DC Circuit Breakers

Not enough information, what are you trying to do?

i don't think one can "improve" the DC rating of an already existing circuit breaker. The absence of current zero makes DC difficult to break. Techniques like blowout coils, long arcing horns etc are used to achieve DC breaking. These are inherent in the design, cannot be added later to an existing breaker.

Rule #75

I think first (as TonyS was likely alluding to) one must define the term "improve". Improve from what? Higher voltage rating? Less resistance across the connection? faster operations? Better color coordination with your wall paper?

Better colour coordination with your wallpaper?

No, it's got to match my electric blue Oxford Bags. And if you can remember them you can join me in the pension queue.