Preparation method for monodisperse nanometer beryllium oxide

Abstract

Provided in the present invention is a preparation method for monodisperse nanometer beryllium oxide, comprising the following steps: (S1) uniformly mixing urea and an aqueous formaldehyde solution, adjusting the pH with an organic amine to be weakly alkaline, and adding hydroxyalkyl (meth)acrylate, C12-16 alkyl (meth)acrylate and polyethylene glycol diacrylate to obtain a premix; (S2) adding a water-soluble beryllium salt to the premix, and under an inert atmosphere, adding a water-soluble initiator and slowly raising the temperature to 60-80°C for reaction to obtain a gel precursor; and (S3) after the gel precursor is dried, calcining same, washing same, and filtering same to obtain monodisperse nanometer beryllium oxide. The present invention involves a simple process and low costs, and the obtained beryllium oxide is nanoscale and has a monodisperse particle size.

Description

Preparation method of monodisperse nano beryllium oxide TECHNICAL FIELD

[0001] The present application belongs to the technical field of beryllium oxide preparation, and particularly relates to a preparation method of monodisperse nano beryllium oxide. BACKGROUND

[0002] Beryllium oxide has the characteristics of high thermal conductivity, high melting point, high strength, high insulation, low dielectric constant and low grafting loss, and is applied in many fields such as microwave technology, electronic information, nuclear industry and optoelectronics. In the past, the existing technology is mainly to manufacture micron-level beryllium oxide. However, with the development of current technology, the demand for nano beryllium oxide gradually increases, and in particular, the nano beryllium oxide material with uniform particle size dispersion is quite popular in the market. The nano beryllium oxide is mainly manufactured by deposition method, emulsion method and sol-gel method, but there is a problem of non-uniform particle size dispersion.

[0003] The inventor's previous patent CN116553583A discloses a preparation method of nano beryllium oxide, comprising the following steps: S1. Preparation of beryllium hydroxide suspension: stirring and adding organic amine in beryllium sulfate aqueous solution, controlling the pH value of the suspension, continuing to stir, standing and aging to obtain the suspension; S2. Preparation of beryllium hydroxide gel: stirring the suspension uniformly, filtering and washing to obtain the gel; S3. Hydrothermal pretreatment of beryllium hydroxide gel: dissolving the gel in deionized water, adding high molecular compounds with different polymerization degrees and ammonium persulfate, stirring uniformly, ultrasonic treatment, and transferring the mixed solution to a hydrothermal synthesis kettle; S4. Hydrothermal treatment: controlling the hydrothermal synthesis temperature and reaction time; S5. Formation of nano beryllium oxide: after the hydrothermal treatment is completed, the mixed solution is filtered and washed, the obtained solid material is dried and calcined, and nano beryllium oxide material is obtained. The patent utilizes high molecular compounds with different polymerization degrees, and the high polymerization degree high molecular compound is beneficial to form a stable three-dimensional network structure of molecular chain, and the low polymerization degree high molecular compound is beneficial to optimize the dispersion performance, so that the molecular chain in the three-dimensional structure is easy to stretch, thereby the beryllium oxide crystal grains are not easy to aggregate, and the finally obtained nano beryllium oxide has more uniform particle size distribution. CN116239133A discloses a preparation method of beryllium oxide, comprising the following steps: (1) premixing: mixing beryllium salt with eutectic solvent to obtain mixture A; (2) ion liquid coating: mixing mixture A obtained in step (1) with ion liquid to obtain mixture B; (3) carbonization: carbonizing mixture B obtained in step (2); (4) calcination: calcining the carbonization product of step (3) to obtain beryllium oxide. The present application can "narrow down" the action of beryllium salt and the outermost ion liquid coating through the pre-coating of eutectic solvent, thereby improving the interaction force among beryllium salt, eutectic solvent and ion liquid, so as to make the ion liquid coating more compact and reduce the particle size range of beryllium oxide. CN114671444A discloses a beryllium oxide and a preparation method thereof, comprising the following steps: (1) mixing beryllium salt and ion liquid, and coating the ion liquid on the surface of beryllium salt to obtain a mixture; (2) carbonizing the mixture to obtain beryllium salt coated with a carbon layer; (3) calcining the beryllium salt coated with a carbon layer to obtain beryllium oxide with small particle size and concentrated particle size distribution, which not only prevents the aggregation of nanoparticles, but also reduces the thermal decomposition temperature of the precursor beryllium salt, further reducing the production cost. The above patents have prepared monodisperse nano beryllium oxide to different degrees. However, the preparation process is complex, the cost is high, and reagents such as ion liquid are used, which still needs to be improved in industrial large-scale production.

