A METHOD OF SYNTHESISING TITANIUM ALUMINIUM CARBIDE MAX PHASE

Abstract

A method of synthesising Ti3AlC2 MAX phase is disclosed herein. Said method broadly comprises steps of: mixing elemental powders of titanium, aluminium, and Carbon, with ethanol; subjecting to probe sonication; centrifuging and drying; grinding to form pellets; and sintering the pellets. The sintered pellets may be crushed and ground after naturally cooling down to room temperature. The disclosed method offers at least the following advantages: is cost-effective; offers a facile, time saving and effective method to produce Ti3AlC2 MAX phase; is scalable; and/or reduces presence of intermetallics or secondary phases.

Specification

Description:TITLE OF THE INVENTION: A METHOD OF SYNTHESISING TITANIUM ALUMINIUM CARBIDE MAX PHASE
FIELD OF THE INVENTION
The present disclosure is generally related to titanium aluminium carbide MAX phase. Particularly, the present disclosure is related to a method of synthesising titanium aluminium carbide MAX phase. More particularly, the present disclosure is related to: a method of synthesising titanium aluminium carbide phase as an alternative method to high energy ball milling.
BACKGROUND OF THE INVENTION
Titanium Aluminium Carbide (Ti3AlC2) MAX phase is a hexagonal layered transition metal carbide belonging to P63/mmc symmetry. The Ti3AlC2 MAX phase is a precursor in synthesising MXene nanosheets - a new class of layered 2D nanoscale Ti3C2Tx (MXene) material, with potential applications in various fields including flexible electronics, sensors, hard coatings, and energy storage devices.
Conventional methods of synthesising Ti3AlC2 MAX phase such as high energy ball milling are already known in the art. However, in high energy ball milling, ball to powder ratio; feed ratio; duration of milling; and/or rise in internal temperature due to friction between the balls and powders, make the method quite challenging.
In addition, long milling times; maintenance of instruments; and/or TiC or zirconia-based balls and milling jars increase costs of milling.
There is, therefore, a need in the art, for: a method of synthesising Ti3AlC2 MAX phase, which overcomes the aforementioned drawbacks and shortcomings.
SUMMARY OF THE INVENTION
A method of synthesising Ti3AlC2 MAX phase is disclosed herein. The disclosed method broadly comprises following steps:
Initially, elemental powders of titanium (Ti), aluminium (Al), and carbon (C) of about 325 mesh, in a molar ratio of about 3:1.1:1.8, are mixed with ethanol, and gently stirred for about 10 minutes, to obtain a mixture.
The mixture is subjected to probe sonication at a frequency of about 20 kHz and a power rate of about 40%, using a pulse mode of about 2 seconds ON and about 2 seconds OFF, for a duration ranging from about 60 to about 120 minutes, to obtain a homogenous mixture.
The homogenous mixture is centrifuged to remove the ethanol, followed by drying in a hot air oven at about 80°C for about 1 hour to obtain a dried mixture. The dried homogenous mixture is manually ground, and subjected to a hydraulic press (pressure of about 15 kg/cm2) to form Ti3AlC2 pellets with a diameter of about 10 mm.
The pellets are subjected to sintering in a vacuum tubular furnace at a temperature of about 1,500°C for about 2 hours under an inert atmosphere at a flow rate of about
2 mL/min, to obtain sintered pellets. After naturally cooling down to room temperature, the sintered pellets may be crushed and ground to obtain fine powders of Ti3AlC2 MAX phase.
The disclosed method offers at least the following advantages: is cost-effective; offers a facile, time saving and effective method to produce Ti3AlC2 MAX phase; is scalable; and/or reduces presence of intermetallics or secondary phases.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 illustrates a powder X-Ray Diffraction (XRD) pattern of synthesised Ti3AlC2 MAX phase by pressureless sintering at about 1,500℃ for about 2 hours at different probe sonication time intervals from about 5 to about 120 minutes, in accordance with an embodiment of the present disclosure;
Figure 2 illustrates a powder XRD pattern of synthesised Ti3AlC2 MAX phase by pressureless sintering at about 1,500℃ for about 2 hours at different probe sonication time intervals from about 5 to about 120 minutes showing growth of (002) and (104) plane, in accordance with an embodiment of the present disclosure;
