Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a rapid preparation method of a Co/SmCo composite magnetic material with a special structure, which utilizes Co/Sm (OH)3The special structure of the precursor, which is published in Journal of Materials Chemistry C in 2018 of this group of subjects, A novel strategy to Synthesis and a novel and isomeric SmCo5 particles from Co/Sm(OH)3composition with specific morphology is mentioned in the article, where Sm (OH) is distributed on branches of Co-urchin clusters3This structural advantage produces a composition distribution by calcium reductionHomogeneous SmCo5Single phase particles. The invention utilizes the special structural advantage to reduce all Sm (OH) on the surface through calcium in an ultra-short time3Reducing to Sm and combining with partial Co nucleus to form SmCo5And Sm2Co17And (2) waiting for the hard magnetic phase, reserving a part of Co core, and preparing the composite magnetic particles taking the Co soft magnetic phase as the core and the SmCo hard magnetic phase as the shell, wherein the hard magnetic phase wraps the soft magnetic phase so that the soft magnetic phase and the hard magnetic phase are distributed more uniformly, the exchange coupling effect is facilitated, the magnetic performance is improved, and the reaction time is shortened to a great extent.
In order to achieve the above object, the technical solution of the present invention comprises the following steps:
s1, SmCl is adopted3·6H2Preparing Sm (OH) from O powder serving as a raw material by a hydrothermal method3A precursor;
s2, Sm (OH) prepared in step S13Preparing Co/Sm (OH) from the precursor, cobalt laurate and hexadecylamine by an alcohol heating method3A precursor;
s3, mixing the Co/Sm (OH) in the step S23And (3) fully mixing the precursor with CaO and Ca, and then carrying out short-time calcium reduction reaction to obtain the Co/SmCo composite magnetic particles with the core-shell structure and CaO generated in the reaction.
S4, dissolving unreacted Ca in the product obtained in the step S3 by using deionized water, adding acetic acid, pouring out supernatant after the pH of the solution is neutral or slightly acidic, centrifugally washing the dark gray powder for 2-3 times by using the deionized water to remove redundant acid, and centrifugally washing for 1-2 times by using absolute ethyl alcohol to obtain the Co/SmCo composite magnetic material.
Preferably Sm (OH)3The preparation process of the precursor comprises the following steps: adding 10-12mmol of SmCl into the hydrothermal kettle3·6H2Adding 30-40ml of deionized water, stirring uniformly, dropwise adding 20-30ml of 1.8-2mol/l NaOH solution, allowing 15-20% of NaOH to pass through, reacting at 180 ℃ for 2-3 hours after magnetic stirring for 30-40 minutes, cooling, centrifugally washing with deionized water for 2-3 times, centrifugally washing with absolute ethyl alcohol for 1-2 times at 6000-8000r/min for 5-8 minutes, dryingGrinding and storing.
Preferably, Co/Sm (OH)3The preparation process of the precursor comprises the following steps: adding Sm (OH) into the hydrothermal kettle in a molar ratio of 1:4-1:73And cobalt laurate in an amount of 1 to 1.5mmol of Sm (OH)3Adding 1.2-3.6mmol of hexadecylamine and 60-70ml of 1, 2-butanediol, fully stirring, performing ultrasonic water bath at 80 ℃ for 60-70 minutes, putting the mixture into a muffle furnace, heating to 250 ℃ at the heating rate of 8-10 ℃/min, keeping the temperature for 80-100 minutes, taking out, cooling, performing centrifugal washing for 2-3 times by using toluene at the rotating speed of 6000-8000r/min, and performing centrifugal time for 5-8 minutes each time.
Preferably, Co/Sm (OH) is added in each calcium reduction reaction30.2g of precursor, corresponding to 0.3-0.5g of CaO and 3-4g of Ca.
Preferably, the calcium reduction reaction is carried out in an argon-hydrogen mixed atmosphere (93% Ar + 7% H)2) Wherein the temperature is 840-870 ℃, the heating rate is 8-10 ℃/min, the heat preservation time is 8-15min, and the further optimization is 10 min.
Preferably, the phase compositions of the prepared Co/SmCo composite magnetic material are Co and SmCo5And Sm2Co17A composite phase is formed.
As a preferred scheme, the microstructure of the prepared Co/SmCo composite magnetic material takes Co soft magnetic phase as a core, and SmCo5And Sm2Co17The formed SmCo hard magnetic phase is a shell layer.
