Effect of ulexite on thermal and mineralogical properties of mullite-zirconia composite

Effects of sintering and zirconmullite doping on nanostructural vacancies of bovine hydroxyapatite by positron techniques

“…X‐ray diffraction phase analysis (XRD) of pure zircon mullite and composite samples (12.5 wt.%) sintered at 1000, 1100, 1200 and 1300°C was performed with a Bruker d2 phaser instrument using CuKα radiation ( λ = 1.541 Å) with 30 kV, 10 A conditions, and the results are shown in Figure 2. In Figure 2, two main phases were determined: the first is mullite (PDF 74–4144) with the chemical formula Al 4.52 Si 1.48 O 9.74 with an orthorhombic crystal structure 15,16 and the second phase is badeleyite (PDF 37–1484) with the chemical formula ZrO 2 with a monoclinic crystal structure. The peaks in the graph are compatible with the literature 4,10,15,28‐30 …”

“…In Figure 2, two main phases were determined: the first is mullite (PDF 74–4144) with the chemical formula Al 4.52 Si 1.48 O 9.74 with an orthorhombic crystal structure 15,16 and the second phase is badeleyite (PDF 37–1484) with the chemical formula ZrO 2 with a monoclinic crystal structure. The peaks in the graph are compatible with the literature 4,10,15,28‐30 …”

“…The common structural defects of Ca and OH ions in HA are located along the main structural c axis so called ‘OH‐channel’. Especially OH‐OH vacancies form along the c axis, in a hexagonal supercell of 88 atoms leading to the non stochiometric HA and its derivatives in ambiant atmosphere with water vapor at low pressure following the postulated reaction 15,16 as in Figure 1: $$$$\begin{eqnarray} \text{C} {{\text{a}}_{\text{10}}} {{\left( \text{P}{{\text{O}}_{\text{4}}} \right)}_{\text{6}}} {{\left( \text{OH} \right)}_{\text{2}}}&\to & \text{ }\!\!\!\! \text{ C} {{\text{a}}_{\text{10}}} {{\left( \text{P}{{\text{O}}_{\text{4}}} \right)}_{\text{6}}} {{\left( \text{OH} \right)}_{\text{2-2x}}} {{\text{O}}_{\text{x}}} {{\left( {{\text{V}}_{\text{OH}}} \right)}_{\text{x}}}\nonumber\\ &&+ \, {x} {{\text{H}}_{\text{2}}}{{\text{O}}_{\text{gas}}} \end{eqnarray}$$$$…”