Continuous SiC fiber-reinforced titanium matrix composites (SiCf/Ti) have a wide range of applications in aerospace and other fields, but challenges related to processing quality and efficiency remain in machining the structural components. Femtosecond laser processing is an effective technique for high-efficiency and lowdamage machining of SiCf/Ti, but small heat losses and oxidation still damage the processed surface. To reveal ablation and surface morphology evolution mechanisms of SiCf/Ti, this paper conducted ablation experiments with different laser powers and number of scans, compared the height information of ablation position, surface morphologies, elemental distributions and compound compositions. The study found that due to different properties of fiber and matrix, selective ablation and non-synchronous removal occur between different components of composite material. The volume removal is positively correlated with laser power and number of scans. After femtosecond laser ablation, SiC fiber surface exhibits spore-like morphology, while Ti matrix shows scaly morphology. The response of SiC fibers involves "sublimation-expansion-solidification" process, which is suppressed by high or low energy levels. The oxide formation mechanism in fibers involves the generation and accumulation of SiO2, while in matrix, it involves the competition between the generation and removal of TiO2. The number of scans is decisive factor in controlling the uniformity of surface ablation. At 10 scans, fluctuation range of surface roughness is 0.731 mu m and element distribution is more uniform, enabling low-damage simultaneous removal of both fibers and the matrix. This paper provides valuable insights for laser ablation process of SiCf/Ti and promotes the engineering application of advanced material.

In this study, two superhydrophobic blade surfaces of propellers were prepared using nanosecond laser processing and superhydrophobic coating. Numerical calculations of the open water characteristics indicated that superhydrophobic propellers provide higher efficiency over the entire range of operating conditions. Towing tank tests showed that superhydrophobic propellers generate greater thrust but require more torque from an advanced coefficient of 0.3. The increased thrust was caused by the increased pressure differential between the pressure and suction sides. The change in torque was mainly attributed to the gradual loss of the air layer and the increased shape resistance of the rough structure. Within an advance coefficient of 0.3, the laser-processed superhydrophobic propeller exhibited a more apparent drag reduction effect, and the efficiency was improved by a maximum of approximately 2.8%. In contrast, the propeller with superhydrophobic coating has a stable drag reduction effect owing to the stable air layer on its surface during the entire testing process, with an average efficiency improvement of approximately 2.0%. The results confirmed that the superhydrophobic surface, especially the rough structure, significantly affected propeller efficiency. This research extends the practical engineering applications of superhydrophobic surfaces in vessel propulsion.

Purpose The purpose of this study is to process the wettability surface of the ZrO2 ceramics to improve their surface friction performance. Design/methodology/approach Microtexture was processed on the surface of ZrO2 ceramics using a femtosecond laser. The three-dimensional texture morphology, surface contact angle, friction curve and wear morphology were measured by the laser confocal microscope, the contact angle meter, the reciprocating friction and wear tester and the scanning electron microscope, respectively. Based on Wenzel and partial impalement models, a geometric model of micro pits is established to study the influence mechanism of micro pit depth, diameter and distribution density on wettability and to analyze the relationship between surface wettability and tribological properties. Findings The results show that changing the geometric characteristics of the texture will lead to a change in the solid-liquid contact mode, and then lead to a change of in the surface contact angle. Wettability is an essential factor that affects the reduction of surface friction. The construction of a reasonable texture can enhance the surface hydrophilicity, which is conducive to the formation of a lubricating film on the ceramic surface, thereby reducing abrasive and adhesive wear, and improving the wear resistance of the ZrO2 ceramic surface. Originality/value The results provide a theoretical reference for femtosecond laser surface texture wettability regulation and tribological performance improvement.

It is crucial to investigate the mechanism of ultrashort pulse laser processing of ZrO2 ceramics to improve its processing accuracy and efficiency. An ultrashort pulse laser was used to fabricate square grooves on the surface of ZrO2 ceramics. The depth, surface roughness, and surface topography of grooves were analyzed by the laser confocal microscope, optical profiler, and scanning electron microscope. The effects of different laser parameters on the material removal efficiency and processing quality of ZrO2 ceramics were studied. The results show that as the laser fluence increases, material removal efficiency first increases and then decreases, while the surface roughness first decreases and then increases. The heat accumulation effect is severe when using high repetition frequency, and the processed surface shows melt damage. As the pulse width increases from 390fs to 6ps, the ablation threshold increases from 1.28 J/cm(2) to 1.92 J/cm(2). However, the material removal efficiency decreases gradually. Furthermore, the material removal efficiency in burst mode significantly reduces due to the plasma shielding and redeposition of distinct granular deposits within the grooves. These findings can serve as a guide for controlling and optimizing the process parameters of an ultrashort pulse laser processing of ZrO2 ceramics.

