Preparation, Structure And Performance Of Thin-walled Carbon Foam Based On Loose Medium Component Separated From Tongting Coal

Thin-walled carbon foams were prepared by self-foaming method using the loose medium components separated from Tongting raw coal by all group components separation method under normal pressure and inert atmosphere.The effects of foaming conditions and nano-zirconia?Nano-ZrO₂?addition on the structure and mechanical properties of nascent carbon foams?NCF?were investigated.On this basis,the effects of carbonization and graphitization conditions on the microstructure,microcrystalline structure,mechanical properties,electrical conductivity and thermal insulation properties of carbonized carbon foams?CCF?and graphitized carbon foams?GCF?before and after Nano-ZrO₂ modification were investigated.The results are showed as follows:The heating rate and foaming temperature had a great influence on the NCF pore structure.The optimum conditions for preparing NCF with uniform pore distribution and uniform pore size were:heating rate 5°C/min,foaming temperature 550°C,constant temperature 1 h and tableting pressure 5 MPa.The basic properties,mechanical properties and electrical conductivity of CCF were affected by the carbonization process conditions:carbonization temperature>constant temperature time>heating rate.When the amount of deformation was 70%?the same below?,the compressive strength of CCF made under the excellent scheme was 0.6 MPa,the specific strength was 4.6 MPa/?g/cm³?,the electrical conductivity was 9.2 s/cm,and the thermal conductivity was about 0.080 W/?m·K?.The average compressive strength of GCF was 0.48 MPa,and the average specific strength was 3.55 MPa/?g/cm³?;the average degree of graphitization was39.88%,the conductivity was 31.8 s/cm,and the electrical conductivity was significantly higher than that of CCF;the powdered GCF had a thermal conductivity of 0.082 W/?m·K?and the bulk GCF had a thermal conductivity of 0.059 W/?m·K?.The bulk was better than the powdered GCF.Thin walled carbon foams had an average wall thickness of 1⁴?m.With the increase of the amount of Nano-ZrO₂ in NCF,the pore size became smaller,the structure of the pores was denser and the mechanical property was improved.The optimum addition amount was 15 wt.%.Compared with unmodified CCF,the mechanical properties of CCF with 15 wt.%Nano-ZrO₂ were significantly enhanced,the compressive strength was 3.7 MPa,the specific strength was 9.0MPa/?g/cm³?,the electrical conductivity was slightly lower,the thermal conductivity was 0.074 W/?m·K?and the insulation performance was improved.The compressive strength of GCF with 15 wt.%Nano-ZrO₂ was 1.3 MPa,the specific strength was 3.2MPa/?g/cm³?,the degree of graphitization was as high as 99.77%,the electrical conductivity was 66.9 s/cm which was greatly improved compared with the unmodified GCF,and the thermal conductivity was 0.077 W/?m·K?.The average wall thickness of the carbon foams modified by Nano-ZrO₂ increased to 2⁵?m.There are 66 figures,23 tables and 114 references in this paper.