Morphology motivation

An even coarser description is attempted in Ginzburg-Landau-type models. These continuum models describe the system configuration in temis of one or several, continuous order parameter fields. These fields are thought to describe the spatial variation of the composition. Similar to spin models, the amphiphilic properties are incorporated into the Flamiltonian by construction. The Flamiltonians are motivated by fiindamental synnnetry and stability criteria and offer a unified view on the general features of self-assembly. The universal, generic behaviour—tlie possible morphologies and effects of fluctuations, for instance—rather than the description of a specific material is the subject of these models. 

Data for step-mobilities shown in Fig. 6 span an impressively large range a factor of 10 " separates step-mobilities measured by STM from the step-mobilities extracted from the relaxation of micron-sized gratings. Some discrepancies exist, but most of the step-mobilities are consistent with a single activation energy of 1.8 eV and an attempt rate given by the frequency of atomic vibrations. We hope that this initial comparison of step-mobility data will help motivate more detailed theoretical analysis and experiments on the coimections between step-mobility and the evolution of surface morphology. 

The first type of cruciform or cross-like material that we present is based on the so-called tetrahedral approach . The motivation for constructing it-conjugated materials using such tetrahedral cores (e.g. tetraarylmethane or -silane building blocks) stems from the perception that a bulky, sterically hindered architecture should be less prone to self-aggregation in the solid state and hence should lead to more efficient and morphologically stable photo- and electroluminescence. 

The motivation of this chapter was to show that despite the enormous prospects of ionic liquids in electrodeposition some troublesome aspects have to be expected. Apart from the purity and price of ionic liquids the optimum temperature for any process has to be found. Furthermore, suitable additives for electrodeposition will have to be developed and cation/anion effects that can strongly alter the morphology of deposits have to be expected. Finally, the electrochemical window alone is not the only factor that needs to be considered for the deposition of reactive metals. Suitable precursors will have to be tailor-made and it is our personal opinion that the electrodeposition of metals like Mg, Ti, Ta and Mo may not be possible from metal halides but rather metal bis(trifluoromethylsulfonyl)amide salts and other ones may be more suitable. 

Another motivation for measurement of the microhardness of materials is the correlation of microhardness with other mechanical properties. For example, the microhardness value for a pyramid indenter producing plastic flow is approximately three times the yield stress, i.e. // 3T (Tabor, 1951). This is the basic relation between indentation microhardness and bulk properties. It is, however, only applicable to an ideally plastic solid showing no elastic strains. The correlation between H and Y is given in Fig. 1.1 for linear polyethylene (PE) and poly(ethylene terephthalate) (PET) samples with different morphologies. The lower hardness values of 30-45 MPa obtained for melt-crystallized PE materials fall below the /// T cu 3 value, which may be related to a lower stiff-compliant ratio for these lamellar structures (BaM Calleja, 1985b). PE annealed at ca 130 °C... 

The variation of the chemical composition of the substrate (not realized in a continuous tunable fashion) leads to drastic modifications of surface fields exerted by the polymer/substrate (i.e.,II) interface [94,97, 111, 114,119]. The substrate may, for instance, change contact angles with the blend phase from zero to a finite value. As a result the final morphology changes from a layered structure of Fig. 5b into a column structure of Fig. 5c [94,114]. On the other hand our very recent experiment [16] has shown that the surface fields are temperature dependent. Therefore, although it has been shown that surface-induced spinodal decomposition yields coexisting bilayer structure (Fig. 5b) at a singular temperature [114,115], that in principle may not be necessary true for other temperatures. This motivated our comparative studies [107] on coexistence compositions determined with two techniques described above interfacial relaxation and spinodal decomposition. 

A second motivation for using a monomer-feed semibatch procedure is to control copolymer composition and/or particle morphology. Delayed feed of part of the more reactive monomer can be used to eliminate or reduce the composition drift of the copolymer. The delayed feed of a comonomer mixture when the reactor is operated in the monomer-starved regime can also be used to prevent copolymer composition drift. Such operations will produce polymer particles with more uniform morphology. Different monomer addition schemes can be employed to control nonuniform particle morphology (see papers by Bassett et al. in General References 7 and 9). 

In the present work, we investigated the influence of the metal precursor and of the nature of the support on the performences of ruthenium catalysts for the wet air oxidation of p-hydroxybenzoic (p-HBZ) acid chosen as a model of phenolic pollutants. Titanium and zirconium oxides were selected as supporting materials. The preparation method adopted for supports was sol-gel combined with the use of supercritical drying. The motivation of such combination is to prepare aerogel supports with high BET surface area and unique morphological and chemical properties [9,10]. 

---