纳米材料导论 复习题.doc

纳米材料 复习题关键词翻译：1、Nanomaterials (纳米材料) Scanning Tunneling Microscope (STM)（扫描隧道显微镜） Zero (one, two, three)-dimension（零、一 、二、三维） Size Effect - Kubo theory（尺寸效应-库伯理论）(1) Quantum size effect （量子尺寸效应） (2) Small size effect（小尺寸效应）Surface effect（表面效应） Coulomb blockade and Quantum tunneling effect（库仑堵塞和量子隧穿效应） Dielectric confinement effect（介电限域效应）2、Clusters（ 团簇） Nanoparticle （纳米微粒） Supersaturated Vapor （过饱和蒸气） Heterogeneous nucleation （异相成核） Homogeneous nucleation （均相成核） Magic Numbers （幻（魔）数）3、Primary particles （初始颗粒、一次颗粒）Secondary particles（二次颗粒）Precipitation（沉淀）Agglomeration （团聚）Scanning electron microscope (SEM) 扫描电镜Transmission electron microscope (TEM) （透射电镜）High-resolution transmission electron microscope (HRTEM) （高分辨率透射电镜）4、Mechanical Attrition/ Mechanical Alloying (MA) （机械研磨、机械合金化）High-energy Ball Milling （高能球磨）Contamination （污染物）Comminution （破碎、粉碎）Intermetallic（金属间化合物）Oxide-dispersion strengthened superalloys （弥散氧化物强化合金） Nanocomposites（纳米化合物）Dislocation（位错）5、sol-gel 溶胶-凝胶alkoxide solution 醇盐溶液colloidal sols 胶体溶液microporous monoliths 多孔块体材料anisotropic / isotropic shrinkage 各向异性、各向同性收缩polymer pyrolysis 聚合物高温分解hydrolysis 水解6、A green body （素坯）Pressureless sintering（无压烧结）Inhomogeneous sintering （非均一烧结）Densification（致密化）Porosity（多孔性）Pressure Assisted Sintering（压力辅助烧结）Sinter-forging（烧结锻压）7、Electronic effects (电子效应) Support effects (载体效应)Shape effects（形状效应）Zeolite ( Molecular sieve) (沸石 、分子筛) Catalyst （催化剂） Adsorbent（吸附剂）8、Yield Strength （屈服强度）Hall-Petch equation （霍尔佩奇方程）Diffusion creep rate （扩散蠕变速率）Coble creep （扩散蠕变Coble 蠕变）Triple junctions （三叉晶界）Superplasticity （超塑性）9、Mass spectra 质谱 Fullerene 富勒烯Bucky ball 巴基球 Electric arc 电弧 High-performance liquid chromatography 高效液相色谱法Nuclear magnetic resonance 核磁共振 Allotrope 同素异形体Pentagon/hexagon 五边形、六边形 名词解释及问答：一、The definition of Nanomaterials ：Materials having a characteristic length scale less than about a hundred nanometers.（长度尺寸小于一百纳米的材料）Classification according to dimensions ：（1）Three-dimension Nanomaterials (Zeolite)（2）Two-dimension film, superlattice （3） One-dimension nanowire, nanotube（4）Zero-dimension particle,clusterBasic theory of nanoparticles1. Size Effect - Kubo theory（尺寸效应-库伯理论）：当纳米材料的组成尺寸（如晶粒的尺寸、第二相粒子的尺寸减少时，纳米材料的性质会发生变化，当组成尺寸小到某一临界尺寸相当时，材料的性能将发生明显的变化或突变。小尺寸效应：随着颗粒尺寸量变，在一定条件下，会引起颗粒性质突变，由于颗粒尺寸变小所引起的宏观物理性质的变化称为小尺寸效应。量子尺寸效应：电子能量被量子化，形成分立的电子态能级，电子在该系统中的运动受到约束。随金属微粒尺寸减少，金属费米能级附近的电子能级由准连续变成离散能级的现象，以及半导体微粒存在不连续的最高位占据分子轨道和最低未被占据分子轨道的能隙变宽的效应。2. Surface effect（表面效应）：纳米材料颗粒尺寸与表面原子数的关系。纳米微粒含有大量晶界，因而晶界上的原子占有相当高的比例，晶界原子结构不同于块体材料，使纳米微粒自由能增加，处于不稳定状态。3. Coulomb blockade （库仑堵塞）：进入纳米量级，体系是电荷量子化的，即充电和放电过程是不连续的，充入一个电子所需能量为： 其中Ec为库仑堵塞能（前一个电子对后一个电子的库仑排斥能）。 导致对一个小体系充放电过程中电子不能集体传输，而是一个一个单电子传输，通常把小体系这种单电子输运行为称为库仑堵塞效应。Quantum tunneling（量子隧穿）：如果两个量子点通过一个结点连接起来，一个量子点上的单电子穿过能垒到达另一个量子点上的行为称为量子隧穿效应。4. Dielectric confinement effect（介电限域效应）纳米微粒分散在异质介质中，由于界面引起的体系介电增强的现象。二、1、How do you build something so small? “Top-down” and “Bottom-up”？ “Top-down” building something by starting with a larger component and carving away material (like a sculpture). In nanotechnology: patterning (using photolithography) and etching away material, as in building integrated circuits。 “Bottom-up” building something by assembling smaller components (like building a car engine). In nanotechnology: self-assembly of atoms and molecules, as in chemical and biological systems。2、Basic concepts (Clusters（团簇）smaller nanoparticles containing fewer than 104 atoms or molecules.（包含少于104个原子或分子的小微粒。）Magic Numbers（幻数）the unusually high mass spectral abundances that occur for certain cluster sizes which represent special electronic or geometric configurations（具有异乎寻常的高质谱峰度的团簇原子数，一般代表着特殊的电子构象或几何模型。）; Nanoparticle （纳米微粒）:物质颗粒体积效应和表面效应两者之一显著变化或者两者都显著出现的颗粒。)3、How to achieve supersaturation vapor? (1) the physical cooling of a vapor by sonic or supersonic expansion techniques; (2) a gas phase chemical or photochemical reaction that can produce nonvolatile condensable products; (3) directly by thermal evaporation, sputtering, or laser ablation. Educe the formula of surface to volume ratio of clusters Two important differences between the nanoparticles and the clustersFirst, nanoparticles are usually larger than the clusters. They range in size from 1 to 100 nm. Secondly, in much larger quantities than the clustersReasons： high particle density； Out of the vacuum chamber。