Preparation And Microwave Absorption Properties Of FeS₂/Co-BTC Composite Nanomaterials And The Effect Of Their Addition On The Properties Of LDPE

Nanocomposite materials are multiphase materials composed of two or more substances,which are widely used in various fields due to their rich interface nanoscale systems and adjustable microstructure.Therefore,it is of great significance to use high-performance monomer materials to prepare different composite nanomaterials,and systematically analyze their UV performance,absorption performance,thermal conductivity,dielectric performance,etc.In this paper,FeS₂ nanospheres,Co-BTC micro crystals and FeS₂/Co-BTC nanocomposites were prepared by solvothermal method.The SEM results indicate that FeS₂ is a spherical particle composed of 10nm～20nm nanosheets,while Co-BTC is a rectangular crystal with a layered structure composed of 30nm～40nm nanosheets stacked together,and the composite performance of FeS₂/Co-BTC material is good;The XRD diffraction peaks of the three samples all correspond to the standard card one by one,and there are no other impurity peaks;The results of vibrating sample magnetometer show that FeS₂ has the strongest ability of external magnetic field,followed by FeS₂/Co-BTC,and Co-BTC has almost no ability of external magnetic field;The UV spectrum results show that FeS₂ has the highest absorbance and an exciton absorption peak.The absorption peak of Co-BTC reaches its maximum at550nm～620nm.The overall size of FeS₂/Co-BTC increases compared to FeS₂,resulting in a red shift in the exciton absorption peak.The size decreases compared to Co-BTC,resulting in a blue shift of the maximum absorption peak to 530nm～610nm;The absorption results indicate that FeS₂ material has the strongest electrical energy storage and loss ability,and has the smallest reflection loss value.FeS₂/Co-BTC material has the strongest magnetic energy storage and consumption ability,and has the widest optimal absorption bandwidth value.FeS₂ and FeS₂/Co-BTC materials have a larger range of effective impedance matching values and higher attenuation constants,making electromagnetic waves more easily converted into thermal energy by the material for internal loss.In order to investigate the influence of the above-mentioned powder samples on the dielectric properties of low density polyethylene（LDPE）,they were added to LDPE by melt blending method with mass fractions of 0.5wt%,1.0wt%,1.5wt%,and2wt%.Observing the dispersion of powder in LDPE using SEM,analyzing the effect of the sample on the structure of LDPE using infrared spectroscopy（FTIR）,testing the thermal conductivity of the composite sample using laser thermal conductivity instruments,and analyzing the insulation performance using broadband dielectric spectroscopy and AC breakdown equipment.The SEM results indicate that the powder sample has a good composite effect with LDPE;The FTIR results showed that the addition of powder samples did not affect their chemical structure;The thermal conductivity results show that the thermal diffusion coefficient of LDPE is improved due to the addition of powder samples.The amount of sample added is positively correlated with the thermal diffusion coefficient and thermal conductivity.When the amount of powder samples reaches 2wt%,the thermal conductivity of FeS₂/LDPE,Co-BTC/LDPE,and FeS₂/Co-BTC/LDPE samples increases by 51.83%,52.35%,and54.45%,respectively;The broadband dielectric spectroscopy results show that the addition of powder samples increases the number of high dielectric carriers in LDPE,and the material dipole is more prone to turning under the action of an electric field.The dielectric constant of LDPE increases,and when 2wt%FeS₂/Co-BTC/LDPE composite material is added,the dielectric constant reaches the highest,reaching 2.48;The AC breakdown results indicate that the addition of powder samples in LDPE increases its defects,resulting in an increase in hole carriers and a decrease in spacing.Internal defects dominate,reducing the breakdown field strength of the material and making it more prone to breakdown.