Preparation And Thermodynamic Properties Of Nano-particle Suspension

Nano suspension is uniform,stable and high thermal conductivity heat transfer medium, prepared by dispersing nano-particles in water,alcohol,oil and other tradition heat transfer medium.It is known to all,solid material's thermal conductivity coefficient is higher than liquid,and thus dispersing solid particles into liquid can enhance the thermal conductivity of the liquid.Nano suspension overcomes the flaws of common particle suspension.Due to Brown-movement,the particle can stay stability in suspension,which is the foundation of technology application.There are a lot of ways in preparing nanoparticles,such as Sputtering method, coprecipitation method,sol - gel method and hydrothermal method.Hydrothermal method with feature such as a response speed,a high purity product and controllable particle size,better crystallinity,less reunion.It has been widely used in preparation metals,oxides and sulfides nano-materials.However,hydrothermal synthesis is also subject to certain restrictions,such as in the preparation of carbide,nitride,phosphide,silicide,and other non-oxide,the reactant is water sensitive and hydrothermal synthesis can not be used.Using organic solvents as reaction medium,be able to use non-aqueous media characteristics,can achieve many reactions which can not be carded out in aqueous solution,thus some nano-materials with special nature and structure can be prepared.In addition,using organic solvents instead of water as a reaction medium can avoid the existence of solid surface hydroxyl groups effectively,and improve the dispersion of nano-materials.Therefore organic solvent-thermal method has gradually become an important nano-materials synthesis technology.Separately in this thesis through the hot water and organic solvents prepared hot suspension of iron oxide,and through X-ray diffraction(XRD),transmission(scanning) electron microscope,721-type spectrophotometer methods studyed the system under different conditions,the particle size,morphology,suspension stability,suspension of the thermodynamic properties have been studied.Specific research results are as follows:1.At 70℃With water as the solvent,urea and FeCl₃·6H₂O as reactants react for 5 h, the adoption of hydrothermal preparedβ-FeOOH suspension,and its thermodynamic properties were determined.2.At 180℃ethylene glycol as solvent,anionic surfactant SDBS as an additive,FeCl₃·6H₂O,sodium acetate as the reactants,Solvothermal Preparation for 12 h of one-step preparation of Fe₃O₄ suspension,when the add SDBS concentration is 0.5 mM,the Fe₃O₄ stable suspension is prepared,and proposed a possible additive mechanism of SDBS. 3.At 140℃N-butanol as the solvent,Fe(acac)₃ as precursor,β-CD and SDBS form a complex as a template,whenβ-CD and SDBS concentration ratio is 1:2,react for 24 h Solvothermal Preparation Fe₃O₄ stable suspensions and to study the effect of different concentrations ofβ-CD and SDBS to structure of Fe₃O₄ and Fe₃O₄ suspension stability.4.At 190℃Methanol as organic solvents,Fe(acac)3 as precursor,1 - ethyl -2 -pyrrolidone as stabilizer,react for 3 h one-step Solvothermal Preparation of a stable a-Fe₂O₃ Suspension.By centrifugal slurry leaching can get good crystallinity magnetic particles,and proposed a 1 - ethyl -2 - pyrrolidone's possible mechanism as a stabilizer.5.At 70℃N-butanol as solvent,FeCl₃·6H₂O and urea as reactants SDBS as an additive, when SDBS at 3 mM or 5 mM concentration,react for 5 h Solvothermal Preparation of a stableβ-FeOOH suspension,its thermodynamic properties were measured.By Millipore centrifugal suspension obtained nanoparticles are one-dimensionalβ-FeOOH.