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A new titanium alloy improving the operation of implants additively manufactured and including laterally closed lattice structures is proposed. The new alloy possesses an increased affinity to the bone. The measured bone–interface implant (BII) of less than 10 mm and bone–implant contact (BIC) of 95% demonstrated an excellent osseointegration. Furthermore, since additive manufacturing naturally leads to a high-roughness surface finish, the wettability of the implant is increased. The combination of these factors is pushing ossification beyond its natural limits. In addition, the quality and speed of the ossification and osseointegration in/around laterally closed lattice implants open the possibility of bone spline key of prostheses. This enables the stabilization of the implant into the bone while keeping the possibility of punctual hooks allowing the implant to be removed more easily if required.
Ancient Inks
(2023)
In the last decade scientists and scholars have accumulated more knowledge on black ink used for writing in Antiquity and the early Middle Ages.
Ready availability of non-destructive testing instruments employed in interdisciplinary projects on historic manuscripts have made it possible to determine the composition of ink and to compare it with the extant records.
The current state of preservation of the DSS results from the synergetic effect of various factors such as great age, post-discovery treatments, poor storage conditions, environmental influences and exhibitions. With rare exceptions, neither the initial state nor a list of the treatments performed on each DSS fragment is known. Reconstruction of the individual fragment history will have to rely upon advanced analytical techniques to identify the treatments and their effects.
Management of the scrolls may be divided roughly into three periods: a) the scholarly archiving period, from 1948 to the mid-1960s; b) first attempts at conservation, from the mid-1960s to late-1980s; c) Israel Antiquities Authority Scrolls Lab, from 1991 onwards.
Only the nano-scaled structure of the nanocomposite and the dispersion of nanoparticles within the polymer matrix harbor multifunctional potential including superior fire retardancy. Thus, this chapter focuses on the dispersion of nanoplates, based mainly on studies of layered silicates and graphene/graphene-related nanoplates. The nanostructure and properties of the nanocomposites are dependent mainly on thermodynamic and kinetic factors during preparation. Improving nano-dispersion often directly improves flame retardancy. Therefore, the modification of the nanoplates as well as the preparation of nanocomposites becomes very important to control this dispersion. The dispersion of nanoplates functions as a prerequisite for the formation of an efficient protective layer, changing the melt flow and dripping behavior, or the improvement of the char properties.
We discuss the non-linear stress–strain behavior of microcracked polycrystalline ceramics under uniaxial tension and compression (displacement control).
Micromechanics explanation and modeling of its basic features, such as non-linearity and hysteresis in stress–strain curves, are developed, with stable microcrack propagation and “roughness” of intergranular cracks playing critical roles in tension and crack sliding playing a critical role in compression. Experiments involving complex loading histories are explained, and themodel is shown to reproduce the basic features of the observed stress–strain curves.
Lehmmauerwerk bietet sich aufgrund seiner zahlreichen ökologischen Vorteile für die Errichtung klimafreundlicher und ressourcenschonender Gebäude an. Um den Anwendungsbereich tragenden Lehmmauerwerks durch eine zeitgemäße Nachweisführung zu erweitern, werden in diesem Beitrag Grundlagen für die Entwicklung eines eurocodekonformen Bemessungskonzepts erarbeitet. Hierzu werden die Ergebnisse umfangreicher experimenteller Untersuchungen an Lehmmauerwerk sowie Lehmsteinen und -mörteln nach Konditionierung bei unterschiedlichen Klimata vorgestellt. Darauf aufbauend erfolgt eine Traglastanalyse druckbeanspruchter Lehmmauerwerkswände mittels numerischer und analytischer Methoden. Die daraus gewonnenen Erkenntnisse werden abschließend in einen an DIN~EN~1996-3/NA angelehnten Bemessungsvorschlag überführt, welcher die materialspezifischen Besonderheiten von Lehmmauerwerk berücksichtigt und eine fundierte Grundlage für eine wirtschaftliche und zuverlässige Nachweisführung darstellt.
Irradiation of solid surfaces with intense ultrashort laser pulses represents a unique way of depositing energy into materials. It allows to realize states of extreme electronic excitation and/or very high temperature and pressure and to drive materials close to and beyond fundamental stability limits. As a consequence, structural changes and phase transitions often occur along unusual pathways and under strongly nonequilibrium conditions. Due to the inherent multiscale nature—both temporally and spatially—of these irreversible processes, their direct experimental observation requires techniques that combine high temporal resolution with the appropriate spatial resolution and the capability to obtain good quality data on a single pulse/event basis. In this respect, fourth-generation light sources, namely, short wavelength and short pulse free electron lasers (FELs), are offering new and fascinating possibilities. As an example, this chapter will discuss the results of scattering experiments carried out at the FLASH free electron laser at DESY (Hamburg, Germany), which allowed us to resolve laser-induced structure formation at surfaces on the nanometer to submicron length scale and in temporal regimes ranging from picoseconds to several nanoseconds with sub-picosecond resolution.
Surface nanostructures provide the possibility to create and tailor surface functionalities mainly via controlling their topography along with other chemical and physical material properties. One of the most appealing technologies for surface functionalization via micro- and nanostructuring is based on laser processing. This can be done either via direct contour-shaping of the irradiated material using a tightly focused laser beam or in a self-ordered way that allows employing larger laser beam diameters along with areal scanning to create a variety of laser-induced periodic surface structures (LIPSS). For the latter approach, particularly ultrashort pulsed lasers have recently pushed the borders across long-lasting limitations regarding the minimum achievable feature sizes and additionally boosted up the production times. This chapter reviews the plethora of recently investigated applications of LIPSS—for example, via imposing diffractive or plasmonic structural colors, the management of liquids and surface wetting properties, biomedical and bioinspired functionalities, beneficial effects in tribology for reducing friction and wear, the manipulation of optical scattering and absorption in photovoltaics, or the modification of magnetic or superconducting surface properties in other energy applications. The footprint of the LIPSS-based technology is explored in detail regarding the current state of industrialization, including an analysis of the market and associated LIPSS production costs.
