铝合金焊前激光清洗工艺研究及接头性能评估

针对铝合金焊前激光清洗,以表面氧含量为指标,研究平均功率、扫描频率对清洗效果的影响,以表面硬度、表面耐腐蚀性评价其服役性能,最终获得高质量剥离铝合金表面氧化膜的工艺窗口,确定有损/无损激光清洗边界条件,对激光清洗与人工打磨进行全方位对比,最终显示两者的作用效果差异。结果表明,在平均功率125～175 W,扫描频率100～150 Hz范围内可实现铝合金氧化膜的高质量剥离;当激光清洗功率密度为(2.24～3.14)×10⁶ W/cm²时,可实现无损激光清洗,当激光功率密度>3.14×10⁶ W/cm²时,即为有损激光清洗;焊前进行激光清洗可全面提升焊缝质量,接头强度可达281.4 MPa,可有效替代人工打磨。     

铝合金表面有机污染物等离子体清洗机理及验证

针对惯性约束核聚变装置中铝合金零件表面的有机污染去除问题,提出大气常压等离子清洗方式。 通过有限元方法研究等离子清洗机理,并通过铝合金零件的清洗试验进行验证,从而实现聚变装置中机械零件的超洁净制造。 研究结果表明:通过建立等离子表面清洗的热力学耦合方程,仿真分析得到清洗应力随清洗距离的减小而增大, 随清洗速度和基体厚度的增大而减小。 通过试验验证了铝合金零件在等离子清洗后表面自由能增大,极性分量与色散分量都有所增加,并且在等离子清洗过程中清洗的距离比清洗速度对清洗效果影响更大,清洗距离为 5 mm 时最好。     

常压空气等离子处理对铝合金胶接接头强度的影响

为改善铝合金表面润湿性与胶接强度,采用常压空气射流等离子体对5052铝合金进行表面处理。通过接触角测试,表面自由能计算和胶接接头剪切强度测试表明处理时间对铝合金表面改性效果影响不大,随着处理距离减短,铝合金表面自由能、胶接接头强度均逐步提升。处理距离为5 mm时等离子处理铝合金获得最佳表面改性效果,铝合金胶接接头剪切强度由10.6 MPa提升至19.3 MPa,失效模式由界面失效转变为内聚失效。利用SEM,XPS,傅立叶变换红外光谱等检测手段分析不同处理距离对应表面理化特性的变化,结果表明:处理距离较远时,等离子体并未改变铝合金表面物理形貌,其主要改性效果体现为表面清洗;处理距离较近时,铝合金表面高温熔融产生复杂微结构的粗糙氧化层,同时氧化层表面吸附羟基等极性官能团,显著提升了其表面自由能与胶接强度。     

回火时间对BS960E钢快速加热淬火后组织与性能的影响

采用光学显微镜、扫描电镜、电子背散射衍射、能谱仪和X射线衍射等研究了回火时间对BS960E钢快速加热淬火后组织与性能的影响。结果表明：BS960E钢淬火后组织为板条状马氏体,其原始奥氏体平均晶粒尺寸为5.69μm,位错密度为4.02281×10¹⁵ cm^-2。随着回火时间的延长,马氏体板条结构逐渐分解;回火2 min时仍存在部分板条组织,有效晶粒尺寸(马氏体板条块)为2.47μm,位错密度急剧下降至9.48079×10¹⁴ cm^-2;回火15和30 min时马氏体板条开始粗化,小角度晶界密度占比降低,此时有效晶粒尺寸分别为2.57和2.59μm,位错密度分别为7.80957×10¹⁴和6.75406×10¹⁴ cm^-2;回火60 min时,马氏体板条块合并明显,大角度晶界密度及占比下降,有效晶粒尺寸粗化达到2.99μm,位错密度降低至5.19655×10¹⁴ cm^-2。碳化物的析出位置可分为...     

