单一尺寸球形氢氧化铝颗粒的形成及其机理

FORMATION AND MECHANISM OF MONOSIZED SPHERICAL ALUMINUM HYDROXIDE PARTICLES BY HOMOGENEOUS PRECIPITATION

用尿素均相沉淀法首次制得了单一尺寸的球形氢氧化铝颗粒。为获得单一尺寸的颗粒,需仔细控制沉淀过程:如温度、保温时间及Al^(3+)的浓度。在沉淀过程中通过对溶液pH值的测量,研究了单一尺寸颗粒的形成机制。氢氧化铝的成核极限仅达到一次,可形成单一尺寸的颗粒。相反,如溶液多次达到成核极限,则导致颗粒的多尺寸分布。另外,影响单一尺寸形成的因素尚有阴离子种类等。

Monosized spherical aluminum hydroxide particles were first prepared by homogeneous precipitation using the urea method below its boiling temperature. To obtain monosized particles a careful control of temperature, holding time and concentration of Al^(2+) during the precipitation process is required. The formation chemistry of monosized particles is studied through the measurement of pH and concentration of Al^(2+) during precipitation. It is found that when the nucleation limit of aluminum hydroxide is reached only once, monosized particles can be formed; if the nucleation limit is attained more than once, a multisize particle distribution would appear. Other factors like types of an ons would also affect the formation of monosized particles. Monosized parti les can only be obtained with SO_4^(2-), not with NO_3^- or Cl^-.