不单一是吸收谱线宽化的主要因素。共振电光响应信号的峰值位置、过零点位置以及电吸收谱的线形几乎不随外电场强度而变化 ,信号幅度随外电场强度的平方线性增加。 Cd S0 .1 Se0 .9纳米晶体的电光效应是Kerr效应 ,纳米晶体具有三阶非线性光学极化率 Χ( 3 )。     

分子动力学模拟纳米晶体铜的结构与性能

通过分子动力学方法模拟纳米面心立方晶体铜的结构，并对模拟的结果进行了不同晶粒尺寸的纳米晶体的密度、能量分布以及弛豫前后的X射线衍射、径向分布函数等计算.结果表明，大体积分数的晶界和畸变的晶粒是纳米晶体有别于传统的粗晶粒晶体材料结构的重要方面，由此导致纳米晶体一系列不同性能. 关键词：     

InSb纳米晶体的生长和吸收光谱的研究

采用在惰性气体中蒸发的方法获得了沉积在ZnS基片上的InSb纳米晶体,其平均尺寸随惰性气体的压强增加而增大.从实验测量的室温吸收谱上看到,当纳米晶体的平均直径从27.9 nm减小到24.2nm再到21.4 nm时,其吸收边分别向高能方向移动了0.0151 eV和0.0145 eV.用有效质量近似模型计算了半导体纳米晶体的吸收边相对其体材料的移动,将理论计算与实验结果进行了比较.     

基于纳米光学等离子晶体的新型纳米光子学器件的发展

通过设计合适的纳米表面等离子结构,纳米光学等离子晶体具有光场增强效应,能调控近场范围内的光场分布,可用来设计新型的纳米光子学器件。介绍了纳米光学等离子晶体的原理、结构特点、制作工艺和纳米光子学器件的设计方法,对纳米光学等离子晶体和普通光子晶体做了比较。归纳了纳米光学等离子晶体的物理机制、光学特征,描述并分析了波长选择性场增强效应和束流效应等。给出几种基于纳米光学等离子晶体的纳米光子学器件应用实例。     

聚丙烯胺稳定铜纳米粒子的制备及其SERS活性研究

报道了聚丙烯胺稳定的球形和棒状铜纳米粒子的制备方法。在水溶液中空气条件下,通过水合肼还原二价铜离子到铜纳米粒子。聚丙烯胺的作用除稳定粒子防止聚集外,也可使粒子分散在水溶液中。该法的优点是在室温下,无需惰性气体保护,即可制备水溶液中分散的铜纳米粒子。紫外光谱和透射电镜监测了铜纳米粒子的生长过程。发现氢氧化钠的用量,聚丙烯胺浓度,反应时间等因素都影响到铜纳米粒子的组成,尺寸,形貌和聚集程度。氢氧化钠用量决定了制备粒子的组成成分是铜或氧化亚铜。所制备的球形铜纳米粒子表现出优良的表面增强拉曼散射活性。     

表面活性剂对合成碘化亚铜晶体微观结构的影响

利用液相沉淀法,以粗碘为碘源合成了碘化亚铜晶体。采用XRD和SEM分析技术考察了表面活性剂种类对合成碘化亚铜产品晶相组成和微观形貌的影响。结果表明,表面活性剂对合成碘化亚铜产品晶相组成影响较小,但对晶体微观形貌具有较大的影响。分别以柠檬酸、十二烷基磺酸钠、十六烷基三甲基溴化铵、聚乙二醇-6000为表面活性剂制得碘化亚铜晶体尺寸较大、易团聚。以聚乙二醇-6000和1%水合肼为表面活性剂可制备出尺寸均匀(50—100nm),分散较好的纳米球形γ-CuI晶体。     

纳米晶体微观畸变与弹性模量的模拟研究

采用分子动力学方法模拟纳米晶体铜原子的结构,又对纳米晶体铜原子进行了X射线衍射模拟．计算了晶粒尺寸和点阵畸变,还计算了能量分布和弹性模量等．结果表明不但晶界产生很大的应力场,而且晶粒内部的畸变也起着与晶界相似的重要作用．由于原子半径的增加,导致弹性模量的减少. 关键词：     

