20.500.12556/DiRROS-29023 In-situ hydroxyapatite mineralization in beech and pine wood effects of leaching on fire behavior This study presents the in-situ synthesis of hydroxyapatite (HAp) within the structure of beech and pine wood. The modification process utilized a two-step vacuum-pressure impregnation coupled with chemical precipitation using calcium nitrate tetrahydrate and diammonium hydrogen phosphate solutions, followed by exposure to ammonium hydroxide vapors. While the initial focus was on the overall physicochemical changes, microstructural characteristics and fire behavior of the mineralized wood, the main aim is to specifically investigate the effects of leaching. Because HAp synthesis produces water-soluble ammonium nitrate (NH4NO3) as a by-product, this research systematically addresses how the removal of this component affects the final properties of wood. HAp formation was confirmed by FTIR and X-ray diffraction, while scanning electron microscopy and microcomputed tomography revealed HAp deposits primarily in the cell lumen of both wood species. Fire behavior was evaluated using thermal analysis and the cone calorimeter. The incorporation of non-flammable HAp synthesized within the wood structure may act as a barrier and mass transfer during pyrolysis. This results to comparable or slightly enhanced key fire performance parameters when comparing leached HAp synthesized samples with leached reference samples. In contrast, the unleached HAp synthesized samples, which still contained residual NH4NO3, showed deterioration in fire growth rate (FIGRA) and heat release rate (HRR) parameters, confirming that NH4NO3 acts as an oxidant. However, this oxidative property also leads to improvements in total heat release (THR) and total smoke production (TSP) parameters compared to unleached references, representing a complex interaction when studying the fire properties of mineralized wood. chemical precipitation method fire retardancy hydroxyapatite HAp leaching process wood metoda kemijskega obarjanja odpornost na ogenj hidroksiapatit HAp mineralizacija les true false true Springer Angleški jezik Slovenski jezik © The Author(s) 2026 Neznano 2026-04-17 12:52:20 2026-04-17 12:54:04 2026-04-18 03:52:04 0000-00-00 00:00:00 2026 0 0 str. 1-14 issue 2, article no. 58 Vol. 84 Apr. 2026 0000-00-00 Zaloznikova Objavljeno NiDoloceno 0000-00-00 0000-00-00 2026-04-15 54 1436-736X 10.1007/s00107-026-02412-6 275407619 https://link.springer.com/article/10.1007/s00107-026-02412-6 1 85082b53-3a4b-11f1-9cc3-001a4af901a5 https://dirros.openscience.si/Dokument.php?lang=slv&id=43329 RAZ_Sitar_Matic_2026.pdf RAZ_Sitar_Matic_2026.pdf 1 6242382027D36F1841BA49BE2A1A974B e05679c252f7cf0d28e5efca414acba65b8257f066728f2d4f0fd1e249635879 b1238661-3a4b-11f1-9cc3-001a4af901a5 https://dirros.openscience.si/Dokument.php?lang=slv&id=43330 RAZ_Sitar_Matic_2026.docx RAZ_Sitar_Matic_2026.docx 1 EEE358664E62E1566FE570029849160A ae97d2f3a05d11157fd2985bbe4c1afa0c6374b81c40eeb229afbe683c264b97 bceb854a-3a4b-11f1-9cc3-001a4af901a5 https://dirros.openscience.si/Dokument.php?lang=slv&id=43331 Zavod za gradbeništvo Slovenije 0 0 0