Delamination Process Research Articles

Hydrofluoric Acid-Free Synthesis of Ti3C2Tx MXene Nanostructures for Energy Applications

The preparation of titanium carbide (Ti3C2Tx) thin sheets (T represents surface termination), an emerging class of two-dimensional materials, heavily relies on the etching of interlayered aluminum (Al) of MAX (M, A, and X represent transition metals, Al, and carbon, respectively) using concentrated hydrofluoric acid (HF). However, HF is an acutely toxic chemical. Herein, for the first time, we propose a dissolution-driven delamination method to prepare Ti3C2Tx MXene thin sheets using an HF-free solvent to remove the interlayers of Al. Bis(trifluoromethanesulfonyl)imide (TFSI) is a delaminating agent that can directly and effectively dissolve the Al interlayers of MAX. The role of TFSI in this delamination process, i.e., the preferential formation of the surface of a Ti3C2Tx thin sheet, is a key parameter for superior supercapacitor application. The prepared Ti3C2Tx sheets were loaded on Ni foam (NF) via a hydrothermal reaction to form a Ti3C2Tx MXene/NF-4 h composite electrode. This Ti3C2Tx MXene/NF-4 h composite electrode exhibits the highest unprecedented capacitance of 3090 F/g at a current density of 10 A/g in a 1 M KOH electrolyte. It also exhibits excellent rate capabilities at different current densities (from 10 to 30 A/g) while maintaining 76.4% capacity retention after long life cycles. This study provides fundamental insights into the effect of the dissolution of interlayered Al of Ti3AlC2 on the preparation of Ti3C2Tx thin sheets as well as sheds light on the development of next-generation flexible and simple integrated supercapacitors with excellent gravimetric performance.

A thermodynamic framework for additive manufacturing of crystallizing polymers, Part II: Simulation of the printing of a stent

We use the theory developed by [43] to simulate in Abaqus the printing of a drug-eluting bioresorbable stent (BRS), which is used to treat a stenosed renal artery, by fused deposition modeling (FDM). The stent is assumed to be printed using a semi-crystalline polylactic acid (PLA). We control the process parameters to architect the microstructure of the stent such that the stent has an amorphous glassy phase on a crystalline backbone, which would ensure sufficient strength along with the regulated release of the drug into the bloodstream. Through this simulation, we highlight those regions in the stent geometry that should adhere to strict quality control requirements during the fabrication process. In this regard, it is observed that a preexisting crack at the core of the third layer has a very high tendency to propagate along the ‘r’ or ‘z’ direction, whereas a preexisting crack at the core of the second layer has a very high tendency to propagate along the ‘r’ direction, thus increasing the probability of an intra-layer delamination process during service. Similarly, the stent has a high chance of inter-layer delamination between the second and third layers by the mode-I mechanism for cracking. Moreover, the final cup-like warped geometry of the stent could injure the arterial wall during deployment by balloon expansion and also during service, thus increasing the risk of neointimal hyperplasia.

A wrinkling-assisted strategy for controlled interface delamination in mechanically-guided 3D assembly

Mechanically-guided three-dimensional (3D) assembly is a recently established method for the fabrication of 3D structures and devices at micro/nanoscale. Such assembly methods typically involve a process of compressive buckling in a patterned high-modulus thin film integrated with a low-modulus elastomer substrate at selective regions. A successful assembly requires, simultaneously, a sufficiently strong interface in selective regions to stay undelaminated, and a sufficiently weak interface in remaining regions to be fully separated. However, such requirements are very challenging to meet for highly flexible 3D mesostructures or those with large-area suspended features. Here, we propose a wrinkling-assisted strategy to substantially facilitate the delamination at desired regions of the film/substrate system. An additional assisting layer is introduced such that a weaker film/assisting-layer interface replaces the original film/substrate interface, and the wrinkles formed in the assisting layer induce additional driving forces to separate the film/assisting-layer interface. An analytical model is developed to capture the delamination of the thin film from the wrinkled assisting layer, which is validated by both experiments and finite element analyses (FEA). The model shows that a combined material/geometry parameter governs the process of delamination in the bilayer film/substrate system, offering a useful design reference for the mechanically-guided 3D assembly. Furthermore, our experiments and FEA demonstrate that the wrinkling-assisted strategy can enable the assembly of highly flexible 3D mesostructures and those with large areas attached to the substrate in the initial configuration, which are particularly challenging to achieve by using previous strategies.

