Ceramic Matrix Composites Obtained by the Reactive Sintering of Boron Carbide with Intermetallic Compounds from the Ti-Si System

In this study, we investigated the effect of adding two different intermetallics, Ti₅Si₃ and TiSi₂, for the preparation of TiB₂-SiC-B₄C composites. As part of the research, stoichiometric composites consisting only of two phases TiB₂ and SiC were obtained. The TiB₂-SiC-B₄C composites were prepared via pressureless sintering. The presence of the phases in the sintered composites was confirmed using X-ray diffraction and scanning electron microscopy. The SEM-EDS examination revealed that the TiB₂ and SiC phases were formed during the composite process synthesis and were distributed homogeneously in the B₄C matrix. The obtained results allowed us to usually exceed 2000 °C and the use of specialized equipment for firing, that is, vacuum or protective atmosphere furnaces as well as control and measurement equipment. Such an approach generates high costs that are decisive for the economics of the technological processes. In the case of our compositions, it is possible to lower the temperature to 1650 °C. The TiB₂-SiC-B₄C composites were classified as UHTCs.

Preparation of TiSi2 Powders with Enhanced Lithium-Ion Storage via Chemical Oven Self-Propagating High-Temperature Synthesis

Although silicon has highest specific capacity as anode for lithium-ion battery (LIB), its large volume change during the charge/discharge process becomes a great inevitable hindrance before commercialization. Metal silicides may be an alternative choice because they have the ability to accommodate the volume change by dispersing Si in the metal matrix as well as very good electrical conductivity. Herein we report on the suitability of lithium-ion uptake in C54 TiSi₂ prepared by the "chemical oven" self-propagating high-temperature synthesis from the element reactants, which was known as an inactive metal silicide in lithium-ion storage previously. After being wrapped by graphene, the agglomeration of TiSi₂ particles has been efficiently prevented, resulting in an enhanced lithium-ion storage performance when using as an anode for LIB. The as-received TiSi₂/RGO hybrid exhibits considerable activities in the reversible lithiation and delithiation process, showing a high reversible capacity of 358 mAh/g at a current density of 50 mA/g. Specially, both TiSi₂ and TiSi₂/RGO electrodes show a remarkable enhanced electrochemical performance along with the cycle number, indicating the promising potential in lithium-ion storage of this silicide. Ex-situ XRD during charge/discharge process reveals alloying reaction may contribute to the capacity of TiSi₂. This work suggests that TiSi₂ and other inactive transition metal silicides are potential promising anode materials for Li-ion battery and capacitor.