The Synthesis Of Bismuth Oxychloride Crystal As Pearlescent Pigment

Bismuth Oxychloride (BiOCl) is an insoluble inorganic bismuth compound inliquid. It is widely used as pearlescent pigment, especially sheet-like BiOCl crystal,for it could show well pearlescent luster which is ascribed to the direct reflection ofthe products. The mean factors that affect the pearlescent effect include characteristicdiameter and dispersity. The comprehensive study to synthesis methods of BiOClshows that currently, reactive crystallization is the first choice at home. However,there are several disadvantages in the methods, including the high request toproduction and the small characteristic diameter of products. So this paper came upwith three simple and economic synthesis methods which could attain products withlarge characteristic diameter and well dispersity. The specific content is as follows:Solid synthesis method is used to synthesize sheet-like BiOCl with bismuthoxide as the source of element bismuth. The products are characterized by severalrelevant instruments, which include the structure and morphology. In order tooptimize the operating parameters, the purity and pearlescent effect are considered asthe standard. A series of experiments show that the products with pearlescent effectare attained on the condition that reactive temperature is250℃, the mixtureproportion of bismuth oxide and ammonium chloride is1:5, the reactive time is0.5h.The process mechanism that the compound with element bismuth firstly sublimatedand then deposited to product was uncovered.The solvothermal synthesis method was used to synthesize square plate-likeBiOCl with bismuth chloride as the source of bismuth. Several relevant instrumentswere used to characterize the products, including the structure and morphology. Theparticle size distribution and morphology were referred as the standard to optimize theoperating parameter. A series of experiments showed that the regular product withcharacteristic diameter between50and100micrometer was attained on the conditionthat the concentration of HCl is0.25mol/L, the reactive temperature is120℃, theamount of BiCl3is0.2mmol, the amount of tartaric acid is less than1.5×10-2g.Theprocess mechanism is that the growth of crystal is the result of Ostwald ripening. The reactive crystallization method was introduced to synthesize sheet-likeBiOCl, with bismuth nitrate as the raw material. The characterization of the productswas conducted with several relevant instruments. The dispersity of the products wastaken as the standard to optimize the operating parameter. The result showed that thewell products with the characteristic particle size largely in20—50μm was acquiredon the condition that the amount of cetyl trimethyl ammonium bromide (CTAB) wasin5×10-3g,the volume of flow for bismuth salt solution was0.354ml/min, the rate ofHCl and ethanol (mixture solution) was5:4, the rate of the bismuth salt solution andmixture solution was1:30, the reactive temperature was50℃, the revolving speedwas400r/min.This paper reported the pearlescent effect sheet-like BiOCl for the first time withsolid state synthesis method, and it utilized ammonium chloride which is theby-product of producing sodium carbonate; Regular square-like BiOCl crystal in50—100μm was firstly produced with solvothermal method, which was more simple,lower reactive temperature and time-saving; The well sheet-like BiOCl wassynthesized in lower temperature (50℃) with reactive crystallization method. Also,according to different condition, the paper used three kinds of bismuth compoundsand expanded the application of various bismuth compounds.The similar works reported in this paper have not been published in literature upto date.