碳离子注入对硅片微摩擦学行为的影响

对单晶硅片进行不同剂量的碳离子注入,测量碳离子注入前后硅片的纳米硬度、弹性模量、硅表面与探针之间的摩擦系数和划痕深度以及硅片与Si3N4球的摩擦磨损,研究试样在过程中摩擦系数及磨损量的变化.结果表明,碳离子注入可能导致硅片表面结构的改变,从而影响了力学性能,但改善了微摩擦学特性.碳离子注入剂量为2×1015 ions/cm2时硅片的纳米硬度和弹性模量都明显降低,但其划痕摩擦系数和划痕深度均大于未注入硅片;碳离子注入后硅片的减摩效果和耐磨性能在小载荷下得到了大幅度提高,当载荷达到一定值后,摩擦系数迅速增加并产生磨损痕迹.其磨损机制在小载荷下以粘着磨损为主,在大载荷下以材料的微疲劳和微断裂为主.     

Mo+C双元离子注入65Nb钢表面的研究

利用 MEVVA源引出 Mo离子和 C离子 ,对 65Nb钢进行了不同剂量的离子注入 ,通过硬度测量、XRD、AES等方法研究了注入前后 65Nb钢改性层的性能、成分及相组成的变化。试验发现 Mo+ C双元离子注入 ,可在 65Nb钢注入层形成弥散的 Fe2 Mo C相 ,这是使该种基体钢经离子注入后表面硬度显著提高的重要原因。     

碳离子注入能量对硅表面摩擦性能的影响

以不同能量的碳离子注入方法得到的单晶硅片作为研究对象,利用原位纳米力学测试系统对其纳米硬度和弹性模量进行测定,在UMT-2型摩擦试验机上进行摩擦试验,利用S-3000N型扫描电镜表征其磨损后的磨痕形貌.结果表明,碳离子注入后硅片的纳米硬度和弹性模量发生变化,注入后硅片的的减摩效果和耐磨性能在0.1～0.3N载荷下得到了大幅度提高.注入前单晶硅片的磨损机制在0.1N载荷下以粘着磨损为主,在0.6N载荷下以疲劳剥落为主;注入后单晶硅片的磨损机制以粘着磨损为主.     

硼离子注入对三维C／C复合材料氧化性能的影响

介绍一种加入了高能硼离子的三维Ｃ／Ｃ复合材料。用热解分析法可研究未处理过的或已处理过的复合材料的氧化动力学。用次价离子质谱测定法，Ｘ射法光电子光谱测定法和螺旋扫描光谱测法进行化学分析。用扫描电镜观察氧化表面的组织结构。加入硼离子使初始氧化温度从５５０℃提高到７００℃，并将低温氧化速率降低了一半。硼抑制机理似乎是氧化硼和电子转移所形成的一种特殊的组合阻力。     

低能载条件下C/C复合材料滑动摩擦磨损性能

采用MM-200型环-块摩擦磨损试验机测试了针刺碳毡增强C/C复合材料试样在不同载荷和转速条件下的摩擦磨损性能,借助数码显微镜和扫描电镜观察分析了摩擦表面形貌。结果表明:当转速较低时,摩擦系数比较稳定,磨损率随载荷提高而增大;当转速较高时,低载荷试样摩擦系数不大,磨损率有所增加,而高载荷试样的摩擦系数在5分钟左右时出现峰值然后回落并保持稳定,磨损率急剧增加,说明磨损机制发生变化;摩擦面平行于X-Y向的C/C复合材料磨损率较小,具有较好的摩擦磨损性能。     

制动用C/C-SiC复合材料摩擦学性能研究现状

C/C-SiC复合材料是高速制动材料的优良候选材料。摩擦磨损性能是衡量制动材料的主要性能指标,也是制约材料进一步应用的主要因素。主要从材料微观结构和成分以及工况条件对C/C-SiC复合材料的摩擦磨损性能的影响两方面阐述了C/C-SiC复合材料摩擦磨损性能的研究现状;分析了影响C/C-SiC复合材料摩擦磨损性能的主要材料因素和工况条件;讨论了各自影响机制;并提出了进一步提高C/C-SiC复合材料摩擦磨损性能和使役安全所需解决的问题。     

