Influence of annealing temperature on microstructure and phase transformations of oxide system Bi2O3/TiO2 formed in aqueous solutions

Bismuth titanate is widely used in various fields of science and technology due to its unique physical and chemical properties. Nanostructured metal oxide compounds of the Bi–Ti–O system, consisting of columnar TiO2 nanostructures obtained by electrochemical anodization of a two-layer Ti/Al composition, and platelet Bi2O3 nanostructures formed by sequential ion-layer deposition were synthesized. Morphological changes and phase transformations in the microstructure of the Bi2O3/TiO2 oxide system, which occur during its thermal annealing at temperatures of 150, 300, 500, and 700 °C, have been studied. Annealing of the oxide system in the range of 150–300 °C degrees leads to inconsequential morphological and structural changes: the mixture of oxides is densified, in addition to anatase, a rutile phase appears in TiO2. The crystal system of the Bi2O3 phase is hexagonal. After annealing at 500 °C, not only morphological changes occurred in the studied composite, but also significant transformations in the microstructure. In the film volume, oxide phases Ti2O3 and Bi2O3 began to transform into three-component compound Bi4Ti3O12, and this process is completed at 700 degrees with the formation of single-phase Bi4Ti3O12 nanocomposite with an orthorhombic lattice with the crystal space group Fmmm

Bismuth Oxide-based Matrix Nanosystems for X-ray Contrast Diagnostics and Protection from Ionizing Radiation

The features of the bismuth oxide deposition by the ion layering method on matrices of anodic alumina and anodic titania have been studied. The formed nanostructured systems have been studied by means of electron micros copy, X-ray microanalysis, and X-ray spectroscopy. Two-layer nanocomposites consist of porous matrix or TiO2 island film with vertically oriented Bi2O3 plates placed on the surface. The photoluminescence spectrum of Al2O3/Bi2O3 oxide structure contains two photoluminescence channels with peaks at 460 and 560 nm upon excitation at 345 nm. Analysis of the EDX spectra showed that the atomic ratio of Bi, Ti and O was 31.46 % Bi : 3.78 % Ti : 51.05 % O. The possibility of using complex nanocomposite as contrast agents in X-ray diagnostics and for protection against ionizing radiation is shown

Formation of multicomponent matrix metal oxide films in anodic alumina matrixes by chemical deposition

The metal oxide films of Sn[x]Zn[y]O[z] and Sn[x]Mo[y]O[z] systems deposited onto anodic alumina matrixes by chemical and ion layering from an aqueous solutions were characterized by scanning electron microscopy, Raman spectroscopy, electron probe X-ray microanalysis and IR spectroscopy. The obtained matrix films had reproducible composition and structure and possessed certain morphological characteristics and properties

Multicomponent Sn–Mo–O-containing films formed in anodic alumina matrixes by ionic layer deposition

Multicomponent metal oxide compounds of the composition Sn–Mo–O, Sn–Ni–Mo–O and Sn–Bi–Mo–O were formed by successive ionic layer adsorption and reaction (SILAR) method deposition into anodic alumina matrixes. The growth mechanism of the Sn–Mo–O-containing films in the porous anodic alu- mina was investigated. It was found that the degree of pore filling, specific thickness and surface mor- phology of the deposited layer depend not only on the number of cycle’s treatment, but also on the composition of the used solutions. The morphology of Sn–Mo–O and Sn–Ni–Mo–O surfaces had granular structures, while Sn–Bi–Mo–O layer had flake-like structure. The differences in microstructure and depo- sition of the layers on the surface of the matrixes can be explained by the insufficient activation of anodic alumina pores before deposition. The investigations of the formed layers composition by the electron- probe X-ray spectral microanalysis showed that the ratio of tin to molybdenum in tin-molybdenum con- taining oxides changes. The Sn/Mo atomic ratio for Sn–Mo–O layer is 1.29/2.72; for Sn–Ni–Mo–O layer is 5.83/4.85; for Sn–Bi–Mo–O layer is 0.60/0.87. The using of SILAR method allows forming multicomponent films in the anodic alumina matrixes, which have great potential to applicate in high-sensitivity gas sensors

Конструкционные упрочняющие композитные покрытия на алюминиевых сплавах из матричных углеродных и металлоксидных наноструктур

