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The dynamics of transient plasmas generated by high-fluence nanosecond laser ablation has been investigated by recording the ionic current with a Langmuir probe. Systematic measurements have been carried out on a plasma produced in vacuum by Nd:YAG laser irradiation of a copper target. The temporal evolution of the ionic current for different fluences was investigated, revealing the presence of some periodic oscillations. A theoretical model is proposed in order to describe the nonlinear behavior of the expanding plasma by assuming that the motion curves of the ablated particles are fractals. The behaviors predicted by the proposed theoretical model are in good agreement with the experimental findings.

In cases where an explosive atmosphere contains several types of inflammable and/or combustible gases, steams or powders, the protection measures must be appropriate to the highest possible danger. However, the employer must pay special attention to the workplace and to any factor that can influence the working conditions, especially to those related to the workers. Therefore, any device, tool or equipment used by the human operator must possess special properties. In addition to protective clothing, workers who work at heights must receive personal protective equipment against falling that includes multiple linking elements known as carabiners. The carabiners used in this equipment must be made of non-sparking material. The aim of this paper is to propose a spark characteristic improvement of carbon steel used in carabiners manufacturing by deposition of zinc phosphate coating.

Steel depositsobtained by thermal spray arc have physical-chemical and mechanical properties dependent on operational parameters of the spraying process. Thus, the electric current intensity, the spray distance, the velocity, respectively the driving gas pressure are the parameters that influence the mechanical properties of the steel deposits obtained by thermal spraying. The interaction between particles- gas drive seen in the classic arc spray has the effect the lowering of particles temperature and implicitly of the physical and mechanical properties of the deposit. Using a new device, combined, in which over the thermal field, created by the electric arc, would overlap a second thermal field, created by a gaseous fuel burning, would determine the maintaining of high temperature of the particles and implicitly changes of the physical, chemical and mechanical properties of the deposit. Such a combined spraying device would be called device for spraying in electric arc-thermally activated. The paper aims to present a comparative study of the physic chemical and mechanical properties of steel deposits obtained with two spraying processes: the classical process and the combined spraying process - in electric arc thermally activated.Investigations carried out on the structure of deposits by electron microscopy SEM, XRD analysis and image analysis performed at zone level Layer-Substrate as well the deposits adherence assessment in accordance with EN 582-allows the highlighting properties, the arguing of differences between the properties of the deposits made by the two methods as well as the establishing advantages and disadvantages using those processes.