Open Access. Powered by Scholars. Published by Universities.®
Nanoscience and Nanotechnology Commons™
Open Access. Powered by Scholars. Published by Universities.®
- Discipline
- Keyword
Articles 1 - 8 of 8
Full-Text Articles in Nanoscience and Nanotechnology
Multiscale Nature Of Hysteretic Phenomena: Application To Copt-Type Magnets, Kirill D. Belashchenko, Vladimir P. Antropov
Multiscale Nature Of Hysteretic Phenomena: Application To Copt-Type Magnets, Kirill D. Belashchenko, Vladimir P. Antropov
Nebraska Center for Materials and Nanoscience: Faculty Publications
We suggest a workable approach for the description of multiscale magnetization reversal phenomena in nanoscale magnets and apply it to CoPt-type alloys. We show that their hysteretic properties are governed by two effects originating at different length scales: a peculiar splitting of domain walls at twin boundaries and their strong pinning at antiphase boundaries. We emphasize that such multiscale nature of hysteretic phenomena is a generic feature of nanoscale magnetic materials.
Rectangular Bursting Energy Absorber, John D. Reid, John R. Rohde, Dean L. Sicking
Rectangular Bursting Energy Absorber, John D. Reid, John R. Rohde, Dean L. Sicking
Department of Mechanical and Materials Engineering: Faculty Publications
A bursting energy absorber System having an impact head, and energy absorption mechanism. The energy absorbing mechanism has a generally rectangular mandrel for rupturing cooperating thin-walled generally rectangular tubes in a controlled rupture to absorb impact forces for a colliding vehicle. A frame may be used to mount the System to a truck, trailer, guardrail, median barrier end treatment, or a crash cushion. Stress concetrators such as saw cuts or scoring may be incorporated into the absorption tubes to selectively control rupturing and energy dissipation. The mandrels may be tapered, rectangulary shaped with beveled edges to reduce frictional forces along …
In Situ Corrosion Studies On The Battleship Uss Arizona, John D. Makinson, James D. Carr, Matthew A. Russell, David L. Conlin, Larry E. Murphy
In Situ Corrosion Studies On The Battleship Uss Arizona, John D. Makinson, James D. Carr, Matthew A. Russell, David L. Conlin, Larry E. Murphy
Department of Mechanical and Materials Engineering: Faculty Publications
U.S. National Park Service Submerged Resources Center archaeologists and University of Nebraska-Lincoln metallurgists are assessing hull corrosion by drilling through accumulated concretions and measuring pH and corrosion potentials. Concretion samples are being analyzed to determine the role of microbes in the corrosion process, identify chemical species, and measure electrical and physical properties. The lowest values of pH and E corr occur at the metal/concretion interface. Analysis suggests a variable corrosion rate supported by hydrogen discharge and/or oxygen reduction inside the concretion.
