Method for Synchronously Improving Mechanical and Optical Properties of Reaction-Sintered Silicon Carbide by Laser Irradiation
By using nanosecond laser irradiation in a nitrogen atmosphere to form micro-nano structures and silicon-based nitrides, the problem of improving the surface hardness and reflectivity of RB-SiC was solved, achieving both increased hardness and reduced reflectivity, thus broadening its application in the optical field.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- JILIN UNIVERSITY
- Filing Date
- 2024-06-27
- Publication Date
- 2026-05-26
AI Technical Summary
Existing technologies have not been able to effectively improve the surface hardness of reaction-bonded silicon carbide (RB-SiC) and reduce its reflectivity simultaneously, which limits its application in the optical field.
The RB-SiC surface was treated with nanosecond laser irradiation in a nitrogen atmosphere. By controlling the laser parameters, micro-nano structures and silicon-based nitrides were formed, which improved the surface hardness and reduced the reflectivity.
Laser irradiation increases the surface hardness of RB-SiC by 44.6% and reduces its reflectivity by 95.2%, significantly improving its photoelectric conversion efficiency.
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Figure CN118771908B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for simultaneously enhancing the mechanical and optical properties of reaction-sintered silicon carbide (RB-SiC) through laser irradiation, belonging to the field of ceramic material surface modification technology. This invention can simultaneously increase the surface hardness and decrease the reflectivity of RB-SiC, facilitating its practical application as a surface functional material. Background Technology
[0002] Reactive sintered silicon carbide (RB-SiC) is a promising semiconductor material composed of hard silicon carbide particles and a brittle silicon matrix. Its excellent chemical resistance, outstanding wear resistance, and high rigidity have led to its widespread application in various mechanical devices. Furthermore, RB-SiC possesses excellent photoelectric properties, superior oxidation resistance, and outstanding thermal stability, making it a potential candidate for applications in optics, such as solar cells and ultraviolet optoelectronic devices. However, its relatively low photoelectric conversion efficiency hinders its widespread use in optics. Additionally, RB-SiC inevitably experiences wear and damage during practical use; therefore, further improvements in its surface hardness are necessary to enhance its applicability.
[0003] Studies have shown that fabricating micro- and nanostructures on material surfaces can significantly reduce surface reflectivity, thereby improving photoelectric conversion efficiency. For example, in the 2013 issue of *Solar Energy Materials and Solar Cells*, Volume 108, pp. 93-97 (Fabrication of micro-nano surface texture by CsCl lithography with antireflection and photoelectronic properties for solar cells), Liu et al. fabricated cone and nanopillar array structures on silicon surfaces using a combination of self-assembly photolithography and dry etching. This reduced the surface reflectivity of silicon from over 35% to below 5% in the 400-1000 nm wavelength range, thus improving its photoelectric conversion efficiency. Furthermore, laser nitriding has been widely used to enhance the hardness of material surfaces. For example, in the 2019 issue of *Optics & Laser Technology*, Volume 116, pp. 305-314 (Effect of laser-assisted nitriding with a high-power diode laser on surface hardening of aluminum-containing martensitic steel), Ahjin Sim et al. prepared plate-like micro / nanostructures mainly composed of aluminum-based nitrides (AlN) on the surface of AISIP21 through continuous laser ablation in a nitrogen atmosphere, increasing the surface hardness by approximately 40%. Therefore, laser irradiation in a nitrogen atmosphere is an effective method for simultaneously improving surface hardness and constructing micro / nanostructures. However, to date, no reports have described how this method can simultaneously improve the surface hardness and reduce the reflectivity of RB-SiC. Therefore, it is necessary to develop a method for simultaneously improving the mechanical and optical properties of reactive-sintered silicon carbide through laser irradiation. Summary of the Invention
[0004] The technical problem to be solved by this invention is to provide a method for simultaneously enhancing the mechanical and optical properties of reaction-sintered silicon carbide (RB-SiC) by laser irradiation. This method utilizes nanosecond lasers with different laser parameters to irradiate the RB-SiC surface, resulting in surfaces with different micro / nano structures and silicon-based nitride contents. Adjusting the silicon-based nitride content can increase the surface hardness of RB-SiC, with a maximum increase of up to 44.6%. Furthermore, the abundant formation of silicon-based nitrides with high refractive index and unique micro / nano structures reduces the surface reflectivity of RB-SiC from over 20.8% in the 200-2500 nm wavelength range to 1%, a reduction of 95.2% compared to the original surface.
[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:
[0006] A method for simultaneously enhancing the mechanical and optical properties of reaction-sintered silicon carbide through laser irradiation includes the following steps:
[0007] (1) The RB-SiC surface was ultrasonically cleaned for 30 minutes, then mechanically ground and polished to obtain a mirror surface. Finally, it was wiped with alcohol and left to stand at room temperature for 5 minutes to obtain a clean and dry RB-SiC surface.
