第六讲界面化学

第六讲界面化学

6.1 水溶液的表面化学• 水溶液的表面张力

作用力和存在形态：分子间（原子间离子间）


表面能 γ （ mJ·m-2 ）

表面张力 γ （ mN·m-1 ） γ 的变化分类

表面活性和表面活性剂


• 表面活性剂

表面活性剂的分子特征：端基极性亲水基非极性疏水基

洗涤剂消泡剂乳化剂

疏水基亲油性－“相似相容”原理


两个基本性质：表面吸附和定向排列

分子有序组合体

胶团（ micelle ）

临界胶团浓度 CMC (critical micelle concentration)

“ 水包油” 和 “油包水”

体系：乳化、破乳、起泡、消泡、分散、絮凝

“ 矿石浮选” 和 “油田开发”


• 疏水效应水溶液中，非极性分子或基团结合在一起的力量称为疏水效应

疏水效应的本质：较强的水分子之间的氢键力对非极性分子或

非极性基团的挤压使得体系的能量降低


6.2 固－气界面化学• 固体的表面结构固体表面结构的复杂性

理想结构－体相的中止

实际结构－体相的延续表层的微结构和化学组成的变化

洁净的固体表面的结构图像


固体表面剖面结构


表面层的微观结构：

金属的表面层结构

形成氧化膜的情况

高分辨电子显微镜

扫描隧道显微镜

光电子能谱，等等

FIG. (color). STM images 11 nm × 11 nm of the Pb cluster array on Si111-7x7. The bias voltages are (a) 1:0 V and (b) 1:5 V. The inset shows an empty-state STM image of an In6 cluster.

Electron-based techniques for examining surface and thin film process

AES (Auger electron spectroscopy)LEED (Low energy electron diffraction)RHEED (Reflection high energy electron microscopy)TEM (Transmission electron microscopy)REM (Reflection electron microscopy)STM (Scanning tunneling microscopy)AFM (Atomic force microscopy)PEEM (Photoemission microscopy)SEM (Scanning electron microscopy)SNOM (Scanning near field optical microscopy)XPS (X-ray photoemission spectroscopy)UPS (Ultra-violet photoemission spectroscopy)


• 固体表面吸附


• 分子筛筛分分子

具有空旷结构（分子量级）的化合物

孔径（ 2A, 3A 等）均匀的孔道

内表面较大的空穴

硅铝酸盐型分子筛


6.3 固－液和固－固界面化学• 固体表面的浸润性能表面处理液体的表面张力液固表面张力固气表面张力

sg-sl = lg cos

FIG. (color). Equilibrium structure of (a) water monomer, (b) dimer, (c) H-up bilayer, and (d) H-down bilayer on the Pt(111) surface. The red, blue, and gray balls represent O, H, and Pt atoms, respectively. The green and yellow lines denotethe two different hydrogen bonds in the bilayer.


• 钎焊：铝材的焊接

钎焊的原理：与固－液界面过程

钎焊的过程（包括物理过程和化学过程）

熔化－浸润－毛细流动－填充－铺展－融合－冷凝－后处理

钎焊与熔焊钎焊的应用－高技术中的一项精密连接术

科学－技术－生产工艺 / 经验


• 氧化物和盐类在载体表面自发单层分散

原理：固－固界面过程热力学上有利 G = H-TS < 0 , 熵增过程 S >0

应用：新型高效催化剂 / 吸附剂 / 固体电解质

FIG. (color). Filled and empty state images of the Na clusters with bias voltage of 2:0 V for (a) and 0:8 V for (b). (c) The structural model of the Na cluster with the highest Eb (2:13 eV=atom). One of the Na adatoms near the Si dimer is pushed outwards (red arrow), the structure being triply degenerated (d),(e) Simulated filled and empty state STM images, at 2:0 V and 0:8 V, respectively. The top part of (c) shows the adsorption scheme for a single Na atom. The green hexagon indicates an ‘‘attraction basin.’’ The three open circles (black arrow marked) correspond to the lowest energy sites (Eb 2:26 eV for the FHUC and 2.20 eV for the UHUC).

Two arrangements for four deposited atoms in the samephase epitaxy

7 AA bonds

8 AA bonds (stable state)

In the case of the same phase epitaxy, the stable state is one-Layer-arrangement, namely, two demitional growth.