Spontaneous Planarization Of Nanoscale Phase Separated Thin Film, Ravi F. Saraf, Sanjun Niu, Eric Stumb
Spontaneous Planarization Of Nanoscale Phase Separated Thin Film, Ravi F. Saraf, Sanjun Niu, Eric Stumb
Papers in Nanotechnology
Structure of complex fluid at mesoscales is influenced by interfacial effects. We describe the dynamic response in such films to sudden change in interfacial tension. In a self-assembled block copolymer film, the monolayer of 15 nm diam cylindrical discrete phases close to the surface commence to sink at an average rate of 0.16 nm/day in response to the interfacial tension change. Surprisingly, this spontaneous planarization occurs, even though the cylinders are covalently stitched to the matrix. A simple model explains the observed behavior. The observation may lead to approaches to tailor the structure of mesoscale thin films of complex fluids …
Structure Of Macrodomain Walls In Polytwinned Magnets, Kirill D. Belashchenko, Vladimir P. Antropov
Structure Of Macrodomain Walls In Polytwinned Magnets, Kirill D. Belashchenko, Vladimir P. Antropov
Nebraska Center for Materials and Nanoscience: Faculty Publications
We propose a microscopic approach to the studies of magnetic configurations in hard magnets which may be conveniently used for nanoscale systems; the microstructure of the magnet is easily and naturally included in the calculations. This approach is applied to find the structure of macrodomain walls in polytwinned magnets of the CoPt family. Magnetostatic fields are small compared to the anisotropy field in these magnets; direct simulation shows that in this case the macrodomain wall is not continuous, but rather comprised of segments held together by relatively small magnetostatic forces. This segmentation is expected to have a strong effect on …
Magnetization Reversal Of Individual Nanowires With Controlled Defects, Andrei Sokolov, Renat F. Sabirianov, W. Wernsdorfer, Bernard Doudin
Magnetization Reversal Of Individual Nanowires With Controlled Defects, Andrei Sokolov, Renat F. Sabirianov, W. Wernsdorfer, Bernard Doudin
Nebraska Center for Materials and Nanoscience: Faculty Publications
Low temperature magnetization reversal measurements were performed on individual permalloy nanowires of diameters between 30 and 60 nm. During the electrochemical growth of the wire, a defect was induced by a short pulse in the deposition potential modifying locally the microstructure and composition. Magnetic measurements performed with micro-superconducting quantum interference devices were performed. The angular dependence of switching field revealed significant deviations from classical predictions. For specific angles, magnetization curves indicate a reversal occurring in two steps.
Characterization Of Crbn Films Deposited By Ion Beam Assisted Deposition, S.M. Aouadi, F. Namavar, E. Tobin, N. Finnegan, R.T. Haasch, R. Nilchiani, Joseph A. Turner, S. L. Rohde
Characterization Of Crbn Films Deposited By Ion Beam Assisted Deposition, S.M. Aouadi, F. Namavar, E. Tobin, N. Finnegan, R.T. Haasch, R. Nilchiani, Joseph A. Turner, S. L. Rohde
Nebraska Center for Materials and Nanoscience: Faculty Publications
This article reports on the growth and analysis of CrBN nanocrystalline materials using an ion beam assisted deposition process. In addition, this article addresses the utilization of spectroscopic ellipsometry for in situ analysis of ternary nitrides. Coatings, with a total thickness of 1.5 ±0.2 μm, were deposited at low temperatures (<200 °C) on silicon substrates using ion beam assisted deposition. These coatings were characterized postdeposition using x-ray diffraction (XRD), atomic force microscopy (AFM), x-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), visible-light spectroscopic ellipsometry (VIS-SE), infrared spectroscopic ellipsometry (IR-SE), and nanoindentation. The primary phases in the films were investigated using XRD. The surface morphology and nanocrystalline nature of the coatings (grain size of 5–7 nm) were deduced using AFM. The elemental composition and phase composition of the samples were determined from XPS and AES measurements and were subsequently deduced from the analysis of the VIS-SE data, and these correlated well. XPS, AES, and IR-SE revealed the crystal structure of the BN phase in the ternary compounds. The correlation of the results from these various techniques indicates that in situ SE may be a potential technique to control the growth of ternary nitride coatings in the future. The mechanical properties of the coatings were evaluated using nanohardness testing. The hardness and elastic modulus were measured to be 19–22 GPa and 250–270 GPa, respectively.
Prediction Of Soakout Time Using Analytical Models, B. Chakravarthy, H. P. Cherukuri, R. G. Wilhelm
Prediction Of Soakout Time Using Analytical Models, B. Chakravarthy, H. P. Cherukuri, R. G. Wilhelm
Department of Mechanical and Materials Engineering: Faculty Publications
In precision manufacturing enterprises, machine parts at nonstandard temperatures are often soaked to standard temperature prior to making any dimensional measurements. The soakout times are usually determined using lumped heat-transfer models where the part temperatures are assumed to be uniform. This article discusses conditions under which lumped model assumptions are valid by comparing lumped analyses for various shapes and materials with the more general finite element results. In addition, the effect of ambient temperature cycling on part response is also studied.