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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/6

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Now showing 1 - 7 of 7
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    PublicationOpen Access
    Grain boundary engineering with nano-scale InSb producing high performance InxCeyCo4Sb12+z skutterudite thermoelectrics
    (Elsevier, 2017) Li, Han; Su, Xianli; Tang, Xinfeng; Zhang, Qingjie; Uher, Ctirad; Snyder, G. Jeffrey; Department of Chemistry; Aydemir, Umut; Faculty Member; Department of Chemistry; College of Sciences; 58403
    Thermoelectric semiconductors based on CoSb3 hold the best promise for recovering industrial or automotive waste heat because of their high efficiency and relatively abundant, lead-free constituent elements. However, higher efficiency is needed before thermoelectrics reach economic viability for widespread use. In this study, n-type InxCeyCo4Sb12+z skutterudites with high thermoelectric performance are produced by combining several phonon scattering mechanisms in a panoscopic synthesis. Using melt spinning followed by spark plasma sintering (MS-SPS), bulk InxCeyCo4Sb12+z alloys are formed with grain boundaries decorated with nano-phase of InSb. The skutterudite matrix has grains on a scale of 100-200 nm and the InSb nano-phase with a typical size of 5-15 nm is evenly dispersed at the grain boundaries of the skutterudite matrix. Coupled with the presence of defects on the Sb sublattice, this multi-scale nanometer structure is exceptionally effective in scattering phonons and, therefore, InxCeyCo4Sb12/InSb nano-composites have very low lattice thermal conductivity and high zT values reaching in excess of 1.5 at 800 K.
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    PublicationOpen Access
    On the mechanical response and microstructure evolution of NiCoCr single crystalline medium entropy alloys
    (Taylor _ Francis, 2018) Picak, S.; Liu, J.; Jozaghi, T.; Karaman, I.; Chumlyakov, Y. I.; Kireeva, I.; Department of Mechanical Engineering; Uzer, Benay; Canadinç, Demircan; Faculty Member; Department of Mechanical Engineering; College of Engineering; Graduate School of Sciences and Engineering; N/A; 23433
    Unusual strain hardening response and ductility of NiCoCr equiatomic alloy were investigated through microstructural analysis of [111], [110] and [123] single crystals deformed under tension. Nano-twinning prevailed at, as early as, 4% strain along the [110] orientation, providing a steady work hardening, and thereby a significant ductility. While single slip dominated in the [123] orientation at the early stages of deformation, multiple slip and nanotwinning was prominent in the [111] orientation. Significant dislocation storage capability and resistance to necking due to nanotwinning provided unprecedented ductility to NiCoCr medium entropy alloys, making it superior than quinary variants, and conventional low and medium stacking fault energy steels.
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    PublicationOpen Access
    High-throughput molecular simulations of metal organic frameworks for CO2 separation: opportunities and challenges
    (Frontiers, 2018) Eruçar, İlknur; Department of Chemical and Biological Engineering; Keskin, Seda; Faculty Member; Department of Chemical and Biological Engineering; College of Engineering; 40548
    Metal organic frameworks (MOFs) have emerged as great alternatives to traditional nanoporous materials for CO2 separation applications. MOFs are porous materials that are formed by self-assembly of transition metals and organic ligands. The most important advantage of MOFs over well-known porous materials is the possibility to generate multiple materials with varying structural properties and chemical functionalities by changing the combination of metal centers and organic linkers during the synthesis. This leads to a large diversity of materials with various pore sizes and shapes that can be efficiently used for CO2 separations. Since the number of synthesized MOFs has already reached to several thousand, experimental investigation of each MOF at the lab-scale is not practical. High-throughput computational screening of MOFs is a great opportunity to identify the best materials for CO2 separation and to gain molecular-level insights into the structure-performance relationships. This type of knowledge can be used to design new materials with the desired structural features that can lead to extraordinarily high CO2 selectivities. In this mini-review, we focused on developments in high-throughput molecular simulations of MOFs for CO2 separations. After reviewing the current studies on this topic, we discussed the opportunities and challenges in the field and addressed the potential future developments.
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    PublicationOpen Access
    A remarkable class of nanocomposites: aerogel supported bimetallic nanoparticles
    (Frontiers, 2020) Özbakır, Yaprak; Department of Chemical and Biological Engineering; Güneş, Hande; Barım, Şansım Bengisu; Yousefzadeh, Hamed; Bozbağ, Selmi Erim; Erkey, Can; Researcher; Faculty Member; Department of Chemical and Biological Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; N/A; N/A; 29633
    Aerogels are a unique class of materials due to their low density, high porosity, high surface area, and an open and interconnected pore structure. Aerogels can be organic, inorganic and hybrid with a plethora of surface chemistries. Aerogel-based products for thermal insulation are already in the market and many studies are being conducted in many laboratories around the world to develop aerogel-based products for other applications including catalysis, adsorption, separations, and drug delivery. On the other hand, bimetallic nanoparticles dispersed on high surface area carriers, which have superior properties compared to their monometallic counterparts, are used or are in development for a wide variety of applications in catalysis, optics, sensing, detection, and medicine. Investigations on using aerogels as high surface area carriers for dispersing bimetallic nanoparticles are leading to development of new composite materials with outstanding properties due to the remarkable properties of aerogels. The review focuses on the techniques to synthesize these materials, their properties, the techniques to tune their pore properties and surface chemistry and the applications of these materials.
