Formation of nanocrystalline BiFeO3 under hydrothermal conditions

Nanoscale systems occupy the most important place among the vehicles intended for targeted drug delivery. Such vehicles are considered in this review. Attention is paid to the nanocluster polyoxometalate-based systems which are promising for transdermal iontophoretic transport. In this relation, and due to the characteristics of the skin as a transport medium, the problems of the transfer processes modeling are considered.

Section: Nanostructured Systemsmentioning

confidence: 99%

The use of nanocluster polyoxometalates in the bioactive substance delivery systems

Остроушко¹,

Gagarin²,

Данилова³

et al. 2019

“…Another important property of the nonautonomous finite-thickness phase is its melting point. If early papers [75,78,80,81,117,118] provided discussion that the melting temperature of surface (nonautonomous) phases may differ from the melting temperature of volume phases of the same composition, the recent papers generally consider only the value of these differences and expressions describing the dependence of the melting temperature of different nonautonomous phases on certain parameters [13,15,95,[97][98][99]108,214]. Information on the component distribution between the nonautonomous and volume phases, which makes it possible to predict the material properties and behavior over a wide temperature range, is of great importance for the analysis of polycrystalline and other disperse systems [78,79,117].…”

Section: Status Of Nonautonomous Phases and Materials With The High Vmentioning

confidence: 99%

“…In this respect, it should be noted that there is a significant advantage, explained in detail in [78,82], of considering the component redistribution between the volume phases and the nonautonomous finite-thickness phases, as compared to the approach considering the concentration of impurity components at the volume phase interface as their adsorption or segregation on a two-dimensional surface. However, the latter way of consideration is widespread and also provides useful information for analyzing the properties and behavior of materials [1,6,13,15,71,95,[97][98][99][105][106][107].…”

Section: Status Of Nonautonomous Phases and Materials With The High Vmentioning

confidence: 99%

Thermodynamics and kinetics of non-autonomous phase formation in nanostructured materials with variable functional properties

Коваленко¹,

Тугова²

2018

The review addresses physico-chemical aspects of interaction between macro-, micro-and nano-structured units of matter with the analysis of interface and grain boundary entities (nonautonomous phases) mechanisms and formation, as well as methods of their control in order to achieve the desired functional properties of nanostructured materials. Construction of these materials involves identification of thermodynamic and kinetic regularities in the organization processes, state and genesis parameters of nonautonomous phases formed as specific nanosized structures in a limited space between the macroscopic volume phases and with the limited amount of substance, which differ significantly on their properties, structure and composition from the appropriate characteristics of volume phases. Studying them is based on the application and development of theoretical and experimental methods of non-equilibrium thermodynamics, chemical kinetics, nonlinear dynamics and fractal analysis to determine the conditions of self-organization or materials directed synthesis with a high content of nonautonomous phases.

“…As a rule, the conditions of hydrothermal synthesis (HTS), significantly affect the composition, structure, and size of particles and crystallites of the synthesized products [1][2][3][4][5][6][7]. Important factors in this case are the sequence and rate of reagents mixing and the pH of the hydrothermal fluid [8,9]. Changes in pH usually significantly affect the state and composition of phases resulting from hydrothermal treatment [10,11].…”

Section: Introductionmentioning

confidence: 99%

Influence of hydrothermal synthesis conditions on the composition of the pyrochlore phase in the Bi2O3-Fe2O3-WO3 system

Lomakin¹,

Проскурина²,

Гусаров³

2020

The paper deals with a study of the effect which the hydrothermal fluid pH has on the formation of a pyrochlore-structured phase in the Bi 2 O 3-Fe 2 O 3-WO 3 system. It was shown that at pH of 1 and 8, the formation of pyrochlore-structured phase particles with crystallite sizes of 38 and 118 nm, respectively, is accompanied by the formation of the Bi 2 WO 6 compound with the Aurivillius phase structure. At pH values from 2 to 7, only pyrochlore-structured nanocrystalline particles with a variable composition are formed. Under these conditions, the dependence of the average size of crystallites of the pyrochlore-structured phase particles on pH is extreme, as the size increases from ∼ 67 nm at pH 2 up to ∼ 126 nm at pH 5 and then decreases to ∼ 102 nm at pH 7. The samples obtained at pH 3-4 have a composition that is the closest to that specified for the synthesis. When pH increases up to 10, there forms a non-single-phase product that contains the Bi 2 WO 6 phase and δ-Bi 2 O 3-based phase.