Academic literature on the topic 'Mechanical engineering. Nanostructured materials'

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Journal articles on the topic "Mechanical engineering. Nanostructured materials"

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Yang, Ming, Xiaohua Chen, Zidong Wang, Yuzhi Zhu, Shiwei Pan, Kaixuan Chen, Yanlin Wang, and Jiaqi Zheng. "Zero→Two-Dimensional Metal Nanostructures: An Overview on Methods of Preparation, Characterization, Properties, and Applications." Nanomaterials 11, no. 8 (July 23, 2021): 1895. http://dx.doi.org/10.3390/nano11081895.

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Metal nanostructured materials, with many excellent and unique physical and mechanical properties compared to macroscopic bulk materials, have been widely used in the fields of electronics, bioimaging, sensing, photonics, biomimetic biology, information, and energy storage. It is worthy of noting that most of these applications require the use of nanostructured metals with specific controlled properties, which are significantly dependent on a series of physical parameters of its characteristic size, geometry, composition, and structure. Therefore, research on low-cost preparation of metal nanostructures and controlling of their characteristic sizes and geometric shapes are the keys to their development in different application fields. The preparation methods, physical and chemical properties, and application progress of metallic nanostructures are reviewed, and the methods for characterizing metal nanostructures are summarized. Finally, the future development of metallic nanostructure materials is explored.
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Xu, Wenjing, Yaocai Bai, and Yadong Yin. "Surface Engineering of Nanostructured Energy Materials." Advanced Materials 30, no. 48 (July 23, 2018): 1802091. http://dx.doi.org/10.1002/adma.201802091.

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Padmanabhan, K. A. "Mechanical properties of nanostructured materials." Materials Science and Engineering: A 304-306 (May 2001): 200–205. http://dx.doi.org/10.1016/s0921-5093(00)01437-4.

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Seifert, Gotthard, Tommy Lorenz, and Jan-Ole Joswig. "Layered Nanostructures – Electronic and Mechanical Properties." MRS Proceedings 1549 (2013): 3–9. http://dx.doi.org/10.1557/opl.2013.858.

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ABSTRACTIn addition to graphene, 2D transition-metal chalcogenides as, e.g., MoS2 and WS2 nanostructures are promising materials for applications in electronics and mechanical engineering. Though the structure of these materials causes a highly inert surface with a low defect concentration, defects and edge effects can strongly influence the properties of these nanostructured materials. Therefore, a basic understanding of the interplay between electronic and mechanical properties and the influence of defects, edge states and doping is needed. We demonstrate on the basis of atomistic quantum-chemical simulations of a circular MoS2 platelet, how the mechanical deformation can vary the electronic properties and other device characteristics of such a system.
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Salcedo, Daniel, C. J. Luis-Pérez, Javier León, Rodrigo Luri, and Ignacio Puertas. "A Method for Obtaining Spur Gears from Nanostructured Materials." Advanced Materials Research 498 (April 2012): 7–12. http://dx.doi.org/10.4028/www.scientific.net/amr.498.7.

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ECAE process is a novel technology which allows us to obtain materials of sub-micrometric and/or nanometric grain size as a result of accumulating very high levels of plastic deformation in the presence of high hydrostatic pressure. This avoids the material being fractured and permits very high values of plastic deformation to be obtained (ε>>1). Therefore, these nanostructured materials can be used as starting materials for other manufacturing processes such as: extrusion, rolling and forging among others; with the advantage of providing nanostructure and hence improving the mechanical properties. In this present study, forging by finite element of materials that have been previously predeformed by ECAE is analysed. MSC.MarcTMsoftware will be employed with the aim of analysing the possibility of manufacturing mechanical components (spur gears) from materials nanostructured by ECAE.
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Gleiter, Herbert. "Nanostructured Materials." Advanced Materials 4, no. 7-8 (July 1992): 474–81. http://dx.doi.org/10.1002/adma.19920040704.

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Lu, Yulin, and Peter K. Liaw. "The mechanical properties of nanostructured materials." JOM 53, no. 3 (March 2001): 31–35. http://dx.doi.org/10.1007/s11837-001-0177-6.

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Solozhenko, Vladimir. "Creation of nanomaterials by extreme pressure-temperature conditions." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C193. http://dx.doi.org/10.1107/s2053273314098064.

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Nanomaterials in the form of zero-, one- and two-dimensional nanostructures make a high-impact background for both science and technology. At the same time, the synthesis of bulk nanostructured materials remains the least-explored but challenging domain that allows combining the desired physical, chemical and mechanical properties and gives rise to nanoelectronics, nanomechanics, band-gap engineering, etc. The common methods of soft chemistry allow obtaining nanoparticles whose direct sintering unavoidably leads to the grain growth and lost of nanostructure. The extreme pressure is a parameter of choice to suppress the self-diffusion responsible for high-temperature recrystallization. The bulk nanostructured materials shows the superior fracture toughness and extremely high hardness as compared to corresponding microcrystalline bulks. The remarkable changes in physical and mechanical properties, however, do not affect the original thermal and chemical stability of the phase(s). All this opens unique opportunities for high-temperature superabrasive and electronic applications of such materials. Finally, the extreme pressure-temperature conditions are powerful and promising tool for grain-size control during direct solid-state phase transformations. The simultaneous variation of pressure and temperature makes possible to combine different nucleation, growth and aggregation regimes with high flexibility, and, therefore, to go deep into nanoscale engineering.
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TURNER, PAUL A., GAURAV V. JOSHI, C. ANDREW WEEKS, R. SCOTT WILLIAMSON, AARON D. PUCKETT, and AMOL V. JANORKAR. "NANO AND MICRO-STRUCTURES OF ELASTIN-LIKE POLYPEPTIDE-BASED MATERIALS AND THEIR APPLICATIONS: RECENT DEVELOPMENTS." Nano LIFE 03, no. 04 (December 2013): 1343002. http://dx.doi.org/10.1142/s1793984413430022.

