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- Materials Science and Engineering Faculty Research & Creative Works (13)
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Ac Conductivity Relaxation Processes In Cacu₃Ti₄O₁₂ Ceramics: Grain Boundary And Domain Boundary Effects, Wei Li, Robert W. Schwartz
Ac Conductivity Relaxation Processes In Cacu₃Ti₄O₁₂ Ceramics: Grain Boundary And Domain Boundary Effects, Wei Li, Robert W. Schwartz
Materials Science and Engineering Faculty Research & Creative Works
The ac conductivity of CaCu₃Ti₄O₁₂ ceramics associated with electrical charge carrier motion (ions or vacancies) was investigated as a function of frequency at different temperatures. The long range migration of charge carriers within the ceramic is restricted by two kinds of insulating barriers, namely, grain boundaries and domain boundaries. The potential barriers associated with these boundaries lead to two anomalies in conductivity response and three frequency-dependent contributions to conductivity: long range diffusion of carriers, carrier migration localized within grains, and carrier migration localized within domains.
Humidification Factors From Laboratory Studies Of Fresh Smoke From Biomass Fuels, D. E. Day, J. L. Hand, C. M. Carrico, Guenter Engling, W. C. Malm
Humidification Factors From Laboratory Studies Of Fresh Smoke From Biomass Fuels, D. E. Day, J. L. Hand, C. M. Carrico, Guenter Engling, W. C. Malm
Materials Science and Engineering Faculty Research & Creative Works
Measurements of smoke aerosol humidification factors were performed in a laboratory for different biomass fuel types and burn conditions. Two nephelometers simultaneously measured dry and humidified light scattering coefficients (bsp(dry) and bsp(RH), respectively), providing the first observations of the temporal evolution of the humidification factor (f(RH) = bsp(RH)/bsp(dry)) for fresh (minutes-old) smoke. Hygroscopic characteristics of the smoke aerosols varied with fuel type and fire conditions, with the mean f(RH) ranging from 1.01 to 1.95 for fresh minutes-old smoke for the relative humidity (RH) range of 70-94%. These f(RH) values exhibited temporal variability, with some fuels alternating from hygroscopic to nonhygroscopic …
Applications Of A Hybrid Manufacturing Process For Fabrication And Repair Of Metallic Structures, Frank W. Liou, Kevin P. Slattery, Mary Kinsella, Joseph William Newkirk, Hsin-Nan Chou, Robert G. Landers
Applications Of A Hybrid Manufacturing Process For Fabrication And Repair Of Metallic Structures, Frank W. Liou, Kevin P. Slattery, Mary Kinsella, Joseph William Newkirk, Hsin-Nan Chou, Robert G. Landers
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Since its appearance, rapid prototyping technology has been of interest to various industries that are looking for a process to produce/build a part directly from a CAD model in a short time. Among them, the direct metal deposition process is the only process which directly manufactures a fully dense metal part without intermediate steps. However, challenges of the direct metal deposition process include building overhang structures, producing precision surfaces, and making parts with complex structures. Coupled between the additive and the subtractive processes into a single workstation, the integrated process, or hybrid process, can produce a metal part with machining …
Comparison Of Thermal Properties Of Laser Deposition And Traditional Welding Process Via Thermal Diffusivity Measurement, Yu Yang, Omoghene Osaze Obahor, Yaxin Bao, Todd E. Sparks, Jianzhong Ruan, Jacquelyn K. Stroble, Robert G. Landers, Joseph William Newkirk, Frank W. Liou
Comparison Of Thermal Properties Of Laser Deposition And Traditional Welding Process Via Thermal Diffusivity Measurement, Yu Yang, Omoghene Osaze Obahor, Yaxin Bao, Todd E. Sparks, Jianzhong Ruan, Jacquelyn K. Stroble, Robert G. Landers, Joseph William Newkirk, Frank W. Liou
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Laser deposition is an effective process for mold and die repair. In order to improve the part repair quality, the process impact on thermal diffusivity and thermal conductivity needs to be understood for laser deposited, welded and virgin H13. In this paper, H13 tool steel samples were made by laser deposition, welding and virgin H13 and then cut into pieces. Experiments were conducted to investigate the thermal diffusivity and conductivity. A laser flash method is used to test these samples. The future work and opportunities are also summarized.