Figure 3 illustrates a two-phase Rietveld refinement of synthesised Ti3AlC2 MAX phase sonicated for about 60 minutes, in accordance with an embodiment of the present disclosure;
Figure 4 illustrates phase composition (in %) from a two-phase Rietveld refinement of synthesised Ti3AlC2 MAX phase sonicated at different time intervals followed by pressureless sintering at about 1,500℃ for about 2 hours, in accordance with an embodiment of the present disclosure;
Figure 5 illustrates Field Emission Scanning Electron Microscopy (FE-SEM) images of synthesised Ti3AlC2 MAX phase sonicated for about 60 minutes at different magnification scales, in accordance with an embodiment of the present disclosure;
Figure 6 illustrates Raman spectra of synthesised Ti3AlC2 MAX phase sonicated for about 60 minutes, in accordance with an embodiment of the present disclosure;
Figure 7 illustrates powder XRD patterns comparing synthesised Ti3AlC2 MAX phase using two different stoichiometric molar ratios of elemental powders (Ti: Al: C), in accordance with an embodiment of the present disclosure; and
Figure 8 illustrates a comparative analysis of powder XRD pattern of Ti3AlC2 MAX phase sample synthesised through probe sonication for about 60 minutes, a commercial sample, and a ball-milled sample, in accordance with an embodiment of the present disclosure.
DETAILED DESCRIPTION OF THE INVENTION
Throughout this specification, the use of the words "comprise" and "include", and variations, such as "comprises", "comprising", "includes", and "including", may imply the inclusion of an element (or elements) not specifically recited. Further, the disclosed embodiments may be embodied, in various other forms, as well.
Throughout this specification, the disclosure of a range is to be construed as being inclusive of: the lower limit of the range; and the upper limit of the range.
Throughout this specification, the words "the" and "said" are used interchangeably.
Throughout this specification, the use of the acronym "Ti3AlC2" is to be construed as: "Titanium Aluminium Carbide".
Also, it is to be noted that embodiments may be described as a method. Although the operations, in a method, are described as a sequential process, many of the operations may be performed in parallel, concurrently, or simultaneously. In addition, the order of the operations may be re-arranged. A method may be terminated, when its operations are completed, but may also have additional steps.
A method of synthesising Ti3AlC2 MAX phase (also referred to as "method") is disclosed herein. The disclosed method broadly comprises following steps:
Initially, elemental powders of titanium (Ti), aluminium (Al), and carbon (C) of about 325 mesh were weighed in a molar ratio of about 3:1.1:1.8, for example, about 1.45 grams: about 0.30 grams: and about 0.22 grams respectively.
Said elemental powders of Ti, Al, and C were mixed in a glass beaker with about 50 mL of ethanol, stirred gently for about 10 minutes using a glass rod, and subjected to probe sonication at a frequency of about 20 kHz and a power rate of about 40%, using a pulse mode of about 2 seconds ON and 2 about seconds OFF, for different time intervals starting from about 5 minutes to about 120 minutes, to obtain a homogenous mixture.
The homogenous mixture was centrifuged to remove the ethanol and dried in a hot air oven at about 80℃ for about 1 hour to obtain a dried homogenous mixture. The dried homogenous mixture was manually ground using a mortar and pestle, and subjected to a hydraulic press (pressure of about 15 kg/cm2) to form Ti3AlC2 pellets with a diameter of about 10 mm.
The Ti3AlC2 pellets were subjected to sintering by placing inside a vacuum tubular furnace and heating to about 1,500℃ with a dwell period of about 2 hours in an inert atmosphere (argon), at a flow rate of about 2 mL/min. This step produced about 99% of phase pure Ti3AlC2 MAX phase pellets. After naturally cooling down to room temperature, the Ti3AlC2 MAX phase pellets were crushed and ground using a mortar and pestle to obtain fine powders of Ti3AlC2 MAX phase.
In an embodiment of the present disclosure, the stoichiometric molar ratio of elemental powders of titanium (Ti), aluminium (Al), and carbon (C) may be increased to (6:2.2:3.6, i.e., 3.62 grams, 1.22 grams, 0.91 grams).
Energy Estimation
Calculations for energy consumption for the probe sonication (present disclosure method) and high energy ball milling (conventional method) are given below:

