An experimental investigation of the fabrication of biodegradable zinc–hydroxyapatite composite material using microwave sintering

Abstract

<jats:p> The present work focuses on the fabrication of zinc–hydroxyapatite biodegradable composite with the use of pressureless microwave sintering for the orthopedic load-bearing application. The samples were prepared using the powder metallurgy process. The powders of both materials were homogeneously mixed in the quantified proportions to form the uniform mixture. For the fabrication of samples, the planning of experiments was done with the central composite design. The effect of process factors such as the weight percentage of hydroxyapatite, compaction pressure, and microwave sintering factors such as sintering temperature, heating rate, and soaking time on the compressive yield strength and sintered density was evaluated. Cylindrical samples were prepared for compression testing. The experimental results exhibited the increase in the compressive yield strength as well as the sintered density with the decrease in the hydroxyapatite percentage and an increase in the compaction pressure. The results also revealed that the compressive yield strength and sintered density were found to be increased as the heating rate and sintering temperature increased. Sample characterization was carried out for phase determination and composition of the elements. The optimum process factors were obtained after the regression analysis, and the results of the optimum process factors were also verified with the confirmation experiments. The in vitro corrosion testing of the sample prepared with optimum factors was also carried out in the simulated body fluid at a temperature of 37 ± 0.5 ℃. The fabricated sample showed a good agreement between the mechanical and degradation properties as required for a human bone. </jats:p>

Recent research and progress of biodegradable zinc alloys and composites for biomedical applications: Biomechanical and biocorrosion perspectives

“… Composition &Fabrication Corrosion medium Immersion time (day) Corrosion properties Ref. Icorr (μA/cm 2 ) Ecorr (V) C.R (elec) (mm/y) C.R (imm) (mm/y) Zn SPS HBSS 50 4.900 ± 2.810 −0.942 ± 0.075 0.073 ± 0.042 0.0048 [ 91 ] Zn-1HA SPS 50 21.076 ± 3.251 −1.281 ± 0.037 0.327 ± 0.050 0.0026 Zn-5HA SPS 50 39.127 ± 0.661 −1.274 ± 0.005 0.630 ± 0.011 0.0101 Zn-10HA SPS 50 51.044 ± 1.803 −1.290 ± 0.010 0.856 ± 0.031 0.0250 Zn HE SBF 14 – – – 0.15 [ 305 ] Zn-8HA HE 14 – – – 0.40 Zn-3HA PM – 5.164 −1.070 0.084 ± 0.012 – [ 310 ] ...…”

Evaluation of in vitro corrosion behavior of zinc–hydroxyapatite and zinc–hydroxyapatite–iron as biodegradable composites

“…Second, it resulted in the increased random microvoids with the higher weight percentage of HA in Zn matrix due to lower sintering temperature and lack in the interfacial reaction between Zn and HA. [32,33,52] These microvoids significantly activated the penetration of the corrosive fluid in the composite samples, thereby increasing the corrosion rate of the composite samples with a high wt% of HA in the Zn matrix. Furthermore, the incorporation of Fe in the Zn-HA matrix led to produce micro galvanic effects to prompt the degradation more.…”

“…In the present work, pure Zn, Zn‐3HA, Zn‐3HA‐2Fe, and Zn‐5HA‐2Fe samples were prepared with the aforesaid mentioned methodology. The weight percentage ( wt %) of HA was decided based on the authors' previous work, [ 33 ] which demonstrated the compressive yield strength (CYS) of the Zn‐HA composites decreased beyond 6 wt % of HA. In order to confirm the wt % of Fe in Zn‐HA matrix, pilot experiments were carried out with the optimized process factors mentioned above.…”

“…The fabrication methodology for the preparation of samples was described in the authors' previous work. [ 33 ] In brief methodology, after the selection of powders of Zn, HA, and Fe, respectively, the powders were resized and mechanically alloyed in a planetary ball mill under argon gas (zero grade) inert atmosphere. In the next step, the mechanically alloyed powder mixture was cold compacted using a uniaxial hydraulic compaction machine (capacity 41 MPa ) to form the cylindrical green compacts.…”

“…The optimum set of process factors utilized for the fabrication of samples was evaluated using a central composite design and Genetic Algorithm, respectively. [ 33 ] These optimum process factors were found to be 34 MPa compaction pressures; 408° C sintering temperature; 9° C / min heating rate; and 13 min holding time.…”