pinecone/core-2020-05-10-deduplication huggingface dataset:
The effect of pre-processing and grain structure on the bio-corrosion and fatigue resistance of magnesium alloy AZ31

Magnesium alloys are broadly used for structural applications in the aerospace and automotive industries as well as in consumer electronics. While a high specific strength is the forte of magnesium alloys, one serious limitation for Mg alloys is their corrosion performance. Unlike aluminium, it does not form a stable passive film to provide long-term protection from further corrosion. The poor corrosion resistance of magnesium and magnesium alloys is regarded as a major drawback, and significant effort has been focused on improving this.[1-3] However, the high reactivity of magnesium alloys in corrosive media can be used to advantage in biomedical applications, particularly in temporary implants where the capacity of a material for bio-degradation is one of the most sought after properties. Indeed, permanent implant materials, such as stainless steel, titanium alloys or Nitinol (55Ni-45Ti), are the only choices currently available for hard tissue implantation. They can cause permanent physical irritation, long-term endothelial dysfunction and chronic inflammatory local reaction. Sometimes a second operation is needed for the implant to be removed. Given the ability of the human body to gradually recover and regenerate damaged tissue, the ideal solution would thus be a degradable implant, which would offer a physiologically less invasive repair and temporary support during tissue recovery. After fulfilling its function, this implant would be obliterated, being absorbed by the body. This philosophy of implant surgery would also be of particular interest for endovascular stent
Bio-inspired mineral growth on porous spherulitic textured poly(L-lactic acid)/bioactive glass composite scaffolds

It has been shown that texture can strongly influence the adhesion, orientation and proliferation of cells onto the surface of biomaterials. Additionally, it is possible to imprint micrometer level textures throughout the scaffolds by melt compounding PLLA/polyethylene oxide (PEO) blend, quenching followed by leaching of PEO in water. The objective of this work is to verify how the texture in 3D porous PLLA/Bioglass®composite scaffolds may influence the precipitation of apatite in vitro. © 2008 WILEY-VCH Verlag GmbH  &  Co. KGaA.Financial support for this work was provided by FCT, through tire POCTI and FEDER programmes, and projects POCTI/FIS/61621/2004 and PTDC/QUI/69263/2006. S. Ghosh thanks FCT for awarding the PhD grant, SFRH/BD/12657/2003. This work was also partially supported by the European Union funded STREP Project HIPPOCRATES(NMP3-CT-2003-505758)
Novel rice-shaped bioactive ceramic nanoparticles

A study was conducted to synthesize needle-like or rice-shaped bioactive ceramic (BAC) nanoparticles. These nanoparticles were formulated with an unusually low silicon content and a relatively high phosphorus concentration. This system combined the advantages of hydroxyapatite and bioactive glasses, enhancing its potential applicability in regeneration strategies for mineralized tissues or more conventional medical applications. It was observed that nanoparticles can be mixed with some bridgeable polymers to develop new biomaterials with improved mechanical properties and adequate bioactivity. The study produced new rice-shaped or claviform low-silicon-content bioceramic nanoparticles using an improved sol-gel method, with sizes of about 70nm in diameter and 210nm in length. It was concluded that these bioactive nanoparticles contained small quantity of silicon and showed excellent biomineralization capability.This work was financially supported by the Foundation for Science and Technology (FCT) via a grant for postdoctoral research (SFRH/BPD/25828/2005) and by project PTDC/QUI/69263/2006
Hexagonal honeycombs with zero Poisson's ratios and enhanced stiffness

In view of their potential applications in sandwich structures, there has been increasing interest in honeycomb networks. Several different types of honeycomb systems have been proposed each exhibiting different mechanical properties. Here we propose a new hexagonal honeycomb structure composed of two different geometrical features: a re-entrant feature which is known to generate auxetic behavior, and a non re-entrant feature found in regular hexagonal honeycombs which leads to conventional behavior. This results in a “semi re-entrant honeycomb” built of alternate conventional and auxetic layers. Finite element analysis and analytical modeling of these honeycombs show that they exhibit a zero Poisson ratio in one direction and a higher than normal Young's modulus in the orthogonal direction. We also show that by virtue of its zero Poisson's ratio, this honeycomb has a natural tendency to form cylindrical shaped curvatures, something which is very difficult to achieve with conventional or auxetic honeycombs.peer-reviewe
Transparent alumina/ceria nanocomposites by spark plasma sintering

