Engineering Commons^™

Metal-Organic Chemical Vapor Deposition Of Sr-Co-Fe-O Films On Porous Substrates, C.-F. Xia, P. Atanasova, Robert W. Schwartz, T. L. Ward

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Aerosol-assisted chemical vapor deposition using the b-diketonate precursors Sr(tmhd)2•2H2O, Fe(tmhd)3 and Co(tmhd)3 was investigated for depositing thin films of the mixed-conducting ceramic SrCoyFe1-yO3-d onto porous a-Al2O3 substrates. Single-phase SrCoyFe1-yO3-d perovskite films were obtained at a deposition temperature of 550°C and pressure of 15 mm Hg, whereas deposition at atmospheric pressure produced mixed-phase films. The Co/Fe elemental ratios in the films reflected those in the precursor solution, but the films were depleted in Sr. Reduced-pressure deposition provided a more uniform film morphology than atmospheric-pressure, and led to a supported film which was leak-tight to N2 flow.

Deuterium Nmr Of Adsorbed Poly(Methyl Acrylate)-D₃, Frank D. Blum, Wuu-Yung Lin

Chemistry Faculty Research & Creative Works

The dynamics of polymers at interfaces are important in a variety of applications, especially where those applications depend on the mechanical or surface properties. Unfortunately, the surface properties of interfacial species like polymers used in composites are not easily measured macroscopically. Microscopic techniques, especially spectroscopic ones, have been successful. In our laboratory we have been successful in applying NMPR to determine the behavior of absorbed polymers. NMR has several advantages for this kind of study, the principal ones being that it can be used on opaque materials, different nuclei can be used as probes, and interfacial material can sometimes be …

Magnetoresistance Of Magnetic Tunnel Junctions In The Presence Of A Nonmagnetic Layer, Shi C. Zhang, P. M. Levy

Materials Science and Engineering Faculty Research & Creative Works

We find that electron propagation across a uniform nonmagnetic metallic layer di in a magnetically layered structure is coherent up to a critical length dc. This provides a possible explanation for the slow decay of the magnetoresistance of magnetic tunnel junctions when a layer of Cu or Ag is inserted between the magnetic electrode and the barrier. However, for many (most) structures the roughness of the interfaces breaks the coherence for di ≪ dc. While the loss of coherence is not fatal for the magnetoresistance of metallic multilayers, it is for tunnel junctions. The quantum well states arising from the …

Analysis Of The Value Of The Fe Examination For The Assessment Of Student Learning In Engineering And Science Topics, John L. Watson

Materials Science and Engineering Faculty Research & Creative Works

This paper presents the results of a project, which investigated the potential of fully using previously unreleased data from the nationally normed Fundamentals of Engineering (FE) examination to assess learning in key engineering and science topics. In the past, very limited information was released by the National Council of Examiners for Engineers and Surveyors (NCEES) for the eight hour FE examination, which is composed of 150-200 questions in ten morning and five afternoon topics. For the purposes of this project the NCEES agreed to release information to the University of Missouri-Rolla (UMR) to permit the value of the FE data …

Evolution Of In Situ Refractories In The 20th Century, William E. Lee, Robert E. Moore

Materials Science and Engineering Faculty Research & Creative Works

A common theme over the past 100 years in refractories science and technology has been to generate a protective refractories layer in a high-temperature container, often by reaction of the refractory materials with the contents (glass, slag, or atmosphere). The history of refractories during the 20th century is used in this review to illustrate how techniques - such as slag splashing, in situ spinel generation in castables, magnesia dense layer formation in magnesia-carbon brick in steelmaking, clinker adhesion in cement kilns, and viscous boundary layer generation in glass tanks - have evolved to their present status.

