Macrostructure characterization

Although macrostructure characterization is important for the interpretation of adsorption dynamics and catalysis effectiveness, it has received very hmited attention for MCM-41, though some electron microscopic observations of uncalcined material have been reported. This is possibly because of the other novel features associated with these materials, which have attracted the bulk of the attention. The total surface area estimated from gas adsorption is reported to... 

A structure formed by the reversible association of am-phiphiles in apolar solvents. In inverted micelles, the polar portion of the amphiphile is concentrated in the interior of the macrostructure. Such association usually occurs with aggregation and is not typically characterized by a definite nucleation stage. Thus, inverted micelles (also referred to as inverse or reverse micelles) often fail to exhibit critical micelle concentration behavior. See Micelle... 

The close interplay of analytical methods gives much additional information especially in those areas where the analyzed substances are very complex. Thus, while ultracentrifuge analyses for petroleum (32, 33, 34) gave much information, the broad approach used by others (35, 36, 37) involved x-ray scattering, infrared, NMR, oxidation rates, GPC, MS, pyrolysis, and vapor pressure osmometry (VPO) applied to macrostructures of asphaltic fractions. Molecular complexes substantially larger than the foregoing macrostructures are difficult to characterize by methods short of ozonolysis (38) and general pyrolysis (39). 

For a discrete molecule with a simple structure, a microstructure is sufficient to characterize the given molecule. For a complex system such as that of asphaltene, the information required for characterization has to include association as well as micelle formation. The microstructure has been chosen arbitrarily to refer to short-range bonding, that is, distances between 0.5 A-2.0 A whereas the macrostructure (bulk structure) pertains to molecular interactions or orders at larger distances (20 A-2000 A). 

Table IV. Parameters for the Characterization of the Macrostructure of Coal-Derived Asphaltenes and Related Derivatives...

For the image in Figure la, the rose plot indicates that the majority of edges are oriented in the direction 0=Jt/2 but the rose pattern also includes a main orientation nearly 0=ii/3. A direct observation of Figure Ic suggests that the orientation 0=Jt/2 account for most of the largest channels that correspond to the ultramacropore structure, whereas the other directions characterize the edges inside those channels (ladder-like macrostructure). 

Reflectance-based optical characterization techniques offer the advantages of high energy resolution and sensitivity to both macrostructural and microstructural effects while nondestructively providing real-time information with the sample in any transparent ambient. Experimental and analytical methods are discussed, and examples are given to illustrate representative applications to problems of current interest in semiconductor technology. 

Compositional Characterization. The composition of the bulk samples was not determined since the components to these refractories were not considered sufficiently volatile to distort the nominal stoichiometry. Micro-analysis of the materials was performed in an effort to determine the homogeneity of the product crystals. These EDAX (Energy Dispersive X-ray Analysis) studies were performed by use of a Phillips model 505 scanning electron microscope. Microscopic investigation of the macrostructure of the ceramic were also performed using this instrument. 

Suction controlled oedometer tests were performed to gain insight into the characterization of the material, which exhibits a marked double structure a microstructure, which describes the dense aggregates of clay platelets and a macrostructure which includes the inter-aggregate and inter-pellet voids. An important feature of this material is the evolution of the microstructure as the mixture hydrates. 

The loess mass determined by in-situ immersion test is large in extent and capable of reflecting influence of microstructure and macrostructure on loess property, being representative and taken as the most practical and reliable method to obtain self-weight collapse settlement, but it is characterized by high cost and long time. It is an important... 

In FRP composite strengthening for civil engineering applications, two generally accepted material models are utilized in the mechanical characterization and stress analysis of FRP adhesive joints, viz. microstmctural and macrostructural material models. Microstmctural models take into account FRP material heterogeneity, and accordingly make use of the fibre and matrix properties, individually, in analysing FRP behaviour. On the... 

Intensive research efforts have been devoted to the NMR characterization of the new benzofulvene polymers in order to determine the nature of some general and peculiar aspects. In particular, poly-BFl was studied in details by means of NMR spectroscopy in order to confirm its polymeric nature and to determine its structure. Moreover, an extensive series of polybenzofulvene derivatives have been studied to determine, for each of them (1) the vinyl nature of the polymers and the presence of aromatic stacking interactions (2) the role of the electron-withdrawing groups (or donors) present on the benzofulvene fragment in affecting the macrostructure (3) the influence of a sterically demanding substituents on the conformational behavior. 

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