EVALUACIÓN DEL DESGASTE ADHESIVO DE RECUBRIMIENTOS METÁLICOS DUROS DEPOSITADOS POR PROCESOS DE SOLDADURA, CON UN TRIBÓMETRO DE CILINDROS CRUZADOS

RESUMENCuando dos materiales están en contacto bajo condiciones dinámicas, el desgaste es influenciado por las propiedades físicas y las fuerzas de interacción. Estas fuerzas son difícilmente controlables; sin embargo, las propiedades físicas pueden mejorarse seleccionando adecuadamente el material para lograr un buen funcionamiento y durabilidad del sistema. Esta investigación presenta la evaluación del desgaste adhesivo de cuatro recubrimientos metálicos duros depositados por procesos de soldadura: dos aceros de baja aleación de Cr y Cr-V-Mo; y dos fundiciones blancas de Cr-Mo-V y Cr–Mo–Nb-V-W. Los ensayos se realizaron en un tribómetro de cilindros cruzados. Se determinó el perfil de desgaste y los coeficientes de fricción de cada material. Se obtuvo un coeficiente de variación máximo del 10%, indicando una buena correlación de los datos. Los coeficientes de fricción calculados se consideran acertados y los perfiles presentan las tres etapas propias del proceso de desgaste adhesivo.Palabras claves: Fricción, Desgaste Adhesivo, Coeficiente de Desgaste, Tribosistema, Tribómetro de Cilindros Cruzados.ABSTRACTWhen two materials are in contact under dynamic conditions, the wear is influenced by the physical properties and the forces of interaction. These forces are difficult to control; however, the physical properties can be improved by selecting appropriate materials to ensure a smooth functioning and durability of the system. This research presents the results of adhesive wear of four hard coatings deposited by metal welding processes: two low alloy steels Cr and Cr-Mo-V and two white foundries of Cr-Mo-V and Cr-Mo-Nb–V-W. The tests were carried out in a cylinder crossed tribometer. It was determined the profile of wear and friction of each material. We obtained a variation of the friction coefficient up to 10%, indicating a good correlation of data. The friction coefficient calculated was considered accurate and the profiles showed the three stages of the wear process, which is completely adhesive.Keywords: Tribology, Friction, Wear, Friction Coefficient, Tribosistem

EVALUACIÓN DEL DESGASTE ADHESIVO DE RECUBRIMIENTOS METÁLICOS DUROS DEPOSITADOS POR PROCESOS DE SOLDADURA, CON UN TRIBÓMETRO DE CILINDROS CRUZADOS

RESUMENCuando dos materiales están en contacto bajo condiciones dinámicas, el desgaste es influenciado por las propiedades físicas y las fuerzas de interacción. Estas fuerzas son difícilmente controlables; sin embargo, las propiedades físicas pueden mejorarse seleccionando adecuadamente el material para lograr un buen funcionamiento y durabilidad del sistema. Esta investigación presenta la evaluación del desgaste adhesivo de cuatro recubrimientos metálicos duros depositados por procesos de soldadura: dos aceros de baja aleación de Cr y Cr-V-Mo; y dos fundiciones blancas de Cr-Mo-V y Cr–Mo–Nb-V-W. Los ensayos se realizaron en un tribómetro de cilindros cruzados. Se determinó el perfil de desgaste y los coeficientes de fricción de cada material. Se obtuvo un coeficiente de variación máximo del 10%, indicando una buena correlación de los datos. Los coeficientes de fricción calculados se consideran acertados y los perfiles presentan las tres etapas propias del proceso de desgaste adhesivo.Palabras claves: Fricción, Desgaste Adhesivo, Coeficiente de Desgaste, Tribosistema, Tribómetro de Cilindros Cruzados.ABSTRACTWhen two materials are in contact under dynamic conditions, the wear is influenced by the physical properties and the forces of interaction. These forces are difficult to control; however, the physical properties can be improved by selecting appropriate materials to ensure a smooth functioning and durability of the system. This research presents the results of adhesive wear of four hard coatings deposited by metal welding processes: two low alloy steels Cr and Cr-Mo-V and two white foundries of Cr-Mo-V and Cr-Mo-Nb–V-W. The tests were carried out in a cylinder crossed tribometer. It was determined the profile of wear and friction of each material. We obtained a variation of the friction coefficient up to 10%, indicating a good correlation of data. The friction coefficient calculated was considered accurate and the profiles showed the three stages of the wear process, which is completely adhesive.Keywords: Tribology, Friction, Wear, Friction Coefficient, Tribosistem

