Morphology hollow spheres

Application of Pore-Forming Agents and Hollow Sphere Morphology... 

However, while the above was a rather crude approach to fabricate more porous electrode layers with oxidic support materials, a more elegant way was chosen for home-made ATO by 3D morphology engineering. ATO powder with unique hollow-sphere morphology was synthesized by ultrasonic spray p)irolysis (USP). Depending on precursor concentration and temperature, this process yields a powder composed of individual nano-crystallites forming the shells of hollow spheres with a controlled nano- and microporosity [98]. This offers efficient mass transport and is assumed to prevent the collapse of the electrode structure with time during operation. 

Figure 10.16 shows a TEM image of the home-made ATO powder. The hollow sphere morphology is clearly visible. The shells of the spheres are made up from individual nanocrystallites and thus offer nanoporosity between the crystals as well as microporosity due to... 

FIGURE 10.16 Survey image of the home-made ATO powder in hollow-sphere morphology. Reproduced from Ref. [98]. Copyright 2012 Wiley-VCH Verlag GmbH Co. KGaA, Weinheim. 

By changing the ultrasound power, changes in the mesoporosity of ZnO nanoparticles (average pore sizes from 2.5 to 14.3 nm) have been observed. In addition to the changes in mesoporosity, changes in the morphology have also been noted [13]. Recently, Jia et al. [14] have used sonochemistry and prepared hollow ZnO microspheres with diameter 500 nm assembled by nanoparticles using carbon spheres as template. Such specific structure of hollow spheres has applications in nanoelectronics, nanophotonics and nanomedicine. 

Cao, S.W. and Zhu, Y.J. (2009) Iron oxide hollow spheres microwave-hydrothermal ionic liquid preparation, formation mechanism, crystal phase and morphology control and properties. Acta Materialia, 57 (7), 2154-2165. 

We have developed the solvothermal synthesis as a convenient approach for controlling morphology, by which non-oxides nanomaterials, such as nanoparticles, one-dimensional nanomaterials and those with very special shapes have been fabricated, which include nano-metered tubes, rods, wires, balls, hollow spheres and peanut-like nanostructures, etc. 

At least five groups have attempted polymerization in vesicles [7-11]. Pertinent experimental conditions, results, and appropriate references are summarized in Table 1. The polymerized morphologies observed are hollow polymer shells, parachutes , matrioshka structures, and necklaces as shown in Fig. 3. ( Matrioshka refers to the concentric sphere morphology that resembles the nesting Russian dolls bearing the same name.) Structures of the surfactants and monomers used in the experiments are shown in Fig. 4. 

Hollow silicon carbide (SiC) spheres have been synthesized by a microwave heating and carbothermal reduction method with carbon spheres as template and fly ash (a solid waste from coal-fired power plant) as silica source. X-ray diffraction and scanning electron microscope were employed to characterize the morphology, structure of the products. The results show that hollow spheres prepared at 1300 "C under argon atmosphere have a hollow core and SiC shell structure. The shell of a hollow SiC sphere is composed of a lot of irregular SiC nanowires with 5-20 pm in length and 50-500 nm in diameter which belongs to the p-SiC. Moreover, the formation mechanism of the hollow SiC spheres is also discussed. 

In the discussion of the results a distinction is made, with help of the scanning electron microscopy (SEM), between spheres (solid or hollow), distorted and sponge-like 6) particles. All the other morphologies are defined by the combination of these three basic shapes e.g. distorted agglomerated hollow spheres. The three shapes are shown in Figure 7. 

In Table 5 the effect of the melt temperature on the particle morphology is shown. In all experiments hollow spheres were formed. At 60-65 C melt temperature distorted particles were formed. At 80 C and 140 bar atomization pressure agglomeration occurred. Whereby at 80 C and 70 bar atomization pressure. Figure 10, hollow and spherical particles are formed. 

The synthesis approaches for fabrication of hollow spheres of different semiconductor materials through irradiation route in large scale and under mild conditions could be of interest for both applications and fundamental studies. Indeed, it has been found that the combination of ionizing radiation and microemulsion can afford more unique conditions to control the composition, morphology, and size of NPs. Compared with other routes of building hollow spheres, radiation chemical approach is a one-step facile and effective method and has potential to produce various inorganic/polymer nanocomposite hollow spheres with potential applications in the fields of materials science and biotechnology. 

SBA-15, MCM-48, HMS and MCM-41. Xia etal. also used CVD with acetonitrile as precursor to prepare graphitic mesoporous carbon materials with diverse morphologies, such as sphere, hollow sphere, rod and nano-tubeP Su et al. used a similar CVD method and benzene as... 

The morphology of ordered mesostructured carbons is another important factor with respect to their practical applications. Various macroscopic morphologies are required, for example, films (in sensor, separation and optical applications), uniformly sized spheres (in chromatography) or transparent monoliths. Using suitable synthesis strategies, it is possible to control the external shape of the templated mesoporous carbon materials to generate powders, films and membranes, spheres, hollow spheres, rods, fibres, nanowires, nanotubes and monoliths. 

The other type of nanoparticulate structure and fabrication morphology is the core-shell and associated hollow spheres. In this instance, a spherical nanostructure is established by polymerization onto a preformed nanoparticle. Different template materials have been used for fabrication. For chemical-sensing applications, the two most widely used have been silica and polystyrene, as highly monodisperse nanoparticles of these materials can be reliably synthesized. In addition, their surface chemistry can be modified to achieve different monomer interactions. Core-shell structures could be formed from the... 

Munaiah, Y., B. G. Sundara Raj, T. Prem Kumar, and P. Ragupathy. 2013. Facile synthesis of hollow sphere amorphous MnOj The formation mechanism, morphology and effect of a bivalent cation-containing electrolyte on its supercapacitive behavior. Journal of Materials Chemistry A 1 4300-4306. 

Jagadeesan, D., Mansoori, U., Mandal, P, Sundaresan, A., and Eswaramoorthy, M. Hollow Spheres to Nanocups Tuning the Morphology and Magnetic Properties of Single-Crystalline a-Fe Oj Nanostructures. Angewandte Chemie International Edition, 47(40), 7685-7688 (2008). 

Fig, 27. Morphological development of the hollow spheres from a negatively charged coacervate drop of the complex coacervate gelatin-gum arabic. 

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