The anodic growth conditions of titania with a tubular structure are investigated. We propose a mechanism of anodic growth of tubular titania, which presupposes that electrochemical oxidation of titanium is predominantly confined to the bottom of pores in a barrier layer, i.e., where the anodic current density is higher, which causes a temperature rise in these regions. As the barrier layer temperature exceeds a certain threshold, the structure of growing oxide changes from the commonly obtained porous honeycomb-like structure to a tubular one. The proposed mechanism is supported by experimental results.

The conditions for the formation of anodic titanium oxide with a tubular structure were studied. The mechanism for the formation of tubular titanium oxide based on the localization of the electrochemical oxidation of titanium in the places of the barrier layer at the bottom of the pore, where the density of the flowing anodic current is increased, as a result of which the temperature of these regions increases. With an increase in the temperature of the barrier layer above the threshold value, a transition from the traditional «honeycomb-like» porous structure to the tubular structure takes place. The proposed mechanism is confirmed by the results of experimental research.

The growth of bone tissue on titanium plates and mounting screws during surgical treatment of mandibular fractures was studied. The growth of bone tissue was more intensive on the developed surface in comparison with a polished surface. The methods of electrochemical treatment of titanium surface in order to control the regeneration process of bone tissue on the titanium constructions used during surgery were proposed.

The surface potential of anodic alumina films and their charge properties have been studied. The surface potential of anodic alumina films after anodic process has positive values, but then this potential is decreased to zero level with subsequent transition to negative values. The negative displacement of the surface potential is associated with a negative built-in electric charge of aluminum anodic oxide. The mechanism of transition from the positive built-in electric charge to the negative one inside the anodic oxides is proposed. The highest density of the negative charge is observed in the films formed in electrolytes based on the aqueous solutions of the citric and phosphoric acids.

Studying of anodic titania formation has showen that anodization forming factor at low anodic voltages is 3,3 nm/V, while at high anodic voltages it’s value decreases till 1,5 nm/V. The investigation of optical properties of anodic titania has showed the possibilities to tune the titania refractory index in the whole visible ranges. The application of anodic titania in maxillofacial surgery has been demonstrated for visualization of titanium objects.

The formation conditions of anodic alumina with a tubular structure have been investigated. It is shown that alumina has the self-ordered tubular structure at temperature of barrier oxide layer to be several tens of degrees more than electrolyte temperature in cases of viscous electrolytes (viscosity more than 10-2 Pa·s at 20 °C) and hundred degrees more in cases of low viscous electrolytes (viscosity less than 10-2 Pa·s at 20°C). It is assumed that temperature of the barrier layer during the formation of the self-ordered tubular alumina can reach several hundred degrees because of the presence of spherical structures in the pores mouths. These spheres are expected to be formed due to the melting of an aluminum substrate during the anodizing process.

Porous aluminium anodization process has been investigated in 63 wt % sulfuric electrolyte. Porous alumina formed at anodic voltages till 16 V had the «honey comb» cell structure while porous alumina formed at anodic voltages more than 16 V displayed the tubular cell structure with thickness expansion factor more than 2,5. The obtained results can be explained by resulted of Al(OH)3 formation during anodization process at high electric field inside anodic films.

Physics, Chemistry and Application of Nanostructures, pp. 333-340 (2017) No AccessCORRELATED EVOLUTION OF SURFACE MORPHOLOGY, STRUCTURE AND MAGNETIC PROPERTIES OF NANOPOROUS Co/Pd FILMS WITH PERPENDICULAR MAGNETIC ANISOTROPYJ. Fedotova, J. Kasiuk, V. Bayev, O. V. Kupreeva, T. N. Anh Nguyen, H. M. Do, and D. L. VuJ. FedotovaInstitute for Nuclear Problems, Belarusian State University, 220030 Minsk, Belarus, J. KasiukInstitute for Nuclear Problems, Belarusian State University, 220030 Minsk, Belarus, V. BayevInstitute for Nuclear Problems, Belarusian State University, 220030 Minsk, Belarus, O. V. KupreevaBelarusian State University of Informatics and Radioelectronics, 220013 Minsk, Belarus, T. N. Anh NguyenInstitute of Materials Science, Vietnam Academy of Science and Technology Hanoi, Vietnam, H. M. DoInstitute of Materials Science, Vietnam Academy of Science and Technology Hanoi, Vietnam, and D. L. VuInstitute of Materials Science, Vietnam Academy of Science and Technology Hanoi, Vietnamhttps://doi.org/10.1142/9789813224537_0077Cited by:0 PreviousNext AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsRecommend to Library ShareShare onFacebookTwitterLinked InRedditEmail Abstract: In this study, we consider the technological route to conserve perpendicular magnetic anisotropy in porous Co/Pd multilayer thin films deposited over porous anodized templates of TiO2 and Al2O3 with smoothed surface morphology. It is proved that these templates with large contribution on flat-surface interpore areas promote conservation of high magnetic anisotropy constants Keff up to 1.9×106 erg/cm3) and Mr/MS (up to 0.99) as well as magnetic hardening with twice increase of the coercive force HC (up to 2.7 kOe) indicating an excellent potential of the fabricated materials for various magnetic and spintronic devices. FiguresReferencesRelatedDetails Physics, Chemistry and Application of NanostructuresMetrics History PDF download

