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Full-Text Articles in Engineering Science and Materials

Coupled Mechanochemical Theories For Reacting Systems With Application To Nanovoid Nucleation And Li-Ion Batteries, Hamed Attariani Feb 2015

Coupled Mechanochemical Theories For Reacting Systems With Application To Nanovoid Nucleation And Li-Ion Batteries, Hamed Attariani

Hamed Attariani

Hollow nanoparticles (NPs) are produced by void nucleation and growth during chemical reactions. However, there is no proper understanding of nucleation and growth mechanisms, and their predictive modeling. Furthermore, models based on the Kirkendall effect predict the process time, which is larger by orders of magnitude than in the experiment. A continuum-mechanics approach for nucleation and growth of a nanovoid in reacting NPs based on the Kirkendall effect is developed, which quantitatively describes the experimental results for oxidation of copper NPs. The results show that the core is under compression (which eliminates fracture hypothesis) which promotes void nucleation by decreasing ...


Temperature-Dependent Thermal And Electrical Conduction In Metallic Nanostructures, Zhe Cheng Jan 2015

Temperature-Dependent Thermal And Electrical Conduction In Metallic Nanostructures, Zhe Cheng

Graduate Theses and Dissertations

In this work, temperature dependent electrical and thermal conduction in the bio-supported 3.2 nm-thin Ir nanofilm and individual silver nanowire are studied at reduced temperatures. For the Ir film, by studying the temperature-dependent behavior (300 K down to 43 K) of electron thermal conductivity (), we quantify the extremely confined defect-electron scatterings and isolate the intrinsic phonon-electron scattering that is shared by the bulk Ir. At low temperatures below 50 K,  of the film has almost two orders of magnitude reduction from that of bulk Ir. The film has ∂/∂T>0 while the bulk Ir has ∂/∂T <0. We introduce a unified thermal resistivity (=T/) to interpret these completely different ~T relations. It is found that the film and the bulk Ir share a very similar ~T trend while they have a different residual part (Θ0) at 0 K limit: 0~0 for the bulk Ir, and 0=5.5 mK2/W for the film. The Ir film and the bulk Ir have very close ∂Θ/∂T (75 to 290 K): 6.33×10-3 mK/W for the film and 7.62×10-3 mK/W for the bulk Ir. This strongly confirms the similar phonon-electron scattering in them. The temperature dependent behavior of the Lorenz number of the Ir film is also reported down to 10 K. Due to the strong defect-electron scattering, a very large residual electrical resistivity (1.2410-7 ·m) is observed for the film that dominates the overall electron transport (1.24~1.5510-7 ·m). The Debye temperature (221 K) of the film is found much smaller than that of bulk (308 K). This phonon softening strongly confirms the extensive surface and grain boundary electron scatterings. We find the Wiedemann-Franz Law still applies to our film even at low temperatures. The overall Lorenz number and that of imperfect structure (~2.25×10-8 W·Ω/K2) are close to the Sommerfeld value and shows little temperature dependence. This is contrast to other studied low dimensional metallic structures that have a much larger Lorenz number (3~7×10-8 W·Ω/K2). Electron tunneling and hopping in the biomaterial substrate are speculated responsible for the observed Lorenz number.

Additionally, the thermal ...


Review Of Materials Property Data For Nondestructive Characterization Of Pipeline Materials, Lucinda Jeanette Smart Jan 2015

Review Of Materials Property Data For Nondestructive Characterization Of Pipeline Materials, Lucinda Jeanette Smart

Graduate Theses and Dissertations

The oil and gas industry relies on an aging infrastructure of pipeline for transportation and distribution of product; therefore, it is important to assess the condition of the pipeline, using accurate material and mechanical properties, to ensure failures are minimized. Nondestructive evaluation techniques are currently being used to assess pipeline, but necessary mechanical properties (yield strength, tensile strength, fracture toughness, and ductile-to-brittle transition temperature) are not yet able to be adequately characterized by these methods.

There are many issues to consider when addressing this problem. There is variability within the manufacturing processes due to simple inaccuracies in the processes themselves ...


Lasers Processing Of Ultra-Hard Materials, Ammar Abdulghani Melaibari Jan 2015

Lasers Processing Of Ultra-Hard Materials, Ammar Abdulghani Melaibari

Graduate Theses and Dissertations

Laser processing of ultra-hard materials is a relatively new field that have the potential to improve variety of products and different industries. This dissertation explores specific new development in this field through three main subjects: laser machining, laser deposition of thin film, and laser treatment. In laser machining of ultra-hard material, controlled crack propagation mechanism -as opposed to the typical ablation mechanism- was investigated, and micromachining of ultra-hard thin film was also observed. For the laser deposition of ultra-hard thin film, designing new microstructured materials was explored, and the utilization of the inherent particulate formation associated with the pulsed laser ...


Thermal Behavior Of The Stm Tip Under Laser Irradiation, Christopher G. Reilly Jan 2015

Thermal Behavior Of The Stm Tip Under Laser Irradiation, Christopher G. Reilly

Graduate Theses and Dissertations

This thesis discusses the thermal behavior of the STM tip under laser irradiation. The thermal expansion of the tip was researched with varying laser spot size, frequency, location, and power. In order to determine the thermal expansion of the STM tip, the behavior in both the time and frequency domain were investigated. By employing the FFT analysis, the noise of the thermal behavior in the frequency domain was greatly reduced when compared to the time domain behavior, allowing for higher resolution expansions. With noise reduced, a thermal expansion of 1 nm, equating to a 0.03 K average temperature rise ...