CN108342698A - It is a kind of6The preparation process of LiF target membranes - Google Patents

Abstract

The invention belongs to isotope target preparing technical fields, disclose one kind⁶The preparation process of LiF target membranes.The technique be by⁶After LiF is prepared into reunion shape, it is deposited onto on bottom liner using electron bombardment equipment, what which prepared⁶LiF target membranes and the binding force of bottom liner are good, not easily to fall off.This method can farthest save material simultaneously, improve the utilization rate of material.

Description

A preparation process of 6LiF target film

technical field

The invention belongs to the technical field of isotope target material preparation, and in particular relates to a preparation process of ⁶ LiF target film.

Background technique

⁶ Li is the lightest solid isotope in atomic weight. It is an important material and fuel for fusion reactors and thermonuclear devices. It can also be used as neutron measurement and neutron shielding materials. The isotope is used to measure and monitor ^neutrons . This stable form of LiF was performed to estimate the energy and spectrum of the neutron field.

In order to use ⁶ LiF to measure neutrons, it needs to be plated on the substrate through a certain process to make a ⁶ LiF target film, and the thickness of the target film is usually above 10 μm. The existing technology is to use thermal evaporation and ordinary large electron gun bombardment evaporation to obtain ⁶ LiF target film, but this method has poor bonding force between the film and the substrate, the film layer is easy to peel off, and it is easy to cause ⁶ LiF droplet splashing during evaporation. The surface of the film is rough and a large number of macroscopic particles are formed on the surface. In order to obtain ⁶ LiF film, magnetron sputtering method can also be used in theory, but because the material is very expensive, a large piece of ⁶ LiF is needed as the sputtering source, so it is not suitable. At present, there is an urgent need for a preparation technology of ⁶ LiF target film that can reasonably control the cost, have good adhesion to the substrate, and have good thickness uniformity.

Contents of the invention

(1) Purpose of the invention

According to the problems existing in the prior art, the present invention provides a preparation process of a ⁶ LiF target film with good bonding force with the substrate, uniform thickness and good surface finish.

(2) Technical solution

In order to solve the existing problems of the prior art, the technical solutions provided by the invention are as follows:

A kind of preparation technology of ⁶ LiF target film, this technology comprises the following steps:

1) Pretreatment of the substrate

This preprocessing consists of two steps:

(a) Use alcohol and acetone to degrease and clean the underlay successively;

(b) putting the substrate obtained in step (a) into a vacuum for glow discharge cleaning to further remove impurities adsorbed or contaminated on the substrate;

The substrate is an aluminum sheet, a stainless steel sheet or a titanium sheet;

2) Raw material pretreatment

Prepare powdery ⁶ LiF raw materials into agglomerates; then degas the agglomerated ⁶ LiF by electron bombardment for 2-4 hours;

The equipment used for the electron bombardment mainly includes a vacuum chamber, a graphite crucible, a stainless steel shielding cylinder, a first tungsten wire, a second tungsten wire and a power supply, wherein the graphite crucible, the stainless steel shielding cylinder, the first tungsten wire and the second tungsten wire are all located in the vacuum chamber Inside; the first tungsten wire disc is circular, located above the graphite crucible, the circular diameter is smaller than the diameter of the stainless steel shielding cylinder and the height of the first tungsten wire is flush with the upper end of the stainless steel shielding cylinder; the power supply is an integrated power supply, It includes an AC pole and a high voltage pole, which can provide alternating current and high voltage direct current respectively. The first tungsten wire is connected to the AC pole of the power supply; the voltage, current and power parameters of the high voltage pole of the power supply can be continuously adjusted from 0;

The graphite crucible extends into the stainless steel shielding cylinder from the bottom of the stainless steel shielding cylinder. The graphite crucible is used to place ⁶ LiF, and an insulator is arranged below it. A second tungsten wire with a height of 0.9-1.2mm in diameter, one end of which is connected to the bottom of the graphite crucible, and the other end is connected to the high voltage pole of the power supply through an insulator;

The agglomerated ⁶ LiF degassing operation only needs to turn on the AC pole switch of the power supply, set the current to 5-8A, and the time is 2-4 hours to make the vacuum stable, and the degassing ends after the vacuum is stable;

3) Preparation of ⁶ LiF target film by electron bombardment

⁶ LiF after the degassing are continued to be deposited on the substrate by electron bombardment in the electron bombardment equipment described in step 2), and the time of electron bombardment in this step depends on the thickness of required ⁶ LiF target film;

Among them, the parameters of the AC pole are that the voltage is fixed at 12V, and the current is 8-10A; the parameters of the high-voltage pole are that the voltage starts from 0 and increases by 25V every 10 minutes, and the voltage is adjusted to the highest value according to the size of the graphite crucible and the amount of ⁶ LiF. The maximum value is limited so that ⁶ LiF does not melt to a liquid state.

