Chemical and Materials Sciences: Research Findings Vol. 8

Investigation of Mechanical Behaviour of Tungsten and Magnesium Particle Reinforced Al6063 Metal Matrix Composites

P. Umar Ahamed — 2026-06-16

The growing demand for lightweight, high-strength materials in automotive and aerospace applications has driven research into aluminium-based metal matrix composites. This study investigates the mechanical behaviour of AL6063 aluminium alloy reinforced with tungsten carbide (WC) and magnesium (Mg) particles. Hybrid metal matrix composites were fabricated using crucible casting — one with 2.5% WC and the other with 5%, both of which included 1% Mg. Mechanical tests such as Hardness, tensile strength, compressive strength, and impact energy were conducted. Hardness increased from 39 HRB (pure AL6063) to 47 HRB and 53 HRB for 2.5% and 5% WC composites, respectively. Similarly, ultimate tensile strength improved from 75.4 MPa to 103.15 MPa and 135.7 MPa, while compressive strength increased from 229.28 MPa to 230.78 MPa and 279.52 MPa. However, impact strength decreased from 11 J (base alloy) to 7 J and 9 J for the reinforced composites, indicating reduced toughness due to increased brittleness and particle agglomeration. Scanning Electron Microscopy (SEM) analysis confirmed relatively uniform particle distribution at lower reinforcement levels and clustering at higher WC content. The results demonstrate that the addition of WC significantly enhances strength and hardness, although with a trade-off in impact resistance, making these composites suitable for applications requiring a high strength-to-weight ratio.

Alumina and Hydroxyapatite Reinforced Glass-Ceramic Composites for Bone Filler and Dental Filler Applications

Khushi Bijalwan — 2026-06-16

Alumina and hydroxyapatite were reinforced into apatite-based glass-ceramics to prepare glass-ceramic composites. The study aims to improve the mechanical properties, bioactivity and biocompatibility of the resultant composites. Developed composites were evaluated by physical, mechanical and biological characterisations. Hardness and Young’s modulus of 40 wt.% hydroxyapatite reinforced glass-ceramic composites were 1.76±0.15 GPa and 41.44±1.12 GPa, respectively, whereas 12 wt.% alumina reinforced glass-ceramic composites showed slightly lower hardness (1.25±0.11 GPa) and Young’s modulus (16.39±0.75 GPa). Apatite was formed on the surfaces of glass-ceramics and their composites when immersed in Simulated Body Fluid (SBF) solution, thereby showing good bioactivity. In vitro cytotoxicity assessment showed non-toxicity of the glass-ceramics and their composites. Thus, the experimental studies indicated that the developed glass-ceramics and composites with good mechanical and biological properties might be used for bone filler and dental filler applications.

Rice Husk Ash in Metakaolin-Derived Geopolymer Binders

Maria Kaka Etete Enoh — 2026-06-16

Geopolymers are inorganic aluminosilicate binders produced through alkali activation of precursors such as metakaolin, fly ash, and slag using alkaline activators commonly based on sodium hydroxide and sodium silicate. Owing to their lower greenhouse gas emissions and improved durability characteristics, they are increasingly investigated as sustainable alternatives to ordinary Portland cement. Current research efforts are focused on reducing dependence on commercially manufactured activators and increasing the utilisation of biomass-derived waste materials within geopolymer systems.

Rice husk ash (RHA), a silica-rich agricultural by-product containing predominantly amorphous SiO₂, has emerged as a promising supplementary material for modifying geopolymer chemistry through both precursor substitution and activator enhancement. This chapter reviews the chemistry and functional role of RHA in metakaolin-based geopolymer systems and experimentally evaluates the combined influence of RHA incorporation and alkaline activator composition on mechanical performance.

Metakaolin was produced by calcining kaolin at 700 °C, while RHA was obtained through controlled combustion at 600 °C. The experimental programme investigated RHA incorporation levels of 0–10 wt.% and sodium silicate-to-sodium hydroxide (SS/SH) ratios ranging from 0 to 1.0 using a factorial experimental design. Compressive and flexural strengths were evaluated after ambient curing, and statistical analysis was performed using analysis of variance (ANOVA).

The results demonstrated that RHA incorporation significantly improved mechanical performance, with compressive strength increasing by approximately 41% at 10 wt.% RHA and an SS/SH ratio of 1.0. Strength development was governed by the combined effects of silica availability from RHA and soluble silicate concentration within the activator system.

Overall, the findings demonstrate that RHA can serve as an effective and sustainable silica source for tailoring reaction chemistry and enhancing the performance of metakaolin-based geopolymer binders while simultaneously promoting agricultural waste valorisation.

