Synthesis Of Nano-alumina By An Integrated Method With Precipitating In High Gravity Condition And Calcining In Microwave Field Using Aluminum Nitrate

Alumina is a kind of material which widely used in the fields of abrasive material, refractory, material of construction, catalyst and its support. What is more, nano alumina has broad application prospect because its nano structure bring it special characters that non-nanometer alumina doesn’t has. Among the current approaches of synthetizing alumina, gas phase method requires an expensive cost; solid phase method could not get an uniform particle size distribution. So we adopt liquid phase method to synthetize alumina in this paper, which cost less, has an easy controlled operational path and easy to amplify the production. But alumina is easy to agglomerate in the whole process of synthetizing and that will impact the performance of the product using liquid phase method.Aiming at reducing the agglomeration phenomenon in synthetizing alumina using liquid phase method, several method below is adopted:firstly, super gravity reaction device which called Rotating Bed with Helix Channels(RBHC) is used to strengthen the intensity of mass transfer and mixing; secondly, sucrose is added as an additive in the react material, whose dispersion capcitiy could prevent the agglomeration of aluminum hydroxide, and it would become carbon in heat treatment process which could also protect the product; finally, microwave is used as heating source to prepare gamma and alpha alumina because its features of even heating and fast sintering, and obvious effect is gotted.In this paper, we studied the effect of technological conditions to the product in the process of synthetizing alumina first, for example, the choice of precipitant, the proportioning of aluminium nitrate and sucrose, the terminal pH value, the operating conditions(including revolving speed of RBHC, adding speed of precipitant and ageing time).The optimized method of synthetizing alumina is got though analysing the changing of pH-t, TG/TA figure, X-ray diffractogram, infrared absorption spectrum, particle size distribution and scanning electron microscpoe. And alumina with small particle size, even distribution, good dispersity and high crystallinity is prepared by adding ammonia at the speed of 10ml/min, reacting until pH value=7(if using ammonia as precipitant, react until pH value=9),ageing 2 h at 80℃, calcining 4 h in microwave muffle furnace.Then, the effect of calcining conditions on preparating alumina of is studied in this paper. Calcining conditions is found have great infuence on the product though analysing the X-ray diffractogram and transmission electron microscope graph: calcining in microwave helped to get better crystallographic and dispersive gamma-alumina than muffle furnace does because its even heating effect. The effect of calcining temperature is also got:gamma alumina is got by calcining precursor at 700℃for 4 h, which has an average particle size of about 9 nm; a compound of gamma and alpha alumina is got by calcining precursor at 1100℃for 4 h, of which gamma alumina has an average particle size of about 9 nm and alpha alumina about 26 nm; complete lamellar alpha alumina powder is got by calcining precursor at 1200℃for 4 h without the gamma phrase, which has a calculated primary particle size of 40.3 nm through Scherrer equation.