A low-density hollow spherical nickel powder and its preparation method and use

Abstract

The present invention relates to a low-density hollow spherical nickel powder and a preparation method and use thereof, wherein the low-density hollow spherical nickel powder has a bulk density of 0.9-2.2 g / m 3 , a nickel powder having a particle size D50 of 15-90 μm, and a wall thickness of the hollow spherical nickel powder of 2-8 μm; its impurities include Fe, Cu and Co, the content of the Fe is ≤0.02wt.%, and the content of the Cu is ≤0.02wt.%. The preparation method of the present invention is a one-step reduction synthesis method, which uses nickel hydroxide as a template and a nickel source, hydrazine hydrate as a reducing agent, and a surfactant is added to synthesize a low-density hollow spherical nickel powder. The nickel hydroxide is a nickel hydroxide ball, and a pH regulator other than the nickel hydroxide ball is not used in the one-step reduction synthesis method. The preparation method of the present invention omits the template removal process of the conventional method, and can realize the one-step synthesis of hollow nickel powder / nickel balls; using high-concentration nickel, the alkalinity of hydrazine hydrate itself can be effectively utilized, which can reduce the cost of raw materials and simplify the process.

Description

Technical Field

[0001] The invention relates to the field of powder metallurgy, and in particular to a low-density hollow spherical nickel powder and a preparation method and application thereof. Background Art

[0002] Materials with hollow structures can usually exhibit some special optical, electrical and magnetic properties, which are of great significance in industrial applications. For example, by assembling inside hollow powder, composite powders with completely different electrical and magnetic properties inside and outside can be obtained. The bulk material prepared by sintering hollow metal powder is considered to be a very promising engineering material due to its low thermal conductivity and extremely light weight. At present, the method for preparing ultrafine hollow powder is mainly the template construction method, that is, a template is made of surfactants, microemulsion droplets, organic particles and hollow ceramic powders, and then reacts or adsorbs on the template interface to form a coating structure on the surface. The template is then removed by burning or dissolving to obtain a hollow structure. In this method, the selection of the template is the key to preparing hollow powders.

[0003] In the prior art, the preparation method of hollow nickel powder requires the use of a template (such as ceramic powder) and a nickel salt with a low nickel content as a Ni source (such as nickel sulfate hexahydrate, nickel chloride hexahydrate). The synthesis process is long and it is easy to introduce new SO4 2- or Cl - Impurities, at the same time, the template is difficult to remove, the process is long and the cost is high. Summary of the invention

[0004] In view of the above problems, the object of the present invention is to provide a low-density hollow spherical nickel powder with a short preparation process and a preparation method and use thereof, which directly uses nickel hydroxide as both a nickel source and a template.

[0005] In one aspect, the present invention provides a low-density hollow spherical nickel powder, wherein the low-density hollow spherical nickel powder has a bulk density of 0.9-2.2 g / m 3 , low-density hollow spherical nickel powder with a particle size D50 of 15-90 μm; the wall thickness of the low-density hollow spherical nickel powder is 2-8 μm.

[0006] Furthermore, in the low-density hollow spherical nickel powder described in the present invention, impurities include Fe, Cu and Co; wherein the content of Fe is ≤0.02wt.%, the content of Cu is ≤0.02wt.%, and the content of Co is ≤0.01wt.%.

[0007] Furthermore, the impurities in the low-density hollow spherical nickel powder also include Cl and S, wherein the content of Cl is ≤0.01wt.%, and the content of S is ≤0.01wt.%.

[0008] On the other hand, the present invention provides a method for preparing the low-density hollow spherical nickel powder described above, characterized in that the preparation method is a one-step reduction synthesis method;

[0009] The one-step reduction synthesis method uses nickel hydroxide as a template and a nickel source, hydrazine hydrate as a reducing agent, and a surfactant is added to synthesize the low-density hollow spherical nickel powder as described in any one of the above items; the nickel hydroxide is a nickel hydroxide sphere;

[0010] The one-step reduction synthesis method does not use a pH regulator other than hydrazine hydrate.

