Porous, well crystalline LiFePO4/C composites with different amounts of carbon have been prepared by a sol-gel technique. The thickness of carbon coatings (paintings) has been determined by ...high-resolution transmission electron microscopy. It is shown that carbon coating thickness can be controlled by the amount of carbon and it has an impact on the obtained reversible capacity. Furthermore, it is shown that atomic ratio of nonactive Fe(III) phase (presumably Fe3P) in as-synthesized LiFePO4/C composites depends on the amount of carbon in the composite. Using Mossbauer spectroscopy, we have confirmed that the nonactive Fe(III) remains nearly unchanged in the composite during cycling. The lowest amount of carbon in LiFePO4/C composites obtained from citrate anion as a gelling agent was 3.2 wt % and this particular amount corresponds to the carbon coating thickness of about 1-2 nm. The reversible capacity obtained from the above-mentioned composite delivers close to 80% of the theoretical capacity at room temperature with a current density of 170 mA/g (C/1 rate).
► Investigation of boundary-lubrication with MoS2 multi-wall nanotubes in PAO oil. ► Mechanisms for the significant friction and wear reduction are discussed. ► Two mechanisms for different tribofilm ...formations were proposed. ► Four mechanistic routes for the adhesion of MoS2 nano-sheets to the surface were proposed.
Several types of nanoparticles have been experimentally investigated as possible lubrication agents and the results suggest that this is a promising idea. However, so far, MoS2 nanotubes have not been experimentally evaluated in this respect. Accordingly, this study is focused on the tribological behavior of MoS2 multi-wall nanotubes (MWNTs) as a potential additive in lubricating oils. The experiments were performed in the boundary-lubrication regime under a contact pressure of 1GPa (Hertz, max) and a sliding velocity of 0.005m/s using a ball-on-disc tribotester. The results were compared to a reference base oil, and it was found that MoS2 nanotubes significantly decreased the friction and wear compared to the base lubricant. The friction was more than 2-times lower and the wear as much as 5–9-times lower. Several tribological mechanisms and effects due to the MoS2 nanotubes are presented. It was established that a wear-protective and low-shear film was forming on the surface. This tribofilm was formed either by (i) the adhesion of thin MoS2 nano-sheets on the surface, where these sheets were deposited on the surface by one of the four possible sub-mechanisms proposed in this work; or by (ii) the compaction and deformation of nanotube aggregates, which resulted in a thicker boundary film. Thus, in contrast to the rolling of the nanotubes, which we do not consider to be plausible, the exfoliation and deformation of the nanotubes were found to be the prevalent effects for the nanotubes in the boundary-lubrication regime.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Porous LiMPO
4/C composites (where M stands for Fe and/or Mn) with micro-sized particles were synthesised by sol–gel technique. Particles porosity is discussed in terms of qualitative results ...obtained from SEM micrographs and in terms of quantitative results obtained from N
2 adsorption isotherms. Porous particles could be described as an inverse picture of nanoparticulate arrangement, where the pores serve as channels for lithium supply and the distance between the pores determines the materials kinetics. Tests show that the electrochemical behaviour of porous LiMPO
4/C composite is comparable with the results from the literature. The best electrochemical results were obtained with a LiFePO
4/C composite (over 140
mAh
g
−1 at
C/2 rate during continuous cycling). The capacity obtained with LiMnPO
4/C composite is much lower (40
mAh
g
−1 at
C/20 rate), although the textural properties are similar to those observed in the LiFePO
4/C composite.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
We report on the synthesis, structure, and self-assembly of single-wall subnanometer-diameter molybdenum disulfide tubes. The nanotubes are up to hundreds of micrometers long and display diverse ...self-assembly properties on different length scales, ranging from twisted bundles to regularly shaped "furry" forms. The bundles, which contain interstitial iodine, can be readily disassembled into individual molybdenum disulfide nanotubes. The synthesis was performed using a novel type of catalyzed transport reaction including C(60) as a growth promoter.
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MoS2 nanopods, spherical MoS2 nanoparticles grow in a confined geometry of MoS2 nanotube reactors, which subsequently serve as nanocontainers and enable safe handling and simple release of the ...particles on stimulation.
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Since the first report on the synthesis of inorganic WS2 nanotubes in 1992, the number of articles on the successful growth of different inorganic nanotubes has increased rapidly, emphasizing the ...importance of this field for nanotechnology. Although there are some geometrical similarities to carbon nanotubes, inorganic nanotubes are distinguished by important peculiarities, from their growth mechanisms to the physical and chemical properties that are attractive for potential applications. Their structural properties, which are important for such applications, are discussed in this review.
Over the last decade, nanotubes have become a symbol of new and fast‐developing nanotechnology. Inorganic nanotubes are distinguished from carbon ones by important peculiarities, from their growth mechanisms to physical and chemical properties. The current status of research into inorganic nanotubes is discussed with an emphasis on structural properties, which are important for applications. The Figure shows a Au–WS2 nanotube.
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Diamond-like carbon (DLC) coatings provide low friction and wear in the most demanding tribological contacts. However, their chemical reactivity with oil additives is poor and difficult to optimise. ...Moreover, even the partially effective, but high-SAPS (sulphuric ash, phosphor, sulphur) additives, will be phased out in the near future for environmental reasons. Based on recent advancements in the nanotechnology of inorganic MoS2 and WS2 nanoparticles, which lubricate through the low shear of basal planes, we propose a potential replacement of the current chemical-based lubrication with this novel, physical-based additive lubrication technology for poorly reactive DLC coatings. In our work, 30% less friction compared to steel surfaces and 50% less friction compared to the base oil was achieved by employing MoS2 nanotubes in the base oil in self-mated DLC contacts. This physical-based lubrication technology represents an innovative solution for highly effective but non-reactive surfaces and simultaneously provides green-lubrication performance.
•Study of DLC and steel lubricated with MoS2 nanotubes in all lubrication regimes.•Physically based lubrication has environmental benefits vs. chemically-based.•Proof of successful physically based lubrication of DLC with nanoparticles is given.•Tribofilm that reduces friction in DLC contacts can be thick or ultra-thin.•Friction reduction of DLC contacts (50%) is even larger than in steel contacts (40%).
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10.
W5O14 Nanowires Remškar, M.; Kovac, J.; Viršek, M. ...
Advanced functional materials,
08/2007, Volume:
17, Issue:
12
Journal Article
Peer reviewed
We report on the synthesis of quasi‐1D W5O14 crystals using NiI2 as a growth promoter. Photoelectron spectroscopy revealed the metallic conductivity of the W5O14 nanowires, which was also confirmed ...by direct‐transport measurements on a double‐stranded nanowire. Scanning electron microscopy and transmission electron‐diffraction data are correlated with details of crystal growth revealing the possible mechanism of the formation of this rarely synthesized phase, which was reported as a homogeneous phase only in 1978 by McColm et al., and in the meantime has been declared as a compound that is rare.
Quasi‐one‐dimensional W5O14 nanowires (see figure) are grown using NiI2 as a growth promoter. Photoelectron spectroscopy and direct‐transport measurements reveal metallic conductivity. The possible growth mechanism of this rarely synthesized phase is discussed based on scanning electron microscopy and transmission electron diffraction.
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