7 páginas.-- El pdf del artículo es el manuscrito de autor.The influence of oxides (such as MgO, TiO2, CaO, etc.) on the transparency of polycrystalline alumina compacts are widely studied in the literature. In this work, a completely different approach is developed, consisting of precipitating 0.5 wt.-% CeO2 nanoparticles (< 5 nm) on the surface of the starting alumina nanopowder (d50 approximately 170 nm) using cerium(III) acetate as precursor. It is shown that the ceria nanoparticles strongly enhance the transparency of the spark plasma sintered compacts due to: i) the ceria nanoparticles acting as powder lubricant, increasing by around 15% the initial density of the powder in the SPS die, and, ii) the CeO2 nanoparticles, having a very low solid solubility in the alumina grains, locating at grain boundaries, hindering alumina grain growth by pinning during SPS sintering at 1 430 °C, 80 MPa for 2 min. This effect is found to be effective only under SPS vacuum conditions. In order to explain the light scattering behavior in the near-infrared and visible range, a light scattering model under the Rayleigh-Gans-Debye approximation for polycrystalline alumina is used. This model offers an additional and simple tool for a completed bulk evaluation of the SPS compacts microstructure.This work was supported by the Spanish Ministry of Science and Innovation (MICINN) under projects MAT2007-66719-C03-01, MAT2009-14542-C02 and FUNCOAT-Consolider CSD2008-00023. Likewise, the work was supported by CSIC through the PIE Project 200860I118. IA-C was supported by the Fundacion para el Fomento en Asturias de la Investigacion Cientıfica aplicada y la Tecnologia (FICYT) under the program Severo Ochoa. GM-O was supported by the Spanish Ministry of Education and Science under the project MAT2006-10249-C02-01.Peer reviewe
A Numerical Model for Powder Densification by SPS Technique

This is the pre-peer reviewed version of the following article: A Numerical Model for Powder Densification by SPS Technique, Mondalek P., Silva L., Bellet M., Advanced Engineering Materials 13, 7 (2011) Pages 587-593, which has been published in final form at http://dx.doi.org/10.1002/adem.201000340International audienceSpark plasma sintering (SPS) belongs to a class of sintering techniques that employs electric current to assist compaction. This technology seems very promising to obtain net-shape components made of intermetallic alloys with a fine microstructure. However, the SPS process is difficult to stabilize because of density heterogeneities arising from non-homogeneous temperature or stress in the powder. This motivates the development of a three-dimensional finite element simulation in order to understand the distribution of current, temperature and porosity. The model couples three physical problems: electrical, thermal and mechanical. The numerical implementation is based on a monolithic formulation consisting in solving the different conservation equations on a single mesh including the specimen and the tooling. The general set of equations is described; the effect of the powder physical properties and of the geometry of the set up on the distribution of electrical current and temperature is discussed. A macroscopic Abouaf constitutive model is used to simulate powder densification; first results involving porosity evolution are presented
Category theory based solution for the building block replacement problem in materials design

An important objective in materials design is to develop a systematic methodology for replacing unavailable or expensive material building blocks by simpler and abundant ones, while maintaining or improving the functionality of the material. The mathematical field of category theory provides a formal specification language which lies at the heart of such a methodology. In this paper, we apply material ologs, category-theoretic descriptions of hierarchical materials, to rigorously define a process by which material building blocks can be replaced by others while maintaining large-scale properties, to the extent possible. We demonstrate the implementation of this approach by using algebraic techniques to predict concrete conditions needed for building block replacement. As an example, we specify structure–function relationships in two systems: a laminated composite and a structure–function analogue, a fruit salad. In both systems we illustrate how ologs provide us with a mathematical tool that allows us to replace one building block with others to achieve approximately the same functionality, and how to use them to model and design seemingly distinct physical systems with a consistent mathematical framework
Influence of the type of phase change materials microcapsules on the properties of lime-gypsum thermal mortars

