Transitions transmission electron microscopy

SAXS), IR spectroscopy, NMR, transmission electron microscopy (TEM), or atomic force microscopy (AFM) and the thermal transitions by DSC and DMA. 

Transition metal oxides, rare earth oxides and various metal complexes deposited on their surface are typical phases of DeNO catalysts that lead to redox properties. For each of these phases, complementary tools exist for a proper characterization of the metal coordination number, oxidation state or nuclearity. Among all the techniques such as EPR [80], UV-vis [81] and IR, Raman, transmission electron microscopy (TEM), X-ray absorption spectroscopy (XAS) and NMR, recently reviewed [82] for their application in the study of supported molecular metal complexes, Raman and IR spectroscopies are the only ones we will focus on. The major advantages offered by these spectroscopic techniques are that (1) they can detect XRD inactive amorphous surface metal oxide phases as well as crystalline nanophases and (2) they are able to collect information under various environmental conditions [83], We will describe their contributions to the study of both the support (oxide) and the deposited phase (metal complex). 

Ffirai and Toshima have published several reports on the synthesis of transition-metal nanoparticles by alcoholic reduction of metal salts in the presence of a polymer such as polyvinylalcohol (PVA) or polyvinylpyrrolidone (PVP). This simple and reproducible process can be applied for the preparation of monometallic [32, 33] or bimetallic [34—39] nanoparticles. In this series of articles, the nanoparticles are characterized by different techniques such as transmission electronic microscopy (TEM), UV-visible spectroscopy, electron diffraction (EDX), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) or extended X-ray absorption fine structure (EXAFS, bimetallic systems). The great majority of the particles have a uniform size between 1 and 3 nm. These nanomaterials are efficient catalysts for olefin or diene hydrogenation under mild conditions (30°C, Ph2 = 1 bar)- In the case of bimetallic catalysts, the catalytic activity was seen to depend on their metal composition, and this may also have an influence on the selectivity of the partial hydrogenation of dienes. 

Application of transmission electron microscopy (TEM) techniques on heterogeneous catalysis covers a wide range of solid catalysts, including supported metal particles, transition metal oxides, zeolites and carbon nanotubes and nanofibers etc. 

Transition metal oxides attract great interests mainly due to their redox nature, which is thought to be related with their flexible stmcture modiflcation under reductive and oxidative conditions. Such stmcture modiflcation takes place by forming so called crystallographic shear (CS) stmctures to accommodate anion vacancies in speciflc crystallographic planes by simultaneous shear displacement and crystal stmctural collapse [30-32]. High-resolution transmission electron microscopy (HRTEM) is a... 

Many of the characterization techniques described in this chapter require ambient or vacuum conditions, which may or may not be translatable to operational conditions. In situ or in opemndo characterization avoids such issues and can provide insight and information under more realistic conditions. Such approaches are becoming more common in X-ray adsorption spectroscopy (XAS) methods ofXANES and EXAFS, in NMR and in transmission electron microscopy where environmental instruments and cells are becoming common. In situ MAS NMR has been used to characterize reaction intermediates, organic deposits, surface complexes and the nature of transition state and reaction pathways. The formation of alkoxy species on zeolites upon adsorption of olefins or alcohols have been observed by C in situ and ex situ NMR [253]. Sensitivity enhancement techniques play an important role in the progress of this area. In operando infrared and RAMAN is becoming more widely used. In situ RAMAN spectroscopy has been used to online monitor synthesis of zeolites in pressurized reactors [254]. Such techniques will become commonplace. 

Tip-sample interactions 36, 195—210 force and deformation 37 local modification of sample wavefunctions 195 uncertainty principle, and 197 wavefunction modification 37 Topografiner 44—47 Topographic images 122, 125 Transient response 261, 262 Transition probability 67 Transmission electron microscopy 43... 

TCLP TDB TDF THC TBP TEM TLM TM-AFM TOC TRLFS TRU TSP TST TVS Toxicity characteristics leaching procedure Thermodynamic database Tyre-derived fuel Total hydrocarbon Tri-n-butyl phosphate Transmission electron microscopy Triple layer model Tapping mode atomic force microscopy Total organic carbon Time-resolved laser fluorescence spectroscopy Transuranic Total suspended particles Transition state theory Transportable vitrification system... 

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