Accelerator neutron source target composite transition layer and hydrothermal-magnetron sputtering preparation method thereof

Abstract

The invention relates to the field of neutron source targets, and discloses an accelerator neutron source target composite transition layer and a hydrothermal-magnetron sputtering preparation method thereof. The composite transition layer is located between a base material and a target material layer and comprises a TiO2 layer which is deposited through a hydrothermal method and attached to the surface of the base material through acid pickling and roasting, and a tantalum layer deposited on the surface of the TiO2 layer. According to the preparation method, the TiO2 layer with the specific morphology is deposited on the surface of the base material through a hydrothermal method, and then the tantalum layer is deposited through magnetron sputtering. On one hand, the TiO2 layer can reduce stress generated between the base material and the tantalum layer due to mismatching of thermal expansion coefficients through self deformation, so that a buffering effect is achieved; on the other hand, it is found that the TiO2 lattice structure with the specific morphology can induce tantalum atoms to be deposited in the specific direction in the growth process, stress generated by disordered arrangement of the atoms in the tantalum layer is avoided, finally, the binding force of the tantalum layer and the base material is improved, and the cracking risk of the tantalum layer is reduced.

Description

Technical Field

[0001] The invention relates to the field of neutron source targets, and in particular to an accelerator neutron source target composite transition layer and a hydrothermal-magnetron sputtering preparation method thereof. Background Art

[0002] Boron neutron capture therapy (BNCT) is a promising tumor treatment method, especially for tumors that are difficult to cure with traditional radiotherapy. Through the targeted delivery of boron drugs and neutron capture reactions, BNCT can kill tumor cells to the greatest extent and reduce damage to normal tissues. As a core element of BNCT, the neutron source must efficiently provide neutron beams to react with boron drugs. At present, there are two main sources for neutron beam generation in the world, one is to generate neutron beams through nuclear reactors, and the other is to generate neutron beams through accelerators. Accelerator neutron sources generate neutron beams by accelerating particles (such as protons or deuterons) to contact target materials to produce nuclear reactions. Compared with traditional nuclear reactors, they have higher flexibility and precision and can provide more controllable and directional neutron beams. And due to its advantages in radiation safety, operational flexibility and operation and maintenance costs, accelerator neutron sources have shown broad application potential in materials science, irradiation research, and especially clinical medicine.

[0003] Target materials play a core role in accelerator neutron sources. The selection and design of neutron source target materials directly affect the quality, energy distribution, output flux and durability of the neutron beam. During long-term operation, the target material will be affected by radiation damage and material fatigue, so optimizing the target material and structural design is of great significance to improving the generation efficiency, accuracy and treatment effect of the neutron beam. The neutron source target system generally uses lithium or beryllium as the main nuclear reaction layer (i.e., the target material layer, usually deposited on the substrate surface) to produce neutrons. At the same time, the target system needs to have good radiation resistance, thermal stability and mechanical properties to withstand the heat and stress generated by a large number of high-energy particle impacts. Most protons produce bubbles when they pass through the target material layer and are deposited on the substrate surface, which in turn causes hydrogen embrittlement and affects the service life of the target material.

[0004] Tantalum is considered to be an ideal material for the transition layer (located between the substrate and the target layer) of the target system in accelerator boron neutron capture therapy (AB-BNCT) due to its high hydrogen diffusion coefficient. It can effectively prevent the migration of hydrogen, reduce hydrogen embrittlement, and protect the substrate material under proton beam bombardment. There are many methods for preparing tantalum films, including vacuum plasma spraying (VPS), chemical vapor deposition (CVD), physical vapor deposition (PVD), and magnetron sputtering. Among them, magnetron sputtering is the best choice due to its significant advantages such as fast sputtering speed, large deposition area, dense and uniform film, and strong adhesion. However, the disadvantage of using tantalum as a transition layer is that it requires a thickness of 20μm to effectively block the proton flow and reduce hydrogen diffusion, thereby improving the stability and durability of the system. However, the physical properties of tantalum are significantly different from those of the substrate material (usually copper). When the tantalum film deposited by magnetron sputtering reaches a certain thickness, due to factors such as temperature changes and stress accumulation, significant stress concentration will appear inside the film layer, which may cause the film to crack and fall off.

[0005] To this end, the current solution is mainly to roughen the surface of the target substrate, such as using etching, sandblasting, polishing and other surface treatment technologies to increase the surface roughness of the substrate (CN110914922A). Although the above methods can improve the bonding force between the tantalum film and the substrate to a certain extent, on the one hand, the effect is not ideal, and on the other hand, it is difficult to achieve uniform treatment on the surface of the substrate with a more complex surface shape. For example, when using sandblasting, mechanical polishing and other methods to treat the irregular substrate surface, only the contacted surface can be roughened, and it is difficult to take into account the local with tiny fine structures such as through-hole structures. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides an accelerator neutron source target composite transition layer and a hydrothermal-magnetron sputtering preparation method thereof. The present invention first deposits a TiO2 with a specific morphology on the surface of the substrate by a hydrothermal method. 2 layer, and then deposited a tantalum layer by magnetron sputtering. On the one hand, TiO 2 The layer can reduce the stress caused by the mismatch of thermal expansion coefficients between the substrate and the tantalum layer by its own deformation, thereby playing a buffering role; on the other hand, the present invention also found that the TiO 2 The lattice structure can also induce tantalum atoms to deposit in a specific direction during the growth process, avoiding stress inside the tantalum layer due to disordered arrangement of atoms, ultimately improving the bonding strength between the tantalum layer and the substrate and reducing the risk of cracking of the tantalum layer.

