阅读说明：本技术 一种无衬底超薄镍-63放射源的制备方法 (Method for preparing substrate-free ultrathin nickel-63 radioactive source ) 是由 苏冬萍 梁帮宏 罗婷 张劲松 甘泉 李顺涛 陈云明 王国华 姚亮 周春林 于 2021-06-23 设计创作，主要内容包括：本发明公开了一种无衬底超薄镍-63放射源的制备方法,包括以下步骤：S1、将电沉积液中的镍金属离子沉积在铜衬底的一侧形成镍层；S2、在镍层上覆一层有机膜,即在镍层的两个对称面上分别为铜衬底和有机膜；S3、将步骤S2制备的镍-63放射源浸没在衬底去除溶液中去除铜衬底；S4、去除步骤S3制备的无衬底镍-63放射源上的有机膜,获得无衬底超薄镍-63放射源。本发明制备得到无衬底超薄镍-63放射源为双面放射源,厚度小于2μm,表面平整,无褶皱和破损,镍层致密均匀,有金属光泽；本发明工艺简便,操作简单,电沉积率大于90％。(The invention discloses a preparation method of a substrate-free ultrathin nickel-63 radioactive source, which comprises the following steps: s1, depositing nickel metal ions in the electrodeposition solution on one side of the copper substrate to form a nickel layer; s2, covering a layer of organic film on the nickel layer, namely, a copper substrate and an organic film are respectively arranged on two symmetrical surfaces of the nickel layer; s3, immersing the nickel-63 radioactive source prepared in the step S2 in a substrate removing solution to remove the copper substrate; s4, removing the organic film on the substrate-free nickel-63 radioactive source prepared in the step S3 to obtain the substrate-free ultrathin nickel-63 radioactive source. The substrate-free ultrathin nickel-63 radioactive source prepared by the invention is a double-sided radioactive source, the thickness is less than 2 mu m, the surface is flat, no fold or damage exists, the nickel layer is compact and uniform, and the nickel layer has metallic luster; the invention has simple and convenient process and simple operation, and the electrodeposition rate is more than 90 percent.)

1. A method for preparing a substrate-free ultrathin nickel-63 radioactive source is characterized by comprising the following steps:

s1, depositing nickel metal ions in the electrodeposition solution on one side of the copper substrate to form a nickel layer;

s2, covering a layer of organic film on the nickel layer;

s3, immersing the nickel-63 radioactive source prepared in the step S2 in a substrate removing solution to remove the copper substrate;

s4, removing the organic film on the substrate-free nickel-63 radioactive source prepared in the step S3 to obtain the substrate-free ultrathin nickel-63 radioactive source.

2. The method of claim 1, wherein in step S1, the formula of the electrodeposition bath is:

0.1-0.8 g/L of nickel, 0.5-3.5 g/L of sulfuric acid, 0.02-0.1 g/L of sulfamic acid and 20-60 g/L of boric acid;

the pH value of the electrodeposition solution is adjusted to 3.5-5.5.

3. The method for preparing the substrate-free ultrathin nickel-63 radioactive source as claimed in claim 1, wherein in step S1, the copper substrate has a thickness of 10 μm to 50 μm, is soaked in ethanol for 10min to 60min, is cleaned with deionized water, and is naturally dried.

4. The method for preparing a substrate-free ultrathin nickel-63 radioactive source as claimed in claim 1, wherein in step S1, the deposition is performed by using an electrodeposition source, and the specific process is as follows:

fixing the copper substrate at the bottom of the electrodeposition tank, adding electrodeposition solution into the electrodeposition tank for electrodeposition with electrodeposition current density of 1.5A/dm²～8.0A/dm²The rotating speed of the platinum electrode is 50 r/min-120 r/min, and the electrodeposition time is 40 min-100 min.

5. The method for preparing a substrate-free ultrathin nickel-63 radioactive source as claimed in claim 1, wherein in step S2, the coating process is as follows:

dripping the film solution on the nickel layer with the dripping amount of 0.1mL/cm²～0.5mL/cm²And then spin-coating the film solution by a spin coater, and finally drying to form an organic film, wherein the drying temperature is 130-220 ℃, and the drying time is 0.5-2 h.

6. The method for preparing the substrate-free ultrathin nickel-63 radioactive source as claimed in claim 5, wherein the film solution is obtained by dissolving a film forming agent in a solvent, the content of the film forming agent in the film solution is 10 g/L-100 g/L, the film forming agent is polymethyl methacrylate, and the solvent is anisole.