[0011] Furthermore, in the preparation method described in the present invention, the particle size D50 of the nickel hydroxide balls is 8-50 μm, and the purity of the nickel hydroxide balls is greater than or equal to 99.7%.

[0012] Furthermore, in the preparation method of the present invention, the one-step reduction synthesis method specifically comprises the following steps:

[0013] Step 1) mixing the nickel hydroxide with water to prepare a nickel hydroxide suspension; adding an appropriate amount of surfactant to the nickel hydroxide suspension to obtain a first reaction mixture; the mass ratio of the added surfactant to the nickel hydroxide suspension is 1:50-1:200; the mass ratio of water to nickel hydroxide is 2:1-4.5:1;

[0014] Step 2) transferring the first reaction mixture to a water bath and heating and stirring for 8-12 minutes, and adding hydrazine hydrate once more to obtain a second reaction mixture; reacting the second reaction mixture at a temperature of 60° C. to 80° C. and a stirring speed of 200 r / min to 500 r / min for 30 min to 150 min, and obtaining a reaction complete mixture after the reaction is complete;

[0015] The mass ratio of hydrazine hydrate to nickel hydroxide is 2.3:1-3.5:1;

[0016] Step 3) The reaction mixture is filtered and washed with deionized water or anhydrous ethanol, and then vacuum dried to obtain low-density hollow spherical nickel powder; the vacuum drying temperature is 50° C.-70° C. and the drying time is 2 h-10 h.

[0017] Furthermore, in the preparation method of the present invention, in the step 1), the nickel hydroxide suspension contains negatively charged nickel hydroxide colloid, the surfactant is a cationic surfactant, and the surfactant is adsorbed on the surface of the nickel hydroxide colloid to form a monodisperse nickel hydroxide colloid core.

[0018] Furthermore, in the preparation method of the present invention, during the reaction process of step 2), after the reaction is completed, the content of nickel hydroxide in the completely reacted mixed solution is 0.

[0019] Furthermore, in the preparation method of the present invention, the pH value of the first reaction mixture in step 1) is less than or equal to 10, the pH value of the second reaction mixture in step 2) is greater than 13, and the pH value of the complete reaction mixture is greater than 11.

[0020] Furthermore, in the preparation method described in the present invention, the cationic surfactant is selected from at least one of hexadecyltrimethylammonium bromide, octadecyldimethylbenzyl quaternary ammonium chloride or alkyltrimethylammonium chloride.

[0021] In another aspect, the present invention provides a use of the low-density hollow spherical nickel powder described above, characterized in that the low-density hollow spherical nickel powder is used for coating absorbing materials.

[0022] Compared with the prior art, the present invention has the following beneficial technical effects:

[0023] The method for preparing low-density hollow spherical nickel powder of the present invention uses nickel hydroxide balls as both template and nickel source, which not only provides a nickel source with a high nickel content (the mass fraction of nickel element in nickel hydroxide is about 63.3%) for the reaction, but also gradually disappears as a template in the reaction, eliminating the template removal process of the conventional method, and can achieve one-step synthesis of hollow nickel powder / nickel balls. No new SO4 is introduced in the preparation process. 2- or Cl - Impurities.

[0024] The preparation method of the present invention adopts high-concentration nickel and can effectively utilize the alkalinity of hydrazine hydrate itself. Under the high-concentration system, the pH value can still be maintained above 11 only by the alkalinity of hydrazine hydrate itself, which can provide a good alkaline environment for reduction, and no additional pH regulator is needed to control the pH value during the reduction process. It can reduce the cost of raw materials and simplify the process.

