Tuning the structure and the mechanical properties of epoxy-silica sol-gel hybrid materials

A new route for the synthesis of a monolithic porous hybrid organic-inorganic material composed of silica and an epoxy resin is reported. This ormosil material is prepared by supercritical drying of a gel obtained by a one-pot procedure and using ethanol as the only solvent. The microscopic analysis reveals that the material presents an open network of micrometric pores. The characteristics of the pore structure strongly depend on the ratio between silica and epoxy. While in most cases the structure is formed by homogeneous hybrid primary particles, a foam-like structure is observed for a specific composition, which seems related to a phase-separation effect. The material presents rubber-like behavior under compression. Moreover, the compression modulus can be continuously tuned along two orders of magnitude through the variation of the silica-epoxy ratio, allowing the preparation of a material with tailored mechanical properties.MATGAS is acknowledged for allowing the use of their supercritical drying facilities. Dr Daniel Crespo (Departament de Física Aplicada, Escola d'Enginyeria de Telecomunicació i Aeronàutica de Castelldefels, Universitat Politècnica de Catalunya) is acknowledged for his help in the DMA tests. SOPREMA (France), the Spanish Ministerio de Economía y Competitividad (Grant No.ENE-2012-36368-C02-02) and the Generalitat de Catalunya (Grant No. 2014SGR1643) are acknowledged by their financial support. support.Peer Reviewe

Polymer-stabilized palladium nanoparticles for catalytic membranes: ad hoc polymer fabrication

Metal nanoparticles are known as highly effective catalysts although their immobilization on solid supports is frequently required to prevent aggregation and to facilitate the catalyst application, recovery, and reuse. This paper reports the intermatrix synthesis of Pd0 nanoparticles in sulfonated polyethersulfone with Cardo group membranes and their use as nanocomposite catalytic membrane reactors. The synthesized polymer and the corresponding nanocomposite were characterized by spectroscopic and microscopic techniques. The catalytic efficiency of catalytic membranes was evaluated by following the reduction of p-nitrophenol in the presence of NaBH4

Bulk supercrystalline ceramic-organic nanocomposites: New processing routines and insights on the mechanical behavior

In the strive to produce nature-inspired hierarchical materials with an enhanced combination of mechanical properties, supercrystalline ceramic-organic nanocomposites have been produced in bulk form and characterized from a variety of perspectives. Through an interdisciplinary collaboration at the crossroad between materials science, chemistry and mechanical engineering, a bottom-up approach has been designed. It consists of a sequence of self-assembly, pressing and heat treatment, and it leads to macroscopic poly-supercrystalline materials with exceptional mechanical properties and behavior. The crosslinking of the organic phase induced by the heat treatment does not only increase the materials’ stiffness, hardness and strength (elastic modulus up to 70 GPa, hardness up to 5 GPa and bending strength up to 630 MPa), but alters also their constitutive response. Fracture toughness values higher than theoretical predictions have emerged (~ 1 MPa·m1/2), implying the presence of extrinsic toughening mechanisms, such as the crack-path deviation observed at indents’ corners. Ex-situ nanoindentation and in-situ SAXS/microcompression studies also suggest the possibility for supercrystalline materials to accommodate compressibility and plastic-like deformation. Defects analogous to the ones typically observed in crystalline lattices, such as stacking faults, dislocations and slip bands, are detected at the superlattice scale (even if one order of magnitude larger than the atomic one, and with interactions among the nano-building blocks controlled by the organic phase). Correlations between defects, processing and mechanical properties have been drawn by adapting the classic theories of mechanical behavior of materials. These same materials are additionally being used as bricks for the development of novel hierarchical composites, via additive manufacturing or fluidized bed techniques. Please click Additional Files below to see the full abstract

El Rol del pedagog i les funcions que desenvolupa en els processos d'adopció internacional

L'adopció internacional ha passat a ocupar un lloc important en el nostre context social, polític i educatiu i, com a pedagogs experts en l'àmbit, volem reflexionar, entorn de la importància d'aquesta figura professional en els equips interdisciplinaris que treballen amb les famílies i la infància adoptada i entorn de la seva implicació en les diferents etapes del procés d'adopció. Per presentar aquest perfil professional fem un recorregut per les diferents funcions que desenvolupa, tant durant el període preadoptiu, com en el postadoptiu, destacant la formació a famílies i professionals, la seva participació en el procés de valoració dels sol·licitants d'adopció i la intervenció en els processos d'orientació i assessorament postadoptiu.La adopción internacional ha pasado a ocupar un sitio importante en nuestro contexto social, político y educativo y como pedagogos expertos en este ámbito, queremos reflexionar sobre la importancia de esta figura profesional en los equipos interdisciplinarios que trabajan con las familias y los niños adoptados, al igual que sobre su implicación en las diferentes etapas del proceso de adopción. Para presentar este perfil profesional hacemos un recorrido por las diferentes funciones que desarrollamos, tanto durante el periodo preadoptivo como en el postadoptivo, destacando la formación de familias y profesionales, la participación en el proceso de valoración de los solicitantes de adopción y la intervención en los procesos de orientación y asesoramiento postadoptivo.International adoption has become very significant in our social, political, and educational context, and we, as pedagogues with expertise in this field, want to reflect upon the importance of this professional figure in the interdisciplinary teams that work with families and adopted children, as well as their involvement in the different stages of the adoption process. To present this professional profile, we describe their different functions, both during the preadoption period and after the adoption, focusing on family and professional training, their participation in the assessment process of adoption applicants, and their intervention in post-adoption guidance and counselling processes

