【作者】 丁大伟；

【导师】 蔡伟民；

【作者基本信息】 上海交通大学 ， 环境工程， 2011， 博士

【摘要】 传统化石能源使用导致的环境污染、全球变暖等问题已是全球环境工程中重中之重的首要问题。穷目前实际,罄所有可预见的替代能源中,即环保又可持续的太阳能已是唯一的选择。但目前当红的太阳能技术中,光伏电池、燃料敏化电池或因次生污染、能耗低,或因效率低等问题均难敷大用。因此更科学有效的利用太阳能并期望其从根本上替代化石能源已是人类生存与发展的不二选择。本课题-太阳能吸收转化涂层的研究因此而生,希望通过光热转化达到对太阳能的充分利用,提供人类所需的各种形式可直接利用的能量。光热系统中将太阳光转化为热能的吸收涂层是整个系统的核心部分。吸收涂层在高温环境下要求保持高的吸收率和低的热辐射损耗,一些在低温环境下表现良好的涂层在高温下由于热稳定性差,材料结构发生变化,致使吸收率下降。多孔氧化铝模板在构建复合纳米结构方面具有广泛的应用,由于其结构稳定,纳米孔尺寸可控,尤其氧化铝本身的低介电常数和对入射光弱反射性,是构建吸收涂层的良好模板。本文在研究多孔氧化铝膜结构特点和制备技术的基础上,探索了基于氧化铝膜的结构稳定的复合吸收涂层的制备。首先,考察铝片的前处理,电解液的种类,浓度,阳极电压及温度等因素对成孔效果的影响,利用两步阳极氧化法,常温范围内（15℃ 25℃）,在高纯铝上制备出孔径40 nm 300 nm,厚度从几百纳米到几十微米的有序多孔氧化铝。在此基础上,探索了工业纯铝上制备有序多孔氧化铝膜的工艺参数,结合两步腐蚀方法,制备出有序性高,孔径40 100 nm,厚度几百纳米至几微米的氧化铝膜。接着,研究不同孔径、厚度的氧化铝膜的光学特征以及填充了金属颗粒构成的吸收涂层其光学吸收性,总结出适合用在构建选择性吸收涂层的薄膜特征。以氧化铝为模板,通过交流电沉积,制备出Cu-Al₂O₃,Ni-Al₂O₃,Cu-Mo-Al₂O₃,Ni-MoO_x-Al₂O₃复合吸收涂层。具有最好的吸收效率的涂层是Cu-Al₂O₃系列薄膜,吸收比α最高可达0.972,发射比ε= 0.105。Ni-Al₂O₃涂层具有最好的热稳定性,其涂层在300℃空气气氛中退火100小时反射曲线基本不变,吸收比α达0.928,发射比小于0.1,其吸收效率也达到目前商业应用的水平。合金氧化铝涂层在吸收比和热稳定方面的表现不如前两种涂层。同时,在多孔氧化铝模板中利用电化学方法原位沉积尖晶石CuAl₂O₄/Cu复合物纳米棒,利用SEM,TEM,XPS,EDS,DRS等检测手段分别对复合物的形貌,组成,结构作了分析。CuAl₂O₄/Cu复合物纳米棒的长度为600 700纳米,直径40 ⁵0纳米, CuAl₂O₄晶型为立方尖晶石结构,金属Cu粒子为多晶。由CuAl₂O₄/Cu/Al₂O₃构成的涂层表现出良好的太阳光选择性吸收,吸收比/发射比为0.92/0.06（T = 100℃）,涂层在200℃下由于失去结合水造成结构发生变化,吸收比下降,但此后在300℃下保持不变。由于CuAl₂O₄/Cu复合物特殊的化学结构,对其在可见光驱动下的催化氧化作用也进行了研究,实验表明纳米棒阵列在可见光下具有良好的光催化性,3小时内降解目标污染物甲基橙60%以上。该复合结构是集光热/光催化为一体的多效吸收涂层。以多孔氧化铝为模板,利用电沉积手段在孔洞中“栽入”金属及金属-半导体复合物,植入纳米棒的尺寸更易控制,可利用其小尺寸效应达到光热、光催化效果,这种技术易于放大,也解决了催化剂的固定问题,对实际应用具有重要意义。更多还原

