Layered Ternary Carbide Research Articles

Manufacturing of High Purity Cr2AlC MAX Phase Material and Its Characterization

AbstractPresent study discusses about a technique for producing high-purity Cr2AlC MAX phase materials and gaining insight into their thermal behavior for high-temperature applications. The research conducted involved synthesizing a pure layered ternary carbide Cr2AlC MAX phase material by mixing powders of Chromium, Aluminum, and Carbon and then subjecting them to two-step pressureless sintering process in argon atmosphere. First step involves the annealing of ball-milled mixture at 750 °C for 2 h followed by the second step in which the annealed mixture is subjected to heat-treatment at 1350 °C for 2 h. Analysis using XRD and Raman techniques revealed that the synthesized product consists of Cr2AlC phase, without any impurities. SEM studies confirmed that the Cr2AlC had a layered topography, while EPMA analysis indicated that the atomic percentage of Cr, Al, and C was consistent with the XRD phase analysis. XPS investigations confirmed the presence of Cr-C bonds representing Mn+1Xn of the MAX phase material. TG-DSC results showed an approximately 2% increase in weight. The Cr2AlC phase exhibited an endothermic pattern below 725 °C, an exothermic pattern above it, and did not decompose up to 1400 °C in vacuum environment. High-temperature XRD analysis at various temperatures also confirmed no formation of Al2O3 or CrO impurity compounds.

Soliton interaction in a MXene-based mode-locked fiber laser.

MXenes are a class of two-dimensional layered structure ternary metal carbide or/and nitride materials. Recently, the MXene V2CTx has demonstrated excellent long-term stability, strong saturable absorption, and fast optical-switching capability, used to generate Q-switched and ultrashort pulsed lasers. However, bound-state fiber lasers based on V2CTx have not been reported yet. In this study, V2CTx is combined with a D-shaped fiber to form a saturable absorber device, whose modulation depth is measured to be 1.6%. By inserting the saturable absorber into an Er-doped fiber laser, bound states with different soliton separation and munbers are successfully obtained. Additionally, bound states with a compound soliton structure, such as the (2 + 2)- and (2 + 1)-type, are also realized. Our findings show that V2CTx can be developed as an efficient ultrafast photonics candidate to further understand the complex nonlinear dynamics of bound-state pulses in fiber lasers.

Multifunctional Ti3AlC2-Based Composites via Fused Filament Fabrication and 3D Printing Technology

MAX phase, as a group of layered ternary carbides and nitrides exhibiting combined properties of metallic and ceramic materials, attracts increasing interest because they own exceptionally chemical, physical, electrical, thermal, and mechanical properties. In the present paper, a novel Ti3AlC2-based green part was manufactured by extrusion-based fused filament fabrication (FFF) and 3D printing technologies. The morphology, thermal/electrical conductivity, thermal stability, electromagnetic interference (EMI) shielding effectiveness (SE), and mechanical properties of Ti3AlC2/binder with the volume ratio of 1:1 were investigated. The tensile and compressive strengths and elongation are measured to be 8.29 MPa and 18.20%, 44.90 MPa and 33.76%, respectively. The morphology of the filament reveals that Ti3AlC2 powders are well bonded by the thermoplastic binder. More importantly, the composite shows good thermal and electrical conductivities together with the excellent EMI shielding effectiveness, which is of great potential in the practical applications as conductor, heat dissipating, anti-static, and EMI shielding materials. The successful fabrication of Ti3AlC2-based composites via FFF-based 3D printing technology is beneficial to develop other MAX phase products with complex geometries and additional functionalities.

Q-switched and noise-like mode-locked fiber laser based on ternary transition-metal carbide Nb2AlC saturable absorber

The saturable absorption of layered ternary transition-metal carbide (MAX) Nb2AlC is investigated in this work. Nb2AlC-based saturable absorber (SA) device is prepared and applied in an Er-doped fiber laser (EDFL). The EDFL can generate Q-switched and noise-like mode-locked pulses based on the excellent Nb2AlC SA. The EDFL operates in a Q-switched pulses mode state when the pump power is up to a threshold value of 50 mW. For the Q-switched pulse, the maximum single pulse energy is 66 nJ. The laser pulse generation mode switches to a noise-like mode-locked state when the pump power increases to 170 mW. The coherent spike duration is 2.8 ps and the corresponding maximum single pulse energy is 1.5 nJ at a pump power of 439 mW. A preliminary review of available literature indicates no reports of layered ternary carbide Nb2AlC as SA in an EDFL to generate switchable laser pulse modes. Results of this study suggest that ternary MAX Nb2AlC can be a remarkable nonlinear optical (NLO) device to explore switchable laser pulse generation modes and can encourage further studies on the ternary transition-metal carbides.

