High temperature quasistatic and dynamic mechanical behavior of interconnected 3D carbon nanotube structures

CNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL E NÍVEL SUPERIORFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCarbon nanotubes (CNTs) are one of the most appealing materials in recent history for both research and commercial interest because of their outstanding physical, chemical, and electrical properties. This is particularly true for 3D arrangements of CNTs which enable their use in larger scale devices and structures. In this paper, the effect of temperature on the quasistatic and dynamic deformation behavior of 3D CNT structures is presented for the first time. An in situ high-temperature nanomechanical instrument was used inside an SEM at high vacuum to investigate mechanical properties of covalently interconnected CNT porous structures in a wide range of temperature. An irreversible bucking at the base of pillar samples was found as a major mode of deformation at room and elevated temperatures. It has been observed that elastic modulus and critical load to first buckle formation decrease progressively with increasing temperature from 25 degrees C to 750 degrees C. To understand fatigue resistance, pillars made from this unique structure were compressed to 100 cycles at room temperature and 750 degrees C. While the structure showed remarkable resistance to fatigue at room temperature, high temperature significantly lowers fatigue resistance. Molecular dynamics (MD) simulation of compression highlights the critical role played by covalent interconnections which prevent localized bending and improve mechanical properties.142291299CNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL E NÍVEL SUPERIORFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL E NÍVEL SUPERIORFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOSem informaçãoSem informação2013/08293-7S.O. acknowledges financial support from a LANL Director's Postdoctoral Fellowship. LDM, and DSG acknowledge the Brazilian Research Agencies CNPq, CAPES, and FAPESP for financial support. DSG also acknowledges the Center for Computational Engineering and Sciences at Unicamp through the FAPESP/CEPID Grant No. 2013/08293-7, for computational and financial support. N.M.P. is supported by the European Commission H2020 under the Graphene Flagship Core 2 grant no. 785219 (WP14, Composites) and under the FET Proactive ("Neurofibres. no. 732344), as well as by the Italian Ministry of Education, University and Research (MIUR) under the "Departments of Excellence" grant no. L.232/2016 and by Fondazione Caritro under "Self-Cleaning Glasses" no. 2016.0278. R.A.B. acknowledges financial support from Fondazione Caritro

No evidence for association between SLC11A1 and visceral leishmaniasis in India.

BACKGROUND: SLC11A1 has pleiotropic effects on macrophage function and remains a strong candidate for infectious disease susceptibility. 5' and/or 3' polymorphisms have been associated with tuberculosis, leprosy, and visceral leishmaniasis (VL). Most studies undertaken to date were under-powered, and none has been replicated within a population. Association with tuberculosis has replicated variably across populations. Here we investigate SLC11A1 and VL in India. METHODS: Nine polymorphisms (rs34448891, rs7573065, rs2276631, rs3731865, rs17221959, rs2279015, rs17235409, rs17235416, rs17229009) that tag linkage disequilibrium blocks across SLC11A1 were genotyped in primary family-based (313 cases; 176 families) and replication (941 cases; 992 controls) samples. Family- and population-based analyses were performed to look for association between SLC11A1 variants and VL. Quantitative RT/PCR was used to compare SLC11A1 expression in mRNA from paired splenic aspirates taken before and after treatment from 24 VL patients carrying different genotypes at the functional promoter GTn polymorphism (rs34448891). RESULTS: No associations were observed between VL and polymorphisms at SLC11A1 that were either robust to correction for multiple testing or replicated across primary and replication samples. No differences in expression of SLC11A1 were observed when comparing pre- and post-treatment samples, or between individuals carrying different genotypes at the GTn repeat. CONCLUSIONS: This is the first well-powered study of SLC11A1 as a candidate for VL, which we conclude does not have a major role in regulating VL susceptibility in India.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are

