I have several utensils made of silicone (as opposed to plastic). How do I Kasher them for Pesach? Or are they like plastic utensils and don’t require special Kashering for Passover?

I also have knives with ceramic blades. Are they like knives with metal blades that require immersion in boiling water? Or are they like ceramic pots that don’t require special Kashering for Passover?