Micron-sized powders

This paper is a follow-up of the previous study (Ref 7) whereby the adsorption of the carbon-14-labeled quaternary salt, stearyltri-methyl ammonium bromide (STAB), from soln by HMX was investigated in more detail. A solvent system for STAB, consisting of 90% water and 10% ethanol, yielded improved adsorption isotherms on 10-micron size powdered HMX. The data was shown to be quantitative and reproducible with a std deviation of O.Olmg... 

For refractory applications, when the mixed oxide route is followed, temperatures as high as 1900 °C are necessary to sinter to high density. The high interest in SOFCs has stimulated efforts to develop novel fabrication routes to zirconia ceramics and yttria-stabilized sub-micron sized powders have been prepared which sinter to 95% theoretical density at a temperature as low as 1150 °C [4],... 

The highest remanence available is achieved in Nd2Fei4B/a-Fe nanocomposite materials with typical grain size 20 - 30 nm jU()Mr = 0.98 T, juoHc = 1.1 T, and BHW = 127 kJ/m3 [133], However, due to the difficulty in material processing, the commercial development of these materials remains very limited. Anisotropic NdFeB powders are produced by the HDDR process. Nanosize grains form within micron sized powder particles and they are therefore protected against corrosion. Thanks to the induced texture... 

As a result Bertrand and Vukasovitch of Climax Molybdenum carried out an intensive study of different cleaning techniques applied to various forms of molybdenum disulphide film. The types of film used were a burnished film from a sub-micron sized powder, a burnished film from a soap-containing molybdenum disulphide powder, an air-cured inorganic-bonded coating, and a film formed from a dispersion in oil. The films were formed on steel pins which were then pressed through an undersized bush. This ensured highly-loaded contact on the film, and consolidation of the film. The burnished powder and the resin-bonded films could be... 

Comparatively soft powdered substances can be densified by compacting pressures of up to 100 MPa to a relative density of 0.75 at the most and talc materials under pressures of 400 MPa up to 0.94. With micron-sized powders of hard substances, the relative density of compacts is 0,50 - 0.70. These materials can be densified to... 

Both EDLCs and pseudocapacitors benefit from tailored, high surface area architectures because they each store charge on the surface by electrostatic or faradaic reactions, respectively. There are numerous examples in the hterature which show that materials possessing such features as nanodimensional crystallite size and mesoscale porosity exhibit significantly higher specific capacitance as compared to nonpotous materials or materials composed of micron-sized powders. The assembly of nanoscale materials is also important. One structure envisioned to be of interest is an array of vertically aligned carbon nanotubes where the spacing between the tubes is matched to the diameters of the solvated electrolyte ions (3). 

Higher rate of hthium ion insertion /de-insertion because of short hthium ion transport distance. The characteristic time constant for diffusion, t, is given by, T = L /D where L is the diffusion length and D is the diffusion coefficient Thus, the time for interealahon decreases substantially as micron-sized powders are replaced by nanometer particles. 

Another example of how materials at the nanoscale may exhibit entirely different properties is shown in the intercalation behavior of hematite, a-Fe203. When relatively small amounts of lithium are intercalated (0.005 Li per Fe203), micron-sized particles of hematite undergo an irreversible phase transformation. However, with 20 nm-sized hematite particles, 0.6 Li per Fe203 can be reversibly intercalated, as the phase transformation is suppressed. This response underscores an important point for nanoscale materials compositions that were previously disregarded because of the intercalation response with micron-sized powders should now be reconsidered. 

Particle-size analysis is a critical measurement in the pharmaceutical industry. From micron-sized powders for use in dry inhalation impellers to millimetre-sized granules for compression, size does matter. Furthermore, knowledge of the distribution and range of sizes within a sample as well as the shape of the particles is often vital to a successful formulation. The field of particle-size analysis is too vast to cover here and so a cursory outline of the topic will be presented since many books are available on the subject [87-91]. 

Much of the work in this area has been done in emulsions having a droplet size of more than 1 pm, and the application of submicron (nano) emulsions in encapsulation of oils and flavors is relatively new in the literature. Some works have been carried out to determine the influence of submicron emulsions produced by different emulsification methods on encapsulation efficiency and to investigate the encapsulated powder properties after SD for different emulsion droplet sizes and surfactants. The process has been referred to as nanoparticle encapsulation since a core material in nanosize range is encapsulated into a matrix of micron-sized powder particles (Jafari et al., 2008). This area of research is developing. Some patents were filed in the past describing microemulsion formulations applied to flavor protection (Chung et al., 1994 Chmiel et al., 1997) and applications in flavored carbonated beverages (Wolf and Havekotte, 1989). However, there is no clear evidence on how submicron or nanoemulsions can improve the encapsulation efficiency and stability of food flavors and oils into spray-dried powders. 

Alternatively, the DTA trace of the dry powder mix of Fe203/Al commercial micron-sized powders is significantly different than that of the nanoconq>osite. There are no low ten erature events in this DTA, as the Fe203 phase is dry and crystalline. This is not surprising, as the oxidizer in this mixture is crystalline Fe203 and not amorphous hydrous sol-gel Fe203. The main... 

Laser evaporation method (LE) is based on the usage of pulsed CO2 laser to evaporate the ceramic target, prepared from micron-sized powders of the given chemical composition. The dispersion of the powders doesn t play any role here. The as-formed oxide particles are carried from the working chamber to the devices of caching and separation of the powder (electro filters and cyclones) by the gas flow (Ar, N2 and O2 mixture). For example, figure 1, (c) represents TEM image of the YSZ solid solution particles. 

Working Group on Sub-micron Size Measurement (Soc. Powder Techn., Japan) H. Yamamoto (Tokyo Univ. ->Soka Univ.) Mainly about sub-micron size powder 30 (10 principles) 55(groups and individuals) on working... 

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