No abstract

A full-factorial 33 experiment was used in this study to determine the optimal values of the tensile properties of three composite materials manufactured based on three polymeric resins: Derakane Momentum epoxy vinyl ester based on bisphenol-A (DM-411), polyester based on terephthalic acid (P115-A), and isophthalic polyester (P2000). Such materials were reinforced with magnetite powders at concentrations of 10, 20, and 30 wt %, and the particle sizes were classified with three sieves: #200 (46–75 μm), #325 (26–45 μm), and #500 (0–25 μm). The compounds were manufactured using the hand lay-up method at room temperature in accordance with ASTM D638-14 for M1-type specimens. A tensile test was conducted on a universal Microtest EM2/300/FR machine at a test speed of 5 ± 25 % mm/min using an Epsilon extensometer calibrated in accordance with the ASTM E83 standard at 20 ± 2 °C. The magnetite powders and compound morphology were studied by Scanning Electron Microscopy. The mechanical properties of the compounds and the optimal response found by Analysis of Variance (ANOVA) and Response Surface Methodology (RSM) are also reported. The best response to the mechanical stimuli occurs with the composite material prepared with the epoxy vinyl ester resin DM-411, a concentration of 29.4 % of magnetite (Fe3O4), a particle size of 58.5 microns, and a 200 sieve.

RESUMEN:Este trabajo presenta los resultados de la evaluación de propiedades de pastas de cemento comercial (CPC), mezcladas con ceniza volante (FA) y escoria de alto horno (GBFS). Inicialmente un total de 30 combinaciones fueron evaluadas en términos de resistencia a la compresión para establecer las proporciones óptimas de las materias primas. Después de esto, cuatro mezclas optimizadas fueron caracterizadas durante el proceso de fraguado y endurecimiento. Se realizaron ensayos electroquímicos en cilindros de concreto elaborados con los cementantes y con una varilla de acero de construcción embebida en su interior. Con el objetivo de evaluar el comportamiento frente a la corrosión se estudiaron aspectos termodinámicos y cinéticos. Los resultados mostraron que cementos comerciales mezclados con ceniza volante y escoria de alto horno, como los usados en esta investigación, presentan menor resistencia mecánica y a la corrosión que un cemento comercial. ABSTRACT: Effect of incorporation of fly ash and granulated blast furnace in the electrochemical behavior of concretes of commercial cement.This paper presents the findings of the research properties evaluation pastes of commercial cement (CPC), mixed with fly ash (FA) and granulated blast furnace slag (GBFS). Initially, the sample of 30 combinations were evaluated in terms of compressive strength to establish the optimal proportions from raw material. After that, four optimized blends were characterized during the setting and hardening process. Electrochemical tests were performed on concrete cylinders samples prepared with cementitious materials and a structural steel rod placed in the center of the specimen. With the objective to evaluate the performance before corrosion, thermodynamic and kinetic aspects were taken into consideration. The findings showed that commercial cements blended with fly ash and blast furnace slag as the ones used in this research presents a decreased behavior in mechanical and corrosion strength regarding to CPC.

Elastomers are natural or synthetic polymers used in the automotive, mining, mold, assembly and other industries, due to their mechanical resistance in a wide temperature range from 60 °C to 320 °C; however, the waste generated is not disposed of properly, especially in the manufacture of tires, which generates environmental problems like inadequate final disposal, generation of toxic gases and public health problems; Therefore, in order to recycle these wastes, the present investigation modified elastomers superficially in order to produce strong adhesion with inorganic compounds like cement, through oxidation and sulfonation processes. For this purpose, NaOH and KMnO4 solutions were prepared at a concentration of 5% and then impregnated in saturated NaHSO3 solution. Subsequently, the modified elastomer was morphologically characterized by scanning electron microscope, thermogravimetrically by differential scanning calorimeter; compositionally by infrared spectroscopy, Raman spectroscopy, X-ray fluorescence, energy dispersive X-ray analysis and hydrophobic tests using contact angle techniques, in order to establish morphological and chemical compatibility with inorganic compounds. Results evidenced inclusion of functional groups OH, C = O and SO3, the reduction of carbon present in weak bonds and the presence of inorganic components such as potassium, sodium, manganese and sulfur were evident. The scanning electron microscope shows an increase in the roughness and contact surface of the elastomer as a function of the inclusion of polar functional groups by surface chemical treatment. These characteristics are to generate greater inclusion and compatibility of elastomers of an organic nature in inorganic compounds like cement matrices.

RESUMEN:En este estudio se muestra un análisis del comportamiento del coeficiente de desgaste en seco de compuestos de matriz metálica (MMC), base acero inoxidable 316 reforzado con partículas de carburo de titanio (TiC) de acuerdo con la norma ASTM G 99-05 en un tribómetro para la realización de ensayos de desgaste mediante el contacto y rozamiento de dos materiales entre sí, uno en forma de disco y otro en forma de varilla o bola (pin-on-disk). En el estudio se evalúa el efecto que tiene el porcentaje de refuerzo en los MMC fabricados con 3, 6 y 9% (vol.) de TiC, en muestras compactadas a 800 MPa, dando lugar a diferentes valores de tamaño de grano, dureza y densidad, los cuales son sinterizados por medio de descarga luminiscente anormal, a una temperatura de 1200 °C ±5 °C, con atmósfera de protección de H 2 -N 2 y tiempo de permanencia de 30 minutos. De acuerdo a los resultados obtenidos se concluye que la mejor condición de fabricación de los MMC, se consigue cuando la mezcla contiene 6% de TiC, alcanzando el menor tamaño de grano, la mayor dureza y el más bajo coeficiente de fricción. En este sentido, se observó que la incorporación de partículas de cerámica (TiC) en matriz de acero austenítico (316) presentan mejoras significativas en la resistencia al desgaste. ABSTRACT: Effect of the percentage of reinforcement on the wear in the metal matrix composites sintered with abnormal glow discharge.In this study an analysis of the behavior of dry wear coefficient of a Metal Matrix Composite (MMC) in 316 stainless steel reinforced with particles of titanium carbide (TiC) according to ASTM G 99 standards, in a pin-on-disk test. In this research it is tested the effect of the percentage of reinforcement in the MMC manufactured with 3, 6 y 9% (vol.) of TiC, in samples compacted at 800 MPa, generating different values of grain size, hardness and density, they are sintered with abnormal glow discharge, at a temperature of 1200 °C ±5 °C, with a protection atmosphere H 2 -N 2 and a permanence time of 30 minutes. According to the results obtained it is concluded that the best condition for the MMC manufacturing, in relation to the reinforcement percentage, is the one obtained when the mixture contains 6% of TiC compacted at 800 MPa. In these conditions, it was obtained: achieving smaller grain size, the greater hardness and the lowest coefficient of friction. In this respect, it was observed that the incorporation of the ceramic particles (TiC) in a matrix of austenitic steel (316) shows significant improvements in the resistance to the wear.