Nanostructure of Vortex During Explosion Welding

Diffusivities of the ternary liquid mixture 2-propanol—water—glycerol and three-component mass transfer in liquids

It is shown that a strong joint is formed on the contact surface in explosive welding. A band of material on which plastic deformation is localized is formed along the boundary of the surface, this band representing a qualitatively new structure. Use of the laws governing strain localization, obtained from a study of the collapse of thick-walled cylinders that were subjected to explosive shock loading, makes it possible to predict the collision parameters in explosive welding in accordance with the grain size of the materials that are used.

Study on explosive welding A1060/3D-Printed-SUS316L

Diffusion in liquids is an old but still important field of research, since a sound understanding and predictive models are lacking. In this chapter, established and novel techniques to obtain concentration-dependent multicomponent diffusion coefficients are presented: (1) Experimental methods: we present established measurement methods but also recently developed techniques which allow for substantial reductions of measurement time and effort. (2) Molecular Dynamics simulations: we present methods for the successful and efficient determination of diffusion coefficients as well as the thermodynamic factor from equilibrium Molecular Dynamics simulations, which allow for prediction of diffusion based on force-field models. (3) Engineering models: established as well as improved, recently developed engineering models for the simple determination of multicomponent diffusion coefficients are described.

Turbulent transport is widely considered to be the main driver for cross-field transport in the scrape-off layer (SOL) of toroidal magnetized plasmas. Here, reciprocating Langmuir probes are employed to measure both the plasma profiles and the turbulent particle transport in the SOL of the Wendelstein 7-X stellarator. The relation between turbulent radial particle flux Γr and the local pressure gradient is often approximately linear across the entire SOL width, indicating that radial turbulence spreading is absent. This observation holds across a wide range of magnetic configurations and different plasma heating and density scenarios. The magnitude of the turbulent transport for a given gradient reveals a dependence on the magnetic configuration and the position in the SOL, which we relate to the cross-spectral characteristics of multi-tip floating potential measurements. Magnetic islands can add further complexity due to non-monotonic SOL profiles and the breaking of the transport-gradient relation. Finally, anomalous diffusion coefficients are determined from the probe measurements.

The article presents the results of studying the transformation of the structure and phase composition of the aluminum layer during heating of a three-layer composite of aluminum AD1 + Cr20Ni80 alloy + aluminum AD1 above the eutectic transformation temperature. It is shown that it is possible to form layers with a structure strengthened by intermetallics from row to matrix, with a hardness of 6 to 8 GPa in the composition of layered metal-intermetallic composites obtained by explosion welding with subsequent rolling. It is established that the growth of the diffusion zone during HT occurs both towards aluminum AD1 and towards the Cr20Ni80 alloy. It is revealed that during HT according to the contact melting mode, a «row» structure of the eutectic type with alternating layers of intermetallics CrAl7 and NiAl3 is formed in the initial aluminum layer, the size of which increases with increasing HT time. In the transition zone with a thickness of ≈ 3 μm between the Cr20Ni80 alloy and the layer with a row structure, there is a smooth decrease in the Al content and an increase in the concentration of Cr and Ni with subsequent equalization of the chemical composition in the Cr20Ni80 alloy layer. At a temperature above the melting point of Al during the HT, which ensures the liquid-phase interaction of its melt with the Cr20Ni80 alloy, the «row» structure is absent, and the transformed Al layer is a mixture of a complex phase composition NiAl3 + Cr (Al) + Al (Cr). The thickness of the transition zone between the Cr20Ni80 alloy and the transformed Al layer is ≈ 2 μm.

Sorption and diffusion of organic liquids into fluoropolymer (FC-2179) membranes have been investigated from 30 to 60°C using a gravimetric method. Diffusion coefficients, percent mass uptake, and apparent activation energies for the transport processes have been estimated. Diffusion coefficients of the liquids into the membrane have been computed from Fick's relation. A Flory–Huggins-type interaction parameter was obtained from the solubility parameter concept. Furthermore, the activation parameter values and heat of sorption data have been studied in terms of heat of mixing. The values of diffusion coefficients did not show any considerable dependence on solvent concentration. However, solvent transport as analyzed from an empirical equation was found to be of the anomalous type. Molecular transport also showed a dependence on the chemical nature of the liquids. The concentration profiles of liquids have been calculated at different penetration depths of the membrane at different time intervals by solving Fick's differential equation under suitable initial and boundary conditions. A numerical method based on the finite difference technique was also used to predict the concentration profiles of liquids, and these are compared with the profiles computed from an analytical solution of Fick's equation.