[0025] The low-density hollow spherical nickel powder of the present invention has a bulk density of 0.9-2.2 g / m 3 , the particle size D50 is 15-90μm, the wall thickness of the low-density hollow spherical nickel powder is 2-8μm, and the impurities in the low-density hollow spherical nickel powder include Fe, Cu and Co; wherein the content of Fe is ≤0.02wt.%, the content of Cu is ≤0.02wt.%, and the content of Co is ≤0.01wt.%. In addition, the content of Cl in the impurities is ≤0.01wt.%, and the content of S is ≤0.01wt.%. Therefore, the low-density hollow spherical nickel powder has high purity and good performance, and can be used in coating absorbing materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 XRD diffraction patterns of the nickel powder in the intermediate state and the complete state of the reaction in step 2) of the method for preparing low-density hollow spherical nickel powder of the present invention;

[0027] Figure 2 This is a microscopic morphology image of the reaction intermediate state of the nickel powder in step 2) of the method for preparing low-density hollow spherical nickel powder of the present invention, magnified 200 times;

[0028] Figure 3 This is a microscopic morphology image of the low-density hollow spherical nickel powder of the present invention magnified 200 times;

[0029] Figure 4 This is a microscopic morphology image of the low-density hollow spherical nickel powder of the present invention magnified 500 times;

[0030] Figure 5 This is a microscopic morphology image of the low-density hollow spherical nickel powder of the present invention magnified 1000 times;

[0031] Figure 6 This is a microscopic morphology image of the nickel hydroxide sphere of the present invention magnified 200 times. Implementation

[0032] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific implementation methods of the present invention are now described in detail with reference to the accompanying drawings. The described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. If the specific conditions are not specified in the specific implementation methods, they shall be carried out according to the conventional conditions or the conditions recommended by the manufacturer.

[0033] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present disclosure. Instead, they are merely examples of devices and methods consistent with some aspects of the present disclosure as detailed in the appended claims. The terms used in the present disclosure are for the purpose of describing specific embodiments only and are not intended to limit the present disclosure. Specific implementation method 1

[0035] like Figure 3-Figure 5 As shown, the low-density hollow spherical nickel powder of the present invention has a bulk density of 0.9-2.2 g / m 3, low-density hollow spherical nickel powder with a particle size D50 of 15-90 μm; the wall thickness of the low-density hollow spherical nickel powder is 2-8 μm.

[0036] The impurities in the low-density hollow spherical nickel powder include Fe, Cu and Co; wherein the Fe content is ≤0.02wt.%, the Cu content is ≤0.02wt.%, and the Co content is ≤0.01wt.%. In addition, the Cl content in the impurities is ≤0.01wt.%, and the S content is ≤0.01wt.%. Specific implementation method 2

[0038] A method for preparing low-density hollow spherical nickel powder as in the first embodiment of the present invention is specifically a one-step reduction synthesis method;

[0039] The one-step reduction synthesis method uses nickel hydroxide as a template and a nickel source, hydrazine hydrate as a reducing agent, and a surfactant is added to synthesize the low-density hollow spherical nickel powder described in the first specific embodiment; the nickel hydroxide is nickel hydroxide spheres;

[0040] In the above one-step reduction synthesis method, no pH adjuster other than hydrazine hydrate is used.

[0041] like Figure 6 As shown, the particle size D50 of the nickel hydroxide spheres is 8-50 μm.

[0042] like Figure 1 and Figure 2 As shown, the above one-step reduction synthesis method specifically comprises the following steps:

[0043] Step 1) mixing the nickel hydroxide and water to prepare a nickel hydroxide suspension; adding an appropriate amount of surfactant to the nickel hydroxide suspension to obtain a first reaction mixture; the mass ratio of the added surfactant to the nickel hydroxide suspension is 1:50-1:200; the mass ratio of the water to the nickel hydroxide is 2:1-4.5:1;

[0044] Step 2) the first reaction mixture is transferred to a water bath and heated and stirred for 8-12 minutes, and hydrazine hydrate is added once again to obtain a second reaction mixture; the second reaction mixture is reacted at a temperature of 60°C-80°C and a stirring speed of 200r / min-500r / min for 30min-150min, and after the reaction is complete, a reaction complete mixture is obtained; the mass ratio of the hydrazine hydrate to the nickel hydroxide is 2.3:1-3.5:1;

[0045] Step 3) The reaction mixture is filtered and washed with deionized water or anhydrous ethanol, and then vacuum dried to obtain low-density hollow spherical nickel powder; the vacuum drying temperature is 50°C-70°C and the drying time is 2h-10h.