Micromachining uniform features inside transparent materials is of great importance. The generation of highly uniform parallel laser beams based on spatial light modulators is a valid way to realize it. A movable magnifying optical feedback approach is proposed. By using a flip mirror and adjusting a movable stage, magnified 3D information such as energy and the position of the split individual parallel laser beams could be obtained and fed back for optimization. Thanks to this setup, active adjustment of holographic algorithm parameters for the energy uniformity and accurate temporal distribution of the parallel laser beams becomes possible. The feasibility and effectiveness of the proposed method are then demonstrated by laser scribing inside silica glass. We pave a way for uniform 3D laser manipulation and subtle microfabrication.

使用波长为1 030 nm飞秒脉冲激光在M35高速钢表面加工微凹坑阵列,运用光学显微镜、白光干涉仪和接触角测量仪分别测量样品表面的三维形貌和接触角,探究不同参数对样品表面形貌和接触角的影响规律.结果表明,随能量密度和扫描次数增加,微凹坑的半径和深度均增大,M35高速钢表面接触角减小,样品表面亲水性增大,微凹坑间距减小可提高M35高速钢表面的亲液性.试验结果可为高速钢表面润湿性的研究提供参考.

扩散冷却、射频激励的板条结构CO2激光器具有效率高、体积小和光束质量好的优势,在激光精密退火、工业加工等应用领域越来越被重视.高功率射频激励、扩散冷却板条CO2激光器在千瓦级及以上的CO2激光精密加工及微电子装备中占有重要地位,已成为高功率、高光束质量连续CO2激光器的主流发展方向.就CO2激光器技术发展,重点围绕射频驱动板条结构高功率CO2激光器技术的国内外研究动态进行了调研,梳理了技术发展阶段及应用情况,并对技术发展趋势进行了展望.

