[XEHRpa]

Actually, jet velocities can range, depending on design, from 4 to 11 km/s. The upper limit is governed by a sonic criterion, kind of like the Mach 1 barrier of the liner's metal (the sound speeds in metals are significantly higher than in air). It varies from material to material.

You are right that jet temperatures are measured on the surface, not in the core, but I am confidant to a reasonably high level that code computations corroborate that interior temps are still sub-melting.

And indeed, you are corret that the best way to defeat a shaped charge's jet is to either prevent initial formation (e.g. standoff bar armor, or active armors) or disperse the concentration of the penetrating element after jet formation (reactive or special armors). However, for bullets, as opposed to jets, there are armor designs of ceramic that attempt to resist (rather than disperse) the force of the impact, literally turning the bullet into a flat pancake on the surface of the armor.

[SauronOfMordor]

There's also Chobham armor, consisting of layers of ceramic and steel. Although the exact details of Chobham are still classified, it seems there is something about the shattering effect of the penetrator on the ceramic that dissipates the energy.

I'm not convinced the explanation in Wikipedia has any grounding in reality, though. I'm suspecting that perhaps the passage of the jet thru the shattered ceramic layer experiences an effect similar to the plastic armor used in WW-II on British merchant ships. Consisting of sharp granite stones suspended in an asphalt matrix, it reportedly was pretty effective in protecting against strafing by up to 20mm shells. It appears to have worked by inducing keyholing of the bullets

Which brings me back to my original thought, of what would happen to a shaped-charge jet should it encounter very hard objects (I suggested tungsten carbide particles, but perhaps bits of DU would work better) suspended in an ultra-light matrix that would allow a lot of depth without hugely weighing down the vehicle

[SauronOfMordor]

However, for bullets, as opposed to jets, there are armor designs of ceramic that attempt to resist (rather than disperse) the force of the impact, literally turning the bullet into a flat pancake on the surface of the armor.

The metallic inserts attempt to do the. The ceramic inserts absorb the energy by shattering, and in the process breaking the bullet into fragments which are then absorbed into the backing Kevlar. See here. The effect is dependent upon the speed of sound in ceramic ( > 10,000 m/sec ) being much higher than the velocity of the bullet it's trying to stop