## 4 Discussion
### Microstructure, Mechanical Properties, and Corrosion Behavior of the Developed Porous Composite  
The current work focused on synthesizing three different types of composite samples: a porous Mg-HA substrate (sample name: Pure Mg) without any additions; an aloe vera loaded Mg-HA substrate (sample name: Mg-HA-AV); and a PLA-coated aloe vera loaded Mg-HA substrate (sample name: Mg-HA-AV-PLA). It can be observed through the EDS results that the peaks of Mg seemed to reduce as the aloe vera solution was added and diminished further after PLA coating. This can be due to a barrier provided by the PLA layer to X-ray signals generated by the electron beams striking the surface of the sample. Moreover, the surface developed through coating was crack-free and successfully covered the entire sample. In addition, the XRD results showed a reduction in peak intensity, which could be the hindrance developed by the aloe vera solution and PLA layer to the electron beams. Although no additional phases were seen to be formed after the sintering process, the development of a CaCO\({}_{3}\) compound was observed with sharp peaks showing the crystallinity of the compound in the matrix. The presence of HA was also validated by the Raman intensity peaks of the PLA-coated sample with a corresponding PO\({}_{4}\)\({}^{-3}\) stretching vibration. Moreover, the FTIR spectra of the composite developed and its native materials highlighted the presence of C-O bonded peaks that were in agreement with that of the PLA and pure aloe vera peaks. In addition, the presence of HPO\({}_{4}\)\({}^{-2}\) depicted the successful reinforcement of HA in the matrix. The developed composites were compared with the non-porous Mg material, and it was found that the presence of a high amount of porosity reduced the mechanical strength of the composites. Nonetheless, it was higher than the effective strength of cancellous bone [72]. The pores developed were seen to be of two types: micropores and macropores with a pore diameter of 44.72 \(\upmu\)m and 26.12 \(\upmu\)m, respectively. The addition of aloe vera did not improve the strength of the substrate material; however, when a coating layer of PLA was added to the substrate, it immensely enhanced the material's compressive strength by 28% compared to the Pure Mg sample. A surprising phenomenon was also observed in this study: after the incorporation of aloe vera into the porous substrate, a sudden increase in the compressive strength of the material was encountered. This could be due to the sticky nature of the aloe vera that generated a binding factor in the material, increasing its strength relatively. The increase in strength of the composite after PLA coating could be due to resistance to the load provided by the polymeric layer to reach the substrate material, hence increasing its strength. Despite its higher strength, no change in microhardness was observed in the samples. Although there was a trifling amount of reduction in microhardness values when aloe vera and PLA were added, the values were quite similar. Impressive surface properties were induced in the samples after coating with PLA. It was observed that the surface hydrophilicity was increased with a coating that is in good agreement for osteoblast cells to attach and proliferate over the surface, as discussed in the next section. The sample without coating or aloe vera addition consists of a highly porous surface, resulting in higher surface roughness, hence more hydrophobicity. Whereas, improved hydrophilicity also resulted in enhanced surface roughness due to the smooth surface developed after coating, as depicted in the FESEM micrographs. Surface roughness is a factor that is directly proportional to hydrophobicity. As the roughness increases, the hydrophobicity increases, leading to the more spherical shape of the water droplets [73; 74; 75]. The developed results are in agreement with the above statement. To work as an effective bioimplant, the developed composite should withstand the corrosive physiological environment until the bone heals.