Approaches in biotechnological applications of natural polymers

Natural polymers, such as gums and mucilage, are biocompatible, cheap, easily available and non-toxic materials of native origin. These polymers are increasingly preferred over synthetic materials for industrial applications due to their intrinsic properties, as well as they are considered alternative sources of raw materials since they present characteristics of sustainability, biodegradability and biosafety. As definition, gums and mucilages are polysaccharides or complex carbohydrates consisting of one or more monosaccharides or their derivatives linked in bewildering variety of linkages and structures. Natural gums are considered polysaccharides naturally occurring in varieties of plant seeds and exudates, tree or shrub exudates, seaweed extracts, fungi, bacteria, and animal sources. Water-soluble gums, also known as hydrocolloids, are considered exudates and are pathological products; therefore, they do not form a part of cell wall. On the other hand, mucilages are part of cell and physiological products. It is important to highlight that gums represent the largest amounts of polymer materials derived from plants. Gums have enormously large and broad applications in both food and non-food industries, being commonly used as thickening, binding, emulsifying, suspending, stabilizing agents and matrices for drug release in pharmaceutical and cosmetic industries. In the food industry, their gelling properties and the ability to mold edible films and coatings are extensively studied. The use of gums depends on the intrinsic properties that they provide, often at costs below those of synthetic polymers. For upgrading the value of gums, they are being processed into various forms, including the most recent nanomaterials, for various biotechnological applications. Thus, the main natural polymers including galactomannans, cellulose, chitin, agar, carrageenan, alginate, cashew gum, pectin and starch, in addition to the current researches about them are reviewed in this article.. }To the Conselho Nacional de Desenvolvimento Cientfíico e Tecnológico (CNPq) for fellowships (LCBBC and MGCC) and the Coordenação de Aperfeiçoamento de Pessoal de Nvíel Superior (CAPES) (PBSA). This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2013 unit, the Project RECI/BBB-EBI/0179/2012 (FCOMP-01-0124-FEDER-027462) and COMPETE 2020 (POCI-01-0145-FEDER-006684) (JAT)

Microstructural and mechanical behavior study of suction cast Nb-Si binary alloys

The solidification pathways of Nb rich Nb-Si alloys when processed under non-equilibrium conditions require understanding. Continuing with our earlier work on alloying additions in single eutectic composition 1,2], we report a detailed characterization of the microstructures of Nb-Si binary alloys with wide composition range (10-25 at% Si). The alloys are processed using chilled copper mould suction casting. This has allowed us to correlate the evolution of microstructure and phases with different possible solidification pathways. Finally these are correlated with mechanical properties through studies on deformation using mechanical testing under indentation and compressive loads. It is shown that microstructure modification can significantly influence the plasticity of these alloys

Effect of Mg addition on microstructural, mechanical and environmental properties of Nb-Si eutectic composite

The paper reports the effect of addition of small amount of Mg on the mechanical and oxidation properties of Nb-Nb3Si eutectic composites in Nb-Si system under the condition of suction casting. Mg addition increases the volume fraction of primary dendrites of Nb solid solution. This phase contains significant amount of strengthening precipitates. Two different precipitates are identified. The large plate shaped precipitates are that of hcp phase, while fine coherent precipitates have the structure similar to recently identified delta-Nb11Si2 phase. The Mg addition improves both the strength and ductility of the composite at room temperature (similar to 1.4 GPa and similar to 5% engineering strain) as well as at 700 degrees C(similar to 1.2 GPa and similar to 7% engineering strain). The presence of Mg results in a complex barrier layer which significantly increases the oxidation resistance up to a temperature of at least 1000 degrees C. (C) 2012 Elsevier B.V. All rights reserved

Simple chemical aqueous synthesis of dahlia nanoflower consisting of finger-like ZnO nanorods and observation of stable ultraviolet photoluminescence emission

In this work, we have reported the synthesis of dahlia flower-like ZnO nanostructures consisting of human finger-like nanorods by the hydrothermal method at 120 degrees C and without using any capping agent. Optical properties of the samples, including UV-vis absorption and photoluminescence (PL) emission characteristics are determined by dispersing the samples in water as well as in ethanol media. The quenching of PL emission intensity along-with the red shifting of the PL emission peak are observed when the samples are dispersed in water in comparison to those obtained after dispersing the samples in ethanol. It has been found that PL emission characteristic, particularly the spectral nature of PL emission, of the samples remains almost unaltered (except some improvement in UV PL emission) even after thermally annealing it for 2 h at the temperature of 300 degrees C. Also the synthesized powder samples, kept in a plastic container, showed a very stable PL emission even after 15 months of synthesis. Therefore, the synthesized samples might be useful for their applications in future optoelectronics devices. (C) 2014 Elsevier Ltd. All rights reserved

Effect of indium addition on microstructural, mechanical and oxidation properties of suction cast Nb-Si eutectic alloy

The paper reports effect of small ternary addition of In on the microstructure, mechanical property and oxidation behaviour of a near eutectic suction cast Nb-19.1 at-%Si-1.5 at-%In alloy. The observed microstructure consists of a combination of two kinds of lamellar structure. They are metal-intermetallic combinations of Nb-ss-beta-Nb5Si3 and Nb-ss-alpha-Nb5Si3 respectively having 40-60 nm lamellar spacings. The alloy gives compressive strength of 3 GPa and engineering strain of similar to 3% at room temperature. The composite structure also exhibits a large improvement in oxidation resistance at high temperature (1000 degrees C)

Effects of Minute Addition of Ni on Microstructure and Mechanical Properties of Sn-Zn Eutectic Alloy

