17 results on '"Zachary R. Hinton"'
Search Results
2. Innovations Toward the Valorization of Plastics Waste
- Author
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Zachary R. Hinton, Michael R. Talley, Pavel A. Kots, Anne V. Le, Tan Zhang, Michael E. Mackay, Aditya M. Kunjapur, Peng Bai, Dionisios G. Vlachos, Mary P. Watson, Michael C. Berg, Thomas H. Epps, and LaShanda T.J. Korley
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General Materials Science - Abstract
Plastics are an extremely important class of materials that are prevalent in all facets of society; however, their widespread use over time, combined with limited end-of-life strategies, has led to increasing levels of waste accumulation. Although currently considered a burden, plastics waste is potentially an untapped feedstock for numerous chemical and manufacturing processes. In this review, we discuss the state of the art of approaches for valorization of plastics waste from a materials research perspective, including previous efforts to utilize plastics waste and recent innovations that have opportunities to add significant value. Although additional progress is necessary, we present several diverse capabilities and strategies for valorization that, when brought together, address end-of-life challenges for plastics at every stage of design and product consumption. In short, a materials research–based framework offers a unique perspective to address the urgent issues posed by plastics, unlocking the potential of polymers and plastics waste.
- Published
- 2022
3. Antioxidant-induced transformations of a metal-acid hydrocracking catalyst in the deconstruction of polyethylene waste
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Zachary R. Hinton, Pavel A. Kots, Mya Soukaseum, Brandon C. Vance, Dionisios G. Vlachos, Thomas H. Epps, and LaShanda T. J. Korley
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Environmental Chemistry ,Pollution - Abstract
This work details the effect of common antioxidants on the activity and functionality of a hydrocracking catalyst, along with associated changes to the product distribution in the deconstruction of high-density polyethylene.
- Published
- 2022
4. Surface tensions at elevated pressure depend strongly on bulk phase saturation
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Nicolas J. Alvarez and Zachary R. Hinton
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Work (thermodynamics) ,Materials science ,Capillary action ,Thermodynamic equilibrium ,02 engineering and technology ,Mechanics ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,law.invention ,Biomaterials ,Surface tension ,Colloid and Surface Chemistry ,Pressure measurement ,law ,Surface-tension values ,0210 nano-technology ,Saturation (chemistry) ,Microscale chemistry - Abstract
Hypothesis Understanding interfacial phenomena at elevated pressure is crucial to the design of a variety of processes, modeling important systems, and interpreting interfacial thermodynamics. While many previous studies have offered insight into these areas, current techniques have inherent drawbacks that limit equilibrium measurements. Experiments In this work, we adapt the ambient microtensiometer of Alvarez and co-workers into a high pressure microtensiometer (HPMT) capable of experimentally quantifying a wide range of interfacial phenomena at elevated pressures. Particularly, the HPMT uses a microscale spherical interface pinned to the tip of a capillary to directly measure surface tension via the Laplace equation. The stream of microscale bubbles used to pressurize the system ensures quick saturation of the bulk phases prior to conducting measurements. The HPMT is validated by measuring the surface tension of air–water as a function of pressure. We then measure the surface tension of CO2 vapor and water as a function of pressure, finding lower equilibrium surface tension values than originally reported in the literature. Findings This work both introduces further development of a useful experimental technique for probing interfacial phenomena at elevated pressures and demonstrates the importance of establishing bulk equilibrium to measure surface tension. The true equilibrium state of the CO2-water surface has a lower tension than previously reported. We hypothesize that this discrepancy is likely due to the long diffusion timescales required to ensure saturation of the bulk fluids using traditional tensiometry. Thus we argue that previously reported elevated pressure measurements were performed at non-equilibrium conditions, putting to rest a long standing discrepancy in the literature. Our measurements establish an equilibrium pressure isotherm for the pure CO2-water surface that will be essential in analyzing surfactant transport at elevated pressures.
