Hybrid sol-gel coatings for reducing wettability and storage degradation of biomass pellets

Long transport distances and extended storage of biomass pellets especially in humid environments provide a suitable setting for enhanced degradation in the form of moisture sorption, cracking and attrition. We developed an optically transparent, low-cost and environmentally friendly coating to reduce moisture sorption and storage degradation of pellets. The developed coating is a hybrid sol–gel, based on tetraethoxysilane (TEOS) and 3-glycidoxypropyl-trimethoxysilane (GPTMS) precursors. We coated two types of untreated and one type of torrefied wood pellets and stored them in a climate chamber during 1 month simulating a ship's hold, at a constant condition of 40 °C and 85% relative humidity. After 1 month of storage, the mean water contact angle increased by a factor of two compared to the uncoated ones. The lower wettability of the sol-gel coated untreated pellets compared to the non-coated torrefied pellets might provide an alternative to torrefaction.</p

Hybrid PEO/sol-gel coatings loaded with Ce for corrosion protection of AA2024-T3

Plasma electrolytic oxidation (PEO) has been targeted as an eco-friendly alternative technology to conventional chromic acid anodizing (CAA) for corrosion protection of aluminium alloys in the aircraft industry. However, conventional PEO technology implies high energy consumption. Flash-PEO coatings (≤10 μm) produced in short treatment times (≤ 5 min) constitute a feasible way to overcome this limitation. Nevertheless, the long-term corrosion resistance is compromised, thus requiring novel sealing post-treatments. The present work studies the effect of stand-alone hybrid sol-gel (HSG) and Ce-doped hybrid sol-gel (HSG–Ce) coatings as a sealing post-treatment to evaluate the long-term corrosion resistance of Flash-PEO coatings on aluminium alloy (AA) 2024-T3. The characterization of the PEO, HSG, and HSG-Ce coatings was performed by scanning electron microscopy, X-ray diffraction, water contact angle, dry adhesion tests (ISO 2409), optical profilometry and Fourier transform infrared spectroscopy. The corrosion behaviour was assessed by electrochemical impedance spectroscopy up to 21 days (3.5 wt% NaCl). Active corrosion protection was assessed by immersion tests of artificially scratched coatings. Present findings reveal that low-energy-cost Flash-PEO coatings were successfully formed on AA2024-T3 alloy. Both HSG and HSG-Ce coatings were homogeneously formed on Flash PEO coating. Regarding the corrosion resistance, HSG-Ce showed significant scratch protection during 21 days of immersion in 3.5 wt% NaCl. The results suggest that, while the release of Si and Ce from the coating provided corrosion protection, NO3−release promoted localized corrosion phenomena in the scribe. This was associated with the preferential pitting corrosion phenomena at the Cu-rich intermetallic compounds instead of forming a thick and stableNO3−-rich passive layer.</p

The Effect of Environmental Conditions on the Degradation Behavior of Biomass Pellets

Biomass pellets provide a pivotal opportunity in promising energy transition scenarios as a renewable source of energy. A large share of the current utilization of pellets is facilitated by intensive global trade operations. Considering the long distance between the production site and the end-user locations, pellets may face fluctuating storage conditions, resulting in their physical and chemical degradation. We tested the effect of different storage conditions, from freezing temperatures (−19 °C) to high temperature (40 °C) and humidity conditions (85% relative humidity), on the physicochemical properties of untreated and torrefied biomass pellets. Moreover, the effect of sudden changes in the storage conditions on pellet properties was studied by moving the pellets from the freezing to the high temperature and relative humidity conditions and vice versa. The results show that, although storage at one controlled temperature and RH may degrade the pellets, a change in the temperature and relative humidity results in higher degradation in terms of higher moisture uptake and lower mechanical strength.Transport Engineering and LogisticsLarge Scale Energy Storage(OLD) MSE-

