Oxidation Of Nickel Surface Research Articles

Oxidation of nickel surfaces through the energetic impacts of oxygen molecules: Reactive molecular dynamics simulations.

Molecular dynamics approach accompanied by reactive force field is used to study the characteristics of the oxide growth process on Ni(100) and Ni(111) surfaces at the temperatures of 300, 600, and 900 K and 5 eV as the energy of the O2 impacts. The exposure of Ni surfaces to the high-energy O2 impacts indicates that the primary oxide nuclei can be formed on any impact site. The results of kinetic studies clarify that the oxide growth kinetics cannot be accurately explained with the island growth model and increasing the surface temperature raises failure of the model. Under the present conditions, the growth kinetics is found to obey a Langmuir growth model. Increasing the surface temperature from 300 to 900 K results in ∼18.75% and ∼23% more oxygen consumption by (100) and (111) surfaces of Ni, respectively. The structure of nickel oxide (NiO) film formed after 200 successive O2 impacts per surface super-cell is investigated utilizing radial distribution functions and oxygen density profiles. These calculations demonstrate that the structure of the formed NiO film is amorphous. Moreover, the charge profiles in Ni/NiO system are illustrated and discussed.

Oxidation of nickel surfaces by low energy ion bombardment

We have studied formation of oxides on Ni surfaces by low energy oxygen bombardment using X-ray photoemission spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). Different oxidation states of Ni ions have been identified in XPS spectra measured around Ni 2p and O 1s core-levels. We have compared our results with thermal oxidation of Ni and shown that ion bombardment is more efficient in creating thin oxide films on Ni surfaces. The dominant Ni-oxide in both oxidation processes is NiO (Ni2+ oxidation state), while some Ni2O3 contributions (Ni3+ oxidation state) are still present in all oxidised samples. The oxide thickness of bombarded Ni samples, as determined by SIMS, was shown to be related to the penetration depth of oxygen ions in Ni.

Research on Surface Coating Technology of PCB Based on ENEPIG

Now the protection method for PCB welding board, widely used coating technology is ENIG , but in use course found that the coating will appear “black mat” that is fatal flaw in the welding process, in order to solve this problem, the engineers and technicians have taken various methods of strict control parameter, despite the improvement, but has not eradicated “black mat” this hidden trouble .Electroless palladium layer is introduced in ENEPIG surface coating new technology, from the reaction mechanism stopped nickel-plate oxidation, in the process of immersion gold blocked off nickel-plate contacted with Immersion gold solution, and effectively prevent pervasion and migration of nickel , thus effectively inhibit oxidation of nickel surface, prevent the “black mat” flaw . Not only have given the technology production process and parameter control, but also have microcosmic appearance and diffusibility analysis for the products by using SEM and EDS , the results showed that palladium layer is non-crystalline film with good uniformity of coating thickness, and did not find pervasion of nickel on gold surface, successfully achieve ENEPIG PCB mass production, replace ENIG technology .

Hydroxylation of NiO films: the effect of water and ion bombardment during the oxidation of nickel foils with O 2 under vacuum

The effect of water on the oxidation of nickel surfaces under vacuum was investigated using X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS) and temperature-programmed desorption (TPD). It was found that the presence of a small amount of water in the gas phase (of H 2O partial pressures as low as 10 −8 mbar) is enough to create a monolayer of surface hydroxyl groups on top of nickel oxide films. The formation of the OH groups was detected by both XPS and SIMS, and their superficial nature was assessed by angle-resolved XPS and depth profiling experiments. It was also found that the simultaneous ion bombardment of the surface during combined O 2 + H 2O treatments leads to an enhancement in the rate growth for the NiO film but does not affect the formation of the OH layer in any way other than via sputtering of the surface. The most interesting observation from this work is the fact that adsorbed water appears to induce the reduction of nickel oxides, as it becomes apparent by the thinning of the grown NiO films. Two temperature extremes were observed in relation to this phenomena. On the one end, exposure of nickel substrates to a combination of oxygen, argon ions and water below 200 K results in a decrease in NiO film thickness by about a factor of two, a behavior likely to be associated with the enhancement in water adsorption at those low temperatures. At the other extreme, temperatures above 650 K are also sufficient to trigger the NiO film thinning, in this case even in the absence of argon ions. Two possible explanations for these observations are discussed.

Influence of argon ion bombardment on the oxidation of nickel surfaces

The effect of argon ion bombardment on the oxidation of nickel films was studied using X-ray photoelectron spectroscopy (XPS). In the absence of any ion beams, exposure of nickel surfaces to oxygen leads to the moderately rapid formation of a thin (3–5 monolayers thick) nickel oxide overlayer. At room temperature the oxygen uptake stops once this limit is reached, but at higher temperatures the slow growth of a thicker oxide is seen. The NiO growth kinetics can be phenomenologically described by a diffusion coefficient for either oxygen or (more likely) nickel ions through the forming oxide film of the order of 2 × 10 −18cm 2 s −1 at 625 K. The simultaneous impingement of argon ions on the surface during oxygen exposures was found to enhance the oxidation process, and ion beam current densities as low as 0.01 μA cm −2 were found to be sufficient to induce nickel oxidation past the 3–5 ML limit at room temperature. The oxidation rate was found to be roughly proportional to both the ion flux and the square of the oxygen pressure, suggesting that the Ar + bombardment oxidation enhancement may be due to an increase in diffusivity through the NiO surface film induced by local heating around the ion impact areas. The build-up of an NiO film during this Ar +- ion oxygen treatment was also found to slow down at higher temperatures, presumably because of the combined effect of a higher probability for desorption of molecular oxygen from the surface and a higher atomic-oxygen mobility into the bulk. The oxide films prepared at low temperatures appear to be quite disordered, and display an extra feature in the Ni 2p XPS spectra around 853.2 eV which could be assigned to partially reduced nickel, Ni x+, x < 2. Annealing of those films to temperatures above 400 K leads to the possible ordering of the surface and to the disappearance of the signal for the Ni x+ species in XPS, and further heating above 600 K leads to the diffusion of oxygen atoms into the bulk and to the partial reduction of the surface nickel to its metallic state.