7. The method for preparing the substrate-free ultrathin nickel-63 radioactive source as claimed in claim 5, wherein the spin coating process comprises the following steps:

firstly setting the rotating speed to be 100 r/min-400 r/min and the glue homogenizing time to be 10 s-20 s; setting the rotating speed to be 1000 r/min-5000 r/min and the glue homogenizing time to be 30 s-120 s.

8. The method of claim 1, wherein in step S3, the substrate removing solution is obtained by dissolving a substrate remover in water, the content of the substrate remover in the substrate removing solution is 10g/L to 100g/L, and the substrate remover is ferric chloride, ammonium persulfate or potassium persulfate.

9. The method for preparing a substrate-free ultrathin nickel-63 radioactive source as claimed in claim 1, wherein the immersion time in step S3 is 10min to 60 min.

10. The method for preparing a substrate-free ultrathin nickel-63 radioactive source as claimed in claim 1, wherein the specific process of removing the organic film in step S4 is as follows:

the organic membrane is wiped by wetting absorbent cotton with acetone solution, then the solution is sucked dry by using dry absorbent cotton, and the wiping and sucking are repeated until the organic membrane is completely removed.

Technical Field

The invention relates to the technical field of radioactive source preparation, in particular to a preparation method of a substrate-free ultrathin nickel-63 radioactive source.

Background

At present, micro mechanical electronic system (MEMS) technology is widely used in the exploration of special environments such as space, deep sea, polar region and the like and in biomedical treatment, and due to the extreme nature of the environment, batteries are difficult to maintain and replace, so that micro nuclear batteries are mainly used for energy supply. The nickel-63 micro nuclear battery is an important attack and defense direction in the development of the micro nuclear battery, and the nickel-63 radioactive source is a core energy component of the micro nuclear battery. Nickel-63 emits low-energy pure beta rays, the half-life period is 100.2a, the beta particle energy is moderate, no damage is caused to a semiconductor energy conversion component, and the radioactive source has the advantages of long service life, good safety performance, easiness in miniaturization and integration and the like, and is the most widely used radioactive source in a radiant volt battery.

At present, electrodeposition is one of the main methods for preparing nickel-63 radioactive sources by depositing⁶³Ni²⁺Conversion of ions to metals⁶³And depositing Ni on the metal substrate to make the nickel layer and the metal substrate combined tightly, thereby preparing the nickel-63 planar source.

The nickel-63 radioactive source prepared by the prior art method has two defects: the radioactive source is a substrate which is a supporting material of the radioactive source; secondly, the radioactive source is thicker, and the thickness of the nickel layer is generally larger than 10 mu m except the thickness of the substrate. The method comprises the following specific steps:

(1) there are disadvantages of the substrate: because the nickel-63 emits low-energy beta rays, the penetration distance is short, the substrate can completely block the beta rays of the radioactive source, and only one surface of the radioactive source prepared by the existing method can provide energy for a nuclear battery. In order to increase the energy utilization rate of the nuclear battery and reduce the volume of the nuclear battery, a double-sided radioactive source is required. If the existing method is adopted to prepare the double-sided radioactive source, the nickel-63 electrodeposition needs to be carried out on the other side of the substrate again, so that raw material waste is caused, and the workload and the radioactive irradiated dose of personnel are multiplied. In addition, the substrate also increases the thickness of the radioactive source, so that the volume and the weight of the battery are increased, and the miniaturization and the light weight of the battery are not facilitated.

(2) The disadvantage of large thickness: due to the self-absorption effect of the nickel-63, when the thickness of the nickel layer exceeds 2 μm, beta rays at the lower part of the nickel layer are shielded, and the increase of the thickness cannot increase the surface emissivity, but can cause serious waste of nickel-63 raw material.

Disclosure of Invention

The invention aims to provide a preparation method of a substrate-free ultrathin nickel-63 radioactive source, which solves the problems that the nickel-63 has a substrate and is large in thickness and further low in nickel-63 utilization rate in the existing preparation method.

The invention is realized by the following technical scheme:

a method for preparing a substrate-free ultrathin nickel-63 radioactive source comprises the following steps:

s1, depositing nickel metal ions in the electrodeposition solution on one side of the copper substrate to form a nickel layer;

s2, covering a layer of organic film on the nickel layer, namely, a copper substrate and an organic film are respectively arranged on two symmetrical surfaces of the nickel layer;

s3, immersing the nickel-63 radioactive source prepared in the step S2 in a substrate removing solution to remove the copper substrate;

s4, removing the organic film on the substrate-free nickel-63 radioactive source prepared in the step S3 to obtain the substrate-free ultrathin nickel-63 radioactive source.

The ultrathin film of the invention specifically refers to the thickness of less than 2 μm.

