Multilayered materials and structures are of special interest to both academic researchers and industrial engineers as they have been used in an increasing number of applications, such as micro- electromechanical system (MEMS) on polymer substrate, protective coating on metal structure for anti-corrosion, ceramic coating on metal substrate for abrasion resistance, thermal barrier coatings, metal or metal oxide coating on metal-coated polymer for reflectance tuning and protection, as well as laminated composites and structures, etc. However, the surface layer and joint interface are commonly prone to premature failures because of cracking and delamination due to their different thermal and mechanical properties. In return, the premature failures will affect the performance and structural integrity of the device and eventually cause the failure of the multilayered structures to perform their functions. Therefore, it is essential to understand the mechanical behavior and corresponding failure mechanisms of the multilayered systems. This Ph.D. dissertation focuses on the study of opening-mode fracture (OMF) behavior and interfacial delamination in different types of multilayered structures, such as the aluminum plate or wire with alumina protective coating, multilayered advanced polymeric reflectors, and asphalt pavements. In addition, another failure mechanism, i.e. the material degradation and aging, is also studied. Firstly, a two-dimensional (2D) elasoplastic fracture model in Cartesian coordinates is developed to study the OMF in the thin alumina film fully bonded to an aluminum plate undergoing large- scale yielding. The stress field in the coating layer is described by one section between two adjacent cracks. The 2D plane strain formulations are employed to analyze the elastic field in the thin film, while a one-dimensional (1D) linear hardening plastic model is applied to account for the large plastic deformations in the substrate under substantial yielding. An elastoplastic shear lag model is established to transfer the tensile stress in the substrate to the thin film. General formulations and explicit expressions of the elastic/elastoplastic solutions of the thin film/substrate system under different loading stages have been presented. The elastic field in the thin film is then verified with the finite element (FE) results. The fracture energy release rate (ERR) is calculated and corresponding elastoplastic fracture analysis is conducted. Experimental characterization is further conducted to validate the present model; the results show that this fracture modle can capture the fracture initiation, infilling, and saturation in the thin film successfully. This model has been extended to cylindrical coordinates, where the alumina coating is fully bonded to an aluminum wire/rod. Due to the axial symmetry, the proposed 2D elasoplastic fracture model has been reproduced in polar coordinates and be used to study the OMF behavior of alumina coating fully bonded to an aluminum wire. For the case where thermal loading is applied on coating/substrate structures, neither the plane strain nor plane stress assumption can be applied because the thermal loading would introduce multi axial normal stress, therefore, a three-dimensional (3D) elastic fracture model is then developed to study the OMF in the coating fully bonded to the elastic substrate. When the temperature change reaches a certain level, block cracking will initiate in the surface layer to release the accumulated thermal stress. For simplicity, we assume the top surface of the coating would keep flat and in a rectangular shape after deformation. Then the elastic field in both coating and substrate is analyzed and verified with the FE results. The fracture ERR is then obtained based on the solved elastic field and used to analyze the fracture initiation, infilling, and saturation. In order to verify the fracture analysis, the theoretical fracture analysis results are compared with FE simulation results based on the cohesive zone model (CZM) and experimental data from the literature. The good agreement demonstrates the accuracy of the proposed 3D fracture model. In addition, this model for coating/substrate system is extended to study multilayered structures with arbitrary number of layers. In order to verify this extended model, the predicted elastic field in an advanced polymeric solar reflector is compared with FE simulation results and parametric studies are conducted to investigate the effect of geometry on the accuracy of this model. Furthermore, the fracture behavior of the surface layer in the advanced polymeric solar reflector is studied using the calculated fracture ERR. Additionally, the delamination behavior, as another common failure mode of the coating/substrate structures, is then studied. The delamination fracture energy of a multilayered glass solar reflec- tor is tested by employing the width-tapered beam method. The testing results indicate that the weakest interface of the multilayered solar reflector would be the glass-copper interface with a de- lamination fracture energy 4.4 J/m2. Using the tested fracture energy as an input, an FE model is built based on the CZM and the returned peeling force from simulation is then compared with the test results to verify the accuracy of the test method. The good agreement between the simulation and test results demonstrates that the width-tapered beam method is accurate enough to measure the delamination fracture energy of this multilayered solar reflector. Additionally, the effect of aging on the delamination fracture energy is investigated by measuring the delamination fracture energy after 50 hrs’ accelerated aging test. The results show that the aging has minor effect of delamination fracture energy for samples with alumina (Al2O3) protective coating, while it reduces the delamination fracture energy for samples with titania (TiO2) protective coating. As another failure mechanism, the material degradation or aging behavior is studied in this dissertation. The weight percentage of oxygen (WPO) in three types of asphalt binders extracted from reclaimed asphalt pavements (RAPs) and one extracted from fresh Hot Mix Asphalt (HMA), that have been aged under continuous ultraviolet (UV) or UV/moisture/condensation exposure for different period, is measured using a energy-dispersive X-ray spectroscopy (EDX). Then the tested data are fitted based on two classic aging models, namely the fast-rate constant-rate (FRCR) and nonlinear differential dynamic (NDD) models. The good fitted results show that both FRCR and NDD models can capture the aging behavior of asphalt binders extracted from both RAPs and fresh HMA under continuous UV or UV/moisture/condensation exposure. Meanwhile, although exposed under UV for the same time, the WPO in samples after UV/moisture/condensation aging are lower than those in samples after continuous UV aging, which indicates that condensation and moisture reduce the UV-induced photo-oxidative aging rate.

Thesis (M.S.)--Rochester Institute of Technology, 2007. / Typescript. Includes bibliographical references.

