Filters

Settings

Now showing1 - 10 of 17
  • Some of the metrics are blocked by your 
    consent settings
    Item type:Project, Access status: without files ,
      27
  • Some of the metrics are blocked by your 
    consent settings
    Item type:Project, Access status: without files ,
    Aqueous Electrolytes in Nanoporous Media: Structure, Dynamics and Electrochemo-Mechanical Actuation
    An electrolyte solution near a charged solid surface forms an electric double layer (EDL). While the theory of EDLs has been known since the 1850s, their structure and dynamics are much less understood in the confined geometry of nanoporous media. There, large interfacial curvatures and overlapping EDLs of opposing interfaces can lead to significant property changes compared to planar geometries. Furthermore, EDL formation can lead to changes in mechanical interfacial stresses at the single pore scale and thus to macroscopic material deformation. In this project, this electrochemo-mechanical actuation will be related to the structure and dynamics of the EDL for aqueous electrolytes in nanoporous carbons. For this purpose, experiments and molecular simulation will be combined from the nanoscopic single-pore scale to the macroscopic scale of the porous medium.We will synthesize electrically conducting nanoporous carbons with high specific surface area, defined pore sizes (1-10 nm) and pore geometries. This will allow fine-tuning of the effect of the interfacial region compared to the rest of the pore volume. By adding heteroatoms to the carbon structure and controlling the defect concentrations, different surface chemistries (hydrophobic vs. hydrophilic) are introduced. Depending on the applied electrical voltage between electrolyte and solid, the surface chemistry and the pore diameter, we will investigate EDL formation and mechanical actuation in the material. We will focus on aqueous solutions of simple salts and investigate the role of salt concentration among other parameters. We will use synchrotron-based X-ray scattering to study the EDL in-operando, with special attention to the charge/discharge and thus ion transport kinetics. We will use molecular dynamics simulations to represent the structural properties of the surface of the nanoporous medium and the electrolyte. This should allow us to derive the structural, thermodynamic and transport properties of the geometrically confined electrolyte and relate them to the experimental results, both in terms of the electrochemo-mechanical couplings and the charge capacities at the scale of the single pore and the porous medium.In addition to these fundamental insights into aqueous electrolytes in geometric confinement, these studies provide the basis for supercapacitors with green, water-based electrolytes. They will also contribute to the development of materials for electromechanical actuators based on novel actuation principles, avoiding the usual piezoceramic systems that contain predominantly environmentally hazardous materials, such as lead.
      99
  • Some of the metrics are blocked by your 
    consent settings
    Item type:Project, Access status: with files ,
      45  5
  • Some of the metrics are blocked by your 
    consent settings
    Item type:Project, Access status: without files ,
      45
  • Some of the metrics are blocked by your 
    consent settings
    Item type:Project, Access status: without files ,
    I³-Projekt - Adaptive optical material based on water condensation in nanoporous structures
    It is expected to demonstrate an adaptive optical material based on water condensation in nanoporous materials. Water-infused nanoporous silica or alumina represent particularly environmentally friendly platform for sustainable development of materials. Such adaptive materials can be used as functional coating for self-regulating surfaces and smart windows where depending on the illumination and temperature the sun radiation can be transmitted, absorbed, or reflected. It can also be used to have an adaptive structural color sensitive to temperature, humidity or even the wavelength of incident radiation. These smart surfaces and windows have large palette of potential applications in the area of effective solar energy utilization overcoming effects of climate change. Self-adjustment is an important property of natural materials. Development of artificial materials with similar capability based on environmentally friendly materials is an important further step in material science. In this I3 project we propose to show one example of such a material with an optical functionality.
      83
  • Some of the metrics are blocked by your 
    consent settings
    Item type:Project, Access status: without files ,
    Energy harvesting via wetting/drying cycles with nanoporous electrodes
    Innovative low-grade waste heat harvesting Conversion, transportation and end-use processes result in massive amounts of energy waste in the form of low-grade heat. Existing technologies for conversion of low-grade waste heat into electricity are expensive. The EU-funded EHAWEDRY project proposes an innovative conversion concept that relies on coupling charging/discharging cycles of electrochemical supercapacitors with the drying/wetting of their nanoporous electrodes. The concept exploits the proportionality of the capacitor capacity to its electrode/electrolyte contact area. The project envisages an innovative harvester prototype that reaches volumetric power densities, comparable to established waste heat recovery technologies such as Rankine cycle engines. The prototype presents design flexibility, scalability and potential for the cost-effective harvesting of low-grade waste heat.
