Quantum spin liquids (QSLs) have emerged as one of the most actively investigated states of correlated quantum matter, yet classification remains ambiguous due to the absence of a universally accepted parameter definition. The frustration index ( f=|θ_CW |/T_c ) is proposed here as the dominant classification criterion. It directly measures how far a spin configuration deviates from the equilibrium order its exchange interactions would otherwise favor, the defining signature of frustration, and is obtainable from a routine susceptibility measurement. Thermodynamic and spectroscopic probes offer confirmatory evidence, but their reliance on sub-Kelvin cryogenics and reactor- or beamline-scale facilities limits their use as universal standards. Standardizing f on a single reference temperature resolves much of the inconsistency in the literature, where reported values vary by orders of magnitude. This framework is applied across candidate families, establishing frustration as the primary criterion and dynamic probes as a confirmatory characterization.
A comparative study with theoretical calculations about structure–property relationship was performed on EDTA-centered dendrimers bearing two different architectures: PAMAM-like and Fréchet-type dendrimers bearing EDTA core and peripheral β-cyclodextrin (βCD) units. The molecular structures and aqueous solubility of the Fréchet-type dendrimers (EDTA-βCD4 and EDTA-βCD8) were studied to evaluate the influence of architecture on their physicochemical properties. Although Fréchet-type dendrimers exhibited slightly lower solubility in water than their PAMAM-like EDTA-centered βCD analogs, they maintained excellent solubility in aqueous medium while providing a more rigid molecular framework and a higher density of peripheral βCD units. Semiempirical GFN2-xTB calculations revealed they show expanded molecular conformations, in which the Fréchet dendrons increase the spatial separation between neighbor βCD moieties leading to a more organized three-dimensional arrangement. These results demonstrate that architecture governs not only aqueous solubility but also the structural organization of multivalent βCD dendrimers.
The quenching heat treatment determines the microstructure and mechanical properties of AISI-52100 steel used in wear-resistant components. This study evaluated the influence of cooling rate on microstructural evolution and hardness to identify optimal processing conditions. A Jominy test specimen instrumented with five type-K thermocouples and a data acquisition system was used to record the thermal history after austenitization at 915 °C. Cooling rates ranged from 1.75 ± 0.036 °C/s to 46.15 ± 1.430 °C/s, promoting heat-extraction-dependent microstructural transformations. Higher rates resulted in a martensitic microstructure, while rates below 2.5 °C/s favored pearlite formation. Hardness decreased from 63.78 to 31.31 HRC as the cooling rate decreased. Scanning electron microscopy confirmed pearlite growth below 4.3 ± 0.120 °C/s. Although the fastest cooling resulted in maximum hardness, the appearance of thermal fractures indicates that a rate close to 4.3 °C/s offers the best compromise between structural integrity and wear resistance. This can be achieved with commercial cooling methods.
Conventional sulfuric acid leaching of zinc silicates like willemite ( Zn_2SiO_4 ) suffers from severe silica gelation, increased pulp viscosity, and filtration failure. In this study, methanesulfonic acid (MSA) was evaluated as a selective alternative lixiviant to overcome the silica barrier. Leaching at 0.83 M MSA and 25 °C achieved an optimal zinc extraction of 69.7
Issues such as rapid engine wear and the inefficiency of conventional lubricants have become prominent topics worthy of investigation. Therefore, this study explores the effectiveness of carbon dots/chitosan nanocomposites as lubricant additives to enhance tribological performance and reduce mechanical wear. AAS analysis revealed that ferro-lubricants exhibit lower heavy metal adsorption capacities Fe(III): 26.30 mg/g and Pb(II): 38.75 mg/g compared to conventional lubricants. TEM analysis showed that the nanocomposite has a uniform nanoparticle morphology with an average size of 119.01 nm. FTIR spectroscopy confirmed the presence of functional groups (–OH, –NH, and C–O–C). Viscosity measurements demonstrated increases in static (from 120 to 123 Pa s) and dynamic (from 123 to 125 Pa s), attributed to strong intermolecular interactions and nanoparticle agglomeration. Furthermore, the coefficient of friction decreased to 0.002 under static and 0.003 under dynamic conditions using ferro-lubricants. These findings confirm that nanocomposites significantly improve lubricant stability and offer strong potential for high performance.