Acoustic intensity of the probe sonicator was calculated from intensity of the acoustic wave equation given below;
I= 1⁄2 (ρω^2 A^2 ν)
where,
I = acoustic intensity (W/cm2)
ρ = density of the medium (for ethanol, about 0.789 g/mL)
ω = angular frequency (ω=2πf with f=20 kHz)
A = amplitude of the wave (about 10 μm)
ν = velocity of the ultrasonic sound wave in ethanol.
Velocity of the ultrasonic wave in ethanol medium was calculated by using an ultrasonic interferometer. The velocity was calculated from the equation given below;
v= ϑ*λ
where,
ϑ = frequency of the oscillator (about 2 MHz)
λ = wavelength of the ultrasonic wave in ethanol.
The velocity of the ultrasonic wave was thus found to be about 1,157 ± 5 m/s in ethanol medium. From the calculated acoustic intensity, energy of the ultrasound waves was calculated from the equation given below;
E=I*Area*t
where,
E is the energy estimation (kJ)
I = acoustic intensity (W/cm2), area of the vessel (beaker)
t = time duration (seconds)
For energy estimation of high energy ball milling, the milling time; milling power; speed (rpm); and the ball efficiency with load (powders) were considered. Following equation provides the value of energy consumption;
E=P*t
where,
E = energy estimation (kJ)
P = power consumption (about 500 Watts)
t = milling time.
Energy estimation of probe sonication method (present disclosure) at different time intervals is given in the table below.
Probe Sonication Time (min) Probe Sonication Energy Estimation (kJ)
5 24.2
15 72.3
30 144.2
60 287.6
120 575.2
Energy estimation of high energy ball milling at different time intervals is given in the table below.
Ball Milling Time (hours) Ball Milling Energy Estimation (kJ)
10 18
18 32.4
24 43.7
The energy estimated from the above calculations reveals that high energy is utilised to mix the elemental powders of Ti, Al and C by probe sonication method; hence, time required for mixing the elemental powders of Ti, Al and C is reduced to about 60 minutes compared to about 10 hours required in high energy ball milling.
Moreover, from the aforementioned tables, it can be observed that a minimum of about 18 kJ of energy is estimated for about 10 hours of high energy ball milling; however, an energy of about 72.3 kJ is estimated for about 15 minutes of probe sonication, which indicates the energy efficiency of the probe sonication in mixing the powders is achieved at a relatively lower time when compared to high energy ball milling, which requires prolonged time to reach required energy.
In another embodiment of the present disclosure, probe sonication time may be varied from about 5 minutes to about 120 minutes to evaluate the influence of probe sonication time in synthesising pure MAX phase.
In yet another embodiment of the present disclosure, the disclosed method facilitates synthesising of phase pure Ti3AlC2 (phase composition of about 99%) at a relatively low probe sonication time of about 60 minutes followed by pressureless sintering at about 1,500℃ for about 2 hours.
Commercial Ti3AlC2 MAX phase (about 25 grams, ≥about 90% purity) costs about Rs. 30,000/-. However, the present disclosure reduces the costs up to 1/10th of the total cost (2 grams cost about approximately Rs. 295/-).
Results
As illustrated in Figure 1, on increasing the sonication time to about 30 minutes and beyond, major phase is found to be Ti3AlC2, with emergence of diffraction planes (002), (004), (101), (103), (104), (105), (106), (107), (108), (109) and (110), which are well-matched with the standard JCPDS 52-0875. Hence, it was clear that the phase formation of Ti3AlC2 is highly favoured when the sonication time is increased above about 30 minutes
Figure 2 illustrates powder XRD pattern of the synthesised Ti3AlC2 MAX phase by pressureless sintering at about 1,500℃ for about 2 hours at different probe sonication time intervals from about 5 minutes to about 120 minutes, where growth of a basal plane (002) and dominant (104) planes (located at 9.66 and 39.10 degrees) of Ti3AlC2 phase were clearly visible. Appearance of the first basal plane (002) and the dominant (104) planes indicated the phase formation of Ti3AlC2. These peaks are characteristic features associated with the MAX phase structure.
Two-phase Rietveld refinement was performed for the synthesised Ti3AlC2 MAX phase (sonicated at about 60 minutes) using FullProf software, as illustrated in Figure 3. From the Rietveld refinement analysis, two phases were identified as Ti2AlC (211) and Ti3AlC2 (312) from their respective CIF (Crystallographic Input Files). The Rietveld refinement of XRD pattern clearly showed about 99.19 % of Ti3AlC2 phase and about 0.8 % of Ti2AlC phase.
