Reversible bending motion of unimorph composites driven by combining LaNi₅ alloy powders dispersed polyurethane and thin supporting copper sheet under partial hydrogen gas pressure

The polyurethane composites dispersed with powders mixture of LaNi ₅ hydrogen storage alloy (35 vol% of LaNi₅) and Pd-Al ₂O₃ catalyst powders were prepared by solution cast method, which easily controlled the shape and mixed ratio of the composites. In order to generate the bending strain of reversible up motions at vertical and horizontal directions, the unimorph (PU+LaNi₅/Cu) sheet constructed with the driving polyurethane composite and supporting copper thin sheet of 10 μm thickness with high specific stiffness (apparent hardening modulus per specific weight) was prepared. Although the bending motion of the unimorph sheet operated by hydrogenation under 0.3 MPa H₂ gas was irreversible, the reversible motion was detected under 0.2 MPa H₂ gas. The maximum strain of reversible bending motion (ε^max) of the PU+LaNi ₅/Cu sheet is more than 1520 and 1120ppm on vertical and horizontal directions, respectively. The ε^max of the PU+LaNi₅/Cu sheet at vertical direction was slightly higher than that of the ABS resin unimorph (ABS+LaNi₅/ABS) sheet constructed with the driving ABS resin composites and pure ABS resin supporting sheet, whereas it was slightly lower than that of the silicone rubber unimorph (SR+LaNi₅/SR) sheet constructed with the driving silicone rubber composites and pure silicone rubber supporting sheet. It can be estimated that the responsiveness (dε/dt) of cyclic motion of the (PU+LaNi₅/Cu) sheet is slightly higher than ABS+LaNi₅/ABS sheet.