三、(1) The advantages and potential difficulties advantages ：1). versatility in designing and synthesizing new materials2). the manipulation of matter at the molecular level ： mixing at the molecular level；good chemical homogeneity can be achieved ；3). molecular synthetic chemistry can be tailor designed to prepare novel starting components 4). Better control of the particle size, shape, and size distribution can be achieved in particle synthesispotential difficulties：the chemistry is complex and hazardous：Entrapment of impurities in the final product Scaling up for the economical production of a large quantity of material may be relatively easy for some but not all systems undesirable agglomeration at any stage of the synthesis process can change the properties(2) Primary particles and secondary particles The small subunits are defined as the primary particles and the agglomerates of these primary particles are called secondary particles.(3) Factors influencing the rate of precipitated reactions Factors influencing the rate of reactions include the concentration of reactants, the reaction temperature, the pH, and the order in which the reagents are added to the solution。(4) The reasons of agglomerationAgglomeration of fine particles is caused by the attractive van der Waals force and/or the driving force that tends to minimize the total surface energy of the system。(5) Measures to against agglomeration：Repulsive interparticle forces are required to prevent the agglomeration of these particles（为了防止分散的粒子团聚，可以加入表面活性剂使其吸附于粒子表面形成微抛状态，由于活性剂的存在而产生粒子间的排斥力，使粒子间不能接触，静电斥力产生双电层。）四、(1)high-energy ball milling （高能球磨）：利用球磨机的转动或振动使硬球对原料进行强烈撞击、研磨或搅拌，把金属或合金粉末粉碎成纳米级微粒的方法。mechanical attrition （机械研磨）：若将两种或两种以上金属粉末同时放入球磨机的球磨罐中进行高能球磨，粉末通过压延-压合-碾碎的反复过程最后获得组织和成分分布均匀的合金粉末，由于该方法利用机械能达到合金化，而不用热电能，所以把高能球磨制备合金粉末的方法称为机械研磨。(2) What is the major problem of mechanical attrition (or the disadvantages of MA)? Explain them and which measures can be to take? surface and interface contamination。 the milling tools (Fe) and atmosphere (trace elements of O2, N2 in rare gases) can be a problem.Measures: minimizing the milling time; using the purest, most ductile metal powders, a thin coating of the milling tools; sealing the vial with a flexible O ring after the powder has been loaded in an inert gas glove box .(3)Mechanism of Grain-size Reduction ( The processes leading to the grain size refinement include three basic stages).(i) Initially, the deformation is localized in shear bands consisting of an array of dislocations with high density.(ii) At a certain strain level, these dislocations annihilate and recombine as small-angle grain boundaries separating the individual grains. The subgrains formed via this route are already in the nanometer range (2030 nm).(iii) The orientations of the single-crystalline grains with respect to their neighboring grains become completely random.五、1)The reactions in alkoxide solutionhydrolysis to make the solution active (reaction I) condensation polymerization (reaction II) along with further hydrolysis These reactions increase the molecular weight of the oxide polymer (reactions III and IV). solgel transition:the solution reacts to a point where the molecular structure is no longer reversible2) The fundamental difference between alkoxide precursors and colloidal sol precursorsColloidal sols are also referred to as precursors for solgel processing 。In this case, the sol in solgel processing is not shorthand for solution, but, in fact, a colloidal solution.the aggregation of sol particles is caused by changing the pH or changing the concentration (Ludox )difference between alkoxide precursors and colloidal sol precursors discrete features 。pores within secondary particles and pores between secondary particles。3) Powder-free Processing of Gel Shapes (monoliths, fibers, thin films)4) The processing steps of sol-gel that are common to all geometries(I) dissolving and reacting the precursors; (II) forming and gelling the shapes; (III) drying;(IV) firing to partial or full density.六、1、The definitions of pressureless sintering, pressure assisted sintering and sinter-forging无压烧结：纳米晶粉末压制成型后，高温烧结致密化而不需压力。压力辅助烧结：对样品施加一个大于大气压的外力进行烧结。烧结锻压：在烧结时对样品施加一个等轴的压缩应力，使样品的变形与致密化同时进行。2、Why we cant use wet processed to fabricate metals? Because particles can slide and rearrange much more easily in a liquid medium, it is often advantageous to fabricate powder compacts, particularly ceramic powder compacts by wet-processing techniques. Note: metal particles are typically not wet processed due to their relatively good behavior in dry pressing and their tendency to form oxide layers during exposure to aqueous media3、Three stages of densification of nanocrystalline ceramics during pressureless sintering. 