Ingenieurwissenschaften und zugeordnete Tätigkeiten
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- 5 Werkstofftechnik (10)
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- 5.2 Metallische Hochtemperaturwerkstoffe (7)
- 4.5 Kunst- und Kulturgutanalyse (5)
- 6.6 Physik und chemische Analytik der Polymere (5)
- 9 Komponentensicherheit (5)
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- 7.4 Baustofftechnologie (3)
The chapter gives a brief introduction to (nano)compositecomposite materials having the focus on polymer-based nanocomposites. The different dimensionalities of nanoparticles are introduced, along with their distribution in the matrix.
Different application fields of polymer-based nanocomposites, like flame retardancy, filled rubbers, nanofilled thermosets and thermoplastics, separation membranes and nanodielectrics, are considered in greater detail.
The characterization of the mechanical properties and behaviour of adobe masonry is fundamental for the understanding of the structural behaviour of adobe constructions. Thus, in the last decades, experimental studies focused on this topic have been carried out by different authors. Many of the existing experimental works, however, were carried out aiming to support broader studies focused on the seismic behaviour of adobe constructions and are not very detailed. Moreover, authors tend to adopt different procedures in their experimental work, since there are few indications in existing standards for testing adobe masonry. The wide variety in materials used, both for the adobes and mortars, further complicates this work, making it difficult to compare results obtained in different studies. This chapter provides an overview of the indications given by standards and other technical recommendations for the mechanical testing of adobe masonry. It presents a review of existing research on the mechanical behaviour of adobe masonry, addressing studies that focus on: (i) compression behaviour, (ii) shear behaviour, (iii) joint shear behaviour. It provides a global analysis of the existing knowledge, suggesting improvements for normative documents and identifying future Research needs.
The mechanical characterization of adobe bricks is an important first step in the study of the behaviour of adobe masonry. For this reason, in the last decades, different authors have conducted research on the mechanical behaviour of adobes from various regions of the world. Despite the importance of mechanical characterization, there are still only a few standards and normative documents with clear indications for the mechanical testing of earthen materials and, in general, These indications are not thorough and vary among different countries. Consequently, authors tend to adopt different types of test specimens and procedures in their experimental work, thus obtaining results that are not directly comparable. The fact that the materials and procedures traditionally used are also not standardized,varying greatly from region to region, also contributes to the difficulty of comparing results from different studies. This chapter presents a review of the indications provided by codes, standards and other technical recommendations for the mechanical testing of adobe bricks, as well as a detailed review of procedures adopted, and results obtained by different authors regarding the mechanical characterization of traditional adobe bricks. This chapter focuses, in particular, on the behaviour of adobe bricks when subjected to simple compression. It provides an overview of the existing knowledge and identifies needs for future research and development.
Laser-induced periodic surface structures (LIPSS) are a universal phenomenon and can be generated on almost any material by irradiation with linearly polarized radiation. This chapter reviews the current state in the field of LIPSS, which are formed in a “self-ordered” way and are often accompanying materials processing applications. LIPSS can be produced in a single-stage process and enable surface nanostructuring and, in turn, adaption of optical, mechanical, and chemical surface properties. Typically, they feature a structural size ranging from several micrometers down to less than 100 nm and show a clear correlation with the polarization direction of the light used for their generation. Various types of LIPSS are classified, relevant control parameters are identified, and their material-specific formation mechanisms are analyzed for different types of inorganic solids, i.e., metals, semiconductors, and dielectrics. Finally, technological applications featuring surface functionalization in the fields of optics, fluidics, medicine, and tribology are discussed.
Whilst a decisive role of the particle-matrix interphase on the mechanical properties of nanoparticle-filled polymers has been demonstrated in the last years, the arbitrary design of this interphase remains a very challenging goal. In principle, this could be realized via an appropriate surfacemodification of the nanofiller prior to its incorporation in the polymer. For most systems, such as for boehmite nanofillers, however, the interaction of organic modifiers with the particle surface has not been studied in detail, and only single studies are known rather than systematic investiga- tions on the effects of different chemical functions anchored on the particle surface. In this chapter, we present an extensive study on the binding of APTES, a common silane surface modifier, with boehmite, and show that thermogravimetric analysis (TGA) coupled with mass spectrometry (MS) is a convenient and highly suitable method to elucidate the ligand binding in detail. Furthermore, a two-step coupling strategy is presented, demonstrating that based on APTES anchored to the parti- cle surface, the condensation of various carboxylic acids can be utilized to enable highly diverse chemical properties of the nanofillers, which leads to very different particle-matrix interactions in the nanocomposites.