Compared with other prior art, the invention has the main advantages that:
the invention provides a method for preparing a Co/SmCo composite magnetic material with a special structure by utilizing the structural advantages of a precursor through short-time incomplete calcium reduction reaction, namely, a Co soft magnetic phase is taken as a core, a SmCo hard magnetic phase is taken as a shell layer, and the hard magnetic phase is uniformly distributed around the soft magnetic phase. The technology solves the problems of agglomeration and oxidation phenomena and uneven distribution of soft and hard magnetic phases in the prior art, and the prepared composite particles have even distribution of the soft and hard magnetic phases and are beneficial to exchange coupling effect. And the calcium reduction reaction time is short, the reaction time is greatly reduced, and the rapid preparation of the composite magnetic particles is realized.
Detailed Description
The invention is further illustrated by the following examples and figures.
Example 1
(1) 3.7580g of SmCl3·6H2O was dissolved in 40ml of deionized water and 1.4688g of NaOH was dissolved in 20ml of deionized water. Dropwise adding NaOH solution into SmCl under magnetic stirring3And (3) putting the solution into a muffle furnace after 30min, preserving the heat at 180 ℃ for 12 hours, and centrifugally washing the solution for 3 times by using deionized water when the temperature is reduced to room temperature, wherein the rotating speed is 6000 r/min. Air-blast drying at 60 ℃ for 12 hours, and grinding to obtain Sm (OH)3And (3) precursor.
(2) 0.2265g of Sm (OH) in step (1)3Adding 2.0589g of cobalt laurate and 0.5810g of hexadecylamine into a polytetrafluoroethylene lining filled with 60ml of 1, 2-butanediol, ultrasonically treating at 80 ℃ for 1 hour, putting the mixture into a muffle furnace, heating to 250 ℃ at a heating rate of 10 ℃/min, preserving the temperature for 80min, cooling along with the furnace, pouring out supernatant, centrifugally washing for 3 times by using methylbenzene, and drying in a vacuum drying oven at room temperature for 30 minutes to obtain Co/Sm (OH)3A precursor of wherein nSm/nCo=1:4。
(3) Mixing the Co/Sm (OH) prepared in the step (2)3After 0.2g of the precursor and 0.3g of CaO powder are mixed uniformly, 4g of Ca particles are added and mixed uniformly, and the mixture is put into a crucible and a tube furnace. Argon-hydrogen mixture (93% Ar + 7% H) was used2) Washing the furnace for 3 times, heating to 870 deg.C at a heating rate of 10 deg.C/min under the above mixed atmosphere, maintaining for 10min, and rapidly cooling to room temperature with fan.
(4) And (4) taking out the mixture in the crucible after the reaction in the step (3), putting the mixture into a beaker, adding deionized water, dropwise adding acetic acid while stirring when the Ca is fully dissolved, namely when the Ca is not bubbled, centrifugally washing twice by using the deionized water to remove redundant acid when the PH is approximately equal to 7, centrifugally washing twice by using absolute ethyl alcohol at the rotating speed of 6000r/min, and thus obtaining the Co/SmCo composite magnetic material.
(5) The phase composition of the product was analyzed by XRD, and the results are shown in the left panel of FIG. 1, where the sample consists of SmCo5Phase Sm2Co17Phase and Co phase (Sm is burnt in the reaction). Indicating that Co is not completely reacted in the reaction process and is remained. And the magnetic properties of the product were tested using VSM, the results of which are shown in the right panel of fig. 1.
Example 2
(1) 3.7580g of SmCl3·6H2O was dissolved in 40ml of deionized water and 1.4688g of NaOH was dissolved in 20ml of deionized water. Dropwise adding NaOH solution into SmCl under magnetic stirring3And (3) putting the solution into a muffle furnace after 30min, preserving the heat at 180 ℃ for 12 hours, and centrifugally washing the solution for 3 times by using deionized water when the temperature is reduced to room temperature, wherein the rotating speed is 6000 r/min. Air-blast drying at 60 ℃ for 12 hours, and grinding to obtain Sm (OH)3And (3) precursor.
(2) 0.2265g of Sm (OH) in step (1)3Adding 2.0589g of cobalt laurate and 0.5810g of hexadecylamine into a polytetrafluoroethylene lining filled with 60ml of 1, 2-butanediol, ultrasonically treating at 80 ℃ for 1 hour, putting the mixture into a muffle furnace, heating to 250 ℃ at a heating rate of 10 ℃/min, preserving the temperature for 80min, cooling along with the furnace, pouring out supernatant, centrifugally washing for 3 times by using methylbenzene, and drying in a vacuum drying oven at room temperature for 30 minutes to obtain Co/Sm (OH)3A precursor of wherein nSm/nCo=1:7。
(3) Mixing the Co/Sm (OH) prepared in the step (2)3After 0.2g of the precursor and 0.3g of CaO powder are mixed uniformly, 4g of Ca particles are added and mixed uniformly, and the mixture is put into a crucible and a tube furnace. Argon-hydrogen mixture (93% Ar + 7% H) was used2) Washing the furnace for 3 times, heating to 870 deg.C at a heating rate of 10 deg.C/min under the above mixed atmosphere, maintaining for 10min, and rapidly cooling to room temperature with fan.
