Nickel zinc ferrites (NZF) have been considered as one of the basic components in high frequency electromagnetic applications especially in the field of telecommunications. In the present study, the aim was to produce high quality nickel zinc ferrite ceramics at low soaking temperatures. For this purpose, conventional ceramic manufacturing method based on mixed oxide precursors was followed using calcium fluoride, CaF2, as sintering additive. During the sintering studies, it was noticed that both the microstructure and the electromagnetic properties of the NZF ceramics were modified to a great extent by CaF2. Therefore, material characterization studies involving microstructural, dielectric and magnetic properties were conducted with respect to CaF2 content of ceramics and soak duration. The results showed that due to the presence of CaF2 in ceramics, significant improvements were achieved not only in kinetics of sintering but also in the parameters / DC electrical resistivity, dielectric constant and dielectric loss factor. For example, 1.0 wt% CaF2 added NZF ceramic produced in this study had a DC electrical resistivity of 1011 &amp / #61527 / -cm which was 100,000 times bigger than the one attained in pure NZF ceramic. On the other hand, the dielectric constant exhibited a flat behavior up to 40 MHz with a value around 16. In addition, no resonance peak was observed in dielectric loss factor spectra, and the typical values of dielectric loss factor lied below 0.01. Besides the achievements mentioned, the magnetic properties such as relative magnetic loss factor and hysteresis parameters were also improved.

In this work, adhesion between electrolessly deposited copper and dielectric materials for use in microelectronic devices is investigated. The microelectronics industry requires continuous advances due to ever-evolving technology and the corresponding need for higher density substrates with smaller features. At the same time, adhesion must be maintained in order to preserve package reliability and mechanical performance. In order to meet these requirements two approaches were taken: smoothing the surface of traditional epoxy dielectric materials while maintaining adhesion, and increasing adhesion on advanced dielectric materials through chemical bonding and mechanical anchoring. It was found that NH3 plasma treatments can be effective for increasing both catalyst adsorption and adhesion across a range of materials. This adhesion is achieved through increased nitrogen content on the polymer surface, specifically N=C. This nitrogen interacts with the palladium catalyst particles to form chemical anchors between the polymer surface and the electroless copper layer without the need for roughness. Chemical bonding alone, however, did not enable sufficient adhesion but needed to be supplemented with mechanical anchoring. Traditional epoxy materials were treated with a swell and etch process to roughen the surface and create mechanical anchoring. This same process was found to be ineffective when used on advanced dielectric materials. In order to create controlled roughness on these surfaces a novel method was developed that utilized blends of traditional epoxy with the advanced materials. Finally, combined treatments of surface roughening followed by plasma treatments were utilized to create optimum interfaces between traditional or advanced dielectric materials and electroless copper. In these systems adhesion was measured over 0.5 N/mm with root-mean-square surface roughness as low as 15 nm. In addition, the individual contributions of chemical bonding and mechanical anchoring were identified. The plasma treatment conditions used in these experiments contributed up to 0.25 N/mm to adhesion through purely chemical bonding with minimal roughness generation. Mechanical anchoring accounted for the remainder of adhesion, 0.2-0.8 N/mm depending on the level of roughness created on the surface. Thus, optimized surfaces with very low surface roughness and adequate adhesion were achieved by sequential combination of roughness formation and chemical modifications.

The objective of this thesis is to understand and improve optical and electrical confinement to achieve cost-effective high-efficiency thin p-type Si solar cells. Optical confinement is achieved by front surface texturing in conjunction with an internal reflective layer on the back surface. Electrical confinement is obtained through the use of a high-lifetime material coupled with high-quality passivation on both surfaces. This research is divided into five tasks. In the first task, Ga-doped Cz Si was investigated to achieve a high and stable lifetime. It was found that for 1 ohm-cm nominal-resistivity screen-printed Al-back surface filed (BSF) cells, the Ga-doped ingot gave ~1.5% higher absolute efficiency after light-soaking relative to the B-doped counterpart. The benefit of using Ga is therefore quite explicit. In the second task, the screen-printed Al-BSF was investigated to explore its potential and limitations for achieving high-efficiency cells. It was found that there exists a critical alloying temperature for a given Al-thickness, above which the Al-BSF becomes non-uniform and cell performance starts to degrade. This puts a limit on the quality of the Al-BSF that can be achieved. An alternative way of back passivation involving dielectric/metal layers was therefore explored. In Task three, two key requirements for achieving high-efficiency dielectric back-passivated cells were established through device modeling. These are (1) a formation of a high-quality BSF underneath the local back contact through vias in the dielectric and (2) a high-quality dielectric passivation with either a moderate positive charge density or a high negative charge density. Task four involved the development of a metallization technique through vias in the dielectric to achieve a high-quality contact and an efficient internal reflector in conjunction with a high-quality local BSF. Further, a novel dielectric system composed of a spin-on SiO<SUB>2</SUB> layer capped with SiN<SUB>x</SUB> was developed that exhibited excellent passivation and a moderate positive charge density. The final task involved fabrication and analysis of dielectric back-passivated cells. The new dielectric and process sequence developed in this thesis resulted in screen-printed solar cells with efficiency as high as 19% with the potential for 20% efficient cells on 100-µm thick Si substrates.

