本文選題：硝酸鉀 + SiO_2納米顆粒��； 參考：《南京理工大學》2017年碩士論文

【摘要】：能量儲存是能源安全與可持續(xù)發(fā)展的前提與保障,從目前的能源結(jié)構(gòu)分類情況看,熱能是最重要的能源形式之一,熱能的儲存和利用對社會生活有很大影響。熱能的存儲主要有潛熱儲存、顯熱儲存和化學反應(yīng)儲熱三種。由于潛熱儲能密度大,儲熱、放熱過程近似等溫過程,運行控制簡單,因此其已成為主要的儲熱手段。而儲熱技術(shù)的核心和關(guān)鍵是儲熱材料,因此研究和發(fā)展新型高性能的相變儲熱材料具有重要的戰(zhàn)略意義和應(yīng)用前景。本文所制備的超細硝酸鉀粉體屬于熔融鹽相變儲熱材料。本文以納米SiO2以及硝酸鹽為原料,先研究了納米SiO2在硝酸鹽中的分散情況;再通過納米SiO2誘導(dǎo)結(jié)晶生成超細硝酸鉀粉體;接著利用反溶劑法生成超細磷酸二氫銨粉體,并將該方法運用到硝酸鉀結(jié)晶上,生成超細硝酸鉀粉體。具體工作如下:1.研究了 SiO_2納米顆粒濃度、硝酸鹽濃度、分散劑對納米SiO_2在硝酸鹽溶液中分散情況的影響。實驗得出SiO_2納米顆粒在4種鹽中達到聚集臨界點時,對應(yīng)的鹽濃度大小次序K~+Na~+Li~+NH_4~+;增大納米顆粒濃度不利于納米顆粒的分散;分散劑六偏磷酸鈉促進了納米SiO_2的分散。2.采用納米SiO_2誘導(dǎo)制備硝酸鉀超細纖維狀晶體。研究了分散方式、納米SiO_2濃度、硝酸鉀濃度、酸堿度、分散劑、溶劑等因素對超細纖維狀硝酸鉀結(jié)晶的影響。最佳工藝條件:用超聲破碎機分散、納米SiO_2濃度0.05 wt%(相對于水的含量,下同)、硝酸鉀濃度1 wt%。用偏光顯微鏡及掃描電鏡照片觀察產(chǎn)物大小、形貌。從產(chǎn)物的偏光顯微鏡及掃描電鏡照片發(fā)現(xiàn),產(chǎn)物纖維結(jié)晶的最小直徑在2 μm左右。超細纖維狀硝酸鉀結(jié)晶樣品與純硝酸鉀粉末熔融熱焓基本一致;但其固相平均比熱容、液相平均比熱容相較于純硝酸鉀粉末分別提高了 22.3%與41.4%。3.對反溶劑法制備磷酸二氫銨、硝酸鉀超細粉體的條件進行了研究。研究了鹽溶液初始濃度、溶劑反溶劑體積比、超聲功率及超聲時間對晶體大小及形貌的影響。實驗得到生成磷酸二氫銨超細粉體的最優(yōu)工藝條件:磷酸二氫銨水溶液初始濃度0.1 mo1/L,超聲時間4 min,溶劑反溶劑體積比2:8,超聲功率為9%,在此條件下可制備出粒徑在500 nm左右的納米流體,離心烘干后磷酸二氫銨固體超細粉體的粒徑范圍在2-3 μm。實驗得到反溶劑超聲結(jié)晶法制備硝酸鉀超細粉體最優(yōu)工藝條件:采用硝酸鉀水溶液初始濃度0.75 mo1/L,超聲時間4 min,溶劑反溶劑體積比2:8,超聲功率為9%,在此條件下可制備出粒徑在187 nm左右的納米流體,但離心烘干后硝酸鉀固體超細粉體的粒徑平均在3 μm左右。如何在超聲結(jié)束的后續(xù)離心烘干過程中減少粒徑的長大仍需進一步研究。
[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.
【學位授予單位】：南京理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TQ131.13

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