scholarly journals Microstructure Simulation and Constitutive Modelling of Magnetorheological Fluids Based on the Hexagonal Close-packed Structure

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1674 ◽  
Author(s):  
Jintao Zhang ◽  
Wanli Song ◽  
Zhen Peng ◽  
Jinwei Gao ◽  
Na Wang ◽  
...  
Keyword(s):  
Constitutive Model ◽  
Yield Stress ◽  
Single Chain ◽  
Shear Yield Stress ◽  
Hexagonal Close Packed ◽  
Close Packed Structure ◽  
Field Dependent ◽  
Shear Yield ◽  
Hexagonal Close Packed Structure ◽  
Packed Structure

This paper presents a new constitutive model of high particles concentrated magnetorheological fluids (MRFs) that is based on the hexagonal close-packed structure, which can reflect the micro-structures of the particles under the magnetic field. Firstly, the particle dynamic simulations for the forces sustained by carbonyl iron powder (CIP) particles of MRFs are performed in order to investigate the particles chain-forming process at different time nodes. Subsequently, according to the force analyses, a hexagonal close-packed structure, which differs from the existing single-chain structure and body-cantered cubic structure, is adopted to formulate a constitutive model of MRFs with high concentration of the magnetic-responsive particles. Several experiments are performed while considering crucial factors that influence on the chain-forming mechanism and, hence, change the field-dependent shear yield stress in order to validate the proposed model. These factors include the magnetic induction intensity, volume fraction and radius of CIP particles, and surfactant coating thickness. It is shown that the proposed modeling approach can predict the field-dependent shear yield stress much better than the single-chain model. In addition, it is identified that the shear yield stress is increased as the particle volume fraction increases and surfactant coating thickness decreases. It is believed that the proposed constitutive model can be effectively used to estimate the field-dependent shear yield stress of MRFs with a high concentration of iron particles.

Two-dimensional silicon monolayers generated on c-BN(111) substrate

2015 ◽  
Vol 17 (24) ◽  
pp. 15694-15700 ◽  
Author(s):  
Haiping Wu ◽  
Yan Qian ◽  
Shaohua Lu ◽  
Erjun Kan ◽  
Ruifeng Lu ◽  
...  
Keyword(s):  
Type Structure ◽  
Two Dimensional ◽  
Compound Structure ◽  
Hexagonal Close Packed ◽  
Close Packed Structure ◽  
Hexagonal Close Packed Structure ◽  
Packed Structure ◽  
Chain Type

Three Si monolayer structures, a Si chain-type structure, a two-dimensional hexagonal close packed compound structure, and a two-dimensional hexagonal close packed structure, are generated on a c-BN(111) substrate.

INTERFACES BETWEEN CARBON NANOTUBES AND NICKEL NANOPARTICLES IN CARBON NANOTUBES

2013 ◽  
Vol 06 (06) ◽  
pp. 1350056 ◽  
Author(s):  
BAI LIU ◽  
LIRUI LIU
Keyword(s):  
Carbon Nanotubes ◽  
Rechargeable Batteries ◽  
Dislocation Model ◽  
Face Centered Cubic ◽  
Hexagonal Close Packed ◽  
Close Packed Structure ◽  
Hexagonal Close Packed Structure ◽  
Packed Structure ◽  
Cnts Surface ◽  
Face Centered

Carbon nanotubes (CNTs) filled with metals can be used in capacitors, sensors, rechargeable batteries, and so on. Their interface significantly affects the properties of the composites. Here, we show that three kinds of interfaces between crystalline Ni and CNTs exist, namely, ordered, distorted, and disordered. They presented lattice states of Ni atoms near the interface, whereas the (111) Ni plane was parallel to the CNTs' surface and appeared apart in a smaller or bigger angle. The coherent face-centered cubic (f.c.c)/hexagonal close-packed structure (h.c.p) boundary was formed between the crystalline Ni and CNTs at the ordered interface, in which the match was (111) Ni //(0001) Carbon . We suggested a dislocation model for the coherent interface. The model explained why the angle between (200) Ni and the CNTs' inner surface was 52.9° rather than the theoretical value of 54.75°. The [Formula: see text] dislocation was formed to fit the coherent relationship. Thus, Ni lattice shrinkage occurred. Further study indicated that the formation mechanism of crystalline Ni in CNTs was through heterogeneous nucleation on the inner wall surface and growth of the crystal nucleus.

