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The role that resource extraction, particularly mining and oil palm plantation, has played in enabling a form of racism in West Papua is presented. The history of mining projects in West Papua, and how this has displaced indigenous populations, is covered. This development of mining reserves and oil palm plantations at the expense and the destruction of indigenous life is discussed. This process has relied on a dehumanisation of indigenous people, and an ignorance of their agency in determining their own needs. The effects of resource extraction, on cultural sustainability, and its supplantation with industrial colonialism is presented as a form of racism; concepts of 'industrial racism' and 'industrial colonisation' are introduced within this context. It is demonstrated that this racism has been both explicitly and implicitly supported by Western and Global South governments, highlighting the need for a voice for indigenous groups in self-determination. The more recent reparations to help achieve self-determination, even in this modern context of understanding, are shown to have a colonial approach. The view that matters have improved, through various awards for sustainability, is presented and critiqued, demonstrating the conflict between that view and that of the indigenous within a colonial power structure. [ABSTRACT FROM AUTHOR]

Densification is commonly adopted to increase the mechanical performance of wood, but research on the micromechanical behaviour of the material during transverse compression is limited. Robust numerical models will enable better predictions of the performance of wood during compression and optimise the manufacturing process of densified wood minimising experimentation. The densification stress–strain response of wood after chemical treatment is reported via numerical simulations. A 3D finite element model of wood microstructure is studied under transverse compression using ABAQUS/Explicit software. A lower cellulose, hemicellulose and lignin content in the chemically treated wood is considered in the material parameters of the cell wall, and an ideal elastoplastic material model is used to represent the nonlinear stress–strain response. Parametric studies regarding the cell wall thickness, yield stress and chemical treatment are also considered. The numerical predictions agree well with microscopy studies of densified wood, and the nominal stress–strain curve obtained is similar to experimental findings under transverse compression as found in the literature. The cell wall thickness and yield stress are found to significantly affect the compressive stress–strain response of wood. [ABSTRACT FROM AUTHOR]

History has taught us that the Global North's attempts to 'civilise' the rest of the world's population, both now and in colonial times, have been fraught with difficulty. This paper argues that this difficulty is mainly owing to the political standpoint and positioning of our perceived engineering and technical superiority. A failure to recognise this viewpoint and to change the way in which we work together—in a global sense—to solve issues such as climate change, threatens our ability to survive as a species. Political standpoints on such issues still assume a superiority of governments in the Global North. This paper retraces colonial engineering projects, mainly directed from the UK, that failed to consider the development of other populations in the world, and their needs. It is also posited that our exploitation in the Global North, which assumes historical superiority as a basic premise, will fail in tackling major issues. Change is needed through a decolonisation of engineering projects, and western engineering curricula that are used to train future professionals. Evidence of the impact of decolonisation on the engineering discipline itself is scarce, but nevertheless, a response is needed to ensure that a more inclusive curriculum and narrative is developed. [ABSTRACT FROM AUTHOR]

Polyethylene oxide (PEO) has been used to produce a porous composite with cellulose nanocrystals via solvent-free aqueous processing and freeze-drying. This material has a microporous structure and an amphipathic nature with a high affinity for oils. The porous structure is retained after carbonisation, producing conductive carbon aerogel-like material. [ABSTRACT FROM AUTHOR]

The article focuses on how cracks propagate in a cross-section of an ensis siliqua mollusk shell during an in situ three-point bending test done in an electron microscope. It mentions that most of the cracks were formed at the innerside of the shell, in which images of the cracks are taken during the deformation process. Moreover, it states that the approach of putting multiple delaminations near the surface of an engineering material is useful in improving fracture resistance.

Abstract: Microfocus X-ray diffraction can be used in a scanning acquisition mode to image a fibre reinforced composite material in terms of a range of different parameters. This includes microstructural information, as well as detail of emerging stress fields around open hole geometries. In this study, the in situ deformation of a cross-ply laminate specimen is investigated. The results show a number of interesting phenomena related to stress transfer in such systems. This includes stress concentrations in fibres adjacent to the open hole and local shear forces acting upon fibres perpendicular to the deformation axis. In addition to imaging the sample, the technique also allows a number of mechanical parameters to be estimated. This includes transverse strain and longitudinal stiffness. Using isotropic elasticity theory, the stress concentration tangential to the open hole can be determined analytically. [Copyright &y& Elsevier]

A method is presented for the measurement, using small-angle X-ray scattering (SAXS), of the microfibril angle and the associated standard deviation for the cellulose microfibrils in the S2 layer of the cell walls of softwood specimens. The length and orientation of over 1000 cell walls in the irradiated volume of the specimen are measured using quantitative image analysis. From these data are calculated the azimuthal variation of the scattered intensity. The calculated values are compared with the measured values. The undetermined parameters in the analysis are the microfibril angle (M) and the standard deviation (σΦ) of the intensity distribution arising from the wandering of the fibril orientation about the mean value. The two parameters are varied to give the best fit between the calculated and the measured values. Six separate pairs of values are determined for six different values of the angle of incidence of the X-ray beam relative to the normal to the radial direction in the specimen. The results show good agreement. The azimuthal distribution of scattered intensity for the real cell-wall structure is compared with that calculated for an assembly of rectangular cells with the same ratio of transverse to radial cell-wall lengths. Despite the existence of marked differences in the intensity distributions around the zero azimuth angle, the position of the extreme flanks of the distribution is very close for the real and the rectangular cells. This means that useful values of the microfibril angle can be obtained from the curve for the real cells using the Meylan parameter T derived by drawing tangents to the flanks of the intensity distribution and using M = kT. The value of k is M/(M + 2σ Φ). Since both of these parameters are determined in the work now described, k is also determined. It is also demonstrated that for β = 45° (where β is the angle between the plane face of the wood specimens and the radial direction) the peaks in the azimuthal intensity distribution for the real and the rectangular cells coincide. If this peak position is Φ45, then the microfibril angle can be determined from the relation M = tan-1(tanΦ45/cos45°), which is precise for rectangular cells. [ABSTRACT FROM AUTHOR]

