Presence Of Oxide Film Research Articles

Stabilization of closed-cell aluminum foam by particles in the presence of oxide film: CFD-DEM simulation on particle behavior for node-Plateau borders system

In order to reduce the particle addition in closed-cell aluminum foam, the effect of particles on foam drainage behavior was investigated numerically. The coupled CFD-DEM method was used to analyze the particle behavior within the node-PBs system. The predicted results agree well with experimental results. The results show that the trajectory of particles in metallic foam is consistent with literatures. Particles grow into clusters and deposit on the oxide film, leading to foam clogging and suppressing the drainage in aluminum foam. The above mechanism explains the phenomenon in literatures that the viscosity obtained from the drainage experiment is much greater than the apparent viscosity of the particle-melt mixture. The effect of particles on suppressing drainage is summarized as the blockage effect of stationary particles and the increasing apparent viscosity of moving particles. There is an optimization possibility of particle size and volume fraction, achieving better performance and lower production costs.

Nickel improving the combustion of boron powder

Boron (B) powder has a very high energy density and is often used as an additive to solid propellants. However, its high melting point and the presence of oxide film on its surface make it more difficult to ignition and incomplete combustion. This problem can be effectively improved by the addition of other metal particles. Therefore, nickel-modified boron-based complexes (B/Ni) were prepared by adding nickel (Ni) nanoparticles to the B powder. The effect of different Ni contents on the ignition and combustion of B powder was investigated. The appropriate addition amount of Ni nanoparticles to B powder can significantly decrease the onset oxidation temperature, and effectively increase the exothermic heat, but it has little effect on the maximum combustion intensity of B powder. The addition of Ni nanoparticles changes the reaction path of B and promotes its oxidation. These results may provide a reference for the application of Ni nanoparticles in boron-based solid propellants.

Investigation of Metal Composite Briquette Operation in Absorption Equipment Friction Units

Reasons are considered for unsatisfactory operation of the energy-absorbing device of railway wagon drawbar, whose main element is a friction plate with special energy-absorbing cermet coating. The main specifications for the friction plate are resistance to shock loads, resistance to thermal cycles in the temperature range from ambient temperature to 850–870°C, good resistance to shear stresses, friction coefficient stability in this temperature range, lack of seizure to friction wedge material made of steel, and long operating life up to 10,000 loading cycles. According to results of metallographic studies using optical and scanning electron microscopy with energy dispersion microanalysis it is established that the poor quality of the friction plate metal composite coating is caused by the following factors: localization of eutectic containing sulfur, iron, and manganese along the “ceramic-substrate” boundary, and presence of oxide films on the surface of precursor powder particles. As a result of this excess interfaces arise in cermet material that are areas of microcrack formation during cermet operation. Thermal stresses arising during metal composite briquette manufacture lead to crack development at the interface of metal composite and a steel base. Application of unevenness to the steel base of metal composite material in a hydrogen or endogas atmosphere makes it possible to avoid both thermal cracks and subsequent metal composite separation during operation. An improvement in operating characteristics is confirmed during laboratory tests under conditions approximating operational.

Multi-Criteria Assessment of Physical Properties of Nanostructured Decorative Protective Coatings

One of the most efficient methods of improving the durability of a product is applying different coatings to the working surface. The quality of decorative and protective coatings is determined by the quality of workpiece surface (roughness, texture, etc.), preparation of workpiece surface (contamination, presence of oxide films, degree of surface activation by ion etching), and the production methods. The article presents the results of a series of experiments in creating multi-component ion-plasma coatings by vacuum deposition on Ti-Al basis. A series of experiments aimed at obtaining single-layer coatings have been carried out using a certain pattern of sputtering in argon and nitrogen environment. The obtained coatings can have a wide variety of colors. Different properties of the created coatings including spectral characteristics, reflection coefficient at different angles of incidence of light as well as chemical composition have been studied. The energy-dispersive electron microprobe analysis revealed the dependence of coating reflection coefficient and spectral characteristics on the chemical composition.

