The Pd77Cu6Si17 (PCS) thin film metallic glasses (TFMGs) with high glass forming ability and hardness are selected as a hard coating for improving the surface hardness of the AZ31 magnesium alloy. Both micro- and nano-indentation tests are conducted on the specimens with various PCS film thicknesses from 30 to 2000 nm. The apparent hardness and the relative indentation depth (£]) are integrated by a quantitative model. The involved interaction parameters and relative hardness values are extracted from iterative calculations. According to the results, surface hardness can be enhanced greatly by PCS TFMGs in the shallow region, followed by gradual decrease with increasing £] ratio. In addition, the specimens with thinner coating (for example, 200 nm) show greater substrate-film interaction and those with thick coating (for example, 2000 nm) become prone to film cracking. The optimum TFMG coating thickness in this study is estimated to be around 200 nm. Keywords: Magnesium alloys, hardness, sputtering, thin film metallic glass, nanoindentation

BMGs (bulk metallic glasses) exhibit many exceptional advantages for engineering applications, such as high strength, good corrosion resistance, etc. Despite of having these excellent properties, the brittle nature of metallic glasses in the bulk and thin film forms inevitably imposes limitation and restricts the wide application of BMGs and TFMGs. Composite concept might be another idea to solve this dilemma. In order to manufacture the bulk metallic glass composites (BMGCs), the approaches are classified into two categories: the intrinsic and extrinsic methods. For the intrinsic method, the in situ process and heat treatment process are two kinds of ways in common uses. Adding reinforcements into the BMGs or TFMGs is extensively used to manufacture composites in the extrinsic method. In this study, the deformation behaviors of multilayer (amorphous/nanocrystalline) micropillars are studied by uniaxial microcompression tests at room temperature. The nanocrystalline layer to be coupled with the amorphous layer can be of either face-centered cubic (FCC), hexagonal close-packed (HCP) or body-centered cubic (BCC) in crystal structure. The current study demonstrates that brittle problem of a metallic glass coating can be alleviated by percolating with a nanocrystalline metallic underlayer. The brittle thin film metallic glass can become highly ductile and exhibit a plastic strain over 50% at room temperature. The present study has an important implication for MEMS applications, namely, the life span of a brittle amorphous layer can be significantly improved by using an appropriate metallic underlayer. The brittle problem of thin film ZrCu metallic glasses was also treated by invoking soft Cu layers with optimum film layer thickness. Such multilayered amorphous/crystalline samples exhibit superplastic-like homogeneous deformation at room temperature. It is found that the deformability of the resultant micropillars depends on the thickness of Cu layers. Microstructural observations and theoretical analysis suggest that the superplastic-like deformation mode is attributed to homogeneous co-deformation of amorphous ZrCu and nanocrystalline Cu layers because the 100 nm-thick Cu layers can provide compatible flow stress and ¡§plastic zone¡¨ size well matched with those of ZrCu amorphous layers. Besides, we also made attempts to investigate the critical sample size below which shear band localization would disappear and the sample can deform homogeneously. In situ TEM compression was conducted on amorphous ZrCu nanopillars to study shear band formation behavior. The nanopillar is 140 nm in diameter and with a taper angle of 3¢X. Experimental observations and simulations based on a free-volume model both demonstrate that the deformation was localized near the top of the tapered metallic glass pillar. Eventually, the interface nature of metallic glass amorphous/crystalline was characterized through evaluating its energy and validated by the mechanical response of micropillar with ~45o inclined interface under compression. The calculated results showed that the ZrCu/Zr interface energy resides several joules per meter square, meaning that the Zr/ZrCu interface is inherently strong. The high strong adhesion ability of ZrCu/Zr interface was further confirmed by shear fracture happening rightly within the Zr layers rather than along the interface when compressing the ZrCu/Zr micropillars with 45o inclined interface.

This study is separated into two parts. Firstly, the Ag thin film was deposited on substrates with different average roughness by sputtering to examine the effect of substrate roughness on optical reflection. The results exhibit 10 percent difference of reflectivity within several nanometer changing in average roughness, indicating the reflectivity is easily affected by surface roughness. Secondly, optical reflectivity and electrical resistivity of multi-component AgMgAl alloys, both crystalline and amorphous, were measured. The crystalline alloys exhibit high reflection in infrared region but a steeper drop in visible and ultraviolet regions. By contrast, amorphous alloys show a lower but relatively uniform reflectivity in the visible and infrared regions. In both cases, the reflectivity was observed to scale with the square root of electrical resistivity. The scaling law was explained based on classical reflection theory. The different scaling factors for crystalline and amorphous alloys could be rationalized by the difference in the mean free time of charge carriers. Moreover, the mechanical properties of crystalline and amorphous thin film alloys, including hardness and modulus, were measured by nanoindentation. The hardness of thin film metallic glasses (TFMGs) is obviously higher than crystalline metals, while the modulus of TFMGs is similar to crystalline metals.

