Current Materials Science - Volume 19, Issue 1, 2026

Macadamia nuts find widespread use in cuisine, cosmetics, and healthcare products, leaving behind a substantial amount of nutshell residue post-hulling. Capitalizing on the remarkable compressive strength inherent in macadamia nutshell (MS) compared to other plant shells, this study investigates the utilization of MS as a partial aggregate replacement in fly ash-based geopolymer composites for sustainable construction applications, highlighting the need to optimize the content for balanced mechanical properties.

The effects of MS content (0%, 20%, 25%, and 30%) on the mechanical properties (compressive and flexural strength), density, water absorption, and thermal resistance of the composites were evaluated. Results indicated that the compressive and flexural strength of plain geopolymer increased with rising NaOH concentrations.

However, an increase in MS content led to a decline in the flexural strength of the composites due to the brittle nature of the aggregate. Conversely, the compressive strength of 20% MS mix displayed a similar trend to plain geopolymer, while 25% and 30% MS mixes exhibited an inferior trend. Scanning electron microscopy revealed that the adhesion between geopolymer and MS resulted from a physical interlocking mechanism. While the compressive strength of plain geopolymer improved after heat treatment at 400°C, a noticeable deterioration was observed in the composites with MS aggregate.

Notably, 20% MS and 25% MS mixes (at 4 M and 6 M) demonstrated suitable compressive strength (16.54-22.50 MPa) and density (1.20-1.26 g/cm³) to serve as load-bearing components in accordance with ASTM C90 standard.

45 Steel is an important structural carbon steel and significantly influences human life and social development. Ni-based composite coatings are widely used in 45 steel workpieces to improve surface properties and expand their applications.

In this study, the plasma cladding technique was employed to produce Ni-based cladding with different WC contents on 45 steel surfaces. The microstructure, phase structure, microhardness, residual stress, and corrosion resistance of Ni-based cladding coatings were investigated.

The results showed that the coatings were made up mostly of Ni3Fe, Cr23C6, Cr7C3, WC, and W2C phases.

The microhardness of the Ni-based alloy coatings was greatly increased due to the presence of the WC hard phase on the Ni matrix. The highest microhardness was found to be more than triple the microhardness of the substrate with the addition of 60% WC. In addition, the largest residual stress at the center of the cladding channel was more than five times higher than the substrate-affected zone. The corrosion resistance of 45 steel-containing Ni-based coatings increased in acidic, neutral, and alkaline environments due to the formation of passivation films.

Nowadays, polymers, as an important application material in drilling engineering, have obvious advantages in solving the rock-carrying problem at the bottom of deep wells, and improving the drilling speed due to their excellent viscosity enhancement effect.

In this study, the effects of polymer type, concentration, shear time, electrolyte, and clay on the rheological properties of polymer solutions at high temperature and high pressure were investigated using a Fann 50SL rheometer. The experimental results showed that, except for the polymer additive amount and clay, the increase in shear time and the amount of salt both led to a decrease in the viscosity of the polymer solution, with 190°C as the critical temperature above which the viscosity decreased significantly.

The polymer solution containing formate showed higher viscosity retention during heating and then cooling compared to chlorides. The presence of clay enhances the reticulation of polymer molecules in the blend, which facilitates the carrying of rock cuttings at high temperatures. In addition, regression analyses showed that the increase in temperature resulted in an enhanced tendency for the polymer solution to evolve from a pseudoplastic to a Newtonian type.

This research provides theoretical basis and data support for developing high-temperature polymers and formulating high-temperature drilling fluid systems.

In this study, nano-dispersed polymer gel electrolytes containing polymethylmethacrylate (PMMA), lithium perchlorate (LiClO4), diethyl carbonate (DEC), dimethylacetamide (DMA), and nano-sized fumed silica (SiO2) have been synthesized and characterized.

Polymer gel electrolytes were prepared by adding PMMA (Aldrich) to the liquid electrolytes of LiClO4 (Aldrich) in DEC and DMA (Merck), along with continuous stirring. Nanosized fumed silica (SiO2) (Aldrich) having particle size 7 nm with surface area 380 m²/g was added (wt% of gel electrolytes) along with continuous stirring to obtain homogeneous nano-dispersed polymer gel electrolytes.

The electrolytes showed high ionic conductivity for electrolytes with higher dielectric constant solvents. The polymer enhanced the ionic conductivity of liquid electrolytes having a lower dielectric constant solvent (DEC) at all PMMA concentrations than the electrolytes containing a high dielectric constant solvent (DMA). Further, with the addition of nano-sized fumed silica, the ionic conductivity showed a small increase along with an increase in the mechanical stability of the electrolytes. The viscosity behavior of the electrolytes was also discussed, and it was correlated with the results of the ionic conductivity of electrolyte. Nano-dispersed polymer gel electrolytes exhibited high ionic conductivity (10^-2 S/cm).

Further, the conductivity showed only a small change (by a factor, not by an order) over the 25-100°C temperature range and did not vary with time, which is desirable for their use in practical applications.

Chemical graph theory is a crucial tool for characterizing molecular properties and reactions. It utilizes a rigorous mathematical framework to reveal the complex structures and dynamics of molecules.

The atomic structure of boron is incorporated into an n-dimensional oxide network to create two sets of boron-embedded benzenoid networks. By employing mathematical analysis and graph theory, degree-based topological indices are derived.

Analytical solutions for molecular descriptors of degree-based topological indices in boron-embedded benzenoid networks are computed.

The unique structures of boron-embedded benzenoid networks significantly influence the topological indices, highlighting the interplay between molecular structures.

This article proves that the microemulsion was prepared successfully with the addition of metal chlorides. And the metal chloride would affect the interfacial tension (IFT), salt concentrate required for phase transition and shear viscosity of different mixtures. Experiments have shown that much quantities metal chloride salts can be dissolved in microemulsions, so it is possible in theoretically to prepare mercury-free catalysts using the microemulsion method.

The oil-water IFT of the surfactant solution with metal chloride added was tested, the metal chloride concentration required for the phase transition of microemulsions was determined using salinity scanning, and the viscosity of each microemulsion was tested.

The results indicated that the IFTs of nearly all microemulsions decreased, with values decreasing from 10^–1 mN/m to 10¹ mN/m and a maximum reduction of 47.25 mN/m. The phase transitions observed were Winsor I → Winsor III → Winsor II. Metal chloride concentrations required for the Winsor I to Winsor III transition ranged from 0.5% to 5%, while the Winsor III to Winsor II transition required a concentration between 8% to 20%. Increasing metal chloride concentrations led to higher viscosity, with MnCl2 causing the largest increase (15.4 mPa·s) and CuCl2 the smallest.

The metal chloride concentration required for phase behavior transitions in microemulsions correlated with the effectiveness in reducing the oil-water IFT and increasing shear viscosity. Specifically, metal chlorides that necessitate lower concentrations for phase transitions led to a more significant reduction in IFT and lower shear viscosity in the microemulsion.