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Materials Science and Engineering Faculty Research & Creative Works

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Full-Text Articles in Materials Science and Engineering

Simulation Of The Fluid Flow-Related Phenomena In The Electrolyte Of An Aluminum Electrolysis Cell, Yufeng Wang, Lifeng Zhang, Xiangjun Zuo Oct 2011

Simulation Of The Fluid Flow-Related Phenomena In The Electrolyte Of An Aluminum Electrolysis Cell, Yufeng Wang, Lifeng Zhang, Xiangjun Zuo

Materials Science and Engineering Faculty Research & Creative Works

A full-scale water model and mathematical simulation were used to study the fluid flow-related phenomena in a water model of an aluminum electrolysis cell. the time-dependent, multiphase fluid flow model was developed to represent the complex transient flow in the electrolysis bath. the accuracy of the mathematical model was validated by the ink dispersion and laser doppler velocimetry measurements in the water model. the shape, motion, release frequency of large-size bubbles, the fluid flow pattern, and the electrolyte-metal interface were predicted by the mathematical simulation. the design and operation of the anode were discussed, including the effect of the anode …

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Kinetic Analysis Of The Thermal Degradation Of Printed Wiring Boards, Alex Luyima, Lifeng Zhang, Lucas Nana Wiredu Damoah Aug 2011

Kinetic Analysis Of The Thermal Degradation Of Printed Wiring Boards, Alex Luyima, Lifeng Zhang, Lucas Nana Wiredu Damoah

Materials Science and Engineering Faculty Research & Creative Works

The non-isothermal pyrolysis of printed wiring boards (PWBs) was investigated by simultaneous thermogravimetric and differential thermal analysis (TG-DTA) in the temperature range of 300-1200 K. Pyrolysis experiments were carried out on PWBs samples at three different heating rates of 10, 20, and 30°C/min. in this study, the kinetic parameters of PWBs pyrolysis have been estimated using model free and model fitted methods. © 2011 TMS.

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Large Kinetic Asymmetry In The Metal-Insulator Transition Nucleated At Localized And Extended Defects, W. Fan, Jinbo Cao, J. Seidel, Yijia Gu, J. W. Yim, For Full List Of Authors, See Publisher's Website. Jun 2011

Large Kinetic Asymmetry In The Metal-Insulator Transition Nucleated At Localized And Extended Defects, W. Fan, Jinbo Cao, J. Seidel, Yijia Gu, J. W. Yim, For Full List Of Authors, See Publisher's Website.

Materials Science and Engineering Faculty Research & Creative Works

Superheating and supercooling effects are characteristic kinetic processes in first-order phase transitions, and asymmetry between them is widely observed. In materials where electronic and structural degrees of freedom are coupled, a wide, asymmetric hysteresis may occur in the transition between electronic phases. Structural defects are known to seed heterogeneous nucleation of the phase transition, hence reduce the degree of superheating and supercooling. Here we show that in the metal-insulator transition of single-crystal VO 2, a large kinetic asymmetry arises from the distinct spatial extension and distribution of two basic types of crystal defects: point defects and twin walls. Nanometer-thick twin …

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Effect Of Slide Gate And Embr On The Transport Of Inclusions And Bubbles In Slab Continuous Casting Strands, Yufeng Wang, Anping Dong, Lifeng Zhang Apr 2011

Effect Of Slide Gate And Embr On The Transport Of Inclusions And Bubbles In Slab Continuous Casting Strands, Yufeng Wang, Anping Dong, Lifeng Zhang

Materials Science and Engineering Faculty Research & Creative Works

This study is to investigate the effect of electromagnetic brake (EMBr) on fluid flow and particle motion in steel slab continuous casting strands. the effect of slide gate moving on fluid flow pattern was discussed. a strong swirl and asymmetrical flow at the outports and, subsequently, inside the slab mold, was induced by slide gate. the application of EMBr would be a remedy to the swirl flow in the casting mold. Flow pattern has great influence on the trajectories of injected bubbles and nonmetallic inclusions. More bubbles tend to release from the top surface near the wide face opposite to …

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Batio3–Srtio3 Layered Dielectrics For Energy Storage, Sheng Chao, Fatih Dogan Mar 2011

