Crystal morphology chapter

Various zeolites have been studied as the dispersed phase in the mixed-matrix membranes. Zeolite performance in the zeolite/polymer mixed-matrix membrane is determined by several key characteristics including pore size, pore dimension, framework structure, chemical composition (e.g., Si/Al ratio and cations), crystal morphology and crystal (or particle) size. These characteristics of zeolites are summarized in Chapter 6. 

Of the morphological phenomena mentioned in the last few paragraphs, that of twinning is likely to be of most frequent value in identification problems, but all the phenomena are significant from the point of view of crystal structure and the relation between internal structure and growth characteristics. The subject of crystal morphology in relation to internal structure will not, however, be pursued further at present it will be taken up again in Chapters VII and VIII. For the present, we shall continue our consideration of the problem of the identification of microscopic crystals we pass oij to discuss crystal optics, the relation between optical properties and crystal shape and symmetry, and the determination of refractive indices and other optical characteristics under the microscope. 

As for the physical properties of crystals, some account of crystal morphology and optics has been given in Chapters II and III, where, however, these subjects were developed only as far as was necessary for identification purposes. For structure determination further consideration of both these subjects, as well as others such as the magnetic, pyroelectric, and piezo-electric properties of crystals, is desirable this will be found in Chapter VIII. 

The main chapters (4-14) are concerned with the preparative methods. For the majority of oxides particularly hematite and goethite more than one preparative method is described. Properties such as crystal morphology and surface area frequently depend on preparative conditions and a selection of methods is presented to enable a range of oxides with specific characteristics to be produced. The production of so-called monodis-perse Fe oxides, i. e. products with a rather narrow particle size distribution, is also included. 

One of the many unique features of crystals is crystal habits. Crystals can have different shapes and faces that make them unique and distinct from hquid or gaseous materials. In view of the focus of this book, crystal morphology means the approximate shape of crystals. Our purpose is to describe quahtatively the aspect ratios of crystals in three-dimensional space with relevance to the crystallization process. Therefore, we refer the reader to (Mullin 2001, Chapter 1) for a more thorough and comprehensive classifications of crystal morphology. 

Impurities are known to profoundly affect crystal morphology. The texts referred to near the beginning of this chapter offer some structural models of impurities that interface with the growth of specific faces. An example from the authors experience is shown in Fig. 4-19. The three microphotographs are of the same crystal form of a compound spiked with small amounts, respectively, of each of three known impurities normally present in much smaller amounts in the mother liquors from which growth is taking place. 

This chapter, related to the crystallization, morphological structure and melting of polymer blends has been divided into two main parts. The first part (section 3.1) deals with the crystallization kinetics, semicrystalline morphology and melting behavior of miscible polymer blends. The crystallization, morphological strucmre and melting properties of immiscible polymer blends are described in the second part of this chapter (section 3.4). 

Microscopic examination (OM), small angle light scattering (SALS), scanning (SEM) or transmission electron microscopy (TEM) wide (WAXS) and small angle X-ray scattering (SAXS) spectroscopy are other techniques usually necessary to characterize fully the polymer crystal morphology but will not be dwelt upon in this chapter. 

In the first chapter, an overview of thermodynamic behaviors of non-equilibrium polymers is discussed. In the consecutive chapters, different properties of polymer blends are discussed, including surface tension, transition, crystallization, morphology, and flow behaviors. Miscibility and molecular characterizations of polymer blends are also covered in this book. Applications to various systems are reviewed, and both experimental concerns and references are supplied. 

A good nanoclay dispersion is a prerequisite to obtain a nanocomposite—rather than a microcomposite—structure and therefore to achieve interesting physical properties. During the discussion of various nanocomposite properties, in the remaining part of this chapter, other factors of paramount importance will also need to be taken in account such as the content and orientation of nanoclays, the polymer-filler interaction, the degree of crystallinity, and the crystal morphology of the polymeric phase. 

Recent years have seen a great deal of effort expended to control crystal forms. Crystal morphology can play an important role in the manufacturing processes in pharmaceutical, dye, explosives, and other industries. This is because the shape and size of crystals influence their properties for processes such as flow and tabletting. In these industries serious consideration is given to the specifics of crystal packing, that is, polymorphism, which has become a familiar topic to solid-state chemists. The topic of this chapter is the closely related subject of supramolecular isomerism in network structures. First used in the context of substrates absorbed in zeolite cavities, or the isomerism of discrete supermolecules of 18-crown-6 with a sulfonylamine derivative, the term supramolecular isomerism has come to be understood as the phenomenon of several network structures being built from the same molecular or other... 

This review will focus on the use of SAMs in crystallization processes. We will begin with a short introduction on crystallization on SAMs. Then, we will review the latest advances in crystallization on patterned SAM s and effects of SAMs on crystal morphology and crystal polymorphism. This chapter will also include a description of chiral SAMs and their role in enantioselective crystallization. 

It is interesting that the simple HSP approach seems to capture the essence of the plasticizer literature and provides a comprehensive explanatory and predictive framework. It cannot, of course, explain all the complex details of crystal morphology and mechanical properties, but this is a chapter... 

Due to length limitation of this chapter, many theoretical approaches on the phenomenological aspects of polymer crystallization have to be skipped. The isothermal and non-isothermal kinetic analysis of overall crystallization appears as technically important in the data treatment of DSC measurements. Some theoretical considerations on the metastable aspects of crystal morphologies and their evolution under various circumstances appear as practically important and case sensitive (see Chap. 1). In this sense, a combination of this chapter with other contributions of this book will provide reader a broad cutting-edge knowledge about our basic understanding of polymer crystallization. 

Mixing can also play a key role in affecting the morphology of a crystalline product. This effect results from the complex interaction between the impeller and nucleation and growth. The reader is referred to the discussion on mixing and crystallization in Chapter 17. 

Table 13.1 Number of qualifiers of crystal morphology in the Z(1) database (see Chapter 8) 8,519 total entries. 3D, 2D, and ID approximately label crystals grown in globnlar, plate or acicnlar form, respectively.

In this chapter, an attempt is made to synthesize the principal founding on this polymer and analyze it in terms of structural organization and crystal morphology. 

Groeninckx G, Vanneste M, Everaert V. Crystallization, morphological structure and melting of polymer blends. In Utracki LA, editor. Polymer blends handbook, vol. 1. Dordrecht Kluwer Academic Publishers 2002. p. 203-94 [chapter 3],... 

In isotactic polypropylene [73,76], the smectic phase or the monoclinic a phase can be obtained according to cooling conditions. Furthermore, the a phase may, in certain conditions, exhibit a bimodal crystalline texture, that is, two populations of crystals with their c or their a-Sixis along the fiber axis, respectively (a is the axis of the reciprocal lattice related to a). This is revealed by additional arcs or spots on the 110 and 130 reflections, while the 040 reflections remain unchanged [79] (Fig. 15.21). This can be interpreted in terms of a cylindritic morphology with two types of lamellae classical radial lamellae and tangential ones obtained by epitaxial growth, which is a particular feature of polypropylene crystallization (see Chapter 8). 

---