No description available.

This thesis deals with certain aspects of the solution chemistry of the simple dicarboxylate anions: oxalate, malonate and succinate, up to high concentrations. These ions are either significant impurities in the concentrated alkaline aluminate solutions used in the Bayer process for the purification of alumina, or are useful models for degraded organic matter in industrial Bayer liquors. Such impurities are known to have important effects on the operation of the Bayer process. To develop a better understanding of the speciation of oxalate (the major organic impurity in Bayer liquors) in concentrated electrolyte solutions, the formation constant (Log£]) of the extremely weak ion pair formed between sodium (Na+) and oxalate (Ox2ƒ{) ions was determined at 25 oC as a function if ionic strength in TMACl media by titration using a Na+ ion selective electrode. Attempts to measure this constant in CsCl media were unsuccessful probably because of competition for Ox2ƒ{ by Cs+. Aqueous solutions of sodium malonate (Na2Mal) and sodium succinate (Na2Suc) were studied up to high (saturation) concentrations at 25 oC by dielectric relaxation spectroscopy (DRS) over the approximate frequency range 0.1 „T £h/GHz „T 89. To complement a previous study of Na2Ox, formation constants of the Na+-dicarboxylate ion pairs were determined and they were shown to be of the solvent-shared type. Both the Mal2ƒ{ and Suc2ƒ{ ions, in contrast to Ox2ƒ{, were also shown to possess large secondary hydration shells Apparent molal volumes (Vf) and heat capacities at constant pressure (Cpf) of aqueous solutions of Na2Ox, Na2Suc, Na2Mal and K2Ox were determined at 25 oC up to their saturation limits using vibrating tube densitometry and flow calorimetry. These data were fitted using a Pitzer model. The adherence of Vf and Cpf of various Na+ and K+ salts to Young¡¦s rule was examined up to high concentrations using the present and literature data. Young¡¦s rule was then used to estimate hypothetical values of Cpf and Vf for the sparingly soluble Na2Ox at high ionic strengths, which are required for the thermodynamic modelling of Bayer liquors. The solubility of Na2Ox in various concentrated electrolytes was measured, at temperatures from 25 oC to 70 oC in media both with (NaCl, NaClO4, NaOH) and without a common ion (KCl, CsCl, TMACl). The common ion effect was found to dominate the solubility of Na2Ox. The solubility of calcium oxalate monohydrate (CaOx„ªH2O) was also determined. The solubilities of both Na2Ox and CaOx„ªH2O in media without a common ion increased with increasing electrolyte concentration, except in TMACl media, where they decreased. The solubility of Na2Ox was modelled using a Pitzer model assuming the Pitzer parameters for Na2SO4 and minimising the free energy of the system. The data were modelled successfully over the full concentration and temperature range of all the electrolytes, including ternary (mixed electrolyte) solutions.

19 Dec 2004. / Published through the Information Bridge: DOE Scientific and Technical Information. "IS-T 2082" Henry Hao-Chuan Kang. 12/19/2004. Report is also available in paper and microfiche from NTIS.

Thesis (Ph. D.)--Oregon State University, 1993. / Typescript (photocopy). Includes bibliographical references (leaves 102-110). Also available on the World Wide Web.

Thesis (Ph. D.)--University of Alabama at Birmingham, 2007. / Additional advisors: Yogesh K. Vohra, Renato P. Camata, Herbert C. Cheung, Craig A. Elmets. Description based on contents viewed June 23, 2009; title from PDF t.p. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 165-173). Also available on the World Wide Web.