[0007] The specific technical scheme of the present invention is: In a first aspect, the present invention provides an accelerator neutron source target composite transition layer, which is located between a substrate and a target layer, and comprises TiO deposited by a hydrothermal method and attached to the surface of the substrate by calcination. 2layer, and deposited on TiO 2 Tantalum layer on the surface of the layer.

[0008] The present invention first deposits TiO2 with a specific morphology on the surface of the substrate by a hydrothermal method. 2 layer, and then deposited a tantalum layer by magnetron sputtering. On the one hand, TiO 2 The layer can reduce the stress caused by the mismatch of thermal expansion coefficients between the substrate and the tantalum layer by its own deformation, thereby playing a buffering role; on the other hand, the present invention also found that the TiO 2 The lattice structure can also induce tantalum atoms to deposit in a specific direction during the growth process, avoiding stress generated inside the tantalum layer due to disordered atomic arrangement. According to the previous research of the present invention, the microstructural characteristics of the tantalum layer, such as grain size and orientation, have an important influence on stress. Thin films with smaller grains have more grain boundaries, which cannot effectively diffuse heat during the deposition process, and the grain boundaries will block stress transfer, making the stress more concentrated. Especially during the growth of thin films, strongly oriented films usually have smaller internal stresses, because the orientation of the grains can effectively reduce lattice mismatch and stress transfer; when the grain orientation is uneven or random, the internal stress of the film is larger. Specifically, the lattice structure of titanium dioxide has a good match with certain crystal planes of tantalum, thereby promoting the orderly growth of tantalum on its surface. At the same time, titanium dioxide has a variety of nanostructures (such as nanotubes, nanowires, nanospheres, etc.), which can be used as templates or substrates to induce tantalum to self-assemble in a specific way. In summary, the specific morphology of TiO 2 The layer can reduce stress by inducing the orderly growth of tantalum atoms, providing nucleation sites for tantalum atoms, and alleviating the lattice mismatch between the tantalum layer and the substrate, thereby promoting the growth of high-quality tantalum film and ultimately achieving the purpose of improving its bonding strength with the substrate surface.

[0009] Specifically, the TiO 2 The microscopic morphology of the layer includes at least one of the following: (a) Stacked nanotube structure; (b) Stacked nanosheet structure; (c) Nano-network porous structure; (d) The structure of stacked nanospheres; (e) Stacked nanoneedle-like protrusion structure.

[0010] In the present invention, the above-mentioned several TiO 2The order of the effect of the layer morphology is: (a) > (b) > (c) > (d) > (e). The nanosheet and nanotube morphology have relatively flat surfaces and low lattice defects, which can effectively alleviate the lattice mismatch. The nanosphere morphology has a larger surface area, but due to the larger particle spacing and the surface structure is not as uniform as the nanosheet, the stress improvement result is not as good as the nanosheet. Compared with the nanosphere, the nano-network porous structure has better stress dispersion ability. The nano-needle-like protrusion structure will cause partial stress concentration due to the spike structure during the subsequent coating process, so the effect is the worst.

[0011] Preferably, the TiO 2 The layer is formed by hydrothermal reaction of an alkaline deposition liquid containing a titanium source to generate titanate which is deposited on the surface of the substrate and then pickled and calcined.

[0012] The above reaction principle is: the titanium source is TiO 2 Take TiO powder as an example. 2 The powder is added to an alkaline solution (such as NaOH), TiO 2 The surface undergoes hydroxylation and partial dissolution to generate soluble titanate ions. The reaction formula is: TiO 2 (solid)+2OH − +2H 2 O→[Ti(OH) 6 ] 2- ; After the substrate is immersed in the alkaline deposition solution, under hydrothermal conditions, the dissolved [Ti(OH) 6 ] 2- With Na in solution + Combined to form a layered titanate solid, it will nucleate on the surface of the matrix to build a carbonate skeleton layer. The reaction formula is: 3[Ti(OH) 6 ] 2- +2Na + →Na 2 Ti 3 O 7 (Solid) +7H 2 O; After the hydrothermal reaction is completed, the substrate is transferred to an acidic solution where H + Participate in dynamic ion exchange, replace cations in the titanate system, and convert titanate into titanate H 2 Ti 3 O 7 More active sites are exposed, and the reaction equation is: Na 2 Ti 3 O 7 +2H 2 O→H2 Ti 3 O 7 (solid) + 2NaOH; During the calcination process, the O-H bonds of two adjacent -OH groups (Ti-OH) in the titanium-oxygen framework are broken under high temperature, releasing H 2 O molecules, and continuous Ti-O-Ti bonds form a three-dimensional network structure, finally generating a crystalline TiO 2 layer, and the reaction formula is: H 2 Ti 3 O 7 →3TiO 2 +H 2 O.