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Elastin-like polypeptide (ELP) containing materials have spurred significant research interest for biomedical applications exploiting their biocompatible, biodegradable and nonimmunogenic nature while maintaining precise control over their chemical structure and functionality through genetic engineering. Physical, mechanical and biological properties of ELPs could be further manipulated using genetic engineering or through conjugation with a variety of chemical moieties. These chemical and physical modifications also achieve interesting micro- and nanostructured ELP-based materials. Here, we review the recent developments during the past decade in the methods to engineer elastin-like materials, available genetic and chemical modification methods and applications of ELP micro and nanostructures in tissue engineering and drug delivery.
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Yao, Jimin, An-Phong Le, Stephen K. Gray, Jeffrey S. Moore, John A. Rogers, and Ralph G. Nuzzo. "Nanostructured Plasmonic Materials: Functional Nanostructured Plasmonic Materials (Adv. Mater. 10/2010)." Advanced Materials 22, no. 10 (March 9, 2010): n/a. http://dx.doi.org/10.1002/adma.201090026.

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Dissertations / Theses on the topic "Mechanical engineering. Nanostructured materials"

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Shafiullah, Mohammad. "Synthesis of Nanostructured Silicon - Germanium Thermoelectric Materials by Mechanical Alloying." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-175143.

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Silicon-germanium (SiGe) thermoelectric material is especially suited in power generation operating above 700 °C to 1000 °C to convert heat into electricity. Traditional bulk SiGe alloy thermoelectric materials has the value of dimensionless thermoelectric figure of merit (ZT) at maximum about 0.93 at 900 °C. It corresponds to 8% highest device efficiency to convert heat into electricity for commercial SiGe thermoelectric devices. Recently, many efforts have been made to increase the ZT value of SiGe thermoelectric materials. Among them, nanostructuring of SiGe alloy is an effective mechanism to enhance the ZT value of the thermoelectric material. In this approach, the ZT value increases due to the reduction of thermal conductivity caused by enhanced phonon scattering off the increased density of nanograin boundaries. There are different approaches to make nanostructured SiGe alloy bulk thermoelectric materials. Mechanical alloying of elemental Si and Ge powder is one of them. In this thesis work, different compositions of elemental Si and Ge micro powders have been mechanically alloyed using ball milling technique to produce SiGe alloy nanopowder and then were compacted and sintered by spark plasma sintering (SPS) method. Different characterization techniques have been used to see the effect of compositions, milling parameters and sintering conditions on the properties of the synthesized nanopowders and sintered compact samples.
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Zhao, Qing Ph D. Massachusetts Institute of Technology. "First-principles approaches for accurate predictions of nanostructured materials." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/121849.

