Profile image

Figure 4. False-color optical profile images of ball wear surface for metal/metal contact...

In many catalytic systems, nanoscopic metallic particles are dispersed on ceramic supports and exhibit different stmctures and properties from bulk due to size effect and metal support interaction etc. For very small metal particles, particle size may influence both geometric and electronic structures. For example, gold particles may undergo a metal-semiconductor transition at the size of about 3.5 nm and become active in CO oxidation [10]. Lattice contractions have been observed in metals such as Pt and Pd, when the particle size is smaller than 2-3 nm [11, 12]. Metal support interaction may have drastic effects on the chemisorptive properties of the metal phase [13-15]. Therefore the stmctural features such as particles size and shape, surface stmcture and configuration of metal-substrate interface are of great importance since these features influence the electronic stmctures and hence the catalytic activities. Particle shapes and size distributions of supported metal catalysts were extensively studied by TEM [16-19]. Surface stmctures such as facets and steps were observed by high-resolution surface profile imaging [20-23]. Metal support interaction and other behaviours under various environments were discussed at atomic scale based on the relevant stmctural information accessible by means of TEM [24-29]. 

Carpenter A, Jones T, Lamprecht M et al (2006) Cell Profiler image analysis software for identifying and quantifying cell phenotypes. Genome Biol 7 R100... 

Briscoe et al 1984). Figure 2.1 b) shows a surface profile image (Datye et al 1992). 

Figure 5.23. (a) HRTEM profile image of a CO-reacted Cu-Pd particle indicating a Pd surface. Inset Pd surface with simulated image. The flat surfaces (at B) are (100) the stepped ones (D) are (110). Away from the surface the structure has equal Cu and Pd (inset enlarged area A with image simulation), (b) Extended unit cell model used for image simulations, (a = 0.3 nm.) It minimizes wrap-around effects. 

Application Depth profiling, imaging, trace and isotope analysis, micro-and nano-analytics Depth profiling, imaging... 

Surface properties of mesoporous materials are sometimes important and TEM surface profile imaging is often used to investigate the surface structures of these materials. The advantages of this method are that it can be used to study the surfaces of small crystallites of almost any morphology, that the specimen preparation is as simple as that for the studies of bulk structures without requiring any special treatment and that, unlike scanning tunnelling... 

Figure 3. TEM surface profile images of MCM-41 specimens overheated at 165 °C for (a) 96 h and (b) 48 h. The view directions are along (a) the [100] direction and (b) the pore axis.

F l G U RE 6.11 (See color insert following page 390.) Schematic of the application of x-ray CT analysis to provide density profile images of different sections of a hydrate core contained in a cylindrical high pressure aluminum cell. (From Gupta, A., Methane Hydrate Dissociation Measurements and Modeling The Role of Heat Transfer and Reaction Kinetics, Ph.D. Thesis, Colorado School of Mines, Golden, CO (2007). With permission.)... 

The knowledge of the structure and the morphology of the metal clusters is necessary if we want to understand the reaction kinetics at the atomic level. The more versatile technique to study the structure and the morphology of supported metal cluster is TEM. It can provide directly the structure and the epitaxial relationships on a collection of clusters in the diffraction mode. By High Resolution TEM it is possible to get this information at the level of one cluster [83]. By using high-resolution profile imaging it is possible to measure the lattice distortion at the interface [84], These capabilities are very unique for TEM. Such structural information can be obtained in situ by diffraction techniques but only on a collection of clusters [14, 29]. To illustrate the structural characterization by TEM we present the case of Pd clusters on MgO(l 0 0), which will be discussed in the next sections. 

Figure 10.11b shows a typical HRTEM surface profile image of La2Cu04. It was found that the image contrast pattern in the top surface layers is different from that in the bulk area. Image simulation revealed that the (001) surface of La2Cu04 crystals was frequently coated by several atomic layers of C-La203 [47, 48]. 

By exposing a clean crystal surface to the electron beam, a series of H RTEM surface profile images can be recorded and a movement of surface atoms from a high-energy site to a low-energy site may be observed [47]. 

When HRTEM is used for examining nanoparticles of oxides, in which the proportion of surface area greatly increases, most structural information concerns the surface. For example, HRTEM images of core-shell quantum dots can show the shell structure and its thickness directly. HRTEM images of metal oxide nanotubes can also be regarded as surface profile images. The appHcation of TEM in nanomaterials will be further discussed below. 

Bulk samples Small samples profiling Imaging and depth... 

---