[0013] Preferably, the substrate is a flat or irregular surface; for example, a surface with a grid-like structure.

[0014] Compared with traditional processes such as sandblasting and polishing, which are only applicable to flat substrate surfaces, the present invention can form a transition layer with an ideal morphology on the surface of an irregular substrate through hydrothermal-magnetron sputtering technology.

[0015] Preferably, it is characterized in that: the thickness range of the TiO 2 layer is 200 - 800 nm.

[0016] Preferably, the thickness range of the tantalum layer is 1 - 20 μm.

[0017] Preferably, the substrate is a copper substrate; the target is a lithium target or a beryllium target.

[0018] In a second aspect, the present invention provides a method for preparing the accelerator neutron source target composite transition layer described above, which includes the following steps: 1) Place the substrate in an alkaline deposition solution containing TiO 2 for hydrothermal reaction. TiO 2 undergoes hydroxylation and gradually dissolves to generate soluble titanate ions. The titanate ions combine with cations in the solution (such as Na + / K + ) to nucleate on the substrate surface and form a solid titanate layer.

[0019] 2) Immerse the substrate in an acidic solution. The cations in the titanate are replaced by H + to form titanic acid. Further ion exchange on the substrate surface through pickling forms a titanic acid framework with more active sites, and continue to wash with water until neutral.

[0020] 3) Through calcination, the titanic acid layer on the substrate surface undergoes dehydroxylation condensation at high temperature (Ti-OH + HO-Ti → Ti-O-Ti + H2 O) Forming crystalline TiO with different morphologies 2 layer, while releasing the internal participating stress.

[0021] 4) Magnetron sputtering on TiO 2 A tantalum layer is deposited on the surface of the layer.

[0022] In addition, the present invention can also adjust the TiO 2 The microscopic morphology of the layer. When the reaction temperature is low (100-110°C), the solubility of titanate ions is low. Under high alkali concentration, the supersaturation of titanate ions increases, and the nucleation rate of titanate on the substrate surface is much higher than the growth rate. Therefore, the particles cannot preferentially grow along a specific crystal plane, and can only form a fine spherical structure by minimizing the surface energy. Under low alkali concentration, the supersaturation decreases, the nucleation rate slows down, and it is more inclined to form larger nanospheres. Due to the van der Waals force, secondary aggregation is caused to form a cluster network structure. When the reaction temperature increases (130-140°C), the solubility of titanate ions increases. When the alkali concentration is low, smaller nanoneedle structures are preferentially generated on the surface of the substrate. With the increase of alkali concentration, the concentration of titanate ions increases, and there is sufficient diffusion energy at high temperature, and there is sufficient diffusion space in the vertical direction. The hydrothermal products on the surface of the substrate grow along the axial direction, thus forming a nanosheet shape. When the hydrothermal time is extended, the nanosheets have enough time to curl up to form nanotubes. The details are as follows: Preferably, the TiO 2 The nanotube structure is stacked in layers; the alkali concentration in the alkaline deposition solution is 9-11 mol / L, TiO 2 The content is 0.4-0.5g / L; the hydrothermal reaction temperature is 130-140℃, and the time is 22-24h.

[0023] Preferably, the TiO 2 The layer is a stacked nanosheet structure; the alkali concentration in the alkaline deposition solution is 9-11 mol / L; TiO 2 The content is 0.4-0.5g / L; the hydrothermal reaction temperature is 130-140℃, and the time is 10-12 h.

[0024] Preferably, the TiO 2 The layer presents a nano-network porous structure; the alkali concentration in the alkaline deposition solution is 5-7 mol / L; TiO 2 The content is 0.4-0.5g / L; the hydrothermal reaction temperature is 100-110℃, and the time is 10-12 h.

[0025] Preferably, the TiO 2 The layer is a stacked nanosphere structure; the alkali concentration in the alkaline deposition solution is 9-11 mol / L; TiO 2The content is 0.4-0.5g / L; the hydrothermal reaction temperature is 100-110℃, and the time is 10-12 h.

[0026] Preferably, the TiO 2 The layer is a stacked nano needle-like protrusion structure; the alkali concentration in the alkaline deposition solution is 5-7 mol / L; TiO 2 The content is 0.4-0.5g / L; the hydrothermal reaction temperature is 130-140℃, and the time is 10-12 h.

[0027] Preferably, in step 1), the alkali in the alkaline sedimentation solution is NaOH or KOH.

[0028] Preferably, in step 1), the substrate is pre-ground, polished, cleaned and dried.

[0029] Preferably, in step 2), the acidic solution is a 0.1-0.5 mol / L hydrochloric acid solution.

[0030] Preferably, in step 3), the calcination temperature is 300-500° C. and the calcination time is 1-3 h.

