Intermediate Layer Formation Research Articles

Optimized intermediate layer formation and electroless plating methods to obtain supported dense Pd surfaces.

Dense metallic membranes, especially Pd and Pd alloys, have been intensely investigated to provide an alternative and economical way to obtain H2 with ultrahigh purity. To overcome the high cost of Pd, composite membrane structures that comprise a thin layer of Pd are utilized. However, it is a challenge to obtain a thin, dense, and uniform Pd layer on the support materials. This study investigates the parametric analysis of γ-Al2O3 interlayer formation and the electroless Pd plating (Pd ELP) procedures on α-Al2O3 supports with the aim to achieve a thin, uniform Pd surface without annealing. Adjustments in PEG/PVA concentration, dipping time, and heat treatment enabled creating a thin γ-Al2O3 interlayer on α-Al2O3, minimizing pore size and density. Hydrazine concentration, heat treatment, and bath temperature were adjusted to optimize Pd ELP to achieve maximum yield from the plating bath and a dense, uniform surface without annealing. Pd/γ-Al2O3/α-Al2O3 structures were analyzed using scanning electron microscopy, X-ray diffraction, and thermogravimetric analysis to observe the impact of varied parameters on surface structures. Optimized sample was compared to an annealed Pd/α-Al2O3 prepared in accordance with literature methods and a Pd/graphite/α-Al2O3 sample to validate the use of optimized ELP procedure and the γ-Al2O3 interlayer. Results show that a dense and uniform 13 μm Pd coating was achieved on a γ-Al2O3-coated α-Al2O3 support without annealing, using three fresh ELP baths. This was done using sequential hydrazine addition with a decreased concentration (1 M) into the ELP baths at 30 °C, and applying heat treatment at 120 °C between each fresh ELP bath.

Slag heterogeneity of autogenous copper concentrates smelting

ABSTRACT Due to the deterioration of the raw material base of copper production, it becomes necessary to optimise the autogenous smelting of copper sulfide concentrates, intensify the thermal regime and reduce the loss of copper with slags. There were carried out physico-chemical studies of the properties of slag produced during smelting of copper sulfide concentrates from the Balkhash copper smelter (BCS) in Vanyukov furnaces (VF), using X-ray fluorescence, mineralogical, X-ray diffraction, X-ray microanalysis, thermal analysis. Slag samples were taken at various distances from the furnace bottom (800–2400 mm) when the furnace was stopped. An intermediate layer of variable composition and considerable thickness (250–400 mm), was detected especially at lower smelting temperature, it is located at the bottom of the slag melt, directly on the border with the matte in the VF furnace. The novelty in the obtained data consists in finding the dependence of the formation of the intermediate layer between the slag and matte on the temperature and the content of magnetite in the slag. In addition, it was found that the necessary condition for more complete separation of slag and matte and prevention of intermediate layer formation, is the melting of slag phases, regardless of its composition.

Enhanced Adhesion Strength of Pt/γ-Al2O3 Catalysts on STS-444 Substrate via γ-Al2O3 Intermediate Layer Formation: Application for CO and C3H6 Oxidation

Pt/γ-Al2O3 catalysts coated on honeycomb-shaped stainless STS-444 steel substrates with a γ-Al2O3 intermediate layer were prepared using a conventional washcoating method. The intermediate layer was formed on the substrate surface through oxidation using pack cementation. The monolithic catalysts with the intermediate layer were fabricated for potential applications to pre-turbocharger catalysts, which suffer from severe conditions such as vibrations of the engine and high flow rates of exhaust gas. Adhesive strength tests and simultaneous oxidation reactions of CO and C3H6 were carried out for the Pt/γ-Al2O3 monolithic catalysts with and without the intermediate layer. The catalysts with an intermediate layer showed much stronger adhesion than the catalysts without an intermediate layer. Thus, the formation of a γ-Al2O3 intermediate layer by surface oxidation through pack cementation facilitated a significant enhancement of the catalyst adhesion strength without catalytic performance degradation.

