Grain refinement with increasing magnetron discharge power in sputter deposition of nanostructured titanium aluminium nitride coatings

Nanostructured titanium aluminium nitride coatings were produced via magnetron co-sputtering. The results showed the significant effect of magnetron discharge power on structural refinement of the coatings. As the aluminium magnetron power increased from 1.5 to 6.0 W/cm², the average grain diameter of the coatings was reduced from ∼210 to ∼90 nm.     

Influence of Static Low Electromagnetic Field on Copper Corrosion in the Presence of Multispecies Aerobic Bacteria

The effects of low electromagnetic field(EMF)( B = 2 mT) on the corrosion of pure copper in the absence and presence of multispecies marine aerobic bacteria were investigated in this work. The results showed that EMF has an inhibitory effect on copper metals and decreases the corrosion rate of copper metals in sterile artificial seawater. However, microbiologically influenced corrosion of Cu was increased in the presence of electromagnetic field due to its effect on the biofilm morphology and structure. EMF reduced the growth rate of bacteria and decreased bacterial attachment, thereby forming a heterogeneous and non-stable biofilm on the Cu surface in the presence of EMF. Moreover, the biofilm was dispersed throughout the surface after 7 days, whereas the scattered bacteria were observed on the surface after 10 days. Confocal laser scanning microscopy images showed large and deep pits on the surface in the presence of EMF and confirmed the acceleration of Cu corrosion in the presence of EMF and multispecies bacteria. Furthermore, XPS and FTIR results demonstrated that the corrosion products and metabolic by-products were significantly changed in the presence of EMF.     

刻蚀工艺对四面体非晶碳膜生长及其性能的影响

目的研究不同等离子体刻蚀工艺对基体和四面体非晶碳膜(ta-C)的影响,并进一步考察不同电弧等离子体刻蚀时间对ta-C薄膜结构的影响。方法采用自主设计研制的45°单弯曲磁过滤阴极真空电弧镀膜设备,进行不同等离子体刻蚀以及ta-C薄膜的沉积。使用等离子体发射光谱仪表征离子种类及其密度,使用椭偏仪表征薄膜厚度,原子力显微镜表征刻蚀后的基体粗糙度,拉曼光谱仪和XPS表征薄膜结构,TEM分析薄膜的膜基界面结构。结果辉光刻蚀工艺中,作用的等离子体离子以低密度的Ar离子为主;而电弧刻蚀时,作用的等离子体离子为高密度的Ar离子和少量的C离子,并且能够在基体表面形成约15 nm的界面层,并实现非晶碳膜(a-C)的预沉积。随电弧等离子体刻蚀时间增加,ta-C薄膜的sp3含量有所降低。结论相比于辉光刻蚀,电弧刻蚀利于制备较厚的ta-C薄膜。这主要是因为电弧刻蚀时,基体表面形成良好的界面混合层,并预沉积了非晶碳膜,形成a-C/ta-C的梯度结构,有助于增强膜基结合力。     

Electronic,optical and thermoelectric properties of Ce3PdIn11 and Ce5Pd2In19: An ab initio study

Density functional calculations with Engel and Vosko generalized gradient approximation are applied to investigate the electronic, optical and thermoelectric properties of Ce₃PdIn₁₁ and Ce₅Pd₂In₁₉ compounds. Analysis of the calculated band structure of Ce₃PdIn₁₁ and Ce₅Pd₂In₁₉ demonstrates their metallic character. The calculated densities of states N(E_F) of Ce₃PdIn₁₁ and Ce₅Pd₂In₁₉ at the Fermi level are 19.60 states/eV and 33.50 states/eV, respectively. The bonding nature in these compounds is discussed via the calculated contour map of the charge density in (1 1 0) crystallographic plane. Imaginary parts of the complex dielectric function show considerable isotropy between 3 and 14 eV Ce₃PdIn₁₁ have large dielectric constant. Thermoelectric properties results reveal that both compounds possess high Seebeck coefficient and electrical conductivity at high temperature. This is the first quantitative theoretical prediction of the theremoelectric properties for these investigated compounds and still awaits experimental confirmations.     

Reducing the self-healing temperature of Ti2AlC MAX phase coating by substituting Al with Sn

In an effort to overcome the property degradation of Ti₂AlC MAX phase coating used in harsh environments, we fabricated a solid solution Ti₂(Al_0.6Sn_0.4)C coating with amount of Ti₅Sn₃ (20 wt.%) by a combined technique composing of magnetron sputtering and post-heat treatment. The cracks induced by Vickers indentation on coating surface were self-healed at 700 ℃, which is the lowest self-healing temperature among the Al-based MAX phase coatings till now. The structural evolution and kinetic diffusion revealed that the formation of SnO₂ is the key factor to achieve the crack self-healing at such a low temperature for Al-based MAX phase coatings. Additionally, the self-healed Ti₂(Al_0.6Sn_0.4)C coating exhibited better oxidation resistance compared to the unhealed one at 800 ℃. The results provide a novel and facile strategy to develop the protective MAX phase coatings with high performance at high temperature by partially substituting Al with Sn.     