Nickel-Iron-Alloy Modification to Enhance Additively Welded Microstructure for Subsequent Milling
(2022)
The aerospace industry uses nickel–iron alloys, e.g., FeNi36, to create moulding tools for composite materials, since these alloys have a low coefficient of thermal expansion. Nickel–iron alloys are hard-to-cut materials. The moulding tools are large in size and involve complex structures, making them cost-intensive and difficult to manufacture. Thus, the focus is set on additive manufacturing, which can additionally enable the repair of components in order to eliminate local defects. However, the process usually results in a heterogeneous microstructure and anisotropic mechanical properties. As there is a high demand for a precise and exact fit of the precision moulds and the surface quality, the welded components must be subsequently machined. Additionally, inhomogeneous microstructure may lead to unstable cutting forces and conditions. Consequently, a modification of the microstructure morphology is achieved through specific alloy modifications in order to stabilise and improve the subsequent machining process. Therefore, titanium and zirconium are chosen as modification elements with a maximum 1% weight percent and are added to nickel–iron alloy powder. The elements are alloyed, and build-up welded by plasma-transferred-arcwelding. The resulting microstructure morphology of the welded wall structure and the machining properties are then determined. It can be shown that titanium has a significant effect on the structural morphology of the welded layers, as well as on the machining.
Epoxy-Based Nanocomposites—What Can Be Learned from Dielectric and Calorimetric Investigations?
(2022)
Epoxy-based nanocomposites are promisingmaterials for industrial applications (i.e., aerospace, marine, and automotive industries) due to their extraordinary mechanical and thermal properties. Regardless of the broad field of applications, there is still a considerable need to identify their structure–property relationships. Here, a detailed dielectric and calorimetric (DSC and fast scanning calorimetry) study on different epoxy-based nanocomposites was performed. Bisphenol A diglycidyl ether (DGEBA) cured with diethylenetriamine (DETA) was employed as the polymeric matrix, which was reinforced with three diverse nanofillers that exhibit different interaction strengths with the epoxy matrix (halloysite nanotubes, surface modified halloysite nanotubes, and taurine-modified layered double hydroxide). The structure, molecular mobility, and vitrification behavior are discussed in detail, focusing on the intrinsic structural and dynamic heterogeneity, as well as interfacial properties.
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.
Properties of interstitial liquid phase in cement paste, including the species and concentrations of polymers and ion etc., play an important role for the rheological properties of cementitious materials. In order to better understand their effect, an inert model substance, spherical silica beads (SBs) with defined surface and granulometry were used in the presence of electrolytes (CaCl2) and/or different polymers, including polycarboxylate superplasticizer (PCE) and polyethylene glycol (PEG). It was found the presence of Ca2+ greatly increases the viscosity and yield stress of silica beads paste (SBP), which is proportional to the [Ca2+]. For the effect of PCE, the addition of PCE is beneficial to the flowability of SBP, but a high dosage of PCE leads to a reversal effect. Furthermore, the yield stress firstly increases and then decreases with increasing [Ca2+] under the same dosage of PCE. The addition of PEG always increases the yield stress of SBP, regardless of the ion concentration and the presence or not of PCE.
The flowability of cement paste is of great importance in today’s construction industry and is influenced by additives such as superplasticizers (SP). One type of SPs are polycarboxylate ether type SPs. These additives electrostatically bind with the negatively charged carboxylic groups at the backbone to the positively charged clinker phases.
To model positively charged clinker phases with adsorbed SP, silicon Wafers are pre-coated with cationic polyethylenimine (PEI) and SP is adsorbed onto the coated surface (Si/PEI/SP). Two different polycarboxylate ether type (PCE) SP are compared – one for ready-mix concrete and one for precast concrete. In this preliminary study the interaction forces between Si/PEI/SP surface and a silica microsphere (colloidal probe) are investigated under mild physico-chemical conditions (pH *6, ion concentration <10−5 M) using Colloidal Probe Atomic Force Microscopy (CP-AFM).
The interaction force between the model surfaces is attractive for low concentration of SP. The force changes from attractive to repulsive by increasing amount of SP. The force upon approach reveals a biexponential behavior. The exponential decay at large and short surface separations are attributed to electrostatic and steric interactions, respectively. The steric forces of the SP for ready-mix concrete show a steeper onset than the SP for precast concrete.
The quantification of these interaction forces will be compared to rheological measurements of similar systems. Furthermore, the parameters will be changed to better approach the conditions in real systems, i.e. higher pH and ionic strength. This helps to understand how the forces on the nanoscale influence the macroscopic rheology.
Special applications like pumping, spraying or printing of concrete require the precise adjustment of very specific rheological properties at different time steps during the casting process. Superplasticizers such as polycarboxylate ethers (PCE) can be used to obtain the required flowability, which, possibly in combination with additional rheology modifying admixtures, generate the required specified consistency. However, after the application, the concrete should change the rheological properties immediately in order to avoid deformations at rest. Therefore, the use of accelerators can be effective. Accelerators influence the hydration of cementitious materials, and thus the rheological properties over the course of time and the setting.
In this paper, the influence of different accelerators on the rheology and early hydration of cement paste as well as the interaction of accelerator and PCE are presented. Methods like rheometry, needle penetration tests and practical Tests like spread flow were applied. The used accelerators showed accelerating behavior on the cement pastes without and in the presence of PCE. At the same time an influence on the rheology could be observed. This effect was less in the mixes with PCE, especially at the highest water/cement ratio (w/c).