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    PublicationOpen Access
    Soft actuators for real-world applications
    (Springer Nature, 2022) Li, Meng; Pal, Aniket; Aghakhani, Amirreza; Pena-Francesch, Abdon; Department of Mechanical Engineering; Sitti, Metin; Faculty Member; Department of Mechanical Engineering; School of Medicine; College of Engineering; 297104
    Soft actuators are flexible and compliant and thus perfectly suited to interact with the human body. This Review discusses tethered, untethered and biohybrid soft actuation strategies, highlights promising real-world applications of soft robots and identifies key future challenges, such as implementing physical intelligence and end-of-life strategies. Inspired by physically adaptive, agile, reconfigurable and multifunctional soft-bodied animals and human muscles, soft actuators have been developed for a variety of applications, including soft grippers, artificial muscles, wearables, haptic devices and medical devices. However, the complex performance of biological systems cannot yet be fully replicated in synthetic designs. In this Review, we discuss new materials and structural designs for the engineering of soft actuators with physical intelligence and advanced properties, such as adaptability, multimodal locomotion, self-healing and multi-responsiveness. We examine how performance can be improved and multifunctionality implemented by using programmable soft materials, and highlight important real-world applications of soft actuators. Finally, we discuss the challenges and opportunities for next-generation soft actuators, including physical intelligence, adaptability, manufacturing scalability and reproducibility, extended lifetime and end-of-life strategies.
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    PublicationOpen Access
    Visual acuity response when using the 3D head-up display in the presence of an accommodation-convergence conflict
    (Taylor _ Francis, 2019) Department of Electrical and Electronics Engineering; Ürey, Hakan; Soomro, Shoaib Rehman; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; Graduate School of Sciences and Engineering; 8579; N/A
    Visual discomfort and fatigue due to accommodation-convergence (AC) conflict in stereoscopic displays has been widely reported, but little is known about its impact on visual acuity, particularly when automotive three-dimensional (3D) head-up displays (HUDs) are involved. This paper presents a study on the visual acuity response when an indigenously developed 75% transparent retroreflective screen is used as a windshield 3D HUD. The simulated optical collimation technique was used to provide the virtual content at a farther depth (i.e. on the road while driving). Two user test experiments were performed. The first test was performed under the see-through condition, where the real scene (i.e. roadside view) was perceived through the 3D HUD, while the second test was performed under the simulated collimation condition, where a stereo-collimated virtual content was projected on the HUD at a farther depth. The results showed a slightly declining trend (from 20/20 to 20/25) in visual acuity response when the HUD screen was placed between the viewer and the scene. An inverse relation between the amount of AC conflict and visual acuity was observed under the simulated collimation condition. The >100 cm user-to-screen distance was found to be comfortable, providing the highest acuity response.
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    PublicationOpen Access
    Computational investigation of multifunctional MOFs for adsorption and membrane-based separation of CF4/CH4, CH4/H-2, CH4/N-2, and N-2/H-2 mixtures
    (Royal Society of Chemistry (RSC), 2023) Department of Chemical and Biological Engineering; Keskin, Seda; Demir, Hakan; Faculty Member; Department of Chemical and Biological Engineering; College of Engineering; 40548; N/A
    The ease of functionalization of metal-organic frameworks (MOFs) can unlock unprecedented opportunities for gas adsorption and separation applications as the functional groups can impart favorable/unfavorable regions/interactions for the desired/undesired adsorbates. In this study, the effects of the presence of multiple functional groups in MOFs on their CF4/CH4, CH4/H-2, CH4/N-2, and N-2/H-2 separation performances were computationally investigated combining grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulations. The most promising adsorbents showing the best combinations of selectivity, working capacity, and regenerability were identified for each gas separation. 15, 13, and 16 out of the top 20 MOFs identified for the CH4/H-2, CH4/N-2, and N-2/H-2 adsorption-based separation, respectively, were found to have -OCH3 groups as one of the functional groups. The biggest improvements in CF4/CH4, CH4/H-2, CH4/N-2, and N-2/H-2 selectivities were found to be induced by the presence of -OCH3-OCH3 groups in MOFs. For CH4/H-2 separation, MOFs with two and three functionalized linkers were the best adsorbent candidates while for N-2/H-2 separation, all the top 20 materials involve two functional groups. Membrane performances of the MOFs were also studied for CH4/H-2 and CH4/N-2 separation and the results showed that MOFs having -F-NH2 and -F-OCH3 functional groups present the highest separation performances considering both the membrane selectivity and permeability.