[0046] In the above step 1), the nickel hydroxide suspension contains negatively charged nickel hydroxide colloid, the surfactant is a cationic surfactant, and the surfactant is adsorbed on the surface of the nickel hydroxide colloid to form a monodisperse nickel hydroxide colloid core.

[0047] During the reaction process of step 2), the content of nickel hydroxide in the complete reaction mixture is 0.

[0048] like Figure 1 As shown, it is the XRD diffraction pattern of the hollow nickel powder in the above step 2) in the intermediate state and the complete state of the reaction; Figure 1 The complete state shown refers to the hollow nickel powder after the complete reaction. Figure 1 The intermediate state shown refers to hollow nickel powder that has not been completely reacted; as can be seen from the figure, the intermediate state powder is composed of two phases of nickel hydroxide and nickel, and the complete state powder is composed of a single nickel phase.

[0049] like Figure 2 As shown, the intermediate state of the above step 2) is hollow nickel powder, that is, hollow nickel powder that has not reacted completely, which is manifested as nickel nucleating on the surface of nickel hydroxide and then wrapping nickel hydroxide, and the nickel hydroxide is gradually dissolved.

[0050] The pH value of the first reaction mixture in the above step 1) is less than or equal to 10, the pH value of the second reaction mixture in the above step 2) is greater than 13, and the pH value of the reaction complete mixture is greater than 11.

[0051] The cationic surfactant is selected from at least one of hexadecyltrimethylammonium bromide, octadecyldimethylbenzyl quaternary ammonium chloride or alkyltrimethylammonium chloride. Specific implementation method three:

[0053] A use of the low-density hollow spherical nickel powder as described above, wherein the low-density hollow spherical nickel powder is used for coating wave absorbing materials.

[0054] The present invention is further described in detail below in conjunction with specific embodiments. Example 1

[0055] The present invention discloses a method for preparing low-density hollow spherical nickel powder, which is a one-step reduction synthesis method and specifically comprises the following steps:

[0056] Step 1) nickel hydroxide and water are mixed to form a nickel hydroxide suspension; hexadecyl trimethyl ammonium bromide is added to the nickel hydroxide suspension as a cationic surfactant to obtain a first reaction mixture; the mass ratio of water to nickel hydroxide is 4.5:1; the mass ratio of hexadecyl trimethyl ammonium bromide to the nickel hydroxide suspension is 1:75. In this step, the nickel hydroxide suspension contains negatively charged nickel hydroxide colloid, the surfactant is a cationic surfactant, and the surfactant is adsorbed on the surface of the nickel hydroxide colloid to form a monodisperse nickel hydroxide colloid core; and the pH value of the first reaction mixture is less than or equal to 10. The particle size D50 of the above nickel hydroxide spheres is 8-50μm.

[0057] Step 2) The first reaction mixture is transferred to a water bath and heated with stirring for 12 minutes, and hydrazine hydrate is added once again to obtain a second reaction mixture, and the pH value of the second reaction mixture is greater than 13; the second reaction mixture is reacted at a temperature of 80° C. and a stirring speed of 500 r / min for 130 minutes, and after the reaction is complete, a reaction complete mixture is obtained; the mass ratio of hydrazine hydrate to nickel hydroxide is 2.3: 1, and the pH value of the reaction complete mixture is greater than 11.

