Carbonisation of biomass-derived chars and the thermal reduction of a graphene oxide sample studied using Raman spectroscopy

Chars and carbonised chars were produced from three different oxygen-rich precursors (Pinus radiata wood, Phormium tenax leaf fibres, and sucrose crystals). These non-graphitisable carbons were analysed with Raman spectroscopy in order to study the nanostructural development which occurs with increasingly severe heat treatments up to approximately 1000 °C. The thermal reduction of a graphene oxide sample was similarly studied, as this is considered to involve the development of nanometre-scale graphene-like domains within a different oxygen-rich precursor. Increasing the heat treatment temperatures used in the charring and carbonisation processes, led to significant changes in a number of parameters measured in the Raman spectra. Correlations based on these parameter changes could have future applications in evaluating various char samples and estimating the heat treatment temperatures employed during their manufacture. After production heat treatment temperatures exceeded 700 °C, the Raman spectra of the carbonised chars appeared to be largely precursor independent. The spectra of these carbonised chars were similar to the spectra obtained from thermally-reduced graphene oxides, especially when compared to a wide range of other carbonaceous materials analysed using this particular methodology. Partial reduction of a graphene oxide sample due to reasonably mild laser exposures during Raman analysis was also observed

Characterization of Microstructure and Property Evolution in Advanced Cladding and Duct: Materials Exposed to High Dose and Elevated Temperature

Designing materials for performance in high-radiation fields can be accelerated through a carefully chosen combination of advanced multiscale modeling paired with appropriate experimental validation. The studies reported in this work, the combined efforts of six universities working together as the Consortium on Cladding and Structural Materials, use that approach to focus on improving the scientific basis for the response of ferritic–martensitic steels to irradiation. A combination of modern modeling techniques with controlled experimentation has specifically focused on improving the understanding of radiation-induced segregation, precipitate formation and growth under radiation, the stability of oxide nanoclusters, and the development of dislocation networks under radiation. Experimental studies use both model and commercial alloys, irradiated with both ion beams and neutrons. Transmission electron microscopy and atom probe are combined with both first-principles and rate theory approaches to advance the understanding of ferritic–martensitic steels

Characterisation of watersoluble polysaccharides produced during prehydrolysis of pinus radiata

An aqueous prehydrolysate (or prehydrolysis liquor) was produced during a mild hot-water prehydrolysis (90 minute ramp to 175 C) of commercial radiata pine wood chips. Oligosaccharide and polysaccharide material was separated from the concentrated prehydrolysate using solvent precipitation after most of the noncarbohydrate material was removed. These polymeric carbohydrates were fractionated based on charge and molecular weight by size-exclusion chromatography (SEC). The fractions were each analysed by a number of methods including MALDI-ToF mass spectrometry, and NMR. A number of different types of carbohydrate polymer structures were found that were produced due to the partial de-polymerisation of the wood hemicelluloses during the prehydrolysis process. The O-acetylated (galacto)glucomannans were the most extensively characterised. These partially-acetylated hexose-based polymers were the main type found and accounted for approximately 54% by mass of the polymeric carbohydrates. Most appeared to contained between 5 and 79 hexose units with differing degrees of acetylation. The average mol ratio of components in these polymers was calculated to be approximately 3.7 : 1.3 : 1 : 0.2 (D-mannosyl : acetyl : D-glucosyl : D-galactosyl). They had a structure consistent with a linear backbone of β-1,4- linked D-mannopyranosyl and β-1,4-linked D-glucopyranosyl units with acetyl groups attached at C-2 and C-3 positions of some D-mannopyranosyl units. The terminal D-galactopyranosyl units were likely to be attached at 1,4,6-linked Dmannopyranosyl branch points. Of the neutral (non-anionic) polysaccharides, this type was most prevalent in the higher molecular weight fractions. Anionic pentose-based polymers with a backbone of β-1,4-linked D-xylopyranosyl units were also characterised. Identified as (arabino)glucuronoxylans, they featured uronic acid groups consistent with 4-O-methyl-α-D-glucopyranosyluronic acids attached to the C-2 position of some D-xylopyranosyl units. Smaller amounts of terminal α-L-arabinofuranosyl units likely to be attached at β-1,3,4- linked D-xylopyranosyl branch points were also detected. These polymers appeared to mostly contain between 5 and 40 pentose units with between 1 and 4 uronic acid groups attached. The anionic fractions (approximately 30% by mass) also contained large amounts of D-galactopyranosyl and L-arabinosyl units along with some D-glucuronic and D-galacturonic acid residues. This suggested the presence of carbohydrates produced from the partial hydrolysis of arabinogalactans and pectins. The smaller molecular weight fractions of non-anionic polysaccharides were enriched in both 1,4-linked D-galactopyranosyl units and non-acetylated hexosebased polymers that contained between 5 and 30 hexose units; this suggested that significant amounts 1,4-galactan derived carbohydrates were present. Small amounts of oligomers containing only pentose units were detected in these smaller molecular weight fractions along with what appeared to be other uncharged fragments of the polysaccharide-types that were present in the anionic fractions

