Early studies on Cr-Coated Zircaloy-4 as enhanced accident tolerant nuclear fuel claddings for light water reactors

High temperature steam oxidation of chromium-coated zirconium-based alloys: Kinetics and process

High temperature oxidation and microstructural evolution of cold spray chromium coatings on Zircaloy-4 in steam environments

Microstructure, corrosion resistance and oxidation behavior of Cr-coatings on Zircaloy-4 prepared by vacuum arc plasma deposition

Porosity in plasma-sprayed coatings is vital for most engineering applications. Porosity has its merits and demerits depending on the functionality of the coating and the immediate working environment. Consequently, the formation mechanisms and development of porosity have been extensively explored to find out modes of controlling porosity in plasma-sprayed coatings. In this work, a comprehensive review of porosity on plasma-sprayed coatings is established. The formation and development of porosity on plasma-sprayed coatings are governed by set spraying parameters. Optimized set spraying parameters have been used to achieve the most favorable coatings with minimum defects. Even with the optimized set spraying parameters, defects like porosity still occur. Here, we discuss other ways that can be used to control porosity in plasma-sprayed coating with emphasis to atmospheric plasma-sprayed chromium oxide coatings. Techniques like multilayer coatings, nanostructured coatings, doping with rare earth elements, laser surface re-melting and a combination of the above methods have been suggested in adjusting porosity. The influences of porosity on microstructure, properties of plasma-sprayed coatings and the measurement methods of porosity have also been reviewed.

Porosity and its significance in plasma-sprayed coatings

To fabricate the oxidation resistance accident tolerance fuel cladding, Cr layer and FeCrAl alloys were deposited on Zircaloy-4 using atmospheric plasma spraying technology. The specimens were exposed under a simulated loss-of-coolant accident condition. XRD, SEM and EDS techniques were carried out to explore their high temperature behavior. According to the analysis results, both Cr coating and FeCrAl coating were successfully prepared by atmospheric plasma spraying system. Cr coating had superior oxidation resistance. Compact Cr2O3 scale forming on Cr coating acted as an oxygen diffusion barrier, whereas FeCrAl coating degraded due to inter-diffusion, leading to its poor protection for the cladding. Difference in standard Gibbs free energy of formation of Fe and Zr caused the prior oxidation of Zr. Accordingly, Zr-rich and Zr-depleted zones occurred in FeCrAl-coated specimens.

Behavior of plasma sprayed Cr coatings and FeCrAl coatings on Zr fuel cladding under loss-of-coolant accident conditions

The Ti3SiC2/glass composite coatings were prepared by atmospheric plasma spraying. There are no evident microcracks between Ti3SiC2 and glass matrix due to low residual stress resulting from the matching CTE of them. The XRD patterns of the as-sprayed Ti3SiC2/glass composite coatings are composed of glass matrix, Ti3SiC2, TiC, and a small amount of Ti5Si3. The short dwell time and quite low oxygen partial pressure in plasma jet flow restrain TiC and Ti5Si3 from further oxidation. Both the real and imaginary part of the complex permittivity increase with rising Ti3SiC2 content. The coating with 25 wt% Ti3SiC2 possesses excellent microwave absorption properties. The minimum reflection loss is −47.7 dB (> 99.99 % absorption) at 10.6 GHz with a thickness of 1.4 mm and the bandwidth (<−5 dB) can be obtained in the frequency range of 8.2–12.4 GHz. The impedance matching and dielectric loss of the coating result in the microwave absorption properties improved. The enhanced microwave absorption performance suggests that the Ti3SiC2/glass coating could be a good candidate for highly efficient microwave absorption material.

Enhanced microwave absorption of plasma-sprayed Ti3SiC2/glass composite coatings

Effects of calcium doping on yttrium titanate for microwave absorbing applications

The shape and particle size of the filler are highly relevant to the composite’s performance and application. We herein report the role of boron nitride (BN) shapes and sizes for polyethylene composites on the rheological properties, thermal conductivity (TC) and passive cooling via melt blending. Fillers with large sizes are adverse to form a rheological network in the composites, but they are beneficial to high thermal conductivity and their maximum increase (1.535 Wm −1 K −1 ) relative to the matrix is 256%. Additionally, due to the high solar reflectance (90%) and thermal emittance (85%), the composites endow a cooling performance of 4 °C at daytime and 10 °C at night compared to the contrast temperature in the device. This work is helpful to provide guidance for the optimization of BN fillers for applications in the fields of thermal management and passive cooling. 

Yiding Wang

Papers

Behavior of plasma sprayed Cr coatings and FeCrAl coatings on Zr fuel cladding under loss-of-coolant accident conditions

Enhanced microwave absorption of plasma-sprayed Ti3SiC2/glass composite coatings

Effects of calcium doping on yttrium titanate for microwave absorbing applications

The influence of boron nitride shape and size on thermal conductivity, rheological and passive cooling properties of polyethylene composites

Advances in Formation of C—X Bonds via Cleavage of C—N Bond of Quaternary Ammonium Salts