First, the content introduction
Flexible graphite has excellent sealing characteristics and is the first choice for sealing materials in nuclear power plants. Widely used in various occasions of liquid and gas sealing, it is known as the "king of sealing". However, flexible graphite has its inherent disadvantages: first, its strength is too low, and the strength of ordinary flexible graphite sheet (density is about 1g/cm3) is only 3 ~ 5 MPa, so it is difficult to use it alone in many occasions and needs to be reinforced with metal plates; Another disadvantage is that flexible graphite is too stable in electrochemical systems. When it is paired with most metals, it is always the cathode, leading to anodic oxidation and electrochemical corrosion of the paired metals. However, it is not allowed to corrode the metal pipes and parts of the sealing system in occasions requiring high safety and precision, such as nuclear power and fine chemicals. In view of these two shortcomings, the Eighth Five-Year Plan listed two research topics: high strength flexible graphite and slow corrosion flexible graphite.
According to the reinforcing mechanism of dispersed particles and the principle of adding corrosion inhibitor, Tsinghua University proposed and successfully developed a composite technology of adding reinforcing agent or corrosion inhibitor precursor to expanded graphite, so that the reinforcing particles or corrosion inhibitor particles were uniformly dispersed and distributed in flexible graphite during the expansion and post-treatment of flexible graphite preparation process, forming high-strength flexible graphite or corrosion inhibitor flexible graphite. High strength flexible graphite takes boric acid as precursor. After expansion molding, boron oxide nano/submicron particles are dispersed in the flexible graphite matrix, which makes the strength of flexible graphite more than double, reaching more than 65438±00 MPa. Molybdate is used as the corrosion inhibitor of flexible graphite, and the duality of flexible graphite and 45 # steel is in 3%NaCl solution. Compared with ordinary flexible graphite, the anodic oxidation current corrosion inhibition rate of flexible graphite is reduced by more than 50%, that is, the corrosion resistance life is more than doubled.
Two. Identification, awards and patents
This technology was developed in the national key scientific and technological project 199 1 ~ 1995 during the Eighth Five-Year Plan. This achievement won an invention patent (ZL93 10378 1.6), and was appraised as the first technology at home and abroad through the scientific and technological achievements appraisal of the State Building Materials Bureau and the State Education Commission. This achievement was included in the building materials science and technology award of China Building Materials Association and China Silicate Society in 2006, and the first prize of technological invention, "Research and application of new modification technology of natural flake graphite".