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Articles 1 - 18 of 18
Full-Text Articles in Mechanical Engineering
Melting Point Suppression In New Lanthanoid(Iii) Ionic Liquids By Trapping Of Kinetic Polymorphs: An In Situsynchrotron Powder Diffraction Study, Anthony S.R. Chesman, Mei Yang, Bert Mallick, Tamsyn M. Ross, Ian A. Gass, Glen B. Deacon, Stuart R. Batten, Anja V. Mudring
Melting Point Suppression In New Lanthanoid(Iii) Ionic Liquids By Trapping Of Kinetic Polymorphs: An In Situsynchrotron Powder Diffraction Study, Anthony S.R. Chesman, Mei Yang, Bert Mallick, Tamsyn M. Ross, Ian A. Gass, Glen B. Deacon, Stuart R. Batten, Anja V. Mudring
Anja V. Mudring
he inclusion of lanthanoids in ionic liquids (ILs) offers an ideal route to incorporate their unique luminescent and magnetic properties into a bulk solution.1,2 However, lanthanoid compounds often exhibit a poor solubility in commonly used ILs because the IL anions are typically very weakly coordinating, prohibiting the simple dissolution of a lanthanoid salt by complexation to any beneficial extent.2 One strategy used to achieve high lanthanoid concentrations is to incorporate the lanthanoid cation directly into an anion that will form ILs.3 This is best accomplished by employing a ligand which readily coordinates to a lanthanoid atom and possesses properties, such …
Ultrasound-Assisted Synthesis Of Mesoporous Β-Ni(Oh)2 And Nio Nano-Sheets Using Ionic Liquids, Tarek Alammar, Osama Shekhah, Jonas Wohlgemuth, Anja V. Mudring
Ultrasound-Assisted Synthesis Of Mesoporous Β-Ni(Oh)2 And Nio Nano-Sheets Using Ionic Liquids, Tarek Alammar, Osama Shekhah, Jonas Wohlgemuth, Anja V. Mudring
Anja V. Mudring
Via a facile ultrasound synthesis from nickel acetate and sodium hydroxide with ionic liquids as the solvent and template it is possible to obtain nano-β-Ni(OH)2 of various dimensionalities depending on the reaction conditions with the ionic liquid (IL) being the most important factor. Scanning electron microscopy (SEM) imaging showed β-Ni(OH)2 to form as nanosheets, nanorods and nanospheres depending on the IL. ILs with strong to moderate hydrogen bonding capability like [C3mimOH][Tf2N] (1-(3-hydroxypropyl)-3-methylimidazolium bis(trifluoromethanesulfonylamide)), [C4mim][Tf2N] (1-butyl-3-methylimidazolium bis(trifluoromethanesulfonylamide)) and [Edimim][Tf2N] (1-ethyl-2,3-diemethylimidazolium bis(trifluoromethanesulfonylamide)) lead to the formation of nanosheets whilst [Py4][Tf2N] (butyl-pyridinium bis(trifluoromethanesulfonylamide)) leads to nanoparticles and [N1888][Tf2N] (methyltrioctylammonium bis(trifluoromethanesulfonylamide)) to nanorods. Subsequent …
A Large Deformation, Rotation-Free, Isogeometric Shell, D. J. Benson, Y. Bazilevs, Ming-Chen Hsu, T. J. R. Hughes
A Large Deformation, Rotation-Free, Isogeometric Shell, D. J. Benson, Y. Bazilevs, Ming-Chen Hsu, T. J. R. Hughes
Ming-Chen Hsu
Conventional finite shell element formulations use rotational degrees of freedom to describe the motion of the fiber in the Reissner–Mindlin shear deformable shell theory, resulting in an element with five or six degrees of freedom per node. These additional degrees of freedom are frequently the source of convergence difficulties in implicit structural analyses, and, unless the rotational inertias are scaled, control the time step size in explicit analyses. Structural formulations that are based on only the translational degrees of freedom are therefore attractive. Although rotation-free formulations using C0 basis functions are possible, they are complicated in comparison to their C1 …
Isogeometric Shell Analysis: The Reissner–Mindlin Shell, D. J. Benson, Y. Bazilevs, Ming-Chen Hsu, T.J.R. Hughes
Isogeometric Shell Analysis: The Reissner–Mindlin Shell, D. J. Benson, Y. Bazilevs, Ming-Chen Hsu, T.J.R. Hughes
Ming-Chen Hsu
A Reissner–Mindlin shell formulation based on a degenerated solid is implemented for NURBS-based isogeometric analysis. The performance of the approach is examined on a set of linear elastic and nonlinear elasto-plastic benchmark examples. The analyses were performed with LS-DYNA, an industrial, general-purpose finite element code, for which a user-defined shell element capability was implemented. This new feature, to be reported on in subsequent work, allows for the use of NURBS and other non-standard discretizations in a sophisticated nonlinear analysis framework.
