Interfaces with Fluorinated Amphiphiles: Superstructures and Microfluidics

The present mini-review discusses recent developments in research on interfacial phenomena of fluorinated amphiphiles, focusing on applications that exploit the unique and manifold interfacial properties associated with these amphiphiles. Most notably, fluorinated amphiphiles form stable aggregates with often distinctly different morphologies than their non-fluorinated counterparts. Consequently, fluorinated surfactants have found wide use in high-performance applications such as microfluidic-assisted screening. Additionally, their fluorine-specific behaviour at the solid/liquid interface, such as the formation of superhydrophobic coatings after deposition on surfaces, will be discussed. As fluorinated surfactants and perfluorinated materials in general pose potential environmental threats, recent developments in their remediation based on their adsorption onto fluorinated surfaces will be evaluated

Grenzflächen mit fluorierten Amphiphilen: Überstrukturen und Mikrofluidik

Der vorliegende Aufsatz diskutiert die jüngsten Entwicklungen in der Forschung zu Grenzflächenphänomenen fluorierter Amphiphile und konzentriert sich auf Anwendungen, die die einzigartigen und vielfältigen Grenzflächeneigenschaften dieser Amphiphile ausnutzen. Vor allem bilden fluorierte Amphiphile stabile Aggregate mit oft deutlich anderer Morphologie als ihre nicht fluorierten Analoga. Folglich finden fluorierte Tenside vielfältigen Einsatz in Hochleistungsanwendungen wie dem Mikrofluidik-unterstützten Screening. Darüber hinaus wird ihr fluorspezifisches Verhalten an der Fest/Flüssig-Grenzfläche thematisiert, wie zum Beispiel die Bildung superhydrophober Beschichtungen nach der Abscheidung auf Oberflächen. Da fluorierte Tenside und perfluorierte Materialien im Allgemeinen potenzielle Umweltbedrohungen darstellen, werden auch die jüngsten Entwicklungen der Schadstoffsanierung durch ihre Adsorption an fluorierte Oberflächen bewertet

Shape optimization of road tunnel cross-section by simulated annealing

The paper concerns shape optimization of a tunnel excavation cross-section. The study incorporates optimization procedure of the simulated annealing (SA). The form of a cost function derives from the energetic optimality condition, formulated in the authors’ previous papers. The utilized algorithm takes advantage of the optimization procedure already published by the authors. Unlike other approaches presented in literature, the one introduced in this paper takes into consideration a practical requirement of preserving fixed clearance gauge. Itasca Flac software is utilized in numerical examples. The optimal excavation shapes are determined for five different in situ stress ratios. This factor significantly affects the optimal topology of excavation. The resulting shapes are elongated in the direction of a principal stress greater value. Moreover, the obtained optimal shapes have smooth contours circumscribing the gauge

Application of Nanoindentation and 2D and 3D Imaging to Characterise Selected Features of the Internal Microstructure of Spun Concrete

The spinning of concrete is a process in which concrete mixture is moulded and compacted under the action of the centrifugal force arising during the fast rotational motion of the mould around its longitudinal axis. As a result of the spinning of the liquid concrete mixture, an element annular in cross section, characterised by an inhomogeneous layered wall structure, is produced. The heavier constituents tend towards the cross-section wall’s outer side, while the lighter components tend towards its inner side. The way in which the particular constituents are distributed in the element’s cross section is of key importance for the macro properties of the manufactured product. This paper presents procedures for investigating spun concrete and interpreting the results of such investigations, which make it possible to characterise the microstructure of the concrete. Three investigative methods were used to assess the distribution of the constituents in the cross section of the element: micro-computed tomography (µCT), 2D imaging (using an optical scanner) and nanoindentation. A procedure for interpreting and analysing the results is proposed. The procedure enables one to quantitatively characterise the following features of the microstructure of spun concrete: the mechanical parameters of the mortar, the aggregate content, the pore content, the cement paste content, the aggregate grading and the size (dimensions) of the pores. Special attention is devoted to the determination of the variation of the analysed quantities in the cross section of the element. The result of the application of the investigative procedures is presented for an exemplary spun concrete element. The proposed procedures constitute a valuable tool for evaluating the process of manufacturing spun concrete elements