[0031] Compared with the prior art, the beneficial effects of the present invention are: (1) The present invention first deposits TiO with a specific morphology on the surface of the substrate by a hydrothermal method. 2 layer, and then deposited a tantalum layer by magnetron sputtering. On the one hand, TiO 2 The layer can reduce the stress caused by the mismatch of thermal expansion coefficients between the substrate and the tantalum layer by its own deformation, thereby playing a buffering role; on the other hand, the present invention also found that the TiO 2 The lattice structure can also induce tantalum atoms to deposit in a specific direction during the growth process, avoiding stress inside the tantalum layer due to disordered arrangement of atoms, ultimately improving the bonding strength between the tantalum layer and the substrate and reducing the risk of cracking of the tantalum layer.

[0032] (2) The present invention obtains TiO with different microscopic morphologies by controlling the conditions of the hydrothermal reaction. 2 layer.

[0033] (3) Compared with the traditional sandblasting and polishing processes which are only applicable to flat substrate surfaces, the present invention can form an ideal transition layer on the surface of irregular substrates through the hydrothermal-magnetron sputtering technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a scanned image of the Cu substrate after cleaning in Example 1.

[0035] Figure 2 The Cu / TiO obtained after calcining the Cu substrate in Example 12 Scanned images of .

[0036] Figure 3 The Cu / TiO obtained after calcining the Cu substrate in Example 2 2 Scanned images of .

[0037] Figure 4 The Cu / TiO obtained after calcining the Cu substrate in Example 3 2 Scanned images of .

[0038] Figure 5 The Cu / TiO obtained after calcining the Cu substrate in Example 4 2 Scanned images of .

[0039] Figure 6 The Cu / TiO 2 Scanned images of .

[0040] Figure 7 This is a scanning image of a 20 μm Ta layer prepared on an original Cu substrate by magnetron sputtering in Comparative Example 1.

[0041] Figure 8 This is a scanning image of a 20 μm Ta layer prepared by magnetron sputtering after hydrothermal deposition pretreatment in Example 1-5.

[0042] Fig. 9 The Cu / TiO obtained after hydrothermal deposition pretreatment in Example 5 2 LSCM diagram of the .

[0043] Fig.10 This is the LSCM image of a 20 μm Ta layer prepared by magnetron sputtering after hydrothermal deposition pretreatment in Example 5.

[0044] Fig.11 The actual pictures are of the samples obtained by plating a 20 μm Ta layer on the original copper substrate in Comparative Example 1 and plating a 20 μm Ta layer after hydrothermal deposition pretreatment in Examples 1-5. DETAILED DESCRIPTION

[0045] The present invention will be further described below in conjunction with the embodiments.

[0046] In a first aspect, the present invention provides an accelerator neutron source target composite transition layer, which is located between a substrate and a target layer, and comprises TiO deposited by a hydrothermal method and attached to the surface of the substrate by calcination. 2 layer, and deposited on TiO 2 Specifically, the TiO 2 The microscopic morphology of the layer includes at least one of the following: (a) Stacked nanotube structure; (b) Stacked nanosheet structure; (c) Nano-network porous structure; (d) The structure of stacked nanospheres; (e) Stacked nanoneedle-like protrusion structure.

[0047] Preferably, the TiO 2 The layer is formed by hydrothermal reaction of an alkaline deposition solution containing titanate ions to generate titanate deposited on the surface of the substrate and then acid-washed and calcined to form TiO 2 layer.

[0048] The above reaction principle is: first, TiO 2 The powder is added to an alkaline solution (such as NaOH), TiO 2 The surface undergoes hydroxylation and partial dissolution to generate soluble titanate ions. The reaction formula is: TiO 2 (solid)+2OH − +2H 2 O→[Ti(OH) 6 ] 2- ; After the substrate is immersed in the alkaline deposition solution, under hydrothermal conditions, the dissolved [Ti(OH) 6 ] 2- With Na in solution + Combined to form a layered titanate solid, it will nucleate on the surface of the matrix, and the reaction formula is: 3[Ti(OH) 6 ] 2- +2Na + →Na 2 Ti 3 O 7 (Solid) +7H 2 O; As the hydrothermal reaction is completed, the substrate is transferred to an acidic solution where H + Participate in dynamic ion exchange, replace cations in the titanate system, and convert titanate into H 2 Ti 3 O 7 More active sites are exposed, and the reaction equation is: Na 2 Ti 3 O 7 +2H 2 O→H 2 Ti 3 O 7 (Solid) + 2NaOH; After deionized water washing, during the calcination process, the two adjacent –OH groups (Ti-OH) in the titanium oxide skeleton break the OH bonds under high temperature, releasing H 2 O molecules, continuous Ti-O-Ti bonds form a three-dimensional network structure, and finally form crystalline TiO 2 layer, the reaction formula is: H 2 Ti 3 O 7 →3TiO 2 +H 2 O.

[0049] Preferably, the substrate is a plane or irregular surface, such as a grid-like structured surface.

[0050] As a preferred embodiment, it is characterized in that: the TiO 2 The thickness of the layer ranged from 200-800 nm.

[0051] Preferably, the thickness of the tantalum layer is in the range of 1-20 μm.

[0052] Preferably, the substrate is a copper substrate; and the target is a lithium target or a beryllium target.

