High-quality interfaces and well-crystalline nature of the exfoliated MXene flakes were confirmed through the development of realistic and scalable multifunctional coating processes. The last part reports the development of MXene noble metal adsorbent with improved dispersibility to address the restacking problem of delaminated flakes and serious oxidation problems in aqueous solvents (Chapter 5).
Development of MXene Adsorbent for Recovery of Precious Metals and
Photographs of the free-standing MBP hybrid films with varying B4C fractions of 20–60 wt% and cross-sectional SEM images demonstrating the highly ordered in-plane orientation of the B4C integrated between the Ti3C2Tx MXene flakes and PVA layers. EDX mapping images of the free-standing MBP hybrid films showing the uniform distribution of boron with the fractions ranging from 20–60 wt%.
List of Tables
List of Abbreviations
Exfoliation Procedure for Scalable 2D MXene Synthesis 1. Formation of the layered structure
The lower the exfoliation energy, the smaller the total force constant of the A elements provided by surrounding atoms. In the last two years, it has been reported that fused-salt etching method using Lewis acid salts as the etchants can provide fan-folded MXenes with tunable surface terminations. Fan-folded MXenes can be delaminated to generate single-layer nanosheets, and obstruction of the delamination process is closely related to the configuration of surface functional groups.
In addition, the modulus of elasticity (G′) and viscosity (G′′) of large MXene flakes were greater than those of small flakes at a similar concentration (Figure 1.12f). The internal morphology of the blade-coated assemblies with large flakes bent by 180°, consistent with a bend radius of 62.5 μm, consisted of compressed stacks of closely aligned large flakes of MXene (Figure 1.12g).
A short ball mill process was introduced to control the MXene flake size to be smaller while maintaining the quality and composition of the nanocrystals, thereby increasing the surface area available for chemical reactions. When flakes of different sizes were coated on other conductive materials, transformations in morphology and electrochemical impedance were observed, indicating less charge transfer resistance with size reduction.
Direct Integration of High-Quality 2D Carbide MXene Flakes for Electromagnetic Interference Shielding
Furthermore, by investigating the rheological property and fluid behavior of the colloidal dispersion with different concentrations, an aqueous ink of 2D MXene flakes was produced without any agent or additive. The 2D MXene flakes were directly integrated into structurally uniform films on a variety of base materials with different surface properties (i.e., contact angle and roughness) by facile painting of the ink.
Deposition of very pure MXene flakes and subsequent alignment were performed by filtration and thermal compression methods, respectively, resulting in conductive MXene membranes with tunable morphology and electrical conductivity properties. The amount of vacuum filtered solution added determined the thickness of the MXene membrane.
Formation of a High-Quality Parent MAX Phase 1. Optimization of the sintering process
SEM micrographs of (g) surface of heated pellets and (h) the milled MAX precursor powder with layered morphology. i) EDX result of a sample showing the elemental components of Ti3AlC2 MAX phase, and (j) of the hexagonal configuration of Ti3AlC2 , similar to the JCPDS file card number, was confirmed by XRD examination (Figure 2.3j).
Exfoliation of MXene Flakes and Deposition with Tunable Structural and Electrical Properties
The morphology of single flakes and the profiled thickness, measured by the colored dashed line, demonstrate consistent thickness of MXene with a predominance of 1~2 layers in the flakes (Figure 2.8d). Cross-sectional SEM micrographs (Figure 2.8e) revealed flakes that were orderly stacked with interlayer gaps. The membrane underwent XRD analysis to validate the structural modifications in the flakes and their crystal quality (Figure 2.9b).
Fabrication of an MXene Ink and Large-Area Painting Process 1. Precipitation of the delaminated MXene flakes
34;MXene" paint that could be applied to the face on a variety of base materials was developed by concentrating fully distorted flakes, as depicted in Figure 2.12. On one filter paper in particular, MXene was first coated with fiber and then aggregated, showing that MXene Ink was applied conformably based on the morphology of the base material (Figure 2.16) Cross-sectional SEM micrograph of Ti3C2Tx MXene ink applied to PP filter (a and e), (b and f) glass, (c and g ) PC filter, and (d and h) filter paper.
Comparison of Structural Uniformity and Electrical Performance Depending on the Deposition Methods
Three samples with the same number of paints were used to determine the mean and standard error of the skin resistance in (b). For comparison with the EMI shielding efficiency of the hybrid MXene/PP membrane, ≈40 × 40 mm2 of MXene ink was applied to filter paper. As the effective area over which the wave travels, the thickness played a key influence in the EMI SE of the membrane.
