Ti3AlC2 MAX PHASE 

Background Information

Greenhouse gases have an important and widely applicable effect on environmental and fitness outcomes. Extreme weather and accelerated wildfires and different outcomes of weather extrade resulting from greenhouse gases. Emission of greenhouse gases such as CO2 from fossils fuels and industry comprise of 90% of all CO2 emissions from human activities. As a result of the Framework Convention on Climate Change in 1992, and the subsequent Kyoto Protocol in 1997, many countries have come to realize the need to reduce greenhouse gas emissions in order to minimize the global impact on the environment and corresponding climate change.

Emission Of CO2 by fossil fuels

More than 80% of C02 emissions are caused by the combustion of fossil fuels which include natural gas, coal and oil. The major sector which contributes to the emission of greenhouse gases is mainly power consumption and energy supply. Therefore, it has a high potential to degrade the environment quality and effect on human health.CO2 emissions are the primary driver of global climate change. It’s widely recognized that to avoid the worst impacts of climate change, the world needs to urgently reduce emissions.

Sustainable Energy Sources

Energy is an essential component of modern world. Depleting of fossil fuels, global warming and pollution caused increase in the use of renewable energy. Efforts are being made in order to achieve sustainable energy resources. To overcome this issue, the world is moving towards the alternative energy options such as solar energy, wind energy and energy storage devices such as batteries.

Energy Storage Devices

As the fossil fuels are running out, the world is running towards the renewable energy sources and related energy storage technologies. The research community is putting a lot of efforts into developing energy storage solutions, which are essential for replacing the use of fossil fuels and to commercialize the alternative energy sources. Among the various ways of energy storage applications, batteries play a significant role in energy storage system. Batteries are used in many applications. As a result they play a crucial role in the modern life.

Metal-Air Batteries

Metal-air batteries have received a significant prominence due to their high-energy density as compared to the conventional batteries and fuel cells. Lithium-ion batteries are one of the kinds of metal-air batteries, and it has a tremendous attention owing to its highest theoretical energy density alongside a large cell capacity. The lithium ion batteries initially marketed in 1991 and today are used as the most portable devices all around the world.

Cathode of Lithium ion Batteries

Since, lithium ion batteries have received a significant prominence, but there are some technical challenges related to the cathode such as voltage drop, carbon electrode corrosion, etc., still persist and hinder their commercial success. So, in order to improve their overall performance various cathode materials are being investigated by the researchers around the world, where MXenes have recently emerged as a strong candidate with their unique properties such as high mechanical stability. Over the past few years, more than 30 MXenes have been synthesized for various application. Yet, titanium carbide MXene (Ti3C2Tx) remains the most studied MXene, for its high electrical conductivity, which make it suitable choice for electrode material. 

  TITANIUM BASED MAX PHASE

Studies have shown that most of the carbon based MAX phases; especially that containing Ti is counteracting conductors in which the concentrations of electrons and holes are nearly equal. Compatible with their counteracting nature, many MAX phase compounds exhibit a thermo power near zero over a wide range of temperature. 

The most well studied MAX phase with promising commercial future are discussed below:

• Ti2AlC MAX Phase

Due to the layered atomic structure, Ti2AlC MAX phase have an excellent combination of mechanical properties. Moreover, with self-governing crack healing capability, it also showed good creep and fatigue resistance showing massive potential for high temperature structural and protective coating applications. As, it contains oxides formatting elements such as Ti and Al shows excellent oxidation resistance. It can be stable within an extensive range of temperature and this MAX phase is light weighted, which makes it has an advantages in the application of marine gas turbines. 

Studies show that at 1000oC dense Al2O3 layer is formed on the surface of Ti2AlC and protect the bulk material from further oxidation, and after 8h of oxidation 5µm thick oxide layer is formed, which indicated an excellent oxidation resistance. 

Due to the stable chemical properties, this MAX phase also possess excellent corrosion resistance, which attracted much attention. For Example: studies reported that when Ti2AlC MAX phase coated in 600oC water vapor with NaCl deposit, then  the corrosion layer composed of fine NaxTiyOz grains and Al2O3 amorphous phase are formed during the reaction. Due to the unique layered structure of MAX phase, Ti2AlC samples can self-repair the defects during the corrosion process.

• Ti3SiC2 MAX Phase

Ti-Si-C is the most studied system. Ti3SiC2 is the most stable combination and stable within an extensive temperature range and also commercially available.

Studies found that the Ti3SiC2 bulk could form an oxide composed of TiO2 and SiO2 in a temperature range of 900-1200oC, exhibits a good oxidation resistance. It was reported that the oxide scales were 0.34, 0.54 and 0.59 µm at 1000oC, 1100oC and 1200oC respectively.

However, a phenomenon known as oxidation break way has been reported in many studies. It was found that when the content of Al element is exhaust below the critical value, then the protection of Al2O3 layered will be lost, at that moment the oxidation rate and weight increase rapidly. Studies shows that at 1100oC for 4000h, when Al content is lesser then 5.99% in the become oxidized and as a result Al2O3 completely lose its protection and oxidation rate significantly increased.  

• Ti2AlN MAX Phase

Ti2AlN MAX phase has a hexagonal crystal structure and exhibits a great importance as structural material for operation under harsh environment due to its excellent mechanical performance. This phase exhibits a very excellent oxidation resistance. Ti2AlN MAX phase films can be synthesized by post-annealing process of as-deposited Ti, Al, and N films. Ti-Al-N films were deposited on Si and Al2O3 substrate by sputtering.

• Ti3AlC2 MAX-Phase

Recently, a class of ternary layered compound MAX has received much attention because of its unique combination system of metals and ceramics like properties. Ti3AlC2 is a member of this family that possesses a unusual combination properties of metals and ceramics. Like metals, it is thermally and electrically conductive and like ceramics it has high strength, high melting temperature and thermal stability. It can be used in high temperature applications instead of using expensive high-temperature alloys.