      200
  • Some of the metrics are blocked by your 
    consent settings
    Item type:Project, Access status: without files ,
    Ionic Liquid Crystals Confined in Nanoporous Solids: Self-Assembly, Molecular Mobility and Electro-Optical Functionalities
    Ionic liquid crystals (ILC) bridge the gap between conventional liquid crystalline and ionic matter. Discotic columnar phases along with very high 1-D ion mobility in columnar phases have been found and studied with regard to potential functionalities. These functionalities depend strongly on the type of orientation and translation order. In principle, these orders can be optimized by embedding ILCs in nanostructured solid templates. However, very sparse knowledge is available about the effect of nanoconfinement on ILCs, even though it provides entirely novel self-assembly paths and thus electro-optical functionalities. Here we propose the exploration of the phase behavior of ionic liquid crystals in nanoporous solids and to relate it to the corresponding bulk phenomenology. It shall be scrutinized how the behavior changes as a function of pore-size and pore-surface chemistry, in particular with regard to hydrophilic and hydrophobic pore walls. To this end synchrotron-based X-ray diffraction, dielectric spectroscopy, calorimetry on ILCs confined in monolithic nanoporous silica, silicon and alumina membranes shall be performed. This will allow detailed insights in the structure and dynamics of the confined mesogens. The project particularly profits from the complementary expertise of the research groups involved, i.e. microscopic translational and orientational order (Huber), thermodynamics and molecular dynamics (Schoenhals) and tailored synthesis of ILCs (Laschat). Moreover, the functionalities with regard to optical anisotropy, optical activity, dielectric properties and electrical conductivity will be systematically explored and the mesogen interactions tailored with respect to mesophase formation and mesogen-pore wall interaction in order to optimize these functionalities. Specifically, we intend to explore ILCs forming discotic hexagonal phases with high charge carrier mobilities along the columnar axis. In addition, interactions of chiral ILCs with the pores will be studied regarding confinement-induced formation of chiral mesophases, absent in the bulk state. It is expected that by proper pore surface-grafting and pore-size selection optical and electrical functionalities can be tuned. The study is aimed at a fundamental understanding of the physical chemistry of confined ILCs, but also at the functionalities of the resulting hybrid materials, consisting of soft functional ILC fillings in monolithic solids providing mechanical stability.The successful realization of the project requires an intense cooperation between the three research groups because the chemical molecular structure (synthesis) determines the supermolecular structures and the molecular dynamics as well as the interaction with the confining walls in nanoporous solids. Besides the expected synergistic benefit on the scientific results the PhD students will significantly profit in their scientific education and from the cooperative spirit of this research project.
      197
  • Some of the metrics are blocked by your 
    consent settings
    Item type:Project, Access status: without files ,
      81
  • Some of the metrics are blocked by your 
    consent settings
    Item type:Project, Access status: without files ,
    SFB 986: Subproject C10 - Photonic Metamaterials with Adjustable and Switchable Anisotropy by Functionalization of Porous Solids with Liquid Crystals
    In this project, liquid crystals are to be combined with the self-organized nanoporosity in solids of silicon, quartz glass and anodically oxidized aluminum (AA0) to design optical materials with adjustable and switchable linear and circular birefringence. Thermotropic chiral and achiral systems of rod and disc-shaped molecules are investigated as liquid crystalline systems. On the one hand, the fundamental understanding of the self-assembly of these mesogens in porous media will be expanded. On the other hand, it will be investigated from a materials science point of view how porosity on the meso- and macroscale in solids can be combined with soft matter to produce mechanically robust 3-D photonic metamaterials.
      215
  • Some of the metrics are blocked by your 
    consent settings
    Item type:Project, Access status: without files ,
    Dynamic Electrowetting at Nanoporous Surfaces: Switchable Spreading, Imbibition, and Elastocapillarity
    Electrically conductive substrates, such as surfaces of nanoporous metals and semiconductors allow one to control the wetting energies of electrolytes by electrical potentials. Thereby, it is possible to tune droplet shape and liquid spreading dynamics at surfaces, however also the imbibition into the porous surface is under external control via electrical potential-dependent curvatures of the liquid menisci within the nanopores. Moreover, the enormous Laplace pressures and fluid-solid interfacial stresses, typical of nanopore-confined liquids, induce noticeable deformations of the porous solids, and thus result in the case of electrowetting in a potential-dependent coupling of liquid capillarity with solid elasticity, i.e. electrically switchable elastocapillarity. The complex interplay of these phenomenologies (droplet shape dynamics, imbibition and deformation behaviour) have been barely explored to date. Here, it is proposed to explore experimentally the wetting dynamics of aqueous electrolytes at tailored, single-crystalline silicon surfaces traversed by a parallel array of tubular nanopores along with the intimately related elastic deformation of the solids under electrical potential control of the solid-liquid interfacial tension. Both direct and electrowetting with dielectric oxide layers at the nanopore surfaces shall be studied. The existence of precursor films, droplet spreading and imbibition dynamics as well as the deformation on the microscopic (atomic silicon lattice) and macroscopic (substrate) scale will be scrutinized by time-dependent droplet shape analysis, opto-fluidic interferometry, dilatometry and synchrotron-based in-situ x-ray diffraction under variation of the mean pore diameter and porosity of the surface. The experiments shall be analysed in close cooperation with projects in this priority program focusing on computational modelling and mesoscopic phenomenological theories for liquid spreading, imbibition and elastocapillarity at planar and porous surfaces. The overarching objective of this project is a fundamental, predictive understanding of electrically switchable static and dynamic wetting at nanoporous surfaces.
      125