title: The effects of alkaline digestion, bleaching and ultrasonication treatment of fibre on 3D printed harakeke fibre reinforced polylactic acid composites

authors: Beg, Mohammad Dalour Hossen

subjects: Biocomposites

abstract: This paper documents an investigation of the effects of fibre treatment on New Zealand flax (harakeke) fibre reinforced polylactic acid (PLA) composites. The raw fibre was alkali digested, followed by bleaching and then modified with ultrasonication. Alkali treatment removed lignin and other non-cellulosic components and partially separated fibre bundles while bleaching further removed lignin and improved the separation of elementary fibres, resulting in microfibres with a cellulose content 92 wt%. With subsequent ultrasonication, microfibrils could be seen partially separated (defibrillation) at fibre surfaces. Treated fibres were compounded with PLA at a fibre loading of 30 wt% and extruded into composite filaments. Filaments from alkali, bleached and ultrasonication-treated fibres had smooth surfaces, which translated into high-quality printability along with good mechanical performance. The combination of chemically treated microfibres with selective surface defibrillation using ultrasonication and fibre alignment induced by the printing process resulted in 3D printed samples with a tensile strength of 79 MPa and Young’s modulus of 8.7 GPa, which are the highest values reported so far for 3D printed PLA-based composites reinforced with short fibres.

text: The effects of alkaline digestion, bleaching and ultrasonication treatment of fibre on 3D printed harakeke fibre reinforced polylactic acid composites This paper documents an investigation of the effects of fibre treatment on New Zealand flax (harakeke) fibre reinforced polylactic acid (PLA) composites. The raw fibre was alkali digested, followed by bleaching and then modified with ultrasonication. Alkali treatment removed lignin and other non-cellulosic components and partially separated fibre bundles while bleaching further removed lignin and improved the separation of elementary fibres, resulting in microfibres with a cellulose content 92 wt%. With subsequent ultrasonication, microfibrils could be seen partially separated (defibrillation) at fibre surfaces. Treated fibres were compounded with PLA at a fibre loading of 30 wt% and extruded into composite filaments. Filaments from alkali, bleached and ultrasonication-treated fibres had smooth surfaces, which translated into high-quality printability along with good mechanical performance. The combination of chemically treated microfibres with selective surface defibrillation using ultrasonication and fibre alignment induced by the printing process resulted in 3D printed samples with a tensile strength of 79 MPa and Young’s modulus of 8.7 GPa, which are the highest values reported so far for 3D printed PLA-based composites reinforced with short fibres.

year: 2023-03

title: Geological imprint of methane seepage on the seabed and biota of the convergent Hikurangi Margin, New Zealand: Box core and grab carbonate results

authors: Campbell, Kathleen A.

subjects: Hikurangi Margin

abstract: Short box cores (to 30 cm bsf) and seafloor carbonate grab samples were acquired at mapped hydrocarbon seep sites (600–1200 m water depths) during the 2007 RV SONNE SO191 cruise on the Hikurangi Margin offshore eastern North Island, New Zealand, to evaluate the influence of methane seepage on sedimentologic, biotic, mineralogic and stable isotopic attributes of seabed sediments. Sedimentary horizons in the box cores consist of siliciclastic silts and sands, shell beds and nodular, microcrystalline aragonite bands up to 15 cm thick. The megafauna is dominated by infaunal to semi-infaunal chemosymbiotic bivalves (Calyptogena, Lucinoma, and Acharax), as well as associated worms and carnivorous and grazing gastropods. Burrows in silts, some occupied by worms or juvenile Acharax, mainly have simple morphologies more typical of high-energy, nearshore settings than deep-sea environments, while a few are large and sparsely branched with wall scratch marks inferred to be of decapod crustacean origin.
The box core silts and nodular carbonate samples vary in TOC content from 0.2 to 0.9 wt.%, carbonate content from 4 to 78%, and δ13C and δ18O values from − 50.3 to − 0.6‰ PDB and + 0.77 to + 3.2‰ PDB, respectively. Low carbonate content silt samples have the most enriched δ13C values, implying a seawater source for their pore water bicarbonate. Negative δ13C and positive δ18O values typify the nodular, microcrystalline aragonite bands, indicating formation during microbially mediated, sulphate-dependent anaerobic oxidation of methane (AOM) in a cold, near-seafloor environment, as is also supported by lipid biomarker data. A clear isotopic mixing trend of decreasing δ13C and increasing δ18O and carbonate content in the fine (< 100 µm) carbonate fraction of the host silts also has been reported from other methane seep provinces, and suggests a heterogeneous influx of methane-rich seep fluids through the shallow seabed, displacing pore waters of seawater origin.
Seafloor grab carbonate samples show greater textural variability and are divided into two types. Fresh-appearing, grey to white blocks yield similar mineralogic, isotopic and biomarker signatures to the nodular carbonate bands in the cores. A largely seep-related epifauna affiliated with these grab samples include chemosymbiotic bathymodiolin mussels, siboglinid tube worms, methanotrophic suberitid sponges and grazing limpets which, in places, are entombed within the carbonate. By contrast, some dark reddish to brown, iron-stained, microcrystalline dolomitic slabs and tubular concretions support abundant non-seep epifaunal encrusters from the surrounding deep sea, indicative of long exposure on the seafloor. Distinct stable isotopic signatures of these exhumed dolostones (δ13C c. − 20‰ PDB, δ18O up to + 7‰ PDB) suggest derivation from an oxidised methane pool, and pore fluid freshening by gas hydrate dissociation or from mobilized burial fluids that have undergone clay mineral dehydration.