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Thesis: Ph. D. in Mechanical Engineering and Computation, Massachusetts Institute of Technology, Department of Mechanical Engineering, 2019
Cataloged from PDF version of thesis. "February 2019."
Includes bibliographical references (pages 154-180).
Nanostructured materials have attracted increasing interest in recent years due to their unusual mechanical, electrical, electronic and optical properties. First-principles electronic structure calculations (e.g., with density functional theory or DFT) provide unique insights into the structure-property relationships of nanostructured materials that can enable further design and engineering. The favorable balance between efficiency and accuracy of DFT has led to its wide application in chemistry, solid-state physics and biology. However, DFT still has limitations and suffers from large pervasive errors in its predicted properties. For small systems, more accurate methods are available but challenges remain for studying nm-scale materials. In the solid-state, unique challenges arise from both the strong sensitivity of correlated transition metal oxides on approximations in DFT and the periodic boundary condition.
Therefore, a greater understanding of approximations inherent in DFT is needed for nanostructured materials. In this thesis, we study nanostructured semiconducting materials, where conventional DFT can be expected to perform well. We develop methods for sampling amorphous materials, rationalizing periodic table dependence in material stability for materials discovery of ordered materials, and bring a surface reactivity perspective to understanding growth processes during materials synthesis. Within the challenging cases of transition metal oxides, we explore how common approximations (e.g., DFT+U and hybrids) affect key nanoscale properties, such as the nature of density localization, and as a result, key observables such as surface stability and surface reactivity. Observation of divergent behavior between these two methods highlights the limited interchangeability of DFT+U and hybrids in the solid-state community.
Finally, leveraging the understanding developed in the first two parts of the thesis, we employ a multiscale approach to systematically tailor DFT functional choice for challenging condensed phase systems using accurate reference data from higher level methods. The combination of large-scale electronic structure modeling with state-of-the-art methodology will provide important, predictive insight into tailoring the nanoscale properties of useful materials, and further development in approximate DFT.
by Qing Zhao.
Ph. D. in Mechanical Engineering and Computation
Ph.D.inMechanicalEngineeringandComputation Massachusetts Institute of Technology, Department of Mechanical Engineering
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Lenert, Andrej. "Tuning energy transport in solar thermal systems using nanostructured materials." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/92164.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 137-146).
Solar thermal energy conversion can harness the entire solar spectrum and theoretically achieve very high efficiencies while interfacing with thermal storage or back-up systems for dispatchable power generation. Nanostructured materials allow us to tune the spectral properties and heat transfer behavior to enable such systems. However, under high temperature conditions, thermal management, system optimization and minimization of parasitic losses are necessary to achieve competitive solar power generation. This thesis seeks to achieve spectral control and thermal management through manipulation of nanostructured materials. First, this thesis presents the design and development of a nanophotonic solar thermophotovoltaic (STPV) that harnesses the full spectrum of the sun, in a solid-state and scalable way. Through device optimization and control over spectral properties at high temperatures (~1300 K), a device that is 3 times more efficient than previous STPVs is demonstrated. To achieve this result, a framework was developed to identify which parts of the spectrum are critical and to guide the design of nanostructured absorbers and emitters for STPVs. The work elucidated the relative importance of spectral properties depending on the operating regime and device geometry. Carbon nanotubes and a silicon/silicon dioxide photonic crystal were used to target critical properties in the high solar concentration regime; and two-dimensional metallic photonic crystals were used to target critical properties in the low solar concentration regime. A versatile experimental platform was developed to interchangeably test different STPV components without sacrificing experimental control. In addition to demonstrating significant improvements in STPV efficiency, an experimental procedure to quantify the energy conversion and loss mechanisms helped improve and validate STPV models. Using these validated models, this thesis presents a scaled-up device that can achieve 20% efficiencies in the near term. With potential integration of thermal-based storage, such a technology can supply power efficiently and on-demand, which will have significant implications for adoption of STPVs. Second, the thesis shifts focus away from solid-state systems to thermal-fluid systems. A new figure of merit was proposed to capture the thermal storage, heat transfer and pumping power requirements for a heat transfer fluid is a solar thermal system. Existing and emerging fluids were evaluated based on the new metric as well as practical issues. Finally, sub-micron phase change material (PCM) suspensions are investigated for simultaneous enhancement of local heat transfer and thermal storage capacity in solar thermal systems. A physical model was developed to explain the local heat transfer characteristics of a flowing PCM suspension undergoing melting. A mechanism for enhancement of heat transfer through.control over the distribution of PCM particles inside a channel was discovered and explained. Together, this thesis makes significant contributions towards improving our understanding of the role and the effective use of nanostructured materials in solar thermal systems.
by Andrej Lenert.
Ph. D.
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Kuryak, Chris A. (Chris Adam). "Nanostructured thin film thermoelectric composite materials using conductive polymer PEDOT:PSS." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/79270.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 65).
Thermoelectric materials have the ability to convert heat directly into electricity. This clean energy technology has advantages over other renewable technologies in that it requires no sunlight, has no moving parts, and is easily scalable. With the majority of the unused energy in the United States being wasted in the form of heat and the recent mandates to reduce greenhouse gas emissions, thermoelectric devices could play an important role in our energy future by recovering this wasted heat and increasing the efficiency of energy production. However, low conversion efficiencies and the high cost of crystalline thermoelectric materials have restricted their implementation into modem society. To combat these issues, composite materials that use conductive polymers have been under investigation due to their low cost, manufacturability, and malleability. These new composite materials could lead to cheaper thermoelectric devices and even introduce the technology to new application areas. Unfortunately, polymer composites have been plagued by low operating efficiencies due to their low Seebeck coefficient. In this research, we show an enhanced Seebeck coefficient at the interface of poly(3,4- ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) spin coated onto silicon substrates. The maximum Seebeck coefficient achieved was 473 uV/K with a PEDOT:PSS thickness of 7.75 nm. Furthermore, the power factor of this interface was optimized with a 15.25 nm PEDOT:PSS thickness to a value of 1.24 uV/K2-cm, which is an order of magnitude larger than PEDOT:PSS itself. The effect of PEDOT:PSS thickness and silicon thickness on the thermoelectric properties is also discussed. Continuing research into this area will attempt to enhance the power factor even further by investigating better sample preparation techniques that avoid silicon surface oxidation, as well as creating a flexible composite material of PEDOT:PSS with silicon nanowires..
by Chris A. Kuryak.
S.M.
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Choi, Hyungryul. "Nanostructured multifunctional materials for control of light transport and surface wettability." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/92156.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 221-234).
Biological surfaces have evolved to optimize their structures and physical and chemical properties at the micro/nanoscale for adaptation to different environments, exhibiting a wide variety of beneficial functions, ranging from optical properties to wettability, such as anti-reflection coatings in moth eyes and self-cleaning surfaces of lotus leaves. Combining optical and wetting functions in multifunctional materials is critical for practical engineering applications such as energy harvesting, color generation, and operation of optical instrumentation in humid conditions. However, analyses of the functional design constraints of specified optical and wetting functions followed by integrative optimization have been rare, and limited to simple pairwise combinations from two distinct research disciplines. Furthermore, fabricating the desired multifunctional nanostructured materials remains a difficult engineering challenge due to the limitations of existing nanofabrication methods. The work in this thesis focuses on the joint control of light transport and surface wettability. It starts with analysis and design, followed by implementation of new multifunctional nanostructured materials using novel nanolithographic fabrication techniques. We first consider multifunctional silica surfaces consisting of conical nanostructures (nanocones) for enhanced omnidirectional broadband transmissivity in conjunction with structural superhydrophilicity or robust superhydrophobicity. This is achieved through a systematic approach to concurrent design of nanostructures in both domains and an innovative fabrication procedure that achieves the desired aspect-ratios and periodicities in the nanocones with few defects, high feature repeatability, and large pattern area. Enhanced optical transmissivity exceeding 98% has been achieved over a broad bandwidth and range of incident angles independent of the polarization state. These nanotextured surfaces also demonstrate robust anti-fogging or self-cleaning properties, offering potential benefits for applications such as photovoltaic solar cells. As an extended function of this silica nanocone surface, we propose the systematic design and development of nanostructured transparent anti-fingerprint surface coatings that degrade fingerprint oils using photocatalytic effects. The TiO₂-based porous nanoparticle surfaces exhibit short timescales for decomposition of fingerprint oils under ultraviolet light, plus they have transparency comparable to typical glass with low optical haze (< 1%), and are mechanically robust. These TiO₂ nanostructured surfaces are anti-fogging, anti-bacterial, compatible with flexible glass substrates, and remain photocatalytically active in natural sunlight Lastly, instead of eliminating all reflections over the broadband wavelengths of light for enhanced super-transmissivity, 2-dimensional (2D) periodic nanorod surfaces capable of generating vivid colors by wavelength-selective reflection have also been designed and developed. The geometry of the nanorod structures on top of a silicon substrate is optimized to obtain high contrast of colors while still allowing for scalable nanopatterning with the help of newly invented nanofabrication processes. By developing an integrated understanding of optical and wetting properties of nanostructured materials, we have been able to realize novel functionalities using nanostructured surfaces conceived by concurrent design in the two domains and created by new nanofabrication techniques.
by Hyungryul Choi.
Ph. D.
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Garg, Jivtesh. "Thermal conductivity from first-principles in bulk, disordered, and nanostructured materials." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/65280.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 133-138).
Thermal conductivity is an important transport property that plays a vital role in applications such as high efficiency thermoelectric devices as well as in thermal management of electronics. We present a first-principles approach based on density-functional perturbation theory (DFPT) to predict the thermal conductivity of semiconducting materials. Heat in these materials is conducted by lattice vibrations (phonons). The most important ingredients in the prediction of thermal conductivity in such materials are the second- and third-order derivatives of energy with respect to atomic displacements. Typically, these are derived using empirical potentials which do not produce the correct harmonic and anharmonic behavior, necessary to accurately compute phonon frequencies and relaxation times. We obtain these derivatives from quantum mechanics through DFPT, and use them along with the solution of the phonon Boltzmann transport equation to predict thermal conductivity. We apply the approach to isotopically pure silicon and germanium as well as materials with disorder such as silicon-germanium alloys and show how this leads to excellent agreement between computed and experimentally measured values. The approach is also applied to predict thermal transport in nanostructured materials such as superlattices. In isotopically pure silicon and germanium, phonons scatter only through the three-phonon anharmonic scattering processes. Using the single-mode relaxation time approximation and estimating the scattering rate of these processes based on the force constants derived from DFPT, excellent agreement is obtained between computed and measured values of thermal conductivity. The approach predicts that in isotopically pure silicon, more than 90% of the heat is conducted by phonons of mean free path larger than 40 nm, providing avenues to lower thermal conductivity through nanostructuring. To predict thermal transport in disordered silicon-germanium alloys of any composition, we make use of the phonon modes of an average crystal which has the two atom unit cell and average mass and force constants appropriate for that composition. The disorder is taken to lead to elastic two-phonon scattering in addition to the three-phonon scattering present in pure materials. The idea was first proposed by Abeles in 1963; however we are able to compute all the ingredients from firstprinciples. The force constants for the composition Sio.5 Geo.5 are obtained by using the virtual crystal where the atomic potential at each site is an average of the silicon and germanium potentials. We demonstrate how this approach can be used to guide design of nanostructured materials to further lower thermal conductivity. In superlattices, we again use the virtual crystal to obtain the second-order and third-force constants. Computed thermal conductivity is found to lower with increase in superlattice period; however, the predicted values are higher than experimentally measured values, and we discuss the cause of this discrepancy. In the limit of very small period superlattice, we find that thermal conductivity can increase dramatically and can exceed that of isotopically pure silicon. This cause of this unexpected result is discussed, and its implications for high thermal conductivity materials, important for applications in thermal management of electronics.
by Jivtesh Garg.
Ph.D.
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Zhang, Liang. "Stability analysis of atomic structures." Diss., University of Iowa, 2006. http://ir.uiowa.edu/etd/70.

