Abstract AISI D6 tool steel and AISI 304 stainless steel are among the most widely used material in the industry. However, this application field can still be expanded through the coatings deposition. In this regard, the objective of this work was to evaluate the impact of coatings application by cathodic cage technique using Hastelloy’s cathodic cage, on corrosion resistance of these steels. Two treatment temperatures were compared. The samples were characterized by Optical Microscopy, Scanning Electron Microscopy, Energy Dispersive Spectroscopy, X-Ray Diffraction with the application of the Rietveld routine and corrosion test. The results showed the formation of multiphase layers that contributed to corrosion potentials reduction for treatments at 400 °C, being more effective when applied on AISI D6. It was observed that the corrosion resistance is influenced by the temperature, which was attributed to the precipitation of chromium nitride and iron oxide at 450 ºC.
Abstract The world is moving at a fast pace in the consumption of non-renewable natural resources, causing several ecological problems. The search for the cost reduction by implementing renewable energies implies in the optimization of the manufacturing processes parameters of consolidated technologies, such as solar thermal energy collectors. One of the applications of selective surfaces is to improve performance of solar absorbers. The purpose of this work is to produce selective coatings with high absorption in range of UV/Vis and low emittance in the IR range. It was prepared a selective surface composed of ilmenite deposited on substrates of AISI 304 stainless steel using technique of cathodic cage plasma nitriding/deposition for application in solar thermal absorbers. Ilmenite was initially characterized by X-Ray Diffractometry (XRD), X-Ray Fluorescence (FRX) and Thermal Analysis (TGA). The coatings produced were optically characterized in range UV/Vis/IR and emittance and data on the roughness parameters of the films were obtained by Optical Profilometry. Selective surfaces with high solar absorbance (87%) compared with state-of-the-art commercial ones (70-80%) and low thermal emission (14%) compared with state-of-the-art commercial ones (20-30%) were obtained by validating the potential of ilmenite to produce selective surfaces for thermal solar collectors.
Mesonephric hyperplasia (MH) is a very rare condition. There are few cases in the literature. Mesonephric remnants (MR) or MH can be a rare source of abnormal Papanicolaou smears. The most common, often difficult, in the differential diagnosis of MH is mesonephric carcinoma that has a poor prognosis. We report a case of a 29-years-old with a routine Papanicolaou smear reported as atypical glandular cells. The patient underwent to a loop electrosurgical excision procedure and because it is a benign condition and a strong desire to preserve fertility, we opted for clinical surveillance.
ABSTRACT Objective To correlate magnetic resonance imaging (MRI) findings with the microbiological and anatomopathological diagnosis of spinal infection. Methods A retrospective, cohort review of online medical records (laboratory, anatomopathology and diagnostic imaging sector) of patients diagnosed with spondylodiscitis, who underwent a full spine MR scan between January 2014 and July 2018 at the Department of Orthopedics and Traumatology of the Universidade Federal de São Paulo. Results Staphylococcus aureus was the most commonly found etiological agent (57%). Blood culture was positive in 76% of cases and 82% of the patients who underwent biopsy had a spondylodiscitis diagnosis. Pain was the most prevalent clinical symptom and the lumbosacral spine was the most frequent site of infection. T1 hyposignal, T2/STIR hypersignal, and terminal plate destruction were verified in almost all MR scans. Conclusions No direct correlation was found between MR findings and any specific etiological agent. Blood culture and biopsy are important diagnostic tools that should be used for accurate diagnosis of the infectious agent . Level of evidence IV; Diagnostic Study.