Additive-free Electrophoretic-deposited Ti3AlC2 MAX phase Li-ion battery anode

• We demonstrated its excellent cycling stability and reversible recovery for MAX anode. • Delamination process activates both faradic and non-faradaic processes. • Pseudocapacitive redox reactions led to reversible battery charging/discharging cycles. M n+1 AX n (MAX, n=1, 2, 3…) is the precursor of Mxene, which is two-dimensional layered transition metal carbides and nitrides. The two-dimensional Mxene layers are fabricated through selective etching of element “A”. To probe the intrinsic electrochemical properties of Ti 3 AlC 2 MAX phase as Li-ion battery anode, we fabricated an additive-free electrophoretically-deposited MAX phase anode electrode. As demonstrated in this report, the MAX phase is highly reversible during charging and discharging cycles, as a result of pseudocapacitive redox reactions caused by delamination of Ti 3 AlC 2 nanolayer aggregates into nanosheets during delithiation. In the present study, we demonstrate excellent cycling reversibility for a Ti 3 AlC 2 MAX phase electrode electrophoretically deposited without additives with a specific capacity of ∼120 mAh/g after cycles up to 10 C-rate.

Ethanol Conversion Catalyzed by MCM-22 and Its Dealuminated and Delaminated Forms

The conversion of ethanol into hydrocarbons, particularly into light olefins, was studied over MCM-22 zeolite in their acid form (HMCM-22) and its derived forms obtained by dealumination with oxalic acid (HMCM-22(OA)) and delamination (HITQ-2). The treatment with oxalic acid did not affect zeolite textural properties but reduced the total density and strength of the acid sites. As to the delamination process, HITQ-2 zeolite presented the highest Brunauer, Emmett and Teller (BET) specific area, mesopore volume, and external area, but the microporosity was not affected. This sample showed a lower SiO2/Al2O3 ratio than the precursor HMCM-22, resulting in the highest acid site density but with the predominance of acid sites with weak and intermediate strength. Both dealumination and delamination led to an increase in the number of structural defects in the samples. The comparison of the catalytic performance at 500 ºC showed that despite the differences in the acidic and textural properties of the samples, they were active for ethanol conversion and highly selective for ethylene production. Ethanol conversion, followed by in situ diffuse reflectance spectroscopy (DRIFTS), was also investigated. It showed that, for both samples, the “coke band” intensity was already significant after 1 min of reaction, similar to what was detected for HMCM-22.

Petrogenesis of the Wadi El-Faliq Gabbroic Intrusion in the Central Eastern Desert of Egypt: Implications for Neoproterozoic Post-Collisional Magmatism Associated with the Najd Fault System