MXene-Based Boron Carbide Hybrid Coating for Neutron Radiation Shielding
Then, evaluation of the layered structure of MXene flakes with different surface properties, incorporated content and B4C filler size enabled optimization of the matrix capacity, resulting in tunable neutron shielding capability. Furthermore, as a new form of neutron shielding coating, an easily process-applicable 2D MXene/B4C hybrid ink was produced to concentrate the solution while maintaining dispersion stability. Given the excellent mechanical properties and much better quality of our MXene/B4C composites compared to those previously reported using conventional matrices, our study represents significant progress toward the fabrication of face-face neutron shielding films and coatings. with high protective efficiency.
Using the maximum stress and cross-sectional areas of the strips before failure, the tensile strength was calculated. The front of the detector was protected with a Cd filter and then the total neutron count rate (Rt) was measured. The counting rate for epithermal neutrons (>0.6 eV) was then determined when the Cd filter was placed in front of the detector (Re).
A TEM micrograph revealed that the edge and surface of the Ti3C2Tx flake was essentially free of oxidized particles. Structural characterization of the mixed-acid-etched MXene flakes. a) XRD patterns of synthesized Ti3AlC2 MAX phase (black) and delaminated Ti3C2Tx MXene (red). Zeta potential analysis of the AR- and S-B4C. a) Change of the zeta potential after size selection.
Complexation with a polymer for enhanced structural stability of the MXene matrix
XRD investigation of the MBP hybrid film showed an ordered lateral structure when the weight fraction of B4C in the hybrid film changed from 20 to 60 wt. % (MBP 20 to 60). A magnified plot of the XRD peaks reveals the crystal structure of the B4C particles in the composite films, corresponding to the B4C pattern (inset in Figure 3.14a). The contact angles of the coated base materials are shown in the upper right corner (i–iii).
Evaluation of Neutron Shielding Ability of MXene-Based Hybrid Films
Comparison of macroscopic cross section versus film thickness with previously investigated materials showed that our hybrid films exhibited superior neutron shielding ability at ultrathin thicknesses (Figure 3.20c). Based on a similar macroscopic cross-section cm-1) through all the hybrid films with increasing thickness, it was with a repeated process of coating the bare SS foil (Fig. 3.20d). Neutron shielding ability of MBP hybrid films. a) Neutron absorption ability of MBP hybrid films with different B4C compositions.
Patterning of MXene Assemblies for 2D Electrode Fabrication
- Experimental Methods
- Scalable Fabrication of MXene Mesh for Transparent Electrodes 1. Large-area coating of MXene films with enhanced adhesion of substrates
- Development of MXene Patterning for Electrical Contacts
In addition, the structural stability of MXene mesh showed dependence on the cycle number of ALD (Figure 4.3d and e). OM micrographs for the morphology of MXene mesh on (a) bare SiO2, (b) PECVD-SiO2, and (c) ALD-deposited Al2O3. OM photomicrographs of MXene mesh morphologies after lifting the photoresist patterns with heights of (a).
Development of MXene Adsorbent for Recovery of Precious Metals and Water Treatment
- Experimental Methods
- Fabrication of Shape-Controlled MXene Adsorbents
- Measurements of Adsorption Efficiency and Precious Metal Recovery 1. Investigation of electrostatic interaction and reductive adsorption of the MXenes
Where Ci and Ce (mg L-1) represent the initial and final concentration of ions in the solutions, V (L) represents the volume of the ion solution and M (g) represents the mass of the adsorbent. In order to determine the adsorption capacity of the MXene flake itself, we also performed a Cu(II) adsorption test using the MXene dispersion (Figure 5.1c). The corresponding EDX micrograph for mapping clearly showed the presence of nanoparticles on the exfoliated flakes, suggesting that the dispersed MXene adsorbent provided a reduction site for Au and Ag (Figure 5.11c).
Conclusions and Perspectives
To date, this research has mainly focused on the metallic nature of TM carbide MXenes and the processing of the flakes while maintaining high crystallinity. Using the preliminary study conducted in this thesis, novel synthesis and operations of TM-nitride MXenes for structurally variable optoelectronics and energy devices will be developed in the future. Ultimately, scalable and reproducible synthesis of low-control nitride MXenes with optimization of interface properties should be adapted to investigate the reaction kinetics in energy reservoir and transformation without impurities, which can strongly influence the behavior of MXenes. Research into the nanoconfined fluids between the high interfacial bonds of MXenes will likely extend beyond the energy industry to areas such as H2O desalination and ion-selective reinforced membranes.