The ecological and economic benefits of mycelium composites offer a promising opportunity for supporting sustainable development in Africa. This study focuses on assessing the environmental impact of mycelium composites for building and construction (MCBs) by conducting a life cycle assessment (LCA) in the context of Africa. It is demonstrated that the potential environmental impact of MCBs is substantially influenced by the use and source of electrical power for autoclaves, incubators, and ovens, making the culturing and post-processing phases the major environmental hotspots. The impact of MCB production is also relative to the energy mix of specific countries, being higher in countries that rely on fossil fuel energy (e.g., South Africa) and lower in those that rely more on renewable sources (e.g., Democratic Republic of the Congo, DRC). Furthermore, the impact of MCB production is found to be sensitive to travel distance, suggesting that situating production facilities closer to agricultural, agro-industrial, and/or forestry waste sources could be more beneficial than interregional sourcing, for example. It is also demonstrated that MCBs have the potential to be a more ecologically sustainable alternative to some conventional construction materials (e.g., concrete) over an entire life cycle. Based on the insights obtained from this LCA, some recommendations have been proposed to address potential environmental repercussions pre-emptively and proactively: this is particularly important for nations, mainly in the Global South, that exhibit low resilience to climate change due to limited economic resources. Furthermore, with the rapid expansion of mycelium composite technology, there is a need to increase awareness about its potential environmental impact and, ultimately, to mitigate its potential contribution to pressing environmental concerns (e.g., global warming and climate change). Consequently, this study also adds to the existing body of literature on LCA studies, delineating key factors for consideration in future LCA studies and providing guidance for the sustainable establishment and expansion of this technology. [ABSTRACT FROM AUTHOR]

The stiffness of 10 nm diameter cellulose nanowhiskers is reported. These whiskers are produced by acid hydrolysis. These whiskers are dispersed in epoxy resin and placed on the surface of a beam of the same material and deformed in tension and compression using a four-point bending device. By following the molecular deformation of the whiskers using Raman spectroscopy it is shown that, by theoretical models of their dispersion and matrix reinforcement, their stiffness can be derived. The effects of debonding, matrix yielding, and buckling of whiskers are also discussed using this method as a means for studying nanocomposite materials. [ABSTRACT FROM AUTHOR]

Bacterial cellulose (BC)/Fe3O4 aerogels were fabricated by a simple immersion of BC hydrogels in commercially available ferrofluid solution followed by freeze-drying. The BC/Fe3O4 aerogels were converted into carbon nanofiber (CNF)/Fe3O4 aerogels by pyrolysis at 600 °C. With our fabrication methods, the Fe3O4 nanoparticles (NPs) were effectively impregnated and homogeneously distributed in the nanostructures of BC and CNF. The average diameters of the BC and CNF nanofibers were found to be about 79.3 ± 14.1 nm and 56.7 ± 13.6 nm, respectively. Increasing the ferrofluid concentration resulted in a nonlinear increase of Fe3O4 NPs loaded into the BC and CNF structure, but the functional groups were not affected. The saturation magnetization (Ms) of CNF/Fe3O4 was larger than those of BC/Fe3O4 and increased with the amount of impregnated Fe3O4 NPs. The maximum magnetization in our work was larger than literature values, with the highest Ms of 82.9 emu/g approaching the bulk value of Fe3O4. The materials presented could be used as pollutant absorbers for wastewater treatment. We have demonstrated the capability of using magnetic CNF aerogels in absorbing a common dye pollutant from water. The dye was absorbed efficiently, and the aerogels were easily magnetically removed from the solution and are reusable. [ABSTRACT FROM AUTHOR]

The degree of crystallinity in cellulose significantly affects the physical, mechanical, and chemical properties of cellulosic materials, their processing, and their final application. Measuring the crystalline structures of cellulose is a challenging task due to inadequate consistency among the variety of analytical techniques available and the lack of absolute crystalline and amorphous standards. Our article reviews the primary methods for estimating the crystallinity of cellulose, namely, X-ray diffraction (XRD), nuclear magnetic resonance (NMR), Raman and Fourier-transform infrared (FTIR) spectroscopy, sum-frequency generation vibrational spectroscopy (SFG), as well as differential scanning calorimetry (DSC), and evolving biochemical methods using cellulose binding molecules (CBMs). The techniques are compared to better interrogate not only the requirements of each method, but also their differences, synergies, and limitations. The article highlights fundamental principles to guide the general community to initiate studies of the crystallinity of cellulosic materials. [ABSTRACT FROM AUTHOR]

Novel cellulose-derived hybrid carbon nanofibre (CNF)/carbon nanotubes (CNTs) electrode-based structural supercapacitors, combined with a solid electrolyte, have been produced. Galvanostatic charge/discharge and electrochemical impedance spectroscopy measurements were used to assess the electrodes’ performance. The CNF/CNTs electrodes have a better capacitive performance than the plain CNF electrodes; 0.91 ± 0.02 and 3.35 ± 0.05 mF cm−2 for CNF and CNF/CNTs, respectively. A Raman spectroscopic approach was used to investigate the stress transfer properties of the CNF within a poly(methyl methacrylate) (PMMA) resin matrix. Deformation of the carbon structures was observed via shifts towards a lower wavenumber position of the G band (~ 1590 cm−1) for CNF and CNF/CNTs samples processed at a carbonization temperature of 2000 °C. Moduli of these fibres were estimated to be ~ 145 and ~ 271 GPa, respectively, suggesting the growth of CNTs not only enhances the capacitive performance but also the mechanical performance of the structural supercapacitors. [ABSTRACT FROM AUTHOR]

Magnetically responsive and flexible bacterial cellulose (BC) membranes were successfully fabricated using a simple diffusion of a ferrofluid solution. BC hydrogels were either water-substituted by alcohol (BC-N) or freeze dried (BC-F) prior to their immersion in the ferrofluid. The presence of both crystalline BC and Fe 3 O 4 phases, and the homogeneous distribution of nanoparticles (NPs) in BC nanofibrils were observed. Higher concentrations of Fe 3 O 4 NPs were found in the BC-N samples than for the BC-F samples. Higher magnetization in the BC-N samples was observed compared to the BC-F samples. Mechanical properties tests showed the higher strength and Young’s modulus for the BC-F samples was possibly due to their more compacted nanostructure compared to BC-N. Using this simple process, the magnetic BC membranes show elastic properties upon deformation, returning to their original shape without damage. Also, they were highly sensitive to external magnetic forces giving them potential for many applications. [ABSTRACT FROM AUTHOR]

Abstract: There is a need to develop high‐performance cellulose fibers as sustainable replacements for glass fibers, and as alternative precursors for carbon filaments. Traditional fiber spinning uses toxic solvents, but in this study, by using dimethyl sulfoxide (DMSO) as a co‐solvent with an ionic liquid, a novel high‐performance fiber with exceptional mechanical properties is produced. This involves a one‐step dissolution, and cost‐effective route to convert high concentrations of low molecular weight microcrystalline cellulose into high stiffness cellulose fibers. As the cellulose concentration increases from 20.8 to 23.6 wt%, strong optically anisotropic patterns appear for cellulose solutions, and the clearing temperature (Tc) increases from ≈100 °C to above 105 °C. Highly aligned, stiff cellulose fibers are dry‐jet wet spun from 20.8 and 23.6 wt% cellulose/1‐ethyl‐3‐methylimidazolium diethyl phosphate/DMSO solutions, with a Young's modulus of up to ≈41 GPa. The significant alignment of cellulose chains along the fiber axis is confirmed by scanning electron microscopy, wide‐angle X‐ray diffraction, and powder X‐ray diffraction. This process presents a new route to convert high concentrations of low molecular weight cellulose into high stiffness fibers, while significantly reducing the processing time and cost. [ABSTRACT FROM AUTHOR]

