RESUMEN
This paper aimed to analyse the mechanical and sanitary properties of artificial cast stone. To create an artificial stone product of the desired shape and design, a thermoforming process is used, during which heavy presses shape the artificial stone parts at a certain temperature. According to experimental studies, the most suitable temperature for monochromatic and patterned cast stone thermoforming is 160 °C when the material has the least bending resistance and does not react strongly to heat. It is observed that the cast stone bends more easily as the distance increases. The bending test of the glued samples made it possible to find out which of the three gluing methods is the most resistant to the forces acting on the samples during bending. The sanitary properties of the artificial stone were compared with the properties of other commonly used surfaces. In the microbiological study, suspensions of three different bacteria were spread on stainless steel, laminated particleboard and artificial cast stone, and washes were taken from 100 cm2 after 25 min. The results showed that the artificial stone after washing had the lowest number of colonies forming units per cm2, which supports the claim of excellent sanitary properties of the product.
RESUMEN
The present study utilized a metal inert gas welding (MIG) to make a dissimilar weld of stainless steel AISI 304, 314, 316L, 420 grades and a standard structural steel S355MC. It refers to a weld joining two materials from different alloy systems commonly used in heat exchangers, pressure vessels, and power plant systems. Obviously, maintaining the integrity of such welds is of paramount importance to the safety issues. Therefore, detailed microscopic and experimental studies were performed to evaluate the reliability of these welds. The microscopic analysis did not reveal any presence of weld defects such as porosity or cracks, which ensured that MIG process parameters were properly selected. The performance of dissimilar welds was assessed by hardness and tensile tests. The hardness profiles revealed differences between austenitic and martensitic steel welds that later showed extremely high values in the heat-affected zone (HAZ), which caused fractures in this zone during tensile test. The welds of all austenitic steel grades withstood the tensile test, showing an average tensile strength of 472 MPa with fractures observed in the base metal zone. It made clear that the use of a filler rod 308LSI is suitable only for the austenitic stainless and structural steel dissimilar welds and not appropriate for martensitic-structural steel welds. The achieved results revealed that the higher hardness of the martensitic phase in the HAZ of AISI 420 is closely related with the formation of untempered coarse martensitic structure and higher carbon content.
RESUMEN
Waste Printed Circuit Boards (WPCBs) were classified as one of the most important resources for urban mining containing high purity Copper (Cu) and other valuable materials. Recently, a dissolution recycling approach enhanced by ultrasonic treatment succeeded in the liberation of Cu foils from WPCBs as received. This research aims to synthesize Copper Nanoparticles (Cu-NPs) from the recovered Cu by using an advanced chemistry approach to obtain nano-product with high added value taking into consideration environmental risks. The experiments were carried out on the Cu foils recovered from the three types of WPCBs with different purity of Cu (Motherboard, Video Card, and Random Access Memory (RAM)). The synthesis process was performed in two stages: (a) preparation of Copper (II) Sulfate aqueous solutions from the recovered Cu and (b) chemical reduction of solutions for synthesis of Cu-NPs by using Native Cyclodextrins (NCDs), particularly ß-NCD as stabilizers. The efficiency of the developed approach for raw material of different purity was assessed and the final yield and the estimated recovery cost of synthesized Cu-NPs were calculated with high accuracy as well as the properties of the synthesized Cu-NPs. The obtained Cu-NPs were examined using SEM-EDS, TEM, XRD, Raman Spectroscopy, and TGA. To maximize the potential biomedical application benefits, the antibacterial activity of Cu-NPs was investigated by the standard microdilution method for E. coli, P. aeruginosa, and S. aureus bacterial cultures. The results showed that the produced Cu-NPs had an average size of 7â¯nm and yield 90%, while the preparation costs were 6 times lower in comparison to the commercial counterparts. In addition, the results indicated that the synthesized Cu-NPs from RAM sample had a good antimicrobial action.