The Experimental Study Of Nanometer Cacium Carbonate By Vacuum Frozen Drying

In recent years, with development of nanotechnology the nanophase matericals has won extensive attention of various fields. As a great padding Caco3can be widely used in the fields like rubber,plastic,paper making,dope,printing ink and medicine because of its low cost,no poison and on smell. At the present nanometer Calcium carbonate can be prepared by the Double Decomposition method, Carbonation Production method,Microemalsion method,and Sol-Gel method.The nanopowder synthesided by the method of Vacuum freeze-drying has many sound characteristics such as regular particle shape, small and even diameter,narrow granularity distributing, pure chemical composition,weak agglomeration, easy dispersal and so on. So the method of lyophilization has aroused much attention around the world.Therefore, the synthesis of Calcium carbonate nanopowder by freeze-drying is chose as the research subject in this thesis. And also we have use the Lyophilized microscope which developed by ourselves to research the process of freeze-drying and the data during freeze-drying was recorded in this paper.Taking the solution of Calcium bicarbonate as the precursor solution, the functional inorganic nanopowder of Calcium carbonate is successfully synthesized in this paper.In this paper part of the solution was freezed by vacuum evaporation and other part of solution was freezed directly. And all of the solution was tested in the same conditions.XRD and TEM spectrometer were used to characterize the structure and morphology. The powder was Caco3blende structure and its has two crystal types. The powder was pure and osteoporosis porous. Used the two freezed method we can obtain nanometer Calcium carbonate,the size of Caco3powder was50nm. There are little differences between the two method but when we made the solution freezed by vacuum evaporation it will save us much energy. So in order to application of the freeze-drying in preparing the Calcium carbonate power to the industrial production,the study on its process is very important.In this paper experiment have been designed in order to study how to prevent boiling(Pressure and temperature factors were not included). Take deionized water for example we have the conclusion that the gases dissolved in the water has a great influence on the first boiling when the solution freezed by vacuum evaporation. And the degassed water with broken ceramics can reduce the second boiling during the experiment.This paper introduced a lyophilized microscope which developed by ourselves and described its structure, working principle and its actual working. The Freeze-drying microscopy can studing the freeze-drying at the microscopic level and at the same time the sample’s temperature and pressure can be recorded. We analyed the crystalline state during the sample freezing and also gain the microcosmic characters of during the solution vacuum evaporation drying and vacuum freeze-drying. In this paper we have verified the segregate of the solution. All the conclusions in this paper will have an important influence on how to prepare high quality calcium carbonate nanopowder.