• An electrospun oil sorbent, derived from cigarette filters, was produced. • The sorbent exhibited an oil sorption capacity of 93.7 g/g. • The result is higher than that of all previous cigarette filter derived sorbents. A highly effective oil sorbent, made from cigarette filters, was produced using a low complexity, single-step process. This was done to address the dual issues of oil pollution and cigarette filter litter. The oil sorption capacity was found for electrospun cellulose acetate sorbents, made from both virgin cellulose acetate and cigarette filters. Not only did the cigarette filter derived sorbent have a higher oil sorption capacity than sorbents found in other studies (with a capacity of 93.7 g/g), but the sorbent was also produced using a less complex and less energy-intensive method. Additionally, the oil sorption capacity for the cigarette filter sorbent was found to be higher than that of a virgin cellulose acetate sorbent. This was thought to be due to the additive, glycerol triacetate (GA), found within the cigarette filters. This means that not only does sourcing the cellulose acetate from cigarette filters tackle cigarette filter pollution, but it also produces a more effective sorbent. Therefore, the cigarette filter derived oil sorbent produced in this study has the potential to be a highly effective, and more sustainable, solution for the remediation of oil pollution. [ABSTRACT FROM AUTHOR]

Cellulose is known to interact well with water, but is insoluble in it. Many polysaccharides such as cellulose are known to have significant hydrogen bond networks joining the molecular chains, and yet they are recalcitrant to aqueous solvents. This review charts the interaction of cellulose with water but with emphasis on the formation of both natural and synthetic fiber composites. Covering studies concerning the interaction of water with wood, the biosynthesis of cellulose in the cell wall, to its dispersion in aqueous suspensions and ultimately in water filtration and fiber-based composite materials this review explores water–cellulose interactions and how they can be exploited for synthetic and natural composites. The suggestion that cellulose is amphiphilic is critically reviewed, with relevance to its processing. Building on this, progress made in using various charged and modified forms of nanocellulose to stabilize oil–water emulsions is addressed. The role of water in the aqueous formation of chiral nematic liquid crystals, and subsequently when dried into composite films is covered. The review will also address the use of cellulose as an aid to water filtration as one area where interactions can be used effectively to prosper human life. [ABSTRACT FROM AUTHOR]

The ability to reproducibly produce and effectively collect electrosprayed polymeric microspheres with controlled morphology and size in bulk form is challenging. In this study, microparticles were produced by electrospraying polycaprolactone (PCL) of various molecular weights and solution concentrations in chloroform, and by collecting materials on different substrates. The resultant PCL microparticles were characterized by optical and electron microscopy to investigate the effect of molecular weight, solution concentration, applied voltage, working distance, and flow rate on their morphology and size. The work demonstrates the key role of a moderate molecular weight and/or solution concentration in the formation of spherical PCL particles via an electrospraying process. Increasing the applied voltage was found to produce smaller and more uniform PCL microparticles. There was a relatively low increase in the particle average size with an increase in the working distance and flow rate. Four types of substrates were adopted to collect electrosprayed PCL particles: a glass slide, aluminium foil, liquid bath, and copper wire. Unlike 2D bulk structures collected on the other substrates, a 3D tubular structure of microspheres was formed on the copper wire which could find application in the construction of 3D tumor mimics. [ABSTRACT FROM AUTHOR]

Polystyrene nanofibres reinforced with cellulose nanocrystals have been produced by electrospinning. Two different orientations of the nanofibres were produced, namely aligned and random, and these nanofibrous interleaves were investigated both as-spun and after thermal treatment. Aligned nanofibres exhibited a 2500% increase in their Young's modulus compared to the randomly orientated materials, while the ultimate tensile strength increased by up to 300%. It is also demonstrated that crazing occurs in the nanofibres, which is thought to enhance the fracture properties of the materials. Interleaves of both orientations were then included in a carbon fibre-reinforced polymer laminate. The fracture toughness of the laminate was determined under both mode I and mode II testing. No increases in mode I toughness were observed. It was, however, found that the aligned interleaves increased the mode II toughness of the composite laminate (from 1.9 ± 0.3 to 2.7 ± 0.2 kJ m−2). This increase is demonstrated to be due to a combination of nanofibre bridging and the formation of microcracks in the resin under applied tensile and shear load. [ABSTRACT FROM AUTHOR]

The development of co-electrospun (co-ES) hollow microfibrous assemblies of an appreciable thickness is critical for many practical applications, including filtration membranes and tissue-mimicking scaffolds. In this study, thick uniaxially aligned hollow microfibrous assemblies forming fiber bundles and strips were prepared by co-ES of polycaprolactone (PCL) and polyethylene oxide (PEO) as shell and core materials, respectively. Hollow microfiber bundles were deposited on a fixed rotating disc, which resulted in non-controllable cross-sectional shapes on a macroscopic scale. In comparison, fiber strips were produced with tuneable thickness and width by additionally employing an x – y translation stage in co-ES. Scanning electron microscopy (SEM) images of cross-sections of fiber assemblies were analyzed to investigate the effects of production time (from 0.5 h to 12 h), core flow rate (from 0.8 mL/h to 2.0 mL/h) and/or translation speed (from 0.2 mm/s to 5 mm/s) on the pores and porosity. We observed significant changes in pore size and shape with core flow rate but the influence of production time varied; five strips produced under the same conditions had reasonably good size and porosity reproducibility; pore sizes didn't vary significantly from strip bottom to surface, although the porosity gradually decreased and then returned to the initial level. [ABSTRACT FROM AUTHOR]

Sodium‐ion batteries (SIBs) and potassium‐ion batteries (PIBs) are prospective candidates for large‐scale energy storage systems cause of their abundant resources. However, unsatisfactory rate and cycling performance of carbon‐based anodes present a bottleneck for the applications of SIBs/PIBs due to the large sizes of sodium/potassium ions. Herein, oxygen‐doped vertically aligned carbon aerogels (VCAs) with hierarchically tailored channels are synthesized as anodes in SIBs/PIBs via a controllable unidirectional ice‐templating technique. VCA‐3 (cooling rate of 3 K min−1) delivers the highest reversible capacity of ≈298 mAh g−1 at 0.1 C with an excellent cycling performance over 2000 cycles at 0.5 C for SIBs, while VCA‐5 manifests a superior capacity of ≈258 mAh g−1 at 0.1 C with an 82.7% retention over 1000 cycles at 0.5 C for PIBs. Moreover, their full cells demonstrate the promising potential of VCAs in applications. This novel controllable ice‐templating strategy opens unique avenues to tune the construction of hollow aligned channels for shortening ion‐transport pathways and ensuring structural integrity. New insights into structure‐performance correlations regulated by the cooling rates of an ice‐templating strategy and design guidelines for electrodes applicable in multiple energy storage technologies are reported. [ABSTRACT FROM AUTHOR]