The current work explores the effects of a small addition of Ni on the microstructure and mechanical properties of Sn-Zn eutectic solder alloy (Sn-14.9 at.%Zn). In two sets of experiments, Ni is either added to the eutectic alloy or Zn in the eutectic alloy is replaced by an increasing amount of Ni. The study indicates that small additions of Ni in eutectic Sn-Zn solder (similar to 0.017 at.%) refines the eutectic microstructure together with the appearance of the small amount of primary Zn plates. Increasing the Ni content to 0.142 at.% and beyond, an intermetallic phase gamma-Ni5Zn21 with dendritic morphology appears in the microstructure along with dendrites of primary Sn. The scale of eutectic microstructure shows a decreasing trend till 0.902 at.%Ni with eutectic spacing of 1.98 +/- 0.12 lm for this alloy. Further addition of Ni coarsens the microstructure. The replacement of Zn with Ni in the eutectic composition follows a similar trend with a lesser refinement of the microstructure. In both the scenarios, the addition of a small amount of Ni increases the eutectic temperatures till a critical concentration is reached beyond which one can observe a decrease in the eutectic point. The trend is similar for the solid solubility of Zn in Sn while the trend is opposite for the measured eutectic composition, which decreases at the initial stages of Ni addition. Through a detailed measurement of mechanical properties, the study establishes significant improvement of the strength of Sn-Zn solder with small additions of Ni in the alloy with a maximum hardness of 26 +/- 2 HV and 0.2% proof stress of 72 +/- 3 MPa at room temperature for the eutectic alloy with 0.902 at.%Ni

Effects of Cu and In Trace Elements on Microstructure and Thermal and Mechanical Properties of Sn-Zn Eutectic Alloy

The effects of addition of small amounts of copper (Cu) and indium (In) on the microstructure and thermal and mechanical properties of Sn-Zn eutectic alloy have been investigated. Cu and In were added in varying amounts to Sn-14.9at.%Zn alloy by replacing an equal amount of Sn. Addition of Cu changed the eutectic composition, leading to the appearance of primary phases followed by the formation of intermetallic compounds (IMC) CuZn5 and Cu5Zn8. However, addition of indium (In) did not lead to formation of any new IMCs. With addition of Cu or In to the binary eutectic, the eutectic microstructure coarsened (the eutectic spacing increased). Addition of 1.919at.% indium decreased the Sn-Zn eutectic temperature from 198.8 degrees C to 192.0 degrees C. On the other hand, addition of Cu did not affect the eutectic temperature as much as In addition did. The mushy (or pasty) range (the temperature range between the eutectic temperature and the melting temperature of the primary phase) increased with addition of Cu or In. Addition of a small amount of copper increased the yield strength of the binary eutectic alloy. The maximum hardness and yield strength of 24 +/- 2HV and 60 +/- 3MPa, respectively, were found with addition of 0.841at.% Cu; this improvement in strength can be attributed to formation of hard IMCs. In contrast, addition of a small amount of In initially decreased the strength, but the strength increased to 50 MPa at 1.919at.% In. This can be attributed to the effect of solid-solution strengthening due to the In solute in soft beta-Sn

Microstructure and mechanical properties of oxidation resistant suction cast Nb-Si-Al alloy

In this paper, we report a significant improvement in mechanical and oxidation properties of near eutectic Nb-Si alloys by the addition of aluminum (Al) and control of microstructural length scale. A comparative study of two alloys Nb-18.79at%Si and Nb-12.3at%Si-9at%Al were carried out. The processing for microstructure refinements were carried out by vacuum suction casting in water cooled thick copper mould. It is shown that addition of Al suppresses Nb3Si phase and promotes beta Nb5Si3 phase under nonequilibrium solidification condition. The microstructural length scale and in particular eutectic spacing reduces significantly to 50-100 nm in suction cast ternary alloy. A detailed TEM study shows the presence of delta-Nb11Si4 phase in Nb matrix. The hardness of Nb solid solution can be increased as a consequence to a level observed in Nb3Si intermetallic due to the well oriented precipitates. Compression test yields the ultimate strength of 1.8 +/- 0.1 GPa and engineering strain of 2.3 +/- 0.03%. In comparison, the binary Nb-18.79 at% Si alloy possesses an ultimate strength of 1.35 +/- 0.1 GPa and strain of 0.2 +/- 0.01% when processed under identical conditions. The latter exhibits coarser microstructural length scale (300-400 nm) and a brittle behavior. The indentation fracture toughness of Al containing suction cast alloy shows a value of 20.2 +/- 0.5 MPa root m which represents a major improvement over bulk Nb-Si eutectic alloy. The detailed thermal studies confirm a multifold improvement in oxidation resistance up to 1000 degrees C. (C) 2012 Elsevier B.V. All rights reserved