Preparation method for double-layer working medium target tape with plasma-enhanced interfacial bonding force for micro laser thruster

Abstract

Provided is a preparation method for a double-layer working medium target tape with a plasma-enhanced interfacial bonding force for a micro laser thruster. Aiming at the problem that in an existing micro laser thruster, when a working medium is ablated by a laser beam, due to a weak interlayer interfacial bonding force between a transparent film substrate and the coating working medium, sputtering or bulging occurs, which remarkably reduces propulsive performance, a method for treating a surface of a transparent film substrate with a low-temperature plasma is used to increase surface energy of a film and an adhesive force of a working medium layer on a surface of the film, thereby enhancing the interlayer interfacial bonding force. According to the method in the present disclosure, the transparent film substrate is treated with the low-temperature plasma.

Claims

1. A plasma treatment based preparation method for a working medium target tape for a micro laser thruster, comprising the following steps: step 1) treating a surface of a transparent polymer film substrate by a plasma; and step 2) coating the surface of the transparent polymer film substrate subjected to the plasma treatment with working medium slurry; the transparent polymer film substrate is a polyethylene terephthalate film or a polyimide film.

2. The plasma treatment based preparation method for a working medium target tape for a micro laser thruster according to claim 1, wherein the surface of the transparent film substrate is coated with the working medium slurry within 5 s after being subjected to the plasma treatment.

3. The plasma treatment based preparation method for a working medium target tape for a micro laser thruster according to claim 1, wherein the transparent polymer film substrate is a polymer film with a single surface coated with silicon; in the step 1), the surface not coated with the silicon of the transparent polymer film substrate is treated by the plasma; the transparent polymer film substrate has a thickness ranging from 20 ?m to 200 ?m; and the transparent polymer film substrate has a width ranging from 5 cm to 15 cm.

4. The plasma treatment based preparation method for a working medium target tape for a micro laser thruster according to claim 1, wherein in the step 1), the transparent polymer film substrate is subjected to cleaning pretreatment; the cleaning pretreatment is to clean the surface of the transparent polymer film substrate with ethanol, and after being air-dried, the transparent polymer film substrate is dried at a temperature ranging from 40? C. to 50? C. for later use; and in the step 2), after coating is completed, the slurry is dried at a temperature ranging from 40? C. to 50? C.

5. The plasma treatment based preparation method for a working medium target tape for a micro laser thruster according to claim 1, wherein the plasma is made from at least one of air, argon, nitrogen or oxygen.

6. The plasma treatment based preparation method for a working medium target tape for a micro laser thruster according to claim 1, wherein low-temperature plasma treatment power ranges from 1000 W to 2000 W; a transparent polymer film substrate transmission speed ranges from 1 m/min to 4 m/min; and a gas pressure ranges from 80 kPa to 120 kPa, and a low-temperature plasma treatment region has an area ranging from 150 cm.sup.2 to 400 cm.sup.2.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1: Flow diagram of preparing double-layer working medium target tape having plasma-enhanced interfacial bonding force

(2) FIG. 2: Schematic diagram of low-temperature plasma treatment; numerals in the figure:

(3) 1-transparent film, 2-guide roller, 3-corundum discharge electrode, 4-electric discharge roller, 5-blade coater and 6-working medium

(4) FIG. 3: XPS (x-ray photoelectron spectroscopy) curve of element C in chemical groups of surface before and after plasma treatment

(5) FIG. 4: XPS curve of element O in chemical groups of surface before and after plasma treatment

(6) FIGS. 5A-5B: Measurement results of contact angles, wherein FIG. 5A illustrates a contact angle between polyethylene terephthalate (PET) and a liquid glycidyl azide polymer (GAP) that are not subjected to plasma treatment is about 68 degrees; and FIG. 5B illustrates a contact angle between PET and a liquid GAP that are subjected to plasma treatment is about 25 degrees.

(7) FIGS. 6A-6B: Results of atomic force microscope, wherein FIG. 6A illustrates Untreated samples: PET not subjected to plasma pretreatment has low surface roughness, and a height difference between a highest point and a lowest point is about 8.95 nm and FIG. 6B illustrates Treated samples: PET subjected to plasma pretreatment has a high surface roughness, and a height difference between a highest point and a lowest point is about 129.85 nm.

(8) FIGS. 7A-7D: XPS analysis diagram including different elemental bonds before and after plasma treatment, wherein FIG. 7A illustrates C 1s, FIG. 7B illustrates O 1s, FIG. 7C illustrates Si 2p and FIG. 7D illustrates N 1s.