Figure 4 illustrates that, with increase in probe sonication time, the Ti3AlC2 phase became dominant, when compared to Ti2AlC.
Figure 5 illustrates Field Emission Scanning Electron Microscopy (FE-SEM) images of the Ti3AlC2 MAX phase synthesised with a sonication duration of about 60 minutes. A thick brick like layer morphology was observed and grains were interconnected with metallic bonding. Preferred orientation of grain growth was observed along the "c" direction.
To find lattice vibrations of the Ti3AlC2 MAX phase, Raman spectra were recorded for the Ti3AlC2 MAX phase sonicated for 60 minutes, as illustrated in Figure 6. Ti3AlC2 exhibited a D_6h^4-〖P6〗_3/mmc space symmetry that indicated crystalline lattice structure. This symmetry allows for theoretical prediction of seven Raman-active vibration modes: (2A1g, 2E1g, 3E2g). Raman peaks at 141.42 cm-1, 241.21 cm-1, 435.85 cm-1 and 607.44 cm-1 were assigned to Ti-Al vibrations with E2g, E1g, E1g and, E2g Raman modes, respectively. All the observed Raman peaks corresponded to the Ti3AlC2 MAX phase.
The powder X-ray Diffraction (XRD) pattern comparison in Figure 7 illustrates the synthesis of the Ti₃AlC₂ MAX phase using two different stoichiometric molar ratios of elemental powders: large scale synthesis (elemental powders of titanium (Ti), aluminium (Al), and carbon (C), in a stoichiometric molar ratio of about 6:2.2:3.6) and smaller scale synthesis (elemental powders of titanium (Ti), aluminium (Al), and carbon (C), in a stoichiometric molar ratio of about 3:1.1:1.8.
Interestingly, the Ti3AlC2 MAX phase was formed even at large scale synthesis, which confirmed that the disclosed method can be extended at industrial scale levels.
Figure 8 illustrates comparative analysis of Ti3AlC2 MAX phase synthesised through various methods: probe sonication for about 60 minutes, commercial sample, and high energy ball milling. All the observed diffraction peaks matched with standard data, indicating the quality of the synthesised Ti3AlC2 MAX phase. These findings clearly demonstrated that it is possible to synthesise pure Ti3AlC2 MAX phase on a small to large scale (up to about 7 grams).
The disclosed method of synthesising Ti3AlC2 MAX phase offers at least the following advantages: is cost-effective; offers a facile, time saving and effective method to produce Ti3AlC2 MAX phase; is scalable; and/or reduces presence of intermetallics or secondary phases. Further, the disclosed method may be extended to synthesise other possible MAX phases, as well.
It will be apparent to a person skilled in the art that the above description is for illustrative purposes only and should not be considered as limiting. Various modifications, additions, alterations, and improvements, without deviating from the spirit and the scope of the disclosure, may be made, by a person skilled in the art. Such modifications, additions, alterations, and improvements, should be construed as being within the scope of this disclosure.
, Claims:1. A method of synthesising titanium aluminium carbide MAX phase, comprising steps of:
mixing elemental powders of titanium, aluminium, and carbon in a molar ratio of 3:1.1:1.8, with ethanol, and gently stirring;
subjecting to probe sonication at a frequency of 20 kHz and a power rate of 40%, with a pulse mode of 2 seconds ON and 2 seconds OFF, for 60 to 120 minutes, to obtain a homogenous mixture;
centrifuging the homogenous mixture and drying in a hot air oven at 80°C for 1 hour to obtain a dried mixture;
grinding the dried mixture and subjecting to a hydraulic press by applying a pressure of 15 kg/cm2 to form pellets; and
sintering the pellets at a temperature of 1,500°C for 2 hours under an inert atmosphere at a flow rate of 2 mL/min.
2. The method of synthesising titanium aluminium carbide MAX phase, as claimed in claim 1, wherein: said elemental powders of titanium, aluminium, and carbon are mixed in a molar ratio of 3:1.1:1.8, with ethanol, and gently stirred for 10 minutes.

3. The method of synthesising titanium aluminium carbide MAX phase, as claimed in claim 1 or claim 2, wherein: said elemental powders of titanium, aluminium, and carbon are of 325 mesh.

4. The method of synthesising titanium aluminium carbide MAX phase, as claimed in claim 1, wherein: said sintering is performed under an inert atmosphere of argon.
5. The method of synthesising titanium aluminium carbide MAX phase, as claimed in claim 1, wherein: diameter of said pellets obtained after subjecting to hydraulic press is 10 mm.

Documents