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  • 1
    Electronic Resource
    Electronic Resource
    Covering of substrate holes through particle deposition (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 2331-2335 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A methodology is proposed to determine the minimum coating thickness for covering substrate holes through particle deposition. The particle deposition process is carried out with a combined, two-dimensional, on-lattice model, in which both deterministic and nondeterministic driving forces are taken into account. The normalized covering thickness (hc/Dw) is investigated subject to variation in the Peclet number (Pe) and the size of the depositing particle, normalized hole size (Dw/L), and degree of postcontact restructuring allowed. It is found that ballistic particle movement gives a slightly better covering structure for smaller holes while diffusive particle movement much more efficiently covers larger holes. The normalized covering thickness increases with increasing normalized hole size and with decreasing normalized depositing particle size. Postcontact restructuring first improves the covering capability of the depositing particle, but then impairs it if further restructuring is allowed. It is further found that the normalized covering thickness scales with the normalized hole size as hc/Dw∼(Dw/L)E with E=0.67, 0.56, and 0.36 for Pe of infinity, 0.5, and 0.1, respectively. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1286330
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  • 2
    Electronic Resource
    Electronic Resource
    Evaporation-Assisted Formation of Three-Dimensional Photonic Crystals (2005)
    Oxford, UK : Blackwell Science Inc
    Journal of the American Ceramic Society 88 (2005), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The process of evaporation-assisted formation of three-dimensional photonic crystals was studied. The photonic crystals were fabricated by stacking uniform-sized silica spheres into regularly arranged structure with solvent evaporation and sedimentation. Effects of important process parameters, including type of solvent (water and ethanol), system temperature (40° and 60°C), and material for sedimentation cell (quartz, polymethyl methacrylate, and Teflon), on structure regularity of the resulting photonic crystal were investigated. The structure regularity was evaluated with scanning electron microscope graphs and stop band depth achieved in optical absorption spectra. As revealed from the experimental results, photonic crystals of better quality were obtained by using suspending solvents of higher surface tension (water), lower system temperatures (40°C), and sedimentation cell materials of higher critical surface tension of wetting (quartz).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2005.00153.x
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  • 3
    Electronic Resource
    Electronic Resource
    A General Process for Preparation of Core-Shell Particles of Complete and Smooth Shells (2005)
    Oxford, UK : Blackwell Science Inc
    Journal of the American Ceramic Society 88 (2005), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Core-shell particles have attracted much research attention in recent years because of the great potential in protection, modification, and functionalization of the core particles with suitable shell materials to achieve specific physical, chemical, and biological performance. A general approach for preparation of core-shell particles possessing complete and smooth shells is presented. The shell layer was constructed by introducing nanoparticles of desired shell material, prepared with the reverse micelle process, onto the core particle surface via layer-by-layer electrostatic adsorption, hydrophilic and hydrophobic interactions, and subsequent sintering. The proposed process is illustrated by coating silica spheres with four different shell materials, including Ag, CdS, ZnS, and TiO2. The successful formation of complete and smooth shell was examined with a novel light scattering intensity decay method and also by direct observation of scanning electron microscope and transmission electron microscope images.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2005.00070.x
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  • 4
    Electronic Resource
    Electronic Resource
    Size Effects on Silica Polymorphism (2002)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 85 (2002), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In this study, we found that the polymorphism and sintering behavior of silica can be affected by the size of starting particles. The formation of the stable tridymite phase, which is metastable unless a flux or mineralizer is present, is achieved with sintering of very fine silica particles of about 10 nm without the presence of a flux or mineralizer. Cristobalite phase is obtained as an intermediate as the amorphous phase transforms into the stable tridymite phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2002.tb00504.x
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  • 5
    Electronic Resource
    Electronic Resource
    Deposition of Nano-Size Titania—Silica Particles in a Hot-Wall CVD Process (2000)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 83 (2000), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The deposition of nano-size titania—silica particles is carried out in a hot-wall CVD reactor by using two premixed precursors, titanium tetraisopropoxide (TTIP) and tetraethyl orthosilicate (TEOS). The deposition occurs mostly in two regions, one near the reactor entrance and the other near the reactor exit. Deposits collected near the reactor entrance are densely packed micrometer-size aggregates/particles of good adhesion to the substrate, while those near the reactor exit are loosely packed nano-size particles with a poor adhesion to the substrate. It is conjectured that the more reactive TTIP reacts first and produces TiO2 particles later covered by SiO2 formed via a catalytic surface reaction of the less reactive TEOS on TiO2 particle surfaces. The presence of surface SiO2 retards the growth of TiO2 particles, leading to deposits formed by micrometer-size aggregates containing nano-size primary particles of 30 to 40 nm in the first deposition region. With less or no SiO2 present on TiO2 particle surfaces, the deposits formed in the first deposition region are densely packed micrometer-size particles. The Ti/Si ratio of the produced particles, for a furnace temperature of 750°C, increases with increasing TTIP/TEOS concentration ratio, and is lower than the Ti/Si ratio of the incoming reactant stream. The Ti/Si ratio of the particles is also found to decrease with increasing furnace temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2000.tb01263.x
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  • 6
    Electronic Resource
    Electronic Resource