稀磁ZnO纳米颗粒的生长和性能

利用Zn、Fe、Mn、Co的铜铁试剂盐为前驱体,胺为表面包裹剂,在200℃N2保护下生长了2%的过渡金属离子掺杂的ZnO稀磁纳米晶体,研究了纳米晶体的结构、形态、光学和磁学性能。所有ZnO纳米晶体均为近圆形的颗粒,晶体结构为六角纤锌矿结构,无其他氧化物相的析出,但过渡金属离子的掺入使纳米颗粒的尺寸增大。在掺杂纳米颗粒的吸收谱和发射谱中均可以观察到明显的激子吸收和发射峰,所有纳米颗粒在温度高于43K时只有顺磁性。     

High-frequency magnetic properties of soft magnetic cores based on nanocrystalline alloy powder prepared by thermal oxidation

FeSiBNbCu nanocrystalline alloy powder was thermally oxidized in an air atmosphere to enhance an oxide layer formation on the surface of the powder and subsequently toroidal shape FeSiBNbCu nanocrystalline alloy powder cores were prepared by compaction at room temperature. The phase change on the surface of FeSiBNbCu nanocrystalline alloy powder by thermal oxidation was analyzed and its effect on the high frequency magnetic properties of the compacted cores was investigated. By thermal oxidation, the formation of the oxide layer consisting of Fe₂O₃, CuO, and SiO₂ on the surface of FeSiBNbCu nanocrystalline alloy powder was enhanced and the thickness of oxide layer could be controlled by changing the thermal oxidation time. FeSiBNbCu nanocrystalline alloy powder core prepared from the powder treated by thermal oxidation exhibits a stable permeability up to high frequency range over 10 MHz. The core loss could be reduced remarkably and the dc-bias property could be improved significantly, which were due to the formation of oxide layer consisting of Fe₂O₃, CuO, and SiO₂ on the FeSiBNbCu nanocrystalline alloy powder. The improvement in high-frequency magnetic properties of the FeSiBNbCu nanocrystalline alloy powder cores could be attributed to the effective electrical insulation by oxide layer between the FeSiBNbCu nanocrystalline alloy powders.     

粗晶和纳米晶Sm_3Co合金的制备及其性能研究

本文针对Sm3Co粗晶和纳米晶合金材料的制备和基础性能进行了研究.采用磁悬浮熔炼技术多次精炼制备出Sm3Co粗晶合金.以此为母材,利用高能球磨非晶化和放电等离子烧结致密化并同步晶化的技术路线,制备出平均晶粒尺寸为8 nm的超细纳米晶Sm3Co合金块体材料.构建了Sm3Co纳米晶合金的晶体结构模型,并结合其显微组织的表征,分析了Sm3Co纳米晶合金的磁性能和力学性能,并与粗晶合金进行了比较粗晶Sm3Co合金不具有硬磁特性,而同种成分的纳米晶合金则表现出一定的硬磁特性.纳米晶Sm3Co合金的显微硬度和弹性模量分别达到4.87 GPa和63.7 GPa,比粗晶合金增大约8.7%和13.3%.本文研究结果为Sm-Co体系合金的基础性能及其纳米尺度效应提供了系统的参考依据.     

立方相β-GaN纳米晶的气相化学反应制备研究

在氮气氛中，以GaP纳米晶为原料，在相对较低的反应温度下，通过N-P取代的气相化学反应 制备立方相β-GaN纳米晶.这是由于GaP纳米晶具有较大的比表面积和表面众多的空位键，使 之具有较高的反应活性造成的.不同升温速率造成不同的化学反应机理，从而生成不同形貌 的β-GaN纳米晶材料. 关键词： 氮化镓 立方相 纳米晶     

脉冲激光晶化超薄非晶硅膜的分子动力学研究

利用准分子脉冲激光晶化非晶硅薄膜是制备高密度尺寸可控的硅基纳米结构的有效方法之一.本文将脉冲激光对非晶硅超薄膜的影响处理为热传导问题,采用了基于Tersoff势函数的分子动力学方法模拟了在非晶氮化硅衬底上2.7 nm超薄非晶硅膜的脉冲激光晶化过程.研究了不同激光能量对非晶硅薄膜晶化形成纳米硅的影响,发现在合适的激光能量窗口下,可以获得高密度尺寸可控的纳米硅薄膜,进而模拟了在此能量作用下非晶硅膜中成核与生长的机理与微观过程,并对晶化所获得的纳米硅薄膜的微结构进行了分析. 关键词： 非晶硅 分子动力学 脉冲激光晶化     