RESUMEN Objetivo Correlacionar los hallazgos de resonancia magnética (RNM) con el diagnóstico microbiológico y anatomopatológico de infección de la columna vertebral. Métodos Un estudio de cohorte retrospectivo de revisión de prontuarios en línea (laboratorio, anatomopatológico y sector de diagnóstico por imagen) de pacientes con diagnóstico de espondilodiscitis, sometidos al examen de RNM de la columna vertebral y acompañados por el Departamento de Ortopedia y Traumatología de la Universidad Federal de São Paulo, entre enero de 2014 y julio de 2018. Resultados El agente etiológico más común encontrado fue el S. aureus (57%). El hemocultivo se mostró positivo en 76% de los casos y 82% de los pacientes sometidos a biopsia presentaron diagnóstico de espondilodiscitis. El dolor fue el hallazgo clínico más prevalente y la columna lumbosacra fue el sitio más frecuente de infección. En el examen de RNM, la presencia de hiposeñal en T1, hiperseñal en T2/STIR y destrucción de las placas terminales fueron identificadas en casi todos los casos. Conclusiones No hubo correlación directa de los hallazgos de la RNM con un agente etiológico específico en la espondilodiscitis. El hemocultivo y la biopsia son herramientas diagnósticas importantes, que deben ser utilizadas para el diagnóstico preciso del agente infeccioso. Nivel de evidencia IV; Estudio Diagnóstico.
RESUMO Objetivo Correlacionar os achados de ressonância magnética (RNM) com o diagnóstico microbiológico e anatomopatológico de infecção na coluna vertebral. Métodos Estudo de coorte retrospectivo de revisão de prontuários online (laboratório, anatomopatológico e setor de diagnóstico por imagem) de pacientes com diagnóstico de espondilodiscite, submetidos ao exame de RNM da coluna vertebral e acompanhados pelo Departamento de Ortopedia e Traumatologia da Universidade Federal de São Paulo, entre janeiro de 2014 e julho de 2018. Resultados O agente etiológico mais comum encontrado foi o S. aureus (57%). A hemocultura mostrou-se positiva em 76% dos casos e 82% dos pacientes submetidos à biópsia apresentaram diagnóstico de espondilodiscite. A dor foi o achado clínico mais prevalente e a coluna lombossacra foi o sítio mais frequente de infecção. No exame de RNM, a presença de hipossinal em T1, hipersinal em T2/STIR e destruição das placas terminais foram identificados em quase todos os casos. Conclusões Não houve correlação direta dos achados na RNM com um agente etiológico específico na espondilodiscite. A hemocultura e a biópsia são ferramentas diagnósticas importantes que devem ser utilizadas para o diagnóstico preciso do agente infeccioso. Nível de evidência IV; Estudo diagnóstico.
Abstract Vegetable fibers are widely used as reinforcement in the production of composites. In this work, the photodegradative potential of polymer composites containing babassu fiber was characterized and evaluated. The fibers were extracted manually and immersed in a 10% NaOH solution (Mercerization). After drying, they were crushed and incorporated into the low-density polyethylene matrix in proportions of 5%, 10%, and 20% of the total mass of the composite. The composites were subjected to Scanning Electron Microscopy analysis (showed the incorporation of fibers into the polymeric matrix), Infrared Spectroscopy (the presence of fiber was observed with peaks at 3200-3600 cm-1, and 1596 cm-1-1036 cm-1), Mechanical Tests (with 20% fiber, there is a 44% decrease in tension, 48% in strain and 12% in Young's modulus) and Thermogravimetric Analysis (inicial fiber degradation starts between 220-337 °C, and matrix degradation between 333-550 °C). The composites were subjected to degradation processes by solar radiation and under artificial UV-B. Samples of oxy-biodegradable plastic bags were also degraded under the same degradation conditions of the composites. These results show that the materials used in the research, besides presenting an excellent degree of compatibilization, also reveal an improvement in the photodegradation potential of composites.
Abstract TiO2 immobilized in Sepiolite (TiO2/Sep) was successfully prepared by the sol-gel technique, with titanium isopropoxide as the precursor for the formation of TiO2 in the anatase phase calcined at 400 °C. The prepared samples were characterized by X-ray diffraction, Fourier Transform Infrared spectroscopy, Scanning Electron Microscopy coupled to energy dispersive spectroscopy, and thermogravimetric analysis. The results showed that TiO2/Sep structure was identified in all characterizations, showing the specific peaks, bands, mass loss, and morphology after the impregnation process. Photocatalytic experiments were performed under UV irradiation with various photocatalyst concentrations and pH effects in the reaction. The prepared samples presented 72% photocatalytic efficiency for eosin (EA) dye discoloration after 150 min under UV light. This efficiency was attributed to the radicals generated from the TiO2 and the high specific surface area, showing that TiO2/Sep is promising candidate in the degradation of organic pollutants.
