The physical properties of polyurethane/graphite nanosheets/carbon black foaming conducting nanocomposites

Using polyester polyol and diphenylmethane diisocyanate (MDI) as basic component, and using graphite nanosheets (GN) and carbon black (CB) as conductive filler, polyurethane/graphite nanosheets/carbon black foaming conducting nanocomposites have been prepared by filling mold curing reaction. The morphology, electrical properties and mechanical properties of the prepared PU/GN foams have been investigated. It showed that the percolation threshold effect of PU/GN composite occurred at the content around 12 wt.% of the GN, which was lower than that of carbon black (CB) composite. Besides, PU/GN foams showed much better conductive properties and mechanical properties than that of CB system.     

Carbon film growth and hydrogenic retention of tungsten exposed to carbon-seeded high density deuterium plasmas

Tungsten (W) targets have been exposed to high density (n_e ? 4 × 10¹⁹ m^?3), low temperature (T_e ? 3 eV) CH₄-seeded deuterium (D) plasma in Pilot-PSI. The surface temperature of the target was ～1220 K at the center and decreased radially to ～650 K at the edges. Carbon film growth was found to only occur in regions where there was a clear CII emission line, corresponding to regions in the plasma with T_e ? 2 eV. The maximum film thickness was ～2.1 μm after a plasma exposure time of 120 s. ³He nuclear reaction (NRA) analysis and thermal desorption spectroscopy (TDS) determine that the presence of a thin carbon film dominates the hydrogenic retention properties of the W substrate. Thermal desorption spectroscopy analysis shows retention increasing roughly linearly with incident plasma fluence. NRA measures a C/D ratio of ～0.002 in these films deposited at high surface temperatures.     

Effect of bias voltage on microstructure and properties of Ti-doped graphite-like carbon films synthesized by magnetron sputtering

Ti-doped graphite-like carbon (GLC) films with different microstructures and compositions were fabricated using magnetron sputtering technique. The influence of bias voltages on microstructure, hardness, internal stress, adhesion strength and tribological properties of the as-deposited GLC films were systemically investigated. The results showed that with increasing bias voltage, the graphite-like structure component (sp² bond) in the GLC films increased, and the films gradually became much smoother and denser. The nanohardness and compressive internal stress increased significantly with the increase of bias voltage up to −300 V and were constant after −400 V. GLC films deposited with bias voltages in the range of -300--400 V exhibited optimum adhesion strength with the substrates. Both the friction coefficients and the wear rates of GLC films in ambient air and water decreased with increasing voltages in the lower bias range (0--300 V), however, they were constant for higher bias values (beyond −300 V) . In addition, the wear rate of GLC films under water-lubricated condition was significantly higher for voltages below −300 V but lower at high voltage than that under dry friction condition. The excellent tribological performance of Ti-doped GLC films prepared at higher bias voltages of −300--400 V are attributed to their high hardness, tribo-induced lubricating top-layers and planar (2D) graphite-like structure.     

THE EFFECTS OF NEGATIVE BIAS AND FLUX RATIO ON THE PROPERTIES OF TiN THIN FILMS FORMED BY FILTERED CATHODIC ARC PLASMA TECHNIQUE

The filtered cathodic vacuum-arc (FCVA) technique is a supplementary and alternative technique with respect to convendtional physical and chemical vapour deposition which can remove macro-particles effectively and make the deposition process at ambient temperature. In this work, high quality TiN thin films were deposited on silicon substrates at low temperature using the improved filtered cathodic arc plasma (FCAP) technique. AFM, XRD, TEM were employed to characterize the TiN thin films. The effects of the negative substrate bias on the grain size, preferred crystalline orientation, surface roughness of TiN thin films were discussed.     

Preparation and characterization of gold/poly(vinyl alcohol)/MoS2 intercalation nanocomposite

Gold-molybdenum disulfide nanocomposites were prepared by means of exfoliation of a layered host and subsequent in situ oxidation–reduction of the intercalated auric compounds, using the interlayer of MoS₂ as the nanoreactor and poly(vinyl alcohol) (PVA) molecules as the dispersant. The nanocomposites were characterized by means of powder X-ray diffraction, Fourier transformation infrared spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. The electrical conductivity of the Au/PVA/MoS₂ nanocomposites at various temperatures was investigated. Results indicated that Au and PVA were intercalated in the layered MoS₂, at an interlayer distance of 2.072 and 0.928 nm. The intercalation of Au and PVA led to a significant increase in the electrical conductivity value of MoS₂, while the electrical conductivity value of the intercalation nanocomposites decreased with decreasing temperature.     

