Research On Solution Combustion Synthesis And Properties Of Iron-based Nanomaterials

Iron-based nanomaterials have a wide application prospect in a vast range of fields such as energy storage and conversion,water treatment,environmental remediation,high-efficiency catalysis,magnetic media,etc.,due to their peculiar electric,magnetic,optical,thermal,chemical properties,etc.The existing preparation methods for iron-based nanomaterials have faced several limitations such as complicated process,high cost,low productivity,etc.Solution combustion synthesis(SCS)is a fast-growing wet-chemical method to prepare nanomaterials and has lots of superiorities,such as convenience,time-saving,energy efficiency,high productivity,etc.In this study,the SCS method has been applied to prepared iron-based nanomaterials.The main research contents are listed as follows:(1)Network-like porous hematite(?-Fe2O3)nanosheets have been successfully prepared by a facile and novel combustion-based route with three simple steps of solution combustion synthesis,calcination and heat treatment by using ferric nitrate as an iron source and an oxidizer,glycine as a fuel and glucose as an addictive.First,a sheet-like precursor with uniformly mixed amorphous iron oxide and carbon was fabricated through solution combustion synthesis.Subsequently,ultrasmall intermediate Fe3C nanoparticles with the size of 5?10nm were formed and evenly embedded into the sheet-like carbon support through calcination of the precursor in argon at 500? for 0.5h.Finally,the decarbonization and pore formation were carried out by heat-treating the calcined product in air at 500? for 0.5h.The as-prepared ?-Fe2O3 nanosheets exhibit a network-like porous structure,perforated by a large quantity of well-formed round single-pores with?40nm in diameter as well as a small quantity of through-pores.The specific surface area of the porous nanosheets is 71m2/g.A possible formation mechanism for the network-like porous nanosheets during the heat treatment has been proposed,namely,the formation process of the network-like porous nanosheets during the heat treatment mainly consists of the generation of?-Fe2O3 nanoparticle subunits,their follow-up aggregation and sintering.(2)Iron nanopowders have been successfully prepared through hydrogen reduction of combustion-synthesized iron oxide precursors from glycine-ferric nitrate and glucose-glycine-ferric nitrate combustion systems.The effect of the molar fuel-to-oxidizer ratio(cp)on the combustion temperature,the phase composition,specific surface area(SSA)and micromorphology of the precursor was investigated.And the influence of the reduction temperature on the phase composition,particle size and magnetic property of the reduction product was also discussed.For the glycine-ferric nitrate combustion system,the combustion temperature of the solution(?-1)is 574?.the precursor obtained with ? = 1 is a mixture of ?-Fe2O3and ?-Fe2O3,exhibits high SSA(50.8m2/g)and high porosity,and its complete reduction temperature is 400?.The particle size of iron nanopowders reduced at 400? for 2h is?60nm,and the saturation magnetization is 201.7emu/g and the coercivity is 380.6Oe.For glucose-glycine-ferric nitrate combustion system,the addition of glucose changes the combustion reaction condition and makes the reaction mild and controllable.The as-synthesized precursor is ?-Fe203,exhibits higher SSA(75m2/g)and higher reactivity,and its complete reduction temperature is 275?.The particles size of iron nanopowders reduced at 275? for 2h 20?50nm,the saturation magnetization is 196.3emu/g and the coercivity is 611.40e(3)Sheet-like Fe/C nanocomposites have been successfully synthesized by a facile combustion-based method with two simple steps of solution combustion synthesis and hydrogen reduction by using ferric nitrate as an iron source and an oxidizer,glycine as a fuel and glucose as a carbon source.First,a sheet-like precursor consisting of evenly mixed amorphous iron oxide and carbon was prepared through solution combustion synthesis.Subsequently,sheet-like Fe/C nanocomposites were synthesized via hydrogen reduction of the as-prepared precursor at 400?.The obtained Fe/C nanocomposites are composed of iron nanoparticles and amorphous carbon and the iron nanoparticles are homogenously embedded into the sheet-like carbon support.For the Fe/C nanocomposites reduced at 400? for 2h,the size of the iron nanoparticles is?20nm,the carbon content is 23.2wt.%,the SSA is 274.9m2/g,the saturation magnetization is 145.7emu/g and the coercivity is 428.1 Oe.(4)The densification of the iron nanopowders obtained from the glycine-ferric nitrate combustion system has been performed through pressureless sintering and SPS sintering.The influence of sintering temperature on the density,microstructure,mechanical property and magnetic property of sintered pure iron is deeply investigated.The iron nanopowders exhibit high sintering activity.The relative density of pressurelessly sintered pure iron at 800? reaches 97.3%.The pressurelessly sintered pure iron at 900?1300? have high saturation induction,high tensile strength and high hardness.The relative density of SPS sintered pure iron at 600? reaches 96.1%,and it exhibits high hardness(HRC44.5).