In the present work, the microstructure, electrochemical behavior and localized corrosion of the AA2198-T851 Al-Cu-Li alloy were studied. The microstructure was correlated with corrosion results obtained by immersion, gel visualization and scanning electrochemical microscopy (SECM) tests. Immersion and gel visualization tests showed high kinetics of corrosion attack during the first hours of immersion. SECM analyzes by means of surface generation/tip collection (SG/TC) mode detected hydrogen evolution generated during spontaneous corrosion from severe localized corrosion (SLC) sites on the metal surface. SECM results revealed sites of intense hydrogen evolution after 2 h of immersion and increased amounts of corrosion products after 4 h of immersion. Hydrogen evolution sites detected by SECM were associated with severe localized corrosion (SLC).
A study of the electrical transport properties of calcium aluminate (CA) with coexisting C3A and C12A7 phases was carried out. In this work, powders resulting from synthesis based on the polymer precursor method. The resulting product was characterized by means of XRD, Raman, and UV-visible analysis to obtain the optical BG and by EIS. From the XRD and Raman analyses, the presence and coexistence of the two self-modified phases were confirmed. In this biphasic composition, celite phase was estimated to be the major phase. An optical BG of 5.69 eV at room temperature was calculated, and under the condition of a reducing atmosphere in the temperature range of 750-950 ºC, an activation energy for conduction of 2.98 eV was determined by EIS measurements. Further, in this biphasic sample, the electronic conduction transport might be governed by the mayenite minor phase due to its large defect nature and concentration compared to celite. In oxidizing conditions, the activation energy for electrical conduction was 1.42 eV, which is somewhat higher than that observed by other authors in mayenite single phase; this result was explained by taking into account the coexistence of biphasic material and an actual chemical defect scenario in SMCM is discussed.
An experimental study with an A356-AlSiMgFe alloy was developed to evaluate the microhardness performance in the microstructure resulting of an unsteady-state horizontal solidification process. The Al-7wt%Si-0.3wt%Mg-0.15wt%Fe alloy was elaborated and directionally solidified in a water-cooled horizontal solidification device. In order to experimentally determine the cooling and growth rates (VL and TR, respectively), a thermal analysis was also conducted during solidification. Microstructural characterization by optical microscopy, SEM/EDS elemental mapping and microanalysis of the punctual EDS compositions allowed to observe the presence of an Al-rich dendritic phase (Al(α)) with interdendritic phases second composed of an eutectic mixture: Al(α-eutectic) + Si + Al8Mg3FeSi6(π) + Mg2Si(θ). Furthermore, the dendritic microstructure was characterized by measuring the secondary dendritic spacings (λ2) along the horizontally solidified ingot. Higher HV values were observed within the eutectic mixture.
The properties of ceramic materials and microstructural changes are dependent on the raw materials from which they are made and on the manner in which they are processed, from the composition to the established thermal treatment, heating rate, and firing temperature. In this study, the influence of some processing parameters (formulation, maturation time, and firing temperature) on the physical-mechanical properties and microstructural aspects of ceramic pieces produced from natural aluminosilicates was investigated. Because Brazil does not have many quality ball clays reserves, bentonite was included as a plasticizing agent in this study. The formulations were submitted to maturation for a period of one to four weeks and their characteristics were determined to evaluate plasticity. Following this, the specimens were extruded and subjected to heat at temperatures of 1200, 1300, and 1400ºC. The physical-mechanical properties determined were: water absorption, linear retraction, and flexural strength. Statistical analysis was applied. The results showed that, for the analyzed masses, neither the maturation time nor the physical and mechanical properties analyzed had influence on plasticity. The firing temperature was the factor that generated the greatest alteration in results, increasing the mechanical resistance and altering the size and interlocking of the mullite needles.