The late Neoproterozoic gabbroic intrusion of the Wadi El-Faliq area in the central Eastern Desert of Egypt (north Arabian–Nubian Shield; henceforth, ANS) is a fresh, undeformed elliptical body elongated in a NW–SE trend following the main sinistral strike-slip faults of the Najd fault system. Mineralogical and geochemical evidence suggest that they were derived from hydrous tholeiitic mafic magmas with arc-like geochemical fingerprints resembling the post-collisional gabbroic intrusions in Saudi Arabia. Despite the arc-like signatures, their fresh and undeformed nature, together with the field relationships, indicates that the studied gabbroic intrusion post-dates the main collisional phase, supporting its emplacement after subduction ceased and during the post-collisional stage. As a result, the arc-like signatures were possibly transmitted from the earlier ANS subduction episode. Indeed, the high (La/Sm)N, and negative-Nb and positive-Pb anomalies suggest contributions from subduction components. Lithospheric delamination was possibly facilitated by the Najd faults and shear zones formed during the post-orogenic crustal extension associated with the Pan-African orogenic collapse. The delamination process could have generated a rapid upwelling and melting of the asthenosphere mantle. The melt-rock reaction process likely played an important role in the genesis of the studied rocks through the interaction of the asthenosphere melts with lithosphere mantle rocks during ascent. The HREE fractionation suggests a probable mixing between melts from both spinel- and garnet-bearing peridotites. We suggest that the Wadi El-Faliq gabbroic intrusion was likely emplaced due to the stretching and thinning of the lithosphere during the extensional tectonism following the Pan-African orogeny.

A novel approach for 3D discrete element modelling the progressive delamination in unidirectional CFRP composites

This study proposed a novel approach based on the 3D discrete element method (DEM) to simulate the progressive delamination in unidirectional carbon fibre reinforced polymer (CFRP) composite laminates. A hexagonal packing strategy was used for modelling 0∘ representative plies, the interface between different plies was modelled with one bond and seven bonds following the conservation of energy principle and a power law. The number of representative layers and the stiffness of bonds within these layers were calibrated with a comparison of results obtained from finite element method and theoretical analysis. DEM simulations of delamination with both interface models were conducted on unidirectional composites for double cantilever beam (DCB), end-loaded split (ELS) and fixed-ratio mixed-mode (FRMM) tests. It was found that the seven-bond interface model has a better agreement with experimental data in all three tests than the one-bond interface model by adopting the proposed seven-bond arrangement in terms of the progressive delamination process. The main advantages of the present interface model are its simplicity, robustness and computational efficiency when elastic bonds are used in the DEM models.

Multifunctional MXene sediment-based composite film for electromagnetic interference shielding and joule heating

Owing to outstanding conductivity, hydrophilicity and large specific surface area, MXenes are widely applied for energy storage, electromagnetic interference shielding, sensors, and biomedicine. However, the exfoliation and delamination process to prepare single-layer MXenes is apparently low-efficiency, remaining a great amount of abandoned MXene sediment (MS) wastes. Herein, considering the appreciable electrical conductivity of MS, a flexible composite film was fabricated by integrating MS and waterborne polyurethane (PU). The as-synthesized MS-PU films exhibit maximum tensile strength of 25.4 MPa and large elongation of 51.4%, which subsequently leads to high toughness of 10.9 MJ m−3. Furthermore, the MS-PU films with small thickness (<50 μm) present good EMI shielding efficiency (∼30 dB) and fast Joule heating performance (thermal response <20 s). This work explores the practical application of MXene sediments for EMI shielding and Joule heating, thus promotes the full utilization of the whole MXene industry.

Do Aqueous Suspensions of Smectite Clays Form a Smectic Liquid-Crystalline Phase?

Bottom-up strategies for the production of well-defined nanostructures often rely on the self-assembly of anisotropic colloidal particles (nanowires and nanosheets). These building blocks can be obtained by delamination in a solvent of low-dimensionality crystallites. To optimize particle availability, determination of the delamination mechanism and the different organization stages of anisotropic particles in dispersion is essential. We address this fundamental issue by exploiting a recently developed system of fluorohectorite smectite clay mineral that delaminates in water, leading to colloidal dispersions of single-layer, very large (≈20 μm) clay sheets at high dilution. We show that when the clay crystallites are dispersed in water, they swell to form periodic one-dimensional stacks of fluorohectorite sheets with very low volume fraction (<1%) and therefore huge (≈100 nm) periods. Using optical microscopy and synchrotron X-ray scattering, we establish that these colloidal stacks bear strong similarities, yet subtle differences, with a smectic liquid-crystalline phase. Despite the high dilution, the colloidal stacks of sheets, called colloidal accordions, are extremely robust mechanically and can persist for years. Moreover, when subjected to AC electric fields, they rotate as solid bodies, which demonstrates their outstanding internal cohesion. Furthermore, our theoretical model captures the dependence of the stacking period on the dispersion concentration and ionic strength and explains, invoking the Donnan effect, why the colloidal accordions are kinetically stable over years and impervious to shear and Brownian motion. Because our model is not system specific, we expect that similar colloidal accordions frequently appear as an intermediate state during the delamination process of two-dimensional crystals in polar solvents.

