The development of nanoscale reinforcements that can be used to improve the mechanical properties of a polymer remains a challenge due to the long-standing difficulties with exfoliation and dispersion of existing materials. The dissimilar chemical nature of common nanofillers (e.g., carbon nanotubes, graphene) and polymeric matrix materials is the main reason for imperfect filler dispersion and, consequently, low mechanical performance of their composites relative to theoretical predictions. Here, aramid nanofibers that are intrinsically dispersible in many polymers are prepared from commercial aramid fibers (Kevlar) and isolated through a simple, scalable, and low-cost controlled dissolution method. Integration of the aramid nanofibers in an epoxy resin results in nanocomposites with simultaneously improved elastic modulus, strength, and fracture toughness. The improvement of these two mutually exclusive properties of nanocomposites is comparable to the enhancement of widely reported carbon nanotube reinforced nanocomposites but with a cost-effective and more feasible method to achieve uniform and stable dispersion. The results indicate the potential for aramid nanofibers as a new class of reinforcements for polymers.

This study reports the sintering of zinc oxide (ZnO) through the comparison between the hydrothermal sintering (HS) and the cold sintering process (CSP) operating in closed and open conditions, respectively. Sintering was performed at 155 ± 5°C applying a pressure of 320 MPa, and during different holding times (0 min, 20 min, 40 min and 80 min). Whatever the low sintering process used, ceramics characteristics are almost similar in terms of relative densities and ZnO structure. However, several differences such as the nature of stabilized phases, grain sizes and quantities of residual molecules in the densified pellets, were characterized and explained. The formation of zinc acetate "bridges" was observed ex situ in hydrothermally sintered samples. A detailed ReaxFF molecular dynamics simulation was performed to help understand the formation mechanisms of zinc acetate "bridges" and compare the chemical activities between HS and CSP. Closed systemsEarly investigations on low temperature densification of materials were conducted on closed systems. In the early 70′s, D.M. Roy et al. prepared, at Penn State University, cement pastes with excellent mechanical properties and almost no porosity by hot pressing Cementous powders and water [1,2]. In the mid-70′s, further studies were made by S. Sōmiya et al. on reactive hydrothermal sintering to obtain densified oxides, starting from metal powders at temperatures higher than 900°C [3,4]. In combining both these approaches, N. Yamasaki, K. Yanagisawa et al. from Kochi University developed an apparatus for "hydrothermal hot pressing", based in uniaxial pressure of a mixture of powder and solvent in a system sealed with PTFE (Teflon ™) gaskets [5]. This technique led to the sintering of several oxides such as SiO 2 , TiO 2 , hydroxyapatite, CaCO 3 , Ca 3 Co 4 O 9 , zeolites,

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