[0058] Step 3) The reaction mixture is filtered and washed with deionized water or anhydrous ethanol, and then vacuum dried to obtain 1# low-density hollow spherical nickel powder; the vacuum drying temperature is 50° C. and the drying time is 8 hours. Example 2

[0059] The difference between this embodiment 2 and embodiment 1 is that:

[0060] In step 1), the mass ratio of water to nickel hydroxide is 3.5:1, and the mass ratio of hexadecyltrimethylammonium bromide to nickel hydroxide suspension is 1:100.

[0061] In step 2), the first reaction mixture is transferred to a water bath and heated with stirring for 12 minutes, and hydrazine hydrate is added once more to obtain a second reaction mixture; the second reaction mixture is reacted at a temperature of 60° C. and a stirring speed of 500 r / min for 120 minutes, and the mass ratio of hydrazine hydrate to nickel hydroxide is 2.45:1.

[0062] In step 3), the vacuum drying temperature is 70° C. and the drying time is 2 h to obtain 2# low-density hollow spherical nickel powder. Example 3

[0063] The difference between this embodiment 3 and embodiment 1 is that:

[0064] In step 1), the mass ratio of water to nickel hydroxide is 3:1, and the mass ratio of hexadecyltrimethylammonium bromide to nickel hydroxide suspension is 1:100.

[0065] In step 2), the first reaction mixture is transferred to a water bath and heated with stirring for 8 minutes, and hydrazine hydrate is added once more to obtain a second reaction mixture; the second reaction mixture is reacted at a temperature of 75° C. and a stirring speed of 500 r / min for 105 minutes, and the mass ratio of hydrazine hydrate to nickel hydroxide is 2.6:1.

[0066] In step 3), the vacuum drying temperature is 55° C. and the drying time is 9 h to obtain 3# low-density hollow spherical nickel powder. Example 4

[0067] The difference between this embodiment 4 and embodiment 1 is that:

[0068] In step 1), the mass ratio of water to nickel hydroxide is 3:1, and the mass ratio of hexadecyltrimethylammonium bromide to nickel hydroxide suspension is 1:150.

[0069] In step 2), the first reaction mixture is transferred to a water bath and heated and stirred for 12 minutes, and hydrazine hydrate is added once again to obtain a second reaction mixture; the second reaction mixture is reacted at a temperature of 65° C. and a stirring speed of 400 r / min for 90 minutes, and the mass ratio of hydrazine hydrate to nickel hydroxide is 2.85:1.

[0070] In step 3), the vacuum drying temperature is 70° C. and the drying time is 3 h to obtain 4# low-density hollow spherical nickel powder. Example 5

[0071] The difference between this embodiment 2 and embodiment 1 is that:

[0072] In step 1), the mass ratio of water to nickel hydroxide is 3:1, and the mass ratio of hexadecyltrimethylammonium bromide to nickel hydroxide suspension is 1:120.

[0073] In step 2), the first reaction mixture is transferred to a water bath and heated with stirring for 10 minutes, and hydrazine hydrate is added once more to obtain a second reaction mixture; the second reaction mixture is reacted at a temperature of 68° C. and a stirring speed of 300 r / min for 75 minutes, and the mass ratio of hydrazine hydrate to nickel hydroxide is 3:1.

[0074] In step 3), the vacuum drying temperature is 70° C. and the drying time is 3 h to obtain 5# low-density hollow spherical nickel powder. Example 6

[0075] The difference between this embodiment 6 and embodiment 1 is that:

[0076] In step 1), the mass ratio of water to nickel hydroxide is 2.5:1, and the mass ratio of hexadecyltrimethylammonium bromide to nickel hydroxide suspension is 1:175.

[0077] In step 2), the first reaction mixture is transferred to a water bath and heated with stirring for 8 minutes, and hydrazine hydrate is added once more to obtain a second reaction mixture; the second reaction mixture is reacted at a temperature of 70° C. and a stirring speed of 500 r / min for 60 minutes, and the mass ratio of hydrazine hydrate to nickel hydroxide is 3.15:1.