Lu, S.; Shao, J.; Ma, K.; Chen, D.; Wang, X.; Zhang, L.; Meng, Q.; Ma, J., Flexible, mechanically elastic carbon nanotube composite films for high-efficiency electromagnetic interference shielding. Gao, M.; Chen, Z.; Li, L.; Guo, E.; Kang, H.; Xu, Y.; Wang, T., Microstructure and improved mechanical properties of 6061Al matrix composites reinforced with hybrid size B4C particles. Chen, L.; Tang, J.; Zhang, X.; Wang, S.; Ren, Z., A novel benzothiazole-modified chitosan with excellent adsorption capacity for Au(III) in aqueous solutions.
2, 2021 (mundtlig) . 4) Shi-Hyun Seok, Seungjun Choo, Jinsung Kwak, Hyejin Ju, Ju-Hyoung Han, Woo-Seok Kang, Joonsik Lee, Se-Yang Kim, Do Hee Lee, Jungsoo Lee, Jaewon Wang, Seunguk Song, Wook Jo, Byung Mun Jung, Han Gi Chae, Jae Sung Son og Soon-Yong Kwon*, "Synthesis of 2D carbide MXene flakes using a very clean precursor for ink applications", ICAE 2021, Jeju, Korea, Nov. Poster) . 5) Shi-Hyun Seok, Seungjun Choo, Jinsung Kwak, Hyejin Ju, Ju-Hyoung Han, Woo-Seok Kang, Joonsik Lee, Se-Yang Kim, Do Hee Lee, Jungsoo Lee, Jaewon Wang, Seunguk Song, Wook Jo, Byung Mun Jung, Han Gi Chae, Jae Sung Son og Soon-Yong Kwon*, "Inkable 2D carbide MXene flages showing high yield and performance via very-rensed-precursor-synthesis", IUMRS-ICA 2021, Jeju, Korea, Oct. 3-8, 2021 (mundtligt) . 6) Shi-Hyun Seok, Seungjun Choo, Jinsung Kwak, Hyejin Ju, Ju-Hyoung Han, Woo-Seok Kang, Joonsik Lee, Se-Yang Kim, Do Hee Lee, Jungsoo Lee, Jaewon Wang, Seunguk Song, Wook Jo, Byung Mun Jung, Han Gi Chae, Jae Sung Son og Soon-Yong Kwon*, "Ink Application of 2D carbide MXene Flakes Exhibiting High Yield and Performance via Highly-Purified-Precursor Synthesis", den 28. koreanske konference om halvledere, On- linje (Korea), jan.
29, 2021 (Poster) . 7) Shi-Hyun Seok, Seungjun Choo, Jinsung Kwak, Hyejin Ju, Ju-Hyoung Han, Woo-Seok Kang, Joonsik Lee, Se-Yang Kim, Do Hee Lee, Jungsoo Lee, Jaewon Wang, Seunguk Song, Wook Jo, Byung Mun Jung, Han Gi Chae, Jae Sung Son, and Soon-Yong Kwon*, "Synthesis of Inkable 2D Carbide MXene Flakes Exhibiting High Yield and Performance Using Highly Purified Precursor", The 6th International Conference on Electronic Materials and Nanotechnology for Green Environment, Jeju, Korea, 3 Nov. 2020 (Poster) . 8) Shi-Hyun Seok, Seungjun Choo, HyeJin Ju, Jinsung Kwak, Woo-Seok Kang, Se-Yang Kim, Do Hee Lee, Jungsoo Lee, Ju-Hyoung Han, Jaewon Wang, Wook Jo, Han Gi Chae, Jae Sung Son, and Soon-Yong Kwon*, "Synthesis of Solution-Processed Two-Dimensional Transition Metal Carbide (MXene) Using Highly Purified Precursors for Ink Applications", The 27th Korean Conference on Semiconductors, Gangwon, Korea, 13 February 2019 (Poster). 10) Shi-Hyun Seok, Seungjun Choo, Jinsung Kwak, Hye-jin Ju, Woo-Seok Kang, Se-Yang Kim, Do Hee Lee, Wook Jo, Han Gi Chae, Jae Sung Son, and Soon-Yong Kwon*, "Synthesis of solution-processed 2D MXene flakes using highly purified precursors for ink applications", ICAE 2019, Jeju, Korea, Nov.