First-principles Study Of The Interfacial Properties Of Graphene Reinforced Magnesium Matrix Composites

Magnesium alloys and magnesium-based composites have many properties: high specific strength, excellent mechanical and physical properties. However, the elastic modulus of magnesium-based composite material is generally low, which greatly restricts its wide application in the field of construction materials. Graphene have many excellent mechanical properties, such as: high elastic modulus(approximately 1TPa) and breaking strength(approximately 125GPa). So graphene as a reinforcement of magnesium matrix composites can effectively improve the strength, elastic modulus and other properties of it.The interfacial properties of graphene reinforced magnesium matrix composites were studied comprehensively using first-principles theory in this paper. The configuration of interface, interfacial energy and the distribution of interface charge were investigated, then the stability, electronic structure and bonding behavior of the interface were analysed. The main content and the results of this thesis are summarized as below:(1) Using supercell modeling method to establish adsorption models of magnesium atoms and graphene surface. The representative adsorption models were selected to study on their adsorption energy, the results showed that vacancy or doped atoms could enhance adsorption strength between graphene and magnesium atom in the order: vacancy> B> Si> N> S.(2) The electronic charges distribution of magnesium atoms and graphene adsorption model were calculated. It found that the adsorption of magnesium atoms and intrinsic graphene were dominated by Van Der Waals force which belong to physical adsorption; And the adsorption between magnesium atoms and vacancy modified graphene were dominated by chemical adsorption due to a strong hybridized covalent bond. The charge density difference was higher for magnesium atoms on the vacancy modified or doped graphene surface and the principal charge transfer mainly came from the magnesium atomic orbitals.(3) A series of adsorption interface model of graphene and magnesium atoms with different atomic configurations were established. The interface energy and interface electronic structure were optimization calculated respectively. The results showed that the carbon atoms in graphene and the first proximal magnesium of the interface had a strong binding strength. It involved a strong hybridization between C atom on graphene and magnesium atom which belongs to the chemisorption. It had a higher interfacial strength formed by graphene and magnesium metal. Graphene can be used as an excellent reinforcing phase of magnesium and magnesium alloys.(4) The value of charge density difference on magnesium and graphene adsorption surface was high. The bonds formed between the C and Mg atoms were strong hybrid covalent interactions. The bonding charges provided by the atomic orbitals of carbon and magnesium together and it mainly focused on the joint surface of the carbon atoms and the first neighbor magnesium atoms.