Nanotechnology is the key solution for many human problems such as energy conversion, water treatment, and material science. In composite materials, nanoparticles are dispersed in a matrix material such as metals, ceramics, or polymers to enhance their mechanical and thermophysical properties. Polymer nanocomposite materials found their applications in vital fields such as the automotive and aircraft industries. There are many techniques adopted to produce polymer nanocomposites, and they are summarized and discussed according to our best known in this paper. All techniques aim to produce nanocomposite materials with uniform dispersion and without aggregations. Melt-mixing, mixing, in-situ polymerization, electrospinning, and selective laser sintering techniques are the most commonly used techniques to produce polymer nanocomposite. The utilization of water, atomic layer deposition, and plasma-assisted mechanochemistry are found to eradicate the issue of nanoparticles aggregation for melt-mixing technique. Also, sonication with high frequencies plays the same role for mixing techniques. In-situ polymerization provides fabrication of nanocomposites that are thermodynamically stable. Electrospinning represents an effective method which is suitable for producing porous structures. In addition, fabrication of nanocomposites via selective laser sintering has obvious benefits to overcome the problem of aggregation. The working principles of each technique, including the advantages and disadvantages, are discussed.

In fracture toughness tests, a number of notched specimens with identical artificial pre-cracks are essential to obtain accurate fracture parameters. The test results are critically depending on the initiation stage quality. Any slight variance in pre-cracks front shape, length and orientation could significantly affects the test results; therefore, producing identical pre-cracks is a critical issue to obtain accurate results. The pre-cracking technique should be selected carefully to fulfil controllably and repeatability requirements of the standard pre-cracks for a certain material while preserving the induced residual stresses at the crack tip at a minimal value. The notching and pre-cracking standards for metallic material have been well specified in ASTM E399. However, the case is more cumbersome for polymeric materials due their viscoelastic nature. ASTM D5045, ISO 13586:2000 and ASTM D6068 specified different procedures to prepare a sharp pre-crack for polymeric materials. Many pre-cracking techniques have been proposed in literature. The present work introduces an overview of the pre-cracking techniques for polymeric materials.

No abstract

No abstract

Increasing the evaporation zone inside the solar distiller (SD) is a pivotal method for augmenting its freshwater production. Hence, in this work, a newly designed prismatic absorber basin covered by linen wicks was utilized instead of the conventional flat absorber basin to increase the surface area of the vaporization zone in a double-slope solar distiller (DSSD). Meanwhile, for further enhancement of modified DSSD performance, dual parallel spraying nozzles are incorporated underneath the glass cover as a saltwater feed supply to minimize the thickness of the saltwater film on the wick, which enhances the heating process of the wick surface and, consequently, the evaporation and condensation processes are improved. Two double slope distillers, namely a double slope solar distiller with wick prismatic basin and dual parallel spraying nozzles (DSSD-WPB&DPSN) and a traditional double slope solar distiller (TDSSD), are made and tested in the outdoor summer conditions of Tanta, Egypt (31° E and 30.5° N). A comparative energic–exergic-economic analysis of the two proposed solar stills is also conducted, in terms of the cumulative distillation yield, daily energy efficiency, daily exergy efficiency, and cost per liter of distilled yield. The present results show that the cumulative distillation yield of the DSSD-WPB&DPSN was 8.20 kg/m2.day, which is higher than that of the TDSSD by 49.64%. Furthermore, the energy and exergy efficiencies were increased by 48.51% and 118.10%, respectively, relative to TDSSD. Additionally, the life cost assessment reveals that the cost per liter of the distilled yield of the DSSD-WPB&DPSN is decreased by 11.13% compared to the TDSSD.