Ti2AlC MAX Phase Research Articles

Influence of cutting damage on the bending strength of Ti<sub>2</sub>AlC MAX phase machinable ceramics

Ti2AlC MAX phase ceramics are excellent candidates for high-temperature heat resistant materials. In addition, they are machinable using cemented carbide tools. However, heavy machining induces many surface cracks, reducing the mechanical strength and reliability of ceramic parts. Herein, we investigated the influence of the machining process on the bending strength and microstructure of Ti2AlC ceramics. Nearly fully dense Ti2AlC ceramics with elongated grains were machined using a carbide end mill in brittle mode, producing numerous cracks; however, the roughness of the ceramic was similar to that of tool steel cut in ductile mode. Despite its rough surface, the bending strength of the machined Ti2AlC was only slightly lower than that of polished Ti2AlC. The cracks in the machined Ti2AlC ceramics were induced with a kinking structure; however, they stopped at a length equivalent to one grain. The minimum strength of the machined Ti2AlC ceramics with a fracture toughness of 6.9 MPa·m1/2 was estimated by assuming a machining through-crack shape that was as deep as the maximum grain size. Cutting damage was limited to a single grain; thus, the bending strength of the machined Ti2AlC was not significantly reduced.

Effect of Substitutional Oxygen on Properties of Ti3 C2 Tx MXene Produced Using Recycled TiO2 Source.

MXenes are an emerging class of 2D materials with unique properties including metallic conductivity, mechanical flexibility, and surface tunability, which ensure their utility for diverse applications. However, the synthesis of MXenes with high crystallinity and atomic stoichiometry in a low-cost process is still challenging because of the difficulty in controlling the oxygen substitute in the precursors and final products of MXenes, which limits their academic understanding and practical applications. Here, a novel cost-effective method is reported to synthesize a highly crystalline and stoichiometric Ti3 C2 Tx MXene with minimum substitutional oxygen impurities by controlling the amount of excess carbon and time of high-energy milling in carbothermal reduction of recycled TiO2 source. The highest used content (2wt%) of excess-carbon yields TiC with the highest carbon content and minimal oxygen substitutes, which leads to the Ti3 AlC2 MAX phase with improved crystallinity and atomic stoichiometry, and finally Ti3 C2 Tx MXene with the highest electrical conductivity (11738 S cm-1 ) and superior electromagnetic shielding effectiveness. Additionally, the effects of carbon content and substitutional oxygen on the physical properties of TiC and Ti3 AlC2 are elucidated by density-functional-theory calculations. This inexpensive TiO2 -based method of synthesizing high-quality Ti3 C2 Tx MXene can facilitate large-scale production and thus accelerate global research on MXenes.

Structural, physical, wear and anticorrosive properties of electroactive polyamide/Ti3C2Tx MXene nanocomposite

The 2D few-layered Ti3C2Tx MXene nanosheets have been prepared by etching and delamination of aluminium layers from the Ti3AlC2 MAX phase. The electroactive polyamide (EPA)/Ti3C2Tx MXene nanocomposites (NCs) containing (0.6, 1.2 and 1.8 wt%) MXene were prepared via in-situ oxidative coupling polymerization. The structural properties of NCs indicated close interaction between EPA and MXene resulting in improvement in physical properties such as electrical conductivity, thermal stability and adhesion strength. The surface roughness and water contact angle were not affected by the addition of Ti3C2Tx MXene in the EPA matrix. The tribological properties were improved for NCs coated samples. The corrosion study revealed the excellent corrosion protection ability of EPA/Ti3C2Tx MXene NCs containing 1.2 wt% MXene.

Green, HF-Free Synthesis of MXene Quantum Dots and their Photocatalytic Activity for Hydrogen Evolution.

A general methodology to prepare MXene quantum dots (MxQDs) with yields over 20% by liquid-phase laser ablation of the MAX phase is reported. Mechanical and thermal shock by 532nm laser pulses (7ns fwhp, 50mJ × pulse-1 , 1Hz pulse frequency) produces MAX etchingandexfoliationtoformMXene QDs, avoiding the use of HF. The process can be followed by absorption and emission spectroscopy and by dynamic laser scattering and it appears to be general, being applied to Ti3 AlC2 , Ti2 AlC, Nb2 AlC, and V2 AlC MAX phases. Densityfunctionaltheory calculations indicate that, depending on the surface terminal groups, the diminution of the MXene size to the nanometric scale makes it possible to control the band gap of the MXene. The photocatalytic activity of these MXene QDs for hydrogen evolution has been observed, reaching an H2 production for the most efficient Ti3 C2 QDs as high as 2.02 mmol × g-1 × h-1 .