Effect of Sound Waves on Decarburization Rate of Fe-C Melt

Sound waves have the ability to propagate through a gas phase and, thus, to supply the acoustic energy from a sound generator to materials being processed. This offers an attractive tool, for example, for controlling the rates of interfacial reactions in steelmaking processes. This study investigates the kinetics of decarburization in molten Fe-C alloys, the surface of which was exposed to sound waves and Ar-O2 gas blown onto the melt surface. The main emphasis is placed on clarifying effects of sound frequency, sound pressure, and gas flow rate. A series of water model experiments and numerical simulations are also performed to explain the results of high-temperature experiments and to elucidate the mechanism of sound wave application. This is explained by two phenomena that occur simultaneously: (1) turbulization of Ar-O2 gas flow by sound wave above the melt surface and (2) motion and agitation of the melt surface when exposed to sound wave. It is found that sound waves can both accelerate and inhibit the decarburization rate depending on the Ar-O2 gas flow rate and the presence of oxide film on the melt surface. The effect of sound waves is clearly observed only at higher sound pressures on resonance frequencies, which are defined by geometrical features of the experimental setup. The resonance phenomenon makes it difficult to separate the effect of sound frequency from that of sound pressure under the present experimental conditions.

Liquid Phase Diffusion Bonding of AC2C/ADC12 Aluminum Casting Alloy by Using Metal Salt Coated Zn Sheet

Currently, the common way of bonding aluminum together is brazing. However, brazing creates problem when the high brazing temperature causes the formation of brittle intermetallic compound in between the joints prompting the need to circumvent this difficulty by considering transient liquid phase diffusion bonding method as a possible alternative. Being considered as a possible alternative solution, transient liquid phase diffusion bonding is not without problems that need to be overcome. One of these problems is the presence of oxide film on the insert material surface (Zn) necessitating the need to remove or destroy the oxide film without using high temperature and high load. Hence, in this study, the aim is to treat the bonding surface with formic acid for the removal of oxide film and substitution to a metal salt to determine the effectiveness of such treatment by performing tensile test and observation on the fractured surface of samples. From this study, it is found out that the tensile strength of the joint increased with the rise in bonding temperature with or without metal salt generation processing. However, it is understood that with metal salt generation processing, high strength joint can be obtained with lower bonding temperature compared with unmodified joints. It is hypothesized that this is because metallic zinc is generated as a result of surface modification and thermal decomposition of formate in the bond interface at low bonding temperatures.

Effect of Fe, Sr, P, Ti and Undercooling on the Precipitation of β-Al5FeSi in A319.2 Type Alloys

The present work was performed on an A319.2 alloy with different amounts of Fe. The melt was poured from two temperatures, i.e. 750 and 950 °C. The results show that increasing the melt superheat leads to an increase in the undercooling, e.g., 1.2 and 3 °C for melt temperatures of 750 and 950 °C, respectively. The presence of oxide films accelerates the precipitation of the β-Al5FeSi iron intermetallic phase platelets. The amount of oxide films increases with the increase in the melt temperature, coupled with the addition of Sr and P. Strontium has a strong tendency to break down the length of the β-platelets, e.g., 160 and 109 µm, for non-modified and Sr-modified alloys containing 1.2% Fe, respectively. In the absence of Sr and for a melt temperature of ~950 °C, P precipitates in the form of (Al, P)O2 oxide films. These films act as nucleation sites for the precipitation of β-platelets much finer (60 µm) than those obtained for samples poured at 750 °C. The addition of P to the 319 alloy modified with Sr results in the precipitation of (Al, P, Sr)2O5, which significantly reduces the beneficial effect of Sr. Titanium precipitates in the form of Ti(Al, Si)3 platelets at 740 °C. Relatively fine β-platelets (~130 µm) can precipitate along the long sides of the Ti–rich platelets. Iron has a harmful effect on the alloy strength due to the precipitation of dense β-platelets. The addition of Sr improves the alloy mechanical properties through fragmentation of β-platelets, especially at low content of Fe. Finally, phosphorus has an abnormal effect on the three tensile parameters, and the Sr–P interaction diminishes the beneficial effect of Sr.

