Preparation and characterization of MAO-Si3N4 composite coating on AZ31B magnesium alloy

Micro arc oxidation process was carried out on AZ 31 B magnesium alloy using alkaline silicate based bath at a constant current density of 0.04 A/cm2. Nano size silicon nitride (Si3N4) particles were added in the bath to obtain MAO- Si3N4 composite coatings. Plain oxide coatings were also prepared for comparison. The developed coatings were characterised for their surface morphology, composition, structure, roughness, nanohardness and wear resistance properties. Field Emission Scanning Electron Microscopy (FE-SEM) analysis of the coating exhibited the irregular porous structure with cracked morphology. Energy Dispersive Analysis of X-ray (EDX) over the surface of the composite coating showed the presence of O (42.8 wt.%), Si (13.2 wt.%), F (4.8 wt.%), Al (0.63 wt.%) and N (7.8 wt.%) with balance Mg respectively. XRD pattern obtained for composite coating revealed the characteristic peaks corresponding to Mg, MgO and Mg2SiO4. Apart from these peaks the presence of a low intensity peak corresponding to Si3N4 was also observed. Composite coating exhibited about 56% increase in nanohardness value (387 HV) compared to plain oxide coating (167 HV). Dry reciprocating wear test experiment was carried out for composite, plain oxide and substrate materials against alumina ball. Wear loss obtained for the composite is 3 times less (10 µms) compared to plain oxide coating which indicated improved wear resistance of the MAO-Si3N4 composite

Conversion of biomass platform molecules into fuel additives and liquid hydrocarbon fuels

[EN] In this work some relevant processes for the preparation of liquid hydrocarbon fuels and fuel additives from cellulose, hemicellulose and triglycerides derived platform molecules are discussed. Thus, it is shown that a series of platform molecules such as levulinic acid, furans, fatty acids and polyols can be converted into a variety of fuel additives through catalytic transformations that include reduction, esterification, etherification, and acetalization reactions. Moreover, we will show that liquid hydrocarbon fuels can be obtained by combining oxygen removal processes (e.g. dehydration, hydrogenolysis, hydrogenation, decarbonylation/descarboxylation etc.) with the adjustment of the molecular weight via C C coupling reactions (e.g. aldol condensation, hydroxyalkylation, oligomerization, ketonization) of the reactive platform molecules.This work has been supported by the Spanish Government-MINECO through Consolider Ingenio 2010-Multicat and CTQ.-2011-27550, ITQ thanks the "Program Severo Ochoa" for financial support.Climent Olmedo, MJ.; Corma Canós, A.; Iborra Chornet, S. (2014). Conversion of biomass platform molecules into fuel additives and liquid hydrocarbon fuels. Green Chemistry. 16(2):516-547. https://doi.org/10.1039/c3gc41492bS51654716

Utilization of Glycerol from Biodiesel Industry By-Product into Several Higher Value Product

Since the 1980s the energy demand has been increasing steadily, including diesel fuel. On the other hand the oil reserve in the world was increasingly limited because of being the product that could not be renewed. Therefore, effort was carried out to look for the alternative fuel that could be renewed and environment friendly. The alternative energy from new renewable energy is a solution to reduce the dependence of fossil energy. The renewable energy consists of the energy of water, wind, biomass or biofuels, solar energy, ocean energy, and geothermal energy. One of the biofuels is biodiesel. Biodiesel is diesel fuel which is made from vegetable oil by transesterification. The abundance of glycerol will result in declining sales value of glycerol as a by-product of the biodiesel plant. It should be anticipated to improve the usefulness of glycerol both in terms of quantity and its variants. The increasing usefulness of glycerol will result in the higher price of glycerol that will increase the profitability of biodiesel plants. Among the usefulness of glycerol investigated is as an ingredient in pharmaceutical products, polyether, emulsifiers, fabric softener, stabilizers, preservatives in bread, ice cream, cosmetic ingredients, a propellant binder, and others. This chapter explains the utilization of glycerol to produce triacetin as bioadditive and polyglycidyl nitrate (PGN) as a propellant binder. Triacetin is used to increase octane number of fuel and improve the biodiesel’s performance. Propellant binder consists of two kinds of non-energetic polymers and polymer energetic. The most energetic polymer is PGN. The focus of this chapter is to determine each step of reactions, operating conditions of process and the results of products