Experimental and Numerical Analyses of Cooling and Intermediate Layer Formation Process at the Magnetic Pulse Welded Al/Fe Joint Interface

Experimental and Numerical Analyses of Cooling and Intermediate Layer Formation Process at the Magnetic Pulse Welded Al/Fe Joint Interface

Spring cold water intrusions as the beginningof the cold intermediate layer formation in the Baltic sea

Thermohaline intrusions are a typical feature of the Baltic Sea water body. We report observations of vivid colder/saltier intrusion activity in intermediate layers and upper pycnocline of the Gdansk Bay (the south-eastern part of the Baltic Sea) in early spring (March–April, 2013). Extremely low water temperature (down to 1.4–2 °C) and specific water salinity (SÃ7.5–7.8) of the intrusions point at a possible area of the intrusion waters formation: within the upper mixed layer in the Arkona/Bornholm basins at the end of March. Data on water temperature and salinity available from the International Council for the Exploration of the Sea (ICES) data repository, data of the Arkona Becken automated station, meteorological information, and remote sensing data for March–April 2013 are used to confirm the conclusions. It is confirmed once again that the transfer from the two-layered winter water stratification to the three-layered summer one in the Baltic Sea is a consequence of the sea-scale exchange process. The latter is manifested as simultaneous advection in upper and intermediate layers of waters with lower and higher salinity, correspondingly. The reported extremely cold intrusions indicate the beginning of the formation of the Cold Intermediate Layer (CIL), which thus contains waters of the Arkona/Bornholm basins. The main environmental factors driving the observed vivid intrusions in April 2013 are easterly winds and negative buoyancy fluxes due to seasonal solar heating of waters with the temperature below that of the density maximum. Substantial prolongation of the period of seasonal vertical mixing might be the most important process related to the transition of water temperature over the temperature of the density maximum (Tmd) in the Baltic Sea. With the climate warming, the cooling of surface waters below the Tmd becomes rare, limiting deep ventilation of Baltic waters in spring.

Effect of sodium diffusion on the properties of CIGS solar absorbers prepared using elemental Se in a two-step process

The influence of Na diffusion from various glass substrates during a high-temperature slenization process on the microstructure and morphology of two-step formed CIGS absorber layers is investigated. In order to minimise the CIGS absorber formation time, elemental Se vapour is used to prepare the CIGS absorber. The grain sizes of the CIGS films are found to increase with increasing sodium in the glass substrates (extra clear glass, soda-lime glass, borosilicate glass). TiN and SiN thin films are used as diffusion barrier layers inserted between the glass substrate and the Mo rear conatct to tune the Na diffusion from the soda-lime glass. The interdiffusion between the In-rich CuInSe2 surface layer and the Ga-rich CuGaSe2 layer is promoted by the barrier layer, leading to larger CIGS grains. Efforts are also taken to understand the differences in Na diffusion (from the glass substrates) and their effects on the MoSe2 intermediate layer formation during the high-temperature CIGS absorber formation processes. We find that excess amounts of Na and Se are essential for the MoSe2 growth. The excessive Na in the form of Na2Sex at the CIGS/Mo interface works as a Se source and catalyses the MoSe2 formation. The Se flow in the two-step CIGS formation process must be sufficiently high to obtain high-efficiency CIGS solar cells.

Chronostratigraphic interpretation of intermediate layer formation cycles based on OSL-dates from intercalated slope wash sediments

Stratified periglacial sediments extensively cover the slopes of central European low mountain areas. Periglacial cover beds and loess-like sediments as most abundant strata influence many near-surface processes, forming an important component of the Earth's critical zone.The present study focusses on the analysis of a complex sequence of periglacial slope deposits with multiple intermediate layers and intercalated slope wash sediments in order to determine and date periods of intermediate layer formation.Since luminescence dating often provides inconsistent data for cover beds, there is need to reconsider the numerical dating strategy. This study hence places stronger emphasis on numerical dating of interbedded, sufficiently bleached slope wash sediments. The gained OSL-ages are more reliable and consistent and thus, provide a temporal framework for relative dating of intermediate layer formation cycles. In combination with paleosol relics the numerical ages allowed a chronostratigraphic interpretation of Late Pleistocene paleoenvironmental dynamics and slope evolution.Our findings not only prove multiple phases of intermediate layer formation in the study area during the last glacial period but also enabled the correlation of single intermediate layers with specific time spans, including Early and Middle Weichselian as well as the Late Glacial. Remnants of the Eemian soil in the studied sequence even indicate a Saalian age for the lowermost intermediate layer.The present study shows that luminescence dating of intercalated slope wash deposits instead of cover beds is a promising numerical dating strategy for the chronostratigraphic interpretation of cover bed sequences. The findings further illustrate that complex, fanned out periglacial sediment sequences form despite their scarcity important paleoenvironmental archives for Late Pleistocene periglacial landscape dynamics in central European low mountain areas.

Kinematic-wave model of viscous fingers with mixing layer

A new one-dimensional kinematic model of viscous fingers growth is proposed. This model is based on the assumption of an intermediate layer formation. The shear instability of the flow is developed in this layer due to intensive mixing of liquids of different viscosities. The thickness of the intermediate layer between outer ones is determined by the velocity difference in the layers. The results of the calculation of the growth rate of the fingers in the framework of this model are in a good agreement with the calculations carried out on the basis of more general two-dimensional equations as well as with the known Koval model.

