Study Of High-temperature Stability Of W-Doped Ni-AlN Solar Selective Absorbers

With the purpose of improving the high-temperature stability of Ni-AlN solarselective absorbers, the degradation mechanism of Ni-AlN solar selective absorbers wasinvestigated as well as the influence of the W doping-amount on the structural stabilityof Ni1-xWxand the high-temperature stability of Ni1-xWx/Ni-AlN(II)/Ni-AlN(I)/AlNand Ni1-x’Wx’/Ni1-xWx-AlN(II)/Ni1-xWx-AlN(I)/AlN solar selective absorbers. Theresults were listed as follows:(1) The optimal structure of Ni-AlN solar selective absorber is: Ni (200nm)/Ni0.46-AlN (60nm)/Ni0.28-AlN (30nm)/AlN (35nm). The absorptance and emmitanceof the designed Ni-AlN solar selective absorber are0.906and0.14(100℃),respectively.(2) The dominant degradation mechanism of Ni-AlN solar selective absorber athigh temperature is as follows: recovery and recrystallization of Ni IR reflector at hightemperature result in change of grain orientation, which would influence the surfacemorphology, spectral reflectance of Ni IR reflector and optical performance of the Ni/Ni-AlN (II)/Ni-AlN (I)/AlN solar selective absorber. The structural stability ofmetallic IR reflector has significant influence on the high-temperature stability ofNi-AlN solar selective absorbers. Choosing structurally stable metallic IR reflector, Mo,for example, would improve the high-temperature stability of Ni-AlN solar selectiveabsorbers.(3) The structural stability of Ni IR reflector could be improved by doping Welement. And thus the high-temperature stability of Ni1-xWx/Ni-AlN (II)/Ni-AlN (I)/AlN solar selective absorbers would be improved significantly. When W doping amount(atomic content) x is0.18, the change in the aspects of grain orientation, surfacemorphology and roughness, spectral reflectance of the Ni1-xWxIR reflector tends to berelatively small. Thus, the Ni0.82W0.18/Ni-AlN (II)/Ni-AlN (I)/AlN solar selectiveabsorbers tend to be thermally stable.(4) Ni1-xWx-AlN cermet film is composed of Ni, W, amorphous AlN, NiAlintermetallic compound and W-N compound. W doping amount has no significant influence on the type of phase structure, chemical combination state and opticalconstants of Ni1-xWx-AlN cermet films with certain metal volume fraction. W dopingamount has significant influence on the high-temperature stability of Ni0.82W0.18/(Ni1-xWx)0.46-AlN/(Ni1-xWx)0.28-AlN/AlN solar selective absorbers. When W dopingamount (atomic content) x is0.16, the Ni0.82W0.18/(Ni1-xWx)0.46-AlN/(Ni1-xWx)0.28-AlN/AlN solar selective absorbers tend to be desirably stable.