First-principles study of illite-smectite and implications for clay mineral systems

Illite-smectite interstratified clay minerals are ubiquitous in sedimentary basins and they have been linked to the maturation, migration and trapping of hydrocarbons(1), rock cementation(2), evolution of porewater chemistry during diagenesis(3) and the development of pore pressure(4). But, despite the importance of these clays, their structures are controversial. Two competing models exist, each with profoundly different consequences for the understanding of diagenetic processes: model A views such interstratified clays as a stacking of layers identical to endmember illite and smectite layers, implying discrete and independently formed units (fundamental particles)(5), whereas model B views the clays as composed of crystallites with a unique structure that maintains coherency over much greater distances, in line with local charge balance about interlayers(6). Here we use first-principles density-functional theory to explore the energetics and structures of these two models for an illite-smectite interstratified clay mineral with a ratio of 1:1 and a Reichweite parameter of 1. We find that the total energy of model B is 2.3 kJ atom(-1) mol(-1) lower than that of model A, and that this energy difference can be traced to structural distortions in model A due to local charge imbalance. The greater stability of model B requires re-evaluation of the evolution of the smectite-to-illite sequence of clay minerals, including the nature of coexisting species, stability relations, growth mechanisms and the model of fundamental particles.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62760/1/nature01155.pd

Effects of variable selection and processing of NIR and ATR-IR spectra on prediction of extractives content in Eucalyptus bosistoana heartwood

The use of quick attenuated total reflectance infrared (ATR-IR) spectroscopy and near infrared (NIR) spectroscopy to predict extractives content (EC) in heartwood of E. bosistoana with partial least squares regression (PLSR) models was studied. Different spectra pre-processing methods and variable selection were tested for calibration optimisation. While variable selection substantially improved the NIR-PLSR models, only small effects were observed for spectra pre-processing methods and ATR-IR-PLSR models. Both of the NIR-PLSR and ATR-IR-PLSR models yielded reliably EC results with high R2 and low root mean square error (RMSE). NIR based models performed better (RMSE 0.9%) than ATR-IR based models (RMSE 1.6%). Analysis showed that the models were based on IR signals assigned to chemical structures known from eucalyptus heartwood extracts. Combined with PLSR and variable selection, both, ATR-IR and the NIR spectroscopy, can be used to quickly predict EC in E. bosistoana, a measure needed in tree breeding and the quality control of for durable timber

Properties of rotary peeled veneer and laminated veneer lumber (LVL) from New Zealand grown Eucalyptus globoidea

Background: Eucalyptus species can be alternative plantation species to Pinus radiata D.Don (radiata pine) for New Zealand. One promising high value use for eucalypts is laminated veneer lumber (LVL) due to their fast growth and high stiffness. This study investigated the suitability of Eucalyptus globoidea Blakely for veneer and LVL production. Methods: Twenty-six logs were recovered from nine 30-year-old E. globoidea trees. Growth-strain was measured using the CIRAD method for each log before they were peeled into veneers. Veneer recovery, veneer splitting and wood properties were evaluated and correlated with growth-strain. Laminated veneer lumber (LVL) panels were made from eucalypt veneers only or mixed with radiata pine veneers to investigate the bonding performance of E. globoidea. Results: Veneers with no, or limited, defects can be obtained from E. globoidea. Veneer recovery (54.5%) correlated with growth-strain and was highly variable between logs ranging from 23.6% to 74.5%. Average splitting length in a veneer sheet was 3.01 m. There was a moderate positive association between splitting length and growth-strain (r = 0. 73), but no significant association with wood stiffness (r = 0.27). Bond quality of LVL panels prepared using E. globoidea veneer and a phenol formaldehyde adhesive did not satisfy AS/NZ 2098.2. Conclusion: Usable veneers for structural products could be obtained from E. globoidea at yields of up to 74.5%, but variation in the existing resource (which has not been genetically improved) was large. In particular, growth-strain reduced veneer recovery by splitting, largely independent of stiffness. The considerable variation in growth-strain and stiffness indicated a possibility for genetic improvement. Furthermore, a technical solution to improve bonding of E. globoidea veneers needs to be developed

Bioactivity of ethanol extracts from Eucalyptus bosistoana F. Muell. heartwood

Variability in bioactivity and chemical composition of Eucalyptus bosistoana F. Muell. heartwood extracts between individual trees from two different sites were investigated. Combining the results of fungal assays and quantitative gas chromatography (GC) of the extracts allowed the investigation of bioactive compounds. The bioactivity of extracts was assessed against white rot (Trametes versicolor [L.] Lloyd) and brown rot (Coniophora cerebella Pers.). Ethanol extracts from E. bosistoana heartwood were less effective on the white rot than against the brown rot. Variability in the bioactivity of extracts against the two fungi was observed between the trees. A site effect in the bioactivity was found for the white rot but not the brown rot. Bioactivity of the extracts against the white rot was not correlated to that against the brown rot. The absence of a relationship between of effects of the extracts on the relative growth rates of the white rot and the brown rot indicated that the two fungi were affected by different compounds. Thirty two compounds were quantified in E. bosistoana ethanol extracts by GC, of which six (benzoic acid, hexadecanoic acid, 1,5-dihdroxy-12-methoxy-3,3-dimethyl-3,4-dihydro-1H-anthra[2, 3-c]pyran-6,11-dione, octadecanoic acid, polyphenol and beta-sitosterol) were identified. Significant variability in eight compounds was found between the two sites. Multivariate (PLSR) analysis identified compounds at the retention times 10.2 and 11.5 min (hexadecanoic acid) to be most related to the bioactivity of the E. bosistoana heartwood extracts against white rot and brown rot

Thickness-dependent stiffness of wood: potential mechanisms and implications

When wood is split or cut along the grain, a reduction in tensile stiffness has been observed. The averaged mechanical properties of wood samples, veneers or splinters therefore change when their thickness is less than about 1 mm. The loss of stiffness increases as the thickness approaches that of a single cell. The mechanism of the effect depends on whether the longitudinal fission plane is between or through the cells. Isolated single cells are a model for fission between cells. Each cell within bulk wood is prevented from twisting by attachment to its neighbours. Separation of adjacent cells lifts this restriction on twisting and facilitates elongation as the cellulose microfibrils reorientate towards the stretching direction. In contrast when the wood is cut or split along the centre of the cells, it appears that co-operative action by the S1, S2, and S3 cell-wall layers in resisting tensile stress may be disrupted. Since much of what is known about the nanoscale mechanism of wood deformation comes from experiments on thin samples, caution is needed in applying this knowledge to structural-sized timber. The loss of stiffness at longitudinal fracture faces may augment the remarkable capacity of wood to resist fracture by deflecting cracks into the axial plane. These observations also point to mechanisms for enhancing toughness that are unique to wood and have biomimetic potential for the design of composite materials