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1999

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Articles 91 - 120 of 122

Full-Text Articles in Materials Science and Engineering

Studies Of Electrochemical Characteristics Of Pasted Nickel Hydroxide Electrode With Surface Deposited Cobalt, Xian-You Wang, Yun-Shi Zhang, Jie Yan, Zheng Zhu, Hua-Tang Yuan, De-Ying Song Feb 1999

Studies Of Electrochemical Characteristics Of Pasted Nickel Hydroxide Electrode With Surface Deposited Cobalt, Xian-You Wang, Yun-Shi Zhang, Jie Yan, Zheng Zhu, Hua-Tang Yuan, De-Ying Song

Journal of Electrochemistry

The surface of the spherical nickel hydroxide particles used as an active material in pasted nickel electrodes is surface-deposited with cobalt. This paper investigated the effects of the amount of cobalt deposit on the characteristics of nickel hydroxide electrode. The performances of the electrode, such as discharge capacity, utilization of active material and reversibility of Ni(OH)2/NiOOH redox reaction, were studied by comparing the charging/discharging curves and cyclic voltammograms. The mechanism of action of cobalt deposits has been described in terms of the electrochemical impedance spectroscopy of nickel hydroxide electrode.

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Electrohydrodimerization Of Fumarodinitrile On Liquid Gallium Electrode, He Wei, Huang Ying, Sheng-Tao Zhang Feb 1999

Electrohydrodimerization Of Fumarodinitrile On Liquid Gallium Electrode, He Wei, Huang Ying, Sheng-Tao Zhang

Journal of Electrochemistry

Electrohydrodimerization (EHD) of fumarodinitrile on liquid gallium electrode can take place not only in hydrotropic solution of tetraethylammonium p-toluenesulphonate (TEA-PTS), but also in aqueous solution containing low concentration of strong surfactants, such as TritonX-100. In solution without organic surfactant, FDN yields a single two-electron reduction wave corresponding to the formation of a saturated monomer called as butanedinitrile. If some TEA-PTS or TritonX-100 is added into the solution, the original two-electron wave is splitted into two continuous single-electron reduction wave and corresponding EHD of fumarodinitrile is obtained.

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Study Of Localized Corrosion Of Metals By Using The Electrochemical Techniques With Spatial Resolution, Chang-Jian Lin, Xiang-Dong Zhuo, Zu-De Feng, Rong-Gui Du, Zhao-Wu Tian Feb 1999

Study Of Localized Corrosion Of Metals By Using The Electrochemical Techniques With Spatial Resolution, Chang-Jian Lin, Xiang-Dong Zhuo, Zu-De Feng, Rong-Gui Du, Zhao-Wu Tian

Journal of Electrochemistry

The electrochemical inhomogeneities at interface of metal/solution play an important and often controlling role in localized corrosion of metals. The traditional electrochemical techniques involving potential, current density or ac impedance measurements over bulk specimens can only provide average and general information of the interface. Thus, the development of in situ imaging techniques is essential for further characterizing electrochemical inhomogeneities at the metal/solution interface of localized corrosion system. The electrochemical techniques with spatial resolution,including scanning single micro electrode, scanning double micro electrodse and scanning micro chemical probes are reviewed. The effects of electrochemical inhomogeneities on the corrosion behavior, and the mechanism …

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Electrochemical Surface Characterization Of Titanium Alloy(Ti-6al-4v), Jian-Zhong Chen, Qing-Liang Gao, Zhong-Yi Wang, Wen-Jing Xue Feb 1999

Electrochemical Surface Characterization Of Titanium Alloy(Ti-6al-4v), Jian-Zhong Chen, Qing-Liang Gao, Zhong-Yi Wang, Wen-Jing Xue

Journal of Electrochemistry

With its low density and high strength ratio, titanium alloy(Ti6Al4V) has become one of the most important materials both in the fields of aerospace and biomedical assays. Recently, titanium alloy was used as the implantation materials in human body because of its biocompatibility. The elecrochemical impedance techniques were then used to investigate the corrosion behavior of this material in hydrochloride and sulfuric acid solutions. A comparison between impedance spectra and anodic polarization over the correlated range of applied voltage confirms that AC impedance data can be used as a powerful tool for surface characterization of titanium …

