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  • 1
    Electronic Resource
    Electronic Resource
    Formation of magnetic nanocrystals in a glass ceramic studied by small-angle scattering (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 2279-2286 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The formation of nanosized crystallites of magnetite, Fe3O4, by heat treatment of a glass containing iron oxide was investigated. The magnetic properties of the glass ceramic manufactured strongly depend on the heat treatment conditions. The evolution of size distribution and volume fraction of the nanocrystallites formed was studied by small-angle x-ray scattering (SAXS). The size distribution of the nanocrystalline phase turned out to show bimodal shape. The possibility of magnetic contrast variation offered by small-angle neutron scattering (SANS) was utilized in order to distinguish the small-angle scattering of magnetite from the scattering contributions of nonmagnetic iron containing crystallites that can additionally be formed during the heat treatment. The results obtained reveal that both size grades of particles observed in the size distribution are superparamagnetic consisting of magnetite. The evolution of the volume fraction of magnetite in dependence on the heat treatment was found to be correlated with the magnitude of the specific saturation magnetization of the glass ceramic. The volume size distributions derived from magnetic SANS revealed peaks at smaller radii in relation to those from nuclear SANS and SAXS data. Therefore, the existence of a nonmagnetic surface layer is suggested that surrounds the magnetically active core of the magnetite nanocrystals. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369538
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  • 2
    Electronic Resource
    Electronic Resource
    Reversion of precipitates in phase separated soda lime silica glass (2000)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 33 (2000), S. 492-495 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The glass with composition 13Na2O-11CaO-76SiO2 (mol%) undergoes subliquidus phase separation via a binodal mechanism. At temperatures below the binodal temperature, Tb = 978 K, the glass separates into two amorphous phases, silica-enriched droplets and a silica-poor matrix. Small-angle X-ray scattering was used to study the formation of the droplet phase at 923 K as well as the process of reversion where the precipitates dissolve after an increase in temperature. After a heat treatment of 48 h at 923 K the system is in the stage of coarsening. However, the equilibrium volume fraction of the droplet phase, we = 0.073, has not yet precipitated. The reversion of the droplets was studied at T = 983 K and T = 963 K. For T 〉 Tb, the precipitates dissolve completely by an interdiffusion process resulting in a decrease of the silica concentration of the droplets, while the phase boundary is preserved over long times. For T 〈 Tb, the reversion process shows two distinct stages. In the first stage, the silica concentration inside the droplets decreases and all precipitates shrink until the concentration in the matrix reaches its new equilibrium value. Afterwards, the largest droplets grow again by slow coarsening.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S002188989901688X
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  • 3
    Electronic Resource
    Electronic Resource
    Determination of the correlation function directly from slit-smeared small-angle X-ray scattering curves (1982)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 15 (1982), S. 143-147 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A simple technique has been developed for calculating the correlation function directly from small-angle X-ray scattering curves obtained with an `infinitely long' primary beam profile. The method is based on expanding the correlation function in a series of zero-order Bessel functions of the first kind, where the coefficients of the series are proportional to the intensities of the measured curve. The correlation function thus is represented by an analytical expression and can be calculated easily.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889882011686
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  • 4
    Electronic Resource
    Electronic Resource
    Particle size distribution from small-angle X-ray scattering data (1985)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 18 (1985), S. 205-213 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: An improved transform technique has been developed [Gerber (1983). Thesis, Wilhelm-Pieck-University Rostock, German Democratic Republic] for calculating the particle size distribution N(R) for spherical particles with radii R from small-angle X-ray scattering data. This method permits N(R) to be calculated from analytical expressions that were derived for point collimation and for infinitely long slit collimation. A special procedure has been introduced in order to reduce termination errors. The technique described and those developed by Schmidt [Brill, Weil & Schmidt (1968). J. Colloid Interface Sci. 27, 479–492], Vonk [J. Appl. Cryst. (1976), 9, 433–440] and Glatter [J. Appl. Cryst. (1980), 13, 7–11] were used for calculating particle size distributions from theoretical scattering curves and from an experimental scattering curve of suspended SiO2 particles (Ludox). The results obtained by the different techniques were compared, and reasonable results are given by all methods employed. The accuracy of the size distributions calculated by the improved method is somewhat higher than that obtained by Schmidt's transform technique. With Glatter's procedure, the deviations from the exact distributions are comparable to those from this improved transform technique, but the use of Glatter's program requires a large computer, whereas the new method has the advantage of being suitable for a small computer. Vonk's program also requires a large computer, and the deviations obtained are larger than those produced by other methods. The experimental scattering curve of the Ludox sample was also evaluated by assuming a log-normal distribution for the particles. The parameters μ and σ of this function were determined from a set of small-angle X-ray scattering structural parameters. The resulting log-normal distribution is significantly different from the size distribution calculated by our method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889885010160
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  • 5
    Electronic Resource
    Electronic Resource
    Investigation of single-phase glasses using small-angle X-ray scattering techniques (1991)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 24 (1991), S. 616-623 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The study of single-phase glasses by X-ray scattering experiments requires special techniques. Experimental methods and data evaluation procedures aimed at obtaining reliable scattering data in the range of small and intermediate scattering angles are described. These techniques have been applied to the study of the intermediate-range order of silica and phosphate glasses. For commercial silica glasses and for phosphate glasses, the zero-angle scattering was found to be a very suitable parameter to quantify the optical homogeneity. The zero-angle scattering of alkaline-earth metaphosphate glasses was analyzed in terms of the formalism of Bhatia & Thornton [Phys. Rev. B. (1970), 2, 3004–3012]. From the results, conclusions were drawn about the chemical short-range order. In magnesium phosphate glasses, the presence of small clusters of about 1 nm diameter was established.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889891000456