磁控溅射TiC／a—C薄膜的结构和摩擦学性能研究

采用磁控溅射法制备不同碳含量的碳化钛薄膜.采用SEM、XRD及HR-TEM等手段分析了TiC/a-C薄膜的微观组织结构,采用摩擦磨损仪和台阶仪研究了薄膜的摩擦学性能.研究结果表明,碳含量在40%～74%时,随碳含量的增加,薄膜结构由疏松变得致密,(111)择优取向逐渐转变为无明显择优取向生长.当碳含量为60%时,薄膜结构为TiC晶粒镶嵌在非晶碳基体中的纳米复合结构,此时薄膜的机械性能及耐磨性最佳.磨损机制主要为粘着磨损和磨粒磨损,通过调节薄膜中非晶碳的含量及晶粒大小并增加薄膜的硬度可改善其摩擦学性能.     

C/C复合材料飞机刹车盘的结构与性能

采用企业、行业及国家相关标准的试验方法，对超码复合材料公司，英国Dunlop公司，法国CarbonIn-dusty公司，美国B．F．Goodrich、ALS公司等生产的9种C／C复合材料飞机刹车盘的物理、力学、热学、摩擦磨损的性能特征，以及中南大学生产的C／C复合材料刹车盘的有关性能，进行了对比分析。结果表明，选择适宜的炭纤维预制体结构，控制热解炭基体微观结构为光学粗糙层结构，合理的热处理温度是获得高性能炭刹车盘材料的关键。我国拥有自主知识产权研发的大型民机炭刹车盘在高摩擦特性方面获得了重大突破，已用于波音757—200型飞机，实现了国内C／C复合材料具有里程碑意义的第四个重大突破。     

石墨化度对2.5D碳/碳复合材料在低能条件下的摩擦学性能影响

在MM-200型摩擦磨损实验机上,对2.5D编织结构的不同石墨化度的碳/碳(C/C)复合材料进行低能条件下的摩擦磨损实验,用扫描电子显微镜对其磨损表面形貌进行了观察分析.结果表明:石墨化温度升高到一定值之后,可使摩擦系数下降,而试样的摩擦系数不稳定,相应磨损量也会增大.在摩擦初始时,摩擦系数呈现交错变化,随时间的推移,摩擦系数出现分化,石墨化度高的试样摩擦系数较低,当石墨化度增加50%时,磨损率增加0.05%,磨损量变化不是很大.石墨化程度以及石墨化的均匀程度都对材料的摩擦磨损性能有很大影响.     

MOCVD法制备SnO2单晶薄膜的结构和光学性质

用金属有机物化学气相沉积（MOCVD）法在蓝宝石（0001）衬底上制备出高质量的氧化锡（SnO2）单晶薄膜。对制备薄膜的结构和光学性质进行了研究。制备样品具有纯snO2的四方金红石结构，其外延生长方向为SnO2（100）∥Al2O3（0001）。薄膜均匀、致密，具有很好的取向性和结晶性。透射谱测量结果表明，在可见光区薄膜的绝对透过率达到了90％以上。     

二氧化硅/木材复合材料的晶胞与Matrix区域的变化

为了弄清楚由于二氧化硅介入木材细胞壁引起结晶区与Matrix区域的变化,通过二氧化硅/木材复合材料细胞壁膨胀率、XRD测定及分析其结晶度、结晶区长度、宽度,研究结晶区与Matrix区域的形态变化及二氧化硅凝胶粒子介入木材细胞壁的空间位置.结果表明:溶胶-凝胶法制备的二氧化硅/木材复合材料,细胞壁的膨胀率随着增重率的增加而增大,且有两个不同的增大过程,相同增重率条件下,加硅烷偶联剂法制备的细胞壁膨胀率比直接溶胶-凝胶法制备的大.XRD谱分析表明,结晶度随着增重率的增加而减小,有两个不同的减小过程,衍射峰的位置不变,晶胞不变;Scherrer公式计算表明结晶区的宽度及长度均不变.     

