Magnesium trisilicate compound tablets

Plasma electrolytic oxidation (PEO) is a technique used to create oxide-ceramic coatings on lightweight metals, such as aluminium, magnesium, and titanium. PEO is known for producing coatings with high corrosion resistance and strong adhesion to the substrate. The process involves generating short-lived microdischarges on the material surface through anodic dielectric breakdown in a conductive aqueous solution. To investigate single microdischarges (SMDs) during PEO, a SMD setup was developed, where the active anode surface is reduced to the tip of a wire with a diameter of 1 mm. In this work the focus is on the effect of electrolyte concentration, anode material, and electrical parameters on the microdischarges. The electrolyte is composed of distilled water with varying concentrations of potassium hydroxide (0.5–4 g l−1). High-speed optical measurements are conducted to gain insights into the formation and temporal evolution of individual microdischarges and the induced gas bubble formation. Optical emission spectroscopy is used to estimate surface and electron temperatures by fitting Bremsstrahlung and Planck’s law to the continuum spectrum of the microdischarges. To evaluate the impact of the microdischarges on coating morphology, the resulting oxide layers on the metal tips are analysed using scanning electron microscopy. The study demonstrates that microdischarge behaviour is significantly influenced by the substrate material, treatment time, and electrolyte concentration, all of which impact the coating morphology. Under the conditions studied in this work, aluminium exhibits longer microdischarge and bubble lifetimes, with fewer cracks on the top layer of the coating, whereas titanium showed faster, shorter-lived bubbles due to more rapid microdischarge events.

Abstract licence: CC BY

Graphene‐based materials have great potential for electrochemical energy storage applications, but their performance is often limited by the restacking of nanosheets, which restricts ion accessibility. In this study, a straightforward method to fabricate reduced graphene oxide (rGO) laminates intercalated with magnesium–aluminium layered double hydroxide (MgAl‐LDH) nanosheets is presented. Due to electrostatic interactions, the positively charged LDH nanosheets strongly bind to the negatively charged rGO layers, forming a stable, alternating laminar structure with well‐defined nano‐capillaries. Detailed characterization confirms the intended architecture of the rGO‐LDH hybrid. Electrochemical analysis shows nearly ideal electric double‐layer capacitor (EDLC) behavior, with the rGO‐LDH reaching a specific capacitance of up to 410 F g−1 at 1 A g−1. This work highlights the vital role of LDH nanosheets as interlayer spacers that effectively prevent restacking, providing new insights into designing 2D materials for high‐performance supercapacitors and energy storage systems.

Abstract licence: CC BY

The initial formation of corrosion products in pure humid air on magnesium alloys AZ91 and AZ31 was studied using infrared reflection absorption spectroscopy (IRRAS), infrared spectroscopic imaging, and SEM-EDS. The kinetics of corrosion product formation were monitored in situ with IRRAS during exposure to humid air (95% relative humidity) under two different CO2 concentrations: low (≤1 ppm) and ambient (400 ppm). For low CO2 concentrations, the primary corrosion product detected on both alloys was magnesium hydroxide (Mg(OH)2). In contrast, under ambient CO2 conditions (400 ppm), magnesium hydroxy carbonate was the dominant product. After 16 h of exposure, the amount of magnesium converted into corrosion products was approximately 8–10 times higher under low-CO2 conditions compared to ambient levels. The smaller formation of corrosion products but increased magnesium carbonate formation on AZ91D is attributed to its higher aluminium content compared to AZ31. Corrosion attack and product formation were largely localised to the centre of the α-phase in AZ91D, with the β-phase likely serving as sites for cathodic reactions.

Abstract licence: CC BY