Dissolution–precipitation synthesis and thermal stability of magnesium whitlockite

Abstract

Magnesium whitlockite (Mg-WH, Ca18Mg2(HPO4)2(PO4)12) is a promising candidate for biomedical application in bone regeneration; however, the fabrication of Mg-WH bioceramics by conventional methods is limited. Mg-WH is known to be...

A copper-containing analog of the biomineral whitlockite: dissolution–precipitation synthesis, structural and biological properties

“…The parameter a was calculated as 10.330 Å, while the parameter c was 37.077 Å. These values are slightly lower compared to those previously reported for Mg-WH, 38,39 Zn-WH 22 and Cu-WH. 27 The Rietveld analysis did not indicate the presence of secondary crystalline phases.…”

“…Thus, it can be concluded that the synthetic procedure requires at least 3 h. This value is significantly lower compared to those reported for the solvothermal synthesis of Mn-WH 24 or Zn-WH 23 and comparable to the data reported for hydrothermally synthesized Mg-WH. 38,39 On the other hand, previously it was shown that in an aqueous medium, Zn-WH can be formed just in 1 h. 22 The observed time-dependent phase evolution from DCPD to Cu-WH suggests that the transformation via a dissolution–precipitation reaction could occur not directly, but in two steps with an intermediate HA phase. Previously, it was shown by Jang et al 37 that under certain conditions HA can be converted into Mg-WH via a multistep process; however, it is difficult to compare the phase transformations in certain systems due to plenty of influencing factors such as pH, temperature, pressure, chemical composition of the reaction mixture, etc .…”

“…Overall, both spectroscopic techniques agree very well with the results reported in the literature in terms of the spectral shape and band wavenumbers. 22,32,39,41…”

“…Similarly to 1 H data, the lines in 31 P data after annealing show narrower linewidths, indicating the formation of the Cu-WH phase of higher crystallinity. The 31 P MAS spectrum after annealing consists of lines at 2.2, 1.3, and −0.5 attributed to P(2), HP(1)O 4 2− and P(3) moieties, which are typical in the WH structure, 22,39 and a line at 0.4 ppm, which is an impure phosphate phase. One more remark has to be made that in comparison with Zn- and Mg-WH, Cu-WH possesses significantly broader lines which is due to the paramagnetic nature of the Cu 2+ environment.…”

“…It is worth noting that the detection of the transformation of WH into β-TCP is impossible by means of XRD due to their nearly identical patterns; 39 however, XRD is a suitable method for the monitoring of the formation of secondary phases, which can serve as an indicator of the thermal decomposition. The appearance of the secondary crystalline phase starts after annealing at 600 °C.…”