[0008] (2) Under a nitrogen atmosphere, the RB-SiC surface was irradiated with nanosecond lasers using different laser parameters to obtain surfaces with different micro / nano structures and varying silicon-based nitride contents. The micro / nano structures were formed by recasting molten material in the molten pool under the combined effects of recoil pressure, plasma effect, and Marangoni effect. The formation of the silicon-based nitrides can be attributed to the chemical reaction between molten Si or Si vapor and nitrogen. Adjusting the silicon-based nitride content can increase the surface hardness of RB-SiC, with a maximum increase of 44.6%. Furthermore, the formation of silicon-based nitrides with high refractive index and unique micro / nano structures reduced the surface reflectivity of RB-SiC from over 20.8% to 1% in the 200-2500 nm wavelength range, a reduction of 95.2% compared to the original surface.
[0009] Furthermore, the surface roughness of RB-SiC after mechanical polishing in step (1) is below 100 nm.
[0010] Furthermore, the laser irradiation parameters mentioned in step (2) include: a laser wavelength of 1064 nm, a frequency of 700 kHz, a pulse width of 7 ns, and a Gaussian distribution of laser energy.
[0011] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:
[0012] Nanosecond laser irradiation of RB-SiC surfaces under a nitrogen atmosphere introduces micro / nano structures and silicon-based nitrides. During the fabrication process, the content of silicon-based nitrides and the surface microstructure can be controlled by altering the laser irradiation parameters, thereby simultaneously increasing the surface hardness and decreasing the reflectivity of RB-SiC. Laser irradiation can increase the surface hardness of RB-SiC by 44.6% compared to the original surface, and reduce its surface reflectivity by 95.2%. Furthermore, the fabrication method of this invention has advantages such as simple operation, high efficiency, and low cost. Attached Figure Description
[0013] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate the invention and are used to explain it, but do not constitute an undue limitation of the invention.
[0014] Figure 1 This is a schematic diagram of the nanosecond laser processing system of the present invention.
[0015] Figure 2 The average hardness and light reflectance of the surface after irradiation with a nanosecond laser with a power of 7.6 / 14.7 / 22.0W under a nitrogen atmosphere, compared with the original surface.
[0016] Figure 3 The Fourier transform infrared (FTIR) spectra of the surface after irradiation with a nanosecond laser at a power of 14.7 / 22.0W under a nitrogen atmosphere and the original surface are the results of the present invention.
[0017] Figure 4 The SEM morphology, three-dimensional morphology, and cross-sectional profile curves of the surface after irradiation with nanosecond lasers at laser powers of 7.6 / 14.7 / 22.0W under a nitrogen atmosphere according to the present invention. Detailed Implementation
[0018] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.
[0019] The method for simultaneously enhancing the mechanical and optical properties of reaction-sintered silicon carbide by laser irradiation according to the present invention specifically includes the following steps:
[0020] (1) The RB-SiC surface was ultrasonically cleaned for 30 minutes, then mechanically ground and polished to obtain a mirror surface. Finally, it was wiped with alcohol and left to stand at room temperature for 5 minutes to obtain a clean and dry RB-SiC surface.
[0021] (2) Under a nitrogen atmosphere, the RB-SiC surface was irradiated with nanosecond lasers using different laser parameters to obtain surfaces with different micro / nano structures and varying silicon-based nitride contents. The micro / nano structures were formed by recasting molten material in the molten pool under the combined effects of recoil pressure, plasma effect, and Marangoni effect. The formation of the silicon-based nitrides can be attributed to the chemical reaction between molten Si or Si vapor and nitrogen. Adjusting the silicon-based nitride content can increase the surface hardness of RB-SiC, with a maximum increase of 44.6%. Furthermore, the formation of silicon-based nitrides with high refractive index and unique micro / nano structures reduced the surface reflectivity of RB-SiC from over 20.8% to 1% in the 200-2500 nm wavelength range, a reduction of 95.2% compared to the original surface.
[0022] Furthermore, the surface roughness of RB-SiC after mechanical polishing in step (1) is below 100 nm.
[0023] Furthermore, the laser irradiation parameters mentioned in step (2) include: a laser wavelength of 1064 nm, a frequency of 700 kHz, a pulse width of 7 ns, and a Gaussian distribution of laser energy.
[0024] Example 1:
[0025] A 1 mm thick RB-SiC sample was selected, and its surface was irradiated with nanosecond lasers with different laser parameters. The implementation process and beneficial effects of the present invention are further illustrated by the following examples.