(4) And (4) taking out the mixture in the crucible after the reaction in the step (3), putting the mixture into a beaker, adding deionized water, dropwise adding acetic acid while stirring when Ca is fully dissolved, namely the bubbling phenomenon of the solution is stopped, centrifugally washing twice by using the deionized water to remove redundant acid when the PH is approximately equal to 7, and centrifugally washing twice by using absolute ethyl alcohol at the rotating speed of 6000r/min to obtain the Co/SmCo composite magnetic material.
(5) The phase composition of the product was analyzed by XRD, and the results are shown in the left panel of FIG. 1, where the sample consists of SmCo5Phase Sm2Co17Phase and Co phase. Indicating that Co is not completely reacted in the reaction process and is remained.
Example 3
(1) 3.7580g of SmCl3·6H2O was dissolved in 40ml of deionized water and 1.4688g of NaOH was dissolved in 20ml of deionized water. Dropwise adding NaOH solution into SmCl under magnetic stirring3And (3) putting the solution into a muffle furnace after 30min, preserving the heat at 180 ℃ for 12 hours, and centrifugally washing the solution for 3 times by using deionized water when the temperature is reduced to room temperature, wherein the rotating speed is 6000 r/min. Air-blast drying at 60 ℃ for 12 hours, and grinding to obtain Sm (OH)3And (3) precursor.
(2) 0.1294g of Sm (OH) in step (1)3Adding 2.0589g of cobalt laurate and 0.5810g of hexadecylamine into a polytetrafluoroethylene lining filled with 60ml of 1, 2-butanediol, ultrasonically treating at 80 ℃ for 1 hour, putting the mixture into a muffle furnace, heating to 250 ℃ at a heating rate of 10 ℃/min, preserving the temperature for 80min, cooling along with the furnace, pouring out supernatant, centrifugally washing for 3 times by using methylbenzene, and drying in a vacuum drying oven at room temperature for 30 minutes to obtain Co/Sm (OH)3A precursor of wherein nSm/nCo=1:4。
(3) Mixing the Co/Sm (OH) prepared in the step (2)3After 0.2g of the precursor and 0.3g of CaO powder are mixed uniformly, 4g of Ca particles are added and mixed uniformly, and the mixture is put into a crucible and a tube furnace. Argon-hydrogen mixture (93% Ar + 7% H) was used2) Washing the furnace for 3 times, heating to 840 ℃ at a heating rate of 10 ℃/min under the mixed atmosphere, preserving heat for 10min, and then rapidly cooling to room temperature by using a fan.
(4) And (4) taking out the mixture in the crucible after the reaction in the step (3), putting the mixture into a beaker, adding deionized water, dropwise adding acetic acid while stirring when the Ca is fully dissolved, namely the solution is not foamed, centrifugally washing twice by using the deionized water to remove redundant acid when the pH is approximately equal to 7, centrifugally washing twice by using absolute ethyl alcohol at the rotating speed of 6000r/min, and thus obtaining the Co/SmCo composite magnetic material.
(5) The phase composition of the product is analyzed by XRD, and the main phase of the sample is Sm2Co17Phase and Co phase. Indicating that Co is not completely reacted in the reaction process and is remained.
Example 4
(1) 3.7580g of SmCl3·6H2O was dissolved in 40ml of deionized water and 1.4688g of NaOH was dissolved in 20ml of deionized water. Dropwise adding NaOH solution into SmCl under magnetic stirring3And (3) putting the solution into a muffle furnace after 30min, preserving the heat at 180 ℃ for 12 hours, and centrifugally washing the solution for 3 times by using deionized water when the temperature is reduced to room temperature, wherein the rotating speed is 6000 r/min. Air-blast drying at 60 ℃ for 12 hours, and grinding to obtain Sm (OH)3And (3) precursor.