[0004] The prior art also prepares nanoscale beryllium oxide by a sol-gel method, which is mostly an acrylamide polymer, and a three-dimensional network structure of polyacrylamide formed after polymerization separates and blocks ions in the solution to obtain a gel containing a salt solution in a small space unit. After drying and calcining, nanometer powder can be obtained. However, acrylamide has neurotoxicity, and there is still a certain safety risk in large-scale industrial production. Moreover, although nanoscale beryllium oxide can be obtained through experiments, the particle size uniformity still needs to be improved. Therefore, a simple, low-cost, green and low-toxicity production method is needed to prepare monodisperse nanoscale beryllium oxide. SUMMARY

[0005] In order to solve the defects of complex preparation process and high cost of monodisperse nanoscale beryllium oxide in the prior art, the present application provides a method for preparing nanoscale beryllium oxide with uniform particle size by using a sol-gel method and synthesizing two different types of polymers to cooperate with each other at low cost and simple operation. In order to achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0006] A preparation method of monodisperse nanometer beryllium oxide, comprising the following steps:

[0007] (S1) uniformly mix urea and formaldehyde aqueous solution, adjust the pH to weak alkaline by organic amine, add hydroxyalkyl (meth) acrylate, C12-16 alkyl (meth) acrylate and polyethylene glycol diacrylate to obtain a premix solution;

[0008] (S2) add water-soluble beryllium salt to the premix solution, add water-soluble initiator under inert atmosphere, slowly heat to 60-80 DEG C to obtain a gel precursor;

[0009] (S3) after drying the gel precursor, calcination treatment, washing, filtering to obtain monodisperse nanometer beryllium oxide.

[0010] Further, in step (S1), the concentration of formaldehyde aqueous solution is 20-40wt%, such as 37wt%; the organic amine is selected from at least one of isopropylamine, n-butylamine, cyclohexylamine, diethylamine, triethylamine, diethylmethylamine, diethylisopropylamine and diethylene triamine, and the weak alkaline is adjusted to pH 8-9.

[0011] Further, in step (S1), the (meth) acrylate hydroxyalkyl ester is selected from at least one of (meth) acrylate hydroxyethyl ester, (meth) acrylate hydroxypropyl ester and (meth) acrylate hydroxybutyl ester; the (meth) acrylate C12-16 alkyl ester is selected from at least one of (meth) acrylate dodecyl ester, (meth) acrylate tetradecyl ester and (meth) acrylate hexadecyl ester; and the polyethylene glycol segment number average molecular weight of polyethylene glycol diacrylate is 200-400.

[0012] Further, in step (S1), the molar ratio of urea to formaldehyde is 1:2-2.5; the molar ratio of urea, (meth)acrylate hydroxyalkyl ester, (meth)acrylate C12-16 alkyl ester and polyethylene glycol diacrylate is 1:0.6-0.8:2.2-3.4:0.2-0.3.

[0013] Further, in step (S2), the water-soluble beryllium salt is selected from at least one of beryllium sulfate, beryllium chloride, and beryllium nitrate; the amount of water-soluble beryllium salt added is such that the Be concentration in the system is 1-2 mol / L.

[0014] Further, in step (S2), the inert atmosphere is at least one of nitrogen, helium, and argon; the water-soluble initiator is selected from at least one of ammonium persulfate, potassium persulfate, and sodium persulfate. The amount of water-soluble initiator added is 1-3 wt% of the total mass of (meth)acrylate hydroxyalkyl ester, (meth)acrylate C12-16 alkyl ester, and polyethylene glycol diacrylate; the slow heating is a heating rate controlled at 1-3 °C / min.

[0015] Furthermore, in step (S3), the drying process is not particularly limited, such as vacuum drying. Calcination involves heating to 600-1000℃ at a rate of 1-5℃ / min and holding at that temperature for 5-10 hours. Washing is performed alternately with ethanol and deionized water. During calcination, the heating rate should not be too high, otherwise carbonization may easily occur.

