Solids, Volume 3, Issue 4 (December 2022) – 7 articles

The aqueous and thermal stabilities of aragonite (CaCO${}_3$) powders against phase conversion are important for industrial applications that rely on calcium carbonate. We describe the synthesis and characterization of solution-precipitated aragonite powders before and after exposure to different aqueous polyphosphate (SHMP) or orthophosphate (PO${}_4$) treatments with concentrations ranging between 1–10 mM (∼1 g/L). Based on infrared spectra, differential scanning calorimetry, and thermogravimetric analyses, results show that orthophosphate treatments lead to secondary phase formation and complex thermal annealing behaviors. In contrast, polyphosphate treatments help to prevent against aragonite dissolution during water exposure, and also provide a slight increase in the thermal stability of aragonite with regard to conversion to calcite. Full article

Nitrogen oxides (NO_x) gases, such as nitrous oxide (N₂O), nitrogen oxide (NO), and nitrogen dioxide (NO₂), are considered the most hazardous exhausts exhaled by industries and stationary and non-stationary application engines. Investigation of catalytic decomposition of NO has been carried out on copper ion exchanged with different bases, such as COK12, Nb₂O₅, Y-zeolite, and ZSM5. The catalytic decomposition of NO is widely accepted as an excellent method for the abatement of NO. However, the catalyst that achieves the highest reactivity in terms of NO decomposition is still a matter of research. The present paper aims to extend the research on the reactivity of non-noble metal-based catalysts using the direct decomposition method to remove NO from diesel engine exhaust. The reactivity of catalysts was observed in a quartz fixed bed reactor of 10 mm diameter placed in a furnace maintained at a temperature of 200 °C to 600 °C. The flow of NO was controlled by a mass flow controller, and the gas chromatography technique was used to observe the reactivity of the catalysts. Analysis showed that adding Cu to COK12, Nb₂O₅, Y-zeolite, and ZSM5 supports resulted in a rise in NO decomposition compared to stand-alone supports. Further experimental trials on the performance of Cu-ZSM5 at varying flow rates of NO showed that the NO decomposition activity of the catalyst was higher at lower flow rates of NO. Full article

A phase field framework of elasticity, inelasticity, and fracture mechanics is invoked to study the behavior of ceramic materials. Mechanisms addressed by phase field theory include deformation twinning, dislocation slip, amorphization, and anisotropic cleavage fracture. Failure along grain and phase boundaries is resolved explicitly, whereWeibull statistics are used to characterize the surface energies of such boundaries. Residual stress incurred by mismatching coefficients of thermal expansion among phases is included. Polycrystalline materials of interest are the ultra-hard ceramics boron carbide (B₄C) and boron carbide-titanium diboride (B₄C-TiB₂), the latter a dual-phase composite. Recent advancements in processing technology enable the production of these materials via spark-plasma sintering (SPS) at nearly full theoretical density. Numerical simulations invoking biaxial loading (e.g., pure shear) demonstrate how properties and mechanisms at the scale of the microstructure influence overall strength and ductility. In agreement with experimental inferences, simulations show that plasticity is more prevalent in the TiB₂ phase of the composite and reduces the tendency for transgranular fracture. The composite demonstrates greater overall strength and ductility than monolithic B₄C in both simulations and experiments. Toughening of the more brittle B₄C phase from residual stress, in addition to crack mitigation from the stronger and more ductile TiB₂ phase are deemed advantageous attributes of the composite. Full article

Protective coatings can prolong the lifespan of engineering components. Electroless Ni-P coating is a very hard coating with high corrosion resistance, but low toughness. The addition of NiTi nanoparticles into the coating has shown the potential to increase the toughness of electroless Ni-P and could expand its usability as a protective coating for more applications. However, the study of the tribological behaviour and wear mechanisms of Ni-P-NiTi composite coating has been minimal. Furthermore, there is no studies on the effect of coating thickness on monolithic and composite electroless Ni-P coating wear behaviour. The wear rates of each coating were found by measuring the volume loss form multi-pass wear tests. The wear tracks were examine using a confocal microscope to observe the wear mechanisms. Each sample was tested using a spherical indenter and sharp indenter. It was found that the NiTi nanoparticle addition displayed toughening mechanisms and did improve the coating’s wear resistance. The 9 μm thick Ni-P-NiTi coating had less cracking and more uniform wear than the 9 μm thick Ni-P coating. For both the monolithic and composite coatings, their thicker version had higher wear resistance than their thinner counterpart. This was explained by the often observed trend in coatings where it has higher tensile stress near the substrate interface, which decreases and becomes compressive as thickness increases. Overall, the 9 μm thick Ni-P-NiTi coating had the highest wear resistance out of all the coatings tested. Full article

Utilization of alternative asphalt binders and additives from renewable sources, given the scale and the impact of the asphalt pavement industry, is an important step toward a sustainable future for the surface transportation infrastructure. Among several sources available for harvesting sustainable construction materials, bio-based materials from agricultural feedstock are known to be one of the most reliable, renewable, environmentally friendly, and economically feasible solutions to achieve this goal. Lignin, one of the most abundant materials in nature, is the byproduct of several industries, specifically pulp processing and biofuel production facilities. Given its physical properties, the use of lignin as a partial replacement for petroleum-based asphalt binder has been studied and proven promising. However, lignin’s properties vary depending on its source and processing techniques. Therefore, incorporating lignin in asphalt binders can result in different mechanical properties, depending on its type and chemical composition. The present study was undertaken to evaluate the effect of three different lignin types, when used as an asphalt binder modifier, on the rheological properties of the asphalt binder, aging characteristics, and its adhesion to different aggregates. This study’s findings showed that, when incorporated in an asphalt binder at the same amount, different lignin types have significantly different effects on asphalt binder blends’ rheological, aging, and adhesion properties. Different rheological, aging, and adhesion properties of the binders result in different mechanical characteristics in asphalt mixes containing lignin-modified asphalt binders. Full article

Quantum dots (QDs) play a fundamental role in nanotechnology because of their unique optical properties, especially photoluminescence (PL). Quantum confinement effects combined with tailor-made materials make QDs extremely versatile for understanding basic physical phenomena intrinsic to them as well as defining their use in a vast range of applications. With the advent of graphene in 2004, and the discovery of numerous other two-dimensional (2D) materials subsequently, it became possible to develop novel 2D quantum dots (2DQDs). Intensive research of the properties of 2DQDs over the last decade have revealed their outstanding properties and grabbed the attention of researchers from different fields: from photonics and electronics to catalysis and medicine. In this review, we explore several aspects of 2DQDs from their synthesis, functionalization, and characterization to applications, focusing on their bioimaging, biosensing, and theranostic solutions Full article

Over time, high-temperature superconductor (HTS)-coated conductors (CCs) have proven to be promising candidates for future high-efficiency and high-power density electrical machines. However, their commercialization is handicapped due to the AC dissipative loss that occurs upon exposure to external magnetic fields. In rotating electromagnetic devices, the external magnetic field is a combination of alternating and rotating magnetic fields. Most of the research is devoted to the effect of exposure of the superconductors to alternating magnetic fields only. This article presents an investigation to observe the behavior of HTSCCs under rotating magnetic fields, particularly the AC loss, using a finite-element-based homogeneous H-formulation technique. Our investigation shows that the AC loss could be considerably high when HTSCCs are exposed to rotating magnetic fields and, ultimately, could affect the cooling efficiency of future high-efficiency and high-power density electrical machines. Full article