齿轮轴用40CrNiMo钢的表面热处理工艺研究

采用渗碳与氮碳共渗两种方法对40CrNiMo齿轮轴用钢进行了表面热处理,并根据钢表面硬度与渗透深度的结果对热处理工艺进行了优化。结果表明,适宜的氮碳共渗工艺为(520⁵60℃)×(4560℃)×(4⁶ h)。     

SmCo5纳米颗粒和纳米薄片的制备、结构和磁性能

采用表面活性剂增强高能球磨技术及颗粒清洗、分级筛选工艺,制备了具有较高矫顽力、颗粒尺寸分布狭窄的SmCo₅纳米颗粒与纳米薄片,利用XRD,SEM,TEM,激光粒径分析（LPSA）和振动样品磁强计（VSM）等手段分别对其相结构、微观形貌、颗粒尺寸分布及磁性能进行了表征.结果表明,平均颗粒尺寸分别为9.8和47.5 nm的SmCo₅纳米颗粒,其室温矫顽力分别为6.8×10⁴和7.3×10⁵A/m;SmCo₅纳米薄片的平均颗粒尺寸为1.4μm,平均厚度为75 nm,具有明显的c轴织构和较强的磁各向异性,其难磁化轴和易磁化轴上的室温矫顽力分别可达5.5×10⁵和1.6×10⁶A/m;SmCo₅纳米颗粒和纳米薄片的矫顽力表现出显著的颗粒尺寸依赖性.     

SmCo5纳米颗粒和纳米薄片的制备、结构和磁性能

采用表面活性剂增强高能球磨技术及颗粒清洗、分级筛选工艺,制备了具有较高矫顽力、颗粒尺寸分布狭窄的SmCo₅纳米颗粒与纳米薄片,利用XRD.SEM,TEM.激光粒径分析（LPSA）和振动样品磁强计（VSM）等手段分别对其相结构、微观形貌、颗粒尺寸分布及磁性能进行了表征.结果表明,平均颗粒尺寸分别为9.8和47.5 nm的SmCo₅纳米颗粒,其室温矫顽力分别为6.8×10⁴和7.3×10⁵A/n;SmCo₅纳米薄片的平均颗粒尺寸为1.4μm,平均厚度为75 nm,具有明显的c轴织构和较强的磁各向异性,其难磁化轴和易磁化轴上的室温矫顽力分别可达5.5×10⁵和1.6×10⁶A/m;SmCo₅纳米颗粒和纳米薄片的矫顽力表现出显著的颗粒尺寸依赖性.     

网电极沿面介质阻挡放电等离子体润湿性改性及清洗性能研究

目的 针对大气压等离子体装置存在的等离子体面积小、温度高及均匀性差等问题，研发一种网电极沿面介质阻挡放电装置和等离子体清洗平台。方法 通过静电场仿真和实验，优化装置的结构参数，通过分析放电波形探究装置的放电特性。最终确定网孔的对角线尺寸为6 mm，采用厚度为0.3 mm的云母片作为介质材料。通过清洗平台对涂有润滑油的玻璃表面和铝片表面进行清洗实验，并通过AFM、SEM、EDS对清洗前后的表面形貌和元素组分进行分析，探究等离子体清洗机理。结果 放电装置的电场强度和放电功率与网孔尺寸、介质材料的相对介电常数及放电电压呈正相关，与介质厚度呈负相关，放电装置的放电功率随着频率的增加呈先增大后减小的趋势，样品表面接触角随着电压的增大显著降低，随着放电频率的增加呈先减小后增大的趋势，并在5.29 kHz时达到最大放电功率(79 W)。通过试验得到了玻璃的最优清洗参数，电压峰值为11.52 kV，放电频率为5.29 kHz，处理距离为0.3 mm，处理时长为20 min，样品移动速度为2 mm/s。得到了铝片的最优清洗参数，放电电压峰值为11.60 kV，放电频率为5.29 kHz，处理距离为0.3 mm，处理时长为30 min，样品移动速度为2 mm/s。结论 从润湿性改变、光学显微镜照片、扫描电镜、原子力显微镜及表面元素的角度对样本表面的油污进行检验，经检验发现，样品表面的油污被去除，并显著改善了其润湿性。等离子体清洗以化学反应为主，可在不对表面造成损伤的前提下去除表面有机污染物。     