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Izadi, Sina. "Al/Ti Nanostructured Multilayers: from Mechanical, Tribological, to Corrosion Properties." Scholar Commons, 2016. https://scholarcommons.usf.edu/etd/6265.

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Nanostructured metallic multilayers (NMMs) are well-known for their high strength in smaller bilayer thicknesses. Six Al/Ti (NMM) with different individual layer thickness were tested for their mechanical hardness using a nanoindentation tool. Individual layer thicknesses were chosen carefully to cover the whole confined layer slip (CLS) model. Nano-hardness had a reverse relation with the square root of individual layer thickness and reached a steady state at ~ 5 nm bilayer thickness. Decreasing the layer bilayer thickness from ~ 104 nm to ~ 5 nm, improved the mechanical hardness up to ~ 101%. Residual stresses were measured using grazing incident X-ray diffraction (GIXRD). Effect of residual stress on atomic structure and dislocation propagation was then investigated by comparing the amount and type of stresses in both aluminum and titanium phases. Based on the gathered data from GIXRD scans tensile stress in Ti phases, and compressive stress in Al would increase the overall coherency of structure. Wear rate in coatings is highly dependent on design and architect of the structure. NMM coatings are known to have much better wear resistance compare to their monolithic constituent phases by introducing a reciprocal architect. In current study wear rate of two Al/Ti NMMs with individual layer thicknesses of ~ 2.5 nm and ~ 30 nm were examined under normal loads of 30 µN, 60 µN, and 93 µN. Wears strokes were performed in various cycles of 1, 2, 3, 4 5 and 10. Wear rates were then calculated by comparing the 3D imaging of sample topology before and after tests. Nano-hardness of samples was measured pre and post each cycle of wear using a nanoindentation tool. The microstructure of samples below the worn surface was then characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), focus ion beam (FIB) and an optical profilometer. Orientation mapping was performed to analyze the microstructure of layers beneath the nano indents. TEM imaging from the cross section of worn samples indicated severely plastically deformed layer (SPDL) below the worn surface. Shear bands and twins are visible after wear and below the worn surface. Decreasing the layer thickness from 30 nm to 2.5 nm resulted in ~ 5 time’s better wear resistance. Nanowear caused surface hardening which consequently increased nano hardness up to ~ 30% in the sample with 2.5 nm individual layer thickness. Increasing the interfaces density of NMMs will significantly improve the corrosion resistance of coating. Reciprocal layers and consequently interfaces will block the path of aggressive content toward the substrate. Corrosion rate evolution of Al/Ti multilayers was investigated through DC corrosion potentiodynamic test. Results seem to be very promising and demonstrate up to 30 times better corrosion resistance compared to conventional sputtered monolithic aluminum. Corrosion started in the form of pitting and then transformed to the localized galvanic corrosion. Decreasing the bilayer thickness from ~ 10.4 nm to ~ 5 nm will decrease the corrosion current density (icorr) of ~ 5.42 × 10-7 (A/cm2) to ~ 6.11 × 10-10 (A/cm2). No sign of corrosion has been seen in the sample with ~ 2.5 nm individual layer thickness. Further AFM and TEM analysis from surface and cross section of NMMs indicate that a more coherent layer by layer structure improves the corrosion rate. Interfaces have a significant role in blocking the pores and imperfections inside coating.
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Basnayaka, Punya A. "Development of Nanostructured Graphene/Conducting Polymer Composite Materials for Supercapacitor Applications." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4864.

