Multi-element Plasma Research Articles

Resistance of amorphous TiAlCrZrSi/polyimide high entropy alloy films to atomic oxygen erosion

To alleviate the atomic oxygen (AO) degradation of the polyimide deployed in the low Earth orbit (LEO) environment, we fabricate a set of amorphous TiAlCrZrSi/polyimide films under various negative bias values via the 3rd generation co-filter cathode vacuum arc (C-FCVA). Our rational technical design realizes the noninterference regulation and filtration of mixed multielement plasma compositions. In addition, the atomic size difference (δ, 0.075–0.081), mixing enthalpy (ΔHmix, −48.98 to −46.84 kJ mol−1), and mixing entropy (ΔSmix, 12.83–12.91 J K−1 mol−1) are all within the range of parameters required for the formation of amorphous TiAlCrZrSi high-entropy alloys (HEAs). Moreover, the TiAlCrZrSi/polyimide (no bias) film can realize an equilibrium of AO resistance and durability (Ey = 2.02 × 10−26 cm3 atom−1), which is only 0.67 % of that calculated for pristine polyimide. This can be attributed to the excellent AO penetration barrier ability of the generated HEA oxide scales. Furthermore, the thickening of HEA films can reduce the sensitivity of residual defects to AO undercutting erosion, as discussed by the existing empirical theoretical models.

Comparing the kinetics of ionized and neutral atoms from single and multi-element laser-produced plasmas

Kinetics of ion and neutral atom emission features were compared for nanosecond laser-produced plasmas generated from several metal targets (i.e., Al, Ti, Zr, Nb, Ta) and an alloy containing all of these as principal alloying elements. Plasmas were produced by focusing 6 ns, 1064 nm pulses from an Nd:YAG laser on the targets of interest in a vacuum. A Faraday cup was used for collecting ion temporal features while spatially and temporally resolved emission spectroscopy was used for measuring the optical time of flight of various neutral atomic transitions. Our results highlight that most probable ion and atom velocities decay with increasing atomic mass. Trends for ions from the alloy target represent a weighted average where all ions contribute. For both ions and atoms, velocities decrease with increasing heat of vaporization and melting temperature, consistent with the thermal mechanisms that contribute to nanosecond laser ablation. Kinetic energies for neutral atoms from pure metal targets have some variability with atomic mass, whereas kinetic energies for atoms from the alloy target are more similar. These more similar kinetic energies observed for neutral atoms in the multi-element plasma may be attributed to collisions between species from all elements in the Knudsen layer.

Control of the Directional Pattern of Multielement Plasma Vibrator Antennas

This paper presents an analysis on the possibilities of controlling the radiation pattern of Yagi-type multielement plasma vibrator antennas. The plasma vibrator antenna in its operating band is shown as a narrow-band filter. In a multielement linear plasma vibrator antenna, turning off a passive plasma vibrator makes it possible to control the beam width electronically.

Поверхностное натяжение многоэлементных плазменных покрытий

Поверхностное натяжение многоэлементных плазменных покрытий

Effect of ion irradiation on the properties multi-element plasma coatings

The paper presents the results of the study of ion irradiation on the properties of multi-element plasma coatings. The coatings were bombarded by argon ions using heavy current ion source with a hollow cathode. After ion irradiation, the structure and physical properties of the coatings change, however, the nature of the changes is different for different coatings. To predict the behavior of the coating exposed to irradiation is virtually impossible. Therefore, structural studies and investigation of physical properties of the coatings to determine their functional characteristics are to be conducted.

Nonlinear Transport Processes in Non‐Ideal Media

AbstractThe theory of non‐linear transport is elaborated to determine the Burnett transport properties of non‐ideal multielement plasma and neutral systems. The procedure of the comparison of the phenomenological conservation equations of a continuous dense medium and the microscopic equations for dynamical variables operators in the form of the generalized nonlinear Langevin equations is used for the definition of these properties. In consequence, the microscopic expressions of transport coefficients corresponding to second order thermal disturbances (temperature, mass velocity, etc.) have been found in the long‐wavelength and low frequency limits of correlations functions. Situations are considered when the use of nonlinear transport characteristics (in the Burnett approximation) significantly affects the results of modeling of hydrodynamic processes in dense charged and neutral media. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Nonlinear transport properties of non-ideal systems

The theory of nonlinear transport is elaborated to determine the Burnett transport properties of non-ideal multi-element plasma and neutral systems. The procedure for the comparison of the phenomenological conservation equations of a continuous dense medium and the microscopic equations for dynamical variable operators is used for the definition of these properties. The Mori algorithm is developed to derive the equations of motion of dynamical value operators of a non-ideal system in the form of the generalized nonlinear Langevin equations. In consequence, the microscopic expressions of transport coefficients corresponding to second-order thermal disturbances (temperature, mass velocity, etc) have been found in the long wavelength and low frequency limits.

