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Particle
About: Particle is a research topic. Over the lifetime, 96582 publications have been published within this topic receiving 1954327 citations.
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TL;DR: Geldart et al. as mentioned in this paper proposed a theory to describe horizontal turbulent diffusion of fine particles towards the freeboard walls, where the fine particles descend as a falling film which may drag down gas and thus generate a gas circulation current.
49 citations
TL;DR: In this paper, high-energy density metastable nanocomposites with high energy density, were prepared by arresting the milling process prior to the spontaneous reaction, and the resulting powders were structurally characterized by electron microscopy and x-ray diffraction.
Abstract: Highly metastable, nano-scale energetic materials were prepared by Arrested Reactive Milling (ARM). When reactive milling is carried out with materials systems suitable for Self-Propagating High Temperature Synthesis (SHS), reaction between the components occurs spontaneously and violently after a certain period of milling. In this research, metastable nanocom-posites with high energy density, were prepared by arresting the milling process prior to the spontaneous reaction. Products thus obtained are powders with particle sizes in the 10–50 μm range. Individual particles are intimate mixtures of reactive components, comparable to Metast-able Intermolecular Composites (MIC), with near theoretical maximum density. The time of arrest determines the degree of grain refinement and therefore the sensitivity to mechanical, electrical, or thermal initiation. Particle sizes of the product powders can be adjusted by appropriate choice of milling parameters. This paper describes the application of ARM to the material systems Al-Fe2O3 and Al-MoO3. After empirical determination of optimum milling parameters, the reactive composites are structurally characterized by electron microscopy and x-ray diffraction. First results of combustion tests are presented.
49 citations
TL;DR: In this paper, the melting of small lead particles embedded in a silicon monoxide matrix has been studied by dark-field electron microscopy and it was shown that the width of the molten layer depends on the particle curvature as well as on temperature indicating a continuous transition.
Abstract: The melting of small lead particles embedded in a silicon monoxide matrix has been studied by dark-field electron microscopy. Thomson's idea from 1888, that the melting temperature depends on the size of the particles and Faraday's idea from 1860, that melting of the surface occurs below the bulk melting temperature, are demonstrated here straight-forwardly. The electron microscope pictures give the most direct observation on the existence of a molten surface layer in equilibrium with a solid core at temperatures below the melting point. The width of the molten layer is demonstrated to depend on the particle curvature as well as on temperature indicating a continuous transition. Quantitatively, it was found that for the small lead particles, the width of the molten layer is wider than the reported one for bulk lead.
49 citations
Patent•
02 Sep 2011
TL;DR: In this paper, the authors proposed a composition comprising a plurality of electroactive porous particle fragments comprising silicon as an electroactive material characterised in that each porous particle fragment comprises a network of pores defined and separated by silicon containing walls.
Abstract: The invention provides a composition comprising a plurality of electroactive porous particle fragments comprising silicon as an electroactive material characterised in that each porous particle fragment comprises a network of pores defined and separated by silicon containing walls. The network of pores suitably comprises a three dimensional arrangement of pores extending through the volume of the particle in which the pore openings are provided on two or more planes over the surface of the particle. The composition of the first aspect of the invention is an electroactive material that is able to form an alloy with lithium and can be used in the fabrication of anodes for use in lithium ion secondary batteries. A method of fabricating the silicon containing porous particle fragments is also disclosed.
49 citations
TL;DR: The use of neutron imaging is demonstrated for visualizing and quantifying water distribution in partially saturated granular porous media and a quantitative analysis provides detailed information on the arrangement and distribution of particles, voids, and water.
Abstract: The use of neutron imaging is demonstrated for visualizing and quantifying water distribution in partially saturated granular porous media. Because of the unique difference in the total neutron cross sections of water, sand, and air, a significant contrast for the three phases is observed in a neutron transmission image, and a quantitative analysis provides detailed information on the arrangement and distribution of particles, voids, and water. The experiments in this study are performed at the Neutron Imaging Facility (NIF) at the National Institute of Standard and Technology (NIST). An amorphous silicon flat panel detector was used in this research with a spatial resolution of approximately 250 μm (127 μm/pixel). The effect of particle morphology on water distribution in compacted granular columns is investigated by using round and angular silica sand. Silica sand specimens with different bulk gravimetric water contents (0%, 6%, 9%, and 12%) are studied for evaluating the water phase-distribution spati...
49 citations