[en] The influence of Al₂O₃ content in refining slag on the cleanliness and fatigue property of ultra-low carbon (ULC) automotive steel were investigated based on the industrial experiments. The inclusion adsorption capacity of the refining slag was calculated and the total [O] (T.O) content of ULC automotive steel was measured. The number density, size distribution and morphology of inclusions were analyzed and their effects on the cleanliness and fatigue property of ultra-low-carbon (ULC) automotive steel were investigated. The results showed that as the Al₂O₃ content in refining slag increased from 19.92% to 39.73%, the inclusion-adsorption capacity of ULC automotive steel decreased from 210.30 down to 57.12, and the fatigue life from 1.4x10⁴ down to 0.9x10⁴ cycles, while the T.O content of steel increased from 12 up to18 ppm and the inclusion number density from 4 up to 9 per mm² . (author)

[en] This work investigates the effect of eco-friendly chemical treatments on the mechanical and physical properties of composite laminates based on sisal fibres. A 2²3¹ full-factorial design is conducted to test the influence of chemical solution types, fibre treatment time, and polymer matrix type on the mechanical and morphological characterisation of the composites. Chemical treatments remove impurities from fibre surfaces, and enhance fibre-matrix adhesion. The treatments, especially with sodium carbonate (Na₂CO₃), also progressively reduce the hemicellulose fibre content. Polyester composites made with sisal fibres treated with Na₂CO₃ for 96h achieve enhanced strength and stiffness under tensile, compressive and impact loads. The results evidence the feasibility and efficiency of the proposed eco-friendly treatments for natural fibres and the application of renewable fibre laminates in secondary structural applications. (author)

[en] Our work presents a comparative study of morphological characteristics and the osteogenic potential of MC3T3-E1 cells on different modified surfaces of titanium: nanostructured TiO₂ with 20 and 100 nm nanotube diameter, and sandblasting and acid etching, commercially known as SLA. Nanostructured TiO₂ surface was prepared by anodizing of titanium plates, while SLA surface was provided by commercial supplier. Surfaces were characterized by SEM, EDS, AFM, and water contact angle measurements. In order to evaluate cell response, in vitro tests of MTT, alkaline phosphatase and staining with alizarin red were performed. From the results of in vitro tests, 100 nm nanotubular surface showed lower levels of cell mineralization, differentiation and adhesion. In general, 20 nm TiO₂ nanotubular and SLA surfaces promoted similar response from osteoblasts. As a result, 20 nm nanotubular surface proved to be a possible alternative to SLA surface with potential for use in oral implantology market. (author)

[en] The microstructure of a melt-spun Zr₂₈Ni₄₄Cu₂₈ (at. %) alloy was characterized in order to determine the structures and compositions of the crystalline phases that compete with glass formation during rapid solidification. Two crystalline phases were identified, namely, a face centered cubic (FCC) zirconium oxide phase and a primitive cubic version of the big-cube oxide phase, using a combination of scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and transmission electron microscopy techniques. Our results indicate that the Zr-O atomic pair interaction is preferential compared to the other atomic pair possibilities, supporting the formation of Zr-based oxides over the equilibrium phases in the ternary Zr-Ni-Cu system. Further, the results provide insight into the mechanisms of oxygen-induced crystallization in Zr-based BMGs and the corresponding decrease in glass forming ability (GFA) with increasing oxygen concentrations. (author)

[en] Poly(methyl methacrylate) (PMMA) is a polymer with applications in the medical and aerospace industries that require resistance to gamma radiation. However, the effects caused by gamma radiation on PMMA properties may make its application in situations of exposure to gamma radiation unfeasible. In this study, the impact of commercial additives on the radiolytic stabilization of PMMA will be studied through viscosimetric assays. In a preliminary trial, additives with different mechanisms of action were tested, and the efficacy of two additives (Tinuvin 770 and Tinuvin 622) hindered amine stabilizers (HAS) types were registered. PMMA films with the additives at different concentrations were exposed to gamma radiation and studied through viscosimetric molar mass and G-value. The Tinuvin 622 at 0.3 wt% showed the best performance in the radiolytic stabilization of p PMMA films at the 20-50 kGy range. Antagonism was observed when Tinuvin 700 and Tinuvin 622 mixture was studied in different proportions. These results show the potential of commercial additives, initially produced for other purposes, in the radiolytic stabilization of PMMA. (author)