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Study On The Mechanism Of Ni/Zro2 Composite Electrodeposition, Qun-Jia Peng, Dao-Bin Mu, Ju-Sheng Ma, Xiang-Yun Tang Feb 1999

Study On The Mechanism Of Ni/Zro2 Composite Electrodeposition, Qun-Jia Peng, Dao-Bin Mu, Ju-Sheng Ma, Xiang-Yun Tang

Journal of Electrochemistry

The effects of cathodic current density and amount of particle dispersion in solution on the codeposition of Ni/ZrO2 composite in Watts bath were studied, and the machanism of the composite electrodeposition was investigated. The study shows that the composite electrodeposition is controlled by the transfer of particles to the cathode when the dispersion amount is small, causing the decrease of the codeposition with the increase of current density. With large amount dispersion, the composite electrodeposition is first controlled by the strong adsorption of particles on the cathode at low current density, resulting in the increase of the codeposition with …

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Electrodeposition Of Neodymium-Iron Group Alloy Films In (P-Ch3C6H4So3)3Nd System, Peng Liu, Ye-Xiang Tong, Qi-Qin Yang, Yan-Sheng Yang Feb 1999

Electrodeposition Of Neodymium-Iron Group Alloy Films In (P-Ch3C6H4So3)3Nd System, Peng Liu, Ye-Xiang Tong, Qi-Qin Yang, Yan-Sheng Yang

Journal of Electrochemistry

Neodymium p-toluenesulfonate was prepared and applied to the electrodepositon of neodymium-iron group alloy films. This salt has high solubility in DMF and can be dehydrated easily. Cyclic voltammograms of Pt electrode in (p-CH3C6H4SO3) 3Nd + MCl2(M=Fe,Co,Ni) + DMF indicated that the neodymiun-iron group alloys can be elcetrodeposited from this medium, the Nd-Fe, Nd-Co and Nd-Ni films were obtained by electrolysis at constant potential. The Nd-Fe, Nd-Co and Nd-Ni films are amorphous in which the rare earth contents are in the range of 15 at%～60 at% as analyzed by XRD and …

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Pitting Corrosion Of Ni-Based Alloy In Thiosulfate-Ion Containing Chloride Solutions, Yung-Fa Lee, Ting-Yu Wang, Wen-Ta Tsai Feb 1999

Pitting Corrosion Of Ni-Based Alloy In Thiosulfate-Ion Containing Chloride Solutions, Yung-Fa Lee, Ting-Yu Wang, Wen-Ta Tsai

Journal of Electrochemistry

The effect of thiosulfate ion on the pitting corrosion behavior of Ni-Based Alloy 690 in chloride solution was investigated. In plain sodium thiosulfate solution, Alloy 690 was immune to pitting corrosion. However, the addition of low concentration of sodium thiosulfate can enhance the initiation of pitting corrosion of Alloy 690. Nevertheless, inhibition of pitting corrosion was observed at high concentration of addition.

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Effect Of Stress On Electrochemical Behaviour Of Various Thermal History Zones And Different Phase Structures On The Weldment For Low Alloy Steel, Yin-Shun Wu, De-Yu Liu, Bei Cao, Feng-Li Wang, Zhi Fang, Lin Zhang, Zheng-Rong Zhang, Hai Yang Feb 1999

Effect Of Stress On Electrochemical Behaviour Of Various Thermal History Zones And Different Phase Structures On The Weldment For Low Alloy Steel, Yin-Shun Wu, De-Yu Liu, Bei Cao, Feng-Li Wang, Zhi Fang, Lin Zhang, Zheng-Rong Zhang, Hai Yang

Journal of Electrochemistry

The electrochemical behaviour of various thermal history zones on the weldment for steel 16Mn and also of the ferrite, pearlite in various zones was measured by use of a self-developed measuring technique for investigating the electrochemicl behaviour of single and mixed phase structures in metal materials. Especially the effect of stress on this electrochemical behaviour was investigated. The results showed that by comparison with non-stress condition, the free corrosion potential of the various thermal history zones and of the ferrite, pearlite under stress condition was shifted in negative direction, correspondingly their free corrosion current density was increased, the free corrosion …

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Study On Steel Corrosion In Simulated Biofilm Environment In Seawater, Qing-Fei Wang, Jing Sui, Run-Xi Su, De-Ying Kong, Shi-Zhe Song Feb 1999

