It is shown that the maximum and the minimum value of the shear modulus of a polycrystal could be given by the highest and the lowest value of the shear modulus of a single crystal. The experimental shear modulus of 26 polycrystals is examined. Except for silicon, the rest of the elements confirmed this hypothesis.
The multifunctional novolac epoxy/Al2O3 nanocomposites were fabricated by high-speed mechanical mixing of epoxy resin with varying concentration of nano Al2O3 (0–5 wt%) of particle size 13 nm for 30 min, followed by curing with triethylenetetramine (TETA) at 110°C for 1 h and post-curing at 80°C for 5 h. The fabricated nanocomposite samples were characterized for mechanical properties (viz., tensile strength, elongation-at-break, impact strength, toughness, and hardness shore D), thermal stability, and fire retardancy. It was observed that the 3 wt% nano-Al2O3 containing sample showed significant enhancement in the tensile strength, elongation-at-break, impact strength, hardness shore D, thermal stability, and fire retardancy compared to the neat epoxy sample. The Differential Scanning calorimetry (DSC) confirmed the 3-D curing reaction between TETA and nano-alumina modified epoxy and neat epoxy samples. The reactivity effect of alumina towards resin was investigated by Fourier Transform Infrared (FTIR) spectroscopy. The morphological studies of nanocomposite samples were investigated by Scanning Electron Microscopy (SEM) to justify the enhancement of mechanical properties via dispersion of nanoparticles.
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