Materials Science and Engineering Commons^™

Heat Treatment Of Gamma Titanium Aluminide Alloys, Thomas J. Kelly, Michael J. Weimer, Curtiss M. Austin, Blair London, Donald E. Larson Jr., Dean A. Wheeler

Materials Engineering

A gamma titanium aluminide alloy article, is prepared using a piece of a gamma titanium aluminide alloy having a composition capable of forming alpha, alpha-2, and gamma phases. The alpha transus temperature of the gamma titanium aluminide alloy piece is determined. The gamma titanium aluminide alloy piece is consolidated by hot isostatic pressing at a temperature of from about 50 F. to about 250 F. below the alpha transus temperature and at a pressure of from about 10,000 to about 30,000 pounds per square inch, for a duration of from about 1 to about 20 hours. The piece is heat …

Time-Resolved Electron Diffraction Studies Of Phase Transitions At Low-Index Germanium Surfaces, Xinglin Zeng

Electrical & Computer Engineering Theses & Dissertations

The phase transitions at the low-index surfaces of germanium were investigated using conventional and 100-ps time-resolved reflection high-energy electron diffraction. For the time-resolved studies, the surface is heated by 100-ps laser pulse while a synchronized electron beam probes the structure. When heated by 100-ps laser pulse, Ge(111)-c(2x8) and Ge(100)-(2x1) reconstruction is seen to overheat above the onset temperatures for the disordering under thermodynamic equilibrium. Slow heating shows that the adatoms in the Ge(111)-c(2x8) reconstruction state start to disorder at ∼510 K and are converted to a totally disordered adatom arrangement at 573 K. For heating with 100-ps laser pulses, time-resolved …

Elastic Properties, Strength And Damage Tolerance Of Pultruded Composites, Mrinal Chandra Saha

Mechanical & Aerospace Engineering Theses & Dissertations

Pultruded composites are candidate materials for civil engineering infrastructural applications due their higher corrosion resistance and lower life cycle cost. Efficient use of materials like structural members requires thorough understanding of the mechanism that affects their response. The present investigation addresses the modeling and characterization of E-glass fiber/polyester resin matrix pultruded composites in the form of sheets of various thicknesses.

The elastic constants were measured using static, vibration and ultrasonic methods. Two types of piezoelectric crystals were used in ultrasonic measurements. Finally, the feasibility of using a single specimen, in the form of a circular disk, was shown in measuring …

A Substructuring Technique With Application To Spot Weld Placement Design, Yang Wang

Mechanical & Aerospace Engineering Theses & Dissertations

It is quite common in the industry to use various interface methods, such as welding, fasteners, bolts, adhesive bonding, etc., to join substructures together. The quality of the assembled structure is directly related to the type of the interface methods used in the manufacturing process. Thus, it is important to include the interface conditions as part of design variables in any design process. To this end, this work develops a reanalysis method that can efficiently analyze structures with variations on the interface conditions. This reanalysis method is based upon a new two-step substructuring technique. The first step performs substructural level …

Processing Of Erbium Doped High-Tc Superconductor Yba2cu3o7-X Single Crystals For Improved Flux Pinning, William C. Hicks, Fatih Dogan, Michael Strasik, Arthur C. Day, Kevin E. Mccrary

Materials Science and Engineering Faculty Research & Creative Works

The effect of selected Rare Earth (RE) oxide addi- Tion on growth behavior of large single crystals and the super- conducting properties of YBa₂Cu₃0_7-x, (Y123) was investigated. The results show that even a small amount (cl mol %) of rare earth addition can have a significant effect on the flux pinning capacity of Y123 single crystals. It was further observed that for Nd and Yb the continuous crystal growth became very unstable for additions greater then 1 mol % while crystal growth remains stable even for additions up to 30 mol % Er_{2 …}

Processing Of Erbium Doped High-Tc Superconductor Yba2cu3o7-X Single Crystals For Improved Flux Pinning, William C. Hicks, Fatih Dogan, Michael Strasik, Arthur C. Day, Kevin E. Mccrary

Materials Science and Engineering Faculty Research & Creative Works

The effect of selected Rare Earth (RE) oxide addition on growth behavior of large single crystals and the super- conducting properties of YBa₂Cu₃O_7-x, (Y123) was investigated. The results show that even a small amount (cl mol %) of rare earth addition can have a significant effect on the flux pinning capacity of Y123 single crystals. It was further observed that for Nd and Yb the continuous crystal growth became very unstable for additions greater then 1 mol % while crystal growth remains stable even for additions up to 30 mol % Er₂BaCuO …