Diffusion Bonding of Cu–Cu with Al–Ni Nano Multilayers

Nano multilayers have excellent properties, such as super hardness, magnetic property, high thermal conductivity and low friction coefficient etc.1) The Al­Ni nano multilayers have been investigated as a reactive nano material which could intensively release heat after an ignited self-propagation reaction. Therefore it has the potential to be used in micro-joining.2) To joining copper and copper materials, the choice should be solder or brazing materials to adapt to the needs of the components where heating furnaces were commonly used. If using nano multilayers films as heating source or joining material, the joining process could be simplified and some low heat resistant component can be protected in the joining process. The Indium Company has developed a system to do joining with nanofoils, however the rate of running such a reaction in the system is difficult to control because of the large size of its components, poor contact or presence of oxide films on their surface, hence the technology has not been widely applied. This paper investigates the probability of joining copper with Al/Ni nano multilayer films and shows several critical points which are worth to be concern in future study.

Testing validity of the Tafel extrapolation method for monitoring corrosion of cold rolled steel in HCl solutions – Experimental and theoretical studies

The protection influence of glycine (Gly) and a one of its derivatives, namely 2-(bis(2-aminoethyl)amino) acetic acid, designated here as GlyD; where GlyD stands for “glycine derivative”, against cold rolled steel (CRS) corrosion was studied in aerated stagnant 1.0 M HCl solutions at 25 °C. Measurements were conducted under various experimental conditions using Tafel polarization, linear polarization and impedance techniques. These studies have shown that Gly and GlyD are very good “green”, mixed-type inhibitors. GlyD is more effective than Gly itself in inhibiting the acid corrosion of CRS. Electrochemical frequency modulation (EFM) and inductively coupled plasma-atomic emission spectroscopy (ICP-AES) method of analysis are also presented here for monitoring corrosion. Corrosion rates obtained from both EFM and ICP-AES methods are comparable with those recorded using Tafel extrapolation method, confirming validation of corrosion rates measured by the latter. Adsorption via H-bond is discussed here, based on the presence of oxide film on the electrode surface as well as the number of NH linkages in the inhibitor molecule. Quantum chemical method was also employed to explore the relationship between the inhibitor molecular properties and its protection efficiency. The density function theory (DFT) is used to study the structural properties of Gly and GlyD in aqueous phase in an attempt to understand their inhibition mechanism. The protection efficiencies of these compounds showed a certain relationship to highest occupied molecular orbital (HOMO) energy, Mulliken atomic charges and Fukui indices.

A Method for Characterizing the Degree of Inter-particle Bond Formation in Cold Sprayed Coatings

The degree of bonding between particles within cold-sprayed deposits is of great importance as it affects their mechanical and physical properties. This article describes a method for characterizing the bonding between aluminum and copper particles following deposition by cold spraying. Aluminum and copper powders were blended in the ratio 1:1 by volume, deposited onto a copper substrate and subsequently heat treated at 400 °C for 15 min. An intermetallic layer formed along some regions of the aluminum-copper boundaries, believed to be where true metal to metal contact had occurred. In other regions, metal to metal contact was inhibited by the presence of oxide films. Image analysis was employed to measure the fraction of the aluminum-copper interface covered with intermetallic phases and to estimate intermetallic thicknesses. By increasing the primary gas pressure in the cold-spray process, an increase in the degree of inter-particle bond formation was observed.

Study on oxygen contamination during atomisation of solder powders for microelectronics

Solder paste used in electronics for interconnects in micro circuitry is the most important component, being seen as the governing factor for miniaturisation. As a result, the quality levels of solder paste are being constantly upgraded. Solder balling is a type of prominent defect generated during soldering operation encountered mostly due to the presence of oxide film on the solder powder surface. This phenomenon becomes particularly conspicuous when a fine solder powder is used in order to enhance the printability. This paper encompasses the results of studies carried out on oxygen pick up in Pb–Sn solder powders during melting, atomisation and powder storage stages for fine pitch solders. Hydrogen annealing has been conducted on the inert gas atomised solder powders before storage to avert oxygen pickup and the results have been compared with as atomised powders. It was found that, hydrogen annealing is a mandatory process to overcome problems arising out of oxides.

Factors affecting wettability and bond strength of solder joint couples

Abstract The paper discusses the scientific understanding of the role of interfacial phenomena in joining of dissimilar materials using liquid-phase-assisted processes. From the example of the Sn-alloy/Cu system, it is demonstrated that interaction in the liquid solder/substrate couples is accompanied by a number of complex interfacial reactions leading to significant changes in the structure and chemistry of interfaces (solder/substrate, solder/environment, substrate/environment) and remaining solder layer that finally influence the mechanical properties of solder joints. The experimental data on wetting behavior, interface characterization, and mechanical properties of different solder/metal substrate couples are analyzed in order to display the role of such factors as time and temperature of interaction, environment (protective atmosphere, flux), presence of oxide films on interfaces, alloying additions to a solder, formation of interfacial phases, and porosity.

