Ultrafine grained (UFG) and nanocrystalline materials have attracted considerable interest because of their unique mechanical properties as compared with coarse grained conventional materials. The fabrication of relatively large amounts of these materials still remains a challenge, and a thorough understanding of the relationship between microstructure and mechanical properties is lacking. The objective of this study was to investigate the mechanical properties of UFG and nanocrystalline copper obtained respectively by a top down approach of severe plastic deformation of wrought copper and a bottom up approach of consolidation of copper nanoparticles using equal channel angular extrusion (ECAE). A critical assessment and correlation of the mechanical behavior of ECAE processed materials to the microstructure was established through the determination of the effect of strain level and strain path on the evolution of strength, ductility and yield anisotropy in UFG oxygen free high conductivity copper in correlation with grain size, grain morphology and texture. ECAE was shown to be a viable method to fabricate relatively large nanocrystalline consolidates with excellent mechanical properties. Tensile strengths as high as 790 MPa and fracture strain of 7 % were achieved for consolidated 130nm copper powder. The effects of extrusion route, number of passes and extrusion rate on consolidation performance were evaluated. The relatively large strain observed was attributed to the bimodal grain size distribution and accommodation by large grains. The formation of bimodal grain size distribution also explains the simultaneous increase in strength and ductility of ECAE processed wrought Cu with number of passes. Texture alone cannot explain the mechanical anisotropy in UFG wrought copper but we showed that grain morphology has a strong impact and competes with texture and grain refinement in controlling the resulting yield strength. Tension-compression asymmetry was observed in UFG wrought copper. This asymmetry is not always in favor of compression as reported in literature, and is also influenced by grain morphology through the interaction of dislocations with grain boundaries. Different prestrains in tension and compression should be experimented to have a better understanding of the encountered anisotropy in Bauschinger parameter in relation with the observed tension-compression asymmetry.

Copper is a widely used conductor in the manufacture of printed wiring boards (PWB). The trends in miniaturization of electronic devices create increasing challenges to all electronic industries. In particular PWB manufacturers face great challenges because the increasing demands in greater performance and device miniaturization pose enormous difficulties in manufacturing and product reliability. Nanocrystalline and ultrafine grain copper can potentially offer increased reliability and functionality of the PWB due to the increases in strength and achievable wiring density by reduction in grain size. The first part of this thesis is concerned with the synthesis and characterization of nanocrystalline and ultra-fine grain-sized copper for potential applications in the PWB industry. Nanocrystalline copper with different amounts of sulfur impurities (25- 230ppm) and grain sizes (31-49nm) were produced and their hardness, electrical resistivity and etchability were determined. To study the thermal stability of nanocrystalline copper, differential scanning calorimetry and isothermal heat treatments combined with electron microscopy techniques for microstructural analysis were used. Differential scanning calorimetry was chosen to continuously monitor the grain growth process in the temperature range from 40C to 400C. During isothermal annealing experiments samples were annealed at 23C, 100C and 300C to study various potential thermal issues for these materials in PWB applications such as the long-term room temperature thermal stability as well as for temperature excursions above the operation temperature and peak temperature exposure during the PWB manufacturing process. From all annealing experiments the various grain growth events and the overall stability of these materials were analyzed in terms of driving and dragging forces. Experimental evidence is presented which shows that the overall thermal stability, grain boundary character and texture evolution of copper is greatly related to changes in driving and dragging forces, which in turn, are strongly depended on parameters such as annealing temperature and time, total sulfur impurity content and the distribution of the impurities within the material. It was shown that a simple increase in the sulfur impurity level does not necessarily improve the thermal stability of nanocrystalline copper.

