Research On The Preparation And Structure Characterization Of Nano-layered Double Hydroxides

Layers double hydroxides(LDH)having special samdwich,controllability of layers interval,anion quantity and variety of layer board,to be preparated inorganic inorganic/organic compound function material,can be widely applied to some fields such as catalysis, medicine,absorption,etc,especially in the fire-retardant field,received the great concern. Because of Nano Mg/Al-LDH structure and size effect,its fire-retardant restraining smoke is further more obvious compared with regular LDH,so to be prepared Nano Mg/Al-LDH already become domestic and international research focus of the field. However,it is still researched at laboratory at present.Obviously having optimized the technics,lowed costs,prevented reunion,have already become the key of Nano Mg/Al-LDH that could be realized industrialization.This text systematicly study nano Mg/Al-LDH prepared craft,drying processes and surface organizing modification how to impact on reunion two times of nano particle.1. Nano-LDH was prepeared by one step linquid phase reaction under constant pH,having varied pH,Mg/Al molar ration,reaction time etc.For synthetic the sample's phase and aspect the influences of interval.(1)XRD Analysis indicated,to rise pH is favorable to the formation of LDH.At the pH9.5,Mg/Al-LDH phase is unobvious;pH10,it has brucite phase;pH>11,Mg/Al-LDH crystal is better;pH>11.5,the crystallization is complete,single;(2) Element analysis indicate,when Mg/Al ratios are between 3:1,the crystal phase is single and pure.2. The work of the surface organizing modification and drying processes on the aggregate of Nano Mg/Al-LDH was done,in order to obtain non-aggregation and uniform diffusion samples.We found(1)Mg/Al-LDH particle sizes relate to dry way.Experiments indicate that the solvent replacement drying can prevent the nano particles from hardagglomeration.The shape of the sample is needle,about long 50nm, wide 5nm;(2)Studies of the organizing suggest it effectively prevents the hard agglomeraties Adopt,unite pharmaceutical to be surface organic to take treatment to LDH,can dispel particle soft hard reunion effectively.3. Changed reaction medium,the samples of different shapes have been synthesized.As a result,using alcohol (10%) as solvent and pH higher than 12.5,we obtained the crystal nano-powder with purity more than 98%.Using polyvinyl alcohol as dispersant, we obtained spherical particles that are single crystal phase,pure,well dispersive. and the size is about 20nm.4. Nano-LDH was prepeared by solid state reaction under room temperature.The results show that (1) By controlling Mg/Al molar ration,a series of samples can be successfully obtained.when Mg/Al ratios are between 3:1 and 4:1,the particles are single crystal phase,pure,well dispersive.when between 1:1 and 1:2, LDH phase is not obvious;(2)It is essential to prepear nano-LDH for grinding time.about 60min,the particles prepared are brilliant and single.Grind time to be relatively long,diffraction peak intensity increase,size become growing up directly(90min).But grind time to be relatively short(30min),the particle can not reach the purpose to fully mix;(3) The particles take the form of needle,about long 120nm,wide 20nm.