Dopant Structural Distortions In High-Temperature Superconductors: An Active Or A Passive Role?, Daniel Haskel, Edward A. Stern, Fatih Dogan, Arnie R. Moodenbaugh

Materials Science and Engineering Faculty Research & Creative Works

The parent compounds of high-temperature superconductors, such as YBa2Cu3O6 and La2CuO4, are strongly interacting electron systems, rendering them insulators with Mott-Hubbard gaps of a few electronvolts. Charge carriers (holes) are introduced by chemical doping, causing an insulator-metal (IM) transition and, at low temperatures, superconductivity. the role of dopants is widely seen as limited to the introduction of holes into the CuO2 planes (i.e. occupying electronic states derived from Cu and O 2px,y atomic orbitals). Most theories of high-Tc superconductivity deal with pairing interactions between these planar holes. Local distortions around dopants are poorly understood, because of the experimental difficulty in …

Network Formalism For Modeling Functionally Gradient Piezoelectric Plates And Stacks And Simulations Of Rainbow Ceramic Actuators, Robert W. Schwartz, A. Ballato, John Ballato

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A simple network representation is given for a stack of thin, homogeneous piezoelectric plates, executing a single thickness mode of motion. All plates may differ in thickness and material properties, including dielectric loss, ohmic conductivity, and viscous loss. Each plate is driven by a thickness-directed electric field, and all stack elements are connected electrically in series. Functionally gradient single plates and composites are readily modeled by the network, to a desired precision, using a sequence of circuit elements representing stepwise variations in material properties and layer thicknesses. Simulations of RAINBOW (reduced and internally biased oxide wafer) ceramics are given.

Photoluminescence Of Single Quantum Well Structures In Gallium Arsenide, Christian A. Bartholomew

Theses and Dissertations

The continued development of state-of the-art semiconductor technologies and devices by the United States Air Force and the Department of Defense requires accurate and efficient techniques to evaluate and model these new materials. Of particular interest to the Air Force are quantum well structures which can be used for small-scale laser sources in fly-by-light applications, as efficient infrared countermeasures to heat-seeking missiles, or as advanced seekers in optically guided missiles. This thesis provides the initial experimental procedures and data necessary to begin producing accurate yet robust models. Although carrier effective masses could not be evaluated using hot-electron photoluminescence, photoluminescence excitation …

Numerical Study Of Optical Delay In Semiconductor Multilayer Distributed Bragg Reflector And Tunable Microcavity Structures, Michael I. K. Etan

Theses and Dissertations

The Air Force has a growing need for the greater bandwidth, speed, and flexibility offered by optical communication links. Future space systems and airborne platforms will most likely use optical signals for efficient power transmission and to minimize the possibility of spoofing and eavesdropping. Tunable optical delays play an important role in the implementation of free space optical communication links. The primary challenge in implementing these systems is the active maintenance of coherent wave fronts across the system's optical aperture. For space applications, this aperture may he hundreds of meters in diameter. Spatial segmentation of a large aperture into smaller …

Optical And Etching Studies Of Native Aluminum Oxide Layers For Use In Microcavity Photonic Devices, William L. Bernhard

Theses and Dissertations

Optical communication and computing systems are required to meet future information transfer and processing needs. Microcavity devices serve as an enabling technology to implement and integrate optoelectronic systems. It is important to understand the optical and mechanical properties of materials utilize within microcavity devices. Only then is it possible to accurately model and analyze structures. Microcavity structures incorporating a high aluminum content AlGaAs layers are designed, grown, processed, and measured. The processing of these devices includes the conversion of high aluminum-content AlGaAs layers to native aluminum oxide (AlO) layers through the process of thermal oxidation. This selective conversion of microcavity …

Fatigue Response Of Thin Stiffened Aluminum Cracked Panels Repaired With Bonded Composite Patches, Jason B. Avram

Theses and Dissertations

This research investigated the fatigue response of precracked and patched 2024-T3 Aluminum panels with stiffeners. Patches were single-sided, unidirectional three ply boron/epoxy. Stiffeners were 2024-T3 aluminum and were riveted and bonded on. Disbonds were introduced into the repair bondline by inserting teflon strips. Three disbond configurations were investigated rack tip disbond (CTD) located at the edge of the patch in the path of crack propagation, full-width disbond (FWD) covering the entire crack, and end disbond (ED) located at each end of the patch and covering the full width. Each repaired panel was subjected to tension/tension cyclic fatigue with a maximum …

