Materials Science and Engineering Commons^™

Evaluation Of The Sensitivity Of Radar Cross Section Predictions To Uncertainties In Material Characteristics, Greg A. Barnhart

Theses and Dissertations

The purpose of this study was to evaluate the effects of material characteristics uncertainties on Radar Cross Section (RCS) predictions. Many methods have been developed to predict the RCS of metal objects, but for material coated objects, these methods depend on the accuracy of measured material characteristics. Material characteristics of three dielectrics were measured by two separate X-band waveguide set-ups. RCS measurements were then made to evaluate the accuracy of RCS predictions using these measured material characteristics. A six inch square slab of each material was measured with and without a metal plate backing. A six inch square flat metal …

A Finite Element Analysis Of The Forward Rod Extrusion Process With An Emphasis On Die Profile Optimization, Mahmoud Mohamed Nagui Shatla

Archived Theses and Dissertations

No abstract provided.

Electrical Characterization Of 4h-And 6h-Silicon Carbide Schottky Diodes, Jeffrey C. Wiemeri

Theses and Dissertations

The electrical properties of silicon carbide (SiC) make it an excellent candidate for use in high temperature/high power devices due to its wide bandgap, high breakdown field, high electron mobility, etc. In this work two Schottky diodes of platinum (Pt) on n-type carbon faced 4H-SiC and three Schottky diodes of nickel (Ni) on n-type silicon faced 6H-SiC were electrically characterized. The diodes exhibited good performance up to 698 K for both the forward and reverse (up to -100v) bias voltages. The barrier heights measured by I-V-T tests were found to be 0.32 and 0.61 eV for the Pt/4H-SiC samples, but …

Electrical Characterization Of 4h-Silicon Carbide P-N Junction Diodes, Michael E. Dunn

Theses and Dissertations

The current conduction mechanisms of 4H-SiC p+n mesa diodes were studied using current-voltage-temperature (I-V-T), capacitance-voltage-temperature (C-V-T), deep level transient spectroscopy (DLTS), optical observations, and reverse breakdown measurements. Temperature and voltage dependencies of diffusion, recombination, and tunneling current processes are shown to be consistent with Sah-Noyce-Shockley theory. Recombination currents having an ideality factor of A=1.85-2.1 yielded an activation energy of E_A=1.56 eV, whereas for ideal recombination, A=2 and E_A=1.6 eV. Forward I-V curves of poor diodes dominated by tunneling and recombination processes, showing low reverse breakdown voltages of approx. 100 V, can be correlated to DLTS results …

Photoluminescence And Electroluminescence Of Erbium And Neodymium Implanted Semiconductors, James R. Hunter

Theses and Dissertations

Low temperature photoluminescence (PL) and electroluminescence (EL) measurements were used to study the excitation of erbium- and neodymium-implanted GaAs and Al_xGa_1-xAs (x=0. 1, 0.3) pn-junctions. The rare-earth (RE) emissions were investigated as a function of ion dose, aluminum mole fraction, laser excitation power, and applied forward bias voltage for the implanted samples. Low temperature PL was also measured from Er doped silicon grown by the metalorganic chemical vapor-phase deposition (MOCVD) method using various growth parameters.. The MOCVD-grown Si samples were studied as a function of metalorganic source temperature, silane (SiH₄) flow, growth time, and …

Thermal Stresses In End-Heated Layered Media, Jerry R. Couick

Theses and Dissertations

Thermal stresses in semi-infinite layered beams heated on the end are calculated using an extension to simple bimetallic thermostat theory. Recently, researchers have used the concept of interfacial compliance to determine interlaminar stresses in a simple thermostat of finite length subjected to a uniform temperature increase. In the present work, the thermostat theory is extended to apply to the beams of interest. A closed-form solution to the problem is obtained. It is not applicable within about one beam thickness (St Venant boundary region) of the end. Various classes of layered materials are analyzed to determine if significant stresses exist outside …

