Zn-Al-CO_3水滑石晶粒尺寸控制与光屏蔽作用研究

在旋转液膜反应器中制备成核浆液 ,通过控制晶化温度制备了不同粒径且晶体结构完整的Zn Al CO3水滑石 (LDHs)。将不同粒径的Zn Al CO3LDHs配成质量分数为 0 0 2 %的水分散液 ,测定在紫外 -可见光范围的透过率 ,结果发现 ,随晶化温度的升高 ,LDHs粒径增大 ,样品对紫外及可见光的阻隔作用增强 ;Zn Al CO3LDHs在不同波长下的吸光度与晶体粒子在a轴和c轴方向的尺寸呈线性关系。由外推法求得了Zn Al CO3LDHs对各波长紫外 -可见光产生屏蔽作用的晶粒尺寸阈值。对波长分别为 2 90、3 2 0、40 0、60 0和 80 0nm光波能够产生屏蔽作用的Zn Al CO3LDHs ,其粒子尺寸在a轴方向需分别大于 3 2 92、3 3 77、3 4 77、3 5 5 6、3 5 79nm ;在c轴方向需分别大于 9 73、12 79、16 47、19 3 5、2 0 2 2nm。

Preparation of Zn-Al-CO3 LDHs with Controllable Particle Size and Variation of Their Light Attenuating Properties with Particle Size

Zn-Al-CO_3 layered double hydroxides(LDHs) were prepared by a new method involving separate nucleation and aging steps. Material with different narrow particle size of narrow ranges were prepared by altering the aging temperature.The degree of attenuation of ultraviolet-visible radiation in the range 200-800 nm through scattering by dispersions of the materials(0.02%) in water was found to increase with increasing particle size.Furthermore, linear relationships were found to exist between the degree of attenuation and the mean crystallite sizes in both a and c directions. The minimum values of mean crystallite size required to scatter radiation of different wavelengths were obtained by extrapolation. For scattering to occur at 290 nm,the crystallite size in the a direction must exceed 33 nm and that in the c direction must exceed 10 nm.At 800 nm,the corresponding values are 36 and 20 nm respectively.