Urea and phosphoric acid are essential for the isolation of phosphorylated cellulose nanocrystals (CNCs). Besides limiting dissolution of nanocrystals, urea facilitates the swelling of fibres thus increasing access for the phosphorylating agent. The aim of this study was to determine optimal conditions for isolation of highly charged phosphorylated CNCs. Using a design of experiments approach, seventeen experiments in which reaction time, urea, and acid concentrations were varied, were conducted. A two-step process was used, in which CNCs were first isolated by treatment in phosphoric acid, and then treated with metaphosphoric acid, and urea. It is shown that a design of experiments approach to the phosphorylation of CNCs allows a much lower ratio of urea to acid than has previously been reported. CNCs with high surface charge (~1800 mmol kg−1) are possible using this method. This information is instructive to phosphorylation of cellulose nanomaterials which have a variety of applications e.g., water purification and medical biomaterials. [Display omitted] [ABSTRACT FROM AUTHOR]

Orientation of cellulose nanowhiskers (CNWs) derivedfrom tunicates,in an all-cellulose nanocomposite, is achieved through the applicationof a magnetic field. CNWs are incorporated into a dissolved cellulosematrix system and during solvent casting of the nanocomposite a magneticfield is applied to induce their alignment. Unoriented CNW samples,without the presence of a magnetic field, are also produced. The CNWsare found to orient under the action of the magnetic field, leadingto enhanced stiffness and strength of the composites, but not to thelevel that is theoretically predicted for a fully aligned system.Lowering the volume fraction of the CNWs is shown to allow them toorient more readily in the magnetic field, leading to larger relativeincreases in the mechanical properties. It is shown, using polarizedlight microscopy, that the all-cellulose composites have a domainstructure, with some domains showing pronounced orientation of CNWsand others where no preferred orientation occurs. Raman spectroscopyis used to both follow the position of bands located at ∼1095and ∼895 cm–1with deformation and also theirintensity as a function rotation angle of the specimens. It is shownthat these approaches give valuable independent information on therespective molecular deformation and orientation of the CNWs, andthe molecules in the matrix phase, in oriented and nonoriented domainsof all-cellulose composites. These data are then related to an increasein the level of molecular deformation in the axial direction, as revealedby the Raman technique. Little orientation of the matrix phase isobserved under the action of the magnetic field indicating the dominanceof the stiff CNWs in governing mechanical properties. [ABSTRACT FROM AUTHOR]

Abstract: Detection of bacterial and fungal contamination is of extreme importance in the fields of medical products or food packaging. Here a diagnostic tool based on pectinase and cellulase triggered release of a dye from a crosslinked polysaccharide matrix was developed. The hydrogel-based bioresponsive matrix consisted of carboxymethylcellulose (CMC) as a substrate for cellulases and polygalacturonate (PGA) as substrate for pectinases. To improve the stability of the hydrogels, methacrylic groups were inserted as crosslinking molecules. For polymerisation, two different methods were used, namely UV and thermal crosslinking. Controlled release triggered by extracellular enzymes of potentially pathogenic/contaminating microorganisms was investigated by the incorporation of Alizarin into the hydrogels. UV polymerised hydrogels turned out to be more suitable than thermal crosslinked polymers. Integration of such polymer based bioresponsive systems in medical surfaces or package systems could therefore act as an in situ monitoring system for detecting the presence of bacteria or fungi like e.g. Aspergillus species. [Copyright &y& Elsevier]

Abstract: In this work, the effects of process parameters on the deposition of single component and compound core–shell jets in near-field electrospinning are reported. It is shown that the working distance and fibre collector speed have a more significant influence on the deposition of a single jet than the flow rate. In the case of a compound jet, it is shown that jet deposition onto aluminium foil results in a linear fibre form, but on glass slides it appears as a random fibre network. The fabrication of aligned and patterned core–shell structured fibres is demonstrated by coaxial electrospinning of sugar and polycaprolactone (PCL) solutions. Aligned sugar-PCL core–shell fibres with diameters of ∼1.2 μm are deposited on an x–y translation stage, 10 cm below the coaxial spinneret. Complex patterns of sugar-PCL core–shell fibres with average diameters ranging from 72 to 175 μm are fabricated by reducing the working distance to 2 cm. [Copyright &y& Elsevier]

Abstract: The study of the interfacial stress transfer for glass fibres in polymer composites through the fragmentation test requires certain assumptions, such as a constant interfacial shear stress. In order to map the local interfacial properties of a composite, both Raman spectroscopy and luminescence spectroscopy have been independently used. Unlike other polymer fibre composites, the local strain state of a glass fibre cannot be obtained using Raman spectroscopy, since only very broad and weak peaks are obtainable. This study shows that when single-walled carbon nanotubes (SWNTs) are added to the silane sizing as a strain sensor, it becomes possible to map the local fibre strain in glass fibres using Raman spectroscopy. Moreover, if this model glass fibre contains a small amount of Sm2O3, as one of the components, luminescence spectroscopy can be simultaneously used to confirm this local fibre strain. A combined micromechanical properties study of stress transfer at the fibre–matrix interface using luminescence spectroscopy, together with Raman spectroscopy, is therefore reported. The local strain behaviour of both Sm3+ doped glass and SWNTs in the silane coating are shown to be consistent with a shear-lag model. This indicates that Sm3+ dopants and SWNTs are excellent sensors for the local deformation of glass fibre composites. [Copyright &y& Elsevier]

Fingernails are a characteristic anatomical feature of primates and their function is dictated by the environment in which they are utilised. The present study examined the mechanical properties of human fingernails as a function of relative humidity (RH) and the subsequent moisture content of the nail material. Nail clippings were stored at a range of RH values and then weighed in order to determine their moisture content. There was a non-linear relationship between the moisture content of nails and the RH of their local environment. The in vivo moisture content of nails, measured from 55% to 80% RH, was between 14% and 30%, similar to other keratinous materials such as claws, hooves and feathers. Cutting tests on the nail samples showed that the work of fracture was between 11 and 22kJm2, rising to a peak at 55% RH and falling at higher and lower humidities. At all RH values there was anisotropy within the nail between the proximal and lateral directions, the work of fracture being greater proximally. This anisotropy was greatest at 55% RH, at which point the proximal work of fracture was double the lateral value. These results suggest that the mechanical behaviour of human fingernails is optimised at in vivo conditions; they resist tearing most strongly under these conditions and particularly resist tearing into the nail bed. At more extreme humidity levels the fracture properties of the nail deteriorate; they are brittle when fully dry and fracture and split when wet. [ABSTRACT FROM AUTHOR]

