What is a neutron's MeV after traveling through graphite?

Does graphite slow a neutron down to a set limit depending on the thickness/density of the graphite? Does a neutron with a high MeV and one with a lower MeV reach the same speed after passing through identical graphite blocks? Probably not. I don't know if graphite acts like a linear or non-linear nuclear limiter. What would be the calculations for determining the final MeV of a neutron after passing through a graphite block with a known thickness and density?