The substrate-free ultrathin nickel-63 radioactive source prepared by the preparation method is a double-sided radioactive source, the thickness is less than 2 mu m, the utilization rate of the nickel-63 radioactive source can be improved, the surface is smooth, no wrinkles or damage exists, the nickel layer is compact and uniform, and the nickel layer has metallic luster.

The invention combines the coating and substrate dissolving technologies, avoids the generation of folds and damages of the micron-sized nickel layer, ensures the integrity and the flatness of the ultrathin nickel-63 radioactive source without substrate support, can cause the situation that the nickel layer is broken after the copper substrate is dissolved if the organic film is not coated, and is easy to damage in the transferring process.

Further, in step S1, the formula of the electrodeposition solution is:

0.1-0.8 g/L of nickel, 0.5-3.5 g/L of sulfuric acid, 0.02-0.1 g/L of sulfamic acid and 20-60 g/L of boric acid;

the pH value of the electrodeposition solution is adjusted to 3.5-5.5.

Further, in step S1, the copper substrate has a thickness of 10 μm to 50 μm, is soaked in ethanol for 10min to 60min, is cleaned with deionized water, and is naturally dried.

Further, in step S1, the deposition adopts an electrodeposition source, and the specific process is as follows:

fixing the copper substrate at the bottom of the electrodeposition tank, adding electrodeposition solution into the electrodeposition tank for electrodeposition with electrodeposition current density of 1.5A/dm²～8.0A/dm²The rotating speed of the platinum electrode is 50 r/min-120 r/min, and the electrodeposition time is 40 min-100 min.

The electrodeposition parameters are used for depositing the deposition solution, so that the nickel layer can be formed by the electrodeposition solution through deposition, the nickel layer is flat in surface, free of wrinkles and damages, compact and uniform, and has metal luster, meanwhile, the deposition rate is greater than 90%, and the electrodeposition rate of the existing method is about 60%.

Further, in step S2, the specific process of coating the film is as follows:

dripping the film solution on the nickel layer with the dripping amount of 0.1mL/cm²～0.5mL/cm²And then spin-coating the film solution by a spin coater, and finally drying to form an organic film, wherein the drying temperature is 130-220 ℃, and the drying time is 0.5-2 h.

Further, the film solution is obtained by dissolving the film forming agent in a solvent, and the content of the film forming agent in the film solution is 10 g/L-100 g/L.

The film forming agent is polymethyl methacrylate (PMMA), and the solvent is anisole (C)₇H₈O)。

Further, the spin coating process is as follows:

firstly setting the rotating speed to be 100 r/min-400 r/min and the glue homogenizing time to be 10 s-20 s; then the rotating speed is set to be 1000r/min to 5000 r/min.

The spin coating is to uniformly attach the organic solvent on the nickel layer through centrifugal force, a thin organic film can be attached on the nickel layer only at the rotating speed of 1000 r/min-5000 r/min, and the thin organic film is beneficial to removal and can also play a role in protecting the micron-sized nickel layer. And directly dripping the organic film forming agent solution onto the nickel layer, and throwing a large amount of organic film forming agent solution out of the nickel layer if the rotating speed of the spin coater is directly adjusted to 1000-5000 r/min, so that the organic film forming agent solution is greatly lost and cannot be uniformly adhered to the nickel layer. Therefore, when the organic film forming agent solution is spin-coated, the speed is slow firstly, the organic film forming agent solution is filled in the whole nickel layer, and then the rotation is fast, so that the redundant organic film forming agent solution is thrown out, and finally a thin layer of organic film is attached to the nickel layer.

Further, in step S3, the substrate removing solution is obtained by dissolving a substrate remover in water, the content of the substrate remover in the substrate removing solution is 10g/L to 100g/L, and the substrate remover is ferric chloride, ammonium persulfate or potassium persulfate.

Further, in step S3, the immersion time is 10 to 60 min.

Further, in step S4, the specific process of removing the organic film is as follows:

wetting the absorbent cotton with an acetone solution to wipe the organic membrane, then drying the absorbent cotton to suck the solution, and repeating the wiping and sucking steps for 2-3 times to completely remove the organic membrane.

Compared with the prior art, the invention has the following advantages and beneficial effects:

1. the substrate-free ultrathin nickel-63 radioactive source prepared by the invention has the advantages that the thickness of a nickel-63 nickel layer is smaller, and a substrate is not arranged; the volume and the mass of a nuclear battery energy supply component can be obviously reduced, the self-absorption effect of nickel-63 is reduced, and the waste of the nickel-63 raw material is avoided.

