Comparison of Cu−Al−Ni−Mn−Zr shape memory alloy prepared by selective laser melting and conventional powder metallurgy

This work aimed to investigate and critically analyze the differences in microstructural features and thermal stability of Cu−11.3Al−3.2Ni−3.0Mn−0.5Zr shape memory alloy processed by selective laser melting(SLM)and conventional powder metallurgy.PM specimens were produced by sintering 106−180μm pre-alloyed powders under an argon atmosphere at 1060°C without secondary operations.SLM specimens were consolidated through melting 32−106μm pre-alloyed powders on a Cu−10Sn substrate.Mechanical properties were measured through Vickers hardness testing.Differential scanning calorimetry was conducted to assess the martensitic transformation temperatures.X-ray diffraction patterns were collected to identify the metallurgical phases.Optical and scanning electron microscopy was used to analyze the microstructural features.b′1 martensite was found,irrespective of the processing route,although coarser martensitic variants were present in PM-specimens.In conventional powder metallurgy samples,intergranular eutectoid constituents and stabilized austenite also formed at room temperature.PM-specimens showed similar average hardness values to the SLM-specimens,albeit with high standard deviation linked to the porosity.The specimens processed by SLM showed reversible martensitic transformation(T0=171°C).PM-processed specimens did not show shape memory effects.

Utilization of Pineapple Crown Fiber and Recycled Polypropylene for Production of Sustainable Composites

Nowadays,the production of consumer goods is based on the use of non-renewable raw materials,which in recent years has been performing as a problem for the environment.Considering the large number of available biofibers in nature,their use in the development of polymeric composites has inevitably emerged,it is also necessary to take into account the countless discarded plastics that still have the potential to be reused.In this work,fibers were extracted from pineapple crown residues and utilized to compose sustainable composites using recycled polypropylene from cups discarded in the trash as a matrix.However,it is known that for good performance,it is necessary to achieve a good chemical interaction between the fiber and the matrix.In order to improve this interaction,alkaline mercerization treatment was carried out on the surface of the fibers removing some components incompatible with the polymer.In this work,the effect of the mercerization treatment on the properties of the fibers was studied,as well as their interaction with the matrix.The effect of fiber concentration on the mechanical and thermal properties of composites was also evaluated.Levels of 5 and 7 wt%were used for both natural and mercerized fibers.A decrease in the number of degradation stages was observed through thermogravimetry analyses(from four in natural fiber to two in mercerized fibers),showing that the mercerization performed on the fibers was effective.An increase in the degree of crystallinity of mercerized fibers was also observed through the results of X-ray diffraction.Both techniques indicate that amorphous compounds,such as hemicellulose and lignin,were partially removed.Through the tensile test,it could be noted that all composites presented higher values of de elastic modulus than recycled polypropylene without added load;however,there were no differences in the elastic modulus between the different types of fibers and load levels.Therefore,it is interesting to use fibers as reinforcing agents in polymers;however,the treatment did not increase the mechanical properties of the composites.In parallel,other factors,such as the dispersion of the components,must be taken into account to justify this result.

Chemical Composition,Antioxidant and Antimicrobial Activity of the Oil and Plant Extract Myrocarpus frondosus Allemao

The objective of this study was to evaluate the chemical profile of extracts (aqueous and ethanol) and the essential oil of Myrocarpus frondosus Allem?o, the sensitivity of strains of Escherichia coli, Staphylococcus aureus, Salmonella typhimurium and Listéria monocytogenes, front the extracts and essential oil, by means of the microdilution method in broth, the antioxidant activity by the ABTS method, and the content of phenolic compounds present in the extracts and oil. For the preparation of extracts from plant leaves used with ethanol and water, then separated, the chemical identification of compounds was performed by high-performance liquid chromatography (CLAE-DAD) and gas chromatography coupled to mass spectrum (CG/MS). With the chemical analysis of the extracts obtained the presence of the major compound rutin, and oil major compound was found germacrene B. In the microdilution method in broth, oil and extracts showed inhibition against all the bacteria tested in the concentrations 1 mg/ml to 0.25 mg/ml, except for Staphylococcus aureus at a concentration of 0.25 mg/ml of the essential oil and trans-caryophyllene. The results of Minimum Bactericidal Concentration showed that the essential oil had bactericidal activity at a concentration of 1mg/ml for all bacteria tested and trans-caryophyllene at the same concentration only for Listeria monocytogenes. In relation to the essential oil, antioxidant activity showed higher radical reduction capacity of 40.92% and the content of phenolic compounds ethanol extract showed more 12.72%. The in vitro results support the conclusion that the essential oil is very promising both in antimicrobial action as antioxidant activity and the leaf extracts on antioxidant activity.