Study of the fatigue delamination behaviour of adhesive joints in carbon fibre reinforced epoxy composites, influence of the period of exposure to saline environment

This work analyses the fatigue delamination and fracture stress behaviour under mode I of adhesive joints made on an epoxy matrix composite material with unidirectional carbon fibre reinforcement and a commercial epoxy-based adhesive. DCB type tests (for mode I) were used with the aim to quantify the influence of the period of exposure to a degradation process in a salt spray chamber, to which the tested samples were subjected, on their fatigue behaviour. For this purpose and after a previous static characterisation of the material in which the critical values of the energy release rate for different exposure periods were determined, the levels of the energy release rate to be applied in the fatigue tests and the exposure periods to be considered (no exposure, exposure during one week and twelve weeks) and a ratio of fatigue stress levels of R = Gmin/Gmax = 0.1 were defined. From this experimental data, the G-N fatigue initiation curves and the G-da/dN growth curves were obtained. The experimental data obtained, in the fatigue initiation phase of the delamination process, have been treated by means of a probabilistic model based on a Weibull distribution, the application of models of these characteristics has allowed a better interpretation of the experimental results obtained. The most relevant result of the work is that, in general, the fatigue limits obtained for the adhesive joint, under mode I fracture, when subjected to a degradation process in a saline environment, do not translate into a relevant loss of its resistance capacity against this fatigue delamination phenomenon, in its initiation phase. On the other hand, the crack growth rates of the material subjected to different periods of exposure to a saline environment are similar and higher than those obtained for the material without exposure.

The delamination of metalized multilayer flexible packaging using a microperforation technique

Multilayer flexible packaging waste is a critical issue in the field of waste management as it is considered a non-recyclable material. One of the solutions to increase its recyclability is the delamination, which allows the recycling of the different polymer layers separately. This study investigated the optimization of the delamination by microperforating this plastic. The diffusion model was described by Fick's first law. The delamination process was tested at three different temperatures (50, 65 and 80 °C) with caustic soda. In addition, the influence of other parameters such as the thickness of aluminium layer, the presence of inks and the use of surfactants was tested. As a result, the microperforation technique improved the delamination rate by decreasing the residence time by 83% at the optimum conditions studied, being the thickness of the metal and the temperature essential factors affecting the process. However, the presence of inks and surfactant had no effect.

Experimental and Numerical Research of Delamination Process in CFRP Laminates with Bending-Twisting Elastic Couplings.

This paper aims at experimental and numerical research of delamination process in carbon/epoxy composite laminates with different fiber orientation angles in stacking sequence exhibiting the bending-twisting elastic couplings. Experimental specimens were subjected to the double cantilever beam (DCB) tests according to the ASTM D5528 regulations. Values of the mode I strain energy release rates were calculated by using three different data reduction schemes: the modified beam theory, the compliance calibration method and the modified compliance calibration. Determination of delamination initiation point was conducted in twofold way: by visual observation of crack tip using high resolution camera and by utilization of the acoustic emission technique. Numerical analyss were prepared in Abaqus/CAE Software environment by using the virtual crack closure technique (VCCT). The numerical beam model consisted of SC8R continuum shell elements. Obtained outcomes revealed that extensive fiber bridging phenomenon occurring during delamination process pronouncedly affected propagation values of strain energy release rate (GIprop) and numerically obtained load-displacement curves. Nevertheless, in initial stage of delamination, results obtained by using the VCCT were in agreement with experimental data. The greatest value of the mode I fracture toughness equal 0.56 N/mm was obtained for the BT45 laminate.

