Multicomponent Layers Research Articles

Properties of Composite Borided Layers on Steel Produced by Combined Surface Treatments

Abstract With the increasing progress in engineering a growing need has been felt for materials that show improved surface properties, such as an increased resistance to wear and corrosion. A new method combining the known techniques of chemical and electrochemical nickel plating and plasma bonding is discussed. The paper presents properties of such produced composite and multicomponent borided layers.

Multicomponent double layers and selective acceleration of charged particles

Multicomponent double layers, defined as layers composed of more than two kinds of charged particles, are supposed to constitute the predominant type of double layer in cosmic plasmas. A model of a steady and strong multicomponent double layer is studied in both the nonrelativistic and relativistic approximations. In particular, such properties of the layer as the structure, potential drop, and current composition are investigated. It is demonstrated that the density distribution of each kind of positive and negative particle in the nonrelativistic multicomponent layer is of the same shape as the density distribution of the ions and electrons, respectively, in Langmuir's two‐component layer. Also, the shape of the distribution of the electric field corresponds to that of the two‐component layer. In the relativistic layer the charges are distributed among two very thin layers of high positive and negative charge density close to the high‐potential and low‐potential boundaries of the layer, respectively, and a constant but low charge density in the rest of the layer. It is shown that the potential drop across the multicomponent layer is proportional to the thickness of the layer raised to 4/3 in the nonrelativistic case while it is directly proportional to the thickness in the relativistic case. Current conditions prescribing the allowed sets of current densities of the various kinds of particles in the layer are derived in the nonrelativistic and relativistic approximations. Correspondingly, abundance conditions for the particles accelerated through the layer are also obtained. The abundance of the particles accelerated by the double layer is expected generally to be different from the abundance of the ambient plasma. It is suggested that the abundance of the accelerated particles might serve as a means to detect double layers, especially in space plasmas.

Designing Advanced Coatings for Wear Protection

Improved knowledge of the ways in which the structures, properties, and behaviour of coated materials are interrelated, as well as technical advances in the production of specific layers, constitutes a basis on which advanced coatings with improved properties and wear resistance can be realised. Many of the relations between constitution, microstructure, properties, and application behaviour, elaborated for bulk materials, can also be used to understand the behaviour of layer materials and to optimise coatings. After a survey and a classification of the most common protective layer materials, typical examples of advanced coating concepts with improved properties, including gradient layers, multicomponent mixed layers, metastable layer materials, multi/ayers, and multiphase layer materials, are discussed.

Tribological Properties of Superhard PVD Coatings

AbstractIn order to advance the development of extremely hard coatings, new homogeneous and metastable films were prepared by magnetron sputter ion plating (MSIP) and arc ion plating (AIP) in the DC. or RF. mode.In the present study coatings in the systems Ti-B-C-N, Si-C-N and amorphous carbon coatings (ADLC) were investigated and compared with other hard coatings. Multicomponent layers of different compositions and structures were deposited by varying the reactive gases methane (CH4) and nitrogen (N2) and the dominant process parameters (e. g. C/V-characteristic of the cathode, substrate bias).X-ray diffraction studies of the Ti-B-C-N coatings revealed either an amorphous structure or crystallization in a hexagonal lattice. The ADLC and Si-C-N coatings were always amorphous. Electron microprobe analysis and auger electron spectroscopy were used to determine the coating compositions.The tribological properties were determined by a ball on disc tribometer (e.g. friction coefficent), a pin on disc tribometer and a special abrasive wear test.

Superhard Ti-B-C-N coatings

In order to advance the development of extremely hard coatings, new homogeneous and metastable films within the Ti-B-C-N system were prepared by magnetron sputter ion plating using a TiB 2 target in the d.c. mode. Multicomponent layers of different compositions and structures were deposited by varying the reactive gases methane (CH 4) and nitrogen (N 2) and the dominant process parameters ( e.g. sputtering power and substrate bias). X-ray diffraction studies of the coatings revealed either an amorphous structure or crystallization in a hexagonal lattice. The lattice parameters were strongly influenced by the quantity of carbon and nitrogen incorporated. Electron microprobe analysis was used to determine the coating compositions. Evaluation of the characteristic light element X-ray spectra provided initial qualitative data on chemical bonding properties. Auger electron spectroscopy confirmed the construction of the films. The Palmquist method and hertzian indentations were used to characterize film toughness. The remaining mechanical coating properties were investigated by means of microhardness measurements and the CSEM scratch test. Scanning electron microscopy indicated an extremely dense coating structure. Superhardness up to values of 7000 HV 0.05 was the dominant property. Coating thicknesses ranging from 6 to 25 μm were realized. Behaviour of the Ti-B-C-N layers in abrasive wear tests was favourable.