Sum Frequency Generation Vibrational Spectroscopy Of Pyridine Hydrogenation On Platinum Nanoparticles, Kaitlin M. Bratlie, Kyriakos Komvopoulos, Gabor A. Somorjai
Sum Frequency Generation Vibrational Spectroscopy Of Pyridine Hydrogenation On Platinum Nanoparticles, Kaitlin M. Bratlie, Kyriakos Komvopoulos, Gabor A. Somorjai
Kaitlin M. Bratlie
Pyridine hydrogenation in the presence of a surface monolayer consisting of cubic Pt nanoparticles stabilized by tetradecyltrimethylammonium bromide (TTAB) was investigated by sum frequency generation (SFG) vibrational spectroscopy using total internal reflection (TIR) geometry. TIR-SFG spectra analysis revealed that a pyridinium cation (C5H5NH+) forms during pyridine hydrogenation on the Pt nanoparticle surface, and the NH group in the C5H5NH+ cation becomes more hydrogen bound with the increase of the temperature. In addition, the surface coverage of the cation decreases with the increase of the temperature. An important contribution of this study is the in situ identification of reaction intermediates adsorbed …
Platinum Nanoparticle Shape Effects On Benzene Hydrogenation Selectivity, Kaitlin M. Bratlie, Hyunjoo Lee, Kyriakos Komvopoulos, Peidong Yang, Gabor A. Somorjai
Platinum Nanoparticle Shape Effects On Benzene Hydrogenation Selectivity, Kaitlin M. Bratlie, Hyunjoo Lee, Kyriakos Komvopoulos, Peidong Yang, Gabor A. Somorjai
Kaitlin M. Bratlie
Benzene hydrogenation was investigated in the presence of a surface monolayer consisting of Pt nanoparticles of different shapes (cubic and cuboctahedral) and tetradecyltrimethylammonium bromide (TTAB). Infrared spectroscopy indicated that TTAB binds to the Pt surface through a weak C-HâââPt bond of the alkyl chain. The catalytic selectivity was found to be strongly affected by the nanoparticle shape. Both cyclohexane and cyclohexene product molecules were formed on cuboctahedral nanoparticles, whereas only cyclohexane was produced on cubic nanoparticles. These results are the same as the product selectivities obtained on Pt(111) and Pt(100) single crystals in earlier studies. The apparent activation energy for …
Modeling Of The Size Effects On The Behavior Of Metals In Microscale Deformation Processes, Gap-Yong Kim, Jun Ni, Muammer Koc
Modeling Of The Size Effects On The Behavior Of Metals In Microscale Deformation Processes, Gap-Yong Kim, Jun Ni, Muammer Koc
Gap-Yong Kim
For the accurate analysis and design of microforming process, proper modeling of material behavior at the micro/mesoscale is necessary by considering the size effects. Two size effects are known to exist in metallic materials. One is the “grain size” effect, and the other is the “feature/specimen size” effect. This study investigated the feature/specimen size effect and introduced a scaling model which combined both feature/specimen and grain size effects. Predicted size effects were compared with three separate experiments obtained from previous research: a simple compression with a round specimen, a simple tension with a round specimen, and a simple tension in …
An Experimental Investigation On Semi-Solid Forming Of Micro/Meso-Scale Features, Gap-Yong Kim, Jun Ni, Rhett Mayor, Heesool Kim
An Experimental Investigation On Semi-Solid Forming Of Micro/Meso-Scale Features, Gap-Yong Kim, Jun Ni, Rhett Mayor, Heesool Kim
Gap-Yong Kim
The potentials of semi-solid forming technology have generated much interest regarding its application in micromanufacturing. This study investigates the feasibility of using semi-solid forming technology to produce parts with micro/meso features. An experimental setup has been developed to study the effects of die/punch temperature, initial solid fraction, punch speed, and workpiece shape on the semi-solid forming process. A part has been produced for a microreactor application and has been analyzed with an optical measurement system for feature formation. The results indicated complex interaction among the process parameters and the material flow, which affected the final pin formation. The punch temperature …
Modeling Of The Semi-Solid Material Behavior And Analysis Of Micro-/Mesoscale Feature Forming, Gap-Yong Kim, Muammer Koc, Rhet Mayor, Jun Ni
Modeling Of The Semi-Solid Material Behavior And Analysis Of Micro-/Mesoscale Feature Forming, Gap-Yong Kim, Muammer Koc, Rhet Mayor, Jun Ni
Gap-Yong Kim