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The developments in mobile/portable electronics and alternative energy vehicles prompted engineers and researchers to develop electrochemical energy storage devices called supercapacitors, as the third generation type capacitors. Most of the research and development on supercapacitors focus on electrode materials, electrolytes and hybridization. Some attempts have been directed towards increasing the energy density by employing electroactive materials, such as metal oxides and conducting polymers (CPs). However, the high cost and toxicity of applicable metal oxides and poor long term stability of CPs paved the way to alternative electrode materials. The electroactive materials with carbon particles in composites have been used substantially to improve the stability of supercapacitors. Furthermore, the use of carbon particles and CPs could significantly reduce the cost of supercapacitor electrodes compared to metal oxides. Recent developments in carbon allotropes, such as carbon nanotubes (CNTs) and especially graphene (G), have found applications in supercapacitors because of their enhanced double layer capacitance due to the large surface area, electrochemical stability, and excellent mechanical and thermal properties. The main objective of the research presented in this dissertation is to increase the energy density of supercapacitors by the development of nanocomposite materials composed of graphene and different CPs, such as: (a) polyaniline derivatives (polyaniline (PANI), methoxy (-OCH3) aniline (POA) and methyl (-CH3) aniline (POT), (b) poly(3-4 ethylenedioxythiophene) (PEDOT) and (c) polypyrrole (PPy). The research was carried out in two phases, namely, (i) the development and performance evaluation of G-CP (graphene in conducting polymers) electrodes for supercapacitors, and (ii) the fabrication and testing of the coin cell supercapacitors with G-CP electrodes. In the first phase, the synthesis of different morphological structures of CPs as well as their composites with graphene was carried out, and the synthesized nanostructures were characterized by different physical, chemical and thermal characterization techniques, such as Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), UV-visible spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy, Raman spectroscopy, BET surface area pore size distribution analysis and Thermogravimetric Analysis (TGA). The electrochemical properties of G-CP nanocomposite-based supercapacitors were investigated using Cyclic Voltammetry (CV), galvanostatic charge-discharge and Electrochemical Impedance Spectroscopy (EIS) techniques in different electrolytes, such as acidic (2M H2SO4 and HCl), organic ( 0.2 M LiClO4) and ionic liquid (1M BMIM-PF6) electrolytes. A comparative study was carried out to investigate the capacitive properties of G-PANI derivatives for supercapacitor applications. The methyl substituted polyaniline with graphene as a nanocomposite (G-POT) exhibited a better capacitance (425 F/g) than the G-PANI or the G-POA nanocomposite due to the electron donating group of G-POT. The relaxation time constants of 0.6, 2.5, and 5s for the G-POT, G-PANI and G-POA nanocomposite-based supercapacitors were calculated from the complex model by using the experimental EIS data. The specific capacitances of two-electrode system supercapacitor cells were estimated as 425, 400, 380, 305 and 267 F/g for G-POT, G-PANI, G-POA, G-PEDOT and G-PPy, respectively. The improvements in specific capacitance were observed due to the increased surface area with mesoporous nanocomposite structures (5~10 nm pore size distribution) and the pseudocapacitance effect due to the redox properties of the CPs. Further, the operating voltage of G-CP supercapacitors was increased to 3.5 V by employing an ionic liquid electrolyte, compared to 1.5 V operating voltage when aqueous electrolytes were used. On top of the gain in the operating voltage, the graphene nano-filler of the nanocomposite prevented the degradation of the CPs in the long term charging and discharging processes. In the second phase, after studying the material's chemistry and capacitive properties in three-electrode and two-electrode configuration-based basic electrochemical test cells, coin cell type supercapacitors were fabricated using G-CP nanocomposite electrodes to validate the tested G-CPs as devices. The fabrication process was optimized for the applied force and the number of spacers in crimping the two electrodes together. The pseudocapacitance and double layer capacitance values were extracted by fitting experimental EIS data to a proposed equivalent circuit, and the pseudocapacitive effect was found to be higher with G-PANI derivative nanocomposites than with the other studied G-CP nanocomposites due to the multiple redox states of G-PANI derivatives. The increased specific capacitance, voltage and small relaxation time constants of the G-CPs paved the way for the fabrication of safe, stable and high energy density supercapacitors.
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Trelewicz, Jason R. "Nanostructure stabilization and mechanical behavior of binary nanocrystalline alloys." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/46679.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, February 2009.
Includes bibliographical references (leaves 131-145).
The unique mechanical behavior of nanocrystalline metals has become of great interest in recent years, owing to both their remarkable strength and the emergence of new deformation physics at the nanoscale. Of particular interest has been the breakdown in Hall-Petch strength scaling, which is frequently attributed by atomistic simulations to a mechanistic shift to interface dominated plasticity. Experimental validation has been less abundant, primarily due to the processing challenges associated with achieving homogeneous nanocrystalline samples suitable for mechanical testing. Alloying has been proposed as a potential route to high-quality nanocrystalline metals, although choice of an appropriate alloy system, based on available thermodynamic data, remains elusive. In this thesis, we propose a thermodynamic model for nanostructure stabilization that derives from the energetic state variables characteristic of binary alloys. These modeling results motivate the study of Ni-W alloys in particular, which may be synthesized via aqueous electrodeposition, accessing grain sizes across the entire Hall-Petch breakdown regime as characterized by x-ray diffraction and transmission electron microscopy. Ambient temperature nanoindentation testing is employed to evaluate the mechanical behavior of the as-deposited alloys, assessing the nature of flow, the rate sensitivity, and pressure sensitivity of deformation, with emphasis on property inflections required to bridge the behavior of nanocrystalline metals to amorphous solids. The rate sensitivity, in particular, demonstrates an inherent dependence on nanocrystalline grain size, exhibiting a maximum in the vicinity of the Hall-Petch breakdown as a consequence of a shift to glass-like shear localization. In light of this finding, we study the Hall-Petch breakdown at high strain rates, and show that an "inverse Hall-Petch" weakening regime emerges at high rates. Additional effects from structural relaxation are investigated, and illustrated to strongly influence the strength scaling behavior and shift to inhomogeneous flow. Relaxed samples are also subjected to elevated temperature indentation tests, and the results discussed in the context of thermally-activated plasticity, thus providing a more quantitative analysis of the nanoscale deformation mechanisms.
by Jason R. Trelewicz.
Ph.D.
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Books on the topic "Mechanical engineering. Nanostructured materials"

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Turkey) International Conference on Advanced Computational Engineering and Experimenting (6th 2012 Istanbul. Advanced computational engineering and experimenting II: Selected, peer reviewed papers from the Sixth International Conference on Advanced Computational Engineering and Experimenting , July 1-4, 2012, Istanbul, Turkey. Durnten-Zurich: Trans Tech Publications Ltd., 2013.

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Spain) International Conference on Advanced Computational Engineering and Experimenting (7th 2013 Madrid. Advanced computational engineering and experimenting III: Selected, peer reviewed papers from the Seventh International Conference on Advanced Computational Engineering and Experimenting, (ACE-X 2013), July 1-4, 2013, Madrid, Spain. Durnten-Zurich: Trans Tech Publications Ltd, 2014.

