Browsing by Author "Gogotsi, Yury"
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Item 2D metal carbides and nitrides (MXenes) for energy storage(Nature Publishing Group, 2017-01-17) Anasori, Babak; Lukatskaya, Maria R.; Gogotsi, Yury; Mechanical Engineering and Energy, School of Engineering and TechnologyThe family of 2D transition metal carbides, carbonitrides and nitrides (collectively referred to as MXenes) has expanded rapidly since the discovery of Ti3C2 in 2011. The materials reported so far always have surface terminations, such as hydroxyl, oxygen or fluorine, which impart hydrophilicity to their surfaces. About 20 different MXenes have been synthesized, and the structures and properties of dozens more have been theoretically predicted. The availability of solid solutions, the control of surface terminations and a recent discovery of multi-transition-metal layered MXenes offer the potential for synthesis of many new structures. The versatile chemistry of MXenes allows the tuning of properties for applications including energy storage, electromagnetic interference shielding, reinforcement for composites, water purification, gas- and biosensors, lubrication, and photo-, electro- and chemical catalysis. Attractive electronic, optical, plasmonic and thermoelectric properties have also been shown. In this Review, we present the synthesis, structure and properties of MXenes, as well as their energy storage and related applications, and an outlook for future research.Item Beyond Ti3C2Tx: MXenes for Electromagnetic Interference Shielding(ACS, 2020-03) Han, Meikang; Shuck, Christopher Eugene; Rakhmanov, Roman; Parchment, David; Anasori, Babak; Koo, Chong Min; Friedman, Gary; Gogotsi, Yury; Mechanical and Energy Engineering, School of Engineering and TechnologyNew ultrathin and multifunctional electromagnetic interference (EMI) shielding materials are required for protecting electronics against electromagnetic pollution in the fifth-generation networks and Internet of Things era. Micrometer-thin Ti3C2Tx MXene films have shown the best EMI shielding performance among synthetic materials so far. Yet, the effects of elemental composition, layer structure, and transition-metal arrangement on EMI shielding properties of MXenes have not been explored, despite the fact that more than 30 different MXenes have been reported, and many more are possible. Here, we report on a systematic study of EMI shielding properties of 16 different MXenes, which cover single-metal MXenes, ordered double-metal carbide MXenes, and random solid solution MXenes of M and X elements. This is the largest set of MXene compositions ever reported in a comparative study. Films with thicknesses ranging from nanometers to micrometers were produced by spin-casting, spray-coating, and vacuum-assisted filtration. All MXenes achieved effective EMI shielding (>20 dB) in micrometer-thick films. The EMI shielding effectiveness of sprayed Ti3C2Tx film with a thickness of only ∼40 nm reaches 21 dB. Adjustable EMI shielding properties were achieved in solid solution MXenes with different ratios of elements. A transfer matrix model was shown to fit EMI shielding data for highly conductive MXenes but could not describe the behavior of materials with low conductivity. This work shows that many members of the large MXene family can be used for EMI shielding, contributing to designing ultrathin, flexible, and multifunctional EMI shielding films benefiting from specific characteristics of individual MXenes.Item Colloidal Gelation in Liquid Metals Enables Functional Nanocomposites of 2D Metal Carbides (MXenes) and Lightweight Metals(ACS, 2019) Kamysbayev, Vladislav; James, Nicole M.; Filatov, Alexander S.; Srivastava, Vishwas; Anasori, Babak; Jaeger, Heinrich M.; Gogotsi, Yury; Talapin, Dmitri V.; Mechanical Engineering and Energy, School of Engineering and TechnologyNanomaterials dispersed in different media, such as liquids or polymers, generate a variety of functional composites with synergistic properties. In this work, we discuss liquid metals as the nanomaterials’ dispersion media. For example, 2D transition-metal carbides and nitrides (MXenes) can be efficiently dispersed in liquid Ga and lightweight alloys of Al, Mg, and Li. We show that the Lifshitz theory predicts strong van der Waals