Influence of current density on the morphology and corrosion properties of MAO coatings on AZ31B magnesium alloy

Micro-arc oxidation (MAO) coatings were prepared on AZ31B magnesium alloy using alkaline silicate electrolyte at different current densities (0.026, 0.046 and 0.067 A/cm2). Field Emission Scanning Electron Microscopy (FESEM) analysis of the coating revealed an irregular porous structure with cracked morphology. Compositional analysis carried out for MAO coating showed the presence of almost an equal amount of Mg and O (34 wt.%) apart from other elements such as F, Si and Al. The cross-sectional FESEM images clearly portrayed that the MAO coating was dense along with the presence of very few fine pores. The surface roughness (Ra) of the coatings increased with an increase in the current density. Potentiodynamic polarization and electrochemical impedance spectroscopic (EIS) studies were carried out for both the bare and MAO coated AZ31B Mg alloy in 3.5% NaCl solution. The corrosion potential (Ecorr) and corrosion current density (icorr) values obtained for the bare substrate were − 1.49 V and 46 μA/cm2, respectively. The coating prepared at 0.046 A/cm2 exhibited the lowest icorr value of 7.79 × 10− 10 A/cm2 and highest polarization resistance (41.6 MΩ cm2) attesting to the better corrosion resistance of the coating compared to other samples. EIS results also indicated almost similar corrosion behavior for the MAO coatings. Mott–Schottky analysis showed n-type and p-type semiconductor behavior for the oxide layer present on the bare magnesium alloy and MAO coatings respectively

Preparation and characterization of environmentally friendly sol-gel hybrid coatings for corrosion protection of AA2024

Sol-gel hybrid coatings were developed as potential replacement for the environmentally hazardous chromate conversion coatings for AA2024 aluminum alloy. The sol was prepared by acid catalysis of a mixture of glycidoxypropyltrimethoxysilane (GPTMS) and Zirconium (IV) tetrapropoxide (TPOZ) and doped with an inorganic corrosion inhibitor like cerium salt. It was applied on to AA2024 substrate by spray-coating technique. Coated coupons were characterized by Field emission scanning electron microscopy (FESEM) and micrographs of the as-prepared sol-gel coatings showed a pore-free and crack-free surface. Corrosion resistance of the sol-gel coatings in 3.5% NaCl solution was evaluated by potentiodynamic polarization measurements. Coatings have also been evaluated by continuous salt spray exposure. The effect of cerium salt concentration on the corrosion protection efficiency of the sol-gel hybrid coatings was studied. The GZC sol-gel coating doped with optimized cerium inhibitor were applied on (10 x 3 inch2) size samples and subjected to salt spray test. The developed GZC sol-gel coatings were comparable to CCC and offered excellent protection to the AA2024 substrate. Chemical composition of the coated substrates after salt spray test indicated increased concentration of cerium indicating migration of cerium to the exposed area resulting in corrosion protection of the surface

Inhibitor doped Sol-gel nanocomposite coatings for the corrosion protection of aircraft aluminum alloys

Aircraft aluminum alloys such as AA2024 are susceptible to severe corrosion in aggressive environments because of its heterogeneous microstructure. Chromate conversion coatings (CCC) are usually applied as the state of the art pre-treatment for corrosion protection of these alloys. However, since chromates are hazardous and carcinogenic, there is need for environmentally safe alternatives. Sol-gel coatings are environment-friendly barrier coatings that have been studied for corrosion protection of metals and alloys. In the present work, sol-gel nanocomposite coatings are developed using a mixture of methyltriethoxysilane (MTEOS) and colloidal silica. They are doped with an inorganic corrosion inhibitor like cerium nitrate and applied on Alclad AA2024 by spray-coating technique. The sol-gel process parameters were optimized to obtain a uniform pore-free and crack-free coating. Coated coupons were characterized by FESEM and EDX. Corrosion resistance of the sol-gel coatings in 3.5% NaCl solution was evaluated by potentiodynamic polarization technique, electrochemical impedance spectroscopy (EIS) and Neutral Salt Spray test