In this study,The bottom electrode(TiN),middle insulator(Hf:SiOx),and top electrode(Pt) were deposited respectively by sputtering technique for fabricating the RRAM with MIM structure.The mole fraction of hafnium were about 5%.Instead of non-doped SiO2 base device has no switching characteristic,the Hf-doped SiO2 RRAM could be operator over 100 times and resistive state was kept stable over 104 second. In this researches,the double layer structure(Pt/Hf:SiO2/Hf:SiO2(doped N2 and NH3)).The Resistance switching characteristics of double layer structure device has particular I-V characteristics due to the doping of N.The doping of NH3 cause hydrogen plasma treatment on double layer device also bring about particular I-V characteristics. The physical mechanism we had proposed were proof by the Current-Voltage fitting and the material analysis.By control stop-voltage,the double layer structure device can operation by multi-bit. The detail physical mechanism is studied by the stable RRAM device(Ti/HfO2/TiN).In this study,the model of reset process we had proposed were proof by the special measurement methods(Constant-voltage sampling) and the principle of chemical reaction mechanism.

Thermal behavior and molecular packing of alkylated poly(ethylene- alt- maleic anhydride) and poly(styrene-alt-maleic anhydride) were studied by means of differential scanning calorimetry, thermogravimetry, polarizing optical microscopy, and X-ray diffraction. Effects of the length and graft density of alkyl side chains and backbone rigidity on the thermal behavior and on the structure of the mesophases are discussed.

Thermal behavior and molecular packing of a series of £\-helical poly(L-glutamates), with n-alkyl side chain of various lengths (m(number of carbons in the alkyl group) = 1, 2, 6, 12,18), were studied by means of differential scanning calorimetry, polarizing light microscopy and X-ray diffraction. For polymers of m = 1 and 2, There is a pseudohexagonal structure below ca. 130 oC and above this temperature the stable phase is the hexagonal columnar phase. There exists a layered structure in the polymer of m = 6, as well as a solvent induced hexagonal columnar structure which formed during solution casting process. In the polymer of m = 12, a layered structure was formed in the temperature range between 20 to 255 oC. However, for longer side chain, m = 18, tendency of crystallization of alkyl long side chain forced the backbone to pack into layer structure. There are two distinct melting temperature at ca. 60 oC, and the enthalpy are ca. 53 and 19 J/g, which corresponding to the melting of hexagonal and monoclinic side chain crystallines. The polymers with longer side chain (m = 6, 12 and 18) tend to be lyotropic liquid crystalline phase within lamellar inter-rod distance of 1.25 nm in solution state, and the structure will remain after drying. However, the inter-rod distance will collapse at the temperature above ca. 200 ¢J and will not recover after cooling.

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (p. 104-108).

Thesis (M.S.)--Mississippi State University. Department of Chemistry. / Title from title screen. Includes bibliographical references.

Thesis (Ph.D.) -- McMaster University, 2001. / Includes bibliographical references (leaves 136-143). Also available via World Wide Web.

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In this thesis a technique that is being used in another area of technology to optimize light reception in a photographic camera was also applied to the dielectric resonator antenna. The technique consisting of the use of thin film to couple the media and camera impedances resulted in a dielectric resonator antenna bandwidth enhancement technique. The bandwidth enhancement technique was found when thin film dielectric layer structure was used to couple the dielectric resonator and its feed mechanism. Remarkable good performance was detected with a coplanar waveguide fed cylindrical dielectric resonator antenna which resulted in an improvement to its fractional bandwidth from 7.41% to 50.85%. Extensive experimental work was undertaken in order to explore the extent offered in bandwidth performance by using thin film dielectric layer structure in the dielectric resonator antenna performance. The experimental tasks were designed in order to investigate the influence of the thin film dielectric layer structure in relation to its size, shape, thickness, position and direction. Experimental results were supported with simulation work with the computer simulation technology microwave studio. The pieces of the material used for undertaking this experimental work were manually handcrafted. Four different dielectric resonator antenna designs were used in order to carry out the experimental work including the coplanar waveguide fed cylindrical dielectric resonator antenna. The other three dielectric resonator antennas were implemented using the same microstrip feed mechanism. Improved performance in bandwidth was achieved for all the designs. Optimization of the incoming signal was observed when a piece of thin film dielectric layer structure was placed in position between the feed mechanism and the dielectric resonator antenna. The optimization was observed as an enhancement in both the return loss level and the bandwidth of work. Different unexpected operational modes from were activated, such modes being called perturbed modes. Two different shapes were used in this project. Cylindrical dielectric resonator antenna (ɛr = 37) from a commercial provider and two novel rectangular dielectric resonator antennas. The novel rectangular dielectric resonator antennas were created with the methodology presented in this thesis. The rectangular dielectric resonator antennas were elaborated with transparent ceramic material (ɛr = 7) and TMM10i (ɛr = 9.8) from the Rogers Corporation company. The bandwidth enhancement technique was tested in novel embedded dielectric resonator antennas. A coplanar waveguide fed embedded cylindrical dielectric resonator antenna achieved a maximum bandwidth enhancement of 156.77% around f = 3.79 GHz with a thin film dielectric layer structure modified rectangular piece on one edge. Escalation to dielectric resonator antenna design at millimeter wave frequencies was achieved by using thin film dielectric layer structure bandwidth enhancement technique and a handcrafted printed circuit board millimeter wave feed mechanism. The millimeter wave feed mechanisms were achieved using a low cost alternative technique conceived as part of this project. Millimeter wave dielectric resonator antennas were implemented using thin film dielectric layers structure. The antennas deliver an adequate performance in bandwidth. The work presented in this thesis demonstrates dielectric resonator antenna simpler geometry, simple couple schemes, small size, low profile, light weight, and ease of excitation and orientation. Other parameters have also been investigated covering reduced complexity, high degree of flexibility, ease of fabrication and the use of low cost technology to escalate to millimeter wave frequencies.