Study On Steel Corrosion In Simulated Biofilm Environment In Seawater, Qing-Fei Wang, Jing Sui, Run-Xi Su, De-Ying Kong, Shi-Zhe Song

Journal of Electrochemistry

Biofilm is one of the main factors that influence metal corrosion in seawater environment. According to the structure and property of biofilm, a natural biopolymeric gel, calcium alginate(an extracellular biopolymer containing carboxylate functional groups) can deposite on metal surfaces to form films. Corrosion behavior of alloyed steel E2, 10CrMoAl and 18-8 stainless steel were studied in simulated biofilm environment by various electrochemical methods ,including measurements of the corrosion potential, polarization curves,galvanic current and electrochemical impedance. The results show that such an approach is informative to reveal “how” and “to what extent” biofilm can influence the metal corrosion process.

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Structural And Electrochemical Studies On Todorokite/Vernadite As Cathodes For Rechargeable Lithium Ion Batteries, Wei Chu, De-Yao Liu, Jin-Kua You, Yong Yang, Zu-Geng Lin Feb 1999

Structural And Electrochemical Studies On Todorokite/Vernadite As Cathodes For Rechargeable Lithium Ion Batteries, Wei Chu, De-Yao Liu, Jin-Kua You, Yong Yang, Zu-Geng Lin

Journal of Electrochemistry

XRD, TEM, ICP, low scan-rate CV and charge/discharge tests were carried out for the studies on the structural and electrochemical behavior of a prepared 3 V manganese oxide cathode for rechargeable lithium ion batteries.XRD analysis revealed that the cathode sample is mainly composed of tunneled Todorokite and layered Vernadite. TEM investigation confirmed that the morphology of the sample is a laminated construction with approximate 10nm layer space. The reversibility of Li+ removal/intercalation and structural stability of this sample framework to lithium insertion are good in CV and charge/discharge tests. The discharge capacities were found to be about 129mAh/g obtained …

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Paint Gun Incorporating A Laser Device, Richard J. Klein Ii, Douglas L. Sevey Feb 1999

Paint Gun Incorporating A Laser Device, Richard J. Klein Ii, Douglas L. Sevey

Patents (University of Northern Iowa)

A spray gun for applying a liquid spray coating, such as paint, to a surface incorporates a light source and detection system for analyzing the position of the spray gun relative to a worksurface in order to optimize application of the coating to the surface. The light source is preferably in the form of a laser which emits a beam of light toward the worksurface. The laser is interconnected with the housing of the spray gun in a location over the spray gun handle so as not to effect the center of gravity of the spray gun. Optical sensors are …

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Characterization Of Tantalum Coatings On Steel Substrates, Prabha Shivaramkrishnan Jan 1999

Characterization Of Tantalum Coatings On Steel Substrates, Prabha Shivaramkrishnan

Theses

Sputtered tantalum can be used as an effective corrosion resistant barrier if the coating is continuous, free from defects and is adherent to the substrate it is intended to protect. For corrosion-applications 100% bcc phase tantalum is preferred. X-ray diffraction results indicate that sputtered tantalum deposits typically contain a mixture of bcc and beta phases. Depending on the deposition conditions the morphology of tantalum coatings as studied using scanning electron microscopes can vary from irregular, dendritic structure to a defined step type structure. A "cauliflower type" structure has also been observed. Extended x-ray absorption fine structure measurement was used to …

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Room Temperature Fatique Response Of Γ-Tial To Impact Damage, Trevor S. Harding, J. Wayne Jones, P. S. Steif, T. M. Pollock Jan 1999

Room Temperature Fatique Response Of Γ-Tial To Impact Damage, Trevor S. Harding, J. Wayne Jones, P. S. Steif, T. M. Pollock

Materials Engineering

Gamma based titanium aluminides have received considerable attention recently as candidate materials in gas turbine applications, particularly low pressure turbine blades (1–3). Their low density and high specific stiffness, result in potentially significant weight savings in structures such as gas turbine engines if substituted for current materials. Two γ-TiAl microstructures are predominately identified in the literature: a lamellar microstructure consisting of alternating plates of γ and α2, and a duplex microstructure consisting of equiaxed γ grains and lamellar colonies (3,4). Lamellar alloys generally exhibit better fracture toughness and fatigue crack growth resistance (5–7). Duplex alloys, on the other …