The Applications Of Confocal Raman Micro-Spectroscopy For Study Of Practical Electrode Materials, Yong Yang, Wei Chu, Jun-Min Nan, Xun-Guang Chen, Zu-Geng Lin

Journal of Electrochemistry

Some recent research work about applications of confocal Raman micro spectroscopy for study of practical electrode materials carried out in our lab has been briefly introduced. The examples include study of electrochemical Li⁺ intercalation process, characterization of surface oxide film on AB₅ type electrodes and passive film and pitting corrosion of Rebar electrodes.

A Study On The Performance Of Matrix Prepared By Tape Cast And Its Molten Carbonate Fuel Cells (Mcfcs), Hua-Xin Lin, Bao-Lian Yi, Li Zhou, Chang-Qing He, Lian-Ying Kong, En-Jun Zhang

Journal of Electrochemistry

The matrix prepared with γ-LiAlO₂ powder and by tape cast displayed higher ability of preventing from gas cross over and lower ohmic polarization. The voltages of the stack (three cells, 122 cm²) stacked with the matrix were 2.02 and 1.78 V at 200 and 246 mA/cm², respectively, and the output power reached 53.4 W. The cell (28 cm ²) voltages were 0.85 and 0.75 V at 200 and 300 mA/cm², respectively, and the output power was about 6.6 W. Compensating the shrinkage of matrix in stacking cells promoted the enhancement of the …

Two-Dimensional Surface Raman Imaging Of A Roughened Iron Electrode In Saline Water, Pei-Gen Cao, Jian-Lin Yao, Jun-Wei Zheng, Bin Ren, Ren-Ao Gu, Zhong-Qun Tian

Journal of Electrochemistry

The analysis of the composite and distribution of iron oxide due to pit corrosion in saline solutions (3.4% NaCl) is of great importance. Many electrochemical methods, XPS, and other photoelectronic techniques have been applied to this domain. Surface enhanced Raman scattering (SERS) spectroscopy can provide the vibrational information of surface species with high sensitivity and is very useful in the study of surface chemistry of iron. Notwithstanding, the application of SERS in iron corrosion is hampered for its SERS-inactivity. Efforts have been devoted to extend the use of SERS to the study of iron.

How Can Direct Mthanol Fuel Cell Benefit From Carbonate Media, Lin Zhuang, Yang Wang, Jun-Tao Lu

Journal of Electrochemistry

The kinetics of methanol oxidation and oxygen reduction in 0.5 mol/L K₂CO₃ were compared with those in 0.5 mol/L H₂SO ₄. Experiments revealed that carbonate media could be more beneficial to direct methanol fuel cell(DMFC). Firstly, both electrode reactions show better performance in the carbonate than in the acid; secondly, materials other than noble metals become possible to be used as the anodic and cathodic catalysts; thirdly, the potential dectease caused by methanol crossover could be depressed by using metal oxide catalysts not stable in acid, such as MnO₂.

Synthesis Of Limn2O4-ΔClΔ Cathode Material By Like-Sol-Gel Methode, Zhao-Yong Chen, Yi He, Xing-Quan Liu, Zhi-Jie Li, Zuo-Long Yu

Journal of Electrochemistry

LiMn₂O_4-δCl_δ was synthesized by like sol gel methode, with calculated LiOH·H₂O, Mn(No₃)₂⋅6H₂O and LiCl·H₂O, and made electrochemical test with these compounds as positive materials. Result demostrated that LiMn₂O_4-δCl_δ cathode material has exellent stability and nearly no capacity loss after reaching stability.

In Situ Raman Spectroelectrochemical Characterization Of The Prussian Blue/Platinum Modified Electrode, Xiao-Wei Cao, Rong Wang, Gui-Hua Wang, Zong-Rang Zhang

Journal of Electrochemistry

Prussian Blue is known to be deposited electrochemically on the electrode surface, producing a dense redox active layer. Since the Prussian Blue modified electrode was first reported by Neff in 1978, different in situ spectroelectrochemical techniques have been widely used to investigate its electrochemical mechanism. But no research work related to the in situ Raman spectroscopic studies on it has been reported. In this paper we try to characterize the nature of thin Prussian Blue films on platinum substrates with in situ Raman spectroelectrochemical technique.