The Composition Structure And Corrosion Resistance Of Al-Mn Alloy Plating, Jiaju Guo, Naiming Guo

Journal of Electrochemistry

The Al-Mn alloy plating was electrodeposition from low temperature molten salts (below 200℃), its chemical composition control, corrosion resistance as well as the relationshipbetween chemical composition and structure were studied. The results indicate that the main effect onchemical composition of Al-Mn alloy plating is Mn ion concentration in molten salts. The Mn contentin the range of 25～40(wt)%, Al-Mn alloy plating has amorphous structure. In 0.5 mol/L H₂SO₄ and NaCl solution ,corrosion resistance of the alloy plating is much better. When the alloy has amorphous structure, corrosion resistance of plating has been remarkably increased.

Study Of The Action Mechanism Of A New Type Additive Sd-1 On The Electrodepositional Process Of Zinc, Huaqiang Wu, Yiqin Yan, Guangming Ni

Journal of Electrochemistry

The action mechanism of a new type additive SD-1 on the electrodepositionalprocess of zinc is reported.The results showed that the additive SD-1 is not electrochemistry activesubstane in the range of adsorption potential at rotating disk electrode surface. The action of additive SD-1 on the electrodepositional process of zinc is considerated to be fitting in with the diffusion controlmechanism.

Catalytic Oxidation Of Methanol On Pt/C-Spe And Ptru/C-Spe Electodes, Aihua Su, Changzhi Li, Gongquan Sun, Ying Zhang, Tianhong Lu

Journal of Electrochemistry

Anode catalysts of methanol oxidation for direct methanol fuel cell, Pt/C and PtRu/C, ere prepared by chemical reduction in this work. The results indicated that the PtRu/C showed higher electrocatalytic activity than that of Pt/C. It was explained by XRD and XPS analyses that the existence of Ru enhanced the catalytic activity for electrochemical oxidation of methanol.

A Photoelectrochemical Investigation Of A.C.Modulated Passive Films On 304 Stainless Steel In Weak-Alkaline And Neutral Solution, Tianbao Du, Chunan Cao, Jiakang Yu, Haichao Lin

Journal of Electrochemistry

A photoelectrochemical investigation has been carried out on AISI 304 stainless steeI AV modulated passive film in 0.1mol/L Na₂B₄O₇ and 0.5 mol/L Na₂SO₄ solution. Photo current curve depends on the potential, passive condition and testing solutions. The results of the measurements indicate that the photoresponse is determined by the defects in the electronic structure of the films whenthe defects lead to localized states in the bandgap region. It is concluded that the passive film on AISI 304 stainless steel is in a highly disordered amorphous state.

Growth Kinetics And Breakdown Of Passive Films On Rebar Electrodes In Simulated Cement Pore Solution, Wei Chu, Yuanxiang Shi, Baoming Wei, Yong Yang, Xuguang Chen, Zugeng Lin

Journal of Electrochemistry

The growth kinetics and breakdown of passive films on REBAR electrodes insimulated cement solution (pH=12.5 and 13.8) have been investigated using in situ photoelectrochemical methods and potential step method. The results show that there are two mainstages in the growth of the film, with two rate functions characterized by linear relation between thefilm thickness and the direct logarithm of time. There is a sign in laser-scanning photoelectrochemical microscopic image just before the passive film breaks down. The addition of inhibitor NaNO₂ changes the growth kinetics and thickness of the film, and therefore improves the resistance of pitting corrosion induced …

Cyclic Voltammetric Calorimetry Studying The Deposition Of Copper Of Pt Electrodes, Yongchun Zhu, Robin. H. J. Clark

Journal of Electrochemistry

In the present paper, cyclic voltammetric calorimetry has been used to study thedeposition of copper on platinum electrode from LiClO₄ aqueous solution. Cyclic voltammetric thermogram and cyclic voltammetric differential thermogram show that the deposition of copper on theelectrode is an exothermal process with a strong interaction between copper and platinum layer (-3227.0 kJ /mol). The electrochemical oxidation of the deposited copper is composed of twoprocesses: an endothermal activation process with 747.0 kJ/mol of activation enthalpy, and an exothermal oxidation reaction with -189.9 kJ/mol of the reaction enthalpy, which are accord with the data from the theoritical estimation and thermodynamic …