等离子体密度调控CrN薄膜结构改性Ti6Al4V双极板

目的 满足质子交换膜燃料电池双极板的使用要求。方法 采用热丝增强等离子体磁控溅射技术,通过改变热丝放电电流调控溅射等离子体密度,在Ti6Al4V（TC4）合金表面制备了氮化铬（CrN）薄膜。结果 随着热丝放电电流从0A增加至32A,真空腔内等离子体密度增强,-50V偏压下基体偏流密度从0.07 mA/cm²增至0.7 mA/cm²。CrN薄膜择优取向从低应变能的（111）转变成表面能更低的（200）择优取向。薄膜表面形貌由较疏松的四棱锥型转变成致密球形;无热丝时,CrN薄膜显示有铬的（110）衍射峰且铬原子数分数为52.16%,为富金属薄膜。热丝放电电流为16 A和32 A时,Cr N薄膜中的铬原子数分数分别降至50.79%和49.82%,且无Cr的衍射峰,即逐渐转变为贫铬。采用热丝辅助磁控溅射,将使氮气离化率增大,活性增强,引起薄膜贫铬。模拟双极板工作环境下,与TC4腐蚀电流密度1.5×10^-8 A/cm²相比,CrN薄膜的腐蚀电流密度由无热丝的3×10^-5 A/cm     

BOPET基镀铝薄膜静电场中表面吸附能力的研究

目的通过对一种双向拉伸聚酯(BOPET)基镀铝薄膜表面高压静电场中吸附能力的研究,找到提高高压静电提取灰尘足迹能力的途径。方法使用普通提取灰尘足迹用高压静电提取仪,对BOPET基镀铝薄膜表面施加高压静电场,控制电极与镀铝薄膜之间的距离,并采用不同粒径的Si O2颗粒对薄膜在静电场中的吸附能力进行表征。使用光学显微镜、电子显微镜、XRD分析技术及精密分析天平,对薄膜组织结构进行了研究,分析了在高压静电场环境中影响薄膜表面静电吸附能力的原因,并对引起变化的因素进行了讨论。结果 BOPET薄膜在静电场中会向下压紧物体表面,压紧和静电吸附力会随高压电极与镀铝薄膜表面距离的变化而不同。薄膜对颗粒的吸附能力与其带电量显著相关,随颗粒带电量的增加,薄膜表面的吸附能力明显增强。减小电极与薄膜之间的距离可增大薄膜附近的电场强度,是提高其表面静电吸附能力的有效途径。结论 BOPET基镀铝薄膜在高压静电场中会与其下的地面构成平板电容器。静电场中颗粒所带电荷的大小与其形状显著相关,微米颗粒所带电荷较多,从而在BOPET薄膜表面的吸附增重率最大。随电极与薄膜间距离的增加,电场强度降低,颗粒所带电量同时减小,吸附增重率迅速降低,15~10 mm的距离为电场对不同颗粒的静电吸附能力变化最大区间。     

Optical diffraction gratings embedded in BK-7 glass by low-density plasma formation using femtosecond laser

The optical embedded diffraction gratings with the internal refractive index modification in BK-7 glass plates were demonstrated using low-density plasma formation excited by a high-intensity femtosecond (130 fs) Ti: sapphire laser (λ_p=790 nm). The refractive index modifications with diameters ranging from 400 nm to 4 μm were photoinduced after plasma formation occurred upon irradiation with peak intensities of more than 1×10¹³ W/cm². The graded refractive index profile was fabricated to be a symmetric around the center of the point at which low-density plasma occurred. The maximum refractive index change (Δn) was estimated to be 1.5×10^?2. Several optical embedded gratings in BK-7 glass plate were demonstrated with refractive index modification induced by the scanning of low-density plasma formation.     

