Porous‐Alumina‐Assisted Growth of Nanostructured Anodic Films on Ti−Nb Alloys

Abstract

Porous-anodic-alumina (PAA)-assisted anodizing is employed, for the first time, for growing arrays of oxide nanocolumns on TiÀNb alloy films with up to 58 at% Nb. Beyond about 24 at% Nb in the alloy, the system allows for high formation potentials of 250-420 V, giving columns that are 500-700 nm long, which are 100 % stable during the PAA etch. The stability worsens when lowering the Nb content in the alloy, owing to contamination of the column roots by alumina, which arises from the amorphous-to-crystalline transition of the anodic oxide, oxygen evolution, formation of O 2 -filled nanobubbles within the roots, and development of bigger voids. The voids force the roots to regrow and spread laterally along with anodizing the surrounding Al residues, which increases alumina content in the titania-based nanoroots. The incorporation of sufficient amounts of Nb 2 O 5 in the anodic TiO 2 hinders oxide crystallization and lowers alumina content in the roots, which stabilizes the columns. The two oxides are distributed uniformly along the columns, indicating comparable migration rates of Ti 4 + and Nb 5 + ions in the mixed anodic oxide. This uniform distribution, combined with possibly mixing the oxides at atomic level, is expected to narrow the band gap of the material, which is of vast importance for solar energy conversion applications.[a] Dr.

The Growth, Composition, and Functional Properties of Self‐Organized Nanostructured ZrO2‐Al2O3 Anodic Films for Advanced Dielectric Applications

“…The presence of O 2 ‐filled voids in the column bases may be attributed to oxidation of the migrating O 2− ions on the zirconium‐oxide nanocrystallites under the alumina barrier layer, generation of oxygen gas, and partial dissociation of the Al‐O bonds under the high electric field in the manner described in previous works on anodizing of aluminum on n‐type Si, [ 42 ] TiNb, [ 34 ] or TiN [ 43 ] substrates. The formation of a uniform continuous sponge‐like bottom sublayer that thickens proportionally to re‐anodizing voltage has not been reported for any of the valve metals anodized through the alumina nanopores.…”

“…To avoid electron‐beam‐induced crystallization of the anodic oxide, a fresh area of interest was imaged by a short exposure at 200 or 300 kx magnification, as described elsewhere. [ 34 ] Well‐recorded parts of the HRTEM images were subjected to fast Fourier transform (FFT) analysis using FEI software Velox version 2.14. Energy dispersive X‐ray (EDX) spectroscopy and elemental mapping were performed in STEM mode using a windowless Super‐X detector via scanning an area of interest using a beam current of 1 nA and 20 µs dwell time.…”

Overview of Engineering Carbon Nanomaterials Such As Carbon Nanotubes (CNTs), Carbon Nanofibers (CNFs), Graphene and Nanodiamonds and Other Carbon Allotropes inside Porous Anodic Alumina (PAA) Templates

“…This trend can be correlated with the boom of 2D materials that seldom requires the use of nanostructured templates. Nonetheless, there are still many applications that require the use of PAA templates [ 31 , 32 , 33 , 34 , 35 ] and novel hybrid materials such as metals sulphides [ 36 ] and metal alloys nanowires [ 37 ] that are suitable for nanostructured templates.…”

“…This trend can be correlated with the boom of 2D materials that seld requires the use of nanostructured templates. Nonetheless, there are still many appl tions that require the use of PAA templates [31][32][33][34][35] and novel hybrid materials such metals sulphides [36] and metal alloys nanowires [37] that are suitable for nanostructu templates. Very interesting review articles were published recently that provide an extens description of the signs of progress made on the PAA fabrication [38,39], characterizat [40], formation mechanisms [41,42] and applications [43,44].…”

Propriedades magnéticas e supercondutoras de redes de nanofios de Ni acopladas a filmes de Nb

“…Estudos recentes aplicam essa ideia em supercondutores de NbN [16] e PbBi [17], e ainda a supercondutores de alta temperatura crítica [18]. Também tem sido estudadas nanocolunas de Ti-Nb em alumina nanoporosa [19], e nanoredes de NbN fabricadas usando uma matriz de silício porosa [20].…”