Characterization of dry sliding wear resistance of laser surface hardened En 8 steel

Laser surface hardening, because of inherently high rates of heating and cooling associated with it, leads to the formation of inhomogeneous martensite in hypo-eutectoid steels. This is in contrast to conventional transformation hardening where sufficiently long soaking period above Ac 3 temperature ensures homogenization of carbon in the resultant martensite. The present study aimed at characterization of dry sliding wear resistance of laser surface hardened En 8 steel specimens and its comparison with those of conventionally hardened and quenched and tempered. The results of the study demonstrated that wear rate is critically dependent on the presence of oxide film on the surface which, in turn, is significantly influenced by testing parameters as well as by dynamic conditions during the course of testing. Under the experimental conditions of dry sliding wear, used in this work, laser surface hardened En 8 steel specimens exhibited superior wear resistance than conventionally hardened specimens. Wear resistance of laser surface hardened specimens was largely comparable to that of quenched and tempered specimens.

Corrosion-Resistant Steels for Force-Measuring Elastic Members

The mechanical and corrosion properties of copper-bearing maraging steels used for fabricating force-measuring elastic members of electronic strain-measuring scales are studied. The effects of aging temperature, process heating, and presence of oxide film on the hardness, impact toughness, and parameters of the anode process in potentiodynamic tests are investigated. After an analysis of the obtained results, a steel composition is recommended for the production of force-measuring members, and a regime for its heat treatment is chosen.

Effects of Aluminum on Weldability of Nonoriented Electrical Steel Sheets.

The effects aluminum has on the weldability of nonoriented electrical steel sheets as related to blowholes and welding bead width was studied. The addition of aluminum to steel sheets decreased the numbers of blowholes and widened the welding bead width in Gas Tungsten Arc Welding. The following effect of aluminum in steel sheets on welding blowholes was observed. The organic components in the inorganic-organic coating applied on steel sheets gasified due to welding heat and CO gas was generated. The gas dissolved in weld pool and CO gas became dissolving C and O. Aluminum acted as a deoxidizer and decreased dissolving oxygen. CO gas which generated at solidification of the weld pool was decreased. As a result, the addition of aluminum in steel decreased blowholes. The effect of aluminum in steel sheets had on welding bead width was as follows. Oxygen has been known to make the shape of welding bead deep and narrow. In the case of welding after consumer annealing, oxide film formed on the cut surface during consumer annealing. Aluminum deoxidized the dissolved oxygen which penetrated from the oxide film into the weld pool at the time of welding. As a result, the addition of aluminum in steel made the shape of welding bead shallow and wide. The driving force of convection in the weld pool of nonoriented electrical steel sheets was the surface tension because the penetration changed by the presence of oxide film on the surface in Al-free specimens even in laser welding in which electromagnetic force did not work.

On the behaviour of an oil lubricated fretting contact

Although many engineering situations involving fretting damage are lubricated, comparatively little has been reported on this aspect of fretting wear. The viscosity of the lubricating oil and its boundary layer performance are expected to influence fretting behaviour, in addition to the normal fretting parameters, such as stroke and contact force. This paper examines the effect of lubrication regime, oil viscosity and stroke on the behaviour of a ball-against-flat specimen arrangement. Ball and flat specimens were both manufactured from a bearing steel (SUJ2). Polybutane oils, without additives, covering a range of viscosities from 1 to 10 000 cSt, and fretting strokes up to 35 μm were investigated. The lubricating oil was added to the fretting interface after 0, 3 and 2000 fretting cycles had been completed. Lubrication regime, oil viscosity and stroke were all found to affect fretting behaviour in terms of both coefficient of friction (or traction coefficient) and wear. For strokes less than 9 μm, i.e. for conditions approaching almost complete ‘stick’, coefficient of friction values under oil lubrication were well in excess of double those observed without it. These high values suggest that the oil was unable to penetrate into the fretting contact region, but did maintain a shield around it, so that metal-on-metal contact was maintained under oxygen deprived conditions. The lowest values of steady state coefficient of friction (≈ 0.2) were observed when oil lubrication was applied after 2000 cycles had been completed, indicating that surface roughening and the presence of oxide films and oxidised debris assisted penetration of the lubricant into the fretting contact zone.

