A multi-scale micro-nano structure laser shock preparation method based on water-restrained layer micro-nano inclusion doping

Abstract

The present application relates to the technical field of laser force effect micro-nano manufacturing, and particularly relates to a laser impact micro-nano structure preparation method based on a water constraint layer micro-nano inclusion doping. The method comprises the following steps: performing smoothing treatment on a material to be processed, then sequentially arranging an absorption layer and a micro-nano inclusion doping constraint layer to obtain a flattened plate material; performing surface laser impact treatment on the flattened plate material, and the method is completed; wherein, the preparation method of the micro-nano inclusion doping constraint layer is as follows: according to the micro-nano structure processing size and density requirements, different particle sizes and densities of micro-nano inclusions are added to the constraint layer medium. The present application realizes quantitative control of the turbidity degree of the water constraint layer by changing the particle size and density of the impurities in the water constraint layer; the particle size and density of the impurity particles in the water constraint layer affect the size and density of the laser impact pits and protrusions, thereby achieving the purpose of laser impact micro-nano structure preparation.

Description

Technical Field

[0001] This invention belongs to the field of laser force effect micro / nano manufacturing technology, specifically relating to a laser shock blasting method for fabricating micro / nano structures based on water-constrained layer micro / nano inclusions. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Micro / nanotechnology generally refers to the materials, design, manufacturing, measurement, control, and technologies for nanoscale / microscale products. Micro / nanostructure fabrication, as a crucial component of micro / nanotechnology, has received significant attention from researchers worldwide. Currently, common methods for micro / nanostructure fabrication include photolithography, self-assembly, vapor deposition, sol-gel methods, magnetron sputtering, and additive manufacturing. While these methods can produce high-precision, high-performance surface micro / nanostructures, many problems remain to be solved. For example, photolithography technology is mature and highly precise, but the equipment is complex and costly; high-precision additive manufacturing methods suffer from expensive equipment, high costs, low efficiency, and difficulty in mass production.

[0004] Compared to other micro / nanostructure fabrication methods, laser processing can obtain high-precision micro / nano composite structures on material surfaces with virtually no restrictions on material selection, making it a more controllable technology. Laser micro / nano processing typically utilizes the physical and chemical interactions between a high-energy laser beam and the material surface to fabricate micro / nano structures through melting, ablation, and induction. Currently, most laser micro / nano processing technologies rely on the thermal effect of lasers, inevitably leading to defects such as recast layer buildup, material delamination, heat-affected zones, and thermal cracks in the processed area. Therefore, exploring a low-damage laser micro / nano processing technology is of significant practical importance. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a method based on the principle of pulsed laser force effect, which modulates the micro-nano morphology of the target surface after laser shock by changing the doping degree of micro-nano inclusions in the water-constrained layer, thereby obtaining multi-scale micro-nano structures. This invention achieves quantitative control of the turbidity of the water-constrained layer by altering characteristics such as the particle size and density of impurities. When impurity particles in the water cause changes in the flat-top energy distribution of the laser beam, the plasma becomes unevenly distributed on the material surface. The presence of impurity particles leads to a significant reduction in laser shock pressure at the particle location, resulting in several randomly distributed irregular protrusions in the laser-shocked area, despite the overall depression. Based on these protrusions, micro-nano structures of different scales emerge within the pits on the material surface.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] Currently, pulsed laser shock blasting, which utilizes the laser force effect for surface processing, based on the heat-free pulsed laser shock method, has become a new direction for green micro-nano manufacturing.

[0008] Therefore, in a first aspect, the present invention provides a method for laser shock blasting fabrication of multi-scale micro / nano structures based on water-confined layer micro / nano inclusions, comprising:

[0009] The material to be processed is smoothed, and then an absorption layer and a micro-nano inclusion doping constraint layer are sequentially set to obtain a flattened sheet material.

[0010] The planarized sheet material is subjected to surface laser impact treatment to obtain the final product;

[0011] The method for preparing the inclusion-doped confinement layer is as follows: according to the micro-nano structure processing size and density requirements, micro-nano inclusions of different particle sizes and densities are added to the confinement layer medium.

[0012] In some embodiments, to prepare micro / nano structures of a certain shape on the surface of a sheet material by laser impact, the surface of the sheet material to be processed needs to be smoothed after the sheet material is determined. Specifically, the processing method includes, but is not limited to, mechanical grinding, polishing, etc., and the surface roughness of the material surface before laser impact should not exceed Ra0.01.