Der Aufbau der Werkstoffe wird durch Merkmale wie Bindungsart, atomare Strukturen, Kristallstrukturen einschließlich ihrer Gitterbaufehler, Körner und Phasen bestimmt. Die Mikrostruktur (Gefüge) stellt den Verbund der Kristalle, Phasen und Gitterbaufehler auf mikroskopischer und nanoskopischer Skala dar. Die Grundlagen der Phasenumwandlungen werden behandelt und die Bedeutung von Diffusionsprozessen erläutert. Werkstoffe sind bedeutend für Kultur, Wirtschaft, Technik und Umwelt. Ihre Herstellung benötigt Ressourcen und Energie. Recycling ist eine Möglichkeit zur Erhöhung der Ressourcenproduktivität.
The European building sector is moving towards more complex and high-tech building approaches. While focusing on energy efficiency, aspects e.g. occupant health, sustainability and life cycle costing are often neglected. This study highlights the potential of earthen plasters in combination with natural ventilation for low-tech solutions.
The EU funded project [H]house established the outstanding performance of earthen materials in light of hygrothermal and air purifying properties, which were further supported by experimental data from monitoring of naturally ventilated pilot buildings in Berlin. Additionally, [H]house demonstrated through LCC an increased cost efficiency of earth based low-tech solutions in comparison to conventional constructions relying on mechanical ventilation.
Elastomers are usually reinforced by large amount of fillers like carbon black (CB) or silica in order to improve various mechanical properties, such as Young’s modulus, hardness, tear resistance, abrasion resistance, and gas barrier properties. In recent years, such improvements were also obtained by using nanoparticles at significantly lower filler loadings. Graphene is a twodimensional (2D) sheet of a thickness in the atomic scale, composed of a honeycomb structure of sp2 carbon atoms. Besides significant mechanical reinforcement, graphene harbors the potential to be used as a multifunctional filler, as it can also increase the conductivity and weathering stability of elastomer matrices. Ultraviolet (UV) irradiation and oxidative agents can lead to the degradation of elastomers due to a multistep photooxidative process, including the formation of radicals. Carbon-based fillers have an influence on these reactions, as they can absorb UV radiation and act as radical scavengers.
This chapter summarizes the results of our larger project on multilayer graphene (MLG)/elastomer nanocomposites, previously published, which present a comprehensive case study of MLG as a multifunctional nanofiller in elastomer/graphene nanocomposites. Different elastomeric matrices are compared in order to demonstrate the outstanding impact of MLG as a general benefit. The dependency of this effect on concentration is discussed in detail. Taking into account the key role of dispersion, different mixing procedures are compared, evaluating a facile implementation of graphene nanocomposites into conventional rubber processing. Finally, the most probable commercial uses of MLG nanofillers in combination with conventional CB are studied. The nanocomposites were prepared in the kg scale in order to obtain enough specimens to investigate various properties of the uncured and vulcanized rubbers at the highest quality level, including rheology, curing, morphology, several mechanical properties, abrasion, conductivity, gas permeation, burning behavior, and weathering stability. The structure property relationships are asserted and questioned, for example, by investigating the radical scavenging ability or aspect ratio of the MLG. This chapter illustrates the state of the art of graphene/rubber nanocomposites targeted for commercial mass applications.
Various methods have been used for introducing fire retardant additives into polymers. Deposition of thick fire retardant coatings directly onto polymer substrates is an alternative technique. An important advantage of the coating technique is the preservation of the physical and chemical integrity of the polymer material. Moreover, the fire retardancy of the polymer materials can be achieved following their production. Suitable coating materials are inorganics, intumescent, char-forming, oxygendiluting, and cooling or radical quenching layers. The most important problem is to achieve sufficient coating thickness to withstand the direct attack of flame and to protect the polymer bulk from pyrolysis, otherwise blistering of coating, caused by emitted pyrolysis gases, is often observed. To avoid blistering of coating, the adhesion between polyolefin substrate and fire retardant coating has to be extraordinarily high.
In order to achieve such a high level of adhesion, the polymer surface has to be modified with adhesion-promoting functional groups. The deposition of thin plasma polymers as adhesion-promoting layers with NH2, OH or COOH groups has been the most suited method. These functional groups are able to form covalent bonds and other interactions between the fire-resistant coating and the plasma-modified polyolefin substrate. Additionally, the plasma polymer counteracts the strong mechanical stresses in the laminate on exposure to high temperatures by its flexibility.
This chapter deals with the development of polyetheretherketone (PEEK) and polytetrafluoroethylene (PTFE)-based composites, optimized for low friction and low wear performance under extreme environments. It is demonstrated that the incorporation of a harder polymer component into PTFE (such as PEEK particles), a short fiber reinforcement (e.g. carbon fibers (CFs)) and internal lubricants (e.g. PTFE particles) helps to reduce the friction and to improve the wear resistance over a very wide temperature range.
A combination of different complementary methods is employed to investigate scaling of the molecular dynamics of two different liquid crystals. Each method is sensitive to different kind of fluctuations and provides therefore a different window to look at the molecular dynamics. In detail, broadband dielectric spectroscopy is combined with specific heat spectroscopy and neutron scattering. As systems the nematic liquid crystal E7 and a discotic liquid crystalline pyrene are considered. First of all it was proven that both systems show all peculiarities which are characteristic for glassy dynamics and the glassy state. Especially for the nematic liquid crystal E7 it could be unambiguously shown by a combination of dielectric and specific heat spectroscopy that the tumbling mode is the underlying motional process responsible for glassy dynamics. Dielectric investigations on the discotic liquid crystalline pyrene reveal that at the phase transition from the plastic crystalline to the hexagonal columnar liquid crystalline phase the molecular dynamics changes from a more strong to fragile temperature dependence of the relaxation rates. Moreover a combination of results obtained by specific heat spectroscopy with structural methods allows an estimation of the length scale relevant for the glass transition.