Parameters of the constitutive model of geomaterials formed with the use of DSM dry technology

Numerical modelling of geomaterials is always complex due to the variability of parameters within the soil massif (created in the natural geological processes) and the orthotropy caused by this. In the case of the soil substrate modification with the use of hydraulic binders, this issue is complicated even more due to the fact the degree of mixing can be differentiated for various areas, while in the dry mixing technology, it is additionally differentiated with the depth of consolidation stress. Additional factor that makes it difficult to predict the behaviour of stabilised soil is the possible content of organic parts. Due to the development of substrate reinforcement technology, as well as the growing market for such works, a need emerged to provide parameters of the numerical model for various materials or, at least, to provide a method for reverse analysis on the basis of available data. This paper presents an example of calibration of the selected numerical model (through parameter selection of this model) based on the conducted examinations of cubic sample in the conditions of uniaxial compression. The results of laboratory tests, reverse analysis in the numerical model with a pre-selected strength hypothesis and finally, the recommendations for selection of the model in calculations of real structure on a reinforced substrate, are demonstrated

Multi-Scale Structural Assessment of Cellulose Fibres Cement Boards Subjected to High Temperature Treatment

The methodology of multi-scale structural assessment of the different cellulose fibre cement boards subjected to high temperature treatment was proposed. Two specimens were investigated: Board A (air-dry reference specimen) and Board B (exposed to a temperature of 230 °C for 3 h). At macroscale all considered samples were subjected to the three-point bending test. Next, two methodologically different microscopic techniques were used to identify evolution (caused by temperature treatment) of geometrical and mechanical morphology of boards. For that purpose, SEM imaging with EDS analysis and nanoindentation tests were utilized. High temperature was found to have a degrading effect on the fibres contained in the boards. Most of the fibres in the board were burnt-out, or melted into the matrix, leaving cavities and grooves which were visible in all of the tested boards. Nanoindentation tests revealed significant changes of mechanical properties caused by high temperature treatment: “global” decrease of the stiffness (characterized by nanoindentation modulus) and “local” decrease of hardness. The results observed at microscale are in a very good agreement with macroscale behaviour of considered composite. It was shown that it is not sufficient to determine the degree of degradation of fibre-cement boards solely on the basis of bending strength; advanced, microscale laboratory techniques can reveal intrinsic structural changes

Influence of bedding and backfill soil type on deformation of buried sewage pipeline

In the paper, the influence of different types of bedding and backfill soil surrounding underground sewage duct on its deformation was analysed. Impact of increased soil lateral pressure was examined by considering the construction of an embankment nearby the underground pipeline. Numerical computations of three different variants of bedding and backfill soil surrounding the pipe were carried out. Displacements and deformation of the pipe were calculated using the finite element method with adoption of elastic-perfectly plastic constitutive model of soil. Subsequent stages of the construction were taken into account. Shear strength reduction method was applied to evaluate the factor of safety of the entire system. Finally, the results and conclusions were depicted

A comprehensive approach to the optimization of design solutions for dry anti-flood reservoir dams

The article proposes the methodology of designing dams of dry flood control reservoirs. The algorithm is developed so as to meet all the requirements given in the Eurocode 7 and, at the same time, to be efficient in terms of necessary calculation time. Furthermore, the presented numerical procedure enables the optimization of design solutions, e.g. the depth and length of the anti-filtration barrier, by means of parametric analyses. The approach assumes the use of numerical methods, in particular, finite element (FE) analysis. Three-dimensional (3D) reconstruction of the terrain topography and subsoil layer arrangement performed in step (1) sets the base for further analyses. In step (2), the filtration phenomena are assessed based on the 3D analysis of a transient groundwater flow. In step (3), the state of displacement is evaluated and the stability is verified for all the relevant phases of construction and operation of the facility, in particular, in the course of simulated flood detention. The analyses in step (3) are carried out on 2D models corresponding to the design cross-sections of the dam. This significantly reduces the computation time (compared to 3D analysis) and, at the same time, provides a safe estimate of factor of safety. The performance of the proposed algorithm is shown on the numerical examples of the computations concerning the dam of Szalejów Górny dry anti-flood reservoir located in Poland