Synthesis of Ti3AlC2 max phase under vacuum, its structural characterization and using for Ti3C2Tx MXene preparation

The MAX phase (Ti3AlC2) was synthesized by sintering Ti, TiC, Al precursors under vacuum. The effect of temperature on the formation of the Ti3AlC2 phase was studied. The MAX phase with a minimum amount of impurities was obtained under vacuum at 1300 °C. The phase composition, structure, and state of the surface of the MAX phase were investigated. It was found that carbon vacancies are formed in the Ti3AlC2 lattice. Oxidized states of Ti, C, and Al elements are present on the surface of Ti3AlC2 crystallites. Despite the presence of structural defects and oxidized surface states of titanium and aluminum, the synthesized MAX phase was suitable for preparing 2D MXene particles (Ti3C2Tx) and highly concentrated stable colloidal solutions (up to 5 g/L) based on them. Thin MXene films, prepared from such Ti3C2Tx colloidal solution, were characterized by a high electrical conductivity of 3000 S/cm.

An experimental approach to delineate the reaction mechanism of Ti3AlC2 MAX-Phase formation

A comprehensive reaction mechanism of Ti3AlC2 MAX-phase formation from its elemental powders while spark plasma sintering has been proposed. Microstructural evaluation revealed that Al-rich TiAl3 intermetallic forms at around 660 °C once Al melts. Gradual transition from TiAl3 to Ti-rich TiAl and Ti3Al intermetallic phases occurs between 700 °C and 1200 °C through formation of layered structure due to diffusion of Al from periphery toward the centre of Ti particles. Formation of TiC and Ti3AlC transient carbide phases were observed to occur through two different reactions beyond 1000 °C. Initially, TiC forms due to interaction of Ti and C, which further reacts with TiAl and Ti and gives rise to Ti3AlC. Later, Ti3AlC also forms due to diffusion of C into Ti3Al above 1200 °C. Above 1300 °C, Ti3AlC phase decomposes into Ti2AlC MAX-phase and TiC in presence of unreacted C. Finally, Ti2AlC and TiC reacts together to from Ti3AlC2 MAX-phase above 1350 °C and completes at 1500 °C.

Исследование фазовых превращений в двухслойном жаростойком покрытии Ti–Al–C+Y–Al–O на жаропрочном никелевом сплаве

Currently, an active increase in requirements for fuel efficiency and specific gravity of aircraft turbojet engines is observed. Existing coatings based on zirconium dioxide intended for protecting engine parts are largely outdated and have exhausted their development potential, so new ceramic systems for the production of protective coatings based on them are an area of research. The authors carried out a study of a heat-resistant two-layer coating based on the Y–Al–O system (outer layer) and the Ti2AlC MAX phase of the Ti–Al–C system (sublayer) produced using vacuum-arc deposition on the Inconel 738 heat-resistant nickel alloy and molybdenum by alternate deposition of layers based on Ti–Al–C and a Y–Al–O layer. Using synchrotron radiation, phase transformations in the coating were examined when samples were heated to 1400 °C in a vacuum and to 1100 °C in the atmosphere to study the process of oxidation and coating formation in the presence of oxygen. Using scanning electron microscopy, the authors studied the microstructure and chemical composition of the coating. The study identified that heating the coating in a vacuum and in the atmosphere causes various phase transformations in it, but in both cases, the formation of a mixture of oxides of the Y–Al–O group and destabilization of the Ti–Al–C-based sublayer are observed. After heating the coating in the atmosphere without preliminary heat treatment, the coating was destroyed upon cooling, which was not observed when the coating was heated in a vacuum.

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.

Self-healing of indentation damage in Ti2AlC MAX phase ceramics

Although the crack-healing capacity of Ti2AlC ceramics has been sufficiently studied, the ability of Ti2AlC to self-heal large-scale damage, such as foreign object damage (FOD), remains unknown. This paper investigates the self-healing ability of Ti2AlC ceramics with large-scale damage (∼1000 μm in diameter). Extensive healing was observed even in the plastic damage and radial cracks. The damage and cracks caused by indentations made using a tungsten carbide sphere were filled and covered with newly formed oxides, such as titanium oxide and alumina, by the oxidation of Ti2AlC after heat treatment in air at 1000 °C. The strength, hardness, toughness, and elastic modulus of the Ti2AlC samples were measured before and after healing. The results show that the mechanical properties of Ti2AlC were similar or even slightly higher after the damage had been healed. Thus, Ti2AlC ceramics are attractive healing agents for foreign object damage in high-temperature applications.