Mechanical properties of amorphous alloy compacts prepared by a closed processing system

Recently, Al-based and Mg-based amorphous alloys have attracted much attention as light weight structural materials because of their high tensile strength and good ductility. The development of a process for consolidating amorphous alloy powders to amorphous alloy bulks is essential to the structural application of these new alloys. The consolidation of Fe-based and Co-based amorphous alloy powders has been carried out by a number of techniques, such as explosive compaction, dynamic compaction, static high pressure compaction, extrusion and rolling. More recently, it has been reported that mechanical properties of amorphous alloy compacts deteriorate in the presence of oxide films in interparticle boundaries. In the present study, a closed processing system for consolidation of amorphous alloy powders has been developed in order to suppress the formation of oxide layers in the interparticle boundaries and to avoid the dangers of explosions. In this system, a series of processing from the powder production to the extrusion of them can be performed in a vacuum or an inert gas atmosphere. The compressive strength of Al[sub 85]Ni[sub 10]Mm[sub 5] (Mm: mischmetal) amorphous compacts prepared by this process is examined and compared with that prepared by the ordinary one.

Mass Balance in Near-Cathode Plasma and Initiation of Quick-Moving Cathode Spots

The explosive model of a quick-moving cathode spot [2], [3] allows us to describe many experimental facts qualitatively. However, some details of the model need further physical explanation, in particular because of the analysis of the latest experimental data [4]. Estimations given in this paper show it is possible to include in the framework of the explosive model mass balance in the plasma ball and explain the fact of the appearance of a new spot at the periphery of an old one observed in experiments [9], [10]. From the physical point of view, solution of this question is connected in the paper with the presence of oxide film on the cathode surface. Besides, it is shown that the discrepancy in erosion, observed in experiments [2], [4], can be connected with the difference in the thickness of oxide film.

Thermodynamic analysis of the chemical mechanism for the hot-salt corrosion of titanium alloys

From an examination of the AZT = = f(T) relationships for the oxidation reactions (Fig. la) it can be concluded that at temperatures up to 600~ oxide layers of complex chemical composition, viz., titanium oxides and oxides of the alloying components may be formed on the surface of titanium alloys. At the temperatures of hot-salt corrosion the nor~alaffinity of titanium and the alloying components for oxygen decreases to almost the same degree but remains fairly high. These calculations agree with the experimental data on the presence of oxide films at sites of corrosion failure. The oxidation of salts to form oxides and free chlorine is thermodynamically For the majority of salts their affinity for oxygen increases with an increase in temperature. In decreasing probability of oxidation salts can be placed in the orderz ZrCla, MoCI2, AICIs, CrCI2, TiCIa, FeCI,. When salts react with water vapor, reactions which are accompanied by the formation of the metal hydroxides or oxides and hydrogen chloride (Fig. ib)are themodynamically probable. The reactions with MoCI4 and AICIs have a high probability of taking place. In the case of the reaction between titanium chlorides and water vapor it can be expected that up to 400~ the pyrohydrolysis of TiCI4 is more probable, while above 400~ the pyrohydrolysis of TIC13 is more likely. Here the pyrohydrolysis of TiCI~ and TiCI3 is more probable thermodynamically than that of TiCI~. From a comparison of the results of a thermodynamic analysis of the type of reactions "salt + H20" and"salt + 02" it follows that at hot-salt corrosion temperatures oxidation reactions of the salts are more probable than their pyrohydrolysls, i.e., the presence of free chlorine in the corrosion products is more probable thermodynamically than that of hydrogen chloride. When chlorine reacts with the layer of oxides, a number of chlorides of the alloying components are formed on the surface of the alloy besides the titanium chlorides. It is characteristic than many impurity oxides are chlorinated appreciably more readily than the

Optical constants of copper and nickel

The optical constants of copper and nickel polycrystals have been measured at 5461 and 6328 Å. The measurements were made on samples that were mechanically polished, annealed in UHV, and ion bombardment cleaned to approach the ideal smooth, clean annealed state. Calculations are presented of values the optical constants would have if the presence of oxide films, surface roughness, and experimental errors are neglected. Comparison with literature values is given.