Copper is a widely used conductor in the manufacture of printed wiring boards (PWB). The trends in miniaturization of electronic devices create increasing challenges to all electronic industries. In particular PWB manufacturers face great challenges because the increasing demands in greater performance and device miniaturization pose enormous difficulties in manufacturing and product reliability. Nanocrystalline and ultrafine grain copper can potentially offer increased reliability and functionality of the PWB due to the increases in strength and achievable wiring density by reduction in grain size. The first part of this thesis is concerned with the synthesis and characterization of nanocrystalline and ultra-fine grain-sized copper for potential applications in the PWB industry. Nanocrystalline copper with different amounts of sulfur impurities (25- 230ppm) and grain sizes (31-49nm) were produced and their hardness, electrical resistivity and etchability were determined. To study the thermal stability of nanocrystalline copper, differential scanning calorimetry and isothermal heat treatments combined with electron microscopy techniques for microstructural analysis were used. Differential scanning calorimetry was chosen to continuously monitor the grain growth process in the temperature range from 40C to 400C. During isothermal annealing experiments samples were annealed at 23C, 100C and 300C to study various potential thermal issues for these materials in PWB applications such as the long-term room temperature thermal stability as well as for temperature excursions above the operation temperature and peak temperature exposure during the PWB manufacturing process. From all annealing experiments the various grain growth events and the overall stability of these materials were analyzed in terms of driving and dragging forces. Experimental evidence is presented which shows that the overall thermal stability, grain boundary character and texture evolution of copper is greatly related to changes in driving and dragging forces, which in turn, are strongly depended on parameters such as annealing temperature and time, total sulfur impurity content and the distribution of the impurities within the material. It was shown that a simple increase in the sulfur impurity level does not necessarily improve the thermal stability of nanocrystalline copper.

In this study, the mechanical properties of nanocrystalline Mo and Zr thin films are examined. The specimens of nanocrystalline Mo and Zr thin films were all fabricated by DC magnetron sputtering at various temperatures. These specimens were annealed in RTA system and then investigated by X-ray diffractormeter as well as TEM. After that, nanocrystalline Mo and Zr thin films were tested by nanoindentation. The average grain sizes in Zr thin films annealed are larger than deposited at high temperature, but the films after annealing are stripped away from the substrates due to the thermal shock. The average grain sizes estimated by XRD patterns are in common with those estimated by TEM images. We suggest that the difference is deviation. Nanocrystalline Mo thin films were first tested by both nanoindentation and tensile tests. Mo thin films were stripped away during tensile tests. We consider that the phenomenon is due to the honeycombed structure of the films. The X-ray diffraction patterns and TEM observations indicated that there is no evident grain growth in the nanocrystalline Zr thin films, deposited at 100 ¢XC, 200 ¢XC, and 300 ¢XC, except at 400 ¢XC. The deposition temperature for apparent grain growth in the Zr thin films is at least above 300 ¢XC. After nanoindentation tests, the hardness (H) and Young¡¦s modulus (E) of specimens deposited at 400 ¢XC are higher than that of other specimens. Compared to coarse-grained Zr metals, we suggest that the slope k in the Hall-Petch relationship is quite small and in the range of nanocrystalline Zr thin films.

The effect of ball milling on the compaction and sintering of nanocrystalline FC-0205 powder was studied in this work. As-received micron-sized FC-0205 powder was subjected to High Energy Ball Milling (HEBM) in an argon atmosphere at different milling time of 0, 8, 16, 20 and 24 hours to obtain nanocrystalline structures. Unmilled, 8 and 16 hour milled powder were compacted using uniaxial die compression at a pressure ranging from 274 MPa to 775 MPa to obtain a relative density from 74% to 95%. The steel powder compacts were sintered at temperatures ranging from 400 °C (752 °F) to 1120 °C (2048 °F) in a controlled atmosphere. Microscopy analysis using Optical Microscope (OM), Scanning Electron Microscope (SEM) and X-ray Diffraction (XRD) was performed on the milled powder, and on the green and sintered compacts to examine the grain size, morphology and agglomeration.

Nanocrystalline cellulose (NCC) has great potential as a reinforcing agent in thermoplastics (such as polyesters, polyamides and polycarbonates) due to its high mechanical strength and aspect ratio – being compared with reinforcements like steel and carbon nanotubes. In order to maintain its strength when compounded with thermoplastics, the high-temperature processing must not damage the structural integrity of the nanocrystalline cellulose. The processing temperature for polyesters, polyamides and polycarbonates is relatively high and near to the onset of thermal degradation of cellulose bio products, therefore care must be taken to ensure the preservation of the structural integrity of nanocrystalline cellulose. The thermal stability and the kinetics of thermal degradation of five different cellulose samples were studied using an Ozawa-Flynn-Wall method and thermogravimetric analysis data. To complete the characterization of the NCC for polymer processing applications, the crystallinity index was determined using X-ray diffraction; surface morphology was studied with scanning electron microscope, chemical composition was studied using FT-IR, and moisture content was measured using a moisture analyser. Each of these properties observed is essential to the end mechanical properties of the polymer nanocomposite as these properties will affect the dispersion and interfacial adhesion of the fibres to the polymer matrix. After a complete investigation of the cellulose reinforcements, a procedure was developed for dispersion of the NCC fibres into a polycarbonate matrix followed by the moulding of specimen bars. The mechanical properties of the five cellulose-polycarbonate nanocomposites – for example, tensile modulus, flexural modulus and impact strength – were tested and compared to the homo-polycarbonate. The motivation for this project was to design a new material for use as strong, lightweight window substitute; an alternative to conventional residential/commercial windows and a lightweight alternative to conventional automotive glass, offering increased fuel efficiency.

