Preparation of sodium zirconium silicate phosphate (NaSICon), Na 1+x Zr 2 Si x P 3 -x O 12 (0.25 ≤ x ≤ 1.0), thin films has been investigated via a chemical solution approach on platinized silicon substrates. Increasing the silicon content resulted in a reduction in the crystallite size and a reduction in the measured ionic conductivity. Processing temperature was also found to affect microstructure and ionic conductivity with higher processing temperatures resulting in larger crystallite sizes and higher ionic conductivities. The highest room temperature sodium ion conductivity was measured for an x = 0.25 composition at 2.3 3 10 -5 S/cm. The decreasing ionic conductivity trends with increasing silicon content and decreasing processing temperature are consistent with grain boundary and defect scattering of conducting ions.
Aramid fibers composed of poly( p-phenylene terephthalamide) (PPTA) polymers are attractive materials due to their high strength, low weight, and high shock resilience. Even though they have widely been utilized as a basic ingredient in Kevlar, Twaron, and other fabrics and applications, their intrinsic behavior under intense shock loading is still to be understood. In this work, we characterize the anisotropic shock response of PPTA crystals by performing reactive molecular dynamics simulations. Results from shock loading along the two perpendicular directions to the polymer backbones, [100] and [010], indicate distinct shock release mechanisms that preserve and destroy the hydrogen bond network. Shocks along the [100] direction for particle velocity Up < 2.46 km/s indicate the formation of a plastic regime composed of shear bands, where the PPTA structure is planarized. Shocks along the [010] direction for particle velocity Up < 2.18 km/s indicate a complex response regime, where elastic compression shifts to amorphization as the shock is intensified. While hydrogen bonds are mostly preserved for shocks along the [100] direction, hydrogen bonds are continuously destroyed with the amorphization of the crystal for shocks along the [010] direction. Decomposition of the polymer chains by cross-linking is triggered at the threshold particle velocity Up = 2.18 km/s for the [010] direction and Up = 2.46 km/s for the [100] direction. These atomistic insights based on large-scale simulations highlight the intricate and anisotropic mechanisms underpinning the shock response of PPTA polymers and are expected to support the enhancement of their applications.
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