Proton NMR study of hydrogen mobility in (TiCr1.8)1-xVx hydrides

• Published in: Journal of alloys and compounds Vol. 778; pp. 962 - 971
• Main Authors: Shelyapina, M.G., Skryabina, N.E., Surova, L.S., Dost, A., Ievlev, A.V., Privalov, A.F., Fruchart, D.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 25.03.2019; Elsevier
• Subjects: bct metal hydrides; Hydrogen mobility; Percolation threshold; Physics; Ti-V-Cr alloys; Hydrogen mobility; Percolation threshold; Ti-V-Cr alloys; bct metal hydrides
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2018.10.382

A series of (TiCr1.8)1-xVx alloys with x = 0.2, 0.4, 0.6 and 0.8 was synthetized by induction melting of a mixture of TiCr1.8 alloy and pure V. It has been found that after hydrogenation all the compounds turn into bct structure. The present bct metal hydrides could be considered forming a pre-martensite state during the transformation (Ti-V-Cr)Hxmin (bcc) ↔ (Ti-V-Cr)Hxmax (fcc). Proton NMR studies reveal that distribution of hydrogen over all samples is not homogeneous. The modified Bloembergen-Purcell-Pound model, which supposes existence of two hydrogen fractions in different metal environment, provides the lowest averaged activation energy of hydrogen motion corresponding to (TiCr1.8)0.6V0.4, the composition that exhibits the highest reversible hydrogen capacity. Following a regularity in changes of both structural parameters of the studied compounds before and after hydrogenation and those parameters that answer for hydrogen mobility we anticipate the existence of a percolation threshold in properties of the alloys (close to the compositions x = 0.4÷0.5). •Hydrogen storage properties of Ti-V-Cr alloys are impacted by metal atom distribution.•1H NMR reveals inhomogeneous distribution of hydrogen for all studied samples.•A percolation threshold in hydrogenation properties of (TiCr1.8)1-xVx hydrides is pointed out for x ≈ 0.5.