Использование современных конструкционных материалов обычно ограничивается тем, что увеличение прочности приводит к снижению пластичности. Однако более глубокое изучение физики деформационных процессов наноструктурированных материалов показало, что уменьшение их микроструктуры и наноструктурирование приводят к появлению в них новых качеств и созданию новых видов материалов с повышенной прочностью и пластичностью. Проведенные исследования при разработке конструкционных композитных покрытий с наполнителями из матричных наноструктур на основе металлооксидных и углеродных материалов показали перспективы для их применения в качестве упрочняющих покрытий на алюминии при изготовлении литых изделий точной формы из цветных сплавов с повышенной износостойкостью и ударной вязкостью, создании наноструктурированных защитных термо- и коррозионностойких покрытий, обладающих повышенной прочностью и низкой воспламеняемостью

Anodic Niobia Column-like 3-D Nanostructures for Semiconductor Devices

Two types of anodic niobia (niobium oxide) column-like three-dimensional (3-D) nanostructures were synthesized by anodization in 0.4 mol•dm -3 oxalic acid aqueous solution at 37 V, reanodizing in 1% citric acid aqueous solution up to 300 and 450 V, and chemical etching of magnetron sputter-deposited Al/Nb metal layers. The dependence of the synthesized niobia column-like 3-D nanostructures' morphological properties on formation conditions were defined by scanning electron microscopy. The niobia column-like 3-D nanostructures' electrophysical characteristics were investigated in two measurement schemes. Aluminum layers of 500-nm thickness were used as contact pads. The current-voltage characteristic (I-V) has nonlinear and nonsymmetrical character. The nonsymmetrical I-V reached ~10 V. The breakdown voltages were 80 and 125 V, self-heating begins at voltage direct connection 33 and 60 V, initial resistance at 23 °C was 60 and 120 kΩ, specific resistance to the height of the columns was 87 and 116 Ω•nm -1 , and the calculated temperature coefficient of resistance in the range 20-105 °C appeared to be negative and rather low, -1.39•10 -2 and -1.28•10 -2 K -1 , for the niobia column-like 3-D nanostructures reanodized at 300 and 450 V, respectively

A Micropowered Chemoresistive Sensor Based on a Thin Alumina Nanoporous Membrane and SnxBikMoyOz Nanocomposite

This work presents and discusses the design of an efficient gas sensor, as well as the technological process of its fabrication. The optimal dimensions of the different sensor elements including their deformation were determined considering the geometric modeling and the calculated moduli of the elasticity and thermal conductivity coefficients. Multicomponent SnxBikMoyOz thin films were prepared by ionic layering on an anodic alumina membrane and were used as gas-sensitive layers in the sensor design. The resistance of the SnxBikMoyOz nanostructured film at temperatures up to 150 ◦C exceeded 106 Ohm but decreased to 104 Ohm at 550 ◦C in air. The sensitivity of the SnxBikMoyOz composite to concentrations of 5 and 40 ppm H2 at 250 ◦C (10 mW) was determined to be 0.22 and 0.40, respectively

Columnar Niobium Oxide Nanostructures: Mechanism of Formation, Microstructure, and Electrophysical Properties

The morphology and microstructure of columnar niobium oxide nanostructures are studied and the dependences of their morphological sizes on anodizing voltages (100–450 V) and anodic alumina pore diameters (40–150 nm) are established. The features of ion transport during local anodization of niobium are studied and the transport numbers of electrolyte anions and niobium cations are calculated; a mechanism of formation and growth is proposed and the phase composition and electrophysical properties of columnar nanostructures are studied

A Micropowered Chemoresistive Sensor Based on a Thin Alumina Nanoporous Membrane and SnxBikMoyOz Nanocomposite

This work presents and discusses the design of an efficient gas sensor, as well as the technological process of its fabrication. The optimal dimensions of the different sensor elements including their deformation were determined considering the geometric modeling and the calculated moduli of the elasticity and thermal conductivity coefficients. Multicomponent SnxBikMoyOz thin films were prepared by ionic layering on an anodic alumina membrane and were used as gas-sensitive layers in the sensor design. The resistance of the SnxBikMoyOz nanostructured film at temperatures up to 150 ◦C exceeded 106 Ohm but decreased to 104 Ohm at 550 ◦C in air. The sensitivity of the SnxBikMoyOz composite to concentrations of 5 and 40 ppm H2 at 250 ◦C (10 mW) was determined to be 0.22 and 0.40, respectively