Organically Deposited Metallic Films For Device Fabrication, Thomas J. O'Keefe, M. Stroder, Matthew O'Keefe

Materials Science and Engineering Faculty Research & Creative Works

Advances in integrated circuit density, speed and complexity are dependent on lower resistance, finer line width on-chip interconnections. Methods for incorporating copper interconnects into IC fabrication processes have been developed which accomplish this objective but most of these methods use some form of blanket metal deposition that requires mechanical and/or chemical removal of excess material. To date, investigations into the selective deposition of conductor materials for device fabrication have met with limited success. A new process for selectively depositing metallic conductors using inexpensive, organic-based chemical solutions could potentially force a paradigm shift in the deposition of metals for microelectronic applications. …

Maskless, Direct Deposition Of Copper Onto Aluminum Bond Pads For Flip Chip Applications, M. Fang, Thomas J. O'Keefe, M. Stroder, W. Shih, Matthew O'Keefe, R. Strawser, D. Via

Materials Science and Engineering Faculty Research & Creative Works

Flip chip interconnection of integrated circuits (IC) for packaging applications such as direct chip attachment use Pb-Sn solders as the connection between the die and the substrate. Under bump metallization is typically used to transition from the non-solderable Al bond pad on the IC to a solderable surface such as copper using traditional blanket metal deposition, photolithography and etching procedures. In this study, we report for the first time the use of a novel process for selectively depositing adherent copper directly onto aluminum thin films, eliminating the need for adhesion promoting transition layers and additional patterning steps. Utilizing copper bearing …

An Evaluation Of The Aws Entry Level Welder Training Program, John R. Rice

Dissertations and Theses @ UNI

The purpose of this study was to evaluate the effectiveness of a training program for Entry Level Welders and to provide this information to the American Welding Society (AWS), industry, and educators. The problem of this study was to evaluate the AWS Entry Level Welder Training Program (ELWTP) by obtaining the opinions of faculty members who taught the program and welders who had completed the program.

Two groups comprised the research population for this study. The first group consisted of faculty members who were actually involved in teaching the course at institutions accredited by the AWS to offer the curriculum. …

White Light Interferometric Surface Profiler, Vincent Toal, Brian Bowe

Articles

We describe an optical system for 3-D profilometry based on the white light interferometer. We detail a simple way to construct a profiler that uses two simple algorithms which deal efficiently and quickly with the data. The system has a theoretically unlimited range and can deal with rough and smooth surfaces

Formation Of A Metastable Bcc Solid Solution And Decomposition To A C15 Laves Phase In Melt-Spun Crnb10Ti10, Katherine C. Chen, P. G. Kotula, F. Chu, Dan J. Thoma

Materials Engineering

A metastable, disordered bcc phase has been formed from the melt in a Cr-rich alloy of the Nb-Cr-Ti system, where large volume fractions of the Laves phase would develop under equilibrium solidification conditions. X-ray diffraction (XRD) studies and lattice constant determinations confirm that the melt-spun ribbons contain a bcc phase beyond its terminal solid solution limits. Solidification pathways are proposed based upon metastable and equilibrium phase diagrams. Microstructures have been studied using optical microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Cross-sectional TEM reveals tiny, dispersed Laves phase precipitates within the metastable bcc grains near the chill (wheel) …

Measurement Of Ultrafast Carrier Recombination Dynamics In Mid-Infrared Semiconductor Laser Material, William T. Cooley

Theses and Dissertations

Shockley-Read-Hall, radiative, and Auger recombination rates in mid-infrared laser structures are measured and reported using time resolved photoluminescence (TRPL) frequency upconversion. The mid-IR lasers studied were actual InAsSb/InAlAsSb multiple-quantum-well (MQW) diode lasers emitting near 3.3 micrometers which were previously characterized for laser performance. This effort extends the initial studies and reports on the carrier recombination dynamics. Shockley-Read-Hall, radiative and Auger recombination rates at low temperature (77 K) were measured and found to be A_SRH ≈ 10 x 10⁷sec^-1, B_rad ≈ 2 x 10^-10 cm³sec^-1 and C_Auger < 10^-29 cm^{6 …}

Recycling Of Composite Material, Shereen Hassanein El Attawi

Archived Theses and Dissertations

No abstract provided.