Preferably, the main operating parameters of the glow discharge cleaning described in step 1) include cleaning time of 3-5 minutes, vacuum degree of 1-10 Pa, and voltage of 400-500V.

Preferably, the insulator in step 2) is disc-shaped boron nitride.

Preferably, the vacuum degree of the vacuum chamber in step 2) is higher than 10 ^-3 Pa.

Preferably, the agglomerated ⁶ LiF in step (2) is prepared by molding.

Preferably, the agglomerated ⁶ LiF in step (2) is in the shape of a cylinder with a diameter of 6-9 mm and a thickness of 5-8 mm.

Preferably, the substrate is connected to a quartz crystal film thickness monitor.

Preferably, the distance between the substrate and the upper end of the ⁶ LiF material in the graphite crucible is 10-15 cm.

(3) Beneficial effects

Utilizing the preparation process of the ⁶ LiF target film provided by the present invention, the prepared ⁶ LiF target film has good binding force with the substrate and is not easy to fall off. At the same time, since ⁶ LiF materials are not easy to purchase, this method can save raw materials as much as possible and improve the utilization rate of materials.

Description of drawings

Fig. 1 is the schematic diagram of the electron bombardment equipment that specific embodiment experiment example 1 provides; Wherein 1 is a vacuum chamber; 2 is the second tungsten wire; 3 is the first tungsten wire; 4 is a stainless steel shielding cylinder; Boron carbide; 7 is a power supply.

Detailed ways

The present invention will be further elaborated below in conjunction with specific experimental examples and accompanying drawings.

The basic principle of preparing ⁶ LiF by the method provided by the present invention is: pass an alternating current to the first tungsten wire, and apply high voltage to the crucible through the second tungsten wire, the first tungsten wire generates heat and emits a large amount of electrons under the action of an electrostatic field, Bombard the crucible to make the temperature rise, and the ⁶ LiF target material in the crucible evaporates and deposits on the substrate.

Experimental example 1

A kind of preparation technology of ⁶ LiF target film, this technology comprises the following steps:

1) Pretreatment of the substrate

This preprocessing consists of two steps:

(a) Use alcohol and acetone to degrease and clean the underlay successively to remove the grease and dirt stained on the underlay;

(b) Put the substrate obtained in step (a) into a vacuum for glow discharge cleaning to further remove impurities adsorbed or contaminated on the substrate. Impurities found to ensure a more reliable combination of ⁶ LiF and the substrate; the main parameters of the glow discharge cleaning operation are cleaning time of 3 to 5 minutes, vacuum of 1 to 10Pa, and voltage of 400 to 500V.

The substrate is an aluminum sheet with a thickness of 100 μm.

2) Raw material pretreatment

The powdery ⁶ LiF raw material is prepared into agglomerates; then the agglomerated ⁶ LiF is degassed by electron bombardment in a high vacuum for 2-4 hours; the equipment used for the electron bombardment is shown in Figure 1, mainly including a vacuum chamber 1. Graphite crucible 5, stainless steel shielding cylinder 4, first tungsten wire 3, second tungsten wire 2 and power supply 7, wherein graphite crucible 5, stainless steel shielding cylinder 4, first tungsten wire 3, and second tungsten wire 2 are all located in a vacuum Inside the room; the power supply 7 is an integrated power supply, including an AC pole and a high-voltage pole, which can provide alternating current and high-voltage direct current respectively. The key point is that the voltage, current and power parameters of the high-voltage pole can be continuously adjusted from 0; the stainless steel The function of the shielding cylinder 4 is to reduce the loss of electrons, so that the electrons are bombarded on the graphite crucible 5 as much as possible, and the vacuum degree in the vacuum chamber 1 is 10 ⁻⁴ Pa. The first tungsten wire 3 disk is circular, located above the graphite crucible, the diameter of the circle is slightly smaller than the diameter of the stainless steel shielding cylinder and the height of the first tungsten wire is flush with the upper end of the stainless steel shielding cylinder; the first tungsten wire 3 and the power supply 7 AC pole connection. The graphite crucible 5 extends into the stainless steel shielding cylinder 4 from the bottom of the stainless steel shielding cylinder 4, the graphite crucible 5 is used to place ⁶ LiF, an insulator is arranged below it, and a high voltage and A second tungsten wire capable of adjusting the height of the graphite crucible, the diameter of the second tungsten wire is 0.9-1.2mm, one end of which is connected to the bottom of the graphite crucible, and the other end is connected to the high voltage pole of the power supply through an insulator;