In present chapter, the potential usage of peroxy-fuels (usually known as organic peroxides) either in technically pure or in a blended form in engine combustion processes are explored. Although as additives (in small quantities <5% to conventional fuels, e.g., diesel, gasoline) peroxy-fuels are well known for many years their commercial applications as a main or primary fuel are not investigated in detail as such except a few. Their thermal instability and energy density demand great care during processing, which restricts their commercial exploitation. However, once the issues with safety are resolved they can be much more advantageously employed than conventional fuels. Some of these advantages are significant amount of fuel saving, reduction in amount of inducted air, or even the complete absence of air, i.e., anaerobic combustion, smaller volume of combustion (chamber), oxygenated fuel quality, and low emissions. An idea to develop the components of an engine operating solely on peroxy-fuels is also introduced. The engine concept is based on single and multiple injectors in a cylinder with special material coating to ensure a temperature-controlled processing.
Performing mechanical tests at high temperatures is a nontrivial issue: Compared to room temperature testing, additional phenomena like time-dependent Deformation processes and oxidation effects raise the complexity of the material’s response, while more sophisticated test setups and additional control parameters increase the number of potential sources of error. To a large extent, these complications can be overcome by carefully following all recommendations given in the respective high temperature testing standards, but more comprehensive background information helps to identify points of specific importance in particular test campaigns. In this chapter, an overview is given on general high temperature testing issues like the appropriate choice of experimental equipment and key aspects of temperature measurement. In subsequent sections, the major static and dynamic high temperature test methods are reviewed and their Special features, as compared to testing at room temperature, are highlighted based on example data sets. Influences of specimen size and environmental effects are shortly outlined in a concluding section. In the whole chapter, a focus is set on testing of “classical” metallic high temperature materials, but many considerations are equally valid for testing of intermetallics, composites, and high temperature ceramics.
The implementation of fluorescent methods is of outstanding importance in the field of optical chemical sensor Technology and biosciences. Their bioanalytical applications are manifold including fluorescence microscopy, fluorescence in situ hybridization, DNA sequencing, fluorescence-activated cell sorting, immunoassays, analysis of DNA and Protein microarrays, and quantitative PCR, just to name a few examples. Particularly, fluorescence microscopy is a valuable method in the versatile field of biomedical imaging methods which nowadays utilizes different fluorescence Parameters like emission wavelength/Color and lifetime for the discrimination between different targets. Sectional Images are available with confocal microscopes. Tissue, cells or single cellular compartments can be stained and visualized with fluorescent dyes and biomolecules can be selectively labeled with fluorescent dyes to Monitor biomolecular interactions inside cells or at Membrane bound receptors.
On the other hand , fluorophores can act as indicator (or "molecular probe") to visualize intrinsically colorless and non-fluorescent ionic and neutral analytes such as pH, Oxygen (pO2), metal ions, anions, hydrogen peroxide or bioactive small organic molecules such as Sugars or nucleotides. Thereby, their photoluminescent properties (fluorescence or phoporescence intensity, exitation and/or Emission wavelength, emission lifetime or anisotropy) respond to the presence of these species in their immediate Environment. In general, the use of luminescent probes has the advantage that they can be delivered directly into the sample, and detected in a contactless remote mode. By now, these probes are often encapsulated in different types of nanoparticles (NPs) made from (biodegradable) organic polymers, biopolymers or inorganic materials like silica or bound to their surface.
Sintern
(2018)
Unter Sintern versteht man allgemein die Überführung eines aus Pulver geformten Rohlings in ein Formteil mit angestrebter Mikrostruktur bzw. gewünschten Gebrauchseigenschaften durch thermische Prozesse. In diesem Kapitel werden die Grundlagen zu Triebkräften und Kinetik sowie die prinzipiellen Mechanismen für Stofftransport und Verdichtung vorgestellt. Die verschiedenen Sintermechanismen Festphasensintern, Flüssigphasensintern und Reaktionssintern werden erläutert und mit einem Überblick über Drucksinterverfahren ergänzt. Abschließend wird ein Überblick über technologische Einflussfaktoren auf die Sinterung gegeben.
Given their unique properties, ultrashort laser pulses with durations in the femtosecond to picosecond range currently open new avenues in the field of laser materials processing, resulting in groundbreaking new applications based on laser-induced surface functionalization. This article reviews the usability of temporally distributed energy deposition via double-pulse irradiation in applications based on laser ablation. This includes simple new techniques for surface nanostructuring and improved sensitivities in spectroscopic material analyses.
Im Beitrag wird über die mühevolle Sanierung von Objekten eines Kunstzweiges in Polen berichtet, der eine besondere diffizile Stellung in der langen Reihe von Werken der Kunst einnimmt. Es geht dabei um die bleiverglasten farbigen Fensterverschlüsse in Kirchen oder Profangebäuden. Das sind feingliedrige Gitterwerke aus zerbrechlichen und korrosionsanfälligen Materialien, die durch aggressive Umweltschadstoffe schweren Belastungen ausgesetzt sind. Wie bei keinem anderen Kunstzweig haben die einzelnen Bestandteile der Glasmalerei sowohl praktisch-technische als auch ästhetisch-künstlerische Aufgaben zu erfüllen. Bei der Restaurierung dieser Glasmalereifenster geht darum, neuentwickelte Methoden der Restaurierung oder Konservierung anzuwenden und letzte Erkenntnisse naturwissenschaftlicher Forschung zu nutzen. Diese Projekte sind ein Beispiel der interdisziplinären Zusammenarbeit zwischen Denkmalpflegern, Naturwissenschaftlern und Restauratoren aus Deutschland und Polen. An ausgewählten Restaurierungsobjekten wird von der fachgerechten, denkmalpflegerisch verantwortungsbewussten Arbeit berichtet.
