Fabrication of Multidimensional Sustainable Materials from Wood via Alkaline Periodate Oxidation
Doctoral thesis
Date of Examination:2024-01-11
Date of issue:2024-01-22
Advisor:Prof. Dr. Kai Zhang
Referee:Prof. Dr. Kai Zhang
Referee:Prof. Dr. Carsten Mai
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Abstract
English
Producing multidimensional sustainable materials from wood using alkaline periodate oxidation (APO) is a promising path toward new materials that take advantage of the inherent properties of wood and the environmentally friendly characteristics of the oxidation process. The present work investigates and uses innovative methods to synthesize materials ranging from one-dimensional nanocellulose to three-dimensional ordered microporous honeycomb structures. The primary focus was directed toward one-dimensional (1D) materials, specifically periodate oxidized cellulose nanofibers (PO-CNFs) and cellulose nanocrystals (PO-CNCs), synthesized from native Spruce and Beech woods utilizing the APO technique. The resultant nanocellulose content derived from Spruce and Beech exhibited a noticeable upward trend in reaction time, reaching 1.35 ± 0.20 and 1.24 ± 0.10 mmol g -1 after a 7-day oxidation period. Both PO-CNFs and PO-CNCs produced transparent films with excellent mechanical properties. The investigation systematically delved into the surface characteristics of these nanocellulose-based materials, which provided comprehensive insight into the details of the APO process. Expanding into the two-dimensional (2D) realm, an ion-selective wood membrane (ISWM) was developed through APO, demonstrating efficient osmotic energy capture. The aligned nanofibers and nanopores of the membrane enabled selective ion transportation, yielding an impressive power density under a salinity gradient of KCl. The research investigated the synthesis process and explored practical applications, emphasizing osmotic energy capture. The investigations were directed towards three-dimensional (3D) structures, emphasizing the fabrication of sustainable porous scaffolds derived from wood biomass.These scaffolds are made from alkaline periodate-oxidized wood (POW) as the fundamental substrate and preserved lignin as an additive for light absorption. The inherent porosity of the POW framework imparted good dimensional stability and effectively mitigated potential liquid leakage, typical of phase change materials (PCMs). Furthermore, the structural composition resulted in remarkable properties for photothermal energy conversion. Notably, the POW/PCM composites exhibited a noteworthy capacity for sustaining a consistent indoor temperature when strategically positioned on the roof of a model house. This distinctive attribute underscored the considerable potential of these composites for practical applications in the thermal regulation of intelligent buildings. The method proved to be economical and environmentally friendly, aligning with the principles of sustainable materials preparation. This thesis is a cumulative work comprising three publications that contribute significantly to understanding wood-based materials synthesis through APO, offering novel insights and ways for future research in sustainable materials fabrication. All papers were submitted to peer-reviewed journals; two have already been published, and one is under review. Sections 1- 4 present the background, the study's objective, results, discussion of the three publications, and conclusion.
Keywords: Alkaline Periodate Oxidation; Wood; nano cellulose; thermal energy; photothermal conversion; salt differential energy