text: Geological imprint of methane seepage on the seabed and biota of the convergent Hikurangi Margin, New Zealand: Box core and grab carbonate results Short box cores (to 30 cm bsf) and seafloor carbonate grab samples were acquired at mapped hydrocarbon seep sites (600–1200 m water depths) during the 2007 RV SONNE SO191 cruise on the Hikurangi Margin offshore eastern North Island, New Zealand, to evaluate the influence of methane seepage on sedimentologic, biotic, mineralogic and stable isotopic attributes of seabed sediments. Sedimentary horizons in the box cores consist of siliciclastic silts and sands, shell beds and nodular, microcrystalline aragonite bands up to 15 cm thick. The megafauna is dominated by infaunal to semi-infaunal chemosymbiotic bivalves (Calyptogena, Lucinoma, and Acharax), as well as associated worms and carnivorous and grazing gastropods. Burrows in silts, some occupied by worms or juvenile Acharax, mainly have simple morphologies more typical of high-energy, nearshore settings than deep-sea environments, while a few are large and sparsely branched with wall scratch marks inferred to be of decapod crustacean origin.
The box core silts and nodular carbonate samples vary in TOC content from 0.2 to 0.9 wt.%, carbonate content from 4 to 78%, and δ13C and δ18O values from − 50.3 to − 0.6‰ PDB and + 0.77 to + 3.2‰ PDB, respectively. Low carbonate content silt samples have the most enriched δ13C values, implying a seawater source for their pore water bicarbonate. Negative δ13C and positive δ18O values typify the nodular, microcrystalline aragonite bands, indicating formation during microbially mediated, sulphate-dependent anaerobic oxidation of methane (AOM) in a cold, near-seafloor environment, as is also supported by lipid biomarker data. A clear isotopic mixing trend of decreasing δ13C and increasing δ18O and carbonate content in the fine (< 100 µm) carbonate fraction of the host silts also has been reported from other methane seep provinces, and suggests a heterogeneous influx of methane-rich seep fluids through the shallow seabed, displacing pore waters of seawater origin.
Seafloor grab carbonate samples show greater textural variability and are divided into two types. Fresh-appearing, grey to white blocks yield similar mineralogic, isotopic and biomarker signatures to the nodular carbonate bands in the cores. A largely seep-related epifauna affiliated with these grab samples include chemosymbiotic bathymodiolin mussels, siboglinid tube worms, methanotrophic suberitid sponges and grazing limpets which, in places, are entombed within the carbonate. By contrast, some dark reddish to brown, iron-stained, microcrystalline dolomitic slabs and tubular concretions support abundant non-seep epifaunal encrusters from the surrounding deep sea, indicative of long exposure on the seafloor. Distinct stable isotopic signatures of these exhumed dolostones (δ13C c. − 20‰ PDB, δ18O up to + 7‰ PDB) suggest derivation from an oxidised methane pool, and pore fluid freshening by gas hydrate dissociation or from mobilized burial fluids that have undergone clay mineral dehydration.

year: 2010

title: Hei Āwhina Mātua: A kaupapa Māori response to behaviour

authors: Berryman, Mere

abstract: Hei Āwhina Mātua (strengthening parents and other adults), a kaupapa Māori research and development project, sought to capitalise on the strengths available within both whānau and teachers so that both groups could take joint responsibility for students' learning and behaviour. This required professionals trained in delivering learning and behavioural programmes for individual students working in culturally responsive and collaborative ways with adults, whānau, teachers and community members, This chapter returns to this study to reconsider the key findings.

text: Hei Āwhina Mātua: A kaupapa Māori response to behaviour Hei Āwhina Mātua (strengthening parents and other adults), a kaupapa Māori research and development project, sought to capitalise on the strengths available within both whānau and teachers so that both groups could take joint responsibility for students' learning and behaviour. This required professionals trained in delivering learning and behavioural programmes for individual students working in culturally responsive and collaborative ways with adults, whānau, teachers and community members, This chapter returns to this study to reconsider the key findings.

year: 2015