Microstructural degradation during the storage of biomass pellets

The use of biomass pellets as a source of renewable energy has increased in recent times. However, pellet storage during transportation can compromise their properties, due to fluctuating temperature and humid environments. Here, we show that extended storage of one month at 40 °C and 85% relative humidity causes significant biomass pellet degradation. This was evidenced by higher pellet porosity, weight gain, increased inclusion body formation and creation of an internal network of cracks. We quantify the inclusion and pore growth processes at the surface and within the pellets, which has implications for subsequent thermochemical conversion. The global bioenergy transition may depend upon biomass pellets, and this study shows that storage conditions are critical in the supply chain, so to maintain their quality. Without the development of stronger policies to avoid premature degradation of biomass pellets, they may not realize their full potential as a bioenergy source.Large Scale Energy StorageTeam Arjan MolTransport Engineering and Logistic

Cleavage fracture micromechanisms in thick-section quenched and tempered S690 high-strength steels

For structural assessment and optimal design of thick-section high-strength steels in applications under harsh service conditions, it is essential to understand the cleavage fracture micromechanisms. In this study, we assess the effects of through-thickness microstructure of an 80-mm-thick quenched and tempered S690 high-strength steel, notch orientation, and crack tip constraint in cleavage nucleation and propagation via sub-sized crack tip opening displacement (CTOD) testing at −100 °C. The notch was placed parallel and perpendicular to the rolling direction, and the crack tip constraint was analysed by varying the a/W ratio: 0.5, 0.25, and 0.1. The notch orientation does not play a role, and the material is considered isotropic in-plane. Nb-rich inclusions were observed to act as the weak microstructural link in the steel, triggering fracture in specimens with the lowest CTOD values. While shallow-cracked specimens from the top section present larger critical CTOD values than deep-cracked ones due to stress relief ahead of the crack tip, the constraint does not have a significant influence in the middle due to the very detrimental microstructure in the presence of Nb-rich inclusions. Some specimens show areas of intergranular fracture due to the combined effect of C, Cr, Mn, Ni, and P segregation along with precipitation of Nb-rich inclusions clusters on the grain boundaries. Several crack deflections at high-angle grain boundaries were observed where the neighbouring sub-structure has different Bain axes.Team Vera PopovichTeam Peyman TaheriTeam Arjan MolShip Hydromechanics and StructuresTeam Jilt Sietsm

Hybrid sol-gel coatings applied on anodized AA2024-T3 for active corrosion protection

The effect of the presence of an anodic film and hybrid sol-gel coating loaded with corrosion inhibitors was evaluated as a strategy for enhanced barrier and active corrosion protection of aluminium alloy 2024-T3. In this study, AA2024-T3 specimens were anodized in a modified sulphuric-citric acid bath (SCA) as the first layer of a corrosion protective multilayer system and subsequently protected by the application of silica-based hybrid sol-gel coatings. These coatings were doped with LiNO3 and Ce(NO3)3 as corrosion inhibitors and studied in comparison with the inhibitor-free sol-gel coating in terms of morphology, composition and corrosion protection of intact and scribed specimens. The anodized AA2024-T3 with an overlaying inhibitor-free sol-gel coating showed the highest impedance modulus during long-term immersion in 0.1 mol·L−1 NaCl aqueous solution. Active corrosion protection of scribed coated specimens was studied by exposure to a 0.5 mol·L−1 NaCl solution and evaluated by surface analytical techniques. The addition of Li- and Ce-based salts into the hybrid sol-gel formulation showed active corrosion protection compared to the inhibitor-free scribed hybrid sol-gel coating. The Ce-doped sol-gel coating showed less visual corrosion and higher active corrosion protection than the Li-containing one during the long-term immersion test in 0.5 mol·L−1 NaCl. Present findings reveal that the combination of the anodic/hybrid sol-gel layers on AA2024-T3 enhances the corrosion protective properties barrier properties of both stand-alone systems and the incorporation of Li- and Ce-based inhibitors provide active corrosion.Team Arjan Mo

Scrutinizing the importance of surface chemistry versus surface roughness for aluminium / sol-gel film adhesion