The synthesis of high purity Ti3AlC2 MAX phase via molten salt method

Many methods have been used to synthesize the Ti3AlC2 MAX phase, but obtaining high-purity (>99.0 %) Ti3AlC2 is still a challenge. In this work, nano/submicro-sized Ti3AlC2 powder was prepared using Ti/Al/C elemental powders by the molten salt method in a vacuum quartz tube system. The effects of reaction temperature and dwell time, mechanical activation, the ratio of flux to reactants, and the ratio of Al on the synthesis of Ti3AlC2 were systematically investigated. The results show that Ti3AlC2 powder with a high purity of up to 99.0 % was prepared using ball milled 3Ti/1.1Al/2C mixture as the reaction material, and NaCl-KCl as the molten salt at 1150 °C for 2 h. The reaction mechanisms of Ti3AlC2 in molten salt have been discussed.

Sliding wear of MAX phase composites Ti3SiC2–TiC and Ti3AlC2–Ti2AlC at 400 °C and the influence of counterface material (steel, Al2O3, and Si3N4) on wear behaviour

This study explores the feasibility of employing MAX phase composite as impregnated solid lubricants and/or as bulk material for advanced high temperature tribological applications. The development of microstructure of Ti-based MAX phase composites Ti3SiC2–TiC and Ti3AlC2–Ti2AlC fabricated by spark plasma sintering and their dry sliding tribological properties against bearing steel, Si3N4, and Al2O3 counterfaces were investigated using a ball on disc tribometer at 400 °C. An orientation relationship between the Ti3SiC2 matrix and TiC particle was established wherein Ti3SiC2/TiC interphase is a coherent boundary from which Ti3SiC2 grows epitaxially from TiC. Against steel, the MAX phase composites – in stark contrast to Si3N4 and Al2O3 – exhibited a negative wear behaviour due to the excessive wear and subsequent sintering of the transferred Fe particles at the sliding interface. Intrinsic lubrication mechanisms involving tribo-oxidation, tribochemical reaction, and mechanochemical reaction played a vital role in the friction and wear properties. The friction and wear properties of the Ti3AlC2–Ti2AlC MAX phase composite was superior to the Ti3SiC2–TiC composite owing to better oxidation kinetics governing the oxide growth and their retention. Evidently, the wear of the MAX phase is expected to proceed upon extensive deformation incorporating a range of microscale micromechanisms.

Ti3AlC2 max phase- graphene oxide (GO) nanocomposite for selective solid phase microextraction of palladium in environmental samples and medical appliances prior to its detection with high-resolution continuum source flame atomic absorption spectrometry (HR-CS-FAAS)

Palladium is an important metal as it has a wide range of applications in different fields but can cause cancer in human beings. Therefore, precise quantification of palladium is important. For this purpose, new material Ti3AlC2 max phase having unique properties like high stability, thermal conductivity and environmental friendly has been synthesized. To increase its surface area of Ti3AlC2 max phase, graphene oxide (GO) has been incorporated to form Ti3AlC2 max phase GO nanocomposite. Ti3AlC2 max phase GO nanocomposite was used as solid phase extracting material for microextraction and preconcentration of Pd(II) in environmental samples and medical appliances. Characterization of the adsorbent was achieved by using fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX) and surface area analyzer (SAA). All the parameters that influence the extraction efficiency of the adsorbent like solution pH, amount of adsorbent, volume of sample, vortex time, desorption condition and interferences effect were determined and optimized. The limit of detection (0.327 µg/L) and limit of quantification (1.09 µg/L) show that the method is highly sensitive. The relative standard deviation was calculated as 5.48 % for five repeated measurements, which shows that the developed method is reproducible. The method is highly efficient with large values of preconcentration factor (20) and enhancement factors (20). The method was validated by applying the method to real water samples, soil samples and medical appliances with satisfied recovery results (94–106 %).