(9) FIG. 8: Stress results and tensile samples, wherein FIG. 8A illustrates Measurement results of tension stress. Adhesion between PET and GAP before and after plasma treatment is represented by a red line and a black line respectively. Tension stress at a point A is about 9.84 MPa, and a result of tensioning a double-layer tape is indicated by an arrow at the point A. Tension stress at a point B is about 22.98 MPa, a result of a double-layer tape: a tensioned double-layer tape is indicated by an arrow at the point B.

(10) FIG. 8B illustrates a Three-dimensional schematic diagram of tensile samples. FIG. 8C illustrates a Physical picture of tensile samples.

(11) FIG. 9: Comparison of impulses of single pulse of ten times of consecutive lase ablation

(12) FIGS. 10A-10B: Separation phenomena of target tape before and after plasma treatment, wherein FIG. 10A illustrates Target tape not subjected to plasma treatment; and FIG. 10B illustrates Target tape subjected to plasma treatment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(13) The present disclosure will be further described below in combination with specific implementation steps. These implementation steps are only used for describing the present disclosure, but do not limit the scope of application of the present disclosure.

(14) A processing device in the present disclosure is as shown in FIG. 2, and a transparent film sequentially passes through a low-temperature plasma treatment station and a blade coater. The low-temperature plasma treatment station includes a corundum discharge electrode and an electric discharge roller that are of a sector structure, and that transparent film passes through a space between the corundum discharge electrode and the electric discharge roller.

(15) A flow diagram of treating a transparent substrate film with a low-temperature plasma in the present disclosure is as shown in FIG. 1.

(16) 1. A wound transparent polyethylene terephthalate (PET) film having a thickness of 50 ?m with a single surface coated with silicon is placed on a winding and unwinding device of a coating machine, where a surface not coated with silicon faces upwards. When the transparent PET film is wound and unwound, two surfaces of the transparent PET film are rapidly wiped by means of cotton dipped with absolute ethanol, and the transparent PET film is rapidly air-dried by a hot air blower. After the transparent PET film is cleaned and wound, the transparent PET film is placed in a constant-temperature drying oven to be dried for 2 h at a temperature of 40? C.

(17) 2. The wound transparent PET film dried in the step 1 is placed on a special transmission apparatus of a low-temperature plasma treatment station, the transparent PET film is placed between a discharge electrode and a conductive roller, and the surface not coated with silicon faces upwards to be right opposite the discharge electrode. The transparent PET film of 10 cm is moved at a speed of 1.5 m/min at a normal temperature, under a normal pressure and in the presence of an air plasma, plasma treatment power is 1800 W, and a plasma treatment area is 200 cm.sup.2.

(18) 4. The transparent PET film subjected to low-temperature plasma treatment in the step 2 is connected to a transmission apparatus of the coating machine, after the transparent PET film is subjected to the low-temperature plasma treatment, the plasma-treated surface of the transparent PET film is immediately coated with prepared working medium slurry by a blade coater, and a plasma treatment process of the transparent PET film and a coating process of glycidyl azide polymer (GAP) working medium slurry are synchronously carried out.

(19) 5. A working medium target tape after coating is placed in a normal-pressure constant-temperature drying oven to be slowly dried, a temperature of the drying oven is maintained at about 40? C., and after a solvent in the working medium slurry is completely volatilized, a solidified working medium target tape is obtained.

(20) Test of plasma treatment effect:

(21) A variation of surface tension of a transparent PET film before and after treatment is tested by means of a dyne liquid, and the surface tension of the transparent PET film subjected to the low-temperature plasma treatment may be increased from less than 40 dynes to 70 dynes or above.

(22) Embodiment 2 Variation representation of PET substrate of target tape before and after plasma treatment

(23) 1. A contact angle between a liquid GAP mixed solution and substrate PET is measured by a contact angle measuring instrument (POWEREACH JC2000D3, Shanghai Zhongcheng Technology Co., Ltd.).

(24) Measurement results are as shown in FIGS. 5A-5B. A contact angle between PET and a liquid GAP mixture that are not subjected to plasma treatment is about 68 degrees. A contact angle between PET and liquid GAP that are subjected to plasma treatment is about 25 degrees. It can be found that the contact angle between the PET and the liquid GAP that are subjected to plasma treatment is remarkably decreased. It is indicated that wettability of a PET surface subjected to plasma treatment is remarkably improved.

