Correlations between a materials microstructure and mechanical behavior are important for materials development. As materials characterization methods must consider instrument accessibility, sample dimensions and economical aspects, developing functional techniques in order to obtain better understanding of materials behavior in micro and nano scale is crucial. Procedures for assessing and interpreting the mechanical responses at small scales, combined with investigating the microstructure, are considered as significant steps to design and develop the effective frameworks for evaluating bulk properties. This research demonstrates how fundamental understanding of microstructures can assist interpreting of mechanical performance of bulk materials. Testing of materials at small scales is very important because the mechanical failure of any bulk material starts with the formation, extension, or local accumulation of initially small defects, leading finally to a catastrophic fracture by an expanding crack. Thus, any bulk material profits from an in-depth understanding of its deformation and mechanical phenomena at the nano- and micrometer length scale.<div><br></div><div>This thesis shows how the micro constituents’ interactions and grain boundaries reactions to dislocations in alloys and thin films contribute to understanding material flow behavior and differences in the mechanical properties of these materials in a wide range of material systems with variations in appropriate sizes which need to be probed. Among other things, this work shows that sources of variation can be specified and quantified as predictive tools for designing materials. Several examples are presented. First, the strength and strain hardening of martensite and ferrite in a dual phase steel with a grain size less than 5 μm were determined using an inverse technique. The yield strength of the ferrite and martensite phases are obtained as 370 MPa and 950 MPa respectively. The calculated hardening exponent of the alloy was exactly the same as experimental tensile test results (0.11). The constraint phenomena was effective in restricting deformation of this elastic-plastic alloy. Secondly, the differences in hardness and pop-in behavior were used to understand of the influences of different types of grain boundaries, high density dislocations, and twins in Al thin films before and after plasticity. The third example assesses the strength of several species of diatom frustules for the first time using a combination of indentation techniques. Lightweight materials with densities well below 1000 kg/m3 demonstrated strengths on the order of 100’s of MPa. Finally, conditions for laser grown oxides and laser shock peening on a commercial steel which lead to an optical marking without a change in strength around the marking have been identified.<br></div>

The content of this study is focused on the influence of the structure of wood at microscopic and submicroscopic level on its mechanical properties. The wood cell wall consists of several layers, the dominant layer being layer S2, which occupies up to 80 % of the total thickness of the wood cell wall. Unique feature of this layer is that cellulose microfibrils placed in this layer are highly aligned and spirally wound around the cell axis. The inclination of these microfibrils is called microfibril angle (MFA) and is the key feature that affects mechanical properties of wood and its shrinkage. In theoretical part of this thesis methods for measuring microfibril angle are described. A method for measuring mechanical properties of the wood cell wall called nanoindentation is discussed in detail. In the practical part of this thesis, microfibril angle is measured by means of polarized light microscopy and mechanical properties of wood cell wall is determined by means of nanoindentation.

The main goal of this work is to find a methodology of the fabrication of microcompressive specimens (pillars) from thin metallic film prepared by means of PVD. The studied film was prepared by the ON Semiconductor company, Roznov pod Radhostem. Its chemical composition was Al-1.5 wt.% Cu; such films are used for electric connections on integrated circuits. At first, a thin intermediate layer of W-10 wt.% Ti was deposited on the Si single crystalline substrate with the purpose of improving adhesion properties of the studied film. The geometry of the microcompressive specimen should be as close to the cylindrical shape as possible. The height of the cylinder is given by the film thickness, its diameter is approximately 1 m. Such specimens were prepared in Quanta 3D FEG Dual BeamTM facility using focused ion beams technology. Experiments were done at FEI Company in Brno. In total, 39 microcompressive specimens were prepared at various ion milling conditions. The required geometry was finally attained by the optimization of processing parameters, in particular the parallelism of lateral faces was improved, the bottom of the removed zone in the vicinity of the pillar was almost flat and the transition pillar – flat bottom was regular. The prepared pillars are suitable for the microcompression tests; the first of them have been already performed within the cooperation with the Institut of Physics, Academy of Sciences of the Czech Republic, Praha.

