Ligno cellulosic materials for energy storage

The constantly increasing production of a large variety of portable consumer electronic devices and the urgent request of replacement of polluting, internal combustion cars with more efficient, controlled emissions vehicles, such as hybrid or electric vehicles require the development of new reliable and safe power sources. Furthermore the continuous decrease of the oil resources and the growing concern on the climate changes call for a larger use of green, alternative energy sources, such as solar and wind. But wind does not blow on command and the sun does not always shine thus, this discontinuity in operation leads to the need of suitable storage systems to efficiently run renewable energy plants. It is evident that a new energy economy has to emerge, and it must be based on a cheap and sustainable energy supply. Lithium ion batteries, due to their high-energy efficiency, appear as ideal candidates. Although these batteries are well established commercial products, further research and development is required to improve their performance to meet the market requirements. In particular, enhancement in safety, cost, and energy density are needed. A big portion of the R&D studies are nowadays devoted to the search for optimal materials both for the electrodes and the electrolyte of the battery: as far as the electrolyte is concerned, the main goal is to replace the liquid electrolyte with a solid one. The passage to a solid configuration gives concrete promise of increasing cell safety and reliability and, at the same time, of offering modularity in design and ease of handling. Behind the optimization of existing batteries a big effort in this field is the transformation of current batteries into a light, flexible, portable device. If integrated structures containing the three essential components (electrodes, spacer, and electrolyte) of the electrochemical cells can be made mechanically flexible, it would enable these to be embedded into various functional devices in a wide range of innovative products such as smart cards, displays, and implantable medical devices. In the fabrication of such a device the exploitation of cellulose as a flexible material and at the same time the exploitation of the papermaking and printing techniques for the development of paper electrodes and electrolytes and, in a future, of the full paper battery, is under consideration. This will also open the way to a reinvestment of the paper technologies in a high tech field such as the Lithium based batteries. Paper industry, as a matter of fact, is in Europe an important manufacturing industry but the economic change together with the development of electronics highly threaten the role and the surviving of such an activity. In this context grows the urgent need for higher value-added paper products and the conversion of the traditional paper industry. Introducing paper into new products with more profitable markets is crucial. The research work of the present thesis has been developed in collaboration with the "Centre Technique du Papier "(CTP) in Grenoble (Fr). The work has been focused on the use of cellulose in the form of handsheet or microfibrils for the production of innovative electrolyte membranes to be used in Li-based batteries. Two research lines have been followed: 1- Development of composite membranes based on cellulose microfibrils and a polymeric matrix obtained by photopolymerisation of reactive oligomers. 2- Development of multilayered membranes made of cellulose handsheet and polymeric layers obtained by photopolymerisation of reactive oligomers. Both the research lines adopt the photopolymerisation process for developing the membranes. In particular using multifunctional monomers, highly cross-linked polymer membranes are obtained which can be successfully used as gel or solid polymer electrolytes. The process is fast, low cost and versatile. In fact a fully cured polymer is obtained in seconds at room temperature irradiating a proper mixture of reactive molecules and photoinitiato