[0026] Figure 2 The average hardness of the RB-SiC surface after 10 nanoindentation tests following laser irradiation at a laser scanning speed of 10 mm / s, a repetition frequency of 700 kHz, a pulse width of 7 ns, and laser power of 7.6 / 14.7 / 22.0 W, as well as the light reflectance of the surface in the wavelength range of 200-2500 nm, are shown. It can be seen that when the indentation load is 150 mN, as the laser power increases from 7.6 W to 22.0 W, the average hardness of the laser-irradiated surface decreases from 29.90 GPa to 22.26 GPa, but remains higher than the original average surface hardness (20.11 GPa), with an increase of 10.6-44.6%. This indicates that controlling the laser power during laser nitriding of the RB-SiC surface can significantly improve its surface hardness. Furthermore, the original surface reflectivity was above 20.8%, and as the laser power gradually increased to 22.0W, the reflectivity of the laser-irradiated surface gradually decreased to about 1%, meaning that the reflectivity of the laser-irradiated surface was reduced by 95.2% compared to the original surface. Combining the above results, it can be concluded that laser nitriding can simultaneously improve the surface hardness of RB-SiC and reduce the surface reflectivity of RB-SiC.
[0027] Figure 3 The Fourier Transform Infrared (FTIR) spectra of the RB-SiC surface after laser irradiation at a scanning speed of 10 mm / s, a repetition rate of 700 kHz, a pulse width of 7 ns, and a laser power of 14.7 / 22.0 W are shown, comparing the original surface with the irradiated surface. It can be seen that the Si-N intensity detected on the laser-irradiated surface increases with increasing laser power, indicating that more silicon-based nitrides are introduced into the surface under a nitrogen atmosphere. Since silicon-based nitrides are harder than the silicon matrix and have a higher refractive index, this also explains the increase in surface hardness and decrease in reflectivity after laser irradiation.
[0028] Figure 4The SEM morphology, 3D morphology, and cross-sectional profile of the RB-SiC surface obtained after laser irradiation under the conditions of a laser scanning speed of 10 mm / s, a repetition frequency of 700 kHz, a pulse width of 7 ns, and laser power of 7.6 / 14.7 / 22.0 W are shown. It can be seen that laser irradiation in a nitrogen atmosphere induces dendritic structures, microconical structures, and network structures on the RB-SiC surface. These micro / nanostructures prevent the incident light beam from escaping, thus causing more light beam to dissipate within the micro / nanostructures, which is an important reason for the decrease in surface reflectivity after laser irradiation.
[0029] The results from the examples demonstrate that the method proposed in this invention for simultaneously enhancing the mechanical and optical properties of reactive-sintered silicon carbide (RB-SiC) through laser irradiation, using nanosecond pulsed lasers in a nitrogen atmosphere, introduces micro / nano structures and silicon-based nitrides onto the laser-irradiated surface, simultaneously achieving an increase in surface hardness and a decrease in reflectivity. This method is applicable to the simultaneous improvement of the mechanical and optical properties of RB-SiC samples of different sizes and shapes, thereby enhancing their applicability.
[0030] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Those skilled in the art will recognize that various modifications and variations can be made without departing from the spirit and scope of the invention. Any modifications, equivalent substitutions, and improvements made to the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for simultaneously enhancing the mechanical and optical properties of reactive sintered silicon carbide by laser irradiation, characterized in that, The method includes irradiating reaction-sintered silicon carbide (RB-SiC) with nanosecond pulsed lasers under a nitrogen atmosphere to introduce micro / nano structures and silicon-based nitrides. By changing the laser irradiation parameters, different types of micro / nano structures are induced to form, and the content of silicon-based nitrides is controlled, thereby regulating the surface hardness and reflectivity of RB-SiC. Specific steps include: (1) The RB-SiC surface was ultrasonically cleaned for 30 minutes, then mechanically ground and polished to obtain a mirror surface. Finally, it was wiped with alcohol and left to stand at room temperature for 5 minutes to obtain a clean and dry RB-SiC surface. (2) Under nitrogen atmosphere, the RB-SiC surface was irradiated with nanosecond laser with different laser parameters to obtain surfaces with different micro-nano structures and different silicon-based nitride contents. The micro-nano structures were formed by recasting molten material in the molten pool under the combined action of recoil pressure, plasma effect and Marangoni effect. The silicon-based nitrides were formed by the chemical reaction between molten Si or Si vapor and nitrogen. The silicon-based nitride content was adjusted to increase the surface hardness of RB-SiC, with a maximum increase of 44.6%. After laser irradiation, the surface reflectivity of RB-SiC decreased from 20.8% to 1% in the wavelength range of 200-2500nm, which was 95.2% lower than that of the original surface.
2. The method for simultaneously enhancing the mechanical and optical properties of reactive sintered silicon carbide by laser irradiation according to claim 1, characterized in that: In step (1), the surface roughness of the RB-SiC after mechanical grinding and polishing is below 100 nm.
3. The method for simultaneously enhancing the mechanical and optical properties of reactive sintered silicon carbide by laser irradiation according to claim 1, characterized in that: In step (2), the laser irradiation parameters include: laser wavelength of 1064nm, frequency of 700kHz, pulse width of 7ns, and laser energy distribution of Gaussian distribution.