Batio3–Srtio3 Layered Dielectrics For Energy Storage, Sheng Chao, Fatih Dogan

Materials Science and Engineering Faculty Research & Creative Works

BaTiO3–SrTiO3 (BST) thick films (~ 250–390 μm) with layered structures were fabricated by tape-casting and lamination process. Layered composites with various Ba/Sr ratios were obtained by lamination of BaTiO3 (BT) and SrTiO3 (ST) tapes in different spatial configurations (2–2). As-prepared BST ceramics showed much improved sinterability over the laminates of pure BT or pure ST tapes. Dielectric properties of materials were measured in the temperature range of 25 °C to 200 °C. The method of utilizing of layered structures offered flexibility to maximize the energy storage capability at specific operating conditions: (temperature and electric field) …

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Corrosion-Resistant Glasses For Steel Enamels, Richard K. Brow, Signo Tadeu Dos Reis, Michael L. Koenigstein, Genda Chen Mar 2011

Corrosion-Resistant Glasses For Steel Enamels, Richard K. Brow, Signo Tadeu Dos Reis, Michael L. Koenigstein, Genda Chen

Materials Science and Engineering Faculty Research & Creative Works

A cementitious composite material wherein glass-coated steel rods are positioned in a cementitious matrix. The glass composition for coating the steel reinforcing rods includes between about 33-45 weight percent SiO2, 13.5-19.5 weight percent B2O3, 3.5-4.6 weight percent Al2O3, 4.0-13.5 weight percent K2O, 5.5-15.5 weight percent ZrO2, 8.6-15.9 weight percent Na2O, 4.6-5.1 weight percent CaO, 0.6-0.7 weight percent MnO2, 1.0-1.0 weight percent NiO, and 1.0-1.1 weight percent CoO. The glass composition is typically in compression on the rods at ambient temperatures, has a …

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Friction Stir Lap Welded Advanced High Strength Steels: Microstructure And Mechanical Properties, M. Ghosh, K. Kumar, R. S. Mishra Jan 2011

Friction Stir Lap Welded Advanced High Strength Steels: Microstructure And Mechanical Properties, M. Ghosh, K. Kumar, R. S. Mishra

Materials Science and Engineering Faculty Research & Creative Works

Friction stir welding was carried out under different heat input and cooling rates to produce lap joints between high strength martensitic steel sheets. the microstructure of the welds was characterized, and microhardness was evaluated. Joint efficiency was determined by lap shear test. Variation in processing conditions governed total heat input, peak temperature and cooling rate during friction stir welding. Weld nugget microstructure depended principally on cooling rate. the slowest cooling rate promoted ferrite-pearlite and the fastest cooling rate resulted in martensite formation in the weld nugget. the weakest region of all the joints was the heat affected zone, which consists …

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Beneficial And Technological Analysis For The Recycling Of Solar Grade Silicon Wastes, Anping Dong, Lifeng Zhang, Lucas N.W. Damoah Jan 2011

Beneficial And Technological Analysis For The Recycling Of Solar Grade Silicon Wastes, Anping Dong, Lifeng Zhang, Lucas N.W. Damoah

Materials Science and Engineering Faculty Research & Creative Works

In the current paper, different kinds of silicon wastes during the production of SoG-Si were summarized and the beneficial analyses, such as financial value, energy value, CO2 emissions, and efficiency and energy payback time, were briefly discussed for the recycling of SoG-Si wastes. Possible technologies to recycle and purify SoG-Si wastes were reviewed: such as filtration, sedimentation, solidification control, electromagnetic separation, plasma oxidation, centrifugation, and high temperature remelting process, et al. © 2011 TMS.

