MAX Phase Powders Research Articles

Preparation of Ti3AlC2 MAX-phase as a precursor material using industrial waste carbon flex for MXene synthesis

MAX phase represents a new class of solids that combine some of the best attributes of metals and ceramics, exhibiting unusual, mechanical, electrical, and thermal properties. Further Ti3AlC2 MAX phase is exfoliated to create 2D nanosheet material called Ti3C2 MXene and both have unmatched qualities for difficult and unusual applications. The Ti3AlC2 MAX phase powder is the precursor material to synthesize the Ti3C2 MXene nanosheets, but the cost effective synthesis of Ti3AlC2 powder is still a challenging problem which ultimately decides the quality and cost of Ti3C2 MXene. In this paper, we present the novel synthesis of Ti3AlC2 MAX phase using carbon flex generated as an industrial waste from aluminum, Steel, and other metal industries in composites production. To the best of our knowledge we first time novely report the use of Industrial waste carbon flex as a base carbon material to partially replace commercial graphitic carbon powder in Ti3C2 synthesis. The effect of adding carbon flexes precursor to synthesizing Ti3AlC2 MAX phase solving many current challenges. In present work we comparatively report the physicochemical study of the MAX phase synthesized with three different carbon precursors to establish the role of industrial waste carbon flex in the quantitative growth of Ti3C2MXene as the final product.

Novel 2D heterostructure composites of V2C MXene/TiO2 and graphene/TiO2 for platinum replacement in dye-sensitized solar cells

This study evaluates the potential of V2C MXene/TiO2 and Graphene/TiO2 composites as alternatives to platinum for counter-electrodes in dye-sensitized solar cells (DSSCs). V2C MXene was synthesized by selectively etching the aluminum layer from V2AlC MAX phase powder, resulting in multilayered V2C MXene. The layered morphologies of MXene and graphene were confirmed via Scanning Electron Microscopy (SEM), while their crystalline structures were validated using X-ray diffraction (XRD) analysis. SEM analysis confirmed the delaminated layered structure of graphene and the distinct layers of V2C MXene. XRD findings showed that MXene has significantly greater interlayer spacing than graphene, offering more catalytic sites for charge injection. Electrocatalysts were prepared by incorporating TiO2 paste with MXene and graphene, with TiO2 serving as a binder. These composites were then employed as counter-electrode materials in dye-sensitized solar cells. The MXene-based counter electrode achieved a photoconversion efficiency of 1.625 %, surpassing graphene-based (1.149 %) and Pt-based (1.567 %) counterparts under standard illumination. The efficiency of cells was meticulously characterized over an extended period. The results indicated that the efficiency of these cells remained stable over time. This stability suggests that MXene/TiO2 and Graphene/TiO2 based catalysts are robust and do not degrade with time.

Effect of oxygen substitution and oxycarbide formation on oxidation of Ti3AlC2 MAX phase

AbstractMAX phases, ternary transition metal carbides and nitrides, represent one of the largest families of layered materials. They also serve as precursors to MXenes, two‐dimensional (2D) carbides and nitrides. The possibility of oxygen substitution in the carbon sublattice, forming oxycarbide MAX phases and MXenes, was recently reported using secondary ion mass spectrometry. However, while the effect of oxygen substitution on the properties of MXenes was investigated, little is known about its effect on the properties of MAX phases. Here, we explore the influence of process parameters (e.g., particle size, synthesis temperature, annealing time, etc.) and oxygen presence in the lattice on the oxidation resistance of Ti3AlC2 MAX phase powders. We show that X‐ray diffraction measurements can identify oxygen substitution and assist in selecting MAX precursors to synthesize stable and highly conductive MXenes. Eliminating the substitutional oxygen from the MAX phase lattice increases the onset of oxidation by 400°C, from approximately 490 to 890°C. Finally, we discuss the impact of oxygen substitution in the MAX phases on the synthesis of MXenes and their resulting properties.

Rapid synthesis of high‐yield Ti3AlC2 MAX phase powders from TiC0.67 and Al with induction heating assistance

AbstractThe development of new low‐carbon emission methods for the synthesis and processing of materials is an urgent task today. Here, we present a rapid, efficient, and low‐energy‐consuming synthesis method for high‐yield Ti3AlC2 MAX phase powders. Our method is based on induction heating‐assisted combustion synthesis (IH‐CS), where the heat of the reaction is used as a driving force of the process, and the conditions of the process are finely controlled using IH at the same time. Ti3AlC2 MAX phase was synthesized using TiC0.67 and Al powders as starting materials. The introduction of TiC0.67 reduced the total exothermic effect of the reaction, facilitating better control of the reaction process. IH was used to ignite the reaction and to hold the temperature after ignition at an optimal value to complete the synthesis process. The effects of holding temperature, Al, and Si addition on Ti3AlC2 yield were investigated. As a result, Ti3AlC2 MAX phase powders containing only .7 wt% of the secondary phase were synthesized in a very short time. Our findings suggest that IH‐CS is a highly effective and promising alternative for the facile fabrication of high‐purity MAX phase powders.

