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Sarvašová Kvietková, M., Dvořák, O., Kubista, K., Těhníková, K., Lin, C.-F. & Jones, D. (2025). Determination of the Critical Voltage for the Observation of Uncoated Wood Samples in Electron Microscopy. Materials, 18(2), Article ID 236.
Open this publication in new window or tab >>Determination of the Critical Voltage for the Observation of Uncoated Wood Samples in Electron Microscopy
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2025 (English)In: Materials, E-ISSN 1996-1944, Vol. 18, no 2, article id 236Article in journal (Refereed) Published
Abstract [en]

Electron microscopy (EM) is a key tool for studying the microstructure of wood; however, observing uncoated samples poses a challenge due to surface charging. This study aims to identify the critical voltage that allows for the effective observation of uncoated wood samples without significant loading. As part of the experiment, samples of different wood species were tested, including Acacia (Robinia pseudoacacia L.), Oak (Quercus robur L.), Maple (Acer pseudoplatanus spp.), Ash (Fraxinus excelsior L.), Spruce (Picea abies (L.) Karst.), Thermowood (Thermal modifed Spruce), Garapa (Apuleia leiocarpa), Ipé (Handroanthus spp.), Merbau (Intsia bijuga), and Massaranduba (Manilkara spp.). Several methods were tested for surface preparation for SEM analysis, including the use of a circular saw, a hand milling machine, and a microtome. The results show that the optimal voltage for observing uncoated wood samples varied depending on the wood species. Regarding the selection of wood species and the results obtained, it was found that uncoated samples could be effectively observed. This finding suggests that practical observations can be accelerated and more cost-effective, as all wood species exhibited the required voltage range of 1 kV to 1.6 kV. Additionally, it was determined that using a secondary electron detector was optimal for such observations, as it provided a sufficiently strong signal even at relatively low voltages. Conversely, when using a backscattered electron detector, it was more beneficial to use coated samples to achieve a sufficient signal at higher voltages. This study brings new knowledge that will facilitate further research and applications of electron microscopy in the study of other wood species or wood-based materials.

Place, publisher, year, edition, pages
MDPI, 2025
Keywords
electron microscopy (EM), SEM analysis, surface, wood, voltage, density
National Category
Wood Science
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-111241 (URN)10.3390/ma18020236 (DOI)001404432700001 ()39859708 (PubMedID)2-s2.0-85215777292 (Scopus ID)
Note

Validerad;2025;Nivå 2;2025-03-17 (u8);

Full text license: CC BY;

Funder: project IGA A_02_24 (Development and analysis of thermal insulation material based on foamed wood);

Available from: 2025-01-08 Created: 2025-01-08 Last updated: 2025-06-24Bibliographically approved
Jones, D. (2025). Editorial. International Wood Products Journal
Open this publication in new window or tab >>Editorial
2025 (English)In: International Wood Products Journal, ISSN 2042-6445, E-ISSN 2042-6453Article in journal, Editorial material (Other academic) Epub ahead of print
Place, publisher, year, edition, pages
Sage Publications, 2025
National Category
Wood Science
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-112696 (URN)10.1177/20426445251339295 (DOI)001483418200001 ()2-s2.0-105007647425 (Scopus ID)
Available from: 2025-05-19 Created: 2025-05-19 Last updated: 2025-06-24
Kim, I., Ross, L., Alfredsen, G., Karlsson, O., Kaynak, E., Das, O., . . . Sandberg, D. (2025). Enhancement of Biological Durability and Fire Safety in Wood Modified with Maleic Anhydride and Sodium Hypophosphite. Forests, 16(3), Article ID 526.
Open this publication in new window or tab >>Enhancement of Biological Durability and Fire Safety in Wood Modified with Maleic Anhydride and Sodium Hypophosphite
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2025 (English)In: Forests, E-ISSN 1999-4907, Vol. 16, no 3, article id 526Article in journal (Refereed) Published
Abstract [en]

