Preparation Of Photothermal Materials Based On Metal Foam And The Study Of Solar Interface Evaporation Performance

With the rapid development of human society,the problem of water shortage is becoming more and more serious.The fresh water resources available for human use only account for 4%of the total water quantity.Therefore,desalination of seawater by special technology is an effective way to solve the serious problem of insufficient fresh water resources.In recent years,solar steam generation technology is the most effective and promising method for seawater desalination,so it has been favored by researchers.At present,most researchers focus on high photothermal conversion efficiency and tolerance in harsh environment.Due to the existence of a large number of oily wastewater in daily life,therefore,from the perspective of practical application,the use of solar steam generation technology to treat oily water has a certain research significance in daily life,and explore the preparation of a series of oil-repellent photothermal conversion materials is the focus of this paper.Since the acicular crystal of metal foam material has excellent light absorption and has not been reported in previous studies,this paper takes this material as the matrix material and further modificates it to achieve good oil-repellent effect,so as to study its photothermal evaporation performance in oil-bearing wastewater.Specifically,in this paper,a new type of solar interfacial evaporative photothermal material was prepared with a simple process based on nickel/copper foam and waste pitch,and a series of factors affecting the photothermal conversion efficiency were systematically studied.The research results not only provide a new research idea for the preparation of photothermal materials,but also provide a new way for the design and optimization of the solar interface evaporative photothermal conversion system.Main contents of this paper:(1)The nickel foam was prepared into high light absorption sample by one-step hydrothermal method.The nickel foam was chemically modified with inorganic sulfur,and the sulfur powder was attached to the nanometer nickel wire generated on the surface of the nickel foam skeleton,which made the network structure more dense to significantly enhance the light absorption,and on the other hand,the surface wetting of the sample was enhanced.In addition,the two-layer structure is constructed during the test.The upper layer is the prepared nickel foam sample(named S-Ni foam),which is conducive to good light absorption capacity,and the lower layer is the wood matrix,whose lower thermal conductivity reduces the heat loss of the surrounding environment,so as to realize the efficient solar light-heat conversion efficiency.The experimental results show that,due to its porous structure,high light absorption ability and good heat insulation performance,it has excellent performance of solar energy driven photothermal steam generation.Under 1 k W m^-2radiation,the evaporation rate can reach 1.33 kg m^-2h^-1,and the photothermal conversion efficiency is up to 83.6%.What is more interesting is that the photothermal conversion efficiency in oily water is as high as 79.1%through simple modification,which greatly expands the application range of solar photothermal materials.(2)Copper foam was washed with hydrochloric acid and prepared into high light absorption sample with rough surface.Because of its three-dimensional network structure,it can provide a good transport channel for water molecules.The two-layer structure was constructed during the test.The upper layer was the prepared copper foam sample(named R-CF)to improve the light absorption rate,and the lower layer was the polyurethane foam,which reduced the heat loss through its good heat insulation effect and realized the efficient solar photothermal drive steam production.The experimental results show that the photothermal conversion efficiency is 85.25%and 70.19%in pure water and high concentration salt solution under 1 k W m^-2radiation,respectively.After simple surface modification,it still has good oleophobic property,and the photothermal conversion efficiency in wastewater can reach 77.0%,which makes it can be used as an ideal functional photothermal material in actual seawater or oily water.(3)Because the high cost of metal materials restricts its further practical application,further exploration with pitch as a raw material not only provides a new idea for the application of solar steam generation,but also provides a new way for the design and optimization of solar interface evaporative photothermal conversion system.Using pitch as the base material,the composite template of Ca CO₃and Na Cl is used to carbonize it into a porous structure sample(named PCN),which can be used as a solar receiver to effectively solar steam generation.The sample exhibits excellent porosity and mesoporous characteristics,with an average pore diameter of26.8 nm,excellent absorbance(86%)and good thermal insulation(thermal conductivity 0.993 W m^-1K^-1),so it effectively reduces heat loss and promotes interface evaporation.The experimental results show that PCN shows superior light-to-heat conversion performance,and the light-to-heat conversion efficiency under 1 k W m^-2radiation is as high as 88%.Therefore,the use of rich raw material and low-cost pitch to prepare solar receivers may contain huge potential,such as sewage treatment,fresh water production and seawater desalination.