The processing and characterization of thin film metallic glasses (TFMGs) and bulk metallic glass foams (BMGFs), prepared by the dealloying corrosion process, have been studied. The TFMGs were fabricated by the co-sputtering with the Zr65Cu25Ti10 (wt%) alloy target and the pure Ta target. For BMG, there are two kinds of amorphous metallic powders adopted, namely, Zr53Cu30Ni9Al8, and Ti40Cu36Pd14Zr10. The Zr- and Ti-based powders were sintered at the temperature that Zr- and Ti-based powders overlap their supercooled regions. To fabricate the porous structure, these materials were selectively dissolved using electrochemical treatments in 0.1 M HNO3 solution. The glassy nature and the pore morphology of the corroded materials were confirmed by X-ray diffraction and scanning electron microscopy. In the current study, the pore size is about 10-30 £gm and the porosity volume faction is about 43%. By using different combinations of the powders size and volume fraction, the resulting pore size and porosity fraction can be upgraded to 200-500 £gm and 60-80%, respectively.

A percentage of insulating glass (IG) units break each year due to thermally induced perimeter stresses. The glass industry has known about this problem for many years and an ASTM standard has recently been developed for the design of monolithic glass plates for thermal stresses induced by solar irradiance. It is believed that a similar standard can be developed for IG units if a proper understanding of IG thermal stresses can be developed. The objective of this research is to improve understandings of IG thermal stresses and compare the IG thermal stresses with those that develop in monolithic glass plates given similar environmental conditions. The major difference between the analysis of a monolithic glass plate and an IG unit is energy exchange due to conduction, natural convection, and long wave radiation through the gas space cavity. In IG units, conduction, natural convection, and long wave radiation combine in a nonlinear fashion that frequently requires iterative numerical analyses for determining thermal stresses in certain situations. To simplify the gas space energy exchange, a numerical propagation procedure was developed. The numerical propagation procedure combines the nonlinear effects of conduction, natural convection, and long wave radiation into a single value. Use of this single value closely approximates the nonlinear nature of the gas space energy exchange and simplifies the numerical analysis. The numerical propagation procedure was then coupled with finite element analysis to estimate thermal stresses for both monolithic glass plates and IG units. It is shown that the maximum thermal stresses that develop in IG units increase linearly with input solar irradiance during the transient phase. It is shown that an initial preload stress develops under equilibrium conditions due to the thermal bridge effects of the spacer. It is shown that IG units develop larger thermal stresses than monolithic glass plates under similar environmental conditions. Finally, it is shown that the use of low-e coatings increase IG thermal stresses and that the location of low-e coating as well as environmental conditions affect which glass plate develops larger thermal stresses.

In this paper, single mode buried optical waveguides based on hybrid sol-gel glasses and PECVD oxide were fabricated. Two different buried waveguide devices are investigated, and their optical characteristics are characterized. The first buried waveguide was obtained by etching a shallow trench on SiON layer. Then sol-gel material used as the guiding layer was deposited onto the layer and cured in proper conditions. Finally, the waveguides were completed by coating a sol-gel top cladding layer onto the guiding layer. The propagation loss of the waveguide is 0.59dB/cm at £f=1310nm. The second buried waveguide was fabricated by etching a trench of 5£gm on SiON layer and then burying sol-gel material into the trench.Proximity printing was used to define the waveguide core on sol-gel films.The waveguide was packaged for measurement after coating a UV glue on top of the core layer. The propagation losses of this waveguide device are 0.6dB/cm and 0.57dB/cm for TE and TM polarized lights. The coupling losses are 2.21dB and 2.41dB for TE and TM lights.

In this study, the reactive rf magnetron sputtering was used to deposit Ba(Zr0.1,Ti0.9)O3 (BZT) ferroelectric thin films on ITO/Glass substrate, and MFM structure was fabricated. The effects of various sputtering parameters on the characteristics of thin films, such as the oxygen concentrations, substrate temperature, rf power and chamber pressure were discussed, and then the optimal sputtering parameters were determined. The annealing process of rapid thermal annealing (RTA) and conventional thermal annealing (CTA) were used to promote the ferroelectric characteristics. The physical characteristics of BZT thin films were obtained by the analyses of SEM, XRD patterns and AFM morphologies. The surfaces, cross-section, crystallization and surface roughness of thin films were discussed. To investigate the electrical properties, the capacitance-voltage (C-V), current-voltage (I-V) and P-E hysteresis characteristics of BZT thin films were measured by the HP4284A impedance analyzer, HP4156C semiconductor parameter analyzer and computerized radiant technology (RT66), respectively. Furthermore, characteristics of the MFM structure were discussed. From the experimental results, the dielectric constant with optimal sputtering parameters was about 84, and the leakage current of thin film was about 6 ¡Ñ 10-8 A/cm2 when the applied electrical field of thin film was at 0.4 MV/cm. The remanent polarization (Pr) and coercive field (Ec) were 2.87 £gC/cm2 and 259 kV/cm from the P-E hysteresis loops, respectively. In addition, the ferroelectric characteristics of the thin film could be improved after rapid thermal annealing at 550¢J for 3 minutes. The remanent polarization (Pr), coercive field (Ec) and saturated polarization (Ps) were 3.42 £gC/cm2, 266 kV/cm and 6.99 £gC/cm2, respectively.

