20 research outputs found
Creep en cemento Portland y en Concreto: una revisi贸n
Spa: Este trabajo presenta una revisi贸n del estado del arte sobre el creep en cemento y concreto tipo Portland. Incluye una descripci贸n de las teor铆as sobre los mecanismos de los diferentes tipos de creep a baja temperatura, de la fenomenolog铆a asociada y de los aspectos t茅cnicos que se deben tener en cuenta para realizar las pruebas de creep de acuerdos a las normas ASTM vigentes y de la metodolog铆a usual de establecer las relaciones convenientes de modelos experimental para creep
Nd:YAG laser enameling on glazed tiles coated with cobalt varnishes with and without borax frit
Las industrias de materiales cer谩micos y arquitect贸nicos emplean diferentes t茅cnicas de marcado con dos aplicaciones cl谩sicas, para identificaci贸n y decoraci贸n de piezas elaboradas. La utilizaci贸n de t茅cnicas l谩ser para estos prop贸sitos se viene implementando de forma creciente, debido a las ventajas que presenta respecto al horneado convencional: la concentraci贸n del calor s贸lo en la zona irradiada, lo que conlleva un menor consumo de energ铆a sin afectar significativamente el resto de la pieza; se obtienen patrones gr谩ficos de alta resoluci贸n espacial; permite introducir cambios durante el proceso sin requerir largas paradas, y la generaci贸n de residuos es m铆nima o casi nula. En este estudio se presentan los resultados obtenidos en el vidriado con l谩ser Nd:YAG (l=1064 nm) sobre las superficies esmaltadas de azulejos, las cuales fueron previamente recubiertas con pigmento cer谩mico negro de cobalto y un barniz constituido por este mismo pigmento y frita bor谩cica. Con el l谩ser operando en modo continuo (CW), se marcaron una serie de l铆neas, cuyo ancho y profundidad evidenciaron una dependencia directa, con la variaci贸n de la potencia y velocidad de desplazamiento del haz l谩ser sobre la superficie del azulejo. Finalmente estas l铆neas vidriadas fueron analizadas por microscop铆a 贸ptica, espectroscopia de dispersi贸n de energ铆a (EDS) y difracci贸n de rayos X.Ceramic and architectonic materials industries employ different marking techniques with two classical applications, identification and decoration of manufactured objects. Laser techniques using for these proposes are been implemented in growing way, due to theirs advantages with regard to the conventional baking such as: heat is concentrated only on the radiated zone which involves a smaller energy consumption without affecting significantly the rest of the piece; graphic patterns with of highly spatial resolution are obtained; it permits to introduce changes during the process no requiring long stops and low or almost none generation of residues. In this study the results obtained from Nd:YAG (l=1064 nm) laser glazing on the enameled surfaces of glazed tiles, which were previously covered with cobalt black pigment and an enamel constituted with this same pigment and borax frit, are presented. With the laser operating in continuous wave (CW), a series of lines were marked, whose width and depth showed a direct dependence with the variation in the power and scan speed of the laser beam on the glazed tile surface. Finally, these glazed lines were characterized by optical microscopy, energy dispersi贸n spectroscopy (EDS), and X- ray diffraction (XRD)
Efeito do conte煤do de carbono sobre a resist锚ncia ao desgaste abrasivo de recobrimentos de CrC depositados por pulveriza莽茫o cat贸dica magnetr茫o
Los recubrimientos de carburo de cromo sobre acero son un buen candidato para aplicaciones de conformado y moldes de inyecci贸n. La alta resistencia mec谩nica, resistencia qu铆mica y estabilidad a alta temperatura de la fase Cr3C2 pueden ser compatibles con el intenso desgaste abrasivo y la corrosi贸n en tales operaciones de fabricaci贸n. En este trabajo se depositaron recubrimientos de CrC por pulverizaci贸n cat贸dica magnetr贸n RF, los cuales mostraron contenidos de carbono entre el 25 % y el 58 % por an谩lisis EDS. Los valores de dureza de estos recubrimientos fueron entre 15 y 24 GPa; los m谩s duros de las muestras tuvieron contenido de carbono en el rango de 39-53 %. El desgaste abrasivo de los recubrimientos se evalu贸 utilizando un equipo de disco abrasivo con polvo de diamante. El volumen de las huellas de abrasi贸n se midi贸 con las im谩genes obtenidas en el microscopio interferom茅trico y adem谩s se corrobor贸 con el c谩lculo del volumen geom茅trico basado en secciones medidas con el perfil贸metro. El comportamiento al desgaste abrasivo mostr贸 una marcada dependencia con el contenido de carbono. El desgaste abrasivo m谩s bajo se obtuvo para los recubrimientos con el m谩s alto contenido de carbono.Chromium carbide coatings on steel are a good candidate for applications on forming and molding dies. The high mechanical