Study On The Electrothermal Properties Of Graphite/Carbon Fiber-Phosphorus Building Gypsum

Phosphogypsum is a solid waste of phosphorus industry that can pollute living resources such as land and water,It's annual emissions and stockpiles are very huge,Therefore,it is very urgent to solve the comprehensive utilization of phosphogypsum.On the one hand,it can alleviate the environmental pollution caused by phosphogypsum,On the other hand,sustainable development of phosphorus chemical enterprises can be achieved.In addition,as people's living standards continue to improve,Increasing demands on the comfort and functionality of housing,Such as winter heating,indoor humidity control.Gypsum is a functional building material with thermal insulation ? sound insulation and humidity regulation,Phosphorous building gypsum produced by treating phosphogypsum also has these excellent characteristics.Therefore,this paper combines the comprehensive utilization of phosphogypsum,by incorporating carbon fiber and graphite into phosphorous building gypsum,Preparation of green functional building materials with electrothermal properties,Therefore,the research on the electrothermal performance of graphite/carbon fiber-phosphorus building gypsum was born.First,for the inertness of the carbon fiber surface,Removal of organic protective layer on carbon fiber surface by Soxhlet extraction,The surface treatment of the carbon fibers with a strong acid is then performed to enhance the binding ability of the carbon fibers to the matrix.Secondly,starting from the conductive properties of phosphorous building gypsum,The effects of carbon fiber and graphite on the resistivity of phosphorous building gypsum matrix were investigated in combination with the conductive behavior of conductive composites.By changing the amount of carbon fiber and graphite,and using the quadrupole method to measure the resistance,under the single-doped carbon fiber and single-doped graphite,percolation threshold for the amount of conductive phase,the test found that the percolation threshold of carbon fiber is 0.2?0.4% of the volume content.The resistivity of carbon fiber-phosphorus building gypsum at the lower limit of the seepage threshold is as low as 0.83?·m,which is 99.95% lower than that of phosphorus building gypsum.The percolation threshold of graphite is 6?12% by mass.The specific resistance ofgraphite-phosphorus building gypsum at the lower limit of the seepage threshold is62.9?·m,which is 96.54% lower than that of phosphorus building gypsum.And with0.2% volume ratio of carbon fiber and 6% mass ratio of graphite,conductive graphite/carbon fiber-phosphorus building gypsum can be prepared with a resistivity of 0.8?1.2 ?·m.Third,carbon fiber and graphite not only have excellent electrical and thermal conductivity,the proper amount of carbon fiber and graphite also affect the mechanical properties of the substrate to varying degrees.Next,the effect of carbon fiber on the mechanical properties of the phosphorous building gypsum matrix and its mechanism analysis were investigated by changing the amount and fiber length.At the same time,the effects of single-doped graphite and multiple-doped graphite on the mechanical properties of phosphorous building gypsum substrates were also explored.The tests show that:9mm carbon fiber has the best reinforcement effect on the matrix,when the volume content is 0.5%,It has the greatest help on the flexural strength of the substrate,and the flexural strength of carbon fiber-phosphorus building gypsum reaches6.14 Mpa.When the carbon fiber is added with a volume ratio of about 3.5%,the compressive strength of the matrix is the most helpful.The compressive strength of the carbon fiber-phosphorus building gypsum reaches 13.81 Mpa.At the same time,at low dosages,ultrafine graphite with a volume content of less than 2% also slightly improves the mechanical properties of the phosphorous building gypsum matrix.Under complex doping,although graphite has an adverse effect on the strength of the matrix,However,the graphite with a content of less than 8% and the appropriate amount of carbon fiber can still maintain a good flexural and compressive strength of the matrix.Finally,on the basis of Joule heat,combining experiment and multiphysics finite element simulation software COMSOL Multiphysics to explore the electrothermal performance of graphite/carbon fiber-phosphorus building gypsum,the experiment shows:the temperature-voltage relationship of the composite is linear and the temperature-temperature drop rule is symmetrical about the straight line T= ? Tm/2+T0,at low input voltage,the temperature stability of the composite is good.In addition,the thermal properties of graphite/carbon fiber-phosphorus building gypsum were measured.Provide thermal material parameters for simulation,the simulationresults show:when using thermal conductivity,specific heat capacity,input power,and ambient temperature as a single variable for simulation analysis,the COMSOL Multiphysics simulation results data can reflect,Increasing the thermal conductivity and reducing the specific heat capacity have positive significance for increasing the heating rate of graphite/carbon fiber-phosphorus building gypsum,At the same time,the effect of specific heat capacity on the rate of heating is greater than the effect of thermal conductivity on the rate of heating.Under actual working conditions,the input power has a significant effect on changing the heating rate of the composite material.As long as the input power is changed by a small amount,it can cope with the greatly changed ambient temperature.In addition,the simulation results and experimental results are compared and analyzed.Although there are errors,However,the error range is between 4?9%,and the error is small.It shows that the simulation results of COMSOL Multiphysics can effectively reflect the electrothermal performance of graphite/carbon fiber-phosphorus building gypsum.