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Abstract: 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.
Keywords: chemical precipitation method, fire retardancy, hydroxyapatite, HAp, leaching process, wood
Published in DiRROS: 17.04.2026; Views: 134; Downloads: 133
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Abstract: Študija se osredotoča na analizo vzrokov za prezgodnji propad lesenih daljnovodnih drogov v severovzhodni Sloveniji, kjer je bilo zabeleženih več primerov hitrega glivnega razkroja drogov, kljub načrtovani življenjski dobi 30 do 50 let. Drogovi so bili izdelani iz lesa rdečega bora in impregnirani z baker-etanolaminskim biocidnim proizvodom. Namen raziskave je bil oceniti stanje stoječih drogov in preučiti ključne vzroke za njihovo prezgodnjo degradacijo na primeru dveh podrtih drogov. Uporabljene metode vključujejo uporabo rezistografa za določanje razkrojenosti lesa po preseku, izolacija izvrtkov za določanje penetracije in retencije. Poleg tega je bila opravljena mikroskopska in hiperspektralna analiza na vzorcih lesa za natančno karakterizacijo razkroja. Rezultati so pokazali, da je bila impregnacija lesa večinoma nezadostna, kar je vodilo v razširjen razkroj, zlasti na območjih, kjer je v les prodrlo premalo biocidnega proizvoda oziroma ni bila prepojena celotna beljava borovih drogov. Pospešen propad drogov je posledica delovanja gliv rjave trohnobe. Raziskava poudarja potrebo po izboljšani impregnaciji in rednem nadzoru drogov za zagotavljanje njihove življenjske dobe in s tem povezano zanesljivostjo oskrbe z električno energijo.
Keywords: daljnovodni drogovi, impregnacija, bakrovi biocidni proizvodi, glivni razkroj, rezistograf, penetracija, retencija
Published in DiRROS: 04.07.2025; Views: 1080; Downloads: 576
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Abstract: Fungal growth and degradation of wood may be caused by damage in the surface coating. The larger the cracks, the greater in principle the possibility of moisture-induced problems. Measuring basic unknown material parameters and employing hygrothermal simulations, the suitability and the maximum acceptable vertical crack size in the surface coating for a given bottom window profile made of thermally modified (TM) spruce(wood) with that made of native spruce were compared for location Ljubljana. Validation with the field test data was the second objective of the respective research. The average calculated maximum moisture content in TM spruce is about 4% (kg/kg) lower than that of native spruce. The 3 mm wide crack in the surface coating of a window frame made of native spruce is of the highest concern, whereas a 9 mm wide crack in the coating of a TM spruce profile is still acceptable. As far as moisture content is concerned in our study the TM spruce window frames were proved to be significantly more suitable for installation than the corresponding frames made of native Norway spruce. It was shown that isopleth, VTT and biohygrothermal models for mould growth do not properly capture the comparison between both materials, mainly because they classify both in the same material class/substrate category and they do not consider the material moisture content.
Keywords: hygrothermal simulations, mould growth modelling, cracks in surface coating, thermally modified wood, wooden window frame
Published in DiRROS: 16.10.2024; Views: 1447; Downloads: 1186
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Abstract: Rudarska tradicija v Litiji, segajoča v staro železno dobo, je vključevala intenzivno uporabo lesa v rudnikih, še posebej za podporo in zaščito rovov. Rudnik Sitarjevec je bil znova odprt za turizem leta 2017, in v letu 2021 so odprli glavni rov. Les ostaja ključen material v rudnikih, čeprav so ga v preteklosti nadomeščali z drugimi materiali. Uporabljeni les je izpostavljen razkroju zaradi visoke vlažnosti in gliv, kot je bela hišna goba. Ta gliva lahko povzroči razgradnjo lesa in je pogosta v vlažnih okoljih rudnikov. Obstoj gliv je pomemben, saj lahko vplivajo na obiskovalce rudnika. Visoka relativna zračna vlažnost (96,6 %) in stalna temperatura (10,1 °C) v rudniku ustvarjata razmere, ki so ugodne za rast gliv, vendar pa relativno nizka temperatura ni omejujoč dejavnik za razgradnjo lesa. Koncentracija glivnih spor v rudniku je visoka in je razložena z razširjenostjo gliv v samem rudniku. Poleg tega smo opazili, da je v lesu veliko anorganskih onesnaževal ter veliko kristalov.
Keywords: razkroj, bela hišna goba, težke kovine, kristali, spore
Published in DiRROS: 21.06.2024; Views: 2049; Downloads: 681
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Abstract: The importance of thermal modification is increasing worldwide. Increased use of thermally modified timber (TMT) has resulted in a need for reliable quality control, comprising control of variation of the production within defined limits, allowing third-party control in the case of certification and the regulation of customer complaints and claims. Techniques are thus needed to characterise the modification of quality in terms of improved target properties of TMT during industrial production, and of TMT products that have been in service for an arbitrary time. In this study, we aimed to utilise dynamic vapor sorption (DVS) for this purpose. Norway spruce (Picea abies) and European beech (Fagus sylvatica) samples were thermally modified at different temperatures according to different heat treatment techniques: (1) the Silvapro process based on an initial vacuum; (2) an air heat treatment, whereby samples were wrapped in aluminium foil; (3) thermal modification of wood samples in the ambient atmosphere in a laboratory oven. Wood samples from closed processes were analysed for validation. TMT was characterised with respect to mass loss, colour and density. Mass loss of wood due to modification (MLTM) was correlated with factors derived from DVS analysis. The present DVS measurements suggest that the equilibrium wood moisture content (EMC95% RH), the time to reach 10% wood moisture content (t10% MC), and the elongation factor, c, derived from a logarithmic function, can serve as alternative parameters to characterise the quality of several thermal modification processes. Further studies are recommended using other wood species, different modification processes and further parameters gained from DVS measurements to understand the robustness and the predictive power of the applied technique
Keywords: thermal modification, quality control, dynamic vapour sorption, wood, moisture content
Published in DiRROS: 31.08.2023; Views: 1634; Downloads: 1062
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