Estudio de las propiedades fisicoquímicas y texturales de polímeros acetilénicos y diacetilénicos como cadenas principales y grupos cromóforos en cadenas laterales

Se sintetizaron dos polímeros diacetilénicos que contienen grupos polares diacetilénicos y tolanos como cromóforos a través de la técnica de acoplamiento oxidativo. También se realizó un electrohilado de uno de los polímeros para poder observar y hacer un análisis textural comparativo. A partir de la isoterma de adsorción de nitrógeno a 77 K se obtuvo el área superficial específica para el polímero 2,5. La isoterma del material refleja las características de sólidos con baja porosidad, lo cual se corrobora con los estudios de microcopía de barrido. Con la finalidad de explorar su afinidad con el dióxido de carbono (CO₂), se obtuvieron las isotermas de adsorción de CO₂ a la temperatura de 298 K, para ambos polímeros.Two diacetylene polymers containing diacetylene polar groups and tolan as chromophores were synthesized through the oxidative coupling technique. An electro-spinning of the polymer was also performed to observe and make a comparative textural analysis. The specific surface area for polymer 2.5 was obtained from the nitrogen adsorption isotherm at 77 K. The isotherm of the material reflects the characteristics of solids with low porosity, which is corroborated by scanning microcopy studies. In order to explore their affinity with carbon dioxide (CO₂), the CO₂ adsorption isotherms at a temperature of 298 K were obtained for both polymers

Manufacturing of Cu-Sn foams through SDP

<div><p>ABSTRACT This work reports the processing of bronze foams manufactured by using the powder metallurgy method known as Sintering Dissolution Process. During the sintering step, a device with controlled atmosphere separated from the heating furnace was employed to avoid the quick oxidation of metal particles. The device allows to control its internal atmosphere with an inert gas avoiding the employment of a controlled atmosphere furnace (a furnace of this kind incorporates the heating and the control atmosphere systems itself). The metal used for the present study was bronze powders with a composition of 85%Cu–15%Sn, ~8.7g/cm3 in density, and particle size of 74µm. Spherical carbamide (CH4N2O) with particle size of ~1mm was chosen as Space Holder Particles (SHP). The maximum porosity Pf and minimum density ρf values were 42.8% and 3.61g/cm3, respectively. As the carbamide content is increased, the bronze powders content is diminished and consequently Pf is increased and ρf is diminished, as it would logically be expected. The minimum obtained ρf value corresponds only to 41.4 % of the bronze density (~8.7g/cm3). On the other hand, the plots of stress σ vs strain ε indicated σmax values between 26.86 and 8.45 MPa (20 and 35%vol. of carbamide, respectively). These obtained values indicate a good metallurgical bond among particles, caused by the uniaxial compression step and sintering at the correct Ts, previously determined (580ºC). The σmax decreases as the SHP content increases, which is due to a significant amount of porosity generated by the SHP dissolution and by the inclusion of void spaces among the metal particles; the both of them imply a lower area supporting the load, and consequently a reduction in σmax value for the samples. The results are interpreted in terms of increase and decrease of the carbamide and the bronze powder content in the sample, respectively.</p></div

Quadratic Non-Linear Optical Properties of the poly(2,5-bis(but-2-ynyloxy) Benzoate Containing the 2-(ethyl(4-((4-nitrophenyl)buta-1,3-diynyl)phenyl)amino)ethanol) Chromophore

Excellent quadratic non-linear optical (ONL-2) properties of the poly(2,5-bis(but-2-ynyloxy) benzoate, containing a polar diacetylene as a chromophore, were found. According with the Maker fringes method, oriented polymer films showing an order parameter of &sim;0.23 can display outstanding and stable Second Harmonic Generation (SHG) effects under off-resonant conditions (SHG-532 nm). Also, the macroscopic non-linear optical (NLO)-coefficients were evaluated under the rod-like molecular approximation, obtaining: &chi;zzz(2) and &chi;zxx(2) in the order of 280 &plusmn; 10 and 100 &plusmn; 10 pm V&minus;1, respectively. The mechanical and chemical properties, in addition to the large ONL-2 coefficients exhibited by this polymer, make it a promising organic material in the development of optoelectronic/photonic devices