Synthesis in hydride cycle of Ti–Al–C based MAX phases from mixtures of titanium carbohydrides and aluminum powders

MAX phases are new type of easily machinable cermets, demanded in modern materials science as construction materials. One of the most widely studied and promising representatives of the titanium-based MAX phases are hexagonal Ti2AlC and Ti3AlC2. Current methods of their synthesis are unsuitable for their mass production. The creation and development of new methods and technologies for their producing are urgent tasks of materials science. The modern technologies are required providing high quality and productivity, cost-effective, environmentally friendly and easily scaled methods. In 2007, in our Laboratory of High-Temperature Synthesis of the IChPh of Armenian NAS, the Hydride Cycle method (HC) for synthesis of refractory alloys and intermetallic compounds was elaborated. The gist of this method is the use of the synthesized by Self-propagating High-temperature Synthesis mode (SHS) transition metal hydrides as starting materials. In the present work, for the first time, the HC method was applied in the synthesis of Ti2AlC and Ti3AlC2 MAX phases. Preliminarily, HCP TiC0.45H1.07÷1.17, FCC TiC0.5H0.22÷0.73 and TiC0.67H0.31-0.39 titanium carbohydrides were synthesized in the SHS mode and used as starting reagents. The present work was set to study the effect on the phase composition and structure of the synthesized MAX phases of conditions of HC. The analysis methods, used to certify the synthesized MAX phases, were: chemical, differential-thermal, X-ray phase. The microstructures of the samples were snapshot on SEM Prisma E scanning electron microscope. The work resulted in the synthesis in HC of single-phase Ti2AlC and Ti3AlC2 MAX phases with unit cell parameters [а = 3.0553; c = 13.6459; c/a = 4.466; P63/mmc] and [a = 3.0552; c = 18.7396; c/a = 6.132], respectively. This work demonstrated advantages of HC over the traditional methods of MAX phases synthesis.

Preparation of Silicon Bronze-Based Hybrid Nanocomposites with Excellent Mechanical, Electrical, and Wear Properties by Adding the Ti3AlC2 MAX Phase and Granite Via Powder Metallurgy

Preparation of Silicon Bronze-Based Hybrid Nanocomposites with Excellent Mechanical, Electrical, and Wear Properties by Adding the Ti3AlC2 MAX Phase and Granite Via Powder Metallurgy

Self-propagating high-temperature synthesis of MAX phases in Ti–Zr–Al–C system (C:P15)

The paper reports the results of the Self-propagating High-temperature Synthesis (SHS) in ternary Ti–Al–C and quaternary 2xTi - 2(1-x)Zr − Al – C (x = 0.5–0.9) systems, combusted in argon and hydrogen environments. The effect of the initial mixture composition on the microstructure, phase composition, and crystallographic parameters of the synthesized compounds was investigated. Rietveld analysis of X-ray diffraction patterns was used to calculate the lattice parameters and quantitative phase composition. The combustion of the Ti–Al–C system resulted in the formation of Ti2AlC and Ti3AlC2 MAX phases (85–89%), as well as TiCx phase (11–15%). The combustion of Ti–Zr–Al–C system depending on the Ti/Zr ratio and Al and C contents, along with the main Ti2AlC, Ti3AlC2, Zr2AlC MAX phases, the FCC carbides of transition metals also formed. The highest percentage (91%) of MAX phases was produced by SHS of the 0.9Ti+0.1Zr+0.5Al+0.5C mixture in the argon atmosphere.

High-energy Q switched Yb-doped fiber laser based on a ternary layered structured Ti2AlC saturable absorber.

Ti2AlC is a kind of ternary layered structured ceramic metal compound, combining the advantages of both ceramic and metal. Herein, the saturable absorption performance of Ti2AlC at the 1-µm wave band is investigated. The Ti2AlC behaves with excellent saturable absorption, which has a modulation depth of 14.53% and a saturable intensity of 13.27 MW/cm2. An all-normal dispersion fiber laser based on the Ti2AlC saturable absorber (SA) is constructed. The repetition frequency of the Q switched pulses increased from 44 to 49 kHz as the pump power rose from 276 to 365 mW, and the corresponding pulse width decreased from 3.64 to 2.42 µs. The maximum output single Q switched pulse energy is as high as 169.8 nJ. Our experiments prove that the MAX phase Ti2AlC has potential as a low-cost, simple preparation, and broadband SA material. To the best of our knowledge, this is the first demonstration of Ti2AlC serving as a SA material achieving Q switched operation at the 1-µm wave band.

