Soft mechanochemical synthesis and thermal stability of hydroxyapatites with different types of substitution

Abstract

The feasibility of soft mechanochemical synthesis was studied here for hydroxyapatite with various types of substitution. It was shown that this method allows obtaining hydroxyapatites substituted with copper or iron cations and hydroxyapatites cosubstituted with zinc cations and silicate groups. Thermal stability of the synthesized samples was evaluated. It was found that to preserve phase homogeneity of the material, the temperature during the preparation of ceramic products and coatings should not exceed 600–800 °C. An exception is the hydroxyapatite where a hydroxyl group is expected to be replaced by a copper cation during the synthesis at a degree of substitution x = 0.5. For this sample, the temperature of the the heat treatment can be increased to 1100–1200 °C because copper cations return to the hydroxyapatite crystal lattice at these temperatures, and the material becomes single-phase.

Modeling and computational research of the Hydroxyapatite properties

“…Проведенные ранее исследования, моделирование и расчеты структуры и свойств ГАП показало, что свойства реальных ГАП определяются наличием в нем различных структурных дефектов (вакансий кислорода и гидроксильных групп, внедрений и замещений ионов различных атомов и атомных групп в структуре ГАП) и особенностями его нековалентных взаимодействий и молекулярноподобной внутренней конфигурации с тубулярными каналами, состоящих из цепочек гидроксильных ОН-групп, связанных водородными связями [1,2,4,7]. Важным моментом являются и особенности термической стабильности ГАП [8,9], которые сильно зависят и от концентраций этих ОН-групп.…”

Molecular Dynamics Simulation of the Thermal Behavior of Hydroxyapatite

“…This is determined by the features of non-covalent interactions and the molecular-like internal configuration of HAP with tubular channels, which consist of chains of hydroxyl OH groups linked by hydrogen bonds [ 6 , 7 , 8 , 9 ]. An important point here is also the thermal stability of HAP [ 13 , 14 , 15 ], which strongly depends on the concentrations of the OH groups into the channels at different temperatures.…”

“…Various defects have different effects on the change in the properties of a regular HAP periodic lattice. Therefore, for example, the HAP samples during fabrication and treatment are heated to certain temperatures (700–900 K and above [ 13 , 14 , 15 , 22 , 23 , 24 , 25 ]). It is known that OH groups under these conditions leave the samples.…”

“…As a result, HAP is dehydrated [ 7 , 13 , 25 , 26 ]. During subsequent cooling, OH groups from the environment are reintroduced into these channels, but their concentration depends on the humidity of the environment and the OH vacancies partially can remain in the HAP samples after cooling in air [ 4 , 6 , 7 , 8 , 13 , 14 , 25 , 26 ].…”

“…Moreover, oxygen vacancies can be of different types depending on the position of the oxygen atom and the symmetry of the given atomic PO 4 group [ 7 , 12 ]. Their formation is possible at higher temperatures (1300–1500 K) [ 13 , 14 , 15 , 24 , 25 , 26 , 27 , 28 ] or also under radiation exposure [ 29 ].…”