Elements Of X Ray Diffraction

We investigated the synthesis of quasi-two-dimensional carbide (Ti 3 C 2 ), with the name of MXene, by immersing Ti 3 AlC 2 in 40% or 49% hydrofluoric acid (HF) at 0 °C, 15 °C or 60 °C. The influences of time, temperature, and source of Ti 3 AlC 2 on the synthesis were researched. It was found that Ti 3 C 2 synthesized from pressureless synthesized Ti 3 AlC 2 was highly oriented compared to that from hot-pressed Ti 3 AlC 2 . As-synthesized Ti 3 C 2 could be further exfoliated by intercalation with urea, dimethylsulfoxide or ammonia. From the results of thermogravimetry and differential scanning calorimetry, Ti 3 C 2 MXene with F/OH termination was found to be stable in argon atmosphere at temperature up to 800 °C. In oxygen atmosphere, at 200 °C, parts of MXene layers were oxidized to obtain an interesting structure: anatase nano-crystals were evenly distributed on 2D Ti 3 C 2 layers. At 1000 °C, MXene layers were completely oxidized and anatase phase fully transformed to rutile in oxygen atmosphere.

Synthesis and thermal stability of two-dimensional carbide MXene Ti3C2

Rational design of silicon and carbon nanocomposite with a special topological feature has been demonstrated to be a feasible way for mitigating the capacity fading associated with the large volume change of silicon anode in lithium ion batteries. Although the lithiation behavior of silicon and carbon as individual components has been well understood, lithium ion transport behavior across a network of silicon and carbon is still lacking. In this paper, we probe the lithiation behavior of silicon nanoparticles attached to and embedded in a carbon nanofiber using in situ TEM and continuum mechanical calculation. We found that aggregated silicon nanoparticles show contact flattening upon initial lithiation, which is characteristically analogous to the classic sintering of powder particles by a neck-growth mechanism. As compared with the surface-attached silicon particles, particles embedded in the carbon matrix show delayed lithiation. Depending on the strength of the carbon matrix, lithiation of the embedde...

In situ TEM study of lithiation behavior of silicon nanoparticles attached to and embedded in a carbon matrix.

Preparation, mechanical and anti-friction performance of MXene/polymer composites

Flash sintering is a novel densification technology for ceramics, which allows a dramatic reduction of processing time and temperature. It represents a promising sintering route to reduce economic, energetic and environmental costs associated to firing. Moreover, it allows to develop peculiar and out-of-equilibrium microstructures. The flash process is complex and unusual, including different simultaneous physical and chemical phenomena and their understanding, explanation and implementation require an interdisciplinary approach from physics, to chemistry and engineering. In spite of the intensive work of several researchers, there is still a wide debate as for the predominant mechanisms responsible for flash sintering process. In the present review, the most significant and appealing mechanisms proposed for explaining the “flash” event are analyzed and discussed, with the aim to point out the level of knowledge reached so far and identify, at least, possible shared theories useful to propose future scientific activities and potential technological implementations.

Flash sintering of ceramics

Coarsening and grain growth in sintering of two particles of different sizes

Measurement and modelling of electrical resistivity by four-terminal method during flash sintering of 3YSZ

Anisotropic shrinkage induced by particle rearrangement in sintering

A layered ternary carbide Ti3AlC2 was synthesized by pressureless calcining process from the mixture of titanium, aluminum and graphite powders. Almost single-phase Ti3AlC2 was obtained after calcining at 1400°C for 4 h. The microstructural evolution during the formation of Ti3AlC2 was examined at the temperature from 900°C to 1400°C. Ti3AlC2 was formed through an intermediate carbide of Ti3AlC, which was seldom reported in previous literatures. Based on the results of X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS), a possible reaction mechanism was proposed to explain the formation of Ti3AlC2.

Reaction mechanism for the synthesis of Ti3AlC2 through an intermediate carbide of Ti3AlC from elemental Ti, Al, and C powder mixture

A layered ternary carbide Ti 3 AlC 2 was synthesized by pressureless calcining process from the mixture of Ti/Al/2TiC. Almost single phase Ti 3 AlC 2 was obtained after calcining at 1400 °C for 1 h. The microstructural evolution during the formation of Ti 3 AlC 2 was examined at the temperature from 900 °C to 1400 °C. Based on the results of X-ray diffractometry (XRD) and energy-dispersive X-ray spectroscopy (EDS), a possible reaction mechanism was proposed to explain the formation of Ti 3 AlC 2 . Above the melting point of aluminum, liquid Al reacts with titanium to form the intermetallic compound of AlTi. As the temperature is increased to 1400 °C, the intermetallic compound of AlTi reacts with TiC to form Ti 2 AlC and then, Ti 2 AlC further reacts with TiC to form the final product of Ti 3 AlC 2 .

Michiyuki Yoshida

Papers

Coarsening and grain growth in sintering of two particles of different sizes

Measurement and modelling of electrical resistivity by four-terminal method during flash sintering of 3YSZ

Anisotropic shrinkage induced by particle rearrangement in sintering

Reaction mechanism for the synthesis of Ti3AlC2 through an intermediate carbide of Ti3AlC from elemental Ti, Al, and C powder mixture

Microstructural evolution during the formation of Ti3AlC2