China Science

We report on the observation of new variants of metadislocations in the orthorhombic complex metallic alloy phase Al–Pd–Fe. At Fe contents above about 3 at.% we find a novel type of metadislocation in the ?-structure, which has a complementary counterpart hosted in all ?-type phases possessing phason lines as structural elements.

M. Feuerbacher aEmail:m.feuerbacher@fz-juelich.de?S. Balanetskyya?M. Heggena
[a]Institut für Festkrperforschung, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany

The objective of the study is to understand the nanoscale near-surface deformation response of two polymer nanocomposite systems with significant differences in ductility during nanoscratching with a Berkovich indenter using a load of 1 mN and a scratch velocity of 1 ?m s?1. An accompanying objective is to investigate the commonality in surface deformation behavior between nano- and microscale deformation to reinforce the underlying fundamental principles governing surface deformation. An understanding of surface deformation response is accomplished through determination of physical and mechanical properties, structural characterization and electron microscopy analysis of surface deformation tracks and residual plastically deformed structures. The study suggests for the first time that the understanding derived from microscale surface deformation studies can be extended to nanoscale surface deformation. The microscale response in a polypropylene-based system is characterized by periodic multiple ripple-type deformation tracks that form via a mechanism identical to the periodic single-ripple-type tracks during nanoscale deformation. Similarly, in a less ductile polyethylene-based system, the periodic parabolic tracks and ironing mode of deformation during microscale deformation tend to be significantly reduced in intensity, with ironing being the primary deformation mechanism at the nanoscale. The surface deformation topography suggests that both micro- and nanoscale response is material specific. Additionally, the study suggests that reinforcement of polymers with nanoclay is a viable route to significantly decrease the susceptibility of polymeric materials to micro- and nanoscale deformation and can be discussed in terms of physical and mechanical properties of materials notably percentage crystallinity and elastic recovery.

Q. Yuana?N. Ramisettia?R.D.K. MisraaEmail:dmisra@louisiana.edu
[a]Center for Structural; Functional Materials, University of Louisiana at Lafayette, P.O. Box 44130, Lafayette, LA 70504-4130, USA;[b]Department of Chemical Engineering, University of Louisiana at Lafayette, P.O. Box 44130, Lafayette, LA 70504-4130, USA

Previous pressure-volume calculations during oil cracking to gas,based on the conventional model that presupposes oil cracking to be completed by approximately 150°C,underestimate the potential for gas accumulation in petroleum reservoirs.In this article,a compositional kinetic model of gas generation from oil cracking is suggested based on pyrolysis data using sealed gold tubes,and the pressure-volume changes are recalculated based on the new kinetic model under various geological conditions.The kinetic modeling of oil cracking confirms that crude oil begins cracking at about 160°C for a heating rate of 2°C/m.y.,and that the oil-cracking process has two distinct stages with significant differences in gas composition.The first stage is characterized by dominant C_(2-5)wet gases,whereas the second is characterized by the recracking of C_(2-5)wet gases to methane and pyrobitumen,leading to a progressive increasing dryness of the gas.The pressure-volume-temperature simulations of oil cracking to gas show that initial oil saturation,temperature-pressure gradients,and openness of reservoirs are important geological factors that control gas accumulation in original petroleum reservoirs.For a reservoir that is geologically open and saturated with 100% oil,gas spills out of the trap at 196°C.The gas loss at 240°C is almost 50% of the total gas,far lower than the 75% based on the conventional model of oil destruction.With lower oil saturation,the gas loss decreases because the gas-water contact can shift downward,and the gas loss occurs mainly by solution.For effectively isolated reservoirs,oil cracking readily exceeds lithostatic pressure,leading to reservoir fracturing,which becomes more obvious when oil saturation-decreases.The calculated fracturing temperatures for 100 and 50 vol.% oil saturations correspond to oil destructions of 95% and 86.4%,greatly exceeding the value of 1% as suggested by previous studies.A conceptual model of gas accumulation and loss in isolated and open geological conditions for a reservoir with 50% oil saturation is suggested.On the basis of this model,the Triassic carbonate gas pool in northeastern Sichuan Basin was discussed as a typical example for in-situ accumulation of gas cracked from reservoired oils.The present model infers that the reservoired oils were completely cracked into gas at 87.6 Ma,and that 75-85% of the gas has been preserved in the original reservoir rocks to form the in-situ gas pools with a huge amount of gas resources.We believe that gas accumulation from oil cracking in original petroleum reservoirs is much more prospective than previously thought,and that gas cracked from oil has great potential in other areas of the Sichuan Basin and the eastern Tarim Basin.

Hui Tian?Xianming Xiao?Ronald W.T.Wilkins

Scientific evidence can make or break a case, and experts can help juries understand what it all means. But first, lawyers need to persuade the judicial gatekeepers that an expert’s testimony is relevant and reliable. Here is help on meeting the tough admissibility standards for evidence.

William C. Smith

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