[0053] In a second aspect, the present invention provides a method for preparing the above-mentioned accelerator neutron source target composite transition layer, which comprises the following steps: 1) Place the substrate in a solution containing a titanium source (TiO 2 powder) in an alkaline deposition solution for hydrothermal reaction, TiO 2 The powder undergoes hydroxylation and gradually dissolves to form soluble titanate ions, which combine with cations in the solution to nucleate on the substrate surface to form a solid titanate layer; 2) The hydrothermal product is immersed in a weak acid solution, and the cations in the titanate are ionized by the H + Titanic acid is formed by substitution, and after pickling, the substrate is washed with deionized water to remove excess HCl; 3) Calcination: The titanium oxide skeleton contains Ti-OH groups, which form three-dimensional crystalline TiO with different morphologies through dehydroxylation condensation at high temperature. 2 layer, and remove the residual stress in the film at the same time; 4) Magnetron sputtering on TiO 2 A tantalum layer is deposited on the surface of the layer.

[0054] Preferably, the TiO 2 The nanotube structure is stacked in layers; the alkali concentration in the alkaline deposition solution is 9-11 mol / L, TiO 2 The addition amount is 0.4-0.5g / L; the hydrothermal reaction temperature is 130-140℃, and the time is 22-24h.

[0055] Preferably, the TiO 2 The nanosheet structure is stacked in layers; the alkali concentration in the alkaline deposition solution is 9-11 mol / L; TiO 2 The addition amount is 0.4-0.5g / L; the hydrothermal reaction temperature is 130-140℃, and the time is 10-12 h.

[0056] Preferably, the TiO 2 The layer presents a nano-network porous structure; the alkali concentration in the alkaline deposition solution is 5-7 mol / L; TiO 2 The addition amount is 0.4-0.5g / L; the hydrothermal reaction temperature is 100-110℃, and the time is 10-12 h.

[0057] Preferably, the TiO 2 The layer is a stacked nanosphere structure; the alkali concentration in the alkaline deposition solution is 9-11 mol / L; TiO 2 The addition amount is 0.4-0.5g / L; the hydrothermal reaction temperature is 100-110℃, and the time is 10-12 h.

[0058] Preferably, the TiO 2 The layer is a stacked nano needle-like protrusion structure; the alkali concentration in the alkaline deposition solution is 5-7 mol / L; TiO 2 The addition amount is 0.4-0.5g / L; the hydrothermal reaction temperature is 130-140℃, and the time is 10-12 h.

[0059] Preferably, in step 1), the alkali in the alkaline sedimentation solution is NaOH or KOH.

[0060] Preferably, in step 1), the substrate is pre-ground, polished, cleaned and dried.

[0061] Preferably, in step 2), the acidic solution is a 0.1-0.5 mol / L hydrochloric acid solution.

[0062] Preferably, in step 3), the calcination temperature is 300-500° C. and the calcination time is 1-3 h. Specific embodiments

[0064] Example 1 (Nanotube structure morphology) (1) At 10 mol·L -1 Add 0.4 g·L NaOH aqueous solution -1 TiO 2 The powder constitutes the sedimentation solution for use, and 0.1 mol·L -1 HCl solution is used as pickling solution: (2) The Cu substrate is ground, polished, cleaned and dried for later use. Figure 1 As shown; (3) placing the Cu substrate and the deposition liquid together in a polytetrafluoroethylene reactor, setting the hydrothermal temperature to 130°C and the hydrothermal time to 24 h for a hydrothermal deposition reaction to form a titanate layer; (4) Clean the deposited Cu substrate with an acid wash solution to remove Na + Then rinsed with deionized water, calcined in a muffle furnace at 400 °C for 2 h to obtain Cu / TiO 2 , the surface morphology is Figure 2 As shown, the hydrothermal reaction temperature of this process is relatively high. The high temperature environment and long reaction time provide sufficient energy for the construction of the titanate skeleton, and the curled nanotube morphology is formed after acid washing and calcination. (5) Target pretreatment: The Ta target is installed in the first target position of the magnetron sputtering coating machine; the Cu substrate treated in step (4) is fixed on the substrate table and then fixed on the sample trolley. The sputtering chamber is closed and low vacuum extraction is performed first. When the pressure in the sputtering chamber reaches below 10 Pa, the molecular pump is started to extract high vacuum. When the vacuum degree in the sputtering chamber reaches 8×10 -5 After Pa, argon gas is introduced for pre-sputtering to remove contaminants on the target surface; (6) Coating: The gas pressure in the sputtering chamber was adjusted to 0.5 Pa, the sputtering power of the Ta target was adjusted to 500 W, and the duty cycle was adjusted to 90% for sputtering coating. After the sputtering was completed, the magnetron was turned off and the substrate stage was taken out to obtain a TiO substrate with a thickness of about 590 nm. 2 layer and a 20μm tantalum layer on a Cu substrate.