Experimental studies showed the feasibility of adding metallic catalysts and tetralin for the upgrade and increased recovery of heavy oil during the in situ combustion process. Further experimental studies also showed the applicability of in situ combustion as a viable method of upgrading and improving recovery of intermediate oils. Three successful experimental runs were performed with heavy oil from Mexico (10.1 degrees API gravity). The first run was the control run without the addition of tetralin or metallic catalysts; the second run used heavy oil premixed with 3 wt% tetralin and 500ppm nickel catalyst; and the third run was with heavy oil premixed with 3 wt% tetralin and 500ppm iron catalyst. For the three runs, the cell production pressure was kept constant at 300 psig. The combustion cell was placed in a vacuum jacket and set to a temperature of 60 degrees C. For the only successful run with the intermediate Texas oil (22.0 degrees API gravity), the production pressure was also kept constant at 300 psig but the vacuum jacket temperature was set to a reservoir temperature of 40oC. During the runs for both oils, samples of produced oils and combustion flue gases were collected at regular intervals for analysis. These analyses included determination of oil viscosity and density, oil recovery, combustion front velocity, and apparent H/C ratio. Experimental results for the intermediate oil run, the oil gravity increased by 6 points showing the upgrading effects of in situ combustion on intermediate oils. Also, the high average combustion temperatures observed during the run indicated that in situ combustion may be applicable to reservoirs of similar characteristics to the intermediate Texas oil reservoir. Heavy oil experimental run results indicated that the use of tetralin and metallic catalysts increase the average combustion front temperature from 484 degrees C to 501 degrees C for the run with nickel catalysts, and from 484 degrees C to 492 degrees C for the run with iron catalysts. These results also show an increase in produced oil recovery from 83% to 90% of oil initially in place for the nickel catalyst run, and 83% to 86% of oil initially in place for the iron catalyst run.

The multi-scale modeling of ion-solid interactions presented can lead to a fundamentally new approach for understanding temperature evolution and damage formation. A coupling of the Monte Carlo code, SRIM, to a C FEM heat transfer code was performed, enabling a link between the damage cascade event to the subsequent heat transfer. Modeling results indicate that for 1 MeV Ni ion irradiation in Ni52.5Nb10Zr15Ti15Pt7.5, the heat transfer rate is too large for direct crystallization. Although the damage cascade induces a peak temperature of 5300 K, within 6 picoseconds the temperature is below the glass transition temperature. This result implies that there is a cooling rate of 10^14 K/s, which is much greater than the critical cooling rate for this material. Ion irradiation was performed to compare modeling with experiment. No evidence of direct crystallization is observed under TEM. Nanocrystals are formed as a consequence of series of multistage phase transitions. This provides evidence that the energy dissipation occurs too quickly for direct crystallization, as crystals are found in regions having undergone substantial compositional changes. A host of conventional electron microscopy methods were employed to characterize the structural changes induced by 1 MeV Ni ion irradiation in Ni52.5Nb10Zr15Ti15Pt7.5 and identify the phases that form, Ni3Nb, Ni3Ti and Ni3Zr. Scanning TEM analysis revealed Pt segregation near crystal regions due to irradiation. Due to a lack of Pt crystal phases observed and high concentrations of Pt in crystal regions it is postulated that Pt is substituting for Ni to form (Ni,Pt)3Nb and (Ni,Pt)3Ti.

It has been reported that the Zr-based amorphous alloys exhibit high corrosion resistance, good mechanical properties, better thermal stability and good glass-forming ability. The thermal properties of the Zr-Al-Cu-Ni amorphous alloys could be improved by adding boron and silicon that also has been reported. Therefore, the Zr-Al-Cu-Ni amorphous alloys are chosen as the base materials for investigating the effect of the thermal properties by adding boron and silicon at the same time. According to the results of the experiment, the Zr60Al7.5Cu17.5Ni10B1Si4 amorphous alloy ribbons with the highest GFA index (g value) and the value is 0.42; the maximum supercooled liquid region (DTx) is about 85 K for the Zr60Al7.5Cu17.5Ni10B1Si4 amorphous alloy ribbons. For the isothermal analysis or non-isothermal analysis, the Avrami index (n value) is not constant, and the Zr60Al7.5Cu17.5Ni10B1Si4 amorphous alloy ribbons with the largest activation energy which was more than 300 kJ/mol. When the Zr60Al7.5Cu17.5Ni10B1Si4 amorphous alloy ribbons were heated to 721 K and held for 4000 seconds, the crystallized phases were ZrO2 with orthorhombic structure and Zr2Ni with tetragonal structure. When the Zr62Al7.5Cu17.5Ni10B2Si1 amorphous alloy ribbons were heated to 724 K and held for 4000 seconds, besides the ZrO2 phase with orthorhombic structure and the Zr2Ni phase with tetragonal structure, a Zr2Ni crystallized phase with cubic structure is also included. According to the observation of the TEM image for heating Zr62Al7.5Cu17.5Ni10B2Si1 amorphous alloy ribbons to 694 K and held for 4000 seconds, there are many grains distribute in the amorphous matrix, and the grain size is about 20 ~40 nm.