Interface stability of electrode/Bi-containing relaxor ferroelectric oxide for high-temperature operational capacitor

The interface stability between electrodes (Pt, TaC, TiC, and RuO2) and a Bi-containing relaxor ferroelectric oxide, BaTiO3–Bi(Mg2/3Nb1/3)O3 (BT–BMN), applied to a high-temperature operational capacitor was investigated by hard X-ray photoelectron spectroscopy. All the electrodes showed electron filling at the Fermi level after annealing at 400 °C. However, Pt and TaC indicated electrical property degradations due to the thick intermediate layer formation and defect formation of the BT–BMN layer relating to the Bi diffusion into the electrodes. In contrast, TiC inhibited the Bi diffusion and did not show any change in the band alignment after annealing. Furthermore, RuO2 eliminated the defect formation in BT–BMN and showed no change in the band alignment although the Bi diffusion was also observed. These results suggest that the TiC/RuO2/BT–BMN stack structure is a potential candidate for the high-temperature operational capacitor.

STUDY OF WEAR PROCESSES OF WELD CLADS

This paper deals with the analysis of the renovation layer quality of continuous casting steel rolls, developed through the submerged arc surfacing method (SAW). The continuous casting roll was analysed via the degradation phenomena which act during the operation. Four kinds of filler materials were used for the renovation of the worn roll. Surfacing was carried out as a three-layer in order to eliminate the need for intermediate layer formation. The quality of weld deposits was evaluated in terms of the structure, hardness and wear resistance of weld deposits at 23°C and 400°C using pin-on-disc wear test. The best properties showed newly developed filler material W8-WLDC8 from the point of view of the hardness, together with wear resistance of the deposited layers in room and elevated temperatures.

Change in Mechanical Properties of Weld Claddings after Cyclic Thermal Loading

This contribution deals with the analysis of the renovation layer quality of continuous casting steel rollers, developed through the submerged arc surfacing method (SAW). The continuous casting roller was analysed through the degradation phenomena which act during the operation. Four kinds of filler materials were used for the renovation of the worn roller. Surfacing was carried out as a three-layer in order to eliminate the need for intermediate layer formation. The quality of weld deposits was evaluated in terms of the structure and microhardness after thermal cyclic loading. The best properties showed newly developed filler material W8-WLDC8 from point of view of the microhardness.

Functional Corrosion-Resistant Enamel Coatings and Their Adherence Strength

Functional corrosion-resistant glass enamel coatings make it possible to protect inner surface of oil pipelines in extreme operating conditions. The aim of this study is to propose competitive fluorine-free coatings for energy-effective direct-on enameling technology of pipes. The enamel coatings were applied on the steel surface by the slip method (coatings thickness 450 μm). Their physicochemical and production parameters were defined. The strong adhesion of synthesized enamels to the steel substrate has been achieved by using of the complex adherence promoter, containing optimal quantity of CoO and CuO oxides. The coatings forming mechanism on steel substrate by flexible regime 1 coat–1 firing have been studied. It is established that high level of the coating adhesion is the result of a complex heterogeneous interaction of metal with oxide melt, dissolution and diffusion processes and, as a consequence, intermediate layer formation at the phases boundary during melting (770–780 ◦C). As a result of conducted research, obtained nonnickel rust-resistant glass enamels have been accepted for production of steel pipes with enameled surface.

Features of Intermediate Layer Formation in Water-Oil Emulsions

New data on the mechanisms of intermediate layer formation in petroleum emulsions are reported. The possibility of structural phase transitions preceding the inversion points of these multicomponent media was experimentally demonstrated. Many features of these transitions are similar to the phase transitions in model dispersions of the Winsor III type. In manufacturing processes, the formation of undesirable “intermediate layers’ can be interpreted as the appearance of a bicontinuous phase at ratios of the volume fractions of water and crude close to unity.

A kinetic model of diamond nucleation and silicon carbide interlayer formation during chemical vapor deposition

