Synthesis and Sintering

Synthesis and characterization of mullite (3Al2O3.2SiO2) sol by sol-gel route using inorganic salts

Sahar Sajjadi Milani — 2024-12-24

Mullite, also referred to as 3Al₂O₃.2SiO₂, is recognized as the only chemically stable intermediate phase in the SiO₂–Al₂O₃ system, as indicated by mineralogical studies. Several synthesis techniques can be employed to obtain mullite. In this research, the synthesis of mullite particles is aimed to be achieved via the sol-gel route using inexpensive materials, specifically silica sol and aluminum nitrate hydrate [(Al(NO₃)₃.9H₂O] as sources for silica and alumina, respectively. The article is organized into two sections which describe and discuss the systematic synthesis of the mullite sol. The first section emphasizes the influence of the stoichiometric values of Al and Si elements on the formation of the mullite phase at 1200 °C. The effects of sintering temperature on the microstructure and composition of the synthesized mullite sol, with a 3:1 alumina-to-silica ratio, are discussed in the following section. This includes pH, density, solid content, particle size distribution, thermal analysis, phase evolution with temperature, nature of bonds, and microstructural analysis. The XRD results for the mullite sol with a 3:1 alumina-to-silica ratio show strong crystalline diffraction peaks of the mullite phase and the absence of a free silica phase at 1200 °C. The solution exhibits a clear, stable, and homogeneous appearance, with a density of 1.17 g/cm³, a pH ranging from 4 to 5, and a solid content of approximately 15%, measured after heating at 1000 °C for 2 h.

Platinum-based electrochemical sensors for glucose detection: a mini-review

Milad Khanchoupan — 2024-12-22

This mini-review provides a comprehensive overview of platinum-based electrochemical sensors for glucose detection, focusing on recent advancements in material design, fabrication techniques, and the application of single-atom catalysts. Platinum's exceptional electrocatalytic properties and inherent stability have made it a cornerstone material for developing sensitive, selective, and stable glucose sensors. Performance evaluations from the literature reveal sensors with sensitivities exceeding 850 μA/mM cm² and detection limits as low as 3.6 μM. This review examines various approaches to enhancing sensor performance, including the use of different platinum nanostructures (e.g., nanoparticles, nanowires), the incorporation of conductive polymers or metal oxides, and the application of various electrochemical techniques (e.g., amperometry, cyclic voltammetry). Despite these advancements, challenges remain in achieving improved selectivity, stability, and cost-effectiveness. Future research directions include exploring novel platinum-based materials, developing advanced fabrication techniques such as 3D printing, integrating microfluidic platforms, and leveraging single-atom catalysis to enhance sensor performance further. Developing reliable and efficient platinum-based electrochemical glucose sensors is crucial for advancing diabetes management, biomedical research, and point-of-care diagnostics. This review aims to inspire continued research and innovation in this promising field.

High-temperature spark plasma sintering of h-BN composites reinforced with carbon nanotubes, carbon fibers, and graphene nanoplates

Hossein Eslami-Shahed — 2024-12-16

In this study, two h-BN-based composites reinforced with carbon fibers (CF) and carbon fibers/carbon nanotubes (CNTs)/graphene nanoplates (GNPs) have been produced successfully through a high-temperature spark plasma sintering. 1 Wt.% short carbon fibers (length of 5 mm) with 0.1 Wt.% of CNTs and also 0.1 Wt.% of GNPs as hybrid composite were mixed through a simple mixing method including a high energy sonicating and stirring on the hot plate in ethanol media until drying. Moreover, h-BN/1 Wt. % CF composite was mixed with a similar method to compare impacts of CNTs and GNPs addition on the mechanical properties and microstructure of h-BN/CF composite. The high-temperature spark plasma sintering processes were performed at vacuum conditions of almost 20-25 MPa with a starting pressure of 10 and a final applied pressure of 50 MPa at a maximum temperature of 1900˚C. Both prepared samples showed near full densification of higher than 98.1 % of the theoretical density determined by Archimedes’ principle. Investigation of the crystalline phases by XRD represented only related peaks to h-BN. The FESEM images indicated an almost uniform distribution of reinforcement in the h-BN matrix. Furthermore, the polished surface of the provided samples showed only the pulled-out carbon fibers effects while the fracture surfaces confirmed the presence of CF and it’s tunneling effects. The obtained mechanical properties revealed 273±12 MPa of bending strength, 1.32±0.1 GPa of Vickers hardness, and 4.79±0.2 MPa.m^0.5 fracture toughness for the prepared hybrid composite.

Silver nanowires: recent advances in synthesis, transparent conductive coatings, and EMI shielding applications

Ali Borchloo — 2024-12-12

Indium tin oxide (ITO) is a broadly utilized transparent conductor, although it possesses several limitations such as high cost and brittleness. This paper investigates silver nanowires (AgNWs) as suitable material due to their improved electrical conductivity, flexibility, and transparency. We investigated several techniques for creating AgNWs, including template, chemical, polyol, and electrochemical approaches. The polyol method is highlighted as very cost-effective and efficient; however, it produces nanoparticle byproducts. We explore changes to the polyol technique that aim to improve yield and purity. The review examines how AgNWs are made, talking about nucleation, phase transitions of silver atoms, and the formation of pentagonal grains. These characteristics show how effectively the polyol approach works for generating high-quality AgNWs on a large scale. We investigated the relationship between AgNW concentration of, the additive's characteristics, and the surface tension and viscosity of the resultant ink, with a focus on how these variables influence different coating processes. The study reviews the process of converting AgNWs into conductive inks for use in transparent conductive films (TCFs), with applications including transparent heaters, touch panels, sensors, solar cell electrodes, and electromagnetic interference (EMI) shielding devices. The research overview concludes with a discussion of potential future directions and the promising role of AgNWs in advancing TCF technologies.