Morphology cubes

Crystal Morphology. Size, shape, color, and impurities are dependent on the conditions of synthesis (14—17). Lower temperatures favor dark colored, less pure crystals higher temperatures promote paler, purer crystals. Low pressures (5 GPa) and temperatures favor the development of cube faces, whereas higher pressures and temperatures produce octahedral faces. Nucleation and growth rates increase rapidly as the process pressure is raised above the diamond—graphite equiUbrium pressure. 

Zeolite crystals can be grown in sizes ranging from 0.5 pm to several hundreds pm and often have a characteristic morphology. Thus type A zeolites are cubes,... 

Morphologies of synthetic hematite include plates and discs, rods, spindles, spheres, ellipsoids, double ellipsoids, rhombohedra, stars, cubes and peanuts. In the absence of additives, hexagonal plates, which are often rounded, and rhombohedra predominate. Each morphology can be obtained by more than one synthesis route. Two common ways of producing idiomorphic hematite crystals in aqueous systems... 

NiO is a cubic oxide characterized by ionicity and lattice parameters very similar to those of MgO. Furthermore, the preparation procedures of the two oxides may be similar (i) Stoichiometric high-surface-area NiO is prepared (as is MgO) from the hydroxide precursor by decomposition under vacuum and (ii) low-surface-area materials are obtained by progressive sintering at high temperatures. The evolution of the microcrystal morphology on passing from high- to low-surface-area (sintered) NiO is also similar to that for MgO, as demonstrated by Escalona Platero et al. (73,265,266) the final habit of the microcrystals is represented by nearly perfect cubes predominantly defined by atomically flat (001) faces and terraces. 

The products with Si/Al >2.0 displayed on unusual morphology for A-type materials where the cubes show an octahedral prism development. 

FIGURE 8-67 Schematic diagrams of the principal morphologies occurring in block copolymers, (i) Spheres in a body centered cube, (/i) cylinders, (fix) lamellea and (iv) bicontinuous structures. 

The size and shape of ceria NCs are proven fo appreciably change the chemical and physical properties hence, their control in synthesis is one chief objective for study, and various nanoparticles, nanocubes, nanooc-tahedra, nanowires, and nanotubes have been obtained for this purpose. Owing to the cubic fluorite structure, ceria tends to form isometric particles, which present sphere-like morphology and are usually intermediates between the shape of cubes and octahedra. The major exposed crystal surfaces for ceria NCs are low index ones, that is, 100, llOj, and 111, with considerable surface relaxation and reconstructions. Figure 1 shows some typical morphologies of ceria NCs. 

To maximize fluorophore excitation and increase the fluorescence quantum yield, the spectral properties of the metal nanoparticles need to be optimized. While spherical colloidal nanoparticles of noble metals have been well known for many years, it is only recently that there has been an explosion of reports on the preparation and properties of anisotropically-shaped materials. As will be discussed in the following sections, a wide range of morphologies can be produced, including triangular nanoplates (nanoprisms), cubes, octahedra, nanowires, nanorods and bi-pyramids. The last few years have also seen major developments in our understanding of the growth processes involved, so that now it is possible to prepare many types of shaped p>articles in a controlled fashion. 

Higher concentrations of bromide result in increased etching and, as mentioned for chloride, the single crystal morphology is preferred. However, unlike with chloride, the nanoparticles formed are not cubes but are elongated into nanorod-like structures, termed nanobars [60]. This is discussed in more detail in Section 11.4 1.3 2, which deals with the synthesis of nanocubes by the polyol process. 

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