[en] The effect of heat treatment on hydrogen diffusion and trapping on the API 5CT P110 steel was investigated trough electrochemical permeation tests and microstructural analysis techniques. Samples of as-received steel were tempered at different temperatures to obtain hydrogen permeation and trapping parameters and to characterize microstructural modifications that may alter these parameters. After permeation tests on each heat-treatment condition were verified changes on hydrogen kinetic parameters. Microstructural analysis revealed changes in dislocations density and volumetric fraction of titanium carbides, responsible to alterations in diffusivity, solubility and in hydrogen trapping characteristics. As these carbides are considered irreversible hydrogen traps, are beneficial because they become the steels less susceptible to hydrogen embrittlement. Therefore, the results suggest that there is an optimal tempering temperature which can make the API 5CT P110 steel more resistant against hydrogen embrittlement, since promote the formation of a higher number of irreversible hydrogen traps. (author)

[en] The present work investigates the aquatic biodegradation of poly(3-hydroxybutyrate) (PHB)/nanoclay bionanocomposites containing PP-g-MA as compatibilizing agent. Both pristine and organically modified (Cloisite20A®) montmorillonite clay were used as fillers in different content (1 and 3 wt%). The bionanocomposites were prepared by melt intercalation in a single screw extruder. There after films (50x50x0.5mm) were prepared by compression and assessed by X-ray diffraction. Aquatic biodegradation of the films was appraised by visual inspection, optical microscopy, counting and identification of bacteria. Results proposed that the water of the Parnaíba River in the city of Teresina (Piauí, Brazil) has microorganisms (Pseudomonas putida and Pseudomonas aeruginosa) capable of degrading these bionanocomposite films, particularly the films with 3 wt% organoclay. Our data indicated the bacteria Pseudomonas aeruginosa degraded dexterously all the films. This work collaborates with the preservation of the environment and expands the use of bionanocomposites in expendable items with the development of films with properties favorable to biodegradation in aquatic environments. It is believed that PHB/clay/PP-g-MA films emerge as a promising alternative for the packaging industry. (author)

[en] This study seeks to synthesize, by the sol-gel method, an organic-inorganic hybrid coating of polyurethane, siloxane and silver nanoparticles to cover titanium prostheses, aiming to act as an anticorrosive protection barrier, inhibiting the release of metallic ions in the human body. In this context, a hybrid based on the TEOS (tetraethyl orthosilicate) alkoxide precursor was used to carry out the acid hydrolysis/condensation process. Then, silver nanoparticles were added, and the mixture was done with the incorporation of polycaprolactone diol, followed by the addition of hexamethylene diisocyanate, to form polyurethane. The hybrid coatings were applied on titanium plates, and morphological, physical-chemical and electrochemical characterizations were carried out, as well as the evaluation of bactericidal and antifungal activity, in order to evaluate the performance of the coatings and the influence of different concentrations of silver nanoparticles (10 mL, 20 mL and 40 mL). The results showed that although Hibríbrido 10 (lowest concentration of silver nanoparticles, 10 mL) presented the best morphological characteristic without cracks and with satisfactory roughness to obtain the best bacterial behavior, the Hibríbrido 20 sample presented the best electrochemical performance. (author)

[en] Usually, scraps of X22CrMoV12-1 alloy are obtained through machining of steam turbine blades and recycled through casting. However, this process is considered too costly. The viability of recycling X22CrMoV12-1 scraps with addition of vanadium carbide (VC) through powder metallurgy was analyzed in this study. Scraps of X22CrMoV12-1 alloy with VC were milled in a planetary ball mill during 10, 30 and 60 hours. The granulometry of the powder was determined through laser granulometry. The evolution in particles morphology and amorphization was conducted using scanning electron microscope (SEM) and x-ray diffraction (DRX) techniques. Stress-strain curves were obtained through compressive strength test. The results indicated that the best milling condition found was 60 hours. Also, the X22CrMoV12-1 alloy with VC addition produced by powder metallurgy showed good mechanical strength. Thus, this route was considered promising to reshape this material with smaller energy involved in the process. (author)

[en] High chromium cast irons (HCCIs) are widely applied in the mining industry as components of equipment for iron ore transportation, in which their surfaces are subjected to abrasive and erosive wear. The present work evaluated the erosion-abrasion behavior of a HCCI possessing different amounts of austenite and martensite, using a laboratory impeller-tumbler wear test apparatus and iron ore pellets as abrasive material. The results showed that the wear dominant mechanism on the worn surface of the as-cast material depends upon the material microstructure. For HCCI destabilized at 930 and 990 °C, the matrix has high martensite/austenite ratio and finely dispersed secondary carbides, offering high abrasion-erosion wear resistance. The absence of fractured eutectic carbides indicates that such matrix has hardness and load bearing capacity, enough for mitigating a significant plastic deformation during the impact pellets. For HCCI destabilized at 1050 °C, the matrix has a low martensite/austenite ratio and coalesced secondary carbides, leading to high wear rates during erosion-abrasion tests. (author)