Ligno cellulosic materials for energy storage

The constantly increasing production of a large variety of portable consumer electronic devices and the urgent request of replacement of polluting, internal combustion cars with more efficient, controlled emissions vehicles, such as hybrid or electric vehicles require the development of new reliable and safe power sources. Furthermore the continuous decrease of the oil resources and the growing concern on the climate changes call for a larger use of green, alternative energy sources, such as solar and wind. But wind does not blow on command and the sun does not always shine thus, this discontinuity in operation leads to the need of suitable storage systems to efficiently run renewable energy plants. It is evident that a new energy economy has to emerge, and it must be based on a cheap and sustainable energy supply. Lithium ion batteries, due to their high-energy efficiency, appear as ideal candidates. Although these batteries are well established commercial products, further research and development is required to improve their performance to meet the market requirements. In particular, enhancement in safety, cost, and energy density are needed. A big portion of the R&D studies are nowadays devoted to the search for optimal materials both for the electrodes and the electrolyte of the battery: as far as the electrolyte is concerned, the main goal is to replace the liquid electrolyte with a solid one. The passage to a solid configuration gives concrete promise of increasing cell safety and reliability and, at the same time, of offering modularity in design and ease of handling. Behind the optimization of existing batteries a big effort in this field is the transformation of current batteries into a light, flexible, portable device. If integrated structures containing the three essential components (electrodes, spacer, and electrolyte) of the electrochemical cells can be made mechanically flexible, it would enable these to be embedded into various functional devices in a wide range of innovative products such as smart cards, displays, and implantable medical devices. In the fabrication of such a device the exploitation of cellulose as a flexible material and at the same time the exploitation of the papermaking and printing techniques for the development of paper electrodes and electrolytes and, in a future, of the full paper battery, is under consideration. This will also open the way to a reinvestment of the paper technologies in a high tech field such as the Lithium based batteries. Paper industry, as a matter of fact, is in Europe an important manufacturing industry but the economic change together with the development of electronics highly threaten the role and the surviving of such an activity. In this context grows the urgent need for higher value-added paper products and the conversion of the traditional paper industry. Introducing paper into new products with more profitable markets is crucial. The research work of the present thesis has been developed in collaboration with the “Centre Technique du Papier “(CTP) in Grenoble (Fr). The work has been focused on the use of cellulose in the form of handsheet or microfibrils for the production of innovative electrolyte membranes to be used in Li-based batteries. Two research lines have been followed: 1- Development of composite membranes based on cellulose microfibrils and a polymeric matrix obtained by photopolymerisation of reactive oligomers. 2- Development of multilayered membranes made of cellulose handsheet and polymeric layers obtained by photopolymerisation of reactive oligomers. Both the research lines adopt the photopolymerisation process for developing the membranes. In particular using multifunctional monomers, highly cross-linked polymer membranes are obtained which can be successfully used as gel or solid polymer electrolytes. The process is fast, low cost and versatile. In fact a fully cured polymer is obtained in seconds at room temperature irradiating a proper mixture of reactive molecules and photoinitiator

Development of New Hybrid Acrylic/Epoxy DLP-3D Printable Materials

Light induced three dimensional (3D) printing techniques generally use printable formulations that are based on acrylic monomers because of their fast reactivity, which is balanced with their good final properties. However, the possibility to enlarge the palette of 3D printable materials is a challenging target. In this work, hybrid printable formulations that are based on acrylic and epoxy resins are presented and their printability on DLP (Digital Light Processing) machines is demonstrated. Hexanediol diacrylate (HDDA) and an epoxy resin—3,4-Epoxycylohexylmethyl-3',4' epoxycyxlohexane carboxylate (CE)—in different ratios are used and the influence of a bridging agent, Glycidyl methacrylate (GMA), is also investigated. The reactivity of the different active species during irradiation is evaluated and the mechanical properties, including the impact toughness, the thermo-mechanical properties, and the volumetric shrinkage, are studied on printed samples

Light Processable Starch Hydrogels

Light processable hydrogels were successfully fabricated by utilizing maize starch as raw material. To render light processability, starch was gelatinized and methacrylated by simple reaction with methacrylic anhydride. The methacrylated starch was then evaluated for its photocuring reactivity and 3D printability by digital light processing (DLP). Hydrogels with good mechanical properties and biocompatibility were obtained by direct curing from aqueous solution containing lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP) as photo-initiator. The properties of the hydrogels were tunable by simply changing the concentration of starch in water. Photo-rheology showed that the formulations with 10 or 15 wt% starch started curing immediately and reached G' plateau after only 60 s, while it took 90 s for the 5 wt% formulation. The properties of the photocured hydrogels were further characterized by rheology, compressive tests, and swelling experiments. Increasing the starch content from 10 to 15 wt% increased the compressive stiffness from 13 to 20 kPa. This covers the stiffness of different body tissues giving promise for the use of the hydrogels in tissue engineering applications. Good cell viability with human fibroblast cells was confirmed for all three starch hydrogel formulations indicating no negative effects from the methacrylation or photo-crosslinking reaction. Finally, the light processability of methacrylated starch by digital light processing (DLP) 3D printing directly from aqueous solution was successfully demonstrated. Altogether the results are promising for future application of the hydrogels in tissue engineering and as cell carriers

3D Printing of PDMS-Like Polymer Nanocomposites with Enhanced Thermal Conductivity: Boron Nitride Based Photocuring System

