Low density carbon/graphite material has a good physical and chemical properties, in recent years,the study on the low density graphite material is very active.The expanded graphite block made of flexible graphite sheet,is also one kind of the low density graphite material.
The method to make the expanded graphite block can be simply describe as below:
Make the flexible graphite sheet dipped in the concentrated sulfuric acid and concentrated nitric acid,then,under the situation of 200℃～750℃ to make the expanded graphite block.
The intercalator,dipping time,shape of the flexible graphite sheet and the operating temperature all have an influence on the density and shape integrity of the expanded graphite block.
The density will be lower with the rise of operating temperature, but the shape of the block is harder to complete.during the experiment,we could use the flexible graphite sheet or flexible graphite plate.
The picture showing is the appearance of expanded graphite blocks obtained with different extemal dimensions of flexible graphite sheet.And the intercalator isconcentrated sulfuric acid. From the picture,we can tell apparently that different shape of the graphite sheet has a big influence on the shape of the expanded graphite block.
The shape of the expanded graphite block also has a relationship with the temperature,when the temperature are 550℃~700℃,the density of the block can change stablely,and when the temperature exceed 700℃, the fracture failure rate will sharp rise,and appear different degree of the fracture.
The expanded graphite block has two typical appearance,one is uniform appearance and another one is non uniform appearance.