太阳能选择性吸收涂层制备技术

太阳能选择性吸收涂层制备技术是太阳能热利用的关键技术之一,目前存在高温稳定性差、工艺稳定差、制备工艺复杂等问题。将Ni-AlN材料体系和中频反应磁控溅射技术结合起来有可能开发出光学性能和高温性能优异的选择性吸收涂层的低成本工业化生产技术。本论文对中频反应磁控溅射工艺参数对TiN薄膜结构及性能的影响进行了研究,结果表明氮气流量和靶功率对薄膜结构及性能的影响较大。对中频反应磁控溅射工艺参数对Al靶放电特性和制备的AlN薄膜显微结构的影响进行了研究,结果表明:氮气流量、氩气流量、靶功率和靶面磁场对Al靶的放电特性有显著影响;Al靶电压随着氮气流量的增加而减小,当氮气流量超过临界值后,Al靶电压随着氮气流量增加而下降的速度加快;减小氩气流量和增加靶电流使Al靶开始发生严重靶中毒所对应的临界氮气流量有所增加。随着氮气流量的增大,沉积的AlN薄膜含氮量不断增加,其相组成由以单质铝相为主逐渐转变为以AlN相为主,薄膜的致密性有明显改善;增大氩气流量或减小靶电流使制备完全符合理想化学计量比的AlN薄膜的氮气流量范围变小,AlN薄膜的相结构由纳米晶向非晶转变;增大氩气流量和靶电流有利于薄膜表面粗糙度和致密性的改善。对Ni-AlN复合薄膜的共溅射沉积工艺和显微结构的研究表明:当同时开启Ni靶和Al靶时,Al靶表面开始发生严重靶中毒所对应的临界氮气流量有所增加; Ni-AlN复合薄膜表面的颗粒尺寸明显小于相同条件下沉积的AlN薄膜;制备的Ni-AlN复合薄膜由非晶态的AlN和纳米晶的Ni组成,N/Al比低于理想化学计量比,Ni含量明显高于Al含量。对梯度Ni-AlN选择性吸收涂层结构对其性能的影响进行了研究,并与制备的梯度Al-AlN选择性吸收涂层进行了比较,结果表明:随着Ni-AlN复合材料吸收亚层层数的增加,制备的选择性吸收涂层的可见光反射率有所下降,在制备AlN减反射膜后,选择性吸收涂层的可见光反射率明显降低;随着梯度Ni-AlN选择性吸收涂层的浓度梯度减缓,选择性吸收涂层的可见光反射率不断减小;当单层Ni-AlN复合材料吸收亚层的沉积时间为10min时制备的梯度Ni-AlN选择性吸收涂层在可见光范围内的反射率小于15%,且具有明显的光谱选择性。
逆变焊机
Solar selective absorbing films, which are a key technology for solar energy thermal utilization, were restricted in application for their disadvantages such as poor high temperature stability, poor process stability and complex fabrication process. The industrial fabrication technology for solar selective absorbing films with excellent optical properties and high temperature stability at low cost can be developed through the combination of the Ni-AlN material system and medium frequency magnetron reactive sputtering.The influence of medium frequency magnetron reactive sputtering process on the structure and properties of TiN were studied, and it is shown that nitrogen flow rate and Ti target power are the key factors.The influence of medium frequency magnetron reactive sputtering process, such as nitrogen flow rate, argon flow rate, Al target current, and magnetic field on Al target surface, on the discharge characteristics of Al target and the microstructures of deposited AlN films were studied. It was found that the discharge characteristics of Al target was obviously affected by nitrogen flow rate, argon flow rate, Al target current, and magnetic field on Al target surface; Al target voltage was decreased with increasing nitrogen flow rate, and the decreasing rate of voltage with increasing nitrogen flow rate was obviously increased after the nitrogen flow rate exceed a critical value; the critical nitrogen flow rate corresponding with serious poisoning of Al target could be increased by decreasing argon flow rate or increasing Al target current. With increasing the nitrogen flow rate, the nitrogen content in AlN films was increased, the phase composition was changed from mainly pure aluminum to pure AlN, and the density of AlN films were improved also. The synthesis of pure AlN with an ideal stoichiometric proportion became more difficult and the crystalline structure of AlN films was changed from nanocrystalline to amorphous phase with increasing argon flow rate or decreasing Al target current; the density of AlN films could be improved with increasing argon flow rate and Al target current.The reactive cosputtering process and microstructure of Ni-AlN composite films were studied. It is shown that the critical nitrogen flow rate corresponding with serious poisoning of Al target was increased when Al target was ignited with Ni target. Ni-AlN films, having finer grains on their surface and a smaller surface roughness, was composed of amorphous AlN and nanocrystalline Ni; the atomic ratio of nitrogen to aluminum was lower than the ideal stoichiometric proportion of AlN and nickel content was obviously higher than aluminum content in Ni-AlN composite films.The influences of the structure of graded Ni-AlN solar selective absorbing films on their properties were studied and the graded Al-AlN solar selective absorbing films were fabricated. It it shown that the visible light reflectance of graded Ni-AlN solar selective absorbing films was reduced with increasing the layer number of Ni-AlN absorbing layer, and it could be further obviously decreased after depositing AlN antireflection layer. The visible light reflectance of graded Ni-AlN solar selective absorbing films was reduced with decreasing the composition gradual slope of graded Ni-AlN solar selective absorbing films; the visible light reflectance of graded Ni-AlN solar selective absorbing films was less than 15% and an obvious spectral selectivity was found when the deposition duration of every Ni-AlN absorbing layer was 10min.