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Band Gap Energy In Nanocrystalline Zro2:16%Y Thin Films, Igor Kosacki, Vladimir Petrovsky, Harlan U. Anderson Jan 1999

Band Gap Energy In Nanocrystalline Zro2:16%Y Thin Films, Igor Kosacki, Vladimir Petrovsky, Harlan U. Anderson

Materials Science and Engineering Faculty Research & Creative Works

The results of optical absorption measurements on nanocrystalline ZrO2:16%Y thin films are presented. Dense 0.7 μm thick films with 1-300 nm grain size have been obtained on sapphire substrate using a polymeric precursor spin coating technique. The relationship between the energy gap and microstructure of ZrO2:16%Y has been determined and discussed. The quantum confinement effect was observed at the grain size lower than 100 nm with the band gap energy shift of 0.25 eV when the microstructure was changed up to 1 nm. Some limitation of the model has been observed and discussed. The band gap energy of 5.62±0.05eV has …

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Paint Gun Incorporating A Laser Device, Richard J. Klein, Douglas L. Sevey, Alireza Badakhshan, Ricky Jay Bauer Jan 1999

Paint Gun Incorporating A Laser Device, Richard J. Klein, Douglas L. Sevey, Alireza Badakhshan, Ricky Jay Bauer

Patents (University of Northern Iowa)

A spray gun for applying a liquid spray coating, such as paint, to a surface incorporates a light source system for gauging the position of the spray gun relative to a worksurface in order to optimize application of the coating to the surface. The light source is preferably in the form of a laser which emits a pair of light beams toward the worksurface. The pair of light beams converge toward each other in a direction toward the surface, and the position of the beams on the surface is used by the operator to judge the distance of the spray …

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A Literature Review Of The Effect Hot Reduction Has On The Structure, Mechanical Properties, And Fatigue Performance Of Continuous Cast Steel, Stanley J. Syhlman Jan 1999

A Literature Review Of The Effect Hot Reduction Has On The Structure, Mechanical Properties, And Fatigue Performance Of Continuous Cast Steel, Stanley J. Syhlman

Graduate Student Work

The purpose of the investigation is to review the published literature concerning investigatlons of the effects of hot reduction and other factors have on the structure, properties, and performance of continuously cast steel products. Of principle interest is the recognition of a minimum reduction ratio needed to provide steel with acceptable design options for industrial customers. The minimum reduction or rolling ratio is the cross-sectional area of the cast billet divided by the corresponding area of the final rolled product required to assure the breakdown of the as cast structure, and the attainment of satisfactory mechanical properties. The investigation is …

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Copper Nucleation On Titanium For Thin Film Applications, A. J.B. Dutra, Thomas J. O'Keefe Jan 1999

Copper Nucleation On Titanium For Thin Film Applications, A. J.B. Dutra, Thomas J. O'Keefe

Materials Science and Engineering Faculty Research & Creative Works

Copper nucleation and growth on titanium substrates from concentrated acidic copper sulfate solutions was studied at 45 and 65 °C and high cathodic potentials. Electrochemical experiments allied to SEM examination were performed to characterize the mechanism of nucleation and its evolution with time. Particular emphasis was given to the influence of potential and agitation on the initial stages of nucleation and growth. Results indicated that most of copper nucleation on titanium from a 83 g dm-3 Cu2+ solution, at 65 °C, is achieved in a matter of milliseconds. As expected, the initial stages of the copper nucleation and growth is …

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Modeling The Dielectric Response And Relaxation Spectra Of Relaxor Ferroelectrics, Huh Tswen Lin, David C. Van Aken, Wayne Huebner Jan 1999

Modeling The Dielectric Response And Relaxation Spectra Of Relaxor Ferroelectrics, Huh Tswen Lin, David C. Van Aken, Wayne Huebner

Materials Science and Engineering Faculty Research & Creative Works

A multi-Debye relaxation model that is based upon the Boltzmann superposition principle has been used to determine the frequency-dispersion behavior of Pb (Mg1/3-Nb2/3)O3 (PMN) and Pb0.88La0.08 (Zr0.65Ti0.35) O3 (PLZT 8/65/35) relaxor ferroelectrics. For PMN, relaxation times on the order of seconds contribute to the dispersive character of the dielectric properties. A defect-relaxation mechanism that involves Mg cation hopping in a structure that is composed of interpenetrating 〈111〉 chains of ordered Pb (Mg1/2Nb1/2) O3 is proposed for PMN. Motion of the Mg cations …

