【作者】 陈宏霞；

【导师】 马学虎；

【作者基本信息】 大连理工大学 ， 化学工程， 2009， 博士

【摘要】 面对能源消耗与日俱增和能源利用率相对较低的现状,采用第二类吸收式热泵将低品位的废热提高到较高品位,从而实现废热回收利用的技术受到广泛关注。吸收工质-LiBr溶液的高温腐蚀限制了热泵技术的应用范围,是高温吸收式热泵的关键技术之一,本文将针对高温吸收式热泵中的腐蚀及其防护问题进行研究。选择不添加任何缓蚀剂的LiBr溶液,考察了SUS304奥氏体不锈钢在150～200℃LiBr溶液中的腐蚀规律。结果表明,在高温环境中,LiBr溶液浓度是腐蚀速率和溶液中溶解金属离子浓度的主要影响因素;同时发现,SUS304不锈钢在高温高浓度LiBr溶液中的腐蚀状态存在由点蚀转变为膜状腐蚀的演化规律,并分析了腐蚀状态的转变机理。基于不锈钢在高温高浓度LiBr溶液中由点蚀向膜状腐蚀的转变规律,利用改进水热合成法,在溶液中添加微溶的无机硅配制成膜溶液,在腐蚀体系内边腐蚀边沉积原位制备新型的无机复合硅膜。通过对其结构和性能的表征,证实复合硅膜层主要由两部分组成:腐蚀溶液中不锈钢腐蚀生成的金属氧化物和溶液中溶解并同时沉积到试样表面的硅网状结构。而且两部分并非独立存在,无机硅在热碱中溶解并通过脱水缩合反应与金属氧化物及试样基体发生键合作用,在试样表面形成复合硅膜。脱水缩合形成的-Si-O-Fe、-Si-Fe键,使得膜层较致密且结合力增强,可显著提高其抗腐蚀性。选择SiO₂颗粒为无机硅源,在LiBr溶液中制备无机复合硅膜。通过考察Si添加量、LiBr溶液浓度、溶液pH值以及成膜时间对腐蚀体系内制备抗腐蚀性无机复合硅膜的工艺参数进行了优化研究。确定了最佳成膜工艺参数为:加Si量为29ppm,溶液pH值为10.6,溶液浓度为57.8%。制备膜的点蚀电位为0.75V、自腐蚀电位为0V、接触角为69°,具有一定的亲水性和良好的抗腐蚀性。选用双功能性硅氧烷1,2-二（甲基二乙氧基硅基）乙烷（BMBSE）为原料,在SUS304不锈钢基体表面,利用提拉法成功制备了双功能性硅氧烷BMBSE有机硅膜。检测结果表明,双功能性BMBSE硅膜具有-Si-O-Fe、Si-O-Si网状结构,提高了膜层的致密性和结合力,显著提高了SUS304不锈钢的耐腐蚀能力。根据BMBSE的结构及对成膜机理的分析,采用羟基含量高的TEOS对BMBSE膜进行改进,提高了复合膜内-Si-O-Fe、Si-O-Si的键合密度,膜层结构更加致密,抗腐蚀性进一步增强。最后考察了各成膜影响因素对复合硅膜性能的影响,得到了最优成膜溶剂配比。更多还原

【Abstract】 A lot of lower grade thermal energy in industrial processes has been emitted into environment every year in the world,causing energy waste and serious thermal pollution by exhaust gases,cooling water or cooling air.On the other hand,many industrial processes require numerous steam or hot water to heat the fluid stream.As a very effective technique, absorption heat transformer（AHT） can be applied to upgrade the large quantity of low grade waste heat.Due to the high recovery ratio of waste heat,good contribution to environment protection,and little power consumption,AHT is currently becoming a considerable interest in waste heat reutilization in industrial processes.As the working fluid,Lithium bromide solution can cause serious corrosion problems on the metallic component,which is the bottleneck in the development of high temperature AHT.In this dissertation,the preparation and characterization of anti-corrosion film on SUS304 stainless steel in LiBr solution at high temperature has been investigated.The corrosion of stainless steel in LiBr solution without any anti-corrosion and anti-fouling inhibitions at 150～200℃was experimentally investigated by means of static immersion test,in which the concentration of dissolved oxygen has been controlled by vacuumizing.The experimental results indicated that the concentration of LiBr solution was the most important factor not only to the corrosion rate but also to the concentration of ions dissolved in solution.It was found that the usual pitting corrosion has a trend to transform into film corrosion in the process at high temperature and high LiBr concentration.This transformation mechanism of corrosion pattern states has been analyzedBased on the modified hydrothermal method,a novel inorganic silica composite film was prepared on SUS304 stainless steel substrates.The experimental tests demonstrated that the composite film remarkably improved the anti-corrosion characteristics of substrate.XPS, XRD and FT-IR analysis revealed that two simultaneous sub-processes,i.e.the corrosion of stainless steel stimulated by aqueous Lithium bromide solution and the dissolution of silica from inorganic silica,took place during preparation.The silica dissolved in the solution constituted a network with a layer of hydroxyls on the substrate surface and incorporated with the corrosion products to form -Si-O-Fe,-Si-Fe bonds.Silicon dioxide particle was chosen to prepare inorganic composite silica film.Effects of added content of solicon,concentration and pH of LiBr solution and the time of preparation on the performance of composite film were studies.As a result,the optimum condition was determined as follows:silicon content of 29ppm,pH of 10.6,LiBr concentration of 57.8%.An organic silica composite film of 1,2- Bis[methylbisethoxysilyl]ethane（BMBSE） was prepared on the surface of stainless steel directly without pre-plating metal with symmetrical structure of groups such as -OH,-CH₄ and -CH₂-CH₂- after hydroxylations.The structure and properties of the films were investigated by FT-IR,SEM,EIS, Potentiodynamically polarization curve and static contact angle.As a result,the structure of -Si-O-Fe,Si-O-Si could improved the anti-corrosion performance of SUS 304 stainless steel obviously.Furthermore,tetraethyl orthosilicate（TEOS:（OH）₃SiOSi（OH）₃） with high density of-OH was chosen to modify the BMBSE film.The content of-Si-O-Fe,Si-O-Si in the film was increased.Addition of TEOS increased the density of the reaction sites of condensation and modified BMBSE films in terms of compactness and anti-corrosion performance at room and higher temperatures.更多还原