Chemical and Materials Sciences: Research Findings Vol. 5

Microstructural and Functional Characterisation of Indian Silk Varieties: A Review on Their Industrial and Biomedical Potential

Janhiphula Kanhar — 2025-09-20

Silk is one of the most prized natural fibres due to its exceptional tensile strength, elasticity, and thermal insulation, which go beyond its aesthetic appeal. India is the world's second-largest producer of silk. This review looks at the various kinds of Indian silk, focusing on their microstructural characteristics and industrial potential. India, a major producer of silk, offers a wide variety of silk, including mulberry (bivoltine and crossbreed) and non-mulberry (tasar, muga, and eri) varieties. The study explores important microstructural characteristics that show the biochemical and mechanical distinctions between mulberry and non-mulberry silks, including filament length, degumming loss, denier, cross-sectional structure, and moisture regain. The different amino acid compositions of non-mulberry silks are responsible for their higher moisture regain, inherent viscosity, and distinctive structural characteristics such as microvoids. Additionally, the review places the historical and evolutionary development of silk in India in context, highlighting the conservation issues with non-mulberry silks. Examining the mechanical characteristics and biochemical taxonomy of silk fibres, this study highlights the value of Indian silk in both conventional textile applications and new industrial fields like advanced materials and biomedical engineering.

Post-Processing Heat Treatment of LPBF 316L Steel: Influence on Microstructure-Properties Evolution

Efremenko B.V. — 2025-09-20

This study evaluates the effects of post-processing annealing (900-1200 ^oC) and work hardening followed by recrystallisation annealing on the microstructure and properties of laser powder bed fused (LPBF) 316L stainless steel, aiming to optimise its mechanical and corrosion performance. As-built LPBF 316L exhibits a cellular microstructure with Cr/Mo segregations, providing high strength and hardness. Annealing at 900-1050 ^oC eliminates the cellular structure, reduces dislocation density, and forms recrystallised grains, decreasing yield tensile strength (YTS) and hardness by 1.3-1.4 times while peaking ductility (total elongation 68 %) and impact toughness (128 J/cm²) at 900 ^oC. However, higher temperatures (1200 ^oC) moderately increase strength but significantly reduce ductility, toughness, and corrosion resistance due to nano-sized (MnCrSiAl)O₃ inclusion precipitation and transition to Mo-rich oxides, coarsening particles, and degrading the passive film. Corrosion resistance is least affected at 1050 ^oC but remains inferior to the as-built state. Prestraining (0.12 plastic strain) increases YTS by 1.2-1.7 times (to 690-699 MPa) and ultimate tensile strength by ~1.2 times (762-770 MPa) but reduces ductility by 1.5 times. Subsequent annealing at 900-1050 ^oC induces recovery and partial recrystallisation, restoring ductility and achieving a strength-ductility product of 40.3 GPa·%, though prior thermal stabilisation hinders recrystallisation. All specimens exhibit ductile fractures with fine/ultra-fine dimples. High-temperature annealing (900-1200 ^oC) fails to comprehensively enhance properties (including corrosion resistance), suggesting that as-built or prestrained-and-annealed LPBF 316L offers a better balance of strength, ductility, and impact toughness for engineering applications.

Marcus Cross-relationship Probed by CIDNP Study of Degenerate Electron Exchange Reactions of Short-lived Radicals

Maksim P. Geniman — 2025-09-20

The time-resolved CIDNP method can provide information about degenerate exchange reactions (DEEs) involving short-lived radicals. The purpose of this study is to probe the applicability of the Marcus cross-relation, with better accuracy provided through knowledge of the temperature dependences of the corresponding DEE rate constants. In the temperature range from 8 to 65 °C, the DEE reactions of the guanosine-5′-monophosphate anion GMP(-H)⁻ with the neutral radical GMP(-H)^•, of the N-acetyltyrosine anion N-AcTyrO⁻ with a neutral radical N-AcTyrO^•, and of the tyrosine anion TyrO⁻ with a neutral radical TyrO^• were studied. The setup for the time-resolved CIDNP experiments was based on a Bruker DRX200 NMR spectrometer (Bruker Corporation, Billerica, MA, U.S.; magnetic field 4.7 Tesla, resonance frequency of protons 200 MHz). In all the studied cases, the radicals were formed in the reaction of quenching triplet 2,2′-dipyridyl. The reorganisation energies were obtained from Arrhenius plots. The rate constant of the reductive electron transfer reaction in the pair GMP(-H)^•/TyrO⁻ was determined at T = 25 °C. Rate constants of the GMP(-H)^• radical reduction reactions with TyrO⁻ and N-AcTyrO⁻ anions calculated by the Marcus cross-relation differ from the experimental ones by two orders of magnitude. The rate constants of several other electron transfer reactions involving GMP(-H)⁻/GMP(-H)^•, N-AcTyrO⁻/N-AcTyrO^•, and TyrO⁻/TyrO^• pairs calculated by cross-relation agree well with the experimental values. The rate of nuclear paramagnetic relaxation was found for the 3,5 and β-protons of TyrO^• and N-AcTyrO^•, the 8-proton of GMP(-H)^•, and the 3,4-protons of DPH^• at each temperature. In all cases, the dependences of the rate of nuclear paramagnetic relaxation on temperature are described by the Arrhenius dependence. These findings demonstrate that time-resolved CIDNP, with microsecond resolution, provides a powerful approach for studying the kinetics of DEE reactions and validating theoretical models of electron exchange.