Freeform Extrusion Of High Solids Loading Ceramic Slurries, Part Ii: Extrusion Process Control, Michael S. Mason, Tieshu Huang, Robert G. Landers, Ming-Chuan Leu, Greg Hilmas
Freeform Extrusion Of High Solids Loading Ceramic Slurries, Part Ii: Extrusion Process Control, Michael S. Mason, Tieshu Huang, Robert G. Landers, Ming-Chuan Leu, Greg Hilmas
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Part I of this paper provided a detailed description of a novel fabrication machine for high solids loading ceramic slurry extrusion processes and presented an empirical model of the ceramic extrusion process, viewing ram velocity as the input and extrusion force as the output. A constant extrusion force is desirable as it correlates with a constant material deposition rate and, thus, good part quality. The experimental results used to construct the model demonstrated that a constant ram velocity will not necessarily produce a constant extrusion force. In some instances the extrusion force increased until ram motor skipping occurred, and process …
Freeze-Spray Processing Of Layered Ceramic Composites, Qiang Fu, Oratai Jongprateep, Ashlee Abbott, Fatih Dogan
Freeze-Spray Processing Of Layered Ceramic Composites, Qiang Fu, Oratai Jongprateep, Ashlee Abbott, Fatih Dogan
Materials Science and Engineering Faculty Research & Creative Works
Thermal gradients and associated stresses are critical in designing with ceramic composites having low thermal conductivity. In order to reduce the stresses from thermal gradients, compositional gradients are employed in designing of composite structures. This study addresses development of freeze-spray process to fabricate layered ceramic structures with controlled layer thickness and microstructural development. The composites were processed by spraying of ceramic slurries with low binder content and relatively high solids loadings (up to 40 vol%) on a cooled substrate. The frozen parts were freeze-dried and sintered at elevated temperatures. The relationship between microstructural development and thermal expansion behavior of Al …
Freeform Extrusion Of High Solids Loading Ceramic Slurries, Part I: Extrusion Process Modeling, Michael S. Mason, Tieshu Huang, Robert G. Landers, Ming-Chuan Leu, Greg Hilmas
Freeform Extrusion Of High Solids Loading Ceramic Slurries, Part I: Extrusion Process Modeling, Michael S. Mason, Tieshu Huang, Robert G. Landers, Ming-Chuan Leu, Greg Hilmas
Mechanical and Aerospace Engineering Faculty Research & Creative Works
A novel, solid freeform fabrication method has been developed for the manufacture of ceramic-based components in an environmentally friendly fashion. The method is based on the extrusion of ceramic slurries using water as the binding media. Aluminum oxide (Al2O3) is currently being used as the part material and solids loading as high as 60 vol. % has been achieved. This paper describes a novel manufacturing machine that has been developed for the extrusion of high solids loading ceramic slurries. A critical component of the machine is the deposition system, which consists of a syringe, a plunger, …
Evaluation Of Mechanical Properties And Microstructure For Laser Deposition Process And Welding Process, Yaxin Bao, Jianzhong Ruan, Todd E. Sparks, Jambunathan Anand, Joseph William Newkirk, Frank W. Liou
Evaluation Of Mechanical Properties And Microstructure For Laser Deposition Process And Welding Process, Yaxin Bao, Jianzhong Ruan, Todd E. Sparks, Jambunathan Anand, Joseph William Newkirk, Frank W. Liou
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Laser Aided Manufacturing Process (LAMP) can be applied to repair steel die/molds which are currently repaired using traditional welding process in industry. In order to fully understand the advantages of laser deposition repair process over traditional welded-repair process, the mechanical properties such as tensile strength and hardness of H13 tool steel samples produced by these two processes were investigated. The microstructure and fracture surface of the samples were analyzed using optical microscope and SEM (Scanning Electron Microscope). Moreover, depositions on substrates with different shapes were studied to evaluate the performance of LAMP on damaged parts with complicated geometric shape.