Optical and Morphological Study of Bi₂S₃ Thin Films Deposited by Chemical Bath Method

Prashant A. Chate — 2026-06-16

Bismuth sulfide is one of the important compounds of bismuth that has garnered research attention due to its interesting properties and numerous applications. Strong optical absorption, good chemical stability, and relatively low toxicity make Bi₂S₃ thin films suitable for photovoltaic, photodetector, sensor, and thermoelectric applications. However, despite extensive investigations, a systematic understanding of the relationship between synthesis parameters and the resulting optical and morphological properties of Bi₂S₃ thin films remains limited. This chapter presents a comprehensive overview of the synthesis, optical properties, and surface morphology of Bi₂S₃ thin films deposited by the chemical bath deposition (CBD) method. The influence of various deposition parameters, such as precursor concentration, pH, temperature, and deposition time, on film growth and properties was discussed. The optical transmittance of Bi₂S₃ thin films shows a strong dependence on both wavelength and film thickness. As the wavelength increases toward the near-infrared region (>800 nm), transmittance gradually increases, often reaching values of 60–80%, especially for thinner films. Films with thickness below 200 nm may exhibit higher transparency, while thicker films (>500 nm) become increasingly opaque. For Bi₂S₃ thin films, the band gap generally lies in the range of 1.3–1.7 eV, with most reported values between 1.4 and 1.6 eV. The refractive index of Bi₂S₃ thin films is relatively high, typically ranging from 2.0 to 3.5 across the visible spectrum. Morphological studies using techniques such as scanning electron microscopy (SEM) and atomic force microscopy (AFM) indicated that the films are uniform, well-adherent, and composed of nanocrystalline grains with sizes ranging from 20 to 150 nm. Surface roughness and grain structure were found to depend strongly on deposition conditions. Overall, the chapter demonstrates that CBD-grown Bi₂S₃ thin films possess desirable optical and morphological characteristics for applications in photovoltaics, photodetectors, and other optoelectronic devices. Careful control of synthesis parameters is essential for optimising film quality and performance.

Application of Particle Tracking Model in Sulphur Dioxide Transport through a Porous Medium

Sheilla J. Kiprotich — 2026-06-16

The transport of pollutants in porous media is a hydrodynamic dispersion phenomena has been a research subject for more than four decades. Factory activities and uncontrolled use of pesticides in agriculture cause serious damage to the environment in the area and affected groundwater. The transport of contaminants emanating from localised sources such as factories and agricultural farms in porous media is of hydro dispersion phenomena has been the major subject for more than four decades. Because of industrial and agricultural activities, inorganic wastes, mainly biodegradable and non-biodegradable substance example sulphur dioxide, oil spills, human wastes, fertilisers, among others, percolate through porous media and eventually find their way to water bodies like streams, rivers and boreholes. This research study aims to describe a particle tracking model of sulphur dioxide in flow-through porous media from Chemelil milling wastes (molasses) and agricultural inputs, example fertilizers, fungicides, and herbicides, with respect to concentration between two points, concentration along the contour field and velocity and the effects of decay and sorption in three dimensions. The governing equation of three-dimensional concentration distribution in fluid flow through porous media will be determined in terms of a three-dimensional non-linear advection-dispersion equation. The finite difference method will be used to solve the MATLAB software will be used to validate the results using data from Chemelil factory as the source point. The velocity vectors of toxic substances obey the diffusion law that diffusion of a contaminant occurs due to the presence of a diffusion gradient between the two regions. The diffusion gradient is the driving force which determines the direction of the flow of toxic substances. Therefore, the lives of the inhabitants and animals will be at high risk because most of these chemicals are hazardous if they are consumed by people and animals’ water with sulphur dioxide and other toxic chemicals.

Zeolite M-BEA (M = Ga(Ta, Nb), Cr,Zn(Y)) Catalysts: Insights into Activity, Selectivity, and Stability in CO₂-Assisted Propane Dehydrogenation

S. M. Orlyk — 2026-06-16

CO₂-assisted propane dehydrogenation offers a route to propylene production in which carbon dioxide can influence reaction equilibrium, hydrogen removal, and catalyst carbonisation. This chapter compares post-synthetically modified M-BEA zeolite catalysts containing Ga(Ta, Nb), Cr/Zn, and Zn(Y), with emphasis on relationships among metal identity, surface acid–base properties, activity, selectivity, and stability. The catalysts were prepared by dealumination of BEA zeolite followed by incorporation of the relevant metal cations and were characterised using XRD, XPS, NMR, nitrogen adsorption/desorption, temperature-programmed desorption and oxidation, hydrogen temperature-programmed reduction, and FTIR spectroscopy of adsorbed pyridine. Catalytic performance was evaluated at 500–650 °C, including time-on-stream tests of 2.5 and 10 h. Regeneration behaviour was also examined after carbon removal in an oxidising gas mixture. The findings indicate that balanced acid–base characteristics govern performance. Medium-strength Lewis acid sites support propane activation, whereas strong Brønsted acid sites promote cracking and oligomerisation, leading to carbon deposition and loss of accessible surface area. Basic sites influence CO₂ conversion and can contribute to limiting carbon accumulation. Among the systems examined, Ga₄.₀SiBEA and Zn₂.₀SiBEA achieved high propylene yields, while Zn₂.₀SiBEA showed greater stability during prolonged operation. The BEA framework remained structurally stable, and regeneration substantially restored catalytic performance. Overall, catalyst stability depended primarily on controlling surface acidity and carbon formation.