Scots pine (Pinus sylvestris L.) sapwood was modified using maleic anhydride (MA) and sodium hypophosphite (SHP) to improve its durability against wood-deteriorating fungi, mechanical strength, and fire retardancy (thermal stability). The modification significantly reduced mass loss caused by wood-decaying fungi (Trametes versicolor, Rhodonia placenta, and soft rot fungi) due to the formation of cross-links between wood, MA, and SHP, which limited the moisture uptake and altered the chemical structure of wood. On the other hand, the modification did not provide improved resistance to fungi growth on the wood surface, which indicated that the modification had little impact on the accessibility of nutrients on the surface. A bending test showed that the modulus of elasticity (MOE) was not affected by the treatment, whilst the modulus of rupture (MOR) decreased to half the value of untreated wood. Thermal resistance was improved, as demonstrated by micro-scale combustion calorimeter testing, where the total heat release was halved, and the residue percentage nearly doubled. These results indicate that phosphonate protects the modified wood via the formation of a protective char layer on the surface and the formation of radical moieties. Based on the results, wood modified with MA and SHP shows potential for possible use in outdoor, non-loadbearing structures.

Place, publisher, year, edition, pages
MDPI AG, 2025
Keywords
Scots pine, thermal stability, timber modification, wood-impregnation treatment
National Category
Wood Science
Research subject
Wood Science and Engineering; Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-112064 (URN)10.3390/f16030526 (DOI)001452286700001 ()2-s2.0-105001095762 (Scopus ID)
Note

Validerad;2025;Nivå 2;2025-04-09 (u2);

Funder: The Swedish Research Council for the Environment, Agricultural Sciences, and Spatial Planning (FORMAS), (2021-00818);

Full text: CC BY license;

Available from: 2025-03-19 Created: 2025-03-19 Last updated: 2025-06-24Bibliographically approved
Kopač, L., Scharf, A., Lin, C.-F., Sandberg, D., Medved, S. & Jones, D. (2025). Investigation into a bio-based adhesive in combination with fire retardants for particleboard manufacture. Wood Material Science & Engineering, 20(1), 236-238
Open this publication in new window or tab >>Investigation into a bio-based adhesive in combination with fire retardants for particleboard manufacture
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2025 (English)In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 20, no 1, p. 236-238Article in journal (Refereed) Published
Abstract [en]

The sawmill industry generates substantial waste in the form of wood chips, shavings, and sawdust, which can be repurposed to manufacture particleboards. Conventional particleboards rely on formaldehyde-based adhesives, posing health risks due to formaldehyde emissions. Seeking alternatives, this study explored a bio-based adhesive system composed of citric acid and sorbitol (10 wt%) combined with 0–20 wt% fire retardants (imidazolium-based ionic liquid or ammonium dihydrogen phosphate) for particleboards made from residual sawmill processing. The objective was to assess the efficacy of the adhesive system in enhancing fire retardancy, moisture resistance, and mechanical properties of particleboards. Results indicate that incorporating ammonium dihydrogen phosphate significantly improves fire retardancy, evidenced by limiting oxygen index values of 50–78% and a thickness swelling after water immersion of 9.7%. However, with an internal bonding strength of max 0.24 MPa and modulus of rupture of max 4.3 MPa, the bio-based boards fell short of meeting standard requirements. Future research should focus on optimising the general citric acid and sorbitol-based adhesive formulations to overcome this limitation. Achieving sustainability and safety standards in particleboard production remains a critical objective for future research and industry implementation.