(2) 0.1294g of Sm (OH) in step (1)3Adding 2.0589g of cobalt laurate and 0.5810g of hexadecylamine into a polytetrafluoroethylene lining filled with 60ml of 1, 2-butanediol, ultrasonically treating at 80 ℃ for 1 hour, putting the mixture into a muffle furnace, heating to 250 ℃ at a heating rate of 10 ℃/min, preserving the temperature for 80min, cooling along with the furnace, pouring out supernatant, centrifugally washing for 3 times by using methylbenzene, and drying in a vacuum drying oven at room temperature for 30 minutes to obtain Co/Sm (OH)3A precursor of wherein nSm/nCo=1:7。
(3) Mixing the Co/Sm (OH) prepared in the step (2)3After 0.2g of the precursor and 0.3g of CaO powder are mixed uniformly, 4g of Ca particles are added and mixed uniformly, and the mixture is put into a crucible and a tube furnace. Argon-hydrogen mixture (93% Ar + 7% H) was used2) Washing the furnace for 3 times, heating to 840 ℃ at a heating rate of 10 ℃/min under the mixed atmosphere, preserving heat for 10min, and then rapidly cooling to room temperature by using a fan.
(4) And (4) taking out the mixture in the crucible after the reaction in the step (3), putting the mixture into a beaker, adding deionized water, dropwise adding acetic acid while stirring when the Ca is fully dissolved, namely the solution is not foamed, centrifugally washing twice by using the deionized water to remove redundant acid when the pH is approximately equal to 7, centrifugally washing twice by using absolute ethyl alcohol at the rotating speed of 6000r/min, and thus obtaining the Co/SmCo composite magnetic material.
(5) By XRD on the productThe phase composition is analyzed, the result is shown in the left picture of figure 1, and the main phase of the sample is Sm2Co17Phase and Co phase. Indicating that Co is not completely reacted in the reaction process and is remained.
Comparative example
(1) 3.7580g of SmCl3·6H2O was dissolved in 40ml of deionized water and 1.4688g of NaOH was dissolved in 20ml of deionized water. Dropwise adding NaOH solution into SmCl under magnetic stirring3And (3) putting the solution into a muffle furnace after 30min, preserving the heat at 180 ℃ for 12 hours, and centrifugally washing the solution for 3 times by using deionized water when the temperature is reduced to room temperature, wherein the rotating speed is 6000 r/min. Air-blast drying at 60 ℃ for 12 hours, and grinding to obtain Sm (OH)3And (3) precursor.
(2) 0.1294g of Sm (OH) in step (1)3Adding 2.0589g of cobalt laurate and 0.5810g of hexadecylamine into a polytetrafluoroethylene lining filled with 60ml of 1, 2-butanediol, ultrasonically treating at 80 ℃ for 1 hour, putting the mixture into a muffle furnace, heating to 250 ℃ at a heating rate of 10 ℃/min, preserving the temperature for 80min, cooling along with the furnace, pouring out supernatant, centrifugally washing for 3 times by using methylbenzene, and drying in a vacuum drying oven at room temperature for 30 minutes to obtain Co/Sm (OH)3A precursor of wherein nSm/nCo=1:4。
(3) Mixing the Co/Sm (OH) prepared in the step (2)3After 0.2g of the precursor and 0.3g of CaO powder are mixed uniformly, 4g of Ca particles are added and mixed uniformly, and the mixture is put into a crucible and a tube furnace. Argon-hydrogen mixture (93% Ar + 7% H) was used2) Washing the furnace for 3 times, heating to 870 deg.C at a heating rate of 10 deg.C/min under the above mixed atmosphere, maintaining for 90min, and rapidly cooling to room temperature with fan.
(4) Taking out the mixture in the crucible after the reaction in the step (3), putting the mixture into a beaker, adding deionized water, dropwise adding acetic acid while stirring when the Ca is fully dissolved, namely the solution is not foamed, centrifugally washing twice by using the deionized water to remove redundant acid when the pH is approximately equal to 7, centrifugally washing twice by using absolute ethyl alcohol at the rotating speed of 6000r/min, and thus obtaining SmCo5A magnetic material.
(5) The phase composition of the product was analyzed by XRD, and the result is shown in the left panel of FIG. 2, where the sample was SmCo5And (4) phase(s). And adopting VSM to pair the productsThe magnetic properties of the material were tested and the results are shown in the right panel of FIG. 2.
The magnetic property results of example 1 and comparative example were compared as shown in table 1.
Table 1: magnetic Property test results in examples of the present invention and comparative examples
In conclusion, the Co/SmCo sample with the core-shell structure can be successfully prepared by combining the incomplete calcium reduction reaction in a short time with the special structure of the precursor, and the hard magnetic phase is uniformly distributed around the soft magnetic phase, thereby being beneficial to the exchange coupling effect. Compared with a comparative example, the residual magnetization and the saturation magnetization under a 3T magnetic field are both improved, the reaction time is greatly shortened, the preparation method is simple, and a new idea is provided for the rapid preparation of the composite magnetic material.