This thesis focuses on the study of the size effect in the elastic-viscoplastic response of pure face centered cubic polycrystalline materials. First, the effect of vacancy diffusion is studied via the use of a two-phase self-consistent scheme in which the inclusion phase represents grain interiors and the matrix phase represents grain boundaries. The behavior of the inclusion phase is driven by the activity of dislocations, described with typical strain hardening laws, and by the activity of Coble creep. The behavior of the matrix phase is modeled as elastic-perfect plastic. This model is then extended to account for the possible activity of Lifschitz sliding. The active role of grain boundaries to the viscoplastic deformation is studied with the introduction of a novel method allowing the scale transition from the atomistic scale to the macroscopic scale. A model describing the mechanism of grain boundary dislocation emission and penetration is informed with molecular simulations and finite element simulations. The macroscopic response of the material is then predicted with use of several self-consistent schemes, among which two novel three-phases schemes are introduced. The most refined micromechanical scheme proposed is based on a two-phase representation of the material and is valid in the elastic-viscoplastic regime and accounts for the effect of slightly weakened interfaces.

Nanocrystalline cellulose (NCC) has great potential as a reinforcing agent in thermoplastics (such as polyesters, polyamides and polycarbonates) due to its high mechanical strength and aspect ratio – being compared with reinforcements like steel and carbon nanotubes. In order to maintain its strength when compounded with thermoplastics, the high-temperature processing must not damage the structural integrity of the nanocrystalline cellulose. The processing temperature for polyesters, polyamides and polycarbonates is relatively high and near to the onset of thermal degradation of cellulose bio products, therefore care must be taken to ensure the preservation of the structural integrity of nanocrystalline cellulose. The thermal stability and the kinetics of thermal degradation of five different cellulose samples were studied using an Ozawa-Flynn-Wall method and thermogravimetric analysis data. To complete the characterization of the NCC for polymer processing applications, the crystallinity index was determined using X-ray diffraction; surface morphology was studied with scanning electron microscope, chemical composition was studied using FT-IR, and moisture content was measured using a moisture analyser. Each of these properties observed is essential to the end mechanical properties of the polymer nanocomposite as these properties will affect the dispersion and interfacial adhesion of the fibres to the polymer matrix. After a complete investigation of the cellulose reinforcements, a procedure was developed for dispersion of the NCC fibres into a polycarbonate matrix followed by the moulding of specimen bars. The mechanical properties of the five cellulose-polycarbonate nanocomposites – for example, tensile modulus, flexural modulus and impact strength – were tested and compared to the homo-polycarbonate. The motivation for this project was to design a new material for use as strong, lightweight window substitute; an alternative to conventional residential/commercial windows and a lightweight alternative to conventional automotive glass, offering increased fuel efficiency.

Mesoporous aggregates of nanocrystalline zeolites with MFI and BEA frameworks have been synthesized using a one-pot and single structure directing agent method. The effect of different reaction conditions, such as temperature, time, pH and water content, on the particle size, surface area and mesopore volume has been studied. Nanocrystalline and mesoporous ZSM-5, β and Y zeolites were modified with different transition metals and the resulting single- and double metal containing catalyst materials were characterized. Nanocrystalline Silicalite-1 zeolite samples with varying particle size were functionalized with different organosilane groups and the cytotoxic activity of the zeolite nanocrystals was studied as a function of particle size, concentration, organic functional group type, as well as the type of cell line. Framework stability of nanocrystalline NaY zeolite was tested under different pH conditions. The synthesized zeolites used in this work were characterized using a variety of physicochemical methods, including powder X-ray diffraction, Solid State NMR, nitrogen sorption, electron microscopy, Inductively Coupled Plasma - Optical Emission Spectroscopy and X-ray Photoelectron Spectroscopy.

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