A comparative study of the magnetization curves of continuous and porous multilayered Pd 10 nm /[Co 0.3 nm ]/Pd 0.55 nm ]15/Pd 2 nm films deposited on an anodized TiO 2 template was performed by magnetometry. Based on the comparison of the dependences of coercive field H C on angle θ between the easy-magnetization axis and the direction of external magnetic field H with theoretical dependences H C (θ) for the magnetization reversal by domain walls motion (according to the Kondorski model) and the rotation of magnetic moments (by the Stoner–Wohlfarth model), the differences in the mechanisms of magnetization reversal for two mentioned types of the films were revealed. The correlation between the difference in the morphologies of the continuous and porous films and revealed change in the mechanisms of the magnetization reversal, as well as the changes in values of H C and calculated constants of the magnetic anisotropy, is discussed.

Методом магнитометрии проведено сравнительное исследование кривых намагниченности сплошной и пористой многослойной пленки Pd10nm/[Co0.3nm/Pd0.55nm]15/Pd2nm, осажденной на темплат анодного TiO2. На основании сопоставления зависимостей коэрцитивной силы HC от угла theta между осью легкого намагничивания и направлением внешнего магнитного поля H с теоретическими зависимостями HC(theta) для перемагничивания путем движения доменных стенок (по модели Кондорского) и вращения магнитных моментов (по модели Стонера-Вольфарта) выявлены различия в механизмах перемагничивания двух указанных типов пленок. Обсуждается взаимосвязь между различием в морфологии сплошной и пористой пленок и выявленной сменой механизма перемагничивания, а также изменениями значений HC и рассчитанных констант магнитной анизотропии. Работа выполнена в рамках Государственной программы научных исследований "Физическое материаловедение, новые материалы и технологии" (задание 2.44), договора Ф16В2-004 с БРФФИ (Беларусь), гранта 2014/13/N/ST8/00731 National Science Centre (NCN, Poland).

Double-walled titanium dioxide (TiO2) nanotubes have been successfully fabricated by electrochemical anodization at low temperature with subsequent annealing. The low temperature allows for suppression of the chemical etching. The as-fabricated and annealed TiO2 nanotubes are typically single-walled for tubes with diameters less than 150 nm. For nanotubes with diameters greater than 150 nm, it was observed that annealing initiated tube splitting of one to two and hence resulted in double-walled nanotubes. Raman spectroscopy analysis showed anatase phase for the nanotubes. Compared to the single-walled TiO2 nanotube, double-walled nanotubes have enlarged surface areas. This makes TiO2 nanotubes with a double-walled structure more effective for catalytic applications. Photocatalytic testing under ultraviolet (UV) radiation proved enhanced photocatalytic activity with a faster degradation rate of the organic chemical with double-walled nanotube film compared to the single-walled sample.

We describe a process for obtaining tubular nanostructured (nanotubular) titanium oxide by electrochemical anodizing. We have studied the elemental composition of the films formed by x-ray spectral analysis and Auger analysis, and have also studied the photocatalytic properties of TiO2 exposed to UV and visible radiation.

Double-walled TiO2 nanotubes have been fabricated for the first time by anodization of Ti foil or film providing a layer of densely packed single-walled TiO2 nanotubes with a diameter of 100-250 nm and their subsequent annealing at 450 degrees C to split the tubes into two concentric tubes. Peculiarities of the tubes structure and possible mechanism of their formation are discussed.

The porous titania growth during electrochemical anodization of titanium films and foils in the 0.1M ammonium fluoride (FNH4) solution in ethyleneglycol has been studied in the temperature range from −5°C to +20°C. Titania films with a smooth tubular morphology was found to be formed at the electrolyte temperatures below 0°C. The growth rate was as high as 1.5μm/min provided that the tube diameters were up to 300nm and the film porosity was less than 1%. Porous titanium anodization at the electrolyte temperature of 0°C and below induces formation of porous titania with a structure close to ideal packed hexagonal prisms with a smooth tubular surface. The mechanism of the appearance of such structure is discussed.