In this dissertation, the ternary Mg-based amorphous ribbons are characterized and analyzed first. Among the three Mg65Cu25Y10, Mg65Cu25Gd10 and Mg65Ni25Gd10 amorphous ribbons, the Mg65Cu25Gd10 amorphous ribbon exhibits the best thermal properties in terms of the glass forming ability (GFA) indexes, such as 68 K of the supercooled liquid region (£GTx), 29 K of the liquidus region (£GTl), 0.582 of the reduced glass transition temperature (Trg), 0.427 of the £^ value and 0.768 of the £^m value. In spite that the Mg65Cu25Gd10 amorphous ribbons do not show the best performance in mechanical properties, such as micro-hardness value of 231 Hv (2.26 GPa), nano-hardness value is 3.24 GPa (300 Hv) and modulus from nano-indentation of 62.4 GPa, this composition is close to the two prediction compositions of Mg62Cu27Gd11 (the e/a-variant criterion) and Mg67Cu23Gd10 (the binary eutectic clusters criterion). However, among a series of ternary of Mg-Cu-Gd amorphous ribbons, the better overall thermal properties are seen in the Mg54Cu32Gd14 and Mg54Cu31Gd15 amorphous ribbons. In terms of the bulk Mg65Cu25Gd10 amorphous alloys, the 6 mm bulk metallic glass (BMG) rod can be fabricated successfully with minimum porosity. In order to improve the brittle properties of the Mg65Cu25Gd10 BMG rod, there are two methods applied in this study, namely, the intrinsic toughening method by heat treatment and the extrinsic toughening method of adding reinforcements. For the heat treated Mg65Cu25Gd10 BMG rod, both of the one-step and two-steps BMG rods show no distinct plastic deformation in the engineering stress-strain curves, while the micro-hardness and compressive stress are increased from 270 Hv to higher than 300 Hv and from 804 to 830 MPa. But, for the ductile metal-reinforced Mg-based BMG rods, the brittle properties are improved. For the Nb-reinforced Mg65Cu25Gd10 BMG rods, the compressive stress decreases from 804 to 595 MPa and the plastic strain increases from 0 to 0.48% with increasing volume fraction from 0 to 17.3%. But, for Mg65Cu25Gd10 BMG rod reinforced by 21.6% porous Mo, the compressive stress and plastic strain are 821 MPa and 1.63%, respectively. Moreover, for the porous Mo-reinforced Mg58Cu28.5Gd11Ag2.5 BMG rods, the compressive stress increases from 827 to 1111 MPa and the plastic strain increases from 0 to 7.84% with increasing volume fraction from 0 to 25.4%.

This study investigates sub 200nm half-pitch polymer structures by nanoimprint process. The trench structures were fabricated on quartz glass with various depths and widths by FIB. To investigate the best nanoimprint process on SU-8, we studied various parameters such as: imprinting temperature, imprinting pressure, and temperature for de-molding, etc. ¡@This study had successfully defined 50nm width with different depths on to SU-8 by imprint. ¡@Imprint temperature above Tg 30¢J with constant pressure on continuous impressing and de-mold in room temperature would result in better imprinting results. The filling rate of this nanoimprint technology was measured by atomic force microscopy. ¡@For structures above/near 100nm half-pitch, the filling rate is nearly 100%.

Over the past decades, bulk metallic glasses (BMGs) have attracted extensive interests because of their unique properties such as good corrosion resistance, large elastic limit, as well as high strength and hardness. However, with the advent of micro-electro-mechanical systems (MEMS) and other microscaled devices, the fundamental properties of micrometer-sized BMGs have become increasingly more important. Thus, in this study, a methodology for performing uniaxial compression tests on BMGs having micron-sized dimensions is presented. Micropillar with diameters of 3.8, 1 and 0.7 £gm are fabricated successfully from the Mg65Cu25Gd10 and Zr63.8Ni16.2Cu15Al5 BMGs using focus ion beam, and then tested in microcompression at room temperature and strain rates from 1 x 10-4 to 1 x 10-2 s-1. Microcompression tests on the Mg- and Zr-based BMG pillar samples have shown an obvious sample size effect, with the yield strength increasing with decreasing sample diameter. The strength increase can be rationalized by the Weibull statistics for brittle materials, and the Weibull moduli of the Mg- and Zr-based BMGs are estimated to be about 35 and 60, respectively. The higher Weibull modulus of the Zr-based BMG is consistent with the more ductile nature of this system. In additions, high temperature microcompression tests are performed to investigate the deformation behavior of micron-sized Au49Ag5.5Pd2.3Cu26.9Si16.3 BMG pillar samples from room to their glass transition temperature (~400 K). For the 1 £gm Au-based BMG pillars, a transition from inhomogeneous flow to homogeneous flow is clearly observed at or near the glass transition temperature. Specifically, the flow transition temperature is about 393 K atthe strain rate of 1 x 10-2 s-1. For the 3.8 £gm Au-based BMG pillars, in order to investigate the homogeneous deformation behavior, microcompression tests are performed at 395.9-401.2 K. The strength is observed to decrease with increasing temperature and decreasing strain rate. Plastic flow behavior can be described by a shear transition zone model. The activation energy and the size of the basic flow unit are deduced and compared favorably with the theory.

Thesis (Ph. D.)--Lehigh University, 2001. / Includes bibliographical references and vita.

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Includes bibliographical references (p. 80-83).