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Liu, W. K. Nano Mechanics and Materials. New York: John Wiley & Sons, Ltd., 2006.

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A, Pineau, and Zaoui A. 1941-, eds. Mechanical behaviour of materials. Dordrecht: Kluwer Academic Publishers, 1998.

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Khataee, A. R. Mechanical and dynamical principles of protein nanomotors: The key to nano-engineering applications. New York: Nova Science Publishers, 2010.

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Khataee, A. R. Mechanical and dynamical principles of protein nanomotors: The key to nano-engineering applications. Hauppauge, N.Y: Nova Science Publishers, 2009.

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G, Karpov Eduard, and Park Harold S, eds. Nano mechanics and materials: Theory, multiscale methods and applications. Chichester, West Sussex, England: John Wiley, 2006.

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Harik, Vasyl Michael. Trends in Nanoscale Mechanics: Analysis of Nanostructured Materials and Multi-Scale Modeling. Dordrecht: Springer Netherlands, 2003.

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P, Miannay Dominique, ed. Advances in mechanical behaviour, plasticity and damage: Proceedings of Euromat 2000. Amsterdam: Elsevier Science Ltd., 2000.

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Antoun, Bonnie. Challenges in Mechanics of Time-Dependent Materials and Processes in Conventional and Multifunctional Materials, Volume 2: Proceedings of the 2012 Annual Conference on Experimental and Applied Mechanics. New York, NY: Springer New York, 2013.

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Book chapters on the topic "Mechanical engineering. Nanostructured materials"

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Shushkov, A. A., and A. V. Vakhrushev. "Methods for Determination of Nanostructures Mechanical Properties." In Composite Materials Engineering, 17–34. Includes bibliographical references and index.: Apple Academic Press, 2019. http://dx.doi.org/10.1201/9780429242762-2.

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Yang, Xiao Hua, Wei Zhen Dui, and Gang Liu. "Mechanical Properties of 316L Stainless Steel with Nanostructure Surface Layer Induced by Surface Mechanical Attrition Treatment." In Key Engineering Materials, 1810–13. Stafa: Trans Tech Publications Ltd., 2007. http://dx.doi.org/10.4028/0-87849-456-1.1810.

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Waltz, L., T. Roland, D. Retraint, A. Roos, P. Olier, and J. Lu. "Global Mechanical Behavior of a Nanostructured Multilayered Composite Material Produced by Smat and Co-Rolling." In Experimental Analysis of Nano and Engineering Materials and Structures, 45–46. Dordrecht: Springer Netherlands, 2007. http://dx.doi.org/10.1007/978-1-4020-6239-1_21.

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Popov, Viktor, Gennadiy Kostyuk, Mykola Nechyporuk, and Kateryna Kostyk. "Study of Ions Energy, Their Varieties and Charge on Temperature, Rate of Temperature Rise, Thermal Stresses for Nanostructures on Construction Materials." In Lecture Notes in Mechanical Engineering, 470–77. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-40724-7_48.

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Panchula, Martin L., and Jackie Y. Ying. "Enhanced Transformation and Sintering of Transitional Alumina Through Mechanical Seeding." In Nanostructured Materials, 319–33. Dordrecht: Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-011-5002-6_16.

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Trudeau, Michel L. "Nanostructured Materials Produced by High-Energy Mechanical Milling and Electrodeposition." In Nanostructured Materials, 47–70. Dordrecht: Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-011-5002-6_4.

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Gleiter, H. "Nanostructured Materials." In Mechanical Properties and Deformation Behavior of Materials Having Ultra-Fine Microstructures, 3–35. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-1765-4_1.

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Siegel, R. W. "Nanostructured Materials." In Advanced Topics in Materials Science and Engineering, 273–88. Boston, MA: Springer US, 1993. http://dx.doi.org/10.1007/978-1-4615-2842-5_17.

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Alam, Parvez. "Mechanical Properties of Bio-Nanostructured Materials." In Handbook of Mechanical Nanostructuring, 211–33. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2015. http://dx.doi.org/10.1002/9783527674947.ch10.

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Fan, Jiyang, and Paul K. Chu. "SiC Nanostructured Films." In Engineering Materials and Processes, 295–315. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-08726-9_7.

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Conference papers on the topic "Mechanical engineering. Nanostructured materials"

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Swaminathan, Srinivasan, M. Ravi Shankar, Balkrishna C. Rao, Travis L. Brown, Srinivasan Chandrasekar, W. Dale Compton, Alexander H. King, and Kevin P. Trumble. "Nanostructured Materials by Machining." In ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-81242.

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Large strain deformation, a key parameter in microstructure refinement by Severe Plastic Deformation (SPD) processes, is a common feature of chip formation in machining. It is shown that the imposition of large plastic strains by chip formation can create metals and alloys with nanocrystalline or ultra-fine grained microstructures. The formation of such nanostructured materials is demonstrated in a wide variety of material systems including pure metals, light-weight aluminum alloys, and high strength steels and alloys. Nanocrystalline microstructures with different morphologies are demonstrated. The hardness and strength of the nanostructured chips are significantly greater than that of the bulk material. The production of nanostructured chips by machining, when combined with comminution and powder processing methods, may be expected to lead to the creation of a number of advanced materials with new and interesting combinations of properties. These materials are expected to find wide-ranging applications in the discrete products sector encompassing ground transportation, aerospace and bio-medical industries.
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Rupp, Cory, M. Frenzel, A. Evgrafov, K. Maute, and Martin L. Dunn. "Design of Nanostructured Phononic Materials." In ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-82206.