For agglomerated ⁶ LiF degassing, you only need to turn on the AC pole switch of the power supply, set the current to 5-8A, and the time is 2-4 hours to stabilize the vacuum and complete the degassing;

The degassing step can significantly improve the purity of the target film and keep the vacuum as stable as possible. This is mainly because the powdery material will inevitably absorb moisture, air and other impurities in the air, so it is degassed before electron bombardment. Otherwise, the adjusted vacuum will rise sharply and bring impurities such as O, H, and N to the target film.

3) Preparation of ⁶ LiF target film by electron bombardment

Put ^{the 6} LiF that step 2) obtains into the electron bombardment equipment and deposit on the substrate in the mode of electron bombardment, the time of electron bombardment in this step depends on the thickness of required ⁶ LiF target film; The substrate distance ⁶ LiF material upper end The distance is 10 ~ 15cm.

During the preparation of the ⁶ LiF target film, the parameters of the AC electrode are fixed at 12V, the current ^is 8-10A, and the parameters of the high voltage electrode are adjusted from 0 to 25V every 10min. Adjust the voltage to the highest value that does not make ^{the 6} LiF melt into a liquid state.

^{The 6} LiF target film is deposited on the substrate without melting into a liquid state, which avoids splashing of a large number of droplets caused by the liquid ⁶ LiF, and finally forms a rough and uneven target film.

In this experimental example, an insulator instead of a conductor is arranged under the graphite crucible, because the applicant cleverly used the principle of the electric field, and the effect it brings is very obvious. Because the graphite crucible is connected to the high voltage, if there is a conductor under the high voltage, then the potential of the conductor is the same as that of the graphite crucible, and the electrons emitted by the first tungsten wire will move from top to bottom in parallel to the high voltage direction. In this experimental example, the graphite crucible Below is the insulator, and the electric field is focused on the graphite crucible in a cone-like shape, and the heat is more concentrated. At the same time, the diameter of the second tungsten wire is relatively large, which can effectively support the graphite crucible.

The agglomerated ⁶ LiF is prepared by molding. The agglomerated ⁶ LiF is in the shape of a cylinder with dimensions of 8 mm in diameter and 7 mm in thickness.

The parameter settings during the electron bombardment are as follows: the high voltage starts from 0, increases by 25V ^every 10 minutes, and adjusts the voltage to the highest value according to the size of the graphite crucible and the amount of ⁶ LiF. In this experimental example, the high voltage is 300V. In addition, the successful preparation of ⁶ LiF can also be achieved comprehensively by adjusting the distance between ⁶ LiF and the first tungsten wire, which avoids the rough surface of the target film caused by splashing of droplets caused by melting ⁶ LiF into a liquid state.

Experimental results: ① A ⁶ LiF target film with a diameter of Ф50 mm and a thickness of 22 μm was prepared on an Al substrate with a thickness of 100 μm. The target film has a smooth surface, does not fall off, and has good adhesion.

② After being placed in the atmospheric environment for 6 months, there is almost no change, the surface does not fall off or loosen, and after wiping with gauze and other wiping tools, the surface of the target film remains unchanged;

③Heat the sample in a vacuum of 5×10 ^-4 Pa, the heating temperature is 300°C, and the heating and holding time is 6h. The results show that there is almost no change on the surface, and the surface does not fall off. Weighing before and after heat treatment showed little change in mass.

