Elena Stojanovska

A review on non-electro nanofibre spinning techniques

A large surface area, scalable porosity, and versatility have made nanofibres one of the most widely investigated morphologies among the nanomaterials. The characteristic properties of nanofibres have made them useful in a broad range of applications, such as filters, membranes, tissue engineering, wound dressings, protective clothing, reinforcement in composite materials, and sensors. So far, various top-down and bottom-up approaches were proposed to produce nanofibres. In this paper, a comprehensive review is presented on non-electro fiber spinning techniques, along with their mechanisms. The parameters of these techniques are also discussed in detail, while process-specific gains were emphasized according to the end uses. This review paper also provides a literature insight into the biomedical, filtration, optical, and energy applications of nanofibres produced via the most typical and widely used methods.

Lignin as an Additive for Advanced Composites

Lignin, an abundant renewable resource material next to cellulose, can be one of the most essential bio-resources as a raw material for the production of environmentally friendly polymers and polymer composites. Due to its chemical structure, lignin can provide additional functionalities in composites. It can be used as reinforcers, fillers, compatibilizers and even stabilizing agents in polymer composites. In this chapter use of lignin in composites, its additional benefits and possible applications were summarized. Structure—process—property relations were particularly emphasized. Because of the aromatic structure and multifunctional side groups, lignin can be a promising, environmentally friendly additive as a free radical scavenger which prevents oxidation reactions. For the structural composite applications, material properties were found to be highly dependent on process conditions. One can observe controversy in the reported mechanical properties of composites with similar components and similar lignin concentrations. Thus in some studies addition of lignin resulted with enhanced strength and modulus; while lignin just acted as a filler in some others. Those studies should be carefully evaluated considering the process conditions. Further improvements can also be achieved after modifying lignin chemically.

Developing lignin-based bio-nanofibers by centrifugal spinning technique

Lignin-based nanofibers were produced via centrifugal spinning from lignin-thermoplastic polyurethane polymer blends. The most suitable process parameters were chosen by optimization of the rotational speed, nozzle diameter and spinneret-to-collector distance using different blend ratios of the two polymers at different total polymer concentrations. The basic characteristics of polymer solutions were enlightened by their viscosity and surface tension. The morphology of the fibers produced was characterized by SEM, while their thermal properties by DSC and TG analysis. Multiply regression was used to determine the parameters that have higher impact on the fiber diameter. It was possible to obtain thermally stable lignin/polyurethane nanofibers with diameters below 500nm. From the aspect of spinnability, 1:1 lignin/TPU contents were shown to be more feasible. On the other side, the most suitable processing parameters were found to be angular velocity of 8500rpm for nozzles of 0.5mm diameter and working distance of 30cm.

Nanofibrous composites for sodium-ion batteries

Abstract Rechargeable energy storage systems have become a focus of interest, owing to the booming need to store large amounts of energy, especially from renewable energy sources. For this purpose, new systems—either based on lithium or other materials—are a must in order to satisfy the new energy requirements, and sodium is one of the candidates to join the game, again after a long time. This implies increased research and development of new materials, including electrodes and electrolytes that can be applied in sodium-ion chemistry. On the side of the electrodes, there has been an extensive progress on the development of anode and cathode materials that increase battery capacity and provide cycling stability. In addition, a variety of structures have also been investigated, including nanofibers due to their 1-D geometry, high surface-to-weight ratio, low density, and the possibility to be produced with different techniques and from different materials. In this regard, this chapter gives a brief introduction into energy storage and explains the mechanism of energy storage in sodium-ion rechargeable batteries. Special focus is put on the recent progress in the development of nanofibrous electrodes for sodium-ion batteries. Nanofiber anodes and cathodes made of different active materials are reviewed, their production methods are described, and their electrochemical performances are analyzed.

Polymer nanocomposites for dye-sensitized solar cells

Abstract Increasing energy demand and global warming problems have pushed humanity to search for new energy sources, such as solar, wind, geothermal, and biomass. Among the renewable energy sources, solar energy is at the forefront with clean and most abundant form of energy and affordable cost/efficiency performance of solar cells. From the various types of solar technologies, dye-sensitized solar cell (DSC) technology is an inexpensive and environmentally friendly solution to meet todays increasing energy needs. The production of DSCs with polymer-based materials enables the production of flexible, lightweight, greener solar cells. These features have also reduced transportation and production costs and have greatly expanded the application. However, the low-temperature resistance of polymer-based materials has been an obstacle to the production of highly efficient flexible cells, which requires the development of new deposition methods and materials. Counter electrodes constructed by the usage of conductive polymers or their composite structure with carbon and its derivatives have enabled the production of more efficient, stable, and cheaper cells by replacing the traditionally used Pt. Additionally, problems like solvent leakage and low chemical stability of volatile liquid electrolyte used in DSCs have been avoided by the use of polymer-based solid-state or quasi-solid-state electrolytes. In this context, polymer nanocomposite structures used in dye-sensitive solar cells with their deposition method and effects on the cell performance are examined in this chapter. Factors and strategies for improving the performance of polymers in DSCs have been reviewed and analyzed. In addition, the benefits and challenges of polymers and their composite structures for use in DSCs have been assessed.