Investigation Of Two-Phase Air Water Flow Using Annubar, Ehab Fouad Shoukry

Archived Theses and Dissertations

No abstract provided.

Absolute Measurements Of The High-Frequency Magnetic Dynamics In Hihg-Tc Superconductors, Stephen M. Hayden, Gabriel Aeppli, Pengcheng Dai, Herbert A. Mook, Toby G. Perring, S-W Cheong, Zachary Fisk, Fatih Dogan, Thomas E. Mason

Materials Science and Engineering Faculty Research & Creative Works

We review recent measurements of the high-frequency dynamic magnetic susceptibility in the high-T~ superconducting systems La_2-xSr_xCuO₄ and YBa₂Cu₃O_6+x. Experiments were performed using the chopper spectrometers HET and MARI at the ISIS spallation source. We have placed our measurements on an absolute intensity scale; this allows systematic trends to be seen and comparisons with theory to be made. We find that the insulating S = ½ antiferromagnetic parent compounds show a dramatic renormalization of the spin wave intensity. The effect of doping on the response is to cause broadenings in …

Pseudogap And Incommensurate Magnetic Fluctuations In Yba2cu3o6.6, Pengcheng Dai, Herbert A. Mook, Fatih Dogan

Materials Science and Engineering Faculty Research & Creative Works

Unpolarized inelastic neutron scattering is used to study the temperature and wave vector dependence of the dynamical magnetic susceptibility, X"(q, w), of a well-characterized single-crystal YBa2Cu3O6.6 (Tc = 62.7 K). We find that a pseudo gap opens in the spin-fluctuation spectrum at temperatures well above Tc. We speculate that the appearance of the low-frequency incommensurate fluctuations is associated with the opening of the pseudo gap. To within the error of the measurements, a gap in the spin-fluctuation spectrum is found in the superconducting state.

Pseudogap And Incommensurate Magnetic Fluctuations In Yba2cu3o6.6, Pengcheng Dai, Herbert A. Mook, Fatih Dogan

Materials Science and Engineering Faculty Research & Creative Works

Unpolarized inelastic neutron scattering is used to study the temperature and wave vector dependence of the dynamical magnetic susceptibility X"(q,w) of a well-characterized single-crystal YBa₂Cu₃O_6.6 (Tc = 62.7 K). We find that a pseudogap opens in the spin-fluctuation spectrum at temperatures well above T_c. We speculate that the appearance of the low-frequency incommensurate fluctuations is associated with the opening of the pseudogap. To within the error of the measurements, a gap in the spin-fluctuation spectrum is found in the superconducting state.

The Activity Of Alloy Cu-Ni Electrode In Electroreduction Of Aromatic Nitro-Compounds, Chunan Ma, Shaoping Tong, Xiaojun Cheng, Hui Wang

Journal of Electrochemistry

Cu-Ni alloy on the basis of copper at different ratio Cu/Ni are prepared by codepostion. The cathode activtiy of film are studied by steady-state polarization for electroreduction nitro-benzene (NB) and 1,5-dinitroanthraquinone (1,5-DNA) to p-aminophenol and 1,5-diamino-4,8-dihydroanthraquinone respectly. The results show that the alloy cathodes at different ratio Cu/Ni have different exchange current density (i^o) and apparent activition energy (E_A). The alloy (CN-30) has maximal i^o and minimal E_A by codeposition at the following conditions: electrolyte: 0.05 mol/L CuSO₄·5H₂O+0.6 mol/L NiSO₄·6H₂O+0.25 mol/L Na₃Cit·2H₂O; …

Preparation Of High Rate Discharge Foamed Ni-Cd Battery, Yuming Wang, Jinsheng Chen

Journal of Electrochemistry

A novel device of SC type foamed NiCd battery is presented, in which, the innerresistance of battery is appeared to be reduced, and the electrode performance is gained to very improved, and so, this battery can be suited to using of the powerdrive pistol drill.