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A Study On The Combined Effect Of Forging And Aging In Mg-Y-Re Alloy, S. K. Panigrahi, W. Yuan, R. S. Mishra, R. Delorme, B. Davis, R. A. Howell, K. Cho Jan 2011

A Study On The Combined Effect Of Forging And Aging In Mg-Y-Re Alloy, S. K. Panigrahi, W. Yuan, R. S. Mishra, R. Delorme, B. Davis, R. A. Howell, K. Cho

Materials Science and Engineering Faculty Research & Creative Works

The combined effect of forging and aging on microstructural evolution and mechanical properties of a Mg-Y-RE alloy was studied in the present work by employing hardness measurements, tensile tests, optical microscopy (OM), scanning electron microscopy (SEM) and electron back scattered diffraction (EBSD) analysis. the -F temper treated bulk Mg-Y-RE alloy samples were subjected to forging for microstructural refinement and subsequent aging to maximize the strength-ductility combination. the forged samples combined with peak aging treatment (60 h at 180 °C) exhibited an excellent combination of high strength (388 MPa) and high ductility (23%). the combined effect of grain refinement, work hardening, …

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A Stress-Strain Model For A Two-Phase Ultrafine-Grained Aluminum Alloy, P. S. De, J. Q. Su, R. S. Mishra Jan 2011

A Stress-Strain Model For A Two-Phase Ultrafine-Grained Aluminum Alloy, P. S. De, J. Q. Su, R. S. Mishra

Materials Science and Engineering Faculty Research & Creative Works

Two-phase ultrafine-grained (UFG) aluminum alloys with different precipitate and low-angle boundary distributions were examined for their monotonic stress-strain behavior. Precipitates in combination with low-angle grain boundaries were found to determine the deformation micro mechanism. It is proposed that thermally activated vacancy movement plays a central role in this regard. the experimental stress-strain curves matched well with the trend predicted by a modified Blum-Zheng model based on vacancy-assisted dislocation annihilation mechanism. © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

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Hollow Hydroxyapatite Microspheres For Controlled Delivery Of Proteins, H. Fu, M. N. Rahaman, D. E. Day Jan 2011

Hollow Hydroxyapatite Microspheres For Controlled Delivery Of Proteins, H. Fu, M. N. Rahaman, D. E. Day

Materials Science and Engineering Faculty Research & Creative Works

Hollow hydroxyapatite (HA) microspheres were prepared by reacting solid microspheres of a lithium-calcium-borate glass (106-150 microns) for 2 days in K2HPO4 solution (0.02 M; 37°C) and evaluated as a controlled delivery device for a model protein, bovine serum albumin (BSA). the as-prepared HA microspheres had a hollow core with a diameter equal to 0.6 the external diameter, a surface area of V100 m2/g, and a mesoporous shell wall (pore size of ≈13 nm). after loading the hollow HA microspheres with a solution of BSA, release of the BSA into a medium of phosphate-buffered saline (PBS) …

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Femtosecond Laser Writing Of Waveguides In Zinc Phosphate Glasses [Invited], Luke B. Fletcher, Jon J. Witcher, Neil Troy, Signo Tadeu Dos Reis, Richard K. Brow, R. M. Vazquez, R. Osellame, Denise M. Krol Jan 2011

Femtosecond Laser Writing Of Waveguides In Zinc Phosphate Glasses [Invited], Luke B. Fletcher, Jon J. Witcher, Neil Troy, Signo Tadeu Dos Reis, Richard K. Brow, R. M. Vazquez, R. Osellame, Denise M. Krol

Materials Science and Engineering Faculty Research & Creative Works

We have studied the relationship between the initial glass composition and the structural changes associated with laser-induced refractive index modification in a series of Er-Yb doped and undoped zinc phosphate glasses. White light microscopy and waveguide experiments are used together with Raman and fluorescence spectroscopy to characterize the structural changes. The correlation between Raman peak shifts and fluorescence from phosphorus-oxygen hole center (POHC) defects indicates that fs-laser writing results in a depolymerization of the phosphate glass network. The results also show that the exact glass composition should be taken into account when fabricating waveguide devices in phosphate glasses, in order …

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Direct Femtosecond Laser Waveguide Writing Inside Zinc Phosphate Glass, Luke B. Fletcher, Jon J. Witcher, Neil Troy, Signo Tadeu Dos Reis, Richard K. Brow, Denise M. Krol Jan 2011

Direct Femtosecond Laser Waveguide Writing Inside Zinc Phosphate Glass, Luke B. Fletcher, Jon J. Witcher, Neil Troy, Signo Tadeu Dos Reis, Richard K. Brow, Denise M. Krol