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Influence Of Chemical Reactions In Magnesia-Graphite Refractories: I, Effects On Texture And High-Temperature Mechanical Properties, Carmen Baudín, Carlos Alvarez, Robert E. Moore Jan 1999

Influence Of Chemical Reactions In Magnesia-Graphite Refractories: I, Effects On Texture And High-Temperature Mechanical Properties, Carmen Baudín, Carlos Alvarez, Robert E. Moore

Materials Science and Engineering Faculty Research & Creative Works

Four formulations of magnesia-graphite-aluminum metal (antioxidant) bricks were prepared from the same raw materials, using the standard commercial practices. Chemical analysis and determination of room-temperature modulus of rupture and Young's modulus, as well as a complete microstructural characterization of the as-received materials, were performed. For high-temperature modulus-of-rupture and Young's modulus data, test samples of the four brick compositions were heated to 1000°, 1200°, and 1450 °C in flowing argon (< 1000 ppm oxygen at 1000 °C) and then loaded mechanically in flexure. Modulus-of-elasticity values ranged from 3.7 to 16.2 GPa and reflected strong effects of aluminum-metal concentration and treatment temperature. Young's modulus evolution with temperature was determined by the evolution of the micro-structure in the bulk of the specimens. Modulus-of-rupture values ranged from 6 to 21 MPa, and their evolution with temperature was determined by the evolution of the micro-structure in the bulk of the specimens at the lower testing temperatures (T≤1200 °C) and by phase assemblages in the surface regions of the specimens - essentially by the presence of the dense MgO zone - at 1450 °C.

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Influence Of Chemical Reactions In Magnesia-Graphite Refractories: Ii, Effects Of Aluminum And Graphite Contents In Generic Products, Carmen Baudín, Carlos Alvarez, Robert E. Moore Jan 1999

Influence Of Chemical Reactions In Magnesia-Graphite Refractories: Ii, Effects Of Aluminum And Graphite Contents In Generic Products, Carmen Baudín, Carlos Alvarez, Robert E. Moore

Materials Science and Engineering Faculty Research & Creative Works

A group of magnesia-graphite and magnesia-graphite-aluminum materials, the compositions of which represent a wide range of graphite contents (approximately 10-16.4 wt.%), aluminum contents (0-5.2 wt.%), and MgO and graphite qualities, were fabricated, using standard commercial practices. Chemical analysis and determination of room-temperature modulus of rupture (MOR) and Young's modulus, as well as a complete microstructural characterization of the as-received materials, were performed. Mechanical characterization at high temperature (1000°, 1200°, and 1450 °C) was done in terms of Young's modulus and MOR in an argon atmosphere (°C). Modulus-of-elasticity values ranged from 4 to 16 GPa, and their evolution with temperature was …

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High Breakdown Strength, Multilayer Ceramics For Compact Pulsed Power Applications, Wayne Huebner, Brian L. Gilmore, Shi C. Zhang, Mike L. Krogh, B. C. Schultz, R. C. Pate, L. F. Rinehart, J. M. Lundstrom Jan 1999

High Breakdown Strength, Multilayer Ceramics For Compact Pulsed Power Applications, Wayne Huebner, Brian L. Gilmore, Shi C. Zhang, Mike L. Krogh, B. C. Schultz, R. C. Pate, L. F. Rinehart, J. M. Lundstrom

Materials Science and Engineering Faculty Research & Creative Works

Advanced ceramics are being developed for use in large area, high voltage devices in order to achieve high specific energy densities (greater than 10^6/ J/m^3/) and physical size reduction. Initial materials based on slip cast TiO2 exhibited a high bulk breakdown strength (BDS greater than 300 kV/cm) and high permittivity with low dispersion (epsilon approximately equal to 100). However, strong area and thickness dependencies were noted. To increase the BDS, multilayer dielectric compositions are being developed based on glass/TiO2 composites. The addition of glass increases the density (approximately equal to 99.8% theoretical), forms a continuous grain boundary phase, and also …

