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Celluloses and nanofibrillar celluloses, and the basis of their luminescence are studied. Comparative studies of photoluminescence of birch kraft pulp and microfibrillar and nanofibrillar celluloses manufactured from the same pulp were made with the aim to investigate their luminescence properties. Comparison was made with the earlier literature and the origin of the photoluminescence of these cellulose variants is discussed.

Nanocellulose containing materials, such as micro-fibrillated cellulose (MFC) and nanofibrillated cellulose (NFC), are potential additives which could improve strength properties of coated paper and board surfaces and thus substitute natural and synthetic cobinders, such as carboxymethyl cellulose (CMC) and polyacrylic thickeners, in pigmented coating formulations. The aim of this study is to evaluate whether MFC/NFC can be used in coating colours as sole co-binder. In this investigation, the change of rheological and dewatering behaviour of coating colours, having a single blend of pigments (ground calcium carbonate and kaolin clay) together with a latex emulsion binder, is studied when CMC is used as sole co-binder and during its partial and finally total replacement with MFC/NFC. The findings suggest that even though all coatings show viscoelasticity, MFC/NFC is seen to relate to the gel-like nature of the nanoparticles in the coating colour whereas the viscoelastic behaviour in the case of CMC is induced by differential flocculation amongst the pigment and latex binder. The flocculation mechanism is predicted to be necessary in order to provide the link between water retention and elastic structure recovery where anti-sagging is a prerequisite, such as in the coating of rough substrates, e.g. for board and packaging.

3rd Generation photovoltaic systems such as dye-sensitized solar cells offer almost limitless material base that can be tested in variety of combinations with unique cell designs. One of the key challenges that remains with the dye-sensitized solar cells is to reduce their fabrication cost without compromising the performance. Such a target can only be achieved by fabricating inexpensive and abundantly available materials with simple and rapid preparatory methods that could deliver robust characteristics within the cell. With this motivation, we report here successful implementation of a highly conductive flexible fiber based substrate in dye-sensitized solar cell which is fabricated by coating a low temperature single walled carbon nanotube ink over a laminated fiber sheet. The substrate exhibited extraordinary durability under severe mechanical stability test conditions, reasonable overall efficiency (6.0±0.3%) and charge transfer resistance (3.3±1.6 Ω cm 2 ).

An algorithm on geometrical data extraction, material reconstruction and numerical analysis is presented in order to reconstruct the actual wood-like cellular materials and investigate their linear elastic material behavior in the transverse plane under different loading conditions. The algorithm implemented by Mathematica technical computing software is used to read the pixel data of cellular material images with a wide range of material scales, e.g. from micro- to millimeter scale. As a result of this process, geometrical properties including cell wall thicknesses, cell connectivities, vertex and center coordinates are determined. Identified geometrical properties are transferred to Abaqus/CAE computer aided engineering software by using a Python script and also converted into stereolithography STL model format enabling prototype generation and visualization. As an application example, the reconstructed model by means of the algorithm was used to investigate the in-plane effective stiffness properties of Norway spruce earlywood specimens in the frameworks of homogenization and finite element analysis.

Carbon based perovskite solar cells are fabricated for the first time in a room temperature environment by employing inkjet infiltration of perovskite precursor ink. The fabricated perovskite solar cells exhibit impressive performance reproducibility with this automated method and exhibit high stability when exposed to 35 degrees C for a period of 1046 hours.

Biocomposites were prepared by solvent casting from poly(vinyl) alcohol and mechanically microfibrillated (MFC) birch pulp. Preparations varied in concentration of polymer solution, mixing time of cellulose/PVA dispersion and were either degassed or not. In addition, specimens were tested in different levels of relative humidity at a constant temperature. The results show that the preparation method has a significant influence on mechanical properties. It was observed that aggregation of microfibrills was easier at lower concentrations of polymer solution leading to inferior properties of composites. Degassing provided increase in Young’s modulus and tensile strength at MFC loads below 10% (w/w). However, there was no significant change in composites density. Longer mixing time significantly deteriorated mechanical properties of biocomposites. The relative humidity proved to be very important factor. The properties of composites conditioned at 45% RH showed higher strength and stiffness properties than conditioned at 55 %RH. The experimental data were in a good agreement with percolation model.

Thermal conductivity of paper coatings is increasingly important in the performance of many printing processes, including traditional heatset web offset and thermal papers, as well as digital processes, such as electrophotography. This work studies the extension of a Modified Lumped Parameter Model, previously used successfully to describe talc coatings, to model the thermal conductivity–coating structure relationships of calcium carbonate (gcc: 60 wt% < 2 μm) coatings. A series of compact tablets were used to provide experimental values of thermal diffusivity and conductivity. The samples studied covered a range of latex binder addition levels, namely 0–25 parts, based on 100 parts pigment, of 0.2 μm styrene acrylate latex. Combining the observed thermal properties with knowledge of the pore structure changes induced by the latex addition, it is possible to establish initial correlation with the model, in which the connectivity of the structure is increased at low latex dose illustrating the initial increase in effective thermal conductivity. The practically hard sphere properties of the latex used, combined with the broad size distribution of the gcc, produce a disruptive packing effect as the dose level increases, such that the conductivity reflects a competition between the increasing connectivity provided by the latex versus the increasing relative pore size in the network structure. It is recognized that the fixed pigment volume in the model unit cell diverts from a true representation of the residual porosity. At the highest latex dose levels, the intrinsically less conducting properties of the latex begin to dominate.

Polymeric and activated carbon composite membranes were prepared and their morphology quantitatively, tensile properties and performance (flux and cut-off) were characterized. Both types of membranes were prepared by using polysulfone and di-methyl formamide as polymer and solvent, respectively. In order to obtain a wide range of morphologies, two non-solvents were used (water and iso-propanol) and eight coagulation baths were produced by using the non-solvents alone, by mixing them and by mixing each one with the solvent. Numerical values for the main morphological properties of the membrane were determined from micrographs obtained by scanning electron microscopy, atomic force microscopy and IFME® software. The tensile properties were also determined. Finally, the performance of the membranes in terms of flux and cut-off was determined. Results show that varying the coagulation bath can lead to a wide range of morphologies and cut-off. In the range studied, the presence of activated carbon on the membranes does not significantly change the properties studied. Neither the morphology nor the tensile properties are significantly modified. Finally, the presence of water in the coagulation bath very clearly determines the tensile properties of membranes.

We demonstrate that superhydrophobic and superoleophobic nanocellulose aerogels, consisting of fibrillar networks and aggregates with structures at different length scales, support considerable load on a water surface and also on oils as inspired by floatation of insects on water due to their superhydrophobic legs. The aerogel is capable of supporting a weight nearly 3 orders of magnitude larger than the weight of the aerogel itself. The load support is achieved by surface tension acting at different length scales: at the macroscopic scale along the perimeter of the carrier, and at the microscopic scale along the cellulose nanofibers by preventing soaking of the aerogel thus ensuring buoyancy. Furthermore, we demonstrate high-adhesive pinning of water and oil droplets, gas permeability, light reflection at the plastron in water and oil, and viscous drag reduction of the fluorinated aerogel in contact with oil. We foresee applications including buoyant, gas permeable, dirt-repellent coatings for miniature sensors and other devices floating on generic liquid surfaces.