512 research outputs found
Tiling of the five-fold surface of Al(70)Pd(21)Mn(9)
The nature of the five-fold surface of Al(70)Pd(21)Mn(9) has been
investigated using scanning tunneling microscopy. From high resolution images
of the terraces, a tiling of the surface has been constructed using pentagonal
prototiles. This tiling matches the bulk model of Boudard et. al. (J. Phys.:
Cond. Matter 4, 10149, (1992)), which allows us to elucidate the atomic nature
of the surface. Furthermore, it is consistent with a Penrose tiling T^*((P1)r)
obtained from the geometric model based on the three-dimensional tiling
T^*(2F). The results provide direct confirmation that the five-fold surface of
i-Al-Pd-Mn is a termination of the bulk structure.Comment: 4 pages, 4 figure
DPD Guided Insight on the Formation Process of Polyethersulfone Membranes by Nonsolvent Induced Phase Separation and the Effects of Additives
Dissipative particle dynamics (DPD), a coarse grain simulation method, was applied to the membrane formation process of non-solvent induced phase separation (NIPS) to gain further insight on the mechanism of certain variables and how they affect the final morphology. NIPS involves two solutions, an organic polymer dissolved in an organic solvent colloquially called the dope and an aqueous coagulation bath, brought into contact with one another. The solvents then mix, causing the polymer to fall out of solution as an asymmetric membrane with a dense surface layer and a more open subsurface layer in response to the decreasing solubility. Polyethersulfone (PES), a common industrial choice we have previously studied, was utilized as the polymer with N-methyl-2-pyrrolidone (NMP) as the organic solvent and water as the coagulation bath. In this study, our previous model construction was altered in several ways. Firstly, the simulation area was enlarged, allowing for a better sampling of subsurface behavior. Secondly, polymer chain length was increased to bring it more in line with the high molecular weight of industrially common polymers, with our experimental systems ranging from 100 to 200 monomers. Lastly, polyvinylpyrrolidone (PVP) was introduced as an additive to the polymer solution in concentrations varying from 1 to 10% by volume of the dope. PVP is a common polymer additive utilized in industry to produce larger pores, a result that was successfully replicated. We also investigated the effects of adding solvent to the coagulation bath as well as the effects of adding water to the polymer solution
DPD Guided Insight on the Formation Process of Polyethersulfone Membranes by Nonsolvent Induced Phase Separation and the Effects of Additives
Dissipative particle dynamics (DPD), a coarse grain simulation method, was applied to the membrane formation process of non-solvent induced phase separation (NIPS) to gain further insight on the mechanism of certain variables and how they affect the final morphology. NIPS involves two solutions, an organic polymer dissolved in an organic solvent colloquially called the dope and an aqueous coagulation bath, brought into contact with one another. The solvents then mix, causing the polymer to fall out of solution as an asymmetric membrane with a dense surface layer and a more open subsurface layer in response to the decreasing solubility. Polyethersulfone (PES), a common industrial choice we have previously studied, was utilized as the polymer with N-methyl-2-pyrrolidone (NMP) as the organic solvent and water as the coagulation bath. In this study, our previous model construction was altered in several ways. Firstly, the simulation area was enlarged, allowing for a better sampling of subsurface behavior. Secondly, polymer chain length was increased to bring it more in line with the high molecular weight of industrially common polymers, with our experimental systems ranging from 100 to 200 monomers. Lastly, polyvinylpyrrolidone (PVP) was introduced as an additive to the polymer solution in concentrations varying from 1 to 10% by volume of the dope. PVP is a common polymer additive utilized in industry to produce larger pores, a result that was successfully replicated. We also investigated the effects of adding solvent to the coagulation bath as well as the effects of adding water to the polymer solution
Formation of a quasicrystalline Pb monolayer on the ten-fold surface of the decagonal Al-Ni-Co quasicrystal
Lead has been deposited on the ten-fold surface of decagonal Al72Ni11Co17 to
form an epitaxial quasicrystalline single-element monolayer. The overlayer
grows through nucleation of nanometer-sized irregular islands and the coverage
saturates at 1 ML. The overlayer is well-ordered quasiperiodically as evidenced
by LEED and Fourier transforms of STM images. Annealing the film to 600 K
improves the structural quality, but causes the evaporation of some material
such that the film develops pores. Electronic structure measurements using
X-ray photoemission spectroscopy indicate that the chemical interaction of the
Pb atoms with the substrate is weak.Comment: 12 pages, 5 figure
New Insight on Volatile Fission Products (I and Cs) release from high burnup UO2 fuel under LOCA type conditions
International audienc
Microwave properties of diluted composites made of magnetic wires with giant magneto impedance effect
International audienceIn this paper, the theoretical description of wire media made of magnetic wires. We show that there is a close link between the Giant Magneto Impedence effect (GMI) in individual wires, and free-space microwave properties of the composite wire media. The demonstration with tunable dielectric constant under a static magnetic field
A Tale of Two Tilings
What do you get when you cross a crystal with a quasicrystal? The surprising
answer stretches from Fibonacci to Kepler, who nearly 400 years ago showed how
the ancient tiles of Archimedes form periodic patterns.Comment: 3 pages, 1 figur
Influence of strain in Ag on Al(111) and Al on Ag(100) thin film growth
We demonstrate the influence of interfacial strain on the growth modes of Ag films on Al(111), despite the small magnitude of the lattice misfit in this system. The strain is relieved by the formation of stacking fault domains bounded by Shockley partial dislocations. The growth mode and the step roughness appear to be strongly connected. Growth is three-dimensional (3D) as long as the steps are straight, but switches to 2D at higher coverage when the steps become rough. Anisotropic strain relaxation and straight steps seem to be related. We also report related observations for Al deposited on Ag(100)
Surfaces of quasicrystals
International audienceThe remarkable surface properties of quasicrystals have motivated extensive investigations of their intrinsic atomic and electronic structures. In this article, we summarize some of the main conclusions obtained so far. We also describe adsorption experiments where quasiperiodic surfaces are used as templates to grow thin films with novel structures. Finally we discuss some of their useful properties of current interest
Single crystal growth, crystal structure and surface characterisation of the binary phase Al45Cr7.
International audienc
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