Effect of clay mineral content on soil strength parameters

The impact of clay mineralogy on engineering properties relevant to road design, such as the strength and stiffness of road materials, has recently been the subject of intensive investigations, aiming at providing indirect measures of soil performance out of mineralogical data. This study deals with the effects of clay minerals on soil strength, expressed in terms of California Bearing Ratio (CBR) and Unconfined Compressive Strength (UCS), and stiffness, represented by the constrained modulus, which are commonly used as engineering properties for pavement materials. The study is performed on six clayey soils (S1-S6) of different geographic origins. Five of the six soils are highly plastic, potentially swelling, and one is kaolinitic soil. The mineralogical characteristics of the samples were analyzed through X-ray diffraction (XRD). The testing program included Atterberg limits, sieve analysis, CBR, UCS, and consolidation tests. The measured properties of the samples were compared in light of the mineralogical composition of the soils. The investigation showed that the kaolinite mineral is significantly more effective than the montmorillonite in reducing the plasticity of the clays. Higher strength indicators (CBR and UCS) were observed for samples with high kaolinite content (S4, S5, and S6). Moreover, the kaolinitic soil samples are characterized by a larger constrained modulus (Ec) than the other samples

Spectral Downshifting and Passivation Effects Using 2D Perovskite (OAm)₂SnBr₄ Films to Enhance the Properties of Si Nanowire Solar Cells

Si nanowires (Si NWs) are emerging as a promising candidate for photovoltaics due to their significant light-trapping characteristics. However, Si NWs have a high density of surface traps, which lead to carrier recombination; also, thermalization due to the absorption of high-energy photons causes the dissipation of input solar energy. In this study, Ag/Ti/n+/p-Si NWs/MoOx/Ag solar cells were formed based on Si NWs with MoOx as a hole transport layer. A highly luminescent 2D perovskite (C18H35NH3)2SnBr4 was applied to the front surface of the cell. This 2D perovskite with oleylamine (OAm) spacer passivates the surface of the Si NWs. In addition to the passivation effect, the 2D perovskite (OAm)2SnBr4 causes a downshifting and energy-transfer effect, which reduces the heat loss and raises the conversion efficiency. This effect has often been observed in semiconductor quantum dots and is also evident in 2D perovskite films, resulting in improved Jsc, Voc, and fill factor and an increase in the overall cell efficiency to 18%