Bragg nanocomposites

Fig. 68 Comparison of temperature-dependent intensity of first-order Bragg peak for bare matrix copolymer (A) containing 0.5 wt% nanocomposites with plate-like (V), spherical (o) and rod-like ( ) geometry. Data are vertically shifted for clarity. Inset dependence of ODT temperature on dimensionality of fillers (spherical 0, rod-like 1, plate-like 2). Vertical bars width of phase transition region. Pure block copolymer is denoted matrix . From [215]. Copyright 2003 American Chemical Society...

Figure 17.5. Bragg (x-ray) diffraction peak and typical satellites off a copper-nickel nanocomposite (electrochemically grown).

The WAXS patterns of two nanocomposites at different LDH concentrations are shown in Fig. 55. The similarity of these patterns between the two systems is that the first three Bragg s reflections of LDH-C10 can be detected in both. This means that the LDH particles are not fully exfoliated in any of the matrices. 

The key question regarding the structure of a thermoset/clay nanocomposite system is whether a true nanocomposite has formed or not. If not, the material is comparable to a conventional filled microcomposite. Generally, wide angle X-ray diffraction (WAXD) analysis and transmission electron microscopy (TEM) are used to elucidate the structure of a nanocomposite. Due to its easiness and availability, WAXD is most commonly used to establish the nanocomposite structure [30, 31]. By monitoring the position, shape, and intensity of the basal reflections from the distributed silicate layers, the nanocomposite structure (intercalated or exfoliated) may be identified. The X-ray technique is often applied to identify nanocomposite structures through Bragg s relation, which is given below ... 

Due to its ease of use and availability, simple Bragg-refiection powder x-ray diffraction is most commonly used to probe nanocomposite structure, especially for polymer/layered-inorganic filler hybrids where the [Pg.42]

Diffraction pattern for a particular sample is obtained by plotting the intensity of diffracted X-rays as a function of 20. Bio-nanocomposites are characterized by monitoring the intensity, width, and position of the peak in the diffraction pattern. Intensity of the peak provides information about the location of atoms in the unit cell. Higher intensity corresponds to higher electron density around the atom. Peak width provides information on the size of crystal and imperfections in the crystal. Peak width increases as the size of the crystal decreases. Position of the peak is used to estimate interlayer spacing by using the Bragg s equation as mentioned above. 

As widely available and easy method, WAXS is often used to define the nanocomposite structure and rarely to study the kinetics of the polymer melt intercalation. Most commonly, WAXS is applied for studies of layered nanocomposites with addition of montmorillonite (MMT) or silicates. This method, based on Bragg s law, enables understanding the intercalated or exfoliated structure of nanocomposites by describing direction, intensity and shape of the basal reflection resulting from the distribution of nanofiller layers [64]. X-ray patterns presented in Fig. 21.37 prove that intercalation of polymer chains is followed by increase of... 

Diffraction studies were carried out to investigate the delamination/exfo-liation of MMT in polymer matrix. A Bruker D8 Advance difiactometer was used to measure the d-spacing of the hybrid filler-filled nanocomposite films. The diffraction patterns were obtained at room temperature in the range 2<29<10 degree by step of 0.02°. The X-ray beam Cu Ka radiation (A. = 0.154 nm), operated at 30 kV and 10 mA. The interlayer distance was determined by the peak, using the Braggs equation... 

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