Porous bioactive glass-based scaffolds containing CRT glass and hydroxyapatite: morphological and structural analysis (Part I).

Porous scaffolds based on bioglass 45S5 were produced with the addition of a constant amount of cathode ray tube (CRT) glass cullet and a variable content of hydroxyapatite (HAp - 1.5, 5 and 10 wt%). Porous materials were fabricated using a foaming method with water glass as a pore-forming agent, and the influence of thermal treatment parameters was analysed for four sintering variants, including a one-step sintering process (900 and 950 °C) and a two-step sintering process. The study focuses on analysis of the morphology and structure of the obtained materials, in particular pore architecture, surface porosity, phase composition, and the nature of chemical bonding. Quantitative image analysis showed median pore diameters in the range of approximately 317-640 μm, and the highest surface porosity, reaching ~ 59%, was obtained for samples sintered at 950 °C with the lowest HAp content. Increasing the HAp fraction led to a reduction in pore size and porosity, particularly at higher sintering temperatures. SEM observations confirmed a developed, partially interconnected pore network, while FTIR and XRD analyses revealed the presence of characteristic functional groups of bioglass and an amorphous-crystalline structure involving calcium silicates, sodium-calcium phosphates, and strontium-containing phases originating from CRT cullet. The presented results constitute Part I of the study and establish the process-structure relationships in porous bioactive glass scaffolds modified with CRT cullet and HAp, providing a basis for subsequent analyses of mechanical properties and biological response, which will be presented in a separate publication.