2024 aluminium alloy wettability and superficial cleaning improvement by air cold plasma treatment

2024 aluminium alloy is used for parts and structures which demand high-strength/weight ratio. In particular, Al2024 is, for its high specific strength and good chemical stability, a suitable material for aerospace application. Aluminium alloys are involved in corrosive phenomena when they are used in critical applications, such as the aeronautic ones. The solution commonly adopted to solve corrosive problems is to paint aluminium alloy surface including 2024 aluminium alloy which is the subject of this study. The applied paint film protects the aluminium alloy from corrosion. In order to improve the adhesion of the paint film it is necessary to pre-treat the manufactured surface. The objective of the pre-treatment is to develop a cleaned, uniform, wettable surface. Cold plasma is an efficient, economic and environmentally attractive alternative to the use of the traditional pre-treatment. This work aims to study the relationship between cold plasma and 2024 aluminium alloy wettability and cleaning. Surface samples have been analysed by: (i) standard procedure to measure the quantitative wettability; (ii) Energy Dispersive X-ray Spectroscopy or EDS to determine a quantitative measure of organic contaminant.This work demonstrates that air cold plasma treatment improves significantly wettability and cleaning of 2024 aluminium alloy surfaces both associated with pre-cleaning by MEK^® and without pre-cleaning by MEK^®: the wettability reducing has been greater than 70% and the contaminants reducing greater than 65%.     

Ageing effect in atmospheric plasma activation of paper substrates

This work concerns the ageing effect of the atmospheric plasma and corona treatments when used to treat paper substrates. Pigment coated and surface sized papers were modified using two types of atmospheric plasma equipment; one at the pilot scale and one at the laboratory scale. In addition, the plasma treatments were compared to conventional corona treatment. Surface energy was estimated by contact angle measurements and surface chemistry by X-ray photoelectron spectroscopy (XPS) as a function of the time during three months. The treatments increased surface energy and oxidation level of surface for both papers. The ageing effect could be detected only in the surface energy, whereas the oxidation level remained stable during the twelve weeks. The decay in surface energy was faster during the first weeks of storage and subsequently leveled off leading to a permanent change. The permanent change was explained as a contribution of oxygen containing polar molecular groups, which were detected by XPS. The ageing effect was suggested to originate from already existing polar molecular groups, which have rotated on the surface by plasma-related process and then rotate back into the material in time. A part of the decay was also explained by the plasma cleaning model, in which the ageing effect occurred through re-contamination. Paper is a multicomponent system, where the constituents that have the lowest surface energy were suggested to migrate to paper surfaces.     

The Kelvin probe technique for assessing efficiency of stearic acid removal from gold surfaces using atmospheric-pressure plasma

Plasma removal is an alternative cleaning method used to avoid effluents and volatile organic compounds resulting from the use of detergents and solvents. An innovative method to estimate residual stearic acid (C₁₈H₃₆O₂) after the atmospheric-pressure plasma cleaning process of a gold surface is presented. This method, based on surface potential measurement by a Kelvin probe, enables monitoring of treated samples. The Quartz Crystal Microbalance (QCM) technique is used as a reference technique to specify with precision both initial and residual stearic acid masses. Stearic acid remaining on gold surfaces is proportional to the time of exposure to plasma and initial contamination. Moreover, the results reveal that surface potential evolution post-plasma exposure is a function of residual stearic acid, whatever the degree of initial contamination.     

Performance improvement of ZnO film by room-temperature oxygen plasma pretreatment

The room-temperature oxygen plasma treatment before depositing ZnO films on nanocrystalline diamond substrates was studied. The nanocrystalline diamond substrates were pretreated in oxygen plasma at 50 W for 30 min at room temperature and then ZnO films were sputtered on diamond substrates at 400 W. The X-ray diffraction （XRD） patterns show that the c-axis orientation of ZnO film increases evidently after oxygen plasma pretreatment. The AFM and SEM measurements also show that the high c-axis orientation of ZnO film and the average surface roughness is less than 5 nm. The resistivity of ZnO films increases nearly two orders of magnitude to 1.04 - 10^8 Ω.cm. As a result, room-temperature oxygen plasma pretreatment is indeed a simple and effective way to improve the performance of ZnO film used in SAW devices by ameliorating the combination between diamond film and ZnO film and also complementing the absence of oxygen atoms in ZnO film.     