Mechanical and tribological behaviour of nano scaled silicon carbide reinforced aluminium composites

ABSTRACT

This work assesses the impact of the presence of Nano scaled silicon carbide on the Mechanical & Tribological behavior of aluminium matrix composites. Aluminium matrix composites containing 0, 0.5, 1, 1.5, 2 and 2.5 wt.%-nano scaled silicon carbide was set up by a mechanical stirrer. The trial comes about to demonstrate that the inclusion of Nano silicon carbide brings about materials with progressively high elastic modulus and likewise brings about expanded brittle behavior, fundamentally lessening failure strain. Shear modulus and flexural shear modulus likewise increases with silicon carbide increase. The presence of Nano scaled silicon carbide in the aluminium matrix diminishes subsurface fatigue wear and increases wear resistance, because of silicon carbide lubricant activity. Wear testing, microstructure & morphological, density & void testing, hardness, flexural and tensile test of the readied composites were investigated and outcomes were analyzed which demonstrated that including nano-SiC in aluminum (Al) matrix increased wear resistance, tensile strength, and 2 wt. % of nano scaled SiC for Al MMC indicated maximum wear resistance, tensile strength, and an optimum balanced mix of both Tribological and Mechanical properties. Microstructural observation uncovered uniformand homogeneous distribution of SiC particles in the Al matrix.     

Mechanical characterization of single crystal silicon and UV-LIGA nickel thin films using tensile tester operated in AFM

This paper describes the mechanical characteristics of microscale single crystal silicon (SCS) and UV‐LIGA nickel (Ni) films used for microelectromechanical systems (MEMS). A compact tensile tester, operated in an atomic force microscope (AFM), was developed for accurate evaluation of Young's modulus, tensile strain and tensile strength of microscale SCS and UV‐LIGA Ni specimens. SCS specimens with nominal dimensions of 20 μm in thickness, 50 μm in width and 600 μm in length were prepared by a conventional photolithography and etching process. UV‐LIGA Ni specimens, with a thickness of 15 μm, a width of 50 μm and a length of 600 μm in nominal dimensions, were also fabricated by electroplating using a UV thick photoresist mould. All specimens have line patterns on their specimen gauge section to measure axial elongation under tensile loading. The SCS specimens showed a linear stress–strain response and fractured in a brittle manner, whereas the UV‐LIGA Ni specimens showed elastic–inelastic deformation behaviour. Young's modulus of SCS and UV‐LIGA Ni specimens obtained from tensile tests averaged 169.2 GPa and 183.6 GPa, respectively, close to those of bulk materials. However, the tensile strength of both materials showed a larger value than the bulk materials: 1.47 GPa for the SCS and 0.98 GPa for the Ni specimens. Yield stress and breaking elongation of UV‐LIGA Ni specimens were also quite different from those of the bulk Ni because of the specimen size effect on inelastic properties.     

Structural and mechanical properties of diamond-like carbon films deposited by an anode layer source

An anode layer source is a special ion gun, which can be fed with carbon precursors like acetylene to deposit hard and highly defect-free hydrogenated diamond-like carbon films at room temperature. The present study focuses on the influence of the process parameters — discharge voltage, process pressure and acetylene flow — on structure and mechanical properties of the deposited films. Raman spectra show that an increased discharge voltage yields decreased structural disorder, i.e. a lower C-C sp³ hybridised fraction of carbon atoms in the films. By an elevation of the discharge voltage from 1 to 3 kV the full width at half maximum of the G-band decreases from 194 ± 0.2 cm^− 1 to 183 ± 0.7 cm^− 1. Films deposited at the lowest discharge voltage show in accordance to the spectroscopic data the highest nanohardness (36 ± 1 GPa), stress (− 2.34 ± 0.2 GPa) and reduced elastic modulus (180 ± 4 GPa).     

