【作者】 王伟；

【导师】 文怀兴；

【作者基本信息】 陕西科技大学 ， 轻工装备及控制， 2019， 博士

【摘要】 光热转换技术是将太阳能转换为热能的最为直接和有效的方式,在传统的太阳能水热装置、太阳能空气干燥设备、太阳能集热发电技术中,关键的光热转化效率问题是涂覆在集热装置表面的光热转换涂层,为了获得高的光吸收性能,传统的涂层工艺需要采用一个复杂的共溅射技术,通常存在结构工艺复杂、成本高的问题,不利于实际的工业化生产。本文引入自掺杂设计思路,利用单一靶材的反应溅射技术,设计了一种新型自掺杂Me-MeOx(Me=W或Mo)光热转换涂层,其具有非常优异的光学吸收性能和热稳定性能,并且溅射工艺简单、制造成本低、光学吸收易调控、结构易扩展,非常适合于传统的低成本、大规模的中高温光热利用技术。将新型的自掺杂光热转换技术应用于调控人体温度的可穿戴技术中,可以克服传统的采用焦耳热效应和反射红外波长的被动式加热方式,达到主动吸收太阳光温暖人的身体,并反射人体红外热辐射进行保温的光热效果,在户外应急取暖衣料方面具有非常好的应用价值,拓宽了光热转换涂层在柔性、可穿戴人体热转换技术中的应用。具体的研究内容如下所述:(1)研究了单层WOx薄膜的本征吸收特性,引入了介质性WOx、SiO2和Al2O3薄膜作为减反射层,分析其对掺杂WOx薄膜光吸收的调控性,考察了涂层的热稳定性;结果表明,掺杂WOx薄膜具有非常优异的本征光学性能,吸收率(α)最大为0.83,发射率(ε)为0.05;介质性WOx薄膜具有一定的减反射作用,可进一步将WOx薄膜的α提高到0.91,ε仍保持不变;热退火结果表明,由于元素的扩散和氧化导致了涂层在空气中的热稳定性较差,但在真空400℃下,涂层却显示了非常优异的耐热性;(2)基于自掺杂原理,结合WOx薄膜的高吸收特性及减反射作用,制备了一种新型的自掺杂W-WOx基多层光热转换涂层,研究了涂层的光学性能和结构特征,阐明了温度诱发的热扩散和氧化的失效机理;结果表明,涂层具有非常优异的光学吸收(α=0.932,ε=0.058),光热效率η达到90%,这主要归因于掺杂WOx薄膜的本征吸收,各界面层之间的光学干涉和金属W层的近场增强效应;热处理表明,该涂层在空气中低于300℃下具有非常优异的热稳定性,但由于涂层中W颗粒的扩散,在较高的温度下被严重的氧化,改变了涂层的结构和成分,导致涂层的光学性能下降;(3)研究了不同气压下单层MoOx薄膜的光学吸收性能,分析了 Si02和MoOx介质薄膜的减反射效果,考察了涂层在不同环境下的热稳定性;结果表明,非化学计量比MoOx薄膜显示了非常优异的光学吸收能力,α最大为0.83,ε为0.05。同样地,介质性MoOx薄膜也具有非常好的减反射效果,在光热转换涂层的设计中可以作为一种新型的减反射材料;热退火结果也表明,涂层在真空450℃下都具有非常优异的热稳定性,然而由于涂层中元素的扩散和氧化现象,导致样品在空气下的耐热性较差;(4)结合前述设计思路,还制备了一种结构性能更加稳定,环境适应性更好的自掺杂Mo-MoOx多层渐变光热转换涂层,并对其光学常数、晶体结构及物相成分进行了分析,研究了涂层在不同环境下的热稳定性;结果表明,该涂层在可见光和近红外区域内产生了非常优异的光学吸收性能,其α最高为0.93,ε为0.055,η达到92%;进一步在空气下热退火,涂层表面发生了严重的氧化,表现了非常差的耐热性;而在真空450℃下,涂层的光学吸收没有发生明显改变,显示了非常优异的热稳定性;(5)基于上述的研究结果,研究了Me-MeOx基光热转换涂层在柔性PET和PI薄膜以及棉布和涤纶织物上的光学吸收、弯曲变形性能及光热转换效果;结果表明,在柔性聚合物和织物上,涂层都显示了非常好的光吸收能力和弯曲变形性能,其α分别为48%～54%和82%～83%,ε均为30%～35%;在1KW/m2的模拟太阳光下,柔性涂层的表面稳态温度可达到78℃,而织物涂层约为90℃,显示了非常好的光热转换效果;此外,在户外阴天的自然光照射下,织物涂层的表面稳态温度可以达到10～11℃,与空白织物相比较,其温度差接近6℃,可以有效的温暖人的身体。综上所述,自掺杂Me-MeOx基光热转换涂层具有非常优异的光学吸收性能和热稳定性,适合于中高温光热转换技术。另外,在柔性聚合物和织物上,其对太阳光具有优异的光热转换效果,对柔性和可穿戴能源相关的人体热调控技术具有非常重要的工业应用价值,同时也拓宽了传统光热转换涂层在光热技术中的应用领域,提供了一定的理论依据和实践经验。更多还原