Elucidating the role of Ti3AlC2 and Ti3SiC2 in oxidation mechanisms of MgO–C refractories

Two types of Ti-containing layered ternary carbides, Ti3AlC2 and Ti3SiC2, were incorporated to fabricate low-carbon MgO–C refractories, and the oxidation behaviors after exposure to 1100 °C and 1500 °C were investigated in the present work. The oxidation resistances of the samples with Ti3AlC2/Ti3SiC2-adding have an approximately 50% increase over that of conventional MgO–C with 4 wt% graphite. CT results indicated stress cracks occurred in the sample with Ti3AlC2/Ti3SiC2-adding after exposure to 1100 °C, it was attributed to the anomalous oxidation behavior of Ti3AlC2/Ti3SiC2 grains and the formation of TiO2 with volume expansion at ∼600 °C according to TG and corresponding XRD results. At 1500 °C, a white reaction product layer was formed at the boundaries of oxide/non-oxide layers of the sample with Ti3AlC2/Ti3SiC2-adding, which was confirmed as magnesium titanate spinel. The oxidation behaviors of the samples with Ti3AlC2/Ti3SiC2-adding showed a mass gain process owning to the further disintegration of Ti3AlC2/Ti3SiC2. Furthermore, the oxidation mechanism and the roles of Ti3AlC2/Ti3SiC2 grains were elucidated in detail.

Synthesis of MAX Phase Nanofibers and Nanoflakes and the Resulting MXenes.

Layered ternary carbides and nitrides, also known as MAX phases, have attracted enormous attention for many applications, especially as precursors to produce 2D metal carbides and nitrides called MXenes. However, it is still challenging to tune and control the shape/morphology of MAX phase particles at the nanoscale, as they are typically manufactured as large grains using ceramic technology. Herein, nanostructured Ti-Al-C MAX phases with fine-tuned morphology of nanofibers and nanoflakes are prepared by using 1D and 2D carbon precursors at a synthesis temperature of 900°C. The nanostructured MAX phases are used as precursors to produce nanosized multilayered MXenes, with a considerably shorter etching time and a low reaction temperature. These nanosized MXenes exhibit good electrochemical lithium-ion storage properties and a pseudocapacitive electrochemical signature. The obtained Ti2 CTx MXene electrode can deliver delithiation capacity of 300 mAh g-1 at low rates and 100 mAh g-1 when the lithiation/delithiation cycle happens within 30 s. Availability of nanoscale MAX phases and MXene nanoflakes with small lateral size may open new opportunities for both classes of materials.

Lithium-ions uptake by MAX/graphene hybrid

Combining nanoparticles in well-designed architecture with complementary properties is an attractive strategy used for developing multi-functional, high-performance materials. Herein, to explore the mechanism of Li-ions uptake and storage potential of layered ternary carbides (MAX phases), we report on the Ti2SC and Ti3SiC2 with two-dimensional (2D)-reduced graphene oxide (rGO) that electrically connects MAX phase particles. The heterostructure formation was achieved through in-situ wet chemical processing. The method efficiently prevented restacking of rGO nanosheets, aggregation of MAX particles, and generated a porous heterostructure permeable for electrolyte. This facilitated the electrolyte transport and the access of ions to the electrode. In addition, there was a strong coupling effect between MAX phase compound and rGO in these hybrids. When tested as anodes for Li-ion batteries, the hybrids displayed high reversible capacity, very good rate performance, and excellent cycling stability. Specifically, the capacity of in-situ synthesized Ti2SC/rGO hybrid showed an increasing trend during cycling. After a few initial cycles, 576 mAh·g−1 was achieved after 500 charge/discharge cycles with a current of 400 mA·g−1. This work further demonstrates the Li-ion storage potential of MAX phases and suggests the need for further exploration of this large family of layered materials.Graphical abstract

