This work investigates the thermal–physical and rheological properties of hexagonal boron nitride/carbon nanotubes (hBN/CNTs) applied to reinforce water-based working fluid in a flat plate solar collector (FPSC). The hybrid nanoadditives of hBN and the chemically functionalized CNTs (CF-CNTs) were suspended in distilled water (DW) with a nonionic surfactant. The hybridization ratio between CF-CNTs and hBN was optimized to be 40:60. The thermal efficiency tests on the solar collector were carried out using different volumetric flow rates (2, 3, and 4 L/min) under the ASHRAE-93-2010 standard. The morphological characteristics of the hybrid nanoadditives were evaluated using X-ray diffraction (XRD), ultraviolet–visible spectroscopy (UV–vis), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). Different concentrations of hBN/CF-CNTs were added to the water-based working fluid to record the optimal wt.% for maximum enhancement in the FPSC’s efficiency. The results revealed that using only 0.1 wt.% of hBN/CF-CNTs with a flow rate of 4 L/min remarkably improved the collector efficiency by up to 87% when compared to the conventional working fluid used in FPSC.

Due to the importance of these alloys in the manufacture of aircraft, coatings, radiation shields, and electronic circuits, the study’s objectives include investigating previously unstudied structural properties of some aluminum alloys, alloy A (Al-Zn-Mg-Ti) and alloy B (Al-Zn-Mg-Mn) were prepared using the casting method, and their structural properties were studied using X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques (granular size and theoretical density). The results of analyzing the X-ray diffraction data and determining the phases formed on the two alloys after matching them with the international standard cards (JCPDS) revealed that it is polycrystalline, with structures (cubic and hexagonal) on alloy A and structures (cube, hexagonal, and anorthic) on alloy B. The results revealed that the average grain size estimated by the Debye-Scherer method is less than that estimated by the Williamson-Hall method, and that the grain size of alloy A is less than that of alloy B due to the presence of titanium in alloy A’s composition, which works to reduce particle size. The theoretical density of Alloy A and B that was used in X-ray diffraction was calculated. SEM analysis of the spherical shape of the grains on the surfaces of alloys A and B revealed that the average grain size on the surface of alloy A is smaller than on the surface of alloy B, which is consistent with the results of XRD analyses.