Synthesis of low‐oxygen Ti3AlC2 powders by hydrogenation–dehydrogenation and deoxidation from titanium scraps

AbstractThe MAX phase is a material with excellent electrical and thermal conductivity and thermal shock and oxidation resistance owing to its metallike bonding properties. The impurities in the Ti3AlC2 MAX phase must be controlled because the oxides and TiC derived from the synthesis process remain in MXene and markedly affect the electrical conductivity and chemical stability. This study investigated whether the Ti3AlC2 MAX phase can be synthesized from titanium powder prepared from low‐cost titanium scrap by hydrogenation–dehydrogenation (HDH) and deoxidation in the solid‐state (DOSS) processes. Almost single‐phase Ti3AlC2 MAX phase was obtained by synthesis at 1450°C for 5 h. The oxygen concentrations of the HDH‐MAX and DOSS‐MAX powders (25–45 μm) were 7215 and 3875 ppm, respectively. Oxygen reduction of titanium powder through DOSS can help improve the purity of Ti3AlC2 MAX phase by minimizing the imbalance in the stoichiometric ratio during synthesis. The HDH‐MAX and DOSS‐MAX powders prepared from titanium scrap displayed a higher Ti3AlC2 phase fraction and lower oxygen concentration than those of commercial Ti3AlC2 MAX phase powders. This cost reduction and purity improvement will increase the accessibility of the Ti3AlC2 MAX phase, supporting further research into its applications.

Synthesis of Ti3SiC2 MAX phase powder through molten salt method

AbstractTitanium silicon carbide (Ti3SiC2) MAX phase powder was synthesized from elemental reactants using the molten salt synthesis (MSS) method. Optimum experimental parameters were also investigated to determine the purity and synthesis pathway of the Ti3SiC2 MAX phase. The results showed that Ti3SiC2 was not synthesized using carbon black as the carbon source in the starting materials because of the high quantity of TiC formed along with the TiSi2 silicide phase. However, Ti3SiC2 was successfully synthesized in a relatively high purity (93%) at 1200°C for 2 h using graphite as the source of carbon because of the formation of TiC and Ti5Si3 intermediate phases. The Ti5Si3 silicide phase was found to play a crucial role in the formation of the Ti3SiC2 MAX phase using the MSS method. Moreover, applying a pressure of 150 MPa to the prepared samples and using the eutectic mixture of NaCl–KCl (molar ratio: 1:1) instead of NaCl also resulted in the higher formation of the Ti3SiC2 MAX phase. The formation mechanism of Ti3SiC2 was determined to be the reaction among Ti5Si3, TiC, and residual carbon through the template‐growth and dissolution–precipitation mechanisms that occurred at different stages of the synthesis process.

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

Microstructure and reaction mechanism of Ti-Al-C based MAX phase coatings synthesized by plasma spraying and post annealing

This work explored the feasibility of fabricating thick Ti2AlC and Ti3AlC2 coatings by plasma spraying from Ti/Al/graphite agglomerates and post annealing. The phase transformation and microstructure evolution of the sprayed coatings annealed at 500–900 °C were proposed. The as-deposited coating exhibited a micro-laminated structure with mainly of (Ti, Al)Cx, Ti2AlC, residual Al and minor TixAly. The short reaction time of spraying process led to insufficient reaction in C@Ti-Al agglomerates, thus forming dominate (Ti,Al)Cx and limited amount of Ti2AlC. The phase in the coating changed little when annealing below 600 °C. As increasing temperature to 700 °C, both of Ti3AlC2 and Ti2AlC showed obvious growth but Ti3AlC2 was predominate. Under higher temperature (>700 °C), Ti3AlC2 in the coating decreased while Ti2AlC grew apparently. The residual Al, transition phase (Ti, Al)Cx and high temperature annealing were main factors to promote the formation of Ti2AlC phase in sprayed coatings. The as-annealed coating showed increasing hardness with elevated temperature because of the formation of Ti2AlC, reduced pores and homogenous structure. This study implied that element agglomerates would be an effective alternative of expensive MAX phase powders as feedstock for plasma spraying MAX phase coatings.

