Temporal Evolution of Pressure Generated by a Nanosecond Laser Pulse Used for Assessment of Adhesive Strength of the Tungsten–Zirconium–Borides Coatings

The article presents theoretical and experimental study of shock waves induced by a nanosecond laser pulse. Generation of surface plasma pressure by ablation of the graphite absorption layer in water medium and shock wave formation were analyzed theoretically and experimentally. The amplitude and temporal variation of the shock wave pressure was determined basing on a proposed hydrodynamic model of nanosecond laser ablation and experimentally verified with use of a polyvinylidene fluoride (PVDF) piezoelectric-film sensor. The determined pressure wave was used for examination of adhesive strength of tungsten–zirconium–boride coatings on steel substrate. The magnetron sputtered (MS) W–Zr–B coatings show good adhesion to the steel substrate. The obtained experimental results prove the correctness of the proposed model as well as the suitability of the procedure for assessment of adhesive strength.

Nanocrystalline Composite Smart Coating Deposition for Corrosion Self-Healing of Mild Steel

This work examine the potential of ZrB2 in the presence of Ni-P-Zn sulphate rich bath coating on mild steel under change in time from 10-25 min. The coating pH of 5, current density of 1 A/cm2, and stirring rate of 250 rpm was considered in the fabrication process. The microstructure evolution and properties of the deposited coating was analysed using a scanning electron microscope enhanced with energy dispersive spectroscopy (SEM/EDS). All deposited composite coating was investigated in 0.5 M H2SO4 and 3.5% NaCl with the help of linear polarization and open circuit potential. From the result, a solid crystal formation containing zirconium boride was seen from the SEM study. At 25 min a remarkable dispersed and even thin film was noticeable at the interface. From all indication, coating produced with Ni-P-Zn-10ZrB2 at 25 min provides a passive response against corrosion damage. Keywords: Electrodeposition, interface, nanocrystalline, structure, coating

Effect of ZrB2 nanopellets on microstructure, dielectric, mechanical and thermal stability of polyimide

Zirconium boride (ZrB2) with high electrical, thermal conductivity, chemical stability and low coefficient of thermal expansion has been considered promising boride ceramic. In this study, the new type polyimide(PI)-based composites filled with ZrB2 nanopellets were prepared via in-situ polymerization. The results show that the ZrB2 nanopellets are dispersed uniformly in the PI matrix and the ZrB2/PI composites with 0.5 wt.% loading exhibits outstanding dielectric, mechanical properties and thermal stability. A mechanism related to the microstructure is proposed to explain the performance improvement. ZrB2 with strong electron affinity could trigger charges to accumulate on its surface, which promotes the interface polarization and consequently enhance dielectric constant. The strong interactions between ZrB2 and PI beneficial to stress effectively transfer from the PI matrix to the ZrB2. The dense structure of the composites and the intrinsically high thermal conductivity of ZrB2 are conducive to heat transfer in the matrix and reduce heat accumulation. The dielectric constant, tensile strength and elongation at break of the composites are increased by 17.5%, 63% and 59.4% compared to pure PI. Meanwhile, the ZrB2/PI composites possess superior electrical insulation property. The comprehensive performance improvement of the composites share a broader prospect for its application in engineering.

Structure and properties of the surface layer of zirconium-niobium alloy subjected to high-dose implantation with 10B+ boron isotope ions

The creation of layers implanted with boron isotope 10B on the elements of the core of a nuclear reactor can, due to the anomalously large neutron capture cross-section, provide a decrease in the reactivity of the reactor at the beginning of the company for its operation. The aim of this work is to study the effect of high-dose implantation with 10B + boron isotope ions (ion energy 22 keV, exposure doses from 1×1016 to 7×1016 ion/cm2) on the structure and properties of the surface of E110 alloy samples. It was found that implantation with 10B+ boron ions with an energy of 22 keV at a dose of 7×1016 ions/cm2 leads to an increase in the surface microhardness from 3 GPa for the initial one to 3.7 GPa for the implanted sample. It was found that the corrosion rate of E110 alloy samples in 1% HF solution after implantation (ion energy 10B + 22 keV, dose 7×1016 ion/cm2) is 1.2-1.4 times lower than for the initial alloy. It is shown that the implantation of the E110 alloy with 10B + boron ions is accompanied by the formation of a subgrain structure with dimensions 100-200 nm in the surface layer, an increase in the scalar dislocation density, and the release of nanosized 1.8-2.3 nm zirconium boride particles.