- Published
- 2021
5. A novel scCO2 dyeing strategy for superior coloration of UHMWPE fiber
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Yao Zhou, Thamires Andrade Lima, Zachary R. Hinton, Christopher K. Henry, Madhu Anand, and Nicolas Javier Alvarez
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Polymers and Plastics ,Organic Chemistry ,Materials Chemistry - Published
- 2023
6. The effect of pyrolysis on the chemical, thermal and rheological properties of pitch
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Daniel J. Ryan, Kazem V. Edmond, Nicolas J. Alvarez, Manesh Gopinadhan, Zachary R. Hinton, Stuart Smith, Heedong Yoon, James Heinzman, and Clarence Chase
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Shear (sheet metal) ,Work (thermodynamics) ,Materials science ,Rheology ,Thermal ,General Chemistry ,Fiber ,Composite material ,Condensed Matter Physics ,Pyrolysis ,Scaling ,Isothermal process - Abstract
Pitch-based carbon fibers are of considerable interest as high-performance materials. There are reports over the last several decades detailing (i) methods of improving pitch-based carbon fiber performance, and (ii) reducing the cost of production via novel processing techniques. However, there remain considerable challenges in producing high-performance pitch-based carbon fibers consistently on an industrial scale. This is arguably due to the difficulty of scaling the melt-spinning process to compensate for variability in pitch feedstock quality and a lack of understanding of processing-structure-performance relationships. This work focuses on the early stages of heat treatment (pyrolysis) of isotropic pitch and its effect on the chemical, thermal, and rheological properties of the pitch, which help determine its processability. More specifically, we quantify significant changes in chemical structure, Mw, Tg, Ts, and shear and extensional rheology as a function of pyrolysis time at 400 °C. The extensional rheology, in particular, shows that the ‘stretchability’ of the pitch samples strongly depends on pyrolysis severity, and is important for characterizing ‘drawability’. Using a novel analysis of the uniaxial stretching kinematics, we show an isothermal ‘drawability window’ that allows for the largest axial and radial Hencky strains at constant rate. We hypothesize that this extensional drawability window could facilitate the successful processing of pitch into high quality fiber, minimizing the trial-and-error approach currently used in the field.
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- 2021
7. Metathesis, molecular redistribution of alkanes, and the chemical upgrading of low-density polyethylene
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Doyoung Kim, Zachary R. Hinton, Peng Bai, LaShanda T.J. Korley, Thomas H. Epps, and Raul F. Lobo
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Process Chemistry and Technology ,Catalysis ,General Environmental Science - Published
- 2022
8. The trade-off between processability and performance in commercial ionomers
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Zachary R. Hinton and Nicolas J. Alvarez
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chemistry.chemical_classification ,Work (thermodynamics) ,Materials science ,010304 chemical physics ,Ionic bonding ,Polymer ,Condensed Matter Physics ,01 natural sciences ,Viscoelasticity ,010305 fluids & plasmas ,Condensed Matter::Soft Condensed Matter ,chemistry.chemical_compound ,chemistry ,Rheology ,0103 physical sciences ,Thermal ,Solid mechanics ,General Materials Science ,Composite material ,Ionomer - Abstract
Strong ionic interactions between macromolecular chains improve physical and mechanical properties beyond those of the base polymer. Associating groups strongly affect the rheological properties and therefore the polymer processing window. Typically, there is a trade-off between mechanical properties and processability of associating polymers. From a molecular design perspective, we are interested in defining the chemical structure parameters that independently control mechanical properties and melt processability. In this work, we measure the effect of association strength on the mechanical properties of the solid, and the viscoelastic properties of the melt for poly-(ethylene-co-methacrylic acid) and its zinc ionomer. The linear and non-linear solid mechanics are dependent on the strength of associations. The linear viscoelasticity and thermal rheological complexity of the melt are also strongly dependent on association strength. We examine the non-linear flow properties via uniaxial extensional rheology. We show that the processing window for a given associating polymer is bounded by three timescales, namely the association lifetime, the bare sticker lifetime, and the longest relaxation time measured via small amplitude oscillatory shear. The presence of entanglements strongly impacts the magnitude of the longest relaxation time and has a positive impact on the processing window. These findings should increase our ability to design associating polymers for given processes.
