Reversible Bending Motion of Unimorph Composites Driven by Combining LaNi<SUB>5</SUB> Alloy Powders Dispersed Polyurethane and Thin Supporting Copper Sheet under Partial Hydrogen Gas Pressure

Abstract

The polyurethane composites dispersed with powders mixture of LaNi 5 hydrogen storage alloy (35 vol% of LaNi 5 ) and Pd-Al 2 O 3 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+LaNi 5 /Cu) sheet constructed with the driving polyurethane composite and supporting copper thin sheet of 10 mm 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 H 2 gas was irreversible, the reversible motion was detected under 0.2 MPa H 2 gas. The maximum strain of reversible bending motion (" max ) of the PU+LaNi 5 /Cu sheet is more than 1520 and 1120 ppm on vertical and horizontal directions, respectively. The " max of the PU+LaNi 5 /Cu sheet at vertical direction was slightly higher than that of the ABS resin unimorph (ABS+LaNi 5 /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+LaNi 5 /SR) sheet constructed with the driving silicone rubber composites and pure silicone rubber supporting sheet. It can be estimated that the responsiveness (d"=dt) of cyclic motion of the (PU+LaNi 5 /Cu) sheet is slightly higher than ABS+LaNi 5 /ABS sheet.

An Improved H₂-Gas Pressure Operated LaNi₅ Powder-Dispersed Polyurethane/Titanium 2-Layer Actuator with Reversible Giant and Rapid Expansion by Hydrogenation

“…9) To solve these problems we fabricate PU:LaNi 5 /Ti actuator using thinner 5 μm titanium (Ti) sheet since Ti has high stiffness and strength. We demonstrate reversible bending motion, ε max in vertical and horizontal directions in PU:LaNi 5 /Ti can be raised 60% over that of PU:LaNi 5 / Cu 11) by Ti. Moreover, we show maximum responsiveness (dε/dt) max by hydrogenation of cyclic motion of the PU:LaNi 5 /Ti will be higher than that of the PU:LaNi 5 /Cu 11) .…”

“…By implementing use of thin Ti foil as substrate in the PU:LaNi 5 /Ti the maximum responsiveness (dε/dt) max generated by hydrogenation in the vertical set of PU:LaNi 5 /Ti reaches 950 ppm ks −1 , improved 1.36, 3 and 32 times higher than those reported for PU:LaNi 5 /PU, PU:LaNi 5 /Cu and ABS:LaNi 5 /ABS at 700, 300 and 30 ppm ks −1 , repectively. 10,11) However, the (dε/dt) max is apparently 32% lower than that of the SR:LaNi 5 /SR. 9) (dε/dt) max (SR:LaNi 5 /SR) = 1250 9) > (dε/dt) max (PU:LaNi 5 /Ti) = 950 > (dε/dt) max (PU:LaNi 5 /PU) = 700 10) > (dε/dt) max (PU:LaNi 5 /Cu) = 300 11) > (dε/dt) max (ABS:LaNi 5 /ABS) = 30 10)…”

“…Figure 1 compares motion strain, ε vs. time, t graphs for our unimorph PU:LaNi 5 /Ti actuator with those of the literature. [9][10][11] At room temperature although cyclic bending motion is irreversible at H 2 pressure of 0.3 MPa, the reversible cyclic bending motion is achieved at 0.2 MPa. The cyclic bending motion occurs with alternating H 2 pressure ←→ vacuum cycles.…”

“…The vertical ε max of 2450 ppm of PU:LaNi 5 /Ti is slightly and tremendously higher than that (2300 and 250 ppm) reported for PU:LaNi 5 /PU 10) and ABS:LaNi 5 /ABS 10) , respectively, although it is slightly lower than that (2500 ppm) of the SR:LaNi 5 /SR. Table 1 The maximum reversible strain (ε max ) and responsiveness (dε max /dt) in vertical direction, as well as elastic load resistivity (dF/dε) and elasticity (dσ/dε) of the PU:LaNi 5 /Ti along with those reported for PU:LaNi 5 /Cu 11) , PU:LaNi 5 /PU 10) , ABS:LaNi 5 /ABS 10) and SR:LaNi 5 /SR 9) , together with ε max on horizontal direction of the PU:LaNi 5 /Ti and PU:LaNi 5 /Cu, 11) as well as elasticity of Pd 13) The maximum bending strain (ε max ) of reversible motion of the unimorph sheet strongly depends on not only hydrogenation expansion of LaNi 5 powders, but also both elasticity and its limits of the composites. Thus, the bending stressstrain curves have been obtained.…”

“…9) However, when rotated 90 deg for horizontal motion both PU:LaNi 5 /PU 10) and SR:LaNi 5 /SR 9) sag with spontaneous bending due to gravity the horizontal motion not attained. 11) On the other hand, research of replacing PU substrate with 10 μm thick Cu for PU:LaNi 5 /Cu 11) actuator successfully achieved reversible bending motion, ε max of more than 1520 and 1120 ppm on vertical and horizontal directions, respectively in 0.20 MPa-H 2 gas atmosphere. However, the tradeoff is its vertical ε max of 1500 ppm is less than those of PU:LaNi 5 /PU 10) and SR:LaNi 5 /SR.…”