Theoretical Frameworks for Chemical Bonding and Molecular Structure: A Critical Integrative Review of Orbital, Real-Space and Energy-Decomposition Approaches

Riffat Basharat — 2026-06-16

Chemical bonding is indispensable to chemical explanation but is not represented by a single quantum-mechanical observable. Contemporary theory therefore relies on complementary models that partition wavefunctions, electron densities or molecular energies into chemically interpretable components. This critical narrative review evaluates the conceptual foundations, evidential strengths and limitations of valence-bond and molecular-orbital theories, correlated wavefunction methods, density functional theory, localised-orbital and natural-bond-orbital analyses, bond-order indices, quantum chemical topology, electron-localisation descriptors, noncovalent-interaction visualisation, and fragment- and real-space energy-decomposition schemes. Literature was selected through transparent searches of accessible scholarly indexes and DOI-linked sources, supplemented by citation chaining, with emphasis on foundational theory, methodological validation and applications that expose disagreement among bonding models. The evidence indicates that valence-bond and molecular-orbital descriptions are not competing ontologies in the exact limit but become differently informative under practical truncations. Localised orbitals and donor–acceptor models provide high chemical legibility, whereas real-space approaches offer orbital invariance and direct access to density topology, electron sharing and atomic-energy partitions. Energy-decomposition analyses add mechanistic resolution but remain sensitive to fragment choice, electronic reference states and the sequence of imposed constraints. Difficult cases—including hypervalency, charge-shift bonding, transition-metal donation and back-donation, aromaticity, weak interactions and heavy-element bonding—show that no isolated descriptor reliably establishes bond existence, strength or mechanism. A defensible interpretation should instead triangulate an adequately converged electronic structure with mutually independent orbital, real-space and energetic evidence, while reporting reference, basis-set and functional sensitivity. Emerging entanglement-based and machine-learning approaches may extend bonding analysis, but their chemical meaning remains conditioned by the partition and training level adopted. The most productive theoretical position is therefore disciplined model pluralism: chemical bonds are robust explanatory constructs when claims are matched to the questions, assumptions and invariances of the methods used.

Novel Cr (VI)-Based Oxidants for Kinetic and Mechanistic Investigations

Dinesh Panday — 2026-06-16

Chromium(VI) oxidants remain historically important in physical organic chemistry because their reactions combine synthetic usefulness with unusually rich redox speciation. Since the introduction of pyridinium chlorochromate, numerous halochromates, dichromates, heterocyclic onium salts, tetraalkylammonium reagents and polymer-supported formulations have been described as novel oxidants. Their value for kinetic and mechanistic investigation is less straightforward than their synthetic labels imply. This critical narrative review examines how reagent structure, counterion, halide, acidity, solvent and support influence observed rate laws and the interpretation of chromium-mediated oxidation pathways. Literature published from 1 January 1975 to 31 May 2026 was selected through live scholarly searching, DOI and bibliographic verification, citation chaining and critical appraisal of mechanistic relevance. Across alcohols, aldehydes, diols, hydroxy acids, sulfides, thioacids, amino acids and alkenes, recurring observations include first-order dependence on chromium(VI), acid acceleration, substrate saturation in some systems, substantial primary kinetic isotope effects and negative substituent reaction constants. These findings support pre-equilibrium association followed by rate-limiting bond reorganisation in many cases, but they rarely identify a unique transition state. Claims of direct hydride transfer, concerted chromate-ester elimination, radical exclusion or a common mechanism across reagent families are often stronger than the underlying evidence. Direct isolation of chromium(IV), spectroscopic detection of chromium(V), rigorous chromium mass balance and time-resolved speciation provide substantially greater mechanistic discrimination than kinetic correlations alone. Reagent novelty has chiefly altered solubility, acidity, ion pairing, handling and microenvironment rather than the fundamental redox chemistry of chromium(VI). Polymer support and phase separation can simplify work-up but do not remove the carcinogenic hazard or stoichiometric chromium waste. Future progress depends on integrating stopped-flow kinetics, electron paramagnetic resonance, X-ray absorption spectroscopy, isotope tracing, validated speciation models, microkinetic analysis and transparent uncertainty assessment.