Place, publisher, year, edition, pages
Taylor & Francis, 2025
Keywords
Ammonium dihydrogen phosphate, citric acid, limited oxygen index, wood composite
National Category
Wood Science
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-110705 (URN)10.1080/17480272.2024.2421931 (DOI)001348376000001 ()2-s2.0-85209208681 (Scopus ID)
Note

Validerad;2025;Nivå 2;2025-02-12 (u2);

Full text license: CC BY 4.0; 

Funder: VINNOVA (2022-00998); Formas (2022-00998); Energimyndigheten (2022-00998);

Available from: 2024-11-12 Created: 2024-11-12 Last updated: 2025-02-12Bibliographically approved
Kim, I., Antzutkin, O., Shah, F. U., Karlsson, O., Jones, D. & Sandberg, D. (2024). Chemical Bonds Formed in Solid Wood by Reaction with Maleic Anhydride and Sodium Hypophosphite. Materials, 17, Article ID 4856.
Open this publication in new window or tab >>Chemical Bonds Formed in Solid Wood by Reaction with Maleic Anhydride and Sodium Hypophosphite
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2024 (English)In: Materials, E-ISSN 1996-1944, Vol. 17, article id 4856Article in journal (Refereed) Published
Abstract [en]

The reaction of wood with maleic anhydride (MA) and sodium hypophosphite (SHP) has been identified as a viable modification method, with macroscopical properties indicating formation of cross-linking to explain the results. However, the chemical reaction between wood and the modification reagents has not been studied yet. To resolve this, the reaction was studied with solid-state 13C cross-polarization magic-angle-spinning (CP-MAS) and 31P MAS nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS) to reveal the formation of bonds between wood components, MA and SHP during the treatments to explain the formation of cross-linking and the possible fixation of phosphorus in wood. XPS, solid state 13C and 31P MAS NMR revealed the maleation of wood in the absence of SHP, whilst its presence led to forming a succinic adduct observed through the C-P bond formation, as evidenced by the loss of the maleate C=C bonds at around 130 ppm and the upfield shift of the peak at 165–175 ppm, which was also significantly smoothed, as well as the increase in a peak at 26 ppm due to the reaction between the maleate group and SHP; however, the C-P-C bond could not be unambiguously rationalized from the obtained data. On the other hand, a resonance line at 16 ppm in 31P MAS NMR and the peaks in the XPS P 2p spectrum suggested the formation of a cross-linked structure at low concentrations of SHP, which was more likely to be phosphonate (C-P-O) than organophosphinic acid (C-P-C). The results herein provide a greater fundamental understanding of the mechanisms involved in the reaction of wood, MA and SHP, providing further scope for improved treatment systems in the future.

Place, publisher, year, edition, pages
MDPI, 2024
Keywords
wood modification, maleic anhydride, sodium hypophosphite, 13C and 31P MAS NMR, XPS
National Category
Physical Chemistry Wood Science
Research subject
Wood Science and Engineering; Chemistry of Interfaces
Identifiers
urn:nbn:se:ltu:diva-110224 (URN)10.3390/ma17194856 (DOI)001334126600001 ()39410427 (PubMedID)2-s2.0-85206474296 (Scopus ID)
Funder
Swedish Research Council Formas, 2021-00818
Note

Validerad;2024;Nivå 2;2024-10-03 (sarsun);

Full text license: CC BY 4.0; 

Available from: 2024-10-02 Created: 2024-10-02 Last updated: 2025-03-26Bibliographically approved
Jones, D. (2024). Editorial. International Wood Products Journal, 15(2-4), 77-77
Open this publication in new window or tab >>Editorial
2024 (English)In: International Wood Products Journal, ISSN 2042-6445, E-ISSN 2042-6453, Vol. 15, no 2-4, p. 77-77Article in journal (Other academic) Published
Place, publisher, year, edition, pages
Sage Publications, 2024
National Category
Wood Science
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-110836 (URN)10.1177/20426445241290302 (DOI)001465434700001 ()2-s2.0-85210451285 (Scopus ID)
Note

Godkänd;2024;Nivå 0;2024-11-27 (joosat);

Available from: 2024-11-27 Created: 2024-11-27 Last updated: 2025-06-24Bibliographically approved
Scharf, A., Švajger, Č., Lin, C.-F., Humar, M., Sandberg, D. & Jones, D. (2024). Effect of fire-retardant treatment of wood prior to thermo-mechanical densification. Wood Material Science & Engineering, 19(3), 790-793
Open this publication in new window or tab >>Effect of fire-retardant treatment of wood prior to thermo-mechanical densification
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2024 (English)In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 19, no 3, p. 790-793Article in journal (Refereed) Published
Abstract [en]