The sol-gel synthesis process is a versatile method used to produce a wide diversity of materials and is being increasingly used as a surface modification method to alter porosity, wettability, catalytic activity, biocompatibility and corrosion performance of underlying substrates. Silane sol–gel films deposited on aluminium and aluminium alloys have been widely studied as chemical conversion coatings and as coupling agent between the substrate and organic layers. This study set out to investigate the effect of the surface chemical treatment prior to sol-gel application on the interfacial adhesion properties of a hybrid sol-gel film. Different surface pre-treatments, including two abrasive treatments and three chemical surface pre-treatments were used and their effect on surface chemistry and surface roughness was assessed. Surfaces were characterized by scanning electron microscopy, x-ray photoelectron spectroscopy, roughness measurements and static contact angles. Cerium nitrate loaded hybrid sol-gel films were deposited and adhesion on commercially pure aluminium was evaluated using pull-off testing. Statistical analysis revealed that, although highest adhesion values were obtained on rougher surfaces, the strongest correlation exists between the surface hydroxyl fraction and adhesion strength.Team Arjan MolTeam Yaiza Gonzalez Garci

Influence of indirectly heated steam-blown gasification process conditions on biochar physico-chemical properties

Our work provides a thorough characterization of different biochars produced by a novel 50 kWth Indirectly Heated Bubbling Fluidized Bed Steam Reformer. This study investigates the effect of temperature and gasification agent on the physico-chemical properties of biochars. We combined macro, micro and nano characterization techniques to provide a clear picture of the biochar characteristics, surface functionality and its “inert” nature toward potential applications. Our results demonstrate that indirect gasification is capable of producing carbon-rich biochars (&gt; 92%) with increased porosity (89–198 cm3.g−1), high heating value (28–31 MJ.kg−1 a.r.) and aromaticity compared to the parent biomass. All biochars have lower O/C (0.02–0.04) and H/C atomic ratios (0.09–0.19), similar to anthracite. For the range of tested gasification conditions, air/steam gasification at an equivalence ratio of 0.20 and steam-to-biomass ratio of 1.2 provides the highest biochar yield (7.3%), while maintaining syngas composition optimal. On the other hand, air gasification produces biochars with relatively high content of inorganic elements. Indirectly heated biochars are compliant with the European Biochar Certificate regarding the carbon content, O/C ratio, H/C ratio. Our biochars may provide an improvement in agricultural yield and CO2 adsorption, especially those produced under air/steam gasification conditions. Our novel indirect design not only constitutes a promising development in the field of biomass allothermal gasification but also can help improving gasification circularity through the production of high quality biochar.Large Scale Energy StorageTeam Peyman Taher

Controlling the Morphology of Barrel-Shaped Nanostructures Grown via CuZn Electro-Oxidation

Herein, we report a feasible method for forming barrel-like hybrid Cu(OH)2-ZnO structures on α-brass substrate via low-potential electro-oxidation in 1 M NaOH solution. The presented study was conducted to investigate the electrochemical behavior of CuZn in a passive range (−0.2 V–0.5 V) and its morphological changes that occur under these conditions. As found, morphology and phase composition of the grown layer strongly depend on the applied potential, and those material characteristics can be tuned by varying the operating conditions. To the best of our knowledge, the yielded morphology of barrel-like structure has not been previously observed for brass anodizing. Additionally, photoactivity under both UV and daylight irradiation-induced degradation of organic dye (methyl orange) using Cu(OH)2-ZnO composite was explored. Obtained results proved photocatalytic activity of the material that led to degradation of 43% and 36% of the compound in UV and visible light, respectively. The role of Cu(OH)2 in improving ZnO photoactivity was recognized and discussed. As implied by both the undertaken research and the literature on the subject, cupric hydroxide can act as a trap for photoexcited electrons, and thus contributes to stabilizing electron-hole recombination. This resulted in improved light-absorbing properties of the photoactive component, ZnO.Team Peyman Taher