Structure Characterizations,Surface Functionalization & Applications Of Detonation Nanodiamonds

In condense matter,the dimensionality is very important and materials can be classified according to their dimensions for better understanding and promising applications.The zero dimensional nanocarbon with crystalline diamond structure at nanoscale is termed as Nanodiamond(ND).In this dissertation,role of nanodiamonds(NDs)have been exploited and critically analyzed as reinforcement in nanocomposite and hydrogen production via water splitting using sunlight.The structure of detonation nanodiamond(DND)has been reviewed and the effects of surface modifications on DND properties have been discussed.The aim of this study is the potential use of nanodiamond to make the light weight and strong nano-composites.Here,effects of size and surface modification of DND on mechanical performance of epoxy based nanocomposites is presented.Our characterizations reveal that the process of functionalization not only removes the non-diamond content and impurities by significantly reducing detonation nanodiamonds(DNDs)size but also introduces oxygen containing functional groups on its surface.The average size of functionalized DND aggregations could be decreased from 300 to 100 nm in contrast to pristine DND,which greatly benefits its homogeneous dispersion in epoxy matrix.In addition,strong chemical bonding among functionalized DND and epoxy resin due to functional groups leads to the formation of efficient interface.These interfaces overlap at high concentrations making a network which in turn significantly enhances the tensile properties.The enhancement in Young's modulus can reach up to2.5 times higher than that of neat epoxy whereas the enhancement in tensile strength is about 1.5 times in functionalized DND/epoxy nanocomposites.The concentration and small size of NDs plays a crucial role in the mechanical performance of epoxy-based nanocomposites by modifying the interface strength.Herein,we systemically analyzed the relation between the high concentration and small size of ND and the fracture properties of its epoxy-based nanocomposites.It was observed that there is a two-fold increase in fracture toughness and a three-fold increase in fracture energy.Rationally,functionalized-NDs(F-NDs)showed a much better performance for the nanocomposite than pristine NDs(P-NDs)because of additional functional groups on its surface.The F-ND/epoxy nanocomposites exhibited rougher surface in contrast with the P-ND/epoxy,indicating the presence of a strong interface.We found that the interfaces in F-ND/epoxy nanocomposites at high concentrations of NDs overlap by making a web like structure,which can efficiently hinder further crack propagation.In addition,the de-bonding in P-ND/epoxy nanocomposites occurred at the interface with the appearance of plastic voids or semi-naked particles,whereas the de-bonding for F-ND/epoxy nanocomposites happened within the epoxy molecular network instead of the interface.Because of the strong interface in F-ND/epoxy nanocomposites,at high concentrations the de-bonding within the epoxy molecular network may lead to subsequent cracks,parallel to the parent crack,via crack splitting which results in a fiber-like structure on the fracture surface.The plastic void growth,crack deflection and subsequent crack growth were correlated to higher values of fracture toughness and fracture energy in F-ND/epoxy nanocomposites.The hydrogen evolution reaction(HER)may contribute substantially to energy resources in the future through solar energy conversion.In this study,mesoporous graphitic carbon nitride(g-C3N4)layers modified by DND were synthesized by condensation from urea to obtain a robust and efficient hybrid(g-C3N4-DND)photocatalyst for the HER.Our characterizations revealed that no significant structural changes occurred in g-C3N4 during the synthesis of the g-C3N4-DND hybrid.Compared with pure g-C3N4,hydrogen production increased by almost 50%when using the hybrid photocatalyst due to the synergetic effect of the enhanced charge transfer,high surface area and low recombination rate of the photogenerated charge carriers.