Study On The Oxygen Electrodes Of Alkaline Fuel Cells Effect Of Dopant On The Activity Of Ag/C Catalyst, Jiawei Teng, Linhua Jin, Luncheng Tang

Journal of Electrochemistry

A new kind of nonnoble catalyst for the oxygen electrodes of Alkaline Fuel Cells was investigated. The AgNiBiHg/C catalyst, which was prepared by chemical reduction, was active for the cathodic reduction of oxygen in alkaline fuel cells. It was found that the catalytic activity was improved by adding Ni, Bi, Hg to Ag/C catalyst, and the maximum activity was observed at Ag50%-Ni2%-Bi3%-Hg3%-C42%(wt%). XRD inconjunction with SEM indicated that the crystalline silver turned into amorphous in the presence of doping agents and the grain size of silver was reduced. No dramatic deactivation of the catalyst occured after 5200 hours of service.

Molten Carbonate Fuel Cell Materials And Technology, Naichao Li, Baolian Yi

Journal of Electrochemistry

Molten Carbonate Fuel Cell materials are reviewed, and the technology of Molten Carbonate Fuel Cell are discussed.

Study On Perchlorate Produced By Electrolysis With Oxygen Cathode, Zhigang Shao, Baolian Yi, Naichao Li, Ming Han

Journal of Electrochemistry

A new method of measuring the flow capacity of cell gas in the perchlorate cell process equipped with an oxygen cathode is applided to investigate the influence of changes in the concentration of solution (chloride, chlorate, perchlorate and metal ion) and changes in the operation parameters (current density, temperature and pH) on perchlorate current efficiency. The main abstacle that the oxygen cathode is used in the perchlorate cell process is put forward and a method is provided to resolve it.

The Effect Of Solution Composition On The Corrosion Behavior Of Electrodeposited Zinc Powder, Qingwen Li, Qin Yang, Xi Xia

Journal of Electrochemistry

Zinc powder as a widely anode material can be electrowon from ZnCl₂ or ZnO+KOH media. The properties of zinc powder are likely to be modified with electrolytic conditions such as the composition of bath solution, electrolysis manner, current density and additives etc.. In this paper, we have discussed the effect of the compositions of bath solution on the microstructure and corrosion resistance of zinc powder.

Development Of A New Type Ni-S Evolution Hydrogen Electrode For Water Electrolysis, Xiaoyou Yuan, Jinyu Wang

Journal of Electrochemistry

A new type evolution hydrogen electrode NiS(N) has been made from nickel plating electrode in NiSO₄CS(NH₂)₂ bath by electrodeposition. It is analyzed by SEM and X-ray energy spectrum. The NiS(N) electrode is different from the NiS(O) electrode (which is used in plant at present time) in surface metallograph configuration and surfer content. The results of measurement polarization curves and water electrolysis 480 hours at 5 000 A·m^-2 show that the evolution hydrogen overpotential of NiS(N) electrode is decreased at least 160 mV relative to NiS(O) electrode and the stablisum of NiS(N) electrode is better …

Advances In Solid Polymer Electrolytes, Liming Ding, Shaojun Dong, Erkang Wang

Journal of Electrochemistry

The formation, classification, applications and ion-transport mechanism studies of solid polymer electrolytes were reviewed. While the recent SPE reports on the preparation of novel materials, the full structure determinations of PEO/salt complexes, the exploration of ion-transport mechanism and the applications in electrochemical devices being introduced, some prospects on the future SPE research were suggested.