strength, chemical resistance and high temperature stability of Cr3C2 phase can be compatible with the severe abrasive wear and corrosion found in those manufacture operations. In this work chromium carbide coatings deposited by means of RF magnetron sputtering showed carbon contents between 25 % and 58 % by EDS analysis. Hardness values of these coatings were between 15 and 24 GPa, being the hardest values in the samples with carbon content in the 39-53 % range. The abrasive wear behavior of the coatings was evaluated by using a dimple grinder with diamond powder. The volume of the abrasion craters was measured from the images obtained with the interferometric microscope, and further corroborated by geometrical volume calculation based in profilometer sections that were measured. Abrasive wear behavior showed a marked dependence with carbon content. The lowest abrasive wear was obtained for the coatings with the highest carbon content
Efectos adversos de la exposici贸n prenatal al material particulado del aire sobre el feto y el reci茅n nacido
El material particulado (PM) es un grupo de elementos s贸lidos y l铆quidos producidos por diferentes actividades antropog茅nicas y naturales, que son emitidos directamente al aire. Tiene diferentes propiedades fisicoqu铆micas y termodin谩micas y seg煤n su di谩metro aerodin谩mico se puede clasificar en PM10 (<10 渭m), PM2.5 (<2.5 渭m) y PM0.1 (<0.1 渭m);pueden inhalarse y llegar desde los pulmones a otros 贸rganos, causando enfermedades respiratorias, cardiovasculares y neurol贸gicas, entre otras. Considerando que el feto es susceptible a contaminantes atmosf茅ricos a trav茅s de la exposici贸n gestacional y que las perturbaciones en la vida temprana son cruciales para el desarrollo, elPM puede causar complicaciones,incluyendo parto prematuro, bajo peso al nacer y da帽os neuropsicol贸gicos, entre otras. Esta revisi贸n resume evidencia epidemiol贸gica que demuestra la relaci贸n entre la exposici贸n materna a PMy los resultados adversos en el desarrollo del feto, el nacimiento y la infancia, as铆 como algunos mecanismos moleculares que podr铆an explicar estas asociaciones.Particulate matter (PM) is a group of solid and liquid elements produced by different anthropogenic and natural activities, which are emitted directly into the air. It has different physicochemical and thermodynamic properties and according to its aerodynamic diameter, it can be classified asPM10
(<10 渭m), PM2.5 (<2.5 渭m) and PM0.1 (<0.1 渭m). It can be inhaled and reach other organs from the lungs, causing respiratory, cardiovascular and neurological diseases, among others. Considering that the foetus is susceptible to air pollutants such as PM through gestational exposure and that early life disturbances are crucial for development, PM can cause various disorders or complications, including premature birth, low birth weight and neuropsychological damage, among others. This review summarizes the epidemiological evidence that demonstrates the relationship between maternal exposure to PM and adverse outcomes in foetal development, birth, and childhood, as well as some molecular mechanisms that could explain these associations.https://orcid.org/ 0000-0003-3433-7288diana.gomezga@[email protected]@campusucc.edu.c
Comportamento mec芒nico e de pega de morteiros de cimento Portland cinzento tipo III com aditivos
En el presente trabajo se estudi贸 la variabilidad en el desempe帽o de morteros con el empleo de diferentes lotes de dos tipos de aditivos, uno retardante y uno acelerante de fraguado, para tal fin, se compar贸 su comportamiento con un mortero sin aditivo. Se analizaron las propiedades f铆sicas, qu铆micas y mec谩nicas del cemento P贸rtland gris tipo III procedente de Cementos Rioclaro, se midieron los tiempos de fraguado inicial y final utilizando diferentes dosis de aditivos, adem谩s, se realizaron medidas de resistencia a la compresi贸n de los morteros con aditivo retardante. Se encontr贸 poca variabilidad entre los lotes de los aditivos estudiados; con el aditivo retardante usado se encontr贸 que cuanto mayor es el tiempo de fraguado inicial, mayor es el tiempo de fraguado final. Utilizando el aditivo en dosis hasta de 0,6 % en peso del cemento, aument贸 el tiempo de retardo a valores entre 550 y 600 min con el aumento del contenido de aditivo. De forma similar, con el aumento en el contenido del aditivo retardante, baj贸 la resistencia inicial y aument贸 la resistencia final del mortero. Con dosis crecientes de aditivo acelerante disminuy贸 el tiempo de fraguado de las mezclas estudiadas.In the present work the variability in the performance of mortars by using different batches of two types of additives, one retardant and one accelerant of setting was studied, for this purpose, their behavior was compared with a mortar