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  • 1
    Electronic Resource
    Electronic Resource
    A Comparison of the Nanostructure of Lead Zirconate, Lead Titanate and Lead Zirconate Titanate Sols (1999)
    Springer
    Journal of sol gel science and technology 15 (1999), S. 13-22 
    Details
    ISSN: 1573-4846
    Keywords: precursor chemistry ; lead zirconate titanate ; hydrolysis ; PCS ; SAXS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Sol-gel processing has been widely used for the fabrication of lead zirconate titanate (PZT) thin films. To successfully and consistently make high quality thin films for different applications, we must develop a fundamental understanding of the structures of the sols. In this study, the characters of lead titanate (PT) and lead zirconate (PZ)sols were studied by measuring the rheological properties and particle sizes in them and comparing their behaviours. The average particle sizes in unhydrolysed PT, PZ and PZT sols are 11.5, 1.0, and 6.0 nm, respectively. PT sol has the highest rate of hydrolysis. It gels at about 24 h after hydrolysis. PZ and PZT sols have a quite similar feature in hydrolysis. The reasons for the differences in the hydrolysis behaviour of the different types of sol are discussed in terms of a model which indicates that the inhomogeneous sols consist of 5 to 6 nm PT particles surrounded by much smaller PZ particles, which tend to dominate the sol behaviour.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008759520087
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Determination of Particle Size and Shape during the Hydrolysis of Pb(Zr0.3Ti0.7)O3 Precursor Solutions (1998)
    Springer
    Journal of sol gel science and technology 11 (1998), S. 141-152 
    Details
    ISSN: 1573-4846
    Keywords: precursor chemistry ; lead zirconate titanate ; hydrolysis ; PCS ; SAXS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The formation and growth of polymeric particles during the hydrolysis and condensation of PbZr0.3Ti0.7 O3 (PZT 30/70) sol-gel precursor solutions have been investigated by using photon correlation spectroscopy (PCS), small angle X-ray scattering (SAXS) and by measuring their rheological properties. The measurements showed that the growth of the particles in the transition of PZT sol to gel followed a simple polymerisation process. Solution A (containing ‘by-products’) and Solution B (‘by-products’ removed) displayed a similar plot of logarithmic viscosity against logarithmic time, indicating that the particles in both solutions have similar structures after hydrolysis. The changes in viscosity and particle size with time were described by single logarithmic growth models. However, the increasing rate of logarithmic particle size in Solution B is higher than that in Solution A. A model for the form of the aggregates is discussed which is applicable to PZT organometal-particle aggregation process in systems with acetic acid as a modifier.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008641429895
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    A numerical study of the effect of free surface and water depth on the stability of wakes: use of GDQ formulation (1997)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 24 (1997), S. 1079-1090 
    Details
    ISSN: 0271-2091
    Keywords: wake flow ; free surface ; instability ; GDQ method ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The instability character of a wake in the presence of a free surface is examined by a recently developed GDQ (generalized differential quadrature) numerical method. It is shown that at low Froude number the wake near a free surface is convectively unstable, but when the Froude number is increased further it becomes absolutely unstable. The effect of water depth on the stability property of the wake flow is also investigated. It is found that the influence of water depth on the critical point of instability is limited to at most 20% variation in the complex frequency, while the change in temporal growth rate is also limited to about 20%. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 4
    Electronic Resource
    Electronic Resource
    Design sensitivity coefficients for elasto-viscoplastic problems by boundary element methods (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 34 (1992), S. 947-966 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This paper is concerned with accurate and efficient determination of design sensitivity coefficients (DSCs) for solid mechanics problems with small strains and rotations, but with material non-linearities present (elasto-plastic or elasto-viscoplastic problems). This approach is based on direct differentiation (DDA) of the relevant derivative boundary element method (DBEM) formulation of the problem. Analytical differentiation of the DBEM equations leads to singular integral equations for the DSCs with weakly (logarithmically for 2-D) singular kernels which are easy to deal with. Also, stress components and their sensitivities are obtained on the boundary of a body with great accuracy. These quantities are typically difficult to obtain accurately from finite element methods (FEM).A computer program for general two-dimensional (plane strain and plane stress) problems has been developed based on the above formulation. Numerical results are presented for some sample problems and these are compared against direct solutions. The agreement between the DBEM and direct solutions is excellent for these examples.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620340318
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    Paper (German National Licenses)
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