attraction between nanoscale objects interacting through liquid metals. However, a uniform distribution of MXenes in liquid metals can be achieved through colloidal gelation, where particles form self-supporting networks stable against macroscopic phase segregation. This network acts as a reinforcement boosting mechanical properties of the resulting metal–matrix composite. By choosing Mg–Li alloy as an example of ultralightweight metal matrix and Ti3C2Tx MXene as a nanoscale reinforcement, we apply a liquid metal gelation technique to fabricate functional nanocomposites with an up to 57% increase in the specific yield strength without compromising the matrix alloy’s plasticity. MXenes largely retain their phase and 2D morphology after processing in liquid Mg–Li alloy at 700 °C. The 2D morphology enables formation of a strong semicoherent interface between MXene and metal matrix, manifested by biaxial strain of the MXene lattice inside the metal matrix. This work expands applications for MXenes and shows the potential for developing MXene-reinforced metal matrix composites for structural alloys and other emerging applications with metal–MXene interfaces, such as batteries and supercapacitors.Item Distinguishing electronic contributions of surface and sub-surface transition metal atoms in Ti-based MXenes(IOP, 2020) Yang, Yizhou; Hantanasirisakul, Kanit; Frey, Nathan C.; Anasori, Babak; Green, Robert J.; Rogge, Paul C.; Waluyo, Iradwikanari; Hunt, Adrian; Shafer, Padraic; Arenholz, Elke; Shenoy, Vivek B.; Gogotsi, Yury; May, Steven J.; Mechanical and Energy Engineering, School of Engineering and TechnologyMXenes are a rapidly-expanding family of 2D transition metal carbides and nitrides that have attracted attention due to their excellent performance in applications ranging from energy storage to electromagnetic interference shielding. Numerous other electronic and magnetic properties have been computationally predicted, but not yet realized due to the experimental difficulty in obtaining uniform surface terminations (Tx), necessitating new design approaches for MXenes that are independent of surface terminations. In this study, we distinguished the contributions of surface and sub-surface Ti atoms to the electronic structure of four Ti-containing MXenes (Ti2CTx, Ti3C2Tx, Cr2TiC2Tx, and Mo2TiC2Tx) using soft x-ray absorption spectroscopy. For MXenes with no Ti atoms on the surface transition metal layers, such as Mo2TiC2Tx and Cr2TiC2Tx, our results show minimal changes in the spectral features between the parent MAX phase and its MXene. In contrast, for MXenes with surface Ti atoms, here Ti3C2Tx and Ti2CTx, the Ti L-edge spectra are significantly modified compared to their parent MAX phase compounds. First principles calculations provide similar trends in the partial density of states derived from surface and sub-surface Ti atoms, corroborating the spectroscopic measurements. These results reveal that electronic states derived from sub-surface M-site layers are largely unperturbed by the surface terminations, indicating a relatively short length scale over which the Tx terminations alter the nominal electron count associated with Ti atoms and suggesting that desired band features should be hosted by sub-surface M-sites that are electronically more robust than their surface M-site counterparts.Item Electrode material–ionic liquid coupling for electrochemical energy storage(Nature, 2020) Wang, Xuehang; Salari, Maryam; Jiang, De-en; Chapman Varela, Jennifer; Anasori, Babak; Wesolowski, David J.; Dai, Sheng; Grinstaff, Mark W.; Gogotsi, Yury; Mechanical and Energy Engineering, School of Engineering and TechnologyThe development of new electrolyte and electrode designs and compositions has led to advances in electrochemical energy-storage (EES) devices over the past decade. However, focusing on either the electrode or electrolyte separately is insufficient for developing safer and more efficient EES devices in various working environments, as the energy-storage ability is determined by the ion arrangement and charge and/or electron transfer at the electrode–electrolyte interface. In this Review, we assess the fundamental physicochemical and electrochemical properties at the electrode–electrolyte interfaces in Li-ion batteries and supercapacitors using safe and