As an important upconversion illuminant material, LiREF4 nanocrystals were efficiently synthesized in a continuous reactor with the assistant of a new precursor solution. The employed trioctylamine solvent in the solu...As an important upconversion illuminant material, LiREF4 nanocrystals were efficiently synthesized in a continuous reactor with the assistant of a new precursor solution. The employed trioctylamine solvent in the solution had a strong interaction with HF, and helped to avoid the generation of unnecessary solid components as LiF and NH4REF4 during the reaction. A silicon carbide reactor was developed to carry out the synthesis reaction, where LiYF4:Yb,Er/Ho/Tm quickly nucleated in 5 min at 300℃. The reaction time to successfully prepare 15 nm sized nanocrystals was less than 30 min, and the space-time yield of the flow synthesis method was 14.8 times that of a control group batch reaction. The prepared nanocrystals had a strong illuminant ability, which could find its use in the area of security mark printing.展开更多
To break through the thermodynamic limitation that sodium fluosilicate only can be completely decomposed at high temperature,the technology of pre-decomposition under SiF_(4) atmosphere and deep decomposition under ai...To break through the thermodynamic limitation that sodium fluosilicate only can be completely decomposed at high temperature,the technology of pre-decomposition under SiF_(4) atmosphere and deep decomposition under air condition at lower temperature was developed.The hydrolysis reaction of sodium fluosilicate can be effectively restrained when drying under vacuum or low temperature.Thermal decomposition results of sodium fluosilicate indicate that temperature has a very significant effect on its decomposition.The decomposition ratio can reach 79.4%at 600℃ for 1 h,and 99.6% at 700℃ for 1 h under air condition,respectively.Gas velocity and the type of inert gas have no significant effect on its decomposition.Fine particles affect its decomposition performance due to agglomeration,while coarse particles have good thermal decomposition performance without significant differences.The decomposition reaction process in fluidized bed satisfies the classical Avrami Erofe'EV model,with the reaction order of 1.5 and the activation energy of 61.35 kJ·mol^(-1).展开更多
A continuous synthesis method for the less than 10 nm core-shell upconversion nanoparticles was developed via coiled tube embedded flask reactors and a flow solvothermal co-participation reaction up to 300℃.Fast nucl...A continuous synthesis method for the less than 10 nm core-shell upconversion nanoparticles was developed via coiled tube embedded flask reactors and a flow solvothermal co-participation reaction up to 300℃.Fast nucleation of hexagonal nanocrystals in less than 9 min residence time was achieved owing to the excellent heating ability of the reactors,and a two-step reaction strategy was created for the synthesis of β-NaYF4:Gd,Yb,Er/Ho/Tm@NaYF_(4) particles without intermediate purification.展开更多
基金The authors acknowledge the support from the National Natural Scienle Fundatiu1 uf Clhilla(Nu.U1607118)allul also appreciated the technical support from Shandong JINDE new material Co,Ltd.in preparing the SiC reactor.
文摘As an important upconversion illuminant material, LiREF4 nanocrystals were efficiently synthesized in a continuous reactor with the assistant of a new precursor solution. The employed trioctylamine solvent in the solution had a strong interaction with HF, and helped to avoid the generation of unnecessary solid components as LiF and NH4REF4 during the reaction. A silicon carbide reactor was developed to carry out the synthesis reaction, where LiYF4:Yb,Er/Ho/Tm quickly nucleated in 5 min at 300℃. The reaction time to successfully prepare 15 nm sized nanocrystals was less than 30 min, and the space-time yield of the flow synthesis method was 14.8 times that of a control group batch reaction. The prepared nanocrystals had a strong illuminant ability, which could find its use in the area of security mark printing.
基金financial support from the National Natural Science Foundation of China (22078326,21878305,22078342)the financial supports of the National Key Research and Development Project of China (2020YFC1909701)。
文摘To break through the thermodynamic limitation that sodium fluosilicate only can be completely decomposed at high temperature,the technology of pre-decomposition under SiF_(4) atmosphere and deep decomposition under air condition at lower temperature was developed.The hydrolysis reaction of sodium fluosilicate can be effectively restrained when drying under vacuum or low temperature.Thermal decomposition results of sodium fluosilicate indicate that temperature has a very significant effect on its decomposition.The decomposition ratio can reach 79.4%at 600℃ for 1 h,and 99.6% at 700℃ for 1 h under air condition,respectively.Gas velocity and the type of inert gas have no significant effect on its decomposition.Fine particles affect its decomposition performance due to agglomeration,while coarse particles have good thermal decomposition performance without significant differences.The decomposition reaction process in fluidized bed satisfies the classical Avrami Erofe'EV model,with the reaction order of 1.5 and the activation energy of 61.35 kJ·mol^(-1).
基金supports from the National Natural Science Foundation of China(Nos.21991104 and 92034303).
文摘A continuous synthesis method for the less than 10 nm core-shell upconversion nanoparticles was developed via coiled tube embedded flask reactors and a flow solvothermal co-participation reaction up to 300℃.Fast nucleation of hexagonal nanocrystals in less than 9 min residence time was achieved owing to the excellent heating ability of the reactors,and a two-step reaction strategy was created for the synthesis of β-NaYF4:Gd,Yb,Er/Ho/Tm@NaYF_(4) particles without intermediate purification.