The large number of TEM investigations and the regular microstructure
of single-crystal nickel-base superalloys has boosted the development of a number of physically motivated constitutive laws. In contrast to the more phenomenological models discussed in the next chapter, these models use dislocation densities as internal variables. Obvious advantages are that the computed densities can be compared to TEM observations and the Deformation mechanisms can be easier translated into mathematical equations.
The elastic constants are the most basic mechanical properties of a material and are needed for any structural analysis of a component. For example, they have a major influence on the eigenfrequencies of vibrating parts. Single crystals of Ni-base superalloys are strongly anisotropic, which means that the observed properties are orientation dependent. Tensor algebra is then required to mathematically formulate the elastic properties and their relations to the crystal orientation. Hence, this chapter first summarizes some basic definitions and calculation rules for Rotation matrices, including the definition of the Euler angles, which are most commonly used to define the relative orientations of the crystal and the component. Parts of this chapter closely follow the lines of the excellent exposition of the topic by Olschewski.
High-temperature corrosion is a widespread problem in various industries.
As soon as a hot and reactive gas (CO2, O2, H2O, SO2, NOx, etc.) is in contact with a solid, physico-chemical processes at the surface and interfaces lead to material degradation. The processes are dynamic and controlled by thermodynamic and kinetic boundary conditions. Whether a reaction product is protective or not depends on various factors, such as chemical composition of the solid and the reactive media, surface treatment as well as diffusion and transport paths of cations and anions. Resulting chemical and structural inhomogeneities with the corrosion layers are characterized by off stoichiometry within cationic and anionic sub lattices. The competitive processes can be studied by various techniques of applied crystallography.
This chapter gives an overview on the challenges of chemical-structural Analysis of reaction products by crystallographic methods such as X-ray diffraction and X-ray near-edge structure spectroscopy and scanning electron microscopy electron backscatter diffraction (SEM-EBSD) for corrosion science.
If a component is cyclically loaded, its load carrying capacity is considerably lower than in the monotonic loading case. This general observation applies in particular to L-PBF parts. The causes of this are mainly material defects such as pores and unwelded regions (Chapter 8) and a pronounced surface roughness in the as-built condition (Chapter 9). In addition, effects due to the anisotropy of the microstructure (Chapter 6) and a complex residual stress pattern (Chapter 7) play an important role. A consequence is that common strategies of fatigue assessment cannot be transferred to L-PBF applications without modifications. Due to the inhomogeneity of the material, the determination of representative material properties and the transfer to the component is a problem, and this is also the case with regard to the consideration of defects, surface roughness and residual stresses. The chapter gives a brief introduction to these problem areas.
In this chapter, the current state-of-the-art of in situ monitoring and in situ NDE methods in additive manufacturing is summarized. The focus is set on methods, which are suitable for making statements about the quality and usability of a component currently being manufactured. This includes methods which can be used to determine state properties like temperature or density, other physical properties like electrical or thermal conductivity, the microstructure, the chemical composition, the actual geometry, or which enable the direct detection of defects like cracks, voids, delaminations, or inclusions. Thus, optical, thermographic, acoustic, and electromagnetic methods, as well as methods being suitable for investigating particle and fume emission are presented. The requirements of in situ monitoring methods with a focus on thermographic methods are discussed by considering different additive manufacturing processes like laser powder bed fusion (PBF-LB/M) and direct energy deposition (DED-LB/M). Examples of the successful implementation and applications of such monitoring methods at BAM are given. The in situ monitoring and NDE methods are compared against post-process NDE methods. The advantages and challenges of in situ methods concerning real-time data analysis and the application of AI algorithms are addressed and discussed.
