Powder particle morphology

The initial studies on nickel-aluminide synthesis defined a number of important issues in shock-induced solid state synthesis. This work was extended to the influence of powder particle morphology in recent work of Thadhani and... 

The effects of all the membrane preparation steps (from the powder particle morphology and size distribution, starting composition and membrane shape-forming process and the subsequent thermal treatment) on the structure and permeation behaviour of the resulting... 

Perhaps the first practical application of carbonaceous materials in batteries was demonstrated in 1868 by Georges Le-clanche in cells that bear his name [20]. Coarsely ground MnO, was mixed with an equal volume of retort carbon to form the positive electrode. Carbonaceous powdered materials such as acetylene black and graphite are commonly used to enhance the conductivity of electrodes in alkaline batteries. The particle morphology plays a significant role, particularly when carbon blacks are used in batteries as an electrode additive to enhance the electronic conductivity. One of the most common carbon blacks which is used as an additive to enhance the electronic conductivity of electrodes that contain metal oxides is acetylene black. A detailed discussion on the desirable properties of acetylene black in Leclanche cells is provided by Bregazzi [21], A suitable carbon for this application should have characteristics that include (i) low resistivity in the presence of the electrolyte and active electrode material, (ii) absorption and retention of a significant... 

ZnO particle morphologies are very complex and diversiform in comparison with Ti02. Thus, monodispersed ZnO particles with well-defined morphological characteristics, such as spherical, ellipsoidal, needle, prismatic, and rod-like shapes, have been obtained. Aggregates composed of these basic shape particles have also been achieved. The methods used for synthesis of these ZnO powders include alkali precipitation [214-216], thermal decomposition [217], hydrothermal synthesis [218], organo-zinc hydrolysis [219], spray pyrolysis [220], and other routes. 

Two important morphological parameters characterizing ball-milled powders are the particle and grain size of constituent phases within the powders. In our laboratory, the size measurement of the powder particles is carried out by attaching loose powder to sticky carbon tape and taking pictures under secondary electron (SE) mode in the SEM. The images are then analyzed by an image analysis software. The size of the powders is calculated as the particle equivalent circle diameter, ECD = AA/nf, where A represents the projected particle area. Usually from -300 to 700 particles are analyzed for each batch. 

Fig. 2.3 (a) Scanning electron micrograph of the morphology of as-received Tego Magnan MgH powder and (b) powder particle size distribution (equivalent circle diameter, ECD)... 

Scanning electron micrographs showing the particle morphology of as-received constituents and milled (NaBH -i- MgH ) composites with low (10-50 wt%) content of MgH are presented in Fig. 3.40. The particles of as-received NaBH and MgH powders have irregular shape and average size 145 and 36 pm, respectively (Fig. 3.40a, b). 

Fig. 3.40 Scanning electron micrographs showing morphology of as-received powder particles (a) NaBH and (b) MgH, and the morphology of composites (c) (NaBH + 10 wt%MgH ) (5 h milled), (d) (NaBH + 20 wt%MgH2) (20 h milled) and (e) (NaBH + 50 wt%MgH2) (20 milled)...

Fig. 3.41 Scanning electron micrographs showing morphology of powder particles after ball milling for 20 h for (a) (NaBH + 70 wt%MgH2), (b) (NaBH + 80 wt%MgH2) and (c) (NaBH + 90 wt%MgH2) composites. Particle size ECD shown...

Fig. 3.47 Scanning electron micrographs of the morphology of powder particles after ball milling for (a) NaBH + 12 wt%Mg, (b) NaBH + 55 wt%Mg, (c) NaBH + 73 wt%Mg, (d) NaBH + 92 wt%Mg composites...

Particle morphology refers to the external features or form of a powder s primary particles. This includes descriptions of shape, including aspect ratio, or crystal habit (plate, needle, lath, equant, etc.). Particles are not always observed as discrete entities. Rather, they are often associated with other particles, sometimes loosely held... 

Crowder TM, Rosati JA, Schroeter JD, Hickey AJ, Martonen TB. Fundamental effects of particle morphology on lung delivery predictions of Stokes law and the particular relevance to dry powder inhaler formulation and development. Phanna Res 2002 19 239-245. 

Bulk Density. The bulk densities determined by the tapping method for three powders were 0.424, 0.426 and 0.425 g/ml. From a theoretical viewpoint, particles with a smaller diameter should contribute to a tighter packing and thus lead to an increase in bulk density. This difference was not noted. Again, this could result from the difference in particle morphology. The increased tendency to expand or form internal voids in small size fractions (8) may have offset the expected effect of particle size itself. Therefore, no significant difference was observed. 

Barium titanate and BaTi03-based materials are most commonly used for ceramic capacitors with high dielectric permittivity. BaTi03 powder of extremely high quality (in respect of its purity, stoichiometry, particles morphology) is required for most of the modem applications. This characteristic may be considerably improved by the application of alkoxide precursors. Thus, it is of no surprise that synthesis of BaTi03 and BaTi03-based materials from metal alkoxides attracted considerable attention for several decades. The first works on... 

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