Sarin and Air Permeation Through a Nanoporous Graphene

ABSTRACTSarin gas is a dangerous chemical warfare agent (CWA). It is a nerve agent capable of bringing a person to death in about 15 minutes. A lethal concentration of sarin molecules in air is about 30 mg/m3. Experimental research on this gas requires very careful safety protocols for handling and storage. Therefore, theoretical and computational studies on sarin gas are very welcome and might provide important safe guides towards the management of this lethal substance. In this work, we investigated the interactions between sarin, air and nanoporous graphene, using tools of classical molecular dynamics simulations. Aiming to cast some light in the possible sarin selective filtration by graphene, we designed a bipartite simulation box with a porous graphene nanosheet placed at the middle. Sarin and air molecules were initially placed only on one side of the box so as to create an initial pressure towards the passage of both to the other side. The box dimensions were chosen so that the hole in the graphene was the only possible way through which sarin and air molecules can get to the other side of the box. The number of molecules that passed through the hole in graphene was monitored during 10 ns of simulation and the results for different temperatures were compared. The results show that, as far as the size of the holes are small, van der Waals forces between graphene and the molecules play a significant role on keeping sarin near graphene, at room temperature.

Suction effects in cratered surfaces

It has been shown experimentally that cratered surfaces may have better adhesion properties than flat ones. However, the suction effect produced by the craters, which may be chiefly responsible for the improved adhesion, has not been properly modelled. This paper combines experimental, numerical simulation and analytical approaches towards developing a framework for quantifying the suction effect produced by isolated craters and cratered surfaces. The modelling approach emphasizes the essential role of large elastic deformation, while the airflow dynamics, microscopic mechanisms, like surface tension and air permeation, and rate-dependence are neglected. This approach is validated using experimental data for isolated hemi-spherical craters. The modelling approach is further applied to spherical cap (not necessarily hemi-spherical) craters with the objective of identifying optimal geometric and material properties, as well as the minimum preload necessary for attaining the maximum suction force. It is determined that stiff polymers with deep craters are capable of producing large suction forces. For soft materials, central to biomedical applications, large suction forces can be attained by reinforcing deep craters with thin stiff layers. Parametric optimization studies of reinforced craters reveal that some of them perform beyond common expectations. However, those high-performance reinforced craters are prone to surface instabilities, and therefore the practical use of such craters may be problematic.

Way Forward to Halt Pressure Loss in Automotive Tyres

Tyre is one of the most crucial components in a vehicle structure not only to have the vehicle running smoothly on the road, but also to provide physical and acoustic comfort for the passengers. But, since the day the inflatable tyres were invented, sudden loss of air in a tyre acts as a major problem associated with tyres; and are still being treated to date by professional researchers and giant tyre manufacturers. The phenomena where tyre experiences natural pressure loss over the time is called air permeation which causes tyre to deflate on its own. Besides reviewing the primary theories and findings that contribute to natural air permeation that literally causes the pressure drop of an automotive tyre, this paper also reveals the experimentally validated results of the significant factor which contributes to air permeation of an automotive tyre. Additionally, a relevant nanobased solution to reduce the air permeation rate to stop the tyre deflation is also highlighted to establish the way forward total solution suiting wide range of tyres used on domestic cars.

Test and Analysis on the Wearability of Bamboo Pulp Fabric

In order to have a better understanding the wearability of bamboo pulp fabric and enhance the research and development level of this kind of products, the fabric performances such as the strength, elongation, air permeability, moisture permeability have been test and discussed in this paper. The results shown that: the breaking strength of fabric increases when the bamboo pulp fiber content reduces; when the bamboo pulp fiber content increased, the breaking elongation, wear resistance performance, wicking performance, crease recovery performance, moisture permeability, air permeation rate and tearing strength of fabric also increased.