Materials Science and Engineering Faculty Research & Creative Works

We report the relationship between the initial glass composition and the resulting microstructural changes after direct femtosecond laser waveguide writing with a 1 kHz repetition rate Ti:sapphire laser system. A zinc polyphosphate glass composition with an oxygen to phosphorus ratio of 3.25 has demonstrated positive refractive index changes induced inside the focal volume of a focusing microscope objective for laser pulse energies that can achieve intensities above the modification threshold. The permanent photo-induced changes can be used for direct fabrication of optical waveguides using single scan writing techniques. Changes to the localized glass network structure that produce positive changes in …

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Purification Of Solar Grade Silicon Using Electromagnetic Field, Anping Dong, Lucas N.W. Damoah, Lifeng Zhang, Hui Zhu Dec 2010

Purification Of Solar Grade Silicon Using Electromagnetic Field, Anping Dong, Lucas N.W. Damoah, Lifeng Zhang, Hui Zhu

Materials Science and Engineering Faculty Research & Creative Works

Non-metallic particles and the metallic impurity elements in the solar cell silicon have a strong detrimental effect on the conversion efficiency of the solar cell. Removing these impurities is one of the important tasks for silicon refining. the current paper proposed a new approach to purify silicon - electromagnetic (EM) separation. Since the non-metallic particles and the metallic impurity elements are non- or less conductive while the molten silicon is well conductive, under EM field, the Lorenz force will push the particles to the boundary layer, thus separate these inclusions. in the current study, a high frequency EM field was …

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Non-Metallic Particles In Solar Grade Silicon (Sog-Si), Lucas Nana Wiredu Damoah, Anping Dong, Lifeng Zhang, Hui Zhu Dec 2010

Non-Metallic Particles In Solar Grade Silicon (Sog-Si), Lucas Nana Wiredu Damoah, Anping Dong, Lifeng Zhang, Hui Zhu

Materials Science and Engineering Faculty Research & Creative Works

This study investigated the non-metallic inclusions in Solar 2rade Silicon (SoG-Si), especially the distribution of inclusions in the top 15mm layer of multicrystalline silicon ingot. the SoG-Si ingot produced from directional solidification process usually pushes the impurities to the top and finally cut off and discarded, which leads to material loss. the hard inclusions lead to wire breakages during the cutting of the ingot into wafers. the main kinds of inclusions found in top-cut silicon scraps from two manufacturers have been investigated using acid extraction, automated feature analysis techniques and SEM-EDS and optical Microscope: They are needle-like Si3N4 and lumpy …

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Transient Fluid Flow Phenomena During Continuous Casting: Part I-Cast Start, Yufeng Wang, Lifeng Zhang Dec 2010

Transient Fluid Flow Phenomena During Continuous Casting: Part I-Cast Start, Yufeng Wang, Lifeng Zhang

Materials Science and Engineering Faculty Research & Creative Works

This work presents a three-dimensional numerical simulation of transient fluid flow phenomena during continuous casting of steel. in the Part I, the process of cast start was investigated. Cast start involved the filling process and the caster start process. in the filling process, molten steel was continuously filled into the mold cavity with surrounding mold walls and a dummy bar head at the bottom. to simulate the interface between the molten steel and the air, an algorithm of volume of fluid has been employed. in the cast start process, the dummy bar was gradually dragged out with a low casting …

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Transient Fluid Flow Phenomena During Continuous Casting: Part Ii-Cast Speed Change, Temperature Fluctuation, And Steel Grade Mixing, Yufeng Wang, Lifeng Zhang Dec 2010

Transient Fluid Flow Phenomena During Continuous Casting: Part Ii-Cast Speed Change, Temperature Fluctuation, And Steel Grade Mixing, Yufeng Wang, Lifeng Zhang

Materials Science and Engineering Faculty Research & Creative Works

Many complicated phenomena are associated with transient stages during the continuous casting process, especially inside the casting mold cavity. a deep understanding of the phenomena and optimized control over the process ensure the high-quality product and low costs. This work presents a three-dimensional numerical simulation of transient fluid flow phenomena during steel continuous casting. in the Part II, the process of casting speed change (increase or decrease), temperature fluctuation, and steel grade mixing in a slab mold were investigated. the phenomena, such as flow pattern, inclusion removal fraction, temperature variation, top surface profile, and steel transportation, were addressed to evaluate …