In this thesis, the design rule of the tag antenna and the properties of the high impedance surface structure are studied. We proceed to design the low profile and miniature high impedance surface structure. In order to be more competitive, we use PCB plates for fabrication to reduce the cost. The tags are intended to be placed inside two shorted metallic plates. In order to reduce the effect of the two parallel metallic plates, we use the slots to design the tag antenna. The EBG structure behaves as a high impedance surface and suppresses the surface wave. We add the EBG structure on the back of the antenna to reduce the back metallic effect. We use slot structure to design the non-planar RFID reader antenna that can be placed inside the three metallic plates to read the data. For the slot structure design, the electric field between the slots is perpendicular to the upper and lower metallic plates. According to the image theory, the induced image current will result in constructive effect to reduce the metallic effect. Finally, the hand-held RFID reader may not identify the RFID tag as the RFID tag placed at position deeper inside. The proposed non-planar reader can solve this problem to be used for more applications.

On the toughening of bulk metallic glasses (BMGs), successful results in the phase-separated Zr63.8Ni16.2Cu15Al5 BMG have achieved compressive ductility over 15% through the computational-thermodynamic approach. In this study, the phase-separated Zr63.8Ni16.2Cu15Al5 BMG was compressed to nominal strains of 3%, 7%, and 10% at low strain rates (~10-4 s-1) and the results demonstrated that the BMG exhibited apparent uniform deformation initially, followed by visible local shear bands development. Afterwards, a single shear along the principal shear plane was soon developed and mainly dominated the whole deformation process. The principal shear contributed more than 2/3 of the overall plastic strain until failure. It was also found that the local shear strain varied along the principal shear plane and decreased monotonically from the shear band initiation site. Subsequently, in-situ compression experiments were conducted to monitor the change of sample shape during deformation in order to properly correlate with the stress-strain curve. The observed images showed that there was a one-to-one correspondence between the intermittent sample sliding and flow serration in the plastic region of stress-strain curve. Further investigations on flow serration were conducted on the Pd40Ni40P20 BMG through the compression experiments equipped with high-sensitivity strain gauges directly attached to two opposite sides of the test sample. There was an accompanied displacement burst when a shear band starts to propagate during deformation and this displacement burst would be accurately captured by the high-sensitivity strain gauges. Based on the displacement-time profile for one serration, shear-band propagating speed can be estimated and found to be insensitive to the applied strain rates (or the applied crosshead speeds). The disappearance of flow serration at high strain rates should be a result that the signal of displacement burst was overwhelmed by the applied strain rate. Using the shear strain rate data, the measured viscosity within a propagating shear band was found to be relatively low, which is in similar to the viscosity values reported in the supercooled liquid region during homogeneous deformation. In comparison with shear band propagation in the brittle Mg58Cu31Y6Nd5 and Au49Ag5.5Pd2.3Cu26.9Si16.3, moderately ductile Cu50Zr43Al7 and Pd40Ni40P20, and highly ductile phased-separated Zr63.8Ni16.2Cu15Al5 systems, the ductility of BMGs appears to be closely related to the dynamics during shear band propagation. The more ductile in nature the metallic glass is, the slower the shear band propagating speed would become. We also made attempts to investigate the shear band propagation in the porous Mo particles reinforced Mg58Cu28.5Gd11Ag2.5 bulk metallic glass composites (BMGCs) with up to 10% compressive failure strain. It was found that flow serration was absent in the stress-strain curve. Using high-sensitivity strain gauges, no distinct displacement burst was detected in the displacement-time profile. The diappearance of flow serration for the current porous Mo particles reinforced Mg58Cu28.5Gd11Ag2.5 BMGC is apparently associated with the lack of long-range shear band propagagtion. By employing the approach of separating the homogeneous amorphous matrix into many individual compartments, only short-range shear band propgagation is possible in the current Mg-based BMGC. An effective free spacing considering the spacing between two porous Mo particles and porous Mo particle size was applied to interpret the development of shear band propagation and is a useful indicator for the design of BMGC with high ductility.

The synthesis and characterization of some phosphonic acids as well as the modification of indium tin oxide (ITO) substrates using these phosphonic acids are presented in this thesis. Phosphonic acids have been known to bind strongly to the surface of a number of metal oxides. ITO substrates were reported to be modified with a variety of surface modifiers. Herein the ITO substrates were modified with the chosen phosphonic acids with different functional groups in order to tune the work function and compare the work function changes with the functional group properties.

Thesis (Ph. D.)--University of Missouri-Columbia, 1998. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.