SELF-ASSEMBLY DRIVEN CRYSTALLIZATION IN KEPLARATE-TYPE POLYOXOMETALATES

2014 ◽  
Vol 02 (01) ◽  
pp. 1440005 ◽  
Author(s):  
KAPARAPU GOUTHAM ◽  
ETHAYARAJA MANI
Keyword(s):  
Self Assembly ◽  
Replica Exchange ◽  
Hollow Shell ◽  
Hexagonal Close Packed ◽  
Close Packed Structure ◽  
Hexagonal Close Packed Structure ◽  
Packed Structure ◽  
Replica Exchange Monte Carlo ◽  
Patchy Colloids ◽  
Closed Shells

In this paper, we present direct evidences for two-stage mechanism of crystallization of patchy colloids from replica exchange Monte Carlo simulations. The patchy model colloid mimics the structure and interactions of a certain class of polyoxometalates (POM). We find that individual colloids self-assemble into two-dimensional sheets in hexagonal close-packed structure, and these sheets themselves stack to form crystals. The simulation explains the formation of hollow shell-like objects in POM solution [T. Liu, B. Imber, E. Diemann, G. Liu, K. Cokleski, H. Li, Z. Chen and A. Muller, J. Am. Chem. Soc.128, 15914 (2006)]. Simulation also predicted the formation of pentagonal caps that are essential for the formation of hollow, closed shells of POMs. Similar two-step crystallization of apoferritin protein was earlier found in experiments [S. T. Yau and P. G. Vekilov, Nature406, 494 (2000)]. The simulation study suggests nonclassical route to crystallization in patchy colloids.

Deformation-induced γ → DI-α2 phase transformation occurring in the twin-intersection region of TiAl alloys

2007 ◽  
Vol 22 (9) ◽  
pp. 2416-2422 ◽  
Author(s):  
C.L. Chen ◽  
W. Lu ◽  
L.L. He ◽  
H.Q. Ye
Keyword(s):  
Phase Transformation ◽  
Room Temperature ◽  
Compositional Analysis ◽  
Hexagonal Close Packed ◽  
Partial Dislocations ◽  
Close Packed Structure ◽  
The Matrix ◽  
Hexagonal Close Packed Structure ◽  
Packed Structure ◽  
Face Centered

Deformation-induced γ → DI-α2 phase transformation was verified to occur in the twin-intersection region of a Ti–45Al–8Nb (at.%) alloy compressed at room temperature. High-resolution image observations of the deformation-induced DI-α2 phase suggested that the orientation relationship between the DI-α2 and γ phases remained the typical one: (0001)DI−α2//{111}γ, [11¯20]DI−α2//〈101]γ. The conversion of stacking sequence from ordered face-centered tetragonal to ordered nonequilibrium hexagonal close-packed structure was accomplished by the movement of a/6〈11¯2] Shockley partial dislocations on every other {111}γ plane. Compositional analysis based on energy dispersive spectra revealed that the DI-α2 phase had the same composition as the matrix γ phase. No compositional diffusion occurred because the plastic deformation was carried out at room temperature. The strong stress concentration in the intersection region was the major force to induce the γ → DI-α2 phase transformation in the process of room-temperature compression.

A Simple Synthetic Route to MoS2 and WS2 Nanoparticles and Thin Films

2003 ◽  
Vol 17 (08n09) ◽  
pp. 1134-1140 ◽  
Author(s):  
G. H. Lee ◽  
J. W. Jeong ◽  
S. H. Huh ◽  
S. H. Kim ◽  
B. J. Choi ◽  
...  
Keyword(s):  
Thin Films ◽  
Particle Diameter ◽  
Chemical Vapor ◽  
Solid Lubricants ◽  
Ambient Atmosphere ◽  
Hexagonal Close Packed ◽  
Close Packed Structure ◽  
Hexagonal Close Packed Structure ◽  
Packed Structure ◽  
Hot Filament

We produced both MoS2 and WS2 nanoparticles by thermally decomposing M(CO)6 (M = Mo, W) in excess of H2S by using a hot filament. Both highly pure crystalline MoS2 and WS2 nanoparticles were efficiently produced over the filament temperature range from 300 to 800 °C. Particle diameter ranged from 2.0 to 5.0 nm and from 3.0 to 6.0 nm for MoS2 and WS2 nanoparticles, respectively. Fullerene-like particles such as nanotubes, onions, and empty and nested hollows were not produced. Both MoS2 and WS2 nanoparticles have a hexagonal close packed structure. Cell constants are determined to be a = 3.09 and c = 12.61 Å and a = 3.09 and c = 12.47 Å for MoS2 and WS2 nanoparticles, respectively, which are all consistent with the corresponding bulk values. Thin films of MoS2 and WS2 were also prepared by chemical vapor deposition of MoS2 and WS2 on stainless steel disks at 600-650 °C and low friction coefficients were obtained at an ambient atmosphere for both MoS2 and WS2 thin films, implying that they can serve as good solid lubricants.

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