Objective Due to its excellent electrical insulation and hydrophobicity, silicone rubber has been widely used in outdoor power transmission lines. The superhydrophobic silicone rubber surface can be etched by a femtosecond pulse laser, which makes it possess an excellent self-cleaning effect. However, in practical applications, the performance and aging resistance of the superhydrophobic silicone rubber surfaces are still unclear due to the long-term exposure to the natural environments such as sunshine, rain, and high and low temperatures. Therefore, it is necessary to further study the aging resistance of the surface. In this paper, an artificially accelerated aging chamber is used to study the hydrophobicity stability of the superhydrophobic silicone rubber processed by a femtosecond laser. In order to understand the aging phenomenon of the superhydrophobic silicone rubber surfaces, the physical and chemical changes of the sample surface are detected by the analytical techniques. A simple and effective heat treatment method is adopted to quickly recover the hydrophobicity of the silicone rubber surface. This study has good guiding significance for the preparation of anti-aging silicone rubber surfaces and explains the change of surface hydrophobicity of superhydrophobic silicone rubbers after aging. Methods The silicone rubber surface sample is etched with a femtosecond laser at wavelength of 1030 nm and pulse duration of 480 fs. To evaluate the long-term performance of the superhydrophobic silicone rubber in the outdoor environment, the samples are tested in an artificial accelerated aging chamber equipped with two xenon lamps. A vacuum drying oven at 200 degrees C is used for the heat treatment of aged samples. The wettability of the surface is characterized by measuring the contact angle and rolling-angle of the sample surface with a contact angle measurement system. The morphology of the sample surface is detected by an optical interferometer and the scanning electron microscope (SEM). The chemical compositions of the sample surfaces are investigated by the attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR). Results and Discussions The superhydrophobic silicone rubber surface can be obtained by the femtosecond laser treatment. After aging for 700 h, the contact angle decreases to similar to 150 degrees, and the water droplets on the surface cannot roll. From the change of the contact angle, the silicone rubber sample with a 5.0 J.cm(-2) laser has the best hydrophobicity after aging for 700 h (Fig. 5). The experimental results show that the surface microstructure of the sample aggregates and gradually deteriorates, which may be due to the decomposition of the polymer chain triggered by the experimental irradiation (Fig. 8). The formation of more photoinduced hydrophilic species on the surface increases the adhesion of water droplets, which is what triggers the surface transition from the Cassie state to the Wenzel state. The microstructure of the sample with a 5. 0 J.cm(-2) laser has little change and the surface deterioration is not obvious. As a result of rain and sun exposure, the carbonyl degradation products appear on the surface (Fig. 9). The loss of hydrophobicity of the silicone rubber surface is caused by the increase of -OH groups. The silicone rubber with a 5.0 J.cm(-2) laser produces the least carbonyl degradation products, which is the reason for the best hydrophobicity of silicone rubber samples under this laser fluence after aging. The hydrophobicity of the aged silicone rubber surface is recovered after the heat treatment (Fig. 11). The reduction of hydrophilic OH groups on the surface of the silicone rubber and the change of microstructure are the reasons for the recovery of hydrophobicity of the silicone rubber surface. Conclusions The superhydrophobic surface is obtained by etching the silicone rubber with a femtosecond laser, and the contact angle increases from 110 degrees to 160 degrees. After the accelerated aging test for 700 h, the surface contact angles of superhydrophobic samples decrease from 160 degrees to 150 degrees, indicating that it has excellent aging resistance. The wettability of the silicone rubber is mainly related to the surface microstructure and chemical element compositions. Therefore, in order to analyze the reasons for the decrease of hydrophobicity, the white light interferometer is used to find that the roughness of the silicone rubber sample increases at the initial stage. However, after the further accelerated aging, the surface roughness of samples decreases and becomes stable after 210 h. The analysis of the surface microstructural morphology shows that the microstructure of the sample surface aggregates and deteriorates gradually when the accelerated aging experimental time reaches 700 h. The polymer chain may have been broken down by experimental irradiation. Fourier transform attenuated total reflection infrared spectroscopy is used to identify the chemical changes on the surfaces of silicone rubber samples before and after aging. It is found that some -CH3 groups are destroyed under the action of the radiation energy. The chemical groups on the surface of aging samples change obviously, and the increase of hydrophilic -OH groups on the surface causes the loss of hydrophobicity of silicone rubber surfaces. At the same time, the hydrophobicity of the aged silicone rubber surface is recovered quickly after heat treatment. Therefore, this study has good guiding significance for the preparation of anti-aging performance of silicone rubber surfaces, and provides a simple and effective heat treatment method that can quickly improve the hydrophobicity of aged surfaces.

During the laser surface texturing process, scanning overlap is usually misused, because it cannot only be dimple overlap, but also can be laser spot overlap. Experiments were conducted to investigate the relationship between laser spot overlap and dimple overlap during laser surface texturing. Moreover, the effect of dimple overlap on the laser textured microstructures, wettability, and corrosion performances of stainless steel was analyzed. The results have shown that, due to changing radiation conditions, the dimple diameter and dimple overlap varied in a non-linear way with the increase in laser spot overlap. Furthermore, the variation of dimple overlap rather than laser spot overlap had a direct effect on roughness, wettability, and corrosion resistance. When the dimple overlap was greater than 55%, the surface reached the superhydrophobic state and the maximum apparent contact angle was 162.6°. When the dimple overlap was 83.52%, due to passivation layer formed by laser remelting deposition and oxides compaction, corrosion current density was 2.8 × 10−8 A·cm−2, which was 4% of the original value. Consequently, it was determined that it is easier to control the surface roughness, wettability, and corrosion resistance via dimple overlap rather than laser spot overlap in laser surface texturing process.