2. Compared with the existing single-sided radioactive source, the substrate-free ultrathin nickel-63 radioactive source prepared by the invention is a double-sided radioactive source, both sides can be used, and double energy can be released by nickel-63 with the same activity; because both sides emit beta rays, the two-dimensional nuclear battery can be placed between the two energy conversion parts, so that the energy utilization rate of the nuclear battery is multiplied.

3. The invention combines the film covering technology and the substrate dissolving technology, avoids the generation of folds and damages of the micron-sized nickel layer, and ensures the integrity and the flatness of the ultra-thin nickel-63 radioactive source without the substrate support.

4. Compared with the prior art, the invention has high electrodeposition rate.

5. The substrate-free ultrathin nickel-63 radioactive source prepared by the method has the advantages of excellent quality, compact and uniform nickel layer and metallic luster.

6. The method has the advantages of simple and convenient process flow, simple operation and easy realization.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not used as limitations of the present invention.

Example 1:

a method for preparing a substrate-free ultrathin nickel-63 radioactive source comprises the following steps:

the first step is as follows: preparation of electrodeposition liquid

1.1 preparation of electrodeposition liquid L1: the following solutions were added sequentially to a 10mL glass beaker: 1mL of nickel-63 solution with nickel content of 1.1g/L (nickel content of 0.22g/L in the prepared electrodeposition solution), 3 μ L of 98% concentrated sulfuric acid (sulfuric acid content of 1.08g/L in the prepared electrodeposition solution), 10 μ L of 20g/L of sulfamic acid solution (sulfamic acid content of 0.04g/L in the prepared electrodeposition solution), and 4mL of 35g/L of boric acid solution (boric acid content of 28g/L in the prepared electrodeposition solution). The solution was stirred uniformly to obtain electrodeposition solution L1.

1.2 adjusting the pH value: to the solution L1 was added a sodium hydroxide (NaOH) solution and/or sulfuric acid (H)₂SO₄) Each addition was slightly upgraded to a final pH of 3.9 to give a solution L2.

The second step is that: preparation of copper substrate radioactive source

2.1 pretreatment of the copper substrate: taking a brand new round red copper substrate with the thickness of 20 mu m and the diameter of 20mm, soaking the round red copper substrate in ethanol for 20min, cleaning the round red copper substrate with deionized water, and naturally drying the round red copper substrate.

2.2 electrodeposition Source preparation: the copper substrate obtained in 2.1 was fixed to the bottom of an electrodeposition bath using an electrodeposition apparatus as a source, and 5mL of a solution L2 was added to the electrodeposition bath. The current density of the electrodeposition is 1.5A/dm²The rotating speed of the platinum electrode is 60r/min, and the electrodeposition time is 60 min.

2.3, cleaning: after step 2.2 is completed, the copper substrate is removed and the surface of the copper substrate is rinsed with deionized water to obtain copper substrate radiation source Y1.

The third step: film coating

3.1 preparation of film solution L3: weighing polymethyl methacrylate (PMMA) solid, using anisole (C)₇H₈O) the above solid was dissolved so that the content of polymethyl methacrylate in the solution was 50g/L, and the solution was referred to as a film solution L3.

3.2 dropwise addition of membrane solution L3: y1 was placed in the middle of the spin coater stage, and solution L3 was added dropwise to the surface of Y1 in an amount of 0.5 mL.

3.3 spin coating: starting a spin coater, setting the rotating speed at 200r/min, and setting the spin coater time at 20 s; setting the rotating speed at 4000r/min and the glue homogenizing time at 40 s. Radiation source Y2 was obtained which was spin-coated with film solution L3.

3.4, drying the membrane liquid: and (3) placing Y2 in a blast oven, wherein the drying temperature is 180 ℃, and the drying time is 1h, so that an organic film is formed on the surface of the radioactive source, and the radioactive source Y3 covered with the organic film is obtained.

The fourth step: substrate removal

4.1 formulation of substrate removal solution L4: weighing Potassium persulfate (K)₂(SO₄)₂) And dissolving the solid in deionized water to make the content of potassium persulfate in the solution be 50g/L, thereby obtaining a substrate removal solution L4.

4.2 substrate removal: the radioactive source Y3 covered with organic film was placed in the substrate removal solution L4, so that L4 completely immersed Y3 for a reaction time of 20 min. The copper substrate is completely dissolved, and the nickel layer is intact.

4.3, cleaning: after completing step 4.2, the nickel layer was taken out and the surface of the nickel layer was cleaned with deionized water to obtain a substrate-free ultra-thin nickel-63 radiation source Y4 covered with an organic film.