Water-Based Synthesis of 2-Hydrazinobenzothiazoles: An Improved Approach

Karan Singh — 2025-09-20

A novel, eco-friendly synthesis of 2-hydrazinylbenzo[d]thiazoles via the reaction of benzo[d]thiazol-2-amines with hydrazine hydrate in water under reflux has been reported in this book chapter. This method demonstrates broad substrate scope, accommodating various electron-donating and withdrawing groups, and efficiently yields the corresponding 2-hydrazinobenzothiazole derivatives. The aqueous-based approach highlights the method's potential for green chemistry, making it an appealing strategy for synthesising diverse heterocycles such as hydrazones, pyrazoles, pyrazolines, triazoles, and others.

Room-temperature Transformation of Alkyl to Vinyl Carbocations in Organic Solutions: A New Path to Stable Vinyl Cation Salts

Evgenii S. Stoyanov — 2025-09-20

It was found that alkyl carbocations, such as tert-butyl and methylcyclopentyl cations, decompose to unsaturated vinyl-type carbocations when their salts are dissolved in common organochlorine solvents. These transformations yield thermally stable vinyl cation salts, which were characterised by IR spectroscopy and, in some cases, X-ray crystallography. This method provides a convenient approach to isolating crystals of vinyl carbocation salts and studying them in solution, with implications for understanding carbocation stability and reactivity beyond superacidic media.

Silicon-Carbon Paste Electrode Interface in Contact with Redox Indigo Carmine for Electrochemical Sensor Application

Seiny Roger N'dri — 2025-09-20

Cyclic voltammetry characterisation of the silicon-carbon paste electrode interface in contact with indigo carmine (5, 5′-indigodisulfonic acid sodium salt) showed 3 redox peaks in acidic medium at pH =3. These are the Indigo Carmine (IC) /Leucoindigo carmine (LIC) pair and that of dehydroindigo carmine (DHIC). These peaks appear at the respective potentials IC (- 0.05V), LIC (- 0.1 V) and DHIC (0.5 V). In basic medium, only one peak appears, that of dehydroindigo carmine at the potential 0.69 V Vs Ag/ AgCl / KCl_sat. Dehydroindigo carmine obtained in a basic medium is adsorbed on the surface of the working electrode. It has in its chemical structure the carbonyl group capable of complexing mercury. During these redox reactions, there is a transfer of two protons, H^+,and two electrons. These redox reactions take place at the surface of the working electrode containing the active sites, thanks to the transport of matter by diffusion and adsorption. Each redox peak has an electrochemical impedance consisting of the resistance of the electrolyte, the electrochemical double layer capacity, the charge transfer resistance and the Warburg impedance. Their study allows the equivalent electrical circuit of the interface to be produced.

Effects of Carbonation on the Properties of Concrete Made with Crushed Sand and Admixtures

Jacques Herve Koung à Bediang — 2025-09-20

Carbonation is a natural ageing process that occurs in all types of concrete. Carbonation impacts the durability of concrete, involving a reaction of carbon dioxide (CO₂) with cement hydration products to reduce the pH of the concrete pore solution from around 12 to less than 9. A key implication of carbonation is the acceleration of steel corrosion caused by the phenomenon of depassivation. The goal of this research is to investigate the carbonation of quarry sand-based concrete. The concrete is made of 100% crushed sand 0/6.3, gravel 8/16, and 15/25 from the Arab Contractor quarry in Nomayos, Cameroon, with CEM II B-P 42.5 R from CIMENCAM (Cimenteries du Cameroun). The study employed two admixtures: one with a dual superplasticizing and reducing action (Sikamen) and another with a water-repellent effect (Sika liquid). The Dreux-Gorisse method was applied for mix design. Carbonation was performed on concrete samples at the following dates: 0, 7, 14, 28, 56, 90, 180 days, one year, one year and six months. Carbonated concrete (CC) and non-carbonated concrete (NCC) samples are compared firstly in terms of their physical attributes and mineralogical characteristics, secondly in microstructure terms, aspect as X Ray Diffraction (XRD) and Scanning Electron Microscope (SEM) observation. The results of this investigation reveal that after more than a year and six months of carbonation, porosity decreases and permeability increases. The microstructure becomes firmer and more resistant to hostile treatments. Despite the high fineness modulus of quarry sand, the compressive strength of quarry sand-based concrete is satisfactory. Carbonation depth is relatively high on some dates, exceeding the minimal cover value for concrete reinforcement. A reduction in water and pore space causes mass loss, which leads to an increase in elastic deformation. Sikament additive increases concrete compactness and durability while decreasing permeability. Sika water repellent mixes with the lime in cement to generate complementary crystallisations that block the mortar's capillaries, making it watertight.