Literature provides a wide range of hydrogen diffusion coefficients for low alloyed steels used in power plants. In fact, experimental boundary conditions and calculation methods have influence on the determination of these coefficients. The diffusion and trapping behavior in creep-resistant steel 7CrMoVTiB10-10 has been studied. Based on experimental carrier gas hot extraction (CGHE) data, a numerical model has been developed to describe the hydrogen transport and respective hydrogen distribution at elevated temperatures. The numerical results suggest that common calculation methods for diffusion coefficients are limited for experimental data analysis. The sample preparation time before CGHE experiment influences the determined diffusion coefficients with the consequence that non-homogeneous hydrogen concentration profiles have to be considered in the simulations.
Unterschiedliche Werkstoffeigenschaften reagieren auf jeweils spezifische Weise auf Gittertyp, Gefüge und Defekte. Für die schadenstolerante Betrachtung von Werkstoff und Bauteil ist das Verständnis dieser Zusammenhänge essentiell. Der Beitrag gibt mit Hinblick auf additiv gefertigte metallische Bauteile mittels Selective Laser Melting einen kurzen, keineswegs vollständigen Überblick über Faktoren, die die Steifigkeit, Festigkeit, Duktilität, Zähigkeit, Ermüdungsrissausbreitung und Schwingfestigkeit beeinflussen. Es wird aufgezeigt, wie die bruchmechanische Betrachtung zur Quantifizierung der Zusammenhänge beitragen kann.
China
(2017)
The contributions included in the book provide a reconnaissance on the conservation rules and current protection policies of more than 100 countries, with particular attention to the emerging nations and twentieth-century architecture. The contributions illustrate the critical issues related to architectural listings, with a brief history of national approaches, a linkography and a short bibliography. The book also provides a short critical lexicography, with 12 papers written by scholars and experts including topics on identities, heritages, conservation, memories and the economy. By examining the methods used to designate building as heritage sites across the continents, this book provides a com¬prehensive overview of current protection policies of twentieth-century architecture as well as the role of architectural history.
In diesem Beitrag werden numerische Analysen der mechanischen Eigenschaften von Lehmsteinmauerwerk unter Druck- und Schubbeanspruchung vorgestellt. Ergebnisse von einachsigen Druck- und Schubversuchen an Wandprüfkörpern lieferten dafür grundlegende mechanische Kennwerte im elastischen Bereich und im nichtelastischen Versagenszustand.Die Testergebnisse zeigten, dass verschiedene Vorlasten keinen wesentlichen Einfluss auf die Schubfestigkeit haben. Außerdem bestätigten die Ergebnisse das spröde Verhalten von Lehmsteinmauerwerk unter einachsiger Druckbelastung und es zeigte sich, dass das Versagen des Lehmsteinmauerwerks unter Scherbelastung entlang der Mörtelfugen erfolgt.
Die experimentellen Ergebnisse wurden verwendet, um das Verhalten von Lehmsteinmauerwerk durch nichtlineare Finite-Elemente-Methoden auf der Basis von Makro- und Mikro-Modellierungsansätzen zu simulieren. Entsprechendes konstitutives Materialverhalten und Zwängungen, die in den Versuchen durch die Art der Lasteinleitung in Form von Stahlprofilen und Stahlschuhen verursacht wurden, wurde in den Modellen berücksichtigt. Es wurde zuerst ein auf der Grundlage der experimentellen Daten kalibriertes Makro-Modell entwickelt, was zu einer brauchbaren Vorhersage des Versagensverhaltens der Mauerwerksprüfkörper führte. Die simulierten Spannungs-Dehnungs-Kurven, berechnet unter einachsiger Druckbelastung, zeigten eine gute Übereinstimmung mit den Ergebnissen der geprüften Mauerwerkskörper, sowohl im elastischen als auch im nichtelastischen Bereich. Ein vereinfachter Ansatz, basierend auf der Makro-Modellierung und einem homogenisierten Prüfkörper, kann für die Untersuchung größerer Tragsysteme oder ganzer Gebäude angewendet werden, wobei eine zufriedenstellende Genauigkeit bei geringerem Rechenaufwand erreicht wird. Obwohl das globale Spannungs-Dehnungs-Verhalten zufriedenstellend wiedergegeben wurde, ist ein solches nichtlineares isotropes Kontinuumsmodell für Lehmsteinmauerwerk nicht in vollem Umfang geeignet, um das bei den Versuchen beobachtete Rissbild an den Prüfkörpern zu simulieren.
Eine detailliertere Analyse des mechanischen Verhaltensdes Mauerwerks wurde mit einem Mikro-Modellierungsansatz durchgeführt. Das Modell, in dem ein Wandabschnitt nicht mehr homogenisiert, sondern in konkrete Stein- und Fugenelemente diskretisiert wird, hat sich insbesondere für das Verhalten von Lehmsteinmauerwerk unter Schubbeanspruchung als geeignet erwiesen. Die Auswertung der Spannungsverteilungen bei der nichtlinearen Analyse lieferte Informationen über die tatsächlichen Mechanismen der Lastübertragung zwischen Steinen und Mörtelfugen. Mit dem Mikro-Modell war es möglich, das nichtlineare Verhalten von Lehmsteinmauerwerk vorherzusagen. Es stellt somit ein geeignetes Werkzeug für die Untersuchung der Versagensmechanismen von Lehmsteinmauerwerk dar. Allerdings sind aufgrund der Komplexität des Modells für die Beschreibung der Stein/Mörtel-Schnittstelle und die hohe Anzahl an erforderlichen mechanischen Parametern umfassendere Untersuchungen notwendig. Die zukünftige Forschung wird sich daher einerseits auf die Verfeinerung der numerischen Modelle und andererseits auf die Simulation komplexer Belastungssituationen und Gebäudekomponenten konzentrieren.
