Introduction to Ceramics

Day 2

Today is Day 2 of research shadowing programme, and I have been following Dr Du around as she introduces me to what she does-Ceramic research for armor applications.

There are many uses of ceremic in modern world, from ordinary uses such floor tiling, to high tech uses such as space shuttles, and now even in the military. Of course, these ceremic tiles have different properties and chemical structures - why would you want a ceremic floor tile to be bullet proof and heat proof?

Testing lab

First, I was show around a lab for testing the material properties.

There were dynamic compressor which test the mechenical behaviour of material under high speed projectiles.
There were gas launcher which can shoot projectiles at high velocities (M16's muzzle velocity: 0.98km/s, tank's muzzle velocity: 1.7km/s) to test how well a material is at absorbing impact and how much penetration it can resist.
From the first visit to the lab, I have learnt:

• armor does not only consist of a single material, but a system of materials to absorb impact as well as to prevent penetration.
• With exactly the same materials, the way that those materials are stacked can make a difference to its penetration resistance.
• a more effective projectile is a heavier one where armor penetration is concerned.
• a conical projectile can penetrate 10% more than a flat tipped one.

The making of ceremic

Next, Dr Du showed me around the different labs and equipments which are required to prepare the ceramics, as well as the materials used. She also introduced to me the method and sequence of preparations, so that a good ceremic can be produced, and how different starting materials and preparation method can produce different ceramics.
Different properties of ceramics have to be created for different usage. For example, transparent ceramics (yes they exist) could be used for windows of military vehicles or generating solid state laser and the opaque ones can be used as the armor.

What ceramics start from!

Different ceramics

Where it is prepared

polished (right) and unpolished (left) ceramics

Different doping changes the colours of the ceramics

Why ceramics?

Pros

Compared to traditional armor plating such as steel, ceremic is much lighter (less dense), has higher strength and is harder than steel. Not only that, it is also cheaper than steel (some, like alumina, is). This will allow more protection for vehicles as well as increased mobility and maximum load of vehicles. This will improve survivability of soilders in wartime, as vehicles could offer more protection, move faster, and transport more.

Cons

Although they are harder, ceremic also shatters upon impact, causing it to not be able to sustain multiple hits. In practical purposes, ceremic have a backing of steel as well as a cover layer, so that upon impact, the ceremic, although shattered, will have its fragmented pieces remaining on the vehicle, allowing it to absorb absorb shock from more bullets (although MUCH less effective). The backing will provide the real protection, such that the ceramics greatly reduce the penetrating power of the bullet into the steel backing, allowing the vehicle to sustain stronger hits.

That's all for today!