6,015 research outputs found
Characterization and measurement of polymer wear
Analytical tools which characterize the polymer wear process are discussed. The devices discussed include: visual observation of polymer wear with SEM, the quantification with surface profilometry and ellipsometry, to study the chemistry with AES, XPS and SIMS, to establish interfacial polymer orientation and accordingly bonding with QUARTIR, polymer state with Raman spectroscopy and stresses that develop in polymer films using a X-ray double crystal camera technique
Electronic chemical potentials of porous metal-organic frameworks
The binding energy of an electron in a material is a fundamental
characteristic, which determines a wealth of important chemical and physical
properties. For metal-organic frameworks this quantity is hitherto unknown. We
present a general approach for determining the vacuum level of porous
metal-organic frameworks and apply it to obtain the first ionisation energy for
six prototype materials including zeolitic, covalent and ionic frameworks. This
approach for valence band alignment can explain observations relating to the
electrochemical, optical and electrical properties of porous frameworks
Spin Hall effect and Weak Antilocalization in Graphene/Transition Metal Dichalcogenide Heterostructures
We report on a theoretical study of the spin Hall Effect (SHE) and weak
antilocal-ization (WAL) in graphene/transition metal dichalcogenide (TMDC)
heterostructures, computed through efficient real-space quantum transport
methods, and using realistic tight-binding models parametrized from ab initio
calculations. The graphene/WS 2 system is found to maximize spin proximity
effects compared to graphene on MoS 2 , WSe 2 , or MoSe 2 , with a crucial role
played by disorder, given the disappearance of SHE signals in the presence of
strong intervalley scattering. Notably, we found that stronger WAL effects are
concomitant with weaker charge-to-spin conversion efficiency. For further
experimental studies of graphene/TMDC heterostructures, our findings provide
guidelines for reaching the upper limit of spin current formation and for fully
harvesting the potential of two-dimensional materials for spintronic
applications.Comment: This document is the unedited Author's version of a Submitted Work
that was subsequently accepted for publication in Nano Letters,
copyright\c{opyright}American Chemical Society after peer review. To access
the final edited and published work see
http://pubs.acs.org/articlesonrequest/AOR-c2pZ8WnmG7pcF4MIivj
Spin transport in graphene/transition metal dichalcogenide heterostructures
Since its discovery, graphene has been a promising material for spintronics:
its low spin-orbit coupling, negligible hyperfine interaction, and high
electron mobility are obvious advantages for transporting spin information over
long distances. However, such outstanding transport properties also limit the
capability to engineer active spintronics, where strong spin-orbit coupling is
crucial for creating and manipulating spin currents. To this end, transition
metal dichalcogenides, which have larger spin-orbit coupling and good interface
matching, appear to be highly complementary materials for enhancing the
spin-dependent features of graphene while maintaining its superior charge
transport properties. In this review, we present the theoretical framework and
the experiments performed to detect and characterize the spin-orbit coupling
and spin currents in graphene/transition metal dichalcogenide heterostructures.
Specifically, we will concentrate on recent measurements of Hanle precession,
weak antilocalization and the spin Hall effect, and provide a comprehensive
theoretical description of the interconnection between these phenomena.Comment: 21 pages, 11 figures. This document is the unedited Author's version
of a Submitted Work that was subsequently accepted for publication in Nano
Letters, copyright\c{opyright}American Chemical Society after peer review. To
access the final edited and published work see
http://pubs.rsc.org/en/Content/ArticleLanding/2018/CS/C7CS00864
Effect of lubricant extreme-pressure additives on surface fatigue life of AISI 9310 spur gears
Surface fatigue tests were conducted with AISI 9310 spur gears using a formulated synthetic tetraester oil (conforming to MIL-L-23699 specifications) as the lubricant containing either sulfur or phosphorus as the EP additive. Four groups of gears were tested. One group of gears tested without an additive in the lubricant acted as the reference oil. In the other three groups either a 0.1 wt % sulfur or phosphorus additive was added to the tetraester oil to enhance gear surface fatigue life. Test conditions included a gear temperature of 334 K (160 F), a maximum Hertz stress of 1.71 GPa (248 000 psi), and a speed of 10,000 rpm. The gears tested with a 0.1 wt % phosphorus additive showed pitting fatigue life 2.6 times the life of gears tested with the reference tetraester based oil. Although fatigue lives of two groups of gears tested with the sulfur additive in the oil showed improvement over the control group gear life, the results, unlike those obtained with the phosphorus oil, were not considered to be statistically significant
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