摘要
复合微粒制备技术不仅可以避免单一超细微粒的团聚问题，还可以改变超细微粒的功能化特性和表面反应特性。通过表面包覆而获得良好表面特性对于包覆型复合微粒的实用化设计和广泛应用具有重要意义，使其在化工、结构材料、军事和生物等领域有着广阔的应用前景。
超临界溶液快速膨胀(RESS)技术是近年来提出的一种制备复合微粒的新方法，温和的操作条件使得该方法在处理热敏性以及生物活性物质时具有传统技术无可比拟的优势。目前应用RESS技术制备复合微粒尚处于初步实验阶段，仍然面临着许多问题。
本文应用一种改进的RESS技术，分别对石蜡、苯甲酸和聚乳酸包覆细微颗粒进行了系统的实验研究，考察了萃取压力、萃取温度、膨胀前温度以及撞击距离对包覆效果的影响。
利用光学显微镜、SEM和TGA等仪器对实验制备的复合微粒进行了表征，结果表明：应用这种改进的RESS过程能够对细微颗粒进行包覆处理，制备出包覆层厚度可控的复合微粒。通过该过程制备的复合微粒，包覆层连续、均匀，微粒问无明显团聚现缘。
在实验范围内，萃取压力的升高会使复合微粒包覆层厚度增加；萃取温度对包覆层厚度影响不大；膨胀前温度的升高导致复合微粒包覆层厚度增加；撞击距离的增大会使复合微粒包覆层厚度增加。萃取压力、膨胀前温度、撞击距离是影响复合微粒包覆层厚度的主要因素。
通过本文的研究，为复合微粒的制备提供了一种新方法，同时，了解了各过程参数对复合微粒包覆层厚度的基本影响规律，为进一步研究提供了必要的基础性数据。
The preparation technology of composite particles can not only solve the problem of fine particles agglomeration, but also change the functional characteristics and surface reaction characteristics of the fine particles. Good characteristics can be obtained by surface coating, which is very important for the practical design and extensive application of composite particles. It has a broad prospect for the composite particles used in the fields of chemical engineering, structure material, military and biological industry.
The rapid expansion of supercritical solution (RESS) technology is a new method for the preparation of composite particles. It has incomparable advantages over the traditional methods in the treatment of heat sensitive and bioactive materials because of its mild operation conditions. At present, it is still in preliminary experiment stage using RESS technology to prepare composite particles and many problems have to be faced with.
An improved RESS technology is presented in this paper. The coating of fine particles using wax, benzoic acid and lactic acids were studied respectively by experiment. The influences of extraction pressure, extraction temperature, pre-temperature and impinging distance on coating effect were investigated.
The optional microscope, SEM and TGA were adopted to characterize the composite particles. The results show that the coating of fine particles can be accomplished by the improved RESS process and the thickness of the coating layer of composite particles can be controlled. The coating layer prepared by this process is continuous, uniform and combining without obvious agglomeration.
Over the investigated range of the experiments, the thickness of coating layer increases with the increase of pressure, pre-temperature and impinging distance. The extraction temperature has little effect on the coating layer. Therefore, the extraction pressure, pre-temperature and impinging distance are the main influencing factors.
The research in this paper provides the preparation of composite particles with a new method. Moreover, the influences of process parameters on the thickness of coating layer were obtained and the experimental results can be used as necessary fundamental datum for further study.
引文
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