In a society with a high growth rate and increased standards of comfort arises the need to minimize the currently high energy consumption by taking advantage of renewable energy sources. The mortars with incorporation of phase change materials (PCM) have the ability to regulate the temperature inside buildings, contributing to the thermal comfort and reduction of the use of heating and cooling equipment, using only the energy supplied by the sun. However, the incorporation of phase change materials in mortars modifies its characteristics. The main purpose of this study was the production and characterization of mortars with incorporation of two different phase change materials. Specific properties of two phase change materials, such as particle size, shape and enthalpy, were determined, as well as the properties of the fresh and hardened state of the mortars. The proportion of PCM was 0%, 10%, 20% and 30% of the total mass of the solid particles. In order to minimize some problems associated with shrinkage and consequent cracking of the mortars, the incorporation of polyamide fibers and superplasticizer was tested. It was possible to observe that the incorporation of phase change materials in mortars caused differences in properties such as compressive strength, flexural strength and shrinkage. Even though the incorporation of PCM microcapsules resulted in an increase in the shrinkage, it was possible observe a significant improvement in mechanical properties.The authors wish to express their thanks to the Portuguese Foundation for Science and Technology, for funding the project PTDC/ECM/102154/2008, Contribution of Thermal Active Mortars for Building Energy Efficiency
Field-Assisted Sintering Technology / Spark Plasma Sintering: Mechanisms, Materials, and Technology Developments

Field-assisted sintering technology/Spark plasma sintering is a low voltage, direct current (DC) pulsed current activated, pressure-assisted sintering, and synthesis technique, which has been widely applied for materials processing in the recent years. After a description of its working principles and historical background, mechanical, thermal, electrical effects in FAST/SPS are presented along with the role of atmosphere. A selection of successful materials development including refractory materials, nanocrystalline functional ceramics, graded, and non-equilibrium materials is then discussed. Finally, technological aspects (advanced tool concepts, temperature measurement, finite element simulations) are covered
Crystal Structure of the ZrO Phase at Zirconium/Zirconium Oxide Interfaces

Zirconium-based alloys are used in water-cooled nuclear reactors for both nuclear fuel cladding and structural components. Under this harsh environment, the main factor limiting the service life of zirconium cladding, and hence fuel burn-up efficiency, is water corrosion. This oxidation process has recently been linked to the presence of a sub-oxide phase with well-defined composition but unknown structure at the metal–oxide interface. In this paper, the combination of first-principles materials modeling and high-resolution electron microscopy is used to identify the structure of this sub-oxide phase, bringing us a step closer to developing strategies to mitigate aqueous oxidation in Zr alloys and prolong the operational lifetime of commercial fuel cladding alloys
Skins and Sleeves for Soft Robotics: Inspiration from Nature and Architecture

© 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim. This paper is on the design, fabrication, and testing of skins and sleeves for soft robotics with the focus on the mechanical features of the microstructure of these skins, drawing inspiration from nature and architecture. Biological inspirations drawn from animals are used for designing skin membranes or skin structures for soft robotic actuators, in particular pneumatic actuators that protect, guide, and contribute to the development of the actuated shape. The results presented in this paper will be a new step toward advancing the state-of-the-art of biologically inspired soft robots for minimally invasive surgery. Inspirations from architecture are of particular interest in the areas of formability of design and continuous flow. The report presents a trade-off study using various skin and sleeve technologies of innovative fiber structures and combinations of different materials in different innovative designs, surrounding a pneumatically actuated, soft robot of variable stiffness
Hybrid Filtration Membranes incorporating Nanoporous Silica within a Nanoscale Alumina Fibre Scaffold