Growth kinetics of tin whiskers in Ti2SnC phase

The extrusion of Sn whiskers from Ti2SnC phase, a layered ternary carbide ceramic MAX phase, has ultrafast whisker growth behaviors and good experimental repeatability. This makes MAX phase an ideal research platform for the investigation of metallic whiskers. This work aims at revealing the growth kinetics of Sn whiskers from Ti2SnC substrate, which still does not exist. By conducting a quantitative analysis on the whisker growth behavior, three stages of the growth of Sn whiskers on the Ti2SnC substrate are identified: nucleation, germination and saturation. Moreover, the function of volume change versus cultivation time is well fitted using the Avrami equation, implying that the growth of Sn whiskers from Ti2SnC substrate follows a general crystallization pattern.

The Key Role of Tin (Sn) in Microstructure and Mechanical Properties of Ti2SnC (M2AX) Thin Nanocrystalline Films and Powdered Polycrystalline Samples.

Layered ternary Ti2SnC carbides have attracted significant attention because of their advantage as a M2AX phase to bridge the gap between properties of metals and ceramics. In this study, Ti2SnC materials were synthesized by two different methods—an unconventional low-energy ion facility (LEIF) based on Ar+ ion beam sputtering of the Ti, Sn, and C targets and sintering of a compressed mixture consisting of Ti, Sn, and C elemental powders up to 1250 °C. The Ti2SnC nanocrystalline thin films obtained by LEIF were irradiated by Ar+ ions with an energy of 30 keV to the fluence of 1.1015 cm−2 in order to examine their irradiation-induced resistivity. Quantitative structural analysis obtained by Cs-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) confirmed transition from ternary Ti2SnC to binary Ti0.98C carbide due to irradiation-induced β-Sn surface segregation. The nanoindentation of Ti2SnC thin nanocrystalline films and Ti2SnC polycrystalline powders shows that irradiation did not affect significantly their mechanical properties when concerning their hardness (H) and Young’s modulus (E). We highlighted the importance of the HAADF-STEM techniques to track atomic pathways clarifying the behavior of Sn atoms at the proximity of irradiation-induced nanoscale defects in Ti2SnC thin films.

Investigation of AC Electrical Properties of MXene-PCL Nanocomposites for Application in Small and Medium Power Generation

The paper examined Ti3C2Tx MXene (T—OH, Cl or F), which is prepared by etching a layered ternary carbide Ti3AlC2 (312 MAX-phase) precursor and deposited on a polycaprolactone (PCL) electrospun membrane (MXene-PCL nanocomposite). X-ray Diffraction analysis (XRD) and Scanning Electron Microscopy (SEM) indicates that the obtained material is pure Ti3C2 MXene. SEM of the PCL-MXene composite demonstrate random Ti3C2 distribution over the nanoporous membrane. Results of capacitance, inductance, and phase shift angle studies of the MXene-PCL nanocomposite are presented. It was found that the frequency dependence of the capacitance exhibited a clear sharp minima in the frequency range of 50 Hz to over 104 Hz. The frequency dependence of the inductance shows sharp maxima, the position of which exactly coincides with the position of the minima for the capacitance, which indicates the occurrence of parallel resonances. Current conduction occurs by electron tunneling between nanoparticles. In the frequency range from about 104 Hz to about 105 Hz, there is a broad minimum on the inductance relationship. The position of this minimum coincides exactly with the position of the maximum of the phase shift angle—its amplitude is close to 90°. The real value of the inductance of the nanocomposite layer was determined to be about 1 H. It was found that the average value of the distance over which the electron tunnels was determined with some approximation to be about 5.7 nm and the expected value of the relaxation time to be τM ≈ 3 × 10−5 s.

Shape Control of MAX Phases by Biopolymer Sol-Gel Synthesis: Cr2GaC Thick Films, Microspheres, and Hollow Microspheres.