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- 2019
9. Nylon-6/Ti3C2Tz MXene Nanocomposites Synthesized by in Situ Ring Opening Polymerization of ε-Caprolactam and Their Water Transport Properties
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Zachary R. Hinton, Michel W. Barsoum, Maxim Sokol, Nicolas J. Alvarez, and Michael Carey
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Thermogravimetric analysis ,Materials science ,Water transport ,Caprolactam ,02 engineering and technology ,Permeation ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,chemistry.chemical_compound ,Differential scanning calorimetry ,Nylon 6 ,chemistry ,Chemical engineering ,General Materials Science ,Dynamic vapor sorption ,In situ polymerization ,0210 nano-technology - Abstract
Clay-reinforced nylon-6 nanocomposites (NCs)-characterized by the full exfoliation of the nanoreinforcement-were introduced in the marketplace in the 1990s. Herein, we demonstrate, for the first time, that Ti3C2T z MXene can be incorporated into nylon-6 to synthesize melt-processable nanocomposites with excellent water barrier properties (94% reduction in water vapor permeation). To intercalate the e-caprolactam monomer between the MXene multilayers, the latter were first treated with 12-aminolauric acid, a low-cost, nontoxic, biodegradable, and long shelf life compound. Upon heating to 250 °C, in the presence of 6-aminocaproic acid, in situ polymerization occurred, yielding melt-processable nylon-6/MXene NCs that were, in turn, studied by thermogravimetric analysis, differential scanning calorimetry, X-ray diffraction, scanning and transmission electron microscopy, infrared spectroscopy, and dynamic vapor sorption analysis. Using the latter, moisture-sorption isotherms of a neat and a 1.9 vol % NC, at 60 °C, were fit to the Guggenheim, Anderson, and de Boer equation. Solubility, permeation, and diffusion coefficients of water through the NCs were measured as a function of temperature and found to be the lowest ever reported for nylon-6, despite the fact that, at ∼1.9 and 5.0 vol %, the MXene loads were relatively low. This record low diffusivity is ascribed to the very large aspect ratios-500 to 1000-of Ti3C2T z flakes and their dispersion. The water permeation rate is a factor of 5 lower than the best reported in the much more mature nylon/clay field, suggesting lower values can be achieved with further optimization. Lastly infrared spectroscopy spectra of neat and NC samples suggest the surface terminations of the 12-Ti3C2T z flakes bind with nylon-6, limiting water adsorption sites, resulting in reduced solubility in the NC films.
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- 2019
10. Accounting for optical errors in microtensiometry
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Zachary R. Hinton and Nicolas J. Alvarez
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Physics ,Observational error ,business.industry ,Spherical cap ,02 engineering and technology ,Radius ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Curvature ,01 natural sciences ,Measure (mathematics) ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Biomaterials ,Colloid and Surface Chemistry ,Optics ,Cardinal point ,Calibration ,0210 nano-technology ,business ,Geometric modeling - Abstract
Hypothesis Drop shape analysis (DSA) techniques measure interfacial tension subject to error in image analysis and the optical system. While considerable efforts have been made to minimize image analysis errors, very little work has treated optical errors. There are two main sources of error when considering the optical system: the angle of misalignment and the choice of focal plane. Due to the convoluted nature of these sources, small angles of misalignment can lead to large errors in measured curvature. We demonstrate using microtensiometry the contributions of these sources to measured errors in radius, and, more importantly, deconvolute the effects of misalignment and focal plane. Our findings are expected to have broad implications on all optical techniques measuring interfacial curvature. Experiments A geometric model is developed to analytically determine the contributions of misalignment angle and choice of focal plane on measurement error for spherical cap interfaces. This work utilizes a microtensiometer to validate the geometric model and to quantify the effect of both sources of error. For the case of a microtensiometer, an empirical calibration is demonstrated that corrects for optical errors and drastically simplifies implementation. Findings The combination of geometric modeling and experimental results reveal a convoluted relationship between the true and measured interfacial radius as a function of the misalignment angle and choice of focal plane. The validated geometric model produces a full operating window that is strongly dependent on the capillary radius and spherical cap height. In all cases, the contribution of optical errors is minimized when the height of the spherical cap is equivalent to the capillary radius, i.e. a hemispherical interface. The understanding of these errors allow for correct measure of interfacial curvature and interfacial tension regardless of experimental setup. For the case of microtensiometry, this greatly decreases the time for experimental setup and increases experiential accuracy. In a broad sense, this work outlines the importance of optical errors in all DSA techniques. More specifically, these results have important implications for all microscale and microfluidic measurements of interface curvature.