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A Simple Model To Calculate Dendrite Growth Rate During Steel Continuous Casting Process, Mujun Long, Lifeng Zhang, Fei Lu Dec 2010

A Simple Model To Calculate Dendrite Growth Rate During Steel Continuous Casting Process, Mujun Long, Lifeng Zhang, Fei Lu

Materials Science and Engineering Faculty Research & Creative Works

In the current paper, the relationship between the casting speed and the dendrite growth during steel continuous casting process was studied; and a simple mathematical model to calculate the primary dendrite growth rate according to the casting speed was developed. the model was used to predict the distribution of the dendrite growth rate along width direction and casting direction during a continuous casting process, indicating a dendrite growth rate of 0.1-3.0 mm/s, which is much higher than that in regular ingot casting. the dendrite growth rate fluctuates along casting direction because of the different cooling intensity in each zone of …

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Thermal Properties Of Lunar Regolith Simulants, Kenneth W. Street, Chandra Ray, Doug Rickman, Daniel A. Scheiman Nov 2010

Thermal Properties Of Lunar Regolith Simulants, Kenneth W. Street, Chandra Ray, Doug Rickman, Daniel A. Scheiman

Materials Science and Engineering Faculty Research & Creative Works

Various high temperature chemical processes have been developed to extract oxygen and metals from lunar regolith. These processes are tested using terrestrial analogues of the regolith. But all practical terrestrial analogs contain H2O and/or OH-, the presence of which has substantial impact on important system behaviors. We have undertaken studies of lunar regolith simulants to determine the limits of the simulants to validate key components for human survivability during sustained presence on the moon. Differential Thermal Analysis (DTA) yields information on phase transitions and melting temperatures. Thermo-Gravimetric Analysis (TGA) with Fourier Transform Infrared (FTIR) analysis provides information on …

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Plasma Processing Of Lunar Regolith Simulant For Oxygen And Glass Production, S. Sen, D. Butts, J. S. O'Dell, C. S. Ray Nov 2010

Plasma Processing Of Lunar Regolith Simulant For Oxygen And Glass Production, S. Sen, D. Butts, J. S. O'Dell, C. S. Ray

Materials Science and Engineering Faculty Research & Creative Works

Tools for extracting life-sustaining resources from the moon are needed to support the vision for space exploration. of particular interest is the production of oxygen for life support and propulsion. on the lunar surface the only practical source for oxygen is the lunar regolith. Described in this paper is an innovative plasma reduction technique for the production of oxygen from lunar regolith. Thermodynamic calculations showed that the regolith oxides could be dissociated to yield up to 7.3 weight percent oxygen when exposed to extremely high temperatures of up to 3000°C. Subsequently the use of a plasma flame to obtain oxygen …

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Effect Of Process Parameters On Abnormal Grain Growth During Friction Stir Processing Of A Cast Al Alloy, S. Jana, Rajiv S. Mishra, J. A. Baumann, G. Grant Nov 2010

Effect Of Process Parameters On Abnormal Grain Growth During Friction Stir Processing Of A Cast Al Alloy, S. Jana, Rajiv S. Mishra, J. A. Baumann, G. Grant

Materials Science and Engineering Faculty Research & Creative Works

The effects of process parameters and friction stir processing (FSP) run configurations on the stability of nugget microstructure at elevated temperatures were evaluated. Cast plates of an Al-7Si-0.6Mg alloy were friction stir processed using a combination of tool rotation rates and tool traverse speeds. All single pass runs showed some extent of abnormal grain growth (AGG), whereas multi-pass runs were more resistant to AGG. Additionally, higher tool rotation rate was found to be beneficial for controlling AGG. These effects were analyzed by comparing the result of this work with other published results and AGG models. © 2010 Elsevier B.V.

