Ti-Al-C MAX phases by aluminothermic reduction process

International audienceA new approach to synthesis of Ti₂AlC-Ti₃AlC₂/Al₂O₃ compounds is developed based on thermite reaction in the TiO₂-Al-C system. The effect of Al excess is also discussed. XRD analysis has proved that this parameter can be used to improve the product purity, i.e., the amount of TiC in the final product. It has also been shown that, with increasing Al excess, the composition of a major MAX phase undergoes a change from Ti₂AlC to Ti₃AlC₂

Interaction of Graphite with a Ti–Al Melt during Self-Propagating High-Temperature Synthesis

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Study on the Synthesis and Structural Characterization of the Cermets TiC/Fe by Self-Propagating-High-Temperature and by Thermal Explosion

International audienceA study of the TiC/Fe cermets produced by self-propagating high-temperature synthesis and by thermal explosion with various quantities of added iron was performed. It was established that both experimental and calculated adiabatic temperature of combustion and the propagation velocity of the reaction front decrease with the addition of iron in the reactants. The addition of iron was optimized at 30 wt % to ensure the stability of the propagation. The products were characterized by X-ray diffraction (XRD); the reaction seems to start at the surface of the solid titanium particle and to proceed by solid-state diffusion of iron and carbon to form TiFe and TiC/Fe cermets composite. The evolutions of the phases, size, and density of TiC grains during both kinetics reactions were highlighted by X-rays diffraction, optical and scanning electronic microscopy equipped with microindentation and energy-dispersive X-ray spectroscopy, respectively

A novel method for synthesis of low-cost Ti-Al-C-based cermets

International audienceTi₂AlC-Ti₃AlC₂/Al₂O₃ samples have been successfully synthesized by aluminothermic reduction of TiO₂ in the presence of C. Phase composition of resultant products obtained at different Al excess was characterized by XRD. Microstructures of the samples were observed by SEM. XRD analysis proved that it is possible to improve the yield of MAX phases using Al excess. With increasing Al excess, a major MAX phase was found to change from Ti₂AlC to Ti₃AlC₂

From nanoparticles to bulk crystalline solid: nucleation, growth kinetics and crystallisation of mixed oxide Zr x Ti 1−x O 2 nanoparticles

International audienceWe describe the preparation of mixed metal oxide nanoparticles of a desirable composition and their transformation to the crystalline solids Zr x Ti 1−x O 2 (0.0 ≤ x ≤ 1.0) after heat treatment

SHS of high-purity MAX compounds in the Ti-Al-C system

International audienceDuring the synthesis of MAX phases using combustion synthesis (or Self-Propagating High-temperature Synthesis), the main drawback is the presence of binary phases, and especially the simple MX carbide, when X = C. Our experiments were designed in order to check whether the cooling rate of the sample immediately after synthesis might play a key role for obtaining samples with low-level carbide contents. In the best conditions, a TiC content of about 2% only has been observed. A systematic study on the direct effect of the cooling rate on the final composition has then been conducted, and confirms that high cooling rates allow the synthesis of high-purity MAX phases in the Ti-Al-C system

One-step synthesis and densification of Ti-Al-C-based cermets by ETEPC

International audienceThe Electro-Thermal Explosion under Pressure with Confinement (ETEPC) mode of SHS has been studied for producing possibly low-porosity Ti₂AlC and Ti₃AlC₂ from elemental powders in a very short processing time. The effect of maintaining the electric current after the ignition of exothermic reaction has also been studied. A better achievement of the desired reaction, with a total yield of MAX phases up to 73%, was obtained with maintaining the electric current for 4 s after ignition of the exothermic reaction in the Ti:Al:C = 2:1:1 composition. XRD studies revealed also composition gradients

Synthesis of high-purity polycrystalline MAX phases in Ti–Al–C system through Mechanically Activated Self-propagating High-temperature Synthesis

International audienceTernary MAX phase compounds were synthesized using an alternative route called MASHS (Mechanically Activated Self-propagating High-temperature Synthesis). This original process combines a short duration ball milling (MA) of reactants (Ti, Al, C) with a self-sustaining combustion (SHS). The particle size evolution of the powder mixture during Mechanical Activation was monitored using XRD profile analysis. The effect of Al-excess was also discussed. XRD and SEM analyses have proved that the activation of the reaction kinetics must be accompanied by a decrease in the overall exothermicity in order to synthesize pure Ti–Al–C MAX phases by MASHS