[0065] Example 2 (Nanosheet structure morphology) (1) At 10 mol·L -1 Add 0.4 g·L NaOH aqueous solution -1 TiO 2 The powder constitutes the sedimentation solution for use, and 0.1 mol·L -1 HCl solution is used as pickling solution: (2) The Cu substrate is ground, polished, cleaned, and dried for use; (3) placing the Cu substrate and the deposition liquid in a polytetrafluoroethylene reactor, setting the hydrothermal temperature to 130°C and the hydrothermal time to 12 h for a hydrothermal deposition reaction to form a titanate layer; (4) Clean the deposited Cu substrate with an acid wash solution to remove Na + Then rinsed with deionized water, calcined in a muffle furnace at 400 °C for 2 h to obtain Cu / TiO 2 , the surface morphology is Figure 3As shown, at higher reaction temperatures, the solubility of titanate ions increases, and at high temperatures there is sufficient diffusion energy and sufficient diffusion space in the vertical direction. The hydrothermal products on the substrate surface grow along the axial direction, thus forming a nanosheet structure morphology. (5) Target pretreatment: The Ta target is installed in the first target position of the magnetron sputtering coating machine; the Cu substrate treated in step (4) is fixed on the substrate table and then fixed on the sample trolley. The sputtering chamber is closed and low vacuum extraction is performed first. When the pressure in the sputtering chamber reaches below 10 Pa, the molecular pump is started to extract high vacuum. When the vacuum degree in the sputtering chamber reaches 8×10 -5 After Pa, argon gas is introduced for pre-sputtering to remove contaminants on the target surface; (6) Coating: The gas pressure in the sputtering chamber was adjusted to 0.5 Pa, the sputtering power of the Ta target was adjusted to 500 W, and the duty cycle was adjusted to 90% for sputtering coating. After the sputtering was completed, the magnetron was turned off and the substrate stage was taken out to obtain a TiO2 layer with a thickness of about 530 nm. 2 layer and a 20μm tantalum layer on a Cu substrate.

[0066] Example 3 (Nanosphere structure morphology) (1) At 10 mol·L -1 Add 0.4 g·L NaOH aqueous solution -1 TiO 2 The powder constitutes the sedimentation solution for use, and 0.1 mol·L -1 HCl solution is used as pickling solution: (2) The Cu substrate is ground, polished, cleaned, and dried for use; (3) placing the Cu substrate and the deposition liquid together in a polytetrafluoroethylene reactor, setting the hydrothermal temperature to 100 °C and the hydrothermal time to 12 h for hydrothermal deposition reaction to form a titanate layer; (4) Clean the deposited Cu substrate with an acid wash solution to remove Na + Then rinsed with deionized water, calcined in a muffle furnace at 400 °C for 2 h to obtain Cu / TiO 2 , the surface morphology is Figure 4 As shown, the reaction temperature of this process is low, the solubility of titanate ions is low, and under high alkali concentration, the supersaturation of titanate ions increases, and the nucleation rate of titanate on the substrate surface is much higher than the growth rate. Therefore, the particles cannot preferentially grow along a specific crystal plane, and can only form a fine nano-spherical structure by minimizing the surface energy. (5) Target pretreatment: The Ta target is installed in the first target position of the magnetron sputtering coating machine; the Cu substrate treated in step (4) is fixed on the substrate table and then fixed on the sample trolley. The sputtering chamber is closed and low vacuum extraction is performed first. When the pressure in the sputtering chamber reaches below 10 Pa, the molecular pump is started to extract high vacuum. When the vacuum degree in the sputtering chamber reaches 8×10 -5 After Pa, argon gas is introduced for pre-sputtering to remove contaminants on the target surface; (6) Coating: The gas pressure in the sputtering chamber was adjusted to 0.5 Pa, the sputtering power of the Ta target was adjusted to 500 W, and the duty cycle was adjusted to 90% for sputtering coating. After the sputtering was completed, the magnetron was turned off and the substrate stage was taken out to obtain a TiO2 layer with a thickness of about 480 nm. 2 layer and a 20μm tantalum layer on a Cu substrate.

[0067] Example 4 (Nano-network porous structure morphology) (1) At 5 mol·L -1 Add 0.4 g·L NaOH aqueous solution -1 TiO 2 The powder constitutes the sedimentation solution for use, and 0.1 mol·L -1 HCl solution is used as pickling solution: (2) The Cu substrate is ground, polished, cleaned, and dried for use; (3) placing the Cu substrate and the deposition liquid together in a polytetrafluoroethylene reactor, setting the hydrothermal temperature to 100 °C and the hydrothermal time to 12 h for hydrothermal deposition reaction to form a titanate layer; (4) Clean the deposited Cu substrate with an acid wash solution to remove Na + Then rinsed with deionized water, calcined in a muffle furnace at 400 °C for 2 h to obtain Cu / TiO 2 , the surface morphology is Figure 5 As shown, when the reaction temperature is low and the alkali concentration is low, the supersaturation of titanate ions decreases, the nucleation rate slows down, and it tends to form larger nanospheres. Due to the van der Waals force, secondary aggregation occurs, forming a clustered nano-network-like porous structure. (5) Target pretreatment: The Ta target is installed in the first target position of the magnetron sputtering coating machine; the Cu substrate treated in step (4) is fixed on the substrate table and then fixed on the sample trolley. The sputtering chamber is closed and low vacuum extraction is performed first. When the pressure in the sputtering chamber reaches below 10 Pa, the molecular pump is started to extract high vacuum. When the vacuum degree in the sputtering chamber reaches 8×10 -5 After Pa, argon gas is introduced for pre-sputtering to remove contaminants on the target surface; (6) Coating: The gas pressure in the sputtering chamber was adjusted to 0.5 Pa, the sputtering power of the Ta target was adjusted to 500 W, and the duty cycle was adjusted to 90% for sputtering coating. After the sputtering was completed, the magnetron was turned off and the substrate stage was taken out to obtain a TiO layer with a surface area of ​​about 450 nm. 2 layer and a 20μm tantalum layer on a Cu substrate.