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Microstructural Evolution During Fatigue Of Ultrafine Grained Aluminum Alloy, P. S. De, Rajiv S. Mishra Nov 2010

Microstructural Evolution During Fatigue Of Ultrafine Grained Aluminum Alloy, P. S. De, Rajiv S. Mishra

Materials Science and Engineering Faculty Research & Creative Works

A comparative study of the surface microstructural changes during fatigue of a precipitation hardened (PH) aluminum alloy in ultrafine grained (UFG) and microcrystalline conditions was done using orientation imaging microscopy (OIM). with increase in applied stress amplitude, the fatigue life of fine-grained PH alloy deteriorated. on the other hand, at lower stress amplitudes an improvement in fatigue life was noted. This trend was reversed for the coarse-grained PH alloy. in UFG alloy, the fatigue life improved at all stress amplitudes. the variation in fatigue life response between coarse, fine and ultrafine grain PH alloy was due to the increased interaction …

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Method For Determining The Dielectric Constant Of Particles, Vladimir Petrovsky, Fatih Dogan Oct 2010

Method For Determining The Dielectric Constant Of Particles, Vladimir Petrovsky, Fatih Dogan

Materials Science and Engineering Faculty Research & Creative Works

A method of measuring the dielectric constant of a powder, including selecting a powder having an unknown first dielectric constant, selecting a liquid having a known second dielectric constant, and introducing a predetermined amount of powder into a predetermined volume of liquid to define a slurry characterized by a known volume fraction of powder. Next, the impedance spectra of the slurry are plotted over a predetermined frequency range, the measured dielectric constant data is read and the appropriate equivalent circuit for the slurry is determined. Appropriate equivalent circuit equations are applied to the measured dielectric constant data, and the first …

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Thermodynamics Of Strained Vanadium Dioxide Single Crystals, Yijia Gu, Jinbo Cao, Junqiao Wu, Long-Qing Chen Oct 2010

Thermodynamics Of Strained Vanadium Dioxide Single Crystals, Yijia Gu, Jinbo Cao, Junqiao Wu, Long-Qing Chen

Materials Science and Engineering Faculty Research & Creative Works

Vanadium dioxide undergoes a metal-insulator transition, in which the strain condition plays an important role. To investigate the strain contribution, a phenomenological thermodynamic potential for the vanadium dioxide single crystal was constructed. The transformations under the uniaxial stress, wire, and thin film boundary conditions were analyzed, and the corresponding phase diagrams were constructed. The calculated phase diagrams agree well with existing experimental data, and show that the transformation temperature (and Curie temperature) strongly depends on the strain condition.

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Analysis Of Microstructural Evolution During Friction Stir Welding Of Ultrahigh-Strength Steel, M. Ghosh, K. Kumar, R. S. Mishra Oct 2010

Analysis Of Microstructural Evolution During Friction Stir Welding Of Ultrahigh-Strength Steel, M. Ghosh, K. Kumar, R. S. Mishra

Materials Science and Engineering Faculty Research & Creative Works

Friction stirs lap-welded advanced high-strength M190 steel exhibited formation of lath martensite at weld nuggets, a ferrite layer at faying surfaces and a ferrite-pearlite microstructure at the bottom of the stir zone. the phase transformation was governed by severe plastic deformation in the austenitic region followed by cooling. the strain rate and peak temperature played key roles in controlling the prior-austenitic grain size and were correlated to the Zener-Hollomon parameter. an empirical relationship has been obtained for dynamically recrystallized austenite grains. © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

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Effect Of Friction Stir Processing On Microstructure And Tensile Properties Of An Investment Cast Al-7si-0.6mg Alloy, Saumyadeep Jana, Rajiv S. Mishra, John A. Baumann, Glenn J. Grant Oct 2010

Effect Of Friction Stir Processing On Microstructure And Tensile Properties Of An Investment Cast Al-7si-0.6mg Alloy, Saumyadeep Jana, Rajiv S. Mishra, John A. Baumann, Glenn J. Grant

Materials Science and Engineering Faculty Research & Creative Works

Friction stir processing (FSP) is emerging as a promising tool for microstructural modification. the current study assesses the effects of FSP on the microstructure and mechanical properties of an investment cast Al-7Si-Mg alloy. FSP eliminates porosity and significantly refines eutectic Si particles. the extent of particle refinement varied with changes in processing conditions. a high tool rotation rate and a low-to-intermediate tool traverse speed generated a higher volume fraction of finer particles. Tensile ductility changed significantly as a result of FSP, whereas ultimate tensile strength improved only marginally. Yield strength was similar in both cast and FSP samples under various …