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Preparation Of Phase Homogeneous Mn-Zn Ferrite Powder By Spray Pyrolysis, Xinyu Zhao, Baicun Zheng, Hongchen Gu, Chunzhong Li, Shi C. Zhang, P. D. Ownby Jan 1999

Preparation Of Phase Homogeneous Mn-Zn Ferrite Powder By Spray Pyrolysis, Xinyu Zhao, Baicun Zheng, Hongchen Gu, Chunzhong Li, Shi C. Zhang, P. D. Ownby

Materials Science and Engineering Faculty Research & Creative Works

Two kinds of aqueous precursor solutions are used to synthesize Mn-Zn ferrite powders: (i) nitrate (NO) precursor-derived from solutions of Mn(NO3)2, Zn(NO3)2, and Fe(NO3)3; and (ii) acetate (AC) precursor-derived from solutions of Mn(CH3COOO)2, Zn(CHCH3COOO)2, and Fe(NO3)3. The composition of the powders synthesized from the precursor AC is very uniform, whereas powders derived from the precursor NO have Mn and Zn segregated on the particle surfaces. In addition, the powders synthesized from precursor AC are solid spherical …

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Measurement Of The Dielectric Strength Of Titanium Dioxide Ceramics, Wayne Huebner, J. M. Lundstrom, L. F. Rinehart, R. C. Pate, T. L. Smith, Mike L. Krogh Jan 1999

Measurement Of The Dielectric Strength Of Titanium Dioxide Ceramics, Wayne Huebner, J. M. Lundstrom, L. F. Rinehart, R. C. Pate, T. L. Smith, Mike L. Krogh

Materials Science and Engineering Faculty Research & Creative Works

Titanium dioxide ceramics (TiO2) are candidate materials for high energy density pulsed power devices. Experiments to quantify the dielectric strength of TiO2 have been performed on a limited number of unoptimized samples. A high voltage test set was constructed to test the titanium dioxide. All samples had a relative dielectric constant of 100, all samples were of 3 mm nominal thickness, and all tests were performed in water dielectric to reduce the effect of the triple point field enhancement at the electrode edge. Both single layer and laminated samples were tested and the breakdown field strengths were recorded. Voltage risetimes …

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Copper Alloy-Impregnated Carbon-Carbon Hybrid Composites For Electronic Packaging Applications, S. K. Datta, Surendra N. Tewari, Jorge E. Gatica, W. Shih, L. Bentsen Jan 1999

Copper Alloy-Impregnated Carbon-Carbon Hybrid Composites For Electronic Packaging Applications, S. K. Datta, Surendra N. Tewari, Jorge E. Gatica, W. Shih, L. Bentsen

Chemical & Biomedical Engineering Faculty Publications

Porous carbon-carbon preforms, based on three-dimensional networks of PAN (Polyacrylonitrile)-based carbon fibers and various volume fractions of chemical vapor-deposited (CVD) carbon, were impregnated by oxygen-free, high-conductivity (OFHC) Cu, Cu-6Si-0.9Cr, and Cu-0.3Si-0.3Cr (wt pct) alloys by pressure infiltration casting. The obtained composites were characterized for their coefficient of thermal expansion (CTE) and thermal conductivity (K) along the through-thickness and two in-plane directions. One composite, with a 28 vol pct Cu-0.3Si-0.3Cr alloy, showed outstanding potential for thermal management applications in electronic applications. This composite exhibited approximately isotropic thermal expansion properties (CTE = 4 to 6.5 ppm/K) and thermal conductivities (k greater than …

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X-Ray Absorption, Neutron Diffraction, And Mössbauer Effect Studies Of Mnzn-Ferrite Processed Through High-Energy Ball Milling, D. J. Fatemi, V. G. Harris, Mingxing Chen, Satish K. Malik, William B. Yelon, Gary J. Long, Amitabh Mohan Jan 1999

X-Ray Absorption, Neutron Diffraction, And Mössbauer Effect Studies Of Mnzn-Ferrite Processed Through High-Energy Ball Milling, D. J. Fatemi, V. G. Harris, Mingxing Chen, Satish K. Malik, William B. Yelon, Gary J. Long, Amitabh Mohan

