| Under the background of green and efficient development,the winter indoor heating method with coal as the main heat source needs to be changed urgently.With the emergence and development of nano-materials,self-heating building materials have emerged as the times require.Self-heating building materials fabricated by adding a conductive phase to the building materials,so that building components have conductivity,and then generate heat by Joule effect,so as to achieve the purpose of indoor heating.Good electrical conductivity also makes this material have great prospects for deicing and snow removal on roads and intelligent building monitoring.However,although the commonly used conductive phases,such as steel fibers,iron powder,or other metal additives,can reduce the resistance of the cement matrix,the matrix itself has poor thermal conductivity and the conductive phase is prone to corrosion.As a result,the heating efficiency of this self-heating material is very low and the durability is not satisfactory.Nanomaterials,such as carbon nanotubes and graphene,are the best choice for the conductive phase of a new generation of self-heating building materials because of their excellent electrical and thermal conductivity,as well as strong mechanical and corrosion resistance.However,the difficulty of dispersing nano-materials and the characteristics of easy agglomeration hinder the further development of self-heating cement-based nano-composites.Graphene oxide,a precursor of graphene,has a large amount of oxygen-containing functional groups on the surface.Therefore,graphene oxide has good hydrophilicity,which helps it disperse well in solution,but it is necessary to restore its advantages of excellent electrical conductivity,thermal conductivity,high strength and corrosion resistance by reduced to graphene through chemical treatment or high temperature treatment.Clay,as a traditional building material,has good hydrophilicity.After sintering at high temperature,clay obtains better compressive strength.Therefore,the combination of graphene oxide and clay forms a brand new self-heating building material system,and the conductive phase of graphene oxide can be well dispersed in the material system.Taking the above content as the guiding ideology,this experiment incorporates graphene oxide into clay to form a graphene oxide-clay material system,and conducts detailed research on the electrical,thermal and mechanical properties of the system.Moreover,to make full use of the outstanding conductive property,further exploration happen to find the application prospect of this material system in the field of pressuresensitive mechanical sensors and 3D printing.Based on the above experiments,the main conclusions of this article are as follows:(1)By controlling the doped amount of graphene oxide and the value of conducting resistivity test on samples,it was found that the material system has good electrical conductivity,and the lowest resistivity is 2.88 Ω · cm.In addition,an evident percolation threshold was found and the value is about 0.5 wt.%.(2)Because of excellent electrical conductivity,good thermal conductivity and high dispersibility of graphene oxide,the graphene oxide-clay sintered body has outstanding heating performance.When applied 5 voltage,the sample with 4 wt.% graphene oxide can be heated to 160 ℃ in 300 s.When applied 10 voltage,the sample with 5 wt.% graphene oxide can be heated from room temperature to 160 ℃ in 50 s.(3)By applying a regular cyclic load,it was found that the sample with 0.7 wt.% graphene oxide had good pressure-sensitivity performance;and when applied a sinusoidal load 1,000 times,the performance has not deteriorated,and it means a good stability.(4)A large number of experiments show that when the doped amount of graphene oxide is 2 wt.%,the graphene oxide-clay system is suitable for direct ink writing 3D printing. |
