US Patent 10975658 Wellbore isolation barrier including negative thermal expansion material

A downhole tool for forming a seal in a wellbore includes a housing configured for attachment to a string usable to transport the tool in the wellbore to a target depth; a holding chamber disposed within the housing, the holding chamber configured to receive a combination of a metal, a metal oxide, and a negative thermal expansion material in the holding chamber; an initiator operable to initiate a chemical reaction; a pressure applicator configured to apply pressure to seal material in the holding chamber; and an opening in a surface of the housing through which the seal material is expellable from the holding chamber.