Effect of the Treatments of the Surface on Mechanical Performance of Concrete Containing Chemical Admixtures

The aim of this paper is to investigate two different concrete mixes, one with Limestone Powder (LSP) and the other with Ground Granulated Blast-Furnace Slag (GGBS), both mixes containing superplasticizer, in order to analyse their compressive strengths at 7 and 28 days, their abrasion resistance and slip resistance. The two mixes are treated with two different surface protection finishers, applied on the surface after the concrete has cured and analysis of how these finishers affect the abrasion resistance and slip resistance of the concrete is discussed.

Cold Gas Spraying of Solution-Hardened 316L Grade Stainless Steel Powder

Austenitic steels are characterized by their outstanding corrosion resistance. They are therefore suitable for a wide range of surface protection requirements. The application potential of these stainless steels is often limited by their poor wear resistance. In the field of wrought alloys, interstitial surface hardening has become established for simultaneously acting surface stresses. This approach also offers great potential for improvement in the field of coating technology. The hardening of powder feedstock materials promises an advantage in the treatment of large components and also as a repair technology. In this work, the surface hardening of AISI 316L powder and its processing by thermal spraying is presented. A partial formation of the metastable expanded austenitic phase was observed for the powder particles by low-temperature gas nitrocarburizing. The successful deposition was demonstrated by cold gas spraying. The amount of expanded austenitic phase within the coating structure strongly depends on the processing conditions. Microstructure, corrosion and wear behavior were studied. Process diagnostic methods were used to validate the results.

Korozja pokrycia samolotu i względy bezpieczeństwa konstrukcyjnego

The aim of this article is to point out some peculiarities of airframe corrosion, the impact of external forces on aircraft skin elements and their impact on structural integrity. The corrosion process is generally associated with fatigue of aircraft structural elements due to the effect of many factors such as the type of loading, the properties of the materials, the corro-sive environment, etc. The article is not focused on corrosion processes, but on load factors that are specific to aircraft wing design elements and their influence on corrosion of critical struc-tural elements. Corrosion of the wing is perceived as a consequence of environmental impact on damaged surface protection of the skin and connecting parts (rivets, screws, and welded joints) caused by static and dynamic stress of the wing and also by the interaction of the indi-vidual structural elements as a whole. The dynamics of operation of individual structural ele-ments is further enhanced by the fatigue of the material. Early detection of corrosion processes has generally been and is crucial to overall safety of the aircraft. The proposals presented in the article are formulated in order to improve the system of work to ensure the safety of aircraft operation in terms of resistance to corrosion damage.

Exfoliating silica bilayers via intercalation at the silica/transition metal interface

The growth of the silica (SiO2) bilayer (BL) films on transition metal (TM) surfaces creates a new class of two-dimensional (2D) crystalline, self-contained materials that interact weakly with the TM substrate. The BL-silica/TM heterojunction has shown unique physical and chemical properties that can lead to new chemical reaction mechanisms under the sub-nm confinement and broad potential applications ranging from surface protection, nano transistors, molecular sieves to nuclear waste removal. Novel applications of BL-silica can be further explored as a constituent of van der Waals assembly of 2D materials. Key to these applications is an unmet technical challenge to exfoliate and transfer BL-silica films in a large area from one substrate to another without material damage. In this study, we propose a new exfoliation mechanism based on gas molecule intercalation from density functional theory studies of the BL-silica/TM heterojunction. We found that the intercalation of O atoms and CO molecules at the BL-silica/TM interface weakens the BL-silica – TM hybridization, which results in an exponential decrease of the exfoliation energy against the interface distance, as the coverage of interfacial species increases. This new intercalation mechanism opens up the opportunity for non-damaging exfoliation and transfer of large area silica bilayers.

Surface and corrosion properties of Type 430 ferritic stainless steel in parsley (Petroselinum Sativum) essential oil-containing sulphuric acid solution

This study examined the corrosion inhibiting properties of parsley (petroselinum sativum) essential oils, for Type 430 ferritic stainless steel in 0.5 molar sulphuric acid solutions. In this study, weight loss, electrochemical and scanning electron microscope techniques were used in gaining a detailed understanding of inhibition effects of parsley (petroselinum sativum) essential oils (PEO) on Type 430 ferritic stainless steel corrosion. The inhibitor studied exhibits good anti-corrosion performance with 98.65 % inhibition efficiency. This result could be ascribed to the adsorbed PEO on the surface of the stainless steel, and this was verified by surface visualization using optical and scanning electron microscope techniques while the crystallographic variation of the inhibited sample is studied by X-ray diffraction (XRD). The adsorption of PEO onto stainless steel surface is controlled by Langmuir adsorption isotherms. Optical images of non-inhibited specimens showed a severely corroded surface with a visible macro pit on the stainless steel from sulphuric solutions. The inhibited sample shows improved surface owing to the surface protection effect of PEO molecules. The corrosion inhibition performance of PEO is due to the presence of active constituents which enhanced the film formation over the surface of the metal, thus, mitigating corrosion.

Effect of Al Concentration on Microstructure and Properties of AlNbTiZr Medium-Entropy Alloy Coatings

The AlNbTiZr medium-entropy alloy (MEA) coatings with different Al contents were prepared on N36 zirconium alloy substrates by RF magnetron co-sputtering. The morphology, microstructure, mechanical properties, surface wettability and corrosion resistance of the AlNbTiZr MEA coatings were studied to evaluate the surface protection behavior of zirconium alloy cladding under operation conditions of a pressurized water reactor. The results showed that all the coatings were composite structures with amorphous and bcc-structured nanocrystals. With the increase of Al content, both the elastic modulus and hardness decreased first and then increased. The hydrophobicity of the coatings was enhanced compared with that of the substrate. The 10.2 at.% Al AlNbTiZr coating had the best corrosion resistance and the minimum oxygen penetration depth, which originated from the formation of a denser oxide layer consisting of Nb2Zr6O17 and ZrO2. This study provides an improved idea for the design and development of Al-containing MEA coating materials for accident tolerant fuel.

Development of Multifunctional CoAl Based Layered Double Hydroxide Protective Film on Aluminum Alloy

A protective CoAl-layered double hydroxide (LDH) thin film was developed directly on the aluminum substrate. Further, the low-surface-energy molecules (1H, 1H, 2H, 2H perfluorododecyl trichlorosilane) were incorporated inside the LDH network through an anion exchange mechanism to obtain a superhydrophobic CoAl-LDH surface. The developed films were characterized by scanning electron microscopy (SEM-EDS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR), and additional contact angle measurements were made to evaluate the superhydrophobicity of modified CoAl-LDHs against different solutions. The water contact angle (WCA) of the modified CoAl-LDH surface was observed to be about 153° and remained sufficiently stable after long-term immersion in NaCl solution. The effect of excessive ultrasonication on film structural variations and superhydrophobicity was also analyzed for outdoor applications. The high charge transfer resistance observed from the analysis of long-term electrochemical impedance spectroscopy (EIS) indicates the significant corrosion-resistance properties of the developed CoAl-LDHs. This research on protective CoAl-LDHs will bring insights into the understanding of new aspects of surface protection and implementation in many engineering applications.