Thesis (M.S.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains ix, 107 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 76-83).

EFFECTS OF ETCHING DURATION ON THE SURFACE ROUGHNESS, SURFACE LOSS, FLEXURAL STRENGTH OF E.MAX CAD GLASS CERAMIC AND SHEAR BOND STRENGTH TO A RESIN CEMENT Background: Long-term retention of ceramic restorations is dependent on the bond strength of the luting resin to both the tooth and porcelain substrates. In order to achieve successful bonding, the surface of the porcelain substrate must be modified to increase the surface roughness, and this can be achieved chemically by hydrofluoric (HF) acid etching. However, prolonged HF acid etching has shown to have a weakening effect on the evaluated lithium disilicate glass-ceramics. Therefore, it is essential to quantify the required etching duration of HF acid to minimize the possible deleterious effects on ceramic strength while maximizing the bond strength to tooth structure. Objectives: To evaluate the effects of HF acid etching duration on the surface roughness, surface loss, flexural strength, and shear bond strength of IPS e.max CAD (Ivoclar Vivadent) lithium disilicate-based glass ceramic to a resin cement. Hypothesis: The differences in HF acid etching durations will not have a significant effect on the surface roughness, surface loss, flexural strength, or shear bond strength of IPS e.max CAD to a resin cement. Methods: 168 specimens were prepared from IPS e.max CAD blocks. All specimens were polished and sonically cleaned in distilled water. Specimens were fired in the vacuum pump furnace according to the manufacturer’s instructions. Specimens were then divided into 4 groups, according to etching durations, then further divided into 3 subgroups, according to the properties tested. Group A was not etched (control), Groups B, C and D were etched with 5-percent HF acid (IPS Ceramic Etching gel, Ivoclar Vivadent) for 20 s, 60 s and 90 s respectively. The morphologies of both etched and non-etched surfaces in specimens of subgroup 1 of each etching group (n = 16/group) were observed under scanning electron microscopy (SEM). In addition, non-contact surface profilometry (Proscan 2000) was used to calculate the surface loss and to examine the surface roughness of the etched ceramic surfaces and roughness values (Ra, Rq) were documented for each group. Furthermore, etched specimens of subgroup 2 (n = 16/group) were silanated (Monobond Plus, Ivoclar Vivadent) and cemented with a resin cement (Multilink Automix, Ivoclar Vivadent). The shear bond strength (SBS) was measured using a universal mechanical testing machine. For each etching group, subgroup 3 specimens (n = 10/group) were loaded to failure in a three-point bending test to measure their flexural strength values using a universal mechanical testing machine. Data for surface roughness, surface loss, and flexural strength were analyzed using one-way analysis of variance (ANOVA), to identify the significant effects of different HF acid etching durations. Data for shear bond strength test were analyzed using two-way ANOVA to test the effects of etching duration, storage for 24 hours/thermocycling, and their interaction. All pair-wise comparisons from ANOVA analysis were made using Fisher’s Protected Least Significant Differences to control the overall significance level at 5 percent. Results: Difference in HF etching durations did not have a significant effect on surface roughness values Ra or Rq (p = 0.3408; p = 0.3245) respectively, but had a significant effect on surface loss (p = 0.0006). SBS values were not significantly different between experimental groups (p = 0.4650); however, SBS values after 24-h storage were significantly higher than that found after thermocycling (p = 0.0166) among different etching durations. Finally, different HF etching durations did not have a significant effect on flexural strength values (p = 0.1260). Conclusion: Within the limitations of this study, different HF etching durations did not have a significant effect on surface roughness, flexural strength, or shear bond strength of IPS e.max CAD. However, the different etching durations significantly affected the surface loss of the lithium disilicate glass ceramics.

The continuously increasing demand for innovation in the miniaturization of microelectronics has driven the need for ever more precise fabrication strategies for device packaging, especially for printed circuit boards (PCBs). Subtractive copper etching is a fundamental step in the fabrication process, requiring very precise control of etch rate and etch factor. Changes in the etching chemical equilibrium have significant effects on etching behavior, and CuCl2 / HCl etching baths are typically monitored with several parameters including oxidation-reduction potential, conductivity, and specific gravity. However, the etch rate and etch factor can be difficult to control even under strict engineering controls of those monitoring parameters. The mechanism of acidic cupric chloride etching, regeneration and recovery is complex, and the current monitoring strategies can have difficulty controlling the interlocking chemical equilibria. A complimentary tool, thin-film UV-Vis spectroscopy, can be utilized to improve the current monitoring strategies, as UV-Vis is capable of identifying and predicting etching behavior that the current standard methodologies have difficulty predicting. Furthermore, as a chemically-sensitive probe, UV-Vis can investigate the complex changes to the chemical equilibrium and speciation of the etch bath, and can contribute overall to significant improvements in the control of the copper etching system in order to meet the demands of next-level design strategies.

Silicon micromachining is the collective name for several processes by which three dimensional structures may be constructed from or on silicon wafers. One of these processes is anisotropic etching, which utilizes etchants such as KOH and ethylene diamine pyrocatechol (EDP) to fabricate structures from the wafer bulk. This project is a study of the use of KOH to anisotropically etch (lOO)-oriented silicon wafers. The thesis provides a thorough review of the theory and principles of anisotropic etching as applied to (100) wafers, followed by a few examples which serve to illustrate the theory. Next, the thesis describes the development and experimental verification of a standardized procedure by which anisotropic etching may be reliably performed in a typical research laboratory environment. After the development of this procedure, several more etching experiments were performed to compare the effects of various modifications of the etching process. Multi-step etching processes were demonstrated, as well as simultaneous doublesided etching using two different masks. The advantages and limitations of both methods are addressed in this thesis. A comparison of experiments performed at different etchant temperatures indicates that high temperatures (800 C) produces reasonably good results at a very high etch rate, while lower temperatures (500 C) are more suited to high-precision structures since they produce smoother, higher-quality surfaces. / Master of Science

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Thesis (Ph. D.)--University of Washington, 1985. / Vita. Bibliography: leaves [135]-145.

Thesis (M.E.E.)--University of Delaware, 2006. / Principal faculty advisor: James Kolodzey, Dept. of Electrical and Computer Engineering. Includes bibliographical references.

There is no abstract available for this thesis.

The purpose of this thesis is to design and fabricate the S-shaped profile in depth. The results are applied to design a beam expander. In the experiments, we use the local etch-rate control, i.e. diffusion-limited etching, to fabricate the S-shaped profile. The etchant solution and recipe is H3PO4:H2O2:H2O =98:1:1 at 21¢J without stirring. The diffusion length of the etchant solution is 12.5mm. The device includes active semiconductor laser and passive tapered waveguide (beam expander). The design of the passive waveguide includes the lateral and vertical directions. In the lateral aspect, we use FimmWave to simulate the best symmetrical far field angle. When the waveguide width is 2.5mm and the etching depth is 1.4mm, we can get the best symmetrical far field angle which is lateral 27.88¢X and vertical 27.76¢X. In the vertical aspect, we use diffusion-limited etching to fabricate the depth changing. In this thesis, we use the beam expander length 350, 400, 450, 500mm.