RESS法制备超细萘粒子

采用常规、简便的喷射装置，建立了一套超临界溶液快速膨胀（Rapid Expansion of Supercritical Solutions,RESS)实验装置。该装置能有效地防止堵塞。以CO2为溶剂，萘为溶质，考察了喷嘴直径及收集距离对沉积微粒粒径的影响，研究了在不同的收集距离时粒径随浓液浓度的变化规律。结果表明喷嘴直径增大将使产物粒子粒径增大；在50mm的范围内，产物粒径随着收集距离的增回而明显增加，结果也显示出RESS产物是通过更小粒子之间的碰撞凝结而生长。当收集距离较大时，晶体的生长过程相比于晶核的形成过程对沉积微粒的粒径影响更大，故粒子粒径随溶液浓度增加而增大；当收集距离较小时，晶核的形成过程占主导地位，因此产物粒径随溶液浓度的增加而减小，符合经典成核理论。

Formation of Naphthalene Microparticles by Rapid Expansion of Supercritical Solutions

The RESS process (Rapid Expansion of Supercritical Solutions) is an innovative and promising technology to produce small particles and offers interesting applications for difficult-to-comminute species. An RESS apparatus was set up with a simple, normal nozzle that could avoid jamming. The RESS experiment for naphthalene-supercritical CO2 was carried out to clarify the effect of nozzle diameter, collecting distance and solution concentration on the size and morphology of the formed particles. The characterization of the formed particles indicates that the particles have narrower size distribution and better morphology, and grow up through coagulating smaller particles. The size of particles formed in RESS process with a nozzle of 0.4~1.0 mm increases with increase in nozzle diameter. The particle size increases with increasing the collecting distance until 50 mm. Therefore, the crystal growth and nucleation are supposed to be involved in the RESS process. The process of crystal growth strongly affect the particle size and is determinative factor at large collecting distance, so the particle size at large collecting distance increases with increasing solution concentration, whereas, at small collecting distance the nucleation process is determinative factor, and the particle size decreases with increasing solution concentration, which coincides with the classic nucleation theory.