electrochemically stable ionic-liquid electrolytes. Key reactions and interactions at the electrode–electrolyte interface, as well as geometric constraints and temperature effects, are highlighted. Building on the fundamental understanding of interfacial processes, we suggest potential strategies for designing stable and efficient ionic-liquid-based EES devices with emerging electrode materials.Item Enhanced Ionic Accessibility of Flexible MXene Electrodes Produced by Natural Sedimentation(Springer, 2020-04-11) Sun, Ning; Guan, Zhaoruxin; Zhu, Qizhen; Anasori, Babak; Gogotsi, Yury; Xu, Bin; Mechanical and Energy Engineering, School of Engineering and TechnologyMXene nanosheets have been used for preparing highly flexible integrated electrodes due to their two-dimensional (2D) morphology, flexibility, high conductivity, and abundant functional groups. However, restacking of 2D nanosheets inhibits the ion transport in MXene electrodes, limiting their thickness, rate performance, and energy storage capacity. Here, we employed a natural sedimentation method instead of the conventional vacuum-assisted filtration to prepare flexible Ti3C2Tx MXene films with enlarged interlayer spacing, which facilitates the access of the lithium ions to the interlayers and thus leads to a greatly enhanced electrochemical performance. The naturally sedimented flexible film shows a double lithium storage capacity compared to the conventional vacuum-filtered MXene film, along with improved rate performance and excellent cycle stability.Item Enhancement of Ti3C2 MXene Pseudocapacitance after Urea Intercalation Studied by Soft X-ray Absorption Spectroscopy(ACS, 2020-02) Al-Temimy, Ameer; Anasori, Babak; Mazzio, Katherine A.; Kronast, Florian; Seredych, Mykola; Kurra, Narendra; Mawass, Mohamad-Assaad; Raoux, Simone; Gogotsi, Yury; Petit, Tristan; Mechanical and Energy Engineering, School of Engineering and TechnologyMXenes have shown outstanding properties due to their highly active hydrophilic surfaces coupled with high metallic conductivity. Many applications rely on the intercalation between Ti3C2Tx (Tx describes the -OH, -F and -O- surface terminations) flakes by ions or molecules, which in turn might alter the Ti3C2Tx surface chemistry and electrochemical properties. In this work, we show that the capacitance, rate capability, and charge carrier kinetics in Ti3C2Tx MXene electrodes are remarkably enhanced after urea intercalation (u-Ti3C2Tx). In particular, the areal capacitance increased to 1100 mF/cm2, which is 56% higher than that of pristine Ti3C2Tx electrodes. We attribute this dramatic improvement to changes in the Ti3C2Tx surface chemistry upon urea intercalation. The oxidation state and the oxygen bonding of individual Ti3C2Tx flakes before and after urea intercalation are probed by soft X-ray absorption spectroscopy (XAS) at the Ti L- and O K-edges with 30 nm spatial resolution in vacuum. After urea intercalation, a higher Ti oxidation state is observed across the entire flake compared to pristine Ti3C2Tx. Additionally, in situ XAS of u-Ti3C2Tx aqueous dispersions reveal a higher Ti oxidation similar to dry samples, while for pristine Ti3C2Tx the Ti atoms are significantly reduced in water compared to dry samples.Item Evidence of a magnetic transition in atomically thin Cr2TiC2Tx MXene(Royal Society of Chemistry, 2020-12) Hantanasirisakul, Kanit; Anasori, Babak; Nemsak, Slavomir; Hart, James L.; Wu, Jiabin; Yang, Yizhou; Chopdekar, Rajesh V.; Shafer, Padraic; May, Andrew F.; Moon, Eun Ju; Zhou, Jun; Zhang, Qinghua; Taheri, Mitra L.; May, Steven J.; Gogotsi, Yury; Mechanical and Energy Engineering, School of Engineering and TechnologyTwo-dimensional (2D) transition metal carbides and nitrides known as MXenes have shown attractive functionalities such as high electronic conductivity, a wide range of optical properties, versatile transition metal and surface chemistry, and solution processability. Although extensively studied computationally, the magnetic properties of this large family of 2D materials await experimental exploration. 