采用纳秒脉冲激光对印制电路板表面的有机硅树脂三防漆进行清洗,考察了不同激光能量密度与激光脉冲宽度对印制电路板表面有机硅树脂的剥离效果.当输入的激光能量密度较低且激光脉冲宽度较大时,有机硅树脂发生局部热解,在与印制电路板接触的界面产生气化现象,使有机硅树脂涂层发生膨胀.随着激光能量密度的增大,有机硅树脂部分结构发生降解,有机硅树脂涂层形成鳞状裂纹.当激光能量密度为11.19 J/cm2且激光脉冲宽度为120 ns时,有机硅树脂处于由膨胀向裂解转变的临界状态,此时能够更轻易地从印制电路板表面剥离三防漆,并且对印制电路板基材无明显损伤.

Electronic ceramic substrates have been widely used in various markets, which include the automotive industry, electronics, aviation, and sensor due to their good thermal conductivity and thermal stability. The holes in ceramic substrates are very important for their application, many techniques are studied to drill holes of different sizes. This research presents the results of UV ultrashort pulse laser drilling of ceramic substrates with different laser parameters. Normally, the ultrashort pulse laser can be used to process materials due to its less heat-affected zone, so the heat-affected zone of the hole is also observed around the laser-drilled holes.

The surface wettability control of cemented carbide tools is beneficial to the improvement of tool life and surface quality of workpieces in wet cutting. To clarify the correlation between the surface topography and wettability, squared microdimples are fabricated on the cemented carbide surface using a femtosecond laser. The dependencies of the side length, the depth, and the distribution density of squared microdimples on the surface topography and contact angle are studied. As the average laser power, and the number of scanning passes, increase, both the side length and depth of the squared microdimples increase. The contact angle decreases from hydrophilic to superhydrophilic. Moreover, the roughness height parameters have a great influence on the surface wettability, the larger the surface arithmetic average height, the smaller the kurtosis, the larger the skewness, and the better the hydrophilicity. The results of the scanning electron microscope (SEM) and energy‐dispersive spectrometer (EDS) reflect that the changes in the micro–nano protrusions, carbon, and oxygen elements cause deviation between the calculated contact angle and the actual contact angle. The friction coefficient of textured tools is lower than that of untextured tools at high sliding speed. Reasonable design of surface texture accurately controls surface wettability.

Investigating the wettability of the tool surface made of cemented carbide is of great significance to improve its working life and quality. The micropit array was processed on the surface of cemented carbide YT15 by a 1064 nm femtosecond pulse laser. Then, the optical microscope, the optical profilometer, and the contact angle measuring instrument were applied to measure the surface morphology and the surface contact angle of micropits. The influence of different laser parameters on surface morphology and the surface contact angle was studied. The geometric morphology model of the micropit was established. The influence of the morphology of micropits on the surface contact angle is analyzed based on the Wenzel theory. The results show that the radius and depth of micropits have a positive correlation with the average laser power and scanning times. As the spacing increases, the surface roughness factor and the surface contact angle decrease. There is a strong correlation between the characterization parameters kurtosis, skewness, and surface wettability in a 3D height parameter system. The smaller the kurtosis, the greater the skewness and the better the surface hydrophilicity.

在WC粒径0.7～0.8 μm、质量分数91.5％～92.0％的Co-WC二元硬质合金上进行了恒定单脉冲能量下,不同填充间距和加工次数的皮秒脉冲激光加工工艺试验研究,发现在小于光斑宽度的填充间隔尺寸范围内,填充间隔增大,加工面呈现表面粗糙度降低的光整加工效果;填充间距减小,激光对材料的蚀除效果增加;加工次数越多,材料去除深度越大;加工次数持续增加,材料表面钝化失活,激光的蚀除作用减弱;通过对激光加工区域的残余应力检测,发现皮秒激光加工对硬质合金表面残余应力影响不明显;对硬质合金钻头副切削刃口进行脉冲激光刃口修磨,去除了砂轮修磨残留的微观缺口,获得了更好的刃口质量和前刀面表面质量.