[0013] In some embodiments, the absorbing layer is made of black tape, black paint, or graphite. When a pulsed laser is applied to the absorbing layer, it generates high-temperature, high-pressure plasma within a very short time, forming a laser shock wave that acts as a driving force, causing the material to undergo high-strain-rate plastic deformation. In addition, the absorbing layer also protects the material from thermal effects.

[0014] In some embodiments, the medium of the constraint layer is a material into which impurities can be added and whose impurity distribution characteristics can be changed, commonly water or glass.

[0015] In some embodiments, the impurity particles are graphite or fine sand. The turbidity of the water-bound layer is controlled by adjusting the particle size and density of the impurity particles.

[0016] In some embodiments, impurity particles in the water-constrained layer are kept uniformly distributed. During the laser shock process, the water-constrained layer is sprayed onto the surface of the material to be processed. It is necessary to ensure that the flow rate of the liquid confinement layer is less than 10 mm / s to avoid the incorporation of air bubbles during the flow of the confinement layer.

[0017] In some embodiments, the size of the laser spot should be much larger than the size of the water confinement layer particles, on the order of mm, while the particle size of the inclusions within the confinement layer is on the order of μm or nm. Impurities in the confinement layer will not excessively consume the laser beam energy, allowing the plasma shock wave to induce the formation of pits on the material surface.

[0018] In some embodiments, the power density of the pulsed laser is greater than 0.1 GW / cm². 2 The laser power is selected based on the mechanical properties of the material to be processed, with specific values ​​depending on the pulse width, spot size, and laser energy. Furthermore, the laser power should be sufficient to create explosive plasma on the material surface.

[0019] In some embodiments, the laser beam energy distribution is a flat-top distribution; that is, the laser energy is the same at any position on the same cross section of the beam.

[0020] In some embodiments, a laser beam forming a square spot is used;

[0021] In some embodiments, the object of observation and evaluation is the size and density of the irregular protrusions at the bottom of the laser-induced pit.

[0022] More specifically, it includes the following steps:

[0023] (1) Pretreatment of materials to be processed: The surface of the micro-nano structure material to be manufactured is smoothed by mechanical grinding, polishing and other methods.

[0024] (2) Setup of the pulsed laser shock device: Before laser shock, an absorption layer and a constraint layer are applied to the surface of the material in sequence. The absorption layer is made of black tape, and the constraint layer is made of deionized water curtain with different degrees of turbidity.

[0025] (3) Preparation of inclusion-doped confinement layer: Graphite powder and other materials are selected as the material basis for laser energy loss. Powders of different particle sizes and densities are added to deionized water according to the micro-nano structure processing size and density requirements.

[0026] (4) Surface processing based on laser shock: Set the laser shock process parameters, perform laser shock treatment on the surface of the flattened sheet, observe the changes in surface micromorphology, and adjust the particle size and density of powder in the constraint layer as needed.

[0027] It should be noted that the technical solution of this invention takes the default use of a circular laser beam as an example.

[0028] In a second aspect, the present invention provides multi-scale micro / nano structures prepared by the above-described method.

[0029] A third aspect of the invention provides the application of a confinement layer doped with micro / nano inclusions in the fabrication of thermally-free and low-damage laser micro / nano fabrication.

[0030] Beneficial effects of the present invention

[0031] (1) The present invention utilizes the uneven energy distribution during the laser shock process to create micro-nano structures on the material surface or to control its surface roughness.

[0032] (2) The purpose of this invention is mainly achieved by controlling the laser shock confinement layer. The selected water confinement layer and the doped graphite and fine sand powder are all materials that are readily available and easy to obtain.

[0033] (3) This invention belongs to the category of cold working. The heat generated during the surface processing is absorbed by the absorption layer coated on the outer surface of the target material, and there is no heat-affected zone on the surface of the target material.

[0034] (4) Based on the surface strengthening effect of laser shock wave, the surface of the target material obtains a certain level of residual stress introduction and microstructure evolution while obtaining micro-nano structure.

[0035] (5) The method of the present invention is simple, practical and easy to promote. Attached Figure Description

[0036] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. Exemplary embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0037] Figure 1 This is a diagram of the apparatus for pulsed laser surface processing involved in the present invention;

[0038] Figure 2 This is a schematic diagram of the morphology within the laser-induced spot region using a confinement layer doped with impurity particles of different sizes, as described in this invention.