For the different phase epitaxy

-4uAB – 12uAA

-8uAB-10uAA

If uAA > 2uAB the case of (a) is beneficial for the reduction of energy

(a)

(b)

The condition for double layers arrangement (Island):(a) N=8, uAA>2uAB, (b) N=18, uAA>1.5uAB, (c) N=32,uAA>1.33uAB, (d) N=50, uAA>1.25uAB, (e) N=72, uAA>1.24 uAB.


6.4 纳米化学基本粒子层次 <Å

原子分子层次 Å~nm

微观 nm

介观 1nm---100nm

细观 mm ~ um

宏观 > mm

宇观 AU ly (150 亿光年 )

• 纳米材料：三维空间尺度至少有一维处于纳

米量级的材料

零维（纳米微粒）一维（纳米纤维 / 纳米管）二维（薄膜）

尺度：约 1 ～ 100nm ，含

原子或分子数102~105

FIG. (color). (a) STM image of In nanoclusters on Si(111) at an In coverage of 0.05 ML (1 ML one adsorbed atom per substrate atom). (b) Perfectly ordered In nanocluster arrays at 0.12 ML In coverage. (c) I-V curves measured on bare Si surface (red) and on top of In clusters (green).

纳米材料性质特点：

过渡亚稳态物质：介于宏观与微观之间，具有特殊的

表面结构

效应：特殊的表面和界面效应，临界尺寸效应，

量子尺寸效应量子隧道效应

物理 / 化学特性：熔点显著降低吸收光和电磁波能力增强

表面活性提高



• 纳米技术之一－扫描探针显微术（ SPM ）扫描隧道显微术 (STM) 原子力显微术 (AFM) 磁力显微术 (MFM)

应用：•超高空间分辨本领：获取表面原子分子的大小形状和堆积信息•针尖产生局域场：构建微结构和微器件•分辨力和控制力：研究单分子结构和性质

Scanning Tunneling Microscopy(STM)

• The tunneling current is measured by W needle• The distance between the tip and sample surface is below 1 nm; resolution along vertical is 0.01nm and in transverse is 0.1nm• The tip is applied a few voltage and the tunneling current is 0.1 to 1.0 nA• The current is related not only to the height of atom on the surface, but also to the atomic density (density state)

Scanning electron microscopy image of a square arrayof electodeposited Ni pillars of high 300nm and period.

Low noise,high density

硅晶体结构隧道扫描硅晶体结构隧道扫描

Atomic Force Microscopy (AFM)Atomic Force Microscopy (AFM)

STM is only applied to bserve surface for conductor or semi-conductor, while AFM is an ppropriate tool for all samples.

The reflect light place is 3-10nm after the height of tip changes 0.01nm.

Three operation models of AFM:(1) contact (2) non-contact (3)tapping model.

Geometry for description of MFM technique. A tip scanned to thesurface and it is magnetic or iscoated with a thin film of a hard or soft magnetic material.

Magnetic Force Microscopy (MFM)

Domain structure of epitaxial Cu/tNi /Cu(100) films imaged byMFM over a 12 µm square: (a) 2nm Ni, (b) 8.5 nm Ni, (c) 10.0Nm Ni; (d) 12.5nm Ni (Bochi et al., PRB 53(1996)R1792).

(a)(a) Domain pattern as measured byDomain pattern as measured byMFM above the surface of an eiptaixMFM above the surface of an eiptaixCu/200nmNi/Cu(100) film.Cu/200nmNi/Cu(100) film.


6.5 膜的化学

膜：二维伸展的结构体

基本化学功能：有选择地透过或输送特定的物质

分离功能能量转化功能生物功能

特异物理功能：特异光热电磁性质

高密度磁记录巨磁电阻磁光磁热磁制冷

量子点阵

功能材料

Thin film recording head. Left, layout of pole pieces and windings; right, enlarged, cross-sectional view of magnetic pole pieces

Film thickness2-3 micrometer;Gap 200 nm.

Media: Co69.48-xTb30.52Agx, x=0-25.68

hybrid recording

第六讲界面化学

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Transcript of 第六讲界面化学

第六讲 界面化学

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Transcript of 第六讲 界面化学

第六讲界面化学

Transcript of 第六讲界面化学