Method For Fabricating Nanostructured Solid Oxide Fuel Cells And Cell Components, Harlan U. Anderson, X.-D. Zhou, Wayne Huebner
Method For Fabricating Nanostructured Solid Oxide Fuel Cells And Cell Components, Harlan U. Anderson, X.-D. Zhou, Wayne Huebner
Materials Science and Engineering Faculty Research & Creative Works
A method of fabricating a nanostructured solid oxide fuel cell includes dispersing ceria and doped ceria nanoparticles in a first colloidal solution, atomizing the first colloidal solution into a spray, depositing the spray onto a substrate to form a thin film electrolyte, dispersing a nanocomposite powder including ceria and CuO in the first solution, forming a second colloidal solution, atomizing the second colloidal solution into a second spray, and depositing the second spray over the thin film electrolyte as an interfacial layer.
Method Of Preparing A Solid Oxide Fuel Cell, Greg Hilmas, Dustin Beeaff
Method Of Preparing A Solid Oxide Fuel Cell, Greg Hilmas, Dustin Beeaff
Materials Science and Engineering Faculty Research & Creative Works
A solid oxide fuel cell having a multichannel electrode architecture and method for preparing the same, the method including forming a first carbon laden composition, including a first thermoplastic binder, into a rod, applying a first zirconia laden composition, including a second thermoplastic binder, onto the rod to form a composite feed rod, extruding the composite feed rod to form a controlled geometry filament, bundling the extruded composite feed rod to form a multicellular feed rod, extruding the multicellular feed rod to form a multicellular rod, cutting the multicellular rod into multicellular discs, applying a zirconia laden material to one …
Application Of Chip-Level Emc In Automotive Product Design, Kuifeng Hu, H. Weng, Daryl G. Beetner, David Pommerenke, James L. Drewniak, K. Lavery, Jason Whiles
Application Of Chip-Level Emc In Automotive Product Design, Kuifeng Hu, H. Weng, Daryl G. Beetner, David Pommerenke, James L. Drewniak, K. Lavery, Jason Whiles
Electrical and Computer Engineering Faculty Research & Creative Works
Integrated circuits (ICs) are often the source of the high-frequency noise that drives electromagnetic emissions from electronic products. A case study is presented where emissions from a printed circuit board containing an automotive microcontroller are reduced significantly through analysis of the coupling mechanisms from the chip to the board and attached cables. Noise generated by the IC is explored through measurements in a semi-anechoic chamber and TEM cell, through near-field scans, and through modifications to the printed circuit board. Noise is driven by the IC through both power and I/O connections. Results show that a ferrite in series with I/O …
Dielectric Constant Of Particles Determined By Impedance Spectroscopy, Vladimir Petrovsky, Abhishek Manohar, Fatih Dogan
Dielectric Constant Of Particles Determined By Impedance Spectroscopy, Vladimir Petrovsky, Abhishek Manohar, Fatih Dogan
Materials Science and Engineering Faculty Research & Creative Works
Electrical characterization of slurries prepared by mixing dielectric powders with solvents can be used to estimate dielectric properties of the particles. In particular, dielectric constant of the particles can be calculated from effective dielectric constant of the slurry measured at high frequency by using the Lorentz-Lorenz or similar equations based on mixing rules. Unfortunately, this approach leads to high margin of errors in dielectric constant estimation and is very sensitive to any slurry nonidealities such as sedimentation or agglomeration of particles. Impedance spectroscopy techniques are introduced to measure dielectric properties of particles at different frequency ranges. Dielectric constant of strontium …
Cerium-Based Spontaneous Coating Process For Corrosion Protection Of Aluminum Alloys, James O. Stoffer, Thomas J. O'Keefe, Matthew O'Keefe, Eric L. Morris, Scott A. Hayes, Paul Yu, Alex Williams, Berny F. Rivera Vasquez, Xuan Lin
Cerium-Based Spontaneous Coating Process For Corrosion Protection Of Aluminum Alloys, James O. Stoffer, Thomas J. O'Keefe, Matthew O'Keefe, Eric L. Morris, Scott A. Hayes, Paul Yu, Alex Williams, Berny F. Rivera Vasquez, Xuan Lin
Chemistry Faculty Research & Creative Works
A cerium-based coating for corrosion resistance is applied by exposing a cleaned aluminum-based component to a corrosion-inhibiting cerium solution containing cerium ions in the presence of an oxidizing agent. The coating deposits spontaneously without an external source of electrons.