The class of MAX phases represents intriguing materials, as they combine ceramic and metallic properties quite exotically. Although many potential areas of application have been identified, a commercialization is still to be realized. This is particularly odd considering their existence of more than 60 years, however, less so considering the common synthesis techniques used. In fact, MAX phases are typically studied in either bulk or thin films, considerably hindering their integration into highly functional applications. Here, a facile and versatile sol-gel-based approach for the biopolymer-templated synthesis of MAX phase Cr2GaC is introduced, capable of preparing the layered ternary carbide in a variety of technological useful shapes. We demonstrate for the first time how our wet chemical synthesis strategy immensely increases the accessibility of specific shapes and morphologies via the targeted synthesis of thick films, microspheres, and hollow microspheres.

Ion Implantation Induced Structural Modifications and Functionalization of Ti3C2Tx MXenes

MXenes are single or few-layered two-dimensional (2D) transition metals carbides and/or nitrides successfully synthesized in 2011, with chemical composition Mn+1XnTx, where M stands for an early transition metal, X is C and/or N, Tx are a surface terminations and n = 1, 2, or 3 [1]. These materials are considered as promising candidates in many applications such as energy storage, sensing, catalysis, and optoelectronics. For instance, MXenes combine high conductivity and hydrophilicity making them interesting candidates for applications involving aqueous media and requiring good electronic properties or easy processing. Moreover, they exhibit a wide chemical variability thanks to their parent MAX phases precursors, a 150-plus member family of layered ternary carbides or nitrides with chemical composition Mn+1AXn (where the A-element mainly belong to the columns 13 and 14 of the periodic table). This offers the unique opportunity to design the MXenes on demand, with considerably different physicochemical properties for target applications [2-4]. Tuning the MXene properties is also possible through the manipulation of their surface termination groups T (i.e., T = −F, −OH, −O, or −Cl). The crucial role of the surface groups has recently triggered many studies aiming at controlling and characterizing the MXene surface structure/chemistry mainly by using different etching protocols [5]. However, the nature of the surface groups, inherited from the A element exfoliation step of the MAX phases by chemical reactions, is hardly tunable by this mean except by changing the etching protocole which might have significant impact on the quality of the synthetized MXenes.Here, we demonstrate that medium energy ion implantation can be used to modify the MXene surface functionalization, through the controlled formation of structural defects and the incorporation of foreign species in Ti3C2Tx thin films fabricated by spin coating (Fig.1 a-b). Defects created by Mn implantation in a wide fluence range (1x1014-5x1016 cm-2) are characterized at different depths by XPS on Ti2p core-level spectra, ToF-SIMS and EELS analyses. For the latest, we use an original approach that we have developed [6], allowing an estimation of the level of damage in the material by studying the C-K edge. Our results show that the 60 keV Mn implantation leads to successful incorporation of Mn in the Ti3C2 thin film. This is accompanied by the structural distortion of the Ti-C layers as evidenced by EELS experiments (Fig. 1c), preferential Ti sputtering as compared to C without any significant amorphization or phase transformation up to a fluence of 1x1016 cm-2. However, for the highest fluence studied (5x1016 cm-2), complete amorphization was observed. For the subthreshold amorphization fluence, the study of the fine structure of the O K-edge and of the electron diffraction pattern suggest the formation of extended defects in the Ti layers including the occupation of the defective Ti sites by oxygen, leading to local environment for the oxygen atoms like graphene oxide. Finally, our results show that the number of defects can be directly and in a reproductible way tunned by the implantation fluence.[1] M. Naguib, M. Kurtoglu, V. Presser, J. Lu, J. Niu, M. Heon, L. Hultman, Y. Gogotsi, M.W. Barsoum, Adv. Mater. 2011, 23, 4248−4253[2] Y. Gogotsi, B. Anasori, ACS Nano 2019, 13, 8491−8494[3] Q. Tao, M. Dahlqvist, J. Lu, S. Kota, R. Meshkian, J. Halim, J. Palisaitis, L. Hultman, M. W. Barsoum, P. O. Persson, J. Rosen, Nat. Commun. 2017, 8, No. 14949.[4] B. Anasori, C. Shi, E.J. Moon, Y. Xie, C.A. Voigt, P. R. Kent, S.J. May, S.J. Billinge, M.W. Barsoum, Y. Gogotsi, Nanoscale Horiz. 2016, 1, 227−234[5] M. Benchakar, L. Loupias, C. Garnero, T. Bilyk, C. Morais, C. Canaff, N. Guignard, S. Morisset, H. Pazniak, S. Hurand, et al. Appl. Surf. Sci. 2020, 530, No. 147209[6] T. Bilyk, M. Benchakar, M. Bugnet, L. Loupias, P. Chartier, H. Pazniak, M.-L. David, A. Habrioux, S. Celerier, J. Pacaud, and V. Mauchamp, J. Phys. Chem. C (to be published, https://dx.doi.org/10.1021/acs.jpcc.0c06798) Figure 1