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The ability of a material containing a periodic arrangement of second-phase inclusions to prevent transmission of waves in certain frequency ranges is well known. This is true for all types of waves including acoustic, electromagnetic, and elastic. These forbidden regions are called band gaps. They arise as incident waves are effectively attenuated by interference among the scattered wave fields. Indeed much of current semiconductor technology revolves around band-gap engineering with regard to electron flow in the periodic potentials resulting from atoms in their lattice positions. The phenomena are also being heavily explored in the context of light via the development of photonic crystals. Things become more interesting if instead of thinking of periodic arrangements, one selectively removes some of the inclusions in the periodic geometry creating defects. If done right, this can result in a material microstructure that can guide waves through the material. Advances in nano and micromanufacturing technologies in the last couple of years have opened up the possibility to fabricate heterogeneous material systems with precise positional control of the constituent materials. For example, it is now possible to place thin-film materials precisely at a resolution of fractions of a micron. Depending on how it is done, one can envision designing a material so that a wave will be guided to a particular location and/or away from another and as a result damping or amplifying the wave locally. In this work we develop a topology optimization approach to design such nanostructured materials. We demonstrate the approach through the design of three multifunctional phononic composite materials composed of silicon and aluminum: i) a grating designed to stop wave propagation at a specified frequency, ii) a waveguide that bends the propagation path of an elastic wave, and iii) an elastic switch that switches an input signal between two output ports based on the state of the input signal.
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Yu, Shuangcheng, Yichi Zhang, Chen Wang, Won-kyu Lee, Biqin Dong, Teri W. Odom, Cheng Sun, and Wei Chen. "Characterization and Design of Functional Quasi-Random Nanostructured Materials Using Spectral Density Function." In ASME 2016 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/detc2016-60118.

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Quasi-random nanostructured material systems (NMSs) are emerging engineered material systems via cost-effective, scalable bottom-up processes, such as the phase separation of polymer mixtures or the mechanical self-assembly based on thin-film wrinkling. Current development of functional quasi-random NMSs mainly follows a sequential strategy without considering the fabrication conditions in nanostructure optimization, which limits the feasibility of the optimized design for large-scale, parallel nanomanufacturing using bottom-up processes. We propose a novel design methodology for designing quasi-random NMSs that employs spectral density function (SDF) to concurrently optimize the nanostructure and design the corresponding nanomanufacturing conditions of a bottom-up process. Alternative to the well-known correlation functions for characterizing the structural correlation of NMSs, the SDF provides a convenient and informative design representation to bridge the gap between processing-structure and structure-performance relationships, to enable fast explorations of optimal fabricable nanostructures, and to exploit the stochastic nature of manufacturing processes. In this paper, we first introduce the SDF as a non-deterministic design representation for quasi-random NMSs, compared with the two-point correlation function. Efficient reconstruction methods for quasi-random NMSs are developed for handling different morphologies, such as the channel-type and particle-type, in simulation-based design. The SDF based computational design methodology is illustrated by the optimization of quasi-random light-trapping nanostructures in thin-film solar cells for both channel-type and particle-type NMSs. Finally, the concurrent design strategy is employed to optimize the quasi-random light-trapping structure manufactured via scalable wrinkle nanolithography process.
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Kumar, D., S. Yarmolenko, J. Sankar, J. Narayan, A. Tiwari, H. Zhou, C. Jin, A. V. Kvit, S. J. Pennycook, and A. Lupini. "Processing and Properties of Nanostructured Magnetic Materials." In ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-39364.

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We report here a novel thin film processing method based upon pulsed laser deposition to process nanocrystalline materials with accurate size and interface control with improved mechanical and magnetic properties. Using this method, single domain nanocrystalline Fe and Ni particles in 5–10 nm size range embedded in amorphous alumina as well as crystalline TiN have been produced. By controlling the size distribution in confined layers, it was possible to tune the magnetic properties from superparamagnetic to ferromagnetic behavior. Magnetic hysteresis characteristics below the blocking temperature are consistent with single-domain behavior. The paper also presents our results from investigations in which scanning transmission electron microscopy with atomic number contrast (STEM-Z) and energy loss spectroscopy (EELS) were used to understand the atomic structure of Ni nanoparticles and interface between the nanoparticles and the surrounding matrices. It was interesting to learn from EELS measurements at interfaces of individual grains that Ni in alumina matrix does not from an ionic bond indicating the absence of metal-oxygen bond at the interface. The absence of metal-oxygen bond, in turn, suggests the absence of any dead layer on Ni nanoparticles even in an oxide matrix.
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Hussein, Mahmoud I., Michael J. Leamy, and Massimo Ruzzene. "Wave Beaming in Nanostructured Materials With Engineered Defects." In ASME 2008 International Mechanical Engineering Congress and Exposition. ASMEDC, 2008. http://dx.doi.org/10.1115/imece2008-68257.

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Recent advances in the fabrication of nanoscale material systems have made it possible to alter precisely the atomic structure in ways that enhance the properties and allow for certain functions to be realized. This work is concerned with two-dimensional periodic structures and emphasizes the effects of intentional defects on their wave propagation characteristics. In this draft paper, investigations are limited to a two-dimensional spring-mass lattice, composed of “super-cells” where mass inclusions are added to alter band-gap properties, as well as low frequency directionality. The presented results will then be extended to two-dimensional nanostructures, such as graphene nanosheets, in order to investigate their application as nanoscale acoustic waveguides, where engineered defects, uniformally distributed across the entire sheet, are introduced by design with the objective of rendering the medium anisotropic. Such anisoptropy leads to acoustic directionality, which can be exploited for waveguiding or acoustic-focusing purposes.
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Ahmed, I., and T. L. Bergman. "Optimization of Plasma Spray Processing Parameters for Deposition of Nanostructured Coatings." In ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-33944.

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When nanostructured material is thermally sprayed to produce coatings, the retention of the original nanostructure that is engineered into the raw stock is a principal objective, along with production of some molten material in order to adhere the sprayed material to the surface being coated. Therefore, in contrast to spraying conventional material, complete melting of the nanostructured raw stock is to be avoided. In this study, the melting and re-solidification of sprayed material is correlated to a spray process parameter that has been introduced in the literature by others. Using computer modeling, processing of zirconia agglomerates with plasma spraying has been simulated. Transition regions of the phase change response of the material to the thermal processing conditions are identified. The retained nanostructure content and liquid fraction of the sprayed material is correlated to the particle diameters, as well as the thermal processing parameter. Finally, a novel method to produce desired coatings composed of partially molten sprayed material, by using a bimodal particle size distribution of the sprayed powder, is presented and discussed.
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Jibhakate, Piyush D., and George J. Nelson. "Fabrication and Characterization of Nanostructured Cathodes for Li-Ion Batteries." In ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-67873.

