Synthesis and characteristics of carbon-coated iron and nickel nanocapsules produced by arc discharge in ethanol vapor

Fe(C) and Ni(C) nanocapsules with low carbon content have been produced via an arc discharge process in ethanol vapor. It is clarified by X-ray diffraction that the core of the Fe(C) nanocapsules consists of γ-Fe, α-Fe and Fe₃C phase, while that of the Ni(C) nanocapsules contains only nickel. High-resolution transmission electron microscopy imaging confirms that these particles have a broad size distribution and the core/shell structure. Besides mutually independent nanocapsules with segregate graphitic shells, those with sharing shells are also observed in the Fe(C) nanocapsules. The remanence and the coercivity at room temperature of both the nanocapsules are higher than those of the corresponding microcrystallines, while the saturation magnetization is lower.     

Thermal desorption of gases and solvents from graphite and carbon nanotube surfaces

The interaction of 23 gases and solvents with the basal plane of highly oriented pyrolytic graphite (HOPG) and with single-wall carbon nanotube (SWCNT) samples is studied using thermal desorption spectroscopy. Pre-exponential frequency factors used for analysis of desorption traces are obtained from vapor pressure data. Activation energies for desorption at monolayer coverage are determined using the Redhead peak-maximum method. Binding energies of non-polar adsorbates to the HOPG surface are found to scale with the adsorbate polarizability providing clear evidence for the van der Waals character of the interaction. Low coverage desorption temperatures on SWCNT samples are found to be 50-100% higher than on HOPG. Such increase has previously been attributed to physisorption in higher coordinated sites such as grooves on the external SWCNT rope surfaces. Polar adsorbates on the other hand typically desorb at much higher temperatures from SWCNT samples which is here tentatively attributed to stronger interaction with defect sites.     

Effect of graphite particles as additive on the curing behaviour of β-tricalcium phosphate suspensions and scaffold fabrication by digital light processing

Reducing the viscosity of high solid-loading ceramic suspensions and controlling the resolution of ceramic green parts produced by digital light processing (DLP) 3D printing are two important concerns in the ceramic additive manufacturing industry. The presence of ceramic particles within a photopolymerizable system leads to light scattering that reduces the resolution of the ceramic green scaffolds. This study introduced a graphite additive to solve these problems and focused on the effects of graphite concentration on the viscosity, curing behaviour and scaffold fabrication of β-TCP ceramic suspensions. As a result, it was found that an appropriate addition of graphite reduced the viscosity of the ceramic suspensions, and the light scattering decreased with the increase of graphite concentration. Both the cure depth (C_d) and excess width (C_ex) also decreased with the increase of graphite concentration. But, graphite has a larger effect on the width curing than depth curing.     

石墨表面无敏化及活化的化学镀铜法

由于石墨表面具有特殊性,具备自动催化的功能,因此无需敏化、活化等工艺,可直接在石墨表面进行化学镀铜,获得的铜镀层光滑致密,镀液的稳定性好,同时对石墨表面化学镀铜的机理进行了探讨,分析了镀液能稳定进行镀覆反应的原因,并利用SEM对反应初期以及后期的复合粉末进行了观察,证明反应时石墨表面能直接生成大量均匀分布的铜微晶,生长至彼此侧面相连时就得到完整镀层,并且石墨颗粒越小,化学镀铜的活性越高,因而非常适合用于制备高性能的金属石墨复合材料.     

Al4C3的形成及对Gr-Al-Si复合材料的作用

Al4C3的生成会影响Gr-Al-Si复合材料的界面反应，然而研究证明在原料中少量的Al4C3存在，有利于提高石墨分布的均匀性，又不影响该材料的高温抗拉强度等综合性能。Al4C3的形成温度以550～600℃为宜，Al4C3的含量可用X射线定量分析来确定。     

石墨颗粒表面化学镀铜研究

为了充分利用Cu的导电性能，碳石墨的润滑性能，改善Cu/C的润湿性，用化学镀铜的方法成功地对石墨颗粒表面进行镀覆，详细地研究了镀铜液组分及工艺与石墨颗粒表面镀铜层厚度、沉积速率的关系，并得出较好的组分工艺方案，采用优化工艺可以得到平均厚度约7．1μm的镀铜层。同时应用X射线、金相显微镜、扫描电镜及电子探针对镀铜层的厚度、表面形貌、镀铜层与基体的界面进行了全面观察。分析表明，Cu/C界面存在过渡层，界面成锯齿状，机械冶金结合的特征十分明显，改善了铜碳界面的相溶性。     

球墨铸铁件软氮化后加工形成的石墨坑对表面质量的影响

介绍了粗糙度的定义,指出球墨铸铁件在软氮化后进行珩磨加工时形成的石墨坑对表面质量的影响,并提出相应的表面质量控制方法。