Nanoindentation creep of supercrystalline nanocomposites

Supercrystalline nanocomposites (SCNCs) are inorganic-organic hybrid materials with a unique periodic nanostructure, and thus they have been gaining growing attention for their intriguing functional properties and parallelisms with hierarchical biomaterials. Their mechanical behavior remains, however, poorly understood, even though its understanding and control are important to allow SCNCs’ implementation into devices. An important aspect that has not been tackled yet is their time-dependent deformation behavior, which is nevertheless expected to play an important role in materials containing such a distribution of organic phase. Hereby, we report on the creep of ceramic-organic SCNCs with varying degrees of organic crosslinking, as assessed via nanoindentation. Creep strains and their partial recoverability are observed, hinting at the co-presence of viscoelasticity and viscoplasticity, and a clear effect of crosslinking in decreasing the overall material deformability emerges. We rationalize our experimental observations with the analysis of stress exponent and activation volume, resulting in a power-law breakdown behavior and governing deformation mechanisms occurring at the organic sub-nm interfaces scale, as rearrangement of organic ligands. The set of results is reinforced by the evaluation of the strain rate sensitivity via strain rate jump tests, and the assessment of the effect of oscillations during continuous stiffness measurement mode.</p

Bifunctional Polymer-Metal Nanocomposite Ion Exchange Materials

Peer ReviewedPostprint (published version

Development of novel catalytically active polymer-metal-nanocomposites based on activated foams and textile fibers

In this paper, we report the intermatrix synthesis of Ag nanoparticles in different polymeric matrices such as polyurethane foams and polyacrylonitrile or polyamide fibers. To apply this technique, the polymer must bear functional groups able to bind and retain the nanoparticle ion precursors while ions should diffuse through the matrix. Taking into account the nature of some of the chosen matrices, it was essential to try to activate the support material to obtain an acceptable value of ion exchange capacity. To evaluate the catalytic activity of the developed nanocomposites, a model catalytic reaction was carried out in batch experiments: the reduction of pnitrophenol by sodium borohydridePostprint (published version

Constitutive and fracture behavior of ultra-strong supercrystalline nanocomposites

Supercrystalline nanocomposites are a new class of hybrid and nanostructured materials that can reach exceptional mechanical strength and can be fabricated at low temperatures. Hierarchically arranged, they bridge the gap from the nano- to the macro-scale. Even though their mechanical properties are starting to be characterized, their constitutive behavior is still largely unexplored. Here, the mechanical behavior of supercrystalline nanocomposites of iron oxide nanoparticles, surface-functionalized with oleic acid and oleyl phosphate ligands, is investigated in both bending and compression, with loading-unloading tests. A new bar geometry is implemented to better detect deformation prior to unstable crack propagation, and notched bending bars are tested to evaluate fracture toughness. Micro-mechanical tests result in the values of strength and elastic modulus that are extremely high for supercrystals, reaching record-high numbers in the oleic acid-based nanocomposites, which also show a significant tension-compression asymmetry. The constitutive behavior of both materials is predominantly linear elastic, with some more marked nonlinearities arising in the oleyl phosphate-based nanocomposites. The fracture toughness of both types of nanocomposites, ∼0.3 MPa√m, suggests that extrinsic toughening, associated with both material composition and nanostructure, plays an important role. Fractographic observations reveal analogies with shear and cleavage in atomic crystals. The influence of material composition, nanostructure, and processing method on the mechanical behavior of the nanocomposites is analyzed.</p

Perioperative management and early complications after intestinal resection with ileocolonic anastomosis in Crohn’s disease: analysis from the PRACTICROHN study

This study is aimed at describing the prevalence of and risk factors associated with early post-operative complications after Crohn’s disease-related intestinal resection. Methods: This was a retrospective analysis of data from the PRACTICROHN cohort. Adult Crohn’s disease patients who underwent ileocolonic resection with ileocolonic anastomosis between January 2007 and December 2010 were included. The complications evaluated included death, ileus, anastomotic leak, abscess, wound infection, catheter-related infection, digestive bleeding and other extra-abdominal infections that occurred in the 30 days after surgery.Results: A total of 364 patients (median age at surgery 38 years and 50% men) were included. Indication for surgery was: stricturing disease (46.4%), penetrating disease (31.3%), penetrating and stricturing disease (14.0%) or resistance to medical treatment (5.8%). Early complications were recorded in 100 (27.5%) patients, with wound infection, intra-abdominal abscess and anastomotic leakage being the most frequent complications. Median hospitalization duration was 16 days for patients with complications vs. 9 days without complications (P<0.001). Complications were more common among patients with penetrating disease (36/114, 31.6%) and those refractory to treatment (9/21, 42.9%) compared with stricturing disease (45/169, 26.6%) or stricturingþpenetrating disease (6/51, 11.8%) (P¼0.040). The rate of complications was higher among patients with diagnosis made at the time of surgery (15/31, 48.4%) compared with the rest (85/331, 25.7%) (P¼0.013). Medication received at the time of surgery did not affect the rate of complications. Conclusions: Almost a quarter of patients developed early complications after intestinal resection. Penetrating disease and urgent surgery were associated with an increased risk of complicationsThis study was supported by Merck Sharp and Dohme, Spai