Heat sinks are commonly used for cooling electronic devices and high-power electrical systems. The ever-increasing performance of electronic systems together with miniaturization calls for better heat dissipation. Therefore, the heat sink materials should not only have high thermal conductivities, low densities, and cost, but also have coefficients of thermal expansion matching to those of semiconductor chips and ceramic substrates. As traditional materials fail to meet these requirements, new composite materials have been developed with a major focus on metal matrix composites (MMCs). MMCs can be tailored to obtain the desired combination of properties by selecting proper metallic matrix and optimizing the size and type, volume fraction, and distribution pattern of the reinforcements. Hence, the current review comprehensively summarizes different studies on enhancing the thermal performance of metallic matrices using several types of reinforcements and their combinations to produce composites. Special attention is paid to the types of commonly used metallic matrices and reinforcements, processing techniques adopted, and the effects of each of these reinforcements (and their combinations) on the thermal properties of the developed composite. Focus is also placed on highlighting the significance of interfacial bonding in achieving optimum thermal performance and the techniques to improve interfacial bonding.

An aluminum oxide-impregnated carbon nanotube (CNT-Al₂O₃) membrane was developed via a novel approach and used in the removal of toxic metal cadmium ions, Cd(II). The membrane did not require any binder to hold the carbon nanotubes (CNTs) together. Instead, the Al₂O₃ particles impregnated on the surface of the CNTs were sintered together during heating at 1400 °C. Impregnated CNTs were characterized using XRD, while the CNT-Al₂O₃ membrane was characterized using scanning electron microscopy (SEM). Water flux, contact angle, and porosity measurements were performed on the membrane prior to the Cd(II) ion removal experiment, which was conducted in a specially devised continuous filtration system. The results demonstrated the extreme hydrophilic behavior of the developed membrane, which yielded a high water flux through the membrane. The filtration system removed 84% of the Cd(II) ions at pH 7 using CNT membrane with 10% Al₂O₃ loading. A maximum adsorption capacity of 54 mg/g was predicted by the Langmuir isotherm model for the CNT membrane with 10% Al₂O₃ loading. This high adsorption capacity indicated that adsorption was the main mechanism involved in the removal of Cd(II) ions.

Fly ash (FA) is a major industrial waste generated from power stations that add extra cost for proper disposal. Recent research efforts have consequently focused on developing ways to make use of FA in environmentally sound applications. This study, therefore, investigates the potential ability of raw fly ash (RFA) and polyelectrolyte-coated fly ash (PEFA) to remove cadmium (Cd) from polluted water. Using layer-by-layer approach, functionalized fly ash was coated with 20 layers from 0.03% (v/v) of cationic poly(diallyldimethylammonium chloride) (PDADMAC) and anionic polystyrene sulfonate (PSS) solutions. Both surface morphology and chemical composition of the adsorbent (PEFA) were characterized using Field-Emission Scanning Electron Microscope (FE-SEM), X-Ray Diffraction (XRD), Fourier-Transform Infrared (FTIR), and X-Ray Fluorescence (XRF) techniques. The effects of pH, adsorbent dosage, contact time, initial contaminant concentration, and mixing rate of the adsorption of Cd were also studied in batch mode experiments. Results of the study revealed that a 4.0 g/L dosage of PEFA removed around 99% of 2.0 mg/L of Cd in 15 min at 150 rpm compared to only 27% Cd removal achieved by RFA under the same conditions. Results also showed that adsorption by PEFA followed both Langmuir and Freundlich models with correlation coefficients of 98% and 99%, respectively.