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Li-ion batteries have emerged as a leading energy storage technology for several applications including portable electronics devices and electric vehicles. Rigorous efforts are made to develop these batteries with higher energy density, higher power density, and better cycling stability while reducing cost and environmental impact. To better understand how electrode microstructure contributes to the electrode performance, the spinel LiMn2O4 (LMO) cathode material was prepared using a template-assisted sol-gel synthesis method. This method involves soaking of polycarbonate template membranes in the precursor solution followed by drying, to remove the solvent. The dried templates containing precursor materials were etched in an oxygen plasma to remove the template, and the nanostructured electrode formed was then calcined to convert these nanostructures to spinel LiMn2O4. Simultaneously, powdered LMO was prepared using the same synthesis procedure, but without the aid of a template to control electrode morphology. A series of tests were performed to study the effect of processing conditions on the structure and morphology of the nanostructured electrodes. The resulting electrodes were characterized using X-ray diffraction (XRD) and scanning electron microscope (SEM) in support of efforts to understand the effects of process parameters on the electrochemical performance of the electrode. The template assisted synthesis approach yielded an electrode of well-defined nanotubules. Extending the template soaking time was found to provide better definition of individual tubule structures. Increasing calcination temperature was found to create a better defined spinel structure for the LMO. These observations provide insight into process parameters relevant to electrode preparation and substrate selection when producing nanostructured electrodes using template-assisted methods.
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Stellman, P., W. Arora, S. Takahashi, E. D. Demaine, and G. Barbastathis. "Kinematics and Dynamics of Nanostructured Origami™." In ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-81824.

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Two-dimensional (2D) nanofabrication processes such as lithography are the primary tools for building functional nanostructures. The third spatial dimension enables completely new devices to be realized, such as photonic crystals with arbitrary defect structures and materials with negative index of refraction [1]. Presently, available methods for three-dimensional (3D) nanopatterning tend to be either cost inefficient or limited to periodic structures. The Nanostructured Origami method fabricates 3D devices by first patterning nanostructures (electronic, optical, mechanical, etc) onto a 2D substrate and subsequently folding segments along predefined creases until the final design is obtained [2]. This approach allows almost arbitrary 3D nanostructured systems to be fabricated using exclusively 2D nanopatterning tools. In this paper, we present two approaches to the kinematic and dynamic modeling of folding origami structures. The first approach deals with the kinematics of unfolding single-vertex origami. This work is based on research conducted in the origami mathematics community, which is making rapid progress in understanding the geometry of origami and folding in general [3]. First, a unit positive “charge” is assigned to the creases of the structure in its folded state. Thus, each configuration of the structure as it unfolds can be assigned a value of electrostatic (Coulomb) energy. Because of repulsion between the positive charges, the structure will unfold if allowed to decrease its energy. If the energy minimization can be carried out all the way to the completely unfolded state, we are simultaneously guaranteed of the absence of collisions for the determined path. The second method deals with dynamic modeling of folding multi-segment (accordion style) origamis. The actuation method for folding the segments uses a thin, stressed metal layer that is deposited as a hinge on a relatively stress free structural layer. Through the use of robotics routines, the hinges are modeled as revolute joints, and the system dynamics are calculated.
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Broido, D. A., Natalio Mingo, and Derek Stewart. "Phonon Thermal Transport in Bulk and Nanostructured Materials From First Principles." In ASME 2008 International Mechanical Engineering Congress and Exposition. ASMEDC, 2008. http://dx.doi.org/10.1115/imece2008-67049.

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Current theories of phonon thermal transport in nanomaterials are often based on highly parametrized approximations or on purely classical molecular dynamics calculations. We present a rigorous theoretical approach to accurately describe phonon thermal transport in bulk and nanostructured materials. This technique is based on Boltzmann and non-equilibrium Green’s function calculations of thermal transport, and employs ab-initio calculations of harmonic and anharmonic interatomic force constants using density functional perturbation theory. The approach has been applied to bulk semiconductors, where excellent agreement is obtained between the calculated and measured intrinsic lattice thermal conductivities of silicon and germanium without any adjustable parameters. In addition, ab initio calculations of phonon thermal conductance in carbon nanotubes with isolated Stone-Wales and substitutional defects are presented and discussed.
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Tiano, Thomas, Margaret Roylance, Benjamin Harrison, and Richard Czerw. "Intralaminar Reinforcement for Biomimetic Toughening of Bismaleimide Composites Using Nanostructured Materials." In ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-81689.

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Many conventional composite materials are composed of multiple layers of continuous fiber reinforced resin produced by lamination of b-staged prepreg and subsequent cure. These materials exhibit very high strength and stiffness in the plane, dominated by the properties of the fibers. The Achilles heel of such composites is the interlaminar strength, which is dependent on the strength of the unreinforced resin, often leading to failure by delamination under load. Current methods for increasing the interlaminar shear strength of composites consist of inserting translaminar reinforcement fibers through the entire thickness of a laminated composite, such as z-pin technology developed by Foster-Miller [1]. While effective, this technique adds several processing steps, including ultrasonic insertion of the z-pins into the laminate, subsequently causing a significant cost increase to laminated composites. Described in this paper is a process utilizing single-walled carbon nanotubes (SWNTs) and vapor grown carbon nanofibers as reinforcing elements promoting interlaminar shear strength and toughness in carbon fiber/bismaleimide (BMI) resin composites. The resulting composites mimic the natural reinforcing mechanism utilized in insect cuticles. Three different methods of increasing the affinity of these carbon nanofillers for the BMI matrix were explored. The mechanical properties of these composites were assessed using end notch flexure testing. The results indicated that including nanofiller at the laminae interface could increase the interlaminar shear strength of carbon fiber/BMI composites by up to 58%. SEM micrographs revealed that the nanofiller successfully bridged the laminae of the composite, thus biomimicking the insect cuticle. Composite fabrication techniques developed on this program would have a wide variety of applications in space and aerospace structures including leading and trailing edges of aircraft wings.
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Reports on the topic "Mechanical engineering. Nanostructured materials"

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Mullins, M., T. Rogers, J. King, J. Holles, J. Keith, P. Heiden, B. Cornilsen, and J. Allen. Michigan Technological Center for Nanostructured and Lightweight Materials in the Department of Chemical Engineering (Phase II). Office of Scientific and Technical Information (OSTI), December 2009. http://dx.doi.org/10.2172/943572.

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