Microstructural Evolutions and its Impact on the Corrosion Behaviour of Explosively Welded Al/Cu Bimetal

In this study, the microstructural evolutions and corrosion resistance of aluminium/copper joint fabricated through explosive welding process have been thoroughly investigated, while stand-off distance was variable. Microstructural analyses demonstrate that, regardless of grain refinement in the welding boundary, increasing the stand-off space is followed by a higher thickness of the localized melting pool. X-Ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS) analyses recognized the binary intermetallic layers as a combination of Al2Cu and AlCu. Polarization and electrochemical impedance spectroscopy (EIS) corrosion tests revealed that a higher stand-off distance resulted in the increment of corrosion potential, current rate, and concentration gradient at the interface owing to the remarkable kinetic energy of the collision, which impaired corrosion resistance

Prediction total specific pore volume of geopolymers produced from waste ashes by fuzzy logic

In the present work, total specific pore volume of inorganic polymers (geopolymers) made from seeded fly ash and rice husk bark ash has been predicted by fuzzy logic. Different specimens, made from a mixture of fly ash and rice husk bark ash in fine and coarse form together with alkali activator made of water glass and NaOH solution, were subjected to porosimetry tests at 7 and 28 days of curing. The curing regime was different: one set of the specimens were cured at room temperature until reaching to 7 and 28 days and the other sets were oven cured for 36 hours at the range of 40-90 °C and then cured at room temperature until 7 and 28 days. A model based on fuzzy logic for predicting the total specific pore volume of the specimens has been presented. To build the model, training and testing using experimental results from 120 specimens were conducted. The used data as the inputs of fuzzy logic models are arranged in a format of six parameters that cover the percentage of fine fly ash in the ashes mixture, the percentage of coarse fly ash in the ashes mixture, the percentage of fine rice husk bark ash in the ashes mixture, the percentage of coarse rice husk bark ash in the ashes mixture, the temperature of curing and the time of water curing. According to the input parameters, in the fuzzy logic model, the pore volume of each specimen was predicted. The training and testing results in the fuzzy logic model have shown a strong potential for predicting the total specific pore volume of the geopolymer specimens in the considered range

Modeling split tensile strength of high strength self compacting concrete incorporating randomly oriented steel fibers and SiO2 nanoparticles

In the present study, split tensile strength of self compacting concrete with SiO2 nanoparticles and different amount of randomly oriented steel fibers has been investigated. Steel fibers were added to the concrete specimens containing SiO2 nanoparticles with the average particle size of 80 nm and split tensile strength of the specimens was measured. The obtained results show that randomly oriented steel fibers up to 12 wt.% can improve the concrete strength. A model based on the rule of mixtures has been presented to predict the split tensile strength of the specimens to compare the effect of nanoparticles on split tensile strength of the specimens. The obtained results from the proposed model are in good agreement with those obtained from the experiment

Application of ANFIS for modeling of microhardness of high strength low alloy (HSLA) steels in continuous cooling

The paper presents some results of the research connected with the development of new approach based on the Adaptive Network-based Fuzzy Inference Systems (ANFIS) of predicting the Vickers microhardness of the phase constituents occurring in five steel samples after continuous cooling. The independent variables in the model are chemical compositions, initial austenite grain size and cooling rate over the temperature range of the occurrence of phase transformations. To construct these models, 114 different experimental data were gathered from the literature. The data used in the ANFIS model is arranged in a format of twelve input parameters that cover the chemical compositions, initial austenite grain size and cooling rate, and output parameter which is Vickers microhardness. In this model, the training and testing results in the ANFIS systems have shown strong potential for prediction of effects of chemical compositions and heat treatments on hardness of microalloyed steels

Synthesis of silver nanoparticles from electronic scrap by chemical reduction

In the present research, the use of electronic waste in the synthesis of silver nanoparticles was investigated. For this purpose, electronic scraps were used as a consumable part to synthesize silver nanoparticles. The results revealed that by optimizing the time and temperature of the dissolution process using nitric acid solution up to 90%, silver can be extracted from these parts. The results indicated that the concentration of initial silver nitrate had a significant impact on the quality of the final product, so that the best conditions for the synthesis of silver nanoparticles with suitable properties were provided at 1 molar concentration. Phase studies indicated that the main phase of the synthesized silver particles had an FCC structure and no unwanted phase was observed. Ultraviolet–visible analysis of the synthesized powder revealed that the main peak for the silver nanoparticles appeared in the wavelength range of 400 to 450 nm. DLS analysis revealed that precursor’s particles inside the sol were below 15 nm. Based on AFM and TEM investigations, the particles synthesized under these conditions had nanometric spherical morphology with uniform particle size distribution

Evaluation of APC impact on controlling precursors properties in the sol for synthesizing meso porous ZrC nanopowder through sol-gel process

In this research, the dispersion characteristics of the suspension containing precursors were investigated in terms of charge, particle size, and rheological properties. Zirconium carbide nanopowder was prepared in the four-component system of alkoxide-resin-dispersant-catalyst based on the sol-gel chemical process under acidic conditions. Ammonium polycarboxylate (APC) was manipulated as a sol-dispersing agent to reach a particle size of less than 5 nm. Results depicted that the amount of surface charge of precursors was changed in the presence of ammonium polycarboxylate agent, and the PZC point was shifted towards acidic pHs less than 6.1. According to electrokinetic data, the interaction of surface sites and APC cause alteration of free specific energy for surface adsorption with a negative value. With regard to DLS analysis, the presence of APC stabilizes particles in the sol with precise control over their sizes in less than 10 nm. At intermediate pHs, the viscosity of the sol containing precursor increases which leads to a decrease in the particles stability. FTIR analysis of gel powder confirmed the proper formation of Zr–O–C bonds through hydrolysis and condensation reactions. The surface of the synthesized nanopowders is porous and in the meso range, so that their specific surface area is 165 m2/g. DTA analysis indicated that initial nuclei of ZrC were formed at around 1320 °C, which XRD patterns confirm this. SEM microstructure images showed that ZrC particles were created in the nanometer dimensions, and particle size distribution were reported in a narrow range with uniform morphology. TEM images and their diffraction patterns represented the synthesis of crystalline ZrC particles less than 50 nm

Improvement compressive strength of cementitious composites in different curing media by incorporating ZrO2 nanoparticles

In the present work, the effect of curing medium on microstructure, physical, mechanical and thermal properties of ZrO2 nanoparticles blended concrete has been investigated. ZrO2 nanoparticles were partially used instead of cement by 0.5, 1.0, 1.5 and 2.0 weight percent. Curing of the specimens was carried out in water and saturated limewater for 7, 28 and 90 days. The results indicate that ZrO2 nanoparticles up to maximum of 2.0% produces cementitious composite with improved compressive strength by curing in saturated limewater. The optimum level of replacement for the specimens cured in water was 1.0 weight percent. ZrO2 nanoparticles can improve the filler effects and also the high activity of fine particles substantially increases the quantity of strengthening gel. Although the limewater reduces the strength of concrete without nanoparticles when compared with the specimens cured in water, curing the specimens in saturated limewater results in more strengthening gel formation around ZrO2 nanoparticles blended concrete causes high strength