Ab initio screening of metallic MAX ceramics for advanced interconnect applications

The potential of a wide range of layered ternary carbide and nitride Mn+1AXn [an early transition metal (M), an element of columns 13 or 14 of the periodic table (A), and either C or N (X)] phases as conductors in interconnect metal lines in advanced complementary metal-oxide-semiconductor (CMOS) technology nodes has been evaluated using automated first-principles simulations based on density-functional theory. The resistivity scaling potential of these compounds, i.e., the expected sensitivity of their resistivity to reduced line dimensions, has been benchmarked against Cu and Ru by evaluating their transport properties within a semiclassical transport formalism. In addition, their cohesive energy has been assessed as a proxy for the resistance against electromigration and the need for diffusion barriers. The results indicate that numerous MAX phases show promise as conductors in interconnects of advanced CMOS technology nodes.

Synthesis and characterization of submicro-sized V2AlC ceramics by a two-step modified molten salt method

High-purity ternary layered carbide V2AlC powders have been prepared by a two-step modified molten salt method, i.e. by firstly synthesizing V2C with V and C powders at 900 °C, followed by preparing V2AlC with V2C and Al powders as reactants at 900–950 °C in molten (Na,K)Cl. The average particle distribution of V2AlC powders was estimated to be ~400 nm. Molten salt as a reaction medium could promote the synthesis of V2C and V2AlC at lower temperatures. The synthesizing mechanisms of V2C and V2AlC in molten salts have also been discussed.

Effect of grain orientation on the compressive response of highly oriented MAX phase Ti3SiC2

The MAX phases comprise of a group of layered ternary carbides that exhibit unique mechanical properties which bridge the gap between their metal and ceramic constituents. To study the effects of the global grain orientation, Ti, Si and TiC powders were hot pressed to synthesize highly oriented bulk Ti3SiC2. X-ray diffraction (XRD) was used to verify the grain orientation and a Lotgering factor of 0.87 with respect to the c-axis was obtained. Prepared Ti3SiC2 samples have been compressed in two orientations, loading along the c-axis (∥c-axis) and perpendicular to the c-axis (⊥c-axis) at 10−3 s−1 using a standard load frame and at 102 s−1 using a Kolsky (split-Hopkinson) bar. The average compressive strength along the ⊥c-axis orientation was 761 MPa under quasi-static conditions and 987 MPa under dynamic loading, exhibiting a 30% increase on average. The ∥c-axis orientation exhibited no rate dependence in compressive strength; however both orientations exhibited an increase of strain at failure under dynamic conditions by over 0.5%, on average. The orientation-dependent failure behavior at different strain rates were examined using high-speed imaging and 2D digital image correlation (DIC) during loading and via scanning electron microscopy (SEM) post-mortem. Results indicate that the ⊥c-axis fracture surface exhibited a mixture of transgranular and intergranular cracks, kink bands and delaminations, whereas ∥c-axis was limited to a combination of intergranular and transgranular cracks. Such fracture distinctions due to the availability (or lack thereof) for kink band formation appear to be responsible for the anisotropic compressive behavior.

Covalent Surface Alteration of MXenes and Its Effect on Superconductivity

Surface functional groups such as F, O, and OH attached to MXenes have a profound impact on the electronic properties. Generally, MXenes are synthesized by the aqueous acidic etching of the MAX phase, and these functional groups are inherently incorporated during the synthesis. Recently, covalent surface modification of MXene has been demonstrated at low temperature using molten inorganic salts.