Adsorption Behavior Of Co At The Ultrathin Rh And Pt Film Electrodes, Yong Xie, Xiao-Qin Li, Bin Ren, Zhong-Qun Tian

Journal of Electrochemistry

Pt group metals have been widely used in catalysis such as hydrogenation of organic compounds and the oxidation of carbon monoxide. The information about CO adsorption on the Pt group surfaces and the influence of other surface species, such as hydrogen and CO₂ will be greatly helpful to elucidate the adsorption behavior of CO on Pt group metal surfaces and get a deeper understanding of catalytic mechanisms of Pt group metals. Surface enhanced Raman spectroscopy (SERS) has been becoming an increasingly important means to characterize the electrochemical metal solution interface over the past two decades. Our laboratory has successfully …

Adsorption And Oxidation Of Ethanol On Nm-Pt/Gc Electrode Ii. Eqcm And In-Situ Ftir Spectroscopic Studies In Acid Media, Guo-Liang Chen, Sheng-Pei Chen, Zhi-You Zhou, Chun-Hua Zhen, Shi-Gang Sun

Journal of Electrochemistry

The adsorption and oxidation of ethanol on nm Pt/GC electrode in acid solutions containing 0.1 mol·L ^-1 H₂SO₄ +0.1 mol·L ^-1 CH₃CH₂OH was investigated by using cyclic voltammetry, EQCM and in situ FTIR spectroscopy. The experimental results demonstrated that the oxidation of CH₃CH₂OH is closely relaed to solution acidity and oxygen species on electrode surface; CH₃CH₂OH was oxidized on nm Pt/GC electrode in acidic media via a dual path reaction mechanism, i.e . CH₃CH₂OH may be oxidized into CO₂ through …

The Photoelectrochemistry Of Tio2-Polyaniline Composite Film, Huai-Guo Huang, Zhi-Xin Zheng, Jin Luo, Hong-Ping Zhang, Ling-Ling Wu, Zhong-Hua Lin

Journal of Electrochemistry

A TiO₂ and polyaniline (PANI) composite film was obtained by electrochemical methods. The SEM image of the composite film showed that the PANI film is almost completely covered with TiO₂ efficiency. The spectra of photocurrent for the TiO₂-PANI composite film were different from these of TiO₂ film photosensitized by PANI. The bandgap energy of TiO₂ film on partially oxidized PANI film was determined as 3.0 eV by the threshold energy of photocurrent band for TiO₂. The spectra of photocurrent for partially oxidized PANI film electrode suggested that it has the characteristics of …

Catalytic Effect Of Cl- On Electrodeposition Of Binary Zinc Alloys With Iron Group Metals, Ren-He Yin, Zheng-Hua Fang, Wei-Min Cao, A.Za Karia, Rong-Ming Zhou

Journal of Electrochemistry

Zinc iron group metal alloys were deposited under coulostatic (10C⋅cm^-2) at 40 ℃ chloride baths. The deposited alloys were quantitatively analyzed by Atomic Absorption Spectrometry. The current efficiency, percent content and partial polarization curves were obtained by the results. The morphology of the deposits was observed by means of Scanning Electron Microscopy(SEM). We observe that the electrodeposition of zinc iron group metal alloys is one of the best known examples of anomalous codeposition. We found the catalytic effect of Cl^- on the electrodeposition behavior of iron group metal. Overpotential of iron group metal droped abruptly at high …

Deposition Of Tantalum On Steel By Sputtering, Bhavin Shah

Theses

Recent interest in tantalum deposition comes from two different applications. One is in microelectronics where thin tantalum films (< 1 µm) are used as diffusion barrier layers for copper interconnects. The other involves its application as a material for corrosion and wear resistant coating on surfaces that are subjected to high stresses and harsh chemical and erosive environments.