[0016] This invention utilizes a simple and low-cost sol-gel method, where hydroxymethylurea produced from urea and formaldehyde, and acrylic acid derivative monomers, simultaneously polymerize under heating initiation conditions. The two polymers intertwine to form a three-dimensional network polymer structure, thereby containing Be in the solution. 2+ and SO4 2- Ion encapsulation occurs as polymerization progresses, separating all ions in the solution into small units within a three-dimensional network structure formed by the two polymers. Following drying and calcination, the polymers in the three-dimensional network structure undergo thermal decomposition during calcination, preventing the aggregation of beryllium oxide particles. The resulting beryllium oxide is nanoscale and monodisperse. The preparation of the polymer network requires precise control of the monomer concentration ratio to obtain a dense polymer three-dimensional network, directly affecting the particle size and dispersibility of the resulting beryllium oxide. Attached Figure Description

[0017] Figure 1 is a SEM image of beryllium oxide prepared in Example 1.

[0018] Figure 2 is a SEM image of beryllium oxide prepared in Comparative Example 1. Detailed Implementation

[0019] The present invention will be further described below with reference to specific embodiments, but the present invention is not limited to the following embodiments.

[0020] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0021] Example 1

[0022] (S1) Mix 1 mol of urea and 37 wt% formaldehyde aqueous solution (the amount of formaldehyde is 2.2 mol) evenly, adjust the pH to 8.5 with triethylamine, add 0.8 mol of hydroxyethyl methacrylate, 3.4 mol of dodecyl methacrylate and 0.2 mol of polyethylene glycol diacrylate (PEG segment number average molecular weight 400) to obtain a premixed solution;

[0023] (S2) Beryllium sulfate was added to the premixed solution to make the Be concentration in the system 1 mol / L. Under a nitrogen atmosphere, ammonium persulfate was added. The amount of ammonium persulfate added was 1 wt% of the total mass of the monomers. The monomers were the sum of hydroxyethyl methacrylate, dodecyl methacrylate and polyethylene glycol diacrylate. The temperature was increased to 70℃ at a heating rate of 2℃ / min and reacted for 4 h to obtain the gel precursor.

[0024] (S3) After vacuum drying of the gel precursor, the temperature was increased to 850℃ at a rate of 5℃ / min and kept at that temperature for 10h. The precursor was washed three times with alternating ethanol and deionized water, filtered, and vacuum dried to obtain monodisperse nano-beryllium oxide.

[0025] Example 2

[0026] The other conditions and operations are the same as in Example 1, except that in step (S1), the acrylic monomers are replaced with 0.6 mol hydroxybutyl methacrylate, 2.2 mol hexadecyl methacrylate and 0.3 mol polyethylene glycol diacrylate (PEG segment number average molecular weight 200).

[0027] Example 3

[0028] Other conditions and operations are the same as in Example 1, except that in step (S2), the amount of ammonium persulfate added is 3 wt% of the total mass of the monomers.

[0029] Example 4

[0030] The other conditions and operations are the same as in Example 1, except that in step (S3), the temperature is increased to 1000°C at a rate of 5°C / min.

[0031] Example 5

[0032] The other conditions and operations are the same as in Example 1, except that in step (S3), the temperature is increased to 600°C at a rate of 5°C / min.

[0033] Comparative Example 1

[0034] The other conditions and operations are the same as in Example 1, except that in step (S1), hydroxyethyl methacrylate is replaced with an equimolar amount of ethyl methacrylate.

[0035] Comparative Example 2

[0036] The other conditions and operations are the same as in Example 1, except that in step (S1), dodecyl methacrylate is replaced with an equimolar amount of hexyl methacrylate.

[0037] Comparative Example 3

[0038] The other conditions and operations are the same as in Example 1, except that in step (S1), polyethylene glycol diacrylate is replaced with an equimolar amount of diethylene glycol diacrylate.

[0039] Comparative Example 4

[0040] The other conditions and operations are the same as in Example 1, except that polyethylene glycol diacrylate is not added in step (S1).

[0041] Comparative Example 5

[0042] The other conditions and operations are the same as in Example 1, except that in step (S1), urea and formaldehyde aqueous solution are not added, and the monomer is directly added to deionized water of the same volume as the formaldehyde aqueous solution.