Wood densification itself does not, in general, improve the fire-retardant properties sufficiently to reach the standard requirements. The object of this study was to enhance the fire-retardant properties of thermo-mechanically densified wood without any loss of moisture stability and hardness. Scots pine sapwood was pretreated before densification by impregnation with a fire retardant (FR) consisting of ammonium dihydrogen phosphate and urea and then cured in-situ by hot pressing at 150 °C or 210 °C. Densified specimens without FR were used as a control. Set-recovery, fire retardancy in an open flame test, and Brinell hardness were determined. The set-recovery was slightly reduced as a result of the FR treatment, but the pressing temperature and time had a much greater influence. In the open flame test, specimens without FR-treated ignited within 15-50s of exposure to the flame, whereas all the FR-treated specimens exhibited ignition resistance over the 10 minutes duration of the test. Water-soaking cycles had no impact on the ignition resistance in these groups, indicating a strong resistance to water leaching of FR after pressing at 210 °C for 60 minutes. The hardness increased due to the presence of FR after pressing at 210 °C, but sharply decreased after water immersion.

Place, publisher, year, edition, pages
Taylor & Francis, 2024
Keywords
Wood compression, open flame, urea, ammonium dihydrogen phosphate
National Category
Wood Science
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-104919 (URN)10.1080/17480272.2024.2329734 (DOI)001194237700001 ()2-s2.0-85189563856 (Scopus ID)
Note

Validerad;2024;Nivå 2;2024-11-13 (sarsun);

Full text license: CC BY-NC-ND;

Available from: 2024-03-28 Created: 2024-03-28 Last updated: 2024-11-13Bibliographically approved
Klaas, P., Emmerich, L., Militz, H. & Jones, D. (2024). Effects of a Combined Elevated-Pressure Hybrid Wood-Modification System Demonstrating Synergistic Effects on Durability Performance. Macromol, 4(3), 634-649
Open this publication in new window or tab >>Effects of a Combined Elevated-Pressure Hybrid Wood-Modification System Demonstrating Synergistic Effects on Durability Performance
2024 (English)In: Macromol, E-ISSN 2673-6209, Vol. 4, no 3, p. 634-649Article in journal (Refereed) Published
Abstract [en]

The combination of different wood-modification technologies to obtain improved performance is increasingly receiving attention in research. In this study, Scots pine (Pinus sylvestris) sapwood was impregnated with furfuryl alcohol (FFA) in pure aqueous 20, 40, and 60% solution strength without adding any catalyst. In a second step, the FFA was polymerized while simultaneously performing thermal modification in a closed system at 130, 150, or 180 °C. After leaching and ageing tests, the nine different combinations were tested in use class 4 applications (in contact with or very close to the ground and frequently wet) according to CEN/TS 15083-2 (2005) decay laboratory test. It was noted that even the minimum-intensity combination of 20% FFA at 130 °C resulted in maximum durability class (DC) 1 performance. On the contrary, DC 4 was assigned to thermally modified control samples, even at the maximum intensity of thermal modification. Similarly, for FFA modifications, previous research has suggested that an uptake of 35% solution strength is required to obtain an adequate durability performance in use class 4 applications. High levels of resistance against termites were also noted by corresponding termite lab tests. Moisture studies showed the combined treatments resulted in improved stability and reduced moisture uptakes. Thus, the results obtained by this study revealed synergistic performance effects, which originate from the combined thermo-chemical modification approach, and which were higher than simple accumulation of the individual performance of purely thermally or chemically modified wood. Thus, the presented findings have provided positive implications for industrial applications of thermo-chemical modification techniques and offers an array of new research opportunities.

