No abstract

MoO 3 and MoO 2 materials have been successfully synthesized by thermal decomposition of ammonium paramolybdate in air and a sealed quartz tube, respectively. The microstructure of as-synthesized MoO 3 is composed of irregular lamellar plates with a plate thickness around 100 nm and MoO 2 has the larger grain size with lamellar plates connected with each other. A maximum specific capacitance of 318 F/g at 0.5 A/g is obtained for MoO 2 prepared in a closed environment. On the other hand, the sample MoO 3 exhibits excellent rate capacity with specific capacitances of 218, 209, 196, 188, 176, and 160 F/g at current densities of 0.5, 1, 2, 3, 4, and 5 A/g, respectively. These results pave the way to consider MoO 3 and MoO 2 as prospective materials for energy-storage applications.

The effect of variation in Ni/Sn ratio on martensitic transformation (MT) and magnetic properties was investigated in high‐Mn content Mn2Ni1.64−xSn0.36+x alloys. With the increase of Sn content, the MT temperature shifts substantially towards lower temperature, while the Curie temperature of austenite remains almost unchanged. The reverse MT temperature decreases from 268 to around 80 K for Mn2Ni1.64−xSn0.36+x alloys as x increases from 0.02 to 0.08. Under the low field of 1.2 T, the peak values of magnetic entropy changes are 9.8 J/kg K, 10.1 J/kg K, 10.3 J/kg K, and 6.1 J/kg K for x = 0.02, 0.04, 0.06, and 0.08, respectively. The abrupt changes in magnetization around MT temperatures and the field‐induced metamagnetism should account for the large magnetic entropy changes. Incorporating the advantages of inexpensive and non‐toxic raw materials, these high‐Mn content alloys exhibit very promising prospects for the applications in magnetic refrigeration.

The rapidly solidified Ni41.98Mn42.97V2.08Sn12.97 ribbons are prepared by the melt‐spinning technique. The microstructure, martensitic transformation (MT), and magnetocaloric effect of the ribbons are greatly affected by annealing treatment. The equiaxed crystallized grains with the relatively homogeneous size distribution are observed for these ribbons. After annealing, the grain size becomes obviously large, the lattice constants decreases, and the exchange bias effect gets improved. The MT temperatures increase obviously for the annealed ribbons. Large magnetic entropy change (ΔS) is obtained in the annealed Ni–Mn–V–Sn ribbons. The peak values of ΔS in the annealed ribbons are 41.6 and −2.3 J kg−1 K−1 in the vicinity of MT temperature and Curie temperature of austenite, respectively, for the field change of 30 kOe.