<div>Due to the inherent dangers associated with handling high explosive materials, it is often useful to have access to inert simulant materials that mimic certain physical or mechanical properties, called "mock" materials. Mock materials can take the place of explosives in experiments, allowing experimental results to be obtained with less difficulty and risk. Recently there has been an interest in identifying new mechanical mock materials for the explosives HMX and PETN. These energetic materials and their prospective mocks are often used and tested in the form of small submillimeter crystals, with which typical size and geometry make many mechanical tests difficult or impossible. Additionally, these materials are typically prone to brittle fracture, which can further limit the usage conditions of the material as well as the range of conditions in which mechanical testing results are valid. Nanoindentation is a useful technique to measure mechanical properties in particulate form without the need to grow large single crystals or do additional processing on existing crystals.</div><div><br></div><div>Here, nanoindentation tests were performed on PETN, HMX, and several inert molecular crystals selected as potential mocks based on density, crystal structure, and previous thermal testing results. Comparisons were made on the basis of hardness, elastic modulus, yield point behavior, indentation fracture response, and sensitivity to non-uniform indenter orientation. Based on the results of these experiments, the inert material idoxuridine was selected for further consideration as an HMX mock, and the inert materials meso-erythritol and 2,4,6 trifluorobenzoic acid were selected for further consideration as PETN mocks.</div><div><br></div><div>As a result of this study, potential mechanical mocks were selected for two energetic materials, nanomechanical properties were reported for the first time ever for 6 inert molecular crystals, and nanoindentation was shown to be a versatile tool for rapid initial screening of materials as well as detailed investigations of materials of interest. <br></div>

In this work the author presents simulation procedures (mathematical models) with the aim to help determining and analysing the mechanical properties of coating-substrate-systems and finding an “optimal” coating structure which should protect the compound from inelastic deformation under a given range of load conditions. Such procedures may be used as a tool to minimise the search field for experimental work. For this purpose one would need a mathematical model which allows one to calculate the complete elastic field with all its displacement and stress components within a multilayer film on a substrate under given mechanical loading and intrinsic stress conditions. Due to copyright restrictions the author is not allowed to publish the Part II of his habilitation thesis at this place. It concerns the references in meta data. / In der Arbeit werden mathematische Modelle zur Berechnung der mechanischen Eigenschaften geschichtet aufgebauter Materialien unter unterschiedlichsten Lastbedingungen (Kontakt- und intrinsische Beanspruchung) vorgestellt und diskutiert. Auf Grund von Schutzrechtsbestimmungen ist eine Veröffentlichung der in der Habilitation angegebenen Literatur im Teil II an dieser Stelle nicht möglich. Der interessierte Leser wird gebeten die Arbeiten in den entsprechenden Journalen einzusehen. Dies betrifft die in den Metadaten angegebenen Veröffentlichungen des Autors.

<div>Electrochemical energy storage devices play an integral role in the energy transition from fossil fuels to renewable. Still, technological breakthroughs are warranted to expand this progress and enable their use where hydrocarbons are still the dominant option. The requirements restricting further adoption of electrochemical devices are related to energy density, hampering costs of raw materials with the increased global demand, and safety in large scale operations. Furthermore, new applications in flexible electronics add new requisites to this list. Pushing these limits involves multidisciplinary efforts where the mechanics are a crucial part.</div><div> </div><div>This thesis explores the mechanical and kinetic behaviors of batteries at the nano to micro-meter scale through operando mechanical and optical characterization during ongoing electrochemical reactions. A unique experimental platform that enables simultaneous nanoindentation and electrochemical testing of active materials is developed. The validity of mechanical testing during operation in the customized liquid cell is systematically addressed. The evolution of the mechanical properties of electrodes as a function of lithium concentration is probed in real-time. This functional dependence between mechanical properties and composition is then used to introduce the concept of mechanics-informed chemical profiling. This new capability enables characterizing transport kinetics in a detailed and quantitative way, including the role of pressure gradients on diffusion. Pairing these experiments with multi-physics modeling led to a new understanding of the mechanisms regulating charging-rate capability and capacity loss in Li-ion batteries. Experiments on composite electrodes showed that liquid electrolytes change the mechanical properties of both conductive matrix and secondary particles. These observations help understand the interactions between the different components of a battery and demonstrate the need for in-situ mechanical characterization capabilities. </div>

