The influence of Sr and Mn incorporated ions on the properties of microwave single- and two-step sintered biphasic HAP/TCP bioceramics

Abstract

The aims of this study were to investigate the effects of Sr-and Mn-doped ions on the sintering behaviors, microstructure and mechanical properties of the bioceramics processed by single-and two-step microwave sintering (MWSSS and MWTSS). Nano-sized calcium hydroxyapatite powders doped with Sr and Mn ions, obtained by modified precipitation synthesis, were isostatically pressed at 400 MPa and processed by MWSSS and MWTSS at different temperatures. In all cases during the sintering, the doped HAP powders turned into biphasic mixtures of HAP and TCP, but the amount of TCP was certainly lower in the case of MWTSS. It was shown that the doped ions significantly affected: density, microstructure, grain size, porosity, hardness, and fracture toughness of the processed bioceramics. Two-step microwave sintering was successfully applied for the processing of HAP/ TCP bioceramics doped with strontium and manganese ions. Both two-step microwave sintered doped bioceramics had similar and high hardness values, but the strontiumsubstituted bioceramic material certainly had higher fracture toughness (1.54 MPam 1/2 ), with an average grain size of 195 nm. Based on the results presented in this paper, it was concluded that the two-step microwave sintered strontium-doped bioceramics could be suitable materials in the bone regenerative field.

Bioinspired approaches to toughen calcium phosphate-based ceramics for bone repair.

“…Pure HA ceramics sintered at 1100-1250 °C are ~98% dense and feature submicrometric grains of 1 to 10 µm, leading to a compressive strength of 40 MPa and a toughness of 1-1.4 MPa.m 0.5 . Substituting HA with ions such as Zn, Ni, Sr and Mn was found to aid the sintering but leads to thermal decomposition and BCP phases without improvement in toughness [26][27][28]. An increase in toughness to 2.7 MPa.m 0.5 could be nevertheless achieved by sintering HA powders in inert atmosphere [29] or by adding fluoroapatite to retain small nanometric grains after sintering [30].…”

“…(C,D) Toughness and brittleness index as functions of the grain size in sintered CPCs. Data points extracted from [20,22,26,28,29,[38][39][40].…”

Sic Parvis Magna: Manganese-Substituted Tricalcium Phosphate and Its Biophysical Properties

“…In an earlier study, an even more drastic, fourfold increase in the fracture toughness, from 0.28 to 1.07 MPa m 1/2 , was detected upon doping the biphasic mixture of HA and β-TCP with Mn sintered down to 0.2% porosity, along with the doubling of hardness, from 2.39 to 4.78 GPa. 38 Another study demonstrated variable contents of HA and β-TCP in their sintered biphasic mixtures as a function of the Mn content in the material and an optimal value (4.3 at. %) at which the amount of β-TCP in it was maximized.…”

Structural analysis of strontium in human teeth treated with surface pre-reacted glass-ionomer filler eluate by using extended X-ray absorption fine structure analysis

“…SrHAP (composed of 2 wt% Sr in the preparation) was synthesized using the modified chemical precipitation method, as described in detail previously 27) . SrHAP was used in the XAFS analysis as the reference material.…”