Wood is a sustainable structural material, but it cannot be easily shaped while maintaining its mechanical properties. We report a processing strategy that uses cell wall engineering to shape flat sheets of hardwood into versatile three-dimensional (3D) structures. After breaking down wood’s lignin component and closing the vessels and fibers by evaporating water, we partially re-swell the wood in a rapid water-shock process that selectively opens the vessels. This forms a distinct wrinkled cell wall structure that allows the material to be folded and molded into desired shapes. The resulting 3D-molded wood is six times stronger than the starting wood and comparable to widely used lightweight materials such as aluminum alloys. This approach widens wood’s potential as a structural material, with lower environmental impact for buildings and transportation applications. [ABSTRACT FROM AUTHOR]

Locust bean/xanthan gum (LBG/XG) synergistic networks have previously been well studied, with evidence that junction zones between the two polymers result in hydrophobic domains. Here we report on the effect of both hydrophilic and hydrophobic cellulose nanocrystals (CNCs) on the rheological properties of the individual gums, the gum networks, and emulsion gels consisting of the gum network and corn oil. We also take advantage of differences in the autofluorescent spectra for each of the components to map their distribution within the gel and emulsion gel systems. Whilst both types of CNC confer thermal stability to the systems, hydrophilic CNCs induce minor changes in rheological properties of synergistic gels and prove to be detrimental to the stability of the emulsion gels. In contrast, hydrophobic CNCs associate with the LBG/XG network, affecting the rheological response. Their inclusion in the emulsion gel system results in smaller, more homogeneously distributed oil droplets with a resultant increase in the storage modulus by an order of magnitude compared to the CNC-free and hydrophilic CNC systems. We conclude that hydrophobic CNCs play a critical role in stabilising LBG/XG network gels and emulsions. [ABSTRACT FROM AUTHOR]

Hybrid nanocomposites of bacterial cellulose (BC) and magnetic iron oxide nanoparticles (NPs) are of interest due to their potential for novel applications. Magnetic NPs are typically synthesized by co-precipitation since it is facile, enabling control of their size and distribution. This work investigates the effect of using different starting reactants (Fe(II) and Fe(III) salts) in the fabrication and control of the properties of BC/iron oxide nanocomposites. It was found that the choices of starting reactants are not important for synthesizing NPs outside of the BC networks. However, the starting reactants do affect the formation of NPs when they are synthesized in the BC network. Significant differences in the morphologies, sizes, crystal structures, and magnetic phases of NPs occurs when in this environment. The nanopores of BC networks in some instances force the aggregation of the NPs, either within the pores, or on the surfaces of the fibrils. Nanocomposites synthesized from Fe(II) sulfate and Fe(III) chloride were found to exhibit the highest magnetization. These nanocomposites have potential for flexible sensors, actuators, or electromagnetic shielding. Nanocomposites from Fe(II) acetate and Fe(III) chloride, though exhibiting lower magnetization, preserve a porous structure. Thus, they have potential as adsorbents or for wound healing applications. Unlabelled Image • The starting reactants are not important for the characteristics and properties of the Fe 3 O 4 NPs without BC. • When NPs are formed inside BC networks, the starting materials influence the nanocomposites characteristics and properties. • Morphology, size, crystal structure, loading amount, and magnetic phase of Fe 3 O 4 NPs are affected by the BC networks. • The ability to alter and control the properties of the NPs enables one to direct towards specific target applications. [ABSTRACT FROM AUTHOR]

Understanding the fine details of the self‐assembly of building blocks into complex hierarchical structures represents a major challenge en route to the design and preparation of soft‐matter materials with specific properties. Enzymatically synthesised cellodextrins are known to have limited water solubility beyond DP9, a point at which they self‐assemble into particles resembling the antiparallel cellulose II crystalline packing. We have prepared and characterised a series of site‐selectively fluorinated cellodextrins with different degrees of fluorination and substitution patterns by chemoenzymatic synthesis. Bearing in mind the potential disruption of the hydrogen‐bond network of cellulose II, we have prepared and characterised a multiply 6‐fluorinated cellodextrin. In addition, a series of single site‐selectively fluorinated cellodextrins was synthesised to assess the structural impact upon the addition of one fluorine atom per chain. The structural characterisation of these materials at different length scales, combining advanced NMR spectroscopy and microscopy methods, showed that a 6‐fluorinated donor substrate yielded multiply 6‐fluorinated cellodextrin chains that assembled into particles presenting morphological and crystallinity features, and intermolecular interactions, that are unprecedented for cellulose‐like materials. [ABSTRACT FROM AUTHOR]

• Porous superhydrophobic nanofibers were prepared using electrospinning. • A highly volatile solvent combined with electrospinning in humid conditions yielded pores on the surface of the fibers. • The porous fibers were superhydrophobic with a water contact angle of 165° and an oil contact angle of ∼0°. • The prepared fibers exhibited an oil sorption capacity of 60 g/g. Porous superhydrophobic nanofibrous networks based on cellulose acetate butyrate (CAB) were prepared using electrospinning. The morphology and wettability of the prepared fibrous networks was studied using scanning electron microscopy and static contact angle measurements. The porous nanofiber networks exhibited superhydrophobicity and superoleophilicity with a water contact angle of ∼165° and an oil contact angle of ∼0°. The porous nature of the nanofibres themselves is thought to lead to an increased surface area making them suitable for sorption applications. Due to their hydrophobic and oleophilic nature, they were tested for their oil sorption capacity. They demonstrated an oil sorption capacity of ∼60 g/g for motor oil, which is four times that of commercially used polypropylene. The nanofibrous mats also demonstrated excellent reusability, retaining ∼80% of their sorption capacity for up to 5 cycles of use. [ABSTRACT FROM AUTHOR]

Photoluminescence of cellulose, and other polysaccharides, has long been presumed to be due to contamination of the material by other autofluorescent compounds – such as lignin, or proteins. This is attributed to the lack of known fluorescent chemical groups present in the molecular structure of polysaccharides and the weak emission intensity when compared to typical fluorophores. However, recent research suggests that the observed luminescence may actually be due to transitions involving the n orbitals containing lone electron pairs present in oxyl groups, stabilised by the molecular forces between the polysaccharide chains. Here we investigate this theory further by varying the physicochemical environment (concentration and pH) of oxidised cellulose nanofibril suspensions and observing the resultant fluorescent spectra using multi-channel confocal laser scanning spectroscopy. We confirm that both factors affect the material photoluminescence, specifically changing the intensity ratio between two localised emission maxima, supporting current theories. Furthermore, we demonstrate that this variation enables the determination of critical aggregation concentrations and the apparent pKa values of hydroxyl groups that undergo deprotonation within the examined pH range, enabling use of the technique to track rapid changes in the fibril physicochemical environment. [ABSTRACT FROM AUTHOR]