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  • 6
    Electronic Resource
    Electronic Resource
    Phase Formation Kinetics in a Glass Ceramic Studied by Small-Angle Scattering of X-rays and Neutrons and by Visible-Light Scattering (1997)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 30 (1997), S. 1056-1064 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The kinetics of the primary phase formation in a glass ceramic base glass near the cordierite composition in the MgO–Al2O3–SiO2 system, with additions of ZrO2 and TiO2 as nucleating agents, have been investigated by combining different small-angle scattering techniques. Phase formation in the base glass heated isothermally at 1093 K has been studied in order to elucidate the structural processes that take place during controlled nucleation before volume crystallization begins. Complementary results of X-ray diffraction, transmission electron microscopy and electron microprobe analysis reveal that in the final stages of annealing, different crystalline phases, which are dispersed in the residual glassy phase, are developed. The largest particles have sizes of the order of several hundreds of nanometers and consist of magnesium petalite as well as a high-quartz solid solution. Besides these crystals, two populations of smaller particles, the sizes of which can be resolved by small-angle scattering, were detected and found to be enriched with TiO2 and/or ZrO2. The growth of particles of intermediate size was studied in situ. The radius, R, of each of these particles increases with increasing treatment time, t, according to the power law R ∝ t1/2, indicating diffusion-limited independent growth. The scattering patterns are modified by diffusion zones surrounding the growing particles. The characteristics of the diffusion zones are evaluated by fitting appropriate model scattering curves to the experimental scattering data. The structural arrangement of the Ti and Zr ions was studied by contrast variation with the help of anomalous small-angle X-ray scattering and small-angle neutron scattering. As revealed by the contrast variation experiments, Ti ions are concentrated in the interface between the intermediate-sized particles and the glass matrix, whereas Zr is homogeneously distributed in these particles. Additionally, the Zr ions participate in the formation of the smallest particles, which are crystallites enriched with ZrO2. Finally, the catalyzing effect of TiO2 and ZrO2 on the nucleation and volume crystallization of the glass ceramic is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889897001313
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  • 7
    Electronic Resource
    Electronic Resource
    On the calculation of a slit-smeared small-angle X-ray scattering function for coated spheres (1974)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 7 (1974), S. 445-446 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A formula is presented for calculating `infinite-slit' smeared small-angle X-ray scattering curves for concentrically coated spheres of uniform electron densities ρ1 and ρ2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889874010119
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  • 8
    Electronic Resource
    Electronic Resource
    Small-Angle X-ray Scattering of Inorganic Glasses. Data Treatment and Analysis (1997)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 30 (1997), S. 1048-1055 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The treatment and analysis of small-angle X-ray scattering data are reviewed with specific concern for the glass science. The studies detail the characterization of the submicroscopic structure existing in terms of two-phase particulate systems, multiphase particle systems, non-particulate systems, including those of fractal surfaces, and the application of small-angle X-ray scattering to the examination of the intermediate-range order of glasses. The methods developed are illustrated by small-angle X-ray scattering and anomalous small-angle X-ray scattering results obtained from optical filter glass, glass produced by the sol–gel technique, optical colorless glass inclining to opalescence, porous glass and single-phase phosphate glass.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889897001015
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  • 9
    Electronic Resource
    Electronic Resource
    Small-Angle X-ray Scattering Size Parameters and Higher Moments of the Particle-Size Distribution Function in the Asymptotic Stage of Ostwald Ripening (1995)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 28 (1995), S. 553-560 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Small-angle X-ray scattering (SAXS) is a powerful tool to study the kinetics of phase separation in materials. A simple procedure is presented that allows one to prove if the particle-size distribution established in a system in the late stages of phase separation corresponds to the predictions of the classical Lifshitz–Slyozov–Wagner (LSW) theory for the asymptotic stage of Ostwald ripening. The method is based on the correlations between certain SAXS size parameters and the higher moments of the LSW size distribution functions for diffusion-limited or reaction-limited ripening. It is suggested that the use of these size parameters, which can be obtained with high accuracy from the scattering curve, is frequently more advantageous than a direct comparison of the experimentally obtained size distributions with the asymptotic size-distribution functions predicted by the LSW theory. The method is applicable if the suppositions made in the LSW theory that the precipitated particles should be homogeneous spheres with volume fraction tending to zero are fulfilled. The method is applied to a photochromic glass; although the silver-halide precipitates contained in the glass develop according to the power law of diffusion-limited Ostwald ripening, their size distribution is shown not to correspond to the features of the LSW size distribution. Consequently, in this case the LSW theory cannot describe quantitatively the kinetics of ripening.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889895003827
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  • 10
    Electronic Resource
    Electronic Resource
    Sol-gel processing of titanium-containing thin coatings (1993)
    Springer
    Journal of materials science 28 (1993), S. 2353-2360 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Using tetrabutylorthotitanate as a precursor, titanate coatings with and without modifiers such as SnO2 and Fe2O3 have been successfully obtained. The hydrolysis and polycondensation mechanism is discussed in relation to the sol-gel transition. The gel-formation region was obtained as well as stable-layer formation and phase-separation regions in the Ti(OBun)4-C2H5OH-H2O system. Coatings deposited on glass substrates exhibited a strong tendency to aggregate and with increasing temperature to crystallize in anatase or rutile phases (500 and 1000 °C, respectively). Structural characteristics of the gel products were investigated by SEM, X-ray and electron diffraction measurements, as well as by small-angle X-ray scattering. It was established that after thermal treatment at 500 °C for 10 min, spherical aggregates were formed in the coatings, having an average radius of approximately 5.1 nm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01151665
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