The aim of this work is to understand the characteristics of the pozzolanic reactivity of nanoSiO2 from studies of its pozzolanic reaction kinetics, morphology and structure of the hydrates and the ...influences of these features on the properties of cement-based materials, so as to explore a more targeted way of using nanoSiO2 in cement or concrete. It revealed that the pozzolanic reaction of nanoSiO2 is of the first-order and the apparent reaction rate constant of nanoSiO2-4nm is about one order of magnitude bigger than that of silica fume, but the specific reaction rate constant is about one half to that of silica fume. A compacter gel structure and poorer crystallinity of the hydrates of nanoSiO2 to those of silica fume are found, as well. The rate of hydration of cement at very early ages is enhanced by nanoSiO2, but the rate slows down with aging due to the compact gel structure. To make the use of the high pozzolanic reactivity and ultrafine particle size of nanoSiO2, as well as its resulting compact gel structure, colloidal nanoSiO2 was applied onto the hardened cement mortar by brushing technique and a less permeable surface was resulted, which shows the potential of using nanoSiO2 as a surface treatment material for cement-based materials.
•Critical applications require materials with superior surface characteristics.•High energy density and cooling rate make lasers suitable for such application.•Laser cladding and surface alloying may ...develop coating with high bonding strength.•Theoretical and experimental result suggest for better clad and surface properties.•Analysis of clad leads to defect free surface with wide industrial acceptance.
Laser cladding and surface alloying are surface modification techniques employed to fabricate thin coating/layer with improved surface properties or to refurbish surface defects by forming highly resistant gradient coatings/layers on the substrate. High energy density and cooling rates make these techniques suitable to process a wide range of materials. In recent years, due to the development of high power lasers, improved controlling and delivery mechanisms have attracted extensive research in laser surface treatment. Researchers have analyzed various process factors to improve process performance. The experimental and theoretical studies show that the performance of laser cladding and surface alloying techniques can be enhanced significantly by the proper selection of input process parameters. This paper summarizes various research works carried out so far in the area of laser cladding and surface alloying of different materials and their applications. It reports the research outcomes of experimental and theoretical studies conducted to improve the process performance. A brief introduction of various laser surface treatment processes is also included. Besides these various problems, their solutions and trend for future works have also been discussed.
The need for alternative eco-friendly and sustainable materials has forced many researchers to focus on composites made using natural fibers and biodegradable polymer matrices. In addition to that, ...these natural fibers are low in cost, have good mechanical properties, biodegradability, and require less production energy. Therefore, this review paper will focus on one of the natural fibers known as Luffa cylindrica (LC) by understanding all the natural fibers' benefits. A detailed overview is provided for commonly used fiber surface treatments, surface treatment techniques, and processing techniques for various LC composites from numerous other researches. Furthermore, this paper will also discuss the characteristics, mechanical properties, and water absorption properties of LC composites before and after surface treatments, where a comprehensive understanding of LC reinforced polymer composites' behavior has been reviewed.
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•Effect of five surface treatments on surface topography of LB-PBF IN718 was studied.•Surface measurements using optical microscopy and X-ray CT (XCT) were compared.•Surface profiles ...were constructed from XCT images by curving-fitting edge detection.•The effect of surface roughness was more significant in high cycle fatigue regime.•A modified fatigue notch factor model correlated surface parameters with fatigue life.
In this study, the effect of various surface treatments, including sand-blasting, drag-finishing, turning, grinding, and grinding + drag-finishing, on surface roughness and fatigue properties of laser beam powder bed fused Inconel 718 was examined. The surface roughness values obtained from two surface measurement techniques, i.e., optical microscopy and X-ray computed tomography, were compared. Both surface measurement techniques consistently indicated that all surface treatments led to improvements in surface roughness, although optical microscopy was influenced by surface glares and overestimated the surface roughness values of drag-finished specimens. Accordingly, all surface treatments also led to improvement in fatigue resistance with sand-blasting and drag-finishing yielding the least while grinding + drag-finishing causing the most. Notably, only the cracks of grinding + drag-finished specimens initiated from crystallographic facets while those in other conditions were surface initiated. Furthermore, by treating the surface valleys as micro notches, an effective fatigue notch factor model using a hybrid surface roughness metric that incorporates several standard surface roughness parameters was shown to correlate the fatigue lives of 94 % of specimens with various surface conditions within a scatter band of three.
High-performance thermoplastics, such as polyether ether ketone (PEEK) and polyester sulfone (PES), are extensively utilized across various industries owing to their exceptional properties. However, ...their relatively low surface energy often leads to insufficient bonding strength when adhering PEEK or PES. Commonly used surface pretreatments, such as acid-base and plasma treatments, have drawbacks including the use of toxic acids and bases, complex procedures, and poor stability. In this study, we synthesized four catechol-functionalized prepolymers by reacting bisquinone A with dithiols or diamines in a 1:1 M ratio. These catechol-containing prepolymers were employed as surface primers, and the adhesion performance before and after primer treatment was examined using epoxy adhesive for bonding tests. Compared to untreated samples, the lap shear strengths of surface primed PEEK and PES were significantly enhanced by 181 % and 114 %, respectively. These results indicate that the synthesized prepolymers with catechol structures can effectively serve as adhesive primers for bonding.
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•Easy synthesis of catechol-based prepolymers as surface primers for bonding.•PEEK and PES bond strength increased by 181 % and 114 % respectively.•The mechanisms for the enhancement of bonding are revealed.•Environmentally friendly and universally applicable surface treatment method.
•The number of through-pores in the coating determines the anodized Mg corrosivity.•The Mg dissolution in the through-pores is a time dependent multi-reaction process.•A more stable substrate alloy ...has a lower Mg dissolution rate in the through-pores.
The corrosion of anodized Mg alloys is investigated by means of immersion, salt spray, polarization curve, AC electrochemical impedance spectroscopy (EIS), SEM and optical microscopy analyses. Based on the blocking, retarding and passivating effects of an anodized coating on corrosion of Mg alloys, a corrosion model is proposed to illustrate the corrosion reaction at the coating/substrate interface in coating through-pores. It is found that EIS can sensitively respond to the occurrence of corrosion in anodized Mg alloys and reflect the protection performance of anodized coatings, which may be used as an in situ method of monitoring corrosion for anodized Mg alloys.
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