We identify two distinct regimes for the diffusion of the ionic liquid [BMIM][PF6] confined between parallel graphene walls using molecular dynamics simulations. Within 2 nm of the wall, the cations and anions form a well-defined layered structure. In this region, the in-plane diffusion coefficients are suppressed when compared to their bulk values and increase monotonically with the distance away from the wall. Beyond 2 nm from the wall, the density profile and in-plane diffusion coefficients recover their bulk values. The channel-averaged in-plane diffusion coefficients increase monotonically with wall separation and recover the bulk values at a separation of 15 nm. A simple semianalytical model is proposed that mirrors this trend. The results also highlight the importance of applying a finite-size correction to molecular dynamics-predicted diffusion coefficients of confined liquids, which may otherwise be unusually larger than their bulk values.

The aim of this study was to demonstrate the potential for holographic interferometry to be used for diffusion studies of large molecules in gels. The diffusion and partitioning of BSA (67,000 g/mol) and pullulans (5,900-112,000 g/mol) in agarose gel were investigated. The gel diffusion coefficients obtained for BSA were higher when distilled water was used as a solvent compared to those obtained with 0.1 M NaCl as the solvent. Furthermore, the gel diffusion coefficient increased with increasing BSA concentration. The same trend was found for liquid BSA diffusion coefficients obtained by DLS. BSA partition coefficients obtained at different agarose gel concentrations (2-6%, w/w) decreased slightly with increasing gel concentration. However, all BSA gel diffusion coefficients measured were significantly lower than those in pure solvent and they decreased with increasing agarose concentration. The gel diffusion coefficients obtained for pullulans decreased with increasing pullulan molecular weight. The same effect from increased molecular weight was seen in the liquid diffusion coefficients measured by DLS. The pullulan partition coefficients obtained decreased with increasing molecular weight. However, pullulans with a larger Stokes' radius than BSA had partition coefficients that were higher or approximately the same as BSA. This implied that the pullulan molecules were more flexible than the BSA molecules. The results obtained for BSA in this study agreed well with other experimental studies. In addition, the magnitude of the relative standard deviation was acceptable and in the same range as for many other methods. The results thereby obtained showed that holographic interferometry is a suitable method for studying diffusion of macromolecules in gels.

IVIDIL experiment onboard the ISS

We report on the measurement of diffusion (D), thermodiffusion (D(T)), and Soret (S(T)) coefficients in water-isopropanol mixtures by three different instrumental techniques: thermogravitational column in combination with sliding symmetric tubes, optical beam deflection, and optical digital interferometry. All the coefficients have been measured over the full concentration range. Results from different instruments are in excellent agreement over a broad overlapping composition (water mass fraction) range 0.2 < c < 0.7, providing new reliable benchmark data. Comparison with microgravity measurements (SODI/IVIDIL (Selected Optical Diagnostic Instrument/Influence of VIbration on DIffusion in Liquids)) onboard the International Space Station and with literature data (where available) generally gives a good agreement. Contrary to theoretical predictions and previous experimental expectations we have not observed a second sign change of S(T) at low water concentrations.

Identification of diffusive transport by means of an incremental approach

Concentration-dependent diffusion coefficients from a single experiment using model-based Raman spectroscopy

The formation of transition zones during explosive welding of aluminium with copper in vacuum and in air is studied.The distribution of element concentrations is used to determine the coefficient of mutual mass transfer in the undetachable Al-Cu joint.It turns out that the mass transfer of copper into aluminium in the conditions of explosion welding occurs at greater depths compared to the depth of penetration of aluminium into copper.This is explained by the fact that the nature of the penetrating atoms does not have such a strong influence as in conditions of diffusion annealing, and the determining factor is the lattice period, which in aluminium is larger than in

Influence of icosahedral short range order on diffusion in liquids: A study on Al-Zn-Cr alloys