多弧离子镀制备TiSiN-Cu涂层的结构和摩擦学性能

目的通过在TiSiN涂层中掺杂软金属Cu,提高TiSiN涂层的摩擦性能。方法采用多弧离子镀技术,在316L不锈钢基体上沉积TiSiN-Cu涂层。用扫描电子显微镜(SEM)观察涂层的表面形貌,用X射线光电子能谱仪(XPS)和X射线衍射仪(XRD)来分析涂层的元素组成和相组成,通过纳米压痕硬度测试和摩擦磨损实验,表征不同Cu含量TiSiN-Cu涂层的力学性能和摩擦学性能。结果 Cu含量对TiSiN涂层的结构、硬度和摩擦性能有明显影响。Cu在涂层中主要以单质形式存在,由于与空气接触,涂层表面有少量的CuO。随着Cu含量的增加,TiN的晶粒尺寸先减小后增加,硬度先升高后降低。在Cu原子数分数为6.28%时,硬度达到最大值29.26 GPa。在干摩擦条件下,TiSiN-Cu涂层的磨损率在Cu原子数分数为12.93%时达到最低,为6.65×10-7 mm~3/(N·m)。在海水环境下,涂层的磨损率较大。结论软金属Cu作为固体润滑颗粒可以明显改善Ti Si N涂层的干摩擦性能,在海水条件下,摩擦与腐蚀的交互作用加速了涂层材料的损耗。     

Effect of ball milling treatment on the microstructures and properties of Cr2AlC powders and hot pressed bulk ceramics

Ball milling was used on synthesized Cr₂AlC powders, and dense Cr₂AlC bulk ceramics with almost pure phase were fabricated by hot pressing these ball milled Cr₂AlC powders at 1300 °C for 2 h under 30 MPa. The phase compositions and the microstructures of powders and bulk ceramics were characterized. The mechanical properties and dislocation analysis of bulk ceramics were also investigated. Our results indicated that the grain size of powders became uniform and smaller after ball milling, which was also inherited in the bulk ceramics. Moreover, the mechanical properties of hot pressed Cr₂AlC ceramics, including flexural strength, fracture toughness, and Vickers hardness, significantly increased by using ball milled powders treated at speed 200 rpm. The organization of hexagonal dislocation networks during hot pressing and reduction of grain size both had a positive effect on improving mechanical properties.     

Impulse Excitation Technique IET as a non-destructive method for determining changes during the gelcasting process

Gelcasting is a good method for obtaining ceramic components with a pre-defined shape. From the point of view of the course of the ceramic casting process, a very important issue is the so-called idle time or gelation time whose measurement is usually based on determining changes in ceramic slurry viscosity by means of rheometers. However, searches are being continued to find methods which would have the least impact on the interactions between ceramic powder particles and the forming polymeric structure and would allow more time range to observe changes in gelcasting process compared to classic measurements of viscosity.In the article, based on measurements on Al₂O₃, ZrO₂ and SiC-based gelcasting systems with various water-soluble acrylic monomers, it has been demonstrated that such requirements may be fulfilled by IET (Impulse Excitation Technique).     

TC4钛合金表面Cr2AlC涂层的制备及高温氧化行为

目的为提高钛合金在高温条件下的服役性能,探索Cr_2AlC MAX相涂层对TC4钛合金高温氧化行为的影响。方法采用低温反应直流磁控溅射技术再经后续退火处理的方法,在TC4钛合金基体表面制备高纯度的Cr_2AlC MAX相涂层。利用X射线衍射仪、拉曼光谱仪、扫描电子显微镜和能谱仪,分析了Cr_2AlC涂层试样和TC4钛合金经750℃静态空气恒温氧化前后的相结构、组织形貌和组分,并采用分析天平测定了TC4钛合金和Cr_2AlC涂层试样在750℃静态空气中氧化后的氧化动力学曲线。结果经750℃空气中氧化10 h后,TC4钛合金表面形成厚度达13μm的疏松团絮状TiO_2和Al_2O_3混合物氧化膜。而Cr_2AlC涂层表面能够形成以α-(Al,Cr)2O3为主的致密氧化膜,可有效阻止氧元素向内扩散。Cr_2AlC涂层试样在750℃空气中氧化90 h后的氧化增重仅为无涂层TC4钛合金在750℃空气中氧化10 h后的6.6%。结论 Cr_2AlC涂层具有优异的抗高温氧化性能,能够明显提高TC4钛合金的使用温度,使其氧化增重速率大幅降低。     

镁锂合金腐蚀行为及干法镀膜防护工艺研究

目的利用PVD磁控溅射技术,在样品上沉积纯铝膜,以提高镁锂合金的耐腐蚀性能。方法采用动态极化曲线、交流阻抗方法研究镁锂合金在去离子水和3.5%Na Cl溶液两种介质中的电化学行为,并利用感应耦合等离子体发射光谱仪技术和荧光金相显微镜,分别测定合金的成分,分析微观组织结构。采用扫描电子显微镜和EDS能谱仪分析镁锂合金纯铝膜的组织形貌与结构成分。此外,采用电化学技术测试纯铝膜的保护行为。结果在3.5%Na Cl溶液中,镁锂合金的腐蚀电流密度比去离子水介质中的高约两个数量级,且腐蚀电位较负;交流阻抗结果显示,比去离子水中的阻抗模值低一个数量级,说明镁锂合金抗Cl?侵蚀的能力较差。通过磁控溅射技术,获得了厚度为4μm致密的纯铝膜。镀铝后,镁锂合金的腐蚀电流密度降低了约一个数量级,腐蚀电位正移,耐蚀性提高。结论致密的纯铝膜在3.5%Na Cl溶液介质中容易发生钝化,阻碍Cl?的扩散,进而提高了镁锂合金耐Cl?侵蚀性。