Sliding Wear of Ni–17.5Si–29.3Cr Alloy under Water Lubrication

The tribological properties of Ni–17.5Si–29.3Cr alloy against Si₃N₄ under water lubrication conditions were studied on a ball-on-disc reciprocating 1tribotester. The effects of load and sliding speed on tribological properties of the alloy were investigated. The worn surfaces of the alloy were examined with SEM, TEM and an X-ray photoelectron spectroscope (XPS). It was found that the tribological properties of the alloy were closely dependent on the sliding conditions. Wear rate with the load of the alloy increased slightly at low and moderate load and increased dramatically at high load. Wear rate with the sliding speed of the alloy increased slightly at low and moderate sliding speed and increased dramatically at high sliding speed, which showed the same trend as that with the load. The friction coefficient increased with the load (especially at high load), and decreased with sliding speed at low sliding speed and increased significantly at high sliding speed. Wear mechanism of the alloy was mainly microploughing and delamination at low and moderate load and transformed to microfracture and delamination at high load.     

Preparation and characterization of polystyrene grafted nano-sized silica

The radical copolymerization of styrene with the vinyl groups introduced onto the surface of the nano-sized silica via solvent polymerization method was developed. γ-Methacryloxy propyltriethoxysilane (MPTES) was used as coupling agent to introduce vinyl groups onto surfaces of the nano-sized silica. The methacryloxypropyl nano-sized silica (MPNS) was used as macromonomer and copolymerized with styrene by initiating with AIBN in toluene. The conversion (C), percentage of grafting (PG) and grafting efficiency (GE) were found to be 60.7%, 24.0% and 1.31% from the elemental analysis results, respectively. It was found that the surface of the nano-sized silica could be covered by PS chains efficiently so as to improve the dispersibility of the nano-sized silica in organic matrices. The addition of the nano-sized silica could improve the thermal stability of PS. Electronic Publication     

Structure and tribological properties of Ag films deposited at low temperature

The effects of substrate temperature on the structure and tribological properties of Ag films deposited at low temperatures (LT, 130-217 K) by arc ion plating (AIP) have been studied. The structure and morphology of the Ag films were analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and field emission scanning electron microscope (FESEM). The results showed that there exist (1 1 1) and (2 0 0) preferred orientation transitions for decreasing temperature at different bias voltages. The tribological properties were evaluated by a ball-on-disk tribometer and wear tracks were analyzed by means of scanning electron microscopy (SEM). The results show that substrate deposition temperature significantly affected the wear of LT Ag films. For each bias voltage studied, the film showing the highest wear rate was deposited at the lowest temperature and the film with the lowest wear rate, (significantly lower than room temperature (RT) deposited Ag films), was deposited at a temperature between the highest and the lowest temperatures examined. The wear mechanism was discussed in terms of lubrication effect of film material transferred to the counterpart and its dependence on the microstructure of the original deposited film.     

蒙脱土吸附季胺盐CTAB的动力学研究

以钠蒙脱土（MMT）为吸附剂材料，对不同初始浓度的吸附质十六烷基三甲基溴化铵（CTAB）溶液进行吸附规律研究。结果显示，室温下蒙脱土对CTAB的吸附符合Freundlich等温吸附经验式。在0．008～0．012mol／L浓度范围内，MMT对于CTAB可得到良好的吸附效果（30min的△C=0．003～0．0056mol／L），MMT吸附CTAB的反应速率常数为k=5．71×10^-6exp（-Eα/RT），其吸附过程的表观活化能Eα=-8．018kJ／mol。基于对MMT夹层结构、表面状态等特征和其对CTAB吸附规律的综合分析，表明MMT对CTAB的吸附主要是物理吸附以及脱附的复合过程，具有反应温度低、吸附速度快和反应速率常数具有较弱的负温度系数的特点。     

Fabrication of superhydrophobic copper by wet chemical reaction

A wet chemical reaction was employed herein to fabricate a stable superhydrophobic surface on a polished copper substrate at ambient temperature. The resulting surface showed superhydrophobic properties as evidenced by a water contact angle (CA) of about 154° and a water sliding angle (SA) of about 4°, which may be attributed to the combination of the roughened surface morphology by means of wet chemical reaction and the formed low surface free energy per chemical modification with poly (dimethysiloxane) vinyl terminated (PDMSVT). Scanning electron microscopy (SEM) images of the resulting surface reveal the resulted copper oxalate microscopic sizes with average diameter of about 0.5 μm and circular submicroscopic structures with diameter of about 100 nm, constructing a hierarchical structure consisted by micro- and nano-scale elements similar to that of lotus leaf in some extent. The elemental and chemical compositions of the resulting surface were also identified by Powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. This work provides improved understanding of the effect of surface roughness and surface energy on superhydrophobicity.