On the theory of nonlinear response in a nonideal plasma

A theory of nonlinear response is developed for studying nonlinear phenomena and nonlinear transport processes in nonideal Coulomb systems. Temporal plasma echo and transformation of waves in a nonideal Coulomb system are studied on the basis of the theory of nonlinear response to mechanical perturbations. General constraints imposed on nonlinear response functions are considered, and the model for determining quadratic response functions is formulated. The conditions for the emergence of temporal plasma echo and wave transformation are determined. It is shown that these nonlinear effects in a nonideal plasma can be initiated by ultrashort field pulses. A theory of transport is developed for determining the Burnett transport properties of a nonideal multielement plasma. A procedure is proposed for comparing the phenomenological conservation equations for a charged continuous medium and equations of motion for the operators of corresponding dynamic variables. The Mori algorithm is used for deriving the equations of motion for operators of dynamic variables in the form of generalized Langevin equations. The linearized Burnett approximation is considered in detail. The properties of the matrices of coefficients of higher-order derivatives in the system of conservation equations in the linearized Burnett approximation, which are important for hydrodynamic applications, are discussed. Various versions of the theory of nonlinear response are compared.

The hydrodynamic equations for chemically equilibrium flows of a multielement plasma with exact transport coefficients

Explicit expressions for all of the effective transport coefficients are derived for thermochemically equilibrium flows using the exact mass and heat transfer equations, which are resolved with respect to the “forces” (the gradients of the hydrodynamic variables) via the flukes. It is shown that, in a mixture where the components have different diffusion properties, separation (diffusion) of the chemical elements occurs which leads to a state of affairs where the equilibrium concentrations, and together with them, the effective transport coefficients will be functions not only of the pressure and temperature but will also depend on the concentrations of the elements, determined when solving the problem (self-consistent concentrations of the elements). It is shown that the existence of an electric current and lack of quasineutrality (flow around electrically conducting walls—electrodes) does not change the structure of the expressions for the effective transport coefficients and does not add anything new. The approximate and incomplete treatment of thermochemically equilibrium flows of multicomponent gas mixtures and a plasma in previously published papers are especially noted. Numerical estimates of the effective transport coefficients are presented for an air plasma and the domains in the pressure-temperature plane with the required number of approximations in order to obtain results with an error of no worse than ∼5% are indicated.

Elemental composition of ions associated with low mass carbon clusters generated by UV laser ablation of polyimide

Previously, it has been shown that three types of C clusters, characterized by mass range and relative intensities, are produced upon laser ablation of polyimide. The low mass clusters, C n 9 < n < 25, always appear coincident with peaks 2 amu greater than the bare C cluster. Using perdeuterated polyimide, we have established the elemental composition of these peaks to be predominately, C n H 2, rather than C n-1 N, which is allowed since polyimide contains 5 at% N. These results establish the positive ion spectrum of polyimide to be composed of C and H with little contribution from heteroatoms, and show that low mass C clusters preferentially add 2 H atoms in the high energy, multi-element plasma induced by the laser.

Effects of multicomponent diffusion in a problem of high temperature gas dynamics

Various characteristics of hypersonic flow past a space probe in a helium--hydrogen atmosphere simulating the upper layers of that of the planet Jupiter have been intensively studied recently [1-6]. The point of the present paper, which completes the cycle begun by [7, 8], is to take into account consistently the interaction of the basic physical processes in the shock layer plasma between the detached shock wave and the graphite surface of a spherical probe in determining the convective and radiant heat fluxes in the front stagnation point of the probe. The processes concerned include: the injection of the graphite heat shield into the shock layer under the effect of powerful heat fluxes, radiant and convective heat transfer through the shock layer to the sur-face of the probe, and the multicomponent nature of the diffusion mixing of the plasma components in the shock layer. The thermophysical properties of the local-equillbriura multielement plasma of the shock layer with strong Coulomb interaction necessary for calculating the heat fluxes were tabulated in [8, 9]. The Coulomb interaction has a particular effect on the optical properties of the shock layer plasma [9].

Loss of equilibrium and the quasistationary state in an expanding recombining plasma

The authors consider the loss of equilibrium in a nonsteady plasma and obtain criteria for the loss of ionization equilibrium, the equilibrium distribution of levels, and thermal equilibrium for the expansion of a plasma which is initially in equilibrium. The closely related conditions for a quasistationary occupation of the excited states in a recombining plasma are studied. The properties of the nonlinear and nondiagnonal matrix to the leading derivatives in the system of equations of diffusion and energy for a multielement plasma in an ideal multielement plasma are investigated.

Matrix of transfer coefficients of a multielement plasma and its application in problems of high-temperature gasdynamics

The authors propose to use the system of classic kinetic equations, the collision integrals of which are defined in the Boltzmann form with allowance for the elementary processes important in a nonideal plasma, the qualitative properties of its composition, and data on the kinetic coefficients of nonideal classic Coulomb systems. Such an approach allows one to separate the contributions to the kinetic coefficients due to the concrete composition of the plasma and to the strong Coulomb interaction in it.