Research On The Preparation Of Graphene And Graphene-aluminum Matrix Composites

Graphene has become one of the most popular two-dimensional materials due to its excellent electrical and thermal conductivity and remarkable physical and chemical properties.There are many ways to prepare graphene,among which chemical oxidation-reduction method has become one of the most important methods to prepare graphene-based materials due to its advantages of low cost and easy scale preparation.Based on the traditional Hummers three-stage oxidation method,the effects of oxidant addition and oxidation time on the structure of graphene oxide during low temperature?0°C?one-step oxidation were studied.The microwave dielectric properties of graphene oxide were investigated.The effect of microwave and aluminum powder reduction on the structure and properties of reduced graphene oxide;graphene-aluminum matrix composites prepared by in-situ reduction of aluminum powder and microwave vacuum sintering,the conclusions are as follows:?1?Graphene oxide was prepared by using the strong oxidizing property of potassium permanganate in concentrated sulfuric acid under low temperature conditions.By controlling the amount of oxidant added and the oxidation time during low-temperature one-step oxidation process,the optimum process parameters for the low-temperature preparation of low-defect graphene oxide at low temperature were determined.The oxidation time was 48h,and the mass ratio of oxidant mass to flake graphite was 3:1,the prepared graphene oxide has a higher degree of oxidation(layer spacing d₀₀₁=9.3?,carbon-oxygen atomic ratio C:O=1.98),but the corresponding defect?ratio of Raman D peak to G peak I_D:I_G=0.63?lower.XPS analysis of graphene oxide prepared by low temperature one-step oxidation showed that the C-O content of the obtained product was increased by about 10%compared with the Hummers method.?2?The dielectric properties of graphene oxide were studied by dielectric perturbation.The study of the dielectric properties of graphene oxide with different degrees of oxidation showed that even the insertion of a small amount of oxygen-containing groups seriously affected the dielectric properties of graphite.As the degree of oxidation increases,the dielectric constant and dielectric loss decrease,but the rate of decline decreases significantly.The dielectric constant and dielectric loss are stable around 1.36 and 0.04,respectively.The high-temperature dielectric properties of graphene oxides show that the dielectric parameters increase with the increase of temperature.When the temperature is 800°C,the corresponding dielectric constant and dielectric loss are 52.22,8.32,respectively.The study of the temperature-dependent reflection loss of graphene oxide shows that the maximum reflection loss absorption peak of graphene oxide appears at a temperature of 650°C,thickness 10mm,the corresponding reflection loss is-15.99dB.The microwave penetration depth of graphene oxide was found to be the largest penetration depth of graphene oxide when the temperature was raised to 550°C,and its value was 0.032m.?3?Under a nitrogen atmosphere,in a 1000W microwave tube furnace,graphene oxide was heated to 300°C and held for 10 min to obtain reduced graphene oxide.The properties are as follows:2?=23.5,C:O=7.75,I_D:I_G=0.85.Compared with the products after the microwave reduction of the graphene oxide prepared by the modified Hummers,the quality of the product is greatly improved after microwave reduction by the low-temperature oxidation of the graphene oxide.Further,we studied the properties of reduced graphene oxide prepared by reduction of graphene oxide by aluminum powder as follows:2?=24.5,C:O=9.20,I_D:I_G=1.39.It is shown that the reduction of graphene oxide by aluminum powder has a higher degree of reduction,lower defects,and more complete sheet structure of graphene.?4?Graphene-aluminum matrix composites were prepared by microwave vacuum sintering.The properties of graphene-aluminum matrix composites show that even with the addition of a small amount of reduced graphene oxide,the bending properties and thermal conductivity of the composites are significantly improved.When the mass of the reduced graphene oxide in the alloy is only 0.3 wt.%,the bending property of the alloy is improved by 31%,and the heat diffusion capacity and the specific heat capacity are increased by 10.5%?3.6%,respectively.