Fabrication and characterization of metallic nanowires

The shape of metallic constrictions of nanoscopic dimensions (necks) formed using a scanning tunneling microscope is shown to depend on the fabrication procedure. Submitting the neck to repeated plastic deformation cycles makes it possible to obtain long necks or nanowires. Point-contact spectroscopy results show that these long necks are quite crystalline, indicating that the repeated cycles of plastic deformation act as a “mechanical annealing” of the neck.

Influence of using slag cement on the microstructure and durability related properties of cement grouts for micropiles

Today, the use of micropiles for different applications has become very common. In Spain, the cement grouts for micropiles are prepared using ordinary Portland cement and w:c ratio 0.5, although the micropiles standards do not restrict the cement type to use, provided that it reaches a certain compressive strength. In this study, the influence of using slag cement on the microstructure and durability related properties of cement grouts for micropiles have been studied until 90 hardening days, compared to an ordinary Portland cement. Finally, slag cement grouts showed good service properties, better than ordinary Portland cement ones.

Impedance spectroscopy study of the effect of environmental conditions in the microstructure development of OPC and slag cement mortars

In this work, the microstructure of mortars made with an ordinary Portland cement and slag cement has been studied. These mortars were exposed to four different constant temperature and relative humidity environments during a 180-day period. The microstructure has been studied using impedance spectroscopy, and mercury intrusion porosimetry as a contrast technique. The impedance spectroscopy parameters make it possible to analyze the evolution of the solid fraction formation for the studied mortars and their results are confirmed with those obtained using mercury intrusion porosimetry. The development of the pore network of mortars is affected by the environment. However, slag cement mortars are more influenced by temperature while the relative humidity has a greater influence on the OPC mortars. The results show that slag cement mortars hardened under non-optimal environments have a more refined microstructure than OPC mortars for the studied environmental conditions.

Digital Fabrication and Free Culture. One More Minor Becoming?

Diferentes autores se refieren a la fabricación digital como la Tercera Revolución Digital, después de las revoluciones de la computación y la comunicación. Como ocurriera con las dos revoluciones precedentes, se generaron grandes expectativas en torno a las virtualidades políticas de estas nuevas tecnologías para dar lugar a relaciones de producción más libres e individuos más autónomos. Sin embargo, como también ocurriera con la computación y la comunicación, lo que realmente está ocurriendo demuestra que las supuestas virtualidades no llegarán a hacerse actuales sin una intensa implicación, organización y trabajo por parte de sectores activistas técnicos y sociales. Se discute el caso de la compra corporativa de la empresa pionera de hardware libre Makerbot, como ejemplo de la situación y punto de inflexión en las expectativas de los nuevos tecno-visionarios. Para concluir se propone una serie de posibles estrategias que podrían promover el desarrollo efectivo de un ecosistema libre y open source de fabricación digital.