公开(公告)号：US20160362803A1

公开(公告)日：2016-12-15

申请号：US15179337

申请日：2016-06-10

Applicant: Advanced Diamond Technologies, Inc.

Inventor： Hongjun Zeng ,  John Arthur Carlisle ,  Ian Wakefield Wylie

IPC: C25B11/12 ,  C25B1/02 ,  C25B1/26 ,  C25B1/28 ,  C25B11/04 ,  C25B1/13

CPC classification number: C25B11/12 ,  C25B1/02 ,  C25B1/13 ,  C25B1/26 ,  C25B1/28 ,  C25B1/285 ,  C25B11/0405 ,  C25B11/041 ,  C25B11/0478

Abstract: A novel durable composite diamond electrode comprising at least a relatively thicker conductive layer of UNCD (Ultrananocrystalline Diamond) layer with a Young's modulus of less than 900 GPa on a niobium substrate underlying a relatively thinner conductive MCD (Microcrystalline Diamond) layer with a Young's modulus of greater than 900 GPa, has been shown to exhibit superior delamination resistance under extreme shear stress during electrochemical oxidation reliability testing. Highly accelerated lifetime testing of these durable composite diamond electrodes at a constant current density of 2.5 amps/cm2 (25000 amps/m2) in a 1 M NaCl (58 g/L) solution, have demonstrated lifetimes before delamination failure of greater than 2000 hours (i.e. >5000 Ahr/cm2). Using a conservative estimate of lifetime to failure with a cubed dependence on current density, the lifetime at a more typical operating current density of 0.25 amps/cm2 (2500 amps/m2) would be at least 2,000,000 hours (228 years) and >3.5 years at 1.0 amps/cm2 (a more typical current density for ozone generation). It is hypothesized that this improvement in durable diamond electrode reliability is due to a combination of stress relief by the composite film with a slightly “softer” underlying UNCD layer, a disruption of the fracture propagation mechanism between the two layer(s), and the near ideal chemical and thermal expansion coefficient match between the two diamond layers and the hardness and durability of the overlying MCD layer as deposited on an electrode substrate. The combination of a thick but “softer” underlying UNCD layer with a thin but harder overlying MCD layer provides an excellent compromise between the low deposition cost and conductivity of UNCD with the extreme hardness, large grain size and unparalleled chemical and biochemical inertness of even a thin layer of MCD. The inventive two layer diamond composite electrode can be applied to any electrochemical application requiring extreme voltages/current densities, extreme reliability, hardness or biomedical inertness such as electrochemical systems to generate ozone, hydroxyl radicals, deep sea chlorine generators or biomedical electrode applications such as pacemakers, biosensors, cardiovascular devices or automatic defibrillators.