Preparation And Morphology Of Low-dimensional Iron Oxide Powder

The unique properties of nano-materials which is caused by the distinct structure have attract more and more people’s attention.Today the researchers have found numerous means to synthesis the nano-materials.In these ways,the hydrothermal and precipitation method are wildly used in the synthesis of nano-materials due to its lower requirements for experimental equipment,simple process and controlled experoment process,etc.Iron is a common element in people’s life,the content of it is rank fourth in all elements in the earth’s crust.At the same time,it is a element with changeable valence and have several oxide,such as FeO,Fe2O3 and Fe3O4.In these oxide,the Fe2O3 has many different characteristics such as wide range of raw materials,environmentally friendly,low price,high resistance to corrosion,good thermal stability,etc.So it has been widely used in the field of catalysis,environmental protection,coatings,gas sensing,anode materias for lithium ion battery and hydrogen storage,etc.In this dissertation,hydrothermal and homogeneous precipitation were used to prepare the low dimension iron oxide and find out the best reaction conditions for the experiment.The main contents are as follows:(1)The cuboidal α-Fe2O3 powders were synthesized by hydrothermal method using FeCl3·6H2O and NaOH as raw materials.The micro-structure and micro-appearance ofα-Fe2O3 was influenced by hydrothermal temperature,ratio of reactants and hydrothermal time.It is found that the product is FeOOH in a lower temperature and shorter hydrothermal time.When the concentration of FeCl3 was 0.6 mol/L,the cubic block structure α-Fe2O3 powders with regular morphologies can be obtained after 24 h hydrothermal treatment under 200 ℃.The effects of different precipitation agents and surfactants on the structure and micro morphology of the product were studied at the same time.The result show that,under the condition of no precipitation agent,the α-Fe2O3 powder which is composed of a spherical particle is obtained by the aggregation of the scale structure.The α-Fe2O3 powder with a small spherical structure was obtained by the precipitation of ammonia water,Na2CO3 and NH4HCO3.The maximum size of the microspheres was obtained when Na2CO3 was used as precipitator.The micro structure of α-Fe2O4 powder show irregular morphology with the CTAB,PVP and PEG-20000 as cosurfactants,only the CTAB as cosurfactant,can we obtain the α-Fe2O3 with bigger diameter.(2)The rice shaped precursor of FeOOH was prepared by homogeneous precipitation method with FeCl3·6H2O and urea as materials,calcining the FeOOH under 500 ℃.The α-Fe2O3 red powder with a spherical structure was obtained by calcining the FeOOH under 500℃.Studying the effects of different FeCl3 concentration,reactant ratio,reaction temperature,reaction time and surfactants to the structure and morphology of the precursors.The tests showed that under the conditions of the concentration of FeCl3 is 0.4 mol/L,nFeCl3:nCO(NH2)2=1:5,the α-Fe2O3 powders with regular morphologies can be obtained after 2 h treatment under 85 ℃.The spherical α-Fe2O3 powder has been obtained after calcining under 500 ℃.Adding the CTAB,PVP and PEG-20000 espectively to the reaction system,the result shows that the aggregation of particles is serious after adding the surfactant.The product with spherical and bulk morphology is obtained by calcining the precursor which adds CTAB,the product is spherical particle by calcining the precursor which adds PVP or PEG-20000.