8,877 research outputs found
Carbon nanotube grafted fibres: a route to advanced hierarchical composites
The feasibility of reinforcing conventional fibre/polymer composites by grafting
carbon nanotubes (CNTs) onto the fibre surfaces has been investigated. Different
methods were developed for directly growing CNTs on silica and carbon (C320
and IM7) fibres. Pure and N-doped CNTs with controllable length were grown
on silica fibres using an injection chemical vapour deposition (ICVD) method.
The diameter and crystallinity of both types of CNTs increased during growth,
which proceeded via the base-growth mechanism. However, the nature surface of
carbon fibres is not favourable for the ICVD method. As an alternative, CNT-grafted
carbon fibres were produced using the incipient wetness technique or
electrochemical deposition to pre-load catalyst for subsequent CNT growth. The
effects of growth parameters on the morphology, density, and alignment of CNTs
were explored. The CNT-grafting process maintained or improved the fibre tensile
modulus, but resulted in strength degradations, to different extents, depending
on the fibre type and growth parameters. The impact of CNT-grafting on the
interfacial shear strength (IFSS) was studied using different micromechanical
interface tests, based on different fibre/polymer systems. The IFSS was unchanged
in push-out tests, likely due to an unusual internal failure of the fibres. In all
other cases, the IFSS was significantly increased. Single fibre pull-out tests on
C320 carbon fibre/epoxy composites showed a 60% increase, whilst fragmentation
tests on poly(methyl methacrylate) composites yielded improvements of 26% and
80-150% for IM7 carbon fibres and silica fibres, respectively. The improvements
can be attributed to the increased surface area, excellent fibre wettability by the
matrix and mechanical interlocking of CNTs with the matrix. In addition, a new
combined in situ AFM/Raman technique proved to be a useful tool to study CNT
distribution and orientation within hierarchical composites
Orientational Imaging of Subwavelength Au Particles with Higher Order Laser Modes
We present a new method for the imaging of single metallic nanoparticles that provides information about their shape and orientation. Using confocal microscopy in combination with higher order laser modes, scattering images of individual particles are recorded. Gold nanospheres and nonorods render characteristic patterns reflecting the different particle geometries. In the case of nanorods, the scattering patterns also reveal the orientation of the particles. This novel technique provides a promising tool for the visualization of nonbleaching labels in the biosciences
Calorific values and ash contents of different organs of Masson pine (Pinus massoniana) in southern China
Calorific values of plants are important indices for evaluating and reflecting material cycle and energy conversion in forest ecosystems. Based on the data of Masson Pine (Pinus massoniana) in southern China, the calorific values (CVs) and ash contents (ACs) of different plant organs were analyzed systematically using hypothesis test and regression analysis in this paper. The results show: (i) the CVs and ACs of different plant organs are almost significantly different, and the order by AFCV (ash-free calorific value) from the largest to the smallest is foliage (23.55 kJ/g), branches (22.25 kJ/g), stem bark (21.71 kJ/g), root (21.52 kJ/g) and stem wood (21.35 kJ/g); and the order by AC is foliage (2.35%), stem bark (1.44%), root (1.42%), branches (1.08%) and stem wood (0.33%); (ii) the CVs and ACs of stem woods on top, middle and lower sections are significantly different, and the CVs are increasing from top to lower sections of trunk while the ACs are decreasing; (iii) the mean GCV (gross calorific value) and AFCV of aboveground part are larger than those of belowground part (roots), and the differences are also statistically significant; (iv) the CVs and ACs of different organs are related, to some extent, to diameter, height and origin of the tree, but the influence degrees of the factors on CVs and ACs are not the same
Scattering universality classes of side jump in anomalous Hall effect
The anomalous Hall conductivity has an important extrinsic contribution known
as side jump contribution, which is independent of both scattering strength and
disorder density. Nevertheless, we discover that side jump has strong
dependence on the spin structure of the scattering potential. We propose three
universality classes of scattering for the side jump contribution, having the
characters of being spin-independent, spin-conserving and spin-flip
respectively. For each individual class, the side jump contribution takes a
different unique value. When two or more classes of scattering are present, the
value of side jump is no longer fixed but varies as a function of their
relative disorder strength. As system control parameter such as temperature
changes, due to the competition between different classes of disorder
scattering, the side jump Hall conductivity could flow from one class dominated
limit to another class dominated limit. Our result indicates that magnon
scattering plays a role distinct from normal impurity scattering and phonon
scattering in the anomalous Hall effect because they belong to different
scattering classes
Study on radiative decays of and into by means of LFQM
The observed resonance peak around 2.86 GeV has been carefully reexamined by
the LHCb collaboration and it is found that under the peak there reside two
states and which are considered as
and with slightly different masses and
total widths. Thus, the earlier assumption that the resonance
was a state should not be right. We suggest to measure the partial widths
of radiative decays of and to confirm their
quantum numbers. We would consider as or a pure
state, or their mixture and respectively calculate the corresponding
branching ratios as well as those of . The future precise
measurement would provide us information to help identifying the structures of
those resonances .Comment: 8 pages, 4 figures, 1 tabl
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