Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 39 for “"polycrystalline materials"”.
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Grain boundary engineering in additively manufactured polycrystalline materials
… and reducing corrosion susceptibility in polycrystalline materials by increasing the fraction of low-energy grain boundaries. However, conventional GBE relies on complex cycles of mechanical deformation and annealing, which is incompatible with the precision-engineered geometries of …
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Practical Pathways to Efficient MRAM: Spin-Orbit Torques, Low-Damping, and Anomalous Hall Conductivity in Polycrystalline Materials
… next pathway investigated is an easy-to-grow, polycrystalline alternative to non-collinear antiferromagnets which require high temperature growth (>400°C). We find that sputter-grown γ-FeMn with no post-annealing, has a small non-zero net magnetization (≈(0.02-0.07)μB/atom) and perpendicular …
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Trace Level Impurity Quantitation and the Reduction of Calibration Uncertainty for Secondary Ion Mass Spectrometry Analysis of Niobium Superconducting Radio Frequency Materials
… performance. This knowledge gap is bridged by materials characterization. Secondary ion mass spectrometry (SIMS) is a characterization technique which has become a staple of SRF cavity characterization that details elemental concentration profiles as a function of depth into the niobium surface …
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Quantification of Elastic Incompatibilities at Triple Junctions via Physics-Based Surrogate Models
… and loss of desirable macroscopic properties in polycrystalline materials. As a result, there have been significant efforts in the field of grain boundary engineering to understand the sources of grain boundary incompatibilities in polycrystals and potential mitigation strategies through …
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A yield function to simulate earing in the deep drawing of aluminium
… develop during the sheet rolling process. In polycrystalline materials it may be modelled via either crystallographic texture models or phenomenological yield surface models. Crystallographic models have the advantage over phenomenological ones in that they are able to describe both initial …
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An evaluation of grain boundary engineering technology and processing scale-up
… and provides a method of producing more robust polycrystalline materials. This evaluation presents an introduction to the fundamental principles of grain boundary engineering, reviews the processing techniques and relevant intellectual property, analyzes the processing variables and their effect …
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Scaling and Pattern Formation in Condensed Matter Systems
Finally, I study multiscale patterns in polycrystalline materials, with the phase field crystal (PFC) model. I first show that the complex amplitudes representation incorporates the correct form of nonlinear elasticity. I then analyze the plastic properties of the model by applying a shearing …
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Interfacial Segregation in Perovskites and Applications to Boundary Layer Devices
… that exists between the bulk and interface in materials due to interfacial effects which are distinct from bulk effects. Segregation in solids is of great theoretical importance, and also plays an active role in modifying the properties of many materials. For example, surface segregation in …
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Compliant Epitaxy of Iii-V Compound Semiconductors for Optoelectronic Device Applications
… (VLT-MBE) which involves growth of amorphous and polycrystalline materials. Using GaP and laterally oxidized AlAs materials, substrate independent DBRs were fabricated at wavelengths in both the visible spectrum, 480 nm to 550 nm, as well as those used in the telecommunications industry, 1310 nm …
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Modeling the deformation and failure behavior of FCC and HCP nanocrystalline materials
… nowadays are miniaturizing structures in materials to achieve better performance as concerned in technical applications. Reducing grain sizes in polycrystalline materials into the range of less than 100nm, for example, could achieve extraordinary high strength in these so called …
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Quantitative Analysis of Microstructural Evolution in Polycrystalline Metal Matrix with Embedded Second Phase Particle
… unique microstructural patterns and stability of polycrystalline materials. By employing the versatile multi-phase field modeling methodology, the role of inert, secondary particles on the dynamics of grain boundaries under conditions of uncooperative migration has been analyzed. Systematic …
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Considerations in the design and operation of synchrotron radiation beamlines (including a discussion on the properties of synchrotron radiation
… of the integrated intensities from polycrystalline materials is considered. The calculations show that except for the most fine grained materials, representative intensity measurements can only be made when the sample is permitted to move.
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A microstructure based fatigue life prediction framework and its validation
Fatigue crack initiation in polycrystalline materials can be attributed to various mechanistic and microstructural features acting in concert like the elastic stress anisotropy, plastic strain accumulation, resolved shear stress, normal stress, slip-system length, and grain boundary character. In …
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Topological analysis of the grain boundary space
… and structural properties of every class of polycrystalline materials and play a critical role in structural evolution and phase transformations. Recent experimental advances enable a full crystallographic characterization, including the boundary misorientation and inclination parameters, of …
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Microfabrication and characterization of a new box-shaped high frequency (7.5 MHz) low aperture 2D phased ultrasound transducer array
… MHz transducer array, based on commercial PZT-5H polycrystalline materials, as tiny as 70x70 µm per transducer with a pitch of 102 µm to maintain an inter-element separation below 50% of the lambda. The study employs a square box-shaped structure that houses the transmitters and receivers …
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An investigation into the synthesis, structural characterisation, thermal and polymorphic behaviour of organic crystalline materials
… synthesis and application of solid state organic materials have a big impact upon society, e.g. pharmaceuticals. Traditionally, the process of selecting active pharmaceutical ingredients (APIs) was limited to free drug or accepted salt formulations. The cocrystallisation of APIs with a former …
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Effects of composition and ausaging on microstructures and magnetic shape memory response of Fe-Ni-Co-Ti alloys
Magnetic Shape-Memory (MSM) materials are a new category of actuator materials with the potential to produce both large actuator strain and rapid response. To explore the possibility of developing MSM materials based on Fe-Ni-Co-Ti alloys, the effects of chemical composition (Co/Ni ratio) and …
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Investigations into leakage current variation in titanium dioxide dielectrics
… a more complete study of single crystal and polycrystalline TiO₂ material was undertaken. Leakage current studies of SrTiO₃ suggest that ionic motion is the cause of the leakage current variation. It is reasonable to assume that this is also true for TiO₂. For TiO₂ there are several theories …
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Deformation and residual stresses at the intragranular scale – a study using high energy x-ray diffraction and modeling in polycrystalline alloys
Deformation and internal stress distribution in polycrystalline materials depend upon interactions among neighboring grains and sub-grains (substructure inside a grain). With the advent of high energy x-ray diffraction (HEXD), using synchrotron radiation, it has become possible to probe the bulk of …
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Nonlinear Dynamics of Vortices in Different Types of Grain Boundaries
… accelerating gradient. SRF cavities are made of polycrystalline materials in which grain boundaries can limit maximum RF currents and produce additional power dissipation sources due to local penetration of Josephson vortices. The essential physics of vortex penetration and mechanisms of …
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