One of the major challenges in simulation of semi-solid forming is characterizing the complex behavior of a material that consists of both solid and liquid phases. In this study, a material model for an A356 alloy in a semi-solid state has been developed for high solid fractions (>0.6) and implemented into a finite element simulation tool to investigate the micro-/mesoscale feature formation during the forming process. Compared to previous stress models, which are limited to expressing the stress dependency on only the strain rate and the temperature (or the solid fraction), the proposed stress model adds the capability of …
Modeling Of The Size Effects On The Behavior Of Metals In Microscale Deformation Processes, Gap-Yong Kim, Jun Ni, Muammer Koc
Modeling Of The Size Effects On The Behavior Of Metals In Microscale Deformation Processes, Gap-Yong Kim, Jun Ni, Muammer Koc
Gap-Yong Kim
For the accurate analysis and design of microforming process, proper modeling of material behavior at the micro/mesoscale is necessary by considering the size effects. Two size effects are known to exist in metallic materials. One is the “grain size” effect, and the other is the “feature/specimen size” effect. This study investigated the feature/specimen size effect and introduced a scaling model which combined both feature/specimen and grain size effects. Predicted size effects were compared with three separate experiments obtained from previous research: a simple compression with a round specimen, a simple tension with a round specimen, and a simple tension in …
Modeling Of The Semi-Solid Material Behavior And Analysis Of Micro-/Mesoscale Feature Forming, Gap-Yong Kim, Muammer Koc, Rhet Mayor, Jun Ni
Modeling Of The Semi-Solid Material Behavior And Analysis Of Micro-/Mesoscale Feature Forming, Gap-Yong Kim, Muammer Koc, Rhet Mayor, Jun Ni
Gap-Yong Kim
One of the major challenges in simulation of semi-solid forming is characterizing the complex behavior of a material that consists of both solid and liquid phases. In this study, a material model for an A356 alloy in a semi-solid state has been developed for high solid fractions (>0.6) and implemented into a finite element simulation tool to investigate the micro-/mesoscale feature formation during the forming process. Compared to previous stress models, which are limited to expressing the stress dependency on only the strain rate and the temperature (or the solid fraction), the proposed stress model adds the capability of …
An Experimental Investigation On Semi-Solid Forming Of Micro/Meso-Scale Features, Gap-Yong Kim, Jun Ni, Rhett Mayor, Heesool Kim
An Experimental Investigation On Semi-Solid Forming Of Micro/Meso-Scale Features, Gap-Yong Kim, Jun Ni, Rhett Mayor, Heesool Kim
Gap-Yong Kim
The potentials of semi-solid forming technology have generated much interest regarding its application in micromanufacturing. This study investigates the feasibility of using semi-solid forming technology to produce parts with micro/meso features. An experimental setup has been developed to study the effects of die/punch temperature, initial solid fraction, punch speed, and workpiece shape on the semi-solid forming process. A part has been produced for a microreactor application and has been analyzed with an optical measurement system for feature formation. The results indicated complex interaction among the process parameters and the material flow, which affected the final pin formation. The punch temperature …
Piezoelectric In Situ Transmission Electron Microscopy Technique For Direct Observations Of Fatigue Damage Accumulation In Constrained Metallic Thin Films, Xiaoli Tan, T. Du, J.K. Shang
Piezoelectric In Situ Transmission Electron Microscopy Technique For Direct Observations Of Fatigue Damage Accumulation In Constrained Metallic Thin Films, Xiaoli Tan, T. Du, J.K. Shang
Xiaoli Tan
A piezoelectricin situtransmission electron microscopy(TEM) technique has been developed to observe the damage mechanism in constrained metallic thin films under cyclic loading. The technique was based on the piezoelectric actuation of a multilayered structure in which a metallic thin film was sandwiched between a piezoelectric actuator and a silicon substrate. An alternating electric field with a static offset was applied on the piezoelectric actuator to drive the crack growth in the thin metallic layer while the sample was imaged in TEM. The technique was demonstrated on solder thin films where cavitation was found to be the dominant fatigue damage mechanism.