Sacrificial template synthesis of (V0.8Ti0.1Cr0.1)2AlC and carbon fiber@(V0.8Ti0.1Cr0.1)2AlC microrods for efficient microwave absorption

The morphology of MAX phase powders significantly influences their microwave absorption properties. However, the traditional synthesis via solid-state reactions produces irregular powders, and the preparation of MAX phase powders with specific morphology remains a challenge. Herein, (V0.8Ti0.1Cr0.1)2AlC MAX phase microrods were fabricated for the first time in NaCl/KCl molten salts using vanadium, titanium, chromium, aluminum, and short carbon fibers as precursors. It was found that despite acting as a carbon source, carbon fibers also acted as sacrificial templates. By adjusting the molar ratio of metal powders and short carbon fibers, a series of carbon [email protected](V0.8Ti0.1Cr0.1)2AlC microrods with core-sheath structure were also obtained. Carbon [email protected](V0.8Ti0.1Cr0.1)2AlC microrods with a molar ratio of 8:2 showed the optimum microwave absorption performance. The reflection loss (RL) value reached up to –63.26 dB at 2.40 mm, and the effective absorption bandwidth (EAB) was about 5.28 GHz with a thickness of 2.02 mm. Based on the electromagnetic parameter analysis and theoretical simulation, the enhanced microwave absorption performance was attributed to the synergistic effect of different factors like dielectric loss, magnetic loss, multiple reflection, and scattering. This work offers a facile route to modulate the morphology of MAX phase powders and may accelerate its application as microwave absorbers.

Formation of Bulk Samples from the Ti3AlC2 MAX-Phase Powder by Selective Laser Sintering

Formation of Bulk Samples from the Ti3AlC2 MAX-Phase Powder by Selective Laser Sintering

Phase formation and microstructure evolution of plasma sprayed Cr2AlC MAX phase coatings under post annealing

In this study, thick Cr2AlC coatings were first synthesized via plasma spraying of Cr3C2–Al–Cr agglomerated powders and post annealing. The microstructure evolution and mechanical properties of the Cr2AlC coatings annealed at 500–1000 °C were investigated. The as-sprayed coatings exhibited a lamellar structure, primarily consisting of Cr2AlC, Cr7C3, Cr23C6, and (Cr, Al)Cx solid solutions. The short residence time during spraying led to incomplete reactions in the Cr3C2@Al–Cr agglomerates, resulting in the formation of (Cr, Al)Cx. Post annealing provided sufficient energy for the transition of (Cr, Al)Cx → Cr2AlC. With an increase in the annealing temperature (<900 °C), gradual transition of the (Cr, Al)Cx phase led to a slight increase in the Cr2AlC content, and thus, the as-annealed coatings maintained high hardness (>1000 HV0.2) with improved fracture toughness. Higher annealing temperatures (>900 °C) promoted clear enhancement of the Cr2AlC content, thus reducing the coating hardness. The transition phase (Cr, Al)Cx and high temperature annealing were the primary factors to promoting the formation of the Cr2AlC phase in sprayed coatings. This study indicates that the Cr3C2@Al–Cr agglomerates can be effective alternatives to expensive MAX phase powders as feedstock for plasma spraying of Cr2AlC coatings.

Removal of Malachite Green Dye from Water Using MXene (Ti3C2) Nanosheets

In the present study, new emerging 2D Mxene nanosheets (MXNSs) were synthesized from MAX phase powders of Ti3AlC2 and then characterized using a scanning electron microscope (SEM) and X-ray diffraction (XRD) to explore the chemical and physical properties of the prepared MXNS. The characterization of the synthesized MXNS indicated the formation of exfoliated 2D MXene nanosheets (Ti3C2) as a result of the HF treatment of the MAX phase, which was confirmed by XRD measurements, as the characteristic peaks of 2D MXene nanosheets were only observed. The synthesized MXNS was then used as a solid adsorbent for removing malachite green dye (MG) from water. The effects of different operational factors such as MXNS dose, solution temperature, time, MG concentration, solution pH, and ionic strength have also been evaluated. The adsorption results showed that the temperature of the solution, as well as its pH, significantly influenced MG removal when using MXNS. The optimum removal was obtained within 150 min, with 20 mg of MXNS at ambient temperature and a pH value of 6.0. The maximum removal capacity obtained was 4.6 mg MG per g of MXNS using 5 mg of MXNS with a removal efficacy of 46.0%, and the minimum removal capacity obtained was 2.5 mg MG per g of MXNS using 20 mg of MXNS with a removal efficacy of 99.1%. Finally, the results displayed that the MXNS solid adsorbent was able to absorb a high percentage of MG and maintained reasonable efficiency for four consecutive cycles, indicating that MXNS could be a promising adsorbent in wastewater remediation and environmental sustainability.