[0039] Among them, 1. a flat-topped laser beam; 2. a constraint layer; 3. a black adhesive absorption layer; 4. the material to be processed; 5. impurity particles in the constraint layer; 6. the phenomenon of the bottom of the pit in a spot area caused by the dispersion of laser energy by impurities: a. a schematic diagram of the longitudinal section micro-scale morphology of the pit in a spot area after laser impact when the constraint layer has no impurities; b. a schematic diagram of the longitudinal section micro-scale morphology of the pit in a spot area after laser impact when the constraint layer has a certain density of fine particulate impurities; c. a schematic diagram of the longitudinal section micro-scale morphology of the pit in a spot area after laser impact when the constraint layer has a certain density of coarse particulate impurities. Detailed Implementation

[0040] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0041] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are explanations of the present invention and not limitations thereof.

[0042] Laser shock equipment parameter adjustment: A circular spot laser beam is used, with a beam diameter of 2mm, laser energy of 6J, pulse width of 12ns, and pulse frequency of 1Hz. The laser beam energy distribution is flat-topped.

[0043] Unless otherwise specified, all the following embodiments use this laser shock process parameters.

[0044] Example 1:

[0045] A. Pretreatment of the material to be processed: The material to be processed is TC11 titanium alloy, and the sample size is a 10mm*10mm*10mm block. Mechanical grinding and polishing are used to smooth the surface until the surface roughness of the target material is no higher than Ra0.005. The laser is adjusted to better process the material. This step ensures that the laser beam is perpendicular to the material surface to maximize its energy.

[0046] B. Apply an absorbent layer to the material surface: Use 100μm thick black 3M tape and apply it tightly to the material surface. This step should be done slowly to prevent air bubbles from forming during application.

[0047] C. Adding a confinement layer: Prepare turbid water with an impurity volume concentration of 65% using deionized water and quartz material with a particle size of 1-50 μm. After stirring evenly, use this prepared water as the confinement layer for laser shock. Control the flow rate of the turbid water confinement layer to be less than 10 mm / s, the water flow width to be 15-30 mm, and the water curtain formed to be approximately 2 mm thick on the workpiece surface.

[0048] This process mainly requires covering the surface of the material with the treated water constraint layer onto the material with the already coated absorption layer, and the water curtain coverage area should be larger than the laser shock spot area.

[0049] D. Perform laser shock treatment: Adjust the laser parameters and perform laser shock treatment on the pretreated material.

[0050] E. Observation of the surface morphology of the material after treatment: Irregular protrusions appear on the surface of the treated material. The size and density of the protrusions are measured and characterized using a white light interferometer. The material surface exhibits a raised microstructure without thermally induced defects, with a size range of 30–100 μm.

[0051] Example 2:

[0052] A. Pretreatment of the material to be processed: The Ti60 titanium alloy is wire-cut into 5mm*10mm*10mm blocks, and its surface roughness is maintained at no higher than Ra0.001 by mechanical grinding and chemical polishing. The laser is adjusted to process the material. Because Ti60 is less hard than TC4, this step allows the laser beam to be tilted, maintaining a 30° angle with the axis of the material to be impacted, in order to reduce the incident energy input.

[0053] B. Applying the Absorbent Layer: Black paint is selected as the absorbent layer. The black paint is evenly sprayed onto the surface of the material to be processed.

[0054] C. Preparation of the confinement layer: A cloudy glass with an impurity volume concentration of 70% was prepared using pure K9 glass and graphite powder with a particle size of 100–1000 μm. This cloudy glass was then used as the confinement layer for laser shock. The thickness of the prepared cloudy glass confinement layer was 2 mm.

[0055] D. Perform laser shock treatment: Adjust the laser parameters and perform laser shock treatment on the pretreated material.

[0056] E. Observation of the surface morphology of the material after treatment: Irregular protrusions appeared on the surface of the treated material. The size and density of the protrusions were measured and characterized using a laser confocal microscope. The material surface exhibited a raised microstructure without thermally induced defects, with a size range of 300–2000 μm.

[0057] Comparative example:

[0058] A. Pre-treatment of the material to be processed: The TC4 titanium alloy is wire-cut into 10mm*10mm*10mm blocks, and its surface roughness is maintained at no higher than Ra0.001 by mechanical grinding and chemical polishing. The laser is adjusted to better process the material to be processed. In this step, the laser beam should be perpendicular to the material surface to maximize its energy on the material surface.