The fifth step: organic film removal

5.1 placing radioactive sources: placing Y4 on a flat surface with the side covering the organic film facing up;

5.2 wiping the radioactive source: wetting the absorbent cotton with an acetone solution, clamping the absorbent cotton by using a pair of tweezers, and lightly wiping an organic film on the upper surface of Y4; the surface solution on Y4 was blotted dry with dry absorbent cotton. Repeating the steps for three times, and removing the organic film to obtain the substrate-free ultrathin nickel-63 radioactive source Y5 which can be used on two sides and is arranged between two energy conversion devices of the miniature nuclear battery.

The substrate-free double-sided nickel-63 source piece obtained in the experiment has a bright surface and is tightly combined, the thickness of the nickel layer is about 0.6 mu m, the electrodeposition rate is 94%, and the thickness of the nickel layer is controlled according to the activity requirement of a scene on the nickel-63 source piece in practical application.

Example 2:

a method for preparing a substrate-free ultrathin nickel-63 radioactive source comprises the following steps:

the first step is as follows: preparation of electrodeposition liquid

1.1 preparation of electrodeposition liquid L1: the following solutions were added sequentially to a 20mL glass beaker: 4mL of a nickel-63 solution with a nickel content of 1.0g/L (the nickel content in the prepared electrodeposition solution is 0.40g/L), 10 μ L of 98% concentrated sulfuric acid (the sulfuric acid content in the prepared electrodeposition solution is 1.80g/L), 40 μ L of a 20g/L sulfamic acid solution (the sulfamic acid content in the prepared electrodeposition solution is 0.08g/L), and 6mL of a 35g/L boric acid solution (the boric acid content in the prepared electrodeposition solution is 21 g/L). The solution was stirred uniformly to obtain electrodeposition solution L1.

1.2 adjusting the pH value: to the solution L1 was added a sodium hydroxide (NaOH) solution and/or sulfuric acid (H)₂SO₄) The final pH was 3.5 at slightly elevated levels of each addition to give solution L2.

The second step is that: preparation of copper substrate radioactive source

2.1 pretreatment of the copper substrate: taking a brand new round red copper substrate with the thickness of 10 mu m and the diameter of 20mm, soaking the round red copper substrate in ethanol for 30min, cleaning the round red copper substrate with deionized water, and naturally drying the round red copper substrate.

2.2 electrodeposition Source preparation: preparing a source by using an electrodeposition instrument, fixing the copper substrate obtained in step 2.1 at the bottom of an electrodeposition tank, adding 10mL of solution L2 into the electrodeposition tank, and performing electrodeposition at a current density of 2.5A/dm²The rotating speed of the platinum electrode is 80r/min, and the electrodeposition time is 40 min.

2.3, cleaning: after step 2.2 is completed, the copper substrate is removed and the surface of the copper substrate is rinsed with deionized water to obtain copper substrate radiation source Y1.

The third step: film coating

3.1 preparation of film solution L3: weighing polymethyl methacrylate (PMMA) solid, using anisole (C)₇H₈O) the solid is dissolved, so that the content of the polymethyl methacrylate in the solution is 20g/L, and the solution is the membrane solution L3.

3.2 dropwise addition of membrane solution L3: y1 was placed in the middle of the spin coater stage, and solution L3 was added dropwise to the surface of Y1 in an amount of 0.2 mL.

3.3 spin coating: starting a spin coater, setting the rotating speed at 100r/min, and setting the spin coater time at 10 s; then the rotating speed is set to be 2000r/min, and the glue homogenizing time is 100 s. Radiation source Y2 was obtained which was spin-coated with film solution L3.

3.4, drying the membrane liquid: and (3) placing Y2 in a blast oven, wherein the drying temperature is 150 ℃, and the drying time is 1.2h, so that an organic film is formed on the surface of the radioactive source, and the radioactive source Y3 covered with the organic film is obtained.

The fourth step: substrate removal

4.1 formulation of substrate removal solution L4: weighing Potassium persulfate (K)₂(SO₄)₂) And dissolving the solid in deionized water to make the content of potassium persulfate in the solution be 20g/L to obtain a substrate removal solution L4.

4.2 substrate removal: the radioactive source Y3 covered with organic film was placed in the substrate removal solution L4, so that L4 completely immersed Y3 for a reaction time of 20 min. The copper substrate is completely dissolved, and the nickel layer is intact.

4.3, cleaning: after completing step 4.2, the nickel layer was taken out and the surface of the nickel layer was cleaned with deionized water to obtain a substrate-free ultra-thin nickel-63 radiation source Y4 covered with an organic film.