Solar driven photocatalytic dye degradation through the novel Ti2C– ZnCo2O4MXenes nanocomposite

Two-dimensional (2D) zinc cobalt oxide (ZnCo2O4) has considerable promise material for efficient dye photocatalytic degradation. A novel family of two-dimensional anisotropic carbides and nitrides from early transition metals (MXenes) is particularly fascinating among 2D materials, such as graphene, due to their potential uses in electronics, medicine, and photo-catalysis. The extended Ti2C phases were created by synthesizing them from their parent Ti2AlC MAX phases under the same circumstances as the traditional acidic aluminum extraction procedure. However, due to its limited specific surface area and high carrier recombination rate, photo-catalytic performance is usually inadequate. Preparation, morpho-structural characterization, band gap measurement, and congo red photo-degradation potential of Ti2C MXene and three nano-composites made up of MXene enhanced by ZnCo2O4 are presented in this study. SEM images revealed hill like agglomerated rough microstructure with round shape many particles morphology. The experimentally obtained band gaps using Tauc's approach are in the 2.60–2.84 eV range. In recent years, the approach of photo-catalytic breakdown of contaminants employing semiconductor photo-catalysts with UV–visible light has grown in importance. The addition of ZnCo2O4 boosted the establishment of strong interfacial coupling between Ti2C and ZnCo2O4, shortening the route of carrier transfer and promoting the direct transfer of photo-generated electrons from Ti2C's valence band to ZnCo2O4.The specific surface area of composites increased significantly at the same time, which was beneficial for improving the UV-absorption capability of Ti2C composites. This research proposes a practical design method for increasing the degrading performance of 2D photo-catalysts, which may serve as a technical suggestion for the modification design of additional photo-catalysts. The MXene based nano-composites revealed high activity in the congo-red photo-degradation reaction (56%–78% of degraded congo-red after 270 min). Ti2C(97%)/ZnCo2O4(3%) composite showed an enhanced efficiency for degradation of congo-red.

Novel Alumina Matrix Composites Reinforced with MAX Phases-Microstructure Analysis and Mechanical Properties.

This article describes the manufacturing of alumina composites with the addition of titanium aluminum carbide Ti3AlC2, known as MAX phases. The composites were obtained by the powder metallurgy technique with three types of mill (horizontal mill, attritor mill, and planetary mill), and were consolidated with the use of the Spark Plasma Sintering method at 1400 °C, with dwelling time 10 min. The influence of the Ti3AlC2 MAX phase addition on the microstructure and mechanical properties of the obtained composites was analyzed. The structure of the MAX phase after the sintering process was also investigated. The chemical composition and phase composition analysis showed that the Ti3AlC2 addition preserved its structure after the sintering process. The increase in fracture toughness for all series of composites has been noted (over 20% compared to reference samples). Detailed stereological analysis of the obtained microstructures also could determine the influence of the applied mill on the homogeneity of the final microstructure and the properties of obtained composites.

A new strategy to fabricate Ti2AlC MAX coatings by the two-step laser method

High-content Ti2AlC MAX coatings were efficiently prepared on TC4 plates by two-step laser method (laser cladding and post-laser treatment). The microstructure and phase composition of the coatings were analyzed, and the in-situ synthesis mechanism of MAX phases was explored. According to the results, the diffusion of Al atoms in the cladded coatings led to the formation of a core-shell structure with TiC as the core and Ti2AlC as the shell. During post-laser treatment, the diffusion of C and Al atoms was intensified, which facilitated the nucleation-growth of the Ti2AlC phase, producing two types of MAX phase structures. The short rod-shaped MAX phase was precipitated directly from the coating matrix, while the blocky MAX phase gradually formed owing to atomic diffusion. Finally, the content of Ti2AlC MAX phase in as-obtained coatings after post-laser treatment at the laser power of 1.2 kW and the scanning speed of 1 mm/s reached 82.93 wt%, which was 9.03 times higher than that in the cladded coating. Therefore, the two-step laser technique proposed in this work enables the production of high-content MAX coatings, which opens up new prospects for efficient preparation of MAX phase coatings and related structures.

A facile and almost HF-free synthesis of Ti3C2@CuCl composite for supercapacitors

This work demonstrates a distinctive almost HF-free route of etching Ti3AlC2 MAX phase by metal displacement reaction at room temperature. The Ti3AlC2 particles are directly etched by CuCl2 solutions in different concentrations instead of HF. The etchant is reduced to nano CuCl particles, adhering to the surface of Ti3C2 layers to form the Ti3C2@CuCl composite which is evaluated as working electrodes for supercapacitors. Due to the synergistic effect between CuCl and Ti3C2 matrix, the appropriate amount of CuCl enhances the specific capacitance to 508.7 F·g−1 at 1A·g−1 in 6 M KOH electrolyte solution, which is much higher than pure Ti3C2 electrode. This work shows the possibility of synthesis of various Mxene-based frameworks by other metallic cations with lower metal activity.