Mechanical Properties

This study investigated the effect of nanosilica (NS) as a partial replacement for ordinary Portland cement (OPC) on the mechanical and durability properties of concrete. The aim was to assess the suitability of nanosilica in improving concrete performance and to determine its optimum replacement level for sustainable construction applications in Nigeria.Concrete was produced using a nominal mix ratio of 1:2:4 and a constant water–cement ratio of 0.5. Nanosilica was used to replace cement at levels of 0%, 1%, 2%, and 3% by weight. Tests carried out included slump test, setting time determination, compressive strength test, flexural strength test, and water absorption test. Statistical analysis of the results was performed using oneway analysis of variance (ANOVA).Results showed that workability increased with increasing nanosilica content, while both initial and final setting times decreased. Compressive and flexural strengths increased up to an optimum nanosilica content of 2%, where 28-day values of 24.4 N/mm² and 5.25 N/mm² were recorded, compared to 22.5 N/mm² and 4.67 N/mm² for the control mix. Water absorption reduced to 7.3% at 2% nanosilica replacement compared to 9.7% for the control, indicating improved durability. ANOVA results showed no significant differences in compressive strength, flexural strength, and workability (p > 0.05), while setting time showed significant variation (p < 0.05). The study concluded that 2% nanosilica replacement provided the best overall performance and is recommended for producing stronger and more durable concrete

The prospective use of lead(II) sulfide (PbS) perovskite in thermometric, optoelectronics, and photovoltaic have attracted a lot of interest. However, a number of issues, such as inadequate optical absorption, mechanical softness, suboptimal electrical characteristics, and structural instability, make practical use of it difficult. In this work, we thoroughly examine the structural, mechanical, electrical, and optical characteristics of PbS perovskite using first-principles density functional theory (DFT) computations. Our study reveals the fundamental stability requirements by analyzing formation energies and elastic constants. By analyzing the material's mechanical characteristics, including bulk modulus, shear modulus, and Poisson's ratio, the mechanical resilience of the material is evaluated. In order to maximize light-harvesting capabilities, optical characteristics such as the dielectric function and absorption coefficient are also investigated. We suggest doping, strain engineering, and defect passivation techniques to improve PbS's stability, mechanical strength, and optoelectronic efficiency in order to get beyond current restrictions. Our research provides important information for improving PbS-based materials for upcoming electrical and energy applications.