[1. Nano materials]
纳米材料特殊性质举例
materials in nano size range exhibit some remarkable specific properties, for example:
1.Crystals in the nanometer scale have a low melting point and reduced lattice constants.
2.Bulk semiconductors become insulators when the characteristic dimension is sufficiently small.
纳米材料举例
Nanostructure materials are those with at least one dimension falling in nanometer scale, and include:
nanoparticles, nano rods and nanowire, thin films, bulk materials made of nanoscale building blocks or consisting of nanoscale structures.
纳米材料分类
Classification of NSMs (nanostructured materials)
zero-dimensional(0-D), 0 dimension is not confined to the nanoscale range (<100nm)./ all dimensions are confined… {nanoparticles}
1-D, {nanowires, nanorods, nanotubes}
2-D, {nano coatings and nanofilms}
3-D, {dispersions of nanoparticles, bundles of nanowires and nanotubes, multinanolayers}
1.matrix-reinforced nano composites: matrix reinforced with nanoparticles, matrix reinforced with nanowires/nanotubes
2.layered nano composites: laminates, sandwiches
carbon
diamond: sp3; graphite: sp2
0D: fullerenes; 1D: carbon nanotubes; 2D: graphene; 3D: graphite
Surface energy
for a given surface with a fixed surface area, the surface energy can be reduced through: 1. surface relaxation; 2. surface restructuring; 3. surface adsorption; 4. composition segregation.
Therefore, a crystalline particle normally forms facets, instead of having a spherical shape. (reduction of the overall surface area)
Chemical potential
) convex surface, the curvature is positive, chemical potential of an atom is higher than that on a flat surface. (concave is lower than flat)
[2. Fabrication of nano materials]
分类
top-down: etching
bottom-up: growth of thin films, nano lithography, nano manipulation
physical methods
evaporation technique
sputtering technique 溅射
lithography processes 平板印刷 (coat expose develop etch strip)
hot and cold plasma
spray pyrolysis 喷射 高温分解
inert gas phase condensation technique
pulsed laser ablation
sono-chemiacal reduction
chemical methods
electrochemical deposition
electroless deposition
hydrothermal and solvothermal techniques
sol-gel technique (chemical solution deposition)
chemical vapor deposition
laser chemical vapor deposition technique
[3. Characterization of nano materials]
characterization techniques
X-ray diffraction(XRD)
scanning electron microscopy(SEM)
transmission electron microscopy(TEM)
scanning probe microscopy(SPM)
atomic force microscopy(AFM)
scanning tunneling microscopy(STM)
透射电子显微镜TEM（样本必须非常薄）
扫描电子显微镜SEM（有立体感）(可配套WDX波谱仪 ,EDX能谱仪）
扫描隧道显微镜STM（隧道效应，必须是导电样品）
扫描探针显微镜SPM（工作环境不苛刻）
原子力显微镜AFM（不需要处理，导电和高真空）
optical spectroscopy
1.absorption and emission spectroscopy: absorption and transmission spectroscopy, photoluminescence spectroscopy
2.vibrational spectroscopy: infrared spectroscopy, Raman spectroscopy
[4. Applications of nano materials]
based on
1.the peculiar physical properties of nano sized materials (gold nanoparticles used as inorganic dye to introduce colors into glass)
2.the huge surface area (nanoparticles for various sensors )
3.the small size
举例
water repellent fabrics from hydrophobic louts
[5. Nano hazard]
1.hazards to human: Some nanoparticles can pass to the brain via the central nervous system following inhalation.
2.environmental hazards: effects in groundwaters and soils.