Studying carbonisation with raman spectroscopy

Raman spectroscopy can provide fast and non-destructive analysis of carbonaceous materials. As it is able to detect nanometre-sized structural features, Raman spectroscopy is widely used in the study of carbon nanotubes, fullerenes, graphenes, and many other carbon-rich materials. Raman analysis has previously shown potential for estimating the heat treatment temperatures (HTT) employed in the preparation of Japanese cedar charcoals which suggested future usefulness in quality control . In the current work, Raman spectroscopy was used to investigate the nanostructural development which had occurred within various chars prepared and carbonised at a range of heat treatment temperatures between ≈ 340°C and 1000°C. Chars were produced from sucrose sugar as standard precursor of high purity and two sources of biomass common in New Zealand (Radiata pine wood and Harakeke leaf fibres). In chars produced at lower HTTs, signals could be detected which were interpreted as representing hydrogen-rich amorphous carbon structures. In contrast, the Raman spectra of well-carbonised chars produced at higher HTTs featured signals consistent with graphene-like structures with coherent domains limited in size to below a few nanometres across. Measurement of such signals provides the ability to evaluate the extent of nanostructural development, identify char samples which are ‘undercooked’ when compared to other char samples, and estimate effective HTTs used in the production of a given char sample. More detailed Raman analysis of Radiata-derived chars was carried out, including analysis of chars produced from carbonising pyrolysis tars. Results of Raman analysis were correlated to H/C atom ratios obtained through elemental analysis for these chars produced from Radiata pine

Correlation Between the Microstructure and Mechanical Properties of Irradiated Fe-9Cr ODS

The growing global demand for energy will increasingly call upon fusion reactors and Generation IV nuclear fission reactors to supply safe and reliable energy worldwide. Ferritic/martensitic (F/M) alloys are leading candidates for structural components in these reactors because of their high strength, dimensional stability, and low activation. In novel reactor concepts, these materials will be subject to extreme operating conditions, accumulating doses of irradiation up to a few hundred displacements per atom (dpa) at temperatures as high as 600°C. Oxide dispersion strengthened (ODS) F/M alloys containing a dispersion of Y-Ti-0 nanoclusters have been developed to operate at even higher temperatures

A Systematic Study of Radiation-Induced Segregation in Ferritic–Martensitic Alloys

A systematic approach to measuring radiation-induced segregation (RIS) was used on four ferritic–martensitic (F–M) alloys: T91, HCM12A, HT9, and a Fe–9Cr model alloy, irradiated with 2.0 MeV protons over a range of doses (1–10 dpa) and temperatures (300–700°C). The experimental conditions are established so as to isolate the dependence of RIS on the experimental parameters: temperature, dose and bulk composition. RIS is measured at prior austenite grain boundaries (PAGBs) using the STEM/EDX technique. Chromium is found to enrich at PAGBs in all conditions with the exception being T91 irradiated to 3 dpa at 700°C. The magnitude of enrichment is small (\u3c2 at%). Minor elements Si, Ni, and Cu also enrich consistently. A bell-shaped temperature dependence of RIS is observed in all elements. The amount of Cr enrichment decreases as a function of increasing bulk Cr concentration. Lastly, it is found that the 9Cr model alloy reaches a steady-state Cr RIS behavior at approximately 7 dpa, while the T91 reaches what may be a steady state near 3 dpa, then the amount of enrichment decreases at 10 dpa

Irradiation-induced NanoCluster Evolution

Oxide dispersion strengthened steel (ODS) and commercial ferritic-martensitic (F-M) alloys are widely accepted candidate structural materials for designing advanced nuclear reactors. Nanoclusters embedded in the steel matrix are key microstructural features of both alloy types. Irradiation from nuclear fusion and fission affects the morphology of these nanoparticles, altering the performance of the alloys and potentially decreasing their usable lifetime. Thus, it is important to understand the effect of irradiation on these nanoparticles in order to predict long-term nuclear reactor performance. It was found that the evolution of nanoclusters in each material is different depending on the experimental irradiation parameters. The Nelson-Hudson-Mazey (NHM) model has been refined based on previous experimental work, and has been shown to be an effective model to simulate irradiation-induced nanocluster evolution in ODS and F-M steels. In this work, an NHM simulation tool was developed for nanoHUB, with a simplified user interface that enables rapid prediction of the effect of irradiation on the size of nanoclusters in a variety of Fe-based steels

Hiding, Hunting, and Habitat: An Environmental Re-Analysis of the Slave Narratives

This thesis conducts an environmental analysis of narratives written or dictated by fugitive American slaves in the early to mid-nineteenth century. It re-examines previously studied information from a different perspective—one that incorporates people’s interaction with their surrounding natural environments, both cultivated and uncultivated—which reveals new information and leads to some new potential conclusions. Specifically, this reanalysis of the slave narratives shows that the rural enslaved population of the antebellum South had an intimate and cooperative relationship with the natural world, one that enabled them to develop critical skills that maximized their chances of successfully escaping slavery permanently. Further, the southern plantation owners had increasingly removed themselves from the land and had a much more remote relationship with the natural world, a factor that made it more difficult for them to control their slave labor and to find fugitives once they had escaped. This analysis, based on the primary source slave narratives and on information previously compiled and analyzed by slavery and environmental historians, shows that such factors as the structure of the southern plantation, the strictures of the institution of slavery itself, and the day-to-day lifestyles of the rural enslaved people, combined to provide slaves with the opportunity to develop skills that would help them successfully escape. Consequently, in addition to clearly revealing how rural field slaves were able to survive in the uncultivated environment after leaving a plantation or farm, this analysis also leads to a reasonable conclusion that more slaves may have escaped slavery and the South prior to the Civil War than is currently generally accepted by historians