It is generally acknowledged that to advance the application of cellulose nanofibrils (CNFs) in product formulations, challenges associated with the drying and redispersion of this material must be addressed. Despite increased research efforts in this area, these interventions still involve the use of additives or conventional drying technologies, which both have the capacity to drive up the cost of the final CNF powders. Herein, we prepared dried and redispersible CNF powders with varying surface functionalities without the use of additives nor conventional drying technologies. Rapid drying in air was achieved after liquid phase exchange from water to isopropyl alcohol. The surface properties, morphology and thermal stabilities were the same for the never-dried and redispersed forms. The rheological properties of the CNFs were also unaffected after drying and redispersion of unmodified and organic acid modified materials. However, for 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO)-mediated oxidised CNFs with higher surface charge and longer fibrils, the storage modulus could not be recovered to the never-dried state because of the possible non-selective reduction in length upon redispersion. Nevertheless, this method provides an effective and low-cost process for the drying and redispersion of unmodified and surface modified CNFs. [ABSTRACT FROM AUTHOR]

Bioinspiration from hierarchical structures found in natural environments has heralded a new age of advanced functional materials. Nanocellulose has received significant attention due to the demand for high-performance materials with tailored mechanical, physical and biological properties. In this study, nanocellulose fibrils, nanocrystals and a novel mixture of fibrils and nanocrystals (blend) were prepared from softwood biomass using the AVAP® biorefinery technology. These materials were characterized using transmission and scanning electron microscopy, and atomic force microscopy. This analysis revealed a nano- and microarchitecture with extensive porosity. Notable differences included the nanocrystals exhibiting a compact packing of nanorods with reduced porosity. The NC blend exhibited porous fibrillar networks with interconnecting compact nanorods. Fourier transform infrared spectroscopy and X-ray diffraction confirmed a pure cellulose I structure. Thermal studies highlighted the excellent stability of all three NC materials with the nanocrystals having the highest decomposition temperature. Surface charge analysis revealed stable colloid suspensions. Rheological studies highlighted a dominance of elasticity in all variants, with the NC blend being more rigid than the NC fibrils and nanocrystals, indicating a double network hydrogel structure. Given these properties, it is thought that these materials show great potential in (bio)nanomaterial applications where careful control of microarchitecture, surface topography and porosity are required. [ABSTRACT FROM AUTHOR]

Microfibrillated cellulose (MFC) obtained from eucalyptus was embedded in gelatin from two sources; namely bovine and salmon gelatin. Raman spectroscopy revealed that stress is transferred more efficiently from bovine gelatin to the MFC when compared to salmon gelatin. Young’s modulus, tensile strength, strain at failure and work of fracture of the nanocomposite films were improved by ∼67, 131, 43 y 243% respectively when using salmon gelatin as matrix material instead of bovine gelatin. Imaging of the tensile fracture surface of the MFC-gelatin nanocomposites revealed that crack formation occurs predominantly within bovine and salmon gelatin matrices rather than within the MFC or at the MFC/gelatin interface. This suggests that the mechanical failure mechanism in these nanocomposite materials is predominantly governed by a matrix-cohesive fracture mechanism. Both strength and flexibility are desirable properties for composite coatings made from gelatin-based materials, and so the findings of this study could assist in their utilization in the food and pharmaceutical industry. [ABSTRACT FROM AUTHOR]

A new family of materials comprised of cellulose, cellulose nanomaterials (CNMs), having properties and functionalities distinct from molecular cellulose and wood pulp, is being developed for applications that were once thought impossible for cellulosic materials. Commercialization, paralleled by research in this field, is fueled by the unique combination of characteristics, such as high on-axis stiffness, sustainability, scalability, and mechanical reinforcement of a wide variety of materials, leading to their utility across a broad spectrum of high-performance material applications. However, with this exponential growth in interest/activity, the development of measurement protocols necessary for consistent, reliable and accurate materials characterization has been outpaced. These protocols, developed in the broader research community, are critical for the advancement in understanding, process optimization, and utilization of CNMs in materials development. This review establishes detailed best practices, methods and techniques for characterizing CNM particle morphology, surface chemistry, surface charge, purity, crystallinity, rheological properties, mechanical properties, and toxicity for two distinct forms of CNMs: cellulose nanocrystals and cellulose nanofibrils. [ABSTRACT FROM AUTHOR]

In this work, alloying of CoPt and FePt nanoparticles (NPs), i.e. the Co 1-x Fe x Pt NPs (x = 0, 0.25, 0.5, 0.75, 1), were synthesized by the polyol process. These as-synthesized NPs show the A1 phase with a particle size less than 5 nm. After annealing at 700 °C, the A1 (cubic) phase was transformed to L1 0 (tetragonal) phase in all samples. The lattice parameters varied as a function of the composition. The particle size grew larger after annealing and the size distribution was wide ranging from <10 nm to >100 nm. The size and distribution was however independent of the Co(Fe) concentration. X-ray absorption spectroscopy indicated that there was a random distribution of Co and Fe atoms in the layered structure. Magnetic measurements of the annealed NPs showed that the magnetic hysteresis loop depends on the composition. The coercivity (H c ) was very high for the CoPt and FePt NPs, whereas the M s value was maximized for the Co 0.5 Fe 0.5 Pt NPs. The variation of H c was attributed to the change in lattice parameters which could alter the exchange interaction, and thus the magnetocrystalline anisotropy. On the other hand, higher polarization and increased magnetic moments of Fe atoms were believed to be the reason for the enhanced M s in the Co(Fe)Pt NPs. In addition, all NPs were magnetically stable against temperature variation with changes in M s of less than 10%. The Curie temperature was expected to be as high as 800–900 K. Given these properties, these new forms of magnetic nanoparticles may find use in advanced magnetic recording technology. [ABSTRACT FROM AUTHOR]

Sustained release and prevention of burst release for low half-life drugs like Diclofenac sodium is crucial to prevent drug related toxicity. Electrospun nanofibers have emerged recently as potential carrier materials for controlled and sustained drug release. Here, we present a facile method to prevent burst release by tuning the surface wettability through template assisted micropatterning of drug loaded electrospun cellulose acetate (CA) nanofibers. A known amount of drug (Diclofenac sodium) was first mixed with CA and then electrospun in the form of a nanofabric. This as-spun network was hydrophilic in nature. However, when electrospinning was carried out through non-conducting templates, viz nylon meshes with 50 and 100 μm size openings, two kinds of hydrophobic micro-patterned CA nanofabrics were produced. In vitro transdermal testing of our nanofibrous mats was carried out; these tests were able to show that it would be possible to create a patch for transdermal drug release. Further, our results show that with optimized micro-patterned dimensions, a zero order sustained drug release of up to 12 h may be achieved for the transdermal system when compared to non-patterned samples. This patterning caused a change in the surface wettability, to a hydrophobic surface, resulting in a controlled diffusion of the hydrophilic drug. Patterning assisted in controlling the initial burst release, which is a significant finding especially for low half-life drugs. [ABSTRACT FROM AUTHOR]