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- 2018
11. Single pot catalyst strategy to branched products via adhesive isomerization and hydrocracking of polyethylene over platinum tungstated zirconia
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Pavel A. Kots, Dionisios G. Vlachos, LaShanda T. J. Korley, Cong Wang, Zachary R. Hinton, Thomas H. Epps, Brandon C. Vance, and Caitlin M. Quinn
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chemistry.chemical_classification ,Materials science ,Process Chemistry and Technology ,chemistry.chemical_element ,02 engineering and technology ,Polymer ,Polyethylene ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Catalysis ,0104 chemical sciences ,Bifunctional catalyst ,Polyolefin ,Low-density polyethylene ,chemistry.chemical_compound ,Chemical engineering ,chemistry ,0210 nano-technology ,Platinum ,Isomerization ,General Environmental Science - Abstract
Hydrocracking is an insufficiently explored route for chemical recycling of plastics waste. Platinum tungstated zirconia (Pt-WZr) was used in a batch reactor at low temperatures of 250 °C and 30 bar H2 pressure for 1−24 h reaction times using low-density polyethylene (LDPE, Mw∼76 kDa). We find Pt-WZr is a bifunctional catalyst for LDPE hydrocracking leading to higher value branched fuel- and lubricant-ranged alkanes. We demonstrate that the catalyst metal-to-acid site molar ratio (MAB) shifts the product distribution to larger cracked products and increases the isomerization degree in the residual polymer. We propose a new adhesive isomerization mechanism between the metal and Bronsted acid sites in parallel with slow polymer chain cracking, caused by competitive adsorption of the polymer over the liquid products and stereochemical hindrance of methines. This study provides a blueprint on how to engineer effective catalysts for hydrocracking polyolefin plastic wastes using the MAB as a catalyst descriptor.
- Published
- 2021
12. Surface Treatment of TUFF Pitch-Based Carbon Fiber for Adhesion Promotion in High TG Thermoplastic Composites
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Zachary R. Hinton, Amod A. Ogale, Giuseppe R. Palmese, J. S. Riffle, M.C. Tang, Nicolas J. Alvarez, Sam Lukubira, T. Schumaker, Lavenia Thursch, Ronald M. Joseph, Jacob J. Fallon, Rui Zhang, Munetaka Kubota, Michael J. Bortner, Sagar Kanhere, John W. Gillespie, and Joseph M. Deitzel
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Materials science ,Adhesion ,Composite material ,Thermoplastic composites - Published
- 2019
13. High Throughput Carbon Fiber Surface Modification
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Zachary R. Hinton, Munetaka Kubota, Nicolas J. Alvarez, Joseph M. Deitzel, Giuseppe R. Palmese, and Lavenia Thursch
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Materials science ,Interfacial shear ,Coating ,X-ray photoelectron spectroscopy ,Composite matrix ,Compatibility (mechanics) ,Industrial scale ,engineering ,Surface modification ,engineering.material ,Composite material ,Thermoplastic composites - Abstract
Typical commercial surface treatments for continuous carbon fibers are often unavailable for discontinuous fibers. As such, there is little variety of chopped fiber surfaces leading to non-ideal coating solutions which result in poor interfacial compatibility between fibers and a composite matrix. A method of applying a highly effective coating using a high throughput technique for chopped carbon fibers. The method provides the ability to tune both the coating thickness and chemical functionality using processing parameters. The coatings are evaluated using X-ray photoelectron spectroscopy (XPS) for uniformity and composition. Using this technique, thermoplastic composites are highlighted showing an increase in interfacial shear strength (IFSS) of 25 MPa. This process shows promise for increasing the throughput of surface treatment of chopped fiber on the industrial scale.
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- 2019
14. Multiscale Approaches to Formation of Thermoplastic Prepreg Short Carbon Fiber
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Zachary R. Hinton, Lavenia Thursch, Charleine Ngantsan, Prem Patel, Nicolas J. Alvarez, Simge Uzun, Joy Baxter, Maria Diaz-Acevedo, and Giuseppe R. Palmese
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chemistry.chemical_classification ,Thermoplastic ,Materials science ,chemistry ,Composite material - Published
- 2019
15. Dynamics of Supramolecular Self-Healing Recovery in Extension
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Zachary R. Hinton, Aamir Shabbir, and Nicolas J. Alvarez
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chemistry.chemical_classification ,Work (thermodynamics) ,Materials science ,Polymers and Plastics ,Rheometer ,Organic Chemistry ,Supramolecular chemistry ,Context (language use) ,02 engineering and technology ,Polymer ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Inorganic Chemistry ,Supramolecular polymers ,chemistry ,Creep ,Chemical physics ,Self-healing ,Materials Chemistry ,0210 nano-technology - Abstract
Self-healing materials are prized for their ability to recover mechanical properties after damage. Supramolecular polymer networks have been demonstrated to have the ability to recover without the need for extraneous material components or the use of external stimuli. Surprisingly, there is little quantitative measure of self-healing dynamics and recovery. In this work, we develop a tool using a filament stretching rheometer to probe self-healing dynamics in creep and constant rate of extension. We experimentally determine the effect of process time scales, τ H and τ W , on the degree of recovery for two distinct supramolecular architectures. These results are put into the context of molecular time scales such as disengagement time, the Rouse time, and bond lifetime. We find that entangled polymers undergo sequential healing, whereby at short times, dynamics are dominated by entanglement recovery followed by recovery of associations. For an unentangled polymer, recovery is seemingly dominated by association dynamics. Our experimental results are put into the context of leading theoretical models. We also introduce the importance of the measurement flow time scale on perceived material recovery. These initial results and reliable experimental tools begin to construct a framework for measuring, understanding, and predicting recovery of self-healing soft materials.
