Three-dimensional Aspect Ratio Research Articles

Three dimensional post-mortem study of damage after compression of cast Al–Si alloys

The damage introduced by compressive deformation at room temperature and 300°C in three cast AlSi alloys with different additions of Cu and Ni is investigated by synchrotron X-ray microtomography. The same damage mechanisms are identified for all alloys independent of the heat treatment and test temperature: fracture of aluminides, fracture of eutectic Si, debonding between Si and Al-matrix, debonding between aluminides and Al-matrix and fracture of primary Si. The volume fraction of damage decreases with solution treatment time and deformation temperature due to the partial spheroidisation of rigid phases and increase in flowability of the matrix, respectively. The morphology of voids is quantified in terms of their three-dimensional aspect ratio and is correlated with their orientation to obtain information on the load carrying capability of the networks formed by Si and aluminides.

ChemInform Abstract: Graphene and Its Derivatives: Switching ON and OFF

AbstractReview: 221 refs.

Graphene-based functional materials for organic solar cells [Invited

Graphene is of great interest for future applications in organic photovoltaics (OPVs) due to its high three-dimensional aspect ratio, large specific surface area, remarkable optical transmittance, extraordinary thermal response, excellent electron/hole transport properties, superior mechanical stiffness and flexibility. Graphene-based functional materials can be used as transparent window/counter electrodes, interface layers, hole/electron transport materials and can also function as buffer layers to retard charge recombination in OPVs. Future work would focus on the following aspects: (a) design and preparation of novel graphene-based functional materials with good stability, high transparency and excellent conductivity for OPVs; (b) development of the new approaches that constitute a significant advance toward the production of graphene-based transparent conductive electrodes in OPVs; (c) evaluation on the long terms stability of devices with GO based modifying layers; (d) delicate control of unique graphene nanostructures; and (e) interface engineering of the graphene in terms of modifying its work function and surface free energy.

Graphene and its derivatives: switching ON and OFF

As the thinnest material ever known in the universe, graphene has been attracting tremendous amount of attention in both materials science and condensed-matter physics since its successful isolation a few years ago. This one-atom-thick two-dimensional pseudo-infinite nano-crystal consists of sp(2)-hybridized aromatic carbon atoms covalently packed into a continuous hexagonal lattice. Graphene exhibits a range of unique properties, viz., high three-dimensional aspect ratio and large specific surface area, superior mechanical stiffness and flexibility, remarkable optical transmittance, extraordinary thermal response and excellent electronic transport properties, promising its applications in the next generation electronics. To switch graphene and its derivatives between ON and OFF states in nanoelectronic memory devices, various techniques have been developed to manipulate the carbon atomic sheets via introducing the valence-conduction bandgap and to enhance their processability. In this article, we review the utilization of electrically, thermally and chemically modified graphene and its polymer-functionalized derivatives for switching and information storage applications. The challenges posed on the development of novel graphene materials and further enhancements of the device switching performance have also been discussed.

An Equation which Relates the Real Three-Dimensional Aspect Ratio to the Apparent Cross Sectional Aspect Ratio

The relation between grain morphology and mechanical properties has been extensively studied. Although mechanical properties are related to the real three-dimensional forms of grains, the real three-dimensional form can not be observed. Grains through a cross section can only be observed. The difference between the real three-dimensional and cross sectional form is large especially in rod-like grains. In this report, the aspect ratio of rod-like grains, which have a great influence on the mechanical properties, was studied. A relationship between the real three-dimensional aspect ratio (=A) and the cross sectional aspect ratio (=AR) was derived from model calculation; AR=-ln{cos(tan-1A)}+A(π/2-tan-1A). The model ueed assumed that the grains were rod-like, of uniform length and orientated randomly. The corresponding cross sectional aspect ratios were calculated to be 2.1, 2.6, 3.3, 4.0 for the real three-dimensional aspect ratios of 3, 5, 10 and 20. When the real aspect ratio is large, the difference between the real and cross sectional aspect ratios is also large. The calculated results were compared with the experimental data for a 20wt% SiC whisker-Si3N4 pressureless sintered body. Close agreement between calculated and experimental results was obtained.