Fabrication And Electrochemical Behaviors Of Thin Films Of Polyaniline By Langmuir-Blodgett Technique And Electropolymerization, Benzeng Hua, Zhaoxiong Xie, Yanzhen Chen, Yunhong Zhang

Journal of Electrochemistry

Hydrogen-bond between stearic acid and aniline in subphase lead to Langmuir monotayers of stearic acid-aniline, the molecular area of stearic acid-aniline is 26 nm². With surfacepressure increased into 50 mN/M, the hydrogen-bond would be rearranged, aniline molecular transales into vertical from horizontal, surface pressure decreased quickly. A new kind of Langmuirmonolayer is formed instead of collapse, it's molecular area decreases into 24 nm² and thicknessin creases with 0.25 nm. After electroreduction of L-B films depeited onto the surface of SnO₂ electrode, anilne layers between two stear acid matix could be polymerized into thin films of polyanilne. …

Electrochemical Behaviors Of The Loaded Stainless Steel In Dilute Thiosulphate Solution, Changjian Lin, Zude Feng, Fuling Lin, Fayang Wang, Jianguang Tang, Yuanhui Wang

Journal of Electrochemistry

The electrochemical behavior of 18/8 stainless steel in dilute thiosulphate solutionduring strained loading was studied by various electrochemical techniques and scanning electronmicroscope. It is evidenced that the corrosion activity of stainless steel increased with strained loading. The dynamic process of repassivation, which may datermine the initiation, the cease and development of the stress corrosion cracking for stainless steel, was strongly influenced by both electrochemical andloading conditions. Pitting corrosion may locate preferentially on the sites which was suffered mostloading. The propagation of pitting corrosion of stainless steel may induce stress corrosion crakingunder certain conditions.

Study Of The Modified Electrolytic Manganese Dioxide, Guohui Yuan, Dewei Chu, Rihui Shen, Hongwei Pan, Cuifen Zhang

Journal of Electrochemistry

A modified electrolytic manganese dioside doped with Bi (Bi-EMD)wasprepared and examined by XRD and XPS. It is predominantly γ-mnO₂ and the Bi exists as Bi₂O₃ in the modified material. The content of Bi in Bi-EMDs increased with the increasement of Bi³⁺ concentration in electrolyte, and reached 14.3(wt)% from the bath of 0.008 mol·L^-1 Bi³⁺ used. Some Zn/Bi-EMD prototype batteries of AA size were assembled, and which cycle life tests showedthat the Bi-EMD has better reversibility.

Influence Of O-Phenylenediamine On The Catalysis At Hrp Enzyme Electrode In 1,4-Dioxane, Hong Chen, Hui-Huang Wu

Journal of Electrochemistry

Horseradish peroxidase (HRP) was immobilized by crosslinkage on the glassycarbon electrode to prepare the enzyme electrode, where the reduction of H₂O₂ was studied in 1,4-dioxane media. It was shown that HRP electrode can catalyze the reduction of H₂O₂ without anymedintor, however, as an activator, o-phenylenediamine can promote the bio-catalysis. In thepresence of the activator, the parallel reactions occurred on the enzyme electrode. The workingcondition of the HRP electrode was investigated as the sensors for H₂O₂ and o-phenylenediamine, also the influence of water content in organic phase was discussed on the performance …

Finite Element Study Of The Flat Strip Rolling Process Using A Deformable Roll Model, Hany George Harmouch

Archived Theses and Dissertations

No abstract provided.

