Crack Propagation in nanocrystalline Iron-Nitrogen Via Molecular Dynamics Simulation

Recently, nitrogen alloyed steels have attracted the attention of researchers and industrial specialists due to their combination of strength and elongation. The identification of mechanical properties of nitrogen alloyed steels is very important for using these alloys with high reliability in various applications. Meanwhile, the resistance of material to crack propagation is one of the important parameters. Nowadays, nanoscience and computer simulations at nanoscale are noticed as the most studied subjects in the world. Molecular Dynamics Simulation (MDS) is one of the numerical methods at nanoscale which is the most deterministic method among available methods for the solution of molecular systems. The aim of this study is to simulate the crack propagation in Iron-Nitrogen nanocrystalline. In this regard, Iron-Nitrogen nanocrystalline is modeled by applying Modi?ed Embedded Atom Method (MEAM) interatomic potential using the related parameters for Iron-Nitrogen alloy. The microstructure of crack growth in nanocrystalline with dimension are investigated under tensile loading with velocity magnitude of 0.8 /ps at temperature of 300K. The results show that crack velocity increases with the increase in crack length. The increase in the peak of radial distribution function curve during different time steps is as a result of change in the positions of particles during crack propagation. Also, the results indicates that the magnitudes of stress at three crystal directions has firstly nonlinear behavior and then changes to linear one which is due to the change of direction of crack growth during simulation time steps. Also, the track-growth direction and the track opening are investigated under simulation conditions.In this study, the OPLS all-atom model was developed for sulfur mustard in order to study the adsorption of this compound on graphene. Intramolecular bonding parameters and Lennard?Jones nonbonding parameters are taken from the OPLS all-atom force field database. Partial charges are determined by ab initio calculations at HF/6-31g(d) level. The results showed that the OPLS all-atom force field predicts the physical properties of sulfur mustard like density and heat of evaporation with the mean error of less than 1% and 5% respectively at temperatures of 298 K and 293 K compared to experimental data. The comparison of intramolecular bonding parameters obtained from molecular dynamics simulation and quantum mechanical calculations showed that these results are well consistent with each other. Also, the study of the interaction energy between sulfur mustard and graphene by molecular mechanics and quantum mechanics on coronene as a model of graphene indicated that OPLS force field can be used as an accurate and reliable model in the molecular dynamics simulation studies of this compound on the adsorbents based on graphene.In this study, Ce oxide and Ru-Ce mixed oxide were prepared by co-precipitation method in alkaline media. Also, the Ru-Ce mixed oxide nanoparticles were synthesized by a reverse micelle approach. All of the samples were characterized with XRD and BET methods and the size of nanoparticles synthesized in the reverse micelle was measured by the TEM technique. The catalytic activities of synthesized samples were investigated for oxidation of benzyl alcohol in the presence of molecular oxygen and solvent free condition. The obtained results show that the nano-catalyst is suitable candidates for the oxidation of benzyl alcohol to the benzaldehyde. In order to obtain maximum conversion of benzyl alcohol, the reaction parameters, like reaction temperature, amount of catalyst and reaction time, were optimized. Under the optimized conditions, a maximum of 99%benzyl alcohol conversion and 94 % selectivity for benzaldehyde was achieved with Ru-Ce nano mixed oxide as catalyst, at 80 oC and 3h.