2D magnetic materials have recently attracted significant interest as model systems to understand low-dimensional magnetism and for potential spintronic applications. Here, we report on synthesis of Cr2TiC2Tx MXene and a detailed study of its magnetic as well as electronic properties. Using a combination of magnetometry, synchrotron X-ray linear dichroism, and field- and angular-dependent magnetoresistance measurements, we find clear evidence of a magnetic transition in Cr2TiC2Tx at approximately 30 K, which is not present in its bulk layered carbide counterpart (Cr2TiAlC2 MAX phase). This work presents the first experimental evidence of a magnetic transition in a MXene material and provides an exciting opportunity to explore magnetism in this large family of 2D materials.Item Interface binding and mechanical properties of MXene-epoxy nanocomposites(Elsevier, 2020-05) Sliozberg, Yelena; Andzelm, Jan; Hatter, Christine B.; Anasori, Babak; Gogotsi, Yury; Hall, Asha; Mechanical and Energy Engineering, School of Engineering and TechnologyThermosetting epoxy polymers exhibit excellent stiffness and strength and are commonly utilized as matrices to make fiber reinforced composites. However, epoxy thermosets are brittle and typically possess a low fracture toughness that restricts their applications. One promising mechanism for improving mechanical properties of epoxy is the integration of micro- and nano-scale fillers. MXenes, a large family of 2D transition-metal carbides, carbonitrides, and nitrides, can be used to produce multifunctional polymer nanocomposites due to their excellent electrical, thermal, and mechanical properties. We employed density functional theory and coarse-grained molecular dynamics simulations to evaluate binding energy and microscopic mechanisms of fracture under uniaxial tension for MXene-epoxy composites. The simulation results were verified by manufacturing Ti3C2Tx MXene-epoxy composites and studying their structure and fracture surfaces. MXene-epoxy binding energies are largely unaffected by MXene type (Ti2CTx or Ti3C2Tx). Binding between Ti3C2Tx and epoxy becomes stronger with less hydrogen coverage of Ti3C2Tx surface due to increase in favorable electrostatic interactions. The Young's modulus of MXene-epoxy composites is greater compared to the neat epoxy which originates from stress transfer between the matrix and the nanofiller, the modulus linearly increases with the filler loading up to 1 vol %. At higher filler contents, the increase of the modulus is reduced due to filler aggregation. Void formation was detected near edges of the particles in MXene-epoxy composites under deformation from both experimental and simulation studies of the fracture surfaces. From these observations, we expect the MXene fillers to improve epoxy toughness and enhance its mechanical performance.Item MXene Composite and Coaxial Fibers with High Stretchability and Conductivity for Wearable Strain Sensing Textiles(Wiley, 2020-03) Seyedin, Shayan; Uzun, Simge; Levitt, Ariana; Anasori, Babak; Dion, Genevieve; Gogotsi, Yury; Razal, Joselito M.; Mechanical and Energy Engineering, School of Engineering and TechnologyThe integration of nanomaterials with high conductivity into stretchable polymer fibers can achieve novel functionalities such as sensing physical deformations. With a metallic conductivity that exceeds other solution-processed nanomaterials, 2D titanium carbide MXene is an attractive material to produce conducting and stretchable fibers. Here, a scalable wet-spinning technique is used to produce Ti3C2Tx MXene/polyurethane (PU) composite fibers that show both conductivity and high stretchability. The conductivity at a very low percolation threshold of ≈1 wt% is demonstrated, which is lower than the previously reported values for MXene-based polymer composites. When used as a strain sensor, the MXene/PU composite fibers show a high gauge factor of ≈12900 (≈238 at 50% strain) and a large sensing strain of ≈152%. The cyclic strain sensing performance is further improved by producing fibers with MXene/PU sheath and pure PU core using a coaxial wet-spinning process. Using a commercial-scale knitting machine, MXene/PU fibers are knitted into a one-piece elbow sleeve, which can track various movements of the wearer's elbow. This study establishes fundamental insights into the behavior of MXene in elastomeric composites and presents strategies to achieve MXene-based fibers and textiles with strain sensing properties suitable for applications in health, sports, and entertainment.