Membranes were produced from fine (∼10 nm) alumina fibres, by dispersing them in liquid and using controlled sedimentation to produce two types of membrane – one a duplex structure (layers of well-dispersed fibres and micro-bundles) and the other entirely micro-bundles. Incorporation of silica, via a sol-gel route, produced “hybrid” forms. Filtration and separation efficiencies were assessed using two ionic dyes of similar molecular weight, but opposite charge. Successful separation of these is attributed to surface electrical effects within nano-pores. Hybrid duplex membranes give an excellent combination of fine scale filtration efficiency and high permeability.Financial support for this work has been provided by Trinity Hall College, Cambridge and the Cambridge Commonwealth TrustThis is the author accepted manuscript. The final version is available from Wiley at http://dx.doi.org/10.1002/adem.20150022
Producing high-strength metals by I-ECAP

Incremental equal channel angular pressing (I-ECAP) is used in this work to produce ultrafine-grained (UFG) pure iron, aluminum alloy 5083, commercial purity titanium (grade 4), and magnesium alloy AZ31B. Pure iron is processed at room temperature, aluminum alloy at 200 °C, titanium at 320 °C, and magnesium alloy at 150 °C. Strength improvement, attributed to the grain refinement below 1 μm, is reported for all processed materials. The yield strength increase is the most apparent in pure iron, reaching almost 500 MPa after one pass of I-ECAP, comparing to 180 MPa in the as-forged conditions. UFG titanium, aluminum, and magnesium alloys obtained in this study reached yield stress of 800, 350, and 300 MPa, respectively, in each case exhibiting the yield strength increase by at least 30%, comparing to the alloys processed by conventional metal forming operations such as forging and rolling
Adhesion of Volcanic Ash Particles under Controlled Conditions and Implications for their Deposition in Gas Turbines

A particular (representative) type of ash has been used in this study, having a particle size range of ~10-70 µm.  Experimental particle adhesion rate data are considered in conjunction with CFD modeling of particle velocities and temperatures.   This ash becomes soft above ~700˚C and it has been confirmed that a sharp increase is observed in the likelihood of adhesion as particle temperatures move into this range.  Particle size is important and those in the approximate range 10-30 µm are most likely to adhere.  This corresponds fairly closely with the size range that is most likely to enter a combustion chamber and turbine.This work forms part of a research programme funded by EPSRC (EP/K027530/1).  In conjunction with this project, a consortium of partners has been set up under the PROVIDA ("PROtection against Volcanic ash Induced Damage in Aeroengines") banner and information about its operation is available at http://www.ccg.msm.cam.ac.uk/initiatives/provida.  The invaluable assistance of Kevin Roberts (Materials Department in Cambridge) with operation of the plasma spray facility is gratefully acknowledged.  The authors are also grateful to Dr. Margaret Hartley, of the University of Manchester, for kindly collecting the Laki ash (and several other types) during field trips to Iceland, which were funded by EasyJet.This is the author accepted manuscript. The final version is available from Wiley via http://dx.doi.org/10.1002/adem.201500371 In compliance with current EPSRC requirements, input data for the modelling described in this paper, including meshing and boundary condition specifications, are available at the following URL: www.ccg.msm.cam.ac.uk/publications/resources. These files can be downloaded and used in COMSOL Multiphysics packages. Data supplied are for a representative case
Assembly-Dependent Interfacial Property of Carbon Nanotube Fibers with
  Epoxy and Its Enhancement via Generalized Surface Sizing

In building up composite structures using carbon nanotube (CNT) fibers, the
fiber-to-matrix interfacial shear strength (IFSS) is one of the most important
issues. Originating from the assembly characteristics of CNT fiber, the IFSS
strongly depends on the fiber's twisting level and densification level.
Furthermore, there are rich ways to modify the fiber surface and thus enhance
the IFSS, including the physical and chemical modification on fiber surface,
the infiltration of matrix resin into CNT fiber, and the introduction of silane
coupling agent. A new feature differing from carbon fibers is that all these
treatments either change the fiber's surface structure or form a
several-hundreds-nm-thick interphase inside rather than around the fiber. These
"generalized" treatments obviously extend the common concept of surface sizing
and can be used for various forms of CNT assembly structures.Comment: 7 pages, 5 figure
First Cold Spraying of Carbonated Biomimetic Nanocrystalline Apatite on Ti6Al4V: Physical-Chemical, Microstructural, and Preliminary Mechanical Characterizations