Theoretical and experimental validation of thermal and heat transfer performance of novel ethylene glycol - Cr2AlC nanofluids

Synthesizing stable nanofluids with favourable thermal properties that can cater to practical applications is a challenge over the past few years. This paper presents the preparation and analyzes the thermal efficiency of the novel nanofluid prepared by the suspension of nanocrystalline Cr2AlC MAX phase powder in ethylene glycol (EG). Incorporation of h-BN, MoS2, Al2O3, and Cr2AlC showed a thermal conductivity enhancement at 303 K when compared to EG. Accurate experimental models for the thermal conductivity and the viscosity of EG + Cr2AlC nanofluids are estimated. The theoretical analysis of the flow profiles of EG + Cr2AlC/Al2O3/MoS2/h-BN nanofluids is carried out with Blasius and Sakiadis flow models. The Cr2AlC MAX phase possesses both ceramic and metal properties that help these nanofluids to show high heat transfer performance. The results show that 0.50 wt% EG + Cr2AlC nanofluid displays maximum improvement in heat transfer performance. There is a substantial rise in the thermal conductivity when both temperature and weight fraction increase. The simulated flow of the nanofluid past a plate indicated superior heat transfer and thermal profiles for the EG + Cr2AlC nanofluids. For the flow past a moving plate, the nanofluid possesses less skin friction at the plate, which is favourable for various practical applications.

Sinterability, Mechanical Properties and Wear Behavior of Ti3SiC2 and Cr2AlC MAX Phases

MAX phases are a promising family of materials for several demanding, high-temperature applications and severe conditions. Their combination of metallic and ceramic properties makes MAX phases great candidates to be applied in energy production processes, such as high temperature heat exchangers for catalytic devices. For their successful application, however, the effect of the processing method on properties such as wear and mechanical behavior needs to be further established. In this work, the mechanical and wear properties of self-synthesized Ti3SiC2 and Cr2AlC MAX phase powders consolidated by different powder metallurgy routes are evaluated. Uniaxial pressing and sintering, cold isostatic pressing and sintering and hot pressing were explored as processing routes, and samples were characterized by analyzing microstructure, phase constitution and porosity. Wear behavior was studied by reciprocating-sliding tests, evaluating the wear rate by the loss of material and the wear mechanism.

Production and characterization of carbide-derived-nanocarbon structures obtained by HF electrochemical etching of Ti3AlC2

In this research, we propound a facile and efficient strategy for the synthesis of carbide-derived nanocarbon structures (CDCs) by electrochemical etching of Ti3AlC2 MAX phase in hydrofluoric acid solutions. Al, Ti and C powders were milled and used to synthesize Ti3AlC2 MAX phase powders and then, the obtained powders were sintered using spark plasma sintering (SPS) method. The obtained bulk sample was then electrochemically etched for 2 h at 5v and 20v and concentrations of 20 wt% and 10 wt% hydrofluoric acid to obtain CDC. The results showed that titanium and aluminum were extracted from the Ti3AlC2 MAX phase structure by electrochemical etching in HF solution. Structural and morphological studies of CDCs obtained by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and scanning field emission electron microscopy (FESEM) were performed. Examination of SEM and FESEM illustrations showed that the structure of CDCs consisted of graphene nanosheets. The distance and number of graphene layers were obtained according to the XRD results and the ID/IG value was assessment to be 0.81 according to Raman spectroscopy, demonstration plenty of oxygen functional groups on the surface of graphene sheets. Also, EDS analysis and XRD and Raman spectroscopy outcomes were in well agreement with SEM and FESEM images. The results were shown, at constant voltage, increasing the concentration has led to the production of more CDC nanostructures. At a constant concentration with increasing voltage amorphous carbon was formed instead of graphite. Eventually it was found that by changing the voltage and concentration of the solution, both titanium and aluminum were still extracted and CDC was formed.

Influence of selective laser treatment on thermal stability of Ti3AlC2 and Ti3AlC2/Cu powders

Commercial Ti3AlC2 MAX phase powder and Ti3AlC2/Cu powder blends were used to obtain bulk materials using selective laser sintering/melting technique. In the present work, the influence of laser line energy on the stability of Ti3AlC2 composition was investigated. The structure of MAX phases was better maintained in composites with copper addition, forming a metal matrix composite with a copper matrix and Ti3AlC2 inclusions.