without additive. The physical, mechanical, and chemical properties of the gray Portland cement type III from Cementos Rioclaro, the initial and final setting times using different doses of additive were measured; besides, compression strength tests of mortars with retardant additive were made. Between the additives batches studied a small variability was found; the retardant additive used with a content of 0,6 wt % of cement showed that as the higher initial setting time, final setting time is higher. Using the additive in doses up 0,6 % wt of cement and increase of the retard time around 550 y 600 min with the increase in the additive content. Similarly, with the increase of the retardant additive diminishes the initial strength and increases the final strength of the mortar. With growing doses of accelerant content additive diminished the setting time of the mixes studied
Marcado con l谩ser sobre cer谩mica vidriada por aporte superficial de un pigmento de cobalto
El procesamiento de materiales por l谩ser tiene gran aplicaci贸n a escala industrial, para imprimir
patrones gr谩ficos sobre superficies cer谩micas. La r谩pida implementaci贸n de este proceso se debe a que,
respecto al proceso convencional de horneado, tiene ventajas tales como: se concentra el calor s贸lo en la
zona irradiada, lo que conlleva un menor consumo de energ铆a sin afectar significativamente el resto de la
pieza; se obtienen patrones gr谩ficos de alta resoluci贸n espacial; permite introducir cambios durante el proceso
sin requerir largas paradas, y la generaci贸n de residuos es m铆nima o casi nula. En este estudio se presentan
los resultados obtenidos en el vidriado con l谩ser Nd:YAG (位=1064 nm) sobre las superficies esmaltadas de
azulejos, las cuales fueron previamente recubiertas con pigmento negro de cobalto. Con el l谩ser operando
en modo continuo (CW), se marcaron una serie de l铆neas, cuyo ancho y profundidad evidenciaron una
dependencia directa con la variaci贸n de la potencia y velocidad de desplazamiento del haz l谩ser sobre la
superficie del azulejo. Estas l铆neas vidriadas fueron finalmente caracterizadas por microscop铆a 贸ptica, espectroscopia
de dispersi贸n de energ铆a (EDS) y difracci贸n de rayos X.Laser materials processing has great application to industrial scale, to print graphic patterns on ceramics
surfaces. The fast implementation of this process is due to the fact that, with respect to the conventional
baking process, has advantages, such as: heat is concentrated only in the radiated zone that involves
a smaller energy consumption without affecting significantly the rest of the piece, graphic patterns with of
highly spatial resolution are obtained, it permits to introduce changes during the process without requiring
long stops, and low or almost none generation of residues. In this study the results obtained from Nd:YAG
(位=1064 nm) laser glazing on the enameled surfaces of glazed tiles, which were previously covered with
black of cobalt pigment, are presented. With the laser operating in continuous wave (CW), a series of lines
were marked, whose width and depth showed a direct dependence with the variation in the power and
scan speed of the laser beam on the surface of the glazed tile. Finally, these glazed lines were characterized
by optical microscopy, energy dispersion spectroscopy (EDS), and X-ray diffraction (XRD)
Atmospheric deterioration of ceramic building materials and future trends in the field: a review
Multiple techniques have been developed and implemented around the world to monitor structures and minimize the costs of repairing, maintaining, and losing ceramic building materials due to environmental factors. Understanding the different degradation phenomena that affect ceramic building materials and evaluating their condition can help reduce material losses caused by deterioration and the need for interventions. This study reviews the main forms of atmospheric degradation that affect ceramic materials and the commonly employed methods to evaluate their deterioration. The aim is to illustrate the different types of atmospheric deterioration that affect ceramic materials and to demonstrate the current monitoring methods and testing. In addition to a literature review, a bibliometric analysis was conducted to highlight the available tools to counter atmospheric deterioration. The analysis shows that CO2, sulfates, and temperature are the most important types of degradation for ceramic construction materials. It was also discovered that due to their porous nature, ceramic construction materials require careful control as contaminants and water can easily penetrate them. The two most severe types of deterioration identified in this analysis for reinforced concrete were chloride-induced corrosion and carbonation