[0068] Example 5 (Nano-needle-like protrusion structure morphology) (1) At 5 mol·L -1 Add 0.4 g·L NaOH aqueous solution -1 TiO 2 The powder constitutes the sedimentation solution for use, and 0.1 mol·L -1 HCl solution is used as pickling solution: (2) The Cu substrate is ground, polished, cleaned, and dried for use; (3) placing the Cu substrate and the deposition liquid in a polytetrafluoroethylene reactor, setting the hydrothermal temperature to 130°C and the hydrothermal time to 12 h for a hydrothermal deposition reaction to form a titanate layer; (4) Clean the deposited Cu substrate with an acid wash solution to remove Na + Then rinsed with deionized water, calcined in a muffle furnace at 400 °C for 2 h to obtain Cu / TiO 2 , the surface morphology is Figure 6 As shown, when the reaction temperature is high and the alkali concentration is low, nano-needle-like protrusions with smaller sizes are preferentially generated on the substrate surface; (5) Target pretreatment: The Ta target is installed in the first target position of the magnetron sputtering coating machine; the Cu substrate treated in step (4) is fixed on the substrate table and then fixed on the sample trolley. The sputtering chamber is closed and low vacuum extraction is performed first. When the pressure in the sputtering chamber reaches below 10 Pa, the molecular pump is started to extract high vacuum. When the vacuum degree in the sputtering chamber reaches 8×10 -5 After Pa, argon gas is introduced for pre-sputtering to remove contaminants on the target surface; (6) Coating: The gas pressure in the sputtering chamber was adjusted to 0.5 Pa, the sputtering power of the Ta target was adjusted to 500 W, and the duty cycle was adjusted to 90% for sputtering coating. After the sputtering was completed, the magnetron was turned off and the substrate stage was taken out to obtain a TiO2 deposited with about 420 nm. 2 layer and a 20μm tantalum layer on a Cu substrate.

[0069] Comparative Example 1 (without TiO 2 layer) (1) The Cu substrate is ground, polished, cleaned and dried for use; (2) Target pretreatment: The Ta target was installed in the first target position of the magnetron sputtering coating machine; the Cu substrate treated in step (1) was fixed on the substrate table and then fixed on the sample trolley. The sputtering chamber was closed and low vacuum was extracted first. When the pressure in the sputtering chamber reached below 10 Pa, the molecular pump was started to extract high vacuum. When the vacuum in the sputtering chamber reached 8×10 -5 After Pa, argon gas is introduced for pre-sputtering to remove contaminants on the target surface; (3) Coating: The gas pressure in the sputtering chamber was adjusted to 0.5 Pa, the sputtering power of the Ta target was adjusted to 500 W, and the duty cycle was adjusted to 90% for sputtering coating. After the sputtering was completed, the magnetron was turned off and the substrate stage was taken out to obtain a Cu substrate with a 20 μm tantalum layer deposited on it (such as Figure 7 As shown), without TiO 2 The surface of the 20μm tantalum layer obtained by magnetron sputtering on the copper substrate showed cracking due to stress.

[0070] Performance Testing Figure 7 This is a scanning image of a 20 μm Ta layer prepared on an original Cu substrate by magnetron sputtering in Comparative Example 1. Figure 8 This is a scanned image of a 20 μm Ta layer prepared by magnetron sputtering after hydrothermal deposition pretreatment in Example 1-5. By comparison, it can be seen that Figure 7 Obvious local cracking and spalling occurred in the middle Ta layer.

[0071] Fig. 9 The Cu / TiO obtained after hydrothermal deposition pretreatment in Example 5 2 From the LSCM image, it can be seen that the surface roughness of the substrate is large at this time. Fig.10 This is the LSCM image of a 20 μm Ta layer prepared by magnetron sputtering after hydrothermal deposition pretreatment in Example 5. The tantalum atoms fully fill the Fig. 9 The gaps in the film make the film bond stronger, and the internal stress can be released along the rough surface. 2 / Ta surface roughness is reduced and surface height difference is reduced.

[0072] Fig.11 The actual pictures are of the samples obtained by plating a 20 μm Ta layer on the original copper substrate in Comparative Example 1 and plating a 20 μm Ta layer after hydrothermal deposition pretreatment in Examples 1-5 (arranged from left to right). After the original copper substrate is plated, the surface is almost completely cracked to expose the copper base, while the sample morphology obtained by first hydrothermal deposition to construct the microstructure morphology and then magnetron sputtering coating is smoother and more uniform, without cracking and peeling.