Place, publisher, year, edition, pages
MDPI, 2024
Keywords
wood modification, hybrid system, furfuryl alcohol, synergistic effect, thermal modification
National Category
Wood Science Composite Science and Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-110217 (URN)10.3390/macromol4030038 (DOI)001323433600001 ()2-s2.0-85205071954 (Scopus ID)
Note

Validerad;2024;Nivå 1;2024-10-04 (sarsun);

Full text license: CC BY 4.0;

Available from: 2024-10-02 Created: 2024-10-02 Last updated: 2025-04-23Bibliographically approved
Jué, S., Scharf, A., Lin, C.-F., Moutou Pitti, R., Sandberg, D. & Jones, D. (2024). Enhancing wood UV stability: novel treatment strategies with citric acid and urea. Wood Material Science & Engineering, 19(4), 993-996
Open this publication in new window or tab >>Enhancing wood UV stability: novel treatment strategies with citric acid and urea
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2024 (English)In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 19, no 4, p. 993-996Article in journal (Refereed) Published
Abstract [en]

Wood, a fundamental material in construction, confronts durability and weathering challenges, notably UV-induced degradation leading to colour changes. This study investigated a novel treatment using citric acid and urea to enhance the UV stability of wood. The reaction between these compounds generates water-soluble fluorescent species and insoluble particles upon thermal treatment which may provide wood with UV protection. Specimens were treated with two different treatment methods and then exposed to 2016 h of accelerated weathering, during which colour was measured regularly. Citric acid and urea were either pressure impregnated into the wood and thermally reacted in situ during heat treatment or pre-reacted in the absence of wood with subsequent implementation into melamine formaldehyde (MF) and water-based surface coatings. The results showed that water-soluble fluorophore compounds were formed with both treatment methods. Accelerated weathering tests revealed significant colour changes over time, where specimens coated with a mixture of MF and fluorescent particles from the reaction between citric acid and urea, exhibiting the least alteration. The lowest colour change ΔE of 5.9 was observed for specimens coated with a MF-based coating containing 1 wt% of citric acid and urea thermally pre-reacted at a temperature of 180 °C, showcasing potential wood protection applications.

Place, publisher, year, edition, pages
Taylor & Francis, 2024
Keywords
Fluorescence, leaching stability, surface coating, weathering resistance, wood protection
National Category
Materials Chemistry Wood Science
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-108361 (URN)10.1080/17480272.2024.2371493 (DOI)001267654000001 ()2-s2.0-85198534451 (Scopus ID)
Funder
Luleå University of TechnologyÅForsk (Ångpanneföreningen's Foundation for Research and Development), 24-222
Note

Validerad;2024;Nivå 2;2024-08-14 (signyg);

Fulltext license: CC BY-NC-ND

Available from: 2024-07-22 Created: 2024-07-22 Last updated: 2024-08-14Bibliographically approved
John, W. & Jones, D. (2024). Evaluating the potential for re-using timber from deconstructed sea defence groynes from the Bournemouth groyne field. Annals of Marine Science, 8(1), 011-013
Open this publication in new window or tab >>Evaluating the potential for re-using timber from deconstructed sea defence groynes from the Bournemouth groyne field
2024 (English)In: Annals of Marine Science, E-ISSN 2640-2300, Vol. 8, no 1, p. 011-013Article, review/survey (Refereed) Published
Abstract [en]

Groynes have been part of the coastal appearance for centuries, helping prevent coastal erosion resulting from the littoral drift of material with prevailing sea currents. Whilst the use of rock groynes increased during the late 20th Century, the use of timber still remains the material of choice. Their performance depends upon the timber species used, and often sections are suitable for re-use. Assessment of the replacement of groyne fields in Bournemouth, United Kingdom appears to show the suitability of certain species to be re-used. Results indicated that ekki was the most suitable species for re-use, closely followed by greenheart.

Place, publisher, year, edition, pages
Peertechz Publications, 2024
National Category
Other Civil Engineering Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-110723 (URN)10.17352/ams.000044 (DOI)
Note

Godkänd;2024;Nivå 0;2024-11-15 (hanlid);

Full text license: CC BY

Available from: 2024-11-15 Created: 2024-11-15 Last updated: 2024-11-15Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-5565-6651

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