Melting And Resolidification Of A Substrate Caused By Molten Microdroplet Impact, Daniel Attinger, D. Poulikakos
Melting And Resolidification Of A Substrate Caused By Molten Microdroplet Impact, Daniel Attinger, D. Poulikakos
Daniel Attinger
This paper describes the main features and results of a numerical investigation of molten microdroplet impact and solidification on a colder flat substrate of the same material that melts due to the energy input from the impacting molten material. The numerical model is based on the axisymmetric Lagrangian Finite-Element formulation of the Navier–Stokes, energy and material transport equations. The model accounts for a host of complex thermofluidic phenomena, exemplified by surface tension effects and heat transfer with solidification in a severely deforming domain. The dependence of the molten volume on time is determined and discussed. The influence of the thermal …
An Experimental Study Of Molten Microdroplet Surface Deposition And Solidification: Transient Behavior And Wetting Angle Dynamics, Daniel Attinger, Z. Zhao, D. Poulikakos
An Experimental Study Of Molten Microdroplet Surface Deposition And Solidification: Transient Behavior And Wetting Angle Dynamics, Daniel Attinger, Z. Zhao, D. Poulikakos
Daniel Attinger
The basic problem of the impact and solidification of molten droplets on a substrate is of central importance to a host of processes. An important and novel such process in the area of micromanufacturing is solder jetting where microscopic solder droplets are dispensed for the attachment of microelectronic components. Despite the recent appearance of a few numerical studies focusing on the complex transient aspects of this process, no analogous experimental results have been reported to date to the best of our knowledge. Such a study is reported in this paper. Eutectic solder (63Sn37Pb) was melted to a preset superheat and …
In Situ Transmission Electron Microscopy Study Of Electric-Field-Induced Microcracking In Single Crystal Pb(Mg1/3nb2/3)O3–Pbtio3, Z. Xu, Xiaoli Tan, P. Han, J.K. Shang
In Situ Transmission Electron Microscopy Study Of Electric-Field-Induced Microcracking In Single Crystal Pb(Mg1/3nb2/3)O3–Pbtio3, Z. Xu, Xiaoli Tan, P. Han, J.K. Shang
Xiaoli Tan
In this letter, we report in situ transmission electron microscopy (TEM) study of effect of a cyclic electric field on microcracking in a single crystal piezoelectric 0.66Pb(Mg1/3Nb2/3)O3–0.34PbTiO3. A TEM heating stage was modified to permit the in situ application of an electric field on the TEM sample surface. Microcrack initiation from a fine pore under an applied cyclic electric field was directly observed in the piezoelectric single crystal. Experimental procedures for in situ TEM studies were described.
Brittle Composites Modeling: Compazisons With Mosi2/Zro2, S.P. Chen, Richard Alan Lesar, A. D. Rollett
Brittle Composites Modeling: Compazisons With Mosi2/Zro2, S.P. Chen, Richard Alan Lesar, A. D. Rollett
Richard Alan Lesar
We have calculated the mechanical properties of brittle composites with spring-network (SN) model. The composites that we studied involve the transformation toughening effects and the accompanying micro-cracking. Our simulation results are consistent with experiments of MoSi2 toughened with ZrO2. By monitoring the stress changes due to the transformation and micro-cracking we are able to separate, for the first time, the contributions from these two competing effects. We also found that the fracture toughness of the composite increases as the modulus, interfacial cohesion of particle increases.
Free Energy Simulation Of Grain Boundary Segregation And Thermodynamics In Ni3−Xal1+X, R. Najafabadi, H.Y. Wang, D. J. Srolovitz, Richard Alan Lesar
Free Energy Simulation Of Grain Boundary Segregation And Thermodynamics In Ni3−Xal1+X, R. Najafabadi, H.Y. Wang, D. J. Srolovitz, Richard Alan Lesar
Richard Alan Lesar
The free energy simulation method is employed to study segregation to Σ5 and Σ13 (001) twist grain boundaries and their free energies in ordered Ni3−xAl1+x. In the temperature range studied (300–900K), it is shown that there is almost no segregation, strong Al segregation, and weak Ni segregation to the grain boundary for the stoichiometric, Al-rich, and Ni-rich bulk compositions respectively. It is also shown that the segregation is limited to a few (002) planes around the grain boundary and its magnitude decreases with increasing temperature. For Al-rich bulk composition, it is demonstrated that segregation at low temperature substantially lowers the …