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Corrosion control for metals has technical, economical, environmental, and aesthetical importance. The use of corrosion inhibitors from natural product is one of the best ways to slow the rate of corrosion of metals and alloys. The use of extract inhibitors from natural product is the best alternative because it does not contain heavy metals and is nontoxic, environmentally friendly, biodegradable, easy to obtain, inexpensive, and available in large quantities. The organic compounds contained in the extracts of natural products such as tannins, amino acids, phenolics, and alkaloids contain heteroatomic groups, which can inhibit corrosion rate and are interesting to study. With the development of science and technology, many methods are used to protect the corrosion, such as electroplating and coating, and organic inhibitor shows real promise such as Theobroma cacao peel extract. Although substantial research has been devoted to corrosion inhibition by plant extracts, reports on the detailed mechanisms of the adsorption process and identification of the active ingredient are still scarce. The addition of polar extract of cacao peel into a solution of HCl 1.5 M is very effective to reduce the attack surface corrosion on mild steel and can maintain its mechanical properties. This chapter consciously restricts itself mainly to plant materials, especially Theobroma cacao peel extract, as green corrosion inhibitors.

This study was carried out to examine the potential of conversion of rubber seed oil into biodiesel. A series experiments was conducted using CaO and CaO/SiO 2 as catalyst and coconut oil as co-reactant, with the main purpose to assess the effect of calcination temperatures on the performance of the catalysts. The results obtained demonstrate that the use of coconut oil as coreactant significantly promoted conversion of fatty acids in rubber seed oil into their corresponding methyl esters. It was also found that the catalytic activity of both CaO and CaO/SiO 2 was significantly influenced by calcination temperatures and at the same temperature, CaO/SiO 2 exhibited higher activity than unsupported CaO. The highest yield was achieved using CaO/SiO 2 catalyst subjected to calcination at 800 o C

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Nanocrystalline cerium oxide is synthesized by precipitation method using a mixture of water solvent and isopropanol with a ratio of 1: 6 at room temperature has been successfully synthesized. Nanocrystalline cerium oxide was characterized by using X-Ray diffraction (XRD), DRS UV-Vis Analytic, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). XRD results showed the peak intensity of Cerium Oxide (CeO2) was absorbed at an angle of 2Ɵ which is 28.7o, 33.2 o, 47.5 o, 56.7 o, 59.2 o, 69.5 o, 76.8 o, 79 , 1o, 88.3 o, and 95.5 o. The size of cerium oxide crystals was calculated using the debye schrerer equation and obtained a crystal size value of 11.04 - 99.19 nm. Based on the XRD data it can be concluded that the crystal size is included in the nanocrystal category with a size range of 1-100 nm. Microstructure results were analyzed by SEM and TEM showing rounded cerium oxide particles clumping like fine crystals. Optical properties of nanocrystalline cerium oxide were analyzed by DRS UV-Vis Analytic which showed that cerium oxide absorbs UV light at wavelengths of 200, 245 and 290 nm with an energy band gap value of 2.43 eV.

Hydroxyapatite (HAp) has been used for various applications such as orthopedics, drug delivery material, and bone tissue engineering. It is well known that HAp has a good biocompatibility and osteoconductivity, so HAp can be used in biomedical applications. Hydroxyapatite can be combined with other materials, in particular polymer, to expand its range of applications. In this study, the polymer that will be used as a support for the HAp composite is alginate (Alg). The HAp/Alg composite has been synthesized by the precipitation method. The XRD results show that the crystal system of HAp was hexagonal. The spheric-like shaped particles can be observed from SEM images, and particle size distribution spread from 400 to 1100 nm. The EDS spectrum exhibited the peak of Ca, C, P, and O elements, indicating that alginate had interacted with hydroxyapatite in the synthesized composite. The as-fabricated composite showed not only good crystallinity but also high thermal resistance. Thermogravimetric-differential thermal analysis (TGA-DTA) revealed that the HAp/Alg composites have a constant weight at 750 °C, so it might be applied in advanced applications such as bioimaging, drug carrier, and other cancer treatments.

Objective: In this study, the effect of hydrothermal temperature on the synthesis of hydroxyapatite (HAp) from limestone was investigated.Methods: Precursors of limestone (CaCO3) and diammonium hydrogen phosphate ((NH4)2HPO4) with Ca/P ratio of 1.67 was mixed at pH 10 in order to synthesize hydroxyapatite by hydrothermal method. The solution was hydrothermally treated in an autoclave at various temperatures of 120, 160 and 200 °C for 24 h. Nano powder formed was then characterized.Results: The hydroxyapatite obtained by hydrothermal method at various temperatures was characterized. The analysis of Fourier Transform Infrared (FTIR) revealed that HAp had phosphate (PO43-) and hydroxyl (O-H) groups although carbonate (CO32-) group remained. X-Ray Diffraction (XRD) revealed that the size of nanosize crystals was formed and then provided a large surface area. Scanning Electron Microscopy (SEM) results showed that HAp had a spherical shape. There was more agglomeration at 200 °C than at 160 °C. The ratio of the results of Energy Dispersive X-ray (EDX) analysis in 160 °C was 1.95 and at 200 °C was 1.71Conclusion: The hydroxyapatite prepared at a temperature of 200 °C had smaller crystal size than the hydroxyapatite prepared at the temperatures of 120 and 160 °C. SEM pictures showed that the nanoparticle hydroxyapatite had a spherical shape.

ZnO-NiFe 2 O 4 magnetic nanocomposite photocatalysts were successfully synthesized by simple solvothermal method using nitric salts as starting materials and ethanol as solvent. The synthesized samples were characterized by XRD, FESEM-EDX, TEM, DRS-UV-vis, VSM, and FTIR instruments. Photocatalytic activity of the samples was evaluated by dye degradation under solar light irradiation. The results show that the diffraction peaks of nanocomposites correspond to the hexagonal wurzite of ZnO and spinal cubic structure of NiFe 2 O 4 . The microstructure studies revealed that nanocomposites were dominated by granular-like of ZnO nanoparticles were synthesized at 180°C and rod-like at 200°C. The estimated band gap value of ZnO-NiFe 2 O 4 (1:0.01) nanocomposites is 2.78 eV which is lower than ZnO. The magnetic saturation (Ms) result showed a superparamagnetic behavior for nanocomposites. It was found that the photocatalytic activity of synthesized nanocomposites were higher than ZnO and NiFe 2 O 4 .