Physics Faculty Research & Creative Works

MnZn-ferrite has been prepared via high-energy ball milling of elemental oxides MnO, ZnO, and α-Fe2O3. Neutron diffraction measurements suggest a high density of vacancies in a spinel structure. The spinel phase appears to comprise 99.8 wt % of the material in the sample milled for 40 h, with the remainder attributable to unreacted α-Fe2O3. The x-ray absorption near-edge structure was analyzed to provide an understanding of the charge state of the constituent Fe ions. This analysis reveals about 2/3 of Fe cations to be trivalent, increasing to about 3/4 after a 5 …

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Thermal Characterization Of Pmma Thin Films On Silica Using Modulated Differential Scanning Calorimetry, Crystal E. Porter, Frank D. Blum Jan 1999

Thermal Characterization Of Pmma Thin Films On Silica Using Modulated Differential Scanning Calorimetry, Crystal E. Porter, Frank D. Blum

Chemistry Faculty Research & Creative Works

The number of studies of thin polymer films has increased over recent years as technological processes incorporate the use of nanomaterials. An enhanced understanding of these films would enable us to predict bound-polymer behavior and thus improve the efficiency of processes and the quality of products. This is especially true as the thickness of the films approach molecular dimensions. The glass transition temperature of a polymer is one of the most important properties for characterization because it indicates how the polymer might perform macroscopically. when a polymer is confined, such as one the surface of a substrate, its behavior is …

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Dynamics Of Acrylic Coupling Agents At Interfaces Of Composites, Hyoryoon Jo, Frank D. Blum Jan 1999

Dynamics Of Acrylic Coupling Agents At Interfaces Of Composites, Hyoryoon Jo, Frank D. Blum

Chemistry Faculty Research & Creative Works

Most applications of polymers involve composites, wherein a polymer is used in conjunction with another material, typically a solid fiber or filler. A coupling agent can enhance the adhesion between a polymer matrix and an inorganic filler. Organofunctional silanes, RSiX are often used as coupling agents. The methoxy or ethoxy group, X, can typically be hydrolyzed with water and an acid or a base catalyst in a protic solvent. The silanol groups of a hydrolyzed coupling agent can condense with other silanol groups from a glass surface, while the alkyl group, R, blends physically or bonds chemically to the polymer …

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Structural Disorder And The Origin Of High-Tc Suppression In La₁.₈₇₅Ba₀.₁₂₅ Cuo4−Δ, Daniel Haskel, Edward A. Stern, Fatih Dogan, Arnie R. Moodenbaugh Jan 1999

Structural Disorder And The Origin Of High-Tc Suppression In La₁.₈₇₅Ba₀.₁₂₅ Cuo4−Δ, Daniel Haskel, Edward A. Stern, Fatih Dogan, Arnie R. Moodenbaugh

Materials Science and Engineering Faculty Research & Creative Works

Polarized x-ray absorption fine structure (XAFS) measurements at all La, Ba and Cu sites were used to study local structural features that accompany the strong Tc suppression at: r,,, 1/8 in La2BaCuO4. Two critical parameters regulating the strength of hole-lattice coupling in this material were determined, ie, the direction and magnitude of CuO6 octahedra local tilts. Our findings include the existence of large disorder in the magnitude of the tilt angle about its average value (0), with an rms~~ 2 (0). We suggest that this large disorder strongly scatters a large fraction of states at …

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Experimental Investigation Of The Performance Of A Solar Crop Dryer, Sherif Nabil Abd Jan 1999

Experimental Investigation Of The Performance Of A Solar Crop Dryer, Sherif Nabil Abd

Archived Theses and Dissertations

No abstract provided.

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Application Of Pvd Coatings To Enhance The Wear Life Of Needles Used In The Textile Industry, Neil Donnelly Jan 1999

Application Of Pvd Coatings To Enhance The Wear Life Of Needles Used In The Textile Industry, Neil Donnelly

Masters

Needles are used in the textile industry for weaving. In high volume textile production a problem is wear of the needle eyelet as the threat is pulled through. This wear results in a cost to the textile manufacturer both in needle replacement, but in many cases more importantly, lost production during needle substitution The objective of this study was to examine the potential of wear resistant coatings deposited using the magnetron sputtering technique to increase the life-time of textile needles. Four coatings were evaluated, titanium nitride, titanium carbonitride, titanium diamond-like carbon and a novel coating titanium nitride/molybdenum disulphide. These coatings …

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