Several modern cutting edge technologies, including the superconducting technology, green energy generation/storage technology, and the emerging 5G networks technology, have some form of thin-film coatings. Hence, this critical review showcased the historical evolution, conventional deposition technologies with its application areas, growth modes, specific thin-film stress-state micro/nano-level measurement and models, and prospects projection of thin-film coatings. Specifically, the authors included simple schematics of the primary thin-film coating methods (chemical vapor deposition and physical vapor deposition methods), growth modes, residual stress evolution behavior from valuable up to date models to enhance in-depth understanding of the underlying principles of thin-film coatings techniques and challenges. Also, the authors pointed out specific deficiencies in the reported thin-film stress measurement/models approaches. It is scientifically shown that no coating technique or model has superior results in all scenarios, selecting a suitable coating technique or model depends on the targeted materials and functions of the thin-film system. According to the evaluated reports, the societal demand and specific challenge in the fabrication/applications of thin-film systems indicated that thin-film coatings and its associated challenges would remain vibrant and active research areas for periods far into the future. Thus, this report would serve as a guide and reference material for potential researchers in these areas for a considerable time.

Nano-CaCO3 (NCC) obtained from Achatina achatina shells were used as single filler and as partial replacement of carbon black (CB) to produce vulcanized natural rubber (NR) filled at 5, 10, 15, 20, 25 and 30 pphr. The SEM micrographs showed that the dispersion of the fillers in the hybrid composites up to 15wt% replacement of CB was very good. Higher strengths were obtained up to 25 pphr for composites that contained 95wt%CB/5wt%NCC and 90wt%CB/10wt%NCC, while the composites that contained 85wt%CB/15wt%NCC showed higher strength up to 20 pphr compared to the CB filled samples. The NR filled with hybrid CB/NCC up to 15wt% replacement of CB offered comparative hardness and abrasion resistance; while 95wt%CB/5wt% NCC filled sample showed lower compression set over CB reinforced samples up to 30 pphr and comparative tensile strength, hardness, elastic modulus and abrasion resistance. As single filler, the synthesized nanoparticles imparted significant improvement in the mechanical properties of vulcanized NR; however, the properties were inferior to the CB reinforced sample due to poor dispersion of the NCC in vulcanized NR. The thermal and oxidative stability of the hybrid composites up to 15wt% replacement of CB were better than those of the CB filled samples.

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Soil samples were obtained from three different locations; Ijapo, Ibule and FUTA North Gate in Akure, Ondo State, Nigeria. The materials were dried, crushed and calcined by heating the samples in a muffle furnace to 850 °C, holding for three hours and and then brought out of the furnace to cool in the laboratory so that the organic and volatile matter escaped, and the oxide content increased. The calcined materials were milled with a ball mill and then sieved with 75 µm mesh size British standard sieves. The samples that passed through the sieves were collected for analysis to determine their extender characteristics through x-ray flouresence (XRF) spectroscopy, x-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), specific gravity, oil absorption, pH and refractive index measurements as well as the determination of their resistance to chemicals. XRF results showed that materials are kaolinite in nature. XRD results showed the phase compositions of each sample as materials suitable for applications as extenders in the paints industry. SEM micrographs showed the homogeneity of the samples from Ijapo and FUTA North Gate while the sample from Ibule showed segregation of the phase compositions. The specific gravity, pH, oil absorption and refractive index of each material were within the range of those of commercial extenders used in the paints industry. The calcined materials were found to be resistant to various chemical media. The characterized materials will be suitable as extenders and pigments in the paints industry.

ABSTRACT. The consumable palm wine has never been used in heat treatment process of steels. This research therefore focuses on the utilization of the consumable palm wine and other palm tree products as quenchants. The mechanical and physical properties of the samples were also evaluated to determine which of the quenchants that influences the hardness and corrosion rate values of medium carbon steel the most. The corrosion test was performed in 1.0 M of HCl solution and homemade vinegar using potentiodynamic polarization method. The results revealed a hardness value of 431, 351, 359 and 265 HB for the samples quenched in palm wine, palm kernel oil, palm oil and as-received, respectively. The corrosion rates of palm oil tempered samples showed more susceptibity to corrosion in HCl solution with a value of 2.261e+003 mil/year. Vinegar offers the highest corrosion rate with a value of 4.017e+002 mil/year for palm wine tempered. The corrosion rate of the as-received samples pulled the lowest values while on the treated samples, palm kernel oil showed the least corrosion rate values.   KEY WORDS: Consumable palm wine, Palm oil, Hardness, Corrosion rate, Austenitization, Quenching   Bull. Chem. Soc. Ethiop. 2022, 36(4), 893-901.                                                               DOI: https://dx.doi.org/10.4314/bcse.v36i4.14