The complex effect of nanoparticles on an epoxy-based and anhydride cured DGEBA/Boehmite nanocomposite with different particle concentrations is considered in this chapter. A combination of X-ray scattering, calorimetry (fast scanning and temperature modulated calorimetry) and dielectric spectroscopy was employed to characterize the structure, vitrification kinetics and the molecular dynamics of the nanocomposites. Firstly, the unfilled polymer was found to be intrinsically heterogeneous, showing regions with different crosslinking density, indicated by two separate dynamic glass transitions. Moreover, the glass transition temperature decreases with increasing nanoparticle concentration, as a result of changes in the crosslinking density. In addition, it was shown that the incorporation of nanoparticles can result in simultaneous increase in the number of mobile segments for low nanoparticle concentrations and on the other hand, for higher loading degrees the number of mobile segments decreases, due to the formation of an immobilized interphase.
The chapter starts with a brief introduction about corrosion, which is defined as the interdependency between a metal, a corrosive environment, and the respective component design. The second section introduces the most important forms of aqueous electrochemical corrosion (uniform corrosion, galvanic corrosion, selective and intergranular corrosion, and finally pitting and crevice corrosion in the case of passive layer forming metals). In addition, electrochemical corrosion under applied mechanical load is introduced (stress corrosion cracking, hydrogen-assisted cracking, corrosion fatigue), as well as special forms of corrosion (erosion, fretting, and microbiologically induced corrosion). The third section of this chapter introduces (mostly dry) chemical corrosion and high-temperature corrosion (oxidation, carburization, high-temperature hydrogen attack, sulfurization, nitriding, halogenation). As in the case of electrochemical corrosion, chemical corrosion can also be superimposed by mechanical loads. Finally, general facts on the testing of corrosion are introduced.
Das Kapitel beginnt mit einer kurzen Einführung über die Korrosion (Wechselwirkung zwischen einem Metall, einer korrosiven Umgebung und der der jeweiligen Konstruktion). Im zweiten Abschnitt werden die wichtigsten Formen der wässrigen elektrochemischen Korrosion (Flächenkorrosion, galvanische, selektive und interkristalline Korrosion sowie Loch- und Spaltkorrosion) betrachtet. Darüber hinaus wird die elektrochemische Korrosion unter mechanischer Belastung betrachtet (Spannungsrisskorrosion, wasserstoffunterstützte Rissbildung, Korrosionsermüdung), sowie Sonderformen der Korrosion (Erosion, Fretting und mikrobiologisch induzierte Korrosion). Der dritte Abschnitt befasst sich mit der chemischen und Hochtemperaturkorrosion (Oxidation, Aufkohlung, Hochtemperatur-Wasserstoffangriff, Aufschwefelung, Nitrierung, Halogenierung). Zusätzlich enthält das Kapitel Maßnahmen zur Vermeidung der Korrosion.
Die Eigenschaften verschiedener Werkstoffe werden behandelt und typische Werkstoffkennwerte angegeben. Es werden Arten der Beanspruchung von Bauteilen und Werkstoffen vorgestellt, die diese in technischen Anwendungen unterworfen sind. Im Betrieb von Bauteilen kann Materialschädigung und unter Umständen auch Versagen eintreten. Mögliche Mechanismen und Ursachen werden erläutert und Einblicke in die Methodik der Schadensanalyse gegeben.
The Montserrat Codex Miscellaneus (TM 59453/LDAB 552) has been the subject of numerous studies since the publication of ist first text by its owner, father Ramon Roca-Puig. Scholars have dealt with the content of its texts, as well as interrogated its origin and materiality. It is a fourth-century papyrus single quire codex, which contains texts in both Latin and Greek. It has been argued that it belonged to the Bodmer library, connected to a Pachomian library in the Thebaid. In this paper we want to contribute to the material study of the codex by presenting the first results of an archaeometric analysis performed upon the inks. The Analysis was carried out within the framework of the ‘PAThs’ project based at Sapienza University of Rome, and executed with the close cooperation of DVCTVS, a team of scholars who curate the Roca-Puig collection. The results obtained have not only cast light on the history of production of the codex, but also, and perhaps most importantly, point out that a meaningful interpretation of the analytical data is only possible through an interdisciplinary collaboration between the humanities and the natural sciences.