Simulations Of A New Continuous Steelmaking Process, Jorg Annie Peter, Kent D. Peaslee, D. G. C. Robertson
Simulations Of A New Continuous Steelmaking Process, Jorg Annie Peter, Kent D. Peaslee, D. G. C. Robertson
Materials Science and Engineering Faculty Research & Creative Works
A new continuous steelmaking process has been designed in an effort to reduce meltshop costs and increase productivity beyond the possibilities of current EAF-LMF-CC meltshops. This paper discusses possible operational performance based on industrially-verified kinetic, thermodynamic, and heat-transfer models. Dynamic simulations predict variations in steel chemistry and temperature, resulting from steel treatment and upsets. Savings in costs are projected because of increased metallic yield, lower energy requirements, more efficient use of deoxidants and alloys, fewer man-hours per ton, and decreased capital investment.
Method And Apparatus For Solder-Less Attachment Of An Electronic Device To A Textile Circuit, James A. Zollo, Bonnie Bachman, Alan R. Beatty, Stephen O. Bozzpme, Nitin B. Desai, Ronald J. Kelley, Rami C. Levy
Method And Apparatus For Solder-Less Attachment Of An Electronic Device To A Textile Circuit, James A. Zollo, Bonnie Bachman, Alan R. Beatty, Stephen O. Bozzpme, Nitin B. Desai, Ronald J. Kelley, Rami C. Levy
Economics Faculty Research & Creative Works
A method and apparatus form electrical connections between electronic circuits and conductive threads (102, 104, 106, 108) that are interwoven into textile material (130). Electronic circuits (128), such as semiconductor dies, are connected to a carrier (132) and electrical connections (136) are made to conductive connection areas (110, 112, 114, 116) on the carrier (132). Conductive stitching (202, 204, 206, 208) provides electrical contacts for both the conductive connection areas (110, 112, 114, 116) on the carrier (132) and the conductive threads (102, 104, 106, 108) that are interwoven into the textile material (130). Optionally, a thin, flexible substrate material …
Method For Preparation Of Nanometer Cerium-Based Oxide Particles, X.-D. Zhou, Wayne Huebner, Harlan U. Anderson
Method For Preparation Of Nanometer Cerium-Based Oxide Particles, X.-D. Zhou, Wayne Huebner, Harlan U. Anderson
Materials Science and Engineering Faculty Research & Creative Works
The invention comprises novel undoped and doped nanometer-scale CeO2 particles as well as a novel semi-batch reactor method for directly synthesizing the novel particles at room temperature. The powders exhibited a surface area of approximately 170 m2/g with a particle size of about 3-5 nm, and are formed of single crystal particles that are of uniform size and shape. The particles’ surface area could be decreased down to 5 m2/g, which corresponds to a particle size of 100 nm, by thermal annealing at temperatures up to 1000° C. Control over the particle size, size distribution …
Structural And Magnetic Properties Of La Mn₁₋ₓfeₓo₃ (0 < X < 1.0), X.-D. Zhou, L. R. Pederson, Qingsheng Cai, Jinbo Yang, B. J. Scarfino, M. Kim, William B. Yelon, William Joseph James, Harlan U. Anderson, C. Wang
Structural And Magnetic Properties Of La Mn₁₋ₓfeₓo₃ (0 < X < 1.0), X.-D. Zhou, L. R. Pederson, Qingsheng Cai, Jinbo Yang, B. J. Scarfino, M. Kim, William B. Yelon, William Joseph James, Harlan U. Anderson, C. Wang
Materials Science and Engineering Faculty Research & Creative Works
Electronic, structural, and magnetic properties of Mn-doped lanthanum ferrites were studied by neutron diffraction, superconducting quantum interference device, and impedance spectroscopy. Neutron diffraction refinements were performed with the constraint of full La occupancy, which showed the presence of excess oxygen when x < 0.4. Mixed valent Mn cations and cation vacancies, therefore, exist in all the samples. The samples with x > 0.7 are magnetically ordered at room temperature with orthorhombic symmetry (Pbnm). When x < 0.3 the structure is rhombohedral and magnetically disordered above 16 K. The majority carriers, electron holes, correspond to high oxidation states of Mn. The carrier concentration is determined from the Seebeck coefficients, and is a function of temperature and Fe concentration. The measurements of conductivity and Seebeck coefficients show polaron hopping at elevated temperatures.