Systematic variation of inorganic additives and their impact on interfacial delamination processes of automotive coating systems

Inorganic fillers incorporated in adhesives for the automotive industry enable both functional and mechanical tuning of adhesive properties. While integral effects of additives are well understood, the individual effects of single components and how they may lead to synergies as well as antagonistic effects remain unclear. Here, we systematically vary the concentration of CaO, CaCO3 and hydrophobic fumed SiO2 to understand individual and combined effects. For this purpose, the inorganic additives were mixed into a model formulation without inorganic additives and compared with a close to real application one-component epoxy adhesive, which also contained these fillers. The water uptake of the filled adhesives was measured with EIS and the results were compared with findings from cataplasma tests under atmospheric conditions. These results indicated that hydrophobic SiO2 can result in accelerated water uptake, although the opposite would be expected due to the more hydrophobic surface coating. In addition, blistering was observed on all galvanized steel (ZE) surfaces, while filiform corrosion was observed on all hot-dip galvanized Zn-Al-Mg steels (ZM). Cataplasma tests in oxygen-depleted and oxygen-rich atmospheres allowed to identify interfacial delamination processes. Our results showed that CaO can cause osmotic blistering and accelerate the diffusion of water into the adhesive due to a local increase in pH near the hydrated CaO particles, while CaCO3 reduces water diffusion. However, coating defects may occur due to the addition of CaCO3, leading to increased cathodic blistering. A strategy for improving beneficial and synergistic effects is discussed.

Chemical-free pressure washing system as pretreatment to harvest cathode materials

Recycling cathode materials from spent lithium-ion batteries has the potential to reduce damages to the environment and human health due to hazardous waste treatment, and mitigate supply risks of raw materials. Related political incentives or regulations have led to increased research and development efforts on cathode recycling. Promising approaches include direct recycling and hydrometallurgical processes, where delamination is the first step after collection of cathodes. In this study, we examined a pressure washing system’s ability to harvest cathode materials. A high-pressure water jet provides strong forces to overcome the adhesion provided by organic binders. Four factors (water pressure, distance between nozzle and cathode, incident angle of water jet, and nozzle type) were investigated using a 34-1 fractional factorial design to screen important parameters and find the optimal conditions. Compared with other delamination processes where chemical reagents and heating are involved, the chemical-free pressure washing system can achieve separation in a few seconds (∼74 min/m2) at room temperature, which remarkably improves the efficiency of delamination. The particle size of recycled products (D50 of 31.87 μm) is significantly reduced without Al contamination from current collectors or morphological damages. In addition, three types of recycled cathode materials were used as inputs for the acid leaching process. High leaching efficiencies of lithium (>90 %) and cobalt (>85 %) suggest that the pressure washing system could be a practical, economical, and eco-friendly pretreatment process to harvest cathode materials.

Synthesis of Large-Area MXenes with High Yields through Power-Focused Delamination Utilizing Vortex Kinetic Energy.

Evaluating the delamination process in the synthesis of MXenes (2D transition metal carbides and nitrides) is critical for their development and applications. However, the preparation of large defect‐free MXene flakes with high yields is challenging. Here, a power‐focused delamination (PFD) strategy is demonstrated that can enhance both the delamination efficiency and yield of large Ti3C2T x MXene nanosheets through repetitive precipitation and vortex shaking processes. Following this protocol, a colloidal concentration of 20.4 mg mL–1 of the Ti3C2T x MXene can be achieved after five PFD cycles, and the yield of the basal‐plane‐defect‐free Ti3C2T x nanosheets reaches 61.2%, which is 6.4‐fold higher than that obtained using the sonication–exfoliation method. Both nanometer‐thin devices and self‐supporting films exhibit excellent electrical conductivities (≈25 000 and 8260 S cm‐1 for a 1.8 nm thick monolayer and 11 µm thick film, respectively). Hydrodynamic simulations reveal that the PFD method can efficiently concentrate the shear stress on the surface of the unexfoliated material, leading to the exfoliation of the nanosheets. The PFD‐synthesized large MXene nanosheets exhibit superior electrical conductivities and electromagnetic shielding (shielding effectiveness per unit volume: 35 419 dB cm2 g–1). Therefore, the PFD strategy provides an efficient route for the preparation of high‐performance single‐layer MXene nanosheets with large areas and high yields.

