Mo effect on the phase stability and room-temperature fracture toughness of Nb/Nb_5Si_3 in-situ composites

Nb/Nb5Si3 in-situ composites are very attractive structural materials because these materials perform a good balance in mechanical properties, including high strength at high temperature (> 1000 degrees C) and reasonably high fracture toughness at room temperature. Metastable phase Nb3Si plays an important role in the properties of Nb/Nb5Si3 composites by affecting the volume fraction of ductile phase. The addition of Mo affects on the microstructure of ductile phase and the stability of metastable phase Nb3Si. In this paper, Nb-10Si-xMo and Nb-18Si-xMo (x = 0, 5, and 15) alloys were prepared by arc melting and annealed at 1473 K for 100 h. Single edge-notched bending (SENB) test was used to study the fracture toughness of Nb-Si-Mo alloys. The room temperature fracture toughness of Nb-10Si is 10.48 MPa center dot m(1/2) and higher than that of binary Nb-18Si alloys at near-eutectic composites. The addition of 5 at.% Mo improved the fracture toughness of as-cast Nb-Si alloys from 4.1 MPa center dot m(1/2) to 9.99 MPa center dot m(1/2) at near-eutectic compositions and reduced it from 10.48 MPa center dot m(1/2) to 8.86 MPa center dot m(1/2) at hypoeutectic compositions.

A Review of Metal Silicides for Lithium-Ion Battery Anode Application

Lithium batteries(LIBs) with low capacity graphite anode(~372 mAh g-1) cannot meet the ever-growing demand for new energy electric vehicles and renewable energy storage.It is essential to replace graphite anode with higher capacity anode materials for high-energy density LIBs.Silicon(Si) is well known to be a possible alternative for graphite anode due to its highest capacity(~4200 mAh g-1).Unfortunately,large volume change during lithiation and delithiation has prevented the Si anode from being commercialized.Metal silicides are a promising type of anode materials which can improve cycling stability via the accommodation of volume change by dispersing Si in the metal inactive/active matrix,while maintain greater capacity than graphite.Here,we present a classification of Si alloying with metals in periodic table of elements,review the available literature on metal silicide anodes to outline the progress in improving and understanding the electrochemical performance of various metal silicides,analyze the challenges that remain in using metal silicides,and offer perspectives regarding their future research and development as anode materials for commercial LIBs application.