Defects and temperature effects on the mechanical properties of hexagonal boron nitride sheet (h-BN) containing randomly distributed defects are investigated by molecular dynamics simulations and the reasons of the results are discussed. Results show that defect deteriorate the mechanical performance of BNNS. The mechanical properties are reduced by increasing percentage of vacancy defects including fracture strength, fracture strain and Young’s modulus. Simulations also indicate that the mechanical properties decrease with the temperature increasing. Moreover, defects affect the stable configuration at high temperature. With the percentage of defect increases the nanostructures become more and more unstable. Positions of the defect influent the mechanical properties. The higher the temperature and the percentage of defect are, the stronger the position of the randomly distributed defect affects the mechanical properties. The study provides a theoretical basis for the preparation and performance optimization of BNNSs.

The thermal properties of single-walled boron nitride nanotubes (BNNTs) are studied in this paper based on molecular dynamics (MD) simulations. The influence and mechanism of tubular configuration, temperature, length, diameter and chirality on the thermal conductivity of BNNTs are systematically analyzed. The results show that the thermal conductivity decreased with increasing temperatures. The values of thermal conductivity of BNNTs and boron nitride nanoribbons (BNNRs) confirm that the tubular configuration is more conducive to phonon propagation. The thermal conductivity is raised by increasing the length of BNNTs. Moreover, the thermal conductivity changes slightly with further increase of diameter and various chirality. The results share guiding significance for thermal transport characterization of nanoscale thermal conductive component based on boron nitride nanotubes.

The axial mechanical properties of calcium silicate hydrate during uniaxial tension or stress have been investigated by molecular dynamic simulations. Based on the classic calcium-silicate-hydrate model, the influence of calcium to silicate ratio and temperature are studied in detail. It demonstrated that calcium silicate hydrate with different Ca/Si ratio have similar stress-strain curves under uniaxial compression, but greatly difference on the uniaxial tension behaviors. The uniaxial tensile properties was affected by temperature that the strain rate in the low-temperature is higher than that in high temperature. The work in this paper reveals the mechanical properties of calcium silicate hydrate at the nanoscale and establishes the foundation explore the failure mechanism of cement or cement-based materials.

Boron nitride nanosheets (BNNSs), a new type of wide bandgap nanomaterial, has attracted great attention due to their excellent properties and potential applications. Thus, it is necessary to have a comprehensive understanding of the mechanical properties of BNNSs in various working conditions. This paper presents an analytical model based on molecular mechanics to study the size effect and temperature effect on the Young’s modulus of BNNSs. A closed-form formulation is derived for Young’s modulus as a function of the length of B–N bonds and the out-plane displacement. It is shown that the chirality and the size of the BNNSs affect the length of BN bonds in molecular dynamic (MD) simulations. It is also found that the length of BN bonds and the out-plane displacement in a monolayer BNNS is remarkably temperature dependent. Therefore, the sizes and the temperatures can affect the Young’s modulus of BNNSs. The expressions developed in this paper are employed to investigate the Young’s modulus for zigzag and armchair BNNS with various sizes and temperatures. The present model, associating with a beam model, provides a simple method to calculate elastic properties which takes into account all bonded energies and force coefficient changes with atoms distance. The results of size effect and temperature effect are in good agreement with data of simulation performed in finite element method (FEM) simulation and MD simulation. The present study provides a molecular mechanics model to predict the Young’s modulus of a monolayer BNNS, and the present model may be applied to other two-dimensional (2D) materials in further study.