[0078] In step 3), the vacuum drying temperature is 50° C. and the drying time is 6 h to obtain 6# low-density hollow spherical nickel powder.

[0079] The difference between this comparative example 1 and example 1 is only that:

[0080] In step 1), the mass ratio of water to nickel hydroxide is 3.5:1, and the mass ratio of hexadecyltrimethylammonium bromide to nickel hydroxide suspension is 1:225.

[0081] In step 2), the mass ratio of hydrazine hydrate to nickel hydroxide is 2.45: 1, and 7# nickel powder is obtained.

[0082] The difference between this comparative example 2 and example 1 is only that:

[0083] In step 1), the mass ratio of water to nickel hydroxide is 3:1, and the mass ratio of hexadecyltrimethylammonium bromide to nickel hydroxide suspension is 1:25.

[0084] In step 2), the mass ratio of hydrazine hydrate to nickel hydroxide is 2.6: 1, and 8# nickel powder is obtained.

[0085] The difference between this comparative example 3 and example 1 is only that:

[0086] In step 2), the first reaction mixture is transferred to a water bath and heated and stirred for 8 minutes, and hydrazine hydrate is added once again to obtain a second reaction mixture; the second reaction mixture is reacted at a temperature of 50° C. and a stirring speed of 600 r / min for 28 minutes to obtain 9# nickel powder.

[0087] The difference between this comparative example 4 and comparative example 3 is only that:

[0088] In step 2), the first reaction mixture is transferred to a water bath and heated and stirred for 8 minutes, and hydrazine hydrate is added once again to obtain a second reaction mixture; the second reaction mixture is reacted at a temperature of 90° C. and a stirring speed of 260 r / min for 180 minutes to obtain 10# nickel powder.

[0089] The low-density hollow spherical nickel powders in the above Examples 1-6 and the spherical nickel powders in Comparative Examples 1-4 were tested respectively to obtain the results shown in Table 1 below.

[0090] Table 1 Test results of low-density hollow spherical nickel powder of Examples 1-6 and Comparative Examples 1-4

[0091] serial number purity% Cl content wt.% S content wt.% Fe content wt.% Cu content wt.% Co content wt.% Nickel powder D50μm <![CDATA[Bulk density / g / m 3 > Hollow wall thickness μm Hollow sphericity Reaction time / min 1# Low density hollow spherical nickel powder 99.7 ＜0.01 ＜0.01 ＜0.02 ＜0.02 ＜0.02 75 1.97 6.8 good 130 2# Low density hollow spherical nickel powder 99.6 ＜0.01 ＜0.01 ＜0.02 ＜0.02 ＜0.02 67 1.74 6.5 good 120 3# Low density hollow spherical nickel powder 99.8 ＜0.01 ＜0.01 ＜0.02 ＜0.02 ＜0.02 55 1.6 5.3 good 105 4# Low density hollow spherical nickel powder 99.6 ＜0.01 ＜0.01 ＜0.02 ＜0.02 ＜0.02 49 1.55 5.1 good 90 5# Low density hollow spherical nickel powder 99.7 ＜0.01 ＜0.01 ＜0.02 ＜0.02 ＜0.02 28 1.17 3.2 good 75 6# Low density hollow spherical nickel powder 99.9 ＜0.01 ＜0.01 ＜0.02 ＜0.02 ＜0.02 22 0.96 2.7 good 60 7# Nickel powder 99.6 ＜0.01 ＜0.01 ＜0.02 ＜0.02 ＜0.02 65 1.72 9.3 Difference 180 8# Nickel powder 99.8 ＜0.01 ＜0.01 ＜0.02 ＜0.02 ＜0.02 105 2.33 7.2 Difference 130 9# Nickel powder 95.7 ＜0.01 ＜0.01 ＜0.02 ＜0.02 ＜0.02 72 1.95 1.7 Difference 28 10# Nickel powder 99.9 ＜0.01 ＜0.01 ＜0.02 ＜0.02 ＜0.02 37 1.24 3.5 Difference 180

