Early Stage Of Deposition Process Research Articles

Cleaning action of spherical projectiles in tubular heat exchangers

Projectiles of different properties, i.e. shape, materials, hardness, can be propelled through the heat exchanger tubes to mitigate fouling when used at the early stage of deposition process. In the present study, fouling experiments have been performed in which CaSO4 was used as foulant and plain tubes as heat transfer surfaces. The rate of projectile injection was also varied to discern its impact on the cleaning. The experimental results showed that at fouling conditions, the inner layer of the deposit, i.e. near the heated surface, is sintered while the outer layer of the deposit, i.e. near the solution side, is porous and crystalline. As the fouling process reaches an asymptote, the whole fouling layer is sintered. Sintering changes the whole fouling layer to a robust and non-porous structure which does not allow the projectile to remove crystals from the deposit layer anymore. Two mechanisms are simultaneously dominant once projectiles are injected (i) sintering of the fouling layer near the tube surface and (ii) removal of precursors from the deposit layer near the solution side due to projectiles. If the removal rate is faster than the sintering rate then it is expected to end up with a very thin sintered layer and vice versa. Furthermore, using high injection rates will minimize the deposit thickness and once an asymptote is reached then it is not recommended to use projectiles anymore.

The early stage of deposition process for Fe–Cu magnetic multilayer systems: molecular dynamics simulation

The deposition behaviour for a Fe–Cu magnetic multilayer system in an early stage of the deposition process was investigated by molecular dynamics (MD) simulation. Specifically, the steering effect was quantitatively investigated through extensive measurements of the trajectory, deposition flux and force of atoms near the artificially structured Fe or Cu step positioned on the Cu(0 0 1) or Fe(0 0 1) surface. Near the step edges of the planar structure at a low incident energy of 0.1 eV, the steering effect for the case of Fe/Cu(0 0 1) was observed more significantly than for Cu/Fe(0 0 1). Additionally, the mechanism of down-diffusion from the step was discussed and the corresponding energetic was calculated using the molecular statics method.

Preparation of pzt thin films on Pt/Ti/SiO2 and Pt/SiO2 Substrates by ECR Plasma Enhanced DC Magnetron Multi-target Reactive Sputtering

AbstractPerovskite-phase lead zirconate titanate (PZT) thin films were fabricated at 4751C by the electron cyclotron resonance (ECR) plasma enhanced DC magnetron multi-target reactive sputtering method on Pt/Ti/SiO2/Si and Pt/SiO2/Si substrates. Stoichiometric perovskite PZT films were readily obtained on Pt/Ti/SiO2/Si substrates because Ti atoms which were out-diffused to the Pt surface facilitated Pb incorporation by forming lead titanate at the early stage of deposition process. Activation of oxygen by ECR plasma facilitated the oxidation reaction and Pb incorporation into the film. Thus perovskite-phase PZT can be obtained on the Pt/SiO2/Si substrate.