The fifth step: organic film removal

5.1 placing radioactive sources: placing Y4 on a flat surface with the side covering the organic film facing up;

5.2 wiping the radioactive source: wetting the absorbent cotton with an acetone solution, clamping the absorbent cotton by using a pair of tweezers, and lightly wiping an organic film on the upper surface of Y4; the surface solution on Y4 was blotted dry with dry absorbent cotton. Repeating the steps twice, the organic film can be removed, and the substrate-free ultrathin nickel-63 radioactive source Y5 which can be used on both sides and is arranged between two energy conversion devices of the miniature nuclear battery is obtained.

The double-sided nickel-63 source piece without the substrate obtained in the experiment has bright surface and tight combination, the thickness of the nickel layer is about 2 mu m, and the electrodeposition rate is 91 percent.

Example 3:

a method for preparing a substrate-free ultrathin nickel-63 radioactive source comprises the following steps:

the first step is as follows: preparation of electrodeposition liquid

1.1 preparation of electrodeposition liquid L1: the following solutions were added sequentially to a 10mL glass beaker: 2mL of a nickel-63 solution with a nickel content of 1.5g/L (the nickel content in the prepared electrodeposition solution is 0.6g/L), 7.8. mu.L of 98% concentrated sulfuric acid (the sulfuric acid content in the prepared electrodeposition solution is 2.81g/L), 25. mu.L of a 20g/L sulfamic acid solution (the sulfamic acid content in the prepared electrodeposition solution is 0.1g/L), and 3mL of a 60g/L boric acid solution (the boric acid content in the prepared electrodeposition solution is 36 g/L). The solution was stirred uniformly to obtain electrodeposition solution L1.

1.2 adjusting the pH value: to the solution L1 was added a sodium hydroxide (NaOH) solution and/or sulfuric acid (H)₂SO₄) Each addition was slightly upgraded to a final pH of 4.2 to give a solution L2.

The second step is that: preparation of copper substrate radioactive source

2.1 pretreatment of the copper substrate: taking a brand new round red copper substrate with the thickness of 10 mu m and the diameter of 20mm, soaking the round red copper substrate in ethanol for 10min, cleaning the round red copper substrate with deionized water, and naturally drying the round red copper substrate.

2.2 electrodeposition Source preparation: preparing a source by using an electrodeposition instrument, fixing the copper substrate obtained in step 2.1 at the bottom of an electrodeposition tank, adding 5mL of solution L2 into the electrodeposition tank, and performing electrodeposition at a current density of 3.5A/dm²The rotating speed of the platinum electrode is 100r/min, and the electrodeposition time is 100 min.

2.3, cleaning: after step 2.2 is completed, the copper substrate is removed and the surface of the copper substrate is rinsed with deionized water to obtain copper substrate radiation source Y1.

The third step: film coating

3.1 preparation of film solution L3: weighing polymethyl methacrylate (PMMA) solid, using anisole (C)₇H₈O) the above solid was dissolved so that the content of polymethyl methacrylate in the solution was 40g/L, and the solution was referred to as a film solution L3.

3.2 dropwise addition of membrane solution L3: y1 was placed in the middle of the spin coater stage, and solution L3 was added dropwise to the surface of Y1 in an amount of 0.3 mL.

3.3 spin coating: starting a spin coater, setting the rotating speed at 300r/min, and setting the spin coater time at 15 s; then setting the rotating speed to 3000r/min and the glue homogenizing time to 100 s. Radiation source Y2 was obtained which was spin-coated with film solution L3.

3.4, drying the membrane liquid: and (3) placing Y2 in a blast oven, wherein the drying temperature is 180 ℃, and the drying time is 0.8h, so that an organic film is formed on the surface of the radioactive source, and the radioactive source Y3 covered with the organic film is obtained.

The fourth step: substrate removal

4.1 formulation of substrate removal solution L4: ammonium persulfate ((NH) was weighed₄)₂(SO₄)₂) And dissolving the solid in deionized water to obtain a solution containing potassium persulfate in an amount of 80g/L, thereby obtaining a substrate removal solution L4.

4.2 substrate removal: the radioactive source Y3 covered with organic film was placed in the substrate removal solution L4, so that L4 completely immersed Y3 for 10 min. The copper substrate is completely dissolved, and the nickel layer is intact.

4.3, cleaning: after completing step 4.2, the nickel layer was taken out and the surface of the nickel layer was cleaned with deionized water to obtain a substrate-free ultra-thin nickel-63 radiation source Y4 covered with an organic film.

The fifth step: organic film removal

5.1 placing radioactive sources: placing Y4 on a flat surface with the side covering the organic film facing up;

5.2 wiping the radioactive source: wetting the absorbent cotton with an acetone solution, clamping the absorbent cotton by using a pair of tweezers, and lightly wiping an organic film on the upper surface of Y4; the surface solution on Y4 was blotted dry with dry absorbent cotton. Repeating the steps for three times, and removing the organic film to obtain the substrate-free ultrathin nickel-63 radioactive source Y5 which can be used on two sides and is arranged between two energy conversion devices of the miniature nuclear battery.