开放式低温等离子体对树脂基复合材料表面处理性能研究

目的 采用开放式低温等离子体对树脂基复合材料表面处理,研究其对树脂基复合材料粘接性能的影响。方法 运用响应曲面法,对开放式低温等离子体加工工艺与树脂基复合材料表面自由能交互性进行研究。采用接触角测量仪、扫描电子显微镜(SEM)、三维形貌仪、X射线光电子能谱仪(XPS)、傅里叶红外光谱仪(FT-IR)等仪器对开放式低温等离子体处理前后复合材料的接触角与表面能、表面微观形貌与表面粗糙度、表面化学成分进行分析,使用万能试验机对处理前后复合材料的粘接强度进行研究。结果 输入功率、喷枪距离与试样移动速度3个响应因子中,喷枪距离对试样表面能的影响最为显著,其次是试样移动速度与输入功率。当开放式低温等离子体加工工艺为P=800 W,d=11.8 mm,v=10 mm/s时,表面能最大,从24.8 mJ/m²增加到78.3 mJ/m²,表面粗糙度与未处理试样相比提高了约2.5倍。处理后试样表面的氧元素含量明显增加,氧元素主要以含氧官能团的形式存在,材料表面极性增加。开放式低温等离子体对树脂基复合材料处理后,粘接试样平均拉伸剪切强度从16.6 MPa增加到27.5 MPa,粘接强度提高了约65.7%,粘接接头破坏形式从界面破坏到材料基材破坏。结论 开放式低温等离子体对树脂基复合材料表面处理后,能够有效地增加其粘接强度,树脂基复合材料润湿性与表面能、表面粗糙度以及表面含氧官能团数量增加,是粘接强度提高的主要因素。     

ZM5镁合金无铬前处理化学镀镍层的性能

采用优化的Na4P2O7+Na2SO4+NaNO3体系的化学蚀刻无铬前处理化学镀镍工艺,在ZM5镁合金上制备Ni-P镀层。利用扫描电镜、能谱仪、X射线衍射仪分析镀层的微观形貌、成分和相结构。通过电化学方法和摩擦磨损试验评价了镀层的耐蚀性和耐磨性。结果表明:无铬前处理工艺制备的镀层中P的质量分数为12.90%。与ASTM标准的含铬前处理工艺得到的镀层的耐蚀性和耐磨性相比,无铬前处理得到的镀层的自腐蚀电位为-0.506V,腐蚀电流密度为2.132×10-6 A/cm2,接近ASTM工艺含铬前处理得到的镀层的耐蚀性能;同时其磨损率为3.056×10-4 mg/s,与ASTM工艺的1.778×10-3 mg/s相比,其抗摩擦磨损性能明显优于含铬前处理的镀层。无铬前处理化学镀镍显著提高了ZM5镁合金的耐蚀性和耐磨性。     

Reversible Polarization Recording in As<Subscript>2</Subscript>S<Subscript>3</Subscript>–Se Multilayer Nanostructures

Polarization holographic recording of diffraction gratings and their subsequent erasure have been investigated on As₂S₃–Se multilayer nanostructures. The work investigates how preexposure to actinic laser radiation up to complete photoinduced changes in the optical properties affects the formation of diffraction gratings in the studied structure. It is shown that the preexposure of an As₂S₃–Se multilayer nanostructure (MNS) leads to photobleaching, and the maximum achievable diffraction efficiency (DE) of 35% does not change; however, the required exposure value is increased. It is also shown that exposure using one laser beam results in complete erasure of the diffraction grating recorded up to the maximum. Seven recording–erasure cycles show that the kinetics of the increase in diffraction efficiency and its maximum value do not change, which indicates that the As₂S₃–Se multilayer structure is capable of reversible holographic recording under orthogonal circular polarization. Study of the gratings recorded with an atomic-force microscope shows that the main factor determining the diffraction efficiency value is modulation of the relief, the depth of which is greater than 200 nm.