研究氩气氛围下钛合金Ti6Al4V激光抛光作用机理对提高材料表面质量和使役性能具有重要意义.采用纳秒脉冲光纤激光器以弓字形扫描路径抛光8 mm×8 mm局部钛合金区域.运用偏光显微镜、光学表面轮廓仪观察抛光后材料表面形貌并测量材料表面粗糙度,研究不同平均功率、光斑重叠率、脉冲宽度、扫描次数及不同原始表面粗糙度对钛合金表面粗糙度的影响规律.通过全自动显微硬度仪、扫描电子显微镜、X射线衍射分析仪分析抛光后材料钛合金Ti6Al4V组织性能.试验结果表明:随着激光平均功率、光斑重叠率和扫描次数的增大,钛合金表面粗糙度先减小后增大.随着脉冲宽度的增加,钛合金表面粗糙度呈下降趋势.原始表面粗糙度越大,抛光后表面粗糙度缩减率越大;原始表面粗糙度越小,抛光后表面粗糙度越小.试验获得的最小钛合金表面粗糙度Ra=0.164 μm,表面粗糙度缩减率为60％,抛光后材料表面显微硬度相对于基体提高了6％.抛光后钛合金表面组织由白色等轴状转变为细针状马氏体.

在介绍SLM进行光束整形原理的基础上,分析了二元光栅、闪耀光栅和正弦光栅三种光栅的结构特性,并根据影响整形光束质量的性能指标,以方向光斑为例,设计了不同周期的相位掩模图.成像和加工试验表明,SLM上加载三种光栅形成的掩模图,均可以将高斯分布的圆形光斑整形为平顶的方形光斑,但闪耀光栅的整形效果明显优于另外两种光栅.在闪耀光栅周期为120 μm时,局部能量利用率达到91.86％,均方根误差为0.039,整形后光束具有较好的均匀性.

针对单光束激光加工QR二维码效率的不足,提出了基于空间光调制器的QR二维码并行加工方法.利用GS反馈算法生成了高均匀性的QR二维码多光束全息图,结合空间光调制器以及飞秒激光在不锈钢表面标刻出能被有效识别的QR二维码.研究了单脉冲能量、脉冲数量、离焦量以及光束均匀性对QR二维码加工质量的影响,通过试验得到了最优QR二维码并行加工工艺参数.

采用振镜进行加工的激光切割设备,为了提高切割精度,首先需要对振镜进行标定,通行的标定方法是使用振镜在金属片或其他刚性材料上切割出一组具有固定图案(通常被称作mark点)的阵列,然后用相机逐一读取该阵列中每个图案的具体位置,据此计算校正网格并实施校正.圆形和十字形是两种最常使用的mark点形状.对这两种mark点对振镜标定精度的影响进行了对比试验,结果表明,圆形mark点标定的精度更好.在平台重复定位标准差约为1 μm的情况下,圆形mark点标定后的振镜平均误差为1.99 μm,标准差为1.09μm;十字形mark点标定后的振镜平均误差为2.95 μm,标准差为 1.60 μm.

It is important to study the gradient wettability of a Si3N4 ceramic tool surface to improve the lubrication performance of cutting tools. A gradient microstructure was processed on the surface of Si3N4 ceramic using a femtosecond and a nanosecond laser. The effects of different laser fluences, scanning passes, and laser overlap rates on the surface roughness and the surface contact angle under two lasers were studied. The result shows that the surface roughness and surface contact angle processed by two lasers have a similar trend, however, the femtosecond laser requires lower energy. The surface roughness gradually increases with the increase of the laser fluence, the scanning passes, and the laser overlap rate. With the increase of the laser fluence and the scanning passes, the surface contact angle first increases and then decreases. However, with the increase of the laser overlap rate, the surface contact angle continues to decrease. By designing the surface roughness distribution reasonably, different gradient wettability surfaces can be obtained. The larger the gradient, the faster the droplet wetting speed. Through the friction test, the great effect and potential of gradient wettability surface on reducing the friction has been confirmed, which provides a new direction for the development of new ceramic tools.

利用紫外皮秒激光器对单晶硅材料进行切割实验研究,探讨不同激光能量密度、光斑重合度、切缝宽度及切割次数对切缝表面形貌和切割深度的影响.通过不同单脉冲能量的打孔实验测得在波长355 nm、脉宽12 ps的情况下,单晶硅的损伤阈值为3.22 J/cm2,并对最佳能量密度进行测试.实验结果表明,激光能量密度为2～4倍的损伤阈值、光斑重合度为50％～60％时可以获得良好的切缝效果且热影响区最小达到1.01 μm.切缝的最大切割深度由切缝宽度决定,与切割次数无关,实验测得的最大宽深比约为1∶5.