Biological apatites contain several elements as traces. In this work, magnesium and fluorine co-substituted hydroxyapatites with the general formula Ca 9 Mg(PO 4 ) 6 (OH) 2-y F y , where y = 0, 0.5, 1, 1.5 and 2 were synthesized by the hydrothermal method. After calcination at 500˚C, the samples were pressureless sintered between 950˚C and 1250˚C. The substitution of F − for OH − had a strong influence on the densification behavior and mechanical properties of the materials. Below 1200˚C, the density steeply decreased for y = 0.5 sample. XRD analysis revealed that compared to hydroxylfluorapatite containing no magnesium, the substituted hydroxyfluorapatites decomposed, and the nature of the decomposition products is tightly dependent on the fluorine content. The hardness, elastic modulus and fracture toughness of these materials were investigated by Vickers's hardness testing. The highest values were 622 ± 4 GPa, 181 ± 1 GPa and 1.85 ± 0.06 MPa·m 1/2 , respectively.
The aim of this study is to characterise the behaviour and fabric of four clayey samples before and after electrokinetic tests. The samples are formed by either kaolinite or a mixture of 70% kaolinite and 30% of carbonate. The samples are mixed with water and a lead solution and then consolidated. The electrokinetic tests show that for the samples prepared with water, a little increase in current intensity and conductivity is observed, which is due to the H+ ions diffusion into the samples. For the lead solution prepared samples, the current intensity and the conductivity decrease. The tests show that the current intensity decrease is due to cation migration. However, the carbonate presence, leading to high pH values, improves the lead precipitation with carbonate. The electroosmotic flow happens towards the cathode for all the samples, but some observed differences can be attributed to the heterogeneity of the net surface charges during the tests. X-ray diffraction analyses and specific surface area measurements show that, after the electrokinetic tests, the fabric of the samples changes as function of the presence of carbonate and lead.
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