二氧化硅源对活性氧化镁水化的抑制机制

Inhibition mechanisms of silica sources on hydration of active magnesia

为了探明不同二氧化硅源对抑制MgO水化的机制，以d50为6．119μm的活性氧化镁粉为主要原料，d50=0．111μm的纳米SiO2粉和硅酸钠为二氧化硅源，在25℃恒温条件下制备了水与固体粉质量比为8：1的氧化镁-氧化硅悬浮液，借助pH仪、电感耦合等离子体发射光谱仪、X射线衍射仪及热重-差热仪等设备并结合热力学分析探讨了纳米SiO2粉、Na2SiO3对悬浮液中活性氧化镁水化的抑制作用。结果表明：随着纳米SiO2粉引入量（W）由20％增加到60％，活性氧化镁的水化程度降低；添加0．3％～0．6％（W）硅酸钠可以有效抑制活性氧化镁的水化，当添加量为0．6％（W）时，活性氧化镁的水化率最低；添加Na2SiO3能显著增加悬浮液中SiO2-的质量浓度，同时使该悬浮液的pH升高到11．4～12．0，从而有效抑制氢氧化镁的生成。

To investigate the inhibition mechanisms of different silica sources on hydration of magnesia, mag- nesia-silica suspensions with water/solid mass ratio of 8 ： 1 were prepared at 25 ℃ using active magnesia powder （d50 =6. 119 μm） as main starting material,nano SiO2 powder （d50 =0.111 μm） or sodium silicate as the silica source. The inhibition mechanisms of nano SiO2 powder and sodium silicate on active magnesia hy- dration were studied by a pH tester,an inductively coupled plasma atomic emission spectroscope,an X-ray diffractometer and a thermogravimetric-differential thermal analyzer. The results show that ：the hydration rate of active magnesia decreases as nano-SiO2 powder addition increases from 20 mass% to 60 mass% ;adding 0. 3 mass% -0.6 mass% sodium silicate can effectively inhibit the active magnesia hydration;when sodium silicate addition is 0.6 mass% ,the hydration rate of active magnesia is the lowest;the addition of sodium sili- cate can significantly increase the concentration of SiO32- and simultaneously increase the pH value of the magnesia suspension to 11.4- 12.0,thus effectively inhibit the generation of magnesium hydroxide.