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Powder Properties (powder + property)
Selected AbstractsSolid-State Synthesis of Nanocrystalline BaTiO3: Reaction Kinetics and Powder PropertiesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2008Maria Teresa Buscaglia The formation of BaTiO3 nanoparticles by a solid-state reaction between nanocrystalline raw materials BaCO3 and TiO2 was studied as a function of temperature (400°,800°C), time (1,24 h), and titania particle size (15 and 30 nm). The reaction starts at 500°C and a high reaction rate is already observed at 600°C for the finest titania, with up to 90% conversion after 2 h. Two main reaction stages were observed at 600°,700°C. The first step is dominated by nucleation and growth of BaTiO3 at the TiO2,BaCO3 contact points and at the TiO2 surface. Surface diffusion of BaCO3 is, most likely, the prevailing mass transport mechanism responsible for the rapid formation of BaTiO3, even in the absence of a significant contribution from lattice diffusion. The second stage begins when the residual TiO2 cores are completely covered by the product phase. For longer times, the reaction can only proceed by the slower lattice diffusion, resulting in a strong decrease of the reaction rate. Single-phase BaTiO3 nanopowders with a specific surface area of 12,15 m2/g, an average particle size of 70,85 nm, a relative density of 96.5%,98.3%, and a tetragonality of 1.005 were obtained by calcination at 700°,800°C. Critical parameters in the preparation of ultrafine powders by solid-state reactions are the particle size of both raw materials, the absence of large hard agglomerates, and the homogeneity of the mixture. The use of fine raw materials and optimization of the reaction conditions make mechanical activation unnecessary. [source] Physico-chemical properties of protein-bound polysaccharide from Agaricus blazei Murill prepared by ultrafiltration and spray drying processINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 1 2007Joo Heon Hong Summary This study was conducted to develop the powder material and investigate the various physico-chemical properties of protein-bound polysaccharide with different molecular weight from Agaricus blazei Murill using ultrafiltration and spray-drying process. Powder properties of the three spray-dried powders were very different based on their molecular weights. The inlet temperature had less influence than pump rate on particle size of spray-dried powders. The moisture content of powders was increased with increasing pump rate and decreasing inlet temperature. Among these powders, SD-1, the molecular weight of which is below 10 kDa, was less flowable by internal cohesion. The decomposition temperature for the powders was in the range of 200,400 °C and showed relatively good enough for their thermal stabilities. [source] Preparation of LiMn2O4 powders via spray pyrolysis and fluidized bed hybrid systemAICHE JOURNAL, Issue 7 2006Izumi Taniguchi Abstract A novel technique has been developed to directly produce fine ceramic powders from liquid solution using a spray pyrolysis and fluidized bed hybrid system. Using this technique, the preparation of lithium manganese oxides LiMn2O4, which are the most promising cathode materials for lithium-ion batteries, has been carried out for various superficial gas velocities U0 = 0.30-0.91 m/s, static bed heights Ls = 50-150 mm, and medium particle sizes dpm,g = 294-498 ,m. The resulting powders had spherical nanostructured particles that comprised primary particles with a few tens of nanometer in size, and they exhibited a pure cubic spinel structure without any impurities in the XRD patterns. Moreover, the as-prepared powders showed better crystallinity and smaller specific surface area than those by conventional spray pyrolysis. The effects of process parameters on powder properties, such as specific surface area and crystallinity, were investigated for a wide range of superficial gas velocities and static bed heights. An as-prepared sample was used as cathode active materials for lithium-ion batteries and the cell performance has been investigated. Test experiments in the electrochemical cell Li/1M LiClO4 in PC/LiMn2O4 demonstrated that the sample prepared by the present technique was superior to that by the conventional spray pyrolysis and solid-state reaction method. © 2006 American Institute of Chemical Engineers AIChE J, 2006 [source] A review of the terms agglomerate and aggregate with a recommendation for nomenclature used in powder and particle characterizationJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 10 2002Gary Nichols Abstract The terms "agglomerate" and "aggregate" are widely used by powder technologists to describe assemblages of particles that are found in dry powders and powders in liquid suspensions. Each term has a specific meaning but, unfortunately, they are frequently interchanged at will and this has resulted in universal confusion. This confusion is perpetuated by conflicting definitions in national and international standards and this presents problems when describing powder properties or communicating results in reports and research papers. This paper reviews the current status of the definitions, with particular emphasis on their use in the pharmaceutical industry. It is proposed that just one term, agglomerate, should be used to describe an assemblage of particles in a powder and that the term aggregate should be confined to pre-nucleation structures. © 2002 Wiley-Liss Inc. and the American Pharmaceutical Association J Pharm Sci 91:2103,2109, 2002 [source] Synthesis of Nanocrystalline Zirconium Nitride Powders by Reduction,Nitridation of Zirconium OxideJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2004Bo Fu Nanocrystalline ZrN powder was synthesized by reduction,nitridation of nanosized ZrO2 powder in ammonia gas with magnesium as the reducing agent. The effects of nitridation temperature, holding time, and Mg:ZrO2 mole ratio on the powder properties were investigated. Cubic phase ZrN powder with a 30,100-nm particle size was synthesized at 1000°C for 6 h, under a Mg:ZrO2 mole ratio of 10:1. [source] Reflectance spectra of iron meteorites: Implications for spectral identification of their parent bodiesMETEORITICS & PLANETARY SCIENCE, Issue 2 2010Edward A. CLOUTIS Powder spectra are invariably red-sloped over this wavelength interval and have a narrow range of visible albedos (approximately 10,15% at 0.56 ,m). Metal (Fe:Ni) compositional variations have no systematic effect on the powder spectra, increasing grain size results in more red-sloped spectra, and changes in viewing geometry have variable effects on overall reflectance and spectral slope. Roughened metal slab spectra have a wider, and higher, range of visible albedos than powders (22,74% at 0.56 ,m), and are also red-sloped. Smoother slabs exhibit greater differences from iron meteorite powder spectra, exhibiting wider variations in overall reflectance, spectral slopes, and spectral shapes. No unique spectral parameters exist that allow for powder and slab spectra to be fully separated in all cases. Spectral differences between slabs and powders can be used to constrain possible surface properties, and causes of rotational spectral variations, of M-asteroids. The magnitude of spectral variations between M-asteroids and rotational and spectral variability does not necessarily imply a dramatic change in surface properties, as the differences in albedo and/or spectral slope can be accommodated by modest changes in grain size (for powders), small changes in surface roughness (for slabs), or variations in viewing geometry. Since metal powders exhibit much less spectral variability than slabs, M-asteroid spectral variability requires larger changes in either powder properties or viewing geometry than for slabs for a given degree of spectral variation. [source] Determining Contact Angles of Powders by Liquid PenetrationPARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 4 2004Ulrich Teipel Abstract The wettability of a powder is important, especially in chemical and pharmaceutical technologies when considering the manufacturing process and the properties of the final product. However, contact angle methods for powders are problematic. The common measurement techniques are the sessile drop method and the liquid penetration method. In this work the determination of contact angles of powders by liquid penetration is considered. In particular, we investigated the influence of the sample preparation and sampling device on the wetting process. A bulk with constant properties during the measurement must be guaranteed. We postulate a packing procedure to obtain reproducible measurements by ensuring constant powder properties. [source] | |||||||||||||