In this letter, we present a facile approach to fabricate hydrophobic surfaces based on electrostatic field assisted self-assembly of fibers onto conductive micropillars. Hydrophobic patterns fabricated in this work are inspired by an underwater fern Salvinia molesta. Hydrophilic cellulose acetate nanofibers were electrospun on a conducting micro-patterned surface to create a hierarchical structure. The water contact angle increased from just below 70° (hydrophilic) on the micro-patterned structures to -140° (hydrophobic) for the hierarchical structures. Introduced hydrophobicity is due to the pinning of the water droplet to suspended hydrophilic nanofibers and a reduced solid-water interface. [ABSTRACT FROM AUTHOR]

Graphene-cellulose interactions have considerable potential in the development of new materials. In previous computational work (Biomacromolecules 2016 , 16, 1771), we predicted that the model 100 hydrophobic surface of cellulose interacted favourably with pristine graphene in aqueous solution molecular dynamics simulations; conversely, a model of the hydrophilic 010 surface of cellulose exhibited progressive rearrangement to present a more hydrophobic face with the graphene, with weakened hydrogen bonds between cellulose chains and partial permeation of water. Here, we extend this work by simulating the interaction in aqueous solution of the amphiphilic 110 surface of a cellulose Iβ microfibril model, comprising 36 chains of 40 glucosyl residues, with an infinite sheet of pristine graphene. This face of the microfibril is of intermediate hydrophilicity and progressively associates with graphene over replicate simulations. As cellulose chains adhere to the graphene surface, forming interactions via its CH and OH groups, we observe a degree of local and global untwisting of the microfibril. Complementary rippling of the graphene surface is also observed, as it adapts to interaction with the microfibril. This adsorption process is accompanied by increased exclusion of water between cellulose and graphene although some water localises between chains at the immediate interface. The predicted propensity of a cellulose microfibril to adsorb spontaneously on the graphene surface, with mutual structural accommodation, highlights the amphiphilic nature of cellulose and the types of interactions that can be harnessed to design new graphene-carbohydrate biopolymer materials. [Display omitted] • Cellulose fibril-graphene interface modelled using molecular dynamics with explicit water. • Cellulose fibril adheres to the graphene with increased CH-π and OH-π interactions. • Cellulose fibril untwists to adhere to graphene which also ripples to maximise interaction. [ABSTRACT FROM AUTHOR]

The molecular deformation and crystal orientation of a range of next generation regenerated cellulose fibers, produced from an ionic liquid solvent spinning system, are correlated with macroscopic fiber properties. Fibers are drawn at the spinning stage to increase both molecular and crystal orientation in order to achieve a high tensile strength and Young’s modulus for potential use in engineering applications. Raman spectroscopy was utilized to quantify both molecular strain and orientation of fibers deformed in tension. X-ray diffraction was used to characterize crystal orientation of single fibers. These techniques are shown to provide complimentary information on the microstructure of the fibers. A shift in the position of a characteristic Raman band, initially located at ∼1095 cm −1 , emanating from the backbone structure of the cellulose polymer chains was followed under tensile deformation. It is shown that the shift rate of this band with respect to strain increases with the draw ratio of the fibers, indicative of an increase in the axial molecular alignment and subsequent deformation of the cellulose chains. A linear relationship between the Raman band shift rate and the modulus was established, indicating that the fibers possess a series aggregate structure of aligned crystalline and amorphous domains. Wide-angle X-ray diffraction data show that crystal orientation increases with an increase in the draw ratio, and a crystalline chain slip model was used to fit the change in orientation with fiber draw ratio. In addition to this a new model is proposed for a series aggregate structure that takes into better account the molecular deformation of the fibers. Using this model a prediction for the crystal modulus of a cellulose-II structure is made (83 GPa) which is shown to be in good agreement with other experimental approaches for its determination. [ABSTRACT FROM AUTHOR]

Sustainability of fibre reinforced polymer composites has become vital for reaching the global sustainable development goals. Natural fibres, particularly flax, and bioderived matrices are possible sustainable solutions for the composites industry, due to the constituents' embedded environmental impact reduction. According to the circular economy paradigm, sustainability can also be achieved by delaying the disposal of materials. This work reports the interfacial properties of flax fibres with three potentially sustainable advanced matrices, i.e., a vitrimer that combines the beneficial properties of both thermosets and thermoplastics, an entirely bio-based thermoset, and an advanced thermoplastic resin. Each of the selected matrices offers the potential for either recyclability, repairability, reusability, or the use of renewable sources and a reduction in the emissions of volatile organic compounds. Microbond tests were used to evaluate the interfacial shear strength and critical fibre length. It was found that the vitrimer and the bio-based thermoset matrices had a higher level of adhesion with flax fibres (∼ 20 and ∼ 24 MPa, respectively) compared to a traditional epoxy matrix (∼ 12 MPa); the advanced thermoplastic resin (∼ 6 MPa) shows the poorest adhesion. The vitrimer matrix was selected as a candidate for a sustainable and repairable discontinuous flax fibre reinforced composite. Mechanical and low-temperature rapid repair performance of an aligned discontinuous flax fibre composite, produced using the HiPerDiF method, were investigated. End-to-end and single patch repair methods were performed: vitrimer matrix composites show the potential for a mechanical strength recovery (∼ %50-70) that would allow them to be reused over several life cycles, enabling a circular economy. • The interfacial shear strengths of flax fibre with three matrices: advanced thermoplastic, bio-based, and vitrimer, were reported and compared with standard epoxy. • Vitrimer and bio-based thermoset matrices showed higher levels of adhesion compared to standard epoxy and advanced thermoplastic matrices. • A rapid and low-temperature repair performance of aligned discontinuous flax fibre reinforced vitrimers were mechanically and physically investigated. [ABSTRACT FROM AUTHOR]

