Editorial: Metallic foams special section

Producción CientíficaPorous metals and metallic foams have been, for the last 25 years, the focus of very active research and development activities around the world, both at the academic and industrial levels. These materials are used when the combination of metal properties with the characteristics of a properly designed cellular structure provides advantages over other types of materials. They possess a spectrum of unique properties that can be tailored as a function of the final application, such as high impact energy absorption under mechanical load, high specific stiffness and strength, high fire resistance, air and water permeability, unusual acoustic properties for a metallic component, and low relative thermal conductivity. This special issue of Advanced Engineering Materials mainly contains a selection of the papers presented during MetFoam2015. The conference encompasses papers dealing with basic fundamentals, fabrication, morphological, and microstructural characterization, property profiles, secondary operations, and various applications of porous metals and metallic foams

Light transmission in nanocellular polymers: Are semi-transparent cellular polymers possible?

This work presents the light transmission through a collection of solid cellular polymers based on poly (methyl methacrylate) (PMMA) with cells sizes covering the micro and nano-scale. The obtained results showed that the behavior of light transmission when cell size is in the nano-scale is opposite to the one shown by microcellular foams or the one predicted by theoretical models of light scattering (LS). In fact, the expected trend is that a reduction of cell size increases the opacity of the samples. However, for nanocellular polymers based on amorphous polymers reducing the cell size increases the light transmission. Therefore, this result indicates that a further reduction of the cell size could result in cellular polymers optically semi-transparen

17th Conference on Defects (DRIP XVII)

PósterMinisterio de Economía, Industria y Competitividad (Project BFU2014-53469P

In-situ understanding of pore nucleation and growth in polyurethane foams by using real-time synchrotron X-ray tomography

Producción CientíficaThe nucleation and growth of pores in PU foams have been visualized and quantified for the first time in 4D using in-situ tomographic microscopy. Acquiring sequences of 3D images in 156 ms each, we describe homogeneous and heterogeneous nucleation and subsequent bubble growth dynamics for materials with and without nucleating nanoparticles. Exploiting the time resolved tomographic sequences we obtained the bubble nucleation rate, bubble density and size evolution, based on which the diffusion coefficient of gas molecules in polymer can be calculated, evidencing the reduction of diffusivity provoked by the inclusion of nanoparticles. We found that nucleation and growth are in a large extend decoupled in time.Ministerio de Economía, Industria y Competitividad - Fondo Europeo de Desarrollo Regional (project MAT2015-69234-R)Junta de Castilla y León (project VA275P18)Universidad de Valladolid - Banco Santander (contract E-47-2015-0094701

New non-destructive optical approach to determine the crystallization kinetics of PLA under a CO2 atmosphere with spatial and temporal resolution

Producción CientíficaThe kinetics of crystallization of Polylactic Acid (PLA) in the presence of CO2 pressures from 1.5 to 4 MPa, has been studied by measuring the optical absorbance evolution of the material with time. To perform this study, an own-designed pressure vessel provided with windows has been used. The non-destructive approach presented in this paper allows for obtaining very accurate crystallinity data as a function of time for a wide range of pressures. Besides, this new approach allows measuring with spatial resolution, i.e., obtaining the crystallization kinetics' evolution in different areas of the samples, which helps to analyze in detail the crystallization mechanisms by using the Avrami approach. The results obtained have allowed observing an unexpected peak in the absorbance curve connected with the physical phenomena taking place during the CO2 uptake and the associated crystallization of PLA.Junta de Castilla y León (grant VA202P20)Ministerio de Ciencia e Innovación (grants RTI2018-098749-B-I00 and RTI2018-097367-A-I00

The water ingress characteristics of stressed masonry

SIGLEAvailable from British Library Document Supply Centre-DSC:DXN030669 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Turbulence-enhanced combustion of lean mixtures

SIGLEAvailable from British Library Document Supply Centre- DSC:D42796/82 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Heat transfer in polyolefin foams

This chapter is dedicated to the study of heat transfer in polyolefin-based foams, particularly thermal conductivity, as a function of their structure and chemical composition. A small review of the main experimental techniques used to measure the thermal conductivity of these materials is also given, focusing on the transient plane source method (TPS), as well as different theoretical models commonly used for estimating its value. Alongside cellular structure (cell size, anisotropy, etc) and composition considerations, particular importance is given to the analysis of the presence of micrometric and nanometric-sized fillers in the resulting cellular composite thermal properties. This is a novel research field of particular interest, thought to extend the application range of these lightweight materials by tailoring their conductivity.Peer Reviewe

13th EXMATEC ‐ Expert Evaluation and Control of Compound Semiconductor Materials and Technologies.

Producción CientíficaThe photoluminescence imaging (PLi) technique allows for the fast qualification of mc-Si wafers and solar cells, giving information of the presence and distribution of carrier capture centres, which obviously affect the final efficiencies. In this work, we characterize a wide collection of solar cells by PLi, correlating some aspects extracted from the PL images to their efficiencies. The desired goal of this approach is to provide a tool allowing a robust prediction of solar cell efficiency from the PL images of the wafers.40th WOCSDICE ‐ Workshop on Compound Semiconductor Devices and Integrated Circuits held in Europe & 13th EXMATEC ‐ Expert Evaluation and Control of Compound Semiconductor Materials and Technologies, 6-10 June 2016, Aveiro, PortugalMinisterio de Economía, Industria y Competitividad (Project ENE2014- 56069-C4-4-R

Study of the cellular structure heterogeneity and anisotropy of polypropylene and polypropylene nanocomposite foams

This article presents the analysis of the processing parameters influence on the foaming behavior and cellular structure of PP-montmorillonite foams. Polypropylene nanocomposites containing 5.0 phr of an organically- modified montmorillonite (MMT) were initially melt-compounded in a twin-screw extruder with azodicarbonamide (ADC) and later foamed using a one-step compression-molding process. The cellular structure and morphology of the foams was assessed using both scanning and transmission electron microscopies. A time-dependant double-effect was observed during foaming: (1) first of all, the melt strength of the polymer, too high for shorter times, not allowing full cell growth, and too low for high foaming times due to thermal oxidation; (2) and polymer degradation, clearly observed for very high foaming times, directly affecting polymer’s melt resistance. Comparatively, PP-MMT foams exhibited a broader foaming time processing window, a more isometric type of cellular structure and decreased open-cell contents, indicating an effective nucleation and cell wall stabilization induced by the exfoliated MMT particles.Peer Reviewe