【Deep Painting Society Popular Science Knowledge】Ceramic materials that cannot be broken

In 1990, Imperial Chemical Industries manufactured a ceramic car engine that was resistant to high temperatures and did not require a cooling system, which is a typical example
of successful research on advanced ceramic materials.
Because the ceramic is very hard and resistant to high temperatures, it can be used as a car engine without a cooling system, which greatly reduces the weight of the engine itself and achieves the purpose of
saving fuel.
However, ordinary ceramics are very brittle, can not withstand the bumps and vibrations of speeding cars, and are easy to break, so ceramics have not been applied
to cars for a long time.

Can you produce a ceramic that is hard and tough to break? Shells are a great inspiration to scientists, and materials scientists have found that shells are a very hard but not easy to break material, why can they be hard and tough? After the study, it was found that the shell is composed of many layers of calcium carbonate, and in the middle of each layer of calcium carbonate is a layer of organic protein, which sticks the layers of calcium carbonate together
.
The calcium carbonate in the shell is very hard and brittle, but the reason why it is not easy to break is because the cracks that occur in each layer of calcium carbonate do not expand into other calcium carbonate layers, but are blocked by the soft organic protein in the middle
.

Scientists took inspiration from the structure of the shell and decided to imitate the shell to make unbreakable ceramics
.
The method is to select extremely hard silicon carbide ceramics sintered into thin sheets, and then coated with graphite layers on each silicon carbide ceramic sheet, and then the silicon carbide coated with graphite layers are stacked and heated and extruded, so that the hard silicon carbide ceramic is bonded to graphite, graphite and organic proteins in the shell, play a binder role, and stick very firmly, silicon carbide in the encounter with shock vibration can only make several layers of the surface take off, and the surface of a few layers can absorb most of the energy after taking off, to avoid the fragmentation
of the entire part 。 According to experiments, the power of trying to break the 'mille-feuille cake' type silicon carbide ceramic with graphite layer is 100 times greater than that of breaking the whole piece of silicon carbide without graphite bonding, and its toughness is close to the toughness
of wood.
Automotive engines made of shell-type ceramic materials are expected to be installed on flying cars for real-world testing
in the near future.

Source: New Think

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