The price for the 13.5% interest stake was determined by an independent valuation conducted on HTI, which included the acquired nanomaterials business, Advanced Composite Materials.
Haydale now owns the entire issued share capital of HTI.
Ray Gibbs, CEO of Haydale, said: "We are pleased to have obtained 100% ownership of our US operations. HTI is already making a meaningful contribution to the Group's performance and we believe there is significant further sales potential for our high quality silicon carbide fibres and whiskers.
Broker Cantor Fitzgerald described it as clearly positive and will boost sales opportunities for HTI’s high quality silicon carbide fibres and whiskers. Buy with a target price of 230p.
Shares rose a touch to 200p.