This thesis is a part of the investigation done at the Ion Beam and Thin Film Research Laboratory at NJIT to study the deposition conditions and properties of tantalum thin films. It includes the design and construction of Planar D.C. Magnetron Sputtering System and Cylindrical D.C. Magnetron Sputtering System for deposition on the planar and cylindrical surfaces of steel, respectively. The electrical characteristics of the cylindrical system were tested in a range of pressures and conditions for initiation and maintaining of …

Method And Apparatus For Adaptive Process Control Of Critical Dimensions During Spin Coating Process, Richard N. Savage, Emir Gurer

Materials Engineering

A spin coating process for controlling the mean thickness of photoresist on the surface of a semiconductor wafer. The wafer surface has a central axis normal to the surface. The process comprises the steps of applying the solution to the wafer surface and spinning the wafer about the central axis at a spindle speed until the solution has dried. The spindle speed is a function of the desired mean thickness of the photoresist, the barometric pressure and the relative humidity. The spindle speed is determined from a statistical model described by the equation: MT=A+BxRH+CxBP+D/SS^1/2 wherein: MT is mean thickness …

Evolution Of The Resonance And Incommensurate Spin Fluctuations In Superconducting Yba2⁢Cu3⁢O6+X, Pengcheng Dai, Herbert A. Mook, Rodney Dale Hunt, Fatih Dogan

Materials Science and Engineering Faculty Research & Creative Works

Polarized and unpolarized neutron triple-axis spectrometry was used to study the dynamical magnetic susceptibility X″⁡(q,w) as a function of energy (ħ⁢w) and wave vector (q) in a wide temperature range for the bilayer superconductor YBa₂⁢Cu₃⁢O_6+x with oxygen concentrations, x, of 0.45, 0.5, 0.6, 0.7, 0.8, 0.93, and 0.95. The most prominent features in the magnetic spectra include a spin gap in the superconducting state, a pseudo gap in the normal state, the much-discussed resonance, and incommensurate spin fluctuations below the resonance. We establish the doping dependence …

Application Of Dynamic System Identification To Timber Beams - Part I, S T. Peterson, D I. Mclean, M D. Symans, David Pollock, W F. Cofer, R N. Emerson, Kenneth J. Fridley

Faculty Publications - Biomedical, Mechanical, and Civil Engineering

In this first part of a two-part paper, development of a method of dynamic system identification for timber beams is presented with an analytical verification of the method using a finite-element model. A method of global nondestructive evaluation for identifying local damage and decay in timber beams is investigated in this paper. Experimental modal analysis is used in conjunction with a previously developed damage localization algorithm. The damage localization algorithm utilizes changes in modal strain energy between the mode shapes of a calibrated model, representing the undamaged state of the beam of interest, and the experimentally obtained mode shapes for …

Application Of Dynamic System Identification To Timber Beams - Part Ii, S T. Peterson, D I. Mclean, M D. Symans, David Pollock, W F. Cofer, R N. Emerson, Kenneth J. Fridley

Faculty Publications - Biomedical, Mechanical, and Civil Engineering

In a companion paper, a method of global nondestructive evaluation (NDE) for identifying local damage and decay in timber beams was developed and verified analytically using a finite-element model of a timber beam. The previously presented method of damage localization employs experimental modal analysis and an algorithm that monitors changes in modal strain energy between the mode shapes of a damaged beam with respect to the undamaged state of the beam. In this second part of a two-part paper, experimental laboratory tests on simply supported timber beams are presented to verify the capabilities and determine the limitations of the proposed …

A Direct Correlation Function For Mesomorphic Polymers And Its Application To The ‘Smectic’ Phase Of Isotactic Polypropylene, Y Cohen, Ravi F. Saraf

Papers in Materials Science

A general model to calculate the structure of a smectic to nematic-like order in polymer systems is proposed. The model is limited to well-aligned molecules with respect to each other. It is especially suited for systems where the packing between neighboring chains is described by liquid-like disorder with axial registration in the chain-axis direction. In such a case the diffraction pattern from the oriented structure exhibits broad liquid-like reflections on the equatorial but sharper reflections on the layer lines. An Ornstein-Zernike approach is adopted to calculate the inter-chain packing and inter-chain registration, where the direct correlation function of packing and …

Cationic Surfactant Mediated Hybridization And Hydrophobization Of Dna Molecules At The Liquid/Liquid Interface And Their Phase Transfer, Murali Sastry, Ashavani Kumar, Mrunalini Pattarkine, Vidya Ramakrishnan, Krishna N. Ganesh

Faculty Works

Hybridization of complementary oligonucleotides mediated by a cationic surfactant at the water/hexane interface leads to hydrophobic, double-helical DNA which may be readily phase transferred to the organic phase and cast into thin films on solid substrates.

Preparation Of Magnetic Nanoparticles And Their Assemblies Using A New Fe(Ii) Alkoxide Precursor, Suresh Pillai, Grainne Biddlecombe, Yurii Gun’Ko, John Kelly, J. Michael Coey, Alexis Douvalis

Articles

No abstract provided.