铝纳米晶的正电子湮没研究

采用自悬浮定向流-真空热压法,在不同压强下制得铝纳米晶材料,并利用X射线衍射(XRD)和正电子湮没寿命谱(PALS)分析手段对铝纳米晶的结构和微观缺陷进行表征.XRD分析表明:所制备的铝纳米晶的晶粒度为48 nm.PALS分析表明:铝纳米晶的微观缺陷主要为类空位以及空位团,而微孔洞很少;短寿命τ1,中间寿命τ2以及其对应的强度I1,I2随压强变化而呈现阶段性变化;压制压强(P)低于0.39 GPa时制得的纳米晶空位团随压强的增加而逐渐转变为类空位;0.39 GPa P 0.72 GPa时,各类缺陷发生消除;P 0.72 GPa时,各类缺陷进一步发生消除.随压强的提高,铝纳米晶的密度增加,其显微硬度也明显增高.     

Synthesis of Nanocrystalline Ceria Particles for High Temperature Oxidation Resistant Coating

Cerium oxide has been investigated to be an effective coating material for high temperature applications for various alumina- and chromia-forming alloys. The present study investigates the use of microemulsion method to obtain monodispersed, non-agglomerated nanocrystalline ceria particles in the range of 5nm using sodium bis(2-ethylhexyl) sulphosuccinate (AOT) as a surfactant. Furthermore, the use of non-agglomerated nanocrystalline ceria particles to develop improved high temperature oxidation resistant coatings on AISI 304-grade stainless steel was investigated. It was found that non-agglomerated nanocrystalline ceria particles were more effective in improving the oxidation resistance than the agglomerated nanocrystalline particles.     

Generation of glide split-dislocation half-loops by grain boundaries in nanocrystalline Al

A three-dimensional model for the generation of split dislocations by grain boundaries in nanocrystalline A1 is proposed. In terms of this model, rectangular glide split-dislocation half-loops nucleate at glide lattice dislocation loops pressed to grain boundaries by an applied stress. The level of the applied stress and the grain size at which the emission of such dislocation half-loops becomes energetically favorable are determined. The dependences of the stacking-fault width on the grain size and the applied stress are found. The anomalously wide stacking faults experimentally detected in nanocrystalline A1 are shown to be caused by high internal stresses forming in the stages of preparation, treatment, or local loading of nanocrystalline samples.     

不同粒径纳米晶硫化锌的高压结构相变研究

 应用原位能量色散X射线散射和金刚石对顶砧技术，对纳米晶ZnS进行了高压结构相变研究。初始相为纤锌矿结构的10 nm和3 nm硫化锌分别在16.0 GPa和16.7 GPa时转变为岩盐矿结构，相变压力均高于纤锌矿结构的体材料硫化锌。该相变为一可逆的结构相变。应用大型科学计算软件Materials Studio（MS）计算了纳米晶ZnS的状态方程，根据Birch-Murnaghan方程拟合了纳米晶ZnS的零压体模量，得到的零压体模量高于相应体材料的零压体模量，表明纳米晶ZnS较难压缩。     

Nanostructures, disordered ferromagnetism and spin glasses

Magnetic systems with a considerable amount of irregular interfaces were investigated by ⁵⁷Fe Mössbauer spectroscopy. Chemically homogeneous ferromagnets around the percolation threshold composition of disappearing magnetism and chemically heterogeneous alloys prepared by nanocrystallization of amorphous alloys belong to this class of materials. Low temperature and high field measurements were performed on nanocrystalline FeZrBCu alloys, on ball‐milled Fe with nano‐size grains and on melt‐quenched amorphous Fe–Zr and Fe–Y alloys in order to clarify the origin of large high‐field susceptibility and to investigate the common features of the approach to magnetic saturation. Curie point determination of the residual amorphous phase in the nanocrystalline FeZrBCu alloys, results on the structure of the nanocrystalline b.c.c. phase and of the interfacial region will be reported.     

Stabilization of high-pressure phases in nanocrystalline metals and alloys

It is shown experimentally that the formation of submicrocrystalline and nanocrystalline states significantly affects the stability of the high pressure hcp phase in iron-based alloys. It is established that the manganese segregation from the bulk of ɛ-phase grain to the grain boundary under high hydrostatic pressure can influence the stability of this phase in nanocrystalline alloys.