Studies on gypsum modified by polymers have been conducted to assess the potential of improvement in the mechanical performance, water resistance and increasing the setting time, facilitating its handling. Gypsum-based compounds made with different additions of redispersible polymers were studied, such as: ethylene-vinyl acetate (EVA), vinyl acetate terpolymer, vinyl laurate and vinyl chloride (VA/VL/VC), and vinyl acetate and vinyl versatate (VA/VeoVA). The influence on setting time, microstructural formation and on the bending performance was assessed, as well as and compression of the hardened gypsum. The composites were prepared using a polymer concentration of 5% and 10%, and water/gypsum ratio of 0.6. The addition of the polymer decreased the structural robustness and change in the microstructure. We concluded that the reduction in the amount of water through additives may allow a more complete and robust training of gypsum crystals and compounds with better mechanical performance.
Low surface energy and poor adhesion are well-known characteristics of polypropylene (PP). Surface treatments such as plasma, corona, and laser are usually applied to overcome these limitations. However, current studies highlight the incorporation of hydrophilic or amphiphilic polymers into hydrophobic low-surface-energy polymers as an alternative for increasing surface energy and thus improving adhesion. Lignin could be a promising amphiphilic polymer for use in increasing surface energy. In this work, PP/kraft lignin composites were obtained by incorporating up to 5 wt% of kraft lignin (KL) into a PP matrix. Corona treatment was applied to pristine PP and composites surfaces. Contact angle measurements and peeling tests were carried out to investigate the effects of KL incorporation and corona treatment on the surface energy and the mechanical strength of adhesion. Differential scanning calorimetry (DSC) was used to evaluate the PP’s crystallinity index and recrystallization temperature and to dismiss their effects on the surface energy changes. Scanning electron microscopy (SEM) was applied to investigate the lignin dispersion. The results show that KL incorporation has potential as a method to improve the surface energy of PP, improve its poor adhesion, and enhance the effects of corona treatment.
Development of new ceramic membranes has recently grown due to its superior thermal and mechanical stability. An interesting approach to manufacture asymmetric membranes is the production of aligned pore structure by the freeze-casting method. The lack of studies involving membrane production with tubular freeze-cast substrates warrants more research. In this study, a novel tubular freeze-cast alumina substrate was used for deposition of a silica top layer. The substrate showed radially aligned pores, indicating precise structure control. The obtained pore structure shows high potential for membrane manufacture. The silica layer was produced by the sol-gel method and dip-coated on the substrates with two different withdrawal speeds. The microporous silica showed pores smaller than 2 nm. The highest withdrawal speed resulted in broader substrate coverage. However, a uniform silica layer was only obtained after a second deposition. These results confirm the viability to use tubular freeze-cast substrates for production of nanofiltration membranes.
The mechanical behavior of the API 5L X80 steel exposed to the produced water by the petroleum industry, besides being dependent on the intrinsic properties of the steel, is influenced by the corrosivity characteristics of the electrolyte that may be associated with the presence of microorganisms. The objective of this work was to investigate the plastic deformation of API 5L X80 steel exposed to produced water. The tests were conducted in static systems (abiotic and biotic) containing produced water after 360 days. The process of corrosion of the coupons were evaluated by topographic 3D analysis and roughness, and the mechanical behavior by tensile test and fracture analysis by scanning electron microscopy. Surface topography and roughness were modified by the interaction of the consortium of microorganisms with the substrate associated with the corrosion process. The results indicate that microorganisms induced the formation of pits which caused the coupons to lose plasticity.
Titanium is used in orthopedic and orthodontic implants because it has good corrosion resistance and excellent biocompatibility. Thus, studies seek to obtain a coating to improve the adhesion between the bone and the implant, by modifying the metal’s surface. The objective of this work was to biomimetically coat C.P. Ti with hydroxyapatite doped with silver nitrate, a component with antimicrobial properties, coating the metallic-ceramic composite with a polycaprolactone polymer film, which is known by generate improved implant-tissue interaction, and reducing postoperative complications from bacterial infections. The characterization of the material demonstrated the existence of the coating overall surface of the metallic substrate. The results obtained from the bacterial culture tests with Staphylococcus aureus showed that nitrate was effective in reducing the amount of live bacteria present in the supernatant, as well as those adhered to the surface of the material. In addition, the polymeric coating did not prevent the release of the bactericidal agent, not interfering in the effect there.