【Abstract】 The use of fossil fuel lead to series of environmental problem such as acid rain, greenhouse effect etc, and depletion of this kind fuel itself raise question in front of the mankind development. Solar energy is without doubt the most extensive renewable energy in its class, and also is reseach on this field. Among different means of solar energy utilization, only photovoltaic and photothermal are performed in practice. Phtotovoltaic features high-cost and limited applicaition, while photothermal boost advantages of low-cost, easy scale-up, etc, especially solar thermal plant can provide electricity too. The receiver plays an important role in the solar thermal plant. Electricity generation demand the absorbing coating in the receiver performe in higher temperature, absorbs more and emmit less. Absorbing coating based on porous alumina features easy prepation and low energy consumption. Improvement of thermal stability and application of itself in constructing particular absorbing surface become two main development directions for this kind of absorber. Along this direction, focus is given on improving the absorber thermal stability based on a clear aware of the propety of porous alumina in this paper.In this paper, a necessary effort is given to analyze the influence of different parameters on the formation effect of AAO, including the pre-treatment of aluminum, electrolytes, concentration, applied potential, reaction temperature, etc. Optimization is done to the synthesis procedure in different electrolytes, and AAO of 40 nm 300 nm diameters, hundreds of nanometer to micrometers length is successfully manufactured on the high-purity aluminum at room temperature. Then, we try the effort to use commercial aluminum to produce AAO template. Through two-step anodic process, AAO film of 40 100 nm diameter, hundreds of nanometer to several micrometers length has been available.Following, optical charactaristic of AAO film with different diameter and depth as well as metal pigmented ones were studied; proper AAO film was selected for construction of selective absorber. Cu-Al₂O₃, Ni-Al₂O₃, Cu-Mo-Al2O, Ni - MoO_x - Al₂O₃ was prepared through AC deposition in the AAO template. The best convertion efficiency was abtained on the Cu-Al₂O₃ film, with absorptionα= 0.972,ε= 0.105. Ni-Al₂O₃ film boasted the best thermal stability, optical properties was not changed after 100 h annealling at 300℃in air, the absorptionαreached 0.928,ε< 0.10, which is applicable for the practical use. Metal alloy pigmented alumina was less effective both in optical efficiency and thermal stability compared with the former ones, resonable explanation was proposed.A new selective solar absorber coating of Cu–CuAl₂O₄ hybrids deposited in anodic aluminum oxide （AAO） on aluminum substrate has been prepared through an electrochemical process. The structure, composit and morphology was investigated by SEM, TEM, XPS, EDS, DRS, the CuAl₂O₄ belongs to spinel class, while Cu is crystallines. The filled Cu–CuAl₂O₄ hybrids was 600 700 nm length, 40 50 nm diameter, of which an overall optical performance of absorptance （α= 0.923） and emittance （ε= 0.06） was achieved. The stability of the absorber was tested at high temperature and condensation at high humidity. While a decreased after annealing at 200 for 24h,εwas slightly in?uenced; the absorber showed high selectivity （α/ε） of 0.87/0.04. Even after exposing to 300℃for 48h, the optical property did not change. XRD analysis showed that crystalline structure of the hybrids did not change after annealing treatment; probable reasons for the optical degradation are presented.Using electro-deposition technique to implement metal and metal-semiconductor composite into porous anodic alumina realize the easy control of nanorods size, which can favor the photo-thermal, photocatalytic effect of nano-size materials. It’s more convenient for this technique to scale-up and to solve the immolization problem of catalyst, which contribute to the practical application of the nano materials.更多还原