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Particle Orientation (particle + orientation)
Selected AbstractsElectric Field-Directed Convective Assembly of Ellipsoidal Colloidal Particles to Create Optically and Mechanically Anisotropic Thin FilmsADVANCED FUNCTIONAL MATERIALS, Issue 20 2009Manish Mittal Abstract A method of simultaneous field- and flow-directed assembly of anisotropic titania (TiO2) nanoparticle films from a colloidal suspension is presented. Titania particles are oriented by an alternating (ac) electric field as they simultaneously advect towards a drying front due to evaporation of the solvent. At high field frequencies (,,>,,25,kHz) and field strengths (E,>,300,V cm,1), the particles orient with their major axis along the field direction. As the front recedes, a uniform film with thicknesses of 1,10,µm is deposited on the substrate. The films exhibit a large birefringence (,n,,,0.15) and high packing fraction (,,=,0.75,±,0.08), due to the orientation of the particles. When the frequency is lowered, the particle orientation undergoes a parallel,random,perpendicular transition with respect to the field direction. The orientation dependence on field frequency and strength is explained by the polarizability of ellipsoidal particles using an interfacial polarization model. Particle orientation in the films also leads to anisotropic mechanical properties, which are manifested in their cracking patterns. In all, it is demonstrated that the field-directed assembly of anisotropic particles provides a powerful means for tailoring nanoparticle film properties in situ during the deposition process. [source] Spreadsheet for cyclone and hydrocyclone design considering nonspherical particle geometryCOMPUTER APPLICATIONS IN ENGINEERING EDUCATION, Issue 2 2007Marcelo K. Lenzi Abstract Cyclones and hydrocyclones are widely used for gas,solid and liquid,solid particle separations, respectively. The key feature is the presence of a centrifugal field. Equilibrium zone concept is one of the most used approaches for equipment design. This work revisits the design equations for nonspherical particles and compares design results considering nonspherical geometry to results considering spherical geometry and correcting the values to the non-spherical particle geometry. A didactic spreadsheet was prepared for analysis and instruction, and depending on the particle shape and on the particle orientation, errors up to 38% may be obtained in the cut diameter and 10% in the global collection efficiency. © 2007 Wiley Periodicals, Inc. Comput Appl Eng Educ. 15: 134,142, 2007; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae.20102 [source] Electric Field-Directed Convective Assembly of Ellipsoidal Colloidal Particles to Create Optically and Mechanically Anisotropic Thin FilmsADVANCED FUNCTIONAL MATERIALS, Issue 20 2009Manish Mittal Abstract A method of simultaneous field- and flow-directed assembly of anisotropic titania (TiO2) nanoparticle films from a colloidal suspension is presented. Titania particles are oriented by an alternating (ac) electric field as they simultaneously advect towards a drying front due to evaporation of the solvent. At high field frequencies (,,>,,25,kHz) and field strengths (E,>,300,V cm,1), the particles orient with their major axis along the field direction. As the front recedes, a uniform film with thicknesses of 1,10,µm is deposited on the substrate. The films exhibit a large birefringence (,n,,,0.15) and high packing fraction (,,=,0.75,±,0.08), due to the orientation of the particles. When the frequency is lowered, the particle orientation undergoes a parallel,random,perpendicular transition with respect to the field direction. The orientation dependence on field frequency and strength is explained by the polarizability of ellipsoidal particles using an interfacial polarization model. Particle orientation in the films also leads to anisotropic mechanical properties, which are manifested in their cracking patterns. In all, it is demonstrated that the field-directed assembly of anisotropic particles provides a powerful means for tailoring nanoparticle film properties in situ during the deposition process. [source] Influence of particle shape and angularity on the behaviour of granular materials: a numerical analysisINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 14 2003C. Nouguier-Lehon Abstract This paper analyses the influence of grain shape and angularity on the behaviour of granular materials from a two-dimensional analysis by means of a discrete element method (Contact Dynamics). Different shapes of grains have been studied (circular, isotropic polygonal and elongated polygonal shapes) as well as different initial states (density) and directions of loading with respect to the initial fabric. Simulations of biaxial tests clearly show that the behaviour of samples with isotropic particles can be dissociated from that of samples with anisotropic particles. Indeed, for isotropic particles, angularity just tends to strengthen the behaviour of samples and slow down either local or global phenomena. One of the main results concerns the existence of a critical state for isotropic grains characterized by an angle of friction at the critical state, a critical void ratio and also a critical anisotropy. This critical state seems meaningless for elongated grains and the behaviour of samples generated with such particles is highly dependent on the direction of loading with respect to the initial fabric. The study of local variables related to fabric and particle orientation gives more information. In particular, the coincidence of the principal axes of the fabric tensor with those of the stress tensor is sudden for isotropic particles. On the contrary, this process is gradually initiated for elongated particles. Copyright © 2003 John Wiley & Sons, Ltd. [source] An alternative approach to the modification of talc for the fabrication of polypropylene/talc compositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007Tao Wang Abstract We report an alternative method to modify talc for use in the fabrication of composites of polypropylene (PP) and talc. Grinding pulverization is employed to prepare talc fillers (referred to hereafter as p -talc). The properties of composites made with p -talc compare favorably with composites made with pulverized talc that has been further treated with a silane coupling agent (referred to as s -talc). The morphology of PP/p -talc composites illustrates particle orientation and a uniform dispersion of pulverized talc in the PP matrix. Modulated DSC analysis shows the ability of p -talc and s -talc to nucleate PP crystallization. The mechanical properties (i.e., the dynamic modulus, tensile strength, and impact resistance) of the PP/p -talc composites are very similar to PP/s -talc composites. The modification of talc by grinding is thus a highly effective alternative method to prepare PP/talc composites that does not require chemical treatment of the talc. The pulverization method is simpler and less expensive in comparison to silane treatment. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Constrained Sintering of a Glass Ceramic Composite: II.JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2009Symmetric Laminate The sintering behavior of symmetric laminates has been experimentally measured and modeled. Two cases are distinguished: (i) sintering of a viscous layer between viscous substrates and (ii) sintering of a viscous layer between elastic substrates. A simple model based on a persisting isotropic microstructure allowed computation of developing in-plane stresses. These in conjunction with a viscous Poisson's coefficient were taken to predict out-of-plane stresses and finally densification rate. This approach, however, proved unsuccessful to predict the large observed differences in densification rate between laminates constrained by either green or dense alumina substrates. The discrepancy was found to be due to widely different microstructures developing with different degrees of elastic constraint. Pore area and pore and particle orientation were determined to quantify these microstructural changes. [source] Crystallographic Orientation of Y2Ba4CuMOx (M=Nb, Zr, Ag) Nanoparticles Embedded in Bulk, Melt-Textured YBCO Studied by EBSDJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2007A. Koblischka-Veneva Crystallographic orientations of Y,Ba,Cu,O (YBCO) and embedded Y2Ba4CuMOx (M=Nb, Zr, Ag) nanoparticles in bulk, melt-textured YBCO samples are studied by electron backscatter diffraction. Y2BaCuO5 particles exhibit no preferred orientation but have a strong negative influence on the matrix orientation. In contrast, the nanoparticles do not disturb the texture of the YBCO matrix. Depending on the preparation route, a different particle orientation with respect to the matrix is obtained. Untextured nanoparticles are formed by solid-state reaction during the melt process by adding oxides (Nb2O5 or Y2O3) to the precursor powder. Preformed Y2Ba4CuMOx particles added to the precursor in the form of prereacted nanopowder exhibit a dominant single orientation related to the surrounding YBCO matrix. [source] | |||||||||||||