Study on the Effect of Annealing Temperature on the Compressibility and Microscopic Structure of Pure Graphite

The problem of improving the physical and mechanical properties of graphite is
not receivin~ considerable attention despite ~phite bein~ used widely in critical and
dangerous applications in many industries such as in nuclear reactors, automotive
components, rocket nozzles and hi!Pt temperature heat exchangers. Studies have
indicated that, if a metal powder is annealed, the compressibility of the powder will
improve. Therefore, it is the purpose of this report to investigate and establish an
extensive study to improve the compressibility of graphite powder, one of the many
mechanical properties of graphite. The objective of this report is to study on the effect
of annealing temperature of pure graphite powder on the compressibility and
microscopic structure of its pellet produced by powder metallur~ process. The ~phite
powder will undergo powder metallurgy processes in order to produce the pellets;
~ndin~, annealin~ and compacting. Four sets of samples comprising of 10 pellets each
will be produced. I set will be left unannealed as the datum, and the other 3 set of
samples will be annealed at three different annealing temperatures; 700°C, 800°C and
~00°C. The pellets will be compressed using compaction pressure between 14-140 MPa
(2000psi-20000psi). Next, the density of all the pellets will be measured and
compressibility curves comparing the compressibility of all set of samples will be
plotted based on the densities recorded. After that, the microstructure of pellets
compressed at 137.~0 MPa (20000psi) at all annealing temperature (unannealed, 700°C,
800°C and 900°C) will be analyzed using SEM and recorded. The analysis carried out to
the compressibility curve of the samples shows that, the compressibility of the samples
increase as the annealing temperature increases. The microstructures of the samples
indicated that necking and bridging structures formed vigorously as the annealing
temperature increases. As a conclusion~ the compressibility of graphite increases as its
annealing temperature increases.