(25) 2. Flatness of a surface of a PET film before and after plasma treatment is scanned by an atomic force microscope (AFM).

(26) A given result of an AFM represents a mean of at least five times of repeated measurement. Test results are as shown in FIGS. 6A-6B. Surface morphology of PET is observed by means of the AFM, and a mean and root mean square of surface roughness are obtained, which are as shown in Table 1. Surface roughness Ra of PET not subjected to plasma treatment is about 1.45 nm, and root mean square Rq is about 1.74 nm. Surface roughness Ra of PET subjected to plasma treatment is about 14.30 nm, and root mean square value Rq is about 19.10 nm. It can be seen from the figure that a PET surface not subjected to plasma pretreatment is smooth and flat, and the surface roughness is low. A PET surface subjected to plasma treatment becomes rough, and plenty of conical protrusions appear. It is indicated that the PET surface is eroded through ion and electron bombardment in a plasma treatment process. An increase in surface roughness increases a contact area between PET and GAP. Therefore, adhesive performance of PET is improved, and a bonding force of a double-layer target tape is enhanced.

(27) TABLE-US-00001 TABLE 1 Test results of AFM Sample name Ra nm Rq nm Sample not subjected 1.45 (?0.22) 1.74 (?0.39) to plasma treatment Sample subjected to 14.30 (?5.86) 19.10 (?6.34) plasma treatment

(28) 3. A monochromatic x-ray of an aluminum anode (hv=?1486.6 eV) is subjected to x-ray photoelectron spectroscopy (XPS) analysis by means of a thermodynamic K-? type x-ray photoelectron spectroscopy (XPS, Thermo Fisher Scientific, Waltham, MA, USA). An energy step is 0.100 eV, and on-state energy is 20.0 eV. Peaks were fitted by software XPS Peak.

(29) XPS representation results are as shown in FIGS. 3, 4 and 7A-7D and Tables 2 and 3.

(30) TABLE-US-00002 TABLE 2 Test results of AFM PET Sample name C 1s at % O 1s at % N 1s at % Si 1s at % Sample not subjected 68.21 28.03 2.77 to plasma treatment Sample subjected to 65.47 32.49 1.16 0.88 plasma treatment

(31) From FIGS. 3, 4 and 7A-7D and tables 2 and 3, it can be seen that a N 1 s element most varies, and an atomic concentration thereof is increased from 0% to 1.16%. The reason is that after plasma treatment, a small quantity of N is absorbed by a surface of a PET sample in a form of a CON group. At the same time, after plasma treatment, a content of a C is element is decreased, and a content of a 0 is element is increased. By fitting a C is spectrum of PET subjected to plasma treatment, it can be found that a bonding energy peak corresponds to O?CO (289.00 eV), COH/COOH (286.70 eV), CO (286.12 eV), CON (288.44 eV) and CC/CH (284.80 eV). A variation of chemical composition of C 1s is as shown in Table 3. Compared with a C is spectrum before plasma treatment, the novel spectrum shows that a large quantity of COH/COOH bonds appear after plasma treatment. It is indicated that after plasma treatment, a C?O bond is disconnected from a PET surface, and a new bond is formed. CO and CC/CH peaks shift rightwards (about 0.02 eV), and a O?CO peak shifts rightwards (about 0.11 eV). It is indicated that electron transfer occurs in a process of forming a COH/COOH bond in a sample subjected to plasma treatment, which means that a valence state of free ions on the PET surface varies. The existence of the COH/COOH bond greatly enhances adhesion of PET.

(32) When a O is spectrum is fitted, it is found that C?O and OH bonds appear after plasma treatment. After plasma treatment, C?O bonds and OH bonds appear on the surface of the sample, and there are more oxygen-containing groups. O?CO and OC peak positions slightly shift due to the formation of new chemical bonds. The OH bonds may come from water vapor, and in a plasma treatment process, the OH bonds are slowly formed on the PET surface. Accordingly, when a sample is treated with a plasma, CO.sub.2 in the air dissociates, thereby forming a C?O bond. The formation of two C?O bonds and a OH bond enhance wettability of the PET surface to different degrees. In general, plasma treatment of the PET surface will introduce a large quantity of free radicals. In addition, they further contribute to enhancement of an adhesive force between high-energy polymers and PET. When a Si 2p spectrum is fitted, it is found that a concentration of a Si 2p element is decreased from 2.77% to 0.88%. There is no Si element in PET, but in order to enhance lubricity between tapes, in factories, the PET surface is coated with Si. Therefore, after plasma treatment, Si element is reduced, lubrication between the tapes is reduced, and the adhesive force is further enhanced.