Experimental example 2

The difference from Experimental Example 1 is that the substrate is connected to a quartz crystal film thickness monitor, which can monitor the thickness of the target film on-line; the substrate is a stainless steel sheet.

Claims (8)

1. a kind of⁶The preparation process of LiF target membranes, which is characterized in that the technique includes the following steps：

1) pretreatment of bottom liner

The pretreatment includes two steps：

(a) cleaning of deoiling successively is carried out to bottom liner with alcohol, acetone；

(b) bottom liner that step (a) obtains is put into vacuum carry out Glow Discharge Cleaning with further remove on bottom liner absorption or The impurity of contamination；

The bottom liner is aluminium flake, stainless steel substrates or titanium sheet；

2) pre-treatment of raw material

It will be powdered⁶LiF raw material are prepared into reunion shape；Then by shape of reuniting⁶Degasification 2 in a manner of electron bombardment LiF ~4h；

The electron bombardment device therefor includes mainly vacuum chamber, graphite crucible, stainless steel shielding cylinder, the first tungsten filament, the second tungsten filament And power supply, wherein graphite crucible, stainless steel shielding cylinder, the first tungsten filament, the second tungsten filament are respectively positioned on internal vacuum chamber；First tungsten Wire tray is circle, is located above graphite crucible, which is less than the diameter and the first tungsten filament height of stainless steel shielding cylinder It is concordant with stainless steel shielding cylinder upper end；The power supply is integrated power supply, including exchange pole and high-pressure stage, can provide alternating current respectively And high voltage direct current, the first tungsten filament exchange pole connection with power supply；Voltage, electric current and the power parameter of the power supply high-pressure stage all may be used To be continuously adjusted since 0；

The graphite crucible is stretched to from stainless steel shielding cylinder bottom in stainless steel shielding cylinder, and the graphite crucible is for placing⁶LiF, There are one insulators for setting below, are equipped between the insulator and graphite crucible and are capable of providing high pressure and can adjust graphite crucible The bottom connection of second tungsten filament of height, a diameter of 0.9~1.2mm of second tungsten filament, one end and graphite crucible, the other end It is connected across the high-pressure stage of insulator and power supply；

Reunion shape⁶LiF degasification operation need to only open capable AC pole switch, and electric current is set as 5~8A, and the time is 2~4h So that vacuum stablize, vacuum stablize after degasification terminate；

3) prepared by electron bombardment⁶LiF target membranes

After degasification⁶LiF continues to be deposited on bottom liner in a manner of electron bombardment in the electron bombardment equipment described in step 2) On, the time of electron bombardment is depending on required in the step⁶The thickness of LiF target membranes；

The parameter of wherein exchange pole is that voltage is fixed as 12V, and electric current is 8~10A；The parameter of high-pressure stage is voltage from 0 Adjust, 25V increased per 10min, according to graphite crucible size and⁶The amount of LiF adjusts voltage to peak, and the peak is not to make⁶LiF is molten into liquid and is limited.

2. one kind according to claim 1⁶The preparation process of LiF target membranes, which is characterized in that the aura described in step 1) The main operating parameters of Discharge Cleaning include that scavenging period is 3~5min, and vacuum degree is 1~10Pa, and voltage is 400~500V.

3. one kind according to claim 1⁶The preparation process of LiF target membranes, which is characterized in that insulator described in step 2) For discoid boron nitride.

4. one kind according to claim 1⁶The preparation process of LiF target membranes, which is characterized in that vacuum chamber described in step 2) Vacuum degree be better than 10^-3Pa。

5. one kind according to claim 1⁶The preparation process of LiF target membranes, which is characterized in that shape of reuniting described in step (2) 's⁶LiF is prepared by die pressing.

6. one kind according to claim 1⁶The preparation process of LiF target membranes, which is characterized in that shape of reuniting described in step (2) 's⁶LiF is cylindrical shape and cylinder dimensions are：6~9mm of diameter, thickness 5-8mm.

7. one kind according to claim 1⁶The preparation process of LiF target membranes, which is characterized in that the bottom liner and quartz crystal Film thickness monitor connects.

8. a kind of preparation process of 6LiF target membranes according to claim 1, which is characterized in that the bottom liner is apart from graphite earthenware In crucible⁶The distance of LiF materials upper end is 10~15cm.