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Complex Impedance Study Of Fine And Coarse Grain Tio2 Ceramics, Sheng Chao, Vladimir Petrovsky, Fatih Dogan Oct 2010

Complex Impedance Study Of Fine And Coarse Grain Tio2 Ceramics, Sheng Chao, Vladimir Petrovsky, Fatih Dogan

Materials Science and Engineering Faculty Research & Creative Works

Titanium dioxide (TiO2) ceramics with various grain sizes were investigated by impedance spectroscopy techniques. Dielectric loss peak identified in coarse grain TiO2 was attributed to space charge polarization occurring at the grain boundaries. Electric modulus representation of the impedance data showed two types of relaxation processes in coarse grain TiO2, whereas only one type was observed in fine grain TiO2. Long-range migration of oxygen vacancies was found to be the dominant conduction mechanism for fine grain TiO2, while electron hopping between localized states was attributed to dielectric relaxation in coarse grain …

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Freeze Extrusion Fabrication Of 13-93 Bioactive Glass Scaffolds For Bone Repair, Tieshu Huang, Nikhil D. Doiphode, M. N. Rahaman, Ming-Chuan Leu, B. Sonny Bal, D. E. Day Aug 2010

Freeze Extrusion Fabrication Of 13-93 Bioactive Glass Scaffolds For Bone Repair, Tieshu Huang, Nikhil D. Doiphode, M. N. Rahaman, Ming-Chuan Leu, B. Sonny Bal, D. E. Day

Materials Science and Engineering Faculty Research & Creative Works

There is an increasing demand for synthetic scaffolds with the requisite biocompatibility, internal architecture, and mechanical properties for the bone repair and regeneration. In this work, scaffolds of a silicate bioactive glass (13-93) were prepared by a freeze extrusion fabrication (FEF) method and evaluated in vitro for potential applications in bone repair and regeneration. The process parameters for FEF production of scaffolds with the requisite microstructural characteristics, as well as the mechanical and cell culture response of the scaffolds were evaluated. After binder burnout and sintering (60 min at 700°C), the scaffolds consisted of a dense glass network with interpenetrating …

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Processing And Characterization Of New Oxy-Sulfo-Telluride Glasses In The Ge-Sb-Te-S-O System, C. (Charmayne) Smith (Lonergan), J. Jackson, L. Petit, C. Rivero-Baleine, K. Richardson Aug 2010

Processing And Characterization Of New Oxy-Sulfo-Telluride Glasses In The Ge-Sb-Te-S-O System, C. (Charmayne) Smith (Lonergan), J. Jackson, L. Petit, C. Rivero-Baleine, K. Richardson

Materials Science and Engineering Faculty Research & Creative Works

New oxy-sulfo-telluride glasses have been prepared in the GeSbTeSO system employing a two-step melting process which involves the processing of a chalcogenide glass (ChG) and subsequent melting with TeO2 or Sb2O3. The progressive incorporation of O at the expense of S was found to increase the density and the glass transition temperature and to decrease the molar volume of the investigated oxy-sulfo-telluride glasses. We also observed a shift of the visNIR cut-off wavelength to longer wavelength probably due to changes in Sb coordination within the glass matrix and overall matrix polarizability. Using Raman spectroscopy, correlations …

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Removal Of Inclusions From Aluminum Through Filtration, Lucas Nana Wiredu Damoah, Lifeng Zhang Aug 2010

Removal Of Inclusions From Aluminum Through Filtration, Lucas Nana Wiredu Damoah, Lifeng Zhang

Materials Science and Engineering Faculty Research & Creative Works

Filtration experiments were carried out using both an AlF3 slurry-coated and an uncoated Al2O3 ceramic foam filter to study the removal of nonmetallic inclusions and impurity elements. the results showed that the 30-ppi ceramic foam filter removed up to 85 pct inclusions from aluminum. Several pictures of two- and three-dimensional morphologies of both nonmetallic and intermetallic inclusions also have been presented. the following contributing mechanisms for the removal of nonmetallic inclusions in the deep-bed filtration mode are proposed: (1) collision with walls and interception effect and (2) the formation of both intermetallic and nonmetallic inclusion bridges during filtration. Fluid dynamics …

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