The presence of thin silicon carbide intermediate layers on silicon substrates during nucleation and the early stages of diamond deposition have been frequently reported. It is generally accepted that the intermediate layer is formed by the bulk diffusion of carbon atoms into the silicon carbide layer and the morphology and orientation of the diamond film subsequently grown on the intermediate layer are strongly affected by that layer. While there have been considerable attempts to explain the mechanism for intermediate layer formation, limited quantitative data are available for the layer formation under the operating conditions conducive to diamond nucleation. This study employs a kinetic model to predict the time evolution of a β-SiC intermediate layer under the operating conditions typical of diamond nucleation in hot filament chemical vapor deposition reactors. The evolution of the layer is calculated by accounting for gas-phase and surface reactions, surface and bulk diffusions, the mechanism for intermediate layer formation, and heterogeneous diamond nucleation kinetics and of its dependence on the operating conditions such as substrate temperature and inlet gas composition. A comparison between the time scales for intermediate layer growth and diamond nuclei growth is also performed. Discrepancies in published adsorption energies of gaseous hydrocarbon precursors on the intermediate layer—ranging from 1.43 to 4.61 eV—are examined to determine the most reasonable value of the adsorption energy consistent with observed saturated thicknesses, 1–10 nm, of the intermediate layer reported in the literature. The operating conditions that lead to intermediate layer growth followed by diamond deposition vs. those that yield heteroepitaxial diamond nucleation without intermediate layer formation are discerned quantitatively. The calculations show that higher adsorption energies, 3.45 and 4.61 eV, lead to larger surface number densities of carbon atoms, lower saturated nucleation densities, and larger intermediate layer thicknesses. The observed saturated thicknesses of the intermediate layer may be reproduced if the true adsorption energy is in the range of 3.7–4.5 eV. The intermediate layer thickness increases by increasing substrate temperature and inlet hydrocarbon concentration and the dependence of the thickness on substrate temperature is especially significant. Heteroepitaxial diamond nucleation without intermediate layer formation reported in experimental results can be readily explained by the significant decrease of the intermediate layer thickness at lower substrate temperatures and at higher diamond nucleation densities. Further, the present model results indicate that the intermediate layer thickness becomes saturated when growing diamond nuclei cover a very small surface area of that layer.

Sequential observations of the local neutral wind field structure associated with E region plasma layers

The first sequential rocket experiment to study intermediate layers in over 30 years was launched from Wallops Island, Virginia on the night of 29–30 June 2003. Using an onsite digisonde to determine the presence of sporadic E and conditions indicating the possible presence of an intermediate layer, four rockets were launched over a 4‐hour period. Three of the rockets launched with at least an hour separation; they each contained chemical release experiments and plasma impedance probes. All four payloads encountered two plasma layers on both the ascent and descent of the flights. The lower‐altitude layer, located at approximately 100 km, is clearly a sporadic E layer. The higher‐altitude layer, located between 120 and 130 km, displays many characteristics of an intermediate layer, but it exhibits little downward motion over time. The neutral wind profiles resulting from the chemical tracer experiment are presented here along with the vertical drift velocities derived from the wind measurements. These are compared with the electron density profiles. They show a good agreement between the convergent regions in the velocity profiles and the location of the sporadic E layers. However, agreement between the center of the convergent vertical drift regions and the location of the higher‐altitude layer is poor. The inclusion in the drift calculation of electric field data from the instrumented rocket significantly improves the overall agreement between the convergent vertical drift region center and the intermediate layer center. The convergent region is within 4 km of the intermediate layer. Further, the density depletions surrounding the layers coincide with the regions of divergent drift. The relatively large discrepancy observed between the shear in the vertical drift and the location of the intermediate layer implies that other factors such as horizontal motion structure variations may be important. Thus intermediate layer formation theory and subsequent evolution is still not fully understood.

NbSi2 coating on niobium using molten salt

For obtaining better oxidation resistance of niobium in air, a niobium silicide was non-electrolytically deposited onto niobium from the molten salt, where a disproportional reaction occurs between Na2SiF6, SiO2, and Si. A single phase of NbSi2 was formed with a homogeneous thickness of about 10 μm above 1073 K. The oxidation resistance of pure niobium with this coating layer was improved. During the oxidation at the high temperatures, Nb5Si3 was formed at the interface between the Nb substrate and the NbSi2 layer. Due to this intermediate layer formation, the oxidation resistance became better than for pure NbSi2.

Ageing effects in bimetallic films

Abstract Measurements of adhesion have been made on films of silver, gold, copper and aluminium with under layers of chromium. The films have all been deposited on glass microscope slides by vacuum evaporation and the adhesion has been measured by drawing a smoothly rounded point across the surface whilst increasing the load on the point until a clear, well-defined channel was produced. It has been shown that in the case of bimetallic films, abnormally high figures may be obtained due to the formation of an intermediate layer by diffusion or intermetallic reaction. The results show a dependence upon the thickness of the chromium underlayer and time as well as upon the metal of the upper layer. Explanations are based upon a structural model for chromium films which assumes an aggregated structure formed of oxide-coated particles below 400 A thickness and a continuous metallic structure above this thickness. It is shown that intermediate layer formation occurs only when the thickness of chromium exceeds 400...