[0073] The stress test was performed on the samples obtained from each embodiment and comparative example, and the results are shown in the following table:

[0074] During the cooling process, the thermal expansion coefficients of copper and tantalum are 16.5 µm·m -1 ·K -1 and 6.3 µm·m -1 ·K -1 The larger difference will cause the copper substrate to shrink more than the tantalum layer, resulting in more internal stress accumulation on the tantalum layer (Comparative Example 1). 2 After layer, TiO 2 The average thermal expansion coefficient varies according to the crystal structure, and is about 8-8.5 µm·m -1 ·K -1 , between copper and tantalum, can alleviate the stress problem caused by the mismatch of thermal expansion coefficients between the substrate and the tantalum film. Although the rough surface of the copper substrate can also cause stress concentration, it also provides a path and way to release stress, so that the stress in Examples 1-5 is lower than that of the original copper. At the same time, the lattice structure of titanium dioxide has a good match with certain crystal planes of tantalum, thereby promoting the orderly growth of tantalum on its surface. At the same time, the various nanostructure morphologies of titanium dioxide (such as nanotubes, nanosheets, nanospheres, etc.) can induce its tantalum to self-assemble in a specific way. The order of the effects is: nanotube structure>nanosheet structure>nano-network-like porous structure>nanosphere structure>nano-needle-like protrusion structure.

[0075] The raw materials and equipment used in the present invention, unless otherwise specified, are all commonly used raw materials and equipment in the art; the methods used in the present invention, unless otherwise specified, are all conventional methods in the art.

[0076] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent transformation made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. An accelerator neutron source target composite transition layer, characterized in that: Located between the substrate and the target layer, including a TiO2 layer deposited by a hydrothermal method and attached to the surface of the substrate after baking, and a tantalum layer deposited on the surface of the TiO2 layer; The microscopic morphology of the TiO2 layer includes at least one of the following: (a) Stacked nanotube structure; (b) Stacked nanosheet structure; (c) Nano-network porous structure; (d) The structure of stacked nanospheres; (e) Stacked nanoneedle-like protrusion structure.

2. The accelerator neutron source target composite transition layer according to claim 1, characterized in that: The TiO2 layer is formed by hydrothermal reaction of an alkaline deposition liquid containing a titanium source to generate titanate which is deposited on the surface of the substrate and then pickled and calcined.

3. The accelerator neutron source target composite transition layer according to claim 1, characterized in that: The substrate is a flat surface or an irregular surface.

4. The accelerator neutron source target composite transition layer according to claim 1, characterized in that: The thickness of the TiO2 layer ranges from 200 to 800 nm.

5. The accelerator neutron source target composite transition layer according to claim 1 or 4, characterized in that: The thickness of the tantalum layer is in the range of 1-20 μm.

6. A method for preparing a composite transition layer for an accelerator neutron source target according to any one of claims 1 to 5, characterized in that include: 1) placing the substrate in an alkaline deposition solution containing TiO2 for hydrothermal reaction to nucleate and generate a titanate layer on the surface of the substrate; 2) Immerse the substrate in an acidic solution to convert the titanate layer into a titanate acid layer, and then wash with water; 3) Calcination to convert the titanate layer into a TiO2 layer; 4) Depositing a tantalum layer on the surface of the TiO2 layer by magnetron sputtering.

7. The preparation method according to claim 6, characterized in that: The TiO2 layer is a stacked nanotube structure; the alkali concentration in the alkaline deposition solution is 9-11 mol / L, and the TiO2 content is 0.4-0.5 g / L; the hydrothermal reaction temperature is 130-140° C., and the time is 22-24 hours; or The TiO2 layer is a stacked nanosheet structure; the alkali concentration in the alkaline deposition solution is 9-11 mol / L; the TiO2 content is 0.4-0.5 g / L; the hydrothermal reaction temperature is 130-140° C., and the reaction time is 10-12 h; or The TiO2 layer has a nano-network porous structure; the alkali concentration in the alkaline deposition solution is 5-7 mol / L; the TiO2 content is 0.4-0.5 g / L; the hydrothermal reaction temperature is 100-110° C., and the time is 10-12 h; or The TiO2 layer is in a stacked nanosphere structure; the alkali concentration in the alkaline deposition solution is 9-11 mol / L; the TiO2 content is 0.4-0.5 g / L; the hydrothermal reaction temperature is 100-110° C., and the time is 10-12 h; or The TiO2 layer presents a stacked nano needle-like protrusion structure; the alkali concentration in the alkaline deposition solution is 5-7 mol / L; the TiO2 content is 0.4-0.5 g / L; the hydrothermal reaction temperature is 130-140° C., and the reaction time is 10-12 h.

8. The preparation method according to claim 6 or 7, characterized in that: In step 1), the alkali in the alkaline sedimentation solution is NaOH or KOH.

9. The preparation method according to claim 6 or 7, characterized in that: In step 2), the acidic solution is a 0.1-0.5 mol / L hydrochloric acid solution.

10. The preparation method according to claim 6 or 7, characterized in that: In step 3), the calcination temperature is 300-500° C. and the calcination time is 1-3 h.

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