Carbonated Biomimetic Nanocrystalline Apatite (BNAc) coatings are obtained for the first time by Cold Spray. The coatings are characterized by FTIR, Raman, XRD, and SEM and compared to the powders. No significant chemical and structural changes are detected and the nanostructure features of these very reactive BNAc are preserved in the coating. These results and preliminary mechanical assays show that Cold Spray can produce an operational biomimetic coatings offering a high potential for implants functionalization and osseointegration. However, these first results need further studies in order to understand the mechanism of adhesion and the interactions at the coating–substrate interface
Deterministic Switching of Hierarchy during Wrinkling in Quasi-Planar Bilayers

Emergence of hierarchy during compression of quasi-planar bilayers is preceded by a mode-locked state during which the quasi-planar form persists. Transition to hierarchy is determined entirely by geometrically observable parameters. This results in a universal transition phase diagram that enables one to deterministically tune hierarchy even with limited knowledge about material properties.United States. Department of Energy (DE-AC52-07NA27344)Lawrence Livermore National Laboratory (LLNL-JRNL-680043
Bone-Inspired Materials by Design: Toughness Amplification Observed Using 3D Printing and Testing

Inspired by the fact that nature provides multifunctional composites by using universal building blocks, the authors design and test synthetic composites with a pattern inspired by the microstructure of cortical bone. Using a high-resolution multimaterial 3D printer, the authors are able to manufacture samples and investigate their fracture behavior in mechanical tests. The authors’ results demonstrate that the bone-inspired design is critical for toughness amplification and balance with material strength. The failure modes of the authors’ synthetic composites show similarities with the cortical bone, like crack deflection and branching, constrained microcracking, and fibril bridging. The authors’ results confirm that our design is eligible to reproduce the fracture and toughening mechanism of bone
Identification of the Norton-Green Compaction Model for the Prediction of the Ti-6Al-4V Densification During the Spark Plasma Sintering Process

One of the main challenges for the industrialization of the spark plasma sintering (SPS) is to resolve issues linked to the compaction of real parts with complex shapes. The modeling of powder compaction is an interesting tool to predict how the densification field varies during sintering. However, expressing the behavior law which reflect the powder compaction is often a difficult and long step in the model establishment. In this paper, a simple methodology for the identification of the densification parameters is proposed. Dense and porous creep tests combined with SPS die compaction tests are employed to determine a complete densification law on a Ti–6Al–4V alloy directly in a SPS machine. The compaction model obtained is successfully validated through prediction of the densification of new SPSed samples
Mechanical behavior and adhesion of the Ti/Cr/Au metallization scheme on diamond substrate

The mechanical properties of a Ti/Cr/Au metallization system deposited on a heavily doped diamond substrate are valuated, first using nano-indentation tests. Various kinds of conditions are adopted, such as small and high force loadings. These tests are completed by in situ scanning electron microscopy observations of the surface. The adhesion of such multilayer on the diamond substrate is assessed using nano-scratching tests. The profiles of the\ud
obtained scratches are analyzed to detect any singularities or defects. Finally, a cross-section topography is performed, in order to obtain the cross profile\ud
of the scratch, and to determine the scratch hardness parameter of the metallization system. The Ti/Cr/Au metallization system is a potential candidate to play the role of ohmic contact on diamond. Therefore, its\ud
adhesion to diamond is important, since the whole power electronic assembly is mainly subjected to thermal cycling during service. The metallization system must adhere well to diamond, so as to resist temperature gradients and thermal strains that are widely observed in extreme thermal conditions. Otherwise, debonding phenomena may occur,\ud
and the whole electronic packaging fail