The double-sided nickel-63 source piece without the substrate obtained in the experiment has bright surface and tight combination, the thickness of the nickel layer is about 1.6 mu m, and the electrodeposition rate is 96 percent.

The invention adopts an electrodeposition method, takes a micron-sized copper sheet as a substrate, and the substrate does not need to be subjected to pre-electrodeposition treatment, so that the preparation steps of the radioactive source can be simplified, the personnel dosage is reduced, and the source preparation efficiency is improved; in the invention, the nickel content is 0.1-0.8 g/L during electrodeposition, the deposition rate of the obtained Ni-63 radioactive flaky source can reach more than 90 percent, and high-quality source preparation under low nickel concentration is realized; the copper substrate can be removed through dissolution, the prepared substrate-free ultrathin nickel-63 radioactive source is a double-sided radioactive source, both sides can be used, and double energy can be released by nickel-63 with the same activity.

Compared with the prior patent of 'an electrodeposition method of Ni-63 radioactive flaky source, patent No. CN 108893762B', the patent also adopts an electrodeposition method, a stainless steel substrate is used, the substrate needs to be subjected to pre-electrodeposition treatment, the nickel content during electrodeposition is 1.5 g/L-100 g/L, the deposition rate of the obtained Ni-63 radioactive flaky source can reach 60%, and the method does not remove the stainless steel substrate, so that the utilization rate of the nickel-63 raw material is low. The specific comparison results are shown in Table 1.

Two key technologies of the electrodeposition process are as follows: electrodeposition bath formulation and electrolysis parameters. As can be seen from Table 1, the formulation and electrolysis parameters of the electrodeposition bath of the present invention are quite different from those of the comparative patent CN 108893762B. The components, contents, proportions and pH ranges of the formula are all inconsistent and have no similarities. The nickel content of the invention is far lower than that of the comparative patent; the present invention uses sulfamic acid, while the comparative patent uses sodium dodecyl sulfate and hydrochloric acid; the present invention uses a copper substrate, while the comparative patent uses a stainless steel substrate. The two key technologies of the electrodeposition process are different, and the conclusion can be drawn that the method is a brand-new and inventive method.

TABLE 1 differences between the present invention and the comparative patents

Comparative example 1:

the preparation of the nickel-63 radioactive source is carried out by adopting the stainless steel substrate under the experimental conditions of the invention, because the pretreatment step of the stainless steel substrate has great influence on the electrodeposition performance, if the pretreatment of the stainless steel substrate is not carried out, the electrodeposition experiment fails, and for comparison, the pretreatment step of the stainless steel substrate is added, and the specific treatment mode is consistent with the patent 'an electrodeposition method of a Ni-63 radioactive flaky source, and the patent No. CN 108893762B'. The other experimental conditions are consistent with the invention, and the specific steps are as follows:

the first step is as follows: preparation of electrodeposition liquid

1) Preparing an electrodeposition solution L1: the following solutions were added sequentially to a 10mL glass beaker: 1mL of nickel-63 solution with nickel content of 1.1g/L (nickel content of 0.22g/L in the prepared electrodeposition solution), 3 μ L of 98% concentrated sulfuric acid (sulfuric acid content of 1.08g/L in the prepared electrodeposition solution), 10 μ L of 20g/L of sulfamic acid solution (sulfamic acid content of 0.04g/L in the prepared electrodeposition solution), and 4mL of 35g/L of boric acid solution (boric acid content of 28g/L in the prepared electrodeposition solution). The solution was stirred uniformly to obtain electrodeposition solution L1.

2) Adjusting the pH value: to the solution L1 was added a sodium hydroxide (NaOH) solution and/or sulfuric acid (H)₂SO₄) Each addition was slightly upgraded to a final pH of 3.9 to give a solution L2.

The second step is that: pretreatment of stainless steel substrates

1) Preparing a pre-electrodeposition solution: so that NiSO is in the solution₄·6H₂The O content was 300g/L, HCl and the content was 200 g/L.

2) Cleaning of the stainless steel substrate: taking a clean and intact stainless steel substrate, washing the substrate with deionized water, sequentially soaking the substrate in acetone for 10min, then soaking the substrate in absolute ethyl alcohol for 5min, and then washing the substrate with deionized water.

3) Pre-electrodeposition of stainless steel substrate: placing the stainless steel substrate on an electrodeposition instrument, adding 5mL of pre-electrodeposition solution into an electrodeposition tank, soaking the stainless steel substrate at room temperature for 5min, and controlling the current density to be 0.4A/dm²And pre-electrodepositing for 5min, removing the pre-electrodepositing solution, and washing the stainless steel substrate by deionized water.