Ziel der vorliegenden Untersuchung war es zu überprüfen, inwiefern eine Bemessungsvorschrift auf Basis von Teilsicherheitsbeiwerten im Lehmmauerwerksbau möglich ist. Bemessungsvorschriften im konventionellen Mauerwerksbau und im Lehmmauerwerksbau waren aufgrund des prinzipiell gleichen Tragverhaltens stets eng miteinander verknüpft. Die im Rahmen dieser Arbeit durchgeführten Druckversuche an Lehmmauermörtel, Lehmsteinen und Lehmmauerwerk konnten zeigen, dass die Streuungen der Festigkeiten von Lehmbaustoffen aufgrund der industriellen Herstellung sehr gering sind. Es konnte festgestellt werden, dass eine Bemessung auf Grundlage des semiprobabilistischen Bemessungskonzeptes in Anlehnung an den konventionellen Mauerwerksbau möglich ist. Neben einem ersten Vorschlag des Teilsicherheitsbeiwertes für den Lastzustand Druck werden Vorschläge für Prüfvorschriften im Lehmbau beziehungsweise deren Modifikation unterbreitet und künftige Forschungsschwerpunkte herausgearbeitet.
Gravity has significant effects on alloy solidification, primarily due to thermosolutal convection and solid phase buoyancy. Since 2004, the European Space Agency has been supporting investigation of these effects by promoting in situ X-ray monitoring of the solidification of aluminium alloys on microgravity platforms, on earth, and in periodically varying g conditions. The first microgravity experiment-investigating foaming of liquid metals - was performed on board a sounding rocket, in 2008. In 2012 the first ever X-ray-monitored solidification of a fully dense metallic alloy in space was achieved: the focus was columnar solidification of an Al-Cu alloy. This was followed in 2015 by a similar experiment, investigating equiaxed solidification. Ground reference experiments were completed in all cases. In addition, experiments have been performed on board parabolic flights-where the effects of varying gravity have been studied. We review here the technical and scientific progress to date, and outline future perspectives.
Im Frühjahr 1969 wurde bei Ausgrabungen der Universität Bonn unter Leitung von Elmar Edel auf der Qubbet el-Hawa ein außergewöhnliches Depot mit Materialien einer antiken Gusswerkstatt gefunden. Im Zuge der Fundteilung gelangten die meisten Stücke des Konvolutes in das Ägyptische Museum der Universität Bonn und werden dort aufbewahrt.
Die Deponierung des für die Forschung zur antiken Metallurgie bisher einzigartigen Konvoluts geschah im Zuge der Nachnutzung von Grabanlagen aus dem Alten Reich (um 2100 v. u. Z.) in der ägyptischen Spätzeit (um 550 – 400 v. u. Z.). Das Depot enthält Objekte, die alle Fertigungsstufen von Metallgegenständen im Wachsausschmelzverfahren dokumentieren. Es wurden Stücke von Rohwachs sowie Wachsmodelle und die zu deren Herstellung genutzten Negativformen gefunden. Weiterhin enthielt es vollständige Gussformen, die in einem aufwendigen Mehrschalenverfahren hergestellt wurden und teilweise bereits für den Guss ausgebrannt worden sind. Schließlich zählen einige Metallfiguren sowie weitere figürliche Objekte zum Konvolut, die alle in den Bereich einer kunsthandwerklichen Werkstatt deuten. Eine Besonderheit stellen zudem Gussformen dar, in denen Fragmente von Metallfiguren zur Reparatur im Überfangguss vorbereitet waren.
Das Depot wurde in der Gesamtpublikation der Bonner Grabungen bisher nur summarisch vorgestellt. 2014/15 initiierten die Abteilung Ägyptologie der Universität Bonn und das LVR-LandesMuseum Bonn unter Ludwig D. Morenz und Michael Schmauder ein gemeinsames und von der Fritz-Thyssen-Stiftung gefördertes Forschungsprojekt, das von Martin Fitzenreiter, Johannes Auenmüller und Frank Willer geleitet wurde. In Kooperation mit Dietmar Meinel (Bundesanstalt für Materialforschung und -prüfung Berlin / BAM, Fachbereich 8.5 Mikro-ZfP), Roland Schwab (Curt-Engelhorn-Zentrum Archäometrie gGmbH, Mannheim), Gerwulf Schneider (FU Berlin, Exzellenzcluster TOPOI), Ursula Baumer und Patrick Dietemann (beide Doerner-Institut / München), Thorsten Geisler-Wierwille (Steinmann Institut für Geologie, Mineralogie und Paläontologie der Universität Bonn) sowie Ursula Tegtmeier (Labor für Archäobotanik der Universität Köln) wurden die Objekte des Konvolutes eingehend und mit zeitgemäßen Verfahren untersucht. Die Ergebnisse dieses Forschungsprojekts werden in dieser Publikation vorgelegt.
Welding is the most important joining technology. In the steel construction
industry, e.g. production of windmill sections, welding accounts for a
main part of the manufacturing costs and resource consumption. Moreover, social
issues attached to welding involve working in dangerous environments. This aspect
has unfortunately been neglected so far, in light of a predominant focus on economics
combined with a lack of suitable assessment methods. In this chapter,
exemplary welding processes are presented that reduce the environmental and
social impacts of thick metal plate welding. Social and environmental Life Cycle
Assessments for a thick metal plate joint are conducted for the purpose of
expressing and analysing the social and environmental impacts of welding.