This study demonstrates the possibility of forming 3D structures with enhanced thermal conductivity (k) by vat printing a silicone–acrylate based nanocomposite. Polydimethylsiloxane (PDSM) represent a common silicone-based polymer used in several applications from electronics to microfluidics. Unfortunately, the k value of the polymer is low, so a composite is required to be formed in order to increase its thermal conductivity. Several types of fillers are available to reach this result. In this study, boron nitride (BN) nanoparticles were used to increase the thermal conductivity of a PDMS-like photocurable matrix. A digital light processing (DLP) system was employed to form complex structures. The viscosity of the formulation was firstly investigated; photorheology and attenuate total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) analyses were done to check the reactivity of the system that resulted as suitable for DLP printing. Mechanical and thermal analyses were performed on printed samples through dynamic mechanical thermal analysis (DMTA) and tensile tests, revealing a positive effect of the BN nanoparticles. Morphological characterization was performed by scanning electron microscopy (SEM). Finally, thermal analysis demonstrated that the thermal conductivity of the material was improved, maintaining the possibility of producing 3D printable formulations

In Situ Thermal Generation of Silver Nanoparticles in 3D Printed Polymeric Structures

Polymer nanocomposites have always attracted the interest of researchers and industry because of their potential combination of properties from both the nanofillers and the hosting matrix. Gathering nanomaterials and 3D printing could offer clear advantages and numerous new opportunities in several application fields. Embedding nanofillers in a polymeric matrix could improve the final material properties but usually the printing process gets more difficult. Considering this drawback, in this paper we propose a method to obtain polymer nanocomposites by in situ generation of nanoparticles after the printing process. 3D structures were fabricated through a Digital Light Processing (DLP) system by disolving metal salts in the starting liquid formulation. The 3D fabrication is followed by a thermal treatment in order to induce in situ generation of metal nanoparticles (NPs) in the polymer matrix. Comprehensive studies were systematically performed on the thermo-mechanical characteristics, morphology and electrical properties of the 3D printed nanocomposites

3D Printing of PDMS-Like Polymer Nanocomposites with Enhanced Thermal Conductivity: Boron Nitride Based Photocuring System

This study demonstrates the possibility of forming 3D structures with enhanced thermal conductivity (k) by vat printing a silicone–acrylate based nanocomposite. Polydimethylsiloxane (PDSM) represent a common silicone-based polymer used in several applications from electronics to microfluidics. Unfortunately, the k value of the polymer is low, so a composite is required to be formed in order to increase its thermal conductivity. Several types of fillers are available to reach this result. In this study, boron nitride (BN) nanoparticles were used to increase the thermal conductivity of a PDMS-like photocurable matrix. A digital light processing (DLP) system was employed to form complex structures. The viscosity of the formulation was firstly investigated; photorheology and attenuate total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) analyses were done to check the reactivity of the system that resulted as suitable for DLP printing. Mechanical and thermal analyses were performed on printed samples through dynamic mechanical thermal analysis (DMTA) and tensile tests, revealing a positive effect of the BN nanoparticles. Morphological characterization was performed by scanning electron microscopy (SEM). Finally, thermal analysis demonstrated that the thermal conductivity of the material was improved, maintaining the possibility of producing 3D printable formulations

Tunable photo-responsive elastic metamaterials

The metamaterial paradigm has allowed an unprecedented space-time control of various physical fields, including elastic and acoustic waves. Despite the wide variety of metamaterial configurations proposed so far, most of the existing solutions display a frequency response that cannot be tuned, once the structures are fabricated. Few exceptions include systems controlled by electric or magnetic fields, temperature, radio waves and mechanical stimuli, which may often be unpractical for real-world implementations. To overcome this limitation, we introduce here a polymeric 3D-printed elastic metamaterial whose transmission spectrum can be deterministically tuned by a light field. We demonstrate the reversible doubling of the width of an existing frequency band gap upon selective laser illumination. This feature is exploited to provide an elastic-switch functionality with a one-minute lag time, over one hundred cycles. In perspective, light-responsive components can bring substantial improvements to active devices for elastic wave control, such as beam-splitters, switches and filters

Study on the Printability through Digital Light Processing Technique of Ionic Liquids for CO2 Capture

Here we present new 3D printable materials based on the introduction of different commercially available ionic liquids (ILs) in the starting formulations. We evaluate the influence of these additives on the printability of such formulations through light-induced 3D printing (digital light processing-DLP), investigating as well the effect of ionic liquids with polymerizable groups. The physical chemical properties of such materials are compared, focusing on the permeability towards CO2 of the different ILs present in the formulations. At last, we show the possibility of 3D printing high complexity structures, which could be the base of new high complexity filters for a more efficient CO2 capture