Mechanical properties of porous silicon by depth-sensing nanoindentation techniques

Porous silicon (PS) was prepared using the electrochemical corrosion method. Thermal oxidation of the as-prepared PS samples was performed at different temperatures for tuning their mechanical properties. The mechanical properties of as-prepared and oxidized PS were thoroughly investigated by depth-sensing nanoindentation techniques with the continuous stiffness measurements option. The morphology of as-prepared and oxidized PS was characterized by field emission scanning electron microscope and the effect of observed microstructure changes on the mechanical properties was discussed. It is shown that the hardness and Young's elastic modulus of as-prepared PS exhibit a strong dependence on the preparing conditions and decrease with increasing current density. In particular, the mechanical properties of oxidized PS are improved greatly compared with that of as-prepared ones and increase with increasing thermal oxidation temperature. The mechanism responsible for the mechanical property enhancement is possibly the formation of SiO₂ cladding layers encapsulating on the inner surface of the incompact sponge PS to decrease the porosity and strengthen the interconnected microstructure.     

Mn离子注入Mg掺杂GaN的微结构和光学特性研究

通过Mn离子注入Mg掺杂GaN外延层制备了铁磁性GaN∶Mn薄膜,利用拉曼散射和光致发光谱研究了退火温度对薄膜微结构和光学特性的影响。拉曼谱测试显示由离子注入相关缺陷引起了新的声子模,分析认为Mn离子相关的局域振动(LVM)紧邻Ehigh2峰。光致发光谱观察到位于1.69,2.54和2.96eV的3个新的发光峰,分析认为2.96eV的发光峰来自MgGa-VN复合体深施主能级和Mg的浅受主能级之间的辐射复合跃迁,2.54eV的发光峰来自浅施主能级和深受主能级之间的辐射复合跃迁,对于位于1.69eV的新发光峰不排除来自MgGa-VN复合体深施主能级和Mn相关深受主能级之间辐射复合跃迁的贡献。     

Structural and optical verification of residual strain effect in single crystalline CdTe nanowires

Single crystalline CdTe nanowires have been synthesized using Au-catalyzed chemical vapor deposition. X-ray diffraction reveals the existence of non- negligible inhomogeneous compressive strain in the nanowires along the 〈111〉 growth direction. The effect of the strain on the electronic structure is manifested by the blue-shifted and broadened photoluminescence spectra involving shallow donor/acceptor states. Such residual strain is of great importance for a better understanding of the optical and electrical behaviors of various semiconductor nanomaterials as well as for device design and applications.     

Formation and characterization of Si5C3 type silicon carbide by carbon ion implantation with a MEVVA ion source

A Si₅C₃ type silicon carbon has been prepared via carbon ion implantation into silicon substrate using a MEVVA ion source. Carbon ions were implanted into silicon substrate at a fluence of 5 × 10¹⁷ ions/cm² and then the as-implanted samples were annealed at 1250 °C for 2 h. The thermal annealing produced a silicon carbide layer on the surface of silicon substrate. The results of X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) confirm the existence of Si₅C₃, rather than SiC. The results of Fourier transform infrared reflection (FTIR) and Raman spectroscopy analyses show that the Si–C vibration frequency in crystalline Si₅C₃ is slightly less than that in crystalline β-SiC.     

真空高温热退火对单晶磷化铟纳米孔阵列的形貌、微结构影响

利用真空热退火的方法，研究了单晶InP方形纳米孔阵列退火后的形貌和晶相等特征。发现随着退火温度的不断升高，单晶InP中P的挥发性也越来越剧烈，到650℃后P完全挥发，样品变成h单质，而单晶InP方形纳米孔阵列的形貌也逐渐变得不均一，当退火温度高于550℃，整个纳米孔阵列被完全破坏。