Structured particles

A-B relative or external motion undergo free-free transitions (E., E. + dE.) (Ej Ej+ dE within the translational continuum, while the structured particles undergo bound-bound (excitation, de-excitation, excitation transfer) or bound-free (ionization, dissociation) transitions = (a, 3) ->/= (a, (3 ) in their internal electronic, vibrational or rotational structure. The transition frequency (s ) for this collision is... 

R. F. Cracknell, D. Nicholson, N. G. Parsonage, H. Evans. Rotational insertion bias a novel method for simulating dense phases of structured particles, with particular application to water. Mol Phys 77 931-943, 1990. 

Catalyst Structure Particle Size BET Surface Area Isoelectric Point pH... 

Metals Structure Particle size Precursors Protecting agent Reducing agent Analysis Literatures... 

Kan et al. reported preparation of Au-core/Pd-shell bimetallic nanoparticles by successive or simultaneous sonochemical irradiation of their metal precursors in ethylene glycol, respectively. In the successive method, Pd clusters or nanoparticles are first formed by reduction of Pd(N03)2, followed by adding HAUCI4 solution. As a result, Au-core/Pd-shell structured particles are formed, although Pd-core/Au-shell had been expected. In their investigations, the successive method was more effective than the simultaneous one in terms of the formation of the Au-core/Pd-shell nanoparticles [143]. 

This technique has been used in the preparation of metal alloys ceramics and composite materials. To this end a chemical precursor converted to the gas phase is decomposed at either low or atmospheric pressure to produce the nano-structured particles which, transported in a carrier gas, are collected on a cold substrate. 

O. Velev, A. Lenhoff, and E.W. Kaler A Class of Micro structured Particles Through Colloidal Crystallization. Science 287, 2240 (2000). 

Seeded polymerization is defined as polymerization of post-added monomer in the presence of particles. A conventional example of seeded polymerization is the polymerization of styrene (St) and acryronitrile (AN) in the dispersion of polybutadiene (PB) particles. In this polymerization, a portion of St and AN penetrates into the PB particle and the other portion stays in the aqueous phase. The former graft-polymerize with PB or polymerize by themselves in PB particle. The progress of polymerization in the particle leads to phase inversion to form a salami structured particle in which PB islands are dispersed in a poly(St-co-AN) sea. St and AN in aqueous phase may polymerize to form independent particles. 

SEM-microscopy Amorphous structure, particle sizes are between 1000-40000 nm... 

Figure 19.16 Spherical structure (particle, bubble, droplet) with radius r0 surrounded by a concentric fluid boundary layer with thickness 5. r is the spherical coordinate. The concentration inside the sphere is Cs. There is a phase change at the surface of the sphere with the equilibrium partition coefficient KSlf = Csl Cp Cp is the fluid concentration in equilibrium with Cs.

Powder Preparation. There are several routes to preparing SiC powders having variable purity levels, crystal structure, particle size, shape, and distribution. Methods that have been examined include growth by sublimation from the vapor phase, carbothermic reduction, and crystallization from a melt. 

The value of pigments results from their physical—optical properties. These are primarily determined by the pigments physical characteristics (crystal structure, particle size and distribution, particle shape, agglomeration, etc) and chemical properties (chemical composition, purity, stability, etc). The two most important physical—optical assets of pigments are the ability to color the environment in which they are dispersed and to make it opaque. 

The most commonly measured pigment properties are elemental analysis, impurity content, crystal structure, particle size and shape, particle size distribution, density, and surface area. These parameters are measured so that pigments producers can better control production, and set up meaningful physical and chemical pigments specifications. Measurements of these properties are not specific only to pigments. The techniques applied are commonly used to characterize powders and solid materials and the measuring methods have been standardized in various industries. 

