TEM studies

Unlike melting and the solid-solid phase transitions discussed in the next section, these phase changes are not reversible processes they occur because the crystal stmcture of the nanocrystal is metastable. For example, titania made in the nanophase always adopts the anatase stmcture. At higher temperatures the material spontaneously transfonns to the mtile bulk stable phase [211, 212 and 213]. The role of grain size in these metastable-stable transitions is not well established the issue is complicated by the fact that the transition is accompanied by grain growth which clouds the inteiyDretation of size-dependent data [214, 215 and 216]. In situ TEM studies, however, indicate that the surface chemistry of the nanocrystals play a cmcial role in the transition temperatures [217, 218]. 

CNT capillarity was firstly discovered by heating a sample composed of tubes and lead nanoparticles in air, and TEM studies revealed that a few tubes presented some material inside their cavities [9J. Although fillings could present impressive length (100 nm) and diameters as small as 2 nm. The phase that had entered the tubes could not be clearly identified by the authors and they also speculated on the possible formation of new phases. 

Most of our results have been obtained by TEM studies of individual tubes that can be considered nanolaboratories the ability to control and observe such small objects is very impressive. However, it also strains a limitation concerning the lack of an efficient method to generate macroscopic quantities of filled tubes, where we could be able to apply conventional macroscopic characterisation techniques. 

Another example of favorable synergistic effects in ionomer/homopolymer blends is evident from a study of the tensile properties of blends of an SPS ionomer with PS. Over most of the composition range these two polymers are incompatible. For small additions of the SPS ionomer to PS, TEM studies of cast thin films show that... 

Ye H, Naguib N, Gogotsi Y (2004) TEM study of water in carbon nanotubes. JEOL News 39 2-7 Yen T-H, Shji M, Takemura F, Suzuki Y, Kasagi N (2006) Visuahzation of convective boiling heat transfer in single micro-channels with different shaped cross-sections. Int J Heat Mass Transfer 49 3884-3894... 

SEM), and transmission electron microscopy (TEM). Study of mechanical and thermal properties shows significant improvement over the gum. The thermal results are given in Table 2.1. 

Pochan D.J., Pakstis L., Ozbas B., Nowak A.P., and Deming T.J. SANS and cryo-TEM study of self-assembled diblock copolypeptide hydrogels with rich nano through microscale morphology. Macromolecules, 35, 5358, 2002. 

The durability of the catalytic system was investigated by employing it in five successive hydrogenations. Similar TOFs were observed due to the water solubihty of the protective agent which retains nanoparticles in aqueous phase. The comparative TEM studies show that (i) the average particle size was 2.2 0.2 nm (ii) the coimter anion of the surfactant does not allow a major influence on the size and (iii) nanoparticle suspensions have a similar size distribution after catalysis. 

Nepijko SA, Klimenkov M, Kuhlenbeck H, Zemlyanov D, Herein D, Schldgl R, Ereund H-J. 1998. TEM study of tantalum clusters on Al2O3/NiAl(110). Surf Sci 412/413 192-201. 

TEM Studies. Electron micrographs were obtained on JE0L, TEMSCAN --100 CX11 combined electron microscope and a HITACHI H1M1B (TEM) operated at 2 x 10 magnification. The specimens for TEM were obtained by placing a drop of the colloid solution on a copper grid coated by a carbon film. 

Oberlin, Agnes. Fligh Resolution TEM studies of carbonization and graphitization . In Chemistry and physics of carbon, Vol 22, Thrower P.A. (Ed.), Marcel Dekker, New-York, 1989, p. 1-143. 

Visual estimation of nanoscrolls yield is difficult because they concentrate near the edges of copper grid support used in TEM studies. Nevertheless TEM images provide clear evidence of nanoscrolls presence in large amount. 

The three-stage mechanism of the cooperative self-assembly during the SBA-15 synthesis is illustrated in Figure 4. Our SANS results confirm, in agreement with a recent TEM study [4], that the transformation from spherical to cylindrical micelles takes place before the precipitation of the ordered SBA-15 material, and that the precipitation is associated with the self-assembly of hybrid cylindrical micelles into the two-dimensional hexagonal structure of SBA-15. 

TEM study of regulated mesoporous Mn203 hexagonal nanoplates... 

Kreuter and Speiser [77] developed a dispersion polymerization producing adjuvant nanospheres of polymethylmethacrylate) (PMMA). The monomer is dissolved in phosphate buffered saline and initiated by gamma radiation in the presence and absence of influenza virions. These systems showed enhanced adjuvant effect over aluminum hydroxide and prolonged antibody response. PMMA particles could be distinguished by TEM studies and the particle size was reported elsewhere to be 130 nm by photon correlation spectroscopy [75], The particle size could be reduced, producing monodisperse particles by inclusion of protective colloids, such as proteins or casein [40], Poly(methylmethacrylate) nanoparticles are also prepared... 

Murr LE, Soto KP (2005) A TEM study of soot, carbon nanotubes, and related fullerene nanopol-yhedra in common fuel-gas combustion sources. Mater Characteriz. 55 50-65. 

At the same time, one should notice that the real catalysts are applied in the gas/liquid environments at usually an increased temperature so that dynamic structural evolution of a real catalyst would not be probed in a conventional electron microscope. To bridge the gap, in situ environmental electron microscope is developed by placing a micoreactor inside the column of an electron microscope to follow catalytic reaction processes [58-62], However, the specimen in an in situ TEM may suffer from interaction with ionised gas (plasma), making the interpretation of in situ TEM study of catalytic reaction more complicated. Characterisation of static, post-reaction catalysts is still the most commonly used. Well-designed model catalysts and reasonable interpretation of the results are essential to a successful study. 

Kovalevski V.V., Buseck P.R., Cowley J.M. Comparison of carbon in shungite rocks to other natural carbons An X-ray and TEM study (2001). Carbon, 39,243-256 pp. 

---