    Effective conductivity of composites with spherical inclusions: Effect of coating and detachment (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 609-618 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An expression for the reduced effective thermal conductivity, keff/k1, of a random array of coated or debonded spherical inclusions with pair interactions rigorously taken into account is derived. Pair interactions are evaluated through solution of a boundary value problem involving two coated or debonded spheres with twin spherical expansions. The resulting keff/k1 is of O(f2) accuracy, where f is the combined volume fraction of the inclusion and interface. The effect of interfacial characteristics manifested as the reduced thermal conductivity, σ3, and relative thickness, δ/a, of the interfacial layer is thoroughly investigated. It is found that keff/k1 can be approximately viewed as a function of f and the dimensionless dipole polarizability, θ1, over a large parameter domain, despite the existence of higher order polarizabilities in the expression of keff/k1. The value of θ1 alone determines whether the effective inclusion is enhancing (θ1(approximately-greater-than)0), neutral (θ1=0), or impairing (θ1〈0) to the matrix. Furthermore, the evaluation of keff/k1 for the present model system can be approximately replaced with that for composites containing inclusions of no interface but possessive of a reduced thermal conductivity of (1+2θ1)/(1−θ1). A contour plot of keff/k1 on the θ1−f domain that is useful in estimating keff/k1 for interfacial properties characterized by an arbitrary combination of σ3 and δ/a, is constructed. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360803
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  • 7
    Electronic Resource
    Electronic Resource
    Anisotropy in effective conductivities of rectangular arrays of elliptic cylinders (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 2641-2647 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Effective conductivities of inhomogeneous systems with rectangular arrays of elliptic cylinders are accurately evaluated with a boundary collocation scheme. The investigation is conducted from 0 to the close packing in inclusion volume fractions f, and from 0 to ∞ in conductivity ratios of the inclusion to matrix σ. Results of the calculation agree very well with a reciprocal theorem developed by Keller [J. Appl. Phys. 34, 991 (1963); J. Math. Phys. 5, 548 (1964)]. The effect of different array arrangement on effective conductivities is studied by changing the aspect ratio of the inclusion ra, from 2 to 10 and the array edge length ratio re, from 1 to 10. The anisotropy in effective conductivities of the array is also examined. It is found that, with unit ra/re, the enhancement in conductivity in the direction parallel to the major axis of the inclusion increases appreciably when compared to that of the square array of circular cylinders of equal inclusion volume fractions, while the enhancement in the perpendicular direction decreases only slightly.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357561
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  • 8
    Electronic Resource
    Electronic Resource
    Critical interfacial characteristics for effective conductivities of isotropic composites containing spherical inclusions (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 5215-5219 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A study of the critical behavior of effective thermal conductivities of isotropic composites containing spherical inclusions is presented. Three types of problems are investigated: the debonded inclusion, coated inclusion, and contact resistance problems. For the first two problems, a critical relative interfacial layer thickness, (δ/a)c, is shown to exist and is derived to be a simple function of the reduced thermal conductivities of the inclusion, σ2, and of the interfacial layer, σ3. It depends much more strongly on σ3 than on σ2. As to the third problem, a critical Biot number, (Bi)c, is found to exist and can be simply expressed as 1/(σ2−1). Finally, the critical condition for the contact resistance problem is shown to be a special case of that of the debonded inclusion problem. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359270
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  • 9
    Electronic Resource
    Electronic Resource
    Effective conductivity of composites containing aligned spheroidal inclusions of finite conductivity (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 6761-6769 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effective conductivity of composites containing aligned spheroids of finite conductivity is determined with the pair interaction rigorously taken into account. The pair interaction is evaluated by solving a boundary-value problem involving two aligned spheroids with a boundary collocation scheme. Our results are in the form of virial expansion in the inclusion volume fraction f, truncated at the O(f2) term. Effective conductivities obtained from this study agree well with Willis's [J. Mech. Phys. Solids 25, 185 (1977)] bounds and Kim and Torquato's [J. Appl. Phys. 74, 1844 (1993)] first-passage-time simulation results. An expression for the effective conductivity tensor based on an equivalent inclusion method originated by Hasselman and Johnson [J. Compos. Mater. 21, 508 (1987)] is also derived, from which a criterion for testing the virial expansion validity is constructed. The relevant series ratio is found to be a good measure of intensity of the system thermal interaction. The smaller the value of the series ratio, the better agreement of the virial expansion with the simulation results. Explicit expressions for the second-order virial expansion for the parallel and perpendicular components of the effective conductivity tensor are tabulated for inclusion aspect ratios 1, 10/9, 2, 5, 10 and phase conductivity ratios σ=0, 0.1, 2, 10, 100, 10 000, and ∞. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361498
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  • 10
    Electronic Resource
    Electronic Resource
    Effective conductivities of aligned spheroid dispersions estimated by an equivalent inclusion model (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 2647-2655 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A simple equivalent inclusion model is proposed to estimate the effective conductivities of dispersions containing aligned spheroids. The spheroids are either in perfect contact with the matrix, possessive of certain contact resistance, or coated with a confocal layer of a third material. For the perfect contact case, our results coincide with Willis' bounds [J. Mech. Phys. Solids 25, 185 (1977)] and, for the coating case, they compare extremely well with those of Hatta and Taya [J. Appl. Phys. 59, 1851 (1986)]. New results are readily obtained for the contact resistance case through use of the proposed model. For the present systems, there exist two independent effective conductivities, one defined in the direction parallel with the symmetric axis of the spheroid and the other defined in the perpendicular direction. Interestingly, the inclusion effect for both the contact resistance and coating cases may be enhancing in one direction, but impairing in the other. But for the perfect contact case, the inclusion effect is always consistent in both directions. It is found that, for the perfect contact case, the reduced effective conductivity (σeff) is a function of the spheroid volume fraction, spheroid aspect ratio, and reduced spheroid conductivity. One more parameter, the Biot number, is needed for the contact resistance case, while two more parameters, the reduced coating layer conductivity and the relative coating thickness, appear in the coating problem. Effects of these parameters on σeff are thoroughly investigated. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368377
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