Due to the variety in porous structure, particle size and surface area, pure silica gels and powders find a very wide range of applications. Variation in preparation methods and parameters allows the tailoring of the substrate properties for specific application needs. The main features in the silica applications are its porosity, active surface, hardness, particle size and the viscous and thixotropic properties. Although most applications are based on a combination of those, a classification according to the main properties of interest may be set up. For references, the reader is referred to the works of Iler6 and Unger7 and to the references cited in chapter 8. 

This review has shown that most studies on barley starches have been focused on understanding the fine structures, particle size distribution, chemical composition, gelatinization properties and susceptibility towards enzyme hydrolysis. However, there is a dearth of information on the rheological and retrogradation characteristics of barley starches from different cultivars. Furthermore, the response of small and large barley starch granules towards physical and chemical modification needs investigation. Research in the above areas is underway in our laboratories. It is hoped that this study may improve the utilization of different types of barley starches for specific products within the food and paper industry. 

Smith WE, Zukoski CF. (2004) Flow properties of hard structured particle suspensions. J Rheol 48 1375-1388. 

Of particular interest are phthalocyanines with strong absorption in the near infrared. A considerable effort has gone into the synthesis of new compounds and the development of methods for conversion of known phthalocyanines into morphologies that are infrared sensitive. This lias been difficult because the absorption spectra and photogeneration efficiencies depend on the chemical and crystal structure, particle size and morphology, as well as the presence of absorbed surface species (Sappok, 1978 Whitlock et al., 1992 Kubiak et al., 1995). As a consequence, specific methodologies must be developed for the synthesis, purification, and treatment of each compound. Methods of fabrication must also be designed to ensure that the desired characteristics are retained or induced (Mayo et al., 1994 Yao et al., 1995). 

Stable colloids of nanometer-sized lamellar manganese oxides have been prepared by intercalation and self-assembly direct reduction methods. The structures, particle sizes, and optical properties of the materials have been described. Organic amine/ammonium species (TAA and DA) were used to intercalate birnessite H-OL-1 to prepare TAA-OL-1. Many kinds of structures and their formation processes were also described. The effects of organic ammonium cations and organic amines on the preparation of the manganese oxides were studied systematically. 

It has been well known that HRTEM is a powerful tool to investigate structures of low-dimensional oxides, such as nanoparticles, nanowires, nanorods and nanotubes, while the information from powder dilfraction of these low-dimensional materials is normally very Hmited merely because their small crystaUite sizes. For the nanoscale oxides, HRTEM can give useful information on particle size, crystal structure, particle morphology, structural defects and possible inter-particle connections. 

Matthews and Rhodes, Haines and Martin, Hie-stand, and Ecanow and co-workers are credited-with establishing the structured particle concept or flocculated pharmaceutical suspension. The following definitions should prove useful in avoding confusion among three closely related terms flocculation, agglomeration, and coagulation. The term aggregation can apply to all three. 

Raw materials and their properties are of prime significance in the technology of ceramics. The manufacturing process and properties of the product are affected by the chemical and mineral composition of the raw materials, by their crystalline structure, particle size and their surface condition. All these factors may vary over wide ranges, in particular with natural raw materials. Detailed information on the raw materials, obtained by suitable test methods, is essential for mastering the manufacturing process. 

The performance targets, such as reactivity of the reaction mixture, selectivity, extension of a production campaign or reproducibility, are controlled by quite a number of parameters. The most important parameters are temperature, pressure, catalyst and promoters, poisons and inhibitors, silicon composition and structure, particle size distribution of solids, dust removal from fluidized-bed reactor, homogeneity of fluidized-bed and the purity of chloromethane. 

Simultaneously, with the rapid growth of electrodeposition in microelectronics, a new trend based on the electrodeposition of materials, structures, particles, devices, etc., generally called nano-objects, with dimensions below 100 nm commenced. Nano-objects are fundamental for nanoscience investigations and nanotechnology development. A nano-object is of particular interest if it has physical properties that differ from objects that have macroscopic sizes. Quantization of energy, for example, is observed in systems with greatly reduced size, such as atoms, molecules, and nanostructures. 

Particle internal structure Particle-particle association... 

---