Treatments to reduce thrombogeneticity in heart valves made from titanium and its alloys

A medical implant having at least one substrate comprising titanium coated with a sequential gradient as follows:

• silicon chemically bonded to said titanium, forming a first layer comprising titanium-silicide;
• silicon cohesively bonded to said titanium-silicide, forming a second layer comprising silicon;
• carbon chemically bonded to said silicon, forming a third layer comprising silicon carbide;
• and
• carbon cohesively bonded to said silicon carbide, forming a fourth layer comprising diamond-like carbon.

A solid substrate comprising titanium coated with diamond-like carbon by a process comprising:

• exposing said substrate to a vacuum at a pressure of about 10.sup.-5 torr or less;
• heating said substrate to between at least about 600.degree. C.-650.degree. C. (1112.degree. F.-1202.degree. F.);
• depositing silicon onto said substrate in an amount sufficient to form an inner bonding layer of titanium-silicide cohesively bonded to an outer layer of silicon;
• substantially simultaneous with said depositing of silicon, bombarding said deposited silicon with a first energetic beam of ions at a first energy, a first ion density, and for a first amount of time sufficient to form said inner titanium-silicide bonding layer cohesively bonded to said outer layer of silicon;
• condensing a diamond-like carbon precursor onto said outer layer of silicon at a second temperature and for a second amount of time sufficient to form a film of precursor molecules on said outer layer of silicon, wherein said second temperature is sufficiently low that said diamond-like carbon precursor is not vaporized off of said substrate;
• substantially simultaneous with said condensing of a diamond-like carbon precursor, bombarding said diamond-like carbon precursor with a second energetic beam of ions at a second energy, a second ion density, and for a third amount of time sufficient to form an inner silicon carbide layer cohesively bonded to an outer coating of diamond-like carbon.