Effects of growing integrated layer [GIL] formation on bonding behavior between hydroxyapatite ceramics and Ti-based bulk metallic glasses via hydrothermal hot-pressing

The authors successfully formed a bond between bioactive hydroxyapatite (HA) ceramics and titanium (Ti)-based bulk metallic glasses (Ti₄₀Zr₁₀Cu₃₆Pd₁₄: BMG) through a growing integrated layer (GIL) to develop a new type of biomaterial. The GILs were formed on the BMG surfaces by hydrothermal-electrochemical (HE) techniques. The BMG substrates were treated in a 5 mol/L NaOH solution at 90 °C for 10-120 min while a constant electric current of 0.5 mA/cm² was maintained between the electrodes. Then the BMG disks with the GIL and a powder mixture of CaHPO₄·2H₂O and Ca(OH)₂ were simultaneously treated with an autoclave for hydrothermal hot-pressing (HHP) (150 °C, 40 MPa, 2 h). Direct bonding between the HA ceramics and the BMG disks could be achieved through the above processing method. Consequently, to the best of our knowledge, this is the first demonstration of the usefulness of a series of hydrothermal techniques (HE and HHP) for direct bonding of bulk ceramics and bulk metallic materials.