Dynamic buckling-driven delamination of thin films

This paper studies the dynamic buckling-driven delamination of thin films. A 1D case of an initial delamination in a thin film bonded to a rigid substrate through a cohesive interface and subjected to thermally-induced stresses is investigated. Emphasis is placed on the dynamic nature of the compressive delamination process. For that purpose, a 1D problem and its weak form are formulated based on the cohesive interface approach, the well-established geometrically nonlinear Bernoulli-Euler beam model for the thin film, and Newtonian dynamics. Based on this formulation, the Finite Element numerical counterpart of the model is derived to analyze and capture the dynamic effects of the mutual and coupled dynamic evolution of the buckling and delamination nonlinear phenomena. The innovative aspects of the formulation are the consideration of the current problem in a dynamic framework and the consideration of the inertial forces. In that sense, it innovates by the combination of methodologies (cohesive interfaces, Bernoulli-Euler beam theory, geometrical nonlinearity, Newtonian dynamics) and by the application of the combined methodology to investigate a realistic problem that was not studied in this framework before. The model is used to examine the coupled nonlinear dynamic structural response. It shows that the mutual and coupled evolution of the buckling and delamination phenomena may lead to a simultaneous and unstable evolution of the two, which results in significant dynamic effects. A detailed comparison of the dynamic results with a reference static solution highlights the role played by the inertial forces and the time scales associated with the dynamic instability. The buckling-driven delamination then evokes a significant time dependent evolution of displacements, energies, delamination length, reactions, and internal forces. The sensitivity to changes in the parameters defining the problem is also demonstrated. The novelty of this paper is the consideration of the Newtonian dynamics in the problem of buckling-driven delamination of thin film systems and the investigation and description of their significant dynamic effects on the structural response. This study establishes and demonstrates the significance of the dynamic aspects of the buckling-driven delamination process in thin film systems.

Nanofriction Properties of Mono- and Double-Layer Ti3C2Tx MXenes.

Unique structure and ability to control the surface termination groups of MXenes make these materials extremely promising for solid lubrication applications. Due to the challenging delamination process, the tribological properties of two-dimensional MXenes particles have been mostly investigated as additive components in the solvents working in the macrosystem, while the understanding of the nanotribological properties of mono- and few-layer MXenes is still limited. Here, we investigate the nanotribological properties of mono- and double-layer Ti3C2Tx MXenes deposited by the Langmuir-Schaefer technique on SiO2/Si substrates. The friction of all of the samples demonstrated superior lubrication properties with respect to SiO2 substrate, while the friction force of the monolayers was found to be slightly higher compared to double- and three-layer flakes, which demonstrated similar friction. The coefficient of friction was estimated to be 0.087 ± 0.002 and 0.082 ± 0.003 for mono- and double-layer flakes, respectively. The viscous regime was suggested as the dominant friction mechanism at high scanning velocities, while the meniscus forces affected by contamination of the MXenes surface were proposed to control the friction at low sliding velocities.