On the formation, structural and mechanical characterization of nanolayered Zr2AlC MAX phase via aluminum molten infiltration

This research study aimed to investigate the synthesis, microstructural and mechanical characterization of novel Zr-based layered ternary carbide, Zr2AlC MAX phase, by using liquid aluminum infiltration from ZrC preform. For this purpose, a stoichiometric mixture of high-purity powders of ZrH2 and C with a molar-ratio of 2:1 was subjected to intense milling. Infiltration of molten Al to mixed-powders was performed in different conditions. The morphological observation and mechanical behavior manufactured samples were identified by X-ray diffractometry, scanning electron microscopy and microhardness measurements. The experimental findings confirmed that after an optimum infiltrating of 5 h, the Zr2AlC MAX phase with Vickers hardness of 4.5 GPa and fracture toughness of 23 MPa.m0.5 can be achieved. Conversion of ZrC preform and liquid Al during infiltration occurred directly in a single-stage manner without formation of impurity phases. The investigation results revealed that this approach is innovative and can constitute an effective strategy for manufacturing single-phase Zr2AlC with nanolaminated structure and suitable morphology.

Ti₃SiC₂/Carbon Nanofibers Fabricated by Electrospinning as Electrode Material for High-Performance Supercapacitors.

As an Mn+1AXn phase ternary layered carbide, Ti₃SiC₂ possesses the advantages of both excellent stability and high electrical conductivity, which are considered to be promising electrode materials for supercapacitors. Ti₃SiC₂/Carbon nanofiber composites with one-dimensional nanostructures were successfully synthesized via electrospinning. Systematic electrochemical tests showed that the Ti₃SiC₂/Carbon composite possesses a large specific capacitance of 133.1 F/g at the current density of 1 A/g, high rate capability of 113.7% capacitance retention from 1 to 10 A/g, and low resistance of 1.07 Ω. After assembling the asymmetrical supercapacitor, Ti₃SiC₂/Carbon provides the energy density of 7.02 Wh/kg at the power density of 140 W/kg. In addition, Ti₃SiC₂/Carbon composite is highly stable, with 74.6% capacity retention after 4000 cycles. Ti₃SiC₂/Carbon's superior electrochemical properties are ascribed to the 1D nanowire structure and the high specific surface area. Ti₃SiC₂/Carbon is a prospective electrode material for future supercapacitors.

Theoretical investigations on structural and thermo-mechanical properties of layered ternary carbide Th–Al–C systems

With the concept of accident tolerant fuel systems being proposed, the new generation of nuclear fuels have attracted wide attention. In this work, a novel type of layered ternary carbides Th–Al–C are found by first-principles calculations via the density functional theory and the structures, electronic structures, thermal and mechanical properties are predicted. The calculation results show that all the Th–Al–C materials inspected are elastically and dynamically stable. From the decomposition reaction analysis, the ThAl3C3 phase is thermodynamically stable and Th2Al3C4 might also be obtained in the laboratory. These compounds have good elastic moduli and thermal properties. Th2AlC is a ductile material whereas others are brittle. The shear modulus and Debye temperature of Th–Al–C series decreases as the thickness of Th–C or Al–C slabs increases. The lattice thermal conductivity of the Th–Al–C system increases in the sequence of Th3Al4C6, Th2AlC, Th2Al3C5, Th2Al4C5, Th3Al3C5, Th4Al3C6, Th2Al3C4 and ThAl3C3. Moreover, both the ThAl3C3 and Th2Al3C4 not only have satisfactory mechanical properties, but also exhibit excellent thermal properties, which are comparable to those of Zr/Hf–Al–C compounds. The current theoretical investigations may promote the exploration of the novel layered ternary actinide carbides and may provide a new clue for finding high performance nuclear fuels.

Q-Switched YDFL generation by a MAX phase saturable absorber

A stable Q -switching pulse train in a ytterbium-doped fiber laser (YDFL) cavity was generated using MAX-polyvinyl alcohol (PVA) thin film, which is composed of layered ternary metal carbide ( T i 3 A l C 2 ) as a passive saturable absorber (SA) and incorporates it in the laser cavity. MAX-PVA SA was fabricated using a solution-casting method. A self-started pulse train with a maximum repetition rate of 92 kHz and a decreasing pulse width (from 3.5 to 1.92 µs) with increasing pump power (from 214 to 260 mW) was produced. The laser’s stability was notable, with a high signal-to-noise ratio of 52 dB obtained at the highest repetition rate of 92 kHz. This finding suggests that MAX-SA could be used as an alternative to other SAs in Q -switched fiber lasers.