An interdisciplinary approach to the study of manuscript traditions is here applied to the analysis of the leaves from the White Monastery, one of the greatest centres of literary production in Late Antique Egypt. In the framework of the ‘PAThs’ project, archaeometric analyses complement the information pieced together by a range of disciplines in the field of humanities. The use of different complementary analytical techniques provides information on the type of ink used and its elemental composition, unveiling interesting details regarding the materials and methodology of manufacturing of writing media. Moreover, this contribution takes a step forward and discusses the possible existence of a regional arrangement in the elemental composition revealed in the inks studied.
A new race for high performance structural materials has started since the discovery of high entropy alloys at the beginning of the 21st century. The possible combination of several elements in an, until then, unknown composition space opened the ground for discovering new materials. Solid solution strengthening remains the most prominent mechanisms that is active in this family of materials, but it is supported by all other strengthening mechanism on the path to better and better performing materials. Chemical, thermal and mechanical approaches are combined to optimize these alloys. Optimum performances can be reached by using a high number of different strengthening mechanisms, induced both by composition and processing. The most prominent with composition induced mechanism is precipitation hardening, and on the processing side it is cold working such as cold-rolling, torsion or extrusion. The contribution uses tensile test data at room temperature solely for comparison – high temperature and cryogenic data are omitted because it would lead beyond the scope of this manuscript.
Materialprüfung
(2019)
Die Materialprüfung dient der Analyse der Eigenschaften, der Qualität und der Sicherheit vonMaterialien undWerkstoffen. Die häufigsten Verfahren umfassen die Analyse der chemischen Zusammensetzung und der Mikrostruktur sowie die Ermittlung von Werkstoffkennwerten. Dazu zählt auch die Bestimmung des Materialverhaltens unter verschiedenen Beanspruchungen bis hin zu komplexen Beanspruchungen. Die Verwendung von Referenzmaterialien, Referenzorganismen und Referenzverfahren dient der Zuverlässigkeit und Richtigkeit von Messungen, Prüfungen und Analysen.
Twenty years ago, research involving ionic liquids was a minor field of interest, and only a few chemists and even fewer engineers were interested in salts with melting points near room temperature. In April 2000, the first NATO advanced research workshop on ionic liquids was held in Heraklion, Crete. The conference was the first international meeting devoted to ionic liquids and attracted most of the active researchers at that time. Following that meeting, activity in the field began to flourish and the first books and international conferences devoted to ionic liquids began to appear. By the end of 2018, more than 80,000 scientific papers had been published, and 17,000 patents were applied for in the field of ionic liquids! This book provides an overview of the current and emerging industrial applications of ionic liquids covering the core processes and products, the practical implementation and technical challenges involved, and the potential future directions for Research and development. The individual chapters were written by leading scientists in the field from industry and academia to address specific processes and products that are or will be soon commercialized. Examples include the use of a chloroaluminate ionic liquid as a next-generation alkylation catalyst to a new class of capillary gas chromatography (GC) columns with stationary phases based on ionic liquids. Over the past twenty years, there has been a growing realization that ionic liquids have moved from being mere academic curiosities to having genuine applications in fields as wide-ranging as advanced materials, biotechnology, catalysis, pharmaceuticals, renewable fuels, and sustainable energy. There are many optimistic indications that ionic liquids are on their way to becoming a commercial success story. This first book on “Commercial Applications of Ionic Liquids” provides over 50 applications that are either at the pilot scale or have been commercialized, which indicates that an exciting new chapter in the field of ionic liquids is about to begin!
Die Werkstoffklassen
(2020)
Es werden die vier Werkstoffklassen Metalle, Keramiken, Polymere und Verbundwerkstoffe sowie ihre Untergruppen vorgestellt. Die metallischen Werkstoffe umfassen die Eisen- wie die Nichteisenwerkstoffe und ihre Legierungen. Neben den Ingenieurkeramiken werden auch Glas und Glaskeramik, Naturstoffe und Erdstoffe sowie Baustoffe behandelt.