The third step: preparation of radiation source with stainless steel substrate

1) Preparing an electrodeposition source: adopting an electrodeposition instrument to prepare a source, fixing the stainless steel subjected to pre-electrodeposition at the bottom of an electrodeposition tank, adding 5mL of solution L2 into the electrodeposition tank, and controlling the current density of electrodeposition to be 1.5A/dm²The rotating speed of the platinum electrode is 60r/min, and the electrodeposition time is 60 min.

2) Cleaning: and after the step 2.2 is completed, taking out the stainless steel substrate, and washing the surface of the source plate substrate by using deionized water to obtain the stainless steel substrate radioactive source.

Because the invention adopts a dissolution method to remove the copper substrate, the stainless steel can not be well dissolved in the substrate removing solution of the invention. If other substrate removing solutions are adopted to dissolve the stainless steel, but the nickel layer is also dissolved, and a substrate removing solution formula which can dissolve the stainless steel and can keep the nickel layer complete cannot be found. This in turn demonstrates that the present invention is a key condition for the preference of copper as the substrate material. The removal of the stainless steel substrate was therefore not considered in this comparative example.

Results of example 1 and comparative example 1 as shown in table 2, under the experimental conditions of the present invention, if the preparation of the nickel-63 radioactive source is developed by using the stainless steel substrate of the prior patent, the pre-electrodeposition step of the stainless steel substrate is increased, and the electrodeposition rate is only 76%, which is much lower than the electrodeposition rate 94% of the present invention. The invention can remove the substrate and further improve the utilization rate of the nickel-63.

The results of example 1 and comparative example 1 are shown in table 2:

table 2 comparison of results of example 1 and comparative example 1

Comparative example 2:

in order to prove the importance and the beneficial effect of the key parameter range of the invention, the nickel electrodeposition experiment is carried out in the nickel concentration and other experimental conditions in the prior patent 'Ni-63 radioactive sheet source electrodeposition method, patent No. CN 108893762B', the specific operation is as follows:

the first step is as follows: preparation of electrodeposition liquid

1) Preparing an electrodeposition solution L1: the following solutions were added sequentially to a 10mL glass beaker: 0.25mL of a nickel-63 solution having a nickel content of 81.4g/L (nickel content in the prepared bath was 4.07g/L), 7.8. mu.L of 98% concentrated sulfuric acid (sulfuric acid content in the prepared bath was 2.81g/L), 25. mu.L of a 20g/L sulfamic acid solution (sulfamic acid content in the prepared bath was 0.1g/L), and 3mL of a 60g/L boric acid solution (boric acid content in the prepared bath was 36 g/L). The solution was stirred uniformly to obtain electrodeposition solution L1.

1.2 adjusting the pH value: to the solution L1 was added a sodium hydroxide (NaOH) solution and/or sulfuric acid (H)₂SO₄) Each addition was slightly upgraded to a final pH of 4.2 to give a solution L2.

The second step is that: preparation of copper substrate radioactive source

2.1 pretreatment of the copper substrate: taking a brand new round red copper substrate with the thickness of 10 mu m and the diameter of 20mm, soaking the round red copper substrate in ethanol for 10min, cleaning the round red copper substrate with deionized water, and naturally drying the round red copper substrate.

2.2 electrodeposition Source preparation: the copper substrate obtained in 2.1 was fixed to the bottom of an electrodeposition bath using an electrodeposition apparatus as a source, and 5mL of a solution L2 was added to the electrodeposition bath. The current density of the electrodeposition is 3.5A/dm²The rotating speed of the platinum electrode is 100r/min, and the electrodeposition time is 100 min.

2.3, cleaning: after step 2.2 is completed, the copper substrate is removed and the surface of the copper substrate is rinsed with deionized water to obtain copper substrate radiation source Y1. Through detection, the Y1 coating is black and loose, a compact and uniform coating is not formed, and the preparation of the radioactive source fails.

The nickel concentration and other parameters in the nickel concentration in the prior patent 'an electrodeposition method of Ni-63 radioactive flaky source, patent No. CN 108893762B' are consistent with the invention, and a compact and uniform coating cannot be obtained; the electrodeposition method of the nickel-63 radioactive source can realize the preparation of the high-quality nickel-63 radioactive source with low nickel concentration, the electrodeposition formula is mutually coupled with electrodeposition parameters, the formulas and the parameters have relevance, and the electrodeposition failure or the reduction of the quality of a coating can be caused by changing any optimized parameter.

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.