[0043] Comparative Example 6

[0044] The other conditions and operations are the same as in Example 1, except that in step (S1), acrylic monomers are not added, that is, hydroxyethyl methacrylate, dodecyl methacrylate and polyethylene glycol diacrylate are not added.

[0045] The homogeneous particle size D50 was measured using Nano Measure software based on electron microscopy images, and the particle size distribution index was calculated using the formula D90 - D10 / D50. BET It is obtained through calculation by testing the specific surface area of ​​the powder. The inventors found that the conventional particle size distribution index D90-D10 / D50 is not sufficient to accurately determine particle size uniformity, which is highly dependent on the selected SEM image. This invention introduces particle size distribution... BET / D50 is also used as an indicator of particle size distribution, and the results are shown in Table 1, Figure 1, and Figure 2.

[0046] Figure 1 is a SEM image of beryllium oxide prepared in Example 1; Figure 2 is a SEM image of beryllium oxide prepared in Comparative Example 1.

[0047] Table 1. Beryllium oxide particle size and particle size distribution index

[0048] As can be seen from the data in Table 1, the beryllium oxide nanoparticles obtained according to the method of this invention have a particle size of <20 nm and good particle size dispersibility. The inventors speculate that this is because the invention uses two different polymers to form a three-dimensional network structure, which divides the ions in the solution into small units. During the subsequent drying and calcination processes, this prevents the agglomeration of beryllium oxide particles and maintains good particle size uniformity. The absence of either of the two polymers would prevent the achievement of small and uniform beryllium oxide particle size.

Claims

1. A method for preparing monodisperse nano-beryllium oxide, characterized in that, Includes the following steps: (S1) Mix urea and formaldehyde aqueous solution evenly, adjust the pH to weakly alkaline with organic amine, and add (meth)acrylate hydroxyalkyl ester, (meth)acrylate C12-16 alkyl ester and polyethylene glycol diacrylate to obtain a premixed solution; the molar ratio of urea to formaldehyde is 1:2-2.5; the molar ratio of urea, (meth)acrylate hydroxyalkyl ester, (meth)acrylate C12-16 alkyl ester and polyethylene glycol diacrylate is 1:0.6-0.8:2.2-3.4:0.2-0.3; (S2) Water-soluble beryllium salt is added to the premixed solution. Under an inert atmosphere, a water-soluble initiator is added, and the temperature is slowly raised to 60-80℃ to react and obtain the gel precursor. (S3) After drying the gel precursor, it was calcined, washed, and filtered to obtain monodisperse nano-beryllium oxide.

2. The preparation method according to claim 1, characterized in that, In step (S1), the concentration of the formaldehyde aqueous solution is 20-40 wt%; the weak alkalinity is achieved by adjusting the pH to 8-9.

3. The preparation method according to claim 1, characterized in that, In step (S1), the organic amine is selected from at least one of isopropylamine, n-butylamine, cyclohexylamine, diethylamine, triethylamine, diethylmethylamine, diethylisopropylamine, and diethylenetriamine.

4. The preparation method according to claim 1, characterized in that, In polyethylene glycol diacrylate, the number-average molecular weight of the polyethylene glycol segments is 200-400.

5. The preparation method according to claim 1, characterized in that, In step (S2), the water-soluble beryllium salt is selected from at least one of beryllium sulfate, beryllium chloride, and beryllium nitrate.

6. The preparation method according to claim 1, characterized in that, The amount of water-soluble beryllium salt added makes the Be concentration in the system 1-2 mol / L.

7. The preparation method according to claim 1, characterized in that, In step (S2), the inert atmosphere is at least one of nitrogen, helium, and argon; the water-soluble initiator is selected from at least one of ammonium persulfate, potassium persulfate, and sodium persulfate.

8. The preparation method according to claim 1, characterized in that, In step (S2), the amount of water-soluble initiator added is 1-3 wt% of the total mass of (meth)acrylate hydroxyalkyl ester, (meth)acrylate C12-16 alkyl ester, and polyethylene glycol diacrylate.

9. The preparation method according to claim 1, characterized in that, In step (S2), the slow heating is a heating rate controlled at 1-3℃ / min.

10. The preparation method according to claim 1, characterized in that, In step (S3), calcination is carried out by heating the temperature to 600-1000℃ at a rate of 1-5℃ / min and holding it at that temperature for 5-10 hours.

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