Iron transmission electron microscopy

The cores of individual mammalian ferritin molecules are clearly visible by transmission electron microscopy as well defined nanoparticle crystallites encapsulated within the protein shell which can attain a size close to that of the 8 nm interior diameter of the protein shell (Massover, 1993). This is illustrated in Figure 6.13 for a sample of human ferritin. The amount of iron in the core is variable, and can range from zero to a maximum of approximately 4500 atoms (Fischbach and Anderegg, 1965) this corresponds to the capacity of the internal cavity for Fe(III) as... 

Nanocrystalline iron-doped Ti02 samples (as-prepared S2 and annealed at 500°C S4 [7]) and undoped samples (Si and S3 [8]) were S5mthesised by a modified sol-gel method. The details of preparation were reported earlier [7, 8]. The X-ray diffiaction of the samples was carried out at room temperature using a Philips powder diffractometer (PW 1820) with monochromatized CuXa radiation. Transmission electron microscopy (TEM) and SAED investigations were carried out by using a JEOL JEM 2010 200 kV microscope, Cs=0.5 mm, point resolution 0.19 nm. 

Figure 7.1. (a) Transmission electron microscopy image of a collection of 200-nm magnetic emulsion droplets obtained from emulsifying an octane-based ferrofluid. (b) One droplet is shown after polymerization. A polymer shell is visible that encapsulates the iron oxide nanoparticles. (With permission of Ademtech). 

Frost, B.R. Lindsley, D.H. (1991) Occurrence of iron-titanium oxides in igneous rocks. In Lindsley, D.H. (ed.) Oxide minerals. Reviews in Mineralogy 25, Min. Soc. Am., 433-468 Frost, B.R. (1991) Stability of oxide minerals in metamorphic rocks. In Lindsley, D.H. (ed.) Oxide minerals. Reviews in Mineralogy 25, Min. Soc. Am., 469-488 Fryer, J.R. (1979) The chemical applications of transmission electron microscopy. Academic Press, London New York, 231 p. 

Fe(OH), using Mdssbauer spectroscopy, optical spectroscopy and transmission electron microscopy. Phy. Chem. Min. 22 11-20 McCreadie, H. Blowes, D.W. (2000) Influence of reduction reactions and solid-phase composition on porewater concentrations of arsenic. Environ. Sd. Tedm. 34 3159-3166 McFadden, L.D. Hendricks, D.M. (1985) Changes in the content and composition of pedogenic iron oxyhydroxides in a chronose-quence of soils in Southern Cahfomia. Quart. Res. 23 189-204... 

To find the distribution of iron within the nanotube walls an energy dispersive x-ray spectroscopy (EDS) line scan was performed via scanning transmission electron microscopy (STEM), see Fig. 5. 55. The intensity of both the TiK and FeKa lines are maximum at the center of the wall due to its torus shape. Despite the presence of isolated hematite crystallites, a more or less uniform distribution of iron relative to the titanium can be seen across the wall. STEM line scans were performed across a number of walls, and while the average relative intensity of the TiK and FeKa lines varied from wall to wall the relative distribution across a single wall remained uniform. It appears that some of the iron goes into the titanium lattice substituting titanium ions, and the rest either forms hematite crystallites or remains in the amorphous state. 

Recently, we reported that an Fe supported zeolite (FeHY-1) shows high activity for acidic reactions such as toluene disproportionation and resid hydrocracking in the presence of H2S [1,2]. Investigations using electron spin resonance (ESR), Fourier transform infrared spectroscopy (FT-IR), MiJssbauer and transmission electron microscopy (TEM) revealed that superfine ferric oxide cluster interacts with the zeolite framework in the super-cage of Y-type zeolites [3,4]. Furthermore, we reported change in physicochemical properties and catalytic activities for toluene disproportionation during the sample preparation period[5]. It was revealed that the activation of the catalyst was closely related with interaction between the iron cluster and the zeolite framework. In this work, we will report the effect of preparation conditions on the physicochemical properties and activity for toluene disproportionation in the presence of 82. ... 

The gas reactants and products of the reaction were studied with a mass spectrometer and the solid reaction of the oxidation of iron was studied with Mossbauer spectrometry with electron diffraction. The Mossbauer study of the oxidized iron powder was carried out in a constant acceleration equipment [121], The electron diffraction study of the oxidized iron film, evaporated over a carbon covered transmission electron microscopy sample holder and introduced into the 5L spherical Pyrex glass container, where the Fe evaporation takes place, was carried out with the help of an Hitachi 100C transmission electron microscope [119],... 

Changes in the morphological and structural characteristics of the carbon deposit resulting from pretreatment of the iron catalyst in H2S were determined from a combination of transmission electron microscopy techniques, X-ray diffraction, surface area measurements and controlled oxidation studies in CO2. Iron powder 200 mesh) was purchased from Johnson Matthey Inc. (99 99% purity) and had a BET surface area of 0.3 m2/g at -196°C, The gases used in this work CO (99 9%), hydrogen (99.999%), ethylene (99.999%), H2S/argon mixtures and helium (99,999%) were obtained from Alphagaz company and used without further purification. 

Catalyst preparation and inspection by microscopy. Preparation by impregnation with ammonium iron citrate and iron nitrate resulted in a homogeneous iron distribution as determined by light microscopy. Ammonium iron EDTA as a precursor yielded an eggshell distribution of the iron compound. Finely divided material deposited on the support was observed with Transmission Electron Microscopy in all catalysts. Tn addition to this, some material deposited next to the support was observed in catalysts ex nitrate. It was therefore decided to focus on the catalysts prepared with ammonium Fe(ITI) citrate. 

The promoted WZ catalysts containing lwt% Pt and/or lwt% Fe203 were characterized by CO chemisorption and by transmission electron microscopy (TEM) in combination with EDX.33 The state of iron and its redox behavior was also analyzed by x-ray absorption spectroscopy (XANES and EXAFS at the Fe K-edge), by in situ EPR spectroscopy and by Mossbauer spectroscopy. 

Electron microscopy, with its high spatial resolution, plays an important role in the physical characterization of these catalysts. Scanning electron microscopy (SEM) is used to characterize the molecular sieve particle sizes and morphologies as a function of preparation conditions. Transmission electron microscopy (TEM) is used to follow the changes in the microstructure of the iron silicates caused by different growth conditions and subsequent thermal and hydrothermal treatments. 

Transmission electron microscopy of ion-thinned sections provides data at higher resolution than can be obtained with polished sections. Rodger and Groves (R24) described regions which had probably formed in situ from the ferrite phase, and which consisted of C-S-H, a hydrotalcite-type phase and a poorly crystalline phase containing iron that could have been the precursor of a hydrogarnet. The particles of this last constituent were almost spherical and some 200 nm in diameter. The same investigation also showed that much of the product formed in situ from alite or belite was essentially pure calcium silicate hydrate. 

---