(33) TABLE-US-00003 TABLE 3 Variations of chemical composition of C 1s element Proportion (%) Proportion (%) Bonding of samples not of samples Possible energy subjected to subjected to functional (eV) plasma treatment plasma treatment groups 289.00 19.09 16.25 O?CO 286.70 14.69 COH/COOH 286.12 17.15 7.45 CO 288.44 4.77 CON 284.80 63.76 56.84 CC/CH

(34) 4. Test of bonding force:

(35) In order to test a bonding force between a fuel layer and a substrate layer of a target tape before and after plasma treatment, a bonding force of the target tape is measured by an electronic tensile tester QBD-100 (Jinan Fangyuan Test instrument Co., Ltd., Jinan, China), and a tensile speed is 0.5 mm/min A sample for a tensile test is a double-layer target tape having a diameter of 20 mm, and the double-layer target tape is composed of PET having a thickness of 100 ?m and GAP having a thickness of 100 ?m. Two identical copper tensile moldes are attached to two surfaces of a double-layer tape by a super glue (Adbest two-component epoxy adhesive manufactured by Shanghai Huayi Resin Co., Ltd.), stress results are as shown in FIG. 8A, and tensile samples are as shown in FIGS. 8B-8B. It can be seen from figures that tension stress without plasma treatment is about 9.84 MPa, which is as shown at a point A. After plasma treatment, the tension stress is about 22.98 MPa, which is as shown at a point B in the figure. The tension stress is increased by about 133.5%. By comparing joint surfaces after a mold is pulled apart, it can be found that GAP and PET are completely separated without plasma treatment, leaving no residual components. However, after plasma treatment, the GAP and PET are not completely separated. A small quantity of residue remained on the PET surface. It is indicated that an adhesive force of the PET surface after plasma treatment is remarkably enhanced.

(36) In order to compare variations of performance of a target tape before and after plasma treatment, variations of impulses of a single pulse of laser ablation are measured ten times by a torsional pendulum system. A laser pulse width is 200 ?s, an ablation pit interval is about 800 ?m, and an impulse of a single pulse is continuously measured ten times, and results are as shown in FIG. 9. In the figure, a dot curve is a result without plasma treatment, and an asterisk curve is a result after plasma treatment. It can be seen from the figure that impulses of a single pulse of a target tape subjected to plasma treatment is more stable and less volatile. An impulse value of the single pulse of the target tape not subjected to plasma treatment is remarkably decreased and is extremely unstable. The reason is that adhesion of the target tape not subjected to plasma treatment is not well, and GAP is separated from PET in a laser ablation process. There are two reasons for a decrease in the impulse values of the single pulse due to separation of GAP and PET. One reason is that separation of GAP and PET results in laser defocusing, which greatly reduces laser power density and ablation efficiency. Another reason is that after separation, there is a lack of a bottom support when a plume is sprayed, such that a force generated by laser ablation of the GAP may not fully transferred to the PET. Stability of impulses of a single pulse is the premise of ensuring thrust stability of a micro thruster for laser ablation. In a continuous ablation process, a separation phenomenon not only decreases mean thrust, but also leads to thrust instability, thus affecting mission execution of a micro-nano satellite.

(37) 5. Sectional views of an ablation pit before and after plasma treatment are observed by a scanning electron microscope (SEM).

(38) FIG. 10A is a sectional view of an ablation pit of a target tape not subjected to plasma treatment, and FIG. 10B is a sectional view of an ablation pit subjected to plasma treatment. A laser pulse width is 200 ?s. It can be seen from the figure that there is a large separation region around the ablation pit of the target tape not subjected to plasma treatment, while no separation phenomenon is found around the ablation pit after plasma treatment. It is indicated that an adhesive force between a fuel layer and a substrate of a target tape is remarkably increased after plasma treatment.

(39) What is described above is only several embodiments of the present disclosure, and is not intended to limit the present disclosure in any form. Although the present disclosure is disclosed above with preferred embodiments, it is not intended to limit the present disclosure. Any change or modification made by those skilled in the art using the technical content disclosed above without departing from the scope of the technical solution of the present disclosure is equivalent to an equivalent embodiment, and all fall within the scope of the technical solution.