The Effect Of Bismuth On Microstructure Of The Cathodic Copper Deposition Of Copper Electrorefining, Daorong Lu, Jianxing Lin

Journal of Electrochemistry

The electrocrystal formation, crystal orientation and the chemical composition of the cathodic copper deposition in the presence of Bi³⁺ in the electrolyte of acidified CuSO₄ are studies by scanning electron microscopy, X-ray diffraction, atomic absorption and EDAM. The results indicate that the Bi could′t deposit on cathode when copper electrolysed at common current density i=200 A·mol/L^-2 and t=60 ℃. Bi³⁺ scarcely effected on the crystal orientation (220) of copper deposition. High concentration Bi³⁺ in the electrolyte promoted (220) growth and inhibited the other crystal orientation growth. Bi³⁺ effected on electrocrystal formation and the cell …

Mechanism Of Electrodeposition Of Cu/Co Multilayer Thin Films, Jiangyun Xue, Jixun Wu, Dejun Yang

Journal of Electrochemistry

The mechanism of electrodeposition of Cu/Co multilayer thin films has been studied by means of potentodynamic sweep, cyclic voltammetry sweep and AC impendance. The results indicated that the copper deposition is mass transfer controlled process and the cobalt deposition is related to the absorbed intermediate species such as Co(OH)_ads. The cobalt ions first form Co(OH)_ads, then was deoxygenated to cobalt on the electrode surface.

Photoluminescence Of Photoelectrochemically Etched N+-Si, Guozheng Li, Chengqian Zhang, Xiumei Yang

Journal of Electrochemistry

PS layer on n⁺-Si with (111) orientation prepered by means of photoelectrochemically etched has photo-luminescent (PL) ability like PS layer on usual n-Si. The data of PL spectra and quenching are given.

Milled Carbon Fiber Reinforced Polymer Composition, Brian Massengale, Paul Schauer, Charles Dahle, Barry Gregerson, Bonnie Bachman, Thomas Oesterle

Economics Faculty Research & Creative Works

A milled carbon fiber reinforced polymer having increased abrasion resistive characteristics. The reinforced polymer comprises a base resin selected from the group consisting of polyolefins and polyamides. The base resin is combined with an amount of milled carbon fibers and further may be combined with polytetrafluoroethylene. The resulting composite materials have excellent friction and wear characteristics and are useful in the production of injection molded parts. The molded parts have a high impact strength, exhibit dimensional stability, are abrasion resistive, and are static dissipative, with the composite materials having particular utility as support fixtures for semiconductors during certain processing operations.

Synthesis And Characterization Of Phosphosilicate Glass Films By Lpcvd For Sensor Application, Hui Wu

Theses

This study was dedicated to the synthesis of the thin film materials required to fabricate the waveguide and the reference arm barrier for integrated optical sensor. Phosphosilicate glass (PSG) thin films were synthesized on silicon and quartz wafers by LPCVD using Ditertiarybutylsilane(DTBS), Trimethylphosphite(TMP) and oxygen as precursors. The films were processed at different temperatures between 600°C and 700°C at a constant pressure, and at different flow rate of TMP.

The effect of TMP flow rate and deposition temperature on deposition parameters and the properties of PSG films were investigated. The films deposited were uniform, amorphous, low stress and the composition …

Increased Radiative Lifetime Of Rare Earth-Doped Zinc Oxyhalide Tellurite Glasses, David L. Sidebottom, Michael A. Hruschka, B. G. Potter, Richard K. Brow

Materials Science and Engineering Faculty Research & Creative Works

We have investigated the structural and optical properties of rare earth-doped zinc tellurite glasses modified by the substitution of ZnF₂. Raman and phonon sideband spectroscopies were employed to characterize changes in the glass structure as well as to probe vibrational behavior in the immediate vicinity of the rare earth ion. These measurements are combined with photoluminescence and optical absorption to monitor the effect of halide substitution upon the optical behavior of the rare earth dopant. A substantial increase in the intrinsic radiative lifetime of Nd³⁺ is observed with increasing halide concentration.