Fusion Of Microwave And Eddy Current Data For A Multi-Modal Approach In Evaluating Corrosion Under Paint And In Lap Joints, Kapil Gupta, Mohammad Tayeb Ahmad Ghasr, Sergey Kharkovsky, R. Zoughi, R. Joe Stanley, Ajay Padwal, Matthew O'Keefe, Donald D. Palmer, J. Blackshire, Gary Steffes, N. Wood
Fusion Of Microwave And Eddy Current Data For A Multi-Modal Approach In Evaluating Corrosion Under Paint And In Lap Joints, Kapil Gupta, Mohammad Tayeb Ahmad Ghasr, Sergey Kharkovsky, R. Zoughi, R. Joe Stanley, Ajay Padwal, Matthew O'Keefe, Donald D. Palmer, J. Blackshire, Gary Steffes, N. Wood
Electrical and Computer Engineering Faculty Research & Creative Works
Critical aircraft structures are susceptible to hidden corrosion. Find-it and fix-it approaches are inefficient as it relates to managing the problems associated with corrosion. More comprehensive corrosion information may be obtained using data fusion from several detection and evaluation methods. To this end, microwave, conventional and pulsed eddy current data from a multi-layer corroded panel, representing an aircraft lap joint, are fused and used as inputs to a structural analysis model to obtain a comprehensive snapshot of the corroded environment. This paper presents the data fusion algorithm and the structural analysis model along with a discussion of the results.
Millimeter Wave Imaging Of Corrosion Under Paint: Comparison Of Two Probes, Mohammad Tayeb Ahmad Ghasr, Sergey Kharkovsky, R. Zoughi, Matthew O'Keefe, Ajay Padwal, Donald D. Palmer
Millimeter Wave Imaging Of Corrosion Under Paint: Comparison Of Two Probes, Mohammad Tayeb Ahmad Ghasr, Sergey Kharkovsky, R. Zoughi, Matthew O'Keefe, Ajay Padwal, Donald D. Palmer
Electrical and Computer Engineering Faculty Research & Creative Works
Critical aircraft structures are susceptible to harsh environmental conditions that cause corrosion of these structural components. It is of great importance to detect corrosion under paint, particularly in its early stages. Millimeter wave nondestructive evaluation methods have shown great potential for detecting corrosion under paint and evaluating its properties. This paper presents and compares the results of using two distinct millimeter wave detection methods; namely a standard single probe and a newly developed differential probe for detecting corrosion under paint.
Modeling Of Dielectric Mixtures Containing Conducting Inclusions With Statistically Distributed Aspect Ratio, Marina Koledintseva, Sandeep K. R. Chandra, Richard E. Dubroff, Robert W. Schwartz
Modeling Of Dielectric Mixtures Containing Conducting Inclusions With Statistically Distributed Aspect Ratio, Marina Koledintseva, Sandeep K. R. Chandra, Richard E. Dubroff, Robert W. Schwartz
Electrical and Computer Engineering Faculty Research & Creative Works
An analytical model of composites made of a dielectric base and randomly oriented metal inclusions in the form of nanorods is presented. This model is based on the generalized Maxwell Garnett (MG) mixing rule. In this model, the nanorod particles are modeled as prolate spheroids with a statistically normal distribution of their aspect ratios. It is shown that parameters of the distribution laws affect the frequency characteristics of the composites both at microwave and optical frequencies. The results of computations are represented.
