High refractory pressure-less sintered carbide ceramics (HfC based) and ternary composites of AlN-SiC-MoSi2 polished by mechanical grinding to a surface roughness Ra ~ 40 nm, have been treated in vacuum by fs Ti: sapphire laser, operating at 800 nm wavelength, 100 fs pulse duration, and increasing fluence, to generate a sort of "black ceramic material", able to minimize solar radiation reflectance, in such a way that they could be used as the absorber material in an innovative conversion module of solar radiation into electrical energy. Circular specimens of approximately 3 cm in diameter and 3 mm thick have been treated by normal incident laser beam, generating a scanning pattern of parallel lines, at a distance of about 75 mm, using a stage in motion, in the x, y, z directions, driven by a computer. The experimental conditions of laser treatment (energy fluence, speed of transition and distance of steps), have been optimized to maximize the absorption properties of the patterned surface. In some samples this value was increased by about 15%, compared to untreated surface, up to a value of final absorbance of about 95%, all over the range of solar radiation spectrum (from UV to NIR). The morphological and chemical effects have been evaluated by SEM-EDS analysis. At higher fluence, we obtained the characteristic ablation craters and corresponding local material decomposition, while at lower fluence (over the threshold) a typical ordered periodic structure has been obtained, exploitable for its high capacity of entrapment of visible light. The treated ceramics, which we define, by similarity of absorption properties with laser treated Silicon, "black ceramics", were used as active material in conversion modules, installed in a solar test platform. A brief description of the steps in the preparation of these new modules for solar energy conversion is also provided .
fs Ti:Sapphire surface treatment to improve solar radiation absorbance of high-tech ceramics - "Black ceramics" generation for new solar absorbers
E Cappelli;S Orlando;D M Trucchi;A Bellucci;D Sciti;A Lettino
2013
Abstract
High refractory pressure-less sintered carbide ceramics (HfC based) and ternary composites of AlN-SiC-MoSi2 polished by mechanical grinding to a surface roughness Ra ~ 40 nm, have been treated in vacuum by fs Ti: sapphire laser, operating at 800 nm wavelength, 100 fs pulse duration, and increasing fluence, to generate a sort of "black ceramic material", able to minimize solar radiation reflectance, in such a way that they could be used as the absorber material in an innovative conversion module of solar radiation into electrical energy. Circular specimens of approximately 3 cm in diameter and 3 mm thick have been treated by normal incident laser beam, generating a scanning pattern of parallel lines, at a distance of about 75 mm, using a stage in motion, in the x, y, z directions, driven by a computer. The experimental conditions of laser treatment (energy fluence, speed of transition and distance of steps), have been optimized to maximize the absorption properties of the patterned surface. In some samples this value was increased by about 15%, compared to untreated surface, up to a value of final absorbance of about 95%, all over the range of solar radiation spectrum (from UV to NIR). The morphological and chemical effects have been evaluated by SEM-EDS analysis. At higher fluence, we obtained the characteristic ablation craters and corresponding local material decomposition, while at lower fluence (over the threshold) a typical ordered periodic structure has been obtained, exploitable for its high capacity of entrapment of visible light. The treated ceramics, which we define, by similarity of absorption properties with laser treated Silicon, "black ceramics", were used as active material in conversion modules, installed in a solar test platform. A brief description of the steps in the preparation of these new modules for solar energy conversion is also provided .I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