Variscan Inheritance Induces Alpine Upper Crustal Delamination in East Spanish‐Portuguese Central System

AbstractThe Spanish‐Portuguese Central System (SPCS) is an Alpine Mountain range with crystalline basement characterized by a two‐layer rheological structure. This structure formed after primary (protolith) and secondary (tectonometamorphic) processes during the extensional collapse of the Variscan Orogen. The SPCS structure is usually controlled by foreland‐directed thrusts and strike‐slip faults. However, the eastern SPCS is dominated by NW‐directed, imbricate backthrusts and lacks the main thrust directed to the foreland basin located southeast of the mountain range (Madrid Cenozoic Basin). The SPCS exhibits a crustal root (&gt;40 km depth) supporting SE‐directed crustal‐scale thrusting. Alpine backthrusts sole into an SE‐dipping décollement within the Variscan basement. Variscan extension‐related structures parallel the SE‐dipping geometry of Alpine backthrusts, so they provided favorably oriented rheological weaknesses to accommodate Alpine shortening. Backthrusts geometry, their hanging wall position within the fault that raised the SPCS and gravity modeling support an Alpine crustal delamination process. Tectonic wedging and delamination of the more competent basement occurred in the footwall of Variscan extensional faults (Daurius domain), which enforced the shearing off of a rheologically weaker upper layer of the crust, located in the hanging wall of the Variscan extensional faults (Arriaca domain) by inverting Variscan extensional faults. This led to NW‐directed incipient continental subduction of the weaker crust. Intraplate subduction and crustal delamination can be independent from lithosphere‐scale inheritance and be conditioned by structural inheritance in the overlying crust. Alpine shortening for the Cretaceous cover is around 17.7 km (10.5% shortening), and 11 km (7%) for the upper‐lower crust limit.

Fatigue damage assessment of metal sandwich panels under four-point bending cyclic loading conditions

This paper aims to investigate the effects on metal sandwich panels with different dimple core designs using four-point bending simulation under constant and variable amplitude loading. A core design with cavity and porosity in the body structure was found to reduce the panel structural integrity. This would lead to unstable bonding between the panels and initiate an early delamination process. Sandwich panels consisting of AR500 as the outer layer and magnesium alloy AZ31B as the core material were simulated using dimples of different diameters and depths; 5.0 / 2.5 mm, 6.0 / 3.0 mm, 7.0 / 3.5 mm and 8.0 / 4.0 mm, at a range of 50 % to 90 % of maximum strength, based on the lowest material strength for cyclic loading. The results indicate that the highest fatigue damage of 85 % occurred at the effective region of the dimple area, where force was applied to the panel. A hemispherical dimple core 6.0 mm in diameter and 3.0 mm in depth produced a reduction of failure at the effective zone of more than 85 % and the regression coefficient was over 0.89. This illustrates that a large dimple size was vulnerable to early delamination failure at the dimple region.

Ultralarge Flakes of Ti3C2Tx MXene via Soft Delamination.

Two-dimensional (2D) titanium carbide MXene (Ti3C2Tx) has attracted significant attention due to its combination of properties and great promise for various applications. The size of the 2D sheets is a critical parameter affecting multiple properties of assembled films, fibers and 3D structures. The increased lateral size of MXene flakes can benefit not only their assemblies by improving the interflake contacts and alignment but also fundamental studies at the individual flake level, allowing for facile patterning and investigation of intrinsic physical properties of MXenes. Increasing the average size of the parent MAX phase is one of the strategies previously used to increase the flake size of the resultant MXene. Here, we show that the protocol used for the next step of the synthesis procedure, delamination of multilayer MXene into individual nanosheets, significantly affects the lateral size of the resultant flakes. We developed a soft delamination approach, which prevents fracture of flakes and preserves their size. Combining this approach with the large-grain Ti3AlC2 MAX phase precursor, we achieved individual flakes of up to 40 μm in lateral size. These flakes can be used for patterning multiple contacts and fabrication of field-effect transistors for multiprobe electrical characterization and other measurements. These findings indicate the importance of controlling the delamination process in order to achieve large MXene flakes and improve properties of MXene-based materials and devices.