Segmental Mobility Of Chain Ends In Poly(Methyl Acrylate)-D3, Burak Metin, Frank D. Blum
Segmental Mobility Of Chain Ends In Poly(Methyl Acrylate)-D3, Burak Metin, Frank D. Blum
Chemistry Faculty Research & Creative Works
Better control of polymeric materials can be achieved with a thorough understanding of the dynamics of their constituents. In the present study, we consider polymer chains as composed of chain middles and chain ends. Even though chain ends do not comprise much of the sample by mass, they may play a crucial role in the ultimate properties of the polymers. Although chain ends have been assigned a higher mobility, as compared to chain middles, there have not been a large number of experimental studies that directly probe their mobility. Among those, the studies of Kitahara et al.1 and Miwa et …
Improving Melting Efficiency Through The Application Of New Refractory Materials, Kent D. Peaslee, Semen Naumovich Lekakh, Von Richards, Todd P. Sander, Jeffrey D. Smith, Mangesh Vibhandik
Improving Melting Efficiency Through The Application Of New Refractory Materials, Kent D. Peaslee, Semen Naumovich Lekakh, Von Richards, Todd P. Sander, Jeffrey D. Smith, Mangesh Vibhandik
Materials Science and Engineering Faculty Research & Creative Works
Ladle design and ladle practices have a significant effect on a foundry operation and product quality. Large steel temperature losses or instabilities in the pouring temperature are frequently compensated by tapping at higher temperatures dramatically increasing furnace and ladle lining wear, oxidation of the steel, alloying element losses, and energy consumption in steel melting. Ladle lining materials need to satisfy a complex array of often conflicting requirements. For example, ceramic materials for linings must possess a high strength at liquid steel temperatures to prevent erosion and crack formation. However, linings need to also have a low thermal conductivity which typically …
Vibration Testing Of Repaired Lead-Tin/Lead-Free Solder Joints, Matthew O'Keefe, S. Vetter, D. Murry, J. Smith, P. Amick, Martin G. Perez, D. W. Kleine, Richard S. Colfax
Vibration Testing Of Repaired Lead-Tin/Lead-Free Solder Joints, Matthew O'Keefe, S. Vetter, D. Murry, J. Smith, P. Amick, Martin G. Perez, D. W. Kleine, Richard S. Colfax
Materials Science and Engineering Faculty Research & Creative Works
No abstract provided.
Decreasing Electrical Energy Consumption Through Sic Additions, Kent D. Peaslee, Semen Naumovich Lekakh, Von Richards, John Carpenter, Chen Wang
Decreasing Electrical Energy Consumption Through Sic Additions, Kent D. Peaslee, Semen Naumovich Lekakh, Von Richards, John Carpenter, Chen Wang
Materials Science and Engineering Faculty Research & Creative Works
This paper summarizes results of industrial experiments investigating the introduction of supplemental chemical energy in Electric Arc Furnaces (EAF). Specifically, this research evaluates the effects of adding 0.4-0.6% of the scrap charge weight as SiC (10 lbs per scrap ton charged) in the EAF. SiC additions increase the available exothermic reactions during oxygen boiling in an attempt to reduce the electrical energy requirements. Results from 180 trial heats at two different steel foundries are highlighted and statistically evaluated. In both cases, the SiC additions had a measurable effect on decreasing the electrical energy consumption.
Electrochemical Deposition And Characterization Of Fe₃O₄ Films Produced By The Reduction Of Fe(Iii)-Triethanolamine, Hiten M. Kothari, Elizabeth A. Kulp, Steven J. Limmer, Philippe Poizot, Eric W. Bohannan, Jay A. Switzer
Electrochemical Deposition And Characterization Of Fe₃O₄ Films Produced By The Reduction Of Fe(Iii)-Triethanolamine, Hiten M. Kothari, Elizabeth A. Kulp, Steven J. Limmer, Philippe Poizot, Eric W. Bohannan, Jay A. Switzer
Chemistry Faculty Research & Creative Works
In this paper, we demonstrate that films of magnetite, Fe3O4, can be deposited by the electrochemical reduction of a Fe(III)-triethanolamine complex in aqueous alkaline solution. the films were deposited with a columnar microstructure and a [100] preferred orientation on stainless steel substrates. In-plane electrical transport and magnetoresistance measurements were performed on the films after they were stripped off onto glass substrates. the resistance of the films was dependent on the oxygen partial pressure. We attribute the increase in resistance in O2 and the decrease in resistance in Ar to the oxidation and reduction of grain …
Molecular Mass And Dynamics Of Poly(Methyl Acrylate) In The Glass Transition Region, Burak Metin, Frank D. Blum
Molecular Mass And Dynamics Of Poly(Methyl Acrylate) In The Glass Transition Region, Burak Metin, Frank D. Blum