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- 2019
16. A molecular parameter to scale the Gibbs free energies of adsorption and micellization for nonionic surfactants
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Zachary R. Hinton and Nicolas J. Alvarez
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Molecular model ,Extrapolation ,Thermodynamics ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Gibbs free energy ,chemistry.chemical_compound ,symbols.namesake ,Colloid and Surface Chemistry ,Adsorption ,Pulmonary surfactant ,chemistry ,Critical micelle concentration ,symbols ,0210 nano-technology ,Ethylene glycol ,Equilibrium constant - Abstract
A long standing goal in the interfacial thermodynamics community is free energies of adsorption and micellization in terms of molecular parameters. Historically, correlations for C i E j 's, a common class of nonionic surfactants, have been proposed between the number of ethylene glycol groups and/or the number of carbons and thermodynamic parameters, such as the critical micelle concentration (CMC), the equilibrium constant ( K ), and the maximum surface concentration ( Γ ∞ ). However, no such correlations to date are capable of capturing a large dataset of C i E j thermodynamic parameters. In this paper we propose the functional form of the critical micelle concentration and adsorption isotherm parameters in terms of molecular parameters for nonionic, C i E j surfactant chemistry. An extensive review of the literature is performed to generate interfacial thermodynamic parameters for a wide-range of C i E j chemistries. The data are used to parameterize and validate the molecular models. More specifically, we combine the well known linear dependence of CMC and K on the number of carbons, N C , with the theorized dependence on hydrophilic-lipophilic balance (HLB), represented as y phob , which is capable of collapsing all experimental data onto mastercurves. The resulting free energy models represent the first successful phenomenological theory which is able to collapse a broad range of experimental data for C i E j surfactants. Furthermore, the proposed models for the free energies of micellization and adsorption are capable of predicting the maximum surface concentration of C i E j surfactants at the air–water interface, thus providing a link between the physics of adsorption and self-assembly. This theory is a step towards engineering interfacial thermodynamics by chemical design which enables prediction of interfacial properties of novel surfactants without extrapolation. In addition, this paper summarizes the many years of experimental and theoretical understanding of surfactant structure property relationships for C i E j 's and the resulting theory quantitatively explains many hypotheses about their interfacial thermodynamics.
- Published
- 2021
17. Dispersion and Stabilization of Alkylated 2D MXene in Nonpolar Solvents and Their Pseudocapacitive Behavior
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Rahul Pai, Vibha Kalra, Nicolas J. Alvarez, Zachary R. Hinton, Michel W. Barsoum, Michael Carey, Varun Natu, and Maxim Sokol
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Materials science ,nonpolar ,Oxide ,General Physics and Astronomy ,chemistry.chemical_element ,LLDPE ,chemistry.chemical_compound ,Colloid ,General Materials Science ,colloid ,Nanocomposite ,nanocomposite ,General Engineering ,General Chemistry ,Polyethylene ,Toluene ,lcsh:QC1-999 ,solvents ,General Energy ,chemistry ,Chemical engineering ,Lithium ,MXene ,MXenes ,Dispersion (chemistry) ,lcsh:Physics - Abstract
Summary To date, MXene dispersions have been mostly limited to polar solvents. Here, we show that when the lithium cations present between MXene multilayers after etching are exchanged with di(hydrogenated tallow)benzyl methyl ammonium chloride (DHT), they become organophilic and form highly stable colloidal suspensions in nonpolar solvents. The rapid cation exchange occurs under ambient conditions and the resulting two-dimensional flakes are well dispersed and remain oxide free. A 142 ± 0.7-μm thick film (≈10 mg ⋅ cm−2) made from a DHT-Ti3C2Tz suspension in toluene exhibits pseudocapacitive behavior, with a capacitance of 305 F ⋅ g−1 at a scan rate 2 mV ⋅ s−1. The moduli and tensile strengths of solution-processed polyethylene nanocomposites are increased by ≈11% and 32% with a loading of ≈1 vol% DHT-Ti3C2Tz. Our approach may enable the use of MXenes in multiple research and industrial fields.
- Published
- 2020
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