Furthermore, it is shown that state-of-the-art technologies like Gas Metal Arc
Welding with modified spray arcs and Laser Arc-Hybrid Welding serve to increase
social and environmental performance in contrast to common technologies, and
therefore offer great potential for sustainable manufacturing.
Cylinder valves for oxygen service that meet the standard DIN EN ISO 10297 should be safe, if properly handled by the user. In the last few years, however, the number of incidents with oxygen valves that has been reported to Federal Institute for Materials Research and Testing (BAM) has increased. According to the incident reports, incorrect handling can be ruled out. People were seriously injured and in most cases, the causes of these incidents were not clear. Very often, such incidents occurred during opening and closing of the valves. Therefore, the technical-scientific community has put the existing test methods for type testing more and more into question. Besides other mandatory tests, the above-mentioned standard allows to perform the endurance test with air or with nitrogen. This is appropriate for all other gases but not for oxygen. Up to now, this test does not consider the fact that cylinder valves also contain nonmetallic seat materials and lubricants that may react with oxygen in a dangerous way. Because of this unsatisfactory situation, BAM initiated a research project to perform endurance testing of cylinder valves for oxygen service much more practice related with oxygen. This test simulates very well real life situations when the cylinder valve is opened or closed. The first part of this project was the development of a new oxygen operated endurance tester in accordance with DIN EN ISO 10297. In a second part, endurance testing of valves with air and with oxygen was performed and the results were compared. In addition, another mandatory test of the standard, the oxygen pressure surge test was carried out on new valves and on valves that had undergone endurance tests with air or oxygen, to see the influence on the burn-out safety of such pre-stressed valves. This paper presents the main results of the project. The findings clearly speak for implementing the oxygen endurance test not only to DIN EN ISO 10297 but also to various other standards to increase the burn-out safety of oxygen cylinder valves.
Reference nanomaterials
(2016)
This chapter reviews relevant aspects of the still less explored field of RNMs. In the first part, definition of RMs according to different metrological levels was presented as well as the general strategy on their development. In the second part, the importance of RNMs in material science and nanotoxicology is explained and considerations on the use of silica nano-objects as potential future reference material was discussed. Overall, several points should be highlighted from this chapter: Definition of a reference material depends on the level of standardization. Certified reference material represents the highest level of traceability. Different types of reference materials, standard materials and certified reference materials are available, as shown in Table 3.1. The preparation of nano-objects with well-defined mechanical properties is still an unsolved issue and thus needs further R&D activities. Nevertheless, amorphous silica seems to be a promising candidate for reaching this objective. Traceable properties of nanomaterials are still limited to few cases such as primary particle size and thickness measurements of very thin films. In general, developed RMs are monoparametric thus, only one characteristic of the nano-objects is reported. In nanotoxicology, the challenge is in the development of suitable RNM that bears similarities to the measurements made on the sample analysed.
The one-phase methods described in Chapter 2 were shown to be able to predict casting to some extent, but could not depict segregation, sedimentation and blockage occurring during flow. On the other hand, the distinct element methods described in Chapter 3 did not take into account the presence of two phases in the system and describes concrete as distinct elements interacting through more or less complex laws. A reliable numerical model of a multiphase material behaviour shall take into account both phases (solid and liquid). From the numerical point of view, concrete flow shall be seen therefore as the free surface flow of a highly-concentrated suspension of rigid grains.
Alumina thin films
(2016)
This chapter gives an overview over preparation, properties and applications of alumina thin films. The preparation of polymeric and colloidal alumina sols and their deposition on diverse substrate materials with different geometries are described first. Consideration of properties (surface tension, particle size, viscosity, aging of the sols and their optimization by using certain additives) is included, too. A description of post-treatments of the coatings, which initiate phase transformations and also determine their microstructure, completes the part on coating preparation. Data on adhesion, thickness, surface roughness and mechanical, textural as well as optical properties of alumina thin films are provided in a further paragraph. In a third main part experience concerning possible applications, such as (i) membranes for catalysis, separation and filtration, (ii) barrier layers against electrochemical and high temperature corrosion or inter-diffusion of ions between different phases, (iii) mechanical protection, (iv) sensor construction, (v) improvement of optical properties, as well as (vi) achieving water repellency is summarized.
Im Rahmen des abgeschlossenen EU-Projekts NIKER (www.niker.eu) wurden die mechanischen Eigenschaften von Lehmsteinmauerwerk untersucht. Im ersten Teil wurde das mechanische Verhalten unter statischer Druck- und Schubbeanspruchung bestimmt. Ziel dieser Untersuchungen war es, grundlegende Daten zum Verformungs- und Versagensverhalten von Lehmbauteilen zu erhalten und dieses mit einem numerischen Modell zu beschreiben. Die Versuchsergebnisse belegten das spröde Verhalten von Lehmmauerwerk bei uniaxialer Druckbelastung und zeigten, dass das Versagen von Lehmmauerwerk infolge Schubbelastung nach Erstrissbildung in Mörtelfugen und Lehmsteinen durch Gleiten der Lehmsteine entlang der Mörtelfugen erfolgt. Mit der Software DIANA® wurden numerische Modelle entwickelt. Eine Makromodellierung erbrachte zufriedenstellende Resultate hinsichtlich des Spannungs-Dehnungs-Verhaltens unter statischem Druck, während mit einer Mikromodellierung zufriedenstellende Ergebnisse hinsichtlich des Spannungs-Dehnungs-Verhaltens unter statischer Schubbeanspruchung erzielt wurden. Für beide Fälle, d.h. Makromodellierung von statischem Druck und Mikromodellierung von statischem Schub, wurde eine gute Übereinstimmung der simulierten Rissbildung mit den tatsächlichen Rissbildern beobachtet.
