2D transition metal carbides, carbonitrides, and nitrides, known as MXenes, are a rapidly growing family of 2D materials with close to 30 members experimentally synthesized, and dozens more studied theoretically. They exhibit outstanding electronic, optical, mechanical, and thermal properties with versatile transition metal and surface chemistries. They have shown promise in many applications, such as energy storage, electromagnetic interference shielding, transparent electrodes, sensors, catalysis, photothermal therapy, etc. The high electronic conductivity and wide range of optical absorption properties of MXenes are the key to their success in the aforementioned applications. However, relatively little is currently known about their fundamental electronic and optical properties, limiting their use to their full potential. Here, MXenes' electronic and optical properties from both theoretical and experimental perspectives, as well as applications related to those properties, are discussed, providing a guide for researchers who are exploring those properties of MXenes.

Electronic and Optical Properties of 2D Transition Metal Carbides and Nitrides (MXenes).

2D MXenes: Electromagnetic property for microwave absorption and electromagnetic interference shielding

Since their inception in 2011, from the inaugural synthesis of multi-layered Ti3C2Tx by etching Ti3AlC2 with hydrofluoric acid (HF), novel routes with a myriad of reducing agents, etchants and intercalants have been explored and many new members have been added to the two-dimensional (2D) material constellation. Despite being endowed with the rare combination of good electronic conductivity and hydrophilicity, their inherent low capacities, for instance, temper their prospect for application for electrodes in energy storage systems. MXene-based composites, however, with a probable synergistic effect in agglomeration prevention, facilitating electronic conductivity, improving electrochemical stability, enhancing pseudocapacitance and minimizing the shortcomings of individual components, exceed the previously mentioned capacitance ceiling. In this review, we summarise the development and progress in the synthesis of various multi-layered carbides, carbonitrides and nitrides, and intercalants, as well as the subsequent processing in order to delaminate them into single- and/or few-layered and incorporate into MXene-based composites, focusing on their performance and application as transparent conductive films, environmental remediation, electromagnetic interference (EMI) absorption and shielding, electrocatalysts, Li-ion batteries (LIBs), supercapacitors and other electrochemical storage systems.

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Recent progress in layered transition metal carbides and/or nitrides (MXenes) and their composites: synthesis and applications

It remains challenging to fabricate strain-sensing materials and exquisite geometric constructions for integrating extraordinary sensitivity, low strain detectability, high stretchability, tunable sensing range, and thin device dimensions into a single type of strain sensor. A percolation network based on Ti3C2Tx MXene/carbon nanotube (CNT) composites was rationally designed and fabricated into versatile strain sensors. This weaving architecture with excellent electric properties combined the sensitive two-dimensional (2D) Ti3C2Tx MXene nanostacks with conductive and stretchable one-dimensional (1D) CNT crossing. The resulting strain sensor can be used to detect both tiny and large deformations with an ultralow detection limit of 0.1% strain, high stretchability (up to 130%), high sensitivity (gauge factor up to 772.6), tunable sensing range (30% to 130% strain), thin device dimensions ( 5000 cycles). The versatile and scalable Ti3C2Tx MXene/CNT strain sens...

Stretchable Ti3C2Tx MXene/Carbon Nanotube Composite Based Strain Sensor with Ultrahigh Sensitivity and Tunable Sensing Range

This review critically examines the current state of graphene reinforced metal (GNP-MMC) and ceramic matrix composites (GNP-CMC) The use of graphene as reinforcement for structural materials is motivated by their exceptional mechanical/functional properties and their unique physical/chemical characteristics This review focuses on MMCs and CMCs because of their technological importance for structural applications and the unique challenges associated with developing high-temperature composites with nanoparticle reinforcements The review discusses processing techniques, effects of graphene on the mechanical behaviour of GNP-MMCs and GNP-CMCs, including early studies on the tribological performance of graphene-reinforced composites, where graphene has shown signs of serving as a protective and lubricious phase Additionally, the unique functional properties endowed by graphene to GNP-MMCs and GNP-CMCs, such as enhanced thermal/electrical conductivity, improved oxidation resistance, and excellent bi

Graphene reinforced metal and ceramic matrix composites: a review

Synthesis of two-dimensional Ti3C2Tx MXene using HCl+LiF etchant: Enhanced exfoliation and delamination

Isothermal oxidation behaviour of powdered boron carbide (B 4 C) with the fine (1.52 μm), medium (22.5 μm) and coarse (59.6 μm) particle size has been studied in air ranging from 500 to 800 °C. The oxidation rate strongly depends on the particle size of boron carbide and temperature. The smaller particle size the higher oxidation rate of B 4 C powder due to its larger surface area. When B 4 C powder is oxidized in air, a B 2 O 3 glass film is formed on the surface of B 4 C grain which retards the further oxidation reaction. The oxidation kinetics is approximately fitted to the diffusion-controlled rate law which can be described by the Jander's equation. The apparent activation energy for the fine-, medium- and coarse-B 4 C powders is 209.4 ± 11.4, 212.7 ± 35.8 and 219.2 ± 45.3 kJ mol −1 , respectively, slightly varying with the impurity content of B 4 C powders. The type of rate law suggests that the diffusion of oxygen through the oxide layer is the rate-limiting step in the oxidation reactions. In addition, the change in the oxidation process at higher oxidation fraction might associate with the B 2 O 3 volatilization at higher temperatures.

Tai Qiu

Papers

Synthesis of two-dimensional Ti3C2Tx MXene using HCl+LiF etchant: Enhanced exfoliation and delamination

Oxidation behaviour of boron carbide powder

Mechanical, electrical, and thermal properties of graphene nanosheet/aluminum nitride composites

Calcium copper titanate/polyurethane composite films with high dielectric constant, low dielectric loss and super flexibility

Effects of isothermal annealing on the oxidation behavior, mechanical and thermal properties of AlN ceramics