1. Quality control of thermally modified timber using dynamic vapor sorption (DVS) analysisMiha Humar, Rožle Repič, Davor Kržišnik, Boštjan Lesar, Romana Cerc Korošec, Christian Brischke, Lukas Emmerich, Gregor Rep, 2020, izvirni znanstveni članek Povzetek: 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
Ključne besede: thermal modification, quality control, dynamic vapour sorption, wood, moisture content
Objavljeno v DiRROS: 31.08.2023; Ogledov: 138; Prenosov: 77
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2. Environmentally friendly protection of European beech against fire and fungal decay using a combination of thermal modification and mineralisationRožle Repič, Andreja Pondelak, Davor Kržišnik, Miha Humar, Nataša Knez, Friderik Knez, Andrijana Sever Škapin, 2023, izvirni znanstveni članek Povzetek: The demand for construction timber is continuously increasing, due to its favourable characteristics. However, the adequate protection of wood is key to its successful use, as it is flammable and susceptible to biodegradation. Given that thermal modification enhances the durability of wood, and mineralisation with CaCO3 considerably improves its fire properties, it is worth considering the combined effects of the two methods. European beech (Fagus sylvatica) was selected to determine the effects of a) thermal modification, b) mineralisation through the in-situ formation of CaCO3, and c) a combination of the two procedures, on resistance to decay fungi, reaction to fire and the mechanical properties of the wood. Microscopic analysis and comparisons of the samples before and after exposure to fungi were also conducted. Mineralised wood generally had a slightly alkaline pH value and higher equilibrium moisture content, while thermal modification lowered the equilibrium moisture content. The present study demonstrated the combined effect of thermal modification and mineralisation: the best response to fire as well as resistance to fungi was achieved when the two treatments were combined. Results from the Brinell hardness and three-point bending tests indicate that both modification procedures can slightly impair the mechanical properties of the wood.
Ključne besede: wood, protection, durability, mechanical properties
Objavljeno v DiRROS: 12.07.2023; Ogledov: 166; Prenosov: 109
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3. Combining mineralisation and thermal modification to improve the fungal durability of selected wood speciesRožle Repič, Andreja Pondelak, Davor Kržišnik, Miha Humar, Andrijana Sever Škapin, 2022, izvirni znanstveni članek Povzetek: The development of non-biocidal and environmentally friendly systems to protect wood against biological decay has become a high priority in recent years. In the present study the impact of an innovative modification procedure, combining two environmentally friendly modification methods: thermal modification and mineralisation, using an aqueous solution of calcium acetoacetate as a precursor, on the fungal durability of wood was evaluated. European beechwood (Fagus sylvatica) and Norway sprucewood (Picea abies) were selected as model wood species. Wood samples were treated using either a single or combination of both methods and exposed to four different fungi: Gloeophyllum trabeum, Rhodonia placenta, Trametes versicolor and Pleurotus ostreatus. The effect of the different modifications on moisture content, dynamic vapour sorption, contact angle and pH value was also evaluated. Overall, the highest durability against Rhodonia placenta, Trametes versicolor and Pleurotus ostreatus was achieved through thermal modification in both wood species, while the combination of mineralisation and thermal modification has a synergistic effect against degradation by Gloeophyllum trabeum. In the case of beechwood the mass loss decreased from 41% for native to 6% for combined modified samples. We proved that the effectiveness of different treatment against fungal decay of wood were in strong dependence of their moisture content, dynamic vapour sorption, contact angle and pH values. The role of fungi on the morphology of the wood and on crystal structure of formed carbonate was investigated using SEM-EDS analysis.
Ključne besede: thermal modification, wood mineralization, fungal durability, environmentally friendly modification methods
Objavljeno v DiRROS: 20.06.2023; Ogledov: 186; Prenosov: 192
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5. Gostota lesa : metode določanja in pomen pri razvoju gozdno lesnega biogospodarstvaDomen Arnič, Miha Humar, Davor Kržišnik, Peter Prislan, Luka Krajnc, 2021, strokovni članek Ključne besede: Slovenija, gostota lesa, določanje gostote, biogospodarstvo
Objavljeno v DiRROS: 12.11.2022; Ogledov: 336; Prenosov: 84
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6. Late blight resistance conferred by Rpi-Smira2/R8 in potato genotypes in vitro depends on the genetic backgroundEva Blatnik, Marinka Horvat, Sabina Berne, Miha Humar, Peter Dolničar, Vladimir Meglič, 2022, izvirni znanstveni članek Ključne besede: potato, potato genotype, potato R8 genotypes, in vitro infection, late blight, resistant cultivars, oomicete, Sárpo Mira
Objavljeno v DiRROS: 01.09.2022; Ogledov: 339; Prenosov: 132
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7. Ocena stanja lesenega kipa japonski festival Tanake EisakujaMiha Humar, Boštjan Lesar, Davor Kržišnik, 2022, izvirni znanstveni članek Povzetek: Les na prostem je izpostavljen delovanju raznolikih dejavnikov razkroja, še posebno glivam. Nekatere lesne vrste so bolj odporne na glivni razkroj kot druge. V Kostanjevici na Krki že 60 let deluje forma viva, kjer so razstavljeni kipi, izdelani pretežno iz hrastovega lesa. Tanaka Eisaku, japonski kipar, je izdelal najstarejši kip z naslovom Japonski festival na prvi kostanjeviški Formi vivi leta 1961. Po 60 letih zunanje izpostavitve smo kip vizualno pregledali in ocenili njegovo stanje z uporabo rezistografa in vlagomera. Iz kipa smo izolirali nekaj vzorcev, jih preiskali s FTIR in XRF spektroskopijo, vzorcem določili gostoto s piknometrom GeoPyc in jih analizirali z lasersko in digitalno mikroskopijo. Na kipu je opaziti znake glivnega razkroja, izletne odprtine insektov in poškodbe zaradi delovanja ptic. Ocena razkrojenosti z rezistografom je pokazala, da je les razkrojen predvsem na čelih in v sredici. Poleg tega je na nekaj mestih močno razkrojena tudi beljava. Les je bil v zadnjih letih obdelan s površinskim premazom, po drugi strani v lesu ni bilo mogoče zaznati ostankov biocidov. V primeru, da želimo kip ohraniti zanamcem, ga je treba ustrezno konzervirati.
Ključne besede: les, hrast, glive, razkroj lesa, Forma viva, leseni kipi, Tanaka Eisaku
Objavljeno v DiRROS: 01.06.2022; Ogledov: 7840; Prenosov: 6290
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9. Znanost in znanje o gozdu, gozdarstvu in lesarstvuHojka Kraigher, Miha Humar, Maja Peteh, Primož Simončič, 2015, objavljeni znanstveni prispevek na konferenci Ključne besede: znanost, raziskovanje, gozdarstvo, lesarstvo, publiciranje, znanstveni rezultati, znanstveni učinki, evalvacije, financiranje
Objavljeno v DiRROS: 03.11.2021; Ogledov: 689; Prenosov: 229
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10. Fungal and bacterial communities in spruce wood samples exposed to outdoors environmental conditionsTijana Martinović, Marko Bajc, Nejc Thaler, Miha Humar, Hojka Kraigher, Barbara Kraigher, 2015, objavljeni povzetek znanstvenega prispevka na konferenci Ključne besede: degradacija lesa, konstrukcijski les, glive, bakterije
Objavljeno v DiRROS: 03.11.2021; Ogledov: 734; Prenosov: 233
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