| Calcium carbonate whisker is a kind of environmental-friendly materials. Similar to short fibers, which have high ratio of length to diameter, it is a kind of excellent enhancing toughening materials. On the other hand, as having a short length leads to the good processing properties, available products have a highly smooth surface. Thanks to the widely existence of raw material and low price, it has a broad application prospect in industrial areas such as plastic, papermaking and painting. This thesis used industrial calcium oxide as a raw material, and magnesium chloride hexahydrate as crystal control agent, uses Gas-liquid reaction synthesis method to form the calcium carbonate whiskers. Through polarizing microscopy, X-ray Diffraction and Scanning Electron Microscopy and other tools to observe and analysis the appearance and crystalloid structure of whiskers. The result indicated that calcium carbonate whiskers with a length of 30μm and length-diameter ratio of 25 can be got when the react temperature is 80℃, the ratio of magnesium and calcium is 2,the flow of CO2 is 70 ml.min-1, and stirring speed is 100r.min-1.On the basis, we can improve the purity and length-diameter ratio of calcium carbonate whiskers by optimizing the parameters design. The result indicated that the purity of calcium carbonate whiskers by changing the digestion of calcium oxide, because it can improve the purity of calcium hydroxide solution and increase the ratio of magnesium and calcium. The content of calcium carbonate whiskers in product 97.5% increased to 98.7% when 11.2g calcium oxide digested slowly to 80℃and mixed with magnesium chloride solution. At the same time, using digital pH/mV meter to test the pH value of reaction solution. We can restrain the adverse effects of calcium carbonate whiskers by adding calcium hydroxide solution. It can manage the ratio of magnesium and calcium and reduce the concentration of Mg2+.The aspect of calcium carbonate whiskers can increase from 25 to 30 when one-time additional 625ml 0.16mol.L-1 calcium hydroxide after the reaction of 1h.Furthermore, we can cost saving by recycling resource. Studying of recycling of magnesium chloride solution on the synthesis of calcium carbonate whiskers, the result indicated that we can increase the length-diameter ratio of it by reducing the ratio of magnesium and calcium suitably. When magnesium to calcium ratio is 1.7, calcium carbonate whiskers with length 27.7μm and aspect ratio 26 can be acquired. To recycle the waste materials, we should refine the calcium hydroxide solution. The 25g waste materials dissolve in 2L80℃water and stirring fast make its digesting fully. Using 200# standard sieve to filter the reaction solution after it drops to room temperature.The filtrates are then aged 2-3 days in a beaker. Through refining the calcium hydroxide solution can gain length 53μm and aspect ratio 31.5 of calcium carbonate whiskers.As one of the most common crystal control agent, many mechanisms of magnesium chloride still remain unknown. Based on the kinetics of reaction, we know that magnesium chloride can decrease effectively the supersaturation of reaction solution, and accelerate the nuclei growth of calcium carbonate whiskers.When the ratio of calcium and magnesium involved in the reaction is less than 1,through analyzing the effect on the synthesis of calcium carbonate whiskers by the state of Mg2+ in magnesium hydroxide and magnesium chloride, the result indicated that flocculation magnesium hydroxide could gather the crystal nucleus, which could prompted the growth of arborization calcium carbonate whiskers on its surface, at the mean time, through comparison and analysis effects to calcium carbonate whiskers caused by the react time, we could know that the Mg2+ not only restraining the calcium carbonate whiskers transform into calcite, and improving the purity of the products, but also increasing the length-diameter ratio by restraining the over-fast growth of diameter of the calcium carbonate whiskers. Due to evidence above, it could get the conclusion that the growths of calcium carbonate whiskers is the result of screw dislocation induced growth mechanism.
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