1）. Neck growth occurs at the contact points between adjacent particles 2）. The ceramic has a sponge-like structure consisting of an extensive network of tubular pores open to the outside surface of the ceramic sample. Most of the actual densification takes place during this second stage, as the tubular pores shrink to smaller and smaller diameters. Once these pores are very narrow relative to their length, they become unstable and pinch off to form isolated, closed, spherical pores. 3）. The elimination of closed pores.4、How to overcome the problem of inhomogeneous sintering?For small samples: one might can be to use fast heating rates for the densification of nanocrystalline thin filmsFor moderate-to-large-sized samples:() slowing heating rates during sintering () changing the samples starting microstructure (precoarsening treatment, in which the sample is heated at a low temperature long enough for pores and grains to grow somewhat ) () choosing low sintering temperatures with long times(薄膜样品,使用快的升温速率.；中、大型样品采用慢的升温速率；改变样品的初始微结构；低温长时间烧结。)5、Minimizing Grain Growth and Maximizing Densification during Pressureless Sintering (Principles for metals and ceramics during pressureless sintering)Some simple principles for the production of fully dense materials with sub-100 nm grain size from ultrafine starting powders. 8.1 Metals(i) Compact to the highest possible density prior to sintering(ii) Sinter at a low temperature (to avoid grain growth) for as long as necessary to remove residual porosity and establish equilibrium grain boundaries between neighboring particles. 8.2 Ceramics(i) Choose a non-agglomerated starting powder。(ii) Maximize densification rates by minimizing the pore size within the starting compact: For small samples, narrow pores can be achieved by compacting at large pressures; for larger samples, fabricating the powder compact by wet-processing techniques is an option. (iii)Minimize grain growth kinetics by choosing a low-sintering-temperature /long-sintering-time combination. (iv) Avoid fast heating rates, especially in ceramics which are not thermally conductive (v) For select ceramics in which grain growth is limited by the presence of pores, grain growth will be severely curtailed up to 90% density .七、1. Surface chemistry is of vital importance in numerous processes and this is for two reasons. Please explain them respectively? First, the huge surface areas of the nanostructured material dictate that many of the atoms are all the surface, thus allowing good atom economy in surface-gas, surface-liquid, or even surface-solid reactions. Second, nanoparticles feature is enhanced intrinsic chemical reactivity as size gets smaller. (纳米结构材料具有很大表面积,表明表面有很多原子,原子利用率高.而且增强了本征化学反应,尺寸降低.)The reasons for this enhanced reactivity are most likely due to changes in crystal shape. However, there are other features that can affect surface energy. As crystal size becomes smaller, anion/ cation vacancies of the Frenkel or Schottky type become prevalent. Also, atoms on the surface can be distorted in their bonding patterns.2. Why metallic nanoparticles can be used as catalysts, there exist three effects, explain them respectively? 电子效应: Electron density changes at catalytic sites can vary due to particle size. (由于粒子尺寸改变,催化中心电子密度发生变化) 载体效应: 一些载体在金属表面进行沉积从而形成一些活性点. (the phenomenon is the tendency of some supports to form deposits on the catalytic metal particles, thereby forming catalytically active interface sites.） 形状效应 ：（1）Certain chemical reactions are structure-sensitive (hydrogenolysis of cyclopropane, dehydrocyclization, etc.). This means, that as the reactant approaches, several adjacent surface metal atoms are required for the adsorption and catalytic transformation to proceed. （2）In another manifestation of shape effects, it is often assumed that the active sites are at low coordination (edges, corners), and the smallness of the catalytic particle can affect crystal shape and therefore surface concentration of edge/corner sites. (for example)3. As absorbents, why nanostructured materials are so useful in chemistry? First, they possess very large surface areas. Second, nano-crystal shapes usually afford large surface concentrations of edge/corner and various defect sites, or other unusual structural features, such as channels or well-defined cavities. Third, in addition to these aspects nano-structured materials, when consolidated, can exhibit unusual pore structure, and in this way exhibit steric effects on adsorption processes.八、List the five different regulations of Hall-Petch effect in nanometer materials and explain the possible existent reasons. First write out the Hall-Petch equation Empirical HallPetch equation relates yield stress sy to average grain size d in common multicrystal materials。 where is a