Synthesis and characterization of Cr2AlC MAX phase for photocatalytic applications

MAX phase, a layered ternary carbide/nitride, displays both ceramic and metallic properties, which has significantly attracted the materials research. In this work, Cr2AlC MAX phase powder with high purity was fabricated via a facile and cost-effective pressure-less sintering methodology and utilized for photocatalytic degradation of different organic pollutants for the first time. Various characterization techniques were used for confirming the morphological and other physico-chemical properties of the catalyst. Cr2AlC MAX phase with a low band gap of 1.28 eV has shown 99% efficiency in the degradation of malachite green, an organic pollutant under visible light irradiation. The scavenger studies conclude that, O2•−and h+ as the active species during the photocatalytic reaction. Furthermore, the kinetic study revealed that the reaction obeys pseudo-first-order kinetics and can be reused for four cycles without losing the activity. This novel approach can give new insight into the potential application of MAX phase materials in the field of wastewater treatment under visible light irradiation.

Synthesis and enhanced mechanical properties of compositionally complex MAX phases

A novel strategy of fabricating compositionally complex MAX phases was successfully developed. Multicomponent 413 MAX phase solid solutions (Ti0.36Nb0.27Ta0.37)4AlC2.8 and (Ti0.28Nb0.26Ta0.28V0.18)4AlC2.9 simultaneously containing 3 and 4 transition-metal elements at M site were experimentally synthesized via hot pressing equimolar mixture of 211 type MAX phase powders. By elemental analysis and structural characterization, it can be verified that those uniform compositionally complex solid solutions can be obtained only in the presence of Cr2AlC in raw powders. Those compositionally complex MAX phase solid solutions exhibit typical layered structures with distinct elongated grains. This discovery further enriches the MAX phases family and provide a new avenue for tailoring the properties of these materials. MAX phase composites containing around 87.5 vol.% (Ti0.36Nb0.27Ta0.37)4AlC2.8 exhibit a high flexural strength of 720 MPa and a high fracture toughness of 9.5 MPa m0.5.

Porous TaCx ISOL target materials from mould-casted Ta4AlC3

Mould casting and sacrificial templating techniques, common in bioceramic technology, were employed to process porous TaCx ultra-high temperature ceramics intended as novel target materials for isotope separation on-line (ISOL) facilities, aiming primarily at the production of medical radioisotopes. A feedstock of Ta4AlC3 MAX phase powder, polyamide spheres and wax was used to obtain different porous TaCx grades with bimodal pore size distributions. The ‘green’ bodies underwent de-binding and vacuum annealing to decompose the MAX phase, whereas a reference material was also produced from commercial TaC powders. The thermal stability of the porous TaCx ceramics was assessed at ISOL-relevant conditions by heating in high vacuum up to 2200 °C. The MAX phase-derived TaCx porous ceramics evolved from biphasic TaCx/α-Ta2C to single-phase TaCx at higher temperatures, due to carbon incorporation. The porous TaCx microstructure was stable at 2200 °C with a specific surface area stabilizing at ∼0.25 m2/g and thermal conductivity of 1−4 W/m K.

Synthesis, sintering, and effect of surface roughness on oxidation of submicron Ti2AlC ceramics

AbstractSubmicron Ti2AlC MAX phase powder was synthesized by molten salt shielded synthesis (MS3) using a Ti:Al:C molar ratio of 2:1:0.9 at a process temperature of 1000°C for 5 hours. The synthesized powder presented a mean particle size of ~0.9 µm and a purity of 91 wt. % Ti2AlC, containing 6 wt. % Ti3AlC2. The Ti2AlC powder was sintered by pressureless sintering, achieving a maximal relative density of 90%, hence field‐assisted sintering technology/spark plasma sintering was used to enhance densification. The fine‐grained microstructure was preserved, and phase purity of Ti2AlC was unaltered in the latter case, with a relative density of 98.5%. Oxidation was performed at 1200°C for 50 hours in static air of dense monolithic Ti2AlC with different surface finish, (polished, ground and sandblasted) which resulted in the formation of an approx. 8 µm thin aluminum oxide (Al2O3) layer decorated with titanium dioxide (rutile, TiO2) colonies. Surface quality had no influence on Al2O3 scale thickness, but the amount and size of TiO2 crystals increased with surface roughness. A phenomenon of rumpling of the thermally grown oxide (TGO) was observed and a model to estimate the extent of deformation is proposed.