Abstract: All-cellulose nanocomposites, comprising two different forms of cellulose nanowhiskers dispersed in two different matrix systems, are produced. Acid hydrolysis of both tunicate (T-CNWs) and cotton cellulose (CNWs) is carried out to produce the nanowhiskers. These nanowhiskers are then dispersed in a cellulose matrix material, produced using two dissolution methods; namely lithium chloride/N,N-dimethyl acetamide (LiCl/DMAc) and sodium hydroxide/urea (NaOH/urea). Crystallinity of both nanocomposite systems increases with the addition of nanowhiskers up to a volume fraction of 15 v/v%, after which a plateau is reached. Stress-transfer mechanisms, between the matrix and the nanowhiskers in both of these nanocomposites are reported. This is achieved by following both the mechanical deformation of the materials, and by following the molecular deformation of both the nanowhiskers and matrix phases using Raman spectroscopy. In order to carry out the latter of these analyses, two spectral peaks are used which correspond to different crystal allomorphs; cellulose-I for the nanowhiskers and cellulose-II for the matrix. It is shown that composites comprising a LiCl/DMAc based matrix perform better than NaOH/urea based systems, the T-CNWs provide better reinforcement than CNWs and that an optimum loading of nanowhiskers (at 15 v/v%) is required to obtain maximum tensile strength and modulus. [Copyright &y& Elsevier]

Cellulose nanofibres have been fabricated by electrospinning of a cellulose acetate solution followed by deacetylation. The cellulose nanofibres were then carbonized using temperatures in the range 800–2200°C and the resulting carbon nanofibres (CNFs) were characterized using transmission electron microscopy, X-ray diffraction and Raman spectroscopy. A graphitic structure was observed for CNFs treated at a relatively low temperature of 1500°C, with no obvious skin-core heterogeneity observed for fibres treated up to 2200°C, suggesting a possible advantage of using nano-scale precursors. The effective Young’s modulus of the CNFs was assessed using an in situ Raman spectroscopic technique following the shift in the position of the G′ (2D) band located at ∼2660cm−1 and relating this to a calibration established for a range of other carbon fibres. Using this approach the moduli of the CNFs were found to be ∼60 and ∼100GPa for samples carbonized at 1500 and 2200°C, respectively. [ABSTRACT FROM AUTHOR]

The deformation micromechanics of bacterial cellulose(BC) andmicrofibrillated cellulose (MFC) networks have been investigated usingRaman spectroscopy. The Raman spectra of both BC and MFC networksexhibit a band initially located at ∼1095 cm–1. We have used the intensity of this band as a function of rotationangle of the specimens to study the cellulose fibril orientation inBC and MFC networks. We have also used the change in this peak’swavenumber position with applied tensile deformation to probe thestress-transfer behavior of these cellulosic materials. The intensityof this Raman band did not change significantly with rotation angle,indicating an in-plane 2D network of fibrils with uniform random orientation;conversely, a highly oriented flax fiber exhibited a marked changein intensity with rotation angle. Experimental data and theoreticalanalysis shows that the Raman band shift rate arising from deformationof networks under tension is dependent on the angles between the axisof fibrils, the strain axis, the incident laser polarization direction,and the back scattered polarization configurations. From this analysis,the effective moduli of single fibrils of BC and MFC in the networkswere estimated to be in the ranges of 79–88 and 29–36GPa, respectively. It is shown also that for the model to fit thedata it is necessary to use a negative Poisson’s ratio forMFC networks and BC networks. Discussion of this in-plane “auxetic”behavior is given. [ABSTRACT FROM AUTHOR]

Biominerals exhibit morphologies, hierarchical ordering and properties that invariably surpass those of their synthetic counterparts. A key feature of these materials, which sets them apart from synthetic crystals, is their nanocomposite structure, which derives from intimate association of organic molecules with the mineral host. We here demonstrate the production of artificial biominerals where single crystals of calcite occlude a remarkable 13?wt% of 20?nm anionic diblock copolymer micelles, which act as 'pseudo-proteins'. The synthetic crystals exhibit analogous texture and defect structures to biogenic calcite crystals and are harder than pure calcite. Further, the micelles are specifically adsorbed on {104} faces and undergo a change in shape on incorporation within the crystal lattice. This system provides a unique model for understanding biomineral formation, giving insight into both the mechanism of occlusion of biomacromolecules within single crystals, and the relationship between the macroscopic mechanical properties of a crystal and its microscopic structure. [ABSTRACT FROM AUTHOR]

Quantitative insights into the stress-transfer mechanisms that determine the mechanical properties of tunicate cellulose whisker/poly(vinyl acetate) nanocomposites were gained by Raman spectroscopy. The extent of stress-transfer is influenced by local orientation (or anisotropy) of the whiskers, which in turn is governed by the processing conditions used to fabricate the nanocomposites. Solution-cast materials display no microscopic anisotropy, while samples that were cast and subsequently compression molded contain both isotropic regions as well as domains of locally oriented whiskers. Polarized optical microscopy showed these regions to have dimensions in the hundreds of μm. Polarized Raman spectroscopy of the 1095 cm−1 Raman band, associated with C−O ring stretching of the cellulose backbone, was used to quantify the local orientation of the cellulose whiskers. Clear and discernible shifts of this Raman band upon uniaxial deformation of nanocomposite films were further used to determine the level of stress experienced by the cellulose whiskers, ultimately reflecting the levels of stress-transfer predominantly between the poly(vinyl acetate) matrix and the tunicate whiskers, but also between the whiskers within the network. In the isotropic regions, where whiskers form a percolating network, the observed Raman shift rate with respect to strain is smaller than in the regions where the whiskers are uniaxially orientated. The Raman shift is strongly affected by the presence of water, leading to a lack of stress-transfer when the samples are fully hydrated, which is clearly detected by the Raman technique. Heating of the nanocomposites above the glass transition temperature of the poly(vinyl acetate) matrix also reduces the stress experienced by the individual whiskers. [ABSTRACT FROM AUTHOR]

Abstract: Interfacial stress transfer in a model hybrid composite has been investigated. An Sm3+ doped glass fibre and a high-modulus regenerated cellulose fibre were embedded in close proximity to each other in an epoxy resin matrix dumbbell-shaped model composite. This model composite was then deformed until the glass fibre fragmented. Shifts of the absolute positions of a Raman band from the cellulose fibre, located at 1095cm−1, and a luminescence band from a doped glass fibre, located at 648nm, were recorded simultaneously. A calibration of these shifts, for both fibres deformed in air, was used to determine the point-to-point distribution of strain in the fibres around the breaks in the glass fibre. Each break that occurred in the glass fibre during fragmentation was shown to generate a local stress concentration in the cellulose fibre, which was quantified using Raman spectroscopy. Using theoretical model fits to the data it is shown that the interfacial shear stress between both fibres and the resin can be determined. A stress concentration factor (SCF) was also determined for the regenerated cellulose fibre, showing how the presence of debonding reduces this factor. This study offers a new approach for following the micromechanics of the interfaces within hybrid composite materials, in particular where plant fibres are used to replace glass fibres. [Copyright &y& Elsevier]