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Development of a Novel Nanocomposite Coating for Tribological Applications
Published in Catalin I. Pruncu, Jamal Zbitou, Advanced Manufacturing Methods, 2023
Arti Yadav, M. Muthukumar, M. S. Bobji
Figure 9.4 shows the SEM image of the top surface of porous alumina after filling copper into porous alumina. When a continuous sine wave of applied voltage 17 V ac at 250 Hz frequency was applied (Figure 9.4a), It was seen that the porous alumina surface was damaged in a few places. The operating frequency of applied voltage was increased to 500 Hz, numerous pyramids were observed on the top of the surface. The size of pyramids varied from ∼200 nm to ∼800 nm over the surface (Figure 9.4b). When the frequency was maintained at 700 Hz, it was seen that bunches of pyramids were accumulated together and formed an island of pyramids. The surface was found damaged at the edges of these pyramids. It might be because of aluminium oxide/hydroxide dissolution producing hydrogen gas, as discussed by Zhao et al. [39]. Therefore, the evolution of hydrogen gas is becoming more dominant, resulting in damage to the porous alumina layer.
Hydrometallurgical Waste Production and Utilization
Published in Sehliselo Ndlovu, Geoffrey S. Simate, Elias Matinde, Waste Production and Utilization in the Metal Extraction Industry, 2017
Sehliselo Ndlovu, Geoffrey S. Simate, Elias Matinde
The amount of bauxite residue produced by an alumina producing plant is primarily dependent on the sources of the bauxite and on the extraction conditions used at the plant. The most important factors are the aluminium content of the bauxite, the type of aluminium oxide/hydroxide present (e.g. gibbsite, boehmite or diaspore) and the temperature and pressure conditions used for the extraction. For every ton of alumina produced, the red mud generated can vary from 0.3 to as high as 2.5 tonnes, though typically it lies between 0.7 and 2 tonnes per ton of alumina produced. According to the World Aluminium Report (2015), aluminium mining leaves behind a staggering 120 million metric tonnes (Mt) per year of the salty, highly alkaline, heavy-metal–laden residue material. Because of the chemical nature and the mineralogical species present in the red mud, this solid material causes a negative impact on the environment, and thus, proper disposal of red mud presents a huge challenge where alumina industries are installed.
Influence of the casting process on corrosion behaviour of 2024-T6 aluminium alloy in different conditions of pH and NaCl concentration
Published in Corrosion Engineering, Science and Technology, 2023
E. Mardaras, Naroa Imaz, R. González-Martínez, Eva García-Lecina, E. Aguado
The corrosion current density, icorr, estimated from anodic plus cathodic current density, is lower at pH 3.5 and pH 7 (Figure 5(a)) than in pH 12. But, the corrosion current density, icorr, at pH 7 is slightly lower than the pH 3.5 for each NaCl concentration. Similar behaviour was reported by Rout et al. [32], relating the change in icorr values with the increase of the cathodic reaction rate at higher concentration of H+ ions. Considering that the experiments were performed in a solution with chlorides, the current plateau observed in the cathode curves at pH 3.5 and 7 could be associated with the oxygen reduction reaction on the passive aluminium oxide/hydroxide layer. At these conditions, the cathodic process is controlled by mass transport and the cathodic current density is dominating due to the precipitates and intermetallic phases acting as local cathodes and to the dissolved oxygen in the solution.
Influence of nanoparticles on emission and performance characteristics of biodiesel-diesel blends in a DI diesel engine
Published in Australian Journal of Mechanical Engineering, 2022
Harish Venu, Prabhu Appavu, Venkata Ramanan M, Jayaprabakar Jayaraman
Rao and Anand (2016) experimentally investigated the effect of ALO(OH) (aluminium oxide hydroxide) nano particles as fuel borne additives for jatropha biodiesel based emulsion fuel operated in a single cylinder diesel engine. Adopted test fuels arediesel, BD5W (93% biodiesel + 5% water + 1% span 80 surfactant + 1% tween 80 surfactant) and BD10W (88% biodiesel + 10% water + 1% span 80 surfactant + 1% tween 80 surfactant) and doped the nano additives with dosage levels of 25 ppm, 50 ppm and 100 ppm respectively. BD10W100 (100 ppm CuO blended with BD10W) exhibited improved engine performance, lowered BSFC and high BTE in comparison with diesel and other test blends owing to the presence of higher nano particle which enhances micro-explosion and improvement in combustion. BD10W100 resulted in lowered HC, CO, NOx and smoke emissions by 39%, 50%, 37% and 25% respectively in comparison with diesel fuel owing to high surface area to volume ratio and catalytic activity of ALO(OH) nanoparticles which improves the combustion rate, homogenises the reactant mixture and lowered the exhaust gas temperature of products of combustion inside the combustion chamber. In-cylinder pressure and HRR of ALO(OH) blend is less in comparison with neat emulsified biodiesel owing to the presence of nano particles leading to early combustion and reduced ID period (faster evaporation rate and improved catalytic activity which causes very less fuel to take part in PCP resulting in lowered cylinder pressure and heat release rate).
Corrosion behaviour of Al–20Cu intermetallic alloy in synthetic sea water
Published in Canadian Metallurgical Quarterly, 2021
J. E. Flores-Chan, A. Torres-Islas, C. Patiño-Carachure, G. Rosas-Trejo, M. A. Espinosa-Medina
The effect of the pH of synthetic sea water and room temperature on the corrosion behaviour of the Al–20Cu intermetallic alloy using electrochemical techniques was studied. The most important results are: Corrosion of the Al–20Cu showed anodic dissolution and limiting current density at the anodic branches, where the highest icorr and the more active Ecorr were observed at pH 14. That was associated with the higher anodic dissolution rate and H2 evolution.The main corrosion mechanism of alloy at all pH conditions was by charge transfer. The EIS results showed capacitive behaviour at middle frequencies with an increase in the corrosion products detachment with the pH of the sea water solution. It is observed in the angle phase Bode plot. This behaviour was associated with the formation of stable or unstable aluminium oxide/hydroxide corrosion products formed under the pH conditions.The highest H2 generation was observed at pH 14. The hydrogen reduction at the cathode and the anodic dissolution of Al were the mechanisms associated. The diffusion of Al3+ towards the corrosion products/electrolyte interface, and the electrochemical reaction with OH− ions there were associated with the governed corrosion mechanisms. In this way, the Al–20Cu alloy could be a potential alloy for use in hydrogen generation applications.