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Preparation And Characterization Of Magnesium Borate Whiskers

Posted on:2019-07-05Degree:MasterType:Thesis
Country:ChinaCandidate:H Y WangFull Text:PDF
GTID:2371330572460079Subject:Materials Science and Engineering
Abstract/Summary:PDF Full Text Request
In this paper,hydrothermal method and microwave hydrothermal method were used to prepare nano-structured basic magnesium borate whiskers(MgBO2(OH))and magnesium borate whiskers(Mg2B2O5)were prepared by precipitation method.The microstructure and morphology of the products were characterized by XRD,SEM,TG-DSC,FT-IR.Analyze their growth process according to the crystal growth mechanism.The optimum conditions for preparation of MgBO2(OH)whiskers by hydrothermal method and microwave hydrothermal method were obtained.The optimum reaction conditions for the preparation of Mg2B2O5 whiskers by precipitation method were studied.The hydrothermal method for the preparation of MgBO2(OH)whiskers was studied,using MgCl2·6H2O and Na2BaO7·10H2O as raw materials.The effects of reaction temperature,reaction time,solvent type,surfactant and pH on the structure and morphology of the product were investigated.The optimum reaction conditions for the preparation of MgBO2(OH)whiskers by hydrothermal method are as follows:molar ratio of reactants n(B):n(Mg)=2:1,reaction temperature 200?,reaction time 24h and addition of surfactant PEG.The MgBO2(OH)whiskers with a length of 6?8?m,a diameter of 50?80nm,an aspect ratio of 75?160,and good dispersibility were obtained.The microwave hydrothermal method was used to synthesize MgBO2(OH)whiskers using MgCl2·6H2O and Na2BaO7·10H2O as raw materials.The effect of the molar ratio of reactants,reaction temperature and reaction time on the structure and morphology of the products was investigated.The optimal reaction conditions for the preparation of MgBO2(OH)whiskers by microwave hydrothermal method were as follows:molar ratio of reactants n(B):n(Mg)=2:1,reaction temperature 200? and reaction time 2h.The MgBO2(OH)whisker having a length of 2?5 ?m,a diameter of 50nm,and an aspect ratio of 40?100 was obtained.Using MgCl2·6H2O and H3BO3 as raw materials,NaOH as precipitant,the precursor was obtained by precipitation method,and then the Mg2B2O5 whisker was finally obtained by high temperature roasting.The conditions for the preparation of Mg2B2O5 whiskers by precipitation method were studied.The effects of the molar ratio of reactants,calcination temperature,reaction time,addition of surfactant and the amount of NaCl added on the structure and morphology of the products were investigated.The optimal reaction conditions for preparation of Mg2B2O5 whiskers by precipitation method are as follows:molar ratio of reactant n(B):n(Mg)=3:2,calcination temperature 750?,reaction time 2h,addition of surfactant PEG,the amount of flux NaCl added was 80%of the total mass of the reactants.The obtained Mg2B2O5 whiskers have a length of 5?7?m,a diameter of 90?150nm,an aspect ratio of 30?75.The Mg2B2O5 whiskers have regular morphology,high homogeneity and good dispersibility.
Keywords/Search Tags:Hydrothermal method, Microwave hydrothermal method, Precipitation method, Basic magnesium borate whiskers, Magnesium borate whiskers
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