Im zweiten Teil des Projekts wurden Verfahren zur experimentellen Beurteilung von Verpressankern für Lehmsteinmauerwerk erprobt. Die Versuchsergebnisse zeigten, dass die gewählten Versuchsabläufe mit Betrachtung der Verformungen bzw. Relativverschiebungen der Ankerkomponenten und des Mauwerwerks geeignet sind, die am häufigsten wiederkehrenden Versagensarten zu bestimmen und Traglastkurven für Verpressanker zu erstellen.
Anhand von Versuchsergebnissen und zuverlässigkeitstheoretischen Grundlagen erfolgte die Ermittlung eines Teilsicherheitsbeiwertes für Lehmmauerwerk unter dem Lastzustand Druck nach der Kalibrationsmethode der DIN EN 1990. Darüber hinaus fanden Untersuchungen zur Ermittlung der Parameter zur Bestimmung der rechnerischen Mauerwerksfestigkeit statt. Aufgrund der derzeit noch ungenügenden Datengrundlage konnten lediglich erste Empfehlungen für Teilsicherheitsbeiwerte ausgesprochen werden. Ein Bemessungskonzept im Lehmmauerwerksbau auf Basis von Teilsicherheitsbeiwerten, welches sich an der gültigen Mauerwerksnormung anlehnt, scheint aber prinzipiell möglich. Es bedarf allerdings noch weiterer Forschung, insbesondere im Hinblick auf andere Lastzustände und auf das Feuchtigkeitsverhalten von Lehmmauerwerk.
This study presents diagnostic techniques to assess the structural vulnerability of earthen buildings. Medieval structures at Ambel (near Zaragoza, Spain), once a preceptory or monastic house belonging to the Military Orders, provide a useful case study. After more than a thousand years of construction, failure and repair from the 10th century to the present day, Ambel preceptory today is characterised by marked inhomogeneities: construction materials and structural typologies are juxtaposed, with structural discontinuities at the interfaces between construction phases. This paper argues that, while static analysis is an essential prerequisite before a suitable maintenance program can be defined, no evaluation of the structural behaviour of any historic building can ignore an understanding of the building’s history.
A new technique to fix bioceramic powder on a titanium alloy by using femtosecond laser pulses is presented. It is shown that gentle fixation of a bioactive dielectric material on a metallic model implant is successful. This is potentially a new tool for the improvement of bone prostheses. An advantage of the ultrashort pulses is the very low heat influx into the whole sample. There is only a very thin interaction zone during the fixing, which is the metal surface in contact with the ceramic layer. Neither the fixed ceramic particles nor the major part of the metal suffer any modification. The stability of the model implant (ceramic on metal) is investigated by rotating bending fatigue tests. No indication of a reduction of the mechanical stability compared to untreated metallic reference samples was found.
Neutron imaging
(2016)
Neutron imaging methods are appropriate to investigate hydrogen distributions in several metallic systems. The large total neutron cross section of hydrogen compared to those of elements or isotopes, respectively, in usual structural materials like steels or zirconium alloys allows the detection even of small amounts of hydrogen in such materials. The dependence of the total macroscopic neutron cross section of the sample or component on the hydrogen concentration can be determined experimentally by means of calibration specimens with known hydrogen concentrations. Such a calibration allows for a full quantitative determination of the local hydrogen concentration with a spatial resolution better than 20 μm. Because neutron radiography is fast and non-destructive, in situ investigations of time-dependent processes like hydrogen absorption and release or hydrogen bulk diffusion can be performed. This chapter gives an introduction into the main neutron imaging methods, radiography and tomography, and gives as examples results of neutron imaging investigations of hydrogen in different steels and in zirconium alloys,respectively.
In the last two decades, the solubility of gases in ionic liquids has attracted a lot of attention. While at the beginning most publications dealt with the solubility of a single gas in a pure ionic liquid, recently the interest starts to shift to the – from an application-oriented point of view – more challenging area of the simultaneous solubility of several gases in an ionic liquid and/or the solubility of a single gas in solvent mixtures with ionic liquids. The current state of information on experimental data (and the phenomena encountered) in such systems is summarized and discussed.
Pyrolysis, flammability, fire behavior, melt viscosity, and gas diffusion of bisphenol A polycarbonate/acrylonitrile-butadiene-styrene (PC/ABS) were investigated, with bisphenol A bis(diphenyl phosphate) (BDP), with 10 wt.% talc and with BDP in combination with 5, 10 and 20 wt.% talc, respectively. Compared to PC/ABS, PC/ABS + BDP results in an increased decomposition temperature of PC, a higher char yield, a significantly increased LOI, a V-0 classification in UL 94, a reduced peak heat release rate (pHRR), and a reduced total heat release (THR) in the cone calorimeter. This efficient flame retardancy is due to mechanisms in both the gas and condensed phases. PC/ABS + 10 wt.% talc shows a decrease in the PC decomposition temperature. The fire behavior is improved in part compared to PC/ABS, with an increased LOI and reduced pHRR. PC/ABS + BDP + 10 wt.% talc shows a strong synergism in LOI, a V-0 classification, and a decrease in pHRR, whereas THR is slightly increased compared to PC/ABS + BDP. Talc decreases the gas diffusion and enhances the flow limit for low shear rates, both of which influence the pyrolysis and flammability results. Further, talc improves the protection properties of the fire residues. Nevertheless it also partly suppresses flame inhibition and the charring effect of BDP. The synergism between BDP and talc in LOI is obtained even for low talc loadings in PC/ABS + BDP + talc, whereas for higher loadings saturation is observed.