[0092] As can be seen from Table 1 above, the low-density hollow spherical nickel powder prepared by the present invention has high purity, good hollow sphericity and good performance. The present invention is illustrated by the above specific embodiments, and those skilled in the art should understand that various changes and equivalent substitutions can be made to the present invention without departing from the scope of the present invention. The parts not described in detail in the specification of the present invention are well-known technologies to those skilled in the art. In addition, various modifications can be made to the present invention for specific situations or specific circumstances without departing from the scope of the present invention. Therefore, the present invention is not limited to the disclosed specific embodiments, but should include all implementation methods falling within the scope of the claims of the present invention.

Claims

1. A method for preparing low-density hollow spherical nickel powder, characterized in that: The preparation method is a one-step reduction synthesis method; The one-step reduction synthesis method uses nickel hydroxide as a template and a nickel source, hydrazine hydrate as a reducing agent, and a surfactant is added to synthesize a low-density hollow spherical nickel powder; the nickel hydroxide is a nickel hydroxide sphere, and the particle size D50 of the nickel hydroxide sphere is 8-50 μm; the one-step reduction synthesis method does not use a pH regulator other than hydrazine hydrate; The one-step reduction synthesis method specifically comprises the following steps: Step 1) mixing the nickel hydroxide with water to prepare a nickel hydroxide suspension; adding an appropriate amount of surfactant to the nickel hydroxide suspension to obtain a first reaction mixture; the mass ratio of the added surfactant to the nickel hydroxide suspension is 1:50-1:200; the mass ratio of water to nickel hydroxide is 2:1-4.5:1; Step 2) transferring the first reaction mixture to a water bath and heating and stirring for 8-12 minutes, and adding hydrazine hydrate once more to obtain a second reaction mixture; reacting the second reaction mixture at a temperature of 60° C. to 80° C. and a stirring speed of 200 r / min to 500 r / min for 30 min to 150 min, and obtaining a reaction complete mixture after the reaction is complete; The mass ratio of hydrazine hydrate to nickel hydroxide is 2.3:1-3.5:1; Step 3) The reaction mixture is filtered and washed with deionized water or anhydrous ethanol, and then vacuum dried to obtain low-density hollow spherical nickel powder; the vacuum drying temperature is 50° C.-70° C., and the drying time is 2 h-10 h; The low-density hollow spherical nickel powder has a bulk density of 0.9-2.2 g / m 3 , low-density hollow spherical nickel powder with a particle size D50 of 15-90 μm; the wall thickness of the low-density hollow spherical nickel powder is 2-8 μm; The impurities in the low-density hollow spherical nickel powder include Fe, Cu and Co; wherein the content of Fe is ≤0.02wt.%, the content of Cu is ≤0.02wt.%, and the content of Co is ≤0.01wt.%; In the step 1), the nickel hydroxide suspension contains negatively charged nickel hydroxide colloid, the surfactant is a cationic surfactant, and the surfactant is adsorbed on the surface of the nickel hydroxide colloid to form a monodisperse nickel hydroxide colloid core; During the reaction of step 2), the content of nickel hydroxide in the complete reaction mixture is 0.

2. The preparation method according to claim 1, characterized in that: The pH value of the first reaction mixture in step 1) is less than or equal to 10, the pH value of the second reaction mixture in step 2) is greater than 13, and the pH value of the reaction complete mixture is greater than 11.

3. The preparation method according to claim 2, characterized in that: The cationic surfactant is selected from at least one of hexadecyltrimethylammonium bromide, octadecyldimethylbenzyl quaternary ammonium chloride or alkyltrimethylammonium chloride.

4. Use of low-density hollow spherical nickel powder prepared by the preparation method according to any one of claims 1 to 3, characterized in that: The low-density hollow spherical nickel powder is used for coating wave-absorbing materials.

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