Chemistry Faculty Research & Creative Works
The segmental dynamics of bulk poly(methyl acrylate) (PMA) were studied as a function of molecular mass in the glass-transition region using 2H NMR and modulated differential scanning calorimetry (MDSC). Quadrupole-echo 2H NMR spectra were obtained for four samples of methyl-deuterated PMA-d3 with different molecular masses. The resulting spectra were fit using superpositions of simulated spectra generated from the MXQET simulation program, based on a model incorporating nearest-neighbor jumps from positions on the vertices of a truncated icosahedron (soccer-ball shape). The lower molecular-mass samples, influenced by the presence of more chain ends, showed more heterogeneity (broader distribution) and lower glass transitions …
Segmental Dynamics Of Poly(Isopropyl Acrylate)-D7 On Silica, Piyawan Krisanangkura, Frank D. Blum
Segmental Dynamics Of Poly(Isopropyl Acrylate)-D7 On Silica, Piyawan Krisanangkura, Frank D. Blum
Chemistry Faculty Research & Creative Works
For a polymer film deposited on a surface, the strength of the surfacesegment interaction affects the mobility of polymer-chain segments. The selfconsistent field lattice model of Scheutjens and Fleer,1 based on mean-field lattice models of polymer at interfaces,2 has been used to describe the distribution of conformations of polymers on surfaces. Adsorbed-polymer segments may be classified as belonging to loops, trains or tails. There are different techniques used to study the molecular motion of the polymer including modulated differential scanning calorimetry (MDSC)3 and nuclear magnetic resonance (NMR).4,5 in this work, solid-state deuterium (2H) NMR was used to characterize the polymer …
Synthesis And Thermal Behavior Of Poly(Methyl Acrylate) Attached To Silica By Surface-Initiated Atrp, Manikantan B. Nair, Frank D. Blum
Synthesis And Thermal Behavior Of Poly(Methyl Acrylate) Attached To Silica By Surface-Initiated Atrp, Manikantan B. Nair, Frank D. Blum
Chemistry Faculty Research & Creative Works
The modification of the surface of an object dictates the response of the object to an external environment.1 Surface-modified materials and nanoparticles have attracted immense interest due to the various desirable electronic, optical and magnetic properties they possess.2 Silica is widely used as an inorganic filler. Surface modification of the silica, with a variety of organic moieties, facilitates the utilization of silica in conjunction with organic systems. The resulting organic/inorganic hybrid materials have significant potential applications. This work reports the synthesis and characterization of modified silica, and poly(methyl acrylate) attached to the modified silica. An observation of the thermal behavior …
Segmental Dynamics In Poly(Methyl Acrylate) On Silica: Molecular-Mass Effects, Burak Metin, Frank D. Blum
Segmental Dynamics In Poly(Methyl Acrylate) On Silica: Molecular-Mass Effects, Burak Metin, Frank D. Blum
Chemistry Faculty Research & Creative Works
The effect of molecular mass on the segmental dynamics of poly(methyl acrylate) (PMA) adsorbed on silica was studied using deuterium quadrupole-echo nuclear magnetic resonance (NMR) and modulated differential scanning calorimetry. Samples adsorbed on silica (all about 1.5 mg PMA/m2 silica) were shown to have more restricted segmental mobility, and higher Tg's, than the corresponding bulk PMA samples. Around the glass-transition region, adsorbed samples exhibited segmental mobility, which could be classified as heterogeneous due to a superposition of more-mobile and less-mobile components present in the deuterium NMR spectra. This heterogeneity was consistent with a motional gradient with more-mobile segments near the …
Maxwell-Wagner Relaxations And Their Contributions To The High Permittivity Of Calcium Copper Titanate Ceramics, Wei Li, Robert W. Schwartz
Maxwell-Wagner Relaxations And Their Contributions To The High Permittivity Of Calcium Copper Titanate Ceramics, Wei Li, Robert W. Schwartz
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Calcium copper titanate ceramics were fabricated by cold isostatic pressing at various calcination and sintering conditions. Depending on fabrication condition, three electrical responses were observed in the combined modulus and impedance plots, indicating the presence of two Maxwell-Wagner relaxations. These electrical responses show different response to temperature and applied field. The activation energies, as well as the driving force factors, were calculated for these relations. The determined activation energy values are in the range of 0.57 to 0.65 eV. The contribution of Maxwell-Wagner relaxations to the high permittivity of CCTO and related materials is briefly discussed.