Graphene composite aerogel with high thermal conductivity, compressibility and flexibility meets phase-change materials: A material innovation with rigidity and flexibility

Characterization testing: Analyze the morphology through field emission scanning electron microscopy. Analyze the defects and crystal structure of the sample using a Raman spectrometer. Continuous scanning range of 100-4000 cm-1 at room temperature, laser wavelength of 532 nm. The crystal structure was studied by powder X-ray diffraction (Cu K α, λ=0.154 nm). The approximate density method is used to estimate the porosity of graphene composite aerogels with different thicknesses: P=(1- ρ 0/ρ) * 100%, where P is the porosity and ρ 0 is the actual density of graphene composite aerogels. The graphene composite aerogels are cut into regular sizes. Through calculation, ρ is the theoretical density of graphene, 2.2 g/cm3 Mechanical testing: (1) Compression cycle test: The equipment used is Shimadzu AGS-X500N, with test conditions: room temperature of around 23 ℃, load sensor of 100 N (0.5 level), test fixture of compression fixture (100 mm diameter pressure plate), test rate of 0.5 mm/min. The sample size is 30 * 30 mm. Set the preload force to 0.005 N to ensure sufficient contact between the pressure plate and the sample. Ensure that the preload force is stable and maintain this state to proceed to the next step. Set the loading speed to 0.5 mm/min, start the electronic universal testing machine, and begin the test. Compress the specimen to 80% strain and monitor the load and displacement during the testing process. Revoke loading to restore the sample to its initial position, ensuring complete recovery and stability of the sample. Record the changes in stress-strain. (2) Compression rebound performance test: The equipment used is Shimadzu AGS-X500N. With reference to GB/T 343361 Nano Aerogel Composite Thermal Insulation Products, cut the sample into a 20 * 20 mm square sheet. Use a thickness gauge to measure the initial thickness of the sample, h0, accurate to 0.01 mm. The compression speed of the tester is 2 mm/min. When the sample is pressed to (100 ± 5) kPa, stop the compression and keep the tester at this position for (5 ± 0.5) min, take out and recover (5 ± 0.5) min, and use a thickness gauge to measure the recovery thickness of the sample, h ', accurate to 0.01 mm (3) Horizontal thermal conductivity performance test:Using LFA-467 Hyper Flash and referring to ASTM-E1461 standard, the horizontal thermal diffusion of a sample with a diameter of 25.4 mm was tested. Horizontal thermal conductivity=thermal diffusivity * density * specific heat capacity calculation (specific heat capacity: 0.85, use formula: ρ=m/v to calculate sample density). (4) Bending resistance test:The equipment is MIT bending resistance tester. Take 100 mm × 180 mm graphene aerogel samples, and use a knife die to cut a 150 mm × 20 mm sample on each graphene aerogel. Take the bending fixture with a radius of R4, clamp the sample, and the sample should be in a straight state without excessive stretching. Load a weight of 20 g, bend at an angle of 180 °, adjust the testing speed to 60 times/min, and record the number of bends.