[0059] B. Apply an absorbent layer to the material surface: Use 100μm thick black 3M tape and apply it tightly to the material surface. This step should be done slowly to prevent air bubbles from forming during application.

[0060] C. Adding a constraint layer: Deionized water is used as the constraint layer for laser shock. The flow rate of the deionized water constraint layer is less than 10 mm / s, the water flow width is 15-30 mm, and the water curtain formed is approximately 2 mm thick on the workpiece surface.

[0061] D. Perform laser shock treatment: Adjust the laser parameters and perform laser shock treatment on the pretreated material.

[0062] E. Observation of the surface morphology of the material after treatment: Irregular protrusions appeared on the surface of the treated material. The size and density of the protrusions were measured and characterized using a laser confocal microscope. No surface roughness or microscopic morphology was observed on the material surface.

[0063] It should be noted that if the flat-top laser beam is obstructed in its propagation path, energy loss will occur. Because the impact force on the energy loss area is smaller than in other areas, the deformation in the energy loss area is also smaller, specifically manifesting as a slight bulge in the overall concave shape. The larger the impurity particles in the constraint layer, the greater the energy loss of the flat-top laser at the dopant site, and the larger the bulge at the bottom of the impacted pit. Similarly, the higher the density of impurity particles in the constraint layer, the more energy is lost from the flat-top laser, and the greater the density of the bulge at the bottom of the impacted pit. This achieves the goal of controlling the microstructure of the laser-shocked material surface. Therefore, by analogy... Figure 2 In example 1, 'a' is analogous to 'a'. Figure 2 b in Example 2 is analogous Figure 2 c in the text.

[0064] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A laser shock lithography method for fabricating multi-scale micro / nano structures based on water-constrained layer micro / nano inclusions, characterized in that, include: The material to be processed is smoothed, and then an absorption layer and a micro-nano inclusion doping constraint layer are sequentially set to obtain a flattened sheet material. The planarized sheet material is subjected to surface laser impact treatment to obtain the final product; The method for preparing the inclusion-doped confinement layer is as follows: according to the micro-nano structure processing size and density requirements, micro-nano inclusions of different particle sizes and densities are added to the confinement layer medium. The impurity particles are graphite or fine sand; the size of the laser spot is larger than the size of the water-constrained layer particles, on the order of mm; the particle size of the inclusions in the confinement layer is on the order of μm or nm. The presence of impurity particles leads to a significant reduction in laser shock pressure at the particle location. The laser shock area exhibits several randomly distributed irregular protrusions in the overall concave state. Based on these protrusions, micro-nano structures of different scales appear inside the pits on the material surface.

2. The laser shock blasting fabrication method for multi-scale micro / nano structures based on water-constrained layer micro / nano inclusions as described in claim 1, characterized in that, The smoothing process includes: mechanical grinding and polishing; Alternatively, the surface roughness of the material to be processed before laser impact does not exceed Ra0.

01.

3. The laser shock blasting fabrication method for multi-scale micro / nano structures based on water-constrained layer micro / nano inclusions as described in claim 1, characterized in that, The absorbent layer is made of black tape, black paint, or graphite.

4. The laser shock blasting fabrication method for multi-scale micro / nano structures based on water-constrained layer micro / nano inclusions as described in claim 1, characterized in that, The medium of the constraint layer is a material in which impurities can be added and the distribution characteristics of the impurities can be changed. Alternatively, the medium of the constraint layer may be water or glass.

5. The laser shock blasting fabrication method for multi-scale micro / nano structures based on water-constrained layer micro / nano inclusions as described in claim 1, characterized in that, Impurity particles in the water-constrained layer are kept uniformly distributed, and the water-constrained layer is sprayed onto the surface of the material to be processed during the laser shock process; Furthermore, the flow rate of the liquid confinement layer is less than 10 mm / s.

6. The laser shock blasting fabrication method for multi-scale micro / nano structures based on water-constrained layer micro / nano inclusions as described in claim 1, characterized in that, The power density of pulsed lasers is greater than 0.1 GW / cm². 2 ; Alternatively, the laser beam energy distribution may be a flat-top distribution; Alternatively, a laser beam that forms a square spot can be used; Alternatively, the object of observation and evaluation is the size and density of the irregular protrusions at the bottom of the laser-induced pit.

7. The multi-scale micro / nano structures prepared by the method according to any one of claims 1-6.

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