Formation of porous anodic titanium oxide films in hot phosphate/glycerol electrolyte

Abstract

ISE member 2The present study reveals the formation of porous anodic films on titanium at an increased growth rate in hot phosphate/glycerol electrolyte by reducing the water content. A porous titanium oxide film of 12 µm thickness, with a relatively low content of phosphorus species, is developed after anodizing at 5 V for 3.6 ks in 0.6 mol dm -3 K 2 HPO 4 +0.2 mol dm -3 K 3 PO 4 /glycerol electrolyte containing only 0.04%water at 433 K. The growth efficiency is reduced by increasing the formation voltage to 20 V, due to formation of crystalline oxide, which induces gas generation during anodizing. The film formed at 20 V consists of two layers, with an increased concentration of phosphorus species in the inner layer. The outer layer, comprising approximately 25% of the film thickness, is developed at low formation voltages, of less than 10 V, during the initial anodizing at a constant current density of 250 A m -2. The pore diameter is not significantly dependent upon the formation voltage, being ~10 nm.

Growth of porous anodic alumina films in hot phosphate–glycerol electrolyte

“…The importance of water content in the formation of porous anodic films on valve metals in hot phosphate-glycerol electrolytes has been reported previously [20,22]. The growth rate of porous niobium oxide films at a formation voltage of 10 V is highly enhanced by the reducing water content to less than 0.1 mass% [22], which is associated with a reduced thickness of the barrier layer, and hence increased field strength in the barrier layer during film growth.…”

“…Keywords: porous anodic alumina, organic electrolyte, growth mechanism, TEM, GDOES [19][20][21]. In the present study, the growth of porous anodic alumina films has been investigated in K 2 HPO 4 -glycerol electrolyte at 433 K using field emission gun scanning electron microscopy (FEG-SEM), 5 transmission electron microscopy (TEM) and glow discharge optical emission spectroscopy (GDOES).…”

“…Recently, it has been found that porous anodic oxide films are formed in phosphate-glycerol electrolyte at an elevated temperature of 433 K. In this electrolyte, porous films may be developed on a range of valve metals, including aluminium [17], niobium [18], tantalum [17] and titanium [19][20][21]. In the present study, the growth of porous anodic alumina films has been investigated in K 2 HPO 4 -glycerol electrolyte at 433 K using field emission gun scanning electron microscopy (FEG-SEM), 5 transmission electron microscopy (TEM) and glow discharge optical emission spectroscopy (GDOES).…”

“…In the present study, the growth of porous anodic alumina films has been investigated in K 2 HPO 4 -glycerol electrolyte at 433 K using field emission gun scanning electron microscopy (FEG-SEM), 5 transmission electron microscopy (TEM) and glow discharge optical emission spectroscopy (GDOES). In particular, the influence of the water content of the electrolyte on the formation of the films has been examined, since its significant influence on the growth rate of porous titania and niobia films has recently been reported [20,22].…”

“…Using a niobium oxide outer layer to suppress chemical dissolution resulted in films that were about 1.2 times the thickness of the consumed aluminium for an electrolyte containing 0.25 mass% water. The expansion suggests possible contribution of field-assisted flow of film material in growth of the porous anodic film.Keywords: porous anodic alumina, organic electrolyte, growth mechanism, TEM, GDOES [19][20][21]. In the present study, the growth of porous anodic alumina films has been investigated in K 2 HPO 4 -glycerol electrolyte at 433 K using field emission gun scanning electron microscopy (FEG-SEM), 5 transmission electron microscopy (TEM) and glow discharge optical emission spectroscopy (GDOES).…”