A Characterization Of Alternative Tooling Materials Using Impact Abrasion Testing, Michael C. Formanek

Graduate Research Papers

The purpose of this study was to evaluate the wear resistance of tooling materials using impact abrasion testing. Materials tested are being used or are being considered for use in pattern and corebox construction. This study used 14 materials for evaluation. The materials were chosen on the basis of recommendations made by manufacturers and patterns shops. This study used the same procedure established in a study done in 1992 by Vondra to evaluate materials against a standard sample.

Of the materials tested three were included in the ceramics group. These materials demonstrated average wear resistance. The percent weight loss ranged …

Q Dependence Of Self-Energy Effects Of The Plane Oxygen Vibration In Yba2cu3o7, D. Reznik, Bernard Keimer, Fatih Dogan, Ilhan A. Aksay

Materials Science and Engineering Faculty Research & Creative Works

We have measured the temperature dependence of the peak position and linewidth of the 42.5 meV phonon branch in a twinned single crystal of YBa₂Cu₃O₇ as a function of wave vector q. In the (100)/(010) direction in the Brillouin zone, considerable softening and broadening occur below the superconducting transition temperature T_c at some values of q. We observe an order of magnitude smaller softening and no linewidth broadening for q in the (110) / (1⁢1⁢0^-) direction. Possible implications of these findings for the symmetry of the superconducting order parameter are …

Optical Characterization Of Indium Arsenide Antimonide Semiconductors Grown By Molecular Beam Epitaxy, Michael A. Marciniak

Theses and Dissertations

The material parameters and crystalline quality of undoped, MBE-grown InAs_1-xSb_x nearly lattice-matched to (100) GaSb (-0.617% ≤ Δ a-a ≤ +0.708%) similar to material used for mid-infrared semiconductor lasers were determined by optical characterization. Absorption measurements at temperatures between 6-295 K determined the energy gap and wavelength-dependent absorption coefficient for each sample. The compositional dependence of the energy gap was anomalous when compared to previously reported data, suggesting phase separation existed in the material. The samples were also studied by temperature- and excitation-dependent photoluminescence (PL), which, for the majority of cases, showed only a single band-edge peak, …

Studies Of Cl- On The Electrochemical Oscillation Behaviour Of Electrodeposited Silver Indium Selenide Thin Films By Using Dynamic Impedance And The Condensance Method, Shaoai Xie, Xunnan Deng, Jinkua You

Journal of Electrochemistry

The electrochemical oscillation behaviour of hydrogen peroxide cathodic reductionprocess on the electro deposited silver indium selenide electrode has been studied by using in-situ dynamic impedance and the condensance measurement technique in different supporting electrolytes solutions. The surface composition of AglnSe₂ electrodes (before and after oscillating) were also givenby AES. According to the experimental results, the influence of Cl^- on the mechanism of this electrochemical oscillaton process has been discussed in detail.

Theory Of Cyclic Voltammetry At Microdisk Electrode For Reversible Systems, Qiankun Zhuang, Hongyuan Chen

Journal of Electrochemistry

By means of a new approach, the current equations of cyclic voltammetry which describes two cases of quasi-steady-state and fast linear scan at microdisk electrode for reversiblesystem were presented and verified experimentally. It has been shown that the features of this currentessentially depend on the ration of, which is described in detail. ln extreme cases, the equationsare the same as those listed in literatures for large plane and spherical electrodes. Using the quasi-steady-state equation, the causes and conditions for forming steady state, quasi-steady state andhysteresis current for linear sweep voltammetry are all explained and discussed. The width of the ″hysteresis …

Coadsorption Of Para-Toluene Sulfamide And 1.4-Butynediol At Mercury Electrode, Shukun Huang, Naixian Xie, De Gao, Qiang Liu

Journal of Electrochemistry

The coadsorption characteristics of para-toluene sulfamide and 1,4-butynediol atmercury electrode have been studied by means of electrocapillary curve, differential capacity curve, Stuart model and the SCFMO method (CNDO/2). The coadsorption is a physical adsorption occuringnaturally. Lateral and flat orientations in the two adsorbates close to their maximum adsorptionpotential were considered respectively. Unlike attractive interactions of their own, there was arepulsive interaction at their coadsorption layer. A preferred adsorption of 1,4-butynediol occurred when they were at the same volume concentration.