Fourier transform infrared and Raman studies on solid nitrogen dioxide: Temperature cycling of ordered, disordered, and multicomponent layers

Fourier transform infrared (FTIR) spectra of nitrogen dioxide layers deposited at various rates and substrate temperatures, are reported. Bands assignable to N2O4(D2h) (ordered and disordered layers), to O=N–O–NO2 ‘‘D’’ and ‘‘D′’’ isomers, to NO+NO−3 nitrosonium nitrate and to the NO2 monomer were observed. The relative amounts of species depends upon deposition conditions. Temperature cycling effects were followed up to 205 K. Solid N2O4(D2h) behaves like a normal, stable molecular solid, its disordered layer exhibiting small frequency shifts, but also being stable with respect to temperature cycling. The observation of NO+NO−3 bands is related to the existence of the D′ isomer and of monomeric NO2. Raman experiments overemphasize the NO+NO−3 form due to resonant enhancement.

Quantitative XRF analysis of surface layers: Influence of primary energy distribution and enhancement

AbstractA theoretical approach to quantitative x‐ray fluorescence analysis of multicomponent surface layers is described. It includes both the determination of the primary energy distribution of the tube and the calculation of the x‐ray intensities according to the fundamental parameter method. The effects of several inaccuracies, such as those from the primary distribution, from the treatment of secondary excitation and from the analytical representation of attenuation cross‐sections, are discussed in detail. Their influence on the XRF intensities was studied theoretically and compared with experimental data for a wide variety of well defined multilayer systems. The final accuracy of the theoretical calculations allows one to dispense with calibration reference standards in practical analytical work.

Quantitative Analysis of Multicomponent Surface Layers by Means of XRF

X-ray fluorescence (XRF) analysis is used for the determination of thickness and composition of surface layers such as electroplated or evaporated coatings. The composition and thickness data evaluation from X-ray yields is done with the help of computer routines where the main prerequisite consists in an accurate calculation of the X-ray production for any given structur of the layer under consideration. Here the so-called enhancement effect plays an important role. In this paper a considerably simplified fundamental parameter treatment of secondary fluorecsence is derived and applied. It is demonstrated that XRF analysis even may be used for nondestructive depth profiling if the measured X-ray yields are influenced by the depth profile with sufficient sensitivity. In the case of strong interelement effects within the layer this technique may be applied successfully, as shown for FeNi foils as a typical example.

Amorphous and crystalline dip coatings obtained from organometallic solutions: Procedures, chemical processes and products

Substrates, particularly large panes of glass, are withdrawn from organometallic solutions into a humid atmosphere. Evaporation of the solvent, hydrolysis of the organometallic compounds and polycondensation take place until the oxidic state is reached. The optical and physical properties of various single films and multilayer systems are described. Their history, the dip-coating procedure and especially the chemical processes are described. Single oxide layers and crystalline and amorphous multicomponent oxide layers such as, for instance, glasses and multilayer systems can be fabricated.

Formation of an anomalous acoustic plasmon in spatially separated plasmas

The collective excitation spectrum of a spatially separated, two-component, two-dimensional plasma is investigated within a generalized random-phase approximation. It is shown that in addition to the regular optical and acoustic plasmons, a high frequency mode may exist in such a system provided the separation between the two charge components exceeds a critical length. This mode is undamped in leading order and is linear in wave vector in the long wavelength limit. It may thus be viewed as “acoustic” in nature, and referred to as an Anomalous Acoustic Plasmon. The existence criteria for the regular acoustic plasmon, which is a low frequency damped mode, is also helped by the spatial separation since its phase velocity is enhanced with respect to its damping rate. The regular optical plasmon remains unaffected by the separation in leading order. Finally, the dynamical structure factor of the system is analyzed and the feasibility of observing these modes in InAs/GaSb superlattices or in multi-component inversion layers, is discussed.

Definition and calculation of effective ambipolar diffusion coefficients for a laminar multicomponent ionized boundary layer

Effective diffusion coefficients substantially facilitate solution of detailed problems for multicomponent boundary layers with frozen-in reactions in the flow and heterogeneous reactions at the wall; they provide physically lucid correlation formulas and final equations for the convective heat flow to the undamaged solid as well as for the mass loss rate or effective erosion enthalpy if the walls are subject to thermochemical attack [1–5].

New Routes to Multicomponent Oxide Glasses

AbstractMulticomponent oxide glasses can be produced not only by melting methods but also by hydrolysis and condensation of alkoxide complexes with several metals. This requires temperatures only up to the transformation range of the glass in question, usually 500–600 °C. The process does not pass through the molten phase. It is possible to obtain glasses or polycrystalline substances, depending on the composition. The method is particularly suitable for the production of thin, transparent multicomponent oxide layers of almost any composition on substrates. Some of these layers provide protection against climatic attack or against oxidation.

The oxidation of pure U in CO 2 between 700° and 1000°C

Oxidation of uranium in carbon dioxide has been studied morphologically. On β-uranium the oxide is cracked and oxidation is controlled by O 2− diffusion through a thin compact layer of UO 2. Self-heating occurs at ⩾ 750°C leading to rapid oxidation rates between 750° and 850°C. Between 900° and 1000°C the oxide is considerably more compact, rates are not excessively high and self-heating is hardly significant. Carbon in the oxide is predominantly located near cracks around 700°C, but as the temperature increases its distribution becomes more uniform and its high mobility leads to the formation of multi-component reaction product layers.