【Abstract】 Photothermal conversion technology is utilized worldwide to convert solar energy into thermal energy.This includes solar water heating,solar air drying,concentrated solar power,among which,the key issue is the design of solar selective absorber coatings(SSACs)applied to the thermal-harvesting surface of the heat collecting device.To acquire high optical absorption,these traditional SSACs are often more complicated and material cost.This is because co-sputtering with multiple sputtering targets during the fabrication process is required,inevitably imiting the actual industrial productions.Based on the concept of self-doping,a novel self-doped Me-MeOx(Me＝W or Mo)SSAC is fabricated by using single metal target with limited reactive sputtering,which exhibits excellent optical absorptivity and thermal stability.The as-abtained SSAC presents simple fabrication processes,low material cost,optical adjustability and structural extensibility,which is promising for low-cost and large-scale photothermal technology in mid-and high-temperature applications.The novel self-doped photothermal technology is used as wearable technology that regulating personal thermal,which can overcome the traditional passive heating way using joule heating and reflecting infrared(IR)wavelength,and actively absorb sunlight to warm the human body.It also reflects the IR thermal radiation of human body to maintain the temperature.Such result shows very effective application value in outdoor emergency heating fabrics,and broadens the application of SSACs in flexible and wearable personal thermal conversion technology.The specific works are as follows.(l)The intrinsic absorption properties of monolayer WOx films are studies,and the dielectric WOx,Si02 and A12O3 films are introduced as the anti-reflective(AR)layer to investigate the evolution of the optical absorption of the doped WOx films.The thermal stabilities of the as-fabricated SSACs are discussed.The results show that the doped WOx film possesses excellent optical absorption,and the highest a value is 0.83 and ε value is 0.05.Moreover,the dielectric WOx film shows the anti-reflective effect,and the corresponding a of doped WOx film is rasied to 0.91 and ε remains at 0.054.The thermal annealing results show that the as-obtained SSACs have poor thernal stability due to the diffusion and oxidation of the element,whereas the coatings show excellent thermal tolerance in vaccum at 400℃.(2)By combining the self-doping concept,the intrinsic absorptions and the AR properties of WOx films,the novel self-doped W-WOx based SSACs are successfully fabricated.And the optical properties and phase compositions are studied.The failure mechanism induced by the diffusion and oxidation at operating temperature is discussed.The results show that the as-fabricated SSACs possess excellent optical absorptivity,where a value is 0.93 and 0 value is 0.058,and η is 90%,which can be attributed to the intrinsic absorption of the WOx film,the optical interference effect between the interface layers,and the near field enhancement effect of the metal W layer.In addition,the thermal annealing results indicate that the W-WOx based SSACs have excellent thermal tolerance in air at below 300℃.The dominant failure mechanism is mainly attributed to the diffusion of W nanoparticles,and then oxidized significantly as the annealing temperature rose.This causes changes in the crystal structure and composition of the SSACs,resulting in degradation in the spectral absorption.(3)The optical absorption of monolayer MoOx film at differemt pressure is analyzed.The AR effects of Si02 and MoOx dielectric films are investigated,and the thermal stabilities of the coatings under different atmospheres are discussed.The results indicate that the non-stoichiometric MoOx film exhibites excellent absorption properties,the highest a is 0.83 and ε is 0.05.Similarly,the dielectric MoOx film can also act as a novel AR layer in the design of SSAC.The thermal annealing results also show that the coatings show excellent thermal stability in vacuum at 450℃,whereas the coatings show poor thermal stability due to the diffusion and oxidation of the element.(4)Combining with the aforementioned analyses,a self-doped Mo-MoOx based multilayer SSAC with more stable structural property is fabricated,and the optical constant,crystal structure and phase composition are studied.The thermal stabilities of the coatings under different atmospheres are discussed.The results show that the coating has excellent optical absorption in visible and near-IR region,where a value is 0.93 and ε value is 0.055,and η is 92%.Moreover,as thermal annealing in air,the surface of the SSAC is severely oxidized,and the SSACs show poor thermal tolerance.When annealing in vacuum at 450℃,the optical properties of the coatings do not show significant change,indicating the outstanding thermal stability.(5)Based on the above results,the Me-MeOx SSACs are fabricated on flexible PET and PI sheets as well as cotton cloth and polyester fibre,and the corresponding optical absorption,bending properties and the photothermal conversion effect are analyzed and discussed.The results show that the coatings on flexible polymers and fabrics show excellent light absorbing ability and bendable nature,where a values are 47%～52%and 82%～83%respectively,and both ε values are 30%～35%.Under one sun illumination(1 KW/m2),the surface temperature of the coatings on flexible polymers and fabrics is 78℃ and 90℃,showing good soalr thermal conversion effect.In addition,under natural sunlight the fabric sample also shows obvious endothermic effect,and the steady temperature is up to 10～11℃,and the temperature difference is close to 6℃compared with the blank fabric.In summary,the self-doped Me-MeOx SSACs possess excellent optical absorption properties and thermal stability,which are suitable for mid-and high-temperature solar thermal conversion technology.In addition,the SSACs on flexible ploymer and wearable fabric show excellent bendable nature and light-to-heat conversion efficiency.Such result shows significant important industrial application value for flexible and wearable energy related personal thermal management,and it also broadens the application of traditional SSAC in solar thermal technology and provides the theoretical basis and practical experience.更多还原