This work presents findings in the combined experimental and computational study of the effects of anisotropy and microstructure on the behavior of HMX-based energetic materials. Large single crystal samples of β-HMX were meticulously created by solvent evaporation for experimental purposes, and respective orientations were identified via x-ray diffraction. Indentation modulus and hardness values were obtained for different orientations of β-HMX via nanoindentation experiments. Small-scale dynamic impact experiments were performed, and a viscoplastic power law model fit, to describe the anisotropic viscoplastic properties of the crystal. The anisotropic fracture toughness and surface energy of β-HMX were calculated by studying indentation-nucleated crack system formations and fitting the corresponding data to two different models, developed by Lawn and Laugier. It was found that the {011} and {110} planes had the highest and lowest fracture toughnesses, respectively. Drop hammer impact tests were performed to investigate effects of morphology on the impact-induced thermal response of HMX. Finally, the anisotropic properties obtained in this work were applied in a cohesive finite element simulation involving the impact of a sample of PBX containing HMX crystals with varying orientations. Cohesive finite element models were generated of separate microstructure containing either anisotropic (locally isotropic) or global isotropic properties of HMX particle. In comparison, the isotropic model appeared to be more deformation resistant.

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There is a need to discover advanced materials to address the pressing challenges facing humanity, however there are far too many combinations of material composition and processing conditions to explore using conventional experimentation. One powerful approach for accelerating the rate at which materials are explored is by miniaturizing the scale at which experiments take place. Reducing the size of samples has been tremendously productive in biomedicine and drug discovery through standardized formats such as microwell plates, and while these formats may not be the most appropriate for studying polymeric materials, they do highlight the advantages of studying materials in ultra-miniaturized volumes. However, precise and controlled methods for handling diverse samples at the sub-femtoliter-scale have not been demonstrated. In this thesis, we establish that scanning probes can be used as a technique for realizing and interrogating sub-femtoliter scale polymer samples. To do this, we develop and apply methods for patterning materials with control over their size and composition and then use these methods to study material systems of interest. First, we develop a closed-loop method for patterning liquid samples using scanning probes by utilizing tipless cantilevers capable of holding a discrete liquid drop together with an inertial mass sensing scheme to measure the amount of liquid loaded on the probe. Using these innovations, we perform patterning with better than 1% mass accuracy on the pL-scale. While dispensing fluid with tipless cantilevers is successful for patterning pL-scale features and can be considered a candidate for robust nanoscale manipulation of liquids for high-throughput sample preparation, the minimum amount of liquid that can be transferred using this method is limited by number of factors. Thus, in the second section of this thesis, we explore ultrafast cantilevers that feature spherical tips and find them capable of patterning aL-scale features with in situ feedback. The development of methods of interrogating polymers at the pL-scale led us to explore how the mechanical properties of photocurable polymers depend on processing conditions. Specifically, we investigate the degree to which oxygen inhibits photocrosslinking during vat polymerization and how this effect influences the mechanical properties of the final material. We explore this through a series of macroscopic compression studies and AFM-based indentation studies of the cured polymers. Ultimately, the mechanical properties of these systems are compared to pL-scale features patterned using scanning probe lithography and we find that not only does oxygen prevent full crosslinking when it is present during the post-print curing, but the presence of oxygen during printing itself irreversibly softens the material. In addition to developing new methods for realizing ultra-miniaturized samples for study, the novel scanning probe methods in this work have led to new paradigms for rapidly evaluating complex interactions between material systems. In particular, we present a novel method to quantitatively investigate the interaction between the metal-organic frameworks (MOFs) and polymers by attaching a single MOF particle to a cantilever and studying the interaction force between this MOF and model polymer surfaces. Using this approach, we find direct evidence supporting the intercalation of polymer chains into the pores of MOFs. This work lays the foundation for directly characterizing the facet-specific interactions between MOFs and polymers in a high-throughput manner sufficient to fuel a data-driven accelerated material discovery pipeline. Collectively, the focus of this thesis is the development and utilization of novel scanning probe methods to collect data on extremely small systems and advance our understanding of important classes of materials. We expect this thesis to provide the foundation needed to transform scanning probe systems into instruments for performing reliable nanochemistry by combining controlled and quantitative sample preparation at the nanoscale and high-throughput characterization of materials. To conclude, we present an outlook about the necessary technological advancements and promising directions for materials innovations that stem from this work.