I'm trying to tinker with a little home radioactive material, like Americium-241. I'm taking all the precautions for shielding, even though Americium isn't that dangerous behind any surface. So I understand the physics behind WHY radioactive decay generates heat, I'm wondering, though, what the Americium decay particles (or any radioactive material) need to be interacting with to heat? Is there a certain material specific for Americium that will allow the decay process to generate heat? Otherwise, why isn't the Americium in my smoke detector heating up? Sorry if I didn't explain it properly, hope someone can help! Thanks!