A Relativistic Density-Functional Investigation Of Vibrational Frequencies Of Cn- On Cu And Ag Electrodes, Mengsheng Liao, Xin Lv, Qianer Zhang

Journal of Electrochemistry

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Studies On The Structure Of Licoo2 Synthesized With Tartaric Acid And The Behaviorof Its Rechargeable Lithium Battery, Fuping Zhang

Journal of Electrochemistry

The structure of LiCoO₂ synthesized with tartaric acid and the behavior of itsrechargeable Lithium battery have been studied by XRD, XPS, CV, CT. It has been shown that LiCoO₂ has a space group R3m with hexagonal parameters a=0.2810 nm, c=1.4088 nm. Low-spin state Co³⁺ configuration in LiCoO₂ has been suggested. Also, Li₂O, was identified onits surface. Furthermore, the capacity and the middle working voltage of its Lithium battery are about 120 mA·h·g^-1 and 3.8 V, respectively. The EMF of the cell changes with the Lithium composition of itscathode following E=4.318-0.450 X^2/3 in …

Studies On The Bright Zinc-Nickel Alloy Palting In Alkaline Baths, Jiale Cai, Shaomin Zhou

Journal of Electrochemistry

The electrochemical properties of the Zn-Ni plating baths and the structure andperformance of the obtained deposits were investigated. The results show that the nickel content of theobtained deposits is incereased with decreasing of Zn²⁺/Ni²⁺ ratio in the baths and with increasing of cathodic current density; The cathode current efficiency is increased with increasing of Zn[Ⅱ] content in the bath and with decreasing of cathodic current density. The ZN-11 additive used is thereaction product of heterocyclic compound and polyamines with epichlorohydrin, it has a higheradsorptivity on Hg-electrode at potential between -0.16～-1.68 V (vs. Hg/HgO, 1 mol·L^-1 KOH). …

Study On The Surface States Of Zinc Sulfide Thin Film Doped With Erbium And Their Effect On The Relaxation Luminance, Yujiang Wang, Zhaohong Liu, Zhenxiang Chen

Journal of Electrochemistry

X-ray photoelectron spectrum and characteristics of the capacity, versus thevoltage of the thin film devices are measured to study the surface states of the zinc sulfide thin film.The transient electroluminescence excited by pulses shows the relaxation luminance peaks during anon-exponential decay process of the characteristic transitions activated by Er³⁺ in the ZnS directcurrent thin film electroluminescence (DCTFEL) devices.The surface structures of ZnS:Cu, Cl, Erfilm with the absorption of oxygen, and the effect of the surface states on the relaxation luminance ofthe devices are discussed.

Self-Assembled Monolayers: Preparation,Properties And Application, Xiandui Dong, Juntao Lu, Chuansin Cha

Journal of Electrochemistry

Self-assembling technique is a versatile approach to the preparation of monolayersof well-defined composition, structure, thickness and physicochemical properties. Different aspects, such as wettability, adhesion, corrosion, tribology, electrontransfer, protein adsorption, molecular recognition, and applications of SAMs are widely studied. The developments in the last decade arereviewed, with special attention to the electrochemical studies related to electrodes modified with thiol-derivative-based SAMs.

Problems On The Study Of Anodic Films On Pb In Sulfuric Acid Solution (Ⅰ), Wenbin Cai, Houtian Liu, Weifang Zhou

Journal of Electrochemistry

The identification of the phase composition of the anodic film on Pb formed in H₂SO₄ solution in PbO potential region has long been argued, together with the explanation of thecathodic peak at about -0.9V (Hg/HgSO₄) in the linear sweep voltammogram for a Pb-H₂SO₄ system. In this article, a review of our recent investigations was presented on the above problems.

Progress In R&D Of Lithium Rechargeable Batteries In China, Jiqiang Wang

Journal of Electrochemistry

No abstract provided.