超细硝酸钾制备及其热物理性能研究

发布时间：2018-05-04 15:05

本文选题：硝酸钾 + SiO_2纳米颗粒　；参考：《南京理工大学》2017年硕士论文

【摘要】：能量储存是能源安全与可持续发展的前提与保障,从目前的能源结构分类情况看,热能是最重要的能源形式之一,热能的储存和利用对社会生活有很大影响。热能的存储主要有潜热储存、显热储存和化学反应储热三种。由于潜热储能密度大,储热、放热过程近似等温过程,运行控制简单,因此其已成为主要的储热手段。而储热技术的核心和关键是储热材料,因此研究和发展新型高性能的相变储热材料具有重要的战略意义和应用前景。本文所制备的超细硝酸钾粉体属于熔融盐相变储热材料。本文以纳米SiO2以及硝酸盐为原料,先研究了纳米SiO2在硝酸盐中的分散情况;再通过纳米SiO2诱导结晶生成超细硝酸钾粉体;接着利用反溶剂法生成超细磷酸二氢铵粉体,并将该方法运用到硝酸钾结晶上,生成超细硝酸钾粉体。具体工作如下:1.研究了 SiO_2纳米颗粒浓度、硝酸盐浓度、分散剂对纳米SiO_2在硝酸盐溶液中分散情况的影响。实验得出SiO_2纳米颗粒在4种盐中达到聚集临界点时,对应的盐浓度大小次序K~+Na~+Li~+NH_4~+;增大纳米颗粒浓度不利于纳米颗粒的分散;分散剂六偏磷酸钠促进了纳米SiO_2的分散。2.采用纳米SiO_2诱导制备硝酸钾超细纤维状晶体。研究了分散方式、纳米SiO_2浓度、硝酸钾浓度、酸碱度、分散剂、溶剂等因素对超细纤维状硝酸钾结晶的影响。最佳工艺条件:用超声破碎机分散、纳米SiO_2浓度0.05 wt%(相对于水的含量,下同)、硝酸钾浓度1 wt%。用偏光显微镜及扫描电镜照片观察产物大小、形貌。从产物的偏光显微镜及扫描电镜照片发现,产物纤维结晶的最小直径在2 μm左右。超细纤维状硝酸钾结晶样品与纯硝酸钾粉末熔融热焓基本一致;但其固相平均比热容、液相平均比热容相较于纯硝酸钾粉末分别提高了 22.3%与41.4%。3.对反溶剂法制备磷酸二氢铵、硝酸钾超细粉体的条件进行了研究。研究了盐溶液初始浓度、溶剂反溶剂体积比、超声功率及超声时间对晶体大小及形貌的影响。实验得到生成磷酸二氢铵超细粉体的最优工艺条件:磷酸二氢铵水溶液初始浓度0.1 mo1/L,超声时间4 min,溶剂反溶剂体积比2:8,超声功率为9%,在此条件下可制备出粒径在500 nm左右的纳米流体,离心烘干后磷酸二氢铵固体超细粉体的粒径范围在2-3 μm。实验得到反溶剂超声结晶法制备硝酸钾超细粉体最优工艺条件:采用硝酸钾水溶液初始浓度0.75 mo1/L,超声时间4 min,溶剂反溶剂体积比2:8,超声功率为9%,在此条件下可制备出粒径在187 nm左右的纳米流体,但离心烘干后硝酸钾固体超细粉体的粒径平均在3 μm左右。如何在超声结束的后续离心烘干过程中减少粒径的长大仍需进一步研究。
[Abstract]:Energy storage is the premise and guarantee of energy security and sustainable development. According to the current classification of energy structure, thermal energy is one of the most important forms of energy, and the storage and utilization of heat energy have a great impact on social life. Heat storage includes latent heat storage, sensible heat storage and chemical reaction heat storage. Because the latent heat storage energy density is high, the heat storage and exothermic process is similar to isothermal process and the operation control is simple, it has become the main means of heat storage. The core and key of heat storage technology is heat storage material, so the research and development of new high performance phase change heat storage material has important strategic significance and application prospect. The ultrafine potassium nitrate powder prepared in this paper belongs to the phase change thermal storage material of molten salt. In this paper, nanometer SiO2 and nitrate were used as raw materials, the dispersion of nanometer SiO2 in nitrate was studied, then the ultrafine potassium nitrate powder was crystallized by nanometer SiO2, and then the ultrafine ammonium dihydrogen phosphate powder was obtained by antisolvent method. The method was applied to the crystallization of potassium nitrate to produce ultrafine potassium nitrate powder. The work is as follows: 1. The effects of the concentration of SiO_2 nanoparticles, nitrate concentration and dispersant on the dispersion of nano SiO_2 in nitrate solution were studied. The results show that when the concentration of SiO_2 nanoparticles reaches the critical point of aggregation in the four salts, the order of salt concentration is K ~ Na ~ Li-NH _ 4 ~; the increase of the concentration of nanoparticles is not conducive to the dispersion of nanoparticles, and the dispersant sodium hexametaphosphate promotes the dispersion of nanometer SiO_2. 2. Ultrafine fibrous potassium nitrate crystals were prepared by nanocrystalline SiO_2 induction. The effects of dispersion mode, nanometer SiO_2 concentration, potassium nitrate concentration, pH, dispersant and solvent on the crystallization of ultrafine fibrous potassium nitrate were studied. The optimum technological conditions are as follows: dispersing with ultrasonic crusher, nanometer SiO_2 concentration 0. 05 wt2 (relative to water content, the same as next, potassium nitrate concentration 1 wt). The size and morphology of the product were observed by polarizing microscope and scanning electron microscope. From the polarizing microscope and scanning electron microscope, it is found that the minimum diameter of the crystal of the product is about 2 渭 m. The melting enthalpy of ultrafine fibrous potassium nitrate powder is basically consistent with that of pure potassium nitrate powder, but the average specific heat capacity of solid phase and liquid phase increase by 22.3% and 41.4% respectively compared with that of pure potassium nitrate powder. The preparation conditions of ammonium dihydrogen phosphate and potassium nitrate ultrafine powder by anti-solvent method were studied. The effects of initial concentration of salt solution, volume ratio of solvent to solvent, ultrasonic power and ultrasonic time on crystal size and morphology were studied. The optimum technological conditions of producing ultrafine powder of ammonium dihydrogen phosphate were obtained: initial concentration of ammonium dihydrogen phosphate solution was 0.1 mol / L, ultrasonic time was 4 min, volume ratio of solvent to solvent was 2: 8, ultrasonic power was 9. Under these conditions, the particle size of ammonium dihydrogen phosphate solution could be obtained. About 500 nm nanoscale fluid, The particle size of solid ultrafine powder of ammonium dihydrogen phosphate after centrifugal drying is 2-3 渭 m. The optimum conditions of preparing ultrafine potassium nitrate powder by antisolvent ultrasonic crystallization method were obtained as follows: initial concentration of potassium nitrate solution was 0.75 mol / L, ultrasonic time was 4 min, volume ratio of solvent to solvent was 2: 8, ultrasonic power was 9. Nanoscale fluids with a diameter of about 187 nm were prepared. However, the particle size of potassium nitrate solid ultrafine powder was about 3 渭 m after centrifugal drying. How to reduce the particle size growth in the subsequent centrifugal drying process needs further study.
【学位授予单位】：南京理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ131.13

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